• Bulletin of the Korean Chemical Society
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• v.24 no.4
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• pp.489-493
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• 2003

2-Mercaptobenzothiazole was used as a highly selective and efficient carrier for the uphill transport of silver ion through a chloroform bulk liquid membrane. In the presence of thiosulfate ion as a suitable metal ion acceptor in the receiving phase, the amount of silver transported across the liquid membrane after 180 min was 90 ± 3.0%. The selectivity and efficiency of silver ion transported from aqueous solutions containing equimolar mixtures of $Zn^{2+}, Cu^{2+}, Co^{2+}, Ni^{2+}, Cd^{2+}, Pb^{2+}, Bi^{3+}, Fe^{2+}, Fe^{3+}, Pd^{2+}, Mn^{2+}, Hg^{2+}, Sn^{2+}, Ca^{2+}, Mg^{2+}, K^+, Na^+ and Li^+$ were investigated.

• Journal of Welding and Joining
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• v.31 no.3
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• pp.22-30
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• 2013

Due to ELV banning, automotive electronics cannot use four kinds of heavy metal element (Pb, Hg, Cd, $Cr^{6+}$) from 2016. Therefore, this study was focused on degradation characteristics of Sn-3.0Ag-0.5Cu Lead-free solder joint with OSP and ENIG finsh under various reliability assessment method, as like to thermal shock test and high temeprature/high humidity test with test duration for cabin electronics. Also, we compared bonding strength degradation to other advanced research results of electronic control unit for engine room because of difference service temperature with mount location in automotive. Whisker growth phenomenon and mitigation method which were essentially consideration items for Pb-free car electronics were examined. Conformal coating is a strong candidate for mitigating whisker growth in automotive electronics. Necessary condition to adapt Pb-free in car electronics was shown.

• ETRI Journal
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• v.35 no.2
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• pp.340-343
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• 2013

A novel bumping process using solder bump maker is developed for the maskless low-volume solder on pad (SoP) technology of fine-pitch flip chip bonding. The process includes two main steps: one is the aggregation of powdered solder on the metal pads on a substrate via an increase in temperature, and the other is the reflow of the deposited powder to form a low-volume SoP. Since the surface tension that exists when the solder is below its melting point is the major driving force of the solder deposit, only a small quantity of powdered solder adjacent to the pads can join the aggregation process to obtain a uniform, low-volume SoP array on the substrate, regardless of the pad configurations. Through this process, an SoP array on an organic substrate with a pitch of $130{\mu}m$ is successfully formed.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1067-1072
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• 2002

A new polystyrene-divinylbenzene resin containing 2-(2-thiazolylazo)-5-dimethylamino-phenol (TAM) functional groups has been synthesized and its sorption behavior for nineteen metal ions, including Zr(Ⅳ),Hf(Ⅳ) and U(Ⅵ) has been investigated by batch and column methods. The chelating resin showed high sorption affinity for Zr(Ⅳ) at pH 1-5 and U(Ⅵ) at pH 4. Some parameters affecting the sorption of the metal ions have been detailed. The breakthrough and overall capacities were measured under optimized conditions. The overall capacities of Zr(Ⅳ), Th(Ⅳ) and U(Ⅵ), which showed higher than the other metal ions, were 0.90,0.84 and 0.80 mmol/g, respectively. The elution order of metal ions at pH 4 was evaluated as Zr(Ⅳ) > Th(Ⅳ) > U(Ⅵ) > Cu(Ⅱ) > Hf(Ⅳ) > W(Ⅵ) > Mo(Ⅵ) > In(Ⅲ) > Sn(Ⅳ) > Cr(Ⅲ) > V(Ⅴ) > Fe(Ⅲ). Quantitative recovery of most metal ions except Zr(Ⅳ) was achieved using 2M HNO3. Desorption and recovery of Zr(Ⅳ) was successfully performed with 2 M HClO4 and 2 M HCl.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.7-13
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• 2019

Power module is getting attention from electronic industries such as solar cell, battery and electric vehicles. Transient liquid phase (TLP) boding, sintering with Ag and Cu powders and wire bonding are applied to power module packaging. Sintering is a popular process but it has some disadvantages such as high cost, complex procedures and long bonding time. Meanwhile, TLP bonding has lower bonding temperature, cost effectiveness and less porosity. However, it also needs to improve ductility of the intermetallic compounds (IMCs) at the joint. Wire boding is also an important interconnection process between semiconductor chip and metal lead for direct bonded copper (DBC). In this study, TLP bonding using Sn-based solders and wire bonding process for power electronics packaging are described.

• YAKHAK HOEJI
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• v.45 no.5
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• pp.448-454
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• 2001

The contents of heavy metals in boiled Sibjeonaebotang with those in its herbal ingredients are compared. The herbal medicines of Sibjeonaebotang were bought at 10 defferent markets. The contents of 14 heavy metals (Ag, As, Ba, Cd, Cr Cu, Fe, Hg, Mn, Ni, Pb, Sb, Sn, Zn) were analysed using ICP It was found out that 5 heavy metals (Pb, As, Ba, Fe, Sb) were detected in only one boiled Sibjeonaebotang But they were detectable in all Sibjeonaebotang and its herbal before boiling. For example the content of Hg in one pack of Sibjeonaebotang before boiling was 0.064$\pm$0.016 me and Hg in boiled one was 0.002$\pm$0.005mg. These results suggest that boiled Sibjeonaebotang which we take is less harmful than herbal medicine itself by heavy metals.

