Many years ago I learned a neat trick for very easily and quickly
stripping off the enamel from an enameled magnet wire.
Take an aspirin tablet, place it on a suitable surface such as a scrap of wood.
Lay the enameled wire on the aspirin. Heat both from the top, pressing
gently down, using a hot soldering iron. The aspirin turns brown and starts
bubbling as the enamel burns off of the wire. The result is a very clean
bright bare copper wire, and a somewhat melted brown remaining portion
of the aspirin tab.
Great useful technique when one needs cleanly stripped enameled wire
ends. Now for the chemistry question: What is going on there?
Why does this work so well to eliminate the enamel that was on the wire?Twospoons - 13-9-2022 at 18:54
What kind of enameled wire? Urethane or polyimide?
The old aspirin trick
sodium_stearate - 14-9-2022 at 14:52
The kind of enameled wire that is coated with an insulating layer.
That's what kind it is.
As for the chemical makeup of this enamel layer, your guess is as good as mine.
[Edited on 14-9-2022 by sodium_stearate]njl - 14-9-2022 at 16:02
Either way, the aspirin might be doing a couple things. One is melting and forming a protective layer around the copper so it can be heated without
oxygen. It might also be reacting with oxygen or formed copper oxide, itself being oxidized in the process. If that cant prevent oxide formation, it
might also be acidic enough to remove the oxide that forms on the copper and leave a shiny surface.Deathunter88 - 14-9-2022 at 20:58
As I understand it the PU coatings are the cheapest and usually "good enough". It's also pretty much "self fluxing", at least on the smaller wire
diameters. Junk_Enginerd - 18-9-2022 at 02:07
Oh yay, I can finally teach instead of only learn in this forum!
Aspirin will pyrolyse largely into phenol, among other things. I once did that, for the purpose of getting phenol, to use as a nylon solvent, to
smooth out nylon 3d prints. It worked! Nylon isn't easily dissolved by most solvents, but phenol does it well! Whether it does anything to
polyurethane I don't know, but it remains a powerful solvent so it makes sense it would work on most laquers.
So, you heat it up, it pyrolyses to phenol, which happily dissolves the laquer which is now also hot and therefore all melty and reactive. The mix of
phenol and laquer can probably be absorbed by the bulk material of the aspirin pill like a sponge, and therefore is removed from the wire. Any phenol
left on the wire will evaporate at soldering temperatures so it won't affect the soldering.
Edit: Also, thanks for the tip. I've never known in the 10+ years I've been an electronics designer lol
As I understand it the PU coatings are the cheapest and usually "good enough". It's also pretty much "self fluxing", at least on the smaller wire
diameters.
Yeah that's more "theoretically" solderable than it is practically. I've never come across enamel wire that was easy to solder. Sure, the ones that
aren't sold as solderable are basically impossible to solder without mechanically removing the enamel, but the solderable kind is still way more
annoying to solder than a bare copper wire. It almost always has to be a two step process of first tinning the wire thoroughly, and you need to ensure
it burns through the enamel, and then you can solder it.
