JPH11168011A - Microinductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microinductor which is capable of being downsized and applied to highly efficient, high-output converters. SOLUTION: A copper-plated flat coil 2a is formed on the surface of a magnetic substrate 1a. Furthermore, a magnetic core 3 is arranged on the substrate 1a. A closed magnetic path structure is formed by the substrate 1a and the core 3. The substrate 1a and the core 3 constituting the closed magnetic path structure are made of materials having an initial permeability μi of 500 or higher and an energy loss E of 100 or lower, at measured frequencies which range from 100 to 1,000 kHz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-inductor which can be applied to a high-efficiency and high-output DC-DC converter, and more particularly to a micro-inductor capable of realizing miniaturization.

[0002]

2. Description of the Related Art Conventionally, for the purpose of reducing the size, weight, and function of portable devices such as notebook personal computers, small and high-sized switching power supplies used for these portable devices have been used. There is a need to develop efficient DC-DC converters. As a microinductor applied as a DC-DC converter, for example, an inductor having an open magnetic circuit structure including a winding coil has been disclosed (Japanese Patent Application Laid-Open Nos. 8-322421, 8-28937 and 8-28937). Kaihei 8-2939691
No.). FIG. 16 is a perspective view showing a conventional inductor composed of a winding coil. The drum type ferrite core 12 is formed by a core 12b and walls 12a attached to both ends of the core 12b. The inductor 11 is formed by winding a copper wire 13 around the drum type ferrite core 12.

In the inductor 11 configured as described above, when a DC voltage is applied to the copper wire 13, a magnetic field is generated around the inductor 11, the core 12b, and the like. Thus, in a converter (not shown) on which the inductor 11 is mounted, the input power supply voltage can be boosted, stepped down, or inverted and output.

However, since the conventional coiled inductor shown in FIG. 16 has an open structure, magnetic flux leaks from the wall portion 12a to the outside, and good magnetic characteristics cannot be obtained. Therefore, in order to improve the magnetic characteristics, it is necessary to increase the number of turns of the copper wire 13.
As the number of turns increases, the length of the copper wire increases, and there is a problem that the DC resistance increases. As a result, the efficiency decreases due to heat generation. On the other hand, there is a method of increasing the thickness of the copper wire 13 to reduce the DC resistance. However, if this method is used, the size of the inductor is further increased. Further, the wound coil is manufactured by manually winding a copper wire around a core, and is not suitable for mass production because automation is difficult.

[0005] In view of the above, there have been proposed inductors which can improve the magnetic characteristics as compared with an inductor comprising a winding coil and can be reduced in size (JP-A-5-299282, JP-A-6-299282). No. 84644, JP-A-5-326260 and JP-A-6-2
No. 52350). These inductors have a magnetic part constituting a closed magnetic circuit structure and a planar coil. In particular, JP-A-5-299282 and JP-A-6-84644 disclose a thin-film inductance element in which a core constituting a closed magnetic circuit structure is formed on each side of a rectangular coil. . Also, Japanese Patent Application Laid-Open
JP-A-326260 discloses a thin-film magnetic element in which a core constituting a closed magnetic circuit structure is formed on a pair of opposing sides of a coil wound in a rectangular shape. Further, Japanese Unexamined Patent Publication No.
JP-A-252350 discloses a microinductor having a completely closed magnetic circuit structure in which a planar coil is covered with an insulating magnetic material and no gap is formed between the magnetic material and the coil.

The planar coils used in these inductors are manufactured by using, for example, a thin film forming technique or a printed board technique. As described above, when the thin-film plated coil is manufactured by the thin-film forming technique, the thickness of the conductor portion can be significantly reduced, so that the inductor can be downsized. Further, a copper coil is bonded to the surface of the substrate, and the copper foil is etched into a desired shape, whereby a printed coil having a shape in which a strip-shaped conductor layer is wound around can be formed.

