Check Footprint Origins Before Trusting Placement Coordinates

A placement file can have consistent units and still position a component incorrectly if the footprint’s origin does not represent the expected reference point. Rotation adds another layer of interpretation. Before changing every coordinate in a spreadsheet, determine how the library object, board placement, export, and assembly import each define the reference.

KiCad’s surface-mount anchor convention places the anchor at the component body center and explains its relationship to the footprint origin. This is a library convention, not a guarantee that every downloaded or custom footprint follows it, nor that every assembler interprets data identically.

Choose a component that reveals orientation

Use an asymmetric IC or connector with a clear pin-one feature. A two-terminal resistor can hide a rotation mistake because its ends may be interchangeable for the specific circuit. Record the part number, reference designator, board side, footprint origin, and known pad coordinates. Keep the original export untouched while investigating, so an experimental adjustment cannot become an accidental release.

Compare the exported position with the placed footprint’s reference. If the discrepancy is a constant offset, check the export datum and units first. If only one footprint family is displaced, inspect that family’s anchor. If bottom-side parts differ, review mirroring and viewing conventions before applying a global correction.

Trace one placement end to end

1. Mark the component’s anchor and pin one in the board view.
2. Read its exported coordinates, rotation, and side.
3. Import the file into the intended assembly review workflow.
4. Compare the predicted body and pads with the board artwork.
5. Record the confirmed interpretation for that export path.

Have the assembler identify any rotation conversion it applies. A correction that works for one library convention may be wrong for another. Avoid treating a supplier-specific adjustment as a permanent change to the electrical footprint unless the library itself is demonstrably incorrect.

Keep geometry and placement evidence together

After correcting the cause, regenerate placement data from the controlled design. Check representative parts on both sides and include any unusual library families. Preserve the confirmed preview with the assembly release, so the next build does not depend on an undocumented spreadsheet adjustment. See assembly data preparation for the other files that must match.