Patent ID: 8829355

Claim:
A multilayer printed wiring board comprising: a substrate comprising a core base material and having a penetrating portion; a low-thermal-expansion substrate comprising a low-thermal-expansion resin and accommodated inside the penetrating portion of the substrate, the low-thermal-expansion substrate having a first surface for mounting a semiconductor element and a second surface on the opposite side of the first surface; a first through-hole conductor provided inside the low-thermal-expansion substrate and configured to provide electrical connection between the first surface and the second surface of the low-thermal-expansion substrate; a filler filling a gap between the low-thermal-expansion substrate and an inner wall of the substrate; and a buildup layer formed on at least one of the first surface and the second surface of the low-thermal-expansion substrate and comprising a resin insulation layer and a conductive layer, wherein the buildup layer has a via conductor connecting the first through-hole conductor in the low-thermal-expansion substrate and the conductive layer in the buildup layer, the low-thermal-expansion resin of the low-thermal-expansion substrate has a thermal expansion coefficient in a range of 2.5 to 10 ppm, the buildup layer is formed on the first surface of the low-thermal-expansion substrate, and at least a portion of the buildup layer and at least a portion of the conductive layer are positioned inside the penetrating portion of the substrate to mount a semiconductor thereon, wherein the first through-hole conductor is tapered in a first direction, and the via conductor formed in the buildup layer is tapered in a second direction opposite to the first direction.