Polyimide stress cushion for multichip glass-ceramic module packaging

Abstract

The performance of the IBM glass ceramic-copper multilayer ceramic module (MLC) is significantly enhanced by a revolutionary set of packaging materials, although the mechanically weaker nature of the glass material has created a significant challenge in maintaining zero failure. One area of concern is the joining of I/O pins to the Bottom Surface Methodology Metallurgy (BSM) pads, where the reliability of the pin joint depends critically on the mechanical strength of the ceramic substrate. To avoid ceramic fracture, stress on the pin joint should be limited so that combined stresses from the pin joint, pin loading, and I/O pad should not exceed the fracture strength of the glass ceramic module.