JP2007081349A - Inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sufficiently downsized and highly integrated inductor by which a sufficiently high inductance can be maintained. <P>SOLUTION: The inductor 1 is provided with a ferrite substrate 11 whose thickness T is equal to or more than 10 μm and less than 200 μm, conductor layers 15 which are provided on one side of the ferrite substrate 11 and form coil patterns, an upper magnetic layer 12 formed of an amorphous metal magnetic substance which is opposed to the ferrite substrate 11 through the medium of the conductor layers 15 and an insulating layer 20 which is interposed between the conductor layers 15 and the upper magnetic layer 12 for insulating them from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inductor.

Along with the downsizing and thinning of electronic devices, communication devices, etc., the miniaturization of inductors mounted on them has been studied. For example, a thin film inductor (Patent Document 1) in which a conductor coil is formed on a magnetic substrate, and an inductor (Patent Document 2) in which an amorphous metal magnetic thin film and a conductor coil are formed on a silicon substrate are known. Yes.
JP-A-5-67526 Japanese Patent No. 3382215

  However, a conventional inductor including a conductor coil and a magnetic layer needs to increase the thickness of the magnetic layer to some extent in order to maintain high inductance. For this reason, the conventional inductor has a larger volume than other elements such as semiconductor elements, and does not always satisfy the recent demand for further downsizing and higher integration. In particular, it has been difficult to achieve further downsizing, higher integration, and higher performance of the inductor while maintaining the inductance sufficiently high in a high frequency band such as 1 MHz or higher.

  Accordingly, an object of the present invention is to provide an inductor that is capable of maintaining a sufficiently high inductance and that is sufficiently downsized, highly integrated, and high in performance.

  As described above, conventionally, it has been considered that the thickness of the magnetic layer needs to be increased to some extent in order to keep the inductance of the inductor including the conductor coil and the magnetic layer high. On the other hand, the present inventors paid attention to the thickness of the ferrite substrate as the magnetic layer and examined the relationship between this and the inductance in detail. In the case of an inductor having a specific laminated structure, the ferrite As a result of finding out that a sufficiently high inductance can be maintained even when the thickness of the substrate is made thinner than before, and further studying based on this knowledge, the present invention has been completed.

  That is, the inductor of the present invention includes a ferrite substrate having a thickness of 10 μm or more and less than 200 μm, a conductor layer provided on one side of the ferrite substrate and forming a coil pattern, and a ferrite substrate sandwiching the conductor layer And an upper magnetic layer made of an amorphous metal magnetic material disposed opposite to each other, and an insulating layer interposed between the conductor layer and the upper magnetic layer so as to be insulated from each other.

  The inductor according to the present invention can be used as a magnetic layer by combining a ferrite substrate and an amorphous metal magnetic layer, and a sufficiently high inductance can be maintained by setting the thickness of the ferrite substrate within the specific range. At the same time, it was sufficiently downsized and highly integrated.

  The inductor of the present invention further includes a lower magnetic film made of an amorphous metal magnetic material provided between the ferrite substrate and the conductor layer, and the insulating layer includes the conductor layer, the upper magnetic layer, and the lower magnetic layer. Are preferably interposed between them so that they are insulated. Thereby, the inductance can be further increased.

  The amorphous metal magnetic body preferably contains a CoZrTa alloy. Thereby, the inductance can be further increased.

  According to the present invention, a sufficiently high inductance can be maintained, and an inductor that is sufficiently downsized and highly integrated is provided. In addition, the amount of material used for the magnetic layer or the like is minimized, and the time required for the manufacturing process is shortened, which is advantageous in terms of cost reduction.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a plan view showing a first embodiment of an inductor according to the present invention, and FIG. 2 is a schematic sectional view taken along line II-II in FIG. The inductor 1 shown in FIGS. 1 and 2 is disposed opposite to the ferrite substrate 1, a conductor layer 15 provided on one surface of the ferrite substrate 11 in contact with the ferrite substrate 11, and the conductor layer 15 interposed therebetween. The upper magnetic layer 12, and the insulating layer 20 interposed between the conductor layer 15 and the upper magnetic layer 12 so as to be insulated from each other. FIG. 1 is a view of the inductor 1 as viewed from the upper magnetic layer 12 side.

