Affects of Citric Acid Concentration and System pH on the Speed and the Stability of Nickel Electroless Plating

Analyzing the experiment results theoretically, this paper mainly studied the affect of content of lactic acid as main complexant and pH value with citric acid as auxiliary complexant to plating speed and the system stability in nickel electroless plating. The results of our researches indicate that: (1) When the total nickelous concentration is 0.10mol/L, the total lactic acid concentration is 0.20 mol/L and the pH value is 4.8, the speed of nickel electroless plating will decrease as the total citric acid concentration increase. Otherwise, the stability time of PbCl2 in the plating bath will increase; (2) When the total nickelous concentration is 0.10 mol/L, the total lactic acid concentration is 0.20 mol/L and the total citric acid concentration is 15 g/L, the speed of nickel electroless plating would increase as the pH value increases, but the stability time of PbCl2 in the plating bath would decrease a lot. Considering comprehensively the plating speed and the bath stability, the total citric acid concentration 10~20 g/L, pH value 4.8~5.2 will be acceptable.