Power Cycling of Sintered SiC Power MOSFET Baseplate-less Modules with Aluminum Oxide and Silicon Nitride Substrates

This paper shows a comparison of power cycling (PC) lifetime between SiC power MOSFET baseplate-less modules with Si3N4 and Al2O3 DBC substrates at heating on/off-times of 2 s. As the modules were designed with soft Si-gel encapsulation and silver sinter die attach, the dominant failure mechanism was bond wire lift-off. Electro-thermal-mechanical (ETM) simulations are performed to support the lifetime analysis on a small set of statistical data. The results point out that the PC capability of the Al wires is not significantly affected by changing the semiconductor material from Si to SiC. Furthermore, the developed ETM simulations show that Si3N4 substrates will cause a faster temperature rise time, but will not lead to a significantly higher thermo-mechanical stress of the bond wire foot.