JP2008098392A - Electromagnetic interference suppressor using soft magnetic powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic interference suppressor using a soft magnetic powder which can suppress suprious radiation noise easily in a wide band. <P>SOLUTION: The electromagnetic interference suppressor is made by pasting together two kinds of composite magnetic substances, each consisting of a soft magnetic powder which has either a flat or needlelike particle configuration and has a different average particle diameter and an aspect ratio, and organic binder, and therefore has at least two magnetic resonances provided by anisotropic magnetic fields (Hk) having a different magnitude. As for the soft magnetic powder, pure iron, iron-aluminum-silicon alloy, iron-nickel alloy, amorphus alloy, or the like which is powderized by pulverization is used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnetic interference suppressor using a soft magnetic powder made of an organic binder and a soft magnetic powder excellent in magnetic loss characteristics for suppressing noise disturbance caused by interference of unwanted radiation noise in a high frequency region.

  In recent years, the spread of highly integrated semiconductor elements that operate at high speed is remarkable. Examples include logic circuit elements such as random access memory (RAM), read only memory (ROM), microprocessor (MPU), central processing unit (CPU) or image processor arithmetic logic unit (IPALU). In these active elements, calculation speed and signal processing speed are increasing rapidly, and electric signals propagating through high-speed electronic circuits are accompanied by large fluctuations in voltage and current. It is easy to generate and becomes a high frequency unnecessary radiation noise source.

  On the other hand, electronic components and electronic devices are proceeding at a rapid pace without stopping the trend of lighter, thinner and smaller electronic devices. Along with this, the degree of integration of semiconductor elements and the density of electronic components mounted on a printed wiring board have become extremely high. Accordingly, electronic components, printed wiring, inter-module wiring, and the like are very close to each other, and in addition to the increase in the signal processing speed described above, high-frequency unnecessary radiation noise is more easily induced.

  There are methods such as using low-pass filters and shielding as countermeasures against noise in these high-speed, high-functionality, high-density electronic devices, and electromagnetic interference, especially in the quasi-microwave band. I was taken.

  However, noise countermeasures by providing components require a space for mounting, and it is difficult to reduce the size and thickness. In addition, the inductance component contributes to the real part permeability μ ′ and is insufficient for inductance in the current quasi-microwave band. Furthermore, when shielding is performed, secondary electromagnetic coupling may occur due to careless shielding.

  Therefore, the unnecessary radiation noise can be easily and effectively suppressed by installing the electromagnetic interference suppressing body in the vicinity of the unnecessary radiation noise source. This electromagnetic interference suppressor means that the shape magnetic anisotropy appears when the shape of the soft magnetic powder is made flat or needle-shaped, and the imaginary part permeability μ ”based on magnetic resonance is increased in the high frequency region. The mechanism of unnecessary radiation attenuation using the magnetic loss body is due to the addition of an equivalent resistance component to the electronic circuit that is the source of unnecessary radiation noise. know.

  Here, the size of the equivalent resistance component depends on the magnitude of the imaginary part permeability μ ″, and depends on the frequency range in which the noise suppression effect appears and the frequency dispersion of the imaginary part permeability μ ″. As described above, as an electromagnetic interference suppressor using a high real part permeability part μ ′ and an imaginary part permeability μ ”corresponding to the quasi-microwave band, it suppresses unnecessary radiation noise and performs secondary electromagnetic coupling. There are also provided composite magnetic bodies that can easily suppress electromagnetic interference, and that can suppress magnetic interference at lower frequencies by shifting magnetic resonance to the low frequency side.

Japanese Patent Laid-Open No. 7-212079 Japanese Patent Laid-Open No. 9-035927 JP 2001-210510 A

  However, as the above-mentioned electronic components and electronic devices have been improved in function and density, the frequency distribution of unnecessary radiation actually generated in various electronic circuits is almost quasi-micro. It covers a wide band from below the waveband to the quasi-microwave band. For this reason, the frequency dispersion of the steep imaginary part permeability μ "due to magnetic resonance found in ordinary soft magnetic materials cannot be sufficiently covered, and a noise suppression effect in a wide band cannot be expected. It is an object of the present invention to provide an electromagnetic interference suppressor for dealing with the effect, and a composite magnetic body here.The present invention eliminates unnecessary radiation noise generated from such semiconductor elements and electronic devices that operate at high speed. An object of the present invention is to provide an electromagnetic interference suppressor using a soft magnetic powder that can be easily suppressed in a wide band.

  In the present invention, two types of composite magnetic bodies composed of a soft magnetic powder having a flat or needle-like particle shape having different average particle diameters and aspect ratios and an organic binder are bonded to each other, thereby having different sizes. An electromagnetic interference suppressor using a soft magnetic powder having at least two magnetic resonances caused by an anisotropic magnetic field (Hk).

