• Journal of Welding and Joining
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• v.32 no.5
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• pp.80-86
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• 2014

We have successfully fabricated high strengthening Cu/STS/Cu 3 layered clad metal of $70kgf/mm^2$ grade for electric device lead frame, and investigated thermal effect of the mechanical and physical properties on the Cu/STS/Cu 3 layered clad metal lead frame material at different temperatures ranging from RT to $200^{\circ}C$. The fabricated clad metal shows a good thermal stability under 6% degrading of mechanical tensile strength and hardness change at $200^{\circ}C$ and also physical properties show stable thermal and electrical conductance of over $220W/m{\cdot}K$ and 58.44% IACS upto the $200^{\circ}$. The results confirm that fabricated high strengthening Cu/STS/Cu 3 layered clad metal can be applied for the high performed electrical lead frame devices.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.5
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• pp.383-390
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• 2008

The SCR in Static Transfer Switch (STS) is used for reliability improvement of important load's power supply in industry field. However an average of 2% fault in thyristor(SCR) occurs, so that the attached mechanical switch is paralleled with SCR's both end points and SCR operates only during the $12{\sim}208$[mS] before operation of the mechanical switch. Also, an ISC (Ideal State Conditioning Interlock Device) - STS system that two power supply paths may not be thrown at the same time is developed to remove the overlap section perfectly when a short or earth fault is generated in one system. This method has reduced the fault rate remarkably through the reduction of SCR's fatigue degree by using SCR in conversion operation corresponding to 0.89 times a year. Also, in case of fault generations, it does not affect to supply power to the load, therefore it contributes to the promotion of reliability in the power supply.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.155-156
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• 2015

Recently, electricity consumption has rapidly increased along with economic growth. The operating strategy using emergency generator is aimed, to resolve a demand response management. For strategy of peak shedding using emergency generator, it is essential to introduce the fast transfer switching device. One of the most effective solutions is to use a static transfer switch (STS) based on thyristor. However, the characteristic of natural commutated SCR thyristor should anticipate short duration voltage sag. STS system thus requires more than a quarter cycle to successfully complete transfer process. This paper proposes the operation scheme of the STS system using the forced-commutation technique to mitigate instantaneous voltage sag during peak transfer process. Proposed STS system improved turn-off characteristic thus accomplishes the peak load shedding satisfied power quality. Performance of the proposed STS system is evaluated using electromagnetic transient program (EMTP) to confirm the effectiveness.

• Journal of The Korean Association For Science Education
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• v.13 no.1
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• pp.66-79
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• 1993

The purposes of this study are to analyse trend of STS movement in Korea and to collect basic data on application of STS to school science education. It investigated, from 1990 to March 1993, journals of 6 associations, a monthly magazine of science education, and printed materials of seminars or workshops about science education. It also surveied a question to 47 science teachers and 26 researchers who had experienced STS workshop. The results of the study are as follows: (1) The studies of STS increased since 1990, but they are made at a introduction or background of STS. (2) The 98.7% of the respondents want to apply STS in school science education. (3) They responded that a device for the application of STS which is added last part of each chapter or last chapter, will use the STS program that made by subject, still maintain current science curriculum. (4) They responded that the knowledge & compreshion domain and inquiry process domain contain more high than others. 5) The STS subjects for application to the school science education are as follows; Environment pollution, science for living, ethics of science, human health and disease, information communication, an ecosystem destruction, development and storage of natural resources. This study suggested that establishment of a research institute for systematic research of STS, in-service training, a new evaluation process, a balancing of other subjects and increasing learning hour and changing objectives.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.281-288
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• 2021

Due to advancement of the industry, operation of a device in a harsh environment is increasing. Especially, the marine environment contains Cl^- ions which causes localized corrosion such as pitting and crevice corrosion of stainless steel and various metals. In this study, electrochemical corrosion behaviors of austenitic stainless steel (STS 316L) and nickel alloy (Inconel 600) with different seawater concentrations (fresh water, seawater, mixed water) were investigated. The STS 316L and Inconel 600 were etched in 10% oxalic acid and composed of an austenitic phase. Results of Tafel analysis in seawater showed that STS 316L and Inconel 600 presented the highest corrosion current densities of 7.75 × 10^-4 mA/cm² and 1.11 × 10^-4 mA/cm² and the most negative pitting potentials of 0.94 V and 1.06 V, respectively. The maximum damage depths and surface damage ratio by pitting corrosion increased with chloride concentration. The STS 316L had higher PREN than Inconel 600. However, the surface damage and weight loss of Inconel 600 were superior to STS 316L. It was difficult to compare the pitting resistance of STS 316L based on Fe and Inconel 600 based on Ni with PREN simply.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.77-81
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• 2013

We have investigated thermal stability of the mechanical and thermal conductive properties of Cu/STS/Cu 3 layered clad metal lead frame material for a LED device package at different temperatures ranging from RT to $200^{\circ}C$. The fabricated Cu/STS/Cu clad metal has a good thermal stability for the mechanical tensile strength and thermal conductivity of the over 50 $Kg/mm^2$ to the $150^{\circ}C$ and 270 $W/m{\cdot}K$ to the $200^{\circ}C$, respectively. This clad metal lead frame material at a high temperature of $150^{\circ}C$ shows a reinforced mechanical tensile strength by 1.5 times to conventional pure copper lead frame materials and also a comparable thermal conductivity to typical copper alloy lead frame materials.

