• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.40-45
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• 2022

The electrical/thermal stabilities and magnetic field controllability of a no-insulation (NI) high-temperature superconducting magnet are characterized by contact resistance between turn-to-turn layers, and the contact resistance characteristics are determined by properties of conductor surface and winding tension. In order to accurately predict the electromagnetic characteristics of the NI coil in a design stage, it is necessary to control the contact resistance characteristics within the design target parameters. In this paper, the contact resistance and critical current characteristics of a rare-earth barium copper oxide (REBCO) conductor were measured to analyze the effects of surface treatment conditions (roughness and oxidation level) of the copper stabilizer layer in REBCO conductor. The test samples with different surface roughness and oxidation levels were fabricated and conductor surface analysis was performed using scanning electron microscope, alpha step surface profiler and energy dispersive X-ray spectroscopy. Moreover, the contact resistance and critical current characteristics of the samples were measured using the four-terminal method in a liquid nitrogen impregnated cooling environment. Compared with as-received REBCO conductor sample, the contact resistance values of the REBCO conductors, which were post-treated by the scratch and oxidation of the surface of the copper stabilizer layer, tended to increase, and the critical current values were decreased under certain roughness and oxidation conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.25-26
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• 2008

Electrical properties of Pt/Ti/Au/Pt contacts to n-GaAs were characterized as the V/III ratio of GaAs grown by metalorganic chemical vapor deposition were 25, 50, and 100, respectively. The samples have been annealed during 30sec at 350 and $450^{\circ}C$ in rapid thermal annealing, and those specific contact resistance investigated by using transmission line method. According to experimental results, the specific contact resistance between p-metal and GaAs was decreased as the V/III ratio was lower. These results indicate that Si doping concentration of GaAs increased as the vacancy of V-series of GaAs was high.

• Journal of the Korean institute of surface engineering
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• v.23 no.3
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• pp.173-182
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• 1990

In order to prevent the thermal and enviromenatal degradation of contact materials a nickel layer was plated as an undercoat of gold plating on the surface phosphorous bronze. The thickness of nikel and gold coating and chemical resistance of the coatings were measured at various conditions. Variation of morphology and chemical composition was studied by SEM, EDS and ESCA, respectively. Nickel layer was found to act as a thermal diffusion barrier and to retard the diffusion of copper from substrate to gold coating in the temperature $200^{\circ}C$~$400^{\circ}C$. below $200^{\circ}C$gold coated contacts showed a stable and low contanct resistance, while above $200^{\circ}C$ rapid diffusion of copper formed copper oxide on the surface layer and raised the contact resistance. With the nickel thinkness of abount 5$\mu$m as an undercoat the gold thinkness of $0.5\mu$m, showed satistactory (less than 1 m$\Omega$) contact resistance below 20$0^{\circ}C$ and corresponding gold thinkness increased to 1.0 m at $300^{\circ}C$~$400^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.27 no.1
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• pp.40-46
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• 2018

In this paper, we focus on optimization of a boron ($^{11}B$)-implanted n type Si epi substrate for obtaining near-zero temperature coefficient of resistance (TCR) at temperature range from 25 to $125^{\circ}C$. The $^{11}B$-implantation on the N type-Si epi substrate formed isolation from the rest of the N-type Si by the depletion region of a PN junction. The TCR increased as the temperature of rapid thermal anneal (RTA) was increased at the temperature range from $900^{\circ}C$ to $1000^{\circ}C$ for the $p^+$ contact with implantation at dose of $1E16/cm^2$, but sheet resistance of this film was decreased. After the optimization of anneal process condition, the TCR of $1126.7{\pm}30.3$ (ppm/K) was obtained for the $p^-$ resistor-COB package chips contained $p^+$ contact with the implantation of $5E14/cm^2$. This shows the potential of the $^{11}B$-implanted n type Si epi substrate as a resistor for pressure sensor in thermal stable environment applications..

