tThe mechanisms proposed to explain ACD electroless Ni–P deposition are re-examined and the mostimportant features underlined. Oxidation of hypophosphite on the Ni–P surface is recognized as therate determining step of the process. The possibility of a bridged intermediate with hypophosphite andhydrolyzed nickel adsorbed at the surface is examined and proved feasible by quantum mechanical calcu-lations. A comparison of electrodeposition and ACD electroless deposition shows that the two processesare anti-correlated, ACD being directly related to the electrolytic hydrogen discharge. Addition of otherelements can greatly influence ACD electroless NiP plating process. Metals giving anomalous alloy elec-trodeposition, such as Zn, Co and Fe behave normally in electroless baths. Elements electrodeposited byinduction, such as W and Mo, decrease the P content and the deposition rate. A similar effect occurs forRe, Ce and Cu. Some of the metal stabilizers have also a brightening effect on NiP deposits. This is the caseof Cd, Bi, Te and Cu and brightening is related to their interaction with adsorbed hydrogen, stabilized bythese additives.
Influence of added elements on autocatalytic chemical deposition electroless NiP
CAVALLOTTI, PIETRO LUIGI;MAGAGNIN, LUCA;CAVALLOTTI, CARLO ALESSANDRO
2013-01-01
Abstract
tThe mechanisms proposed to explain ACD electroless Ni–P deposition are re-examined and the mostimportant features underlined. Oxidation of hypophosphite on the Ni–P surface is recognized as therate determining step of the process. The possibility of a bridged intermediate with hypophosphite andhydrolyzed nickel adsorbed at the surface is examined and proved feasible by quantum mechanical calcu-lations. A comparison of electrodeposition and ACD electroless deposition shows that the two processesare anti-correlated, ACD being directly related to the electrolytic hydrogen discharge. Addition of otherelements can greatly influence ACD electroless NiP plating process. Metals giving anomalous alloy elec-trodeposition, such as Zn, Co and Fe behave normally in electroless baths. Elements electrodeposited byinduction, such as W and Mo, decrease the P content and the deposition rate. A similar effect occurs forRe, Ce and Cu. Some of the metal stabilizers have also a brightening effect on NiP deposits. This is the caseof Cd, Bi, Te and Cu and brightening is related to their interaction with adsorbed hydrogen, stabilized bythese additives.File | Dimensione | Formato | |
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