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18 DESIGN007 MAGAZINE I MAY 2024 Not long ago, high-frequency and RF boards required specialized laminates, which tend to be costly and difficult to manufacture. But now, high-frequency designers use traditional PCB laminates for certain high-frequency boards. How is this possible? For some insight, we asked Ed Kelley, founder of Four Peaks Innovation and former CTO of Isola, to discuss how traditional mate- rials have improved and what this means to PCB designers and design engineers today. Andy Shaughnessy: Kris Moyer at IPC is teaching designers how to avoid overcon- straining their board materials. There are ways to build high-frequency boards, even RF boards, without using high-frequency materi- als. What are your thoughts? Traditional Materials, High-frequency Boards? Ed Kelley: If we look back in history, there was a great divide between FR-4 materials and what people used for RF/microwave applica- tions, which really boiled down to Dk and Df properties. If you look back at the loss range, or dissipation factors, and the typical types of polymers that were used in those applications, FR-4s back then would fit into the high-loss and standard-loss categories of today's material sets. Even back then, the products used in RF applications were in today's ultra- or extremely low-loss categories. e two markets were separate and there wasn't a lot in the middle. But as digital appli- cations began to require more speed and higher frequencies, those of us involved in developing materials decades ago began to introduce lower Dk, lower-loss materials, with GETEK being Feature Interview by the I-Connect007 Editorial Team