• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.29-32
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• 2013

The surface roughness and reflectivity of electroless-plated Sn-3.5 wt%Ag on a LED (light emitting diode) lead frame were investigated. Cu electroplating was carried out prior to electroless plating of Sn-3.5Ag to improve the reflectivity of the Sn-3.5Ag deposit. In order to investigate the effect of stirring speed and temperature of the plating solution, surface roughness and reflectivity was measured. The experimental results revealed that the thickness of the deposit layer increased with stirring speed and temperature of the plating solution. Stirring speed is increased from 100 to 300 rpm, the surface roughness was reduced from 0.513 to 0.266 ${\mu}m$, and the reflectivity increased from 1.67 to 1.84 GAM. As temperature of the plating solution increased from 25 to $45^{\circ}C$, the surface roughness reduced from 0.507 to 0.350 ${\mu}m$, and the reflectivity increased from 1.68 to 1.84 GAM.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.3
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• pp.51-56
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• 2014

The reliability of solder joint is significantly affected by the property of surface finish. This paper reports on a study of high speed shear energy and failure mode for Sn-4.0wt%Ag-0.5wt%Cu (SAC405) solder joints with the time of Pd activation. The nodule size of electroless Ni-P deposit increased with increasing the time of Pd activation. The roughness (Ra) of electroless Ni-P deposit decreased with increasing the time of Pd activation. Then, with $HNO_3$ vapor, the quasi-brittle and brittle mode of SAC405 solder joint decreased with increasing the time of Pd activation. This results indicate that the increase in the Pd activation time for Electroless Ni/ Electroless Pd/ Immersion Au (ENEPIG) surface finish play a critical role for improving the robustness of SAC405 solder joint.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.54-61
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• 1998

A numerical simulation is attempted for the regenerative cooling heat transfer processes of the liquid propellant rocket engine. The heat transfer from the combustion gases to the thrust chamber wall is called gas side heat transfer. This heat is conducted radially to the coolant through the carbon deposit and metallic wall of thrust chamber Finally, this heat is convected away by the coolant flowing along the passages in the thrust chamber. The equivalence of these three heat fluxes of the above processes is utilized to determine the coolant side wall temperature, gas side wall temperature and the heat flux. When the number and shape(width, height) of coolant passages, the shape(size) of thrust chamber, oxidant and fuel properties, coolant properties, oxidant/fuel mixture ratio, coolant inlet temperature, the thickness of carbon deposit formed along the thrust chamber wall during combustion are given, reasonable radial direction temperature distributions and heat fluxes along the thrust chamber axis are obtained.

• Solar Energy
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• v.15 no.2
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• pp.91-99
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• 1995

The influence of deposition parameters on the deposition of $SnO_2$ thin films by spray pyrolysis has been studied. In the case of spray solution with tile concentration of 0.01M, at low deposition temperature the deposition was controlled by surface reaction and portion controlled by mass transfer is increased with increasing deposition temperature to $400^{\circ}C$. Above $400^{\circ}C$, the deposition is controlled by mass transfer at low spray pressure, and by surface reaction at high spray pressure. As the concentration of spray solution increased the deposition rate increased, and in this experiment the deposition depends on the Rideal-Eley mechanism. The deposition rate increased with increasing substrate temperature up to $400^{\circ}C$ and then decreased due to homogeneous nucleation. The thickness of the deposit increased with increasing spray duration, and the adhesion between substrate and deposit was formed physically.

• Korean Journal of Materials Research
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• v.28 no.4
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• pp.235-240
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• 2018

