IPC International Community magazine an association member publication
Issue link: https://iconnect007.uberflip.com/i/1544975
102 I-CONNECT007 MAGAZINE I MAY 2026 A ll designers should be familiar with the 1993 engineering masterpiece, "High-Speed Dig- ital Design: A Handbook of Black Magic", by Howard Johnson and Martin Graham. So, is the discussion on high-speed or signal integrity really talking about black magic? Yes, and at the same time, absolutely not. I agree that Johnson and Graham nailed the experience every first-time designer goes through: You follow the rules, the schematic looks clean, layout passes checks, and then the signal misbe- haves. It reflects, rings, and does things that seem completely disconnected from the lines you just drew. That disconnect is what creates the "black magic" feeling. But nothing mystical is happening. Signal integ- rity follows physics that are consistent, predict- able, and fully explainable. But those rules don't show up in the schematic. Instead, they live in the electromagnetic fields around the traces, in the stackup, and in the relationship between conduc- tors and their return paths. The authors weren't claiming black magic; they were calling out how it feels until you learn what's going on. The fact that BY J O H N WATS O N , PA LO M A R C O L L EG E E L E M E N TA RY, M R . WATS O N CONTROLLED IMPEDANCE When 'Connecting the Dots' Stops Working