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Gerber format

The Gerber format is a file format used by printed circuit board (PCB) industry software to describe the images of a printed circuit board (copper layers, solder mask, legend, drill holes, etc.). The Gerber format is the de-facto industry standard for printed circuit board image transfer.[1][2][3]

The Gerber format specification can be freely downloaded.[4]

There are two versions. RS-274X ("extended Gerber") is the most commonly used today. The previous version was a subset of EIA RS-274-D ("standard Gerber"); it is deprecated and is largely superseded by RS-274X.

The Gerber format was developed by Gerber Systems Corp., a company founded by Heinz Joseph "Joe" Gerber.[5] The format is now controlled and owned by Ucamco through its acquisition of Barco ETS, a company that previously acquired Gerber Systems Corp.[6][7]


Inside many electronic devices is a PCB onto which components are connected. These PCBs may be designed using a computer aided design (CAD) system.[8] One way to physically realize a design is to transfer the computerized design information to a photolithographic computer aided manufacturing (CAM) system.[9] Gerber is a widely used file format for performing this transfer.[10] Once the bare board is fabricated the Gerber file plays no role in the final assembly of components onto the board.

RS-274X extended Gerber

The RS-274X Gerber format, also known as extended Gerber or X-Gerber, is a 2D bi-level vector image description format.[4] It is a superset of RS-274-D standard Gerber, which is itself a subset of the EIA RS-274-D format for numerically controlled machines.

It is a human readable ASCII format.[11] It consists of a sequence of commands and coordinates. Its imaging primitives are line draw, flash (display) predefined shapes at a given location and outline fill. Positive and negative graphics objects can be combined.

An example of a RS-274X file:

G04 Film Name:    paste_top*
G04 Origin Date:  Thu Sep 20 15:54:22 2007*

An RS-274X file contains the complete description of a PCB layer image without requiring any external files. It has all the imaging operators needed for a PCB image. Any aperture shape can be defined. Positive and negative objects can be combined. Planes can be specified without the need to "paint" or "vector-fill" as in RS-274-D.

RS-274X is a complete, powerful and unambiguous standard to describe a PCB layer. It can be input and processed fully automatically. This makes it well suited for fast and secure data transfer and for reliable and automated workflows.

The format specification is published.[4] A tutorial is available.[12]


Gerber files are typically produced by PCB designers using specialized Electronic Design Automation (EDA) or PCB CAD software. These files are sent to PCB fabricators where they are loaded into a CAM system to prepare data for each step of the PCB production process. In this workflow they transfer the layer information from CAD to CAM. They are also used to specify drilled hole information, which can be viewed as image layers; however, the Excellon Format is used more often to transfer drilling information.[13] Gerber files are also used to drive quality control machines, such as automated optical inspection.

A quality RS-274X file is very convenient to work with.[14] Sometimes the numerical precision is too low, causing significant rounding errors on tight-tolerance PCBs. The Gerber output resolution (grid) should always be at least a factor of 10 better than the resolution (grid) of the CAD system. Some systems still use "painting" to define copper areas instead of using outline fill, or use painted SMD pads instead of the flexible aperture definitions. Painting does not make a file invalid, but it makes it very difficult, time-consuming and error-prone for manufacturers to process. Painting should not be used.[15] Note that these issues are not due to the RS-274X format itself but due to poor implementations. Many outstanding implementations exist, producing top quality RS-274X files.

The RS-274X format does not specify which PCB layer the file represents. Extensions have been proposed to specify this.[14] In any case, it is sufficient to specify the function in the file name and to specify the format in the extension - e.g. ".GER" for Gerber. Some designers, however, use cryptic file names and document them in a free-format text file. This means that the manufacturer has to browse all the files in the dataset to find the necessary production information. In other cases the function is indicated by misusing the file extension - e.g. .BOT for Bottom Layer.[14] In this case the manufacturer has to open the file to find out the format. Contrast this with the rest of the world; nobody has to open a PDF file to know it is a PDF file.

Supplementary data

An RS-274X file specifies a single conductor or mask layer image. The drill data is usually specified in Excellon format. The netlist, if present, is usually specified in IPC-D-356.[16] Layer names, material stack up are typically provided in informal text files or drawings. However, Ucamco itself recommends[14] the use of a subset of IPC-2581 for these. Typically, all these files are "zipped" into a single archive.

