Silver Plating
ELECTROPLATED SILVER--which was developed primarily for use on holloware, flatware, and tableware--has proven
its usefulness in both decorative and functional applications in both engineering and electrical/electronic applications.
Decorative applications of silver plating still predominate; however, silver has been successfully substituted for gold in
some functional uses in electronics. Its greatest success has been the virtually complete replacement of gold on metallic
leadframes, the devices that support the majority of silicon chips. Here the development of new silicon-to-silver bonding
techniques and ultimate encapsulation of the silver allow for the replacement of a much more expensive precious metal
without loss of performance. In electrical contact applications, where the long-term integrity of the surface is of
paramount importance, silver has been less successful as a gold substitute due to its tendency to form oxides and sulfides
on its surface and the resultant rise in contact resistance. Silver has been employed as a bearing surface for many decades.
It is particularly useful where the load-bearing surfaces are not well lubricated (e.g, in kerosene fuel pumps on gas turbine
engines.)
Solution Formulations. The first patent concerning electroplating was filed in 1840 and reported a process for plating
silver from a cyanide solution. To this day, silver is plated almost exclusively with cyanide-based solutions, despite the
considerable research effort that has been expended on evaluating less toxic alternatives. A formulation for such a
solution is given in Table 1. This type of electrolyte would be used for plating decorative or functional deposits of silver
in a conventional way (i.e., on a rack or in a barrel). It is possible to produce fully bright deposits that require no further
buffing or polishing. This is achieved by including a brightening agent in the solution formula, (one of several sulfurbearing
organic compounds, or selenium or antimony added as soluble salts). Antimony containing silver deposits are
harder than pure silver. A typical antimony content might be 0.1 to 0.2% by weight. However, it should be noted that
antimony content will vary with the current density employed during deposition; lower current densities will produce a
deposit with higher antimony content.

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