Novel failure mechanism on 60-Volt technology beam-lead SIC: Field and experimental results on HICs.

The 620AF SIC is a beam-lead 60-volt technology device which performs a relay driving function. This SIC and its predecessor, the 620E, have a history of field reliability problems. The purpose of this memorandum is to examine the primary field- failure mechanism, summarize the field-failure data on HICs, and compare the field data with experimental results from laboratory accelerated tests on HICs. Field data on the 620AF indicates that this SIC exhibits a maximum long-term failure rate which is about two orders of magnitude higher than expected. The primary failure mode is corrosion occurring at the beam/substrate interface. This failure mode has been reproduced in the laboratory under bias-humidity-temperature (BHT) test conditions. A comparison of the failure kinetics under both field and BHT test conditions indicates an acceleration factor which is alarmingly low, suggesting that further investigation of humidity acceleration factors for ICs and a reassessment of BHT test requirements is necessary. The use of wire- bond technology has been investigated as an alternative to beam leads and appears to minimize the effects of the type of corrosion prevalent in the 620AF. For improved device reliability, the use of wire-bond technology is suggested for all SICs designed for use at or above a beam-to-substrate potential of 60 volts.