JP2002222712A - Lc composite device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LC composite device which is equipped with an inductor and a capacitor smaller and thinner than usual and capable of carrying a current of hundreds of mA or above. SOLUTION: Dielectric layers and electrode layers are alternately laminated into a capacitor, and an inductor is laminated on the one side of the capacitor for the formation of an LC composite device. A plane inductor is used as the above inductor, and the plane inductor is composed of a first ferrite magnetic film coming into contact with the capacitor, a plane coil provided on the surface of the first ferrite magnetic film, and a second ferrite magnetic film formed on the plane coil and equipped with an external electrode formed on the side of the second ferrite magnetic film and electrically connected to the terminal of the plane coil and the capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LC composite device in which a capacitor portion and an inductor portion are stacked.

[0002]

2. Description of the Related Art In recent years, the use of battery-driven small electronic devices such as portable devices and notebook personal computers has become popular. These electronic devices are not only required to be smaller and lighter than before, and recently, have been adapted to multimedia, that is, enhanced communication functions and display functions, or including image data. There is a demand for advanced functions such as high-speed processing of large amounts of information. Accordingly, there has been an increasing demand for a power supply capable of converting a single voltage from a battery to a plurality of voltage levels required by various mounting heights such as a CPU, an LCD module, and a communication power amplifier. Therefore, in order to achieve both the reduction in size and weight of electronic devices and the enhancement of their functions, reductions in the size and thickness of magnetic elements such as transformers and inductors mounted on power supplies and capacitors have been promoted.

First, the current state of the magnetic element is as follows. Transformers and inductors wound with coils have conventionally been mounted on sintered ferrite cores, but they have not been able to be made very thin, which has hindered the thinning of power supplies. Therefore, a power supply composed of a metal magnetic film layer / insulating layer / planar coil layer / insulating layer / metal magnetic film layer on a Si substrate, that is, a planar inductor (for example, Journal of the Japan Society of Applied Magnetics 20 (1996) 92)
2, JP-A-4-363006) has been proposed. However, the planar inductor has problems in manufacturing cost and characteristics.

That is, the planar inductor has a size of 6 to 7 μm.
Since it is necessary to form a metallic magnetic film having a thickness of m by a sputtering method or to form an insulating layer between the metallic magnetic film and the planar coil, an increase in the cost of the magnetic element itself was inevitable.
In terms of characteristics, when the planar inductor is driven at a high frequency in the MHz band, an eddy current is generated inside the metal magnetic film which is electrically conductive, or the upper and lower metal magnetic layers are formed through a slight nonmagnetic space. Since they face each other, the vertical alternating magnetic flux interlinks with the plane coil to generate an eddy current, and iron loss increases.
Among them, the generation of eddy current inside the metal magnetic film is
Forming a high-resistance region on the same plane as the metal magnetic film to subdivide the eddy current (see JP-A-6-7705)
In order to prevent eddy current from being generated when the vertical alternating magnetic flux interlinks the plane coil, the plane coil conductor is divided into a plurality of conductor lines (see Japanese Patent Application Laid-Open No. Hei 9-134820).
We are taking measures to improve the characteristics. However, these measures are not yet sufficient. Therefore, Japanese Patent Application Laid-Open
As disclosed in -26239, a planar magnetic element using a ferrite magnetic film formed by a printing method or a sheet method instead of a metal magnetic film has been proposed. In this planar magnetic element, a high-resistance ferrite magnetic film was formed by printing and firing a magnetic paste obtained by mixing a binder with ferrite powder on a Si substrate, and a coil pattern was formed on the film by plating or the like. Thereafter, a ferrite magnetic film is further formed thereon to form a magnetic element.

