WO2017061443A1 - Sn-COATED COPPER POWDER, CONDUCTIVE PASTE USING SAME, AND PRODUCING METHOD FOR Sn-COATED COPPER POWDER - Google Patents

Abstract

Provided is an Sn-coated copper powder which can be suitably used in a conductive paste, an electromagnetic-wave shield, etc., by preventing aggregation of the copper powder particles while ensuring excellent conductivity, through an increase in the number of contact points where copper powder particles coated with Sn come into contact with each other. The Sn-coated copper powder according to the present invention is formed by aggregating copper particles, which each have a surface coated with Sn or an Sn alloy and each have a specific shape, so as to have a dendritic shape or a form of an aggregate of the copper particles. Such an Sn-coated copper powder has copper powder particles having an increased number of contact points therebetween, and thus, exhibits excellent conductivity.

Description

Sn-coated copper powder, conductive paste using the same, and method for producing Sn-coated copper powder

The present invention relates to copper powder (Sn coated copper powder) whose surface is coated with nickel (Sn) or an Sn alloy, and more specifically, to improve conductivity by using it as a material such as a conductive paste. The present invention relates to a Sn-coated copper powder having a new shape.

For the formation of wiring layers, electrodes, and the like in electronic devices, many pastes and paints using metal fillers such as copper powder and silver powder, such as resin pastes, fired pastes, and electromagnetic wave shielding paints, are used. Metal filler pastes such as copper powder and silver powder are applied or printed on various base materials, and are subjected to heat curing or heat baking treatment to form a conductive film to be a wiring layer or an electrode.

In addition, as integration and density increase in the electronic material field, as a multilayering method, a through hole (through hole) is provided in the wall surface portion to obtain conduction between the front surface and the back surface of the printed wiring board. There is a method of performing through-hole plating and further filling the through-hole with a conductive paste.

For example, a resin-type conductive paste is made of a metal filler, a resin, a curing agent, a solvent, etc., printed on a conductor circuit pattern or terminal, and cured by heating at 100 ° C. to 200 ° C. An electrode is formed. In the resin-type conductive paste, since the thermosetting resin is cured and contracted by heat, when the metal filler is pressed and brought into contact, the metal filler overlaps and an electrically connected current path is formed. Since the resin-type conductive paste is processed at a curing temperature of 200 ° C. or less, it is used for a substrate using a heat-sensitive material such as a printed wiring board. As the metal filler used in this resin-type conductive paste, silver powder, copper powder, silver-coated copper powder, or the like is used.

Firing-type conductive paste consists of a metal filler, glass, solvent, etc., printed on a conductor circuit pattern or terminal, and heated and fired at 600 ° C. to 800 ° C. to form wiring and electrodes as a conductive film. To do. The fired conductive paste is processed at a high temperature to sinter the metal filler and ensure conductivity. Since the fired conductive paste is treated at such a high firing temperature, the metal particles are diffused and alloyed to conduct, and high connection reliability can be expected. Examples of the metal filler used in the sintered conductive paste include eutectic solder (Sn—Pb alloy), Pb-free solder powder (for example, Sn—Ag—Cu alloy), copper powder with tin (Sn) plating, and silver powder. And those plated with Sn.

However, in the case of lead-containing solder, when a wiring board or the like using it is discarded, lead is eluted and there is a risk of environmental pollution. .

As a Pb-free solder powder that is an alternative to the Sn—Pb alloy, binary or multi-element Sn alloys containing silver, bismuth, copper, indium, antimony, zinc, and the like can be cited as candidates. With this Pb-free solder powder, from the viewpoint of producing a higher-performance wiring board, it is required that the conductive paste composition in the via is highly metal-diffused to reduce the resistance value of the via. However, the Sn alloy having a melting point lower than the stacking temperature is melted by the temperature at the time of stacking, and there is a problem that the connection reliability in the via hole is lowered due to deformation and shrinkage behavior of the filled shape.

In order to solve these problems, it is necessary to minimize shape deformation due to melting, and it is necessary to reduce as much as possible the region of the Sn alloy that is melted by the lamination temperature. For that purpose, the metal filler particles used are not Pb-free solder powder, but are made of metal filler particles coated with an Sn alloy with copper or silver as the core, so that the Sn alloy region melts and shrinks. Can be minimized, and the connection reliability in the via hole can be ensured.

On the other hand, in the field where high conductivity or high thermal conductivity is required as the baked conductive paste, it is necessary to increase the blending amount of the conductive powder in order to increase the conductivity and thermal conductivity. As a method for producing the highly filled conductive powder, there is a method in which large and small spherical particles are combined and mixed. In this way, the filling rate can be increased by combining large and small particles. In addition, it is reported that a packing density of 80% or more is theoretically obtained by arranging spherical particles regularly and filling small spherical particles between large spherical particles (Non-patent Document 1). . However, actual spherical particles do not exist as completely independent particles, and the particles are partially agglomerated, resulting in a packing rate lower than the theoretical packing density.

In general, when filling a through hole with a conductive paste filled in a hole and performing interlayer connection of multilayer wiring boards, in order to increase the conductivity, fill as much of the conductive paste as possible in the through hole to eliminate gaps. It is necessary to embed a metal filler. Therefore, conventionally, in the conductive paste for filling holes used for this purpose, it is desired to increase the blending amount of the metal filler. However, when the compounding amount of the metal filler is increased, the viscosity of the conductive paste is increased and the filling property to the through hole is deteriorated. On the other hand, when the ratio of the binder in the conductive paste is increased, the viscosity is decreased and the filling property to the through hole is improved, but there is a disadvantage that the conductivity is deteriorated.

Here, when a spherical metal filler is used, contact between particles or a particle plane becomes point contact, and contact efficiency is deteriorated. Therefore, in order to improve this, it is necessary to bring the particles into contact with each other by making the metal filler into a flake shape.

As a method for producing a flaky metal filler, for example, Patent Document 1 discloses a method of mechanically processing a spherical copper powder into a flat shape to obtain a flaky copper powder. Specifically, a spherical copper powder having an average particle size of 0.5 μm to 10 μm is used as a raw material, and a ball mill or a vibration mill is used to mechanically process it into a flat plate by the mechanical energy of the media loaded in the mill. is there.

Further, for example, Patent Document 2 discloses a technique relating to a copper powder for conductive paste, more specifically, a disk-shaped copper powder having high performance as a copper paste for through-holes and external electrodes, and a method for producing the same. Specifically, the granular atomized copper powder is put into a medium agitating mill, and a steel ball having a diameter of 1/8 inch to 1/4 inch is used as a grinding medium. % To 1% is added and processed into a flat plate shape by grinding in air or in an inert atmosphere.

In general, in order to produce metal filler particles coated with Sn alloy with flaky copper powder as a core, mechanically plastically deforming copper powder into flakes as described above, It can be produced by coating Sn on the surface of the copper particles.

As a method for coating the surface of the copper powder with Sn, for example, an electroless Sn plating method can be used. Electroless Sn plating is a substitutional Sn plating in which Sn ions in the plating solution are reduced and precipitated with elution of the underlying copper powder, and a reduction in which Sn ions in the plating solution are reduced with a reducing agent to perform Sn coating. Type Sn plating and disproportionation reaction type Sn plating in which Sn coating is performed by utilizing the fact that Sn is disproportionated to form metal Sn.

Further, when the Sn alloy is coated by Sn alloy plating, silver, bismuth, zinc, or the like constituting the alloy is included in the substitutional Sn plating solution, the reduction Sn plating solution, or the disproportionation reaction type Sn plating solution. By adding a soluble salt and precipitating these metals simultaneously with Sn, a film of Sn alloy can be produced.

Now, as copper powder, electrolytic copper powder deposited in dendritic shape called dendritic shape is known, and since the shape is dendritic, it is characterized by a large surface area. Due to the dendritic shape as described above, when this is used for a conductive film or the like, the dendritic branches are overlapped with each other, conduction is easy, and the number of contact points between particles is larger than that of spherical particles. Therefore, there is an advantage that the amount of conductive filler such as conductive paste can be reduced. For example, Patent Document 3 discloses a technique for ensuring oxidation resistance by forming an Ni alloy layer on a copper surface and performing Ag coating thereon, and the copper powder used here is a dendritic electrolytic copper powder. Is preferable from the viewpoint of entanglement between particles.

On the other hand, when developing a branch of electrolytic copper powder, the electrolytic copper powder will be entangled more than necessary when used in a conductive paste, etc., which makes it easy to agglomerate and lowers the fluidity. It has been pointed out in Patent Document 5 that it becomes difficult to reduce productivity. As a method for solving this, in Patent Document 4, in order to increase the strength of the electrolytic copper powder itself, by adding a tungstate to the aqueous copper sulfate solution of the electrolytic solution for depositing the electrolytic copper powder, the electrolytic copper powder It is said that it can improve its strength, make it difficult to break the branches, and can be molded with high strength.

On the other hand, when developing a branch of electrolytic copper powder, when used in conductive paste, etc., the electrolytic copper powder is entangled more than necessary and agglomeration occurs, so that it does not disperse uniformly in the resin, and the fluidity is It is pointed out in Patent Document 4 that it decreases and becomes very difficult to handle, causing problems in wiring formation by printing or the like and reducing productivity. In addition, in this patent document 4, in order to raise the intensity | strength of electrolytic copper powder itself, the strength of electrolytic copper powder itself is improved by adding tungstate in the copper sulfate aqueous solution of the electrolytic solution for depositing electrolytic copper powder. It is said that the tree branches can be made difficult to break and can be molded with high strength.

As described above, it is not easy to use the dendritic copper powder as a metal filler such as a conductive paste, and the improvement of the conductivity of the paste has been difficult.

Japanese Patent Laid-Open No. 2005-200734 JP 2002-15622 A Japanese Patent Laid-Open No. 2002-075057 JP 2011-58027 A

The present invention has been proposed in view of such circumstances, and agglomeration of copper powders while ensuring excellent conductivity by increasing the number of contacts when the copper powders coated with Sn are in contact with each other. An object of the present invention is to provide a Sn-coated copper powder that can be suitably used as a conductive paste or the like.

The present inventor has intensively studied to solve the above-described problems. As a result, the copper particles having a specific shape coated with Sn or Sn alloy on the surface are aggregated, and are Sn-coated copper powder having a dendritic shape or a form of an aggregate of the copper particles, It has been found that the number of contacts between the copper powders increases and exhibits excellent conductivity, and the present invention has been completed. That is, the present invention provides the following.

[1] A first aspect of the present invention is a tree branch having a main trunk that is formed by linearly growing a main trunk of copper particles coated with tin (Sn) or an Sn alloy on the surface and a plurality of branches separated from the main trunk. The copper particles having an Sn-shaped copper powder, the surface of which is coated with Sn or an Sn alloy, have an average cross-sectional thickness of 0.02 μm to 5.5, as determined by scanning electron microscope (SEM) observation. The Sn-coated copper powder, which is a flat plate having a size of 0 μm and is configured by aggregating the copper particles, has an average particle diameter (D50) of 1.0 μm to 100 μm, with respect to the flat surface of the copper particles. Thus, the Sn-coated copper powder has a maximum height in the vertical direction that is 1/10 or less of the maximum length in the horizontal direction of the flat surface.

[2] A second invention of the present invention is an Sn-coated copper powder in which copper particles whose surfaces are coated with tin (Sn) or an Sn alloy are aggregated to form a dendritic shape having a plurality of branches. The copper particles having the surface coated with Sn or Sn alloy have a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. The Sn-coated copper powder, which is an ellipsoid and is configured by aggregating the copper particles, is Sn-coated copper powder having an average particle diameter (D50) of 5.0 μm to 20 μm.

[3] A third invention of the present invention is Sn-coated copper powder according to the second invention, wherein the average thickness of the branch portions constituting the dendritic shape is 0.5 μm to 2.0 μm.

[4] The fourth invention of the present invention is a tree branch having a main trunk that is formed by linearly growing a main trunk of copper particles coated with tin (Sn) or Sn alloy on the surface and a plurality of branches separated from the main trunk. A copper particle having a shape of a shape, the copper particle having the surface coated with Sn or an Sn alloy is a flat plate having a cross-sectional average thickness of 0.2 μm to 5.0 μm, and the copper particle The Sn-coated copper powder constituted by the aggregates is an Sn-coated copper powder having an average particle diameter (D50) of 1.0 μm to 100 μm.

[5] A fifth invention of the present invention is an Sn-coated copper powder comprising a plurality of pieces of copper particles whose surfaces are coated with tin (Sn) or an Sn alloy and having an aggregate form. The copper particles coated with Sn or Sn alloy have an average major axis diameter determined by observation with a scanning electron microscope (SEM) of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 μm to The Sn-coated copper powder, which is a flat plate having a thickness of 1.0 μm and is configured by aggregating the copper particles, is an Sn-coated copper powder having an average particle diameter (D50) of 1.0 μm to 30 μm.

[6] A sixth invention of the present invention is a tree branch having a main trunk in which copper particles coated with tin (Sn) or an Sn alloy are gathered on a surface, and a plurality of branches separated from the main trunk. A copper particle having a shape of a shape and having a surface coated with Sn or an Sn alloy is a dendritic shape having a main trunk grown in a dendritic shape and a plurality of branches separated from the main trunk. The Sn-coated copper powder, which is a flat plate having a cross-sectional average thickness of the main trunks and branches of the copper particles of 0.02 μm to 0.5 μm and is configured by aggregating the copper particles, has an average particle diameter ( D50) is Sn-coated copper powder having a thickness of 1.0 to 30 μm.

[7] A seventh invention of the present invention is the Sn according to the sixth invention, wherein the surface of the copper particles has fine convex portions, and the average height of the convex portions is 0.01 μm to 0.4 μm. Coated copper powder.

[8] The eighth invention of the present invention is the entire Sn-coated copper powder according to any one of the first to seventh inventions, wherein the Sn content coated as Sn or Sn alloy is coated with Sn or Sn alloy. The Sn-coated copper powder is 1 to 50% by mass with respect to 100% by mass.

[9] A ninth invention of the present invention is the invention according to any one of the first to eighth inventions, wherein the surface of the copper particles is coated with a Sn alloy, and cobalt, zinc, tungsten, molybdenum, palladium, platinum, Coated with a Sn alloy containing at least one selected from the group consisting of tin, phosphorus, and boron at a content of 0.1% by mass to 50% by mass with respect to 100% by mass of the Sn alloy. Sn-coated copper powder.

[10] A tenth aspect of the present invention is an Sn-coated copper powder according to any one of the first to ninth aspects, wherein the bulk density is in the range of 0.5 g / cm ³ to 5.0 g / cm ^3. is there.

[11] Eleventh aspect of the present invention, in any one of the first to 10, BET specific surface area is 0.2m ² /g~5.0m ² / g, in Sn-coated copper powder is there.

[12] A twelfth aspect of the present invention is a metal filler containing the Sn-coated copper powder according to any one of the first to eleventh aspects in a proportion of 20% by mass or more.

[13] A thirteenth invention of the present invention is a conductive paste obtained by mixing a metal filler according to the twelfth invention with a resin.

［式（１）中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９は、それぞれ別個に、水素、ハロゲン、アミノ、ＯＨ、＝Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、及びＣ１～Ｃ８アルキルからなる群から選択される基であり、Ｒ_５は、水素、ハロゲン、アミノ、ＯＨ、－Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、低級アルキル、及びアリールからなる群から選択される基であり、Ａ^－がハライドアニオンである。］

［式（２）中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、Ｒ_１０は、それぞれ別個に、水素、ハロゲン、アミノ、ＯＨ、＝Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、低級アルキル、及びアリールからなる群から選択される基である。］

［式（３）中、Ｒ_１、Ｒ_２、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、Ｒ_１０、Ｒ_１１、Ｒ_１２、Ｒ_１３は、それぞれ別個に、水素、ハロゲン、アミノ、ＯＨ、＝Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、及びＣ１～Ｃ８アルキルからなる群から選択される基であり、Ｒ_３は、水素、ハロゲン、アミノ、ＯＨ、＝Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、低級アルキル、及びアリールからなる群から選択される基であり、Ａ^－がハライドアニオンである。］ [14] A fourteenth aspect of the present invention is a method for producing an Sn-coated copper powder according to the first aspect, wherein the copper powder is deposited on the cathode from the electrolytic solution by an electrolysis method, and the copper powder A step of coating tin (Sn) or Sn alloy, and the electrolytic solution is represented by the following formula (2), a compound having a copper ion and a phenazine structure represented by the following formula (1): One or more selected from the group consisting of a compound having an azobenzene structure and a compound having a phenazine structure and an azobenzene structure represented by the following formula (3), and one or more nonionic surfactants: Is a method for producing Sn-coated copper powder in which electrolysis is performed.

[In Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. And A ⁻ is a halide anion. ]

[In the formula (2), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ are each independently hydrogen, halogen, amino, OH, = O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, a group selected from the group consisting of benzenesulfonic acid, lower alkyl, and aryl. ]

[In the formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, Selected from the group consisting of halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, A group selected from the group consisting of lower alkyl and aryl, and A ⁻ is a halide anion. ]

[15] A fifteenth aspect of the present invention is a method for producing Sn-coated copper powder, wherein, in the fourteenth aspect, the electrolytic solution further contains chloride ions.

[16] A sixteenth aspect of the present invention is a method for producing an Sn-coated copper powder according to the second or third aspect of the invention, wherein the copper powder is deposited on the cathode from the electrolytic solution by an electrolysis method, A process for coating tin powder with tin (Sn) or an Sn alloy, wherein the electrolytic solution contains copper ions and a polyether compound to conduct electrolysis. is there.

［式（１）中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９は、それぞれ別個に、水素、ハロゲン、アミノ、ＯＨ、＝Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、及びＣ１～Ｃ８アルキルからなる群から選択される基であり、Ｒ_５は、水素、ハロゲン、アミノ、ＯＨ、－Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、低級アルキル、及びアリールからなる群から選択される基であり、Ａ^－がハライドアニオンである。］ [17] A seventeenth aspect of the present invention is a method for producing Sn-coated copper powder according to the fourth aspect of the present invention, comprising the step of depositing copper powder on the cathode from the electrolytic solution by an electrolysis method, and the copper powder Coating with tin (Sn) or Sn alloy, and the electrolytic solution contains one or two selected from copper ions and a compound having a phenazine structure represented by the following formula (1) It is the manufacturing method of Sn coat | court copper powder which contains the above and performs electrolysis.

[In Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. And A ⁻ is a halide anion. ]

［式（３）中、Ｒ_１、Ｒ_２、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、Ｒ_１０、Ｒ_１１、Ｒ_１２、Ｒ_１３は、それぞれ別個に、水素、ハロゲン、アミノ、ＯＨ、＝Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、及びＣ１～Ｃ８アルキルからなる群から選択される基である。また、Ｒ_３は、水素、ハロゲン、アミノ、ＯＨ、＝Ｏ、ＣＮ、ＳＣＮ、ＳＨ、ＣＯＯＨ、ＣＯＯ塩、ＣＯＯエステル、ＳＯ_３Ｈ、ＳＯ_３塩、ＳＯ_３エステル、ベンゼンスルホン酸、低級アルキル、及びアリールからなる群から選択される基である。また、Ａ^－は、ハライドアニオンである。］ [18] An eighteenth aspect of the present invention is a method for producing a Sn-coated copper powder according to the sixth or seventh aspect of the invention, wherein the copper powder is deposited on the cathode from the electrolytic solution by an electrolysis method, A step of coating the copper powder with tin (Sn) or Sn alloy, and the electrolytic solution is selected from compounds having a copper ion and a phenazine structure and an azobenzene structure represented by the following formula (3): The manufacturing method of Sn coat | cover copper powder which electrolyzes containing 1 type, or 2 or more types.

[In the formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, Selected from the group consisting of halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl It is a group. R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion. ]

According to the present invention, it is possible to secure a large number of contacts and a large contact area, to ensure excellent conductivity, and to prevent agglomeration between copper powders. It can utilize suitably for uses, such as a shield.

It is the figure which showed typically the specific shape of the dendritic Sn coat | court copper powder which concerns on 1st Embodiment. It is the figure which showed typically the specific shape of the dendritic Sn coat | court copper powder which concerns on 1st Embodiment. In 1st Embodiment, it is a photograph figure which shows an observation image when the dendritic copper powder before coat | covering Sn is observed by SEM by 1000-times multiplication factor. In 1st Embodiment, it is a photograph figure which shows an observation image when the dendritic copper powder before coat | covering Sn is observed by SEM with a magnification of 5,000 times. It is a photograph figure which shows an observation image when the dendritic Sn coat | court copper powder which concerns on 1st Embodiment is observed by 1000-times multiplication factor by SEM. It is a photograph figure which shows an observation image when the dendritic Sn coat | court copper powder which concerns on 1st Embodiment is observed by 1000-times multiplication factor by SEM. In 2nd Embodiment, it is the figure which showed typically the specific shape of the dendritic copper powder before coat | covering Sn. In 2nd Embodiment, it is a photograph figure which shows an example of an observation image when the dendritic copper powder before coat | covering Sn is observed by SEM with a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when the dendritic Sn coat | court copper powder which concerns on 2nd Embodiment is observed by 5,000 times magnification by SEM. It is a photograph figure which shows an example of the observation image when the dendritic Sn coat | court copper powder which concerns on 2nd Embodiment is observed by 10,000 times by SEM. It is the figure which showed typically the specific shape of the dendritic Sn coat | court copper powder which concerns on 3rd Embodiment. In 3rd Embodiment, it is a photograph figure which shows an example of an observation image when the dendritic copper powder before coat | covering Sn is observed by SEM with a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when the dendritic Sn coat | court copper powder which concerns on 3rd Embodiment is observed by 5,000 times by SEM. It is a photograph figure which shows an example of an observation image when the dendritic Sn coat | court copper powder which concerns on 3rd Embodiment is observed by 1000-times multiplication factor by SEM. It is the figure which showed typically the specific shape of Sn coat | court copper powder which concerns on 4th Embodiment. It is a photograph figure which shows an example of an observation image when the Sn coat copper powder which concerns on 4th Embodiment is observed by 5,000 times magnification by SEM. It is a photograph figure which shows an example of an observation image when the Sn coat copper powder which concerns on 4th Embodiment is observed by 10,000 times by SEM. It is a photograph figure which shows an example of an observation image when the Sn coat copper powder which concerns on 4th Embodiment is observed by 30,000 times with SEM. It is the figure which showed typically the specific shape of the copper particle with which Sn or Sn alloy which comprises the dendritic Sn coat | court copper powder which concerns on 5th Embodiment was coat | covered. In 5th Embodiment, it is a photograph figure which shows an example of an observation image when the dendritic copper powder before coat | covering Sn is observed by SEM with a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when the dendritic Sn coat | court copper powder which concerns on 5th Embodiment is observed by 5,000 times magnification by SEM. It is a photograph figure which shows an example of an observation image when another location of the dendritic Sn coat | court copper powder which concerns on 5th Embodiment is observed by 1000-times multiplication factor by SEM. It is a photograph figure which shows an observation image when the Sn coat copper powder obtained in the comparative example 3 is observed by 5,000 times magnification by SEM. It is a photograph figure which shows an observation image when the Sn coat copper powder obtained in the comparative example 5 is observed by 5,000 times magnification by SEM. It is a photograph figure which shows an observation image when the Sn coat copper powder obtained in the comparative example 7 is observed by 5,000 times by SEM. It is a photograph figure which shows an observation image when the Sn coat copper powder obtained in the comparative example 9 is observed by 5,000 times magnification by SEM.

Hereinafter, specific embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and Various modifications can be made without departing from the scope of the invention. In this specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

<< 1. Tin (Sn) coated copper powder >>
The tin-coated copper powder according to the present invention is a copper powder having a surface coated with tin (Sn) or an Sn alloy. In the present specification, tin-coated copper powder is referred to as “Sn-coated copper powder”. Further, tin or tin alloy to be coated is expressed as “Sn” and “Sn alloy”, respectively, and the case where Sn is coated on the copper powder surface or the case where Sn alloy is coated on the copper powder surface is generally “Sn coat”. ".

<1-1. First Embodiment>
[Configuration of Sn-coated copper powder]
When the Sn-coated copper powder according to the first embodiment is observed using a scanning electron microscope (SEM), the Sn-coated copper powder has a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. The main trunk and branch are formed by aggregating tabular copper particles having a specific cross-sectional average thickness, and the surface of the tabular copper particles is coated with Sn or an Sn alloy. Hereinafter, this Sn-coated copper powder is also referred to as “dendritic Sn-coated copper powder”.

More specifically, in this dendritic Sn-coated copper powder, the main trunk and branches are composed of flat copper particles having an average cross-sectional thickness of 0.02 μm to 5.0 μm determined by SEM observation. Thus, the average particle diameter (D50) of the Sn-coated copper powder composed of flat copper particles is 1.0 μm to 100 μm. In this dendritic Sn-coated copper powder, the height of the flat copper particles in the vertical direction with respect to the flat surface is 1/10 or less of the maximum length in the horizontal direction. It has a smooth surface that suppresses growth in the vertical direction.

Such a dendritic Sn-coated copper powder will be described in detail later. For example, the anode and the cathode are immersed in a sulfuric acid electrolyte containing copper ions, and a direct current is applied to perform electrolysis to form copper on the cathode. It can be produced by depositing powder and coating the surface of the obtained copper powder with Sn or an Sn alloy by an electroless plating method or the like.

1 and 2 are diagrams schematically showing a specific shape of the dendritic Sn-coated copper powder according to the first embodiment. As shown in FIG. 1, the dendritic Sn-coated copper powder 11 has a dendritic shape having a main trunk 12 grown linearly and a plurality of branches 13 separated from the main trunk 12. The branch 13 in the dendritic Sn-coated copper powder 11 means not only the branch 13a branched from the main trunk 12, but also the branch 13b further branched from the branch 13a.

As described above, the main trunk 12 and the branch 13 are constituted by a collection of tabular copper particles having an average cross-sectional thickness of 0.02 μm to 5.0 μm determined by SEM observation. The formation of such flat copper particles is caused by the fact that specific additives added to the electrolytic solution when electrolytically depositing copper powder are adsorbed on the surface of the copper particles, as will be described later. As a result, it is thought that it grows flat. In addition, Sn coat | court copper powder 11 is comprised by coat | covering Sn or Sn alloy on the surface of such a flat copper particle.

However, for example, when copper powder grows in a direction perpendicular to the flat surface shown in FIG. 2 (the Z direction in FIG. 2), the copper particles of the grown branches themselves become flat, but the vertical Copper powder in which copper particles grow like protrusions is also formed in the direction. FIG. 2 is a diagram showing a horizontal direction (flat plate direction) to the flat plate surface and a direction perpendicular to the flat plate surface. The flat plate direction indicates the XY direction, and the vertical direction. Indicates the Z direction.

Here, FIG. 3 shows an observation image when the copper powder grown in the direction perpendicular to the flat plate-like surface is observed by SEM (magnification 1,000 times) in the dendritic copper powder before coating with Sn. It is a photograph figure which shows an example. In the dendritic copper powder shown in this photograph, copper particles grow in a direction perpendicular to the flat surface to form protrusions, and some flat surfaces are bent to have a height in the vertical direction. It has a shape.

When the copper particles grow in the vertical direction as shown in the photograph of FIG. 3, for example, when the Sn-coated copper powder produced based on the copper powder is used for applications such as conductive paste and conductive paint, the vertical Since the copper powder becomes bulky due to the growth of the copper particles in the direction, the filling density cannot be obtained, and there is a problem that sufficient conductivity cannot be ensured.

In contrast, in the Sn-coated copper powder 11 according to the first embodiment, the growth in the direction perpendicular to the flat surface is suppressed, and the copper powder has a substantially smooth surface. Specifically, as shown in FIG. 2, the Sn-coated copper powder 11 has a maximum height in the vertical direction (reference numeral “15” in FIG. 2) with respect to the flat plate-like surface. It becomes 1/10 or less with respect to the maximum length (symbol “14” in FIG. 2) that is long in the direction. Note that the maximum height 15 in the direction perpendicular to the flat surface is not the thickness of the flat surface, but, for example, when the protrusion is formed on the flat surface, the height of the protrusion. Yes, it means the “height” in the direction opposite to the thickness direction with respect to the flat “surface”. Moreover, the maximum length 14 in the horizontal direction with respect to the flat surface means the major axis length of the flat surface.

