solder joint, pull test & charred flux

prkaye · #1 03-19-2009, 04:22 PM

I just did my first soldered terminal... an uninsulated ring terminal on 8AWG wire. I followed Bob Nuckoll's wonderful article (including use of a copper wedge).
Two questions:
1) should I do a "pull test" of a soldered joing just as I would for a crimped joint?
2) I used a paste flux to help the solder flow. THere remains some of this flux in the form of a black charred residue over part of the joint. Is this OK? Should I just leave this?
Thanks!
Phil

vlittle · #2 03-19-2009, 05:41 PM

Phil, you cannot use acid flux on an electrical connection. You need to use electronics grade solder with rosin flux. It's not clear which you used from your post, but the acid flux will eventually corrode your connection.

You can clean rosin flux residue off with MEK, but be careful not to get it on your skin.

Vern

Mike S · #3 03-19-2009, 06:06 PM

Quote:

Originally Posted by vlittle

Phil, you cannot use acid flux on an electrical connection. You need to use electronics grade solder with rosin flux.
Vern

Exactly what came to my mind when I saw the word "paste".

If your flux container doesn't specifically state that it is for electrical use, I would recommend you do not use it for the planes wiring system.

prkaye · #4 03-19-2009, 06:16 PM

yikes, glad I asked. The guy at a local eletronics place sold me Acid Paste Flux SP-30, and he told me flux was flux.
I'll re-do that joint. As per Bob Nuckoll's recommendation, I'm using SN 63, PB 37 Solder. But the solder they sold me at that place says Flux, OAJ 2%, which a quick lookup tells me is "Water Soluable Core". This doesn't sound good.
So it sounds like that guy was an idiot. So what I need is 63/37 solder with Rosin Core, and some liquid Rosin flux? Would 60/40 Rosin Core be equally suitable? That's what they have at Radio Shack.

rv7charlie · #5 03-19-2009, 06:30 PM

If you're soldering clean copper, no additional flux should be needed.

And not to 'one-up' Mel, but a crimped connector isn't structural, either. Its wire needs to be supported outside the joint, just like the soldered one.

Charlie

Norman CYYJ · #6 03-19-2009, 07:30 PM

I was taught many years ago that all electrical connections must be first electrically secure and mechanically secure if not it is either going to heat up or pull apart or both. Not good. There is no second. If you follow this practice you will have no problems. Get rid of the paste which is acid and use only rosin core solder 60/40 is good. No other flux should be needed if the connectors and wire are clean.

airguy · #7 03-19-2009, 07:37 PM

Good advice so far, you can buy the right stuff at many electronics outlets including Radio Shack, much as I dislike them. Ask for "electronics grade" solder, it will have the wire-friendly flux inside the hollow strand of solder and will be labeled "flux core". If in doubt about the cleanliness of the metal you're trying to solder, hit it vigorously with a scotchbrite pad for about 20 seconds by hand and it'll work. Shiny is your friend.

pczar3 · #8 03-19-2009, 07:49 PM

refers to clean up after soldering. If you use hot water on the connection within about 3 hours of soldering, the flux residue can be washed off. This makes PC board fabrication easier. As for the Acid core, it is a no-no for electronics circuits since it will continue to attack the metal and will eventually weaken it. You shouldn't need additional flux if you use the 63/37 solder you have. Just as an aside, while in the Air Force we were forbidden to solder wires since the solder wicks up into the wire and makes the connection more brittle. If you support the wires close to the terminal then it's not a problem.
Hope this helps,
Paul

prkaye · #9 03-19-2009, 09:18 PM

OK, so the water soluable flux in my solder is OK then? Doesn't have any of the problems associated with acid flux? I found the following in a google search:

"Water soluble fluxes (WSFs) are more aggressive in their ability to strip oxides. The degree of aggressiveness depends on the activators used. A WSF, as a corrosive material, does not know when to stop stripping oxide. Consequently, if you don’t clean the flux residues off, then it will continue to eat away the base metal".

So this means I should use water to clean the connection after soldering? But what about the WSF that runs down between the strands of my wire? The above suggests that the WSF will continue to eat away at my wire...

alpinelakespilot2000 · #10 03-20-2009, 10:15 AM

Quote:

Originally Posted by prkaye

So this means I should use water to clean the connection after soldering? But what about the WSF that runs down between the strands of my wire? The above suggests that the WSF will continue to eat away at my wire...

This is NOT a "crimping is always better than soldering" comment, Phil, but if you're not very sure what you are doing when soldering big wires, I would highly recommend crimping the connection rather than soldering. (No offense intended, as I knew I fell into that category when dealing with my big wires.) It's a lot easier to mess up a large solder connection than it is to mess up a crimped connection. I would argue that these large wires are not the place to be learning to solder. The $8.85 tool from weldingsupply.com mentioned in a number of other threads will more than adequately handle these crimps and pass the required pull tests. Hope this helps.