• Proceedings of the Korean Reliability Society Conference
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• 2011.06a
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• pp.49-54
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• 2011

반도체 칩과 패키지는 wire로 연결되는데, 이 때 반도체의 용도에 따라 다양한 wire와 pad의 조합이 사용되며, 이 두 개의 다른 금속물질 결합부위는 IMC(Inter Metallic Compound)를 형성하게 된다. 그러나, 결함 및 오염 등에 의하여 인접재료의 원자들이 이동하는 확산(Diffusion)이 발생하게 되어 IMC가 성장하고, 두 개의 금속물질간의 확산율은 상호 다르며, 확산율은 온도에 따른 함수가 된다. Au wire와 Ag pad를 이용하여 제조한 IR 수신모듈를 대상으로 3가지 고온조건에서 가속수명시험을 실시하였고, 각 온도별 수명분포를 바탕으로 가속계수와 활성화에너지 도출 및 정상온도에서의 수명도 예측할 수 있었다.

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.175-176
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• 2008

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.444-452
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• 2020

This study investigated the cathode catalyst of direct borohydride/hydrogen peroxide fuel cells for space exploration. Various catalysts such as Au, Ag, and Ni were supported on multiwalled carbon nanotubes (MWCNTs). Various techniques, such as transmission electron microscopy, Brunauer-Emmett-Teller method, scanning electron microscopy, and X-ray diffraction were conducted to investigate the characteristics of the catalysts. Fuel cell tests were performed to evaluate the performance of the catalysts. Ag/MWCNTs exhibited better catalytic activity than the Ni/MWCNTs and better catalytic selectivity of the Au/MWCNTs. Ag/MWCNTs presented good catalytic activity and selectivity even at an elevated operating temperature. The performance of Ag/MWCNTs was also stable for up to 60 minutes.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.3
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• pp.19-27
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• 2003

Surface finishes of PCB laminates are important in the solder joint reliability of flip chip package because the types and thicknesses of intermetallic compound(IMC), and compositions and hardness of solders are affected by them. In this study, effects of surface finishes of PCB on the low cycle fatigue resistance of Sn-based lead-free solders; Sn-3.5Ag, Sn-3.5Ag-XCu(X=0.75, 1.5), Sn-3.5Ag-XBi(X=2.5, 7.5) and Sn-0.7Cu were investigated for the Cu and Au/Ni surface finish treatments. Displacement controlled room temperature lap shear fatigue tests showed that fatigue resistance of Sn-3.5Ag-XCu(X=0.75, 1.5), Sn-3.5Ag and Sn-0.7Cu alloys were more or less the same each other but much better than that of Bi containing alloys regardless of the surface finish layer used. In general, solder joints on the Au/Ni finish showed better fatigue resistance than those on the Cu finish. Cross-sectional fractography revealed microcracks nucleation inside of the interfacial IMC near the solder mask edge, more frequently on the Cu than the Au/Ni surface finish. Macro cracks followed the solder/IMC interface in the Bi containing alloys, while they propagated in the solder matrix in other alloys. It was ascribed to the Bi segregation at the solder/IMC interface and the solid solution hardening effect of Bi in the $\beta-Sn$ matrix.

• Economic and Environmental Geology
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• v.21 no.2
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• pp.149-164
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• 1988

Electrum-sulfide mineralization of the Samgwang and Sobo mines of the Cheongyang Au-Ag area was deposited in two stages of quartz and calcite veins that fill fault zones in granite gneiss. Radiometric dating indicates that mineralization is Early Cretaceous age (127 Ma). Fluid inclusion and sulfur isotope data show that ore mineralization was deposited at temperatures between $340^{\circ}$ and $180^{\circ}C$ from fluids with salinities of 1 to 8 wt. % equiv. NaCl and a ${\delta}^{34}S_{{\sum}S}$ value of 2 to 5 per mil. Evidence of fluid boiling (and $CO_2$ effervescence) indicates a range of pressures from < 200 to $\approx$ 700 bars, corresponding to depths of ${\approx}1.5{\pm}0.3\;km$ in a hydrothermal system which alternated from lithostatic toward hydrostatic conditions. Au-Ag deposition was likely a result of boiling coupled with cooling. Meaured and calculated hydrogen and oxygen isotope values of ore-forming fluids indicate a significant meteoric water component, approaching unexchanged paleometeoric water values. Comparison of these values with those of other Korean Au-Ag deposits reveals a relationship among depth, Au/Ag ratio and degree of water-rock interaction. All investigated Korean Jurassic and Cretaceous gold-silver-bearing deposits have fluids which are dominantly evolved meteoric waters, but only deeper systems (${\geq}1.5\;km$) are exclusively gold-rich.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.1
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• pp.1-6
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• 2014

Flip chip bonded LED packages possess lower thermal resistance than wire bonded LED packages because of short thermal path. In this study, thermal and bonding properties of flip chip bonded high brightness LED were evaluated for Au-Sn thermo-compression bonded LEDs and Sn-Ag-Cu reflow bonded LEDs. For the Au-Sn thermo-compression bonding, bonding pressure and bonding temperature were 50 N and 300oC, respectively. For the SAC solder reflow bonding, peak temperature was $255^{\circ}C$ for 30 sec. The shear strength of the Au-Sn thermo-compression joint was $3508.5gf/mm^2$ and that of the SAC reflow joint was 5798.5 gf/mm. After the shear test, the fracture occurred at the isolation layer in the LED chip for both Au-Sn and SAC joints. Thermal resistance of Au-Sn sample was lower than that of SAC bonded sample due to the void formation in the SAC solder.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.835-842
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• 1999

