How-To: Properly Apply Thermal Paste and Install a CPU

Building a PC is a many-step process, but one in particular stands out as being intimidating to first-timers: properly mounting a CPU and cooler. Why? Because, generally speaking, that one little cpu chip is simultaneously the smallest, most delicate, and most expensive part of your system. Mount the cooler wrong, or improperly apply the thermal paste and you’re looking at (at best) a drop in performance and system crashes, or (at worst) a $200 disaster.

But don’t worry! It’s actually not terribly hard to install a new CPU, as long as you know what you’re doing. And so that you do know what you’re doing, we’ve put together a quick primer on installing a new CPU. If you’re a newbie getting ready to build a new system, or an old pro looking to make sure your technique is the best, read on to find out everything you need to know about properly mounting a CPU.

So what is thermal paste anyway?

Thermal paste is a type of heat transferring agent that serves to fill in the microscopic gaps that naturally occur when two flat metal surfaces—such as your CPU and cooler—are pressed against one another. These air-filled gaps hinder the rate at which the cooler is able to absorb heat from the CPU, and filling them with thermal material greatly increases performance.
There are several different types of thermal material, including ceramic- and metal-based pastes and solid, waxy thermal pads. Some coolers come with pre-applied pads, but most don’t, and we recommend using a paste. Our two favorites are Arctic Silver 5 and Arctic Silver Ceramique.

Step 1: Prep the CPU and cooler

If you’re using a CPU, cooler, or both that’s already seen a tour of duty, then they’re likely to have some gunky thermal paste residue. Don’t be tempted to just reuse this old paste, as it dries out over time, and you won’t get a clean connection between your CPU and cooler.

So the first order of business is to clean off the old thermal material. Here in the lab we use a two-stage cleanser called ArctiClean, although high-percentage rubbing alcohol will do the job just fine. Just apply a drop or two to the old material and let it sit for a minute while the cleaner breaks up the grease in the thermal paste. Then, wipe it clean with a lint-free cloth. A coffee filter makes a terrific, cheap lint-free cloth. Repeat the process until both the CPU and cooler are totally clean, and then move on.

Step 2: Apply the thermal paste

Looking around the internet, you’ll find a lot of different philosophies about how to apply thermal paste. Some people say you should apply it in a dot, some a line, some two lines, some an “X,” and so on. Truth is, all you’re trying to do when applying thermal paste is to get a paper-thin layer of the stuff over as much of your CPU as possible. For that, a dot is pretty much perfect, since a dot will squish into a circle, which will hopefully reach to all 4 edges of the CPU.

Here’s what we recommend:

First, insert the CPU into its socket on your motherboard.

Next, squeeze out a dot of thermal paste directly onto the center of your CPU. Your dot should be about the size of a BB (as in, what BB guns shoot), or a little smaller than a pea. Next, take your cooler and press it straight down onto the CPU so that the thermal paste spreads evenly in all directions. If you feel comfortable doing it, you can use a very very slight rubbing motion as you press down on the cooler to help spread the paste better.

Ideally, you’re now finished. You simply lock your cooler down (using whatever mechanism yours comes with) and then move on. However, if you’re afraid the thermal paste didn’t get spread properly, you can give it a quick look by lifting the cooler back up, twisting slightly to break the vacuum seal that may have formed. If you’ve got too much paste on the CPU, you can wipe up the excess from around the edges, and if you’ve got too little, you can add some more. Of course, if you somehow totally screwed it up, you can always clean everything up and try again.

Note that we don’t recommend doing this more than once—every time you lift up the cooler, you risk adding more air bubbles into the thermal paste, which will lower you coolers efficiency. Don’t let yourself get too worried about that, though—unless you’re doing some real overclocking, it isn’t going to make or break your system.

And that’s about it. Good luck with your build!