Patent ID: 8975742
Filing Date: 2015-03-10
Classification: H01L

Abstract:
1. A printed wiring board, comprising: a substrate having a first surface and a second surface on an opposite side of the first surface; a first buildup layer formed on the first surface of the substrate and comprising a resin insulation layer and a plurality of conductive layers including an outermost conductive layer; and a second buildup layer formed on the second surface of the substrate and comprising a resin insulation layer and a plurality of conductive layers including an outermost conductive layer, wherein the outermost conductive layer of the first buildup layer has a plurality of pads positioned to connect a semiconductor element, the first buildup layer has a component mounting region directly under the semiconductor element such that the outermost conductive layer of the first buildup layer has a conductive portion in the component mounting region, and the outermost conductive layer of the second buildup layer has a conductive portion directly under the component mounting region such that the conductive portion in the component mounting region in the first buildup layer and the conductive portion directly under the component mounting region in the second buildup layer satisfy a ratio value in a range of from 1.1 to 1.35, where the ratio value is obtained by dividing a planar area of the conductive portion in the outermost conductive layer of the second buildup layer by a planar area of the conductive portion in the outermost conductive layer of the first buildup layer.