Statistical study of nickel and phosphorus contents in electroless Ni–P coatings

Abstract

Electroless nickel phosphorus plating process has been studied considering pure copper (99·99%) as a substrate material. Preliminary experiments were performed to obtain the autocatalytic deposition of electroless Ni–P coatings on copper. Deposited percentages of nickel and phosphorus in electroless Ni–P coatings have been evaluated by energy dispersive X-ray analysis (EDAX) and these percentages have been considered as response variables for statistical analysis. The individual and combined effects of process parameters on deposited percentages of nickel and phosphorus have been studied. Full factorial experimental design, regression analysis and Student's t test have been used to identify the influencing process parameters. It has been observed that reducing agent (NaH₂PO₂.H₂O) significantly affects the percentages of nickel and phosphorus contents in the Ni–P coatings. Mathematical modelling has been carried out using a second order response surface model to take into account the effect of curvature in the predicted responses. Equations for response surfaces that relate the deposited percentages of nickel and phosphorus with process parameters have been determined using MATLAB software package. The surface and contour plots have been generated and these plots give visual pictures about the effect of process parameters on the deposited percentages of nickel and phosphorus in the Ni–P coatings.