Acid-flux soldering trick.

Educate me! Why are you using acid flux instead of rosin flux?

John S.

You already found out why if you went through the rest of the thread.

The acid flux slightly etches the metal as well as removing any last vestages of oil or dirt, and thereby provides a cleaner and slightly rougher surface for the solder to get a grip on. (Or so I'm told.)

~Pete

Erm, rosin does the same. The residue is also corrosive, not quite as strong as acid flux residue. Mostly, it's easier to clean - you just sloosh the circuit board in a solvent-based washing fluid. That washing fluid is environmentally not nice at all, in case you wanted to know.

HTH

Not quite. You apply the acid flux thirty seconds or so before you apply the heat, and that gives it time to work that the rosin doesn't normally have.

So how does that make cleaning rosin "easier"? The axid flux I use just washes off with plain old dish soap and water, both of which

*are* reasonably "nice" to the environment.

In any case both the solder and the matching flux are made by Tix, and their products are pretty much available in better train hobby shops and are almost universally used by the brass repairmen and builders that I know, as are resistance soldering rigs.

~Pete.

On 1/8/2009 10:54 AM Twibil spake thus:

Ackshooly, Wolf isn't quite correct about rosin flux. Look at any piece of electronics equipment that's been soldered with rosin-core solder (lots out there, I've looked at it): generally, the flux is allowed to stay on the solder joint, where it does absolutely no harm. It is not corrosive, as acid flux is. That's why they always say not to use acid flux on electrical connections (you can find this advice just about anywhere).

So far as Pete's questions go, there's nothing magical about using acid flux as opposed to rosin that guarantees a better connection when soldering rail connections. It is true that brass builders use acid flux because it's simpler in that case, and because it can be washed off. Obviously, it cannot be washed out (at least not easily and certainly not effectively) when soldering rail on a layout, which is why it should never be used in that situation.

Simply cleaning the joint and carefully soldering with rosin-core solder will work just as well for any rail connection you can make. Cleanliness is the key here.

On 1/8/2009 6:06 AM Wolf Kirchmeir spake thus:

As I said elsewhere, not true. Found this article, a short reprint from Kester which makes it pretty much from the horse's mouth, about how rosin flux works:

Turns out rosin contains an acid, abietic acid, which does the work of cleaning the metal, but it's not corrosive to copper (and therefore presumably not to other metals likely to be soldered on a model railroad layout).

On 1/8/2009 6:06 AM Wolf Kirchmeir spake thus:

More good stuff on fluxes here:

Got me confused with another poster, I think. I didn't ask 'bout that.

I use normal everyday rosin-cored electrical solder and a small iron to solder wiring and track connections, and aside from melting the occasional platic tie, no problems. (Ya gotta work *fast*!)

Soldering is sort of a neat skill because there are so many ways of doing it and so many specialized tools that are designed to do slightly different jobs. At last count I had one resistance soldering rig, two different sorts of handpieces for same, two soldering torches (small and tiny), one full-scale blowtorch, and two differtent wattages of electrical soldering iron as well.

Although sometimes more than one of them can do a given job just as well as another, more often than not one is perfectly suited to the job where all the others would be clumsy at best: either not strong enough or massive over-kill.

~Pete

On 1/8/2009 1:15 PM Twibil spake thus:

Ah, right, you talked about that baking soda thing. My bad.