• Proceedings of the KWS Conference
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• 2006.05a
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• pp.30-32
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• 2006

The interfacial reaction and reliability of eutectic Sn-Pb and Pb-free eutectic Sn-Ag ball-grid-array (BGA) solders with an immersion Ag-plated Cu substrate were evaluated following isothermal aging at $150^{\circ}C$. During reflowing, the topmost Ag layer was dissolved completely into the molten solder, leaving the Cu layer exposed to the molten solder for both solder systems. A typical scallop-type Cu-Sn intermetallic compound (IMC) layer was formed at both of the solder/Cu interfaces during reflowing. The thickness of the Cu-Sn IMCs for both solders was found to increase linearly with the square root of isothermal aging time. The growth of the $Cu_3Sn$ layer for the Sn-37Pb solder was faster than that for the Sn-3.5Ag solder, In the case of the Sn-37Pb solder, the formation of the Pb-rich layer on the Cu-Sn IMC layer retarded the growth of the $Cu_6Sn_5$ IMC layer, and thereby increased the growth rate of the $Cu_3Sn$ IMC layer. In the ball shear test conducted on the Sn-37Pb/Ag-plated Cu joint after aging for 500h, fracturing occurred at the solder/$Cu_6Sn_5$ interface. The shear failure was significantly related to the interfacial adhesion strength between the Pb-rich and $Cu_6Sn_5$ IMC layers. On the other hand, all fracturing occurred in the bulk solder for the Sn-3.5Ag/Ag-plated Cu joint, which confirmed its desirable joint reliability.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.35-42
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• 2024

Recently, with the miniaturization and high integration of semiconductor chips, the bump bridge phenomenon caused by fine pitches is drawing attention as a problem. Accordingly, Cu pillar bump, which can minimize the bump bridge phenomenon, is widely applied in the semiconductor package industry for fine pitch applications. When exposed to a high-temperature environment, the thickness of the intermetallic compound (IMC) formed at the joint interface increases, and at the same time, Kirkendall void is formed and grown inside some IMC/Cu and IMC interfaces. Therefore, it is important to control the excessive growth of IMC and the formation and growth of Kirkendall voids because they weaken the mechanical reliability of the joints. Therefore, in this study, isothermal aging evaluation of Cu pillar bump joints with a CS (Cu+ Sn-1.8Ag Solder) structure was performed and the corresponding results was reported.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.23-34
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• 2000

This paper reports the effects of curing temperature and aging on the strength and the modulus of elasticity. In oder to determine the strength and the modulus of elasticity with curing temperature and aging, experimental and analytical methods are adopted. The tests of 480 cylinders are carried out for type I, V and V with 15 percent replacement of fly ash cement concretes, which are cured at isothermal conditions of 10, 23, 35 and 5$0^{\circ}C$. and the concrete cylinders are tested at the ages of 1, 3, 7 and 28 days. According to the experimental results, the concrete subjected to high temperature at early ages attaines higher early-age compressive and splitting tensile strength but eventually attaines lower later-age compressive and splitting tensile strength. Even if modulus of elasticity has the same tendency, the variation of modulus of elasticity with curing temperature is smaller than that of compressive strength. Based on these experimental results, the relationships among compressive strength, modulus of elasticity and splitting tensile strength are proposed considering the effects of curing temperature, aging and cement type.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.2
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• pp.108-114
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• 2000

The effects of heat treatments in Al-Si-Mg alloys on the microstructure and hardness have been investigated by the optical microscope, scanning electron microscope(SEM), and Rockwell hardness tester. The materials of various compositions are melted in a vacuum induction furnace under argon atmosphere. Five different Al alloys are prepared from commercial purity aluminium, magnesium and Al-25Si alloy. Two types of aging treatments are performed: i) Isothermal aging of the specimens at $150^{\circ}C$, $170^{\circ}C$ and $190^{\circ}C$. ii) Pre-aging of the specimens at $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$, and followed by final-aging at $170^{\circ}C$ and $190^{\circ}C$. After the heat treatments, Rockwell hardness are measured with all the specimens.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.148-151
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• 2002

