Electrically conductive material and method for producing same

Abstract

Provided is a method for producing an electrically conductive material having an electrically conductive layer having a proper thickness without requiring the bonding with an adhesive agent and without requiring the use of a vacuum facility. The present invention is a method for producing an electrically conductive material, comprising the steps of: applying a dispersion, which contains 0.5 mass% or more of microparticles (2) of at least one metal selected from the group consisting of gold, silver, copper and platinum which are protected by a compound having a nitrogen atom, a sulfur atom, a phosphorus atom or an oxygen atom, on an insulating base (1) to form a non-electrically-conductive layer (3); and subjecting the base (1) having the non-electrically-conductive layer (3) formed thereon to electroless plating to form an electrically-conductive layer.

Description

technical field [0001] The present invention relates to a method for producing a conductive material that can be suitably used as a laminate base material for a printed wiring board. In addition, the present invention also relates to a conductive material produced using the production method. Background technique [0002] The laminate base material for printed circuit boards is a material having a structure in which a low dielectric constant material and a conductive thin layer are laminated. Conventionally, for example, flexible copper-clad laminates (FCCL) have been manufactured using methods such as bonding a heat-resistant polymer film to copper foil with an epoxy resin-based adhesive, coating the copper foil surface with Cloth resin solution and let it dry etc. method. [0003] In recent years, due to the miniaturization and high speed of electronic equipment, higher density and higher performance of printed circuit boards are required. In order to meet these requirem...

AI Technical Summary

Problems solved by technology

[0011] However, when a coating film coated with a dispersion of these fine metal particles and metal thin film precursor particles is heated and sintered to form a conductive film, it is difficult to completely fill the gaps between the particles, and internal residues are formed. Metal film with more voids

In addition, although the shape of the particles in the film changes due to welding and particle growth, and some particles are connected to each other, the phenomenon that the coating density decreases in the entire film is often observed

As a result, there are problems in that plating cannot be performed because sufficient conductivity cannot be exhibited, it takes a very long time even if plating can be performed, or plating occurs due to the occurrence of local non-conductive portions. Defects, unevenness of plating, etc.

In addition, in such a metal thin film with a low local coating density and many voids, there is a problem that the voids become the origin of failure and the conductive layer is peeled off from the insulator base material.

[0012] As a countermeasure against this problem, the aforementioned Patent Document 3 proposes to eliminate poor conduction and reduce damage that would cause peeling by filling the voids in the first conductive layer formed on the insulator base material by electroless metal plating. The starting point, but the voids in the conductive film welded by heating and sintering often exist in the form of isolated spaces inside the film, and the chemical solution does not penetrate. Therefore, sometimes it still exists in the form of voids after electroless plating, which cannot be called sufficient. the solution

[0013] In addition, as a catalyst for electroless plating, palladium is generally used, but when expensive palladium is used as a catalyst metal, not only the cost of the electroless plating process becomes large, but also there is a problem that the electroless plating using the palladium catalyst fills the When the voids in the conductive layer are formed by heating and sintering, palladium is randomly absorbed into the conductive layer, palladium cannot be sufficiently removed in the subsequent etching process, and it may cause deterioration of the characteristics of the circuit board, etc.

However, this method has the following disadvantages: a large amount of reducing agent is required, the production cost is high, and the stability of the formed silver hydrosol is low, and it is easy to produce aggregation and precipitation

[0016] In the methods described in above-mentioned patent documents 4 and 5, the object to be plated is immersed in the dilute dispersion of silver colloid, and the silver colloid is mainly attached to the surface of the object to be plated by the electrostatic interaction between the silver colloid and the surface of the object to be plated. , used as a catalyst for electroless plating, the amount of silver colloid attached is controlled by the immersion time, but when the concentration of the catalyst attached to the object to be plated is insufficient, and the base material with a large area such as a laminated base material for a printed circuit board, It needs to be carried out in a large dipping tank for a long time, so it is difficult in practical application

In addition, for such a method of naturally adsorbing in liquid, since the adsorption of silver colloid to the object to be plated is low, the catalyst material (silver colloid) is easily absorbed by itself in the washing process and electroless plating after the silver colloid catalyst is given. If the plating material falls off, there will be problems such as uneven plating precipitation, and the decomposition of the plating bath due to contamination of the plating solution.

Also mentioned in these documents are coating silver colloid on the object to be plated and give the possibility of catalyst, but there is following problem: for the low concentration silver colloid of disclosing, can't be coated on the object to be plated Given a sufficient amount of silver colloid, it is impossible to implement uniform plating on the object to be plated, and when the disclosed silver colloid is concentrated, aggregation will occur, and coating and film formation cannot be performed.

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