Hi John:
Clearance is defined as the shortest distance
between conductors in air.
Creepage is not an insulator, but the interface
between air and solid insulation. Creepage is
defined as the shortest distance between
conductors across the surface of the interposed
solid insulation. (Physically, creepage cannot be
shorter than clearance.)
Encapsulation and conformal coatings supposedly
displace the air with a solid insulation; since
there is no air, there is no clearance or creepage
between conductors. (Some authorities and
standards will disagree with this statement.)
There is only distance through solid insulation.
The issue is whether the encapsulation and
conformal coatings truly displace the air. And,
if the encapsulation and conformal coating
material is impervious to air. And, the
"stick-to-it-ness" of the materials to the
conductors and substrate. And maybe some other
parameters.
If your product complies with the required
clearance and creepage without the encapsulation
or conformal coating, then you don't have to
address the encapsulation and conformal coating
requirements.
I know that I haven't answered your questions.
But, maybe, I have given you a perspective.
Good luck,
Rich
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