• 조명전기설비학회논문지
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• 제29권4호
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• pp.1-10
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• 2015

The light emitting diodes(LED) package of new structure is proposed to promote the reliability and lifespan by maximize heat dissipation occurred on the chip. We designed and fabricated the LED packages mixing the advantages of chip on board(COB) based on conventional metal printed circuit board(PCB) and the merits of Si sub-mount using base as a substrate. The proposed LED package samples were selected for the superior efficiency of the material through the sealant properties, chip characteristics, and phosphor properties evaluations. Reliability test was conducted the thermal shock test and flux rate according to the usage time at room temperature, high-temperature operation, high-temperature operation, high-temperature storage, low-temperature storage, high-temperature and high-humidity storage. Reliability test result, the average flux rate was maintained at 97.04% for each items. Thus, the Si sub-mount based LED package is expected to be applicable to high power down-light type LED light sources.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.49-49
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• 2009

Phosphors with oxide host material, YAG:$Ce^{3+}$ and $(Ca,Sr,Ba)_2SiO_4:Eu^{2+}$ yellow phosphor, has been used for LED applications. The WLEDs using these phosphors are widely used for LCD backlighting, automobile, and general lighting applications since they have high conversion efficiency and good thermal and chemical stability which can meet necessary life time of LED products up to now. With advances of LED chip technology, the external quantum efficiency and driving current in chip get higher so that the phosphors for high power chip are required to maintain high conversion efficiency and stability at high temperature due to the heat dissipated from LED chips. In addition, higher color rendering index of LED lighting and color reproducibility of LCD than those of LEDs with single yellow phosphors are required. In order to overcome these technical issues rising from evolution of LED technology, new phosphors are in demand and nitride phosphors, one of the promising new candidate materials, will be discussed here.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.22-26
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• 2013

The author analyzes the luminous efficiency of the phosphor-conversion white light-emitting diode (LED) that consists of a blue LED chip and a yellow phosphor. A theoretical model is derived to find the relation between luminous efficiency (LE) of a white LED, wall-plug efficiency (WPE) of a blue LED chip, and the phosphor absorption ratio of blue light. The presented model enables to obtain the theoretical limit of LE and the lower bound of WPE. When the efficiency model is applied to the measured results of a phosphor-conversion white LED, the limit theoretical value of LE is obtained to be 261 lm/W. In addition, for LE of 88 lm/W at 350 mA, the lower bound of WPE in the blue LED chip is found to be ~34%. The phosphor absorption ratio of blue light was found to have an important role in optimizing the luminous efficiency and colorimetric properties of phosphor-conversion white LEDs.

• 한국기계가공학회지
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• 제14권6호
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• pp.104-110
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• 2015

LED has added value as a lighting source in the illuminating industry because of its high efficiency and low power consumption. In LED production processes, the chip cutting process, which mainly uses a scribing process with a laser has an effect on quality and productivity of LED. This scribing process causes problems like heat deformation, decreasing strength. The inner laser method, which makes a void in wafer and induces self-cracking, can overcome these problems. In this paper, cutting sapphire wafer for fabricating LED chip using the inner laser scribing process is proposed and evaluated. The aim is to settle basic experiment conditions, determine parameters of cutting, and analyze the characteristics of cutting by means of experimentation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.191-191
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• 2009

In this paper, we have confirmed the temperature of LED chip and McPCB with thermal simulation program which is CFDedign V10 for analysis the thermal flow of HP LED package. we have known that the heat from LED chip is transferred through heat slug to copper layer of McPCB. the temperature of LED chip shows 85.11 [$^{\circ}C$], which shows the temperature gap of 7.52 [$^{\circ}C$] against McPCB. the gap of temperature affect reliability of the wire bonding and die attachment. therefore, copper layer of heat slug on the McPCB should designed with the largest dimension.

