On Wednesday, April 11, 2018 at 10:38:19 PM UTC-7, wrote:
When mounting power transistors and chips to a heat sink they often use
heat shrink grease

That greasy stuff (also available in waxy and rubbery forms) is thermal transfer compound;
like a grease, but it is NOT grease.

It has to stay put in small crevices in order to work.

If you use a 'grease' formula instead of a 'thermal compound' formula, it might only
work for a few hours, then flow away.

If you try to add particles with high thermal conductivity to grease, you might
just be making spacers to keep the metal parts at a distance (it's distance times
resistance-to-heat-trasfer that you want to minimize). Don't fall for the 'better
conductivity' argument, it's conductivity DIVIDED BY GAP DISTANCE you care about.