Soldering Difficult Connections

Almost three years ago, I blogged about splicing my 40m dipole back together. The problem was that the wire had corroded, and I just couldn’t solder it properly. This episode came to mind when I read the following e-mail by Chuck, W5USJ, to the qrp-l.org mailing list:

Not a new thing and came up recently — problems soldering oxidized wire like coax shield and connections that are bright nickel plated and so on.

I used to have the old type rosin flux used for soldering copper plumbing. It worked really well for difficult surfaces (used sparingly). But that’s no longer available in favor of fluxes that will work with lead-free solders.

What I found that works really well is something called NoKorode Regular Paste Flux made by Rectorseal. It’s designed for lead-free solder but seems to work well on just about any metal. On the label there is this note: “Non-aggressive paste flux. Works on copper, galvanized iron, lead, tinned steel and other metals.”

One particular problem I have is with the shield on RG-174, the silver plated stuff anyway. With regular solder, even with high heat the solder wouldn’t stick well and often the insulation melted to the point of damage.

I had prepared some 174 with a short pigtail of twisted shield.

With the NoKorode, I applied a really thin coating on the shield. Then when I applied the solder it completely wicked into the shield almost instantly with complete coverage. As the name suggests, it does not seem to be corrosive in any way.

On some RCA connectors with what looks like nickel plating, I lightly dipped the end of my solder into the paste. Then tinned the area around the holes for the connections. That worked great too when I attached the wires; it was much easier to make a proper connection. No where near as much time was needed to heat the joint to get the solder to stick to the bright nickel surface.

It doesn’t take much to do the job with this flux and used sparingly should be fine for soldering other than electronics circuits. I’m going to try it with some of the bright metal finish on connectors like PL-259s. The 1.7oz container that I bought should last a very long time.

Sounds like I need to go get some of this stuff. If you go to the Rectorseal website, you’ll find that they make a whole bunch of different fluxes for use in different situations.

UPDATE
I just got this update from W5USJ:

Got some replies asking where to find the flux I used. One mentioned a few times was ACE hardware. My source is a local hardware, plumbing supply, lumber yard, welding supply, mini-Walmart affiliated with no national chain. It’s located in the county seat city of Emory, population 1100, Rains County, population 11,000. Sort of a rural location you might say…8^)

Also, I’d expect some plumbing supply stores would handle the NoKorode brand. Oatey has a similar product and a much bigger name in the brand stores. But the NoKorode seemed like a better idea to me. So I haven’t tried the Oatey brand.

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