The printed circuit board, or PCB, is the flat surface containing all the wiring and components of electronic devices. PCBs are layered in order to increase capacity, with small openings known as vias between the layers. Vias provide more connections which translates into a more effective PCB. Different types of vias are used, with each one serving a different purpose.
Standard Via
A standard via, usually referred to as just a via, starts at one end of a multilayered PCB and continues all the way through the layers until it reaches the other end. The via's purpose consists of providing a means for the trace, a strip of metal, to make electrical connections within the PCB. A standard via is used when the designer of the PCB needs to send a connection, generally a trace made of copper, in a straight line all the way through the layers. As PCBs contain more layers, the via becomes more important as a conduit for the electrical connection from one layer to another.
Buried Via
When designing a PCB it sometimes becomes necessary to make connections within the board without exposure to either end. A buried via provides the means to accomplish this. A buried via runs vertically between the internal layers, starting below the top of the PCB and ending above the bottom. This allows for trace connections between as many layers as desired within the internal structure of the PCB.
Blind Via
On occasion a via is needed to start at one end of the PCB, either the top or bottom, and then stop somewhere in the middle without reaching the other end. A blind via does just that. The length of the via and how many layers it crosses all depend on the connection needed by the designer. A PCB can have more than one blind via, with one at the same spot on opposite ends that head towards each other but never touch.
Thermal Via
Thermal vias are used to transfer heat from the top copper layer in a PCB to internal or bottom layers. Well placed vias provide the means to maximize heat transfer within the PCB..
Tented Via
Also known as a capped via or cap plating, this type of via has a dry film solder mask placed over it. The mask, or cap, prevents leakage and is used when the demands of the electrical or thermal components require protection.