Next, the current state of the capacitor will be described. As shown in FIG. 5, as a capacitor used for a signal noise filter, a dielectric layer 1 and an internal electrode layer 2 are formed by a doctor blade method or a printing method. Thus, a so-called “multilayer ceramic capacitor” 6 that is alternately stacked is frequently used. However, this multilayer ceramic capacitor 6
Has a problem that the capacity is generally small. In order to increase the capacity, the number of stacked layers must be increased, so that the thickness is increased, and the power supply cannot be made thinner. By the way,
FIGS. 4 (a) and 4 (b) show a power supply obtained by combining the multilayer ceramic capacitor 6 with an inductor. The total power including the inductor 4 and the connection portion 5 of the planar magnetic element is 1.8 mm in height and has a bottom area. Is about 31 mm ² .

Recently, an LC composite device obtained by laminating this capacitor with a chip inductor, which is a magnetic device, to form a composite has been put to practical use. However, in this LC composite device, as shown in FIG.
Since the structure has the coil 8 formed three-dimensionally by printing and firing g paste, the coil resistance is high, and
It can be used only for a signal noise filter that passes a current of mA or less. Therefore, several hundred mA such as a switching power supply
At present, a so-called “power-type” LC composite element in which the above current flows is not realized.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the inductor and the capacitor are smaller than before.
It is another object of the present invention to provide an LC composite device which is not only thin but can flow a current of several hundred mA or more.

[0008]

Means for Solving the Problems The inventor has conducted intensive studies to achieve the above object and has embodied the results in the present invention.

That is, the present invention relates to a capacitor part in which dielectric layers and electrode layers are alternately laminated, and an LC composite device in which an inductor part is further laminated on one side of the capacitor part, wherein the inductor part is a planar inductor. A planar ferrite magnetic film contacting the capacitor portion, a planar coil provided on a surface of the magnetic film, and a second ferrite magnetic film provided on the planar coil. And an external electrode on the side surface of the second ferrite magnetic film, the terminal being connected to the terminal of the planar coil and the capacitor section.

According to the present invention, both the capacitor and the inductor are planarized and laminated.
It is possible to provide an LC composite device which is smaller and thinner than the conventional one and can be used for both a signal system and a power system.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

First, the inventor has proposed a magnetic element (inductor)
Was changed from a structure using a three-dimensional coil to a planar one, and an LC composite device as shown in FIGS. 1A, 1B and 1C was considered. Here, (a) is a view from the top, (b) is a view of (a) cut by a diagonal line 17 and a side view is shown, and (c) is a view from the top view of (a) with the external electrode 3 and a later-described view. FIG. 3 is a view in which a second ferrite magnetic film 11 has been removed.

Therefore, this LC composite element is constructed by stacking a multilayer ceramic capacitor and a planar magnetic element (inductor). Specifically, a planar inductor portion 4 is further laminated on one side of the capacitor portion 6 in which the dielectric layers 1 and the internal electrode layers 2 are alternately laminated, and the planar inductor portion 4 is brought into contact with the capacitor portion 6. A first ferrite magnetic film 9 to be formed, a planar coil 10 provided on the surface of the magnetic film 9, and a second ferrite magnetic film 11 provided on the planar coil 10. 2 is formed on the side surface of the ferrite magnetic film 11 by the external electrode 3 through which the terminals of the planar coil 10 and the capacitor section are conducted. In this case, the multilayer ceramic capacitor 6 and the planar magnetic element (inductor) 4 are electrically connected by one external electrode on the side of the multilayer ceramic capacitor 6 and one terminal on the side of the magnetic element. With such a structure, as compared with the switching power supply shown in FIGS. 4A and 4B, the area of the planar capacitor 6 itself and the connection portion (wiring) connecting the planar capacitor 6 and the planar magnetic element 4 is reduced. Thus, the entire area can be further reduced in size. However, the overall thickness is increased by overlapping the capacitor 6 and the magnetic element 4, but in the present invention, the increase in the thickness can be minimized for the following reasons.

That is, the capacitance C of the multilayer ceramic capacitor 6 is generally expressed by the following equation.

C = ε ₀ ε _r (nA / d) where ε ₀ is the dielectric constant of vacuum, ε _r is the relative dielectric constant, n is the number of layers, A is the electrode area, and d is the thickness of the dielectric. .

