JPH07288210A - Surface mount inductor - Google Patents

Abstract

PURPOSE:To provide a surface mount inductor available for the use of the d-c superimposing or other various uses by forming a columnar magnetic piece separate from a ferrite core surrounding an annular coil into which this piece is inserted and set. CONSTITUTION:An outer core structure 1 composed of a first ferrite core 10 having a coil fitting recess and electrodes 14 formed on its outside and second ferrite core 20 having a coil fitting recess 21 and annular coil 2 has wound wires settled by an adhesive material like an annular shape and having lead parts 31 and 32 at the winding start and end and is fitted in the recesses 11 and 21 of the core structure 1. A columnar magnetic piece 3 is separate from the first and second ferrite cores 10 and 20 and inserted in a central opening of the coil 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-mounting inductor having a low-height structure having a surface-mountable electrode on a printed circuit board and suitable for applications such as DC superposition.

[0002]

2. Description of the Related Art Surface-mounted components are becoming smaller and smaller as electronic equipment products are becoming smaller and thinner, and the requirements are not limited to simply reducing the size of conventional products (simply reducing the size) to include production costs. It is becoming difficult to respond.

In particular, noise filter parts for superimposing DC current, smoothing chokes for switching power supplies, non-insulating O
N control type converter (forward converter) and O
FF control type converters (flyback converters) such as chokes and the like that have been downsized and surface-mounted (SMD) have not been commercialized. The reason is as follows.

(1) In noise filter parts, chokes for switching power supplies, etc., in order to secure the necessary current capacity, the wire diameter of the wire material that composes the wire loop increases, but its ends are surface-mounted terminals (SMD terminals). ), There was a dislike that the reliability of the splice wire in brazing or welding was not sufficient.

(2) If the shape is made small, the magnetic core becomes small, the magnetic path length becomes short, and when a direct current is superposed on the coil, the core is saturated with a slight current. In addition, even if an air gap is formed in the magnetic core to prevent magnetic saturation, the inductance cannot be taken and the coil cannot function sufficiently.

As a conventionally proposed small-sized inductor, a coil is arranged in a pair of pot-type cores, and a loop-out end portion of the coil is entwined with a entangled portion formed in a part of the core. There is (Saikaihei 5-6814). However, it still includes the problems of (1) and (2) above.

[0007]

As described above, in the case of a small and thin surface mounting inductor used for superimposing a DC current, it is necessary to solve the problem of magnetic saturation of the magnetic core. It is not possible to use a conventional pot-type core (in which the outer peripheral portion and the central columnar portion are integrally connected by a flat plate portion).

In view of the above points, the present invention makes the columnar magnetic body to be inserted and arranged in the center hole of the annular coil separate from the ferrite core surrounding the outside of the annular coil, so that the direct current superposition is achieved. It is an object of the present invention to provide a surface-mount inductor that can be used for various applications and other various applications.

[0009]

In order to achieve the above object, a surface mounting inductor according to the present invention comprises a first ferrite core having a recess for accommodating a wire ring and an electrode formed on at least a side surface thereof. An outer shell core structure composed of a second ferrite core adhered to the first ferrite core so as to close the recess for accommodating the wire wheel, and the wound wire rod is fixed in an annular shape by an adhesive substance, An annular coil having lead portions at least at the beginning and at the end of winding and arranged in a coil-housing recess in the outer shell core structure;
And a columnar magnetic body that is separate from the second ferrite core and that is inserted into the center hole of the annular coil. The lead portions are connected to the electrodes, respectively.

Here, the wire may be a metal foil whose surface is subjected to an insulation treatment.

Further, a plurality of the annular wire rings may be arranged in the wire ring housing recess in the outer shell core structure.

The first ferrite core is a high resistance ferrite, a lead portion leading groove portion is formed on the abutting surface of the first ferrite, and an extension portion of the electrode is formed on the bottom surface of the lead portion leading groove portion. In addition, the lead portion may be welded to the extended portion.

