Most Common Gerber Files Problems & Solutions: A Comprehensive Guide

 

Introduction

Gerber files are the standard format for PCB manufacturing, serving as the primary method for communicating design intent to fabricators. Despite their widespread use, numerous issues can arise during file generation, verification, and manufacturing. This comprehensive guide addresses the most common problems and provides detailed solutions.

Understanding Gerber Files

File Types and Purposes

File Extension
Layer Type
Purpose
Critical Parameters
.GTL
Top Layer
Copper traces and pads
Polarity, scale
.GBL
Bottom Layer
Copper traces and pads
Polarity, scale
.GTO
Top Overlay
Silkscreen markings
Text size, clearance
.GTS
Top Solder Mask
Solder mask openings
Expansion, tolerance
.GBS
Bottom Solder Mask
Solder mask openings
Expansion, tolerance
.GTP
Top Paste
Solder paste apertures
Reduction ratio
.GBP
Bottom Paste
Solder paste apertures
Reduction ratio
.GKO
Keep-Out
Board outline
Completeness

Critical Elements

Essential Components

1. Coordinate information
2. Aperture definitions
3. D-codes
4. G-codes
5. Layer polarity

Common File Generation Issues

Export Problems

Problem Type
Common Causes
Impact
Prevention Methods
Missing Layers
Incorrect export settings
Incomplete fabrication data
Export checklist
Wrong Scale
Unit mismatches
Dimensional errors
Verify units before export
Polarity Issues
Software defaults
Reversed features
Check layer polarities
Misaligned Data
Multiple coordinate systems
Assembly problems
Use consistent origins
Resolution Errors
Incorrect precision settings
Feature distortion
Set appropriate resolution

Software-Specific Issues

CAD Export Settings

Software
Common Problems
Required Settings
Verification Steps
Altium
Unit mismatches
Set to inches/mm
Check output preview
Eagle
Missing apertures
Enable all D-codes
Verify D-code list
KiCAD
Layer alignment
Set correct origin
Check alignment marks
OrCAD
Resolution issues
Set precision
Compare measurements

Layer-Related Problems

Layer Stack-up Issues

Issue
Symptoms
Cause
Solution
Missing Layers
Incomplete data
Export error
Verify layer selection
Incorrect Order
Assembly problems
Stack-up definition
Review layer stack-up
Mirrored Layers
Reversed features
Export settings
Check mirror settings
Layer Shift
Misaligned features
Origin inconsistency
Align to common origin

Layer Registration

Critical Factors

1. Alignment marks
2. Fiducial marks
3. Reference holes
4. Edge clearances
5. Layer-to-layer registration

Aperture and Pad Issues

Common Aperture Problems

Problem
Description
Impact
Solution
Missing Apertures
Undefined D-codes
Missing features
Verify aperture list
Wrong Sizes
Incorrect definitions
Component mismatch
Check aperture sizes
Flash vs Draw
Incorrect command
Quality issues
Use appropriate command
Overlapping
Multiple definitions
Fabrication errors
Clean aperture list

Pad Definition Issues

Critical Considerations

1. Pad sizes
2. Shapes
3. Rotations
4. Thermal relief
5. Clearances

Drill File Problems

Common Drill Issues

Issue Type
Symptoms
Causes
Solutions
Missing Holes
Incomplete drilling
Export errors
Verify hole selection
Wrong Sizes
Mismatched holes
Unit conversion
Check drill sizes
Tool Assignment
Incorrect tools
Definition errors
Review tool list
Location Errors
Misplaced holes
Coordinate issues
Verify coordinates

Drill File Format

Essential Elements

1. Tool definitions
2. Coordinates
3. Units
4. Format specification
5. Tool changes

DFM Verification Issues

Manufacturing Checks

Check Type
Parameters
Common Failures
Solutions
Minimum Track Width
Width violations
Design rules
Adjust design
Clearances
Spacing violations
Component placement
Modify spacing
Copper Balance
Distribution issues
Pour settings
Adjust copper pours
Silkscreen
Text overlap
Component density
Relocate text

Design Rule Verification

Critical Rules

1. Trace width and spacing
2. Hole size and spacing
3. Copper to edge clearance
4. Component clearance
5. Thermal relief settings

File Format Compatibility

Format Specifications

Format
Version
Key Features
Common Issues
RS-274X
Standard
Self-contained
Software support
RS-274D
Legacy
Separate wheel file
Missing apertures
Extended
Modern
Enhanced features
Compatibility
X2
Latest
Additional metadata
Limited support

Conversion Problems

Common Issues

1. Format mismatches
2. Lost metadata
3. Unit conversion errors
4. Feature interpretation
5. Precision loss

Solutions and Best Practices

Prevention Strategies

Phase
Action Items
Tools
Verification
Design
DRC checks
CAD tools
Design rules
Export
Settings verification
Export templates
Preview
Verification
Gerber viewer
Validation tools
Layer check
Documentation
Manufacturing notes
Specification sheets
Review

Best Practices

Essential Guidelines

1. Use consistent units
2. Maintain organized layer structure
3. Include manufacturing notes
4. Verify all exports
5. Document special requirements

Quality Control Methods

Verification Procedures

Step
Tool
Purpose
Critical Checks
Visual Inspection
Gerber viewer
Layout verification
Layer alignment
DFM Analysis
DFM software
Manufacturing checks
Design rules
Comparison
Reference files
Consistency check
Feature matching
Documentation
Checklist
Completeness
Required files

Validation Tools

Recommended Software

1. GerbView
2. ViewMate
3. GC-Prevue
4. CAM350
5. GenCAD

Frequently Asked Questions

Q1: What are the essential Gerber files needed for PCB fabrication?

A1: The essential Gerber files typically required for PCB fabrication include:

• Top and bottom copper layers (.GTL, .GBL)
• Solder mask layers (.GTS, .GBS)
• Silkscreen layers (.GTO, .GBO)
• Board outline (.GKO)
• Drill file (.TXT or .XLN)
• Solder paste layers if required (.GTP, .GBP)

Q2: How can I verify my Gerber files before sending them to manufacturing?

A2: To verify Gerber files:

• Use a Gerber viewer to check all layers
• Verify layer polarity and scale
• Check drill file alignment
• Confirm all features are present
• Run DFM checks
• Compare against original design

Q3: Why do my Gerber files show different dimensions than my PCB design?

A3: Dimensional discrepancies usually occur due to:

• Unit mismatch (inches vs. millimeters)
• Incorrect scale factor during export
• Resolution settings in the CAD software
• Coordinate system misalignment
• Rounding errors in the export process

Q4: What causes missing features in Gerber files?

A4: Missing features can be caused by:

• Incorrect layer selection during export
• Missing aperture definitions
• Wrong polarity settings
• Export filter settings
• Software bugs or limitations

Q5: How do I fix overlapping or misaligned layers in my Gerber files?

A5: To fix layer alignment issues:

• Verify origin point settings
• Check for mirrored layers
• Ensure consistent coordinate systems
• Review layer stack-up settings
• Re-export with correct alignment parameters