• Advances in materials Research
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• v.1 no.1
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• pp.83-92
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• 2012

The effect of under-bump-metallization (UBM) on electromigration was investigated at temperatures ranging from $135^{\circ}C$ to $165^{\circ}C$. The UBM structures were examined: 5-${\mu}m$-Cu/3-${\mu}m$-Ni and $5{\mu}m$ Cu. Experimental results show that the solder joint with the Cu/Ni UBM has a longer electromigration lifetime than the solder joint with the Cu UBM. Three important parameters were analyzed to explain the difference in failure time, including maximum current density, hot-spot temperature, and electromigration activation energy. The simulation and experimental results illustrate that the addition 3-${\mu}m$-Ni layer is able to reduce the maximum current density and hot-spot temperature in solder, resulting in a longer electromigration lifetime. In addition, the Ni layer changes the electromigration failure mode. With the $5{\mu}m$ Cu UBM, dissolution of Cu layer and formation of $Cu_6Sn_5$ intermetallic compounds are responsible for the electromigration failure in the joint. Yet, the failure mode changes to void formation in the interface of $Ni_3Sn_4$ and the solder for the joint with the Cu/Ni UBM. The measured activation energy is 0.85 eV and 1.06 eV for the joint with the Cu/Ni and the Cu UBM, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.86.2-86.2
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• 2015

Cu2ZnSn(S,Se)4 thin film solar cells have been fabricated using sputtered Cu/Sn/Zn metallic precursors on Mo coated sodalime glass substrate without using a toxic H2Se and H2S atmosphere. Cu/Sn/Zn metallic precursors with various thicknesses were prepared using DC magnetron sputtering process at room temperature. As-deposited metallic precursors were sulfo-selenized inside a graphite box containing S and Se pellets using rapid thermal processing furnace at various sulfur to selenium (S/Se) compositional ratio. Thin film solar cells were fabricated after sulfo-selenization process using a 65 nm CdS buffer, a 40 nm intrinsic ZnO, a 400 nm Al doped ZnO, and Al/Ni top metal contact. Effects of sulfur to selenium (S/Se) compositional ratio on the microstructure, crystallinity, electrical properties, and cell efficiencies have been studied using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscope, I-V measurement system, solar simulator, quantum efficiency measurement system, and time resolved photoluminescence spectrometer. Our fabricated Cu2ZnSn(S,Se)4 thin film solar cell shows the best conversion efficiency of 9.24 % (Voc : 454.6 mV, Jsc : 32.14 mA/cm2, FF : 63.29 %, and active area : 0.433 cm2), which is the highest efficiency among Cu2ZnSn(S,Se)4 thin film solar cells prepared using sputter deposited metallic precursors and without using a toxic H2Se gas. Details about other experimental results will be discussed during the presentation.

• Journal of Welding and Joining
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• v.30 no.2
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• pp.65-69
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• 2012

Environmental and health concerns over the lead have led to investigation of the alternative Pb-free solders to replace commonly used Pb-Sn solders in microelectronic packaging application. The leading candidates for lead-free solder alloys are presently the near eutectic Sn-Ag-Cu alloys. Therefore, extensive studies on reliability related with the composition have been reported. However, the insufficient drop property of the near eutectic Sn-Ag-Cu alloys has demanded solder compositions of low Ag content. In addition, the solder interconnections in automobile applications like a smart box require significantly improved vibration resistance. Therefore, this study investigated the effect of alloying elements (Ag, Bi, In) on the vibration fatigue strength. The vibration fatigue was conducted in 10~1000Hz frequency and 20Grms. The interface of the as-soldered cross section close to the Cu pad indicated the intermetallic compound ($Cu_6Sn_5$) regardless of solder composition. The type and thickness of IMC was not significantly changed after the vibration test. It indicates that no thermal activities occurred significantly during vibration. Furthermore, as a function of alloying composition, the vibration crack path was investigated with a focus on the IMCs. Vibration crack was initiated from the fillet surface of the heel for QFP parts and from the plating layer of chip parts. Regardless of the solder composition, the crack during a vibration test was propagated as same as that during a thermal fatigue test.

