Current-Leakage Failures in Hybrid Microcircuits

Electrical failures due to excessive current leakage have been observed in several hybrids during both hot and cold temperature testing. Failures have been correlated with increased amounts of ionic and gaseous contamination in the package. Short-term failures at cold temperature appeared to be due to ammonia (from the substrate-attach epoxy) condensing on the substrate and acting as a conductive medium for ionic and polar species adsorbed on the surface. Short-term failures at hot temperature were consistent with surface inversion leakage. Long-term failures after burn-in at 125°C were due to silver electromigration from the die-attach epoxy. Associated materials and electronic testing are also reported.