Fabrication Data Review Before Release

Most problems found during fabrication originate in the front end, in the data and the instructions rather than in the process, and the cost of correcting them is paid in schedule. A short review before the data is released removes most of them.

Data Completeness

The data set should contain one file per layer, one drill file, a stack drawing, the notes and a readme that identifies the revision. A missing layer is usually noticed, while a duplicate or a differently named layer is not.

The naming should map to the stack rather than to the software’s default. A layer called internal one means nothing until the drawing says which physical layer it is. Our fabrication notes guidance describes the entries.

Units and Format

Old data often uses inches, newer data uses millimetres, and some files carry a format statement that is no longer accurate. The result is a board a factor of twenty-five too large or too small.

The check is quick and worth doing explicitly: compare the outline dimension in the data with the dimension on the drawing. A discrepancy of a factor of twenty-five is not subtle, but a discrepancy of two per cent is.

Minimum Features and the Capability List

The minimum line width, the minimum space, the smallest drill and the smallest annular ring should each be compared with the capability of the shop that will build the board. The comparison is mechanical and takes a few minutes.

Where the design sits at a limit, the review should confirm that the limit applies to the specific shop and to the specific stack, because capability varies with the material and the layer count. Our plating thickness notes describe the related constraints.

Outline, Slots and Edge Features

The outline should be on one layer, closed, and dimensioned. A duplicate outline on several layers, or an outline that is a drawn centreline without a tool diameter, is a query that stops the job.

Slots, cut-outs and edge plating each need a dimension and a note. Where edge plating is required, the note should state how far the copper wraps onto the surface, because the plating thickness at the edge is difficult to control.

<img src="https://www.gopcba.com/wp-content/uploads/2026/08/Array-of-Beryllium-Oxide-BeO-Ceramic-PCB-LED-boards-768×476-1.webp" alt="Drill table and stack drawing on a PCB fabrication drawing” />

Drill Table Consistency

The drill table should agree with the drill file, and the finished sizes should be consistent with the plating thickness. A table that lists a size without saying whether it is finished or drilled is the most common source of hole-related queries.

Where a hole is not plated, that should be stated. A non-plated hole is drilled at its finished size, while a plated one is drilled oversize and reduced by plating.

Solder Mask and Legend Data

The mask data should define the openings and the legend data the printed text, and both should be checked for features below the process limit. A mask dam narrower than the capability is a defect that will appear on every board.

Legend text that falls on a pad or over an opening will be clipped. The check is visual and takes a minute on a dense board, and it prevents a legibility problem that affects assembly.

Adding Up the Front End

Each of these items is trivial on its own, and together they account for the majority of the engineering queries a shop raises. Removing them before the data is released is what allows the job to start on the day it is planned to start.

The review is also cheap, because it is a comparison rather than a design exercise. The most efficient form is a checklist that is applied by the same person every time. Our design release checklist is structured that way.

Handling the Queries That Remain

Some queries are unavoidable, and the response time matters more than the count. A shop that raises a question and receives an answer within the hour loses almost nothing; one that waits a day loses a day.

Naming a single contact on each side, with the authority to answer, removes most of that delay. The alternative, where every question is routed through a project manager, adds a day to each exchange.

Additional Considerations for This Build

Practical attention to data review pays for itself here, because it decides whether the finished board behaves as the drawing intended. Where the requirement is not stated on the fabrication drawing or in the assembly notes, the shop has to assume a default, and that default is rarely the value the design was simulated with. Stating data review explicitly, together with the tolerance that applies, removes the assumption and keeps the result predictable from batch to batch.

Deliberate attention to layer naming pays for itself here, because it decides whether the finished board behaves as the drawing intended. Where the requirement is not stated on the fabrication drawing or in the assembly notes, the shop has to assume a default, and that default is rarely the value the design was simulated with. Stating layer naming explicitly, together with the tolerance that applies, removes the assumption and keeps the result predictable from batch to batch.

Process Control and Verification

On a design of this kind, outline is the item that decides how the rest of the board is arranged. Running a first article through the same checks as the production panel confirms that the two agree, and that comparison is the cheapest form of process control available at prototype stage. Keeping a sample from the panel turns a dispute into a measurement, because the same coupon can be re-examined by both parties without rebuilding the batch.

Reviewing the design before the data is released is cheaper than correcting it after the panel is in the tank, because every step downstream inherits the decision made at the front end. Documenting the assumption is part of the design work, and a short note on the drawing prevents a question that would otherwise arrive a day later and cost a day of schedule.

The process window is set by the narrowest step in the flow, so an improvement anywhere else shows up as margin rather than as yield until that step is addressed. A short note on the drawing about handling, storage or packaging is often worth more than an extra decimal place on a tolerance.

Process Control and Verification

On a design of this kind, outline is the item that decides how the rest of the board is arranged. Running a first article through the same checks as the production panel confirms that the two agree, and that comparison is the cheapest form of process control available at prototype stage. Keeping a sample from the panel turns a dispute into a measurement, because the same coupon can be re-examined by both parties without rebuilding the batch.

FAQ

What is the most common data error? A stack-up that is absent or that does not map to the layer names in the data. It costs a query and a delay, and it is entirely preventable with a table on the drawing.

Is a Gerber set sufficient on its own? It is sufficient to build a board, and insufficient to build the right board. The drawing carries the intent, the tolerance and the notes, and the Gerber carries the geometry.

What does gopcb do when it finds a problem in the data? We raise a query and hold the panel rather than making an assumption, unless the assumption is trivial and can be stated in the review. Every query and its resolution is recorded against the job.