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I'd like to reuse a PCB in non-intended way and I have to remove the green solder mask to expose the copper traces in 1 x 3 cm area. Is there any safe method to do it without damaging the traces?

I've tried acetone first, then a bunch of other household chemicals, but it is resistant.

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    \$\begingroup\$ I usually use a box-cutter to scrape the solder mask off. I'm guessing an X-Acto knife will work just as well.. \$\endgroup\$ – m.Alin Sep 9 '13 at 13:45
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    \$\begingroup\$ Any sharp thing is too risky, I have very narrow traces, and the area is too big for scraping. \$\endgroup\$ – csadam Sep 9 '13 at 17:07
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    \$\begingroup\$ I've used exactos to create a "bonus" solder pad on 5 mil x 1 oz traces countless times without accidentally cutting them. Use a scraping motion, not slicing; good chance you'll snap off the end of the blade, but it doesn't matter. \$\endgroup\$ – Nick T Sep 11 '13 at 20:42
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Google "fiberglass brush pencil", once you try that you won't want anything else.

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  • \$\begingroup\$ another thing I've never heard of :) Although I've already done my work, I've ordered one to try it out. \$\endgroup\$ – csadam Sep 11 '13 at 21:36
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    \$\begingroup\$ It was arrived. You are right it is better than anything else I've tried. Fast, and precise, like a sandpaper pencil. \$\endgroup\$ – csadam Sep 19 '13 at 10:15
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Usually a little wet/dry abrasive paper does the trick, use it dry first then damp it a little.

You may get the same results with fine sandpaper, but I think wet/dry is better as it has a finer grain, which is less likely to damage copper traces (especially thin or shallow ones).

That's how I did it when I got a faulty batch which did not have enough mask clearance.

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I've used an electric eraser equipped with an eraser stick that was the firm pink colored one that had some bite to it. This would be similar to the eraser on a #2 pencil. These have a certain amount of fine grit in them that will remove the solder mask and shine up the underlying copper. (Of course if you grind away at it long enough it would also remove the copper too).

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    \$\begingroup\$ lol, I've never heard about electric eraser before. At least now I know that it exists. Based on the idea, I've ended up using a dremel clone with polishing head. It took some time, but successfully removed the mask, and I have shiny polished copper surface for gratis. However the sandpaper method looks faster, I have none of them at home. \$\endgroup\$ – csadam Sep 9 '13 at 17:03
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I find that a razor knife is too sharp and will easily dig into the copper.

What works better for me is a cheapo jeweler's screwdriver. The smaller sizes of straight ends are ground and just sharp enough to scrape off solder mask without digging into the copper. And the shape is easier to control than a knife or sandpaper.

enter image description here

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  • \$\begingroup\$ Yes, using a relative blunt screwdriver would be good for a few traces, but currently I have 30+ of them. \$\endgroup\$ – csadam Sep 9 '13 at 17:05
  • \$\begingroup\$ paint stripper is probably the easiest choice then. \$\endgroup\$ – markrages Sep 9 '13 at 17:30
  • \$\begingroup\$ @markrages If the solder mask does not dissolve with acetone, it is some kind of cross-linked epoxy-like coating. I would be worried that any paint stripper which can attack it will probably not stop there and go on to attack the board itself. \$\endgroup\$ – Kaz Sep 11 '13 at 23:33
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Fiberglass brush pencil is good but the ultimate tool for solder mask removal is a "micro sandblaster". These used to be very expensive but there are now some nice units on eBay that are not too expensive. I load mine with baking soda and it gently takes away even the toughest solder mask with little to no damage to the underlying copper.

The only drawback is that it makes static electricity so there is some potential to damage boards but I have never had any problem with damaged boards.

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I had boards manufactured and all of them showed up with soldermask coating the exposed pads on the bottom fo the PCB. The solution that worked best for me was to use a motorized 'manicure pedicure set'- https://www.lidl.de/de/sanitas-manikuere-pedikuere-set-sma-35/p241592?gclid=EAIaIQobChMIyKeC6Piy1QIVbTPTCh2_JA4MEAQYAiABEgIG6PD_BwE

The motorized sanding surface was perfect to easily remove the soldermask. Just wanted to post this affordable solution here incase someone came here looking for a quick easy solution to their problem.

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