Thermal Transfer Compound Comparison

An Anonymous Coward writes:

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Most CPUs don't produce enough heat that the stuff you put between the chip package and the heat sink matters very much, as long as the computer case has decent ventilation and the ambient temperature isn't sauna-like. There just has to be something between CPU and heat sink.

The reason why there has to be something there is that the two mating surfaces of processor and sink aren't flat. They may look flat. They may have a mirror polish. But, on the microscopic scale, they look like a scale model of the Andes. And the mountains on one item do not match the valleys on the other.

Without thermal transfer compound, everywhere heat sink metal doesn't mate with CPU package material is a teeny-tiny air gap. Air is a good thermal insulator. As long as your heat sink looks flat when you lay a ruler on it then there'll be a decent amount of actual contact, of course, but the amount of heat that'll actually make it around the air gaps may be surprisingly small.

Hence, thermal compound. It's grease with lots of minuscule thermally conductive particles mixed into it, basically. It doesn't conduct heat as well as direct contact, but it's a heck of a lot better than air gaps.

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