[0013]

In the surface mounting inductor of the present invention, the columnar magnetic body separate from the first and second ferrite cores surrounding the annular wire ring is inserted and arranged in the center hole of the annular wire ring. The magnetic characteristics of the columnar magnetic body can be appropriately set according to the application. For example, in a case where a direct current is superimposed on the annular wire, magnetic saturation can be prevented by using a magnetic material having a high saturation magnetic flux density (for example, sendust) as the columnar magnetic body. In addition, the columnar magnetic body and the first
Further, since a minute air gap (magnetic gap) is generated between the second ferrite core and the second ferrite core, this minute air gap can also contribute to prevention of magnetic saturation.

Further, if inductance is required,
A magnetic material having a high magnetic permeability (higher magnetic permeability than the second ferrite core) may be selected as the columnar magnetic body.

Further, in the outer shell core structure composed of the first and second ferrite cores, magnetic saturation can be prevented by appropriately selecting the magnetic characteristics of the columnar magnetic body without providing a gap, and the leakage inductance is small. A transformer with a magnetic shield structure that almost completely surrounds the annular wire ring,
An inductor or the like can be obtained.

When a metal foil whose surface is insulated is used as the wire material of the annular coil, the space factor of the conductor can be increased as compared with a wire having an ordinary round cross section, and the current capacity and heat generation can be reduced. Can be planned.

Further, when a plurality of the annular wire rings are arranged in the wire ring accommodating recess in the outer shell core structure, a transformer (common transformer), a common mode choke coil, etc. can be constructed, and a mating surface between the wire rings is formed. The generated distributed capacitance forms an LC distributed constant circuit, which has the advantage of increasing the effect of removing noise. Furthermore, the inductance can be increased by connecting a plurality of ring-shaped loops in series, and conversely, by connecting a plurality of ring-shaped loops in parallel, the current capacity can be increased and the eddy current loss can be reduced, resulting in a high-frequency coil. Can handle.

The first ferrite core is made of high-resistance ferrite, a lead portion lead-out groove portion is formed on an abutting surface of the first ferrite core, and an extension portion of the electrode is formed on a bottom surface of the lead portion lead-out groove portion. In addition, when the lead portion of the annular wire is welded to the extended portion,
The lead portion can be reliably pulled out, and furthermore, the connection between the electrode and the lead portion can be reliably performed by soldering or the like. Further, it is possible to prevent a gap from being generated between the first and second ferrite cores due to the thickness of the lead portion.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a surface mounting inductor according to the present invention will be described below with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS. In these figures, 1 is an outer shell core structure, 2 is an annular wire ring, and 3 is a columnar magnetic body.

The outer shell core structure 1 has a rectangular plate-like outer shape, and has a recess 11 for accommodating the wire ring formed on the abutting surface 12 of Ni-Z.
Similarly to the first ferrite core 10 of n-type high resistance ferrite (insulating ferrite), it has a rectangular plate shape and the recess 2 for accommodating the wire ring.
1 and the second ferrite core 20 of the same material formed on the abutting surface 22 are made to face each other with the coil housing accommodating recesses 11 and 21 and abutted to be integrated. The wire ring receiving recesses 11 and 21 are cylindrical recesses having a small depth. As shown in FIGS. 1 and 5, on the abutting surface 12 of the first ferrite core 10, lead lead-out grooves 13 extending from the coil housing recess 11 to the side surface are formed at a plurality of intervals. A plurality of electrodes 14 as surface-mounting terminals (the same number as the lead portion leading groove portion 13) are formed on both side surfaces of the first ferrite core 10, and each electrode 1 is formed as shown in FIG.
Reference numeral 4 extends to a part of the bottom surface of the first ferrite core 10 and the bottom surface of the lead portion lead-out groove portion 13. The electrodes 14 are directly formed on the first ferrite core 10 by printing, for example, a silver paste, baking, and then solder plating.

