What is Automated Optical Inspection (AOI)?
Automated Optical Inspection (AOI) is a machine-based technology for testing and inspecting PCBs for potential errors such as surface defects, dimensional defects, and component placement defects. AOI plays an important role in inspecting printed circuit boards after assembly.
Advantages of Automated Optical Inspection
Positional Accuracy: As component sizes decrease, positional accuracy of inspection equipment and manufacturing becomes more and more important. AOI systems should have sub-pixel accuracy as a rule of thumb, ensuring the system is accurate enough to detect small positional deviations that can lead to 01005 defects.
Low cost: AOI testing can improve the qualification rate of PCB, thereby reducing the cost of PCB.
Multiple detection objects: AOI testing is not only applicable to PCB, but also applicable to PCB assembly. For PCBs, it checks for defects such as shorts, opens, and insufficient solder. However, for PCB assembly, it checks for issues such as component soldering, polarity and values.
Web-enabled software: An important function of any AOI system is data collection and retrieval. Data can be text output, image collections, databases, or a combination of formats. Collecting data is a basic function of most AOI systems, but retrieving information is often more complex and depends on the configuration of the production line.
Good flexibility: AOI can be used at any stage of the manufacturing process according to needs and affordability. The reason why it is best to do AOI testing after reflow soldering is because most of the defects are caused by failures in the soldering process, which can reduce the corresponding cost and improve the detection efficiency. It can also immediately modify manufacturing or assembly parameters to correctly manufacture subsequent products.
Why AOI is better than visual inspection:
There are many reasons why you should choose AOI inspection over visual inspection. But many PCB fabs still use visual inspection. Some of the main reasons to choose AOI over visual inspection are
1- Human eyes get tired when visually inspecting tiny components on a PCB, and fatigue is common. On the other hand, the machine is not tired or tired
2- Human eye inspection is error prone and may mistakenly miss faults on the PCB. If fault details are programmed into the AOI machine memory, the AOI machine will never miss a fault. So the accuracy of AOI is better than visual inspection
3- Humans can get bored of doing the same type of work, while machines can do the same job repeatedly, exactly forever.
4- AOI is helpful for mass production runs of PCB fabrication and assembly, while visual inspection is not suitable for mass production, it is suitable for prototype level production
5- AOI is faster, which saves time and money, while visual inspection is slower and requires more attention and time to complete the inspection
6- AOI is a machine-based inspection method, so it provides a valuable data record of the types of errors or defects that occur at various stages of PCB manufacturing and PCBA. While multiple visual inspections will not record failures and types of defects, defects can be easily corrected.
At IBE, AOI is one tool we use to provide our customers with high quality boards. It does work and uses cameras and image processing software to identify assembly errors such as soldering shorts, missing or misplaced components, and disconnected components. As well as AOI improved error detection for visual inspection of more complex PCBs and larger production volumes.