you really don't need much.. just put a little blob there and then with a credit card (or something like that) smooth it out so it's a uniform thickness. You don't want to make it too think, because then it will spill over to the sides and that's no good. All you need it to do is fill in the tiny little grooves in the bottom of the H-Sink.
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Yeah, that was me on the .5mm. That's a 'uniform' layer, .5mm in thickness. I usually just put a blob of it on the cpu, then spread it around with a 1-sided razor blade. Basically, just drag it back an forth till it's consistantly thick is the trick. It's probably a little more than what I actually use, but that was a close estimate. Don't be afraid to experiment with the arctic silver, but you might put a superficial coat of Silicone around your cpu (but not on it). If you see a noticable difference, give it a write up......
as thin as you can possibly get it. all it is designed to do is fill the microscopic gaps between the core and the heatsink, and, well, you can imagine how small those are. if you put too much it will actually <i>insulate</i> the cpu and do the opposite job it was designed for.
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Exactly right, Grizely1. The best thermal conduction you will get is direct contact between the heatsink and CPU. Of course, there will always be tiny little gaps in there. The world is an imperfect place. These gaps would normally have air in them. Air is a poor conductor. A thermal gel, i.e. Arctic Silver 2, is a better conductor. So, ideally, all the gaps would be filled with the gel, but, you wouldn't want so much gel that separation of the HS and CPU occurs. Your main objective is to keep air bubbles out of there and not have it gooing all over the ceramic part. It's really that simple.
For people that have way too much time on their hands, "lapping" the HS can get you a little(repeat: little) better heat transfer.