What is Thermal Paste & How Does it Keep the Processor Cool?



Category: CPU / APU

what is thermal paste

When building a PC, some people tend to be excited about the graphics card, RAM and new processor rather than the tube of thermal paste they bought. Besides, thermal paste is an often neglected product in most new builders' computer installations, and this might be because of a lack of experience or the fact that coolers already have thermal paste pre-applied. Though pre-applied thermal paste works, it's often quite old and has been sitting in a box for a long period. It's usually a good idea to buy and apply thermal paste when installing your CPU for better temperatures at stock cooler speeds. So, what is a thermal paste, and how does it maintain the processor cool?

What Are the Main Types of Thermal Paste?

1. Ceramic thermal paste

Made from ceramic. This paste has thermal conductivity but is electrically non-conductive. As a result, ceramic pastes are the easiest and most secure to apply to your processors. Also, they are the most popular, and they're usually the most economical.

2. Liquid metal thermal paste

This paste is both thermally and electrically conductive. As a result, liquid metal thermal pastes can be dangerous if not applied well. Though liquid metal thermal grease is the most effective of the thermal pastes available, if you spill even a little bit on your Pc's components, you could cause damage. Also, it is more expensive.

3. Carbon-based thermal paste

Carbon-based thermal pastes are thermally conductive but not electrically conductive, like ceramic thermal pastes. As a result, these pastes may also have a longer shelf life than other forms of thermal paste.

4. Thermal pads 

Usually come in various materials, the most popular of which are silicone and graphite. These pads are solid at ambient temperature, but when the CPU temperature rises, they soften and melt into the air pockets between the heatsink and the CPU. However, these pads can't compete with thermal paste in cooling performance.

What Is Thermal Paste?

Thermal paste (also known as thermal compound or thermal grease) is a substance commonly used to connect the CPU and heat sink. It usually functions as a heat transfer agent on the heat spreader or integrated heat spreader (IHS) of a CPU. Its primary constituent is zinc oxide. Small tubes of thermal paste sometimes come accompanied by small shovel-like equipment called an applicator.

Your processor usually creates a significant amount of heat. It has so much heat that you could cook an egg on it. When assembling a PC, you'll need a tube of thermal paste to ensure that everything runs smoothly. Some CPU heat sinks feature thermal paste already applied, so you can plug it in and go. Conversely, some performance enthusiasts swear by and manually apply their preferred brand of thermal paste.

Thermal paste's primary role is to help transfer heat from the CPU and into the heat sink. Subsequently, the heat is dissipated away from the hardware via the heat sink. This keeps the CPU cool, particularly while working hard to complete tasks.

Why Would You Need Thermal Paste?

Though the IHS of the CPU and the metal base of the CPU cooler appear smooth to the human eye, these metal plates have microscopic imperfections that might result in poor heat transfer. Since the two surfaces are not completely in touch due to the irregularities, thermal paste fills the air gaps, providing an optimal heat transfer. Therefore, put thermal paste to help your CPU cooler do its job since a cooler CPU means fewer potential performance problems like throttling.

When Do You Need to Use Thermal Paste?

When installing any cooling system, you use thermal transfer material. When most people think about heat paste in the context of PC construction, they're generally thinking of the procedure of installing a CPU cooler. For example, the thermal solution is already built-in when purchasing a graphics card. So, unless you're interested in aftermarket solutions such as custom liquid cooling, you shouldn't have to bother about fitting a cooler onto a GPU. You may select the one you want with a CPU cooler, but you will always have to install it yourself.

Step by Step on How to Apply Thermal Paste

1. Read all instructions before starting.

The reading includes the CPU cooler and the thermal interface material that came with it. Every brand of the CPU cooler and thermal past is a bit different, and understanding your specifics before you begin will make the procedure go more smoothly.

2. Apply thermal paste to the CPU's IHS in the middle.

(If your cooler already has thermal paste applied, you may skip this step). You only need to apply a small amount, around the size of a grain of rice or a pea — apply to the centre of the integrated heat spreader.

3. Install the CPU cooler

Put your cooler's base plate or water block onto the CPU with light, top-down pressure, and maintain that pressure while connecting the cooler to the mounting mechanism. You will need to use enough force to prevent the cooler from moving and uniformly spread the CPU thermal paste; however, avoid applying too much that you bend the motherboard or harm the CPU.

Maintain the cooler's position when attaching it to the motherboard in a diagonal pattern, fastening the screws (if you're using a screw mechanism) such as drawing an "X" with them. To ensure uniform pressure, do not fully fasten the screws until you have attached all of them, then turn each a few times before going on to the next.

