I'm sorry, Jerry, any coating that easily permits the passage of
moisture cannot have, by definition, good dielectric properties. The
dielectric constant will increase dramatically, as will the loss factor,
if there is moisture absorbed into the coating. Many RTVs even depend on
their moisture absorption to polymerise! If you want the best dielectric
qualities, some of the acrylics are unbeatable.

Brian

Jerry Mosur wrote:
>
> Actually we use RTV for its good dielectric properties, and not for its
> moisture blocking capabiliteis.
> The root of this problem lies in insuficient space for a given electrical
> characteristics of a circuit. If one can not open up spacing, one must
> resort to other techniques like routing the board in-between pads and
> encapsulating.
> As far as the conventional coatings go, we have found that in order to
> prevent delamination we have to plasma etch boards as well. With rework
> being easier with RTVs, we decided to use them instead.
>
> Graham, I will e-mail you for more info on solventless or water based
> coatins. How easy is the rework?
>
> Jerry Mosur
>
> Spellman High Voltage
>
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--
Brian Ellis
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