Intermetallic compounds formation and interfacial adhesion strength of Sn–9Zn–0.5Ag solder alloy hot-dipped on Cu substrate

Abstract

The intermetallic compounds formation and interfacial adhesion strength of the Sn–9Zn–0.5Ag lead-free solder alloy hot-dipped on Cu substrate have been investigated by pull-off test, X-ray diffractometry, optical microscopy, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometry. The intermetallic compounds of Ag 3Sn, Cu 6Sn 5 and Cu 5Zn 8 were identified for Sn–9Zn–0.5Ag solder alloy–Cu, in which the thickness of Cu 6Sn 5 increased from 0.69±0.18 to 1.59±0.46 μm when the dipping time increased from 10 to 30 s. The interfacial adhesion strength increased from 3.21±0.73 to 4.11±0.56 MPa when the Ag content increased from 0 to 0.5 wt.% at the dipping temperature of 250 °C for 10 s. The interfacial adhesion strength of Sn–9Zn–0.5Ag alloy–Cu substrate also increased to 4.46±0.48 and 5.49±0.67 MPa when the dipping time increased to 20 and 30 s, respectively. The fracture path was observed at the Sn–9Zn–Cu 5Zn 8 interface, and within the Sn–9Zn–0.5Ag solder alloy.