JP6273498B2 - Common mode noise filter - Google Patents

Description

  The present invention relates to a small and thin common mode noise filter used in various electronic devices such as digital devices, AV devices, and information communication terminals.

  As shown in FIG. 10, the conventional common mode noise filter of this type has a first coil 2 and a second coil 3 formed on a plurality of laminated insulator layers 1a to 1g. One coil 2 is configured by connecting spiral first and second coil conductors 4a and 4b, and the second coil 3 is configured by connecting spiral third and fourth coil conductors 5a and 5b. Further, the first and second coil conductors 4a and 4b constituting the first coil 2 and the third and fourth coil conductors 5a and 5b constituting the second coil 3 are alternately arranged. It had been. Then, the first coil conductor 4a and the third coil conductor 5a are magnetically coupled to form the first common mode filter unit 6, and the second coil conductor 4b and the fourth coil conductor 5b are magnetically coupled. The second common mode filter unit 7 is formed by coupling, and the first common mode filter unit 6 and the second common mode filter unit 7 are connected in series to improve the common mode impedance and reduce the common mode noise. I was trying to remove it.

  As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.

JP 2002-373810 A

  In mobile terminals as represented by recent smartphones, it is necessary to cover a plurality of communication methods and communication bands. In particular, in the cellular radio system, a wide communication band from 700 MHz to 3 GHz is used, and a noise attenuation characteristic in the frequency band is also desired in the noise filter.

  However, in the above-described conventional common mode noise filter, when common mode noise enters, the first common mode filter unit 6 and the second common mode filter unit 7 function as inductors, and further in the stacking direction. Because of magnetic coupling, the impedance between the input and output becomes high, and this causes a potential difference between the input and output, so that stray capacitance occurs between the input and output. As a result, self-resonance occurs when the frequency is increased, so that the common mode impedance is reduced in the high frequency region above the self resonance frequency, thereby deteriorating the attenuation characteristics of the common mode noise in the high frequency region. .

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a common mode noise filter capable of improving the attenuation characteristics of common mode noise in a high frequency region.

In order to achieve the above object, according to the present invention, the first coil is constituted by the spiral first coil conductor and the second coil conductor, and the second coil is constituted by the spiral third coil conductor and the second coil conductor. 4 coil conductors, the first coil conductor, the third coil conductor, the second coil conductor, and the fourth coil conductor are stacked in that order from the top, and further, the first coil conductor And the third coil conductor are magnetically coupled to form a first common mode filter portion, and the second coil conductor and the fourth coil conductor are magnetically coupled to form a second common mode filter portion, The first common mode filter unit and the second common mode filter unit are connected in series, and a metal conductor connected to the ground is laminated between the second coil conductor and the third coil conductor, Metal conductor Opening the end, the first via electrode when viewed from the top, and at least one of the second via electrode a structure which is adapted to surround the metal conductor. Furthermore, the metal conductor is formed in a spiral shape, the number of turns of the metal conductor is made smaller than the number of turns of the second and third coil conductors, and the metal conductor is placed on the innermost side of the second and third coil conductors in a top view. It was made to be provided at the location.

  In the common mode noise filter of the present invention, when common mode noise enters, the noise is attenuated by the action of the inductors of the first common mode filter unit and the second common mode filter unit, and further in the high frequency region. Since a low impedance component is added by a capacitance component generated between the second coil conductor or the third coil conductor and the metal conductor connected to the ground, the first common mode filter unit and the second common mode The impedance of the filter section gradually rises with the frequency, which increases the self-resonance frequency, and also allows high-frequency common mode noise to be bypassed to the ground in the high-frequency region. Can improve the attenuation characteristics of common mode noise in the high frequency range In which an excellent effect of being able to obtain a noise attenuation characteristic of the band.

