JPH0714716A - Multilayer ceramic magnetic component and production thereof - Google Patents

Abstract

PURPOSE:To make the saturation of the main magnetic body composing a laminate difficult and to increase the allowable current level by disposing a layer, having permeability lower than that of the magnetic body, at a position blocking the flow of flux in the magnetic laminate. CONSTITUTION:A layer 8 having permeability lower than that of a magnetic body incorporating a coil 7 is disposed at a position blocking the flow of flux. Since the allowable current level and the saturation field strength of multilayer ceramic magnetic component can be increased easily without requiring any modification of coil conductor pattern or the improvement in the characteristics of magnetic body, design of the multilayer ceramic magnetic component can be revised easily and such problem as the magnetic body is saturated magnetically with excess overcurrent to cause abrupt decrease of inductance can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated ceramic magnetic component having a large allowable current value and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a monolithic ceramic magnetic component, a monolithic ceramic inductor or a monolithic ceramic transformer in which a plurality of inductors are inscribed is known. In the monolithic ceramic inductor, for example, a coil conductor is inscribed in a ferrite magnetic body, and a coil conductor terminal is led out to a peripheral surface of the magnetic body and connected to an external terminal electrode provided on the peripheral surface.

A monolithic ceramic transformer has two or more coils embedded in a ferrite magnetic body, or a single coil having a tap, so that a primary side coil and a secondary side coil are formed. A device for inductively coupling a plurality of electric circuits, which is a miniaturized electronic component in which these electric circuits are embedded in a ceramic magnetic body by a laminated ceramic technique.

As a method of manufacturing the monolithic ceramic transformer, there are the following methods, for example. A slurry obtained by kneading ferrite magnetic powder and an organic binder is continuously applied on a base film to form a long ferrite green sheet. The ferrite green sheet is cut into a size that allows acquisition of several hundreds to several hundreds or more of laminated ceramic parts. A green sheet in which through holes corresponding to the acquired number are formed at predetermined positions of the ferrite green sheet and a cover green sheet in which no through holes are formed are prepared. The same coil conductor pattern for several hundreds to one thousand and several hundreds is printed on the green sheet on which the through holes are formed by using a conductor paste such as Ag so that the through holes are covered. The green sheets are stacked in a predetermined stacking order to form a primary coil, and then several green sheets for a cover are stacked, and further the green sheets on which the coil patterns are printed are stacked in a predetermined stacking order to form a secondary coil. A predetermined number of green sheets for a cover are laminated on the upper and lower sides of a laminated body of the secondary coil, which are then pressure-bonded, and cut into individual laminated ceramic parts. The cut laminated body is arranged in the magnetic body so that the coils are vertically overlapped with the magnetic core axes aligned with each other, and an external terminal connected to the coil conductor terminal is formed on the peripheral surface of the laminated body. In this way, a monolithic ceramic transformer having a plurality of coils embedded in a ferrite magnetic body can be obtained.

The method of manufacturing a laminated inductor is a method of manufacturing a laminated body in which a coil is embedded by a method substantially similar to the method of manufacturing the laminated ceramic transformer.

When a material having a high magnetic permeability is used for the magnetic body of these magnetic electronic parts, a high inductance can be obtained, but loops of magnetic flux are formed between the conductors of the coil, so-called leakage magnetic flux becomes large, and magnetic characteristics are increased. Is damaged. As a means for solving the problem, the present inventors have already proposed a method for solving the above problem by covering the conductor with a low magnetic permeability material and forming the other portions with a high magnetic permeability material. The method is a method in which a coil conductor pattern is printed using a green sheet of a low magnetic permeability material, a low melting point inorganic paste is further applied to a portion of the surface other than the coil conductor, and the paste is baked. As a result, the low-melting-point inorganic paste can be diffused into the green sheet to locally increase the sinterability and locally increase the magnetic permeability. That is, the periphery of the coil conductor is covered with the low magnetic permeability layer, and the other portions are composed of the high magnetic permeability layer.

