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

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)6Sn5 exhibits distinctly higher hardness and lower fracture toughness than bull: 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. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.