JP4843612B2 - Soft magnetic film, anti-electromagnetic wave component and electronic device using the same - Google Patents

Description

  The present invention relates to a soft magnetic film, an electromagnetic wave countermeasure component using the same, and an electronic device.

  In recent years, there has been remarkable progress in the development of portable communication devices, and in particular, mobile phones have been rapidly reduced in size, weight and thickness. In connection with these, the installation position of the antenna in a mobile phone or the like has come closer to a human head or other electronic devices that are vulnerable to noise. For this reason, the interaction between the antenna and the human head or other electronic devices is a problem.

  In a mobile phone, a part of radio waves radiated from an antenna is absorbed by the closest human head and the rest is radiated into space. Based on the absorption of electromagnetic energy by the human head, the radiation efficiency and communication characteristics of the antenna are degraded. Furthermore, since the antenna is close to the head when the mobile phone is used, the head is locally exposed to a strong electromagnetic field, and there is a concern about the influence on the human body due to an increase in the amount of local power absorption. For this reason, a radio wave local absorption guideline (local power absorption amount per unit weight: SAR) for mobile phones has been set one after another in the United States, Europe, and Japan.

  From such a background, in a portable communication device represented by a mobile phone, it is desired to reduce the amount of electromagnetic energy absorbed by the human body (for example, the amount of electromagnetic energy exposed to the human head). Furthermore, with the increase in the number of functions of portable communication devices, the transmission / reception signal has been made into a plurality of frequencies and a multi-system. For this reason, there are cases in which transmission and reception are performed simultaneously with a plurality of antennas. When a plurality of antennas are used simultaneously, interference between adjacent antennas becomes a problem. Furthermore, the need for an electromagnetic wave absorber is increasing in various fields, not limited to the field of portable communication devices (see, for example, Patent Document 1).

  As a technique for reducing the electromagnetic field level generated in the vicinity of an antenna, it is known to dispose a composite magnetic body containing a soft magnetic powder and an organic binder at the antenna base of a mobile phone (for example, Patent Document 2). 3). Here, electromagnetic waves are consumed as heat loss by utilizing the fact that the magnetic permeability μ ″ (imaginary component of the complex magnetic permeability μ) of the composite magnetic material suddenly rises in the vicinity of the operating frequency. However, there is a problem that the electromagnetic field level in the vicinity of the antenna is lowered, so that the signal strength of the transmission signal is lowered.

  In contrast, according to the soft magnetic film in which the real component μ ′ of the complex permeability μ in the high frequency region is increased, the electromagnetic wave in the unnecessary direction of the radiated electromagnetic wave is suppressed while suppressing the decrease of the transmitted signal intensity. The field strength can be effectively reduced. In order to realize a large μ ′ in the high frequency region, it is effective to increase the ferromagnetic resonance frequency by adding shape anisotropy to the anisotropy inherent to the material of the soft magnetic film, for example. As a method for imparting shape anisotropy to a soft magnetic film, a method of forming a soft magnetic film on a base provided with a concave portion and a convex portion is known. Also, a method is known in which a magnetic domain of a soft magnetic film is controlled by providing a slit-like groove on a polymer film and forming a soft magnetic film thereon (see Patent Document 4).

  However, the method using a base having a concave portion and a convex portion requires a base having a low degree of freedom in shape and a certain volume, and therefore can be freely installed in a small device such as a mobile phone. It is not possible to obtain possible electromagnetic wave countermeasure parts. In the method using a polymer film having a slit-like groove, the magnetic material is planarly separated by the groove. Therefore, a gap is generated between the magnetic materials, and electromagnetic waves leak. This cannot be used effectively as an electromagnetic wave countermeasure component. Furthermore, there is a problem in that chipping or chipping tends to occur at the edge portion when grooves are formed in the polymer film. These are factors that reduce the controllability of the magnetic domains.

A method of punching or etching a magnetic thin film formed by a vapor deposition method such as a vacuum deposition method or a sputtering method into a predetermined size and shape is also known. However, when punching is applied, a strained structure remains, and an etching process leaves a corrosive structure. As a result, there is a problem in that the structure of the magnetic thin film is disturbed and the soft magnetic properties are deteriorated. Further, in the case of a laminated film of a magnetic film and an insulating film, there is a problem that if the film is processed after the film formation, the cross section of the film is exposed and the magnetic film is oxidized or deteriorated to easily disturb the magnetic domain.
JP 2002-076681 A JP 2002-158484 A JP 2001-200305 A JP 2004-015038 A

  An object of the present invention is to provide a soft magnetic thin film that can effectively impart shape anisotropy to the soft magnetic thin film without causing a decrease in the degree of freedom in shape, an increase in volume, and a separation of planar magnetic materials. An object is to provide a magnetic film, an electromagnetic wave countermeasure component and an electronic device using the magnetic film.

A soft magnetic film according to an embodiment of the present invention includes a base film having a bent shape in which a plurality of concave and convex portions are repeatedly provided, and at least a top surface of a convex portion and a bottom surface of a concave portion of the base film. A thin film comprising a soft magnetic thin film having a discontinuous portion of the product of permeability μ ′ and film thickness T , wherein the base film has a repetition period of the concave and convex portions of 1000 μm or less. It is said.

  An electromagnetic wave countermeasure component according to another aspect of the present invention includes the soft magnetic film according to the aspect of the present invention. An electronic device according to still another aspect of the present invention is an electromagnetic wave countermeasure component including an electronic device main body having an electromagnetic wave transmission unit and a soft magnetic film according to an aspect of the present invention, and the electromagnetic wave radiated from the electromagnetic wave transmission unit And an electromagnetic wave countermeasure component arranged so as to selectively reduce the electromagnetic field strength with respect to the unnecessary direction.

