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space 10th April 2007 11:04 AM

What solvent for best removal of solder flux?
I've finished soldering an Amp32 (small 2 sided amp with mostly SMD-components) from and now want to remove solder flux. I'm a chem. eng. and have a small lab with some different solvents avalible. Which of these would be best?
Methanol (CH3OH), Ethanol (CH3CH2OH), Isopropyl alcohol (CHCHOHCH3), dichloromethane (CH2Cl2), acetonirtrile (CH3CN)

I've also got an ultrasonic cleaner (with heating if needed) and are considering using it, or should I just use a soft brush?

I've used a cheap solder with flux inside and don't know what type it would be. I've also used small amount of flux made for copper plumbing containing zinkchloride as the active ingredient. It is stated as partially soluble in water.


Conrad Hoffman 10th April 2007 12:57 PM

Not sure if there's a best, but I use isopropyl. You'll also want to use soap and water with a toothbrush because of the acid flux, and the whole thing should be given a good rinse in DI water when done. The usual test is that the water should run off in sheets, not drops, if the surface is truly clean. The ultrasonic is good, but heavier deposits will go faster with mechanical means like the toothbrush ;-) Watch out for unsealed pots- no solvents or water there, and styrene capacitors- don't use anything that will penetrate the styrene and raise the DF or short out the cap!

Pjotr 10th April 2007 05:07 PM


If all components are washable you can put your board in the dishwasher to clean it. Really, no joke, many smaller professional PCB assembly shops do it that way.

Isopropropanol and a sturdy brush is a good way. For the tough flux residues I use methylene chloride. But be careful with that, most components can stand it but not all plastics will do


Jeb-D. 10th April 2007 05:41 PM

I wouldn't recommend Iso-alcohol if the board has solder-masking. It can cause a haze. If it's a bare bones board though then its ok.

Pjotr 10th April 2007 07:07 PM


Originally posted by Jeb-D.
I wouldn't recommend Iso-alcohol if the board has solder-masking. It can cause a haze. If it's a bare bones board though then its ok.
True, some solder masks have that habit, they stand only water and soap. But with a good well cured solder mask it is no problem.


XEAGLEKEEPER 13th April 2007 04:17 AM

Dont laugh.I use Everclear 98proof grain alcohol(ethyl alcohol) and a trimmed acid brush then a rinse down with circuit cleaner.


TwoSpoons 13th April 2007 05:58 AM

Electrolube FLU Fluxclene is the best I've ever used. Comes in a handy spray can.

space 13th April 2007 06:09 AM

I've cleaned my circuit board now using isopropyl alcohol heated to about 40-50 deg. C in an ultrasonic cleaner. Left the board in for about 10-15 min. Rinsed it of with fresh isopropyl alcohol and dried it using compressed air. Seem to have worked very well.

Thanks for all your inputs!


XEAGLEKEEPER 13th April 2007 03:32 PM

FYI . Plumbers flux is corrosive to electronics.But your alcohol bath has probably nuetralize that issue.


gmphadte 18th April 2007 04:31 AM

The easiest available flux remover is petrol used in cars but how it behaves with the solder mask, no idea.

Gajanan Phadte

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