Influence of Ni-CNT particle size on the interface organization and mechanical properties of Sn58Bi/Cu joints

The primary focus of this research lies in systematically investigating the impact of Ni-carbon nanotube composite particle dimensions on interfacial morphology and load-bearing characteristics in Sn58Bi/Cu solder connections. Through comprehensive microstructural characterization employing SEM-EDS and mechanical evaluation via standardized shear testing, the solder-Cu interfacial evolution and associated strengthening mechanisms were quantitatively examined. Experimental evidence reveals that nano-scale Ni-CNT reinforcement induces substantial microstructural refinement and mechanical enhancement. Specifically, the incorporation of 10-20 nm Ni-CNT additives resulted in a 28% reduction in intermetallic compound (IMC) layer thickness at the solder/copper interface (from 1.467 µm to 1.146 µm), accompanied by a remarkable 44.1% improvement in joint shear resistance. These findings underscore the critical role of nanoscale reinforcement particle size optimization in achieving superior mechanical performance in lead-free solder interconnect systems.