JP6633037B2 - Near-field noise suppression sheet - Google Patents

Description

  The present invention relates to a near-field noise suppression sheet used to suppress extra radiated radio waves (noise) in electronic devices and communication devices.

  In recent years, as electronic devices and communication devices have become smaller and lighter, the mounting density of components mounted on electronic circuits has increased. For this reason, malfunctions of electronic devices and communication devices due to radio interference and magnetic field coupling between electronic components or between electronic circuits due to radio noise radiated from the electronic components become a problem.

  In order to prevent this problem, a near-field noise suppression sheet (hereinafter, also referred to as a “noise suppression sheet”) that converts unnecessary radiated radio waves (noise) into heat and can prevent unnecessary magnetic field coupling is provided in equipment and the like. Has been implemented. Since this noise suppression sheet has a thickness of 0.05 mm to 2 mm, it can be inserted near an electronic component or an electronic circuit, and is easily processed and has a high degree of freedom in shape. Therefore, the noise suppression sheet can be adapted to miniaturization and weight reduction of electronic devices and communication devices, and is widely used as a noise suppression component of electronic devices and communication devices.

  A typical noise suppression sheet is composed of a soft magnetic alloy powder processed in a flat shape and an organic binder, and a noise suppression effect is obtained by magnetic loss of the soft magnetic alloy powder due to magnetic resonance. Therefore, the noise suppression performance of the noise suppression sheet depends on the magnetic permeability of the soft magnetic alloy powder included in the noise suppression sheet. In general, the magnetic permeability is represented by the complex magnetic permeability μ = μ′−j · μ ″ using the real part magnetic permeability μ ′ and the imaginary part magnetic permeability μ ″, but the magnetic loss is used like a noise suppression sheet. In this case, the imaginary part magnetic permeability μ ″ is important. That is, it is important that the imaginary part magnetic permeability μ ″ be distributed over the frequency band of radio wave noise to be absorbed (hereinafter also referred to as “target band”). Hereinafter, in this specification, the distribution of the imaginary part magnetic permeability μ ″ with respect to the frequency is referred to as “μ” dispersion. The μ ″ dispersion has a different μ ″ value and distribution depending on the material and shape of the soft magnetic alloy powder included in the noise suppression sheet. Therefore, in order to enhance the effect of noise suppression, it is necessary to select a noise suppression sheet suitable for the target band.

  For example, in a noise suppression sheet using a flat soft magnetic alloy powder typified by an Fe-Si-Al alloy having a so-called sendust composition, the target band is as low as the kHz to MHz band, and the higher the frequency, the higher the transmittance. Magnetic susceptibility decreases. In particular, in the GHz band, the μ ″ value substantially approaches 1, so that the noise suppression effect cannot be exhibited. To cope with this, Patent Documents 1 and 2 disclose a flat soft sendust composition. A noise suppression sheet including a magnetic alloy powder and a carbon powder has been proposed, that is, a magnetic loss caused by a soft magnetic alloy powder is used in a low frequency band, and a dielectric loss caused by a carbon powder is used in a high frequency band. Thus, the target band is set to a wide band.

Further, the magnetic permeability of the magnetic member is also affected by the electric resistance of the magnetic member, and it is advantageous to use a soft magnetic alloy powder having a large electric resistance in order to increase the μ ″ dispersion of the noise suppression sheet. Therefore, the use of an amorphous soft magnetic alloy having an electric resistance higher than that of a crystalline soft magnetic alloy is an effective means for increasing the frequency of μ ″ dispersion. For example, Patent Literature 3 mainly includes flat soft magnetic particles made of an iron-based amorphous alloy and an organic binder, and has a complex relative magnetic permeability μ ″ at 10 GHz of 7 or more. electromagnetic interference suppressing body which is described here, as the soft magnetic particles, the composition _{formula:. {Fe a (Si x} B y P z) 1-a} 100-b L b ( where, L is Al , Cr, Zr, Nb, Mo, Hf, Ta, W, at least one element selected from the group consisting of 0.70 ≦ a ≦ 0.82 atomic%, 0 <b ≦ 8 atomic%, and 0.05 ≦ x ≦ 0. 60 atomic%, 0.10 ≦ y ≦ 0.85 atomic%, 0.05 ≦ z ≦ 0.70 atomic%, x + y = z = 1) or a composition formula: (Fe _1-a TM) _{a) 100-w-x-} y-z P w B x L y Si z ( where, TM is Co, 1 or more selected from Ni And L is one or more elements selected from Al, V, Cr, Y, Zr, Mo, Nb, Ta, and W, 0 ≦ a ≦ 0.98 atomic%, 2 ≦ w ≦ 16 atomic%, 2 ≦ Particles represented by x ≦ 16 at%, 0 <y ≦ 10 at%, 0 ≦ z ≦ 8 at%) are mentioned.

Patent Documents 4 and 5 describe soft magnetic alloys having a structure in which α-Fe crystals are precipitated in an amorphous state. Specifically, Patent Document 4, the average particle diameter has an amorphous structure in which alpha-Fe crystal grains of 5~30nm precipitated, composition _{formula: Fe 100-a-b-} c-d Si a B _b C _c Cu _d (1% ≦ a ≦ 3%, 9% ≦ b ≦ 14%, 1% ≦ c ≦ 4%, 0.3% ≦ d ≦ 1.5%, 80% ≦ 100-a −b−c−d ≦ 86%). Further, Patent Document 5, an average particle size having an amorphous tissue precipitated alpha-Fe crystal grains of 5 to 30 nm, the composition _{formula: Fe 100-a-b-} c-d Si a P b C c Cu _d (where, 0% ≦ a ≦ 3% , 9% ≦ b ≦ 13%, 4% ≦ c ≦ 6%, 0.3% ≦ d ≦ 1.5%, 80% ≦ 100-a-b- (cd ≦ 86%). As an example, it is described that these soft magnetic alloys can be applied to magnetic components such as a noise suppression sheet.

