Jesse Lackey wrote:
> Hello all, I have a client who wants to pot the board I'm making to make
> it as indestructible as possible.
> 
> I haven't done this before, and wonder a few things.
> Maybe someone would like to offer advice?

Some issues to think about...

1. Thermal conductivity: how readily will heat get out?

2. Mechanical stresses: if the potting compound has a significant 
thermal expansion coefficient, stresses can tear parts off the board. 
This can be either during curing of the compound or after it has cured 
if it is subjected to heat/cold or both.

3. Dielectric of the compound: not an issue with low impedance parts 
usually but something to test for.  Run tests before and after potting 
to see if frequency points shift or hi-z circuits operate differently.

4. Repair: usually not possible.

These issues can only be resolved by you knowing your circuit 
characteristics and running compatibility tests.  In the case of 
mechanical stress, sensitive parts may be protected by first coating 
lightly with something like RTV silicone and then coating with the final 
hard coat compound.

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