A Lifetime Prediction Method Of IGBT Module Based On The On-resistance Degradation Model

At present,energy shortage,environmental pollution,and climate change have become serious challenges facing the whole world.Against this background,it is one of the effective ways to replace fossil energy with clean energy,promote energy conservation and emission reduction,and reduce environmental pollution by using power electronics technology to efficiently transform and control electric energy and improve the utilization efficiency of electric energy.The insulated gate bipolar transistor(IGBT)is a composite power semiconductor device with fast switching,low power dissipation and high current processing capabilities,which has been widely used in high-power converter systems due to these favorable electrical characteristics.However,due to the multi-layer structure of IGBT module and the mismatch of thermal expansion coefficient between various layers of materials,IGBT module will be subjected to the repetitive thermal stress with the change of operating conditions in the service process,which can cause the fatigue damage of the interconnect structure and the change of the electrical characteristics of the module,and even lead to the permanent failure.On the one hand,in order to meet the application demand,IGBT module is developing towards higher integration degree,higher power density and higher switching speed.This development trend inevitably leads to higher operating temperature of IGBT module,and consequently increases the failure probability and decrease the reliability of IGBT module.On the other hand,with broadening applications,there has been an increasing demand for higer reliability and longer lifetime of IGBT module.Therefore,it is of great significance to carry out the research related to the reliability assessment of IGBT module,especially about failure mode,failure mechanism and lifetime prediction,so as to improve the reliability of IGBT module.In this paper,a lifetime prediction method of IGBT module based on the onresistance degradation model is proposed,including the power loss model,RC thermal network model and on-resistance degradation model.The on-resistance degradation within each power cycling period is calculated by the on-resistance degradation model,and fed back to the power loss model to calculate the power loss change.According to the power loss change,the junction temperature change is calculated by the RC thermal network model,and junction temperature increasing will aggravate the on-resistance degradation.Until the on-resistance degradation meets the failure criterion,the power cycling is finished,and the lifetime of IGBT module is obtained.In order to implement and verify the lifetime prediction method of IGBT module proposed in this paper,the direct current power cycling tests with different conditions are carried out using the power cycling test facility designed and established by ourselves,and the degradation data of IGBT module saturation voltage drop and failure lifetime are obtained.It shows that the saturation voltage drop increases with aging time,and the larger the junction temperature swing is,the faster the degradation rate of IGBT module saturation voltage drop is and the shorter the lifetime is.In addition,the failure analysis results find that bond wire lift-off is the dominant failure mechanism,which can increase the on-resistance of IGBT module,and lead to a sudden increase in the saturation voltage drop.Based on the lifetime prediction method of IGBT module proposed in this paper,the power loss model and RC thermal network model of IGBT module are established respectively,and the electro-thermal model for IGBT module lifetime prediction is established in MATLAB/Simulink.In addition,the temperature field of IGBT module under different power cycling tests is measured by the infrared camera,and compared with the calculated junction temperature of the electro-thermal model.It shows that the longer the turn-on/turn-off time is,the greater the junction temperature swing of IGBT chip is,while the average junction temperature is approximately unchanged.Besides,due to the switching loss,the junction temperature of IGBT chip under the pulse width modulation power cycling tests is higher than that under the direct current power cycling tests,and the junction temperature swing is also larger.In addition,the calculated junction temperature of the electro-thermal model is close to the junction temperature measured by the infrared camera,indicating that the electro-thermal model can calculate the junction temperature of IGBT chip accurately.According to the results of the direct current power cycling tests,the on-resistance degradation model for IGBT module lifetime prediction is established.By the combination of the power loss model,RC thermal network model and on-resistance degradation model,the lifetime prediction method of IGBT module based on the onresistance degradation model is implemented in MATLAB/Simulink,which adopts the on-resistance degradation of IGBT module as the characteristic parameterthe of bond wire fatigue damage and the precursor parameter of IGBT module aging process and failure,taking into account the effect of bond wire damage accumulation on the lifetime of IGBT module.Based on the results of the direct current power cycling tests and electro-thermomechanical finite element analysis,the parameters of the lifetime models based on temperature and mechanical parameters are obtained respectively,which are compared with the lifetime prediction method proposed in this paper.It shows that the lifetime prediction results of the proposed method are closer to the lifetime models based on mechanical parameters.The proposed method can effectively predict the lifetime of IGBT module,provide guidances for a more reasonable power cycling test design,and improve the test efficiency.The lifetimes of IGBT module under the direct current and pulse width modulation power cycling tests are predicted by the lifetime prediction method proposed in this paper.It shows that the larger the junction temperature swing is and the higher the average junction temperature is,the faster the degradation rate of IGBT module onresistance is and the shorter the lifetime is.Compared with the average junction temperature,the effect of junction temperature swing on the on-resistance degradation rate and lifetime of IGBT module is greater.In addition,under the pulse width modulation power cycling tests,the higher the switching frequency,the faster the degradation rate of IGBT module on-resistance is and the shorter the lifetime is.Compared with the direct current power cycling tests,the junction temperature of IGBT module under pulse width modulation power cycling tests is higher due to switching loss,and the lifetime of IGBT module is shorter.The lifetime prediction of the IGBT module in electric vehicle driving system under different driving cycles is carried out using the lifetime prediction method proposed in this paper.It shows that the IGBT module under the urban driving cycle has the shortest lifetime.Although the vehicles are running at a faster speed under the highway driving cycle and rural driving cycle,the fluctuation of speed is smaller than that under the urban driving cycle,and the junction temperature fluctuation of IGBT module is smaller,and consequently the IGBT module has a longer lifetime.