Patent ID: 8304657

Claim:
A printed wiring board, comprising: a core substrate having a first surface and a second surface on an opposite side of the first surface, the core substrate having a penetrating hole penetrating through the core substrate between the first surface and the second surface; a first circuit formed on the first surface of the core substrate; a second circuit formed on the second surface of the core substrate; and a through-hole conductor formed in the penetrating hole of the core substrate and connecting the first circuit and the second circuit, wherein the penetrating hole has a first opening portion and a second opening portion, the first opening portion of the penetrating hole becomes thinner from the first surface toward the second surface, the second opening portion of the penetrating hole becomes thinner from the second surface toward the first surface, the first opening portion has a first opening on the first surface of the core substrate and has a first portion including the first opening and a second portion contiguous to the first portion of the first opening portion, the second opening portion has a second opening on the second surface of the core substrate and has a first portion including the second opening and a second portion contiguous to the first portion of the second opening portion, the first portion and second portion of the first opening portion form inner walls of the first opening portion which bend inward with respect to a periphery of the penetrating hole at a boundary between the first portion and second portion of the first opening portion, and the first portion and second portion of the second opening portion form inner walls of the second opening portion which bend inward with respect to the periphery of the penetrating hole at a boundary between the first portion and second portion of the second opening portion.