Patent ID: 9661762
Date: 2017-05-23
CPC Classifications: H05K

Claim:
1. A printed wiring board, comprising: a core substrate comprising a resin insulating layer and a plurality of conductor layers; a first wiring structure formed on a first surface of the core substrate and comprising a conductor layer and a resin insulating layer such that the conductor layer in the first wiring structure includes a plurality of pads positioned to mount an electronic component on the first wiring structure; and a second wiring structure formed on a second surface of the core substrate and comprising a conductor layer and a resin insulating layer such that the conductor layer in the second wiring structure includes a plurality of pads positioned to mount a mother board to the second wiring structure, wherein the core substrate is interposed between the first wiring structure and the second wiring structure such that the resin insulating layers and conductor layers in the core substrate, first wiring structure and second wiring structure are alternately laminated, the resin insulating layer in the first wiring structure has a vol % of resin which is larger than a vol % of resin in the resin insulating layer in the second wiring structure such that a difference in the vol % of resin in the first and second wiring structures is in a range of from 0.5% to 5.0% and that a coefficient of thermal expansion of the resin insulating layer in the first wiring structure is larger than a coefficient of thermal expansion of the resin insulating layer in the second wiring structure, the resin insulating layer in the core substrate comprises a first resin layer and a second resin layer such that the first resin layer has a thickness which is substantially equal to a thickness of the second resin layer, the first wiring structure includes an outermost resin insulating layer and an outermost conductor layer formed on the outermost resin insulating layer, the outermost conductor layer in the first wiring structure includes the plurality of pads positioned to mount the electronic component on the first wiring structure, and the coefficient of thermal expansion of the resin insulating layer in the first wiring structure is larger than the coefficient of thermal expansion of the resin insulating layer in the second wiring structure within the difference in the vol % of resin in the range of from 0.5% to 5.0% such that the printed wiring board forms a convex warpage with respect to a mounting surface of the first wiring structure at a mounting temperature of the electronic component.