Research On Physical Lifetime Prediction Model Of IGBT Module For Solder Layer Fatigue

As a key device for medium and high-power converters,IGBT modules are widely used in emerging fields such as electric vehicles,renewable energy generation and smart grids.The reliability research of IGBT modules is a hot topic in the power electronics.The solder layers,one of the most susceptible part in IGBT modules,play a vital role in the heat dissipation performance of IGBT modules.Therefore,it is of great significance to explore the failure mechanism of solder layers and the influence of initiation and propagation of voids on the reliability of IGBT modules.There are many lifetime models for the solder layer failure,among which the lifetime models based on the plastic strain energy is receiving more and more attention of scholars at home and abroad because of its advantages in describing the stress-strain mechanism of the solder material during the aging process.However,in the existing energy-based lifetime models,the plastic strain energy density of the critical region is assumed to be constant,but in fact it changes greatly at different aging stages,and there is no reliable mathematical model to describe the failure process of solder layers.Therefore,in view of the above problems,a half-bridge IGBT module FF150R12ME3 G is carried out this paper.The finite element simulation models for different aging stages of the solder layer are established,which are used to analyzed the relationship between the junction temperature,thermal resistance and propagation of the voids.And based on the Clech algorithm,the failure process of solder layer is described.By using Clech algorithm,it has also been proved that the finite element simulation results of the plastic strain energy density in the dangerous zone of the solder layer will change with the aging of the solder layer.The Clech algorithm greatly reduces the calculation time and improves the calculation efficiency.In addition,combining with the existing lifetime model besed on plastic strain energy,a physical lifetime model that can describe the degradation process of the solder layer is proposed: the solder layer is evenly divided into many elements by the meshing function of FEA(Finite Element Analysis).It is assumed that the critical plastic strain energy of each element is constant.The plastic strain energy density of the solder layer before the crack initiation stage is extracted.The aging experiment is used to determine the moment of crack initiation,which has passed many cycles,and then the failure energy of each element of the solder layer is obtained.The killing element of FEA is used to imitate crack propagation and extract the junction temperature and thermal resistance at different aging stages.And the cycle of aging failure of the element is calculated.In FEA,killing the element will reduce the heat dissipation area of the solder layer and lead to increase of thermal resistance.The thermal resistance is widely used to evaluate the reliability of solder layers.Therefore,in this paper,an 50% increase of the thermal resistance is used as the failure standard of solder layers.The failure process of the solder layer is first "discretized" and then "continued ".The cycles of different aging stages can be summed to predict life of the IGBT module.Combined with the experimental results of paper published,the error between the experimental results and the prediction results of the new proposed life prediction model in this paper is only about 3.82%.Finally,an aging experiment rig is built for subsequent validation of the proposed model and theory.