• Transactions on Electrical and Electronic Materials
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• 제16권4호
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• pp.201-205
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• 2015

This paper dealt with the condensing technology of an LED light source that uses a parabolic reflector to replace a searchlight equipped with a xenon lamp. A ray-tracing simulation was conducted to analyze the influence of the diameter of the reflector and the size of the light source on light condensing. The combination of a parabolic reflector with a diameter of 620 mm and a focal distance of 220 mm, and a 9 mm multi-chip package (MCP) with a luminous flux of 7,000 lm showed the narrowest beam angle. The luminous intensity at the center was measured at 7.7×10⁶ cd. The distance between the light source and the point where the illuminance was 1 lx was calculated to be 2.8 km. The power consumption of the system was 95 W, which is only 9.5% of that of the 1 kW xenon searchlight, and the beam angle was 1.03°. In a site experiment, it was confirmed that the light ray reflected from the LED searchlight proceeds forward without any diffusion because of the narrow beam angle.

• 한국전기전자재료학회논문지
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• 제25권10호
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• pp.849-856
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• 2012

Chip on board type white light emitting diode on metal core printed circuit board with high thixotropy silicone is fabricated by vacuum printing encapsulation system. Encapsulant is chosen by taking into account experimental results from differential scanning calorimeter, shearing strength, and optical transmittance. We have observed that radiant flux and package efficacy are increased from 336 mW to 450 mW and from 11.9 lm/W to 36.2 lm/W as single dome diameter is varied from 2.2 mm to 2.8 mm, respectively. Double encapsulation structure with 2.8 mm of dome diameter shows further significant enhancement of radiant flux and package efficacy to 667 mW and 52.4 lm/W, which are 417 mW and 34.8 lm/W at single encapsulation structure, respectively.

• 조명전기설비학회논문지
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• 제25권2호
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• pp.10-18
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• 2011

In order to develop highly-integrated RGBY(Red, Green, Blue, Yellow) LED light, a high thermal radiation ceramic package was manufactured, and the encapsulation process was applied with a vacuum printing encapsulation system(VPES). After the completion of vacuum printing, the shape of the encapsulation layer could be controlled by heat treatment during the curing process, and the optical power became highly increased as the encapsulation layer approached a dome shape. The optical characteristics involved in a Correlated Color Temperature(CCT), a Color Rendering Index (CRI), and the efficiency of RGBY LED light were able to be identified by the experimental designing method. Regarding the characteristics of the white light of RGBY LED light, which were measured on the basis of the aforementioned optical characteristics, CRI posted 88, CCT recorded 5,720[$^{\circ}K$], and efficiency exhibited 52[lm/W]. The chip temperature of RGBY LEDs was below 55[$^{\circ}C$] when the consumption power of LED chips was 0.1[W] for the red, 0.3[W] for the green, 0.08[W] for the blue, and 0.24[W] for the yellow. Also, the thermal resistance of the highly-integrated RGBY LED light measured by T3Ster was 2.3[K/W].

• 한국전기전자재료학회논문지
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• 제26권8호
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• pp.614-619
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• 2013

Recently, remote phosphor is reported for white LED enhancing of phosphor efficiency compared with conventional phosphor-based W-LED. In this study, Remote phosphor was produced by screen printing coating on glass substrate with phosphor contents rated paste and heat treatment. The paste consists of phosphor, lowest softening glass frit and organic binders. Remote phosphor can be well controlled by varying the phosphor content rated paste. After mounting remote phosphor on top of blue LED chip, CCT, CRI, and luminance efficiency were measured. The measurement results showed that CCT, CRI, and luminance efficiency were 6,645, 68, and 1,16l m/W in phosphor 80 wt.% remote phosphor sintered at $600^{\circ}C$.

• 한국광학회지
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• 제25권4호
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• pp.221-224
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• 2014

고출력 LED 소자의 활용이 많아지면서, 온도상승 문제를 극복하고 신뢰성을 향상해야 하는 요구가 높아짐에 따라 광원 패키지의 방열이 매우 중요해졌다. 패키지에 칩을 접합하는 열전달 물질(TIM, Thermal Interface Material)은 열전도도가 높은 물질과 폴리머를 혼합하여 재료 자체의 열전달 특성을 향상시키는 방안이 사용되어 왔으나, 실제 패키지의 열 특성은 칩 부착계면의 높은 열저항으로 인해 기대에 미치지 못하고 있다. 본 연구는 diamond 분말과 epoxy의 혼합으로 열 특성을 개선함에 있어서, 과산화수소를 적용하면서도 기포를 효율적으로 제거하여, 각 계면의 친화성을 높이고 전체 점도를 낮추어 diamond 분말의 분산을 촉진하고, 결과적으로 대부분의 경우에 전체 열 저항을 약 30% 이상 개선하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.303-304
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• 2005

In this paper, we report a fluxless eutectic die bonding process which uses 80Au-20Sn eutectic alloy. The chip LEDs are picked and placed on silicon substrate wafers. The bonding process temperatures and force are $305\sim345^{\circ}C$ and 10$\sim$100gf, respectively. The bonding process was performed on graphite heater with nitrogen atmosphere. The quality of bonding are evaluated by shear test and thermal resistance. Results of fluxless eutectic die bonding show that shear strength is Max. 3.85kgf at 345$^{\circ}C$ /100gf and thermal resistance of junction to die bonding is Min. 3.09K/W at 325$^{\circ}C$/100gf.

