Experience Exchange Some Thoughts on PCB Design

writer: G January 29, 2018

1. Reasonable arrangement of the power supply filter / decoupling capacitor: 

Generally only a few power supply filter / decoupling capacitors are shown in the schematic, but they are not specified where they should be connected. In fact, these capacitors are for switching devices (gates) or other components that need to be filtered / decoupled. The layout of these capacitors should be as close as possible to these components, and moving them too far will have no effect. Interestingly, when the power filter / decoupling capacitor layout is reasonable, the problem of grounding point becomes less obvious.

2. Lines are exquisite: 

The conditions of a wide line never thin; high-pressure and high-frequency line should be parked slippery, may not have a sharp chamfer, turning can not be used at right angles. Ground should be as wide as possible, the best use of large area copper, the docking problem has a considerable improvement.

3. There should be a reasonable direction: 

Such as input / output, AC / DC, strong / weak signal, high frequency / low frequency, high pressure / low pressure ... their direction should be linear (or separation) blend. Its purpose is to prevent mutual interference. The best way is by straight line, but generally not easy to achieve, the most unfavorable direction is ring, but fortunately can be set to improve the isolation. For DC, small signal, low voltage PCB design requirements can be lower. So "reasonable" is relative.

4. Choose a good grounding point: 

A small grounding point, I do not know how many engineers and technicians have done much discussion of it, indicating its importance. Under normal circumstances require a total of points, such as: forward to the amplifier should be merged after a number of ground and then connected to the trunk and so on .... In reality, due to various restrictions is difficult to fully handle, but should try to follow. This problem is quite flexible in practice. Everyone has their own set of solutions. It's easy to understand if you can interpret it for a specific circuit board.

5. Although some problems occur in the post-production, but it is brought in the PCB design, they are: 

Too many wire holes, copper sinking a slight careless process will be buried potential problems. Therefore, the design should minimize the hole hole. Parallel with the line density is too large, it is easy to connect into a soldering. Therefore, the linear density should be determined by the level of welding process. Solder the distance is too small, is not conducive to artificial welding, only to reduce the work efficiency to solve the welding quality. Otherwise it will leave hidden dangers. Therefore, the minimum solder joint distance should be determined considering the quality of welding personnel and ergonomics.

6. The size of the pad or wire hole is too small, or the size of the pad and the hole size are not properly matched. 

The former is unfavorable to manual drilling, which is disadvantageous to CNC drilling. Easy to drill pad into a "c" shape, while drilling off the pad. The wire is too thin, and large area of ??the wiring area is not set with copper, easily lead to uneven corrosion. That is, when the wiring area is not corroded, the fine wire is likely to corrode too much, or like a broken off, or completely broken. Therefore, the role of setting copper is not only to increase the ground area and anti-jamming. Many of the above factors are detrimental to the quality of the board and the reliability of future products.