Issue link: https://iconnect007.uberflip.com/i/1520701
10 DESIGN007 MAGAZINE I MAY 2024 When we started planning this month's issue, which centers on the use of traditional laminates in certain high-frequency PCBs, we knew we had to interview Kris Moyer and Ed Kelley together. Kris teaches advanced PCB design classes for IPC, and Ed is the former CTO of Isola and founder of Four Peaks Inno- vation. What ensued was a wide-ranging discussion on the evolution of "standard" PCB laminates and the recent trend by some OEMs to use these materials in high-frequency and even RF boards. If you're interested in avoiding the use of expensive, hard-to-manufacture specialty laminates for your high-frequency boards, you won't want to miss this. Andy Shaughnessy: Kris, in previous discus- sions, you said that some designers are now using standard materials for some high-speed designs, and even RF boards. Notice that I'm Don't Overconstrain Your High-speed PCB Designs trying to avoid saying "FR-4." What do design- ers need to know if they are designing a high- speed RF board and are considering using a standard laminate instead of laminates designed for higher speeds? Kris Moyer: e two big things, whether you're coming from the engineer ing side or the designer side, are awareness of Dk (relative per- mittivity), and Df (dissipation factor). We talk about Dk and Df all the time in my classes. e classic FR-4 is not a genuine spec; FR-4 is just a flame-resistance rating for this flame-retardant material. But we are talking about epoxy r e s i n s a n d w o v e n glass-reinforced bases, which is what everybody assumes they're get- ting when they say "FR-4." Hi stor ical ly, we would have D k in that segment on the order of 4 to 4.5. e Df is on the order of 0.015. ey are pretty lossy materials, which was fine for analog and in the early days of digital. But the formulations of the resins Feature Interview by the I-Connect007 Editorial Team