Thermodynamic Study of Complexing Process in Nickel Electroless Plating

The thermodynamic general formula model of complexation reaction between multiple acid complexing agent and nickel salt in Ni electroless plating process was established.The thermodynamic calculations and influence factor analysis of the complexation process for lactic acid,succinic acid,boric acid and pyrophosphate were carried out based on Gibbs free energy as a criterion through the model.The results showed that under certain conditions,ΔG was proportional to pH value,inversely proportional to temperature(when ΔG ≤0) and complexation rate and related to mutually restricted ionization constant and hydrogen element number of the acidic complexing agent.The bath pH value range of the four agents were 4.9 ~ 6.6,5.4 ~ 6.2,12.4 ~ 12.9 and 5.2 ~ 5.7 when ΔG=0 within temperature range of 65~ 95 ℃ and complexing rate range of 65%～99% range,respectively.