Si3N4 -Si3N4 joints were made using Ag-Cu-Ti and Ag-Cu-In-Ti via brazing method and the change in joint strength was investigated after heat treatment at $400^{\circ}C$ or $650^{\circ}C$ for up to 2000h. The initial strength of as-brazed joints with Ag-Cu-In-Ti was lower but the reduction of the strength was less dramatic than that with Ag-Cu-Ti. The joints made of a new brazing alloy Au-Ni-Cr-Mo-Fe which is developed for high temperature applications were heat-treated at $650^{\circ}C$ for 1000h. As the heat treatment time increased the bond strength increased. The results of the joining system with Mo or Cu interlayer showed that the strength of the joint with Mo interlayer was higher but the system incurred problems in joint production Also it was found from oxidation experiment that Ti and In affected the oxidation resistance of brazing alloy.

• Economic and Environmental Geology
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• v.28 no.1
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• pp.9-17
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• 1995

The Kamkye Cu-Pb-Zn-Au-Ag deposits occur as quartz veins that filled fault-related fractures of NW system developed in the Cretaceous Gyeongsang basin. Three major stages of mineral deposition are recognized: (1) the stage I associated with wall rock alteration, such as sericite, chlorite, epidote and pyrite, (2) the early stage II of base-metal mineralization such as pyrite, hematite, and small amounts of sphalerite and chalcopyrite. and the middle to late stage II of Cu-As-Sb-Au-Ag-S mineralization, such as sphalerite, chalcopyrite, galena with tetrahedrite, tennantite, pearceite, Pb-Bi-Cu-S system, argentite and electrum. (3) the stage III of supergene mineralization, such as covellite, chalcocite and malachite. K-Ar dating of alteration sericite is a late Cretaceous ($74.0{\pm}1.6Ma$) and it may be associated with granitic activity of nearby biotite granite and quartz porphyry. Fluid inclusion data suggest a complex history of boiling, cooling and dilution of ore fluids. Stage II mineralization occurred at temperatures between 370 to $220^{\circ}C$ from fluids with salinities of 8.4 to 0.9 wt.% NaCl. Early stage II($320^{\circ}C$, 2.0 wt.% NaCl) may be boiled due to repeated fracturing which opened up the hydrothermal system to the land surface, and which resulted in a base-metal sulfide. Whilst the fractures were opened to the surface, mixing of middle-late stage II ore fluids with meteoric waters resulted in deposition of Cu-As-Sb-Au-Ag minerals from low temperature fluids(${\leq}290^{\circ}C$). Boiling of ore fluids may be occured at a pressure of 112 bar and a depth of 412 m. Equilibrium thermodynamic interpretation of sphalerite-tetraherite assemblages in middle stage II indicates that the ore-forming fluid had log fugacities of $S_2$ of -6.6~-9.4 atm.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.522-525
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• 2003

Mine waters, surface waters and groundwaters were sampled around seven Au-Ag mine areas (Dongil, Okdong, Dongjung, Songcheon, Ssangjeon, Dogok and Gubong Au-Ag mines). The main contamination sources of As in these abandoned Au-Ag mines can be suggested as mine tailings and waste rocks including the sulfide gangue minerals (arsenopyrite). The relatively high concentration of As in mine waters was shown in the Dongil (524 ${\mu}g/L$) and the Dogok (56 ${\mu}g/L$) mine areas. Arsenic concentrations in stream waters from the Dongil ($0.9\~118{\mu}g/L$), the Songchon ($0.8\~63{\mu}g/L$), the Ssangjeon ($1.6\~109{\mu}g/L$) and the Gubong ($3.6\~63{\mu}g/L$) mine areas exceeded the permissible level for stream water in Korea. Groundwaters collected from the Dongil ($0.9\~64{\mu}g/L$ ), the Okdong ($0.2\~69{\mu}g/L$) and the Gubong ($0.5\~101{\mu}g/L$) mine areas contained high As concentration to cause the arsenicosis in these areas. In As speciation, the concentration ratios of As(III) to As(total) present up to $75\%$ and $100\%$ in stream waters from the Okdong and the Songcheon mines, and $70\%$ in groundwaters from the Okdong and the Dongjung mines. Arsenic concentration decreases downstream from the tailing dump correlatively with pH and Fe concentration. Highly elevated As concentrations are found in the dry season (such as April and March) than in the wet season (September) due to the dilution effect by heavy rain during summer in stream waters from the Dongil and the Songcheon mine areas.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.94-94
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• 2018

The gold (LC-AuNPs) and silver (LC-AgNPs) nanoparticles were rapidly synthesized by fruit extract of Lycium chinense within 1.15 and 25 min respectively in an eco-friendly way. The synthesized nanoparticles confirmed by relevant surface plasmon resonance peaks for gold and silver nanoparticles at 536 and 480 nm, respectively. FE-TEM results revealed that LC-AuNPs were 20-50 nm and LC-AgNPs were 50-100 nm. The maximum distribution of gold, silver elements and the crystallographic nature of synthesized were confirmed using EDX, elemental mapping and XRD. LC-AgNPs showed inhibitory activity against pathogenic microorganisms such as E. coli and S. aureus, whereas LC-AuNPs did not show inhibitory activity. The LC-AgNps nanoparticles exhibited significant cytotoxicity to human breast cancer MCF7 cell line and less cytotoxicity to non-diseased RAW264.7 (murine macrophage) cells whereas LC-AuNps showed minimal toxicity to both cell lines. In-depth research on this rapid, facile and greenery nanoparticles may play a potential role in biomedical applications.