• Journal of Welding and Joining
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• v.29 no.5
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• pp.95-98
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• 2011

Recently, there is a growing tendency that fine-pitch electronic devices are increased due to higher density and very large scale integration. Finer pitch printed circuit board(PCB) is to be decrease insulation resistance between circuit patterns and electrical components, which will induce to electrical short in electronic circuit by electrochemical migration when it exposes to long term in high temperature and high humidity. In this research, the effect of soldering flux acting as an electrical carrier between conductors on electrochemical migration was investigated. The PCB pad was coated with OSP finish. Sn3.0Ag0.5Cu solder paste was printed on the PCB circuit and then the coupon was treated by reflow process. Thereby, specimen for ion migration test was fabricated. Electrochemical migration test was conducted under the condition of DC 48 V, $85^{\circ}C$, and 85 % relative humidity. Their life time could be increased about 22% by means of removal of flux. The fundamentals and mechanism of electrochemical migration was discussed depending on the existence of flux residues after reflow process.

• Computers and Concrete
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• v.11 no.4
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• pp.305-316
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• 2013

This paper aims to study the effect of measurement methods and cracking on chloride transport of concrete materials. Three kinds of measurement methods were carried out, including immersion test, rapid migration test and steady-state migration test. All of these measurements of chloride transport show that chloride ion diffusion coefficient decreased with the reduction of water to cement ratio. Results of the immersion test were less than that of rapid migration test and steady-state migration test. For the specimen of lower water to cement ratio, the external electrical field has little effect on chloride binding relatively. Compared with the results obtained by these different measurement methods, the lower water to cement ratio may cause smaller differences among these different methods. The external voltage can reduce chloride binding of concrete, and the higher electrical field made a strong impact on the chloride binding. Considering the effect of high voltage on the specimen, results indicate that results based on the steady-state migration test should be more reasonable. For cracked concrete, cracking can accelerate the chloride ion diffusion.

• Journal of the Korean Electrochemical Society
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• v.21 no.2
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• pp.21-27
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• 2018

In this review, recent researches on ion transport phenomena in organic metal halide perovskite materials, which have been popular all over the world, are summarized. Although different results have been reported depending on the perovskite material composition and applied voltage, iodide seems to migrate under actual solar cell operating conditions, and occasionally methylammonium migration is observed. Perovskite is a so-called mixed conductor in which electrons and ions move simultaneously at room temperature, which greatly influences the hysteresis of the perovskite solar cell current-voltage curve and the performance degradation due to long-term operation.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.165-168
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• 2005

This paper investigated the effect of W/C and the kinds of cement on the chloride invasion resistance of the offshore concrete. W/C set up 0.30, 0.35, 0.40 and The kinds of cement were used four(ordinary portland cement, ground granulated blast-furnace slag cement, belite cement, low heat portland cement). For the electrical migration test, NT BUILD 492's method was used to estimate the migration coefficient of chloride ion. As a result, the migration coefficients of chloride ion of concrete according to w/c were shown reducing with the w/c increasing, and according to kinds of cement were shown discrepancy in chloride invasion resistance. Especially blast-furnace slag cement was most low it. In the each cement, the compressive strength was shown related to the migration coefficient.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.6
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• pp.1-7
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• 1993

After the 1%S-Al metal is deposited, a thin oxide is formed thereon. Then, a single charged Argon(Ar$^{+}$) is ion implanted into the oxide layer, thereby causing the metal grain in the upper surface of the metal layer to become amorphous. Consequently, the grain size will be reduced and the rough surface of the metal layer flattened. However, the remainder of the metal layer beneath the upper surface thereof will still exhibit large grain size and low resistance, because the Argon ion is only implanted to characterized by a dual-sized grain structure which served to reduce interlayer stress, thereby decreasing the rate of stress migration, and to lower the resistivity of the metal line, thereby enhancing the electromigration characteristic thereof. Experiments have shown that the metal line exhibits a metal migration rate which is approximately 700% less than the control group and a standard deviation which is approximately 200% less than these group.p.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.331-337
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• 2015

$LaBO_3$ (B = Cr, Mn, Fe, Co, and Ni) perovskites, the most common perovskite-type mixed ionic-electronic conductors (MIECs), are promising candidates for intermediate-temperature solid oxide fuel cell (IT-SOFC) cathodes. The catalytic activity on MIEC-based cathodes is closely related to the bulk ionic conductivity. Doping B-site cations with other metals may be one way to enhance the ionic conductivity, which would also be sensitively influenced by the chemical composition of the dopants. Here, using density functional theory (DFT) calculations, we quantitatively assess the activation energies of bulk oxide ion diffusion in $LaBO_3$ perovskites with a wide range of combinations of B-site cations by calculating the oxygen vacancy formation and migration energies. Our results show that bulk oxide ion diffusion dominantly depends on oxygen vacancy formation energy rather than on the migration energy. As a result, we suggest that the late transition metal-based perovskites have relatively low oxygen vacancy formation energies, and thereby exhibit low activation energy barriers. Our results will provide useful insight into the design of new cathode materials with better performance.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.224-227
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• 2001

In general, municipal solid waste incinerator fly ash (MSWIF) has a potential hazardous leaching of heavy metal with subsurface environment variation. Therefore, to remove the heavy metal from MSWIF electrokinetic technology were used. With constant current density condition heavy metals in MSWIF removed by ion migration. During 7 days operation 40~80% of Cr, Cd and As were removed and longer operation, 14 days treatment, showed 35~100% removal efficiency.

• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.787-792
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• 2010

It is necessary to predict the penetration of chloride ions for designing RC construction in marine environments. However, it takes a long time to obtain chloride migration coefficients. Therefore, the rapid chloride penetration test (RCPT) is generally used to shorten the test time. But there is a difference between chloride migration coefficients determined by rapid chloride penetration tests and those based on exposure in marine environments. In this study, we evaluated the effect on the chloride ion migration coefficient caused by a change in voltage and NaCl concentration. We also compared the relationship between the chloride ion migration coefficient by RCPT and that by exposure in marine environments. As a result of the experiments, we found that there is only a small change in the experimental factors based on changes in voltage and NaCl concentration and since they are so small, we can conclude that they are in the range of experimental error and test results from chloride ion migration coefficients by RCPT and exposure were very different from each other. In the exposure experiments, when the water-cement ratio was increased, the smaller fine air gaps in concrete affected the chloride ion migration coefficient.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1385-1397
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• 2024

Bentonite is a recommended material for the multiple barriers in the final disposal of low-level radioactive waste (LLW) to prevent groundwater intrusion and nuclear species migration. However, after drying-wetting cycling during the repository construction stage and ion exchange with the concrete barrier in the long-term repository, the bentonite mechanical behaviors, including swelling capacity and hydraulic conductivity, would be further influenced by the groundwater intrusion, resulting in radioactive leakage. To comprehensively examine the factors on the mechanical characteristics of bentonite, this study presented scenarios involving MX-80 and KV-1 bentonites subjected to drying-wetting cycling and accelerated ion migration. The experiments subsequently measured free swelling, swelling pressure, and hydraulic conductivity of bentonites with intrusions of seawater, high pH, and low pH solutions. The results indicated that the solutions caused a reduction in swelling volume and pressure, and an increase in hydraulic conductivity. Specifically, the swelling capability of bentonite with drying-wetting cycling in the seawater decreased significantly by 60%, while hydraulic conductivity increased by more than three times. Therefore, the study suggested minimizing drying-wetting cycling and preventing seawater intrusion, ensuring a long service life of the multiple barriers in the LLW repository.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.700-702
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• 2009