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I have two connectors both gold plated, because of changes I have to consider moving one of these to a tin connector. Now I need to find out what the worst case scenario would be from a design with gold mated with tin. What are the consequences of using a tin plated contact with a gold plated contact?

I can think of a few reasons not to (are there more?):

  • corrosion
  • oxidation
  • reduction of conductivity

Has anyone ran gold plating with tin plating?

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    \$\begingroup\$ I've heard of the 'purple plague' when gold was in contact with aluminium, but I know it's fine with nickel. FWIW these are the electronegativities - Au 2.54, Sn 1.96, Ni 1.91, Al 1.61. That suggests it should be as good with tin as nickel, if it's electronegativiety controlling it. If it's something else, then all bets are off. \$\endgroup\$
    – Neil_UK
    Jul 6, 2021 at 20:14
  • \$\begingroup\$ i suppose it doesn't depend on electronegativity but on the binary phase diagram. Au and Ni segragate completely at room temperature, whereas Au reacts with both Sn and Al. the intermetallic phases can have worse properties than the pure metals (or better). my guess is Sn and Au are fine because it is a rather widespread combination \$\endgroup\$
    – tobalt
    Jul 6, 2021 at 20:47

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If you want reliability, don't mix tin and gold plated connector pins. You end up with fretting corrosion which is hard to remove from the gold surface once it's formed. Personally, I've seen problems with mixed plated audio connectors. TE (Amp) has a Connectors 101: What Lighting Designers Need to Know booklet that discusses fretting corrosion. See pages 6-11, page 10 talks about gold-tin interface.

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