Author Topic: special treatment for wires that refuse to solder? (copper or tin plated copper)  (Read 1995 times)

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Online coppercone2Topic starter

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If you have a wire that refuses to solder, is there any special treatments that exist for making it solderable? I find this sometimes in high quality equipment. I.e. stranded wire, probobly tin plated copper teflon stranded wires, that might be potted into something and it would be very convenient to be able to make it solderable.

This is kinda rare but if you are willing to go through some hoops, what can be done?

I thought maybe a mild dip some dilute hydrochloric acid, followed by a neutralization rinse in ultrasonic cleaner, a DI rinse and a bake out? Are there any special solutions that can be used for this job that are electronics grade? or specific concentrations that are generally accepted

 I got this teflon wire in a pump thing, it looks OK (not too dull) but holy shit it will not accept solder easily. I managed to do that one (tried three different rosin fluxes and used a higher temp). I got some wicking under the insulation.. prefer not to have that happen. I can't control the solder application process good when its like that. It will work fine with the zip ties, heat shrink and extra holder hardware, but it would be nice to be able to do this right without the extra measures to account for non ideal soldering. I think a gaseous acid would be best? since that way even if it wicks into the wire a little bit, you can bake it out? BTW in this case its not like a hermetic feedthrough deal, I can access the solder joint on the other side of the wire, its a piece with a gasket, but its still bonded in that subsection, I don't think I have to worry about acid getting into a sealed thing.... . and you can dip it precisely, that is unfurl the wire, and leave like 2mm above the level of the cleaner, so the insulation does not contact the surface of the liquid (careful lowering). And rinse before neutralizing.

And I don't mean like ratty ass corroded wire, I mean stuff that looks pretty good, and you know its proper, just its not accepting solder.

this one was crimped a long time ago but I had to remove the crimps to service it. DOn't like those crimps so I soldered and heatshrink a extension. And its a lower power device im not doing anything stupid


this might be also good to know for things like thermal sensors etc, often potted with stranded wire coming out of the potting. But those you cant free the other end of the wire so you gotta be damn sure not to let anything wick up there.

Again its a rarity but I think that having a 1oz bottle of something like 3% hydrochloric acid (made this idea up for concept) might be a viable solution to being able to deal with this bullshit when it comes up.

« Last Edit: January 28, 2024, 09:19:24 am by coppercone2 »
 

Online Ian.M

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Absolutely not.  Chloride ion contamination + ambient humidity, over any significant period of time is corrosion death for thin copper.  Its the same reason no-one sane uses acid zinc chloride flux (aka: killed spirits of salt, or plumbers flux) for electronics: You cant get all the acid chloride contamination out of the tiny crevices in stranded wire or under components on circuit boards.  See: https://en.wikipedia.org/wiki/Bronze_disease

One possible option is to fan the strands and use anodic electrocleaning in an ammonia-free, halide free alkaline electrolyte.  Another is to use a fibreglass abrasive pencil to manually remove the tarnish from the strands.
« Last Edit: January 28, 2024, 09:57:02 am by Ian.M »
 

Offline audiotubes

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Unclear if you're talking about wire that can be removed from the board, but it seems you are, since all sorts of chemicals were mentioned.

The guys using litz wire use a solder pot to burn off anything that isn't wire. You melt some solder bar into the pot and then immerse the section of wire you want to eventually solder in the pot for a while. The insulation and impurities burn off and the wire is tinned. It can then be used normally.
I have taken apart more gear than many people. But I have put less gear back together than most people. So there is still room for improvement.
 

Offline jonpaul

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Good day Coppercone,
Bravo! A great topic, I had this problem over the decades. Chemicals or non-electronic flux may cause problems later on.



Several different wire types:

1/ High temperature  wire may have a silver plating to reduce oxidation. Identify by very bright silver finish, hard to scrape off.
  Very common in stranded Teflon and fiberglass covered wire used in appliance automotive, heaters, industrial. Also some Kynar wire wrap wire has this.
Better to crimp a lug or splice as soldering is very difficult.   but silver solder and a hot iron or solder pot might work.

2/ Magnet wire, Litz wire: Some have a nylon, poly nylon, (SPN, HPN) solderable insulation eg "Soldereaze" or Beldease" that burn off with a hot iron or solder pot.
The non-solderable like enamel, Formvar, HPTZ need a mechanical like Exacto knife blade or fine emery paper to remove the insulation before soldering. Afterward, hot iron or solder pot, and 63/37 Rosin core or Kester 44 flux.

