In article , "Arny Krueger" wrote:
"Richard Crowley" wrote in message

"GregS" wrote ...
I have seen the white stuff dry out plenty of times. Its
sure easy to spot and feel. If you can't smear it then
it must be removed. If its still good, I would just even
out the stuff and
reapply components.

I agree in theory. But in practice, thermal grease is so
cheap compared to what it prevents that it is foolish
economy IMHO.

Agreed.

If there is some small particle in the thermal compound, it
would separate the component from the heatsink and could
dramatically decrease cooling.

The best plan is to carefully clean both surfaces and use
new, clean compound.

I was building amps from STK modules. I studied the mating surfaces.
Ideally metal to metal contact is best, even the anodized surfaces
should be milled down. So I was taking the STK module and
sanding it down flat. It really wasn't very flat. I had to start out
with a flat surface for the sandpaper! After much work, I got it
to the point I felt was OK. Even a flat etched surface is worse than a mirrored
flat surface. Very very little grease is needed if everything is smooth and flat.

greg