JPH08191022A - Chip inductor and manufacturing method thereof - Google Patents

Abstract

PURPOSE: To provide a chip inductor having a coil-like conductor the ends of which are connected to external electrodes and hardly disconnected when a high pulse current flows thereon, and manufacturing method thereof, excellent in its mass production. CONSTITUTION: A chip inductor is composed of a coil-like conductor 1 and magnetic core 2 which is formed by baking and buried in the conductor 1. Both ends 4 of the conductor 1 are connected to external electrodes 3 exposed like a circular arc or similar shape and fixed to both end faces of the core 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type inductor using a fired magnetic core and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a kneaded material obtained by kneading a raw material powder of a magnetic material and a binder is pressed to form a rectangular parallelepiped or a cylindrical body and then fired to form a magnetic rod, and a conductor wire is wound around the magnetic rod. A coil is mounted, the end of the coil is extended to the end surface of the magnetic rod and connected to an external electrode formed on the end surface, and then,
There is known a method for manufacturing a chip-type inductor in which a coil is covered with a kneading material of a magnetic material powder and a binder, and then the coil is fired.

[0003]

In the above-mentioned chip type inductor, since the coil is covered with the magnetic material, a circular magnetic circuit is formed so as to surround the coil. Therefore, the inductance value is high and the magnetic field is high. Almost no magnetic field leaks out of the body. Therefore, there is an advantage that the characteristics of the inductor are not affected even if the chip inductors are arranged close to each other, and the mounting density of components on the circuit board or the like can be increased.

However, this inductor has a drawback that when a large pulse current is applied to the inductor, the inductor is easily broken at the connection between the external electrode and the terminal of the coil. An object of the present invention is to provide a conventional chip-type inductor which does not have such a problem and a manufacturing method of the chip-type inductor which is excellent in mass productivity.

[0005]

In order to achieve the above object, a chip-type inductor according to claim 1 comprises a coil-shaped conductor and a magnetic core formed by firing and having the coil-shaped conductor embedded therein. Both ends of the coil-shaped conductive wire are exposed at both end faces of the magnetic core in an arc shape or a similar shape and are connected to external electrodes respectively attached to the both end faces. The coil-shaped conductor is formed of one or a plurality of bundled conductors, and the cross-sectional shape of the one conductor or the bundled plurality of conductors has a flat cross-sectional shape, and the plane is coil-shaped. It is preferably formed along the axial direction of the conductive wire or formed of a plurality of bundled conductive wires. A method of manufacturing a chip inductor according to claim 4,
A winding core is formed by extrusion molding of a kneading material obtained by kneading a magnetic material powder and a binder, and the interval between the conducting wires is about 2 times the width of the conducting wire in the longitudinal direction of the winding core in a section along the longitudinal direction of the winding core.
After winding the conductive wire around the winding core into a coil with less than double, by extrusion molding of the kneading material, the conductive wire is wrapped around the winding core to form a jacket, and then wound. After firing the core and the outer casing, the core is cut into a predetermined length to form a plurality of chip-shaped inductor bodies in which both ends of the conductor are exposed in an arc shape or a similar shape on both end surfaces. External electrodes connected to the exposed ends of the arc-shaped or similar shaped conductors are formed on both end surfaces of the inductor body. It is preferable that the conductive wire is composed of a plurality of bundled conductive wires, or the conductive wire is composed of one or a plurality of bundled conductive wires each having a flat cross-sectional shape or a general cross-sectional shape. It is preferable to wind a plurality of bundled conductors in a coil shape so that the planes thereof are along the axial direction.

According to the method of manufacturing a chip-type inductor of claim 4, the step of kneading the magnetic material powder and the binder and forming the winding core by extrusion molding of the kneaded material, and the interval between the conductor wires The step of winding the conductor wire into a coil around the core with a width of the conductor wire in the longitudinal direction of the core being about twice or less the width of the conductor wire in a cross section along the longitudinal direction, and winding the conductor wire by extrusion molding of the kneading material. By passing through the steps of surrounding the winding core to form the jacket, the step of firing the winding core and the jacket, and the step of creating a plurality of chip-shaped inductor bodies by cutting into a predetermined length, A plurality of chip-type inductor bodies are manufactured at the same time, and chip-type inductors are manufactured by forming external electrodes on both ends of each inductor body.

