Effect of multi-walled carbon nanotubes on the microstructure and properties of Sn-58Bi solder alloys

The influence of multi-walled carbon nanotube (MWCNT) content on the melting properties, wettability, microstructure, and intermetallic compounds (IMCs) of Sn-58Bi-xMWCNT (x = 0, 0.01, 0.02, 0.03, 0.05, and 0.10 wt.%) and the effects of MWCNT on the tensile strength of Cu/Sn-58Bi-xMWCNT/Cu solder joint were analyzed. The results show that MWCNT addition at a small trace amount into Sn-58Bi solder could increase the spreading area of Sn-58Bi solder, refine the solder matrix microstructure, inhibit the growth of interfacial IMCs, and significantly improve the tensile strength of Sn-58Bi solder joints. However, the melting point and melting range remained the same or slightly changed. The wettability of Sn-58Bi alloys increased first and then decreased with the addition of MWCNT. The spreading area and the tensile strength of solder joint were the maximum when the MWCNT content was 0.01 wt.%, and they were 42.23 mm(2) and 50.07 MPa, respectively. The reason may be related to the improved microstructure of solder alloys and the morphology of IMCs due to MWCNT addition at trace level.