End-of-life assessment of silicon IGBT and silicon-carbide MOSFET

Abstract

The reliability of power semiconductor devices is an important feature when designing converter, since the semiconductors are prone to failure and a weak link in the system. Power semiconductor devices are susceptible to thermo-mechanical stresses, and should be investigated to make reliable semiconductors. The power losses inside the device resulting in thermal cycling and expanding and contracting the layers of the semiconductors with different rates, are the cause of the thermomechanical stresses. Thermo-mechanical fatigues are the most frequently encountered forms of failure in power devices, e.g. bond wire lift-off, solder cracks, and reconstruction of chip materialization. In this thesis, the end-of-life assessment of the silicon IGBT and silicon-carbide MOSFET are investigated. Specifically the power cycling test can replicate the thermo-mechanical stresses and wear out the device in a couple of weeks [8], [9]. Multple short power cycling tests are executed to find the relationship between the selected parameters and resulting thermal cycle. Furthermore, the thermal response measurements are used to study the thermal behaviour of the semiconductor devices and thermal fatigues. In addition, the thermal model for the test system is arrived, making it possible to create a testbed for the power cycling test for different thermal cycles. Lastly, the end-of-life assessment is executed for 23 days on eight silicon IGBTs.