The printed circuit board, or PCB, is responsible for connecting all the components with each other, so making even a single error in the design could lead to complete failure. That being said, mistakes are not unlikely for even experienced PCB designers, so if you are relatively new to it, you should try and avoid making the following five common mistakes.
Narrow High Current Traces
The minimum width necessary for traces will not be sufficient anymore once the amount of current which the trace must handle starts to cross the 500mA mark. In other words, a narrow high current trace is a bad idea, especially if it happens to be an inner trace. Traces on the outside have the advantage of receiving better air flow and thus, better heat dissipation. As the internal traces do not have that advantage, they need to be wider to compensate for that.
Incorrectly Placed/Routed Decoupling Capacitors
Decoupling capacitors are typically used on the power supply rail of the PCB to help facilitate the availability of clean and stable power for all important components on the board. If you do not make sure that the power line from the source is routed to the decoupling capacitor first and then to the pin which requires the stabilization, the process fails. Also, in order to maximize the capacitors, they should be placed as close to the component pins as possible.
Landing Pattern Errors
All it needs is an error of half a millimeter or less while measuring the pad to pad spacing and it will become unfit for soldering during the manufacturing process because the pins won’t align. High quality PCB designing software like Altium has a very vast collection of schematic symbols and PCB landing patterns for each component that you can trust, and using them eliminates the chances of such errors. If by chance the component in question is not included in the software’s libraries, you need to be extra careful while manually drawing the landing patterns and marking the schematic symbols.
Incorrect Antenna Layout
In case you are trying to design a PCB for something that uses antennae for wireless communications, you need to be careful of not making a faulty layout. Check out the following tips to avoid this mistake which is extremely common.
- Match the complex impedance of the transceiver and the antenna for maximum power transfer
- The transmission line connecting the transceiver and the antenna should have 50 ohm impedance in general
- An LC pi-network or any other matching circuit is to be placed between the antenna and the transceiver for fine tuning the impedance of the antenna
Long High-Speed Traces
It should be obvious that all high-speed signals on your PCB design are to be as short and as straight as feasible. If it’s longer than it should be, the design poses the following issues.
- The risk of electromagnetic Interference or EMI is significantly increased
- Sensitive circuits are affected because of the resulting EMI
- Longer traces also add to the expense, in addition to reducing efficiency and generating EMI
It would be incorrect to state that these are the only mistakes that PCB designers end up making, but if you manage to avoid these five, you are already ahead of most beginners. Nevertheless, it might be a good idea to get a design review from someone else before sending it to manufacturing.