Abstract
This study investigated the interfacial reaction and mechanical strength of Sn-3.0Ag-0.5Cu solder jointed with electroless Ni-P/immersion Au (ENIG) and electroless Ni-P/electroless Pd/immersion Au (ENEPIG) surface finishes under various reflow times. The morphology of interfacial (Cu,Ni,Pd) 6 Sn 5 was refined to needle-like by the Pd insertion in the ENEPIG surface finish. The impact energy of solder joints with Pd doped declined slower than that without Pd-doped after prolonged reflow. By inspecting the fracture surface, the cleavage of interfacial (Cu,Ni) 6 Sn 5 was frequently observed in the ENIG joints after prolonged soldering, whereas ductile dimple-like failure dominated the fracture surface of ENEPIG joints. The enhanced impact strength and the transition of failure mode in the ENEPIG joints was attributed to the needle-like morphology of (Cu,Ni,Pd) 6 Sn 5 . The detailed mechanism of improved mechanical strength for solder joints with Pd dissolved will be deliberately addressed and discussed regarding the distinct microstructural evolution in the ENEPIG joint. © 2013 Elsevier B.V.