• 한국전기전자재료학회논문지
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• 제31권5호
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• pp.324-329
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• 2018

Red phosphor in glasses (PiGs) for automotive light-emitting diode (LED) applications were fabricated with 620-nm $CaAlSiN_3:Eu^{2+}$ phosphor and Pb-free silicate glass. PiGs were synthesized and mounted on high-power blue LED to make a monochromatic red LED. PiGs were simple mixtures of red phosphor and transparent glass powder. After being fabricated with uniaxial press and CIP at 300 MPa for 20 min, the green bodies were thermally treated at $550^{\circ}C$ for 30 min to produce high dense PiGs. As the phosphor content increased, the density of the sintered body decreased and PiGs containing 30% phosphor had a full sintered density. Changes in photoluminescence spectra and color coordination were studied by varying the thickness of plates that were mounted after optical polishing. As a result of the optical spectrum and color coordinates, PiG plate with $210{\mu}m$ thickness showed a color purity of 99.7%. In order to evaluate the thermal stability, the thermal quenching characteristics were measured at temperatures of $30{\sim}150^{\circ}C$. The results showed that the red PIG plates were 30% more thermally stable compared to the AlGaInP red chip.

• 한국전자파학회논문지
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• 제26권3호
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• pp.311-316
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• 2015

본 논문에서는 저항성 sheet를 이용한 광대역 박형 흡수체 설계법을 제안한다. 제안된 흡수체의 등가회로는 직렬 RLC 공진회로와 종단이 단락된 전송선으로 이루어진다. 이 등가회로를 바탕으로 임의의 설계주파수에서 흡수체가 ${\lambda}/4$보다 얇은 두께를 가지면서도, 광대역 흡수율 특성을 가지는 세가지 조건을 정리하였다. 수치해석을 통해 이를 동시에 만족하는 R, L, C 소자 값을 구했다. 구한 등가 R, L, C값은 특정한 chip 저항이나 표면저항을 가지는 십자 모양의 구조로써 구현이 가능하다. 이러한 설계법을 설계 중심주파수 3 GHz에서 적용해서 두께가 18.75 mm(전기적 길이 $67.5^{\circ}$)이고, 90 % 흡수율 기준으로 116 % 대역폭을 갖는 광대역 흡수체를 설계하였다.

• 디지털콘텐츠학회 논문지
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• 제5권4호
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• pp.251-256
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• 2004

반도체 집적회로를 만드는 토대가 되는 실리콘 웨이퍼의 표면은 고품질 회로를 구성하기 위해 극도의 평탄도가 요구되므로 평탄도는 양질의 웨이퍼를 보증하는 가장 중요한 요소이다. 따라서 실리콘웨이퍼 생산의 10개의 공정 중 거칠어진 웨이퍼 표면을 고도의 평탄도를 갖도록 연마하는 폴리싱공정은 매우 중요시 되는 생산라인이다. 현재 이 공정에서는 담당 엔지니어가 웨이퍼의 모형을 측정장비의 모니터에서 육안으로 관찰하여 판단하고 평탄도를 높이기 위한 제어를 하고 있다. 그러나 사람에 의한 것이므로 많은 경험이 필요하고 일일이 체크해야하는 번거로움이 있다. 본 연구는 이러한 비효율적인 작업의 효율화를 위해 웨이퍼의 모형을 디지털 컨텐츠화하여 폴리싱 공정에 있어 평탄도를 사람이 아닌 시스템에 의해 자동으로 측정하여 제어하는 알고리즘을 제안한다. 또한 제안한 전체 웨이퍼 평탄도 추정알고리즘을 토대로 실제 현장에서 쓰이는 웨이퍼 각 사이트별 평탄도를 측정하기 위한 사이트두께 추정 알고리즘을 제안한다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권2호
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• pp.118-126
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• 2004

Recombinant E.coli ACV 1003 (recA::lacZ) releasing ${\beta}$-galactosidase by a SOS regulon system, when exposed to DNA-damaging compounds, have been used to effectively monitor endocrine disruptors. Low enzyme activity of less than 10 units/mL, corresponding to a $\mu\textrm{g}$/L(ppb) range of an endocrine disruptor (tributyl tin, bisphenol A. etc.), can be rapidly determined, not by a conventional time-consuming and tedious enzyme assay, but by an alternative interferometric biosensor. Heavily boron-doped porous silicon for application as an interferometer, was fabricated by etching to form a Fabry-Perot fringe pattern, which caused a change in the refractive index of the medium including ${\beta}$-galactosidase. In order to enhance the immobilization of the porous silicon surface, a calyx crown derivative (ProLinker A) was applied, instead of a conventional biomolecular affinity method using biotin. This resulted in a denser linked formation. The change in the effective optical thickness versus ${\beta}$-galactosidase activity, showed a linear increase up to a concentration of 150 unit ${\beta}$-galactosidase/mL, unlike the sigmoidal increase pattern observed with the biotin.