In recent years, with the thinning and miniaturization of DC-DC power supplies, there has been a demand for a microinductor having a thinner structure, and the microinductor can be mounted on the same substrate without increasing the outer diameter of a conventional inductor. There is a demand for an inductor that can obtain good performance at a height equal to or lower than the IC and LSI to be formed.

On the other hand, in order to improve the performance of the inductor, it is necessary to increase the driving frequency of the switching power supply as in the case of other components, and the switching frequency is equivalent to the frequency (500 kHz) practically used as a control IC. A higher frequency, for example, a frequency of 1 MHz is required. Further, the output of the small portable device is about 0.5 to 1 W at present, but in the field of the small portable device,
There is a demand for an inductor capable of supporting an output of about 5 W realized in a large-sized device.

In general, the performance of an inductor can be calculated by the following equation (1).

[0010]

## EQU1 ## Q = L × 2πf / R, where Q: figure of merit L: inductance (μH) R: resistance (Ω) f: frequency (Hz)

As shown in the above formula 1, in order to increase the figure of merit Q and obtain a high-performance inductor, the inductance L or the frequency f may be increased or the resistance R may be decreased. Further, an inductance L for obtaining a desired performance.
Can be calculated by the following equation (2).

[0012]

L = {Vout (Vin−Vout)} / (Vin × f ×
Iout × LIR) where Vin; maximum input voltage Vout; output voltage Iout; maximum DC load current f; operating frequency LIR; coil impedance

Therefore, 5W (5V-1) is connected from an AC power supply of 100V to an AC 12V via an AC adapter.
The inductance L for obtaining the notebook personal computer having the output of A) is Vin = 12 (V), Vout =
5 (V), Iout = 1 (A) and LIR = 0.3 (recommended value) by substituting into the above equation 2, L =
9.72 / (Iout × f). For example, if the frequency is 1M
Hz, when the output current Iout is 1 A, the inductance L is 10 μH, and when the output current Iout is 2 A, the inductance L is 5 μH, and the output current Iout
Is 4A, the inductance L is 2.4 μH. Therefore, when the driving frequency is 1 MHz, an inductor having an inductance L of 2.4 to 10 μH is required.

[0014]

However, in an inductor formed of a thin-film plated coil, since the thickness of the coil is about several μm to 10 μm, the cross-sectional area of the conductor portion (line) in the direction perpendicular to the current direction is reduced. Very small, which results in a significantly higher DC resistance. Therefore, a high current cannot be applied to the inductor using the thin film plated coil, and desired performance cannot be obtained.

[0015] In an inductor composed of a printed coil, a strip-shaped conductor layer is formed by etching a copper foil. Therefore, if an attempt is made to make the interval between adjacent strip-shaped conductor layers (interval between lines) smaller than the thickness of the coil, over-etching or the like occurs, making it difficult to pattern a coil of a desired size. As a result, it is necessary to set the interval between the conductor layers larger than necessary, which makes it difficult to reduce the size of the inductor. If the distance between the conductor layers is not properly set, leakage of magnetic flux between the coils occurs, and the efficiency of the coils decreases.

Further, any of the inductors has a magnetic portion constituting a closed magnetic circuit structure, but a desired inductance cannot be obtained depending on the structure of the magnetic portion.

The present invention has been made in view of the above problems, and has as its object to provide a microinductor which can be reduced in size and has high efficiency and can be applied to a high-output converter. And

[0018]

A microinductor according to the present invention is a microinductor having a planar coil and a magnetic part constituting a closed magnetic circuit structure, wherein the magnetic part is initially provided at a measurement frequency of 100 to 1000 kHz. It is made of a magnetic material having a magnetic permeability μi of 500 or more and an energy loss E of 100 or less.

