PCB Drilling Holes
PCB drilling hole is an important part for multilayer PCBs. It can be divided into two parts, one is used for electrical connection between each layers; another is used to fix or position the components.
In PCB manufacturing, the holes are mainly divided into three parts, which are blind vias, buried vias and through holes. Blind vias are always fabricated on the top layer and bottom layer of PCB surface in order to connect surface layer and inner layer. Buried vias are always fabricated in PCB’s inner layer, so they can’t extend to the surface of the circuit board. You can find through holes here and there on a PCB, that’s because they are much cheaper as well as easier to fabricate than other two vias.
As to PCB design, the hole is generally divided into two parts, one is the drilling hole in the center area, and another is the pad around the drilling hole. The size of these two parts determine the hole size. For example, when design a high-speed and high-density PCB, the smaller a hole the better, so it can leave more space for circuit layout. But a much smaller means high fabrication cost, because the process needs more time.