How Tech Works

The Skinny on Thermal Paste

We recently set out on a journey to shed some light on basic repair skills with a series of videos on iFixit’s Youtube channel. Our first video centered on stripped screws: how to avoid them and how to deal with them. We made several suggestions—some more common than others—and the tutorial was met with generally positive feedback. Our second video about thermal paste, on the other hand, kicked off a lot of debate in the YouTube comments section.

Welcome to PasteGate, people.

In case you’re not familiar, thermal paste is a heat conductive adhesive that bridges the gap between your heat source (the CPU) and the heat sink. It serves a dual purpose: it eliminates any air gaps between the two components—which is good, because air is a thermal insulator— and gives a bit of mechanical strength to the assembly. Old thermal paste can crack and cause heat transfer issues, and it’s generally a good idea to replace your paste every time you separate the CPU from the heat sink.

Our video demonstrated how to clean old thermal paste off of a chip and apply new thermal paste. Here’s where we get all controversial: There are many schools of thought on how best to apply thermal paste. And there are impassioned defenders of each distinct method.

Apple likes to use what I like to call “The Glob Method.” They put a very healthy glob of thermal paste on to the chip, and then let the heatsink do the spreading. Personally, I’m not so hot on this method (see what I did there?). The paste gets everywhere, even in the nooks and crannies off the chip where it doesn’t belong. You can see the ill effects of the glob method in the video before we start the cleaning process.

That’s not to say a more measured hand doesn’t get the job done right. A small drop or line of thermal paste on a chip results in the thin, even layer of thermal paste you want. But here’s the downside: You don’t get to check your work. And that’s especially critical for thermal paste newbies. There’s no way of telling if you’ve gotten coverage over your chip unless you separate the CPU and heatsink—but that will invariably take you back to square one.

That’s why we use the “spreading method” at iFixit. It gives us the control we want over the paste. We apply a tiny dot of paste to the chip and spread it in a super thin layer over the chip, with something like a credit card or a plastic-covered finger. Some commenters pointed out that the spreading method can result in slightly higher temperatures—and they’re right. But we’ll take the gain in degrees for the added control, and we’ve yet to encounter a problem with the method.

Application of thermal paste

So that’s how we roll at iFixit. For us, spreading is the goldilocks methods, because it ensures that there’s a “just right” amount of paste on the chip surface—not too little, and not too much. After all, you don’t want your CPU porridge too hot, do you?

That said, no method is strictly wrong. It’s all about preference, practice, and comfort level. The nice thing about thermal paste is that it’s not permanent. If you mess up, just clean it up and try, try again.

P.S. While we’ve found our goldilocks method to work great in every circumstance, spec sticklers can follow Arctic Silver’s recommended guidelines for every modern Intel and AMD processor.

P.P.S. Tell us about your thermal paste methodology in the comments.