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Electrical Properties of SrTiO3-epoxy Composite Thick Films on Cu Plate PCB substrates
함용수,김세호,고중혁 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3
Ceramic-polymer composites have been of great interest as embedded capacitor materials due to process compatibility of polymers and the desired electrical properties of ceramics. In this study, we use SrTiO3-epoxy composite thick films for system-on-package (SOP) applications. The SrTiO3-epoxy composites thick films for SOP applications were fabricated upon a Cu-plated printed circuit board (PCB) substrate by employing a screen printing method. From the X-ray diffraction (XRD) θ-2θ scan image, we observed that SrTiO3 has a pseudo-cubic structure at room temperature. We investigated the frequency-dependent relative dielectric permittivities of SrTiO3-epoxy composite thick-film metal-insulator-metal (MIM) capacitors on a Cu-plated PCB substrate, and their relative dielectric permittivity were 177.9 and 132.8 at 1 MHz, respectively. By measuring the time-dependent leakage current characteristics at respective step biases of 30, 60 and 90 V at room temperature, we observed the current relaxation behavior of the SrTiO3-epoxy composite thick-film MIM capacitors on the Cu-plated PCB substrates.
스크린 프린트된 후막의 Impedance Spectroscopy 특성 분석
함용수,문상호,남송민,이영희,고중혁,정순종,김민수,조경호,Ham, Yong-Su,Moon, Sang-Ho,Nam, Song-Min,Lee, Young-Hie,Koh, Jung-Hyuk,Jyoung, Soon-Jong,Kim, Min-Soo,Cho, Kyung-Ho 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.6
In this study, we fabricate 3 wt% $Li_2CO_3$ doped $(Ba,Sr)TiO_3$ thick films on the Ag/Pd bottom electrode printed $Al_2O_3$ substrates for the LTCCs (low temperature co-fired ceramics) applications. From the X-ray diffraction analysis, 3 wt% $Li_2CO_3$ doped BST thick films on the Ag/Pd printed $Al_2O_3$ substrates, which sintered at $900^{\circ}C$, showed perovskite structure without any pyro phase. The dielectric properties of 3 wt% $Li_2CO_3$ doped BST thick films are measured from 1 kHz to 1 MHz. To investigate the electrical properties of 3 wt% $Li_2CO_3$ doped BST thick films, we employ the impedance spectroscopy. The complex impedance of 3 wt% $Li_2CO_3$ doped BST thick films are measured from 20 Hz to 1 MHz at the various temperatures.
Electrical Properties of Li2CO3-doped 0.7(Ba,Sr)TiO3-0.3MgO Ceramics
함용수,고중혁 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
Recently, a low- temperature sintering process has been widely used for SoP (system on package) applications. The (BaxSr1−x)TiO3-based ceramic has been considered as one of the most important ferro-paraelectric materials widely employed in many applications. However, the sintering temperature of (Ba,Sr)TiO3 prepared by using the conventional method is around 1350 ℃. Therefore, in order to reduce the sintering temperature and improve the dielectric properties, such as the loss tangent and the frequency dispersion of the dielectric permittivity, Li2CO3- doped 0.7(Ba,Sr)TiO3-0.3MgO materials have been investigated. In this experiment, we studied the crystalline structure and the dielectric properties of Li2CO3- doped 0.7(Ba,Sr)TiO3-0.3MgO ceramics for a low-temperature sintering process. By scanning the crystalline structure of Li2CO3- doped 0.7(Ba,Sr)TiO3-0.3MgO ceramics, any pyro phase was not observed in the X-ray diffraction pattern. By adding the Li2CO3 to 0.7(Ba,Sr)TiO3-0.3MgO, the sintering temperature was lowered to 1200 ℃. In addition, a very weak frequency dispersion of the dielectric permittivity was observed from 1 kHz to 1 MHz. To investigate the electrical properties of Li2CO3- doped 0.7BST-0.3MgO ceramics, we employed impedance spectroscopy. The impedance data were measured from 100 Hz to 1 MHz at various temperatures.
