Page:Gametronics Proceedings.djvu/68

 Re-evaluation of the requirement to use gold is a good thing, and undoubtedly many cases of usage will be found where it is a luxury rather than a necessity. On the other hand, the decision to use low-cost alternatives to gold plating should be based on rational engineering criteria as well as cost factors.

Gold plating is used on connector contacts when it is required to handle low-level signal voltages and current with high reliability. The over-simplified statement of justification of gold plating needs to be examined in some detail in order to come to grips with the question of whether or not it can be eliminated.

Gold is a noble metal. By this, it is meant that gold does not easily react with other substances, and in particular, it does not react with the atmosphere to form oxide or tarnish films on its surface. In this respect it is unique among metals. No other metal, even the precious metals like platinum and rhodium, are as completely free of oxide films. In electric contacts this is a very important attribute, because oxide films are contact insulators. When surface films are present they must be removed, mechanically, electrically, chemically, or thermally before adequate electric contact can be established between conductors.

With all its advantages, gold is not needed or desirable for all contact applications. It is of no value in arcing contacts, for instance, where it erodes rapidly and has a strong tendency to weld. And the sliding wear characteristics of pure gold are not very favorable. It tends to stick, gall, smear, and wear-off faults use on high pressure semi-permanent connections or in crimp connections is of dubious value other than in certain corrosive environments. The very characteristics which makes it ideal for some contact applications will compromise its use for others.

Zero-Insertion-Force (ZIF) connector designs have also been proposed. ZIF connectors incorporate some mechanism whereby heavy normal forces are exerted on the contacts after engagement. Mechanical advantage can be built into the loading mechanism to reduce the human effort requirement in such a connector, and the severe wear problems associated with sliding under high normal force can be avoided. ZIF connectors have, in principle, enormous potential advantages. The expense of the added complexity of such a connector must, however, be weighed against the savings obtainable from the use of non-noble contact plating.