Optimization of barrel plating process for electroless Ni–P plating

A plating test was carried out with changes in the concentration of nickel sulfate (NiSO4) and sodium hypophosphite (NaH2PO2) to analyze the plating characteristics depending on the balance of the electroless Ni–P plating solution. The coating thickness increased with the concentrations of NiSO4 and NaH2PO2. The optimum concentrations for electroless Ni–P plating were 27.0 g/L for NiSO4, and 24.0 g/L for NaH2PO2. The coating thickness was thicker at up to pH 4, but it was thinner after that. The deviations in the coating thickness decreased at up to pH 4, but it was increased after that. So the optimum pH of the plating solution was 4. Barrel plating was carried out while varying the open pore ratio, barrel rotation speed, plating temperature, and plating time, which revealed that the coating thickness was increased with the open pore ratio and barrel rotation speed. Therefore, the optimum open pore ratio and barrel rotation speed in electroless Ni–P plating were 22.5% and 2.5 rpm, respectively.