1 is an exploded perspective view of a common mode noise filter according to Embodiment 1 of the present invention. Perspective view of the common mode noise filter Circuit diagram of the common mode noise filter Comparison of common mode noise attenuation characteristics of the common mode noise filter and conventional common mode noise filter The figure which showed the frequency characteristic of the mode conversion in Embodiment 1 and Embodiment 2 Top view of the main part of the common mode noise filter Top view of the main part of the common mode noise filter The disassembled perspective view of the common mode noise filter in Embodiment 2 of this invention Circuit diagram of the common mode noise filter Exploded perspective view of a conventional common mode noise filter

(Embodiment 1)
1 is an exploded perspective view of a common mode noise filter according to Embodiment 1 of the present invention, FIG. 2 is a perspective view of the common mode noise filter, and FIG. 3 is a circuit schematic diagram of the common mode noise filter.

  As shown in FIGS. 1 to 3, the common mode noise filter according to the first exemplary embodiment of the present invention includes first to eighth insulator layers 11 a to 11 h and first to eighth insulator layers 11 a to 11 h. The first coil 12, the second coil 13 and the metal conductor 14 connected to the ground, the first to eighth insulator layers 11a to 11h, the first and second coils 12, 13 and And a laminated body 15 composed of a metal conductor 14.

  Further, the first coil 12 is composed of the spiral first coil conductor 16 and the second coil conductor 17, and the second coil 13 is composed of the spiral third coil conductor 18 and the fourth coil conductor. 19, the first coil conductor 16, the third coil conductor 18, the second coil conductor 17, and the fourth coil conductor 19 are laminated in this order from the top, and further, the first coil conductor 16 and the third coil conductor 19 are stacked. The first common mode filter unit 20 is formed by magnetically coupling the two coil conductors 18, and the second common mode filter unit 21 is formed by magnetically coupling the second coil conductor 17 and the fourth coil conductor 19. The first common mode filter unit 20 and the second common mode filter unit 21 are connected in series.

  The other end 14 b of the metal conductor 14 is opened, and the metal conductor 14 is laminated between the second coil conductor 17 and the third coil conductor 18.

  In the above configuration, the first to eighth insulator layers 11a to 11h are stacked in order from the bottom, and the second to seventh insulator layers 11b to 11g are not ferromagnetic materials, for example, Cu- The sheet is formed of a nonmagnetic material such as Zn ferrite or glass ceramic. The first and eighth insulator layers 11a and 11h are formed of a magnetic material such as Ni—Cu—Zn ferrite formed in a sheet shape.

  In addition, you may form the magnetic substance as a magnetic core in the center part of the 2nd-7th insulator layers 11b-11g, and comprise all the 1st-8th insulator layers 11a-11h with a nonmagnetic material. May be. The number of sheets constituting the first to eighth insulator layers 11a to 11h is not limited to the number shown in FIG.

  The first coil 12 includes a spiral first coil conductor 16 and a spiral second coil conductor 17, and the second coil 13 includes a spiral third coil conductor 18 and A spiral fourth coil conductor 19 is used.

  The first to fourth coil conductors 16 to 19 are each formed by spirally plating or printing a conductive material such as silver.

  At this time, the first coil conductor 16 is the upper surface of the sixth insulator layer 11f, the second coil conductor 17 is the upper surface of the third insulator layer 11c, and the third coil conductor 18 is the fifth insulator layer. The upper surface of 11e and the fourth coil conductor 19 are respectively formed on the upper surface of the second insulator layer 11d.

  That is, the first and second coil conductors 16 and 17 constituting the first coil 12 and the third and fourth coil conductors 18 and 19 constituting the second coil 13 are laminated alternately. Has been. Here, the first coil conductor 16 and a part of the third coil conductor 18 are arranged at substantially the same position in a top view, and are magnetically coupled by setting the winding direction to the same direction, so that the first common mode filter Similarly, a part 20 of the second coil conductor 17 and the fourth coil conductor 19 are arranged at substantially the same position in the top view, and the winding direction is also made the same direction so as to be magnetically coupled. A second common mode filter unit 21 is formed.

  The first coil conductor 16 and the second coil conductor 17 are connected to each other through the first via electrodes 12a formed in the fourth to sixth insulator layers 11d to 11f, respectively. The coil 12 is configured. Further, the third coil conductor 18 and the fourth coil conductor 19 are connected to each other via the second via electrodes 13a formed in the third to fifth insulator layers 11c to 11e, respectively. The coil 13 is configured.

