A plurality of openings are formed in a resin insulation layer on a bottom surface side of a wiring laminate portion which constitutes a multilayer wiring substrate. A plurality of motherboard connection terminals are disposed to correspond to the openings. The motherboard connection terminals are primarily comprised of a copper layer, and peripheral portions of terminal outer surfaces thereof are covered by the outermost resin insulation layer. A dissimilar metal layer made of at least one metal which is lower in etching rate than copper is formed between an inner main surface of the outermost resin insulation layer and peripheral portions of the terminal outer surfaces.