Mechanical properties and electrochemical corrosion behavior of Al-Cu solder joint with Sn-Zn based solder

Three new Sn-Zn based lead-free solders were used to join Al and Cu in this study. Needle-like Zn phases and AgZn3 phases formed in the bulk solder of 1# and 3#, however, globular-like Zn phases were found in the micro structure of 2# bulk solder. 2# solder owned the best wettalility on the Cu substrates and Al substrates. In as-soldered joints of all the solders, the A14.2Cu3.2Zn0.7 compound layer formed at the interface of solder and Cu, while the Al-Zn-Sn solid solution zone formed at the interface of solder and Al. The AgZn3 phase was also found at the interface of 1# and 3# solder and the eutectic mixture of 2# solder had more homogeneous distribution than those of 1#, 3# and Sn-9Zn solder joints. The microstructure of 2# solder joint induced higher shear strength than those of 1#, 3# and Sn-9Zn solder joints. The corrosion potential of 1# solder was more noble than those of 2# solder and 3# solder in 3.5% NaCl solution.