TECHNOLOGY THURSDAY!
Via filling is a special technology in PCB production in which vias are completely filled with a dielectric. Optionally, this surface is also metallised. We use a resin for filling that is cured in a thermal process. Via filling is not to be confused with via plugging, where the vias are only sealed on the surface on one side of the PCB.
Via filling offers the possibility of using vias as connection pads for electronic components. This offers PCB designers more space on the PCB surface and a higher degree of freedom when placing components. In addition, the filling material prevents solder from flowing over the hole or air pockets from forming when soldering the components.
More about via filling and a video can be found here:
https://www.eurocircuits.com/what-is-via-filling/