PCB-Board Profile USD Authoring Guide#

This document describes how to author a USD asset that conforms to the PCB-Board profile: the board-level subset of the PCB contract — the fabricated board’s geometry, the USD core conventions, appearance, and delivery packaging — without the two features that describe placed components.

PCB-Board is what a bare (unpopulated) board is validated against. It is a subset of PCB-Assembly, so a populated board that passes PCB-Assembly also passes PCB-Board; the profile does not forbid components, it simply does not check them. Use it for a board asset that exists without, or ahead of, its component data, whatever produced it.

Profile definition#

Profile 0.1.0 implements the board-level parts of the PCB to USD input contract v1.0.2. Wheel 0.1.0a1, the features and the contract have separate version identifiers; the contract’s document version is not the --version argument.

[PCB-Board]
"0.1.0" = {features = [
    {"FET_213_STANDARD" = {version = "0.1.0"}}, # "PCB Board Geometry"
    {"FET_214_STANDARD" = {version = "0.1.0"}}, # "PCB USD Core"
    {"FET_215_STANDARD" = {version = "0.1.0"}}, # "PCB AOI Appearance"
    {"FET_216_STANDARD" = {version = "0.1.0"}}, # "PCB Delivery Package"
]}

Feature	Codes	What it governs
FET_213_STANDARD — PCB Board Geometry	`BG.001`, `BG.002`, `BG.003`, `BG.005`, `BG.007`, `BG.008`, `BG.010`, `BG.012`	board thickness, copper and mask geometry, barrels at through-hole joints, pad numbers, paste association and side, hole geometry, site occupancy and pin↔pad association
FET_214_STANDARD — PCB USD Core	`UO.001`, `UO.003`, `UO.006`, `UO.009`, `UO.010`, `UO.014`	board root and stage layout, stage conventions (Z-up, millimetres), mesh roles, the `pcba:` namespace, origin convention
FET_215_STANDARD — PCB AOI Appearance	`CG.009`, `CG.010`, `CG.011`, `CG.012`, `UO.011`, `UO.017`	polarity, markings, nominal appearance, per-surface material class, material binding, role/material consistency
FET_216_STANDARD — PCB Delivery Package	`UO.012`, `UO.013`, `UO.015`, `UO.016`	relative self-contained references, package manifest, provenance, file naming

What a conformant asset looks like#

One self-contained USD asset with relative references only and no external dependencies, a package manifest, provenance, and clean ASCII file names.
Discovery is by attribute and role, never by prim name or hierarchy position. The board root is found by its pcba:board:* attributes; every geometry Mesh carries a pcba:mesh:role token from the fixed vocabulary (board_substrate, board_copper, board_mask, board_pad, board_paste, board_barrel, board_hole, …).
Stage conventions: upAxis = Z, metersPerUnit = 0.001 (millimetres), board in the XY plane with Z as its normal, no compensating root transform.
Sites state their occupancy. Every board_pad and board_barrel carries pcba:board:occupied. An occupied site names the component terminal that will land on it (pcba:board:refdes + pcba:board:componentPinNumber); an unoccupied pad states whether it is a no-stuff site (pcba:board:intentionallyUnpopulated). Occupancy not yet known is declared with pcba:prov:occupied.
Materials agree with roles. A mesh bound to a material is bound to one whose class matches its role (copper geometry to a copper-class material, and so on).
No components required. Checks that resolve an association against a component’s pins, or require a barrel for a placed through-hole part, are skipped when the stage carries no components. They apply in full once the board is populated and validated as PCB-Assembly.

Known-missing fields#

A MUST field whose upstream data is not available yet MAY be omitted, provided the prim carries pcba:prov:<attr> = "not_yet_available" (or "source_data_required" where sourcing was attempted and failed). The PCB rules emit these as INFO declared gaps, separately from WARNING advisories and failures.

Reporting limitation: simready-validate filters INFO and WARNING issues out of its returned profile results. Its PASS cannot establish that no declared gaps or advisories remain. To retain all three buckets, use the contract’s reference validator.

Validate#

simready-validate --profile PCB-Board --version 0.1.0 board.usda -v

Select the profile explicitly as above; pcba:* attributes alone do not select it.

Relationship to SimReady core#

The profile shares core’s upAxis = Z convention (UN.006) but its millimetre stage (metersPerUnit = 0.001) differs from core’s UN.007 (metersPerUnit = 1.0), so it does not include core’s Minimal Placeable Visual feature (FET_001_STANDARD).