JPH1161424A - Electroless silver-plated powder and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce electroless silver-plated powder in which a uniform and dense silver coating film is formed on the surface of powder and excellent in electric conductivity and to provide a method for producing the same. SOLUTION: This electroless silver-plated powder is the one in which copper- coated inorganic or organic grains have a nickel plating coating base layer as a base material, and silver coating film is formed on the surface of the base material by an electroless plating method. This powder is produced by successively executing a primary stage in which the inorganic or organic grains are applied with electroless nickel plating, a secondary stage in which the nickel plating-coated grains are applied with copper plating and a third stage in which the copper plating-coated grains are applied with silver plating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless silver-plated powder having a uniform and dense silver film formed thereon and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, in the electronic industry and the like, a large amount of fine silver powder has been used as a conductive filler mixed in a conductive paste or a conductive paint for shielding electromagnetic waves.
Although silver is a noble metal and expensive, it is used for such industrial applications because of its excellent electrical conductivity and environmental resistance. That is, nickel and iron are inexpensive but have poor electrical conductivity, and Cu has excellent electrical conductivity. However, when the surface is oxidized, the electrical conductivity decreases.

Conventionally, the electroless silver plating method has been a method in which an electroless copper plating is applied, followed by an electroless silver plating, and a silver film is formed by a substitution reaction between copper and silver. However, the silver-plated product obtained by the conventional substitution reaction has a double layer of copper and silver with copper as a lower layer, and contains a large amount of copper. Accordingly, there has been a problem that due to the interdiffusion between the lower copper film and the surface silver, the physical properties inherent in silver plating are deteriorated and it is difficult to obtain a good silver plated product.

Therefore, various electroless plating methods for applying silver plating to powder have been proposed. For example, a method of applying an ultrasonic vibration to a metal powder at a specific frequency or more to perform electroless plating (JP-A-1-225778), an electroless plating with a silver plating solution containing silver complex ions, a reducing agent and a stabilizer. (Japanese Unexamined Patent Publication (Kokai) No. 2-173272), a method in which hydrazine hydrate is continuously added to mica powder at room temperature while maintaining the pH of a plating bath at a specific value, and electroless plating is performed (Japanese Unexamined Patent Publication No. 63-173272). 20
No. 486), a method of activating the surface of a spherical phenol resin powder with an aqueous solution containing hydrochloric acid and chloride and then electrolessly plating (Japanese Patent Application Laid-Open No. 1-225776) a method comprising silver nitrate, polyethylene polyamine and water. A method of electroless plating using a plating solution having a specific composition (JP-A-1-201485) has been proposed.

[0005]

However, in any of the methods, not only is it difficult to obtain a dense silver film having good adhesion, but also the plating efficiency and the economic efficiency are poor depending on the plating method. .

Accordingly, an object of the present invention is to provide an electroless silver-plated powder excellent in conductivity, having a uniform and dense silver film formed on the surface of the powder, and a method for producing the same.

[0007]

Under these circumstances, the present inventors have made intensive studies and as a result, have formed a silver film by electroless plating on the surface of copper-coated particles having a nickel plating film underlayer. Then, it has been found that a uniform and dense silver film can be formed, and that the silver film has a small thickness and excellent conductivity, thereby completing the present invention.

[0008] That is, the present invention relates to a method of forming a silver film by electroless plating on the surface of a copper-coated inorganic or organic particle having a nickel plating film base layer as a base material. It is intended to provide a characteristic electroless silver plating powder.

Further, the present invention provides a first step of forming a nickel film by electroless nickel plating inorganic or organic particles, a second step of forming a copper film by electroless copper plating the nickel-coated particles, The present invention provides a method for producing an electroless silver plating powder, characterized by sequentially applying a third step of forming a silver film by a substitution reaction between copper and silver by subjecting the copper-coated particles to electroless silver plating. is there.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the electroless silver plating powder of the present invention, the inorganic or organic particles coated with copper having a nickel plating film base layer as a base material are made of an inorganic or organic material serving as a core material as described later. The organic powder is obtained by applying electroless nickel plating by an ordinary method and then by applying electroless copper plating by an ordinary method, and is subjected to a double base treatment.

