Wiring substrate

A wiring substrate, comprising:

• a core layer;
• a plurality of first conductor layers formed on a first surface of the core layer and comprising a first inner conductor layer formed on the first surface of the core layer, a first outer conductor layer forming an outermost conductor layer on a first surface side of the core layer, and a first intermediate conductor layer formed between the first inner conductor layer and the first outer conductor layer;
• a plurality of second conductor layers formed on a second surface of the core layer on an opposite side with respect to the first surface of the core layer and comprising a second inner conductor layer formed on the second surface of the core layer, a second outer conductor layer forming an outermost conductor layer on a second surface side of the core layer, and a second intermediate conductor layer formed between the second inner conductor layer and the second outer conductor layer;
• and
• a plurality of interlayer insulating layers interposed between the first inner conductor layer and the first intermediate conductor layer, between the second inner conductor layer and the second intermediate conductor layer, between the first intermediate conductor layer and the first outer conductor layer, and between the second intermediate conductor layer and the second outer conductor layer,
• wherein at least one of the first and second inner conductor layers has a first laminated structure comprising a metal foil layer and a plating film layer, at least one of the first and second outer conductor layers has the first laminated structure, at least one of the first and second intermediate conductor layers has a second laminated structure comprising a metal foil layer and a plating film layer, the first and second laminated structures are formed such that a surface of the second laminated structure on a side away from the core layer has an unevenness that is smaller than an unevenness of a surface of the first laminated structure on a side away from the core layer, and each of the first and second intermediate conductor layers has the second laminated structure formed such that the metal foil layer of the second laminated structure has a thickness that is smaller than a thickness of the metal foil layer of the first laminated structure.