How to deal with Weird-ass headphone wire ???

[frogblender]

Attached pic shows a blue-colored single conductor in a set of cheap headphones.   The other headphone channel (not shown) is the same, but red.

The conductor seems to have non-conducting interwoven string (the white strands), presumably for mechanical strength, which I've untwisted for your viewing pleasure.

This conductor is NOT one of those super-tiny coax cables you may see about.

The blue is insulating.


So... I need to cut these wires in half and resolder to the pad.  How do I solder ?    Shoving virgin insulated blue and string into the molten blob on the pad doesn't work very well.   Is there some kind of magic flux which dissolves blue and string, leaving only pristine metal?

Any help is appreciated.

[madires]

Maybe it's colored enamel lacquer and tinning with high temperature will work.

[The Soulman]

First, you don't want the string in your solder joint, so untangle from blue and cut that back.
Second, the blue wire is actually regular copper wire with a heat resistant (up to normal soldering temperatures), electrically insulating coating,
that coating needs to be removed and the copper wire tinned before you attempt to solder it.
The trick I use is to set the soldering iron to a high temp (400+ dgr.C) and dangle a drop of solder underneath the tip
and carefully insert the end of the blue wire in the drop, this high temperature tin will burn the coating of in seconds and will leave some tin on the now bare copper wire.
Third, if necessary twist the loose strands together, reduce the soldering iron temp to normal and solder the wire like you normally would.
Good luck.

[jerryk]

I take a small ceramic tile and lay it flat on the my desk next to my soldering station.  On it I make a small puddle of liquid flux.  Next to it I melt a small puddle of solder on high heat as above and leave the tip of the iron in the puddle to keep it hot.  Trim the wire end with a clean cut.  I then repeatedly dip the wire in the flux and then try to push it in the melted solder.  It will make a perfect tinned end at whatever length you decide and then it's easy to solder to a pad or through hole.  No need to do anything to the string reinforcement core which I think is kevlar.  It will just melt/burn out of the picture as the process of dipping in the flux makes it all clean.  It's fun to watch under a microscope.

Jerry

[Ian.M]

https://www.eevblog.com/forum/beginners/tips-for-soldering-in-ear-earphone-wires/

The aspirin method I described is probably the easiest way of stripping the enamel off very fine magnet wire and litsz style wire to get it to tin.  Afterwards, you should wipe your iron on a moist cellulose sponge, even if you usually use brass turnings bit cleaner, and re-tin, repeating the wipe/re-tin process a couple of times as its not advisable to leave aspirin residue on the bit.

[jerryk]

Here is a better description of the process I use via a couple of photos.  Like I said it's a repetitive process to dip in flux then in solder.  The solder will resist penetration the first couple of tries.  Once the tip of the wire starts to tin you can feed it in the solder to the length you want to tin.  Just keep going back to the flux puddle to keep things clean.  FYI - solder tip temp was 315 C.

 I don't doubt that some like the aspirin method but the problems I encountered were contamination of the aspirin into the core material resulting in a black residue at solder time.  This happened regardless of my efforts to clean afterwards.

It takes around 15 seconds per wire with no need to clean the acetic acid off your tip and you get to forego the fun of smelling the acetic fumes

Good luck - Jerry

[Rasz]

Plopping this enameled wire into a blob of solder usually doesnt work because solder has no way of penetrating between the wires. Flux, even old school rosin is the key here, wetting individual strands and helping with capillary action.

[frogblender]

Victory!

Yous dudes and dudettes are the cat's ass.   I can now solder these enamelled wires like a champ.

I expand on jerryk's solution of using a ceramic tile:   I used a brick (what I had around), and hammerdrilled a couple of very shallow 6mm holes (and then compressed-air-blasted them clean, to avoid masonry powder contamination), into which I put my 1980's extra-poison acid plumbing flux.   Multiple holes means you have several pools of clean flux to choose from when soldering large quantities of wires.

- start with a clean cut wire end, preferably without the strands unravelling (or your finished tinned end will be unravelled)
- leaving the string in the middle is fine; it just seems to mostly disappear with the high heat.
- 400°C iron.
- repeatedly poke wire end into flux, and then molten solder.  my result is exactly as shown in jerryk's picture.   Fast and easy.
- after tinning, give 'er a wipe with a paper towel to remove any black slag.


