I'm in the midst of building a computer (this is my first time).

When I first put the heatsink on the CPU, I was a little off center. Some of the thermal compound came off, so when I re-centered it, it isn't completely evenly distributed.

So how picky are CPUs in terms of how evenly the thermal compound is? Should I take it apart, clean it, and apply a new layer of compound? Or can I just keep an eye on the CPU temperature? I'm not overclocking or anything, if that matters.


Ideally you need a good uniform layer of thermal compound between the CPU and heat sink.

If not too much came away you might be OK.

Get the machine built and then just turn it on to monitor the temperature from the BIOS screen. If it settles down at roughly the correct idle temperature then you're probably OK. If it keeps rising (don't leave it too long) then you'll need to reapply the paste.

  • Where can I find the correct idle temperature for my CPU? It is an Athlon II X2 250. – David Oneill May 3 '10 at 15:35
  • You want to aim for the low to mid 30s, but anything below around 40C is probably fine. It will vary depending on the kind of cooling system and the quality of the heatsink and fan. For the stock sink and fan, 38-39 can be typical. If you have added a good quality after-market sink and fan, you can frequently get an idle in the 29-32 range – BBlake May 3 '10 at 16:19

The whole point of thermal grease is to make sure there is no air between the CPU and the heat sink. That's it, the whole reason. Air is an insulator, and you don't want any insulator between your CPU and your conducting heat sink.

You only need a tiny tiny amount of thermal goo. As long as it's evenly distributed, you're fine.

The symptoms of incorrectly applied thermal grease are pretty obvious: your processor will run slightly hotter if you have too little or too much. So if your fan seems to be running too often or too loud, that's what you're going to need to check.


Over 50% application of the thermal compound should be fine as long as it's distributed all across the CPU.

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