The simulation analysis for the correlation between failure of BGA solder joints and the loading modes

In this paper, three-dimensional finite element model of BGA package was used to be simulated lead-free solder. Sn-3.0Ag-0.5Cu was used as the material of solder joints array in the interconnection structure of BGA. The constitutive equation of power exponent law was applied to represent the stress-strain behavior of lead-free solder joints. The dangerous area of failure in the model was located. The change law of equivalent of stresstime and equivalent of plastic strain-time, and the correlation between failure and the loading modes of solder joints were studied. The results show that: the failure location of solder joints under different loading modes is the same. The position of stress concentration located at the lower left IMC (Intermetallic Compounds), the maximum equivalent plastic strain area located at the upper right solder neck. The residual stress of the lower left IMC under cycle loading unloading is the largest so the crack is most likely to happen. The equivalent plastic strain of the upper right solder neck under step cycle loading unloading is the largest and the ductile failure is most likely to happen. So cycle loading unloading mode and step loading unloading mode should be avoided at practical work.