JP2015021143A - Silver-coated copper alloy powder and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silver-coated copper alloy powder enabling a conductive film having a low volume resistivity and having an excellent storage stability (reliability) and migration resistance to be formed, and a method for producing the same.SOLUTION: The silver-coated copper alloy powder is obtained by: coating a copper alloy powder that has a composition containing at least one of 1 to 50 mass% of nickel and zinc, and the remainder comprising copper and inevitable impurities, with a 7 to 50 mass% silver-containing layer (layer comprising silver or silver compound) (with respect to the silver); then subjecting the copper alloy powder to heat treatment by heating it at 30 to 50°C for 10 to 120 minutes.

Description

  The present invention relates to a silver-coated copper alloy powder and a method for producing the same, and more 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 for the conductive paste, silver-coated copper powder (for example, see Patent Documents 1 and 2) in which the surface of the copper powder is coated with silver, or the surface of the copper alloy is silver. A coated silver-coated copper alloy powder has been proposed (see, for example, Patent Documents 3 to 4).

JP 2010-174411 A (paragraph number 0003) JP 2010-077745 (paragraph number 0006) JP 08-311304 A (paragraph number 0006) JP-A-10-152630 (paragraph number 0006)

  However, in the silver-coated copper powders of Patent Documents 1 and 2, if there is a part that is not coated with silver on the surface of the copper powder, oxidation proceeds from that part, and thus storage stability (reliability) is unsatisfactory. There is a problem that it becomes sufficient and the migration resistance is poor. Further, the silver-coated copper alloy powders of Patent Documents 3 to 4 have a problem that when used in a conductive film, the volume resistivity of the conductive film is high (conductivity is low).

  Therefore, in view of such a conventional problem, the present invention provides a silver-coated copper alloy powder capable of forming a conductive film having a low volume resistivity and excellent storage stability (reliability) and migration resistance, and It aims at providing the manufacturing method.

  As a result of diligent research to solve the above problems, the present inventors have found that a copper alloy powder containing at least one of 1 to 50% by mass of nickel and zinc and having the balance of copper and inevitable impurities having a composition of 7 to 7 After coating with a 50% by mass silver-containing layer, the copper alloy powder coated with the silver-containing layer is heat-treated to produce a conductive film with low volume resistivity and excellent storage stability (reliability) and migration resistance. The inventors have found that a silver-coated copper alloy powder that can be formed can be produced, and have completed the present invention.

  That is, 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 1 to 50% by mass of nickel and zinc and the balance consisting of copper and inevitable impurities. After the coating with the silver-containing layer, the copper alloy powder coated with the silver-containing layer is heat-treated.

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, and the heat treatment is preferably performed by heating at 30 to 50 ° C., preferably for 10 to 120 minutes. . 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 heat processing, and it is preferable that this surface treating agent is a fatty acid. 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 a 0.1-15.

  Further, 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. The crystallite diameter in the (111) plane of the silver containing layer is 40 nm or less.

  In the present specification, “crystallite diameter in the (111) plane of the silver-containing layer” is calculated from the half-value width of the (111) peak of the X-ray diffraction pattern of the silver-containing layer using the Scherrer equation. Crystallite diameter.

  ADVANTAGE OF THE INVENTION According to this invention, the silver coating copper alloy powder which can form the electrically conductive film which is low in volume resistivity, and was excellent in storage stability (reliability) and migration resistance, and its manufacturing method can be provided.

  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 at 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 7 to 50% by mass of a silver-containing layer (a layer made of silver or a silver compound) is heat-treated.

  The content of at least one of nickel and zinc in the 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.

Particle size of the copper alloy powder (by Heroes method) 50% cumulative particle diameter measured by a laser diffraction type particle size distribution apparatus _{(D 50} diameter) is preferably in the range of 0.1-15, in 0.3~10μm More preferably, it is most preferably 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 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 in the silver coating reaction may be a temperature at which the reaction solution is solidified or evaporated, but is preferably set in the range of 10 to 40 ° C, more preferably 15 to 35 ° C. Moreover, although reaction time changes with the coating amount of silver or a silver compound, and reaction temperature, it can set in the range of 1 minute-5 hours.

  The heat treatment of the silver-coated copper alloy powder is preferably 5 to 20 ° C. higher than the reaction temperature in the silver coating reaction, preferably 30 to 50 ° C., more preferably 35 to 45 ° C., preferably 10 to 120 minutes, Preferably it is performed by heating for 15 to 90 minutes.

