关键词: SMT印刷钢网, 坐标映射, Gerber文件, 亚像素边缘定位, 图形拟合

Abstract: For realizing automatic and precise dimension measurement of Surface Mounting Technology (SMT) stencil, a visual measurement method was proposed based on Gerber file information. First, the real image was grabbed by line scanning camera of NUCLi 7K made by NED company and such information as size and shape was derived from Gerber file data, and the coordinates mapping between figure information coordinates system and the real image coordinates system was erected through coordinates transform of proportion, transportation and rotation for obtaining the approximate position of figures in the real image. Then Canny operator and Gray moment operator were adopted to get the pixel and sub-pixel precision edge. Finally figure fitting methods like line and circle fitting were used to fit figures in the real image for measuring figure dimension precisely. The max measure error is 0.0854pixel (0.91μm) and the max STDEV is 0.0282pixel (0.30μm) in the experiment, which show that: the stencil measurement method proposed in this paper is stable, reliable and of high precision, which can meet the requirements of automatic dimension measurement of SMT stencil efficiently.

Key words: Surface Mounting Technology (SMT) stencil, coordinates mapping, Gerber file, sub-pixel edge location, figure fitting