Chip Inductors Research Articles

칩인덕터용 NiZnCu Ferrite의 자기적 특성 연구

칩인덕터용 <TEX>$Ni_{0.4}Zn_{0.4}Cu_{0.2}Fe_2O_4$</TEX> ferrite(NiZnCu ferrite)를 고상반응법 및 졸겔법으로 제조하였다. 고상반응법에 의해 제조된 마이크론크기의 NiZnCu ferrite 분말과 졸겔법에 의해 제조된 나노크기의 분말을 혼합하여 소결성 및 자기적 특성을 증가 시켰다. 나노크기의 분말을 20wt%첨가한 토로이달 코아 시편의 초투자율은 1 MHz에서 <TEX>$880^{\circ}C$</TEX> 소결시 78.1에서 <TEX>$920^{\circ}C$</TEX> 소결시 178.2의 값을 가졌으며 소결온도가 증가할수록 초투자율값이 증가하였다. 소결 밀도, 수축율 및 포화자화값도 소결온도가 증가함에 따라 증가하였으며 이것은 grain사이즈 효과 및 소결성이 증가 되었기 때문이다. 고상반응법에 의해 제조한 ferrite에 졸겔법에 의해 제조한 나노크기의 ferrite 분말을 혼합하여 소결성을 향상시키고 자기적 특성을 향상시킬 수 있었다. <TEX>$Ni_{0.4}Zn_{0.4}Cu_{0.2}Fe_2O_4$</TEX> ferrite was fabricated by solid stat reaction method and sol-gel method. Because of the drawbacks of each method, we combined these two methods together. We proposed and experimentally verified that nanocrystalline ferrite additive was effective on improving the densification behavior and magnetic properties of NiZnCu ferrites for multilayer chip inductors. The initial permeability of the toroidal core Sample with 20 wt% nanocrystalline ferrite increased from 78.1 to 178.2 as annealing temperature is increased from <TEX>$880^{\circ}C$</TEX> to <TEX>$920^{\circ}C$</TEX>. The density, shrinkage and saturation magnetization were increased with increasing annealing temperature, which was attributed to the decrease of additive grain size and increase of sintering density.

Basic investigation of microtemperature sensor by means of a novel transmission-line technique using a temperature-sensitive Li–Zn–Cu ferrite substrate

The polycrystalline Mn-substituted Li–Zn–Cu ferrite exhibits a very strong temperature dependence of magnetic properties, high natural resonance frequency, and high resistivity. The authors carried out the basic investigations of the temperature sensor using this new temperature-sensitive ferrite. As the first step, the temperature-sensitive LC resonance circuit using the Li–Zn–Cu ferrite chip inductor was fabricated, and the temperature dependence of its input impedance was evaluated. The resonance frequency was decreased linearly with a large temperature coefficient. Furthermore, it was also found that the input impedance in a constant frequency operation indicated extremely temperature dependence. In order to integrate and miniaturize the temperature sensing device, a possibility of the integrated temperature-sensitive LC circuit by means of the transmission-line technique was investigated. For our motivation, the monolithic integrated temperature sensor using spiral strip-line with Li–Zn–Cu ferrite substrates, which has the temperature dependent magnetic property, was simulated by the electromagnetic field and the equivalent circuit analysis. It was clarified that the monolithic sensor exhibited remarkable temperature dependent input impedance as well as the temperature-sensitive LC resonance circuit.

Design of the Novel DVB-H Antenna for the Folder-Type Mobile Handheld Terminal

We have proposed a novel DVB-H(Digital Video Broadcast for Handheld) antenna for folder-type mobile handheld terminal by using a coupling element, a stub, and an L-type matching circuit. The L-type matching circuit consisting of two chip inductors is used for achieving an improved impedance matching over the DVB-H frequency band (<TEX>$470{\sim}702\;MHz$</TEX>). Simulated results showed the stub worked to more knot the lower and upper frequency ends of the input impedance curve. The antenna exhibits a flat gain characteristic from 2 to 2.8 dBi over the DVB-H frequency band. The radiation patterns are a stable Figure-of-eight radiation pattern in the frequency range.

