Combinatorial performance characteristics of agitated nickel hypophosphite electroless plating baths

In this article, we present the combinatorial performance characteristics of agitated sodium hypophosphite electroless plating baths. Various performance characteristics assessed include bath conversion, plating efficiency, selective conversion, metal film thickness, average pore size, effective porosity and percent pore densification (PPD). Bath agitation was brought forward by rotating a symmetric disk shaped porous ceramic substrate with a nominal pore size of 275 nm. The plating characteristics were investigated for wide range of nickel solution concentrations (0.04-0.16 mol/L), stirrer speed (0-200 rpm) and for two different loading ratios (defined as substrate surface area per unit volume of plating solution) values (196 and 393 cm(2)/L). It was evaluated that stirring had a profound effect on sodium hypophosphite based electroless nickel baths, which are characterized with lower conversions (10-39%) and higher plating efficiencies (62-99%) without stirring phenomena. The stirred plating baths provided about 20-56% excess nickel plating rate when compared to the baths without stirring. This lead to a reduction in average membrane pore size by 20-42 nm and an enhancement in percent pore densification values by about 2-7%. Further, higher concentrations as high as 0.16 mol/L have been found to be detrimental to reduce the metal plating efficiency to lower values (42%). Observed data trends confirm upon the urgent need to identify suitable mass transfer enhancement techniques that target enhancement in selective conversion while providing good values of plating efficiency and PPD. (C) 2011 Elsevier B.V. All rights reserved.