The ferrite substrate 11 is a substrate configured with ferrite as a main component. The ferrite substrate 11 functions as a magnetic layer for increasing the inductance, and is provided mainly for the purpose of functioning as a substrate for supporting the inductor 1 as a whole. There are two types of ferrite, spinel and hexagonal. From the viewpoint of utilizing the high permeability of ferrite, the spinel is more advantageous than the hexagonal. Typical spinel ferrites are Ni-Zn ferrite such as NiZnCu ferrite and Mn-Zn ferrite. Of these, more of Ni-Zn ferrite, the strength (about 16 kgf / mm ³⁾ is a point stronger than the strength (about 12 kgf / mm ³⁾ of the Mn-Zn ferrite, and excellent insulating properties (ρ> 10 ⁶ Ωcm) From the viewpoint, it is more suitable as a material for the ferrite substrate 11. The relative magnetic permeability of Ni-Zn ferrite is usually about 500 to 600, but in the case of performing composition control such as Fe amount reduction of NiCuZn ferrite and addition of Bi, talc, Pb, etc. in order to increase the strength. , About 200-300. When Mn—Zn ferrite is used, it is preferable to increase the thickness so as to compensate for the lack of mechanical strength.

The thickness T of the ferrite substrate 11 is not less than 10 μm and less than 200 μm. Even if the thickness T is set to 200 μm or more, the inductance is not greatly improved as compared with the case where the thickness T is less than 200 μm. On the other hand, the ratio of the ferrite substrate 11 to the entire volume of the inductor is increased, and the volume of the inductance is remarkably increased. To do. As a result, miniaturization and high integration of inductors are not sufficient, and it becomes extremely difficult to mount inductors on electronic devices, communication devices, and the like. Further, when the thickness T is 200 μm or more, it is easily affected by variations in the composition of the ferrite substrate. For example, the ferrite substrate originally has a high electrical resistivity, but if the composition of the ferrite substrate fluctuates due to manufacturing variations and the content of Fe ²⁺ ions increases, the electrical resistivity of the ferrite substrate becomes relatively low, Particularly in the high frequency band, the skin thickness of the eddy current generated in the ferrite substrate increases. In such a case, when the thickness T is 200 μm or more, problems such as an increase in loss and a decrease in inductance occur. Furthermore, when the thickness T is 200 or more, a loss called core loss due to grain boundaries, impurities, and the like in the ferrite also increases, and this becomes a problem particularly at high frequencies.

  On the other hand, if the thickness T is less than 10 μm, the mechanical strength as a substrate is insufficient, and it is easy to cause damage to the inductance, and a sufficiently high inductance may not be obtained.

  The thickness T is more preferably 100 μm or less. Further, the thickness T is preferably 30 μm or more, and more preferably 50 μm or more. In addition, when the thickness of a ferrite substrate changes with places, the maximum value of the thickness of a ferrite substrate should just be 10 micrometers or more and less than 200 micrometers.

  The relative magnetic permeability of the ferrite substrate 11 is preferably 100 or more, and more preferably 200 or more. By using a ferrite substrate having a relative magnetic permeability of 200 or more, the inductance when the thickness T is reduced is further significantly improved. The higher the relative permeability of the ferrite substrate 11 is, the better, but the upper limit is usually about 2000.

  The surface of the ferrite substrate 11 is preferably mirror-polished. Alternatively, a layer having a surface equivalent to a mirror surface may be formed on the ferrite substrate 11 using a resin such as polyimide or a commercially available sol-gel coating agent.

  The conductor layer 15 is provided in contact with the ferrite substrate 11 and forms a spiral coil pattern wound so that the terminals 15T1 and 15T2 are led out. In FIG. 2, for the sake of simplification, illustration of a portion of the conductor layer 15 through which the terminal 16T2 communicates is omitted. The said part is formed so that it may lead out outside, without contacting the winding part of the conductor layer 15.

