Research On Failure Mechanism Of IGBT Used In Electron Irradiation Accelerator

Insulated gate bipolar transistor(IGBT)is mainly used in high voltage inverter circuit in electron irradiation accelerator.However,due to the change of its working environment,when IGBT works under high voltage and high current conditions,thermal damage will be caused due to thermoelectric shock,which will greatly increase the failure of IGBT.However,the full-bridge circuit structure makes the two transistors of the same arm conduct simultaneously,which will lead to over-current short circuit and damage to multiple devices.In this paper,IGBT is taken as the research object,the analysis of IGBT failure module is carried out reasonably,the steady-state-transient thermal simulation of IGBT module is carried out according to the failure reason,and the actual working condition of IGBT is simulated,and the degradation of IGBT is tested and analyzed.This paper mainly includes:1.Analyze the failure module and give the failure mechanism.In this paper,the IGBT failure module is analyzed.According to the failure analysis process,the field failure data of the failed module is mainly investigated,and the device packaging and the output characteristics before and after dissection are tested.In addition,SAM is used to analyze the micro-regions of the IGBT module,and a preliminary assumption is made on the cause of IGBT module failure,namely,in the high voltage inverter circuit of the electron irradiation accelerator,the main failure causes of IGBT module are overheating damage and overcurrent damage.2.Finite Element Method(FEM)for steady simulation of thermoelectric Stress.In order to understand the effect of thermoelectric stress on IGBT module,the finite element analysis of IGBT module is carried out by ANSYS software.Through steadystate simulation,the following aspects are studied respectively: The effects of different cooling media on the temperature distribution of IGBT modules;the influence of thermal stress on the material form variables of IGBT modules;influence of solder hole area on peak temperature of IGBT Module.Silicone oil as cooling medium has higher heat dissipation capacity than the original transformer oil.Thermal stress will deform each layer of IGBT,thus forming voids or delamination,greatly increasing the thermal resistance the solder layer and Si,reducing the heat dissipation capacity.And finally a vicious cycle is formed,resulting in damage to IGBT modules?3.Finite Element Method(FEM)for transient simulation of thermoelectric stress.The results show that,on the premise of no change in power consumption and frequency,the change of IGBT module peak temperature under different duty cycles is studied.The larger the duty cycle is,the faster the heat accumulation speed is,and the shorter the time for overheating damage is.According to the requirements of actual industrial conditions,the working efficiency can be appropriately reduced to reduce the heat accumulation speed of IGBT modules and reduce heat damage.4.Analysis of punch-through characteristics and parameter degradation in bridge structures.Through simulation and experimental test of IGBT bridge circuit,it can be clearly seen that in rectifying circuit,punch-through phenomenon exists,that is,when dead time is not or lower,short circuit phenomenon is easy to occur in the branch of full bridge structure,thus causing multiple IGBT to burn out.Through actual circuit construction and testing,the influence of different parameters on IGBT induced gate voltage in bridge structure is extracted,and improvement suggestions are given to reduce the punch-through risk.In addition,according to the degradation of its electrical parameters and the temperature distribution in the working process,the causes and possible effects of device parameter drift are discussed,and a feasible optimization scheme is given.