The annular wire ring 2 uses a strip-shaped copper foil 30 having an insulating coating as a wire material, and the surface of the insulating coating is further coated with an adhesive resin.
The annular wire ring 2 is formed by winding the strip-shaped copper foil 30 into a roll so that the wide surface of the strip-shaped copper foil 30 becomes the inner and outer peripheral surfaces.
It is obtained by fusing a coating of an adhesive resin on the surface of the insulating coating of the strip-shaped copper foil 30 and fixing it in an annular shape. A lead portion 31 at the beginning of winding and a lead portion 32 at the end of winding are drawn out from the annular wire ring 2. The lead portions 31 and 32 are bent and drawn so that the wide surface thereof is parallel to the bottom surface of the lead portion lead-out groove portion 13. It should be noted that the wire ring housing recess 1 in the outer shell core structure 1
In the case where one annular wire ring 2 is provided in each of 1 and 12, the width of the strip-shaped copper foil 30 may be set to a size slightly narrower than the sum of the depths of the recesses 11 and 12 for housing the ring.

The columnar magnetic body 3 is, for example, a metal dust core of sendust or the like, and has a diameter slightly smaller than the central hole 33 of the annular wire ring 2 and has the sum of the depths of the wire ring recesses 11 and 12. They have matching heights.

The assembly of the surface mount inductor is carried out, for example, by winding the strip-shaped copper foil 30 in a roll shape and preliminarily fixing it in an annular shape in the coil housing recess 11 of the first ferrite core 10 as shown in FIG. The annular wire ring 2 is arranged and its lead portion 31,
Electrode 1 in which 32 is extended to the bottom of the lead-out groove 13
Weld to 4 (solder) respectively. afterwards,,
The cylindrical magnetic body 3 is inserted and arranged in the center hole 33 of the annular wire ring 2. Then, the second ferrite core 20 is abutted on the first ferrite core 10, and the outer shell core structure 1 is configured by fixing and integrating the second ferrite core 20 with each other by using an adhesive as shown in FIGS. 2 to 4. Such a completed surface mount inductor is obtained.

FIG. 7 shows the relationship between the direct current flowing through the annular wire ring 2 of the surface-mounting inductor and the inductance. The curve P indicates the first and second end surfaces of the cylindrical magnetic body 3 in the first embodiment of the present invention. In the case where the air gap is made extremely small by finely matching with the second ferrite cores 10 and 20 (for example, both end faces of the cylindrical magnetic body 3 are polished), the curve Q is the first embodiment of the present invention. At both end surfaces of the cylindrical magnetic body 3 and the first and second ferrite cores 10, 2
In the case where the air gap is made slightly larger by making a bad match with 0 (for example, when both end faces of the cylindrical magnetic body 3 are not polished), the curve R uses a general ferrite pot type core integrally formed with a cylindrical portion. This is the case. However, the band-shaped copper foil 30 of the annular wire ring 2 has a thickness of 0.06 mm and a width of 1.2 mm.
The number of turns is 10, and the cylindrical magnetic body 3 is made of sendust and has a relative magnetic permeability of 57. The first and second ferrite cores 10 and 20 have a relative magnetic permeability of 600 and a length of 5 m.
It has a square plate-like outer shape with m, width 5 mm, and height 1 mm. From FIG. 7, when a general ferrite pot type core is used, the inductance decreases sharply due to magnetic saturation when the direct current is about 0.7 A, but as the cylindrical magnetic body 3, the sendust having a high saturation magnetic flux density is obtained. Curves P and Q using
At this time, the decrease in inductance with the increase in DC current is gradual. Incidentally, in the case of the curve Q in which the air gaps are slightly increased by making the both end surfaces of the cylindrical magnetic body 3 and the first and second ferrite cores 10 and 20 poorly fitted to each other,
The presence of the minute air gap can further reduce the decrease in inductance in the region where the direct current is high.

According to the first embodiment, the following effects can be obtained.

