Electrical Contact Material

In a critical situation I would use reed relays and small magnets. A totally closed system, no maintenance.

Oh, and if you insist on contact fingers, try hammered silver. It produces nice springs, and even the oxide conducts. They might come to 4 dollars a piece, but satisfaction guaranteed.

What's wrong with plating? It's not that expensive. Maybe nickel plating. (We got a tray full of stuff for

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Platinum?

Not sure about Platinum but IIRC Rhodium was used for some special relays.

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Stuart Winsor

Midland RISC OS show - Sat July 9th 2011

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What about platinum are you unsure of?

0.000050 gold flash over nickel, and it won't matter much which alloy the rest of the contact is. :-)

Or, $olid $ilver ;-P

And I'd use BeCu before I'd use phosphor bronze; just a personal whaddayacallit. ;-)

Cheers! Rich

What's the quantity? Is it a one-off? If so, just get a relay and hack it for the contacts.

For production, see my other post (gold-flash over nickel plate, or $olid $ilver, BeCu for the springy part).

Cheers! Rich

Platinum is the most widely used switch contact media in use by man at present.

Total bullshit. Gold plating that thin is for cheap "Monster" brand level stupid consumer products.

Mil contacts are NOT plated(pins and sockets)(switches are, but it is VERY heavy plating), and yes,the underlying material WOULD matter as that thin of a gold plating will be worn off after not too many cycles. The reason Gold is chosen when it is, is because it, like Platinum, NEVER oxidizes. If your "gold" contacts get a patina on them, they are NOT gold.

Bad news, Silver will easily meld with itself, and electrical current will actually help. High current will weld such a set of contacts together in pretty short order.

Phosphor Bronze is a bearing media, not an electrical switch contact media. D'oh!

BeCu is used for elements that need to be light in weight or have better corrosion properties, like phono cartridge needle arms, or the switch contact's "arm". It is not a very good electrical contact face media choice either.

For production? For production you just buy a damned part. An SSR or a switch based relay... even a miniature job. Hell, I have about ten in my junk box here. Everything from sealed explosion proof mil jobs down to opto-coupled micro-SSRs.

Sheesh.

Sjouke, I'll need to make almost 800 tiny contacts(for just the initial prototype). And one end of each contact will to be soldered to fingerboards that have .156" traces.

As for silver I heard the oxide could be a resistance problem. (And it looks too expensive anyway).

George Herold, I just may have to plate anyway. :-(

Bill, That PDF wouldn't apply that much to me because what I'm making will only entail making and breaking connections *when there is no current*.

Stuart, I settled on Phosphor-Bronze because of what I thought would be it's spring temper, corrosion resistance, and electrical conductivity.(Not to mention cost).

John Fields, Platinum and Rhodium are too exotic to fit my parameters.

Rich Grise, As for why I didn't go with BeCu. One particular reason is that I need the spring of Phosphor-Bronze. As many as 56 out the almost 800 connections will have to be made at one time, and so I need to come up with a flexible backing for the unsoldered ned of the contacts to do this.

Thanks.

Darren Harris Staten Island, New York.

Sjouke,

I'll need to make almost 800 tiny contacts(for just the initial prototype). And one end of each contact will to be soldered to fingerboards that have .156" traces.

As for silver I heard the oxide could be a resistance problem. (And it looks too expensive anyway).

George Herold,

I just may have to plate anyway. :-(

Bill,

That PDF wouldn't apply that much to me because what I'm making will only entail making and breaking connections *when there is no current*.

Stuart,

I settled on Phosphor-Bronze because of what I thought would be it's spring temper, corrosion resistance, and electrical conductivity.(Not to mention cost).

John Fields,

Platinum and Rhodium are too exotic to fit my parameters.

Rich Grise,

As for why I didn't go with BeCu. One particular reason is that I need the spring of Phosphor-Bronze. As many as 56 out the almost 800 connections will have to be made at one time, and so I need to come up with a flexible backing for the unsoldered ends of the contacts to do this.

Thanks.

Darren Harris Staten Island, New York.

That's a perfect storm: no high voltage, no wiping, means that any dust mote will prevent contact. That can only work reliably if you have high contact forces, or if you use reed switch parts (for the sealed glass envelope).

One possibility you might consider is zebra-stripe elastomer conductors; these are compliant enough to make a connection even if that dust mote shows up.

Searcher7 Inscribed thus:

You're not making an electronic one arm bandit, are you ;-)

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Best Regards:
                     Baron.

Zebra-stripe elastomer conductors would be too "exotic", expensive and would require a lot of redesigning, *if* they would work for what I'm doing.

I might however be able to incorporate wiping if I can determine a good material to use, outside of the contact material itself.(I can make it part of the switching mechanics).

Thanks.

Darren Harris Staten Island, New York.

That black tarnish isn't oxide, it's mostly sulfide, and it's almost as conductive as silver is.

Cheers! Rich

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We buy/ use some nice BeCu wave washers. BeCu can be springy too.

George H.

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So what are you doing?