WO2015008628A1 - Silver-coated copper alloy powder and process for producing same - Google Patents

Abstract

A silver-coated copper alloy powder obtained by coating a copper alloy powder having a composition which contains 1-50 mass% nickel and/or zinc, the remainder comprising copper and unavoidable impurities, with 7-50 mass% silver-containing layer (layer comprising silver or a silver compound) is reduced to individual particles, thereby obtaining a silver-coated copper alloy powder which has a tap density of 5 g/cm³ or greater and in which the proportion of the tap density to the true density is 55-70%.

Description

Silver-coated copper alloy powder and method for producing the same

The present invention relates to a silver-coated copper alloy powder and a method for producing the same, and particularly to a silver-coated copper alloy powder used for a conductive paste and the like and a method for producing the same.

Conventionally, in order to form electrodes and wiring of electronic parts by printing methods, etc., conductive pastes prepared by blending a conductive metal powder such as silver powder or copper powder with a solvent, resin, dispersant, etc. have been used. .
However, although silver powder has a very small volume resistivity and is a good conductive material, it is a noble metal powder, and thus costs are high. On the other hand, copper powder has a low volume resistivity and is a good conductive material. However, since it is easily oxidized, it has poor storage stability (reliability) compared to silver powder.
In order to solve these problems, as the metal powder used in the conductive paste, a silver-coated copper powder in which the surface of the copper powder is coated with silver (see, for example, Japanese Patent Application Laid-Open Nos. 2010-174411 and 2010-077795) In other words, silver-coated copper alloy powders in which the surface of a copper alloy is coated with silver have been proposed (see, for example, Japanese Patent Application Laid-Open Nos. 08-311304 and 10-152630).
However, in the silver-coated copper powder disclosed in Japanese Patent Application Laid-Open Nos. 2010-174111 and 2010-077745, if there is a portion that is not coated with silver on the surface of the copper powder, oxidation proceeds from that portion. , Storage stability (reliability) becomes insufficient. Further, in the silver-coated copper alloy powders of JP-A Nos. 08-311304 and 10-152630, the volume resistivity of the conductive film is high (the conductivity is low) when used for the conductive film. There is.

Therefore, in view of the above-described conventional problems, an object of the present invention is to provide a silver-coated copper alloy powder capable of forming a conductive film having a low volume resistivity and a method for producing the same.
As a result of intensive research to solve the above problems, the present inventors have developed a copper alloy powder containing at least one of 1 to 50% by mass of nickel and zinc, with the balance being composed of copper and inevitable impurities. It is found that a silver-coated copper alloy powder capable of forming a conductive film having a low volume resistivity can be produced by coating with a 50 mass% silver-containing layer and setting the tap density to 5 g / cm ³ or more. The present invention has been completed.
That is, the silver-coated copper alloy powder according to the present invention contains 1 to 50% by mass of nickel and zinc, and the copper alloy powder having a composition consisting of copper and inevitable impurities is 7 to 50% by mass of silver. It is covered with a containing layer and has a tap density of 5 g / cm ³ or more.
In this silver-coated copper alloy powder, the silver-containing layer is preferably a layer made of silver or a silver compound, and the ratio of the tap density to the true density of the silver-coated copper alloy powder is preferably 55 to 70%. The aspect ratio of the silver-coated copper alloy powder is preferably less than 2, and the carbon content in the silver-coated copper alloy powder is preferably 0.05 to 0.30% by mass. Further, cumulative 50% particle diameter measured by a laser diffraction type particle size distribution apparatus of the copper alloy powder (D ₅₀ diameter) is preferably from 0.1 ~ 15 [mu] m.
The method for producing a silver-coated copper alloy powder according to the present invention comprises 7 to 50% by mass of a copper alloy powder having a composition comprising at least one of 1 to 50% by mass of nickel and zinc, and the balance consisting of copper and inevitable impurities. The silver-coated copper alloy powder obtained by coating with a silver-containing layer is monodispersed.
In this method for producing a silver-coated copper alloy powder, the silver-containing layer is preferably a layer made of silver or a silver compound. Further, by monodispersion, the tap density of the silver-coated copper alloy powder is preferably 5 g / cm ³ or more, and the ratio of the tap density to the true density of the silver-coated copper alloy powder is preferably 55 to 70%. . Moreover, it is preferable to surface-treat the copper alloy powder coat | covered with the silver containing layer with a surface treating agent before or after monodispersion, and it is preferable to use a fatty acid as the surface treating agent. Further, it is preferable to produce the copper alloy powder by an atomizing method, cumulative 50% particle diameter measured by a laser diffraction type particle size distribution apparatus of the copper alloy powder (D ₅₀ diameter) is preferably from 0.1 ~ 15 [mu] m.
Furthermore, the conductive paste according to the present invention includes a solvent and a resin, and includes the above silver-coated copper alloy powder as a conductive powder. Moreover, the conductive film according to the present invention is formed by curing the conductive paste.
In this specification, “tap density of silver-coated copper alloy powder” means filling a silver-coated copper alloy powder into a bottomed cylindrical container having an inner diameter of 6 mm to form a silver-coated copper alloy powder layer, After applying a pressure of 0.16 N / m ² from the top to this silver-coated copper alloy powder layer, the height of the silver-coated copper alloy powder layer is measured, and the measured value of the height of this silver-coated copper alloy powder layer and The density of the silver-coated copper alloy powder determined from the weight of the filled silver-coated copper alloy powder.
ADVANTAGE OF THE INVENTION According to this invention, the silver covering copper alloy powder which can form the electrically conductive film with low volume resistivity, and its manufacturing method can be provided.