  Before or after the heat treatment, the copper alloy powder coated with the silver-containing layer is preferably surface-treated with a surface treatment agent, and 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.

  The addition amount of the surface treatment agent is preferably 0.1 to 7% by mass, more preferably 0.3 to 6% by mass, and 0.3 to 5% by mass with respect to the silver-coated copper alloy powder. Most preferably. The surface treatment may be performed by mixing the copper alloy powder coated with the silver-containing layer and the surface treatment agent, or by adding the surface treatment agent to the slurry of the copper alloy powder coated with the silver-containing layer. Good. In this way, by surface-treating the silver-coated copper alloy powder with a surface treatment agent (preferably 0.1 to 7% by mass of a surface treatment agent), the tap density is increased to improve dispersibility, and the volume of the conductive film is increased. The resistivity can be lowered and oxidation resistance can be imparted to reduce the rate of change in volume resistivity.

  Further, in the embodiment of the silver-coated copper alloy powder according to the present invention, the copper alloy powder having a composition containing at least one of 1 to 50% by mass of nickel and zinc, and the balance of copper and inevitable impurities is 7 to 50%. The crystallite diameter on the (111) plane of the silver-containing layer is 40 nm or less. The crystallite diameter is preferably 15 to 40 nm, and more preferably 18 to 38 nm.

  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.

[Example 1]
While dropping molten metal heated to 7.2 kg of copper and 0.8 kg of zinc from the bottom of the tundish, high pressure water is sprayed and rapidly solidified. The resulting alloy powder is filtered, washed with water, dried and crushed. Classification was performed to obtain a copper alloy powder (copper-zinc alloy powder).

When the composition and particle size distribution of the copper alloy powder thus obtained (before silver coating) were determined, the copper content in the copper alloy powder was 90.2 mass%, and the zinc content was 9.8. The copper alloy powder was Cu ₉₀ Zn ₁₀ alloy powder. The cumulative 10% particle size (D ₁₀ ) of the copper alloy powder was 0.6 μm, the cumulative 50% particle size (D ₅₀ ) was 1.7 μm, and the cumulative 90% particle size (D ₉₀ ) was 3.2 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.

  Further, a solution (solution 1) in which 61.9 g of EDTA-2Na dihydrate and 61.9 g of ammonium carbonate were dissolved in 720 g of pure water, 136.5 g of EDTA-2Na dihydrate and 68.2 g of ammonium carbonate were purified. A solution obtained by adding a solution obtained by dissolving 22.7 g of silver nitrate in 70 g of pure water to a solution dissolved in 544 g of water was prepared (solution 2).

  Next, 130 g of the obtained copper alloy powder (copper-zinc alloy powder) was added to the solution 1 in a nitrogen atmosphere, and the temperature was raised to 35 ° C. while stirring. After adding solution 2 to the solution in which the copper alloy powder (copper-zinc alloy powder) is dispersed and stirring for 1 hour, the temperature is raised to 45 ° C. at a rate of 1 ° C. per minute and held at 45 ° C. for 15 minutes. Then, it was filtered, washed with water, and dried to obtain a silver-coated copper alloy powder (silver-coated copper-zinc alloy powder).

  Next, 80 g of the obtained silver-coated copper alloy powder and 0.24 g of palmitic acid (0.3% by mass with respect to the silver-coated copper alloy powder) are put into a cutter mill, and pulverized for 20 seconds twice. A silver-coated copper alloy powder surface-treated with palmitic acid was obtained.

  The composition, particle size distribution, BET specific surface area, tap density, oxygen content, carbon content and silver layer crystallite diameter of the silver-coated copper alloy powder thus obtained 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 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 11.0% by mass, the copper content was 81.5% by mass, and the zinc content was 7.5% 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 silver-coated copper alloy powder has a cumulative 10% particle size (D ₁₀ ) of 0.8 μm, a cumulative 50% particle size (D ₅₀ ) of 2.3 μm, and a cumulative 90% particle size (D ₉₀ ) of 4.1 μm. Met.

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 0.54 m ² / g.

