I am looking at this PCB board I've got and these pads are terrible looking. It still works, but this sure doesn't look right. What can I use to clean those up?enter image description here

  • \$\begingroup\$ It's difficult to see what is that "dirt" around the pins, but if it is just a metal oxide, you probably can wash it off with iso-propyl alcohol. Or maybe some other alcohol. You can try - it will not damage the board. Wet the cotton with alcohol and rub on it. \$\endgroup\$ – Nazar Feb 16 '15 at 13:34
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    \$\begingroup\$ Hey, Leon, do you just design schematics or something? Out here in the real world, electronics design also entails getting the design off the page and into existence...and there's some questions that arise because of that. Now, please be quiet and stop bothering us. To everyone else, thank you for your suggestions in solving this real electronics design problem. \$\endgroup\$ – testname123 Feb 16 '15 at 13:46
  • \$\begingroup\$ This absolutely has nothing to do with electronics design. This also has nothing to do with getting a design off the page and into existence. This is about cleaning. You did a bad job of..whatever that was, and you want to know how to clean it. Nothing to do with design. \$\endgroup\$ – efox29 Feb 16 '15 at 13:53
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    \$\begingroup\$ @efox29 We also have questions about soldering boards, removing the flux and other stuff. All this is integral of Electrical engineering field and we all have to deal with it on daily basis. The guy did not ask how to clean a grill after cooking a steak. \$\endgroup\$ – Nazar Feb 16 '15 at 13:56
  • \$\begingroup\$ @Naz I understand. But OP was very persistent that this follows design. Soldering, flux removal etc are not design. Those are skills for assembly and maintenance. \$\endgroup\$ – efox29 Feb 16 '15 at 14:53

I never buy commercial flux remover, which would likely help you with your problem, rather I go down to a local discount beauty supplies emporium and buy a bottle of acetone and a bottle of alcohol (not the drinking kind) and mix in equal parts.

Use a squeeze bottle for easy application of your brew.


I would start with alcohol and a stiff brush, clean up the excess with some qtips. If that doesn't work you could try some of this, best to spray it outside though.

enter image description here


It's hard to say what that residue is. It could be flux left over from soldering or it might be mineral residue from water having evaporated off the board.

If it's flux, Isopropal Alcohol (IPA) followed by a rinse in hot water may remove it. Be sure to blow the water off the board before it has a chance to dry. Use a toothbrush to help the alcohol to loosen the deposits.

You can also use a commercial flux remover - they usually work very well.

If it's mineral deposits, you may need to try vinegar or a dilute solution of CLR (a commercial solution that removes Calcium, Lime, Rust). Be absolutely sure that you completely rinse the board off with hot water afterwards and then blow the water off the board.

I have also seen deposits like this left after boards have been soldered with Water Soluble Flux but not cleaned properly after soldering. However, that flux remains conductive and the board most likely wouldn't work properly if that amount of flux remained on the board.

Some readers may question my suggestion of rinsing the board with hot water and then blowing dry. This is still an industry standard method of cleaning PCBs fresh out of a wave-soldering system that uses Water Soluble Flux. For example, we use Kester AZ2331 flux in our wave-soldering system - this stuff is wonderful because it is so active (promotes soldering very well) and because it washes off the board so completely when it with hot water. Our surface resistivity meter simply shows no conductivity whatsoever whenever we test our boards for cleanliness after washing.

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    \$\begingroup\$ Nice answer. I would just add that probably this water cleaning method uses deionized water. Otherwise, it would leave minerals and they could be a low impedance path between traces and pins. \$\endgroup\$ – gstorto Feb 16 '15 at 17:24
  • \$\begingroup\$ Most large-scale operations do use deionized water. We are a small-scale operation and just use tap water supplied by the city. However, so long as all of the water is blown off the board, we do not get any type of mineral deposit. We use very high velocity air that is static neutralized (Simco "Top Gun" system). \$\endgroup\$ – Dwayne Reid Feb 18 '15 at 3:45

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