Explanation of the Application Location of AOI

In SMT, AOI technology has functions such as PCB board inspection, solder paste printing inspection, component inspection, and post solder component inspection. Its focus also varies during different stages of inspection. In early PCB production, inspection was mainly completed by manual visual inspection combined with electrical inspection. However, with the development of electronic technology, the density of PCB wiring continues to increase, making manual visual inspection more difficult and the misjudgment rate higher. At the same time, the health damage to the inspector increases, making electrical inspection programming more cumbersome, costly, and unable to detect certain types of defects. Therefore, AOI automatic optical inspection instruments are increasingly being used in PCB manufacturing. PCB defects can be roughly divided into short circuits (including base copper short circuits, fine wire short circuits, electroplating open circuits, dust short circuits, pit short circuits, repetitive short circuits, stain short circuits, dry film short circuits, insufficient etching short circuits, excessive coating short circuits, scratch short circuits, wrinkle short circuits, etc.), open circuits (including repetitive open circuits, scratch open circuits, vacuum open circuits, notch open circuits, etc.), and other defects that may cause PCB scrap (including excessive etching, electroplating burning, etc.). In the PCB production process, there may be some defects in the substrate production and copper coating, but the main defects are generated after etching. AOI is generally tested after the etching process to discover the missing and excess parts on it. In PCB inspection, image comparison algorithms are widely used, with 2D detection being the main method. They mainly include data processing (preliminary processing of input data, filtering small holes, residual copper, and holes that do not need to be detected), measurement (feature extraction of input data, recording feature codes, sizes, and positions and comparing them with standard data), and topology (used to detect added or lost features). AOI can generally detect most defects with a small number of missed detections, but the main issue affecting equipment reliability is still false positives. Dust, dirt, and poor reflectivity of some materials during PCB processing can all cause false alarms. Therefore, after using AOI to detect defects, manual re verification is required. This is also why 1-2 manual workers are arranged at the AOI detection location.

The AOI detection equipment independently developed and produced by Shenzhen Hongant Intelligent Equipment Co., Ltd. adopts a global exposure camera, which has a faster exposure time than roller shutter cameras. Not only does it eliminate the phenomenon of ghosting in roller shutter cameras, but the speed is also increased by more than 30%; Due to the differences in heat absorption among various types of components on the board during the furnace process, the board is subjected to uneven heating, resulting in a certain degree of deformation. The CAD coordinates cannot accurately correspond to the positions of the components on the board after passing through the furnace, while Hotan Good's AOI achieves accurate correspondence between the coordinates and the positions of the components after board bending compensation.