The electroless silver plating reaction performed on the surface of the substrate subjected to the double undercoating treatment dissolves and disappears the copper plating layer by a substitution reaction between copper and silver. It is possible to obtain a plating powder having a two-layer structure of a nickel film as a base layer and a silver film as a surface layer. Here, “substantially” means that some copper or copper film remaining unreacted at the end of the electroless silver plating reaction is acceptable. In this case, the content of copper with respect to silver in the electroless silver plating powder is usually 15% by weight or less, preferably 5% by weight or less. The thickness of the nickel film of the underlayer is not particularly limited, but is preferably 0.03 μm to 0.5 μm. If the thickness is less than 0.03 μm, it is practically difficult to completely cover the surface of the substrate with a nickel film, while if it exceeds 0.5 μm, the specific gravity of the plating powder is unnecessarily increased, which is uneconomical. . The thickness of the silver film is not particularly limited, but is preferably 0.03 to 0.5 μm for the same reason as described above.

Further, as described above, the electroless silver plating powder according to the present invention is a silver plating powder on which a uniform silver film is formed, and there is no agglomerated powder which constitutes a rich coat. And are substantially individual, independent dispersions. this is,
It can be easily confirmed with an electron microscope. In addition, the size of the electroless silver plating powder depends on the size of the core material as particles and is designed according to the application, and is not particularly limited, but in most cases, the range from 1 to several mm is practical. And its shape is not particularly limited.

[0013] In the inorganic or organic particles of the core material,
Inorganic particles include metal powders, metal or non-metal oxides (including inclusions), metal silicates including aluminosilicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates , Metal sulfides, metal salts, metal halides or carbon. As organic particles, natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylate, polyacrylonitrile, polyacetal, ionomer, polyester and other synthetic plastic resins, alkyd resins, phenol resins, Synthetic thermosetting resins such as urea resins, melamine resins, xylene resins, silicone resins and diaryl phthalate resins can be exemplified. These inorganic and organic particles may be used alone or as a mixture of two or more. This mixture includes both a mixture having a chemically inhomogeneous composition and a mixture as a core material.

The particle size and shape of the inorganic or organic particles of the core material are not particularly limited, but the particle size is preferably in the range of 1 μm to several mm, and the shape is spherical, plate-like, rod-like or needle-like. , Hollow or fibrous shape. Therefore, it may be powdery or granular in appearance. The material of the core material can be used without any particular limitation as long as it is water-insoluble or hardly water-soluble that can be electrolessly plated. The core material desirably has a chemically uniform composition, but may have a non-uniform chemical composition.

The electroless silver-plated powder of the present invention has a small volume specific electric resistance despite the silver film thickness being thin, since the particle surface forms a dense single layer of silver, usually 4.5. It is less than × 10 ⁻³ Ωcm, preferably 3 × 10 ⁻³ Ωcm or less. Here, the volume-specific electric resistance value is defined as a plastic cylinder having an inner diameter of 1 cm inserted into a protrusion on a copper disk provided with a columnar protrusion electrode having a diameter of 1 cm and having a gold plating on the upper surface of the protrusion. Insert 1 g of sample, insert a cylindrical electrode made of copper with a flange with a diameter of less than 1 cm gold-plated into a plastic cylinder, apply a load of 5 kg from above, and measure the electrical resistance between the electrodes And below
This is a value obtained by calculating the electric resistance value by the equation (1). Volume specific electric resistance (Ωcm) = Measured electric resistance × 0.7856 (cm ² ) / distance between electrodes (cm) (1)

Next, a method for producing the above electroless silver plating powder will be described. In the case where the particles serving as the core material are hydrophobic, the production method includes a pre-process for performing a hydrophilization treatment and a catalyst treatment, a first process for performing electroless nickel plating, a second process for performing electroless copper plating, and And a third step of performing electrolytic silver plating. Hereinafter, each step will be described.

(Hydrophilic and catalyzing treatment step) As a pretreatment step of the first to third steps described later, when the inorganic or organic particles as the core material are hydrophobic, the particles are hydrophilized and catalyzed.

When the core material is organic, there is an etching method using chromic acid-sulfuric acid or an organic solvent-alkali treatment, and when the core material is inorganic, an immersion cleaning method using an alkali or a surfactant is used. There is. Examples of the method of the catalyzing treatment include known methods such as sensitization with a stannous salt or a palladium salt, activation treatment and the like.

