Solder constitutive models and failure criteria selection in board level cyclic bending simulation

Board level bending testing is an effective method to evaluate the solder joint reliability of handheld products. In this work, the solder joints failure mode during cyclic bending was characterized by a board level bending test system with respect to strain range and strain rate. And then the finite element modeling and simulation was conducted to investigate the solder joints reliability by considering different solder constitutive models and different failure criteria. The Elastic-plastic, Creep and Viscoplastic models of solder alloy were measured and input to finite element model to compare their effect on the simulation results of solder joint performance. In addition to solder constitutive model selection, failure criteria for solder joint reliability were discussed in this paper. Stress, plastic strain and plastic work were calculated in simulation and discussed. Base on comparing the actual experimental results and simulation results, it was concluded that the proposed solder constitutive model, Viscoplastic model is the appropriate model which can be used successfully to simulate the failure mechanism of solder joints under cyclic bending condition. The plastic strain was selected as the failure criteria for evaluating the solder joints reliability during cyclic bending simulation.