JP4415530B2 - Connection structure of differential line and noise filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a connection structure of a differential line and a noise filter which are interposed in a differential line and attenuate common mode noise.
[0002]
[Background]
Common mode noise that causes electromagnetic noise radiation flows through the differential line 32 including the line 30 and the line 31 as shown in FIG. 10 due to various causes. For this reason, common mode noise is often removed by providing a common mode choke coil 33 in the differential line 32.
[0003]
[Problems to be solved by the invention]
However, the common mode noise flowing through the differential line 32 may be reflected at the connection portion between the differential line 32 and the common mode choke coil 33. Depending on the frequency of the common mode noise, resonance of the common mode noise may occur between the circuit and the common mode choke coil 33, for example. Due to such reflection and resonance of common mode noise, the waveform of the signal flowing through the differential line 32 is disturbed, and there is a risk of occurrence of a problem that information cannot be transmitted accurately.
[0004]
The present invention has been made to solve the above problems, and its purpose is to provide a differential line capable of attenuating the common mode noise of the differential line without interfering with the accurate information transmission of the differential line. It is to provide a connection structure with a noise filter.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration as means for solving the above problems. That is, the present invention comprises a differential line constituted by juxtaposed two conductors of the line, the noise filter for attenuating common mode noise flowing differential lines built into split site of the differential line The noise filter includes a base, a ground electrode that is a ground portion formed on both the front and back surfaces of the base, and a magnetic layer that is laminated on the surface side of each ground electrode on both the front and back surfaces. A body layer and a line in the filter forming a pair formed by two lines arranged in parallel on the surface of at least one side of these magnetic layers with a gap therebetween, and One of the two lines forming the pair of filter-in-filter lines is the division of the conductor line on one side of the two conductor lines constituting the differential line. Are connected in series to the line of the conductor on one side in a manner of connecting both ends of the unit, and the other line of the two lines forming the paired filter line is the differential line. Of the two conductor lines constituting the line, the both ends of the divided part of the conductor line of the other side are connected in series to the conductor line of the other side, and the divided part of the differential line The common mode noise flowing through the pair of filters in the filter is attenuated by magnetic loss.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described below with reference to the drawings. For convenience of explanation, before describing an embodiment of the present invention, a reference example for explaining the present invention will be described first.
[0007]
1A is a schematic perspective view showing the noise filter of the first reference example, and FIG. 1B is an exploded view schematically showing the noise filter shown in FIG. Yes.
[0008]
In the noise filter 1 of the first reference example, a ground electrode 3 as a ground portion is formed on the surface of the base 2, and a magnetic layer 4 is laminated on the surface side of the ground electrode 3. In the first reference example, the base 2 on which the ground electrode 3 is formed and the magnetic layer 4 are integrated by, for example, firing.
[0009]
When the base body 2 and the magnetic layer 4 are integrated by firing in this way, the base body 2 is configured in order to prevent the base body 2 and the magnetic body layer 4 from being cracked during firing. It is preferable that the material and the material constituting the magnetic layer 4 have substantially the same coefficient of thermal expansion. Considering this, for example, the base 2 and the magnetic layer 4 are made of the same magnetic material (for example, ferrite). Of course, the base 2 and the magnetic layer 4 may be made of different materials.
[0010]
On the surface of the magnetic layer 4, two in-filter lines 5 and 6 are arranged side by side with a gap therebetween. These in-filter lines 5 and 6 are made of, for example, a metal film formed on the surface of the magnetic layer 4 by using a film forming technique such as vapor deposition or printing, and the shape thereof is a spiral shape. In addition, between the filter inner line 5 and the filter inner line 6, the filter inner lines 5, 6 are substantially equally spaced over almost the entire length of the filter inner lines 5, 6. This is an interval that can function as a track.
