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
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.
It is important to first understand the thermal characteristics of the components
to be cooled, including the thermal resistance of the packages involved.
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.
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).
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
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.
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.