• Journal of Institute of Control, Robotics and Systems
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• v.14 no.5
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• pp.453-461
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• 2008

In this paper, new inspection method is proposed for the surfaces of lead frame and IC's. Optimal optical system and the accurate algorithm for the surface inspection are needed in machine vision area. The proposed optical system is composed of rectangular oblique light illumination and coaxial light illumination for the higher contrast and the results shows the better performances through experiments. The markings of IC surface are inspected using the accurate proposed method using the partitioned correlation coefficient, and the result shows reduction of under kill ratio compared to the previous method.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.284-285
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• 2004

We have developed a 10 Gbps receiver consist of an InGaAs PIN PD and an embedded TIA(transimpedance preamplifier). The receiver is assembled in a small form factor (SFF) Package. It shows f-3dB of 10 GHz and the sensitivity more than -20 dBm at 10$^{-10}$ BER (bit-error-rate) for 10 Gbps optical input signal of 2$^{31}$-1 PRBS (pseudo-random-bit-sequence).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.27-34
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• 2015

There has been a critical issue in optical simulation of phosphors in LEDs due to their light-reabsorption properties. To improve the accuracy of optical modeling for a white LED package, we utilized the spectrum data of the phosphor-dispersed encapsulant film instead of the phosphor powder. By measuring white LED packages with green and red phosphors, the maximum difference between simulation and experimental results of a color temperature, a color rendition index number and a color coordinate corresponds to ${\Delta}T=95K$, ${\Delta}Ra=1.7$ and ${\Delta}xy=0.007$, respectively. Based on those results, the proposed method can well explain the change of emission spectra of white LEDs with more than two phosphors which introduce the complex optical phenomena such as absorption, reabsorption, light emission, reflection and scattering, etc.

• Journal of the Semiconductor & Display Technology
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• v.15 no.4
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• pp.1-9
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• 2016

The warpage on mobile phone camera packages occurs due to the CTE(Coefficient of Thermal Expansion) mismatch between a thin silicon die and a substrate. The warpage in the optical instruments such as camera module has an effect on the field curvature, which is one of the factors degrading the optical performance and the product yield. In this paper, we studied the effect of die bonding epoxy on the package and optical performance of mobile phone camera packages. We calculated the warpages of camera module packages by using a finite element analysis, and their shapes were in good agreement showing parabolic curvature. We also measured the warpages and through-focus MTF of camera module specimens with experiments. The warpage was improved on an epoxy with low elastic modulus at both finite element analysis and experiment results, and the MTF performance increased accordingly. The results show that die bonding epoxy affects the warpage generated on the image sensor during the packaging process, and this warpage eventually affects the optical performance associated with the field curvature.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2276-2280
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• 2008

In this paper, we present thermal dependancy of LED package element by changing temperature of MCPCB for design high efficiency LED lamp, and confirmed influence of LED chip against temperature with analysis of thermal resistance and thermal capacitance. As increasing temperature, WPOs were decreased from 25 to 22.5 [%] and optical power were also decreased. that is decreased reason of optical power that forward voltage was declined by decrease of energy bandgap. Therefore optical power by temperature of MCPCB should consider to design lamp for street light and security light. Moreover, compensation from declined optical efficiency is demanded when LED package is composed. Also, thermal resistances from chip to metal PCB were decreased from 12.18 to 10.8[$^{\circ}C/W$] by changing temperature. Among the thermal resistances, the thermal resistance form chip to die attachment was decreased from 2.87 to 2.5[$^{\circ}C/W$] and was decreased 0.72[$^{\circ}C/W$] in Heat Slug by chaning temperature. Therefore, because of thermal resistance gap in chip and heat slug, reliability and endurance of high power LED affect by increasing non-radiative recombination in chip from heat.