JP 2012-186384 A JP 2013-182931 A JP-A-2015-46538 JP 2016-94651 A JP 2016-94652 A

  2. Description of the Related Art In recent years, the performance and diversification of electronic circuit designs of electronic devices and communication devices have been rapidly advanced, and the frequency of noise in electronic circuits has been increased in frequency and bandwidth. For example, personal computers are required to operate at higher speeds, and the driving frequency of the CPU is approaching the band from MHz to GHz. In addition, the capacity of digital contents handled by communication devices such as wireless LANs is increasing, and communication frequencies are mainly in the GHz band. In addition, satellite communications such as digital TV broadcasting and road traffic information systems are rapidly expanding, and the ubiquitous network era is being realized. As such information and communication devices have become more multifunctional and integrated, the frequency of extra radio noise emitted from electronic and communication devices has also increased, and functional interference and malfunctions due to the radio noise have become more worrying than before. Is done. Therefore, while the target band of the conventional noise suppression sheet is the kHz to MHz band, in recent years, a noise suppression sheet having the target band of the MHz to GHz band has been required.

  However, in the noise suppression sheets described in Patent Documents 1 and 2, in the GHz band, not the magnetic loss but only the dielectric loss acts, so even if the electric field noise in the GHz band can be suppressed, the noise in the GHz band is reduced. Magnetic field noise cannot be suppressed. In electronic circuits, it is more important to suppress magnetic field noise than electric field noise due to the interaction of current circuits.

  Further, in the noise suppression sheet described in Patent Document 3, since the rising frequency of the μ ″ dispersion exists at a position exceeding 10 MHz, the noise suppression effect of 1 MHz to 10 MHz cannot be exhibited, and a wide band from MHz to GHz is not achieved. It is not suitable as a noise suppression sheet corresponding to.

  Further, the magnetic permeability of the noise suppression sheet is affected by the degree of orientation and the filling rate of the flat alloy powder in the noise suppression sheet, in addition to the composition of the alloy powder. That is, since the flat alloy powder has magnetic anisotropy in its in-plane direction, it is necessary to increase the degree of orientation of the alloy powder in the in-plane direction of the sheet in order to increase the magnetic permeability of the noise suppression sheet. . The magnetic permeability of the noise suppression sheet is also affected by the filling rate of the alloy powder contained in the sheet. In order to increase the magnetic permeability of the noise suppression sheet, it is necessary to increase the density of the noise suppression sheet. In addition, in recent years, a flame-retardant noise suppression sheet has been demanded due to the properties of a target device that uses the noise suppression sheet, and a flame retardant is generally added as a countermeasure. However, when a flame retardant is added, the degree of orientation of the flat alloy powder is reduced, and as a result, the magnetic permeability of the noise suppression sheet is reduced, so that its frequency characteristics are also affected.

  However, although Patent Documents 4 and 5 aim at obtaining a soft magnetic alloy having excellent soft magnetic properties by optimizing the composition and structure of the soft magnetic alloy, the degree of orientation of the alloy powder in the noise suppression sheet is reduced. No description is given of the density or flame retardancy of the noise suppression sheet. Therefore, even if the noise suppression sheet is manufactured using the soft magnetic alloys described in Patent Documents 4 and 5, even if the target band is the MHz to GHz band, in addition to the noise suppression sheet, the noise suppression sheet also has flame retardancy. The situation is not yet reached.

  In view of the above problems, an object of the present invention is to provide a near-field noise suppression sheet that can cope with magnetic field noise in a wide band from MHz to GHz and has flame retardancy. That is, the present invention provides a flame-retardant near-field noise suppression sheet characterized in that the rising frequency of the μ ″ dispersion exists in a band of 1 to 10 MHz and the μ ″ dispersion is distributed up to the GHz band. The purpose is to provide.

The gist configuration of the present invention for solving the above problems is as follows.
(1) A near-field noise suppression sheet including a substrate made of an organic material, a flat alloy powder supported in the substrate, and a flame retardant dispersed in the substrate,
The alloy powder is represented by the following formula in atomic%: Fe _100-X1-Y1 (Si, P, C) _X1 Cu _Y1 (however, 16 ≦ X1 + Y1 ≦ 24, 14.5 ≦ X1 ≦ 24, and 0 ≦ Y1 ≦ 1.5) Alloy powder and / or composition formula: Fe _100-X2-Y2 (Si, B, C) _X2 Cu _Y2 (16 ≦ X2 + Y2 ≦ 24, 14.5 ≦ X2 ≦ 24, and 0) ≦ Y2 ≦ 1.5), wherein the phase structure of the alloy powder comprises only an amorphous phase or a mixture of an amorphous phase and a crystal phase mainly composed of α-Fe. Consisting of
The average particle size of the flame retardant is 10 μm or less,
Further, a near-field noise suppression sheet having a density of 2.5 g / cm ³ or more.

  (2) The alloy powder has 19 ≦ X1 + Y1 ≦ 21, 18 ≦ X1 ≦ 21, and 0 ≦ Y1 ≦ 1.0, and / or 19 ≦ X2 + Y2 ≦ 21, 18 ≦ X2 ≦ 21, and 0 ≦ Y2 ≦ The near-field noise suppression sheet according to (1), which satisfies 1.0.

  (3) In the near-field noise suppression sheet, at the rise of μ ″ dispersion, the frequency at which the μ ″ value is 1 or more is 1 MHz to 10 MHz, and the μ ″ value at 10 GHz is 2 or more. The near-field noise suppression sheet according to (1) or (2).

  (4) The near-field noise suppressing sheet according to any one of (1) to (3), wherein the coercive force of the alloy powder is 0.5 A / cm or more and 8 A / cm or less.

  (5) The above-mentioned (1), wherein the flame retardant is one or more non-halogen flame retardants selected from aluminum hydroxide, magnesium hydroxide, zinc borate, melamine cyanate, and red phosphorus. The near-field noise suppression sheet according to any one of (1) to (4).