  The first via electrodes 12a are provided at the same position when viewed from above, and the second via electrodes 13a are also provided at the same position when viewed from above. Further, the first via electrode 12a and the second via electrode 13a are formed by drilling holes in predetermined portions of each insulator layer with a laser and filling the holes with silver.

  Further, the metal conductor 14 is formed on the upper surface of the fourth insulator layer 11d by printing or plating a metal such as silver. Therefore, the metal conductor 14 is disposed between the second coil conductor 17 and the third coil conductor 18, that is, between the first common mode filter unit 20 and the second common mode filter unit 21. .

  Further, one end portion 14a of the metal conductor 14 is connected to the ground via an external electrode, but the other end portion 14b is opened and is not connected to an external electrode.

  Here, since the shape of the metal conductor 14 is spiral as shown in FIG. 1, the capacitor component between the metal conductor 14 and the second and third coil conductors 17 and 18 can be easily adjusted. Since the frequency characteristic of common mode noise attenuation can be adjusted, it is more preferable.

  And when the shape of the metal conductor 14 is spiral, it is good also as the same direction as the winding direction of the 1st-4th coil conductors 16-19, and good also as a reverse direction.

  Furthermore, the number of turns of the metal conductor 14 is made smaller than the number of turns of the second and third coil conductors 17 and 18.

  When common mode noise enters, both the first common mode filter unit 20 and the second common mode filter unit 21 function as inductors, but at the same time, the first common mode filter unit 20 and the second common mode filter unit 20 The filter unit 21 is further magnetically coupled in the stacking direction and functions as a large inductor. And since it is set as the structure which open | released the one end 14b of the spiral metal conductor 14, it becomes difficult to shield the magnetic coupling of the 1st common mode filter part 20 and the 2nd common mode filter part 21, Therefore Common mode impedance Of the common mode noise can be prevented. Actually, when the spiral metal conductor 14 forms one closed loop around both the first via electrode 12a and the second via electrode 13a in top view and is connected to the ground, the other end 14b is It has been confirmed that the impedance of the common mode is reduced by about 35% as compared with the single spiral metal conductor 14 opened and opened.

  In FIG. 1, a spiral metal conductor 14 surrounds both the first via electrode 12a and the second via electrode 13a in a top view, but the first via electrode 12a and the second via electrode 12a One of the via electrodes 13a may be surrounded. At this time, one or more metal conductors 14 surround the first via electrode 12a and the second via electrode 13a. Moreover, you may comprise places other than the part surrounding the circumference | surroundings of the 1st via electrode 12a of the metal conductor 14, and the 2nd via electrode 13a in other shapes, such as a meandering shape.

  Further, the metal conductor 14 is provided at a position located on the innermost side of the second and third coil conductors 17 and 18 in a top view.

  And the laminated body 15 is formed as shown in FIG. 2 by the above-mentioned structure. Further, first to fourth external electrodes 22 to 25 are provided on both end faces of the laminate 15, and the first to fourth external electrodes 22 to 25 are respectively first to fourth coil conductors. 16 to 19, that is, both ends of the first coil 12 and both ends of the second coil 13 are connected. Furthermore, on both side surfaces of the multilayer body 15, fifth external electrodes 26 connected to the one end portion 14 a of the metal conductor 14 are formed.

  Furthermore, the first to fifth external electrodes 22 to 26 are formed by printing silver on the end face and the side face of the laminate 15, and a nickel plating layer is formed on these surfaces by plating. A low melting point metal plating layer such as tin or solder is formed on the surface of the nickel plating layer by plating.

  As described above, in the common mode noise filter according to the first exemplary embodiment of the present invention, when common mode noise enters, the first common mode filter unit 20 and the second common mode filter unit 21 function as inductors. The noise is attenuated by the action, and in the high frequency region, a low impedance component is added due to a capacitance component generated between the second coil conductor 17 or the third coil conductor 18 and the metal conductor 14 connected to the ground. Therefore, the impedances of the first common mode filter unit 20 and the second common mode filter unit 21 gradually increase with the frequency, thereby increasing the self-resonance frequency, and in the high frequency region. High frequency common mode noise can be bypassed to ground, which results in It is possible to improve the attenuation characteristics of the common mode noise in the frequency range, in which there is an advantage that it is possible to obtain the noise attenuation characteristic of a wide band.

