In the years of working with hardware entrepreneurs, we have seen too many cases of poorly designed printed circuit boards (PCB), which can never meet the quality requirements of commercial production.

In some cases, these committees are designed by the entrepreneurs themselves, and sometimes by freelance engineers.

In particular, if you want to hire imaginary experts to design PCBs, it is important to be able to judge the quality of their work.

As I think many electrical engineers will agree, most engineers have never taught PCB design in school, so be sure to avoid hiring engineers who lack actual PCB design experience.

Although PCB design experts do need to conduct a proper and complete design review, there are still ways to quickly judge the quality of a PCB design.

The schematic can tell you how to connect the various components together to provide a given function. However, on its own, it provides very limited information on how to actually place and connect the components together to provide a functional product.

For example, the schematic lines are converted to traces on the printed circuit board (PCB). However, unless it is clearly recorded in the schematic, the schematic will hardly provide information about the types of signals carried by these lines.

This schematic document is especially important if the PCB layout is designed by an engineer who is different from the engineer who designed the schematic.

The signals in these lines may be low-level, low-noise signals, which must be led away from the noisier circuit board traces to avoid noise.

Or, they may be fast data or clock signals, which fan out to many pins on multiple chips. In this case, the length of the trace should be matched and kept short to avoid delay mismatch.

If these traces are not designed correctly, some circuit boards may work, and some may not work, depending on the characteristics and tolerances of the components used to fill each circuit board.

In other words, even if the circuit board faithfully implements the interconnection of all the components of the complete working schematic, the final product may not work as expected.

This article introduces 7 ways to quickly judge the quality of PCB design.

The focus here is on layout and component placement, not the actual quality of the circuit board structure itself (it all depends on the circuit board manufacturer).

Finally, this article is not intended to be highly technical, and certainly will not cover all possibilities, especially for highly complex designs or designs with unique requirements.

The purpose of this article is to show you how to quickly determine whether you have a bad PCB design, because there are certain areas in PCB design, and new designers are most likely to do these things wrong.

#1-Circuit board routing

Take a look at the visible traces on the circuit board in general. These will be covered by solder resist, which is a thin layer of lacquer-like polymer, covering the copper traces to prevent oxidation and short circuits.

This layer is usually green, but other colors can also be used. Please note that the white solder mask tends to make the traces the hardest to see. In most cases, just use standard green.

In addition, only the top and bottom layers are actually visible, and if the board has more than two layers, you will not see the inner layers. Nevertheless, reviewing only the external layer should still provide some clues about the quality of the design.

First, check to see if all traces extend in straight segments without sharp bends. Sharp angles may cause trouble for certain high-power and high-frequency traces.

Rather than trying to determine which traces can be bent 90 degrees, it is better to avoid them. In any case, most CAD PCB layout software packages can be set up to avoid this problem.

Please note that there are some exceptions. Some printed inductors are square concentric spirals, and some printed antennas have sharp bends. However, both of these are easy to identify.

#2-Decoupling capacitor

All chips need a power supply to function, but what happens if the power supply is a certain distance away from the chip that needs it? In these cases, the chip must be powered through the circuit board traces (although usually through the PCB power board on the inner layer).

The location of the decoupling capacitor is very close to the power pin of the chip to filter out the negative effects of high-frequency noise on the chip.

Generally, if a chip has multiple VDD pins, each such pin needs at least one decoupling capacitor, and sometimes more.

The physical location of these decoupling capacitors should be very close to the pins to which they should be decoupled. If this does not happen, then its effect will be greatly reduced.

If your PCB design does not place decoupling capacitors next to the power pins of most microchips, then your design has not been completed correctly.

If you hire someone to design the PCB, but they did not handle the decoupling capacitors properly, then you should find a new designer.

#3-PCB trace length is balanced

In designs that require precise timing relationships between multiple signals, the length of the PCB traces must match. For example, this is critical when routing high-speed clock signals to multiple chips or data and address buses that run between a microprocessor and RAM memory.

This ensures that all signals arrive at their destinations with the same delay, thus preserving the relationship between signal edges. This requires access to the schematic and to know which set of signal lines requires precise timing relationships.