How to attach a ground wire to the inside of a 19mm aluminum barrel?

Can you get the inside plated with copper and then solder it?

You can solder aluminum, but you need to keep oxygen away from the area soldered. This all depends on how thick your material is, (how much heat gets sucked away) Them method: Use a large soldering iron, make a puddle of solder, this is the oxygen shield, now inside that puddle scratch with the tip if the soldering iron/gun. By doing the scratching you are removing the oxide from the aluminum allowing the solder to stick. If you have a stainless steel pick a helper could scratch while you hold the iron. I would solder a tab and later solder my wire to the tab. Test it out on some scrap to get a feel for how it works. It takes a lot of heat because the flows easily in the aluminum. I hope the tube is empty when you start.

Mikek

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I can imagine ways that that could get flakey.

Can you drill a small hole in the tube? Then push in a drive pin or a roll pin that solders or somehow attaches to the board.

Or a flathead screw, into a PEM on the board.

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That works well, but be advised, once the oxide is breached, the solder will tend to lift it and spread out a lot, and alloy into the aluminum - making it thinner at the hot point, and could break thru (what was) the aluminum wall. Be quick about doing it,with heat applied in as small area as possible - and NOT a thin aluminum wall. Aluminum solder with Cadmimum alloy has less of the problem (temperate is lower), but BUT !!!*BUT*!!! the fumes can literally kill you. EXTREME ventilation required.

That gives you a 2.5mm wall thickness. That should be sufficient to drill and tap the barrel for a small screw.

Forget about using a spring clip. Anything that's strong and springy, will also produce galvanic corrosion with the aluminum. You won't find many aluminum springs and those that you do find have a very low fatigue limit.

Otherwise, look into aluminum solder and brazing. For example: See the other videos at the bottom of the page. I bought something similar a few years ago. It works, but no way is it as easy as it seems in these video. Of course, it's not cheap:

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My recommendation is to not run any current through the aluminum. Have you ever seen an aluminum flashlight work reliably? The other end of the connection is going to have the same problem with aluminum oxide. Use the spring trick to eliminate ESD and EMI but not for power delivery.

I've used aluminum solder a few times. It dissolves into the aluminum so it's more like a chemical weld than soldering. How far in it dissolves depends on the temperature. I definitely don't recommend it on anything small because the temperature and depth will be nearly impossible to control. The solder's high temperature burns copper so it's not really good for joining the two.

Joining electronics solder to aluminum by scratching through the oxide layer doesn't seem to work. It will appear to wet for a moment then go back to repelled beads. I suspect that the aluminum sucks oxygen out of the solder.

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Must be technique; i never had a problem soldering to aluminum with standard tin-lead solder and a good,hot iron. Other problems i have discussed elsewhere.

Maybe tap it for a M16 set screw, solder the set screw to the end of the board and screw the entire thing into the barrel. I think a M16 is a

14mm tap drill. Pot when done. But then you only have 25mm total to work with. Maybe have someone make you a thin plug you could solder to the board that would screw into the tapped end.

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On a sunny day (Wed, 05 Nov 2014 19:55:24 -0800) it happened Kevin McMurtrie wrote in :

Yes I have six of those.

Aluminum is harder to spot weld than, say, steel because the thermal conductivity is so high.

We have a relatively expensive Miyachi precision spot welder that would probably do it (we use it on copper-like metal), I doubt that the tab welders (capacitive discharge) that battery pack builders use would work well but it might be worth a try.

A good sheet metal fabricator may have a proper spot welder that will work. That would be the first thing I'd try for outsourcing.

As a long shot, you can buy crapola transformer style spot welders at Harbor Fright for less than a couple C notes, maybe try and return it if it doesn't work, if you've got a store nearby. They only recommend it for steel and stainless steel.

However, the manual specifically says: "Not for welding aluminum, copper or copper alloys"

You'd also have to modify one of the electrodes to get it to fit into the tube, but it could be tested on a similar thickness of flat aluminum sheet.

You'll tend to get marring of the outside of the tube unless a special electrode is made but maybe that's not an issue for you.

I've never had very good results with scrape soldering- it tends to turn out like this:

Some fluxes seem to be effective but the joint is not very strong and I have doubts about how well it would stand up to the extreme stresses from potting.

Best regards, Spehro Pefhany

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Aluminum solders fine with the right flux. Search for LACO aluminum flux. (I've been tinning Al strips that are bare on one side and anodized on the other. And then sticking them to a PCB.) The type of solder doesn't seem to matter that much.

George H.

I've soldered copper wire to aluminum foil with no problems.

George H.

Okay, George, I ordered some to try. Thanks for the info.

Cheers, John

Oxygen in solder? That is in the scale on the surface, not in the solder alloy.

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I've been doing the tinning on a hot plate, with an iron to "put it over the top". But it also works with just an iron.

George H.

I think its Nickle plate then Copper. He could try som kits from Casswell, or just go to a plater and ask. I remember we had a copper plated Aluminum tab that was soldered to a steel plate. I believe Nickle was involved.

Cheers

They put on a thin flash of zinc from an alkaline bath. The zinc keeps the aluminum from oxidizing. Then an acid copper is applied. As soon as the aluminum goes into the acid copper, the zinc is removed and the copper plates out. A heavy copper plating is done and then polished to a mirror finish. Then a layer of nickel is plated over the copper. That gets a fine polish followed by a chrome plate. This process is known as "triple plating".

Almost any plater that can do chrome on aluminum could easily plate the parts the OP has.

There are oxide-inhibiting pastes used in crimping Al cable, you could rivet or clip a lug to the tube with such a paste. It'd have to be tested, of course (unless you use aluminum/aluminum) for dissimilar metals issues.