Gold versus Tin contacts. Does it really matter?
Most people don't pay attention to the finish of their connectors
and contacts but they should. There are in fact two commonly used
types of metal for plating connectors and contacts -- gold and
tin.
Ever since day 1, arcade game manufacturers have strived to create their
machines using the cheapest parts possible while still maintaining a
decent level of reliability. Connectors were no exception to
the rule. They used tin plated contacts for everything -- from
high current power connectors to low voltage signaling connectors.
Most industries used gold plated connectors whenever you pass low
voltage signaling such as address lines, data lines, switch matrix
lines, etc. The arcade industry did not. But don't go changing
your crimp contacts to expensive gold plated now...
It is important to make sure that you use gold plated contacts with
gold plated pins, and tin plated contacts with tin plated pins. When
gold and tin are mixed by putting gold plated contact against a tin
plated pin or vice-verse, the direct contact between the two
dissimilar metals causes a chemical reaction over time. It can take
months or even years to happen, but tin oxide will build up on the
gold and eventually, cause the electrical connection between the
socket and connector to become unreliable. While you may get
away with mixing gold and tin in the short run - eventually you will
start getting errors resulting from the oxide buildup.
From an old Intel study: "Studies show that fretting occurs
when tin comes in pressure contact with gold or any other metal. Tin
debris will transfer to the gold surface and oxidize. Continued
transfer will build up an oxide film layer. Mixing gold and
tin leads doesn't always cause an immediate problem, the problem
usually occurs over time."
Moral of the story - don't mix metals! Going with more expensive gold
plated contacts in a machine designed for tin plated contacts should
not be done. Always go with the same contact plating type.