Microwave processing of electroceramic materials and devices

Microwave synthesis of nano-sized BaTiO3 and decrystallized titania, and microwave sintering of electroceramics including BaTiO3, Ba(Zn1/3Ta2/3)O3 (BZT), lead zirconate–titanate (i.e. Pb(ZrxTi1−x)O3, or PZT), etc., as well as multilayer ceramic capacitors based on X7R, C0G, and ferrite multilayer chip inductors are presented. The results indicate that microwave processing significantly accelerated synthesis and sintering kinetics. As a result, processing time can be saved up to 90%, with the product properties comparable to or better than that of the conventional products.

On chip inductors for RF SOC's: a love/hate relationship?

On chip inductors for RF SOC's: a love/hate relationship?

칩인덕터용 저온소성 Nano-glass 연구

[ <TEX>$ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$</TEX> ] nano-glass를 sol-gel 법으로 제조 하였다. 평균 입자 크기는 60.3 nm였으며 매우 균일한 입도 분포를 가졌다. Nano-glass를 NiZnCu ferrite의 저온소성용 소결조제로 사용하였으며 NiZnCu ferrite에 nano-glass를 첨가한 후 <TEX>$840{\sim}900^{\circ}C$</TEX>에서 2시간 소결을 진행하였다. 소결성 및 자기적 특성에 대해 연구하였으며 밀도, 수축율, 초투자율, 품질계수, 및 포 화자화값을 측정하였다. nano-glass를 0.5 wt% 첨가하여 <TEX>$900^{\circ}C$</TEX>에서 소결한 토로이달 core 시편의 초투자율은 1 MHz에서 측정 시 193.3의 값을 가졌다. 초투자율과 포화자화값은 소결온도가 증가함에 따라 증가하는 경향을 나타내었다. sol-gel 법에 의해 제조된 <TEX>$ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$</TEX> nano-glass를 칩인덕터용 NiZnCu ferrite의 저온 소결조제로 사용 가능함을 알 수 있었다. [ <TEX>$ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$</TEX> ] nano-glass has been prepared by sol-gel method. The mean particle size was 60.3 nm with narrow size distribution. The nano-galss has been used as a sintering aid for the densification of the NiZnCu ferrites. The ferrite was sintered with nano-glass sintering aids at <TEX>$840{\sim}900^{\circ}C$</TEX>, 2 h and the initial permeability, quality factor, density, and saturation magnetization were also measured. The initial permeability of 0.5 wt% nano-glass added toroidal sample for NiZnCu ferrites sintered at <TEX>$900^{\circ}C$</TEX> was 193.3 at 1 MHz. The initial permeability and saturation magnetization were increased with increasing annealing temperature. As a result, <TEX>$ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$</TEX> nano-glass systems were found to be useful as sintering aids for multilayer chip inductors.

An ultra-low power ISM-band integer-N frequency synthesizer dedicated to implantable medical microsystems

In this article, the architectural choices and design of a fully integrated integer-N frequency synthesizer operating in the 902---928 MHz Industrial, Scientific and Medical (ISM) band is presented. This frequency synthesizer, optimized for ultra-low power operation, is being integrated in the transceiver of an implantable wireless sensing microsystem (IWSM), which is dedicated to in vivo monitoring of biological parameters such as temperature, pressure, pH, oxygen, and nitric oxide concentrations. This phase-locked loop-based synthesizer includes a 1.830 GHz LC voltage-controlled oscillator (VCO) using a 10 nH on chip inductor. Varactors are implemented using P+ in N-well diodes for their linearity and high quality factor. The transistors of the VCO are operated in moderate inversion, and their bias point was chosen using the g m/I d design methodology. The output of the VCO, operating at twice the ISM frequency band, is divided by 2 to generate differential, quadrature versions of the carrier. Power minimization of the programmable divider was achieved by designing the latches and flip-flops using appropriate circuit techniques such as True Single Phase Clocking (TSPC) and first-type Dynamic Single Transistor Clocking (DSTC1) depending on their operating frequency. The power consumption of the proposed synthesizer is 580 μW under 1 V; almost an order of magnitude lower compared to that of recent synthesizer designs having a similar architecture.

