Local plastic zones of wirebond profiles inspection base on curvature estimation

In ultrasonic wire bonding, the local plastic zones play important roles in determining the wire profile. A way of detecting the local plastic zones using image processing was introduced in this paper. First we divided the video of wire bonding into continuous image sequences, after adaptive threshold segmentation, curve tracking, morphological opening and closing operator, finally we got the thinned curve. The curve was then smoothed with a small width Gaussian kernel in order to remove quantization noise and trivial details. The estimated curvatures distributions were calculated by means of point-to-chord distance accumulation. The local plastic zones of wire were detected based on the estimated curvature distributions by which the position was obtained. The results show that the wire local plastic zones can be detected accurately using this proposed method, and this method has strong robustness.