The tap density of the silver-coated copper alloy powder is such that the silver-coated copper alloy powder is filled 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 .16 N / m ² , the height of the silver-coated copper alloy powder layer was measured, the measured value of the silver-coated copper alloy powder layer, and the weight of the filled silver-coated copper alloy powder From the above, 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 4.2 g / cm ³ .

  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 0.14% 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 0.23% by mass.

  Moreover, about the silver layer of the obtained silver covering copper alloy powder, the range of 42-47 degrees / 2 (theta) was measured with Co line source (40kV / 30mA) with the X-ray-diffraction apparatus (RINT Ultimate III by Rigaku Corporation). Then, X-ray diffraction (XRD) was evaluated. Using the half width β of the (111) plane of the silver layer obtained from this X-ray diffraction pattern, the crystallite diameter (Dx) is calculated from Scherrer's equation D = (K · λ) / (β · cos θ). As a result, the crystallite diameter (Dx) was 22 nm. In the Scherrer equation, D is the crystallite diameter (nm), λ is the measured X-ray wavelength (nm), β is the diffraction width spread by the crystallite, θ is the Bragg angle of the diffraction angle, and K is the Scherrer constant. In this equation, the measured X-ray wavelength λ was 1.79 nm, and the Scherrer constant K was 0.94.

  Next, 93 g of the obtained silver-coated copper alloy powder, 8.2 g of bisphenol F-type epoxy resin (ADEKA RESIN EP-4901E manufactured by ADEKA Corporation) as thermosetting resin, 0.41 g of boron trifluoride monoethylamine, Then, 2.5 g of butyl carbitol acetate as a solvent and 0.1 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 and the storage stability (reliability) was evaluated.

  For the volume resistivity of the conductive film, the line resistance of the obtained conductive film was measured with a digital multimeter (AD7451A manufactured by ADC Corporation), and the film thickness was measured with a surface roughness profile measuring machine (Surfcom manufactured by Tokyo Seimitsu Co., Ltd.) 1500 DX), and volume resistivity (Ω · cm) = line resistance (Ω) × film thickness (cm) × line width (cm) / line length (cm) was calculated. As a result, the volume resistivity of the conductive film was 106 μΩ · cm.

  The storage stability (reliability) of a conductive film is calculated by calculating the volume resistivity (volume resistivity after storage for 6 weeks) of a conductive film stored for 6 weeks in a test chamber maintained at a constant temperature (150 ° C.). Resistivity change rate (%) = {(Volume resistivity after 6 weeks storage) − (Initial volume resistivity)} × 100 / (Initial volume resistivity) As a result, the volume resistivity after storage for 6 weeks was 222 μΩ · cm, and the rate of change in volume resistivity was 109%.

  In order to evaluate the migration resistance of the conductive film, the obtained conductive paste was printed on a ceramic substrate (made of 96% alumina) by screen printing so that the distance between the electrodes was 2 mm. Then, a pair of electrodes made of a conductive film is prepared by baking and curing at 200 ° C. for 40 minutes in the atmosphere, and a drop of ion-exchanged water is dropped between these electrodes to create a constant voltage power source (Kikusui Electronics Corporation). When a DC voltage of 20V is applied with a PAB32-2A manufactured by Co., Ltd., and the current value is read with a digital multimeter (AD7451A manufactured by ADC Co., Ltd.) connected in series with a constant voltage power supply and electrodes. The time until the current with the threshold current value of 1 mA flows from the short circuit time (until the electrodes are short-circuited by ion migration) It was measured as between). As a result, the short circuit time of the conductive film was 484 seconds.

  These results are shown in Tables 1 to 4.

[Example 2]
A solution (solution 1) of 61.9 g of EDTA-2Na dihydrate and 61.9 g of ammonium carbonate dissolved in 720 g of pure water, 307.1 g of EDTA-2Na dihydrate and 153.5 g of ammonium carbonate, 1223 g of pure water A solution obtained by adding 51.2 g of silver nitrate in 158 g of pure water to the solution dissolved in (a solution 2) was prepared, and the same copper alloy powder (copper- 130 g of zinc alloy powder) is added to solution 1 and heated to 25 ° C. while stirring. Solution 2 is added to the solution in which this copper alloy powder (copper-zinc alloy powder) is dispersed and stirred for 1 hour. The silver-coated copper alloy powder obtained in the same manner as in Example 1 except that the temperature was raised to 35 ° C. at a temperature raising rate of 1 ° C. and the heat treatment was performed by holding at 35 ° C. for 30 minutes. Same method as 1 , Composition, particle size distribution, BET specific surface area, tap density, oxygen content, carbon content, and crystallite diameter of the silver layer, and calculation of volume resistivity of the conductive film by the same method as in Example 1, conductivity The storage stability (reliability) and migration resistance of the film were evaluated.

