Soldering Aluminum Wires vs Copper - Page 1
Forum section: electronics / projects

author: DW1961
author_rank: Frequent Contributor
timestamp: July 19, 2020, 06:05:49 pm
content: So, is there anything that needs to be done when your wire is aluminum and not copper? Or when you are soldering aluminum to a copper pad of some sort?

author: Benta
author_rank: Super Contributor
timestamp: July 19, 2020, 06:26:37 pm
content: The right thing to do: give up.Aluminium is not easy to solder, in fact almost impossible. Combining that with copper is a metallurgic nightmare.I suggest looking for a different solution.

author: Zero999
author_rank: Super Contributor
timestamp: July 19, 2020, 06:28:38 pm
content: Toss it and buy copper wire.

author: Gyro
author_rank: Super Contributor
timestamp: July 19, 2020, 06:31:23 pm
content: Successfully soldering Aluminium wire isHard.You either need a very aggressive flux to strip the oxide (not to mention damaging your soldering iron tip and the copper), or some method of mechanically stripping the oxide layer and keeping Oxygen away from it (the layer re-forms immediately) until you have completed the joint. Some have had success with an inert gas atmosphere or soldering under oil.Flux used for Aluminium needs to be very carefully and neutralised and removed, and you should reserve a soldering iron tip just for the purpose!

author: DW1961
author_rank: Frequent Contributor
timestamp: July 19, 2020, 10:23:49 pm
content: I have some wire that is "tin plated copper core." Is that going to be ok. Also, how would I know if it were aluminum and I was trying to solder with it? Would the solder just roll off of it?

author: langwadt
author_rank: Super Contributor
timestamp: July 19, 2020, 10:42:54 pm
content: Quote from: DW1961 on July 19, 2020, 10:23:49 pmthe copper dissolves in the solder and you are back to trying to solder aluminium

author: Ian.M
author_rank: Super Contributor
timestamp: July 19, 2020, 10:58:03 pm
content: Grab an offcut with pliers and heat it in a gas flame. Aluminum melts at 660 deg C (dull red heat) or a bit lower depending on the alloy, and as you approach that temperature will 'flop', sharply bending or even breaking just inside the flame. Copper melts at 1085 deg C which is barely achievable within a natural gas flame that isn't fed with preheated air and fuel. It will be at bright orange heat, close to yellow heat, and you'll find that to get that temperature it must be in the heart of the flame at the tip of the blue cone. If you melt from the end of the wire, the molten copper will ball up and form droplets.For fine or stranded wires, the luminous flame of a gas lighter offers good discrimination - its not hot enough to readily melt copper but is hot enough to cause the characteristic aluminum 'flop'.Another approach would be chop some up into very short pieces to expose as much suspected aluminum as possible and immerse in a strong lye (sodium or potassium hydoxide) solution in a clear container. Aluminum will react producing tiny bubbles of hydrogen gas. Other metals commonly found in wires will not.You can eliminate the other common 'fake copper' wire easily- copper coated steel is attracted to a magnet and is significantly stiffer than copper or CCA.

author: DW1961
author_rank: Frequent Contributor
timestamp: July 20, 2020, 01:46:58 am
content: Quote from: Ian.M on July 19, 2020, 10:58:03 pmCool.I'm just going to make sure my damn wire are all copper beforehadn.OK so the "tin plated copper core " wire I have is just "tinned?"

author: DaJMasta
author_rank: Super Contributor
timestamp: July 20, 2020, 04:02:28 am
content: As mentioned... just don't bother. There are definitely techniques to be able to solder aluminum, but they are much more exotic than can be expected of a shop not equipped for specifically them. Another option I haven't seen mentioned is a hydrogen atmosphere with an oxygen torch or similar - basically because of the nearly instant corrosion aluminum experiences in the presence of ANY oxygen, so you need an environment without any ambient oxygen to work in.If you have aluminum wires that need to be attached, look for clamping mechanisms, not soldering. You can still get caught connecting dissimilar metals in some cases and you have to be careful about clamping pressure, though as aluminum is more brittle than other cable used.Tin plated copper just keeps the oxidation out and is good for keeping stranded wire ends together. Your solder is a substantial part tin (30% or so with leaded solder), so this one is going to be on your copper wire when it's soldered into anything anyways (and is used on PCB traces and the like to prevent the degradation of the copper pads).

