JP7703178B2 - Inductors - Google Patents

Description

The present invention relates to inductors, and more specifically to planar spiral inductors.

Many electronic devices have switching power supplies. By increasing the switching frequency through the use of GaN power devices, the inductor elements and capacitors in the power supply can be made smaller and lighter, making them particularly suitable for use in portable electronic devices and mobility.

Planar spiral inductors are often used for high-frequency circuit inductors because of their compact size and integration. In the future, it is expected that switching power supplies with frequencies of several hundred MHz will be implemented using power inductors with a magnetic core. However, a low-loss power inductor compatible with switching power supplies of several hundred MHz has not yet been proposed.

In Patent Document 1, the inventor of this application proposes a technology to suppress the proximity effect, which is an issue when using inductors at high frequencies. This technology fills the gap between the coils of the inductor with a magnetic microparticle composite material that has small iron loss even at high frequencies, suppressing the proximity effect and reducing the equivalent series resistance Rs and increasing the Q value (ωL/Rs).

In addition, a planar inductor with a laminated structure has been disclosed in which insulating layers are formed above and below a planar coil, and magnetic films whose magnetization (axis of easy magnetization) directions are mutually orthogonal are laminated on the upper and lower surfaces of the insulating layers (see, for example, Patent Document 2).

Patent No. 6486614 Japanese Patent Application Publication No. 4-363006

In the technology disclosed in the above-mentioned Patent Document 1, the equivalent series resistance Rs is reduced to increase the Q value, but for practical use, it is necessary to increase the inductance L, which is the most important parameter for an inductor element. However, it was difficult to increase the inductance L with conventional technology.

In addition, in the technology disclosed in Patent Document 2 and other documents, in the high frequency range of 100 MHz to several hundred MHz, losses due to eddy currents that occur in proportion to the square of the frequency and inversely proportional to the electrical resistivity are particularly problematic, and there is a limit to how much the Q value can be increased.

The present invention aims to provide an inductor with a large Q value in the high frequency band from 100 MHz to several hundred MHz.

The inductor of the present invention is a planar spiral inductor in which a first magnetic unit, a planar coil, a flat magnetic composite material inter-coil filler filled between the wires of the coil and comprising a magnetic composite material formed by combining magnetic microparticles and an insulating material, and a second magnetic unit are stacked in this order, and each of the first magnetic unit and the second magnetic unit is formed by stacking two layers of in-plane uniaxial magnetic anisotropy films having different directions of easy magnetization with an insulating layer sandwiched between them, and in each of the first magnetic unit and the second magnetic unit, the two layers of in-plane uniaxial magnetic anisotropy films are not magnetically coupled to each other, the magnetic anisotropy of the two layers of in-plane uniaxial magnetic anisotropy films is offset, and the first magnetic unit and the second magnetic unit are each magnetically isotropic in the film plane as a whole .

According to the inductor of the present invention, a magnetic composite material coil inter-filler, in which a magnetic composite material made of a compound of magnetic fine particles and an insulating material is filled between the wires of a coil, is sandwiched between a first magnetic unit and a second magnetic unit, both of which are magnetically isotropic within the film plane. Compared to the laminate of a magnetic film and an insulating layer disclosed in Patent Document 2 and other documents, these first and second magnetic units have a high resistivity in the high frequency band of 100 MHz to several hundred MHz, and can suppress losses due to leakage current. As a result, it is possible to obtain an inductor with a large Q value in the frequency band of 100 MHz to several hundred MHz, compared to the technologies described in Patent Documents 1 and 2 and other documents.

In the inductor of the present invention, for example, each of the two layers of in-plane uniaxial magnetic anisotropy films is made of a nanogranular film.

In the inductor of the present invention, it is preferable that the easy magnetization direction of one of the two in-plane uniaxial magnetic anisotropy films is perpendicular to the easy magnetization direction of the other of the two in-plane uniaxial magnetic anisotropy films.

In this case, it is possible to prevent leakage flux that may occur in the magnetization easy direction of one of the in-plane uniaxial magnetic anisotropy films of the first or second magnetic unit from leaking to the outside by the other in-plane uniaxial magnetic anisotropy film. This makes it possible to further improve the Q value.

