Showing papers in "Plating and Surface Finishing in 1994"

Some mechanisms of the action of additives in electrodeposition processes

Abstract: This review is of mechanisms by which additives have been postulated to affect the rate of deposition of metals and their alloys. Emphasis is on recent work in our laboratories, where mechanisms have been tested by choosing systems expected to exhibit the appropriate chemical behavior. Mechanisms chosen for study include: (a) ion bridging, (b) ion pairing, (c) changes in interfacial tension, (d) hydrogen evolution effects, (e) hydrogen adsorption, and (f) electrode filming. The possible role of electrode filming in electrodeposition of difficult-to-plate metals is discussed, as well as anomalous and induced codeposition of alloys, and deposition of stoichiometric alloys, such as the nickel-tin system

Trivalent chromium solutions for applying chemical conversion coatings to aluminium alloys or for sealing anodized aluminium

Abstract: Corrosion-resistant films were formed on aluminium by immersion in solutions of basic chronic sulfate, plus fluosilicate, with alkali added to near, or slightly beyond, precipitation of insoluble basic compounds. The trivalent chromium films formed on 7075-T6 or 2024-T3 aluminum, when tested in 5-percent NaCl salt spray, provided corrosion resistance in excess of 96 hr. When a post-treatment of peroxide or permanganate solution was applied, corrosion resistance for both alloys almost reached 336 hr and sometimes exceeded this value

Zinc alloy electrodeposition for corrosion protection

Abstract: This paper explores four types of the most widely used commercial zinc alloy electrodeposition systems for application in the automotive and building industries. Process parameters are investigated and optimized conditions determined for each system, using various methods of coating assessment

Rotating ring-disk electrode studies of copper electrodeposition: effect of chloride ions and organic additives

Abstract: A rotating ring-disk electrode (RRDE) was used to investigate the effects of chloride ions, organic additives and hydrodynamic conditions on copper electrodeposition and deposit appearance in deoxygenated acid copper sulfate solutions. The organic additives selected included thiourea (TU), benzotriazole (BTA) and a proprietary commercial brightener (PB). Four distinct regions, the apparent Tafel, transition, limiting current, and post-limiting-current regions, were observed between the rest potential and -1.2 V (vs. SCE). The characteristics of the ring current behavior observed during the cathodic potential sweep of a copper disk supports the two-step electron transfer mechanism for copper electrodeposition in acid CuSO 4 with Cu(I) as an intermediate

Molybdate based Alternatives to Chromating as a Passivation Treatment for Zinc

Abstract: Zinc-plated parts are typically passivated with chromate-based solutions to reduce corrosion. Chromates, however, are a cause of environmental concern, for their toxic effects on plants and wildlife, and allergic effects on workers who come in contact with them. A molybdate-based alternative has been developed that can be used to replace chromates in a wide range of applications. The process has been tested in a project set up by the Danish Government in 1989, at the Centre of Advanced Electroplating (CAG) in Denmark. Procedures used for the alternative process are similar to those used in chromating. The corrosion protection provided by the process on zinc-plated parts is comparable to chromates

Electroless nickel plating is not electro...less

Abstract: Inadequate surface preparation is a common pitfall associated with adhesion or corrosion-resistant failures. This paper addresses the real reason electroless nickel plating works-a no-shortcut pretreatment process. The details of one process that has been successful on all types of ferrous metals, including high alloy, carburized and hardened substrates, is described, with focus on using the proper electrolytic processes

Zinc-nickel electroplate as a replacement for cadmium on high-strength steels

Abstract: In the mid-1980s, cooperative efforts between the steel companies and the major automotive manufacturers led to the widespread introduction of electrogalvanized zinc-coated steels for automotive body panels. These efforts spawned a multitude of zinc-based alloys electroplates, including zinc-iron and zinc nickel, which, in certain applications, were felt to offer advantages over the pure zinc coating. At the same time, the quest for replacement coatings for cadmium, which was being eliminated because of health and environmental concerns, was proceeding apace. Fortuitously, it turned out that zinc-nickel was a prime candidate for replacing cadmium, as it possessed nearly all the attributes for which cadmium had been used.

