Getting rid of heat is one of the central challenges with modern
technology. It doesn’t matter whether the technology is a
high-end server CPU or some pathetically anemic processor in a
no-brand set-top box, someone has had to think about thermal
management. One of the central issues in thermal management is
thermal resistance, a material’s tendency to limit the flow of
heat. The thicker a material, the larger the temperature gradient
required to achieve the same amount of cooling because the thermal
resistance increases with thickness.
Except when it
doesn’t; if the heat is carried by ballistic phonons, then
thermal resistance stays constant.
Energy in motion
Heat is basically energy. In a solid material, energy is stored
in two places: the motion of electrons, and the motion of the
nuclei. The motion of electrons can pull nuclei into motion, while
likewise, nuclei kick electrons around, so energy travels back and
forth between the two.
Source: FS – All – Science – News
Long narrow wires carry heat without little resistance