Any recommendations for cleaning Peggy 2 after soldering

edited November 2013 in LED Matrix Kits
I ask this question for those who have not made the mistake I did: any suggestions on how to best remove the flux residue off of the Peggy 2 board after assembly is complete?

OK, not having bothered to ask the question before acting, I decided that Isopropyl Alcohol followed by a water rinse would probably do the trick.  Bad, bad, really dumb idea: yeah it removes the flux, and the shiny finish on the board, leaves a white sticky film (which I assume is the former board finish), and appears to have lightly oxidized the solder joints.  Other than that, it was a huge success.  Anything I can/should do at this point?  The board seems to be working fine, I'm mainly concerned with anything I should be doing to prevent any longer term oxidation issues as well as anything that can be done to improve the appearance (having done this, I can attest that it now looks far worse than if I had just left the residue alone.  The good news is that I only did this on the back of the board, the front is still pristine.)

P.S. one minor silkscreen / doc bug: both reference removing JP1 when S3 is installed.  Shouldn't that be JP5?


  • In our experience what happens when you wash a board with alcohol is that it partly dissolves the remaining solder flux, and spreads it around in a thin, sticky, sometimes white and flaky, but all-around awful layer that remains when the alcohol evaporates.  If you didn't leave it soaking for a long time, my best guess would be that the finish isn't actually damaged, so much as covered under a thin layer of thinned solder flux, which can be removed with great patience or a professional-grade flux remover.  

    Unless you're using flux that *requires* removal or you are willing to pick up some solder flux, your best bet is probably to just hide the backside, and hope that no one asks to see-- it shouldn't be harmful.

    And on that bug: Yep, you're totally right. That jumper used to be called JP1.   Somehow, you're the first person to notice this after a couple of years, and a surprisingly large number of Peggy 2 kits out there!

  • Out of curiosity, what sort of isopropyl alcohol did you use?  The 30/70 (alc/water) from the store, the less often seen 90/10, or 100% pure isopropyl alcohol?  Companies such as Digikey and Mouser sell the 100% (well, 99.9%) pure stuff and it works tolerably well provided the solder had an ammenable-to-cleanup flux.  The 30/70 stuff leaves a mess; I've never tried the 90/10 myself.  What works best for me is to use solders with "no-clean" fluxes and to just not worry about it.
  • With a fresh pair of eyes, it looks like that's exactly what happened: the finish is still there under a gross layer of gunk.  I assume that's what also dulled to solder joints so glad to hear that I only made a mess and didn't do any damage.

    No biggie on the jumper (the docs *show* the right jumper and with S3 included in the kit probably very few people actually use it), just thought you'd want to know.

    I'm quite pleased with the kit: very well done and high quality.  Looking forward to having fun playing with it.
  • dnewman: it was 91% and I used rosin core solder.  My mistake (aside from attempting to clean it at all) may have been rinsing with water as opposed to wiping clean.  I was assuming that the alcohol was more completely dissolving the flux as opposed to just smearing it around.

    EvilMadScience probably deserves some of the blame for making a PCB that I wanted to keep pretty :-)
  • Personally, I don't even try to clean black PCBs.  They're like a black finish on a car: anything I do shows, no matter how careful I am.  Unfortunately, I don't have a good solder recommendation as I stocked up a few years back on solder and what I'm using (quite successfully) is no longer available. But look for the non-clean varieties.

    If you go to, say, Digikey, you can actually search "solder no-clean" and turn up both leaded and unleaded solders.  Digikey uses the phrase "no-clean" in their descriptions; e.g., "SOLDER NO-CLEAN 21AWG 63/37 1LB".

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