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A Guide to PCB Inspection Methods

PCB inspection

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Ensuring the quality and reliability of PCB in manufacturing relies on the critical step of inspecting PCB. A careful examination is crucial to guarantee the bare circuit boards or the assembled ones meet the required standards before reaching customers. So, what elements contribute to making a PCB inspection comprehensive and successful? Let’s look into the essential aspects of PCB inspections, types, needs, and the standard of PCB inspection.

Why Do We Need PCB Inspection?

PCB Inspection is one of the most essential parts of the PCB manufacturing process. It can help to locate and troubleshoot the PCB defects on time. This helps to improve the overall working operation of PCB.

PCB inspection covers the various PCB testing and verification methods. It also checks if the PCB meets the required standards. It prevents any design or assembly flaws that could exist on the PCB. Going for PCB inspection after each PCB assembly could help you catch any defects.

This helps to save time and money on further defective products. It avoids damages like broken connections, malfunctioning, or other losses due to damaged PCBs. Besides, PCB inspection ensures the device meets the customer’s expected quality. And it makes the product more reliable.

Types of PCB Defects

In PCB manufacturing, various PCB defects could arise. This could affect the performance and reliability of electronic devices. Some of such PCB defects include:

  • Soldering Defects
  • Component placement errors
  • Missing components
  • Insufficient solder or solder bridges
  • Open circuits
  • Short circuits
  • Solder mask issues
  • Copper trace discontinuity
  • Incorrect component values or orientations

PCB Inspection Methods

Manual Visual Inspection

Manual Visual inspection is a fundamental method for examining Printed Circuit Boards (PCBs) in the electronics manufacturing process. This method involves carefully inspecting the PCB for any visible defects. The defects include soldering irregularities, component misalignment, missing components, or physical damage. Skilled technicians use magnifying tools and microscopes to ensure a detailed examination.

Manual PCB Inspection
Manual PCB Inspection

Visual inspection is crucial for identifying issues that may impact the functionality and reliability of the PCB. While it is a manual process, advancements in imaging technology, like automated optical inspection (AOI) systems, have enhanced the efficiency and accuracy of visual inspections.

Automated Optical Inspection (AOI)

It is a modern method that uses special machines with cameras and smart image analysis to check PCBs. AOI systems quickly review the entire board to find problems like bad soldering, missing parts, or things in the wrong place. These machines can notice tiny issues that humans might miss. This makes the evaluation more detailed and reliable.

Automated Optical Inspection (AOI)
Automated Optical Inspection (AOI)

AOI works well for making a lot of PCBs quickly and accurately, especially in big productions. AOI systems also use AI and machine learning. This means they get better at finding problems over time.

Automated X-ray Inspection (AXI)

Automated X-ray inspection is a non-destructive approach for inspecting PCB interior structures. This approach is useful for detecting hidden problems beneath the surface. It can uncover issues like soldering voids, component connections, and probable manufacturing difficulties. X-ray equipment produces images that allow inspectors to see the PCB’s internal layers. This is accomplished without physically disassembling the device.

Automated X-ray Inspection (AXI)
Automated X-ray Inspection (AXI)

This strategy is beneficial for complex multilayer PCBs with limited visibility. To ensure the integrity of electronic components, an X-ray examination is essential. It is critical in areas where precision and dependability are critical, such as aerospace or medical devices.

Functional Testing

Functional testing is a flexible method for PCB examination. Its primary goal is to ensure that the built board executes its intended tasks correctly. This procedure applies electrical signals to the PCB, and the output is monitored to ensure it meets design standards. Functional testing can detect flaws such as broken components, circuitry defects, or connectivity issues by imitating real-world working situations.

Functional PCB Testing
Functional PCB Testing

Functional testing gives a thorough evaluation of the PCB’s functioning. However, it may not identify individual component-level flaws. This procedure is frequently used as the last stage in the inspection process. It confirms the general operation of the PCB before it integrates into the final product.

In-Circuit Testing (ICT)

This method inspects individual components and their connections on a PCB, while the board is powered. Specialized test probes are used to get access to specific spots on the circuit and assess electrical parameters. ICT is effective at detecting problems such as open circuits, short circuits, and component value variations.

