Rich Graziano wrote:

>  Perhaps you could put your circuit in a small plastic container with
> a dessicant and seal it.  If you have a way to partially evacuate the
> container it would also be helpful.

  Nope.  Sorry, you got that the wrong way round!  Unless you use
"hermetic" sealing techniques (all terminations made through conductors
cast into glass seals, like electron valves), it *will* leak.  In
practice, you will wish to open it up for servicing anyway.

  *When* it leaks, if it is evacuated, it *sucks in* moisture-laden air.
Instead, you pressurise it with dry nitrogen (I would think wet carbon
dioxide may indeed be corrosive).  That may leak out, but it'll be
pushing contaminants *out* while it does so.

  And yes, if it is durable, pouring an amount of LN2 into the *cover*
rather than the electronics, and providing an over-pressure blow-off
would be a simple way to do that.

  ([OT]: I've yet to try the "LN2 in a soft-drink bottle" trick yet!)
--
  Cheers,
        Paul B.