Wire-Looping Formation Process Analysis Based On High-Speed Camera

The microelectronics packaging technology is developed to be thinner and smaller with the new technique of stacked chip package, while it also brings the challenge of low-loop for the thermosonic wire bonding process. To further understanding of the dynamic process of the wire loop formation is significant for the stable and reliable design of low-loop wire, thus, in this paper high speed camera was employed to observe and analyse the dynamic wire loop formation process that includes:1. A new experimental method with high speed camera to observe and investigate the wire loop formation process was presented in this study. By considering the high speed and small characteristics of the wire loop formation process, the relative high speed camera parameters, such as its frame rate, exposure time, resolution, ect. can be calculated, and proper extension tube set and lens can be selected as well by calculating the object distance and focal length of the lens from the real photography object. Finally, the experimental devices were set up and clear images can be obtained through synchronized interference between the generating device and receiving device.2. The effect of edge detection and image segmentation algorithm on the wire profiles and capillary was also investigated by writing the associated program in the Matlab software. It is believed that a clear image of wire profile and capillary edge can be observed with the method of adaptive threshold segmentation algorithm, and the phenomenon of wire broken during the edge detection can be solved by adopting morphological dilation as well.3. By employing the eight-direction code to distinguish the wire profiles, and manually identifying some images without obvious wire profile as complementation, a digital wire profile can be generated, while the normalized correlation method was used to capture the capillary motion. Then, the varied trend of capillary motion and wire profile were discussed with respect to different reverse motion.4. It was found that the wire kick up varied with the increase of the reverse motion, and a method of describing the wire profile kick up with respect to the curvature distribution was proposed in this study. According to the wire profile after the fit of the five order polynomial, an accurate wire curvature distribution can be observed, and then with this analyzed result the phenomenon of kick up can be divided into three stages including a forming phase, a mutation phase and a kick up phase.