Impact crack propagation through the dual-phased (Cu,Ni)6Sn5 layer in Sn–Ag–Cu/Ni solder joints

Abstract The interfacial reactions of the Sn–3Ag–0.75Cu/Au/Ni solder joint before and after aging were investigated. The dual-phased (Cu,Ni) 6 Sn 5 with high (20.6 at.%) and low Ni (5.7 at.%) contents formed at the Sn–Ag–Cu/Ni interface, represented as H-(Cu,Ni) 6 Sn 5 and L-(Cu,Ni) 6 Sn 5, respectively. By employing high-speed impact test, the impact fracture morphology reveals that the H-(Cu,Ni) 6 Sn 5 /L-(Cu,Ni) 6 Sn 5 interface facilitates the crack nucleation within the intermetallic compound (IMC). The indentation data shows that bulk H-(Cu,Ni) 6 Sn 5 exhibits distinctly higher hardness and lower fracture toughness than bulk L-(Cu,Ni) 6 Sn 5 . In correlating the impact fracture behavior and mechanical properties of H-(Cu,Ni) 6 Sn 5 and L-(Cu,Ni) 6 Sn 5 , cracks tend to propagate through the H-(Cu,Ni) 6 Sn 5 IMC due to the relatively low fracture toughness of H-(Cu,Ni) 6 Sn 5 . In addition, mechanisms for the formation of the dual-phased (Cu,Ni) 6 Sn 5 IMC are discussed in details.