Electro-thermal-mechanical Stress Multiphysics Modeling And Failure Analysis Of Nanosilver Sintered Package Press Pack IGBT

The Press Pack Insulated Gate Bipolar Transistor(PP-IGBT)devices with the advantages of high power density,double-sided cooling,and short-circuit failure.Such characteristics make PP-IGBTs are suitable for the working condition of Modular Multilevel converter(MMC)in Voltage Source Converter based High Voltage Direct Current Transmission system(VSC-HVDC).The sintered package can improve the heat dissipation capability of the PP-IGBT device,and it will also change the electrothermal stress distribution inside the device,which may affect the reliability of PP-IGBT.However,the current modeling method cannot characterization the sintered package effect on the electro-thermal stress and fatigue failure of IGBTs,studying the multiphysics modeling and failure analysis of sintered package IGBT(SP-IGBT)with great significance of the device package optimization and the reliability improvement of MMC.In this paper,an electro-thermal-mechanical multi-coupling field model is established based on the structure of a 3.3k V / 50 A single-chip SP-IGBT device,the electro-thermal stress is analyzed,the power cycling aging test is performed on the domestic IGBT and the packaging failure mechanism is studied based on the test results and the finite element model.The main research contents of the thesis include:1 For the existing modeling methods difficult to accurately characterize the influence of sintered package on the internal thermal stress of PP-IGBT devices,the electrothermal-mechanical multi-coupling field finite element model of a 3.3kV/50 A press pack IGBT device is established based on the actual structure and material properties of silver sintered package IGBT based on the actual size structure and material properties of the device,and verified the rationality of the model by the test bench.Firstly,the electrothermal performance of the SP-GBT devices under rated conditions and transient conditions are analyzed.Secondly,the electro-thermal stress characteristic inside the IGBT following the change of clamping pressure and conduction current is analyzed.Then,the aging failure process of the voids in the solder layer is simulated,and the effect of solder fatigue on the internal thermal stress of the silver sintered IGBT device is analyzed.Finally,the impact of solder voids on the reliability of sintered IGBT devices is evaluated.2 Aiming at the problem that the package styles may have effect on the fatigue failure lifetime of IGBT devices,the methods for evaluating the lifetime of IGBT chips based on the improvd stress-strain fatigue of materials and the lifetime of silver solder layers based on creep fatigue are proposed.First,the power cycling simulation of the IGBT device is implemented based on the finite element model to simulate the effect of different junction temperature conditions on the failure effect of IGBT.Secondly,the strain fatigue parameters of IGBT chips and the creep fatigue parameters of solder layers under different junction temperature conditions were extracted.Then,the strain fatigue failure lifetime of the fully pressure package IGBT chip,the silver sintered IGBT chip,and the creep fatigue failure lifetme of the sintered solder layer were calculated.Finally,the fatigue life and reliability difference of fully pressure package and silver sintered package IGBT devices were compared and evaluated.3 In order to compare the long-term reliability difference between the SP-IGBT and the PP-IGBT device,a test platform was established to perform the power cycling accelerate aging test on the domestic 3.3k V / 50 A single-chip press pack IGBT device.First,the results of aging experiments of SP-IGBT devices is analyzed.Secondly,the failure mechanism of the solder layer melting of the SP-IGBT is studied.Finally,the experimental results of SP-IGBT and PP-IGBT devices are compared,and the performance advantages and potential defects of SP-IGBT devices are obtained.The research results lay theoretical foundation for the failure analysis and test of high voltage and high power press-pack IGBTs,which also provide technical support for the packaging design optimization and reliability improvement of press-pack power devices.