Reliability Optimization of Gold-Tin Eutectic Die Attach Layer in HEMT Package

This paper compared the fatigue damage accumulation of the gold-tin eutectic die attach layer in different high electron mobility transistor (HEMT) packages with various types of die attach layers and substrates under thermal cyclic loading. The fatigue damage per cycle used in this study was characterized by the accumulation of plastic work, which was derived by the finite element analysis (FEA). The effects of die attach layer's standoff height and thickness of substrate on fatigue damage accumulation was discussed. The results show that increasing the standoff height of the die attach layer is an effective way to prevent the early crack initiation in gold-tin die attach layer especially for a gallium nitride (GaN) die. It is also indicated that for a GaN die, a thicker die attach layer and a thinner substrate are preferable in order to retain a comparable lifetime with silicon (Si) die and Cu substrate system.