JP2001126532A - Conductive fine particle and conductive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive fine particle consisting of a silicone resin fine particle having an effective plated layer on a surface thereof and exhibiting an excellent conductivity, and also a conductive material made from the conductive fine particle. SOLUTION: A conductive fine particle consists of a silicone resin fine particle having an electroless-plated layer formed thereon. The conductive fine particle is a silicone resin fine particle in which a silioxane leakage is a cross-linked structure having a three-dimensional network (polymethylsilsesquioxane structure). Also, the conductive fine particle has an electorless nickel-plated layer, which is formed on a surface of the resin fine particle using an alkali catalyst. Also, a conductive material is made from the conductive fine particle as disclosed above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to conductive fine particles used for connection between electrodes and a conductive material produced using the conductive fine particles.

[0002]

2. Description of the Related Art Conductive fine particles are used for bonding a lead electrode or a wiring board of an electronic component to a conductive paste, an adhesive for vertical conduction, an anisotropic conductive adhesive, a conductive material for electromagnetic wave shielding, and the like. Is widely used for various conductive materials. Examples of the conductive fine particles used in such an application include solder balls made of lead and tin, and fine particles made of a non-conductive material coated with metal.

[0003] A molded article made of a non-conductive material coated with a metal is, for example, a molded article made of a plastic, particularly an engineering plastic, a super engineering plastic or a reinforced plastic, on which an electroless metal plating layer is formed. For example, Toshiro Okamura, Shigemitsu Kawagishi, Tokuzo Kobe, Osamu Takano: "Application of Electroless Plating", p. 83-1
33, Maki Shoten (1991)｝.

[0004] Examples of the metal-coated fine particles (powder) made of a non-conductive material include, for example, those in which an electroless metal plating layer is formed on the surface of plastic fine particles. (For example, the above-mentioned “Application of Electroless Plating”, pp. 135-141).

Further, specific techniques for imparting conductivity by forming a plating layer on plastic fine particles are disclosed in, for example, JP-A-8-31655 and JP-A-9-22620.

[0006] However, there are plastics for which it is difficult to form a plating layer with these conventional techniques. That is, for example, it is difficult to form a plating layer on a plastic which is difficult to etch or has poor adhesion of a plating metal, and a silicone resin is a typical example. For this reason, it is difficult to use silicone resins as conductive fine particles, despite having excellent properties such as flexibility and elasticity as compared with other plastics. Was constrained.

[0007]

The present inventors have made intensive studies to form an effective plating layer on the surface of silicone resin fine particles and to impart excellent conductivity, and as a result, have found the following. It was completed.

[0008] Silicone resin is inferior in chemical resistance and solvent resistance as compared with, for example, engineering plastics and super-engineering plastics. Therefore, when etching with an alkali at the time of plating, depending on the strength of the alkali, fine particles of the silicone resin are obtained. A problem that the surface of the particles dissolves and agglomerates. Therefore, although it was not possible to perform etching with a strong alkali, it was found that a plating reaction would not occur with a general-purpose chlorine-based catalyst unless etching was performed. It has also been found that an effective plating layer is not formed even if oxidation etching is performed instead of alkali etching.

That is, in view of the above, an object of the present invention is to perform etching on a surface with a weak alkali at the time of plating, or use an alkali catalyst as a plating reaction catalyst without performing the etching, so that an effective surface is obtained. It is an object of the present invention to provide conductive fine particles formed of a silicone resin fine particle on which a plating layer is formed and exhibiting excellent conductivity, and a conductive material manufactured using the conductive fine particles.

[0010]

The conductive fine particles according to the present invention are characterized in that an electroless plating layer is formed on the surface of silicone resin fine particles.

According to a second aspect of the present invention, there is provided the conductive fine particles according to the first aspect, wherein the silicone resin fine particles have a structure in which siloxane bonds are cross-linked in a three-dimensional network (polymethylsilsesquioxane structure). ).

The conductive fine particles according to a third aspect of the present invention are characterized in that an electroless nickel plating layer is formed on the surface of the resin fine particles using an alkali catalyst.

According to a fourth aspect of the present invention, there is provided a conductive material manufactured using the conductive fine particles according to any one of the first to third aspects.

The conductive fine particles according to the first aspect are obtained by forming the electroless plating layer (conductive layer) by coating the surface of the silicone resin fine particles with a metal by an electroless plating method. Examples of the metal include nickel,
Gold, silver, copper, cobalt and the like can be mentioned, and among them, nickel is particularly preferable.

