Relation Between High-Frequency Properties and Direction of Anisotropy Magnetic Field in Magnetic Thin Film for RF Inductor Applications

A relation between high-frequency properties, and angle theta of the easy axis in soft magnetic film and ac applied field was investigated in order to fabricate the film for RF spiral inductor without a localized EMI (Electro-Magnetic Interference). This relationship was measured using a soft CoFeSiO/SiO2 granular multilayer magnetic thin film and simulated by using LLG (Landau-Lifshitz-Gilbert) micromagnetic simulator. The measured and calculated frequency dependence of the film's complex relative permeability, mu(r)' and mu(r)'' compared well with 10% mean error. The real part of complex relative permeability mu(r)' was dependent on approximately sin(2) theta. The ferromagnetic resonance (FMR) frequency, f(r), and the FMR half-width, Delta f(r) were not dependent on the angle theta. They were estimated to be 2.54 GHz and 0.3 GHz, respectively. These results are significant for the design of various magnetic thin film spiral inductors in RF integrated circuits without localized EMI.ArticleIEEE TRANSACTIONS ON MAGNETICS. 48(11):4515-4517 (2012)journal articl

Carbonyl-Iron/Epoxy Composite Magnetic Core for Planar Power Inductor Used in Package-Level Power Grid

Our research objective is to realize the basic technology for a next generation package-level power grid (PLPG) for plural application large scale integrated circuits (LSIs). In this study, a carbonyl-iron powder (CIP)/epoxy composite magnetic core, for large-current power inductor used for the main dc-dc converter in the PLPG, has been fabricated and evaluated. 54 vol.%-CIP/epoxy composite core made by screen-printing had a relative permeability of 7.5 and loss tangent of about 0.03 at 100 MHz. The planar power inductor using composite core was fabricated and evaluated, which had a quasi closed magnetic circuit consisting of low permeability composite core and embedded 35-mu m-thick, two-turn copper spiral coil. The fabricated inductor with a 1-mm-square in size had 5.5 nH inductance, Q-factor of 15 at 100 MHz, and 18 m Omega dc coil resistance. Inductance was constant even when the superimposed dc current increased up to around 5.5 A.ArticleIEEE TRANSACTIONS ON MAGNETICS. 49(7):4172-4175 (2013)journal articl

Characterization of Tunable Magnetic Sensor Using Bias Magnetic Field of a Hard Magnetic Film Magnetized by Pulsed-Magnetic Field

A tunable magnetoresistance (MR) sensor with variable sensitivity and measuring range is fabricated and characterized. The sensor has been fabricated using a combination of Ni-Fe soft magnetic film, Fe-Co-Sm hard magnetic film. The sensor is placed in a magnetizing coil for the process of magnetizing the hard magnetic film. The sensitivity and the measuring range of the sensor are tuned by bias magnetic field produced by the magnetic poles of the hard magnetic film. The sensitivity change was about 60%, and the measuring range change was about 30% in the tunable MR sensor from the experimental results. The bias magnetic field is controlled by changing amplitude of the pulsed magnetic field in the magnetizing for the hard magnetic film. The control power for one time tuning is about 18 mu Wh.ArticleIEEE TRANSACTIONS ON MAGNETICS. 49(7):3854-3857 (2013)journal articl

Increase of QQ-Factor of RF Magnetic Thin Film Inductor by Introducing Slit-Patterned Magnetic Thin Film and Multiline-Conductor Spiral Coil

In order to increase Q-factor of radio-frequency (RF) magnetic thin film inductor integrated in chip-size-package RF-ICs, two schemes have been investigated experimentally. For suppressing the in-plane eddy current of the magnetic thin film, a slit-patterned structure was introduced, and it was found that the slit-patterned magnetic thin film is very effective for increasing Q-factor. On the other hand, for suppressing alternating current (ac) copper loss, a multiline-conductor spiral coil was introduced, and it was found that the multiline coil is effective for improving decrease of inductance at high frequencies. By introducing the two schemes, a maximum Q-factor of 18 at 1.5 GHz was obtained in a spiral inductor with a bottom slit-patterned CoFeSiO/SiO granular multilayer film and triple-line-conductor spiral coil.ArticleIEEE TRANSACTIONS ON MAGNETICS. 47(10):3196-3199 (2011)journal articl

Increase of Q-Factor of RF Magnetic Thin Film Inductor by Introducing Slit-Patterned Magnetic Thin Film and Multiline-Conductor Spiral Coil

In order to increase Q-factor of radio-frequency (RF) magnetic thin film inductor integrated in chip-size-package RF-ICs, two schemes have been investigated experimentally. For suppressing the in-plane eddy current of the magnetic thin film, a slit-patterned structure was introduced, and it was found that the slit-patterned magnetic thin film is very effective for increasing Q-factor. On the other hand, for suppressing alternating current (ac) copper loss, a multiline-conductor spiral coil was introduced, and it was found that the multiline coil is effective for improving decrease of inductance at high frequencies. By introducing the two schemes, a maximum Q-factor of 18 at 1.5 GHz was obtained in a spiral inductor with a bottom slit-patterned CoFeSiO/SiO granular multilayer film and triple-line-conductor spiral coil.ArticleIEEE TRANSACTIONS ON MAGNETICS. 47(10):3196-3199 (2011)journal articl

