JP2000331841A - Coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coil which is lessened in number of component parts and manufacturing processes, decreased in height, and improved in reliability by a method wherein a part of a magnetic path is formed of the insulating base of a composite magnetic molded body, and the terminal of a winding is led out direct as an outer terminal to a base side. SOLUTION: This coil is equipped with a magnetic core structure composed of a magnetic core 1 of ferrite or the like and a plate-like insulating base 10 of composite magnetic molded body, and a winding 20 is arranged as housed inside the structure. The winding 20 is formed of a flat-type wire 22 which is edgewise wound, and the terminal of the winding 20 is put through a slit provided in the base 10 and folded back to serve as an outer terminal 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil used for a power supply unit and the like, and more particularly to a reduction in power consumption and a low-profile SMD.
The present invention relates to a coil having a product structure suitable for use as a power choke coil or the like that requires a low voltage, a large current, and a low inductance for the purpose of (surface mounted components).

[0002]

2. Description of the Related Art FIG. 17 shows a typical example of a coil structure in which a winding is provided by forming a gap in a magnetic core such as ferrite. FIG. 17A shows a structure in which the windings 60 are provided on the EE core 50 and the gaps 51 are formed and butted. FIG. 17 (B) shows the EI core 52 provided with the windings 60 and the gaps 53 formed and joined together. FIG. 17C shows a configuration in which the winding 60 is provided on the drum core 54 and the ring core 55 is arranged outside the drum core 54. FIG. 17 (D) shows the winding 6 on the drum core 54.
0, the ring core 55 is arranged outside the drum core 54, and an insulator base 57 having an external terminal 56 is provided at the bottom thereof. In FIG. 17E, the ring core is omitted, the winding 60 is provided on the drum core 54, and the insulator base 57 having the external terminal 56 is provided on the bottom.

Each of the configurations shown in FIGS. 17A to 17E has the following problems.

(1) When an insulating magnetic material such as a Ni—Zn ferrite is used for the magnetic core In general, the saturation magnetic flux density is low, and a power choke coil for a large current often does not satisfy the characteristics. Further, it is necessary to form a gap, which leads to an increase in cost and variation in characteristics. When forming external terminals, there are typically the following two types. External terminals are formed on the insulator base, and winding terminals are connected thereto. External terminals are formed directly on the core, and the winding terminals are connected thereto. However, each has its own problems. That is, the number of parts increases, the cost increases, and if the base is formed on the lower surface of the core, the product height increases, and it becomes impossible to cope with severe low-profile requirements. In the case of the above structure, since the ferrite core has no processing flexibility, there is a limitation in the forming method.

(2) When a non-insulating magnetic material such as Mn-Zn-based ferrite is used for the core Mn-Zn-based ferrite is superior to Ni-Zn-based ferrite in that it has a larger saturation magnetic flux density, but also has a DC superposition characteristic. In order to improve the performance, it is necessary to form a gap, which leads to an increase in cost and characteristic variation. When forming external terminals, there are typically the following two types. External terminals are formed on the insulator base, and winding terminals are connected thereto. External terminals are formed directly on the core, and the winding terminals are connected thereto. However, each has its own problems. That is, the number of parts increases, the cost increases, and if the base is formed on the lower surface of the core, the product height increases, and it becomes impossible to cope with severe low-profile requirements. However, since the insulation process is required between the core and the external terminal, the cost increases, and the ferrite core has no processing flexibility, so that the method of forming the ferrite core is limited.

On the other hand, a magnetic circuit formed by combining a ferrite core and a composite magnetic material is disclosed in Japanese Patent Laid-Open No. 1-6891.
No. 1, "Coil device", and JP-A-4-342106, "Magnetic shield structure of coil component".
FIG. 18 shows examples of coils according to these known techniques. FIG. 18A shows a structure in which a winding 80 is provided on a drum core 70 of a composite magnetic material, and the outside thereof is surrounded by a ferrite core 71. FIG. 18B shows a structure in which a winding 80 is provided on a ferrite drum core 72, a ring core 73 of a composite magnetic material is disposed outside, and an insulator base 75 having an external terminal 74 is provided on the bottom thereof. FIG. 18C shows a configuration in which a ferrite drum core 76 is placed sideways, a winding 80 is provided, a periphery of which is surrounded by a composite magnetic body 77 and an external terminal 78 is provided.

