Via is one of the important components of multi-layer PCB, and the cost of drilling usually accounts for 30% to 40% of PCB manufacturing cost.
From a design point of view, a via is mainly composed of two parts, one is the drill hole in the middle, and the other is the pad area around the drill. The size of these two parts determines the size of the via. .
Obviously, in high-speed, high-density PCB design, designers always hope that the smaller the via hole is, the better, so that more wiring space can be left on the board. In addition, the smaller the via hole, the parasitic capacitance of its own. The smaller it is, the more suitable it is for high-speed circuits.
However, the reduction in hole size also brings about an increase in cost, and the size of vias cannot be reduced indefinitely. It is limited by process technologies such as drilling and plating: the smaller the hole, the more drilling The longer the hole takes, the easier it is to deviate from the center position; and when the depth of the hole exceeds 6 times the diameter of the drilled hole, it cannot be guaranteed that the hole wall can be uniformly plated with copper.
