High Temperature Film Formation on Cobalt‐Hardened Gold

Thomas, Jürgen; Sharma, Sachin

doi:10.1149/1.2129060

Cited by 11 publications

(6 citation statements)

References 11 publications

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“…The codeposition of an insulating film from cobalt-or nickel-hardened acid gold baths has caused significant problems for electrical contacts. High electrical resistivity can be observed upon thermal aging (e.g., 150 C), especially in films plated at high speeds with high cobalt concentration [26]. The subject has received considerable attention since the late 1960s when high contact resistance on telephone spring contacts was correlated with an orange-brown film on gold-plated contacts.…”

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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Section: Acid Cyanide Bathsmentioning

confidence: 99%

Electrodeposition of Gold

Kohl¹

2010

Modern Electroplating

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“…ening agent such as a cobalt salt. Recently, it was found that the inclusion of cobalt in the gold at concentrations above a certain limit may cause the formation of a highly resistive, cobalt-containing surface film (COO) when the gold is aged at moderately high temperatures (,--150~ (1). As a practical solution to this…”

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Inclusions in Electroplated Additive‐Free Hard Gold

Nakahara¹,

Okinaka²

1981

J. Electrochem. Soc.

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Hard gold deposits plated from an additive‐free phosphate bath have been analyzed for codeposited inclusions using transmission electron microscopy. Electron diffraction analyses of residues obtained from aqua regia dissolution of the gold deposits and those collected from the surface of thermally aged deposits showed that these residues consist of aurous cyanide false(normalAuCNfalse) . These results and other electrochemical evidences suggest that normalAuCN is codeposited in additive‐free hard gold, bringing about a grain refining effect and the resulting increase in hardness.

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“…This phenomenon occurs especially severely when the metallic cobalt content of the gold is high, because the increased contact resistance is a result of the formation of CoO on the surface, which is produced upon thermal oxidation of metallic Co, and not by the Co-CN complex included in the gold (52,53).…”

Section: (I) Electrical Contact Resistancementioning

confidence: 99%

Significance of inclusions in electroplated gold films for electronics applications

Okinaka

2000

Gold Bull

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Minute amounts of metallic as well as non-metallic inclusions significantly affect both bulk and surface properties of the electroplated gold films being used by the electronics industry. Surface effects are caused by the presence of extraneous materials diffused out from the interior to the surface, while bulk effects are brought about by the influence of inclusions on the microstructure of the gold films. This article reviews the current status of understanding of such inclusion effects in both soft and hard gold: these play essential roles in the fabrication of today's microelectronic devices.

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High Temperature Film Formation on Cobalt‐Hardened Gold

Cited by 11 publications

References 11 publications

Electrodeposition of Gold

Electrodeposition of Gold

Inclusions in Electroplated Additive‐Free Hard Gold

Significance of inclusions in electroplated gold films for electronics applications

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