The Reliability of High Temperature Pb-Free Solder for High Power Semiconductor Device Packaging

Abstract:
The die attach material which can withstand high temperature is significant in the power module device packaging. SAC and SnSb alloys are the popular material for the Pb-free type of die attach applications where their melting temperature are typically around 220℃ and 240℃ respectively. Here the Pb-free solder alloy which has a melting temperature of ~340℃ has considered to achieve better reliability and significantly higher shear strength than base line solders. The solder material after the processes of isothermal aging at 200℃ and thermal shock test for 1000 cycles (DeltaT=225K) maintained their superior shear strength. Thermal resistance of this solder material and SAM scan for different sizes of die has confirmed no significant changes and no die soldered degradation after isothermal aging and thermal shock tests. There are no significant changes of IMC layer thickness after the aging test which has confirmed the material is suitable for Ni metallized AMB substrate and Ag metallized die surfaces. The substrate level power cycling with DeltaT=120K confirmed the high temperature Pb-free solder material (HT solder) performed 2.48 times cycles considered the forward voltage VCE(on) less than 5% and the end of life 2.1 times cycles compared to the SAC solder without die solder degradation.