Power Cycling Test And Lifetime Modeling Of Press-pack IGBT

The development of traditional wire-bonded IGBT has encountered the bottleneck because of wire-bonded and welding technology problems.Press-pack IGBT can apply into traditional wire-bonded IGBT area and new area above both because of the advantage of low thermal resistance,impact resistance and the failure mode of short circuit which are in favor of fulfill the demand of high voltage and high power in VSC-HVDC.Recent research analyzes press-pack IGBT's characteristic and improves its performance based on COMSOL.These research are lack of accelerate test and lifetime prediction.This article sets up a press-pack IGBT power-cycling rig and experiments on press-pack IGBT under different conditions,analyzes its failure mechanism and conducts press-pack IGBT lifetime modeling based on test results and failure mechanism.The main research are as follows:(1)At first,this article introduces the main failure mechanism of press-pack IGBT.Then,this article uses COMSOL to build up press-pack IGBT model and sets up electromagnetic heat source,thermal expansion and temperature coupling to realize multi-physics coupling.At last,this article carries out electro-thermal coupling and thermomechanical coupling step by step,and use the results of the former to solve the latter.Finite element simulation result shows that the weak point of the module is the lower surface of the chip,especially the surface between the chip and molybdenum.(2)This article comes up with press-pack IGBT power cycling rig design.Firstly,this article analyzes the aim of power cycling rig design.Secondly,this article conducts specific hardware and software design.At last,this article tests the availability and accuracy of the rig.This rig can control DC source and the driver,collect and store data and stop power cycling when accident happens.This rig lays the foundation of subsequent power cycling tests.(3)This article conducts 1200 N and 600 N power cycling tests,and the test result shows that the main failure modes of press-pack IGBT are fretting wear and gate oxide breakdown by analyzing the changing of test data and microcosmic physical phenomenon.Fretting wear is the main failure mechanism of press-pack IGBT under long time condition while gate oxide breakdown may appears when device has a high degree of aging.The surface of press-pack IGBT is pressed by lower molybdenum during power cycling.Silicon of the chip and metal oxide are destroyed because of horizontal and vertical fretting wear at last.This result lays the foundation of lifetime prediction.At last,this article studies the reliability of sintered/unsintered chip and press-pack IGBT under deferent pressure.(4)This article fits the lifetime model parameters of press-pack IGBT based on test data,and analyze the validity of these models according to physical characteristics of press-pack IGBT.This article gets some conclusions: morrow modified model accords with physical laws while the model ignores the influence of average chip temperature,Coffin-Manson modified model is suitable to predict the lifetime of press-pack IGBT within pressure limit.