Yong-Su Ham

COMPLEX IMPEDANCE SPECTROSCOPY ON ZnO-B2O3 DOPED (Ba, Sr)TiO3 CERAMICS

BST ceramics with doping of 1, 3, and 5 wt.% ZnBO were prepared by the conventional mixed oxide method and sintered at 1100°. X-ray diffraction analyses were carried out to verify the structural properties. 1, 3, and 5 wt.% ZnBO doped BST ceramics were crystallized with weak tetragonal structure at 1100°C. The grain growth behavior and shapes were investigated by scanning electron microscopy images. The electrical properties of 1, 3, and 5 wt.% ZnBO doped BST ceramics were investigated by impedance spectroscopy at the different temperatures (350, 375, and 400°C). Impedance spectroscopy data presented in Nyquist plot show the existence of both grain and grain boundary effects in all specimens. 1, 3, and 5 wt.% ZnBO doped BST ceramics showed negative temperature coefficient of resistance (NTCR). Also, the capacitances and resistances of grains and grain boundaries for 1, 3, and 5 wt.% doped BST ceramics were simulated through equivalent circuit with the parallelly connected capacitors and resistors. The capacitance and resistance were decreased when temperature and ZnBO dopants were increased.

A Study on the Electrical Properties of SrTiO3-Epoxy Composite Thick Films for Embedded Capacitor Applications

System on package (SoP) has been widely spreading to the electronic devices due to its low fabrication cost, fast time to market, and high performance. For the system on package applications, embedded system and its materials should be considered. In this study, SrTiO3 was chosen to the starting material due to its excellent dielectric properties such as high dielectric permittivity around 300 and low loss tangent around 5 × 10−4 at 295 K. Voltage dependent leakage currents have been carried out in the temperature range of 303 K∼363 K. As the epoxy additives were increased, leakage current of SrTiO3-epoxy thick film was increased. In our experiments, SrTiO3-epoxy composite thick film showed the negative coefficient temperature of resistivity properties. The resistivity was calculated by considering its geometry. In this paper, the activation energy of SrTiO3-epoxy composite thick films was investigated by employing the Arrhenius equation. From the Arrhenius plot, we observed the two types of conduction of SrTiO3-epoxy composite thick films.

The Dielectric Characteristics of Screen Printed SrTiO3-Epoxy Composite Thick Films on the Cu Plate PCB Substrates

Novel electronic devices require higher performance and miniaturization. Due to the increased demands for the high density of passive components in the mobile system, integration of passive components in the inner layers of multi-layer substrates has been actively investigated. In this paper, we studied on SrTiO3-epoxy composites thick films for embedded capacitor applications. SrTiO3-epoxy composites were employed to explore its feasibilities of embedded capacitors applications. We have investigated the frequency dependent dielectric permittivity and the temperature dependent dielectric permittivity of SrTiO 3 -epoxy composite thick film metal-insulator-metal (MIM) capacitors. As the amount of epoxy resin was increased, the dielectric permittivity of composites was decreased. In temperature dependent dielectric permittivity characteristics, however, the dielectric permittivity was increased with the elevated temperature. We will show and discuss the leakage current density (j) – electric field (E) characteristics of SrTiO 3 -epoxy composite thick films.

Impedance Spectroscopy Analysis of the Screen Printed Thick Films

In this study, we fabricate 3 wt% doped thick films on the Ag/Pd bottom electrode printed substrates for the LTCCs (low temperature co-fired ceramics) applications. From the X-ray diffraction analysis, 3 wt% doped BST thick films on the Ag/Pd printed substrates, which sintered at , showed perovskite structure without any pyro phase. The dielectric properties of 3 wt% doped BST thick films are measured from 1 kHz to 1 MHz. To investigate the electrical properties of 3 wt% doped BST thick films, we employ the impedance spectroscopy. The complex impedance of 3 wt% doped BST thick films are measured from 20 Hz to 1 MHz at the various temperatures.

Electric Aging Behaviors of Ferroelectric 1 mol% Li2O Excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 Lead Free Ceramics

The electric aging behaviors of 1 mol% Li2O excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 lead free piezoelectric ceramics were investigated under different unipolar electric fields. Lead free 1 mol% Li2O excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 piezoelectric ceramics were selected in these aging experiments. Before the aging experiments, X-ray diffraction analysis was carried out to observe crystalline properties of poled fresh piezoelectric ceramics. X-ray diffraction results of 1 mol% Li2O excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 lead free piezoelectric ceramics indicated that the ceramics were well crystallized and have tetragonal structure before aging process. Electromechanical coupling coefficient kp was calculated through the resonant and anti resonant frequencies. To observe the aging behavior without thermal stress, different unipolar electric fields were applied to the specimens. Aging phenomena of 1 mol% Li2O excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 lead free ceramics strongly depend on time (cycles) under the unipolar electric fields in our experiments.

High Frequency Simulations for the Meander Type Inductors on the MgO and Al 2 O 3 Substrates

We have studied on the microwave characteristics for the meander type inductors on the MgO substrates and 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.

HIGH FREQUENCY SIMULATIONS AND CHARACTERIZATIONS FOR MEANDER TYPE INDUCTORS ON THE MgO AND Al2O3 SUBSTRATES

ABSTRACT Systems on Package (SoP) techniques have been actively investigated for the next emerging technologies for the wireless applications. Many researches have been conducted to decrease the number of passive components in the circuit modules, which occupied the major part of PCB (printed circuit board). For the SoP applications, it is very important to know and extract the proper parameters of passive components in the microwave ranges. We will present simulation characterization results of meander type inductor through the structure simulation and electrical measurement, respectively. Meander type inductors were fabricated on the aluminum oxide (Al2O3) substrates. Proper designs of meander type inductors were proposed and confirmed through the high frequency simulations. All electrodes were lift off through the lithography process. The fabricated Al electrodes were of 282 μm length, 45 μm width, 15 μm gap, and 100 nm thickness. The simulations were carried out from 50 MHz to 30 GHz. 5, 7, 9, 11 and 13 turns meander type inductors have been choose to analyze the electrical properties for the microwave passive component applications. Simulated and measured frequency dependent inductance and quality factor will be presented, respectively. The shift of SRF (Self Resonance Frequency) was confirmed through the simulation. From the microwave measurement, the inductance was extracted through the scattering parameters of S21.