• Journal of Biomedical Engineering Research
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• v.15 no.4
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• pp.389-394
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• 1994

The age-hardening behavior and the structural changes in a commercial dental Au-Ag-Cu-Pd alloy were investigated by means of hardness test, optical and scanning electron microscopic observation, energy dispersive spectroscopy and X-ray diffraction study. The drastic reduction in hardness by prolonged aging occurred after a rapid increase in hardness at the initial stage by the isothermal aging at $350^{\circ}C$. This softening was due to the broad precipitates formation of the lamellar structure which was composed of the f.c.t. AuCu I ordered f.c.t. phase containing Pd and the f.c.c. Ag-rich $\alpha$1 solid solution f.c.c.phase containing Au.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.143-143
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• 2000

MEIS를 이용하여 Cu3Au(100)에서 단원자층 분해능을 얻기 위한 연구를 하였다. 우선 수소이온을 이용한 첫째층과 셋째 Au층의 분리 시도는 extremely glancing exit angle 등 극한의 산란조건에서도 성공하지 못하였다. 깊이 분해능을 정해주는 electronic 에너지 손실을 극대화기 위해 수소이온 대신 질소 이온을 사용하여 에너지 스펙트럼을 측정해 본 결과, 표면 Au 층과 표면 셋째 Au 층을 구분할 수 있었다, <110>으로 정렬된 조건에서는 셋째 층의 Au 원자들이 완전히 shadow cone 내부에 존재하여 관측되지 않지만 9.75$^{\circ}$tilt한 경우 셋째 층의 Au 원자들이 shadow cone 바깥으로 나오게 되어 첫째 층과 셋째 층이 확실히 분리되어 측정되었다. 이 연구에서 MEIS로 단원자층의 분해능을 얻는데 성공하였다. 이러한 단원자층 분해능으로 시료의 온도변화에 따른 표면 첫째 층의 Au 의 조성변화를 관찰하였고 이를 전산 모사 하였다. 이 결과 벌크 전이 온도인 39$0^{\circ}C$이하에서 표면 첫째 층 Au의 조성이 감소하는 것을 관찰하였고 이러한 감소는 45$0^{\circ}C$근처까지 계속되었으며, 다시 온도를 실온으로 낮추면 본래의 질서화된 상태로 되돌아감을 확인하였다. 그리고 이를 전산 모사 한 결과, 표면 첫째 층의 Au가 표면 둘째 층으로 이동해 감을 알 수 있었다.

• Economic and Environmental Geology
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• v.15 no.4
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• pp.189-204
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• 1982

The Geodo mine is located in the southern limb of the Hambaeg syncline. Geology of the area consists of Paleozoic-Mesozoic sedimentary Rocks and Cretaceous igneous rocks. The important igneous rocks presumably related to skarnization and ore mineralization in the area, are the early granodiorite and the late porphyritic granodiorite. Two mineralogical types of ore deposits are recognized in the area. They are the Fe-Cu deposits in the Myobong formation and the Au-Bi-Cu deposits in the Hwajeol formation. Contact metamorphism due to granodiorite intrusion includes hornfelsization, exoskarnization and endoskarnization. Wall-rock alterations related to the Fe mineralization are grouped into the hydrothermal replacement skarnization and the hydrothermal filling skarnization. Another hydrothermal alteration is associated with the Cu mineralization. Various mineralogical analyses have been applied for the identification of minerals. They include optical microscopy, chemical analysis, etching test, X-ray diffraction, and infrared absorption spectroscopic analyses. The ore minerals in these ore deposits are classified into two groups;hypogene and supergene minerals. Hypogene minerals consist of magnetite, pyrite, chalcopyrite, and chalcocite. Supergene minerals consist of chalcocite, bornite, and geothite. Ore minerals show various kinds of ore texture: open-space filling, exsolution, replacement, and cementation texture. The gangue minerals consist of quartz, diopside, epidote, garnet and plagioclase in the hornfelsic zone, garnet, diopside, scapolite, actinolite, sericite, chlorite, quartz, and calcite in the skarn zone, and, epidote, chlorite, sericite, quartz, and calcite in the late hydrothermal alteration zone. This study shows that the Fe-Cu deposits are of metasomatic pipe type with the later hydrothermal fillings, and the Au-Bi-Cu deposits are of hydrothermal fissure-filling type. The mineralization is probably related to the intrusion of porphyritic granite.