According to the chip inductor of the present invention, the ends of the arc-shaped or similar shaped wire are exposed on both end faces of the chip inductor body. Therefore, the external electrodes formed on both end surfaces of the inductor body are connected to the ends of the arc-shaped or similar shaped wire. According to this configuration, the connection area between the external electrode and the end of the conductive wire is large, so that when a pulsed current is passed through this inductor, the conductive wire does not break before the conductive wire itself breaks. As described in claim 2, the coil-shaped conductor is one or a plurality of bundled conductors having a flat cross-sectional shape or a comprehensive cross-sectional shape, and the flat plane is along the axial direction of the coil-shaped conductor. Once formed, with the same magnetic core and the same number of turns, the spacing between conductors becomes narrower than in the case of one conductor with a round or square cross section, so the circle of coiled conductor exposed on both end faces of the inductor body The length of both ends of the arc shape or similar shape becomes longer, and the connection area with the external electrode becomes larger.
Further, when the coil-shaped conductive wire is formed of a plurality of bundled wires as described in claim 3, for example, when a pulsed current flows through the coil-shaped conductive wire, an external electrode and, for example, one conductive wire end portion are formed. Even if the connection with the wire is broken, the connection between the remaining end of the conductive wire and the external electrode is not broken, so the safety is high.

[0008]

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

FIG. 1 shows an example of a chip inductor according to the present invention.

In the figure, 1 is a wire diameter of 20 to 100 μm.
A coil-shaped conductor 2, in which a conductor wire made of silver wire of m is wound with a spacing p between the conductor wires being about twice the diameter of the conductor wire or less,
A rectangular parallelepiped shape (for example, L: 1.0 to 10.0 mm, which is made of ferrite) in which the coiled conductor 1 is embedded.
W: 0.5-10.0 mm, H: 0.5-10.0 m
The magnetic bodies 3, 3 and 3 of m) cover the both end surfaces of the magnetic body 2 and the outer peripheral surface end portions (e: 0 to 4.0 mm) continuous with the magnetic body 2 and are exposed at the both end surfaces. The external electrodes are connected to both ends 4 and 4 of a circular arc or similar shape. The external electrodes 3, 3 are, for example, silver electrodes, on which nickel plating and lead-tin plating are applied. The magnetic body 2 is composed of a magnetic body inside the coil-shaped conductor 1 that serves as a winding core of the coil-shaped conductor 1 and a magnetic body serving as an outer covering that covers the coil-shaped conductor 1. The internal magnetic body has a composition, for example, iron·
Consists of ferrite containing nickel, zinc, copper, etc. as main components. This ferrite is obtained by kneading a magnetic material powder having a particle size of 0.7 μm and a binder of glycerin / methylcellulose at a mixing ratio of 100: 8 to form a columnar shape, and then firing the mixture, and has a magnetic permeability. 100. The shrinkage factor during firing was, for example, 23%. The shrinkage during firing is
It is called firing shrinkage, and the length of the molded body before firing is I ₀ and the length of the molded body after firing is I ₁ , {(I ₀ −I ₁ ).
/ I ₀ } × 100. The magnetic body as the outer cover is made of ferrite having the same composition as the magnetic body inside. In order to produce a magnetic body as an outer jacket, the magnetic body raw material powder having the same composition and particle size as the inner magnetic body and the same binder are used, and the mixing ratio of the magnetic body raw material powder and the binder is 100. : Kneading the kneading material of 6. The shrinkage factor during firing was, for example, 20%. With the above shrinkage rates, the H and W were 4.0 mm each at the time of molding, and the winding core inside the coil-shaped conductor 1 was φ2.6 mm. 3.2 mm, the magnetic substance of the core becomes φ2 mm, and a gap of 0.08 mm is formed between the inner diameter of the magnetic substance as the outer casing including the coil-shaped conductor 1 and the inner diameter of the magnetic substance as the core. It was

According to this inductor configuration, for example,
8 Joule (J) pulse energy φ2.08
When the coil-shaped conductive wire 1 of mm is flowed, the coil-shaped conductive wire 1 and the connecting portion between the arc-shaped end portion and the external electrode are not broken. On the other hand, in the inductor of the comparative example in which a conductor having the same cross-sectional area was used and the tip of the end thereof was connected to the external electrode, when the same pulse current was passed, the connection was broken.

