Enhancing Properties, Microstructure and Interfacial Reaction of SnBiIn Solder with Nickel-Coated Carbon Nanotubes

This paper systematically investigates the impact of nickel-coated carbon nanotubes (Ni-CNTs) on the melting behavior, wettability, microstructure, properties, and fracture characteristics of SnBiIn-based low-temperature solder. The growth kinetics of interfacial intermetallic compounds (IMCs) at SnBiIn-xNi-CNTs/Cu solder joints were also examined. Findings indicated that the addition of Ni-CNTs has a relatively minor influence on the melting point of the SnBiIn solder, with all recorded melting points remaining approximately 85°C. As the Ni-CNTs content increases, the solder wettability initially decreases and subsequently increases, achieving optimal performance at a content of 0.075 wt.%. At this time, the wetting angle is 29.8° and the spreading area is 79.0 mm ² . The Ni-CNTs addition results in significant refinement of the solder microstructure. The minimum average width of the InBi phase, measuring 3.97 µm, was achieved at a Ni-CNTs content of 0.05 wt.%, beyond which a coarsening behavior was observed with increasing concentration. Correspondingly, the tensile strength of the solder exhibited an initial increase followed by a decrease, reaching its maximum value of 66.52 MPa at the optimal Ni-CNTs addition level of 0.05 wt.%. At the solder joint interface, the intermetallic compounds (IMCs) were identified to be composed primarily of Cu₆(Sn,In)₅ and Cu₃(Sn,In) phases.Ni-CNTs addition reduces the formation of prismatic Cu₆(Sn,In)₅ phases, while increasing the generation of scallop-shaped phases. Interfacial IMCs thickness exhibits a minimum (2.49 µm) at 0.075 wt.% Ni-CNTs.