A via (Latin for path or way) is an electrical connection between copper layers in a printed circuit board. Essentially a via is a small drilled hole that goes through two or more adjacent layers; the hole is plated with copper that forms electrical connection through the insulation that separates the copper layers. Vias are important for PCB manufacturing. This is because the vias are drilled with certain tolerances and may be fabricated off their designated locations, so some allowance for errors in drill position must be made prior to manufacturing or else the manufacturing yield can decrease due to non-conforming boards (according to some reference standard) or even due to failing boards. In addition, regular through hole vias are considered fragile structures as they are long and narrow; the manufacturer must ensure that the vias are plated properly throughout the barrel and this in turn causes several processing steps. In printed circuit boards In printed circuit board (PCB) design, a via consists of two pads in corresponding positions on different copper layers of the board, that are electrically connected by a hole through the board. The hole is made conductive by electroplating, or is lined with a tube or a rivet. High-density multilayer PCBs may have microvias: blind vias are exposed only on one side of the board, while buried vias connect internal layers without being exposed on either surface. Thermal vias carry heat away from power devices and are typically used in arrays of about a dozen. A via consists of: Barrel — conductive tube filling the drilled hole Pad — connects each end of the barrel to the component, plane, or trace Antipad — clearance hole between barrel and metal layer to which it is not connected A via, sometimes called PTV or plated-through-via, should not be confused with a plated through hole (PTH). Via is used as an interconnection between copper layers on a PCB while the PTH is generally made larger than vias and is used as a plated hole for acceptance of component leads - such as non-SMT resistors, capacitors, and DIP package IC. PTH can also be used as holes for mechanical connection while vias may not. Another usage of PTH is known as a castellated hole where the PTH is aligned at the edge of the board so that it is cut in half when the board is milled out of the