JP4728665B2 - Conductive fine particles, method for producing conductive fine particles, and anisotropic conductive material - Google Patents

Description

  The present invention relates to conductive fine particles, a method for producing the conductive fine particles, and an anisotropic conductive material using the conductive fine particles.

  Conventionally, metallic particles made of gold, silver, nickel, etc., have been used as conductive fine particles, but the specific gravity is large and the shape is not constant. This was a cause of unevenness in the conductivity of the conductive material.

  In contrast, conductive fine particles in which the surface of non-conductive particles such as glass beads, glass fibers, and plastic balls are plated with a metal such as nickel have been reported as core material particles. For example, Patent Document 1 discloses a conductive electroless plating powder obtained by forming a metal coating on substantially spherical resin powder particles by an electroless nickel plating method.

However, in these metal films by the electroless nickel plating method, since the nickel film contains phosphorus, not only does the conductivity decrease as compared to pure nickel metal, but the phosphorus content in the nickel film is high, The conductivity of the nickel coating tends to be further deteriorated.
In addition, since these electroless nickel plating methods have a large surface area and large cohesive force, the nickel salt solution and nickel hypophosphite that constitute the nickel plating solution in the dispersion at a constant pH are reduced. In the method of adding the agent solution little by little, it is difficult to precisely control the plating reaction rate, and it is not sufficient to suppress the aggregation of the conductive fine particles.

On the other hand, Patent Document 2 discloses conductive fine particles made of nickel or cobalt and provided with a metal coating layer containing 1.5 to 4% by weight of phosphorus on the surface of resin fine particles.
Further, in Patent Document 3, the nickel content is gradually reduced from the core material particle side to the nickel coating surface side by varying the phosphorus content in the nickel coating in the thickness direction of the nickel coating so as not to impair the conductivity. Plating particles are disclosed.

JP-A-8-31655 Japanese Patent No. 2507381 JP 2003-34879 A

  Although the conductive fine particles of Patent Document 2 are excellent in electrical conductivity, the rapid progress of recent electronic devices since the flexibility of the metal coating layer is insufficient and the adhesion with the core particles is insufficient. There is a problem that it is impossible to cope with further improvement in the reliability of electrical connection.

In addition, the method for producing nickel-plated particles of Patent Document 3 has problems such as that the reaction rate is gradually increased to reduce the phosphorus concentration, so that bath decomposition is likely to occur, and bath management is difficult. Moreover, since the phosphorus content on the surface of the nickel coating is low, the plating coating has magnetic properties, and there is a problem that aggregation is likely to occur due to a reaction near the surface of the nickel coating.
Furthermore, the nickel-plated particles of Patent Document 3 have improved conductivity by lowering the phosphorus concentration on the surface of the plating film, but they are still inferior to pure nickel metal and have the effect of improving the overall conductivity. Is not obtained.

  In view of the above situation, the present invention provides conductive fine particles having excellent conductivity, and having high adhesion to core particles and low cohesiveness, and high stability of the plating bath. It is an object to provide a method and an anisotropic conductive material using the conductive fine particles.

  In order to achieve the above object, the invention described in claim 1 provides conductive fine particles in which an alloy plating film containing nickel, copper and phosphorus is formed on the surface of core material particles by electroless plating.

  The invention according to claim 2 provides the conductive fine particles according to claim 1, wherein the phosphorus content in the thickness direction in the alloy plating film is smaller on the surface of the alloy plating film than on the core material particle side.

  The invention according to claim 3 contains nickel and phosphorus in a region of 20% or less from the core particle side in the thickness direction in the alloy plating film, and a region of 80% or less from the surface of the alloy plating film. The conductive fine particles according to claim 1 or 2, which contain nickel, copper, and phosphorus.

  According to a fourth aspect of the present invention, the alloy plating film contains 8 to 15% by weight of phosphorus in the alloy plating composition in a region of 20% or less from the core particle side in the thickness direction in the alloy plating film. The conductive fine particles according to any one of claims 1 to 3, which contain 0.05 to 5% by weight of phosphorus in the alloy plating composition in a region of 80% or less from the surface side.

  Further, the invention according to claim 5 contains 0.5 to 90% by weight of copper in the alloy plating composition in the region of 80% or less from the surface of the alloy plating film in the thickness direction in the alloy plating film. Item 5. The conductive fine particle according to any one of Items 1 to 4.

  According to a sixth aspect of the present invention, the alloy plating film contains 85 to 92% by weight of nickel in the alloy plating composition in a region of 20% or less from the core particle side in the thickness direction in the alloy plating film. The conductive fine particles according to any one of claims 1 to 5, which contain 5 to 99.45 wt% of nickel in the alloy plating composition in an area of 80% or less from the surface side.

  The invention according to claim 7 further provides the conductive fine particles according to any one of claims 1 to 6, wherein a gold film is formed on the surface of the alloy plating film.