• Applied Science and Convergence Technology
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• v.26 no.6
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• pp.208-213
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• 2017

Flexible opto-electronic devices are developed on the insulating layer deposited stainless steel (STS) substrates. The silicon dioxide ($SiO_2$) material as the diffusion barrier of Fe and Cr atoms in addition to the electrical insulation between the electronic device and STS is processed using the plasma enhanced chemical vapor deposition method. Noble silver (Ag) films of approximately 100 nm thickness have been formed on $SiO_2$ deposited STS substrates by E-beam evaporation technique. The films then were annealed at $650^{\circ}C$ for 20 min using the rapid thermal annealing (RTA) technique. It was investigated the variation of the surface morphology due to the interaction between Ag films and $SiO_2$ layers after the RTA treatment. The results showed the movement of Si atoms in silver film from $SiO_2$. In addition, the structural investigation of Ag annealed at $650^{\circ}C$ indicated that the Ag film has the material property of p-type semiconductor and the bandgap of approximately 1 eV. Also, the films annealed at $650^{\circ}C$ showed reflection with sinusoidal oscillations due to optical interference of multiple reflections originated from films and substrate surfaces. Such changes can be attributed to both formation of $SiO_2$ on Ag film surface and agglomeration of silver film between particles due to annealing.

• Journal of Welding and Joining
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• v.30 no.3
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• pp.32-37
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• 2012

Lead frame which has a high thermal conductivity and high mechanical strength is one of core technology for ultra-thin electronics such as LED lead frames, memory devices of semiconductors, smart phone, PDA, tablet PC, notebook PC etc. In this paper, we fabricated a Cu/STS/Cu 3-layered clad metal for lead frame packaging materials and characterized the mechanical properties and thermal conductive properties of the clad metal lead frame material. The clad metal lead frame material has a comparable thermal conductivity to typical copper alloy lead frame materials and has a reinforced mechanical tensile strength by 1.6 times to typical pure copper lead frame materials. The thermal conductivity and mechanical tensile strength of the Cu/STS/Cu clad metal are 284.35 W/m K and $52.78kg/mm^2$, respectively.

• Journal of the Korean Society of Safety
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• v.17 no.3
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• pp.30-35
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• 2002

The magnetic abrasive polishing is the useful method to finish using magnetic power of a magnet. It's not a long time this method was introduced to korea as one of precision finishing techniques. The magnetic abrasive polishing method is not so common for machine that it is not spreaded widely. The are rarely researcher in this field because of no-effectiveness of magnetic abrasive. The mechanism of this R&D is dealing with the dynamic state of magnet-abusive. This paper deals with mediocritizing magnetic polishing device into regular lathe and this experiment was conducted in order to get the best surface roughness at low cost. We need to continue the research on it. This paper contains the result of experiment to acquire the best surface roughness, not using the high-cost polishing material in processing. The average diameters of magnetic abrasive are the particles of 150$\mu\textrm{m}$, 250$\mu\textrm{m}$.

• Journal of Surface Science and Engineering
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• v.39 no.1
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• pp.35-42
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• 2006

In this study, the fatigue properties on the cavitation damage of the flame quenched 8.8Al-bronze (8.8Al-4.5Ni-4.5Fe-Cu) as well as the current nuclear pump impeller materials (8.8Al-bronze, STS316 and SR50A) has been investigated using an ultrasonic vibratory cavitation test. For this the impact loads of cavitation bubbles generated by ultrasonic vibratory device quantitatively evaluated and simultaneously the cavitation erosion experiments have been carried out. The fatigue analysis on the cavitation damage of the materials has been made from the determined impact load distribution (e.g. impact load, bubble count) and erosion parameters (e.g. incubation period, MDPR). According to Miner's law, the determined exponents b of the F-N relation ($F^b$ N = Constant) at the incubation stage (N: the number of fracture cycle) were 5.62, 4.16, 6.25 and 8.1 for the 8.8Al-bronze, flame quenched one, STS316 and SR50A alloys. respectively. At the steady state period, the exponents b of the F-N' curve (N': the number of cycle required for $1{\mu}m$ increment of MDP) were determined as 6.32, 5, 7.14 and 7.76 for the 8.8Al-bronze, flame quenched one, STS316, and SR50A alloys, respectively.