Electronics > Repair
I*really* want to remove Kester 44 flux - what do I need to buy?
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Grandchuck:
Just curious ... will turpentine work?
macboy:
For Kester 44 i have always just used 99% IPA. I place paper towel (kitchen roll across the pond) over to the area to be cleaned, saturate with IPA, scrub with a brush (toothbrush works) through the paper towel. Don't rub the paper towel around, literally scrub through it so it barely moves. The flux residue will be almost entirely trapped in the paper. Lift it off and discard then repeat once more and the board will be quite clean.  This works much better than just pouring IPA onto the board and scrubbing... That loosens and dissolves the flux, but then where does it go? The paper towel traps it.
tooki:
For what it’s worth, despite the fact that tons of people do so, Kester itself says that “IPA will not clean the residues off the surface of the circuit board after the soldering process.”

This suggests that invisible ionic contaminants or activators remain (which otherwise would have remained entombed in rosin). Probably no big deal for most circuits, but still, I think it’s wiser to use flux remover.
macboy:

--- Quote from: tooki on July 18, 2024, 07:20:06 am ---For what it’s worth, despite the fact that tons of people do so, Kester itself says that “IPA will not clean the residues off the surface of the circuit board after the soldering process.”

This suggests that invisible ionic contaminants or activators remain (which otherwise would have remained entombed in rosin). Probably no big deal for most circuits, but still, I think it’s wiser to use flux remover.

--- End quote ---
Most or all solvent based flux removers will do no better. Salts don't dissolve into alcohols or petrochemical solvents. Kester specifically recommends a saponifier, a water based cleaner that will literally convert the organic rosin into soap, and will wash away the halide salts. The ZEP floor finish stripper recommended above is supposedly such a product and is available to consumers.
When using the paper towel method I described above, I don't get any visible residue left behind (especially not that white gunk commonly encountered) and for most purposes of mine, that's good enough. I absolutely agree that for sensitive precision circuits, a better cleaning is needed.
eetechTom:
I've never used the ZEP floor stripper, might have to give it a try. Listed "Hazardous components" on the SDS for the ZEP stripper are: 2-butoxyethanol 111-76-2 >= 10% - < 30% and 2-aminoethanol 141-43-5 >= 5% - < 10%. I have typically used a flux remover such as MG "Flux remover for PC boards", followed by a IPA rinse. I see the MG product contains Ethanol, isopropanol, and ethyl acetate.
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