The planar coil has a thickness of 20 μm or more,
Line width is 20μm or more, spacing between lines is 100μm
Hereinafter, it is preferable that the number of turns be 10 turns or less and the coil size in a plan view be 5 mm × 5 mm or less. In addition,
In the present invention, the energy loss refers to a sum of all of the hysteresis loss, the eddy current loss, and the residual loss. In the present invention, the values of the initial magnetic permeability μi and the energy loss E of the magnetic material are controlled by a method of selecting a material of the magnetic material or a method of forming the magnetic material into a laminated structure of a magnetic thin film and an insulating thin film. can do. Further, in the present invention, the line width refers to the width of a strip-shaped conductor layer formed in a coil shape, and the interval between lines refers to the interval between adjacent strip-shaped conductor layers.

In the present invention, since the magnetic portion constituting the closed magnetic circuit structure of the inductor is made of a magnetic material whose initial magnetic permeability μi and energy loss E are appropriately defined, it is necessary to increase the size of the coil. Therefore, a high-efficiency inductor applied to an electronic device having an output of 5 W can be obtained. Further, if the thickness of the coil, the line width, the interval between the lines, the number of turns, and the coil size are appropriately regulated, a more compact and highly efficient inductor can be obtained.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a micro inductor according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a perspective view showing a structure at the time of assembling a micro inductor according to a first embodiment of the present invention. FIG.
2A is a perspective view showing the structure after the assembly, and FIG.
(B) is a sectional view thereof. 1 and 2 (a) and 2
As shown in (b), a planar coil 2a made of copper plating
Are formed. The coil 2a has a shape in which a strip-shaped conductor layer is circulated on the substrate 1a. The magnetic core 3 is disposed on the substrate 1a. Core 3
On one surface, two wide grooves are provided in parallel, thereby forming convex portions extending parallel to each other on both sides and the center of the surface of the core 3. Therefore, core 3
Are assembled so as to contact only the surface of the substrate 1a at the axis of the coil 2a and on both sides of the coil 2a, and the core 3 and the coil 2a are separated from each other. In this manner, the substrate 1a and the core 3 form a closed magnetic circuit structure. In the present embodiment, the magnetic substrate 1a and the magnetic core 3 forming the closed magnetic circuit structure are
At a measurement frequency of ~ 1000 kHz, the initial permeability μi is 5
It is made of a material having an energy loss E of 100 or more and an energy loss E of 100 or less.

In this embodiment having the above-described structure, the magnetic substrate 1a and the magnetic core 3 constitute a closed magnetic circuit structure. As shown in FIG. Without this, the magnetic permeability of the magnetic material can be effectively utilized. Therefore, the number of turns of the planar coil can be reduced, and the thickness and size of the inductor can be easily reduced. Further, since the number of turns of the coil is small and the coil length can be shortened, the DC resistance is reduced, the efficiency is not easily reduced by heat generation, and a highly efficient inductor can be obtained. Further, in this embodiment, since a planar coil is used, the coil can be formed by, for example, a thin film forming technique or a technique similar thereto. Therefore, unlike the case where the winding coil is used, automation can be performed in the coil forming process, and the productivity can be improved.

In the present invention, various shapes of the magnetic core 3 can be used. FIG.
(A), FIG. 5 (a) and FIG. 6 (a) are plan views showing an inductor applied to the present invention, and FIG. 4 (b), FIG.
(B) and FIG. 6 (b) are perspective views showing the shape of each magnetic core. In FIGS. 4A, 5A and 6A, the planar coils are indicated by hatching. 4 (b), 5 (b) and 6
FIGS. 4 (a), 5 (a), and 6 (b) show the states shown in FIGS.
The upper surface and the lower surface of the magnetic core shown in FIG.

The inductor according to the first embodiment shown in FIGS. 1 and 2 has a magnetic core 3 having the shape shown in FIG. That is, on one surface of the core 3, two wide grooves 3a are provided.
Are provided in parallel with each other, so that three convex portions 3b extending parallel to each other are formed on both sides and the center of the core 3. Accordingly, a closed magnetic circuit structure is formed by bonding the protrusion 3b and the substrate 1a. FIG.
As shown in FIG. 3, the magnetic core 8 is provided with a U-shaped groove 8a, thereby forming a U-shaped convex portion 8b on three sides of the peripheral edge of the core 8 and at the center. A convex portion 8c extending from the vicinity to the other end is formed. Also in the core 8 shown in FIG. 5, a closed magnetic circuit structure is formed by bonding the protrusions 8b and 8c and the substrate 1a.

