Effect of Cu addition in sn-containing solder joints on interfacial reactions with Au foils

Pure Sn, Sn-0.7Cu, Sn-1.5Cu and Sn-3.0Cu solder joints were fabricated by a laser reflow soldering method, and then they were aged at 125°C for various periods. After 600 hours treatment, we found that thickness of Intermetallic Compounds (IMCs) in the pure Sn solder joints was 54μm. However, in the solder joints with Cu addition, formation of AuSn
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IMCs was inhibited, and other two kinds of Sn-Cu-Au ternary phases were found in stead. In the Sn-3.0Cu solder joints, the IMCs and phases were only 34μm in thickness, moreover, growth of the IMCs and phases did not follow the parabolic law.