Another method is to carry out an analysis based on the finite element method (FEM).
This is particularly suited to situations where several interrelated systems are being
considered at the same time, as when analysing a complete IGBT module with its
multitude of individual IGBTand diode chips.
Exampleof a thermal simulation usingFEM software
With the help of an example from
the correct choice and application of the
TIM can be deduced. The TIM layer is the layer that shows the worst thermal
conductivity, not only in the example presented, but in real life in almost any application,
It is therefore important to use only the smallest amount of TIM that is required. See
Theoretically, the best option is extensivemetal-to-metal contact between the baseplate
and the heatsink. Because of the curvature of the baseplate and roughness in the two
surfaces, the requirement can only be partially implemented. Typically, metal-to-metal
contacts can be achieved at the pointswhere the baseplate ismounted on the heatsink.
However, the amount of contact available decreases as the distance from these
mounting points increases. A large number of areas with metal-to-metal contact helps
improve the inherently poor thermal conductivity of theTIM, providing better overall heat
dissipation for the design.
shows an example. On the other hand, a design
without metal-to-metal contact has greater thermal resistance between the baseplate
and the heatsink, as shown i
, taking theuse of a thermal foil as an example.