JP2003034879A - Ni-PLATED PARTICLE AND MANUFACTURING METHOD THEREFOR - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide Ni-plated particles having superior electroconductivity, little cohesiveness, and uniform thickness of the Ni film. SOLUTION: The Ni-plated particle 1 having a Ni film 3 plated by an electroless Ni plating method on the surface of a particle core 2, has a less P content in the surface side 3x than in the particle core side 2, along a depth direction of the whole Ni film 3.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to Ni-plated particles in which electroless Ni-plated coatings are formed on the surface of core material particles by electroless Ni-plating.

[0002]

2. Description of the Related Art Electroless Ni plating has been applied to objects to be plated of various sizes and shapes due to the progress of the technology and the development of applications. For example, as a method of electroless Ni plating on a particulate core material, Is Japanese Patent Publication No. 3-44149,
There are methods described in JP-B-6-96771, JP-A-7-11886, and JP-A-8-31655.

[0003]

However, when the object to be plated is fine particles having a particle size of about 0.1 to 50 μm, the surface is very active, the specific area is large, and the cohesive force is large. As described in Japanese Patent Publication No. 967771 and the like, a Ni salt solution constituting a Ni plating solution and a reducing agent solution such as sodium hypophosphite are added little by little to a dispersion liquid of a core material at a constant pH. However, it is difficult to precisely control the plating reaction rate.

Furthermore, if the P content in the Ni coating is high,
Since the electroconductivity of the Ni coating decreases, it is desirable to reduce the P content in the Ni coating when the Ni plated particles are used as a conductive filler such as a conductive adhesive or an anisotropic conductive adhesive. However, when sodium hypophosphite is used as the reducing agent, P is produced by a side reaction of the Ni plating reaction, as shown in the following formula, so that P in the Ni coating film is formed.
It is also difficult to control the content.

[0005]

Embedded image Local anode reaction H ₂ PO ₂ ⁻ + H ₂ O → H ₂ PO ₃ ⁻ + 2H ⁺ + 2e Local cathode reaction 2e + Ni ²⁺ → Ni 2e + 2H ⁺ → H ₂ side reaction H ₂ PO ₂ ⁻ + 2H ⁺ + 2e → P + H ₂ O

That is, in the low pH range of pH 4 to 5, electroless Ni
When the plating reaction is performed, the rate of the Ni plating reaction (local cathode reaction) is slow and the rate of the side reaction is fast, so that a large amount of P is taken into the Ni coating and the electrical conductivity of the Ni coating is lowered. On the other hand, the agglomeration of the Ni plated particles is reduced.

On the contrary, in the high pH range of pH 7-8, no electric field N
When the i plating reaction is performed, the Ni plating reaction speed is high, so that a Ni coating film with a small P incorporation is formed. However, since the Ni coating film has magnetism and the Ni plating particles agglomerate remarkably, The coating film becomes uneven and its thickness becomes non-uniform, making it difficult to continue Ni plating.
Further, depending on the use of the Ni-plated particles, when gold plating is further applied on the Ni coating, gold plating is performed by replacing Ni forming the Ni coating with gold.
It becomes difficult to obtain a uniform gold plating film.

Therefore, in the production of the Ni-plated particles, how to reduce the P content so as not to impair the conductivity of the Ni-plated particles and to suppress the cohesiveness is an issue. .

On the other hand, the present invention has excellent electric conductivity, less cohesiveness, and a uniform Ni coating thickness.
The purpose is to provide new Ni-plated particles.

[0010]

The inventor of the present invention has found that electroless Ni
When manufacturing Ni plated particles by the plating method, N
The P content in the i coating is varied in the thickness direction of the Ni coating,
When the P content on the surface side of the Ni coating is reduced with respect to the core particle side, excellent electrical conductivity is ensured by the surface side region of the Ni coating having a low P content, and the core having a high P content is secured. It has been found that the material-side region suppresses the cohesiveness of the Ni-plated particles.