Each of the configurations shown in FIGS. 18A to 18C has the following problems.

M, which has a large saturation magnetic flux density and a large current
With n-Zn ferrite, it is difficult to make a drum core (particularly a flat and thin one). Therefore, it becomes an obstacle in reducing the height. Further, FIG. 18C requires a special manufacturing method, and a non-insulating core requires an insulating treatment between the base of the external terminal and the core. When forming external terminals, there are typically the following two types. External terminals are formed on the insulating base, and winding terminals are connected thereto. External terminals are formed directly on the core, and the winding terminals are connected thereto. However, each has its own problems. That is, the number of parts increases, the cost increases, and if the base is formed on the lower surface of the core, the product height increases, and it becomes impossible to cope with severe low-profile requirements. In the case of a non-insulating core, an insulating process is required between the core and the external terminal, which increases the cost. Further, since the ferrite core has no processing flexibility, there is a limitation on the forming method.

Further, a structure in which a magnetic path is formed by combining a ferrite core and a composite magnetic material, and a terminal piece is buried in a composite magnetic substrate, and a winding terminal is connected thereto.
This is proposed in Japanese Utility Model Laid-Open No. 1-146506, "Wounding components such as choke coils and transformers".

However, in the case of this structure, the terminal piece connected to the coil winding is buried in the composite magnetic substrate, and the terminal of the winding is connected thereto. There is a problem of increase in the workability and man-hours (cost increase and soldering man-hour due to increase of the substrate molding cycle). Also,
There is a step in the ferrite core, and unless the dimensions with the step of the substrate are strictly controlled by polishing or the like, an air gap is generated and causes a characteristic variation.

[0011]

DISCLOSURE OF THE INVENTION In view of the above, the present invention has a magnetic path partially constituted by an insulating base of a composite magnetic molded body, and a terminal of a winding is directly used as an external terminal on the base side. It is an object of the present invention to provide a coil capable of reducing the number of parts and manufacturing steps, reducing the height of a product, and improving reliability.

Other objects and novel features of the present invention will be clarified in embodiments described later.

[0013]

In order to achieve the above object, the present invention relates to a coil having a magnetic core structure provided with a winding, wherein a part of a magnetic path of the magnetic core structure is formed as a composite magnetic molded body. And the wire ends of the windings are drawn directly to the base side as external terminals.

[0014] In the coil, the butting surface between the magnetic material constituting the magnetic path other than the base and the base in the magnetic core structure is a flat surface, and the magnetic core structure is joined without providing a gap between the base and the magnetic material. It is good to configure.

The base is prepared by adding a magnetic powder having an average particle diameter of 1 μm to 300 μm to a thermosetting or heat-resistant thermoplastic resin in an amount of 50 to 9 μm.
It is good to be comprised by the composite magnetic compact containing 0 weight%.

The magnetic powder is preferably a soft magnetic material.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a coil according to the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show the overall structure of a first embodiment of the present invention. FIGS. 4 and 5 show a winding structure, and FIGS. 6 to 8 show an insulating base provided with a winding. 9 to 11 show a magnetic core structure made of ferrite or the like to be abutted against an insulating base.

In these figures, a magnetic core structure (magnetic circuit) is constituted by a magnetic core 1 of ferrite or the like and a flat insulating base 10 of a composite magnetic molded body, and a winding 20 is housed inside thereof. , Is located.

