WO2015174299A1 - Conductive paste, production method for conductive paste, connection structure, and production method for connection structure - Google Patents

Abstract

Provided is a conductive paste capable of improving coating properties, capable of efficiently arranging conductive particles upon electrodes, and capable of improving conduction reliability between electrodes. This conductive paste includes a thermosetting component and a plurality of conductive particles. The thermosetting component contains a thermosetting compound that is solid at 25°C and a thermosetting agent. The thermosetting compound that is solid at 25°C is scattered as particles in the conductive paste.

Description

Conductive paste, conductive paste manufacturing method, connection structure, and connection structure manufacturing method

The present invention relates to a conductive paste containing conductive particles and a method for manufacturing the conductive paste. The present invention also relates to a connection structure using the conductive paste and a method for manufacturing the connection structure.

Anisotropic conductive materials such as anisotropic conductive paste and anisotropic conductive film are widely known. In the anisotropic conductive material, conductive particles are dispersed in a binder resin.

In order to obtain various connection structures, for example, the anisotropic conductive material may be connected between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), or connected between a semiconductor chip and a flexible printed circuit board (COF ( (Chip on Film)), connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)), and the like.

For example, when electrically connecting the electrode of the flexible printed circuit board and the electrode of the glass epoxy substrate by the anisotropic conductive material, an anisotropic conductive material containing conductive particles is disposed on the glass epoxy substrate. To do. Next, a flexible printed circuit board is laminated, and heated and pressurized. As a result, the anisotropic conductive material is cured, and the electrodes are electrically connected via the conductive particles to obtain a connection structure.

As an example of the anisotropic conductive material, the following Patent Document 1 includes a resin layer containing a thermosetting resin, solder powder, and a curing agent, and the solder powder and the curing agent include the resin layer. An adhesive tape present therein is disclosed. This adhesive tape is in the form of a film, not a paste.

Further, Patent Document 1 discloses a bonding method using the above-mentioned adhesive tape. Specifically, a first substrate, an adhesive tape, a second substrate, an adhesive tape, and a third substrate are laminated in this order from the bottom to obtain a laminate. At this time, the first electrode provided on the surface of the first substrate is opposed to the second electrode provided on the surface of the second substrate. Moreover, the 2nd electrode provided in the surface of the 2nd board | substrate and the 3rd electrode provided in the surface of the 3rd board | substrate are made to oppose. Then, the laminate is heated and bonded at a predetermined temperature. Thereby, a connection structure is obtained.

Patent Document 2 listed below includes (A) a silica filler having an average particle diameter of 3 to 100 nm that has been subjected to a hydrophobization treatment, (B) an adhesive component, and (C) a conductive particle. An isotropic conductive material is disclosed. In Patent Document 2, the amount of the silica filler is 10 to 60% by mass with respect to the total amount of the adhesive component.

Patent Document 3 listed below includes (1) an epoxy resin having an average of 1.2 or more epoxy groups in one molecule, and (2) a rubber having a softening point temperature of 0 ° C. or less and a primary particle diameter of 5 μm or less. -Like polymer fine particles, (3) thermally active latent epoxy curing agent, and (4) anisotropic conductive material having high softening point polymer fine particles having a softening point temperature of 50 ° C. or higher and a primary particle diameter of 2 μm or less Is disclosed.

WO2008 / 023452A1 JP 2011-233633 A JP 2000-34010 A

The adhesive tape described in Patent Document 1 is a film, not a paste. For this reason, it is difficult to efficiently arrange the solder powder on the electrodes (lines). For example, in the adhesive tape described in Patent Document 1, a part of the solder powder is easily placed in a region (space) where no electrode is formed. Solder powder disposed in a region where no electrode is formed does not contribute to conduction between the electrodes.

Also, even if the anisotropic conductive paste contains solder powder, the solder powder may not be efficiently disposed on the electrodes (lines). In addition, the anisotropic conductive material described in Patent Document 2 may have low coatability when applied by screen printing or the like.

Furthermore, if the viscosity of the anisotropic conductive paste containing solder powder is lowered, the solder powder can easily move onto the electrode (line). However, if the viscosity of the anisotropic conductive paste is lowered, the thickness of the anisotropic conductive paste layer after coating becomes thin, and the anisotropic conductive paste flows excessively and is disposed in an unintended region. It becomes easy to be.

In Patent Document 3, the (1) epoxy resin is (1-1) an epoxy resin that is liquid in the temperature range of 0 to 50 ° C. and (1-2) a solid epoxy resin in the temperature range of 0 to 50 ° C. The use of a mixture with a resin is described. However, in Patent Document 3, in an anisotropic conductive paste, for example, “Epicron EP-1004”, which is a bisphenol A type epoxy resin, is dissolved in 1,6-hexanediol diglycidyl ether in Examples. Only a specific example in which a solid epoxy resin is dissolved is shown. Thus, even if the epoxy resin is solid at 25 ° C. alone, the epoxy resin is not always in a solid state in an anisotropic conductive paste, and the epoxy resin is generally used in a dissolved state. It is.

An object of the present invention is to produce a conductive paste and a conductive paste that can improve the coating property, and further can efficiently dispose conductive particles on the electrodes, and can improve the conduction reliability between the electrodes. Is to provide a method. Moreover, this invention is providing the manufacturing method of the connection structure and connection structure using the said electrically conductive paste.

According to a wide aspect of the present invention, the thermosetting component includes a thermosetting component and a plurality of conductive particles, and the thermosetting component contains a thermosetting compound that is solid at 25 ° C. and a thermosetting agent. In the conductive paste, there is provided a conductive paste in which the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles.

In a specific aspect of the conductive paste according to the present invention, the conductive paste contains a thermosetting compound that is liquid at 25 ° C.

In a specific aspect of the conductive paste according to the present invention, the thermosetting compound that is solid at 25 ° C. is a thermosetting epoxy compound that is solid at 25 ° C.

In a specific aspect of the conductive paste according to the present invention, the thermosetting compound that is solid at 25 ° C. includes a first thermosetting compound that is solid at 25 ° C., and the first thermosetting compound. And a second thermosetting compound that has a different melting point and is solid at 25 ° C.

It is preferable that the conductive particles have solder on a conductive outer surface, and more preferably solder particles.

In a specific aspect of the conductive paste according to the present invention, the melting point of the solder in the conductive particles at −5 ° C. and 5 rpm is higher than the melting point of the solder in the conductive particles at −5 ° C. and the viscosity at 0.5 rpm. The ratio is 1 or more and 2 or less.

In a specific aspect of the conductive paste according to the present invention, the particle size of the particulate thermosetting compound is 1 μm or more and 40 μm or less.

In a specific aspect of the conductive paste according to the present invention, the ratio of the viscosity at 25 ° C. and 5 rpm to the viscosity at 25 ° C. and 0.5 rpm is 2.5 or more and 7 or less, and other specific aspects Then, the ratio of the viscosity at 25 ° C. and 5 rpm to the viscosity at 25 ° C. and 0.5 rpm is 4 or more and 7 or less.

In a specific aspect of the conductive paste according to the present invention, the conductive paste includes a flux.

In a specific aspect of the conductive paste according to the present invention, the conductive paste does not contain a filler or contains 100% by weight of the conductive paste in an amount of 1% by weight or less.

According to a wide aspect of the present invention, there is provided a method for producing the above-described conductive paste, a thermosetting component containing a thermosetting compound that is solid at 25 ° C., and a thermosetting agent, and a plurality of conductive properties. Particles are mixed to obtain a mixture, and then the mixture is heated above the melting point of the thermosetting compound that is solid at 25 ° C. and below the curing temperature of the thermosetting component, and solid at 25 ° C. The thermosetting compound is melted and solidified to obtain a conductive paste in which the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles, or heat that is solid at 25 ° C. A mixture comprising a thermosetting compound that is particulate and solid at 25 ° C., a thermosetting component containing a thermosetting agent, and a plurality of conductive particles after the curable compound is made into particles. And thermosetting compound that is solid at 25 ° C. There is obtained a conductive paste dispersed in particulate, manufacturing method of the conductive paste is provided.

In a wide aspect of the present invention, a first connection target member having at least one first electrode on the surface, a second connection target member having at least one second electrode on the surface, and the first connection. A connection portion connecting the target member and the second connection target member, wherein the connection portion is formed of the conductive paste described above, and the first electrode and the second electrode However, there is provided a connection structure that is electrically connected by the conductive particles in the connection portion.

According to a wide aspect of the present invention, using the conductive paste described above, the step of disposing the conductive paste on the surface of the first connection target member having at least one first electrode on the surface; On the surface opposite to the first connection target member side of the paste, the second connection target member having at least one second electrode on the surface is formed by the first electrode and the second electrode. The first connection target member is arranged to be disposed so as to face each other, and by heating the conductive paste to a temperature equal to or higher than the melting point of the thermosetting compound that is solid at 25 ° C. and higher than the curing temperature of the thermosetting component. And connecting the second connection target member with the conductive paste, and connecting the first electrode and the second electrode to the conductive particles in the connection portion. Electrically connecting with Comprising, a manufacturing method of the connecting structure is provided.

In a specific aspect of the method for manufacturing a connection structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection portion, no pressure is applied, and the conductive paste includes The weight of the second connection target member is added.

It is preferable that the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board.

