Secondary Breakdown In Power Transistors

1E4 987 SECONDARY BREAKDOWN IN POWER TRANSISTORS by Sue Cain a- Ray Ashmore This article examines the different types of secondary breakdown that occur in power transistors, and investigates the phenomena that cause them. It concludes that secondary breakdown is a function of transistor technology, and cannot always be improved without some trade-off in other parameters. One of the basic failure mechanisms in power tran- sistors is second breakdown. This term includes various physical phenomena which are completely different. They de- pend on the different use of transistors in the circuits and have in common the electrical and thermal instability inherent in transistors themselves. The conduction behaviour of an emitter base junction and the current gain of a transistor de- pend significantly on the tem- perature and increase as a function of the temperature. Electrical and thermal in- stabilities may act simul- taneously within the device, thereby giving rise to destruc- tive se...