How to choose thermal paste
For a normal build, paste choice is worth one or two degrees. Application technique and cooler mounting pressure are worth far more. Buy something reputable, apply it properly, and stop optimising.
Conductivity numbers are not comparable across brands
W/mK figures are measured under conditions each manufacturer chooses, and there is no shared standard. A paste claiming 16 W/mK is not demonstrably better than one claiming 8 W/mK. Independent testing under a real cooler is the only meaningful comparison.
Electrical conductivity is the safety spec
Standard ceramic and carbon pastes are non conductive and safe around pins and surface components. Liquid metal is electrically conductive, will short a board if it escapes, and corrodes aluminium. It belongs on a delidded CPU or a bare die, applied by someone who has done it before.
Pads, paste and sheets are different jobs
Paste fills microscopic gaps between two flat surfaces. Pads bridge real physical gaps, for example VRAM and VRM on a graphics card, and the thickness has to match the gap. A pad where paste belongs is a large thermal penalty. Graphite sheets are reusable and forgiving, and slightly worse than good paste.
Pump out and longevity
Laptops and anything that heats and cools sharply suffer pump out, where thin paste migrates away from the die over months. A thicker, higher viscosity paste or a phase change pad holds up much better there than a thin high performance compound.
Quantity
A 4g tube covers several desktop applications. Buying a large syringe for one build means most of it dries out on a shelf.
Common mistakes
- Spreading paste thin by hand and trapping air. A centre dot under even mounting pressure is enough.
- Reusing old paste after removing a cooler.
- Using liquid metal on an aluminium heatsink.
