Application Note
16
<Revision 2.4>
<<2019-06-17>>
Assembly Instructions for the Easy-PressFIT Modules
8
Applying the thermal grease
Due to the individual surface shape (e.g. roughness and flatness) of the heat sink and the module, the lower
surface of the module and the surface of heat sink do not touch across the entire area. Therefore a certain
localized separation between the two components cannot be avoided.
To dissipate the losses occurring in the module and to achieve a good flow of heat into the heat sink, all
localized cavities have to be filled with a thermal compound. When using a heat conductive paste, a
homogenous application needs to be assured.
A well-applied layer will fill all cavities, and at the same time will still allow the metallic contact between
module base and heat sink surface. A compound should be selected which shows permanently elastic features
in order to assure a continuously favorable heat transfer resistance.
Before the module is mounted onto the heat sink, an even layer of thermal grease, 80 µm thick for Easy1B/2B,
and 60 µm thick for Easy3B, is recommended be applied to the module base or to the heat sink according to the
module size and the thermal grease used. This grease can be applied using either a spatula, a roller, or by silk
screen printing. The quantity of thermal grease is sufficient if a small amount of grease is visible around the
module after assembly to the heat sink.
The recommendation is to apply the thermal grease by means of a screen print process. Apart from an
optimized and module-specific distribution of the heat conductive paste, a homogenous and reproducible
layer thickness can be achieved with this procedure. If a screen print process is used, the layer thickness could
be reduced to values under the above-mentioned numbers. The size of the module and the viscosity of the
thermal grease are important factors in this case.
Further notes regarding the application of screen print templates for the application of thermal grease can be
found in the application note AN2006-02 Application of silk screen.