Furthermore, in order to make the P content in the Ni coating different in the thickness direction of the Ni coating, the Ni salt solution and the reducing agent solution are dropped into the dispersion liquid of the core particles to proceed the Ni plating reaction. When the reaction is performed, p
It has been found that increasing H and gradually reducing the P content in the Ni coating is effective.

That is, the present invention is a Ni-plated particle in which a Ni coating is provided on the surface of the core particle by the electroless Ni plating method, and the P content in the thickness direction of the Ni coating is greater than that of the core particle side. Is also less on the Ni coating surface side
Providing plated particles.

Further, the present invention provides an aqueous suspension of core material particles carrying a noble metal catalyst, a Ni salt, a phosphorus-based reducing agent and a pH.
In the method for producing Ni-plated particles in which an electroless Ni-plating reaction is performed by adding a Ni-plating solution containing a regulator to form a Ni coating film on the surface of core material particles, the pH of an aqueous suspension containing the Ni-plating solution is added. Is provided at the end of the reaction rather than at the start of the reaction.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the Ni-plated particles 1 of the present invention are obtained by forming a Ni coating film 3 on the surface of a core material particle 2 by an electroless Ni plating method. The P content is 3x more than the core material particle 2 side Ni coating surface 3
It is characterized by a small number on the side.

In particular, EDX (Energy Dispersing X-ray)
analyzer: energy dispersive X-ray analyzer), the ratio P / Ni of the number of P and Ni atoms contained in the Ni coating is calculated from the core particle side interface to the thickness of the Ni coating 3 of 1
0.15 <P / Ni <0.40, N in the area A of 0% or less
It is preferable to set 0.00 <P / Ni <0.15 in a region C that is 10% or less of the thickness of the Ni coating 3 from the i coating surface 3x, and in particular, the Ni coating sandwiched between the region A and the region C. It is possible to set 0.05 <P / Ni <0.20 in the region B at the center of 3 and make P / Ni larger than the region B in the region A and smaller than P / Ni in the region C in the region C. preferable. As a result, the Ni purity of the surface of the Ni plated particles 1 can be increased, the electric conductivity can be increased, and the cohesiveness of the Ni plated particles 1 can be suppressed.

Such Ni plated particles 1 can be easily manufactured by the method for manufacturing Ni plated particles of the present invention.

The method for producing Ni-plated particles of the present invention is different from the known electroless Ni-plating method in that a noble metal catalyst such as palladium or silver is first supported on the surface of core material particles and then a Ni plating solution is applied. It is the same.

In order to obtain core material particles supporting a noble metal catalyst such as palladium, first, core material particles capable of capturing precious metal ions such as palladium ions as chelates or salts on the surface, that is, the ability to capture precious metal ions. It is preferable to prepare the core material particles having the same, support the precious metal ions thereon, and then apply a reducing agent to support the precious metal catalyst on the surface of the core particles.

The core particles having a precious metal catalyst supported on the surface are not particularly limited in shape, size, etc. as long as they can be suspended in water by an ordinary dispersion method.
For example, the shape of the core material particles may be a specific shape such as a spherical shape, a fibrous shape, a hollow shape, or a needle shape, or may be an unspecified shape. Further, it may be fine particles having a particle size of 50 μm or less.

Further, the material of the core material particles with or without the ability to capture the noble metal ions may be organic or inorganic, and may be crystalline or amorphous. More specifically, examples of the inorganic material forming the core material particles include metals (alloys), glass, ceramics, metal oxides, metal silicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, Examples thereof include metal phosphates, metal sulfides, metal salts, metal halides, carbon, and the like. Examples of organic materials include natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene. , Thermoplastic resins such as polyamide, polyacrylic ester, polyacrylonitrile, polyacetal, polyester, alkyd resin, phenol resin, urea resin,
Examples thereof include thermosetting resins such as melamine resin, xylene resin, silicone resin, epoxy resin, diallyl phthalate resin, and benzoguanamine resin. The core material particles may be formed of one kind among them, or may be formed from a mixture or copolymer of two or more kinds.

