JP2002110428A - Wire-wound common mode choke coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire-wound common mode choke coil which has a superior common mode impedance characteristic in a high frequency band and can effectively suppress the common mode noise of electronic equipment corresponding to the interface USB 2.0. SOLUTION: This wire-wound common mode choke coil 10 is constituted as a whole in a rectangular chip shape which is suitable for automatic surface mounting. Two insulated and covered conductors 8A and 8B are wound around the core of a magnetic core 1 carrying electrodes 7, etc., fitted to its flange sections 2 and 3, and the terminals of the conductors 8A and 8B are respectively electrically connected to the electrodes 7, etc. Then the surface of the core 5 between the flanges 2 and 3 is coated with a packaging resin material 9. Each of insulated and covered conductors 8A and 8B is constituted by coating the surface of a conductor, such as the copper wire, silver wire, etc., having a diameter of 20-100 μm with a ferromagnetic layer having a thickness of 0.1-10 μm and the ferromagnetic layer with an insulating material. Therefore, the common mode impedance characteristic of the choke coil 10 is improved in a high frequency band of several hundreds MHz or higher by a skin effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a winding type common mode choke coil suitable for a common mode noise countermeasure of various electronic devices handling a high frequency signal in a band of several hundred MHz.

[0002]

2. Description of the Related Art Conventionally, a winding type common mode choke coil used for measures against unnecessary radiation noise of power supply lines and common mode noise of high frequency signals has flanges on both sides of a winding core. Two to four insulated conductors are wound around the winding core of the ferrite magnetic core, in which a plurality of electrodes are formed from the peripheral surface to the end surface of the one flange, by winding several to several tens of turns by bifilar winding or the like. Line and
In some cases, the terminal at the beginning of winding and the terminal at the end of winding of the insulated conductor are electrically connected to the electrodes by soldering, thermocompression bonding, or the like.

Further, a plate-shaped magnetic core connecting between the flanges of the magnetic core is used as a magnetic shield, and after winding the winding, it is adhered to the upper peripheral surface of both flanges with an adhesive to form a substantially closed magnetic circuit structure. In some cases, the leakage magnetic flux is reduced to improve the impedance characteristics.

[0004] In some cases, a non-magnetic resin mold is used to form a chip while improving the common mode impedance characteristics at high frequencies.

By the way, a new interface USB (Universal Serial Communication) between a personal computer and a peripheral device is used.
Serial Bus) 2.0 has been released and the development of personal computers and peripheral devices has recently been in full swing.
Is characterized by a very high data transfer rate of 480 Mbps.
Handling a signal line having a high operating frequency of 480 MHz requires special consideration for suppressing distortion of a signal waveform and radiated electromagnetic noise. For example, in the wiring of the main board of a personal computer, it is necessary to take countermeasures against common mode noise such as eliminating impedance mismatch and suppressing radiated electromagnetic noise at the connector.

[0006] In the existing interface USB1.1, a ferrite bead inductor is widely used for the purpose of suppressing radiated electromagnetic noise of a connector portion, etc., but the applicable frequency of this ferrite bead inductor is up to several tens of MHz. It has been pointed out that USB 2.0 operating at 480 MHz is unsuitable because it rather reduces the high-frequency components of the signal waveform. In developing personal computers and peripheral devices compatible with the interface USB 2.0, it is recommended to use a common mode choke coil instead of a ferrite bead inductor in order to prevent common mode noise.

On the other hand, a wire material in which a ferromagnetic thin film layer is coated on the surface of a copper wire for a high-frequency coil and an insulating coating layer of polyurethane or the like is formed around the surface of the wire is already commercially available as a so-called "magnetic plated wire". I have. This reduces the effect of proximity effect generated in the coil by the magnetic shield of the ferromagnetic thin film layer, makes the current distribution of the conductor (copper wire) uniform, and reduces the effective resistance, thereby reducing high frequency loss by several tens. %, Reduced by several MHz
Q of coil applied in high frequency band of about 10 to 10 MHz
It is said that the characteristics can be improved.

For example, FIG. 8 shows f () of a coil A in which the above-mentioned magnetic plating wire (diameter: 80 μm) is wound tightly on a plastic bobbin of φ5.2 mm for 30 turns and a coil B in which a normal insulating coated conductor is wound under the same conditions. Frequency vs. Q (quality fa)
This is an actual measurement graph showing a comparison of the characteristics of the coil A, and it can be seen from the graph that the Q characteristic of the coil A is improved by several tens of% compared to the coil B in the measured frequency band of 4 MHz to 15 MHz. .

[0009]

SUMMARY OF THE INVENTION Interface US
In order to remove high-frequency common mode noise in the range of several hundred MHz or more to GHz such as B2.0, even if a common mode choke coil is used instead of a ferrite bead inductor as described above, a conventional common mode choke may be used. The applied frequency of the coil is a high frequency signal of about several MHz to 200 MHz, and there is a strong demand for improving the frequency characteristics of the common mode impedance in the band of several hundred MHz or more. SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to realize the above-described demand by repeatedly studying an insulated conductor used for a wire-wound common mode choke coil.

