Property Study Of Ni-coated Carbon Nanotubes Reinforced Sn-Ag-Cu Lead-free Solder

Carbon Nanotube (CNT), which possesses the high tensile strength as well asductility and perfect electrical properties, has been regarded as one of the best choiceof reinforcement. In this paper, Ni-Coated multi-walled Carbon Nanotubes (Ni-CNT)reinforced Sn-Ag-Cu composite solders were prepared, and we studied its meltingpoint, density, wetting angle, interfacial reaction, mechanical properties andelectromigration performance.Ni-CNT addition has little effect on the melting point of Sn-Ag-Cu compositesolders. With the Ni-CNT addition to Sn-Ag-Cu, solder density increased and thewetting property was improved. Due to the presence of Ni coated on CNT, thereactions among metal atoms at the solder/Cu interface were changed. The originalscallop-shaped Cu6Sn5intermetallic compounds were replaced by layer-shaped(Cu,Ni)6Sn5.The study of the mechanical properties showed that addition of0.05wt.%Ni-CNT improved the ultimate tensile strength of composite solders (up to9.80%)and solder joints (up to15.95%) respectively. The increase in strengthening effect ofsolder joints can be attributed to the consumption of Ni by interface reaction duringsoldering. Nanoindentation results revealed that the creep behaviors of compositesolders were improved significantly as compared to that of the unreinforced solderalloy. Finite-element modeling showed that load transfer by CNTs took effect but wasfar smaller than the effect of Ni-CNT served as obstacles preventing dislocationsgliding.The study of the electromigration performance showed that the presence ofCNTs can suppress the atomic diffusion effectively in the solder matrix induced byelectromigration. Base on the experimental results and the finite element simulationanalysis, we think CNT networks serves as the role of fast channel for current and canreduce the current density in the solder matrix, which results in the improvement ofelectromigration resistance of the composite solders.