• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.12-12
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• 2008

Ruthenium is one of the noble metals having good thermal and chemical stability, low resistivity, and relatively high work function(4.71eV). Because of these good physical, chemical, and electrical properties, Ru thin films have been extensively studied for various applications in semiconductor devices such as gate electrode for FET, capacitor electrodes for dynamic random access memories(DRAMs) with high-k dielectrics such as $Ta_2O_5$ and (Ba,Sr)$TiO_3$, and capacitor electrode for ferroelectric random access memories(FRAMs) with Pb(Zr,Ti)$O_3$. Additionally, Ru thin films have been studied for copper(Cu) seed layers for Cu electrochemical plating(ECP) in metallization process because of its good adhesion to and immiscibility with Cu. We investigated Ru thin films by thermal ALD with various deposition parameters such as deposition temperature, oxygen flow rate, and source pulse time. Ru thin films were grown by ALD(Lucida D100, NCD Co.) using RuDi as precursor and $O_2$ gas as a reactant at 200~$350^{\circ}C$.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.3
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• pp.182-188
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• 2001

A solenoid-type MEMS inductor with a quality factor over 10 at 2 GHz has been developed using an electroplating technique. The integrated spiral inductor has a low Q factor due to substrate loss and skin effects. It also occupies a large area compared to the solenoid-type inductor. The direction of flux of the solenoid-type inductor is parallel to the substrate, which can lower the substrate loss and other interference with integrated passive components. To estimate the characteristics of the proposed inductor over a high frequency range, the 3D FEM (Finite Element Method) simulation is used by using the HFSS at the Ansoft corporation. The electroplated solenoid-type inductor is fabricated on a glass substrate step by step by using photolithography and copper electroplating. The fabrication process to improve the quality factor of the inductor is also developed. The achieved inductance varies within a range from 0.5 nH to 2.8 nH, and the maximum Q factor is over 10.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.30-34
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• 2002

In this Paper, Insulation of current lead in the conduction-cooled DC reactor for the 1.2kV class 3 high-Tc superconducting fault current limiter(SFCL) is studied. Thermal link which conducts heat energy but insulates electrical energy is selected as a insulating device for the current lead in the conduction-cooled Superconducting DC reactor. It consists of oxide free copper(OFC) sheets, Polyimide films, glass fiberglass reinforced Plastics (GFRP) plates and interfacing material such an indium or thermal compound. Through the test of dielectric strength in L$N_2$, polyimide film thickness of 125 ${\mu}{\textrm}{m}$ is selected as a insulating material. Electrical insulation and heat conduction are contrary to each other. Because of low heat conductivity of insulator and contact area between electrical insulator and heat conductor, thermal resistance of conduction-cooled system is increased. For the reducing of thermal resistance and the reliable contact between Polyimide and OFC, thermal compound or indium can be used As thermal compound layer is weak layer in electrical field, indium is finally selected for the reducing of thermal resistance. Thermal link is successfully passed the test. The testing voltage was AC 2.5kVrms and the testing time was 1 hour.

• Progress in Superconductivity
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• v.3 no.1
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• pp.104-110
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• 2001

Since the strand-to-strand type joint far CICC (Cable-In-Conduit Conductor) is small in size and has low DC resistance, it is expected to be useful type fur a superconducting magnet system which had a compact structure like the KSTAR (Korea Superconducting Tokamak Advanced Research) coil system. The DC resistance is changed according to the distribution patterns of strands in cables connected together in the joint. A commercial code was used for the calculation of the DC resistance. With the decrease of outer diameter of the Joint, Which means the increase of strand volume fraction in the joint, the calculated DC resistance decrease rapidly and non-lineally. The variation of resistance depends mainly on the volume fraction of solder which has higher resistivity than copper. The resistance decrease inversely with the increase of the length of the joint. The resistance increase with increase of number of triplets in each stack contacted with that of another terminal cable. In case of the strand-to-strand joint that has 62mm of outer diameter, 52mm of inner diameter, 100mm of overlap length, and four triplets in each stack, the calculated DC resistance is less than 1 n-Ohm.

• Journal of the Korean institute of surface engineering
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• v.41 no.1
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• pp.33-37
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• 2008

Polycarbonate has a high transmittance to light, low specific gravity, flexibility and cost-effectiveness that extends the application field of the polymer to bio-engineering, optics, electronic parts, etc. Moreover, electro plating of metallic film on PC could endow the parts the electromagnetic interference shielding capability. However, poor adhesion of copper on PC limited the wide usage in the industry. In this work, a composite(PC/ABS) and MmSH(Momentary mold Surface Heating) injection process were used to improve the plating characteristics; plating thickness, gloss and adhesion. Also plasma treatment and chemical treatment were employed for improving adhesion. Plating characteristics on PC/ABS were better than those on PC due to the anchoring effect of butadiene. MmSH injection process could ameliorate the gloss and coating adhesion. Also plating thickness and adhesion of PC and PC/ABS were increased by plasma treatment.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.549-555
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• 2019

