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What is a Gerber file?

A Gerber file describes a two-dimensional manufacturing image, such as a copper layer, solder-mask image or printed legend. A multilayer PCB normally needs several coordinated images and additional manufacturing information. Gerber artwork is not a schematic, and a folder containing artwork is not automatically a complete fabrication release. The practical task is to connect every image with its intended layer, revision, coordinate system and physical board requirement.

For a first review, ask three questions: can the receiving software read the image, can the engineer identify its function, and does it agree with the rest of the manufacturing package? These are different checks. An image may render perfectly while belonging to the wrong board revision. A clearly named file can contain the wrong layer. A valid copper image can still describe an electrically incorrect circuit.

Use this guide when you need to understand or troubleshoot the artwork itself. For the complete quotation package, including drawings and alternative exchange formats, use the PCB file-format and handoff guide. You can also contact 吃瓜tv with an unresolved question; completing the worksheet is optional.

A layer image needs an assigned manufacturing function

Think of a layer image as one transparent sheet placed over a common board outline. Its shapes become meaningful only when the function and position are known. Top copper, bottom copper and inner copper are different physical locations even when portions of their patterns look similar. Mask and paste images may both contain pad-shaped openings, but they serve different operations and should never be substituted on visual similarity alone.

The table is a review map, not a prescribed number of files. A single-sided construction, a multilayer board and a board with blind vias need different populations. Write down the expected stackup first, then reconcile the export against it. Do not infer the required copper count from the number of files in a ZIP, because reports, masks, drawings and duplicate exports also contribute to that count.

What the text tells you, and what it does not

Gerber contains commands describing imaging operations and their interpretation. Units and coordinate-format declarations matter because a sequence of digits needs a scale. Aperture definitions describe imaging shapes; flashes, draws and regions place or construct geometry. A reviewer who understands these concepts can ask better questions without trying to repair production artwork by hand.

X2 attributes add semantic information, including an image's function. They help software identify meaning that otherwise has to come from filenames and documentation. The are the reference for syntax and the applicable specification. This page's small header inspector recognizes only a limited set of declarations; it is not an implementation of that complete specification.

For example, a declaration identifying copper, layer 1 and the top side gives the reviewer useful evidence about intended function. It does not prove the image was exported from the approved revision or that its copper clearance meets the project requirement. Treat each declaration as one piece of evidence to reconcile with the released design, rather than as an acceptance certificate.

Avoid editing coordinate declarations merely to make a viewer display something plausible. If the export and receiving interpretation disagree, record the symptom and return to the original configuration. Changing units, polarity or coordinate interpretation without understanding the complete image can create an attractive but incorrect picture. A corrected release should be regenerated, reviewed and identified as a new controlled package.

Inspect a small Gerber header locally

Paste a short text fragment, or load the clearly marked illustrative example. The inspector reports recognized unit declarations, a supported coordinate declaration, file-function text and the number of recognized TF, TA and TO attribute commands. It removes ordinary G04 comment text before checking those patterns. Conflicting recognized declarations are called out for review.

The result deliberately says 鈥渘ot found in fragment鈥� when the snippet lacks a recognized declaration. A fragment is incomplete evidence: a command may exist elsewhere, be expressed in a form outside this inspector's supported patterns, or belong to an invalid file. None of those possibilities can be decided by this worksheet. Use a full CAM viewer and the official specification for actual syntax and geometry review.

The input stays in this worksheet's memory and is not uploaded by the tool. A downloaded text brief contains what you entered and the reported observations. Attach it manually if useful. The enquiry email control opens a draft; it neither sends a message nor silently uploads the artwork. Editing an input invalidates the previous result and its download so that an old finding is not presented as current.

Review images together, not as isolated thumbnails

Begin with one known dimension from the fabrication drawing. Measure it in the viewer, then compare the outline, copper and drill data using the same reference. A uniform scale error points toward a units or format interpretation problem. A constant translation suggests an origin mismatch. Rotation, reflection and partial alignment need their own investigation; do not classify every mismatch as a simple offset.

Next inspect features that have a relationship across files: connector holes inside their annular lands, mask openings around intended solderable areas, cutouts relative to copper, and legend around pads. Use several locations spread across the board. One aligned hole is weak evidence because unrelated transformations can still coincide at one point. A second and third reference feature make the review more informative.

Finally compare the image set with the written requirements. Material, finished thickness, copper requirements, surface finish, impedance targets and special features may require information outside artwork. A geometric viewer cannot confirm material availability or a qualified manufacturing route. Bring those questions to PCB DFM review with the actual construction and required acceptance basis.

Worked review: a four-layer release with an extra inner file

Consider an illustrative package for a four-layer board. It contains top and bottom copper, two intended inner layers, masks, legend, profile and drill outputs. A fifth copper-looking file remains in the folder from an earlier experiment. All five images open successfully. The import tool has not failed; the release owner has supplied an ambiguous set.

The appropriate response is to reconcile the package with the approved stackup and source revision. Identify which two inner images are authoritative, remove the obsolete file from the new release archive and regenerate the manifest. Do not ask the manufacturer to choose the image with the newest file timestamp. Timestamps can change when a ZIP is extracted, copied or synchronized and do not establish engineering approval.

This example also shows why file counting is insufficient. 鈥淔our copper layers present鈥� is useful only after each selected image has a verified physical position and revision. The same principle applies to a single panel containing repeated boards: clarify whether the supplied artwork represents one board or an approved customer panel before pricing dimensions and quantities.

Turn an image review into an actionable fabrication question

Send a short manifest with the board identifier, revision, expected copper order, profile owner and drill populations. State which files were independently viewed and list unresolved observations. A question such as 鈥渢he plated drill overlay is shifted by the same amount at three reference holes鈥� is much easier to investigate than 鈥渢he Gerbers look wrong.鈥� Include the exporter version and settings record when interpretation is involved.

For a quotation, distinguish board quantity from panel quantity, and specify whether stencil or assembly work is included. Paste data belongs to a different task from bare-board fabrication. If you need populated boards, continue with the required files for PCB assembly rather than assuming the Gerber archive supplies component identities, purchasing data and placement information.

Keep source design data and manufacturing outputs linked by a release identifier. Store the accepted CAM questions and their answers with that release. If a change affects a hole, footprint or copper layer, review the complete affected output set again. Sending one replacement file informally can leave the receiving team with a mixed revision even when each individual attachment is valid.

Resolve the specific ambiguity

If the image opens but its role is unclear, use the Gerber extension and naming guide. If a receiving system reads geometry but loses its meaning, review Gerber versus Gerber X2. If holes are displaced or mis-scaled, work through the NC drill coordinate guide. Each addresses a different failure mechanism.

Gerber file questions