  The present invention is the electromagnetic interference suppressor, wherein the soft magnetic powder is at least one of iron, iron aluminum silicon alloy, iron nickel alloy, amorphous alloy, and iron oxide. The present invention is the electromagnetic interference suppressor in which the soft magnetic powder is oriented.

  A microstrip line with an impedance of 50Ω is used as a method for measuring transmission loss, but this is a widely used method for measuring near-surface noise transmission loss of surface-mounted components. Here, the transmission loss represents an effect of suppressing unnecessary radiation noise in the vicinity. FIG. 1 shows a schematic diagram of the microstrip line used. A linear conductor path is provided on the surface of the substrate, and the electromagnetic interference suppressing body 3 is disposed on the conductor path. Both ends of the conductor path are connected to a network analyzer, the reflection amount (S11) and the transmission (S21) are measured, and the transmission loss can be obtained by the following equation (1) from the difference between them.

Transmission loss [%] = {1-[(γ) ₂ + (τ) ₂ ]} × 100 (1)
Here, the reflection amount (S11) = 20 log | γ | and the transmission (S21) = 20 log | τ |. Further, γ is a voltage reflection coefficient, and τ is a voltage transmission coefficient.

  As described above, according to the present invention, it is possible to provide an electromagnetic interference suppressor using a soft magnetic powder that can suppress unwanted radiation noise in a wider band than a conventional electromagnetic interference suppressor.

  DESCRIPTION OF EMBODIMENTS Embodiments according to the present invention will be described below with reference to the drawings.

  Examples of the flat or needle-like soft magnetic material include those obtained by pulverizing pure iron, iron aluminum silicon alloy, iron nickel alloy, amorphous alloy, etc. by pulverization, stretching and tearing, or atomization granulation. .

  Further, iron oxide may be used, and examples thereof include spinel ferrite, planar ferrite, hematite, magnetite, and maghemite.

  On the other hand, the organic binder is preferably chlorinated polyethylene, which can obtain excellent flexibility and flame retardancy in consideration of use in the vicinity of an electronic circuit, but is not limited thereto. Polyester resin, polyethylene resin, polyvinyl chloride resin, polyvinyl butyral resin, polyurethane resin, cellulose resin, ABS resin, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene rubber, styrene-butadiene rubber, Thermosetting resins such as thermoplastic resins such as silicone rubber, thermoplastic elastomers, epoxy resins, phenol resins, amide resins, and imide resins can be used.

  The electromagnetic interference suppressor obtained by laminating green sheets prepared by mixing the soft magnetic material and the organic binder is preferably used as a thin sheet having a thickness of 10 to 100 μm. More preferably, it is 20-50 micrometers.

  Hereinafter, although the electromagnetic interference suppression body of the present invention will be described with reference to examples and comparative examples, the present invention is not limited to the following examples.

  As the soft magnetic material, an iron aluminum silicon alloy (Sendust) having a large high frequency permeability characteristic was used. Sendust is a raw material that has been flattened by mechanically pulverizing it in a solvent from a spherical or indefinite shape powdered state. As the soft magnetic material, Fe-Si-Al alloy having 9.5 wt% Si, 5.5 wt% Al, and the balance Fe composition was used. As the powder, powders having different resonance frequencies were produced by changing the pulverization conditions (time), and by changing the anisotropic magnetic field obtained by changing the powder shape factors such as the particle diameter and aspect ratio of the powder. The powder properties obtained this time are shown in Table 1.

  Next, the compositions shown in Table 2 were mixed using a mixer to prepare Sample 1 and Sample 2 composite magnetic material pastes. The pastes of Sample 1 and Sample 2 are formed in a predetermined thickness by directing the powder in the in-plane direction by the doctor blade method, respectively, and 1 and 2 shown in the explanatory diagram in FIG. A green sheet was prepared.

  The green sheet of sample 1 and the green sheet of sample 2 were bonded together to produce an implementation sample of the present invention. As an organic binder used for one component of the present invention, a chlorinated polyethylene resin is used, but other polyester resins, polyurethane resins, epoxy resins, etc., or copolymers thereof are similarly used. Since it can be molded, it is not limited to chlorinated polyethylene.

  Moreover, in order to compare with the product of the present invention, Comparative Examples 1 and 2 of the conventional product were added. The comparative product 1 is a property equivalent product of the sample 2 alone, and the comparison product 2 is a property equivalent product of the sample 1 alone.

