Viscoplastic behavior of bulk solder material under cyclic loading and compression of spherical joint-scale granules

The viscoplastic behavior of solder material is investigated from different scales. Due to the thermal stress in Sn–3.0Ag–0.5Cu alloy at elevated temperatures, the continuous accumulation of unrecoverable deformation becomes the key of interconnections failure in microelectronic packaging. In the current study, the rate and temperature dependence of inelastic deformation and cyclic hardening properties of Sn–3.0Ag–0.5Cu alloy under different loading conditions are studied. A novel phenomenological constitutive model is developed to describe the deformation of lead-free solder interconnections in the microelectronic packaging. The developed model is verified by comparing with the experimental data of bulk solder materials. The results show that the proposed model can accurately describe the viscoplastic properties of bulk solder materials and shows excellent numerical stability. For understanding better the overall deformation behaviors of solder joins, especially the strain–stress relationship, uniaxial compression experiments of spherical joint-scale granules were conducted under different loading rates. The developed model is applied to simulate the compression testing of granules. It shows that the developed model can characterize the viscoplastic compression deformation of Sn–3.0Ag–0.5Cu solder on joint-scale with reasonable accuracy.