The conductive paste according to the present invention includes a thermosetting component and a plurality of conductive particles, and the thermosetting component contains a thermosetting compound that is solid at 25 ° C. and a thermosetting agent, Furthermore, in the conductive paste according to the present invention, the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles, so that the coating property of the conductive paste can be improved. Furthermore, when the electrodes are electrically connected using the conductive paste according to the present invention, the conductive particles can be efficiently disposed on the electrodes, and the conduction reliability between the electrodes can be improved.

FIG. 1 is a partially cutaway front sectional view schematically showing a connection structure obtained using a conductive paste according to an embodiment of the present invention. 2A to 2C are cross-sectional views for explaining each step of an example of a method for manufacturing a connection structure using the conductive paste according to the embodiment of the present invention. FIG. 3 is a partially cutaway front sectional view showing a modified example of the connection structure. FIG. 4 is a cross-sectional view schematically showing conductive particles that can be used in the conductive paste according to an embodiment of the present invention. FIG. 5 is a cross-sectional view showing a modification of the conductive particles. FIG. 6 is a cross-sectional view showing another modified example of conductive particles. FIG. 7 is an image showing the thermosetting compound dispersed in the form of particles in the conductive paste according to the embodiment of the present invention.

Hereinafter, the details of the present invention will be described.

The conductive paste according to the present invention includes a thermosetting component and a plurality of conductive particles. In the conductive paste according to the present invention, the thermosetting component contains a thermosetting compound that is solid at 25 ° C. and a thermosetting agent. In the conductive paste according to the present invention, the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles.

In the conductive paste according to the present invention, the above configuration is adopted, so that the coating property can be improved. The conductive paste according to the present invention can be satisfactorily coated by a coating method such as dispenser and screen printing. If the viscosity of the anisotropic conductive paste is lowered, the conductive particles easily move onto the electrodes (lines). The dispersion of the thermosetting compound that is solid at 25 ° C. in the conductive paste in the form of particles greatly contributes to improving the coating property. For example, the viscosity of the conductive paste becomes moderately high, the thixotropy of the conductive paste is appropriately expressed, the thickness of the conductive paste layer after coating is difficult to be thinned, and the conductive paste is difficult to flow excessively. Therefore, it is difficult to place the device in an unintended area. On the other hand, when a predetermined amount of filler is blended to increase the viscosity of the conductive paste, the filler hinders the movement of the conductive particles onto the electrode. On the other hand, the thermosetting compound that is solid at 25 ° C. is less likely to hinder the movement of the conductive particles onto the electrode as compared with the filler. In particular, if the thermosetting compound becomes liquid during the movement of the conductive particles onto the electrode, the liquid thermosetting compound does not hinder the movement of the conductive particles onto the electrode.

In particular, in the conductive paste according to the present invention, the above-described configuration is adopted. Therefore, when the electrodes are electrically connected, a plurality of conductive particles are interposed between the first electrode and the second electrode. It is easy to gather and a plurality of conductive particles can be efficiently arranged on the electrode (line). Moreover, it is difficult for some of the plurality of conductive particles to be disposed in a region (space) where no electrode is formed, and the amount of conductive particles disposed in a region where no electrode is formed can be considerably reduced. . Therefore, the conduction reliability between the first electrode and the second electrode can be improved. In addition, it is possible to prevent electrical connection between laterally adjacent electrodes that should not be connected, and to improve insulation reliability. The reason why such an effect is obtained is considered that the thermosetting compound that is solid at 25 ° C. is less likely to hinder the movement of the conductive particles onto the electrode as compared with the filler.

In the conductive paste according to the present invention, it is possible to obtain both the effect of improving the coating property and the effect of improving the conduction reliability between the electrodes achieved by the efficient movement of the conductive particles onto the electrodes. Can do. Further, in the conductive paste according to the present invention, when the conductive particles have solder on the conductive outer surface, the configuration of the particulate thermosetting compound and the configuration of the conductive particles that easily move in the conductive paste Synergistically exert the effects of the present invention more effectively. Furthermore, in the conductive paste according to the present invention, when the conductive particles are solder particles, the configuration of the particulate thermosetting compound and the configuration of the conductive particles that are particularly easily moved in the conductive paste are synergistic. The effect of the present invention is further effectively exhibited.

The method for producing a conductive paste according to the present invention comprises (1) a mixture of a thermosetting compound that is solid at 25 ° C. and a thermosetting component containing a thermosetting agent, and a plurality of conductive particles. The mixture is then heated to a temperature above the melting point of the thermosetting compound that is solid at 25 ° C. and below the curing temperature of the thermosetting component, and the thermosetting compound that is solid at 25 ° C. Or a solidified thermosetting compound in which the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles, or (2) the thermosetting compound that is solid at 25 ° C. Is a mixture of a thermosetting component that is particulate and solid at 25 ° C., a thermosetting component containing a thermosetting agent, and a plurality of conductive particles, and the above. A thermosetting thermosetting epoxy compound that is solid at 25 ° C. Obtaining a conductive paste dispersed in a child shape. With such a method for producing a conductive paste according to the present invention, the conductive paste according to the present invention can be easily obtained. In the case of the above method (2), when the thermosetting compound that is solid at 25 ° C. is made into particles, a thermosetting agent may be already mixed, and at 25 ° C., which is blended as necessary. A liquid thermosetting compound may already be mixed. When making the thermosetting compound which is solid at 25 ° C. into particles, it is preferable that the conductive particles are not mixed.

The conductive particles contained in the conductive paste preferably have solder on the outer surface of the conductive material, and more preferably are solder particles. If such preferable conductive particles are used, the conductive particles can be arranged more efficiently on the electrode.

The conductive paste according to the present invention can be suitably used for the following manufacturing method of the connection structure according to the present invention.

In the method for manufacturing a connection structure according to the present invention, a conductive paste, a first connection target member, and a second connection target member are used. The conductive material used in the method for manufacturing a connection structure according to the present invention is not a conductive film but a conductive paste. The conductive paste includes a plurality of conductive particles and a thermosetting component. The first connection target member has at least one first electrode on the surface. The second connection target member has at least one second electrode on the surface.

The method for manufacturing a connection structure according to the present invention includes a step of disposing the conductive paste on a surface of the first connection target member, and a surface opposite to the first connection target member side of the conductive paste. Above, the step of arranging the second connection object member so that the first electrode and the second electrode face each other, the melting point of the thermosetting compound that is solid at 25 ° C. and above By heating the conductive paste to a temperature equal to or higher than the curing temperature of the thermosetting component, a connection portion connecting the first connection target member and the second connection target member is formed with the conductive paste, And a step of electrically connecting the first electrode and the second electrode with conductive particles in the connection portion.

In the manufacturing method of the connection structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection portion, no pressure is applied, and the second connection is applied to the conductive paste. The weight of the target member is preferably added. In the method for manufacturing a connection structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection portion, the conductive paste has a weight force of the second connection target member. It is preferable not to apply a pressure higher than.

In the manufacturing method of the connection structure according to the present invention, since the above-described configuration is adopted, the plurality of conductive particles are easily collected between the first electrode and the second electrode, and the plurality of conductive particles are collected. It can arrange | position efficiently on an electrode (line). Moreover, it is difficult for some of the plurality of conductive particles to be disposed in a region (space) where no electrode is formed, and the amount of conductive particles disposed in a region where no electrode is formed can be considerably reduced. . Therefore, the conduction reliability between the first electrode and the second electrode can be improved. In addition, it is possible to prevent electrical connection between laterally adjacent electrodes that should not be connected, and to improve insulation reliability.

Thus, in order to efficiently arrange a plurality of conductive particles on the electrode and to considerably reduce the amount of the conductive particles arranged in the region where the electrode is not formed, a conductive film is used instead of a conductive film. The inventors have found that it is necessary to use a paste.

Furthermore, in the step of arranging the second connection target member and the step of forming the connection portion, if the weight of the second connection target member is added to the conductive paste without applying pressure, the connection portion is The conductive particles arranged in the region (space) where the electrode is not formed before the formation becomes easier to gather between the first electrode and the second electrode, and the plurality of conductive particles are separated from the electrode ( The present inventors have also found that it can be arranged efficiently on the line). In the present invention, a configuration in which a conductive paste is used instead of a conductive film and a configuration in which the weight of the second connection target member is added to the conductive paste without applying pressure are used in combination. This has a great meaning in order to obtain the effects of the present invention at a higher level.

In addition, WO2008 / 023452A1 describes that it is preferable to pressurize with a predetermined pressure at the time of bonding from the viewpoint of efficiently moving the solder powder to the electrode surface, and the pressurizing pressure further ensures the solder area. For example, it is described that the pressure is set to 0 MPa or more, preferably 1 MPa or more. Further, even if the pressure intentionally applied to the adhesive tape is 0 MPa, the member disposed on the adhesive tape It is described that a predetermined pressure may be applied to the adhesive tape by its own weight. In WO2008 / 023452A1, it is described that the pressure applied intentionally to the adhesive tape may be 0 MPa, but there is no difference between the effect when the pressure exceeding 0 MPa is applied and when the pressure is set to 0 MPa. Not listed.

