Autocatalytic plating

Electroless Electrolytic Plating. In electroless or autocatalytic plating, no external voltage/current source is required (21). The voltage/current is suppHed by the chemical reduction of an agent at the deposit surface. The reduction reaction must be catalyzed, and often boron or phosphoms is used as the catalyst. Materials that are commonly deposited by electroless plating (qv) are Ni, Cu, Au, Pd, Pt, Ag, Co, and Ni—Fe (permalloy). In order to initiate the electroless deposition process, a catalyst must be present on the surface. A common catalyst for electroless nickel is tin. Often an accelerator is needed to remove the protective coat on the catalysis and start the reaction. 

Electroless deposition, or autocatalytic plating, may be defined as deposition of a metal coating by a controlled chemical reduction, catalyzed by the metal or alloy being deposited. Electroless deposition has been known for a long time. One of its early uses was the deposition of a mirror-like layer of silver on the internal surfaces of Dewar flasks for improved thermal isolation, and as the back coating of mirrors. Later, it was used for deposition of different metals and alloys, and even for induced codeposition of alloys. 

The Electroless plating deposition (ELP) technique is based upon the controlled auto-catalyzed decomposition or reduction of meta-stable metallic salt complexes on target surfaces [75]. In the case of palladium, usually, the substrate should be pre-seeded with palladium nuclei in an activation solution in order to reduce the induction period of the autocatalytic plating reaction. For some applications, this technique provides strong benefits such as uniformity of deposits on complex shapes and hardness. Palladium and some of its alloys are among the few metals that can be deposited in this way [11]. However, this method presents some drawbacks such as difficult thickness control, costly losses of palladium in the bath, not guaranteed purity of the deposit and so on [75]. 

Autocatalytic plating The deposition of a coating from a solution by use of a reducing agent in the solution rather than an externally applied electrical potential. Also called Electroless deposition Autodeposition Autophoretic deposition. 

Electroless and immersion plating are similar in that no external power supply is required to drive the deposition reaction. In electroless plating, also known as autocatalytic plating, the electrons required to force the deposition reaction are supplied by a chemical reducing agent (R) that donates electrons to the catalytic surface of the substrate. As the deposition reaction proceeds, the reducing agent (R) is subsequently oxidized to species (Rox) as illustrated by the reaction below. 

The electroless nickel/electroless palladium/immersion gold (ENEPIG) finish is simply an ENIG finish into which an intermediate layer of palladium (0.1 to 0.5 pm thick) is deposited between the electroless nickel and immersion gold coatings. Palladium is deposited from an autocatalytic plating bath. Palladium is a noble metal applied to protect oxidizable Ni. Palladium (m.p. 1552°C) is not fusible but rather dissolves in the molten solder in a manner similar to gold, and... 

Sodium borohydride or dimethylarnine borane have found limited use as reduciag agents because of expense. In addition, bath stabiHty, plating rate, and deposit properties are inferior to those of formaldehyde-reduced baths. The deposit is a copper—boron alloy. Copper—hypophosphite baths have been iavestigated, but these are poorly autocatalytic, and deposit only very thin coatings. 

Post-Treatments. Although many post-treatments have been used over plated metals, chromate conversion coatings remain as the most popular. Chromates are used to improve corrosion resistance, provide good paint and adhesive base properties, or to produce brighter or colored finishes. Formulations are usually proprietary, and variations are marketed for use on zinc, zinc alloys, cadmium, copper and copper alloys, and silver (157). Chromates are also used on aluminum and magnesium alloys (158,159). More recently, chromate passivation has been used to extend salt spray resistance of autocatalytic nickel plated parts. 

You are to pultrude a thin fiber reinforced epoxy plate at arate of lcm/s. Assume kinetic properties given in the last two problems and that the material is best represented with the autocatalytic second order reaction kinetic model of the previous problem. You are asked to design the die and the process to manufacture this product. 

Electroless plating — An autocatalytic process of metal deposition on a substrate by reduction of metal ions from solution without using an external source of electrons. It is promoted by specific reductants, namely formaldehyde, sodium hypophosphide, sodium boro-hydride, dialkylamine borane, and hydrazine. Electroless deposition has been used to produce different metal (e.g., nickel, cobalt, copper, gold, platinum, palladium, silver) and alloy coatings. It can be applied to any type of substrate including non-conductors. Some substrates are intrinsic catalytic for the electroless deposition other can be catalyzed usually by sensibilization followed by Pd nucleation also, in some non-catalytic metallic substrates the electroless process can be induced by an initial application of an appropriate potential pulse. In practical terms, the evaluation of the catalytic activity of a substrate for the electroless deposition of a given metal is... 

The activation of nonconducting materials by the deposition of metal-containing polymer films could improve the autocatalytic metallization process by eliminating the aqueous etching and sensitizing steps. In addition, substrates that are hard to etch and activate by the aqueous process could be plated by this technique. 

The electro-copper plating from an aqueous solution of a copper ion has an electrochemical mechanism involving the electron transfer with an external source of electric current. Copper is autocatalytically deposited on the carbon surface as a function of reaction time [10]. 

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