Here, FIG. 4 is an observation image when the dendritic copper powder before coating with Sn or Sn alloy is observed by SEM (magnification of 5,000 times), that is, in a direction perpendicular to the flat surface. It is a photograph figure which shows an example of the observation image of the flat dendritic copper powder which suppressed the growth. Moreover, FIG. 5 is when the dendritic Sn coat | covered copper powder which coat | covered Sn or Sn alloy with the dendritic copper powder which suppressed the growth to the orthogonal | vertical direction shown in FIG. 4 was observed by SEM (magnification 1,000 times). It is a photograph figure which shows the observation image of. In addition, FIG. 6 is a similar graph showing another part of the dendritic Sn-coated copper powder in which Sn or Sn alloy is coated on the dendritic copper powder whose growth in the vertical direction is suppressed by SEM (magnification 1,000 times). It is a photograph figure which shows the observation image when it observes. As shown in these photographic diagrams, it can be seen that the growth in the vertical direction with respect to the flat surface is suppressed, and a dendritic and flat copper powder having a substantially smooth surface is obtained.

Such a flat dendritic Sn-coated copper powder 11 in which the growth in the vertical direction is suppressed can ensure a large contact area between the copper powders. And since the contact area becomes large, low resistance, that is, high conductivity can be realized. Thereby, it is further excellent in electroconductivity, can maintain the electroconductivity favorably, and can be used suitably for the use of an electroconductive coating material or an electroconductive paste. Further, the dendritic Sn-coated copper powder 11 is formed by aggregating flat copper particles, which can contribute to thinning of wiring materials and the like.

As described above, the tabular copper particles coated with Sn or Sn alloy constituting the main trunk 12 and the branches 13 in the dendritic Sn-coated copper powder 11 have an average cross-sectional thickness of 0.02 μm to 5.0 μm. It is. As for the cross-sectional average thickness of the flat copper particles coated with Sn or Sn alloy, the thinner one will exhibit the effect as a flat plate. That is, the trunk 12 and the branches 13 are configured by Sn-coated tabular copper particles having an average cross-sectional thickness of 5.0 μm or less, so that the copper particles and dendritic Sn formed thereby are formed. A large area where the coated copper powders 11 come into contact with each other can be secured.

In addition, as the cross-sectional average thickness of the tabular copper particles coated with Sn or the Sn alloy becomes thinner, the number of contacts when the dendritic Sn-coated copper powders 11 come into contact with each other decreases. If the average cross-sectional thickness of the copper particles coated with Sn or Sn alloy is 0.02 μm or more, a sufficient number of contacts can be secured, and more preferably 0.2 μm or more. Can be increased effectively.

Further, in the dendritic Sn-coated copper powder 11 according to the first embodiment, the average particle diameter (D50) is 1.0 μm to 100 μm. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical crushing or crushing such as a jet mill, a sample mill, a cyclone mill, or a bead mill. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

Here, as pointed out in Patent Document 4, for example, as a problem of powder having a dendritic shape such as a dendritic Sn-coated copper powder, a metal filler such as a conductive paste or a resin for electromagnetic wave shielding When the metal filler in the resin is in a shape that is developed in a dendritic shape, the dendritic copper powders are entangled with each other to cause agglomeration and not uniformly dispersed in the resin. In addition, the agglomeration increases the viscosity of the paste and causes problems in wiring formation by printing. This occurs because the shape (particle diameter) of the dendritic Sn-coated copper powder is large. In order to solve this problem while effectively utilizing the dendritic shape, the dendritic Sn-coated copper powder is used. It is necessary to reduce the shape of the. However, if the particle diameter of the dendritic Sn-coated copper powder is too small, the dendritic shape cannot be secured. Therefore, the effect of being in a dendritic shape, that is, a three-dimensional shape, has a large surface area and excellent moldability and sinterability, and can be molded with high strength by being firmly connected via a branch-like portion. In order to secure the effect, it is necessary that the dendritic Sn-coated copper powder has a size larger than a predetermined size.

In this respect, in the dendritic Sn-coated copper powder 11 according to the first embodiment, the average particle diameter is 1.0 μm to 100 μm, so that the surface area is increased and good moldability and sinterability are ensured. can do. The dendritic Sn-coated copper powder 11 has a dendritic shape because the main trunk 12 and the branch 13 are composed of an aggregate of flat copper particles in addition to the dendritic shape. Due to the three-dimensional effect and the effect that the copper particles constituting the dendritic shape are flat, more contacts between copper powders can be secured.

As a method for producing a flat Sn-coated copper powder, Patent Document 1 and Patent Document 2 show that a flat plate is formed by a mechanical method such as pulverization. In this mechanical method, for example, when spherical copper powder is formed into a flat plate shape, it is necessary to prevent copper oxidation during mechanical processing. Therefore, fatty acid is added and pulverized in air or in an inert atmosphere. This is processed into a flat plate shape. However, it cannot be completely prevented from oxidation, and the fatty acid added at the time of processing may affect the dispersibility when it is made into a paste. The fatty acid may firmly adhere to the copper surface due to the pressure during machining, which causes a problem that it cannot be completely removed. Then, when it uses as metal fillers, such as an electrically conductive paste and resin for electromagnetic wave shielding, the adhesion of the oxide film or fatty acid becomes a cause of increasing resistance.

In contrast, the dendritic Sn-coated copper powder 11 according to the first embodiment can be grown by direct electrolysis to form a flat plate without performing mechanical processing. Therefore, the problem of oxidation and the problem due to the remaining fatty acid, which are problems in this method, do not occur, the surface state of the copper powder becomes good, and the electrical conductivity can be made extremely good. Thereby, when using as metal fillers, such as electroconductive paste and resin for electromagnetic wave shielding, low resistance is realizable. In addition, the manufacturing method of the dendritic Sn coat copper powder 11 will be described in detail later.

Also, in order to realize further low resistance, the filling rate of the metal filler becomes a problem. In order to further increase the filling rate, the smoothness of the flat dendritic Sn-coated copper powder is required. That is, the form of the dendritic Sn-coated copper powder 11 is such that the maximum height in the direction perpendicular to the flat surface is 1/10 of the maximum length in the direction horizontal to the flat surface. By being below, since smoothness is high and a filling rate rises, since the contact in the surface of copper powder increases, further low resistance is realizable.

In addition, if the dendritic Sn coat copper powder of the shape as described above is occupied at a predetermined ratio in the obtained Sn coat copper powder when observed with an electron microscope, Sn of other shapes is used. Even if the coated copper powder is mixed, the same effect as that of the copper powder composed only of the dendritic Sn-coated copper powder can be obtained. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the dendritic Sn-coated copper powder having the shape described above is 65% by number or more, preferably 80% of the total Sn-coated copper powder. As long as it occupies a ratio of several percent or more, more preferably 90 percent or more, Sn-coated copper powder of other shapes may be included.

[Sn coating]
As described above, the dendritic Sn-coated copper powder 11 according to the first embodiment is a flat plate having an average cross-sectional thickness of 0.02 μm to 5.0 μm, and the surface is coated with Sn or an Sn alloy. It is constituted in a dendritic shape by copper particles.

The dendritic Sn-coated copper powder 11 is preferably 1% by mass as Sn content with respect to 100% by mass of the entire Sn-coated copper powder 11 coated with Sn on the dendritic copper powder before being coated with Sn or an Sn alloy. Sn or an Sn alloy is coated at a ratio of ˜50 mass%, and the Sn thickness (coating thickness) is 0.1 μm or less, preferably 0.05 μm or less. Accordingly, the dendritic Sn-coated copper powder 11 has a shape that retains the shape of the dendritic copper powder before coating with Sn or the Sn alloy. Therefore, the shape of the copper powder before coating Sn or Sn alloy and the shape of the Sn-coated copper powder after coating Sn or Sn alloy on the copper powder are both dendritic shapes.

As described above, the content of Sn coated as Sn or Sn alloy in the dendritic Sn-coated copper powder 11 is 1% by mass to 50% by mass with respect to 100% by mass of the Sn-coated Sn-coated copper powder 1 as a whole. % Is preferable. The Sn content coated as Sn or Sn alloy is preferably as low as possible because Sn has a lower electrical conductivity than copper, but if it is too small, a uniform Sn or Sn alloy film cannot be secured on the copper powder surface. This causes a decrease in conductivity. Therefore, as content of Sn coat | covered as Sn or Sn alloy, it is preferable that it is 1 mass% or more with respect to 100 mass of the said Sn coat | covered Sn coating copper powder 11 whole, and is 2 mass% or more. It is more preferable that the content is 5% by mass or more.

On the other hand, if the content of Sn coated as Sn or Sn alloy increases, it is not preferable because the conductivity decreases. Therefore, the coating amount of Sn or Sn alloy is preferably 50% by mass or less, more preferably 20% by mass or less, based on 100% by mass of the Sn-coated copper powder 11 coated with Sn. More preferably, it is 10 mass% or less.

In the dendritic Sn-coated copper powder 11 according to the first embodiment, the average thickness of Sn or Sn alloy coated on the surface of the dendritic copper powder is about 0.001 μm to 0.1 μm, and 0.005 μm More preferably, it is about 0.02 μm. If the Sn or Sn alloy coating thickness is less than 0.001 μm on average, a uniform Sn or Sn alloy coating cannot be secured on the surface of the copper powder, and this causes a decrease in conductivity. On the other hand, when the coating thickness of Sn or Sn alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of cost.

Thus, the average thickness of Sn coated on the surface of the dendritic copper powder is 0.1 μm or less, and the cross-sectional average thickness of the plate-like copper particles constituting the dendritic copper powder before coating with Sn or Sn alloy Is smaller than 0.02 μm to 5.0 μm. Therefore, before and after coating the surface of the dendritic copper powder with Sn or an Sn alloy, the cross-sectional average thickness of the tabular copper particles does not substantially change.

As will be further described later, in the dendritic Sn-coated copper powder 11, Sn covered with the dendritic copper powder may be a Sn alloy. The element added as the Sn alloy is preferably at least one selected from silver, bismuth, and zinc.

[About bulk density]
The dendritic Sn-coated copper powder 11 according to the first embodiment is not particularly limited, but the bulk density is preferably in the range of 0.5 g / cm ³ to 5.0 g / cm ³ . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Sn-coated copper powders cannot be secured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Sn-coated copper powder also increases, and the surface area may decrease, and the formability and sinterability may deteriorate.

[BET specific surface area]
In the first according to the embodiment dendritic Sn coating copper powder 11 is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ² /g~5.0m ² / g. When the BET specific surface area value is less than 0.2 m ² / g, the copper particles coated with Sn or the Sn alloy may not have the desired shape as described above, and high conductivity cannot be obtained. There is. On the other hand, if the BET specific surface area value exceeds 5.0 m ² / g, the coating of Sn or Sn alloy on the surface of the dendritic Sn-coated copper powder becomes non-uniform and high conductivity may not be obtained. Further, the copper particles constituting the dendritic Sn-coated copper powder become too fine, and the dendritic Sn-coated copper powder becomes a fine whisker-like state, which may lower the conductivity. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

<1-2. Second Embodiment>
[Configuration of Sn-coated copper powder]
The Sn-coated copper powder according to the second embodiment forms a dendritic shape having a plurality of branches when observed using a scanning electron microscope (SEM), and has an ellipsoidal shape having a specific size. The copper particles are aggregated, and the surface of these copper particles is coated with Sn or an Sn alloy. Hereinafter, this Sn-coated copper powder is also referred to as “dendritic Sn-coated copper powder”.

More specifically, in this dendritic Sn-coated copper powder, a copper powder having a dendritic shape having a plurality of branches has a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter. The ellipsoid has a size in the range of 0.5 μm to 2.0 μm and is composed of copper particles whose surfaces are coated with Sn or an Sn alloy. The average particle diameter (D50) of the Sn-coated copper powder formed by assembling the copper particles coated with Sn or Sn alloy on the surface is 5.0 μm to 20 μm.

Here, FIG. 7 is a diagram schematically showing a specific shape of the dendritic copper powder before the Sn or Sn alloy is coated on the surface, which constitutes the Sn-coated copper powder according to the second embodiment. It is. As shown in the schematic diagram of FIG. 7, the dendritic copper powder 21 constituting the Sn-coated copper powder has a dendritic shape having a plurality of branches, and is composed of an aggregate of fine copper particles 22. The Sn-coated copper powder is obtained by coating the surface of the dendritic copper powder 21 which is an aggregate of such copper particles 22 with Sn or an Sn alloy.

The copper particles 22 constituting the dendritic copper powder 21 have an ellipsoid having a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. It is the copper particle of the shape. The dendritic copper powder 21 which is an aggregate of the ellipsoidal copper particles 22 has an average particle diameter (D50) of 5.0 μm to 20 μm. Even after the surface of the dendritic copper powder 21 is coated with Sn or an Sn alloy, the minor axis average diameter and the major axis average diameter of the copper particles coated with Sn constituting the Sn-coated copper powder, and its Sn The average particle diameter of the coated copper powder is almost the same.

Although such dendritic copper powder 21 will be described in detail later, for example, the anode and the cathode are immersed in a sulfuric acid acidic electrolyte solution containing copper ions, and a DC current is applied to cause electrolysis to deposit on the cathode. Can be obtained. That is, the dendritic copper powder 21 having a small shape as described above can be deposited and formed by electrolysis without performing physical treatment such as pulverization and crushing. In addition, since the conventional dendritic copper powder has a very large shape and cannot be used as it is, it was used as a small shape by performing a pulverization process. In this case, the crushed shape is a rod-shaped copper powder having a size of 10 μm or less. Therefore, the shape of the conventional dendritic copper powder is considered to be a dendritic copper powder in which shapes of 10 μm or less are assembled.

FIG. 8 is a photograph showing an example of an observation image obtained by SEM (5,000 times magnification) of the dendritic copper powder before coating with Sn or Sn alloy. 9 and 10 are SEM observations of the dendritic Sn-coated copper powder according to the second embodiment, that is, the dendritic Sn-coated copper powder obtained by coating the surface of the dendritic copper powder with Sn or an Sn alloy. It is a photograph figure which shows an example of an image (FIG. 9: 5,000 times magnification, FIG. 10: 10,000 times magnification).

As observed in FIG. 8, the copper powder before coating with Sn exhibits a dendritic precipitation state. Moreover, as observed in FIG. 9 and FIG. 10, the Sn-coated copper powder is composed of copper powder exhibiting a dendritic precipitation state. The dendritic Sn-coated copper powder is formed by coating the surface of the dendritic copper powder 21 formed with the dendritic shape by the aggregation of the copper particles 22 with Sn or Sn alloy. This is an ellipsoidal shape having a minor axis average diameter of 0.5 μm or less and a major axis average diameter of 2.0 μm or less.

Thus, the long axis average diameter of the copper particles 22 constituting the dendritic copper powder 21 is an elongated shape having a diameter of 2.0 μm or less, thereby increasing the number of contacts when the dendritic Sn-coated copper powders are in contact with each other. can do. That is, since the long axis average diameter is an aggregate of the copper particles 22 having a diameter of 2.0 μm or less, as can be confirmed from the observation results shown in FIGS. Fine protrusions will be formed, and this will ensure many contacts between the dendritic Sn-coated copper powders.

However, when the long axis average diameter of the copper particles 22 is longer than 2.0 μm, the interval between the dendritic branches is reduced and the dense shape is formed on the whole. It tends to decrease. Conversely, when the major axis average diameter of the copper particles becomes too short, formation of protrusions cannot be obtained. Therefore, the major axis average diameter of the copper particles 22 is preferably 0.5 μm to 2.0 μm.

Further, the minor axis average diameter of the copper particles 22 is 0.5 μm or less. When the minor axis average diameter of the copper particles 22 is thicker than 0.5 μm, when the fine copper particles 22 are aggregated to form a dendritic shape, the thickness of the branch portion of the dendritic copper powder 21 (for example, FIG. 7). “D1”) in the schematic diagram increases. When the thickness (diameter) of the branch portion increases, the interval between the branches of the dendritic Sn-coated copper powder in which the surface of the dendritic copper powder 21 is coated with Sn or an Sn alloy is narrowed, resulting in a dense shape as a whole. The three-dimensional dendritic effect cannot be exhibited. On the other hand, if the thickness of the branch portion is too thin, it becomes a fine whisker-like state, so that sufficient conductivity cannot be ensured when the dendritic Sn-coated copper powders are in contact with each other. From this, it is preferable that the minor axis average diameter of the copper particles 22 is 0.2 μm to 0.5 μm, so that sufficient conductivity can be obtained while exhibiting a three-dimensional dendritic effect. Sex can be secured.

Furthermore, the average thickness (diameter) (D1) of the branch portion of the dendritic copper powder 21 constituted by the copper particles 22 is preferably 5.0 μm or less. When the average thickness of the branch portion exceeds 5.0 μm, the interval between the branches of the dendritic copper powder 1 is narrowed and the shape becomes dense as a whole. On the other hand, if the thickness of the branch portion is too small, the strength of the dendritic Sn-coated copper powder coated with Sn or Sn alloy on the surface of the dendritic copper powder is insufficient, and the branch portion breaks. There is a possibility of losing conductivity. Therefore, the average thickness of the branch portion of the dendritic copper powder 1 is preferably 0.5 μm to 5.0 μm.

In addition, in the Sn-coated copper powder according to the second embodiment, the average particle diameter (D50) is 5.0 μm to 20 μm. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical crushing or crushing such as a jet mill, a sample mill, a cyclone mill, or a bead mill. With such a size of the Sn-coated copper powder, it is possible to secure a large number of contact points between the copper powders by the effect of the three-dimensional dendritic shape, and to suppress the aggregation in the resin and to disperse it well. And increase in paste viscosity can be suppressed. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

In addition, if the dendritic Sn coat copper powder of the shape as described above is occupied at a predetermined ratio in the obtained Sn coat copper powder when observed with an electron microscope, Sn of other shapes is used. Even if the coated copper powder is mixed, the same effect as that of the copper powder composed only of the dendritic Sn-coated copper powder can be obtained. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the dendritic Sn-coated copper powder having the shape described above is 65% by number or more, preferably 80% of the total Sn-coated copper powder. As long as it occupies a ratio of several percent or more, more preferably 90 percent or more, Sn-coated copper powder of other shapes may be included.

[Sn coating]
In the dendritic Sn-coated copper powder according to the second embodiment, the surface of the dendritic copper powder 21 (see FIG. 7) is coated with Sn or an Sn alloy as described above.

The dendritic Sn-coated copper powder preferably has a Sn content of 1% by mass to 100% by mass of the total Sn-coated copper powder coated with Sn on the dendritic copper powder 21 before being coated with Sn or an Sn alloy. The Sn or Sn alloy is coated at a ratio of 50% by mass, and the Sn thickness (coating thickness) is 0.1 μm or less, preferably 0.05 μm or less. From this, the resinous Sn-coated copper powder has a shape that retains the shape of the dendritic copper powder 21 before being coated with Sn or the Sn alloy. Therefore, the shape of the copper powder before coating Sn or Sn alloy and the shape of the Sn-coated copper powder after coating Sn or Sn alloy on the copper powder are both dendritic shapes.

As described above, the content of Sn coated as Sn or an Sn alloy in the dendritic Sn-coated copper powder is 1% by mass to 50% by mass with respect to 100% by mass of the entire Sn-coated Sn-coated copper powder. A range is preferable. The Sn content coated as Sn or Sn alloy is preferably as low as possible because Sn has a lower electrical conductivity than copper, but if it is too small, a uniform Sn or Sn alloy film cannot be secured on the copper powder surface. This causes a decrease in conductivity. Therefore, as content of Sn coat | covered as Sn or Sn alloy, it is preferable that it is 1 mass% or more with respect to 100 mass of the whole Sn coat | covered Sn coat copper powder, and it is 2 mass% or more. Is more preferable, and it is further more preferable that it is 5 mass% or more.

On the other hand, if the content of Sn coated as Sn or Sn alloy increases, it is not preferable from the viewpoint of cost. Therefore, the coating amount of Sn or Sn alloy is preferably 50% by mass or less, more preferably 20% by mass or less, with respect to 100% by mass of the entire Sn-coated copper powder coated with Sn. More preferably, it is at most mass%.

In the dendritic Sn-coated copper powder according to the second embodiment, the average thickness of Sn or Sn alloy coated on the surface of the copper particles is about 0.001 μm to 0.1 μm, and 0.005 μm to 0.005. It is preferably about 02 μm. If the Sn or Sn alloy coating thickness is less than 0.001 μm on average, a uniform Sn coating cannot be secured on the surface of the copper powder, and this causes a decrease in conductivity. On the other hand, when the coating thickness of Sn or Sn alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of cost.

Thus, the average thickness of the Sn or Sn alloy coated on the surface of the dendritic Sn-coated copper powder is about 0.001 μm to 0.1 μm, and constitutes the dendritic copper powder 21 before coating the Sn or Sn alloy. It is smaller than the size of the copper particles 22 (an ellipsoid having a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm). Therefore, the form of the copper powder does not substantially change before and after the surface of the dendritic copper powder 21 is coated with Sn or an Sn alloy.

As will be further described later, in the dendritic Sn-coated copper powder, the Sn covered with the dendritic copper powder 21 may be a Sn alloy. The element added as the Sn alloy is preferably at least one selected from silver, bismuth, and zinc.

[About bulk density]
The dendritic Sn-coated copper powder according to the second embodiment is not particularly limited, but the bulk density is preferably in the range of 0.5 g / cm ³ to 5.0 g / cm ³ . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Sn-coated copper powders cannot be ensured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Sn-coated copper powder also increases, and the surface area may decrease and formability and sinterability may deteriorate. .

[BET specific surface area]
The dendritic Sn coating copper powder according to the second embodiment is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ² /g~5.0m ² / g. When the BET specific surface area value is less than 0.2 m ² / g, the copper particles coated with Sn or the Sn alloy may not have the desired shape as described above, and high conductivity cannot be obtained. There is. On the other hand, if the BET specific surface area value exceeds 5.0 m ² / g, the coating of Sn or Sn alloy on the surface of the dendritic Sn-coated copper powder becomes non-uniform and high conductivity may not be obtained. Further, the copper particles constituting the dendritic Sn-coated copper powder become too fine, and the dendritic Sn-coated copper powder becomes a fine whisker-like state, which may lower the conductivity. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

<1-3. Third Embodiment>
[Configuration of Sn-coated copper powder]
When the Sn-coated copper powder according to the third embodiment is observed using a scanning electron microscope (SEM), the Sn-coated copper powder has a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. The main trunk and branch are formed by aggregating tabular copper particles having a specific cross-sectional average thickness, and the surface of the tabular copper particles is coated with Sn or an Sn alloy. Hereinafter, this Sn-coated copper powder is also referred to as “dendritic Sn-coated copper powder”.

More specifically, in this dendritic Sn-coated copper powder, the main trunk and branches are composed of flat copper particles having an average cross-sectional thickness of 0.2 μm to 5.0 μm determined by SEM observation. And, the average particle diameter (D50) of the Sn-coated copper powder constituted by aggregating tabular copper particles is 1.0 μm to 100 μm.

Such a dendritic Sn-coated copper powder will be described in detail later. For example, the anode and the cathode are immersed in a sulfuric acid electrolyte containing copper ions, and a direct current is applied to perform electrolysis to form copper on the cathode. It can be produced by depositing powder and coating the surface of the obtained copper powder with Sn or an Sn alloy by an electroless plating method or the like.

FIG. 11 is a diagram schematically showing a specific shape of the Sn-coated copper powder according to the third embodiment. As shown in FIG. 11, the dendritic Sn-coated copper powder 31 has a dendritic shape having a main trunk 32 that grows linearly and a plurality of branches 33 that are separated from the main trunk 32. The branch 33 in the dendritic Sn-coated copper powder 31 means both a branch 33a branched from the main trunk 32 and a branch 33b further branched from the branch 33a.

The dendritic Sn-coated copper powder 31 is a flat plate having a predetermined average cross-sectional thickness, and is composed of copper particles whose surfaces are coated with Sn or an Sn alloy.

More specifically, in the dendritic Sn-coated copper powder 31, the main trunk 32 and the branch 33 are configured by aggregating tabular copper particles having a cross-sectional average thickness of 0.2 μm to 5.0 μm. The formation of such flat copper particles is caused by the fact that specific additives added to the electrolytic solution when electrolytically depositing copper powder are adsorbed on the surface of the copper particles, as will be described later. As a result, it is thought that it grows flat. In addition, Sn coat | court copper powder 31 is comprised by coat | covering the surface of such a flat copper particle with Sn or a Sn alloy.

FIG. 12 is a photographic diagram showing an example of an observation image when the dendritic copper powder before the Sn coating, constituting the dendritic Sn-coated copper powder 31, is observed by SEM (magnification 5,000 times). FIG. 13 is a photograph showing an example of an observation image when the dendritic Sn-coated copper powder obtained by coating Sn on the dendritic copper powder of FIG. 12 is observed by SEM (magnification 5,000 times). Similarly, FIG. 14 is a photographic diagram showing an example of an observation image when the dendritic Sn-coated copper powder in which Sn is coated on the dendritic copper powder is observed by SEM (magnification 1,000 times).

The dendritic Sn-coated copper powder forms a two-dimensional or three-dimensional dendritic shape having a main trunk and branches branched from the main trunk, as shown in the observation images of FIGS.

Here, in the dendritic Sn-coated copper powder 31, the flat copper particles constituting the main trunk 32 and the branch 33 have an average cross-sectional thickness of 0.2 μm to 5.0 μm as described above. The thinner the cross-sectional average thickness of the flat copper particles, the more the flat plate effect is exhibited. That is, the main trunk 32 and the branch 33 are composed of flat copper particles having a cross-sectional average thickness of 5.0 μm or less, thereby increasing the area where the Sn-coated dendritic Sn-coated copper powders 31 are in contact with each other. Since the contact area can be ensured and the contact area becomes large, low resistance, that is, high conductivity can be realized. By this, it is more excellent in electroconductivity, can maintain the electroconductivity favorably, and can use it suitably for the use of an electroconductive coating material or an electroconductive paste. Further, since the dendritic Sn-coated copper powder 31 is composed of fine copper particles coated with a flat Sn plate, it is possible to contribute to thinning of a wiring material or the like.

In addition, even if the cross-sectional average thickness of the copper particles coated with Sn or Si alloy is as thin as 5.0 μm or less, if the size of the flat copper particles is too small, the dendritic Sn-coated copper powder 31 When they come into contact with each other, the number of contacts is reduced. Therefore, as described above, the lower limit value of the average cross-sectional thickness of the copper particles is preferably 0.2 μm or more, which can increase the number of contacts.

The dendritic Sn-coated copper powder 31 has an average particle diameter (D50) of 1.0 μm to 100 μm. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical pulverization such as a jet mill, a sample mill, a cyclone mill, and a bead mill. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

Thus, when the average particle diameter is 1.0 μm to 100 μm, the surface area is increased, and good moldability and sinterability can be ensured. The dendritic Sn-coated copper powder 31 has a three-dimensional effect of being dendritic because the main trunk 32 and the branches 33 are made of flat copper particles in addition to the dendritic shape. Due to the effect of the copper particles constituting the dendritic shape being flat, more contacts between the dendritic Sn-coated copper powders 31 can be secured.

In addition, if the dendritic Sn coat copper powder of the shape as described above is occupied at a predetermined ratio in the obtained Sn coat copper powder when observed with an electron microscope, Sn of other shapes is used. Even if the coated copper powder is mixed, the same effect as that of the copper powder composed only of the dendritic Sn-coated copper powder can be obtained. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the dendritic Sn-coated copper powder having the shape described above is 65% by number or more, preferably 80% of the total Sn-coated copper powder. As long as it occupies a ratio of several percent or more, more preferably 90 percent or more, Sn-coated copper powder of other shapes may be included.

