What are the PCB wiring rules? Understand in one article

In our daily lives, printed circuit boards appear in almost every electronic device we come into contact with. If there are electronic parts in a certain device, then they are all mounted on PCBs of different sizes. To get the best performance of the electronic circuit, the layout of the components and the layout of the wires are very important, and the wiring is the top priority of the PCB design process, which will directly affect the performance of the PCB board. Although many advanced EDA tools now provide automatic wiring functions and are quite intelligent, automatic wiring does not guarantee a 100% wiring rate. The distribution rate of automatic routing depends on a good layout. The routing rules can be preset, including the number of bending times, the number of vias, and the number of steps. Generally, explore the warp line first, quickly connect the short lines, and then perform the labyrinth wiring. First, the wiring to be routed is optimized for the global wiring path. It can disconnect the laid lines as needed. And try to re-wire to improve the overall effect. PCB wiring and classification are also the same, divided into single-sided wiring, double-sided wiring and multi-layer wiring, and there are two wiring methods, automatic wiring and interactive wiring. Before automatic wiring, you can use interactive pre-comparison to compare requirements Strictly route the wiring, and the edges of the input end and the output end should be avoided adjacent to parallel to avoid reflection interference. Ground wire isolation should be added when necessary, and the wiring of two adjacent layers should be perpendicular to each other. Parasitic coupling can easily occur in parallel. In PCB layout, it is inevitable that the trace will bend. When the trace has a right-angle corner, additional parasitic capacitance and parasitic inductance will be generated at the corner. The corner of the trace should be designed to be sharp and right-angled to avoid occurrence Unnecessary radiation. Secondly, the connection should be streamlined, as short as possible, with as few turns as possible, and the lines should be simple and clear, especially in high-frequency circuits. Of course, the exceptions are lines that require special extensions to achieve impedance matching, such as snake walking lines. The width of the copper wire should be designed based on the current it can carry. The current-carrying capacity of the copper wire depends on the following factors: wire width, wire thickness (copper platinum thickness), allowable temperature rise, etc. The table below shows the copper The relationship between the width of the wire and the area of u200bu200bthe wire and the conduction current (military standard) can be based on this basic relationship to properly consider the width of the wire. In addition, the minimum width of the conductors of the printed circuit board is mainly determined by the adhesion strength between the conductors and the insulating substrate and the current value flowing through them. The wires used for the input and output terminals should try to avoid being parallel adjacent to each other. It is best to add ground wires between wires to avoid feedback coupling. The minimum spacing of wires is mainly determined by the worst-case insulation resistance and breakdown voltage between the wires. For integrated circuits, especially digital circuits, as long as the process permits, the pitch can be as small as 5-8 mm. The corners of the printed conductors are generally arc-shaped, and the right angle or the included angle will affect the electrical performance in the high-frequency circuit. In addition, try to avoid the use of large-area copper foil, otherwise, the copper foil will easily expand and fall off when heated for a long time. When a large-area copper foil is necessary, it is best to use a grid shape, which helps to eliminate the volatile gas generated by the heating of the adhesive between the copper foil and the substrate. After the wiring design is completed, it is necessary to carefully check whether the wiring design conforms to the rules set by the designer, and at the same time, it is also necessary to confirm whether the established rules meet the requirements of the printed board production process. General inspections: line and line, line and component pads, Whether the distances between lines and through holes, component pads and through holes, and through holes and through holes are reasonable and whether they meet the production requirements. Whether the best measures have been taken for the key signal lines, such as the shortest length, the protection line is added, and the input line and output line are clearly separated. 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