AVR-Chat

On Sat, Oct 2, 2010 at 10:27 AM, Chuck Hackett <egroupscdh@up844.us> wrote:

> I am looking for a Conformal Coating/Potting Compound that I can coat boards with to
> protect them from moisture that can be removed (component-safe solvent?) to do
> repairs.

A few things to keep in mind with Coatings:

A very common misconception is that Conformal Coating is a Hermetic Seal.

As Conformal Coating is not a hermetic seal, what real happens is the
impurities in the water are kept away from the circuit, but the water
itself reaches the traces over time. Since the water is now fairly
devoid of contaminates the water acts more like a dielectric
insulator. You never notice it in a low impedance digital circuit, but
unless debugging is an obsession don't let it get near a RF tuning
circuit or a high impedance Wireless Sensor Network circuit.

> BTW: I am planning on coating the DB-25, headers, etc. (i.e.: connecting pins) with
> a non-conducting grease, etc. to protect them from moisture in the field.

Coatings, don't know about grease, will migrate up pins. Grease
doesn't strike me as a good thing here, but can't really express why.

Different compounds can interact.  Recently had a problem where the
volume of a device was traced to the interaction of two compounds used
to pop a transformer.  Either compound alone had no effect on the
volume.

Account for out-gassing.

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