Electrocatalysis of oxygen reduction reaction (ORR) using Pt nanoparticles or bimetal on carabon was studied. Currently, the best catalyst is platinum, which is a limited resource and expensive to commercialize. In this paper, we investigated the cheaper and more active electrocatalysts by making Pt nanoparticles and adding 3D transition metal such as copper. Electrocatalysts were obtained by chemical reduction based on ethylene glycol solutions. Elemental analysis and particle size were confirmed by XRD and TEM. The electrochemical surface area (ECSA) and activity of the catalyst were determined by electrochemical techniques such as cyclic voltammetry and linear sweep voltammetry method. The commercialized Pt support on carbon (Pt/C, JM), synthesis Pt/C and synthesis Pt3Cu1 alloy nanoparticles supported on carbon were compared. We confirmed that the synthesized Pt3-Cu1/C has high electrochemical performance than commercial Pt/C. It is expected to develop an electrocatalyst with high activity at low price by increasing the oxygen reduction reaction rate of the fuel cell.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.12
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• pp.999-1005
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• 2016

A brushless direct current (BLDC) motor electronically performs rectification without brushes. It therefore does not have the typical mechanical friction contacts between the brushes and commutators. The BLDC motor has the advantages of high speed, low noise, and electronic noise reduction in addition to high durability and reliability. Therefore, it is mainly used in electric vehicles and electric equipment. However, iron loss and copper loss due to long-term use induce temperature increases in the motor, which reduces its performance and life. The temperatures of the stator and permanent magnet are predicted to be $62.3^{\circ}C$ and $32.2^{\circ}C$, respectively. This study shows the enhanced temperature distribution in a 600 W BLDC motor using unsteady and three-dimensional (3D) numerical investigations validated with experimental data.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.27-31
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• 2013

Magnesium alloy is used on parts of aircraft and electronic equipment because of the highest specific strength among the common metal materials. Recently, studies about appling magnesium alloy sheet to automotive bodies are on the increase rapidly. For application to automotive bodies, researches about characteristics of resistance spot welding of magnesium alloy sheet are essential. Magnesium alloy has low boiling point, so getting sound bead shape is difficult when appling varies welding processes. Resistance spot welding is also particular about setting optimum welding conditions because of spatter generation, pores and cracks occurrence in nugget. And life of electrodes is very short because of alloying with copper that main material of electrodes. This requires frequent dressing and replacement of electrodes and decrease in productivity of resistance spot welding on magnesium alloy. Therefore in this study, for effective analysis of changes in tensile shear load and nugget size during electrode life test, evaluate detail characteristics of resistance spot welding on magnesium alloy sheet using dome type electrode.

• Progress in Medical Physics
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• v.27 no.3
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• pp.125-130
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• 2016

Dual energy computed tomography (DECT) is used to classify two materials and quantify the mass density of each material in the human body. An energy modulation filter based DECT could acquire two images, which are generated by the low- and high-energy photon spectra, in one scan, with one tube and detector. In the case of DECT using the energy modulation filter, the filter should perform the optimization process for the type of materials and thicknesses for generating two photon spectra. In this study, Geant4 Monte-Carlo simulation toolkit was used to execute the optimization process for determining the property of the energy modulation filter. In the process, various materials used for the energy modulation filter are copper (Cu, $8.96g/cm^3$), niobium (Nb, $8.57g/cm^3$), stannum (Sn, $7.31g/cm^3$), gold (Au, $19.32g/cm^3$), and lead (Pb, $11.34g/cm^3$). The thickness of the modulation filter varied from 0.1 mm to 1.0 mm. To evaluate the overlap region of the low- and high-energy spectrum, Geant4 Monte-Carlo simulation is used. The variation of the photon flux and the mean energy of photon spectrum that passes through the energy modulation filter are evaluated. In the primary photon spectrum of 80 kVp, the optimal modulation filter is a 0.1 mm lead filter that can acquire the same mean energy of 140 kVp photon spectrum. The lead filter of 0.1 mm based dual energy CBCT is required to increase the tube current 4.37 times than the original tube current owing to the 77.1% attenuation in the filter.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.144-144
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• 2013

Non-thermal atmospheric pressure plasmas have recently garnered much attention due to their unique physical and chemical properties that are sometimes significantly different from those of low pressure plasmas. It can offer many possible application areas including nano and bio/medical areas. Many different types of plasma sources have been developed for specific needs, which can be one of the important merits of the atmospheric pressure plasmas since characteristics of the produced plasma depend significantly on operating parameters such as driving frequency, supply gas type, driving voltage waveform, gas flow rate, gas composition, geometrical factor etc. Among many source configurations, parallel plate type geometry is one of the simplest configurations so that it can offer many insights for understanding basic underlying physics. Traditionally, the parallel plate type set up has been studied actively for understanding low pressure plasma physics along with extensive employment in industries for the same reason. By considering that understanding basic physics, in conjunction with plasma-surface interactions especially for nano & bio materials, should be pursued in parallel with applications, we investigated atmospheric pressure discharge characteristics in a parallel plate type capacitive discharge source with two parallel copper electrodes of 60 mm in diameter and several millimeters in gap distance. In this presentation, some plasma characteristics by varying many operating variables such as inter-electrode distance, gas pressure, gas composition, driving frequency etc will be discussed. The results may be utilized for plasma control for widening application flexibility.