Multilayer circuit board

摘要

A process for making a multilayer wiring board includes the following steps of: laminating an electrically insulating resin substrate (34), having first and second surfaces and a metal layer (36) formed on the first surface, onto a base material (32) on which a predetermined wiring pattern (30) is formed, so that the second surface of the resin substrate (34) is adhered to the base material (32); removing a predetermined amount (38) of the metal layer (36) to form an opening at a position where a connection with the wiring pattern (30) is to be provided; irradiating a laser beam toward the resin layer (34) through the resin removed region (38) to form a blind via hole (40) having a diameter smaller than that of the opening (38), so that the wiring pattern (30) is exposed at a bottom of the blind via hole (40); electroless plating form an electroless plated film on the exposed wiring pattern (30), a side wall of the blind via hole (40), a step layer (36) at a periphery of the opening (40); electro plating to form an electro plated film on the electroless plated film; and after the electro plating, etching the metal layer to form a predetermined wiring pattern (36a).