Estimated reading time: 5 minutes

Elementary, Mr. Watson: A Nightmare on PCB Street

Can you feel it? One of the best times of the year is finally here. The kids are back in school (finally), the weather is cooling, the days are getting shorter, football is back, and fall is showing up everywhere. Of course, beginning Sept. 1, two groups immediately emerge: those ready to enjoy fall, and those already dragging out the Christmas decorations like October and November no longer exist.

Then there is pumpkin spice: Coffee, cookies, candles, soap, air freshener—the list goes on. Is anything left that someone hasn't tried to turn into pumpkin spice?

In fact, I thought I had seen it all until I was offered a pumpkin spice oil change. Seriously? I can tolerate the candles and hand soap, but pumpkin spice motor oil is taking it too far. What's next? Pumpkin spice brake fluid? Cinnamon-nutmeg transmission fluid? Limited-edition autumn coolant with just a hint of clove?

The Scary Stuff
Personally, I don't rush straight into Christmas as some people do. I like to enjoy October, and, of course, Halloween. It's the one time of year when we actually enjoy being scared. With haunted houses, scary movies, and creepy decorations, we willingly walk straight toward the things designed to make us uncomfortable.

At my age, getting scared has become a lot easier. I really don't need a haunted house anymore. Some mornings, just getting out of bed provides enough suspense. If everything bends, straightens, and starts moving in the right direction without making any new sounds, I already consider the day a major success.

PCB designers also don't need Halloween to know what true terror feels like. This profession has enough built-in “horror” to keep us awake all year long. That probably explains why so many senior PCB designers and engineers eventually fall into one of two categories: gray hair or no hair at all. After enough impossible schedules, last-minute changes, obsolete components, and "quick” revisions, your hair basically decides for you.

The Nightmare on PCB Street
So, in the spirit of Halloween, let’s imagine a typical street lined with typical houses in an ordinary neighborhood in a quiet town. This is PCB Street. At the very end sits one house that looks like all the others. But it isn't.

This is the PCB Fright House. There are no ghosts, chainsaws, or creepy clowns. You’re going to find out that inside this house is much, much worse, especially for PCB designers who like everything just right.

As you approach the front door, it creaks open on its own. At first, everything looks perfectly normal—maybe a little too normal. Then you step inside. The lights are dimmed, but you can see a darkened hallway, and you feel that something scary is waiting in that darkness.

Since this is a typical house on a typical street, logically, you have no need to fear. You start down the hallway. On the first door hangs a small sign: “The Room of Moving Walls.” You reach for the handle, push the door open, and step inside, thinking you know exactly what this room will look like: four straight walls. But you were very wrong. It is, in fact, just like the sign on the door—the walls shift in front of your eyes.

This dimly lit room represents one of the most familiar and frustrating fears in PCB design: changing requirements. You approach the design believing it is finally stable: The board outline is set, the connectors are placed, the stackup is defined, and the major decisions have been made.

Then, without warning, the requirements begin to move. For a moment, you wonder, "Are the “walls” of this design actually moving? Are the requirements changing again?"

Yes, they are. You notice that the enclosure changes, a connector shifts, the stackup gets revised, or a component is replaced. Then you hear those terrifying words that send chills down every PCB designer's spine: "Let's add just one more feature to the design."

Now, individually, each change looks manageable. That’s what makes this room of shifting walls so dangerous. In PCB design, very few changes stay isolated. If you move one connector, the placement changes. Placement changes routing, which can affect signal integrity, power distribution, clearances, thermal performance, and manufacturability.

What looked like a simple adjustment can quietly ripple across the entire design, and before long, the room in this analogy looks nothing like it did when you first walked in.

Don’t Be Afraid of the Change

The real fear isn't that things change. Change is part of every design. The danger comes when those changes happen late, when their impact isn't understood, or when they aren't communicated to everyone involved.

In this imaginary house of horrors, you turn to leave, but the door is no longer where you came in. The walls have shifted one last time. You begin to panic, but you search around, find the door just barely open, and you narrowly slip through just before it closes.

You gather your thoughts and continue down the hallway. It grows darker and quieter, but at least the walls have stopped moving. Another door comes into view, and you can make out a battered sign hanging crookedly across the front: “The Unmapped Room.”

Just like the first door, you reach for the handle. Again, the door creaks open on its own. It’s completely dark inside. You stretch out your hands in front of you, feeling for whatever might be waiting just beyond your reach.

For PCB designers, that is a familiar feeling. Emerging technologies push us into territory where the path forward exists, but it might not be clearly marked or even visible. UHDI, SAP and mSAP, advanced materials, embedded technologies, finer geometries, and AI-assisted design are moving faster than the standards, manufacturing experience, and proven design rules behind them.

We feel uncomfortable. We still have to decide on trace widths, spacing, materials, stackups, via structures, impedance, and fabrication tolerances. Those decisions eventually become something physical that must be built and must work. But what if the answers are still evolving?

As you feel your way through the dark, stepping more fully into the room, you hear voices and recognize them as fabricators: “It can be done,” says one. “That's too aggressive,” says another.

In PCB design, this could be referring to a promising new material, but there isn't enough field history to know what surprises may be waiting. It may be a new process that promises incredible density, but the design guidelines are still being written.

You hear more voices, with different answers and opinions, and you still have to make the design decision. Walking blindly into something new can result in more than just a quick scare. It can mean a failed prototype, fabrication problem, costly respin, or weeks lost from the schedule.

That is what makes this “unmapped” room so frightening. It feels like the scariest room in the house, although it probably isn’t. There’s something even more sinister afoot.

In the Unmapped Room, you feel along the walls until you find another doorway and, oddly enough, you’re back into the hallway. For a moment, there is relief, until you squint in the low light and see one more door at the far end of the hall. Unlike the others, this one is already open. It has no flickering lights, moving walls, or strange sounds.

There’s just nothing, and somehow, that makes it worse.

You step into the doorway and peer into the dimly lit room. You can make out that a desk, a few old drawings, a stack of notes, and one empty chair. You stand there for a moment, wondering if someone will appear, but nobody does.

Now, a real fear starts to envelop your body. Something happened in this room. Someone used to be here, and now they’re gone.

To be continued... .

This column originally appeared in the October 2026 issue of I-Connect007 Magazine.