2021 22nd International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), 2021, pp. 1-4, doi: 10.1109/EuroSimE52062.2021.9410845

Effects of Anisotropic Viscoplasticity on SAC305 Solder Joint Deformation: Grain-scale Modeling of Temperature Cycling

Qian Jiang, Abhishek Deshpande, and Abhishek Deshpande

Center for Advanced Life Cycle Engineering, University of Maryland, USA


The piece-to-piece variation among Sn-based lead-free solder joints is commonly attributed to stochastic variations in grain structure and the anisotropy inherent in the body-centered tetragonal (BCT) β-Sn lattice structure, especially for micron-scale joints that contain only a few grains. Parametric simulations of different microstructures, using grain-scale modeling, offer a convenient approach to estimate the degree of variability. Thus, although it is impossible to accurately predict the response of a given joint without knowing the microstructure, the best-case and worst-case limits of its behavior can be estimated. A crystal viscoplasticity approach has been developed to describe the anisotropic steady-state creep behavior of SAC single crystals and calibrated with results from literature and with in-house testing. The overall response of a single crystal has been characterized by a corresponding homogenized continuum-scale creep model based on Hill's anisotropic potential, in conjunction with Norton power-law model for creep rates. In this study, the Hill-Norton model described above is applied to analyze the effect of grain orientation on the viscoplastic response and durability of a singlecrystal solder joint under the combined action of compressive and thermal cyclic loading. The predicted lifetime, based on volume-averaged creep dissipation energy density, shows 31% variation for best-case and worst-case grain orientations.

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