A heat sink is used in electronic devices to dissipate heat and prevent overheating. It is typically made of a metal such as aluminum or copper. It absorbs and transfers heat from the device’s central processing unit (CPU) or other heat-generating components. Heat sinks work by increasing the surface area available for heat transfer and using fins or other structures to increase the flow of air or other cooling medium over the surface of the heat sink. This helps to keep the device operating at a safe temperature and prevent damage from overheating.

In many applications, the device is an electronic component (e.g. CPU, GPU, ASIC, FET etc.) and the surrounding fluid is air. The device transfers heat to the heatsink by conduction. The primary mechanism of heat transfer from the heatsink is convection, although radiation also has a minor influence.

There are two distinct types of convection:

Natural convection – where the movement of the fluid particles is caused by the local changes in density due to transfer of heat from the surface of a solid to the fluid particles in close proximity.

Forced convection – where the movement of the fluid particles is caused by an additional device such as a fan or blower.

Heatsinks are designed to significantly increase the contact surface area between solid and fluid, thereby increasing the opportunity for heat transfer. A typical ASIC may have a surface area in contact with air of only 1600mm2. The surface area of a typical heatsink used to cool that device may be 10 or 20 times that value.