JPH01199418A - Chip coil - Google Patents

Abstract

PURPOSE:To obtain the subject chip coil, having no decline and irregularity in reactance and inductance, with which sufficient shielding effect can be obtained by simplifying the process of manufacture by a method wherein a pair of external electrodes, which is connected to both ends of the winding of a conductor, are formed in a ring shape almost on both end parts of the outer circumferential surface of a pole-like ferrite core. CONSTITUTION:In a chip coil constituted by winding a wiring 2 on the outer circumferential surface of a pole-like ferrite core 1, or by fixing a spiral conductor 4, a pair of external electrodes 5a and 5b, which are connected to both ends of the wiring 2 or the spiral conductor 4, are formed in a ring shape on almost both end parts of the external circumferential surface of the ferrite core 1. Moreover, the above- mentioned wiring 2 or the conductor 4 is coated with the resin 10 containing about 70-90wt.% ferrite powder. Consequently, as there is no external electrode on the end face of the ferrite core whereon magnetic flux is concentrated, the generation of an eddy current can be prevented, and the problem pertaining to the decline and the irregularity in reactance and inductance can be solved. Also, a sufficient shield effect can be obtained by molding resin, and the time and the labor for sintering can be unnecessitated.

Description

[Detailed description of the invention] The peel part is Ω! The present invention relates to a chip coil that functions as an inductance element.

BACKGROUND OF THE INVENTION Conventionally, there are chip coils shown in FIGS. 6 and 7 as chip coils.

The chip coil shown in FIG. 6 has a coated winding 2 wound around the outer peripheral surface of a cylindrical ferrite core 1 shown in FIG. 8, and metal caps on both ends of the ferrite core 1. The external electrodes 3a and 3b are fitted into the external electrodes 3a and 3b. The outer electrode 3a is provided with a winding 2 whose coating is peeled off.
One end of the winding 2 is electrically connected to the external electrode 3b, and the other end of the winding 2 from which the coating is removed is electrically connected to the external electrode 3b.

On the other hand, in the chip fill shown in FIG. 7, a spiral conductor 4 is fixed to the outer peripheral surface of a cylindrical ferrite core 1, and metal cap-shaped external electrodes 3a and 3b are attached to both ends of the ferrite core 1. It is fitted. One end of the conductor 4 is electrically connected to the external electrode 3a, and the other end of the conductor 4 is electrically connected to the external electrode 3b.

Furthermore, the winding 2. Although not shown, paste-like ferrite is applied to the outer peripheral surface of the conductor 4 for shielding.
It is fired.

By the way, as a method for fixing the spiral conductor 4 on the outer circumferential surface of the ferrite core 1, a groove is formed in the part of the outer circumferential surface of the ferrite core 1 where the conductor 4 is to be fixed, and then a groove is formed on the entire outer circumferential surface of the ferrite core 1. There is a method in which a conductive material such as copper is fixed by a method such as plating, vapor deposition, or paste baking, and then the conductive material fixed to the part other than the groove is removed by polishing, leaving only the conductor 4. A conductive material such as copper is plated on the entire outer circumferential surface of the

It is fixed by methods such as vapor deposition and paste baking,
A method has been adopted in which parts other than the conductor 4 are trimmed with a laser to leave only the conductor 4.

Problems to be Solved by the Invention However, the conventional chip coil described above has the following problems. That is, in both the chip coils shown in FIGS. 6 and 7, cap-shaped external electrodes 3a and 3b made of metal are fitted onto the ends of the ferrite core 1. The end face of the ferrite core 1 is the part where the magnetic flux is most concentrated, and metal external electrodes 3a, 3 are placed in this part.
b exists, when the magnetic flux changes, the external electrodes 3a,
There was a problem in that eddy currents were generated in 3b, resulting in a loss of magnetic flux and a decrease in chip fill actance. In addition, magnetic flux is generated by the thin current generated in the external electrodes 3a and 3b, and this magnetic flux acts to prevent changes in the original magnetic flux of the chip coil, resulting in a decrease in the inductance of the chip coil or a variation in the inductance. There was a problem with this.

On the other hand, the ferrite layer for magnetic shielding must be coated and fired one by one, which has the problem of increasing the number of manufacturing steps. In order to eliminate the firing process,
JP-A-12140 proposes the use of a composite magnetic molding material made of a resin containing 30 to 70% ferrite powder.

However, in this method, the content of ferrite powder is 70
Since it is less than wt%, the effective transmittance is low and there is a problem that a sufficient shielding effect cannot be obtained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a chip coil that is free from deterioration and variation in reactance and inductance, and can obtain a sufficient shielding effect by simplifying the manufacturing process.

Means for Solving the Problems In order to solve the problems above, the chip coil according to the present invention has a winding wire wound around the outer peripheral surface of ferrite powder or a spiral conductor fixed to the outer peripheral surface of the ferrite powder. A pair of external electrodes connected to both ends of the conductor are formed in an annular shape almost at both ends of the outer peripheral surface of the ferrite core.
and the winding or conductor contains about 7 % of ferrite powder.
It is characterized by being fully coated with a resin containing 0 to 90 wt%.

