Blind and buried vias are used to connect the layers in the particularly dense design (HDI).

Blind vias are exposed only on one side of the board,
while Buried vias connect internal layers without being exposed on either surface.

In Brandner we drill blind and buried vias mechanically to ensure the quality of the holes.

For blind vias it is vital to maintain an aspect ratio of 1:1, which means that if blind drills are used, the drilling depth has to be less or equal to the diameter of the drill.

Please do not forget it when planning a stackup for a board with blind vias.