In the case where the core material itself has the ability to capture noble metal ions or has the ability to capture by surface treatment, the catalytic treatment may be replaced by the noble metal capturing treatment. Having the ability to capture a noble metal means that a noble metal ion can be captured as a chelate or a salt, for example, one of an amino group, an imino group, an amide group, an imide group, a cyano group, a hydroxyl group, a nitrile group, a carboxyl group or It has two or more kinds on the surface of the core material. Examples of the substance having the core material itself capable of capturing noble metal ions include an organic substance such as an amino resin, a nitrile resin, or an epoxy resin cured with an amino curing agent. Examples of the amino resin include, for example, a condensation reaction of an amino compound such as urea resin, thiourea resin, melamine resin, benzoguanamine resin, acetoguanamine resin, dicyandiamide resin, aniline and an aldehyde compound such as formamide, paraformamide, acetaldehyde, and glyoxal. And the like.

Those having no noble metal ion-capturing ability may be cured by an amino-substituted organosilane coupling agent or an amino-based curing agent and surface-treated with an epoxy resin. Next, the core material having a noble metal ion capturing ability is dispersed in a dilute acidic aqueous solution of a noble metal salt such as palladium chloride or silver nitrate to capture the noble metal. In this case, the solution concentration is preferably in the range of 0.05 to 0.5 g / L. In addition, at the time of the catalyzing treatment, it is preferable to perform a deagglomeration treatment to prepare an aqueous slurry in which a core material is uniformly dispersed.

<First step: Electroless nickel plating>
The powder that has been subjected to the above catalyzing treatment is then subjected to a base layer coating treatment with an electroless nickel plating solution. When performing electroless nickel plating, perform sufficient dispersion treatment,
It is preferable to prepare an aqueous slurry in a dispersed state close to primary particles from which agglomerates of the core material have been removed as much as possible. If the dispersion is insufficient and the agglomerated core material is plated, the untreated surface is likely to be exposed during use.

The dispersing method varies depending on the physical properties of the core material.
For example, a high-speed stirring from a normal stirring, or a shear dispersion device such as a colloid mill or a homogenizer may be used. In dispersing the core material in water, a dispersant such as a surfactant may be used.

In the dispersion treatment, it is preferable to add an aqueous solution of the complexing agent to the aqueous slurry as a dispersion medium. Examples of the complexing agent include, for example, citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or an alkali metal salt or ammonium salt thereof, an amino acid such as glycine or an alkali metal salt thereof, ethylenediamine,
Amine acids such as alkylamines or alkali metal salts thereof,
Compounds having a complexing effect on nickel, such as EDTA, pyrophosphoric acid or an alkali metal salt thereof, and other ammonium salts are exemplified. The complexing agent is usually added in the form of an aqueous solution, and its concentration is in the range of 0.01 to 1 mol / L, preferably 0.2 to 0.5 mol / L. The preferable pH value of the aqueous slurry at this stage is in the range of 4.5 to 10, though it depends on the physical properties of the inorganic or organic powder as the core material.

The concentration of the aqueous slurry is not particularly limited, but is usually 1 to 500 g / L, preferably 5 to 300 g.
/ L. If the slurry concentration is too low, the plating concentration will decrease and the processing capacity will increase, which is not economically favorable. On the other hand, if the slurry concentration is too high, the dispersibility of the core material will deteriorate.

The aqueous slurry that has been sufficiently deagglomerated is preferably prepared in advance at a plating temperature, often 55 ° C. or higher, in order to effectively perform plating.

An electroless nickel plating solution is prepared by adding at least two aqueous solutions of a nickel salt, a reducing agent and a pH adjuster individually and simultaneously to the aqueous slurry prepared as described above as an electroless plating solution. Perform the reaction. Considering the simplicity of equipment and economics, pH
It is preferable that the adjusting agent and the reducing agent are mixed and prepared in advance.

The nickel salt may be any as long as it dissolves in water to form nickel ions, and examples thereof include nickel sulfate, nickel chloride, nickel acetate, and nickel hypophosphite. Examples of the reducing agent include hypophosphorous acid, sodium hypophosphite, nickel hypophosphite and the like. p
Examples of the H adjuster include ammonia, an amine compound, and an alkali agent such as caustic. The concentration of the nickel salt is not particularly limited, but is preferably 0.7 mol / L near the solubility limit in water in consideration of the subsequent filtration operation and waste liquid treatment.
It is preferable to perform the above. The concentration of the reducing agent is preferably at least 1.4 mol / L for the same reason.