Further, as shown in FIG. 6, the magnetic core 9 has a wall 9b surrounding the four peripheral edges and a projection 9c near the center of the core 9. I have.
An opening 9e for drawing out one end of the coil 2a to the outside is provided in a part of the wall 9b, and the projection 9c is provided.
Is provided with a window 9d for drawing out the other end of the coil 2a to the outside. Therefore, a closed magnetic circuit structure is formed by bonding the wall 9b and the protrusion 9c to the substrate 1a. As described above, in the present invention, for example, cores having various shapes shown in FIGS. 4 to 6 can be used, and in any case, a closed magnetic circuit structure is formed, so that a highly efficient inductor is obtained. be able to.

FIG. 7A is a perspective view showing a structure of a microinductor according to a second embodiment of the present invention.
(B) is a sectional view thereof. As shown in FIGS. 7 (a) and 7 (b), for example, in the central part of the surface of the Si wafer 4 having a thickness of 500 μm, a region extending from one end to the other end opposite thereto is formed. The first magnetic layer 6 composed of a laminate of an amorphous magnetic thin film and an insulator layer has a thickness of about 50 μm.
The thickness is selectively formed. FIG. 8 shows the first magnetic layer 6.
FIG. 2 is an enlarged schematic view showing the structure of FIG. The first magnetic layer 6
An amorphous magnetic thin film 6a made of CoZrNb and FeCoBSi and having a thickness of, for example, 1000 °;
It is made of iO ₂ and Ta ₂ O ₅ and has a thickness of, for example, 500
Are alternately laminated, for example, 333 layers each.

On the Si wafer 4 and the first magnetic layer 6, a coil 2b made of a copper plating layer is formed with a thickness of about 100 μm. As in the first embodiment, the coil 2
“b” has a shape in which a conductor layer extending in a belt shape is circulated on the Si wafer 4 and the first magnetic layer 6. Further, a second magnetic layer 7 having a structure similar to that of the first magnetic layer 6 is formed on the first magnetic layer 6 and the coil 2b thereon with a thickness of about 50 μm. Therefore, in the region where the magnetic layers 6 and 7 are formed, the entire thickness including the wafer 4 is
It is about 0.7 mm. The second magnetic layer 7 is formed in contact with the surface of the first magnetic layer 6 on the axis of the coil 2b and on both sides of the coil 2b.
An insulating layer 10 made of SiO ₂ and polyimide is formed. In the second embodiment, a closed magnetic circuit structure is formed by the first magnetic layer 6 and the second magnetic layer 7, and the initial magnetic permeability μi of the magnetic material forming these magnetic layers 6 and 7 is set. Is 500 or more, and the energy loss E is 100
It is as follows.

In the second embodiment configured as described above, as in the first embodiment, a highly efficient inductor with reduced leakage of magnetic flux can be obtained. In the first and second embodiments, the initial magnetic permeability μi and the energy loss E of the magnetic material constituting the magnetic layer are defined.
FIG. 9 is a graph showing the relationship between the resistance value and the energy loss, with the resistance value on the vertical axis and the energy loss on the horizontal axis. FIG. 10 shows the inductance on the vertical axis,
It is a graph which shows the relationship between an inductance and initial magnetic permeability, taking initial magnetic permeability on a horizontal axis. 9 and 10 show values measured using an inductor having a planar coil of the following dimensions formed at a frequency of 1 MHz. That is, as shown in FIG. 11, the inductor used has three turns and a conductor layer thickness of 10 turns.
0 μm, the line width (the width of the conductor layer) s is 140 μm, the space between the lines (the space between adjacent conductor layers) t is 40 μm,
A planar coil 2 having a coil size a × b of 2.5 mm × 3.0 mm is formed on a substrate, and the height of the inductor is 1 mm.