If a conductive paste is used instead of a conductive film, the thickness of the connecting portion can be adjusted as appropriate depending on the amount of the conductive paste applied. On the other hand, in the conductive film, in order to change or adjust the thickness of the connection portion, it is necessary to prepare a conductive film having a different thickness or to prepare a conductive film having a predetermined thickness. There is.

In the method for manufacturing a connection structure according to the present invention, when the conductive particles are conductive particles having solder on the conductive outer surface, or when the conductive particles are solder particles, the connection portion is formed. In addition, it is preferable to heat the solder to a melting point or higher. In this case, the first electrode and the second electrode are more firmly bonded to each other by the solder portion solidified after being melted. As a result, the conduction reliability between the electrodes is further enhanced.

Hereinafter, the present invention will be clarified by describing specific embodiments and examples of the present invention with reference to the drawings.

First, FIG. 1 schematically shows a connection structure obtained by using a conductive paste according to an embodiment of the present invention in a partially cutaway front sectional view.

The connection structure 1 shown in FIG. 1 is a connection that connects a first connection target member 2, a second connection target member 3, and the first connection target member 2 and the second connection target member 3. Part 4. The connection part 4 is formed with the electrically conductive paste containing a thermosetting component and several electroconductive particle. In this conductive paste, the thermosetting component contains a thermosetting compound that is solid at 25 ° C. and a thermosetting agent. In the conductive paste, the thermosetting compound that is solid at 25 ° C. It is dispersed in the form of particles. In the present embodiment, solder particles are used as the conductive particles.

The connecting portion 4 includes a solder portion 4A (conductive particles) in which a plurality of solder particles gather and are joined to each other, and a cured product portion 4B in which a thermosetting component is thermally cured.

The first connection object member 2 has a plurality of first electrodes 2a on the surface (upper surface). The second connection target member 3 has a plurality of second electrodes 3a on the surface (lower surface). The first electrode 2a and the second electrode 3a are electrically connected by the solder portion 4A. Therefore, the first connection target member 2 and the second connection target member 3 are electrically connected by the solder portion 4A. In the connection portion 4, no solder exists in a region (cured product portion 4B portion) different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a. In an area different from the solder part 4A (hardened product part 4B part), there is no solder separated from the solder part 4A. If the amount is small, the solder may be present in a region (cured product portion 4B portion) different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a.

As shown in FIG. 1, in the connection structure 1, after a plurality of solder particles are melted, the molten solder particles are wetted and spread on the surface of the electrode to solidify to form a solder portion 4 </ b> A. For this reason, the connection area of 4 A of solder parts and the 1st electrode 2a, and 4 A of solder parts, and the 2nd electrode 3a becomes large. That is, by using the solder particles, the solder portion 4A, the first electrode 2a, and the solder portion are compared with the case where the conductive outer surface is made of a metal such as nickel, gold or copper. The contact area between 4A and the second electrode 3a increases. For this reason, the conduction | electrical_connection reliability and connection reliability in the connection structure 1 become high. Note that the conductive paste may contain a flux. In general, the flux contained in the conductive paste is gradually deactivated by heating.

In addition, in the connection structure 1 shown in FIG. 1, all of the solder portions 4A are located in the facing region between the first and second electrodes 2a and 3a. The connection structure 1X of the modification shown in FIG. 3 is different from the connection structure 1 shown in FIG. 1 only in the connection portion 4X. The connection part 4X has the solder part 4XA and the hardened | cured material part 4XB. As in the connection structure 1X, most of the solder portions 4XA are located in regions where the first and second electrodes 2a and 3a are opposed to each other, and a part of the solder portion 4XA is first and second. You may protrude to the side from the area | region which electrode 2a, 3a has opposed. The solder part 4XA protruding laterally from the region where the first and second electrodes 2a and 3a are opposed is a part of the solder part 4XA and is not a solder separated from the solder part 4XA. In the present embodiment, the amount of solder away from the solder portion can be reduced, but the solder away from the solder portion may exist in the cured product portion.

If the amount of solder particles used is reduced, the connection structure 1 can be easily obtained. If the amount of the solder particles used is increased, it becomes easy to obtain the connection structure 1X.

Next, an example of a method for manufacturing the connection structure 1 using the conductive paste according to the embodiment of the present invention will be described.

First, the first connection target member 2 having the first electrode 2a on the surface (upper surface) is prepared. Next, as shown in FIG. 2A, a conductive paste 11 including a thermosetting component 11B and a plurality of solder particles 11A is disposed on the surface of the first connection target member 2 (first step). ). The conductive paste 11 is disposed on the surface of the first connection target member 2 on which the first electrode 2a is provided. After the conductive paste 11 is disposed, the solder particles 11A are disposed both on the first electrode 2a (line) and on a region (space) where the first electrode 2a is not formed.

The arrangement method of the conductive paste 11 is not particularly limited, and examples thereof include application with a dispenser, screen printing, and ejection with an inkjet device. Of these, screen printing is preferable. By using the conductive paste according to the present invention, applicability by screen printing is considerably improved, and even when screen printing is performed, the conductive paste layer can be formed to a predetermined thickness, and excessive wetting and spreading of the conductive paste can be achieved. This makes it difficult to place the conductive paste in an unintended region.

Moreover, the 2nd connection object member 3 which has the 2nd electrode 3a on the surface (lower surface) is prepared. Next, as shown in FIG. 2B, in the conductive paste 11 on the surface of the first connection target member 2, on the surface of the conductive paste 11 opposite to the first connection target member 2 side, The 2nd connection object member 3 is arrange | positioned (2nd process). On the surface of the conductive paste 11, the second connection target member 3 is disposed from the second electrode 3a side. At this time, the first electrode 2a and the second electrode 3a are opposed to each other.

Next, the conductive paste 11 is heated above the melting point of the thermosetting compound that is solid at 25 ° C. and above the curing temperature of the thermosetting component 11B (third step). That is, the conductive paste 11 is heated to a temperature lower than the melting point of the thermosetting compound that is solid at 25 ° C. and the curing temperature of the thermosetting component 11B. Preferably, the conductive paste 11 is heated above the melting point of the solder, that is, above the melting point of the solder particles 11A. At the time of this heating, the solder particles 11A that existed in the region where no electrode is formed gather between the first electrode 2a and the second electrode 3a (self-aggregation effect). In this embodiment, since the conductive paste is used instead of the conductive film, the solder particles 11A are effectively collected between the first electrode 2a and the second electrode 3a. Also, the solder particles 11A are melted and joined together. Further, the thermosetting component 11B is thermoset. As a result, as shown in FIG. 2C, the connection portion 4 connecting the first connection target member 2 and the second connection target member 3 is formed with the conductive paste 11. The connection part 4 is formed by the conductive paste 11, the solder part 4A is formed by joining a plurality of solder particles 11A, and the cured part 4B is formed by thermosetting the thermosetting component 11B. If the solder particles 3 move quickly, the first electrode 2a and the second electrode are moved after the movement of the solder particles 3 that are not positioned between the first electrode 2a and the second electrode 3a starts. It is not necessary to keep the temperature constant until the movement of the solder particles 3 is completed.

Also, a preheating step may be provided in the first half of the third step. This preheating step is a temperature at which the thermosetting component 11B is not substantially thermally cured at a temperature equal to or higher than the melting temperature of the solder in a state where the weight of the second connection target member 3 is added to the conductive paste 11. This refers to the process of heating for 5 to 60 seconds. By providing this step, the action of collecting the solder particles between the first electrode and the second electrode is further enhanced, and between the first connection target member and the second connection target member. Voids that may occur can be suppressed.

In this embodiment, no pressure is applied in the second step and the third step. In the present embodiment, the weight of the second connection target member 3 is added to the conductive paste 11. For this reason, when the connection part 4 is formed, the solder particles 11A are effectively collected between the first electrode 2a and the second electrode 3a. In addition, if pressure is applied in at least one of the second step and the third step, the action of the solder particles trying to collect between the first electrode and the second electrode is hindered. The This has been found by the inventors.

In this way, the connection structure 1 shown in FIG. 1 is obtained. The second step and the third step may be performed continuously. Moreover, after performing the said 2nd process, the laminated body of the obtained 1st connection object member 2, the electrically conductive paste 11, and the 2nd connection object member 3 is moved to a heating part, and said 3rd said You may perform a process. In order to perform the heating, the laminate may be disposed on a heating member, or the laminate may be disposed in a heated space.

The heating temperature in the third step is preferably not less than the melting point of the thermosetting compound that is solid at 25 ° C. and not less than the curing temperature of the thermosetting component 11B, and more than the melting point of the solder and curing of the thermosetting component. It is preferable that the temperature is higher. The heating temperature is preferably 130 ° C. or higher, more preferably 160 ° C. or higher, preferably 450 ° C. or lower, more preferably 250 ° C. or lower, and still more preferably 200 ° C. or lower.

The temperature of the preheating step is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 140 ° C. or higher, preferably less than 160 ° C., more preferably 150 ° C. or lower.

In addition, the said 1st connection object member should just have at least 1 1st electrode. The first connection target member preferably has a plurality of first electrodes. The said 2nd connection object member should just have at least 1 2nd electrode. The second connection target member preferably has a plurality of second electrodes.

The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members include electronic components such as semiconductor chips, capacitors, and diodes, and resin films, printed boards, flexible printed boards, flexible flat cables, rigid flexible boards, glass epoxies. Examples thereof include electronic components such as circuit boards such as substrates and glass substrates. The first and second connection target members are preferably electronic components.

