Autocatalytic Nickel Deposition from a Trifluoromethanesulfonate Electrolyte

Abstract

SUMMARYElectroless nickel plating from low and medium phosphorus solutions containing either sulfate or trifluoromethanesulfonate anions was studied. At the early stages of aging the solutions, the effects of the sulfate and trifluoromethanesulfonate anions on the deposition rate, internal stress, crystallization behaviour, crystallographic structure and appearance are similar. The deposits produced from the trifluoromethanesulfonate solution are harder and contain more occluded phosphorus than the sulfate deposits produced at a similar pH. Deposition of the two coatings at pH 6·5 resulted in lower percent phosphorus in the nickel sulfate coating but the amount of phosphorus in the nickel trifluoromethanesulfonate coating was unaffected by pH. After eight metal turnovers, the surfaces of both deposits were nodular, the deposits exhibited a tensile stress and the plating rates dropped to about 70% of their original rates. Treatment of the electrolytes with calcium to remove orthophosphite resulted in a smooth, compressively stressed coating and a high deposition rate from the trifluoromethanesulfonate solution but poor quality coatings and a continued slower plating rate from the sulfate-based solution.