In the inductor of the present invention, for example, the one of the in-plane uniaxial magnetic anisotropy films is a nanogranular film having a composition of (M1aM2b)1-X(L1cFd)X (M1: at least one selected from the group consisting of Fe, Co, and Ni; M2: at least one selected from the group consisting of Pd and Pt; L1: at least one selected from the group consisting of Li, Mg, Al, Ca, Sr, Ba, Gd, and Y; 0.5≦a≦1.0, 0≦b≦0.5 (a+b=1), 0.2≦c≦0.4, 0.6≦d≦0.8 (c+d=1), 0.15≦X≦0.55 (all atomic ratios)). -film, and the other in-plane uniaxial magnetic anisotropy film is preferably a nanogranular film having a composition of (M3hM4i)1-Y(L2jFk)Y (M3: at least one selected from the group consisting of Fe, Co, and Ni, M4: at least one selected from the group consisting of Pd and Pt, L2: at least one selected from the group consisting of Li, Mg, Al, Ca, Sr, Ba, Gd, and Y, 0.5≦h≦1.0, 0≦i≦0.5 (h+i=1), 0.2≦j≦0.4, 0.6≦k≦0.8 (j+k=1), 0.15≦Y≦0.55 (all atomic ratios)).

In this case, it is possible to obtain first and second magnetic units that have high resistivity in the high frequency band of 100 MHz to several hundred MHz and that suppress leakage of magnetic flux generated from the coil to the outside.

FIG. 1 is a top view showing an inductor 100 according to an embodiment of the present invention. 2 is a cross-sectional view taken along line III-III in FIG. 1. 6 is a graph showing actual measurement results of frequency characteristics of the complex relative permeability of the first and second magnetic units. 6 is a graph showing actual measurement results of frequency characteristics of loss coefficients of the first and second magnetic units. 13 is a graph showing an analysis result of frequency characteristics of inductance L. 13 is a graph showing an analysis result of frequency characteristics of equivalent series resistance Rs. 1 is a graph showing an analysis result of frequency characteristics of a Q value.

As shown in Figures 1 and 2, the inductor 100 according to an embodiment of the present invention is a planar spiral inductor in which a first magnetic unit 10, a magnetic composite inter-coil filler 20, and a second magnetic unit 30 are stacked in this order.

The magnetic composite coil inter-filler 20 comprises a planar coil (winding) 21 and a magnetic composite body 22 in which the spaces between the coil 21 are filled with a magnetic composite material made of a combination of magnetic fine particles and an insulating material.

Here, the magnetic composite inter-coil filler 20 is a rectangular, more specifically, square, flat plate. The dimensions of the magnetic composite inter-coil filler 20, such as the thickness and length of one side, can be appropriately determined according to the power source used, the required inductance, etc.

The coil 21 has a first ground line portion 21a that protrudes upward from one end near the center, and a second ground line portion 21b that protrudes upward from the other end at the periphery. These ground line portions 21a and 21b are located within the first magnetic unit 10.

In the inductor 100, the part that acts as a planar spiral inductor is the central coil 21, and the coil part 21 is an inductor in the pure sense. Inductor 100 is an inductor in the broad sense, and an inductor element.

The magnetic composite material body 22 is provided on the magnetic unit 10 so as to fill the spaces between the coil 21 in the thickness direction and also fill the area outside the coil 21 in the thickness direction. In this embodiment, the coil portion 21 and the ground line portions 21a, 21b have a thickness of 8 μm, and the magnetic composite material body 22 is also 8 μm thick. In other words, the magnetic composite material body 22 is formed to the same thickness as the coil portion 21 and the ground line portions 21a, 21b, and on the same surface as the surface on which the coil portion 21 and the ground line portions 21a, 21b are formed.

The magnetic composite material constituting the magnetic composite body 22 is a magnetic composite material in which magnetic microparticles and an insulating material are mixed. The volume ratio of the magnetic microparticles to the insulating material is, for example, 10:90 to 80:20. More specifically, the Fe-based magnetic microparticles are roughly spherical particles having an average particle size of 1.1 μm made of carbonyl iron powder, and the insulating material is epoxy resin. A solvent is added to the carbonyl iron powder and the epoxy resin so that the volume ratio is 1:1, and the mixture is used in the form of an ink.