The thickness of the electroless plating layer is not particularly limited, but is preferably 50 to 3000 °, more preferably 150 to 2000 °, and particularly preferably 500 to 1500 °. If the thickness of the electroless plating layer is less than 50 °, desired conductivity may not be obtained. Conversely, if the thickness of the electroless plating layer exceeds 3000 °, the electroless plating layer may peel off from the silicone resin fine particles. May be easier.

The step of forming the electroless plating layer is generally divided into an etching step, an activation step, and an electroless plating step. However, in the present invention, the etching step is not always essential.

The etching step is a step of forming irregularities on the surface of the silicone resin fine particles to improve the adhesion of the electroless plating layer. In the present invention, it is preferable to use an alkaline aqueous solution such as an aqueous caustic soda solution as an etching solution. For example, an aqueous solution of an acid such as hydrochloric acid, sulfuric acid, chromic anhydride or the like cannot provide an effective etching effect.

In the present invention, the alkaline aqueous solution is preferably weakly alkaline. For example, when the alkaline aqueous solution is a caustic soda aqueous solution, its concentration is 5% by weight.
The following is preferred. If the concentration of the aqueous caustic soda solution as an alkaline aqueous solution exceeds 5% by weight, dissolution or aggregation of the silicone resin fine particles occurs during etching,
Desired conductive fine particles may not be obtained.

The concentration of the above-mentioned caustic soda is usually 1/3 to 1
Electroless plating is possible even at a concentration of about / 5. However, if etching is performed with an alkali, even a weak alkali, aggregation of silicone resin fine particles tends to occur at the time of etching. It is more preferable to adopt a method of using only an alkali catalyst described below as a plating reaction catalyst without performing etching with an alkali.

The activation step is a step of forming a catalyst layer on the surface of the silicone resin fine particles etched with a weak alkali or the surface of the silicone resin fine particles not etched, and activating the catalyst layer. The activation of the catalyst layer promotes metal deposition in the electroless plating step.

In the present invention, the catalyst used in the activation step is preferably an alkali catalyst (alkali catalyst) such as a commercially available amine complex salt catalyst. Note that, for example, a chlorine-based catalyst such as “Catalyst C” commercially available from Okuno Pharmaceutical Company may not be able to form an effective electroless plating layer on the surface of the silicone resin fine particles.

The electroless plating step is a step of forming a plating layer (conductive layer) on the surface of the silicone resin fine particles having the catalyst layer formed thereon. By immersing the silicone resin particles with the catalyst layer formed in the electroless metal plating solution,
A plating layer (conductive layer) is formed on the surface of the silicone resin fine particles. For example, when forming a nickel plating layer,
After reducing the catalyst layer on the surface of the silicone resin fine particles with a reducing agent such as dimethylaminoborane, the catalyst layer is immersed in an electroless nickel plating solution, or the silicone resin fine particles having the catalyst layer formed thereon are immersed in the electroless nickel plating solution. After that, a nickel plating layer can be formed on the surface of the silicone resin fine particles by adding and reducing the reducing agent. By immersing the silicone resin particles having the nickel plating layer formed thereon in, for example, an aqueous solution of a gold cyanide compound, a gold plating layer can be formed by a substitution reaction.

Among the conductive fine particles according to the first aspect thus obtained, conductive fine particles in which the electroless plating layer is a nickel plating layer formed using the alkali catalyst are particularly preferable.

By making the electroless plating layer a nickel plating layer formed by using an alkali catalyst, the obtained conductive fine particles are more excellent without causing aggregation of the silicone resin fine particles in the electroless plating step. It becomes conductive.

The silicone resin fine particles used for the conductive fine particles according to the first aspect of the present invention may be any fine particles made of a silicone resin containing dimethylpolysiloxane as a main component and collectively referred to as an organopolysiloxane. It may have a functional group such as a vinyl group, an epoxy group, or an amino group. Among them, a structure in which siloxane bonds are cross-linked in a three-dimensional network, as described in claim 2, That is, silicone resin fine particles having a polymethylsilsesquioxane structure are particularly preferred.
These silicone resin particles may be used alone or in combination of two or more.

By using silicone resin fine particles having a structure in which siloxane bonds are crosslinked in a three-dimensional network (polymethylsilsesquioxane structure), the obtained conductive fine particles can have excellent flexibility and elasticity. Become.

The silicone resin particles are not particularly limited, but preferably have an average particle diameter of 1 μm or more. The average particle size of the silicone resin particles is 1
If it is less than μm, aggregation of the silicone resin particles easily occurs during etching in the plating step,
It may be difficult to obtain conductive fine particles without aggregation. The silicone resin fine particles may have any shape, but among them, those having a spherical shape are preferable.

In the conductive fine particles according to the third aspect, an electroless nickel plating layer is formed on the surface of the resin fine particles by the steps and the method using the alkali catalyst.

