Basic Guide to PCB Gerber Files

Constructing a skyscraper is not a task accomplished overnight; it demands meticulous layout planning and precise execution. However, relying solely on a basic architectural blueprint falls short because it lacks intricate internal details. It’s imperative to comprehensively annotate the specifics of each component, encompassing dimensions, lengths, hole placements, and more. A parallel can be drawn with the manufacturing of printed circuit board. During the design phase, we map out the precise locations of interconnections and components. Nevertheless, design documents often amount to mere sketches, devoid of in-depth particulars.

In such scenarios, Gerber files come to the forefront. They serve as a critical conduit for transmitting information from designers to manufacturers, furnishing the graphical representations and manufacturing directives necessary. These encompass pathways, holes, soldering points, textual elements, and more. In this TechSparks article, we will delve deeper into the essence of Gerber files and elucidate the process of their creation. Let’s embark on this journey!

Table of Contents

What is Gerber File

Circuit images consist of lines (traces) and graphics (components, solder pads, etc.). To ensure production accuracy, it’s essential to mark all the details. However, as circuit complexity increases, manual labeling becomes cumbersome, giving rise to Gerber files. Gerber files were developed by the Gerber Scientific Instrument Company (now Gerber Technology) in the 1960s and rapidly became the standard in the PCB design and manufacturing industry.

In circuit design, specifications for identical components are consistent. After inserting components, these specifications are organized into files and documented. Once the circuit design is complete, designers can use design software to export Gerber files. These standardized files contain all the necessary manufacturing details, such as layer information, drill holes, solder pads, solder mask, silkscreen, and more. When manufacturers receive Gerber files, they use Computer-Aided Manufacturing (CAM) tools to analyze and break them down into different modules. These modules are then allocated to various production departments and input into manufacturing equipment for production.

Gerber files exist as open-source documents, using ASCII character encoding to represent vector graphics. This means the files contain line drawings, shapes, and coordinate data, making them relatively easy to read and edit. They have become one of the standard file formats in design and manufacturing.

Currently, there are three main Gerber file formats: RS-274D, RS-274X, and Gerber-X2. Here’s an overview of each format:

  • RS-274D: Originating in the 1960s, this early version of Gerber files, often referred to as “Standard Gerber,” includes basic elements like traces, solder pads, and component outlines. However, due to its lack of three-dimensional models and assembly information, it has become less common in modern circuit design.
  • RS-274X: Also known as “Extended Gerber,” is an enhanced and improved version of RS-274D. It allows for more precise descriptions of circuit designs and supports features like three-dimensional models and test data. It’s favored by users for its ability to automate aperture settings, significantly reducing the designer’s workload.
  • Gerber-X2: The latest Gerber file format, supports all the requirements of modern manufacturing. As manufacturing technologies and demands continue to evolve, Gerber-X2 has emerged as a trend in the PCB industry. More and more design tools and manufacturing equipment support this format.

How to Make PCB Gerber Files

Origin Set

First, you need to set the origin. This section includes general, layer, drill layer, aperture, and advanced options. Start by locating “Edit” in the top toolbar of your design software, then from the drop-down menu, find “Origin,” and finally, select the “Set” button.

Set origin

Upon entering the origin settings, a new window will pop up. Begin by selecting “General” to specify the file format and units. Typically, choose “inches” for units and “2:5” for the scale format.

Unit options window

Next, move on to the “Layers” section. For a double-layer board, as an example, the items to be checked include GTO, GTP, GTS, GTL, GBL, GBS, GBP, GBO, GKO, GPT, and GPB. As for mechanical layers, select according to your actual design requirements.

Set layer

Proceed to the “Drill Layer” section. As shown, choose “Drill Drawing” and “Drill Guide Drawing.” This indicates that all the required drill types will be included in the output.

Drill layer settings

Now, select “Aperture.” As mentioned earlier, RS274X is the most popular Gerber file format specification today and is typically considered the default option. After checking it, apertures will be automatically created each time you use CAM settings to generate output files. If not checked, you can select from the aperture list on the right.

Aperture setting

Finally, choose “Advanced.” In most cases, using the software’s default options is sufficient. However, you may encounter a warning pop-up about the file being too small when creating a Gerber file. If this happens, you can increase the values in the “Film Rules Bar” by a factor of 10.

Advanced tab settings

Once all the settings are complete, click “Confirm.” The software will automatically generate the output file.

Output Gerber file

Drilling File

The drill file and Gerber file will be placed in the same ZIP file and sent to the manufacturer. To output the drill file, you need to return to the design editor page. In the top toolbar, locate “File,” then from the drop-down menu, find “Manufacturing Output,” and finally, select “NC Drill Files.”

Drilling document recording

Upon entering “NC Drill Files,” there’s no need to make any changes; you can use the default settings. Please ensure that the units are set to “inches,” and the scale format is “2:5.” Then, click “Confirm” to proceed with the output.

NC drilling settings

NC drilling file output

IPC Netlist

Professional manufacturers, upon receiving the customer’s PCB Gerber files, conduct a thorough review of their accuracy. One critical aspect of this review is the IPC netlist, which enumerates all the details of components on the circuit board, including identification, packaging, pins, connections, and electrical specifications.

To set up the netlist file, navigate to the “File” option in the top toolbar of the design editing page. From the dropdown menu, select “Assembly Output,” and finally, choose “Testpoint Report.” Opt for IPC-D-356A and then click “Confirm.”

IPC netlist selection

Pick and Place File

The next step after bare board production is the assembly process, where modern PCBA processes employ pick-and-place machines for precise component placement. Pick-and-place robots use the guidance provided by pick and place files to accurately position components.

To set up the pick and place file, navigate to the “File” option in the top toolbar. From the dropdown menu, select “Assembly Output,” and finally, choose “Generate Pick and Place Files.” Here, you can access component information and, as needed, choose either “Text” or “CSV” format for output. Make sure to select “Imperial” as the unit of measurement.

Coordinate file settings

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