How to Create a Centroid (Pick and Place) File Instantly

 

Introduction

A centroid file, also known as a pick and place file, is crucial for automated PCB assembly. It contains the precise coordinates and orientation of every component on a circuit board, enabling pick and place machines to accurately place components during manufacturing. This comprehensive guide explores how to create these files efficiently and accurately.

Understanding Centroid Files

Basic Components

A centroid file contains essential information for each component:

Information
Description
Example
Reference Designator
Unique component identifier
R1, C4, U2
X Coordinate
Position along X-axis
25.4 mm
Y Coordinate
Position along Y-axis
15.7 mm
Rotation
Component orientation
0, 90, 180, 270 degrees
Layer
Board side for placement
Top, Bottom
Package Type
Component footprint
SOT-23, SOIC-8

File Format Types

Format
Extension
Advantages
Common Usage
ASCII
.txt, .csv
Human-readable, universal
Most common
Excel
.xls, .xlsx
Easy editing, sorting
Documentation
Custom
Various
Manufacturer-specific
Special requirements

Creation Methods

Automated Generation

Most modern PCB design software includes centroid file generation capabilities:

Software
Native Format
Export Options
Special Features
Altium Designer
.txt
Multiple
Component grouping
KiCad
.pos
ASCII, CSV
Layer filtering
Eagle
.mnt
Text, CSV
Rotation handling
OrCAD
.txt
Multiple
Batch processing

Manual Creation Steps

1. Component Placement Documentation
2. Coordinate System Definition
3. Reference Point Establishment
4. Component Orientation Verification
5. Layer Assignment

File Format Requirements

Standard Format Elements

Element
Format
Required
Notes
Header
Text
Optional
File information
Units
mm/mil
Required
Consistent throughout
Coordinates
Decimal
Required
Precision to 0.01mm
Rotation
Integer
Required
0.1-degree precision
Comments
Text
Optional
Documentation

Industry Standards

Common industry standards for centroid files:

1. IPC-7351
2. JEDEC
3. ISO 9001 requirements
4. Manufacturing specific guidelines

Quality Control and Verification

Verification Process

Step
Purpose
Tools Required
Format Check
File structure verification
Text editor
Coordinate Verification
Position accuracy
CAD software
Rotation Check
Orientation confirmation
Viewer tool
Layer Assignment
Side verification
Assembly software

Common Errors

Error Type
Cause
Prevention Method
Coordinate Offset
Reference point mismatch
Standardize origin
Rotation Inversion
Different conventions
Document standards
Missing Components
Export settings
Complete verification
Unit Mismatches
Mixed systems
Enforce consistency

Common Software Solutions

CAD Software Integration

Software
Key Features
Automation Level
Altium
Direct export, verification
High
KiCad
Built-in tools, customization
Medium
Eagle
Basic export, manual options
Medium
OrCAD
Advanced options, scripting
High

Third-Party Tools

Specialized tools for centroid file management:

1. File format converters
2. Verification utilities
3. Batch processors
4. Custom script generators

Best Practices

File Naming Conventions

Element
Format
Example
Project Name
Text
Project123
Revision
Number
Rev2
Date
YYYYMMDD
20240103
Side
T/B
Top

Documentation Requirements

Essential documentation elements:

1. File format specification
2. Coordinate system definition
3. Unit system declaration
4. Revision history
5. Special instructions

Version Control

Stage
Action
Documentation
Creation
Initial generation
Version 1.0
Revision
Component updates
Change log
Release
Manufacturing approval
Sign-off

Advanced Techniques

Automation Scripts

Script Type
Purpose
Language
Format Conversion
Standardization
Python
Batch Processing
Multiple boards
Shell
Verification
Error checking
Python/Perl
Integration
Tool connection
Various

Multi-board Handling

Strategies for managing multiple boards:

1. Panel array coordinates
2. Common reference points
3. Nested assignments
4. Batch processing

Manufacturing Considerations

DFM Requirements

Requirement
Purpose
Implementation
Fiducial Marks
Registration
Standard positions
Origin Location
Reference
Consistent placement
Component Spacing
Assembly clearance
Design rules

Machine-Specific Requirements

Different machines may need specific formats:

Machine Type
Format
Special Requirements
Universal
Generic CSV
Basic positioning
Yamaha
Custom
Extended attributes
Panasonic
Custom
Special rotation
ASM
Proprietary
Enhanced data

Troubleshooting Guide

Common Issues

Issue
Symptoms
Solution
Offset Components
Misalignment
Check origin
Wrong Rotation
Incorrect orientation
Verify conventions
Missing Data
Incomplete placement
Review export settings
Format Errors
File rejection
Validate format

Resolution Steps

1. Verify source data
2. Check export settings
3. Validate file format
4. Test with viewers
5. Perform trial runs

Frequently Asked Questions

Q1: What is the most common format for centroid files?

A1: The most common format is CSV (Comma Separated Values) or plain text (.txt) files. These formats are universal, human-readable, and easily imported into various pick and place machines. They typically contain columns for reference designator, X-coordinate, Y-coordinate, rotation, and layer information.

Q2: How do I handle component rotation in centroid files?

A2: Component rotation handling requires attention to:

• Reference orientation (0 degrees)
• Rotation direction (clockwise vs. counterclockwise)
• Machine-specific conventions
• Pin 1 location Always verify rotation conventions with your manufacturer and document any special requirements in your assembly notes.

Q3: What are the essential coordinates for a centroid file?

A3: Essential coordinates include:

• X and Y positions relative to a defined origin point
• Z coordinates for height-sensitive components
• Rotation angle
• Reference designator
• Component side (top/bottom) All coordinates should be in consistent units (typically millimeters) and referenced to a clearly defined origin point.

Q4: How can I verify my centroid file is correct?

A4: Verification steps include:

1. Using PCB design software's built-in viewers
2. Cross-checking against the original design
3. Using third-party verification tools
4. Performing manual spot-checks of critical components
5. Running a test assembly if possible

Q5: What are common mistakes in centroid file creation?

A5: Common mistakes include:

• Incorrect origin point selection
• Mixed units (mixing millimeters and inches)
• Wrong rotation conventions
• Missing components
• Incorrect layer assignments These can be avoided through careful verification and following established procedures.