JP2002175917A - Stacked inductor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated inductor, the permanent magnets of which are not demagnetized, because the inductor can maintain a high magnetic inductance value, even if the electrical current supplied to the inductor has a large value and hardly causes eddy current loses and abnormal current heat generation, and, in addition, which can obtain a stronger magnetic bias effect with no increase in size. SOLUTION: This stacked inductor is constituted, by respectively laminating by printing ferrite magnet layers 3 polarized in their thickness direction upon both surfaces of the laminate of a plurality of conductive layers 2 in the direction of lamination, so that the magnet layers 3 are superimposed upon the conductive layers 2, from the insides of the annular shapes of the layers 2 to the outer peripheries of the layers 2 via a magnetic layer 1 which is formed in a nonconductive layer. The magnetic fluxes Bc generated by the conductive layers 2 will not pass through the ferrite magnet layers 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise suppression component for a DC power supply line and an inductor suitable for use under one-side excitation, such as a choke coil. The present invention relates to a laminated inductor formed by printing and laminating in a solenoid shape via a non-conductive layer having holes.

[0002]

2. Description of the Related Art The improvement in performance of electronic equipment is attributed to the development of semiconductor integrated circuits such as CPUs. These semiconductor integrated circuits are extremely sensitive to noise entering from the outside, and the noise is a major cause of circuit malfunction. For this reason, in recent years, noise regulations have been increasingly reinforced. As a noise countermeasure component, a laminated inductor having a small size and an extremely large impedance at a high frequency is generally used. In addition, recent needs for higher efficiency include CPU, L
The operating voltage of the SI has a remarkable tendency to decrease, which means that the operating current increases. For this reason, a large current is required to drive the CPU and the LSI, and the necessity of a multilayer inductor as a noise suppression component that can operate at a large current has been increasing. However, the conventional laminated inductor needs to have a large shape in order to cope with a large current, and has a problem that goes against the need for miniaturization of equipment. This is due to the magnetic saturation of the magnetic material that occurs when a large current flows through the coil.

[0003] For this reason, there is a demand for a magnetic component which is small and operates as a noise filter even with a large current. In other words, there is a demand for the development of an inductor that can flow a larger current than before even if it has the same shape.

As a measure against this demand, it is effective to arrange a magnet for generating a magnetic flux in a direction to cancel the magnetic flux generated by the exciting coil inside the core constituting the inductor (also called a magnetic bias method). is there.
For example, Japanese Unexamined Patent Publication No. 3-101106 discloses a multilayer inductor that discloses the effectiveness of this method. The method disclosed in this patent has a structure in which Ba ferrite is embedded in a coil of a multilayer inductor composed of NiZn ferrite by a printing lamination method.

[0005]

Problems to be Solved by the Invention
FIGS. 8A to 8C show a laminated inductor having a configuration similar to that disclosed in Japanese Patent Application Laid-Open No. 6-106. Referring to FIGS. 8A to 8C, in the laminated inductor, a plurality of conductive layers 62 having a partial annular shape are formed by a plurality of conductive layers 62 via a magnetic layer 61 having through holes (not shown). When viewed as a whole, they are printed and laminated so as to form one solenoid-shaped coil portion. Further, the ferrite magnet layer 63 polarized in the thickness direction is placed at the center position of the plurality of conductive layers 62 in the stacking direction.
It is printed and laminated inside the annular portion of the conductive layer 62.

When this multilayer inductor is actually used,
As shown in FIG. 8B, a magnetic flux Bc due to the coil portion (conductive layer 62) indicated by a solid arrow and a magnetic flux Bm due to the ferrite magnet layer 13 indicated by a broken arrow are formed.
The magnetic flux Bc from the conductive layer 62 passes through the inside of the ferrite magnet layer 63. Here, the inventors have found that the magnetization reversal phenomenon occurs when the magnetic flux from the conductive layer 62 passes through the ferrite magnet layer 63. The magnetization reversal phenomenon is a phenomenon in which a ferrite magnet layer 63 disposed in a magnetic layer 61 as a core of an inductor is magnetized in a reverse direction by an abnormal magnetic field caused by an inrush current generated when a power supply is used. When this phenomenon occurs, a magnetic flux is generated in the same direction as the magnetic flux generated by the coil section (excitation coil) formed by the conductive layer 62, and the characteristics of the element are significantly deteriorated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a noise prevention means for a semiconductor integrated circuit or the like, which can endure a relatively large current, and can prevent a magnetization reversal phenomenon caused by a conventional magnetic bias method. An object of the present invention is to provide a highly reliable laminated inductor that can exhibit the high cost of the inductor over a long period of time.

