We investigated plating conditions for a tin displacement plating using spherical gel electrolyte particles. Sodium alginate was used as the gelling agent. A 10×10－3 cm3 sodium alginate solution was dropped using a microsyringe into an aqueous solution containing tin chloride, tartaric acid, and thiourea. Optimal results were obtained with 3 wt% sodium alginate concentration and tin plating bath temperature for spherical gel preparation of less than 60 ℃. The alginate spherical gel particle containing the electrolytes adhered to the copper surface. While changing the plating time, tin film thicknesses were investigated using an X-ray fluorescence instrument. The tin film thickness showed a sigmoid growth curve until 120 min of plating time. The tin film thickness at 120 min was estimated as about 800 nm. The gel electrolyte particles on the tin film surface were rougher than those that adhered from an aqueous plating bath. Results suggest that differences in plating film roughness are attributable to the diffusion rate of tin ions to the electrode surface during displacement plating.
Several Ni-P/Cu multilayer films of various thicknesses were formed on polycrystalline copper substrates using electrodeposition in a single bath. The Ni-P/Cu bilayer films which were thinner than 50 nm exhibited higher wear resistance than that of a Ni-P single layer. The wear loss of the films decreased concomitantly with increasing Ni-P layer ratio in the Ni-P/Cu bilayer.