It is sectional drawing which shows the structure of the soft-magnetic film by embodiment of this invention. It is a perspective view which shows the structural example of the base film of the soft-magnetic film shown in FIG. It is sectional drawing which shows the structural example of the soft-magnetic thin film applied to the soft-magnetic film by embodiment of this invention. It is sectional drawing which shows the modification of the soft-magnetic film shown in FIG. It is a figure for demonstrating the collimation sputtering applied to preparation of the soft-magnetic film by embodiment of this invention. It is sectional drawing which shows the structural example of the soft-magnetic thin film formed by applying collimation sputtering. It is sectional drawing which shows the further another modification of the soft-magnetic film shown in FIG. It is a front view which shows schematic structure of the mobile telephone by embodiment of this invention. It is a reverse view of the mobile phone shown in FIG.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 1 ... Soft magnetic film, 2 ... Soft magnetic thin film, 3 ... Base film, 4 ... Convex part, 5 ... Concave part, 10 ... Mobile phone, 16 ... Antenna, 18 ... Electromagnetic wave countermeasure component.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, modes for carrying out the present invention will be described. FIG. 1 is a cross-sectional view showing a configuration of a soft magnetic film according to an embodiment of the present invention. A soft magnetic film 1 shown in FIG. 1 has a base film 3 serving as a base for forming a soft magnetic thin film 2. As shown in FIG. 2, the base film 3 has a bent shape in which a plurality of concave and convex portions are repeatedly provided. For example, when the base film 3 is viewed from one side (A surface / upper surface in the figure), the flat resin film is bent so that the convex portions 4A and the concave portions 5A are sequentially formed. have.

  The base film 3 is used as a base material for forming the soft magnetic thin film 2. The surface on which the soft magnetic thin film 2 is formed may be both surfaces (A surface (upper surface in the drawing) and B surface (lower surface in the drawing)) of the base film 3, or any one surface (A surface or B surface). It is good only as well. When the soft magnetic thin film 2 is formed on both sides of the base film 3, the other side (B side / lower side in the figure) side of the base film 3 is also opposite to the convex part 4A and the concave part 5A on the A side. Thus, the convex portion 4B and the concave portion 5B are repeatedly formed in order.

  About the shape of the uneven | corrugated | grooved part provided to the base film 3, it is preferable that the level | step difference d (the height of convex part 4A, 4B and the depth of recessed part 5A, 5B) of an uneven | corrugated part shall be 1 micrometer or more. When the unevenness d is less than 1 μm, the shape anisotropy of the soft magnetic thin film 2 formed on the base film 3 cannot be sufficiently increased. It is more preferable that the unevenness portion has a step d of 3 μm or more. However, since the formability of the soft magnetic thin film 2 is deteriorated even if the step d of the concavo-convex portion is made too high, the step d of the concavo-convex portion is preferably 100 μm or less.

  The repetition period p of the concavo-convex portion is preferably 1000 μm or less. The width w1 of the top surfaces of the convex portions 4A and 4B and the width w2 of the bottom surfaces of the concave portions 5A and 5B are preferably 500 μm or less, respectively. The widths w1 and w2 do not have to be the same, and the widths w1 and w2 may be partially different. When the repetition period p of the concavo-convex portion exceeds 1000 μm, the shape anisotropy of the soft magnetic thin film 2 cannot be sufficiently increased. The same applies when the widths w1 and w2 exceed 500 μm. However, if the repetition period p of the concavo-convex part is too small, the formability of the soft magnetic thin film 2 is lowered. The widths w1 and w2 are preferably 2 μm or more.

  The base film 3 having such a bent shape can be obtained, for example, by sandwiching a thermoplastic resin film with a pair of upper and lower molds having a shape corresponding to a desired uneven portion and heat compression molding. As the base film 3, it is preferable to apply a thermoplastic resin film excellent in mechanical strength and heat resistance. Examples of such resin films include thermoplastic polyimide resins (for example, polyamideimide resins and polyetherimide resins), polyethylene resins, polystyrene resins, polyester resins, polyvinyl chloride resins, polyurethane resins, polyolefin resins, polycarbonate resins, and the like. Is mentioned.

  The thickness of the resin film applied to the base film 3 may be such that, for example, a desired uneven portion can be formed by heat compression molding and the strength that can withstand the formation of the soft magnetic thin film 2 can be maintained. Good. Specifically, it is preferable to use a resin film having an average thickness of 7 to 200 μm. If the thickness of the resin film is less than 7 μm, although it depends on the material strength, the soft magnetic thin film 2 is easily deformed and the shape of the soft magnetic thin film 2 becomes unstable. On the other hand, when the thickness of the resin film exceeds 200 μm, the thickness as the soft magnetic film 1 increases, which tends to cause an increase in installation volume and a decrease in shape flexibility. The heat compression moldability of the resin film also decreases.

  The soft magnetic thin film 2 is formed on both surfaces (or one surface) of a base film 3 having a bent shape. The soft magnetic thin film 2 includes a CoZrNb-based amorphous alloy film, a CoZrNbTa-based amorphous alloy film, a FeBN-based heteroamorphous film, a CoFeB-SiO-based high electrical resistance film, a CoFeAlO-based nanogranular film, a CoAlPdO-based high electrical resistance film, and a CoFeMn-based fine film. Various Co-based or Fe-based soft magnetic alloy films such as a crystal film, a CoFeN-based soft magnetic film, and a FeNi-based soft magnetic film can be used. The microstructure of the soft magnetic film is not particularly limited, and may be any of an amorphous structure, a heteroamorphous structure, a granular structure, a microcrystalline structure, a crystalline structure, and the like.

