Master Thesis - OUFTI-1

Their study was based on the fact that the material is isotropic. They did not determine
the anisotropic values because, owing to the PCB assembly (which is a piling up of several
layers of FR 4 and copper), these values are too complicated to obtain. So, anisotropic FE
model of the PCB can not be performed in this thesis.
Finally, they give us a value of 1.6 mm for the PCB thickness. But, measuring it by
ourselves, the values obtained are included in a range of: [1.65 − 1.75 mm]. So, the value
which will be imposed to our FE models, is 1.7 mm.
The mesh elements that will be used to mesh the PCB of the OBC 2 card, as already
mentioned in section 4.2.4, are shell elements.
Finally, for the damping, according to reference [49], a modal damping of 2% is a quite
representative value for a PCB because there is a great friction between the dierent layers
which constitute it. In our case, a value of 1% will be applied to the model to keep a
security margin of 1%.
4.3.2 Recognition of the components eects
First of all, we have to decide which type of components will be taken into account
in the FE model of the OBC 2. As already mentioned, these components can be divided
into three dierent categories: light, SMT and heavy components. The classication of
components soldered to this card, is presented in Figure 4.12.
Figure 4.12: Components classication of the OBC 2 card
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