JP2010219126A - Electromagnetic interference suppressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame-retardant electromagnetic interference suppressor formed of complex of an organic binder which does not contain halogen, and soft magnetic powder, is easy to form in a sheet, does not generate gas, and exhibits high real part permeability and tensile strength which is not subject to the Export Trade Control Order. <P>SOLUTION: The electromagnetic interference suppressor 1 is formed by dispersing the soft magnetic powder 2 in the flame-retardant organic binder 3. A surface of the soft magnetic powder 2 is previously treated by a silane coupling agent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electromagnetic interference suppressor to be mounted in order to prevent the influence of unnecessary electromagnetic waves generated in an electronic device to the outside, interference in an internal circuit, malfunction due to external electromagnetic waves, and the like.

  Various problems related to EMI and immunity, such as unintentionally radiating and transmitting electromagnetic waves from communication devices and electronic devices, and causing malfunctions of the devices themselves due to external interference and internal interference, are recent digital technologies. With the evolution of, it has increased rapidly in the high frequency band.

  In addition, electronic devices are becoming lighter, thinner, and smaller, and the mounting density of electronic components on circuits has increased dramatically. Electromagnetic interference caused by electromagnetic interference between components and circuit boards The possibility of failure is extremely high.

  As a countermeasure against the occurrence of such unwanted electromagnetic waves, leakage, and malfunction due to mutual interference, in order to prevent magnetic field sources such as magnets from affecting other electronic circuits, real terms of complex permeability (real part transmission) The use of a magnetic shield material using a magnetic material having a high magnetic permeability (μ ′) and a method of inserting a choke coil or a filter into a noise transmission line are employed.

  As one of countermeasures, a method of arranging a sheet-like electromagnetic interference suppressor in which soft magnetic powder is dispersed in an organic binder in the vicinity of an electronic component or a circuit has been proposed and put into practical use.

  A conventionally used electromagnetic interference suppressor is disclosed in Patent Document 1. The technique disclosed in Patent Document 1 has a shielding effect equivalent to that of a conductive shield material for transmission of electromagnetic waves, and as an electromagnetic interference suppressor that does not promote electromagnetic coupling by reflection for reflection of electromagnetic waves. A conductive support and an insulating soft magnetic layer provided on at least one surface of the conductive support, the insulating soft magnetic layer including a soft magnetic powder and an organic binder; A dielectric layer is provided on the upper or lower surface of the insulating soft magnetic layer, and the conductive support is a conductive soft magnetic support having soft magnetism.

  This type of electromagnetic interference suppressor utilizes a term resulting from magnetic resonance, which is a loss term of permeability, that is, an imaginary term (imaginary permeability) μ ″ of complex permeability, which is disclosed in Patent Document 1. Therefore, it is excellent in processability and mountability and is suitable for a wide range of applications.

  Further, Fe-Si alloys, Fe-Si-Al alloys, Fe-Si-Cr alloys, and metal oxides are used as soft magnetic materials constituting the electromagnetic interference suppressor. In particular, in order to improve the magnetic permeability characteristics, a metal alloy having a large magnetization is used.

  As one of the organic binders, chlorinated polyethylene, chloroprene rubber and the like having excellent powder filling properties, flexibility, and flame retardancy have been used. Such halogen-based organic binders have become difficult to use due to the so-called green procurement and the regulation of two halogen-based flame retardants in accordance with the RoHS directive in Europe. Organic binders are needed.

  Patent Document 2 discloses a flame-retardant electromagnetic interference suppressor that does not use a halogen-based organic binder. The technology disclosed in Patent Document 2 is a composite magnetic body that does not use any of these halogen-based materials such as a halogen-based binder such as a resin or an elastomer and a bromine-based flame retardant containing halogen, and electromagnetic In order to provide an interference suppressor, the composite magnetic body includes a soft magnetic powder and a silicone rubber, and the silicone rubber is a solid silicone rubber or a liquid reaction-curing silicone rubber. Is preferred.

  In the electromagnetic interference suppressor using silicone rubber as the binder as in Patent Document 2, there is a problem that sufficient permeability characteristics cannot be obtained and the sheet cannot be molded. In addition, although it is not harmful because of the use of silicone rubber, the generation of siloxane gas causes problems such as poor insulation at electrical contact points, or because insulation is added. There is a problem that the signal cannot be read.