  The invention according to claim 8 is directed to initial electroless plating by adding a plating solution containing a nickel salt, a phosphorus-based reducing agent, and a pH adjusting agent to an aqueous suspension of core material particles supporting a metal catalyst. The electroconductivity according to any one of claims 1 to 7, wherein the electroless plating reaction is performed by adding a plating solution containing a nickel salt, a copper salt, a phosphorus reducing agent, and a pH adjuster after the reaction. A method for producing conductive fine particles is provided.

  The invention according to claim 9 provides an anisotropic conductive material in which the conductive fine particles according to any one of claims 1 to 7 are dispersed in a resin binder.

Details of the present invention will be described below.
In the conductive fine particles of the present invention, an alloy plating film containing nickel, copper, and phosphorus is formed on the surface of the core material particles by an electroless plating method.
Since the alloy plating film contains copper, it has superior conductivity as compared with a plating film containing nickel and phosphorus or pure nickel metal.

  The method for forming an alloy plating film containing nickel, copper, and phosphorus in the present invention is not particularly limited. For example, when performing electroless nickel plating, nickel salt, copper salt, phosphorus-based reducing agent, etc. And the like.

In the conductive fine particles of the present invention, the phosphorus content in the thickness direction in the alloy plating film is preferably smaller on the surface of the alloy plating film than on the core material particle side.
The phosphorus content in the thickness direction in the alloy plating film is relatively high on the core particle side, so that the adhesion between the alloy plating film and the core material particle is good, and it is relatively low on the alloy plating film surface side. As a result, the conductivity of the alloy plating film is improved.

  The method for producing conductive fine particles in which the phosphorus content in the thickness direction in the alloy plating film is smaller on the surface of the alloy plating film than on the core material particle side is not particularly limited. For example, electroless nickel plating In this method, the pH is gradually increased to increase the speed of the nickel plating reaction (pH raising method); the plating temperature is sequentially increased; the concentration of the reducing agent in the plating solution is successively increased; electroless nickel plating In the initial reaction, a plating solution containing a nickel salt and a phosphorus reducing agent is used, and in the latter reaction, a nickel salt added with a copper salt and a plating solution containing a phosphorus reducing agent are used, and by-product phosphorus is added. Examples include a method of suppressing the generation and reducing the phosphorus content adsorbed in the plating film (late reaction copper salt addition method). These methods may be used alone or in combination of two or more.

  As a method for producing the conductive fine particles of the present invention, it is particularly preferable to use a combination of the pH raising method and the late reaction copper salt addition method. Thereby, it is possible to obtain conductive fine particles in which the phosphorus content in the thickness direction in the alloy plating film is smaller on the surface of the alloy plating film than on the core material particle side.

The conductive fine particles of the present invention contain nickel and phosphorus in a region of 20% or less from the core particle side in the thickness direction in the alloy plating film, and nickel in a region of 80% or less from the surface of the alloy plating film. It is preferable to contain copper, and phosphorus.
In the thickness direction of the alloy plating film, nickel and phosphorus are contained in a region of 20% or less from the core particle side, and nickel, copper, and phosphorus are contained in a region of 80% or less from the alloy plating film surface side. As a result, the adhesion between the alloy plating film and the core particles is good, and the presence of copper in the region of 80% or less from the surface of the alloy plating film results in conductive fine particles with good conductivity of the alloy plating film.

  Hereinafter, a preferred embodiment of the conductive fine particles of the present invention will be described with reference to the drawings. As shown in FIG. 1, the conductive fine particles 1 of the present invention are obtained by providing an alloy plating film 3 on the surface of the core material particle 2 by an electroless plating method, and in the thickness direction in the alloy plating film 3, The region a of 20% or less from the core particle 2 side contains nickel and phosphorus, and the region b of 80% or less from the alloy plating film surface 4 side contains nickel, copper and phosphorus. Moreover, the thing with less phosphorus content in the area | region b than the phosphorus content in the area | region a is more preferable.

The conductive fine particles can be obtained, for example, by adjusting the timing of transition from the initial reaction to the late reaction using the late reaction copper salt addition method.
When the late reaction copper salt addition method is used, in the initial reaction, for example, if the reaction rate is slowed by controlling the pH in the alloy plating solution, the metal deposition rate is slow, and the by-product phosphorus is generated quickly. A large amount of phosphorus is taken into the alloy plating film to form an alloy plating film having a high phosphorus content. Particles with such an alloy plating film have a high phosphorus content, so making the alloy plating film non-magnetic will not only reduce the cohesiveness of the particles, but also provide a uniform and dense alloy plating without unevenness. Since a film can be formed, the adhesiveness with the core particles is excellent.
In addition, since the agglomeration tends to occur particularly in the initial reaction, the agglomeration can be reduced by increasing the phosphorus content in the alloy plating film in the initial reaction.

