Flux problem Q and A

Q. Carl,

I ran into an issue last night while soldering a copper foil project. Thought you might be able to give me some quick in-site.

I am making a copper foil panel and completed the soldering on the first side Wednesday night. Thursday night when I went to solder the second side of the panel the copper foil had a blueish/green mold looking substance on it. When I wiped it off it almost appeared as blue wet ink. It was very difficult to remove and very difficult to solder in those areas. I tried cleaning it off with lacquer thinner and didn’t have a lot of luck. I used lead-free flux on the first side and did not clean it off when I finished soldering the first side. That is the only thing I can imagine that could have caused it. What would have caused this mold looking substance to appear? Have you experienced this in the future? Should I have cleaned the flex off of the entire panel before quitting Wednesday night?

Dave

A. Dave,

Wonderful!

A classic problem and guess who experienced the same thing.

Years ago I went on a trip to Maine for 2 weeks after fluxing both sides of a panel and only soldering one side.

I solved the difficult problem by wire brushing every foil run on the un-soldered side with a soft, brass bristled small brush. (What a job!)

What occurs on a fluxed piece is a buildup of oxides on the foil, over a period of time and it gets worse the longer it sits.

The solution..

Solder fast. (Ha)  Really, what I do now is sectionize my panel and only flux and solder one section at a time when I cannot do both sides in one day.  This way you may only have one quarter of your panel exposed to flux and air over night.

Next you may wipe the back of the flux exposed panel with a very, very light coating of a good flux remover using a soft piece of terry cloth.

I use a cleaner called Classic Neutra Clean and a  flux called “Ruby Fluid” which are both available from my Elite Delphi Dealer store on my website.

I have had pretty good success with both of these, but still try not to delay soldering too much after fluxing.

I loved seeing your studio and I am envious.

Keep in touch.

Carl

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