Analysis and Modeling of Hybrid Planar-Type Electromagnetic-Bandgap Structures and Feasibility Study on Power Distribution Network Applications

A unified 1D analysis model of hybrid planar-type electromagnetic-bandgap (EBG) structures is developed. Based on the analysis results, three types of hybrid design methods to reduce the cutoff frequency of the EBG structures are discussed, and design equations for their noise suppression bandwidths are derived. In order to simulate switching noise characteristics of the hybrid planar-type EBG structures, 2D circuit level models are developed and experimentally verified. With the developed circuit-level models and CMOS active switching devices, feasibility studies on the power distribution network design using the hybrid EBG structures are conducted. The hybrid EBG structure with series lumped chip inductors shows efficient noise suppression characteristics in both the frequency and time domains; however, it has potential limitations because of its generation of higher switching noise voltages depending on power supply connection configurations.

Synthesis and Characterization of Temperature Sensitive Li–Zn–Cu Ferrite

The authors have fabricated the polycrystalline Li–Zn–Cu ferrite as a new temperature sensitive ferrite. The Li–Zn–Cu ferrite had high-frequency permeability profile and high electrical resistivity as well as the Ni–Zn–Cu ferrite for multilayered surface-mounting device such as a high-frequency chip inductor and filter. Since the new Li–Zn–Cu ferrite had both excellent high-frequency magnetic property and temperature sensitivity, it will be suitable for miniaturization of high-frequency inductive temperature sensing device. In this study, the relationship between grain size and the temperature-dependent magnetic properties of polycrystalline Li–Zn–Cu ferrite has been investigated. Three kinds of the Li–Zn–Cu ferrites sintered with Bi2O3 at different temperature were synthesized, and their temperature characteristics were evaluated. The most important result obtained is as follows: as the sintering temperature rose the coarse grain increased without changing bulk density, the permeability and its temperature dependence can be enhanced by grain growth due to higher sintering temperature. Therefore, the temperature dependent permeability of the Li–Zn–Cu ferrite can be controlled by grain size only without a change of the chemical composition.

Microfabrication of solenoid-type RF SMD chip inductors with an Al2O3 core

We investigated micron size, high-performance, and solenoid-type radio-frequency surface-mounted device (SMD) chip inductors with a low-loss Al 2 O 3 core for a GHz drive microwave circuit application. Copper coils with a diameter of 27 μm were used and the chip inductors fabricated in this study are 0.86 × 0.46 × 0.45 mm 3 . The high-frequency characteristics of the inductance ( L ), quality factor ( Q ), and impedance ( Z ) of the developed inductors were measured using a RF impedance/material analyzer (HP4291B with HP16193A test fixture). The developed inductors have a self-resonant frequency of 3.7–5.2 GHz and exhibit L of 15–34 nH. The inductors have Q of 38–49 over the frequency ranges of 900 MHz–1.7 GHz. The calculated data obtained from the equivalent circuit and the derived equation of Q described the high-frequency data of L , Q , and Z of the inductors developed quite well.

Study on electro-magnetic properties of La substituted Ni–Cu–Zn ferrite synthesized by auto-combustion method

(Ni 0.25Cu 0.20Zn 0.55)La x Fe 2− x O 4 ferrite with x=0.00, 0.025, 0.050 and 0.075 compositions were synthesized through nitrate–citrate auto-combustion method. Crystalline spinel ferrite phase with about 16–19 nm crystallite size was present in the as-burnt ferrite powder. These powders were calcined, compacted and sintered at 950 °C for 4 h. Initial permeability, magnetic loss and AC resistivity of different compositions were measured in the frequency range from 10 Hz to 10 MHz. Saturation magnetization and hysteresis parameters were measured at room temperature with a maximum magnetic field of 10 kOe. Permeability and AC resistivity were found to increase and magnetic loss decreased with La substitution for Fe, up to x=0.025. Saturation magnetization and coercive field also increases up to that limit. The electromagnetic properties were found best in the ferrite composition of x=0.025, which would be better for more miniaturized multi layer chip inductor.