The conductive fine particles of the present invention contain 8 to 15% by weight of phosphorus in the alloy plating composition in a region of 20% or less from the core particle side in the thickness direction in the alloy plating film, It is preferable that 0.05 to 5% by weight of phosphorus is contained in the alloy plating composition in an area of 80% to 80%.
When the phosphorus content is 8 to 15 wt% in the alloy plating composition in the region of 20% or less from the core particle side in the thickness direction in the alloy plating film, the cohesiveness is small and the adhesion to the core particle is small. Is expensive. Further, when the phosphorus content is 0.05 to 5% by weight in the alloy plating composition in the region of 80% or less from the surface side of the alloy plating film, the conductivity of the alloy plating film is excellent.

Further, the conductive fine particles of the present invention contain 0.5 to 90% by weight of copper in the alloy plating composition in the region of 80% or less from the surface of the alloy plating film in the thickness direction in the alloy plating film. Is preferred.
When the copper content is 0.5 to 90% by weight in the alloy plating composition in the region of 80% or less from the surface of the alloy plating film in the thickness direction in the alloy plating film, the conductivity of the alloy plating film is excellent. It will be.

  Furthermore, the conductive fine particles of the present invention contain 85 to 92% by weight of nickel in the alloy plating composition in the region of 20% or less from the core particle side in the thickness direction in the alloy plating film. It is preferable to contain 5 to 99.45% by weight of nickel in the alloy plating composition in an area of 80% or less from the surface side.

  The content ratio of each metal, phosphorus, etc. in the alloy plating film in the present invention can be determined by, for example, EDX (Energy Dispersing X-ray analyzer).

  Next, another preferred embodiment of the conductive fine particles of the present invention will be described with reference to the drawings. As shown in FIG. 2, the conductive fine particles 11 of the present invention are obtained by providing an alloy plating film 13 on the surface of the core material particles 12 by an electroless plating method, and in the thickness direction in the alloy plating film 13, In the region A of 20% or less from the core particle 12 side, containing nickel and phosphorus, in the region C of 20% or less from the alloy plating film surface 14 side, and in the region B sandwiched between the region A and the region C, It contains nickel, copper, and phosphorus. Moreover, the phosphorus content in the region B is smaller than the phosphorus content in the region A, and the phosphorus content in the region C is less than the phosphorus content in the region B.

  The conductive fine particles of the present invention are obtained by the above EDX, and the ratio of the number of atoms P / Ni, Cu / Ni between phosphorus (P) or copper (Cu) and nickel (Ni) contained in the alloy plating film 2 is 0.05 <P / Ni <0.5 in the region A in FIG. 2, 0.05 <P / Ni <0.5 and 0 <Cu / Ni <0.05 in the region B, and 0. It is preferable that 03 <P / Ni <0.5 and 0.05 <Cu / Ni <8. Further, it is more preferable that P / Ni is smaller in region B than region A, P / Ni is smaller than region B, and Cu / Ni is larger in region C.

  As a result, the conductive fine particles of the present invention not only have the effect of reducing the phosphorus content on the surface and increasing the conductivity, but also the conductivity significantly higher than that of a normal nickel-phosphorus coating because of the plating containing copper. Furthermore, the cohesiveness of the conductive fine particles can be suppressed and the adhesion with the core material particles can be improved.

The conductive fine particles of the present invention preferably further have a gold film formed on the surface of the alloy plating film.
Examples of the method for forming the gold film include electroless gold plating methods such as a displacement gold plating method and a reduction gold plating method, an electrolytic gold plating method, and a sputtering method. Of these, the electroless gold plating method is preferable.
As the electroless gold plating, for example, when the substitution gold plating is performed, the substitution reaction proceeds more easily as the purity of the nickel plating film, for example, the nickel, is increased. Since the phosphorus content is very low, a dense gold film can be formed.

The production method for obtaining the conductive fine particles of the present invention is preferably the above-mentioned late reaction copper salt addition method. Specifically, a nickel salt, phosphorous is added to an aqueous suspension of core material particles carrying a metal catalyst. An initial electroless plating reaction is performed by adding a plating solution containing a system reducing agent and a pH adjusting agent, and then a plating solution containing a nickel salt, a copper salt, a phosphorus reducing agent, and a pH adjusting agent is added. A method of performing an electroless plating reaction is preferable.
An initial electroless plating reaction is performed by adding a plating solution containing a nickel salt, a phosphorus-based reducing agent, and a pH adjuster to an aqueous suspension of core material particles supporting a metal catalyst, and then nickel salt, copper The method for producing conductive fine particles of the present invention in which a plating solution containing a salt, a phosphorus-based reducing agent, and a pH adjusting agent is added to perform a late electroless plating reaction is also one aspect of the present invention.

Hereinafter, the manufacturing method of the electroconductive fine particles of this invention is demonstrated.
In the method for producing conductive fine particles of the present invention, in the initial reaction, a plating solution containing a nickel salt, a phosphorus reducing agent, and a pH adjusting agent is added to an aqueous suspension of core material particles supporting a metal catalyst. By doing so, the stability of the plating bath becomes high.

