Electronic component

A laminated body is formed by stacking insulating layers to be formed into a rectangular parallelepiped shape. A linear conductor is stacked together with the insulating layers and connects end surfaces of the laminated body that are opposed to each other with respect to a first direction. Lengths of the end surfaces of the laminated body in a second direction, which is perpendicular to the stacking direction and the first direction, are equal to or smaller than the lengths of the end surfaces in the stacking direction.

TECHNICAL FIELD

The technical field relates to an electronic component, and more particularly to an electronic component incorporating a coil.

BACKGROUND

As a conventional electronic component, for example, a multilayer inductance element disclosed by Japanese Patent No. 4,307,822 is known.FIG. 8is an exploded perspective view of a laminated body502of the multilayer inductance element500.FIG. 9is a sectional view of the multilayer inductance element500.

The multilayer inductance element500comprises a laminated body502, a conductor pattern504and external electrodes (not shown). The laminated body502is formed by stacking a plurality of ferrite sheets506and a non-magnetic ceramic layer507, and is formed into a rectangular parallelepiped shape. In the following paragraphs, surfaces of the laminated body502that are located at both ends with respect to the lengthwise direction of the laminated body502when viewed from the stacking direction are referred to as end surfaces, and surfaces of the laminated body502that are located at both ends with respect to the widthwise direction of the laminated body502when viewed from the stacking direction are referred to as side surfaces. A surface of the laminated body502that is located at the top in the stacking direction is referred to as a top surface, and a surface of the laminated body502that is located at the bottom in the stacking direction is referred to as a bottom surface.

The conductor pattern504is provided in the laminated body502and extends linearly to connect the end surfaces of the laminated body502. The conductor pattern504forms a coil. The two external electrodes (not shown) are covered respectively on the both end surfaces and are physically connected respectively to the both ends of the conductor pattern504.

FIG. 9is a sectional view of the thus structured laminated inductance element500, taken perpendicularly to the extending direction of the conductor pattern504. Specifically, the non-magnetic ceramic layer507is arranged on both sides of the conductor pattern504. Magnetic fluxes are difficult to pass through the non-magnetic ceramic layer507and therefore leak out through the side surfaces of the laminated body502. Thereby, magnetic saturation in the laminated body502due to heavy concentration of magnetic fluxes can be prevented.

SUMMARY

The present disclosure provides an electronic component that can achieve a desired DC-superposing characteristic.

An embodiment of an electronic component according to the present disclosure includes a laminated body that is formed by stacking first insulating layers to be formed into a rectangular parallelepiped shape and a linear conductor that is stacked together with the first insulating layers and that connects two end surfaces of the laminated body that are opposed to each other with respect to a first direction, which is perpendicular to a stacking direction of the first insulating layers. Lengths of the end surfaces in a second direction, which is perpendicular to the stacking direction and the first direction, is equal to or smaller than lengths of the end surfaces in the stacking direction.

DETAILED DESCRIPTION

The inventor realized that with the multilayer inductance element500disclosed by Japanese Patent No. 4,307,822, it is difficult to achieve a desired DC-superposing characteristic. More specifically, the section of the laminated body502shown byFIG. 9is a horizontal rectangle, and the distances between the conductor pattern504and the respective side surfaces are relatively long. Therefore, magnetic fluxes flowing around the conductor pattern504are difficult to leak out through the side surfaces of the laminated body502. In the multilayer inductance element500disclosed by Japanese Patent No. 4,307,822, therefore, magnetic saturation in the laminated body502may occur due to heavy concentration of magnetic fluxes. When magnetic saturation occurs, the inductance value of the multilayer inductance element500is lowered. Thus, the multilayer inductance element500is difficult to achieve a desired DC-superposing characteristic.

An electronic component according to an exemplary embodiment that can address the above drawbacks is hereinafter described.

Structure of the Electronic Component: the structure of an electronic component according to an embodiment is described with reference to the accompanying drawings.FIG. 1is a perspective view of an electronic component10aaccording to an embodiment.FIG. 2is an exploded perspective view of a laminated body12of the electronic component10a.FIG. 3is a sectional view of the electronic component10a, taken along the line A-A. The stacking direction, in which layers are stacked, of the laminated body12is defined as a y-axis direction. When the laminated body12is viewed from the y-axis direction, the direction in which longer sides of the laminated body12extend is defined as an x-axis direction, and the direction in which shorter sides of the laminated body12extend is defined as a z-axis direction. The x-axis direction, the y-axis direction and the z-axis direction are perpendicular to each other.

The electronic component10acomprises a laminated body12, external electrodes14(14aand14b) and a conductor16.