• Analytical Science and Technology
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• v.11 no.4
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• pp.281-291
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• 1998

An analytical method for the simultaneous measurement of trace Cu, Sn, and Bi in blood and urine has been investigated by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Microwave oven was used for the pretreatment of blood samples using nitric acid and hydrogen peroxide in a closedvessel digestion system with 1 mL whole blood for 8 minutes. Amberlite IRC-718 resin was used as a solid phase in solid-liquid extraction technique for the removal of matrix interferences such as Na, S, P, and other polyatomic ion species. Detection limits for Cu, Sn, and Bi by this method were 0.000375 ng/mL, 0.000297 ng/mL, and 0.000174 ng/mL, respectively. Recoveries of 99.1% for Cu, 102.5% for Sn, and 98.4% for Bi were obtained for the standard spiked NIST SRM 955a blood sample. The developed method was applied for whole real blood and urine samples.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.29-34
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• 2020

The behavior of brittle fracture of electroless nickel immersion gold (ENIG) /Sn-3.0wt.%Ag-0.5wt.%Cu (SAC305) solder joints was evaluated. The pH of the electroless nickel plating solution for ENIG surface treatment was changed from 4.0 to 5.5. As the pH of the Ni plating solution increased, pin hole in the Ni-P layer increased. The thickness of the interfacial intermetallic compound (IMC) of the solder joint increased with pH of Ni plating solution. The high speed shear strength of the SAC305 solder joint on ENIG surface finish decreased with the pH of the Ni plating solution. In addition, the brittle fracture rate of the solder joint was the highest when the pH of the Ni plating solution was 5.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.68-73
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• 2020

Due to its favorable optical properties, Cu₂SnS₃ (CTS) is a promising material for thin film solar cells. Doping, which modifies the absorber properties, is one way to improve the conversion efficiency of CTS solar cells. In this work, CTS solar cells with selenium doping were fabricated on a flexible substrate using sputtering method and the effect of doping on the properties of CTS solar cells was investigated. In XRD analysis, a shift in the CTS peaks can be observed due to the doped selenium. XRF analysis confirmed the different ratios of Cu/Sn and (S+Se)/(Cu+Sn) depending on the amount of selenium doping. Selenium doping can help to lower the chemical potential of sulfur. This effectively reduces the point defects of CTS thin films. Overall improved electrical properties were observed in the CTS solar cell with a small amount of selenium doping, and a notable conversion efficiency of 1.02 % was achieved in the CTS solar cell doped with 1 at% of selenium.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.869-873
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• 2002

$Cu_2ZnSnS_4$ (CZTS) thin film is one of the candidate materials for the solar cell. It has an excellent optical absorption coefficient as well as appropriate 1.4~1.5eV band gap. The purpose of this study is replacing a half of high-cost Indium(In) atoms with low-cost Zinc(Zn) atoms and the other half with low-cost Tin(Sn) atoms in the lattice of CIS. In annealing process of thin films deposited with mixture target, the thin films were appeared the peeling. The resistivity was decreased. Thin films were deposited on ITO glass substrates using a compound target which were made by $CU_2S$, ZnS, $SnS_2$ powder were sintered in the atmosphere of Al at room temperature by rf magnetron sputtering We investigated potentialities of a low-cost material for the solar cell by measuring of thin film composition, the structure and optical properties. We could get an appropriate $Cu_2ZnSnS_4$ composition A (112) preferred orientation was appeared without annealing temperature as shown in the diffraction peaks of the CIS cells and was available for photovoltaic thin film materials. The band gap increased from 1.4 to 1.7eV as the composition ratio of Zn/Sn.. The optical absorption coefficient of the thin film was above $10^4cm^{-1}$.

