• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.55-65
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• 2020

The use of underfill materials in semiconductor packages is not only important for stress relieving of the package, but also for improving the reliability of the package during shock and vibration. However, in recent years, as the size of the package becomes larger and very thin, the use of the underfill shows adverse effects and rather deteriorates the reliability of the package. To resolve these issues, we developed the package using a solid epoxy material to improve the reliability of the package as a substitute for underfill material. The developed solid epoxy was applied to the package of the application processor in smart phone, and the reliability of the package was evaluated using thermal cycling reliability tests and numerical analysis. In order to find the optimal solid epoxy material and process conditions for improving the reliability, the effects of various factors on the reliability, such as the application number of solid epoxy, type of PCB pad, and different solid epoxy materials, were investigated. The reliability test results indicated that the package with solid epoxy exhibited higher reliability than that without solid epoxy. The application of solid epoxy at six locations showed higher reliability than that of solid epoxy at four locations indicating that the solid epoxy plays a role in relieving stress of the package, thereby improving the reliability of the package. For the different types of PCB pad, NSMD (non-solder mask defined) pad showed higher reliability than the SMD (solder mask defined) pad. This is because the application of the NSMD pad is more advantageous in terms of thermomechanical stress reliability because the solderpad bond area is larger. In addition, for the different solid epoxy materials with different thermal expansion coefficients, the reliability was more improved when solid epoxy having lower thermal expansion coefficient was used.

• Journal of ILASS-Korea
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• v.12 no.3
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• pp.138-145
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• 2007

In the present work, the breakup mechanism of highly viscous epoxy paints discharged from a fan spray nozzle was examined experimentally. The paints tested were non-Newtonian fluids, composed of epoxy resin, solid particles and other additives. The paint spray discharged from the nozzle was visualized and recorded using a digital camera with back illumination. Due to presence of the solid particles, perforation of liquid sheet was observed in most cases, even at low-Reynolds number conditions (Re < 15,000) where the aerodynamic-wave breakup mode is used to be dominant for pure liquids. However, with the increase of the particle concentration, the sheet became longer and the thickness at breakup became thinner to some extent. This is because, with higher concentration of solid particles, the stabilizing effect by the viscosity increase predominates over the destabilizing effect by perforation.

• Structural Engineering and Mechanics
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• v.50 no.2
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• pp.231-240
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• 2014

In the present research, fatigue behavior of chopped strand mat/epoxy composites has been studied with two different techniques. First, the normalized stiffness degradation approach as a well-known model for unidirectional and laminated composites was utilized to predict the fatigue behavior of chopped strand mat/epoxy composites. Then, the capability of the fatigue damage accumulation model for chopped strand mat/epoxy composites was investigated. A series of tests has been performed at different stress levels to evaluate both models with the obtained results. The results of evaluation indicate a better correlation of the normalized stiffness degradation technique with experimental results in comparison with the fatigue damage accumulation model.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.2
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• pp.93-101
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• 2016

This paper presents the surface discharge characteristics in Dry-Air on laminated epoxy solid dielectrics and conductive particles in order to provide the valuable information for the insulation design of eco- friendly gas insulated switchgear. To improve insulation performance, the three types of the laminated epoxy solid dielectrics were proposed, and it was revealed that their surface discharge characteristics were similar to the bakelite dielectrics of same-laminated types. From the surface discharge characteristics of dry air, it was demonstrated that the effect of conductive particles on surface discharge voltage was dominant when there are this particles at the shortest electrode gap and that the degradation of insulation performance on the conductive particles was evident in epoxy than teflon. These phenomena were interpreted in terms of particle-triggered discharge mechanism and electric field of triple junction, respectively.

• Structural Engineering and Mechanics
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• v.64 no.3
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• pp.287-292
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• 2017

In the present research, an available flexural stiffness degradation model was modified and a new comprehensive model called "X-NFSD" was developed. The X-NFSD model is capable of predicting the flexural stiffness degradation of composite specimen at different states of stresses and at room temperature. The model was verified by means of different experimental data for chopped strand mat/epoxy composites under displacement controlled bending loading condition at different displacements and states of stresses. The obtained results provided by the present model are impressively in very good agreement with the experimental data and the mean value of error of 5.4% was achieved.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.275-278
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• 1990

This study investigated electrical characteristics of solid and liquid epoxy rosins by measuring dielectric breakdown and dielectric loss when epoxy resins were exposed to a mixing cure, i.e., Fusion Blend Method. It was found that mixing epoxy resins were superior to dielectric breakdown and has shorter curing time compare with those of pure liquid epoxy resins.