  (6) In the alloy powder, 3 atomic% or less of the Fe is replaced with one or more elements selected from Al, Co, Ni, Cr, Nb, Mo, Ta, and W. The near-field noise suppression sheet according to any one of (1) to (5).

  (7) The near-field noise suppression sheet according to any one of (1) to (6), wherein the average value of the aspect ratio of the alloy powder is 10 or more and 100 or less.

  (8) The near-field noise suppressing sheet according to any one of (1) to (7) above, wherein the average value of the thickness of the alloy powder is 0.1 μm or more and 1.5 μm or less.

(9) The near-field noise suppression sheet according to any one of (1) to (8) above, wherein the near-field noise suppression sheet has a surface resistance of 10 ⁵ Ω / □ or more.

  (10) The near-field noise suppression sheet according to any one of (1) to (9), wherein the base material does not include a halogen element.

  (11) The above-mentioned (1), wherein the noise suppression sheet contains one or more oxides selected from a silicon-based, a titanium-based, an aluminum-based, and a zirconium-based, and the oxide has a particle size of 100 nm or less. The noise suppression sheet for near field according to any one of (1) to (10).

  According to the present invention, it is possible to obtain a near-field noise suppression sheet that can cope with magnetic field noise in a wide band of MHz to GHz and has flame retardancy.

  Hereinafter, an embodiment of a near-field noise suppression sheet according to the present invention will be described.

  A near-field noise suppression sheet according to one embodiment of the present invention includes a base material made of an organic material, a flat alloy powder supported in the base material, and a flame retardant dispersed in the base material.

Flat alloy powder, in atomic%, the composition _{formula: Fe 100-X1-Y1 (} Si a P b C c) X1 Cu Y1 ( where, 16 ≦ X1 + Y1 ≦ 24,14.5 ≦ X1 ≦ 24, and 0 ≦ Y1 alloy powder represented by ≦ 1.5) and / or _{formula: Fe 100-X2-Y2 (} Si d B e C f) X2 Cu Y2 ( where, 16 ≦ X2 + Y2 ≦ 24,14.5 ≦ X2 ≦ 24 and 0 ≦ Y2 ≦ 1.5). Here, a, b, c, d, e, and f are not particularly limited as long as they satisfy a + b + c = X1 and d + e + f = X2, and 0 ≦ a ≦ 10, 8 ≦ b ≦ 19, 3 ≦ c ≦ 6, It can be appropriately adjusted from the ranges of 1 ≦ d ≦ 15, 8 ≦ e ≦ 19, and 3 ≦ f ≦ 6. In this _{specification, Fe 100-X1-Y1 (} Si a P b C c) the X1 _{Cu Y1} is denoted by _{Fe 100-X1-Y1 (Si} , P, C) X1 Cu Y1, Fe 100-X2-Y2 ( _{Si d B e C f) X2} Cu Y2 of _{Fe 100-X2-Y2 (Si} , denoted _B, C) and X2 _{Cu Y2. The} total amount of _{Fe 100-X1-Y1 (Si} , P, C) X1 Cu Y1 and _{Fe 100-X2-Y2 (Si} , B, C) X2 Cu Y2 is preferably not less than 50 mass%. The ratio of each alloy powder when both Fe _100-X1-Y1 (Si, P, C) _X1 Cu _Y1 and Fe _100-X2-Y2 (Si, B, C) _X2 Cu _Y2 is included is not particularly limited. . The phase structure of the alloy powder having the above composition has a structure composed of only an amorphous phase. Alternatively, among these alloy powders, those containing Cu include an amorphous phase and a crystal phase mainly composed of α-Fe, which are subjected to an annealing treatment to be described later to precipitate α-Fe crystals. It can also be a phase.

  From the viewpoint of further increasing the noise suppression effect, X1, X2 and Y1, Y2 of the above composition are 19 ≦ X1 + Y1 ≦ 21, 18 ≦ X1 ≦ 21, and 0 ≦ Y1 ≦ 1.0, and / or 19 ≦ X2 + Y2 ≦ It is preferable to satisfy 21, 18 ≦ X2 ≦ 21 and 0 ≦ Y2 ≦ 1.0.

  Further, 3 atomic% or less of Fe may be replaced with one or more elements selected from Al, Co, Ni, Cr, Nb, Mo, Ta, and W. Here, if the total amount of the elements to be replaced exceeds 3 atomic%, the saturation magnetization of the alloy powder is remarkably reduced, so that the magnetic permeability of the noise suppression sheet is reduced. Therefore, the upper limit is set to 3 atomic%.

  Hereinafter, an example of the method for manufacturing the noise suppression sheet according to the present embodiment will be described.

  First, a flat alloy powder, an organic substance, a flame retardant, and an organic solvent are mixed to prepare a slurry.

  As the raw material powder of the alloy powder, a powder having the above composition is used, and the shape of the raw material powder is preferably spherical. The raw material powder can be obtained by a gas atomizing method or a water atomizing method, which is a general method for synthesizing a powder. The average particle diameter of the raw material powder is preferably 5 μm or more and 70 μm or less. If it is 5 μm or more, a flat alloy powder having a large aspect ratio (= diameter / thickness) described later can be easily obtained, and if it is 70 μm or less, the flattening process described later is efficiently performed in a short time. Because you can do it. The average particle size of the raw material powder means a particle size at an integrated value of 50% (50% cumulative particle size: D50) in a particle size distribution obtained by a laser diffraction / scattering method.

