PCB Gerber Files: Ultimate Guide For Beginners.

What Is A Gerber File?

A Gerber file is a file format that includes information used to guide the manufacturing process of a PCB. Gerber files have been in use since the 1960s and were named after their inventor, H. Joseph Gerber. They are now a widely accepted standard in the industry, and virtually all PCB design software packages can generate Gerber files.

The Gerber format is a type of file format utilized to depict the picture of a PCB. It is essentially a 2D coordinate file that characterizes each layer of the board. In addition to copper traces, drill holes, and silkscreen layers, Gerber files also cover knowledge about solder mask layers, paste layers, and surface mount pads. The compilation of layers contained in a Gerber file can fluctuate relying on the specific requirements of a given PCB design.
The accuracy and precision of a Gerber file are vital for PCB production. PCB manufacturers rely on this file to guide the manufacturing equipment, with even slight errors or inconsistencies leading to critical defects in the final product. As such, designers must ensure that the Gerber file they produce precisely reflects the intended design and follows the manufacturer’s specifications.

Despite its importance, a Gerber file is just one part of the PCB fabrication process. Additional essential stages include design validation, manufacturing preparation, assembly, and testing. PCB designers must maintain close communication with manufacturers throughout each stage to ensure that the final product satisfies their expectations. Overall, the Gerber file is an essential element in PCB design, reflecting the significance of meticulous planning and attention to detail in producing high-quality electronic components.

How Gerber Files Are Used In PCB Manufacturing?

Gerber files are utilized in the PCB fabrication process, being read by manufacturing equipment to produce each layer of the PCB.  PCB Gerber provides exact and precise details of the PCB design, guaranteeing that the final product fulfills all design requirements.  The following are the main uses of Gerber files in the production of printed circuit boards (PCBs):

  • Design validation: Gerber files facilitate a pre-production DFM review of the design layout of the board before manufacturing to identify and correct any errors or issues that could result in costly mistakes during production.
  • Photolithography: Gerber files are utilized to generate photolithographic image films that are used to produce physical PCBs. The Gerber files direct the UV-sensitive material’s precise exposure on the film, which is developed to etch the copper traces and other features onto the board. 
  • Drilling: Gerber files are also used to guide the drilling of the holes on the PCB, ensuring that the drill head is accurately positioned to create precise drill holes according to the design specifications.
  • Solder mask application: Gerber files contain information about the solder mask layer that protects the board from unwanted solder bridges forming between adjacent leads and prevents damage to the copper traces during the soldering process.
  • Silk screen printing: Gerber files include data regarding the silk screen layer, which enables the printing of additional information, such as component reference designators and logos, on the top and bottom of the board.

What Should The Gerber File Contain?

The Gerber file should contain all the necessary information to manufacture a printed circuit board (PCB) accurately. This includes:

  1. Copper Traces and Pads on Top and Bottom Layers: The upper layer houses most components and copper traces, while the bottom layer holds ground planes and other traces that can’t fit on the top one. The Gerber file should provide elaborate information on both layers to ensure successful manufacturing.
  2. Top and Bottom Solder Mask Layers: Solder mask layers are essential in preventing shorts between copper traces, pads, and components. Gerber files should contain specific data on the coverage of solder masks on the top and bottom layers.
  3. Silkscreen Layers on Both Top and Bottom: Silkscreen layers offer visual cues for precise component placement during PCB assembly. Gerber files should specify the size and location of labels, symbols, and other silkscreen markings on both top and bottom layers.
  4. Drill Hole Patterns and Locations: Drill hole patterns and locations are crucial in PCB design and must be included in the Gerber file. Drill files provide manufacturers with patterns, hole sizes, and other details necessary for drilling holes in the PCB.
  5. Continuous Copper Connections: Copper pours are large areas of continuous copper connections designed to enhance the electrical performance of the PCB. The Gerber file should indicate the copper pour size and placement on both top and bottom layers.
  6. Board Dimensions and Outline: The Gerber file must detail the board’s outline, including dimensions, shape, and cutouts for connectors, displays, or other components.
  7. Drill Hit Markings: Gerber files may include drill hit markings, which indicate where the drill bit should hit during drilling to ensure precise hole placement, in addition to information about holes and their locations.
  8. Hidden and Buried Vias: These types of vias are utilized to connect different layers of the PCB without passing through all layers and require special manufacturing techniques. Gerber files should provide information on the placement and size of hidden and buried vias on the PCB.
  9. PCB Panelization: If the PCB design includes multiple copies of the same circuit, Gerber files may be combined into a panel for mass production. The Gerber file should detail the panel layout and the number of circuit copies included in each panel.
  10. PCB Surface Treatment: The Gerber file may contain information about the PCB’s surface finish or specific areas of the board. Surface treatment can impact the PCB’s performance and the solderability of components..

What Are The Different Extensions For Gerber Files?