Then, a magnetic composite material made of the carbonyl iron powder and epoxy resin is supplied by a printing method so as to flatten the unevenness formed by the coil portion 21, and is filled between the wires of the coil 21 and evenly filled in the outer area of the coil 21. After that, the magnetic composite material is heated in the atmosphere, for example, at 120°C for 5 minutes using a hot plate, at 120°C for 120 minutes using an electric furnace, and at 140°C for 180 minutes to remove the solvent contained in the magnetic composite material and completely harden the epoxy resin, thereby obtaining the magnetic composite material 20.

In order to prevent the surface of the coil 21 from being covered with the magnetic composite material, it is preferable to roughly polish the surface using sandpaper or the like, and then mirror-polish the surface to form the second magnetic unit 30 on top. In this way, preventing the surface of the coil 21 from being covered with the magnetic composite material improves the high-frequency characteristics of the inductor, but depending on the application, the surface of the coil 21 may be covered with the magnetic composite material.

The use of Fe-based magnetic microparticles as the magnetic microparticles used in the magnetic composite material is preferable because Fe-based materials have excellent magnetic properties and are easily available. Fe-based magnetic microparticles include Fe microparticles and Fe alloy microparticles. In addition to Fe-based magnetic microparticles, Co-based magnetic microparticles and Ni-based magnetic microparticles can also be used as magnetic microparticles. These microparticles also have the same effect as Fe-based magnetic microparticles.

The reason why magnetic microparticles are used as the magnetic material for the magnetic composite material that fills the gaps between the wires of the coil 21 is that the induced current (eddy current) that occurs in the magnetic microparticles when an external magnetic flux interlinks with them can be ignored, and magnetic loss due to the induced current can be kept extremely low.

The magnetic loss caused by the induced current in the magnetic microparticles can be ignored because the particle size of the magnetic microparticles is small. Even if an induced current occurs in each magnetic microparticle, the particles are so small that it does not follow the magnetic flux change and result in a resistance loss. To take advantage of the effect of such particles, it is preferable to use magnetic microparticles that are as small as possible.

The magnetic microparticles, such as Fe microparticles, are spherical and have an average particle size of 0.1 μm to 20 μm, more preferably 0.5 μm to 5 μm. Although it depends on the material of the magnetic microparticles, magnetic microparticles with a particle size of 2 μm or less can be sufficiently used as the material for the magnetic composite material body 22 of an inductor used in the frequency band of 0.1 to 1 GHz. Note that the magnetic microparticles are not limited to being spherical, and may be other shapes such as ellipsoidal, or may have irregularities on the outer surface.

Here, the first magnetic unit 10 and the second magnetic unit 30 are disk-shaped flat plates. The diameters of the first magnetic unit 10 and the second magnetic unit 30 are determined according to the size of the magnetic composite inter-coil filler 20. Note that the first magnetic unit 10 and the second magnetic unit 30 are not limited to disk-shaped flat plates.

The first magnetic unit 10 and the second magnetic unit 30 are shaped to include all of the coils 21 when viewed from above. It is also preferable that the first magnetic unit 10 and the second magnetic unit 30 have the same size, and in particular, the same shape when viewed from above.

The first magnetic unit 10 is formed by stacking a magnetic anisotropic film 11 having uniaxial magnetic anisotropy in the film plane and a magnetic anisotropic film 12 also having uniaxial magnetic anisotropy in the film plane with an insulating layer 13 sandwiched between them so that they are not magnetically coupled, and as described below, the magnetic anisotropy of these magnetic anisotropic films 11 and 12 is offset, resulting in magnetic isotropy in the film plane. The second magnetic unit 30 is also formed by stacking a magnetic anisotropic film 31 having uniaxial magnetic anisotropy in the film plane and a magnetic anisotropic film 32 also having uniaxial magnetic anisotropy in the film plane with an insulating layer 33 sandwiched between them so that they are not magnetically coupled, and the magnetic anisotropy of these magnetic anisotropic films 31 and 32 is offset, resulting in magnetic isotropy in the film plane.

