Nanoindentation Test and Crystal Plasticity Finite Element Model of SAC305 Solder Joint Considering Grain Orientation

Modern microelectronics packaging technology is continually advancing toward higher integration, which imposes more stringent requirements on reliability. As critical interconnects in packaging structures, the failure of solder joints may lead to the failure of the entire packaging system, making the study of their deformation behavior highly significant. This research investigates the influence of different β-Sn grain orientations in SAC305 solder joints on hardness, Young's modulus, and creep behavior under varying strain rates using nanoindentation with the continuous stiffness measurement (CSM) method and electron backscatter diffraction (EBSD). The results reveal that both the hardness and creep displacement of the material are highly strain-rate sensitive, showing a pronounced increase with rising strain rates. In contrast, Young's modulus shows no substantial dependence on the nanoindentation parameters. However, under different grain orientations, the hardness, Young's modulus, and creep displacement of the solder joints all demonstrate notable orientation dependence. In terms of simulation, a three-dimensional crystal plasticity finite element (CPFE) model was established, and a user-defined material subroutine (UMAT) was developed to simulate the mechanical response and creep behavior of SAC305 solder joints with different grain orientations. The model can accurately capture the dynamic variations of the load during the indentation process. Moreover, in the holding stage, the simulated and experimental load curves exhibit a high degree of agreement, indicating that the model possesses high prediction accuracy for the maximum load in this specific stage. Overall, these results validate the effectiveness of the established crystal plasticity finite element (CPFE) model in characterizing the indentation mechanical behavior of β-Sn grains with different orientations, thereby providing theoretical support for elucidating the failure mechanisms of solder joints.