In the embodiment of the silver-coated copper alloy powder according to the present invention, a copper alloy powder having a composition comprising at least one of 1 to 50% by mass of nickel and zinc and the balance consisting of copper and inevitable impurities is (silver-coated copper alloy). The tap density is 5 g / cm ³ or more, which is covered with 7 to 50% by mass of a silver-containing layer (a layer made of silver or a silver compound).
The content of at least one of nickel and zinc in the copper alloy powder of the silver-coated copper alloy powder is 1 to 50% by mass, and preferably 1 to 20% by mass. If the content of at least one kind of nickel and zinc is less than 1% by mass, copper in the copper alloy powder is significantly oxidized, which causes a problem in oxidation resistance. On the other hand, if it exceeds 50% by mass, the conductivity of the silver-coated copper alloy powder is adversely affected.
The coating amount of the silver-containing layer is 7 to 50% by mass, preferably 8 to 45% by mass, and more preferably 9 to 40% by mass. If the coating amount of the silver-containing layer is less than 7% by mass, the conductivity of the silver-coated copper alloy powder is adversely affected. On the other hand, if it exceeds 50 mass%, the cost increases due to an increase in the amount of silver used, which is not preferable.
The ratio of the tap density to the true density of the silver-coated copper alloy powder is preferably 55 to 70%. If the ratio of the tap density to the true density of the silver-coated copper alloy powder is 55% or more, the powder filling property in the conductive film formed by curing the conductive paste containing this silver-coated copper alloy powder as the conductive powder The contact probability between the silver-coated copper alloy particles is high, the conduction path is easily formed, and the volume resistivity of the conductive film can be reduced.
Particle size of the copper alloy powder is preferably 50% cumulative particle diameter measured by (Heroes method by) a laser diffraction type particle size distribution apparatus _{(D 50} diameter) is 0.1 ~ 15 [mu] m, at 0.3 ~ 10 [mu] m More preferably, it is 1 to 5 μm. The cumulative 50% particle diameter (D ₅₀ diameter) of less than 0.1 [mu] m, since an adverse effect on the conductivity of the silver-coated copper alloy powder is not preferable. On the other hand, if it exceeds 15 μm, it is not preferable because formation of fine wiring becomes difficult.
The aspect ratio of the silver-coated copper alloy powder is preferably less than 2, and more preferably 1.5 or less.
In the embodiment of the method for producing a silver-coated copper alloy powder according to the present invention, a copper alloy powder having a composition comprising at least one of nickel and zinc of 1 to 50% by mass and the balance consisting of copper and inevitable impurities (silver coated) The silver-coated copper alloy powder obtained by coating with a silver-containing layer (layer consisting of silver or a silver compound) of 7 to 50% by mass (based on the copper alloy powder) is monodispersed.
The copper alloy powder may be manufactured by a wet reduction method, an electrolytic method, a gas phase method, etc., but the alloy components are dissolved at a melting temperature or higher and collided with high-pressure gas or high-pressure water while dropping from the lower part of the tundish. It is preferable to produce by a so-called atomizing method (such as a gas atomizing method or a water atomizing method) to obtain a fine powder by rapid solidification. In particular, copper alloy powder with a small particle size can be obtained by manufacturing by the so-called water atomization method in which high-pressure water is sprayed. Therefore, when copper alloy powder is used in a conductive paste, conductivity due to an increase in contact points between particles is obtained. Can be improved.
As a method of coating the copper alloy powder with the silver-containing layer, a method of depositing silver or a silver compound on the surface of the copper alloy powder by a reduction method using a substitution reaction between copper and silver or a reduction method using a reducing agent is used. For example, a method of precipitating silver or a silver compound on the surface of a copper alloy powder while stirring a solution containing the copper alloy powder and silver or a silver compound in a solvent, or a method of depositing a copper alloy powder and an organic substance in a solvent. A method of precipitating silver or a silver compound on the surface of a copper alloy powder while mixing and stirring a solution containing silver or a solution containing a silver compound and an organic substance in a solvent can be used.