I owe the lot of yous a beer   

[Ian.M]

Whoops!!!  Acid flux wicks up between the strands of the wire and is near-impossible to totally remove.  I fear you've set yourself up for future failure due to corrosion as acid flux residue is hygroscopic and corrosive.

[jerryk]

Whoops!!!  Acid flux wicks up between the strands of the wire and is near-impossible to totally remove.  I fear you've set yourself up for future failure due to corrosion as acid flux residue is hygroscopic and corrosive.

Ian,

I am curious about your comment.  I have always used a rosin based flux for this process and any soldering of electronics.  Still I clean the ends of the wire with an acetone/ipa combination.  For my own peace of mind I have cut into the middle of the tinned area, examined it under the microscope, and found it had total penetration.  Do you think rosin core flux a problem too?

The aspirin technique did not sit well with me.  Regardless of my efforts to clean that residue off I could always see some of the residue boil up as black bits of contamination when I tried to make a solder connection.  I also tried many versions of the aspirin technique at various temperatures and never could make it work remotely comparable to the tile technique I posted above.  Nor could I ever be assured all the aspirin residue was out of the core fibers.  I assume aspirin's acetic composition is an enemy of a sound circuit connection too.

Would it be possible for you to expand on how you use the the aspirin technique with the type of reinforced core wire that the op is having problems with?  I hope I'm not sounding like this is a challenge to your experience.  I am just out to learn as much as I can from people with your experience.

Frogblender,

I'm glad you gave it a try and had the same success that I did.  To me it's a very sound technique compared to others out there.

Take care - Jerry

[Ian.M]

Acid fluxes as used for plumbing contains mineral acids, or zinc chloride (aka 'killed spirits of salt').  They are significantly corrosive as are their residue, and are only acceptable for plumbing because acid residue inside the pipe gets washed away, and nearly all the exterior residue will be wiped off, leaving so little relative to the copper thickness that corrosion damage will be insignificant for many decades.  If you loose 0.1mm copper from the outside of a plumbing joint, it doesn't matter, but the same loss from the strands of most finer stranded wire will totally eradicate them.

The residue of rosin R, RMA and most RA fluxes, unless badly burnt, is solid and reasonably inert at near-ambient temperatures.  Therefore any trace organic acids it contains are 'locked up' and it doesn't cause significant corrosion if not removed, so it doesn't matter if its wicked up the wire under its outer insulation. 

The only thing saving Frogblender's wire from rapid corrosion failure is the enamel on the strands.  If its micro-cracked, it may still fail under the outer jacket, or the acid residue may re-mobilise due to  humidity (Zinc chloride is hygroscopic and disproportionates releasing hydrochloric acid) and corrode through the strands where the enamel ends next to the solder joint.

For the aspirin technique any reinforcing strands should be removed first, before twisting the magnet wire strands (in groups per colour if its a multi-core in single jacket wire).  You do *NOT* want an unholy mess of melted plastic and burnt aspirin left in the core of the wire, especially if you are preparing it for solder-cup terminals.  Depending on the reinforcement fibre, fanning the strands and briefly flaming them to burn back the reinforcement may do the job, or you may have to separate and snip them with really sharp small scissors.  Dip the twisted wire end in acid free halide free rosin paste flux, then press into the aspirin with a rolling motion with a solder-loaded hot bit.   Once evenly tinned, clean with IPA on a lint free wipe.   If you start close to the end of the wire, once the aspirin has broken through the enamel, one can usually get the tinning to progress up the wire to the length required just with flux, without further use of the aspirin, which eases cleanup.             

[amyk]

Just because no one earlier has posted it already: https://en.wikipedia.org/wiki/Tinsel_wire

[mikerj]

Just because no one earlier has posted it already: https://en.wikipedia.org/wiki/Tinsel_wire

Tinsel wire is a bit different, it was used in the old corded telephones to connect the receiver to the base (via a "curly" cable) and consists of very thin flat foil conductors wound around the string rather than normal round section copper wire.  ISTR trying to solder an old phone cable when I was younger and fididng out it was aluminium rather than copper.

[Neomys Sapiens]

For RF litz wire, which has strands too fine to be denuded by the scraping tweezers used for other varnish-insulated wire, the following recipe was given:
Heat wire end over blue gas flame (such as gas-operated soldering pencil with the flame nozzle) until short of melting at the fine ends, then very quickly dip into a thimble full of denaturated spirit.
quoted from 'Schliche und Kniffe fuer Radiopraktiker', Fritz Kuehne, Franzis Verlag 1977