i have several thousand terminated wires i can't afford to scrap that won't solder very well.
the insulation is stripped and retained but somehow they must still have oxidation.
i've tried 2 different fluxes but still had poor results.
what is the strongest NO CLEAN flux i can use?
thanks

 

In my limited experience with soldering corroded wires, sometimes cleaning them mechanically helps a lot. Spread the wires and give them a few scrubs with some emery cloth or sand paper, then try again. Maybe someone else will have a better idea.

 

In my limited experience with soldering corroded wires, sometimes cleaning them mechanically helps a lot. Spread the wires and give them a few scrubs with some emery cloth or sand paper, then try again. Maybe someone else will have a better idea.

i have over 15000 wires and they're only 20gauge so that isn't feasible.
and they look clean since i only remove the retained stripped section just before soldering.
thanks anyway.

 

what is the strongest NO CLEAN flux i can use?

I've had good luck using Kester 186. I bought it on Ebay from a guy that buys it in bulk(by the gallon, that was the only other way I found it) and re-bottles it in smaller bottles to resell. I'm not a salesman for him or affiliated with him in any way, but here is his site on Ebay.

http ://stores.ebay.com/Dickies-Garage-Sale

Like him I work on cars where the wiring can be corroded and tried many different fluxes that didn't work but the 186 has worked every time I've used it. It is a liquid and no clean.

 

Are you sure the wires are copper? Are they stranded or solid?

John

 

Are the wires springy? I've had some cheap wires out of china that were springy, like they were made of plastic or something. So frustrating, difficult to solder and when you twist them together they spring back to being perfectly strait as if they were never bent.

 

Steel or aluminum came to my mind. Perhaps time for a magnet?

John

 

I've seen lots of wire, especially untinned copper, that has sufficient surface oxide to make it really hard to solder.

The Kester 186 shortbus recommends sounds good. Usually for wire it is OK to use a fully-activate rosin flux ("RA" type), which is the most aggressive sort that is considered to be safe to leave on for most applications. It used to be the standard type for all sorts of electronic work.

Is it stranded or solid? I'm guessing stranded since you say the insulation is retained. There are ways to chemically clean oxide from copper, but they are dubious on solid wire and very bad on stranded wire.

Do you have a solder pot? Sometimes dipping the wire in flux then in a solder pot will work considerably better than soldering with an iron, but it really depends on how thick the oxide film is. Of course this becomes a two-step process of tinning then soldering which may make the overall process either faster or slower. Pretinning can be great if you have to solder to solder-cup type connector contacts.

 

i'm using a RA type from MGchemicals.
i tried the 186 kester but MG worked better.
it helps but still not up to par with clean wire.
this wire is stranded tinned copper.

 

I use Harris "Stay-Clean" flux for soldering and tinning wires to gator clips.
SG

 

maybe they are not for soldering. Like the wires inside headphone cables are as such. Probably each is coated with insulation.

Whats the specification , do you have a picture

 

it's normal 20ga, 300v, tinned stranded copper.
wire finish is still shiny and looks clean.
i only remove the insulation right before soldering.

 

This is a tough problem. Short of a silly suggestion (which I will get to) the only thing I can think of is to try dipping the wires in RA flux and incubating them for a time at the highest temperature compatible with the insulation in the hope that the activating agents in the flux might start working. I don't hold a lot of hope.

Silly idea: hot carbon monoxide. CO is a reasonably potent reducing agent that can convert metal oxides back to metal. I have no idea offhand how hot it needs to be. And of course it is lethal if you inhale too much. Don't do it.
I can't think of a reducing agent that isn't likely to cause problems.

 

If the wire is still shiney, it rather suggests that oxides may not be the problem. Have you tried an organic solvent in case there is a thin film of oil?

There are all sorts of solvents that would strip oil, but it has to be compatible with the insulation and safe to handle. I would try 99% isopropyl alcohol (also called 2-propanol or isopropanol) or 95% denatured ethyl alcohol. Neither will attack PVC insulation, both are low toxicity, but both are flammable. I would try wiping the strands with a cloth or tissue moistened with alcohol as an experiment. If it works, dipping is probably more practical, but some of it will wick up among the strands under the insulation so "drying" time should be allowed. Again, these solvents are flammable! There are several reasonably common non-flammable solvents, but many are more toxic than the alcohols. If you have any sort of flux removal solvent on hand, it would also work.

 

Could the wire be "headphone" wire? Sometimes they use magnet wire for the strands because they only have to have a single outer insulation for the entire cable. This makes the cable much smaller in diameter and more flexible. I have also seen this done for video camera cables.

The strands normally have a subtle color difference. Each color is one signal in the cable.