  A flat alloy powder can be obtained by mechanically processing such a spherical raw material powder. Here, in order to make the rising frequency of the μ ″ dispersion exist in the band of 1 MHz to 10 MHz and to distribute the μ ″ dispersion to the GHz band, the average value of the thickness of the flat alloy powder is 0.1 μm or more. It is preferable to perform flattening so as to have a thickness of 1.5 μm or less. Further, it is preferable to perform flattening so that the average value of the aspect ratio of the alloy powder is 10 or more and 100 or less. If the average value of the aspect ratio is 10 or more, the influence of the demagnetizing field in the plane of the flat alloy powder can be ignored, and if it is 100 or less, the degree of orientation of the alloy powder in the in-plane direction of the sheet is small. This is because it is possible to obtain a noise suppression sheet which increases during film formation and has a flat surface. For flattening, known or arbitrary machining such as a ball mill, an attritor, and a stamp mill can be suitably used. The “average thickness” is obtained by observing the ion-milled polished surface of the cross section in the thickness direction of the noise suppression sheet manufactured by the method described later with a scanning electron microscope (SEM), and measuring the number of powders in the visual field. About, mean the value of the average value of the thickness of the flat alloy powder, "average value of the aspect ratio", similarly, when observed by SEM, for 10 powder in the field of view, The value of the length / thickness ratio of the flat alloy powder is taken as the average value.

  Next, after flattening, annealing is performed on the alloy powder in an inert atmosphere such as nitrogen or argon. Thereby, α-Fe can be precipitated from the alloy powder containing Cu. In addition, since the residual stress generated in the alloy powder by the flattening process can be removed by the annealing process, a decrease in magnetic permeability can be prevented. Annealing conditions may be, for example, at a temperature of 200 to 500 ° C. for 0.5 to 5 hours. As described above, by appropriately selecting the annealing conditions and controlling the phase structure of the alloy powder, an alloy powder having a desired coercive force can be obtained. It is preferable that the coercive force of the alloy powder be 0.5 A / cm or more and 8 A / cm or less. When the coercive force is 0.5 A / cm or more, the rising frequency of the μ ″ dispersion can be present in the MHz band, and when it is 8 A / cm or less, the μ ″ is sufficiently large to suppress noise. This is because a value can be obtained.

  Further, it is preferable to form a self-oxidized film or an externally processed film on the surface of the flat alloy powder for the purpose of performing the insulating treatment. There are no particular restrictions on the means or material for forming the coating, as long as the insulation can be maintained. The thickness of the coating is suitably 20 to 100 nm. If the coating is formed more than necessary, the volume of the magnetic phase is reduced, so that a sufficiently large μ ″ value cannot be obtained. Typical examples of the method include a heat treatment in the air or a heat treatment in a hydrocarbon-based organic solvent, and a gas-phase method such as dip coating or CVD as a method for forming the externally treated film. Note that the order of the insulating treatment and the annealing treatment is not particularly limited.

  In addition, the flat alloy powder may be subjected to a surface treatment with at least one coupling agent selected from a silicon-based, a titanium-based, an aluminum-based, and a zirconium-based. The method of the coupling treatment is not particularly limited, and a typical treatment method will be described here. That is, the flat alloy powder is put into a solvent in which the above-described coupling agent is dissolved, and after stirring, the alloy powder is collected and dried at a temperature of, for example, 100 to 200 ° C. As a result, an oxide having a particle size of 100 nm or less is formed on the surface of the alloy powder. By this coupling treatment, the degree of familiarity with an organic substance described later is improved, and a noise suppression sheet having a high packing density of the alloy powder can be obtained. As a result, a μ ″ value large enough for noise suppression can be obtained. In addition, since insulating oxide particles resulting from the coupling agent are formed on the surface of the flat alloy powder, it also contributes to improving the insulating properties of the alloy powder.

  As the organic substance constituting the base material, an organic substance containing no halogen element is preferable. In the conventional noise suppression sheet, an organic substance such as chlorinated polyethylene having high flame retardancy was used. However, recently, environmental regulations such as the RoHS Directive require a noise suppression sheet containing no halogen element. Because. Examples of the organic substance not containing a halogen element include, for example, any resin material such as an epoxy resin, a phenol resin, a cellulose resin, a polyethylene resin, and a polyester resin, and any rubber material such as a silicone rubber, an acrylic rubber, a nitrile rubber, and a butyl rubber. Materials and any fibrous materials such as non-woven fabric, polyester fiber and acrylic fiber can be mentioned, and the selection of the organic matter may be appropriately selected according to the purpose. These organic substances have a function of imparting bonding and plasticity and insulating and isolating the alloy powders. In addition, a plasticizer such as dioctyl phthalate can be added as necessary to increase the flexibility of the noise suppression sheet.

  The average particle size of the flame retardant in the finally obtained noise suppression sheet is 10 μm or less, preferably 0.2 μm or more and 8 μm or less, more preferably 0.2 μm or more and 6 μm or less. Since the flame retardant is dispersed between the flat alloy powders, if the average particle size exceeds 10 μm, the degree of orientation of the alloy powder in the sheet surface direction is significantly reduced. Therefore, even if the flame retardancy can be improved, a desired noise suppression effect cannot be obtained. If the average particle size of the flame retardant is 0.2 μm or more, high flame retardancy can be maintained. Here, the “average particle diameter of the flame retardant” refers to the average value of the major axes of the ten flame retardants in the visual field when the ion milling polished surface of the cross section in the thickness direction of the noise suppression sheet is observed by SEM. means. The type of flame retardant is not particularly limited, but is preferably a flame retardant containing no halogen element like organic substances, specifically, aluminum hydroxide, magnesium hydroxide, zinc borate, melamine cyanate, and One or more flame retardants selected from red phosphorus.

The compounding ratio of the flat alloy powder, the flame retardant, and the organic substance is such that when the flat alloy powder is 100 parts by mass, the flame retardant is 5 to 30 parts by mass, and the organic substance is 8 to 30 parts by mass. Parts or less. When the flame retardant is 5 parts by mass or more, it becomes V1 or more in a flame resistance test of UL94 standard, and the flame retardancy required for the noise suppression sheet can be secured. This is because the volume ratio of the alloy powder with respect to the entire sheet does not significantly decrease, so that the magnetic permeability of the noise suppression sheet can be suppressed from significantly decreasing. Further, when the organic substance is at least 8 parts by mass, the plasticity of the noise suppression sheet can be maintained, and when it is at most 30 parts by mass, the flat alloy powder is likely to be oriented in the horizontal direction of the sheet at the time of sheet molding, so that sufficient Here, when the organic substance is added at such a compounding ratio, the surface resistance of the noise suppression sheet can be increased to 10 ⁵ Ω / without performing the above-described insulation treatment. When the above-described insulation treatment is performed, the insulating property of the alloy powder itself is improved, so that the amount of the organic substance added can be reduced as compared with the case where the insulation treatment is not performed. Since the volume of the alloy powder in the noise suppression sheet is improved, the magnetic permeability is increased, and the flame retardancy is also improved.