[Sn coating]
As described above, the dendritic Sn-coated copper powder 31 according to the third embodiment is a flat plate having a cross-sectional average thickness of 0.2 μm to 5.0 μm, and the surface is coated with Sn or an Sn alloy. It is constituted in a dendritic shape by copper particles.

The dendritic Sn-coated copper powder 31 is preferably 1% by mass as Sn content with respect to 100% by mass of the entire Sn-coated copper powder coated with Sn on the dendritic copper powder before being coated with Sn or an Sn alloy. The Sn or Sn alloy is coated at a ratio of 50% by mass, and the Sn thickness (coating thickness) is 0.1 μm or less, preferably 0.05 μm or less. From this, the dendritic Sn-coated copper powder 31 has a shape in which the shape of the dendritic copper powder before being coated with Sn or the Sn alloy is maintained as it is. Therefore, the shape of the copper powder before coating Sn or Sn alloy and the shape of the Sn-coated copper powder after coating Sn or Sn alloy on the copper powder are both dendritic shapes.

As described above, the content of Sn coated as Sn or Sn alloy in the dendritic Sn-coated copper powder 31 is 1% by mass to 50% by mass with respect to 100% by mass of the Sn-coated copper powder 31 as a whole. % Is preferable. The Sn content coated as Sn or Sn alloy is preferably as low as possible because Sn has a lower electrical conductivity than copper, but if it is too small, a uniform Sn or Sn alloy film can be secured on the copper surface. Therefore, it causes a decrease in conductivity. Therefore, as content of Sn coat | covered as Sn or Sn alloy, it is preferable that it is 1 mass% or more with respect to 100 mass of the said Sn coat | covered Sn coating copper powder 31 whole, and is 2 mass% or more. It is more preferable that the content is 5% by mass or more.

On the other hand, if the content of Sn coated as Sn or Sn alloy increases, it is not preferable from the viewpoint of cost. Therefore, the coating amount of Sn or Sn alloy is preferably 50% by mass or less, more preferably 20% by mass or less, based on 100% by mass of the entire Sn-coated copper powder 31 coated with Sn. More preferably, it is 10 mass% or less.

In the dendritic Sn-coated copper powder 31 according to the third embodiment, the average thickness of Sn or Sn alloy coated on the surface of the dendritic copper powder is about 0.001 μm to 0.1 μm, and 0.005 μm More preferably, it is about 0.02 μm. If the Sn or Sn alloy coating thickness is less than 0.001 μm on average, a uniform Sn or Sn alloy coating cannot be secured on the surface of the copper powder, and this causes a decrease in conductivity. On the other hand, when the coating thickness of Sn or Sn alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of cost.

Thus, the average thickness of Sn coated on the surface of the dendritic copper powder is about 0.001 μm to 0.1 μm, compared with the cross-sectional average thickness of the flat copper particles constituting the dendritic copper powder. Very small. Therefore, before and after coating the surface of the dendritic copper powder with Sn or an Sn alloy, the cross-sectional average thickness of the tabular copper particles does not substantially change.

As will be further described later, in the dendritic Sn-coated copper powder 31, Sn covered with the dendritic copper powder may be a Sn alloy. The element added as the Sn alloy is preferably at least one selected from silver, bismuth, and zinc.

[About bulk density]
The dendritic Sn-coated copper powder 31 according to the third embodiment is not particularly limited, but the bulk density is preferably in the range of 0.5 g / cm ³ to 5.0 g / cm ³ . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Sn-coated copper powders cannot be ensured. On the other hand, when the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Sn-coated copper powder also increases, the surface area decreases, and the formability and sinterability may deteriorate.

[BET specific surface area]
In the third dendritic Sn coating copper powder 31 according to the embodiment of, but not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ² /g~5.0m ² / g. When the BET specific surface area value is less than 0.2 m ² / g, the copper particles coated with Sn or the Sn alloy may not have the desired shape as described above, and high conductivity cannot be obtained. There is. On the other hand, if the BET specific surface area value exceeds 5.0 m ² / g, the coating of Sn or Sn alloy on the surface of the dendritic Sn-coated copper powder becomes non-uniform and high conductivity may not be obtained. Moreover, the copper particle which comprises Sn coat | court copper powder will become too fine, and the dendritic Sn coat | court copper powder 1 will be in a fine whisker-like state, and electroconductivity may fall. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

<1-4. Fourth Embodiment>
[Configuration of Sn-coated copper powder]
When the Sn-coated copper powder according to the fourth embodiment is observed using a scanning electron microscope (SEM), a plurality of individual copper particles whose surfaces are coated with Sn or an Sn alloy are aggregated and aggregated. It has the form of a collection.

Here, FIG. 15 is a schematic diagram showing a specific shape of the Sn-coated copper powder according to the fourth embodiment. As shown in the schematic diagram of FIG. 15, the Sn coated copper powder 41 is composed of Sn or Sn alloy on the surface of the copper powder having a form in which the separated flat copper particles 42 are aggregated two-dimensionally or three-dimensionally. The copper particles 42 have a flat plate shape. Hereinafter, this Sn-coated copper powder is also referred to as “flat Sn-coated copper particle aggregated powder 41”.

More specifically, the flat Sn-coated copper particle aggregated powder 41 is in the form of an aggregated copper powder in which a plurality of copper particles 42 whose surfaces are coated with Sn or Sn alloy are aggregated to form an aggregate. The copper particles 42 are in the form of a flat plate having an average major axis diameter d (average major axis diameter) of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 μm to 1.0 μm. The tabular Sn-coated copper particle aggregated powder 41, in which a plurality of tabular copper particles 2 are aggregated to form an aggregate, has an average particle diameter (D50) of 1.0 μm to 30 μm. Yes.

The flat Sn-coated copper particle aggregated powder 41 is described later in detail. For example, the anode and the cathode are immersed in a sulfuric acid electrolyte containing copper ions, and the cathode is electrolyzed by flowing a direct current. It can be produced by depositing the agglomerated powder on top and coating the surface of the obtained agglomerated powder with Sn or an Sn alloy by an electroless plating method or the like.

16 to 18 show the flat Sn-coated copper particle aggregated powder 41 when observed by SEM (FIG. 16: 5,000 times magnification, FIG. 17: 10,000 times magnification, FIG. 18: 30,000 times magnification). It is a photograph figure which shows an example of this observation image.

As observed in FIG. 16, the flat Sn-coated copper particle aggregated powder 41 has a form in which flat copper particles are aggregated. Moreover, as observed in FIGS. 17 and 18, the flat copper particles 42 are separated into pieces and have a flat shape having a flat surface or a curved surface.

Here, as shown in the schematic diagram of FIG. 15, the flat copper particles 42 have a flat surface having a smooth periphery, such as a substantially oval shape, an oval shape, or a so-called corn flake shape, which will be described later. The shape has a cross-sectional average thickness within a specific range. Of course, the surface having a substantially elliptic shape or the like may have protrusions and attached particles having a height of about twice or less the average cross-sectional thickness.

As described above, the average major axis diameter d of the copper particles 42 which are flat and whose surface is coated with Sn or Sn alloy is 0.5 μm to 5.0 μm, more preferably 0.7 μm to 4 μm. 0.0 μm. The average cross-sectional thickness of the copper particles 42 is 0.02 μm to 1.0 μm, more preferably 0.05 μm to 0.4 μm. Here, the average major axis diameter d of the flat copper particles 42 indicates the maximum width of a flat surface having a shape such as an ellipse, as shown in FIG. Further, the average major axis diameter d and the cross-sectional average thickness can be obtained by SEM observation.

When the average major axis diameter d of the tabular copper particles 42 is less than 0.5 μm, or the cross-sectional average thickness exceeds 1.0 μm, the aggregated powders formed by aggregation of these particles are aggregated. A large contact area cannot be secured, and the electrical conductivity may decrease. On the other hand, the upper limit value of the average major axis diameter d of the tabular copper particles 42 is not particularly limited. However, in the method of depositing on the cathode by electrolysis described later, the upper limit is about 5.0 μm. Further, the lower limit value of the cross-sectional average thickness of the flat copper particles 42 is not particularly limited, but in the same method of depositing on the cathode by electrolysis, the lower limit is about 0.02 μm.

The size of the tabular Sn-coated copper particle aggregated powder 41 obtained by aggregating the tabular copper particles 42 into an aggregate is 1.0 μm to 30 μm in average particle diameter (D50). The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical pulverization such as a jet mill, a sample mill, a cyclone mill, and a bead mill. In addition, the average particle diameter (D50) of the flat Sn coat copper particle aggregate powder 41 can be measured by a laser diffraction scattering type particle size distribution measurement method.

In this way, the tabular copper particles 42 having an average cross-sectional thickness of 0.02 μm to 1.0 μm are aggregated to form the tabular Sn-coated copper particle aggregated powder 41. It becomes a powder, and it is possible to ensure a large area where the flat Sn-coated copper particle aggregated powders 41 and the copper particles 42 on the flat plate contact each other. And since the contact area becomes large, low resistance, that is, high conductivity can be realized. By this, it is more excellent in electroconductivity and can be used suitably for the use of a conductive paint and a conductive paste.

Here, as pointed out in Patent Document 4, for example, when used as a metal filler such as a resin for a conductive paste, if the metal filler in the resin has a shape developed in a dendritic shape, Copper powders are entangled with each other and agglomeration occurs, which may not be uniformly dispersed in the resin. In addition, the agglomeration increases the viscosity of the paste and causes problems in wiring formation by printing. This is because the shape of the dendritic copper powder grows in a needle shape, and when trying to prevent agglomeration, the shape of the dendritic copper powder is reduced. It becomes impossible to obtain the effect of securing the contact by eliminating.

In addition, in the case where the plate is formed by the mechanical method of Patent Document 1 or Patent Document 2, it is necessary to prevent copper oxidation during mechanical processing. For example, after adding a fatty acid, in the air or inactive It is crushed in an atmosphere and processed into a flat plate shape. However, oxidation cannot be completely prevented, and the fatty acid added at the time of processing needs to be removed after processing to affect dispersibility when it is made into a paste. There is a problem that the fatty acid cannot be completely removed because it may firmly adhere to the copper surface. Moreover, it becomes difficult to make the flat copper powder obtained to make a flat plate by mechanical pressure flat because it becomes flat by mechanical processing, and it becomes warped. . Since copper powder with a smooth and warped surface is difficult to secure contact points, when using it as a metal filler, not only flat copper powder but also granular copper powder can be mixed with other metal fillers. It is necessary to secure the contact points.

On the other hand, in the flat Sn coat copper particle aggregated powder 41, since the flat copper particles 42 are aggregated, the respective flat copper particles 42 are aggregated in a three-dimensional shape. It has a structure that simultaneously satisfies a two-dimensional contact effect and a three-dimensional contact effect. Further, the flat Sn-coated copper particle aggregated powder 41 has an average particle size (D50) of 1.0 μm to 30 μm, thereby increasing the surface area and ensuring good moldability and sinterability. be able to.

This demonstrates the same effect that the contact rate between metal fillers is improved by using silver powder having a shape described in, for example, Japanese Patent No. 4059486, and a flat Sn-coated copper particle aggregated copper powder. Since 41 is a three-dimensional uneven structure, the contact rate between metal fillers is improved, the filler weight contained in the paste can be reduced, and the cost can be greatly reduced.

In addition, if the Sn coated copper powder having the shape as described above is occupied at a predetermined ratio in the obtained Sn coated copper powder when observed with an electron microscope, the Sn coated copper of other shapes is used. Even if powder is mixed, the same effect as the copper powder which consists only of the Sn coat copper powder can be acquired. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the Sn-coated copper powder having the above-mentioned shape is 65% by number or more, preferably 80% by number of the total Sn-coated copper powder. As described above, Sn-coated copper powder having other shapes may be included as long as it occupies a ratio of 90% by number or more.

[Sn coating]
As described above, the flat Sn-coated copper particle aggregated powder 41 according to the fourth embodiment has an average major axis diameter of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 to 1.0 μm. A plurality of copper particles 42 having a flat plate shape and coated with Sn or an Sn alloy are aggregated to form an aggregate.

The flat Sn-coated copper particle aggregated powder 41 is Sn content with respect to 100% of the total mass of the Sn-coated copper powder 41 coated with Sn on the tabular copper particle aggregated powder before being coated with Sn or an Sn alloy. As an example, the Sn or Sn alloy is coated at a ratio of 1% by mass to 50% by mass, and the Sn thickness (coating thickness) is 0.1 μm or less, preferably 0.05 μm or less. It is covered. Accordingly, the flat Sn-coated copper particle aggregated powder 41 has a shape that retains the shape of the flat copper particle aggregated powder before being coated with Sn or the Sn alloy. Therefore, both the shape of the tabular copper particle aggregated powder before coating with Sn or Sn alloy and the shape of the tabular Sn coated copper particle aggregated powder 41 after coating with Sn or Sn alloy are both two-dimensional or It is the shape which the flat plate which is a three-dimensional form aggregated.

As described above, the content of Sn coated as Sn or Sn alloy in the flat Sn-coated copper particle aggregated powder 41 is 1% by mass to 100% by mass of the Sn-coated copper powder 41 coated with Sn. A range of 50% by mass is preferred. The Sn content coated as Sn or Sn alloy is preferably as low as possible because Sn has a lower electrical conductivity than copper, but if it is too small, a uniform Sn or Sn alloy film can be secured on the copper surface. Therefore, it causes a decrease in conductivity. Therefore, as content of Sn coat | covered as Sn or a Sn alloy, it is preferable that it is 1 mass% or more with respect to 100 mass of the said Sn coat | covered Sn coat | covered copper powder 41 whole, and is 2 mass% or more. It is more preferable that the content is 5% by mass or more.

On the other hand, when the content of Sn coated as Sn or Sn alloy increases, it is not preferable from the viewpoint of cost, and the content of Sn coated as Sn or Sn alloy is the mass of the entire Sn-coated copper powder 41. It is preferably 50% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less with respect to 100%.

In the flat Sn-coated copper particle agglomerated powder 41 according to the fourth embodiment, the average thickness of Sn or Sn alloy coated on the surface of the flat copper particles is about 0.001 μm to 0.1 μm. The thickness is preferably about 0.005 μm to 0.02 μm. If the Sn or Sn alloy coating thickness is less than 0.001 μm on average, a uniform Sn or Sn alloy coating cannot be secured on the surface of the copper powder, and this causes a decrease in conductivity. On the other hand, when the coating thickness of Sn or Sn alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of cost.

Thus, the average thickness of the Sn or Sn alloy coated on the surface of the flat Sn-coated copper particle aggregated powder 41 is about 0.001 μm to 0.1 μm, and the flat copper before coating the Sn or Sn alloy It is smaller than the cross-sectional average thickness (0.02 μm to 1.0 μm) of the flat copper particles 42 constituting the particle agglomerated powder. Therefore, the form of the tabular copper particles is not substantially changed before and after the surface of the tabular copper particle aggregated powder is coated with Sn or an Sn alloy.

Further, as will be described later, in the tabular Sn-coated copper particle aggregated powder 41, Sn covered with the tabular copper particles 42 may be a Sn alloy. The element added as the Sn alloy is preferably at least one selected from silver, bismuth, and zinc.

[About bulk density]
The flat Sn-coated copper particle aggregated powder 41 according to the fourth embodiment is not particularly limited, but its bulk density (tap density) is in the range of 0.5 g / cm ³ to 5.0 g / cm ^3. It is preferable. When the tap density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the Sn-coated copper powders cannot be secured. On the other hand, when the tap density exceeds 5.0 g / cm ³ , the average particle diameter of the Sn-coated copper powder increases, the surface area decreases, and the formability and sinterability may deteriorate.

[BET specific surface area]
In tabular Sn coating copper particles agglomerated powder 41 according to the fourth embodiment is not particularly limited, examples of the BET specific surface area is ^preferably in the range of 0.2m ² /g~5.0m 2 / g . If the BET specific surface area exceeds 5.0 m ² / g, there is a possibility that sufficient contact between the Sn-coated copper powders cannot be ensured. On the other hand, when the BET specific surface area is less than 0.5 m ² / g, the average particle diameter of the Sn-coated copper powder also increases, the surface area decreases, and the formability and sinterability may deteriorate. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

<1-5. Fifth Embodiment>
[Configuration of Sn-coated copper powder]
When the Sn-coated copper powder according to the fifth embodiment is observed using a scanning electron microscope (SEM), the Sn-coated copper powder has a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. The main trunk and the branch are dendritic having a main trunk grown in a dendritic shape and a plurality of branches separated from the main trunk, and copper particles coated with Sn or Sn alloy on the surface are assembled. It is configured. Hereinafter, this Sn-coated copper powder is also referred to as “dendritic Sn-coated copper powder”.

FIG. 19 is a schematic view showing a specific shape of the copper particles whose surface is coated with Sn or an Sn alloy, which constitutes the Sn-coated copper powder according to the fifth embodiment. As shown in the schematic diagram of FIG. 19, the copper particles 51 coated with Sn or an Sn alloy have a dendritic shape that is a two-dimensional or three-dimensional form.

More specifically, the copper particles 51 coated with Sn or Sn alloy have a shape having a main trunk 52 grown in a dendritic shape and a plurality of branches 53 separated from the main trunk 52, and the copper particles 51 are The plate has a flat cross-sectional average thickness of 0.02 μm to 0.5 μm. The branch 53 in the copper particle 51 means both a branch 53a branched from the main trunk 52 and a branch 53b further branched from the branch 53a.

The Sn-coated copper powder according to the fifth embodiment is a dendritic copper powder (dendritic copper powder) having a main trunk and a plurality of branches, which is configured by aggregating such flat copper particles 51. A Sn-coated copper powder having Sn or Sn alloy coated on its surface (see SEM images of the Sn-coated copper powder in FIGS. 21 and 22), and a dendritic Sn-coated copper composed of the tabular copper particles 51 The average particle size (D50) of the powder is 1.0 μm to 30 μm.

Although the dendritic Sn-coated copper powder according to the fifth embodiment will be described in detail later, for example, by immersing the anode and the cathode in a sulfuric acid electrolytic solution containing copper ions and flowing a direct current to perform electrolysis It can be produced by depositing dendritic copper powder on the cathode and coating the surface of the obtained dendritic copper powder with Sn or an Sn alloy by an electroless plating method or the like.

FIG. 20 is a photographic diagram showing an example of an observation image when the dendritic copper powder before being coated with Sn or Sn alloy is observed by SEM (magnification of 5,000 times). FIG. 21 is a photographic diagram showing an example of an observation image when the dendritic Sn-coated copper powder obtained by coating the dendritic copper powder of FIG. 20 with Sn or an Sn alloy is observed by SEM (5,000 times magnification). is there. Moreover, FIG. 22 shows an example of an observation image when another portion of the dendritic Sn-coated copper powder in which the dendritic copper powder is similarly coated with Sn or an Sn alloy is observed by SEM (magnification 1,000 times). FIG.

20 to 22, the Sn-coated copper powder exhibits a two-dimensional or three-dimensional dendritic precipitation state having a main trunk and branches branched from the main trunk. In addition, the main trunk and the branch are flat and have a dendritic shape and are composed of copper particles covered with Sn or an Sn alloy, and the copper particles 51 are fine on the surface. It has a convex part.

Here, the flat copper particles 51 constituting the dendritic Sn-coated copper powder and coated with Sn or the Sn alloy having the main trunk 52 and the branches 53 have a cross-sectional average thickness of 0.02 μm to 0.5 μm. is there. The thinner the cross-sectional average thickness of the flat copper particles 51 coated with Sn or Sn alloy, the more effective the flat plate will be. That is, the main trunk and branches of the dendritic copper powder are constituted by the flat copper particles 51 having an average cross-sectional thickness of 0.5 μm or less, so that the copper particles 51 and the dendritic Sn-coated copper constituted thereby are formed. A large area where the powders come into contact with each other can be secured. And since the contact area becomes large, low resistance, that is, high conductivity can be realized. Thereby, it is more excellent in electroconductivity, can maintain the electroconductivity favorably, and can be used suitably for the use of an electroconductive coating material or an electroconductive paste. Further, since the dendritic Sn-coated copper powder is composed of the flat copper particles 51, it can contribute to thinning of the wiring material and the like.

In addition, the thinner the cross-sectional average thickness of the tabular copper particles 51 coated with Sn or Sn alloy, the smaller the number of contacts when the dendritic Sn-coated copper powders are in contact with each other. If the cross-sectional average thickness of the copper particles 51 is 0.02 μm or more, a sufficient number of contacts can be ensured, and more preferably 0.2 μm or more, thereby effectively increasing the number of contacts. .

Moreover, in the dendritic Sn-coated copper powder according to the fifth embodiment, the average particle diameter (D50) is 1.0 μm to 30 μm. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical pulverization such as a jet mill, a sample mill, a cyclone mill, and a bead mill. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

Thus, when the average particle size is 1.0 μm to 30 μm, the surface area is increased, and good moldability and sinterability can be ensured. And in this dendritic Sn coat copper powder, in addition to having a dendritic shape, the dendritic shape having a main trunk 52 and a branch 53 and a copper particle 51 having a flat plate shape are assembled and configured. More contact points between the copper powders can be secured by the three-dimensional effect of being dendritic and the effect that the copper particles 1 constituting the dendritic shape are flat.

Further, in the dendritic Sn-coated copper powder according to the fifth embodiment, the flat copper particles 51 have fine convex portions on the surface. The average height of the convex portions on the surface is preferably 0.01 μm to 0.4 μm.

Here, as described in Patent Document 1 and Patent Document 2, for example, when spherical copper powder is formed into a flat plate shape by a mechanical method, it is necessary to prevent copper oxidation during mechanical processing. It is processed into a flat plate shape by adding a fatty acid and pulverizing it in air or in an inert atmosphere. However, it cannot be completely prevented from oxidation, and the fatty acid added during processing may affect dispersibility when it is made into a paste, so it is necessary to remove it after the end of processing, The fatty acid may firmly adhere to the copper surface due to the pressure during machining, which causes a problem that it cannot be completely removed. Further, since the surface is flattened by mechanical processing, the surface becomes smooth, and the flat copper powder formed for flattening by mechanical pressure is not a horizontal surface but a warped shape. Therefore, when using as a metal filler such as conductive paste and resin for electromagnetic wave shielding, when trying to secure the contact between the metal fillers, the mechanically flattened copper powder has a smooth and warped surface. Therefore, it becomes difficult to secure the contacts, and when used, the contacts between the metal fillers must be secured by a method of mixing not only the flat copper powder but also the granular copper powder.

On the other hand, the flat copper particles 51 constituting the dendritic Sn-coated copper powder according to the fifth embodiment have fine convex portions on the surface, and the average height of the convex portions is preferably 0.01 μm to 0.4 μm. The dendritic Sn-coated copper powder in which the copper particles 51 are aggregated has a feature that a contact between metal fillers can be easily ensured as compared with a flat copper powder obtained by mechanical processing. ing. That is, since the dendritic Sn-coated copper powder according to the present embodiment has fine convex portions on the surface of the flat copper particles 51 constituting the dendritic Sn-coated copper powder, a metal filler such as a conductive paste or a resin for electromagnetic wave shielding When using as, a contact can be easily ensured by the convex part of the surface of the tabular copper particle 51. Further, this dendritic Sn-coated copper powder is produced by depositing tabular copper particles by direct electrolysis and growing them into the shape of dendritic copper powder without performing mechanical processing. Occurrence of oxidation and removal of fatty acids are not necessary, and the electrical conductivity characteristics can be made extremely good.

As described above, the average height of the fine protrusions on the surface of the flat copper particles 51 is preferably 0.01 μm to 0.4 μm. When the average height is less than 0.01 μm, a sufficient effect cannot be obtained as a shape for securing the contacts. On the other hand, when the average height exceeds 0.4 μm, it is used for a conductive paste or the like. In some cases, the filling rate of the metal filler in the paste does not increase, and a satisfactory resistance value may not be obtained.

In addition, if the dendritic Sn coat copper powder of the shape as described above is occupied at a predetermined ratio in the obtained Sn coat copper powder when observed with an electron microscope, Sn of other shapes is used. Even if the coated copper powder is mixed, the same effect as that of the copper powder composed only of the dendritic Sn-coated copper powder can be obtained. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the dendritic Sn-coated copper powder having the shape described above is 65% by number or more, preferably 80% of the total Sn-coated copper powder. As long as it occupies a ratio of several percent or more, more preferably 90 percent or more, Sn-coated copper powder of other shapes may be included.

[Sn coating]
As described above, the dendritic Sn-coated copper powder according to the fifth embodiment is a dendritic shape having a main trunk 52 and a branch 53, and has a plate-like shape with an average cross-sectional thickness of 0.02 μm to 0.5 μm. The copper particles 51 are formed in a dendritic shape, and the surface of the copper particles 51 is coated with Sn or an Sn alloy.

This dendritic Sn-coated copper powder is preferably 1% by mass as Sn content with respect to 100% by mass of the entire Sn-coated copper powder coated with Sn on the dendritic copper powder before being coated with Sn or Sn alloy. Sn or Sn alloy is coated at a ratio of ˜50% by mass, and the Sn thickness (coating thickness) is 0.1 μm or less, preferably 0.02 μm or less. . From this, the dendritic Sn-coated copper powder has a shape that retains the shape of the dendritic copper powder before being coated with Sn or the Sn alloy. Therefore, the shape of the dendritic copper powder before coating Sn or Sn alloy and the shape of the dendritic Sn coated copper powder after coating Sn or Sn alloy on the copper powder are both two-dimensional or three-dimensional. It is a dendritic shape that is a form of

The content of Sn coated as Sn or Sn alloy in this dendritic Sn-coated copper powder is, as described above, 1% by mass to 50% by mass with respect to 100% by mass of the entire Sn-coated Sn coated copper powder. It is preferable that it is the range of these. The Sn content coated as Sn or Sn alloy is preferably as low as possible because Sn has a lower electrical conductivity than copper, but if it is too small, a uniform Sn or Sn alloy film can be secured on the copper surface. Therefore, it causes a decrease in conductivity. Therefore, as content of Sn coat | covered as Sn or Sn alloy, it is preferable that it is 1 mass% or more with respect to 100 mass of the whole Sn coat | covered Sn coat copper powder, and it is 2 mass% or more. Is more preferable, and it is further more preferable that it is 5 mass% or more.

On the other hand, when the content of Sn coated as Sn or Sn alloy increases, it is not preferable from the viewpoint of cost, and as the content of Sn coated as Sn or Sn alloy, the entire Sn-coated copper powder coated with Sn It is preferably 50% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less with respect to 100% by mass.

In the dendritic Sn-coated copper powder according to the fifth embodiment, the average thickness of Sn or Sn alloy coated on the surface of the copper particles is about 0.001 μm to 0.1 μm, and 0.005 μm to 0.005. It is preferably about 02 μm. If the Sn or Sn alloy coating thickness is less than 0.001 μm on average, a uniform Sn or Sn alloy coating cannot be secured on the surface of the copper powder, and this causes a decrease in conductivity. On the other hand, if the coating thickness of Sn or Sn alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of cost.

Thus, the average thickness of Sn or Sn alloy coated on the surface of the dendritic Sn-coated copper powder is about 0.001 μm to 0.1 μm, and constitutes the dendritic copper powder before coating with Sn or Sn alloy. This is smaller than the average cross-sectional thickness (0.02 μm to 0.5 μm) of the dendritic copper particles 51. Therefore, the form of the dendritic copper powder does not substantially change before and after the surface of the dendritic copper powder is coated with Sn or an Sn alloy.

As will be described later, in the dendritic Sn-coated copper powder, Sn coated with the dendritic copper powder may be a Sn alloy. The element added as the Sn alloy is preferably at least one selected from silver, bismuth, and zinc.

[About bulk density]
The dendritic Sn-coated copper powder according to the fifth embodiment is not particularly limited, but the bulk density is preferably in the range of 0.5 g / cm ³ to 5.0 g / cm ³ . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Sn-coated copper powders cannot be ensured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Sn-coated copper powder also increases, and the surface area may decrease and formability and sinterability may deteriorate. .

