Load Current Injection Modes Affected Power Cycling Lifetime and Failure Mechanism of IGBTs

Abstract

In this paper, the influence of load current injection modes (saturation mode and threshold mode), at standard DC power cycling, on the failure mechanism and lifetime of IGBTs is presented. 6 groups of power cycling tests, at almost the same test conditions, with 2 different current injection modes and 2 different packages are performed. The failure mode after power cycling is confirmed by on-line monitored electrical and thermal parameters (forward voltage drop <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CE</sub> and thermal resistance <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">thjs</sub> ) and further by SAM (Scanning Acoustic Micrography) pictures. Failure mechanism is then analyzed and the power cycling lifetime is compared and explained, with the help of finite element simulations. All results show that the threshold load current injection mode, with the gate and collector shorted, in power cycling can indeed reduce the load current to a large extent for the desired junction temperature swing. However, the power cycling lifetime and failure mechanism are changed, especially for devices with bond wire failure. It is not recommended for power cycling lifetime evaluation.