As this solvent, water, an organic solvent, or a solvent in which these are mixed can be used. When using a mixed solvent of water and organic solvent, it is necessary to use an organic solvent that becomes liquid at room temperature (20 to 30 ° C.). The mixing ratio of water and organic solvent depends on the organic solvent used. It can be adjusted appropriately. In addition, as water used as a solvent, distilled water, ion-exchanged water, industrial water, or the like can be used as long as there is no fear that impurities are mixed therein.
Since silver ions need to be present in the solution as the raw material for the silver-containing layer, it is preferable to use silver nitrate having high solubility in water and many organic solvents. In addition, in order to carry out the reaction of covering the copper alloy powder with the silver-containing layer (silver coating reaction) as uniformly as possible, silver nitrate was dissolved in a solvent (water, an organic solvent or a mixed solvent thereof) instead of solid silver nitrate. It is preferred to use a silver nitrate solution. The amount of silver nitrate solution used, the concentration of silver nitrate in the silver nitrate solution, and the amount of organic solvent can be determined according to the amount of the target silver-containing layer.
In order to form the silver-containing layer more uniformly, a chelating agent may be added to the solution. As the chelating agent, it is preferable to use a chelating agent having a high complex stability constant with respect to copper ions or the like so that copper ions or the like by-produced by substitution reaction between silver ions and metallic copper do not reprecipitate. . In particular, since the copper alloy powder serving as the core of the silver-coated copper alloy powder contains copper as a main component, it is preferable to select a chelating agent while paying attention to the complex stability constant with copper. Specifically, a chelating agent selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), iminodiacetic acid, diethylenetriamine, triethylenediamine, and salts thereof can be used as the chelating agent.
In order to perform the silver coating reaction stably and safely, a pH buffer may be added to the solution. As this pH buffering agent, ammonium carbonate, ammonium hydrogen carbonate, aqueous ammonia, sodium hydrogen carbonate, or the like can be used.
In the silver coating reaction, before adding the silver salt, the copper alloy powder is put in the solution and stirred, and the solution containing the silver salt is added while the copper alloy powder is sufficiently dispersed in the solution. It is preferable to do this. The reaction temperature during the silver coating reaction may be any temperature that does not cause the reaction solution to solidify or evaporate, but is preferably set in the range of 20 to 80 ° C., more preferably 25 to 70 ° C. The reaction time varies depending on the coating amount of silver or silver compound and the reaction temperature, but can be set in the range of 1 minute to 5 hours.
By monodispersing the silver-coated copper alloy powder, the tap density of the silver-coated copper alloy powder is preferably 5 g / cm ³ or more, and the ratio of the tap density to the true density of the silver-coated copper alloy powder is 55 to 70%. It is preferable to do this. Such monodispersion can be performed by strongly crushing silver-coated copper alloy powder with a Henschel mixer or by vacuum drying. Moreover, it is preferable to surface-treat the copper alloy powder coated with the silver-containing layer with a surface treatment agent before or after the monodispersion.
The surface treatment agent is preferably a fatty acid. These fatty acids include butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, oleic acid, vaccenic acid , Linoleic acid, linolenic acid, arachidic acid, eicosadienoic acid, eicosatrienoic acid, eicosatetraenoic acid, arachidonic acid, behenic acid, lignoceric acid, nervonic acid, serotic acid, montanic acid, melicic acid, etc. Although it is possible, it is preferred to use palmitic acid, stearic acid or oleic acid.
Hereinafter, examples of the silver-coated copper alloy powder and the method for producing the same according to the present invention will be described in detail.