  The conductor layer 15 is made of a conductor such as Cu. The shape, width, interval, number of turns, and the like of the coil pattern formed by the conductor layer 15 are appropriately set according to required characteristics. The thickness of the conductor layer 15 is typically about 5 to 100 μm. The cross-sectional shape of the conductor layer is not necessarily rectangular as in this embodiment, and may be, for example, a trapezoidal shape or a polygonal shape such as a hexagon. In order to further improve the inductance, it is preferable to make the thickness T of the ferrite substrate larger than the thickness of the conductor layer 15.

  The upper magnetic layer 12 is made of an amorphous metal magnetic material. Since the upper magnetic layer 12 and the ferrite substrate 11 are disposed to face each other with the conductor layer 15 interposed therebetween, it is possible to develop a high inductance even at a high frequency. The thickness of the upper magnetic layer 12 is preferably 1 to 10 μm, and more preferably 3 to 5 μm. By making the thickness of the upper magnetic layer within these specific ranges, the effect of improving the inductance is more remarkably exhibited. Furthermore, by setting the thickness of the upper magnetic layer 12 to 10 μm or less, it is possible to limit the amount of the amorphous metal magnetic material that is extremely expensive and to reduce the time required for the step of forming the magnetic layer. The

In general, an amorphous metal magnetic body can maintain a high relative magnetic permeability even at a high frequency, and the above-described effects are exhibited when an amorphous metal magnetic body is used. Examples of the amorphous metal magnetic material include Co-based amorphous alloys such as CoZrTa-based alloys, CoZrNb-based alloys, and CoFeSiB-based alloys, and permalloy. Among these, a CoZrNb-based alloy or a CoZrTa-based alloy is preferable because the magnetostriction constant is less than 10 ⁻⁶ and close to zero and a high magnetic permeability can be obtained. Furthermore, considering the direct current superposition characteristics of the inductor, a CoZrTa alloy having a large saturation magnetization is particularly preferable.

  Since the amorphous metal magnetic body has conductivity, an insulating layer 20 made of an insulating material is provided so that the upper magnetic layer 12 and the conductor layer 15 are electrically insulated. As the insulating material, an inorganic material such as silicon oxide or aluminum oxide, or an organic material such as a photosensitive resin or a thermoplastic resin can be used. The insulating layer 20 is not necessarily a single layer, and may be a multilayer structure having a photosensitive resin layer and a silicon oxide layer, for example.

  The inductor 1 according to the first embodiment includes, for example, a step of forming the conductor layer 15 on the ferrite substrate 11 having a thickness of 10 μm or more and less than 200 μm so as to form a coil pattern, and covering the conductor layer 15. And a step of forming the upper magnetic layer 12 made of an amorphous metal magnetic material on the surface of the insulating layer 20 opposite to the ferrite substrate 11. it can.

  A ferrite substrate having a predetermined thickness and a predetermined relative magnetic permeability can be obtained by a conventionally known method. In general, a ferrite substrate obtained by cutting a sintered body into a predetermined shape and thickness by a ceramic firing method is used. However, instead of this, a sheet fired product, a hot press fired product, or the like can also be used. Ferrite substrates are also commercially available.

  The coil pattern of the conductor layer 15 can be suitably formed by a method using photolithography or the like. Specifically, for example, a seed layer made of a conductor is formed on the ferrite substrate 11 by a thin film process such as sputtering, and a photoresist pattern corresponding to the coil pattern is formed so that a predetermined portion thereof is exposed, A conductor layer 15 is formed by forming a layer made of a conductor such as Cu on the exposed seed layer by plating, removing the photoresist pattern, and removing the exposed seed layer by etching. be able to. In this method, an adhesion layer such as a Ti layer may be formed between the ferrite substrate 11 and the seed layer by sputtering or the like.