• Journal of Technologic Dentistry
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• v.24 no.1
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• pp.65-71
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• 2002

This study was performed to observe the microhardness change of the surface and the bonding strength between the porcelain and alloy specimens in order to investigate the effects of appended indium, tin and copper on interfacial properties of Au-Pd-Ag alloys. The hardness of castings was measured with a micro-Vicker's hardness tester. The interfacial shear bonding strength between alloy specimen and fused porcelain was measured with a mechanical testing system(MTS 858.20). The microhardness of Au-Pd-Ag alloy was increased by adding indium and tin, but not increased by adding copper. The shear bonding strength of Au-Pd-Ag-Sn alloy and Au-Pd-Ag-Cu alloy showed 87MPa, 57MPa. The higher concentration of adding elements showed the higher shear bonding strength.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.68-68
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• 2003

최근의 전자부품은 고밀도 고집적화 됨에 따라 여러 가지 문제점들이 발생되고 있다. 그 중 부품이 실장되는 부분에 사용되는 솔더나 전기적 회로를 구성하는 패턴간에 금속 이온 마이그레이션(Metallic Ion Migration)이 발생하여 전기적 단락(Short)를 유발함으로써 전자제품의 치명적 고장을 유발한다. 본 연구는 이온 마이그레이션 현상을 물방울시험(Water Drop Test)을 통하여 재현함으로써 발생 메카니즘을 확인하여 발생원인을 직접적으로 관찰하고, 각 종 패턴의 거리 및 전압에 따른 발생속도의 차이를 조사하기 위하여 수행되었다. 이러한 실험을 위하여 콤 패턴(Comb Pattern)의 FR-4 재질 인쇄회로기판(PCB : Printed Circuit Board)을 사용하였으며, 사용된 전극재질로는 Cu, SnPb, Au를 사용하였고, 패턴간 거리는 0.5, 1.0, 2.0mm의 3가지 종류로 구분하였다. 또한 패턴간에 인간 된 전압은 6.5V, 15V를 인가한 후 마이그레이션이 발생되는 시간을 측정하였다. 이러한 실험으로부터 다음과 같은 결론을 얻었다. (1) 6.5V의 인가전압에서는 Cu 패턴이 대체적으로 가장 빠르게 마이그레이션이 발생하였으며, 다음으로 Au가 발생하였고, Cu와 SnPb의 발생시간은 대체적으로 근사한 값을 나타내었다. 이것은 비슷한 평형전위를 갖는 재료는 마이그레이션 발생시간이 유사하게 나타나며, 높은 (+)전위를 갖을수록 발생시간이 지연됨을 알 수 있다. (2) 15V를 인가하였을 때 패턴간격이 0.5mm인 경우 Cu, Au, SnPb의 순으로 나타났으며, 1.0mm는 SnPb, Cu, Au, 2.0mm인 경우는 SnPb, Au, Cu의 순으로 마이그레이션이 발생하였다. 인가전압이 높은 경우 초기 발생에는 큰 차이가 없지만 수지상이 발생 후 성장하는데 많은 영향을 미치는 것으로 보인다. 이것은 초기 수지상의 형성에 큰 영향을 미치는 것은 재료의 평형전위에 의한 값이 좌우하지만, 수지상이 일정길이 이상 형성된 이후에는 성장속도가 평형전위에 따른 값과는 다소 다르게 나타남을 알 수 있다.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.89-96
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• 2006

Recent ULSI and multilevel structure trends in microelectronic devices minimize the line width down to less than $0.25{\mu}m$, which results in high current densities in thin film interconnections. Under high current densities, an EM(electromigration) induced failure becomes one of the critical problems in a microelectronic device. This study is to improve thin film interconnection materials by investigating the EM characteristics in Ag, Cu, Au, and Al thin films, etc. EM resistance characteristics of Ag, Cu, Au, and Al thin films with high electrical conductivities were investigated by measuring the activation energies from the TTF (Time-to-Failure) analysis. Optical microscope and XPS (X-ray photoelectron spectroscopy) analysis were used for the failure analysis in thin films. Cu thin films showed relatively high activation energy for the electromigration. Thus Cu thin films may be potentially good candidate for the next choice of advanced thin film interconnection materials where high current density and good EM resitance are required. Passivated Al thin films showed the increased MTF(Mean-time-to-Failure) values, that is, the increased EM resistance characteristics due to the dielectric passivation effects at the interface between the dielectric overlayer and the thin film interconnection materials.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.75-87
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• 2001