As a result, the silver coating amount of the silver-coated copper alloy powder was 21.5% by mass, the copper content was 71.6% by mass, and the zinc content was 6.9% by mass. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 1.3 μm, a cumulative 50% particle diameter (D ₅₀ ) of 3.2 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 5.4 μm. there were. The silver-coated copper alloy powder had a BET specific surface area of 0.44 m ² / g and a tap density of 5.1 g / cm ³ . The oxygen content in the silver-coated copper alloy powder was 0.23% by mass, and the carbon content was 0.23% by mass. The crystallite diameter of the silver layer of the silver-coated copper alloy powder was 29 nm. Further, the volume resistivity (initial volume resistivity) of the conductive film was 85 μΩ · cm. The volume resistivity after storage for 6 weeks was 113 μΩ · cm, and the rate of change in volume resistivity was 33%. The short-circuit time of the conductive film was 592 seconds. These results are shown in Tables 1 to 4.

[Example 3]
While dropping molten metal heated from 6.4 kg of copper, 0.8 kg of nickel and 0.8 kg of zinc from the bottom of the tundish, it is rapidly solidified by spraying high pressure water, and the resulting alloy powder is filtered, washed with water and dried. And then pulverized and classified to obtain a copper alloy powder (copper-nickel-zinc alloy powder).

When the composition and particle size distribution of the copper alloy powder thus obtained (before silver coating) were determined, the copper content in the copper alloy powder was 82.9% by mass, and the nickel content was 10.2. The content of mass% and zinc was 6.9 mass%, and the copper alloy powder was a Cu ₈₀ Ni ₁₀ Zn ₁₀ alloy powder. The cumulative 10% particle size (D ₁₀ ) of the copper alloy powder was 0.7 μm, the cumulative 50% particle size (D ₅₀ ) was 1.8 μm, and the cumulative 90% particle size (D ₉₀ ) was 3.3 μm. . The contents of copper, nickel and zinc in the copper alloy powder were determined by the same method as the method for determining the contents of copper and zinc in the copper alloy powder in Example 1, and the particle size distribution of the copper alloy powder was It was determined by the same method as in Example 1.

  In addition, a solution (solution 1) in which 61.9 g of EDTA-2Na dihydrate and 61.9 g of ammonium carbonate were dissolved in 720 g of pure water, 307.1 g of EDTA-2Na dihydrate and 153.5 g of ammonium carbonate were purified. A solution (solution 2) obtained by adding a solution obtained by dissolving 51.2 g of silver nitrate in 158 g of pure water to a solution dissolved in 1223 g of water was prepared.

  Next, 130 g of the obtained copper-nickel-zinc alloy powder was added to the solution 1 in a nitrogen atmosphere, and the temperature was raised to 25 ° C. while stirring. Solution 2 was added to the solution in which the copper-nickel-zinc alloy powder was dispersed and stirred for 1 hour, and then heated to 35 ° C. at a rate of 1 ° C. per minute and held at 35 ° C. for 90 minutes for heat treatment. After that, it was filtered, washed with water, and dried to obtain a silver-coated copper alloy powder (silver-coated copper-nickel-zinc alloy powder).

  Next, 80 g of the obtained silver-coated copper alloy powder and 0.24 g of palmitic acid (0.3% by mass with respect to the silver-coated copper alloy powder) are put into a cutter mill, and pulverized for 20 seconds twice. A silver-coated copper alloy powder surface-treated with palmitic acid was obtained.

  For the silver-coated copper alloy powder thus obtained, the composition, particle size distribution, BET specific surface area, tap density, oxygen content, carbon content, and crystallite diameter of the silver layer were determined in the same manner as in Example 1. While calculating | requiring, by the method similar to Example 1, calculation of the volume resistivity of the electrically conductive film, the storage stability (reliability) of the electrically conductive film, and evaluation of migration resistance were performed.

