Thermal paste

It has to be coupled with a fastener such as screws to hold the heat sink in place and to apply pressure, spreading and thinning the thermal paste.

The filler loading can be as high as 70–80% by mass, and raises the thermal conductivity of the base matrix from 0.17–0.3 W/(m·K) (watts per meter-kelvin)[1] up to about 4 W/(m·K), according to a 2008 paper.

However, metal-based thermal paste can be electrically conductive and capacitive; if some flows onto the circuits, it can lead to malfunction and damage.

The most effective (and most expensive) pastes consist almost entirely of liquid metal, usually a variation of the alloy galinstan, and have thermal conductivities in excess of 13 W/(m·K).

A common application is to drain away waste heat generated by electrical resistance in semiconductor devices including power transistors, CPUs, GPUs, and LED COBs.

Factory PCs and laptops—although seldom tablets or smartphones—typically incorporate thermal paste between the top of the CPU case and a heat sink for cooling.