On the other hand, the area of the planar magnetic element 4 is 5 mm × 5.
mm, which is larger than a general laminated ceramic capacitor 6 of about 2 mm × 2 mm.
Therefore, the area of the multilayer ceramic capacitor 6 combined with the plane magnetic element 4 can be increased to at least the same dimension as the plane magnetic element 4, and A in the above equation can be increased to achieve a large capacity, and a large current can be obtained. It becomes possible to shed. Conversely, if the capacitances C are the same, the number n of stacked layers can be reduced, and a reduction in thickness can be achieved. That is, by stacking the planar magnetic element and the capacitor in the structure according to the present invention, it is possible to make the device thinner than before. At this time, handling and the like are easier if the Si substrate 12 is provided. However, when a thinner structure is strongly required, a structure in which the Si substrate 12 is thinly cut or removed may be used.

As the ferrite used for the planar magnetic element 4, NiZn-based ferrite, which is an insulator, among which NiCuZn-based ferrite having a low firing temperature is preferable.
On the other hand, the dielectric 1 used for the capacitor 6 is SrT
Ceramics containing iO ₃ or BaTiO ₃ as a main component are suitable, but any material used for ordinary multilayer ceramic capacitors can be used. The internal electrode 2 of the capacitor is preferably made of Ag, Pd, Ni, Cu, or an alloy thereof.

Hereinafter, a method for manufacturing an LC composite device according to the present invention will be described with reference to the drawings in the embodiments.

[0019]

(Embodiment 1) On a Si substrate 12, SrTiO
Paste containing dielectric powder containing ₃ as a main component and Ag /
Screen printing is performed by alternately stacking 120 layers of pastes containing alloy powders having a composition of Pd = 80/20. Thus, the capacitor section 6 is completed. The number of layers and the layer thickness depend on the magnitude of the capacitance C of the capacitor section 6 to be manufactured, but are usually adjusted to several hundred layers, and the thickness of each of the fired layers is about 2 to 5 μm. You.

Next, the formation of the inductor portion 4 to be laminated on the capacitor portion 6 will be described. On one side of the capacitor portion 6, Fe ₂ O ₃ / ZnO / CuO / NiO = 49
A paste containing ferrite magnetic powder having a composition of / 23/12/16 (mol%) was formed as a lower ferrite (first ferrite magnetic film 9) by screen printing, and the capacitor portion was heated at 950 ° C. in the air. Fired together with 6. The thickness of the first ferrite magnetic film 9 after firing is 40 μm. A polyimide resin was applied onto the first ferrite magnetic film 9 by spin coating, and then thermally cured.
The thickness of the polyimide resin 13 after thermosetting is 3 μm.
Further, on the resin 13, Cu
0.5 μm was formed by electroless plating. The situation so far is shown in FIG. After applying a photoresist thereon, a resist frame 15 of a 14-turn spiral coil having a line width / line interval = 100/30 (μm) and a thickness of 100 μm was formed by photoetching (see FIG. 2B). After depositing Cu 16 with a thickness of 70 μm in the resist frame 15 by electroplating (see FIG. 2C), the plating underlayer 14 between the coils was removed by resist peeling and chemical etching to obtain the planar coil 10. . This state is shown in FIG.

On this planar coil 10, Fe ₂ O ₃ / Z
nO / CuO / NiO = 49/23/12/16 (mo
An epoxy resin paste containing a ferrite magnetic powder having a composition of 1%) was formed as an upper ferrite (second ferrite magnetic film 11) by a screen printing method and thermally cured at 150 ° C. (see FIG. 2E). . Thus, the lamination of the capacitor 6 and the inductor 4 has been completed. Note that the thickness of the second ferrite magnetic film 11 from the upper surface of the coil after thermosetting is 100 μm.

