5 points in PCB layout, China PCB manufacturer SysPCB_

5 points in PCB layout

1, Wire layout to be reasonable

Such as input / output, AC / DC, strong / weak signal, high frequency / low frequency, high voltage / low voltage and other lines, their layout is not intermingled, but should be separated, the reason for doing so is to prevent them from causing interference. The best direction is straight, but it is difficult to achieve, the ring wire is the worst choice, we can improve the situation by setting up isolation area. For DC, small signal, low voltage circuit board design requirements can be relatively lower. So we say the reasonable standard relative to different circuit boards are different.

2, a good grounding point is very important

It seems about insignificant grounding point, there are very many engineers and technicians have done a lot of discussion on it, which can see its importance. In general, we require a common point of ground, such as: forward amplifiers of multiple ground should be converged and then connected to the trunk ground, etc.. In practice, due to the influence of various factors, so that we want to do the perfect possibility of constantly reduced, but we should still try to follow the principle. This issue is quite flexible in practice, everyone has a different solution, to the specific circuit board design to explain can be more easily understood.

3, reasonable arrangement of power supply filtering / decoupling capacitors

Generally in the schematic diagram just draw a number of power supply filtering / decoupling capacitors, but did not point out where they should be connected to. In fact, these capacitors are set up for switching devices (gates) or other components that need to be filtered/decoupled, and the arrangement of these capacitors should be as close as possible to these components, too far away to be useful. It is worth mentioning that after the power supply filtering/decoupling capacitors are arranged reasonably, the problem of grounding point will become less obvious.

4, the line wire diameter has the requirement, buried hole and through hole size are appropriate
have the condition to do wide line, never do fine; high-voltage and high-frequency lines should be smooth, can not have sharp chamfer, cornering can not use right angles. The ground line should be as wide as possible, try to use a large area of copper plane, which will have a great improvement on the grounding point problem. Pad or via hole size is too small, or pad size and drilling size mismatch. The former is not good for manual drilling, the latter is not good for CNC drilling. Easy to drill the pad into the "c" shape, in serious conditions drilling off the pad. The wire is too thin, and a large area of the un-wired area and not set copper, easy to cause uneven corrosion. That is, when the unwired area after corrosion, the fine wire is likely to corrode over, or seem to break non-break, or completely broken. Therefore, the role of setting copper is not only to increase the ground area and anti-interference.

5, via holes, solder joints and line density

Some problems of the circuit board design is difficult to be detected in the early stage, they tend to emerge at a later stage, such as too many via holes, lack of attention  in copper plating process will be buried hidden problems. Therefore, the design should try to reduce the via holes. The density of lines in parallel in the same direction is too large, and it is easy to join together when soldering. Therefore, the line density should be determined depending on the level of the soldering process. The distance of welding joints is too small is not good for manual welding, and the welding quality can only be solved by reducing the work efficiency. Otherwise, it will leave hidden problems. Therefore, the minimum distance of the welding point should be determined by taking into account the quality of the welders and work efficiency.