Electrochemical corrosion of Sn−0.75Cu solder joints in NaCl solution
(1. School of Materials Science and Engineering, Dalian University of Technology, Dalian 116085, China;
2. School of Materials Science and Engineering, Beijing University of Science and Technology,
Beijing 100083, China)
2. School of Materials Science and Engineering, Beijing University of Science and Technology,
Beijing 100083, China)
Abstract: The corrosion behaviors of Sn−0.75Cu solder and Sn−0.75Cu/Cu joint in 3.5% NaCl (mass fraction) solution were studied by potentiodynamic polarization test and leaching measurement. The polarization curves indicated that the corrosion rate of Sn−0.75Cu solder was lower than that of Sn−0.75Cu/Cu joint. The morphology observation and phase composition analysis on the corroded product at each interesting potential suggested that Sn3O(OH)2Cl2 formed on the surface of Sn−0.75Cu solder at active dissolution stage. As the potential increased from active/passive transition stage, all the surface of Sn−0.75Cu solder was covered by the Sn3O(OH)2Cl2 and some pits appeared after the polarization test. Compared to the Sn−0.75Cu solder alloy, much more Sn3O(OH)2Cl2 formed at active dissolution stage and the pits with bigger size were observed after polarization test for the Sn−0.75Cu/Cu solder joints. The leaching test confirmed that the faster electrochemical corrosion rate resulted in the larger amount of Sn released from the Sn−0.75Cu/Cu solder joints.
Key words: Sn−0.75Cu solder; Sn−0.75Cu/Cu joint; corrosion; potentiodynamic polarization; leaching behavior; corroded products