• Laser Solutions
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• v.14 no.1
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• pp.14-18
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• 2011

Semiconductor industry demands decrease in line/space dimensions of IC substrates. Particularly for IC substrates for CPU, line/space dimensions below $10{\mu}m/10{\mu}m$ are expected to be used in production since 2014. Conventional production technologies (SAP, etc.) based on photolithography are widely agreed to be reaching capability limits. To address this limitation, the embedded circuit fabrication technology using laser ablation has been recently developed. In this paper, we used a nanosecond UV laser and a picosecond UV laser to fabricate embedded circuit patterns into a buildup film with $SiO_2$ powders for IC substrate. We conducted SEM and EDS analysis to investigate surface quality of the embedded circuit patterns. Experimental results showed that due to higher recoil pressure, picosecond UV laser ablation of the buildup film generated a better surface roughness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.04a
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• pp.321-327
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• 1991

High power laser beams are used in a wide variety of materials processing applications such as cutting, welding, drilling and surface treatment. The CO$\sub$2/ laser is increasingly used in laser beam welding because of the highly potential advantages. High power laser welding is a high energy density, no filler metals and low heat input process to join metals. As the comparison with the conventiona welding, precision work and good fit-up to join the metals are required and maintenance is expensive at present. The principal variables of laser beam welding are the laser beam power, travel speed and bean spot size. The penetration depth during laser beam welding is directly related to the power density of the laser beam. Generally, for a constant beam size, the penetration depth increases with increasing laser beam power.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.399-404
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• 1994

Heavyweight(or High density) concrete, which is generally for shiedling structures, differs from normal weight concrete by having a higher density and special compositions to improve its attenuation properties. There are setting 7 Beam Ports around the reactor of the KMRR Project(Korea Multi-purpose Research Reactor) conducted by the KAERI(Korea Atomic Energy Research Institute). High density(p=5.0t/$\textrm{m}^3$) and Heavyweight(p=3.5t/$\textrm{m}^3$) concrete were placed around the Beam Ports in order to shield radiation. This paper was discussed about construction of High density concrete. High density concrete was placed with method of Preplace Aggregate. Coarse metallic aggregate(steel shot) was used. Boron, boron carbide(B4C), was used to capture effctively the neutrom. The mock-up test was carried out. And the consturction of High density concrete was performed successfully.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.10
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• pp.40-44
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• 2010

Laser drilling is an enabling technology for Through Silicon Via (TSV) interconnect applications. Recent advances in picoseconds laser drilling of blind, micron sized vias in silicon is presented here highlighting some of the attractive features of this approach such as excellent sidewall quality. In this study, we dealt with comparison of heat affection around drilled hole between a picosecond laser and a nanosecond laser process under the UV wavelength. Points which special attention should be paid are that picosecond laser process lowered experimentally recast layer, surface debris and micro-crack around hole in comparison with nanosecond laser process. These finding suggests that laser TSV process has possibility to drill under $10{\mu}m$ via. Finally, the laser drilling platform was constructed successfully.

• Laser Solutions
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• v.12 no.4
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• pp.6-11
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• 2009

The LDS(Laser Direct Structuring) process uses thermoplastic polymers with a additive compound that serves as plating seed after the activation by laser. It can realize industry requirement such as miniaturization of electrical component, design flexibility and reduction of production steps. The purpose of this study is to introduce LDS, and to investigate the fundamental mechanism. Also the characteristics of conductive patterns were investigated with respect to laser fluence and intensity. We have used a pulsed fiber laser (wavelength : 1064nm) and copper electroless plating to fabricate conductive patterns. The result showed that laser induced metal-organic complex was caused metalization by electroless copper plating, the critical laser fluence was $1.41\;J/cm^2$ at a scan speed of 1 m/s.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.253-253
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• 2012

Low temperature SiOx film process has being required for both silicon and oxide (IGZO) based low temperature thin film transistor (TFT) for application of flexible display. In recent decades, from low density and high pressure such as capacitively coupled plasma (CCP) type plasma enhanced chemical vapor deposition (PECVD) to the high density plasma and low pressure such as inductively coupled plasma (ICP) and electron cyclotron resonance (ECR) have been used to researching to obtain high quality silicon oxide (SiOx) thin film at low temperature. However, these plasma deposition devices have limitation of controllability of process condition because process parameters of plasma deposition such as RF power, working pressure and gas ratio influence each other on plasma conditions which non-leanly influence depositing thin film. In compared to these plasma deposition devices, neutral beam assisted chemical vapor deposition (NBaCVD) has advantage of independence of control parameters. The energy of neutral beam (NB) can be controlled independently of other process conditions. In this manner, we obtained NB dependent high crystallized intrinsic and doped silicon thin film at low temperature in our another papers. We examine the properties of the low temperature processed silicon oxide thin films which are fabricated by the NBaCVD. NBaCVD deposition system consists of the internal inductively coupled plasma (ICP) antenna and the reflector. Internal ICP antenna generates high density plasma and reflector generates NB by auger recombination of ions at the surface of metal reflector. During deposition of silicon oxide thin film by using the NBaCVD process with a tungsten reflector, the energetic Neutral Beam (NB) that controlled by the reflector bias believed to help surface reaction. Electrical and structural properties of the silicon oxide are changed by the reflector bias, effectively. We measured the breakdown field and structure property of the Si oxide thin film by analysis of I-V, C-V and FTIR measurement.

