How to use liquid solder flux

Stuey · 23rd March 2007, 10:21 AM

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

Conrad Hoffman · 23rd March 2007, 02:27 PM

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.

Pjotr · 23rd March 2007, 06:59 PM

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

Stuey · 23rd March 2007, 11:46 PM

Hi there,

Thanks for the replies. Yes, I think this one is meant to be a no-clean flux, but I clean my board with isopropyl anyway because of the cored flux I'm using.

Now to get stuck in!

Cheers

Stuey

23rd March 2007, 10:21 AM	#1
Stuey diyAudio Member Join Date: Mar 2006 Location: Perth, Western Australia	How to use liquid solder flux 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

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23rd March 2007, 02:27 PM	#2
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	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.

23rd March 2007, 06:59 PM	#3
Pjotr diyAudio Member Join Date: Nov 2002 Location: Netherlands	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

23rd March 2007, 11:46 PM	#4
Stuey diyAudio Member Join Date: Mar 2006 Location: Perth, Western Australia	Hi there, Thanks for the replies. Yes, I think this one is meant to be a no-clean flux, but I clean my board with isopropyl anyway because of the cored flux I'm using. Now to get stuck in! Cheers Stuey

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