  As a specific method for producing the conductive fine particles of the present invention, for example, a noble metal catalyst such as palladium is supported on the surface of the core material particles, and the core material particles supporting the palladium are put into an aqueous solution. Then, after making an aqueous suspension and dropping a plating solution containing a nickel salt, a phosphorus reducing agent, and a pH adjusting agent to complete the initial reaction, a nickel salt, a copper salt, a phosphorus reducing agent, and a pH adjusting agent A plating solution containing is dropped to complete the late reaction. Thereby, electroless-plated electroconductive fine particles can be obtained.

  In the production method described above, in order to obtain core material particles carrying a noble metal catalyst such as palladium, core material particles capable of capturing noble metal ions such as palladium ions as chelates or salts on the surface, that is, noble metal ion capturing ability It is preferable to support the noble metal catalyst on the surface of the core material particles by preparing the core material particles having the following, capturing noble metal ions therein, and then applying a reducing agent.

  As core material particles capable of capturing noble metal ions such as palladium ions as chelates or salts on the surface, core material particles having functional groups such as amino groups or imino groups on the surface are preferable, and core materials having amino group functional groups in particular. Particles are more preferred.

  Moreover, even if it is a core particle which does not have the said functional group, the core particle which can capture noble metal ions, such as palladium ion, on the surface is obtained by performing a surface treatment with a cationic surfactant, for example. be able to.

  The shape of the core particle having the noble metal catalyst supported on the surface is not particularly limited as long as it can be suspended in water by a normal dispersion method. For example, the shape is spherical, fibrous, hollow It may be a particle having a specific shape such as a shape or a needle shape, or may be a particle having an indefinite shape. Of these, the core particles are preferably spherical in order to obtain good electrical connection.

  The particle diameter of the core material particles is not particularly limited, but is preferably 1 to 100 μm, and more preferably 2 to 20 μm.

The material of the core material particles is not particularly limited as long as it has an appropriate elastic modulus, elastic deformability, and resilience, and may be an organic material or an inorganic material. An organic material is preferable.
The organic material is not particularly limited, and for example, phenol resin, amino resin, polyester resin, urea resin, melamine resin, epoxy resin, divinylbenzene polymer; divinylbenzene-styrene copolymer, divinylbenzene- (meta ) Divinylbenzene polymers such as acrylic acid ester copolymers; (meth) acrylic acid ester polymers. The (meth) acrylic acid ester polymer may be used in a cross-linked type or a non-cross-linked type, if necessary, and may be used in combination. Of these, divinylbenzene polymers and (meth) acrylic acid ester polymers are preferably used. Here, (meth) acrylic acid ester means methacrylic acid ester or acrylic acid ester.
Examples of the inorganic material include metal, glass, ceramics, metal oxide, metal silicate, metal carbide, metal nitride, metal carbonate, metal sulfate, metal phosphate, metal sulfide, and metal acid. Examples thereof include salts, metal halides, and carbon.
These core particle | grains may be used independently and 2 or more types may be used together.

Examples of the method for capturing the noble metal ions by the core material particles include a method of dispersing the core material particles in a dilute acidic aqueous solution of a noble metal salt and capturing the noble metal ions by the core material particles.
In the above method, when palladium chloride is used as the noble metal salt in the acidic aqueous solution, the concentration is preferably 0.001 to 0.8% by weight, and when palladium sulfate is used, 0.005 to 0.00%. It is preferable to set it as 2 weight%.

  Further, in order to use the noble metal ions trapped in the core particles as a noble metal catalyst, a phosphorous or boron reducing agent used for nickel plating, for example, is used in the acidic aqueous solution after the noble metal ions are trapped. It is preferable to reduce ions to form a noble metal catalyst.

  In the method for producing conductive fine particles of the present invention, when preparing an aqueous suspension of core material particles supporting a noble metal catalyst, the aqueous suspension is prepared so that aggregation does not occur in the aqueous suspension. The concentration of the core material particles is preferably 0.5 to 1.5% by weight.

  Furthermore, for example, ammonia, sodium hydroxide, sulfuric acid, hydrochloric acid or the like is preferably added to the aqueous suspension in order to adjust the pH of the reaction solution at the start of the plating reaction.

Examples of the phosphorus reducing agent in the method for producing conductive fine particles of the present invention include sodium hypophosphite, calcium hypophosphite, hypophosphorous acid and the like.
The concentration of the phosphorus reducing agent is preferably 3 to 30% by weight.

In the method for producing conductive fine particles of the present invention, it is preferable that the plating solution contains a complexing agent.
The complexing agent is not particularly limited as long as it is a compound having a complexing action on metal ions. For example, carboxylic acids such as malic acid, lactic acid, tartaric acid, citric acid, gluconic acid, hydroxyacetic acid, or alkalis thereof. Examples thereof include metal salts; carboxylates such as ammonium salts; amino acids such as glycine; amines such as ethylenediamine and alkylamine; ammonium, EDTA, pyrophosphate and the like.
The concentration of the complexing agent is preferably 0.1 to 8% by weight.

