Wirebook › Glossary › Thermal paste
What is thermal paste (and when does it need replacing)?
In one sentence: A thin grey goo between a chip and its metal cooler that fills tiny gaps so heat flows across; after years it can dry out and the chip runs hotter.
A little more
A chip and the metal cooler pressed on top of it look flat, but under a microscope both are bumpy, so they only really touch in a few spots with air trapped in between. Air is a poor carrier of heat. Thermal paste (also called thermal compound, or on some laptops a soft thermal pad) fills those gaps so heat can flow from the chip into the cooler, where the fan carries it away.
Over several years, especially in a laptop that runs hot, the paste can dry, crack or get pushed out. The chip then heats up quickly even with a clean fan, the fan roars, and the chip throttles under load. Replacing it means opening the case and removing the cooler, so on a laptop it's usually a job for a repair shop; on a desktop PC many people do it themselves. Dust in the fan is far more common, so clean that first.
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