JP6486614B2 - Inductor - Google Patents

Description

  The present invention relates to an inductor, and more particularly, to an inductor that suppresses a proximity effect and increases a Q value.

Many electronic devices have a power supply circuit and a high-frequency circuit, and various electronic components are used. The inductor is used for smoothing output current and impedance matching. For example, in a high frequency circuit inductor, a planar spiral inductor is often used because of its small size and integration.
FIG. 15 shows a cross-sectional view of a planar spiral inductor. In the air-core inductor as shown in FIG. 15A, the magnetic flux generated by the current flowing through the winding B is linked to the adjacent windings A and C. Then, in windings A and C, an eddy current is generated due to an induction phenomenon, which causes a loss (proximity effect). FIG. 15 (a) shows the effect of the winding B, but the current flowing through the windings A and C similarly has an effect of induction on the other windings.

  As a technique for suppressing the proximity effect, as shown in FIG. 15B, an inductor having a structure in which a magnetic material D is embedded between winding lines has been devised (Patent Document 1). By embedding a magnetic material between the wires, the magnetic flux generated by the current flowing through each winding passes through the magnetic material between the wires, which has a higher magnetic permeability than the winding, and the proximity effect is suppressed and the resistance component is reduced. The Q value can be increased.

JP 2013-214613 A

An inductor having a configuration in which a magnetic material is embedded between lines can increase the Q value by suppressing the proximity effect. However, in order to enable use at a high frequency such as 1 GHz, it is necessary to use a material whose permeability does not decrease even in a high frequency region.
Ferrite, such as Ni-Zn ferrite, has a significantly reduced magnetic permeability in the frequency range of 1 GHz, so it cannot be used as a magnetic material that fills the space between coils and suppresses the proximity effect. Thin film magnetic materials are known as magnetic materials that can be used even in a high frequency range. However, since the thin film magnetic material obtains uniaxiality by using a film forming method such as sputtering, it is possible to form a thin film on a flat substrate surface, but as shown in FIG. It cannot be formed by filling a thin film magnetic material between the lines of the planar coil.

  An object of the present invention is to provide an inductor having a large Q value even in a frequency band of 0.1 GHz to 1 GHz while reducing the size of the inductor.

An inductor according to the present invention is a planar spiral inductor in which a magnetic material is filled between coil wires, and the magnetic material is a composite of a spherical magnetic particle having a particle size of 2 μm or less and a dielectric material. It is made of a magnetic composite material , the volume ratio of the magnetic fine particles to the dielectric material is 1: 1, the magnetic fine particles exist in the magnetic material without being in contact with each other, and the surface of the coil is the magnetic composite. It is not covered with a material.
The magnetic fine particles used in the magnetic composite material, which means that sufficient particle size to the extent that the magnetic loss is negligible external magnetic flux due to the induced current is also generated in the magnetic fine particles as the interlinked magnetic fine particles of the high frequency or the like is small ing. Although depending on the frequency band of the external magnetic flux, in the frequency band of 0.1 GHz to 1 GHz, if the magnetic particle has a particle size of about 2 μm or less, the loss due to the induced current generated in the magnetic particle can be sufficiently ignored.
The magnetic material is preferable in that the Q value can be effectively improved by filling the space between the coils and not covering the coil surface.

The pre-Symbol magnetic particles, Fe particles, and Fe-based magnetic fine particles such as Fe alloy particles, Co-based magnetic fine particles, it is preferable to use one of Ni-based magnetic particles.

  The inductor according to the present invention can be provided as an inductor that can be easily downsized and has a large Q value.

