PRINTED WIRING BOARD AND METHOD FOR MANUFACTURING PRINTED WIRING BOARD

A printed wiring board includes a core substrate having a penetrating hole penetrating through the core substrate and having a first insulation layer, a second insulation layer and an insulative substrate interposed between the first and second layers, a first circuit formed on a surface of the core, a second circuit formed on opposite surface of the core, and a through-hole conductor formed in the penetrating hole of the core and connecting the first and second circuits. The penetrating hole has first and second opening portions, the first opening portion becomes thinner from the first surface toward the second surface, the second opening portion becomes thinner from the second surface toward the first surface, and the first and second insulation layers are comprised of resin materials easier to be processed by laser than resin material of the insulative substrate under same conditions of the laser.