Understanding Gerber File Extensions: Key Info for PCB Design

Introduction to Gerber File Extensions

For anyone involved in the design and manufacturing of PCBs, the Gerber file extensions have a critical importance. These files are in fact used as base formats for sharing PCB design information with manufacturers. Introductory knowledge of Gerber file formats is compulsory and very helpful for each PCB designer as well as an engineer. This guide will provide understanding of gerber files and their extensions, as well as how best to manage them.

What is a Gerber File?

Basically, a Gerber file is a format of the Gerber file containing printable vectors or data on printed layers of the board. PCB individual Gerber files consist of a set of files storing information about every aspect of a PCB’s layout; copper traces and shapes, pads and vias, solder mask areas, silkscreen printing, board outlines, and drill holes.

What Do PCB Gerber File Extensions Mean?

The Gerber file extensions are very important, to determine what kind of information the file contains. It is crucial to know the different extensions to avoid confusion on the actual design layout of your PCB. And make certain that your design’s intention is clear to the manufacturing company.

The Standard Gerber (RS-274-D)

Extended Gerber (X-Gerber’s RS-274)

RS-274X or Extended Gerber or X-Gerber is an improved version of the Gerber format, which came into being in the 1990s and has gradually evolved into the most used format in PCB production. It combines coordinate and aperture information in a single file, so it is faster and has less error than an RS-274-D. In addition to this, this format also supports complex board designs, including the nested aperture definitions. Its related file extensions consist of .gtl, .gbl, .gts, .gbs, .gto, .gbo to .gko. Lastly, the most significant advantage is that the RS-274X format reduces the total number of files required for producing PCBs and minimizes the potential for different aperture definitions for the same drills.

Gerber X2

Introduced in 2014, Gerber X2 stands as the latest version of the Gerber format. It actually extends the basic information set of the RS-274X format with the additional intelligence introduced via additional metadata and attributes, besides being backward compatible with RS-274X. Gerber X2 has extra information on the manufacturing design of the PCB and provides more attributes for enhanced communication. As well as increased automation in production. X2 extends the convention of file extensions with the Gerber RS-274X format and contains additional data necessary for X2-compliant software.

Gerber Files Extension

What Should the Gerber File Contain?

A complete set of Gerber files should be able to give detailed guidelines on how the PCB should be manufactured. Here’s a detailed look at what each component of the Gerber file set should contain;

PCB Dimensions

• Simple board sketch with measurements recorded to the nearest sizes.
• Cutouts/slots in the board or any other accessory part of the board.
• Mounting hole locations
• Summary of the idea of thinness of board.
• Layer stack-up information

Sometimes the PCB dimensions are stored in the board outline file with .GKO. For example, the dimensionals of .GKO file should depict the shape and size of the final board.

Copper Traces

• Each of these layers of the PCB must contain no conductive paths.
• The sizes and shapes of pads used to perform component connections
• Copper pour areas (if any)
• Trace widths and clearances

Panelization

• Arrangement of several PCBs on a single plane if that is the case.
• The gap between the boards, so to speak
• Fiducial marks for assembly
• The V-score or mouse-bite locations for separating boards

Depending on the manufacturer’s instruction, panelization information can either be part of the board outline file or provided in a separate file.

Copper Connections

• Via locations and sizes
• Through-hole pad dimensions

Most of this information is located within the copper layer files and the drill file in .TXT format.

Solder Mask Layers (.GTS & .GBS)

• Where solder masks should be retained or eliminated
• Clearances around the pad and via locations that have solder mask application
• All drawing requirements not addressed by the standard (e.g., HDI, selective solder mask exposure)

The solder mask layers are very important to avoid the formation of solder bridges and to guard the copper against the formation of iron oxide skin.

Silkscreen Layers

• Part codes and values
• Polarity indicators are for Diode symbols, Capacitance symbols, etc.
• Information that may include company logo, mark, or name.
• Minute taking or direction on what needs to be assembled

Silkscreen information is stored in the overlay files with extensions like .GTO or .GBO, the latter sometimes found in system files. Thus, the displayed information should be sensibly provided and easily understandable.

Drill Hole Guideline

• PBX through hole, all-hole PCB
• Hole sizes and tolerances
• A description of plated and non-plated hole standards
• Other special detail requirements (for instance, back-drilling for high-speed kind).