[0007]

In the conventional monolithic ceramic transformer described above, when an overcurrent is applied to the primary side coil, the magnetic core is saturated and the exciting current increases. When the exciting current is increased, the magnetic material surrounding the coil is magnetically saturated, the ratio of the output voltage to the input voltage is decreased, the efficiency is deteriorated, the loss is increased, and the transformer temperature rises. Also in the laminated inductor, there has been a problem that the magnetic substance is magnetically saturated when the current flows too much, and the inductance value sharply decreases.

An object of the present invention is to provide a laminated ceramic magnetic component and a method for manufacturing the same which solve the above-mentioned problems by forming a low magnetic permeability layer 8 which blocks the flow of magnetic flux in a magnetic body in which a coil is provided. To do.

[0009]

The gist of the means for solving the problems is, firstly, that a laminated body is mainly constituted in a laminated ceramic magnetic component in which a single or a plurality of coils are embedded in the ceramic laminated body. A laminated ceramic magnetic component in which a layer having a magnetic permeability lower than that of a magnetic body is provided at a position for blocking the flow of magnetic flux in the main laminated magnetic body. Secondly, a single or a plurality of layers are provided in the ceramic laminated body. In the laminated ceramic magnetic component in which the coil is embedded, the periphery of the coil conductor 7 and the space between the coils are covered with the low magnetic permeability layer 8, and at least the other magnetic core portion is constituted by the high magnetic permeability layer 9, the flow of the magnetic flux in the magnetic body Is a laminated ceramic magnetic component in which a low magnetic permeability layer 8 is provided at a position where
Then, the coil conductor 7 is printed on the ceramic green sheet, laminated and pressure-bonded according to a selective order, cut into the dimensions of individual laminated ceramic parts, the laminated body is fired, and external terminals are formed on the peripheral surface of the laminated body. In the method for manufacturing a laminated ceramic magnetic component, the ceramic green sheet is a high-permeability green sheet, and at least one low-permeability green sheet is interposed in the laminated body. It is a manufacturing method of a magnetic component.

[0010]

It is considered that the magnetic flux generated by the coil goes through the axis of the coil, goes out from one end of the coil, and circulates from the other end of the coil back to the axis of the coil. It is also known that the magnetic flux can easily pass through a magnetic material having a high magnetic permeability and can hardly pass through a magnetic material having a low magnetic permeability. The magnetic flux generated by the coil embedded in the ferrite magnetic body is said to pass through the magnetic body and rarely leak to the outside of the magnetic body.

In the ceramic magnetic component of the present invention, the magnetic permeability layer having a magnetic permeability lower than that of the main magnetic substance forming the laminated ceramic magnetic component is located at a position where the flow of magnetic flux in the main magnetic substance is blocked (for example, the axis of the coil magnetic core). It is most effective for the purpose of blocking the flow of the magnetic flux, because most of the magnetic flux generated by the coil is blocked by the low magnetic permeability layer 8 when it is provided at a position where it is divided on a plane orthogonal to . The magnetic flux is not necessarily shielded by the magnetic core, but may be provided around the coil so as to partially block the flow of the magnetic flux. In addition, in the laminated ceramic magnetic component in which the periphery of the coil conductor 7 and the space between the coils are covered with a low magnetic permeability material, and at least the coil axis and other portions are composed of a high magnetic permeability material, the high magnetic permeability material is used. At least in the coil magnetic core, a low-permeability material layer is configured to block the magnetic core to block the magnetic flux passing through the magnetic core. Will increase.

The present invention will be described in detail below with reference to the drawings, but the technical scope of the present invention is not limited to these examples.

[0013]

Example 1 A large number of sheets were prepared by cutting 100 mm square ferrite magnetic green sheets containing Fe ₂ O ₃ , CuO, NiO and ZnO as main components and having two different composition ratios. These sheets are a high permeability sheet having a permeability of 900 when fired and a low permeability sheet having a permeability of 3 when fired. The size of the sheet is such that hundreds to thousands of laminated ceramic magnetic parts can be obtained.