RS-274-D standard Gerber

Standard Gerber, is largely superseded by extended Gerber. It was created from a subset of the Electronic Industries Association RS-274-D specification,[17] a format to drive mechanical NC machines in a wide range of industries. Be aware that the term RS-274-D is often used incorrectly (with the qualifying "Gerber" postfix omitted) to refer to the standard Gerber subset, rather than the original RS-274-D superset itself. Standard Gerber is used to drive vector photoplotters, which indeed were 2D NC machines. It is a simple ASCII format consisting of commands and X, Y coordinates.[18] An example of a Gerber RS-274-D file:


RS-274-D was designed in the 1960s and 1970s to drive numerical controlled machines such as vector photoplotters, machines now all replaced by raster-photoplotters. An RS-274-D file on its own is not an image description because it does not contain all information: the coordinate unit and the definitions of the apertures are not defined in the RS-274-D file. (Apertures are the basic shapes, similar to fonts in a PDF file.) The coordinate units and apertures were supposed to be set manually by the plotter operator. They were typically described in a free-format text file, called an aperture file or a wheel file (because the apertures were mounted on a wheel and rotated into the light beam), intended for human reading. There are no standards for wheel files in RS-274-D, so the designer and the plotter operator had to agree on these on a case-by-case basis.[18]

It only supports a few simple imaging operators. To work around this limitation constructions such as "stroking," also known as "painting" or "vector-fill" are needed. Standard Gerber was well-suited to drive vector plotters and was constrained by the technology then available. It was designed for a manual workflow. It is not suitable for fully automated data transfer between PCB designers and manufacturers. PCB manufacturers have to enter coordinate units and aperture definitions manually.

RS-274-D has been deprecated by Ucamco.[14]


  • On 27-Aug-1980 the first edition of the Gerber Format: a subset of EIA RS-274-D; plot data format reference book[19] was published by Gerber Systems Corporation as a specification to drive their range of photoplotters.
  • In 1986 the Gerber format was extended to support apertures with variable sizes to produce rectangles of arbitrary sizes within a given range and tapered lines. This functionality is not in practical use any more.
  • In the 1980s the Gerber format was adopted by several other photoplotter vendors and also computer-aided manufacturing systems for PCB manufacturing. It became the de-facto standard.
  • On 26-Apr-1991 with the availability of raster scan capability the Gerber format was extended for polygon areas and Extended Mass Parameters, allowing the user to dynamically define apertures of different shapes and sizes as well as planes and polygons without the need for "painting". The Extended Mass Parameters where originally designed in the early 1990's by Gerber Systems Corp. under impulse of AT&T.[20]
  • On 16-Aug-1994 the last edition of the Gerber Format Guide: a subset of EIA RS-274-D; plot data format reference book was published by Gerber Systems Corporation.
  • In April 1998 Gerber Systems Corporation was taken over by and integrated in Barco, Belgium. Barco's PCB division is now called Ucamco (former Barco ETS).
  • On 21-Sep-1998 the RS-274X Format User's Guide was published by Barco - Gerber Systems Corporation.
  • In January 2012 the RS-274X Format User's Guide was updated to revision H.

Related formats

Over the years there have been several attempts to replace Gerber by formats containing more information than just the layer image, e.g. netlist or component information.[7] None of these attempts have been widely accepted within the electronics manufacturing industry, probably because the formats are complex.[14] Gerber remains the most widely used data transfer format.[1][2][3]