  That is, when common mode noise enters, the first common mode filter unit 20 and the second common mode filter unit 21 operate as inductors. However, in the conventional example, the impedance increases as the frequency increases, and the common mode A potential difference occurs at the input / output part of the filter, stray capacitance occurs between the input and output, and self-parallel resonance occurs. On the other hand, in this embodiment, the first common mode filter unit 20 and the second common mode filter unit 21 operate as inductors to remove common mode noise, and when the frequency increases, the second coil conductor 17 and the third Impedance is reduced due to the capacitive component between the coil conductor 18 and the metal conductor 14 and the potential difference between the input and output of the common mode filter is prevented from becoming too high, and the generation of stray capacitance between the input and output is suppressed. In addition, the self-parallel resonance frequency becomes higher and the common mode noise to the ground can be bypassed by the capacitance component between the second coil conductor 17, the third coil conductor 18 and the metal conductor 14, so that the wideband Can attenuate common mode noise.

  Accordingly, the self-resonant frequency of the first common mode filter unit 20 and the second common mode filter unit 21 and the capacitance component between the second coil conductor 17, the third coil conductor 18, and the metal conductor 14 are more affected. Since the common mode noise in the high frequency band can be bypassed to the ground, the common mode noise can be attenuated in a wide band.

  Here, FIG. 4 shows a graph comparing the common mode noise attenuation characteristics of the common mode noise filter according to the first embodiment of the present invention and the conventional common mode noise filter.

  As is apparent from FIG. 4, the common mode noise filter according to the first embodiment of the present invention can attenuate the common mode noise in the high frequency region more than the conventional common mode noise filter. Common mode noise in a wide band can be attenuated in a communication frequency band of 700 MHz to 3 GHz.

  Further, in the common mode noise attenuation characteristics in FIG. 4, the self-resonant frequency is in the vicinity of 800 MHz in the conventional example, whereas in the first embodiment, the self-resonant frequency extends to near 1.5 GHz and operates as an inductor. Thus, the common mode attenuation can be achieved, and a high common mode attenuation capability can be realized up to the resonance frequency band of the capacitive component between the metal conductor 14 connected to the ground up to about 2.4 GHz.

  However, in this configuration, stray capacitance is generated between the second and third coil conductors 17 and 18 and the metal conductor 14, and the balance of the differential (differential) signal is lost, so that the differential mode is changed to the common mode. Mode conversion may occur, and signal quality may be degraded.

  Here, in the case where the metal conductor 14 is provided at the outermost position of the second and third coil conductors 17 and 18 in a top view, the vicinity of the external electrode 24 of the third coil conductor 18, A stray capacitance is generated between the coil conductor 17 and the vicinity of the external electrode 23, that is, between the input and output terminals of the common mode filter, via the spiral metal conductor 14, and the differential (differential) signal balance is lost. Mode conversion occurs and signal quality deteriorates. However, as shown in FIG. 1, in the first embodiment, the metal conductor 14 is located on the innermost side of the second and third coil conductors 17, 18 in a top view, that is, the first coil 12 and the first coil 12. 2 is disposed in the vicinity of the via electrodes 12a and 13a that connect the laminated layers in the central portion of each coil 13, stray capacitance between the input and output terminals is less likely to occur. Therefore, signal quality is unlikely to deteriorate.

  Note that the metal conductor 14 is provided at the innermost position of the second and third coil conductors 17 and 18 in a top view, which does not necessarily mean that the metal conductor 14 and the second and third coil conductors 17 and 18 are provided. Does not mean that the metal conductor 14 is formed in the vicinity of the via electrodes 12a and 13a.

  That is, when the metal conductor 14 is provided at the outermost position of the second and third coil conductors 17 and 18 in the top view (referred to as outer winding), the metal conductor 14 is second in the top view. When the third coil conductors 17 and 18 are provided at the innermost location (referred to as inner winding), the mode conversion characteristics are better.