Electroless metal deposition as a useful tool for microelectronics and microstructures

Abstract: The quality of metal deposits is a key point for the manufacturing of electronic devices and circuits, and becomes more and more important because of their continually decreasing physical dimensions. Accordingly, there is currently a strong need for reproducible, fast and selectively localized methods of metal deposition in these fields, as well as in all other kinds of microstructure fabrication

Friction and wear characteristics of electroless Ni-P-PFTE composite coatings

Abstract: Electroless nickel has been used as a versatile material to protect parts from corrosion and wear. Its wear resistance has been well-established by suitable heat treatment and as a composite coating by incorporation of hard particles into the matrix. 1-5 Composite coatings, using electroless nickel as the matrix, have interested the surface finishing and engineering communities for many years. A composite coating containing silicon carbide is one of the most successful for preventing wear and for relatively low friction

EMI shielding by electroles plating of ABS plastics

Abstract: Electronic equipment, especially computers, needs to be shielded from stray electromagnetic interference (EMI). Most equipment is contained in plastic housings, so is transparent to EMI. Plating on plastics offers a method for economical and reliable EMI shielding. This review explains the plating process and compares the capabilities of shielding techniques. Theoretical principles of shielding theory are also discussed

Laser surface treatment of aluminum alloy 6061 with SiC powder injection: study of microstructure and wear behavior

Abstract: The microstructure and mechanical properties (hardness and wear resistance) of aluminum Alloy 6061 were studied via laser-induced melting, with SiC particle injection. The upper part of the laser-treated zone was strongly alloyed, showing a fine microstructure with varied morphology and very high microhardness values (500 HV 0.03 ), compared to the substrate (60 HV 0.03 ). In the lower part of this zone, SiC particles remained completely unreacted and had only mechanical adhesion with the matrix. Wear tests revealed that extremely high wear resistance (10 times greater than the untreated substrate surface) resulted from this laser surface treatment technique when a 50-N load was applied

Electrolytic deposition of palladium-iron alloys

Abstract: Electrolytic deposition of palladium and its alloys is nearly 100 years old. As early as 1884, electrolytes based on divalent palladium-chloride-ammonia complexes were discussed. For an equally long period, palladium alloys with the elements of the iron group have been known. Palladium deposition gained wider technical interest, however, only when it was found that electrodeposited palladium and its alloys are possible and can be less costly substitutes for gold for electric connectors

Effects of pretreatment on the structure and properties of electroless nickel coatings

Abstract: The pretreatment process can significantly affect the corrosion resistance of electroless nickel (EN) coatings. One of the most important reasons is that different pretreatment processes can give different surface morphologies of the substrate. The scanning electron microscope (SEM) and the scanning tunneling microscope (STM) have been used to investigate the structure and properties of EN coatings in the as-plated condition for various deposition times, in relation to different mechanical/chemical pretreatment processes. The morphology of the substrate surface is found to be a key factor in control of the porosity of EN coatings. It can significantly affect the formation of EN deposits, not only in the early stage but also in the morphology/ structure during the continued growth of the deposit

Codeposition of mixtures of dispersed particles with nickel-phosphorus electrodeposits

Abstract: Codeposition of SiC, ZrO 2 , Cr 2 O 3 , TiB 2 and MoS 2 powders and their mixtures with a Ni-P coating has been investigated. With the mixtures, more conductive and hydrophobic particles intensified the codeposition of non-conductive and hydrophilic particles; the reverse effect was observed also. This phenomenon suggests an additional possibility for control of the dispersed phase content and composition by selecting the components of powder mixtures. Compared with the matrix, the hot-oxidation resistance at 950°C increased to the greatest extent in the presence of Cr 2 O 3 and ZrO 2 together in the electrolyte

Comparison of alkaline Zn-Ni & acid Zn-Ni as a replacement coating for cadmium

Abstract: Cadmium plating has been used as a corrosion-resistant coating for many years, providing good corrosion resistance with excellent self-lubricating properties. Because of concern regarding cadmium's toxicity, alternative coatings are pursued. Zinc alloyprocesses are suitable candidates as substitutes for cadmium for corrosion resistance. Even pure zinc is a suitable substitute, but its effectiveness is short-lived. This article, which is an edited version of a paper that was presented at the 15th AESF/EPA Pollution Prevention and Control Conference (January 24-27, 1994), documents the testing and investigation undertaken to compare acid and alkaline Zn-Ni processes