The magnetic anisotropic films 11, 12 of the first magnetic unit 10 are both in-plane uniaxial magnetic anisotropic films and have a magnetic anisotropy constant K _u1 , and the magnetic anisotropic films 31, 32 of the second magnetic unit 30 are both in-plane uniaxial magnetic anisotropic films and have a magnetic anisotropy constant K _u2 . Here, in the first and second magnetic units 10, 30, the easy magnetization directions of the magnetic anisotropic films 11, 31 on one side and the easy magnetization directions of the magnetic anisotropic films 12, 32 on the other side are orthogonal to each other. However, since the first magnetic unit 10 and the second magnetic unit 30 are not magnetically coupled, the easy magnetization directions of the magnetic anisotropic film 12 and the magnetic anisotropic film 31 closest thereto may or may not intersect other than orthogonal.

In these magnetic anisotropic films 11, 12, 31, and 32, when a high-frequency magnetic field H _ex with a small amplitude is applied in a direction at an angle θ in the film plane from the easy magnetization direction of the magnetic anisotropic films 12 and 32, the magnetic permeability μ ₂ of the magnetic anisotropic films 12 and 32 is μ ₂ (θ) = M _s2 × sin ² θ / 2K _u2 . The magnetic permeability μ ₁ of the magnetic anisotropic films 11 and 31, whose easy magnetization direction is perpendicular to that of the magnetic anisotropic films 12 and 32, is μ ₁ (θ) = M _s1 × sin ² (90-θ) / 2K _u1 . The magnetic permeability μ (θ) of the ferromagnetic thin film laminate is μ ₁ (θ) + μ ₂ (θ). Note that M _s1 and M _s2 are the saturation magnetizations of the magnetic anisotropic films 11 and 31 and the magnetic anisotropic films 12 and 32, respectively.

In the first and second magnetic units 10, 30, if the specifications of one magnetic anisotropic film 11, 31 and the other magnetic anisotropic film 12, 32 are the same, then _Ms1 = _Ms2 = _Ms and _Ku1 = _Ku2 = _Ku , so in _μ1 (θ) + _μ2 (θ), the coefficient consisting of trigonometric functions disappears and _it becomes _Ms /2Ku, which eliminates the dependence on the incident angle θ of the high-frequency magnetic field _Hex and becomes a constant, and the distribution of magnetic permeability becomes completely isotropic within the film surface. On the other hand, if the specifications of each magnetic anisotropic film 11, 12, 31, 32 do not match due to variations in the manufacturing process, and K _u1 ≠ K _u2 , or M _s1 ≠ M _s2 and K _u1 ≠ K _u2 , the distribution of magnetic permeability will not be completely isotropic but will remain isotropic, but since it will be roughly isotropic, this will not be a major problem.

This principle itself has been known for some time, for example, in Non-Patent Document 1 (Y. Shimada, E. Sugawara, and H. Fujimori: “Initial permeability of composite anisotropy multilayer films”, Journal of Applied Physics, Vol. 76, No.4, pp. 2395-2398 (1994)).

In order to ensure the thickness of the inductor 100 excluding the substrate 40, the magnetic anisotropic films 11, 12, 31, 32 in the first and second magnetic units 10, 30 may be multi-staged, i.e., the magnetic anisotropic films 11, 12 in the first magnetic unit 10 and the magnetic anisotropic films 31, 32 in the second magnetic unit 30 may both be multi-layered, such as four layers or six layers.

One of the magnetic anisotropic films 11, 31 of the first and second magnetic units 10, 30 is made of, for example, a nanogranular film, but it is not limited to being made of a nanogranular film as long as it is a uniaxial magnetic anisotropic film in the film plane. However, if the magnetic anisotropic films 11, 31 are made of a nanogranular film, it has the advantage that the electrical resistivity is high and magnetic resonance is possible up to several GHz in magnetic permeability. Note that the technology described in Non-Patent Document 1 uses a metal magnetic thin film with low resistivity.

The magnetic anisotropic films 11 and 31 herein are nanogranular films having a composition of (M1aM2b) _1-X (L1cFd) _X (M1: at least one selected from the group consisting of Fe, Co, and Ni, M2: at least one selected from the group consisting of Pd and Pt, L1: at least one selected from the group consisting of Li, Mg, Al, Ca, Sr, Ba, Gd, and Y).

