Deformation behavior study of SAC305 solder joints under shear and tensile loading by crystal plasticity finite element method.

Abstract

Micro solder joints experience various loads during operation, and the failure of a single micro solder joint can impact the overall reliability of the entire microsystem. This study utilized the Crystal Plasticity Finite Element Method (CPFEM) to create a polycrystalline model that accurately represents the shape of solder joints. By calibrating the crystal plasticity characteristics of SAC305 material solder joints using macroscopic stress-strain curves, the model successfully simulates the deformation mechanisms of micro-solder joints under both tensile and shear loads. This paper highlights that equivalent plastic strain serves as a key indicator of solder joint fracture behavior, revealing that strain components have varying effects on cracking: shear strain was found to cause crack initiation, while normal strain was found to promote crack extension. Moreover, Grain boundary features and orientation lead to uneven plastic strain by affecting the slip system and the Schmidt factor, especially small Schmidt factor grains at triple grain boundary intersections are more susceptible to crack initiation. Additionally, the study found that solder joints exhibit more pronounced mechanical responses under tensile loading compared to shear loading. These insights offer valuable guidance for the design and manufacturing of micro-solder joints.