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Applying Thermal Paste, Part One

Thermal Paste Comparison, Part One: Applying Grease And More
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A Philosophical Debate: The Application Method

It’s tough to pick a technique for applying paste. Any method only works well if paste quantity and viscosity is absolutely correct for the particular application. In light of the hot spot discussion, however, we believe that smearing paste on the whole CPU is quite pointless and a thing of the past. Instead, we want to focus on the particularities of the CPU, its heat spreader, the heat sink, and the mounting method (in particular the mounting pressure).

Brushes and Low-Viscosity Pastes

Liquid pastes like the Revoltec Thermal Grease Nano can be applied with a brush, and are consequently the easiest to use. However, low viscosity comes at the price of a high silicone content, which impacts thermal conductivity. These pastes typically fall to the bottom of our performance charts. When you try to apply semi-liquid pastes by brush, typically you wind up with too much, and that isn’t optimal, either.

Drop, Sausage, or Wall Painting?

In my opinion, spreading paste on the entire CPU is too tedious and runs the risk of applying too much material, or even causing air pockets. Furthermore, some pastes simply do not want to be smoothed. The more you try to even the surface out, the more it tears open.

Trying to spread a high-viscosity paste with a credit card is a fool’s errand. You'll waste a lot of time and won’t achieve a thin, smooth layer. Yes, you can try to put a latex glove on your hand and use your index finger. But even with this method, the risk of applying too much paste is significant, especially if you have no practice. The higher the viscosity, the less successful you can anticipate being trying to "paint the wall".

A Strip of Paste

When you imagine CPU die under the heat spreader, it may seem smart to put a strip of paste over that area. But don’t apply too much. Otherwise, the paste will ooze out on all sides. If your paste is electrically conductive, you can almost be assured of hardware damage.

 

When you apply the paste strip frugally, the result is better. Don’t worry too much about bare spots. The edges of the heat spreader don’t contribute much to thermal transfer anyway. If your cooler sports a back plate and applies lots of mounting pressure, the paste will spread further. As a rule of thumb, the lower the viscosity of the paste and the higher the heat sink's mounting pressure, the more your compound of choice will spread.

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