Impact of Combined Thermo-Mechanical and Electro-Chemical Stress on the Lifetime of Power Electronic Devices

In this work, the impact of previous thermo-mechanical stress on the humidity ruggedness of IGBTs was investigated. For this purpose, a combined power cycling test (PCT) and high humidity, high temperature, reverse bias (H
³
TRB) reliability test was performed. In order to quantify a possible impact based on the amount of previous stress, devices of different health conditions were used. Some devices were subject to power cycling for 50% of their estimated cycles to failure before being tested in an H
³
TRB test. Other devices were preconditioned in power cycling until the end of life criterion was reached before they were subject to the H
³
TRB test. The results of this work indicate that previous thermo-mechanical stress does have an impact on the H
³
TRB performance of at least some of the tested devices. Furthermore, the test results do not clearly indicate a significant difference between the devices, which were preconditioned with 50% of their cycles to failure and the devices, which were subject to power cycling until end of life.