In order to prevent the failures of underground distribution power cables we need to measure insulation condition in the field. Until now we used DC high voltage as a power source for the cable diagnosis but it was not proper method to the XLPE insulation cables because DC high voltage can affect sound insulation and can't diagnose exactly insulation degradation. For these reasons we imported isothermal relaxation current measurement system called by KDA-1 from germany but it's reliability did not proved in our URD cables. DC voltage decay measurement system was developed by domestic company but they don't have field experience. In this paper we tried to prove reliability of these two systems in the field. Through the field diagnosis and Ac breakdown test the two systems showed similar results.

• Journal of Biomedical Engineering Research
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• v.17 no.2
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• pp.247-254
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• 1996

The relationship between the isothermal age-hardening behavior and the phase transformation in the commercial dental Au-Ag-Cu-Pd alloy was investigated Age-hardening was mostly attributed to the lattice distortions of the supersaturated w phase resulting from the transformation to the metastable phasel which were more distinct at lower aging temperature. The lattice distortions resulting from the transformation of the metastable phases to the equilibrium phases also made a contribution to the age-hardening.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.37-44
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• 1993

Calcia stabilized zirconia polycrystal (Ca-TZP) powders synthesized by hydrothermal treatment was sintered at a temperature range of $1200^{\circ}C~1400^{\circ}C$ and investigated the properties of sintered body and the behaviors of isothermal phase transformation. The sintered bodies of Ca-TZP were shown the density of about 97% and the average mean tetragonal grain size of about $0.1~0.25{\mu}m$. Also, Ca-TZP specimen was more stable during aging at $250^{\circ}C$ than that of Y-TZP ceramics.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.5
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• pp.239-245
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• 2022

The purpose of this study is to evaluate the degree of microstructural change of materials using ultrasonic nonlinear parameters. For microstructure change, isothermal heat-treated ferritic 2.25Cr steel and low-cycle fatigue-damage copper alloy were prepared. The variation in ultrasonic nonlinearity was analyzed and evaluated through changes in hardness, ductile-brittle transition temperature, electron microscopy, and X-ray diffraction tests. Ultrasonic nonlinearity of 2.25Cr steel increased rapidly during the first 1,000 hours of deterioration and then gradually increased thereafter. The variation in non-linear parameters was shown to be coarsening of carbides and an increase in the volume fraction of stable M6C carbides during heat treatment. Due to the low-cycle fatigue deformation of oxygen-free copper, the dislocation that causes lattice deformation developed in the material, distorting the propagating ultrasonic waves, and causing an increase in the ultrasonic nonlinear parameters.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.445-450
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• 2001

The paper investigates the relationships between dynamic elastic modulus and static elastic modulus or compressive strength according to curing temperature, aging, and cement type. Based on this investigation, the new model equations are proposed. Impact echo method estimates the resonant frequency of specimens and uniaxial compression test measures the static elastic modulus and compressive strength. Type I and V cement concretes, which have the water-cement ratios of 0.40 and 0.50, are cured under the isothermal curing temperature of 10, 23, and 50 $^{\circ}C$. Cement type and aging have no large influence on the relationship between dynamic and static elastic modulus, but the ratio of dynamic and static elastic modulus comes close to 1 as temperature increases. Initial chord elastic modulus, which is calculated at lower strain level of stress-strain curve, has the similar value to dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic modulus. The proposed relationship equations between dynamic elastic modulus and static elastic modulus or compressive strength properly estimates the variation of relationships according to cement type, temperature, and aging.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1569-1571
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• 1999

In this work, we have performed the application experiment for real distribution line to diagnose the underground power cables using DC voltage decay measurement system. We have also performed the Isothermal Relaxation Current test for the same distribution line using KDA-l. We could confirmed possibility of grading the insulation aging state of underground power cables. Therefore, we conclude that it is possible to apply DC voltage decay method to the real distribution line.