Issue link: https://resources.pcb.cadence.com/i/1541046
32. Using Guard Traces and Shielding for Ultra-Sensitive or High-Speed Nets How To Implement 1. Plan and route guard traces alongside the sensitive net: f Place a grounded trace on both sides of the signal, as close as your EDA rules and assembly allow (often 5-10 mil/0.13-0.25 mm spacing). f Stitch the guard trace to the ground plane with vias every 2-5 mm, especially at both ends and at every layer transition. f For ultra-sensitive nets, guard on both sides and (if possible) above/below (using adjacent copper pours or "copper sandwich"). 2. Connect guard traces to the nearest solid ground: f Tie guards directly to the main ground net - avoid long, winding connections that introduce impedance. f If the system has split grounds (e.g., AGND, DGND), connect guards only to the appropriate domain for the net being protected. 3. Shield with copper pours or can as needed: f Pour copper (grounded) under and around the sensitive net, ensuring frequent stitching to the main ground plane. f For analog/RF areas, consider a metal shield can with a soldered perimeter or snap-fit to the ground pour, stitched with dense vias. 4. Avoid running aggressor nets near guarded or shielded traces: f Even with guards, don't route clocks, high-speed buses, or switching nodes directly adjacent to ultra-sensitive lines. 5. Maintain layout symmetry for matched nets: f If using guards on a differential or matched pair, ensure both lines are equally shielded to avoid skew or impedance imbalance. 6. Validate performance on prototype: f Use an oscilloscope or spectrum analyzer to confirm that noise pickup, crosstalk, or EMI has been sufficiently reduced. f Adjust spacing, stitching, or shielding strategy as needed in future spins. Common Pitfalls, Their Impact, and How to Avoid Them Common Pitfall How to Avoid it Forgetting to stitch guard traces Unstitched guards can act as antennas rather than shields – Verify connections during layout review. Connecting guards to the wrong ground domain Can inadvertently inject noise rather than drain it – Verify that guard traces connect to the correct ground domain. Insufficient spacing or poor symmetry Can unbalance protected nets or allow field leakage – Maintain consistent spacing. Relying on shielding alone without good placement or spacing Shields should complement, not replace, functional block isolation and good routing – Ensure proper component placement, layer stackup, and return path continuity.