[0011]
Line connection electrodes 8a, 8b, 9a, 9b and ground connection electrodes 10a, 10b are respectively provided on the laminated body 7 of the base 2, the ground electrode 3, and the magnetic layer 4, and in the example of FIG. It is formed from the part to the edge of the bottom through the side. One end of the in-filter line 5 is connected to the line connecting electrode 8a, and the other end of the in-filter line 5 is connected to the line connecting electrode 8b. One end of the in-filter line 6 is connected to the line connecting electrode 9a, and the other end of the in-filter line 6 is connected to the line connecting electrode 9b. Furthermore, the ground connection electrodes 10a and 10b are connected to the ground electrode 3, respectively.
[0012]
The noise filter 1 of the first reference example is configured as described above. For example, the noise filter 1 is surface-mounted on a circuit board on which a differential line is formed. At this time, as shown in FIG. 2A, for example, line connection electrodes 8a, 8b, 9a, 9b is connected to the lines 13 and 14 to be connected to the differential line 12 formed on the circuit board and the like, and the ground connection electrodes 10a and 10b are respectively connected to the ground connection line formed on the circuit board and the like, for example. 15 is aligned so as to be connected via solder.
[0013]
The line connection electrodes 8a, 8b, 9a and 9b are connected to the lines 13 and 14 to be connected to the differential line 12 via solder, respectively, as shown in the equivalent circuit of FIG. In addition, the in-filter lines 5 and 6 are connected to the separate lines 13 and 14 constituting the differential line 12 and are interposed in the differential line 12, respectively.
[0014]
In the noise filter 1 of the first reference example, since the common mode noise has the same direction of the current flowing through the in-filter lines 5 and 6, the in-filter lines 5 and 6 are 1 Act like a book track. Further, the in-filter lines 5 and 6 are formed on the surface of the magnetic layer 4. Therefore, for the common mode noise, the in-filter lines 5 and 6 have an inductance L as shown in the equivalent circuit of FIG. 3 and are connected to the ground electrode 3 by the dielectric constant of the magnetic layer 4. Has a capacity C.
[0015]
That is, the in-filter lines 5 and 6 function equivalently to a distributed constant circuit for common mode noise, and the inductance L and the capacitance C of the common mode noise flowing through the in-filter lines 5 and 6 are kept constant. In the drooping frequency range, it is transmitted without loss. However, as the frequency increases, with the change in the magnetic permeability of the magnetic layer 4, a magnetic loss R is generated in the inductance L as in the equivalent circuit of FIG. 4, so that the common mode noise is attenuated. Become.
[0016]
On the other hand, the current component in the normal mode (that is, the normal current component) is such that the energizing directions of the currents flowing through the filter lines 5 and 6 are opposite to each other and the energizing amounts are substantially equal. Magnetic fluxes based on the normal mode currents of the inner lines 5 and 6 cancel each other. For this reason, in the normal mode current, the in-filter lines 5 and 6 behave as just lines, and no magnetic loss occurs.
[0017]
Unlike the common mode choke coil, the noise filter 1 of the first reference example can substantially remove the common mode noise from the differential line 12 by attenuating the common mode noise using magnetic loss. Since the noise filter 1 is not provided with the choke coil but the in-filter lines 5 and 6 in the differential line 12, common mode noise is reflected at the connection part between the differential line 12 and the noise filter 1. In addition, problems such as resonance of common mode noise between the noise filter 1 and the circuit side can be suppressed.
[0018]
Therefore, the disturbance of the signal waveform due to reflection or resonance of common mode noise can be prevented. As a result, common mode noise can be effectively attenuated without disturbing the transmission of information.
[0019]
Incidentally, the noise filter 1 of the first reference example has a property of transmitting the common mode noise when the frequency of the common mode noise is low, and operates like a low-pass filter. That is, the noise filter 1 has a transmission region and an attenuation region of common mode noise depending on the frequency. The transmission region and the attenuation region are determined by the constituent material of the magnetic layer 4. In the first reference example, considering the frequency of common mode noise, the constituent material of the magnetic layer 4 is selected so that the common mode noise to be attenuated can be surely attenuated.
