Inspection For The Positions Of Solder Joints In SMT System

For the compactness, convenient, connection to network and multimedia of electronical products, SMT(Surface Mount Technology)is becoming more and more widedly used in the electronical industry, moreover, it partly even completely takes the place of the traditional assembly technology in some fileds. The emerge of SMT results in a great change of the electronical assembly technology. AOI(Automated Optical Inspection) refers to the process of photographing the inspected products, transferring the digital pictures to the computer then calculate, analyze and make judgement about the inspected products. In Surface Mount Technology (SMT) production line, Automated Optical Inspection systems use charge-coupled device (CCD) cameras to acquire images of the circuit board, then the images are analyzed to determine whether there are defects in each area of the board.In this paper, researches were taken on the Automatic Optical Inspection System in SMT production line. The solution of Automated Optical Inspection to SMT production quality inspection has been introduced. To solve the problem of the image's position and angle offset, the Rake edge search and MSD line fit were employed in relocating the coordinates system; The characteristics of image matching technology in the Automated Optical Inspection System are analyzed.In conclusion, we introduced the fundamental knowledge about digital image processing, made a representation about the procedures of image preprocessing as well as the according Matlab simulation results; completed the flow charts of the program together with the tests about the according content. Through plenty of tests, the algorithm and program applied were proved right, the inspection to the solder joint'position of SMT was finally realized. The anticipated research goal was achieved.