• Journal of Powder Materials
• /
• v.24 no.5
• /
• pp.395-399
• /
• 2017

Solder paste is widely used as a conductive adhesive in the electronics industry. In this paper, nano and microsized mixed lead-free solder powder (Sn-Ag-Cu) is used to manufacture solder paste. The purpose of this paper is to improve the storage stability using different types of solvents that are used in fabricating the solder paste. If a solvent of sole acetate is used, the nano sized solder powder and organic acid react and form a Sn-Ag-Cu malonate. These formed malonates create fatty acid soaps. The fatty acid soaps absorb the solvents and while the viscosity of the solder paste rises, the storage stability and reliability decrease. When ethylene glycol, a dihydric alcohol, is used the fatty acid soaps and ethylene glycol react, preventing the further creation of the fatty acid soaps. The prevention of gelation results in an improvement in the solder paste storage ability.

• Economic and Environmental Geology
• /
• v.37 no.2
• /
• pp.173-184
• /
• 2004

The geochemical exploration was carried out of the soil systems in the survey areas(Mt. Subang area). The chemical values of soil samples for soil in this area are defined such as over values of Ag : 11 ppm(Average ： 1.91 ppm), Au 548 ppb(Average 42.39 ppb), Cu : 89 ppm(Average：51.40 ppm), Pb：190 ppm(Average ： 23.69 ppm), Zn : 157 ppm(Average : 61.78 ppm), respectively. Anomalous areas for each element have been chosen based on the factors such as, geologic settings, geochemical survey, chemical analysis of ore, chemical analysis of soil. statistical processing of the chemical analysis. Therefore, multi-elements anomalies area were recognized in the east-center part of the study area.

• Journal of Korea Foundry Society
• /
• v.23 no.5
• /
• pp.244-250
• /
• 2003

The aim of this study is fabricating of composite filler metal (CFM) by a combination of selective laser sintering (SLS) of stainless steel powders (RapidSteel $2.0^{TM}$ and liquid phase infiltration of Ag-28 wt.%Cu alloy. Porous stainless steel body with inter-connected pore channels was fabricated by SLS, binder decomposing and densification processes. By the direct contact infiltration, the narrow inter-particle channels of the porous body were completely filled with the Ag-28 wt.%Cu alloy infiltrant. During infiltration, the dissolved elements of Fe, Ni and Cr from the porous body were solved into copper solid solution phases, which consist of eutectic structure of composite metal matrix. The S10C/CFM/S10C joints, which have narrow clearance gaps between them up to 10 micrometers, were joined successfully by self-feeding of filler metal from the matrix of CFM. The CFM kept its original thickness and microstructure after brazing. The tensile strength of brazed specimen was higher than 30 kgf/$mm^2$ and showed a typical ductile fracture mode in the CFM.

• Journal of the Korean Chemical Society
• /
• v.15 no.2
• /
• pp.49-54
• /
• 1971

It is shown that the impurities of Cu(II), Pb(II), Zn(II) and Ag(I) in Bismuth metal and the components of Pb(II), Zn(II) and Sn(IV) in Bismuth alloy are separated into their components from each other by elutions through $3.14cm^2{\times}10cm$ cation exchange resin, $Dowex\;50w\;{\times}\;8$ (100~200 mesh), column with the mixed solutions of HAc and NaAc as the eluents. The elution curve of Fe(III) has a long tailing and is not separated quantitatively from Bi(III). The eluents used for this separation are as follows; 1M HAc + 0.1M NaAc (pH 3.36) for Fe(III) and Bi (III). 0.3M HAc + 0.3M NaAc (pH 4.70) for Cu(II), Pb(II) and Zn(II). 0.5M HAc + 0.5M NaAc (pH4.70) for Ag(I) and Sn(IV). The analysis of cations eluted are carried out by spectrophotometry and EDTA titrimetry. Their recoveries are more than 99%.

• Corrosion Science and Technology
• /
• v.4 no.1
• /
• pp.19-22
• /
• 2005

Two Au-Ag-Cu-Pd dental casting alloys (Au:12% and 20%) used. The test solutions used 0.9 % NaCl solution (isotonic sodium chloride solution), 0.9 % NaCl solution containing 1 % lactic acid, and 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_2S$. The surface of two samples in three sample solutions was not natural discoloration during one year. The alloy containing 12 % gold was easily alloyed and the composition was uniform comparing with the alloy containing 20 % gold. The rest potentials have not a little effect after three months. The kinds of metals could not definitely from the oxidation and reduction waves of metal on the cyclic voltammograms. The dissolutions of gold and palladium were 12 % Au sample in the 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_{2}S$. The pH of solution had an affect on dissolution of copper, and sulfur ion had an affect on dissolution of silver. The copper dissolved amount from 20 % gold sample was about 26 times comparing with that of 12 % gold sample in the 0.9 % solution containing 1 % lactic acid. Corrosion products were silver chloride and copper chloride in NaCl solution, and silver sulfide and copper sulfide in NaCl solution containing $Na_{2}S$.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.19 no.6
• /
• pp.577-582
• /
• 1990

Production and properties of invertase from Aspergillus niger were investigated. Inulin and sucrose were best carbon source and yeast extract was most suitable for the production of the enzyme among tested carbon and nitrogen sources. The enzyme among tested carbon and nitrogen sources. The enzyme was maximally produced by cultivating the organism at medium of pH 4.5 and temperature of 3$0^{\circ}C$ The optimum pH and temperature for the enzyme activity were pH 5.0 and temperature of 5$0^{\circ}C$, respectively. Among tested metal ions. Hg++, Cu++ and Ag+ ions Inhibited the enzyme activity drastically.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2002.11a
• /
• pp.105-108
• /
• 2002

