Synthesizing SnAgCu nanoparticles by electrodeposition of reverse microemulsion electrolyte

Abstract

Solder printing faces challenges in print definition and sustainable volume transfer as the microelectronic industry migrates to smaller footprints. Nano-sized alloy particles mitigate these issues by modifying the solder formulation and rheology. We propose an electrodeposition method using reverse microemulsion (without reducing agent) as electrolyte to synthesize Sn-Ag-Cu solder alloy nanoparticle. SnCl2.2H2O, Ag2SO4 and CuSO4 are used as the precursor. N-hexane, TritonX-100 and n-hexanol are used as oil phase, surfactant and co-surfactant, respectively. Three volume ratios of aqueous to surfactant phase, Wo are carried out namely: 0.20, 0.40 and 0.60 but only the ratio of 4.5:1.0 is able to synthesize the nano-sized SAC particles. Scanning electron microscopy shows the spherical SAC particles are well dispersed and their sizes range from 15 to 90 nm. X-ray diffraction spectra show the formation of Sn, Ag3Sn and Cu6Sn5 without any oxide peaks in the synthesized nanoparticles; their absence suggests the effectiveness of the surfactants in protecting the alloy particles from oxidation. This electrodeposition method compares favourably to the microemulsion (with reducing agent) method in producing spherical and well-distributed nanosized solder particles.