Solder volume effects on fatigue life of BGA structure Cu/Sn-3.0Ag-0.5Cu/Cu interconnects

The influence of solder volume on fatigue life of BGA structure Cu/Sn-3.0Ag-0.5Cu/Cu interconnects of different standoff heights under displacement cyclic loading conditions was studied by finite element (FE) simulation. The geometry of BGA structure solder interconnect was predicted according to the minimum energy principle by FE analysis, and simulation results reveal that the influence of gravity on the geometry of BGA structure solder interconnects can be reasonably ignored when the diameters of solder balls used are less than 0.76 mm. Darveaux's methodology based on plastic strain energy density was employed to predict the fatigue life of solder interconnects of different volumes by FE method. The simulation results show that the decreasing standoff height (i.e., solder volume) of joints can obviously increase the fatigue life of BGA structure solder interconnects, and the value and distribution of accumulated equivalent plastic strain play critical roles in determining the fatigue life of BGA structure solder interconnects.