3 ms·

Any readers understand how the pump out effect works? In my imagination, it seems like the less paste you have between whatever is emitting heat, and the heat

Any readers understand how the pump out effect works? In my imagination, it seems like the less paste you have between whatever is emitting heat, and the heat sink, the better- so long as there aren't air gaps. I see there are many forum posts where people show that it does not, but it feels like the closer proximity of the heat sink to the hot object should _improve_ conduction!

cameronperot 6y ago
In theory, yes, you would want just enough thermal paste to fill any gaps between the heatsink and die as the thermal conductivity of the heatsink (e.g. copper) is much higher than that of the thermal paste. Unfortunately, I haven't been able to find much on the internet beyond forum posts and anecdotal evidence regarding the pump-out effect. It would be interesting to see a more scientific study of this.
sp332 6y ago
If the heatsink expands a bit and pushes the paste out, then when it cools and contracts it will pull away and leave a gap.