Conventionally, the conductive layer 12 usually contains Ag1
00% conductor is used. In this case, since the melting point of Ag is relatively low at 961 ° C., the laminated inductor using Ag as a conductor must be sintered at a low temperature of 961 ° C. or less. For this reason, it is usually sintered at about 900 ° C. Therefore, Ba ferrite for applying a magnetic bias must also be able to be sintered at a low temperature of about 900 ° C. However, Japanese Patent Application Laid-Open No. 3-101106 does not disclose a method of sintering Ba ferrite at a low temperature.

[0009] Therefore, another object of the present invention is to provide a method of manufacturing a laminated inductor capable of forming a ferrite magnet layer without adversely affecting a conductive layer.

[0010]

According to the present invention, there is provided a laminated inductor in which a plurality of conductive layers exhibiting a partial annular shape are printed and laminated in a solenoid shape via a non-conductive layer having a through hole. The ferrite magnet layers polarized in the vertical direction extend from the annular inside of the conductive layer through the non-conductive layer to the outer periphery of the conductive layer on both outer sides in the stacking direction of the plurality of conductive layers. Thus, a multilayer inductor characterized by being printed and laminated is obtained.

According to the present invention, the ferrite magnet layer contains Ba ferrite or Sr ferrite powder and at least one kind of low melting point glass having a softening point of 900 ° C. or less. The laminated inductor added so as to be 5 parts by weight or more is obtained.

According to the present invention, the non-conductive layer further comprises:
The multilayer inductor as a magnetic layer made of a magnetic material is obtained.

According to the present invention, the non-conductive layer further includes a first region in which the plurality of conductive layers are not projected and overlapped with each other;
A second region located between the plurality of conductive layers;
The multilayer inductor is obtained in which the first region is a magnetic layer made of a magnetic material and the second region is a nonmagnetic layer made of a nonmagnetic material.

According to the present invention, there is provided a method for manufacturing a laminated inductor, comprising a step of printing and laminating a plurality of conductive layers exhibiting a partial annular shape through a non-conductive layer having a through hole in a solenoid shape. The ferrite magnet layers polarized in a manner such that the ferrite magnet layers extend from the annular inside of the conductive layer through the non-conductive layer to the outer periphery of the conductive layer so as to be overlapped on both outer sides in the stacking direction of the plurality of conductive layers. The method further comprises a step of printing and laminating, wherein the ferrite magnet layer includes Ba ferrite or Sr ferrite powder and at least one kind of low melting point glass having a softening point of 900 ° C. or less, and the low melting point glass is 5% of the ferrite magnet layer. A method for manufacturing an inductor, characterized in that an inductor is used which is added so as to be not less than part by weight.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a laminated inductor and a method of manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings.

First Embodiment Referring to FIGS. 1 (a) to 1 (c), a multilayer inductor according to a first embodiment of the present invention includes a plurality of conductive layers 2 each of which has a partial annular shape. (Not shown) through a magnetic layer 1, which is a non-conductive layer, and is printed and laminated so as to form a single solenoid-like coil portion when viewed as a plurality of conductive layers 2 as a whole. The pair of conductive layers 2 on the outer side in the stacking direction are exposed on the side surfaces as connection terminals of the multilayer inductor, but are omitted in FIGS. 1B and 1C for convenience of explanation.