比較例１
　銀被覆銅合金の乾燥粉末を周速１５ｍ／ｓで１０分間解砕（通常解砕）した以外は、実施例１と同様の方法により得られた銀被覆銅合金粉末について、実施例１と同様の方法により、組成、粒度分布、アスペクト比、ＢＥＴ比表面積、タップ密度、真密度に対するタップ密度の比、酸素含有量および炭素含有量を求めるとともに、実施例１と同様の方法により、導電膜の体積抵抗率を算出した。
　その結果、銀被覆銅合金粉末の銀の被覆量は１０．５質量％、銅の含有量は８６．５質量％、亜鉛の含有量は３．０質量％であった。また、銀被覆銅合金粉末の累積１０％粒子径（Ｄ_１０）は１．５μｍ、累積５０％粒子径（Ｄ_５０）は３．３μｍ、累積９０％粒子径（Ｄ_９０）は５．６μｍであった。また、銀被覆銅合金粉末のアスペクト比は１．３、ＢＥＴ比表面積は０．４０ｍ^２／ｇ、タップ密度は４．６ｇ／ｃｍ^３、真密度（９．０５ｇ／ｃｍ^３）に対するタップ密度の比は５１％であった。また、銀被覆銅合金粉末中の酸素含有量は０．１１質量％、炭素含有量は０．１８質量％であった。また、導電膜の体積抵抗率は７７μΩ・ｃｍであった。これらの結果を表１~表３に示す。 While dropping molten metal heated from 19 kg of copper and 1 kg of zinc from the lower part of the tundish, it is rapidly solidified by spraying high-pressure water, and the resulting alloy powder is filtered, washed with water, dried, crushed, classified, A copper alloy powder (copper-zinc alloy powder) was obtained.
When the composition and particle size distribution of the copper alloy powder thus obtained (before silver coating) were determined, the copper (Cu) content in the copper alloy powder was 95.4% by mass, of zinc (Zn). The content was 4.6% by mass, and the copper alloy powder was a Cu ₉₅ Zn ₅ alloy powder. Further, the cumulative 10% particle size (D ₁₀ ) of the copper alloy powder was 0.7 μm, the cumulative 50% particle size (D ₅₀ ) was 2.0 μm, and the cumulative 90% particle size (D ₉₀ ) was 3.9 μm. . The content of copper and zinc in the copper alloy powder was determined by placing the copper alloy powder (about 2.5 g) in a vinyl chloride ring (inner diameter: 3.2 mm × thickness: 4 mm) and then compressing the tablet mold. A copper alloy powder pellet was produced by applying a load of 100 kN using a machine (model number BRE-50 manufactured by Maekawa Test Co., Ltd.), and this pellet was placed in a sample holder (opening diameter: 3.0 cm) and subjected to fluorescent X-ray analysis. Software attached to the device from the measurement results set in the measurement position in the device (RIX2000 manufactured by Rigaku Co., Ltd.), the measurement atmosphere under reduced pressure (8.0 Pa), and the X-ray output of 50 kV and 50 mA. It calculated | required by calculating automatically and calculated | required the ratio of the component except the light element less than sodium. The particle size distribution of the copper alloy powder is measured by a laser diffraction type particle size distribution device (Hellos particle size distribution measuring device (HELOS & RODOS) manufactured by SYMPATEC), and the cumulative particle size is 10% (D ₁₀ ) and the cumulative particle size is 50%. (D ₅₀ ), cumulative 90% particle diameter (D ₉₀ ) was determined.
In addition, a solution (solution 1) obtained by dissolving 3.3 kg of EDTA-2Na dihydrate and 3.3 kg of ammonium carbonate in 38.3 kg of pure water, 7.4 kg of EDTA-2Na dihydrate, and 3.7 kg of ammonium carbonate A solution obtained by adding 1.2 kg of silver nitrate in 3.8 kg of pure water to a solution of 29.3 kg of pure water dissolved in 29.3 kg of pure water (Solution 2) was prepared.
Next, 7 kg of the obtained copper-zinc alloy powder was added to the solution 1 under a nitrogen atmosphere, and the temperature was raised to 35 ° C. while stirring. The solution 2 was added to the solution in which the copper-zinc alloy powder was dispersed and stirred for 30 minutes to obtain a slurry containing copper-zinc alloy particles (silver-coated copper alloy particles) coated with silver.
To this slurry, 466 g of a solution obtained by dissolving palmitic acid in alcohol (palmitic acid concentration 5 mass%) was added, stirred for another 30 minutes, filtered, washed with water, and dried at 120 ° C. in a nitrogen atmosphere. Thus, a dry powder of the silver-coated copper alloy was obtained.
Next, 5 kg of the obtained dry powder of the silver-coated copper alloy was put into a Henschel mixer (FM20B manufactured by Nippon Coke Kogyo Co., Ltd.) and pulverized (strongly pulverized) for 20 minutes at a peripheral speed of 31 m / s.
The composition, particle size distribution, aspect ratio, BET specific surface area, tap density, ratio of tap density to true density, oxygen content and carbon content of the crushed silver-coated copper alloy powder were determined.
The contents of copper and zinc in the silver-coated copper alloy powder were determined by preparing pellets of silver-coated copper alloy powder by the same method as the contents of copper and zinc in the copper alloy powder before silver coating. Further, after processing the cross section of the silver-coated copper alloy powder with a focused ion beam (FIB) processing observation apparatus (JEM-9310FIB manufactured by JEOL Ltd.), a field emission scanning electron microscope (FE-SEM) (JEOL Ltd.) Observation with JSM-6700F) made by the company confirmed that the surface of the copper alloy powder was coated with silver. The silver (Ag) coating amount of the silver-coated copper alloy powder was also determined by the same method as the copper and zinc contents in the silver-coated copper alloy powder. As a result, the silver coating amount of the silver-coated copper alloy powder was 10.8% by mass, the copper content was 86.0% by mass, and the zinc content was 3.2% by mass.
