From Millimeter Waves to High-Speed ​​Signals: The Pitfalls I Encountered in PCB Board Design

Looking back on those experiences now, they’ve given me a different perspective on electronic products. For instance, many people only focus on processor parameters when changing phones, unaware that the real determinant of stability is often the multi-layered PCB on the motherboard. It requires arranging over a dozen layers of circuitry within a space the size of a fingernail while ensuring high-frequency signals don’t interfere with each other—this is far more difficult than simply stacking hardware specifications.

I’ve seen many DIY enthusiasts spend a fortune on top-of-the-line components, only to have their overall performance compromised due to the use of cheap printed circuit boards. It’s like using a race car engine with bicycle tires—not that the materials are bad, but the components simply don’t work together effectively.

Sometimes, browsing electronics forums, you see people debating which substrate is better for high-frequency circuits. These discussions often overlook a more fundamental issue—good design is always based on trade-offs made for specific application scenarios. Just as you can’t use the same PCB to simultaneously meet the needs of military equipment and smart bracelets, their reliability standards and space constraints are completely different.

Last year, while repairing a friend’s drone, I disassembled its flight control module and saw the complex eight-layer structure. It suddenly dawned on me that the evolution of modern electronics to its current form is not simply a matter of miniaturizing components. Those seemingly ordinary brown boards actually house a complete ecosystem, from power management to signal transmission.

Now, whenever I see a new electronic product released, I pay more attention to its internal layout. Are the heat dissipation holes positioned to avoid critical circuits? These details often reflect the design team’s dedication more than benchmark scores. After all, the moment the chip is soldered onto the printed circuit board is the true beginning of technology implementation.

I’ve always felt that the most fascinating aspect of PCB design lies in the possibilities it brings to electronic products. Remember the green circuit board you saw when you first disassembled an old radio? Those neat lines resembled a city road map. Now, the PCB boards we face have evolved to the point where they can be bent and folded like paper.

Last week, I was particularly struck by this while helping a friend repair a smart bracelet. That flexible substrate, smaller than a fingernail, was covered with lines thinner than a human hair. The biggest advantage of this flexible PCB isn’t the technical parameter of how many times it can be bent, but rather that it truly changes the product’s form factor. You see, the seamless wristband design of today’s bracelets is thanks to this technology.

Regarding the choice of substrate material, I have a different opinion. Many people blindly pursue the latest materials, but ordinary FR-4 substrates are sufficient for most household appliances. Last year, when I assembled my own speakers, I used ordinary fiberglass substrates, and the sound quality wasn’t affected at all; in fact, I saved 30% on costs.

Recently, while researching drone flight control systems, I found rigid-flex PCBs particularly interesting. The motherboard needs to be rigidly fixed, while the part connecting to the camera needs to rotate constantly—this is where the rigid-flex design comes in handy. However, this type of PCB board has very high requirements for soldering processes; even a slight mistake can lead to broken circuits.

I’ve noticed that many engineers tend to get bogged down in technical details, such as obsessing over the exact micrometers of the line width. But in practical applications, the overall layout is more important. I once saw a power module where the high-voltage lines and signal lines were placed too close together, causing interference. This kind of fundamental error is more fatal than failing to meet technical specifications.

Many smart home devices now use metal substrates, which do offer better heat dissipation, but the cost is also higher. I think it depends on the specific application scenario. Devices like routers that are constantly on are worth investing in, while appliances used only occasionally don’t need to pursue extreme heat dissipation.

Recently, while trying to transform an old mobile phone into a smart home hub, I was amazed by the incredible precision of current IC substrates. Looking at those circuits under a microscope is like examining a miniature work of art. However, the price of this precision is that repair is virtually impossible; once damaged, the entire board must be replaced.

In fact, the most important thing in PCB design is spatial imagination—the ability to foresee the three-dimensional assembly effect on a two-dimensional drawing. Once, a board I designed couldn’t be fitted into its casing because I hadn’t considered the component height. This practical experience is more profound than any textbook.

Every time I see my PCB design become a usable product, I feel a special sense of accomplishment. Perhaps this is why I still enjoy drawing circuit diagrams by hand, even though there are many automated routing tools available now. This creative process from scratch is the most captivating part.

Every time I see those complex circuit designs, I think about the space game behind them. We always want to cram more functionality into a limited space, and the emergence of multilayer boards has perfectly solved this dilemma. I remember the first time I disassembled an old radio, the thin PCB inside… The components on the board were pitifully sparse, while nowadays even a casual smartphone motherboard is as intricate as a mille-feuille cake.

Many people fall into the misconception that the more advanced the material, the better. In reality, the key is the application scenario. I’ve seen people use high-frequency specialized boards for ordinary household appliances, which is a complete waste of resources—like putting racing tires on a scooter. There’s no need. FR4, a conventional material, is reliable enough in most cases. Only in military or aerospace applications do we need to consider more specialized substrates.

What I find truly interesting is the trade-offs in the design process. Adding multiple layers can indeed improve performance, but cost and heat dissipation issues also arise. Once… In a project I participated in, the pursuit of thinness and lightness resulted in compressing an eight-layer PCB to six layers, causing a 20% drop in yield during mass production. Sometimes, excessively pursuing technical specifications can deviate from actual needs.

Many engineers today like to blindly stack layers, ignoring the elegance of simple design. Some classic circuits can operate stably for over a decade using double-sided boards, while those massive twenty-layer boards might collapse entirely due to a single via failure. After working in this field for a while, you’ll find that the best designs are often found at a balance point under constraints, not simply by piling on components.