Specific examples of such nanogranular films include CoPd-- _CaF2 , CoPd-- _MgF2 , CoFePd-- _CaF2 , CoFe-- _CaF2 , CoFe-- _BaF2 , and CoFe-- _MgF2 .

In addition, a and b, which determine the ratio of the metal (magnetic) portion of the nanogranular film that forms the magnetic anisotropic films 11 and 31, are preferably 0.5≦a≦1.0, 0≦b≦0.5 (a+b=1). Similarly, c and d, which determine the ratio of metal L1 and F (fluorine) in the insulating portion that forms this nanogranular film, are preferably 0.2≦c≦0.4, 0.6≦d≦0.8 (c+d=1). Furthermore, X, which determines the ratio of the metal portion to the insulating portion, is preferably 0.15≦X≦0.55 (all atomic ratios). These factors make it possible to efficiently achieve the object of the present invention.

The thickness of the magnetic anisotropic films 11 and 31 is not particularly limited, but if they are made of nanogranular films, it is preferable that the thickness be 100 nm or less in order to obtain high magnetic permeability properties.

The thickness dependence of the magnetic permeability of nanogranular films is described in Non-Patent Document 2 (Masayuki Naoe, Yasushi Endo, Takamichi Miyazaki, Sho Muroga, Jingyan Ma, Shuichiro Hasa, Kazushi Ishiyama: "GHz-range high-frequency complex magnetic permeability and noise suppression effect of (CoPd-CaF2)/(CaF2) nanogranular laminated films," Institute of Electrical Engineers of Japan, pp.51-56, MAG-18-072/LD-18-045 (2018)).

The other magnetic anisotropic film 12, 32 of the first and second magnetic units 10, 30 is, for example, a nanogranular film, but is not limited to a nanogranular film as long as it is a film with in-plane uniaxial magnetic anisotropy. The magnetic anisotropic film 12, 32 is a nanogranular film having a composition of (M3hM4i) _1-Y (L2jFk) _Y (M3: at least one selected from the group consisting of Fe, Co, and Ni, M4: at least one selected from the group consisting of Pd and Pt, L1: at least one selected from the group consisting of Li, Mg, Al, Ca, Sr, Ba, Gd, and Y).

Specific examples of such nanogranular films include CoPd-- _CaF2 , CoPd-- _MgF2 , CoFePd-- _CaF2 , CoFe-- _CaF2 , CoFe-- _BaF2 , and CoFe-- _MgF2 .

In addition, h and i, which determine the ratio of the metal (magnetic) portion of the nanogranular film that forms the magnetic anisotropic films 11 and 31, are preferably 0.5≦h≦1.0, 0≦i≦0.5 (h+i=1). Similarly, j and k, which determine the ratio of metal L2 and F (fluorine) in the insulating portion that forms this nanogranular film, are preferably 0.2≦j≦0.4, 0.6≦k≦0.8 (j+k=1). Furthermore, Y, which determines the ratio of the metal portion to the insulating portion, is preferably 0.15≦Y≦0.55 (all atomic ratios). These factors make it possible to efficiently achieve the object of the present invention.

The thickness of the magnetic anisotropic films 12, 32 is not particularly limited, but if they are made of nanogranular films, a thickness of 100 nm or less is preferable in order to obtain high magnetic permeability. In order to increase the permeance in the magnetic circuit of the inductor, and if it is necessary to increase the total cross-sectional area of the magnetic anisotropic films, the first and second magnetic units 10, 30 may be multi-staged, as described above.

In addition, in the magnetic anisotropic films 11 and 12 of the first magnetic unit 10 or the magnetic anisotropic films 31 and 32 of the second magnetic unit 30, the nanogranular film may be a single layer film, but may also form a periodic multilayer structure with a thin insulating film having a composition of L1cFd or L2jFk. In this periodic multilayer structure, the easy magnetization directions of the in-plane uniaxial anisotropy of the nanogranular film are all oriented in the same direction. The period is not particularly limited and can be, for example, 2 to 400 periods. In this embodiment, it is set to 5 periods.

