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The Shaughnessy Report: Unlock Your High-speed Material Constraints

The world of PCB materials used to be a fairly simple one. It was divided into two groups: the “traditional” laminates, often called FR-4, and the high-speed laminates developed especially for high-speed PCBs.

These were two worlds that usually didn’t collide. FR-4 is used for the lion’s share of the world’s boards. It’s fairly inexpensive, and its characteristics are well known. The high-speed materials are expensive, and some of the boutique laminates like PTFE are notoriously hard to register during fabrication.

But then traditional laminates started getting better, and high-speed designers and design engineers took notice. The resin systems have improved so much that designers are now using flavors of FR-4 for some high-speed PCBs and even boards well into the RF realm. What does this mean to PCB designers and design engineers who work in the high-speed world?

If loss is a big enough issue for your design, even the most improved FR-4 won’t work for you. But some of these materials boast low enough Dk and Df ratings that the high-speed folks would be remiss not to consider them.

What is the cut-off point for using these new FR-4 types? Who should make the decision to consider a more traditional material vs. a specialty type?

In Design007 Magazine this month, our experts share their thoughts on how designers can avoid overconstraining their high-speed PCBs, and they explore the electrical properties of this new version of an old laminate.

We start with an interview with Kris Moyer and Ed Kelley, who take a deep dive into these improved traditional materials and when they can be utilized for high-speed and high-frequency designs. We also chatted just with Ed, former CTO of Isola, to focus more on the materials themselves. Filbert Arzola discusses using improved FR-4 at high speeds and why you might want to let fabricators or materials experts pick your materials. Barry Olney provides a dielectric material selection guide, and Steph Chavez shares a primer on setting design constraints. Martyn Gaudion explains why “communication-driven constraint” is so critical now.

We also have an article by Anaya Vardya, a column by Matt Stevenson, and, sadly, Tim Haag’s final column, One for the Archives. Tim has been writing for us for 10 years, and I know his fan base will miss his PCB design tips and “Iron Man” references. Good luck, Tim! And thanks for the memories.

See you all next month.

This column orginally appears in the May 2024 issue of Design007 Magazine.