Evaluation of the Degradation in Electrothermal Characteristics of IGBTs During Thermal Cycling Cocaused by Solder Cracking and Al-Wires Lifting-Off Based on Iterative Looping

Abstract

The evaluation of dynamic degradation in electrothermal characteristics of insulated gate bipolar transistors (IGBTs) caused by package fatiguing is critical to the operating safe and reliable application of IGBTs under their long-term servicing. In the present work, the degradation mechanism in electro thermal characteristics of IGBTs caused by package fatiguing (die-attach solder cracking and Al-wires lifting-off) was analyzed, first. An iterative looping consisting of the electrothermal simulation, fatigue damage calculation, and degradation of electrothermal characteristics in IGBTs was proposed based on the physics of failure. Based on that, the degradation in electrothermal characteristics of IGBTs during power cycling (PC) caused by the two fatigue modes was investigated. PC tests were carried out to 1700 V/3600 A IGBT modules under various conditions for verifications. Under six various PC conditions, the maximum of errors is lower than 7%. It indicates well consistence with experiments. The proposed iterative looping directly simulates the degradation of electrothermal characteristics of IGBTs during thermal cycling. It may provide a possibility of evaluating offline or online the important electrothermal parameters of IGBTs (such as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_CEsat</i> ) during operating, which is meaningful for diagnosing the safe operating area of IGBTs after long-term servicing.