A Research On The Pin Visual Measurement Technology For QFP And BGA Chip

With the rapid development of the semiconductor industry, SMT(Surface Mount Technology) technology becomes more mature, and has been widely used in IC(Integrated Circuit) manufacturing industry. The chip size detection is a very important link in SMT, the detection efficiency directly affects the level of SMT technology. Visual detection technology is a very promising means of detection, and with the advantages of automatic, rapid, flexible, it has been paid more and more attention in the field of chip appearance detection. SMT visual inspection research began in the 1980 s in foreign countries, and has formed a complete and mature technology system; this aspect of the domestic research has just started, in the stage of development, the core technology has been controlled by others.Based on the requirement of QFP(Plastic Quad Flat Package) and BGA(Ball Grid Array) chip appearance detection, this paper carries out the vision system calibration and two-dimensional geometric size measurement algorithm research, micron high-precision detection is achieved in the IC chips appearance detection. The main contents are as follows:(1) The traditional calibration system adaptability to the calibration plate is not strong. Different feature points extraction algorithms for different calibration plate are proposed in the paper. The feature points extraction accuracy is increased, at the same time, the available calibration plate species is expanded.(2) In view of pathological solution problem in calibration process, this paper puts forward a oriented QFP/BGA chip of the calibration algorithm based on the LM(LevenbergMarquard) optimization theory. The problem of visual system parameters is easy to fall into local optimum has been solved.(3) In view of linear and circular edge with abnormal points extraction problem, a least squares of vision measurement algorithm based on Tukey weight function is proposed. This algorithm has strong robustness and solves the problems of line and circle high precision vision measurement.In conjunction with the specific needs of QFP and BGA chip appearance detection, this paper carries out the work of the practical application of the chip appearance visual inspection algorithm. Experiments show that the detection error of repeatability and stability precision was less than ± 7um, which meet the demand of QFP/BGA chip size detection.