author: paul@yahrprobert.com
author_rank: Regular Contributor
timestamp: July 20, 2020, 04:44:16 am
content: I once visited a lab where they soldered lugs onto the end of heavy aluminum wire. They had a molten tin bath with some high power ultrasonic transducers in the bath. The ultrasound would break up the oxide and allow the tin to coat the aluminum. No flux or chemicals needed. It was interesting to see that if they left the wire in the bath too long with the ultrasound on it would eat away the aluminum and you'd end up with a bath of tin-aluminum alloy.

author: DW1961
author_rank: Frequent Contributor
timestamp: July 20, 2020, 05:28:57 am
content: Quote from: Ian.M on July 19, 2020, 10:58:03 pmSo are you saying that if you try to solder two CCA wires, it's not going to work, right? I'm asking because I have that 22 AWG "tinned copper" wire and I have some Amazon speaker wire, and I don't trust ANYTHING anymore.I mean, I just assumed when I saw a roll of what seems to be copper wire, I thought it was copper wire. I guess the rule now is unless it states it is pure copper wire, it's not. It''s the same thing with "gauge" wire. Better make sure it says AWG not just "gauge.""I'll use the lighter method to test every wire I buy now.I did use that 16 AWG Amazon speaker wire, that looks like copper, to attach two tin alligator clamps to the ends of the wire and it's stuck solid as hell. I tried to pry it off just as an experiment and it's damn well bonded good. I ended up destroying the alligator clip but the wire is still bonded to the clip--lol. Would that be possible it the wire were CCA?

author: Ian.M
author_rank: Super Contributor
timestamp: July 20, 2020, 05:48:32 am
content: Personally, I find Aluminum trivial to solder with regular Sn60/Pb40 solder, provided you can get enough heat into it. With a 100W Weller soldering gun its only a little harder than soldering to tarnished copper. With a wimpy little long conical bit on a low powered iron you wouldn't have a snowflake's chance in hell of getting aluminum to wet with solder. Don't use your best bit as you have to rub the aluminum surface through the solder pool with moderate pressure, and that can be hard on the bit plating. However unlike other aluminum soldering techniques like working under pools of oil and aggressive specialist fluxes, it doesn't immediately mess up your bit, and no special cleanup is required.What I do is prepare the aluminum surface by abrading with a fibreglass pencil, then I immediately apply liquid rosin R flux*and continue abrading it through the flux pool, which excludes most of the oxygen in the air. Before the flux has fully dried out, I tin the desired area by forming a small solder pool and rubbing the surface under it with the bit, (to disrupt the very thin oxide layer that will have reformed because the flux failed to totally exclude all oxygen), till it starts to wet, then expanding the wetted area by working outwards adding fresh solder as I do. The solder slightly dissolves the aluminum, so the oxide at the edge of the pool is undercut and its easy to get the tinned area to expand. I then wipe off the excess solder while still molten, and clean up excess flux with IPA leaving me a tinned area that can be soldered to normally.You don't get the feedback of the solder freely wetting the metal surface that you get with copper alloys when they reach a high enough temperature, so judging if your iron is adequate and technique good enough takes practice.If you practice on thin aluminum sheet, you know you've got there when you can bend the sheet across the tinned patch without any signs whatsoever of it lifting at its edges. Once you've mastered tinning aluminum, getting nice joints to tinned aluminum without preheating takes a bit more practice, as the aluminum conducts heat away so fast its easy to get a 'cold' joint.Here's one I just did to demonstrate on an aluminum coupon cut from a foil takeaway container. I haven't cleaned up the flux residue from the final stage of soldering a wire onto the tinned patch, so it doesn't look as pretty as it should. It took longer to get a decent closeup photo than it did to do, including surface preparation, and even longer to type up this post!* I generally use liquid R flux not RMA or RA, and not a paste or gel flux because used sparingly it can be treated as no-clean, so when working with aluminum, its just what I've got handy on my bench. Any other high solids general purpose liquid flux would work equally well for aluminum, as long as it forms a tenacious liquid film to protect the aluminum round the edges of the solder puddle from rapid oxidisation.

