*** 5 cameras with 1 color in the middle and 4 black and white around.
256-level brightness white LED, which can automatically adjust the illumination brightness and illumination angle.
The inspection speed is 9 ~ 18.8 cm2/ s.
PCB area: minimum W50mm × L50mm and maximum W480mm × L530mm.
Detect and remind defective products in real time.
Automatic learning function, import CAD or mounter data.
When making new programs, the editing of offline programs does not affect the production.
Data of the same device can be copied between machines.
Remote control function.
Unqualified product sorting equipment (NG BUFFER) is available to realize automatic screening.
Abstract: With the increasing complexity and component density of PCB, automatic detection of PCB in production process has become a necessary key step to ensure high quality and high yield.
In today's SMT production line, there are various testing methods, including electrical testing, X-ray testing and optical testing. Although optical inspection is not universally applicable, it can meet most inspection requirements before and after reflow, and it is still the fastest and lowest cost solution. (AOI) refers to the detection of an object (such as a part of a PCB) by imaging it under controlled lighting conditions. Complex machine vision algorithm determines whether the target meets the production standards. AOI is usually used to detect solder paste deposition, parts in place/missing, installation position, polarity and type/distribution verification (OCR/OCV), flux and solder joint quality. Among them, solder joint detection is particularly important.
In this paper, various AOI technologies applied in recent years are summarized, and one of the emerging technologies, SSM technology, is emphatically discussed, and the advantages of this method are analyzed. Different types of information can be extracted from the detected images. Its surface color has been successfully used to check the presence/absence of parts. For solder joint detection, shape information is more helpful to accurately judge the quality of solder joints than color information. Shape information is also useful when the color of the component is similar to the color of the substrate. Therefore, the ability to capture and reconstruct three-dimensional shapes is very necessary in AOI system.
PCB inspection needs traditional three-dimensional imaging technology which can work at micron resolution level, including stereo imaging, laser profiling and * * * focusing microscope technology. Some of these technologies, such as focused scanning, are too time-consuming for online inspection, while others, such as time-of-flight method, cannot provide the resolution required for PCB inspection.
Laser forming technology is a three-dimensional imaging technology successfully applied in AOI system. Use a camera to emit a thin laser line to the detection target at a certain angle. Then, the offset of the thin line in the camera image is used to quickly determine the height of the illumination point. The laser line pattern on the scanning target can form a complete depth profile of the target surface.
The same triangulation method is extended to other structured light technologies, and grid patterns or complex frequency scanning patterns are projected on the target surface, eliminating the need to scan the target surface.
Although these techniques are effective for a variety of targets, they are not effective for the specular reflection surface of solder joints, because the light reflected back at a very narrow angle may not reach the aperture of the camera at all, resulting in inaccurate target height.
In stereo imaging technology, two cameras are used to observe the target from different positions and take two images of the target. In order to obtain 3-D information, a search algorithm is used to determine which pixels of two images correspond to points on the target (pixel correspondence), based on the matching degree of their patterns/structures/edges. Secondly, the difference of each pair of corresponding pixels is calculated. Given the distance between the cameras and the magnification, the difference can be converted into the distance between the cameras and the target, and then a distance map can be formed about the visible target surface.
There are practical difficulties in applying stereo imaging technology in AOI. In order to solve the problem of pixel correspondence, the fields of view of the two cameras need to overlap to a considerable extent. At the magnification level commonly used in PCB inspection, the lens must be placed much closer than most high-quality lenses allow. Therefore, it is necessary to use a lens with lower quality and smaller space, and the magnification is reduced; Either the cameras must be placed at a certain angle to each other, which increases the calculation cost of perspective panoramic correction. For those targets with few surface patterns, such as black components or metal surfaces with smooth solder joints, the pixel correspondence is fuzzy, which makes the difference result analysis uncertain. Due to the fuzziness and complexity of applying stereo imaging technology to AOI, multiple cameras (some AOI systems use 10 or higher) will not automatically form 3-D information.
A complete depth profile is not the only way to describe the shape of the target. Surface features such as surface inclination also provide information about the shape of the target. Some AOI systems are used to capture this kind of information. In a system with an illumination ring, a single camera images objects illuminated from different angles. Images shot with low-angle illumination light show areas with large inclination, while images shot with high-angle illumination light show flat areas. Because a single camera is used, the information collected from a single image has been matched with each other, and there is no need to solve the problem of pixel correspondence. In fact, an AOI system with a single camera and multiple illuminations provides a good starting point for developing more complex 3D imaging systems.
Advantages of machine vision technology
In short, with the maturity and development of machine vision technology itself, it can be expected that its application in modern and future manufacturing enterprises will be more and more extensive.