• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.16-18
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• 2013

A fire outbreak in a reinforcement concrete structure looses the organism by different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So, concrete reinforcement structure is damaged partial or whole structure system. Therefore accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. In this study, consider case of investigation methods and repair work in fire damaged structure concrete.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.9-14
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• 2007

In this study, the thermal reliability on flip chip package with non-conductive pastes (NCPs) was evaluated under accelerated conditions. As the number of thermal shock cycle and the dwell time of temperature and humidity condition increased, the electrical resistance of the flip chip package with NCPs increased. These phenomenon was occurred by the crack between Au bump and Au bump and the delamination between chip or substrate and NCPs during the thermal shock and temperature and humidity tests. And the variation of electrical resistance during temperature and humidity test was larger than that during thermal shock test. Therefore it was identified that the flip chip package with NCPs was sensitive to environment with moisture.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.25-29
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• 2009

High temperature high humidity and thermal shock reliability tests were performed for the board level COB(chip-on-board) flip chip packages using self-formulated and commercial NCPs(non-conductive pastes) to ensure the performance of NCP flip chip packages. It was considered that the more smaller fused silica filler in prototype NCPs is more favorable for high temperature high humidity reliability. The failure of NCP interconnection was affected by the expansion of epoxy due to moisture absorption rather than the fatigue due to thermal stress. It was considered that the NCP having more higher adhesive strength seems to be more favorable to increase the thermal shock reliability.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.53.2-53.2
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• 2010

In this study, we focused on our specialized electrode process for Si back-contact crystalline solar cell. It is different from other well-known back-contact cell process for thermal aspect and specialized process. In general, aluminum makes ohmic contact to the Si wafer and acts as a back surface reflector. And, silver is used for low series resistance metal grid lines. Aluminum was sputtered onto back side of wafer. Next, silver is directly patterned on the wafer by screen printing. The sputtered aluminum was removed by wet etching process after rear silver electrode was formed. In this process, the silver paste must have good printability, electrical property and adhesion strength, before and after the aluminum etching process. Silver paste also needs low temperature firing characteristics to reduce the thermal budget. So it was seriously collected by the products of several company of regarding low temperature firing (below $250^{\circ}C$) and aluminum etching endurance. First of all, silver pastes for etching selectivity were selected to evaluate as low temperature firing condition, electrical properties and adhesive strength. Using the nano- and micron-sized silver paste, so called hybrid type, made low temperature firing. So we could minimize the thermal budget in metallization process. Also the adhesion property greatly depended on the composition of paste, especially added resin and inorganic additives. In this paper, we will show that the metallization process of back-contact solar cell was realized as optimized nano-paste characteristics.

• Journal of the Korea Institute of Building Construction
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• v.20 no.4
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• pp.321-330
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• 2020

The addition of a limestone filler(LF) to fill into the voids between cement and aggregate particles can reduce the cementitious paste volume. In previous studies, it has been found that the addition of LF to reduce the cementitious paste volume would substantially increase the compressive strength, and reduce the heat generation. This paper aim to evaluate the influence of LF contents on the hydration kinetics and compressive strength. Hydration kinetics were evaluate using heat of hydration, ignition loss and thermal analysis. The heat of hydration was measured using Isothermal Calorimetry. The degree of hydration was measured using ignition loss. Hydration product analysis was carried out by Thermal Gravimetric and Differential Thermal Analysis. The results show that the addition of LF reduces not only the initial setting time and heat of hydration peak, also degree of hydration and rate of strength development at early age increase with the addition of LF. It can be concluded the LF fills the pore between cement particles due to formation of carboaluminate, which may accelerate the setting of cement pastes.

