General > General Technical Chat
Why is so much general purpose connecting wire so hard to solder?
tooki:
--- Quote from: GopherT on November 07, 2021, 03:19:34 pm ---If you are using lead/tin alloy and your wire is likely a lead-free tin alloy with higher melt temp than your solder, you will have problems. You'll need to heat the solder a bit longer than usual and set your soldering iron about 50°C hotter (or get a hotter tip if using a weller iron with Mag thermostat).
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Tinned wire isn’t tinned with solder, it’s tinned with tin, so it’s always lead-free.
TimFox:
--- Quote from: T3sl4co1l on November 07, 2021, 04:09:02 pm ---I don't know that I've had new wire that didn't tin well, but I've certainly seen that on wire of old age, or unknown provenance. It seems like the wire is tinned, but the surface has oxidized or corroded or somehow become coated with something that doesn't tin well. You basically have to sand it down to get a good joint.
Note that nickel plating has a similar effect, but its reluctance to solder is natural (surface oxide); I wouldn't expect nickel plating to show up randomly in hookup wire however -- that's more of a high-temp mil spec / teflon thing (with silver plate being probably more common). Nickel can be identified easily as it is magnetic.
Tim
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I inadvertently bought some nickel-plated mil-spec wire (surplus) and it refused to be soldered.
Most Teflon-insulated stranded wire is silver-plated. Freshly-stripped, before it sulfides, it solders well with normal rosin flux solder. Silver is used instead of tin, since the Teflon process is hot enough to melt the tin and tender the stranded wire inflexible.
WattsThat:
Nickel plating is used for high temperature applications. That’s why you crimp with nickel plated lugs as it is not solderable, not to mention the solder would meld at the temps typically seen. Highly doubtful you’d ever see PVC insulation on nickel plated wire, makes no sense.
Standard PVC hookup wire that has been stored for extended periods of time at high temperatures (50-60C and up) is subject to oxidation from the plasticizers in the PVC breaking down. IIRC, hydrochloric acid is released in the process, leading to mild to severe oxidation of the tin plating.
T3sl4co1l:
Not sure about oxidation, but exposure to acid fumes causes a catalytic breakdown: the plasticizer is generally an ester like diisononyl phthalate. Under non-neutral pH and in the presence of moisture, the ester can be cleaved to isononyl alcohol (basically, "long" (oily) IPA; not much of a smell AFAIK, and probably volatile enough that it evaporates over these time scales) and phthalic acid (a modest organic acid on par with say citric or acetic acids). Which under acidic conditions to start, means this is a catalytic (runaway) reaction. The phthalic acid in turn can attack the copper, giving a green to black goo that seeps out of holes in the insulation, or at the ends.
AFAIK, the PVC itself is unchanged through this process, though it may be affected by heavy metal radicals, I don't know (seems like more of an iron thing than a copper thing?, but copper is certainly a metal with catalytic potential), and photodegrades to some extent (obviously, N/A if it's in dark storage). Still, the character of the material can change dramatically, as pure PVC is a brittle material and is wholly dependent on plasticizers (to the tune of >30%wt) for its commonly soft consistency.
I happen to have some test leads that this happened to; ironically, only one went gooey, the other is pretty normal. And they've been paired the whole time (~15yr). Both are reasonably flexible, though maybe not virgin. The reaction would've started in this case from HCl fumes, as they date back to the days when I'd do inorganic chemistry experiments in my parents' basement (much to the detriment of any clean steel in the house... fortunately for me they're tolerant :-DD ).
Tim
David Hess:
--- Quote from: T3sl4co1l on November 07, 2021, 04:09:02 pm ---I don't know that I've had new wire that didn't tin well, but I've certainly seen that on wire of old age, or unknown provenance. It seems like the wire is tinned, but the surface has oxidized or corroded or somehow become coated with something that doesn't tin well. You basically have to sand it down to get a good joint.
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Kester makes cleaners for different metals. For years I have used Copper-Nu #5520 as sort of flux for difficult to solder wire. Kester used to sell it in 4 ounce bottles but no longer does unfortunately.
Dilute HCl works in a pinch. The advantage of HCl is that it leaves no residue but keep it away from steel tools because it will quickly promote rust.
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