As a result, the silver coating amount of the silver-coated copper alloy powder was 22.4 mass%, the copper content was 65.7 mass%, the nickel content was 8.2 mass%, and the zinc content was 3.7. It was mass%. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 1.9 μm, a cumulative 50% particle diameter (D ₅₀ ) of 4.4 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 7.2 μm. there were. The silver-coated copper alloy powder had a BET specific surface area of 0.44 m ² / g and a tap density of 3.7 g / cm ³ . The oxygen content in the silver-coated copper alloy powder was 0.29% by mass, and the carbon content was 0.24% by mass. The crystallite diameter of the silver layer of the silver-coated copper alloy powder was 36 nm. Moreover, the volume resistivity (initial volume resistivity) of the conductive film was 130 μΩ · cm. The volume resistivity after storage for 6 weeks was 126 μΩ · cm, and the rate of change in volume resistivity was −3%. Moreover, the short circuit time of the electrically conductive film was 600 seconds or more. These results are shown in Tables 1 to 4.

[Example 4]
A molten metal heated to 6.8 kg of copper, 0.4 kg of nickel and 0.8 kg of zinc is dropped from the lower part of the tundish and sprayed with high pressure water to rapidly solidify it. The resulting alloy powder is filtered, washed with water and dried. And then pulverized and classified to obtain a copper alloy powder (copper-nickel-zinc alloy powder).

When the composition and particle size distribution of the copper alloy powder thus obtained (before silver coating) were determined, the copper content in the copper alloy powder was 86.0% by mass, and the nickel content was 4.3. The mass%, the zinc content was 9.7 mass%, and the copper alloy powder was a Cu ₈₅ Ni ₅ Zn ₁₀ alloy powder. Further, the cumulative 10% particle diameter (D ₁₀ ) of the copper alloy powder was 0.6 μm, the cumulative 50% particle diameter (D ₅₀ ) was 1.8 μm, and the cumulative 90% particle diameter (D ₉₀ ) was 3.4 μm. . The contents of copper, nickel and zinc in the copper alloy powder were determined by the same method as the method for determining the contents of copper and zinc in the copper alloy powder in Example 1, and the particle size distribution of the copper alloy powder was It was determined by the same method as in Example 1.

  Next, in a nitrogen atmosphere, 130 g of the same copper alloy powder (copper-nickel-zinc alloy powder) as in Example 3 was added to Solution 1 as in Example 3, and the temperature was raised to 30 ° C. while stirring. . By adding the same solution 2 as in Example 3 to the solution in which the copper-zinc alloy powder is dispersed and stirring for 20 minutes, a slurry containing copper-zinc alloy particles (silver-coated copper alloy particles) coated with silver is obtained. Obtained. To this slurry, 16.3 g of a solution obtained by dissolving oleic acid in alcohol (oleic acid concentration: 3% by mass) was added, and the mixture was further stirred for 40 minutes for surface treatment. The temperature is raised to 40 ° C at a temperature rate, and heat treatment is performed by holding at 40 ° C for 30 minutes, followed by filtration, washing with water, and drying at 120 ° C in a nitrogen atmosphere to obtain a dry powder of a silver-coated copper alloy It was.

  For the silver-coated copper alloy powder thus obtained, the composition, particle size distribution, BET specific surface area, tap density, oxygen content, carbon content, and crystallite diameter of the silver layer were determined in the same manner as in Example 1. In addition, the volume resistivity of the conductive film, the storage stability (reliability) of the conductive film, and the migration resistance were evaluated by the same method as in Example 1.

As a result, the silver coating amount of the silver-coated copper alloy powder was 22.1% by mass, the copper content was 68.2% by mass, the nickel content was 3.2% by mass, and the zinc content was 6.5%. It was mass%. The silver-coated copper alloy powder has a cumulative 10% particle diameter (D ₁₀ ) of 1.9 μm, a cumulative 50% particle diameter (D ₅₀ ) of 4.3 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 7.5 μm. there were. The silver-coated copper alloy powder had a BET specific surface area of 0.43 m ² / g and a tap density of 4.0 g / cm ³ . 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 crystallite diameter of the silver layer of the silver-coated copper alloy powder was 30 nm. Further, the volume resistivity (initial volume resistivity) of the conductive film was 80 μΩ · cm. The volume resistivity after storage for 6 weeks was 82 μΩ · cm, and the rate of change in volume resistivity was 3%. Moreover, the short circuit time of the electrically conductive film was 600 seconds or more. These results are shown in Tables 1 to 4.