  FIG. 5 shows frequency characteristics of mode conversion from the differential mode to the common mode in the common mode noise filter of the first embodiment when the spiral metal conductor 14 is wound outward and when it is wound internally. ing.

  As can be seen from FIG. 5, when the metal conductor 14 is externally wound, it rapidly deteriorates in a high frequency region of 1 GHz or higher, and it can be seen that mode conversion is greatly suppressed by making the inner conductor.

  Further, between the first to fourth external electrodes 22 to 25 and the fifth external electrode 26, an electrostatic passage portion 27 that normally functions as an insulator and is energized when a voltage of a predetermined level or higher is applied is formed. May be.

  As shown in FIG. 6, the structure of the static electricity passing portion 27 is connected to the top surface of the static electricity passing insulator layer 28 with the first to fifth external electrodes 22 to 26, respectively (first to fourth). First to fifth electrostatic passages connected to the first to fourth coil conductors 16 to 19 via the external electrodes 22 to 25 and connected to the metal conductor 14 via the fifth external electrode 26. First conductors 16a to 19a, 14c are formed, and first to fourth static electricity passing conductors 16a to 19a connected to the first to fourth coil conductors 16 to 19 and a fifth conductor connected to the metal conductor 14 are formed. A gap is formed between the electrostatic passage conductor 14c and the voltage-dependent resistance material 29 covers the gap.

  The static electricity passing insulator layer 28 is different from the first insulator layer 11a, the seventh insulator layer 11g, or the first to eighth insulator layers 11a to 11h. It is.

  Further, the voltage-dependent resistance material 29 may be omitted, but the function as the static electricity passing portion 27 is further improved when the voltage-dependent resistance material 29 is provided.

  Here, as the voltage-dependent resistance material 29, a varistor material such as a ceramic material mainly composed of zinc oxide, a metal powder containing at least one of aluminum, nickel and copper, and silicon, epoxy and phenol A material made of a resin containing at least one or the like can be used.

  Furthermore, as shown in FIG. 7, the fifth static electricity passing conductor 14 c may be formed on the upper surface of another static electricity passing insulator layer 28 a adjacent to the static electricity passing insulator layer 28.

  In this case, a part of the first to fourth electrostatic passage conductors 16a to 19a and a part of the fifth electrostatic passage conductor 14c are opposed to each other in a top view, and the first to fourth electrostatic passage conductors are used. The static electricity insulating layers 28 and 28a between the conductors 16a to 19a and the fifth static electricity passing conductor 14c are formed of a voltage-dependent resistance material 29. At this time, the static electricity passing portion 27 includes the first to fourth static electricity passing conductors 16a to 19a, the fifth static electricity passing conductor 14c, and the static electricity passing insulator layers 28 and 28a therebetween.

  With the above configuration, the metal conductor 14 has both a function of bypassing high-frequency common mode noise to the ground and a function of releasing overvoltage to the ground. Therefore, when a normal current flows, the static electricity passing portion 27 becomes an insulator and functions as a normal common mode noise filter. When a voltage higher than a predetermined voltage is applied, the static electricity passing portion 27 is energized. The current flows from the first to fourth external electrodes 22 to 25 to the ground through the fifth external electrode.

  Further, since the metal conductor 14 and the second and third coil conductors 17 and 18 are adjacent to each other, the dielectric breakdown is easily caused by static electricity between them, but the fifth external electrode 26 and the second and third external electrodes 23 are easily formed. , 24, that is, between the metal conductor 14 and the second and third coil conductors 17, 18, it is difficult to break down the dielectric. Note that the static electricity passing portion 27 may not be provided between the fifth external electrode 26 and the first and fourth external electrodes 22 and 25. preferable.

(Embodiment 2)
FIG. 8 is an exploded perspective view of the common mode noise filter according to Embodiment 2 of the present invention. In the second embodiment of the present invention, components having the same configurations as those of the first embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  The second embodiment of the present invention differs from the first embodiment of the present invention described above in that a third coil conductor 18 and a fourth coil conductor constituting the second coil 13 are shown in FIG. The first coil conductor 16 and the second coil conductor 17 constituting the first coil 12 are arranged between the first coil 12 and the second coil conductor 19. Here, a circuit schematic diagram in this case is shown in FIG.

