Shielded Inductor

Abstract

To provide an improved shielded inductor.SOLUTION: A shielded inductor 100 includes an inductor 200 having a coil 220 and a magnetic core 250, a metal shield 300, and a buffer member 400 interposed between the metal shield 300 and the inductor 200 to prevent the metal shield 300 from adversely affecting the inductor 200.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a shielded inductor. [Background technology]

[0002] Patent Document 1 discloses a shielded inductor including an inductor and a metal shield attached to the inductor. In the shielded inductor of Patent Document 1, the metal shield is made of copper and prevents electromagnetic noise generated from the inductor from affecting other electronic components. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6771585 Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an improved shielded inductor. [Means for solving the problem]

[0005] The inventors of the present invention have confirmed that attaching a metal shield to an inductor provides a high electromagnetic noise suppression effect, but have noticed that problems such as a deterioration in Q characteristics and an unintended shift in the resonant frequency occur. Furthermore, they have found that by interposing a buffer member such as a composite magnetic part or a dielectric part between the metal shield and the inductor, the influence of the metal shield on the inductor can be suppressed while the electromagnetic noise suppression function of the metal shield is exerted. The present invention has been made based on such findings, and specifically provides the following shielded inductor as a means for solving the problems.

[0006] The present invention provides a first shielded inductor, an inductor having a coil and a magnetic core; A metal shield; a buffer member interposed between the metal shield and the inductor to suppress adverse effects of the metal shield on the inductor; Equipped To provide a shielded inductor.

[0007] The present invention provides a second shielded inductor, which is a first shielded inductor, the buffer member includes a spacer provided on the inductor and a composite magnetic portion provided on the spacer, the spacer is made of a non-magnetic and insulating material; The composite magnetic portion includes a binder and soft magnetic powder dispersed in the binder. To provide a shielded inductor.

[0008] The present invention provides a third shielded inductor, which is the second shielded inductor, The thickness t of the spacer satisfies t≧S / 50, where S is the size of the inductor in the thickness direction of the buffer member. To provide a shielded inductor.

[0009] The present invention provides a fourth shielded inductor, which is any one of the first to third shielded inductors, The buffer member has a dielectric portion. To provide a shielded inductor.

[0010] The present invention provides a fifth shielded inductor, which is any one of the first to fourth shielded inductors, The magnetic core includes a magnetic powder and an organic binder that binds the magnetic powder, The coil is at least partially embedded within the magnetic core. To provide a shielded inductor.

[0011] The present invention provides a sixth shielded inductor, which is any one of the first to fifth shielded inductors, The metal shield is grounded. To provide a shielded inductor. Effect of the Invention

[0012] The shielded inductor of the present invention is equipped with a metal shield, thereby providing high electromagnetic field noise suppression capabilities, and is also equipped with a buffer material interposed between the metal shield and the inductor, thereby suppressing adverse effects from the metal shield to the inductor. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing a shielded inductor according to a first embodiment of the present invention. [Diagram 2] FIG. 11 is a cross-sectional view showing a shielded inductor according to a second embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view showing an inductor of Comparative Example 1. FIG. [Figure 4] FIG. 11 is a cross-sectional view showing a shielded inductor of Comparative Example 2. [Diagram 5] FIG. 11 is a cross-sectional view showing a shielded inductor of Comparative Example 3. [Figure 6] FIG. 11 is a cross-sectional view showing a shielded inductor of Comparative Example 4. [Figure 7] FIG. 11 is a cross-sectional view showing a shielded inductor of Comparative Example 5. [Figure 8] 13 is a graph showing frequency characteristics of noise attenuation effect in the inductor of Comparative Example 1 and the shielded inductors of Comparative Examples 2 and 3. [Figure 9] 1 is a graph showing frequency characteristics of impedance in the inductor of Comparative Example 1 and the shielded inductors of Comparative Examples 2 and 3. [Figure 10]1 is a graph showing frequency characteristics of the Q value of the inductor of Comparative Example 1 and the shielded inductors of Comparative Examples 2 and 3. [Figure 11] 1 is a graph showing frequency characteristics of noise attenuation effect in the shielded inductor of Example 1, the inductor of Comparative Example 1, and the shielded inductors of Comparative Examples 3 and 4. [Figure 12] 1 is a graph showing frequency characteristics of impedance in the shielded inductor of Example 1, the inductor of Comparative Example 1, and the shielded inductors of Comparative Examples 3 and 4. [Figure 13] 1 is a graph showing frequency characteristics of the Q value of the shielded inductor of Example 1, the inductor of Comparative Example 1, and the shielded inductors of Comparative Examples 3 and 4. [Figure 14] 13 is a graph showing the correlation between the inductance change rate R and the ratio of the thickness t of the spacer to the size S of the inductor in the thickness direction of the buffer member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (First embodiment) As shown in FIG. 1, a shielded inductor 100 according to a first embodiment of the present invention includes an inductor 200, a metal shield 300, and a buffer member 400. The inductor 200 includes a metal shield 300 and a buffer member 400. The metal shield 300 is made of a material such as aluminum.

