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The Shaughnessy Report: It’s All About the Physics—or Is It?

Lately, we’ve heard quite a few design experts say, “PCB design is all about the physics. Designers should focus more on understanding the laws of physics and less on circuit theory.”

As feature sizes continue to shrink and we see more challenges popping up like thermal, it’s no wonder that physics has become a hot topic in some corners of the design community. After a few conversations with designers and instructors, we knew we had a good topic for a magazine. We wanted to address these questions:

• How does physics work in PCB design?
• How do the laws of physics fit in with circuit and transmission line theory?
• What should designers understand about physics and how does it apply to PCB design?

While putting this issue together, we investigated potential cover ideas. “What if we had James Maxwell and Gordon Moore boxing on the cover, in a Faraday cage match? Let’s get ready to rumble!” That led us to the Rock ‘Em Sock ‘Em robots that now grace our November 2022 Design007 Magazine cover.

Of course, Maxwell and Moore aren’t really on opposite sides of the ring in the electronics discussion. They’re more like two sides of the same coin. Today’s designers need to understand the laws of physics and electrical circuit theory, both individually and as they work together.

The phrase, “It all goes back to the physics,” implies that designers should return to the fundamentals of electrical and electromagnetic theory, led by pioneers such as Maxwell, Georg Ohm, and Joseph Fourier. But I’m curious: How many physics classes have you taken? Did you major in physics? I know many designers with bios brimming with various types of engineering diplomas, but only a handful seem to have physics degrees.

In the end, the smart designer today needs to know a little bit of everything, from mechanical engineering to RF and microwave. Physics is just one more tool in your toolbox. It can help you understand fields and the properties of the materials, as well as concepts such as how fields affect inductance.

Over the past few months, we noticed something: Physics can involve a lot of heavy math, such as Maxwell’s equations. But as Eric Bogatin, who majored in physics, says, designers can learn the fundamentals of physics without necessarily mastering all the math. It might sound counterintuitive, but don’t let the math keep you from studying physics.

This issue is a great place to start. Here, you will learn why you can't ignore the physics of PCB design, especially as features continue to shrink. Our experts will discuss how the laws of physics (field theory, thermal effects, etc.) relate to solid PCB design practices. We also raise awareness of the need for greater understanding of the laws of physics and discuss a variety of resources related to physics and PCB design.

Our interview with Eric Bogatin leads this "ready to rumble" issue. He explains how a knowledge of physics can help designers master electrical engineering concepts, how these disciplines work together, and why it’s so important to avoid letting the math “get in the way” when learning the laws of physics. Next, Happy Holden describes his brief interaction with Maxwell’s equations in college—avoiding them, primarily. We have a great article by Douglas Brooks and Johannes Adam that uses physics to help illustrate why vias don’t get hot. Columnist Martyn Gaudion discusses how analysis and measurements can help you out of a jam when the laws of physics don’t seem to apply. Finally, Tamara Jovanovic brings us an update on today’s curriculum, fresh from the halls of academia as she pursues her master’s in electrical engineering.

We have columns from our regular contributors Barry Olney, Stephen Chavez, Matt Stevenson, Beth Massey, and Tim Haag, as well as an interview with Joe Clark and Mark Gallant. We also have another article by Anaya Vardya in his DFM101 series.

There’s a lot happening in our segment of the industry, with four months of conferences and trade shows coming up. We’ll be there, bringing you the news you need to know. See you next month.

This column originally appeared in the November 2022 Design007 Magazine.