> Varnish/seal everything. What the army in WWII called "tropicalised".

1.  About the best conformal coating is "Parylene" which is partially
a state of mind and partially a range of products. Application is
annoying so usually done by specialists. Works very well. I only
mention it in case your university uses it . If not then suggestion 2.
is probably the most practical.


          http://en.wikipedia.org/wiki/Parylene

2.  The following will do what you want very well indeed:

Exceptionally good and suitable for DIY use is eg Dow Corning 1-2577.
This can be applied by dipping, spraying or brushing.
eg you CAN dip a pcb in the liquid, pull the board out at the rate
they recommend, dry it as recommened and get a VERY thin (100 micron)
coating that makes your boards about RH proof in most cases.*

A 0.1mm coating is enough to allow a board to operate dripping wet, if
one insists. It gets better - the material is UV fluorescent so you
can check for coverage with a UV lamp AND it can be soldered through
AND you can spot touch it up after soldering.
Needless to say, anything this good (let alone being made by Dow) is
not very cheap but a little goes a VERY long way.

Product page
    http://www.dowcorning.com/applications/search/products/details.aspx?pro=
d=3D01592424&type=3DPROD

Here it is with its cousins. ALL these use the same basic material but
it is "borne" differently.
Low VOC (volatile organic) is ozone safer, less regulatory issues,
kills fewer brain cells and so probably less  fun to sniff.
ie use these ventilated.
2577   The boss
2577 low VOC - more environmentally friendly
2620 - less viscous  version
2620 low VOC - ....

1-2577 data sheet   http://www.bkelectric.com/linked/dowcorning%201-2577.pd=
f

The "Conformal coatings family datasheet" mentioned on the above page
is excelllent - needs free registration.

* BUT add a sealed container with its own dry air and a dessicant bag
to keep it that way under all conditions. eg air at a given
temperature with only modest RH will have water condense out if cooled
far enough.

3. You can get some gain by just spraying with readily available
dometic clear "varnish" eg polyurethane 'plastic'** BUT 2577 is about
3 zillion times better.

** Polyurethane is *NOT* a plastic.
Not many people know that :-).
Even though Wikipedia calls it one and many many many other sites do as wel=
l.
It's actually an "elastomer" fwiw.
Ignore the indignant yelling that will now start and eg read this
which gives a small clue that the statement may be correct :-).
            http://www.mearthane.com/urethane_plastic.html

                       Russell McMahon
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