D98 — Automatic preferred directions on breakout boards

Decision

On a breakout board (two copper layers, at least 70 % of the connections have an end on a ball-grid-like package: at least 30 same-layer SMD pads on at least 5 × 5 distinct positions, at least 40 % of the grid filled) the router sets --layer-dir-pen 0.3 (even layers prefer horizontal, odd vertical) and --package-pen 3 automatically; either can be set (or 0) explicitly. fanout31 breakout points keep the layer and position written in their connection (no override from connectionExitTargets)

Alternatives

Always on for two-layer boards with a package (rejected: quick 89.2 → 87.7 %, mid 53.5 → 51.1 %)

Reason

Preferred directions: srj20 gap boards 28 → 40 % clean, srj19 gap 46 → 50 %; quick and mid byte-identical with the 70 % rule. The override stacked terminals of different buses on one layer (K230 0/12 → 12/12 without it) (doc 16 §11)