JP2012038807A - Electromagnetic shield sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic shield sheet with an excellent magnetic-field shield property even if the sheet is made thinner.SOLUTION: An electromagnetic shield sheet includes a multilayer film having conductor layers 1 laminated to sandwich each of two or more ferromagnetic layers 2, 3. The ferromagnetic layers 2, 3 are made of two or more different kinds of ferromagnets.

Description

  Embodiments described herein relate generally to an electromagnetic shield sheet that shields electromagnetic noise.

  In mobile devices such as mobile phones and notebook personal computers, a sheet metal shield made of a metal plate shaped to cover electronic components is used to shield electromagnetic noise generated from electronic components operating at high frequencies. It has been.

  However, the sheet metal shield is an obstacle to making the mobile device thinner because the height of the shield case is increased.

JP 2000-348916 A

  In order to reduce the thickness of mobile devices, it is conceivable to shield electromagnetic noise by covering electronic components with a thin conductive sheet made of copper (Cu) or silver (Ag) instead of a sheet metal shield. .

  However, when a thin conductive sheet is used, the magnetic field shielding effect is reduced, so the thickness of the conductive sheet needs to be increased to some extent. As a result, the flexibility is inferior and it becomes difficult to completely seal the electronic component, and thus there is a problem that a large shielding effect cannot be obtained.

  The problem to be solved by the present invention is to provide an electromagnetic shielding sheet having excellent magnetic field shielding characteristics even if it is thinned.

  In order to solve the above problems, an electromagnetic shield sheet according to an embodiment includes a laminated film in which a conductor layer is laminated so as to sandwich each of two or more ferromagnetic layers, and the two or more layers of the ferromagnetic material. The layer is characterized by comprising two or more different ferromagnetic materials.

It is sectional drawing which shows the structure of the electromagnetic shielding sheet which concerns on Embodiment 1. FIG. It is sectional drawing which shows the structure of the electromagnetic shielding sheet which concerns on Embodiment 1. FIG. It is a perspective view which shows the structure of the simulation model of the electromagnetic shielding sheet which concerns on Embodiment 1. FIG. It is sectional drawing which shows the structure of the simulation model of the electromagnetic shielding sheet which concerns on Embodiment 1. FIG. Is a diagram showing frequency characteristics of relative permeability of the Ni ₈₀ Fe ₂₀ according to the first and second embodiments. Is a diagram showing frequency characteristics of relative permeability of Co ₈₅ Nb ₁₂ Zr ₃ according to the first embodiment. It is sectional drawing of the electromagnetic shielding sheet which concerns on Embodiment 1. FIG. It is sectional drawing of the electromagnetic shielding sheet only of a conductor. The Ni ₈₀ Fe ₂₀ is a cross-sectional view of an electromagnetic shielding sheet using one layer. The Co ₈₅ Nb ₁₂ Zr ₃ is a cross-sectional view of an electromagnetic shielding sheet using one layer. It is a figure which shows the frequency characteristic of the magnetic field shielding effect of the electromagnetic shielding sheet which concerns on Embodiment 1. FIG. 6 is a perspective view of an electromagnetic shield sheet according to Embodiment 2. FIG. It is sectional drawing of the electromagnetic shielding sheet which concerns on Embodiment 2. FIG. It is sectional drawing of the electromagnetic shielding sheet which concerns on Embodiment 2. FIG. It is sectional drawing which shows the structure of the simulation model of the electromagnetic shielding sheet which concerns on Embodiment 2. FIG. It is sectional drawing which shows the structure of the simulation model of the electromagnetic shielding sheet which concerns on Embodiment 2. FIG. It is sectional drawing which shows the structure of the simulation model of the electromagnetic shielding sheet which concerns on Embodiment 2. FIG. It is sectional drawing which shows the structure of the simulation model of the electromagnetic shielding sheet which concerns on Embodiment 2. FIG. It is a figure which shows the frequency characteristic of the magnetic field shielding effect of the electromagnetic shielding sheet which concerns on Embodiment 2. FIG.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view illustrating a configuration of an electromagnetic shield sheet according to the first embodiment. This electromagnetic shield sheet is constituted by a laminated film composed of five layers in which a base material 4, a conductor layer 1, a ferromagnetic layer 2, a conductor layer 1, a ferromagnetic layer 3 and a conductor layer 1 are sequentially laminated. . The ferromagnetic layer 2 and the ferromagnetic layer 3 are preferably composed of a conductive ferromagnetic material. The ferromagnetic layer 2 and the ferromagnetic layer 3 are made of two different types of ferromagnetic materials.

