• Proceedings of the KSME Conference
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• 2000.04a
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• pp.873-878
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• 2000

Semiconductor packaging technology is changed rapidly according to the trends of the micro miniaturization of multimedia and information equipment. For I/O limitation and fine pitch limitation, DIP and SOP/QFP are replaced by BGA/CSP. This is one of the surface mount technology(SMT). Solder ball is bumped n the die pad and connected onto mounting board. In ball bump formation, vacuum suction type ball alignment process is widely used, However this type has some problems such as ionization, static electricity and difficulty of fifo(first-input first-out) of solder balls. Seesaw type is reducing these problems and has a structural simplicity and economic efficiency. Ball cartridge velocity and ball aligned plate angle are Important variables to improve the ball alignment Process. In this paper, seesaw-type CSP solder ball loader is developed and the optimal velocity and plate angle are proposed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.4
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• pp.231-244
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• 1990

The objectives of this multiyear research are directed toward the investigation of mesoscale circulation dynamics in the Yellow Sea and the East China Sea. With the advent of Supercomputers and increasing necessity of resolving the flow with enough details, a hydrodynamic numerical model of the East China Sea has been developed with resolution of 1/15$^{\circ}$latitude by 1/12$^{\circ}$longitude covering the entire continental shelf. As a first step M$_2$tidal regime representing the domanant tidal conditions of the shelf was computed. Preliminary results are presented and discussions for further developments are presented.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1207-1208
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• 2006

We developed the copper core ball electroplated with Sn-Ag-Cu of the eutectic composition which used mostly as Pb free solder ball with high reliability. In order to search for the practicality of this developed copper core ball, the evaluation was executed by measuring the initial joint strength of the sample mounted on the substrate and reflowed and by measuring the joint strength of the sample after the high temperature leaving test and the constant temperature and the humidity leaving test. This evaluation was compered with those of the usual other copper core balls electroplated with (Sn,Sn-Ag,Sn-Cu,Sn-Bi) and the Sn-Ag-Cu solder ball.

• Environmental Engineering Research
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• v.11 no.3
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• pp.164-171
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• 2006

Numerical modeling of the flow velocity fields for the near corona wire electrohydrodynamic (EHD) flow was conducted. The steady, two-dimensional momentum equations have been computed for a wire-plate type electrostatic precipitator (ESP). The equations were solved in the conservative finite-difference form on a fine uniform rectilinear grid of sufficient resolution to accurately capture the momentum boundary layers. The numerical procedure for the differential equations was used by SIMPLEST algorithm. The Phoenics (Version 3.5.1) CFD code, coupled with Poisson's electric field, ion transport equations and the momentum equation with electric body force were used for the numerical simulation and the Chen-Kim ${\kappa}-{\varepsilon}$ turbulent model numerical results that an EHD secondary flow was clearly visible in the downstream regions of the corona wire despite the low Reynolds number for the electrode ($Re_{cw}=12.4$). Secondary flow vortices caused by the EHD increases with increasing discharge current or EHD number, hence pressure drop of ESP increases.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.1
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• pp.47-54
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• 2004

The friction drag reduction of a ship is of prime importance for the design and production of high-valued/high-tech ship. Thus, this study carried out the development of reliable numerical tools to identify the friction drag reduction mechanism for turbulent boundary layer on the ship surface and to deduce the optimum reduction technique by numerical experiment. The developed LES and DNS numerical tools were applied to simulate the turbulent channel flow These results were very well matched with previous results not only qualitatively but also quantitatively. The parallelization using MPI (Message Passing Interface) technique implemented in the developed code to speed up the simulation and to obtain the accurate results from the fine grid system was testified its computational efficiency.

• Journal of Environmental Science International
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• v.8 no.6
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• pp.645-652
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• 1999

In order to simulate and investigate the major characteristics of El Nino/Southern Oscillation(ENSO) and Madden Jullian Oscillation(MJO), an intermediate type atmosphere-ocean coupled model is developed and their results are examined. The atmosphere model is a time-dependent non-linear perturbation moist model which can determine the internal heating for itself. The counterpart of the atmosphere model is GCM-type tropical ocean model which has fine horizontal and vertical grid resolutions. In the coupled experiment, warm SST anomaly and increased precipitation and eastward wind and current anomalies associated with ENSO and MJO are properly simulated in Pacific and Indian Oceans. In spite of some discrepancies in simulation MJO, the observed atmospheric and oceanic low-frequency characteristics in the tropics are successfully identified. Among them, positive SST anomalies centered at the 100m-depth of tropical eastern-central Pacific due to the eastward advection of warm water and reduced equatorial upwelling, and negative anomalies in the Indian and western Pacific seem to be the fundamental features of tropical low-frequency oscillations.

• Journal of electromagnetic engineering and science
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• v.11 no.1
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• pp.62-69
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• 2011

This paper proposes a novel electrical characterization approach for a high-performance package system using an improved Partial Element Equivalent Circuit (PEEC). As the effect of interconnects becomes a pivotal factor for the performance of high-speed electronic systems, there is a great demand for an accurate equivalent model for interconnects. In particular, an equivalent model of interconnects is established in this paper for the Fine-Pitch Ball Grid Array (FBGA) package using the improved PEEC method. Based on the equivalent model, electrical characteristics are analyzed; furthermore, these are verified through the measurement results of a Vector Network Analyzer (VNA).

• Journal of Ocean Engineering and Technology
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• v.18 no.2
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• pp.1-9
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• 2004

As the first step to investigate the nonlinear interactions between turbulence and marine structures inside a viscous NWT, a LES technique was applied to solve the turbulent channel flow for =150. The employed turbulence models included 4 types: the Smagorinsky model, the Dynamic SGS model, the Structure Function model, and the Generalized Normal Stress model. The simulated data in time-series for the LESs were averaged in both time and space, and statistical analyses were performed. The results of the LESs were compared with those of a DNS, developed in the present study and two spectral methods by Yoon et al.(2003) and Kim et a1.(1987). Based on this research, the accuracy of LESs has been found to be still related to the number of grids for fine grid size).

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.245-252
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• 2002

The roughness of Joomoonjin sand and the Dongchun river sand was analysed by the fractal theory. It was found that the fractal dimension(D$\_$F/) of Joomoonjin sand is a little smaller than the Dongchun river sand. That means Joomoonjin sand is smoother than the Dongchun river sand. The measurements of D$\_$F/ of different fraction of the Donchun river sand showed that large particles were rougher than fine particles. The shapes of both sands were analysed by the Discrete Fourier Transform(DFT) and the Grid-based(GB) method. Normalization of coefficients with respect to size, starting point and its orientation made the coefficients invaried to these characteristics. The mean of the normalized coefficients was used to reconstruct the average shape for both sands, respectively. The measurements of the ellipticity ratio of different fraction of both sands showed that Joomoonjin sand is slightly flatter than the Dongcun river sand.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.558-563
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• 2007

Detached Eddy Simulation(DES) is performed for turbulent flow of the $270^{\circ}$ bend at a Reynolds number of 56,690. A Fine grid generation is used near a wall in order to satisfy the wall boundary condition of y+<1. Turbulence models adopted for DES and Reynolds Average Navier Stokes(RANS) simulation are SST(Shear Stress Transfort) model. Solutions for both streamwise and circumferential velocity components are compared with the experimental data by Lee for $270^{\circ}$ bend and by Chang for $180^{\circ}$ bend.