Cleaning PCB flux the easy way

Over the past year or two the number of etched PCBs I build has dramatically increased. As we all know build quality is very important; leftover solder flux is very unattractive and has the potential to corrode the board over time. Since I started mass building boards, I have always used the traditional isopropyl-alcohol-toothbrush-scrub-until-your-hand-falls-off method. This method, although very effective and safe on most every electronic component, is quite tedious. It takes me approximately 10 minutes per board to clean, scrub, and rinse several times to achieve complete flux removal. I didn’t have the time or patience to be doing this all day, so I was in need of a quick solution.

I had done some research and found sites like this one that mention the use of a paint thinner brand called Polyclens that would quickly remove the flux with little physical effort. Turns out, Polyclens is not sold in the United States and has been recently discontinued. At this point I decided to take a trip to my local hardware store in search of a suitable replacement to Polyclens. Minutes later I found this paint thinner:

Safer Paint Thinner by Klean-Strip

I tested this product on a few populated flux covered boards once I got home, the results were clear. The board had been stripped of flux and none of the components were damaged by the solution in any way.

Board cleaned with Klean-Strip (Sorry, I don't have a before pic...)

If you wish to try this on your boards, I have some advice:

DISCLAIMER: This paint thinner solution or any other paint thinner solution does contain strong chemicals. Execute safe handling. Anything you do I am not responsible for. Do this at your own risk.

-Before completely soaking your board in paint thinner, ensure that none of the components used on your board will be damaged by the solution. I have experimented with other paint thinners and noticed that the plastic labels on electrolytic capacitors does melt and fall off. So far, this has NOT happened with the Safer Paint Thinner by Klean-Strip I have been using. If you are worried that certain components might be damaged by this solution, test them out by placing several components in a cup filled with the paint thinner or install the components after the board is cleaned.

-If additional flux was applied to the board to help in the soldering process, loosen the flux with some isopropyl alcohol, dry the board, then place the board in the paint thinner. The paint thinner may not be able to remove large amounts of flux at once, so removing most of it will help. It is not exactly necessary to scrub when spraying or pouring alcohol on the board.

-Use a large plastic container and fill the container with just enough paint thinner to cover the entire board. Agitate the solution by letting the paint thinner pass over the board a few times. Flip the board over and repeat the agitation process.

-Once the board appears to be flux free, the paint thinner must be washed off the board. The paint thinner may leave a “sludge” residue behind which can be easily rinsed off. Rinse the board until the sludge has been completely washed away. Light toothbrush scrubbing may be required. I recommend that distilled water be used when rinsing the boards. Non-distilled water works too, but make sure to completely dry the board off.

-Dry the boards once finished. I dry with a cloth then use a shop vac which has a blower at one end to blow water from tight spaces and underneath components. Compressed air can be used as well.

Good luck!