[0020]
Further, in order to provide a capacity between the in-filter lines 5 and 6 and the ground electrode 3, the distance between the in-filter lines 5 and 6 and the ground electrode 3 needs to be narrow to some extent. Therefore, the magnetic layer 4 is formed very thin, for example, 100 μm. In addition, if the base 2 is formed as thin as the magnetic layer 4, the entire noise filter 1 becomes very thin, and the strength of the noise filter 1 becomes weak. Therefore, in order to enhance the strength of the noise filter 1, the base 2 is formed thicker than the magnetic layer 4 in the first reference example.
[0021]
The second reference example will be described below. In the description of the second reference example, the first reference example and same components are denoted by the same reference numerals, duplicate description is omitted.
[0022]
FIG. 5A is a schematic perspective view showing the noise filter of the second reference example, and FIG. 5B is an exploded view schematically showing the noise filter of FIG. 5A. .
[0023]
In the second reference example, in addition to the configuration of the first reference example, an insulating layer 17 is laminated on the surface side of the in-filter lines 5 and 6, and a ground electrode 18 as a ground portion is formed on the surface of the insulating layer 17. Has been. Further, an insulating layer 19 is laminated on the surface side of the ground electrode 18. The insulating layer 19 can protect the ground electrode 18.
[0024]
The base body 2 on which the ground electrode 3 is formed, the magnetic layer 4 on which the filter lines 5 and 6 are formed, the insulating layer 17 on which the ground electrode 18 is formed, and the insulating layer 19 are integrated by, for example, firing. Is done. As described in the first reference example, in order to prevent the base 2, the magnetic layer 4, and the insulating layers 17 and 19 from being cracked during firing, the base 2, the magnetic layer 4, The constituent materials for the insulating layers 17 and 19 preferably have substantially the same coefficient of thermal expansion. For example, the base 2, the magnetic layer 4, and the insulating layers 17 and 19 are made of the same magnetic material.
[0025]
In the second reference example, similarly to the first reference example, a laminated body including the base 2, the ground electrode 3, the magnetic layer 4, the filter lines 5 and 6, the insulating layer 17, the ground electrode 18 and the insulating layer 19. 20, line connection electrodes 8a, 8b, 9a, 9b connected to the respective ends of the in-filter lines 5, 6 are formed, and ground connection electrodes commonly connected to the ground electrodes 3, 18 are formed. 10a and 10b are formed. By using these line connection electrodes 8 a, 8 b, 9 a, 9 b, the in-filter lines 5, 6 are connected to the separate lines 13, 14 constituting the differential line 12, respectively. Established. The ground electrodes 3 and 18 are grounded to the ground via the ground connection electrodes 10a and 10b.
[0026]
Noise filter 1 of the second reference example, as in the first reference example, without interfering with accurate information transmission differential line 12, it is possible to attenuate the common mode noise flowing differential lines 12.
[0027]
In the second reference example, the in-filter lines 5 and 6 are sandwiched between the ground electrode 3 formed on the surface of the base 2 and the ground electrode 18 formed on the surface of the insulating layer 17. For this reason, the shield of the filter inner lines 5 and 6 is strengthened, and radiation of electromagnetic noise from the filter inner lines 5 and 6 to the outside can be greatly reduced. In addition, it is difficult to receive induction from an external electromagnetic field.
[0028]
Hereinafter, exemplary embodiments of the present invention will be described. In the description of the implementation embodiment of this, the first reference example and same components are denoted by the same reference numerals, duplicate description is omitted.
[0029]
6A is a schematic perspective view of the noise filter of the present embodiment, and FIG. 6B is an exploded view of the noise filter of FIG. 6A. 6 (c) shows a schematic cross-sectional view of the AA portion of FIG. 6 (a).