• Journal of radiological science and technology
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• v.26 no.1
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• pp.45-50
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• 2003

In this work, we characterized the shieldability and lightweight of radiation protective aprons which were consisted of various metal(Pb, Sn, Ni, Ti and Cu) by measuring the x-ray dose transmitted through the filters. The transmitted ratio and lead equivalent of various metal were obtained by linear interpolation and the lead equivalent of double layered filters contained Pb layer was determined. The transmitted ratio of the apron(0.25 mmPb) specified in KS B 0845 was 5.2%. The transmitted ratio of the filters at the thickness of 0.6 mm was decreased in the other of Ni(32.60%), Ti(17.75%), Cu(13.25%) and Sn(3.84%). From the results of experimental evaluation for combined filter of Pb and Sn, it was founded that in the case of the first Sn layer, the lead equivalent was higher than that of the first Pb layer. The lead equivalent corresponding to apron of 0.25 mmPb was obtained in the double layered filters of Sn(0.19 mm) - Pb(0.1 mm) and Pb(0.1 mm) - Sn(0.37 mm). Thus, the Sn-Pb filter had the lower weight about 13% than apron of 0.25 mmPb.

• Current Photovoltaic Research
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• v.3 no.2
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• pp.54-60
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• 2015

ZnSnO thin films were deposited by atomic layer deposition (ALD) process using diethyl zinc ($Zn(C_2H_5)_2$) and tetrakis (dimethylamino) tin ($Sn(C_2H_6N)_4$) as metal precursors and water vapor as a reactant. ALD process has several advantages over other deposition methods such as precise thickness control, good conformality, and good uniformity for large area. The composition of ZnSnO thin films was controlled by varying the ratio of ZnO and $SnO_2$ ALD cycles. The ALD ZnSnO film was an amorphous state. The band gap of ZnSnO thin films increased as the Sn content increased. The CIGS solar cell using ZnSnO buffer layer showed about 18% energy conversion efficiency. With such a high efficiency with the ALD ZnSnO buffer and no light soaking effect, AlD ZnSnO buffer mighty be a good candidate to replace Zn(S,O) buffer in CIGSsolar cells.

• Korean Journal of Heritage: History & Science
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• v.54 no.2
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• pp.22-37
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• 2021

The wind chime is a longstanding Jangeomgu (majestic article) found in Korea, China, and Japan. However, basic research on wind chimes is currently inadequate as it is difficult to estimate the time of production, and there are few relics. Therefore, this research morphologically classifies the eight bronze wind chimes decorating the baldachin of the Stone Standing Maitreya Bodhisattva of Gwanchoksa Temple, Nonsan. Based on this, the manufacturing techniques and production period are scientifically demonstrated. The synthesis of the research results reveals that the structure and characteristics of the wind chimes of the Stone Standing Maitreya Bodhisattva of Gwanchoksa Temple, Nonsan differ depending on their location on the baldachin. The four large-sized wind chimes on the lower-baldachin were manufactured by casting a Cu-Sn-Pb alloy, and they are estimated to have been made during the early period of Goryeo. The two medium-sized wind chimes of the upper-baldachin's northern direction were manufactured through forging a Cu-Sn or Cu-Sn-Pb alloy, and they appear to have a similar structure to the cylindrical wind chimes appearing during the latter period of Goryeo and the Joseon period. The two small-sized wind chimes of the upper-baldachin's southern direction were manufactured by casting a Cu-Sn-Pb alloy containing Zn, and based on the chemical composition of the alloy and the shape of the clapper, they are estimated to have been manufactured during the latter period of Joseon. Through the observation of microstructures and a chemical composition analysis, it is demonstrated that two wind chimes of the lowerbaldachin were manufactured by casting and slow cooling the alloy with an alloy ratio of Cu:Sn:Pb≒80:15:5. In addition, it is estimated that the wind chimes of the upper-baldachin's northeast direction were manufactured by forging an alloy of Cu-Sn with a similar alloy ratio to that of forged high tin bronze. The results of a comparative analysis of prior research on domestic wind chimes confirm that two wind chimes of the lower-baldachin have a similar composition ratio to the wind chime excavated from Wolnamsaji in Gangjin, containing an amount of tin that corresponds with ancient records. Having a similar alloy ratio to forged high tin bronze, the wind chimes of the upper-baldachin's northeast direction are the only instances among all of the wind chimes that have been examined to date that were manufactured using this forging method. The purpose of this research is to collect baseline data to verify and classify the manufacturing period of wind chimes according to their morphological characteristics based on scientific evidence. It is hoped that this data can be utilized for the restoration and conservation processes of the wind chimes of the Stone Standing Maitreya Bodhisattva of Gwanchoksa Temple, Nonsan.