What Is A Gerber File and How Are They Used in the PCB

The goal of circuit design goes beyond mere conceptualization and designing circuit schematics. Its essence lies in transforming creativity into tangible, manufacturable products. However, upon completion of the design, merely sending the design files to the PCB manufacturer is not sufficient. Alongside the design files, key information such as BoM files and Gerber files is also required. In this article, FS Tech will leverage its professional expertise to provide you with a comprehensive explanation of the concept of Gerber files, elucidating their crucial role in PCB manufacturing projects.

What is Gerber in PCB

A Gerber file serves as a vital format for PCB board production, functioning as a digital blueprint that encapsulates all essential data for crafting PCB boards in alignment with specified criteria. Coined after its originator, Gerber Scientific, which pioneered this format in the 1960s, the Gerber file is an assemblage of ASCII text files, each corresponding to a distinct layer of the board design. These layers encompass an array of elements, including copper traces, solder mask depictions, drill hole coordinates, and silkscreen embellishments. Every layer is characterized by distinct data, encompassing geometric shapes, coordinates, line widths, and clearance specifications. These files are crafted using various PCB design software applications.

Gerber files assume a pivotal role as directives for PCBA manufacturers, steering their production equipment by furnishing precise instructions regarding copper trace placements, drill hole positions, and the application of solder mask and silkscreen graphics. This meticulous precision is integral in guaranteeing that the final board conforms precisely to the desired specifications.

PCB Gerber File Naming Tips

The nomenclature of the Gerber file stands as a pivotal parameter within the board manufacturing process, as it facilitates precise configuration and identification of distinct layers and components in the design. A well-crafted naming standard not only ensures clarity and consistency but also expedites effective communication between designers and manufacturers.

Layer Identification: Each Gerber file is intrinsically linked to a specific layer of the board design—be it the upper copper layer, lower copper layer, solder mask, or silkscreen. To distinguish these layers, detailed and lucid names are imperative. For instance:

Employ “Upper_Copper.gbr” to denote the upper layer.
“Lower_Copper.gbr” designates the lower layer.
“Solder_Mask_Top.gbr” signifies the solder mask layer.

File Extension: Standard file extensions are deployed to elucidate the function of a Gerber file. “.gbr” denotes an authentic Gerber file, “.drl” designates drill files, and “.gko” signifies the board outline.

Version Control: Integration of version numbers or revision identifiers within file names is a prevalent practice. This practice facilitates easy tracking and ensures that manufacturers are working with the latest design iteration. For example:

“Project_Name_v1.0_Upper_Copper.gbr”

Date and Timestamp: Incorporating a date and timestamp into file names contributes to enhanced version control and traceability. This proves especially valuable for extensive projects with frequent updates.

Project or Customer Information: To avert any confusion when handling distinct projects or diverse clients, integrating project-specific or user-specified details within file names is advised. For instance:

“User_Project_v2.1_Lower_Copper.gbr”

Power Plane Layer: For specific power plane layers, adopt explicit file names like “Power_Plane.gbr.”

Component or Function Identification: Files assigned to specific components or functions should be aptly named to aid in clear identification. For instance:

“Component_Outlines.gbr” for component placement outlines.

Assembly Files: If assembly drawings or files are incorporated, ensuring well-defined names to denote their purpose is crucial:

Use “Assembly_Drawing.pdf” for assembly drawings.
“Pick_and_Place.csv” signifies pick-and-place files.

Avoid Special Characters and Spaces: To ensure compatibility with various software and systems, refrain from using special characters and spaces in file names. Instead, opt for alphanumeric characters and underscores.

PCB Gerber File Format Types

RS-274-D

RS-274-D, also known as Extended Gerber, originated in the 1980s as an earlier version of the Gerber file format. It comprises a set of ASCII text files that delineate each layer of a board design. However, it has limitations in representing certain advanced board features like polygon pours and intricate apertures. This format finds primary support from older board manufacturing tools and software. Its simplicity allows for manual reading and adjustments if required. Nonetheless, RS-274-D lacks compatibility with new design elements such as micro vias and complex solder masks. Due to these constraints, it proves less effective for intricate board designs when compared to more modern formats.

RS-274X

RS-274X, also known as Extended Gerber X Format, is a progressive iteration of RS-274-D. This version was developed to address the limitations of its predecessor. RS-274X comes with enhanced capabilities and supports advanced features, including polygon pours, intricate apertures, and flash commands. Notably, it offers improved precision and accuracy in representing complex board designs. This format is compatible with modern board design software and manufacturing equipment, making it a preferred choice. However, it’s important to note that RS-274X lacks some of the advanced features supported by even newer formats.