[0010]

According to the present invention, in order to solve the above-mentioned problems, (1) a plurality of insulated conductors are wound around a core of a magnetic core having a plurality of electrodes attached to a flange portion. In a wire-wound common mode choke coil having terminals each electrically connected to the electrode, the insulated conductor has a diameter of 2 mm.
The surface of the conductor wire of 0 μm to 100 μm has a thickness of 0.1 μm to
A winding type common mode choke coil having a structure in which the ferromagnetic layer is covered with a 10 μm ferromagnetic layer and the outer periphery of the ferromagnetic layer is coated with an insulating material. (2) Further, in the wire-wound common mode choke coil according to the above (1), the insulating-coated conductor is a pair in which a pair of parallel conductor wires whose surfaces are covered with a ferromagnetic layer are integrally coated with an insulating material. A wire-type common mode choke coil characterized by being a wire and being bifilar wound around a core of a magnetic core.

Note that the above-mentioned existing magnetic plated wire can be used as the insulated conductor having a ferromagnetic layer used in the present invention. In this case, the frequency band used in the present invention is not the 10 and several MHz band assumed for the conventional magnetic plated wire, but a high frequency band of several hundred MHz or more to GHz. It is not the purpose of improving the Q characteristic by reducing the proximity effect, but rather the skin effect of the high-frequency current or electric field flowing through the conductor (skin effec
An object of the present invention is to improve the common mode impedance characteristic in the high frequency band of several hundred MHz or more by increasing the effective resistance in the ferromagnetic layer around the conductor line by positively utilizing the method t).

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wound type common mode choke coil according to the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of a cross-sectional structure of an insulated conductor which is a component of the present invention.
(B) is a pair line. FIG. 2 is a diagram showing a wire-wound common mode choke coil according to the first embodiment of the present invention. FIG. 3 is a graph showing the common mode impedance (Z) versus frequency (f) characteristics of the prototype of the present invention. FIG. 4 is a diagram illustrating a wound-type common mode choke coil according to the second embodiment. FIG. 5 is a diagram of a wound common mode choke coil according to the third embodiment. 6 and 7 are views showing a wire-wound common mode choke coil according to another embodiment.

The basic structure of the wound type common mode choke coil according to the present invention is the same as that of the conventional type except for the insulated conductor used. That is, referring to the rectangular parallelepiped chip type wound common mode choke coil 10 shown in FIG. 2, a plurality of directly attached electrodes 7 are provided on the core 5 of the magnetic core 1 provided on the flanges 2 and 3. Is provided with a structure in which the insulated conductors 8A, 8B are wound and their terminals are electrically connected to the electrodes 7,... (The dashed-dotted line 6 indicates an external electrode that finally covers the electrode 7). Shown). In the wound common mode choke coil 10, in addition to the above basic structure, the outer resin material 9 covers the outer periphery of the winding so as to fill the gap between the flanges 2 and 3, so that the whole becomes a rectangular parallelepiped chip shape. The shape is suitable for automatic surface mounting.

In particular, the insulation-coated conductors 8A and 8B
Has a diameter φ1 as shown in the cross-sectional view of FIG.
A ferromagnetic layer 12 having a thickness d of 0.1 μm to 10 μm on the surface of a conductor wire 11 such as a copper wire or a silver wire having a thickness of 20 μm to 100 μm.
And the outer periphery of the ferromagnetic layer 12 is covered with an insulating material 13 such as a polyurethane resin.

The manner of winding the insulated conductors 8A and 8B around the winding core 5 is not limited, but is preferably a bifilar winding in order to form a high-coupling common mode choke coil. As shown in the cross-sectional view of FIG. 1B, a pair of parallel conductor wires 11 whose surfaces are covered with a ferromagnetic layer 12 are covered with an integral insulating material 13 to form a pair wire 15. Is suitable for increasing the degree of bonding.

Next, the insulated conductors 8A and 8B (φ1 = 70 μm) each having the ferromagnetic layer 12 are sized to a diameter of 0.6 mm.
The common-mode impedance (Z) vs. frequency (f) characteristics of a prototype of a wound-type common-mode choke coil wound five turns around a ferrite magnetic core as shown in the graph of FIG. It can be seen that the mode impedance Z sharply rises and is superior in the high-frequency characteristics as compared with the characteristics (broken line) in the case where a normal insulating-coated conductor under the same conditions is used. That is, it can be said that it is effective for removing common mode noise of a high frequency signal exceeding 400 MHz such as the operating frequency 480 MHz of the interface USB 2.0.

Considering the improvement of the high-frequency characteristics qualitatively, the thickness δ at which the strength of the electromagnetic field becomes 1 / e of the surface is given in terms of the magnetic permeability μ of the conductor, the electric conductivity σ, and the angular frequency ω of the electromagnetic field.
= [2 / μσω] 1/2 is called the skin depth. Since δ is inversely proportional to √μ and √ω, the effective resistance of the ferromagnetic conductor becomes large especially at high frequencies.