[0015] (Inductor) As shown in FIG. 1, an inductor 200 of the present embodiment includes a coil 220 and a magnetic core 250 .

[0016] (coil) 1, coil 220 in this embodiment is completely embedded in magnetic core 250. However, the present invention is not limited to this, and coil 220 may be at least partially embedded in magnetic core 250.

[0017] (Magnetic core) 1, the magnetic core 250 of this embodiment is a metal composite core having a dispersed gap. The magnetic core 250 includes magnetic powder 252 and an organic binder 254 that binds the magnetic powder 252 together.

[0018] (magnetic powder) 1, the magnetic powder 252 of this embodiment may be a soft magnetic powder, and in particular may be Fe powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder (Sendust (registered trademark)), amorphous alloy powder, nanocrystal, or a mixture of two or more of these powders. As the Fe-Si alloy powder, for example, Fe-6.5% Si alloy powder or Fe-3.5% Si alloy powder may be used. However, the present invention is not limited thereto, and the magnetic powder 252 is not limited to a soft magnetic powder.

[0019] (organic binder) 1, the organic binder 254 of the present embodiment may be a thermosetting resin, an ultraviolet curing resin, or a thermoplastic resin. The thermosetting resin may be a phenolic resin, an epoxy resin, an unsaturated polyester resin, a polyurethane, a diallyl phthalate resin, a silicone resin, or the like. The ultraviolet curing resin may be a urethane acrylate-based, an epoxy acrylate-based, an acrylate-based, or an epoxy-based resin.

[0020] (Metal Shield) 1, the material of the metal shield 300 in this embodiment is Cu or Al. However, the present invention is not limited to this, and the material of the metal shield 300 may be a metal other than Cu and Al. The metal shield 300 in this embodiment is not grounded. However, the present invention is not limited to this, and the metal shield 300 may be grounded. The metal shield 300 is located above the buffer member 400 in the up-down direction.

[0021] (Cushioning material) 1, buffer member 400 of the present embodiment is interposed between metal shield 300 and inductor 200 to suppress adverse effects of metal shield 300 on inductor 200. Buffer member 400 includes a spacer 420 provided on inductor 200, and a composite magnetic portion 450 provided on spacer 420.

[0022] (Spacer) Referring to FIG. 1, the spacer 420 of this embodiment is made of a non-magnetic and insulating material. Specifically, the material of the spacer 420 may be ceramic or a plastic material such as epoxy, acrylic, or polyimide. More specifically, the material of the spacer 420 is polyetherimide. The thickness t of the spacer 420 satisfies t≧S / 50, where S is the size of the inductor 200 in the thickness direction of the buffer member 400. Specifically, the thickness t of the spacer 420 is 200 μm or more. The thickness direction of the buffer member 400 and the thickness direction of the spacer 420 coincide with each other. The spacer 420 is located above the inductor 200 in the up-down direction. In this embodiment, the up-down direction is the Z direction. Moreover, the up direction is the +Z direction, and the down direction is the −Z direction.

[0023] Unlike the shielded inductor 100 of this embodiment, if spacer 420 is not provided between magnetic core 250 and composite magnetic part 450, that is, if composite magnetic part 450 is directly attached to magnetic core 250 of inductor 200 without providing spacer 420, there is a possibility that the DC superimposition characteristics will deteriorate. However, in this embodiment, spacer 420 is provided between magnetic core 250 and composite magnetic part 450, and therefore deterioration of the DC superimposition characteristics is avoided.

