Reliability and failure analysis of Cu-Sn transient liquid phase sintered (TLPS) joints under power cycling loads

The continuous increase in application temperatures of power electronic devices demands new packaging technologies capable of working reliably at high temperatures. Most critical among these new packaging technologies is the need for a new kind of interconnection due to the expanding ban on application of currently used lead containing solders in electronics. In this paper, the performance of a potential interconnect technology (TLPS) with low processing and high application temperatures is investigated under power cycling loading conditions. A test setup compatible with power packages was designed and assembled for this study. This test setup cycles and continuously monitors the temperature of power packages fabricated from a commercially available power diode, TLPS joints, and three types of substrates. Devices are cycled under constant current condition until failure. The failure criterion is defined as either an excessive (> 30%) increase in the maximum temperature of the power device or complete electrical failure of the device. The failed samples were destructively analyzed to identify failure modes and mechanisms. Optical Microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive Spectrometry (EDS) were used to perform a comprehensive failure analysis. The results show that the stiffness of Cu-Sn TLPS joints can result in fracture of the semiconductor device. The prevalent failure mode was diode failure (short-circuit) and fracture of the device under thermo-mechanical loading was identified as the failure mechanism. Finally, the reliability effects of using different substrates were investigated and compared.