How to use liquid solder flux

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Hi all,

A very simple question; how do you use liquid solder flux on older amp boards when repairing?

I bought the flux as I've had trouble getting the rosin cored solder I normally use to wet on older PCB tracks which I've carefully cleaned up with 800 grit carborundum paper and isopropyl alcohol.

The flux I've bought is an aromatic solvent based one containing rosin, from Cutter Electronics: http://www.cutter.com.au/products.php?cat=9&pg=5

Anyway, do you let it dry, or try to solder while it's still wet, or doesn't it matter?

Cheers

Stuey
 
Not familiar with that one, but it's usually rosin and alcohol. You just brush it on with a small brush and start working. No need to let it dry. IMO, for the best quality work, all flux, including RMA (rosin, mildly activated), should be cleaned off when the board is complete. Use alcohol or a spray solvent made for the purpose- outdoors! FWIW, I once watched a NASA certified solderer come into our plant to do some work on board that were to be launched in a satellite. The person used brush-on rosin flux for all their work, and they did some of the best joints I've seen.
 
Hi,

I use “No Clean” solder flux as an extra flux for SMD components and rework. You must dry it thoroughly because otherwise it will “sputter”, giving unreliable joints and very small solder spats around the PCB board. With small SMD components these spats gives a risk of shorts.

Cheers ;)
 
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