[volt-nuts] PCB cleaning and sealing

[Bob Paddock]

On Sun, Sep 26, 2010 at 8:00 AM, Alan Scrimgeour
<scrimgap at blueyonder.co.uk> wrote:
> Do silicone based conformal coatings allow water in too?

To my knowledge all coatings will allow water to migrate to the board
level eventually.
It is only a mater of defining "eventually".  The best coatings
setting under water may take months, in a normal room it could take
years.
It is one of those very slow drift mechanisms that is rarely accounted for.

If you read up Electrostatic Grade Op-Amps like the AD515 and friends,
they always tell you to "expose to air" the high impedance points.

While on the subject of water migration.  Water can migrate up coaxial
cable.  Took a shower from a cable on the second floor of a building
once, when the cable came down a tower, to ground level, and back up
to the second floor of the building.  The connector had not been
removed in years.