A Dual Imaging System for Flip-Chip Alignment Using Visual Servoing
Daljae Lee*, Xiaodong Tao*, Hyungsuck Cho*, and Youngjun Cho**
*Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-dong, Daejeon, Korea
**Mechatronics Team, Korea Institute of Industrial Technology (KITECH), Chungnam, Chunan-Si, Korea
Electronic components must be precisely aligned on printed circuit (PC) boards in chip packaging, especially in flip-chip assembly. We propose a vision system to provide relative positioning information between the flip-chip and substrate to ensure accurate alignment. The dual imaging system (DIS) we introduce to ensure alignment consists of a zoom lens, beam splitter, mirror, charge-coupled device (CCD) and light-emitting diode (LED) illumination, and simultaneously observes solder bumps on flip-chips and pad patterns on substrates using one camera. Features are extracted from the preprocessed image frame containing the flip-chip and substrate to obtain positioning and orientation errors between the chip and substrate. Based on measured error, visual servoing determines the instantaneous velocity input of flip-chips at each servoing iteration time and controls relative positioning and orientation precisely on-line. Fine servoing on a 3-axis stages uses dual imaging for visual alignment. Experiments under different parameter conditions to evaluate dual imaging system and visual servoing algorithm performance confirmed the feasibility of our proposal.
-  K. Boustedt and E. J. Vardaman, “Tomorrow’s Packaging – Chip Scale Packaging vs Flip Chip,” Microelectronics international: journal of ISHM - Europe, Vol.14, No.3, pp. 31-32, 1997.
-  J. H. Lau, “Flip Chip Technologies,” McGraw-Hill, 1995.
-  G. Burel, F. Bernard, and W. J. Venema, “Vision feedback for SMD placement using neural networks,” Proceedings, 1995 IEEE International Conference on Robotics and Automation, Vol.2, pp. 1491-1496, 1995.
-  D. Y. Lee, K. N. Jang, and H. S. Cho, “A Visual Servoing For High Precision Chip Mounting Technology,” KSPE, Vol.20, No.11, pp. 16-22, 2003.
-  D. J. Lee, X. D. Tao, H. S. Cho, and Y. G. Cho, “Flip-chip alignment with a dual imaging system using a visual servoing method,” SPIE International Symposium on Optomechatronic Technologies (ISOT 2005), Sapporo, Japan, 2005.
-  K. Nickels and S. Hutchinson, “Estimating uncertainty in SSD-based feature tracking,” Image and vision computing, Vol.20, No.1, pp. 47-58, 2002.
-  S. Hutchinson, G. D. Hager, and P. I. Corke, “A Tutorial on Visual Servo Control,” IEEE Transactions on Robotics and Automation, Vol.12, No.5, pp. 651-670, 1996.
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