Wiring substrate and installation structure using the same

A wiring substrate according to the present disclosure has: a first insulating layer having a first surface; a land conductor disposed on the first surface; a second insulating layer covering the first surface and the land conductor and having a second surface on the opposite side of the first insulating layer; a via hole penetrating from the second surface of the second insulating layer to the land conductor; and a via-hole conductor disposed in the via hole and in contact with the land conductor. The via-hole conductor has a first area on a surface of the via-hole conductor that is in contact with the land conductor. The first area has an oxide nickel-chromium alloy layer partially formed thereon.