A three-dimensional finite element analysis model of ball grid array (BGA) package is constructed by SolidWorks software.The Anand constitutive model is used to describe the constitutive relationship of solder SAC305.ANSYS simulation software is used to simulate the temperature

stress

and strain distributions of solder joints under the power cycle of the chip.The results show that the thermal fatigue vulnerable area of BGA solder joints is located at the edges and corners of the model.The viscoplastic strain increases with the prolongation of cycling time

resulting in the accumulation of viscoplastic strain in the solder joints

and eventually leading to thermal fatigue failure.