The key to double-sided PCB board design

Double-sided PCB boards are the basic electronic components of all electronic circuit design, and the design of PCB circuit boards is also what people in the electronics industry need to understand. Because the role of PCB is not only to combine scattered components, but also to ensure the regularity of circuit design, and it is a good way to avoid confusion and errors caused by manual wiring.

1. The double-sided PCB board must have 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 trend is in a straight line, but it is generally not easy to achieve. The most unfavorable trend is a circle. Fortunately, isolation can be set to improve. For DC, small signal, low voltage PCB design requirements can be lower. So “reasonable” is relative.

2.Double-sided PCB board Choose a good grounding point: the grounding point is often the most important.

I don’t know how many engineers and technicians have talked about the small grounding point, which shows its importance. Under normal circumstances, a common ground is required, such as: multiple ground wires of the forward amplifier should be merged and then connected to the main ground and so on. In reality, it is difficult to achieve this completely due to various restrictions, but we should try our best to follow. This problem is quite flexible in practice. Everyone has their own set of solutions. It is easy to understand if they can explain it for a specific circuit board.

3. Double-sided PCB board, reasonable arrangement of power supply filter/decoupling capacitors

Generally, only a number of power filter/decoupling capacitors are drawn in the schematic, but they are not pointed out where they should be connected. In fact, these capacitors are provided for switching devices (gate circuits) or other components that require filtering/decoupling. These capacitors should be placed as close to these components as possible, and too far away will have no effect. Interestingly, when the power supply filter/decoupling capacitors are arranged properly, the problem of the grounding point becomes less obvious.

3.The line diameter is required, and the size of the buried via and through hole is appropriate

If possible, wide lines should never be thin; high-voltage and high-frequency lines should be round and slippery, without sharp chamfers, and corners should 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 grounding points.

The size of the pad or via is too small, or the size of the pad and the hole size are not properly matched. The former is unfavorable for manual drilling, and the latter is unfavorable for CNC drilling. It is easy to drill the pad into a “c” shape, or drill out the pad.

The wire is too thin, and the large area of the unwired area is not provided with copper, which is easy to cause uneven corrosion. That is, when the unwiring area is corroded, the thin wire is likely to be over-corroded, or it may appear to be broken, or completely broken. Therefore, the effect of setting up copper is not only to increase the area of the ground wire and anti-interference.

5. Number of vias, solder joints and line density

Some problems are not easy to be found in the early stage of circuit production, and they tend to emerge in the later stage.For example, if there are too many wire holes, a slight mistake in the copper sinking process will bury hidden dangers.Therefore, the design should minimize the wire hole. The density of parallel lines in the same direction is too large, and it is easy to connect into one piece when soldering. Therefore, the line density should be determined according to the level of the soldering process. The distance between the solder joints is too small, which is not conducive to manual soldering, and the soldering quality can only be solved by reducing the work efficiency. Otherwise, hidden dangers will remain. Therefore, the minimum distance of solder joints should be determined by comprehensive consideration of the quality and work efficiency of the soldering personnel.

If you want to greatly improve the design efficiency of double-sided PCB boards and the quality of products, you must be able to fully understand and master the above-mentioned double-sided PCB board design precautions. Keep in mind the five key points. It can correct the existing errors in the production, saving a lot of time and cost.

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