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DECEMBER 2025 I DESIGN007 MAGAZINE 55 • Power traces: Where possible, use wider traces for high-current paths to reduce resis- tance and voltage drop. This is especially crit- ical on the outer layers, where etching toler- ances can be greater. If you need more robust power handling, expose copper and add solder for thicker traces. • Signal traces: For high-frequency signals, keep your traces short. Use inner layers for tight impedance control, because outer layer tolerances can be less precise. Route high- speed digital and RF signals separately to pre- vent coupling and keep them away from high- power traces. • Spacing: Appropriate spacing helps prevent crosstalk. Separate spaces by at least three times the height of the dielectric between the signal layer and the nearest ground or refer- ence layer. Component Placement and Thermal Management Managing heat and protecting against external interference can be chal-lenging with smaller, more complex boards. Here are four methods to achieve both: 1. Heat dissipation: Use the outer layer as a heat sink or thermal conductor by increasing the copper area on the outer layer. Use ther- mal vias to lower resistance and call out any use of high-conductivity materials. Cluster power components together and place them near heat sinks or thermal vias to spread heat evenly. 2. Grounding: To reduce noise, use solid ground planes and connect power circuitry grounds to the system ground at a single point. 3. Shielding: It is important for designs to pro- tect against external in-terference such as electromagnetic interference (EMI) or radio frequency interference (RFI). Place sensitive components within grounded areas to mini- mize EMI and pay close attention to material selection that aligns with the interference vul- nerabilities of your device. 4. Sensitive components: Heat can create issues with sensitive components, so protect them from thermal variations. Designers can create barriers against heat transfer by min- imizing thermal bridging and using control layers and trapped air spaces to resist heat flow. Manufacturing and Tolerance Keep your manufacturer's processes in mind as you design. These best practices can help facili- tate a smooth manufacturing process: • Impedance control: Designers can help the manufacturer precisely set impedance to prevent signal reflections and ensure clean transmission. Mate signal layers with plane layers across the piece of laminate to ensure impedance accuracy. The plane acts as a ref- erence for the signal, creating a controlled capacitor that dictates the signal's imped- ance. • Edge clearance: Maintain appropriate cop- per-to-edge clearance for manufacturing. A minimum of 0.010 inches is common for outer layers. • Imaging process: Outer layers may use posi- tive film, and their imaging process includes applying photoresist, UV exposure, and chemical development to remove unexposed areas. Etching of the outer layer defines the final traces. By keeping these best practices top of mind and working closely with manufacturers, designers can spend less time worrying about yield or cost and focus on unlocking the innovative power of mod- ern PCB technology like UHDI. DESIGN007 Matt Stevenson is vice president and general manager of ASC Sunstone Circuits. To read past columns, click here. Download Matt's book, The Printed Circuit Designer's Guide to… Designing for Reality and listen to the podcast here. C O N N ECT T H E D OTS