  • IPC-D-350 C Printed Board Description in Digital Format, 1989. This specification was standardized as IEC 61182-1 in 1992 and withdrawn in 2001. Rarely, if ever, used.
  • DXF Sometimes used. These are typically constructed as drawings, PCB objects (tracks and pads) are lost, which makes them very difficult to use in CAM.
  • PDF Rarely used. Very impractical to work with because PCB objects (tracks and pads) are lost.
  • DPF Format, now at v7, a CAM from Ucamco. Sometimes used.
  • The Electronic Design Interchange Format, EDIF. Rarely, if ever, used.
  • ODB++, a CAM format from Mentor Graphics. Sometimes used, the prevalent non-Gerber format.[21]
  • GenCAM: IPC-2511A Generic Requirements for Implementation of Product Manufacturing Description Data and Transfer Methodology, 2000. Rarely, if ever, used.
  • GenCAM: IPC-2511B Generic Requirements for Implementation of Product Manufacturing Description Data and Transfer XML Schema Methodology, 2002. Rarely, if ever, used.
  • Offspring: IPC-2581 Generic Requirements for Printed Board Assembly Products Manufacturing Description Data and Transfer Methodology, 2004. Rarely, if ever, used, but receiving more attention recently.[22]
  • STEP AP210: ISO 10303-210, Electronic assembly interconnect and packaging design, first edition 2001, second edition 2008 (to be published)
  • Fujiko: JPCA-EB02[23], based on work by Prof. Tomokage of Fukuoka University. Rarely, if ever used, but emerging as a new standard in Japan.


  1. Williams, Al (2004). Build your own printed circuit board. McGraw-Hill Professional. p. 121. ISBN 978-0-07-142783-8. Retrieved April 2, 2011.
  2. Schroeder, Chris (1998). Printed circuit board design using AutoCAD. Newnes. p. 283. ISBN 978-0-7506-9834-4. Retrieved April 2, 2011.
  3. Blackwell, Glenn R. (2000). The electronic packaging handbook. 5.18: CRC Press. ISBN 978-0-8493-8591-9. Retrieved April 2, 2011.
  4. "RS-274X Gerber Format Specification". Ucamco. January 2012. Retrieved 25 February 2012.
  5. "Gerber Scientific Instrument Company Records, 1911-1998".
  6. Tanghe, Jean-Pierre. "Barco acquires Gerber Systems Corp". Barco NV. Retrieved 26 November 2011.
  7. "A short History of Electronic Data Formats". Printed Circuits Design and Fab. 28 June 2011. Retrieved 15 October 2011.
  8. "EDA: Where Electronics Begins". Electronic Design Automation Consortium. Retrieved December 18, 2011.
  9. "PCBexpress Printed Circuit Board Tutorial". Retrieved December 18, 2011.
  10. Mike Buetow (28 June 2011). A Short History of Electronic Data Formats. Printed Circuit Design and Fab magazine. Retrieved December 18, 2011.
  11. Sinclair, Ian Robertson; Dunton, John (January 11, 2007). Practical electronics handbook. Elsevier. p. 543. ISBN 978-0-7506-8071-4. Retrieved April 2, 2011.
  12. Steve DiBartolomeo (1995). "What's all this about RS274X Anyway?". Artwork Conversion Software, Inc.. Retrieved 2011 November 03.
  13. "PCB Layout Data". Eurocircuits. Retrieved 26 November 2011.
  14.  Karel Tavernier, Ucamco (2011/2Q). "Improving CAD to CAM Data Transfer: A Practical Approach". Journal of the HKPCA, Issue No.40. Retrieved 2 October 2011. "Use of RS-274-D: Do not use it."
  15. "Painting Considered Harmful". 17 June 2011. Retrieved 25 November 2011.
  16. "Using IPC-D-356 for Importing Net and Node". Retrieved 16 October 2011.
  17. EIA Standard RS-274-D Interchangeable Variable Block Data Format for Positioning, Contouring, and Contouring/Positioning Numerically Controlled Machines. Electronic Industries Association, Engineering Department, 2001 Eye Street, NW, Washington, D.C. 200006. February 1979.
  18. Steve DiBartolomeo (1991). "D-codes, Apertures and Gerber Files". Artwork Conversion Software, Inc.. Retrieved 16 October 2011.
  19. "Google book entry on Gerber format: a subset of EIA RS-274-D ; plot data format reference book".
  20. Coombs, Clyde F. (September 2, 2007). Printed circuits handbook. McGraw-Hill Professional. pp. 18.11. ISBN 978-0-07-146734-6. Retrieved April 3, 2011.
  21. Mike Santarini (1/22/2002 2:33 PM EST). "ODB++ spec tapped for CAD-to-CAM data exchange". EE Times. Retrieved 29 September 2011.
  22. IPC-2581 Panel: A Spirited Discussion on PCB Data Transfer Formats, Richard Goering, Cadence Design Systems blog, October 2, 2011
  23. "JPCA Standards".

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