It is preferable that at least one of the first connection target member and the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. The second connection target member is preferably a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. Resin films, flexible printed boards, flexible flat cables, and rigid flexible boards have the property of being highly flexible and relatively lightweight. When a conductive film is used for connection of such a connection object member, there exists a tendency for electroconductive particle to collect on an electrode easily. On the other hand, since the conductive paste according to the present invention is used, even when a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board is used, the conductive particles are efficiently collected on the electrode. And the conduction reliability between the electrodes can be sufficiently enhanced. When using a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board, the reliability of conduction between electrodes by not applying pressure compared to the case of using other connection target members such as a semiconductor chip. The improvement effect can be obtained more effectively.

Examples of the electrode provided on the connection target member include metal electrodes such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a silver electrode, a molybdenum electrode, a SUS electrode, and a tungsten electrode. When the connection object member is a flexible printed circuit board or a flexible flat cable, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode, or a copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. In addition, when the said electrode is an aluminum electrode, the electrode formed only with aluminum may be sufficient and the electrode by which the aluminum layer was laminated | stacked on the surface of the metal oxide layer may be sufficient. Examples of the material for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

The distance D1 of the connecting portion at the position where the first electrode and the second electrode face each other is preferably 3 μm or more, more preferably 10 μm or more, preferably 100 μm or less, more preferably 75 μm or less. When the distance D1 is equal to or greater than the lower limit, the connection reliability between the connection portion and the connection target member is further increased. When the distance D1 is less than or equal to the above upper limit, the conductive particles are more likely to gather on the electrodes when the connection portion is formed, and the conduction reliability between the electrodes is further enhanced.

In the conductive paste, the particle size of the thermosetting compound which is solid at 25 ° C. is preferably 0.1 μm or more, more preferably 1 μm or more, preferably 40 μm or less, more preferably 30 μm or less. Preferably it is 20 micrometers or less, Most preferably, it is 10 micrometers or less.

The particle diameter of the thermosetting compound that is solid at 25 ° C. in the form of particles indicates a number average particle diameter. The particle size of the thermosetting compound that is solid at 25 ° C. that is in the form of particles is, for example, that 50 thermosetting compounds that are solid at 25 ° C. that are in an arbitrary particle shape are observed with an electron microscope or an optical microscope. It is obtained by calculating an average value.

The viscosity η1 at 25 ° C. and 5 rpm of the conductive paste is preferably 10 Pa · s or more, more preferably 50 Pa · s or more, still more preferably 100 Pa · s or more, preferably 800 Pa · s or less, more preferably 600 Pa · s or less. More preferably, it is 500 Pa · s or less. When the viscosity η1 is not less than the above lower limit and not more than the above upper limit, the coating property of the conductive paste and the arrangement accuracy of the conductive particles are further enhanced.

The viscosity η2 of the conductive paste at 25 ° C. and 0.5 rpm is preferably 1 Pa · s or more, and preferably 100 Pa · s or less. When the viscosity η2 is not less than the above lower limit and not more than the above upper limit, the coating property of the conductive paste and the arrangement accuracy of the conductive particles are further enhanced.

The ratio (η1 / η2) of the viscosity η1 at 25 ° C. and 5 rpm to the viscosity η2 at 25 ° C. and 0.5 rpm is preferably 1 or more, more preferably 2.5 or more, still more preferably 4 or more, preferably It is 7 or less, more preferably 6 or less, and still more preferably 5 or less. When the ratio (η1 / η2) is not less than the above lower limit and not more than the above upper limit, the coating property of the conductive paste and the placement accuracy of the conductive particles are further increased, and the conduction reliability between the electrodes is effectively increased. .

When the conductive particles have solder on the conductive outer surface, the melting point of the solder in the conductive particles is T ° C. The ratio (η1 ′ / η2 ′) of the viscosity η1 ′ at (T-5) ° C. and 5 rpm to the viscosity η2 ′ at (T-5) ° C. and 0.5 rpm is preferably 1 or more, preferably 2 or less. It is. When the ratio (η1 ′ / η2 ′) is not less than the above lower limit and not more than the above upper limit, the arrangement accuracy of the conductive particles is further increased, and the conduction reliability between the electrodes is effectively increased.

The viscosity can be appropriately adjusted depending on the type of blending component, the blending amount of the blending component, and particularly the dispersion state of the thermosetting compound that is solid at 25 ° C.

The viscosity is, for example, using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.) or the like, at 25 ° C. and 5 rpm, at 25 ° C. and 0.5 rpm, (T-5) ° C. and 5 rpm, and ( T-5) Measurement is possible under the conditions of ° C and 0.5 rpm.

The conductive paste includes a thermosetting component and a plurality of conductive particles. The said thermosetting component contains the thermosetting compound (curable compound which can be hardened | cured by heating) and a thermosetting agent which are solid at 25 degreeC. The conductive paste preferably contains a thermosetting compound that is liquid at 25 ° C. (a curable compound that can be cured by heating). The conductive paste preferably contains a flux. The conductive paste may contain a filler.

Hereinafter, other details of the present invention will be described.

(Conductive particles)
The conductive particles electrically connect the electrodes of the connection target member. The conductive particles are not particularly limited as long as they are conductive particles. The said electroconductive particle should just have an electroconductive part on the electroconductive outer surface.

Examples of the conductive particles include organic particles, inorganic particles other than metal particles, organic-inorganic hybrid particles, or metal particles whose surfaces are covered with a conductive layer (metal layer), or substantially only metal. Examples thereof include metal particles.

The conductive particles contained in the conductive paste preferably have solder on the conductive outer surface, and more preferably are solder particles. Hereinafter, conductive particles having solder on a conductive outer surface will be described.

FIG. 4 is a sectional view showing conductive particles that can be used in the conductive paste according to one embodiment of the present invention.

4 has base particles 52 (resin particles and the like) and conductive portions 53 arranged on the outer surface 52a of the base particles 52. The conductive particles 51 shown in FIG. The conductive part 53 is a conductive layer. The conductive portion 53 covers the outer surface 52 a of the base particle 52. The conductive particles 51 are coated particles in which the outer surface 52 a of the base particle 52 is coated with the conductive portion 53. Accordingly, the conductive particles 51 have the conductive portions 53 on the outer surface 51a.

The conductive portion 53 includes a first conductive portion 54 (first conductive layer) disposed on the outer surface 52 a of the base particle 52 and a solder disposed on the outer surface 54 a of the first conductive portion 54. Part 55 (solder layer, second conductive part (second conductive layer)). The outer surface portion (surface layer) of the conductive portion 53 is a solder portion 55. Therefore, the conductive particle 51 has a solder part 55 as a part of the conductive part 53, and is further provided between the base particle 52 and the solder part 55 as a part of the conductive layer 53 separately from the solder part 55. 1 conductive portion 54. As described above, the conductive portion 53 may have a multilayer structure or may have a laminated structure of two or more layers.

As described above, the conductive portion 53 has a two-layer structure. As in the modification shown in FIG. 5, the conductive particles 61 may have a solder portion 62 as a single-layer conductive portion (conductive layer). In the electroconductive particle which has a solder on the electroconductive outer surface, the surface part (surface layer) at least the outer side of the electroconductive part in electroconductive particle should just be a solder part. However, the conductive particles 51 are preferable among the conductive particles 51 and the conductive particles 61 because the conductive particles can be easily produced. Further, as in the modification shown in FIG. 6, the solder particles 11A that do not have the base particles in the core and are not core-shell particles may be used. In the solder particles 11A, both the central portion and the conductive outer surface are formed of solder.

Conductive particles 51 and 61 and solder particles 11A can be used in the conductive paste. From the viewpoint of effectively increasing the conduction reliability between the electrodes and also improving the connection reliability, among the conductive particles 51 and 61 and the solder particles 11A, the solder particles 11A are particularly preferable.

The conductive part is not particularly limited. Gold, silver, copper, nickel, palladium, tin, etc. are mentioned as a metal which comprises the said electroconductive part. Examples of the conductive layer include a gold layer, a silver layer, a copper layer, a nickel layer, a palladium layer, or a conductive layer containing tin.

From the viewpoint of increasing the contact area between the electrode and the conductive particle and further enhancing the conduction reliability between the electrodes, the conductive particle is composed of a resin particle and a conductive layer (on the surface of the resin particle ( First conductive layer). From the viewpoint of further improving the conduction reliability between the electrodes, the conductive particles are preferably conductive particles having at least a conductive outer surface of a low melting point metal layer. More preferably, the conductive particles have base particles and a conductive layer disposed on the surface of the base particles, and at least the outer surface of the conductive layer is a low melting point metal layer. More preferably, the conductive particles include base particles and conductive portions arranged on the surfaces of the base particles, and at least the outer surface of the conductive portions is a low melting point metal layer.

The solder is preferably a low melting point metal having a melting point of 450 ° C. or lower. The solder particles are preferably low melting point metal particles having a melting point of 450 ° C. or lower. The low melting point metal particles are particles containing a low melting point metal. The low melting point metal is a metal having a melting point of 450 ° C. or lower. The melting point of the low melting point metal is preferably 300 ° C. or lower, more preferably 160 ° C. or lower. The solder contains tin. In 100% by weight of the metal contained in the solder, the content of tin is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the content of tin in the solder is not less than the above lower limit, the connection reliability between the solder portion and the electrode is further enhanced.

