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06.02.2020

All about thermal grease

Thermal grease is one of the PC components that usually run under most people's radar. Which doesn't mean that it's not important - it's actually quite the opposite! Let us show you why you should never forget what it does and how to use it properly.

A quick look at the surface of a CPU will show you that it’s perfectly smooth, just as is the base plate of a CPU cooler. But taking a closer look through a powerful microscope shows a cratered landscape - which is inevitable due to the mechanical production of these components. Simply pushing CPU and cooler onto each other leads to tiny air pockets on the surfaces – and as air is notoriously bad at conducting heat, these amassed air-filled pockets diminish the thermal transfer from the CPU to the cooler dramatically, which has a palpably negative effect on the temperatures, the performance and the life span of the CPU.

Here’s where the thermal grease comes into play: Its function is to even out these bumps and craters. Due to the compacting pressure between CPU and cooler the grease spreads out evenly along the surfaces and creates a smooth film which ensures an optimal heat transfer. The grease is usually a compound, consisting of silicone oil and zinc oxide, although you can increase its heat conductivity by adding aluminium, silver, copper or even diamond elements – which increases the quality of the grease but of course also makes it more expensive. Alternatively there’s liquid metal instead of thermal grease which has an even higher heat conductivity – but is also even pricier, more complicated in its application and can’t be used on aluminium surfaces, and is therefore recommended for experienced users only.

Applying thermal grease for the first time usually leads to the same questions: How much do I have to use? And how to apply it correctly? The easiest answer is: Take the syringe it comes in, squeeze a ball about the size of a pea onto the middle of the CPU and install the cooler on top of it. The pressure applied by the evenly tightened screws lets the grease spread out smoothly in a circle between the two – which doesn’t cover the full surface of the CPU but is more than enough for regular PC use. If you want to make absolutely sure that the whole CPU is covered it’s recommended to draw two thin lines across its surface, forming an “X” – that way you’ll cover up almost everything. This method usually leads to a bit of grease oozing out, which is nothing to worry about – CPU and main board are safe albeit slightly messy. The most sure-fire way to apply thermal grease correctly is to use method #1, followed by using a small plastic spatula to spread it out manually across the surface of the CPU.

Yes, you can use too much thermal grease – when you do, you usually get to see it immediately as it oozes out from between CPU and cooler as you tighten the screws. That’s not a problem with regular grease – just take a clean, antistatic cloth or paper towel and wipe it off. Using liquid metal is a horse of a different color – in this case the CPU has to be cleaned thoroughly! If everything works as smoothly and cool as intended you don’t have to renew the grease for years – but if you switch the CPU or its cooler you also need to apply new thermal grease. Some CPU coolers, like our Pure Rock series, come already pre-greased on their base plate – in this case you can just use it out of the box, without having to add anything. One thing you should never forget, and we really do mean NEVER, is to remove the plastic sticker on the base plate of non-greased CPU coolers before installing it! If you forget to do so the heat transfer from CPU to cooler will be almost non-existent, leading to a very hot and therefore very endangered CPU!

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