The particle size distribution of the silver-coated copper alloy powder was determined by the same method as the particle size distribution of the copper alloy powder before silver coating. As a result, the accumulated 10% particle diameter (D ₁₀ ) of the silver-coated copper alloy powder was 1.0 μm, the accumulated 50% particle diameter (D ₅₀ ) was 2.5 μm, and the accumulated 90% particle diameter (D ₉₀ ) was 4.1 μm. Met.
The aspect ratio of the silver-coated copper alloy powder was observed at a magnification of 2000 with a field emission scanning electron microscope (FE-SEM) (S-4700 type manufactured by Hitachi, Ltd.). Using the image analysis type particle size distribution measurement software (Mac-View Ver4 of Mountec Co., Ltd.), the longest length of the particles is measured, and the average long diameter L obtained by arithmetically averaging them is the same particle. The shortest length was measured, and the average thickness T obtained by arithmetically averaging them was used to determine (average major axis L / average thickness T) as an aspect ratio. As a result, the aspect ratio of the silver-coated copper alloy powder was 1.3.
The BET specific surface area of the silver-coated copper alloy powder was determined by the BET method using a BET specific surface area measuring apparatus (4 Sorb US manufactured by Yours IONICS Inc.). As a result, the BET specific surface area of the silver-coated copper alloy powder was 0.38 m ² / g.
The tap density of the silver-coated copper alloy powder is the same as the method described in Japanese Patent Application Laid-Open No. 2007-263860, and the silver-coated copper alloy powder is filled into a bottomed cylindrical container having an inner diameter of 6 mm. After forming a layer and applying a pressure of 0.16 N / m ² from the top to the silver-coated copper alloy powder layer, the height of the silver-coated copper alloy powder layer is measured, and the height of the silver-coated copper alloy powder layer is measured. From the measured value of the thickness and the weight of the filled silver-coated copper alloy powder, the density of the silver-coated copper alloy powder was determined and used as the tap density of the silver-coated copper alloy powder. As a result, the tap density of the silver-coated copper alloy powder was 5.9 g / cm ³ . Further, the true density of the silver-coated copper alloy powder was 9.05 g / cm ³ , and the ratio of the tap density to the true density was 65%.
The oxygen content in the silver-coated copper alloy powder was measured by an oxygen / nitrogen analyzer (TC-436 type manufactured by LECO). As a result, the oxygen content in the silver-coated copper alloy powder was 0.10% by mass.
The carbon content in the silver-coated copper alloy powder was measured with a carbon / sulfur analyzer (EMIA-220V manufactured by Horiba, Ltd.). As a result, the carbon content in the silver-coated copper alloy powder was 0.17% by mass.
Next, 8.92 g of the obtained silver-coated copper alloy powder, 0.79 g of bisphenol F type epoxy resin (Adeka Resin EP-4901E manufactured by ADEKA Corporation) as a thermosetting resin, and 0.73 g of boron trifluoride monoethylamine. 04 g, 0.24 g of butyl carbitol acetate as a solvent, and 0.01 g of oleic acid were mixed by a kneading defoaming machine, and then a three-roll was passed five times to uniformly disperse to obtain a conductive paste. .
This conductive paste is printed on an alumina substrate by a screen printing method (in a pattern having a line width of 500 μm and a line length of 37.5 mm), and then baked and cured in the atmosphere at 200 ° C. for 40 minutes to form a conductive film. The volume resistivity of the obtained conductive film was calculated.
For the volume resistivity of the conductive film, the line resistance of the obtained conductive film was measured with a two-terminal type resistivity meter (3540 mOhm HiTester manufactured by Hioki Electric Co., Ltd.), and the film thickness was measured with a surface roughness shape measuring instrument (stock) It was measured by a surfcom 1500DX type manufactured by Tokyo Seimitsu Co., Ltd., and calculated by volume resistivity (Ω · cm) = line resistance (Ω) × film thickness (cm) × line width (cm) / line length (cm). As a result, the volume resistivity of the conductive film was 65 μΩ · cm.
These results are shown in Tables 1 to 3.

