• Journal of the Korean Vacuum Society
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• v.20 no.6
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• pp.403-408
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• 2011

To develop the MFX (Micro-Focus X-ray) tube, the trajectories of electrons emitted from the field emission cathode was simulated using SIMION program. Regardless of starting position of the electron in emitter, we found out the fact that there is the optimum extractor voltage Ve, which can focus the electron beam on one place. Extractor voltage Ve varies depending on the source voltage Vs, but the ratio of two voltages (Ve/Vs) is always constant, its value was 99.4%. When the ratio of two voltages (Ve/Vs) was 99.4%, the beam diameter in the cross-over point was $1.2{\mu}m$. Because the focal spot size in MFXG (Micro-Focus X-ray Generator) can not be less than the cross-over diameter within MFX tube, it is important to find out the conditions that can make a smaller beam diameter. Therefore, the above results is considered to be a very important ones in the development of the MFXG.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.1-8
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• 2020

In this paper, the principles, characteristics and recent studies of the laser micro soldering are reviewed. The factors which influence laser micro welding and soldering are also included. Laser soldering is a non-contact process that transfers energy to solder joint by a precisely controlled laser beam. In recent electronics industry, the demands for laser soldering are increasing due to bonding for complex circuits and local heating in micro-joint. In laser soldering, there are several important factors like laser absorption, laser power, laser scanning speed, and etc, which affect laser solderability. The laser absorption ratio depends on materials, and each material has different absorption or reflectivity for the laser beam, which requires fine adjustment of the laser beam. Laser types and operating conditions are also important factors for laser soldering performance, and these are also reviewed.

• Laser Solutions
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• v.9 no.3
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• pp.7-13
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• 2006

Auto focusing system to find optimized focal position of laser beam used for material process has been investigated by using fiber confocal method. Wavelength of laser diode (LD) and diameter of single-mode fiber are 780nm and $5.3{\mu}m$, respectively. Intensity distributions of beam reflected from the surface of mirror and silicon bare wafer have been observed in a gaussian form. Experimental results show that focal position obtained by LD is shifted from one observed from surface scribed by laser about $80{\mu}m$. It is due to the difference of wavelength and each divergence of between LD and laser used for material process. It is confirmed that auto focusing control system through position calibration has operated steadily.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.528-532
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• 2013

In this study, an analytical model of micro-beam structure including thermoelastic damping with irregularly distributed masses is investigated. The significance of thermoelastic damping for micro-scale mechanical resonators is evaluated to design -with high quality factor(Q-factor). The beam model of this work is based on Euler-Bernoulli beam theory. In order to determine the natural frequency of the model, energy method is applied. Also, the thermoelatic damping effects are considered by using heat conduction equations, and the Q-factor can be determined. To derive the equation of motion, non-dimensionalization is employed for systematic analysis. Results of the model are verified, and present mode shapes and Q-factors for the micro-beam with thermoelastic damping including random point masses.

• Transactions on Electrical and Electronic Materials
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• v.3 no.1
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• pp.30-37
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• 2002

A focusing grating coupler (FGC) was not fabricated by the 'Continuous Path Control'writing strategy but by an electron-beam lithography system of more general exposure mode, which matches not only the address grid with the grating period but also an integer multiple of the address grid resolution (5 nm). To more simplify the fabrication, we are able to reduce a process step without large decrease of pattern quality by excluding a conducting material or layer such as metal (Al, Cr, Au), which are deposited on top or bottom of an e-beam resist to prevent charge build-up during e-beam exposure. A grating pitch period and an aperture feature size of the FGC designed and fabricated by e-beam lithography and reactive ion etching were ranged over 384.3 nm to 448.2 nm, and 0.5 $\times$ 0.5 mm$^2$area, respectively. This fabrication method presented will reduce processing time and improve the grating quality by means of a consideration of the address grid resolution, grating direction, pitch size and shapes when exposing. Here our investigations concentrate on the design and efficient fabrication results of the FGC for coupling from slab waveguide to a spot in free space.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.211-220
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• 2002

