X-bit labs

Battle of the Titans: Super Coolers from Scythe, Thermaltake and Zalman Face to Face (page 5)

Category: Coolers

by Doors4ever

[ 10/21/2005 | 11:44 AM ]

Let’s recall why too much thermal paste is bad and why thermal paste is at all necessary. We’ve got a well-polished base of the cooler and a rather flat heat-spreading cap of the CPU – so why do we need the additional resistance of thermal paste? Or do you doubt that thermal paste is a hindrance to heat transfer? Think that no one produces heatsinks out of thermal paste – all heatsinks are made from metals and alloys!

Heat transfer is really worsened by thermal paste since it is a worse heat conductor than metal. In this case, however, we have to choose the lesser of two evils – air is such a poor heat conductor that it can even be regarded as a heat insulator. And since it is virtually impossible to make the surfaces absolutely flat, there is a thin layer of air between the cooler’s base and the processor. This layer of air inhibits heat transfer. Replacing it with a layer of thermal paste improves the heat transfer but we must not replace metal with thermal paste! The thicker the layer of thermal paste between the CPU and the cooler is, the worse cooling you have. It usually helps to press the cooler down tightly so that the excess thermal paste went out along the edges, but what if there’s the same thick layer of paste all along the contact zone, including the edges? As a result, two completely different coolers, a copper and an aluminum-copper one, for example, may show the same performance if their capabilities are limited by a thick layer of thermal paste rather than by the properties of the metals employed in them.

I used Zalman’s thermal paste for my tests. I can’t tell you anything about its name, composition or marking, except that such thermal paste in included with noiseless system cases like Zalman TNN500AF (for details see our review called Zalman TNN500AF Case Review or +1 Kilogram of Silence ).

The die size of modern processors is rather large, yet it is considerably smaller than the size of the heat-spreading cap, so you should pay special attention to the center and not bother much about the edges. So I put a thin layer of paste on the CPU.

You don’t have to smooth out the paste since the excess of it will be pressed out and distributed evenly on the entire contact area, if you have not put too much of it.

As you see, I’ve got rather much paste left on the sides, but the result is overall satisfactory since the metal shows through the thin layer of paste.