In the method for producing conductive fine particles of the present invention, a plating solution used for the initial reaction and a plating solution used for the late reaction are prepared.
In the initial reaction, that is, the formation of the plating film on the core particle side having a high phosphorus content, the plating solution is, for example, a nickel salt aqueous solution such as nickel sulfate or nickel chloride, or a phosphorus-based reduction such as sodium hypophosphite. It is preferable to use a single solution containing an agent, a pH adjuster, a complexing agent and the like.

In the latter reaction, the plating solution includes, for example, a solution 1 containing a nickel salt aqueous solution such as nickel sulfate or nickel chloride, a copper salt aqueous solution such as copper sulfate or copper chloride, a complexing agent, and a stabilizer. It is preferable to prepare two liquids with a liquid 2 containing a phosphorus-based reducing agent such as sodium phosphite and a pH adjuster.
The liquid 1 and the liquid 2 are preferably mixed in a late reaction before use and used as a late reaction plating solution.

In the late reaction, the concentration of nickel salt in the late reaction plating solution is determined according to the film thickness of the plating film. For example, the core surface particles having a specific surface area of 1.3 m ² / g and a particle diameter of 4 μm are used. In the case of forming a plating film having a thickness of 0.01 to 0.05 μm, the content is preferably 5 to 25% by weight. The concentration of the copper salt is preferably 1/2 to 5 times the concentration of the added nickel salt.
Furthermore, the concentration of the reducing agent in the late reaction plating solution is preferably 3 to 30% by weight.

  In the present invention, by adjusting the timing of transition from the initial reaction to the late reaction, it contains nickel and phosphorus in a region of 20% or less from the core particle side in the thickness direction in the alloy plating film. The conductive fine particles containing nickel, copper, and phosphorus can be formed in an area of 80% or less from the surface of the alloy plating film.

  In a late reaction, in the thickness direction in the alloy plating film, a method for producing a material having a low phosphorus content on the alloy plating film surface side in a region of 80% or less from the alloy plating film surface side is, for example, electroless In plating, there are a method of increasing the pH sequentially and increasing the speed of the nickel plating reaction; a method of increasing the plating temperature sequentially; a method of increasing the concentration of the reducing agent in the plating solution sequentially. These methods may be used alone or in combination of two or more. Among these, it is preferable to reduce the phosphorus content by a method of sequentially increasing the pH. As described above, when the phosphorus content is small on the alloy plating film surface side, the copper content can be large on the alloy plating film surface side.

Further, in the late reaction, it is preferable to lower the plating temperature as much as possible in order to suppress the aggregation of particles and to stabilize the plating bath. More specifically, the temperature of the plating bath to which the plating solution is added is preferably 20 to 40 ° C.
For this purpose, it is preferable to lower the plating temperature as much as possible in the initial reaction, and this makes it easier to adjust the temperature in the later reaction and to improve workability.

  In addition, when an alloy plating film containing nickel and copper and having a low phosphorus concentration is formed on the surface, particles during plating may easily agglomerate, so that hydrogen generation due to the alloy plating reaction is recognized. It is preferred that the alloy plating reaction be terminated after no longer being agglomerated and before particle agglomeration occurs.

  After completion of the alloy plating reaction, conductive fine particles can be obtained by aging by continuing stirring for about 10 to 20 minutes, and then filtering the particles, washing with alcohol, warm water, etc., and drying.

  The anisotropic conductive material of the present invention is obtained by dispersing the above-described conductive fine particles of the present invention in a resin binder.

  The anisotropic conductive material is not particularly limited as long as the conductive fine particles of the present invention are dispersed in a resin binder. For example, anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive An adhesive, an anisotropic conductive film, an anisotropic conductive sheet, etc. are mentioned.

  The method for producing the anisotropic conductive material of the present invention is not particularly limited. For example, the conductive fine particles of the present invention are added to an insulating resin binder, and mixed and dispersed uniformly. For example, a method of using an anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, etc., or adding the conductive fine particles of the present invention to an insulating resin binder and mixing them uniformly. After preparing the conductive composition, the conductive composition is uniformly dissolved (dispersed) in an organic solvent as necessary, or heated and melted to release a release material such as release paper or release film. Applying to the mold processing surface so as to have a predetermined film thickness, and performing drying or cooling as necessary, for example, an anisotropic conductive film, an anisotropic conductive sheet, etc. Depending on the type of anisotropic conductive material to be produced, Manufacturing methods may Taking. Further, the insulating resin binder and the conductive fine particles of the present invention may be used separately without being mixed to form an anisotropic conductive material.

