How To Remove Coating On Very Thin Headset Wires?

[Lancelot59]

Hello there PF. I'm currently attempting to repair an old headset of mine that had the cord broken. The only thing is that I can't get the wires to make a connection. I know that wires such as these have a special coating on them that prevents shorts when they're bundled inside insulation bare.

The only thing I can't get this coating off. I tried to burn it off with a soldering iron, and that didn't work.

How are these coatings usually stripped?

 

[negitron]

In the production environment, expensive wheel or cone strippers are used for various types of magnet wire. But for you, the easiest method is to burn off the insulation with a lighter or match, then shine up the burnt area with fine steel wool.

 

[vk6kro]

You can also try paint stripper or di ChloroMethane (Methylene Chloride) if it is a type of tough varnish. This works with Litz wire which is similar.

There use to be another one where each wire in a bundle was wrapped in cotton. That was horrible stuff and the best solution was to rewire it with real wire.

 

[Lancelot59]

Well there are two wires, red and blue with the coating in them. Another two plain ones that act as grounds for the microphone and speakers. Then a fifth one in thin insulation.

I'll look around and see if I have any paint thinner/stripper.

Just one thing though, I thought ~650 degrees Fahrenheit would easily burn off such a coating. I've seen my dad burn off coatings like this on a similar wire with a soldering iron.

 

[negitron]

Depends on what the coating is. There are many, many types. I've always used the flame method with excellent results. There are many which can withstand soldering iron temperatures and solvents, but none can hold up to flame.

 

[Lancelot59]

Fire it is then, I'll get the torches and mobs of villagers. The coating shall fall!

 

[vk6kro]

I've tried flames, but usually end up melting the copper wire or always end up oxidizing it so it is hard to solder.
If you can find some paint stripper, I'd try that first.
Just a few drops then wait 30 minutes or so.
Clean it carefully and if you can see copper, go ahead and solder it.

 

[negitron]

I've tried flames, but usually end up...oxidizing it so it is hard to solder.

That's what the steel wool is for!

 

[vk6kro]

Are we talking about the same thing? I think this is 30 gauge wire or thinner in a bundle of about 20 wires. Horrible stuff.
They vanish in a little green flash if you put them in a flame. :)

 

[Lancelot59]

This wire is less than a millimetre across.

 

[vk6kro]

1 mm is quite thick. Is it in a bundle of wires or just one?

 

[Lancelot59]

Just one, but I said less than 1 mm. It's more like .5 mm diameter, very thin. It's just an approximated measurement.

 

[negitron]

Are we talking about the same thing? I think this is 30 gauge wire or thinner in a bundle of about 20 wires. Horrible stuff.

Yes, that's the stuff. You have to do it quickly; just pass the wire end through the flame once or twice. If you do it right, you'll see the end just start to glow red to orange-red with a little puff of smoke. If the wires are twisted in a bundle like Litz wire you want to separate them first. I've been doing it this way for decades.

I was spoiled for a time several years ago when I worked for a transformer manufacturer. They had cone strippers for their fine magnet wire.

 

[vk6kro]

And then you use steel wool to clean the wire? Amazing.

 

[Lancelot59]

You must be pretty dexterous to clean wire that thin without shredding it.

 

[vk6kro]

Yes. Why would you bother?

Paint stripper gives you nice shiny copper which solders easily.

 

[negitron]

You must be pretty dexterous to clean wire that thin without shredding it.

Not at all. It just takes a light touch. Anyone can do it.

Yes. Why would you bother?

Paint stripper gives you nice shiny copper which solders easily.

In 30 minutes, apparently. With my method, I'm done in 30 seconds. And I also wind up with nice, shiny copper that solders easily.

 

[vk6kro]

There is no real hurry.
The actual time varies with the coating. Could be one minute sometimes.
House paint takes about 30 minutes, so thin wire coating would be quicker.

Try it both ways and see which is better in your case.

 

[Lancelot59]

Actually I just tried fire...and the wire ignited. :/

But it worked! I just need to be quicker, I could actually see the coating coming off the wire.

I cleaned it off and the multimeter gave me a nice 0.01 OHM resistance.

I'll check back once I finish with the rest.

 

[Lancelot59]

I'm back. It worked out. The connection job on the broken cable was a bit messy.

For one the cables weren't very willing to accept solder. Secondly I couldn't twist them the way I wanted to, so that they just twined into each other. Instead I had to twist them in a manner such that they stuck out the side, and then had to smear the solder on.

Then a little heatshrink and electrical tape to cover up the whole job. It works now.

Thanks for your help everyone.

 

[vk6kro]

Yes, you would have to get all the oxide off the wires before they would solder properly. Smearing solder on might work for a while, but it isn't a proper joint.

Having used heat, you either have to scrape the oxide off (very hard to do with thin wires) or dip the wires in Hydrochloric acid and then solder quickly.

 

[Lancelot59]

Well lesson learned. Next time I'll be sure to do a better job.

I did go at it with steel wool to get the oxide off...unfourtinately I don't have any chemical stores located anywhere nearby so HCL isn't the easiest thing for me to grab. :/

 

[negitron]

A good RA flux will also aid in soldering lightly or partially oxidized wires. Most flux-cored solders for electronics use an RMA flux which isn't quite strong enough to attack heavier oxide deposits.

 

[Lancelot59]

What is the difference between RA and RMA Flux?

 

[negitron]

http://www.efd-inc.com/Solder/Flux/

Rosin Mildly Activated (RMA)
Consists of rosin, solvent, and a small amount of activator. Most RMA flux is fairly low in activity and best suited to easily solderable surfaces. RMA flux residue is clear, soft, non-corrosive, and non-conductive.Cleaning is optional. Residue may be removed with an appropriate solvent.

Rosin Activated (RA)
Consists of rosin, solvent, and aggressive activators. RA flux has higher activity than RMA for moderately oxidized surfaces. RA flux residue is corrosive and should be removed as soon as possible after reflow to prevent damage to your assembly. Maximum safe time before cleaning is product dependent. Residue may be removed with an appropriate solvent.

 

[Lancelot59]

Ah, I see now.