[Reference example]
The silver coated copper alloy powder obtained by the same method as in Example 1 except that no heat treatment was performed, the composition, particle size distribution, BET specific surface area, tap density, oxygen content were obtained in the same manner as in Example 1. The amount of carbon, the carbon content and the crystallite diameter of the silver layer are determined, and the volume resistivity of the conductive film, the storage stability (reliability) of the conductive film, and the evaluation of migration resistance are obtained by the same method as in Example 1. Went.

As a result, the silver coating amount of the silver-coated copper alloy powder was 10.8% by mass, the copper content was 81.6% by mass, and the zinc content was 7.6% 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 2.3 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 4.0 μm. there were. The silver-coated copper alloy powder had a BET specific surface area of 0.55 m ² / g and a tap density of 4.4 g / cm ³ . The oxygen content in the silver-coated copper alloy powder was 0.15% by mass, and the carbon content was 0.24% by mass. The crystallite diameter of the silver layer of the silver-coated copper alloy powder was 16 nm. Further, the volume resistivity (initial volume resistivity) of the conductive film was 98 μΩ · cm. The volume resistivity after storage for 6 weeks was 216 μΩ · cm, and the rate of change in volume resistivity was 120%. Moreover, the short circuit time of the electrically conductive film was 420 seconds. These results are shown in Tables 1 to 4.

[Comparative Example 1]
Except for using silver powder in place of the surface-treated silver-coated copper alloy powder, the silver powder obtained by the same method as in the reference example was subjected to the same particle size distribution, BET specific surface area, tap density as in Example 1. While calculating | requiring oxygen content, carbon content, and the crystallite diameter of a silver layer, by the method similar to Example 1, calculation of the volume resistivity of a electrically conductive film, the storage stability (reliability) of a electrically conductive film, and migration resistance Was evaluated.

As a result, the cumulative 10% particle diameter (D ₁₀ ) of the silver powder was 0.7 μm, the cumulative 50% particle diameter (D ₅₀ ) was 2.2 μm, and the cumulative 90% particle diameter (D ₉₀ ) was 4.4 μm. Moreover, the BET specific surface area of silver powder was 0.57 m < ² > / g, and the tap density was 4.8 g / cm < ³ >. Moreover, the oxygen content in silver powder was 0.08 mass%, and the carbon content was 0.02 mass%. The crystallite diameter of the silver layer of the silver-coated copper alloy powder was 121 nm. Further, the volume resistivity (initial volume resistivity) of the conductive film was 26 μΩ · cm. The volume resistivity after storage for 6 weeks was 14 μΩ · cm, and the rate of change in volume resistivity was −46%. Moreover, the short circuit time of the electrically conductive film was 51 seconds. These results are shown in Tables 1 to 4.

[Comparative Example 2]
Except for using copper powder instead of copper alloy powder, the composition, particle size distribution, BET specific surface area, tap density of silver-coated copper powder obtained by the same method as in the Reference Example were the same as in Example 1. In addition to obtaining the oxygen content, carbon content, and crystallite diameter of the silver layer, calculation of the volume resistivity of the conductive film, storage stability (reliability) of the conductive film, and migration resistance were performed in the same manner as in Example 1. Sexuality was evaluated.

As a result, the silver coating amount of the silver-coated copper powder was 11.3% by mass, and the copper content was 88.7% by mass. The silver-coated copper powder had a cumulative 10% particle diameter (D ₁₀ ) of 1.2 μm, a cumulative 50% particle diameter (D ₅₀ ) of 2.7 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 4.9 μm. It was. The silver-coated copper powder had a BET specific surface area of 0.72 m ² / g and a tap density of 3.5 g / cm ³ . The oxygen content in the silver-coated copper powder was 0.17% by mass, and the carbon content was 0.25% by mass. The crystallite diameter of the silver layer of the silver-coated copper alloy powder was 30 nm. Further, the volume resistivity (initial volume resistivity) of the conductive film was 154 μΩ · cm. The volume resistivity after storage for 6 weeks was 687 μΩ · cm, and the rate of change in volume resistivity was 346%. The short-circuit time of the conductive film was 291 seconds. These results are shown in Tables 1 to 4.

