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AUGUST 2025 I DESIGN007 MAGAZINE 51 Thermal Management Thermal issues can cripple performance and reliability. Identify components that generate signifi- cant heat (e.g., processors, power ICs, FPGAs). Place them with adequate spacing from other sensitive components and consider their proximity to heat- sinks, thermal vias, or airflow. Keep temperature- sensitive components (e.g., precision references, sensors, crystal oscillators) away from heat-generat- ing parts. Mechanical Constraints Most designs begin in the mechanical domain, and for good reason. • Board outline: As the physical enclosure is ini- tially created within the mechanical domain, the physical envelope derives and dictates the allowable area to create the specific details of the PCB outline, which is then integrated into the electrical domain—the PCB layout. • Connectors and I/O: It is vital to position and place critical components first (i.e., connec- tors, I/O's etc.). These are often fixed loca- tions dictated by the enclosure or system requirements and must be addressed first before all other non-priority components are placed. Their position on the PCB dictates the entry and exit points for signals and the PCB's overall relationship to the enclosure. • Mounting holes: Account for mounting holes, as these are strategically designed in specific locations within the PCB and are a means of attaching the PCB to the enclosure. Ensure no components or traces are placed too close to them. • Tooling holes: These are vital items that need to be included for an optimized DFM approach to PCB design. They are primar- ily used for mechanical purposes during PCB manufacturing and assembly, acting as refer- ence points for alignment and securing the board during various processes. • Heat sinks: These are mechanical compo- nents for mitigating thermal considerations. Implementing heat sinks are optional solu- tions that can be implemented for heat dissi- pation when there is a need to address ther- mal concerns or requirements. • Enclosure fit: Consider the overall board dimensions, height restrictions (keep-ins and keep-outs), and how the PCB fits within its final enclosure. Electromagnetic Compatibility (EMC) and EMI A quiet board is a good board. Isolate noisy com- ponents such as switching power supplies and high-frequency oscillators from sensitive analog or RF circuitry. Plan for robust ground (reference) planes and proper grounding strategies to mini- mize noise coupling, especially when addressing the PDN. If shielding is required, ensure compo- nent placement allows for the integration of shield cans or other shielding solutions. Manufacturability, Assembly, and Test Designing for production isn't optional; it's essential. Considerations for manufacturing, assem- bly, and test, collectively known as design for excel- lence (DFX), must be integrated into the PCB design phase to ensure high yield and cost efficiency. Adhere to minimum spacing requirements between components for pick-and-place machines, soldering processes (e.g., reflow, wave soldering), and rework. Align similar components (e.g., resis- tors, capacitors) in the same orientation to simplify assembly and reduce manufacturing time. 4 5 6 7