In order to make the core material particles have the ability to capture noble metal ions, amino groups, imino groups, amide groups, imide groups, cyano groups, hydroxyl groups, nitrile groups, carboxyl groups and the like are present on the surface thereof. When the surface of the core material particle is made of an amino resin, a nitrile resin, an epoxy resin cured with an amino curing agent, or the like, the core particle can be used as a particle having a capturing ability of noble metal ions. On the other hand, when the core material particles do not have the ability to capture precious metal ions,
Such core material particles are, for example, stirred with a solution of a surface modifier such as an epoxy resin cured with an amino group-substituted organosilane coupling agent or an amine curing agent, dispersed, and then vacuum dried. By so doing, the ability to capture precious metal ions is imparted to the surface.

As a method for capturing the noble metal ions in the core material particles having the ability to capture the precious metal ions, the core material particles having the ability to capture the precious metal ions are dispersed in a dilute acidic aqueous solution of the precious metal salt, and the precious metal particles are added to the core material particles. Capture ions.
In this case, the noble metal ion concentration in the acidic aqueous solution is, for example, when using palladium chloride as the noble metal salt,
It is preferably 0.05 to 1.0 g / L.

Next, in order to use the noble metal ions captured by the core material particles as a noble metal catalyst, the reducing agent used for Ni plating (for example, sodium hypophosphite) is added to the acidic aqueous solution after capturing the noble metal ions. ) Is added dropwise to reduce the noble metal ion to obtain a noble metal catalyst.

In the method for producing Ni-plated particles of the present invention, an aqueous suspension (hereinafter referred to as slurry) of core material particles carrying a noble metal catalyst is prepared. In this slurry, the core material particles are in a state close to the primary particles so that agglomeration does not occur. Therefore, the concentration of the core material particles in the slurry is preferably 0.5 to 2% by weight.

The slurry contains a surfactant, a reducing agent,
It is preferred to add a complexing agent.

Here, a nonionic surfactant or the like is used as the surfactant. The concentration of the surfactant in the slurry is preferably 0.5 to 5% by weight.

As the reducing agent, sodium hypophosphite or the like is used in terms of cost and performance. The concentration of the reducing agent in the slurry is 0.5 in order to reduce the P content.
It is preferable to set it to ˜5% by weight.

As the complexing agent, in the conventional electroless Ni plating, various compounds having a complexing effect on Ni ions, such as malic acid, lactic acid, tartaric acid, citric acid, gluconic acid, hydroxyacetic acid, etc., can be used. Carboxylic acid or an alkali metal salt thereof, carboxylate such as ammonium salt, amino acid such as glycine, aminos such as ethylenediamine and alkylamine, other ammonium, EDTA, and pyrophosphate are used, but in the present invention, In order to adjust the pH at the end of the Ni plating reaction to 5.8 to 6.2, it is preferable to use one having a pH of the buffer system with the pH adjuster having such a value, for example, sodium tartrate, acetic acid. Ammonium, sodium malate, sodium gluconate, etc. are used. The concentration of complexing agent in the slurry is 0.
It is preferably 5 to 5% by weight.

Further, sulfuric acid, hydrochloric acid or the like is added to the slurry in order to adjust the pH of the reaction solution at the start of the Ni plating reaction to 3.8 to 4.2.

On the other hand, a Ni plating solution is prepared. The Ni plating solution is, for example, a nickel salt aqueous solution such as nickel sulfate or nickel chloride, and an aqueous solution containing a reducing agent such as sodium hypophosphite and a pH adjusting agent such as sodium hydroxide or potassium hydroxide. It is preferable to prepare a liquid. In this case, the concentration of the nickel salt in the nickel salt aqueous solution is determined according to the thickness of the plating, but a plating film with a thickness of 150 to 200 nm is formed on core material particles with a specific surface area of 1 m ² / g and a particle size of 5 μm. In this case, it is preferably 20 to 30% by weight. The concentration of the reducing agent in the aqueous solution containing the reducing agent and the pH adjusting agent is determined according to the P content, but the core material particles having a specific surface area of 1 m ² / g and a particle size of 5 μm have a thickness of 150 to 20.
In the case of forming a 0 nm plating film, it is preferably set to 15 to 25% by weight.

