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Fansinks or active heatsinks are a special subsection of heatsinks. By definition, these products include “active” components, meaning that they must be powered in order to work. A fansink or active heatsink generally comprises both a heatsink and an air mover (or fan). The fan is generally attached directly to the heatsink or very near it.


Figure 1 shows a typical fansink used in VGA or video card application. A small fan is used to force air through the fins of a Copper heatsink which attaches directly above the component or components to be cooled. Some of the considerations to be taken into account include: heatsink pressure drop, fan performance (or flow rate capability), dimensional constraints, baseplate heat spreading resistance, and fan life.



            Figure 1: Fansink for VGA application


The design of an active VGA heatsink uses the following approach depending on how much heat needs to be dissipated. As discussed below, we generally begin with an understanding of the components to be cooled, followed by a thermal analysis of the system, and choice of fan that can deliver the expected flow rates and fan life.

  1. It is important to first understand the thermal characteristics of the components to be cooled, including the thermal resistance of the packages involved.
  2. Once this is understood and a physical envelope has been defined for the heatsink (ie. height and plan view dimensions), we can begin to define a heatsink that will fit into the desired volume.
  3. A thermal analysis can be performed where we identify the heat loads (power dissipated, source size and position), preliminary fan selection, and heatsink configuration. The model and results of such an analysis are shown in figure 2. The results of the analysis allow us to establish whether the temperature margins are sufficient, given the operating conditions (ie. ambient air temperature, heat load, etc).
  4. Once the required flow and heatsink configuration are established we can finalize the choice of fan based on life requirements and other parameters. We would likely rerun the analysis with final fan performance curve to ensure that the results are accurate.
  5. The thermal analysis can provide us with significant insight into the design of the active heatsink. For example, we notice in the temperature results of figure 2 that the high temperatures are localized over the hot components (as expected). If we wanted to spread that heat out more, we would possibly consider a high thermal conductivity material such as Copper or perhaps using a large heat spreading pad between the heatsink and components. In addition, a thermal analysis also allows us to quickly study different fin configurations or different fans and assess the optimum active heatsink configuration.
  6. We can then fully define (in 3D CAD model) a fansink that will meet all requirements and have it manufactured for the customer.

Figure 2: Thermal analysis for VGA fansink application


Fansinks can also be used for cooling CPUs or to cool other components for which a passive heatsink design is not adequate. In all cases, the above process would be followed in order to define an adequate fansink. As a heatsink manufacturer, TDMG can help you design and procure the right fansink for your application.

If you have any questions regarding the above or for a specific design question which you may have, please contact us and we will be pleased to help you.

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