First, the high magnetic permeability sheet is used as it is as the cover sheet 3, and the low magnetic permeability sheet is
A sheet having through holes corresponding to the number of parts to be acquired formed at predetermined positions is prepared.

The low-permeability sheets are laminated to form a through-hole connection between the layers, and a coil conductor pattern forming a spiral coil is printed. The coil conductor pattern is a pattern in which two coils are arranged side by side,
One end of the constructed coil is connected and connected in series.

Separately from this, a low melting point inorganic paste 6 is prepared. The low melting point inorganic paste 6 is ZnO, Bi
A paste containing a low melting point inorganic material such as 2 O3 or CuO as a main component, and a paste containing Zn0 as a main component was used in this embodiment.

When this is applied to a predetermined position of the ferrite magnetic green sheet and fired, the sinterability of the green sheet in that portion is increased, and the magnetic permeability can be partially increased.

When a sheet obtained by printing a coil conductor pattern on the low-permeability sheet is overlapped with another sheet inside the coil conductor 7, a portion corresponding to the inside of the pattern in which the coil conductor 7 circulates is formed on the sheet. Low melting point inorganic paste 6
Is printed to prepare the first sheet 1.

Next, on the low-permeability sheet in which neither the through hole nor the coil conductor pattern is formed, the low melting point inorganic paste 6 is applied to the portion corresponding to the inner side of the coil conductor pattern that circulates.
A second sheet 2 coated with is prepared.

When these sheets are prepared, as shown in FIG. 1, 10 sheets of the cover sheet 3 are superposed, one sheet of the second sheet 2 is superposed thereon, and the second sheet 2 is superposed thereon to form a coil. Seven sheets of the first sheet 1 to be formed are piled up in a selective order to form a secondary coil, and then one sheet of the second sheet 2 is piled up. The through hole, the coil conductor 7 and the inorganic paste are not printed, and the low transparency is obtained. Four sheets of magnetic susceptibility 4 are piled up, then one sheet of the second sheet 2 is piled up, and the first sheet is placed thereon.
7 sheets 1 of above are piled up in a selective order to form a primary coil, then one second sheet 2 is piled up, 10 dummy sheets 5 are piled up, and the whole is crimped to form a crimped body. Configured. The pressure-bonded body was cut to the size of the part and fired.

A conductive paste for an external electrode was applied to the side surface of the fired laminate and baked to form the external electrode 10 connected to the coil conductor terminal.

The dimensions of the laminate are 15 mm × 10 mm × 3
The width of the coil conductor 7 embedded in the laminate is 1 mm, and the thickness of the low magnetic permeability layer 8 interposed in the coil axis is 0.15 mm.

Such a monolithic ceramic transformer (see FIG. 2)
Ab terminal) of the primary coil,
The result of measurement by the DC superposition characteristic measurement circuit shown in FIG. 7 is shown in FIG. 10 as the relationship between the current value and the inductance value (L). In the figure, when the direct current is gradually increased from 10 mA, the L value does not change up to a certain current value, but when the current value further increases, the L value starts to decrease. L
The allowable current value was 350 mA when the current value was 5% lower than the initial value, and the value is shown in Table 1. The magnetic saturation state can be known by operating the power supply as a transformer and observing the current waveform of the transistor using the circuit of FIG. The input current when magnetic saturation occurs is shown in Table 1 as the maximum input current value when the transformer is used as a power supply.

[0024]

[Table 1]

[0025]

Second Embodiment In the first embodiment, the thickness of the low magnetic permeability layer 8 interposed in the coil axis is 0.35 instead of 0.15 mm.
The results obtained in the same manner as in Example 1 except that the thickness was 0 mm are shown in FIG. 11 and Table 1.