  The thickness T of the soft magnetic thin film 2 is preferably 3 μm or less. If the thickness T of the soft magnetic thin film 2 exceeds 3 μm, although depending on the level difference d of the concavo-convex portion, there is a possibility that the shape anisotropy cannot be satisfactorily imparted, and the high-frequency magnetic characteristics are also deteriorated. The soft magnetic thin film 2 is not limited to a single layer film, and may be a laminated film as shown in FIG. The soft magnetic thin film 2 shown in FIG. 3 has a laminated film in which a plurality of magnetic layers 7 are laminated via a nonmagnetic insulating layer 6. According to the laminated soft magnetic thin film 2, high frequency magnetic characteristics can be improved. When the laminated structure is applied, the thickness T as a single layer of each magnetic layer 7 is preferably in the range of 0.1 to 1 μm.

  When the soft magnetic thin film 2 is formed by applying a directivity film forming method such as sputtering or vapor deposition, the film thickness of the portion formed on the top surface of the convex portion 4 and the bottom surface of the concave portion 5 of the base film 3 A difference arises between the film thickness of the part formed on the wall surface which connects the convex part 4 and the recessed part 5. FIG. For this reason, even if the soft magnetic thin film 2 is continuous as a film shape, it is magnetically discontinuous. Specifically, the soft magnetic thin film 2 has a portion where the product (P value) of the magnetic permeability μ ′ (the real component of the complex magnetic permeability μ) and the film thickness T is discontinuous. The method for forming the soft magnetic thin film 2 is not limited to a vapor phase growth method (PVD method) such as a sputtering method or a vapor deposition method, and any film forming method capable of causing a difference in film thickness may be used. The soft magnetic thin film 2 may be formed by applying a CVD method, a thermal spraying method, a plating method, or the like.

  As described above, the soft magnetic thin film 2 is in a state in which the portion formed on the top surface of the convex portion 4 of the base film 3 and the portion formed on the bottom surface of the concave portion 5 are magnetically separated. According to such a soft magnetic thin film 2, it is possible to obtain the same shape anisotropy as when the soft magnetic thin films are individually formed on the top surface of the convex portion 4 and the bottom surface of the concave portion 5. Therefore, shape anisotropy can be effectively imparted to the soft magnetic thin film 2. Here, FIG. 1 and FIG. 2 show the base film 3 in which the bending angle θ for forming the concavo-convex portion is about 90 ° (for example, 85 ° to 95 °), but the bending angle θ is limited to this. It is not something that can be done.

  The bending angle θ of the concavo-convex portion of the base film 3 may be an acute angle as shown in FIG. 4, for example. In this case, the bending angle θ is preferably 10 ° or more and less than 90 °, and more preferably 30 ° or more and 70 ° or less. If the bending angle θ is less than 10 °, the formability of the soft magnetic thin film 2 with respect to the bottom surface of the recess 5 is lowered, and the planar continuity of the soft magnetic thin film 2 may be lowered. In addition, the shape stability of the base film 3 is also reduced. The base film 3 having an acute fold angle θ can be obtained by compressing a film formed with a fold angle θ of about 90 ° in the direction in which the concavo-convex portion is repeated.

  According to the base film 3 having the bending angle θ as an acute angle, when the soft magnetic thin film 2 is formed by a sputtering method or the like, a shadow is formed on the flying direction of the film formation particles. Separation between the portion formed on the surface and the portion formed on the bottom surface of the recess is enhanced. This increases the shape anisotropy of the soft magnetic thin film 2. As shown in FIG. 4, the soft magnetic thin film 2 only needs to be formed on at least the top surface of the convex portion 4 and the bottom surface of the concave portion 5 of the base film 3, and the convex portion 4 and the concave portion 5 are separated. May be. That is, the soft magnetic thin film 2 may not be deposited as a continuous film on the wall surface connecting the convex portion 4 and the concave portion 5.

  Even if the portion formed on the top surface of the convex portion 4 of the soft magnetic thin film 2 and the portion formed on the bottom surface of the concave portion 5 are separated, the film is almost uniform when viewed in plan. Therefore, it can function effectively as an electromagnetic wave countermeasure component. 4 shows the case where the soft magnetic thin film 2 is formed on only one surface of the base film, the shape of the soft magnetic thin film 2 when it is formed on both surfaces, and the action and effect based on the shape are the same. is there. The same applies to FIGS. 6 and 7 shown below.

  As described above, the base film 3 with the bending angle θ of the concavo-convex portion being an acute angle separates the portion formed on the top surface of the convex portion 4 and the portion formed on the bottom surface of the concave portion 5 of the soft magnetic thin film 2. It is effective in making it happen. However, when the soft magnetic film 1 is used as an electromagnetic wave countermeasure component, the bending angle θ is preferably about 90 ° (for example, 85 ° to 95 °) in consideration of the shape stability of the base film 3 and the like. There is a case. For such a point, it is effective to apply collimation sputtering in which a slit (solar slit) is disposed between the sputtering target and the film formation material (here, the base film 3).

  FIG. 5 schematically shows the formation state of the soft magnetic thin film 2 to which collimation sputtering is applied. In FIG. 5, T is a sputter target, M is a film forming material (base film 3), and C is a collimator disposed between the sputter target T and the film forming material M. The collimator C has a plurality of slits S arranged in parallel to the flying direction of the sputtered particles sputtered from the sputter target T. Since the flying angle of the sputtered particles is limited by the collimator C, the sputtered particles fly and accumulate in a state closer to the deposition target material M. That is, the straightness of the sputtered particles can be improved.