The laminated inductor further includes a ferrite magnet layer 3 polarized in the thickness direction on both outer sides in the laminating direction of the plurality of conductive layers 2, respectively, from the annular inside of the conductive layer 2 via the magnetic layer 1. The layers are printed and laminated so as to extend to and overlap the outer periphery of the conductive layer 2.

When this laminated inductor is actually used, as shown in FIG. 1B, the magnetic flux Bc generated by the coil portion (conductive layer 2) indicated by the solid arrow and the ferrite magnet layer 3 indicated by the broken arrow. And a magnetic flux Bm is formed. The magnetic flux Bc generated by the conductive layer 2 does not pass through the ferrite magnet layer 3 unlike the conventional example shown in FIGS. Since the magnetic flux from the conductive layer 2 does not pass through the ferrite magnet layer 3, the magnetization reversal phenomenon does not occur. That is, the ferrite magnet layer 3 disposed in the magnetic layer 1 as the core of the inductor is not magnetized in the opposite direction due to the abnormal magnetic field caused by the rush current generated when the power supply is used. As a result, the coil portion (excitation coil) constituted by the conductive layer 2
No magnetic flux is generated in the same direction as the magnetic flux generated by the magnetic field, and the characteristics of the element are not adversely affected.

The ferrite magnet layer 3 contains Ba ferrite or Sr ferrite powder and at least one kind of low melting point glass having a softening point of 900 ° C. or less. The low melting point glass is added so as to be 5 parts by weight or more of the ferrite magnet layer 3.

Next, a method of manufacturing the laminated inductor will be described.

Ferrite magnet layer 3 (Ba ferrite)
Is usually industrially in the range of 1200 ° C to 1250 ° C.
Sintered at temperature. Therefore, Ba ferrite is
In order to co-sinter with the nectar, it is necessary to set
C must be lowered. The present inventors, Ba Ferai
To powder, Bi₂O₃-SiO₂-B₂O₃, Bi₂O
₃-ZnO-SiO₂, SiO₂-B₂O₃-Zr
O₂, Na₂OB₂O₃-ZnO, PbO-B₂O₃
-SiO₂, PbO-BaO-SiO₂Softening point
Weight of at least one kind of low melting point glass of 900 ° C or less
By adding 5% or more in a ratio, the multilayer inductor can be configured.
Temperature sintering that can be co-sintered with the formed NiZnCu ferrite
The inventors have found that a binding reaction occurs.

What is the reason for selecting the amount of addition? It is as follows. If the addition is not more than 5% by weight, the sintering temperature of Ba ferrite does not drop to the required temperature, so it was set to 5% or more.
Further, if added in a weight ratio of 60% or more, the residual magnetic flux density of Ba ferrite decreases and a required bias magnetic field cannot be obtained.

Further, the multilayer inductor of the present invention is also used for high frequency noise countermeasures that have been increasing in demand in recent years. For this reason, NiZn ferrite having high electric resistance is most suitable as the magnetic material. In order not to impair the high electric resistance characteristics of this magnetic material, it is necessary that the incorporated Ba ferrite also has high electric resistance characteristics. Therefore, the composition of Ba ferrite is 81.8% to 85.85% by mol of iron oxide.
A range of 3% is preferred. When the amount of iron oxide is reduced to 81.8% or less, monoferrite is generated and magnetic properties are significantly deteriorated. On the other hand, when it is increased to 85.3% or more, the electric resistance is significantly reduced. Therefore, the above composition range is preferable.

Hereinafter, the present manufacturing method will be described more specifically.

As the magnetic layer 1 (NiCuZn ferrite), a composition having a magnetic permeability of 400 and a specific surface area of 5.2 m was used.
^It was pulverized to ² / g. 5 parts by weight of a binder (polyvinyl butyral) per 100 parts by weight of this powder,
70 parts by weight of a solvent (ethyl cellosolve) was mixed, the above composition was mixed using a spiral mixer, and further kneaded and dispersed in a bead mill to obtain a ferrite paste for forming a magnetic material.