  In the first embodiment, when a differential signal is input, the second coil conductor 17 and the third coil conductor 18 having different potentials face each other in the stacking direction. The mode conversion from the differential mode to the common mode occurred due to the stray capacitance, and the signal quality was deteriorated. In the second embodiment, the first coil conductor 16 and the second coil facing each other in the stacking direction are used. Since the potential is the same as that of the conductor 17 and stray capacitance is less likely to occur, mode conversion from the differential mode to the common mode can be greatly reduced, and deterioration of signal quality can be prevented.

  FIG. 5 shows a comparison of the frequency characteristics of the mode conversion from the differential mode to the common mode in the second embodiment, together with the frequency characteristics of the mode conversion in the first embodiment.

  As is clear from FIG. 5, it can be seen that mode conversion is suppressed more significantly in the second embodiment than in the first embodiment.

  Further, when a differential signal is input, the first coil conductor 16 and the second coil conductor 17 are at the same potential, so that no stray capacitance is generated, and the differential signal is caused by a decrease in the differential mode characteristic impedance. This has the effect of preventing the deterioration.

  Also in the present embodiment, the common mode noise attenuation characteristic in the high frequency region can be improved and the common mode noise attenuation characteristic in a wide band can be realized as in the first embodiment of the present invention.

  In the above-described common mode noise filter according to the first and second embodiments of the present invention, the first coil 12 and the second coil 13 are provided, but two or more arrays are provided. It is good also as a type.

  Furthermore, although what provided the 1st common mode filter part 20 and the 2nd common mode filter part 21 each was demonstrated, you may provide two or more.

  The common mode noise filter according to the present invention has an effect of improving the attenuation characteristic of common mode noise in a high frequency region, and in particular, noise of various electronic devices such as digital devices, AV devices, and information communication terminals. It is useful in a small and thin common mode noise filter used as a countermeasure.

11a-11h 1st-8th insulator layer 12 1st coil 13 2nd coil 14 Metal conductor 15 Laminated body 16 1st coil conductor 17 2nd coil conductor 18 3rd coil conductor 19 4th Coil conductor 20 First common mode filter portion 21 Second common mode filter portion 22 to 26 First to fifth external electrodes

Claims (2)

A plurality of insulator layers;
Metal conductors connected to the first and second coils and the ground formed in the plurality of insulator layers;
A laminate composed of the plurality of insulator layers, the first and second coils, and the metal conductor;
The first and fifth external electrodes respectively connected to both ends of the first and second coils and one end of the metal conductor on the surface of the laminate,
The first coil is configured by connecting a spiral first coil conductor and a second coil conductor via a first via electrode, and the second coil is configured by a second via electrode. A spiral third coil conductor and a fourth coil conductor are connected to each other,
The first coil conductor, the third coil conductor, the second coil conductor, and the fourth coil conductor are stacked in this order from the top, or the third coil conductor and the first coil are stacked from the top. Laminating the conductor, the second coil conductor, and the fourth coil conductor in this order,
Further, the first coil conductor and the third coil conductor are magnetically coupled to form a first common mode filter portion, and the second coil conductor and the fourth coil conductor are magnetically coupled to form a second Forming a common mode filter section, connecting the first common mode filter section and the second common mode filter section in series;
And while laminating | stacking the said metal conductor between the said 2nd coil conductor and the said 3rd coil conductor, the other end part of the said metal conductor is open | released, and the said 1st via electrode, 2nd in top view The metal conductor surrounds at least one of the via electrodes of
Further, the metal conductor is formed in a spiral shape, the number of turns of the metal conductor is less than the number of turns of the second and third coil conductors, and the metal conductors are viewed from the top in the second and third coils. A common mode noise filter provided at the innermost position of the conductor . At least between the second external electrode and the fifth external electrode, and between the third external electrode and the fifth external electrode, usually functions as an insulator and a voltage of a predetermined level or higher is applied. The common mode noise filter according to claim 1, wherein a static electricity passage portion to be energized is formed.

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