  As shown in FIG. 6, even when the base film 3 having a bending angle θ of about 90 ° (for example, 85 ° to 95 °) is used, the soft magnetic thin film 2 is formed by applying collimation sputtering. Thus, the portion formed on the top surface of the convex portion 4 and the portion formed on the bottom surface of the concave portion 5 can be separated. That is, it is possible to prevent the soft magnetic thin film 2 from being deposited as a continuous film on the wall surface connecting the convex portion 4 and the concave portion 5. According to such a soft magnetic thin film 2, shape anisotropy can be increased more neatly. The separability of the soft magnetic thin film 2 can be controlled by the shape of the slit S (ratio of the slit width s to the slit length D).

  The bending angle θ of the concavo-convex portion of the base film 3 may be an obtuse angle as shown in FIG. 7, for example. In this case, the bending angle θ is preferably more than 90 ° and less than 135 °. When the bending angle θ exceeds 135 °, the continuity of the soft magnetic thin film 2 becomes strong and the shape anisotropy decreases. Such a base film 3 is obtained by extending a film formed with a bending angle θ of about 90 ° in the repeating direction of the concavo-convex portion, or by making the mold angle at the time of film forming or film processing an obtuse angle. be able to.

  Even when the soft magnetic thin film 2 is formed on the base film 3 with an obtuse bending angle θ, the film thickness of the portions formed on the top surface of the convex portion 4 and the bottom surface of the concave portion 5 of the soft magnetic thin film 2 is as follows. Since it becomes thicker than the part formed on the wall surface which connects the convex part 4 and the recessed part 5, the magnetically discontinuous soft-magnetic thin film 2 can be obtained. Furthermore, since the continuity of the soft magnetic thin film 2 as the film shape is improved, it is possible to suppress deterioration of the magnetic characteristics of the soft magnetic thin film 2 and the like.

  However, if the bending angle θ of the concavo-convex portion is too large, the magnetic continuity of the soft magnetic thin film 2 becomes strong and the shape anisotropy is lowered. In order to obtain the shape anisotropy based on the magnetic discontinuity of the soft magnetic thin film 2, the permeability μ ′ of the portion formed on the top surface of the convex portion 4 of the soft magnetic thin film 2 and the film thickness T The ratio (P2 / P1) of the product (P2 value) of the permeability μ ′ of the portion formed on the wall surface connecting the convex part 4 and the concave part 5 to the product (P1 value) and the film thickness T is 0.7 or less. It is preferable to set the bending angle θ of the concavo-convex portion so that When the P2 / P1 ratio of the soft magnetic thin film 2 exceeds 0.7, the magnetic continuity increases and the shape anisotropy of the soft magnetic thin film 2 decreases.

  The P2 / P1 ratio of the soft magnetic thin film 2 is not limited to the case where the fold angle θ of the concavo-convex part is an obtuse angle, but when the fold angle θ is about 90 ° (for example, 85 ° to 95 °) or an acute angle (for example, 10 This is also the case when the angle is greater than 90 ° and less than 90 °. Therefore, regardless of the bending angle θ of the concavo-convex portion, the convex portion 4 with respect to the product (P1 value) of the permeability μ ′ and the film thickness T of the portion formed on the top surface of the convex portion 4 of the soft magnetic thin film 2 The product (P2 value) of the magnetic permeability μ ′ and the film thickness T of the portion formed on the wall surface connecting the recess 5 is preferably 0.7 or less, and more preferably 0.5 or less.

  As described above, the bending angle θ of the uneven portion of the base film 3 is typically about 90 ° (for example, 85 ° to 95 °). The bending angle θ is not limited to 90 °, and may be an acute angle or an obtuse angle. Specifically, the bending angle θ of the base film 3 is preferably in the range of 10 ° to 135 °. The bending angle θ is more preferably in the range of 30 ° to 120 °.

  A soft magnetic thin film provided with shape anisotropy without causing a gap when the soft magnetic thin film 2 is viewed in plan by using a base film 3 having a bent shape in which a plurality of concave and convex portions are repeatedly provided. The soft magnetic film 1 having 2 can be obtained. Further, the processing of the end portion of the soft magnetic thin film 2, the structure based on the processing, the disturbance of the magnetic domain, and the like are not caused. Such a soft magnetic film 1 can be effectively used as an electromagnetic wave countermeasure component.

  In the soft magnetic film 1 of this embodiment, since the shape anisotropy is obtained at the portions formed on the top surface of the convex portion 4 and the bottom surface of the concave portion 5 of the soft magnetic thin film 2, when viewed in plan Does not cause a gap in the soft magnetic thin film 2. Therefore, leakage of electromagnetic waves can be suppressed. Furthermore, the soft magnetic thin film 2 is not deteriorated in soft magnetic properties based on the end shape, processing state, and the like. That is, it is possible to effectively impart shape anisotropy to the healthy soft magnetic thin film 2. Since the soft magnetic film 1 itself is flexible and can be thinned, the degree of installation freedom can be improved and the installation volume can be reduced. According to the electromagnetic wave countermeasure component including the soft magnetic film 1, it is possible to effectively reduce the electromagnetic field strength in the unnecessary direction of the radiated electromagnetic wave.

  The effect of reducing the electromagnetic field strength in the unnecessary direction by the electromagnetic wave countermeasure component will be described in detail. According to the soft magnetic thin film 2 of this embodiment, in addition to the anisotropy inherent to the material, shape anisotropy is imparted based on the base film 3 having a plurality of uneven portions. The ferromagnetic resonance frequency fr can be increased based on the material-specific anisotropy and shape anisotropy of the soft magnetic thin film 2.