[BET specific surface area]
The dendritic Sn coating copper powder according to the fifth embodiment is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ² /g~5.0m ² / g. When the BET specific surface area value is less than 0.2 m ² / g, the copper particles coated with Sn or the Sn alloy may not have the desired shape as described above, and high conductivity cannot be obtained. There is. On the other hand, if the BET specific surface area value exceeds 5.0 m ² / g, the coating of Sn or Sn alloy on the surface of the dendritic Sn-coated copper powder becomes non-uniform and high conductivity may not be obtained. Further, the copper particles constituting the dendritic Sn-coated copper powder become too fine, and the dendritic Sn-coated copper powder becomes a fine whisker-like state, which may lower the conductivity. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

≪2. Method for producing Sn-coated copper powder >>
Next, the manufacturing method of Sn coat copper powder concerning the present invention is explained. Below, first, the manufacturing method of the copper powder before Sn coating | cover which comprises Sn coat copper powder is demonstrated, Then, Sn or Sn alloy is coat | covered with respect to the copper powder, and the method of obtaining Sn coat copper powder Will be described.

In addition, the manufacturing method of Sn coat | court copper powder which concerns on the 1st-5th embodiment mentioned above is demonstrated in order, and description is abbreviate | omitted suitably about the item which is common in each embodiment.

<2-1. Manufacturing Method of Sn Coated Copper Powder According to First Embodiment>
The Sn-coated copper powder according to the first embodiment has a dendritic shape in which copper particles whose surfaces are coated with Sn or an Sn alloy are aggregated and have a main trunk that grows linearly and a plurality of branches separated from the main trunk. It is Sn coat copper powder which constituted the shape. The copper particles coated with Sn or Sn alloy on the surface have a flat plate shape having an average cross-sectional thickness of 0.02 μm to 5.0 μm determined by SEM observation, and the copper particles are assembled to form a copper particle. The Sn-coated copper powder has an average particle diameter (D50) of 1.0 μm to 100 μm, and the maximum height in the direction perpendicular to the flat surface of the copper particles is in the horizontal direction of the flat surface. It is 1/10 or less with respect to the maximum length.

<2-1-1. Manufacturing method of copper powder>
As described above, the Sn-coated copper powder (dendritic Sn-coated copper powder) according to the first embodiment is formed by coating the surface of the dendritic copper powder with Sn or an Sn alloy. For example, it can be manufactured by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In electrolysis, for example, a sulfuric acid electrolytic solution containing copper ions is accommodated in an electrolytic cell in which metallic copper is used as an anode (anode) and a stainless steel plate or titanium plate is used as a cathode (cathode). Electrolysis is performed by passing a direct current through the liquid at a predetermined current density. Thereby, a fine dendritic copper powder can be deposited (electrodeposited) on the cathode with energization. In particular, in the first embodiment, a specific additive and a nonionic surfactant are added to the sulfuric acid electrolytic solution containing a water-soluble copper salt serving as a copper ion source to perform electrolysis. A flat dendritic copper powder composed of flat copper particles can be deposited. Further, it is preferable that the electrolytic solution further contains chloride ions.

(1) Copper ions The water-soluble copper salt is a copper ion source that supplies copper ions, and examples thereof include copper sulfate such as copper sulfate pentahydrate and copper nitrate, but are not particularly limited. Alternatively, copper oxide may be dissolved in a sulfuric acid solution to make a sulfuric acid acidic solution. The copper ion concentration in the electrolytic solution can be about 1 g / L to 20 g / L, preferably about 5 g / L to 10 g / L.

(2) Sulfuric acid Sulfuric acid is for making a sulfuric acid electrolyte. The concentration of sulfuric acid in the electrolytic solution can be about 20 g / L to 300 g / L, preferably about 50 g / L to 150 g / L, as the free sulfuric acid concentration. Since the sulfuric acid concentration affects the conductivity of the electrolyte, it affects the uniformity of the copper powder obtained on the cathode.

(3) Additive As the additive, one kind of compound selected from the group consisting of a compound having a phenazine structure, a compound having an azobenzene structure, and a compound having a phenazine structure and an azobenzene structure, or this group Two or more compounds selected from the group consisting of different molecular structures are used in combination. By adding such an additive to the electrolytic solution together with a nonionic surfactant described later and performing electrolysis, copper powder that suppresses growth in a direction perpendicular to the flat surface, that is, copper having a smooth surface Powder can be produced.

The concentration in the electrolyte of one or more additives selected from the group consisting of a compound having a phenazine structure, a compound having an azobenzene structure, and a compound having a phenazine structure and an azobenzene structure may be added. It is preferable that the total amount is about 1 mg / L to 1000 mg / L.

(Compound having phenazine structure)
A compound having a phenazine structure can be represented by the following formula (1). In the first embodiment, one or more compounds having a phenazine structure represented by the following formula (1) can be contained as an additive.

Here, in Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, It is a group selected from the group consisting of CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl. R ₅ is hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

Specifically, examples of the compound having a phenazine structure include 5-methylphenazine-5-ium, eruginosine B, aeruginosine A, 5-ethylphenazine-5-ium, 3,7-diamino-5-phenylphenazine-5. -Ium, 5-ethylphenazine-5-ium, 5-methylphenazine-5-ium, 3-amino-5-phenyl-7- (diethylamino) phenazine-5-ium, 2,8-dimethyl-3,7- Diamino-5-phenylphenazine-5-ium, 1-methoxy-5-methylphenazine-5-ium, 3-amino-7- (dimethylamino) -1,2-dimethyl-5- (3-sulfonatophenyl) Phenazine-5-ium, 1,3-diamino-5-methylphenazine-5-ium, 1,3-diamino-5-phenylphenol Nadin-5-ium, 3-amino-7- (diethylamino) -2-methyl-5-phenylphenazine-5-ium, 3,7-bis (diethylamino) -5-phenylphenazine-5-ium, 2,8 -Dimethyl-3,7-diamino-5- (4-methylphenyl) phenazine-5-ium, 3- (methylamino) -5-methylphenazine-5-ium, 3-hydroxy-7- (diethylamino) -5 -Phenylphenazine-5-ium, 5-azoniaphenazine, 1-hydroxy-5-methylphenazine-5-ium, 4H, 6H-5-phenyl-3,7-dioxophenazine-5-ium, anilinoap Safranin, phenosafranine, neutral red and the like can be mentioned.

(Compound having azobenzene structure)
The compound having an azobenzene structure can be represented by the following formula (2). In 1st Embodiment, the 1 type (s) or 2 or more types of the compound which has an azobenzene structure represented by following formula (2) can be contained as an additive.

Here, in formula (2), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ are each independently hydrogen, halogen, amino A group selected from the group consisting of OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. is there.

Specifically, examples of the compound having an azobenzene structure include azobenzene, 4-aminoazobenzene-4'-sulfonic acid, 4- (dimethylamino) -4 '-(trifluoromethyl) azobenzene, C.I. I. Acid Red 13, Mercury Orange, 2 ', 4'-Diamino-5'-methylazobenzene-4-sulfonic acid sodium, methyl red, methyl yellow, methyl orange, azobenzene-2,4-diamine, alizarin yellow GG, 4- Dimethylaminoazobenzene, orange I, salazosulfapyridine, 4- (diethylamino) azobenzene, orange OT, 3-methoxy-4-aminoazobenzene, 4-aminoazobenzene, N, N, 2-trimethylazobenzene-4-amine, 4 -Hydroxyazobenzene, Sudan I, 4-amino-3,5-dimethylazobenzene, N, N-dimethyl-4-[(quinolin-6-yl) azo] benzenamine, o-aminoazotoluene, alizarin yellow R, 4 '-(Aminosulfonyl) 4-hydroxy-azobenzene-3-carboxylic acid, Congo red, vital red, Metanil Yellow, Orange II, Disperse Orange 3, C. I. Direct orange 39, 2,2'-dihydroxyazobenzene, azobenzene-4,4'-diol, naphthyl red, 5-phenylazobenzene-2-ol, 2,2'-dimethylazobenzene, C.I. I. Examples include Mordant Yellow 12, Mordant Yellow 10, Acid Yellow, Disperse Blue, New Yellow RMF, Vistramine Brown G, and the like.

(Compound having phenazine structure and azobenzene structure)
A compound having a phenazine structure and an azobenzene structure can be represented by the following formula (3). In the first embodiment, one or more compounds having a phenazine structure and an azobenzene structure represented by the following formula (3) can be contained as an additive.

Here, in Formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each separately , Hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl Is a group selected from R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

Specifically, as a compound having a phenazine structure and an azobenzene structure, for example, 3- (diethylamino) -7-[(4-hydroxyphenyl) azo] -2,8-dimethyl-5-phenylphenazine-5-ium , 3-[[4- (dimethylamino) phenyl] azo] -7- (diethylamino) -5-phenylphenazine-5-ium, Janus Green B, 3-amino-7-[(2,4-diaminophenyl) Azo] -2,8-dimethyl-5-phenylphenazine-5-ium, 2,8-dimethyl-3-amino-5-phenyl-7- (2-hydroxy-1-naphthylazo) phenazine-5-ium, 3 -[[4- (dimethylamino) phenyl] azo] -7- (dimethylamino) -5-phenylphenazine-5-ium, 3-amino-7-[[ -(Dimethylamino) phenyl] azo] -5-phenylphenazine-5-ium, 2- (diethylamino) -7- [4- (methylpropargylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene 2- (diethylamino) -7- [4- (methyl-4-pentynylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene, 2- (diethylamino) -7- [4- (methyl-2 , 3-dihydroxypropylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene.

(4) Surfactant A nonionic surfactant is contained as the surfactant. By adding a nonionic surfactant to the electrolyte together with the above-mentioned additives, it is possible to produce copper powder that suppresses growth in a direction perpendicular to the flat surface, that is, copper powder having a smooth surface. it can.

As the nonionic surfactant, one kind can be used alone, or two or more kinds can be used in combination, and the total concentration in the electrolytic solution can be about 1 mg / L to 10,000 mg / L.

The number average molecular weight of the nonionic surfactant is not particularly limited, but is preferably from 100 to 200,000, more preferably from 200 to 15,000, and preferably from 1,000 to 10,000. Further preferred. When the surfactant has a number average molecular weight of less than 100, fine electrolytic copper powder that does not exhibit a dendritic shape may be deposited. On the other hand, when the surfactant has a number average molecular weight exceeding 200,000, electrolytic copper powder having a large average particle size is precipitated, and only dendritic copper powder having a specific surface area of less than 0.2 m ² / g is obtained. There is no possibility. The number average molecular weight is a molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

The type of nonionic surfactant is not particularly limited, but is preferably a surfactant having an ether group, for example, polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant. , Polyoxyethylene glycol / glycerin ether, polyoxyethylene glycol / dialkyl ether, polyoxyethylene polyoxypropylene glycol / alkyl ether, aromatic alcohol alkoxylate, polymer compound represented by the following formula (x), and the like. These nonionic surfactants can be used alone or in combination of two or more.

More specifically, as the polyethylene glycol, for example, one represented by the following formula (i) can be used.

（なお、式（ｉ）中、ｎ１は１～１２０の整数を示す。）

(In the formula (i), n1 represents an integer of 1 to 120.)

Further, as the polypropylene glycol, for example, one represented by the following formula (ii) can be used.

（なお、式（ｉｉ）中、ｎ１は１～９０の整数を示す。）

(In the formula (ii), n1 represents an integer of 1 to 90.)

Moreover, as polyethyleneimine, what is represented, for example by a following formula (iii) can be used.

（なお、式（ｉｉｉ）中、ｎ１は１～１２０の整数を示す。）

(In the formula (iii), n1 represents an integer of 1 to 120.)

Further, as the pluronic surfactant, for example, one represented by the following formula (iv) can be used.

（なお、式（ｉｖ）中、ｎ２及びｌ２は１～３０の整数を示し、ｍ２は１０～１００の整数を示す。）

(In the formula (iv), n2 and l2 represent an integer of 1 to 30, and m2 represents an integer of 10 to 100.)

Further, as the tetronic surfactant, for example, one represented by the following formula (v) can be used.

（なお、式（ｖ）中、ｎ３は１～２００の整数を示し、ｍ３は１～４０の整数を示す。）

(In formula (v), n3 represents an integer of 1 to 200, and m3 represents an integer of 1 to 40.)

Moreover, as polyoxyethylene glycol glyceryl ether, for example, those represented by the following formula (vi) can be used.

（なお、式（ｖｉ）中、ｎ４、ｍ４、及びｌ４はそれぞれ１～２００の整数を示す。）

(In the formula (vi), n4, m4, and l4 each represent an integer of 1 to 200.)

Moreover, as polyoxyethylene glycol dialkyl ether, for example, those represented by the following formula (vii) can be used.

（なお、式（ｖｉｉ）中、Ｒ_１及びＲ_２は水素原子又は炭素数１～５の低級アルキル基を示し、ｎ５は２～２００の整数を示す。）

(In the formula (vii), R ₁ and R ₂ represent a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, and n5 represents an integer of 2 to 200.)

As the polyoxyethylene polyoxypropylene glycol / alkyl ether, for example, those represented by the following formula (viii) can be used.

（なお、式（ｖｉｉｉ）中、Ｒ_３は水素原子又は炭素数１～５の低級アルキル基を示し、ｍ６又はｎ６は２～１００の整数を示す。）

(In the formula (viii), R ₃ represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, and m6 or n6 represents an integer of 2 to 100.)

Moreover, as an aromatic alcohol alkoxylate, what is represented, for example by a following formula (ix) can be used.

（なお、式（ｉｘ）中、ｍ７は１～５の整数を示し、ｎ７は１～１２０の整数を示す。）

(In the formula (ix), m7 represents an integer of 1 to 5, and n7 represents an integer of 1 to 120.)

Further, as the nonionic surfactant, a polymer compound represented by the following formula (x) can be used.

（なお、式（ｘ）中、Ｒ_１は、炭素数５～３０の高級アルコールの残基、炭素数１～３０のアルキル基を有するアルキルフェノールの残基、炭素数１～３０のアルキル基を有するアルキルナフトールの残基、炭素数３～２５の脂肪酸アミドの残基、炭素数２～５のアルキルアミンの残基、又は水酸基を示す。また、Ｒ_２及びＲ_３は、水素原子又はメチル基を示す。また、ｍ及びｎは、１～１００の整数を示す。）

(In the formula (x), R ₁ has a higher alcohol residue having 5 to 30 carbon atoms, an alkylphenol residue having an alkyl group having 1 to 30 carbon atoms, or an alkyl group having 1 to 30 carbon atoms. A residue of alkyl naphthol, a residue of fatty acid amide having 3 to 25 carbon atoms, a residue of alkyl amine having 2 to 5 carbon atoms, or a hydroxyl group, and R ₂ and R ₃ are each a hydrogen atom or a methyl group. M and n are integers of 1 to 100.)

(5) Chloride ions Furthermore, the electrolyte solution can contain chloride ions. Chloride ions contribute to the shape control of the precipitated copper powder together with the above-described additives and nonionic surfactants. Thus, by containing chloride ions in the electrolytic solution, it is possible to more effectively produce a copper powder having a smooth surface that suppresses growth in a direction perpendicular to the flat surface. .

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. The chloride ion concentration in the electrolytic solution is not particularly limited, but can be about 1 mg / L to 500 mg / L.

In the first embodiment, for example, electrolysis is performed using the electrolytic solution having the composition as described above, whereby copper powder is deposited on the cathode to produce dendritic copper powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 30 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-1-2. Sn coating method (production of Sn-coated copper powder)>
The Sn-coated copper powder according to the first embodiment is formed on the surface of the dendritic copper powder prepared by the above-described electrolytic method using, for example, an Sn plating solution (electroless Sn plating solution) by an electroless plating method. It can manufacture by coat | covering Sn alloy.

In order to coat Sn or Sn alloy with a uniform thickness on the surface of the dendritic copper powder, it is preferable to wash before Sn plating, and the dendritic copper powder is dispersed in the cleaning solution and washed with stirring. It can be carried out. This washing treatment is preferably carried out in an acidic solution, and after washing, filtration, separation and washing of the dendritic copper powder are repeated as appropriate to obtain a water slurry in which the dendritic copper powder is dispersed in water. In addition, what is necessary is just to use a well-known method about filtration, isolation | separation, and water washing.

Specifically, when Sn coating is performed by the electroless plating method, the electroless Sn plating solution is added to the copper slurry obtained after washing the dendritic copper powder, or the copper slurry is added to the electroless Sn plating solution. By uniformly stirring, the surface of the dendritic copper powder can be coated more uniformly with Sn or Sn alloy.

The method for coating Sn or Sn alloy by electroless plating is not particularly limited. As electroless Sn plating, substitution type Sn plating in which Sn ions in the plating solution are reduced and precipitated with elution of the copper powder as a base, and Sn ions in the plating solution are reduced with a reducing agent to perform Sn coating. Examples include reduction-type Sn plating and disproportionation-type Sn plating in which Sn coating is performed using the fact that Sn ions are disproportionated to form metal Sn, and any method may be used.

Specifically, as the substitutional Sn plating solution, a tin compound and a complexing agent for keeping the tin compound stable in an aqueous solution are essential components, and a surfactant, a pH adjuster, etc. are added as necessary. Can be used. Further, as the reduced Sn plating solution, a composition obtained by adding a reducing agent to the above-described substitutional Sn plating solution can be used.

In the disproportionation reaction type Sn plating, Sn ions are present as HSnO ₂ ⁻ ions in an alkaline aqueous solution, and the HSnO ₂ ⁻ ions become metal Sn by a disproportionation reaction represented by the following formula. In the disproportionation reaction type Sn plating, Sn plating is performed with metal Sn generated by the reaction, and a plating solution having the same composition as the substitutional Sn plating solution in the strong alkali bath can be used.
2HSnO ²⁻ + 2H ₂ O⇔Sn (OH) ₆ ²⁻ + Sn

The tin compound includes a divalent tin compound and a tetravalent tin compound, and the divalent tin compound and the tetravalent tin compound may be used alone or in combination, respectively.

Specifically, as the tin compound, for example, stannous borofluoride, stannous sulfosuccinate, stannous chloride, stannic chloride, stannous sulfate, stannic sulfate, stannous oxide, stannous oxide Distinous, stannous methanesulfonate, stannous ethanesulfonate, stannous 2-hydroxypropane-1-sulfonate, stannous p-phenolsulfonate, tin borofluoride, tin silicofluoride, tin sulfamate Tin oxalate, tin tartrate, tin gluconate, tin sulfosuccinate, tin pyrophosphate, tin 1-hydroxyethane-1,1-bisphosphonate, tin tripolyphosphate and the like.

As the complexing agent, thiourea derivatives, carboxylic acid or amine compounds, titanium chloride, and the like can be used.

Specific examples of the thiourea derivative include thiourea, 1,3-dimethylthiourea, trimethylthiourea, diethylthiourea (eg, 1,3-diethyl-2-thiourea), N, N′-diisopropylthiourea, Examples include allyl thiourea, acetyl thiourea, ethylene thiourea, 1,3-diphenyl thiourea, thiourea dioxide, and thiosemicarbazide. In addition, as carboxylic acid or amine compound, citric acid, tartaric acid, malic acid, gluconic acid, golcoheptonic acid, glycolic acid, lactic acid, trioxybutyric acid, ascorbic acid, isocitric acid, tartronic acid, glyceric acid, hydroxybutyric acid, leucine acid , Citramalic acid, succinic acid, mercaptosuccinic acid, sulfosuccinic acid, glutaric acid, malonic acid, adipic acid, oxalic acid, maleic acid, citraconic acid, itaconic acid, mesaconic acid, glycolic acid, sodium citrate, glycine, hydroxyethylethylenediamine Triacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid disodium salt, ethylenediaminetetrapropionic acid, nitrilotriacetic acid, iminodiacetic acid, hydroxyethylimino Acetic acid, iminodipropionic acid, aminotrimethylene phosphate, aminotrimethylene phosphate pentasodium salt, benzylamine, 2-naphthylamine, isobutylamine, isoamylamine, 1,3-propanediaminetetraacetic acid, 1,3-diamino- 2-hydroxypropanetetraacetic acid, glycol etherdiaminetetraacetic acid, metaphenylenediaminetetraacetic acid, 1,2-diaminocyclohexane-N, N, N ′, N′-tetraacetic acid, diaminopropionic acid, ethylenediaminetetramethylene phosphate, diethylenetriamine Pentamethylene phosphoric acid, glutamic acid, dicarboxymethyl glutamic acid, ornithine, cysteine, N, N-bis (2-hydroxyethyl) glycine, (S, S) -ethylenediamine succinic acid, methylenediamine, ethylenediamine Ethylenediaminetetraacetic acid, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylene pentamine, pentaethylene hexamine, hexaethyleneheptamine, cinnamylamine, p- methoxy cinnamyl amine.

Examples of the reducing agent include phosphoric acid compounds, borohydride compounds, hydrazine derivatives, and the like. These can be used alone or in combination of two or more.

Specifically, examples of phosphoric acid compounds include hypophosphorous acid, phosphorous acid, pyrophosphoric acid, and polyphosphoric acid. Examples of the borohydride compounds include methyl hexaborane, dimethylamine borane, diethylamine borane, morpholine borane, pyridine amine borane, piperidine borane, ethylenediamine borane, ethylenediamine bisborane, t-butylamine borane, imidazole borane, methoxyethylamine borane, hydrogen Examples thereof include sodium borohydride. As the hydrazine derivative, hydrazine salts such as hydrazine sulfate and hydrazine hydrochloride, hydrazine derivatives such as pyrazoles, triazoles and hydrazides, and the like can be used. Among these, as pyrazoles, pyrazole derivatives such as 3,5-dimethylpyrazole and 3-methyl-5-pyrazolone can be used in addition to pyrazole. Further, as triazoles, 4-amino-1,2,4-triazole, 1,2,3-triazole, and the like can be used. As hydrazides, adipic hydrazide, maleic hydrazide, carbohydrazide, and the like can be used.

In addition, additives such as a pH buffer, a pH adjuster, and a surfactant can be contained as necessary. Furthermore, you may use an antifoamer and a dispersing agent as needed.

A known complexing agent can be used as the pH buffering agent. For example, ammonium chloride, ammonium sulfate, boric acid, sodium acetate and the like can be mentioned.

A known complexing agent can be used as the pH adjuster. For example, an acid or alkali compound can be used, and examples thereof include alkali metal hydroxides such as ammonia and sodium hydroxide, nickel carbonate, sulfuric acid, and hydrochloric acid. In addition, when using ammonia, it can supply as ammonia water.

Surfactants can be used to improve the permeability of the plating solution. Specifically, any of nonionic, cationic, anionic, amphoteric, etc. surfactants should be used as the surfactant. It can be used alone or in combination of two or more.

Furthermore, by making Sn other than Sn contain in the Sn film to be formed, that is, by forming a film of Sn alloy on the surface of the copper powder, the properties such as melting point and wettability are changed. be able to. For example, as a specification of Pb-free solder, use temperature, wettability, and mechanical strength become problems depending on the use and material to be used. In this respect, by forming a film of Sn alloy, it is possible to change to a property suitable for the intended use and material.

Specifically, as an element to be contained in the Sn coating, that is, as an element other than Sn constituting the Sn alloy, silver, bismuth, copper, indium, antimony, zinc and the like can be cited. The Sn alloy can be a binary or multi-component alloy containing these elements. Among them, elements that can be alloyed when Sn coating is performed by electroless plating include silver, bismuth, and zinc. By adding one or more compounds containing these elements to the electroless Sn plating solution described above. The Sn alloy film can be easily coated.

Specifically, when a silver-containing Sn alloy is used, examples of the silver compound added to the electroless Sn plating solution include silver oxide, silver nitrate, silver sulfate, silver chloride, silver bromide, silver iodide, and benzoic acid. Silver, silver sulfamate, silver citrate, silver lactate, silver mercaptosuccinate, silver phosphate, silver trifluoroacetate, silver pyrophosphate, silver 1-hydroxyethane-1,1-bisphosphonate, silver borofluoride, silver tartrate Silver gluconate, silver oxalate, silver methanesulfonate, silver p-phenolsulfonate, silver benzoate and the like.

In addition, when a Sn alloy containing bismuth is used, examples of the bismuth compound added to the electroless Sn plating solution include bismuth nitrate, bismuth chloride, bismuth methanesulfonate, bismuth ethanesulfonate, and bismuth p-phenolsulfonate. Is mentioned.

In addition, when the Sn alloy containing zinc is used, examples of the zinc compound added to the electroless Sn plating solution include zinc oxide, zinc chloride, and zinc sulfate.

The content ratio of metal elements other than Sn constituting these Sn alloys is 0 with respect to 100% by mass of the entire Sn alloy coating film coated with the dendritic Sn-coated copper powder from the viewpoint of melting point and wettability. The content is preferably 1% by mass to 50% by mass. If the content is too large, it causes an increase in melting point and a decrease in mechanical strength, and therefore it is preferably 50% by mass or less. On the other hand, if the content is less than 0.1% by mass, the effect of lowering the melting point or improving the wettability may not be sufficiently obtained even if the metal element that becomes the Sn alloy is contained. . Therefore, the content is preferably 0.1% by mass to 50% by mass with respect to 100% by mass of the entire Sn alloy coating, and more preferably 1% by mass to 20% by mass. The content is more preferably 2% by mass to 10% by mass.

In addition, content of the metal which comprises Sn alloy can be measured by converting content of each element which comprises Sn coat | court copper powder, for example with a high frequency inductively coupled plasma (ICP) emission spectroscopy analysis method. In addition, each element in the Sn alloy coating can be quantitatively analyzed from the cross section of the Sn-coated copper powder or the like by energy dispersive X-ray spectroscopy (EDX) method or Auger electron spectroscopy (AES) method.

Furthermore, the method for forming the Sn alloy film is not limited to the above-described electroless plating method. For example, an element other than Sn constituting the Sn alloy is included in the dendritic copper powder before coating Sn, and after forming a film composed only of Sn (Sn film), it is included in the copper powder in advance. A Sn alloy film can also be formed by diffusing the elements that have been deposited in the Sn film.

<2-2. Manufacturing Method of Sn Coated Copper Powder According to Second Embodiment>
The Sn-coated copper powder according to the second embodiment is Sn-coated copper powder in which copper particles whose surfaces are coated with Sn or an Sn alloy gather to form a dendritic shape having a plurality of branches. The copper particles whose surfaces are coated with Sn or Sn alloy have an elliptical size with a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. The Sn-coated copper powder, which is a body and is composed of the copper particles, has an average particle diameter (D50) of 5.0 μm to 20 μm. Further, the average thickness of the branch portions constituting the dendritic shape is preferably 0.5 μm to 2.0 μm.

<2-2-1. Manufacturing method of copper powder>
As described above, the Sn-coated copper powder (dendritic Sn-coated copper powder) according to the second embodiment is formed by coating the surface of the dendritic copper powder with Sn or an Sn alloy. For example, it can be manufactured by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In the case of electrolysis, a sulfuric acid-containing electrolytic solution containing copper ions is contained in an electrolytic cell in which metallic copper is used as an anode and a stainless steel plate or a titanium plate is used as a cathode, as in the electrolytic treatment in the first embodiment. Then, electrolytic treatment is performed by passing a direct current through the electrolytic solution at a predetermined current density. Thereby, a dendritic copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the second embodiment, a sulfuric acid acidic electrolytic solution containing a water-soluble copper salt serving as a copper ion source is electrolyzed by adding a polyether compound as an additive. Without using a medium such as a ball to mechanically deform the obtained granular copper powder, the ellipsoidal copper particles gathered into a dendritic shape by aggregation only by electrolysis. It can be deposited on the cathode surface.

That is, as the electrolytic solution, for example, an electrolytic solution containing a water-soluble copper salt (copper ion), sulfuric acid, and a polyether compound is used. Further, it is preferable that the electrolytic solution further contains chloride ions. Here, the water-soluble copper salt and sulfuric acid contained in the electrolytic solution are the same as those in the manufacturing method according to the first embodiment, and detailed description thereof is omitted.

