The effects of the addition of CNT@Ni on the hardness, density, wettability and mechanical properties of Sn-0.7Cu lead-free solder

Sn-0.7Cu-xCNT@Ni (x = 0, 0.025, 0.05, 0.075, 0.1 wt.%) nanocomposite solder was prepared by the mechanical alloying method. The effects of CNT@Ni modification on the hardness, electrical conductivity, wettability and mechanical properties of Sn-0.7Cu lead-free solder were studied. The microstructure of the raw material and composite solder were observed with scanning electron microscopy, and the solderability was evaluated through spreading experiments. The experimental results show that the hardness of the composite solder increased with an increased amount of doped CNT@Ni, but the electrical conductivity was lower than that of the original Sn-0.7Cu. At the same time, when the doping content is 0.05 wt.%, the spreading ratio and spreading area of the composite solder were maximized, significantly improving the wettability of the solder. The mechanical properties first increased and then decreased with an increased CNT@Ni doping content. When the doping content was 0.075 wt.%, the maximum yield strength and elongation were reached, and then began to decrease with increased doping. This result may be due to the agglomeration of CNT@Ni.