• ETRI Journal
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• v.41 no.6
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• pp.820-828
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• 2019

A highly reliable conductive adhesive obtained by transient liquid-phase sintering (TLPS) technologies is studied for use in high-power device packaging. TLPS involves the low-temperature reaction of a low-melting metal or alloy with a high-melting metal or alloy to form a reacted metal matrix. For a TLPS material (consisting of Ag-coated Cu, a Sn96.5-Ag3.0-Cu0.5 solder, and a volatile fluxing resin) used herein, the melting temperature of the metal matrix exceeds the bonding temperature. After bonding of the TLPS material, a unique melting peak of TLPS is observed at 356 ℃, consistent with the transient behavior of Ag₃Sn + Cu₆Sn₅ → liquid + Cu₃Sn reported by the National Institute of Standards and Technology. The TLPS material shows superior thermal conductivity as compared with other commercially available Ag pastes under the same specimen preparation conditions. In conclusion, the TLPS material can be a promising candidate for a highly reliable conductive adhesive in power device packaging because remelting of the SAC305 solder, which is widely used in conventional power modules, is not observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.331-332
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• 2006

Ag-ceramic composite materials were investigated as internal electrodes for multilayer ceramic actuators (MLCA). Ag-ceramic pastes were prepared by adding PZT-based ceramic powders to a Ag patse in a range of 0 to 50 wt.%. PZT/Ag-PZT multilayered laminates were fabricated by tape casting and fired at low temperatures below $950^{\circ}C$. The addition of ceramic into the Ag electrode resulted in a decrease in the thermal expansion mismatch between the electrode and the ceramic sheet. The maximum strain of PZT/Ag-PZT multilayered actuators were $9{\times}10^{-4}$ under an electric field of 2.5MV/m. In conclusion, Ag-PZT composite materials are efficient for low cost piezoelectric MLCAs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.190-196
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• 2006

In the existed study, a fire outbreak in a reinforced concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the Properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. Therefore, This study is willing to propose fundamental data for quick and accurate diagnosis of deteriorated concrete structure by fire damage with making variable concrete test specimen, exposing high temperature environment, observing the explosive spalling and examining engineering property.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.149-154
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• 2018

This paper describes the fabrication and heat transfer property of 50 watts rated LED array module where multiple chips are mounted on chip-on-board type ceramic-metal hybrid substrate with high heat dissipation property for high power street and anti-explosive lighting system. The high heat transfer ceramic-metal hybrid substrate was fabricated by conformal coating of thick film glass-ceramic and silver pastes to form insulation and conductor layers, using thick film screen printing method on top of the high thermal conductivity aluminum alloy heat-spreading panel, then co-fired at $515^{\circ}C$. A comparative LED array module with the same configuration using epoxy resin based FR-4 PCB with thermalvia type was also fabricated, then the thermal properties were measured with multichannel temperature sensors and thermal resistance measuring system. As a result, the thermal resistance of the ceramic-metal hybrid substrate in the $4{\times}9$ type LEDs array module exhibited about one third to the value as that of FR-4 substrate, implying that at least triple performance of heat transfer property as that of FR-4 substrate was realized.

• Computers and Concrete
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• v.29 no.4
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• pp.263-278
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• 2022

Limestone calcined clay cement (LC³) is a low carbon alternative to conventional cement. Literature shows that using limestone and calcined clay in LC³ increases the thermal degradation of LC³ pastes and can increase the magnitude of fire risk in LC³ concrete structures. Higher thermal degradation of LC³ paste prompts this study toward understanding the fire performance of LC³ concrete and the associated magnitude of fire risk. For fire performance, concrete prepared using ordinary Portland cement (OPC), pozzolanic Portland cement (PPC) and LC³ were exposed to 16 scenarios of different elevated temperatures (400℃, 600℃, 800℃, and 1000℃) for different durations (0.5 h, 1 h, 2 h, and 4 h). After exposure to elevated temperatures, mass loss, residual ultrasonic pulse velocity (rUPV) and residual compressive strength (rCS) were measured as the residual properties of concrete. XRD (X-ray diffraction), TGA (thermogravimetric analysis) and three-factor ANOVA (analysis of variance) are also used to compare the fire performance of LC³ with OPC and PPC. Monte Carlo simulation has been used to assess the magnitude of fire risk in LC³ structures and devise recommendations for the robust application of LC³. Results show that LC³ concrete has weaker fire performance, with average rCS being 11.06% and 1.73% lower than OPC and PPC concrete. Analysis of 106 fire scenarios, in Indian context, shows lower rCS and higher failure probability for LC³ (95.05%, 2.22%) than OPC (98.16%, 0.22%) and PPC (96.48%, 1.14%). For robust application, either LC³ can be restricted to residential and educational structures (failure probability <0.5%), or LC³ can have reserve strength (factor of safety >1.08).