Patent ID: 8552312

Claim:
A printed wiring board comprising: a substrate having a first surface and a second surface on an opposite side of the first surface, the substrate having a penetrating hole extending through the substrate 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 formed in the penetrating hole of the substrate and connecting the first conductive circuit and the second conductive circuit, wherein the through-hole conductor comprises an electroless plated film formed on an inner-wall surface of the penetrating hole, a first electrolytic plated film formed on the electroless plated film and forming a first opening portion which opens on the first surface, a second opening portion which opens on the second surface and a connection portion partitioning the first opening portion and the second opening portion, a second electrolytic plated film filled in the first opening portion of the first electrolytic plated film, and a third electrolytic plated film filled in the second opening portion of the first electrolytic plated film, and the first opening portion and the second opening portion taper toward a central portion of the penetrating hole with respect to an axis direction of the penetrating hole and have cross sections forming a substantially U-shape, respectively.