7 Ways to Quickly Judge the Quality of Circuit Board Design (Part 6)

6-Trace width and routing

The size of the traces carrying large currents should be adjusted appropriately. Figure 2 below shows the IPC (Printed Circuit Research Institute) recommended trace (sometimes called trace) width for different rated currents:

Due to noise pickup issues, traces carrying small analog signals should not be parallel to traces carrying digital or rapidly changing signals.

7-Ground and ground

For any moderately complex PCB, it is best to use at least a four-layer board, with two inner layers for power and ground. If the design contains both analog and digital parts, the ground plane should be separated and connected only at the common point (usually the negative pole of the power supply). This can prevent the large ground current spike from the digital part from adversely affecting the analog part.

If only two layers are used, the ground return traces of each sub-circuit should be separated, and then all of them should be connected to the negative terminal of the power supply. As shown in Figure 3 below, it is a bad design to connect the ground loop of any sub-part or IC to a common ground loop path and then return to the negative pole of the power supply.

The problem here is that PCB copper traces do have a certain resistance. Therefore, the current through the trace will cause the voltage to drop. In the example above, the chip at the far right of the trace will see that its ground reference voltage is higher than the actual ground reference voltage. Moreover, its ground will bounce according to the return current of all the chips on the left in the figure.

In conclusion

Whether you are learning to design your own PCB or plan to outsource it to an electrical engineer, you need to be able to judge the quality of the PCB design. If you have no design experience and outsource PCB design, then please pay attention to the seven aspects highlighted in this article to determine whether your engineer is worth your effort. In fact, if they do not meet any of these seven criteria, then I suggest you consider looking for a new designer. On the other hand, if you want to design your own PCB, make sure to avoid these common mistakes. In any case, it is always a good idea to have a complete design review by an independent engineer before proceeding with PCB proofing development.