When preparing the slurry or the Ni plating solution, stirring or ultrasonic dispersion treatment is carried out if necessary, and the temperature is controlled to be 50 to 80 ° C.

Next, the Ni plating solution is gradually added to the above-mentioned slurry and the Ni plating reaction is performed to form a Ni coating film on the surface of the core material particles. When the Ni plating solution is adjusted to two solutions, these are added at the same time. The present invention is characterized in that the P content in the Ni coating thus formed is smaller on the Ni coating surface side than on the core side.

As a method of controlling the P content in the Ni coating, the concentration control of the reducing agent sodium hypophosphite,
Although control of the plating temperature and the like are conceivable, it is particularly preferable to control the pH during the Ni plating reaction. More specifically, the pH is 3.8 to 4.2 at the start of the Ni plating reaction.
At the end of the Ni plating reaction, the pH was adjusted to 5.8-6.
It is preferably 2.

In order to control the pH during the Ni plating reaction in this way, the pH of the slurry is set to 3.
It is preferable to adjust the pH to 8 to 4.2 so that the pH is raised during the Ni plating reaction by a pH adjusting agent (alkali) that is gradually added during the Ni plating reaction.
The pH at the end of the reaction can be adjusted to a predetermined value by allowing the pH adjusting agent and the complexing agent contained in the slurry from the beginning to form a buffer system having a pH of 5.8 to 6.2. It is preferable because it can be easily controlled.

By controlling the pH during Ni plating as described above, since the pH is low in the initial stage of the reaction, the deposition rate of Ni on the surface of the core material particles is slow and the production of P, which is a by-product, is fast. , P is taken in a large amount in the Ni coating to form a Ni coating having a high P content. Further, the particles having such a Ni coating film maintain high dispersibility in the slurry. After that, when the pH gradually rises and the pH becomes 5.8 to 6.2 which is the pH of the buffer system, the Ni plating reaction rapidly proceeds, and the Ni coating film contains more Ni than the incorporation of P as a by-product. Deposition has priority, N with high Ni purity
An i-coat is formed. Thus, the P / Ni content ratio P / Ni in the thickness direction of the Ni coating is 1 as the value of EDX from the core particle side interface of the Ni coating to the thickness of the Ni coating.
0.15 <P / Ni <0.40 in the region of 0% or less, and 0.00 <P / Ni <0.15 in the region of 10% or less of the thickness of the Ni coating from the surface of the Ni coating. , N
The P content in the i coating can be gradually reduced from the core particle side toward the Ni coating surface side.

In the Ni-plated particles of the present invention, the P content in the Ni-coating may be varied discontinuously. In this case, the Ni-plated particles may be produced, for example, by using a pH adjusting agent. A large amount of charge or discontinuous charge may be performed.

The end point of the Ni plating reaction is appropriately determined according to the purity of the Ni coating required for the Ni plated particles, the required production amount, the production cost, and the like. For example, N
When the replacement gold plating is applied to the i-plated particles in the next step,
The higher the purity of the Ni coating on the surface of the Ni plated particles, the more Ni
Since the substitution reaction of gold with gold proceeds, the purity of the Ni coating surface is very important.
Sufficiently until a coating is formed on the surface of the Ni-plated particles with a predetermined thickness. When Ni plated particles are used as the conductive filler, it suffices that a predetermined electric conductivity is obtained on the surface of the Ni coating.

However, since particles having a Ni coating film of high Ni purity formed on the surface thereof are likely to agglomerate rapidly, in the present invention, after the generation of hydrogen due to the Ni plating reaction is no longer recognized, the Ni plating is performed. The Ni plating reaction is terminated before the particles agglomerate significantly.

After completion of the Ni plating reaction, stirring is continued to 1
Aging is continued for about 0 to 20 minutes, and then the particles are filtered, washed with alcohol, warm water, etc., and dried.

In the Ni-plated particles thus obtained, since the Ni coating film is uniformly formed on the core material particles,
The bonding strength between the Ni coating and the core particles is high. Therefore,
Even if the Ni-plated particles are kneaded and dispersed with a synthetic resin or the like, the plated coating does not peel off. In addition, the Ni coating surface has high Ni purity and high electric conductivity. Therefore, the Ni-plated particles are useful as a conductive filler for a conductive adhesive or an anisotropic conductive adhesive. It is also useful as particles for gold plating.

