A Brief of Heat Sink

A heat sink is a passive heat exchanger that transfers heat. The heat sink is usually a metal part that can be attached to a device that releases energy in the form of heat, with the purpose of releasing that heat to a surrounding fluid to prevent the device from overheating.

In many applications, the device is an electronic component (e.g. CPU, GPU 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.

HEATSINK CONSTRUCTION

There are many designs for heat sinks, but they usually consist of a base and a series of protrusions attached to that base. The base is the interface to the device being cooled. Heat is conducted through the base into the protrusions. The protrusions can take a variety of shapes, including:

• Plate fin

• Round fin

• Elliptical fin

Heat sinks are usually made of copper or aluminum. Copper has a very high thermal conductivity, which means that the heat transfer rate through copper heat sinks is also very high. The thermal conductivity of aluminum is lower than that of copper, but still high. Aluminum also has the advantage of being less expensive and having a lower density, which makes it useful for applications where weight is an important consideration.

PERFORMANCE

The performance of heatsinks are a consequence of many parameters, including:

• Geometry

• Material

• Surface treatment

• Air velocity

• Interface with device

The last point is very important. Electronic components and heat sinks are manufactured to be very apartment and smooth, but at the microscopic level their surfaces are rough. This results in very few contact points and many tiny air gaps between the component and its heat sink. Air has low thermal conductivity, resulting in poor heat conduction from the device to the heat sink. To counteract this, a thermal conductive material (TIM) can be applied to the underside of the heat sink to fill these gaps and create more conduction paths between the device and the heat sink.

Heatsink performance is characterized by its thermal resistance. This parameter can be thought of as the difference in temperature between the air around the heatsink and the device surface in contact with the heat sink per unit of input power.

MANUFACTURING METHODS OF HEATSINK

Heatsinks can be manufactured in a variety of ways depending on the required performance, cost and volume. These include:

Machining - where a CNC machine is used to cut the metal

Extrusion - where metal is heated and pushed through a mold

Forging - where metal is heated and shaped by pressurization

Stamping - where the metal fin is cut, and then soldered onto the base

Skiving - where a blade is used to slice, and push up the single block of metal

These devices are sealed objects that contain a liquid (usually water). They use heat dissipation during phase changes of the liquid to significantly increase their conductivity compared to a solid metal object of the same geometry. For more complex thermal problems, heat pipes and vapor chambers can be used within the heat sink assembly.

Mstirling Thermal Products offers all of these manufacturing techniques and, therefore, we can  provide you one-stop solution to any thermal requirement.