  The organic solvent is not particularly limited, and toluene, butyl acetate, ethyl acetate and the like can be used. Note that the organic solvent is not included in the noise suppression sheet because it evaporates in a subsequent step.

Next, a method for preparing a slurry will be described. The slurry can be prepared by a known ball mill method. That is, the flat alloy powder, the flame retardant, the organic substance, and the organic solvent adjusted to a predetermined compounding ratio are put into a container together with a ball mill medium that promotes mixing and stirring, and the container is rotated. A homogeneously dispersed slurry can be produced. The slurry in the present embodiment can also be manufactured using a ball mill method. However, in the ball mill method, a large external force is applied to the flat alloy powder by the ball mill media, and it becomes difficult to maintain the coercive force of the flat alloy powder in the range of 0.5 A / cm to 8 A / cm. Therefore, it is preferable to use a planetary mixing / stirring apparatus that does not use a ball medium for preparing the slurry. In this case, the flat alloy powder, the flame retardant, the organic substance, and the organic solvent can be uniformly mixed without applying a large external force to the flat alloy powder. In addition, because of the planetary stirring method, degassing of the gas contained in the slurry is also promoted, so that it is possible to produce a slurry effective for obtaining a noise suppression sheet having a high density of 2.5 g / cm ³ or more. it can.

  Next, a slurry composed of the flat alloy powder, the flame retardant, the organic substance, and the organic solvent is formed into a sheet by a doctor blade method and dried to prepare a formed body. This molded body has a structure in which a flat alloy powder is supported on a substrate made of an organic material, and a flame retardant is dispersed between the alloy powders. The powders are oriented horizontally with respect to each other. Here, as a molding method of the noise suppression sheet, a known or arbitrary method such as a calendar roll method can be used in addition to the doctor blade method, but it is necessary to produce a noise suppression sheet having a thickness of 0.1 mm or less. It is preferable to use a coating method such as a doctor blade method.

Next, in order to increase the degree of horizontal orientation and density of the flat alloy powder, a press is applied to the sheet-shaped molded body while heating the organic material to a temperature equal to or higher than the softening point of the organic substance (for example, about 60 to 150 ° C.). Apply. Thereby, the thickness of the obtained noise suppression sheet can be about 0.05 mm to 0.1 mm, and the density of the noise suppression sheet can be 2.5 g / cm ³ or more. If the density is less than 2.5 g / cm ³ , the number of voids increases, the degree of horizontal orientation of the flat alloy powder decreases, and the ratio of the alloy powder to the entire sheet decreases. No suppression effect is obtained. In order to obtain a noise suppression sheet having a higher magnetic permeability, the density of the noise suppression sheet is preferably set to 2.7 g / cm ³ or more. To this end, it is effective to increase the proportion of the alloy powder in the entire sheet by increasing the proportion of the flat alloy powder as much as possible, as well as eliminating voids.

  By the above method, it is possible to obtain a flame-retardant noise suppression sheet characterized in that the rising frequency of the μ ″ dispersion exists in the band of 1 MHz to 10 MHz and the μ ″ dispersion is distributed up to the GHz band. it can. More specifically, in such a noise suppression sheet, at the rise of the μ ″ dispersion, the frequency at which the μ ″ value is 1 or more exists in the band from 1 MHz to 10 MHz, and the μ ″ value at 10 GHz becomes 2 or more. ing.

  As described above, the near-field noise suppression sheet of the present invention has been described using the present embodiment as an example. However, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the claims.

  For example, the flame retardant may be added in advance when flattening the alloy powder, not when preparing a slurry. In this case, when the alloy powder is flattened, the flame retardant is also pulverized and crushed. Therefore, even if the average particle size of the flame retardant when added is more than 10 μm, the flame retardant contained in the noise suppression sheet is not included. Can be adjusted to 10 μm or less.

(Invention Examples 1 to 12, Comparative Examples 1 to 12)
An alloy powder having a composition shown in Table 1 was obtained as a raw material powder by a water atomizing method. Here, the ratios of Si, P, and C in the alloy powder shown in Table 1 were all 13:63:24. The average particle size of the raw material powder was 40 to 50 μm. Next, each alloy powder was flattened by an attritor to obtain a flat alloy powder. Table 1 shows the average values of the thickness and aspect ratio of the flat alloy powder measured by the method described above. Next, in order to form a self-oxidized film on the surface of the alloy powder, an oxidation treatment was performed at 100 ° C. for 1 hour in the air, and then an annealing treatment was performed at 350 to 450 ° C. for 30 minutes in argon. . Table 1 shows the phase structure measured by the powder X-ray diffraction method and the coercive force measured by the coercive force measuring device for each flat alloy powder after the annealing treatment.

  Next, 100 parts by mass of each flattened alloy powder, 20 parts by mass of polybutyral resin (softening point: about 70 ° C.), 50 parts by mass of butyl acetate, and 5 parts by mass of magnesium hydroxide and red phosphorus 1 as a flame retardant The parts by mass were mixed by a planetary mixing and stirring device to prepare a slurry. In addition, the average particle size of the flame retardant at the time of addition, magnesium hydroxide 9 μm-red phosphorus 7 μm for Invention Examples 1 to 10 and Comparative Examples 1 to 4 and Comparative Examples 9 to 12, and Comparative Examples 5 to 8 Magnesium hydroxide 13 μm-red phosphorus 13 μm, magnesium hydroxide 8 μm-red phosphorus 7 μm for Invention Example 11, and magnesium hydroxide 6 μm-red phosphorus 6 μm for Invention Example 12. Next, this slurry was processed into a sheet-like molded body on a polyethylene terephthalate film by a doctor blade method.

