Polyimide stress cushion for multichip glass-ceramic module packaging

The performance of the IBM glass ceramic-copper multilayer ceramic module (MLC) is significantly enhanced by a revolutionary set of packaging materials. Low dielectric constant cordierite glass ceramic (ε-5.0), co-sintered with high conductivity copper (ρ-3.5 μΩ-cm), was developed and integrated into the high performance glass ceramic thermal conduction modules (TCM) used in the IBM System/390-Enterprise system/9000 series of mainframe computers. Low stress pin attach structures have been developed for the glass ceramic module. They include the multilayer thin film I/O pad, taper headed pin and polyimide-cushioned pin structure. All of the approaches were shown to reduce the pin joint stress significantly and, as a consequence, led to the construction of a robust pin joint that is fully compatible with the glass ceramic substrate