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.

IC chip has gradually become smaller and smaller, and thus it requires high packaging density. In chip packaging, accurate alignment of electronic components with respect to PCB is crucial for high quality packaging, especially in flipchip assembly. In this paper, vision system is used to provide relative pose information between flip-chip and substrate.Based on this information, these two parts are aligned accurately using visual servoing. In order to achieve high accuracy alignment, a dual imaging system (DIS) is introduced in this work, which is composed of zoom lenses, beam-splitter, mirror, CCD, and LED illumination. It can simultaneously observe the solder bumps on flip-chip and the pattern of pads on substrate using one camera. Once the image frame containing flip-chip and substrate is obtained, their features are extracted from the preprocessed image. Extraction of the features enables us to obtain the position and orientation errors between the chip and the substrate. On the base of the measured errors, visual servoing method can determine the instantaneous velocity input of flip-chip at each servoing time and control the relative position and orientation precisely in an on-line manner. We carry out a series of experiments for various magnifications in order to evaluate the performance of the dual imaging system and the visual servoing algorithm as well.