We propose a speedy two-step deposit process to form an Au electrode on hole transport layer(HTL) without any damage using a general thermal evaporator in a perovskite solar cell(PSC). An Au electrode with a thickness of 70 nm was prepared with one-step and two-step processes using a general thermal evaporator with a 30 cm source-substrate distance and $6.0{\times}10^{-6}$ torr vacuum. The one-step process deposits the Au film with the desirable thickness through a source power of 60 and 100 W at a time. The two-step process deposits a 7 nm-thick buffer layer with source power of 60, 70, and 80 W, and then deposits the remaining film thickness at higher source power of 80, 90, and 100 W. The photovoltaic properties and microstructure of these PSC devices with a glass/FTO/$TiO_2$/perovskite/HTL/Au electrode were measured by a solar simulator and field emission scanning electron microscope. The one-step process showed a low depo-temperature of $88.5^{\circ}C$ with a long deposition time of 90 minutes at 60 W. It showed a high depo-temperature of $135.4^{\circ}C$ with a short deposition time of 8 minutes at 100 W. All the samples showed an ECE lower than 2.8 % due to damage on the HTL. The two-step process offered an ECE higher than 6.25 % without HTL damage through a deposition temperature lower than $88^{\circ}C$ and a short deposition time within 20 minutes in general. Therefore, the proposed two-step process is favorable to produce an Au electrode layer for the PSC device with a general thermal evaporator.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.1-4
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• 2004

Three group samples with difference thickness of $CeO_2$ capping layer deposited by PLD were studied. Among them, one group $CeO_2$ films were deposited on stainless steel tape coated with IBAD- YSZ and $CeO_2$ buffer layer ($CeO_2$/IBAD-YSZ/SS); other two groups of $CeO_2 YSZ Y_2O_3$multi-layer were deposited on NiW substrates for fabrication of YBCO coated conductor through RABiTS approach. The pulsed laser deposition (PLD) and DC magnetron sputtering were employed to deposit these buffer layers. On the top of buffer layer, YBCO film was deposited by PLD. The effect of thickness of $CeO_2$ film on the texture of $CeO_2$ film and critical current density ($J_c$) of YBCO film were analyzed. For the case $CeO_2$ on $CeO_2$/IBAD-YSZ/SS, there was a self-epitaxy effect with the increase of $CeO_2$ film. For $YSZ/Y_2O_3$ NiW which was deposited by PLD or DC magnetron sputtering, there is not self-epitaxy effect. However, the capping layer of $CeO_2$ film deposited by PLD improved the quality of buffer layer for $YSZ/Y_2O_3$ which was deposited by DC magnetron sputtering, therefore increased the $J_c$ of YBCO film.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.680-686
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• 2013

Tungsten oxide films were prepared by an electrochemical deposition method for use as the anode in rechargeable lithium batteries. Continuous potentiostatic deposition of the film led to numerous cracks of the deposits while pulsed deposition significantly suppressed crack generation and film delamination. In particular, a crack-free dense tungsten oxide film with a thickness of ca. 210 nm was successfully created by pulsed deposition. The thickness of tungsten oxide was linearly proportional to deposition time. Compositional and structural analyses revealed that the as-prepared deposit was amorphous tungsten oxide and the heat treatment transformed it into crystalline triclinic tungsten oxide. Both the as-prepared and heat-treated samples reacted reversibly with lithium as the anode for rechargeable lithium batteries. Typical peaks for the conversion processes of tungsten oxides were observed in cyclic voltammograms, and the reversibility of the heat-treated sample exceeded that of the as-prepared one. Consistently, the cycling stability of the heat-treated sample proved to be much better than that of the as-prepared one in a galvanostatic charge/discharge experiment. These results demonstrate the feasibility of using electrolytic tungsten oxide films as the anode in rechargeable lithium batteries. However, further works are still needed to make a dense film with higher thickness and improved cycling stability for its practical use.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.603-608
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• 2010

A study has been conducted experimentally to investigate behavior of ignition and flame spread over metal dust deposits with particle size using by a developed apparatus and thermogravimetric analysis(TGA). Zr, Ta and Mg-Al(90:10 wt%) alloy metal powders including Mg and Ti with different particle size were used. Also we used PMMA(Polymethylmethacrylate) powder to compare the combustion properties to those of metal powders. When dust layers were more than 5 mm in thickness, the dependency of deposit depth on flame spread rate over dust layer was not shown. With decreasing mean particle diameter, flame spread rate over Ti dust layer decreased, while the spread rate over Mg dust layer increased. For mean diameter of $51{\mu}m$, fire spread rate over pure Mg dust layer decreased to about 50 percent in Mg-Al(90:10 wt%) dust layer. The oxide thickness of metal dust used in this study tended to be inversely proportional with the spread rate, and it was quite small for influence with particle size. From the results of TGA for Ti and Mg, weight increasing curves(550 for Mg, 578 for Ta) were observed in the oxidation process, and they seems to be caused by ignition of upper dust layer.