Optical disk drives read information by replacing a laser beam on the disk track. As information has become larger, the more accurate position control of a laser beam is necessary. In this paper, we report the analysis and fabrication of the micro mirror for optical disk drivers. A coupled simulation of gas flow and structural displacement of the micro mirror using the Finite-Element-Method is applied to this. The mirror was fabricated by using MEMS technology. Especially, the process using the lapping and polishing step after the bonding of the mirror and electrode plates was employed for the Process reliability. The mirror size was 2.5mm${\times}$3mm and it needed about 35V for displacement of 3.2 ${\mu}$.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.55-62
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• 2015

This paper discusses a new model for investigating the micro-mechanical behavior of beam-like structures composed of various elastic moduli and complex geometries varying through the cross-sectional directions and also periodically-repeated along the axial directions. The original three-dimensional problem is first formulated in an unified and compact intrinsic form using the concept of decomposition of the rotation tensor. Taking advantage of two smallness of the cross-sectional dimension-to-length parameter and the micro-to-macro heterogeneity and performing homogenization along dimensional reduction simultaneously, the variational asymptotic method is used to rigorously construct an effective zeroth-order beam model, which is similar a generalized Timoshenko one (the first-order shear deformation model) capable of capturing the transverse shear deformations, but still carries out the zeroth-order approximation which can maximize simplicity and promote efficiency. Two examples available in literature are used to demonstrate the consistence and efficiency of this new model, especially for the structures, in which the effects of transverse shear deformations are significant.

• Transactions on Electrical and Electronic Materials
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• v.9 no.5
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• pp.193-197
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• 2008

On the purpose of increasing resonant frequency without sacrificing quality factor as well as much decreasing dimensions, corrugated micro beam resonator based on polycrystalline 3C-SiC films is the applicable solution. In this work, appropriate corrugated structure is suggested to increase resonant frequency of resonators. Micro beam resonators based on 3C-SiC films which have a two-side corrugation along the length of beams were simulated by finite element method and compared to a same-size flat rectangular. With the dimension of 36x12x0.5 ${\mu}m^{3}$, the flat cantilever has resonant frequency of 746 kHz. Meanwhile, with this size but corrugation width of 6 ${\mu}m$ and depth of 0.4 ${\mu}m$, the corrugated cantilever reaches the resonant frequency at 1.252 MHz.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.236-242
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• 2003

Thermal bubbles find their diverse application areas in the MEMS (MicroElectroMechanial Systems) technology, including bubble jet printers, microactuators, micropumps, etc.. Especially, microactuators and micropumps, which use a microbubble growing by a controlled heat input, frequently involve mechanical and thermal interaction of the bubble with a solid structure, such as a cantilever beam and a membrane. Although the concept is experimentally verified that an internal pressure of the bubble can build up high enough to deflect a thin solid plate or a beam, the physics of the entire process have not yet been thoroughly explored. This work reports the experimental study of the growth of a thermal bubble while deflecting a thin cantilever beam. A physical model is presented to predict the elastic response of the cantilever beam based on the experimental measurements. The scaling law constructed through this work can provide a design guide for micro- and nano-systems that employ a thermal bubble for their actuation/pumping mechanism.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.129-133
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• 2007

Focused Ion Beam(FIB) systems is a useful tool for the fabrication of micro-nano scale structures. In this study, the effects of FIB etching on the Au microstructure are systematically investigated. As the fabrication parameters, ion dose, dwell time and beam overlap ratio are studied. First, the increases of Ga ion dose makes the milling yield higher and the sidewall of milling profile steeper. Dwell time is found to have little effects on the milling profile due to the relatively large milling area of $1\times1{\mu}m^2$ used in this study. However, beam overlap significantly affects not only milling rate but also milling profile. As the beam overlap ratio changes from positive to negative, the development of regular cross-stripe patterns at the bottom with low milling rate is observed.