Comparative Example 1
The silver-coated copper alloy powder obtained by the same method as in Example 1 except that the dried powder of the silver-coated copper alloy was crushed (normally crushed) for 10 minutes at a peripheral speed of 15 m / s. By determining the composition, particle size distribution, aspect ratio, BET specific surface area, tap density, ratio of tap density to true density, oxygen content and carbon content, Volume resistivity was calculated.
As a result, the silver coating amount of the silver-coated copper alloy powder was 10.5% by mass, the copper content was 86.5% by mass, and the zinc content was 3.0% by mass. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 1.5 μm, a cumulative 50% particle diameter (D ₅₀ ) of 3.3 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 5.6 μm. there were. The silver-coated copper alloy powder has an aspect ratio of 1.3, a BET specific surface area of 0.40 m ² / g, a tap density of 4.6 g / cm ³ , and a tap density with respect to the true density (9.05 g / cm ³ ). The ratio was 51%. The oxygen content in the silver-coated copper alloy powder was 0.11% by mass, and the carbon content was 0.18% by mass. The volume resistivity of the conductive film was 77 μΩ · cm. These results are shown in Tables 1 to 3.

EDTA-2Na dihydrate 2.4 kg and ammonium carbonate 2.4 kg dissolved in pure water 27.7 kg (solution 1), EDTA-2Na dihydrate 11.8 kg and ammonium carbonate 5.9 kg were purified. A solution (solution 2) obtained by adding a solution in which 2.0 kg of silver nitrate was dissolved in 6.1 kg of pure water to a solution in which 47.1 kg of water was dissolved was prepared.
Next, 5 kg of the copper-zinc alloy powder obtained in Example 1 was added to the solution 1 in a nitrogen atmosphere, and the temperature was raised to 35 ° C. while stirring. A solution containing the copper-zinc alloy powder was added to the solution 2 and stirred for 20 minutes to obtain a slurry containing copper-zinc alloy particles (silver-coated copper alloy particles) coated with silver.
To this slurry, 500 g of a solution obtained by dissolving palmitic acid in alcohol (palmitic acid concentration 3 mass%) was added, stirred for 40 minutes, filtered, washed with water, and dried at 120 ° C. in a nitrogen atmosphere. Thus, a dry powder of the silver-coated copper alloy was obtained.
Next, 5 kg of the obtained dry powder of the silver-coated copper alloy was put into a Henschel mixer (FM20B manufactured by Nippon Coke Kogyo Co., Ltd.) and pulverized (strongly pulverized) for 20 minutes at a peripheral speed of 31 m / s.
About the silver-coated copper alloy powder thus crushed, the composition, particle size distribution, aspect ratio, BET specific surface area, tap density, ratio of tap density to true density, oxygen content and While calculating | requiring carbon content, the volume resistivity of the electrically conductive film was computed by the method similar to Example 1. FIG.
As a result, the silver coating amount of the silver-coated copper alloy powder was 21.4% by mass, the copper content was 75.3% by mass, and the zinc content was 3.3% by mass. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 1.4 μm, a cumulative 50% particle diameter (D ₅₀ ) of 3.2 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 5.3 μm. there were. The silver-coated copper alloy powder has an aspect ratio of 1.2, a BET specific surface area of 0.34 m ² / g, a tap density of 5.8 g / cm ³ , and a tap density of true density (9.21 g / cm ³ ). The ratio was 63%. The oxygen content in the silver-coated copper alloy powder was 0.22% by mass, and the carbon content was 0.19% by mass. The volume resistivity of the conductive film was 59 μΩ · cm. These results are shown in Tables 1 to 3.
Comparative Example 2
The silver-coated copper alloy powder obtained by the same method as in Example 2 except that the pulverization was not performed, the composition, particle size distribution, aspect ratio, BET specific surface area, tap by the same method as in Example 1. While calculating | requiring the density, the ratio of the tap density with respect to a true density, oxygen content, and carbon content, the volume resistivity of the electrically conductive film was computed by the method similar to Example 1. FIG.
As a result, the silver coating amount of the silver-coated copper alloy powder was 20.6% by mass, the copper content was 76.9% by mass, and the zinc content was 2.5% by mass. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 1.6 μm, a cumulative 50% particle diameter (D ₅₀ ) of 3.5 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 6.0 μm. there were. Further, the aspect ratio of the silver-coated copper alloy powder is 1.3, the BET specific surface area is 0.37 m ² / g, the tap density is 4.9 g / cm ³ , and the tap density with respect to the true density (9.21 g / cm ³ ). The ratio was 54%. The oxygen content in the silver-coated copper alloy powder was 0.23% by mass, and the carbon content was 0.19% by mass. The volume resistivity of the conductive film was 76 μΩ · cm. These results are shown in Tables 1 to 3.