Drill information is often in Excellon drill file (.TXT) and must be correct for correct positioning of BGA components and operation of boards.

Surface Treatment

• It should also indicate the specifications of the final surface finish (Electroless Nickel Immersion Gold (ENIG), Hot Air Solder Leveling (HASL), and Immersion Silver)
• If some spots deplete more of a metal than others do, the process is referred to as selective plating.
• The thickness shall conform to the following surface finish thickness.

Surface treatment information is usually in a different file from the Gerber files, yet it plays a major part in the quality and functionality of the PCB.

How to Open a Gerber File

Gerber files are not typical document files that can be opened with standard graphic programs or word processors but are required to be viewed with specialized software. It cannot be viewed without special software that is called Gerber Viewers. From Gerber files, these viewers decode the vector data and translate them into an image of the different layers of the PCB.

Different CAD Software Used for the Gerber Files

Altium

Altium Designer is an industrial strength PCB design tool that was developed with many high-end features and an all-encompassing environment.

Key features:

• Solid, powerful, and highly effective schematic capture and printed circuit board layout tools
• Implementation of 3D printed PCB and 3D MCAD integration
• ESD control, High-frequency signal analysis, signal integrity, and power integrity analysis
• Requirement for high-speed and complex designs
• Dynamic management of software components

Gerber output: Altium Designer outputs RS-274X Gerber files used by mainstream PCB manufacturers, as well as Excellon drill files.

KiCad

KiCad is a free, open-source printed circuit board developing software which has rapidly made a market in the present years.

Key features:

• Schematic capture and layout from schematic to PCB layout
• Extensive common part repository that can be modified by community members
• A 3D viewer was used for both the PCB and the component designs.
• Smart flip and nudge router for placing traces efficiently
• Daily updates and constant changes

Gerber output: KiCad generates RS274X Gerber file format and Excellon drill file format and Gerber X2 is available from the latest versions.

Eagle

EAGLE is currently a PCB design software that used to be under Tinkercad, but is easily accessed now with any Autodesk account.

Key features:

• User-friendly navigation that is appropriate for entry-level and experienced users
• Large part library
• Thoughtspace: autoroute for automated trace routing
• Interoperability with Autodesk’s Fusion 360 for modeling
• Both free and paid versions have been developed, which differ in the capabilities outperformed.

Gerber output: EAGLE creates RS-274X Gerber file format and Excellon drill file format.

OrCAD

OrCAD is a PCB design software package that is usually quite large and often used in large organizations.

Key features:

• Advanced technology tools for creating schematic capture and printed circuit board layout
• Sophisticated constraint managing systems
• Both signal integrity and power integrity simulation
• Interface with different Cadence Design Systems products
• Apply for small-scale projects to large-scale high-speed projects

Gerber output: OrCAD generates only RS-274X Gerber consecutively and is compatible with different manufacturing outputs.

PADS

PADS is a highly effective tool of printed circuit board design that belongs to the Siemens company which originally was known as Mentor Graphics.

Key features:

• Flexible design environment capable to accommodate projects of all sizes
• One of the features of today’s routing technologies is auto-interactive routing.
• Power and signal integrity analysis in a combined platform
• Thermal analysis capabilities
• The collaboration and integration capabilities of early supporters for rigid-flex and high-density interconnect (HDI) designs.

Gerber output: The output files are Gerber RS-274X standard files, and PADS supports other standard manufacturing formats as well.

How to Convert Gerber Files to PCB Files

The general conversion process of Gerber files to PCB files is not straightforward but is doable in many ways. For the new PCB design import function, Altium Designer, KiCad, and Eagle have Gerber import options. Custom design interpolation may become required for intricate designs. Other available tools are GerberLogix tools and online services also offer conversion facilities. Nevertheless, when converting a design you have to keep in mind, that not all the intentions are carried out though the process, so always check the converted design carefully.

Important Features You Should Look into for the Gerber File Viewers

Accurate Display

An ideal Gerber viewer should emulate every aspect of the Gerber files including the sizes of each layer, and color codes. The real-time rendering capability, particularly where the scales being depicted are large, coupled with the clarity of even higher resolutions of the visualization output is important. This guarantees all the aspects of PCB are captured in the design as is the case with effective checking and review.

