Thermal Interface Materials (TIM) are used in the installation of any computer cooling solution to transfer heat from a processor to a heat sink. TIM itself does not dissipate heat — it fills microscopic imperfections which result in air gaps on connecting surfaces, allowing for a significantly more efficient transfer of heat.

Thermal paste is one of the most popular means of improving heat transfer. It is not as thermally conductive as metal, so it is important not to use too much — excess paste acts more like an insulator than a thermal improver.

Applying thermal paste correctly minimises air gaps between the CPU and heatsink for optimal cooling. Both the amount and the method matter to avoid insulation-like effects from excess paste.

We have tested various application methods over the years. The X-shape application delivered the best results, with excellent coverage across the CPU die and very few air bubbles, leading to the lowest full-load temperatures. A smooth spread was nearly as effective, just 0.25 °C warmer, whilst a rice-sized dot (or even a “happy face” variant) tied for third place. Excess paste — such as larger dots or thick lines — performed worst, as it squeezed out unevenly.

1. Make sure the CPU is clean and free from any old thermal paste. If necessary, carefully remove it with isopropyl alcohol and a microfibre cloth or lint-free paper towel, then leave it to dry before continuing.
2. Use a simple X-shape: Draw two thin lines crossing at the centre, adjusting thickness slightly for larger CPUs to ensure full coverage. This method is quicker and more consistent than spreading (which risks tiny bubbles) and more reliable than a dot (which may not provide full coverage). It works reliably across CPU sizes, providing fuss-free, consistent cooling.

Reusing paste can cause air bubbles to form. If a problem occurs during installation and you need to remove the CPU cooler, clean off all paste completely and reapply fresh. If you absolutely must reuse an application in the short term — whilst waiting for replacement paste, for example — you can, but a proper reapplication is strongly recommended before long-term use.

In most cases you should not need to reapply thermal paste more than once every few years, though you should always replace it whenever you remove your cooler for any reason. You may also want to reapply if CPU temperatures are rising and you can rule out other causes such as dust build-up. If in doubt, follow the thermal paste manufacturer's recommendations.

Thermal pads are soft, pre-cut sheets made from silicone or reinforced materials with conductive fillers such as ceramic or fibreglass. They handle gaps up to several millimetres, provide electrical insulation, and are easy to apply without mess — ideal for VRAM or lower-heat components. Performance is moderate (typically 1–8 W/mK), but they excel in convenience over paste.

PCMs — often in pad or sheet form, such as the Thermal Grizzly PhaseSheet PTM — start solid at room temperature but soften above approximately 45 °C to fill microscopic gaps like paste. They offer near-paste performance without pump-out or drying, making them suitable for CPUs and GPUs in both laptops and desktops. Electrically non-conductive and durable; initial heat cycles optimise bonding.

Thermal putty is a mouldable, viscous compound (e.g. Honeywell HT10000, Fehonda TP81) that conforms to uneven surfaces without hardening or drying out. It fills variable gaps effectively for GPUs or complex assemblies, providing reliable long-term conductivity better than pads in high-tolerance scenarios. Non-conductive and cost-effective in bulk.

Liquid metal alloys (e.g. gallium-based) deliver top-tier conductivity (70+ W/mK), outperforming most TIMs for extreme overclocking on CPUs and GPUs. Because they are electrically conductive, they risk shorts if misapplied — liquid metal is for experienced users only, and must not be used on aluminium surfaces (most CPU heatspreaders are nickel-plated copper, but direct aluminium contact causes alloying). No drying issues, but requires careful application and is not easily reusable.

Ultra-thin graphite or graphene foils (e.g. Thermal Grizzly Kryosheet) spread heat laterally with high in-plane conductivity and are reusable without degradation. They suit flat interfaces such as CPUs, offering paste-like results in tests without the mess of liquids. Electrically conductive — avoid bridging contacts.

• Gap fillers: Handle large uneven gaps (up to 15 mm) across components with high compressibility.
• Thermal foils: Provide durable insulation and conduction for mid-range needs.
• Metal-based TIMs (SMA-TIMs): Soft alloys offering high performance with easier handling than liquid metal.