Study On The Thermal Stress Distribution And Its Relevance With The Lifetime Of IGBT Module

IGBT power module is one of the most essential power devices in solar,wind and other renewable energy sources distributed generation systems.The reliability and stability of IGBT module will affect the reliable operation of the entire power system.Therefore,we must ensure and improve the reliability of IGBT module.In the long-term cycle of switching operation,IGBT module is under temperature and stress impact.Excessive thermal stress will cause material fatigue,severe overheating will produce stress failure,thus endanger the stability of the whole system.So to explore the relevance of thermal stress distribution and its lifetime is of great significance for improving the reliability of the device.The failure of IGBT module includes electrical overstress failure,mechanical overstress failure,over thermal stress failure.Thermo-mechanical fatigue of packaging material in IGBT module will be caused if work in the long-term thermal stress impact,resulting in solder layer peeling,bonding wires shedding and other over thermal stress failure.In order to analyze the temperature distribution of IGBT module,a temperature acquisition system is built,which realizes online monitoring and synchronization acquisition of the junction temperature and case temperature.Three-dimensional finite element model of IGBT module cooling system is established to obtain the temperature field distribution of the IGBT module.Then the simulation data of junction temperature and case temperature is compared with the measured data to verify the validity of the finite element model.In order to explore the influence of the distribution of the thermal stress to the lifetime of IGBT module,thermal stress simulation analysis is made,which includes the influence of solder layer thickness,void ratio and position of the void to the junction temperature and thermal stress distribution.And it also provides a theoretical basis for optimized design of IGBT module package.At the same time,IGBT module finite element model is built which includes temperature distribution and stress distribution when the bonding wire shedding percentage is different,and analyze the relevance of bonding wires shedding percentage and lifetime of the module.