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심형섭,이성혁,김종민,신영의,Sim, Hyung-Sub,Lee, Seong-Hyuk,Kim, Jong-Min,Shin, Young-Eui 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.3
The present study is devoted to investigate the transient flow and to estimate the filling time fur underfill process by using the numerical model established on the fluid momentum equation. For optimization of the design and selection of process parameters, this study extensively presents an estimation of the filling time in the view points of some important factors related to underfill materials and flip-chip geometry. From the results, we conclude that the filling time changes with respect to the under fill materials because of different viscosity, surface tension coefficient and contact angle. It reveals that, as the gap height increases, the filling time decreases substantially, and goes to the saturated values.
극초단 펄스 레이저가 입사된 박막 구조의 마이크로스케일 열적-광학적 특성 연구
심형섭(Hyung Sub Sim),이성혁(Seong Hyuk Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
This paper is devoted to investigate numerically the microscale thermo-optical characteristics in thin metal and semiconductor films irradiated by ultrashort pulse laser. For metal films, the two temperature model (2TM) is used, and the quantum effects are included. For silicon films, two different models such as the 2TM and the three temperature model (3TM) are utilized and they are compared with each other. In addition, the extended two-dimensional equations of 2TM and 3TM are established for the prediction of crater shapes and ablation depths. For gold films, it is found that thermo-optical properties vary considerably with temperature because of quantum effects during the laser irradiation. For silicon film irradiated by ultrashort pulse laser, it is observed that non-equilibrium state occurs between LO and acoustic phonons for femtosecond pulse lasers because the pulse duration is shorter than LO phonon-acoustic phonon energy relaxation time.