The laminated body12is in the shape of a rectangular parallelepiped, and has side surfaces S1, S2, end surfaces S3, S4, a top surface S5and a bottom surface S6. The side surfaces S1and S2are surfaces of the laminated body12that are located at a positive side and a negative side, respectively, in the z-axis direction. The end surfaces S3and S4are surfaces of the laminated body12that are located at a negative side and a positive side, respectively, in the x-axis direction. The top surface S5is a surface of the laminated body12that is located at a positive side in the y-axis direction. The bottom surfaces S6is a surface of the laminated body12that is located at a negative side in the y-direction.

As shown byFIG. 2, the laminated body12is formed by stacking magnetic layers18ato18f, a non-magnetic layer20and magnetic layers18gto18lin this order from the positive side to the negative side in the y-axis direction. The magnetic layers18are rectangular layers of a magnetic material. The magnetic material means a material that functions as a magnetic material within a temperature range from −55 degrees C. to +125 degrees C., for example. The non-magnetic layer20is a rectangular layer of a non-magnetic material having a lower magnetic permeability than the magnetic layers18(18ato18l). The non-magnetic material means a material that functions as a non-magnetic material within the temperature range from −55 degrees C. to +125 degrees C., for example. In the following paragraphs, with regard to each of the magnetic layers18and the non-magnetic layer20, the surface at the positive side in the y-axis direction is referred to as a front side, and the surface at the negative side in the y-axis direction is referred to as a back side.

With regard to the end surfaces S3and S4of the laminated body12, as shown inFIG. 1, the length L2in the z-axis direction is equal to or shorter than the length L1in the y-axis direction.

The conductor16is stacked together with the magnetic layers18and the non-magnetic layer20, and thereby, the conductor16is embedded in the laminated body12. The conductor16is typically a straight linear conductor having an inductance component. The conductor16connects the end surfaces S3and S4, which are opposed to each other with respect to the x-axis direction, and the conductor16is exemplarily provided on the front side of the non-magnetic layer20. The conductor16extends in the x-axis direction, and is formed by applying conductive paste of an Ag-based or Cu-based material on the front side of the non-magnetic layer20.

As shown inFIG. 3, the conductor16is preferably located substantially in the center of the laminated body12with respect to the z-axis direction. In other words, the distance D1between the conductor16and the side surface S1and the distance D2between the conductor16and the side surface S2are substantially equal to each other.

Also, as shown inFIG. 2, the conductor16is exemplarily located substantially in the center of the laminated body12with respect to the y-axis direction. In other words, the distance D3between the conductor16and the top surface S5and the distance D4between the conductor16and the bottom surface S6are substantially equal to each other.

The external electrode14ais provided to cover the end surface S3of the laminated body12, and the external electrode14ais folded back to the side surfaces S1, S2, the top surface S5and the bottom surface S6. Thereby, the external electrode14ais physically connected to the end of the conductor16at the negative side in the x-axis direction. The external electrode14ais formed, for example, by applying conductive paste on the end surface S3, thereby forming a silver electrode, and by sequential plating Sn and Ni on the silver electrode.

The external electrode14bis provided to cover the end surface S4of the laminated body12, and the external electrode14bis folded back to the side surfaces S1, S2, the top surface S5and the bottom surface S6. Thereby, the external electrode14bis physically connected to the end of the conductor16at the positive side in the x-axis direction. The external electrode14bis formed, for example, by applying conductive paste on the end surface S4, thereby forming a silver electrode, and by sequential plating Sn and Ni on the silver electrode.

The thus structured electronic component10ais used while mounted on a circuit board. When the electronic component10ais mounted on a circuit board, the side surface S2serves as a mounting surface to be opposed to the circuit board.

Manufacturing Method of the Electronic Component: an exemplary method for manufacturing the electronic component10aaccording to the embodiment is described with reference to the accompanying drawings.

First, ceramic green sheets, which are to be used as the magnetic layers18, are prepared. Specifically, as raw materials, diiron trioxide (Fe2O3), zinc oxide (ZnO), nickel oxide (NiO) and cupper oxide (CuO) are put into a ball mill at a predetermined ratio and are wet-blended. The thus obtained mixture is dried and then crushed, whereby powder is obtained, and the powder is calcined at approximately 800 degrees C. for approximately one hour. The calcined powder is wet-milled in a ball mill, dried and cracked, whereby ferrite ceramic powder is obtained.