3/ Vintage equipment with  rubber covered wire , insulation  deteriorated   emitted sulfur, oxidizing  copper. Same solution, knife or emery paper. Same  hot iron or solder pot and 63/37 Rosin core or Kester 44 flux.

Bon chance


Jon

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Online Ian.M

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PTFE insulated wire is almost invariably silver or nickel plated as tin melts at a lower temperature than is used to apply the PTFE insulation, so  tin plating would fuse multi-strand wire solid, or if solid core to start with, even a slight excess of tin would result in blobs and streaks of tin mixed with the insulation compromising it.

Nickel plating is notoriously difficult to solder if oxidised, which is common for old high-temperature wire.
 
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Online jpanhalt

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I have never had a problem soldering copper wire or tin-plated copper.  Flux usually works.  For very old wire that is badly corroded or contaminated with insulation, mechanical cleaning helps.  I started soldering more than 70 years ago at age 9 (4th grade).

Now, as for more abusive treatments?  I use a molten salt bath to prepare enameled wire with insulation that is not solderable.  One can also use nitric acid, but that has gotten very hard to buy as it can also be used to make explosives.  As for the molten salt, try NaOH or KOH in a steel/iron pot.  Adding sodium nitrate (NaN03), readily available) makes it much  more active.  In practice, I use a small steel block with a larger hole in the center (e.g., 1/2" to 3/4" dia.) and a smaller hole for a TC or thermometer.

There are, of course, metals that might look like copper wire or tinned wire, that are harder or even impossible to solder, such as plated aluminum wire, chromel, alumel, SS, and so forth.

Edit:  Here are two attachments that were hard to find.  The MS Word document is my lab record for using molten salt to srip enameled wire.  The picture is the "pot" is use.
« Last Edit: January 28, 2024, 02:05:14 pm by jpanhalt »
 

Offline Stray Electron

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  I'm not sure what kind of wire you have but all of the Teflon insulated wire that I have encountered has been MIL-SPEC and was silver plated.  The silver is necessary to keep the Florine in the Teflon from attacking the copper wire.  The silver plated stuff solders very will.

   Unless you need the Teflon insulation, I would replace that wire with something with a different insulation. If you need Teflon then buy some US Mil Spec wire from E-bay or a surplus company.  Or new, but $$$$$. I'm not a wire expert but I think that the only advantage of Teflon insulted wire is that the insulation has a much higher MP than other insulation.
 
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Online coppercone2Topic starter

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Yeah the teflon wire can sustain a higher peak overload current etc without getting damaged and it wont fuse together in a wiring harness to cause a big boo boo as easily but when it goes it goes really bad. I think they also trust it more to resist infiltration of chemicals. I heard something along the lines of not so properly fused teflon wiring harnessses being repairable but PVC basically causing a nuclear melt down.

It might be silver or nickel. I just don't associate these people buying silver for anything (very greedy) but its possible I suppose. Nickel might be it, I notice the wire is stiffer then the silver plated teflon wire I have. Does the nickel plating make it stiffer? I bought teflon wire of alot of gauges in small batches so I can do proper repairs, I have a very heavy and overloaded drawer full of 'cherrios' (20-50 foot lengths of zip tie wire bundles of different colors and gauges).


I want to know about this method:
One possible option is to fan the strands and use anodic electrocleaning in an ammonia-free, halide free alkaline electrolyte. Baking soda?

and, what concentration of nitric acid is required? Its not very note worthy until you get to concentrations above 50% for any thing too bad.

I put alot of effort last year into developing brush electrocleaning stuff, and I am a fan (if you see the thread of welding cleaning and polishing results). Would the electrocleaning solution I Have (KOH, waterglass, sodium carbonate, TSP) be safe? It does work. If you can work it, electrocleaning is the superior choice for oxidation.... I just did not think to use it on a stranded wire. No dust no noise and at low power levels no smoke (but high current fast brush cleaning makes smoke but its still gotta be better for you then silicate dust!)


