A package for mounting a semiconductor device to a circuit board. An insulating substrate is provided, which has at least one layer, and provides rigidity to the package. A plurality of electrically conductive contacts are disposed on the top surface of the substrate, receive the semiconductor device, and make electrical contact between the semiconductor device and the substrate. A plurality of electrically conductive through-holes are formed in the substrate, and extend from the top surface of the substrate to the bottom surface of the substrate. The through-holes make electrical connection between all of the layers of the substrate. Electrical interconnections between the contacts and the through-holes are provided by a plurality of electrically conductive traces. A z-conductive layer is attached to the bottom surface of the substrate. Electrical continuity between the bottom surface of the z-conductive layer and the through-holes extending to the bottom surface of the substrate is substantially limited to the z axis of the z-conductive layer according to a predetermined pitch. A plurality of electrically conductive connectors are attached to the bottom surface of the z-conductive layer, and are disposed so as to be in electrical contact through the z-conductive layer with no more than one through-hole.