Patent ID: 8742553

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; a first buildup layer laminated on the first surface of the core substrate and comprising an outermost interlayer resin insulation layer and an outermost conductive layer formed on the outermost interlayer resin insulation layer of the first buildup layer; and a second buildup layer laminated on the second surface of the core substrate and comprising an outermost interlayer resin insulation layer and an outermost conductive layer formed on the outermost interlayer resin insulation layer of the second buildup layer, wherein the outermost conductive layer of the first buildup layer includes a plurality of pads positioned to mount a semiconductor device on a surface of the first buildup layer, and the outermost interlayer resin insulation layer of the first buildup layer has a thermal expansion coefficient which is set lower than a thermal expansion coefficient of the outermost interlayer resin insulation layer of the second buildup layer.