  Thereafter, for Invention Examples 1 to 12 and Comparative Examples 1 to 8, by applying a heat press at 100 ° C. for 1 minute under a pressure of 10 MPa, a noise suppression sheet having a density shown in Table 1 and a thickness of 0.05 mm was obtained. I got On the other hand, in Comparative Examples 9 to 12, a noise suppression sheet having a density shown in Table 1 and a thickness of 0.08 mm was obtained without performing hot pressing.

  The magnetic permeability characteristics of the noise suppression sheets of the invention examples and the comparative examples were measured by an S-parameter method using a network analyzer. Table 1 shows the frequency at which the μ ″ value becomes 1 or more at the beginning of the μ ″ dispersion and the magnitude of the μ ″ value at 10 GHz.

  Table 1 shows the average particle diameter of the flame retardant, the density measured by the Archimedes method, and the surface resistance measured by Hiresta for the noise suppression sheets of the invention examples and the comparative examples.

In Invention Examples 1 to 12, since the component composition of the present invention was satisfied, the average particle size of the flame retardant was 10 μm or less, and the density of the noise suppression sheet was 2.5 g / cm ³ or more, the μ ″ dispersion started to rise. The frequency at which the value of μ ″ was 1 or more was in the range of 1 to 10 MHz, and the value of μ ″ at 10 GHz exceeded 2. Particularly, in Invention Examples 2, 3, 11, and 12, the magnetic characteristics were poor. Perhaps because of good, the μ ″ value at 10 GHz exceeded 4.5. On the other hand, in Comparative Examples 1 and 2, the μ ″ value at 10 GHz was less than 2. In Comparative Example 1, since the Fe concentration was low, the magnetic flux density of the flat alloy powder was small, and the μ ″ value at 10 GHz. Is considered to be less than 2. In Comparative Example 2, since the component composition of the present invention was not satisfied and the coercive force of the flat alloy powder exceeded 8 A / cm, the soft magnetic properties were lowered, and the μ ″ value at 10 GHz was It is considered to be less than 2. In Comparative Examples 3 and 4 in which Cu was more than 1.5 atomic%, it was found by X-ray diffraction measurement that an FeP compound having large magnetic anisotropy was formed. As a result, the coercive force exceeded 8 A / cm, the distribution width of μ ″ with respect to frequency was narrow, and the μ ″ value at 10 GHz was 0.0. It is considered that the influence of the magnetic susceptibility on the characteristics is almost negligible.If the value of μ ″ at 10 GHz is 2 or more, it is possible to effectively suppress noise generated in recent electronic devices which are lighter, thinner and smaller and have higher frequencies. It can be.

  In Comparative Examples 5 to 8, the average particle size of the flame retardant exceeded 10 μm, and from SEM observation, portions where the orientation of the alloy powder in the sheet surface was disordered were confirmed everywhere. For this reason, at the beginning of the rise of the μ ″ dispersion, the frequency at which the μ ″ value was 1 or more exceeded 10 MHz, and the μ ″ value at 10 GHz was also below 2.

In Comparative Examples 9 to 12, the density of the noise suppression sheet was lower than 2.5 g / cm ³ , and a portion where the orientation of the alloy powder in the sheet surface was disordered was confirmed everywhere from SEM observation. For this reason, at the beginning of the rise of the μ ″ dispersion, the frequency at which the μ ″ value was 1 or more exceeded 10 MHz, and the μ ″ value at 10 GHz was also below 2.

In Invention Examples 11 and 12, the average particle size of the flame retardant was 8 μm or less, and the density of the noise suppression sheet was 2.7 g / cm ³ or more. The above frequencies were in the range of 1 to 10 MHz, and the μ ″ value at 10 GHz exceeded 5. In these sheets, the smaller the average particle size of the flame retardant was, the more the orientation of the flat powder in the sheet surface was reduced. Was improved, and the μ ″ value at 10 GHz was also larger.

(Invention Examples 13 to 24, Comparative Examples 13 to 24)
An alloy powder having a composition shown in Table 2 was obtained as a raw material powder by a water atomizing method. Here, the ratios of Si, B, and C in the alloy powder shown in Table 2 were all 13:63:24. The average particle size of the raw material powder was 40 to 50 μm. Next, each alloy powder was flattened by an attritor to obtain a flat alloy powder. Table 2 shows the average values of the thickness and aspect ratio of the flat alloy powder measured by the above-described method. Next, the alloy powder was introduced into an ethanol solution containing 2% by mass of 3-aminopropyltriethoxysilane as a silane coupling agent, and the mixture was stirred for 30 minutes. Thereafter, the powder was taken out of the solution and dried in air at 150 ° C. for 8 hours. Thereafter, an annealing treatment was performed in nitrogen at 350 to 450 ° C. for 30 minutes. Table 2 shows the phase structure and the coercive force measured by the method described above.

  Next, 100 parts by mass of each flattened alloy powder, 20 parts by mass of acrylic rubber (softening point: about 70 ° C.), 50 parts by mass of toluene, 5 parts by mass of melamine cyanurate as a flame retardant and 1 part by mass of red phosphorus Was mixed with a planetary mixing and stirring device to prepare a slurry. In addition, the average particle size of the flame retardant at the time of addition, magnesium hydroxide 9μm-red phosphorus 7μm for Invention Examples 13-22 and Comparative Examples 13-16 and 21-24, and for Comparative Examples 17-20, Magnesium hydroxide 13 μm-red phosphorus 13 μm, Invention Example 23 was magnesium hydroxide 8 μm-red phosphorus 7 μm, and Invention Example 24 was magnesium hydroxide 6 μm-red phosphorus 6 μm. Next, this slurry was processed into a sheet-like molded body on a polyethylene terephthalate film by a doctor blade method.

