PCB Fabrication Notes: The Complete Checklist

Every fabricated board carries a set of notes that the designer writes and the shop reads, and the difference between a smooth build and a week of questions is usually decided by how complete those notes are. The list below is the one that removes the most queries per line written.

Layer Stack and Material

The stack drawing should name the dielectric between each pair of copper layers, its thickness, and the copper weight on each side. Where a controlled impedance is required, the same drawing carries the target impedance and the tolerance, because the shop cannot derive a target from a schematic.

Where the material is not the standard FR-4 that the shop stocks, the note should give the manufacturer and grade rather than a generic description. A request for a high glass transition temperature is not the same as a request for a specific laminate, and the difference shows up in the dielectric constant that the impedance calculation used.

Board Outline and Mechanical Features

The outline belongs on one layer and one layer only, with the dimensions drawn on it rather than scaled. Where the outline is defined by a route path rather than by a contour, the note should say so, together with the tool diameter, because a route path that is a single line is ambiguous about which side of the line is the board.

Slots, cut-outs and edge plating all need separate statements. A slot requires a width and a length; edge plating requires a note about whether the copper wraps onto the top and bottom surfaces and by how much. Our board outline notes describe the tolerances that apply to each of these features.

Hole Table and Tolerances

A hole table that lists finished sizes, tolerances and plating condition removes an entire class of question. The distinction between a finished size and a drilled size matters most on small holes, where the plating thickness is a significant fraction of the diameter, and a table that quotes one while the shop assumes the other produces a component that will not fit.

Countersinks, counterbores and press-fit holes each have their own standard, and the note should name the standard rather than describing the feature. Our hole types notes list the usual relationships between lead diameter and finished hole size.

Surface Finish and Solder Mask

The surface finish should be named, not described. Immersion gold, hot air solder levelling, immersion tin and hard gold are different processes with different shelf lives, different flatness and different costs, and a note that says only that the board must be solderable leaves the choice to the shop.

Solder mask needs a colour, a specification of whether it is required between fine-pitch pads, and a statement about the mask over vias. Tenting or not tenting vias is a decision that affects both the appearance and the testability of the board, and it should be made by the designer. Our surface finish notes compare the common options.

Impedance and Tolerance

An impedance requirement is only enforceable if the test coupon is specified at the same time. The coupon carries the same stack and the same trace geometry as the product, and the note should state which coupon pattern is to be used and what the acceptance tolerance is, typically a percentage of the nominal value.

Where several nets have different targets, the note should map each target to a layer and a width. A single impedance number quoted for a whole board is not usable by the shop, and it usually results in a query rather than a controlled build. Our test coupon notes describe the patterns and how they are measured.

Marking and Identification

Every board needs a unique identifier that survives the process, which usually means a mark etched into copper rather than printed on the mask. The note should say which layer carries the mark, the font size, and whether it is a date code, a part number or both.

Where a board goes through assembly, a two-dimensional code is often placed on the bottom side so that it can be read automatically. The size and the quiet zone matter as much as the content, and a code that is too small to read reliably is worse than no code at all.

Panelisation and Delivery Format

If the shop is to panelise the design, the note should give the panel size, the spacing between boards, the border width and the requirement for tooling holes and fiducials. If the customer supplies the panelisation, the note should say what is required of the shop instead, which is usually to confirm that the panel fits a standard production size.

Delivery format is easy to overlook and expensive to correct. Knowing whether the boards are to be delivered as a panel, as individually routed pieces, or with a removable frame determines how the profiling step is programmed, and it should be stated before the panel is released. Our breakaway tab notes cover the mechanical options.

Testing and Quality Requirements

The default test is a continuity and isolation check on every net, and any additional requirement should be stated: a particular isolation voltage, a microsection from a coupon, an ionic cleanliness measurement or a thermal cycle. Each of these changes the routing of the job through the shop and the time it takes.

Acceptance criteria should reference a standard rather than a description. A note that refers to a published class of workmanship is unambiguous, while a note that says the boards must look good is not, and the disagreement it creates surfaces at goods-in rather than at the design review.

File Format and Revision Control

The fabrication data should be delivered in a single archive with a stated revision, containing the Gerber or ODB++ data, the drill file, the stack drawing and the notes. Mixing a drawing from one revision with data from another is the single most damaging error in the whole flow, because it produces a board that is internally inconsistent.

The archive should include a readme that names the revision and the date, so that a shop that receives two versions on the same day can tell them apart. Our design release checklist lists the items to confirm before the archive is sent.

FAQ

How long should fabrication notes be? A single page of tables and short statements is usually enough. The value comes from completeness rather than length, and a list that states the stack, the outline rules, the hole table, the finish, the impedance targets, the marking and the test requirement covers the great majority of what a shop needs.

What is the most commonly missing note? The stack-up, or more precisely the mapping between the drawing and the data layers. Where that mapping is missing, the shop has to infer which inner layer is which, and the inference is occasionally wrong in a way that is only discovered after lamination.

Does gopcb accept customer panelisation? We accept either arrangement, and we confirm the panel fits a standard production size before release. Where the customer supplies the panelisation, we check the spacing, the border, the tooling features and the breakaway tabs, and we report anything that would reduce the yield before the panel is built.