Thermal paste is the compound that fills the microscopic gaps between a processor or graphics chip and the base of its cooler, so heat passes into the heatsink more efficiently. It suits anyone building a PC, fitting a new cooler or replacing dried-out paste on an older machine.
It is usually sold in small syringes for a few applications or in larger tubes for repeated use. Formulations range from non-conductive ceramic and silicone-based pastes to metal-based pastes and liquid metal.
How to choose thermal paste
Electrical conductivity. Most pastes made for general use are non-conductive, so a small smear onto the motherboard is unlikely to cause harm. Metal-based pastes and liquid metal can conduct electricity, so they need a careful hand and are best avoided if you have little building experience.
Thermal performance. Manufacturers quote thermal conductivity in W/mK, but the figures are measured in different ways and cannot be compared directly between brands. Treat them as a rough guide and look at independent temperature tests where you can. For a typical office or gaming processor, a good mainstream paste is enough.
Cooler and chip materials. Liquid metal usually contains gallium, which reacts with aluminium and can damage it. It is generally used only on copper or nickel-plated surfaces, so check the base of your cooler and the heat spreader before buying.
Quantity and format. A syringe of a few grams covers several processor applications. If you plan to repaste a graphics card, a laptop or several builds, choose a larger pack. Some packs include a spreader, which helps with even application.
Lifespan. Paste slowly dries out or migrates over the years, and temperatures creep up as it does. Plan to replace it every few years, or sooner if the processor runs hotter than it used to.
Types of thermal paste
- Ceramic and silicone-based pastes: non-conductive and forgiving to apply, which makes them the usual choice for first-time builders and general upgrades.
- Carbon-based pastes: contain carbon particles and are generally non-conductive, and are often chosen for long service life between repastes.
- Metal-based pastes: contain metal particles such as silver for better heat transfer, and some types are slightly conductive, so check the product description.
- Liquid metal: offers the highest conductivity of the common options, but needs careful application, is conductive and must not be used on aluminium.
When comparing individual products, check the compound type, the weight in grams and whether the paste is electrically conductive before looking at the brand.
Thermal paste FAQ
How often should I replace thermal paste?
Every few years is a sensible interval for most desktop PCs. Replace it sooner if processor temperatures rise noticeably or if you remove the cooler for any reason. Liquid metal and some carbon-based pastes can last longer.
How much thermal paste should I use?
A pea-sized dot, or roughly a grain of rice, in the centre of the processor is enough for most desktop chips. Too much paste can squeeze out of the sides and make a mess, while too little leaves gaps. Larger chips may need slightly more or a thin line pattern.
Do I need new thermal paste with a new cooler?
Many coolers arrive with paste pre-applied or supplied in a small sachet, so you may not need to buy any. You do need fresh paste whenever you remove a cooler and refit it. Old paste should be wiped off with isopropyl alcohol first.
Is liquid metal thermal paste safe to use?
It is safe when used correctly, but it is electrically conductive and can corrode aluminium. Apply it only to compatible copper or nickel-plated surfaces and keep it away from nearby components. If you are unsure, a non-conductive paste is the lower-risk option.
