Analysis Of Electrothermal Characteristics And Short Circuit Failure Of Press-Pack IGBT

Press pack IGBT(PPI)is a key component of flexible DC transmission equipment.Compared with traditional welding type devices,it has the advantages of compact structure,short circuit,double-side heat dissipation,and high reliability.The development of domestically-manufactured PPIs and their extensive use in converter valves and circuit breakers is of great significance for improving the power level of the grid and the reliability of the system.PPI maintains tight contact between the electrodes through pressure.If the pressure is unbalanced or the PPI fails to enter a stable short-circuit failure mode,the PPI will hardly exhibit its packaging advantages and serve the grid stably.Considering this problem,studies will be conducted in two aspects in this paper;On the one hand,simulation and experiments are combined to study the characteristics of PPI and its correlation with stress;On the other hand,the short-circuit failure mode of PPI devices is experimentally studied.The main work includes the following aspects:Firstly,the static and dynamic characteristics of the PPIs and their correlation with pressure and temperature are studied.A characteristics test platform are built following the steps: Combine the B1505 A with the thermostat to test static parameters under different temperature conditions.The experimental fixture of the PPI was developed to test the basic characteristics of PPI under different pressure conditions.The relationship between the temperature and the threshold voltage of the device and the saturation voltage drop was analyzed,and the relationship between the applied pressure and the contact resistance and contact thermal resistance of the PPI device was discussed.Secondly,there is pressure unbalance among the chips in the multi-chip parallel module.In this paper a method is proposed to simulate the influence of unbalanced pressure on multi-chip by connecting single Chips in parallel.Firstly,combining the measured characteristics and material properties,a single-chip PPI finite element model(FEM)is established with COMSOL software,which is further extended to a multi-chip parallel finite element model;then,a two-chip parallel module is established to verify the effectiveness of the established parallel FEM;finally,the parallel model is used to study the 1500 A PPI module through the simulation analysis,involving the electro-thermal distribution under unbalance pressure.Finally,the short circuit failure mode of PPI device is studied,including building a short circuit test platform,conducting a short circuit test,obtaining a chip sample that has failed in a short circuit,and using electron microscopy to analyze the failure point through the microstructure.To analyze the aging mechanism,the short-circuit tolerance test is conducted to study the short-circuit aging of the chip and the process of failure to the final open circuit.The large current pulse short-circuit experiment is conducted by adding the bus inductance based on the short-circuit failure process to simulate the circuit breaker and find out its failure mode and analyze the failure reason.