• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.55-61
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• 2010

An impact bending test method was used to evaluate the reliability for the solder joint of lead-free solder ball. In order to standardize the test method, the four point impact bending test was applied under the conditions of various frequencies and amounts of +/-amplitude respectively. Effects on the results were analysed. The optimum condition for impact bending test achieved in this study was the frequency of 10 Hz, and the amplitude of (+12/-1)~(+15/-1). 3 kinds of surface finishes Cu-OSP (Organic Solderability Preservative), ENIG (Electroless Nickel Immersion Gold), and ENEPIG (Electroless Nickel, Electroless Palladium, Immersion Gold) were used. Fracture surface showed that cracks were initiated and fractured along the intermetallic layer in the case of surface finishes of Cu-OSP and ENIG, while in the case of ENEPIG the cracks were initiated and propagated in the solder region.

• ETRI Journal
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• v.35 no.6
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• pp.1152-1155
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• 2013

A cost-effective and simple solder on pad (SoP) process is proposed for a fine-pitch microbump interconnection. A novel solder bump maker (SBM) material is applied to form a 60-${\mu}m$ pitch SoP. SBM, which is composed of ternary Sn3.0Ag0.5Cu (SAC305) solder powder and a polymer resin, is a paste material used to perform a fine-pitch SoP through a screen printing method. By optimizing the volumetric ratio of the resin, deoxidizing agent, and SAC305 solder powder, the oxide layers on the solder powder and Cu pads are successfully removed during the bumping process without additional treatment or equipment. Test vehicles with a daisy chain pattern are fabricated to develop the fine-pitch SoP process and evaluate the fine-pitch interconnection. The fabricated Si chip has 6,724 bumps with a 45-${\mu}m$ diameter and 60-${\mu}m$ pitch. The chip is flip chip bonded with a Si substrate using an underfill material with fluxing features. Using the fluxing underfill material is advantageous since it eliminates the flux cleaning process and capillary flow process of the underfill. The optimized bonding process is validated through an electrical characterization of the daisy chain pattern. This work is the first report on a successful operation of a fine-pitch SoP and microbump interconnection using a screen printing process.

• Textile Coloration and Finishing
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• v.12 no.6
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• pp.389-395
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• 2000

A natural colorants was extracted from cherry by 10wt% aqueous acetic acid solution as an extractant. Silk and cotton fabrics were dyed with the cherry extract in the temperature range of $40-80^\circ{C}$ and for the time range of 30-60min. by pre- and post-mordanting with various mordants, their dyeability and fastness were investigated. The natural cherry extract prepared in this study has a maximum absorbance at 520nm. It was found that the optimum dyeing temperature and time were $40^\circ{C}$ and 50min, respectively. The pre-mordanting method was more effective than post-mordanting. All mordants except $SnCl_2\cdot{2H}_2O\;and\;FeSO_4\cdot{7H}_2O$ were effective for silk fabrics. However, the dyeability on cotton fabrics increased in the order of $CrK(SO_4)_2\cdot{12H_2O>(CH_3COO)_2Cu\cdot{H}_2O>CuSO_4\cdot{5H}_2O>AlK(SO_4)_2\cdot{12H}_2O>FeSO_4\cdot{7H}_2O>SnCl_2\cdot{2H}_2O$ among the mordants used in this study Fastness(light, water, washing, perpspiration fastness) on the silk and cotton fabrics increased with using mordants. The post-mordanting using mordant$(CH_3COO)_2Cu\cdot{H}_2O$ among the various mordants in this study gave the best fastness.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.05a
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• pp.214-223
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• 2005

In order to recover valuable metals from fine-grained electronic waste, bioleaching of Cu, Zn, Al, Co, Ni, Sn and Pb were carried out using Aspergillus niger as a leaching microorganism in a shaking flask. Aspergillus niger was able to grow in tile presence of electronic scrap. The formation of organic acids(citric and oxalic acid) from Aspergillus niger caused the mobilization of metals from waste electronic scrap. In a preliminary study, in order to obtain the data on the leaching of Cu, Zn, Al, Co and Ni, the metal leaching behaviours were accomplished using Organic acid(Citric acid and Oxalic acid) instead of Aspergillus niger. At the electronic scrap concentration of 50g/L, Aspergillus niger were able to leach more than 95% of the available Cu, Co. But Al, Zn, Pband Sn were able to leach about 15-35%. Ni and Fe were detected in the leachate less than 10%.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.2
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• pp.61-66
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• 2017

