Process for producing multilayer printed circuit board for wire bonding

A process for producing a multilayer printed circuit board comprising the following steps (a)-(h) which are carried out in this order:

• (a) compounding electrically insulating ceramic whiskers in a thermosetting resin varnish, dispersing the whiskers in the varnish uniformly by stirring, coating the resulting mixture on a roughened side of a copper foil, semi-curing the resin by heating to form a thermosetting resin layer, placing this layer on an interlayer circuit board in which plated through-holes and conductor circuits have been formed, and hot pressing them to form an integral laminate;
• (b) forming an etching resist on said copper foil, and etching the copper foil portions exposed from the etching resist into the shape of holes for forming interstitial via holes;
• (c) removing the etching resist;
• (d) applying laser beams to the cured thermosetting resin layer exposed from the fine holes of the copper foil etched into the shape of holes for forming interstitial via holes to remove said resin layer to an extent that the circuit conductors of the interlayer board is to be exposed, thereby forming via holes;
• (e) roughening said cured thermosetting resin layer on the walls of said via holes by using a roughening agent;
• (f) conducting plating to electrically connect the circuit conductors of the interlayer board and the copper foil;
• (g) forming an etching resist on said copper foil and etching away the copper foil portions exposed from said etching resist;
• and
• (h) removing the etching resist.