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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.