The type of the resin fine particles is not particularly limited. For example, the silicone resin, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyisobutylene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene -Styrene terpolymer, polyacrylate, polymethyl methacrylate, polyacrylamide, polyvinyl acetate, polyvinyl alcohol, polyacetal, polyethylene glycol, polypropylene glycol, epoxy resin, amino resin, polyurethane, polyester, fluorine-containing resin, nitrile resin, etc. These fine particles are preferably used, and among them, the above-mentioned silicone resin fine particles are particularly preferably used. These resin fine particles may be used alone or in combination of two or more.

A conductive material according to a fourth aspect is manufactured using the above-described conductive fine particles of the present invention.

Examples of the conductive material include a conductive paste, an adhesive for vertical conduction, an anisotropic conductive adhesive, a conductive material for shielding electromagnetic waves, and the like, but are not limited thereto. Any conductive material may be used as long as the material is made of conductive fine particles.

[0032]

The conductive fine particles of the present invention are subjected to etching with or without a weak alkali in the electroless plating step, and an alkali catalyst is used as a catalyst for the plating reaction. An effective electroless plating layer is formed on the surface of the substrate. Therefore, the conductive fine particles of the present invention have both excellent flexibility and elasticity inherent in silicone resin and excellent conductivity.

In particular, a silicone resin fine particle having a structure in which siloxane bonds are cross-linked in a three-dimensional network, that is, a silicone resin fine particle having a polymethylsilsesquioxane structure is used as the silicone resin fine particles, and the electroless plating layer is formed using an alkali catalyst. By using a nickel plated layer, the above characteristics are significantly improved.

Further, since the conductive material of the present invention is manufactured using the above-mentioned conductive fine particles, it exhibits excellent flexibility and elasticity and excellent conductivity.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 50 g of standard type silicone resin fine particles (standard polymethylsilsesquioxane, trade name "Shin-Etsu Silicone KMP-590", manufactured by Shin-Etsu Chemical Co., Ltd.) was degreased (trade name "A-Screen A"). -22
0 ", manufactured by Okuno Pharmaceutical Co., Ltd.)
After being degreased by stirring for minutes, filtration and washing were performed to obtain degreased silicone resin fine particles. Next, the silicone resin fine particles are added and dispersed in a 5% by weight aqueous solution of caustic soda, stirred at 50 ° C. for 10 minutes, etched, neutralized with acetic acid, filtered and washed, and further 1% by weight of dodecylbenzene sulfone Add and disperse in aqueous sodium acid
The surface was adjusted by stirring at ℃ for 3 minutes. Next, this was filtered and washed, and then dispersed in an amine complex salt-based alkaline catalyst (trade name “OPC-50 INLUSA”, manufactured by Okuno Pharmaceutical Co., Ltd.). The catalyst was adsorbed while stirring, and dimethylaminoborane was added. And reduced at 25 ° C. for 3 minutes.
Next, this was filtered, washed, and dispersed in water. Then, an electroless nickel plating solution (trade name “TMP Chemical Nickel Solution”, manufactured by Okuno Pharmaceutical Co., Ltd.) was added, and the mixture was stirred at 40 ° C. for 7 minutes. Nickel plating was performed. This is then filtered and washed,
After further washing with alcohol, the resultant was dried at 40 ° C. for 12 hours to obtain silicone resin fine particles whose surface was nickel-plated. In the above operation, some pieces of the silicone resin fine particles were generated at the time of etching, and some aggregation was recognized, but the overall evaluation was good.

(Example 2) Epoxy group-containing silicone resin particles (epoxy group-containing polymethylsilsesquioxane, trade name "Shin-Etsu Silicone X-52-830", manufactured by Shin-Etsu Chemical Co., Ltd.) were used as the silicone resin particles. ,
Silicon resin fine particles whose surface was nickel-plated were obtained in the same manner as in Example 1 except that etching was performed with a 3% by weight aqueous solution of caustic soda. In the above operation,
No generation of sections of the silicone resin fine particles was observed, and slight aggregation was observed, but the overall evaluation was good or excellent.

(Example 3) Silicon resin fine particles whose surface was nickel-plated were obtained in the same manner as in Example 1 except that etching with a 5% by weight aqueous solution of sodium hydroxide and neutralization with acetic acid were not performed. In the above operation, generation and aggregation of the silicone resin fine particles were not observed, and the overall evaluation was excellent.

Example 4 Except that epoxy group-containing silicone resin fine particles "Shin-Etsu Silicone X-52-830" were used as the silicone resin fine particles, and etching with a 5% by weight aqueous sodium hydroxide solution and neutralization with acetic acid were not performed. In the same manner as in Example 1, nickel-plated silicone resin fine particles were obtained. In the above operation, generation and aggregation of the silicone resin fine particles were not observed, and the overall evaluation was excellent.

