Figure 5. Fretting corrosion from micromotions
Mating Gold to Tin
So, what about mating a tin-plated connector to a gold-plated connector? One could reason that
you'd get the benefits of both systems. In this case, that reasoning would be wrong. In reality,
what happens is some of the tin actually transfers to the surface of the gold during the initial
mating. This transferred tin forms the nucleus for tin oxide growth on the gold plating. In the
end, you still end up with the same fretting corrosion possibility with a mixed plating system
even though you paid a premium for the gold-plated half of the connector system.
All is not gloom and doom with non-noble platings. A properly designed connector system
mitigates the formation of these oxides, primarily by providing an initial wiping motion on
mating to break through films and the use of a minimum 100 grams of normal force to minimize
micromotions. The use of contact lubricants and anti-oxide compounds in the manufacturing
process further prevents the fretting corrosion from occurring thereby providing a stable long-
term interface. The experience and technical expertise of the connector designer and
manufacturer determines how well the connector performs in the end. The "Tin
