Investigation on shear fracture of different strain rates for Cu/Cu3Sn/Cu solder joints derived from Cu–15μm Sn–Cu sandwich structure

Abstract

Full intermetallics (IMCs) solder joints are of great significance to electronic packaging technology. In this paper, some efforts have been made for bridging research gap on reliabilities of such joints. Shear fracture of different strain rates, for Cu/Cu3Sn/Cu joints derived from Cu–15μm Sn–Cu sandwich structure, was comprehensively analyzed. With the strain rates of 6.67 × 10−2 s−1, 6.67 × 10−1 s−1 , and 6.67 s−1, the shear strength of Cu/Cu3Sn/Cu joints was, respectively, 44 MPa, 48.4 MPa, and 57.6 MPa, which presented an ascending trend. The increased strength of joints was attributed to the intensification of work-hardening effect within interfacial region. For the strain rates of 6.67 × 10−2 s−1 and 6.67 × 10−1 s−1, the fracture of joints was both a mixture of transgranular fracture and intergranular fracture within Cu3Sn, while the fractured path both had no diversion and kept continuous. For the strain rate of 6.67 s−1, only transgranular fracture occurred within Cu3Sn, and the fractured path diverted with the appearance of step. The transgranular fracture at these three strain rates all belonged to cleavage fracture, and their proportion presented the increasing trend of 25.5% → 59.5% → 100% (Strain rates: 6.67 × 10−2 s−1 → 6.67 × 10−1 s−1 → 6.67 s−1). Because of the fracture mechanism of different strain rates, the crack propagation resistance increased by a larger extent for 6.67 × 10−1 s−1 → 6.67 s−1 in comparison with that for 6.67 × 10−2 s−1 → 6.67 × 10−1 s−1. Moreover, the strain rate sensitivity of Cu/Cu3Sn/Cu joints was smaller than that of conventional joints, which was due to the different interfacial structure of two joints.