Pick and place file formats

What are Pick and Place Files?

Pick-and-Place files, also known as centroid files or XY data files, specify the locations and rotations of components on a printed circuit board (PCB) for automated assembly by a pick-and-place machine. These files are essential for electronics manufacturing as they enable the precise placement of components during the Surface Mount Technology (SMT) process.

Pick-and-place files contain information such as:

Reference designator for each component
X and Y coordinates of the component center point
Rotation angle of the component
Side of the board (top or bottom)
Component package type

The specific format of pick-and-place files can vary depending on the software used to generate them and the requirements of the manufacturing facility. However, there are some common standardized formats that are widely used in the industry.

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Common Pick and Place File Formats

1. Centroid File Format

The Centroid file format, also known as a .csv or .txt file, is a simple text-based format that is comma or tab-delimited. It typically contains the following columns of data:

Column	Description
Designator	The reference designator for the component
Footprint	The PCB footprint for the component
Mid X	The X-coordinate of the component center point
Mid Y	The Y-coordinate of the component center point
Ref X	The X-coordinate of the component reference point (pin 1)
Ref Y	The Y-coordinate of the component reference point (pin 1)
Pad X	The X-size of the component pads
Pad Y	The Y-size of the component pads
TB	The side of the board (T=Top, B=Bottom)
Rotation	The rotation angle of the component (in degrees)

Here’s an example of a Centroid file:

Designator,Footprint,Mid X,Mid Y,Ref X,Ref Y,Pad X,Pad Y,TB,Rotation 
C1,0805,112.5000,86.5000,112.1000,86.5000,1.6000,0.8000,T,90
R1,0603,102.5000,81.2500,102.5000,81.5600,1.6000,0.8000,T,180
U1,TQFP32,129.5000,88.0000,128.0000,86.5000,0.4000,1.0000,T,90

2. IPC-D-356 Format

IPC-D-356 is an industry-standard format for exchanging printed circuit board (PCB) manufacturing data, including pick-and-place information. It is a text-based format that uses specific record types to convey information.

The format consists of a header section followed by detail records. Each record is identified by a record type code at the beginning of the line.

Some key record types for pick-and-place data include:

Record type 1: Specifies the filename and revision
Record type 317: Defines the component pickup point and orientation
Record type 327: Defines the fiducial marks used for board alignment
Record type 367: Defines additional placement information like component height

Here’s a simplified example of an IPC-D-356 file snippet:

317+5555+0000C1    +0112500+0086500+0000270     
317+5555+0000R1    +0102500+0081250+0000180    
317+5555+0000U1    +0129500+0088000+0000090

In this example, each line represents a component placement record. The fields are:

Record type (317)
Manufacturer part number (+5555 = generic)
Reference designator (C1, R1, U1)
X-coordinate (in 1/100 mm)
Y-coordinate (in 1/100 mm)
Rotation (in degrees counterclockwise)

3. ODB++ Format

ODB++, which stands for Open Database format, is a comprehensive PCB CAD data exchange format that includes pick-and-place information alongside other manufacturing data. It was developed by Valor Computerized Systems (now part of Mentor Graphics).

An ODB++ job typically consists of a folder structure containing multiple files, each serving a specific purpose. The pick-and-place data is usually found in a file named mat.txt within the steps/pcb/layers subfolder.

The mat.txt file is a tab-separated text file with columns for:

Component reference designator
Footprint name
X-coordinate
Y-coordinate
Rotation
Side of the board
Component height

Here’s an example snippet from an ODB++ mat.txt file:

REF  COMP_REF   PN   FOOTPRINT   X     Y    ANGLE SIDE HEIGHT
J1   J1         CON1  CON-USB-A  62.2300  47.4500  90.0000  TOP  0
C1   C1         CAP1  CAP-0805   26.8700 113.2100 180.0000  TOP  0
R1   R1         RES1  RES-0603   28.6500  29.6400   0.0000  TOP  0

4. GenCAD Format

GenCAD is a generic CAD format used for exchanging PCB manufacturing data, including pick-and-place information. It is a text-based format that organizes data into sections using keywords.

The pick-and-place data is typically found in the %MOUINT ITEM section of a GenCAD file. Each line in this section represents a component and includes fields for:

Reference designator
Footprint name
X-coordinate
Y-coordinate
Rotation angle
Side of the board
Component height

Here’s an example of a GenCAD file snippet containing pick-and-place data:

%MOUNT ITEM
C1  CAP-0805    42.5000  36.7500 270.0  TOP 0
R1  RES-0603    18.4000  29.1200   0.0  TOP 0
U1  QFP-100    102.6500  84.3700  90.0  TOP 0
%END MOUNT ITEM

Generating Pick and Place Files

Pick-and-place files are typically generated from PCB design software after completing the component placement and routing process. The specific steps for generating these files may vary depending on the design software being used.

Here are general guidelines for generating pick-and-place files in popular PCB design software:

Altium Designer

Go to File > Assembly Outputs > Pick and Place Files.
Select the desired output format (e.g., Centroid, IPC-D-356, ODB++).
Configure the output settings, such as units and origin coordinates.
Choose an output location and filename.
Click “OK” to generate the file.

KiCad

Open the PCB file in the Pcbnew editor.
Go to File > Fabrication Outputs > Footprint Position (.pos) File.
Select the desired output format and configuration options.
Choose an output location and filename.
Click “OK” to generate the file.

