Method for manufacturing solder mask of printed circuit board

Abstract

A solder mask manufacturing method adapted to apply a solder mask on a surface of a substrate of a circuit board, said surface is provided with a conductor pattern having an unsheltered portion and a sheltered portion which is covered by said solder mask. The method comprises the steps of: a) disposing a layer of semi-solid solder mask material having an expansion coefficient substantially the same as that of the substrate on the surface of said substrate to cover said copper conductor pattern, and a metal foil covering the material layer; b) applying pressure to the metal foil and applying baking treatment to cure the solder mask material in to solid; c) utilizing chemical solution and plasma etching to remove the metal foil and the solid solder mask material above the unsheltered portion of said copper conductor pattern respectively such that the unsheltered portion can be exposed; and d) using chemical solution to remove the residual metal foil.

What is claimed is:  
     
         1 . A printed circuit board comprising: 
 a substrate having two opposite surfaces, two conductor patterns respectively disposed on the surfaces of said substrate, and at least one plated through hole electrically interconnected with said conductor patterns, each of said conductor patterns having an unsheltered portion and a sheltered portion;    two solder mask layers respectively coated on the surfaces of said substrate and covered over the sheltered portions of said conductor patterns and filling the at least one plated through hole such that the unsheltered portions of said conductor patterns are exposed outside;    wherein each of said solder mask layers has a thermal expansion coefficient substantially identical to that of said substrate;    
     
     
         2 . The printed circuit board as defined in  claim 1 , wherein said substrate is made of a material containing a resin, and each said solder mask layer is made of a material containing a resin which is substantially identical to the resin of said substrate.  
     
     
         3 . The printed circuit board as defined in  claim 2 , wherein the resin contained in the substrate is epoxy resin.  
     
     
         4 . The printed circuit board as defined in  claim 1  further comprising two metal foils respectively covered on said solder mask layers in the way that the unsheltered portions of said conductor patterns are exposed outside.