The winding 20 is, as shown in FIGS.
An insulated flat wire 22 is wound in an edgewise manner (a winding method for bending a narrow surface), and a winding terminal 23 is bent at a right angle and a portion to be an external terminal 24 is subjected to solder plating. It has been subjected.

Insulating base 1 forming a part of the magnetic path of the coil
Numeral 0, as shown in FIGS. 6 to 8, is formed in a plate shape from a composite magnetic molded body, functions as a structural magnetic body having an insulation resistance of 10 ⁶ Ω or more, and functions as a member for fixing external terminals. Therefore, as shown in FIG. 12, a slit hole 11 for inserting a winding terminal 23 serving as an external terminal is provided near the edge.
Is formed and the winding terminal 2 is passed through the slit hole 11.
3 is folded outside the end face of the base 10 to form the external terminals 24.
Is formed on the end face of the base 10. Note that the insulating base 10 may be provided with a dummy terminal 13 as necessary as shown in FIGS. The attachment of the dummy terminal 13 can be performed by insertion bending into a slit hole of the base or insert molding.

The insulating base 10 is made of a thermosetting resin such as epoxy, phenol, polyester or the like, or LCP, P
Composite containing a thermoplastic resin such as PS, PBT, PET, PA or the like as a base resin, and 50 to 90% by weight of magnetic powder having an average particle diameter of 1 to 300 μm in a particle diameter of 0.01 to 500 μm. It is desirable to be composed of a magnetic molded body. When a thermoplastic resin is used as the base resin, a resin having a heat resistance of 230 ° C. or more is desirable because of the characteristics of a chip component.

The magnetic powder is soft ferrite (Mn-Zn,
Ni-Zn, Mn-Mg-Zn, Ni-Cu-Zn type) or powder of soft magnetic material such as carbonyl iron, 6.5% Si-containing iron, permalloy, sendust, amorphous magnetic alloy, etc. It can be properly used depending on the application (frequency, magnetic permeability, magnetic flux saturation density, insulation resistance, etc.).

When the ratio of the magnetic powder to the base resin in the composite magnetic compact is less than 50% by weight,
The performance as a magnetic material is not sufficiently exhibited, and if it exceeds 90% by weight, there is a problem in moldability. If necessary, a reinforcing material such as glass or talc may be added.

The magnetic core 1 made of ferrite or the like has a substantially E-shaped cross section having a center leg 2, side legs 3a, 3b, 3c and a flat plate 4 connecting these, and Mn-Zn, Ni-Z.
It is formed of a sintered body of soft ferrite such as n, Mn-Mg-Zn, Ni-Cu-Zn, a dust core (a dust core), and the like, and the material is properly used depending on the application and purpose. Here, the central leg 2 and the side legs 3a, 3b,
The end face of the base 3c against the base 10 is a flat surface with no step. The core butting surface of the base 10 is also a flat surface. Further, the magnetic core 1 is formed with a window 5 in which the side legs 3a, 3b, 3c are not provided in order to draw out the winding terminal 23. In the case of a power choke coil, the material of the magnetic core 1 is preferably an Mn-Zn based material having a high saturation magnetic flux density.

The above members can be assembled in the following procedure.

The winding 20 formed in advance with the winding terminal 23 is placed on the insulating base 10 of the composite magnetic molded body as shown in FIGS. 6 and 7, and as shown in FIG. Is inserted into the slit hole 11 and turned back into the groove 12 at the end face of the base 10 via the bottom face of the base 10, and an excess portion of the winding end 23 is cut, and the winding end 23 pulled out to the bottom face and the end face of the base 10 External terminal 24.

Then, as shown in FIGS. 1 to 3, the center leg 2 of the magnetic core 1 is abutted to the base 10 with substantially no gap so as to enter the inner periphery of the winding 20, and is fixed with an adhesive. . Thereby, a coil as a surface mounting component (chip component) in which the external terminal 24 as the surface mounting terminal is integrated with the insulating base 10 is obtained.

