How to apply thermal paste to a CPU

How to apply thermal paste to a CPU

Applying thermal paste is a crucial part of the PC building process. The paste is applied on top of the Integrated Heat Spreader (IHS) of the CPU to make sure there are no air gaps between that and the metal base of the CPU cooler. The air gaps are formed due to the microscopic imperfections on the surface of the IHS and the cooler base. The thermal paste fills those gaps to allow a more efficient transfer of heat. In layman’s terms, thermal paste helps your CPU stay cool at all times.

There are a few different ways of laying down the paste on a CPU. Newcomers in the world of PC building may find it overwhelming, especially because of some horrifying stories that come out as a result of poor application methods. Well, if you are looking for a reliable thermal paste application guide to avoid making a rookie mistake, then you have come to the right place.

Things to keep in mind

Before we begin, it’s important to make sure the surface of both your cooler and CPU are clean. Your components will already be squeaky clean if you’re building a new PC, but they might need some work if you’re replacing the paste or installing a new CPU/cooler. You will then have to carefully remove the old thermal paste from the respective surfaces. We recommend using either a microfiber cloth, cotton swabs, or a paper towel with isopropyl alcohol (at least 91%) for this.

old thermal paste residue on a CPU

Once you’re done cleaning the surface, it’s time to make sure your CPU is locked in place and you’re ready to install the CPU cooler. The thermal paste application is essentially the last step in your cooler installation process that comes before mounting your heatsink or waterblock. If you apply the paste, place your cooler, and then realize you forgot the backplate, your only option is to wipe it down and start again.

How to apply thermal paste

As we mentioned earlier, there are a few different ways to apply the paste on the IHS of the CPU. Don’t get confused if one person asks you to apply just one dot and the other one asks you to go for a line of paste. This largely depends on a few things like the size of the CPU die, the quality of paste being applied, etc. Just make sure you get full coverage and the paste is spread evenly on the surface.

You’ve done a good job if :

  • There’s enough paste to cover the CPU die.
  • The paste is not spilling out.
  • You haven’t created a thick layer that reduces the efficiency due to the metal surfaces being too far apart.

Which application method to use

You may have seen people using what’s popularly known as the ‘Dot Method’. It’s a simple method that involves squeezing a small amount of paste — the size of, say, a small grain of rice — onto the center of the CPU. Some people prefer making a dot the size of a transistor on the board. While this method will do the trick for most consumer-grade CPUs, we’re going to try a different method in this guide.

Make a simple line

a line of thermal paste applied on an AMD Ryzen 5 3600 CPU

This method is fairly self-explanatory, isn’t it? Apply a line of paste directly onto the center of the IHS. Avoid manually spreading the paste and let the cooler pressure do the work as you secure it in place. Any good quality thermal paste with a good consistency will settle evenly on the CPU. You can also make a ‘%’ pattern by applying a line directly down the center and making two small dots on either side.

Less is more

Less is more when it comes to applying thermal paste. There’s no need to dump an absurd amount of paste on the CPU thinking it will magically reduce your CPU temperatures. We’re merely trying to fill the surface imperfections on the IHS and the cooler with the paste, remember? If you are doing this for the first time, then now would be a good time to remove the cooler again to see if your method provides an even spread.

Feel free to experiment as long as you keep the amount of thermal paste in check. Everyone has their own way of applying the paste to get the desired results. You can also go with more small dots towards the center if you think what you have already applied isn’t spreading evenly after placing the cooler.

Run stability checks

Congratulations! If you made it this far into the guide and followed each and every step, then you have now successfully applied thermals paste to the CPU. But did it do the trick? If you were simply replacing either the paste, CPU, or the cooler, then you can directly boot into Windows and run some benchmarks to see how hot your CPU gets. We recommend using monitoring software to get temperature readings over a period of time.

If you’re building a new PC, then you can finish putting the rest of the components together and boot into the BIOS to see the CPU temperature before installing Windows. If it’s not alarmingly high for simply sitting in the BIOS menu, then you’re good to proceed further.

graph showing the temperature of CPU under load overtime

We recommend running Cinebench R23 to see how the CPU handles the load. Benchmarking and performing stress tests like this will usually force your CPU to hit the maximum frequency. This means the temperatures will be fairly high during these runs. As long as the system isn’t crashing just a few seconds into the test, you should be fine. Alternatively, you can also let the CPU sit idle and check the idle temperature to see if that’s looking good.

How often should you replace thermal paste?

Thermal paste is not going to wear out as early as you think. However, replacing thermal paste isn’t going to harm your system, and we recommend visiting it every year just for good measure. If you are suddenly noticing a spike in CPU temperature after say a year of building your PC, then it’s likely due to the dust particles choking the components.

But as a rule of thumb, you should always replace the thermal paste after removing the cooler for any reason. Laptops don’t demand this much attention when it comes to replacing the thermal paste. Just make sure you’re buying a good laptop from a reliable OEM and the quality will speak for itself.

Final Thoughts

Now you have successfully applied the thermal paste to your CPU, there are a few things we want to highlight. The process for applying the paste on the GPU is also the same. In fact, you can use the same thermal paste for your GPU as well, even though some might suggest otherwise. The frequency of replacing the thermal paste for the GPU is also more or less the same. The process for that can be tedious depending on the graphics card.

Thermal paste should have the same priority as other components on your shopping list for building a new PC. It deserves the same treatment and we think people should make an informed decision while buying one, similar to how one would search for peripherals like the best monitors or even the best mechanical keyboards. Most people, however, treat thermal paste as an afterthought and pick up whatever meets the eye. Let’s change that and give more importance to it too.

About author

Karthik Iyer
Karthik Iyer

Karthik covers PC hardware for XDA Computing. When not at work, you will find him yelling at his monitors while playing video games.