  Next, the magnetic permeability (μ-f) characteristics of the produced composite magnetic material were measured using an RF impedance analyzer. FIG. 3 shows the permeability characteristic (μ-f) characteristic of the electromagnetic interference suppressor of the present invention. FIG. 4 shows the permeability (μ-f) characteristic of Comparative Example 1 in which the suppression effect at 100 MHz to 5 GHz of the conventional product is effective, and FIG. 5 shows the permeability of Comparative Example 2 in which the suppression effect is effective at 10 MHz to 3 GHz. Magnetic susceptibility (μ-f) characteristics are shown.

  FIG. 6 shows an outline of an evaluation apparatus for verifying the electromagnetic interference suppression effect of the composite magnetic material. Here, a square electromagnetic interference suppressing body 3 having a thickness of 0.5 mm and a side of 50 mm was installed. For the evaluation of the electromagnetic interference suppression effect, as a wave source element and a receiving element using the electromagnetic wave source transmitter 4, an electromagnetic field transmitting micro loop antenna 5 having a loop diameter of 1.5 mm and an electromagnetic field receiving micro loop are used. An antenna 6 was used, and a network analyzer 7 was used to measure the coupling attenuation level. Here, the coupling attenuation level is a signal attenuation when the difference between the presence and absence of the electromagnetic interference suppressor is used as a reference, and the larger the absolute value of the attenuation, the better the electromagnetic interference suppression effect. FIG. 7 shows the result of the coupling attenuation level comparing the electromagnetic interference suppressor of the present invention and the conventional product.

  Moreover, in order to confirm the electromagnetic suppression effect in a high frequency, the amount of reflection (S11) and the amount of transmission (S21) were measured using the network analyzer, and the transmission loss was confirmed. For transmission loss, the higher the transmission loss, the better the suppression effect. FIG. 8 shows the transmission loss result of the present invention compared with the conventional product. Table 3 shows a result of comparison between the electromagnetic interference suppressor of the present invention and a conventional product.

  From Table 3, the effects described below are clear. From the magnetic permeability (μ-f) characteristics of FIG. 3, the present invention has a wider range of μ ″ that has the effect of suppressing unwanted radiation noise than the conventional electromagnetic interference suppressor (FIGS. 4 and 5). In addition, even if the frequency band in which μ ″ is 10 or more is quantitatively confirmed, it can be confirmed that it is more widely distributed than the conventional electromagnetic interference suppressors (Comparative Example 1 and Comparative Example 2). . Therefore, it is clear that it can be suppressed in a wider band than before.

  Moreover, although the signal attenuation amount at 100 MHz to 300 MHz is slightly inferior to the comparative example 2 of the conventional product, the attenuation amount is higher than that of the comparative example 1. In addition, as a result of transmission loss at 500 MHz to 2 GHz, there is a loss equal to or higher than that of Comparative Example 1 and slightly inferior to that of Comparative Example 2 at 500 MHz, but the loss of the present invention is higher at 1.5 GHz or higher. Can be confirmed. From the above results, it is clear that the suppression effect of the present invention is more effective in a wider band than the conventional electromagnetic interference suppression body.

The schematic of the microstrip line used when measuring the transmission loss in this invention. In this invention, explanatory drawing which bonds a green sheet together. The magnetic permeability ((micro | micron | mu) -f) characteristic view of this invention. The magnetic permeability ((micro | micron | mu) -f) characteristic view of the comparative example 1. FIG. The magnetic permeability (μ-f) characteristic diagram of Comparative Example 2. The schematic diagram of the evaluation apparatus for verifying the electromagnetic interference suppression effect of a composite magnetic body in this invention. The coupling attenuation level characteristic figure of this invention and the comparative example 1 and the comparative example 2. FIG. The transmission loss characteristic figure of this invention and the comparative example 1 and the comparative example 2. FIG.

Explanation of symbols

1 Green Sheet 2 of Sample 1 Green Sheet 3 of Sample 2 Electromagnetic Interference Suppressor 4 Transmitter for Electromagnetic Wave Source 5 Micro Loop Antenna for Electromagnetic Field Transmission 6 Micro Loop Antenna for Electromagnetic Field Reception 7 Network Analyzer

Claims (3)

  Anisotropic magnetic fields with different magnitudes can be obtained by laminating two types of composite magnetic materials composed of soft magnetic powders having flat or needle-like particle shapes with different average particle diameters and aspect ratios and organic binders. An electromagnetic interference suppressor using soft magnetic powder, characterized by having at least two magnetic resonances provided by (Hk).   The electromagnetic interference using the soft magnetic powder according to claim 1, wherein the soft magnetic powder is at least one of iron, iron aluminum silicon alloy, iron nickel alloy, amorphous alloy, and iron oxide. Suppressor.   The electromagnetic interference suppressor using the soft magnetic powder according to claim 1, wherein the soft magnetic powder is oriented.

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