[0042]

EXAMPLES Example 1 True specific gravity 1.4, average particle size 4.6 μm, specific surface area 0.95
m ² / g benzoguanamine-based resin particles (Nippon Shokubai Co., Ltd., Eposter GP-H46S) were treated with a 10% solution of an ion adsorbent (Okuno Pharmaceutical Co., Ltd., Condilator SP) for 5 minutes, and then palladium chloride. 0.01% of
Treated with an aqueous solution for 5 minutes, further reduced by adding a 5% solution of sodium hypophosphite, and further added a surfactant (Chemical Electronics Co., CE-80W) at about 1% to these solutions. Then, the mixture was stirred for 20 minutes, filtered, and washed to obtain core material particles carrying palladium.

Next, sodium tartrate (complexing agent) 1%,
Surfactant (Surfynol TG, manufactured by Nissin Chemical Industry Co., Ltd.)
500 ml of ion-exchanged water containing 2% was mixed with 10 g of the above core material particles to prepare a slurry, and sulfuric acid was further added to adjust the pH of the slurry to 4.

On the other hand, as a Ni plating solution, a 22.4% solution of nickel sulfate and 22.4% sodium hypophosphite are used.
And 2% of a solution containing 6% of sodium hydroxide were prepared.

The above-mentioned slurry was heated to 70 ° C., and a nickel sulfate solution and a reducing agent solution, which compose a two-liquid Ni plating solution, were continuously added simultaneously, and a plating reaction was performed by stirring for about 1 hour. PH at the start of this plating reaction
Was 4. As the plating reaction proceeds, sodium hypophosphite, which is a reducing agent, is consumed and H ⁺ is produced, but since the sodium hydroxide solution is constantly supplied and added at an appropriate concentration, the pH gradually rises and the reaction Near the end, the pH approached the pH 6 inherent in the buffer system formed by sodium tartrate and sodium hydroxide.

During this plating reaction, it was confirmed by a commercially available Ni ion tester that there was no significant agglomeration and that all of the charged Ni ions were deposited on the core material particles. The reaction was completed. The plated particles were then filtered, washed and dried at 80 ° C.

The cross section of the Ni-plated particles thus obtained was cut out with a microtome, observed under a transmission electron microscope at 200,000 times, and the P content in the Ni coating was analyzed by EDX. As a result, the Ni coating 3 of the Ni plated particles 1
Has a thickness of 180 nm, and P and N in the Ni coating 3 are
The content ratio P / Ni of i is about 10% of the thickness of the Ni coating 3 from the interface on the core material particle 2 side as shown in FIG.
Is 0.25 and the Ni coating 3 has a thickness of 0.
It was 1, and was 0.05 at the portion c from the Ni coating surface 3x to about 10% of the thickness of the Ni coating 3. Further, as shown in FIG. 2, the Ni-plated particles 1 had a good surface condition in which homogeneous and fine Ni particles were densely deposited.

Example 2 A slurry (pH 4) of core material particles supporting palladium was prepared in the same manner as in Example 1.

On the other hand, as a Ni plating solution, a 22.4% solution of nickel sulfate and 22.4% sodium hypophosphite are used.
And 2 solutions of a solution containing 12% sodium hydroxide,
A plating reaction was performed in the same manner as in Example 1 using this Ni plating solution.

Also in this example, no significant aggregation was observed during the plating reaction. It was confirmed by a commercially available Ni ion tester that all the charged Ni ions were deposited on the core material particles,
Furthermore, the plating reaction was terminated after confirming that hydrogen was not generated. The pH at the end of the plating reaction was 6. Then, in the same manner as in Example 1, the particles were filtered, washed, and dried to obtain Ni-plated particles.