Effect of additives on electrodeposition of composite chromium coatings

Abstract: The effect of additives on particle codeposition with a chromium matrix is considered. It is shown that additives act as particle codeposition stimulators or influence the morphology and phase composition of the matrix. Codeposition stimulators can either reduce electrolyte surface tension or be adsorbed on the surface of the cathode and particles, changing the particle surface charge and adsorptivity. Additives involving matrix phase transformation can improve hardness and wear resistance of the composite coating and thus intensify the positive effect of the incorporated particles

Plated through-hole processing : an integrated approach

Abstract: Printed wiring board manufacturers are faced with their stiffest battle for survival yet: Global competition, environmental regulations, declining profit margins, stricter quality standards, etc. It is evident that survival will depend on the highest quality and yields, while keeping costs under control. One way to enhance quality is to have a thorough understanding of all aspects of the manufacturing press: Chemical and mechanical. The purpose of this article is to focus on plated through-hole (PTH) processing (desmear and electroless copper). Rather than look at desmear and electroless as two separate processes, however, we will treat them as one continuous process. This can be termed, better, «the integrated approach»

Effect of additive conversion on internal stresses in nickel deposits

Abstract: The effect of aromatic sulfo compounds on the internal stresses in nickel deposits is governed by the degree of their conversion into intermediates and the extent of their incorporation in the deposits. In the case of thiourea, the internal stress changes as a function of its concentration, corresponding to the extremes in its conversion kinetics. An analogous pattern was observed in class II brighteners, the lower the degree of hydrogenation of the additive, the stronger its effect on the internal tensile stress. The internal stress in deposits obtained in the presence of a mixture of additives was found to depend on their competitive adsorption, with attendant changes in conversion kinetics and in incorporation of the constituent additives

Electrodeposition of iron-nickel alloys in the presence of organic additives

Abstract: Linear sweep voltammetry was used as an in-situ technique to characterize the electrochemically formed thin layers of Fe-Ni alloys. By using a potentiostatic pulse-plating technique, organic additives were shown to be essential for enabling deposition of the binary alloy from sulfate electrolytes. This study found the optimum plating conditions and a new formulation for a plating bath

Continuous electrolytic treatment of complex metal cyanides with a rotating barrel plater as the cathode and a packed bed as the anode

Abstract: A continuous electrolytic process consisting of a plating barrel cathode and a packed-bed anode was used to recover metals and to destroy cyanide in waste silver, copper and cadmium cyanide solutions. The experiments were carried out with and without the addition of NaCl to the feed solutions. The effluent concentrations of total cyanide, free cyanide and metal ions were examined for various cell currents, solution temperatures, solution feed rates, solution recirculation rates, barrel rotation speeds, and barrel loadings. The total cyanide concentration was reduced from 520 ppm to fewer than 10 ppm, and metal concentrations from 225-486 ppm to less than 1 ppm

Structural Transformations in electroless Ni-P-B deposits

Abstract: Electroless Ni-P-B deposits with weight percentages of 0.72 P and 4.15 B; 1.87 P and 4.87 B, were observed to be a mixture of microcrystalline nickel and amorphous phases, based on X-ray diffraction and transmission electron microscopy. On annealing, Ni 3 P and Ni 3 B precipitated along with crystalline nickel in one step. The microhardness of the deposits showed typical precipitation hardening behavior, with hardness increasing from about 550 VHN in the as-deposited condition, to about 1000 VHN in the fully crystallized condition

The effect of monovalent cations on electroless nickel plating

Abstract: The effect of increasing concentrations of NH 4 + , Li + , Na + and K + on plating rate and bath stability were investigated in a lactate-acetate EN plating solution. The relationship between sulfate and phosphite salt solubilities and metal turnovers was studied. Deposition potentials, microstructures and phosphorus contents were also determined

Plating on plastics : an industry review

Abstract: Electroplating and electroforming typically account for nine to 11 percent of total nickel consumption. In the last few years, world consumption of nickel anodes has been 60,000 to 70.000 tonnes (a metric ton is 1000kg, or 2204.62 Ib) per year, with about 80 percent being used in producing bright, decorative and corrosion resistant finishes. The automotive industry is the largest single end-user of these finishes. One sector of the plating industry that has been heavily dependent on automotive applications is plating on plastics (POP). In 1993, the nickel Development Institut (NiDl) * made a study of this industry because nickel is used in most applications. Discussions were held with plastic producers, chemical process suppliers, electroplaters and end-users. This paper summarizes the findings of the study