• 정보관리연구
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• 제42권3호
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• pp.1-26
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• 2011

이 연구에서는 계량서지적 기법으로 LED 제조기술 분야의 핵심 연구주체와 동향을 파악하여 관련 연구개발 전략 수립을 위한 기반을 제공하고자 하였다. 최근 10년의 논문 데이터를 대상으로 핵심 소주제별 동향 및 핵심 연구자와 연구기관, 주요 국가별 연구경향을 분석하고, 주제 및 기관 차원의 전략 다이어그램을 도출하였다. 이를 위해서 효과적인 전략 다이어그램을 도출할 수 있는 개선된 방법론을 제안하였다. 분석결과, 우리나라는 일부 LED 생산 기술 부분에서 경쟁력이 있는 것으로 판단되나, 차세대 LED 제조 기술과 같은 미래 유망 영역에 대한 연구개발 지원이 필요한 것으로 나타났다. 연구기관 차원에서는 주요 대학 및 연구기관을 중심으로 LED 분야에 대한 연구의 저변이 확대되고 있는 가운데, 최근 LED 분야에 대한 실제적인 기술 개발은 주로 대기업 중심으로 이루어지고 있었다. 따라서 LED 분야에 대한 계열화된 기술과 유망 영역의 기술을 확보하기 위해서는 세부 영역별 관련 전문기업에 대한 지원 및 육성과 함께, 공동연구 및 산학협력 등 기관 간 협력활동을 확대할 필요가 있을 것이다.

• 한국세라믹학회지
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• 제52권4호
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• pp.229-233
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• 2015

Currently, the majority of commercial white LEDs are phosphor converted LEDs made of a blue-emitting chip and YAG yellow phosphor dispersed in organic silicone. However, silicone in high-power devices results in long-term performance problems such as reacting with water, color transition, and shrinkage by heat. Additionally, yellow phosphor is not applicable to warm white LEDs that require a low CCT and high CRI. To solve these problems, mixing of green phosphor, red phosphor and glass, which are stable in high temperatures, is common a production method for high-power warm white LEDs. In this study, we fabricated conversion lenses with LUAG green phosphor, SCASN red phosphor and low-softening point glass for high-power warm white LEDs. Conversion lenses can be well controlled through the phosphor content and heat treatment temperature. Therefore, when the green phosphor content was increased, the CRI and luminance efficiency gradually intensified. Moreover, using high heat treatment temperatures, the fabricated conversion lenses had a high CRI and low luminance efficiency. Thus, the fabricated conversion lenses with green and red phosphor below 90 wt% and 10 wt% with a sintering temperature of $500^{\circ}C$ had the best optical properties. The measured values for the CCT, CRI and luminance efficiency were 3200 K, 80, and 85 lm/w.

• 한국재료학회지
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• 제29권7호
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• pp.437-442
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• 2019

Green $BaSi_2O_2N_2:0.02Eu^{2+}$ phosphor is synthesized through a two-step solid state reaction method. The first firing is for crystallization, and the second firing is for reduction of $Eu^{3+}$ into $Eu^{2+}$ and growth of crystal grains. By thermal analysis, the three-time endothermic reaction is confirmed: pyrolysis reaction of $BaCO_3$ at $900^{\circ}C$ and phase transitions at $1,300^{\circ}C$ and $1,400^{\circ}C$. By structural analysis, it is confirmed that single phase [$BaSi_2O_2N_2$] is obtained with Cmcm space group of orthorhombic structure. After the first firing the morphology is rod-like type and, after the second firing, the morphology becomes round. Our phosphor shows a green emission with a peak position of 495 nm and a peak width of 32 nm due to the $4f^65d^1{\rightarrow}4f^7$ transition of $Eu^{2+}$ ion. An LED package (chip size $5.6{\times}3.0mm$) is fabricated with a mixture of our green $BaSi_2O_2N_2$, and yellow $Y_3Al_5O_{12}$ and red $Sr_2Si_5N_8$ phosphors. The color rendering index (90) is higher than that of the mixture without our green phosphor (82), which indicates that this is an excellent green candidate for white LEDs with a deluxe color rendering index.

• 한국세라믹학회지
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• 제44권3호
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• pp.147-151
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• 2007

An improvement for the efficiency of the $Sr_{2}SiO_{4}:Eu$ yellow phosphor under the $450{\sim}470\;nm$ excitation range have been achieved by adding the co-doping element ($Mg^{2+}\;and\;Ba^{2+}$) in the host. White LEDs were fabricated through an integration of an blue (InGaN) chip (${\lambda}_{cm}=450\;nm$) and a blend of two phosphors ($Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor) in a single package. The InGaN-based two phosphor blends ($Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor) LEDs showed three bands at 450 nm, 550 nm and 640 nm, respectively. The 450 nm emission band was due to a radiative recombination from an InGaN active layer. This 450 nm emission was used as an optical transition of the $Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor. As a consequence of a preparation of white LEDs using the $Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor yellow phosphor and CaS:Eu red phosphor, the highest luminescence efficiency was obtained at the 0.03 mol $Ba^{2+}$ concentration. At this time, the white LEDs showed the CCT (5300 K), CRI (89.9) and luminous efficacy (17.34 lm/W).