Key Takeaways:
What are the Main Types of PCB Fab Files?
- Gerber files define all PCB layers and must be reviewed for accuracy before fabrication.
- Drill files specify hole sizes and locations, which directly affect connectivity and reliability.
- BOM lists all assembly components and must align with schematic and layout data.
- Pick-and-place file guides automated assembly and must match the BOM precisely.
- Mechanical drawings define board dimensions and ensure correct physical fit.
Introduction
In Singapore’s fast-paced electronics sector, completing a circuit layout marks only the beginning of the manufacturing process. Prior to printed circuit board (PCB) fabrication, or PCB fab, it is important to prepare a complete and technically accurate set of manufacturing files. This documentation package enables a controlled and traceable transition from digital design data to physical board production.
This guide outlines the essential files required before submitting your board for fabrication and assembly.
Why File Preparation Matters in PCB Fab
PCB fabrication is a data-driven process. Manufacturers rely entirely on the digital files you provide. If there is missing layer information, unclear drill sizes, or inconsistent component data, the fabrication team must pause production to clarify details. These clarification cycles interrupt production planning, particularly in facilities operating on scheduled panel runs and controlled material allocation.
What are the Different Types of PCB Files?
1. Gerber Files
Gerber files are the industry-standard format used to define each physical layer of your PCB. These files communicate the copper traces, pads, solder mask openings, silkscreen markings, and other graphical elements required to build the board.
Each layer is exported as a separate Gerber file. Typical layers include:
- Top copper
- Bottom copper
- Inner layers for multilayer boards
- Solder mask layers
- Silkscreen layers
- Paste mask layers for assembly
Before sending them out, it is good practice to review the complete Gerber set using a viewer tool. This helps confirm layer alignment, aperture data, and any unintended artefacts that may affect production.
2. Drill Files
Drill files, commonly known as Excellon files, specify the location and diameter of every hole on the board. These include plated through-holes, non-plated holes, and vias. Accurate drill data is essential for maintaining structural integrity and electrical connectivity. Mismatched drill sizes can result in weak joints or assembly issues. Designers should also ensure that tool tables and units are clearly defined to avoid confusion during fabrication.
When a design incorporates controlled impedance traces, high-density interconnect structures, microvias, or tightly spaced via arrays, drill accuracy becomes even more critical. In such designs, small deviations in hole diameter or positional accuracy can alter impedance characteristics, affect signal integrity, or compromise layer-to-layer connectivity. High-density layouts also reduce margin for misalignment, making precise drill registration vital to maintain performance specifications and overall board reliability.
3. Bill of Materials
The Bill of Materials, or BOM, is a structured document that defines every component required to assemble the PCB. It serves as the primary reference for procurement, kitting, and assembly planning.
A typical BOM specifies the components required for assembly, including:
- Manufacturer part numbers
- Component values
- Package types
- Footprints
- Quantity per board
A well-prepared BOM minimises procurement delays and substitution risks. It should align precisely with the schematic and layout files. For companies working with a PCB design partner in Singapore, early coordination on approved component libraries and sourcing preferences can simplify this stage and reduce last-minute revisions.
4. Pick-and-Place File
The pick-and-place file is also known as the centroid file. It contains the XY coordinates, rotation angles, and reference designators for each surface-mounted component. This file guides automated placement machines during assembly. Inaccurate rotation data or inconsistent reference naming can disrupt production flow.
Alignment between the pick-and-place file and the BOM is equally important to prevent misplacement. In automated surface-mount processes, placement machines rely on accurate XY coordinates and rotation data to position components within tight tolerances. If the BOM specifies one package type while the pick-and-place file references another footprint, the machine setup may not align with the actual board layout. This can lead to errors in rotation or footprints for diodes and electrolytic capacitors, or incorrect orientation of integrated circuits.
5. Board Outline and Mechanical Drawings
Board outline and mechanical drawings define the exact physical form of the PCB and ensure dimensional accuracy during fabrication. This mechanical data typically includes overall board dimensions, edge cuts, internal slots, cut-outs, mounting hole locations, and panelisation details where applicable.
Providing clear and fully dimensioned mechanical drawings enables the fabrication team to manufacture the board to the intended shape and tolerances. It also ensures proper alignment with enclosures, connectors, standoffs, and other mechanical interfaces.
What are Some Additional Best Practices Before Submission?
On top of generating the required files, consider the following checks before sending your package to the manufacturer:
- Confirm file naming conventions are clear and consistent
- Include a readme file outlining stack-up, material specifications, surface finish, and special instructions
- Verify design rule checks have been completed
- Ensure units are clearly stated, either in millimetres or inches
- Providing a complete and organised file package helps the fabrication team proceed confidently without repeated clarification cycles.
From Design Data to Reliable PCB Fab Execution
Preparing PCB files for fabrication is not simply an administrative step. It is a critical bridge between design intent and physical production. Clear Gerber files, accurate drill data, a detailed BOM, precise pick-and-place information, and comprehensive mechanical drawings collectively reduce manufacturing risk. By approaching PCB fab documentation methodically, electronic manufacturing service providers in Singapore can strengthen collaboration and improve overall production reliability.
MPN Tech is a PCB manufacturer in Singapore. We support both manual and automated PCB assembly, including hybrid assembly for precision electronics and IPC Class I, II, and III builds. Looking to address practical production considerations? Let us help you maintain operational efficiency and regulatory compliance throughout the manufacturing process.
Contact us to learn how we can support your prototyping and production needs.
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