4. Double-check your work

Once the CPU cooler's base plate or water block is securely installed, you must double-check your work to ensure everything is in order. There should be no thermal paste overflowing over the CPU's edges or anywhere on the motherboard. If there is, it signifies you applied too much CPU thermal paste and should clean it with alcohol before repeating the process. Congratulations if everything appears clean and the CPU cooler doesn't move when touched. You've done with this crucial step.

What Are the Thermal Paste Properties?

What is a Thermal Paste

When looking for the best thermal pastes, you may be unfamiliar with some properties or unsure how a paste affects thermals. Let us look at what they're;

1. Viscosity

This usually refers to the thickness/thinness of the thermal paste. Those with higher viscosity are thicker and more like paste and will typically cling your heat sink to your processor better. Conversely, those with low viscosity will likely dry out after a few days to set in. It's worth mentioning that if you apply too much low viscosity thermal paste, it might easily leak onto your motherboard.

2. Thermal conductivity

Conductivity is the most crucial measurement to keep an eye on. This unit of measurement indicates how well the thermal paste transfers heat from one location to another. It's expressed in watts per square meter of surface area, abbreviated as W/mK.

3. Specific gravity

Specific gravity is how dense and heavy the thermal paste is. It isn't frequently specified on most thermal pastes and is not usually necessary to consider. That being said, specific gravity is usually measured in g/cm3, or grams per cubic centimetre.

Things to Consider Before Applying the Thermal Paste

1. CPU is clean

Check if the CPU is clean and free of any old thermal paste. If there is, thoroughly remove the old paste off the CPU lid with isopropyl alcohol and a paper towel or a non-shedding microfiber cloth before proceeding.

2. The CPU cooler is ready to install

Ensure the rest of your CPU cooler is ready to go before you start adding the thermal paste. Consult the instructions guide, double-check that every step has been performed up to mounting the CPU cooler, and ensure you have all the essential equipment on hand.

3. Use the right amount of thermal paste.

Use the right amount of thermal paste, which should be a thin layer roughly the size of a grain of rice or a pea. Using inadequate amounts may not cover the necessary surface area to be effective. Conversely, too much diminishes the paste's efficiency because the metal surfaces are too far apart. It also runs the danger of pouring out onto the motherboard during the installation process.

4. Avoid reusing the thermal gel.

Reusing paste might also result in the formation of air bubbles. If an issue arises during the installation process, you are forced to remove the CPU cooler, thoroughly clear up all paste, and then try again with a new application. However, if you must reuse an application while waiting for replacement thermal paste — do so, but remember that this is a temporary solution and that we suggest a proper reapplication before long-term usage of your CPU cooler.

5. Avoid spreading the paste to the CPU yourself.

It may be tempting to apply the thermal paste on the CPU by hand. However, we recommend allowing the pressure from the installed water block or base plate does it for you. A wrong manual application might result in air bubbles in the paste, reducing heat conductivity.

Factors to Consider Before Buying the Best Thermal Paste

1. Thermal conductivity

Thermal paste's primary goal is to reduce air pockets between the semiconductor chip's CPU heat spreader and the thermally conductive material that moves thermal energy away from the heat source. Therefore ensure the paste is thermal paste conductive and has a high thermal conductivity. Generally, the higher the number, the better the thermal paste should be in conducting heat away, though there are always other elements to consider, which might not always be the case.

2. Ambient temperature

The air around your CPU system can significantly impact how cool (or hot) it operates. If you reside in a region with high temperatures, you should consider updating your thermal paste since the air within the system impacts outcomes. Besides, if your other components are hot (for example, your GPU), the ambient temperature might affect your system as much as the outside temperature.

3. Thermal Design Power (TDP)

The TDP of your CPU usually indicates how much power it will consume. You can use this to predict how hot it will become. Those with a higher TDP consume more power, resulting in more heat. Therefore this is something to consider before using the paste as a hotter processor will require a thermal paste that keeps up. You will find this number listed on the processor specs under TDP.

4. Familiarity level

The thermal paste solution you choose may influence your comfort level working on your components. If you're a newbie and are concerned about damaging your components, you should consider using thermal pads instead of paste. Though it isn't as effective as a paste, it is much faster and easier to use, and it won't damage your components.

Whether or not it is electrically conductive is something else to think about, especially if your comfort level is low since certain thermal pastes are produced with ingredients that conduct electricity. There are also liquid metal compounds, and these require care to apply without damaging your components.

5. Cooling solution

Choosing the right cooling solution may have a significant impact on the general performance of your system. Even though you have the best thermal paste available, it won't matter if the rest of your system isn't set up to withstand the amount of heat your CPU creates.