Patent ID: 8431833

Claim:
A printed wiring board comprising: a substrate having a first surface, a second surface on an opposite side of the first surface, and a through-hole extending between the first surface and the second surface; a first conductive circuit formed on the first surface of the substrate; a second conductive circuit formed on the second surface of the substrate; and a through-hole conductor filling the through-hole and connecting the first conductive circuit and the second conductive circuit, wherein the through-hole has a first opening portion tapering from the first surface toward the second surface and a second opening portion tapering from the second surface toward the first surface, the substrate comprises a resin and a reinforcing material portion provided in the resin, the reinforcing material portion has a protruding portion protruding from the resin and protruding into the through-hole at an intersection of the first opening portion and the second opening portion, and the protruding portion of the reinforcing material portion encroaches into the through-hole conductor.