A Dual Imaging System for Flip-Chip Alignment Using Visual Servoing
Daljae Lee, Xiaodong Tao, Hyungsuck Cho, Youngjun Cho · Journal of Robotics and Mechatronics · 2006
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.