In-Circuit Testing (ICT) PCB Inspection
In-Circuit Testing (ICT)

While it provides comprehensive coverage, ICT may not be effective for discovering faults in places with limited access. ICT is often used for medium to high-volume production runs, and it assists in ensuring the electrical integrity of the PCB before it moves on to the next manufacturing stage.

Thermal Imaging

Thermal imaging is a non-contact PCB inspection technique that uses infrared cameras to find temperature differences on a PCB’s surface. This technique is useful for detecting problems such as overheating components, improper connections, or insufficient heat dissipation.

Thermal PCB Inspection
Thermal PCB Inspection

Thermal imaging can detect abnormalities that could suggest future failures or areas of concern. It is especially beneficial in applications requiring temperature stability, such as power electronics or high-performance computers. Thermal imaging enhances the overall PCB dependability in a variety of electronic systems by enabling the early detection and resolution of possible thermal problems by giving a visual depiction of the temperature distribution.

Manual Visual Inspection vs Automated Optical Inspection

Manual Visual InspectionAutomated Optical Inspection (AOI)
– Inspected by human eyes– Uses specialized machines with cameras
– Relies on visual scrutiny– Utilizes image processing algorithms
– Prone to human error– Provides rapid and consistent scanning
– Limited to human speed– Detects minute discrepancies
– Subjective interpretation– Enhances efficiency and accuracy
– Suitable for small batches– Particularly effective in high-volume production
– Time-consuming– Integrates AI and machine learning for improved accuracy

PCB Inspection Standards

Several widely recognized standards guide PCB inspection practices in the electronics industry. Some of them include:


  • Acceptability of Printed Boards Standard
  • Defines the acceptance criteria for bare printed boards.
  • Specifies requirements for base materials, conductor patterns, holes, and other features.


  • Acceptability of Electronic Assemblies Standard
  • Outlines acceptability criteria for assembled PCBs.
  • Categorizes defects into different classes based on their impact on performance and reliability.


  • Focuses on qualification and performance specifications for rigid PCBs.
  • Provides requirements for base materials, design, construction, and final finish.


  • Establishes requirements for the soldering process in electronic assemblies.
  • Details criteria for various soldering classes based on the application and end-user requirements.

ISO 9001:

  • A broader standard covering quality management systems applicable to various industries, including electronics manufacturing.
  • Emphasizes continuous improvement, customer satisfaction, and adherence to processes and standards.

UL 796:

  • Addresses the safety aspects of printed wiring boards.
  • Provides requirements for flammability, electrical tracking, and resistance to solvents.

Future Trends in PCB Inspection

In the near future, a spike in sophisticated automation in the future of PCB inspection could be observed. This automation will use artificial intelligence and robotics to conduct faster, more exact exams. Machine learning will make inspection systems more intelligent. They will be capable of identifying and responding to changing flaws. 3D inspection technologies are on the horizon. They will provide a more comprehensive assessment of complicated PCB structures. This will improve defect detection in sophisticated designs. This would allow for real-time monitoring and analysis of production processes. Intelligent data analytics will extract important insights from inspection data.

They will allow for predictive maintenance and continual process improvement. PCB inspection methods will evolve to address the problems caused by reduction. They will ensure effective defect identification in smaller components. Electronic components continue to shrink in size. It is also expected that communication between inspection systems and other phases of the manufacturing process will improve. This would allow for a more integrated and efficient production pipeline. Furthermore, a future emphasis on sustainability may lead to using environmentally friendly materials and techniques in PCB inspection. This would coincide with broader environmental aims.


PCB inspection serves as a gateway to quality assurance in the electronic industry. By implementing advanced PCB inspection techniques like AOI and X-ray PCB inspection, manufacturers can enhance the accuracy of PCB. The electronic manufacturing industry may continue to push the frontiers of innovation. It may also maintain the highest quality and reliability. This requires a thorough understanding of PCB inspection methods and defect kinds.

Thus, ElePCB  will elevate your electronic manufacturing with advanced PCB inspection techniques. Explore the power of AOI, X-ray PCB inspection and more for your accuracy and reliable PCB product with ElePCB. Connect with us today for expert guidance and advanced solutions in PCB inspection.

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About the Author
I am an Electrical and Electronics Engineer, and I have 5 years of work experience with electronics and communication jobs. I'm the full time content creator of ELE company.
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