Eagle

Open the board file in the Eagle PCB editor.
Run the CAM processor (File > CAM Processor).
Select the desired pick-and-place output format from the predefined CAM jobs.
Configure the output settings, if necessary.
Choose an output location and filename.
Click “Process Job” to generate the file.

OrCAD PCB Designer

Open the PCB file in the OrCAD PCB Editor.
Go to File > Export > Pick and Place.
Select the desired output format and configuration options.
Choose an output location and filename.
Click “OK” to generate the file.

Verifying Pick and Place Files

After generating pick-and-place files, it is crucial to verify their accuracy before sending them to the manufacturing facility. Inaccurate or incomplete pick-and-place data can lead to assembly errors, delays, and additional costs.

Here are some steps to verify pick-and-place files:

Visual inspection: Open the pick-and-place file in a text editor or spreadsheet software and visually check for any obvious errors, such as missing or misaligned data.
Cross-reference with BOM: Compare the components listed in the pick-and-place file with the bill of materials (BOM) to ensure all required components are accounted for and correctly identified.
Check coordinates and rotations: Verify that the X and Y coordinates and rotation angles for each component are correct and match the intended placement on the PCB.
Validate file format: Ensure that the pick-and-place file adheres to the expected format and conventions, such as column order, delimiters, and units.
Use visualization tools: Some PCB design software packages offer built-in tools for visualizing pick-and-place data overlaid on the PCB layout. This can help identify placement errors or discrepancies.
Collaborate with the manufacturer: Share the pick-and-place files with the manufacturing facility and ask for their feedback. They may have specific requirements or preferences for file formats and can help identify potential issues.

Best Practices for Creating Pick and Place Files

To ensure smooth and error-free PCB Assembly, follow these best practices when creating pick-and-place files:

Use consistent naming conventions: Adopt a consistent naming scheme for component reference designators, footprint names, and file names to avoid confusion and errors.
Ensure accurate component placement: Double-check component placement in the PCB design software before generating pick-and-place files. Verify that components are properly aligned and spaced.
Include fiducial marks: Add fiducial marks to the PCB design to provide reference points for the pick-and-place machine. Ensure that the fiducial marks are included in the pick-and-place file.
Specify units and origin: Clearly communicate the units (e.g., millimeters or inches) and origin coordinates used in the pick-and-place file to avoid misinterpretation by the manufacturer.
Provide additional instructions: If there are any special requirements or instructions for component placement, include them in the pick-and-place file or provide a separate README file.
Use industry-standard formats: Whenever possible, use widely supported and industry-standard pick-and-place file formats, such as Centroid or IPC-D-356, to ensure compatibility with various manufacturing systems.
Keep files organized: If a project consists of multiple PCBs or assembly variants, keep the pick-and-place files organized and clearly labeled to avoid confusion.
Version control: Implement version control for pick-and-place files, especially when making revisions or updates. This helps track changes and ensures that the correct version is used for manufacturing.

FAQ

1. What is the difference between a pick-and-place file and a BOM?

A pick-and-place file specifies the physical locations and orientations of components on a PCB, while a bill of materials (BOM) is a list of all the components required to assemble the PCB. The pick-and-place file is used by the assembly machine to place components, while the BOM is used for procurement and inventory management.

2. Can I use a spreadsheet to create a pick-and-place file?

While it is possible to manually create a pick-and-place file using a spreadsheet, it is not recommended for complex designs. PCB design software can automatically generate pick-and-place files based on the component placement in the PCB layout, reducing the risk of errors and ensuring consistency with the design.

3. What should I do if my PCB design software doesn’t support the pick-and-place file format required by my manufacturer?

If your PCB design software doesn’t directly support the required pick-and-place file format, you can try exporting the data in a generic format (such as Centroid) and then converting it to the desired format using a third-party tool or script. Alternatively, consult with your manufacturer to see if they can accept alternative formats or provide guidance on how to generate compatible files.

4. How do I handle component rotations in a pick-and-place file?

Component rotations in pick-and-place files are typically specified in degrees, with 0° representing the default orientation (e.g., pin 1 facing up or to the left). Positive rotation angles are usually measured counterclockwise. Consult your manufacturer’s guidelines or the specific file format documentation for the exact convention used.

5. What is the purpose of fiducial marks in pick-and-place files?

Fiducial marks serve as reference points for the pick-and-place machine to align the PCB and ensure accurate component placement. The pick-and-place file includes the coordinates of the fiducial marks, which the machine uses to calibrate its position relative to the PCB. Fiducial marks are typically placed in the corners or edges of the PCB and should be included in the pick-and-place file for proper machine setup.

Conclusion

Pick-and-place files are essential for automated PCB assembly, providing the necessary information for precise component placement. Understanding the various file formats, such as Centroid, IPC-D-356, ODB++, and GenCAD, is crucial for generating compatible files that meet manufacturer requirements.

When creating pick-and-place files, it is important to follow best practices, such as using consistent naming conventions, ensuring accurate component placement, including fiducial marks, and specifying units and origin coordinates. Verifying the accuracy of pick-and-place files before sending them to the manufacturer can help prevent assembly errors and delays.

By adhering to these guidelines and working closely with manufacturing partners, designers can ensure a smooth transition from PCB design to assembly, ultimately leading to faster time-to-market and higher-quality electronic products.