• 보존과학연구
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• s.23
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• pp.149-162
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• 2002

Gilt bronze locks(Treasure No. 1141) excavated from Hancheonsa temple are artifacts of Goryeo Dynasty. The locks underwent a conservation process from October 2001 to July 2002. The process included cleaning and the application of corrosion inhibitors, Benzotriazolesolution, as well as reinforcement treatment with Paraloid NAD-10 solution,an acrylic resin. Non-destructive XRF analysis unveil that the artifacts are made of an alloy of copper(Cu), tin(Sn) and lead(Pb), but the gilt layer is too thin to analyze the purity of the gold or the exact production method. Gilt bronze locks are important materials because they preserve all the structures of locks in Goryeo Dynasty to the smallest detail. The surface pattern is revealed through the conservation process and components of the alloy through material analysis.

• KSBB Journal
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• v.14 no.1
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• pp.96-102
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• 1999

Marine bacterium Bacillus cereus ASK202 produced an extracellular agarase (E.C.3.2.1.81) which showed a high level of enzyme activity in the presence of agar and agarose. In the optimal culture conditions, the agarase production increased 7.7 folds compared with the one obtained from the basal medium. Agarase production reached upto 160 units/L after 24hr of cultivation in a modified marine medium at $25^{\circ}C$. The degree of purification increased 31.5 folds with 27.8% yield through freeze drying, DEAE Sepharose CL-6B and Superose 6HR 10/30 column chromatography. The molecular weight of the purified agarase was determined to be 90,000 daltons by gel-permeation filteration. Optimal temperature and pH for the enzyme activity were $40^{\circ}C$ and 7.8, respectively. The enzyme was stable up to $50^{\circ}C$ and at a broad pH range of 5.0-10.0. The $\beta$-agarase was activated by $Zn(NO_3)_2$, and was inhibited by $CuSO_4$ and $SnCl_2$. The Km and Vmax values of this enzyme for agarose as a substrate was $2.4mg/m\ell$ and 13.6 mg/m$\ell$, respectively.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.441-448
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• 2016

Heavy metal removal study is conducted from synthetic waste water by reduction and oxidation(redox) reaction of Cu-Zn metal alloy and adsorption reaction of aluminium silicate. Heavy metal whose ionization tendency is smaller than zinc are reducted in an aqueous solution, and the concentration of ionized zinc is reduced by adsorption reaction. The average diameter of metal alloy micro fiber is about $200{\mu}m$, and the surface area is wide enough to get equilibrium in a single cycle treatment. A single cycle treatment of redox reaction of Cu-Zn metal alloy, could remove 100.0 % of Cr(III), 98.0 % of Hg, 92.0 % of Sn and 91.4 % of Cu respectively. An ionization tendency of chromium is very close to zinc, but removal efficiency of chromium by redox reaction is significant. This result shows that trivalent chromium ion is expected to generate hydroxide precipitation with $OH^-$ ion generated by redox reaction. Zinc ion generated by redox reaction is readily removed by adsorption reaction of aluminium silicate in a single cycle treatment. Other heavy metal components which are not perfectly removed by redox reaction also showed very high removal efficiency of 98.0 % or more by adsorption reaction. Aluminium ion is not increased by adsorption reaction of aluminium silicate. That means heavy metal ion removal mechanism by adsorption reaction is turned out to be not an ion exchange reaction, but an adsorption reaction.

• Journal of Conservation Science
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• v.34 no.6
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• pp.493-502
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• 2018

Currently, the fabrication of a high-tin bronze spoon by traditional manufacturing techniques involves 10 steps in the bronze ware workshop. Hot forging has a major influence on manufacturing and involves two to three steps. The dendritic ${\alpha}$-phase in the microstructure of the high-tin bronze spoon is refined and finely dispersed through hot forging. In addition, twinning is observed in the ${\alpha}$-phase of the hammered part, and the ${\alpha}$-phase microstructure gradually transform from a polygon to a circular shape due to hammering. In this process, the adjacent ${\alpha}$-phases overlap with each other and remain combined after quenching. The microstructure with the overlapping is also observed in bronze artifacts, and this shows the correlation with technical system. The results of the experimental hot forging of Cu-22%Sn alloys show that the decrease in in the amount of the dendritic microstructure, which forms during casting, is in proportion to the number of processing steps and that the refined grain obtained by hammering contributes to the improvement in the strength of the material. From the hammering marks, which are observed on both the bronze artifact excavated from archaeological sites and on the high-tin bronze spoon produced in the traditional workshop, it is presumed that the knowledge regarding the unrecorded manufacturing system of bronze ware in ancient times has been passed down in a traditional way up to the system used currently.