• Journal of Environmental Science International
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• v.31 no.1
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• pp.1-8
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• 2022

In this study, solid-liquid separation conditions for coagulation and sedimentation experiments using inorganic coagulant (aluminum sulfate and Poly-Aluminum Chloride (PAC)) were optimized with brine wastewater discharged by the epoxy-resin process. When the turbidity and suspended solid (SS) concentration in raw wastewater were 74 NTU and 4.1 mg/L, respectively, their values decreased the lowest in a coagulant dosage of 135.0 - 270.0 mg Al³⁺/L. The epoxy resin was re-dispersed in the upper part of wastewater treated above 405.0 mg Al³⁺/L. The removal efficiencies of turbidity and SS via dosing with aluminum sulfate and PAC were evaluated at initial turbidity and SS of 74 - 630 NTU and 4.1 - 38.5 mg/L, respectively. They increased most in the range from 135.0 - 270.0 mg Al³⁺/L. The solid-liquid separation condition was quantitatively compared to the correlation of SS removal efficiency between the coagulant dosage and SS concentration based on the concentration of aluminum ions. The empirical formula, R = be^aD, shows the relationship between SS removal efficiency (R) and coagulant dosage (D) at 38.5 mg/L; it produced high correlation coefficients (r²) of 0.9871 for aluminum sulfate and 0.9751 for PAC.

• Structural Engineering and Mechanics
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• v.56 no.2
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• pp.157-167
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• 2015

The impact behavior of epoxy-based nanocomposites reinforced with carbon nano tube (CNT), carbon nano fiber (CNF) and mixed contents of these nanoparticles was investigated using Izod impact test. The results showed that while the impact strength of nanocomposites containing 1 wt% of CNT and 1 wt% of CNF increased 19% and 13% respectively, addition of mixed contents of these nanofillers (0.5-0.5 wt%) demonstrated higher improvement (21%) in the impact resistance. The trend of the results is explained on the basis of different fracture mechanisms of nanocomposites. Furthermore, the fracture surface of specimens and the dispersion state of nanoenhancers have been studied using scanning electron microscopy (SEM) photographs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1181-1188
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• 2018

In order to develop new insulating materials for GIS Spacer using environmentally friendly insulating gas, three kinds of dispersed liquid nano composites of solid epoxy /nano layered silicate filled material were prepared. And the epoxy/nano/micro silica composite was prepared by mixing epoxy/nano 3 phr dispersion/4 kinds of filler contents(40,50,60, 70wt%). The electrical insulation breakdown strengths of the nano and nano/micro mixed composites were evaluated by using 8 kinds of samples including the original epoxy. The mechanical tensile strength of the epoxy / nano / micro silica composite were evaluated, also. The TEM was measured to evaluate the internal structure of nano/micro composites. As a result, it was confirmed that the layered silicate nano particles was exfoliated through the process of inserting epoxy resin between silicate layers and the layers. In addition, dispersion of nano / micro silica resulted in improvement of electrical insulation breakdown strength with increase of filling amount of dense tissue with nanoparticles inserted between microparticles. In addition, the tensile strength showed a similar tendency, and as the content of microsilica filler increased, the mechanical improvement was further increased.

• Journal of the Society of Disaster Information
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• v.9 no.2
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• pp.206-213
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• 2013

The paper presents the field applications and evaluation results of solid epoxy asphalt mixture for steel bridge deck. The material was developed in Japan. The material properties of epoxy asphalt mixture were evaluated through various literature review, and the mix design and mixture evaluation were conducted. According to the research results, the application of epoxy asphalt mixture for steel bridge deck was noticeable compare to the conventional ones. In addition, results from 3D finite element analysis showed that the performance of epoxy asphalt mixture for steel bridge deck was proved to be satisfied. As a result, a pilot test section was constructed using the epoxy asphalt mixture produced from conventional batch plant system. BPT test results showed that friction of the epoxy asphalt mixture was higher than the requirements compare to that of the conventional one.