Electronic Design - Experience exchange: some experience on PCB design

Experience exchange: some experience on PCB design

This is a big problem. Let us put aside other factors and share the following lessons for reference for PCB board processing design.

1. Reasonable arrangement of filter/decoupling capacitors: In the general schematic diagram, only a few filter/decoupling capacitors are shown, and it is not shown where they should be connected.

In fact, these capacitors are designed for switching devices (gate circuits) or other components that require filtering/decoupling. They should be as close as possible to these components, if they are too far apart, they will not work. Interestingly, when the filter/decoupling capacitors are properly arranged, the grounding point problem becomes less obvious.

2. Lines should be picky: if conditions permit, wide lines should not be too thin; high-voltage and high-frequency lines should be flat, do not chamfer, do not use right angles. The grounding wire should be as wide as possible, and it is best to use a large area of copper plating, which greatly improves the problem of grounding points.

3. There should be reasonable trends, such as input/output, AC/DC, strong/weak signal, high/low frequency, high/low voltage, etc. Their trends should be linear (or independent) and should not be mixed. Its purpose is to prevent mutual interference. The best trend is to go straight, but it is generally not easy to achieve. The most unfavorable trend is looping. Fortunately, isolation can bring improvements. PCB design requirements for DC, small signal and low voltage can be reduced. Therefore, "reasonable" is relative.

4. Choose a good grounding point: I don't know how many engineers and technicians have discussed a small grounding point, which shows its importance. Generally speaking, it is necessary to have a common foundation, for example: multiple ground wires of the forward amplifier should be combined with the main wire. In reality, due to various restrictions, it is difficult to achieve this completely, but we should try our best to achieve this. This question is very flexible in practice. Everyone has their own solution. If you can explain it with a specific board, it is easy to understand.

5. Although there were some problems in post-production, these problems were caused by PCB design. They are: too many holes, a little careless copper sinking process will bury hidden dangers. Therefore, the through holes should be minimized when designing. Parallel lines in the same direction are too dense and easy to connect together during the welding process. Therefore, the linear density should be determined according to the level of the welding process. The solder joint spacing is too small, which is not conducive to manual soldering. Welding quality problems can only be solved by reducing work efficiency. Otherwise, there will be hidden dangers. Therefore, the quality and efficiency of the welding machine should be considered to determine the minimum distance of the solder joint.

6. The size of the partition or the through hole is too small, or the size of the partition does not match the size of the hole. The former is not conducive to manual drilling, and the latter is not conducive to CNC drilling. It is easy to drill the cushion into a "c" shape, but the heavy drill cushion will come out. The conductor is too thin, the unpacking area is large, the unplated copper layer is not fixed, and it is easy to cause uneven corrosion. That is, after the corrosion of the wireless area is completed, the thin wire is easily eroded or broken or completely broken. Therefore, the role of copper plating is not only to increase the grounding area and anti-interference ability. These factors will greatly reduce the quality of circuit boards and the reliability of future products. ipcb is a high-precision, high-quality PCB manufacturer, such as: isola 370hr PCB, high-frequency PCB, high-speed PCB, ic substrate, ic test board, impedance PCB, HDI PCB, Rigid-Flex PCB, buried blind PCB, advanced PCB, microwave PCB, telfon PCB and other ipcb are good at PCB manufacturing.