The PCB circuit board is the basic electronic component of all electronic circuit designs. As the main support, it carries all the components that make up the circuit. The role of PCB is not only to combine scattered components, but also to ensure the regularity of circuit design, which avoids the confusion and errors caused by manual wiring and wiring.
This article gives a detailed introduction to the five key design points of the PCB circuit board in the power supply design.
1. There must be a reasonable direction
Such as input/output, AC/DC, strong/weak signal, high frequency/low frequency, high voltage/low voltage, etc. Their direction should be linear (or separated) and must not blend with each other. Its purpose is to prevent mutual interference. The best direction is a straight line, but it is generally not easy to achieve. The most unfavorable direction is a circle. Fortunately, isolation can be set to improve. For DC, small signal, low voltage J voltage PCB design requirements can be lower. So "reasonable" is relative.
2. Choose a good grounding point: the grounding point is often the most important
I don’t know how many engineering and technical personnel have done a lot of discussion on the small grounding point, which shows its importance. Generally, a common ground is required, for example, multiple ground wires of the forward amplifier should be merged and then connected to the trunk ground, etc. In reality, it is difficult to do it completely due to various restrictions, but we should try our best to follow it. This problem is quite flexible in practice, everyone has their own set of solutions, and it is easy to understand if it can be explained for a specific circuit board.
3. Reasonable arrangement of power filter/decoupling capacitors
Generally, only a few power filter/decoupling capacitors are drawn in the schematic diagram, but it is not indicated where they should be connected. In fact, these capacitors are set up for switching devices (gate circuits) or other components that require filtering/decoupling. Arranging these capacitors should be as close as possible to these components. If they are too far away, they will have no effect. Interestingly, when the power supply filter/decoupling capacitors are properly placed, the ground point problem is less obvious.
4. The diameter of the line is required, and the size of the buried hole is appropriate.
Lines that are conditionally wide must not be thin; high-voltage and high-frequency lines should be smooth, without sharp chamfers, and corners must not be at right angles. The ground wire should be as wide as possible, and it is best to use a large area of copper, which can greatly improve the problem of the ground point. The size of the pad or via is too small, or the size of the pad does not match the size of the drilled hole properly. The former is not good for manual drilling, and the latter is not good for CNC drilling. It is easy to drill the pads into a "c" shape, and it is heavy to drill out the pads. The wire is too thin, and there is no copper coating in the large area without wiring, which may easily cause uneven corrosion. That is, when the unwired area is corroded, the thin wires are likely to be corroded too much, or they may be broken or completely broken. Therefore, the role of setting the number of copper is not only to increase the ground area and anti-interference.
5. The number of via holes, solder joints and line density
Some problems are not easy to be found in the early stage of circuit production, and they often emerge in the later stage, such as too many wiring holes, and a little careless copper sinking process will bury hidden dangers. Therefore, the design should minimize the number of holes. The density of parallel lines in the same direction is too high, and it is easy to connect together when welding. Therefore, the linear density should be determined according to the level of the welding process. The distance between solder joints is too small, which is not conducive to manual welding, and the welding quality can only be solved by reducing work efficiency. Otherwise there will be hidden dangers. Therefore, the determination of the minimu distance of solder joints should comprehensively consider the quality and work efficiency of welding personnel.
If you can fully understand and master the above PCB circuit board design considerations, you can greatly improve design efficiency and product quality. Correcting existing errors during production will save a lot of time and cost, and save rework time and material input.