Finally, the capacitor section 6 and the inductor section 4
Are electrically connected with the external electrodes 3 to complete the LC composite device (see FIG. 2F). The capacitance of the obtained LC composite device is 1.5 μH for the inductor (magnetic device),
The capacitor is 20 μF and the size is shown in FIGS. 3 (a) and (b).
² This is significantly smaller and thinner than the conventional switching power supply in which the magnetic element and the capacitor shown in FIGS. 4A and 4B are individually arranged on the Si substrate 12 individually. 5 V of the LC composite device of the present invention
DC-DC converter (output current 5
When the converter was tested at 00 mA), it was confirmed that there was almost no heat generation, the converter temperature did not rise, and the converter operated normally. (Example 2) In the same manner as in Example 1, an LC composite device in which the number of layers of the dielectric layer 1 and the internal electrode layer 2 of the capacitor section 6 was 10 and the number of turns of the planar coil was 5 was manufactured. on the other hand,
The manufacturing method of the capacitor and the inductor was the same as the printing method, but a conventional composite element having a three-dimensional inductor coil was manufactured (Comparative Example 1). Table 1 summarizes the characteristics of the LC composite devices obtained in the present invention (Example 2) and Comparative Example 1.

From Table 1, it is clear that the characteristics of both are almost equal, and that the LC composite device according to the present invention can be used as a noise filter. Further, regarding the thickness of both, it is clear that the one according to the present invention is much thinner.

[0024]

[Table 1]

[0025]

As described above, according to the present invention, an inductor and a capacitor which are not only smaller and thinner than conventional ones, but are capable of flowing a current of several hundred mA or more.
A composite device was realized.

[Brief description of the drawings]

FIG. 1 is a view showing an LC composite device according to the present invention;
(A) is a view from the top, (b) is (a) is a diagonal line 17
FIG. 3C is a view in which the external electrode 3 and the second ferrite magnetic film 11 are removed from the top view of FIG.

FIGS. 2A and 2B are cross-sectional views illustrating a manufacturing process of an LC composite device according to the present invention. FIG. 2A shows a state where a plating base is formed on a polyimide resin after thermosetting by an electroless plating method. , (B) shows a situation in which a photoresist was applied to form a resist frame, (c) shows a situation in which Cu was deposited with a thickness of 70 μm in the resist frame, and (d) shows a situation in which Cu was deposited in the resist frame.
Strip resist, remove plating base
(E) shows a state in which an upper ferrite (second ferrite magnetic film) is formed by a screen printing method and is thermally hardened, and (f) shows a state in which the space between the capacitor portion and the inductor portion is formed. This shows a state in which an LC composite device is completed by being electrically connected by external electrodes.

3A and 3B are views showing the appearance of an LC composite device according to the present invention, wherein FIG. 3A is a plan view and FIG. 3B is a side view.

4A and 4B are diagrams showing a switching power supply in which a capacitor and an inductance are arranged in a plane, wherein FIG.
Is the side.

FIG. 5 is a perspective view showing a multilayer ceramic capacitor.

FIG. 6 is a perspective view showing a chip inductor having a three-dimensional coil formed therein.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric (dielectric layer) 2 Internal electrode (internal electrode layer) 3 External electrode 4 Planar magnetic element (inductor) 5 Connection part 6 Multilayer ceramic capacitor (capacitor) 7 Chip inductor 8 Three-dimensional coil 9 First ferrite magnetic film Reference Signs List 10 plane coil 11 second ferrite magnetic film 12 Si substrate 13 polyimide resin 14 plating base 15 resist frame 16 Cu 17 diagonal line 18 terminal of plane coil 19 LC composite element

Claims (1)

[Claims] 1. A capacitor part in which dielectric layers and electrode layers are alternately laminated, and an LC composite device in which an inductor part is further laminated on one side of the capacitor part, wherein the inductor part is a planar inductor. A planar inductor is formed by a first ferrite magnetic film contacting the capacitor portion, a planar coil provided on a surface of the magnetic film, and a second ferrite magnetic film provided on the planar coil. An LC composite device comprising, on a side surface of the second ferrite magnetic film, an external electrode through which a terminal of the planar coil and the capacitor section are connected.