gold plated binding post lugs without the audiophoolery

1: Buy the autophool stuff. 2: sigh. 3: cut away what you don't need, and solder your test leads onto what's left.

This is just a suggestion, mind.

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Tim Wescott 
Control system and signal processing consulting 
www.wescottdesign.com

$17! Ouch...

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Thanks, 
Fred.

'gold plated spade crimps' on ebay gives a few hits, at least in the UK.

Cheers

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Syd

Yes, and I really wanted a smaller crimped part, that includes a 4mm socket for a banana plug I think.

Thanks, I already ploughed through a lot of them but they tend to be big (and expensive).

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John Devereux

:)

I was really looking for a crimped connection as the manufacturers specify. I can always just tin the end of some copper wire and use that, but the point is to reduce the number of thermoelectrically active connections (and also reduce the thermal mass generally so things settle down quickly). With a soldered joint you have copper:tin-lead:copper, albeit over a very short distance (so perhaps negligible overall).

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John Devereux

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http://www.partsconnexion.com/connectors_spade_all.html

I vaguely remember them coming up amidst all the nonsense when I searched before, probably discounted them since non-UK. But that is best one so far.

Thanks John.

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John Devereux

If you're using skinny inny wire, why gold ? You won't be heating anything with current.

I suppose plating your own is out of the question. We use to put gold down on the inside of microwave cavities. (with Aqua regia?? Someone else did it.)

Can you say a bit more about why this is important. What do you mean by "low thermal"? Not too much mass? Not too many thermal EMF's ?(from different metals at different Temps) Or something else.

I'm screwing around with metallurgy today, Soldering to aluminum. I like to make a thermal conducting, electrically insulating stack on copper clad pcb... the dream is thin piece of anodixed Al. (with one face bare) Wet the bare side with solder and stick that down onto the tined pcb. (so far so good, alloys 1100 and 3003 Al seem to work fine.. unto 6061)

George H.

There's a welding/brazing rod called Welco 51. Sold as "miracle rod" at hardware stores. At much higher prices. Here's a durafix link.

I've used it to tin aluminum, then solder to it. Or use it directly as solder. Have no idea the thermal voltage properties.

OOPS. It's Welco 52 now.

A few microinches of gold plating won't change thermal potentials. You need to match the alloys of the wire and the spade and the binding posts, which generally means all copper.

Gold does prevent oxidation, which is mainly a cosmetic issue.

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John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation

opper clad pcb... the dream is thin piece of anodixed Al. (with one face ba re)

Thanks Mike, I've got some Laco aluminum flux

Besides the different Al alloys I've got Sn/Pb solder, some Silver solder ( Ag/Sn I think) and some tin/ zinc that was reccomended for soldering Al.

The 60/40 tin/ lead on 6061 looks just fine. (.. but we can't sell that in Europe.)

George H.

Yes, that is precisely what I am trying to do.

The thermal (Seebeck) coefficient of copper to copper oxide is extremely high (1200uV/K from memory), so the connections for these sort of applications usually use gold plating to prevent the copper oxidising. Silver also works (and copper silver and gold all have virtually the same coefficients).

Now as far as I can see, when you have a copper oxide layer on a terminal in fact you will have a copper - copper oxide - copper junction, say. So the +1200uV/K one way gets balanced almost immediately by -1200uV/K the other way. And the delta-T will be truly microscopic over the tiny oxide thickness. So it should not matter.

But the manufacturers of DC microvolt stuff all go out of their way to stress the importance of very clean or gold plated copper terminals.

See e.g:

(gratuitously huge download, sorry)

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John Devereux

I mean it does not suffer from "thermals" - false microvolt level thermoelectric potentials caused by temperature fluctuations and the Seebeck effect.

E.g. Linear AN86 Appendix J.

That helps too, when you make the connection it can take a long time (minutes) for things to settle down and all come into thermal equilibrium.

Have fun!

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John Devereux

However, gold plated copper is almost invariably gold on nickel on copper. Otherwise the gold diffuses into the copper and disappears.

John

OK, thanks. They are often "Tellurium copper" rather than pure copper in the case of binding posts and banana plugs. Don't know if that makes a difference.

It does seem likely it is the prevention of oxides that is important (if anything).

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John Devereux

those look like the lugs used on old phone equipment. Not sure where you'd get them these days though.

Give or take doping and impurities and stuff. Maybe it matters that the junctions are abrupt or diffused on one side or the other (say, a hunk of clean metal clamped onto a slowly oxidized hunk?), or varying amounts of oxygen, or other stuff nearby (would zinc act as a P-dopant in Cu2O?). I could imagine all these factors could result in not-exactly-1200uV/K coefficients that don't quite balance.

Or maybe not. Really, I don't know. Never hurts to keep things clean and remove the possibility, anyway. Well, wallets aside...

Tim

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Seven Transistor Labs 
Electrical Engineering Consultation 
Website: http://seventransistorlabs.com