Reliability Study of Microwave Transistors

Four types of microwave transistors were tested for D. C. electromigration under accelerated to typical use conditions. A lower activation energy was obtained along with a larger preexponential constant and smaller exponent for current density for the typical electromigration equation. Three of the transistor types were also run in an operational life test at 2.0GHz. After 5,000 hours of testing, the beginnings of a correlation between the D.C. and R.F. testing have appeared. Also oscillators have failed; while amplifiers have not. Power cycling of gold lead wires has shown no fatigue deterioration of the wires or bonds. Temperature step stress showed a semiconductor device cannot be used above its eutectic temperature. A computer model is used to calculate operating temperature at high case temperature and power loading, where actual measurements are difficult to make and intrepret.