  The resin of the insulating resin binder is not particularly limited. For example, vinyl resins such as vinyl acetate resins, vinyl chloride resins, acrylic resins, styrene resins; polyolefin resins, ethylene -Thermoplastic resins such as vinyl acetate copolymers and polyamide resins; Epoxy resins, urethane resins, polyimide resins, unsaturated polyester resins, and curable resins composed of these curing agents; styrene-butadiene-styrene blocks Thermoplastic block copolymers such as copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products thereof; elastomers such as styrene-butadiene copolymer rubber, chloroprene rubber, acrylonitrile-styrene block copolymer rubber ( Rubbers). These resins may be used alone or in combination of two or more. The curable resin may be in any curing form such as a room temperature curing type, a thermosetting type, a photocuring type, and a moisture curing type.

  In addition to the insulating resin binder and the conductive fine particles of the present invention, the anisotropic conductive material of the present invention includes, for example, a bulking agent, a softening agent, etc. 1 type of various additives such as additives (plasticizers), tackifiers, antioxidants (anti-aging agents), heat stabilizers, light stabilizers, UV absorbers, colorants, flame retardants, organic solvents, etc. Or 2 or more types may be used together.

(Function)
For example, the conductive fine particles of the present invention have a low reaction rate by controlling the pH in the alloy plating solution and lowering the pH in the initial reaction. On the core particle side, the metal deposition rate is slow, Since the product phosphorus is generated quickly, a large amount of phosphorus is incorporated into the alloy plating film to form an alloy plating film with a high phosphorus content. Particles with such an alloy plating film have a high phosphorus content, so making the alloy plating film non-magnetic will not only reduce the cohesiveness of the particles, but also provide a uniform and dense alloy plating without unevenness. Since a film is formed, the adhesiveness with the core material particles is high.

In addition, when the transition to the late reaction occurs after the initial reaction, since the copper salt is used in the late reaction, the production of phosphorus, which is a by-product, is suppressed, and instead copper is precipitated, so phosphorus is alloy plated. Less precipitation in the coating. Further, for example, by sequentially increasing the pH in the alloy plating solution, the phosphorus content decreases on the alloy plating film surface side, and the copper content increases on the alloy plating film surface side.
Accordingly, the obtained conductive fine particles have excellent conductivity because the alloy plating film contains copper having good conductivity, and the surface of the alloy plating film has a low content of phosphorus, which is a conductivity-inhibiting substance. Since the copper content is large, it has excellent conductivity.

  Furthermore, since the phosphorus concentration on the surface of the alloy plating film is very low, when gold plating is applied, the substitution reaction with gold is promoted, and a dense replacement gold plating can be easily obtained, which is very excellent. It becomes conductive fine particles.

  Since the conductive fine particles in the present invention are excellent in plating adhesion with the core material particles, the plating film is hardly peeled off even if kneaded and dispersed with a resin binder in order to make an anisotropic conductive material. Moreover, since the alloy plating film contains copper having good conductivity, the anisotropic conductive material of the present invention using the conductive fine particles of the present invention has excellent conductivity.

  Since the conductive fine particles of the present invention have the above-described configuration, it is possible to obtain those having excellent conductivity, and having high adhesion to the core material particles and low cohesion. In addition, the method for producing conductive fine particles of the present invention can provide a production method in which the stability of the plating bath is high, the conductivity is excellent, the adhesiveness with the core particles is high, and the cohesiveness is low. It became. Furthermore, the anisotropic conductive material using the conductive fine particles of the present invention has excellent conductivity.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

Example 1
Divinylbenzene polymer resin particles having a particle size of 4 μm (“SP-204” manufactured by Sekisui Chemical Co., Ltd.) are treated with a 10 wt% solution of an ion adsorbent for 5 minutes, and then a 0.01 wt% palladium sulfate aqueous solution. Then, dimethylamine borane was further added for reduction treatment, followed by filtration and washing to obtain palladium-supported core particles.

  Next, 500 ml of ion-exchanged water containing 1% by weight of sodium succinate is prepared, 10 g of the obtained core material particles are mixed to prepare an aqueous suspension, and sulfuric acid is further added to form an aqueous suspension with pH 5 Prepared.

  On the other hand, an alloy plating solution containing 20% by weight of nickel sulfate, 20% by weight of sodium hypophosphite, and 8% by weight of sodium hydroxide was prepared as an alloy plating solution for initial reaction.

  The obtained aqueous suspension was brought to 80 ° C., and the initial reaction alloy plating solution thus obtained was continuously added dropwise thereto and stirred for 20 minutes to carry out an initial electroless plating reaction. During the plating reaction, it was confirmed that there was no significant aggregation and generation of hydrogen disappeared, and the initial reaction was terminated.

  Next, an alloy plating solution containing 10% by weight of nickel sulfate, 10% by weight of copper sulfate, 5% by weight of sodium hypophosphite, and 5% by weight of sodium hydroxide was prepared as an alloy plating solution for late reaction.