It is a photograph which shows the structural example of the inductor which concerns on this invention. It is a SEM image of the section of a coil. It is explanatory drawing of the magnetic composite material which consists of carbonyl iron powder and an epoxy resin. It is a graph which shows the frequency characteristic of the complex relative magnetic permeability of a magnetic composite material. It is a graph which shows the frequency characteristic of the complex dielectric constant of a magnetic composite material. It is a graph which shows the measured value and analytical value of an inductance about an inductor of an embodiment and a comparative example. It is a graph which shows the measured value and analysis value of resistance about the inductor of embodiment and a comparative example. It is a graph which shows the measured value and analysis value of Q value about the inductor of embodiment and a comparative example. FIG. 2 is a plan view (a) of an analysis model for a planar spiral inductor and an explanatory view (b) showing a configuration of coil wires. It is sectional drawing of the analysis model of an air-core inductor. It is sectional drawing of the analytical model of the inductor using a magnetic composite material. It is a graph which shows the analysis result of the frequency characteristic of an inductance. It is a graph which shows the analysis result of the frequency characteristic of resistance value. It is a graph which shows the analysis result of the frequency characteristic of Q value. It is sectional drawing of the inductor which embedded the air core inductor (a) and the magnetic material between the lines.

(Inductor configuration)
FIG. 1 shows a configuration example of an inductor according to the present invention. This inductor fills the space between the coil portion 10 provided at the center, the ground wire portion 12 extending from one end of the coil portion 10 in a U-shape, and the coil portion 12 and the ground wire portion 12. And a magnetic part 14.

The inductor shown in FIG. 1 includes a coil portion 10 and a ground line portion 12 in order to evaluate the characteristics of the inductor. This is because when the characteristics of the inductor are evaluated using a network analyzer, the measurement probe terminal is brought into contact with the G portion of the ground line portion 12 and the S portion of the proximal end portion of the coil portion 10 for measurement. .
Therefore, in this inductor, the central portion of the coil portion 10 acts as a planar type spiral inductor. That is, the coil unit 10 is an inductor in a pure sense, and the inductor shown in FIG. 1 is an inductor in a broad sense. Hereinafter, the inductor shown in FIG. 1 is referred to as an inductor element.

FIG. 1 shows a state in which the entire coil portion 10, ground wire portion 12, and magnetic body portion 14 (inductor element) are viewed from a plane direction. The entire inductor element has a rectangular flat plate shape, and the size of the entire inductor element is 590 μm long × 530 μm wide.
The magnetic body portion 14 is provided so as to fill the space between the coils of the coil portion 10 in the thickness direction, and to cover an intermediate region between the outside of the coil portion 10 and the ground wire portion 12 and an outer region on the left side of the coil portion 10. ing. The thickness of the coil part 10 and the ground line part 12 of the embodiment is 8 μm, and the thickness of the magnetic body part 14 is also 8 μm. That is, the magnetic body portion 14 is formed on the same surface as the surface on which the coil portion 10 and the ground wire portion 12 are formed, with the same thickness as the coil portion 14 and the ground wire portion 14.

The coil portion 10 of the inductor element shown in FIG. 1 is a two-turn planar coil, and the coil has a line width of 55 μm and a line interval of 15 μm.
The inductor element of the embodiment shown in FIG. 1 is an extremely small-sized inductor having an overall element shape of 1 mm × 1 mm or less and a planar shape of the coil portion 10 of about 300 μm × 300 μm. The inductor of the present embodiment is designed with the number of turns, the line width, and the line interval of the coil section 10 assuming use in a frequency band of 0.1 GHz to 1.0 GHz. It is desirable that the Q value of inductors used in actual applications be 20 or more.

(Inductor manufacturing method)
The inductor element shown in FIG. 1 used for the measurement was manufactured as follows.
First, a Cr (50 nm) film and then a Cu (200 nm) film are formed on the entire surface of the substrate by sputtering. Next, using a spin coater, apply a positive resist to the surface of the upper Cu film, pre-bake with a hot plate, expose the conductor layer pattern with a mask analyzer, post-bake with a hot plate, Develop with. By the developing operation, a resist pattern is formed on the surface of the Cu film so as to expose the portions to be the coil portion 10 and the ground wire portion 12 of the inductor element.

