Inquire: Call 0086-755-23203480, or reach out via the form below/your sales contact to discuss our design, manufacturing, and assembly capabilities.
Quote: Email your PCB files to Sales@pcbsync.com (Preferred for large files) or submit online. We will contact you promptly. Please ensure your email is correct.
Notes: For PCB fabrication, we require PCB design file in Gerber RS-274X format (most preferred), *.PCB/DDB (Protel, inform your program version) format or *.BRD (Eagle) format. For PCB assembly, we require PCB design file in above mentioned format, drilling file and BOM. Click to download BOM template To avoid file missing, please include all files into one folder and compress it into .zip or .rar format.
IPC-A-600 Complete Guide: PCB Inspection Standards, Class 1/2/3 & Certification
Every PCB that leaves a fabrication shop gets inspected. But what exactly are inspectors looking for, and how do they decide whether a board passes or fails? That’s where IPC-A-600 comes in. This visual acceptability standard has become the universal language for PCB quality, providing the photographs, illustrations, and criteria that inspectors worldwide use to evaluate bare printed circuit boards.
After years of receiving boards from various fabricators and dealing with incoming inspection disputes, I’ve come to appreciate how essential IPC-A-600 is. Without it, every conversation about quality becomes subjective—”that scratch looks too deep” versus “it’s within tolerance.” With IPC-A-600, everyone references the same visual examples and criteria.
IPC-A-600, officially titled “Acceptability of Printed Boards,” is the definitive illustrated guide for evaluating the quality of bare printed circuit boards. Published by IPC (Association Connecting Electronics Industries), this four-color document provides photographs and illustrations showing target, acceptable, and nonconforming conditions for both externally and internally observable PCB characteristics.
The standard covers rigid boards, flexible circuits, rigid-flex assemblies, HDI structures, and metal-core PCBs. It serves as the visual companion to IPC-6012 (the performance specification for rigid boards), translating technical requirements into practical inspection criteria that quality personnel can apply consistently.
Measling/crazing clarification, resin fill criteria
The latest revision, IPC-A-600M (2025), incorporates X-ray inspection examples for the first time, recognizing that modern multilayer boards often require internal defect detection beyond what optical inspection can provide.
Understanding IPC-A-600 Product Classes
IPC-A-600 defines three product classes based on the end-use application and reliability requirements. The class designation determines which acceptance criteria apply—what’s acceptable in Class 1 may be nonconforming in Class 3.
IPC-A-600 Class 1: General Electronic Products
Class 1 applies to products where the primary requirement is function of the completed assembly. Cosmetic imperfections are acceptable as long as they don’t affect functionality.
Characteristic
Class 1 Criteria
Typical applications
Consumer electronics, toys, basic appliances
Design life
Limited, not specified
Reliability requirement
Basic functionality
Minimum external annular ring
0.05 mm (0.002″)
Cosmetic defects
Generally acceptable if functional
IPC-A-600 Class 2: Dedicated Service Electronic Products
Class 2 covers products where continued performance and extended life are required, but some imperfections are acceptable. This is the most commonly specified class in commercial electronics.
IPC-A-600 Class 3: High-Reliability Electronic Products
Class 3 applies to products where continued performance or performance-on-demand is critical. Equipment downtime cannot be tolerated, and the product must function when required.
Characteristic
Class 3 Criteria
Typical applications
Medical life support, aerospace, military, automotive safety
Design life
Extended, critical applications
Reliability requirement
No downtime, must function on demand
Minimum external annular ring
0.05 mm (0.002″)
Plating voids
Not acceptable
Class Comparison: Key Acceptance Differences
Defect Type
Class 1
Class 2
Class 3
Plating voids in PTH
Multiple acceptable
≤1 void in ≤5% holes, <5% hole length
None acceptable
Annular ring breakout
180° acceptable
90° acceptable
Not acceptable
Lifted lands
Acceptable if functional
Limited separation
Not acceptable
Measling/crazing
Acceptable
Process indicator
Process indicator
Conductor width reduction
30% reduction acceptable
20% reduction acceptable
20% reduction acceptable
Solder mask misregistration
Visible misregistration acceptable
Slight exposure acceptable
Minimal exposure only
The inspector does not determine which class applies—that decision comes from the procurement documentation, customer specification, or engineering drawing. The inspector’s job is to evaluate against the specified class criteria.
