Wiring substrate

A method for manufacturing a wiring substrate, comprising:

• forming a core substrate having a through-hole conductor;
• forming a resin insulating layer on the core substrate;
• forming a conductor layer on the resin insulating layer such that the conductor layer includes a seed layer and an electrolytic plating layer formed on the seed layer;
• and
• forming a via conductor in the resin insulating layer such that the via conductor electrically connects the through-hole conductor and the conductor layer and that the via conductor includes the seed layer and electrolytic plating layer extending from the conductor layer,
• wherein the forming the core substrate includes forming a through hole penetrating through a glass substrate and forming the through-hole conductor in the through hole, and the forming the via conductor includes forming the seed layer in an opening formed in the resin insulating layer such that the seed layer covers an inner wall surface of the resin insulating layer in the opening, that the seed layer has a first portion and a second portion electrically connected to the first portion and that a part of the first portion is formed on the second portion.