A comparative study between the improved unified creep-plasticity model and Anand model: Experimental investigations at the material-scale and packaging structure-scale

With the increasing miniaturization and complexity of electronic packaging, accurately characterizing internal mechanical responses through finite element simulation has become crucial for reliability assessment. This study comparatively evaluates the damage-coupled Unified Creep Plasticity (UCP) model and Anand model in simulating solder joint behavior under cyclic loading across material and structural levels. Material-level simulations of the SAC305 alloy under uniaxial tension-compression reveal that the damage-coupled UCP model yields smoother stress-strain curves with better experimental agreement, while the Anand model exhibits folded inflections near yield points, showing 12 % strain deviation. Structural-level analysis employing silicon-embedded stress sensors demonstrates that the UCP model's stress evolution correlates strongly with experimental measurements, whereas the Anand model shows 15–20 % peak stress deviations. Three-dimensional flip-chip BGA modeling further clarifies mechanistic differences: The Anand model omits plastic phase evolution, only capturing elastic and creep stages, while the UCP model fully describes three-phase evolution (elastic-plastic-creep), accurately reflecting actual deformation mechanisms. These multi-scale results validate the UCP model's superiority in characterizing visco-plastic behavior of solder joints, providing critical theoretical support for packaging reliability optimization.