To prepare a paste for the conductive layer 2 (Ag for forming a conductor), 5 parts by weight of a binder (ethyl cellulose), 15 parts by weight of a solvent (α-terpineol) and 15 parts by weight of a solvent (butyl carbitol acetate) were used. 10 parts by weight and 100 parts by weight of silver fine powder (average particle size: 0.5 μm) were mixed and kneaded and dispersed with a three-roll mill.

Furthermore, in order to produce a paste of the ferrite magnet layer 3 (Ba ferrite), the composition is 1 mol%.
As shown in Table 1 below, various amounts of low melting point glass were added to Ba ferrite powder of 4.9% BaO-85.1% Fe ₂ O ₃ , and the same process as the above-mentioned NiZnCu ferrite paste making process was performed. To prepare a paste.

[0028]

[Table 1]

Using the ferrite paste and the Ag paste thus produced, the magnetic layer 1a and the through holes 5a to 5m are formed so as to form a laminated winding of a conductor as shown in FIGS.
The magnetic layers 1b to 1g having 5f and the conductive layers 2a to 2g were printed and laminated. The number of coils corresponds to 7 turns.

Ferrite magnet layer 3 (Ba ferrite layer)
As shown in FIGS. 3A and 3B, the ferrite magnet layers 3a and 3b were arranged on the lower surface of the laminate in the height direction, and the thickness was about 20 μm. The overall thickness of the device after the lamination was 1.5 mm.

This is set to a predetermined size (4.5 mm × 3.2).
mm), and after the binder was removed, it was integrally fired at 900 ° C. The lead (conductive layer 2) of the laminated winding of this fired body
a and 2 g) are applied to a surface exposed on the side surface of the multilayer inductor, and a conductive paste containing Ag as a main component is applied, baked at 600 ° C., and external electrodes are formed to form a laminate. Type inductor was fabricated. Thereafter, a magnetic field of 10 kOe was applied by an electromagnet to magnetize the ferrite magnet.

Next, for comparison, at the center in the height direction of the laminate, about 20 μm-thick B
8 (a) to 8 (a) in which a magnet made of ferrite is disposed.
A multilayer inductor having the conventional magnetic bias type structure shown in FIG. This is referred to as Comparative Example 1. Further, a device having the same structure as that of the device of Comparative Example 1 and provided with a magnet made of Ba ferrite containing 40 wt% of low-melting glass was also produced in the same manner as Comparative Example 2, and was designated as Comparative Example 2. Also,
A laminated body in which the magnet portion was replaced with the above-mentioned NiZnCu ferrite and which did not use a magnet was produced in the same manner as Comparative Example 3. Table 1 also shows various addition amounts of the low-melting glass in Comparative Examples 1 to 3.

The inductance of the manufactured laminated inductor was evaluated using an LCR meter HP4284A and a DC superimposed power supply HP42841A manufactured by HP.

In this embodiment, the paste is prepared with the above composition. However, any other components and compounding ratios may be used as long as a printable paste can be obtained. Table 2 below shows the DC superposition characteristics of the inductance of the obtained multilayer inductor. The numbers described are current values when the inductance value is reduced by 10% from the initial value.

[0035]

[Table 2]

Comparative Example 1 is not described because the ferrite magnet was not sintered at all, the mechanical strength of the element was weak, the element was damaged during the operation, and the measurement could not be performed. From these comparisons, the inductor of the present embodiment has a DC superposition characteristic of about 1.5 times that of the conventional inductor.
It was doubled to doubled, and it was confirmed that the embedded ferrite magnet did generate a bias magnetic field.

Although the magnitude of the magnetic field cannot be measured, taking the case of level 4 in the embodiment as an example, the maximum bias magnetic field estimated from the elongation of the DC superimposition characteristic is approximately 1.1 KG.
Is equivalent to Since the residual magnetic flux density of the sintered body of the non-added Ba ferrite is about 1.9 kG, the low melting point glass 40 w
The addition of t% is expected to reduce the magnetic flux density to 1.4 kG. However, a magnetic flux density of about 80% of the expected value is obtained. It was also found that sintering had sufficiently proceeded.

FIG. 4 shows a comparison of the DC superposition characteristics of the inductance between the level 4 of the embodiment and the comparative examples 2 and 3.

