Fault Diagnosis Analysis And Fatigue Life Prediction On Power Devices

As a power switch device, IGBT have the advantages of a big current carrying densityand low saturation voltage, so have been widely used in power transformation and powerelectronic equipment. But with the increase of switching frequency and power density,thepower loss and junction temperature fluctuations of IGBT cause the fatigue damage of powerdevice.At home and abroad have carried on the thorough of failure mechanism of powerdevice caused by the temperature fluctuation, and on this basis,have developed the powermodule fatigue life prediction technology to improve the reliability of the converter when runin a complex environment.Based on the IGBT power module as the research object, this paperhave researched on the thermal-electrical module,the fatigue life prediction and reliabilityevaluation, etc.(1)First introduce the mechanical structure and physical structure of IGBT module, analysethe two main forms of the failure of IGBT modules. From the perspective of thermalmechanical stress, analyse the inner mechanism of the bonding line loss and the fatiguefailure of ageing solder layer of IGBT module.(2) Establish the thermal-electrical model of IGBT module, build the Coffin-Mason fatiguelife prediction model which based on the fatigue cumulative damage theory. Based on theelectrical-thermal analysis and the thermal-mechanical stress analysis, make life prediction ofthe bonding point and solder layer of IGBT. This method can explore the characteristics ofjunction temperature and the fatigue life of module at different condition, and optimizationthe design of thermal-electrical module and long-term reliability of work performance.(3) The thermal shock resistance is one of the important factors affecting the reliability ofmodule, from the Angle of material physics and the power loss to explore the thermal shockresistance of the layers of material, the studies have shown that thermal stability of the IGBTmodule mainly thermal damage, the thermal shock effect cannot directly cause fracture of thelayers.(4) Based on the finite element analysis method, the quantitative explore the overload currentto the influence of thermal characteristics and fatigue properties for the bonding line. Theresearch results show that when the overload current reached20%, overrun the rated junctiontemperature of the module, the fatigue life fell by96%. This method and the results can helpdesigners to evaluate different overload conditions affect the performance of the module andoptimization design of the module.