Here, the ferromagnetic resonance frequency fr is expressed by the following equation.
fr = r / 2π (H _keff · N _dz · M _s / μ ₀ ) ^1/2
H _keff = H _kmat + H _ext. + (N _dy −N _dx ) · M _s / μ ₀
(Where r is the gyromagnetic constant (= μ · e / 2 · me), N _dz is the demagnetizing factor in the sample thickness direction, N _dx is the demagnetizing factor in the sample longitudinal direction, and N _dy is the sample width direction. _{Demagnetizing} factor, H _kmat is anisotropy depending on material composition and residual stress, H _ext. Is an external magnetic field applied to the sample, μ ₀ = 4π × 10 ⁻⁷ , me = 9.1091 × 10 ⁻³¹ [ kg], e = 1.60210 × 10 ⁻¹⁹ [C])

  By increasing the above-described ferromagnetic resonance frequency fr, it is possible to maintain a large magnetic permeability μ ′ (real component of the complex magnetic permeability μ) in the low frequency region up to the high frequency region. That is, a large μ ′ can be obtained in the high frequency region. On the other hand, the imaginary component μ ″ of the complex magnetic permeability μ is extremely small even in the high frequency region. The ferromagnetic resonance frequency fr of the soft magnetic thin film 2 is 1.5 times or more, more preferably 2 times or more of the transmission band frequency. By using such a soft magnetic thin film 2 as an electromagnetic wave countermeasure component, the emitted electromagnetic wave can be guided in a desired direction through the magnetic circuit by the soft magnetic thin film 2. Thereby, the emitted electromagnetic wave It is possible to effectively reduce the electromagnetic field strength in the unnecessary direction.

  Here, although the frequency bands of mobile phones and the like are diverse, the transmission band that is particularly problematic in the electromagnetic wave intensity (SAR) absorbed by the human body is in the range of 824 MHz to 1980 MHz. In such a high frequency region (up to 2 GHz), the conventional electromagnetic wave absorber does not have sufficient μ ′, whereas the soft magnetic film 1 of this embodiment has an anisotropic shape of the soft magnetic thin film 2. Since the magnetic resonance frequency fr is increased by increasing the property, a large μ ′ in the low frequency region can be realized also in the high frequency region. Therefore, the electromagnetic wave can be guided in a desired direction by the magnetic circuit using the soft magnetic thin film 2.

  Further, by increasing the ferromagnetic resonance frequency fr of the soft magnetic thin film 2, μ ″ in the high frequency region is reduced. Therefore, loss due to heat loss of the electromagnetic wave can be reduced. Electromagnetic waves are consumed as heat loss based on the large μ ″. Since the soft magnetic film 1 of this embodiment has reduced loss due to heat loss of electromagnetic waves, it is possible to suppress, for example, a decrease in the signal strength itself of the electromagnetic waves.

  The soft magnetic film 1 of the embodiment described above is effectively used as an electromagnetic wave countermeasure component, for example. The electromagnetic wave countermeasure component according to the embodiment of the present invention includes the soft magnetic film 1 of the above-described embodiment. An embodiment of an electronic apparatus to which such an electromagnetic wave countermeasure component is applied will be described with reference to FIGS. 8 and 9. FIG. 8 is a front view showing a configuration of an embodiment in which the electronic apparatus of the present invention is applied to a mobile phone, and FIG. 9 is a rear view thereof. The folding-type mobile phone 10 shown in these drawings has a structure in which a lower housing 11 and an upper housing 12 are rotatably connected via a hinge portion 13.

  The lower housing 11 houses a circuit board 14 on which a transmission circuit, a reception circuit, a switching circuit, a control circuit, and the like are mounted, and an input keypad 15 is disposed on the surface thereof. Further, the lower housing 11 includes an antenna 16 as an electromagnetic wave transmission unit, and wireless signals (electromagnetic waves) including various data such as voice data, character data, and image data are transmitted and received from the antenna 16. The antenna 16 is connected to the transmission circuit and the reception circuit via antenna wiring or the like provided on the circuit board 14. The upper housing 12 has a display unit 17 such as a liquid crystal display device.

  An electromagnetic wave countermeasure component 18 made of the soft magnetic film 1 is disposed in the vicinity of the antenna 16 serving as an electromagnetic wave transmitter. Specifically, the electromagnetic wave countermeasure component 18 is disposed between the antenna wiring by the circuit board 14 and the surface (surface having the keypad 15 or the like) facing the human body side of the lower housing 11. That is, the electromagnetic wave countermeasure component 18 arranged in the lower housing 11 is interposed between the human head, the antenna 16 and the antenna wiring in the vicinity thereof. The electromagnetic wave countermeasure component 18 is composed of the soft magnetic film 1 of the above-described embodiment.

  In the electromagnetic wave countermeasure component 18 in this embodiment, the ferromagnetic resonance frequency fr of the soft magnetic thin film 2 is high (for example, 1.5 times or more of the transmission band frequency), so that the permeability μ ′ at the transmission band frequency of the mobile phone 10 is increased. large. According to the electromagnetic wave countermeasure component 18 having such a soft magnetic thin film 2, the electromagnetic waves radiated from the antenna 16 and the antenna wiring to the human head side are guided upward or downward via the magnetic circuit of the soft magnetic thin film 2. Can do. That is, the electromagnetic field intensity in the space where the human head is arranged is reduced. It is preferable to set the repetition period p of the concavo-convex portion of the base film 3 based on the operating frequency and the material specific anisotropy of the soft magnetic thin film 2.