An insulated conductor (magnetic plated wire) used in the present invention in which the surface of a copper wire as the conductor wire 11 is covered with a ferromagnetic layer 12 of iron or stainless steel (which is also a conductor).
In 8A and 8B, as the frequency becomes higher, the current shifts to the vicinity of the outer periphery of the copper wire due to the skin effect, and the effective resistance naturally increases. In addition, the resistance contribution of the high-frequency current flowing through the ferromagnetic layer 12 increases. As a result, the increase in the effective resistance appears more remarkably than the general insulated wire. As the material used for the ferromagnetic layer 12, the higher the magnetic permeability, the better, and iron, stainless steel, steel (steel) can be applied. In order to reduce the normal mode impedance and enhance the skin effect, it is desirable to make the conductor wire 11 as thick as possible in comparison with δ.
In general, it is preferable that the thickness is thicker. However, in practice, the thickness of the insulated conductors 8A and 8B is determined best by the coil size, the number of turns, the strength of the magnetic core and other conditions.

The insulated conductors 8A and 8B or the pair wires 15 of the conductor wires 11 covered by the ferromagnetic layer 12 used in the present invention can be applied to wire-shaped common mode choke coils of various shapes and dimensions. Has already been mentioned. For example, the prototype is a wound common mode choke coil 20 having a plate-shaped magnetic core 17 as shown in FIG.
(The core is a circular cross section.)
2.0mm width, 1.2mm height, 1.5 height
mm. Further, the winding type common mode choke coil 30 of FIG. 5 has a height of 0.9 mm, which is further reduced in height, and the winding core has a rectangular cross section.

The electrically conductive connecting portions of the insulated conductors 8A and 8B to the electrodes 7 are provided on the side surfaces of the flanges 2 and 3 as shown in FIG. In this embodiment, the plate-shaped magnetic core 17 is bonded and fixed to the upper surfaces of the flanges 2 and 3 of the main body magnetic core 1 with a resin adhesive 18, and the insulated conductors 8 </ b> A and 8 </ b> B 3 and a wound common mode choke coil 50 shown in FIG.
The plate-shaped magnetic core 17 is adhered and fixed to the upper surface of the main body magnetic core 1 with an adhesive or the like, and the insulated conductors 8A and 8B are joined to the electrodes on the bottom surfaces of both flanges 2 and 3 by thermocompression bonding. Things are conceivable. In both FIGS. 6 and 7, it is preferable that the thermocompression bonding portion is embedded in the electrode material.

As described in detail above, the coil structure of the present invention is applicable to various types of wound type common mode choke coils, and the interface IEEE 139 is used.
Effective common mode noise countermeasures can be taken for personal computers and the like that handle high frequencies of several hundred MHz or more, such as USB 4 and USB 2.0.

[0023]

According to the wound type common mode choke coil of the present invention, the common mode impedance characteristic in a high frequency band of several hundred MHz or more is improved due to the above-described configuration, and the interface IEEE1394 or USB 2.0 is used.
It is effective for common mode noise countermeasures of electronic equipment corresponding to the above.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a cross-sectional structure of an insulated conductor which is a component of the present invention, wherein (a) is a single line and (b) is a pair line.

FIG. 2 is a diagram showing a wire-wound common mode choke coil according to the first embodiment of the present invention.

FIG. 3 is a graph showing common mode impedance (Z) versus frequency (f) characteristics of a prototype of the present invention.

FIG. 4 is a diagram illustrating a wound common mode choke coil according to a second embodiment.

FIG. 5 is a diagram of a wound common mode choke coil according to a third embodiment.

FIG. 6 is a diagram showing a wire-wound common mode choke coil according to another embodiment.

FIG. 7 is a diagram showing a wire-wound common mode choke coil according to another embodiment.

FIG. 8 is an actual measurement graph showing fQ characteristics of a coil in which a normal insulating-coated conductor is wound under the same conditions as a coil in which a magnetic plated wire is closely wound.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Magnetic core 2, 3 Flange 5 Core 6 External electrode 7 Electrode 8A, 8B Insulated conductor wire 9 Exterior resin material 10, 20, 30, 40, 50 Winding type common mode choke coil 11 Conductor wire 12 Ferromagnetic layer 13 Insulation Material 15 Pair wire 17 Plate magnetic core 18 Resin adhesive φ1 Diameter of conductor wire d Thickness of ferromagnetic layer

Claims (2)

[Claims] 1. A winding type common mode having a structure in which a plurality of insulating-coated wires are wound around a core of a magnetic core having a plurality of electrodes attached to a flange portion, and terminals of which are electrically connected to the electrodes. In a choke coil, the insulation-coated conductor has a structure in which a surface of a conductor wire having a diameter of 20 μm to 100 μm is covered with a ferromagnetic layer having a thickness of 0.1 μm to 10 μm and an outer periphery of the ferromagnetic layer is covered with an insulating material. A winding type common mode choke coil characterized by the following. 2. The wire-wound common mode choke coil according to claim 1, wherein the insulated conductor is a pair of parallel conductors whose surfaces are covered with a ferromagnetic layer and which are integrally covered with an insulating material. And a wound common mode choke coil characterized by being wound around a winding core of a magnetic core by bifilar.