Potting compound: Thermal conductivity vs cost?

[treez]

Hello,

We wish to pot our LED driver PCB so as to protect it from rain and moisture during outdor use.

We would also like the potting compound to have a low thermal resistance.

-How much more expensive are the types of potting compound that provide low thermal resistance?

 

[tpetar]

That PCB is exposed to sun UV ?


You can use some urethane coating spray.

 

[treez]

Its exposed to rain.
We'd also like it if the potting compound woudl have a low low thermal resistance..............do all electronics potting compounds have a low thermal resistance?

 

[FvM]

do all electronics potting compounds have a low thermal resistance?

Of course they don't. Manufacturer datasheets tell about details. As addressed in the question title, dedicated thermally conductive compounds can be expected to be more costly.

You'll can at least distinguish these categories
- unfilled expoxy, PU or silicone resin. Low thermal conductance arround 0.2 - 0.25 W/mK
- standard filled compounds around 0.5 W/mK
- filled expoxy, PU or silicone resins with enhanced thermal conductivity 0.8 - 1.3 W/mK
- filled expoxy resin with very high thermal conductivity > 1.5 W/mK

Generally high thermally conductive compounds have large solid (filler) content and higher viscosity in uncured state. Some have a paste-like consitency and aren't flowable.