[sdiy] Gold plated switches vs other types of plating

[Karl Ekdahl]

Roger, thanks a lot for all of this info!

Karl







Den fredag, 22 november 2013 16:35 skrev Roger Mote <rgrmt9 at gmail.com>:

Hi Karl,

Great question. Switch contacts are not one size fits all. It's a big subject. Type of switch, frequency of use, current and voltage being switched, and environment are all factors in which material is best.


Gold is best used with low current and infrequent operation. Its corrosion resistant advantages are often less important as current increases. Gold is not always the best choice. A thin gold plating may be quickly worn through by friction or arcing, leaving the metal underneath as the true contact. Beware of economy brands plating flash gold onto a switch contact for sales purpose. 

Silver and silver alloy contacts are the traditional contact material and are still widely used in switches. The silver oxide which forms is semi-conductive so the best use of silver as a contact is when the switch has a wiping motion, high current, or both. Traditional slide and rotary switches are wiping types. Switchcraft tini-jax use silver contacts and the tip and sleeve often hold up fine over the years but sometimes they still need to be cleaned because the sliding action of the normal leaf is not enough to keep good contact there as many ARP owners can attest. Silver is also found in barrel style DC input jacks. Especially those with higher current ratings. Again there is a wiping motion as the barrel slides into the Jack. Silver in various alloys is the usual go-to material for most switches.

As switches have evolved and product needs have changed the contacts have changed too. Though still desirable, wiping style contacts are not as prevalent in many of the most popular switch types today. Your toggle switch is a good example. Also the tact switches seen everywhere. Lower current switches are more common so both contact material and switch action have changed. Instead of sliding action, many switches use snap-action where the percussive force and hysteresis help to make-and break-reliable long lasting contact. But the softness of silver and gold can become a problem. Silver-nickel alloy is still found in many switches. More exotic contact materials like platinum, palladium, tungsten and iridium are used for increased hardness or special environments.

As Jay replied above your best bet is to read the data sheets, and not just choose the first available switch that fits. Ask the switch manufacturer for advice on your particular use. Two switches with similar life expectancy may not be equal once other factors are included.

You asked about switches, but contact material is also important when choosing things like IC sockets and mating connectors

Cheers, Roger  



On Thu, Nov 21, 2013 at 3:15 PM, Karl Ekdahl <elektrodwarf at yahoo.se> wrote:


>Hi list, i've been wondering about switch plating lately - while i understand that switches that have an internal gold plating is going to last longer than nickel plated ones, i'm wondering just how much longer? Is it time while used or unused (as in time to make build-up happen)? And what coating are switches generally that are not gold plated, is it nickel? What's the life expectancy of those? Confused..
>
>Thanks!
>
>Karl
>
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