  As described above, by using the electromagnetic wave countermeasure component 18 including the soft magnetic thin film 2 having a large μ ′ in the frequency band (for example, a region up to 2 GHz) of the mobile phone 10, unnecessary radiation emitted to the human head side is unnecessary. It becomes possible to reduce the intensity of electromagnetic waves. Furthermore, since the μ ″ in the high frequency region is reduced by increasing the ferromagnetic resonance frequency fr of the soft magnetic thin film 2, loss due to heat loss can be reduced. With these, the signal intensity transmitted from the mobile phone 10 can be reduced. While suppressing the decrease, it is possible to effectively reduce the intensity of electromagnetic waves radiated in unnecessary directions, in other words, the electromagnetic field intensity of the space where the human head is arranged.

  In the above-described embodiment, an example in which the electronic device of the present invention is applied to a mobile phone has been described. However, the present invention is not limited to this, and can be applied to various portable communication devices. Furthermore, the space for reducing the electromagnetic field strength is not limited to the space where the human head is arranged. The electromagnetic wave countermeasure component of the present invention is a reduction in electromagnetic field strength in a space where other electronic devices that are vulnerable to noise (for example, a camera component for a mobile phone) are arranged, and between a plurality of antennas having different frequencies and methods of transmission / reception signals. It also functions effectively for suppressing interference. Therefore, the present invention is applicable to various electronic devices having an electromagnetic wave transmission function.

  Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1
First, a polyimide resin film having a thickness of 25 μm is prepared, and this is sandwiched between molds and subjected to heat compression molding (for example, using a nanoimprint apparatus manufactured by Itricks), whereby a base having a bent shape as shown in FIG. A material film was prepared. The length L parallel to the longitudinal direction of the uneven portion of the base film was 20 mm. Further, the shape of the concavo-convex portion of the base film was such that the width w1 of the top surface of the convex portion and the width w2 of the bottom surface of the concave portion were 100 μm, the repetition period p of the concavo-convex portion was 200 μm, and the step d was 4 μm. The bending angle θ of the uneven portion was 90 °.

After the above polyimide resin base film was washed with acetone, a laminated soft magnetic thin film was formed on both sides of the base film as follows. First, a 0.03 μm thick SiO ₂ film and a 0.01 μm thick Ti film were sequentially formed on a base film by RF sputtering and DC sputtering. A laminated soft magnetic thin film was formed on both surfaces of the base film by alternately laminating a 0.5 μm thick FeCoZrSiO film and a 0.05 μm thick SiO ₂ film on such a base film. The number of these layers was four on both sides.

An RF magnetron sputtering apparatus was used for forming the FeCoZrSiO film. As a sputtering target, 20 SiO ₂ chips (10 mm × 10 mm × 2.3 mm) were formed on an erosion pattern of a disk-shaped alloy target having a diameter of 125 mm × thickness of 3 mm having a composition of Fe ₆₈ Co ₁₇ Zr ₁₅ (atomic%). ) Was used evenly. Using such a sputter target, four layers of FeCoZrSiO film (thickness: 0.5 μm) were sequentially stacked via a SiO ₂ film (thickness: 0.05 μm). The input power during the formation of the soft magnetic film was 3.3 W / cm ² , the target-substrate distance was 75 mm, and the argon pressure was 3.2 Pa (500 SCCM). A permanent magnet was arranged so that a magnetic field of 1.6 × 10 ³ A / m was applied in the longitudinal direction of the uneven portion during film formation.

In this manner, a laminated soft magnetic thin film was formed on both surfaces of a base film having a plurality of uneven portions to produce a soft magnetic film. The structure of the soft magnetic film is [(SiO ₂ film (0.05 μm) / FeCoZrSiO film (0.5 μm)) ₄ / Ti film (0.01 μm) / SiO ₂ film (0.03 μm) // Polyimide resin base Material film (25 μm) // SiO ₂ film (0.03 μm) / Ti film (0.01 μm) / (FeCoZrSiO film (0.5 μm) SiO ₂ film (0.05 μm)) ₄ ].

  When the magnetic properties of the soft magnetic film were measured, the ferromagnetic resonance frequency fr was 3 GHz or more. It was confirmed that μ ′ / μ ″ at 2 GHz is sufficiently large and exhibits good characteristics in the high frequency region. Note that μ ′ · T (P1 value) of the portion formed on the top surface of the convex portion of the soft magnetic thin film. ), The ratio (P2 / P1) of μ ′ · T (P2 value) of the portion formed on the wall surface connecting the convex portion and the concave portion was 0.09.

(Examples 2-9)
In Example 1 described above, soft magnetic films were produced in the same manner as in Example 1 except that the shape of the concavo-convex portions of the base film and the number of laminated soft magnetic thin films were changed. Detailed conditions of each soft magnetic film are as shown in Table 1. In the reference examples in the table, the shape of the concavo-convex part is set outside the preferred range of the present invention. The magnetic properties of these soft magnetic films were measured in the same manner as in Example 1. The results are shown in Table 2.

  In Table 2, fr indicates A when 5.5 GHz or more, B indicates 3.5 GHz or more, and C indicates less than 3.5 GHz. For μ ′ / μ ″, the case where the value at 2 GHz is 3 or more is indicated as A, and the case where it is less than 3 is indicated as C. The overall evaluation is based on μ ′ / μ ″ at fr, 2 GHz. The case where A is A is indicated as A, the case where any item is B, B, and the case where any item is C are indicated as C.

  As can be seen from Table 2, all of the soft magnetic films according to Examples 2 to 9 have a high ferromagnetic resonance frequency fr and are well imparted with shape anisotropy. Furthermore, in order to increase the ferromagnetic resonance frequency fr of the soft magnetic film with good reproducibility, the step d of the uneven portion of the base film is 1 μm or more, the repetition period p is 1000 μm or less, and the thickness T of the soft magnetic thin film is 3 μm or less. It turns out that it is preferable.

