PCB Board Geometry#

Overview#

This capability defines the board-level geometry (BG) an exporter authors on the board USD so a PCB AOI synthetic-data pipeline can generate solder joints and reason about through-hole seating. It covers the fab-derived substrate, copper, mask, pad, paste, and plated-barrel geometry that lives on the board (mesh roles board_substrate, board_copper, board_mask, board_pad, board_paste, board_barrel; board_hole is optional bookkeeping) together with the board-side associations that link those features to placed components and their pins.

The board is the source of truth for source geometry and associations only. The pipeline consumes these to synthesize the downstream-generated solder-joint geometry and per-joint AOI ROIs, which are out of scope for the authored asset. There is no board_solder role: solder is generated, not exported.

Two rules shape every page here (PCBA to USD Input Contract 1.0.2, sections 3, 6, 10):

  • Geometry breakout. Every independently inspectable thing is its own addressable prim — each pad / annular ring, each barrel, each paste deposit. A merged copper or paste mesh cannot be defected or associated.

  • Associations are authored board-side, as the pcba:board:refdes + pcba:board:componentPinNumber pair. The pair lives on the non-instanced board_pad, board_barrel, and board_paste prims, never on the instanced pin prim, so components stay instanceable. pcba:board:component / pcba:board:pasteFor rels are SHOULD direct handles, not the association. See Hole Occupancy and Pin Association (BG.012).

SMT and THT are one model with conditional fields keyed off pcba:component:processClass: SMT contributes paste deposits (pair + solderLayer) and per-contact pads; THT contributes a board_barrel at every occupied joint (press_fit included) carrying the hole data and the pair. pcba:board:occupied applies to both. pcba:board:plated and pcba:board:holeSide are not contract attributes and are ignored when present; a bare board-side pcba:pin:number is read with a warning, never required. This capability realizes the Board-level Geometry (BG) codes BG.001–BG.014; BG.013 is intentionally unassigned and BG.014 has no executable rule.

Requirements#

Code

Requirement

Summary

BG.001

Board Thickness

The board root MUST carry pcba:board:thicknessMm (pressed thickness) and the substrate MUST be a solid slab.

BG.002

Copper and Solder-Mask Geometry

At least one board_copper and one board_mask mesh MUST exist, with role-consistent materials.

BG.003

Plated Barrel at Occupied Through-Hole Joints

Every plated hole at an occupied THT joint (incl. press_fit) MUST have a board_barrel carrying the hole data and the association pair; there is no plated flag.

BG.005

Pad Number

Each board_pad MUST carry pcba:board:padNumber (its footprint designation), present even when unoccupied.

BG.007

Paste Association

Each supplied board_paste at an occupied site MUST name its contact with refdes + componentPinNumber; pasteFor rel is SHOULD.

BG.008

Paste Side

Each board_paste side MUST be determinable: pcba:board:solderLayer or a containing layer’s pcba:layer:side.

BG.010

Hole and Pad Geometry

board_barrel MUST carry centre/shape/dims or a derivable form (drill radius; slot shape + dims + contour); padContour is SHOULD.

BG.012

Hole Occupancy and Pin Association

Pads and barrels declare occupancy or its unresolved marker; occupied sites name refdes + componentPinNumber board-side. Known-empty pads also declare the no-stuff state.

BG.014

Paste in Hole

For THT, paste association MUST be empty unless paste-in-hole applies. No executable rule.
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