환경에 관한 관심이 증대되면서 Sn37Pb 솔더를 대체하기 위한 새로운 무연솔더의 개발이 진행되고 있다1). 또한 연구의 초점이 되고 있는 것이 플럭스의 사용에 관한 것이다. 플럭스는 솔더의 산화막을 제거하는데 필수적이지만, 플럭스 세정제의 독성 문제로 무플럭스 솔더링에 대한 관심이 크게 증대되고 있다2),3). 무플럭스 솔더링의 방법에는 여러 가지가 있으며, 그 중 한가지가 플라즈마를 이용한 방법이다4). 본 연구에서는 솔더표면의 이물질과 산화막을 제거하기 위한 플라즈마 처리가 접합 후, 접합부에 미치는 영향에 대해서 알아보았다. 기판은 Evaporator를 이용하여 Au/Cu/Ni/Al UBM을 증착한 Si-wafer를 사용하였다. 사용된 솔더는 Sn37Pb, Sn3.5Ag와 Sn3.5Ag0.7Cu 솔더볼이며, 열중 및 적외선 겸용 리플로 머신과 Ar＋H$_2$를 이용한 플라즈마 에쳐를 사용하여 범프를 형성하였다. 플라즈마 처리가 계면의 미세조직과 기계적 강도에 끼치는 영향을 알아보기 위하여 플라즈마 처리된 시편과 리플로 한 후의 시편을 비교 분석하였다. 전단시험기로 계면의 강도를 측정하였으며, 주사전자현미경으로 범프의 표면과 계면 및 전단파면을 관찰하고 이에 대하여 고찰하였다. 산화막제거를 위한 플라즈마 처리가 저음점인 솔더의 미세조직을 기존의 솔더링 접합부와는 다르게 변화시킴으로써 솔더부의 전체적인 특성에 영향을 끼치는 것을 알 수 있었다.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.12
• /
• pp.3723-3729
• /
• 2010

We investigated the high-excitation voltage cathodoluminescence (CL) performance of blue light-emitting (ZnS:Ag,Al,Cl) and green light-emitting (ZnS:Cu,Al) phosphors coated with metal oxides ($SiO_2$, $Al_2O_3$, and MgO). Hydrolysis of the metal oxide precursors tetraethoxysilane, aluminum isopropoxide, and magnesium nitrate, with subsequent heat annealing at $400^{\circ}C$, produced $SiO_2$ nanoparticles, an $Al_2O_3$ thin film, and MgO scale-type film, respectively, on the surface of the phosphors. Effects of the phosphor surface coatings on CL intensities and aging behavior of the phosphors were assessed using an accelerating voltage of 12 kV. The MgO thick film coverage exhibited less reduction in initial CL intensity and was most effective in improving aging degradation. Phosphors treated with a low concentration of magnesium nitrate maintained their initial CL intensities without aging degradation for 2000 s. In contrast, the $SiO_2$ and the $Al_2O_3$ coverages were ineffective in improving aging degradation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1995.05a
• /
• pp.85-92
• /
• 1995

HTPB/AP/Al이 기본 조성인 ADP 302 혼합형 추진제를 대상으로 4종의 금속선(Ag, Cu, Al, Ni-Cr)을 삽입하여 금속선 직경(0.1mm~0.8mm)별로 압력에 따른 금속선과 인접한 추진제의 연소 속도($r_w)를 측정하여 금속선 삽입 추진제의 연소 속도 증가비($r_w$/$r_sb$)와 압력 지수( n )의 변화를 고찰한 결과 금속선 종류에 따른 연소 속도 증가비($r_w$/$r_sb$)는 Ag> Cu>Al>Ni-Cr선을 삽입한 추진제의 순으로 나타났고 금속선의 열확 산 계수의 크기순과 일치하였다. Buckingham $\pi$ 이론을 적용한 무차원 해석으로부터 실험식을 구하여, 이 실험식에 의해 계산된 ($r_w)와 실험으로부터 얻어진 ($r_w)를 서로 비교하여 본 결과 잘 부합됨을 알 수 있었다. 또한 금속선 수에 따른 추진제 그레인의 연소 면적을 해석적으로 계산하여,($r_w$/$r_sb$)가 2, 3, 4, 5 배로 증가함에 따른 시간에 따른 연소 면적 증가비의 변화를 금속선 수에 따라서 비교하여 본 결과 정상 상태에서의 그레인의 연소 면적의 증가비($A_b$/$A_0$)는 금속선에 인접한 추진제의 연소 속도 증가비($r_w$/$r_sb$)와 일치했으며, 정상 상태의 연소 면적 증가비는 삽입된 금속선의 수와는 무관하며 정상 상태에 도달하는 시간에만 영향을 주는 것으로 나타났다.

• Journal of Korean Society for Atmospheric Environment
• /
• v.27 no.4
• /
• pp.379-386
• /
• 2011

Catalyst-assisted plasma system with a DBD (Dielectric Barrier Discharge) reactor was used to remove hydrogen sulfide, which is one of the odorous species in this study. The ${\gamma}-Al_2O_3$ and ${\beta}$-Zeolite catalysts impregnated by Ag, Cu and Mn species were employed as catalysts and their $H_2S$ removal characteristics under plasma irradiation were investigated. From the experimental study, we found that the $H_2S$ removal efficiency increases with decreasing space velocity in the system and increasing specific input energy. Furthermore, ${\beta}$-Zeolite catalysts are efficient to remove $H_2S$ than ${\gamma}-Al_2O_3$ catalysts. Especially, the catalysts impregnated by Ag have higher removal efficiency than other catalysts (Cu, Mn).