Next, a Cu plating film is formed on the exposed portion of the Cu film by a Cu plating apparatus.
Next, the resist on the substrate is stripped and removed. Finally, the Cu / Cr sputtered laminated film at the part covered with the resist pattern is removed by dry etching by reverse sputtering.
Thus, the coil portion 10 and the ground line portion 12 are formed on the substrate.

  The most characteristic point in the configuration of the inductor according to the present invention is a magnetic material filled between the coils 10. That is, in the inductor according to the present invention, a magnetic composite material in which magnetic fine particles and a dielectric material are mixed is used as the magnetic material filled between the wires of the coil portion 10. In the embodiment, as the Fe-based magnetic fine particles, substantially spherical particles having an average particle diameter of 1.1 μm made of carbonyl iron powder are used, an epoxy resin is used as the dielectric material, and the carbonyl iron powder and the epoxy resin are used. Was used as an ink by adding a solvent so that the volume ratio was 1: 1.

In the embodiment, a magnetic composite material composed of the carbonyl iron powder and the epoxy resin is supplied to the substrate on which the coil portion 10 and the ground wire portion 12 are formed by a printing method, and is filled between the wires of the coil portion 10. After filling the space between the portion 10 and the ground wire portion 12 and the outer region of the coil portion 10 in a flat state, in the air, 120 ° C. for 5 minutes with a hot plate, 120 ° C. for 120 minutes with an electric furnace, 140 ° C., 180 ° Heating was performed for a while, the solvent contained in the magnetic composite material was removed, and the epoxy resin was completely cured to obtain the inductor element shown in FIG.
In the experiment, the surface of the coil was polished with sandpaper so that the surface of the coil was not covered with the magnetic composite material. The high frequency characteristics of the inductor are improved by preventing the surface of the coil from being covered with the magnetic composite material. However, depending on the application, the surface of the coil may be covered with the magnetic composite material.

FIG. 2 is a cross-sectional view showing a state in which the magnetic composite material is filled between the lines of the coil portion 10. In this example, the magnetic composite material is filled between the coil wires, and the surface of the coil is covered with the magnetic composite material.
FIG. 3 is an explanatory view showing a state in which carbonyl iron powder and an epoxy resin are mixed.
The resistance value of the magnetic composite material composed of carbonyl iron powder and epoxy resin used in the experiment is 111 (Ω · m).
FIG. 4 shows the result of measuring the complex relative permeability of this magnetic composite material, and FIG. 5 shows the result of measuring the frequency characteristic of the complex relative permittivity. 4 and 5, the magnetic composite material composed of carbonyl iron powder and epoxy resin used in the experiment exhibits the characteristics that the real part is constant and the imaginary part is almost zero in the frequency band of 0.1 GHz to 1.0 GHz. It can be seen that this magnetic composite material has a very small loss due to natural resonance, eddy current, and the like in this frequency band.

  In the present embodiment, the reason why the Fe-based magnetic fine particles are used as the magnetic fine particles used in the magnetic composite material is that the Fe-based material has excellent magnetic characteristics and is easily available. Fe-based magnetic fine particles mean to include Fe fine particles and Fe alloy fine particles. As magnetic fine particles, Co magnetic fine particles and Ni magnetic fine particles can be used in addition to Fe magnetic fine particles. These fine particles also have the same function as the Fe-based magnetic fine particles.

In the present invention, the reason why magnetic fine particles are used as the magnetic material used in the magnetic composite material filling the space between the coils is that the induced current (eddy current) generated in the magnetic fine particles when the external magnetic flux is linked to the magnetic fine particles is ignored. This is because the magnetic loss due to the induced current can be kept extremely low.
The reason why the magnetic loss due to the induced current generated in the magnetic fine particles can be ignored is that the magnetic fine particles have a small particle size. This is because even if an induced current is generated in each magnetic fine particle, the particle is small, so that it does not reach resistance loss following the change in magnetic flux. In order to utilize the effect of such particles, it is preferable to use magnetic particles as small as possible.