  An electromagnetic shield sheet in which a conductor layer and a ferromagnetic layer are laminated has a high magnetic field shielding effect at the ferromagnetic resonance frequency of the ferromagnetic material. Therefore, an electromagnetic shield sheet using only one type of ferromagnetic material as shown in FIG. 2 can obtain a particularly high magnetic field shielding effect at the ferromagnetic resonance frequency, but can obtain a high magnetic field shielding effect in a wide band. could not.

  According to the electromagnetic shield sheet shown in FIG. 1 according to the first embodiment, since two types of ferromagnetic materials of the ferromagnetic layer 2 and the ferromagnetic layer 3 are used, different ferromagnetic resonance frequencies and different ferromagnetic resonances are used. A high magnetic field shielding effect can be obtained in a frequency band between frequencies.

  In the example shown in FIG. 1, the ferromagnetic layer 2, the ferromagnetic layer 3, and the three conductor layers 1 formed so as to sandwich them are configured. The number of layers of the conductor layer 1, the ferromagnetic layer 2, and the ferromagnetic layer 3 is not limited to the above. Increasing the number of ferromagnetic layers 2 and ferromagnetic layers 3 can enhance the magnetic field shielding effect.

  The conductor layer 1 is made of a nonmagnetic material (conductor) such as silver (Ag), copper (Cu), or aluminum (Al). Further, a simple substance of nickel (Ni) or cobalt (Co) having a relative permeability of 10 or less at a high frequency, or a ferromagnetic material made of a compound thereof is also considered as a constituent of the conductor layer 1.

The ferromagnetic layer 2 and the ferromagnetic layer 3 are composed of a simple substance of iron (Fe), nickel (Ni) or cobalt (Co), or a compound containing iron (Fe), nickel (Ni) or cobalt (Co). It is comprised from the soft-magnetic body which consists of. Examples of the compound include Ni ₈₀ Fe ₂₀ , Co ₈₅ Nb ₁₂ Zr ₃ , and Co ₆₇ Zr ₈ O ₂₅ .

  The base material 4 is made of an insulator, a conductor, or a semiconductor, and may be a flexible material such as a PET film or a polyimide sheet, or a non-flexible material such as a glass epoxy substrate or a glass substrate. The substrate 4 may be a semiconductor such as silicon, GaAs, SiC, or GaN.

  The conductor layer 1, the ferromagnetic layer 2, and the ferromagnetic layer 3 are formed by a method such as sputtering, vapor deposition, plating, or spraying.

  Moreover, since this magnetic field shield sheet contains the conductor layer 1, it can shield an electric field and becomes an electromagnetic shield sheet that shields not only a magnetic field but also an electric field.

  Next, since the shielding effect of electromagnetic noise of the electromagnetic shielding sheet configured as described above was confirmed by simulation, the result will be described.

FIG. 3 is a perspective view illustrating a configuration of a simulation model of the electromagnetic shield sheet according to the first embodiment, and FIG. 4 is a cross-sectional view thereof. In this simulation model, the wiring 10 in the silicon 4b is used as a noise source, and an electromagnetic field is blocked by an electromagnetic shield sheet. The width of the wiring 10 in the silicon 4b is 0.033 mm, the thickness of the epoxy resin 4a is 0.1 mm, the thickness of the silicon 4b is 0.5 mm, and the thickness of the PET sheet 5 is 0.1 mm. The magnetic field shielding effect was calculated from the difference between the values obtained by dividing the magnetic field strength in the y direction on the magnetic field strength measurement surface A by area. The magnetic field strength measurement surface A was arranged directly above the wiring 10 by 0.622 μm, and the size was 0.1 mm square.

