LAUFFER presses here list some of the most frequently encountered PCB laminate problems and how to confirm them. Once encountering PCB laminate problems, you should consider adding to the PCB laminate specification.

 

 

    1. A reasonable trend:

 

 

    Such as input / output, AC / DC, strong / weak signal, high frequency / low frequency, high voltage / low voltage, etc., their directions should be linear (or separated), and they must not blend with each other. The purpose is to prevent mutual interference. The best direction is to follow a straight line, but it is generally not easy to achieve. The most unfavorable direction is a ring. Fortunately, isolation can be set to bring about improvement. For DC, small signal, low voltage PCB design requirements can be lower. So "reasonable" is relative.

 

 

    2. Choose a good grounding point:

 

 

    I do n’t know how many engineers and technicians have discussed it for a small grounding point, which shows its importance. In general, common ground is required. For example, multiple ground lines of the forward amplifier should be merged and then connected to the main line ground. In reality, it is difficult to do it completely due to various restrictions, but you should try your best to follow it. This problem is quite flexible in practice. Everyone has their own set of solutions. It is easy to understand if it can be explained for a specific circuit board.

 

 

    3. Reasonably arrange the power filter / decoupling capacitor:

 

 

    Generally, only a few power supply filter / decoupling capacitors are drawn in the schematic, but it is not indicated where they should be connected. In fact, these capacitors are set for switching devices (gate circuits) or other components that require filtering / decoupling. Arrange these capacitors as close to these components as possible. They will have no effect if they are too far away. Interestingly, when the power filter / decoupling capacitors are properly arranged, the grounding point problem is less obvious.

 

 

    4. The lines are particular:

 

 

    If conditions permit to make wide lines, never make thin lines; high-voltage and high-frequency lines should be rounded, without sharp chamfers, and no right angles should be used for turning. The ground wire should be as wide as possible, it is best to use a large area of ​​copper, which has a considerable improvement on the ground point problem.

 

 

    Although some problems occur in post-production, they are brought by PCB design. They are: there are too many via holes, and the hidden danger will be buried if the copper sink process is a little careless. Therefore, the design should reduce the number of via holes as much as possible. The density of the lines in the same direction is too large, and it is easy to connect them into one piece when welding. Therefore, the linear density should be determined according to the level of the welding process. The distance of the welding spot is too small, which is not conducive to manual welding, and the welding quality can only be solved by reducing the work efficiency. Otherwise it will leave hidden dangers. Therefore, the determination of the minimum distance of the welding spot should take into account the quality and ergonomics of the welding personnel. The size of the pad or wire hole is too small, or the size of the pad and the size of the drill hole are not properly matched. The former is not good for manual drilling, and the latter is bad for CNC drilling. It is easy to drill the pad into a "c" shape, and then the pad is drilled off. The wire is too thin, and the large area of ​​the unrouted area is not provided with copper, which is likely to cause uneven corrosion. That is, when the non-wiring area is corroded, the thin wires are likely to be over-corroded, or seem to be broken, or completely broken. Therefore, the role of copper is not only to increase the area of ​​the ground wire and to prevent interference. (LAUFFER press)