JPH11186041A - Inductance element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve inductance and Q of an inductance element by exposing an elemental ferrite core body on the surfaces of a ferrite core, where the large outside-diameter portions of the core are in contact with the small outside- diameter portion of the core, except a conductor film section connecting a spiral conductor pattern to terminal electrodes. SOLUTION: In an inductance element, a silver conductor film is formed on an Ni-Zn or Ni-Cu-Zn ferrite core by electroplating after a metallic conductor film of silver, nickel, etc., is formed on the ferrite core through electroless plating. After the conductor films are formed on the ferrite core, the conductor films are laser beam machine. After the laser beam machining, the ferrite core is heat-treated in the air or an oxygen atmosphere to return the metallized ferrite to the original oxidized insulator ferrite. Then, after a spiral conductor pattern 12 is formed on the side faces of the treated ferrite core 10 and terminal electrodes are formed on the large-outside-diameter portions of the core 10, the elemental ferrite core body of the ferrite core 10 is exposed by removing the conductor films on the surfaces of the core 10 on the pattern 12 side, except for the portions required for connection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductance element and a method of manufacturing the same, and more particularly to an inductance element of a type in which a conductor pattern for forming a coil by a conductor film is formed around a ferrite core and a method of manufacturing the same. It is related.

[0002]

2. Description of the Related Art In general, an inductance element in which a conductive wire is wound around a ferrite core has been used. However, due to advances in processing technology and the like, a structure in which a conductor film is formed on a magnetic material instead of a winding is used. Has been put to practical use. In particular, with the advance of laser processing technology, highly accurate conductor patterns can be obtained, and those suitable as chip inductors for medium and high frequencies can be obtained.

FIG. 4 shows an inductance element of this type.
As shown in FIG. 5, a spiral conductive pattern 42 is formed around a ferrite core 40, and terminal electrodes 44 are formed at both ends having a large outer diameter. In manufacturing, a conductor film is generally formed on the entire side surface of the ferrite core, and the conductor film is cut to expose the ferrite body and leave a spiral conductor pattern.

[0004] In order to cut the conductive film, a method of irradiating a laser beam instead of a cutter to remove the conductive film has been adopted. As a result, the conductor pattern can be formed with high accuracy.

[0005]

An inductance element in which the outer diameter of both ends of a magnetic core is increased and a conductor pattern is formed in a portion having a smaller outer diameter has a structure similar to that of a coil in which a drum core is wound. However, since the conductor film remains on the surface of the helical conductor pattern side of the portion having a large outer diameter, the magnetic flux is blocked at this portion, it is difficult to increase the inductance, and the Q cannot be increased. SUMMARY OF THE INVENTION The present invention provides an inductance element capable of improving the inductance without interrupting the magnetic circuit of the inductance element and improving the Q.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by leaving the conductor film on the side of the spiral conductor pattern having a large outer diameter to a minimum.

That is, a portion of a conductor film formed on a side surface of a small outer diameter portion of a prismatic or cylindrical ferrite core having a large outer diameter portion at both ends is removed, and a spiral conductor is formed around the ferrite core. In the inductance element in which a pattern is formed and a terminal electrode is formed in a portion having a large outer diameter, a surface of the portion having a large outer diameter which is in contact with a portion having a small outer diameter is a conductor film portion connecting the spiral conductive pattern and the terminal electrode. Except that the ferrite core body is exposed.

In addition, a portion of a conductor film formed on a side surface of a small outer diameter portion of a prismatic or cylindrical ferrite core having a large outer diameter portion at both ends is removed, and a spiral conductor is formed around the ferrite core. In an inductance element in which a pattern is formed and a terminal electrode is formed in a portion having a large outer diameter,
The surface of the large-diameter portion that contacts the small-diameter portion is a plastic ferrite that exposes the ferrite core body except for the conductor film portion that connects the spiral conductor pattern and the terminal electrode, and covers the spiral conductor pattern. The characteristic feature is that the magnetic material layer is provided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The steps of a method for manufacturing an inductance element according to the present invention are as follows. Ferrite core formation Conductive film formation (electroless plating or electrolytic plating after electroless plating) Dry Laser processing-conductor film cutting-(heat treatment as needed) (if necessary) resin ferrite layer formation

In order to reduce the number of steps, it is preferable to form the terminal electrodes simultaneously with the formation of the conductor film, and to perform solder plating or the like in order to improve the solder wettability at the time of soldering the terminal electrodes. Also, when using Ag, Ni
By forming the film, it is possible to prevent erosion of the silver solder forming the spiral conductor pattern. In addition, when heat treatment of ferrite is performed after laser processing, ferrite reduced and converted into a conductor during laser processing can be returned to an oxide having high insulating properties. Further, a resin ferrite layer may be formed on a conductor pattern covered with a thin non-magnetic layer such as glass. Of course, you may cover directly with resin ferrite.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing an inductance element according to the present invention will be described below.

As a material for an inductance element for medium and high frequencies such as for communication equipment, a ferrite of Ni-Zn type or Ni-Cu-Zn type is used. Oxides of these materials and Fe
A material in which a predetermined amount of ₂ O ₃ is mixed is molded and fired to obtain a ferrite core. The ferrite core is provided with a portion having a large outer diameter at both ends, and this can be used as a terminal.

A conductive film of a metal such as silver or nickel is formed on the ferrite core by electroless plating. In order to reduce the resistance by increasing the thickness of the conductor film, a silver conductor film is further formed thereon by electrolytic plating. As a material of the conductor film, copper may be used, or a metal such as copper may be formed on nickel.