[0030]
The implementation embodiment of this, the ground electrode 3 on the surface of the substrate 2, The ground electrode 22 on the back surface of the substrate 2 are each formed. Further, the magnetic layer 4 is laminated on the surface of the ground electrode 3, and the magnetic layer 23 is laminated on the surface of the ground electrode 22. The implementation embodiment of this, the ground electrode 3 and the ground electrode 22 is configured with a configuration material and shape such that the sides symmetric with respect to the substrate 2. Similarly, the magnetic layer 4 and the magnetic layer 23 are configured with constituent materials and thicknesses that are symmetrical with respect to the base 2.
[0031]
In the example of FIG. 6, in-filter lines 5 and 6 are formed on the surface of the magnetic layer 4.
[0032]
Also in this embodiment, as in the first and second reference examples, the base body 2 on which the ground electrodes 3 and 22 are formed on both the front and back surfaces, and the magnetic layer 4 on which the filter lines 5 and 6 are formed. And the magnetic layer 23 is integrated by baking etc., for example. When the base body 2 and the magnetic layers 4 and 23 are integrated by firing, each constituent material of the base body 2 and the magnetic layers 4 and 23 has a coefficient of thermal expansion from the viewpoint of preventing cracks during firing. It is preferable that they are substantially equal, for example, the same magnetic material is used.
[0033]
The laminated body 24 of the substrate 2, the ground electrodes 3 and 22, and the magnetic layers 4 and 23 has line connection electrodes 8a, 8b, 9a, and 9b connected to the ends of the in-filter lines 5 and 6, respectively. Also, ground connection electrodes 10a and 10b connected in common to the ground electrodes 3 and 22 are formed, respectively. Similarly to the reference example, the noise filter of the present embodiment is also mounted on the part of the lines 13 and 14 of the differential line 12 as shown in FIG.
[0034]
The noise filter 1 of this embodiment can be manufactured as follows. For example, first, as shown in FIG. 7A, the ground electrode 3 is formed on the surface of the substrate 2, and the ground electrode 22 is formed on the back surface of the substrate 2, for example, by vapor deposition or printing. And as shown in FIG.7 (b), the magnetic body layers 4 and 23 are each arrange | positioned on the front and back both surfaces side of the base | substrate 2, and these base | substrate 2 and the magnetic body layers 4 and 23 are integrated by baking etc., for example, A laminate 24 as shown in FIG. 7C is formed.
[0035]
Then, as shown in FIG. 7D, in-filter lines 5 and 6 are formed on the surface of the laminate 24, and line connection electrodes 8a, 8b, 9a and 9b and ground connection electrodes 10a and 10b are formed. To do.
[0036]
In this way, the noise filter 1 of the present embodiment example can be manufactured. In such a manufacturing process, when the in-filter lines 5 and 6 are formed in the laminate 24, the laminate 24 is symmetrical with respect to the base body 2. Therefore, the in-filter lines 5 and 6 can be formed in the laminate 24. Since the laminated body 24 is baked and integrated and is often fine, it is very difficult to distinguish the front and back of the laminated body 24. However, by providing the configuration of this embodiment, the laminated body Since it is not necessary to discriminate between the front and back surfaces of the 24, the manufacturing process of the noise filter 1 can be simplified.
[0037]
The present invention is not limited to the above implementation embodiment, it may take the form of various embodiments. For example, in the present embodiment example, the base 2 is made of the same magnetic material as that of the magnetic layer 4. However, for example, the base 2 is made of a magnetic material different from the constituent material of the magnetic layer 4. Alternatively, the substrate 2 may be made of a dielectric material other than a magnetic material .
[0038]
Further, in the present embodiment, the in-filter lines 5 and 6 are formed only on one side of the front surface and the back surface of the laminate 24. For example, the in-filter lines 5 and 6 are formed on both front and back surfaces of the laminate 24. May be.
[0039]
Furthermore, in the implementation embodiment, the noise filter 1 was rectangular parallelepiped, the shape of the noise filter 1 is not limited to the rectangular shape, be of other shapes, for example cylindrical or polygonal shape, etc. Good.