author: DW1961
author_rank: Frequent Contributor
timestamp: July 20, 2020, 05:53:27 am
content: Quote from: Ian.M on July 20, 2020, 05:48:32 amI don't want to even mess with aluminum. I'm glad I asked this question. I didn't even know I had tocaveat emptoreven wire just to make sure it was really copper. Geeze!I guess aluminum does have better conductivity than copper per weight, but this CCA shit seems like a plague for electronics.

author: Ian.M
author_rank: Super Contributor
timestamp: July 20, 2020, 06:08:11 am
content: CCA is solderable *IF* the copper coating is well bonded to the aluminum and reasonably clean. It only takes a thin 'flash' of copper to prevent the formation of an aluminum oxide layer, and as long as you don't break through the copper when cleaning it, the copper will take solder readily, dissolving in it and letting the solder wet the underlying aluminum. Corroded or badly tarnished CCA is *MUCH* more difficult to solder . . .If the price is too good to be true, it probably isn't! Copper is currently just short of four times the price of aluminum, so even with the difficulty of copper plating it there are large savings to be made by the less scrupulous.

author: jbb
author_rank: Super Contributor
timestamp: July 20, 2020, 07:41:50 am
content: Another method for finding surprise aluminium wire: drag the end over some fine sandpaper and have a look under a magnifying glass.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 21, 2020, 02:37:45 am
content: Quote from: DW1961 on July 20, 2020, 01:46:58 amNo, it is actually plated with metallic tin, not solder, as would be implied by the confusing, but common, term "tinning", used when describing the soldering process.If you buy a reel of "tinned copper wire", sometimes just written as "TCW", you are getting single strand copper wire which ihas been tin plated.Even in flexible multistrand wire, tinned copper strands are probably the most common type used.Tin is far more corrosion resistant than bare copper, which is why it is used.Cheap coaxial cable like the common "RG6" often uses copper coated steel for the inner conductor, & aluminium for the braid screen.The proper connectors for RG6 are the very reliable "compression" type, but it can be used with crimp type BNC by cutting back the plastic outer sheath & crimping on the screen.The centre conductor doesn't crimp reliably, but the "copper coated steel" will solder OK.The removed section of outer sheath is then replaced with self adhesive heatshrink tubing.

author: donlisms
author_rank: Frequent Contributor
timestamp: July 23, 2020, 02:33:52 am
content: A TIG welder would work, right?

author: mikerj
author_rank: Super Contributor
timestamp: July 23, 2020, 09:24:49 am
content: Quote from: donlisms on July 23, 2020, 02:33:52 amIf you were joining a sizeable bit of aluminium to another sizeable bit of aluminium than yes. You can't weld dissimilar metals together, and you certainly wouldn't TIG a tiny hookup sized wires.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 23, 2020, 09:29:45 am
content: Quote from: mikerj on July 23, 2020, 09:24:49 amYou can use TIG to connect small gauge thermocouple wires together quite easily. That is the only thing I use for that purpose now.

author: David Hess
author_rank: Super Contributor
timestamp: July 23, 2020, 11:53:11 pm
content: Quote from: Ian.M on July 20, 2020, 05:48:32 amI have both that and a 100 watt Weller temperature controlled iron. I will have to try that.