In the fourth embodiment and the second comparative example, the change of the DC superimposition characteristic when a pulse current imitating an inrush current was applied was measured. The pulse current was applied using a pulse generator SY-922 and a power amplifier 4025S manufactured by Iwasaki Tsushinki Co., Ltd.
When this was repeated 10 times and the DC superimposition characteristics were measured again, the inductance value was significantly reduced in Comparative Example 2 as compared with no change in Embodiment Level 4. FIG. 5 shows a comparison of the DC superposition characteristics of the inductance between the embodiment level 4 after pulse energization and the comparative example 2.

[Second Embodiment] Referring to FIGS. 6A to 6C, in the laminated inductor according to the first embodiment of the present invention, a plurality of conductive layers 2 having a partially annular shape are formed through through holes (FIG. A plurality of conductive layers 2 via a non-conductive layer (not shown)
2 as a whole, they are printed and laminated so as to form one solenoid-shaped coil portion. The pair of conductive layers 22 on the outer side in the stacking direction are respectively exposed on the side surfaces as connection terminals of the multilayer inductor, but are omitted in FIGS. 6B and 6C for convenience of explanation.

The laminated inductor further includes a ferrite magnet layer 23 polarized in the thickness direction and a conductive layer 22 disposed on both outer sides in the laminating direction of the plurality of conductive layers 22 from the annular inside of the conductive layer 22 via the magnetic layer 21. It is printed and laminated so as to extend and overlap within the outer periphery of the layer 22.

The non-magnetic layer includes a first region 21 on which the plurality of conductive layers 22 are not projected and overlapped, and a second region 24 located between the plurality of conductive layers. First area 21
Is a magnetic layer made of a magnetic material, while the second region 2
Reference numeral 4 denotes a nonmagnetic layer made of a nonmagnetic material.

When the present laminated inductor is actually used, as shown in FIG. 6B, the magnetic flux Bc generated by the coil portion (conductive layer 22) indicated by the solid arrow and the ferrite magnet layer 23 indicated by the broken arrow. And the magnetic flux Bm is formed.
The magnetic flux Bc generated by the conductive layer 22 does not pass through the ferrite magnet layer 23 unlike the conventional example shown in FIGS.

The main points of the method for manufacturing the multilayer inductor are as follows. First, the second region 24 made of a nonmagnetic material
To form NiZnCu as described in the first embodiment.
A printing paste of ZnFe ₂ O ₄ , which is a non-magnetic material, is prepared in the same manner as in the ferrite paste preparing step.
The first region 21 and the second region 24 are formed by applying the same printing paste of NiCuZn ferrite and the same printing paste of ZnFe ₂ O ₄ as the level 4 of the first embodiment to predetermined positions, respectively. Forming a non-magnetic layer including
As a result, a second region made of a non-magnetic material is formed between the conductive layers 22 adjacent in the stacking direction.

With respect to the present multilayer inductor, the DC superposition characteristics of the inductance were measured in the same manner, and the results of comparison between the characteristics of Comparative Example 2 and Comparative Example 3 are shown in FIG.

[0046]

According to the multilayer inductor of the present invention, the ferrite magnet layer polarized in the thickness direction is provided on both outer sides in the stacking direction of the plurality of conductive layers, respectively, from the inside of the annular conductive layer via the non-conductive layer. Printed and laminated so as to extend and overlap within the outer periphery of the layer, so that the magnetic flux due to the conductive layer does not pass through the ferrite magnet layer, so that a relatively large current is used as a means for preventing noise in semiconductor integrated circuits and the like. In addition to this, it is possible to prevent the magnetization reversal phenomenon that occurs in the conventional magnetic bias method, and to provide a highly reliable inductor that can exhibit the effect of an excellent inductor over a long period of time. That is, even if the laminated inductor according to the present invention has the same shape as the conventional laminated inductor, a larger current can flow than the conventional one.

