• Journal of the Microelectronics and Packaging Society
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• v.18 no.4
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• pp.49-53
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• 2011

High-speed Cu filling into a through-silicon-via (TSV) and simplification of bumping process by electroplating for three dimensional stacking of Si dice were investigated. The TSV was prepared on a Si wafer by deep reactive ion etching, and $SiO_2$, Ti and Au layers were coated as functional layers on the via wall. In order to increase the filling rate of Cu into the via, a periodic-pulse-reverse wave current was applied to the Si chip during electroplating. In the bumping process, Sn-3.5Ag bumping was performed on the Cu plugs without lithography process. After electroplating, the cross sections of the vias and appearance of the bumps were observed by using a field emission scanning electron microscope. As a result, voids in the Cu-plugs were produced by via blocking around via opening and at the middle of the via when the vias were plated for 60 min at -9.66 $mA/cm^2$ and -7.71 $mA/cm^2$, respectively. The Cu plug with a void or a defect led to the production of imperfect Sn-Ag bump which was formed on the Cu-plug.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.77-81
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• 2020

Commercialization of flexible OLED displays, such as rollable and foldable displays, has attracted tremendous interest in next-generation display markets. However, during bending deformation, cracking and delamination of thin films in the flexible display panels are the critical bottleneck for the commercialization. Therefore, measuring mechanical properties of the fragile thin films in the flexible display panels is essential to prevent mechanical failures of the devices. In this study, tensile properties of the metal and ceramic nano-thin films were quantitatively measured by using a direct tensile testing method on the water surface. Elastic modulus, tensile strength, and elongation of the sputtered Mo, MoTi thin films, and PECVD deposited SiN_x thin films were successfully measured. As a result, the tensile properties were varied depending on the deposition conditions and the film thickness. The measured tensile property values can be applied to stress analysis modeling for mechanically robust flexible displays.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.582-588
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• 1997

Synthetic reaction of TAME, ETBE, and MTBE compounds used largely for gasoline octane number enhancer to prevent air pollution was investigated using heteropolyacid catalyst in a fixed bed flow reactor. In the synthetic reaction of TAME, ETBE and MTBE, after hetero atom being replaced with poly atom, the activity of the catalyst, $H_4SiW_{12}O_{40}$ with coordinated bond with W and an hetero atom of Si was the highest among the catalysts tested. Also the activity depended upon the metals replaced which are related to the catalyst acidity. $FeHPW_{12}O_{40}$ and $K_3PM_{o12}O_{40}$ catalysts showed high activity in TAME synthesis, while they were not effective in ETBE and MTBE synthesis. In this study catalysts showing high activity were selected and mixed with equal weight combination of $H_4SiW_{12}O_{40}$ and $Sr_2SiW_{12}O_{40}$ ;$H_4SiW_{12}O_{40}$ and $NaH_2PW_{12}O_{40}$ ; $Fe_{1.5}PW_{12}O_{40}$ and $Mg_2SiW_{12}O_{40}$ ; $Mg_2SiW_{12}O_{40}$ and $Ba_2SiW_{12}O_{40}$. The mixed heteropolyacid catalysts showed higher TBA conversion rate and better selectivity of ETBE and MTBE than the single catalysts.

• Journal of Environmental Health Sciences
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• v.37 no.5
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• pp.348-357
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• 2011

Objectives: This study was conducted in order to examine the relationship between heavy metal concentrations in the soil and the level of heavy metals in the blood or urine of 216 local residents living near abandoned metal mines. Methods: Residents around abandoned metal mines were interviewed about their dietary habits, including seafood consumption, medical history, cigarette smoking, and drug history. Metal concentrations in the soil were determined by atomic absorption spectrophotometer (AA-7000, Shimadzu, Japan). Lead (Pb) and cadmium (Cd) contents in the blood or urine were analyzed by GF-AAS (AA-6800, Shimadzu). Mercury (Hg) contents in the blood were determined by means of a mercury analyzer (SP-3DS, NIC). Arsenic (As) content in the soil and urine were measured by a HG-AAS (hydride vapor generation-atomic absorption spectrophotometer). Results: The heavy metal concentrations in the soil showed a log normal distribution and the geometric means of the four villages were 8.61 mg/kg for Pb, 0.19 mg/kg for Cd, 1.81 mg/kg for As and 0.035 mg/kg for Hg. The heavy metal levels of the 216 local residents showed a regular distribution for Pb, Cd, Hg in the blood and As in the urine. The arithmetic means were 3.37 ${\mu}g$/dl for Pb, 3.07 ${\mu}g$/l for Cd and 2.32 ${\mu}g$/l for Hg, 10.41 ${\mu}g$/l for As, respectively. Conclusions: As a result of multi-variate analysis for the affecting factors on the bodily heavy metal concentrations, gender and concentration in the soil (each, p<0.01) for blood lead levels; gender and smoking status (each, p<0.01) for blood cadmium levels; gender (p<0.01) for urine arsenic levels; gender, age and concentration in the soil (p<0.01) for blood mercury levels were shown to be the affecting factors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.582-593
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• 1999

