Research On Failure Mechanism And Health Evaluation Of IGBT Bonding Wire

As the core equipment of electric energy conversion,power converters have been widely used in rail transit,aerospace,new energy vehicles and other fields,its operational safety and reliability have attracted widespread attention from scientific researchers and operation managers.As the core device of the power converter,insulated gate bipolar transistor(IGBT)’s state of health determines the reliability of the entire power converter to a certain extent.As the electrical connection between the IGBT module chip and the Direct Bonding Copper(DBC),the bonding wire is prone to aging failure,once the failure occurs,it will bring high maintenance costs and even cause serious safety accidents and huge economic losses.Therefore,in view of the aging failure of the IGBT module bonding wire,the failure mechanism and failure effects of IGBT module bonding wire are analyzed,and the suitable characteristic parameters of the IGBT module are selected to evaluate the health state of the bonding wire.The main work and research contents of this paper are as follows:Firstly,the structure,operating characteristics,failure types and failure mechanisms of IGBT modules are introduced.The influence of IGBT module bonding wire failure is analyzed in theory,which provides a theoretical basis for subsequent IGBT bonding wire failure analysis and bonding wire health state assessment.Secondly,aiming at the current single electric-thermal simulation model or thermalmechanical simulation model cannot simultaneously consider the influence of electrical,thermal,and mechanical characteristics on the fatigue failure of the IGBT module bonding wire,in this paper,considering the failure of the bonding wire,the IGBT module electricthermal-force multi-physics coupling simulation model is established,and the temperature distribution and stress distribution of the IGBT module under steady-state heat transfer and power cycling conditions are analyzed through this model.The analysis has drawn the following conclusions:(1)The temperature and stress where the bonding wire and the chip are bonded to bear the greatest,and long-term stress fluctuations can easily lead to fatigue accumulation damage and bond fall failure;(2)Excessive junction temperature fluctuations will lead to faster accumulation of bond wire fatigue,and reducing the fluctuation range of junction temperature can prolong the service life of the device;(3)Once the module has a bonding wire falling off,the temperature of the remaining bonding wire of the module will rise and the stress will increase,which will accelerate the aging failure of the module.Finally,aiming at the problems that the internal faults of the IGBT module are not easy to directly monitor and the health status of the bonding wires are difficult to evaluate,this paper proposes an IGBT module bonding wire health evaluation model based on the differential gray wolf pack algorithm optimization support vector machine.Through theoretical analysis and experimental verification,the ambient temperature,saturation voltage drop,and collector current are determined as characteristic parameters for IGBT module bonding wire health assessment.The test data of IGBT modules under different health conditions are verified by experiments,and the evaluation accuracy rate is 94.03%,which verifies the validity of the evaluation model proposed in this paper.