A fabrication archive is a released configuration, not a folder of whatever files were exported most recently. A mixed-revision package can contain valid Gerber and drill files that disagree with each other. The useful preflight question is whether one coherent design state can be reconstructed from the complete archive.
Define the release boundary
Create a release identifier that belongs to the fabrication package as a whole. Tie it to the CAD revision and drawing revision, and identify the intended board variant. The release identifier need not equal a software firmware version; it must uniquely identify the physical data being authorized for manufacture.
Export into an empty release directory. Reusing a directory from the previous revision can leave behind a stale layer or drill file that the new export no longer creates. Once the package is checked, treat it as immutable. Create a new release for a later correction rather than changing bytes under the same identifier.
Build a manifest with meaningful fields
| Manifest field | Example | Purpose |
|---|---|---|
| Release ID | CTRL8-R08-FAB01 | Names the whole package |
| CAD source revision | R08 | Identifies source design state |
| File function | Copper L3 | Explains what the file controls |
| Filename | CTRL8_R08_L3.gbr | Connects manifest to artifact |
| Byte count / SHA-256 | Calculated from the final file | Detects later byte changes |
| Approval state | Approved / unresolved | Separates finished data from questions |
A cryptographic hash detects whether a file changed after the hash was calculated. It does not establish that the file is electrically correct, belongs to the right design or was approved by a responsible person. Keep the approval record separate from the integrity record.
Inspect a concrete mixed-revision failure
Suppose R08 moves a mounting hole by 1.0 mm and updates the copper keepout. The archive contains R08 copper and outline, but the drill export still comes from R07. Each file opens successfully. A syntax check passes, yet the hole is drilled at the old position and no longer matches the revised mechanical intent.
Detect this by opening the final exported archive in a viewer and overlaying the hole map, board profile and nearby copper. Compare the changed coordinate against the revision note and dimensioned drawing. A file timestamp alone is weaker evidence because copying or re-exporting can alter timestamps without proving a coherent design state.
Use a short, repeatable preflight
- Count and identify all eight copper layers in physical order.
- Check top/bottom mask and legend files against the intended variant.
- Verify plated and non-plated hole interpretation and slot geometry.
- Confirm the board profile, cutouts, units and origin.
- Check each feature listed in the revision change summary.
- Match stackup, impedance requirements and special process notes to the drawing revision.
- Generate the manifest from the actual final archive contents.
A change-focused review complements a complete basic preflight. If only a connector footprint changed, inspect that change closely, but still confirm that unrelated layers were not omitted or accidentally substituted during export.
Replace a release without creating an undocumented branch
When a discrepancy is found after submission, state that the earlier release is superseded and provide a complete replacement archive. Identify what changed and whether production has started. Obtain acknowledgment of the controlling release. Do not assume that sending a new attachment automatically stops work on the old one.
If the fabricator proposes a CAM correction, record its exact geometry and reason. Approve it through the project’s change-control process and incorporate the accepted result into the design record. Otherwise the next order can revert to the original uncorrected files and repeat the same issue.
Keep the evidence needed for a repeat order
Retain the approved archive, manifest, fabrication drawing, accepted exceptions and supplier acknowledgment together. Record whether tooling or test fixtures depend on that revision. A repeat purchase should cite the released configuration, not just a familiar board name or the date of an old email.
The release audit is successful when a second person can determine which files were authorized, verify their integrity and reproduce the physical layer order without asking the original designer to interpret ambiguous filenames. It does not replace electrical design review or manufacturing qualification; it makes their approved output traceable.
References and next step
Ucamco: PCB fabrication data guide · Ucamco: Gerber format resources
Use the fabrication requirements guide to document the result. For a project-specific review, include the controlled drawing revision and relevant assumptions in your RFQ.