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Study on the fatigue life of the FC-BGA solder joints with Damage

Previous study shows there are some micro-voids in the SnPb solder joints materials. The imaging of the crack solder joints prove that the physical mechanism of the crack joints is based on the evolution of the micro voids in the interface. But the solder joint material is though as undamaged material in the previous researches. So it is found that the simulation predict value of the fatigue life of solder joints has a relatively big difference with the experiment data. With a specified FC-BGA package as a demonstration, the finite element simulation of the packages under heat cycle load is built in this paper. Firstly, the whole complete distribution of Mises equivalent stress and equivalent strain in the BGA solder joints without damage is obtained. The corresponding fatigue life of the solder joints is also obtained. And then, based on the Gurson damage material constitutive model, the solder joint materials with initial damage is considered and the corresponding fatigue life is analyzed. The comparison of the fatigue life between solder joint material with damage and solder joint material without damage is made. Finally, the influence of the initial damage in the solder joint materials on the fatigue life of the solder joints is investigated