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 (H3TRB) 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 H3TRB test. Other devices were preconditioned in power cycling until the end of life criterion was reached before they were subject to the H3TRB test. The results of this work indicate that previous thermo-mechanical stress does have an impact on the H3TRB 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.