(Example 10)
A base film having the same material and shape as in Example 1 was prepared, and a laminated soft magnetic thin film was formed on both sides of the base film as follows. First, after the substrate film was washed with acetone, a 0.03 μm thick SiO ₂ film and a 0.01 μm thick Ti film were sequentially formed by RF sputtering and DC sputtering. By laminating an FeCoBSiO film having a thickness of 0.5 μm and an SiO ₂ film having a thickness of 0.05 μm alternately on the base film, a laminated soft magnetic thin film was formed on both surfaces of the base film. The number of these layers was four on both sides.

An RF magnetron sputtering apparatus was used for forming the FeCoBSiO film. As the sputtering target, a disk-shaped alloy target having a diameter of 125 mm and a thickness of 3 mm and an SiO ₂ target having a composition (Fe _0.80 Co _0.20 ) ₈₅ B ₁₅ (atomic%) were used. Using these sputter targets, four layers of FeCoBSiO films (thickness 0.5 μm) were sequentially stacked via SiO ₂ films (thickness 0.05 μm). The input power during the formation of the soft magnetic film was 3.3 W / cm ² , the target-substrate distance was 75 mm, and the argon pressure was 1.6 Pa (500 SCCM).

In this manner, a laminated soft magnetic thin film was formed on both surfaces of a base film having a plurality of uneven portions to produce a soft magnetic film. The structure of the soft magnetic film is [(SiO ₂ film (0.05 μm) / FeCoBSiO film (0.5 μm)) ₄ / Ti film (0.01 μm) / SiO ₂ film (0.03 μm) // Polyimide resin base Material film (25 μm) // SiO ₂ film (0.03 μm) / Ti film (0.01 μm) / (FeCoBSiO film (0.5 μm) / SiO ₂ film (0.05 μm)) ₄ ].

  When the magnetic properties of the soft magnetic film were measured, the ferromagnetic resonance frequency fr was 3 GHz or more. When the frequency dependence of μ ′ and μ ″ was measured, it was confirmed that μ ′ of the soft magnetic thin film was large not only in the low frequency region but also in the high frequency region, and the value of μ ″ was small also in the high frequency region. It was confirmed that μ ′ / μ ″ at 2 GHz is sufficiently large and exhibits good characteristics in the high frequency region. Note that μ ′ · T (P1 value) of the portion formed on the top surface of the convex portion of the soft magnetic thin film. The ratio (P2 / P1) of μ ′ · T (P2 value) of the portion formed on the wall surface connecting the convex portion and the concave portion to) was 0.10.

(Example 11)
In Example 10 described above, the soft film was compressed in the same manner as in Example 10 except that the base film having a fold angle θ of 70 ° was used by compressing the resin film in the repeating direction of the concavo-convex portion. A film was prepared. Detailed conditions of the soft magnetic film are as shown in Table 3. For this soft magnetic film, the magnetic properties were measured in the same manner as in Example 10. The results are shown in Table 4.

(Example 12)
In Example 10 described above, the soft film was expanded in the repeating direction of the concavo-convex part, and a soft magnetic material was used in the same manner as in Example 10 except that a base film having a concavo-convex part bending angle θ of 110 ° was used. A film was prepared. Detailed conditions of the soft magnetic film are as shown in Table 3. In addition, the reference example 4 in a table | surface makes the bending angle (theta) of an uneven | corrugated | grooved part 150 degrees. For these soft magnetic films, the magnetic properties were measured in the same manner as in Example 10. The results are shown in Table 4.

  As is clear from Table 4, it can be seen that all of the soft magnetic films according to Examples 10 to 12 have a high ferromagnetic resonance frequency fr and a good shape anisotropy. When the P2 / P1 ratio of the soft magnetic thin film becomes too large, the ferromagnetic resonance frequency fr decreases, and it is understood that the P2 / P1 ratio is preferably 0.7 or less.

(Examples 13 to 15)
A soft magnetic film was produced in the same manner as in Example 1 except that collimation sputtering as shown in FIG. 5 was applied to the formation of the soft magnetic thin film. The shape of the slit during collimation sputtering (ratio of slit width s to slit length D (s / D ratio)) was 1 in Example 13, 0.2 in Example 14, and 0.1 in Example 15. . Detailed conditions of the soft magnetic film are as shown in Table 5. The magnetic properties of these soft magnetic films were measured in the same manner as in Example 1. The results are shown in Table 6. In addition, the side film thickness in Table 5 is the film thickness per layer of the soft magnetic thin film on the wall surface connecting the convex part and the concave part.

  As is clear from Tables 5 and 6, the P2 / P1 ratio can be reduced by applying collimation sputtering. This means that the shape anisotropy of the soft magnetic thin film can be increased more neatly. Further, by reducing the s / D ratio of the slit in the collimation sputtering, the amount of soft magnetic thin film deposited on the wall surface connecting the convex portion and the concave portion can be reduced. In Example 15 in which the s / D ratio of the slit was 0.1, the soft magnetic thin film was observed as a continuous film on the wall surface (side surface) connecting the convex portion and the concave portion when SEM observation (50,000 times) was performed. I could not.

(Example 16)
The anti-electromagnetic wave component 18 using the soft magnetic film of Example 1 was cut into a shape of 20 mm × 5 mm and a shape of 40 mm × 5 mm. As shown in FIGS. 8 and 9, these were pasted on the antenna wiring in the vicinity of the antenna 16 of the mobile phone 10 so that the easy magnetization direction of the soft magnetic thin film was parallel to the substrate wiring pattern. With respect to such a mobile phone 10, the electric field strength distribution excited inside the uniform simulated tissue model using the SAM phantom was measured using an electric field probe.

