An active heatsink refers to a heatsink with a means of moving air, usually a fan. This type of heatsink usually has a metal component that makes contact with the hardware that needs to be cooled. The metal unit is attached to a fan that moves hot air away from the unit. Most often seen on computer processing unit (CPU) chips, the active heatsink is the most commonly used type of heatsink in personal computers.
One advantage of active heatsinks is that they tend to be more compact than passive heatsinks. Since passive heatsinks do not have a fan or other means of moving warm air away from the heatsink, they are physically larger to conduct heat away from the hardware. Some technicians prefer passive heatsinks because they have a more even and predictable method of heat transfer than an active heatsink.
The size of passive heatsinks often makes them impossible to use in a standard computer case setup. In tightly packed cases, an active heatsink is often the only feasible method for adequate CPU cooling. Active heatsinks are generally more lightweight than passive heatsinks, which have been known to occasionally collapse into a user's computer case when the weight of the passive heatsink pulls the screws out from its base. Although they are smaller in size, active heatsinks still require some space around them to circulate air.
Active heatsinks are usually easy to install and remove. An active heatsink connects to cool a CPU chip by attaching to a screwed-in hardware bed that allows the heatsink to be clipped on and off for easy hardware maintenance. When installing any heatsink, one important step is applying thermal paste to facilitate the conduction of heat between the parts of the CPU chip and metal heatsink parts which come into contact. Thermal paste can be purchased in small tubes for single installation applications.
The terms "active" and "passive" are used frequently when referring to the storage and movement of heat. In solar heating, an active solar heating system is a system with a fan, while a passive solar heating system relies on the movement of heat without the aid of a fan. An example of an active solar heating system would be a set of solar panels outside the house with a fan to blow hot air into the house. A passive solar heating system would include roof tiles or windows designed to absorb and retain heat, which conducts to the house by physical contact.