Reapplying thermal paste when changing motherboards
So I finished setting up my pc last week to find out i need a new motherboard, while we were setting it up we added new thermal paste to the cpu. I have the new motherboard coming tomorrow do I need to re add the thermal paste when switch the motherboards? Or is the thermal paste we add less then a week ago fine?
You should always clean the old TIM from the mating surfaces and apply new whenever the cooler/CPU contact has been disturbed. Not because it is too old, but because you are trying to avoid introducing microscopic air bubbles in the TIM.
Having said that... I have skipped the clean/reapply operation a few times when I was in a hurry and the CPU wasn't being OC'ed. But it is best to always start over and use fresh.
As mentioned, it is always advised to clean it off and reapply the paste. But if you are just trying new/old parts making sure they work, as long as the paste is not dried out, you don't necessarily have to clean it up and reapply.
I've done this myself when I ran out of Arctic Silver and reused the paste that was on the bottom of the cooler. But if you intend to keep it together for long periods, I recommend you clean and reapply, its not really that time consuming unless you are one of them people who takes the time to spread the paste manually.