Mechanical Properties of Lead-Free Solder Joints Under High-Speed Shear Impact Loading

In this study we expanded on recently reported research by using a modified miniature Charpy impact-testing system to investigate the shear deformation behavior of Sn–3.0Ag–0.5Cu lead-free solder joints at high strain rates ranging from 1.1 × 10³ s^?1 to 5.5 × 10³ s^?1. The experimental results revealed that the maximum shear strength of the solder joint decreased with increasing load speed in the ranges tested in this study. For solder joints tested at a shear speed exceeding 1 m/s, corresponding to an approximate strain rate that exceeds 1950 s^?1, the brittle fracture mode is the main failure mode, whereas lower strain rates result in a ductile-to-brittle transition in the fracture surfaces of solder joints. In addition, the mode II stress intensity factor (K _II) used to evaluate the fracture toughness (K _C) of an interfacial intermetallic compound layer between Sn–3.0Ag–0.5Cu solder and the toughness of copper substrate was found to decrease from 1.63 MPa m^0.5 to 0.97 MPa m^0.5 in the speed range tested here.