• 대한기계학회논문집A
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• 제29권2호
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• pp.333-340
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• 2005

Feedrate is one of the factors that have the significant effects on the productivity, qualify and tool life in the cutting mechanism as well as cutting velocity, depth of cut and width of cut. In this study, in order to realize the high-efficient machining, a new feedrate optimization method is proposed based on the concept that the optimum feedrate can be derived from the allowable cutting power since the cutting power can be predicted from the cutting parameters as feedrate, depth of cut, width of cut, chip thickness, engagement angle, rake angle, specific cutting force and so on. Tool paths are extracted from the original NC program via the reverse post-processing process and converted into the infinitesimal tool paths via the interpolation process. And the novel NC program is reconstructed by optimizing the feedrate of infinitesimal tool paths. Especially, the fast feedrate optimization is realized by using the Boolean operation based on the Goldfeather CSG rendering algorithm, and the simulation results reveal the availability of the proposed optimization method dramatically reducing the cutting time and/or the optimization time. As a result, the proposed optimization method will go far toward improving the productivity and qualify.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권4호
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• pp.209-215
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• 2001

In this paper a method for analysis and modelling of coplanar transmission interconnect lines that are placed on top of silicon-silicon oxide substrates is presented. The potential function is expressed by series expansions in terms of solutions of the Laplace equation for each homogeneous region of layered structure. The expansion coefficients of different series are related to each other and to potentials applied to the conductors via boundary conditions. In the plane of conductors, boundary conditions are satisfied at $N_d$ discrete points with $N_d$ being equal to the number of terms in the series expansions. The resulting system of inhomogeneous linear equations is solved by matrix inversion. No iterations are required. A discussion of the calculated line admittance parameters as functions of width of conductors, thickness of the layers, and frequency is given. The interconnect capacitance and conductance per unit length results are given and compared with those obtained using full wave solutions, and good agreement have been obtained in all the cases treated

• 한국정밀공학회지
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• 제27권1호
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• pp.91-98
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• 2010

The increasing of power and processing speed and miniaturization of central processor unit (CPU) used in electronics equipment requires better performing thermal management systems. A typical thermal management package consists of thermal interfaces, heat dissipaters, and external cooling systems. There have been a number of experimental techniques and procedures for estimating thermal conductivity of thin, compressible thermal interface material (TIM). The TIM performance is affected by many factors and thus TIM should be evaluated under specified application conditions. In compact packaging of electronic equipment the chip is interfaced with a thin heat spreader. As the package is made thinner, the coupling between heat flow through TIM and that in the heat spreader becomes stronger. Thus, a TIM characterization system for considering the heat spreader effect is proposed and demonstrated in detail in this paper. The TIM test apparatus developed based on ASTM D-5470 standard for thermal interface resistance measurement of high performance TIM, including the precise measurement of changes in in-situ materials thickness. Thermal impedances are measured and compared for different directions of heat dissipation. The measurement of the TIM under the practical conditions can thus be used as the thermal criteria for the TIM selection.

• 한국전자파학회논문지
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• 제19권11호
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• pp.1287-1293
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• 2008

4중 대역의 안테나 스위치 모듈을 개발하였다. 단말기의 front-end 단에서 LTCC 형태의 저역 통과 필터, 다이오드 및 수동 부품들로 구현되는 스위치 부분을 대신하여 수동 집적 회로와 트랜지스터 스위치로 집적화한 것이다. 필터의 수동 소자 및 정합 회로를 통합 구성하여 크기 면에서도 소형화가 가능하고, 가격 경쟁력에서도 우위를 점할 수 있다. 제안하는 안테나 스위치 모듈의 크기는 $5{\times}5\;mm$이고, 두께는 0.8 mm로 제작되었다. 각 대역의 삽입 손실은 평균적으로 1.0 dB이며, 반사 손실은 GSM/EGSM 대역에서 15.1 dB, DCS/PCS 대역에서 19 dB이다.

• Journal of electromagnetic engineering and science
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• 제8권3호
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• pp.129-133
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• 2008

An integrated passive device(IPD) technology by semi-insulating(SI)-GaAs-based fabrication has been developed to meet the ever increasing needs of size and cost reduction in wireless applications. This technology includes reliable NiCr thin film resistor, thick plated Cu/Au metal process to reduce resistive loss, high breakdown voltage metal-insulator-metal(MIM) capacitor due to a thinner dielectric thickness, lowest parasitic effect by multi air-bridged metal layers, air-bridges for inductor underpass and capacitor pick-up, and low chip cost by only 6 process layers. This paper presents the Wilkinson power divider with excellent performance for digital cellular system(DCS). The insertion loss of this power divider is - 0.43 dB and the port isolation greater than - 22 dB over the entire band. Return loss in input and output ports are - 23.4 dB and - 25.4 dB, respectively. The Wilkinson power divider based on SI-GaAs substrates is designed within die size of $1.42\;mm^2$.

• 한국정밀공학회지
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• 제18권7호
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• pp.143-148
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• 2001

In this study, a mechanistic model of cutting force components in up and down end milling process is presented. Using this cutting force model of 4-tooth endmills with various helix angles, cutting force variation of inconel 718 has been predicted. Predicted values of cutting force components are coincide well with the measured ones. As helix angle increases, overlapping effects of the active cutting edges increase. In up endmilling the magnitudes of radial and feed cutting force componts FX and FY are lowest when the helix angle is $40\{\circ}$, but in down endmilling the magnitudes of these values increase slightly as helix angle becomes large.