This paper presents the design and fabrication of the diplexer for a KOREASAT-III Ka-band satellite transponder. The transmission characteristics of the diplexer is analyzed by calculating the generalized scattering matrix using mode matching method. It is composed of 2 bandpass filters, coupled with H-plane T-junction having symmetrical inductive iris and E-plane metal insert structures. Compared with the size and weight of the Rx and Tx filter loaded with a transponders respectively, those of the diplexer can be effectively reduced. In a high power transmission, the variation of the filter characteristics is minimized by the scheme that irises are extended to the exterior of H-plane of the waveguide. This scheme needs no extra heat sinks for dissipating high power. The diplexer is designed to improve the simplification, durability and reliability by eliminating tuning screws, which have been used to compensate for the characteristics of fabricated filters. The bandpass filters of the diplexer show the insertion loss of less than 1.2 dB and the return loss in excess of 15 dB. The isolations of more than 65 dB have been achieved between Rx and Tx filter.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.6-9
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• 2001

[ $SiO_2$ ] effect on the electrochemical properties of polymeric gel electrolytes(PGEs) reinforced with glass fiber cloth(GFC) was investigated . PGEs were composed of polyacrylronitrile(PAN), poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)), $LiClO_4$ and three kind of plasticizer(ethylene carbonate, dietyl carbonate, propylene carbonate). $SiO_2$ was added to PGEs in the weight fraction of 10, 20, $30\%$ respectively. PGEs containing $SiO_2$ showed conductivity of over $10^{-3}S/cm\;at\;23^{\circ}C$ and electrochemical stability window to 4.8V. In the impedance spectra of the cells, which were constructed by lithium metals as electrodes, interfacial resistance increased due to growth of passivation layer during storage time and remarkable difference was not observed with content of $SiO_2$. In the impedance spectra of the lithium ion polymer batteries consisted of $LiClO_2$ and mesophase pitch-based carbon fiber(MCF), ohmic cell resistance of $SiO_2-free$ PGE was changed continuously with number of cycle, but those of $SiO_2-dispersed$ PGEs were not. Discharge capacity of the PGE containing $20wt\%\;SiO_2$ showed 132 mAh/g at 0.2C rate and $85\%$ of discharge capacity was retained at 2C rate.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.1-8
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• 2016

Capacity of layered lithium nickel-cobalt-manganese oxide ($LiNi_{1-x-y}Co_xMn_yO_2$) cathode material can increase by raising the charge cut-off voltage above 4.3 V vs. $Li/Li^+$, but it is limited due to anodic instability of conventional electrolyte. We have been screening and evaluating various sulfone-based compounds of dimethyl sulfone (DMS), diethyl sulfone (DES), ethyl methyl sulfone (EMS) as electrolyte additives for high-voltage applications. Here we report improved cycling performance of $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$ cathode by the use of dimethyl sulfone (DMS) additive under an aggressive charge condition of 4.6 V, compared to that in conventional electrolyte, and cathode-electrolyte interfacial reaction behavior. The cathode with DMS delivered discharge capacities of $198-173mAhg^{-1}$ over 50 cycles and capacity retention of 84%. Surface analysis results indicate that DMS induces to form a surface protective film at the cathode and inhibit metal-dissolution, which is correlated to improved high-voltage cycling performance.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.27-34
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• 2012

$Li_3V_2(PO_4)_3$/carbon composite materials are synthesized from a sucrose-containing precursor. Amorphous $Li_3V_2(PO_4)_3/C$ (a-LVP/C) and crystalline $Li_3V_2(PO_4)_3/C$ (c-LVP/C) are obtained by calcining at $600^{\circ}C$ and $800^{\circ}C$, respectrively, and electrochemical performance as the negative electrode for lithium secondary batteries is compared for two samples. The a-LVP electrode shows much larger reversible capacity than c-LVP, which is ascribed to the spatial $Li^+$ channels and flexible structure of amorphous material. In addition, this electrode shows an excellent rate capability, which can be accounted for by the facilitated $Li^+$ diffusion through the defect sites. The sloping voltage profile is another advantageous feature for easy SOC (state of charge) estimation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.997-1006
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• 2010

For manufacturing modern cars, so-called multi-materials, such as aluminum alloy with high-strength steels, are used. For obtaining such materials, a new joining method is required to achieve the multi-material design. Mechanical clinching is one of joining methods used to join the dissimilar materials. The objective of this study is to investigate the characteristics of mechanical clinching of Al5052 alloy to high-strength steels (SPFC440, 590, 780). Using FE-analysis and clinching experiment, the joinability of Al5052 alloy to high-strength steel is evaluated by geometrical shape of mechanical clinched joint, such as neck-thickness and undercut. Further, the joint strength is evaluated by performing a single-lap shear test. The upper high-strength steel SPFC780 was not clinched because of the necking of the upper sheet. The joint strength increased with increasing strength of the upper sheet. For the lower high-strength steel sheet, the joinability and joint strength decreased with increasing strength of the lower sheet.

• Composites Research
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• v.30 no.3
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• pp.169-174
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• 2017

Demand of glass fiber reinforced composites (GFRC) increased with developing aircraft and defense industries using resin transfer molding (RTM) process to produce complex product. In this research, wetting, interfacial, and mechanical properties were evaluated with different Cross-linking Density by Molecular Weight of Hardener. Epoxy resin as matrices was used bisphenol-A type and amine-type hardeners with different molecular weight. Specimens were manufactured via RTM and wetting property of resin and glass fiber (GF) mat was evaluated to viscosity of epoxy and injection time of epoxy matrix. Mechanical property of GFRC was determined via flexural strength whereas interfacial properties were determined by interlaminar shear strength (ILSS) and interfacial shear strength (IFSS). The difference in mechanical property depends upon the fiber weight fraction (wt %) of GFRC by RTM as well as the different Molecular Weight of Hardener.