A Possibility of Magnetic Field Biasing Tunable Inductive Device Using a Hard Magnetic Film Magnetized by Pulsed-Magnetic Field

In this paper, the authors have proposed a possibility of a magnetic field biasing tunable inductive device. To confirm a new scheme, a tunable coplanar waveguide (CPW) resonator with a combination of soft magnetic thin film and hard magnetic film has been fabricated and evaluated. The magnetic pole of hard magnetic film can be controlled by magnetization using a pulsed magnetic field. A bias magnetic field is applied in the soft magnetic film from the magnetic pole of the hard magnet film. Consequently, permeability of the soft magnetic film can be controlled by changing amplitude of the pulsed magnetic field in the magnetizing for the hard magnetic film. A 20 mm long coplanar wave guide resonator has been fabricated using FeSiO/SiO2 granular multilayer film and FeCoSm amorphous hard magnetic film. From the experimental results, in case of using 0.2 mu m thick soft granular film, by changing amplitude of the 1 ms width current-pulse for magnetizing pulsed magnetic field for hard magnetic film, the maximum inductance change was up to 18%, and maximum change of the resonant frequency was 9.6%. The control energy for one time tuning was small enough (5.4 mu Wh).ArticleIEEE TRANSACTIONS ON MAGNETICS. 49(3):978-981 (2013)journal articl

Development of an Electromagnetic Wave Shielding Textile by Electroless Ni-Based Alloy Plating

A polyester nonwoven textile with Ni-based alloy coating was fabricated, and the effect of electromagnetic wave shielding was evaluated. The Ni-based was coated by electroless plating on the textile. The electromagnetic wave shielding effect of the textile with Ni-B coating was about 99.98% over the induction range of 6-13 GHz. Because the textile has thin, light, flexible, and breathable characteristics, it will be versatile for the various electromagnetic wave shielding applications.ArticleIEEE TRANSACTIONS ON MAGNETICS. 45(10):4173-4175 (2009)journal articl

Cross-Talk Suppression in High-Density Printed Circuit Boards Using Magnetic Composite Filled in Spacing Between Signal Lines

Recently, high-density printed circuit boards (HD-PCBs) with less than 50 mum/50 mum line/space has been developed. In the HD-PCB, since the spacing between adjacent signal lines becomes very small, the crosstalk electromagnetic interference among adjacent lines becomes serious. In general, in order to suppress the crosstalk, the ground line is located at the spacing between signal lines because of the decrease of mutual capacitance among adjacent signal lines. The authors have proposed a magnetic method for reducing the crosstalk. The composite magnetic material was filled in the spacing between signal lines instead of the ground line. The magnetic composite is composed of Fe-Si-B-Cr amorphous particles with a mean diameter of 6 mu m and epoxy resin. From the experiments using the PCB-TEG with a 130 mum/50 mum line/space and 25-mm line length, the crosstalk was suppressed in the wide frequency range by using the magnetic composite. In the case of using 51 vol.% amorphous composite, the crosstalk suppression was up to 20 dB around 1 GHz. The influence of the magnetic composite on the transmission and reflection in the main signal line was very small. Therefore, the proposed method is effective for crosstalk suppression without influence on the signal transmission.ArticleIEEE TRANSACTIONS ON MAGNETICS. 45(10):4801-4803 (2009)journal articl

Fabrication of Planar Power Inductor for Embedded Passives in LSI Package for Hundreds Megahertz Switching DC-DC Buck Converter

Recently, research and development of integrated low-voltage dc-dc converter to LSIs has been active. In order to realize such integrated dc power supply, power magnetic devices must be integrated in it. The authors have fabricated planar power inductor embedded in LSI package for hundreds megahertz switching dc-dc buck converter. In this study, two types of planar power inductors have been fabricated: one was spin-sprayed Zn-ferrite thick film magnetic core inductor, and the other was composite magnetic core (Fe-based amorphous/polyimide) inductor. Footprint of the fabricated inductors was 850 x 850 mu m(2), their inductance was about 10 nH, and the quality factor Q was about 20 at 100 MHz. The rating current which depends on the superimposed dc characteristic was at least up to 2 A.ArticleIEEE TRANSACTIONS ON MAGNETICS. 47(10):3204-3207 (2011)journal articl

Fabrication of Planar Power Inductor for Embedded Passives in LSI Package for Hundreds Megahertz Switching DC–DC Buck Converter

Recently, research and development of integrated low-voltage dc-dc converter to LSIs has been active. In order to realize such integrated dc power supply, power magnetic devices must be integrated in it. The authors have fabricated planar power inductor embedded in LSI package for hundreds megahertz switching dc-dc buck converter. In this study, two types of planar power inductors have been fabricated: one was spin-sprayed Zn-ferrite thick film magnetic core inductor, and the other was composite magnetic core (Fe-based amorphous/polyimide) inductor. Footprint of the fabricated inductors was 850 x 850 mu m(2), their inductance was about 10 nH, and the quality factor Q was about 20 at 100 MHz. The rating current which depends on the superimposed dc characteristic was at least up to 2 A.ArticleIEEE TRANSACTIONS ON MAGNETICS. 47(10):3204-3207 (2011)journal articl