Gold Plating Bath Research Articles

Single-column ion chromatography of weak inorganic acids for materials and process characterization

Single-column ion chromatography allows the separation and direct conductometric detection of anions of weak inorganic acids. Mixtures containing borate, silicate, germanate, fluoride and chloride can be resolved by using a resin-based anion-exchange column and a 0.06 g l −1 sodium hydroxide/2.5 × 10 −5 M sodium benzoate eluent. Judicious selection of sample preparation and of eluent composition is important. Glasses are analyzed for boron and fluoride by fusion with sodium hydroxide, suitable dilution and use of a benzoate eluent. Results on standard glasses are in good agreement with certified values. The separation of arsenite and arsenate in a gold plating bath is outlined.

Ａｕ‐Ｎｉ‐ＳｉＯ２分散めっき皮膜の生成

Au-Ni-SiO2 dispersion coatings were prepared from an acid gold plating bath containing SiO2 particles as a dispersion in an effort to improve hardness and wear resistance of the coating films. SiO2 particles were easily codeposited in 22 karat gold-nickel alloy films. The amount of SiO2 codeposited increased with an increase in the concentration of SiO2 in the bath, depending on plating time and current density. Crystal violet as an addition agent was adsorbed to SiO2, giving a positive charge, and influencing the codeposition of SiO2. The Au-Ni-SiO2 dispersion coatings were harder than 22 karat gold-nickel alloy films Hv 320 compared to Hv 270, and wear resistance, using test apparatus of wear (contacting member: pumice eraser, load: 4kg·cm-2), wear resistance was found to increase about twice. Corrosion resistance, however, somewhat deteriorated.

金の電析におよぼす微量金属イオンの影響

The electrochemical and morphological effects of minute amount of lead, thallium, arsenic, cobalt, indium or nickel ions on the electrodeposition of gold from acidic gold plating baths have been systematically investigated. Heavy metal ions, Pb2+ or Tl+, increased the current efficiency of gold electrodeposition, especially at low current density, and changed the morphology of the electrodeposit. On the other hand, Co2+, In3+ and Ni2+, which easily form alloys with gold in electrodeposition, decreased current efficiency and reduced grain size, so that a bright, smooth deposit was obtained. However, AsO2- ion, which acts as a brightener in gold sulphite plating baths, had unsatisfactory brightening effect in acidic gold plating baths.

Plating in the electronics industry

The analysis and control of gold plating baths used in the fabrication of electrical components and printed circuit boards were highlighted at the American Electroplaters’ Society’s 9th Symposium on Plating in the Electronics Industry held in Atlanta, GA., on February 16th and 17th, 1982. Electronic systems are becoming more complex with greater packing densities and are operating under stringent conditions. It is therefore becoming increasingly critical to optimize, monitor and control existing plating systems, to develop new materials and, at the same time, to work under environmentally acceptable conditions.

Steam Condensation on Various Gold Surfaces

Gold surfaces were investigated as promoters of dropwise condensation (DWC) of steam at atmospheric pressure. Very high heat fluxes at low ΔT’s may be achieved in this manner. Seven gold electroplating baths, one electroless immersion gold bath, and vacuum vapor deposition of gold were used. Five surface preparations for pure gold were tested. Gold deposits ranged in thickness up to 20,000 A.U. Auger electron spectroscopy and scanning electron microscopy were used to describe the surfaces chemically and physically. Deposits from the bright pure gold plating baths and the “acid, hard” baths promoted DWC. Deposits from alloyed baths, the ultrapure bath, and vapor deposition gave mixed or filmwise condensation. Two surface preparations on solid gold gave DWC, one gave mixed, and two gave filmwise condensation. The results indicate that gold provides an oxide-free surface which adsorbs trace organics from the surroundings. These promote DWC.

Cyanoaurate(III) Formation and Its Effect on Current Efficiency in Gold Plating

The cyanoaurate (III) ion has been found to form and accumulate in acidic or neutral gold plating baths containing cyanoaurate(I) as the source of gold. This trivalent gold species brings about a decrease in plating current efficiency because its reduction to gold metal requires three faradays per mole, whereas only one faraday is consumed to reduce one mole of Au (I). The accumulation of Au (III) should therefore be minimized to produce gold deposits with a thickness unaffected by bath age. This paper describes various methods for achieving this objective, which include the use of the so‐called “dimensionally stable anode” and a techniqe of chemically reducing Au (III) to Au (I).

Theoretical Considerations of Acid Gold Plating

SummaryThe paper describes some possible theories which may explain the mechanisms operating in a gold plating bath. Theories are tools which enable us to improve and develop techniques and processes and it is believed that the theories presented here can be used in this way. Some, or all, of these theories will not be acceptable to everyone but it is hoped that they will at least stimulate discussion.

The sulphito complexes of gold

A new nitro-sulphito gold electrolyte has advantages over available commercial sulphito electrolytes in terms of stability, simplicity of control and the minimum non-porous deposit thickness. In describing its development, the authors review what is known of gold sulphite complexes and their use in gold plating baths.

Radioisotopic Investigation of the Codeposition of Iron, Cobalt, and Nickel in Gold Electrodeposits on Electronic Equipment

The effect of contamination of a cyanide, phosphate-buffered gold-plating bath with iron, cobalt, or nickel on the codeposition of these metals with gold, was investigated using 59Fe, 58Co and 63Ni. It was shown that cobalt and nickel were practically not codeposited in gold if present in the solution in amounts up to 1000 or 2000 mg/dm3 respectively. Iron deposited in high amounts (up to 18%) depending on its concentration and the cathode current density. The diminishing in current efficiency of the plating process is proposed as an early signal of the contamination of gold deposit with iron.

The Control and Characteristics of Acid Alloy Gold Used as a Decorative Plate

SummaryBrief comparison has been made between the alkaline cyanide and acid citrate gold plating baths. Operating conditions of a proprietary acid bath and their effect on cathode efficiency have been investigated. The low gold and nickel metal content generally adopted in these baths and the marked effect of slight variation in these metals on the characteristics of the deposit and trouble-free running of the process make regular analytical control important, as this affects economy of process and quality of product. Brief mention has been made of the application of atomic absorption spectrophotometry as a convenient means of analytical control. Plating distribution can be greatly improved by careful consideration of anode configuration and cathode jig design. The most suitable anode material was found to be gold strip, or as an alternative, platinized expanded titanium mesh. In the proprietary acid bath under consideration, carbon or stainless steel anodes were found to be unsuitable.

A microelectronics interconnexion method : H. T. Mortimer and J. S. Schiavo, Electronic Packaging and Production, May (1966), p. 171

According to ultraviolet (UV) spectroscopic studies, a positive AZ photoresist film thicker than 10 (m can hardly transmit UV lights of wavelengths 200–285 nm. A simple photomask for UV photolithography was prepared using a quartz glass plate coated with a light-obstructing film of positive AZ photoresist, and the quality of the photomask and fidelity of the pattern transferred by the photomask were evaluated. The developed AZ photoresist photomask was used for fabrication of gold microelectrode on polycarbonate (PC) sheets. PC sheetswere exposed to the UV lights emitted from a low-pressure mercury lamp and passed through the photomask. The PC sheets were subjected to selective surface photolysis in the exposed area. After a series of wet chemical reactions, nano gold particles serving as the catalyst for electroless plating were deposited on the irradiated area. Gold microelectrodes were then generated by immersing the selectively activated PC sheet in an electroless gold plating bath for a specific time. Without need for a clean room, the photomasks can be prepared by a chemist in a common chemical laboratory with low-cost materials and simple procedures.