• Particle and aerosol research
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• v.9 no.4
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• pp.253-260
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• 2013

For a vertical atmospheric aerosol distribution measurement, a very compact and light particle sampling package is developed. This package includes a compact optical particle counter (Hy-OPC), a light and small condensation particle counter (Hy-CPC), sensors (GPS, wind velocity, temperature, humidity), and a communication and system control board. This package is attached to He balloon and the altitude is controlled by a winch. Using this system the vertical particle size distribution was measured. The test results showed that the ground base atmospheric particle measurement result may be a lot different from that high above the ground.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.10-14
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• 2019

In this study, we synthesized two $Y_3Al_5O_{12}:Ce^{3+}$ phosphors ($7{\mu}m$-sized and $2{\mu}m$-sized YAG) with different sizes by controlling particles sizes of starting materials of the phosphors for white LED. In the smaller one ($2{\mu}m$-sized YAG), its photoluminescence intensity in the reflective mode was 63 % that of the bigger one ($7{\mu}m$-sized YAG); the quantum efficiencies were 93 % and 70 % for the smaller and the bigger ones. Two kinds of white LED packages with the same color coordinates were fabricated with a blue package (chip size $53{\times}30$) and two phosphors. The luminous flux of the white LED package with the smaller YAG phosphor was 92 % of that with the bigger one, indicating that the quantum efficiency of phosphor dispersed inside LED package was higher than that of the pure powder. It was consistently confirmed by the optical simulation (LightTools 6.3). It is notable according to the optical simulation that the white LED with the smaller phosphor showed 24 % higher luminous efficiency. If the smaller one had the same quantum efficiency as the bigger one (~93 %). Therefore, it can be suggested that the higher luminous efficiency of white LED can be possible by reducing the particle size of the phosphor along with maintaining its similar quantum efficiency.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.7
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• pp.1-9
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• 2012

In this paper, resistance temperature detector (RTD) integrated into the LED package is proposed in order to solve the temperature dependence of LED's optical properties. To measure the package temperature in real time, the RTD type temperature sensor having excellent accuracy and linearity between temperature change and resistance change was adopted. A stable metallic film is required for long term reliability and stability of the RTD type temperature sensor. Therefore, deposition and annealing condition for the film were determined. Based on the determined condition, the RTD type temperature sensor with the sensitivity of about $1.560{\Omega}/^{\circ}C$ was fabricated inside the LED package. In order to configurate the LED package system keeping the constant brightness regardless of the temperature, additional conversion circuit and control circuit boards were fabricated and added to the fabricated LED package. The proposed system was designed to compensate the light intensity caused by temperature change using the variable duty rate of driving current. As a result, the duty rate of PWM signal which is the output signal of the configurated system was changed with the temperature change, and the duty rate was similarly varied with the target duty rate. Consequently, it was focused the fabricated RTD can be used for compensating the optical properties of LED and the LED package which exhibits constant brightness regardless of the temperature change.

• Journal of the Optical Society of Korea
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• v.11 no.4
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• pp.149-152
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• 2007

We present a simple and efficient management scheme for gain control of EDFA by using standardized network management protocol(Simple Network Management Protocol) and operating the optical amplifier in a link-control scheme. We have demonstrated the proposed scheme by using SNMP Simulator and optical simulation software package.

• The Optical Journal
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• s.117
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• pp.23-25
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• 2008

RF embedded 기판의 기술은 Module과 Package라는 응용 제품을 거치면서 최종적으로는 기존의 여러 가지 제품의 Mother Board(특히 휴대폰)에 접목 시키기 위한 노력이 계속 진행되고 있다. 업계 및 Research 기관의 조사 결과에 따르면 PCB 시장의 성장세와 맞물려 Embedded 시장규모는 큰 폭의 상승이 예상된다. 본 고에서는 높은 유전율을 가지는 강유전체 물질의 Embedded capacitor 적용을 위해 레이저 기술을 전자부품 제조현장에 적용하는 연구의 진행상황을 소개하고자 한다.