Issue link: https://resources.pcb.cadence.com/i/1541046
22. Building Ground Via Fences and Edge Stitching How To Implement 1. Identify fence zones: f Draw mechanical outlines for areas needing shielding: board perimeter, RF/analog block edges, I/O connector zones, or around shield cans. f Mark these regions in a dedicated mechanical or documentation layer. 2. Set via size and spacing: f Use the smallest via size your fab reliably supports (typically 0.2-0.3 mm finished drill). f Place vias every 2-5 mm (closer for GHz frequencies or tight EMC specs). f For shield cans, use even denser spacing (1-2 mm) around the can footprint. 3. Connect each via to all relevant ground planes: f For multilayer boards, ensure each fence via ties outer layer ground pours to inner layer ground planes, and to any shield can ground pads. f For boards with split grounds, stitch only within the same domain (AGND, DGND, etc.) unless specifically required at a star point. 4. Tie the fence to shield the cans and connectors: f If shield cans are used, align via fence rows with the can's grounding fingers or pads. f Stitch extra ground vias near connectors that exit the shielded region or at cable entry points. 5. Avoid "gaps" and broken fences: f Check that via rows form continuous rings with no major gaps (gaps >2× nominal spacing can leak fields). f Don't let ground pours or fence rows be blocked by routing, copper keepouts, or missing connections. 6. Review and simulate as needed: f Use your EDA tool's 3D field visualization or post-layout EMI simulation to confirm containment. f For ultra-critical designs, review fence density and effectiveness with your EMC engineer. Common Pitfalls, Their Impact, and How to Avoid Them Common Pitfall How to Avoid it Via fences too sparse or with major gaps Allows fields to "leak" through and reduces shielding effectiveness – Check that vias are placed close enough to form a continuous barrier. Vias not connected to all ground layers Limits their usefulness as return path "ladders" – Verify that each via spans all ground planes it's intended to connect with. Skipping fences on shield cans or block boundaries Reduces the value of expensive shield cans or RF partitions – Plan via fences carefully so shields are completely enclosed. Leaving pour/plane breaks along fence lines Creates unintentional current loops or resonance zones – Bridge splits with ground copper and additional stitching.