A multichip package utilizing in-Cu flip-chip bonding

A multichip package is described which is composed of an alumina ceramic base, screen-printed gold and glass crossovers, photolithographically delineated copper conductors, a brazed on Kovar lead frame, indium-copper flip-chip bonded integrated circuit chips, and a glass-severa, interfaces between dissimilar metals, between metals and insulators, and between different insulators. The reasons for selection of the various materials for these interfaces are presented. The major innovation in this package, the indium-copper flip-chip bond, is discussed both from a processing viewpoint and from an analytical viewpoint, supported by diffusion, X-ray crystallographic, and metallurgical data.