In the second embodiment, a polyether compound is used as an additive in the electrolytic solution. This polyether compound, together with chloride ions described later, contributes to shape control of the deposited copper powder, and the copper powder deposited on the cathode is an ellipsoidal copper having a predetermined minor axis average diameter and major axis average diameter. A dendritic copper powder in which particles are aggregated into a dendritic shape can be obtained.

Specifically, the polyether compound is not particularly limited. For example, polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant, polyoxyethylene glycol / glycerin ether, polyoxyethylene Examples thereof include polymer compounds such as glycol dialkyl ether, polyoxyethylene polyoxypropylene glycol alkyl ether, and aromatic alcohol alkoxylate.

Further, the number average molecular weight of the polyether compound is not particularly limited, but is preferably 100 to 200,000, more preferably 200 to 15,000, and 1,000 to 10,000. Is more preferable. If the number average molecular weight is less than 100, fine electrolytic copper powder that does not have a dendritic shape may be deposited. On the other hand, when the number average molecular weight exceeds 200,000, electrolytic copper powder having a large average particle size is precipitated, and only dendritic copper powder having a specific surface area of less than 0.6 m ² / g may be obtained. . The number average molecular weight is a molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

In addition, as a polyether compound, you may add individually by 1 type and may add it in combination of 2 or more types. Further, the addition amount of the polyether compound is preferably such that the concentration in the electrolytic solution is in the range of about 0.1 mg / L to 5,000 mg / L.

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. By containing chloride ions in the electrolytic solution, the shape of the deposited copper powder can be controlled more effectively. The chloride ion concentration in the electrolytic solution can be about 1 mg / L to 1000 mg / L, preferably about 10 mg / L to 800 mg / L, more preferably about 20 mg / L to 500 mg / L.

In the second embodiment, for example, electrolysis is performed using the electrolytic solution having the composition as described above, whereby copper powder is deposited on the cathode to produce dendritic copper powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 30 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-2-2. Sn coating method (production of Sn-coated copper powder)>
The Sn-coated copper powder according to the second embodiment is formed on the surface of the dendritic copper powder prepared by the above-described electrolytic method using, for example, an Sn plating solution (electroless Sn plating solution) by an electroless plating method. It can manufacture by coat | covering Sn alloy.

The specific electroless plating method, the composition of the electroless Sn plating solution (component in the plating solution), and pretreatment such as cleaning treatment before electroless plating are manufactured in the first embodiment. The method is the same as that of the method, and detailed description is omitted.

In addition, as in the formation of the Sn film in the first embodiment, it is preferable that an element other than Sn is contained in the formed Sn film. By forming a Sn alloy film on the surface of the copper powder, properties such as melting point and wettability can be changed. For example, as a specification of Pb-free solder, use temperature, wettability, and mechanical strength become problems depending on the use and material to be used. In this respect, by forming a film of Sn alloy, it is possible to change to a property suitable for the intended use and material.

Specifically, as an element to be contained in the Sn coating, that is, as an element other than Sn constituting the Sn alloy, silver, bismuth, copper, indium, antimony, zinc and the like can be cited. The Sn alloy can be a binary or multi-component alloy containing these elements. Among them, elements that can be alloyed when Sn coating is performed by electroless plating include silver, bismuth, and zinc. By adding one or more compounds containing these elements to the electroless Sn plating solution described above. The Sn alloy film can be easily coated.

The method for forming the Sn alloy film, the content of elements other than Sn in the Sn alloy, the element source of the elements other than Sn, and the like are the same as those of the manufacturing method in the first embodiment. The detailed explanation is omitted.

<2-3. Manufacturing Method of Sn Coated Copper Powder According to Third Embodiment>
The Sn-coated copper powder according to the third embodiment has a dendritic shape in which copper particles whose surfaces are coated with Sn or an Sn alloy are aggregated to have a main trunk that grows linearly and a plurality of branches separated from the main trunk. It is Sn coat copper powder which constituted the shape. The copper particles coated with Sn or Sn alloy on the surface are in the form of a flat plate having a cross-sectional average thickness of 0.2 μm to 5.0 μm, and the Sn-coated copper powder formed by assembling the copper particles is The average particle diameter (D50) is 1.0 μm to 100 μm.

<2-3-1. Manufacturing method of copper powder>
As described above, the Sn-coated copper powder (dendritic Sn-coated copper powder) according to the third embodiment is formed by coating the surface of the dendritic copper powder with Sn or an Sn alloy. For example, it can be manufactured by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In electrolysis, as in the electrolysis treatment in the first and second embodiments, sulfuric acid-acid electrolysis containing copper ions in an electrolytic cell in which metallic copper is used as an anode and a stainless steel plate, a titanium plate or the like is used as a cathode. The solution is accommodated, and electrolytic treatment is performed by passing a direct current through the electrolyte solution at a predetermined current density. Thereby, a dendritic copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the third embodiment, an amine compound is added as an additive to a sulfuric acid electrolytic solution containing a water-soluble copper salt serving as a copper ion source, and thus electrolysis is obtained. The copper powder in the form of particles is formed by dendritic copper powder that is formed by aggregation of flat copper particles only by electrolysis without mechanical deformation using a medium such as a ball. Can be deposited.

That is, as the electrolytic solution, for example, an electrolytic solution containing a water-soluble copper salt (copper ion), sulfuric acid, and an amine compound is used. Further, it is preferable that the electrolytic solution further contains chloride ions. Here, the water-soluble copper salt and sulfuric acid contained in the electrolytic solution are the same as those in the manufacturing method according to the first embodiment, and detailed description thereof is omitted.

In the third embodiment, an amine compound can be used as an additive in the electrolytic solution. This amine compound contributes to shape control of the copper powder deposited together with chloride ions to be described later, and the copper powder deposited on the cathode surface is composed of flat copper particles having a predetermined cross-sectional average thickness. And a dendritic copper powder having a branch branched from its main trunk.

As the amine compound, one kind may be added alone, or two or more kinds may be added in combination. The amount of the amine compound added is preferably an amount such that the concentration in the electrolytic solution is in the range of 0.1 mg / L to 500 mg / L, and an amount in the range of 1 mg / L to 400 mg / L. More preferably.

Specifically, the amine compound is not particularly limited, but a compound having a phenazine structure that can be represented by the following formula (1) can be used. More preferably, for example, safranine (3,7-diamino-2,8-dimethyl-5-phenyl-5-phenazinium chloride, C ₂₀ H ₁₉ N ₄ Cl, CAS number: 477-73-64) is used. Can do.

Here, in Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, It is a group selected from the group consisting of CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl. R ₅ is hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. By containing chloride ions in the electrolytic solution, the shape of the deposited copper powder can be controlled more effectively. The chloride ion concentration in the electrolytic solution can be about 1 mg / L to 1000 mg / L, preferably about 5 mg / L to 800 mg / L, more preferably about 10 mg / L to 500 mg / L.

In the third embodiment, for example, electrolysis is performed using the electrolytic solution having the composition as described above, whereby copper powder is deposited on the cathode to produce dendritic copper powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 30 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-3-2. Sn coating method (production of Sn-coated copper powder)>
The Sn-coated copper powder according to the third embodiment is formed on the surface of the dendritic copper powder prepared by the above-described electrolysis method using, for example, Sn or an electroless plating method using an Sn plating solution (electroless Sn plating solution). It can manufacture by coat | covering Sn alloy.

The specific electroless plating method, the composition of the electroless Sn plating solution (component in the plating solution), and pretreatment such as cleaning treatment before electroless plating are manufactured in the first embodiment. The method is the same as that of the method, and detailed description is omitted.

In addition, as in the formation of the Sn film in the first embodiment, it is preferable that an element other than Sn is contained in the formed Sn film. By forming a Sn alloy film on the surface of the copper powder, properties such as melting point and wettability can be changed. For example, as a specification of Pb-free solder, use temperature, wettability, and mechanical strength become problems depending on the use and material to be used. In this respect, by forming a film of Sn alloy, it is possible to change to a property suitable for the intended use and material.

Specifically, as an element to be contained in the Sn coating, that is, as an element other than Sn constituting the Sn alloy, silver, bismuth, copper, indium, antimony, zinc and the like can be cited. The Sn alloy can be a binary or multi-component alloy containing these elements. Among them, elements that can be alloyed when Sn coating is performed by electroless plating include silver, bismuth, and zinc. By adding one or more compounds containing these elements to the electroless Sn plating solution described above. The Sn alloy film can be easily coated.

The method for forming the Sn alloy film, the content of elements other than Sn in the Sn alloy, the element source of the elements other than Sn, and the like are the same as those of the manufacturing method in the first embodiment. The detailed explanation is omitted.

<2-4. Manufacturing Method of Sn Coated Copper Powder According to Fourth Embodiment>
The Sn-coated copper powder according to the fourth embodiment is an Sn-coated copper powder having a form of an aggregate formed by aggregating a plurality of piece-like copper particles whose surfaces are coated with Sn or an Sn alloy. The copper particles coated with Sn or the Sn alloy have a flat plate shape with an average major axis diameter determined by SEM observation of 0.5 μm to 5.0 μm and a cross-sectional average thickness of 0.02 μm to 1.0 μm. The Sn-coated copper powder composed of the copper particles has an average particle diameter (D50) of 1.0 to 30 μm.

<2-4-1. Manufacturing method of copper powder>
As described above, the Sn-coated copper powder (flat Sn coated copper particle aggregated powder) according to the fourth embodiment is formed by coating the surface of the tabular copper particle aggregated powder with Sn or an Sn alloy. The copper particle agglomerated powder can be produced, for example, by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In the case of electrolysis, a sulfuric acid-containing electrolytic solution containing copper ions is contained in an electrolytic cell in which metallic copper is used as an anode and a stainless steel plate or a titanium plate is used as a cathode, as in the electrolytic treatment in the first embodiment. Then, electrolytic treatment is performed by passing a direct current through the electrolytic solution at a predetermined current density. Thereby, flat copper particle aggregation copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the fourth embodiment, an amine compound or a nonionic surfactant is added as an additive to the sulfuric acid acidic electrolyte solution containing a water-soluble copper salt serving as a copper ion source. The granular copper powder obtained by electrolysis is not subjected to mechanical deformation processing using a medium such as a ball, and the tabular copper particle aggregated powder in which tabular copper particles are aggregated is obtained only by electrolysis. It can be deposited on the surface.

That is, as the electrolytic solution, for example, a material containing a water-soluble copper salt (copper ion), sulfuric acid, and an additive such as an amine compound or a nonionic surfactant is used. Further, it is preferable that the electrolytic solution further contains chloride ions. Here, the water-soluble copper salt and sulfuric acid contained in the electrolytic solution are the same as those in the manufacturing method according to the first embodiment, and detailed description thereof is omitted.

In the fourth embodiment, for example, an amine compound or a nonionic surfactant is used as an additive in the electrolytic solution. The amine compound added as an additive contributes to the shape control of the copper powder deposited together with the chloride ions and nonionic surfactants described later, and the copper powder deposited on the cathode has a flat cross-sectional shape having a predetermined average thickness. It can be set as the tabular copper particle aggregation powder comprised from a copper particle.

Specifically, the amine compound is not particularly limited, but a compound having a phenazine structure and an azobenzene structure represented by the following formula (3) can be used. More preferably, for example, Janus Green B (C ₃₀ H ₃₁ N ₆ Cl, CAS number: 2869-83-2) can be used.

Here, in Formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each separately , Hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl Is a group selected from R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

As the amine compound, one kind may be added alone, or two or more kinds may be added in combination. Further, the addition amount of the amine compound is preferably an amount that is in the range of about 0.1 mg / L to 500 mg / L in terms of concentration in the electrolytic solution.

The nonionic surfactant is not particularly limited, but those having an ether group are preferred. Specific examples include polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant, polyoxyethylene glycol / glyceryl ether, polyoxyethylene glycol / dialkyl ether, polyoxyethylene polyoxypropylene glycol. -Alkyl ether, aromatic alcohol alkoxylate, the compound represented by following formula (x), etc. are mentioned.

（なお、式（ｘ）中、Ｒ_１は、炭素数５～３０の高級アルコールの残基、炭素数１～３０のアルキル基を有するアルキルフェノールの残基、炭素数１～３０のアルキル基を有するアルキルナフトールの残基、炭素数３～２５の脂肪酸アミドの残基、炭素数２～５のアルキルアミンの残基又は水酸基を示し、Ｒ_２及びＲ_３は、水素原子又はメチル基を示し、ｍ及びｎは、１～１００の整数を示す。）

(In the formula (x), R ₁ has a higher alcohol residue having 5 to 30 carbon atoms, an alkylphenol residue having an alkyl group having 1 to 30 carbon atoms, or an alkyl group having 1 to 30 carbon atoms. A residue of an alkyl naphthol, a residue of a fatty acid amide having 3 to 25 carbon atoms, a residue of an alkyl amine having 2 to 5 carbon atoms or a hydroxyl group, R ₂ and R ₃ represent a hydrogen atom or a methyl group, m And n represents an integer of 1 to 100.)

The number average molecular weight of the nonionic surfactant is not particularly limited, but is preferably 100 to 200,000, more preferably 200 to 15,000, and further preferably 1,000 to 10,000. preferable. The number average molecular weight is a molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

These nonionic surfactants may be added singly or in combination of two or more. The amount of the nonionic surfactant added is not particularly limited, but is preferably about 200 mg / L to 5000 mg / L, more preferably about 500 mg / L to 2000 mg / L in terms of the concentration in the electrolytic solution. preferable.

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. Chloride ions contribute to shape control of the deposited copper powder together with the above-described amine compound and nonionic surfactant additives. The chloride ion concentration in the electrolytic solution is not particularly limited, but is preferably about 200 mg / L to 1000 mg / L, and more preferably about 250 mg / L to 800 mg / L.

In the fourth embodiment, for example, by performing electrolysis using the electrolytic solution having the above-described composition, copper powder is deposited on the cathode to produce a tabular copper particle aggregated powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 40 A / dm ² when electrolysis is performed using a sulfuric acid electrolyte, and the electrolyte is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-4-2. Sn coating method (production of Sn-coated copper powder)>
The Sn-coated copper particles according to the fourth embodiment are obtained by using, for example, a Sn plating solution (electroless Sn plating solution) by an electroless plating method on the surface of the tabular copper particle aggregate powder produced by the above-described electrolytic method. It can be produced by coating Sn or an Sn alloy.

The specific electroless plating method, the composition of the electroless Sn plating solution (component in the plating solution), and pretreatment such as cleaning treatment before electroless plating are manufactured in the first embodiment. The method is the same as that of the method, and detailed description is omitted.

In addition, as in the formation of the Sn film in the first embodiment, it is preferable that an element other than Sn is contained in the formed Sn film. By forming a Sn alloy film on the surface of the copper powder, properties such as melting point and wettability can be changed. For example, as a specification of Pb-free solder, use temperature, wettability, and mechanical strength become problems depending on the use and material to be used. In this respect, by forming a film of Sn alloy, it is possible to change to a property suitable for the intended use and material.

Specifically, as an element to be contained in the Sn coating, that is, as an element other than Sn constituting the Sn alloy, silver, bismuth, copper, indium, antimony, zinc and the like can be cited. The Sn alloy can be a binary or multi-component alloy containing these elements. Among them, elements that can be alloyed when Sn coating is performed by electroless plating include silver, bismuth, and zinc. By adding one or more compounds containing these elements to the electroless Sn plating solution described above. The Sn alloy film can be easily coated.

The method for forming the Sn alloy film, the content of elements other than Sn in the Sn alloy, the element source of the elements other than Sn, and the like are the same as those of the manufacturing method in the first embodiment. The detailed explanation is omitted.

<2-5. Manufacturing Method of Sn Coated Copper Powder According to Fifth Embodiment>
The Sn-coated copper powder according to the fifth embodiment has a dendritic shape in which copper particles whose surfaces are coated with Sn or an Sn alloy are aggregated to have a main trunk that grows linearly and a plurality of branches separated from the main trunk. It is Sn coat copper powder which constituted the shape. The copper particles coated with Sn or Sn alloy on the surface are dendritic having a main trunk grown in a dendritic shape and a plurality of branches separated from the main trunk, and the cross-sectional average thickness of the main trunk and the branches of the copper particles The Sn-coated copper powder, which is a flat plate having a thickness of 0.02 μm to 0.5 μm and is constituted by aggregating the copper particles, has an average particle diameter (D50) of 1.0 μm to 30 μm. The surface of the copper particles has fine convex portions, and the average height of the convex portions is preferably 0.01 μm to 0.4 μm.

<2-5-1. Manufacturing method of copper powder>
As described above, the Sn-coated copper powder (dendritic Sn-coated copper powder) according to the fifth embodiment is formed by coating the surface of the dendritic copper powder with Sn or an Sn alloy. For example, it can be manufactured by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In the case of electrolysis, a sulfuric acid-containing electrolytic solution containing copper ions is contained in an electrolytic cell in which metallic copper is used as an anode and a stainless steel plate or a titanium plate is used as a cathode, as in the electrolytic treatment in the first embodiment. Then, electrolytic treatment is performed by passing a direct current through the electrolytic solution at a predetermined current density. Thereby, a dendritic copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the present embodiment, an amine compound is added as an additive to the sulfuric acid acidic electrolytic solution containing a water-soluble copper salt serving as a copper ion source, and thus obtained by electrolysis. Without denaturing the copper powder in a granular form using a medium such as a ball, the dendritic copper powder is formed on the surface of the cathode by gathering flat copper particles and forming a dendritic shape only by electrolysis. It can be deposited.

That is, as the electrolytic solution, for example, an electrolytic solution containing a water-soluble copper salt (copper ion), sulfuric acid, and an amine compound is used. Further, it is preferable that the electrolytic solution further contains chloride ions. Here, the water-soluble copper salt and sulfuric acid contained in the electrolytic solution are the same as those in the manufacturing method according to the first embodiment, and detailed description thereof is omitted.

In the fifth embodiment, an amine compound can be used as an additive in the electrolytic solution. The amine compound contributes to shape control of the copper powder to be deposited together with chloride ions to be described later, and the copper powder to be deposited on the cathode surface is composed of flat copper particles having a predetermined cross-sectional thickness; A dendritic copper powder having branches branched from the main trunk can be obtained.

As the amine compound, one kind may be added alone, or two or more kinds may be added in combination. The amount of the amine compound added is preferably an amount such that the concentration in the electrolytic solution is in the range of 0.1 mg / L to 500 mg / L, and an amount in the range of 1 mg / L to 400 mg / L. More preferably.

Specifically, the amine compound is not particularly limited, but a compound having a phenazine structure and an azobenzene structure, which can be represented by the following formula (3), can be used. More preferably, for example, Janus Green B (C30H31N6Cl, CAS number: 2869-83-2) can be used.

Here, in Formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each separately , Hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl Is a group selected from R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

Specifically, as a compound having a phenazine structure and an azobenzene structure, for example, 3- (diethylamino) -7-[(4-hydroxyphenyl) azo] -2,8-dimethyl-5-phenylphenazine-5-ium , 3-[[4- (dimethylamino) phenyl] azo] -7- (diethylamino) -5-phenylphenazine-5-ium, Janus Green B, 3-amino-7-[(2,4-diaminophenyl) Azo] -2,8-dimethyl-5-phenylphenazine-5-ium, 2,8-dimethyl-3-amino-5-phenyl-7- (2-hydroxy-1-naphthylazo) phenazine-5-ium, 3 -[[4- (dimethylamino) phenyl] azo] -7- (dimethylamino) -5-phenylphenazine-5-ium, 3-amino-7-[[ -(Dimethylamino) phenyl] azo] -5-phenylphenazine-5-ium, 2- (diethylamino) -7- [4- (methylpropargylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene 2- (diethylamino) -7- [4- (methyl-4-pentynylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene, 2- (diethylamino) -7- [4- (methyl-2 , 3-dihydroxypropylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene.

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. By containing chloride ions in the electrolytic solution, the shape of the deposited copper powder can be controlled more effectively. The chloride ion concentration in the electrolytic solution can be about 30 mg / L to 1000 mg / L, preferably about 50 mg / L to 800 mg / L, more preferably about 200 mg / L to 500 mg / L.

In the fifth embodiment, for example, electrolysis is performed using the electrolytic solution having the above-described composition, so that copper powder is deposited on the cathode to produce dendritic copper powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 30 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-5-2. Sn coating method (production of Sn-coated copper powder)>
The Sn-coated copper powder according to the fifth embodiment is formed on the surface of the dendritic copper powder produced by the above-described electrolytic method using, for example, an Sn plating solution (electroless Sn plating solution) by an electroless plating method. It can manufacture by coat | covering Sn alloy.

The specific electroless plating method, the composition of the electroless Sn plating solution (component in the plating solution), and pretreatment such as cleaning treatment before electroless plating are manufactured in the first embodiment. The method is the same as that of the method, and detailed description is omitted.

In addition, as in the formation of the Sn film in the first embodiment, it is preferable that an element other than Sn is contained in the formed Sn film. By forming a Sn alloy film on the surface of the copper powder, properties such as melting point and wettability can be changed. For example, as a specification of Pb-free solder, use temperature, wettability, and mechanical strength become problems depending on the use and material to be used. In this respect, by forming a film of Sn alloy, it is possible to change to a property suitable for the intended use and material.

Specifically, as an element to be contained in the Sn coating, that is, as an element other than Sn constituting the Sn alloy, silver, bismuth, copper, indium, antimony, zinc and the like can be cited. The Sn alloy can be a binary or multi-component alloy containing these elements. Among them, elements that can be alloyed when Sn coating is performed by electroless plating include silver, bismuth, and zinc. By adding one or more compounds containing these elements to the electroless Sn plating solution described above. The Sn alloy film can be easily coated.

The method for forming the Sn alloy film, the content of elements other than Sn in the Sn alloy, the element source of the elements other than Sn, and the like are the same as those of the manufacturing method in the first embodiment. The detailed explanation is omitted.

≪3. Use of conductive paste >>
The Sn-coated copper powder according to the present invention (Sn-coated copper powder according to the first to fifth embodiments) has a large surface area, excellent formability and sinterability, and has a specific shape. A large number of contacts between the Sn-coated copper powders can be ensured because the copper particles are aggregated and configured, and excellent conductivity is exhibited.

In addition, in the Sn-coated copper powder according to the first to fifth embodiments, the Sn-coated copper powder having a specific structure can suppress aggregation even when a copper paste or the like is used. It becomes possible to disperse uniformly in the resin, and it is possible to suppress the occurrence of poor printability due to an increase in the viscosity of the paste.

Therefore, the Sn-coated copper powder according to the first to fifth embodiments can be suitably used for applications such as conductive pastes and conductive paints.

For example, as a conductive paste (copper paste), Sn-coated copper powder is included as a metal filler (copper powder), and kneaded with binder resin, solvent, and additives such as antioxidants and coupling agents as necessary. Can be produced.

Here, in using Sn-coated copper powder as a metal filler, the proportion of the Sn-coated copper powder in the metal filler is 20% by mass or more, preferably 30% by mass or more, more preferably 50% by mass or more. To be included. By setting the ratio of the Sn-coated copper powder in the metal filler to 20% by mass or more, for example, when the metal filler is used in the copper paste, it can be uniformly dispersed in the resin, and the viscosity of the paste is excessive. It is possible to prevent the printability from being increased. Moreover, the more excellent electroconductivity can be exhibited as an electrically conductive paste.

As described above, the metal filler may contain Sn coated copper powder in a proportion of 20% by mass or more, and other examples include spherical copper powder of about 1 μm to 20 μm or spherical Sn coated. You may mix copper powder etc. Also, fillers having different compositions as well as fillers such as silver powder may be mixed.

Specifically, the binder resin is not particularly limited, but an epoxy resin, a phenol resin, or the like can be used. Moreover, as a solvent, organic solvents, such as ethylene glycol, diethylene glycol, triethylene glycol, glycerol, and terpineol, can be used. Moreover, the addition amount of the organic solvent is not particularly limited, but the addition amount is adjusted in consideration of the particle size of the Sn-coated copper powder so that the viscosity is suitable for a conductive film forming method such as screen printing or a dispenser. be able to.

Furthermore, other resin components can be added to adjust the viscosity. For example, a cellulose-based resin typified by ethyl cellulose can be used, and it can be added as an organic vehicle dissolved in an organic solvent such as terpineol. In addition, it is necessary to suppress the addition amount of the resin component to an extent that does not impair the sinterability, and is preferably 5% by mass or less of the whole.

Also, as an additive, an antioxidant or the like can be added in order to improve the conductivity after firing. Although it does not specifically limit as antioxidant, For example, a hydroxycarboxylic acid etc. can be mentioned. More specifically, hydroxycarboxylic acids such as citric acid, malic acid, tartaric acid, and lactic acid are preferable, and citric acid or malic acid that has high adsorptive power to copper coated with Sn or Sn alloy is particularly preferable. The addition amount of the antioxidant can be set to, for example, about 1% by mass to 15% by mass in consideration of the antioxidant effect and the viscosity of the paste.

Hereinafter, examples of the present invention will be described in more detail with reference to comparative examples, but the present invention is not limited to the following examples.

≪Evaluation method≫
The copper powder obtained in the following Examples and Comparative Examples was subjected to shape observation, average particle diameter measurement, specific surface area measurement, and the like by the following methods.

(Observation of shape)
With a scanning electron microscope (manufactured by JEOL Ltd., JSM-7100F type), 20 visual fields were arbitrarily observed at a predetermined magnification, and copper powder contained in the visual field was observed.

(Measurement of average particle size)
The average particle diameter (D50) of the obtained Sn-coated copper powder was measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., HRA9320 X-100).

(The bulk density)
The bulk density was measured as a tap density using a shaking specific gravity measuring device (manufactured by Kuramochi Scientific Instruments, Tapping machine KRS-40).

(BET specific surface area)
The BET specific surface area was measured using a specific surface area / pore distribution measuring apparatus (manufactured by Cantachrome, QUADRASORB SI).

(Specific resistance measurement)
Regarding the specific resistance value of the film, the sheet resistance value was measured by a four-terminal method using a low resistivity meter (Loresta-GP MCP-T600, manufactured by Mitsubishi Chemical Corporation), while the surface roughness shape measuring instrument ( The film thickness of the coating film was measured by SURFCOM130A, manufactured by Tokyo Seimitsu Co., Ltd., and the sheet resistance value was determined by dividing the film thickness by the film thickness.

≪Example, comparative example≫
(1) Test using Sn-coated copper powder according to the first embodiment [Example 1]
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, as the electrolytic solution, a composition having a copper ion concentration of 15 g / L and a sulfuric acid concentration of 100 g / L was used. Further, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the electrolytic solution so that the chloride ion (chlorine ion) concentration in the electrolytic solution was 50 mg / L. In addition, safranin (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure, is added as an additive to the electrolytic solution so that the concentration in the electrolytic solution is 100 mg / L, and a nonionic surfactant is further added. Polyethylene glycol (PEG) having a molecular weight of 1000 (manufactured by Wako Pure Chemical Industries, Ltd.) was added to a concentration of 500 mg / L in the electrolytic solution.

Then, while circulating the electrolytic solution adjusted to the concentration as described above at a flow rate of 15 L / min using a metering pump, the temperature is maintained at 25 ° C. and the current density of the cathode is 10 A / dm ^2. Current was applied to deposit copper powder on the cathode plate.

The electrolytic copper powder deposited on the cathode plate was recovered by mechanically scraping it off the bottom of the electrolytic cell using a scraper, and the recovered copper powder was washed with pure water and then put in a vacuum dryer and dried. .