  When the insulating layer 20 is formed using a photosensitive resin, the photosensitive resin is applied by spin coating or the like so as to cover the ferrite substrate 11 and the conductor layer 15, and is exposed and heated as necessary to cure the photosensitive resin. By doing so, the insulating layer 20 can be formed. When an inorganic material such as silicon oxide is used, the insulating layer 20 can be formed by a sputtering method or the like.

  The upper magnetic layer 12 can be formed on the insulating layer 20 by sputtering or the like.

  FIG. 3 is a schematic cross-sectional view showing a second embodiment of the inductor according to the present invention. The inductor 1 shown in FIG. 3 includes a ferrite substrate 11, a conductor layer 15 provided on one surface side of the ferrite substrate 11, an upper magnetic layer 12 disposed to face the ferrite substrate 11 with the conductor layer 15 interposed therebetween, The lower magnetic layer 13 made of an amorphous metal magnetic material provided between the ferrite substrate 11 and the conductor layer 15 and the conductor layer 15, the upper magnetic layer 12, and the lower magnetic layer 13 are insulated. The insulating layer 20 is interposed between them.

  The ferrite substrate 11, the conductor layer 15, the upper magnetic layer 12, and the insulating layer 20 are the same as those of the inductor 1 according to the first embodiment. In order to further improve the inductance, it is preferable to make the thickness T of the ferrite substrate larger than the shortest distance between the conductor layer 15 and the ferrite substrate 11 or the thickness of the conductor layer 15.

  The lower magnetic layer 13 is made of the same material as the upper magnetic layer 12 and is provided in contact with the surface of the ferrite substrate 11 on the conductor layer 15 side. The thickness is preferably 1 to 10 μm, and more preferably 3 to 5 μm, like the upper magnetic layer 12.

  By providing the lower magnetic layer 13, the effect of improving the inductance is further enhanced. In addition, the inductor 1 according to the second embodiment has a thickness of a magnetic layer made of an amorphous metal magnetic material constituting the inductor while maintaining a sufficiently high inductance as compared with the inductor 1 according to the first embodiment. This is also advantageous in that the thickness (the total thickness of the upper magnetic layer 12 and the lower magnetic layer 13 in the case of the second embodiment) can be further reduced. As a result, the time required for the process of forming the magnetic layer is shortened, so that the cost of the inductor can be further reduced.

  The inductor 1 according to the second embodiment includes, for example, a step of forming the lower magnetic layer 13 on the ferrite substrate 11 having a thickness of 10 μm or more and less than 200 μm, and a part of the insulating layer 20 (lower insulation) on the lower magnetic layer 13. Layer) so as to cover the lower magnetic layer 13, a step of forming the conductor layer 15 on the lower insulating layer so as to form a coil pattern, and an insulating layer 20 so as to cover the conductor layer 15. And a step of forming an upper magnetic layer 12 made of an amorphous metal magnetic material on the surface of the insulating layer 20 opposite to the ferrite substrate 11. Obtainable. Details of each step are the same as those in the method of manufacturing the inductor 1 according to the first embodiment.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Example 1
Using a ferrite substrate having a relative magnetic permeability μ of 200 or 600 and having various thicknesses, an inductor having the same multilayer configuration as that of the first embodiment was manufactured. As the ferrite substrate, a high-strength NiZnCu ferrite sintered body was sliced and then mirror-polished.

