Acid Solder Flux for Wires???

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Thread Starter

Bill

Does anyone know first hand what happens when you solder wire connectors with acid flux, such as Oatey #5. I just found out that some colleagues of mine have been using it on their encoder wires... It sure does make soldering easier, however. Will this definately cause a failure over time? Or am I making a big deal over nothing.


Bill Sturm
 
A

Al Pawlowski, PE

I once used some acid core plumbing solder on one of my first electrical projects. Think I was about 9 and it was a crystal radio. Well, not only
did the wires corrode very quickly, but just about everthing else that the flux hit. I have never tried it again.
 
Bill,

I have heard both sides of this argument . . . . here is my two cents worth. The chances of getting a cold solder joint that will fail due to
simply pulling out of the connector are about 50 times greater than having a failure due to corrosive action from getting carried away with
a fluxing agent. We do a ton of motion applications requiring hundreds of connectors each with dozens of terminations that are soldered. If an acid based flux is not used, I can almost guarantee that at least one and often more of the terminations will fail after a little flexing. I have never personally experienced a failure due to corrosion in 10 years of seeing cable assemblies in motion apps - this includes environments in the wet end of paper machines with high humidity. Of course, you need to do it right and make use of shrink tube where appropriate and ensure that the strain relief on the connector is applied correctly.

Good luck

Ken Brown
Applied Motion Systems, Inc.
 
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Curt Wuollet

Hi Bill

Yes, unless thoroughly cleaned of all residue, you can expect corrosion. How long before things fall apart depends on all kinds of activity factors, like heat, moisture, and the difference of the metals on the electrochemical series. That's not all, if the residue bridges an insulator you can expect leakage. The stuff is
somewhat hygroscopic and tends to creep as it absorbs moisture. Presence of operating voltages can accelerate corrosion. As encoder wires tend to be small and stranded, the long term outlook
is grim. It's even bad to have some of this stuff sealed up in an enclosure as the vapors spread. There are non-corrosive yet very active paste and liquid fluxes on the market if rosin core solder
isn't active enough.

Sorry

Curt Wuollet,
Wide Open Technologies
 
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Wayne Shimanis Vortex Technologies, Inc.

Bill:

I have had some experience with acid solder being inadvertently used in the assembly of printed circuit cards. When the boards went to test, there was a high rate of failure. In addition, a large number of those that passed were tested during a final inspection after final assembly had also failed. We decided to scrap the entire production run. I might note that a few that were
kept from the run are still functional 18 months later.

Wayne Shimanis
Vortex Technologies, Inc.
 
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Mike Milton, CCA

It will cause a problem! I worked in a textile plant and we had circuit boards that we made to replace some old equipment. Someone got hold of acid flux while they were installing the boards and in 4 months time they all had to be replaced. My boss who was a Chem E threw a fit and went through the plant and threw out anything that had acid flux in it. He made us all open
our tool boxes so he could check to see if we had any stashed. Anytime there was any plumbing going on, he would call a meeting and go over it
again.

Mike Milton
 
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Ramer-1, Carl

Bill:

This is definitely NOT a big deal over nothing! Acid flux is meant for soldering steel, and should be rinsed from even that product after the soldering process. Only rosin core solder should be used on copper wires and other copper connections. It too should be cleaned off with alcohol after the process, since it's slightly hygroscopic and will trap some moisture, become sticky, and allow dust to build moist bridges from terminal to terminal.

The acid fluxes universally dissolve copper, forming either copper sulfate or copper chloride salts inside the bead and splattered all over the surrounding area. Both of these salts are corrosive and form low resistance paths when they get moist.

Any good rosin based flux will also make it easy to solder copper, and is a lot easier to clean up. Using acid core solder or acid flux in
electrical/electronic applications will get your products banned from government purchase and open your company to liability in the event a critical system failure causes injury due to improper soldering.

There are a number of standards that can be invoked, but any of the solder/flux vendors will provide more information than you need to inform those engaged in the practice mentioned.

Carl Ramer,
Engineer Controls & Protective Systems Design Space Gateway Support
Kennedy Space Center, Florida

Unsponsored professional comment
 
J

Johan Bengtsson

I would recommend washing away the flux after the sodering is complete. I don't know if that particular flux will affect the solering over time but some types do. (I have some ten-odd years
lifetime of soldering ringing somewhere in my mind, not really telling me about what and where I heard about it)

You could try a non-acid flux and see if it helps making the soldering easy enough and worry a little bit less, it is still a good rule to wash it off however. It is not done in a lot of
places and it is possible modern types of flux don't need that.


/Johan Bengtsson

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Box 252, S-281 23 H{ssleholm SWEDEN
Tel: +46 451 49 460, Fax: +46 451 89 833
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Acid flux residue is hydroscopic, absorbs moisture from the air. Connections may start leaking current after a short time unless you
excessively clean them.
 
W
Bill,

Depending on humidity, temperature, and perhaps some other factors, the connections will corrode, and eventually will break. I have seen this
happen (strangely enough) on encoders used on mobile equipment.

Willy Smith
Numatico SA
 
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Paul McGuire

When we used solder flux to wave solder or hand solder printed circuit boards (in two GE electronics manufacturing facilities, one military and one commercial), there was a post-solder clean operation to remove the excess
flux. I suspect that much of the corrosion concerns can be mitigated or eliminated if the residual flux is cleaned off after soldering.

Paul McGuire
Sr. Mfg Applications Engineer
ObjectSpace Fab Solutions
Austin, TX
- Advanced Process Control Solutions for the Semiconductor Industry -
 
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Pierre Simmen

You're in for some headaches. The acid will in fact over time not only eat at the wires, but will absorb moisture and cause high
conductivity. I discovered that employees were doing the same thing only after many fires and failures. The flux was only used to clean the soldering iron tips and was purchased thru an electronic house. They said that the acid core was on the shelf and the rosin had to be ordered!
 
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Colin Walker

Please realise that resin is acidic at elevated temperatures and will cause corrosion to joints in warm spots, e.g. around power resistors and
semiconductors.

Regards Colin Walker
 
Bill,

REVISED POST, I did a little digging and found that we use Kester SP-44
rosin based flux for our encoder cables.

I have heard both sides of this argument . . . . here is my two cents worth. The chances of getting a cold solder joint that will fail due to
simply pulling out of the connector are about 50 times greater than having a failure due to corrosive action from getting carried away with
a fluxing agent. We do a ton of motion applications requiring hundreds of connectors each with dozens of terminations that are soldered. If a fluxing agent is not used, I can almost guarantee that at least one and often more of the terminations will fail after a little flexing. I have never personally experienced a failure due to corrosion in 10 years of seeing cable assemblies in motion apps - this includes environments in the wet end of paper machines with high humidity. Of course, you need to do it right and make sure you clean the joint and use shrink tube where appropriate to seal out moisture. Also ensure that the strain relief on the connector is applied correctly.

Good luck

Ken Brown
Applied Motion Systems, Inc.
 
J
The answers supplied to this question seem to be in two camps; those who do not know the difference between acid and rosin fluxes and those who absolutely know better than to use acid fluxes on electrical work.
I worked at a small company once that turned out a product where someone accidentally used Acid flux. The printed circuits immediately had intermittent problems. Nothing could be done to remove the effects of the bad flux, short than scraping the parts. The company about went bankrupt due to having to reorder and rebuild the entire line.
 
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