The tin content is determined using a high-frequency inductively coupled plasma emission spectrometer (“ICP-AES” manufactured by Horiba, Ltd.) or a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu). It can be measured.

Using the conductive particles having the above-mentioned solder on the conductive outer surface, the solder is melted and joined to the electrodes, and the solder portion conducts between the electrodes. For example, since the solder portion and the electrode are not in point contact but in surface contact, the connection resistance is lowered. In addition, the use of conductive particles having solder on the outer surface increases the bonding strength between the solder part and the electrode. As a result, peeling between the solder part and the electrode is further less likely to occur. Reliability is effectively increased.

The low melting point metal constituting the solder is not particularly limited. The low melting point metal is preferably tin or an alloy containing tin. Examples of the alloy include a tin-silver alloy, a tin-copper alloy, a tin-silver-copper alloy, a tin-bismuth alloy, a tin-zinc alloy, and a tin-indium alloy. Of these, the low melting point metal is preferably tin, a tin-silver alloy, a tin-silver-copper alloy, a tin-bismuth alloy, or a tin-indium alloy because of its excellent wettability with respect to the electrode. More preferred are a tin-bismuth alloy and a tin-indium alloy.

The solder is preferably a filler material having a liquidus of 450 ° C. or lower based on JIS Z3001: Welding terminology. Examples of the composition of the solder include a metal composition containing zinc, gold, silver, lead, copper, tin, bismuth, indium and the like. Of these, a tin-indium system (117 ° C. eutectic) or a tin-bismuth system (139 ° C. eutectic) which is low-melting and lead-free is preferable. That is, the solder preferably does not contain lead, and preferably contains tin and indium, or contains tin and bismuth.

In order to further increase the bonding strength between the solder part and the electrode, the solder may contain phosphorus and tellurium, and nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, germanium, cobalt, Metals such as bismuth, manganese, chromium, molybdenum, and palladium may be included. Moreover, from the viewpoint of further increasing the bonding strength between the solder portion and the electrode, the solder preferably contains nickel, copper, antimony, aluminum, or zinc. From the viewpoint of further increasing the bonding strength between the solder part and the electrode, the content of these metals for increasing the bonding strength is preferably 0.0001% by weight or more, preferably 1% by weight in 100% by weight of the solder. It is as follows.

The average particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 3 μm or more, particularly preferably 5 μm or more, preferably 100 μm or less, more preferably 30 μm or less, still more preferably 20 μm. Hereinafter, it is particularly preferably 15 μm or less, most preferably 10 μm or less. When the average particle diameter of the conductive particles is not less than the above lower limit and not more than the above upper limit, the conductive particles can be more efficiently arranged on the electrode. The average particle diameter of the conductive particles is particularly preferably 3 μm or more and 30 μm or less.

The “average particle size” of the conductive particles indicates a number average particle size. The average particle diameter of the conductive particles is obtained, for example, by observing 50 arbitrary conductive particles with an electron microscope or an optical microscope and calculating an average value.

In 100% by weight of the conductive paste, the content of the conductive particles is preferably 0.1% by weight or more, more preferably 1% by weight or more, still more preferably 2% by weight or more, and further preferably 10% by weight or more. It is particularly preferably 20% by weight or more, most preferably 30% by weight or more, preferably 80% by weight or less, more preferably 60% by weight or less, and further preferably 50% by weight or less. When the content of the conductive particles is not less than the above lower limit and not more than the above upper limit, the conductive particles can be arranged more efficiently on the electrodes, and it is easy to arrange many conductive particles between the electrodes. Therefore, the conduction reliability is further enhanced. From the viewpoint of further improving the conduction reliability, the content of the conductive particles is preferably large.

(Compound curable by heating: thermosetting component)
The thermosetting compound is not particularly limited as long as it is solid at 25 ° C. and can be dispersed in the form of particles in the conductive paste. For example, at 25 ° C., the thermosetting compound that is solid at 25 ° C. is dispersed in the conductive paste. FIG. 7 shows an image of the thermosetting compound dispersed in the form of particles in the conductive paste according to one embodiment of the present invention.

Examples of the thermosetting compound that is solid at 25 ° C. include oxetane compounds, epoxy compounds, episulfide compounds, (meth) acrylic compounds, phenolic compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, polyimide compounds, and polythiols. Etc. As for the said thermosetting compound which is solid at 25 degreeC, only 1 type may be used and 2 or more types may be used together.

From the viewpoint of improving the dispersion state of the thermosetting compound that is solid at 25 ° C. in the conductive paste and exhibiting the effects of the present invention more effectively, the thermosetting compound that is solid at 25 ° C. is It is preferably a thermosetting epoxy compound that is solid at 25 ° C. Moreover, connection reliability becomes still higher by using an epoxy compound.

From the viewpoint of effectively increasing the conduction reliability between the electrodes, the melting point of the thermosetting compound that is solid at 25 ° C. is preferably 40 ° C. or higher, more preferably 70 ° C. or higher, still more preferably 90 ° C. or higher, Preferably it is 160 degrees C or less, More preferably, it is 140 degrees C or less, More preferably, it is 120 degrees C or less.

From the viewpoint of making it difficult for the viscosity of the conductive paste to drop sharply when melting a thermosetting compound that is solid at 25 ° C., suppressing excessive sedimentation of the conductive particles, and as a result effectively increasing the conduction reliability between the electrodes. The thermosetting compound which is solid at 25 ° C. has a melting point different from that of the first thermosetting compound which is solid at 25 ° C. and the first thermosetting compound and is solid at 25 ° C. It is preferable to contain the 2nd thermosetting compound which is.

From the viewpoint of effectively increasing the conduction reliability between the electrodes, the absolute value of the difference between the melting point of the first thermosetting compound and the melting point of the second thermosetting compound is preferably 1 ° C. or more. Preferably it is 5 degreeC or more, More preferably, it is 10 degreeC or more, Preferably it is 30 degrees C or less, More preferably, it is 20 degrees C or less.

From the viewpoint of improving the dispersion state of the thermosetting compound that is solid at 25 ° C., and more effectively exerting the effects of the present invention, the conductive paste contains a thermosetting compound that is liquid at 25 ° C. It is preferable to include. Examples of the thermosetting compound that is liquid at 25 ° C. include oxetane compounds, epoxy compounds, episulfide compounds, (meth) acrylic compounds, phenolic compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, polyimide compounds, and polythiols. Etc. As the thermosetting compound that is liquid at 25 ° C., only one type may be used, or two or more types may be used in combination.

From the viewpoint of further improving the curability and viscosity of the conductive paste and further enhancing the connection reliability, the thermosetting compound that is liquid at 25 ° C. is a thermosetting epoxy compound that is liquid at 25 ° C. Is preferred.

The total content of the thermosetting compound that is solid at 25 ° C. and the thermosetting compound that is liquid at 25 ° C. in 100% by weight of the conductive paste is preferably 20% by weight or more, more preferably 40%. % By weight or more, more preferably 50% by weight or more, preferably 99% by weight or less, more preferably 98% by weight or less, still more preferably 90% by weight or less, and particularly preferably 80% by weight or less. From the viewpoint of further improving the impact resistance, it is preferable that the content of the thermosetting component is large.

The content of the thermosetting compound that is solid at 25 ° C. and the thermosetting epoxy compound that is solid at 25 ° C. in the conductive paste of 100% by weight is preferably 5% by weight or more, and more preferably 10% by weight. % Or more, preferably 70% by weight or less, more preferably 50% by weight or less. When the content of the thermosetting compound that is solid at 25 ° C. and the content of the thermosetting epoxy compound that is solid at 25 ° C. is not less than the above lower limit and not more than the above upper limit, the coating properties of the conductive paste and the conductive particles The placement accuracy is further increased.

The content of the thermosetting compound that is liquid at 25 ° C. and the thermosetting epoxy compound that is liquid at 25 ° C. is preferably 5% by weight or more, and more preferably 10% by weight in 100% by weight of the conductive paste. % Or more, preferably 70% by weight or less, more preferably 50% by weight or less. When the content of the thermosetting compound that is liquid at 25 ° C. and the content of the thermosetting epoxy compound that is liquid at 25 ° C. is not less than the above lower limit and not more than the above upper limit, The placement accuracy is further increased.

The difference in SP value between the thermosetting compound which is solid at 25 ° C. and the thermosetting compound which is liquid at 25 ° C. is preferably 0.5 or more, more preferably 1 or more, preferably 3 or less, more preferably 2 or less. When the difference in SP value is not less than the above lower limit and not more than the above upper limit, it can stably exist as particles of a thermosetting compound that is solid at 25 ° C., and the arrangement accuracy of the conductive particles of the conductive paste is more It gets even higher.

(Thermosetting agent: thermosetting component)
The thermosetting agent thermosets the thermosetting compound. Examples of the thermosetting agent include an imidazole curing agent, an amine curing agent, a phenol curing agent, a polythiol curing agent, an acid anhydride, a thermal cation initiator, and a thermal radical generator. As for the said thermosetting agent, only 1 type may be used and 2 or more types may be used together.

