The right way of applying thermal paste on CPU surface

The right way of applying thermal paste on CPU surface

Whenever you install a heatsink on a CPU or a video card, you always have to apply thermal paste. No man-made surface is perfectly smooth, and the tiny gaps between a CPU and a heatsink are usually large enough to have a negative impact on cooling. February 5 was World Nutella Day (my lack of knowledge of these things is probably why I don’t get invited to the really good parties). To celebrate this event, Cooler Master decided to illustrate the value of the spreadable hazelnut delight by using it as thermal paste. A good contact between CPU and heatsink is crucial yet it is something more people get wrong than anything else. What is CPU thermal paste used for and what is it made of?

How to Properly fix CPU generated heat

The thermal paste itself is not as thermally conductive as metal, however, so it is important that not too much is used. Back in 2002, Dan, of Dan’s Data, compared a variety of thermal goops against Vegemite and toothpaste. One of the most important factors when building a PC is managing heat output. Using a good thermal compound for the CPU cooling system is inevitable and it’s also an intuitive knowledge for every savvy. If you have ever removed a CPU heat sink, you would notice a gray or white paste on the top of the CPU and at the bottom of the heat sink (see image below).This paste-like or grease-like substance is what we call CPU thermal compound.

  • It is very crucial to the performance of the heatsink.
  • To combat this, thermal paste is used to fill in these air gaps.
  • This experiment isn’t without some history.
  • Read on for a crash-course from the Labs.
  • Learn about the different types of CPU thermal compounds with our CPU thermal grease guide.
  • You could get a very high-end heatsink, and without thermal paste, it will fail to work in the way it was designed too.

Thermal paste internal materials

Thermal paste is a very high heat conductive paste that is used between two objects (usually a heatsink and a CPU/GPU) to get better heat conduction. If that happens, the thermal paste will behave more like an insulator than a means of improving thermal performance. The results, hilariously, favored the toothpaste (Vegemite, otherwise known as Satan’s Hellfood, tied with the other thermal compounds).The video below doesn’t give much context for Nutella’s relative performance but implies that the material is more than capable of keeping a chip nice and cool. A modern CPU packs huge numbers of transistors into increasingly tiny pieces of silicon and when power is applied this has the potential to generate massive amounts of heat that need to go somewhere. It goes by a few other names… including thermal paste, thermal grease or thermal interface material TIM.

Thermal paste features

Carbon-Based is not too preferred

It fills in all those microscopic imperfections on the heatsink and CPU/GPU that can trap air in them and cause a loss in the heatsink’s performance. The way heatsink thermal pastes work is not so difficult to grasp. The best technique to apply thermal paste is something that is often debated on the internet, so in this article we want to do our own testing to find the best method for applying thermal paste. So, should you throw out the Arctic Silver in favor of hazelnut? This is where heatsinks come in. In the image below, we can see the gray thermal paste covering the copper bottom of a CPU heat sink fan:What is CPU thermal grease used for?

Using the high performance thermal paste instead

Air is a very poor conductor of heat. First we will see how each technique spreads the thermal paste across the CPU, and then we will test each technique in a full computer system to see which has the best thermal performance. The first thing to understand about thermal paste is that, from a physics perspective, it’s inherently a kludge. They are designed to take the heat generated in that tiny piece of silicon and take it away, keeping the processor from overheating and the silicon itself from being damaged. It is applied between the contact surfaces of the CPU and heat sink (or water block if you have water cooling) to improve heat dissipation and lower the CPU temperature.

using the right thermal compound for your heatsink

Thermal Interface Materials (TIM) can be up to a 100 times greater conductor of heat than air. To get a clear view of how the thermal past spreads for each technique, and to see if the spread results in any air bubbles, we fabricated a 3/8″ thick acrylic plate to act as an interim heatsink. By the time heat from the CPU core gets to the top of the lid, it’s already passed through the entire chip stack (not counting secondary heat paths), through the solder or thermal paste between the CPU die and the CPU lid, and then passed through the lid material itself. This heat transfer is important, and most of the time PC and laptop overheating can be traced back to poor heatsink efficiency. Applying thermal compound is a must because the contact surfaces are not perfectly even and smooth – Even brand new CPUs and heat sinks have surface imperfections and microscopic scratches that traps pockets of air.

History of thermal paste usage

However, thermal paste is not near as good of a conductor as copper. This acrylic plate has portions removed to clear the capacitors around the CPU, and the mounting is the exact same size and spacing as the Corsair H60 CPU Cooler. In other words, the heat that makes it to the top of the lid is a fraction of the total heat that can be dissipated. There have been thermal compound used for CPU cooling system but they proved inefficiency due to several reasons that we will not be addressing here. You may though want to find our more about the best thermal paste by visiting this page. One of the major causes of this is the interface between the heatsink and the processor. Since air is one of the worst thermal conductors on Earth, it will impede the heat sink’s ability to lower the CPU temperature.

Thus, too much thermal paste will hinder a heatsink’s ability to cool properly. This way, we can ensure that our results match exactly what you would see when using a real heatsink. Once it hits the lid, that heat needs to radiate from the lid to the actual heatsink and fan. Most modern processor packaging includes a heatspreader. Without the humble thermal paste, CPUs will run about 20 to 30°C hotter when operating under load.

