74HC595BQ

@@ -107,6 +107,20 @@ Limits as printed in the datasheet (page.json `metadata.characteristics` carries - 3D model: DHVQFN-16-EP(2.5x3.5), generated from the KiCad footprint (body from the F.Fab outline, terminals on the pads, 0.9 mm nominal VQFN height). Neither the vendor nor KiCad ships a 3D model for this package, so the dimensions are nominal, not the manufacturer's CAD (STEP) - 3D model files: `74hc595bq-etched.step` / `74hc595bq-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `74hc595bq.step` / `74hc595bq.glb` are the bare package body. +### Courtyard: why each corner steps twice++The footprint's courtyard (F.CrtYd, from KiCad's footprint generator) is the union of three rectangles, each grown by 0.25 mm. The body itself is a plain 2.5 x 3.5 mm rectangle (the F.Fab outline):++| Feature | x extent (mm) | y extent (mm) |+|---|---|---|+| Side pad rows (pins 2-7, 10-15) | +/-1.85 | +/-1.625 |+| Package body, 2.5 x 3.5 | +/-1.50 | +/-2.00 |+| End pads (pins 1, 8, 9, 16) | +/-0.625 | +/-2.35 |++The pads overhang the body by 0.35 mm on all four sides, as QFN toe lands do. So the body is wider than the end-pad pair and taller than the side pad rows, and its corner at (1.50, 2.00) lies outside both pad envelopes: the side rows stop at y 1.625, the end pads at x 0.625. Each corner therefore steps side pads (x 1.85) -> body (x 1.50) -> end pads (x 0.625), two steps. The union is 20 vertices and matches the footprint's 20 courtyard segments exactly.++A pads-only outline has one step per corner (12 vertices) but leaves the body corner uncovered. A single step per corner is only possible by growing the courtyard about 0.35 x 0.37 mm at each corner: either the side-pad edge runs down to y 2.0, or the end-pad edge widens to x 1.5. The current outline is the tightest one that covers both body and pads. (Checked 2026-10-16 for the 74HC595 domino molecule, adom/molecule-74hc595bq.)+ ## Provenance  Data extracted from the manufacturer datasheet, not a distributor listing: