Start with the exact ordered package
A footprint connects a component’s mechanical terminals to the board’s electrical nets and assembly process. Verify the complete manufacturer part number and package drawing, including the package option and drawing revision. Similar package names or body outlines do not guarantee the same pad arrangement or pin numbering.
Compare the schematic symbol’s pin mapping with the physical drawing. Check whether a drawing is viewed from the top or bottom, and verify pin one, connector mating direction and any exposed pad. A downloaded library part or 3D model is a useful starting point, not evidence that these relationships have been checked.
Review the copper, mask and paste separately
Copper lands, solder-mask openings and paste apertures serve different purposes. Use the component supplier’s land-pattern guidance where available, then review the result with the intended assembly process. Do not scale all three layers together simply to make the footprint look larger.
For through-hole parts, check the finished hole requirement against the lead geometry and assembly tolerance. For surface-mount packages, distinguish terminal pitch, pad size and the gap between adjacent pads. For exposed pads or via-in-pad designs, resolve paste coverage and via treatment with the assembler and fabricator rather than leaving open holes under solder deposits by accident.
Reserve space for assembly and product integration
A component courtyard describes an assembly envelope and should account for placement and surrounding access. It is different from an electrical insulation requirement. Check connector latches, cables, mounting hardware, rework tools and neighboring component heights against the actual mechanical assembly.
Review polarity markings and reference designators for readability after parts are fitted. Avoid placing essential marks where a component body or mask opening makes them unusable. A mechanical model helps find collisions, but it must correspond to the exact package and cannot prove solder-joint quality.
Approve and maintain the library record
- Record the datasheet and drawing used for the footprint.
- Check pin-to-pad mapping and top/bottom interpretation independently.
- Run the relevant copper, mask, paste and spacing checks.
- Review first-build placement and soldering evidence.
- Version footprint changes and identify the designs affected.
Changing a library pad for a future revision is different from repairing a damaged pad on an assembled board. A lifted pad or damaged trace needs an authorized repair assessment and post-repair acceptance; it should not be “fixed” by silently changing the design record. Keep physical rework and design correction traceable as separate actions.