US Patent 9538664 Wiring substrate

A wiring substrate includes a first wiring layer with a wiring pattern and a metal foil. A first insulating layer includes a first through hole having a first end facing the metal foil and a second end. A second wiring layer includes a first opening having a diameter smaller than the second end. A second insulating layer includes a second through hole having a third end facing the wiring pattern and a fourth end. A third wiring layer includes a second opening having a diameter smaller than the fourth end. A first via is filled in the first opening, the first through hole, and a first recess, in the metal foil, having a diameter greater than the first end. A second via is filled in the second opening, the second through hole, and a second recess, in the wiring pattern, having a diameter greater than the third end.