Wiring substrate and method for manufacturing wiring substrate

A method for manufacturing a wiring substrate, comprising:

• preparing a plurality of first substrates each comprising a first core substrate, a plurality of first conductor layers and a plurality of first insulating layers;
• preparing at least one second substrate each comprising a second core substrate, a plurality of second conductor layers and a plurality of second insulating layers;
• and
• connecting a surface of each of the first substrates to a second surface of the at least one second substrate on an opposite side with respect to a first surface of the at least one second substrate via a plurality of conductor bumps such that the first surface of the at least one second substrate has a component mounting region,
• wherein the first substrates have substantially a same thickness and are formed such that the first conductor layers and the first insulating layers are laminated on a first surface of the first core substrate and on a second surface of the first core substrate on an opposite side with respect to the first surface of the first core substrate, and the at least one second substrate is formed such that the second conductor layers and the second insulating layers are laminated on a first surface of the second core substrate and on a second surface of the second core substrate on an opposite side with respect to the first surface of the second core substrate.