The need of heat dissipation

These pastes have lots of little metal particles in the grease that have a high thermal conductivity. We let the system idle for at least 45 minutes before recording the idle temperatures, and to put the system under 100% load we ran a combination of both Prime95 and Furmark. Nutella, likely has a significant amount of oil in it, which is why it conveys heat particularly well, but as it dries, that oil is going to rapidly evaporate. Heatspreaders first appeared on Intel’s Pentium 4 (and a couple of later generation Pentium3 CPUs) and were introduced by AMD with the Athlon 64. We must stress that CPU thermal paste is used for filling air pockets and NOT to create a separate layer between the two surfaces.

  • Metal-based TIM’s are the most popular as they have the best performance out of the three.
  • CPU temperatures were recorded with a combination of CoreTemp and Speedfan with the temperature reported as the average of the four cores.
  • Air is a miserable conductor of heat, which is why we put various forms of goop in between the CPU surface and the heatsink.
  • This is a metal cap that sits over the silicon itself and helps to move the generated heat to a larger area.
  • Thermal paste fills up the microscopic air pockets between the contact surfaces to allow for better heat dissipation.

One disadvantage of this type of paste is that it is also electrically conductive as well, which can cause a problem. Dynamic fan ramping was disabled from the motherboard since we are primarily concerned about the variances in temperature between each application technique and do not want the fan throttling to affect our results. What’s left will be a sort-of Nutella-dust that transmits heat between CPU and heatsink about as well as a wool blanket. Previous to this, heatsinks needed to be mounted directly onto the silicon die of the processor. This will matter when we’re showing you how to apply CPU thermal grease in the next page.

applying a thermal paste properly on a CPU surface

Choose the right heat sink

Ceramic-based TIM’s are also a popular solution that doesn’t perform quite as well as metal-based pastes, but the difference is minimal (1-3C). These consist of some form of thermally conductive material with lots of little ceramic particles. We are using the built in video controller to help put just a little extra load on the CPU which should accentuate any temperature variances. In short, don’t try this at home. However, as die size continued to shrink so did the silicon size, which caused two problems. There are three main types of CPU thermal compounds: Metal based, Ceramic based, Carbon based – See more at: Metal-based thermal grease (see image above) are gray in color and contain solid metal particles such as aluminum or silver.

The advantage of ceramic-based pastes is that they do not conduct electricity. An open-air test platform was used in place of a chassis since it should allow for more consistent results. But if you have a CPU you don’t care much about, and a list of handy foods you want to experiment with as thermal transfer materials, we promise to publish the results of the first person who conducts a credible test to discover whether ham or turkey makes a better TIM (thermal interface material). Photos are a bonus. The first was that destroying a CPU while trying to mount a heatsink became easier and easier (smaller dies like ‘Barton’ core Athlons were notorious for this) and the second was that it became incredibly thermally inefficient to try to transfer heat from such a small area. Their high thermal conductivities makes them the best CPU thermal compound for lowering temperatures.

The CPU level of temperature during workload

Silicon-based TIM’s are usually what thermal pads that come on stock heatsinks are made of. The techniques we are testing come from the common recommended techniques found online as well as a few we devised ourselves. Testings have shown that this method minimizes the possibility of air bubbles and voids in the thermal interface between the heat spreader and the heatsink. An integrated heatspreader allows the contact area between the processor and the base of a heatsink to be larger, which increases the potential amount of heat transfer. On the average, CPUs with metal-based thermal grease run about 4 to 6°C cooler than those with generic ceramic-based compounds.

These work well, but nowhere near to what other pastes will. We made sure to apply the paste evenly, but did not make it 100% perfect. Since the vast majority of the heat from the core travels directly through the heat spreader, it is more important to have a good interface directly above the actual CPU core than it is to have the heat spreader covered with compound from corner to corner. We have made a list of the best thermal pastes available on the market as of today. It also completely removes the ability to destroy a silicon die while installing a heatsink, making life easier for all. However, this type of CPU thermal grease also has its drawbacks.

Usually they come with cooling kits. We did this on purpose so that our results would be consistent with what you would see in the real world. The photo below shows how the pressure from the heatsink base spreads the compound and also shows a P4 with the heat spreader removed to show the location of the actual CPU core that is the source of the heat. You want to ensure that your heatsink and CPU have as close a contact as possible. One, they conduct electricity.

  • When choosing a paste for your heatsink, you have two main types that are usually considered; metal-based or ceramic-based.
  • Each of these techniques (with the possible exception of the happy face) have some merit to them.
  • While the Cpu core on the Athlon 64 is slightly larger than the P4 core is still much smaller than the metal CPU Cap that covers it.
  • Heatsink brackets are designed to put downwards pressure on the heatsink in order to achieve this, but the mating still isn’t perfect.
  • If you spill them onto the CPU pins or motherboard components by accident, it may lead to a short-circuit and cause damage to your hardware.


In most cases people use the metal-based, simply because it performs better as stated before. The single dot or line should have few air bubbles, but likely will not cover the entire CPU. The reason for this is that, while the base of a heatsink and the top of a heatspreader look to be incredibly smooth to the naked eye, this doesn’t translate at a microscopic level. Two, metal-based thermal compounds tend to be more expensive (especially those with silver content).Widely regarded as the gold standard for thermal compounds, Arctic Silver 5 is a consistent top performer in CPU thermal paste reviews and a longtime best seller on Amazon. But nowadays, especially with GPUs, there are a lot of transistors/electrical components that are very close to the die.

At the same time, the spiral pattern will likely cover the entire CPU, but may have some air bubbles. Microscopic surface imperfections lead to air gaps between the two surfaces. Other plus points: It’s easy to apply (not too viscous) and won’t damage your electronics (Arctic has stated that it isn’t electrically conductive). Downside: Long cure time (takes up to 200 hours to achieve optimal heat transfer).