It is one of the most common first-build questions: does thermal paste go on the CPU, on the cooler, or both? The short version is that you apply it to the CPU, and the cooler’s mounting pressure does the spreading. But the reasoning behind that answer explains a lot about why paste exists at all and how to get contact right the first time.
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Why paste goes on the CPU
Thermal paste fills the microscopic pits and scratches between the CPU’s heat spreader and the cooler base. Neither surface is perfectly flat, and air trapped in those gaps is a poor conductor. Applying a small amount to the center of the CPU lets the cooler press down and squeeze it into an even, thin layer that pushes air out. Putting it on the CPU rather than the cooler gives you a clear view of the application point and keeps the amount controlled.
Do you ever apply it to the cooler instead?
Applying to the cooler base works mechanically, but it is harder to judge placement because you are aligning a coated surface blind as you lower it. The main exception is when you use thermal pads or pre-applied compound on the cooler — in that case the manufacturer has already handled it and you add nothing. For standard paste, the CPU is the cleaner target.
How much and what pattern
The goal is a thin, complete layer with no dry spots and no overflow. Too little leaves gaps; too much acts as insulation and can ooze onto the socket. A small central dot is the most forgiving method for typical square desktop chips, while larger rectangular heat spreaders benefit from a slightly bigger dot or a short line.
| CPU type | Suggested amount | Pattern |
|---|---|---|
| Standard desktop (LGA/AM socket) | Pea-sized, roughly 4–5mm | Single center dot |
| Large rectangular IHS | Slightly larger dot | Center dot or short line |
| High-core-count / bigger die | Two small dots or thin line | Spread by mount pressure |
Should you spread it manually?
For most builds, no. Letting the cooler’s clamping force spread a center dot avoids trapping air bubbles that manual spreading can introduce. Manual spreading with a spatula is mainly used with very thick pastes or on bare-die and delidded setups where precision matters. For a normal build, dot and mount.
Getting good contact
Clean both surfaces with isopropyl alcohol first so old residue or oils do not ruin the bond. Mount the cooler with even pressure, tightening screws in a diagonal cross pattern a little at a time so the base sits flat rather than tilting. Uneven pressure is a bigger cause of high temperatures than the exact paste amount. After mounting, avoid lifting the cooler to “check” — breaking the seal means you should reapply.
Frequently asked questions
Is it bad to put paste on both the CPU and the cooler?
You do not need to, and doing both makes it easy to use too much. Excess paste can squeeze out onto the socket and, with conductive compounds, cause problems. Apply a single controlled amount to the CPU and let mounting pressure do the rest.
What if I used too much paste?
A little overflow is usually harmless with standard non-conductive paste, though it looks messy. If it is oozing across the socket or you used a conductive compound, remove the cooler, clean both surfaces with isopropyl alcohol, and reapply a smaller amount. Excess acts as a mild insulator, so less really is more.
Bottom line
Apply thermal paste to the CPU, use a small central amount sized to the chip, and let the cooler’s mounting pressure spread it into a thin even layer. Skip manual spreading for normal builds, clean both surfaces first, and tighten in a cross pattern for flat contact. Get those basics right and your paste job will match anything a spreadsheet of application methods can promise.
