Gold plating in the electronics industry

Abstract

Predictably enough at a meeting devoted to plating in the electronics industry, gold plating figured prominently at the Fourth Symposium on this theme held by the American Electroplaters' Society in Indianapolis, no less than 11 out of a total of 24 papers dealing with various aspects of this subject. Of these, four were concerned with applications in the semiconductor and microelectronics field, two with the requirements of gold plating for use on sealed reed relay contacts, three with processes and coating properties in the more general context of electrical contact applications, and two with analytical methods for the determination of metallic impurities or organic contaminants in plating baths. A common factor was the preoccupation with coating properties in relation to particular applications as affected by operational parameters, compositional variations and plating solution contaminants, reflecting the increasing specificity and control of coating characteristics demanded by today's electronics industry. The concern felt over the recent rise in the price of gold was also evident; of the various approaches to the problem of off-setting the resulting cost increases, selective plating which limits the gold coating to operational areas only, and the general improvement in deposit characteristics such as porosity, hardness and wear resistance to permit the use of thinner gold deposits, were accorded little more than passing general reference. Two papers were, however, concerned with a third possibility, namely the replacement of pure gold by alloy gold deposits of relatively low gold content. Such coatings have been used for many years in the plating of watch cases, where the requirements in terms of wear resistance and corrosion protection over long periods are not dissimilar to those of engineering applications, but though successful use in the electrical and electronics field has been documented in a number of cases in Europe, this type of coating has been more generally viewed with some suspicion on the general grounds of anticipated difficulty in compositional control and the possible effect of the presence of significant amounts of base metals on oxidation and corrosion resistance, particularly at elevated temperature. The fourth approach to the problem, the replacement of gold by an alternative metal which could match its unique combination of properties in terms of corrosion and oxidation resistance, low and stable electrical contact resistance, high conductivity, good solderability and weldability, seems very distant of realisation. Indeed, E. F. Duffek, of Chemline Industries, Santa Clara, in a general review of the semiconductor and microelectronics field, reported increased usage of gold, notwithstanding the price rise, and attributed this to a market trend toward consumer products as opposed to military and strategic items, again emphasising the need for low cost production.