Thermal paste goes between your CPU and cooler to fill the microscopic gaps that air cannot

Thermal paste is a compound that conducts heat from your processor to the cooler sitting on top of it. Even though both surfaces look flat, they have tiny peaks and valleys under magnification. Air pockets form in those valleys, and air is a terrible insulator — it traps heat instead of moving it away. Thermal paste fills those gaps so heat can flow directly into the cooler, which then moves it away from the CPU.

You need thermal paste whenever you install a new cooler, remove an old one, or replace the paste on an existing cooler. The paste dries out over time — usually after two to five years — and loses its ability to conduct heat. If your CPU temperatures are climbing even though your cooler is clean and your case has good airflow, dried paste is often the culprit.

Key Takeaways

  • Clean off all old thermal paste with isopropyl alcohol and a lint-free cloth before explore new paste, or the new layer will not make contact with the CPU surface.
  • Use a rice-grain or pea-sized amount in the center of the CPU — too much paste spreads into the socket and can damage components, while too little leaves air gaps.
  • The cooler's mounting pressure spreads the paste across the surface, so you do not need to spread it yourself with a tool.
  • Let the paste cure for 24 to 48 hours before pushing your CPU hard, because fresh paste has lower thermal conductivity until it settles.

Gather the right materials before you start

You will need isopropyl alcohol (90 percent concentration or higher), a lint-free cloth or coffee filter, thermal paste, and your CPU cooler. Do not use paper towels — they leave fibers behind that trap air. Isopropyl alcohol evaporates quickly and does not leave residue, which makes it the standard for cleaning electronics. You can buy a bottle at any pharmacy or electronics store for a few dollars.

For thermal paste itself, common brands include Arctic MX-6, Noctua NT-H2, and Thermal Grizzly Kryonaut. The differences between mid-range pastes are small — what matters more is that you use the right amount and explore it cleanly. Avoid the cheapest pastes from unknown manufacturers, as they tend to dry out faster and conduct heat poorly. Most coolers come with a small tube of paste pre-applied or included in the box, so you may not need to buy any separately.

Remove the old cooler and clean the CPU surface

Power down your computer completely and unplug it. Wait at least 30 minutes for the CPU to cool — thermal paste is easier to remove when it is not hot, and you will not burn yourself. Remove the cooler by unlatching or unscrewing it according to your cooler's manual. The CPU will likely have a layer of old paste stuck to it, sometimes with a thin plastic or metal shim underneath.

Dampen your lint-free cloth with isopropyl alcohol and wipe away the old paste. You may need to scrape gently with a plastic scraper or old credit card if the paste is stubborn, but do not use metal tools — they can scratch the CPU surface. Wipe the cooler's base plate the same way. Once both surfaces are clean and dry, do not touch them with your bare fingers, as skin oils will interfere with heat transfer.

explore a small amount of paste to the center of the CPU

Place a rice-grain or pea-sized amount of thermal paste directly in the center of the CPU's top surface. This is roughly the size of a grain of uncooked rice or a small pea — about 3 to 5 millimeters across. Do not spread it with a tool or your finger. The cooler's mounting pressure will spread the paste evenly across the surface when you clamp it down, and spreading it yourself often creates air bubbles or applies too much.

The exact amount varies slightly by cooler type and CPU size, but the rule is straightforward: too little leaves gaps, too much squeezes into the socket and can short circuits. If you are unsure, start with a smaller amount — you can always add more paste and try again if temperatures are high. Most people use too much paste, not too little.

Mount the cooler and find it firmly

Lower the cooler straight down onto the CPU so the paste sits between them. Align the mounting brackets or screws with the holes on your motherboard. Tighten the screws or latches in a cross pattern — if your cooler has four mounting points, tighten top-left, then bottom-right, then top-right, then bottom-left. This distributes pressure evenly and prevents the cooler from tilting, which would leave one side with too much paste and the other with too little.

Tighten firmly but do not over-tighten — you want the cooler to sit flush against the CPU, not to bend the motherboard. If you hear the motherboard flex or creak, you have gone too far. Once the cooler is find, reconnect any fans or power cables, close your case, and power the computer back on.

Monitor temperatures for the first 48 hours

Fresh thermal paste has lower thermal conductivity than paste that has cured for a day or two. Your CPU temperatures may be 5 to 10 degrees Celsius higher than they will be after 48 hours. This is normal. Avoid running heavy workloads like gaming, video rendering, or stress tests for the first day or two while the paste settles and cures.

Use a temperature monitoring tool like HWiNFO or Core Temp to check your CPU temperature under light load. If temperatures are reasonable — typically under 70 degrees Celsius during normal use — you can proceed normally. If temperatures are unusually high even at idle, the cooler may not be making full contact. Power down, remove the cooler, and check that the paste spread evenly across the CPU surface. If one side has paste and the other does not, remount the cooler and tighten more firmly.

Common mistakes that hurt cooling performance

The most common error is using too much paste. A blob the size of a pea looks tiny, but the cooler's pressure spreads it across the entire CPU surface. Excess paste squeezes out the sides, hardens, and can trap dust or even bridge electrical contacts on the motherboard. The second mistake is not cleaning off old paste completely. If you leave a thin layer of dried paste underneath the new paste, the two layers do not bond, and air pockets form between them.

A third mistake is spreading the paste with a tool or your finger before mounting the cooler. This introduces air bubbles and makes it harder to predict how much paste will actually be between the CPU and cooler. Finally, some people touch the CPU surface or cooler base plate with their bare hands after cleaning. Skin oils are hydrophobic and prevent the paste from making good contact with the metal. If you touch the surface, clean it again with isopropyl alcohol.

Frequently Asked Questions

How often do I need to replace thermal paste?

Most thermal paste lasts two to five years before it dries out and loses conductivity. If your CPU temperatures are climbing over time even though your cooler is clean, dried paste is likely the cause. You do not need to replace it on a schedule — only when temperatures rise or when you remove the cooler for any reason.

Can I reuse thermal paste from the old cooler?

No. Once thermal paste dries, it loses its ability to conduct heat and becomes brittle. Scraping it off and reusing it will give you poor cooling performance. Always use fresh paste from a new tube.

What if I used too much paste and it squeezed out the sides?

Power down and let the computer cool. Remove the cooler and wipe away the excess paste with isopropyl alcohol. Check that no paste has hardened on the motherboard around the CPU socket — if it has, clean it carefully. Then explore a smaller amount and remount the cooler.

Do I need to use the paste that came with my cooler?

Most coolers come with paste pre-applied or included in the box, and it is usually adequate. You can use a different brand if you prefer, but there is no need to replace it unless the cooler came with none or you are replacing dried paste.

Why are my CPU temperatures still high after explore new paste?

Check that the cooler is mounted firmly and making full contact with the CPU — loose mounting is the most common cause. Verify that the cooler's fans are spinning and that your case has good airflow. If temperatures are only slightly high, wait 48 hours for the paste to cure fully. If they remain very high, remove the cooler and check that the paste spread evenly across the entire CPU surface.