Characterization of Cobalt‐Hardened Gold Electrodeposits by Mo̸ssbauer Spectroscopy: I . State of Cobalt in the As‐Deposited Material

Cohen, Richard L.; Koch, F.; Schoenberg, L. N.; West, K. W.

doi:10.1149/1.2129341

Cited by 22 publications

(12 citation statements)

References 13 publications

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“…These results do not rule out KCo(Au(CN)2)3 as the main brightening agent but they strongly indicate that these elements are also present in other forms, for instance some workers have identified elemental cobalt, CoOOH and cobalt cyanide in acid gold deposits (23,24).…”

Section: Brightenersmentioning

confidence: 89%

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Understanding gold plating

Wilkinson¹

1986

Gold Bull

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For effective operation, gold plating baths must require the minimum of attention in respect of replenishment and replacement, and must produce as little sub-standard or reject work as possible. To achieve this, an understanding of the processes involved and the factors affecting them is advantageous. This article attempts to provide such an understanding in a simple manner. Special attention is given to the plating of gold from acid baths containing monovalent gold complexes.The use of gold as a contact material on connectors, switches and printed circuit boards (PCB's) is now well established. There is also an awareness that only gold deposits from acid (pH 3.5-5.0) gold(I) cyanide baths containing cobalt, nickel or iron as brightening agents have the appropriate properties for a contact material. Gold deposits from: pure gold(I) cyanide baths; from such baths containing organic materials as brightening agents; or from electrolytes containing gold in the form of the gold(I) sulphite complex, do not have the sliding wear resistance which is necessary for make and break connections (1).It was known for many years that deposits from acid gold(I) cyanide baths brightened with cobalt, nickel or iron contained about 0.25 per cent of base metal, but this did not explain why their densities (16.0-17.0 g/cm 3) were so much lower than the density of pure gold deposits (19.3 g/cm 3). The classical experiment of Munier (2), in which she dissolved the gold of the brightened deposits in aqua regia vapour to reveal a polymer network, showed that deposits of this type were much more complex than was formerly thought.In what follows, an earlier account (3) of the factors involved in the formulation and operation of acid gold plating baths is brought up to date. Brief accounts are also included of the electrodeposition of gold from gold(III) cyanide baths and from gold(I) sulphite baths.

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Section: Brightenersmentioning

confidence: 89%

“…The dislocation theory (24,25) states that impurities cause extra dislocations in the metal lattice, which cause stress in acid golds and sulphite golds. In terms of this theory certain organics should give rise to compressive stress because they disguise some of the surface vacancies which lead to dislocations.…”

Section: Stressmentioning

confidence: 99%

Understanding gold plating

Wilkinson¹

1986

Gold Bull

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“…Thus the higher the solution agitation, the greater is the allowable current density. The cobalt or nickel ions are known to codeposit in the gold in at least two different forms, the cyano complex and as a substitutional alloy [20][21][22]. The increase in hardness is due to the grainrefining effect of the codeposited cyano complex [23].…”

Section: Acid Cyanide Bathsmentioning

confidence: 99%

Electrodeposition of Gold

Kohl¹

2010

Modern Electroplating

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While all that glitters may not be gold, it is the most beautiful of all the elements in their pure form. The name gold comes from the Old English Anglo-Saxon word for geolo meaning "yellow" while the symbol, Au, comes from the Latin word aurum, meaning "glowing dawn." Historically gold was one of the first metals known. Gold has been valuable throughout the ages chiefly because of its physical properties of softness, ductility, corrosion resistance, density, and scarcity. The first gold coin dates back to about 560 BC. Gold cups and jewelry predating 3500 BC have been found in Iraq. The ancient Egyptians knew how to hammer gold into leaf as thin as 66 nm. The importance of gold as a form of currency was at a high point in the 1900s when most countries were on the gold standard. The bullion price of gold over the past 21 years is shown in Figure 4.1.There have been about 160 metric kilotons of gold mined since it was first discovered, and it occupies about 0.005 ppm of the earth's crust. The world demand for gold in 2007 was approximately 80,000,000 troy ounces. Figure 4.2 shows the breakdown of the gold usage by industry. Jewelry comprises the largest fraction of the usage; however, much of that is not electroplated. For jewelry applications, gold is commonly alloyed with group IB or IIB metals, particularly copper, silver, platinum, and palladium, principally to improve its strength and wear resistance.The electrodeposition of gold is a relatively new process; it has been traced to the early work of Brugnatelli in 1805 [1]. The motives behind the use of electroplated gold changed dramatically in the mid-twentieth century when the emerging electronics industry required special-purpose electrical connections. The electronics industry consumed 5,330,000 troy ounces in 1994. Figure 4.3 shows the growth in the use of gold in the electronics industry by year. The use of electroplated gold in a variety of different functions in the electronics industry has led to (1) many advances in our fundamental understanding of the electrodeposition process and (2) new electroplating technologies over the past 25 years.Electrochemically deposited gold has satisfied many of the demands of the electronics industry. Gold has the third best electrical and thermal conductivity of all metals at room temperature. Also it has high ductility and excellent wear resistance, which are important for electrical contacts. The inertness of gold prevents the formation of insulating surface oxides (as compared to metals like aluminum). Group IIB metals (e.g., gold) are not good catalysts for other reactions, thus avoiding certain problems. For example, group IB metals (particularly platinum and palladium) can catalyze the polymerization of organic molecules forming insulating layers. In addition, gold is an excellent metal for wire bonding integrated circuits (ICs). Gold wires can be bonded to pure, soft gold pads by thermocompression bonding (300-400 C at high pressure to form a weld) or thermosonic bonding (150-200 C with ultrasonic energy to fo...

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“…Consequently, when thick bright coatings ( Although the use of complexing or chelating agents tends to decrease efficiency (typically down to 23 or 24 per cent), it ensures hard and bright deposits up to 20 gm in thickness. In addition their use drastically reduces the formation of cobaltcyanide complexes (3), the presence of which is associated partly with embrittlement of gold coatings. The following formulation can produce bright gold-cobalt deposits for jewellery items:…”

Section: Acid Bright Gold Platingmentioning

confidence: 99%