In electronic systems, a heat sink is a passive heat exchanger that cools a device by dissipating heat into the surrounding medium.
A heat sink is designed to maximize its surface area in contact with the cooling medium surrounding it, such as the air. Air velocity, choice of material, protrusion design and surface treatment are factors that affect the performance of a heat sink. Heat sink attachment methods and thermal interface materials also affect the die temperature of the integrated circuit.
A heat sink transfers thermal energy from a higher temperature device to a lower temperature fluid medium. The fluid medium is frequently air, but can also be water, refrigerants or oil. If the fluid medium is water, the heat sink is frequently called a cold plate.
When the air flow through the heat sink decreases, this results in an increase in the average air temperature. This in turn increases the heat sink base temperature. And additionally, the thermal resistance of the heat sink will also increase. The net result is a higher heat sink base temperature.
The increase in heat sink thermal resistance with decrease in flow rate will be shown later in this article. The inlet air temperature relates strongly with the heat sink base temperature. If there is no air flow around the heat sink, energy cannot be transferred.