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.
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Copyright© 2006 by Fuji Technology Press Ltd. and Japan Society of Mechanical Engineers. All right reserved.