A heat sink is a passive heat exchanger that transfers the heat generated by an electronic or mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, thereby allowing regulation of the device's temperature. There are two types of heat sinks, namely the passive heat sink and the active heat sink.
Active Heat Sinks
An active heat sink has a powered device such as a fan, water pump, or air blower to enhance cooling capacity. Such powered devices mounted on a heat sink push or pull a constant fresh air flow across the metal cooler, making thermal dissipation much more effective. Some active heat sinks use water or other liquids to carry heat away from a heat source. In computers and other electronic systems, these sorts of coolers typically run off the PC’s internal power supply. The most common form of active cooling heatsink involves one or more fans being mounted directly above or on the side of the heat fin stack.
Active heat sinks are usually easy to install and remove and are widely used as a temperature control system in electronics, protecting and enhancing the performance of various chips, LEDs, ICs, and other modules.
Passive Heat Sinks
These have no mechanical components. They only use the convection process to dissipate thermal energy. Because they have no moving parts, they are more reliable. But they should still have continuous airflow across their fins. Passive heat sinks
Because of using the extra surface area of the device to improve thermal cooling, which is the trade-off for lacking a fan and its high heat removal capacity, they tend to be larger.
Passive Heat Sinks are often used on lower power draw electronics or machinery that does not get hot enough to warrant active cooling.
Unlike passive heat sinks, active heat sinks use one or more fans to actively drive airflow over the heat sink. This offers greatly increased cooling ability and allows significantly increased fin density for increased surface area per unit of volume, further increasing cooling capacity. Active heat sinks are used on almost all high-end CPUs and GPUs as they emit a lot of heat.