Soldering Aluminum to Copper

1/4" x 3/8" aluminum to 1/10" thick copper sheet. Probably around 200 amps. of current through this connection. Can anyone recommend a good solder product for this purpose?

Thanks for any help. Mike

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Terminate the wire with a crimp on lug and bolt the lug to the plate.

-- Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison

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Thomas D. Horne, Electrician

aluminum wont take solder... you can TIG weld it but i doubt it will weld to copper.

if you crimp I'd use the big hydraulic crimper that working electricians employ.

alternatively a large connector such as found in electrical service boxes could give you your attachment point.

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On a smaller scale, I've used silver solder (2% silver content, IIRC). You also need acid flux and/or clean the aluminium oxide off the surface no more than a few seconds before you solder it, and you need a hotter iron than you might be getting away with for regular soldering of copper.

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Andrew Gabriel

Hi Mike.

I did some of that during the practical component of my EE degree while working for the local power distribution org. making custom switchgear.

The lug crimping IS a good idea, but you would need to ensure that you had a great crimper tool, possibly approaching hydraulic dimensions, and probably some good flat washers above and below to maximize surface contact, to handle that current permanently and safely.

Alternatively, if you have an LPG torch and an old-fashioned pyramidal solder head you can solder Al and Cu like this:

step 1 ensure both electrical surfaces and the solder head mechanically flat and clean all of them with a scouring pad. step 2 buy some special St/Pb/Al solder and 'tin' the Al conductor. With your application, I'd tin a generous length on the wider side. step 3 using a more typical but stronger St/Pb solder and 'tin' the copper along a matching area. step 4 sweat both surfaces (yes simultaneously) with the clean LPG flame and when the 'tinned' surfaces _just_ look like beading clamp them together/bear down on them for a good 30s.

Practice on some scrap before you wreck your nice work!

For additional mechanical strength you could drill and bolt near the end of the conductor.


Damien Mather

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Damien Mather

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