Gerber Format Definition
GERBER is a file format. The standard gerber file formats can be divided into three types: RS-274, RS-274X, and Gerber X2. The gerber file and aperture in RS-274 format are separate files. The aperture in RS-274X format is integrated into the gerber file. Data characteristics of the GERBER format: Data code: ASCII, EBCDIC, EIA, ISO code, commonly used: ASCII code. Data unit: English, metric, commonly used: English. Coordinate form: relative coordinate, absolute coordinate, commonly used: absolute coordinate. Data form: omitting leading zero, fixed length, omitting trailing zero, commonly used: fixed length.
Gerber Classification
Gerber X2
RS-274-X
RS-274-D
RS-274
Fire 9000
Mda 9000
Barco DPF
The standard gerber file format can be divided into two types: RS-274 and RS-274X. The difference is that the gerber file and aperture in RS-274 format are separate files. The aperture in RS-274X format is integrated into the gerber file, so the aperture file is not required (i.e., contains the D code).
Data format: integer + decimal place Commonly used: 3:3 (metric, integer 3 digits, decimal 3 digits) 2:4 (imperial, integer 2 digits, decimal 4 digits) 2:3 (imperial, integer 2 digits, decimal 3 digits) 3:3 (imperial, integer 3 digits, decimal 3 digits) Leading zero, trailing zero and no leading zero: Example: 025690 with leading zero becomes: 25690 (Leading) 025690 with trailing zero becomes: 02569 (Trailing) 025690 with no leading zero becomes: 025690 (None).
Unit: METRIC (mm) ENGLISH (inch or mil).
Unit conversion: 1 inch = 1000 mil = 2.54 cm = 25.4 mm1 mm = 0.03937 inch = 39.37 mil.
Gerber Data Characteristics
Data characteristics of GERBER format:
Data code: ASCII, EBCDIC, EIA, ISO code, commonly used: ASC II code.
Data units: Imperial, Metric, Commonly used: Imperial.
Coordinate form: relative coordinate, absolute coordinate, commonly used: absolute coordinate.
Data format: omitting leading zeros, fixed length, omitting trailing zeros, commonly used: fixed length.
Polarity Introduction
Positive：
The GERBER description is the circuit layer, and the graphics described are mainly copper parts. Or the GERBER description is the solder mask layer, and the graphics described are mainly solder mask parts (i.e. ink covering parts).
Negative:
The GERBER description is the circuit layer, and the graphics described are mainly the copper-free part. Or the GERBER description is the solder mask layer, and the graphics described are mainly the solder mask-free part (i.e. the part not covered with ink).
Composite sheet:
The layers described by GERBER are composed of layers of different polarities. Usually, the dig layer and the positive polarity layer are superimposed. The polarity of the dig layer is c, and it mainly plays the role of circuit protection or additional process data.
Format Introduction
Gerber X2:
Gerber X2, an upgraded version of RS-274X, can not only embed board stacking information, but also insert CAD attributes. The strengthening of the existing image data format and the newly added functions can greatly improve the overall design, engineering and production efficiency.
RS-274X:
RS-274X (also known as the extended Gerber format, or X-Gerber format) is a two-dimensional vector image description format and a standard format for image description in the circuit board industry. RS-274X is a readable ASCII format that contains a series of control codes and coordinate information. The elements that make up the image are lines and flashes that are drawn at specific locations. Positive and negative graphic objects can be combined.
The following is an example of the RS-274X format:
G04 Film Name: paste_top*
G04 Origin Date: Thu Sep 20 15:54:22 2007*
G04 Layer: PIN/PASTEMASK_TOP*
%FSLAX26Y26*MOIN*%
%IPPOS*%
%ADD28R,.11X.043*%
%ADD39O,.07X.022*%
…
%AMMACRO19*
21,1,.0512,.0512,0.0,0.0,45.*%
%ADD19MACRO19*%
%LPD*%
G75*
D10*
X1762513Y1175000D03*
Y1374634D03*
Y1637506D03*
…
D39*
X4962513Y1425000D02*
Y1375000D01*
Y1325000D01*
Y1275000D01*
M02*
RS-274X documents contain a complete description of the images of each layer of the circuit board, with all the elements required for circuit board graphic imaging, and no extension files are required. Aperture can define positive and negative objects. Copper skin does not need to be specified as “fill block” or “fill line” as in RS-274-D.
RS-274X is a complete, powerful, clear standard description of all layers of a circuit board that can be automatically imported and processed. This allows it to be used for fast and secure data exchange and reliable and automated workflows. See the external link for a detailed description of the format.
RS-274-D
The old RS-274-D (also known as the standard Gerber format) is a data format derived from the EIA RS-274-D standard code for controlling multi-domain CNC machine tools. Gerber RS-274-D is used to control vector plotters, which are two-dimensional CNC machine tools. Gerber RS-274-D is an ASCII format that includes control codes and X, Y coordinates. The following is an example of the RS-274-D format:
D11*
X1785250Y2173980D02*
X1796650Y2177730D01*
X1785250Y2181480D01*
X1796650Y2184580D01*
D12*
X3421095Y1407208D03*
X3422388Y1406150D03*
M02*
Gerber RS-274-D was developed in the 1960s and 1970s to control vector plotters. It does not contain coordinate units and aperture information. Aperture is a description of the shape of an object, similar to the font of a PDF document. The plotter operator manually sets the coordinate units and aperture, which are described in a text file called an aperture file or, for historical reasons, a wheel file. Aperture files are mainly used for operators to read and write, and there is no standard. Each EDA software and even each designer has their own aperture file design and name conversion habits. PCB manufacturers must understand and manually input them into the CAM system.
RS-274-D only supports simple image operations. Because of its great limitations, people can only create some complex graphics, such as stroking, which is filled blocks or filled lines.
RS-274-D can conveniently control vector plotters, but it is greatly limited by the technological capabilities of the time. It is suitable for manual operation processes and is not suitable for reliable and automated data conversion for PCB design and manufacturing.
RS-274-D is a CNC standard, not an image description standard. Without an Aperture file to match, an RS-274-D file is useless. However, there is no unified standard for Aperture files.