A binder, such as vinyl acetate or water-soluble acrylic, a plasticizer, a wet material and a dispersant are added to the ferrite ceramic powder and mixed together in a ball mill. Thereafter, the mixture is defoamed by decompression. The thus obtained ceramic slurry is spread on a carrier sheet by a doctor blade method and is dried, whereby a ceramic green sheet is obtained. The thickness of the ceramic green sheet is 20 μm to 25 μm.

Next, a ceramic green sheet, which is to be used as the non-magnetic layer20, is prepared. Specifically, as raw materials, diiron trioxide (Fe2O3), zinc oxide (ZnO) and cupper oxide (CuO) are put into a ball mill at a predetermined ratio and is wet-blended. The thus obtained mixture is dried and then crushed, whereby powder is obtained, and the powder is calcined at approximately 800 degrees C. for about one hour. The calcined powder is wet-milled in a ball mill, dried and cracked, whereby ferrite ceramic powder is obtained.

A binder, such as vinyl acetate or water-soluble acrylic, a plasticizer, a wet material and a dispersant are added to the ferrite ceramic powder and mixed together in a ball mill. Thereafter, the mixture is defoamed by decompression. The thus obtained ceramic slurry is spread on a carrier sheet by a doctor blade method and is dried, whereby a ceramic green sheet is obtained. The thickness of the ceramic green sheet is 20 μm to 25 μm.

On the front side of the ceramic green sheet, which is to be used as the non-magnetic layer20, paste of a conductive material is applied by screen printing, photolithography or the like, whereby the conductor16is formed. The conductive paste is prepared, for example, by adding varnish and a solvent to Ag.

Next, as shown byFIG. 2, the ceramic green sheets to be used as the magnetic layers18ato18f, the ceramic green sheet to be used as the non-magnetic layer20, and the ceramic green sheets to be used as the magnetic layers18gto18lare stacked in this order from the positive side with respect to the y-axis direction, and are provisionally pressure-bonded together. Thereby, a non-fired mother laminate is obtained. The non-fired mother laminate is permanently press-bonded by isostatic press. The isostatic press is carried out under a pressure of approximately 100 MPa and under a temperature of approximately 45 degrees C.

Next, the mother laminate is cut into pieces, whereby individual non-fired laminated bodies12are obtained. The non-fired laminated bodies12are subjected to a binder-removal treatment and to firing process. The binder-removal treatment is carried out, for example, in a hypoxic atmosphere at a temperature of approximately 850 degrees C. for about two hours. The firing process is carried out, for example, at a temperature within a range from 900 degrees C. to 930 degrees C. for about two hours and a half. Thereafter, the laminated bodies12are subjected to barrel polishing and chamfering.

Next, electrode paste of an Ag-based conductive material is applied on the end surfaces S3and S4of each of the laminated bodies12. The electrode paste applied on the end surfaces S3and S4is baked at a temperature of approximately 800 degrees C. for one hour. Thereby, silver electrodes, which will turn into the external electrodes14, are formed. Further, the silver electrodes are plated with Ni and Sn, in this order, whereby the external electrodes14are formed. Through the processes above, the electronic component10ais completed.

Advantageous Effects: the electronic component10aof the above-described structure can achieve a desired DC-superposing characteristic. In the multilayer inductance element500disclosed by Japanese Patent No. 4,307,822, as shown byFIG. 9, a section of the laminated body502is a horizontal rectangle. Therefore, the distances between the conductor pattern504and the respective side surfaces of the laminated body502are relatively long. Accordingly, magnetic fluxes flowing around the conductor pattern504do not leak out from the laminated body502through the side surfaces easily. Therefore, in the multilayer inductance element500disclosed by Japanese Patent No. 4,307,822, magnetic saturation may occur due to heavy concentration of magnetic fluxes in the laminated body502. An occurrence of magnetic saturation in the laminated body502brings about a sharp drop in the inductance value. Thus, it is difficult to achieve a desired DC-superposing characteristic with the multilayer inductance element500.

In the electronic component10a, on the other hand, the conductor16is stacked together with the magnetic layers18and the non-magnetic layer20, and thereby, the conductor16is embedded in the laminated body12. The length L2of the end surfaces S3and S4in the z-axis direction is shorter than the length L1of the end surfaces S3and S4in the y-axis direction. Accordingly, when the electronic component10aand the multilayer inductance element500that are of the same size are compared with each other, the distances D1and D2between the conductor16and the respective side surfaces S1and S2in the electronic component10aare smaller than the distances between the conductor pattern504and the respective side surfaces of the laminated body502in the multilayer inductance element500. Also, the distances D1and D2in the electronic component10aare smaller than the distance between the conductive pattern504and the top surface of the laminated body502and the distance between the conductive pattern504and the bottom surface of the laminated body502in the multilayer inductance element500. Therefore, the number of magnetic fluxes leaking through the side surfaces S1and S2of the electronic component10ais greater than the number of magnetic fluxes leaking through the top surface, the bottom surface and the side surfaces of the multilayer inductance element500. Accordingly, in the electronic component10a, magnetic saturation is prevented, and a desired DC-superposing characteristic can be obtained.