Among these, an imidazole curing agent, a polythiol curing agent, or an amine curing agent is preferable because the conductive paste can be cured more rapidly at a low temperature. Moreover, since a storage stability becomes high when the curable compound curable by heating and the thermosetting agent are mixed, a latent curing agent is preferable. The latent curing agent is preferably a latent imidazole curing agent, a latent polythiol curing agent or a latent amine curing agent. In addition, the said thermosetting agent may be coat | covered with polymeric substances, such as a polyurethane resin or a polyester resin.

The imidazole curing agent is not particularly limited, and 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2, 4-Diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine and 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s- Examples include triazine isocyanuric acid adducts.

The polythiol curing agent is not particularly limited, and examples thereof include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate. .

The amine curing agent is not particularly limited, and hexamethylenediamine, octamethylenediamine, decamethylenediamine, 3,9-bis (3-aminopropyl) -2,4,8,10-tetraspiro [5.5]. Examples include undecane, bis (4-aminocyclohexyl) methane, metaphenylenediamine, and diaminodiphenylsulfone.

Examples of the thermal cation curing agent include iodonium cation curing agents, oxonium cation curing agents, and sulfonium cation curing agents. Examples of the iodonium-based cationic curing agent include bis (4-tert-butylphenyl) iodonium hexafluorophosphate. Examples of the oxonium-based cationic curing agent include trimethyloxonium tetrafluoroborate. Examples of the sulfonium-based cationic curing agent include tri-p-tolylsulfonium hexafluorophosphate.

The thermal radical generator is not particularly limited, and examples thereof include azo compounds and organic peroxides. Examples of the azo compound include azobisisobutyronitrile (AIBN). Examples of the organic peroxide include di-tert-butyl peroxide and methyl ethyl ketone peroxide.

The reaction initiation temperature (curing temperature) of the thermosetting agent is preferably 50 ° C. or higher, more preferably 70 ° C. or higher, still more preferably 80 ° C. or higher, preferably 250 ° C. or lower, more preferably 200 ° C. or lower, still more preferably. 150 ° C. or lower, particularly preferably 140 ° C. or lower. When the reaction start temperature of the thermosetting agent is not less than the above lower limit and not more than the above upper limit, the conductive particles are more efficiently arranged on the electrode. The reaction initiation temperature of the thermosetting agent is particularly preferably 80 ° C. or higher and 140 ° C. or lower.

From the viewpoint of more efficiently arranging the conductive particles on the electrode, the reaction initiation temperature of the thermosetting agent is preferably lower than the melting point of the solder in the conductive particles, and more preferably 5 ° C. or lower. More preferably, it is 10 ° C. or lower.

The reaction start temperature of the thermosetting agent means the temperature at which the exothermic peak of DSC starts to rise.

The content of the thermosetting agent is not particularly limited. The content of the thermosetting agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, preferably 200 parts by weight or less with respect to 100 parts by weight of the thermosetting compound that is solid at 25 ° C. The amount is more preferably 100 parts by weight or less, still more preferably 75 parts by weight or less, still more preferably 50 parts by weight or less, and particularly preferably 37.5 parts by weight or less. The content of the thermosetting agent is preferably 0.01 parts by weight or more with respect to a total of 100 parts by weight of the thermosetting compound that is solid at 25 ° C. and the thermosetting compound that is liquid at 25 ° C. More preferably, it is 1 part by weight or more, preferably 200 parts by weight or less, more preferably 100 parts by weight or less, still more preferably 75 parts by weight or less. When the content of the thermosetting agent is at least the above lower limit, it is easy to sufficiently cure the conductive paste. When the content of the thermosetting agent is not more than the above upper limit, it is difficult for an excess thermosetting agent that did not participate in curing after curing to remain, and the heat resistance of the cured product is further enhanced.

(flux)
The conductive paste preferably contains a flux. In the case where the conductive particles are conductive particles having solder on a conductive surface, it is preferable to use a flux. By using flux, the solder can be more effectively placed on the electrode. The flux is not particularly limited. As the flux, a flux generally used for soldering or the like can be used. Examples of the flux include zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, an organic acid, and pine resin. Etc. As for the said flux, only 1 type may be used and 2 or more types may be used together.

Examples of the molten salt include ammonium chloride. Examples of the organic acid include lactic acid, citric acid, stearic acid, glutamic acid, and glutaric acid. Examples of the pine resin include activated pine resin and non-activated pine resin. The flux is preferably an organic acid having two or more carboxyl groups, pine resin. The flux may be an organic acid having two or more carboxyl groups, or pine resin. By using an organic acid having two or more carboxyl groups, pine resin, the conduction reliability between the electrodes is further enhanced.

The above rosins are rosins whose main component is abietic acid. The flux is preferably rosins, and more preferably abietic acid. By using this preferable flux, the conduction reliability between the electrodes is further enhanced.

The melting point of the flux is preferably 50 ° C. or higher, more preferably 70 ° C. or higher, still more preferably 80 ° C. or higher, preferably 200 ° C. or lower, more preferably 160 ° C. or lower, even more preferably 150 ° C. or lower, still more preferably. 140 ° C. or lower. When the melting point of the flux is not less than the above lower limit and not more than the above upper limit, the flux effect is more effectively exhibited and the solder particles are more efficiently arranged on the electrode. The melting point of the flux is preferably 80 ° C. or higher and 190 ° C. or lower. The melting point of the flux is particularly preferably 80 ° C. or higher and 140 ° C. or lower.

Examples of the flux having a melting point of 80 ° C. or higher and 190 ° C. or lower include succinic acid (melting point 186 ° C.), glutaric acid (melting point 96 ° C.), adipic acid (melting point 152 ° C.), pimelic acid (melting point 104 ° C.), suberic acid Examples thereof include dicarboxylic acids such as (melting point 142 ° C.), benzoic acid (melting point 122 ° C.), and malic acid (melting point 130 ° C.).

The boiling point of the flux is preferably 200 ° C. or lower.

From the viewpoint of more efficiently arranging the solder on the electrode, the melting point of the flux is preferably lower than the melting point of the solder in the solder particles, more preferably 5 ° C. or more, more preferably 10 ° C. or more. Is more preferable.

From the viewpoint of more efficiently arranging the solder on the electrode, the melting point of the flux is preferably lower than the reaction start temperature of the thermosetting agent, more preferably 5 ° C. or more, and more preferably 10 ° C. or less. More preferably.

The flux may be dispersed in the conductive paste or may be adhered on the surface of the conductive particles.

In 100% by weight of the conductive paste, the content of the flux is preferably 0.5% by weight or more, preferably 30% by weight or less, more preferably 25% by weight or less. The conductive paste may not contain a flux. When the flux content is not less than the above lower limit and not more than the above upper limit, it becomes more difficult to form an oxide film on the surface of the solder and the electrode, and the oxide film formed on the surface of the solder and the electrode is more effective. Can be removed.

(Filler)
The conductive paste may contain a filler. By using the filler, the latent heat expansion of the cured product of the conductive paste can be suppressed. However, from the viewpoint of further improving the coating property of the conductive paste and the arrangement accuracy of the conductive particles, it is better not to use a filler, and in the case of using a filler, the smaller the filler content is, the better.

It is preferable that the conductive paste does not contain a filler or contains a filler in an amount of 1% by weight or less in 100% by weight of the conductive paste. When the conductive paste contains a filler, the filler content is more preferably 0.5% by weight or less.

Examples of the filler include inorganic fillers such as silica, talc, aluminum nitride, and alumina. The filler may be an organic filler or an organic-inorganic composite filler. As for the said filler, only 1 type may be used and 2 or more types may be used together.

(Other ingredients)
If necessary, the conductive paste is, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, and a lubricant. In addition, various additives such as an antistatic agent and a flame retardant may be included.

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. The present invention is not limited only to the following examples.

Polymer A
Synthesis of the first reaction product of bisphenol F with 1,6-hexanediol diglycidyl ether and bisphenol F type epoxy resin:
72 parts by weight of bisphenol F (containing 4,4′-methylene bisphenol, 2,4′-methylene bisphenol and 2,2′-methylene bisphenol in a weight ratio of 2: 3: 1), 1,6-hexanediol 70 parts by weight of diglycidyl ether and 30 parts by weight of bisphenol F type epoxy resin (“EPICLON EXA-830CRP” manufactured by DIC) were placed in a three-necked flask and dissolved at 150 ° C. under a nitrogen flow. Thereafter, 0.1 part by weight of tetra-n-butylsulfonium bromide, which is an addition reaction catalyst between a hydroxyl group and an epoxy group, was added and subjected to an addition polymerization reaction at 150 ° C. for 6 hours under a nitrogen flow, whereby polymer A was obtained. Obtained.

After confirming that the addition polymerization reaction has progressed by NMR, the polymer A is a structural unit in which a hydroxyl group derived from bisphenol F and 1,6-hexanediol diglycidyl ether and an epoxy group of a bisphenol F-type epoxy resin are bonded. In the main chain and having an epoxy group at both ends.

Polymer A obtained by GPC had a weight average molecular weight of 10,000 and a number average molecular weight of 3,500.