On-chip matching networks for radio-frequency single-electron transistors

In this letter, the authors describe operation of a radio-frequency superconducting single electron transistor (rf-SSET) with an on-chip superconducting LC matching network consisting of a spiral inductor L and its capacitance to ground Cp. The superconducting network has a lower Cp and gives a better matching for the rf-SSET than does a commercial chip inductor. Moreover, the superconducting network has negligibly low dissipation, leading to sensitive response to changes in the rf-SSET impedance. The charge sensitivity δq=2.4×10−6e∕Hz in the subgap region and energy sensitivity δε=1.9ℏ indicate that the rf-SSET is operating in the vicinity of the shot noise limit.

Design of the novel DVB‐H antenna for mobile handheld terminal

AbstractWe have proposed a novel digital video broadcast for handheld (DVB‐H) antenna for mobile handheld terminal using a U‐shaped radiator and a simple matching circuit. The matching circuit consists of two chip capacitors and one chip inductor, and is used for achieving an improved impedance matching over the DVB‐H frequency band of 470–702 MHz. The proposed antenna was designed, fabricated, and measured. The proposed antenna covers the entire DVB‐H band for VSWR &lt; 2.5. The simulated antenna gain varies from 2.1 to 2.8 dBi over the operating frequency range. The obtained radiation patterns are very close to those of a conventional dipole antenna. Details of the proposed antenna design and the simulated and measured results are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2345–2350, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22786

Design of EBG Power Distribution Networks With VHF-Band Cutoff Frequency and Small Unit Cell Size for Mixed-Signal Systems

Hybrid electromagnetic bandgap (EBG) power distribution networks (PDNs) with VHF-band cutoff frequency, small unit cell size, and wideband noise suppression characteristics are proposed. Commercial lumped chip inductors are used to implement inductive bridges between neighboring metal patches instead of conventional microstrip lines. A 1D analysis model of the EBG structure is developed to find a mathematical ground for the use of the lumped chip inductors in the EBG PDN designs. From 158 MHz to 4528 MHz a measured stopband bandwidth of 4.37 GHz is achieved with over -60 dB noise suppression levels.

Characterization of nanocrystalline NiCuZn ferrite powders synthesized by sol–gel auto-combustion method

The ferrite compositions Ni0.8−xCu0.2ZnxFe2O4 with x = 0.5, 0.55 and 0.6, were synthesized through nitrate–citrate gel auto-combustion method. The autocatalytic nature of the combustion process has been studied by thermal analysis (DTA and TG) of the dried gels. The powders were calcined at 700 °C/2 h and then pressed ferrite parts were sintered at 900 °C/4 h. The ferrite was characterized with respect to phase identification, crystallite size and lattice parameter determination using X-ray diffraction. As-burnt powders showed the presence of crystalline cubic spinel ferrite with about 19–22 nm crystallite sizes. The densification characteristic of the powder was investigated using TMA. The sintered ferrite was characterized for permeability, saturation magnetization, relative loss and ac resistivity measurements. The permeability and magnetization were found to increase and magnetic loss, ac resistivity were decreased with Zn substitution for Ni. The powder is suitable for the application in multilayer chip inductor due to its low temperature sinterability, good magnetic properties and low loss at high frequency.