  The electromagnetic shield sheet is composed of a laminated film of five layers in which the conductor layer 1, the ferromagnetic layer 2, the conductor layer 1, the ferromagnetic layer 3 and the conductor layer 1 are sequentially laminated, and the thickness of the conductor layer 1 is 0. .66 μm, the thickness of the ferromagnetic layer 2 and the ferromagnetic layer 3 is 0.2 μm, and the total thickness of the electromagnetic shield sheet is 2.0 μm.

The conductivity of the conductor layer 1 is 10 uΩcm. The ferromagnetic layer 2 is Ni ₈₀ Fe ₂₀ and has the frequency characteristics of the relative permeability shown in FIG. The ferromagnetic layer 3 is Co ₈₅ Nb ₁₂ Zr ₃ and has a frequency characteristic of relative permeability shown in FIG. The ferromagnetic resonance frequency is 890 MHz. A sectional view of this electromagnetic shield sheet is shown in FIG.

For comparison, in addition to a simulation model of an electromagnetic shield sheet using two types of ferromagnetic materials, an electromagnetic shield sheet having only a conductor shown in FIG. 8 and an electromagnetic shield using one layer of Ni ₈₀ Fe ₂₀ shown in FIG. A simulation of an electromagnetic shielding sheet using one sheet of Co ₈₅ Nb ₁₂ Zr ₃ as shown in FIG. 10 was also performed. The total film thickness of the electromagnetic shield sheet was 2 um.

The simulation result of the magnetic field shielding effect of these four electromagnetic shielding sheets is shown in FIG. In the electromagnetic shield sheets shown in FIGS. 9 and 10, the magnetic resonance effect of Ni ₈₀ Fe ₂₀ is 500 MHz, and the magnetic resonance effect of Co ₈₅ Nb ₁₂ Zr ₃ is 890 MHz. . These have a higher magnetic field shielding effect at 10 to 8000 MHz than the conductor-only electromagnetic shield sheet shown in FIG.

Compared with these, in the electromagnetic shielding sheet shown in FIG. 7, the magnetic resonance shield of Ni ₈₀ Fe _{20 has} a ferromagnetic resonance frequency of 500 MHz or more, and the magnetic resonance frequency of Co ₈₅ Nb ₁₂ Zr _{3 has} a ferromagnetic resonance frequency of 890 MHz or less and 60 dB or more. And has a high magnetic field shielding effect over a wide band.

  From the above, in the electromagnetic shield sheet using two kinds of soft magnetic materials having different ferromagnetic resonance frequencies as shown in FIG. 7, a high magnetic field shielding effect can be obtained at the ferromagnetic resonance frequencies and the band between them. .

  In addition, magnetic anisotropy can be induced in two directions in different layers, and the magnetic field shielding effect can be increased in two orthogonal directions. FIG. 12 shows an example in which the easy axis directions of magnetic anisotropy are orthogonal to each other in different layers. Magnetic anisotropy is induced by a method such as forming a film while applying a magnetic field.

  In addition, a protective film such as Ti or polyimide may be formed on the uppermost layer of the shield for the purpose of preventing oxidation and moisture absorption.

In order to realize an electromagnetic shield sheet having the maximum value of the magnetic field shielding effect at three frequencies and having a broader magnetic field shielding effect, three types of ferromagnetic materials may be used. As the three types of ferromagnetic materials, in addition to NiFe and CoNbZr, Co ₆₇ Zr ₈ O ₂₅ having a ferromagnetic resonance frequency at 2.6 GHz may be used.

(Embodiment 2)
The electromagnetic shield sheet shown in FIG. 13A is a laminated film composed of four layers in which a ferromagnetic layer 2, a conductor layer 1, a ferromagnetic layer 2, and a conductor layer 1 are sequentially laminated on a substrate 4. It is constituted by. The electromagnetic shield sheet shown in FIG. 13B is a laminated film composed of four layers in which a conductor layer 1, a ferromagnetic layer 2, a conductor layer 1, and a ferromagnetic layer 2 are sequentially laminated on a substrate 4. It is constituted by.

