Patent ID: 8707554

Claim:
A method of manufacturing a multilayer wiring substrate having a laminate structure in which a plurality of resin insulation layers, and a plurality of conductive layers are laminated alternately in multilayer arrangement, a plurality of first-main-surface-side connection terminals being disposed on one side of the laminate structure where a first main surface thereof is present, a plurality of second-main-surface-side connection terminals being disposed on an other side of the laminate structure where a second main surface thereof is present, the plurality of conductive layers being formed in the plurality of resin insulation layers and interconnected by means of via conductors whose diameters increase toward the first main surface or the second main surface, the method comprising: a build-up step that includes: a step of separably laminating a metal foil on a side of a base material, and a step of forming a laminate structure that includes alternately laminating the plurality of resin insulation layers made primarily of the same resin insulation material and the plurality of conductive layers in multilayer arrangement on the metal foil separably laminated on the side of the base material; a drilling step of forming a plurality of openings in an outermost resin insulation layer of the laminate structure through laser drilling so as to expose the first-main-surface-side connection terminals of the multilayer wiring substrate; a desmear step of, after the drilling step, removing smears from inside the openings in the outermost resin insulation layer of the laminate structure; and a base-material removing step of, after the build-up step, removing the base material and exposing the metal foil.