The electronic component10ahas a desired DC-superposing characteristic also for the following reasons. In the electronic component10a, the non-magnetic layer20traverses the laminated body12in the z-direction, and the conductor16is provide on the front side of the non-magnetic layer20. Further, the length L1of the side surfaces S3and S4in the y-axis direction is greater than the length L2of the side surfaces S3and S4in the z-axis direction. Accordingly, the distances D1and D2between the conductor16and the respective side surfaces S1and S2are small. Therefore, many of the magnetic fluxes flowing around the conductor16leak out through the side surfaces S1and S2when passing through the non-magnetic layer20. Consequently, in the electronic component10a, magnetic saturation is prevented, and a desired DC-superposing characteristic can be achieved.

When the electronic component10ais mounted on a circuit board, the side surface S2serves as a mounting surface to be opposed to the circuit board. Accordingly, the main surfaces of the conductor16are not opposed to the circuit board, and the area where the conductor16is opposed to the wiring of the circuit board is small. Consequently, floating capacitance between the electronic component10aand the circuit board can be suppressed.

Simulation: in order to prove the effects of the electronic component10a, the inventors conducted a computer simulation as follows.FIG. 4is a perspective view of an electronic component110of a comparative example. The parts of the electronic component110that are the same as those of the electronic component10aare provided with reference marks obtained by adding 100 to the reference marks of the corresponding parts of the electronic component10a.

The inventors fabricated a model of the electronic component10ashown byFIG. 1as a first model and a model of the electronic component110shown byFIG. 4as a second model. The inductance values of each model when electric currents of 1 mA, 500 mA, 1000 mA, 3000 mA and 5000 mA were applied thereto were calculated. Further, the reduction rates in the inductance value when electric currents of 500 mA, 1000 mA, 3000 mA and 5000 mA were applied, compared with the inductance value when an electric current of 1 mA was applied, were calculated. Table 1 shows the simulation results.

As shown by Table 1, the reduction rates in the inductance value of the first model while the current applied thereto was increasing were smaller than the reduction rates in the inductance value of the second model. Thus, the simulation results show that the electronic component10ahas a desired DC-superposing characteristic.

First Modification Example

in the following, an electronic component according to a first modification is described with reference to the accompanying drawings.FIG. 5is a sectional view of the electronic component10baccording to the first modification.

The electronic component10bis of the same structure as the electronic component10a. The electronic component10bis different from the electronic component10ain the mounting surface. More specifically, when the electronic component10bis mounted on a circuit board, the bottom surface S6of the electronic component10bserves as the mounting surface to be opposed to the circuit board.

The electronic component10b, like the electronic component10a, has a desired DC-superposing characteristic.

Second Modification Example

in the following, an electronic component according to a second modification is described with reference to the accompanying drawings.FIG. 6is a sectional view of the electronic component10caccording to the second modification.

The electronic component10cis different from the electronic component10ain the position of the conductor16. Specifically, in the electronic component10a, the conductor16is provided on the front side of the non-magnetic layer20. In the electronic component10c, however, the conductor16is embedded in the non-magnetic layer20. That is, the non-magnetic layer20exists at the positive side and at the negative side of the conductor16with respect to the z-axis direction. The non-magnetic layer20exists at neither side of the conductor16in the y-axis direction, and the magnetic layers18exist at both sides of the conductor16in the y-axis direction.

When the electronic component10cis mounted on a circuit board, the side surface S2of the electronic component10cserves as a mounting surface to be opposed to the circuit board.

The electronic component10c, like the electronic component10a, has a desired DC-superposing characteristic.

Third Modification Example

in the following, an electronic component according to a third modification is described with reference to the accompanying drawings.FIG. 7is a sectional view of the electronic component10daccording to the third modification.

The electronic component10dis of the same structure as the electronic component10c. The electronic component10dis different from the electronic component10cin the mounting surface. More specifically, when the electronic component10dis mounted on a circuit board, the bottom surface S6of the electronic component10dserves as the mounting surface to be opposed to the circuit board.

The electronic component10d, like the electronic component10a, has a desired DC-superposing characteristic.

Although the present disclosure describes an exemplary embodiment and exemplary modifications thereof, it is to be noted that various changes and modifications can be made. Such changes and modifications are to be understood as being within the scope of the disclosure.