• Applied Science and Convergence Technology
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• 제24권4호
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• pp.77-83
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• 2015

Many welding processes are performed to construct cryogenic system. Leak-tight for the cryogenic system is required at low temperature environment. Helium leak detection techniques are commonly used to find leak for the cryogenic system. The helium leak detection techniques for spraying, sniffing and pressurizing techniques are introduced. High vacuum is also necessary to use helium leak detector. So, types of fluid flow, effective temperature, conductance and pumping speed are introduced for vacuum pumping. Leak test procedure is shown for pipe welding, cryomodule and low temperature test. Cryogenic seals which include copper gasket, helicoflex gasket and indium are investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2094-2096
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• 2005

In this paper, we studied the cross section analysis based on the short circuit conditions of the low voltage bare wires. The copper wires prepared for the experiment were 1.2mm 1.6mm and 2.0mm in diameter. Through the cross section analysis(CSA), it was confirmed that the dendrite structure grew at the angle of about $40^{\circ}$ or $60^{\circ}$ when the fusing current was applied to the wires. The larger the fusing current is, the more decreased the growth angle of the dendrite structure is. It was confirmed that the dendrite structure was arranged like the columnar structure. In this paper, the characteristics analysis of short circuit was carried out in the range of transient duration.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권3호
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• pp.319-325
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• 2017

Through silicon via (TSV) technology is extensively used in 3D IC integrations. The special structure of the TSV is realized by CMP (Chemically Mechanical Polishing) process with a high Cu removal rate and, low dishing, yielding fine topography without defects. In this study, we investigated the electrochemical behavior of copper slurries with various inhibitors in the Cu CMP process for advanced TSV applications. One of the slurries was carried out for the most promising process with a high removal rate (${\sim}18000{\AA}/Min$ @ 3 psi) and low dishing (${\sim}800{\AA}$), providing good microstructure. The effects of pH value and $H_2O_2$ concentration on the slurry corrosion potential and Cu static etching rate (SER) were also examined. The slurry formula with a pH of 6 and 2% $H_2O_2$, hadthe lowest SER (${\sim}75{\AA}/Min$) and was the best for TSV CMP. A novel Cu TSV CMP process was developed with two CMPs and an additional annealing step after some of the bulk Cu had been removed, effectively improving the condition of the TSV Cu surface and preventing the formation of crack defects by variations in wafer stress during TSV process integration.

• 대한기계학회논문집A
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• 제36권12호
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• pp.1529-1534
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• 2012

본 연구에서는 DIC 법을 이용하여 두께 $12{\mu}m$ 의 구리박막에 대한 인장시험을 수행하였다. 시험결과 정밀한 응력-변형률 곡선의 시험결과를 얻을 수 있었으며, 특히 잉크젯프린터를 이용한 시험편 표면 스펙클패턴의 작성은 DIC 법을 적용하기가 어려운 시험편 표면의 콘트라스트가 낮은 경우에 유용하게 사용할 수 있을 것이다. 측정된 구리박막의 기계적 물성은 탄성계수 E = 89.2 GPa, 0.2% 오프셋 항복응력 $S_{0.2%}$= 232.8 MPa, 인장강도 $S_u$= 319.2 MPa, 파단연신률 ${\varepsilon}_f$= 16.8 %, Poisson 비 ${\nu}$= 0.34 의 결과를 얻었으며, 탄성계수는 알려진 벌크소재에 대한 결과보다는 작다.

• 전기화학회지
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• 제3권3호
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• pp.152-156
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• 2000

그물구조 다공성 금속을 황산과 황산구리 수용액을 전해질로 사용하여 전기화학적으로 제조하였으며, 이때 균질 전착에 영향을 미치는 구리이온 농도에 대해 살펴보았다. 전해질 중의 황산에 대한 구리이온의 농도비가 감소하면 전해질의 점성이 감소하여 전기전도도의 향상을 가지고 오며, 분극도(polarizability)의 상승을 유발시켜 균일 전류밀도 분포력(throwing power)을 향상시키는 효과를 나타내었다. 그물구조 다공성 금속을 제조하기 위한 최적의 조건은 한계 전류밀도와 균일 전류밀도 분포력을 고려하여 결정되어야 하며, 인가전류가 $10mA/cm^2$일 때 0.2M $CuSO_4\cdot\;5H_2O+0.5\;H_2SO_4$임을 확인하였다.