Japanese Patent Laid-Open No. 7-212079 JP 2001-119189 A

  In Patent Document 2, a silicone rubber is used to achieve halogen-free flame retardant electromagnetic interference suppressors, but there is a problem associated with the generation of siloxane gas. In addition, if rubber or resin that does not contain halogen is used in the binder, soft magnetic powder does not disperse well in the binder, and improvement in magnetic permeability characteristics cannot be expected. There was a problem that it became difficult, even if it could be made into a sheet, the tensile strength was too high as 7 MPa or more, and it was subject to the Export Trade Control Order.

  For example, an acrylic rubber is also conceivable as a rubber containing no halogen. The acrylic rubber can have a crosslinkable group in structure, and examples of the crosslinkable group include an epoxy group. Further, there may be no crosslinking group. However, if there is no crosslinkable group, it is difficult to mold the sheet and there are problems such as powder falling. If it has an epoxy group, if it is made into a sheet as it is, the tensile strength will be 7 MPa or more. In some cases, it became a target item.

  The present invention has been made to solve the above-mentioned problems, and its purpose is a composite of a halogen-free organic binder and a soft magnetic powder, which can be easily formed into a sheet without generating gas. It is to provide a flame retardant electromagnetic interference suppressor having high real part permeability and tensile strength not subject to the Export Trade Control Order.

  As a result of the inventor's earnest study on an electromagnetic interference suppressor obtained by dispersing a soft magnetic powder made of a metal soft magnetic material in an organic binder, the present inventor has achieved halogen-free flame retardancy. In addition, the present invention is based on the finding that the dispersibility of the soft magnetic powder in the organic binder is improved to improve the magnetic permeability, and the sheet can be easily formed.

  In order to solve the above problems, an electromagnetic interference suppressor according to the present invention is an electromagnetic interference suppressor in which a soft magnetic powder is dispersed in a flame-retardant organic binder, and at least a part of the soft magnetic powder is used. Surface treatment is performed in advance with a silane coupling agent.

  The soft magnetic powder is preferably a spherical or flat metal soft magnetic material powder.

  A soft magnetic powder surface-treated with a silane coupling agent may be included in an amount of 70% to 90% by weight, and an organic binder may be included in an amount of 10% to 30% by weight.

  As the organic binder, it is desirable to use an acrylic rubber containing no halogen, and an epoxy group is desirable as the crosslinking group of the acrylic rubber.

  The silane coupling agent used for the surface treatment of the soft magnetic powder is desirably 0.5 wt% or more and 10.0 wt% or less with respect to the soft magnetic powder.

  It is desirable that the electromagnetic interference suppressor has a tensile strength of 7 MPa or less and the real term μ ′ of the complex permeability at 1 MHz is 80 or more.

  According to the present invention, in an electromagnetic interference suppressor composed of a composite in which soft magnetic powder is dispersed in an organic binder, the organic binder is used by using the soft magnetic powder surface-treated with a silane coupling agent. The dispersibility of the soft magnetic powder in the inside can be improved, the magnetic permeability can be improved, and the sheet can be easily formed.

  An electromagnetic wave obtained by constituting so as to contain 70% by weight to 90% by weight of soft magnetic powder surface-treated with a silane coupling agent and 10% to 30% by weight of an organic binder. The interference suppressor has a high permeability characteristic with a real term μ ′ of complex permeability at 1 MHz of 80 or more, has a tensile strength of less than 7 MPa, and can be used not only on a plane but also on a bent surface. Can also be used.

  By using an acrylic rubber having an epoxy group as a crosslinking group as an organic binder, a halogen-free flame-retardant electromagnetic interference suppressor can be obtained.

  As the soft magnetic powder, in addition to Fe-Si-Al alloy powder, pure iron, Fe-Si alloy, Fe-Si-Cr alloy, Ni-Fe alloy, Mo-Ni-Fe alloy powder, or soft magnetic amorphous powder Alloy powder can be used.

  Examples of the silane coupling agent include HMDS (hexamethyldisilazane).

  According to the present invention, it does not contain halogen, has excellent flame retardancy, has a real term with high complex permeability, has excellent workability and mountability, and has tensile strength not subject to the Export Trade Control Order. An electromagnetic interference suppressor can be provided.

It is a conceptual diagram which shows the cross-section of the electromagnetic interference suppression body in this invention. It is a figure which shows the frequency dependence of the real term μ 'and the imaginary term μ "of the complex permeability of the electromagnetic interference suppressor obtained in Example 1 and Comparative Example 1.

  An electromagnetic interference suppressor and a manufacturing method thereof according to the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a conceptual diagram showing a cross-sectional structure of an electromagnetic interference suppressor according to the present invention. The electromagnetic interference suppressor 1 has a structure in which a flat soft magnetic powder 2 is dispersed in an organic binder 3.