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

Specifically, as electroless Sn plating solution, stannous borofluoride 20 g / L, borofluoric acid 200 g / L, thiourea 50 g / L, sodium borohydride 40 g / L, and sodium borate 10 g / L at each concentration. An added plating solution was prepared. In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 60 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder is densely packed with flat copper particles whose surfaces are uniformly coated with Sn. Thus, the dendritic Sn-coated copper powder aggregated and exhibited a dendritic shape. When the dendritic Sn-coated copper powder was recovered and the amount of Sn covered was measured, it was 10.6% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Moreover, about the obtained dendritic Sn coat copper powder, while observing by SEM, it grew in the direction perpendicular | vertical with respect to the flat surface of the flat copper particle and the flat surface of the said dendritic Sn coat copper powder. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Sn-coated copper powder were in the form of a flat plate having a cross-sectional average thickness of 2.2 μm. Moreover, the average particle diameter (D50) of the dendritic Sn-coated copper powder was 25.3 μm. The ratio of the maximum length of the Sn-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.087.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 2.8 g / cm ³ . The BET specific surface area was 1.21 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 55 parts by mass of the obtained dendritic Sn-coated copper powder was mixed with 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 8.4 × 10 ⁻⁵ Ω · cm.

From the result of Example 1, a compound having a phenazine structure and a nonionic surfactant are added to the electrolytic solution to produce a dendritic electrolytic copper powder, and the surface of the obtained copper powder is coated with Sn. Thus, it was found that a plate-like dendritic Sn-coated copper powder with suppressed vertical growth can be produced.

[Example 2]
<Preparation of electrolytic copper powder>
A hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is added to the electrolyte so that the chloride ion concentration is 150 mg / L, and methyl orange (Kanto Chemical Industries, Ltd.), which is a compound having an azobenzene structure as an additive, is added. Manufactured) was added to a concentration of 150 mg / L in the electrolytic solution. Furthermore, polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 1000, which is a nonionic surfactant, (manufactured by NOF Corporation, trade name: UNILOVE 50MB-11) is added to the electrolyte so that the concentration in the electrolyte is 700 mg / L. Added to. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce copper powder.

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium citrate 40 g / L, ethylenediaminetetraacetic acid 20 g / L, and titanium chloride 50 g / L were added at respective concentrations was prepared. In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 65 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder is densely packed with flat copper particles whose surfaces are uniformly coated with Sn. Thus, the dendritic Sn-coated copper powder aggregated and exhibited a dendritic shape. When the dendritic Sn-coated copper powder was recovered and the amount of Sn covered was measured, it was 15.8% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Moreover, about the obtained dendritic Sn coat copper powder, while observing by SEM, it grew in the direction perpendicular | vertical with respect to the flat surface of the flat copper particle and the flat surface of the said dendritic Sn coat copper powder. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Sn-coated copper powder were in the form of a plate having a cross-sectional average thickness of 1.6 μm. The average particle diameter (D50) of the dendritic Sn-coated copper powder was 21.4 μm. The ratio of the maximum length of the Sn-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.078.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 2.0 g / cm ³ . Further, the BET specific surface area was 1.34 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 55 parts by mass of the obtained dendritic Sn-coated copper powder was mixed with 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 8.2 × 10 ⁻⁵ Ω · cm.

From the results of Example 2, a compound having an azobenzene structure and a nonionic surfactant are added to the electrolytic solution to produce a dendritic electrolytic copper powder, and the surface of the obtained copper powder is coated with Sn. Thus, it was found that a plate-like dendritic Sn-coated copper powder with suppressed vertical growth can be produced.

[Example 3]
<Preparation of electrolytic copper powder>
To the electrolyte, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion concentration was 80 mg / L, and Janus Green B (a compound having a phenazine structure and an azobenzene structure as an additive) Kanto Chemical Co., Ltd.) was added at a concentration of 600 mg / L in the electrolytic solution. Furthermore, a nonionic surfactant polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 3000 (manufactured by NOF Corporation, trade name: UNILOVE 50MB-72) is added to the electrolyte so that the concentration in the electrolyte is 1000 mg / L. Added to. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce copper powder.

<Preparation of dendritic Sn-coated copper powder (coated with Sn—Ag alloy)>
Next, using the dendritic copper powder produced by the method described above, the surface of the copper powder was coated with Sn alloy (Sn—Ag alloy) by electroless Sn plating to produce Sn-coated copper powder.

Specifically, 50 g / L of stannous methanesulfonate, 20 g / L of silver citrate, 100 g / L of thiourea, and 30 g / L of sodium hypophosphite were added at various concentrations as the electroless Sn plating solution for alloys. A plating solution was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Ag alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder was coated with a Sn-Ag alloy uniformly on the surface. It was dendritic Sn-coated copper powder in which particles were densely assembled and exhibited a dendritic shape. The dendritic Sn-coated copper powder was recovered and the coating amount of the Sn—Ag alloy was measured. As a result, it was 18.7% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Moreover, content of Ag contained in Sn alloy was 14.1 mass% with respect to 100 mass of Sn alloy.

Moreover, about the obtained dendritic Sn coat copper powder, while observing by SEM, it grew in the direction perpendicular | vertical with respect to the flat surface of the flat copper particle and the flat surface of the said dendritic Sn coat copper powder. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Sn-coated copper powder were flat plate having a cross-sectional average thickness of 1.4 μm. The average particle diameter (D50) of the dendritic Sn-coated copper powder was 18.7 μm. The ratio of the maximum length of the Sn-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.057.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 1.8 g / cm ³ . The BET specific surface area was 2.05 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 55 parts by mass of the obtained dendritic Sn-coated copper powder was mixed with 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 8.0 × 10 ⁻⁵ Ω · cm.

From the results of Example 3, the surface of the obtained copper powder was prepared by adding a compound having a phenazine structure and an azobenzene structure and a nonionic surfactant to the electrolytic solution to form a dendritic electrolytic copper powder. It was found that a plate-like dendritic Sn-coated copper powder with suppressed growth in the vertical direction can be produced by coating Sn on the surface.

[Example 4]
<Preparation of electrolytic copper powder>
A hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is added to the electrolyte so that the chloride ion concentration is 100 mg / L, and methyl orange (manufactured by Kanto Chemical Co., Ltd.), which is a compound having an azobenzene structure as an additive, is added. ) Is added at a concentration of 150 mg / L in the electrolytic solution, and Janus Green B (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure and an azobenzene structure, is added at a concentration of 100 mg / L in the electrolytic solution. It added so that it might become L. In addition, a nonionic surfactant having a molecular weight of 600 polyethylene glycol (PEG) (manufactured by Wako Pure Chemical Industries, Ltd.) is further added to the electrolyte so that the concentration in the electrolyte is 1000 mg / L. Polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 3000 (manufactured by NOF Corporation, trade name: UNILOVE 50MB-72) was added so that the concentration in the electrolytic solution was 1000 mg / L. Electrolytic treatment was performed under the same conditions to produce copper powder.

<Preparation of dendritic Sn-coated copper powder (Coating with Sn-Bi alloy)>
Next, using the dendritic copper powder prepared by the above-described method, the surface of the copper powder was coated with Sn alloy (Sn—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 40 g / L, bismuth methanesulfonate 40 g / L, thiourea 100 g / L, ethylenediaminetetraacetic acid 20 g / L, sodium hypophosphite 80 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Bi alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder was coated with a Sn-Bi alloy uniformly on the surface. It was dendritic Sn-coated copper powder in which particles were densely assembled and exhibited a dendritic shape. The dendritic Sn-coated copper powder was recovered and the amount of Sn-Bi alloy coating was measured. As a result, it was 41.8% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Moreover, the content of Bi contained in the Sn alloy was 41.0% by mass with respect to 100% by mass of the Sn alloy.

Moreover, about the obtained dendritic Sn coat copper powder, while observing by SEM, it grew in the direction perpendicular | vertical with respect to the flat surface of the flat copper particle and the flat surface of the said dendritic Sn coat copper powder. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Sn-coated copper powder were in the form of a flat plate having a cross-sectional average thickness of 0.6 μm. The average particle diameter (D50) of the dendritic Sn-coated copper powder was 19.3 μm. The ratio of the maximum length of the Sn-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.066.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 1.2 g / cm ³ . The BET specific surface area was 2.21 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 55 parts by mass of the obtained dendritic Sn-coated copper powder was mixed with 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 8.7 × 10 ⁻⁵ Ω · cm.

From the results of Example 4, a compound having an azobenzene structure as an additive and a compound having a phenazine structure and an azobenzene structure were mixed and added to the electrolytic solution, and two or more kinds of nonionic surfactants were further added. Addition to prepare dendritic electrolytic copper powder, and coat the surface of the obtained copper powder with Sn alloy to produce flat dendritic Sn-coated copper powder with suppressed vertical growth I found out that

[Example 5]
<Preparation of electrolytic copper powder>
To the electrolyte, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion concentration was 80 mg / L, and Janus Green B (a compound having a phenazine structure and an azobenzene structure as an additive) Kanto Chemical Co., Ltd.) was added at a concentration of 600 mg / L in the electrolytic solution. Furthermore, a nonionic surfactant polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 3000 (manufactured by NOF Corporation, trade name: UNILOVE 50MB-72) is added to the electrolyte so that the concentration in the electrolyte is 1000 mg / L. Added to. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce copper powder.

<Preparation of dendritic Sn-coated copper powder (Coating with Sn-Zn alloy)>
Next, using the dendritic copper powder produced by the above-described method, the surface of the copper powder was coated with Sn alloy (Sn—Zn alloy) by electroless Sn plating to produce Sn-coated copper powder.

Specifically, as the electroless Sn plating solution for alloys, stannous chloride 10 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, and sodium hypophosphite 70 g / L. A plating solution added at a concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Zn alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Sn-coated copper powder is a flat copper whose surface is uniformly coated with a Sn—Zn alloy. It was dendritic Sn-coated copper powder in which particles were densely assembled and exhibited a dendritic shape. The dendritic Sn-coated copper powder was recovered and the amount of Sn-Zn alloy coating was measured. As a result, it was 10.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy was 2.8% by mass with respect to 100% by mass of the Sn alloy.

Moreover, about the obtained dendritic Sn coat copper powder, while observing by SEM, it grew in the direction perpendicular | vertical with respect to the flat surface of the flat copper particle and the flat surface of the said dendritic Sn coat copper powder. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Sn-coated copper powder were in the form of a flat plate having a cross-sectional average thickness of 1.1 μm. Moreover, the average particle diameter (D50) of the dendritic Sn-coated copper powder was 23.2 μm. The ratio of the maximum length of the Sn-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.059.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 1.7 g / cm ³ . The BET specific surface area was 2.12 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 55 parts by mass of the obtained dendritic Sn-coated copper powder was mixed with 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 8.8 × 10 ⁻⁵ Ω · cm.

From the results of Example 5, a dendritic electrolytic copper powder was prepared by adding a compound having a phenazine structure and an azobenzene structure and a nonionic surfactant in the electrolytic solution, and the surface of the obtained copper powder. It was found that a flat dendritic Sn-coated copper powder in which the growth in the vertical direction was suppressed could be produced by coating Sn with an Sn alloy.

[Example 6]
<Preparation of dendritic Sn-coated copper powder (Sn—Ag—Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 2, the surface of the copper powder was coated with Sn alloy (Sn—Ag—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 50 g / L, bismuth methanesulfonate 5 g / L, silver citrate 20 g / L, thiourea 100 g / L, sodium hypophosphite 30 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Ag—Bi alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, it was found that at least 90% by number or more of Sn-coated copper powder was uniformly coated with a Sn—Ag—Bi alloy on the surface. This was a dendritic Sn-coated copper powder in which the copper particles were densely gathered to form a dendritic shape. The dendritic Sn-coated copper powder was recovered and the amount of Sn-Ag-Bi alloy coating was measured. As a result, it was 18.3% by mass with respect to 100% by mass of the entire Sn-coated copper powder. In addition, the content of Ag contained in the Sn alloy is 14.1% by mass with respect to the mass of Sn alloy of 100%, and the content of Bi contained in the Sn alloy is based on 100% of the mass of Sn alloy. It was 5.3% by mass.

Moreover, about the obtained dendritic Sn coat copper powder, while observing by SEM, it grew in the direction perpendicular | vertical with respect to the flat surface of the flat copper particle and the flat surface of the said dendritic Sn coat copper powder. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Sn-coated copper powder were in the form of a plate having a cross-sectional average thickness of 1.5 μm. The average particle diameter (D50) of the dendritic Sn-coated copper powder was 24.6 μm. The ratio of the maximum length of the Sn-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.046.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 1.8 g / cm ³ . Further, the BET specific surface area was 1.89 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 55 parts by mass of the obtained dendritic Sn-coated copper powder was mixed with 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 8.5 × 10 ⁻⁵ Ω · cm.

From the results of Example 6, a compound having a zobenzene structure and a nonionic surfactant were added to the electrolytic solution to produce a dendritic electrolytic copper powder, and the surface of the obtained copper powder was coated with a Sn alloy. It was found that a plate-like dendritic Sn-coated copper powder with suppressed vertical growth can be produced.

[Example 7]
<Preparation of dendritic Sn-coated copper powder (coated with Sn—Zn—Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 2, the surface of the copper powder was coated with Sn alloy (Sn—Zn—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous chloride 10 g / L, bismuth chloride 5 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, hypophosphorous acid A plating solution to which sodium 70 g / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried with ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with Sn—Zn—Bi alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder was uniformly coated on the surface with a Sn—Zn—Bi alloy. This was a dendritic Sn-coated copper powder in which the copper particles were densely gathered to form a dendritic shape. The dendritic Sn-coated copper powder was recovered and the coating amount of the Sn—Zn—Bi alloy was measured. As a result, it was 11.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy is 3.1% by mass with respect to 100% by mass of the Sn alloy, and the content of Bi contained in the Sn alloy is based on 100% by mass of the Sn alloy. It was 1.8% by mass.

Moreover, about the obtained dendritic Sn coat copper powder, while observing by SEM, it grew in the direction perpendicular | vertical with respect to the flat surface of the flat copper particle and the flat surface of the said dendritic Sn coat copper powder. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Sn-coated copper powder were in the form of a flat plate having a cross-sectional average thickness of 1.3 μm. Moreover, the average particle diameter (D50) of the dendritic Sn-coated copper powder was 25.3 μm. The ratio of the maximum length of the Sn-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.051.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 1.9 g / cm ³ . The BET specific surface area was 2.10 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 55 parts by mass of the obtained dendritic Sn-coated copper powder was mixed with 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 9.7 × 10 ⁻⁵ Ω · cm.

From the results of Example 7, a dendritic electrolytic copper powder was prepared by adding a compound having an azobenzene structure and a nonionic surfactant to the electrolytic solution, and the surface of the obtained copper powder was coated with a Sn alloy. It was found that a plate-like dendritic Sn-coated copper powder with suppressed vertical growth can be produced.

[Comparative Example 1]
Copper powder under the same conditions as in Example 1 except that safranin, which is a compound having a phenazine structure, and polyethylene glycol (PEG) having a molecular weight of 1,000, which is a nonionic surfactant, are not added as additives. Was deposited on the cathode plate. Subsequently, Sn was coated on the surface of the obtained copper powder under the same conditions as in Example 1 to obtain Sn-coated copper powder.

As a result of observing the shape of the obtained Sn-coated copper powder by the method using the scanning electron microscope (SEM) described above, the obtained Sn-coated copper powder had a dendritic shape, but the granular copper particles were It was assembled and was not a flat dendritic Sn-coated copper powder. Moreover, the BET specific surface area of the obtained Sn coat copper powder was 0.16 m ² / g. Moreover, when the Sn coating amount of the Sn-coated copper powder was measured, it was 10.9% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Next, 55 parts by mass of the dendritic Sn-coated copper powder was mixed with 15 parts by mass of a phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing is 85.2 × 10 ⁻⁵ Ω · cm, and the specific resistance value is high and inferior in conductivity compared to the conductive paste obtained in Example 1. Met.

[Comparative Example 2]
The characteristic of the conductive paste by Sn coat copper powder which coat | covered Sn on the conventional flat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Sn coat copper powder in an Example.

The flat copper powder was prepared by mechanically flattening granular electrolytic copper powder. Specifically, 5 g of stearic acid was added to 500 g of granular atomized copper powder (manufactured by Mekin Metal Powders Co., Ltd.) having an average particle diameter of 7.9 μm, and flattened with a ball mill. The ball mill was charged with 5 kg of 3 mm zirconia beads, and flattened by rotating for 90 minutes at a rotation speed of 500 rpm.

The obtained tabular copper powder was coated with Sn in the same manner as in Example 2. The coating amount of Sn of the produced flat Sn-coated copper powder was 13.2% by mass with respect to 100% by mass of the flat Sn-coated copper powder.

The plate-like Sn-coated copper powder thus produced was measured with a laser diffraction / scattering particle size distribution analyzer, and as a result, the average particle size (D50) was 20.8 μm. Moreover, as a result of observing with SEM, the cross-sectional average thickness was 0.4 micrometer.

Next, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the obtained flat Sn-coated copper powder. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 35.3 × 10 ⁻⁵ Ω · cm, and the specific resistance value is high and inferior in conductivity compared to the conductive paste obtained in Example 1. Met.

≪Example, comparative example≫
(2) Test using Sn-coated copper powder according to the second embodiment [Example 8]
<Preparation of electrolytic copper powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, an electrolytic solution having a composition with a copper ion concentration of 10 g / L and a sulfuric acid concentration of 100 g / L was used. Further, polyethylene glycol (PEG) having a molecular weight of 400 (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to this electrolytic solution so that the concentration in the electrolytic solution was 500 mg / L, and a hydrochloric acid solution (Wako Pure Chemical Industries, Ltd.) was further added. Yakuhin Kogyo Co., Ltd.) was added at a chloride ion concentration (chlorine ion concentration) of 50 mg / L.

Then, the current density of the cathode is set to 20 A / dm ² under the condition that the temperature is maintained at 30 ° C. while circulating the electrolytic solution whose concentration is adjusted as described above at a flow rate of 10 L / min using a metering pump. Was energized to deposit copper powder on the cathode plate.

The electrolytic copper powder deposited on the cathode plate was recovered by mechanically scraping it off the bottom of the electrolytic cell using a scraper, and the recovered copper powder was washed with pure water and then put in a vacuum dryer and dried. .

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

Specifically, as electroless Sn plating solution, stannous borofluoride 20 g / L, borofluoric acid 200 g / L, thiourea 50 g / L, sodium borohydride 40 g / L, and sodium borate 10 g / L at each concentration. An added plating solution was prepared. In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 60 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder in which Sn was coated on the surface of the dendritic copper powder was obtained. As a result of observing the Sn-coated copper powder with a scanning electron microscope (SEM) at a magnification of 5,000 times, at least 90% by number or more of the Sn-coated copper powder aggregates copper particles and exhibits a dendritic shape. The surface was a dendritic Sn-coated copper powder in which Sn was uniformly coated on the surface of the copper particles. When the obtained dendritic Sn-coated copper powder was recovered and the amount of Sn covered was measured, it was 10.8% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Moreover, as a result of observing the obtained dendritic Sn-coated copper powder by SEM, the minor axis average diameter was 0.2 μm, and the ellipsoidal copper particles having a major axis average diameter of 1.2 μm were assembled and constituted. It had a dendritic shape.

The average particle diameter (D50) of the dendritic Sn-coated copper powder formed by the aggregation of the ellipsoidal copper particles was 18.2 μm, and the average thickness of the branch portion was 2.1 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.89 g / cm ³ . The BET specific surface area was 2.6 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 1.8 × 10 ⁻⁴ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 9]
<Preparation of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L is used, and polyethylene glycol (PEG) as an additive is 150 mg / L as an additive in the electrolytic solution. In addition, the copper powder was deposited on the cathode plate under the same conditions as in Example 8 except that the hydrochloric acid solution was added so that the chlorine ion concentration in the electrolytic solution was 100 mg / L.

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium citrate 40 g / L, ethylenediaminetetraacetic acid 20 g / L, and titanium chloride 50 g / L were added at respective concentrations was prepared. In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 65 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. As a result of observing the obtained dendritic Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder has a dendritic shape as a result of aggregation of copper particles. It was dendritic Sn-coated copper powder in which Sn was uniformly coated on the surface of the particles. When the obtained dendritic Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 16.7% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Moreover, as a result of observing the obtained dendritic Sn-coated copper powder by SEM, the minor axis average diameter was 0.4 μm, and the ellipsoidal copper particles having a major axis average diameter of 1.8 μm were assembled and constituted. It had a dendritic shape.

Further, the average particle diameter (D50) of the dendritic Sn-coated copper powder formed by aggregating the ellipsoidal copper particles was 11.5 μm, and the average thickness of the branch portion was 2.8 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.58 g / cm ³ . The BET specific surface area was 1.8 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 1.7 × 10 ⁻⁴ Ω · cm, and it was found that the film exhibited excellent conductivity.

[Example 10]
<Preparation of dendritic Sn-coated copper powder>
Using 100 g of the dendritic copper powder obtained in Example 9, Sn coating was performed on the surface of the copper powder by electroless Sn plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium hydroxide 100 g / L, and sodium citrate 40 g / L were added at respective concentrations was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 80 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder aggregates copper particles and exhibits a dendritic shape. It was a dendritic Sn-coated copper powder whose surface was uniformly coated with Sn. When the obtained dendritic Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 8.5% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Moreover, as a result of observing the obtained dendritic Sn-coated copper powder by SEM, the short axis average diameter was 0.4 μm, and the ellipsoidal copper particles having a long axis average diameter of 1.9 μm were assembled. It had a dendritic shape.

The average particle diameter (D50) of the dendritic Sn-coated copper powder formed by the aggregation of the ellipsoidal copper particles was 10.8 μm, and the average thickness of the branch portion was 2.7 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.43 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 1.2 × 10 ⁻⁴ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 11]
<Preparation of dendritic Sn-coated copper powder (coated with Sn—Ag alloy)>
Using 100 g of the dendritic copper powder obtained in Example 9, the surface of the copper powder was coated with Sn alloy (Sn—Ag alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, 50 g / L of stannous methanesulfonate, 20 g / L of silver citrate, 100 g / L of thiourea, and 30 g / L of sodium hypophosphite were added at various concentrations as the electroless Sn plating solution for alloys. A plating solution was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Ag alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder aggregates copper particles and exhibits a dendritic shape. It was a dendritic Sn-coated copper powder having a surface uniformly coated with a Sn—Ag alloy. The obtained dendritic Sn-coated copper powder was recovered and the amount of Sn-Ag alloy coating was measured. As a result, it was 19.1% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Moreover, content of Ag contained in Sn alloy was 14.4 mass% with respect to 100 mass of Sn alloy.

Moreover, as a result of observing the obtained dendritic Sn-coated copper powder by SEM, the short axis average diameter was 0.5 μm, and the ellipsoidal copper particles having a long axis average diameter of 1.7 μm were assembled and constituted. It had a dendritic shape.

The average particle diameter (D50) of the dendritic Sn-coated copper powder formed by the aggregation of the ellipsoidal copper particles was 11.2 μm, and the average thickness of the branch portion was 2.5 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.50 g / cm ³ . The BET specific surface area was 1.5 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 1.6 × 10 ⁻⁴ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 12]
<Preparation of dendritic Sn-coated copper powder (Coating with Sn-Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 9, the surface of the copper powder was coated with Sn alloy (Sn—Bi alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 40 g / L, bismuth methanesulfonate 40 g / L, thiourea 100 g / L, ethylenediaminetetraacetic acid 20 g / L, sodium hypophosphite 80 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Bi alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder aggregates copper particles and exhibits a dendritic shape. It was a dendritic Sn-coated copper powder whose surface was uniformly coated with a Sn—Bi alloy. The obtained dendritic Sn-coated copper powder was recovered and the amount of Sn-Bi alloy coating was measured. As a result, it was 43.3 mass% with respect to 100 mass of the entire Sn-coated copper powder. Further, the content of Bi contained in the Sn alloy was 40.8% by mass with respect to 100% by mass of the Sn alloy.

Moreover, as a result of observing the obtained dendritic Sn-coated copper powder by SEM, the short axis average diameter was 0.4 μm, and the ellipsoidal copper particles having a long axis average diameter of 1.5 μm were assembled and constituted. It had a dendritic shape.

The average particle diameter (D50) of the dendritic Sn-coated copper powder formed by the aggregation of the ellipsoidal copper particles was 10.9 μm, and the average thickness of the branch portion was 2.9 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.38 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 1.1 × 10 ⁻⁴ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 13]
<Preparation of dendritic Sn-coated copper powder (Coating with Sn-Zn alloy)>
Using 100 g of the dendritic copper powder obtained in Example 9, the surface of the copper powder was coated with Sn alloy (Sn—Zn alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, as the electroless Sn plating solution for alloys, stannous chloride 10 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, and sodium hypophosphite 70 g / L. A plating solution added at a concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Zn alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder aggregates copper particles and exhibits a dendritic shape. It was a dendritic Sn-coated copper powder having a surface uniformly coated with a Sn—Zn alloy. The obtained dendritic Sn-coated copper powder was recovered and the amount of Sn—Zn alloy coating was measured. As a result, it was 11.8% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy was 2.7% by mass with respect to 100% by mass of the Sn alloy.

Moreover, as a result of observing the obtained dendritic Sn-coated copper powder by SEM, the short axis average diameter was 0.3 μm, and the ellipsoidal copper particles having a long axis average diameter of 1.7 μm were assembled and constituted. It had a dendritic shape.

Further, the average particle diameter (D50) of the dendritic Sn-coated copper powder formed by aggregation of the ellipsoidal copper particles was 10.7 μm, and the average thickness of the branch portion was 3.1 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.62 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 2.0 × 10 ⁻⁴ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 14]
<Preparation of Dendritic Sn Coated Copper Powder (Coating with Sn—Ag—Bi Alloy)>
Using 100 g of the dendritic copper powder obtained in Example 9, the surface of the copper powder was coated with Sn alloy (Sn—Ag—Bi alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 50 g / L, bismuth methanesulfonate 5 g / L, silver citrate 20 g / L, thiourea 100 g / L, sodium hypophosphite 30 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Ag—Bi alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder aggregates copper particles and exhibits a dendritic shape. It was a dendritic Sn-coated copper powder having a surface uniformly coated with a Sn—Ag—Bi alloy. The obtained dendritic Sn-coated copper powder was recovered and the amount of Sn-Ag-Bi alloy coating was measured. As a result, it was 19.1% by mass with respect to 100% by mass of the entire Sn-coated copper powder. In addition, the content of Ag contained in the Sn alloy is 13.8% by mass with respect to the mass of Sn alloy of 100%, and the content of Bi contained in the Sn alloy is based on 100% of the mass of Sn alloy. It was 4.6% by mass.

Moreover, as a result of observing the obtained dendritic Sn-coated copper powder by SEM, the short axis average diameter was 0.4 μm, and the ellipsoidal copper particles having a long axis average diameter of 1.6 μm were assembled and constituted. It had a dendritic shape.

The average particle diameter (D50) of the dendritic Sn-coated copper powder formed by the aggregation of the ellipsoidal copper particles was 11.0 μm, and the average thickness of the branch portion was 3.0 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.59 g / cm ³ . Further, the BET specific surface area was 1.6 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 2.1 × 10 ⁻⁴ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 15]
<Preparation of dendritic Sn-coated copper powder (coated with Sn—Zn—Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 9, the surface of the copper powder was coated with Sn alloy (Sn—Zn—Bi alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous chloride 10 g / L, bismuth chloride 5 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, hypophosphorous acid A plating solution to which 70 g / L of sodium was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried with ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with Sn—Zn—Bi alloy was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder aggregates copper particles and exhibits a dendritic shape. It was a dendritic Sn-coated copper powder having a surface uniformly coated with a Sn—Zn—Bi alloy. The obtained dendritic Sn-coated copper powder was recovered and the amount of Sn—Zn—Bi alloy coating was measured. As a result, it was 11.5% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy is 2.8% by mass with respect to 100% by mass of the Sn alloy, and the content of Bi contained in the Sn alloy is based on 100% by mass of the Sn alloy. It was 1.1 mass%.

Moreover, as a result of observing the obtained dendritic Sn-coated copper powder by SEM, the short axis average diameter was 0.3 μm, and the ellipsoidal copper particles having a long axis average diameter of 1.7 μm were assembled and constituted. It had a dendritic shape.