Three different kinds of substrate used in this study : bare Cu substrate, Ni-P/Cu substrate with a Ni-P layer thickness of $5\mu\textrm{m},$ and Au/Ni-P/Cu substrate with the Ni-P and Au layers of $0.15\mu\textrm{m}$ and $5\mu\textrm{m}$ thickness respectively. The wettability of various Sn-base solders was affected by the substrate metal finish used, i.e., nickel, gold and copper. On the Au/Ni-F/Cu substrate, Sn-base solders wet better than any of the other substrate metal finishes tested. The interfacial reaction between various substrate and Sn-base solder was investigated at $70^{\circ}C,$ $100^{\circ}C,$ $120^{\circ}C,$ $150^{\circ}C,$ $170^{\circ}C$ and $200^{\circ}C$ for reaction times ranging from 0 day to 60 day. Intermetallic phases was formed along a Sn-base solder/ various substrate interface during solid-state aging. The apparent activation energy for growth of Sn-Ag/Cu, Sn-Ag-Bi/Cu, and Sn-Bi/Cu couples were 65.4, 88.6, and 127.9 Kj/mol, respectively. After isothermal aging, the fracture surface shoved various characteristics depending on aging temperature and time, and the types of BGA pad.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2875-2876
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• 2009

• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.7-11
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• 2010

For many large-scale applications of high-temperature superconducting materials, large critical current density($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers(APCs) in $YBa_2Cu_3O_{7-\delta}$(YBCO) films for enhancement of their $J_c$. In this work, we investigated electric characteristic of YBCO films on $SrTiO_3$ (100) substrates whose surfaces were modified by the introduction of Au nanoparticles (AuNPs). Au nanoparticles were uniformly dispersed on STO substrates with one of typical solution techniques, self assembled monolayer. After heating the STO substrates with Au nanoparticles, the size of Au nanoparticles was around 29~32 nm in height and 41~49 nm in diameter. XRD diffraction patterns taken on the YBCO film with Au nanoparticles show the c-axis orientation. The measured $T_c$ of YBCO /AuNPs films was around 89K and the $J_c$ was 0.75 MA/$cm^2$ at 65 K and 1 T.

• Journal of Electrochemical Science and Technology
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• v.11 no.2
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• pp.172-179
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• 2020

The impact of effective parameters on the electrodeposition rate optimization of Au-Cu alloy at high thicknesses on the silver substrate was investigated in the present study. After ensuring the formation of gold alloy deposits with the desired and standard percentage of gold with the cartage of 18K and other standard karats that should be observed in the manufacturing of the gold and jewelry artifacts, comparing the rate of gold-copper deposition by direct and pulsed current was done. The rate of deposition with pulse current was significantly higher than direct current. In this process, the duty cycle parameter was effectively optimized by the "one factor at a time" method to achieve maximum deposition rate. Particular parameters in this work were direct and pulse current densities, bath temperature, concentration of gold and cyanide ions in electrolyte, pH, agitation and wetting agent additive. Scanning electron microscopy (SEM) and surface chemical analysis system (EDS) were used to study the effect of deposition on the cross-sections of the formed layers. The results revealed that the Au-Cu alloy layer formed with concentrations of 6gr·L^-1 Au, 55gr·L^-1 Cu, 24 gr·L^-1 KCN and 1 ml·L^-1 Lauryl dimethyl amine oxide (LDAO) in the 0.6 mA·cm^-2 average current density and 30% duty cycle, had 0.841 ㎛·min^-1 Which was the highest deposition rate. The use of electrodeposition of pure and alloy gold thick layers as a production method can reduce the use of gold metal in the production of hallow gold artifacts, create sophisticated and unique models, and diversify production by maintaining standard karats, hardness, thickness and mechanical strength. This will not only make the process economical, it will also provide significant added value to the gold artifacts. By pulsating of currents and increasing the duty cycle means reducing the pulse off-time, and if the pulse off-time becomes too short, the electric double layer would not have sufficient growth time, and its thickness decreases. These results show the effect of pulsed current on increasing the electrodeposition rate of Au-Cu alloy confirming the previous studies on the effect of pulsed current on increasing the deposition rate of Au-Cu alloy.