Katherine G. Heinen

Multichip assembly with flipped integrated circuits

A multichip module process has been developed using flipped-chip interconnection. The process uses plated copper bumps for superior thermal transport characteristics, active silicon as a substrate material for matched expansion properties, on-chip interconnection metallization that allows bumps to be placed over the active circuitry, and conventional wafer fabrication facilities for low-cost production. For successful design and fabrication of multichip assemblies, an organized methodology similar to that which has proved successful in design and assembly of single VLSI circuits was used. This approach involves: computer-aided modeling of the circuit and package for electrical, thermal, and mechanical simulation; test chips for process development and failure mechanism testing; and fabrication of actual demonstration circuits. Verification of function and reliability was then made through temperature cycle testing (-65 degrees C to 150 degrees C), exposure to accelerated moisture environments, and measure of heat dissipation properties. This approach and an example of its application to a multichip module that demonstrated successful performance on the first design pass are described. >