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등가 이방성 점탄성 모델 기반 열 응력에 따른 휨 해석 기법 개발
김헌수,김학성,Kim, Heon-Su,Kim, Hak-Sung 한국마이크로전자및패키징학회 2022 마이크로전자 및 패키징학회지 Vol.29 No.3
In this study, simulation method was developed to improve the accuracy of the warpage simulation based on the equivalent anisotropic viscoelastic model. First, a package with copper traces and bumps was modeled to implement anisotropic viscoelastic behavior. Then, equivalent anisotropic viscoelastic properties and thermal expansion coefficient for the bump region were derived through the representative volume element model. A thermal cycle of 0 to 125 degrees was applied to the package based on the derived mechanical properties, and the warpage according to the thermal cycle was simulated. To verify the simulation results, the actual package was manufactured, and the warpage with respect to the thermal cycle was measured through shadow moiré interferometer. As a result, by applying the equivalent anisotropic viscoelastic model, it was possible to calculate the warpage of the package within 5 ㎛ error and predict the shape of the warpage.
유리섬유 복합재료 내부 결함 검사를 위한 갈바노 스캐너 기반의 고속 테라헤르츠파 검사 시스템 개발
김헌수(Heon-Su Kim),박동운(Dong-Woon Park),김상일(Sang-Il Kim),김학성(Hak-Sung Kim) 한국비파괴검사학회 2021 한국비파괴검사학회지 Vol.41 No.5
유리섬유 복합재료(GFRP) 내부 결함 검사를 위한 갈바노 스캐너 기반의 고속 테라헤르츠(THz)파 검사 시스템을 개발하였다. 먼저, 기존 스테이지 방식의 검사 시스템의 속도의 한계를 극복하고자, 스테이지를 관성 및 백래시의 영향이 적은 갈바노 스캐너로 대체하였다. 연속형 테라헤르츠파 검사 시스템, 갈바노 스캐너 및 비구면 텔레센트릭 f-세타 렌즈를 결합하였고, 테라헤르츠파 장비와 갈바노 스캐너의 통신을 연동하여 시스템을 제어하였다. 구멍이 가공된 평판을 스캔하여 결합된 시스템의 영상화 성능을 평가하였고, 레이저를 이용한 시스템의 정밀 조절을 통해 THz 신호의 초점을 보정하였다. 이후, 내부 결함이 존재하는 유리섬유 복합재료의 영상화를 진행하였고, 기존 스테이지를 이용한 영상화 결과와 성능을 비교하였다. 결과적으로 개발된 고속 테라헤르츠파 검사 시스템을 통해 90% 이상의 결함 검출 정확도로 유리섬유 복합재료 내부의 결함을 스테이지 방식보다 11배 가량 더 빠르게 검사할 수 있는 것을 확인하였다. A high-speed terahertz (THz) wave inspection system based on a galvano scanner was developed to inspect the defects in glass-fiber-reinforced polymer (GFRP). To overcome the speed limitation of the stage scanning method, the stage was replaced with a galvano scanner, which is less influenced by inertia and backlash. The high-speed THz wave inspection system was manufactured by combining a continuous (CW) THz wave system, a galvano scanner, and an aspherical telecentric f-theta lens. The high-speed THz wave inspection system was controlled by interfacing the galvano scanner and the CW THz wave system. The imaging performance of the combined system was evaluated by scanning a plate with a hole, and the focus of the THz signal was corrected through laser alignment of the system. Scanning for defects in the GFRP was then performed with the high-speed THz wave inspection system, and the imaging result was compared with that obtained using a conventional stage scanning method. Consequently, defects inside the GFRP could be inspected a factor of 11 faster than using the stage scanning method with over 90% probability of detection through the developed high-speed THz wave inspection system.