Isolated heat-sink semiconductor device

Claim 1

In a semiconductor device including a relatively thick mounting plate of high thermal conductivity metal and a semiconductor body having a bottom major face provided with an electrode and a top major face provided with other electrodes, a thin wafer of electrically insulative thermally conductive material overlying a portion of said mounting plate and having its bottom major face thermally-conductively bonded to said mounting plate, the top major face of said wafer having a plurality of spaced metallized external lead bonding sites, a central external wire-like lead and two side external wirelike leads bonded at their respective inner end portions to said respective bonding sites, the inner end portion of the central lead including a thin flattened paddle-like segment having a top surface and having a bottom surface thermally conductively bonded across its entirety to its respective bonding site on said wafer, heat reservoir means consisting of a high thermal conductivity metal slug of much larger mass than the semiconductor body, said slug being thermally and electrically conductively joined to and extending between the entirety of the bottom major face of said semiconductor body and the entirety of the top surface of said flattened segment, respective inner leads joining the inner end portions of said side external leads to the other respective electrodes of said semiconductor body, said wafer, slug, semiconductor body, inner leads, and inner end portions of said external leads all being enclosed in a plastic encapsulant from which said mounting plate and the remainder of said external leads extend.