ODB++

ODB++ stands as the modern and comprehensive format utilized in board manufacturing. It surpasses the older Gerber format by encompassing all PCB design and manufacturing data within a single, structured file. This format not only includes graphical representations of board layers but also incorporates component configurations, netlist information, BOM, and other pertinent details. Its key strength lies in facilitating collaboration between design and manufacturing engineers, offering a standardized layout that minimizes data translation errors across diverse software and tools. However, it’s worth noting that adopting ODB++ may necessitate the use of new software tools and modified processes. Additionally, due to its comprehensive nature, ODB++ files tend to be larger in size.

Gerber X2

Gerber X2 represents the latest iteration of the traditional Gerber format, specifically tailored to enhance communication between designers and manufacturers while overcoming limitations of previous versions. It introduces additional metadata to provide context and clarity for each layer and its intended applications. This format accommodates intricate design components and advanced layer features, such as material specifications, stack-up parameters, and impedance values. The integration of these enhancements leads to improved communication, streamlined data exchange, and a reduction in manufacturing errors. However, it’s important to note that utilizing Gerber X2 requires access to software and tools that support this format, which may not be readily available.

Using Gerber Files in PCB Fabrication

PCB to Gerber

Initial Stage: The process of designing a circuit board begins with engineers and designers utilizing advanced PCB design software to create a digital representation of the circuit. This design comprises various layers, each denoting distinct parameters such as copper traces and solder masks.
Gerber File Generation: Once the board design is completed, the design software generates Gerber files. Each Gerber file corresponds to a specific board layer and contains essential layout and feature information.

Layer Representation

Copper Layers: Gerber files for copper layers meticulously define the precise locations, widths, and shapes of traces, pads, and board components. These files are crucial for accurately etching the copper layer.
Solder Mask Layers: These files outline where solder masks are to be applied for protection, ensuring the proper application of solder during component assembly.
Silkscreen Layers: Silkscreen details encompass labels, component outlines, and part numbers. This information simplifies the placement and identification of components.
Drill Files: Drill files, derived from Gerber data, provide precise coordinates for all holes and vias on the board, facilitating the drilling process.

Photoplotting

Converting to Images: Gerber files serve as input for photoplotters, machines that translate ASCII text-based Gerber data into high-resolution images. These images serve as photographic representations of each board layer.
Film Creation: Images generated during photoplotting are used to create films or masks for various board manufacturing steps. For instance, copper layer films guide the etching process, while solder mask films indicate where the protective layer should be applied.

Manufacturing Processes

Etching: Gerber files guide the chemical etching process, ensuring precise removal of undesired copper and the retention of required copper traces.
Drilling: Accurate drilling machines are directed by Gerber files to create holes and vias at designated points on the board.
Solder Mask Application: This information ensures correct application of the solder mask for protective purposes.
Silkscreen Printing: Silkscreen details provide instructions for the silk-screening process, aiding in the placement of labels and other details.
Quality Control: During manufacturing, quality control inspections are performed, with the manufactured board compared to Gerber files to ensure required accuracy.

Alignment and Registration

Accurate Overlay: Precise alignment and registration of different layers are crucial for proper stacking. Gerber files incorporate alignment marks and reference points that enable accurate overlay and alignment throughout manufacturing.

Manufacturing Consistency

Industry Standard: These files adhere to an industrial standard format for board production, ensuring compatibility and consistency across various production features and techniques.
Efficiency: The utilization of Gerber files streamlines the transition from design to manufacturing, reducing the risk of errors and miscommunication between designers and engineers.

Advanced Features

Support for Advanced Design Elements: Modern Gerber file formats, such as Gerber X2, support advanced design components like material information, impedance profiles, and complex apertures. This provides manufacturers with more specialized details for advanced boards.

Gerber-Related Documents

Bill of Materials: Serves as a comprehensive component list essential for board design. It includes crucial information such as part numbers, component specifications, packaging types, and component packaging details. This document proves valuable for component procurement purposes and efficient inventory management.
Assembly Drawings: Visually depict the precise arrangement of components on the board. These drawings offer clear indications of component orientation, position, and reference designators (e.g., Rx, RY, etc.).
Pick-and-Place (PnP) Files: Machine-readable documents that define accurate coordinates and component orientations on the board. Automated assembly machines utilize these files to ensure precise and error-free connections.
Schematic Diagrams: Illustrate the electrical interconnections and component layouts on the board. These diagrams provide insights into the functioning of circuits.
Netlist: Outlines the intricate connectivity details among components and traces on the board. This file ensures that engineers can easily verify and assess the electrical connections.
Drill File Documentation: For designs involving holes and vias, comprehensive drill file documentation is essential. This documentation specifies the purpose, dimensions, and characteristics of each hole type, aiding in the selection of appropriate drill bits.
Design Notes: Incorporating design notes or comments provides additional information regarding design choices, considerations, and any potential issues. Such notes benefit both board producers and users.

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