(Comparative Example 1) The same as in Example 1 except that epoxy group-containing silicone resin fine particles "Shin-Etsu Silicone X-52-830" were used as the silicone resin fine particles and were etched with a 10% by weight aqueous solution of caustic soda. Although the operation was performed, dissolution and agglomeration of the silicone resin fine particles occurred during etching, so that silicone resin fine particles whose surface was nickel-plated could not be obtained.

(Comparative Example 2) Etching with a 5% by weight aqueous sodium hydroxide solution and neutralization with acetic acid were not performed, and instead of a 1% by weight aqueous sodium dodecylbenzenesulfonate solution, 1
The surface was adjusted with an aqueous solution of alkyltrimethylammonium by weight, and the catalyst was replaced with a chlorine-based catalyst (trade name "Catalyst C", manufactured by Okuno Pharmaceutical Co., Ltd.) in place of the amine complex salt-based alkaline catalyst "OPC-50 Inleusa." Was carried out and the same operation as in Example 1 was carried out except for reducing with a 5% by weight aqueous hydrochloric acid solution, but the surface of the silicone resin fine particles was not nickel-plated.

(Comparative Example 3) Instead of etching with a 5% by weight aqueous solution of caustic soda and neutralization with acetic acid, etching was performed with an oxidizing agent (trade name "E-prep Oxizer OX-1", manufactured by Ebara Densan Co., Ltd.), and sulfuric acid was used. Neutralization with hydroxylamine, and surface conditioning with a 1% by weight aqueous solution of alkyltrimethylammonium instead of a 1% by weight aqueous solution of sodium dodecylbenzenesulfonate;
Chlorine catalyst "Catalyst C" instead of amine complex salt-based alkaline catalyst "OPC-50 Inlusa"
The same operation as in Example 1 was performed except that the catalyst was adsorbed in the bath and reduced with a 5% by weight aqueous hydrochloric acid solution, but the surface of the silicone resin fine particles was not nickel-plated.

(Comparative Example 4) Epoxy-containing silicone resin fine particles "Shin-Etsu Silicone X-52-830" were used as the silicone resin fine particles, and instead of etching with a 5% by weight aqueous sodium hydroxide solution and neutralization with acetic acid, an oxidizing agent " The same operation as in Example 1 was performed except that etching was performed with “E-prep Oxizer OX-1” and reduction was performed with hydroxylamine sulfate, but the surface of the silicone resin fine particles was not nickel-plated.

The results of Examples 1 to 4 and Comparative Examples 1 to 4 are as shown in Table 1.

[0045]

[Table 1]

As is clear from Table 1, the conductive fine particles of Examples 1 to 4 according to the present invention form a good or excellent electroless nickel plating layer on the surface of silicone resin fine particles, which had been difficult to plate conventionally. It had been.

On the other hand, in Comparative Example 1 in which the concentration of the aqueous caustic soda solution used for etching was as high as 10% by weight, the dissolution and aggregation of the silicone resin fine particles occurred remarkably at the time of etching, and the electroless nickel plating layer was formed on the surface. The formed silicone resin fine particles could not be obtained.

In Comparative Example 2 in which etching was not performed, and in Comparative Examples 3 and 4 in which an aqueous solution of caustic soda was not used at the time of etching and an oxidizing agent was used, an electroless nickel plating layer was formed on the surface of the silicone resin fine particles. Had not been.

[0049]

As described above, in the conductive fine particles of the present invention, an excellent electroless plating layer is formed on the surface of the silicone resin fine particles, which has been conventionally difficult to plate. Silicone resin particles on which the electroless plating layer is formed,
Compared to conventional plastic fine particles having a metal plating layer formed thereon, they are rich in flexibility and elasticity, and have excellent conductivity, so they can be used for various conductive materials such as anisotropic conductive adhesives. It is suitably used as a conductive filler.

The conductive material of the present invention prepared using the conductive fine particles of the present invention is more flexible than the conductive material prepared using conventional plastic fine particles having a metal plating layer formed thereon. Excellent in elasticity, elasticity and conductivity,
In addition, it demonstrates extremely high reliability.

Claims (4)

[Claims] 1. Conductive fine particles having an electroless plating layer formed on the surface of silicone resin fine particles. 2. The conductive material according to claim 1, wherein the silicone resin fine particles have a structure in which siloxane bonds are cross-linked in a three-dimensional network (polymethylsilsesquioxane structure). Fine particles. 3. The conductive fine particles, wherein an electroless nickel plating layer is formed on the surface of the resin fine particles using an alkali catalyst. 4. A conductive material produced using the conductive fine particles according to claim 1.