Externally Observable Characteristics
IPC-A-600 divides acceptance criteria into externally observable characteristics (visible from the surface) and internally observable characteristics (requiring cross-section analysis).
Surface and Edge Conditions
Condition
Description
Acceptance Criteria
Edge burrs
Rough or raised material at board edges
Acceptable if within dimensional tolerance
Nicks and scratches
Surface damage to laminate
Acceptable if fibers not exposed (Class 2/3)
Haloing
Light area around holes from mechanical stress
Acceptable within limits per class
Weave texture
Visible glass weave pattern
Acceptable, cosmetic only
Weave exposure
Glass fibers visible at surface
Process indicator, evaluate per class
Measling and Crazing in IPC-A-600
Measling and crazing are subsurface laminate conditions that have historically generated significant debate. IPC formed two Blue Ribbon Committees to study these phenomena, ultimately concluding they are primarily cosmetic concerns.
Condition
Appearance
IPC-A-600 Position
Measling
Discrete white squares at weave intersections
Process indicator, not reliability concern
Crazing
Connected white spots along fiber bundles
Process indicator, not reliability concern
IPC’s extensive testing found no correlation between measling/crazing and PCB reliability failures. However, they remain process indicators that may suggest manufacturing issues worth investigating.
Conductor and Land Conditions
Characteristic
Target
Acceptable
Nonconforming
Conductor width
As designed
Minimum per drawing, ≤20% reduction (Class 2/3)
Below minimum or >30% reduction
Conductor spacing
As designed
Minimum per drawing
Below minimum spacing
Land adhesion
Firmly attached
No separation
Lifted or peeling
Plating adhesion
Firmly attached
No flaking with tape test
Flaking or peeling
Solder Mask Criteria
Attribute
Class 1
Class 2
Class 3
Coverage
Functional
Complete over conductors
Complete, well-defined edges
Registration to lands
Visible misregistration OK
Slight land exposure acceptable
Minimal exposure only
Adhesion
Functional
No flaking
No flaking, well-adhered
Thickness
As specified
As specified
As specified
Voids/bubbles
Acceptable if functional
Small voids acceptable
Minimal, no functional impact
Internally Observable Characteristics
Internal features require microsectioning (cross-section analysis) for proper evaluation. These characteristics are critical for plated through-hole reliability.
Plated Through-Hole Requirements
Attribute
Class 1
Class 2
Class 3
Minimum copper thickness
20 μm (0.8 mil)
20 μm (0.8 mil)
25 μm (1.0 mil)
Plating voids
Acceptable
≤1 void, ≤5% holes, <5% length, <90° circ.
None
Nodules
Acceptable if hole functional
Not extending into hole
Minimal, not extending into hole
Roughness
Acceptable
Acceptable if plating uniform
Smooth preferred
Annular Ring Requirements
The annular ring—the copper pad area around drilled holes—is one of the most commonly evaluated features. Requirements differ for external and internal layers.
Layer Location
Class 1
Class 2
Class 3
External layers
0.05 mm (0.002″) minimum
0.05 mm (0.002″) minimum
0.05 mm (0.002″) minimum
Internal layers
Breakout acceptable
0.0 mm minimum (tangency OK)
0.025 mm (0.001″) minimum
Breakout allowance
180°
90°
Not acceptable
Dielectric Material Criteria
Condition
Description
Acceptance
Laminate voids
Air pockets in base material
Per class, location-dependent
Resin recession
Resin pulled back from glass
Limited depth acceptable
Etchback
Resin removed from hole wall
Positive etchback may be required
Smear
Resin residue on inner layer copper
Must be removed
Delamination
Layer separation
Not acceptable
Foil and Plating Cracks
Crack Type
Class 1
Class 2
Class 3
External foil cracks
Acceptable if isolated
Acceptable if isolated, <50% width
Not acceptable through conductor
Internal foil cracks
Acceptable
Process indicator
Not acceptable
Barrel cracks
Acceptable if isolated
Not acceptable if circumferential
Not acceptable
IPC-A-600 vs Related Standards
Understanding how IPC-A-600 relates to other IPC standards prevents confusion and ensures proper application.