[Comparative Example 3]
A solution (solution 1) of 61.9 g of EDTA-2Na dihydrate and 61.9 g of ammonium carbonate dissolved in 720 g of pure water, 307.1 g of EDTA-2Na dihydrate and 153.5 g of ammonium carbonate, 1223 g of pure water A solution obtained by adding a solution obtained by dissolving 51.2 g of silver nitrate in 158 g of pure water to the solution dissolved in (1) was prepared, and 130 g of copper powder similar to that in Comparative Example 2 was added to solution 1 in a nitrogen atmosphere. For the silver-coated copper powder obtained by the same method as in Reference Example, except for the above, the composition, the particle size distribution, the BET specific surface area, the tap density, the oxygen content, the carbon content by the same method as in Example 1. In addition, the crystallite size of the silver layer was obtained, and the volume resistivity of the conductive film was calculated, the storage stability (reliability) of the conductive film and the migration resistance were evaluated by the same method as in Example 1. .

As a result, the silver coating amount of the silver-coated copper powder was 21.7% by mass, and the copper content was 78.3% by mass. The silver-coated copper powder had a cumulative 10% particle diameter (D ₁₀ ) of 1.7 μm, a cumulative 50% particle diameter (D ₅₀ ) of 3.6 μm, and a cumulative 90% particle diameter (D ₉₀ ) of 6.0 μm. It was. The silver-coated copper powder had a BET specific surface area of 0.51 m ² / g and a tap density of 4.1 g / cm ³ . The oxygen content in the silver-coated copper powder was 0.25% by mass, and the carbon content was 0.17% by mass. The crystallite diameter of the silver layer of the silver-coated copper alloy powder was 32 nm. Further, the volume resistivity (initial volume resistivity) of the conductive film was 135 μΩ · cm. The volume resistivity after storage for 6 weeks was 530 μΩ · cm, and the rate of change in volume resistivity was 293%. Moreover, the short circuit time of the electrically conductive film was 191 seconds. These results are shown in Tables 1 to 4.

  As can be seen from Tables 1 to 4, in the silver-coated copper alloy powders of Examples 1 to 6, the volume resistivity (initial volume resistivity) of the conductive film is low, and the change rate of the volume resistivity of the conductive film is low. (The storage stability is excellent), and the short-circuit time of the conductive film is very long, and the migration resistance is excellent. Compared with the silver-coated copper alloy powder of the reference example, it can be seen that the short-circuit time of the conductive film is extended and the migration resistance is improved. Moreover, compared with the silver powder of the comparative example 1, although the volume resistivity of the electrically conductive film and its change rate are high, the short circuit time of the electrically conductive film is greatly extended, and the migration resistance is greatly improved. I understand. In addition, when compared with the silver-coated copper powders of Comparative Examples 2 to 3, the volume resistivity of the conductive film is low (if the amount of silver is the same), and the change rate of the volume resistivity of the conductive film is also low, so that the storage stability is reduced. It can be seen that the short circuit time of the conductive film is greatly extended and the migration resistance is also greatly improved.

Claims (8)

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 was coated with a silver containing layer of 7 to 50% by mass, and then coated with a silver containing layer. A method for producing a silver-coated copper alloy powder, comprising heat-treating a copper alloy powder. The method for producing a 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 method for producing a silver-coated copper alloy powder according to claim 1 or 2, wherein the heat treatment is performed by heating at 30 to 50 ° C for 10 to 120 minutes. The method for producing a silver-coated copper alloy powder according to any one of claims 1 to 3, wherein the copper alloy powder coated with the silver-containing layer is surface-treated with a surface treatment agent before or after the heat treatment. . The method for producing a silver-coated copper alloy powder according to claim 4, wherein the surface treatment agent is a fatty acid. The method for producing a silver-coated copper alloy powder according to any one of claims 1 to 5, wherein the copper alloy powder is produced by an atomizing method. The silver according to any one of claims 1 to 6, wherein a cumulative 50% particle diameter (D50 diameter) of the copper alloy powder measured by a laser diffraction particle size distribution apparatus is 0.1 to ₁₅ µm. A method for producing a coated copper alloy powder. A copper alloy powder having a composition comprising at least one of nickel and zinc of 1 to 50% by mass and the balance of copper and inevitable impurities is coated with a silver containing layer of 7 to 50% by mass, and (111 The silver-coated copper alloy powder is characterized by having a crystallite diameter in the plane of 40 nm or less.