I use the TSP waterglass stuff to clean my Hp VNA gold SMT test fixture even...

yes electrocleaning might be the ticket here


For an aparatus on wire with only one end accessible for electrocleaning I think you can use a grabber clip (i.e. tektronix micrograbber or larger grabber if possible) fixed right at the wire insulation junction, and dip it into say a 50mL plastic beaker with a small notch cut in the side to allow the grabber to get in there and also get the stands of the wire dipped below the water line. You would just need to hold it steady for a few minutes while it cleans...
« Last Edit: January 28, 2024, 07:31:05 pm by coppercone2 »
 

Offline shapirus

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I just want to say that I first read the title as "special treatment for wives that refuse to solder?" and thought it was a legit question.
 
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Online coppercone2Topic starter

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something about repairing a food processor before a party comes to mind
 
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Online coppercone2Topic starter

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So to consolidate I wanna know if my standard electrocleaning solution of KOH, potassium carbonate, TSP and waterglass is OK for cleaning wire strands prior to soldering if dipped carefully?


And how do you neutralize the alkaline cleaner BTW? Citric acid OK? Or vinegar?

But given since there will be a milimeter or so of unclean material, it should act as a good solder stop to prevent wicking under the insulation too... nice feature actually.

I actually have a few strands in the trash I think, maybe I can experiment on that before I work on the second project. But it would be nice to know if any of this stuff is gonna cause some kinda situation in a year from now lol. It looks like halogen ions are out.

Also means probobly the salt + whatever solutions online are not a good idea either. But phosphate and potassium OK?
« Last Edit: January 29, 2024, 12:04:36 am by coppercone2 »
 

Offline SeanB

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Nickel plated wire will never solder, unless you use some fine sandpaper to remove the nickel coat. Generally the underlying metal is a stainless steel alloy, so it only works with crimp connections that make a gas tight join. Silver plate solders really easy, the nickel does not. No way to solder that nickel high temperature cable at all reliably, you always crimp it.
 

Online coppercone2Topic starter

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alright well its definately not steel I could tell that apart

pulled it from trash, when you cut a bundle its copper inside. and the insulation is definately teflon.

SO I guess its just tarnished silver if it cant be tin?

well whatever it is, I assume you could electroclean it. I see the other end was soldered to a PCB in the factory
« Last Edit: January 29, 2024, 08:04:50 am by coppercone2 »
 

Offline T3sl4co1l

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Now, as for more abusive treatments?  I use a molten salt bath to prepare enameled wire with insulation that is not solderable.  One can also use nitric acid, but that has gotten very hard to buy as it can also be used to make explosives.  As for the molten salt, try NaOH or KOH in a steel/iron pot.  Adding sodium nitrate (NaN03), readily available) makes it much  more active.  In practice, I use a small steel block with a larger hole in the center (e.g., 1/2" to 3/4" dia.) and a smaller hole for a TC or thermometer.

Can also be done in a stainless steel spoon, if you don't mind looking like a crack fiend (heavy /s..).

Have also tried potassium chlorate, which oxidizes organics viciously, but does nothing for the metal; my current favorite is to simply burn the wire, charring and oxidizing the organics, then dipping in molten NaOH to clean the metal.  The resulting sodium cuprate (and various carbonates and hydroxides as molten NaOH absorbs CO2 rapidly in air, from flame, etc.) washes away completely, leaving a rough pickled surface that accepts solder well.  The momentary high temperature also anneals the wire, for whatever that matters (which, if it makes it too soft, consider additional strain relief near the joint, etc.).  Obviously, this isn't feasible for fine stranding, which burns away / melts into a blob too quickly, and nitrate or a nitrate/hydroxide blend, is likely better.


Absolutely not.  Chloride ion contamination + ambient humidity, over any significant period of time is corrosion death for thin copper.  Its the same reason no-one sane uses acid zinc chloride flux (aka: killed spirits of salt, or plumbers flux) for electronics: You cant get all the acid chloride contamination out of the tiny crevices in stranded wire or under components on circuit boards.  See: https://en.wikipedia.org/wiki/Bronze_disease

Can confirm, copper and chloride are strong but sometimes inconvenient friends.  I once had some bus wire that I annealed, pickled (in HCl) and hot dipped in tin, and they still grew green rotty spots, I assume either in pinholes or bumps on the tinned surface, or due to trapped material that continued to react, expand, and penetrate the tin.