• Bulletin of the Society of Naval Architects of Korea
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• v.20 no.2
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• pp.51-59
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• 1983

The versatile practical use of electron beam welding which is very high energy density is still in early stage, but in the special welding field, the welding process is used in manufactured goods. The investigation for electron beam welding up to the present was almost achieved not for the mechanical properties of welded joint but for the process itself. On this investigation, the fatigue strength, crack propergation phenomena and hardness of weld metal and heat affected zone of partially penetrated welded joint of HT80 steel by electron beam welding was accomplished. The tensile fatigue strength in weld line direction of the joint was about $25kg/mm^2$. There still appeared spikes on the tips of penetration, and the crack initiated at the tips of spikes not from the roots. The hardness of the weld metal was higher than it of base metal because of production of martensite by rapid cooling.

• Journal of Radiation Industry
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• v.9 no.1
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• pp.15-20
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• 2015

Carbon fiber has received much attention owing to its properties, including a large surface-to-volume ratio, chemical and thermal stability, high thermal and electrical conductivity, and high mechanical strengths. In particular, magnetic nanopowder dispersed carbon fiber has been attractive in technological applications such as the electrochemical capacitor and electromagnetic wave shielding. In this study, the nickel-oxide-nanoparticle dispersed polyacrylonitrile (PAN) fibers were prepared through an electrospinning method. Electron beam irradiation was carried out with a 2.5 MeV beam energy to stabilize the materials. The samples were then heat-treated for stabilization and carbonization. The nanofiber surface was analyzed using a field emission scanning electron microscope (FE-SEM). The crystal structures of the carbon matrix and nickel nanopowders were analysed using X-ray diffraction (XRD). In addition, the magnetic and electrical properties were analyzed using a vibrating sample magnetometer (VSM) and 4 point probe. As the irradiation dose increases, the density of the carbon fiber was increased. In addition, the electrical properties of the carbon fiber improved through electron beam irradiation. This is because the amorphous region of the carbon fiber decreases. This electron beam effect of PAN fibers containing nickel nanoparticles confirmed their potential as a high performance carbon material for various applications.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.65.4-65.4
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• 2017

The laboratory astrophysics is a new emerging field of basic sciences, and has tremendous discovery potentials. The laboratory astrophysics investigates the basic physical phenomena in the astrophysical objects in controlled and reproducible manners, which has become possible only recently due to the newly-established intense photon and ion beam facilities worldwide. In this presentation, we will introduce several promising ideas for laboratory astrophysics programs that might be readily incorporated in the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL). For example, precise spectroscopic measurements using Electron Beam Ion Trap (EBIT) and intense X-ray photons from the PAL-XFEL can be performed to explore the fundamental processes in high energy X-ray phenomena in the visible universe. Besides, in many violent astrophysical events, the energy density of matter becomes so high that the traditional plasma physics description becomes inapplicable. Generation of such high-energy density states can be also be achieved by using the intense photon beams available from the PAL-XFEL.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.497-497
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• 2012

산업의 발전함에 따라 고기능성 박막의 수요가 증가하고 있으며, magnetron sputtering, e-beam evaporation, ion beam 등을 이용한 박막 증착에 대한 연구가 많이 진행되고 있다. 그러나 기존 방법만으로는 박막 접착계면의 불균일로 인해 고기능성 박막 성장이 어렵다는 단점을 가지고 있다. 이러한 문제를 해결하기 위하여 박막 공정 중 고밀도 플라즈마 소스(high density plasma source)를 통해 추가적인 에너지를 인가하여 박막의 밀도를 bulk 수준으로 증가시키고 내부 응력을 조절하는 연구에 대한 관심이 커지고 있다. 특히 grid를 이용하여 플라즈마 내 이온의 입사에너지를 증가시킴으로써, 기존 공정보다 고기능성 박막을 구현할 수 있다. 본 연구에서는 RF power를 이용한 inductively coupled plasma를 통해 플라즈마를 생성시킨 후 grid에 DC power를 인가하는 플라즈마 소스를 개발하였으며, 시뮬레이션을 통해 plasma density와 ion current density, ion energy 분석 및 grid 디자인을 하였다. 개발된 플라즈마 소스는 ion energy analyzer를 통해 RF power 및 grid에 인가하는 power의 세기에 따라 이온화 정도 및 이온의 입사에너지를 측정하였다.