Considering the efficiency loss due to heat, a general 7
When calculated at 0% efficiency, in order to obtain a high-efficiency inductor applied to an electronic device having an output of 5 W (5 V-1 A), the resistance value may be 1.5 Ω or less in the case of 5 V-1 A. is necessary. As shown in FIG. 9, when the energy loss E exceeds 100, the resistance value R exceeds 1.5Ω,
It cannot support 5W output electronic devices.

Further, in order to obtain an inductor applicable to an electronic device having an output of 5 W (5 V-1 A), the inductance L of the inductor needs to be 2.4 μH or more. As shown in FIG. 10, when the initial magnetic permeability μi is less than 500, the inductance L becomes less than 2.4 μH, and
It becomes impossible to correspond to an electronic device of W output. Therefore, by using a magnetic material having an initial permeability μi of 500 or more and an energy loss E of 100 or less,
It is possible to obtain a high-efficiency inductor applied to an electronic device having an output of 5 W.

Further, in the present invention, an inductor with higher efficiency can be obtained by defining the dimensions, the line width, and the interval between the lines of the planar coil.
Hereinafter, these values will be specifically described.

The coil thickness and line width greatly affect the breakdown current. For example, Table 1 below shows the breakdown current of a conductor layer having a width of 1 mm.

[0033]

[Table 1]

As shown in Table 1, a current of 5.0 (A / 10000 μm ² ) can be supplied when the allowable amount is the largest. In the present invention, since the object is to obtain an inductor applicable to an electronic device having an output of 5 W (5 V-1 A), the breakdown current is 1.0 (A / 2000 μm ² ).
As described above, it is preferable to form a conductor layer having a cross-sectional area of 2000 μm ² or more. That is, when the thickness of the planar coil is 20 μm, the line width s is set to 100 μm.
When the thickness is 100 μm, the thickness of the coil is set to xμ so that the line width s is set to 20 μm or more.
When m is set, the line width is preferably adjusted to (2000 / x) μm or more.

Further, even if it is assumed that the inductor of the present invention is applied to an electronic device having an output of 5 W or less, if the coil thickness is less than 20 μm or the line width is less than 20 μm. , The DC resistance of the coil increases. Therefore, in order to reduce the DC resistance, if the number of turns of the coil is reduced to shorten the entire length of the conductor layer,
The desired inductance L cannot be obtained. Therefore, it is preferable that each of the coil thickness and the line width be 20 μm or more.

Further, a thin-film conductive layer such as a planar coil is
For example, when the frequency is in a high frequency region of 1 MHz or more,
It has a characteristic that current is supplied only to a predetermined depth from the surface of the conductive layer. At this time, the depth of the energized region (skin depth) can be calculated by the following equation (3).

[0037]

Δ = (ρ / πμf) ^0.5 where δ; skin depth (m) ρ; resistance μ; permeability f; frequency (Hz)

According to Equation 3, when the frequency is 1 MHz, the skin depth δ of the coil made of copper is about 60 μm. Therefore, the sum of the depth from the front side and the depth from the back side is 120 μm. Therefore, when a copper coil is formed, even if its thickness is 120 μm or more, it is 1 μm.
Only the same performance as a copper coil having a thickness of 20 μm can be obtained.

It is to be noted that increasing the coil thickness and the line width s also increases the obtained inductance. In particular, when the coil thickness exceeds 200 μm or when the line width s exceeds 200 μm, the coil size increases. Undesirably increases. Also, when the number of turns is increased to obtain a desired inductance, the DC resistance of the coil increases, so that the efficiency decreases or the cross-sectional area of the coil needs to be increased to prevent the DC resistance from increasing. Yes, not preferred. Therefore, in the inductor of the present invention using a magnetic material having an initial magnetic permeability μi of 500 or more and an energy loss E of 100 or less, when the coil thickness and the line width are respectively set to 200 μm or less, the coil dimensions are reduced. There is no increase in size. Preferably, the thickness of the coil and the line width are each 50 μm to 150 μm.