Furthermore, in order to realize the periodic multilayer structure of the magnetic anisotropic films 11, 12, 31, and 32, the component composition of the thin insulating film for separating the nanogranular films may include _CaF2 , _MgF2 , _BaF2 , _AlF3 , and _GdF3 .

As is clear from the above description, it is preferable that the nanogranular films constituting each of the magnetic anisotropic films 11, 12, 31, and 32 have the same component composition. In this case, for example, the same target can be used in the manufacturing method described below, so that the magnetic permeability in the in-plane direction of the ferromagnetic thin film laminate can be easily made isotropic, and isotropic magnetic properties can be easily obtained in the in-plane direction.

The magnetization direction of one magnetic anisotropic film 11, 31 and the magnetization direction of the other magnetic anisotropic film 12, 32 are preferably perpendicular to each other. This prevents leakage flux that may occur in the in-plane magnetization easy direction of one magnetic anisotropic film 11, 31 from leaking to the outside by the other magnetic anisotropic film 12, 32, making it possible to improve the Q value. The magnetization direction of one magnetic anisotropic film 11, 31 and the magnetization direction of the other magnetic anisotropic film 12, 32 do not have to be perpendicular to each other, but it is preferable that they are not parallel.

The insulating layers 13, 33 are located between the magnetic anisotropic films 11, 12 of the first magnetic unit 10 and between the magnetic anisotropic films 31, 32 of the first magnetic unit 10, respectively, and separate the magnetic coupling between one magnetic anisotropic film 11, 31 and the other magnetic anisotropic film 12, 32.

The thickness of the insulating layers 13 and 33 is preferably, for example, 50 to 5000 nm, and more preferably 100 to 1000 nm, depending on the thickness of the magnetic anisotropic films 11, 12, 31, and 32.

As described above, when the first and second magnetic units 10, 30 are configured in a multi-stage structure, it is necessary to provide an insulating layer having a thickness equivalent to that of the insulating layers 13, 33 between the magnetic anisotropic films 11, 12, 31, 32 adjacent to each other vertically so that they are not magnetically coupled.

The insulating layers 13, 33 may have any non-ferromagnetic insulating component composition as long as they magnetically separate one magnetic anisotropic film 11, 31 from the other magnetic anisotropic film 12, 32, respectively. However, since they also function as an undercoat film for the magnetic anisotropic film 12, 32 located above the first or second magnetic unit 10, 30, respectively, it is preferable that they have the same component composition as the insulating portion of these magnetic anisotropic films 12, 32.

The inductor 100 is formed by stacking a first magnetic unit 10, a magnetic composite inter-coil filler 20, and a second magnetic unit 30 in this order on a substrate 40. The first magnetic unit 10 and the second magnetic unit 30 are each formed on an undercoat film 50.

It is necessary to prevent electrical conduction between the coil 21 of the magnetic composite inter-coil filler 20 and the first magnetic unit 10 and the second magnetic unit 30. For this reason, an insulating film 51 may be provided between the magnetic composite inter-coil filler 20 and the first magnetic unit 10 (between the magnetic composite inter-coil filler 20 and the magnetic anisotropic film 12), and an insulating layer may be provided between the magnetic composite inter-coil filler 20 and the second magnetic unit 30 (between the magnetic composite inter-coil filler 20 and the base film 50) as necessary.

The size of the substrate 40 may be the same as that of the magnetic units 10 and 30, or may be larger than the magnetic units 10 and 30. Furthermore, multiple sets of inductors 100 each consisting of a first magnetic unit 10, a magnetic composite inter-coil filler 20, and a second magnetic unit 30 may be formed on a large substrate 40, and multiple inductors 100 may be formed by cutting the substrate 40.

The substrate 40 can be made of a general-purpose material such as ceramic (glass, magnesia, zirconia, sapphire, etc.) or a silicon substrate. An appropriate support may be used instead of the substrate 40. Furthermore, a device made of a resin such as polyimide may be used instead of the substrate 40.