The cross section of the obtained Ni-plated particles was cut out with a microtome, observed with a transmission electron microscope at 200,000 times, and the P content in the Ni coating was analyzed by EDX.
As a result, the thickness of the Ni coating of the Ni plated particles was 17
The content ratio P / Ni of P and Ni in this Ni coating is 0.15 at a portion a which is about 10% of the thickness of the Ni coating from the interface on the core material particle side. It is 0.05 in the central part b, and Ni from the surface of the Ni coating
The value was 0.02 at the portion c which was about 10% of the thickness of the coating. Further, the Ni-plated particles had a good surface condition in which homogeneous and fine Ni particles were densely deposited.

Example 3 A slurry (pH 4) of core particles carrying palladium was prepared in the same manner as in Example 1.

On the other hand, as a Ni plating solution, a 22.4% nickel sulfate solution and 22.4% sodium hypophosphite are used.
And 2% of a solution containing 3% of sodium hydroxide were prepared, and a plating reaction was performed in the same manner as in Example 1 using this Ni plating solution.

Also in this example, no significant aggregation occurred during the plating reaction. It was confirmed by a commercially available Ni ion tester that all the charged Ni ions were deposited on the core material particles,
Furthermore, the plating reaction was terminated after confirming that hydrogen was not generated. The pH at the end of the plating reaction was 6. Then, in the same manner as in Example 1, the particles were filtered, washed, and dried to obtain Ni-plated particles.

The cross section of the obtained Ni-plated particles was cut out with a microtome, observed with a 200,000-fold transmission electron microscope, and the P content in the Ni coating was analyzed by EDX.
As a result, the thickness of the Ni coating of the Ni plated particles was 18
The content ratio P / Ni of P and Ni in this Ni coating is 0.40 at a portion a of about 10% of the thickness of the Ni coating from the interface on the side of the core material particles, which is 0.40 of the thickness of the Ni coating. It is 0.20 in the central part b, and Ni from the surface of the Ni coating
It was 0.15 at the portion c which was about 10% of the thickness of the coating. Further, the Ni-plated particles had a good surface condition in which homogeneous and fine Ni particles were densely deposited.

Comparative Example 1 A slurry of core material particles supporting palladium was prepared in the same manner as in Example 1 except that the pH was not adjusted with sulfuric acid (p.
H6).

On the other hand, as a Ni plating solution, a 22.4% solution of nickel sulfate and 22.4% sodium hypophosphite are used.
And 2 solutions of a solution containing 12% sodium hydroxide,
A plating reaction was performed in the same manner as in Example 1 using this Ni plating solution.

The plating reaction proceeded around pH 6 all the time. Aggregation was remarkable from the initial stage of the plating reaction, and a few percent of a surfactant was added, but it was not possible to completely prevent aggregation.

It was confirmed by a commercially available Ni ion tester that all of the charged Ni ions were deposited on the core material particles, and further, it was confirmed that hydrogen was not generated, and the plating reaction was terminated.

In the same manner as in Example 1, the particles were filtered, washed and dried to obtain Ni plated particles.

The cross section of the obtained Ni-plated particles was cut out with a microtome, observed with a 200,000-fold transmission electron microscope, and the P content in the Ni coating was analyzed by EDX.
As a result, the thickness of the Ni coating of the Ni plated particles was 17
The content ratio P / Ni of P and Ni in the Ni coating is about 10% of the thickness of the Ni coating from the interface on the core material particle side, the central portion b of the thickness of the Ni coating, and Ni.
The value was as low as 0.05 in any of the portions c from the surface of the coating film to about 10% of the thickness of the Ni coating film. Also, N
The surface state of the i coating was not smooth but rough.

Comparative Example 2 A slurry of palladium-supported core material particles was prepared in the same manner as in Example 1 except that the pH was not adjusted with sulfuric acid (p.
H6).

On the other hand, as a Ni plating solution, a 22.4% nickel sulfate solution and 22.4% sodium hypophosphite are used.
And 2% of sodium hydroxide were prepared, and a plating reaction was performed in the same manner as in Example 1 using this Ni plating solution.

The plating reaction proceeded around pH 6 throughout. Compared with Comparative Example 1, the concentration of sodium hydroxide in the plating solution was low, so the plating reaction rate was slow. Also,
The state of aggregation was relatively low.