[0024] (Composite magnetic part) 1, composite magnetic part 450 in the present embodiment is a composite magnetic sheet. Note that the present invention is not limited thereto, and composite magnetic part 450 may be formed in a layer on the upper surface of spacer 420. Composite magnetic part 450 is located above spacer 420 in the vertical direction. Metal shield 300 is located above composite magnetic part 450 in the vertical direction. Composite magnetic part 450 includes binder 452 and soft magnetic powder 454 dispersed within binder 452.

[0025] (Binder) 1, the binder 452 of the present embodiment is not particularly limited, and various binding agents can be used. For example, acrylic rubber, (meth)acrylic polymers such as alkyl acrylate copolymers, acrylonitrile-butadiene rubber (NBR), silicone rubber, polyurethane, polyethylene, ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), BT resin, polyamide-imide, polyimide, or the like can be used as the binder 452. The binder 452 binds the soft magnetic powder 454.

[0026] (Soft magnetic powder) 1, the soft magnetic powder 454 of the present embodiment has a flat shape. Although the shape of the soft magnetic powder 454 is not particularly limited, it is preferable that the soft magnetic powder 454 has a flat shape, and it is preferable that most of the flat soft magnetic powder 454 is aligned in the composite magnetic part 450 so as to be generally parallel to the main surface of the composite magnetic part 450.

[0027] As the material of the soft magnetic powder 454, magnetic stainless steel (Fe-Cr-Al-Si alloy), Fe-Si-Al alloy such as Sendust (registered trademark), Permalloy (Fe-Ni alloy), silicon copper (Fe-Cu-Si alloy), Fe-Si alloy, Fe-Si-B(-Cu-Nb) alloy, Fe-Ni-Cr-Si alloy, Fe-Si-Cr alloy, Fe-Si-Al-Ni-Cr alloy, Mo-Ni-Fe, amorphous alloy, etc. are preferable. In particular, Sendust is more preferable as the material of the soft magnetic powder 454. Such soft magnetic powder 454 may be used alone or in combination. In particular, in order to improve the magnetic permeability characteristics, the soft magnetic powder 454 is preferably a metal alloy with high magnetization.

[0028] (Second embodiment) 2, a shielded inductor 100A according to the second embodiment of the present invention includes an inductor 200, a metal shield 300A, and a buffer member 400A. In the shielded inductor 100A of the present embodiment, components that are substantially the same as those in the shielded inductor 100 of the first embodiment described above are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0029] 2, the buffer member 400A of the present embodiment has a spacer 420 and a dielectric portion 470. However, the present invention is not limited to this, and the buffer member 400A does not have to have the spacer 420. In other words, the buffer member 400A may be composed of only the dielectric portion 470.

[0030] 2, examples of the material of dielectric portion 470 in the present embodiment include ceramics, and plastic materials such as epoxy, acrylic, and polyimide. Dielectric portion 470 may be an air gap, and may be any non-magnetic insulator. Dielectric portion 470 is located above inductor 200 in the up-down direction.

[0031] 2, the material of the metal shield 300A in this embodiment is Cu or Al. However, the present invention is not limited to this, and the material of the metal shield 300A may be a metal other than Cu and Al. The metal shield 300A is grounded. However, the present invention is not limited to this, and the metal shield 300A does not have to be grounded.

[0032] The structures of the shielded inductors 100 and 100A according to the present invention are not limited to the above-described embodiments and modifications. For example, the above-described embodiments and modifications can be combined in various ways.

[0033] The present invention will now be described in more detail with reference to examples and comparative examples.

[0034] The shielded inductor 100 of Examples 1 to 4 of the present invention, the inductor 901 of Comparative Example 1, and the shielded inductors 902, 903, 904, and 905 of Comparative Examples 2 to 5 were fabricated as follows.