In the electroless nickel plating reaction, the plating reaction is started immediately by adding a plating solution to the aqueous slurry, but the nickel film formed by controlling the amount of addition is controlled to a desired thickness. Can be.
After the addition of the electroless nickel plating solution is completed, the reaction is completed by continuing stirring while maintaining the solution temperature for a while after the generation of hydrogen gas is completely stopped. After completion of the plating reaction, the mixture is filtered and separated by a conventional method, further repulped, washed well, and dried, whereby a powder having a uniform nickel film base layer formed on a substrate can be obtained.

<Second Step: Electroless Copper Plating> In the second step, the nickel-coated powder obtained in the first step is subjected to electroless copper plating to form copper, which undergoes a substitution reaction with silver described later. This is a step of forming a uniform layer on the powder surface.

In performing the electroless copper plating treatment, it is preferable to perform a sufficient dispersion treatment in the same manner as in the first step to prepare an aqueous slurry in a dispersed state close to primary particles from which agglomerates of the core material have been removed as much as possible. A dispersant such as a surfactant may be used if desired.

In carrying out the dispersion treatment, it is preferable to add an aqueous solution of the complexing agent to the aqueous slurry as a dispersion medium. Examples of the complexing agent include EDTA, ethylenediamine, Rochelle salt, and alkali metal salts thereof. The concentration of the complexing agent is usually 0.02 to 1 mol /
L, preferably 0.05 to 0.5 mol / L. The concentration of the aqueous slurry is not particularly limited, but is 10 to 500 g.
/ L. It is preferable that the aqueous slurry subjected to the deagglomeration treatment is previously set in a temperature range of 20 to 70 ° C. so that the electroless copper plating reaction is effectively performed.

An electroless plating reaction is carried out by separately and simultaneously adding each aqueous solution of a copper salt, a reducing agent and a pH adjusting agent to the aqueous slurry thus prepared, separately and simultaneously. The copper salt may be one that is dissolved in water to form copper ions, and examples thereof include copper sulfate, copper halide, copper nitrate, and copper acetate. Examples of the reducing agent include formalin, paraformaldehyde, glyoxylic acid and the like. Examples of the pH adjuster include sodium hydroxide, ammonia and the like.

The concentration of the copper salt is not particularly limited, but is preferably 0.6 mol / L or more, which is close to the solubility limit in water, from the viewpoint of economy. For the same reason, the concentration of the reducing agent is preferably 2.4 mol / L or more. In addition,
Copper salt, reducing agent and pH adjuster are based on 1 mole of copper salt.
It is preferable to prepare the reducing agent at a ratio of 3 to 5 mol times and the pH adjusting agent at a ratio of 6 to 11 mol times. After completion of the plating reaction, the powder is separated by filtration by a conventional method, further repulped, washed well, and then dried, whereby a powder having a uniform nickel film and a copper film formed on the underlayer of the nickel film can be obtained.

<Third Step: Electroless Silver Plating> In the third step, the copper film formed in the second step is replaced with silver to form a dense and uniform silver plating film having a thickness corresponding to the amount of copper film. This is the step of forming.

In performing the electroless silver plating treatment, a sufficient dispersion treatment is performed in the same manner as in the first step and the second step to prepare an aqueous slurry in a dispersed state close to primary particles from which agglomerates of the core material have been removed as much as possible. Preferably, a dispersant such as a surfactant may be used if desired.

In carrying out this dispersion treatment, it is preferable to add an aqueous solution of the complexing agent to the aqueous slurry as a dispersion medium. As complexing agents, for example, ammonium salts, amine compounds, tetraethylenepentamine,
Triethylenetetramine, ethylenediamine, triethanolamine, EDTA, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, hydroxyethylimine diacetate, dihydroxyethylglycine, hydrazine, monohydrazine hydrochloride, dihydrazine sulfate, acetohydrazine and the like And the like. The concentration of the complexing agent is usually 0.02 to 1 mol / L, preferably 0.05 to 0.5 mol / L. In addition, the aqueous slurry subjected to the deagglomeration treatment is previously set to 20 to 60 so that the electroless silver plating reaction is effectively performed.
It is preferable to keep the temperature in the range of ° C.