  Thereafter, the resulting late reaction alloy plating solution is continuously dropped into the solution after completion of the initial reaction, and stirred for 1 hour to carry out the late electroless plating reaction, and the conductive fine particles on which the alloy plating film is formed. (Conductive fine particles 1) were obtained.

  The obtained conductive fine particles on which the alloy plating film was formed were further subjected to displacement gold plating to obtain conductive fine particles (conductive fine particles 2) on which the gold film was formed on the alloy plating film.

(Evaluation of conductive fine particles)
The obtained conductive fine particles 1 and conductive fine particles 2 were cut out with a focused ion beam and observed with a 200,000-fold transmission electron microscope to investigate the state and film thickness of the plating film. These conductive fine particles were densely deposited with a homogeneous and delicate alloy plating film.
Further, the conductivity (resistance value) of the conductive fine particles 1 and the conductive fine particles 2 was examined by the following method for measuring the resistance value of the conductive fine particles.
Furthermore, about the electroconductive fine particles 2, content of nickel, copper, and phosphorus in an alloy plating film was investigated with the component measuring method by the following EDX.
These results are shown in Table 1.

(Measurement method of resistance value of conductive fine particles)
Using a micro compression tester (“DUH-200”, manufactured by Shimadzu Corporation) so that the resistance value can be measured, the resistance value of the conductive fine particles is measured by measuring the resistance while compressing the conductive fine particles. did.

(Component measurement method by EDX)
By using EDX (“Energy Dispersive X-ray Spectrometer”, manufactured by JEOL Datum), the cross section of the conductive fine particles is cut out with a focused ion beam, and each component in the alloy plating film is analyzed for components, The detected values of copper and phosphorus were measured. The contents of nickel, copper and phosphorus in the alloy plating composition were calculated from the measured values obtained.

(Example 2)
In Example 1, an alloy plating solution containing 10% by weight of nickel sulfate, 10% by weight of copper sulfate, 5% by weight of sodium hypophosphite, and 5% by weight of sodium hydroxide was not used as the late-stage reaction alloy plating solution. In the same manner, except that an alloy plating solution containing 5% by weight of nickel sulfate, 15% by weight of copper sulfate, 5% by weight of sodium hypophosphite, and 5% by weight of sodium hydroxide was used. Conductive fine particles 2 were obtained.
In the same manner as in Example 1, the conductive fine particles were evaluated. These results are shown in Table 1. These conductive fine particles were densely deposited with a homogeneous and delicate alloy plating film.

(Example 3)
In Example 1, an alloy plating solution containing 10% by weight of nickel sulfate, 10% by weight of copper sulfate, 5% by weight of sodium hypophosphite, and 5% by weight of sodium hydroxide was not used as the late-stage reaction alloy plating solution. In the same manner, except that an alloy plating solution containing 15% by weight of nickel sulfate, 5% by weight of copper sulfate, 5% by weight of sodium hypophosphite, and 5% by weight of sodium hydroxide was used, Conductive fine particles 2 were obtained.
In the same manner as in Example 1, the conductive fine particles were evaluated. These results are shown in Table 1. These conductive fine particles were densely deposited with a homogeneous and delicate alloy plating film.

(Comparative Example 1)
In Example 1, an alloy plating solution containing 10% by weight of nickel sulfate, 10% by weight of copper sulfate, 5% by weight of sodium hypophosphite, and 5% by weight of sodium hydroxide was not used as the late-stage reaction alloy plating solution. Instead, conductive fine particles 1 and conductive fine particles 2 were obtained in the same manner except that an alloy plating solution containing 20% by weight of nickel sulfate, 5% by weight of sodium hypophosphite, and 5% by weight of sodium hydroxide was used. It was.
In the same manner as in Example 1, the conductive fine particles were evaluated. These results are shown in Table 1. These conductive fine particles were densely deposited with a homogeneous and delicate alloy plating film.

From Table 1, the conductive fine particles of Example 1, Example 2, and Example 3 differ in phosphorus content in the thickness direction in the alloy plating film, and are less on the surface of the alloy plating coating than on the core particle side. In addition, it was confirmed that copper was contained on the alloy plating coating surface side. Moreover, it was confirmed that the electroconductive fine particles of Comparative Example 1 do not contain copper.
It can be seen that the conductive fine particles containing copper in the alloy plating film have a low resistance value and excellent conductivity.

Example 4
The conductive fine particles obtained in Example 1 were added to 100 parts by weight of an epoxy resin (“Epicoat 828” manufactured by Yuka Shell Epoxy Co., Ltd.), 2 parts by weight of trisdimethylaminoethylphenol, and 100 parts by weight of toluene as a resin binder resin. 2 was added and mixed thoroughly using a planetary stirrer, and then applied onto a release film so that the thickness after drying was 7 μm, and toluene was evaporated to form an adhesive film containing conductive fine particles. Obtained. In addition, the compounding quantity of electroconductive fine particles made content in a film 50,000 piece / cm < ² >.
Thereafter, an adhesive film containing conductive fine particles was bonded to an adhesive film obtained without containing conductive fine particles at room temperature to obtain a two-layer anisotropic conductive film having a thickness of 17 μm.