A silver-coated copper alloy powder obtained by the same method as in Comparative Example 1 except that it was vacuum dried at 70 ° C. instead of being dried at 120 ° C. in a nitrogen atmosphere, the composition and particle size were the same as in Example 1. The distribution, aspect ratio, BET specific surface area, tap density, ratio of tap density to true density, oxygen content and carbon content were determined, and the volume resistivity of the conductive film was calculated by the same method as in Example 1.
As a result, the silver coating amount of the silver-coated copper alloy powder was 10.7% by mass, the copper content was 86.1% by mass, and the zinc content was 3.2% by mass. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 0.9 μm, a cumulative 50% particle diameter (D ₅₀ ) of 2.4 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 4.1 μm. there were. Further, the aspect ratio of the silver-coated copper alloy powder is 1.4, the BET specific surface area is 0.43 m ² / g, the tap density is 5.6 g / cm ³ , and the tap density with respect to the true density (9.06 g / cm ³ ). The ratio was 62%. The oxygen content in the silver-coated copper alloy powder was 0.08% by mass, and the carbon content was 0.15% by mass. The volume resistivity of the conductive film was 44 μΩ · cm. These results are shown in Tables 1 to 3.

When obtaining a slurry containing copper-zinc alloy particles coated with silver (silver-coated copper alloy particles), the same as in Example 3 except that the temperature of the solution in which the copper-zinc alloy powder was dispersed was 25 ° C. For the silver-coated copper alloy powder obtained by this method, the composition, particle size distribution, aspect ratio, BET specific surface area, tap density, ratio of tap density to true density, oxygen content and carbon content were obtained in the same manner as in Example 1. While calculating | requiring the quantity, the volume resistivity of the electrically conductive film was computed by the method similar to Example 1. FIG.
As a result, the silver coating amount of the silver-coated copper alloy powder was 10.9 mass%, the copper content was 86.1 mass%, and the zinc content was 3.0 mass%. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 0.6 μm, a cumulative 50% particle diameter (D ₅₀ ) of 1.8 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 3.4 μm. there were. The silver-coated copper alloy powder has an aspect ratio of 1.2, a BET specific surface area of 0.46 m ² / g, a tap density of 6.1 g / cm ³ , and a tap density with respect to the true density (9.06 g / cm ³ ). The ratio was 67%. The oxygen content in the silver-coated copper alloy powder was 0.12% by mass, and the carbon content was 0.18% by mass. The volume resistivity of the conductive film was 38 μΩ · cm. These results are shown in Tables 1 to 3.

The silver-coated copper alloy powder obtained by the same method as in Comparative Example 2, except that it was vacuum-dried at 70 ° C. instead of drying at 120 ° C. in a nitrogen atmosphere, the composition and particle size were the same as in Example 1. The distribution, aspect ratio, BET specific surface area, tap density, ratio of tap density to true density, oxygen content and carbon content were determined, and the volume resistivity of the conductive film was calculated by the same method as in Example 1.
As a result, the silver coating amount of the silver-coated copper alloy powder was 21.2% by mass, the copper content was 75.7% by mass, and the zinc content was 3.1% by mass. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 0.9 μm, a cumulative 50% particle diameter (D ₅₀ ) of 2.3 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 4.1 μm. there were. Further, the aspect ratio of the silver-coated copper alloy powder is 1.4, the BET specific surface area is 0.46 m ² / g, the tap density is 5.6 g / cm ³ , and the tap density relative to the true density (9.21 g / cm ³ ). The ratio was 61%. The oxygen content in the silver-coated copper alloy powder was 0.20% by mass, and the carbon content was 0.21% by mass. The volume resistivity of the conductive film was 48 μΩ · cm. These results are shown in Tables 1 to 3.