  For the production of the electromagnetic interference suppressing body 1 according to the present invention, an acrylic rubber whose cross-linking group is an epoxy group is used as the organic binder 3 containing no halogen, and the soft magnetic powder 2 is Fe, which is a soft magnetic alloy. -Si-Al alloy powder can be used.

  In order to use acrylic rubber having an epoxy group as a crosslinking group for the organic binder 3 and to keep the tensile strength to 7 MPa or less, the kneaded product of the soft magnetic powder 2 and the organic binder 3 is processed into a sheet shape. In doing so, it is important to perform molding by a short-time heat press for about several minutes at a temperature lower than 150 to 175 ° C. which is a heat resistant temperature of general acrylic rubber.

  At this time, if the temperature of the hot press is too low, the soft magnetic powder 2 is not filled in the organic binder 3 at a high density. Therefore, it is desirable to perform hot press molding at least at 100 ° C. or higher. Preferably, the electromagnetic interference suppressor 1 can be obtained by performing a heat press at 145 ° C. or higher.

  In addition, the soft magnetic powder 2 other than the Fe-Si-Al alloy includes pure iron, Fe-Si alloy, Fe-Si-Cr alloy, Ni-Fe alloy, Mo-Ni-Fe alloy, and soft magnetism with high magnetization. Amorphous alloys can be used.

  Further, as the soft magnetic powder 2, it is preferable to use an Fe—Si—Al alloy powder having an aspect ratio (D / t) of 20. The soft magnetic powder 2 and the silane coupling agent are put into a biaxial kneader, and the surface of the soft magnetic powder 2 is coated with the silane coupling agent by mixing and stirring. Make it easy to do. The surface treatment is not necessarily performed on the entire soft magnetic powder, and may be performed on only a part within a range where a sufficient effect can be obtained.

  The amount of the silane coupling agent is preferably in the range of 0.5 wt% to 10 wt% with respect to the soft magnetic powder 2. If it is less than 0.5% by weight, the effect of the silane coupling agent cannot be sufficiently obtained. If the amount exceeds 10% by weight, the organic binder 3 is softened, and the soft magnetic powder 2 cannot be filled at a high density. Preferably, 1% by weight of a silane coupling agent may be added to the soft magnetic powder 2.

Example 1
As Example 1, 85 wt% Fe—Si—Al alloy powder and 15 wt% organic whose surface is coated with a silane coupling agent using acrylic rubber having an epoxy group as a crosslinking group as the organic binder 3 are used. Binder 3 was blended. The organic binder 3 and the soft magnetic powder 2 were mixed with a biaxial kneader, kneaded and uniformly dispersed to obtain a kneaded product of the electromagnetic interference suppressor 1.

  Thereafter, the kneaded product of the electromagnetic interference suppressor 1 was processed into a sheet having a thickness of 0.3 mm by hot press molding at 145 ° C. to obtain the electromagnetic interference suppressor 1.

  The blending ratio at the time of producing the electromagnetic interference suppressing body 1 in Example 1 is such that the soft magnetic powder 2 is 70 wt% or more and 90 wt% or less, and the organic binder 3 is 10 wt% or more and 30 wt% or less. Is desirable. When the soft magnetic powder 2 is less than 70% by weight, the magnetic permeability characteristics are not improved, and when the soft magnetic powder 2 is more than 90% by weight, the effect of the organic binder 3 is not sufficiently obtained and processed into a sheet shape. It becomes difficult to do, and powder fall off occurs.

  As Comparative Example 1 with respect to Example 1, acrylonitrile butadiene rubber, which is one of rubbers having neither an epoxy group nor a halogen as a crosslinking group, is used as the organic binder 3, and the other compounding ratios are the same as those in Example 1. The electromagnetic interference suppressor 1 was obtained by the manufacturing method.

  Then, the complex magnetic permeability characteristic of the electromagnetic interference suppression body 1 obtained in Example 1 and Comparative Example 1 was measured using an impedance material analyzer.

  2 is a diagram showing the frequency dependence of the real term μ ′ and the imaginary term μ ″ of the complex permeability of the electromagnetic interference suppressor 1 obtained in Example 1 and Comparative Example 1. Obviously, in Example 1. FIG. The obtained one shows excellent permeability characteristics.

  Moreover, in order to confirm whether the soft magnetic substance powder 2 was disperse | distributed in the organic binder 3, and was filled with high density, the specific gravity of the electromagnetic interference suppression body 1 was measured by the Archimedes method.

