Protecting PCB from condensation?

Discussion in 'General Electronics Chat' started by spinnaker, Dec 5, 2011.

  1. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    4,884
    1,002
    I have a project that I plan to mount outdoors. It will be in a reasonably waterproof container (right now tupperware clone). But I am worried about condensation.

    I want to use something off the hardware store shelf and not have to order anything special. Would a urethane spray do OK or should I go with something like this?

    The advantage of the spray is if I had to get to the circuit I could.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    I'd suggest the clear conformal coating for around $8/can. You can solder through it, and it transmits heat well.

    I've used tupperware for temporary weatherproofing before and have had great results with it. Seal all I/O with silicone, and if you can, toss in a couple of those micro-bead desiccant bags that come with everything to soak up the moisture once it is sealed, then there won't be any humidity to worry about. About 1/2 cubic inch of silica-bag for each 12 cubic inches of container, more won't hurt.
     
  4. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    4,884
    1,002
    Thanks.

    So would an off the shelf Polyurethane be a good choice for moisture?

    Are there HW store silicon solutions? I know there are silicon sprays but I have always thought they were for lubrication.
     
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Silicone for sealing comes in caulk tubes or large squeeze tubes.

    There is also Silicone lubricant, make sure you get the sealing kind, it is easy to tell apart, the sealant is extremely thick and goes "gloop" while the lubricant is watery and goes "drip".
     
  6. JoeFromOzarks

    Active Member

    Apr 14, 2010
    95
    27
    CorrosionX is good stuff!



    :) joe
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Off the shelf Polyurethane clear that is rated for plastic/metal has been used without problems by a few here.

    I haven't personally used it, I use testors transparent candy green for the solder mask look on the bottom, and the Chemtronix conformal clear on the top side.

    I think the major difference between conformal coatings specifically for electronics and others is that they are thicker, which prevents corona from high voltages arcing over components as easily. Polyurethane may have that same property, I don't have a hi-pot test lab to try the idea out in, though.
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    I have a recommendation I still haven't verified (dagnabit) that Krylon brand clear acrylic spray paint is good a conformal coating, just don't get it too thick.

    When I do get around to it I will let you know how it works.
     
  9. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,648
    762
    I do not know if you have chance to do some testing.

    Valuable things that need to be packed safely and cannot be contaminated by the sealant are first bagged in ziplog-like bags. Then, the expanded polyurethane is applied.

    With due care you later can break the foam and recover the goods intact.
     
  10. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    That is closer to potting I would think, as opposed to a conformal coating.
     
  11. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    HUMISEAL conformal coating
     
Loading...