Nickel-phosphorus alloys

Electroless nickel—boron baths use sodium borohydride or dimethyl amine borane [74-94-2] in place of sodium hypophosphite (see Boron COMPOUNDS). The nickel—boron alloy is brittle, highly stressed, and much more expensive than nickel—phosphorus alloys. Nickel—boron is mainly used to replace gold in printed circuit board plating. 

In the nickel processes the reducing agent used most commonly is sodium hypophosphite, which gives a deposit comprising a nickel-phosphorus alloy rather than pure nickel the accelerators commonly are fluorides, and thiourea is a typical stabilizer. 

Weber, T. A., and Stillinger, F. H., Interactions, local order, and atomic rearrangement kinetics in amorphous nickel-phosphorus alloys. Phys. Rev. B 32,5402 (1985). 

To counteract the (vexing) convection effects on kinetic experiments, Aogaki and co-workers, having developed a special electrode assembly to separate mass transport and kinetic effects, report a marked decrease in the exchange current density (about 25%) in magnetic fields imposed on a copper deposition cell. Virtually no effect on the transfer coefficient (a 0.44) was observed. Experimental results obtained in nickel-phosphorus alloy deposition, cupric ion reduction in ethylenediamine solutions, and the electrolytic reduction of acetophenone " are further demonstrations of the interaction of the magnetic fields with polarization characteristics, and point to the difficulty of fully eliminating the effect of convection and/or diffusion on electrode kinetics. 

Ziewiec et al. [24] reported on the preparation, thermal stability and glass-forming ability of copper-nickel-phosphorus alloys. They found that, depending on the composition, melt spinning may result in either amorphous or partially crystalline systems, whose thermal behaviour was characterized by DSC, DTA, andXRD. 

A. Durairajan, A. Krishnaiyer, B. Haran, R.E. White, B.N. Popov, Characterization of hydrogen permeation through a corrosion-resistant zinc-nickel-phosphorus alloy. Corrosion 56 (2000) 283—288. 

This particular formulation deposits nickel at the rate of about 0.015 mm (0.6mil)/h in the form of a nickel-phosphorus alloy [13]. The usual range of phosphorus content in coatings of this kind is 7-9%. Various metal surfaces, including nickel, act as catalysts for the reaction so that deposits can be built up... 

A common metallization scheme for connector contacts used on printed circuit boards is a gold electroplate over copper or copper alloy substrate, usually with an intervening thin diffusion barrier layer (1.2-2.5 pm) of electroplated nickel or nickel-phosphorus alloy. Ordinarily this metallization scheme performs well and is frequently used in high reliability applications. A less reliable and infrequently used metallization has silver as the diffusion barrier. A potential problem with both metallizations is caused by the inevitable pores that exist even in the best quality gold elec-... 

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