1. Conductor

(1) Width

The minimum width of printed wires is mainly determined by the adhesion strength between the wires and the insulating substrate and the current value flowing through them. The printed wires can be as wide as possible, especially the power wires and ground wires, as wide as possible under the conditions allowed by the board surface, even if the area is tight, it is generally not less than 1mm. Especially the ground wire, even if it is not allowed to be widened locally, it should be widened where it is allowed to reduce the resistance of the entire ground wire system. For wires with a length exceeding 80mm, even if the operating current is not large, they should be widened to reduce the influence of the wire voltage drop on the circuit. Circuit board manufacturers

(2) Length

To minimize the length of the wiring, the shorter the wiring, the less interference and crosstalk, and the lower its parasitic reactance, the less radiation. Especially the gate of the FET, the base of the triode and the high-frequency loop should pay more attention to the short wiring. Circuit board manufacturers

(3) Interval

The spacing between adjacent wires should meet the requirements of electrical safety. Crosstalk and voltage breakdown are the main electrical characteristics that affect wiring spacing. In order to facilitate operation and production, the interval should be as wide as possible, and the minimum interval selected should be at least suitable for the applied voltage. This voltage includes operating voltage, additional swing voltage, overvoltage, and peak voltages that occur for other reasons. When there is mains voltage in the circuit, the interval should be wider for safety reasons.

(4) Ways

The width of the signal path, from drive to load should be constant. Changing the path width changes path impedances (resistance, inductance, and capacitance), causing reflections and creating line impedance imbalances. So, stick to the width of the path unchanged. In wiring, avoid using right angles and acute angles. Generally, the corners should be greater than 90°. The edges inside the right-angle pathway can generate a concentrated electric field, which generates noise coupled to adjacent pathways, and the 45° pathway is superior to the right-angle and acute-angle pathways. When two wires meet at an acute angle, the acute angle should be changed to a circle. Circuit board manufacturers

2. Aperture and pad size

The diameter of the device hole of the component should be well matched with the diameter of the lead wire of the component, so that the diameter of the device hole is slightly larger than the diameter of the lead wire of the component (0.15 ~ 0.3) mm. The pins of general DIL packages and most small components use a 0.8mm aperture, and the pad diameter is about 2mm. Regarding the large aperture pad, in order to obtain better adhesion, the ratio of the diameter of the pad to the aperture should be about 2 for the epoxy glass substrate, and (2.5 to 3) for the phenol cardboard substrate. Circuit board manufacturers

Vias are generally used in multi-layer PCBs. Its smaller diameter is related to the thickness of the substrate. Generally, the ratio of the thickness of the substrate to the diameter of the via is 6:1. When high-speed signals are used, the inductance of (1 to 4) nH and the capacitance of (0.3 to 0.8) pF are generated in the via hole. Therefore, when laying out high-speed signal paths, vias should be kept extremely small. For high-speed parallel lines (such as address and data lines), if layer changes are unavoidable, ensure that the number of vias is the same for each signal line. And the number of vias should be reduced as much as possible, and if necessary, a printed conductor maintenance ring or maintenance line should be set to avoid oscillation and improve circuit function. Circuit board manufacturers