• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.202-206
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• 2005

The present investigation provides an electromagnetic radiation absorptive composition which comprises silver-coated ferrite microspheres dispersed in silicon rubber matrix for the aim of thin microwave absorber in GHz frequencies. Ni-Zn ferrite spheres with $50{\mu}m$ size in average were prepared by spray-drying and sintering at $1130^{\circ}C$. Conductive silver layer was plated on ferrite spheres by electroless plating. Conductive Ni-Zn ferrite sphere with uniform silver layer were obtained in the concentration of 10 g/L $AgNO_3$ per 20 g ferrite spheres. For this powder, electrical resistance is reduced as low as $10^{-2}\~10^{-3}\;\Omega$. The most sensitive material parameters with silver plating is real and imaginary parts of complex permittivity. The conductive Ni-Zn ferrite spheres have large values of dielectric constant. Due to this high dielectric constant of microspheres, matching thickness is reduced to as low as 2 mm at the frequency of 7 GHz, which is much thinner than conventional ferrite absorbers.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.562-566
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• 2012

A novel design of tubular segmented-in-series(SIS) solid oxide fuel cell (SOFC) sub module was presented in this paper. The tubular ceramic support was fabricated by the extrusion technique. The NiO-YSZ anode and the yttria-stabilized zirconia (YSZ) electrolyte were deposited onto the ceramic support by dip coating method. After sintering at $1350^{\circ}C$ for 5 h, a dense and crack-free YSZ film was successfully fabricated. Also, the multi-layered cathode composed of LSM-YSZ composite, LSM and LSCF were coated onto the sintered ceramic support by dip coating method and sintered at $1150^{\circ}C$. The performance of the tubular SIS SOFC cell and sub module electrically connected by the Ag-glass interconnect was measured and analysed with different fuel flow and operating temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.1014-1021
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• 1998

We evaluated the effect of processing variables on microstructural evolution interface irregularity between Ag sheath and superconductor core and resultant critical current density(J$_{c}$) of (Bi,Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$_{x}$(2223) superconductor tape. The value of J$_{c}$ was significantly influenced by the interface irregularity, degree of texturing and relative 2223 content. The interface became more irregular(sausage effect), while the degree of texturing gradually improved as the dimension of tape decreased during forming process. As the dimension of wire/tape were changed from diameter of 3.25 mm to thickness of 0.20 mm, J$_{c}$ value was observed to be increased by 10 times. In addition, optimum sintering temperature for improved J$_{c}$ was observed to be 835$^{\circ}C$ in a ambient atmosphere probably due to combined effect of both improved texturing and high 2223 content. Microstructural investigation showed the degree of texturing was degraded by the existence of both second phases and interface irregularity. It was observed that larger grain size and better texturing was developed near relatively flat interface compared to those inside superconducting core.ting core.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.175-176
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• 2008

In this study, in order to develop the composition ceramics for lead-free ultrasonic motor, $[(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}(Nb_{0.96}Sb_{0.04})]O_3$ ceramics were fabricated using $Ag_2O$ as sintering aid and a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $SrTiO_3$ substitution. $SrTiO_3$ substitution enhanced density, dielectric constant$(\varepsilon_r)$ and electromechanical coupling factor$(k_p)$. However, mechanical quality factor was deteriorated. At the 0.5mol% $SrTiO_3$ substitution, density, electromechanical coupling factor$(k_p)$, dielectric constant$(\varepsilon_r)$ and piezoelectric constant$(d_{33})$ of specimen showed the optimum value of 4.437g/$cm^3$, 0.457, 1294, 265pC/N, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.17-25
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• 2017

Recently, research and application for a power module have been actively studied according to the increasing demand for the production of vehicles, smartphones and semiconductor devices. The power modules based on the transient liquid phase (TLP) technology for bonding of power semiconductor devices have been introduced in this paper. The TLP bonding has been widely used in semiconductor packaging industry due to inhibiting conventional Pb-base solder by the regulation of end of life vehicle (ELV) and restriction of hazardous substances (RoHS). In TLP bonding, the melting temperature of a joint layer becomes higher than bonding temperature and it is cost-effective technology than conventional Ag sintering process. In this paper, a variety of TLP bonding technologies and their characteristics for bonding of power module have been described.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.4
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• pp.219-224
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• 2006

Silver paste with low sintered temperature has been developed in order to apply electronic parts, such as bus electrode, address electrode in PDP (Plasma Display Panel) with large screen area. In this study, nano-sized silver particles with 10-30 nm were synthesized from silver nitrate ($AgNO_3$) solution by chemical reduction method and silver paste with low sintered temperature was prepared by mixing silver nanoparticles, conventional silver powder with the particle size 1.6 um and Pb-free frit. Conductive thick film from silver paste was fabricated by screen printing on alumina substrate. After firing at $540^{\circ}C$, the cross section and surface morphology of the thick films were analyzed by FE-SEM. Also, the sheet resistivity of the fired thick films was measured using the four-point technique.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.206.1-206.1
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• 2014