Defines performance; references 600 for visual criteria
IPC-6012 and IPC-A-600 are designed to work together. IPC-6012 specifies what the board must achieve; IPC-A-600 shows what acceptable (and unacceptable) conditions look like. A complete PCB quality program references both.
IPC-A-600 vs IPC-A-610 Comparison
Aspect
IPC-A-600
IPC-A-610
Scope
Bare printed boards
Assembled electronic products
Inspection stage
Before component mounting
After assembly complete
Focus
Board fabrication quality
Soldering and assembly workmanship
Defects covered
Laminate, copper, holes, mask
Solder joints, component placement, cleaning
A board might pass IPC-A-600 incoming inspection but fail IPC-A-610 after assembly if soldering defects occur. The two standards address different stages of the manufacturing process.
Related Standards Reference
Standard
Title
Relationship to IPC-A-600
IPC-6012
Qualification for Rigid Printed Boards
Performance requirements that 600 visualizes
IPC-6013
Qualification for Flexible Printed Boards
Flex board requirements
IPC-A-610
Acceptability of Electronic Assemblies
Post-assembly inspection
IPC-2221
Generic Standard on PCB Design
Design requirements affecting acceptance
IPC-TM-650
Test Methods Manual
Test procedures referenced in 600
IPC-A-600 Training and Certification
IPC offers formal training and certification programs for IPC-A-600, ensuring inspectors and quality personnel have consistent knowledge of the acceptance criteria.
Certification Levels
Level
Abbreviation
Description
Requirements
Certified IPC Specialist
CIS
Operators, inspectors, technicians
70% passing on open-book exam
Certified Standards Expert
CSE
Subject matter experts, coordinators
80% passing, no teaching requirement
Certified IPC Trainer
CIT
Authorized to train and certify CIS
80% passing, must train 10 students per 2-year cycle
Master IPC Trainer
MIT
Trains CITs, works at Licensed Training Centers
CIT + additional IPC requirements
Training Program Details
Aspect
Details
CIS training duration
2-3 days (full certification)
CIS recertification
1-1.5 days
CIT training duration
2.5-3 days
Certification validity
2 years
Training modules
4 modules (Module 1 mandatory, 2-4 optional based on company needs)
For individuals, certification demonstrates competency in PCB inspection to industry-recognized standards. For organizations, having certified personnel shows commitment to quality and facilitates better communication with suppliers and customers. Certification is often a customer requirement for contract manufacturers and PCB fabricators.
How to Use IPC-A-600 for PCB Inspection
Effective use of IPC-A-600 requires a systematic approach to inspection.
Before Inspection Begins
Confirm the applicable class from procurement documentation or customer specification
Review any customer-specific requirements beyond IPC-A-600
Inspection Magnification Requirements
Board Feature
Recommended Magnification
General visual inspection
1x to 4x
Detailed feature inspection
7x to 10x
Microsection analysis
50x to 200x
Referee conditions
As specified in 600
Disposition Options
Condition
Definition
Action
Target
Ideal condition, preferred
Accept
Acceptable
Meets minimum requirements
Accept
Process indicator
Indicates process variation, may need investigation
Accept, may require process review
Nonconforming
Does not meet requirements
Reject, scrap, or MRB review
Common IPC-A-600 Inspection Challenges
Challenge 1: Class Mismatch
Problem: Board ordered as Class 2 but customer expects Class 3 quality.
Solution: Class must be specified before fabrication. Use procurement documentation to clearly communicate requirements. If disputes arise, refer to the documented class designation.
Challenge 2: Measling Rejections
Problem: Inspectors reject boards for measling despite IPC guidance that it’s a process indicator.