[0035] First, the inductor 200, the metal shield 300, and the buffer member 400, which are materials for the shielded inductor 100, were prepared. First, FeSiCr alloy soft magnetic powder as the magnetic powder 252 and phenolic resin as the organic binder 254 were mixed, and the copper coil 220 was embedded in this mixture, and the organic binder 254 was solidified to produce the inductor 200. The produced inductor 200 was a so-called metal composite core, and the size S in the thickness direction of the buffer member 400 was 4 mm. A predetermined shape was also punched out from a copper plate to produce the metal shield 300. Furthermore, a viscous slurry was produced by mixing a flat-shaped Sendust (registered trademark) powder as the soft magnetic powder 454 and an acrylic rubber as the binder 452, and the slurry was applied to a carrier film by a doctor blade method and dried, and the dried coating film was peeled off from the carrier film to produce the composite magnetic part 450. The obtained composite magnetic part 450 and a separately prepared spacer 420 made of polyetherimide and having a thickness of 600 μm were bonded to produce the buffer member 400. Finally, the metal shield 300, the buffer member 400, and the inductor 200 were bonded to each other so as to be stacked from the top in this order, to produce the shielded inductor 100 of Example 1.

[0036] Also, the shielded inductor 100 of Example 2 was produced by the same method as above, except that a spacer 420 made of polyetherimide and having a thickness of 200 μm was used. Furthermore, the shielded inductor 100 of Example 3 was produced by the same method as above, except that a spacer 420 made of polyetherimide and having a thickness of 400 μm was used. Furthermore, the shielded inductor 100 of Example 4 was produced by the same method as above, except that a spacer 420 made of polyetherimide and having a thickness of 800 μm was used.

[0037] With reference to FIG. 3, an inductor 901 of Comparative Example 1 was made up of only the inductor 200 described above. With reference to FIG. 4, a shielded inductor including only the inductor 200 and the metal shield 300 was made up of a shielded inductor 902 of Comparative Example 2. With reference to FIG. 5, a shielded inductor including only the inductor 200, the metal shield 300, and the spacer 420 was made up of a shielded inductor 903 of Comparative Example 3. In addition, with reference to FIG. 6, a shielded inductor including only the inductor 200, the spacer 420, and the composite magnetic portion 450 was made up of a shielded inductor 904 of Comparative Example 4. In addition, with reference to FIG. 7, a shielded inductor including only the inductor 200, the metal shield 300, and the composite magnetic portion 450 was made up of a shielded inductor 905 of Comparative Example 5.

[0038] The frequency characteristics of the noise attenuation effect and the frequency characteristics of the inductance of the shielded inductor 100 of Example 1, the inductor 901 of Comparative Example 1, and the shielded inductors 902, 903, and 904 of Comparative Examples 2, 3, and 4 were measured according to a standard method. The frequency characteristics of the Q value of the shielded inductor 100 of Example 1, the inductor 901 of Comparative Example 1, and the shielded inductors 902, 903, and 904 of Comparative Examples 2, 3, and 4 were measured by a parallel resonance method standardized by JIS. Furthermore, the inductance change rate R (%) was calculated from the inductance measurement values ​​Ls at 100 kHz of Examples 1 to 4 and Comparative Example 5 and the inductance measurement value L1 at 100 kHz of Comparative Example 1 according to the following formula. R(%)=(Ls-L1) / Ls*100... The measurement results are shown in Figs.

[0039] 8 shows the frequency characteristics of the noise attenuation effect in the inductor 200 of Comparative Example 1 that does not have the metal shield 300, and the shielded inductors 902 and 903 of Comparative Examples 2 and 3 that have the metal shield 300. From this measurement result, it can be seen that the noise levels of Comparative Examples 2 and 3 are generally lower than the noise level of Comparative Example 1. This shows that providing the metal shield 300 to the inductor 200 provides a high electromagnetic noise suppression effect.

[0040] 9 shows the impedance frequency characteristics of the inductor 200 of Comparative Example 1 that does not have the metal shield 300, and the shielded inductors 902 and 903 of Comparative Examples 2 and 3 that have the metal shield 300. From this measurement result, it can be seen that the resonance frequency of Comparative Example 2 is shifted to the lower frequency side compared to the resonance frequency of Comparative Example 1. In other words, it can be seen that if the metal shield 300 is provided on the inductor 200 without the spacer 420 there is a possibility that the resonance frequency will shift.

[0041] 10 shows the frequency characteristics of the Q value of the inductor 200 of Comparative Example 1 that does not have the metal shield 300, and the shielded inductors 902 and 903 of Comparative Examples 2 and 3 that have the metal shield 300. From this measurement result, it can be seen that the Q values ​​of Comparative Examples 2 and 3 are lower than the Q value of Comparative Example 1, particularly in the frequency band of 0.01 to 0.1 MHz. That is, it can be seen that providing the metal shield 300 to the inductor 200 deteriorates the Q characteristic.