The undercoat film 50 is also the undercoat film of the nanogranular film that constitutes one of the magnetic anisotropic films 11, 31 of the first and second magnetic units 10, 30, and therefore preferably has the same component composition as the magnetic or insulating portion of this nanogranular film. However, if the component composition is the same as the magnetic portion of this nanogranular film, for example, if the proportion of the metal (magnetic) portion is high, the undercoat film 50 will have ferromagnetic properties, and will have a magnetic effect on the nanogranular film in addition to its effect as an undercoat film. Therefore, in this case, it is preferable to reduce the proportion of the metal (magnetic) portion so that the undercoat film 50 does not become ferromagnetic.

Specifically, the undercoat film 50 is preferably a nanogranular film having a composition of (M5pM6q)1-Z(L3rFs)Z (M5: at least one selected from the group consisting of Fe, Co, and Ni, M6: at least one selected from the group consisting of Pd and Pt, L3: at least one selected from the group consisting of Li, Mg, Al, Ca, Sr, Ba, Gd, and Y). In this case, 0.5≦p≦1.0, 0≦q≦0.5 (p+q=1), 0.2≦r≦0.4, 0.6≦s≦0.8 (r+s=1), and 0.55≦Z≦1.00. When Z=1.00, the undercoat film 50 is a single L3rFs layer. The thickness of the undercoat film 50 is preferably more than 0 nm and less than 500 nm, and more preferably 10 nm to 100 nm.

Because the undercoat film 50 has electrical insulation properties, the undercoat film 50 of the second magnetic unit 30 can be used as an insulating film that blocks electrical conduction between the coil 12 and the second magnetic unit 30 described above. In addition, for the first magnetic unit 10, an insulating film 51 made of a nanogranular film of the same composition as the undercoat film 50 is provided on the upper surface of the magnetic anisotropic film 12 to block electrical conduction between the coil 12 and the first magnetic unit 10.

As described above, according to the inductor 100, the nanogranular films of the first and second magnetic units 10, 30 have a high resistivity in the high frequency band of 100 MHz to several hundred MHz compared to the laminate of a magnetic film and an insulating layer disclosed in Patent Document 2 and other documents, and suppress the leakage of magnetic flux generated from the coil 21 to the outside. This makes it possible to suppress losses due to the generation of leakage current, and makes it possible to obtain an inductor with a large Q value in the frequency band of 100 MHz to several hundred MHz compared to the technologies described in Patent Documents 1 and 2 and other documents.

Below, an example of the inductor 100 according to an embodiment of the present invention was analyzed using electromagnetic field analysis software using the three-dimensional finite element method ("HFSS" manufactured by Ansoft Japan Co., Ltd.).

The first magnetic unit 10 and the second magnetic unit 30 were assumed to be disk-shaped with a diameter of 800 μm and a thickness of 10 μm. The magnetic composite inter-coil filler 20 was assumed to be a square disk with a side length of 1.0 mm and a thickness of 50 μm. The coil 21 was assumed to be a copper wire with two turns, a line width of 30 μm, and a line spacing of 100 μm. The magnetic composite inter-coil filler 20 was formed by filling the composite magnetic material 22 evenly between the coils 21 and in the outer region of the coils 21 with carbonyl iron powder and epoxy resin in a volume ratio of 1:1 using 10.3 volume% HCl as a solvent, and then heating it in an electric furnace at 240°C for 6 hours in the atmosphere to remove the solvent contained in the magnetic composite material and completely harden the epoxy resin.

Assuming that the magnetic anisotropic films 11, 12, 31, and 32 are made of nanogranular films of Co35Fe65PdCaF, the frequency characteristics of the complex relative permeability and loss factor of the first magnetic unit 10 and the second magnetic unit 30 were measured using the results shown in Figures 3 and 4. In Figure 3, the solid line represents μ', which is the real component of the complex relative permeability, and the dashed line represents μ'', which is the imaginary component of the complex relative permeability.

Comparative Example 1 was an inductor that did not have the first magnetic unit 10 and second magnetic unit 30 of Example 1, and consisted only of magnetic composite inter-coil filler 20. Comparative Example 2 was an air-core inductor that did not have the first magnetic unit 10 and second magnetic unit 30 of Example 1, and the portion occupied by the magnetic composite body 22 was space. These Comparative Examples 1 and 2 were also analyzed in the same manner as the Examples. Comparative Example 1 corresponds to the technology described in Patent Document 1 above.

