With the automation of surface mount technology (SMT) in electronic integrated circuits and the development of unmanned factories, the reliability of visual inspection equipment and its verification and maintenance have become increasingly crucial. The types of visual inspection are also growing, covering more industries. This article provides a brief analysis of how to achieve reliability verification for SMT-AOI visual inspection equipment.
It is well known that in manufacturing, maintenance and CPK (Process Capability Index) testing are required periodically. Typically, this occurs in a constant temperature, humidity, and dust-free environment, where equipment must undergo CPK verification once a year to ensure stable and reliable production. If the environment does not meet these conditions, CPK testing should be conducted quarterly. This is a rigorous and responsible manufacturing philosophy for quality control, and AOI visual inspection equipment must also be verified for its detection capability and reliability.
In the field of electronic integrated SMT manufacturing, Automatic Optical Inspection (AOI) equipment is a key link in ensuring product quality. To ensure that the AOI system is efficient, it has now integrated AI edge computing capabilities to accurately identify various defects during the printing process, such as bridging, solder overflow, missed printing, and misalignment. SMT manufacturers need to adopt a series of comprehensive evaluation and optimization strategies rather than simply repeating the same steps. Now, let’s discuss how to verify that the optical inspection equipment can maintain stable detection performance after a period of operation, starting with the following methods:1. First, create a report similar to CPK, listing relevant projects and conducting actual verification for each item;
1.1、Algorithm Verification and Optimization: The primary task is to verify and continuously optimize the AOI equipment’s detection algorithms. By simulating and measuring various types of printing defects, verify the algorithm’s recognition capability to ensure comprehensive coverage and accurate identification of various potential issues. Use standard samples with known defects (such as poorly soldered PCBs) to verify the defect detection rate and false positive rate.
1.2、Standard Defect Board Verification: Introduce standard test boards with clearly marked defects as a benchmark for evaluating the AOI system’s performance. Conduct 100 repeated tests on the standard test board in a CPK style for data comparison. If the equipment has SPC (Statistical Process Control) functionality, observe and analyze the SPC data or record and print it (SPC Note: Real-time data analysis can identify abnormal fluctuations in the production process, and defect data can be statistically analyzed by time, product name, etc., generating pie charts and curve graphs to help adjust parameters in a timely manner to maintain quality stability in a visual report.), this step not only tests whether the equipment can accurately detect known defects but also helps assess the system’s stability and reliability.
1.3、Consistency Testing Enhancement: Under constant conditions, SMT manufacturers need to perform multiple AOI scans on the same test board, focusing on the consistency of the detection results. This aims to reduce random errors and ensure that the AOI system’s detection results are stable and reliable under different times and operations, testing the detection effects of different specifications of products (such as component size, color differences) to verify universality.
1.4、Error Analysis and Adjustment: Conduct in-depth analysis of false positives (false alarms) and false negatives (missed detections) that occur during the AOI detection process. By adjusting equipment parameters or optimizing algorithms, strive to minimize the misjudgment rate, i.e., relaxing parameters, strictly controlling, and adjusting the phenomena that occur in the middle range to the most suitable parameters.
1.5、Human-Machine Comparison Verification: Cross-compare the AOI detection results with the manual inspection results of experienced quality inspectors. This “human-machine battle” not only verifies the accuracy of the AOI system but also provides valuable feedback for subsequent system optimization.
1.6、On-Site Practical Testing: Directly deploy the AOI system into the actual production line for testing, simulating various challenges in a real SMT manufacturing environment to ensure that it can maintain efficient and accurate detection capabilities in practical applications. If conditions allow, observe the detection performance under various environments such as vibration, high temperature, low temperature, vacuum, negative pressure, light, various colored lights, and no light. This verification can be adjusted according to one’s conditions, and it is not necessary to achieve all conditions.
1.7、Continuous Maintenance and Upgrades: Establish a regular maintenance and upgrade mechanism to ensure that the AOI equipment’s software and hardware are always in optimal condition. By timely introducing new technologies and algorithm improvements, continuously enhance detection efficiency and accuracy.
Data records should be kept for the above items as a basis for the next verification, facilitating observation of its lifespan and operational status;2. The above is the overall testing, where the main core of optical detection is the CCD camera, and the camera’s lifespan is also limited. Therefore, detailed testing should be conducted, which is primarily researched by the equipment maintenance team. Below are some simple groups for reference.
Mainly Hardware
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Resolution Testing: Use a standard resolution test card (such as ISO 12233 standard card) to check whether the camera can clearly identify the lines and text on the test card under different lighting conditions.
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Frame Rate and Exposure Testing:
- Test frame rate stability with high-speed moving objects.1
- Adjust exposure time and gain parameters, observing image brightness and noise control.
Light Source Uniformity Check: Use a uniformity test board to verify whether the light source has dark or bright areas and test its stability during long-term operation.
Use time records and observations:
Observe the lifespan and operational status of the camera lights, understanding that the lifespan of the main light source and auxiliary light source is different, so this aspect should be paid more attention to.
3. Maintenance of AOI detection equipment must be performed on time, and the following details should be carried out according to daily, weekly, monthly, and other different cycles for systematic maintenance. Below is a comprehensive organized process:
1. Daily Maintenance (to be performed daily)
Equipment Surface Cleaning: Use a lint-free cloth to wipe the equipment shell and operation panel to avoid dust accumulation affecting heat dissipation.
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Key Component Inspection:
- Check whether the conveyor belt is damaged and whether the pulleys are loose.
- Verify the connection status and cleanliness of the sensors.
2. Function Testing: Execute the self-check program after powering on to confirm that motion control, image acquisition, and other modules are operating normally.
2. Weekly Maintenance (to be performed weekly)
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Motion Component Maintenance:
- Clean the X/Y/W axis ball screw and linear guide.
- Use specialized lubricants for lubrication, being careful to avoid over-lubrication.
Optical System Calibration: Clean the camera lens and light source components, checking focus accuracy.
3. Monthly Maintenance (to be performed monthly)
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Deep Cleaning:
- Disassemble the fan protective cover, clean the blades, dust filter, and metal parts.
- Clean the dust filter and cooling fan filter of the computer host.
System Maintenance:
Environmental Adaptation Check: Confirm that the working environment’s temperature and humidity (5-40℃/35-80%RH) and dust conditions meet requirements.
Electrical Check:
- Check whether the electrical harness connections are normal, re-plugging any loose connections.
- Check for dust on the drive shaft’s cooling fan, cleaning it with a vacuum if necessary.
- Observe whether the electrical components in each process start normally according to the distribution process, replacing any abnormal components.
Precautions:
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Before lubrication operations, power off and wear protective gloves.
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Be cautious when cleaning with corrosive solvents (such as thinner).
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In case of emergencies, immediately press the emergency stop button and contact professionals.
The above is for reference only, applicable to fully automatic AOI detection equipment. Semi-automatic AOI detection equipment and desktop AOI detection equipment may have different details, but the camera checks are similar. The longer the detection equipment is used, the stronger the awareness of equipment supervision must be; otherwise, the equipment replacing manual inspection will become a mere decoration, leading to missed inspections and other defective products flowing out, causing unnecessary losses to the company’s products. Finally, I hope to provide friends with management and usage assistance for AOI detection equipment.
The above information is compiled from the internet and actual sources, and the copyright belongs to the original author.
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