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

(1) By forming a part of the magnetic core structure as the base 10 of a composite magnetic molded body which is hardly magnetically saturated and has insulating properties, the external terminals 24 can be provided without insulation treatment. Compared to a case where an insulator base is arranged separately, cost reduction by reducing the number of parts and downsizing by reducing the product height can be achieved.

(2) The external terminal 24 is formed without a connection point with the winding 20 of the coil (the wire of the winding terminal is directly drawn out). Since the step of connecting to the winding terminal is unnecessary, cost reduction by reducing the number of parts and improvement in reliability by eliminating the connection point can be achieved.

(3) In the case of a coil requiring a large current, the bottom surface of the product is made of an insulating material (insulating composite magnetic molded body serving as base 10).
And a high saturation magnetic flux density material such as power ferrite (high-B
By using the same material for the magnetic powder of the composite magnetic compact, a coil having a larger current value than before can be obtained. As a result, the characteristics can be improved by increasing the degree of freedom of the circuit board design on the customer side, and the characteristics can be improved by increasing the current.

(4) Since the abutting surface of the magnetic core 1 and the insulating base 10 is a flat surface having no step, there is no need to form a gap in the magnetic core 1 which is difficult to process and to control the dimensions. For this reason, the cost can be reduced by reducing the processing cost, and the characteristics can be improved by reducing the variation in processing accuracy.

FIGS. 13 and 14 show a second embodiment of the present invention. In this case, a groove 15 is formed on the edge (bottom and end) of the insulating base 10 of the composite magnetic molded body, and the winding terminal 23 of the coil is guided from the upper surface of the insulating base 10 to the groove 15. External terminals 25 for surface mounting are formed by being bent so as to sandwich the edge of the insulating base 10. The other configuration is the same as that of the first embodiment.

In the case of the second embodiment, no slit hole is required in the insulating base 10 and the winding terminal 2
Forming 3 is also relatively easy.

FIGS. 15 and 16 show a third embodiment of the present invention. In this case, the winding terminals 23 are led out from the upper surface of the insulating base 10 of the composite magnetic molded body, and
The outer terminals 26 are bent into gull wings on both sides of the external terminals 26 for surface mounting. The other configuration is the same as that of the first embodiment.

In the case of the third embodiment, it is not necessary to process the edge of the insulating base 10 and the forming of the winding terminal 23 is easy.

[0038]

EXAMPLE As an example, a power choke coil having the following specifications was prepared. Outline: 12.5 × 12.5 × 3.5 mm Inductance: 2 μH Current value: 10 A Structure: Structure shown in the first embodiment

Mn--Zn ferrite is used as the magnetic core 1, a PPS base and a molded article of a composite magnetic material containing carbonyl iron powder are used as the insulating base 10, and a magnetic path is formed with no gap between them, and a flat wire is used. Then, an edgewise winding winding 20 was incorporated.

As Comparative Example 1, a film gap was formed on the Mn-Zn ferrite (a gap was provided on all bonding surfaces of the core), and as Comparative Example 2, a center gap was formed on the Mn-Zn ferrite (central leg portion). The power choke coil of the example was compared with the DC current superimposition characteristic. FIG. 19 shows the comparison result. However, in both cases, the characteristics at 25 ° C. and at 100 ° C. are also shown.

In the power choke coil of the embodiment, the rate of change of inductance due to the superposition of DC current is small, and the allowable current is large. In particular, at high temperatures, the ferrite + gap products of Comparative Examples 1 and 2 have a low magnetic flux saturation density of the magnetic core material, so that the hysteresis of the rate of change of inductance with respect to temperature is large, whereas the hysteresis is small in Examples. Further, in Comparative Examples 1 and 2, in the current saturation region, the inductance decreases sharply after passing the saturation point, whereas in the embodiment, the inductance decreases gradually, and there is little concern about runaway of the mounted circuit.

Although the winding is a rectangular wire with an edgewise winding, it may be a flatwise winding or a general round wire.