1/ High temperature  wire may have a silver plating to reduce oxidation. Identify by very bright silver finish, hard to scrape off.
Very common in stranded Teflon and fiberglass covered wire used in appliance automotive, heaters, industrial. Also some Kynar wire wrap wire has this.
Better to crimp a lug or splice as soldering is very difficult.   but silver solder and a hot iron or solder pot might work.

Eh?  Silver is extremely solderable; bright silver hardly needs rosin, it's pretty impressive really.  Once tarnished, it can be quite difficult however.  I suppose more or less, because Ag2S is the dominant form of tarnish, and metal sulfides have particularly low solubility in, pretty much everything, really.  It takes time for rosins to break that down.

If you're confusing it for nickel plating though -- that stuff is a bitch to tin, to not mince words.  A more active flux is required to do much of a job with it; regular rosin does work eventually, but in that time you've wicked so much rosin up the cable, impossible to clean out, that it probably won't last very well over time (and assuming you needed the temperature rating for a reason).

Both platings are commonly used with PTFE insulation.  I still have some scraps of MIL-something, mineral-filled PTFE jacket, multistrand nickel-plated copper cable, which is great when you need a lot of temperature handling and stuff, but if you don't have a crimp to make connections, good luck.  I have tinned the stuff before, uh, mostly, it still looks pretty thin -- but it's definitely not something you want to rely on.


Nickel plated wire will never solder, unless you use some fine sandpaper to remove the nickel coat. Generally the underlying metal is a stainless steel alloy, so it only works with crimp connections that make a gas tight join. Silver plate solders really easy, the nickel does not. No way to solder that nickel high temperature cable at all reliably, you always crimp it.

Generally--?  Nickel plated copper with PTFE might be more common overall, but if you're talking about a particular market segment, like, if you've only worked with heating elements, those alloys -- stainless, nichrome, Kanthal, etc. are commonly used, yeah.

Hmm, nickel plating on those, I've never heard of, but not to say I doubt their existence.  It would be one way to make it more solderable, considering anything chrome-bearing basically needs fluorides to beat back that tough of an oxide...  On that note though, I do see some copper-plated materials available / in existence, which would solve that issue extremely well. *shrug*

---

Not mentioned so far:

Some plain PVC jacketed tin-plated wire just does not solder.

I have some light blue stuff that is this way.  Have seen it in old TV sets too (they used wire wrapping instead; maybe it wasn't very solderable even when new..!).  Best solution is simply abrade off the plating.  Again, as said, acid is too risky, and if you don't have any stronger activated rosins, that's about it.

There's also various kinds of corrosion that happen within the cable, give or take environmental conditions.  I have a number of leads that've, probably sat too close to some chemical experiment I did or something like that, and probably a combination of chlorine fumes, and and other oxidation, light exposure, handling/touch, and plain old time, have done a combination of displacing or hydrolyzing the PVC plasticizer, oxidizing the copper (it's brown to black inside, maybe green towards the ends if not joined to something), and dissolving/complexing it (there's brown goo inside).  Most common plasticizers are phthalates, which after hydrolysis, can form copper complexes (salts, namely), and the resulting isononol or etc. would explain the "goo" component.  Also since decomposition liberates an acid (albeit a mild one), this decomposition can be autocatalytic (once triggered, it keeps going).

Tim
« Last Edit: January 29, 2024, 08:39:17 am by T3sl4co1l »
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Online coppercone2Topic starter

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I think the wire got sealed in the assembly then it got caulked with a supposedly safe caulk but that curing gas got pushed into the wire
 

Offline elektryk

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I just did a solar wire soldering test. I tried different fluxes layin' around and they all worked.
Such plated cables can be problem if you only use flux cored solder wire without additional (good) flux.

For me real challenging are wires in the car installation whose copper has turned black or green, they usually need mechanical cleaning and then good flux also.
 

Offline BrokenYugo

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Were any of those rosin fluxes RA? 

Never tried this but perhaps something like Tarn-X would help as a first pass treatment?
 

Offline elektryk

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Were any of those rosin fluxes RA? 

Above test was made using:
-OM338
-TSF6502
-BTFO-81-1 (bought recently https://www.eevblog.com/forum/chat/good-soldering-flux/msg5283400/#msg5283400 )

Never tried this but perhaps something like Tarn-X would help as a first pass treatment?

Well, it may help, but how about residues?
For the same reason I only use zinc chloride sometimes (in challenging cases).
 


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