How to avoid the negative effects of vias in high-speed PCB design
The basic concept of vias
Via is an important part of multilayer PCB. The cost of drilling usually accounts for 30% to 40% of the cost of PCB. Simply put, each hole on the PCB can be called via. From a functional point of view, vias can be divided into two categories: one is used as an electrical connection between layers， the other is used for fixing or positioning devices. In terms of technology process, these vias are generally divided into three categories, namely blind vias, buried vias, and through-hole. The blind holes are located on the top and bottom surfaces of the printed circuit board and have a certain depth. They are used for the connection between the surface layer circuit and the inner layer circuit below. The depth of the hole usually does not exceed a certain ratio (aperture). Buried hole refers to the connection hole located in the inner layer of the printed circuit board, it will not extend to the surface of the circuit board. The above two types of holes are located in the inner layer of the circuit board, which is completed by a through-hole molding process before lamination, and several inner layers may be overlapped during the formation of the via hole.
