Thermal And Mechanical Performance Analyses Of Power Semiconductor Device IGBT Based On Infrared Testing And Numerical Simulation

Electric energy is one of the most important energy sources in the world.The power frequency electric energy obtained from the power grid needs to be converted to meet the needs of ever-changing electrical devices.The Insulated Gate Bipolar Transistor(IGBT)is the most advanced power electronic device that can realize power conversion and control due to its advantages such as high input impedance,fast switching speed,large current density,low saturation voltage and strong current processing capacity.High-power IGBT modules tend to operate at high switching frequency and large current,which makes the IGBT chip have a large power losses,resulting in an increase in the junction temperature of the chip.The temperature has a great influence on the reliability of the IGBT.On the one hand,the high temperature will directly burn down the IGBT chip and cause the failure of the device.On the other hand,due to the different thermal expansion coefficients of different materials in the IGBT module,the fluctuating temperature will generate thermal stress between different layers,and repeated shocks of thermal stress will cause the generation and expansion of cracks,eventually leading to device failure.Therefore,it is of great significance to study the thermal and mechanical performances of IGBT for improving the reliability of IGBT modules.In this paper,the thermal and mechanical performances of power semiconductor device IGBT modules are analysed in detail by the combination of experimental and numerical simulation.The research contents are as follows:(1)Setting up a power cycling test platform to conduct power cycling tests.In this paper,the experimental circuit of DC power cycling test and PWM power cycling test are designed respectively.According to the power rating of IGBT module and experimental principle,the power cycling test platform is built.The DC power cycling tests and PWM power cycling tests under different operating conditions are carried out.During the experiment,the characteristic parameters of the IGBT module such as saturation voltage drop,case temperature and collector current are monitored.(2)The temperature field of the IGBT module under different experimental conditions were measured.With the help of the external signal trigger shootingfunction of the infrared camera,the temperature field of IGBT module under different working conditions is observed by using the synchronous temperature measurement method,the variable integration time temperature measurement method and the delay temperature measurement method.By comparing and analyzing the temperature measurement results under different experimental conditions,it is found that the junction temperature distribution,the junction temperature rise rate and the junction temperature fluctuation range of the chip are quite different under the conditions of DC tests and PWM tests.By changing the integration time of the infrared camera,the influence of once turn-on and turn-off of the IGBT module under high frequency switching state on the junction temperature of the chip is measured.(3)The electro-thermal-mechanical finite element numerical simulation was carried out to study the influence of junction temperature variation on the IGBT module stress.Firstly,the electro-thermal analysis is carried out,and the switching losses of the IGBT module is taken into account in combination with the experimental measurement results.The current density distribution and the temperature field of the module under DC experimental conditions and PWM experimental conditions are obtained.Then,based on the electro-thermal analysis,the thermo-mechanical analysis is carried out,and the stress distribution and stress change process of the IGBT chip under different working conditions are obtained.The results show that the maximum stress appears at the end of the bonding wire,and the change of the junction temperature of the chip will cause the stress to fluctuate.The change of the stress value is synchronous with the change of the junction temperature of the chip.When the junction temperature rises,the stress increases sharply.