(1) Inserting and arranging the cylindrical magnetic body 3 which is separate from the first and second ferrite cores 10 and 20 surrounding the annular wire ring 2 into the center hole 33 of the annular wire ring 2. Therefore, the magnetic characteristics of the cylindrical magnetic body 3 can be appropriately set according to the application. For example, in a case where a direct current is superimposed on the annular wire ring 2, magnetic saturation can be prevented by using a magnetic material having a high saturation magnetic flux density (for example, sendust) as a columnar magnetic body. In addition, the cylindrical magnetic body 3
Since a minute air gap (magnetic gap) is generated between the first and second ferrite cores 10 and 20, this minute air gap can also contribute to prevention of magnetic saturation.

(2) First and second ferrite cores 1
The outer shell core structure 1 composed of 0 and 20 can prevent magnetic saturation by appropriately selecting the magnetic characteristics of the columnar magnetic body 3 without providing a gap, has a low leakage inductance, and has almost no annular ring 2. It is possible to obtain an inductor having a magnetic shield structure that completely surrounds the inductor. That is, the outer shell core structure 1 can function as a magnetic shield case.

(3) Since the strip-shaped copper foil 30 whose surface is insulated is used as the wire material of the annular wire ring 2, the space factor of the conductor can be increased, and the current capacity and the heat generation can be reduced. You can Further, by applying an adhesive resin coating to the insulating coating of the strip-shaped copper foil 30, the strip-shaped copper foil 30 can be wound in a roll shape and then fixed in an annular shape with the adhesive resin. As a result, as the bobbin-less structure, the space of the coil housing recesses 11 and 21 in the outer shell core structure 1 can be effectively used, and the inductance can be increased.

(4) The first ferrite core 10 is made of high-resistance ferrite, the lead portion lead-out groove portion 13 is formed on the abutting surface 12 of the first ferrite 10, and the bottom portion of the lead portion lead-out groove portion 13 is formed. The extended portion of the electrode 14 is formed, and the lead portions 31 and 32 of the annular wire ring 2 are welded to the extended portion.
1 and 32 can be reliably pulled out, and the electrode 14
Can be reliably performed by soldering or the like (for example, if the lead portions 31, 32 are urethane coated copper foil and the electrode 14 has a solder layer, the lead portions 31, 32 are Soldering can be done by heating and pressure bonding.). Also, depending on the thickness of the lead portions 31 and 32, the first
Also, it is possible to prevent a gap from being generated between the second ferrite cores 10 and 20. Since the electrode 14 can be directly formed on the first ferrite core 10 of high-resistance ferrite by printing or baking silver paste or the like, a terminal plate or the like is not necessary, and it is also effective for reducing the number of parts and downsizing. .

FIG. 8 shows a second embodiment of the present invention. In this case, a plurality of (two) circles are provided in the coil housing recesses 11 and 21 inside the outer shell core structure 1 formed by butt-bonding and integrating the first ferrite core 10 and the second ferrite core 20. Annular line wheels 2A and 2B are arranged. Then, the lead portions drawn out from the respective annular wire rings 2A and 2B are connected to the extended portion of the electrode 14 located at the bottom of the predetermined lead portion lead-out groove portion 13 by soldering or the like. The ring-shaped coils 2A and 2B are wound in the same manner as in the ring-shaped coil 2 shown in the first embodiment, but are wound in a roll shape and fixed in an annular shape with an adhesive resin. And the sum of the widths of the strip-shaped copper foils of the annular wire rings 2A and 2B is the outer shell core structure 1
It is set to be slightly narrower than the sum of the depths of the inner ring wheel storage recesses 11 and 21.

The other structure is the same as that of the first embodiment described above, and the same or corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

In the second embodiment, a plurality of annular wire rings 2 are provided in the wire ring housing recesses 11 and 21 in the outer shell core structure 1.
By disposing A and 2B, a transformer (common transformer), a common mode choke coil, etc. can be configured. In this case, the distributed capacitance generated on the mating surfaces of the wire rings 2A and 2B forms an LC distributed constant circuit, and the effect of removing noise is increased. Further, by connecting a plurality of annular wire rings 2A and 2B in series, the inductance can be increased,
On the contrary, by connecting a plurality of annular coils 2A and 2B in parallel, it is possible to cope with a high frequency coil by increasing the current capacity and reducing the eddy current loss.

