Patent ID: 8288665

Claim:
A multi-layer printed circuit board comprising: a first insulating layer having a first surface and a second surface on an opposite side of the first surface; a first conductor layer comprising a plurality of conductor circuits formed on the first surface of the first insulating layer; a second conductor layer comprising a plurality of conductor circuits formed on the second surface of the first insulating layer; a second insulating layer formed on the second conductor layer and the first insulating layer; and a third conductor layer comprising a plurality of conductor circuits formed on the second insulating layer on an opposite side of the second conductor layer, wherein the first insulating layer has an opening and a first via hole formed in the opening of the first insulating layer, the second insulating layer has an opening and a second via hole formed in the opening of the second insulating layer, the first via hole comprises a conductive material filled to a top of the opening of the first insulating layer such that at least one of the conductor circuits in the first conductor layer is connected to at least one of the conductor circuits in the second conductor layer, the second via hole comprises a conductive material filled to a top of the opening of the second insulating layer such that at least one of the conductor circuits in the third conductor layer is connected to at least one of the conductor circuits in the second conductor layer, the first via hole is tapering from the first conductor layer toward the second conductor layer, and the second via hole is tapering from the third conductor layer toward the second conductor layer, wherein the conductive material of the first via hole consists of a metal filled to the top of the opening of the first insulating layer, and the conductive material of the second via hole consists of a metal filled to the top of the opening of the second insulating layer.