Guide to Gerber Files

What Are Gerber Files?

Gerber files, initially developed by Gerber Scientific and now owned by UCAMCO, are the industry-standard file format for PCB fabrication. These files serve as the blueprint manufacturers use to bring a PCB design to life. After creating a PCB layout in design software, the layout is converted into Gerber files, containing critical manufacturing data like copper layers, hole locations, silkscreen, and more.


Each Gerber file represents a 2D image of a specific PCB layer, encoded in ASCII vector format. These images guide the creation of stencils, fixtures, and tooling necessary for PCB fabrication.

Gerber File Formats

  1. RS-274-D: The original version, now largely obsolete, contains basic data like XY coordinates and draw/flash commands.
  2. RS-274-X: Widely used, this extended format combines apertures, configuration parameters, and commands into a single file for efficiency.
  3. Gerber X2: The latest version, featuring advanced capabilities such as layer-specific functions, pad types, and trace impedance locations.

Before sending files to production, designers should thoroughly review Gerber files to catch potential issues overlooked during the design phase.

Other PCB Manufacturing Files

Alongside Gerber files, several additional files are required for complete PCB production:

  • IPC-D-356A netlist: Extracted from schematics.
  • BOM: Includes component sourcing information.
  • NC drill data: Specifies drill hole locations.
  • Fabrication and assembly drawings: Highlight requirements.
  • Pick and place files: Indicate component placement.
  • Test reports: Include test point data and locations.

Other file formats, like ODB++ and IPC-2518, provide more comprehensive data but require specific software support.

Using a Gerber Viewer

A Gerber viewer allows designers to inspect file contents for accuracy and design-for-manufacturing (DFM) readiness before production. While CAD tools check for electrical correctness, a manual review in a viewer can catch fabrication issues, such as:

  • Incorrect solder mask openings on SMD pads.
  • Vias in SMD pads without proper via-in-pad configuration.
  • Acid traps due to sharp corner angles.
  • Improperly sized or positioned vias.
  • Overlapping drill hits or misaligned legends.
 

Final Steps

After reviewing your Gerber files and addressing any issues, re-export the updated package and ensure it meets manufacturer requirements. Manual or automated tools can help streamline this process, ensuring your design is production-ready.


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