As shown in FIG. 5, it was found that the inductance L of the embodiment is approximately 1.3 times larger than that of Comparative Example 1 and approximately 1.5 times larger than that of Comparative Example 2 over the entire frequency range f of 100 MHz to 1000 MHz. This is believed to be the effect of adding the first magnetic unit 10 and the second magnetic unit 30.

Also, as shown in FIG. 6, the equivalent series resistance Rs of the embodiment is higher than those of comparative examples 1 and 2 at frequencies f of about 200 MHz or higher due to the influence of the iron loss of each magnetic material, but is lower than those of comparative examples 1 and 2 at frequencies f of about 200 MHz or lower due to the influence of the reduced proximity effect and reduced copper loss.

As shown in FIG. 7, the Q value of the embodiment is larger than those of comparative examples 1 and 2 when the frequency f is about 300 MHz or less, and is about 1.3 times larger than that of comparative example 1 and about 1.5 times larger than that of comparative example 2 when the frequency f is about 200 MHz. In addition, it is found that the Q value of the embodiment is about 1.5 times larger than that of comparative example 1 and about 1.8 times larger than that of comparative example 2 when the frequency f is about 100 MHz.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

10...first magnetic unit, 11...one magnetic anisotropic film (uniaxial magnetic anisotropic film in the film plane), 12...other magnetic anisotropic film (uniaxial magnetic anisotropic film in the film plane), 13...insulating layer, 20...magnetic composite material inter-coil filler, 21...coil, 22...magnetic composite material body, 30...second magnetic unit, 31...one magnetic anisotropic film (uniaxial magnetic anisotropic film in the film plane), 32...other magnetic anisotropic film (uniaxial magnetic anisotropic film in the film plane), 33...insulating layer, 40...substrate, 50...undercoat film, 51...insulating film, 100...inductor.

Claims (4)

A planar spiral inductor in which a first magnetic unit, a planar coil, a plate-shaped magnetic composite material inter-coil filler having a magnetic composite material formed by combining magnetic fine particles and an insulating material and filled between the wires of the coil, and a second magnetic unit are laminated in this order,
Each of the first magnetic unit and the second magnetic unit is formed by stacking two layers of in-plane uniaxial magnetic anisotropy films having different magnetization easy directions with an insulating layer sandwiched therebetween,
An inductor characterized in that in each of the first magnetic unit and the second magnetic unit, the two-layer in-plane uniaxial magnetic anisotropy film are not magnetically coupled to each other, the magnetic anisotropy of the two-layer in-plane uniaxial magnetic anisotropy film is canceled out, and the first magnetic unit and the second magnetic unit are each magnetically isotropic as a whole in the film plane. The inductor according to claim 1, characterized in that the two layers of in-plane uniaxial magnetic anisotropy film are each a nanogranular film. The inductor according to claim 1 or 2, characterized in that the easy magnetization direction of one of the two in-plane uniaxial magnetic anisotropy films is perpendicular to the easy magnetization direction of the other of the two in-plane uniaxial magnetic anisotropy films. The one of the in-plane uniaxial magnetic anisotropy films is a nanogranular film having a composition of (M1aM2b)1-X(L1cFd)X (M1: at least one selected from the group consisting of Fe, Co, and Ni, M2: at least one selected from the group consisting of Pd and Pt, L1: at least one selected from the group consisting of Li, Mg, Al, Ca, Sr, Ba, Gd, and Y, 0.5≦a≦1.0, 0≦b≦0.5 (a+b=1), 0.2≦c≦0.4, 0.6≦d≦0.8 (c+d=1), 0.15≦X≦0.55 (all atomic ratios)),
4. The inductor according to claim 3, wherein the other in-plane uniaxial magnetic anisotropy film is a nanogranular film having a composition of (M3hM4i)1-Y(L2jFk)Y (M3: at least one selected from the group consisting of Fe, Co, and Ni, M4: at least one selected from the group consisting of Pd and Pt, L2: at least one selected from the group consisting of Li, Mg, Al, Ca, Sr, Ba, Gd, and Y, 0.5≦h≦1.0, 0≦i≦0.5 (h+i=1), 0.2≦j≦0.4, 0.6≦k≦0.8 (j+k=1), 0.15≦Y≦ 0.55 (all atomic ratios)).

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