Patent ID: 6839965

Claim:
The method of making one or more interposers which comprises the following steps: providing an insulative layer with a top surface and a bottom surface, with a first layer of copper bonded to said top surface and a second layer of copper bonded to said bottom surface; drilling a plurality of vias in said insulative layer for each interposer; coating the inside surface of the vias and the top and bottom surface of the insulative layer with a third layer of copper; adding an upper layer of photoresist to said top surface, and a lower layer of photoresist to said bottom surface of the of the insulative layer; using artwork to selectively expose the photoresist layers to light, thereby exposing photoresist around an upper contact pad which defines a central well, and an area around a lower contact pad, with the upper contact pad and the lower contact pad positioned on opposite sides of the insulative layer from each other, and with the vias connecting the upper contact pad and the lower pads, for each interposer; chemically developing the photoresist, so that areas unexposed to light are chemically removed, including the upper contact pad and the lower contact pad areas of each interposer; depositing a fourth layer of copper in areas not covered by photoresist, thus building up said upper and lower contact pads of each interposer and filling said vias between the upper and lower contact pads of each interposer, thus forming the copper body of one or more interposers, each with an upper contact pad which defines a central void, and a lower contact pad, with the contact pads of each interposer connected by a plurality of copper connecting post filling said vias; depositing one or more layers of conductive metal on exposed copper surfaces of an upper or lower contact pad, or both, for improved durability; removing the upper and lower photoresist layers; removing the first and second copper layers, which leaves said insulative layer with one or more interposers, with each interposer comprising an upper contact pad which surrounds and defines an inner well, and a lower contact pad, with said upper and lower contact pads connected by a plurality of vias, in which said inner well is isolated from said lower contact pad by said insulative layer; forming a stencil which is thicker than said lower contact pads and in which are defined a stencil passage corresponding to each lower contact pad of each interposer, and attaching said stencil to said bottom surface of said insulative layer, so that each lower contact pad is positioned in a corresponding stencil passage; applying a conductive elastomeric material to said stencil, so that said stencil passages are filled with said conductive elastomeric material; and removing said stencil, leaving each lower conductive pad with an attached conductive elastomeric pad.