Working with Backdrilling in Allegro PCB Designer: Best Practices
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DRC and Shape Voiding
Internal design layers will have Route Keepout shapes generated using the
BACKDRILL_CLEARANCE KEEP OUT geometry definition in the padstack to maintain
clearance from the backdrill hole to all copper features.
Negative Planes will utilize the BACKDRILL_CLEARANCE ANTI PAD definition in the
padstack to maintain clearance to backdrill.
Tool Tip – It is recommended to enable "Dynamic Unused Pad Suppression" in the
design cross section to avoid a larger than expected clearance at the backdrill locations
based on the pin/via to copper spacing constraints, and to prevent an internal pad being
present during the manufacturing output.
One of the common fabrication vendor requirements is that the internal layer pads at the
backdrill locations are removed in the manufacturing output.