Next, a method of manufacturing the chip inductor according to the present invention shown in FIG. 1 will be described.

As shown in FIG. 2, for example, the binder S and the magnetic material powder B having the above-described mixing ratio are kneaded by a kneader 5 to homogenize the magnetic material powder and the binder, and this kneading is performed. The kneaded material 6 thus prepared is supplied under pressure to the primary extrusion molding machine 7, and a desired, for example, 0.5
The rod body 8 as a winding core having a diameter of 10 mm is, for example, 30 m
Extrude at a rate of / min. The rod body 8 is dried by, for example, a dryer (not shown), and then the wire 10 is wound by the winding machine 9.
Is wound such that the interval p between the wound conductor wire 10 and the conductor wire 10 is not more than about twice the width of the conductor wire 10 in the longitudinal direction of the winding core in the cross section along the longitudinal direction of the winding core. The rotated rod body 8 is fed into the secondary extrusion molding machine 11. In the secondary extrusion molding machine 11, in the kneading machine 5, the kneading material 6 pressurized and supplied to the primary extrusion molding machine 7 is mixed with the kneading material by increasing the mixing ratio of the magnetic material powder and the binder. Since the kneading material 12 having a shrinkage ratio smaller than that of No. 6 is supplied under pressure, the conductor 10 wound around the rod body 8 is covered with the kneading material 12 by the molding machine 11 to form the jacket. . After that, it is cut according to the size of the firing furnace or the shape of the setter to be laid thereunder, fired at 600 to 1000 ° C., for example 900 ° C., and cut with a cutter according to the size of each inductor. Each of the cut inductor bodies 13 is barrel-polished with barrel powder and water to have rounded corners. Then, as shown in FIG. 1, silver paste is applied to both end faces of the magnetic core 2 of the inductor body 13 and end portions of the outer peripheral surface continuous with the magnetic paste, and baked to form the external electrodes 3. At this time, lead wire 1
The exposed arcuate or similar shaped end portions 4 and 4 are connected to the external electrode 3. For the silver layer of the external electrode 3, nickel
Plating and solder plating are applied. In this example,
Since the shrinkage rate of the magnetic material inside the coil-shaped conductor during firing was made larger than the shrinkage rate of the magnetic material that is the jacket,
The stress due to the contraction of the magnetic material of the jacket is not applied to the internal magnetic material through the coil-shaped conductor 1 or through the gap between the coil-shaped conductor 1 and the impedance characteristic of the inductor does not deteriorate.

However, even if the mixing ratios of the magnetic material powder and the binder of the winding core and the outer casing are the same and the contraction rates are the same, the stress due to the contraction of the outer casing during firing is still present. In addition, since no gap is formed between the coiled conductor and the winding core, the impedance characteristic is further improved.

The particle size of the magnetic material powder for the core is, for example, 0.7 μm, and the particle size of the magnetic material powder for the envelope is, for example, coarser than 0.7 μm, or the same. The shrinkage factor during firing of the winding core may be set to be larger than or the same as the shrinkage factor of the outer cover, while making the other conditions the same.

As shown in FIG. 3, the conductor wire may be formed by forming a conductor wire 1a having a flat cross section into a coil shape so that the plane of deviation is along the axial direction of the coiled conductor wire 1. At this time, the interval p between the conductors becomes narrower than that in the case where the conductors having the same length of the magnetic body 2 and the same winding shape of the coil-shaped conductor 1 are used.
Therefore, the length of both ends 4 of the coil-shaped conductor 1 exposed on both end surfaces of the magnetic body 2 becomes long, and the contact area with the external electrode 3 becomes large. Also, as shown in FIG. 4, a plurality of bundled wires having a flat cross-section, for example, two conductors 1a having a circular cross-section, are coiled so that their planes are along the axial direction of the coil-shaped conductor 1. Even if formed, the contact area becomes large similarly.