  Further, the electromagnetic shielding sheet shown in FIG. 14 is constituted by a laminated film composed of three layers in which a ferromagnetic layer 2, a conductor layer 1, and a ferromagnetic layer 2 are sequentially laminated on a substrate 4. Yes. The electromagnetic shield sheet shown in FIGS. 13 and 14 can obtain a higher magnetic field shielding effect than an electromagnetic shield sheet made of only a conductor.

  In the example shown in FIG. 13, two layers of the ferromagnetic layer 2 and the conductor layer 1 are sequentially laminated. However, the layer adjacent to the substrate 4 is the ferromagnetic layer 2 and the uppermost layer is the conductor layer 1. Alternatively, if the layer adjacent to the substrate 4 is the conductor layer 1 and the uppermost layer is the ferromagnetic layer 2, the number of the conductor layers 1 and the ferromagnetic layers 2 is not limited to the above.

  Further, in the example shown in FIG. 14, the conductor layer 1 and the two ferromagnetic layers 2 formed so as to sandwich the conductor layer 1 are included. However, the conductor layer 1 may be sandwiched between the ferromagnetic layers 2. For example, the number of ferromagnetic layers 2 and conductor layers 1 is not limited to the above.

  The conductor layer 1 is made of a nonmagnetic material (conductor) such as silver (Ag), copper (Cu), or aluminum (Al). Further, a simple substance of nickel (Ni) or cobalt (Co) having a relative permeability of 10 or less at a high frequency, or a ferromagnetic material made of a compound thereof is also considered as a constituent of the conductor layer 1.

The ferromagnetic layer 2 is made of a soft magnetic material made of iron (Fe), nickel (Ni) or cobalt (Co) alone or a compound containing iron (Fe), nickel (Ni) or cobalt (Co). Has been. Examples of the compound include Ni ₈₀ Fe ₂₀ , Co ₈₅ Nb ₁₂ Zr ₃ , and CoZrO.

  The base material 4 is made of an insulator or a semiconductor, and may be a flexible material such as a PET film, a polyimide sheet, or a copper sheet, or a non-flexible material such as a glass epoxy substrate, a glass substrate, or the like. The substrate 4 may be a semiconductor such as silicon, GaAs, SiC, or GaN.

  The conductor layer 1 and the ferromagnetic layer 2 are formed by a method such as sputtering, vapor deposition, plating, or spraying. Moreover, since this magnetic field shield sheet contains the conductor layer 1, it can shield an electric field and becomes an electromagnetic shield sheet that shields not only a magnetic field but also an electric field.

  Next, since the shielding effect of electromagnetic noise of the electromagnetic shielding sheet configured as described above was confirmed by simulation, the result will be described.

  The simulation model changed the layer structure of the electromagnetic shield sheet and analyzed four types. 15, FIG. 16, FIG. 17, and FIG. 18 are sectional views of the analyzed simulation models. In the simulation models of FIGS. 15, 16, 17, and 18, the wiring 10 in the silicon 4b is used as a noise source, and an electromagnetic field is blocked by an electromagnetic shield sheet. The width of the wiring 10 in the silicon 4b is 0.033 mm, the thickness of the epoxy resin 4a is 0.1 mm, the thickness of the silicon 4b is 0.5 mm, and the thickness of the PET sheet 5 is 0.1 mm. The magnetic field shielding effect was calculated from the difference between values obtained by dividing the magnetic field strength in the y direction on the magnetic field strength measurement surface A by area. The magnetic field strength measurement surface A was arranged directly above the wiring 10 by 0.622 μm, and the size was 0.1 mm square.

  FIG. 15 shows an electromagnetic shield sheet composed of only the conductor layer 1 and was analyzed for comparison with other electromagnetic shield sheets. The thickness of the conductor layer 1 is 2 um.

  FIG. 16 shows an electromagnetic shield sheet in which a conductor layer 1, a ferromagnetic layer 2, a conductor layer 1 and a ferromagnetic layer 2 are sequentially laminated on a PET sheet 5. The conductor layer 1 has a thickness of 0.8 μm, the ferromagnetic layer 2 has a thickness of 0.2 mm, and the total thickness is 2 μm.

