When semiconductor chips are mounted in the conventional manner, the contact pads on the face of the semiconductor die are wire bonded to lead frame leads, and the back side of the die may or may not be connected to a ground plane or heat spreader.
Flip-chip semiconductors have solder ball contacts on the face side of the die that are connected to a printed circuit base which may be part of the semiconductor package. The back side of the die may be in contact with the semiconductor package, or may be mounted to a heat spreader.
In both of the above devices, heat is basically dissipated only through the back side of the die. The heat generated at the circuit surface of the semiconductor die does not have a good heat dissipation path away from the face of the semiconductor die.
U.S. Pat. No. 5,311,059 discloses backplane grounding for flip-chip integrated circuits, but does not suggest means for removing heat from the face of the device.
U.S. Pat. No. 5,280,409 describes an apparatus for providing a heat sink and protective cover for a Tape Automated Bonding (TAB) integrated circuit device. A printed circuit board has a plurality of thermal vias drilled through it and the TAB device is then mounted on the opposite side of the printed circuit board adjacent to the thermal vias.
Another patent, U.S. Pat. No. 4,396,936 discusses an integrated circuit package with flexible beam leads and the die is mounted active face down on the top of a substrate. A preform comprising a segment of a fiber glass web coated with a thermosetting and thermally conductive plastic is positioned between the chip pad and the active face of the chip. A plurality of thermal passages are formed through the substrate interconnecting the chip face and a heat sink pad.