  In the present embodiment, Fe fine particles having a spherical shape and an average particle diameter of 1.1 μm are used. Depending on the material of the magnetic fine particles, if the magnetic fine particles have a particle size of 2 μm or less, they can be sufficiently used as the magnetic part 14 of the inductor used in the frequency band of 0.1 to 1 GHz. The magnetic fine particles are not limited to those having a spherical shape. The particle diameters of 1 μm and 2 μm are approximate external dimensions of the magnetic fine particles.

  If a magnetic composite material containing magnetic fine particles having a particle size of about 2 μm or less is used as the magnetic material filling the space between the coils, the magnetic material is present in the gap of 15 μm between the wires as in the coil portion 10 of the embodiment. Filling the composite material is easy. That is, the method of manufacturing an inductor by filling a magnetic composite material containing magnetic fine particles between coil wires can be effectively used as a method of manufacturing a minute inductor having an outer diameter of 1 mm × 1 mm.

In this embodiment, carbonyl iron powder and epoxy resin were mixed at a volume ratio of 1: 1. In order to obtain the characteristics (magnetic permeability) as a magnetic material, it is considered effective to increase the composition ratio of the magnetic material in the magnetic composite material as much as possible, but the loss due to the induced current generated in the magnetic fine particles can be suppressed. This is because the magnetic fine particles are minute. That is, when a plurality of magnetic fine particles gather to form a collective state, the effect that the loss due to the induced current is suppressed due to the fine magnetic fine particles is lost. Therefore, when preparing a magnetic composite material, as shown in FIG. 3, the magnetic composite material is filled between the coil wires and the magnetic fine particles are not in contact with each other and have a composition that exists alone. Good.
In the embodiment, the Fe fine particles and the epoxy resin were prepared in a volume ratio of 1: 1. If this volume ratio is set, the amount of the Fe fine particles in the magnetic body portion 14 can be secured, and the Fe fine particles are mutually connected. It is because it is distributed so that it exists without touching.

  In this embodiment, an epoxy resin is used as the dielectric material used for the magnetic composite material. However, in addition to the epoxy resin, an arbitrary resin material such as a polyimide resin, a polymer material, and a dielectric material should be appropriately selected and used. Is possible.

  The above-described photolithography method for forming the coil portion 10 or the ground wire portion 12 and the printing method for forming the magnetic body portion 14 are widely used as methods for manufacturing electronic components such as semiconductor packages and wiring boards. is there. Therefore, in the manufacturing process of an electronic component such as a semiconductor product, it is possible to easily make an inductor in which a magnetic material is filled between coil wires by using the above-described method. The size is about μm × several hundred μm, and can be easily incorporated into an electronic component having a fine structure.

(Characteristic comparison)
6, 7, and 8 show the measurement results and analysis values of the above-described inductor element using the network analyzer for the inductance (L), resistance (R), and Q value. 6, 7, and 8 also show the measurement results and analysis values for an air-core inductor as a comparative example. The air-core inductor has the same coil portion and ground line portion as the inductor shown in FIG. 1 and does not have a magnetic portion between the wires.
The analysis value is a result of analysis using electromagnetic field analysis software using a three-dimensional finite element method.
6, 7, and 8, a line A is an actual measurement value for the inductor of the embodiment, and a broken line a is an analysis value. A line B is an actual measurement value of the air-core inductor, and a broken line b is an analysis value.

  As for the inductance shown in FIG. 6, in the inductor of the embodiment in which the magnetic material is filled between the lines, the inductance value is increased by about 10% as compared with the air core inductor of the comparative example. This is considered due to the fact that the magnetic material is filled between the lines. Also, with respect to the analysis value using the electromagnetic field analysis software, the inductor of the embodiment in which the magnetic material is filled between the wires is higher than the inductor of the air-core inductor.