  After that, for Invention Examples 13 to 24 and Comparative Examples 13 to 20, a noise suppression sheet having a density shown in Table 2 and a thickness of 0.05 mm having a density shown in Table 2 by applying a heat press at 100 ° C. for 1 minute under a pressure of 10 MPa. Was prepared. On the other hand, for Comparative Examples 21 to 24, a noise suppression sheet having a density shown in Table 2 and having a thickness of 0.08 mm was obtained without performing hot pressing.

  The magnetic permeability characteristics, the average particle diameter of the flame retardant, the density of the noise suppression sheet, and the surface resistance of each of the invention examples and the comparative examples were measured by the methods described above. Table 2 shows the measurement results.

In Invention Examples 13 to 24, the average particle size of the flame retardant was 10 μm or less, and the density of the noise suppression sheet was 2.5 g / cm ³ or more. The above frequencies existed in the range of 1 to 10 MHz, and the value of μ ″ at 10 GHz exceeded 2. Particularly, in Invention Examples 14, 15, 23, and 24, 10 GHz was probably due to good magnetic properties. The μ ″ value in was over 4.5. On the other hand, in Comparative Examples 13 and 14, the μ ″ value at 10 GHz was less than 2. In Comparative Example 13, since the Fe concentration was low, the magnetic flux density of the flat alloy powder was small, and the μ ″ value at 10 GHz. Is considered to be less than 2. In Comparative Example 14, since the component composition of the present invention was not satisfied and the coercive force of the flat alloy powder exceeded 8 A / cm, the soft magnetic properties were reduced, and the μ ″ value at 10 GHz was It is considered to be less than 2. In Comparative Examples 15 and 16 in which Cu exceeds 1.5 atomic%, it was found by X-ray diffraction measurement that a FeB compound having large magnetic anisotropy was formed. As a result, the coercive force exceeded 8 A / cm, the distribution width of μ ″ with respect to frequency was narrow, and the value of μ ″ at 10 GHz was 0.0.

  In Comparative Examples 17 to 20, the average particle size of the flame retardant exceeded 10 μm, and from SEM observation, portions where the orientation of the alloy powder in the sheet surface was disordered were confirmed everywhere. For this reason, at the beginning of the rise of the μ ″ dispersion, the frequency at which the μ ″ value was 1 or more exceeded 10 MHz, and the μ ″ value at 10 GHz was also below 2.

In Comparative Examples 21 to 24, the density of the noise suppression sheet was lower than 2.5 g / cm ³ , and a portion where the orientation of the alloy powder in the sheet surface was disordered was confirmed everywhere from SEM observation. For this reason, at the beginning of the rise of the μ ″ dispersion, the frequency at which the μ ″ value was 1 or more exceeded 10 MHz, and the μ ″ value at 10 GHz was also below 2.

In Invention Examples 23 and 24, the average particle size of the flame retardant was 8 μm or less, and the density of the noise suppression sheet was 2.7 g / cm ³ or more. The above frequencies were in the range of 1 to 10 MHz, and the μ ″ value at 10 GHz exceeded 5. In these sheets, the smaller the average particle size of the flame retardant was, the more the orientation of the flat powder in the sheet surface was reduced. Was improved, and the μ ″ value at 10 GHz was also larger.

(Invention Examples 25 to 27)
An alloy powder having a composition shown in Table 3 was obtained as a raw material powder by a water atomizing method. Here, the ratios of Si, B, C and Si, P, C in the alloy powders shown in Table 3 were all 9:65:26, and the mixing ratio of the two types of alloy powders in each of Inventive Examples 25 to 27. Was 1: 1. The average particle size of the raw material powder was 40 to 50 μm. Next, each alloy powder was flattened by an attritor to obtain a flat alloy powder. Table 3 shows the average values of the thickness and aspect ratio of the flat alloy powder measured by the method described above. Next, in order to form a self-oxidized film on the surface of the alloy powder, an oxidation treatment was performed in air at 100 ° C. for 1 hour, and then an annealing treatment was performed in argon at 350 to 450 ° C. for 30 minutes. . Table 3 shows the phase structure measured by the above-described method and the coercive force measured by the coercive force measuring device.

  Next, 100 parts by mass of each flattened alloy powder, 20 parts by mass of a polybutyral resin (softening point: about 70 ° C.), 50 parts by mass of butyl acetate, and magnesium hydroxide 5 having an average particle size of 8 μm as a flame retardant A slurry was prepared by mixing parts by mass and 1 part by mass of red phosphorus having an average particle diameter of 8 μm with a planetary mixing and stirring device (Invention Example 25). Further, 100 parts by mass of each flattened alloy powder, 20 parts by mass of polybutyral resin (softening point: about 70 ° C.), 50 parts by mass of butyl acetate, and 5 parts by mass of magnesium hydroxide having an average particle size of 6 μm as a flame retardant And 1 part by mass of red phosphorus having an average particle diameter of 6 μm were mixed by a planetary mixing and stirring device to prepare a slurry (Invention Examples 26 and 27). Next, these slurries were processed into a sheet-like molded body on a polyethylene terephthalate film by a doctor blade method. Then, a noise suppression sheet having a thickness of 0.05 mm was produced by applying a heat press at 100 ° C. for 1 minute under a pressure of 10 MPa.

  The magnetic permeability characteristics, the average particle size of the flame retardant, the density of the noise suppression sheet, and the surface resistance of each of the inventive examples were measured by the methods described above. Table 3 shows the measurement results.

In Invention Examples 25 to 27, the average particle size of the flame retardant was 8 μm or less, and the density of the noise suppression sheet was 2.7 g / cm ³ or more. The above frequencies were in the range of 1 to 10 MHz, and the μ ″ value at 10 GHz exceeded 2. In particular, Invention Examples 26 and 27, in which the average particle size of the flame retardant was 6 μm or less, correspond to flat powders. And the in-plane orientation was further improved, and the μ ″ value at 10 GHz exceeded 5.

