Multilayer Interconnection Techniques Applied to High Speed Computer Systems

A microcircuit interconnection system has been developed which utilizes the advantages of a metal substrate for heat conduction and power distribution combined with a superimposed logic interconnection plane fabricated on 25/ m polyimide film. The copper substrate component of the assembly is capable of dissipating 4 W/cm2 to a water-cooled duct and maintaining a chip surface temperature of 45°C above ambient. It supports an expansion matched glass ceramic film which electrically insulates the power distribution plane. All the signal connections are formed by 125/ m gold conductors supported on the polyimide film in which through-connections are formed by etched and metallized 38 m holes. Direct connections to the emitter coupled logic chips are formed by etching away areas of the polyimide film under the conductor tracks to leave beam leads. Finally, in assembly, the back of the chips supported on the polyimide film are soldered to prepared cavities in the substrate. Test assemblies have demonstrated a threefold increase in system speed for 1 ns integrated circuits as compared with their performance in comparable assemblies on standard printed circuit boards.