Patent ID: 8895873

Claim:
A printed wiring board, comprising: a core insulation layer comprising a resin and having a via conductor comprising a plating material filling a hole formed through the core insulation layer; a first conductive layer formed on a surface of the core insulation layer and comprising a copper foil laminated on the surface of the core insulation layer and a plated film formed on the copper foil; an interlayer insulation layer formed on the first conductive layer and comprising a resin, the interlayer insulation layer having a via conductor comprising a plating material filling a hole formed through the interlayer insulation layer; and a second conductive layer formed on the interlayer insulation layer and comprising a copper foil laminated on the interlayer insulation layer and a plated film formed on the copper foil of the second conductive layer, wherein the first conductive layer includes a conductive circuit, the second conductive layer has a conductive circuit connected to the conductive circuit in the first conductive layer through the via conductor in the interlayer insulation layer, each of the core insulation layer and the interlayer insulation layer has a dielectric constant of 4.0 or lower for a signal transmission at frequency of 1 GHz and a thermal expansion coefficient of 85 ppm/° C. or lower at or below Tg, and the copper foil of the first conductive layer has a thickness which is set greater than a thickness of the copper foil of the second conductive layer.