Some recent developments in non-cyanide gold plating for electronics applications

Abstract

The plated gold being used by the electronics industry can be broadly classified into two categories: soft gold and hard gold. Soft gold is used for circuit metallization and for bonding semiconductor chips, while hard gold is indispensable as the contact material on electrical connectors, electromechanical relays, and printed circuit boards. The traditional baths from which to plate soft gold as well as hard gold contain the cyanide complex, [Au(CN)2] -, as the source of gold, which liberates free cyanide ions during the plating. The free cyanide is not only highly toxic but also attacks photoresists used to delineate circuit patterns and bonding pads. For these reasons, noncyanide baths are in use to plate soft gold, whereas hard gold can be plated only from cyanide baths at present. In this presentation, the current status of both electrolytic and electroless non-cyanide processes for plating soft gold will be reviewed.

Formulation and characterization of electrolyte for decorative gold plating based on mercaptotriazole

“…The thiourea bath was developed and subsequently improved by a group of investigators at Hitachi Ltd. [23].…”

Thermodynamic assessment of the Au–Ga system

“…The Gold-based materials have gained increasing attention in recent years because of its potential application, as amorphous alloys with concentration range from 30 to 80 at.% Ga [1] and as wire bond, flip chip and off wafer interconnections due to its corrosion resistance, ability to form metallurgical bonds by soldering or cold welding, and ease of fabrication [2][3][4]. The thermodynamic descriptions of relevant alloy systems containing gallium are of crucial importance for understanding the physical properties, chemical behavior and the technological applications of the alloys or compounds.…”

Electrochemistry and speciation of Au+in a deep eutectic solvent: growth and morphology of galvanic immersion coatings

“…1 The key characteristic feature of these noble metal coatings is the lack of insulating surface oxides. 2 Electrolytic, 3 electroless, 4 and immersion plating 5 are the three common electrochemical methods used for the coating of conducting substrates with gold films.…”