In a multi-layer printed circuit board (PCB), the small holes that provide the electrical connection between the layers are called Via. Holes are drilled through the board on the different layers of the circuit board and made conductive by electroplating or by placing a copper cylinder in the hole. Using via makes it possible to design complex circuits and reduce PCB size.
Via basically consists of three components. These; The conductive barrel that fills the hole, pad that connects the ends of the barrel to the tracks and components, and the antipad that separates the barrel from the non-connecting layers. The inside of the via is usually filled with a non-conductive material. This material is in most cases air.
Three main types of vias are used in printed circuit boards: through via, blind via, and buried via.
Through via is a type of via that is created by drilling the entire circuit board and can be used to connect all layers. It is the easiest to make and the most common to use.
Blind via is a type of via that connects the outermost layer of the circuit board to the next layer. It is called a blind via because it is exposed only on one side of the PCB and not on the other.
Buried via is a type of via that starts at one of the inner layers of the circuit board and ends at another inner layer. It is used to connect the inner layers of the PCB and is not visible on the circuit surface.
Through vias are very easy to detect with the naked eye as they pass light from one side to the other. Blind vias and buried vias are more difficult to detect.
The via size is determined during the PCB design process. The smallest drill size used by the PCB manufacturer should be learned before determining the via diameter. The diameter of standard mechanical drills is usually over 0.3 mm. Therefore, the via drawn in the circuit design must have a hole of at least 0.3 mm in diameter. The via pad should be twice the size of the hole.
In case of a simple single layer circuit board, vias may not be needed. The via should be used when it comes to a multi-layered and more complex circuit. In recent years, the use of via has become widespread due to the increasing integration density of electronic components and the need for complex circuits.
