What is a Gerber File in PCB Manufacturing?

A Gerber file contains PCB production data. Not only that, but in a format that manufacturers can read and use. Today’s guide explains all you need to know about this PCB file format, including its creation process and use.

What is a Gerber File?

Gerber files are 2D vector images used to describe the layers of a printed circuit board (PCB). They include the copper layers, the solder masks, the silkscreens, etc.

A single file defines one layer, with the typical PCB requiring several of these files to describe. The final PCB Gerber file has a header, various blocks of data for individual layers, and end-of-file extensions.

Gerber File Role in PCB Fabrication

Gerber files transform PCB design software information into fabrication instructions. In other words, they present the data in a format that machines can use. These machines include photo-plotters and older mask or legend printers.

Gerbers aren’t the only available formats for PCB manufacturing. Other options include ODB++ and IPC-2581. However, most fabricators request Gerber formats, which are the most used types and are widely accepted.

Their acceptance stems from their versatility and flexibility. They are also an open standard that anyone can use. Let’s now examine the files to see what fabrication data they hold.

What is in a Gerber File?

A Gerber stores PCB design data in ASCII text file format. The data is human-readable and manually alterable. Depending on the version, the following are its key parts.

Configuration Parameters

These comprise board fabrication settings. They include resolution and scaling. The settings are necessary

Aperture Definitions

This Gerber data defines the shapes and sizes of the various forms used throughout the PCB. They include pads, through holes, traces, and other features. The shapes can be circles, rectangles, and more.

XY Locations

These position the PCB features using XY coordinates, allowing for their precise locations. In other words, they map the entire PCB, allowing the correct part placement during manufacturing.

Draw and Flash Instructions

Draw and flash instructions direct the PCB manufacturing machine’s operation. They tell the machines what forms to make.

Draw commands generally create lines, such as those connecting to points on the board. On the other hand, flash codes create specific figures. The figures include round shapes for pads and through holes.

Gerber File Format Types

There are various versions of the Gerber file format, ranging from the earliest and simplest to the recent, more advanced type. Let’s examine them below, including their capabilities.

RS 274D

The RS 274D is the older version, and it is no longer in use. It had many manual steps, which increased the possibility of errors. It’s also a simple file with only XY coordinates and flash/draw instructions.

RS 274X

This version succeeds the RS 274D and adds more information. It’s also a more complex file that includes the four elements we mentioned earlier: configurations, apertures, XY coordinates, and flash & draw. It’s also the most popular format.

Gerber X2

The X2 is the newest version. It includes more information than earlier formats. For instance, it allows you to name layer functions, the location of features, and other data. These attributes make it a better version data-wise.

Gerber File Format Extensions

A Gerber file extension names the specific layers, including the legends and solder masks. The following is a list of these extensions and what they represent.

• GTL – top copper layer
  
• GTS – top solder mask layer
  
• GTO – top silkscreen layer
  
• GBL – bottom copper layer
  
• GBS – bottom solder mask layer
  
• GBO – bottom silkscreen layer
  
• TXT – drill data
  
• GML – board outline
  

A multilayer board will also have Gerber file extensions for the various layers and their names, such as GL2, GL3, etc. On the other hand, the drill file is usually an Excellon format.

How to Create Gerber Files

After completing the design process, you typically generate the files using Computer-Aided Design (CAD) software. Many design programs allow that. They include Altium, KiCAD, and Eagle. Check out this video for the creation process.

Some older software types may involve various steps. Newer versions simplify the procedure by automating the generation, with some offering viewing options and tools.

The files you generate depend on the number of layers. Each layer requires a separate file. You must also have separate ones for the top and bottom solder paste and silkscreen layers.

Exporting the Gerber files makes them ready for presentation to the PCB manufacturer. The designer must also use tools to view and inspect the files before sending them. It helps detect errors early on before board production.

Mistakes to Avoid When Creating Gerber Files

Gerber file creation requires utmost caution and precision. Mistakes get carried over to the physical board, causing delays and rework costs. The errors are either design or file-related and include those listed below:

• Missing/Incorrect Layers — check to see that the package has all required layers along with their correct definitions
  
• Incorrect Units — specify the units and ensure their consistency. Ensure they match the manufacturer-recommended units
  
• Incorrect Aperture Definitions — double-check to ensure the aperture accuracy before sending the data
  
• Incorrect Board Outline – ensure the information is correct by checking the data before and after generation
  
• Insufficient Clearance and Overlapping Features — perform a Design Rule Check (DRC) to identify design errors using appropriate tools
  
• Incorrect File Format — avoid obsolete versions, such as the RS 274D. Instead, use a format that your manufacturer recommends.
  

The above steps help ensure your files are ready for production and acceptable by the manufacturer. Other measures worth taking during the process include:

• Using a Gerber viewer to inspect the information before sending them out
  
• Compressing the data
  
• Using efficient graphic representations for layers
  
• Combining redundant layers
  
• Using IP protection features, such as watermarking, encryption, and access restriction
  

How PCB Manufacturers Use Gerber Files

In the PCB industry, it’s standard practice for manufacturers to require these formats from customers. The manufacturer loads the files into the fabrication machines.

You send them in a single zipped file. The file is the PCB blueprint. Your fabricator will usually ask you to present the design file in this format and rarely any other type. Before

Your manufacturer views the data you send them before providing a quote. The human-readable data represents all the board layers in separate files or extensions.

Conclusion

A Gerber file is an essential document in a PCB’s production process. It contains information fabricators can use, and is the industry standard format file.

Venture uses your design files to guide the production process. We understand the need for the files to be in the correct format and other details. That’s why we work with you every step of the way to ensure the success of your project.