[0040]
Furthermore, in the implementation embodiment, although the filter in the line 5 and 6 have been formed in a spiral shape, for example, a filter in the line 5,6 may be formed in a zigzag shape as shown in FIG. 8 9 may be formed in a meandering shape, and the shapes of the in-filter lines 5 and 6 are not limited to the spiral shape. By forming the in-filter lines 5 and 6 in a spiral shape, a zigzag shape, or a meandering shape, the line length of the in-filter lines 5 and 6 can be increased without increasing the size of the noise filter 1. Thereby, the attenuation amount of the common mode noise due to the magnetic loss can be increased while avoiding the increase in size of the noise filter 1. If the size of the noise filter 1 is not concerned, the in-filter lines 5 and 6 may be formed linearly.
[0041]
【The invention's effect】
The connection structure of the differential line and the noise filter according to the present invention has a configuration in which common mode noise flowing through the pair of lines in the filter is attenuated by magnetic loss, and is based on a principle different from that of the common mode choke coil. Reduce noise. In the present invention, the common line noise is reflected at the connecting portion between the differential line and the noise filter (in-filter line) because the line constituting the differential line is merely provided with the in-filter line instead of the choke coil. Or resonance of common mode noise between the noise filter and the circuit side can be suppressed. For this reason, it is possible to prevent the disturbance of the signal waveform due to the reflection and resonance of the common mode noise. Therefore, it is possible to provide a connection structure of a differential line and a noise filter that can attenuate common mode noise without disturbing information transmission.
[0042]
Further, according to the present invention, the ground electrodes are formed on both the front and back surfaces of the substrate, and the magnetic layer is formed on the surface side of each ground electrode on both the front and back surfaces, and at least one side of these magnetic layers. since a pair of filters in line on the surface of the are formed by placing on both sides symmetrically to the ground electrode relative to the substrate, and disposing a magnetic layer on both sides symmetrically, in the manufacturing process, the surface-side magnetic When forming a pair of in-filter lines on one side of the layer and the magnetic layer on the back side, the in-filter line can be formed without worrying about the front and back. Thereby, the manufacturing process can be simplified.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a first reference example for explaining the present invention ;
FIG. 2 is a diagram for explaining an example in which the noise filter of the first reference example is mounted on a circuit board.
FIG. 3 is a circuit diagram showing an equivalent circuit of an in-filter line with respect to common mode noise.
FIG. 4 is an equivalent circuit diagram for explaining common-mode attenuation due to magnetic loss.
FIG. 5 is a diagram for explaining a second reference example;
FIG. 6 is a diagram for explaining an exemplary embodiment of the present invention .
7 is a diagram for explaining an example of a manufacturing process of the noise filter of the present embodiment.
FIG. 8 is a model diagram showing another example of the in-filter line.
FIG. 9 is a diagram for explaining another example of the line in the filter.
FIG. 10 is a diagram for explaining a conventional example for removing a common mode.
[Explanation of symbols]
1 Noise filter 2 Base
3,22 Ground electrode 4,23 Magnetic layer 5,6 In-filter line 12 Differential line

Claims (1)

A differential line constituted by juxtaposed two conductors of the line, met connection structure between the noise filter for attenuating common mode noise flowing differential lines built into split site of the differential line The noise filter includes a base, a ground electrode that is a ground portion formed on both the front and back surfaces of the base, a magnetic material layer that is laminated on the surface side of each ground electrode on both the front and back surfaces, A pair of lines in the filter formed by two lines arranged in parallel on the surface of at least one side of the body layer, and the filter in the pair forming the pair. One of the two lines forming the line is connected to both ends of the divided portion of the conductor line of one of the two conductor lines constituting the differential line. And the other line of the two lines forming the pair of the in-filter lines is the two lines constituting the differential line. The conductor line is connected in series to the other conductor line in a manner of connecting both ends of the other conductor line of the other conductor line, and is interposed in the divided line of the differential line. A connection structure between a differential line and a noise filter , characterized by attenuating common mode noise that flows through the line in the filter forming a magnetic field by magnetic loss.

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