Layer Control

Layer control enables layer manipulation such as turning on and off the layers, changing the level of transparency, moving up or down of a given layer and docking of layers in a single group. The advanced viewers support split screen services for layer comparison. This functionality allows for the precise top-most layer scenario level analysis and the design level review of layer interactions.

Precision Tools

Basic measuring instruments are distance measurement, angle probe, area measurement, overlay and design rule check. The high-end viewers may provide cross-section for layer stack visualization. These are important tools for inspection and to check the tagibility factor or how the part is going to look like after it undergoes manufacturing.

Annotation Features

Annotation features allow for notes, things that interest you, revision tally makers, and comments as well as exporting. Therefore, select the viewers that are compatible with save and share options of annotations that will help in communication with team members and manufacturers.

File Compatibility

A versatile viewer must work with different Gerber formats, drill files, and additional formats, IPC-2581 and ODB++. Greater compatibility with files that are broader in use makes the viewer serve the purpose of different projects and workflows in design reviews.

User-Friendly Interface

A smart navigation system must be implemented in order to be effective. Seek viewers with clear organization of tools and the possibility to customize the interface, hotkeys, and comfortable switching between the views and layers. Select a viewer with a learning difficulty, in line with your level of skillfulness.

Export Options

Sophisticated export features should therefore involve producing clear PCB layers images, producing reports with measurements and annotations, exporting modified Gerber files and production of 3D models of printed circuit boards. All these features help improve interaction and interfacing with other design processes.

Latest File Format Support

Make sure the viewer plays nicely with current generation file format like the Gerber X2, latest ODB++, IPC 2581 formats plus other sectorial formats. Updates to the software create a sense of continuity meaning that the format remains supported in your workflow comparing to the latest industry standards.

Printer Compatibility

However, though not very frequent, there are times when one needs to have physical prints. Among audio printer options look for high print quality, ability to print either a single or multiple layers, accurate scaling and compatibility with large format printers. These features help to make the presentation and the reviewing of designs more flexible.

Common PCB Layout Software Gerber File Extension Comparison

Knowing the naming conventions of various PCB layout software is very important with regard to file organization and inter manufacturer file exchange. Here’s a detailed comparison of common file extensions used by popular PCB design software:

Some Notes:

• Altium: Mechanical layers use: .GM1, .GM2 etc. It is numbered from the top down, and the layers are inner ones.
• KiCad: It is used with a descriptive naming convention. Fixed point is In1.Cu, In2.Cu, etc. and numbered down from the top.
• Eagle: 1 is reserved for the top layer, and the number continues with inner layers from 2 (GL2, GL3, etc.)
• OrCAD: It uses .Ln for the inner layers is where n is the layer number.
• PADS: Use .Ln for inner layers like OrCAD.

FAQs

What Types of Layers do Gerber Files Include?

Copper layers top bottom inner – solder mask layers – silkscreen layers – board outline – drill file – solder paste layers – assembly layers. One layer has its precise function of specifying the structure of the PCB, another for giving instructions on the appropriate conducting patterns to be followed, and still another on the fabrication process to be undertaken.

What Happens If My Gerber Files Are Incorrect?

If Gerber files are incorrect, then manufacturing error occurs, the production process is slowed down, costs escalate, functionality can be disappointing, and assembly issues emerge. To avoid these, always practice using Gerber viewer, get an DRC, or include a detailed readme files, and do prototype runs before going into actual production.

Which is More Popular with Manufacturers Between RS-274X and RS-274D Gerber Formats?

RS-274X (Extended Gerber) is used more often because of higher speed, fewer possible errors, better compatibility with current designs, and because it is standardized in the electronics industry. RS-274X is the most widely used format today and RS-274D is used to some extent, but is not generally popular in the modern manufacturing world of PCBs.

Conclusion

Knowledge of Gerber file extensions in the PCB field is simply vital. Some of them are: awareness of various Gerber formats, function of file extensions, significant information contained in Gerber files and various naming conventions necessary for working with certain software. And with PCB complexity, therefore, comes the importance of accurate Gerber files in those circuits. The dialogue with manufacturers has to be kept open and unimpeded in order to sustain the process effectively.