산화마그네슘 기판과 산화알루미늄 기판을 이용한 Meander 형태 인덕터의 고주파 시뮬레이션
함용수,김성훈,강이구,고중혁,Ham, Yong-Su,Kim, Sung-Hun,Kang, Ey-Goo,Koh, Jung-Hyuk 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.8
We have studied on the microwave characteristics for the meander type inductors on the MgO substrates and $Al_2O_3$ substrates by employing 3-D high frequency simulation, respectively. Proper designs of meander type inductors were proposed and confirmed through the high frequency simulations, 5, 7, 9, 11, and 13 turns meander type inductors have been choose to analyze the electrical properties for the microwave passive component applications. The Al top electrodes have 282 nm length, 45 nm width, 100 nm thickness and 15 nm gap. The simulations were carried out from 50 MHz to 30 GHz, Frequency dependent inductances and quality factor were calculated by employing the equivalent circuit model of meander type inductors. The self resonances frequency of meander type inductor were shifted from high frequency to low frequency range as the number of the turn of inductors was increased. From the microwave simulations, the inductances and quality factors of meander type inductors were extracted through the scattering parameter.
함용수,고중혁 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41
Three (3)-wt% Li2CO3 doped (Ba0.5,Sr0.5)TiO3 thick films were prepared and sintered at a relatively low temperature (900 ℃) for electronic device applications. The thick films were prepared via a screen printing process on Ag-Pd printed alumina substrates. In this experiment, the crystalline and the electrical properties of Li2CO3-doped (Ba0.5,Sr0.5)TiO3 thick films on the Ag-Pd printed alumina substrates sintered at 900 ℃ were investigated. To investigate the electrical properties,we employed impedance spectroscopy and ac conductivity. In this study, we found that the 3-wt%Li2CO3 doped (Ba0.5,Sr0.5)TiO3 thick film exhibited perovskite and pseudo-cubic structures. Also,the relative dielectric permittivity of the 3 wt% Li2CO3 doped (Ba0.5,Sr0.5)TiO3 thick film was 149.25 at 30 ℃, and the activation energies were 0.432 and 0.326 eV at 1 and 81.57 kHz, respectively. The resistances of the grain and the grain boundary were 17.65 kΩand 40.5 kΩat 130 ℃,respectively.
자기유체역학 코드를 이용한 축 대칭 엑스 핀치 플라즈마 구조의 2차원 전산해석
변상민,나용수,정경재,김덕규,이상준,이찬영,함승기,류종현,Byun, Sangmin,Na, Yong-Su,Chung, Kyoung-Jae,Kim, Deok-Kyu,Lee, Sangjun,Lee, Chanyoung,Ham, Seunggi,Ryu, Jonghyeon 한국군사과학기술학회 2021 한국군사과학기술학회지 Vol.24 No.2
This paper deals with the computational work to characterize the formation and pinching of a plasma in an X-pinch configuration. A resistive magnetohydrodynamic model of a single fluid and two temperature is adopted assuming a hollow conical structure in the (r,z) domain. The model includes the thermodynamic parameter of tungsten from the corrected Thomas-Fermi EOS(equation of state), determining the average ionization charge, pressure, and internal energy. The transport coefficients, resistivity and thermal conductivity, are obtained by the corrected Lee & More model and a simple radiation loss rate by recombination process is considered in the simulation. The simulation demonstrated the formation of a core-corona plasma and intense compression process near the central region which agrees with the experimental observation in the X-pinch device at Seoul National University. In addition, it confirmed the increase in radiation loss rate with the density and temperature of the core plasma.
문상호,이영희,남송민,고정혁,윤석우,함용수,Soon-Jong Jeong,김민수 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41
One (1)-mol% Li2O-excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 lead-free piezoelectric ceramics were aged under different unipolar electric fields. Unipolar electric fields of 3, 5, and 7 kV/cm were applied to the specimens to accelerate the electric aging behavior. By employing a unipolar electric field for the piezoelectric actuators, we were able to remove undesirable heating problem from the relaxation current in the ferroelectric domain motions. To accelerate the aging test, we used an applied electric fields with a frequency of 910 Hz. To earn enough time for charging and discharging, we used an accurate time constant for the equivalent model for the piezoelectric actuators. X-ray diffraction analyses were carried out to determine the structural aging behavior of the poled piezoelectric specimens. As the piezoelectric specimens were exposed to high electric fields for aging tests, the actuators lost their tetragonality and took on a pseudo-cubic structure. The cycling dependent piezoelectric coefficient and electromechnical coupling coefficient followed a stretched exponential law as aging process.