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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.48  No.8 (2007)  >  pp.2133-2138

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Effect of Thermal Treatment on the Intermetallic Compounds Formed at Sn-9Zn-1.5Ag-xBi (x = 0 and 1) Lead-Free Solder/Cu Interface

Chih-Yao Liu1), Ying-Ru Chen2), Wang-Long Li2)3), Min-Hsiung Hon1) and Moo-Chin Wang4)
1) Department of Materials Science and Engineering, National Cheng Kung University
2) Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences
3) Institute of Nanotechnology and Microsystems Engineering, National Cheng Kung University
4) Faculty of Fragrance and Cosmetics, Kaohsiung Medical University

The formation of Intermetallic compounds (IMCs) at the interface between an Sn-9Zn-1.5Ag-xBi solder alloy and a Cu substrate dipped at 250°C and heat-treated at 150°C for various times has been investigated by an optical microscope (OM), an X-ray diffractometer (XRD) and a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS). The OM result shows the flat and smooth surface for the Sn-9Zn-1.5Ag-1Bi solder alloy and Cu substrate after dipping at 250°C. The phases of IMCs formed are Cu6Sn5 and Cu5Zn8 for both lead-free solder alloys. After thermal treatment at 250°C for 200 h, the phases of IMCs are Cu6Sn5, Cu5Zn8 and Ag3Sn. The Cu6Sn5 has a scallop morphology, and is located at the interface between the solder and Cu substrate. The adhesion strength for the Sn-9Zn-1.5Ag-1Bi lead-free solder alloy is higher than the Sn-9Zn-1.5Ag solder alloy. After being heat-treated at 150°C, the adhesion strength of the Sn-9Zn-1.5Ag-1Bi solder alloy decreases from 12.67±0.45 to 6.92±0.38 MPa after thermal treatment for 200 h.

lead-free solder, microstructure, morphology, Cu6Sn5, adhesion strength

Received: March 28, 2007
Accepted: May 14, 2007 , Published online: July 25, 2007
Copyright (c) 2007 The Japan Institute of Metals



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