Fabrication Data Package Checklist before Production

A fabrication data package is the complete description of the bare board: geometry, materials, tolerances, finishes and the tests that will verify them. When it is complete, the fabricator builds what the designer intended. When a document is missing or contradictory, the plant makes an assumption, and the assumption is usually discovered after the panels are etched.

What the Package Contains

The core items are the copper and mask artwork, the drill data, the stackup definition, the fabrication drawing and any special instructions. Assembly data such as the placement file and the bill of materials is often included for convenience, but it belongs to the assembly package and should carry its own revision.

Every item should reference the same board revision. A package assembled from files exported on different days is the most common cause of a mismatch between the artwork and the drawing, and the mismatch usually appears as an incorrect hole size or a missing feature rather than as an obvious error.

Gerber Files and Layer Naming

Gerber data defines the copper, solder mask and silkscreen for each layer. Name the files so that the layer order and the side are unambiguous, and avoid a naming convention that only makes sense inside the design office. Include the board outline on its own layer with a defined line width and add the mechanical features in the same file.

Check polarity before sending: a negative plane layer interpreted as a positive image produces a board with no copper where the plane should be. Export the data with the same units and format used by the fabricator, and confirm that the aperture list is complete, since some tools generate apertures that a different reader cannot interpret.

Drill File and Hole Chart

The drill file lists every hole with its tool size and coordinates. Add a hole chart that states which holes are plated and which are not, because the same diameter can appear in both categories. Where a hole is used for a press fit or a connector locating pin, give the tolerance explicitly rather than leaving it to the general note.

Confirm that the drill file matches the artwork pad sizes. A drill that is too large for the pad leaves an insufficient annular ring, and one that is too small may violate the plating aspect ratio on a thick board. Both errors are visible in a fabrication review and expensive to correct after the panels are drilled.

Stackup Drawing

The stackup drawing defines the construction: the material of each layer, its thickness, the copper weight, the dielectric properties and the finished board thickness with its tolerance. Where impedance targets apply, they are written on this drawing together with the layers they affect.

Specify the material by class and by the properties that matter rather than by a single vendor part number, and state whether an equivalent material may be substituted. Review the proposal against high precision PCB material practice where tolerances are tight, because the dielectric constant tolerance affects every controlled impedance line on the board.

Impedance Coupon Requirements

Where controlled impedance lines are used, the package should require a coupon on each panel with lines that replicate the product geometry. State the target impedance, the tolerance and the measurement method, and require the results to be reported with the lot. A coupon that does not match the product geometry measures nothing useful.

Decide in advance what happens when a measurement falls outside tolerance. If the acceptance criterion is a report rather than a limit, the coupon becomes a formality. Treating it as a limit with a defined disposition keeps the process honest and makes the data meaningful over time.

Fabrication Notes and Tolerances

Write the notes that a general specification would not cover: the surface finish and its thickness, the solder mask color and type, the silkscreen requirements, the panel size and the acceptable panelization, the edge finish and the marking requirements. Where a note conflicts with the drawing, the drawing should take precedence, and the order of precedence should be stated.

State the tolerances that matter to the product rather than copying a generic block. Warpage, registration and hole position tolerances all affect assembly, and a tolerance that is tighter than necessary raises cost without improving the product. Where the finish requires a controlled layer thickness, reference the appropriate specification such as the practice covered in electroless nickel thickness control.

Assembly Data and Review before Release

Include the placement file with the reference designators and rotations, the assembly drawing with the polarity marks and the bill of materials with manufacturer part numbers. Where the assembly will be built by a different supplier, provide the same revision of the fabrication and assembly data to both, so the two packages cannot drift apart.

Before release, run a checklist: one revision across all documents, the artwork matching the drawing, the drill chart matching the artwork, the stackup complete with tolerances, the impedance requirement measurable, and the fabrication notes covering the finish and the marking. gopcb works from the same package for fabrication and assembly and can review it before production, which is where design guidelines for manufacturable boards become a practical checklist rather than a general reference.

Marking, Packaging and Storage

State how the boards should be marked, whether with a date code, a lot number, a panel identifier or a customer part number, and where the marking may appear. Marking that overlaps a pad or a component footprint is a defect rather than a cosmetic issue, so the location belongs on the drawing along with the text height.

Also state the packaging and the storage requirement. Vacuum packing with a humidity indicator is appropriate for boards with an immersion finish, and the shelf life guidance described for bare board shelf life and storage should be quoted in the purchase documents so the assembler knows the clock is running.

Cost and Lead Time Impact

Several items in the package influence price more than the designer expects. Tighter tolerances, smaller holes, thinner lines and additional inspection all move the board into a more demanding process class. Stating the requirement accurately allows the fabricator to quote the correct process rather than the cheapest one that might fail.

Lead time follows the same logic. A package that requires a special material, a controlled impedance coupon and a specific finish needs scheduling, while a standard construction may ship from stock material. Sending a complete package with an honest requirement is what makes the quoted lead time achievable rather than optimistic.

FAQ

Can the fabricator work from the layout database instead of gerber files? Some can, and it removes one translation step. The trade is that the plant then interprets the design as the tool describes it, so confirm that the tool version and the export settings are understood by both sides before relying on it.

How detailed should the fabrication drawing be? Detailed enough that a question cannot remain open. Anything that affects the delivered board, including finish thickness, marking and panel preferences, belongs on the drawing or in a referenced specification.

What is the most common omission? A missing or incomplete stackup, followed by an inconsistent revision between the artwork and the drawing. Both are caught by a ten minute review and both cause a full rebuild when they are missed.