White residue after cleaning PCB

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Anyone else see this? It happens when I use either acetone or isopropyl alcohol. With either chemical, I dip a toothbrush in it and rub the PCB until the brown flux disappears. I then rinse with the board water and blow it off with compressed air.

I always get a white residue left over. Could it be from the water I'm using? Perhaps the bristles of the toothbrush (they look fine to me)? I'll go buy some distilled water to check but I'd be interested in hearing your opinions in the meantime.

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I too observe the powdery white residue.

I am told by the solder manufacturer that it is to do with the interaction between the solvent ( methylated spirits and the non iso propyl alcohol content of methylated spirits ) and flux solids content.

Seems You are getting this similar outcome with IPA and or acetone. It may be natural ( expected) outcome of the interaction of solvent and flux.

I use polished water post rinse ( polished water = low solids content water made by straining rain water through reverse osmosis membrane and then recirculating it through an ion exchange bed to remove ionic contaminants )and would not expect any water related issues.

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I really don't know why you would post rinse with water but anyway...

I simply wash in either methylated spirits or IPA and blow dry with compressed air. This blows off any remaining solvent and residue. Depending how dirty your solvents are (in the case of reuse) you may get more/less residue left behind. A 2nd rinse and blow dry with fresh solvent will take care of that.

At a company where I once worked, we used shellite (a petrol based solvent) for the 2nd wash. It's somewhat more volatile than metho and has the added advantage of displacing any remaining water/metho.

Steve

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Specially formulated flux cleaner works for me. Acetone is a bit strong for this application. I used to use acrylic paint thinners, warm the board a little the dunk it into the thinners. Board came out clean as a whistle.

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And plain and simple water works for me, but hey. :-)

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I just brush them with IPA (no water) and it works very well. I think that the water is the cause of the problem.

Leon Heller G1HSM

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We have used a liquid flux and it left this white residue after cleaning the board with iso. alcohol. Now we are using paste flux (when needed) and iso. alcohol and the white residue didn't appear.

As ignoramus said, I think it's a combination of the two components.

Regards,

Bruno Muswieck

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I use flux cleaner, like Farnell order number: 725663
for over7 years now at work and never have any residu.

we spray some flux on the board and use the brush, then all I do to speed up the drying process is to use a piece of hand drying paper (dont know the correct english term, buy you probably will understand) to take of the excess flux remover and the PCB is clean.