(Invention Examples 28 to 35)
An alloy powder having a composition shown in Table 4 was obtained as a raw material powder by a water atomizing method. Here, the ratios of Si, B, C and Si, P, C in the alloy powder shown in Table 4 were all 9:65:26. The average particle size of the raw material powder was 40 to 50 μm. Next, each alloy powder was flattened by an attritor to obtain a flat alloy powder. Table 4 shows the average values of the thickness and the aspect ratio of the flat alloy powder measured by the method described above. Next, the alloy powder was put into an ethanol solution to which 2% by mass of tetranormal butyl titanate was added as a titanium-based coupling agent, followed by stirring for 30 minutes. Thereafter, the alloy powder was taken out of the solution and dried in the air at 150 ° C. for 8 hours to form an oxide having an average particle diameter of 100 nm or less on the surface of the alloy powder. Thereafter, an annealing treatment was performed in nitrogen at 350 to 450 ° C. for 30 minutes. Table 4 shows the phase structure and the coercive force measured by the method described above.

  Next, 100 parts by mass of each flattened alloy powder, 20 parts by mass of acrylic rubber (softening point: about 70 ° C.), 50 parts by mass of toluene, and 5 parts by mass of melamine cyanurate having an average particle diameter of 10 μm as a flame retardant Then, 1 part by mass of red phosphorus having an average particle size of 10 μm was mixed by a planetary mixing and stirring device to prepare a slurry. Next, this slurry was processed into a sheet-like molded body on a polyethylene terephthalate film by a doctor blade method. Thereafter, a heat press was performed at 100 ° C. for 1 minute under a pressure of 10 MPa to produce a noise suppression sheet having a density shown in Table 4 and a thickness of 0.05 mm.

  The magnetic permeability characteristics, the average particle size of the flame retardant, the density of the noise suppression sheet, and the surface resistance of each of the inventive examples were measured by the methods described above. Table 4 shows the measurement results.

In Invention Examples 28 to 35, the average particle size of the flame retardant was 10 μm or less, and the density of the noise suppression sheet was 2.5 g / cm ³ or more. The above frequencies existed in the range of 1 to 10 MHz, and the μ ″ value at 10 GHz exceeded 2. The total substitution amount of Al, Co, Ni, Cr, Nb, Mo, Ta, and W with respect to Fe was Inventive Examples 28, 30, 32, and 34 at 3 atomic% or less had a high μ ″ value at 10 GHz of 2.5 or more. It is considered that the alloy having a total substitution amount of Al, Co, Ni, Cr, Nb, Mo, Ta and W with respect to Fe exceeding 3 atomic% has reduced the magnetic flux density of the alloy powder. It is more preferable that the total substitution amount of Al, Co, Ni, Cr, Nb, Mo, Ta, and W to be 3 atomic% or less.

  According to the present invention, it is possible to obtain a near-field noise suppression sheet that can cope with magnetic field noise in a wide band of MHz to GHz and has flame retardancy.

Claims (11)

A base material made of an organic material, a flat alloy powder supported in the base material, and a flame retardant dispersed in the base material, a near-field noise suppression sheet including:
The alloy powder is represented by the following formula in atomic%: Fe _100-X1-Y1 (Si, P, C) _X1 Cu _Y1 (where 16 ≦ X1 + Y1 ≦ 24, 14.5 ≦ X1 ≦ 24, and 0 ≦ Y1 ≦ 1.5) Alloy powder and / or composition formula: Fe _100-X2-Y2 (Si, B, C) _X2 Cu _Y2 (16 ≦ X2 + Y2 ≦ 24, 14.5 ≦ X2 ≦ 24, and 0) ≦ Y2 ≦ 1.5), wherein the phase structure of the alloy powder comprises only an amorphous phase or a mixture of an amorphous phase and a crystal phase mainly composed of α-Fe. Consisting of
The average particle size of the flame retardant is 10 μm or less,
Further, a near-field noise suppression sheet having a density of 2.5 g / cm ³ or more.   The alloy powder may have 19 ≦ X1 + Y1 ≦ 21, 18 ≦ X1 ≦ 21, and 0 ≦ Y1 ≦ 1.0, and / or 19 ≦ X2 + Y2 ≦ 21, 18 ≦ X2 ≦ 21, and 0 ≦ Y2 ≦ 1.0. The near-field noise suppression sheet according to claim 1, which satisfies the following.   The frequency at which the value of μ ″ is 1 or more is 1 MHz or more and 10 MHz or less, and the value of μ ″ at 10 GHz is 2 or more at the rise of μ ″ dispersion of the near-field noise suppression sheet. The near-field noise suppression sheet according to 1.   The near-field noise suppression sheet according to any one of claims 1 to 3, wherein a coercive force of the alloy powder is 0.5 A / cm or more and 8 A / cm or less.   5. The flame retardant according to claim 1, wherein the flame retardant is one or more non-halogen flame retardants selected from aluminum hydroxide, magnesium hydroxide, zinc borate, melamine cyanate, and red phosphorus. The near-field noise suppression sheet according to any one of the preceding claims.   3. The alloy powder according to claim 1, wherein 3 atomic% or less of the Fe is replaced with one or more elements selected from Al, Co, Ni, Cr, Nb, Mo, Ta, and W. The near-field noise suppression sheet according to any one of claims 5 to 10.   The near-field noise suppression sheet according to any one of claims 1 to 6, wherein an average value of aspect ratios of the alloy powder is 10 or more and 100 or less.   The near-field noise suppression sheet according to any one of claims 1 to 7, wherein the average value of the thickness of the alloy powder is 0.1 µm or more and 1.5 µm or less. The near-field noise suppression sheet according to any one of claims 1 to 8, wherein the near-field noise suppression sheet has a surface resistance of 10 ⁵ Ω / □ or more.   The near-field noise suppression sheet according to any one of claims 1 to 9, wherein the base material does not include a halogen element.   The noise suppression sheet according to any one of claims 1 to 10, wherein the noise suppression sheet includes one or more oxides selected from a silicon-based, a titanium-based, an aluminum-based, and a zirconium-based, and a particle diameter of the oxide is 100 nm or less. The near-field noise suppression sheet according to any one of the preceding claims.