Printed circuit board (PCB) is a substrate for the assembly of electronic components, manufacturing quality PCB board directly affects the reliability of electronic products, so the PCB as the “mother of modern electronics industry.” as the development of the electronic assembly industry toward to a higher density, smaller sized PCB hybrid technology, relying solely on the traditional functional testing and visual inspection of manual means of detection, PCB manufacturing industry has been unable to meet the modern needs of large-scale production. Currently, the one-time pass rate of the PCB was still generally hovering between 70% to 80%, in order to reduce the number of defected PCB transfer to the next manufacturing processes, which lead to a strong demand for PCB detection key equipment – the Automatic Optical Inspection (AOI) system.
Recently, the first China manufacturer of automatic optical inspection systems Ouwei using a proprietary mathematical logic model and a graphic image matching technology, successfully developed a printed circuit board automated optical detector, breaking the Israeli Orbotech and Dainippon Screen monopoly in this area, so that China begins to step into the field of the 30 micron era of automated opticial inspection. The China PCB manufacturer would no longer have to spend costly manual labor costs on mid visual inspection, and also do not have to worry about product quality pass rate, not worry about the high cost of foreign optical detection device, the price compared to a 50% reduction with the similar products in abroad.
Automated optical inspection system is to extract the PCB surface graphics through high-definition linear array camera, digitizer graphical feature point logic and pattern matching, contour lines form a logical alignment, defective dot-determination and extraction processes to implement this PCB surface pattern defect detection technology.
As the core of the system, how the software to accurately determine the defective points and its core mathematical algorithms are the biggest problems, conventional defect detection software is to use pixel contrast technology, which needs high resolution of the original image sharpness, that means the definition of optical image acquisition device determines the overall performance of the device, leading to a direct result of poor equipment performance and high cost of such technology. In order to resolve these problems, Ouwei developed six new algorithm : sub-pixel outline extraction, CAM data contour extraction, precise alignment algorithm, region clipping and distortion, the registration edge, defect classification and filtering of sub-pixels outline matching, and successfully applied into the new equipment. the sub-pixel contour matching techniques to optimize the extraction of the original image quality, accurately determine the graphic edge profiles, simplifying the smallest logical pixel determination unit demand, the original collection of 50μm picture clarity, ultra-fine level optimization to 30μm.
They also designed and developed an integrated an advanced PCB board scanning device with high-speed line scan cameras, linear encoder feedback device, ultra high speed strobe light device and separated zoom lens; negative targeting fast loading and unloading platform; the latest technological achievements of special precise positioning motion control . On the software architecture try the best to keep the operation simple, easy to use, to avoid the tedious operation parameters and commissioning work.