Patent ID: 7121000

Claim:
A method of manufacturing a multilayer wiring board comprising the steps of: providing a prepreg comprising a resin porous film made of polyimide resin impregnated with a thermosetting resin wherein the resin porous film is structured by wet coagulation and does not include a polymeric nonwoven fabric; providing double-sided wiring boards each comprising an insulating layer and a wiring pattern formed on both surfaces of the insulating layer; heating and pressurizing a stacked product to be integrated constituted by the prepreg interposed between the double-sided wiring boards; and controlling the gap between the wiring boards using a pressurizing force to deform the resin porous film and form a flat insulating layer, wherein a flat insulating layer is formed with reduced difficulty as compared to a method in which a polymeric nonwoven fabric is used.