In the above embodiment, the case where sendust is selected as the cylindrical magnetic body 3 is illustrated, but if high inductance is required, the cylindrical magnetic body has a large magnetic permeability (outer shell core structure 1). A magnetic material having a higher magnetic permeability than the first and second ferrite cores 10 and 20 that form

Although the lead portion is pulled out from the winding start and winding end of the annular wire, the lead portion may also be pulled out from the intermediate portion.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to this and various modifications and changes can be made within the scope of the claims. Let's do it.

[0037]

As described above, according to the surface mounting inductor of the present invention, the columnar magnetic body separate from the first and second ferrite cores surrounding the annular wire ring is provided at the center of the annular wire ring. It is inserted and arranged in the hole, and by appropriately setting the magnetic characteristics of the columnar magnetic body, it is possible to meet various uses. For example, in a case where a direct current is superimposed on the annular wire, magnetic saturation can be prevented by using a magnetic material having a high saturation magnetic flux density (for example, a metal dust core such as sendust) as the columnar magnetic body. . Further, since a minute air gap (magnetic gap) is generated between the columnar magnetic body and the first and second ferrite cores, this minute air gap can also contribute to preventing magnetic saturation. If inductance is required, the columnar magnetic material has a high magnetic permeability (higher magnetic permeability than the first and second ferrite cores).
A magnetic material may be selected.

Further, the outer shell core structure composed of the first and second ferrite cores can be prevented from magnetic saturation by properly selecting the magnetic characteristics of the columnar magnetic body without providing a gap, so that it is small and thin. It is possible to realize a transformer, an inductor and the like having a magnetic shield structure that has little leakage inductance and that almost completely surrounds the annular wire ring.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a first embodiment of a surface mounting inductor according to the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is a front sectional view of the same.

FIG. 4 is a side view of the same.

FIG. 5 is a plan view of a first ferrite core.

FIG. 6 is a plan view showing a state in which an annular wire ring is inserted into a wire ring housing recess of a first ferrite core.

FIG. 7 is a graph showing the relationship between the direct current flowing through the annular wire and the inductance of the first embodiment of the present invention.

FIG. 8 is a front sectional view showing a second embodiment of the present invention.

[Explanation of symbols]

 1 Outer Shell Core Structure 2, 2A, 2B Annular Wire Ring 3 Cylindrical Magnetic Material 10 First Ferrite Core 11, 21 Wire Wheel Recessed Recess 12, 22 Butt Face 13 Lead Lead Out Groove 14 Electrode 30 Strip Copper Foil 31, 32 Lead part 33 Center hole

Claims (4)

[Claims] 1. A first ferrite core having a recess for accommodating a wire wheel and at least an electrode formed on a side surface thereof, and a second ferrite core bonded to the first ferrite core so as to close the recess for accommodating the wire wheel. The outer core structure consisting of the ferrite core and the wound wire is fixed in an annular shape by an adhesive substance, and the lead wire is provided at least at the beginning and end of the winding, and the wire inside the outer core structure is An annular wire wheel disposed in the wheel housing recess; and a columnar magnetic body that is separate from the first and second ferrite cores and is inserted into the center hole of the annular wire wheel, wherein the lead portion is A surface mounting inductor, which is connected to each of the electrodes. 2. The surface mounting inductor according to claim 1, wherein the wire is a metal foil whose surface is insulation-treated. 3. The surface-mounting inductor according to claim 1, wherein a plurality of the annular wire rings are arranged in the wire ring housing recess in the outer shell core structure. 4. The first ferrite core is a high resistance ferrite, a lead part lead-out groove is formed on an abutting surface of the first ferrite core, and the electrode is extended on a bottom surface of the lead part lead-out groove. A portion is formed, and the lead portion is welded at the extension portion.
2. The surface mount inductor according to 2 or 3.