The role of AOI in SMT processing
The role of AOI in SMT processing
AOI is the English abbreviation of automatic optical detector. Its main function is to detect the quality of reflow soldering. For example, common bad monuments, bridges, tin beads, multi-tin, missing parts, etc. can be detected. It is generally located in the back of the SMT line (Some AOI will be placed in front of the furnace, which will be discussed below), which greatly improves the detection efficiency and correctness, and improves the pass-through rate.
How AOI works?
AOI is an optical detector. From the text, we can know that it is related to optics. The common optics are cameras (lenses), and one of the core components of AOI is the lens. When the placement machine finishes installing a PCBA, the next workstation is the AOI detection. After the PCBA enters the AOI workbench interface, the lens will scan the PCBA in turn, and then go through the AOI vision algorithm to generate an image visible to the naked eye. If it is bad, an error will be reported and the cause of the defect will be prompted. If it is OK, the data will flow directly to the next workstation.
How to judge whether it is OK or bad?
The premise is that the data of the OK board will be stored in the algorithm library. When there is a difference in the comparison with the database in the algorithm, an error will be reported (in some cases, it is OK after visual inspection, then this data needs to be stored in the database in time to avoid subsequent errors), if the error is reported and then found to be defective after manual visual inspection, the engineering and technology must be notified in time for error analysis, process improvement, and rework.
Why is there AOI in front of the furnace?
Generally, the AOI is behind the furnace, and the AOI in front of the furnace is placed in front of the multi-function placement machine, because some PCBAs need to be mounted with a shielding cover, and there are electronic components mounted under the shielding cover, and the AOI cannot see through the shielding cover to check the placement quality (wrong parts, missing parts, etc.), then you need to add an AOI in front of the multi-function machine to check the placement of the placement machine (generally, the shielding cover is mounted on the multi-function placement machine).
Why is there an AOI but still need manual visual inspection?
AOI can greatly improve the inspection efficiency. Although AOI stores a large amount of data on the poor quality of welding, the placement process is affected by various factors, and there will be many causes of defects. Therefore, sometimes the welding quality is good, but errors are also reported, so manual visual inspection is required. Therefore, with AOI, the post arrangement of manual visual inspection cannot be abandoned.
Why do you need 3D AOI if you have 2D AOI?
Usually many factories have 2D AOI, but with the rapid development of electronic products, more and more integrated ICS are widely used, and 2D AOI cannot detect defects such as floating height and cocking. For the sake of quality and product reputation, customers let processing plants increase 3D AOI.