Polymer B: both ends epoxy group rigid skeleton phenoxy resin, “YX6900BH45” manufactured by Mitsubishi Chemical Corporation, weight average molecular weight 16000

Thermosetting compound 1 (solid at 25 ° C, thermosetting epoxy compound, “EX-201” manufactured by Nagase ChemteX Corporation, crystallized at −5 ° C., washed with hexane, and hexane removed by vacuum drying use)

Thermosetting compound 2 (solid at 25 ° C, thermosetting epoxy compound, “HP-4032D” manufactured by DIC is crystallized at −5 ° C., washed with hexane, and used after removing hexane by vacuum drying)

Thermosetting compound 3 (liquid at 25 ° C., thermosetting epoxy compound, “1,6-hexanediol glycidyl ether” manufactured by Yokkaichi Gosei Co., Ltd.)

Thermosetting compound 4 (liquid at 25 ° C, thermosetting polythiol compound, Showa Denko "Karenz MT PE1")

Thermosetting compound 5 (solid at 25 ° C, thermosetting epoxy compound, ADEKA "EP-3300" crystallized at -5 ° C, washed with hexane, hexane removed by vacuum drying)

Thermosetting compound 6 (solid at 25 ° C, thermosetting epoxy compound, "TEPIC-SS" manufactured by Nissan Chemical Co., Ltd. crystallized at -5 ° C, washed with hexane, hexane removed by vacuum drying and used )

Thermosetting compound 7 (solid at 25 ° C, thermosetting epoxy compound, "TEP-G" manufactured by Asahi Organic Materials Co., Ltd. is crystallized at -5 ° C, washed with hexane, and hexane removed by vacuum drying. After use)

Flux (“Adipic acid” manufactured by Wako Pure Chemical Industries, Ltd.)

Filler (hydrophobic fumed silica, “Leo Seal MT-10” manufactured by Tokuyama)

Conductive particles 1 (SnBi solder particles, melting point 139 ° C., “ST-5” manufactured by Mitsui Kinzoku Co., Ltd., average particle size 5.4 μm)

Conductive particles 2 (SnBi solder particles, melting point 139 ° C., Mitsui Kinzoku “DS-10”, average particle size 12 μm)

Conductive particles 3: (resin core solder coated particles, prepared by the following procedure)
Divinylbenzene resin particles (“Micropearl SP-207” manufactured by Sekisui Chemical Co., Ltd., average particle diameter: 7 μm) were subjected to electroless nickel plating to form a base nickel plating layer having a thickness of 0.1 μm on the surface of the resin particles. Next, the resin particles on which the base nickel plating layer was formed were subjected to electrolytic copper plating to form a 1 μm thick copper layer. Furthermore, electrolytic plating was performed using an electrolytic plating solution containing tin and bismuth to form a solder layer having a thickness of 1 μm. Thus, a 1 μm thick copper layer is formed on the surface of the resin particles, and a 1 μm thick solder layer (tin: bismuth = 43 wt%: 57 wt%) is formed on the surface of the copper layer. Conductive particles (average particle diameter 14 μm, resin core solder-coated particles) were prepared.

Conductive particles 4: Au plated particles of divinylbenzene resin particles (“Au-210” manufactured by Sekisui Chemical Co., Ltd., average particle size 10 μm)

Phenoxy resin (“YP-50S” manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)

(Examples 1 to 10, 12 to 17)
(1) Preparation of anisotropic conductive paste The components shown in Tables 1 and 2 below were blended in the blending amounts shown in Tables 1 and 2 to obtain anisotropic conductive pastes.

Moreover, only the polymer A and the thermosetting compound in the components shown in Tables 1 and 2 below were blended and stirred at 120 ° C. for 1 hour at 60 rpm. Then, it cooled to room temperature over 3 hours, stirring at 60 rpm. Thereafter, the particles were sandwiched between glass plates, and the particle diameter of the precipitated thermosetting compound at 25 ° C. was observed with an optical microscope. The particle size of 100 particles was measured and the average particle size was determined.

(2) Production of first connection structure (L / S = 50 μm / 50 μm) Glass epoxy substrate (FR-4 substrate) having a copper electrode pattern (copper electrode thickness 10 μm) having an L / S of 50 μm / 50 μm on the upper surface (First connection object member) was prepared. Moreover, the flexible printed circuit board (2nd connection object member) which has a copper electrode pattern (copper electrode thickness 10 micrometers) whose L / S is 50 micrometers / 50 micrometers on the lower surface was prepared.

The overlapping area of the glass epoxy substrate and the flexible printed board was 1.5 cm × 4 mm, and the number of connected electrodes was 75 pairs.

The anisotropic conductive paste immediately after fabrication was applied to the upper surface of the glass epoxy substrate so as to have a thickness of 50 μm by screen printing to form an anisotropic conductive paste layer. Next, the flexible printed circuit board was laminated on the upper surface of the anisotropic conductive paste layer so that the electrodes face each other. At this time, no pressure was applied. The weight of the flexible printed board is added to the anisotropic conductive paste layer. Thereafter, while heating the anisotropic conductive paste layer to a temperature of 185 ° C., the solder was melted and the anisotropic conductive paste layer was cured at 185 ° C. to obtain a first connection structure.

(3) Production of second connection structure (L / S = 75 μm / 75 μm) Glass epoxy substrate (FR-4 substrate) having a copper electrode pattern (copper electrode thickness 10 μm) having L / S of 75 μm / 75 μm on the upper surface (First connection object member) was prepared. Moreover, the flexible printed circuit board (2nd connection object member) which has a copper electrode pattern (copper electrode thickness 10 micrometers) whose L / S is 75 micrometers / 75 micrometers on the lower surface was prepared.

2nd connection structure was obtained like manufacture of the 1st connection structure except having used the above-mentioned glass epoxy board and flexible printed circuit board from which L / S differs.

(4) Production of third connection structure (L / S = 100 μm / 100 μm) Glass epoxy substrate (FR-4 substrate) having a copper electrode pattern (copper electrode thickness 10 μm) with L / S of 100 μm / 100 μm on the upper surface (First connection object member) was prepared. Moreover, the flexible printed circuit board (2nd connection object member) which has a copper electrode pattern (copper electrode thickness 10 micrometers) whose L / S is 100 micrometers / 100 micrometers on the lower surface was prepared.

3rd connection structure was obtained like manufacture of the 1st connection structure except having used the above-mentioned glass epoxy board and flexible printed circuit board from which L / S differs.

(5) Production of fourth connection structure (L / S = 50 μm / 50 μm) Glass epoxy substrate (FR-4 substrate) (first connection target member) for obtaining the first connection structure; The flexible printed circuit board (second connection target member) for obtaining the first connection structure was stored at 120 ° C. and a humidity of 20% for 1 hour. A fourth connection structure was obtained in the same manner as the first connection structure except that the first and second connection target members after storage were used.

(6) Production of fifth connection structure (L / S = 75 μm / 75 μm) Glass epoxy substrate (FR-4 substrate) (first connection target member) for obtaining the second connection structure; The flexible printed circuit board (second connection target member) for obtaining the second connection structure was stored at 120 ° C. and a humidity of 20% for 1 hour. A fifth connection structure was obtained in the same manner as the production of the second connection structure except that the first and second connection target members after storage were used.

(7) Production of sixth connection structure (L / S = 100 μm / 100 μm) Glass epoxy substrate (FR-4 substrate) (first connection target member) for obtaining the third connection structure; The flexible printed circuit board (second connection target member) for obtaining the third connection structure was stored at 120 ° C. and a humidity of 20% for 1 hour. Except having used the 1st, 2nd connection object member after storage, it carried out similarly to preparation of the 3rd connection structure, and obtained the 6th connection structure.

(Example 11)
The electrode size / inter-electrode space is 50 μm / 50 μm (for the first and fourth connection structures), 75 μm / 75 μm (for the second and fifth connection structures), 100 μm / 100 μm (the third and sixth A glass epoxy substrate (size 30 × 30 mm, thickness 0.4 mm) having a 5 mm square semiconductor chip (thickness 400 μm) and an electrode facing it is used for the connection structure. 4th, 5th and 6th connection structures were obtained.

(Comparative Example 1)
10 parts by weight of phenoxy resin (“YP-50S” manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) was dissolved in methyl ethyl ketone (MEK) so that the solid content was 50% by weight to obtain a solution. Ingredients other than the phenoxy resin shown in Table 2 below were blended with the blending amounts shown in Table 2 below and the total amount of the above solution, and after stirring for 5 minutes at 2000 rpm using a planetary stirrer, a bar coater was used. It was coated on a release PET (polyethylene terephthalate) film so that the thickness after drying was 30 μm. An anisotropic conductive film was obtained by removing MEK by vacuum drying at room temperature.

The 1st, 2nd, 3rd, 4th, 5th, 6th connection structure was obtained like Example 1 except having used the anisotropic conductive film.

(Evaluation)
(1) Viscosity The viscosity η1 at 25 ° C. and 5 rpm of the anisotropic conductive paste was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.). Further, the viscosity η2 at 25 ° C. and 0.5 rpm of the anisotropic conductive paste was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.). The ratio (η1 / η2) was determined from the measured values obtained.

Further, the melting point of the solder in the conductive particles of the anisotropic conductive paste was measured at −5 ° C. and the viscosity η1 ′ at 5 rpm using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.). Further, the melting point of the solder in the conductive particles of the anisotropic conductive paste was measured at −5 ° C. and the viscosity η2 ′ at 0.5 rpm using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.). The ratio (η1 ′ / η2 ′) was determined from the obtained measured values. The ratio (η1 ′ / η2 ′) was determined according to the following criteria.

