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80 I-CONNECT007 MAGAZINE I JULY 2026 designing for human perception. Here are three lessons I believe all new and expe- rienced PCB designers should keep in mind when designing an LED display for the first time. Every Electrical Decision Becomes a Visual Decision 1 One of the first things I look at during a display board design review isn't the LED array itself. I look at the power distribution network. I know that's surprising, because most engineers naturally focus on signal routing, LED drivers, or interface circuitry. Those are certainly important, but I've learned that many display problems begin with how power is delivered across the board. Unlike many electronic systems, where voltage variations remain invisible to the user, LED displays convert electrical inconsistencies directly into optical inconsistencies. A slight voltage drop across a copper plane may seem insignificant during simulation, yet it can create subtle brightness differences that the human eye detects immediately. The irony is that the design may satisfy every electrical requirement. I've seen layouts that passed design reviews, simu- lations, and bench testing without concern, only to reveal slight brightness gradients once the display was powered on. Nothing was technically "wrong," and the display functioned exactly as designed. Unfortunately, the customer was evaluating visual quality rather than electrical measurements. The human eye is remarkably sensitive to incon- sistency. We instinctively notice when one section of a display appears slightly brighter, a color subtly shifts, or one region responds differently than another. Those differences may represent only a tiny electrical variation, but perception doesn't measure millivolts; it measures uniformity. That's why power integrity becomes far more than simply supplying adequate current. Current balancing, low-impedance power distri- bution, copper geometry, connector placement, decoupling strategies, and return path continuity all influence what the customer ultimately sees. Every milliohm matters because every milliohm has the potential to become visible. When reviewing display layouts, I always encourage designers to stop asking, "Will this circuit work?" and instead ask, "Will the customer notice the difference?" Those are two very different questions. Design for Thermal Uniformity, Not Just Thermal Performance 2 If power distribution determines how a display performs today, thermal management often deter- mines how it performs tomorrow. Most of us under- stand that excessive temperature reduces reliability. That's hardly new. What many first-time display designers don't fully appreciate is that thermal vari- ation often becomes visible even before compo- nents begin to fail. LEDs are current-driven devices where optical characteristics change with junction temperature. As temperatures increase, you'll see brightness decrease, color characteristics shift, efficiency decline, and long-term degradation accelerate. When neighboring LEDs operate at different temperatures, the display loses the uniform appear- ance customers expect. I've participated in design reviews where thermal analysis concluded everything was comfortably within specification, yet the display still exhibited noticeable visual inconsistency because thermal performance and thermal uniformity are not the same thing. A display cares about temperature consistency across the entire viewing surface, making PCB design an integral part of the thermal solution rather than simply a platform for mounting compo- nents. In these designs, copper planes become heat spreaders, thermal vias become thermal high- ways, and component placement influences airflow. Board stackups also affect heat distribution. Mate- rial selection, copper weight, substrate construc- tion, and even connector locations all contribute to maintaining thermal balance across the display. Outdoor displays make this challenge even more demanding. In a lab, you don't have to account for solar loading, elevated ambient temperatures, or continuous high-brightness operation. Designs that appear robust under controlled conditions may behave very differently after years of field operation. One lesson I reinforce repeatedly: Don't design thermal management to keep LEDs alive. Design thermal management to keep every LED looking the same. Those are not always the same objective.