Further, according to the method of manufacturing a laminated inductor according to the present invention, a ferrite magnet layer can be formed without adversely affecting a conductive layer to manufacture the laminated inductor. More specifically, the addition of the low-melting glass makes it possible to sinter Ba ferrite at low temperature simultaneously with low-temperature sintering NiCuZn ferrite.
It can be improved from 5 times to 2 times.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a multilayer inductor according to a first embodiment of the present invention, wherein (a), (b), and (c) are a plan view of the multilayer inductor, an AA ′ cross-sectional view,
And BB 'sectional drawing.

2 (a) to 2 (m) are print lamination process diagrams for describing a method for manufacturing the laminated inductor shown in FIG.

FIGS. 3 (a) and 3 (b) are print lamination process diagrams for explaining a method of manufacturing the laminated inductor shown in FIG.

FIG. 4 is a graph showing a comparison of DC superimposition characteristics between Level 4 of Embodiment 1 and Comparative Examples 2 and 3.

FIG. 5 is a graph showing a comparison of DC superimposition characteristics between Level 4 of Embodiment 1 and Comparative Example 2 after pulse energization.

FIG. 6 is a diagram showing a configuration of a multilayer inductor according to a second embodiment of the present invention, wherein (a), (b), and (c) are a plan view of the multilayer inductor, an AA ′ cross-sectional view,
And BB 'sectional drawing.

FIG. 7 is a graph showing a comparison of DC superimposition characteristics between Embodiment 2 and Comparative Examples 2 and 3.

FIG. 8 is a plan view, an AA ′ sectional view, and a BB ′ sectional view of a conventional laminated inductor.

[Explanation of symbols]

 1, 1a-1g, 61 Magnetic layer 5a-5f Through hole 2, 2a-2g, 22, 62 Conductive layer 3, 3a, 3b, 23, 63 Ferrite magnet layer 21 First region (magnetic layer) 24 Second Area (non-magnetic layer)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Sato 6-7-1, Koriyama, Taishiro-ku, Sendai-shi, Miyagi F-term (reference) 5E062 FF01 5E070 AA01 AB01 BA12 BB03 BB05 CB03 CB13 CB17

Claims (5)

[Claims] 1. A laminated inductor formed by printing and laminating a plurality of partially annular conductive layers in a solenoid shape via a non-conductive layer having a through hole, further comprising a ferrite magnet layer polarized in a thickness direction. It is characterized in that each of the plurality of conductive layers is printed and laminated so as to extend from the annular inside of the conductive layer through the non-conductive layer to the outer periphery of the conductive layer and overlap each other on both outer sides in the laminating direction of the plurality of conductive layers. To be a laminated inductor. 2. A ferrite magnet layer comprising a Ba ferrite or Sr ferrite powder and a softening point of 900 ° C.
2. The multilayer inductor according to claim 1, comprising one or more kinds of the following low-melting glass, wherein the low-melting glass is added so as to be 5 parts by weight or more of the ferrite magnet layer. 3. The multilayer inductor according to claim 1, wherein the non-conductive layer is a magnetic layer made of a magnetic material. 4. The non-conductive layer includes a first region in which the plurality of conductive layers are not projected and overlapped, and a second region located between the plurality of conductive layers, wherein the first region is ,
3. The multilayer inductor according to claim 1, wherein the multilayered inductor is a magnetic layer made of a magnetic material, and the second region is a nonmagnetic layer made of a nonmagnetic material. 4. 5. A method for manufacturing a laminated inductor, comprising a step of printing and laminating a plurality of partially annular conductive layers in a solenoid shape via a non-conductive layer having a through hole, wherein the ferrite magnet polarized in the thickness direction. A step of printing and laminating the layers such that the layers extend from the annular inside of the conductive layer to the outer periphery of the conductive layer via the non-conductive layer and overlap each other on both outer sides in the stacking direction of the plurality of conductive layers. The ferrite magnet layer contains Ba ferrite or Sr ferrite powder and one or more kinds of low-melting glass having a softening point of 900 ° C. or less, and the low-melting glass is 5 parts by weight or more of the ferrite magnet layer. A method for manufacturing a multilayer inductor, characterized by using a material added to a multilayer inductor.