[0026]

[Third Embodiment] In the first embodiment, the coil conductor pattern is replaced with a pattern in which two coils are arranged side by side in a pair, and one coil conductor pattern is formed, and the two coils are vertically independent with their axes aligned. Table 1 shows the results obtained in the same manner as in Example 1 except that the inductor was placed in 1.

[0027]

Example 4 A large number of sheets were prepared by cutting 100 mm square ferrite magnetic green sheets containing Fe ₂ O ₃ , CuO, NiO and ZnO as main components and having two different composition ratios. This sheet is a high magnetic permeability sheet having a magnetic permeability of 900 when fired and a low magnetic permeability sheet having a magnetic permeability of 3 when fired. The size of the sheet is such that hundreds to thousands of laminated ceramic magnetic parts can be obtained.

As the high magnetic permeability sheet, a sheet used as the cover sheet 3 as it is and a sheet having through holes formed at predetermined positions according to the number of parts to be obtained are prepared, and the low magnetic permeability sheet 4 is prepared. Also, a sheet having through holes formed at predetermined positions according to the number of parts to be acquired was prepared.
The sheet having the through holes is printed with a coil conductor pattern forming a coil by stacking layers through the through holes to form a coil. The high magnetic permeability sheet is the first sheet 1 and the low magnetic permeability sheet is the second sheet. Sheet 2 was used. When these sheets are prepared, several sheets of the cover sheet 3 are stacked, and the first sheet 1 is placed on the cover sheet 3 in a selective order.
12 sheets were stacked, two second sheets 2 were stacked thereon, 12 sheets of the first sheet 1 were stacked thereon, and several cover sheets 3 were stacked thereon, and pressure bonding was performed.

This pressure-bonded body was cut to the size of the component and fired. The external electrode conductor paste was applied to the side surface of the fired laminate and baked to form the external electrode 10 connected to the coil conductor end. FIG. 6 shows a sectional view thereof.

The size of the laminate is 15 mm × 10 mm × 3
mm, and the low-permeability layer 8 is interposed at a position perpendicular to the coil axis and divided into two.

Table 2 and FIG. 13 show the results of measuring the DC superposition characteristics of such a monolithic ceramic inductor (FIG. 5) with the DC superposition characteristics measuring circuit shown in FIG.

[0032]

[Table 2]

[0033]

COMPARATIVE EXAMPLE 1 In Example 1, the low magnetic permeability sheet interposed between the primary coil and the secondary coil was removed, and in order to match the inductance value with Example 1, 1
Table 1 and FIG. 9 show the results of the same operation as in Example 1 except that the number of sheets forming each of the secondary coil and the secondary coil was five.

[0034]

[Comparative Example 2] In Example 4, except that the low-permeability layer 8 interposed in the middle of the coil was removed and the number of sheets forming the coil was reduced to match the inductance value with Example 4, The results obtained in the same manner as in Example 4 are shown in Table 2 and FIG.

In the above embodiment, the low magnetic permeability layer 8 is formed between the primary side coil and the secondary side coil of the transformer in the portion corresponding to the coil magnetic core. Is not limited to this, but may be outside the coil even if it does not exist in the coil magnetic core, for example. The low-permeability layer 8 only needs to be located at a position where the flow of magnetic flux is cut off. Therefore, it is most effective to form the low-permeability layer 8 on the magnetic core. Further, if the thickness of the low magnetic permeability layer 8 changes, the effect will naturally change. Furthermore, even if only one low-permeability sheet is interposed between the high-permeability sheets on which the coil conductors 7 are printed, there is an effect of shielding the magnetic flux.

[0036]

According to the present invention, the allowable current value of the laminated ceramic magnetic component can be easily increased and the saturation magnetic field strength can be increased without changing the coil conductor pattern and improving the characteristics of the magnetic material. Therefore, it is easy to change the design of the laminated ceramic magnetic component. The above-mentioned problems relating to the monolithic ceramic magnetic component, that is, in the monolithic ceramic transformer, when an overcurrent is applied to the primary side coil, the magnetic core is saturated and the exciting current increases, and the magnetic body surrounding the coil is magnetically saturated, The ratio of output power to input power is small, efficiency is poor, loss is large, and transformer temperature rises.In a laminated inductor, too much current flows and the magnetic substance is magnetically saturated, causing There is an effect that the present invention solves the problem that the value sharply decreases.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a laminated body constituting a laminated ceramic magnetic component of the present invention.

