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Ordering printed circuit boards (PCBs) requires supplying exact and comprehensive details about the board’s design and technical requirements. Specialized file formats play a critical role in this process, as manufacturers cannot produce PCBs without complete documentation. Design communication relies on essential files including circuit schematics, component lists (BOM), physical layout diagrams, and layer structure specifications.
To overcome compatibility challenges between different electronic design automation tools like Altium Designer, CAD, and Eagle, the industry adopted Gerber files as a standardized solution. These universally recognized format files enable manufacturers to interpret PCB designs accurately regardless of the original design software used, eliminating proprietary system dependencies.
Why is the PCB file format important?
Mastering the Gerber file format has become essential in modern PCB development due to 3 key factors:
Uniform Standards: PCB file formats establish a uniform framework for design data exchange. This guarantees that manufacturers receive precise specifications in a universally interpretable format, streamlining production workflows.
Comprehensive Data: PCB files encapsulate exhaustive details about the board’s architecture, such as component positioning, trace pathways, layer configurations, drilling coordinates, and critical manufacturing parameters. This granularity ensures fabrication accuracy and minimizes defects.
Cross-Platform Consistency: Diverse PCB design platforms produce unique file types, but standardized formats bridge these differences. By adopting universal formats like Gerber, manufacturers seamlessly interpret designs across tools (e.g., Altium, CAD), minimizing translation errors and production discrepancies.
Which PCB file formats are widely used?
To order printed circuit boards (PCBs), specific design files must be provided to convey critical manufacturing details. These include stack-up layer configurations, drill hole specifications, solder mask patterns, and silkscreen artwork. While CAD aperture files alone suffice for PCB fabrication, a Bill of Materials (BOM) becomes essential during the assembly phase to guide component integration.
Key File Types for PCB Production:
- Design Files: Formats such as RS-274X (Gerber X1), Gerber X2, IPC-2581, and ODB++ encapsulate the board’s physical structure, including layer definitions, drill data, and surface finishes.
- BOM: Typically provided in TXT, PDF, CSV, XLSX, or Excel formats, this document lists components, quantities, and reference designators required for assembly.
- Centroid/Placement Files: Also called CPL (Component Placement) or PNP (Pick-and-Place) files, these (often in TXT, CSV, XLSX, or PDF formats) specify component coordinates and orientations, ensuring precise machine placement during assembly.
What is the PCB Gerber File?
A PCB Gerber file serves as a universal standard for transmitting precise design specifications of a printed circuit board to fabrication facilities. Often referred to as a “photoplot,” this format (commonly RS-274D or RS-274X) bridges visual design elements and machine-readable instructions, enabling manufacturers to translate layouts into physical boards.
These files encapsulate layer-specific details, such as copper trace patterns, solder mask coverage, silkscreen markings, and hole locations, as previously illustrated. By providing a clear blueprint for photomask creation, Gerber files ensure manufacturing accuracy and alignment with design intent. Nearly all PCB design software tools support exporting projects into this industry-standard format.
While Gerber files handle layer data, drill specifications are typically conveyed separately via Excellon-formatted files, which define hole positions and dimensions. Despite being distinct from Gerber files, drill data is equally critical for PCB production. Generating these files often involves a separate export step, and omitting them is a frequent cause of manufacturing delays. To avoid issues, designers should always include both Gerber and drill files when submitting production requests, even if only Gerber files are explicitly mentioned.
What is the BOM ( Bill of Materials)?
A Bill of Materials (BOM) is a comprehensive inventory of components and materials required to manufacture or assemble a product. For M2PCB’s turnkey PCB Assembly service, the BOM should be developed and updated throughout the PCB design phase to enhance precision in the final stages. Critical details to include are the Manufacturer Part Number, Reference Designator, and Component Quantity. Below are the essential elements of an effective BOM:
1 Part Numbers: Official identifiers assigned by the component manufacturer.
2 Component Descriptions: Concise classifications (e.g., 10kΩ resistor, 16MHz crystal oscillator, 32-bit microcontroller).
3 Required Quantities: Exact counts of each component per board.
4 Designator Labels: Alphanumeric tags (e.g., R1, C5, U7) mapping components to their locations on the PCB layout.
5 Supplier Details: Manufacturer or distributor information for sourcing parts reliably.
The BOM serves as a foundational document for sourcing, production, and quality control, ensuring the assembled PCB aligns with design intent and functional requirements. Maintaining accuracy in the BOM streamlines procurement, minimizes assembly errors, and verifies adherence to design specifications.
What is Centroid File?
A Centroid file (often called a Pick-and-Place, XY Data, or Component Placement File [CPL]) is a critical document used to configure automated assembly equipment for rapid component placement. While certain PCB design tools auto-generate this file, others may require manual adjustments or custom workflows to produce it. This file defines the precise location, orientation, and placement details for all surface-mount components on the board, including:
- Reference Designator (e.g., R1, C5, U3)
- X and Y Coordinates (ideally centered on the component’s origin, listed in separate columns)
- Rotation Angle Indicates the component’s placement angle, though this value is often approximate and used for reference.
- Board Side (Top/Bottom)
Note: Some design software excludes through-hole components from centroid files, as these parts are not machine-placed and instead require manual soldering. We need always verify file completeness to avoid assembly mismatches.
Above are the commonly used PCB file formats. I hope it will be helpful to you. Besides, usually when we are doing production, our engineer will convert PCB files into Gerber files. However many electronics engineers bypass generating fabrication-ready files like Gerber and drill data when submitting PCB designs to manufacturers. Instead, they provide raw design software files directly. This approach can lead to discrepancies, as PCB manufacturer may interpret design elements differently during their internal file conversion process. For instance, Gerber files generated by the manufacturer might not align perfectly with the engineer’s original intent, due to variations in terminology, layer prioritization, or software-specific interpretations between design and fabrication workflows.
