*4.4.1 Manufacturing process of vias*

Although soldering and fencing vias have different purposes, from the manufacturing point of view, both are metallized holes along the surface layers.

Soldering vias: Soldering vias are metallized holes used to fill in with soldering paste instead of spreading along the layers or to be used as a leak for excessive soldering paste.

Fencing vias: To assure a good isolation of the prototype, sometimes it is necessary to use fencing vias that work as a perfect electromagnetic wall [15], and whose diameter changes with the frequency at which the prototype is designed and the technology used. Fencing vias must be metallized; otherwise, the prototype will have big losses due to the resonant effect of these holes.

These metallized elements can work as resonators if the wavelength of the prototype is similar to the size of these vias, the same happens with the separation between them. The vias must follow these rules and use the formulas for SIWs design [15]:


**Figures 16** and **17** show an schematic view of fencing vias located around cavities. The layer in **Figure 16** has holes for alignment purposes (blue), vias (purple), and the inner cavity (yellow) named as *long*. In the example of **Figure 17** a separation of 0.1 mm toward the cavity was chosen to fulfill the requirement explained above.