[Criteria for ratio (η1 ′ / η2 ′)]
A: 1 or more, 2 or less B: Does not correspond to the standard of A

(2) Dispersion State In the anisotropic conductive paste, the dispersion state and particle size of the thermosetting compound that was solid at 25 ° C. were observed using an electron microscope. The dispersion state was judged according to the following criteria.

[Distribution status criteria]
◯: In the conductive paste, the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles, and the particle size of the particulate thermosetting compound is 1 μm or more and 10 μm or less. In the paste, the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles, and the particle size of the particulate thermosetting compound is more than 10 μm and not more than 40 μm Δ: In the conductive paste The thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles, and the particle size of the particulate thermosetting compound exceeds 40 μm. X: Solid at 25 ° C. in the conductive paste Some thermosetting compounds are not dispersed in particulate form

(3) Coatability Whether or not uneven coating occurs when the anisotropic conductive paste immediately after fabrication is coated to a thickness of 50 μm by screen printing in order to obtain the first connection structure. Evaluated. The coatability was determined according to the following criteria.

[Criteria for coating properties]
○: Can be applied with a thickness variation of less than 5 μm, and the anisotropic conductive paste does not wet and spread in unintended areas. Δ: Can be applied with a thickness variation of 5 μm or more and less than 10 μm, and intended. The anisotropic conductive paste does not wet and spread in the areas where it does not. X: Thickness variation of 10 μm or more occurs after coating, or the anisotropic conductive paste wets and spreads in unintended areas

(4) Inter-electrode spacing By observing a cross section of the obtained first connection structure, the inter-electrode spacing D1 (distance D1 of the connecting portion) at the position where the upper and lower electrodes face each other was evaluated.

(5) Disposition accuracy of conductive particles on electrodes In the cross sections (cross sections in the direction shown in FIG. 1) of the obtained first, second and third connection structures, conductive particles (solder) appearing in the cross section The area A1 (%) of the conductive particles (solder particles, etc.) remaining in the cured product away from the conductive particles disposed between the electrodes was evaluated. In addition, the average of the area in five cross sections was computed. The arrangement accuracy of the conductive particles on the electrode was determined according to the following criteria.

[Judgment criteria for placement accuracy of conductive particles on electrode]
○○: Area A1 is 0%
○: Area A1 exceeds 0% and 10% or less △: Area A1 exceeds 10% and 30% or less ×: Area A1 exceeds 30%

(6) Connection reliability between upper and lower electrodes In the obtained first, second, third, fourth, fifth and sixth connection structures (n = 15), connection resistance between the upper and lower electrodes Was measured by a four-terminal method. The average value of connection resistance was calculated. Note that the connection resistance can be obtained by measuring the voltage when a constant current is passed from the relationship of voltage = current × resistance. The conduction reliability was determined according to the following criteria.

[Judgment criteria for conduction reliability]
○○: Average value of connection resistance is 8.0Ω or less ○: Average value of connection resistance exceeds 8.0Ω and 10.0Ω or less △: Average value of connection resistance exceeds 10.0Ω and 15.0Ω or less × : Average connection resistance exceeds 15.0Ω

(7) Insulation reliability between adjacent electrodes In the obtained first, second, third, fourth, fifth and sixth connection structures (n = 15), 85 ° C. and humidity of 85% After being left in the atmosphere for 100 hours, 5 V was applied between adjacent electrodes, and the resistance value was measured at 25 locations. Insulation reliability was judged according to the following criteria.

[Criteria for insulation reliability]
◯: Average value of connection resistance is 10 ⁷ Ω or more ○: Average value of connection resistance is 10 ⁶ Ω or more, less than 10 ⁷ Ω △: Average value of connection resistance is 10 ⁵ Ω or more, less than 10 ⁶ Ω ×: Connection The average resistance is less than 10 ⁵ Ω

The results are shown in Tables 1 and 2 below.

From the difference between the results of Example 1 and Comparative Example 1 and the difference between the results of Example 11 and Comparative Example 3, when the second connection target member is a flexible printed circuit board, the second connection target member is It can be seen that the effect of improving the conduction reliability by using the conductive paste of the present invention can be obtained more effectively than in the case of a semiconductor chip. In addition, in the evaluation of conduction reliability (results OO) of Examples 16 and 17, since a plurality of thermosetting compounds that are solid at 25 ° C. having different melting points are used, the evaluation of other examples (results ◯) The specific value of the connection resistance was lower than (including ○). In Examples 16 and 17, the conduction reliability was particularly excellent as compared with the other examples.

DESCRIPTION OF SYMBOLS 1,1X ... Connection structure 2 ... 1st connection object member 2a ... 1st electrode 3 ... 2nd connection object member 3a ... 2nd electrode 4, 4X ... Connection part 4A, 4XA ... Solder part 4B, 4XB ... cured material part 11 ... conductive paste 11A ... solder particle 11B ... thermosetting component 51 ... conductive particle 51a ... outer surface 52 ... base particle 52a ... outer surface 53 ... conductive part 54 ... first conductive part 54a ... outside Surface 55 ... Solder part 61 ... Conductive particles 62 ... Solder part

Claims (18)

Including a thermosetting component and a plurality of conductive particles;
The thermosetting component contains a thermosetting compound that is solid at 25 ° C., and a thermosetting agent,
The conductive paste in which the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles in the conductive paste. The conductive paste according to claim 1, comprising a thermosetting compound that is liquid at 25 ° C. The conductive paste according to claim 1 or 2, wherein the thermosetting compound that is solid at 25 ° C is a thermosetting epoxy compound that is solid at 25 ° C. The thermosetting compound that is solid at 25 ° C. has a melting point different from that of the first thermosetting compound that is solid at 25 ° C. and is solid at 25 ° C. The conductive paste according to any one of claims 1 to 3, comprising a second thermosetting compound. The conductive paste according to any one of claims 1 to 4, wherein the conductive particles have solder on a conductive outer surface. The conductive paste according to claim 5, wherein the conductive particles are solder particles. The ratio of the melting point of the solder in the conductive particles at −5 ° C. and 5 rpm to the melting point of the solder in the conductive particles at −5 ° C. and 0.5 rpm is 1 or more and 2 or less. The conductive paste according to 5 or 6. The conductive paste according to any one of claims 1 to 7, wherein the particle size of the thermosetting compound in a particulate form is 1 µm or more and 40 µm or less. The conductive paste according to any one of claims 1 to 8, wherein the ratio of the viscosity at 25 ° C and 5 rpm to the viscosity at 25 ° C and 0.5 rpm is 2.5 or more and 7 or less. The conductive paste according to claim 9, wherein the ratio of the viscosity at 25 ° C. and 5 rpm to the viscosity at 25 ° C. and 0.5 rpm is 4 or more and 7 or less. The conductive paste according to any one of claims 1 to 10, comprising a flux. The conductive paste according to any one of claims 1 to 11, which does not contain a filler or contains a filler in an amount of 1% by weight or less in 100% by weight of the conductive paste. A method for producing a conductive paste according to any one of claims 1 to 12,
A thermosetting component containing a thermosetting compound that is solid at 25 ° C., a thermosetting agent, and a plurality of conductive particles are mixed to obtain a mixture, and then the mixture is added at 25 ° C. By heating to a temperature equal to or higher than the melting point of the solid thermosetting compound and lower than the curing temperature of the thermosetting component, and solidifying after melting the thermosetting compound that is solid at 25 ° C., at 25 ° C. Obtaining a conductive paste in which a solid thermosetting compound is dispersed in the form of particles, or
The thermosetting compound that is solid at 25 ° C. is made into particles, then the thermosetting compound that is particulate and solid at 25 ° C., a thermosetting component containing a thermosetting agent, and a plurality of conductive materials A method for producing a conductive paste, which is a mixture containing conductive particles and obtains a conductive paste in which the thermosetting compound that is solid at 25 ° C. is dispersed in the form of particles. A first connection target member having at least one first electrode on its surface;
A second connection target member having at least one second electrode on its surface;
A connecting portion connecting the first connection target member and the second connection target member;
The connecting portion is formed of the conductive paste according to any one of claims 1 to 12,
The connection structure in which the first electrode and the second electrode are electrically connected by the conductive particles in the connection portion. The connection structure according to claim 14, wherein the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. Using the conductive paste according to any one of claims 1 to 12, disposing the conductive paste on a surface of a first connection target member having at least one first electrode on the surface;
On the surface opposite to the first connection target member side of the conductive paste, a second connection target member having at least one second electrode on the surface, the first electrode and the second electrode And a step of arranging so as to face each other,
The first connection object member and the second connection object member are heated by heating the conductive paste at a temperature equal to or higher than the melting point of the thermosetting compound that is solid at 25 ° C. and higher than the curing temperature of the thermosetting component. Connecting the first electrode and the second electrode with the conductive particles in the connection portion, and forming the connection portion connecting the first and second electrodes with the conductive paste. A method for manufacturing a connection structure. The weight of the second connection target member is added to the conductive paste without applying pressure in the step of arranging the second connection target member and the step of forming the connection part. Method for manufacturing the connection structure of the present invention. The method for manufacturing a connection structure according to claim 16 or 17, wherein the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board.

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