Comparative study on stress–strain hysteresis response of SAC solder joints under thermal cycles

Abstract

The present study attempts to evaluate the stress-strain hysteresis responses of SAC solder joints in Resistor and FleXBGA144 packages subjected to thermal cyclic loading using several constitutive models. The total deformation of the solder material consists of elastic, rate-independent plastic and rate-dependent creep components. The constitutive models discussed in this study each weighted elastic, plastic and creep deformations differently. At low stresses SAC solder alloys were found to be creep resistant, where at higher stresses, the influence of different microstructures disappears as matrix-creep dominates in this region. Thus, the proper constitutive model requires all the three ingredients of the elastic, the creep, and the time-independent plastic data for different stress levels to effectively predict the hysteresis behavior of the SAC solder alloys. The hysteresis loops predicted by constitutive models were also found in close agreement with the loops generated by FEM for the SAC solder joint subjected to thermal cycling.

A hybrid approach to characterization and life assessment of trilayer assemblies of dissimilar materials under thermal cycles

“…In order to obtain the elastic-plastic model for this solder (SAC305), the following approach is used. An initial, instantaneous strain that develops at the start of a creep test includes both the elastic strain and the inelastic strain presenting the time independent plastic flow (Refer to Figure 48) [104]. An incremental analytical model is used to simulate the elastic-plastic behaviour of solder alloy under different temperatures.…”

“…where T is in Kelvin. Figure 51 demonstrates the temperature-dependent Young's modulus of different SAC lead-free solder alloys [104] along with the model presented in this study.…”