Cleaning Flux from Printed Circuit Boards (PCB)

I got some professional looking PCB boards manufactured for a project recently. The boards look great compared to anything I could do myself.

Problem is, after I solder on the components and try to clean the flux off, I’m always left with a mess. My great looking boards end up with white stains from trying to remove the flux.

In researching this problem, I’ve learned about water soluble solder and no clean solder. I will be trying those in the future, but I’m still left with my most recent board which needs to be cleaned.

After looking around the interweb and doing some experiments here is what worked very well (though not quite perfect).

  • Apply all liquids with the board vertical to avoid getting anymore than necessary on the front side of the board.
  • Apply 99.9% isopropyl alcohol with a toothbrush to remove the flux. I don’t seem to need to scrub long or hard to get it loosened up.
  • Apply Simple Green with a sprayer. Brush the whole board again with a toothbrush. It may help to apply plenty of Simple Green to help flush the flux away.
  • Spray the board repeatedly with distilled water until the simple green & flux are flushed from the board.
  • Blow excess water off board with compressed air.
  • Finally, dry the board with a heat gun or hair dryer, taking care not to let it get too hot.

 

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2 Responses to Cleaning Flux from Printed Circuit Boards (PCB)

  1. Sean Straw says:

    compressed air before your drying stage will significantly reduce the amount of fluid you need to contend with (esp under components).

    If your board has certain types of sensors, you’ll need to take special precautions. If you have transformers or wire wound inductors, they’re literally magnets for trapping moisture (pun intended).

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