Further, the interval t between the lines is 100 μm.
Is exceeded, magnetic flux leakage occurs. Therefore, the interval t between the lines is preferably 100 μm or less. In the present invention, the thickness of the inductor is equal to or less than the thickness of an IC or LSI mounted on the same substrate, and the width and length of the inductor are the same as those of the conventional inductor. The following is preferred. Therefore, in order to form a coil with the dimensions of the inductor, the line width, and the interval between the lines set under the above conditions, it is preferable that the number of turns of the coil be 10 turns or less. Further, for example, in order to form 100 to several hundred inductors on a 6-inch wafer, the dimensions of the coil are preferably 5 mm or less × 5 mm or less.

Next, a specific example of a method of manufacturing the microinductor according to the first embodiment of the present invention will be described. FIGS. 12A to 12H and FIGS. 13A and 13B are cross-sectional views illustrating an example of a method of manufacturing the microinductor according to the first embodiment of the present invention in the order of steps. FIG.
As shown in FIG. 2A, a plating electrode Cu film 21 having a thickness of, for example, 2000 .ANG. Is formed on a magnetic substrate 1a made of ferrite by sputtering. Next, FIG.
As shown in (b), a negative resist film 22 is applied on the Cu film 21 to a thickness of, for example, 120 μm. Next, as shown in FIG. 12C, the resist film 22 is selectively exposed and developed to form a groove at a position on the substrate 1a where a coil is to be formed.

Thereafter, as shown in FIG. 12 (d), the surface of the substrate is plated with Cu, so that the grooves formed in the resist film 22 have flat coils 2a made of a Cu plating layer.
Is formed with a thickness of, for example, 100 μm. Then, FIG.
As shown in (e), the resist film 22 is removed. Thereafter, as shown in FIG. 12F, the Cu film 21 in a region not covered with the coil 2a is removed by plasma etching. Thereafter, as shown in FIG.
An insulating film 24 of, for example, polyimide or the like is applied to the entire surface so as to completely cover the coil 2a. Then, FIG.
As shown in (h), the insulating film 24 is selectively removed,
A protective insulating film 24a covering the coil 2a is formed.

On the other hand, as shown in FIG. 13A, a ferrite core is formed by processing a ferrite material and selectively forming grooves on the surface thereof. Thereafter, as shown in FIG. 13B, the core 3 is placed on the substrate 1a with the surface on which the groove is formed facing downward, and the substrate 1a and the core 3 are bonded. Thus, an inductor having a closed magnetic circuit structure is formed.

FIGS. 14 (a) to (e) and FIG. 15 (a)
(E) to (e) are cross-sectional views showing another example of the method of manufacturing the microinductor according to the first embodiment of the present invention in the order of steps. Instead of the steps shown in FIGS. 12A to 12H, the coil 2a can be formed on the substrate by the following steps.

As shown in FIG. 14A, a negative resist film 25 made of, for example, polyimide is formed on a magnetic substrate 1a made of ferrite. Next, FIG.
As shown in (b), a Cu film 26 serving as a mask is formed on the resist film 25 by sputtering. Next, as shown in FIG. 14C, a resist film 27 is applied on the Cu film 26. Thereafter, as shown in FIG. 14D, the resist film 27 is selectively exposed and developed to form a groove in a region where a coil is to be formed. Thereafter, as shown in FIG. 14E, the region of the Cu film 26 exposed by the formation of the groove is removed by etching.

Thereafter, as shown in FIG. 15A, the resist film 27 on the Cu film 26 is removed by reactive ion etching (RIE), and the resist film 25 is not covered with the Cu film 26. The region is etched away. Then, as shown in FIG.
Cu is sputtered on the entire surface to form a Cu film 28 on the exposed surface of the substrate 1a. Thereafter, as shown in FIG. 15 (c), a planar coil 2a made of Cu is formed on the surface of the Cu film 28 by performing Cu plating.
After that, as shown in FIG.
Is removed by polishing. Thereafter, as shown in FIG. 15E, the resist film 25 is selectively removed, and the coil 2a is removed.
Is formed.

