Heat Sink

A structure that is mechanically attached to a device that generates heat, in order to lower the overall thermal impedance between the point source of the heat within the device and its cooler surroundings.

The fundamental aspects to consider in heatsink design are:

Number of Fins

Making the fins thicker will increase the heat transfer through the heatsink and to the fins, but will reduce the number of fins that can be fitted within a given package space and hence thereby reducing the surface area available for heat transfer. In addition, the thickness of each fin has to be sufficient to withstand any vibration that the part may experience in service.

Orientation

The orientation of the heatsink will have an effect on it's efficiency, especially when relying on natural air convection.

Efficiency versus orientation: note that maximum is with the fins oriented vertically.

Surface Finish

A rough surface finish will increase the surface area. If a positive air flow is being used over the heat sink then a rough surface will lead to a thicker boundary layer and this will act as a barrier and reduce heat exchange.

Thermal Cycling

Thermal cycling must be taken into account when designing any heat sink.

See also: Cooling Efficiency, Cooling Fan, Cooling System.

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Subjects: Electronics