Regarding potting: there are potting materials that are modestly thermally conductive. The one that I've used in the past (at work) contained aluminum oxide particles in the potting. It resulted in a very hard potting, which made it very resistant to damage from impacts and such.
Potting is not easy to use, however. There are a lot of little issues that can cause trouble. For hard potting, the thermal coefficient of expansion is usually different from the circuit board, and this can cause damage to the electronics.
A couple of the potting companies are Emerson & Cuming (
http://www.emersoncuming.com/), Dow Corning, GE, or Loctite (search on "Loctite potting and encapsulating").
One of the Emerson Cuming products is this:
http://www.emersoncuming.com/other/1495k.pdf
For the best heat transfer, there's nothing like a direct metallic path from the LED package to the ambient air. A solid piece of aluminum is the typical solution. Heat sink grease or adhesive is helpful at minimizing the thermal resistance between bodies. To maximize the heat transfer from the heatsink to the ambient air, maximize the surface area of the heatsink without making the aluminum too thin for the heat to easily flow through it.
that's the quick lesson. What are the specifics of what you are trying to do??
cheers,
Steve K.
Have you searched some existing threads? This forum contains an overload of info.
