Gold plating vs Silver plating for electrical contacts
June 25, 2008
Q. We would like know if plating aluminum with silver passivation is better or silver coating with gold flash is better to improve conductivity? which of the two processes are better in terms of durability and cost.
isro - bangalore, India
July 1, 2008
A. Hi, G.R. Silver plating with a gold flash would be a more reliable and durable high conductivity contact surface than passivation, but more expensive. Even then, a 'flash' might be too thin for long term durability though.
Ted Mooney, P.E.
Pine Beach, New Jersey
April 30, 2010
Q. Hi ! I am an electrical design engineer looking after low voltage switching contacts. I Have heard that gold plating is well suited for low voltage low current applications, but the heating effect with passage of current is more in case of gold plated contacts than in silver plated contacts, so I would like to know what plating to go for. And also I would like to know how the current behaves while flowing through an electroplated metal.
designer - Mumbai, India
May 5, 2010
A. For switch contacts the way to go is a hard acid gold. It offers low contact resistance along with wear resistance. The gold is normally alloyed with nickel or cobalt to increase hardness of the deposit. Silver may be too soft for the switching mechanism, and increased temperatures involved would increase contact resistance. The current travels along the surface of the electroplated metal. The rate of conductivity and distribution would depend on the metal plated. At room temperature silver is best, copper next, then gold. Platinum is excellent too, but who can afford it?Mark Baker
process engineer - Malone, New York
January 2, 2018
Q. Does silver plating a copper contact, increase conductivity? We see copper wires being gold plated all of the time, is it just for resilience, because copper is more conductive than gold? Why do companies not silver plate, instead of gold? I am really curious if you silver plate copper, if it will increase the conductivity though?Joshua Miller
- Castle Rock, Washington United States of America
A. Hi Joshua. Mark has told us, correctly of course, that silver, copper, and gold -- in that order -- are the most conductive metals. But what also needs to be considered is that metals can corrode and form corrosion products on their surfaces which interfere with their conductivity when used as a contact.
If you accidentally sprayed paint onto your contacts you would know that you must remove it to insure good conductivity, but metals grow corrosion products which, like paint (but not as powerfully), can block the passage of current. In general, copper corrodes and builds insulating corrosion products on its surface which are problematical enough that you can't use bare copper for low voltage contacts although they are fine for house current. Silver is better but still tarnishes. On very low voltage, very low current, digital contacts like on your cell phone or video games, you'll always see gold plating because precious metals like gold do not corrode/oxidize/build up non-conductive corrosion products under normal conditions.
I'm not an electronics engineer, and there's more to it all than just the above, including strange facts like very high frequencies travel on the surface rather than through the bulk of the metal ... but I hope I answered your question, and I can try again if you need further clarification.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"
January 3, 2018
A. Also, silver tends to migrate through the board material and cause partial shorts. Google "silver migration."Chris Owen
- Benton, Arkansas, USA
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