Solution: Train inspectors on IPC’s Blue Ribbon Committee findings. Measling is not a reliability concern and should not be automatically rejected unless contractually specified.
Challenge 3: Annular Ring Measurement
Problem: Inconsistent annular ring measurements between fabricator and customer.
Solution: Ensure both parties measure per IPC-A-600 definitions—external layers measure from inside the plated barrel; internal layers measure from the drilled hole edge.
Frequently Asked Questions About IPC-A-600
What is the difference between IPC-A-600 and IPC-6012?
IPC-6012 is a performance specification that defines what rigid PCBs must achieve in terms of materials, construction, and test requirements. IPC-A-600 is the visual acceptance standard that shows what acceptable and unacceptable conditions look like through photographs and illustrations. They work together—IPC-6012 specifies the requirements, and IPC-A-600 provides the visual interpretation for inspection. Most quality programs reference both standards, using IPC-6012 for fabrication control and IPC-A-600 for incoming and final inspection.
Who determines which IPC class applies to a PCB?
The product class is determined by the procuring organization, not the fabricator or inspector. The class should be specified in the procurement documentation, engineering drawing, or customer specification before fabrication begins. The fabricator builds to that class, and the inspector evaluates against that class. If no class is specified, Class 2 is often assumed as the industry default for commercial electronics, but this should be explicitly confirmed to avoid disputes.
How long does IPC-A-600 certification last?
IPC-A-600 certification is valid for two years from the date of successful completion. Before certification expires, individuals must either attend a recertification class or pass a challenge test to maintain their credentials. For CIT (Certified IPC Trainer) certification, there’s an additional requirement to train at least five students (or one class) per year during the two-year certification period. Letting certification lapse means losing authorization to train or certify others.
Is measling a rejectable defect in IPC-A-600?
No, measling is classified as a process indicator, not a nonconforming condition, in IPC-A-600. IPC’s Blue Ribbon Committees extensively studied measling and crazing, concluding they have no impact on PCB reliability. However, measling indicates potential process variations that may warrant investigation. Some customers may contractually specify tighter requirements for measling, particularly in military applications, so always verify specific contract requirements.
Can IPC-A-600 be used for flexible circuit inspection?
Yes, IPC-A-600 includes a dedicated chapter (Chapter 3) covering acceptance criteria for flexible and rigid-flex printed boards. This section addresses flex-specific concerns like coverlayer adhesion, stiffener bonding, bend radius considerations, and laminate integrity. For comprehensive flex circuit requirements, IPC-A-600 should be used in conjunction with IPC-6013 (Qualification and Performance Specification for Flexible Printed Boards), which defines the performance requirements that complement the visual criteria in IPC-A-600.
Conclusion: Implementing IPC-A-600 Effectively
IPC-A-600 provides the common visual language that enables consistent PCB quality evaluation across the global electronics supply chain. Whether you’re a fabricator shipping boards worldwide, an assembler receiving incoming material, or an OEM qualifying suppliers, this standard establishes the baseline for acceptable quality.
Key implementation points:
Specify class clearly in all procurement documentation before fabrication
Train inspection personnel through IPC certification programs for consistent evaluation
Use IPC-A-600 with IPC-6012 for complete quality control coverage
Understand the visual criteria rather than applying subjective judgment
Reference current revision (IPC-A-600M as of 2025) for latest acceptance criteria
The investment in proper IPC-A-600 implementation pays dividends through reduced inspection disputes, clearer supplier communication, and consistent product quality.
Inquire: Call 0086-755-23203480, or reach out via the form below/your sales contact to discuss our design, manufacturing, and assembly capabilities.
Quote: Email your PCB files to Sales@pcbsync.com (Preferred for large files) or submit online. We will contact you promptly. Please ensure your email is correct.
Notes: For PCB fabrication, we require PCB design file in Gerber RS-274X format (most preferred), *.PCB/DDB (Protel, inform your program version) format or *.BRD (Eagle) format. For PCB assembly, we require PCB design file in above mentioned format, drilling file and BOM. Click to download BOM template To avoid file missing, please include all files into one folder and compress it into .zip or .rar format.
