A Comprehensive Guide to Manual PCB Inspection
As a professional PCB inspection method, visual inspection is crucial for troubleshooting PCB surface issues. It involves a range of techniques such as manual visual inspection, AOI, X-RAY, thermal imaging, ultrasonic, and more. Manual visual inspection (MVI) is a widely used method that relies on the trained technician’s ability to identify faults in the circuit board without the use of specialized equipment.
The quality of manual inspection is highly dependent on the technician’s knowledge and experience. In this article, FS Technology will provide a comprehensive guide on manual visual inspection of PCBs, covering the necessary steps, tools, and techniques required for effective inspection. With our guide, you can perform accurate visual inspections and troubleshoot any issues with ease.
Necessity of Manual Inspection
PCBA manufacturing involves complex processes that require quality control to avoid faults. As the number of layers and component density increases, it becomes more challenging to guarantee quality. Therefore, incorporating various testing links in the manufacturing process has become crucial. Despite being a time-consuming, laborious, and inaccurate testing method, manual inspection is still necessary. For hobbyists, it is an easy-to-implement PCB testing method without limitation; for PCBA companies, it helps to avoid rework and speed up project progress; for customers, it adds a protective barrier without increasing costs.
Let’s analyze the characteristics of this detection method:
- Simplicity: The inspection process does not require professional equipment support, and human eyes or magnifying glasses are enough to perform it.
- Penetration: Manual PCB inspection process is fast, and it can be added at any time during the entire production process.
- Randomness: It is not wise to rely on manual inspection for every board in batch orders. Typically, random sampling is used for inspection. If faults are found in the same batch of products, precise instruments like AOI, X-RAY, and others are necessary for detailed inspection.
- Fault tolerance rate: Manual inspection provides the information needed to eliminate faults present in the board when paired with other detection technologies.
- Guidance: Experienced experts execute manual inspection, and they can understand the design features of the circuit board clearly.
- Limitation: Cannot detect failures outside the line of sight, such as hidden solder joints.
- High error rate: It is difficult to check faults in complex circuit boards, and if the inspector is inexperienced, the process may become a mere formality.
How to Manually Detect
Manual Visual PCB Inspection Checklist
- Monitor the board thickness, surface roughness, and warpage throughout the PCB manufacturing process to ensure consistent quality.
- Inspect the conductive pattern for clarity, burrs, voids, and solder bridges to ensure the integrity of the signal path.
- Check for surface defects such as pits, scratches, pinholes, and dents that may affect the performance of the board.
- Verify the quality of pad plating, including firmness and brightness, to ensure reliable electrical connections.
- Inspect the clearance and integrity of the conductive path to prevent short circuits or other electrical issues.
- Confirm that all vias are in the correct position, and their diameter meets design specifications to ensure proper signal transmission.
- Verify that the components on the board match the BOM list to ensure that the correct parts are used.
- Check the dimensions of electrical connectors and components to ensure they meet the required specifications.
- Verify that the placement machine accurately places components in the center of the solder paste to ensure proper soldering.
- Check the orientation of components to ensure they are correctly placed and oriented.
- Evaluate the quality of the conformal coating to ensure that it provides adequate protection against moisture, dust, and other environmental factors.
Specific Operation Guide
- Understanding IPC Testing Standards: FS Technology adheres to the IPC-A-610-G for PCB and PCBA testing. Customers seeking PCBA services should ensure that their service provider follows the appropriate standards to ensure quality production.
- Handling PCB/PCBA: It is crucial to ground the board when handling it to prevent electrostatic breakdown. At FS Technology, our operators wear protective measures such as electrostatic wrist straps in our manufacturing workshops.
- Inspection Environment: The IPC-A-610 standard requires visual inspection in a well-lit area with a minimum of 1000 lm/㎡.
- Inspection Process: Each link in the above list must be inspected carefully by trained operators using human eyes or a magnifying glass.
- Verification and Repair: After inspection, you can refer to FS Technology’s PCBA failure analysis to check for any obvious defects. If any abnormalities are found, please mark them and repair them in a timely manner to ensure quality production.
Will PCBA companies really conduct manual inspection?
In today’s market, there are numerous PCBA companies and service providers available on the internet. While this gives you the opportunity to compare different vendors, it also means that some companies may cut corners on quality control to reduce costs. For instance, some small-scale or vendor may not perform manual visual inspections even when their clients request them.
At FS Technology, we take service quality and delivery speed seriously. We have our own factory and perform manual inspections on both PCBs and PCBA, even if you don’t specifically request it. Our workers follow the specifications for manual visual inspections created by the FS technical team.
When you choose our turnkey service, your project is protected by us from IC programming to PCBA board delivery. This includes visual inspection, functional test, electrical test, and more. If our technicians identify any quality problems with the boards we produce, we will return them for repair in a timely manner.
During the inspection process, we identify the fault of a single board by considering the type of the board, the connected components, and the manufacturing stage. For example, during solder paste application and component attachment, we check for solder paste contamination. We also verify that the components are correctly connected and that nothing is missing. These checks can be monitored visually.
When you need to develop new products, FS Technology provides prototype PCB assembly services. At the beginning of the prototyping process, we create a copy of the circuit blueprint to confirm that the design meets the intended purpose. We then perform manual inspections on the prototype PCBs to detect basic failures. After confirmation, if you are satisfied with our service, we will proceed to mass production to create more PCBA boards. Throughout the DFM process, we document the results of manual inspections using microscopes and pictures.
FAQ
What tools are needed for manual PCB inspection?
How to ensure that manufacturers implement testing specifications?
Is it ok to just do a visual inspection?
Obviously, this is incorrect.
For hobbyists, there is no other way but to add multimeter measurements.
For manufacturers, it is necessary to perform AOI inspection, X-RAY inspection, and functional testing, among others.
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