[0042] 11 shows frequency characteristics of noise attenuation effect in the shielded inductor 100 of Example 1, the inductor 901 of Comparative Example 1, and the shielded inductors 903 and 904 of Comparative Examples 3 and 4. It can be seen from the measurement results that the noise level of Example 1 is generally lower than the noise levels of Comparative Examples 1, 3, and 4.

[0043] 12 shows the impedance frequency characteristics of the shielded inductor 100 of Example 1, the inductor 901 of Comparative Example 1, and the shielded inductors 903 and 904 of Comparative Examples 3 and 4. It can be seen from the measurement results that the resonant frequencies of Example 1 and Comparative Examples 3 and 4 are almost the same as the resonant frequency of Comparative Example 1.

[0044] 13 shows the frequency characteristics of the Q value of the shielded inductor 100 of Example 1, the inductor 901 of Comparative Example 1, and the shielded inductors 903 and 904 of Comparative Examples 3 and 4. It can be seen from these measurement results that, particularly in the frequency band of 0.01 to 0.1 MHz, the Q value of Example 1 is almost the same as that of Comparative Example 1, while the Q values ​​of Comparative Examples 3 and 4 are significantly lower than that of Comparative Example 1.

[0045] That is, from the measurement results shown in Figures 11 to 13, it can be seen that Example 1, which has a spacer 420 and a composite magnetic portion 450 as the buffer member 400, has a high electromagnetic noise suppression effect while suppressing the shift in the resonant frequency and also suppressing the deterioration of the Q characteristic, compared to Comparative Examples 3 and 4.

[0046] 14 is a graph plotting the inductance change rate R (%) in Examples 1 to 4 and Comparative Example 5. Here, t / S=15% corresponds to Example 1, t / S=5% corresponds to Example 2, t / S=10% corresponds to Example 3, t / S=20% corresponds to Example 4, and t / S=0% corresponds to Comparative Example 5. As a result, it was found that the inductance change rate R tends to decrease with an increase in the thickness t of the spacer 420. In addition, while the inductance change rate R at t / S=0% was 13%, the inductance change rate R at t / S=5% was 6%, and it was found that the inductance change rate R at t / S=5% was less than half of the inductance change rate R at t / S=0%. This shows that when t / S is 5% or more, the change in inductance of inductor 200 due to attachment of buffer member 400 to inductor 200 can be reduced to less than half compared to the case where t / S=0%, i.e., the composite magnetic part 450 is attached directly to magnetic core 250 without the spacer 420 therebetween. [Explanation of symbols]

[0047] 100,100A Shielded Inductor 200 Inductor 220 Coil 250 Magnetic Core 252 Magnetic powder 254 Organic Binder 300,300A Metal Shield 400,400A Buffer material 420 Spacer 450 Composite magnetic part 452 Binder 454 Soft magnetic powder 470 Dielectric section 901 Inductor 902 Shielded Inductor 903 Shielded Inductor 904 Shielded Inductor 905 Shielded Inductor

Claims

1. an inductor having a coil and a magnetic core; A metal shield; a buffer member interposed between the metal shield and the inductor to suppress adverse effects of the metal shield on the inductor; A shielded inductor comprising: the buffer member includes a spacer provided on the inductor and a composite magnetic portion provided on the spacer, the spacer is made of a non-magnetic and insulating material; The composite magnetic portion includes a binder and soft magnetic powder dispersed in the binder, The metal shield is in contact with only the composite magnetic portion. Shielded inductor.

2. A shielded inductor according to claim 1, The metal shield is exposed to the outside. Shielded inductor.

3. A shielded inductor according to claim 1 or claim 2, The thickness t of the spacer satisfies t≧S / 50, where S is the size of the inductor in the thickness direction of the buffer member. Shielded inductor.

4. The shielded inductor according to any one of claims 1 to 3, The buffer member has a dielectric portion. Shielded inductor.

5. The shielded inductor according to any one of claims 1 to 4, The magnetic core includes a magnetic powder and an organic binder that binds the magnetic powder, The coil is at least partially embedded within the magnetic core. Shielded inductor.

6. The shielded inductor according to any one of claims 1 to 5, The metal shield is grounded. Shielded inductor.

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