Research On Heat Transfer Characteristics And Equivalent Thermal Impedance Model Of IGBT Module

IGBT module is widely used in new energy power generation,power system,electric vehicle,rail transit,household appliances and other fields with its unique and excellent performance.However,due to the characteristics of high integration and power density,IGBT module has a high internal chip temperature,which has a great impact on the reliability of electronic devices.Therefore,it is necessary to study the thermal reliability of IGBT module.The thermal impedance model prediction method is widely used in the thermal simulation of semiconductor power modules,in which the Cauer heat transfer equivalent circuit model can predict and calculate the temperature of each layer of IGBT module.However,the calculation of thermal resistance and heat capacity of the traditional Cauer equivalent model is not accurate,and due to the thermal cross coupling effect,it will greatly affect the temperature prediction of IGBT module chip,so it is necessary to improve it.Firstly,based on the traditional Cauer model,this paper presents a method to determine the thermal diffusion angle by using the heat flux curve of the vertical downward path of the chip center.Based on the thermal resistance and heat capacity calculated by the thermal spreading angle,an improved single-chip Cauer network model is established and verified by the finite element software.Then,based on the single-chip Cauer network model,through the study of the thermal coupling effect between chips,the multi chip thermal impedance matrix model of IGBT module is established and the parameters in the model are calculated.The junction temperature calculated by the model is compared with the finite element simulation value.Finally,by studying the relationship between thermal conductivity and temperature,based on the previous single-chip and multi-chip models,a thermal impedance model considering the influence of temperature on the thermal conductivity is established and the parameters in the model are calculated.The validity and accuracy of the model are verified by comparing the junction temperature calculated by the model with the finite element simulation value.At the same time,the influences of chip power consumption,heat dissipation conditions and chip size on the model are also studied.Compared with the traditional thermal impedance model,the model established in this paper fully considers the influence of three factors: thermal diffusion,thermal coupling and thermal conductivity related to temperature,and the calculated junction temperature value is more accurate.