What is thermal contact resistance and how can it be minimized?

Thermal contact resistance occurs at interfaces between solid surfaces due to surface roughness creating air gaps (only 1-2% of nominal area actually contacts). Typical values: 0.5-5×10⁻⁴ m²-K/W for machined metal surfaces. Minimization strategies: Increase contact pressure (reduces air gap volume), Apply thermal interface materials (TIMs) - thermal greases (1-5 W/m-K), thermal pads (3-10 W/m-K), phase change materials, liquid metals (20-70 W/m-K), Improve surface finish (reduce roughness), Use softer materials that conform to surfaces. In electronics, TIM selection is critical; a 0.1mm bondline with 5 W/m-K TIM adds 0.02 K/W resistance to each component.