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

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 Ag3Sn, Cu6Sn5 and Cu5Zn8 were identified for Sn-9Zn-0.5Ag solder alloy-Cu, in which the thickness of Cu6Sn5 increased from 0.69+/-0.18 to 1.59+/-0.46 mum 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 degreesC 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-Cu5Zn8 interface, and within the Sn-9Zn-0.5Ag solder alloy. (C) 2002 Elsevier Science B.V. All rights reserved.