  Further, the obtained electromagnetic interference suppressor 1 has a tensile strength of Specimen No. 3, test speed 50 mm / min, and distance between grippers 40 mm according to JIS K6251 which is the tensile property standard of vulcanized rubber and thermoplastic rubber. It was measured.

  Table 1 shows the real term μ ′ (1 MHz), the specific gravity, and the tensile strength of the complex permeability at 1 MHz of the electromagnetic interference suppressor 1 obtained in Example 1 and Comparative Example 1.

  For the organic binder 3 of Example 1 using an acrylic rubber having an epoxy group as a cross-linking group, the real term μ ′ of the complex permeability at 1 MHz exceeds 80, and a large specific gravity of 2.92 is obtained. Moreover, the tensile strength of 7 MPa or less could be satisfied. In addition, even if the sheet-like electromagnetic interference suppressing body 1 obtained in Example 1 was wound around a cable having a diameter of 6 mm, no cracks or powder drops were observed.

  On the other hand, in Comparative Example 1, the real term μ ′ of the complex permeability at 1 MHz was as low as 40.3, the specific gravity was as low as 2.24, and it was confirmed that the packing density was low.

(Example 2)
Using the acrylonitrile butadiene rubber which is one of the rubbers containing no halogen for the organic binder 3, the electromagnetic interference suppressor 1 was obtained by the same blending ratio and production method as in Example 1.

Example 3
An acrylic rubber having an epoxy group as a crosslinking group was used as the organic binder 3, and 60 wt% Fe-Si-Al soft magnetic powder 2 and 40 wt% organic binder 3 were blended.

(Comparative Example 2)
An acrylic rubber having an epoxy group as a crosslinking group was used as the organic binder 3, and 95 wt% Fe—Si—Al soft magnetic powder 2 and 5 wt% organic binder 3 were blended.

  Thereafter, in the same manner as in Example 1 and Comparative Example 1, the complex permeability characteristics of the obtained electromagnetic interference suppressor 1 were measured. Further, in order to confirm whether the soft magnetic powder 2 is dispersed and filled in the organic binder 3, the specific gravity of the electromagnetic interference suppressor 1 is measured by the Archimedes method, and the tensile properties of the vulcanized rubber and the thermoplastic rubber are further measured. In accordance with JIS K6251 which is a standard, the tensile strength was measured with a test piece shape of No. 3, a test speed of 50 mm / min, and a distance between grips of 40 mm.

  The results are shown in Table 2. The real term μ ′ and imaginary term μ ″ of the complex permeability change corresponding to the type of each binder, and when the acrylic rubber is used for the organic binder 3, the complex permeability μ ′ is higher at 1 MHz. In addition, in Comparative Example 2, since the organic binder 3 was a small amount with respect to the soft magnetic powder 2, the sheet shape could not be maintained after hot pressing. The characteristics could not be evaluated.

  As described above, according to the present invention, it is possible to provide an electromagnetic interference suppressor that has high complex magnetic permeability characteristics without containing halogen, and is excellent in workability and mountability.

  Needless to say, the present invention is not limited to the above-described embodiment, and the design can be changed according to the purpose and application. For example, the metal magnetic material is not limited to the above example. It is also possible to use a dielectric instead of a magnetic material according to the frequency band where noise suppression is performed.

1 Electromagnetic interference suppressor 2 Soft magnetic powder 3 Organic binder

Claims (7)

  An electromagnetic interference suppressor in which a soft magnetic powder is dispersed in an organic binder, and at least a part of the soft magnetic powder is surface-treated with a silane coupling agent in advance.   2. The electromagnetic interference suppressor according to claim 1, wherein the soft magnetic powder is a spherical or flat metal soft magnetic material powder.   The soft magnetic powder surface-treated with the silane coupling agent is contained in an amount of 70 wt% to 90 wt%, and the organic binder is contained in an amount of 10 wt% to 30 wt%. 3. The electromagnetic interference suppressor according to any one of 2 above.   The electromagnetic interference suppressor according to any one of claims 1 to 3, wherein the organic binder is an acrylic rubber that does not contain a halogen and has an epoxy group as a crosslinking group.   5. The surface treatment according to claim 1, wherein the silane coupling agent performs surface treatment in a range of 0.5 wt% to 10 wt% with respect to the weight of the soft magnetic powder. The electromagnetic interference suppressor as described in 1.   6. The electromagnetic interference suppressor according to claim 1, wherein the real term μ ′ of the complex permeability at 1 MHz of the electromagnetic interference suppressor is 80 or more.   The electromagnetic interference suppressor according to any one of claims 1 to 6, wherein the electromagnetic interference suppressor has a tensile strength of less than 7 MPa.

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