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

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

Applying thermal paste correctly minimizes air gaps between the CPU and heatsink for optimal cooling, but the amount and method matter to avoid insulation-like effects from excess paste. Testing various techniques reveals clear winners for coverage, minimal bubbles, and real-world temperatures.

We have tested various 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, while a rice-sized dot (or even a fun “happy face” variant) tied for third place. Excess paste, like in larger dots or thick lines, performed worst as it squeezed out unevenly.

1. Make sure that the CPU is clean and free from any old thermal paste. If there is, carefully remove it from the CPU lid 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 that cross at the centre, adjusting the thickness slightly for larger CPUs to ensure full coverage. This method is quicker and more consistent than spreading, which risks tiny bubbles, and dots, which may not provide full coverage. It is ideal for everyday builds. It works reliably across CPU sizes, providing fuss-free, reliable cooling.

Reusing paste can also cause air bubbles to form. If a problem occurs during the installation process and you have to remove the CPU cooler, you should completely clean off all paste as mentioned above, then try again with a fresh application. If you absolutely need to reuse an application — while waiting for replacement paste, for example — you can, but keep in mind this is a short-term solution, and that we recommend a proper reapplication before long-term use of your CPU cooler.

In most cases, you shouldn’t need to reapply thermal paste more than once every few years, though you should replace it if you remove your cooler for any reason. You may also want to reapply thermal paste if you find that your CPU temperatures are rising and you can rule out other factors, such as dust build-up. If in doubt, consult the thermal paste manufacturer, and follow their recommendations.

Thermal pads are soft, pre-cut sheets made from silicone or reinforced materials with conductive fillers like ceramic or fiberglass. They handle gaps up to several millimeters, 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 like Thermal Grizzly PhaseSheet PTM, start solid at room temperature but soften above ~45°C to fill microscopic gaps like paste. They offer near-paste performance without pump-out or drying, making them suitable for CPUs/GPUs in laptops or desktops. Electrically non-conductive and durable, though initial heat cycles optimize bonding.

Thermal putty is a moldable, 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, though pricier per gram for premiums.

Liquid metal alloys (e.g., gallium-based) deliver top-tier conductivity (70+ W/mK), outperforming most TIMs for extreme overclocking on CPUs/GPUs. Electrically conductive, it risks shorts if misapplied, so it's for experts only on non-aluminum surfaces (most CPU heatspreaders are made of nickel-plated copper, but avoid direct aluminum contact due to alloying). No drying issues, but requires careful damming and isn't reusable easily.

Ultra-thin graphite or graphene foils (e.g., Thermal Grizzly Kryosheet) spread heat laterally with high in-plane conductivity, reusable without degradation. They suit flat interfaces like CPUs, offering paste-like results in tests without liquids. Electrically conductive, so avoid bridging contacts; no outgassing issues.

Gap fillers handle large uneven gaps (up to 15mm) across components with high compressibility. Thermal foils provide durable insulation and conduction for mid-range needs. Metal-based TIMs like soft alloys (SMA-TIMs) offer high performance with easier handling than liquid metal.