After that, similarly to the method shown in FIG.
By forming the core 3 and bonding the core 3 and the substrate 1a, an inductor having a closed magnetic circuit structure is formed.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the microinductor according to the present invention will be specifically described below in comparison with comparative examples.
First, microinductors having various coil dimensions were manufactured using various magnetic materials having different initial magnetic permeability μi and energy loss E, and the inductance L of the inductor, the resistance R of the coil, and the like were measured. As the structure of the inductor, a microinductor having a closed magnetic circuit structure shown in FIG. 2, a microinductor having a closed magnetic circuit structure shown in FIG. 7, and an inductor using an open structure winding coil shown in FIG. 16 were adopted.

In the embodiment No. 1 and Comparative Example No. 1 5
The magnetic substrate 1a made of ferrite and having a thickness of 0.5 mm and the ferrite having a thickness of 0.5 m
m, and the thickness of the inductor is 1 mm and the width is 2.5 mm. Example N
o. 2, Comparative Example No. 6 and Comparative Example Nos. 8 is obtained by forming a first magnetic layer 6 and a second magnetic layer 7 each having a thickness of 50 μm on a Si wafer 4 having a thickness of 0.5 mm, and each magnetic layer is an amorphous magnetic thin film. And an insulating film. This inductor has a thickness of 0.7 mm and a width of 2.5 mm. Further, in Example No. 3 and Comparative Example No. 7 has the structure shown in FIG. 2 and the coil size (a × b) is 4.5 mm × 5 m
m, and the dimensions of the inductor are 5 mm in width, 6.0 mm in length in the longitudinal direction, and 1 mm in thickness. Furthermore,
Comparative Example No. For the coil No. 4, the winding coil shown in FIG.
m, and the width of the ferrite core (the diameter of the wall 12a) is 5 mm.

The structures of the inductor, the initial magnetic permeability μi of the magnetic material at various frequencies, and the energy loss E of the magnetic material are shown in Tables 2 and 3 below, and the shape and dimensions of the coil and the DC resistance R ₀ are shown in Table 4 below. Tables 5 and 6 below show the inductance L, resistance R, and heat loss of the inductor at various frequencies, and the dimensions and volume of the inductor. In the column of the resistance R shown in Tables 5 and 6, the case where the resistance R is less than 0.25Ω is ０．２ (very good), and the case where the resistance R is 0.25Ω or more and less than 0.5Ω is ○ ( (Good), the case where the resistance R was 0.5Ω or more and less than 1.6Ω was evaluated as Δ (good), and the case where the resistance R was 1.6Ω or more was evaluated as × (bad).

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

[Table 5]

[0055]

[Table 6]

As shown in Tables 2 to 6 above, Example N
o. 1 to 3 are 5 W without increasing the line width, thickness and number of turns of the coil because the initial permeability μi and energy loss E of the magnetic material and the shape and size of the coil are within the scope of the present invention. A high-efficiency inductor applicable to an electronic device having the above output can be obtained.

On the other hand, in Comparative Example No. 4 is energy loss E
Is beyond the scope of the present invention, and since the magnetic circuit has an open structure, it is necessary to increase the number of turns of the coil in order to obtain a desired L value. Therefore, the resistance value R was extremely high as compared with the example, and desired characteristics could not be obtained. In addition, since a coil having a large number of turns is used, the size of the coil is increased. Comparative Example No. In Example No. 5, the structure of the inductor and the shape and dimensions of the coil are the same as in Example No. 5. 1, but the inductance L decreased because the initial permeability μi of the magnetic material was less than the lower limit of the range of the present invention.