The average particle diameter (D50) of the dendritic Sn-coated copper powder formed by the aggregation of the ellipsoidal copper particles was 9.7 μm, and the average thickness of the branch portion was 2.8 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.48 g / cm ³ . The BET specific surface area was 1.8 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 2.3 × 10 ⁻⁴ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Comparative Example 3]
<Preparation of electrolytic copper powder>
Copper powder was deposited on the cathode plate in the same manner as in Example 8 except that PEG as an additive and chlorine ions were not added to the electrolytic solution.

<Preparation of Sn-coated copper powder>
Next, Sn was coated on the copper surface using the obtained copper powder in the same manner as in Example 8 to obtain Sn-coated copper powder. When the Sn coating amount of the Sn-coated copper powder was measured, it was 12.8% by mass relative to 100% by mass of the entire Sn-coated copper powder.

FIG. 23 shows the result of observing the shape of the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM. As shown in the photograph of FIG. 23, the shape of the obtained Sn-coated copper powder is a dendritic shape in which granular copper particles are aggregated, and the surface of the copper powder is in a state where Sn is coated. It was. The average particle diameter (D50) of the Sn-coated copper powder was 16.4 μm.

<Conductive paste>
Next, 40 g of Sn-coated copper powder prepared by the above-described method is mixed with 20 g of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 8.3 × 10 ⁻⁴ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 4]
For comparison with PEG added in Example 8, the characteristics of the conductive paste by Sn-coated copper powder in which Sn was coated on copper powder prepared by adding thiourea (manufactured by Wako Pure Chemical Industries, Ltd.) It evaluated and compared with the characteristic of the electrically conductive paste produced using the dendritic Sn coat | court copper powder in an Example.

<Preparation of electrolytic copper powder>
Specifically, thiourea was added to the electrolyte so that the concentration in the electrolyte was 500 mg / L instead of PEG as an additive, and the copper powder was treated in the same manner as in Example 8 except that It was deposited on a plate.

<Preparation of Sn-coated copper powder>
Next, Sn was coated on the copper surface using the obtained copper powder in the same manner as in Example 8 to obtain Sn-coated copper powder. When the Sn coating amount of the Sn-coated copper powder was measured, it was 12.7% by mass relative to 100% by mass of the entire Sn-coated copper powder.

As a result of observing the shape of the obtained Sn-coated copper powder in a field of view with a magnification of 1,000 times by SEM, it was a copper powder having a dendritic shape, but the average thickness of the branch portion was 10 μm or more. The copper powder had a very large dendritic shape, and Sn was coated on the surface of the copper powder. The average particle diameter (D50) of the Sn-coated copper powder was 12.8 μm.

<Conductive paste>
Next, 40 g of Sn-coated copper powder prepared by the above-described method is mixed with 20 g of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 8.5 × 10 ⁻⁴ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

≪Example, comparative example≫
(3) Test using Sn-coated copper powder according to the third embodiment [Example 16]
<Preparation of electrolytic copper powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, as the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L was used. In addition, safranin (manufactured by Kanto Chemical Co., Inc.) as an additive is added to the electrolytic solution so that the concentration in the electrolytic solution is 85 mg / L, and a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is further added to the electrolytic solution. It added so that it might become 55 mg / L as a chloride ion (chlorine ion) density | concentration in it.

Then, the current density of the cathode is 18 A / dm ² under the condition that the temperature is maintained at 25 ° C. while circulating the electrolytic solution whose concentration is adjusted as described above at a flow rate of 15 L / min using a metering pump. Was energized to deposit copper powder on the cathode plate.

The electrolytic copper powder deposited on the cathode plate was recovered by mechanically scraping it off the bottom of the electrolytic cell using a scraper, and the recovered copper powder was washed with pure water and then put in a vacuum dryer and dried. .

As a result of observing the shape of the copper powder thus obtained in the field of view with a magnification of 1,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder was a main chain that grew linearly and the main trunk. It was a dendritic copper powder having a two-dimensional or three-dimensional dendritic shape having a plurality of branches branched linearly from and branches further branched from the branches.

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

Specifically, as the electroless Sn plating solution, stannous borofluoride 20 g / L, borofluoric acid 200 g / L, thiourea 50 g / L, sodium borohydride 40 g / L, sodium borate 10 g / L at each concentration. The plating solution added in was prepared. In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 60 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 10.2% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with Sn, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.40 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 27.9 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.61 g / cm ³ . Moreover, the BET specific surface area was 0.92 m < ² > / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.2 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 17]
<Preparation of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L is used, and safranin is added to the electrolytic solution so that the concentration in the electrolytic solution is 200 mg / L. Further, copper powder was deposited on the cathode plate under the same conditions as in Example 16 except that a hydrochloric acid solution was added so that the chlorine ion concentration in the electrolytic solution was 100 mg / L.

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution prepared by adding stannous chloride 10 g / L, sodium citrate 40 g / L, ethylenediaminetetraacetic acid 20 g / L, and titanium chloride 50 g / L at each concentration was prepared. . In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 65 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 17.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with Sn, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.19 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 9.8 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.63 g / cm ³ . Further, the BET specific surface area was 2.01 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.9 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 18]
<Preparation of dendritic Sn-coated copper powder>
Using 100 g of the dendritic copper powder obtained in Example 17, Sn coating was performed on the surface of the copper powder by electroless Sn plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium hydroxide 100 g / L, and sodium citrate 40 g / L were added at respective concentrations was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 80 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 8.1% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with Sn, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

Also, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross-sectional shape with an average cross-sectional thickness of 0.18 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 9.7 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.71 g / cm ³ . The BET specific surface area was 2.10 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.8 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 19]
<Preparation of dendritic Sn-coated copper powder (coated with Sn—Ag alloy)>
Using 100 g of the dendritic copper powder obtained in Example 17, the surface of the copper powder was coated with Sn alloy (Sn—Ag alloy) by electroless Sn plating to produce Sn-coated copper powder.

Specifically, 50 g / L of stannous methanesulfonate, 20 g / L of silver citrate, 100 g / L of thiourea, and 30 g / L of sodium hypophosphite were added at various concentrations as the electroless Sn plating solution for alloys. A plating solution was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Ag alloy was obtained. The Sn-coated copper powder was recovered and the amount of Sn-Ag alloy coating was measured. As a result, it was 18.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Moreover, content of Ag contained in Sn alloy was 24.8 mass% with respect to 100 mass of Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn—Ag alloy, and a main trunk that grows linearly and a plurality of branches that branch linearly from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having branches further branched from the branches.

Also, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross-sectional shape with an average cross-sectional thickness of 0.18 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.2 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.60 g / cm ³ . Moreover, the BET specific surface area was 2.08 m < ² > / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.2 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 20]
<Preparation of dendritic Sn-coated copper powder (Coating with Sn-Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 17, the surface of the copper powder was coated with Sn alloy (Sn—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 40 g / L, bismuth methanesulfonate 40 g / L, thiourea 100 g / L, ethylenediaminetetraacetic acid 20 g / L, sodium hypophosphite 80 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Bi alloy was obtained. As a result of collecting the Sn-coated copper powder and measuring the coating amount of the Sn—Bi alloy, it was 42.3% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Bi contained in the Sn alloy was 41.9% by mass with respect to 100% by mass of the Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn—Bi alloy, and a main trunk that grows linearly and a plurality of branches that branch linearly from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having branches further branched from the branches.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat shape with a cross-sectional thickness of 0.16 μm on average, and the copper particles were constituted into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.4 μm.

Moreover, the bulk density of the obtained dendritic Sn-coated copper powder was 0.65 g / cm ³ . The BET specific surface area was 2.12 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.9 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 21]
<Preparation of dendritic Sn-coated copper powder (Coating with Sn-Zn alloy)>
Using 100 g of the dendritic copper powder obtained in Example 17, the surface of the copper powder was coated with Sn alloy (Sn—Zn alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as the electroless Sn plating solution for alloys, stannous chloride 10 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, and sodium hypophosphite 70 g / L. A plating solution added at a concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Zn alloy was obtained. As a result of collecting the Sn-coated copper powder and measuring the coating amount of the Sn—Zn alloy, it was 11.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy was 2.1% by mass with respect to 100% by mass of the Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn—Zn alloy, and a main trunk that grows linearly and a plurality of branches that branch linearly from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having branches further branched from the branches.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.19 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.4 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.66 g / cm ³ . Further, the BET specific surface area was 2.03 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.6 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 22]
<Preparation of Dendritic Sn Coated Copper Powder (Coating with Sn—Ag—Bi Alloy)>
Using 100 g of the dendritic copper powder obtained in Example 17, the surface of the copper powder was coated with Sn alloy (Sn—Ag—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 50 g / L, bismuth methanesulfonate 5 g / L, silver citrate 20 g / L, thiourea 100 g / L, sodium hypophosphite 30 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Ag—Bi alloy was obtained. As a result of collecting the Sn-coated copper powder and measuring the coating amount of the Sn—Ag—Bi alloy, it was 18.9% by mass with respect to 100% by mass of the entire Sn-coated copper powder. In addition, the content of Ag contained in the Sn alloy is 14.8% by mass with respect to the mass of Sn alloy of 100%, and the content of Bi contained in the Sn alloy is based on 100% of the mass of Sn alloy. 3.1% by mass.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn-Ag-Bi alloy, and a main trunk that grows linearly and a plurality of linear branches branched from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having a branch further branched from the branch.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder have a flat shape with a cross-sectional thickness of 0.22 μm on average, and the copper particles were constituted into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.8 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.67 g / cm ³ . The BET specific surface area was 2.11 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.7 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 23]
<Preparation of dendritic Sn-coated copper powder (Sn—Zn—Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 17, the surface of the copper powder was coated with Sn alloy (Sn—Zn—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous chloride 10 g / L, bismuth chloride 5 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, hypophosphorous acid A plating solution to which sodium 70 g / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried with ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with Sn—Zn—Bi alloy was obtained. The Sn-coated copper powder was recovered and the amount of Sn-Zn-Bi alloy coating was measured. As a result, it was 11.1% by mass relative to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy is 2.0% by mass with respect to 100% by mass of the Sn alloy, and the content of Bi contained in the Sn alloy is based on 100% by mass of the Sn alloy. It was 1.4% by mass.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before being coated with the Sn alloy. A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with a Sn—Zn—Bi alloy, and a main trunk that grows linearly and a plurality of linear branches branched from the main trunk And a dendritic Sn-coated copper powder having a dendritic shape having a branch further branched from the branch.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.19 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 10.4 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 0.66 g / cm ³ . Further, the BET specific surface area was 2.03 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.9 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 24]
<Preparation of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 5 g / L and a sulfuric acid concentration of 150 g / L was used, and safranin was added to the electrolytic solution so that the concentration in the electrolytic solution was 100 mg / L. Further, copper powder was deposited on the cathode plate under the same conditions as in Example 16 except that a hydrochloric acid solution was added so that the chlorine ion concentration in the electrolytic solution was 10 mg / L.

As a result of observing the shape of the copper powder thus obtained in the field of view with a magnification of 1,000 times by the SEM method described above, the deposited copper powder was linearly grown and branched linearly from the main trunk. The copper powder had a two-dimensional or three-dimensional dendritic shape having a plurality of branches and branches further branched from the branches.

<Preparation of dendritic Sn-coated copper powder>
Next, using the dendritic copper powder produced by the method described above, Sn coating was performed on the surface of the copper powder by electroless Sn plating under the same conditions as in Example 16 to produce Sn-coated copper powder.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 10.7% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic Sn-coated copper powder coated with Sn, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

The copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross-sectional shape with an average cross-sectional thickness of 3.9 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Sn-coated copper powder was 62.0 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 3.10 g / cm ³ . The BET specific surface area was 0.99 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.4 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Comparative Example 5]
<Preparation of electrolytic copper powder>
Copper powder was deposited on the cathode plate in the same manner as in Example 16 except that the conditions were such that safranin as an additive and chlorine ions were not added to the electrolytic solution.

<Preparation of Sn-coated copper powder>
The obtained copper powder was coated with Sn on the copper surface in the same manner as in Example 16 to obtain Sn-coated copper powder. When the Sn coating amount of the Sn-coated copper powder was measured, it was 12.2% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

FIG. 24 shows the result of observing the shape of the obtained Sn-coated copper powder with a SEM field of view at a magnification of 1,000 times. As shown in the photograph of FIG. 24, the shape of the obtained Sn-coated copper powder is a dendritic shape in which granular copper particles are gathered, and the surface of the copper powder is in a state where Sn is coated. The average particle diameter (D50) of the Sn-coated copper powder was 25.2 μm.

<Conductive paste>
Next, 40 g of Sn-coated copper powder prepared by the above-described method is mixed with 20 g of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), the mixture was kneaded at 1200 rpm for 3 minutes three times to obtain a paste. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 82.0 × 10 ⁻⁵ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 6]
The characteristic of the conductive paste by Sn coat copper powder which coat | covered Sn on the conventional flat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Sn coat copper powder in an Example.

The flat copper powder was prepared by mechanically flattening granular electrolytic copper powder. Specifically, 5 g of stearic acid was added to 500 g of granular atomized copper powder (manufactured by Mekin Metal Powders Co., Ltd.) having an average particle diameter of 7.9 μm, and flattened with a ball mill. The ball mill was charged with 5 kg of 3 mm zirconia beads, and flattened by rotating for 90 minutes at a rotation speed of 500 rpm.

The obtained flat copper powder was coated with Sn in the same manner as in Example 16. The coating amount of Sn of the produced flat Sn-coated copper powder was 12.8% by mass with respect to 100% by mass of the flat Sn-coated copper powder.

Moreover, as a result of measuring with a laser diffraction / scattering method particle size distribution measuring instrument, the average particle diameter (D50) was 22.7 μm for the flat Sn-coated copper powder produced in this way, and as a result of observation by SEM, The cross-sectional average thickness was 0.4 μm.

Next, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the obtained flat Sn-coated copper powder. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 35.4 × 10 ⁻⁵ Ω · cm, which is higher in specific resistance value and inferior in conductivity than the copper paste obtained in Example 1. there were.

≪Example, comparative example≫
(4) Test using Sn-coated copper powder according to the fourth embodiment [Example 25]
<Preparation of flat copper particle agglomerated powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, an electrolytic solution having a composition with a copper ion concentration of 10 g / L and a sulfuric acid concentration of 100 g / L was used. In addition, Janus Green B (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to this electrolytic solution so that the concentration in the electrolytic solution was 120 mg / L, and polyethylene glycol having a molecular weight of 2000 (Wako Pure Chemical Industries, Ltd.) was added. Co., Ltd.) was added so that the concentration in the electrolyte was 850 mg / L. Furthermore, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion (chlorine ion) concentration in the electrolyte solution was 50 mg / L.

Then, while circulating the electrolytic solution whose concentration was adjusted as described above at a flow rate of 10 L / min using a metering pump, the temperature was maintained at 30 ° C. and the current density of the cathode was 25 A / dm ^2. Then, copper powder was deposited on the cathode plate.

The electrolytic copper powder deposited on the cathode plate was recovered by mechanically scraping it off the bottom of the electrolytic cell using a scraper, and the recovered copper powder was washed with pure water and then put in a vacuum dryer and dried. .

As a result of observing the shape of the obtained electrolytic copper powder by the method using the above-mentioned scanning electron microscope (SEM), the deposited copper powder is a copper powder having a shape in which flat copper particles are aggregated (flat copper). Particle agglomerated powder).

<Preparation of Flat Sn Coated Copper Particle Aggregated Powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the tabular copper particle aggregated powder prepared by the above-described method, thereby preparing Sn-coated copper powder.

Specifically, as the electroless Sn plating solution, stannous borofluoride 20 g / L, borofluoric acid 200 g / L, thiourea 50 g / L, sodium borohydride 40 g / L, sodium borate 10 g / L at each concentration. The plating solution added in was prepared. To this electroless Sn plating solution, 100 g of the tabular copper particle aggregated powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 60 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with Sn coated on the surface of the tabular copper particle aggregated powder was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder uniformly coats the surface of the copper powder before coating with Sn. The resulting Sn-coated copper powder had a shape of agglomerated powder in which a plurality of Sn-coated copper particles having a flat plate shape were aggregated to form an aggregate. The Sn-coated copper powder (flat Sn-coated copper particle agglomerated powder) was recovered and the amount of Sn covered was measured, and it was 10.2% by mass relative to 100% by mass of the entire Sn-coated copper powder.

Further, the obtained Sn-coated copper powder has a flat plate shape with an average cross-sectional thickness of 0.34 μm, and the size thereof is an average major axis diameter (diameter indicated by “d” in the schematic diagram of FIG. 15). It was 6 μm. The size of the agglomerated copper powder in which a plurality of the flat Sn-coated copper particles aggregated to form an aggregate was 8.3 μm in terms of average particle diameter (D50).

Furthermore, the tap density of the obtained Sn-coated copper powder was 2.88 g / cm ³ . The BET specific surface area was 2.5 m ² / g.

<Conductive paste>
Next, the flat Sn-coated copper particle aggregate powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the tabular Sn-coated copper particle aggregate powder produced. Using a small kneader (Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), a paste was formed by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.4 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 26]
<Preparation of flat copper particle agglomerated powder>
An electrolytic solution having a copper ion concentration of 8 g / L and a sulfuric acid concentration of 110 g / L is used, and Janus Green B as an additive is added to the electrolytic solution to a concentration of 160 mg / L in the electrolytic solution. Polyethylene glycol having a molecular weight of 2000 (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the concentration in the electrolyte was 800 mg / L. Furthermore, the hydrochloric acid solution was added so that the chlorine ion concentration in the electrolytic solution was 125 mg / L.

Then, while circulating the electrolytic solution whose concentration was adjusted as described above at a flow rate of 20 L / min using a metering pump, the temperature was maintained at 35 ° C. and the current density of the cathode was 30 A / dm ^2. Except for these, copper powder was deposited on the cathode plate in the same manner as in Example 25.

<Preparation of Flat Sn Coated Copper Particle Aggregated Powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the tabular copper particle aggregated powder prepared by the above-described method, thereby preparing Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium citrate 40 g / L, ethylenediaminetetraacetic acid 20 g / L, and titanium chloride 50 g / L were added at respective concentrations was prepared. In this electroless Sn plating solution, 100 g of the tabular copper particle aggregate powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 65 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with Sn coated on the surface of the tabular copper particle aggregated powder was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder uniformly coats the surface of the copper powder before coating with Sn. The resulting Sn-coated copper powder had a shape of agglomerated powder in which a plurality of Sn-coated copper particles having a flat plate shape were aggregated to form an aggregate. The Sn-coated copper powder (flat Sn-coated copper particle agglomerated powder) was recovered and the Sn coating amount was measured, and it was 16.9% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Further, the obtained Sn-coated copper powder was a flat plate having an average cross-sectional thickness of 0.22 μm, and the average major axis diameter was 3.7 μm. The size of the agglomerated copper powder in which a plurality of the flat Sn-coated copper particles were aggregated to form an aggregate was 13.4 μm in terms of average particle diameter (D50).

Furthermore, the tap density of the obtained Sn-coated copper powder was 3.67 g / cm ³ . The BET specific surface area was 1.8 m ² / g.

<Conductive paste>
Next, the flat Sn-coated copper particle aggregate powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the tabular Sn-coated copper particle aggregate powder produced. Using a small kneader (Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), a paste was formed by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.1 × 10 ⁻⁵ Ω · cm, and it was found that the film exhibited excellent conductivity.

[Example 27]
<Preparation of flat copper particle agglomerated powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, as the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L was used. In addition, Janus Green B (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to the electrolytic solution so that the concentration in the electrolytic solution was 130 mg / L, and polyethylene glycol having a molecular weight of 2000 (Wako Pure Chemical Industries, Ltd.) was added. Co., Ltd.) was added to a concentration of 900 mg / L in the electrolytic solution. Furthermore, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chlorine ion concentration in the electrolytic solution was 50 mg / L.

Then, while circulating the electrolytic solution whose concentration was adjusted as described above at a flow rate of 10 L / min using a metering pump, the temperature was maintained at 30 ° C. and the current density of the cathode was 25 A / dm ^2. Then, copper powder was deposited on the cathode plate.

<Preparation of Flat Sn Coated Copper Particle Aggregated Powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the tabular copper particle aggregated powder prepared by the above-described method, thereby preparing Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium hydroxide 100 g / L, and sodium citrate 40 g / L were added at respective concentrations was prepared. In this electroless Sn plating solution, 100 g of the tabular copper particle aggregate powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 80 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with Sn coated on the surface of the tabular copper particle aggregated powder was obtained. As a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 times by SEM, at least 90% by number or more of the Sn-coated copper powder uniformly coats the surface of the copper powder before coating with Sn. The resulting Sn-coated copper powder had a shape of agglomerated powder in which a plurality of Sn-coated copper particles having a flat plate shape were aggregated to form an aggregate. The Sn-coated copper powder (flat Sn-coated copper particle agglomerated powder) was recovered and the Sn coating amount was measured, and it was 8.3% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Further, the obtained Sn-coated copper powder is a flat plate having an average cross-sectional thickness (0.15 μm), and the average major axis diameter (diameter indicated by “d” in the schematic diagram of FIG. 15) is 2. .8 μm. The size of the agglomerated copper powder formed by aggregating a plurality of the flat Sn-coated copper particles into an aggregate was 11.3 μm in terms of average particle diameter (D50).

Furthermore, the tap density of the obtained Sn-coated copper powder was 2.63 g / cm ³ . Further, the BET specific surface area was 2.2 m ² / g.

<Conductive paste>
Next, the flat Sn-coated copper particle aggregate powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the tabular Sn-coated copper particle aggregate powder produced. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.6 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 28]
<Preparation of Flat Sn-Coated Copper Particle Aggregated Powder (Coating with Sn-Ag Alloy)>
Using 100 g of the tabular copper particle agglomerated powder obtained in Example 26, the surface of the copper powder was coated with Sn alloy (Sn—Ag alloy) by electroless Sn plating to produce Sn-coated copper powder.

Specifically, 50 g / L of stannous methanesulfonate, 20 g / L of silver citrate, 100 g / L of thiourea, and 30 g / L of sodium hypophosphite were added at various concentrations as the electroless Sn plating solution for alloys. A plating solution was prepared. In this electroless Sn plating solution, 100 g of the tabular copper particle aggregated powder prepared by the above-described method is put in the electroless Sn plating solution and stirred at 25 ° C. for 10 minutes, and then the bath temperature is heated to 70 ° C. to 60 ° C. Stir for minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the Sn—Ag alloy coated on the surface of the tabular copper particle aggregated powder was obtained. The Sn-coated copper powder was recovered and the amount of Sn-Ag alloy coating was measured. As a result, it was 18.3% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Moreover, content of Ag contained in Sn alloy was 14.5 mass% with respect to 100 mass of Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Sn-coated copper powder is uniformly on the surface of the copper powder before coating the Sn alloy. It was Sn-coated copper powder coated with Sn alloy, and the shape of aggregated powder was formed by aggregation of a plurality of Sn-coated copper particles having a flat plate shape.

Further, the obtained Sn-coated copper powder (flat Sn-coated copper particle agglomerated powder) is a flat plate having an average cross-sectional thickness of 0.25 μm, and the size thereof is the average major axis diameter (in the schematic diagram of FIG. 15). The diameter indicated by “d” was 3.4 μm. The size of the agglomerated copper powder formed by aggregating a plurality of the flat Sn-coated copper particles into an aggregate was 14.3 μm in terms of average particle diameter (D50).

Furthermore, the tap density of the obtained Sn-coated copper powder was 3.42 g / cm ³ . The BET specific surface area was 1.9 m ² / g.

<Conductive paste>
Next, the flat Sn-coated copper particle aggregate powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the tabular Sn-coated copper particle aggregate powder produced. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.3 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 29]
<Preparation of Flat Sn Coated Copper Particle Aggregated Powder (Coating with Sn-Bi Alloy)>
Using 100 g of the tabular copper particle aggregate powder obtained in Example 26, the surface of the copper powder was coated with Sn alloy (Sn—Bi alloy) by electroless Sn plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 40 g / L, bismuth methanesulfonate 40 g / L, thiourea 100 g / L, ethylenediaminetetraacetic acid 20 g / L, sodium hypophosphite 80 g A plating solution to which / L was added at each concentration was prepared. In this electroless Sn plating solution, 100 g of tabular copper particle aggregated powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the Sn—Bi alloy coated on the surface of the tabular copper particle aggregated powder was obtained. As a result of collecting the Sn-coated copper powder and measuring the coating amount of the Sn—Bi alloy, it was 42.3% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Bi contained in the Sn alloy was 41.2% by mass with respect to 100% by mass of the Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Sn-coated copper powder is uniformly on the surface of the copper powder before coating the Sn alloy. It was Sn-coated copper powder coated with Sn alloy, and the shape of aggregated powder was formed by aggregation of a plurality of Sn-coated copper particles having a flat plate shape.

Further, the obtained Sn-coated copper powder (flat Sn-coated copper particle aggregated powder) is a flat plate having an average cross-sectional thickness of 0.28 μm, and the size thereof is the average major axis diameter (in the schematic diagram of FIG. 15). The diameter indicated by “d” was 3.5 μm. The size of the agglomerated copper powder in which a plurality of the flat Sn-coated copper particles were aggregated to form an aggregate was 13.9 μm in terms of average particle diameter (D50).

Furthermore, the tap density of the obtained Sn-coated copper powder was 3.55 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

<Conductive paste>
Next, the flat Sn-coated copper particle aggregate powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the tabular Sn-coated copper particle aggregate powder produced. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.4 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 30]
<Preparation of Flat Sn Coated Copper Particle Aggregated Powder (Coating with Sn-Zn Alloy)>
Using 100 g of the tabular copper particle aggregate powder obtained in Example 26, the surface of the copper powder was coated with Sn alloy (Sn—Zn alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as the electroless Sn plating solution for alloys, stannous chloride 10 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, and sodium hypophosphite 70 g / L. A plating solution added at a concentration was prepared. In this electroless Sn plating solution, 100 g of tabular copper particle aggregated powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder in which the surface of the tabular copper particle aggregated powder was coated with Sn—Zn alloy was obtained. As a result of collecting the Sn-coated copper powder and measuring the coating amount of the Sn—Zn alloy, it was 12.3% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy was 2.7% by mass with respect to 100% by mass of the Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Sn-coated copper powder is uniformly on the surface of the copper powder before coating the Sn alloy. It was Sn-coated copper powder coated with Sn alloy, and the shape of aggregated powder was formed by aggregation of a plurality of Sn-coated copper particles having a flat plate shape.

The obtained Sn-coated copper powder (flat Sn-coated copper particle agglomerated powder) has a flat plate shape with a cross-sectional thickness (average cross-sectional thickness) of 0.24 μm, and the size is the average major axis diameter (see FIG. 15) (diameter indicated by “d” in the schematic diagram) was 2.9 μm. The size of the agglomerated copper powder formed by aggregating a plurality of the flat Sn-coated copper particles into an aggregate was 14.8 μm in terms of average particle diameter (D50).

Furthermore, the tap density of the obtained Sn-coated copper powder was 3.21 g / cm ³ . The BET specific surface area was 1.8 m ² / g.

<Conductive paste>
Next, the flat Sn-coated copper particle aggregate powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the tabular Sn-coated copper particle aggregate powder produced. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.6 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 31]
<Preparation of Flat Sn Coated Copper Particle Aggregated Powder (Coating with Sn-Ag-Bi Alloy)>
Using 100 g of the tabular copper particle agglomerated powder obtained in Example 26, the surface of the copper powder was coated with Sn alloy (Sn—Ag—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 50 g / L, bismuth methanesulfonate 5 g / L, silver citrate 20 g / L, thiourea 100 g / L, sodium hypophosphite 30 g A plating solution to which / L was added at each concentration was prepared. In this electroless Sn plating solution, 100 g of tabular copper particle aggregated powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Sn-coated copper powder in which the Sn—Ag—Bi alloy was coated on the surface of the tabular copper particle aggregated powder was obtained. The Sn-coated copper powder was recovered and the amount of Sn-Ag-Bi alloy coating was measured. As a result, it was 18.3% by mass with respect to 100% by mass of the entire Sn-coated copper powder. In addition, the content of Ag contained in the Sn alloy is 12.2% by mass with respect to 100% by mass of the Sn alloy, and the content of Bi contained in the Sn alloy is based on 100% by mass of the Sn alloy. It was 3.4% by mass.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Sn-coated copper powder is uniformly on the surface of the copper powder before coating the Sn alloy. It was Sn-coated copper powder coated with Sn alloy, and the shape of aggregated powder was formed by aggregation of a plurality of Sn-coated copper particles having a flat plate shape.