In this electroless silver plating method, a predetermined amount of a silver salt is added to the aqueous slurry prepared above, and a silver film is formed by a substitution reaction between copper and silver. PH of reaction system
Is preferably in the range of 8 to 14. Therefore, if necessary, an alkaline agent such as ammonia, an amine compound and caustic may be added to the reaction system as a pH adjuster.

In this electroless plating reaction, the amount of silver salt added is preferably twice as much as the amount of copper film. In this reaction, since the silver deposition efficiency is almost 100%, if it is less than 2 mol times, a large amount of unreacted copper will remain, and the lower copper film and the surface layer will elapse over time after silver plating. Of silver plating tends to deteriorate due to mutual diffusion with silver. On the other hand, if it is larger than 2 mol times, unreacted silver ions remain in the plating solution, which is not preferable. After the completion of the plating reaction, it is separated by filtration and dried by a conventional method to obtain a silver-plated powder.

Such a silver-plated powder is obtained by a substitution reaction between copper and silver, and has a nickel film as a base layer, and the upper layer is uniformly coated with silver.

The electroless silver plating powder of the present invention is based on copper-coated inorganic or organic particles having a nickel plating film base layer, and forms a silver film on the surface of the substrate by electroless plating. Therefore, it is different from that obtained by a displacement silver plating reaction in which a copper plating film is formed on a conventional substrate and then electroless silver plating is performed. That is, in the conventional electroless silver plating reaction, since the copper is contained in a large amount, after silver plating, due to the interdiffusion of the lower copper film and the surface silver with time, various physical properties inherent in silver plating are deteriorated and good. Although the silver-plated product is difficult to obtain, the electroless silver-plated powder of the present invention has a nickel-silver two-layer structure containing substantially no copper, so that the mutual diffusion between copper and silver is suppressed. In addition, silver plating is applied uniformly and densely, and the original film properties of silver plating can be obtained. According to the production method of the present invention,
The silver deposition efficiency known from the silver mirror reaction is approximately 50% to 60%, but is approximately 100%, so that the productivity is high and practical.

[0041]

Next, the present invention will be described in more detail with reference to examples, but this is merely an example and does not limit the present invention. Examples 1 to 7 (Pretreatment) 0.5 to 1.
An aminosilane coupling agent (S-3) having a concentration of 0 g / L
00; manufactured by Chisso Co., Ltd.), dispersed for about 10 minutes, separated by filtration and dried. Next, the treated powder was charged into 1 L of an acid acidic aqueous solution containing 0.1 g / L palladium chloride salt, stirred for about 5 minutes, filtered, repulped, and separated by filtration again.

[0042]

[Table 1]

(Electroless Nickel Plating Process) Each of the pretreated powder samples was charged into a plating bath of a complexing agent aqueous solution having the composition shown in Table 2 and subjected to deagglomeration treatment.
An aqueous slurry was prepared by heating to ° C. Sodium hypophosphite 3 g / L was added to the obtained aqueous slurry and dissolved under stirring. Next, the electroless nickel plating solution having the composition shown in Table 3 was separated as a solution a and a solution b, and generation of hydrogen gas by reduction of palladium ions was confirmed. Sent. Table 4 shows the amount and rate of plating solution addition. After adding a predetermined amount of the liquids a and b, the temperature was maintained at 70 ° C. until the generation of hydrogen gas ceased, and an electroless nickel plating reaction was performed with stirring. Next, filtration, washing with water, and drying were performed to obtain powders each subjected to electroless nickel plating.

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

(Electroless Copper Plating Process) 0.1 g of palladium chloride was added to 50 g of the electroless nickel-plated powder.
/ L, and stirred for 5 minutes, followed by filtration, washing, and filtration. Next, this powder was charged in advance into an aqueous solution containing 50 g / L of EDTA-Na, further charged with 1 g / L of sodium hypophosphite, deagglomerated, and kept at 50 ° C. to prepare an aqueous slurry. Next, an electroless copper plating solution having the composition shown in Table 5 was prepared, added to the aqueous slurry under the conditions for adding the plating solution shown in Table 5, and subjected to an electroless copper plating reaction until hydrogen gas was no longer generated. After the completion of the electroless copper plating reaction, filtration,
Washed and separated by filtration.

