Do you know what is AOI?

AOI is a kind of testing equipment, also known as AOI optical automatic testing equipment, which has become an important testing tool and process quality control tool in the electronics manufacturing industry to ensure product quality. The working principle of AOI inspection equipment is that in the process of automatic inspection, the AOI inspection equipment machine automatically scans the PCBA product through a high-definition CCD camera, collects images, and compares the test points with the qualified parameters in the database. After image processing, the solder on the target PCBA is checked. Point defects, and flag defects by display or automatically. Improve process parameters for maintenance personnel maintenance and SMT process personnel.

The AOI system includes a variety of light source lighting, high-speed digital cameras, high-speed linear motors, precision mechanical transmission structures and image processing software. During the test, the AOI equipment automatically scans the PCB, components on the PCB or special components (including the state of printed solder paste, SMD components, solder joint shapes and defects, etc.) Compare and comprehensively judge whether the components and characteristics are qualified, and then test the conclusions, such as missing components, bridges or solder joint quality problems.

AOI works in the same way as the vision systems used in SPI and printing presses in SMT, usually using design rule checking (DRC) and pattern recognition. The DRC method checks the circuit pattern according to some given rules (all lines should end at solder joints, all leads should be at least 0.127mm wide, all leads should be at least 0.102mm spacing, etc.). This method can guarantee the correctness of the circuit to be tested from the algorithm, and has the characteristics of simple production, simple algorithm logic, fast processing speed, small amount of program editing, and small data occupied space, so it is adopted by many people. But this method has poor ability to determine the boundary.

Pattern recognition methods compare stored digital images with actual images. The inspection is carried out according to the complete printed circuit board or according to the inspection file established by the model, or according to the inspection program compiled in the computer axis aided design. Its accuracy depends on the licensing rate and inspection procedures used, and is generally the same as the electronic test system, but the amount of data collected is large, and the real-time data processing requirements are relatively high. Pattern recognition methods that utilize actual design data instead of established design principles in DRC have distinct advantages.

AOl has the functions of component detection, PCB board detection, welding component detection and so on. The general procedure of the AOI inspection system for parts inspection is to automatically count the printed circuit boards of the mounted components and start the inspection; check the lead side of the printed circuit board to ensure that the lead ends are aligned and bent correctly; check whether there are missing parts, Wrong parts, damaged parts, check the type, orientation and position of the mounted IC and discrete devices, check the marking printing quality on the IC device. If the AOI finds a defective part, the system will send a signal to the operator, or trigger a handler, and the machine can automatically remove the defective part. The system analyzes defects, provides the host with the type and frequency of defects, and makes necessary adjustments to the manufacturing process. The efficiency and reliability of AOI detection depends on the integrity of the software used. AOI also has the advantage of being easy to use, easy to adjust, and does not require writing algorithms for visualization systems.