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 Post subject: Soldering tarnished terminals!
PostPosted: Tue Feb 27, 2018 2:14 pm 
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Joined: Thu Oct 26, 2006 7:11 pm
Posts: 1307
Location: Maryland
I just had the need to solder a 100+ Switchcraft A4M and A4F connectors. I got a great price on the large quantity I needed but it seems many of them may have been old new stock.
The contacts, which I assume are silver plated were tarnished and the soldering was not going well. I used a Kester activated flux and it went much better, but not great. Way too much heat to get the flow needed for a good connection was required. I ultimately tried Tarnex, with great success, only on the A4M connector since there are no hidden areas and washing afterwards would not be a problem. The A4F, with its' enclosed contacts are a different issue so I stayed with the conventional flux for those and drying it completely without a bake out may be difficult.

I am well acquainted with Deoxit and their great products but this is a soldering, not a contact issue. Since the contacts wipe when inserted the oxidation is not an problem on that side of the connector.

While on the subject of solderability, I also solder hundreds of small bipin lamps (#7373) to PCBs. These pins are a bear to solder since the pins are plated, I think with nickle, and no 'approved' flux seems to make it better. I recklessly resorted to using Stay-Clean liquid flux, which is a great metal soldering flux, and works like magic on those pins, but it is not recommended for electronics. Immediately after soldering the lamps I drop the assembly into a warm soap water mix then afterwards use a similar mix and ultrasonically clean them. At the end I use a conventional spray flux remover. I did a batch of those a year ago and so far there has been no evidence of corrosion due to the Sta-Clean.
I also considered using Stay-Clean on the A4 connectors, but because I am soldering stranded wire to the pins I am sure the flux would migrate into the connector and wire insulation to cause grief down the road. The lamp assemblies are more straight forward to clean afterwards than the connector.

Years ago I worked at an large local electronics distributor and we often dipped tarnished silver plated contacts into a puddle of something before shipping. Was it Tarnex? Well maybe, but unfortunately I have no idea what was actually used.

I would appreciate any comments or ideas, or tales of soldering success.


“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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 Post subject: Re: Soldering tarnished terminals!
PostPosted: Mon Mar 12, 2018 1:29 pm 
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Joined: Fri Jan 11, 2002 1:01 am
Posts: 3830
Location: NewJersey
Hi Len,

I've used rosin flux in the past. I think it was G and C made for soldering, came in a small bottle.
It comes with a brush, wipe it on, then solder.
I've tried it as a test to solder an old penny and it worked pretty well, much better than with just the rosin core solder.

Also, there are other types of flux cores such as acid. These are much more brutal to metal but in an extreme situation you may need it. They only damage very very thin pieces. I would try the rosin flux first though, that stuff is pretty good.

With either flux, one of the requirements is to "boil" out the flux so that it does not sit there forever and cause problems. That means after the joint is soldered, keep the iron on the joint for another 2 seconds or so. That will help ensure a long lasting connection.

If you find something like this that works well maybe you can post it here after you've tried it.

PS i just looked it up and it is GC Liquid Solder Flux made by GC Electronics, but im sure there are others too.

LEDs vs Bulbs, LEDs are winning.
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 Post subject: Re: Soldering tarnished terminals!
PostPosted: Mon Mar 12, 2018 4:49 pm 

Joined: Wed Nov 24, 2004 1:01 am
Posts: 2284
A little off topic but still related. I have seen various adds for "Aluminum solder" in my travels across the internet. Anyone have experience with these products. Might come in nice for custom chassis fabrication or special grounding situations. I own a 325 watt Weller solder pistol which may be needed for this work.

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