FIG. 2 is an external perspective view of a monolithic ceramic magnetic component of the present invention.

FIG. 3 is a partially cutaway perspective view of the laminated ceramic magnetic component of the present invention.

FIG. 4 is a sectional view of an example of a laminated transformer of the laminated ceramic magnetic component of the present invention.

FIG. 5 is a sectional view of a laminated coil of the laminated ceramic magnetic component of the present invention.

FIG. 6 is a sectional view of a laminated inductor of the laminated ceramic magnetic component of the present invention.

FIG. 7 is a circuit block diagram for measuring the DC superposition characteristics of the monolithic ceramic magnetic component of the present invention.

FIG. 8 is a power supply circuit diagram when the laminated ceramic magnetic component of the present invention is used as a power supply.

FIG. 9 shows the DC superposition characteristics of the laminated ceramic magnetic component of Comparative Example 1. The inductance value with respect to the applied DC current is shown, and the DC current value when the inductance is reduced by 5% is shown.

FIG. 10 shows the DC superposition characteristics of the laminated ceramic magnetic component of Example 1 of the present invention. The inductance value with respect to the applied DC current is shown, and the DC current value when the inductance is reduced by 5% is shown.

FIG. 11 shows the DC superposition characteristics of the laminated ceramic magnetic component of Example 2 of the present invention. The inductance value with respect to the applied DC current is shown, and the DC current value when the inductance is reduced by 5% is shown.

FIG. 12 shows the DC superposition characteristics of the laminated ceramic magnetic component of Comparative Example 2. The inductance value with respect to the applied DC current is shown, and the DC current value when the inductance is reduced by 5% is shown.

FIG. 13 shows the DC superposition characteristics of the laminated ceramic magnetic component of Example 4 of the present invention. The inductance value with respect to the applied DC current is shown, and the DC current value when the inductance is reduced by 5% is shown.

[Explanation of symbols]

 1 1st sheet 2 2nd sheet 3 Cover sheet 4 Low magnetic permeability sheet 5 Dummy sheet 6 Low melting point inorganic paste 7 Coil conductor 8 Low magnetic permeability layer 9 High magnetic permeability layer 10 External electrode

Claims (3)

[Claims] 1. A laminated ceramic magnetic component in which a single or a plurality of coils are embedded in a ceramic laminated body, wherein a layer having a magnetic permeability lower than that of a main magnetic body forming the laminated body is the main laminated body. A multilayer ceramic magnetic component, wherein at least a low-permeability layer is provided at a position where the flow of magnetic flux is blocked in the magnetic body. 2. A laminated body in which a single or a plurality of coils are embedded in a ceramic laminated body, the periphery of the coil conductor and the space between the coils are covered with a low magnetic permeability layer, and at least other magnetic core portions are constituted by a high magnetic permeability layer. Ceramic magnetic parts,
A laminated ceramic magnetic component in which at least a low magnetic permeability layer is provided at a position where the flow of magnetic flux in the magnetic body is blocked. 3. A ceramic green sheet on which a coil conductor is printed is laminated and pressure-bonded in a selective order, and then the pressure-bonded body is cut into individual multilayer ceramic component dimensions and fired, and the periphery of the fired laminate is cut. In the method of manufacturing a laminated ceramic magnetic component, wherein external terminals are formed on the ceramic green sheet, the ceramic green sheet is a green sheet for high magnetic permeability, and at least one green sheet for low magnetic permeability is interposed in these laminated bodies. And a method for manufacturing a laminated ceramic magnetic component.