芯片封装立针微孔加工视觉定位技术研究

A two-step visual positioning method based on template matching for rough positioning and edge detection for fine positioning is proposed to solve the problem of locating microholes of bonding wedges. In the step of rough positioning, a rough positioning method based on shape template matching and support vector machine is proposed. Firstly, the template with mask is established, and then it is based on shape template matching that the matching process is accelerated by an early termination strategy, image pyramid and reducing search area. After extracting the histogram features of oriented gradient from matching results, the classification is carried out based on support vector machine to prevent mismatching. In the fine positioning stage, an edge detection algorithm with angle constraints is proposed to accurately locate the edge of the outer contour. The sub-pixel edge positioning is realized by using a quadratic function to fit the maximum gradient, and the least square method is used to the contour edge to locate the machining location of microholes. In the experimental stage, the SVM is trained with a small number of samples, and the accuracy reaches 99.76%. On this basis, the intersection of union of the proposed coarse positioning method reaches 82.9%, while that of the traditional template matching method is only 36.5%. The fine positioning experiment is carried out by placing the bonding wedges in different positions with different postures and adding Gaussian noise under different light intensities. The maximum positioning error of the proposed fine positioning method is 2.20 microns, while the maximum positioning error based on Canny edge detection method is 5.99 microns. The proposed whole algorithm only takes 328 ms.