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PCBs, Moisture(?), Capacitance and Temperature

Discussion in 'Electronic Design' started by EdV, Apr 4, 2008.

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  1. EdV

    EdV Guest

    We got a batch of boards built and two of them show a curious
    tendency(consitent) to shut down the crystal oscillator at -20 C. We
    also notice that the capacitance of the xtal caps changes more on the
    "bad" PCBs at -20C than the "good" boards.

    1. Moisture in PCB Layers that didn't get baked out?
    2. Uncured epoxy betweem layers?
    3. Residual flux?

    #3 I could address with vapor degreasing or other cleaning. #1 and 2
    would mean baking at 100C or so which I guess is ok to see if it has
    an effect.

    Any thoughts, insights or expereinces as always are welcome.

    Ed V.
  2. neon


    Oct 21, 2006
    if you got moisture then baking the water out is not tht solution get the board hot then cooling it down power-off will claim all water particles from the enviroment. solution conformal coating like cheap old warnish will do it. dipping is better then spraying.
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