(Example 5)
An anisotropic conductive film was obtained in the same manner as in Example 4 except that the conductive fine particles 2 obtained in Example 2 were added.

(Example 6)
An anisotropic conductive film was obtained in the same manner as in Example 4 except that the conductive fine particles 2 obtained in Example 3 were added.

(Comparative Example 2)
An anisotropic conductive film was obtained in the same manner as in Example 4 except that the conductive fine particles 2 obtained in Comparative Example 1 were added.

(Evaluation of conductivity of anisotropic conductive materials)
The obtained anisotropic conductive film was cut into a size of 5 × 5 mm. In addition, two glass substrates having a lead wire for resistance measurement on which an aluminum electrode having a width of 200 μm, a length of 1 mm, a height of 0.2 μm, and an L / S of 20 μm was formed were prepared. After attaching the anisotropic conductive film to the center of one glass substrate, align the other glass substrate so that it overlaps the electrode pattern of the glass substrate to which the anisotropic conductive film is attached. It was.
Two glass substrates were thermocompression bonded under the conditions of a pressure of 10 N and a temperature of 180 ° C., and then the resistance value between the electrodes was measured. The anisotropic conductive films obtained in Example 4, Example 5, Example 6, and Comparative Example 2 were measured.
In addition, after the PCT test (held at 80 ° C. in a high-temperature and high-humidity environment of 95% RH for 1000 hours) was performed on the prepared test piece, the resistance value between the electrodes was measured.
The evaluation results are shown in Table 2.

  From Table 2, the anisotropic conductive film using the conductive fine particles obtained in Examples has a low resistance value and excellent conductivity compared to the anisotropic conductive film using the conductive fine particles obtained in Comparative Examples. It turns out that it has sex.

  According to the present invention, there are provided conductive fine particles having excellent conductivity, and having high adhesion to core particles and low cohesiveness, a method for producing the conductive fine particles having high plating bath stability, and An anisotropic conductive material using the conductive fine particles can be provided.

It is explanatory drawing of the measurement site | part of the phosphorus content in the alloy plating film in electroconductive fine particles with one aspect | mode of the electroconductive fine particles of this invention. It is explanatory drawing of the measurement site | part of the phosphorus content in the alloy plating film in electroconductive fine particles in the other aspect of the electroconductive fine particles of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Conductive fine particle 2,12 Core material particle 3,13 Alloy plating film 4,14 Alloy plating film surface a Area | region of 20% or less from the core material particle side in the thickness direction in an alloy plating film b Alloy plating film In the thickness direction, 80% or less of the area from the surface of the alloy plating film A In the thickness direction of the alloy plating film, in the area of 20% or less from the core particle side C In the thickness direction of the alloy plating film, Area of 20% or less from the surface of the alloy plating film B Area between area A and area C

Claims (7)

Conductive fine particles in which an alloy plating film containing nickel, copper, and phosphorus is formed on the surface of the core material particles by an electroless plating method,
In the thickness direction in the alloy plating film, nickel and phosphorus are contained in the region of 20% or less from the core particle side, copper is not contained, and nickel and copper are contained in the region of 80% or less from the alloy plating film surface side. , and conductive fine particles you characterized by containing phosphorus. In the thickness direction in the alloy plating film, the alloy plating composition contains 8 to 15% by weight of phosphorus in the region of 20% or less from the core particle side, and in the region of 80% or less from the alloy plating film surface side. 2. The conductive fine particles according to claim 1, wherein the gold plating composition contains 0.05 to 5% by weight of phosphorus. 2. The conductive film according to claim 1 , wherein the alloy plating composition contains 0.5 to 90% by weight of copper in a region of 80% or less from the surface side of the alloy plating film in the thickness direction in the alloy plating film. Fine particles. In the thickness direction in the alloy plating film, the alloy plating composition contains 85 to 92% by weight of nickel in the region of 20% or less from the core particle side, and 80% or less in the region of the alloy plating film surface side. The conductive fine particles according to claim 1 , wherein the gold plating composition contains 5 to 99.45 wt% of nickel. 5. The conductive fine particle according to claim 1 , wherein a gold film is formed on the surface of the alloy plating film. To an aqueous suspension of the metal catalyst the core particles supporting, nickel salts, phosphorus-based reducing agent, and viewed including a pH adjusting agent, performs the initial electroless plating reaction by adding a plating solution containing no copper salt , then, nickel salts, copper salts, phosphorus-based reducing agent, and claims 1, 2, 3, 4 or 5, wherein the plating solution was added to perform late electroless plating reactions containing pH adjusting agent Manufacturing method of conductive fine particles. 6. An anisotropic conductive material, wherein the conductive fine particles according to claim 1, 2, 3, 4 or 5 are dispersed in a resin binder.

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