• Journal of Welding and Joining
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• 제32권6호
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• pp.56-63
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• 2014

To develop and understand dissimilar metals joining of Stainless steel and Copper, ultra-high speed laser lap welding was studied using single mode fiber laser in this study. SUS304 and Cu have large differences in materials properties, and Cu and Fe have no intermetallic compounds by typical binary phase of Cu and Fe system. In this study, ultra-high speed lap welds of SUS304 and Cu dissimilar metals using single-mode fiber laser was generated, and weldability of the weld fusion zone was evaluated using a tensile shear test. To understand the phenomenon of tensile shear load, weld fusion zone of interface weld area and fracture parts after tensile shear test were observed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis system. And it was confirmed that Cu was easily melting and penetrating in the grain boundaries of SUS304 because of low melting temperature. And high thermal conductivity of copper occurred dissipate heat energy rapidly. These properties cause the solidification cracking in weld zone.

• Geomechanics and Engineering
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• 제11권2호
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• pp.197-209
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• 2016

Clayey rock has large clay mineral content. When in contact with water, this expands considerably and may present a significant hazard to the stability of the rock in geotechnical engineering applications. This is particularly important in the present work, which focused on mitigating some unwelcomed properties of clayey rock. Changes in its physical properties were simulated by subjecting the rock to a low voltage direct current (DC) using copper, steel and aluminum electrodes. The modified mechanism of the coupled electrical and chemical fields acting on the clayey rock was analyzed. It was concluded that the essence of clayey rock electrochemical modification is the electrokinetic effect of the DC field, together with the coupled hydraulic and electrical potential gradients in fine-grained clayey rock, including ion migration, electrophoresis and electro-osmosis. The aluminum cathodes were corroded and generated gibbsite at the anode; the steel and copper cathodes showed no obvious change. The electrical resistivity and uniaxial compressive strength (UCS) of the modified specimens from the anode, intermediate and cathode zones tended to decrease. Samples taken from these zones showed a positive correlation between electric resistivity and UCS.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권3호
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• pp.58-64
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• 2013

This study proposed a low temperature hydrothermal carbonization to treat and recycle sewage sludge and determined the optimal conditions for the biochar production. The physical and chemical properties of biochar were analyzed and its sorption capacity for heavy metals was evaluated. To produce biochar, 50 g of sewage sludge was heated at 220, 230, and $240^{\circ}C$ for 1, 2, 3, 5, 8, and 10 hours in a reactor. The optimal conditions to produce biochar was $230^{\circ}C$ and 8 hours. Sorption capacity tests were conducted for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn) and nickel (Ni). Among them, lead was shown the highest heavy metal adsorption efficiency of biochar, followed by copper, cadmium, zinc, and nickel, but arsenic was hardly adsorbed overall.

• Journal of Biosystems Engineering
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• 제28권3호
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• pp.209-216
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• 2003

Red pepper calyx cutting devices using a impacting force by a rotational cutter were devised and tested to obtain the fundamental data for development of a calyx removal unit. Fresh red peppers with 80∼87%(w.b.) of initial moisture contents were used as experimental materials. Square and wire type of rotational cutters were used to cut the red pepper calyx and the fresh red peppers were fed into the device both manually and automatically. Three rotational speeds of 250, 500, 700rpm were selected for a square, and 1000, 1500, 1800rpm for a wire type cutter respectively. Four types of red pepper fixing unit were used in manual feeding. The cutting rate of the square type cutter was over 50% regardless the shape and specification of the cutter. For the wire type cutter, the copper wire and nylon chord could not be applied to cut the red pepper calyx because of the low cutting rate. But for the fine wire, the cutting rate was higher and the cutting mechanism was more steady than copper wire and nylon chord. The cutting rate of automatic feeding and wire type cutting unit was about 70% for all levels of the rotational speed. The cutting rate was highly related to the impacting point of red pepper in carrier box. To increase the cutting rate using the rotational cutter, a proper device and mechanism was required to keep the impacting point consistently.

• 한국주조공학회지
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• 제38권3호
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• pp.55-59
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• 2018

To optimize the conductivity and to reduce the weight by as much as possible, Al-Cu composites were prepared through a suction-casting procedure. Pure copper metal foam was infiltrated by melted aluminum with the use of the vacuum, after which warm rolling was conducted to remove several remaining pores at the interface between the Cu foam and the aluminum matrix. Despite the short casting time, significant dissolution of Cu into the melt was observed. Moreover, it was found that various Al-Cu intermetallic compounds arose at the interface during the isothermal heating process after the casting and rolling steps. The average thickness of the Al-Cu intermetallic compound tended to increase in proportion to the heating time. The electrical and thermal conductivity levels of the cast composites were found to be comparatively low, mainly due to the dissolution of the Cu foam and the formation of intermetallics at the interface.