Building your own computer or assembling a repaired computer can seem pretty straight forward. This part connects to this part, you feel a reassuring click and you know that it belongs there. It just fits.

But then you come across some goop in a pouch, or maybe it’s in a syringe, and you find yourself thinking “I’m not a trained medical professional. What do I do with this syringe? Where does this part fit?”

We’ve got the answers about what thermal paste is, what is does, and how to apply it.

What is this thermal paste stuff?

Before you learn how to replace your thermal compound (thermal paste), you should take a second to understand what it actually is and the purpose it’s serving. Thermal paste acts as a bridge between the CPU and the heatsink. The CPU and heatsink are already sandwiched together, but microscopic imperfections in their surfaces reduce the efficiency of heat transfer between them.

The thermal compound fills in the tiny gaps and allows for a much more efficient transfer of heat away from the processor, and boy does the processor generate some serious heat. The thermal compound improves the efficiency of the heat transfer so much that without it, the processor overheats in a matter of seconds or minutes, at which time your computer will likely shut down to protect itself from permanent damage.

Why would the thermal paste need to be replaced?

Over time, thermal compound will dry out and begin to develop cracks which interrupt the heat transfer, making it much less effective. If you use your computer frequently and for longer periods of time, this process happens more quickly. An average user who only does some light web surfing can generally go many years without needing the thermal compound replaced, but the thermal paste is always becoming less efficient at pulling heat away from the processor.

For computer components without moving parts, like the CPU, heat is the silent killer. The hotter your computer runs, the shorter the lifespan. So the more efficiently you can draw heat out of the computer chassis, the longer the internal components will last.

The healthy temperature range for a CPU varies quite a bit by processor type, so it’s best to look up the safe range for your particular processor. A number of things could be responsible for a spike in temperature, but if the obvious reasons are not the culprit, thermal paste could be the cause. There are free apps and software available for Mac computers that will track CPU temperature. Smcfancontrol works wonderfully, and it tracks more than just temperatures.

How to replace the thermal paste.

Below is a step-by-step guide detailing our favorite method for replacing thermal paste. The demonstration was performed on a MacBook Air, but the same steps can be applied to most computers.

Necessary Tools & Supplies

• Antistatic wrist strap
• Isopropyl alcohol (Rubbing alcohol)
• Q-tips and a lint-free cloth (a coffee filter will work)
• All screwdrivers necessary to open your device and remove the logic board and heatsink

And of course, a syringe of thermal paste

Step 1

Take your screwdriver and carefully remove the screws attaching the heatsink to the CPU. Set the heatsink and screws aside.

Installing a heatsink is a bit tricker, but just unscrew to remove.

Step 2

Douse your Q-tip in rubbing alcohol (90% or higher) to prepare for removing the old paste from the CPU and the bottom of the heatsink.

Maybe you have a cool alcohol dispenser like we do? If not, you'll still manage.

Step 3

Remove ALL the thermal paste with the Q-tip, leaving nothing behind. Wipe the small fibers/hairs off with a lint-free cloth or coffee filter.

Step 4

You’re almost ready to start applying the thermal paste! By now, your CPU and heatsink should look something like this:

Step 5

Apply a small amount of paste directly to the surface where the heatsink will rest. Be careful not to apply too much. Thermal paste is generally non-conductive, but there’s no need to make a mess all over your board.

Step 6

Gently place the heatsink directly on top of the CPU where it was first attached. If any thermal paste comes out the sides, then too much was applied. In this case, carefully wipe excess paste up with another coffee filter until none remains on your board.

Step 7

After the heatsink and CPU are reunited, it is crucial not to pull them apart or the seal will be compromised. If this happens, air pockets will have likely formed between the processor and heatsink and the previous steps will need to be performed again.

Now just screw everything back together in the proper order and you are finished!

Whether the board you are operating on looks like the one in the steps shown above or not, the process is pretty similar.

Here are a few different examples of boards with a red outline highlighting the area where thermal paste should be applied:

Think you know a better way? Let us know in the comments!