Study On Failure Analysis And Condition Monitoring Method Of IGBT Bonding Wire Based On Multi-physical Field Model

As the key device of power electronic device,IGBT has been widely used in the fields of new energy generation,smart grid and high-speed train traction.However,in order to meet the development needs of miniaturization and high power density of IGBT module,the severe impact of temperature fluctuation and cyclic shear stress inside the module is also increasing,which makes the failure of IGBT module more and more serious.The existing research shows that the converter fault caused by power module is as high as 31%.Among them,about 70% of the failure of power module is caused by the failure of bonding wire.Therefore,in-depth study on the aging,failure mechanism and condition monitoring of IGBT module bonding wire is the key problem to be solved in the application of power devices.According to the actual structural and material parameters of the IGBT module,the metallization layer on the front of the chip is added.By using the finite element simulation software,the IGBT single chip multi physical field model and the IGBT multi chip electrothermal coupling model are established.On this basis,the influence of IGBT module material selection and matching on its bonding wire failure is analyzed,and an optimal material selection and matching scheme to reduce the failure risk of IGBT module bonding wire is proposed.Finally,the ability of temperature gradient to characterize the thermal behavior of IGBT module is analyzed,and a method of monitoring the bonding wire state of IGBT module based on temperature gradient is proposed.The main innovations of this paper are as follows:(1)An optimal material selection and matching scheme to reduce the failure risk of IGBT module bonding wire is proposed.Based on the model of IGBT single chip and multi physical field,the effects of different bonding wire materials,front metallized layer materials and their material combination on the temperature and shear stress in IGBT module are analyzed.The results show that the bonding wire material has a direct impact on the maximum temperature and the maximum shear stress in the module.Compared with aluminum bonding wire,copper bonding wire can significantly reduce the temperature in the module.The front metallized layer has a direct impact on the shear stress in the module.Compared with the front metallized aluminum layer,the front metallized copper layer can significantly reduce the shearstress in the module.The combination of copper bonding wire and front metallized copper layer can reduce the maximum temperature and shear stress of bonding wire in the module to the greatest extent,which is the best material selection and matching scheme for IGBT module.This scheme can reduce the failure risk of bonding wire to the greatest extent and improve the reliability of IGBT module bonding wire.(2)A temperature gradient based state monitoring method for IGBT module bonding wire is proposed.Taking the failure of bonding wire as the research direction,firstly,the single-chip and multi physical field model of IGBT is improved,and the multi chip electrothermal coupling model of IGBT is established.Secondly,the influence of the number and position of bonding wires on the internal thermal characteristics of IGBT module is analyzed.The simulation results show that the change of the number of bonding wires is the main factor that causes the maximum temperature change of IGBT module.Meanwhile,the part of bonding wires on a single IGBT chip has little influence on the operating temperature of IGBT module,so it will not affect the IGBT module to continue to operate.However,when all bonding wires on the chip fall off,due to the current sharing effect,it will make the operating temperature of other chips rise sharply,and then accelerate the fall off of the remaining bonding wires,which eventually leads to the failure of IGBT module when the operating temperature exceeds the maximum allowable junction temperature.Finally,based on the influence of the failure of bonding wire on the operating temperature of IGBT module,a method of monitoring the bonding wire status of IGBT module based on temperature gradient is proposed.Compared with monitoring the operating temperature of IGBT module,this method has higher accuracy and sensitivity.In addition,the judgment interval and transition interval for monitoring the number of missing bonding wires of IGBT module are defined,which provides the judgment basis for the condition monitoring of bonding wires.