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A heat sink is a thermal conductive metal device designed to absorb and disperse heat away from a high temperature object such as a computer processor. Usually heat sinks are outfitted with built-in fans to help keep both the CPU and the heat sink at an appropriate temperature. Heat sinks are made out of metal, such as a copper or aluminum alloy, and are attached to the processor. Most heat sinks have fins, thin slices of metal connected to the base of the heat sink, which help spread heat over a large area.
The combination of a heat sink and fan (HSF) is referred to as an active heat sink, while a heat sink without a fan is a passive heat sink. In addition to the HSF, a heat sink compound is sometimes used. This is a coating between the device and the heat sink to improve thermal conduction.
Heat sinks are commonly used in all CPUs and are also used in refrigeration and air conditioning systems, GPUs and video card processors.
A computer processor works at a very fast pace, generating a lot of heat. If a processor is overheated and does not have a heat sink, the CPU can be damaged. The computer may be dysfunctional and not able to complete a POST (power on self-test). If a POST fails, nothing will appear on the screen and the computer speakers may produce only a series of beeps.
To prevent overheating, the heat sink dissipates heat from the processor. To transfer heat from the processor to the heat sink, there must be an adequate amount of surface area between the two. This is done by the use of a heat sink compound (also called thermal paste), which is lightly spread over the surface. However, too much thermal paste will insulate the CPU instead of cooling it.
Fans are used to cool the air and push hot air away from the computer and move cool air across the heat sink. Fans near the CPU speed up as the temperature rises, helping cool the processor and heat sink.
Maintaining a cool system is critical. Temperatures should be kept between 90 and 110 degrees Fahrenheit, or 32 and 43 degrees Celsius. Overheating internal components can cause data loss, shortened computer lifespan, system crashes, lock-ups, random reboots and permanent damage. For safety precautions, most motherboards are programmed to shut down if the CPU temperature reaches 85 to 90 degrees Celsius.