$SnO_2$ was electrodeposited on nodule-type Cu foil at varing current density and electrodeposition time. Unlike the previous research results, when the anodic current is applied, the $SnO_2$ layer was not electrodeposited and the substrate is corroded. When the cathodic current was applied, the $SnO_2$ layer could be successfully deposited. At this time, the surface microstructure of the powdery type was observed, which showed similar crystallinity to amorphous and had a very large surface area. Crystallinity increased after low-temperature heat treatment at $250^{\circ}C$ or lower. As a result of evaluating the charge/discharge performances as an anode material for lithium ion battery, it was confirmed that the capacity of the heat treated $SnO_2$ was increased more than 2 times, but it still showed a limit point showing initial low coulombic efficiency and low cyclability. However, it was confirmed that the battery performances may be enhanced through optimizing the electrodeposition process and introducing post heat treatment.

• Journal of Powder Materials
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• v.11 no.3
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• pp.193-201
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• 2004

1960년 Au-Si계 합금에서 처음으로 비정질상이 급속 응고법에 의해 보고된 이래/sup 1)/ 지난 40년 간 많은 합금계에서 비정질상이 보고되어졌다. 대표적으로 Fe-, Ni-, Co기 합금 등 많은 합금계에서 비정질상이 보고되었으나, 비정질상의 형성을 위해서는 약 105 K/s이상의 높은 냉각속도를 필요로 하였다. 1980년대 수백 K/s의 낮은 냉각속도 하에서도 비정질상이 형성될 수 있는 다원계 합금(multi-component alloy)이 Mg-Ln-(Ni, Cu, Zn), Ln-Al-TM 합금에서 보고되어 졌으나 많은 관심을 받지 못하다가 1993년 Zr-Ti-Ni-Cu-Be 합금에서 수 ㎝ 크기의 비정질합금 제조가 보고되면서 전 세계적으로 많은 관심을 받게 되었다. Zr-Ti-Ni-Cu-Be계 벌크 비정질 합금이 보고된 후 Zr-(Nb,Pd)-Al-TM, Pd-Cu-Ni-P, Fe-Co-Zr-Mo-W-B, Ti-Zr-Ni-Cu-Sn등 여러 합금계에서 벌크 비정질 합금이 보고되었다. (중략)

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.352-354
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• 1999

The spectrophotometric determination of Cu(Ⅱ) with α-(2-benzimidazolyl)-α',α"-(N-5-nitro-2-pyridylhydrazone)-toluene has been investigated. The optimum conditions of pH, stability, concentration of ligand and surfactant were evaluated. This method is a simple and sensitive method for determination of Cu(Ⅱ) and offers a selective separation of Cu(Ⅱ) from sample solution containin- I ppm below amount of Ni(Ⅱ), Co(Ⅱ), Zn(Ⅱ) and Sn(Ⅱ). Copper was determined by measuring the absorbance of Cu(Ⅱ)-BINPHT complex extracted with benzene in Brij 58 surfactant at 410 nm. Beer's law is obeyed over the concentration range 0∼2.5 μgmL-1 and the detection limit (S/N=2) is 0.06 μgmL-1. The relative standard deviation at the 0.3 μgmL-1 is 2.4% (N=7). The method was applied for the determination of Cu(Ⅱ) in various milks.

• Journal of Electrochemical Science and Technology
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• v.9 no.4
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• pp.282-291
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• 2018