  • .gbr or .ger: These are the most common extensions used for Gerber files. They contain information about the different layers of a PCB design, including copper traces, drill holes, and silkscreen layers.
  • .pho:This extension is sometimes used for photoplotter output files, which are similar to Gerber files and contain the same type of information.
  • .topand .bot: These extensions are often used to differentiate between the top and bottom layers of a PCB design.
  • .smtand .smb: These extensions indicate the solder mask top and solder mask bottom layers of a PCB design, respectively.
  • .cmp: This extension is sometimes used for the top layer of a PCB design that shows the components.
  • .plc: This extension is sometimes used for the top layer of a PCB design that shows the placement of components.
  • .sol: This extension is sometimes used for the bottom layer of a PCB design that shows the copper traces.
  • .stc: This extension is sometimes used for the top layer of a PCB design that shows the solder stencil information for stencil printing.
  • .sts: This extension is sometimes used for the bottom layer of a PCB design that shows the solder stencil information for stencil printing.
  • .drd: This extension is used to indicate drill data for a PCB design that shows where the holes should be drilled into the board.

Essential Features Of A Gerber File Viewer.

A software application that enables users to examine and view Gerber files, utilized in PCB fabrication, is known as a Gerber file viewer. An excellent Gerber file viewer should comprise the following key attributes:

  • Accurate Display: The Gerber file viewer should accurately and correctly display the Gerber files. It should allow users to zoom, rotate and pan the view to inspect the design in detail.
  • Layer Control: The viewer should be capable of managing different layers of the Gerber files, such as copper layers, solder mask layers, legend layers, and drill files. It should allow users to adjust transparency levels and toggle layers on and off.
  • Precision Tools: The viewer should include different precision tools that enable users to take accurate measurements of distances, angles, and other attributes of the design.
  • Annotation Features: The viewer should provide the ability to add notes, labels, and other annotations to the design. It should have easy-to-use markup features that enable users to highlight specific areas of interest.
  • File Compatibility: The viewer should support a wide range of Gerber file formats, including newer ones like Gerber X2, as well as other formats such as DXF, DWG, and PDF.
  • User-Friendly Interface: The viewer should have a user-friendly interface that is easy to use and allows users to navigate through the design quickly and efficiently.
  • Export Options: The viewer should have the functionality to export the design in various file formats, such as PDF or PNG, making it simple for users to share with others.
  • Latest File Format Support: The viewer should support the latest Gerber file formats, like Gerber X2, to ensure compatibility with modern design tools, and give users access to the latest features.
  • Printer compatibility: The viewer should be compatible with a wide range of printers so that users can easily produce hard copies of the design. It should support common printer formats, such as PCL and PostScript, and provide the ability to adjust print settings like paper size and resolution.

Which CAD Software Can Create Gerber Files?

Several CAD software options can be used to generate Gerber files for PCB design. Some of the commonly used CAD software include:

  • Eagle – Eagle is a popular and user-friendly CAD software with support for Gerber files along with other file formats. It has design rule checking, a component library, and offers ease of use.
  • Altium Designer – Altium Designer assigns a particular file format to each layer of the PCB design when generating Gerber files. For instance, the top copper layer is designated with the .GTL extension, while the bottom copper layer utilizes the .GBL extension. The top solder mask and silkscreen are represented by the .GTS and .GTO extensions respectively, and the drill file is saved with a .TXT extension.
    These Gerber file extensions are crucial to aid manufacturing equipment in identifying and interpreting individual layers during PCB fabrication. The ability of Altium Designer to accurately produce Gerber files with unique extensions is a critical aspect that ensures successful PCB production.
  • KiCAD – KiCAD is a free and open-source CAD software option for PCB design that supports Gerber files. It has schematic capture, 3D visualization, and PCB design features along with a supportive user community. It also allows for the import and export of designs.
  • OrCAD – OrCAD is a professional-level CAD software for PCB design that has features like simulation, schematic capture, and layout tools. It can generate Gerber files and has a library of pre-designed components. It can also import and export designs in various formats.
  • Proteus – Proteus is a popular CAD software for PCB design that can generate Gerber files. It has schematic capture, simulation, and layout tools and can import/export designs in various formats. It also offers a collection of pre-made components in its library.

How To Convert ".Gbr" To ".Pcb" File?

It should be emphasized that a Gerber file cannot be readily transformed into a PCB file due to its distinct file formats that contain varying types of data. A .gbr file, which is the Gerber format, holds fabrication-related information like solder masks, copper traces, and drill holes needed in producing a PCB. Meanwhile, a .pcb file, exclusive to PCB design software, comprises comprehensive details about the logical representation of the PCB design, including routing information, component placement, and schematic diagrams.
To develop a PCB file from the Gerber files, it is necessary to employ PCB design software such as KiCAD, Eagle, or Altium. Here are the primary steps involved:

  1. Launch your PCB design software and create a new project.
  2. Import the Gerber files into the software by accessing “File” > “Import” and choosing the appropriate .gbr file.
  3. Once the Gerber files have been imported, utilize them as a guide to design the layout of the PCB. This will involve tasks such as placing components, routing traces, defining layers, and adding vias. The specific steps required may vary depending on the software in use.
  4. After the design has been completed, export the PCB file in the format required by the manufacturer. This may require selecting “File” > “Export” and choosing the appropriate .pcb file.
  5. Confirm that the exported file contains all of the necessary data and information needed to produce the PCB and pass it along to the manufacturer for manufacturing.

 

 

Back to Licky's Column