– Copied from customer email –
When I was checking the measurements of the Ubiswitch board, the specification said “with heatsink.” Which reminded me that I’m pretty sure your datasheet specification of 79W/m-K for the thermal paste is incorrect based on wanting to achieve .675c/w resistance.
I don’t recall exactly what I had issue with, but I think it was something like the number you have printed was based on the planar area of the contact patch and not the cross sectional area. The result is that your suggested TC4-10G could be replaced with a lower conductive, easier to use solution. I don’t do this a whole lot, so I could be wrong, but it should be checked.