  FIG. 17 shows an electromagnetic shield sheet in which a ferromagnetic layer 2, a conductor layer 1, a ferromagnetic layer 2, and a conductor layer 1 are sequentially laminated on a PET sheet 5. The conductor layer 1 has a thickness of 0.8 μm, the ferromagnetic layer 2 has a thickness of 0.2 mm, and the total thickness is 2 μm.

  FIG. 18 shows an electromagnetic shield sheet in which the ferromagnetic layer 2, the conductor layer 1, and the ferromagnetic layer 2 are sequentially laminated on the PET sheet 5. The conductor layer 1 has a thickness of 1.6 μm, the ferromagnetic layer 2 has a thickness of 0.2 mm, and the total thickness is 2 μm.

The conductor layer 1 has a conductivity of 10 uΩcm. The ferromagnetic layer 2 is Ni ₈₀ Fe ₂₀ . The frequency characteristics of the relative magnetic permeability of Ni ₈₀ Fe ₂₀ were input as shown in FIG.

  The simulation result of the magnetic field shielding effect of these four electromagnetic shielding sheets is shown in FIG. The electromagnetic shielding sheets shown in FIGS. 16 and 17 have a higher magnetic field shielding effect at 10 MHz to 5000 MHz than the electromagnetic shielding sheet having only the conductor shown in FIG.

  Moreover, the electromagnetic shielding sheet shown in FIG. 18 has a higher magnetic field shielding effect at 10 MHz to 900 MHz than the electromagnetic shielding sheet of only the conductor shown in FIG. From the above, it can be seen that the electromagnetic shield sheets shown in FIGS. 16, 17, and 18 have a frequency band with a higher magnetic field shielding effect than the electromagnetic shield sheet having only a conductor.

  When two or more ferromagnetic layers 1 are used, a high magnetic field shielding effect can be obtained in a wide band by using two or more types of soft magnetic materials in different layers. In addition, when two or more ferromagnetic layers 1 are used, magnetic anisotropy can be induced in two directions in different layers, and the magnetic field shielding effect can be increased in two orthogonal directions.

  In addition, a protective film such as Ti or polyimide may be formed on the uppermost layer of the shield for the purpose of preventing oxidation and moisture absorption.

  According to the embodiment described above, a broadband magnetic field shielding effect is obtained by configuring a laminated film in which two or more kinds of conductive ferromagnetic layers and a conductor layer made of a nonmagnetic material are sandwiched therebetween. The electromagnetic shielding sheet which has can be provided.

  As mentioned above, although several embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Conductor layer, 2, 3 ... Ferromagnetic material layer, 4 ... Base material, 4a ... Epoxy resin, 4b ... Silicon, 5 ... PET sheet, 6a, 6b ... Complete conductor, 10 ... Wiring, A ... Magnetic field strength measurement surface .

Claims (6)

  It is composed of a laminated film in which conductor layers are laminated so as to sandwich each of two or more ferromagnetic layers, and the two or more ferromagnetic layers are composed of two or more kinds of different ferromagnetic materials. Electromagnetic shield sheet.   Each of the two or more types of ferromagnetic layers has different ferromagnetic resonance frequencies, and has a high magnetic field shielding effect in a band between different ferromagnetic resonance frequencies and different ferromagnetic resonance frequencies. Item 1. The electromagnetic shielding sheet according to Item 1.   One or more ferromagnetic layers and one or more conductor layers are alternately stacked, and each of the one or more ferromagnetic layers and the one or more conductor layers is formed of a laminated film having the same number of layers. An electromagnetic shield sheet, wherein a base material is disposed in contact with a magnetic layer.   One or more ferromagnetic layers and one or more conductor layers are alternately laminated, and the conductor layer comprises a laminated film in which the one or more ferromagnetic layers and the one or more conductor layers have the same number of layers. An electromagnetic shielding sheet, wherein the base material is placed in contact with the electromagnetic shielding sheet.   An electromagnetic shield sheet comprising a laminated film in which one or more ferromagnetic layers and one or more conductor layers are alternately laminated, and the ferromagnetic layers are laminated so as to sandwich the one or more conductor layers.   6. The electromagnetic shield sheet according to claim 1, wherein the ferromagnetic layer is made of a conductive soft magnetic material.

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