Impedance Measurements for Electroless Nickel Plating Process

Abstract

Electroless nickel (EN) process is the controlled auto catalytic reduction of nickel ions using suitable reducing agent such as sodium hypophosphite on certain catalytic surfaces, which results in the production of sound, coherent coatings for a number of applications. Frequently the rate of deposition of EN with hypophosphite as reducing agent is below 20 microns per hour. Hence the deposition of the electroless nickel with hypophosphite solution in the presence of small concentration of thiourea and its derivatives as accelerators is investigated. The mechanism of accelerated deposition is studied by impedance measurements. The performance of various additives during the plating process is being evaluated by increased Constant Phase Element (CPE) and decreased charge transfer resistance values. A model is proposed for the adsorptive behavior of additives.