In addition, a plurality of bundled wires, for example, four conductors 1a to
As shown in FIG. 5, when 1a is wound in a coil shape and both ends thereof are connected to the external electrodes 3, among the plurality of conductive wires 1a to 1a exposed in an arc shape from the end surface of the magnetic core 2. For example, the ends of the two conducting wires 1 a and 1 a are connected to the external electrode 3. According to this configuration, when the pulsed current is passed through the inductor, the two lead wires 1a connected to the external electrode 3,
It is safer than that shown in FIG. 1 because both 1a are less likely to break.

[0018]

According to the structure of the invention described in claim 1, since the connection area between the external electrode and the end of the conductive wire is large, it is difficult for the connection portion to be disconnected when a pulsed current is applied.
Further, according to the configurations of the inventions described in claims 2 and 3, there is an effect that a chip-type inductor that is more difficult to break can be obtained. According to the structure of the invention described in claims 4 to 6, there is an effect that a manufacturing method excellent in mass productivity of the chip inductor can be obtained.

[Brief description of drawings]

1A, 1B and 1C are a perspective view, a partially cut front view and a side view of a chip-type inductor body of a chip-type inductor manufactured by a manufacturing method according to the present invention.

FIG. 2 is an explanatory diagram of an apparatus used for carrying out a method of manufacturing a chip inductor according to the present invention.

3A and 3B are partially cutaway front views of another example of a chip inductor and a side view of the chip inductor body.

FIG. 4 is a partially cut front view of a third example of the chip inductor.

FIG. 5 is a partially cut front view of a fourth example of a chip inductor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Coil-shaped conductor 2 Magnetic material 3 External electrode 4 End part 5 Kneading machine 6, 12 Kneading material 7 Primary extrusion molding machine 8 Bar body 9 Winding machine 10 Conducting wire 11 Secondary extrusion molding machine 13 Inductor body

Claims (6)

[Claims] 1. A coil-shaped conductive wire and a magnetic core formed by firing and having the coil-shaped conductive wire embedded therein. Both ends of the coil-shaped conductive wire are exposed at both end faces of the magnetic core in an arc shape or a similar shape. Then, the chip-type inductor is connected to the external electrodes respectively attached to the both end surfaces. 2. The coil-shaped conductor is formed of one or a plurality of bundled conductors, and the cross-sectional shape of the one conductor or the total cross-sectional shape of the plurality of bundled conductors is a flat shape. 2. The chip-type inductor according to claim 1, wherein the flat surface is formed along the axial direction of the coil-shaped conductor. 3. The chip-type inductor according to claim 1, wherein the coil-shaped conductor is formed of a plurality of bundled conductors. 4. A core is formed by extruding a kneading material obtained by kneading a magnetic material powder and a binder, and forming a winding core, and the spacing between the conducting wire and the conducting wire in the longitudinal direction of the winding core in a section along the longitudinal direction of the winding core. After winding the conductor wire into a coil shape with a width of about 2 times or less, the kneaded material is extruded to surround the winding core of the conductor wire to form a jacket. Then, after firing the core and the outer cover, the core is cut into a predetermined length to form a plurality of chip-shaped inductor bodies in which both ends of the conductor are exposed in an arc shape or a similar shape on both end surfaces. A method of manufacturing a chip-type inductor, characterized in that external electrodes connected to the ends of the exposed arc-shaped or similar-shaped conductors are formed on both end faces of the chip-type inductor body. 5. The conductor wire is composed of one or a plurality of bundled conductor wires each having a flat cross-sectional shape or a general cross-sectional shape, and the one or a plurality of bundled conductor wires whose axial plane is in the axial direction. The method for manufacturing a chip-type inductor according to claim 4, wherein the winding is performed in a coil shape so as to follow the direction. 6. The method for manufacturing a chip inductor according to claim 4, wherein the conductive wire is a plurality of bundled conductive wires.