• Journal of the Optical Society of Korea
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• 제19권3호
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• pp.311-316
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• 2015

We investigate the temperature dependence of the phosphor conversion efficiency (PCE) of the phosphor material used in a white light-emitting diode (LED) consisting of a blue LED chip and yellow phosphor. The temperature dependence of the wall-plug efficiency (WPE) of the blue LED chip and the PCE of phosphor are separately determined by analyzing the measured spectrum of the white LED sample. As the ambient temperature increases from 20 to $80^{\circ}C$, WPE and PCE decrease by about 4.5% and 6%, respectively, which means that the contribution of the phosphor to the thermal characteristics of white LEDs can be more important than that of the blue LED chip. When PCE is decomposed into the Stokes-shift efficiency and the phosphor quantum efficiency (QE), it is found that the Stokes-shift efficiency is only weakly dependent on temperature, while the QE decreases rapidly with temperature. From 20 to $80^{\circ}C$ the phosphor QE decreases by about 7% while the Stokes-shift efficiency changes by less than 1%.

• 한국전기전자재료학회논문지
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• 제26권1호
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• pp.13-17
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• 2013

In this paper, we designed a charge pump circuit using level shifter for LED driver IC. The designed circuit makes the 15 V output voltage from the 5 V input in condition of 50 kHz switching frequency. The prototype chip which include the proposed charge pump circuit and its several internal sub-blocks such as oscillator, level shifter was fabricated using a 0.35 um 20 V BCD process technology. The size of the fabricated prototype chip is 2,350 um ${\times}$ 2,350 um. We examined performances of the fabricated chip and compared its measured results with SPICE simulation data.

• 한국생산제조학회지
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• 제24권4호
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• pp.448-454
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• 2015

In this paper, the band structural design that is typically in a line was arranged in a ring shape, so as to configure the high power LED lighting in such a way as to form a concentrated light distribution angle of less than 15 degrees. The parabolic aluminized reflector PAR38 that facilitates design using area and the area of the optical system to the same extent, applied a multiple light-source condenser lens optical system for the control of integration. The LED used here implemented a single linear light source using ans LED module with ans LED, flip-chip chip-scale package. The optical system was designed based on the energy star standard.

• 반도체디스플레이기술학회지
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• 제20권3호
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• pp.32-38
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• 2021

We developed an inductively coupled plasma (ICP) etcher for GaN etching using a parallel plasma electrode source with a multifunctional chuck matched to it in order for the low power consumption and low process cost in comparison with the conventional ICP system with a helical-type plasma electrode source. The optimization process condition using it for the micro light-emitting diode (µ-LED) chip fabrication was established, which is an ICP RF power of 300 W, a chuck power of 200 W, a BCl₃/Cl₂ gas ratio of 3:2. Under this condition, the mesa structure with the etch depth over 1 ㎛ and the etch angle over 75° and also with no etching residue was obtained for the µ-LED chip. The developed ICP showed the improved values on the process pressure, the etch selectivity, the etch depth uniformity, the etch angle profile and the substrate temperature uniformity in comparison with the commercial ICP. The µ-LED chip fabricated using the developed ICP showed the similar or improved characteristics in the L-I-V measurements compared with the one fabricated using the conventional ICP method

• 한국표면공학회지
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• 제40권2호
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• pp.103-106
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• 2007

We have investigated the optical and electrical properties of surface mounted white light emitting diode (LED) chips prepared by using yellow phosphors on the blue LED chip. The yellow phosphor mixed with transparent epoxy was coated on the prepared LED chip. The optimum mixing conditions with epoxy and yellow phosphor is obtained at the mixing ratio of epoxy:yellow phosphor = 97:3 wt%. The maximum luminance and light emitting efficiency are above $80,000cd/m^2$ and 23.2 lm/W, respectively, at the bias voltage of 2.9 V. There was no distinct change in the luminance strength with changing of the yellow phosphor ratios. The current of the white LED chip is about 30 mA at 2.9 V.