Co-Firing Behavior and Interfacial Structure of BaO–TiO2–B2O3–SiO2 Glass–Ceramics/NiCuZn Ferrite Composites

This paper presents the co-firing behavior and interfacial structure of BaO–TiO2–B2O3–SiO2 glass–ceramics/NiCuZn ferrite multi-layer composites. Several effective methods, such as sandwich stacking structure and sintering shrinkage modification, are proposed to prevent the camber problem due to the mismatched shrinkage during sintering process to fabricate high-frequency chip inductors that are composite by NiCuZn ferrite and dielectric glass ceramic.

High Q ‐factor NiCuZn ferrite with nanocrystalline ferrite particles and Co2O3 additives

AbstractThis work focuses on the effects of nanocrystalline ferrite particles (NFPs) on the sintering behaviour and magnetic properties of NiCuZn ferrite for multilayer chip inductor use. It was found that the NFPs could evidently improve the sintering behaviour of the ferrite because of their large surface free energy. Because the NFPs had the same chemical composition as the NiCuZn ferrite, samples with appropriate NFPs added could show better magnetic properties than samples with added Bi2O3. Also, to further increase the Q ‐factor of the NiCuZn ferrite, the effects of Co2O3 additive on the magnetic properties of the NFP‐added ferrite were studied. The results revealed that the permeability of the ferrite decreased monotonically due to added Co2O3; the Q ‐factor first increased and reached its peak with 0.2 wt% Co2O3 added, whereupon it began to decrease. With 30 wt% NFPs and 0.2 wt% Co2O3 additives, the NiCuZn ferrite showed a high Q ‐factor of more than 200. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

放射光を用いた銀電極によるフェライト格子歪の評価

The lattice constant of the NiZnCu ferrite was evaluated by X-ray diffraction using the synchrotron radiation source. In the experiment of the powder X-ray diffraction under pressure, the lattice constant shows the different values between the increment process and the decrement process. The behavior is similar to the change of the inductance under pressure. On the other hand, in the experiment of the mapping on the simplified multilayer chip inductor, the lattice constant depends on the sintering temperature and the location in the device. Moreover, Ag particles diffused from the Ag-conductor are found on the sample sintered at 920°C by Electron Probe Micro-Analysis. These results suggest that the lattice distortion of the NiZnCu ferrite caused by the stress from Ag-conductor and Ag-diffusion affects the magnetic permeability.

Comparison Between Experimental Measurements and Numerical Simulations of Spheromak Formation in SSPX

Data from a recently installed insertable magnetic probe array in the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper et al., Nucl. Fusion 39, 863 (1999)] is compared against NIMROD [C. R. Sovinec et al., J. Comp. Phys. 195, 355 (2004)], a full 3D resistive magnetohydrodynamic code that is used to simulate SSPX plasmas. The experiment probe consists of a linear array of chip inductors arranged in clusters that are spaced every 2 cm, and spans the entire machine radius at the flux conserver midplane. Both the experiment and the numerical simulations show the appearance, shortly after breakdown, of a column with a hollow current profile that precedes magnetic reconnection, a process essential to the formation of closed magnetic flux surfaces. However, there are differences between the experiment and the simulation in how the column evolves after it is formed. These differences are studied to help identify the mechanisms that eventually lead to closed-flux surfaces (azimuthally averaged) and flux amplification, which occur in both the experiment and the simulation.

Lattice distortion of NiZnCu ferrite co-fired with silver

In this study, the lattice distortion in the NiZnCu ferrite co-fired with silver (Ag) was evaluated by X-ray diffraction (XRD) using the synchrotron radiation source. The simplified multilayer chip inductor (MLCI) with ∼1.3 mm of width, ∼1.98 mm of length and ∼0.54 mm of height was fabricated by a conventional multilayering technique. Synchrotron experiments were carried out at BL10XU beam line in the SPring-8. It was found that the lattice constant of the ferrite varied depending on place and the value closer to the sample centre (closer to the internal Ag conductor) was larger than one from the edge. The ferrite co-fired at higher temperature also shows larger lattice constant than one at lower temperature. This result is an evidence to show that the lattice of the ferrite has been distorted through the co-firing with Ag and it is enhanced by the higher sintering temperature.