Aging induced structural and electrochemical corrosion behaviour of Sn-1.0Ag-0.5Cu and Sn-3.8Ag-0.7Cu solder alloys

The electrochemical corrosion behaviour of Sn-1.0Ag-0.5Cu (SAC105) and Sn-3.8Ag-0.7Cu (SAC387) solder alloys, isothermally aged at 120 degrees C for two different time periods of 4 h and 72 h, has been investigated in 0.5 M NaCl solution using potentiodynamic polarization measurements and electrochemical impedance spectroscopy. The aging of SAC105 and SAC387 results in significant changes in morphology, size and distribution of intermetallic compounds Cu6Sn5 and Ag3Sn. This study reveals that SAC387 has more corrosion resistance than SAC105 for both aging time periods of 4 hrs and 72 h. SAC105 solder alloy after aging for 72 h became significantly more corrosion resistant than SAC387 aged for 4 hrs. SAC105 and SAC387 aged for 72 hrs exhibit increased charge transfer resistance (R-ct), the impedance value, and maximum bode phase angle. This study signifies that an aging process combined with Ag content in SAC solder alloys can be exploited to enhance the corrosion resistance making them suitable for electronic devices used in harsh environments. (C) 2018 Elsevier B.V. All rights reserved.