Splicing very short AL wires

[soldar]

I was messing with an old fluorescent tube fixture and the electromagnetic ballast got loose and pulled from the cables connected to it but due to the very strong gravitational force we have in this area the cables pulled the screw terminal off and the tiny wires from the coil broke off leaving only a few mm exposed and accessible. If they were copper this would not be a problem as I could just solder a copper whisker but, unfortunately, the ballast winding is aluminum or aluminium, one of the two, so no soldering.

Using screw terminals is impossible. Twisting is impossible.

I can connect to them, barely, using those terminals with a tiny hook at the end but this is unwieldy and not very secure.

What would be the best way to connect to these AL wires?

I do not need any suggestions to get a new electronic ballast, etc. I know all the alternatives very well. This is just for the fun of it.


And, just to digress a bit, and totally unrelated, I have a box full of wall wart SMPS which are not working. I know full well they are not worth repairing as they are so cheap to buy, but yesterday afternoon I repaired three of them just by replacing input or output caps and I felt it was quite an acomplishment to get three out of junk box and into the "available for use" box.

[Postal2]

... What would be the best way to connect to these AL wires? ...

You need pure tin, a couple of drops of gun oil and a 100 watt soldering iron. After the aluminum is tinned (usually a couple of tinned spots), roll the copper wire into a tube, tin it with the same tin, and put it on your wire in a molten state.

Practice on a similar wire first to avoid damaging the small ends.

[tooki]

How long are the wires? If they’re around 8mm or longer, you could use WAGO splices (221-2401). Ideally with WAGO’s contact grease for aluminum.

Can you crimp some kind of splice on?

Spot weld it?

Smaller screw terminals?

[RoGeorge]

Clamp two alligator clips.  Anchor the clips to the box with construction foam or glue-gun plastic so they won't move.

[soldar]

You need pure tin, a couple of drops of gun oil and a 100 watt soldering iron. After the aluminum is tinned (usually a couple of tinned spots), roll the copper wire into a tube, tin it with the same tin, and put it on your wire in a molten state.

What I am getting from the internet is that a tin-zinc alloy works best but it is not worth the trouble or expense of buying such solder. It seems it is mostly the zinc that does the trick.  It is not worth buying the special alloy solder and I cannot think of how I could get a drop of each metal and try to make the alloy myself.

https://www.belmontmetals.com/popular-uses-for-tin-zinc-solders/

I am thinking more in the direction of micro-sized alligator clips or screw terminals. Maybe make myself some kind of crimp terminal.

[soldar]

Clamp two alligator clips.  Anchor the clips to the box with construction foam or glue-gun plastic so they won't move.

I have thought of this but I do not consider the connection reliable or trustworthy. At least with the clips I have.

Once I can get a good connection I can glue or epoxy the connection so it does not move.

[Ian.M]

Soldering aluminum with ordinary Sn60/Pb40 solder is not difficult!  See https://www.eevblog.com/forum/projects/soldering-aluminum-wires-vs-copper/msg3145590/#msg3145590 where I soldered a wire to a piece of thin aluminum from a takeaway container, in less time than it took to write this!


Alternatively, get some small bore^* brass tube from a modelmaking supplier, cut some very short pieces with a Dremel cutting disc and debur the inside of the ends, squish them to an oval so you can get two wires in it side by side, insert the bare wires from opposite ends, crimp it, preferably in a crimper die it fits in nicely, and sleeve with heatshrink.

*an ID of approx 1.5x the wire diameter would work - you don't want it too big or the crimp wont be reliable.

[Psi]

I'd probably just join two small connector crimp pins together at the pin end by soldering.
So basically turning it into a crimp to crimp joiner. Then crimp the existing wire to a new wire and then tape the whole thing up to keep it secure.

Another option might be a wire ferrule, cut it open at the other end so the hole goes all the way through turning it into a joiner.
Then have your existing wire and the new wire running in parallel. The crimp ferrule joins them together.

[Postal2]

... What I am getting from the internet is that a tin-zinc alloy works best but it is not worth the trouble or expense of buying such solder. It seems it is mostly the zinc that does the trick.  ....

I told you what to solder with. I soldered with 99% tin, 90% tin should work. No solder will do, only pure tin. Even a copper tip is specially tinned with this tin. You drip oil, collect tin on an overheated soldering iron and scratch the wire under the oil. You can tin a soldering iron with rosin, but you cannot use rosin when soldering.

Soldering aluminum with ordinary Sn60/Pb40 solder is not difficult!

Don't do that.

[Ian.M]

YMMV.  I've had excellent results soldering aluminum with ordinary rosin flux core Sn60/Pb40 solder and ordinary liquid rosin flux.  See link above.  It was common practice for jointing thin aluminum in various 20th century amateur science/mechanics magazines, as pre-70's hobbyists with anything other than SnPb solder were pretty rare.  I suspect that most Pb-free high Sn solders will work equally well, but I've not tested that.  I didn't and will not use the under oil method as I don't like the fumes or the cleanup.  I suppose with a high enough temperature-stable oil, it may be your best option if you are trying to use an under-powered soldering iron as a deeper oil pool will exclude more oxygen for longer.

Zinc is also notoriously difficult to solder to so although its the major component of those low temperature brazing sticks for aluminum, I don't think its going to be helpful here.

[Postal2]

... See link above.  ...

I tried. No wetting. Just pure tin.