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1959-1963
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• 2007

SMES systems need cryogenic cooling systems. Conduction cooling system has more effective, compact structure than cryogen. In general, 2 stage GM cryocoolers are used for conduction cooling of HTS SMES system. 1st stages of cryocoolers are used for the cooling of current leads and radiation shields, and 2nd stages of cryocoolers for HTS coil. For the effective conduction cooling of the HTS SMES system, the temperature difference between the cryocooler and HTS coil should be minimized. In this paper, a cryogenic conduction cooling system for HTS SMES is analyzed to evaluate the performance of the cooling system. The analysis is carried out for the steady state with the heat generation of the HTS coil and effects of the thermal contact resistance. The results show the effects of the heat generation and thermal contact resistance on the temperature distribution.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.1-9
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• 1994

The transient temperature distribution of materials during upsetting forming is very important for quality of upsetted workpiece and understanding the thermal characteristics of upsetting is essential for optimum control of the forming. In this paper it is shown that the governing equation of heat transfer for axi-symetric body can be derived from minimizing a functional, and from this theory, formulation of analysis by the finite element method is presented. It is also shown that the thermal contact resistance between two bodies can be represented by equivalent coefficient of heat conductivity. Some examples of calsulated transient temperature distributions by the computer program diveloped from the theory presented in this paper are given in graphic forms. It is proven that the results calculations are very plausible.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.5-6
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• 2009

In this paper, plasma ion implant is performed with $PH_3$ gas diluted by helium gas on P-type Si wafer (100). Spike Rapid Thermal Processing(RTP) annealing performed for 30~60 sec from $800\;^{\circ}C$ to $1000\;^{\circ}C$ in $N_2+O_2$ ambient. Crystalline defect is analyzed by Transmission Electron Microscope(TEM) and Double crystal X-ray Diffraction(DXRD). Contact resistivity($\rho c$), contact resistance(Rc) and sheet resistance(Rs) are analyzed by measuring Transfer Length Method(TLM) using 4155C analysis. As annealing temperature increase, Rs decrease and ${\rho}c$ and Rc increase at temperature higher than $850\;^{\circ}C$. We achieve low Rs, ${\rho}c$ and Rc with Plasma ion implant and spike RTP.

• Journal of Ceramic Processing Research
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• v.20 no.5
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• pp.499-504
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• 2019

The effect of coating thickness on the contact fatigue and wear of thermal barrier coatings (TBCs) are investigated in this study. The same bondcoat material thickness (250 ㎛) are used for each sample, which allows the effect of the coating thickness of the topcoat to be investigated. TBCs with different coating thicknesses (200, 400, and 600 ㎛) are prepared by changing processing parameters such as the feeding rate of the feedstock, spraying speed, and spraying distance during APS(air plasma spray) coating. The damage size on the surface are strongly affected by the coating thickness effect. Although the damage size from contact fatigue using a spherical indenter diminish at a TBC of 200 ㎛, a high wear resistance such as a low friction coefficient and little mass change are found at a TBC of 600 ㎛. These results indicate that the coating thickness strongly affects the mechanical behavior in TBCs during gas turbine operation.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.27-32
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• 2010

For the flip chip joints processed using Cu pillar bumps and Sn pads, thermal cycling and high temperature storage reliabilities were examined as a function of the Sn pad height. With increasing the height of the Sn pad, which composed of the flip chip joint, from 5 ${\mu}m$ to 30 ${\mu}m$, the contact resistance of the flip chip joint decreased from 31.7 $m{\Omega}$ to 13.8 $m{\Omega}$. Even after thermal cycles of 1000 times ranging from $-45^{\circ}C$ to $125^{\circ}C$, the Cu pillar flip chip joints exhibited the contact resistance increment below 12% and the shear failure forces similar to those before the thermal cycling test. The contact resistance increment of the Cu pillar flip chip joints was maintained below 20% after 1000 hours storage at $125^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.90.2-90.2
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• 2010

The coated metallic bipolar plates are getting attractive due to their good feasibility of mass production, low contact resistance, high electrical/thermal conductivity, low gas permeability and good mechanical strength comparing with graphite materials. Yet, metallic bipolar plates for polymer electrolyte membrane(PEM) fuel cells typically require coatings for corrosion protection. Other requirements for the corrosion protective coatings include low electrical contact resistance between metallic bipolar plate and gas diffusion layer, good mechanical robustness, low mechanical and fabrication cost. The authors have evaluated a number of protective coatings deposited on stainless steel substrate by electroplating. The coated metallic bipolar plates are investigated with an electrochemical polarization tests, salt dipping tests, adhesion tests for corrosion resistance and then the contact resistance was measured. The results showed that the selective samples electroplated with optimized method, satisfied the DOE target for corrosion resistance and contact resistance, and also were very stabilized in the typical fuel cell environments in the long-term.