Enhancing the properties of a lead-free solder with the addition of Ni-coated carbon nanotubes

In this study, 0.05 wt.% of Ni-coated multi-walled carbon nanotubes (Ni-CNTs) were successfully introduced into the 95.8Sn-3.5Ag-0.7Cu solder using the powder metallurgy technique, to synthesize a new lead-free composite solder system. The samples were characterized in terms of their microstructural and mechanical properties. Microstructural analysis of the polished samples revealed uniformly distributed intermetallic phases throughout the solder matrix and EDS analysis identified the phases as Ag₃Sn and Cu₆Sn₅. Furthermore, with the addition of Ni-CNTs, the tensile results showed an improvement in 0.2% yield strength (~13%) and ultimate tensile strength (~15%), when compared with that of unreinforced SnAgCu solder. Nanoindentation tests were also conducted to assess the creep performance of the samples. The results showed that addition of Ni-CNTs improved the creep resistance of the composite solder. The results in this study convincingly established that nanotechnology coupled with composite technology in electronics solders can lead to the enhancement of mechanical properties. Thus, these advanced interconnect materials will benefit the microelectronics assembly and packaging industry. An attempt is made in this study to interrelate the mechanical properties of the resultant composite solder with the presence of Ni-CNTs.