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 the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0044]

As described above, according to the coil of the present invention, a part of the magnetic path is constituted by the insulating base of the composite magnetic molded body, and the wire ends of the windings are used as the external terminals. Since the structure is directly drawn to the side, the number of parts and the number of manufacturing steps can be reduced, the size of the product can be reduced, and the reliability can be improved.

The reduction in the number of components is, for example, that an insulator base is not required separately from the magnetic core, or that there is no need to prepare independent components as external terminals.

The reduction in the number of manufacturing steps is that the use of the winding terminal of the coil directly as an external terminal eliminates the need for connection work between the external terminal and the winding terminal.

As for the miniaturization of the product, in the case of the conventional product, when the insulator base is used separately from the core, the minimum base thickness that can be molded is about 0.5 mm, and the product height is increased by that much. Assuming that the core height is 3.5 mm, the coil according to the present invention is 3.5 mm, and the conventional product is 4.0 mm.

In the present invention, by adopting a material that is hardly magnetically saturated as the composite magnetic compact, it is possible to improve the allowable current value in a power choke coil and the like. For example, in the example of FIG.
It can be seen that the allowable current value can be increased by 0 to 100%.

[Brief description of the drawings]

FIG. 1 is a front view of a coil according to a first embodiment of the present invention, in which a half is shown in cross section.

FIG. 2 is a side sectional view of a section passing through an external terminal in the first embodiment.

FIG. 3 is a bottom view of the first embodiment.

FIG. 4 is a plan view showing a winding used in the first embodiment.

FIG. 5 is a side view of the same.

FIG. 6 is a plan view showing a state in which a winding is attached to an insulating base in the first embodiment.

FIG. 7 is a front view of the same.

FIG. 8 is a sectional view taken along line VIII-VIII of FIG. 6;

FIG. 9 is a bottom view of the magnetic core used in the first embodiment.

FIG. 10 is a sectional view taken along line XX of FIG. 9;

FIG. 11 is a sectional view taken along line XI-XI of FIG. 9;

FIG. 12 is an enlarged perspective view around an external terminal according to the first embodiment.

FIG. 13 is a side sectional view showing a second embodiment of the present invention.

FIG. 14 is an enlarged perspective view around an external terminal according to a second embodiment.

FIG. 15 is a side sectional view showing a third embodiment of the present invention.

FIG. 16 is an enlarged perspective view around an external terminal according to a third embodiment.

FIG. 17 is a front sectional view showing a conventional example of a coil using a magnetic core having a gap formed therein.

FIG. 18 is a front sectional view showing a conventional example of a coil using a composite magnetic material for a part of a magnetic path.

FIG. 19 is a graph showing DC superposition characteristics of inductances in the example and Comparative Examples 1 and 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic core 2 Central leg 3a, 3b, 3c Side leg 4 Flat plate 5 Window 10 Insulating base 11 Slit hole 12 Groove 13 Dummy terminal 15 Groove 20 Winding 22 Flat wire 23 Winding terminal 24, 25, 26 External terminal

Claims (4)

[Claims] 1. A coil in which a winding is provided on a magnetic core structure, wherein a part of a magnetic path of the magnetic core structure is constituted by an insulating base of a composite magnetic molded body, and a wire end of the winding is formed. A coil drawn as an external terminal directly to the base side. 2. The magnetic core structure, wherein abutting surfaces of a magnetic body constituting a magnetic path other than the base and the base and the base are flat, and are joined without providing a gap between the base and the magnetic body. The coil according to claim 1. 3. The base according to claim 1, wherein the thermosetting or heat-resistant thermoplastic resin is made of a magnetic powder having an average particle diameter of 1 μm to 300 μm.
The coil according to claim 1 or 2, wherein the coil is composed of a composite magnetic compact containing about 90% by weight. 4. The coil according to claim 3, wherein the magnetic powder is a soft magnetic material.