Blind and buried vias are only available on boards with at least four layers. Unlike regular vias on a two layer board which connect the two surface layers, buried and blind vias connect the inner layers with either other adjacent inner layers or adjacent surface layers.
Blind Vias: Connects an inner layer with the adjacent surface layer, they are only visible on one side of the boards and so are called 'blind' vias.
Buried Vias: Connects two adjacent inner copper layers. They are not visible from the surface and so are 'buried'.
Advantages and disadvantages
Using blind and buried vias in a PCB design has its advantages and disadvantages. The advantage, of course is that this technology offers a viable design technique to help meet the density constraints of lines and pads on a typical design without increasing the layer count or board size. The disadvantage of the technology is that due to the additional operations in manufacturing the board, the cost of a board using blind and/or buried vias is significantly higher than a typical multilayer board with the same number of layers.
Peck Drilling Blind Vias
Drill depth is extremely important in vias, because going too shallow or too deep can have a dangerous impact on the board. You can also create spurs and rough edges that cause issues if you’re not being careful.
That said, companies can reduce cost with blind vias if they’re made through peck drilling. Peck drilling plunges the drill into the board multiple times in order to remove material buildup and prevent rough spots. Turn to PCBWay to use peck drilling, because we can prevent air from being trapped during the process, so that plating is always applied and properly connects to internal layers.