The obtained Sn-coated copper powder (flat Sn-coated copper particle agglomerated powder) has a flat plate shape with a cross-sectional thickness (average cross-sectional thickness) of 0.23 μm, and the size is an average major axis diameter (see FIG. 15 (diameter indicated by “d” in the schematic diagram) was 3.9 μm. The size of the agglomerated copper powder in which a plurality of the flat Sn-coated copper particles were aggregated to form an aggregate was 14.1 μm in terms of average particle diameter (D50).

Furthermore, the tap density of the obtained Sn-coated copper powder was 3.18 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

<Conductive paste>
Next, the flat Sn-coated copper particle aggregate powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the tabular Sn-coated copper particle aggregate powder produced. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 7.7 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 32]
<Preparation of Flat Sn Coated Copper Particle Aggregated Powder (Coating with Sn-Zn-Bi Alloy)>
Using 100 g of the tabular copper particle aggregate powder obtained in Example 26, the surface of the copper powder was coated with Sn alloy (Sn—Zn—Bi alloy) by electroless Sn plating to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous chloride 10 g / L, bismuth chloride 5 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, hypophosphorous acid A plating solution to which sodium 70 g / L was added at each concentration was prepared. In this electroless Sn plating solution, 100 g of tabular copper particle aggregated powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder in which Sn—Zn—Bi alloy was coated on the surface of the tabular copper particle aggregated powder was obtained. The Sn-coated copper powder was recovered and the amount of Sn-Zn-Bi alloy coating was measured. As a result, it was 11.0% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy is 1.9% by mass with respect to 100% by mass of the Sn alloy, and the content of Bi contained in the Sn alloy is based on 100% by mass of the Sn alloy. It was 1.8% by mass.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Sn-coated copper powder is uniformly on the surface of the copper powder before coating the Sn alloy. It was Sn-coated copper powder coated with Sn alloy, and the shape of aggregated powder was formed by aggregation of a plurality of Sn-coated copper particles having a flat shape.

The obtained Sn-coated copper powder (flat Sn-coated copper particle agglomerated powder) has a flat plate shape with a cross-sectional thickness (average cross-sectional thickness) of 0.22 μm, and the size is an average major axis diameter (see FIG. 15) (diameter indicated by “d” in the schematic diagram) was 3.8 μm. The size of the agglomerated copper powder formed by aggregating a plurality of the flat Sn-coated copper particles into an aggregate was 15.1 μm in terms of average particle diameter (D50).

Furthermore, the tap density of the obtained Sn-coated copper powder was 3.20 g / cm ³ . The BET specific surface area was 1.8 m ² / g.

<Conductive paste>
Next, the flat Sn-coated copper particle aggregate powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the tabular Sn-coated copper particle aggregate powder produced. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.1 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Comparative Example 7]
Copper powder was deposited on the cathode plate in the same manner as in Example 25, except that the conditions were such that Janus Green B, polyethylene glycol, and chlorine ions were not added to the electrolytic solution. The shape of the obtained Sn-coated copper powder was a dendritic shape in which particulate copper was aggregated.

Then, the surface of the obtained copper powder was coated with Sn in the same manner as in Example 25 to obtain Sn-coated copper powder. When the Sn coating amount of the Sn-coated copper powder was measured, it was 12.6% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

FIG. 25 shows the result of observing the shape of the obtained Sn-coated copper powder with a SEM field of view at a magnification of 1,000 times. As shown in the photograph of FIG. 25, the shape of the obtained Sn-coated copper powder is a dendritic shape in which granular copper particles are aggregated, and the surface of the copper powder is in a state where Sn is coated. The average particle diameter (D50) of the Sn-coated copper powder was 22.5 μm.

40 g of Sn-coated copper powder produced by the above-described method is mixed with 20 g of a phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 82.4 × 10 ⁻⁵ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 8]
The characteristic of the conductive paste by Sn coat copper powder which coat | covered Sn with the conventional flat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the flat Sn coat copper particle aggregate powder in an Example. .

The flat copper powder was prepared by mechanically flattening granular electrolytic copper powder. Specifically, 5 g of stearic acid was added to 500 g of granular atomized copper powder (manufactured by Mekin Metal Powders Co., Ltd.) having an average particle diameter of 7.9 μm, and flattened with a ball mill. The ball mill was charged with 5 kg of 3 mm zirconia beads, and flattened by rotating for 90 minutes at a rotation speed of 500 rpm.

For the obtained flat copper powder, Sn was coated on the surface of the copper powder in the same manner as in Example 25. The coating amount of Sn of the produced flat Sn-coated copper powder was 12.9% by mass with respect to 100% by mass of the flat Sn-coated copper powder.

The flat Sn-coated copper powder thus produced was measured with a laser diffraction / scattering particle size distribution measuring instrument. As a result, the average particle diameter (D50) was 23.8 μm, and the cross section was observed with SEM. The average thickness was 0.40 μm.

Next, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the obtained flat Sn-coated copper powder. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 35.5 × 10 ⁻⁵ Ω · cm, which is higher in specific resistance value and inferior in conductivity than the copper paste obtained in Example 1. there were.

≪Example, comparative example≫
(5) Test using Sn-coated copper powder according to the fifth embodiment [Example 33]
<Preparation of electrolytic copper powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, as the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L was used. In addition, Janus Green B (manufactured by Kanto Chemical Co., Inc.) as an additive is added to the electrolytic solution so that the concentration in the electrolytic solution is 80 mg / L, and a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is further added. It added so that it might become 30 mg / L as chloride ion (chlorine ion) density | concentration in electrolyte solution.

Then, the current density of the cathode is set to 15 A / dm ² under the condition that the temperature is maintained at 25 ° C. while circulating the electrolytic solution whose concentration is adjusted as described above at a flow rate of 15 L / min using a metering pump. Was energized to deposit copper powder on the cathode plate.

The electrolytic copper powder deposited on the cathode plate was recovered by mechanically scraping it off the bottom of the electrolytic cell using a scraper, and the recovered copper powder was washed with pure water and then put in a vacuum dryer and dried. .

As a result of observing the shape of the copper powder thus obtained in the field of view with a magnification of 1,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder was a main chain that grew linearly and the main trunk. It was a dendritic copper powder exhibiting a two-dimensional or three-dimensional dendritic shape in which copper particles having a shape having a plurality of branches branched linearly from the branch and branches further branched from the branch were collected. .

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

Specifically, as the electroless Sn plating solution, stannous borofluoride 20 g / L, borofluoric acid 200 g / L, thiourea 50 g / L, sodium borohydride 40 g / L, sodium borate 10 g / L at each concentration. The plating solution added in was prepared. In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 60 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 10.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Further, as a result of observing the obtained Sn-coated copper powder with a scanning electron microscope (SEM) in a field of view of 5,000 times, at least 90% by number or more of the Sn-coated copper powder was dendritic before coating with Sn. A two-dimensional or three-dimensional dendritic shape in which Sn is uniformly coated on the surface of copper powder, a main trunk that grows linearly, and a plurality of branches that branch straight from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder were flat plate having an average cross-sectional thickness of 0.09 μm, and had fine convex portions on the surface thereof. The height of the convex portions formed on the surface was 0.05 μm on average.

The average particle diameter (D50) of the dendritic Sn-coated copper powder was 21.3 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.22 g / cm ³ . Further, the BET specific surface area was 1.68 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.5 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 34]
<Preparation of electrolytic copper powder>
An electrolytic solution having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L is used, and Janus Green B as an additive is added to the electrolytic solution to a concentration of 150 mg / L in the electrolytic solution. Copper powder was deposited on the cathode plate under the same conditions as in Example 33 except that the hydrochloric acid solution was further added so that the chlorine ion concentration in the electrolytic solution was 100 mg / L.

<Preparation of dendritic Sn-coated copper powder>
Next, Sn coating was performed on the surface of the copper powder by electroless Sn plating using the dendritic copper powder prepared by the above-described method to prepare Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium citrate 40 g / L, ethylenediaminetetraacetic acid 20 g / L, and titanium chloride 50 g / L were added at respective concentrations was prepared. In this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 65 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 17.6% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Sn-coated copper powder is uniform on the surface of the dendritic copper powder before coating with Sn. A two-dimensional or three-dimensional dendritic shape coated with Sn, a plurality of branches branched linearly from the trunk, and branches further branched from the branches It was a dendritic Sn-coated copper powder exhibiting a dendritic shape having

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross section with an average thickness of 0.11 μm and had fine convex portions on the surface. The height of the convex portions formed on the surface was 0.25 μm on average.

The average particle size (D50) of the dendritic Sn-coated copper powder was 8.5 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.26 g / cm ³ . The BET specific surface area was 2.79 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.1 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 35]
<Preparation of dendritic Sn-coated copper powder>
Using 100 g of the dendritic copper powder obtained in Example 34, Sn coating was performed on the surface of the copper powder by electroless Sn plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution, a plating solution in which stannous chloride 10 g / L, sodium hydroxide 100 g / L, and sodium citrate 40 g / L were added at respective concentrations was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 80 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder having a dendritic copper powder coated with Sn was obtained. When the Sn-coated copper powder was recovered and the Sn coating amount was measured, it was 8.4% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

In addition, as a result of observing the obtained Sn-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Sn-coated copper powder is uniformly on the surface of the dendritic copper powder before Sn coating A two-dimensional or three-dimensional dendritic shape covered with Sn, a main trunk that grows linearly, a plurality of branches that branch linearly from the main trunk, and branches that branch further from the branch This was a dendritic Sn-coated copper powder having a dendritic shape.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder were flat plate having a cross-sectional thickness of 0.16 μm on average, and had fine convex portions on the surface. The height of the convex portions formed on the surface was 0.28 μm on average.

The average particle diameter (D50) of the dendritic Sn-coated copper powder was 8.8 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.24 g / cm ³ . The BET specific surface area was 2.81 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.8 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 36]
<Preparation of dendritic Sn-coated copper powder (coated with Sn—Ag alloy)>
Using 100 g of the dendritic copper powder obtained in Example 34, the surface of the copper powder was coated with Sn alloy (Sn—Ag alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, 50 g / L of stannous methanesulfonate, 20 g / L of silver citrate, 100 g / L of thiourea, and 30 g / L of sodium hypophosphite were added at various concentrations as the electroless Sn plating solution for alloys. A plating solution was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Ag alloy was obtained. The Sn-coated copper powder was recovered and the coating amount of the Sn—Ag alloy was measured. As a result, it was 18.2% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Moreover, content of Ag contained in Sn alloy was 14.2 mass% with respect to 100 mass of Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder was found on the surface of the dendritic copper powder before coating with the Sn alloy. A two-dimensional or three-dimensional dendritic shape uniformly coated with a Sn—Ag alloy, and a main trunk that grows linearly, a plurality of branches that linearly branch from the main trunk, and It was a dendritic Sn-coated copper powder having a dendritic shape having branched branches.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross section with an average thickness of 0.14 μm, and had fine convex portions on the surface. The height of the convex portions formed on the surface was 0.31 μm on average.

The average particle diameter (D50) of the dendritic Sn-coated copper powder was 9.1 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.25 g / cm ³ . The BET specific surface area was 2.83 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.3 × 10 ⁻⁵ Ω · cm, and it was found that the film exhibited excellent conductivity.

[Example 37]
<Preparation of dendritic Sn-coated copper powder (Coating with Sn-Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 34, the surface of the copper powder was coated with Sn alloy (Sn—Bi alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous methanesulfonate 40 g / L, bismuth methanesulfonate 40 g / L, thiourea 100 g / L, ethylenediaminetetraacetic acid 20 g / L, sodium hypophosphite 80 g A plating solution to which / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Bi alloy was obtained. The Sn-coated copper powder was recovered and the coating amount of the Sn—Bi alloy was measured. As a result, it was 41.6 mass% with respect to 100 mass of the whole Sn coat copper powder. Moreover, the content of Bi contained in the Sn alloy was 40.2% by mass with respect to 100% by mass of the Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder was found on the surface of the dendritic copper powder before coating with the Sn alloy. A two-dimensional or three-dimensional dendritic shape uniformly coated with a Sn—Bi alloy, a main trunk that grows linearly, a plurality of branches that branch linearly from the main trunk, and It was a dendritic Sn-coated copper powder having a dendritic shape having branched branches.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder had a flat cross section with an average thickness of 0.18 μm, and had fine protrusions on the surface. The height of the convex portions formed on the surface was 0.30 μm on average.

The average particle size (D50) of the dendritic Sn-coated copper powder was 9.0 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.29 g / cm ³ . Further, the BET specific surface area was 2.76 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.0 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 38]
<Preparation of dendritic Sn-coated copper powder (Coating with Sn-Zn alloy)>
Using 100 g of the dendritic copper powder obtained in Example 34, the surface of the copper powder was coated with Sn alloy (Sn—Zn alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, as the electroless Sn plating solution for alloys, stannous chloride 10 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, and sodium hypophosphite 70 g / L. A plating solution added at a concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Zn alloy was obtained. The Sn-coated copper powder was recovered and the coating amount of the Sn—Zn alloy was measured. As a result, the content was 11.0% by mass with respect to 100% by mass of the entire Sn-coated copper powder. Further, the content of Zn contained in the Sn alloy was 2.8% by mass with respect to 100% by mass of the Sn alloy.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder was found on the surface of the dendritic copper powder before coating with the Sn alloy. A two-dimensional or three-dimensional dendritic shape uniformly coated with a Sn—Zn alloy, and a main trunk that grows linearly, a plurality of branches that branch linearly from the main trunk, and It was a dendritic Sn-coated copper powder having a dendritic shape having branched branches.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder were flat plate having a cross-sectional thickness of 0.16 μm on average, and had fine convex portions on the surface. The height of the convex portions formed on the surface was 0.26 μm on average.

The average particle size (D50) of the dendritic Sn-coated copper powder was 8.5 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.28 g / cm ³ . Further, the BET specific surface area was 2.71 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.7 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 39]
<Preparation of Dendritic Sn Coated Copper Powder (Coating with Sn—Ag—Bi Alloy)>
Using 100 g of the dendritic copper powder obtained in Example 34, the surface of the copper powder was coated with Sn alloy (Sn—Ag—Bi alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, as the electroless Sn plating solution for alloys, 50 g / L of stannous methanesulfonate, 5 g / L of bismuth methanesulfonate, 20 g / L of silver citrate, 100 g / L of thiourea, sodium hypophosphite A plating solution to which 30 g / L was added at each concentration was prepared. To this electroless Sn plating solution, 100 g of the dendritic copper powder prepared by the above-described method was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 70 ° C. and stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Sn-coated copper powder with the surface of the dendritic copper powder coated with Sn—Ag—Bi alloy was obtained. The Sn-coated copper powder was recovered and the coating amount of the Sn—Ag—Bi alloy was measured. As a result, it was 18.9 mass% with respect to 100 mass of the whole Sn coat copper powder. Moreover, the content of Ag contained in the Sn alloy is 12.4% by mass with respect to 100% by mass of the Sn alloy, and the content of Bi contained in the Sn alloy is based on 100% by mass of the Sn alloy. 3.1% by mass.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder was found on the surface of the dendritic copper powder before coating with the Sn alloy. A two-dimensional or three-dimensional dendritic shape uniformly coated with a Sn—Ag—Bi alloy, a main trunk that grows linearly, a plurality of branches that branch straight from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder were flat plate having a cross-sectional thickness of 0.16 μm on average, and had fine convex portions on the surface. The height of the convex portions formed on the surface was 0.26 μm on average.

The average particle size (D50) of the dendritic Sn-coated copper powder was 8.5 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.31 g / cm ³ . The BET specific surface area was 2.89 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.7 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 40]
<Preparation of dendritic Sn-coated copper powder (coated with Sn—Zn—Bi alloy)>
Using 100 g of the dendritic copper powder obtained in Example 34, the surface of the copper powder was coated with Sn alloy (Sn—Zn—Bi alloy) by electroless plating to produce Sn-coated copper powder.

Specifically, as an electroless Sn plating solution for alloys, stannous chloride 10 g / L, bismuth chloride 5 g / L, zinc sulfate 5 g / L, thiourea 100 g / L, sodium citrate 40 g / L, hypophosphorous acid A plating solution to which sodium 70 g / L was added at each concentration was prepared. The electroless Sn plating solution was charged with 100 g of the dendritic copper powder prepared by the method described above, stirred for 10 minutes at 25 ° C., then heated to 70 ° C. and stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried with ethanol. As a result, Sn-coated copper powder in which the surface of the dendritic copper powder was coated with Sn—Zn—Bi alloy was obtained. The Sn-coated copper powder was recovered and the coating amount of the Sn—Zn—Bi alloy was measured. As a result, it was 11.1 mass% with respect to 100 mass of the whole Sn coat copper powder. Further, the content of Zn contained in the Sn alloy is 2.0% by mass with respect to 100% by mass of the Sn alloy, and the content of Bi contained in the Sn alloy is based on 100% by mass of the Sn alloy. It was 1.4% by mass.

Moreover, as a result of observing the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Sn-coated copper powder was found on the surface of the dendritic copper powder before coating with the Sn alloy. A two-dimensional or three-dimensional dendritic shape uniformly coated with a Sn—Zn—Bi alloy, a main trunk that grows linearly, a plurality of branches that branch straight from the main trunk, and the branches It was dendritic Sn coat | covered copper powder which exhibited the dendritic shape which has the branch further branched from.

Further, the copper particles constituting the main trunk and branches of the dendritic Sn-coated copper powder were flat plate having a cross-sectional thickness of 0.21 μm on average, and had fine convex portions on the surface thereof. The height of the convex portions formed on the surface was 0.31 μm on average.

The average particle diameter (D50) of the dendritic Sn-coated copper powder was 8.7 μm.

Furthermore, the bulk density of the obtained dendritic Sn-coated copper powder was 1.34 g / cm ³ . The BET specific surface area was 2.91 m ² / g.

<Conductive paste>
Next, the dendritic Sn-coated copper powder produced by the method described above was made into a paste to produce a conductive paste.

That is, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Sn-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.9 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Comparative Example 9]
<Preparation of electrolytic copper powder>
Copper powder was deposited on the cathode plate in the same manner as in Example 33 except that Janus Green B as an additive and chlorine ions were not added to the electrolytic solution. The shape of the obtained copper powder was a dendritic shape in which particulate copper was gathered, and no fine convex portions were formed.

<Preparation of Sn-coated copper powder>
Next, Sn was coated on the copper surface using the obtained copper powder in the same manner as in Example 33 to obtain Sn-coated copper powder. When the Sn coating amount of the Sn-coated copper powder was measured, it was 12.5% by mass with respect to 100% by mass of the entire Sn-coated copper powder.

FIG. 26 shows the result of observing the shape of the obtained Sn-coated copper powder with a field of view at a magnification of 5,000 by SEM. As shown in the photograph of FIG. 26, the shape of the obtained Sn-coated copper powder is a dendritic shape in which granular copper particles are gathered, and the surface of the copper powder is covered with Sn. It was. Moreover, the average particle diameter (D50) of the Sn-coated copper powder was 21.3 μm. In addition, the fine convex part was not formed in the dendritic part.

<Conductive paste>
Next, 40 g of Sn-coated copper powder prepared by the above-described method is mixed with 20 g of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), the mixture was kneaded at 1200 rpm for 3 minutes three times to obtain a paste. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 81.6 × 10 ⁻⁵ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 10]
<Production of mechanically flattened flat copper powder>
The characteristic of the conductive paste by Sn coat copper powder which coat | covered Sn on the conventional flat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Sn coat copper powder in an Example.

The flat copper powder was prepared by mechanically flattening granular electrolytic copper powder. Specifically, 5 g of stearic acid was added to 500 g of granular atomized copper powder (manufactured by Mekin Metal Powders Co., Ltd.) having an average particle diameter of 7.9 μm, and flattened with a ball mill. The ball mill was charged with 5 kg of 3 mm zirconia beads and rotated for 90 minutes at a rotation speed of 500 rpm.

<Preparation of Sn-coated copper powder>
The obtained tabular copper powder was coated with Sn on the surface in the same manner as in Example 33 to obtain Sn-coated copper powder. When the coated amount of Sn of the produced flat Sn-coated copper powder was measured, it was 12.6% by mass with respect to 100% by mass of the flat Sn-coated copper powder.

The flat Sn-coated copper powder thus prepared was measured with a laser diffraction / scattering particle size distribution measuring instrument. As a result, the average particle size (D50) was 23.1 μm, and the flat shape was measured by SEM observation. The thickness (average cross-sectional thickness) of the Sn-coated copper powder was 0.40 μm. In the flat Sn-coated copper powder, no fine protrusions were observed on the surface.

<Conductive paste>
Next, 20 g of a phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the obtained flat Sn-coated copper powder. Using a small kneader (Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), a paste was formed by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 34.9 × 10 ⁻⁵ Ω · cm, which is higher in specific resistance value and inferior in conductivity than the copper paste obtained in Example 33. there were.

11 Sn-coated copper powder (dendritic Sn-coated copper powder)
12 Main trunk 13, 13a, 13b Branch 14 Maximum length in horizontal direction (XY direction) with respect to flat plate surface 15 Maximum height in vertical direction with respect to flat plate surface (XY plane) 21 Copper powder (dendritic copper powder)
22 Copper particle D1 Thickness of branch part 31 Sn coated copper powder (dendritic Sn coated copper powder)
32 trunk 33, 33a, 33b branch 41 Sn coated copper powder (flat Sn coated copper particle agglomerated powder)
42 Copper particles d Long axis diameter of flat Sn-coated copper particles 51 Copper particles 52 Main trunks (of copper particles) 53, 53a, 53b (copper particles) branches

Claims (18)

Copper powder coated with tin (Sn) or Sn alloy on the surface is an Sn-coated copper powder having a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. And
The copper particles coated with Sn or Sn alloy on the surface are in the form of a flat plate having an average cross-sectional thickness of 0.02 μm to 5.0 μm determined by observation with a scanning electron microscope (SEM).
The Sn-coated copper powder constituted by aggregating the copper particles has an average particle diameter (D50) of 1.0 μm to 100 μm,
The Sn-coated copper powder, wherein the maximum height in the vertical direction of the flat surface of the copper particles is 1/10 or less with respect to the maximum length of the flat surface in the horizontal direction. Copper particles coated with tin (Sn) or Sn alloy on the surface are assembled to form a dendritic shape having a plurality of branches, Sn-coated copper powder,
The copper particles whose surface is coated with Sn or Sn alloy have an ellipsoid with a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. And
The Sn-coated copper powder constituted by aggregating the copper particles has an average particle diameter (D50) of 5.0 μm to 20 μm. The Sn-coated copper powder according to claim 2, wherein an average thickness of the branch portions constituting the dendritic shape is 0.5 μm to 2.0 μm. Copper powder coated with tin (Sn) or Sn alloy on the surface is an Sn-coated copper powder having a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. And
The copper particles coated with Sn or Sn alloy on the surface have a flat plate shape with an average cross-sectional thickness of 0.2 μm to 5.0 μm,
The Sn-coated copper powder composed of the copper particles is an Sn-coated copper powder having an average particle diameter (D50) of 1.0 μm to 100 μm. A Sn-coated copper powder comprising a plurality of pieces of individual copper particles coated with tin (Sn) or Sn alloy on the surface and having a form of an aggregate,
The copper particles coated with Sn or Sn alloy have an average major axis diameter of 0.5 μm to 5.0 μm determined by observation with a scanning electron microscope (SEM), and an average cross-sectional thickness of 0.02 μm to 1.0 μm. Is a flat plate shape,
The Sn-coated copper powder composed of the copper particles is an Sn-coated copper powder having an average particle diameter (D50) of 1.0 μm to 30 μm. Copper powder coated with tin (Sn) or Sn alloy on the surface is an Sn-coated copper powder having a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. And
The copper particles coated with Sn or Sn alloy on the surface are dendritic having a main trunk grown in a dendritic shape and a plurality of branches separated from the main trunk, and the cross-sectional average thickness of the main trunk and branches of the copper particle Is a flat plate of 0.02 μm to 0.5 μm,
The Sn-coated copper powder composed of the copper particles is an Sn-coated copper powder having an average particle diameter (D50) of 1.0 μm to 30 μm. The Sn-coated copper powder according to claim 6, wherein the surface of the copper particles has fine convex portions, and the average height of the convex portions is 0.01 μm to 0.4 μm. The Sn content coated as Sn or Sn alloy is 1% by mass to 50% by mass with respect to 100% by mass of the entire Sn-coated copper powder coated with Sn or Sn alloy. 2. Sn-coated copper powder according to item 1. Sn alloy is coated on the surface of the copper particles,
At least one selected from the group consisting of cobalt, zinc, tungsten, molybdenum, palladium, platinum, tin, phosphorus, and boron is 0.1% by mass to 50% by mass with respect to 100% by mass of the Sn alloy. The Sn-coated copper powder according to any one of claims 1 to 8, wherein the Sn-coated copper powder is coated with a Sn alloy containing the content. The Sn-coated copper powder according to any one of claims 1 to 9, wherein a bulk density is in a range of 0.5 g / cm ³ to 5.0 g / cm ³ . Sn-coated copper powder according to any one of claims 1 to 10 BET specific surface area is 0.2m ² /g~5.0m ² / g. A metal filler containing the Sn-coated copper powder according to any one of claims 1 to 11 in a proportion of 20% by mass or more of the whole. An electrically conductive paste obtained by mixing the metal filler according to claim 12 with a resin. A method for producing the Sn-coated copper powder according to claim 1,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with tin (Sn) or Sn alloy,
In the electrolyte,
Copper ions,
A compound having a phenazine structure represented by the following formula (1), a compound having an azobenzene structure represented by the following formula (2), and a compound having a phenazine structure and an azobenzene structure represented by the following formula (3) One or more selected from the group consisting of:
One or more types of nonionic surfactants;
The manufacturing method of Sn coat | cover copper powder which electrolyzes by containing.

[In Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. And A ⁻ is a halide anion. ]

[In the formula (2), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ are each independently hydrogen, halogen, amino, OH, = O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, a group selected from the group consisting of benzenesulfonic acid, lower alkyl, and aryl. ]

[In the formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, Selected from the group consisting of halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, A group selected from the group consisting of lower alkyl and aryl, and A ⁻ is a halide anion. ] The method for producing Sn-coated copper powder according to claim 14, further comprising chloride ions in the electrolytic solution. A method for producing the Sn-coated copper powder according to claim 2 or 3,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with tin (Sn) or Sn alloy,
In the electrolyte,
The manufacturing method of Sn coat | cover copper powder which electrolyzes containing a copper ion and a polyether compound. A method for producing the Sn-coated copper powder according to claim 4,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with tin (Sn) or Sn alloy,
In the electrolyte,
Copper ions,
One or more selected from compounds having a phenazine structure represented by the following formula (1);
The manufacturing method of Sn coat | cover copper powder which electrolyzes by containing.

[In Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. And A ⁻ is a halide anion. ] A method for producing the Sn-coated copper powder according to claim 6 or 7,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with tin (Sn) or Sn alloy,
In the electrolyte,
Copper ions,
One or more selected from compounds having a phenazine structure and an azobenzene structure represented by the following formula (3);
The manufacturing method of Sn coat | cover copper powder which electrolyzes by containing.

[In the formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, Selected from the group consisting of halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl It is a group. R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion. ]

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