Area ratio and aspect ratio
The area ratio is the opening area divided by the aperture-wall area: opening area ÷ (opening perimeter × foil thickness). For a simple aperture, the aspect ratio here is its narrowest opening dimension divided by foil thickness. Circular holes reduce opening area, add an inner wall perimeter, and use the remaining ligament as the minimum width.
The defaults treat area ratio 0.66 and aspect ratio 1.5 as passing, with 0.60 and 1.2 as marginal. They are editable screening thresholds, not universal acceptance criteria. Paste powder, wall finish, nano-coating, aperture shape, board support, print settings, component needs, and supplier capability can change the practical result.
Supported Gerber behavior
The parser supports absolute RS-274X coordinate formats with leading or trailing zero omission, millimetres or inches, C/R/O/P standard apertures and circular holes, flashes, modal coordinates, image polarity, aperture selection, X2 .FileFunction and .AperFunction, mirroring, rotation, scaling, and bounded step-repeat expansion. Aperture macros support circle, vector-line, center-line rectangle, outline, regular-polygon, and thermal primitives plus variables and arithmetic. Standard-aperture geometry is exact; macro area, perimeter, and bounding-span aspect are explicitly labeled raster estimates.
Manufacturing and parser boundary
This is an aperture-screening aid, not a full Gerber renderer, stencil-release simulation, IPC compliance result, CAM validation, or manufacturing approval. Draws, regions, block apertures, clear-image Boolean composition, overlapping or joined flashes, narrow local features inside arbitrary macros, deprecated constructs, and unsupported macro primitives are not converted into final openings. The heatmap plots supported flash origins and status colors; it is not an exact artwork preview.
Confirm that the selected file is the intended top or bottom paste layer, inspect the final composed image in qualified CAM software or Ucamco’s reference viewer, and review the exact foil, paste, aperture modifications, component terminations, and process window with the stencil supplier and assembler before release.
Primary references
Ucamco, the steward of Gerber, publishes the current Gerber Layer Format specification, formal grammar, and test files. Its grammar defines standard and macro apertures, coordinate commands, flashes, regions, transformations, step-repeat, and X2 attributes used by this bounded parser. Indium Corporation’s stencil design application note defines area ratio as opening area divided by wall area and describes 0.66 as an industry guideline, while its odd-shaped aperture example demonstrates the same area/perimeter/thickness method.
Frequently asked questions
Why is my macro aperture estimated?
Macro primitives can overlap or erase one another. The tool evaluates the ordered primitive image on a bounded grid and estimates its contour instead of adding primitive areas, which would double-count overlaps. Near-threshold macros require a qualified CAM measurement.
Why are regions and draws excluded?
They create arbitrary final-image geometry rather than a single reusable flash aperture. Converting them correctly requires complete path, arc, polarity, and Boolean image composition. Exclusion is safer than presenting a partial shape as authoritative.
Does a passing 0.66 area ratio guarantee good paste release?
No. It is a widely used starting guideline. Actual transfer efficiency depends on stencil manufacture and coating, paste rheology and powder, aperture geometry, print parameters, board support, cleanliness, and process capability.
Can I use a copper or solder-mask Gerber?
The parser can read supported constructs, but a declared non-paste X2 FileFunction is an error and a missing function is a warning. Ratio results are meaningful only for the exact stencil openings intended for paste printing.
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