A buried Via means pass through the hole between inner layers of the PCB,

instead of the top and bottom layers, which is used to connect the signals of inner layers.

Application:

it’s widely used in the High density and high speed of PCB design, such as mobile phones and PAD board.

Function:

1)To reduce the rate of signal interference;

2)To maintain the continuity of transmission line about characteristic impedance;

3)To save the routing space.

However, the question is: the cost of buried via is not cheaper actually, which still need to be solved with the aid of the development of drilling technology.