• Economic and Environmental Geology
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• v.48 no.2
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• pp.103-114
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• 2015

Jinsan gold deposit is a hydrothermal vein type deposit consisting of several fissure filling quartz veins developed within the Changri Formation of the Ogcheon Supergroup in Geumsan, Chungnam. This study is to provide an efficient exploration and development strategies based on the characteristics of the geology, geological structure, core logging, and ore vein occurrence and grade for the four pits (New pit, Main pit, Yanghapan pit and Teugho pit). Quartz veins are mostly developed with the strike of $N10^{\circ}-25^{\circ}W$ and $N5^{\circ}-20^{\circ}E$, and the thickness is in the range of 0.1~0.5 m, sometimes extending to over 1m. Although the quartz veins commonly form massive shape, they sometimes show zonal structure, comb structure as well as brecciated texture. Major ore minerals are pyrite and chalcopyrite, and pyrrhotite, sphalerite, galena, marcasite, electrum and chalcocite are also accompanied as minor phases. Gray and milky white quartz veins, which are occasionally crosscut by calcite vein, also include fluorite. Ore evaluations for the 22 samples revealed that the samples from the pits generally have very low Au contents, lower than 1 g/t, but some clay samples of drilled core show very high Au concentrations, up to 141 g/t, indicating that Au content is much higher within fault gouges rather than within fresh quartz veins. This may represent that gold might have been reworked and reprecipitated by hydrothermal fluids in association with reactivation of the faults, and thus suggest that ore occurrence in this deposit is very complex and irregular and therefore more precise and systematic exploration is required.

• Journal of the Mineralogical Society of Korea
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• v.6 no.2
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• pp.122-144
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• 1993

The Kimhae napseok clay deposit was studied to characterize its mineralogy and genesis. Geology of the deposit is composed of Tertiary volcanic rocks and granodiorite. Tertiary volcanic rocks consist of andesitic tuff with minor interstratified tuffaceous shale, and rhyodacitic tuff. The main ore body of 2.4 to 4 m in thickness developed parallel to the bedding of andesitic tuff bed. Its strike and dip are $N70^{\circ}E-N85^{\circ}E$ and $16^{\circ}NW-32^{\circ}NW$, respectively. Two alteration zones; the propylitic zone of albite-epidote-chlorite-quartz assemblage and advanced argillic zone of pyrophyllite-dickite-alunite-diaspore assemblage are developed. Correlation of $SiO_2$ to $Al_2O_3$ shows no relation in propylitic zone, while a negative linear relation in advanced argillic zone. Chemical variation shows that $SiO_2$, $Al_2O_3$, MgO, CaO, $Na_2O$ and $K_2O$ were leached out during hydrothermal alteration. Pyrophyllite, the most abundant mineral in advanced argillic zone, occurs as low temperature 2M polytype. It is closely associated with dickite, diaspore and alunite. The Hinckley index of dickite is 0.83 showing moderate crystallinity. Na content is increasing in the M site with the increasing content of cations in the R-site. the mole percent of Na replacing K in alunite ranges from 53.2 to 71.6. It is also found that pyrophyllite grows in the dissolution site of diaspore. Plagioclase was albitized. Lowering of pH caused mainly by sulfide and sulfate decomposition resulted in preferential leaching of Si. It is inferred that aluminum released from plagioclase in the volcanic rocks as well as from the tuffaceous shale intercalated in andesitic tuff were the main sources of aluminum required for the formation of clay deposit. pH in hydrothermal fluid decreased from propylitic zone to advanced argillic zone with increasing degree of alteration. Based on experimental data reported in the literature and mineral assemblages, the formation temperature of the deposit ranges 270 to $320^{\circ}C$.