The conductor film formed on the ferrite core is cut by laser processing. The conductor film is burned off by the laser beam, and a part of the surface of the ferrite core body is burned off together with the conductor film. At this time, the surface of the ferrite core is heated to a high temperature, so that the ferrite particles are also reduced under the influence of the ferrite core and are converted into a conductor.

Therefore, the ferrite core after laser processing is heat-treated in air or an oxygen atmosphere. By this heat treatment, the metallized ferrite is oxidized and returned to the original insulator ferrite. As a method of heat treatment,
The temperature was raised to 900 ° C at a rate of 20 ° C / min in air or an atmosphere containing more oxygen, held at 900 ° C for 10 minutes, and then cooled. Characteristics were restored.

The terminals for connecting the conductor pattern of the ferrite core processed as described above to the external circuit are formed at both ends of the core, but the metal film formed first can be used as a base electrode as it is. The conductor film connecting the terminal electrode and the spiral conductor pattern is formed on the surface of the spiral conductor pattern side of the portion having a large outer diameter, but the spiral film is formed without leaving the conductor film on the entire surface. Only the conductor pattern that connects the end of the conductor pattern and a part of the terminal electrode is left, and the other part is cut to expose the ferrite body by cutting the conductor film. The terminal electrode portion is preferably plated with nickel, solder, or the like to prevent solder erosion.

FIG. 1 shows an example of the inductance element according to the present invention. The point that the spiral conductive pattern 12 is formed on the side surface of the ferrite core 10 and the terminal electrode 14 is formed on a portion having a large outer diameter is the same as the conventional one. In the present invention, the conductor film on the wall of the spiral conductor pattern 12 in the portion having the large outer diameter is removed except for the portion necessary for connection, and the ferrite core body is exposed. Become.

FIG. 2 shows another embodiment of the present invention. The ferrite core 20, the conductor pattern 22, and the terminal electrode 24 are the same as those in the above-described embodiment, but the plastic ferrite layer 28 is formed on the surface of the conductor pattern 22. Is formed. Conductor pattern
22 has a structure surrounded by a magnetic material, the inductance element has a closed magnetic path, and higher inductance can be obtained. Note that a non-magnetic film such as glass may be formed between the conductor pattern 22 and the plastic ferrite 28.

When the boundary surface between the large outer diameter portion and the small outer diameter portion of the ferrite core is inclined as shown in FIG. 3, the cutting becomes easy, and the conductor pattern 32 is formed on this portion. Also, the length of the conductor pattern can be increased. Alternatively, a conductor pattern may be formed only on a part of the portion having a large outer diameter and connected to the terminal electrode on the end face.

[0020]

According to the present invention, since the interruption of the magnetic flux can be prevented, the inductance and Q can be increased.

Further, by using a plastic ferrite layer together, not only can the inductance be increased, but also the protective layer of the conductor pattern can be obtained, so that an inductance element having high reliability and stable characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an embodiment of the present invention.

FIG. 2 is a front sectional view showing another embodiment of the present invention.

FIG. 3 is a front view showing another embodiment of the present invention.

FIG. 4 is a front view showing an inductance element.

[Explanation of symbols] 10, 20: Ferrite core 12, 22, 32: Conductor pattern 18: Plastic ferrite layer

Claims (4)

[Claims] A helical conductor is formed around a ferrite core by removing a part of a conductor film formed on a side surface of a small outer diameter portion of a prismatic or cylindrical ferrite core having a large outer diameter portion at both ends. In the inductance element in which a pattern is formed and a terminal electrode is formed in a portion having a large outer diameter, a surface of the portion having a large outer diameter which is in contact with a portion having a small outer diameter is a conductor film portion connecting the spiral conductive pattern and the terminal electrode. Except for the above, an inductance element characterized in that the ferrite core body is exposed. 2. A helical conductor formed around a ferrite core by removing a portion of a conductor film formed on a side surface of a small outer diameter portion of a prismatic or cylindrical ferrite core having large outer diameter portions at both ends. In the inductance element in which a pattern is formed and a terminal electrode is formed in a portion having a large outer diameter, a surface of the portion having a large outer diameter which is in contact with a portion having a small outer diameter is a conductor film portion connecting the spiral conductive pattern and the terminal electrode. An inductance element characterized by comprising a magnetic layer of plastic ferrite that exposes a ferrite core body and covers a spiral conductive pattern except for the above. 3. A conductor film is formed on the surface of a prismatic or cylindrical ferrite core having large outer diameter portions at both ends,
In a method of manufacturing an inductance element in which a part of a conductor film having a small outer diameter is cut by laser processing to form a spiral conductor pattern around a ferrite core,
While cutting a part of the conductor film of the conductor pattern of the outer diameter, the conductor film on the surface in contact with the smaller outer diameter part of the larger outer diameter also excludes the part connecting the spiral conductor pattern and the terminal part. A method for manufacturing an inductance element, comprising cutting. 4. A conductor film is formed on the surface of a prismatic or cylindrical ferrite core having large outer diameter portions at both ends,
In a method of manufacturing an inductance element in which a part of a conductor film having a small outer diameter is cut by laser processing to form a spiral conductor pattern around a ferrite core,
A portion of the conductor film of the conductor pattern having a small outer diameter is partially cut, and a portion of the conductor film in contact with the small outer diameter portion of the large outer diameter is also a portion connecting the spiral conductor pattern and the terminal portion. And cutting the spiral conductor pattern with a magnetic material of plastic ferrite.