It was confirmed by a commercially available Ni ion tester that all of the charged Ni ions were deposited on the core material particles, and further, it was confirmed that hydrogen was not generated, and the plating reaction was terminated.

In the same manner as in Example 1, the particles were filtered, washed and dried to obtain Ni plated particles.

The cross section of the obtained Ni-plated particles was cut out with a microtome, observed with a transmission electron microscope at 200,000 times, and the P content in the Ni coating was analyzed by EDX.
As a result, the thickness of the Ni coating of the Ni plated particles was 17
The content ratio P / Ni of P and Ni in the Ni coating is about 10% of the thickness of the Ni coating from the interface on the core material particle side, the central portion b of the thickness of the Ni coating, and Ni.
The value was 0.15 in any of the portions c from the surface of the coating film to about 10% of the thickness of the Ni coating film. The surface state of the Ni coating was relatively smooth.

[0068]

According to the method for producing Ni-plated particles of the present invention, the pH is lowered at the initial stage of the Ni-plating reaction,
By increasing the amount of P taken into the coating, thereby preventing the agglomeration of the Ni plating particles, and conversely, by raising the pH at the end of the Ni plating reaction, the P content in the Ni coating is lowered and the Ni purity in the coating is reduced. And the Ni plating reaction is terminated before the agglomeration of Ni plating particles significantly occurs.
Therefore, Ni-plated particles having a high-purity Ni coating film formed on the surface thereof can be produced with high productivity without causing the problem of aggregation.

In the Ni-plated particles thus obtained, the Ni coating film is uniformly formed on the core material particles without unevenness, and therefore the bonding strength between the Ni coating film and the core material particles is high. Therefore, even if the Ni-plated particles are kneaded and dispersed with the synthetic resin or the like, the plated coating does not peel off. In addition, the Ni coating surface has high Ni purity and high electric conductivity. Therefore, the Ni-plated particles are useful as a conductive filler or the like. It is also useful as particles for gold plating.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a measurement site of P content in a Ni coating in Ni plated particles of an example.

FIG. 2 is a schematic diagram of an electron micrograph of the surface of Ni-plated particles of an example.

[Explanation of symbols]

1 ... Ni plated particles, 2 ... Core particles, 3 ... Ni coating, 3x ... Ni coating surface

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Claims (6)

[Claims] 1. A Ni-plated particle in which a Ni coating is provided on the surface of a core particle by an electroless Ni plating method, wherein the P content in the thickness direction of the Ni coating is higher than that of the core particle side. Ni-plated particles characterized by being less on the side. 2. The Ni-plated particles according to claim 1, wherein the P content in the thickness direction of the Ni coating gradually decreases from the core material particle side to the Ni coating surface side. 3. The content ratio P / Ni of P and Ni in the Ni coating film obtained by EDX is 0.15 <P / Ni <in the region of 10% or less of the thickness of the Ni coating film from the core material particle side interface. 0.
40, 0.00 <P / Ni <0.15 in a region from the surface of the Ni coating to 10% or less of the thickness of the Ni coating.
The described Ni-plated particles. 4. N containing a Ni salt, a phosphorus-based reducing agent, and a pH adjusting agent in an aqueous suspension of core material particles carrying a noble metal catalyst.
In the method for producing Ni-plated particles in which the electroless Ni-plating reaction is performed by adding the i-plating solution to form the Ni coating on the surface of the core material particles, the reaction is started by adjusting the pH of the aqueous suspension containing the Ni-plating solution. A method for producing Ni-plated particles, wherein the temperature is higher at the end of the reaction than at the time. 5. The pH at the start of the plating reaction is 3.8 to 4.
5. The method for producing Ni-plated particles according to claim 4, wherein the pH is 2 and the pH at the end of the plating reaction is 5.8 to 6.2. 6. The aqueous suspension contains a complexing agent which makes the pH of the buffer system with the pH adjusting agent 5.8 to 6.2, and the pH of the aqueous suspension is 3.8 to 3.8. The method for producing Ni-plated particles according to claim 4, wherein the method is 4.2.