Method for forming electric circuits on a base board

Abstract

A method for forming a plurality of electrically conductive circuits of at least four laminations on a single base board having copper laminations attached on both sides thereof, for example, wherein the base board is processed to provide a through-hole therein, subjected to a catalyst treatment, etched to provide a plurality of circuits of a first lamination, effectively processed with a plating-resistant resist and an electrically conductive copper paste to provide a circuit of a second lamination on the circuits of the first lamination by making a pre-plating treatment and a subsequent chemical treatment applied to the copper paste. The base board is then coated again with the plating-resistant resist except a part of the circuits of the first lamination formed around the through-hole, subjected to an activation treatment and then to a nonelectrolytic copper plating applied to the inner periphery of the through-hole to provide thereon a copper plating layer for electrically connecting the circuits of the first lamination on both sides of the base board.