Thermomechanical reliability of low-temperature sintered silver die attached SiC power device assembly

A thermomechanical reliability study was conducted on a low-temperature sintered silver die attached SiC power device assembly. The silver die attachment was formed by sintering nanoscale silver paste in air at 300 degrees C to form a strong bond between silver- or gold-coated direct-bond-copper substrates and silver-metallized SiC Schottky diodes. Using the 50% drop in the die-shear strength as the failure criterion, an accelerated thermal cycling experiment between 50 degrees C and 250 degrees C showed that the silver die attachment can survive more than 4000 cycles, indicating its high thermomechanical reliability at the interested temperature range. Established mainly by scanning electron microscopy/energy-dispersive spectroscopy, the drop of the die-shear strength during the thermal cycling was attributed to the pile-up of creeping dislocations to form microcavities at the grain boundaries of the sintered silver.