Automated Optical Inspection (AOI)

Views: 3     Author: Site Editor     Publish Time: 2020-08-19      Origin: Site

AOI refers to automated optical inspection, and it is an inspection method used in PCB manufacturing and PCB assembly. The AOI inspection machine uses high-resolution cameras and systems with different light sources such as fluorescence, UV, LED, and infrared to capture the image arrays. Then these images will be processed and to remind engineers of any potential problems.

AOI is the most important step in the quality control stage of PCB/PCBA fabrication. It is the last process before delivering the final PCB products to customers. And AOI test performs well in reducing costs and solving problems at an early stage.

The capabilities of AOI

AOI is an effective method to detect surface defects and inner issues for both bare PCB and PCBAs. For the PCBs, insufficient or excessive solder, circuit shorts, opens, scratches, and stains are the example defects that AOI will inspect. For the PCBA, the inspection issues usually are incorrect/missing components, polarity, and values.


The AOI equipment can be adjusted according to the needs of the assembled PCBs. For example, the replacement components or some issues that are acceptable could be marked as defects. But the AOI operators can adjust the programming to filter out these acceptable problems and avoid them being marked in the future inspection.


AOI can check out the defects that are hard to be found through a traditional visual examination. And AOI can be run at any stage of PCB assembly. PCB assembly manufacturers will run AOI multiple times at different production processes to achieve a high-quality standard.


Traditional manual inspection processes need technicians to look at every component and mark them one by one. The entire visual inspection may take few hours. It is a time-consuming work with low accuracy, especially for the complex PCBs. However, AOI only needs few minutes to run through the whole board, which can reduce labor cost and time cost greatly.

The AOI of Onlitex

The demand for AOI is growing due to the trend over ever-smaller SMT components. As a vital inspection system, AOI allows PCB manufacturers to measure and monitor the quality of PCB fabrication and correct any defects at any critical moment in the manufacturing process.

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