Morphologies and grain orientations of CuSn intermetallic compounds in Sn3.0Ag0.5Cu/Cu solder joints

Morphologies and grain orientations of Cu ₆Sn ₅ and Cu ₃Sn intermetallic compounds (IMCs) at the interface of Sn3.5Ag0.5Cu lead-free solder alloy and copper substrates were investigated by Electron Backscatter Diffraction (EBSD) technology combined with Scanning Electron Microscopy (SEM). Scalloped Cu ₆Sn ₅, Cu ₆Sn ₅ planes and six-prism shaped Cu ₆Sn ₅ IMCs were observed at the interface after 48 h of soldering at 250 °C. Moreover, Cu ₆Sn ₅ planes emerged in pairs on top and beside the scalloped Cu ₆Sn ₅, and two adjacent Cu ₆Sn ₅ planes were with an angle of 120°. Cu ₃Sn and scalloped Cu ₆Sn ₅ IMCs had preferred orientations, and they were Cu ₆Sn ₅ (0001)∥substrate surface, and Cu ₃Sn (1̄00) and (100)∥substrate surface.