https://scholar.dgist.ac.kr/handle/20.500.11750/204 Sun, 05 Apr 2026 11:24:54 GMT 2026-04-05T11:24:54Z https://scholar.dgist.ac.kr/handle/20.500.11750/3944 Title: Development of alignment inspection system for ball grid array packaging Author(s): Lee, Hyunki; Jeon, Jeong Yul; Ko, Kwang Ill; Cho, Hyungsuck; Kim, Min Young Abstract: The ball grid array (BGA) has become one of the most popular packaging alternatives for high I/O devices in the industry with many advantages: high interconnection density and less packaging space and so on. In these days, the size of chip becomes small and the size of ball grid also becomes small, so the process of BGA alignment becomes more important and difficult. In this paper, the BGA alignment system before the oven process step is managed. The main difficult of inspecting the BGA alignment is that the substrate is always tilted due to irregular carrier size and in-line process. In this paper, to overcome this problem, tilt angle of substrate is measured by phase measuring profilometry (PMP), and then the compensated alignment offset calc ulation algorithm is suggested. The performance of our system is checked by a series of real experiments. © 2010 IEEE. Thu, 31 Dec 2009 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/3944 2009-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/3950 Title: Depth-of-field extension through focal plane oscillation and variable annular pupil Author(s): Hong, Deokhwa; Cho, Hyungsuck Abstract: In this paper, a depth-of-field extension method is in troduced. The extension is realized by the variable annular aperture method previously proposed by the authors and focal plane oscillation method. By combining those methods, we see a synergetic effect that the depth-of-field is more extended than when each method is applied independently. The variable aperture and the focal plane oscillation are realized by a liquid crystal spatial light modulator and a deformable mirror, respectively. Simulation and experimental results are shown to verify the proposed method. © 2010 IEEE. Thu, 31 Dec 2009 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/3950 2009-12-31T15:00:00Z