What is a .brd File?

A .brd file is a type of software file used for creating and storing circuit design templates, specifically for printed circuit boards (PCBs). This file type provides information about how a PCB will be manufactured, including how components are arranged on the board and how many layers it has. It is used by PCB manufacturers to create a PCB prototype. “brd” stands for “Board Design Rule Document” and thus a .brd file can serve as a Boardview file, which provides a schematic view of a PCB, including its components and layout. Tools like OpenBoardview can be used to visualize these Boardview files. The .brd file format is versatile and can also save Gerber drill data of PCBs, making it compatible with various PCB manufacturing processes.

Originally developed by Autodesk for their EAGLE (Easily Applicable Graphical Layout Editor) software, these files contain detailed PCB drawings. Later, .brd files started getting used by other Computer-Aided Design (CAD) software for PCB Design but these may or may not use a different encoding than EAGLE. While EAGLE encodes .brd files in binary data or XML, other software like KiCad stores its PCB layouts in plain text. This difference in encoding means that .brd files from EAGLE may not be directly usable in other programs without conversion. Hence, .brd files are often proprietary, with different PCB design software developers using unique formats limiting the ability of third-party programs to open them. A particular software’s files might not be compatible with other software without specific tools or conversion processes.

Information Contained in a .brd File

A .brd file encapsulates detailed information about a PCB design. Here are the primary elements typically found in a .brd file: 

• Component Placement: The file outlines the precise locations for each component on the PCB. This includes coordinates, orientation, and any special mounting requirements. 
• Trace Routing: It defines pathways for the copper traces that electrically connect components. This includes details about the width, spacing, and assigned layers of each trace. 
• Drill Holes and Cutouts: The file specifies the locations and dimensions of drill holes used for mounting components or creating vias. It also includes any necessary cutouts or slots to be milled into the PCB. 
• Design Rules and Constraints: Design rules and constraints embedded in the file ensure the PCB layout adheres to specific criteria. These rules cover aspects such as minimum trace spacing, maximum current capacity, and clearance requirements. 
• Layer Stackup: The .brd file details the PCB's layer stack up, including the number and arrangement of copper layers, solder mask layers, and silkscreen layers. This information is crucial for the manufacturing process.

Applications of .brd Files 

Designers and manufacturers utilize .brd files throughout various stages of the electronic design process. Here are some common applications: 

1. Design Creation and Editing: Electronic Design Automation (EDA) software enables designers to develop and modify .brd files, creating the layout of a printed circuit board (PCB). Within these tools, designers can position components, route electrical connections, set design rules, and optimize the layout for both performance and manufacturability. The .brd file serves as a visual blueprint of the design, aiding in collaboration among team members. 
2. Design Validation and Simulation: Prior to fabrication, .brd files are used for design validation and simulation. EDA tools offer features to analyze the design, checking for issues like signal integrity problems or violations of design rules. By simulating the PCB's behavior, designers can detect and resolve potential issues before moving to the manufacturing stage. 
3. Manufacturing and Assembly: After the design is complete, the .brd file is forwarded to the manufacturer for production. Manufacturers rely on the .brd file to understand the design specifications and generate the necessary fabrication files, such as Gerber files. The .brd file serves as a reference for component placement, routing, and other critical manufacturing details.

.brd files play a crucial role in the PCB design and manufacturing process, containing comprehensive information on component placement, trace routing, drill holes, design rules, and layer stackup. These files are essential to designers and manufacturers for understanding the structure and content of PCBs to ensure accurate design validation, simulation, and successful production of these circuit boards. Proper management and utilization of .brd files facilitates collaboration, minimizes design errors, and streamlines the transition from design to manufacturing.