Failure Mechanism Analysis Of IGBT Based On COMSOL Multi Physical Field Coupling Simulation

IGBT module is the core technology of electric vehicles and high-speed rail multiple units.If the aging failure phenomenon occurs and the whole system fails,it will cause a lot of economic losses and casualties.In order to improve the safety and reliability of IGBT module,it is urgent to study its failure mode and failure mechanism.In this regard,scholars at home and abroad have carried out a lot of research,and the research shows that the bonding wire and solder layer of IGBT module are the main failure parts.Therefore,this paper analyzes the coupling relationship among electric field,thermal field and stress field involved in IGBT module of skm50gb12t4.Through COMSOL multiphysis simulation software,the electric thermal mechanical stress multi physical field coupling finite element model of IGBT is established.Through the simulation results,it is concluded that the edge of the foot connecting the bonding wire and the chip is easy to concentrate high temperature and bear high stress,which is easy to break or fall off.The temperature gradient distribution is used to characterize the failure information of solder layer.It is found that when the temperature gradient difference in a continuous region is large,the stress distribution will be large and concentrated on the edge.By establishing the thermal mechanical coupling 2D finite element model of solder layer under temperature cycle,it is confirmed that the fatigue life at the edge of solder layer is obviously lower than that in the interior,which is easy to produce creep Strain,resulting in solder layer aging failure.The reliability and accuracy of the model is verified by comparing with other literatures using the same type of IGBT module.Finally,the above two failure modes are simulated.The temperature distribution of the IGBT module will be seriously affected by the falling off of the bonding wire.The junction temperature of the module will be significantly increased,and the shell temperature will be less affected.The stress of the remaining bonding wire will gradually increase,resulting in chain shedding effect.According to the failure mode of solder layer cavity,a kind of spherical cavity is proposed,and the cavities with different radius are located in the center and corner of upper solder layer respectively.The results show that the hole in the corner position is more likely to affect the IGBT module,and with the increase of the radius of 0.2mm,the negative effect starts to intensify,the junction temperature will increase significantly,and the shell temperature will basically remain stable.The edge of the cavity will concentrate the higher temperature and stress distribution,and the chip above the hole will also concentrate the higher temperature distribution.Finally,the data obtained from fault analysis can help to monitor the failure of IGBT module,and the fault type can be judged by the maximum junction temperature position and the rising trend of diode chip temperature.