Comparative Example No. No. 6 shows the structure of the inductor and the shape and dimensions of the coil in Example No. 1. Same as 2, except that the energy loss E of the magnetic material exceeded the upper limit of the range of the present invention, so that the heat loss was increased. Also, in Comparative Example No. No. 7, the inductor structure, initial magnetic permeability, energy loss, line width, spacing between lines, thickness, and coil dimensions are the same as those of Example No. 7. 3 but the number of turns of the coil exceeds the upper limit of the range of the present invention. The heat loss at the measurement frequency of 1 MHz was higher than that of No. 3. Comparative Example No. 8 shows that the structure of the inductor, the initial magnetic permeability, the energy loss, the number of turns of the coil, the interval between the lines, and the coil dimensions are the same as those of Example N.
o. Example 2 is the same as Example No. 2 except that the line width and thickness of the coil are less than the lower limit of the present invention. The heat loss was higher than that of No. 2.

[0059]

As described in detail above, according to the present invention,
Since the magnetic part constituting the closed magnetic circuit structure is made of a magnetic material whose initial magnetic permeability μi and energy loss E are appropriately defined, it is possible to provide an electronic device having an output of 5 W without increasing the size of the coil. An applicable high-efficiency inductor can be obtained. In addition, coil thickness, line width,
By properly regulating the spacing between lines, the number of turns, and the coil dimensions, a much smaller and more efficient inductor can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure at the time of assembling a micro inductor according to a first embodiment of the present invention.

FIG. 2A is a perspective view showing a structure of a micro inductor according to a first embodiment of the present invention, and FIG. 2B is a sectional view thereof.

FIG. 3 is a cross-sectional view showing a state of a magnetic field generated in an inductor having a closed magnetic circuit structure.

FIG. 4A is a plan view showing an inductor applied to the present invention, and FIG. 4B is a perspective view showing the shape of a magnetic core.

FIG. 5A is a plan view showing an inductor applied to the present invention, and FIG. 5B is a perspective view showing the shape of a magnetic core.

FIG. 6A is a plan view showing an inductor applied to the present invention, and FIG. 6B is a perspective view showing the shape of a magnetic core.

FIG. 7A is a perspective view showing a structure of a micro inductor according to a second embodiment of the present invention, and FIG. 7B is a sectional view thereof.

FIG. 8 is an enlarged schematic view showing a structure of a magnetic layer.

FIG. 9 is a graph showing the relationship between the resistance value and the energy loss, with the vertical axis representing the resistance value and the horizontal axis representing the energy loss.

FIG. 10 is a graph showing the relationship between inductance and initial magnetic permeability, with the vertical axis representing inductance and the horizontal axis representing initial magnetic permeability.

FIG. 11 is a plan view showing dimensions of a planar coil.

FIGS. 12A to 12H are cross-sectional views illustrating an example of a method of manufacturing the microinductor according to the first embodiment of the present invention in the order of steps.

FIGS. 13A and 13B are cross-sectional views showing the next step of FIG. 12 in the order of steps.

FIGS. 14A to 14E are cross-sectional views illustrating another example of the method of manufacturing the microinductor according to the first embodiment of the present invention in the order of steps.

15 (a) to (e) are cross-sectional views showing the next step of FIG. 14 in the order of steps.

FIG. 16 is a perspective view showing a conventional inductor formed by a winding coil.

[Explanation of symbols]

1a, 1b; substrate, 2, 2a, 2b; coil, 3;
Core; 4; silicon wafer; 5; alumina film;
6, 7; magnetic layer, 11; inductor, 12; core,
13; copper wire

Claims (2)

[Claims] 1. A microinductor having a planar coil and a magnetic part constituting a closed magnetic circuit structure, wherein the magnetic part has an initial permeability μi of 500 or more and an energy loss E of 100 at a measurement frequency of 100 to 1000 kHz. A microinductor comprising the following magnetic material. 2. The planar coil has a thickness of 20 μm or more, a line width of 20 μm or more, and an interval between lines of 100 μm or more.
2. The microinductor according to claim 1, wherein the number of turns is 10 μm or less, and the coil size in plan view is 5 mm × 5 mm or less. 3.