Regarding the resistance shown in FIG. 7, in the frequency band of 1 GHz or less, the inductor of the embodiment has a lower resistance value than the air-core inductor. This is a result of the proximity effect being suppressed by filling the magnetic material between the lines.
On the other hand, in the frequency band of 1 GHz or more, the inductor of the embodiment has a significantly larger resistance value than the air-core inductor. This is considered to be due to the loss of the magnetic composite material itself used as the magnetic material.

As for the Q value shown in FIG. 8, in the inductor according to the embodiment, the Q value is improved by about 30% in the vicinity of 1 GHz as compared with the air-core inductor, and greatly exceeds the Q-value of the air-core inductor.
Compared to the measurement results described above, in the inductor (planar spiral inductor) of the present embodiment, only the Q value is significantly improved as compared with the air-core inductor as compared with the inductance and resistance. In other words, the inductor according to the embodiment does not change much in terms of inductance and resistance, and therefore has the effect of selectively improving only the Q value without significantly changing the circuit design from the conventional example. be able to.

(Analysis result)
In the planar spiral inductor shown in FIG. 1, in order to investigate the action of the magnetic composite material when the magnetic composite material is filled between the coil wires, the model of the planar spiral inductor shown in FIG. The frequency characteristics of were analyzed. The planar spiral inductor to be analyzed is a two-turn planar coil with overall dimensions of 590 μm × 530 μm, a line width of 55 μm, and a line spacing of 15 μm (FIG. 9).

FIG. 10 is a cross-sectional view of an analysis model of an air-core inductor, in which a pad portion 10a and a coil wire 10b are formed on a glass substrate 20 with a thickness of 8 μm.
FIG. 11 is a cross-sectional view of an analytical model of an inductor using a magnetic composite material. On the glass substrate 20, a magnetic composite material layer 14a is provided below the coil, and the magnetic composite material 10b is filled between the coil wires 10b. The magnetic composite material layer 14c is provided on the upper layer of the coil.
In the analysis model shown in FIG. 11, the thickness t of the magnetic composite material layer 14a provided in the lower layer of the coil and the magnetic composite material layer 14b provided in the upper layer of the coil was analyzed as t = 0, 1, 4, 8 μm.

FIG. 12 shows an analysis result on the inductance. The analysis result shown in FIG. 12 shows that the inductance increases as the thickness of the magnetic composite material layers 14a and 14b is increased with respect to the air-core inductor.
FIG. 13 shows an analysis result regarding the resistance value. The analysis result shown in FIG. 13 shows that the resistance value increases as the thickness of the magnetic composite material layers 14a and 14b is increased.
FIG. 14 shows the analysis result for the Q value. The analysis result shown in FIG. 14 indicates that the peak position of the Q value shifts to the low frequency side as the thickness of the magnetic composite material layers 14a and 14b is increased. That is, in order to improve the Q value in the frequency band of 0.1 GHz to 1 GHz, it is effective to fill the magnetic composite material between the coil wires so as not to cover the surface of the coil.

  The inductor according to the present invention is provided as a high-Q inductor. A high Q value means a low loss, so that power consumption can be reduced by using it as a circuit component of an electronic circuit. That is, the inductor according to the present invention can be effectively used as a circuit component for reducing power consumption.

  According to the present invention, it is possible to provide an inductor that can be easily downsized and has a large Q value.

DESCRIPTION OF SYMBOLS 10 Coil part 10a Pad part 10b Coil wire 12 Ground line part 14 Magnetic body part 14a, 14b, 14c Magnetic composite material layer 20 Glass substrate

Claims (2)

A planar spiral inductor filled with a magnetic material between coil wires,
The magnetic material is composed of a magnetic composite material in which magnetic particles having a spherical shape and a particle size of 2 μm or less and a dielectric material are combined.
The volume ratio of the magnetic fine particles to the dielectric material is 1: 1,
In the magnetic material, the magnetic fine particles exist without contacting each other,
An inductor, wherein a surface of the coil is not covered with the magnetic composite material. The magnetic fine particles, the inductor of claim 1, wherein the Fe-based magnetic fine particles, Co-based magnetic particles are either Ni-based magnetic particles.