JPH11162742A - Inductance element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inductance element in which the inductance is enhanced and magnetic flux leakage to outside is prevented, by making the inductance element a closed magnetic circuit by forming a resinous ferrite layer on a spiral pattern of a conductor. SOLUTION: A spiral pattern 12 of a conductor is formed on the side surface of a ferrite core 10, and terminal electrodes 14 are formed. Spacing between the conductor pattern 12 and the pattern itself are covered by a resinous ferrite layer 18, which is a magnetic material composed of a resin containing ferrite powder, so that the conductor pattern 12 is buried in the resinous ferrite layer 18. The resinous ferrite layer 18 may be formed after a layer of a non-magnetic material, such as glass, is formed on the spacing between the conductor pattern 12 and on the surface of the pattern itself. By the constitution above stated, it is possible to make the inductance element a closed magnetic circuit, enhancing the inductance and preventing interference to outside circuit elements.

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.

[0003] This type of inductance element is shown in FIG.
As shown in FIG. 5, a spiral conductive pattern 32 is formed around a ferrite core 30 and terminal electrodes 34 are formed at both ends. 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. . The conductor film is generally covered with a resin to protect the conductor film. However, it is difficult to increase the inductance due to the open magnetic circuit structure, and it is easy to cause interference with other elements arranged close to each other. An object of the present invention is to provide an inductance element that can improve the inductance by forming the inductance element into a closed magnetic path, and that can prevent leakage of magnetic flux to the outside.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by forming a resin ferrite layer on a spiral conductive pattern.

That is, in an inductance element in which a spiral conductive pattern is formed around a ferrite core by cutting a part of a conductive film formed on a side surface of a prismatic or cylindrical ferrite core by laser processing, a spiral spiral is formed. It is characterized by having a magnetic layer of plastic ferrite covering the conductor pattern.

In addition, a conductor film is formed on a side surface of a prismatic or cylindrical ferrite core, and a part of the conductor film is cut by laser processing to form a spiral conductor pattern around the ferrite core. The manufacturing method is characterized in that a magnetic layer of plastic ferrite which covers the spiral conductive pattern is formed.

[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 electroless plating followed by electrolytic plating) Drying Laser processing (heat treatment 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. In addition, when the Ni film is formed, it is possible to prevent erosion of silver forming a spiral conductive pattern. Also,
When heat treatment of ferrite is performed after laser processing, ferrite reduced and converted to 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 an epoxy resin.

[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.

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 thickening the conductor film, a silver conductor film is further formed 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,
Raise the temperature in air to 900 ° C at 20 ° C / min, 900
When a method of holding at 10 ° C. for 10 minutes and thereafter cooling was adopted, the composition returned to the original ferrite composition and the properties were recovered.

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 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 spiral conductor pattern 12 is formed on the side surface of the ferrite core 10 and the terminal electrode 14 is formed as in the conventional case. In the present invention, the space between and above the conductor patterns 12 is covered with the plastic ferrite 18. The plastic ferrite is a magnetic material containing ferrite powder in a resin, which means that the conductor pattern 12 is embedded in the magnetic material.

FIG. 2 shows another embodiment of the present invention, in which the ferrite core 20, the conductor pattern 22, and the terminal electrode 24 are the same as those in the above-mentioned example, but between the conductor pattern 22 and the conductor pattern 22. A nonmagnetic layer 26 such as glass is formed on the surface, and a plastic ferrite layer 28 is formed thereon. This is a structure in which the magnetic material between the conductor patterns 22 is replaced with a non-magnetic material.The magnetic permeability between the conductor patterns 22 decreases, and the magnetic field easily moves around the main magnetic path, so that the inductance can be increased. A suitable inductance element is obtained.

[0019]

According to the present invention, since the inductance element can be formed as a closed magnetic circuit, the inductance can be increased and interference with external circuit elements can be prevented.

Further, since the plastic ferrite layer also serves as a protective layer for the conductor pattern, a highly reliable inductance element having 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 an inductance element.

[Explanation of symbols]

 10, 20, 30: Ferrite core 12, 22, 32: Conductor pattern 26: Non-magnetic layer 18, 28: Plastic ferrite layer

Claims (4)

[Claims] In an inductance element in which a part of a conductor film formed on a side surface of a prismatic or cylindrical ferrite core is cut by laser processing to form a spiral conductor pattern around the ferrite core, a spiral conductor is provided. An inductance element comprising a plastic ferrite magnetic layer covering a pattern. 2. The inductance element according to claim 1, wherein a part of the conductor film formed on the side surface of the prismatic or cylindrical ferrite core is cut by laser processing to form a spiral conductor pattern around the ferrite core. An inductance element comprising a nonmagnetic insulating layer on the surface of a core between patterns, and a magnetic layer of plastic ferrite covering the spiral conductive pattern and the insulating layer. 3. An inductance element, wherein a conductor film is formed on a side surface of a prismatic or cylindrical ferrite core, and a part of the conductor film is cut by laser processing to form a spiral conductor pattern around the ferrite core. A method of manufacturing an inductance element, comprising forming a magnetic layer of plastic ferrite covering a spiral conductive pattern. 4. An inductance element in which a conductor film is formed on a side surface of a prismatic or cylindrical ferrite core, and a part of the conductor film is cut by laser processing to form a spiral conductor pattern around the ferrite core. In a manufacturing method, a nonmagnetic insulating layer is formed between spiral conductive patterns, and a magnetic layer of plastic ferrite covering the spiral conductive pattern and the insulating layer is formed. Method.