An accelerated thermal aging platform to monitor fault precursor on-state resistance

Thermal cycling is one of the main techniques to accelerate the package related failure progress. In this paper, a custom designed accelerated ageing platform that can expose multiple discrete power MOSFETs to thermal stress simultaneously, is introduced. Active heating, without using external loads, is used to increase the junction temperatures of the devices from a single current source, where temperature swing for each device can be controlled independently. The issues during the measurements such as high off-state drain- to-source voltage, and transients during turning on instants are addressed. The variation of the on-state resistance is identified as the failure precursor. It is observed that on-state resistance increases by 10%-17% of its initial value before it completely fails. Based on the collected field data, an exponential degradation model that fits successfully with the experimental data is developed.