Heat sink

A heat sink is a block of metal with fins or ridges that keeps a hot part cool. Chips and power transistors waste some energy as heat, and if it builds up they slow down, wear out or fail. The heat sink gives that heat a large surface from which to escape into the air.

It is made from aluminum alloy, which conducts heat well, is light and is easy to shape. The most common method is extrusion: a hot billet is pushed through a steel die with the fin pattern cut into it, like toothpaste from a tube, and the long finned bar that comes out is sawn into pieces. Simpler heat sinks are stamped and bent from flat sheet. Holes or clips are added for mounting, and the surface may be anodized black.

On the power supply board, heat sinks are bolted to the power transistors and rectifiers. On the main board, one sits on the system-on-chip, usually with a soft thermal pad or paste to fill the tiny air gaps between them. Copper conducts heat about twice as well, but it is heavier and costs more.