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32 I-CONNECT007 MAGAZINE I JANUARY 2026 F E AT U R E A RT I C L E BY S T E P H E N V. C H AV E Z , P C E A PCB design has undergone a fundamental yet exhilarating transformation over the past two decades. It truly feels like we're always pushing the boundaries of what's possible, which signif- icantly increases the potential for a whole new set of challenges, and why we must always be forward-looking when it comes to the evolution of PCB design. Once viewed primarily as a physical realization of a schematic, the PCB is now a critical perfor- mance-determining element of nearly every advanced electronic system. Rapid advancements in semiconductor technology, packaging, data rates, and system integration have pushed PCBs into regimes where electrical, thermal, mechanical, and manufacturing effects are tightly coupled. In my view, the most difficult challenge in PCB design is addressing and maintaining signal and power integrity (SI/PI) in increasingly high-speed, high- density, and miniaturized designs. Looking forward, the true difficulty becomes predictably controlling PCB behavior across multi- What Makes Modern PCB Design So Difficult ple physical domains simultaneously, under shrink- ing margins and increasing complexity. Why is this such a formidable hurdle, and where do we see its impact most profoundly? SI and PI: The Persistent Core Challenge Imagine trying to have a clear conversation in a bustling, crowded room where everyone is talking at once, and the lights keep flickering. That's a bit like what's happening inside our modern PCBs. As data rates climb into the tens of gigabits per second and power rails drop below one volt, the PCB has transitioned from a passive interconnect medium into a distributed electromagnetic struc- ture. At this scale, the most difficult challenge is no longer schematic correctness but predictable elec- tromagnetic behavior, specifically, maintaining SI and PI across increasingly dense multilayer struc- tures. This challenge exists because modern PCBs operate firmly in the regime where trace dimen- sions are comparable to signal rise-times and wavelengths, invalidating lumped-circuit assump- tions and forcing designers to confront full trans- mission-line and field-based effects. As components get faster, smaller, and more integrated, the electrical signals and power deliv- ery networks face issues including: • PCBs as electromagnetic structures • Heterogeneous integration and advanced packaging • Thermal–electrical–mechanical coupling • Materials and stackup as design variables • Manufacturability, yield, and statistical design • Toolchain and human complexity limits