US Patent 9516753 Wiring substrate and method for manufacturing wiring substrate

A method for manufacturing a wiring substrate includes forming a through-hole penetrating a core layer from one to another surface of the core layer, forming a first metal layer covering the one and the other surface of the core layer and an inner wall surface of the through-hole, forming a second metal layer on the first metal layer, and forming a patterned third metal layer on the second metal layer toward the one surface of the core layer along with forming a patterned fourth metal layer on the second metal layer toward the other surface of the core layer. The forming of the second metal layer includes covering the one and the other surfaces of the core layer and the first metal layer in the through-hole with the second metal layer and closing up a center part of the through-hole with the second metal layer.