Gerber RS-274X

Gerber RS-274X is the standard photo-plotter format for PCB and semiconductor fabrication. LinkCAD supports both modern RS-274X (extended Gerber with embedded apertures) and legacy RS-274D formats.

Format Summary

Property	Value
Extensions	.gbr, .gbx, .ger, .art
Encoding	ASCII
Import	✓
Export	✓
License	Gerber/ODB++
Hierarchy	Step-and-repeat (SR)
Layers	Single layer per file (multi-file workflows)

Note

The **Gerber/ODB++** bundle covers both Gerber RS-274X and ODB++ workflows in current LinkCAD releases.

Import Options

Arc Resolution

Option	Description	Default
Segments per 360°	Number of line segments for a full circle	72
Tolerance	Absolute deviation from ideal arc	—

Aperture Handling

Option	Description	Default
Load external aperture file	Auto-load .APT files from same directory	Off
Apply layer polarities	Merge clear-field and dark-field data	Off

RS-274D Legacy Options

For older RS-274D files without embedded aperture definitions:

Option	Description	Default
Units	Inches or millimeters	Inches
Coordinate format	Integer and decimal digits for X/Y	2.4
Zero suppression	None, Leading, Trailing, or Decimal	Leading
Coordinate mode	Absolute or Incremental	Absolute
Circular interpolation	90° quadrant or full 360°	360°
Modal flash (D03)	Flash command stays active	Off

Export Options

Geometry

Option	Description	Default
Circular interpolation	Use G02/G03 for arcs instead of line segments	On
Default line width	Width for zero-width polylines	0.0
Step-and-repeat	Use SR commands for array references	On
Force draw mode	Use D03 for flashed apertures	Off
Output board outline	Include outline of drawing extents	Off

Aperture Limits

Option	Description
Min/max circular aperture	Diameter range for round apertures
Min/max rectangular aperture	Edge length range for rectangular apertures

File Output

Option	Description	Default
Single file	Combine all layers into one file	Off
Multiple files	One file per layer	On
Coordinate digits	Integer and decimal digit counts	2.4
Line endings	DOS/Windows, UNIX, or None	DOS

Gerber Concepts

Apertures

Apertures define the shape of the “light beam” used to expose the photo-resist:

• Round — circular aperture with a diameter
• Square — square aperture with an edge length
• Rectangle — rectangular aperture with width and height
• Oblong — rounded rectangle (stadium shape)
• Custom — complex aperture macros

Polarity

• Dark — exposes (adds copper/material)
• Clear — masks (removes copper/material)

LinkCAD can merge dark and clear field layers during import using the Apply layer polarities option.

Step-and-Repeat

Gerber step-and-repeat (SR) commands create arrays of the entire image at specified offsets. LinkCAD maps these to array references during import.

Common Workflows

GDSII → Gerber

Convert IC mask data to photo-plotter format. Each GDSII layer typically becomes a separate Gerber file.

DXF → Gerber

Generate fabrication data from mechanical CAD drawings.

Gerber → DXF

Import Gerber fabrication data into a mechanical CAD environment for design review.

Technical Notes

• RS-274X files embed aperture definitions in the file header (AM/AD commands)
• RS-274D files require an external aperture table (.APT file)
• Gerber coordinates are fixed-point; precision depends on the coordinate format
• Each Gerber file represents a single layer; multi-layer designs use multiple files
• Arc interpolation (G02/G03) produces more compact output than line approximation

CLI / Command-File Options

These option keys can be used on the command line or in command files.

Import

Key	Type	Description
GbrInUnits	int	Import units — 0=inches, 1=millimeters
GbrInCoordinateMode	int	Coordinate mode — 0=absolute, 1=incremental
GbrInFormatXInt	int	X coordinate integer digits
GbrInFormatXDec	int	X coordinate decimal digits
GbrInFormatYInt	int	Y coordinate integer digits
GbrInFormatYDec	int	Y coordinate decimal digits
GbrInZeroSuppression	int	Zero suppression — 0=omit leading, 1=omit trailing, 2=explicit decimal
GbrInQuadrantMode	int	Arc quadrant mode — 0=single quadrant (90°), 1=multi quadrant (360°)
GbrInApertureFile	flag	Use external aperture file
GbrInApertureFilePath	string	Path to aperture definition file
GbrInCustomApertureFile	flag	Use custom aperture definitions
GbrInMergeLayers	flag	Merge all layers on import
GbrInModalD03	flag	Modal D03 interpretation
GbrInModalG02	flag	Modal G02 interpretation

Export

Key	Type	Description
GbrOutDecimals	int	Decimal digits
GbrOutIntegers	int	Integer digits
GbrOutAbsCoordinate	flag	Use absolute coordinates
GbrOutSuppressLeadingZero	flag	Suppress leading zeros
GbrOutUnitsImperial	flag	Use imperial units
GbrOutCircularInterpolation	flag	Use circular interpolation
GbrOutFillPolygons	flag	Fill polygons
GbrOutFlashCircles	flag	Flash circles
GbrOutFlashRectangles	flag	Flash rectangles
GbrOutForceDraw	flag	Force draw mode
GbrOutSingleFile	flag	All layers in one file
GbrOutStepAndRepeat	flag	Use step and repeat
GbrOutWidthUnits	int	Default width unit enum (see Units)
GbrOutWidthValue	float	Default width value
GbrOutRoundAptLimitUnits	int	Round aperture limit units (see Units)
GbrOutRoundAptLimitValue	float	Round aperture limit value
GbrOutRectAptLimitUnits	int	Rect aperture limit units (see Units)
GbrOutRectAptLimitValue	float	Rect aperture limit value
GbrOutEobCharacter	string	End-of-block character
GbrOutParameterDelimiter	string	Parameter delimiter
GbrOutLinebreaks	int	Linebreak style — 0=DOS/Windows (\r\n), 1=UNIX (\n), 2=none