Abstract
In this paper, the force -oblique displacement correction methods of the BGA solder joint specimens and the values of grip stiffness were used to correct the force-oblique displacement curves of the 63Sn/37Pb BGA specimens into the force-displacement data of their solder balls under proportional strain cyclic test. The kernel function of Endochronic cyclic viscoplasticity of 63Sn/37Pb bulk material was employed to predict the cyclic proportional stress-strain curves and then construct the relationship of the effective inelastic strain amplitude and the effective stress amplitude : . Also the BGA oblique displacement amplitude has a relation with of solder ball by . This result connects the research of BGA solder joint specimen in industry and the research of constitutive models in academic. Based on physical phenomena, dependent damage degree depends positively on N cycle and , then the -modified damage power equation and the -Modified Lee-Coffin-Manson equation( -LCM) for the fatigue initiation life of solder ball: can be derived. Finally the -LBGA equation for the fatigue life of BGA specimens: can be obtained. Using the -LBGA equation, both of 63Sn/37Pb and Sn/3.5Ag/0.75Cu BGA fatigue life can be predicted very well.
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