6 Horribly Common PCB Design Mistakes

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For newbies, showing some KiCAD or Fritzing examples to illustrate how the mistakes look and how it should look would really help.

Back in 2001, I was employed (by a UK based German company) as a PCB pre--production proof reader engineer, as in I checked over client's PCB designs before they were committed to production. I would then send them back a detailed report highlighting all the errors that needed fixing before actual production (in German or French). Apart from the occasional "forgot to send a mirrored image for the bottom (underside) of the PCB, ignorance of Kirchoff's Law regarding trace current limits, thus creating adhoc PCB trace fuses, was more common than you'd expect. One memorable designer expected to push just over 4 Amps through a power return T10 trace, which he'd narrowed in order to squeeze it past a component. Not all were bad, as some PCB designs were perfectly designed. It was the terrible ones that were hard work. those clearly designed by an inexperienced rookie, usually with every fault that you listed on one PCB. These could take one or two days to scrutinise. I'm just glad that I don't have to do that job anymore as I'm now retired, due to Parkinson's disease.

After 15 years of PCB design under my wings, with defense and aerospace projects. Comparing myself to my beginner days I would say a large part of these are for advanced designs and generally won't be understood by beginners. One of the most basic and important one to immediately start following is even if you don't understand exactly why is USE decoupling capacitors and place the decouling caps close to the sourcing and loading devices (ie. linear regulator's input and output and microcontroller's power pins). Explaining ground currents and planes is mostly going to be too much, when you're just focusing on getting the correct components into the schematic based on what you have available or are planning to buy, connecting them and then transferring that to the physical reality in the layout side and double checking that you used the correct packages and pinouts. I have made many mistakes over the years, some critical and some that could be fixed with a botch wire, but I kept at it, learned from my mistakes, learned to diagnose and find the problems and fix them for the next board version. Find an interesting project that feels challenging, but preferrably no overwhelming for your skill level and start making!

Excellent video, just one thing I usually advise is to keep a single ground plane for beginners. I have seen way too many digital signals crossing split ground planes and causing EMI, while in most circuits with a proper, single ground plane digital noise does not travel far enough to affect the analog signals.

At 4:30, actually, we don't call trace length equalization lines "delay lines" we call them "serpentine lines", yes they both "delay" a signal using length, but delay lines is a term reserved for components (not traces) that delay a signal in various ways.

Always make sure the area on the top equals the area on the bottom. A mismatch can cause serious problems.

Great video! Splitting ground planes is a complex issue. I default to not splitting the planes even for sensitive mixed signal boards.

Sharp corners are generally fine < 1 GHz or so. Multiple capacitors are generally just a holdover from THT days where there was significant inductance within the cap. These days, use the largest value for the package that's reasonable. Sometimes going up a package size gives you more options.

I’m so glad I’m only a software engineer. You guys are kings among kings.

This was very good. After doing PCB design for years on RF circuitry, I still learned something. I haven't really given it much thought about proximity of inductors. Just positioning.

I really appreciate the effort you've put into creating content on PCB design. While watching, I felt that this video was a bit on the general side and contained some outdated myths - something I've often experienced when seeking information (and mostly in official datasheets). However, I understand that catering to a broad audience can sometimes necessitate this approach - it's easy to follow for new PCB designers. I'm always on the lookout for more in-depth material, much like videos from Altium Academy, Rick Hartley, and Eric Bogatin. Their experienced insights often leave me in awe. In future videos, it would be fantastic to see topics like choosing specific components for different circuits or an explanation of component parameters, or about situations where you can't follow all good practices and have to make compromises. Such content could provide valuable, detailed knowledge for other PCB design enthusiasts like me. Looking forward to exploring your other videos and seeing what else I can learn. Thanks for your contribution to the PCB community!

I came across a memorable one back in the 1980s. A computer video card, complete with "QC" sticker which had a copper bridge (unetched) between two tracks underneath the solder mask. A few seconds with a sharp scalpel took care of it and the card was working. How it passed quality control remains a mystery. A different one, this time heat-related I discovered in a guitar amplifier. The board was mounted vertically with the power amp heatsink placed directly below an LDR which served as the modulation element for the tremolo. Guess what happened to its resistance when the heatsink got hot. Yep, the amp faded out even when the tremolo wasn't in use; the modulating LED was simply switched off leaving the LDR in-circuit. There are many other design blunders I could list - too numerous to mention.

If one has the analog in one section of the board (say one corner or edge) without digital signals or ground returns running through them, than separating the analog ground is unnecessary--at least for boards I've made (which admittedly are not very high speed).

Both AD and TI recommend in their application notes to use a solid ground plane and only separate the circuits, obviously not routing any of the digital signals in the analog section and vice versa. I can't see why I should separate those sections* if located properly and distance is big enough. It's not like fast digital return current start flowing in the analog part of the circuit just to take the path of larg(er) impedance?! Also, routing the digital signals to ADCs/DACs and not having a ground plane underneath would be a big no-no. So at least this point has to be made very carefully - and I feel more nuanced than in this (admittedly short) video. I'd be really interested in hearing your take on that. * For precision analog circuits I see why having a solid ground plane (only?) might be an issue, regardless of whether there are digital circuits on the same board/connected to the ground plane. And what about circuits with multiple ("precision") ADC/DACs? Star grounding like on the demo boards doesn't work, ground planes might be problematic as well.

thanks , now i will have to watch all of your videos. needed this

I fall into the novice/enthusiast category and I deal with a mix of analog circuits and digital. A watched a video on altiums channel a while back where if you have signals above 100kHz the ground signal return will try and return as close to the signal trace as possible. If you have a ground plane on a 2 layer board that ground plane is 1.6mm from the signal trace. Any other trace closer to than 1.6mm to the signal trace will instead carry the ground return for that signal. I redesigned to put explicit ground traces on the same layer either side of and as close to my important analog signal traces. The noise reduction in the signals was amazing.

I don't main English language but I understand over 90% of your video without sub. That's great! You speak and explain are great

Pop up in my feed. Great video. I design pcb many years ago in my first job, now im still making electronics as hobby projects. My best solution to avoid problems i to print every layer from gerber on foil, an check using window as backlight. Thanks for sharing :)

This is actually so nice, to many common mistake videos are honestly something useless and don't pertain to people that already have the bare minimum knowledge. Will definitely reference this in the future as I learn :) Also, when you mentioned placing inductors perpendicular to each other my first thought was of accidentally making a Halbach array and making the problem even worse lmao.