What Are Acceptance Criteria for PCBs?
Acceptance criteria for PCBs (Printed Circuit Boards) are the specific characteristics, standards, and requirements that PCBs must meet to be approved. These criteria ensure that PCBs are manufactured to the highest quality and perform reliably in their intended applications. Key PCB acceptance criteria include:
- PCB Thickness and Dimensional Accuracy
- PCB Surface Finish Quality
- PCB Copper Weight Accuracy
- PCB Solder Mask Coverage, Color, and Transparency
- PCB Silkscreen Printing Accuracy
- Electrical Performance Testing (including continuity, isolation, and power integrity)
Adhering to these criteria helps prevent costly mistakes and redesigns, ensuring you get the best value from your PCB investment. A thorough understanding of PCB acceptance criteria is crucial for successful PCB production.
IPC-A-600 Standard
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The IPC-A-600 standard is the most widely accepted criterion for PCBs. It is an international standard that defines acceptable workmanship criteria for printed circuit boards. The IPC-A-600 standard is utilized across the PCB industry as a comprehensive set of requirements to ensure quality in PCB fabrication.
IPC-A-600 serves as an essential guideline for producing and assembling high-quality PCBs. It is a critical resource for PCB fabricators, designers, assemblers, and quality assurance professionals. The standard covers various aspects, including:
- Bare Material Quality
- Copper Plating
- PCB Thickness & Dimensional Tolerances
- Visual Defects
PCB Acceptance Criteria at ESPCBA
At ESPCBA, we adhere strictly to the IPC-A-600 Class 2 and Class 3 standards to ensure our PCBs meet the highest industry benchmarks. We also inspect and deliver PCBs that comply with specific customer requirements, including stringent tolerances for dimensions, thickness, and impedance.
Differences Between IPC-A-600 Class 2 and Class 3
The IPC-A-600 standard, developed by the IPC (Association Connecting Electronics Industries), categorizes PCBs into different classes based on visual and functional acceptability. Here’s a comparison between IPC-A-600 Class 2 and Class 3:
| Aspect | IPC-A-600 Class 2 | IPC-A-600 Class 3 |
|---|---|---|
|
Reliability |
Normal |
High |
|
Cost |
Normal |
High |
|
Copper Thickness |
>=20um |
>=25um |
|
Industry Applications |
Normal industry and commercial products |
Highly reliable electronics such as automotive, medical, avionics, life support systems |
|
Inspection Standard |
Lower standard for visual defects |
Higher standard for visual defects |
IPC-A-600 Class 2 ensures that all PCBs meet standard quality and reliability, while Class 3 offers the highest levels of quality and safety for critical applications.
PCB Edge/Outline
Board edge roughness due to burrs does not break the edge.
Notch/halo inward infiltration ≤ 50% of board edge spacing; infiltration ≤ 2.54mm.
Warpage exceeds 0.75%.
Continuous burrs on broken edges.
Halo and notch exceed 50% of edge spacing or 2.54mm.
Damaged edges or corners with delamination.
PCB Surface
Fingerprints or corrosion affecting performance.
No indentation causing bridging or reduced line spacing.
External inclusions or garbage within 0.125mm of conductors.
Scratching exposing copper beyond acceptable limits.
Non-sensitive scratching without exposing copper; appearance is acceptable.
The indentation makes exposed burst fibers cause line spacing reduction to be more than 20%, media thickness to be less than 0.09mm.
Cracking, delamination, or blistering on the surface.
Solder Mask
The solder mask is misaligned. For pads with a pitch over 1.25mm, the offset exceeds 0.05mm; for pads between 0.65mm and 1.25mm, the offset exceeds 0.025mm.
Wrinkles in the solder mask ink expose copper underneath.
Inadequate solder mask exposure results in pads being less than 20% of the required size.
Blistering or oil drops from the solder mask exceed two sizes of 0.25mm per side or over 25% of circuit spacing.
Stripping of the solder mask exposes copper, with the ink broken off more than 50% from the nearest conductor.
Characters on the pads are blurred and unreadable.
Copper Trace Issues
Gaps in the circuit exceed 20% of the conductor's width, and scratches expose copper.
Circuit thickness is less than 20% of the conductor's width.
Board warpage exceeds 0.75%.
Rough burrs are greater than 20% of the conductor spacing.
The presence of a short circuit is detected.
Inadequate patching negatively impacts electrical performance.
Vias and Hole Defects
Broken holes and solder rings exceed 90°.
Blockages prevent proper mounting of components.
The warpage of the board exceeds 0.75%.
Lumps in holes result in diameters smaller than specified in procurement documents.
Inappropriate hole properties hinder component assembly.
There are missing, extra, or misplaced drill holes.
Solder Pad Concerns
Solder pads lack tin, with dewetting areas exceeding 5%.
Indentations and edge defects on BGA pads exceed 10% of pad diameter or 20% of circumference.
Ink presence on pads adversely affects soldering performance.
Scratch notches on pads exceed 20% of their size.
Oxidation or plating issues on pads negatively affect soldering.
Pads appear warped and defective.
Carbon ink, blue peelable mask, high-temperature mask concerns
Short circuits caused by carbon oil affect performance.
Blue glue inadvertently covers other processing areas.
There is a broken hole on the blue glue.
Leakage of high-temperature glue is detected.
Drilling issues lead to missing, extra, or misplaced holes.
There are missing drilling holes, extra drilling holes, and misplaced holes.
Outline and Shape Issues
External dimensions exceed required values or tolerances outlined in procurement documents.
V-CUT misalignment or damage to copper occurs.
V-CUTs may be missed, with depths not meeting specified requirements.
Incomplete CNC milling leads to copper exposure, and dimensions fail to meet procurement specifications.
Deep V-CUTs risk board breakage, exceeding specified depth requirements.
Missing or damaged beveled edges on gold fingers expose copper and fail to meet depth and angle specifications.
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