Bob,

Most conformal coatings can and will pass moisture through to the assembly
in varying degrees, Thus, if there are any contaminants on the assembly
prior to coating that can activate with the addition of moisture the coating
will only slow down the effect. Also, if the environment in which your
module will be placed is humid for a significant portion of the time, it
will not have the opportunity to dry out, and its performance may be affected.

Blair Hogg 

On Wed, 4 Mar 2009 10:50:38 -0500, Robert Kondner
<[log in to unmask]> wrote:

>Hi,
>
>  I have been playing with some conformal coating material and I have a
>couple of general questions.
>
>1.	Coatings get VERY thin around sharp corners. Using a number of coats
>seems like the only way to build up any serious thickness.
>
>2.	Potting seems like another name for "Very Thick Conformal Coating".
>
> I am looking as an application where a sensitive electronic module will be
>placed in a wet humid environment. It is a sensor going into the cooling
>tower of a HVAC system.
>
>  After reading about conformal coating and playing with some sprays and
>brush on material I think thick potting is the only option to keep moisture
>out of circuits. We need at least 20 Meg ohm between circuits spaced 10 mils
>on FR4 material.
>
> Can anyone verify I am on the correct track and can they point me towards
>selecting the proper materials and process?
>
>Thanks,
>
>Bob Kondner

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