최근 전자 장비의 금속 전도성 패턴 제작에 있어서 직접적인 프린트가 가능한 프린팅 기술이 기존의 복잡한 photolithography 를 대체할 기술로 주목 받고 있다. 이와 함께 금속 전도성 패턴 제작에 사용되는 고가의 전도성 물질인 Ag ink 및 paste 를 저가의 Cu ink 및 paste 로 대체하기 위한 연구가 진행되고 있다. 하지만 일반적으로 copper 는 대기 중 에서 쉽게 산화되어 높은 저항을 야기시킨다. 따라서 Cu ink 또는 paste 를 제작할 때 copper nanoparticles 을 유기 용매에 분산하여 inert atmosphere에서 합성하거나 [1] copper ink 또는 paste 를 substrate 에 프린트하여 reduction atmosphere 에서 소성시킨다 [2]. 이번 연구에서 Cu paste 를 유리 기판에 screen printing 하여 혼합가스(질소 95%, 수소 5%)와 질소 가스 분위기에서 소성하여 Cu 전극의 소성 거동과 전기적 특성을 분석하였다. 4-point probe를 통해 소성된 Cu 전극의 저항을 측정하여 전도도를 조사하였으며 Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared(FTIR)를 통해 소성된 Cu 전극의 유기물 분해가 전도도에 미치는 영향을 분석하고 Field Emission Scanning Electron Microscopy (FESEM)과 High Resolution Transmission Electron Microscopy (HRTEM)을 통해 Cu nanoparticles 의 grain growth가 전도도에 미치는 영향을 조사하였다.

• Journal of the Korean Ceramic Society
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• v.35 no.11
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• pp.1121-1129
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• 1998

Reactions between Ag-Pd internal electrode materials and{{{{ { {Bi }_{2 }O }_{3 } }} in multilayer chip varistor were in-vestigated. For more than 1 mol%{{{{ { {Bi }_{2 }O }_{3 } }} in varistor composition internal electrode structure was destroyed due to the reaction between internal electrode and{{{{ { {Bi }_{2 }O }_{3 } }} But for typical varistor compositions (below 1 mol% of{{{{ { {Bi }_{2 }O }_{3 } }} content) microstructural changes around the internal electrode were not observed. However SEM-EDS and TEM-EDS analysis showed the uneven distribution of{{{{ { {Bi }_{2 }O }_{3 } }} in the internal electrode which was due to the migration of{{{{ { {Bi }_{2 }O }_{3 } }} to the electorde during sintering. As a results the nonlinear coefficient of multilayer varistor showed very large distribution as well as the breakdown voltage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.484-488
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• 2009

In this study, in order to develop the lead-free piezoelectric ceramics with high piezoelectric and dielectric properties, $[(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}(Nb_{0.96}Sb_{0.04})]O_3$ ceramics were fabricated using $Ag_2O$ as sintering aid and a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $SrTiO_3$ substitution. $SrTiO_3$ substitution enhanced density, dielectric constant(${\varepsilon}_r$) and electromechanical coupling factor($k_p$). However, mechanical quality factor was deteriorated. And also, Curie temperature ($T_c$), and phase transition temperature($T_p$) were rapidly decreased. At the 0.5 mol% $SrTiO_3$ substitution, density, electromechanical coupling factor($k_p$), dielectric constant(${\varepsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum value of $4.437\;g/cm^3$, 0.457, 1294, 265 pC/N, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.9-15
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• 2018

This paper shows the principles and characteristics of the transient liquid phase (TLP) bonding technology for power modules packaging. The power module is semiconductor parts that change and manage power entering electronic devices, and demand is increasing due to the advent of the fourth industrial revolution. Higher operation temperatures and increasing current density are important for the performance of power modules. Conventional power modules using Si chip have reached the limit of theoretical performance development. In addition, their efficiency is reduced at high temperature because of the low properties of Si. Therefore, Si is changed to silicon carbide (SiC) and gallium nitride (GaN). Various methods of bonding have been studied, like Ag sintering and Sn-Au solder, to keep up with the development of chips, one of which is TLP bonding. TLP bonding has the advantages in price and junction temperature over other technologies. In this paper, TLP bonding using various materials and methods is introduced. In addition, new TLP technologies that are combined with other technologies such as metal powder mixing and ultrasonic technology are also reviewed.