Fatigue Life Prediction Of Single-chip Submodule Of Press-Pack IGBTs Based On Finite Element Method

The traditional IGBT module has become more and more difficult to adapt to the more severe working conditions in the field of flexible DC transmission and locomotive traction,and the problem of reliability is more and more prominent.Due to its advantages of double-sided cooling,easy connection and short circuit failure,the new type of Press-Pack IGBTs have been gradually emerging in the field of IGBT new packaging,and has become a hot research topic worldwide.The package structure of the Press-Pack IGBTs is quite different from IGBT modules,so they have completely different long-term reliability problems.The Press-Pack IGBTs is laminating structures superimposed on various metal materials and silicon chips.In the process of working,each material will be squeezed and rubbed because of the cause of heat expansion and contraction.After a period of time,various metal materials will have varying degrees of deformation,which affect the performance of the device.Power cycling test is the most commonly used test for power semiconductor devices,which can be used to assess the reliability of the device through simulating the actual working conditions.But the real test cycle is long and the investment is large,and people lack experience in the encapsulation of new devices.Therefore,we must first simulate and understand some basic characteristics,and make preliminary research on device reliability,so as to lay the foundation for subsequent reliability tests such as power cycling test.Based on the above ideas,we use the finite element simulation software COMSOL Multiphysics to carry out the power cycling simulation of the pedestal-style Press-Pack IGBTs,and predict the fatigue life of the device.During the power cycling process,the elastoplastic behavior of various metal materials is described by the kinematic hardening model.Meanwhile,the fatigue weaknesses of the device are found,and the thermal and mechanical properties of the device are studied.Then,the characteristics of the metal material in the process of power cycle are used,and the fatigue life prediction model is carried out with the fatigue life prediction model.In this paper,the life cycle of IGBT devices under different working conditions is studied by changing the boundary conditions such as cycle period,applied pressure and heat dissipation.At the same time,different strain fatigue life models and fretting fatigue life models were used to predict the life of Press-Pack IGBTs,and the applicability of various life models were compared.Finally,we compare the simulation results with the real IGBT failure chip,explain and analyze the failure mode and failure mechanism of the Press-Pack IGBTs,and provide some ideas for future device optimization direction.