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28 DESIGN007 MAGAZINE I DECEMBER 2023 most basic terms, is a PCB. ese purposes extend beyond mere mechanical support; they're the intricate conductors that orches- trate the symphony of electrical signals within a device. So, at their core, PCBs provide a structured framework, and, I would add, a controlled environment by arranging these components on a board and linking them with conductive pathways (traces). PCBs facilitate the flow of electricity precisely where needed, ensuring proper functionality. Some novices believe that PCB design is just "connecting dots" in the schematic and rout- ing in the PCB, but design encompasses so much more. A PCB is a con- trolled environment. Our PCB refers to the deliberate design and engineering practices implemented to regulate various factors influencing electron flow and electrical performance. is controlled environment ensures reliability, stability, and optimized functionality within an electronic system. With the ever-increasing demand for smaller electronic devices, which in turn means higher-density PCBs, the PCB design process cannot be done in a vacuum. Looking at only one aspect, such as the board shape, without looking at everything else, sets us up for fail- ure. ere is a balance and what I would refer to as a symbiotic relationship within the entire PCB—the flow of electrons in copper and how it interrelates to the fiberglass and other copper areas. Any change in one of these fac- tors will affect the physics of the PCB. Any changes in the "platform" (especially the board shape) further impact the design's physics, such as controlled impedance, signal Integrity, and EMC/EMI consideration. roughout the PCB design, with any changes, there are documented trade-offs for changes; some are improvements, and others are not. Know these trade-offs and know if implementing a change would cause more problems. I have heard various analogies to describe a PCB design, including a city with the build- ings being components, and the streets being routing. But one of my favorites is considering a complex orchestra performance where vari- ous musicians with distinct instruments come together to play a symphony. In this analogy, the PCB represents the stage where this intri- cate performance unfolds. Each electronic component on the PCB is like a musician, playing a unique part in the composition. The conductive pathways on the board act as musical scores, guiding the flow of electrons like musical notes flowing through the air. Ju st a s in an orche str a, where timing, coordination, and harmony are crucial, the PCB maintains a d e l i c a te b a la n c e. Th e precise arrangement of components and traces mirrors the musi- cians' seating arrangement and sheet music, ensuring that every electron (note) reaches its destination at the right time and in the correct sequence. As a conductor guides and coordinates a diverse group of musicians, the controlled environment of the PCB orchestrates the elec- tron flow. It carefully manages impedance, sig- nal integrity, and interference, ensuring each musician plays in tune and at the right tempo, preventing overlaps or disruptions. Just as an orchestra requires a well-designed stage and acoustics to produce a flawless per- formance, a well-engineered PCB provides the environment for electrons to move efficiently, harmoniously, and flawlessly through an elec- tronic system, producing the symphony of functionality that powers modern technology. Let me demonstrate my point. Consider the 62-mil PCB in Figure 1. It features a four-layer stackup of two signal layers on the outside and a ground and power plane on the two internal layers. A differential pair was routed on the top layer with the internal ground plane as its ref- Each electronic component on the PCB is like a musician, playing a unique part in the composition.