When obtaining a slurry containing copper-zinc alloy particles coated with silver (silver-coated copper alloy particles), the same as in Example 5 except that the temperature of the solution in which the copper-zinc alloy powder was dispersed was 25 ° C. For the silver-coated copper alloy powder obtained by this method, the composition, particle size distribution, aspect ratio, BET specific surface area, tap density, ratio of tap density to true density, oxygen content and carbon content were obtained in the same manner as in Example 1. While calculating | requiring the quantity, the volume resistivity of the electrically conductive film was computed by the method similar to Example 1. FIG.
As a result, the silver coating amount of the silver-coated copper alloy powder was 21.1% by mass, the copper content was 76.0% by mass, and the zinc content was 2.9% by mass. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 0.8 μm, a cumulative 50% particle diameter (D ₅₀ ) of 2.2 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 4.0 μm. there were. The silver-coated copper alloy powder has an aspect ratio of 1.3, a BET specific surface area of 0.43 m ² / g, a tap density of 5.4 g / cm ³ , and a tap density with respect to the true density (9.21 g / cm ³ ). The ratio was 59%. The oxygen content in the silver-coated copper alloy powder was 0.15% by mass, and the carbon content was 0.20% by mass. The volume resistivity of the conductive film was 33 μΩ · cm. These results are shown in Tables 1 to 3.

Claims (15)

A copper alloy powder having a composition comprising at least one of nickel and zinc in an amount of 1 to 50% by mass and the balance consisting of copper and inevitable impurities is coated with a silver containing layer of 7 to 50% by mass, and the tap density is 5 g / cm. ^A silver-coated copper alloy powder characterized by being ³ or more. The silver-coated copper alloy powder according to claim 1, wherein the silver-containing layer is a layer made of silver or a silver compound. The silver-coated copper alloy powder according to claim 1, wherein a ratio of a tap density to a true density of the silver-coated copper alloy powder is 55 to 70%. The silver-coated copper alloy powder according to claim 1, wherein the silver-coated copper alloy powder has an aspect ratio of less than 2. Wherein the cumulative 50% particle diameter measured by a laser diffraction type particle size distribution apparatus of the copper alloy powder (D ₅₀ diameter) is 0.1 ~ 15 [mu] m, silver-coated copper alloy powder according to claim 1. A silver-coated copper alloy obtained by coating a copper alloy powder having a composition comprising at least one of nickel and zinc of 1 to 50% by mass with the balance consisting of copper and inevitable impurities with a silver-containing layer of 7 to 50% by mass A method for producing a silver-coated copper alloy powder, wherein the powder is monodispersed. The method for producing a silver-coated copper alloy powder according to claim 6, wherein the silver-containing layer is a layer made of silver or a silver compound. The method for producing a silver-coated copper alloy powder according to claim 6, wherein the tap density of the silver-coated copper alloy powder is 5 g / cm ³ or more by the monodispersion. The method for producing a silver-coated copper alloy powder according to claim 6, wherein a ratio of the tap density to the true density of the silver-coated copper alloy powder is 55 to 70% by the monodispersion. The method for producing a silver-coated copper alloy powder according to claim 6, wherein the copper alloy powder coated with the silver-containing layer is surface-treated with a surface treatment agent before or after the monodispersion. The method for producing a silver-coated copper alloy powder according to claim 10, wherein the surface treatment agent is a fatty acid. The method for producing a silver-coated copper alloy powder according to claim 6, wherein the copper alloy powder is produced by an atomizing method. 7. The silver-coated copper alloy powder according to claim 6, wherein a cumulative 50% particle diameter (D ₅₀ diameter) of the copper alloy powder measured by a laser diffraction particle size distribution device is 0.1 to 15 μm. Production method. A conductive paste containing a solvent and a resin, and containing the silver-coated copper alloy powder according to claim 1 as a conductive powder. 15. A conductive film, wherein the conductive paste according to claim 14 is cured.