Reliability evaluation of car power module using electrical-thermal-structural coupled analysis based on field driving data

Car makers usually use the power cycle test to measure the thermal fatigue life of the solder joint in the module. Power cycle test is a test to impress a constant current at a fixed period and then cool down the module to low temperature repeatedly. But, it is difficult to simulate the field conditions by this test method. Because, in the actual use environment, the irregular current flows with an irregular cycle. In this research, analysis in the conditions near real usage environment was conducted. It aims at establishment of the reliability assessment method of the power module near a real operating condition. A general 1GBT module was designed and FEM analytical model was developed to simulate the fatigue life. Firstly, electrical-thermal-structural coupled analysis were carried out to investigate which factors of the operation condition show the remarkable impact on the fatigue life. Based upon the analytical result from impart rate study, a simple driving model with different actual driving condition was proposed and the fatigue life estimation approach was confirmed. It was shown that the proposed method can be used to simulate the fatigue life in field driving condition and compare the relation of the result between the field date and power-cycle test.