First, an adhesion layer (thickness 50 nm) made of Ti and a seed layer (thickness 250 nm) made of Cu were formed in this order on the mirror-polished surface of the ferrite substrate by sputtering. Next, after forming a resist pattern corresponding to the shape of the coil pattern by photolithography using a positive resist, a coil pattern (coil height 10 μm, coil width 500 μm, coil interval 20 μm, 4 turns) is formed using a copper sulfate plating bath. A Cu plating layer was formed. After peeling off the resist pattern, the portion of the adhesion layer and the seed layer not covered with the Cu plating layer was removed by ion milling to form a conductor layer forming a coil pattern. Thereafter, a SiO ₂ layer (thickness: 1 μm) as a part of the insulating layer was formed by sputtering so as to cover the conductor layer, and further, an insulating layer was formed using photosensitive polyimide to fill the space between the coils. The SiO ₂ layer is a layer provided to prevent copper from diffusing into the polyimide layer. A CoZrTa-based alloy film (thickness 5 μm) is formed as an upper magnetic layer on the insulating layer by DC sputtering, and then heat-treated at 330 ° C. for 1 hour in a rotating magnetic field of 3 kOe, whereby 1 MHz of the upper magnetic layer is formed. The relative permeability was set to 3500.

  The inductance of the manufactured inductor was measured. FIG. 4 is a graph showing the relationship between the inductance and the thickness of the ferrite substrate. For comparison, FIG. 4 shows both the inductance when the upper magnetic layer is not formed and the inductance (Air-Core) of the conductor layer alone.

(Example 2)
An inductor similar to that of Example 1 was fabricated except that the laminated structure was the same as that of the second embodiment, and the lower magnetic layer was a CoZrTa-based alloy film (thickness 5 μm) having a relative permeability μ of 3500. Inductance was measured. FIG. 5 is a graph showing the relationship between the inductance and the thickness of the ferrite substrate. For comparison, FIG. 5 also shows the inductance when the upper magnetic layer is not formed and the inductance (Air-Core) of the conductor layer alone.

(Comparative example)
An inductor having a laminated structure similar to that of Example 1 except that the upper magnetic layer was formed of ferrite was manufactured, and the inductance was measured. FIG. 6 is a graph showing the relationship between the inductance and the thickness of the ferrite substrate. FIG. 6 also shows the inductance (Air-Core) of the conductor layer alone for comparison.

  As shown in FIGS. 1 and 2, the inductors of Examples 1 and 2 having an upper magnetic layer made of an amorphous metal magnetic material have a sufficiently high inductance even when the thickness of the ferrite substrate is less than 200 μm. It was confirmed that it could be maintained. It was also confirmed that the inductance can be further increased by increasing the relative permeability of the ferrite substrate. Further, the direct current superimposition characteristics are improved by adopting such a configuration.

  The thin film type magnetic element having the same configuration as the present invention can achieve the same improvement in electrical and magnetic characteristics and miniaturization even when applied to a thin film type magnetic element other than an inductor such as a transformer or a sensor. Is possible.

1 is a plan view showing a first embodiment of an inductor according to the present invention. It is a schematic sectional drawing along the II-II line of FIG. It is a schematic sectional drawing which shows 2nd embodiment of the inductor which concerns on this invention. It is a graph which shows the relationship between the inductance about the inductance of an Example, and the thickness of a ferrite substrate. It is a graph which shows the relationship between the inductance about the inductance of an Example, and the thickness of a ferrite substrate. It is a graph which shows the relationship between the inductance about the inductance of a comparative example, and the thickness of a ferrite substrate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inductor, 11 ... Ferrite substrate, 12 ... Upper magnetic layer, 13 ... Lower magnetic layer, 15 ... Conductor layer, 20 ... Insulating layer, T ... Thickness of ferrite substrate.

Claims (3)

A ferrite substrate having a thickness of 10 μm or more and less than 200 μm;
A conductor layer provided on one side of the ferrite substrate and forming a coil pattern;
An upper magnetic layer made of an amorphous metal magnetic body disposed opposite to the ferrite substrate with the conductor layer interposed therebetween;
An insulating layer interposed between the conductor layer and the upper magnetic layer so as to be insulated; and
Inductor comprising. A lower magnetic layer made of an amorphous metal magnetic material provided between the ferrite substrate and the conductor layer;
The inductor according to claim 1, wherein the insulating layer is interposed between the conductor layer and the upper magnetic layer and the lower magnetic layer so as to be insulated.   The inductor according to claim 1, wherein the amorphous metal magnetic body includes a CoZrTa-based alloy.

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