The pristine fluorine-doped $SnO_2$ (abbreviated as FTO) inverse opal (IO) was developed using a 410 nm polystyrene bead template. The nanolayered copper tungsten oxide ($CuWO_4$) was decorated on the FTO IO film using a facile electrochemical deposition, subsequently followed by annealing at $500^{\circ}C$ for 90 min. The morphologies, crystalline structure, optical properties and photoelectrochemical characteristics of the FTO and $CuWO_4$-decorated FTO (briefly denoted as $FTO/CuWO_4$) IO film were investigated by field emission scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and electrochemical impedance spectroscopy, showing FTO IO in the hexagonally closed-pack arrangement with a pore diameter and wall thickness of about 300 nm and 20 nm, respectively. Above this film, the $CuWO_4$ was electrodeposited by controlling the cycling number in cyclic voltammetry, suggesting that the $CuWO_4$ formed during 4 cycles (abbreviated as $CuWO_4$(4 cycles)) on FTO IO film exhibited partial distribution of $CuWO_4$ nanoparticles. Additional distribution of $CuWO_4$ nanoparticles was observed in the case of $FTO/CuWO_4$(8 cycles) IO film. The $CuWO_4$ layer exhibits triclinic structure with an indirect band gap of approximately 2.5 eV and shows the enhanced visible light absorption. The photoelectrochemical (PEC) behavior was evaluated in the 0.5 M $Na_2SO_4$ solution under solar illumination, suggesting that the $FTO/CuWO_4$(4 cycles) IO films exhibit a photocurrent density ($J_{sc}$) of $0.42mA/cm^2$ at 1.23 V vs. reversible hydrogen electrode (RHE, denoted as $V_{RHE}$), while the FTO IO and $FTO/CuWO_4$(8 cycles) IO films exhibited a $J_{sc}$ of 0.14 and $0.24mA/cm^2$ at $1.23V_{RHE}$, respectively. This difference can be explained by the increased visible light absorption by the $CuWO_4$ layer and the favorable charge separation/transfer event in the cascading band alignment between FTO and $CuWO_4$ layer, enhancing the overall PEC performance.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.259-273
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• 2012

Chalcogenide-based semiconductors, such as $CuInSe_2$, $CuGaSe_2$, Cu(In,Ga)$Se_2$ (CIGS), and CdTe have attracted considerable interest as efficient materials in thin film solar cells (TFSCs). Currently, CIGS and CdTe TFSCs have demonstrated the highest power conversion efficiency (PCE) of over 11% in module production. However, commercialized CIGS and CdTe TFSCs have some limitations due to the scarcity of In, Ga, and Te and the environmental issues associated with Cd and Se. Recently, kesterite CZTS, which is one of the In- and Ga- free absorber materials, has been attracted considerable attention as a new candidate for use as an absorber material in thin film solar cells. The CZTS-based absorber material has outstanding characteristics such as band gap energy of 1.0 eV to 1.5 eV, high absorption coefficient on the order of $10^4cm^{-1}$, and high theoretical conversion efficiency of 32.2% in thin film solar cells. Despite these promising characteristics, research into CZTS-based thin film solar cells is still incomprehensive and related reports are quite few compared to those for CIGS thin film solar cells, which show high efficiency of over 20%. The recent development of kesterite-based CZTS thin film solar cells is summarized in this work. The new challenges for enhanced performance in CZTS thin films are examined and prospective issues are addressed as well.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.879-888
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• 2001

The effects of final annealing temperature on the microstructure and creep characteristics were investigated for the Zr-lNb-0.2X (X=0, Mo, Cu) and Zr-lNb- 1Sn-0.3Fe-0.1X (X=0, Mo, Cu) alloys. The microstructures were observed by using TEM/EDS, and grain size and distributions of precipitates were analyzed using a image analyzer. The creep test was performed at $400^{\circ}C$ under applied stress of 150 MPa for 10 days. The $\beta$-Zr was observed at annealing temperature above $600^{\circ}C$. In the temperature above$ 600^{\circ}C$, the grain sizes of both alloy systems appeared to be increased with increasing the final annealing temperature. The creep strengths of Zr-1Nb-1Sn-0.3Fe-0.1X alloys were higher than those of Zr-1Nb-0.2X ones due to the effect of solid solution hardening by Sn in Zr-lNb-lSn-0.3Fe-0.1X alloy system. Also, Mo addition showed the strong effect of precipitate hardening in both alloy systems. The creep strength rapidly decreased with increasing the annealing temperature up to $600^{\circ}C$. However, a superior creep resistance was obtained in the sample that annealed to have a second phase of $\beta$-Zr. It was considered that the appearance of $\beta$-Zr would play an important role in the strengthening mechanism of creep deformation.