circuit board cleaning and potting

Community PCB Design
1

Can someone tell me the best way to clean a circuit board once I have fluxed and soldered. seems flux is conductive and can cause failure. Is that true?

Also what is a good way to pot a circuit board with surface-mount IC’s? With what material? polyurethane or silicone?

Thanks

2

99% isopropyl alcohol is the best stuff for removing flux. Conformal coating is often used for protecting boards.

3

If you are using water-soluable flux, then some good distilled water works well. Otherwise, Leon is right, 99% Ethyl alcohol and a good acid brush with short, stiff bristles will do a good job. Keep lint free tissues around to sop up the alcohol after you clean. This will keep it from just settling and drying on the board. Leaving that behind just makes the board look worse than before you tried to clean it.

(I have been teaching soldering school for 1.5 weeks straight now, so its fresh on my mind :smiley: )

4

rpcelectronics:
Otherwise, Leon is right, 99% Ethyl alcohol and a good acid brush with short, stiff bristles will do a good job.

Ethyl alcohol (ie, ethanol) is NOT the same as isopropyl alcohol - for this task, you want isopropyl.
5

leon_heller:
99% isopropyl alcohol is the best stuff for removing flux. Conformal coating is often used for protecting boards.

Agreed on both counts.

To expand a bit on the former, I should mention one system that seems to work pretty well: Set up a couple tubs and fill them with your IPA. Label one “clean” and the other “dirty”. Soak your PCB in the “dirty” tub for an hour or so, then scrub it with a brush (that you leave with the dirty tub) while it’s still in the tub. Remove the PCB, shake off excess IPA, and put it in the “clean” tub. Let it soak there for another hour. Scrub with a different brush (your clean brush), then remove and dry off. Once the clean tub starts to get somewhat dirty (after you’ve used it a good number of times) toss the dirty IPA, pour the “clean” into the “dirty”, and then get new IPA for the “clean” tub. Of course, you want lids for your tubs otherwise all your IPA will evaporate.

6

MichaelN:

rpcelectronics:
Otherwise, Leon is right, 99% Ethyl alcohol and a good acid brush with short, stiff bristles will do a good job.

Ethyl alcohol (ie, ethanol) is NOT the same as isopropyl alcohol - for this task, you want isopropyl.

Shit, I had no idea I put ethyl, I meant Isopropyl!