Every time I take apart an old phone and see that green board inside, I think of it as a miniature city. The densely packed lines are like streets, integrated circuits are like skyscrapers, and the tiny resistors and capacitors are like convenience stores on the street. Many people think of a PCB as just a carrier, but I prefer to see it as the skeleton of an electronic product—without a skeleton, even the smartest brain can’t stand up.

I remember the first time I soldered a circuit board myself, I set the soldering iron temperature too high, and the copper foil curled up. This lesson taught me that even the most perfectly designed circuit is useless if the board material or manufacturing process is inadequate. Some manufacturers cut corners on base materials to reduce costs, causing equipment to malfunction quickly – a particularly short-sighted approach.

My recent experience repairing a drone made me realize the importance of the fine, hair-like wiring on flight control boards. A single break in one area can paralyze the entire system. It’s similar to a city’s power grid: a small fault on a main road can trigger a chain reaction. Therefore, when designing circuits, I always include extra redundant lines, like building backup roads for a city.

Some people are always chasing the latest and most innovative chips, neglecting the fact that the circuit boards supporting them require even more craftsmanship. I’ve seen mobile phone motherboards bulge after only six months of use, and industrial controllers that have worked stably for ten years – the difference lies entirely in the materials and manufacturing process of the PCB. A good circuit board should be like the load-bearing walls of an old house, silently supporting it for decades without deformation.

Recently, I tried using flexible materials to make circuits for wearable devices and discovered a completely different world. Traditional rigid PCBs don’t work here; the circuitry needs to be like the weave of textiles, both conductive and flexible. This exploration made me realize that the form of the circuit board can, in turn, define the possibilities of the product.

Ultimately, while the soul of an electronic product lies in its chip, its physical body is always this unassuming PCB. It must withstand the high temperatures of soldering, resist the wear and tear of daily use, and ensure the accuracy of signal transmission. Next time you marvel at the powerful functions of a device, perhaps you should also consider the physical foundation that supports those functions.

Recently, while tidying up my studio, I found several PCBs from ten years ago. Looking at the yellowed substrate and the oxidized, darkened traces, I suddenly felt a pang of emotion—this thing is truly the most silent workhorse in the world of electronics.

Many people think a PCB is just a layer of solder mask and a few lines. Actually, the choice of substrate alone is enough to cause headaches. Once, while helping a friend modify an RF module, I discovered that ordinary FR4 material was practically a signal black hole at high frequencies. It was only after switching to Teflon substrate that the problem was solved. That feeling is like changing the cables in a speaker—both are copper conductors, but the purity is different, resulting in vastly different sound clarity.

The unit of measurement for copper thickness, ounces, is quite interesting. Once, while making a motor drive board, I was lazy and used standard 1-ounce copper. As a result, the circuitry got so hot under full load that it could fry an egg. Later, the thickness was changed to 3 ounces, which increased the cost, but the temperature control was significantly improved. Now, when I see high-power designs, I always glance at the copper thickness parameter; after all, safety redundancy is far more important than saving a few dollars.

What truly changed my perspective on PCBs was repairing an old radio. Upon disassembling it, I discovered that the 50-year-old board, using a paper substrate, was still functioning perfectly. While modern fiberglass boards offer superior performance, they’ve lost that vintage resilience. Sometimes, high performance doesn’t equate to good design; the difference between solid wood furniture and composite boards isn’t hardness, but rather appropriate elasticity.

Recently, I tried using an aluminum substrate for LED light strip heat dissipation, and the effect was indeed amazing, but I’m always worried about the metal layers breaking when bending them. This kind of dilemma is probably the daily reality for engineers—finding a balance between mechanical strength and electrical performance. Designing a PCB is like building with blocks, except our blocks conduct electricity, generate heat, and have to withstand extreme environments for years.

Perhaps this is the most fascinating aspect of PCBs; they’re never the main character, but without them, all electronic devices would become a pile of disassembled parts.

Whenever I see the intricate internal structures of electronic devices, I’m always reminded of those unassuming yet crucial PCB circuit boards. I remember the awe I felt when I first disassembled an old radio and was struck by the dense wiring—these seemingly simple copper traces actually carried the soul of the entire device.

Performance in high-frequency applications often best reveals the true capabilities of a PCB. I’ve seen many projects suffer severe signal attenuation due to unsuitable substrate selection. Sometimes, a seemingly minor design flaw can drastically reduce the performance of the entire communication system.

Currently, many engineers prioritize feature stacking during the design phase, neglecting the most basic signal integrity considerations. Take, for example, a device we recently tested; despite its fancy features, it suffered from significant signal crosstalk in high-frequency environments. This made me realize that even the most complex functions need to be built upon a solid foundation of design.

Different applications place vastly different demands on PCBs. For instance, the reliability requirements of medical equipment and industrial control far exceed those of consumer electronics. I’ve encountered design specifications for industrial-grade equipment, which have almost stringent requirements for material selection and manufacturing standards. This has given me a profound understanding of why some products can operate stably for over a decade, while others fail after a short period. When choosing a PCB supplier, I prioritize whether their engineering team truly understands the product requirements rather than simply comparing prices. Too many cases have shown that cost savings in the early stages often come back to bite during later debugging and maintenance. A good design team considers often overlooked details like thermal management and electromagnetic compatibility from a holistic product perspective.

With technological advancements, more and more devices are adopting hybrid material solutions to balance performance and cost. This brings more design possibilities but also increases complexity. I believe that truly excellent engineers in the future will be those who can find the optimal balance under multiple constraints, rather than simply pursuing the ultimate performance of a single metric.