  As a result, the electromagnetic wave intensity inside the SAM phantom was reduced by 2.3 dB at a transmission frequency of 2 GHz. Similarly, as a result of measuring the electromagnetic strength of the space using the electric field probe, the antenna efficiency was improved by 2 dB in the space other than the SAM phantom. From this measurement result, by using an electromagnetic wave countermeasure component including a soft magnetic thin film having a high ferromagnetic resonance frequency fr, a human head or the like is arranged while suppressing a decrease in signal intensity transmitted from the mobile phone 10. It can be seen that the electromagnetic field strength in the space can be effectively reduced.

A soft magnetic thin film (soft magnetic film) used as an electromagnetic wave countermeasure component is not significantly affected by other characteristics such as coercive force obtained by DC magnetic field measurement as long as μ ′ is large in a high frequency region. Therefore, a magnetic film by binary sputtering of (Co _35.6 Fe ₅₀ B _14.4 ) and (SiO ₂ ), a soft magnetic film by binary sputtering of (Co ₂₀ Fe ₈₀ ) and (SiO ₂ ), etc. may be applied. Similar effects can be obtained with these soft magnetic films. Further, the soft magnetic film is not limited to the sputtering method, and may be formed by applying a vapor deposition method or the like.

The soft magnetic film according to the embodiment of the present invention effectively imparts shape anisotropy to a soft magnetic thin film without lowering the degree of freedom in shape, increasing the volume, and further causing separation of a planar magnetic material. is there. Therefore, such a soft magnetic film is effectively used for an electromagnetic wave countermeasure component. Furthermore, according to the electromagnetic wave countermeasure component according to the aspect of the present invention, it is possible to reduce the electromagnetic field strength with respect to the unnecessary direction of the radiated electromagnetic wave while suppressing a decrease in the transmitted signal strength. According to the electronic device using such an electromagnetic wave countermeasure component, it is possible to reduce the influence of the electromagnetic wave on, for example, the human body, other electronic components, and the electronic device while maintaining good communication characteristics due to the electromagnetic wave. .

Claims (19)

A base film having a bent shape in which a plurality of uneven portions are repeatedly provided;
A soft magnetic thin film formed on at least a top surface of the convex portion and a bottom surface of the concave portion of the base film, wherein the product of the permeability μ ′ and the film thickness T has a discontinuous portion; equipped with,
The base film has a repetition period of the concavo-convex portions of 1000 μm or less, and is a soft magnetic film. The soft magnetic film according to claim 1,
The soft magnetic film, wherein the base film has a step of 1 μm or more in the uneven portion. In the soft magnetic film according to claim 2 ,
Soft magnetic film characterized by the step of pre Ki凹 convex portion is 3μm or 100μm or less. The soft magnetic film according to any one of claims 1 to 3 ,
The base film has a width of the top surface of the convex portion and a width of the bottom surface of the concave portion of 500 μm or less, respectively. The soft magnetic film according to any one of claims 1 to 4 ,
The base film includes a resin film having an average thickness of 200 μm or less. The soft magnetic film according to any one of claims 1 to 5 ,
The soft magnetic thin film has a thickness T of 3 μm or less. The soft magnetic film according to any one of claims 1 to 6 ,
The soft magnetic thin film has a laminated film in which a plurality of magnetic layers are laminated via a nonmagnetic insulating layer. The soft magnetic film according to claim 7 ,
The soft magnetic film according to claim 1, wherein each of the plurality of magnetic layers has a thickness of 1 μm or less. The soft magnetic film according to any one of claims 1 to 8 ,
The soft magnetic film is characterized in that the soft magnetic thin film is formed on both surfaces of the base film. The soft magnetic film according to any one of claims 1 to 9 ,
The base film has a bent shape in which a bending angle of the concavo-convex portion is in a range of 10 ° to 135 °. The soft magnetic film according to claim 10 ,
Soft film folding angle before Ki凹 protrusions and wherein the range der Turkey of to 95 ° 85 ° or more. The soft magnetic film according to any one of claims 1 to 9 ,
The soft magnetic film according to claim 1, wherein the base film has a bent shape in which a bending angle of the concavo-convex portion is an acute angle. The soft magnetic film according to claim 12 ,
A soft magnetic film, wherein a bending angle of the concavo-convex portion is in a range of 10 ° or more and less than 90 °. The soft magnetic film according to any one of claims 1 to 13 ,
The soft magnetism formed on the wall surface connecting the convex portion and the concave portion to the product (P1 value) of the magnetic permeability μ ′ and the film thickness T of the soft magnetic thin film formed on the top surface of the convex portion. A soft magnetic film, wherein a ratio (P2 / P1) of a product (P2 value) of the magnetic permeability μ ′ and the film thickness T of the thin film is 0.7 or less. The soft magnetic film according to any one of claims 1 to 14 ,
The soft magnetic film is characterized in that a portion formed on the top surface of the convex portion and a portion formed on the bottom surface of the concave portion are separated. An electromagnetic wave countermeasure component comprising the soft magnetic film according to any one of claims 1 to 15 . An electronic device body having an electromagnetic wave transmission unit;
An electromagnetic wave countermeasure component comprising the soft magnetic film according to any one of claims 1 to 15 , wherein the electromagnetic field intensity with respect to an unnecessary direction of an electromagnetic wave radiated from the electromagnetic wave transmission unit is selectively reduced. An electronic device comprising: an electromagnetic wave countermeasure component arranged. The electronic device according to claim 17 .
The electronic device characterized in that the soft magnetic thin film in the soft magnetic film has a ferromagnetic resonance frequency of 1.5 times or more of a transmission band frequency of the electronic device main body. The electronic device according to claim 17 or claim 18 ,
The electronic device is a portable communication device.

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