[Ian.M]

Well try again, with the biggest meanest bit you've got on your most powerful iron.  You *MUST* abrade through the flux pool,  then form a solder blob and keep rubbing and scratching it into the surface till it takes.   If soldering to thin aluminium sheet, it needs to be hot enough to melt solder next to the solder blob without the solder wire contacting the blob or the tip.  You wont get any wetting if the aluminum isn't hot enough or if it takes too long to heat from when you stop abrading through the flux pool till when you get a solder blob over it.

[Postal2]

... and keep rubbing and scratching it into the surface till it takes.  ...

It pretends to be absorbed, but easily bounces off. Tin, however, is thoroughly wetted.

You can solder by dipping in molten zinc, but I have not done this, although I know that this is the standard method for soldering aluminum twists of several wires.

[hanakp]

I'm surprised nobody mentioned it yet, so I'll bite. There are special fluxes for aluminium soldering, google it. They work by (temporarily) chemically removing the oxide that forms on the metal's surface, thus allowing for wetting by solder. I've been using one locally produced flux for about 15 years now and it works great. Its base component is hydrofluoric acid, so your best bet is to buy a similar one. Be sure to thorougly wash the finished joint in DI water. And don't let the flux touch your skin and don't breathe the fumes.

Among other things, I've been using it to solder grounding wires onto popular Hammond extruded aluminium cases. You need to preheat such big components with hot air gun or hot plate.

[Postal2]

I didn't come up with the idea of ​​soldering aluminum with tin. It's written in the book, and the chemical justification is given. There's also an explanation of why there shouldn't be lead in the soldering.

[Ian.M]

I didn't come up with the idea of ​​soldering aluminum with tin. It's written in the book, and the chemical justification is given. There's also an explanation of why there shouldn't be lead in the soldering.

Cite please, and also quote why there shouldn't be lead.

I've just soldered a 4mm² copper wire to the bottom of an aluminum Strongbow cider can using the under oil method.  The oil used was actually Petroleum Jelly (Vaseline), which left the bit clean.  Solder was ordinary Sn60/Pb40 rosin flux core off an approx 30 year old reel I have knocking around the bench. The label's long gone so I don't know the brand or exact flux core.   It did take several minutes scratching through a large blob of solder to get initial wetting.  Strength:  Pulling on the wire has partially inverted the dome  of the can bottom with no signs of separation.

[Postal2]

This is a book for children in Russian, called "Advice for a Beginning Master". I don't even remember where it is.
I tried soldering with regular solder, I soldered a thick copper wire to an aluminum ruler and tried to tear it off. I already wrote the result.

Of course, I have been soldering electrical wires this way for many years, even those hanging from the ceiling.

[Ian.M]

You wont have any joy soldering to thick aluminum unless you can get the whole part up to ~ 200 °C (or more like 230 °C for Pb-free) quickly enough not to form a thick oxide layer and hold it at temperature while scraping the solder pool into the surface to break through the oxide layer and start it wetting.  The can is ~ 100um aluminum sheet, not much thicker than heavy foil, and even so I can barely get enough heat into it with a Weller 8100D 100W soldering gun.  For thicker sheet, I'd need to assist with a hot air tool or a pencil blowtorch or put it on a PCB preheater.

[Postal2]

... Weller 8100D 100W soldering gun. ...

But it's weak, no good. I solder with something like the one in the photo, only the handle is plastic.

Buy Weller as in the second photo - it will fit.

[RoGeorge]

I did solder on Al sheet with normal 60/40 solder for electronics.  The trick is to solder underneath a thick drop of motor oil, so the air don't get to the Al and oxidize it.  Cooking oil might work, too.  Scratch the Al while it is covered with oil, then solder with a powerful enough soldering gun.  It needs a lot of heat.  Never tried that with Al wire, maybe it works, but practice first on another wire.

[Ian.M]

Incidentally the glassfibre pencil brush is https://cpc.farnell.com/unbranded/10191/fibreglass-pencil-4mm/dp/SABU10191 or similar.   If its working right you can see the oil or flux turn black with abraded aluminum particles.   Getting the brush clean afterwards is a PITA - I just burnt off the Vaseline with a lighter then used switch cleaner and its discoloured but at least not greasy - so it may be better to keep a brush insert just for this job.

The problem with soldering wire will be keeping the oil and solder there.  Try making a shallow depression near the edge of a piece of pine wood with a very small V notch up to the edge for the wire, and clamping it at the right height for the wire to be level.

However the last time I needed to get a solder joint to aluminum magnet wire I crimped a duPont pin terminal to it (use a tiny smear of Noalox) and simply soldered to the pin!  Its much easier and is pretty much foolproof.   

[Postal2]

... Solder was ordinary Sn60/Pb40 .........  Strength:  Pulling on the wire has partially inverted the dome  of the can bottom with no signs of separation.

I don't know how you did it. I've always been able to tear a drop of regular solder off the ruler, but with tin the wire itself just comes off. But I've tried both. Why don't you try with tin.

[Ian.M]

.... because I don't have any SN100C solder handy.  I do have a small pack of SAC405 I keep for Pb-free repair work, but at 4% silver that stuff is too pricy to mess about for no reason.  I suspect we are in violent agreement that high tin solder will work to tin aluminum.  You contend SnPb doesn't - others disagree.

[Postal2]

Tin is a food metal, sold for repairing saucepans. I don't think it's a problem to find it. Try it, compare, and don't forget to tell us.

[themadhippy]

Cooking oil might work, too.

it does