In the configuration of m-month or more, a pair of external electrodes are formed in an annular shape at almost both end portions of the columnar ferrite core. In other words, no external electrodes are present on the end face of the ferrite core where magnetic flux is concentrated. This prevents the generation of eddy currents and solves problems such as decreases and variations in actance and inductance as a chip coil. In addition, the molding resin contains about 70 to 90 wt% of ferrite powder, which provides a sufficient shielding effect and eliminates the need for firing ferrite one by one as in the conventional method.

Embodiment FIG. 1 shows a first embodiment of the chip fill according to the present invention, in which 1 is a ferrite core, 2 is a winding wire, 58° 5b is an external electrode, and 10 is a molding resin for shielding.

The external electrodes 5ae and 5b are made of metal and have an annular shape, and are fitted to both ends of the outer peripheral surface of the ferrite core 1, respectively.

One end of the winding 2 from which the sheathing has been peeled is placed on the external electrode 5a, and one end of the winding 2 from which the sheathing has been peeled is placed on the external electrode 5b.
The other ends of the two are electrically connected to each other.

Further, the mold resin 10 covers the outer peripheral surface of the winding 2. This molding resin 10 contains about 70 to 90% ferrite powder, and about 1 to 10% and 4t% of fine powder silica is added to 100wt% of the resin. The reason why the ferrite powder is about 70 wt % or more is to obtain a sufficient magnetic shielding effect.

On the other hand, the reason why the ferrite powder was reduced to about 90 wt% or less was that
If it is contained in excess of this amount, even if finely powdered silica is contained while using a resin with a low melt viscosity, the fluidity will deteriorate and molding by transfer molding, injection molding, etc. will be impossible. In addition, fine powder silica is used to improve fluidity during molding and prevent the occurrence of "burrs", and if the fine powder silica is less than about 1% based on 100 wt% of resin, "r-burrs" are likely to occur. If it exceeds about 10%, the viscosity of the resin increases, and the molding pressure must be increased.

Regarding ferrite powder, one having a particle size of about several tens to 100 μm can be used, and in order to keep the melt viscosity low, it is preferable to use one with an average particle size of about 100 μm. Regarding fine powder silica, In order to prevent the occurrence of “paris”, the average particle size is 0.01-0.1 μm
It is preferable to use one.

FIG. 2 shows a second embodiment, which is the same as the first embodiment except that a conductor 4 is used in place of the winding i2 of the first embodiment. This conductor 4 is provided in a spiral shape on the outer peripheral surface of the ferrite core 1, and one end thereof is electrically connected to an external electrode 5a, and the other end thereof is electrically connected to an external electrode 5b.

FIG. 3 shows a third embodiment, in which a ferrite core 11 with a square cross section is used, and accordingly, the external electrodes 15a, 15b are also square and ring-shaped.

FIG. 4 shows a fourth embodiment, in which the coatings at both ends of the winding 2 wound around the outer peripheral surface of the ferrite core 1 are peeled off to form external electrodes 25a and 25b. In this fourth embodiment, the mold resin 10 has external electrodes 25a and 25b.
covers the entire winding 2 except for the portion connected to the wiring section of the circuit.

Note that the chip fill according to the present invention is not limited to the above embodiments, and can be variously modified within the scope of the gist.

For example, instead of using a metal molded product as the external electrode or using a part of the winding, a method such as baking a conductive paste may be used. Further, the mold resin may not only cover the windings and conductors, but also partially cover the external electrodes.

Furthermore, as shown in FIG. 5, external electrodes 35 having notches may be provided at both ends of the ferrite core 1.

As is clear from the above explanation, the chip coil of the present invention has a pair of annular external electrodes formed on almost both ends of the outer circumferential surface of a columnar ferrite core. Since there is no metal, that is, an external electrode, on the end face of the coil, it is possible to solve the problems that conventional chip coils have, such as a decrease in actance, a decrease in inductance, and variations in inductance. Moreover, the winding wire or conductor is made of ferrite powder of about 70 to 90%
Since it is coated with a resin containing 0wt%, not only can the magnetic shielding effect be sufficiently exhibited, but the shielding material can be easily coated with resin molding, eliminating the complicated process of firing ferrite as in the past. Can be done.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of a chip coil according to the present invention, and is a perspective view with a molded resin cut away, and FIG. 2 shows a second embodiment, a perspective view with a cutout of the molded resin. FIG. 3 is a perspective view showing a third embodiment. FIG. 4 is a perspective view showing a fourth embodiment. FIG. 5 is a perspective view showing a modification of the external electrode. FIGS. 6 and 7 are perspective views showing conventional chip coils, respectively. FIG. 8 is a perspective view showing a cylindrical ferrite core. 1.11... Ferrite core, 2... Winding wire, 4...
・Spiral conductor, 5a, 5b, 15a, 1
5b, 25a, 25b, 35...external electrode, 1
0...Mold tree JL Patent applicant Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] (1) In a chip coil in which a winding is wound around the outer circumferential surface of a columnar ferrite core or a spiral conductor is fixed, a pair of external electrodes are connected to both ends of the winding or spiral conductor. The ferrite core is formed in an annular shape at substantially both end portions of the outer circumferential surface of the ferrite core, and the winding wire or conductor is coated with a resin containing about 70 to 90 wt% of ferrite powder. chip coil.