Component mounting hole diameter should match the element lead wire diameters better, so that the diameter of the mounting holes slightly larger than the diameter of the component leads (0.15~0.3) mm. DIL packages usually pins and the vast majority of small component using the 0.8mm aperture, pad about 2mm in diameter. For a large aperture in order to obtain a better adhesion of the pad, pad diameter of the aperture ratio, for glass epoxy base approximately 2, cardboard base and phenol should be (2.5~3).
Through-hole, are generally used in multilayer PCB, it is the smallest available diameter and thickness of the substrate, usually through-hole diameter and the thickness of the substrate than is 6:1. High speed signals, through-hole (1~4) nH inductors and (0.3~0.8) pF capacitive path. So when laying when the high-speed signal path, the hole should be kept to an absolute minimum. For high-speed parallel lines (such as address and data lines), if the change is inevitable, and should ensure that the number of holes of each signal line. And should try to reduce the number of through-hole, printed wire protection ring if necessary or protection line to prevent oscillation and improve performance.