[0048]

[Table 5]

(Electroless silver plating process) EDTA
To the aqueous solution having a concentration of -Na of 50 g / L adjusted to pH 11, the above-mentioned nickel-copper-plated powder was added, and after deagglomeration treatment, 158 g / L of silver nitrate
Was added under the plating solution addition conditions shown in Table 6. After the addition of silver nitrate, a displacement silver plating reaction was performed with stirring for 10 minutes. Next, the mixture was filtered, washed with water, separated by filtration, and dried to obtain white silver-plated powders.

[0050]

[Table 6]

Comparative Example 1 A silica powder (true specific gravity: 2.50, particle size: 5.4 μm) was used as the powder.
m), except that twice the amount of electroless copper plating was applied.
According to the same method as in Example 2, a dark black plating powder was obtained.

Comparative Example 2 Alumina powder (true specific gravity 2.40, particle size 3.0 μm) 10
g of silver nitrate 20 g / L, 28% ammonia water 30 mL /
After charging into 5 L of an aqueous solution containing L and performing deagglomeration, 600 g / L of Rochelle salt was charged and silver plating was performed for 1 hour. Next, the mixture was filtered, washed with water, separated by filtration, and dried to obtain a gray-white silver-plated powder having a slightly rough surface.

Comparative Example 3 Glass bead powder (true specific gravity 2.50, particle size 30 μm) 1
0 g of silver nitrate 20 g / L, 28% ammonia water 30 mL
5 L of an aqueous solution containing L / L and deagglomeration treatment, and then 600 g / L of Rochelle salt was charged and silver plating was performed for 1 hour. Next, the mixture was filtered, washed with water, separated by filtration, and dried to obtain a gray-white silver-plated powder having a slightly rough surface.

Table 7 shows the effective utilization rate of silver (the ratio of silver in the plating solution used and silver deposited as a silver plating film) during electroless silver plating in Examples 1 to 7 and Comparative Examples 1 to 3. It was shown to.

[0055]

[Table 7]

<Evaluation of Silver Plating Properties> Composition of Metal Coating The metal coating powders obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were added to a silver nitrate solution to dissolve the metal coating. Was measured for its composition and true specific gravity. The results are shown in Table 8.

[0057]

[Table 8]

(Evaluation of Electric Resistance Characteristics) A plastic cylinder having an inner diameter of 1 cm is inserted into a protrusion on a copper disk provided with a columnar protrusion electrode having a diameter of 1 cm and plated with gold on the upper surface of the protrusion. 1 g of the metal film sample obtained in each of Examples 1 to 7 and Comparative Examples 1 to 3 was inserted into the plastic cylinder. Then, a copper-made cylindrical electrode having a flange and a little less than 1 cm in diameter and having a gold-plated end was inserted into a plastic cylinder. The electric resistance between the electrodes was measured while a load of 5 kg was applied from above, and the volume-specific electric resistance value was determined by the formula (1). The results and the film thickness are shown in Table 9.

[0059]

[Table 9]

[0060]

The electroless silver-plated powder of the present invention provides a conductivity by replacing a part of the silver film with an inexpensive nickel film. It has the same conductivity as plating powder and has excellent conductivity, making use of the properties such as light specific gravity of plating powder, and can be used not only as a conductive pigment in paints and adhesives, but also as an addition to resin or other When used in combination with a conductive material, it can be used as an alternative to conventional silver powder in many fields including the electric industry. Further, according to the production method of the present invention, the above-mentioned electroless silver-plated powder can be efficiently produced by an industrially advantageous method, so that the industrial use value is extremely large.

Claims (5)

[Claims] An inorganic or organic particle coated with copper having an underlayer of a nickel plating film as a base material, and a silver film formed on the surface of the base material by electroless plating. Electrolytic silver plating powder. 2. A volume specific electric resistance value of 4.5 × 10 ⁻³ Ω.
The electroless silver-plated powder according to claim 1, which has a diameter of less than 1 cm. 3. A first step of forming a nickel film by electroless nickel plating inorganic or organic particles, a second step of forming a copper film by electroless copper plating the nickel-coated particles, and the copper-coated particles. A silver film by a substitution reaction between copper and silver, followed by a third step of forming a silver film by electroless silver plating. 4. The method according to claim 3, wherein the thickness of the silver film is adjusted by the thickness of the copper film. 5. The method for producing an electroless silver plating powder according to claim 3, wherein the electroless silver plating reaction is performed by adding the silver salt in an amount twice as much as the amount of the copper film.