A via is used to make an electrical connection between the layers of a Multi-Layer PCB. Connecting multiple layers of the board make it possible to reduce the size of the PCB. A via is constructed by placing copper pads on each layer of the PCB and drilling a hole through them. The hole is made conductive through electroplating or by placing copper cylinders directly in the drilled holes.

The inner part of the via, is usually filled with a non-conductive material (air in most cases), while the outer layer of the cylinder has a conductive plating which is used to connect each layer of the Multi-Layer PCB.

Note: It is always good to use multiple smaller vias than one large via since it reduces the inductance and also provides an additional path to the current flow if any of the via fails.

Types of Vias

There are three main types of Vias used in a Printed Circuit Board:

Through Hole Via: This Via goes right through the Multi-Layer PCB from top to bottom and can be used to connect all the layers of a PCB. It is the most common via and is easiest to construct.

Blind Via: This Via connects the outer most layer of a PCB to the next layer. It can not be seen on the other side of the board and is therefore called blind via.

Buried Via: This Via can be used to connect internal layers of a PCB. It will not be seen on the surface of the board.