| In order to meet the needs of high bandwidth,high integration and high performance in the electronic industry,the third-generation wide band gap semiconductor materials have been rapidly developed and applied because of their excellent physical and electrical properties.Silicon Carbide（Si C）,as an important representative of the third-generation semiconductor,has gradually become a substitute for silicon-based（Si）devices because of its excellent high temperature and high frequency characteristics.However,Si C will be accompanied by high temperature due to high power density,which will lead to high failure efficiency and low reliability.In this paper,the effects of connecting material,connecting layer thickness and packaging structure on the heat dissipation characteristics and reliability of Si C power devices are studied through the finite element simulation platform,and the reliability of single-sided mounting structure and double-sided mounting structure under temperature cyclic load is further studied with reference to JEDEC industrial standard.The four connecting materials Nano-Ag,SAC305,Au20 Sn and Pb90Sn10 are compared.The heat dissipation performance of the packaging structure using Nano-Ag as the connecting material is better than that of the other three connecting materials,which can reduce the maximum junction temperature of the chip by nearly4 ℃.And the maximum equivalent stress of the model accounts for about 30%-40% of the maximum equivalent stress of the other three material models.Therefore,Nano-Ag is considered to be the best connecting material in terms of thermal characteristics and reliability.For different connecting layer thickness,the maximum junction temperature of the chip increases by about 0.05 ℃ every 25 microns.The maximum equivalent stress of the model with a connecting layer thickness of 50 microns is similar to that with a connecting layer thickness of 75 microns.The equivalent stress of the 25 microns thickness model is about 1.5 times that of the first two models,and the maximum equivalent stress of the 100 microns thickness model is about 90% of that of the first two models.Considering the thermal characteristics,reliability and cost,it is considered that the thickness of 50 microns is the optimal thickness of the connecting layer.Under the same power,the heat dissipation performance of double-sided mounting structure is 40% higher than that of singlesided mounting structure.In terms of reliability performance,from the analysis of the maximum equivalent stress of the overall structure,the maximum equivalent stress of the double-sided mounting structure is 4.46 MPa lower than that of the singlesided mounting structure.The maximum equivalent stress of single-sided mounting appears at the connecting layer,while the maximum equivalent stress of double-sided mounting appears on the chip.When studying the reliability of single-sided mount structure and double-sided mount structure in the process of temperature cycle,it is found that both of them have periodic warpage deformation,periodic equivalent stress and plastic strain.The deformation amplitude of double-sided mounting is about 3 times that of single-sided mounting structure.The difference of packaging structure leads to a great difference in the stress level of the connection layer between single-sided mount structure and double-sided mount structure.The maximum equivalent stress of single-sided mount structure appears at the connection layer below the diode,while the maximum equivalent stress of double-sided mount structure appears at the connection layer between Si C MOSFET and pad.After cyclic loading,the cumulative plastic strain of double-sided mount structure is about 1.2 times that of single-sided mount structure.The life prediction model based on plastic strain is used to predict the life of the two structures.The results show that under the same cycle conditions,the fatigue life of the double-sided mounting structure is about 85% of that of the single-sided mounting structure. |
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