A heat sink is a passive heat exchanger designed to transfer heat generated by an electronic or mechanical device, regulating temperature by allowing heat to dissipate away from the device.
Heat sinks are generally mounted on top of processors, power devices, and high-powered lasers or LEDs. The heat sink draws heat from the device and, by maximizing the surface area in contact with the fluid around it, transfers the heat away from the component.
Heat sinks are made of copper, which has high thermal conductivity and can transfer heat quickly, or aluminum, which has lower thermal conductivity but reduces costs and weight. They are outfitted with fans or liquid cooling systems, which facilitate cooling by blowing hot air away or absorbing the heat.