Recovery of cadmium and cyanide using a combination of ion exchange and membrane extraction

Abstract: A combination of ion exchange and membrane extraction successfully recovered cadmium and cyanide from simulated cadmium-cyanide rinsewaters. The ion exchange loading was most effective at cyanide-to-cadmium molar ratios of 4:1 or less; when the molar ratio exceeded 4:1, cadmium-cyanide complexes caused a chromatographic displacement of free cyanide from the resin. Cyanide-to-cadmium molar ratios in excess of 4:1 could be reduced to 4:1 or less by pumping the solution through a sand filter loaded with cadmium oxide. Regeneration of the anionic resin with sulfuric acid restored the full resin capacity and recovered the cadmium and cyanide in separate solutions

Cyanide-free electroless gold plating from a bath containing disulfitoaurate and thiourea or its derivatives

Abstract: To develop a cyanide-free electroless gold plating bath, use of disulfitoaurate and thiourea, or its derivatives, was studied. As reducing agents, nine types of sulfur containing compounds were tested. Of these, thiourea, N-methylthiourea, and 1-acetyl-2-thiourea produced thick gold films. With the other compounds, only thin films resulting from substitution plating were obtained. Cyclic voltammograms of these materials support these results. The best composition was obtained in a mixture of thiourea and N-methylthiourea

Designing a new PCB facility for successful pollution prevention & waste minimization

Abstract: When printed circuit board (PCB) fabrication firms are starting new operations or modifying existing facilities is the ideal time to establish a coordinated effort between the engineers in manufacturing and in facilities so that pollution prevention and waste minimization techniques can be implemented successfully, right before start-up. The goal of a design team for a new facility in Puerto Rico was to minimize hazardous waste production. The practical steps taken and ideas presented here may be applicable to your operations

Experimental strategy : application of Taguchi's quality engineering method to zinc phosphate coating uniformity

Abstract: Plating process quality can be improved at no additional cost or even at a saving by Taguchi's quality engineering approach. The experimental strategy described in this paper is different from traditional experimental design, in that it is concerned with reducing variance in the manufactured product by determining the best settings for the manufacturing process parameters without tightening tolerances on them. By employing dynamic characteristic statistics, a process for uniform zinc phosphate coating can be determined from the linear relationship between coating substrate geometric area (signal factor) and coating weight (output characteristic)

Vacuum deposition processes and the properties of thin films

Abstract: The particular process used for deposition of a thin film on a substrate has a definite influence on the microstructure of that film. For vacuum deposition processes (evaporation, spuffering, ion-assisted deposition, ion-beam spuffering, ion plating), the average energy of deposited particles has been found to be the single most important parameter determining the thin film microstructure. This is shown with electron micrographs of fractured thin film cross sections and simple two-dimensional computer simulations, based on a ballistic model

Alternatives for nickel in electroplating processes

Abstract: The potential of nickel as an allergen has caused some surface finishers to avoid its use. Nickel is typically used for its levelling ability to improve substrate quality, and as a diffusion layer. It is also a good alloying-element for gold-based alloy deposition. This edited version of a presentation from the EAST session at SUR/FIN®'94-Indianapolis discusses the use of copper/tin and copper/tin/zinc electroplating as a replacement for nickel intermediate layer for decorative applications, and some technical applications. A more costly alternative presented is a new, very ductile palladium. Gold/nickel, and gold/nickel/indium processes are commonly used in gold alloy plating for decorative use

The effect of some additives on the throwing power and stability of tin(II) solutions during A-C coloring of anodized aluminum. II: Sulfonic acids, amino acids, antioxidants

Abstract: Some commercially important addition agents were used in electrolytic coloring of anodized aluminum from tin(II) solutions. Their influence on throwing power was studied with respect to their molecular structure. Resistance to atmospheric oxidation of the solutions used was evaluated, in comparison with those containing 1,2-dihydroxy-benzene and ferrous ions, as well as a mixture of ferrous and ferric ions