JP2008108903A - Common mode choke coil and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a common mode choke coil of which a capacitance component between spiral conductors is reduced. <P>SOLUTION: The coil comprises a spiral conductor 141 formed on an upper surface 122a of an insulating layer 122, a spiral conductor 142 formed on a lower surface 123b of an insulating layer 123, and a frame-like spacer 190 arranged between the insulating layers 122 and 123. Since a cavity 191 is formed between the spiral conductors 141 and 142 by the spacer 190, the capacitance component generated between the spiral conductors 141 and 142 becomes very small. So, excellent high frequency characteristics are provided compared to a conventional general common mode choke coil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a common mode choke coil and a manufacturing method thereof, and more particularly to a common mode choke coil with improved high frequency characteristics and a manufacturing method thereof.

  In recent years, the USB 2.0 standard and the IEEE 1394 standard are widely used as high-speed signal transmission interfaces, and are used in many digital devices such as personal computers and digital cameras. Unlike the single-ended transmission method that has been common for a long time, interfaces such as the USB 2.0 standard and the IEEE 1394 standard adopt a differential signal method that transmits a differential signal using a pair of signal lines.

  The differential transmission system has an excellent feature that not only the radiation electromagnetic field generated from the signal line is small compared to the single-end transmission system, but also that the differential transmission system is less susceptible to external noise. For this reason, it is easy to reduce the amplitude of the signal, and by shortening the rise time and the fall time due to the small amplitude, it becomes possible to perform signal transmission at a higher speed than the single-ended transmission method.

  FIG. 8 is a circuit diagram of a general differential transmission circuit.

  The differential transmission circuit shown in FIG. 8 includes a pair of signal lines 11 and 12, an output buffer 13 that supplies a differential signal to the signal lines 11 and 12, and an input buffer that receives the differential signal from the signal lines 11 and 12. 14. With this configuration, the input signal IN given to the output buffer 13 is transmitted to the input buffer 14 via the pair of signal lines 11 and 12, and is reproduced as the output signal OUT. Such a differential transmission circuit has a feature that the radiated electromagnetic field generated from the signal lines 11 and 12 is small as described above, but noise common to the signal lines 11 and 12 (common mode noise) is generated. When superposed, a relatively large radiated electromagnetic field is generated. In order to reduce the radiated electromagnetic field generated by the common mode noise, it is effective to insert the common mode choke coil 20 into the signal lines 11 and 12 as shown in FIG.

  The common mode choke coil 20 has a characteristic that an impedance with respect to a differential component (signal) transmitted through the signal lines 11 and 12 is low and an impedance with respect to an in-phase component (common mode noise) is high. For this reason, by inserting the common mode choke coil 20 into the signal lines 11 and 12, the common mode noise transmitted through the pair of signal lines 11 and 12 can be blocked without substantially attenuating the differential signal. . As the common mode choke coil 20, for example, an element described in Patent Document 1 is known.

  Ideally, the common mode choke coil does not attenuate the differential signal at all, but actually the differential signal is attenuated to some extent as the frequency increases. The frequency at which the differential signal attenuates by 3 dB is called a “cut-off frequency” and is evaluated as an important parameter representing the high-frequency characteristics of the common mode choke coil. In recent years, a very high data transfer rate has been required, and the frequency of differential signals has been increased year by year. For this reason, increasing the cut-off frequency of the common mode choke coil is very important for improving signal quality.

  However, it has been difficult to increase the cut-off frequency with the conventional common mode choke coil. The reason will be described below.

  FIG. 9 is a schematic cross-sectional view of a general common mode choke coil.

As shown in FIG. 9, a general common mode choke coil 30 includes a plurality of insulating layers 41 to 43 made of resin, a pair of spiral conductors 51 and 52 formed inside these insulating layers, and an insulating layer. It is comprised by the magnetic body board | substrates 61 and 62 arrange | positioned at both sides. The spiral conductors 51 and 52 are arranged in parallel so as to face each other, and an insulating layer 42 is interposed therebetween. Therefore, a predetermined capacitance component determined by the thickness and relative dielectric constant of the insulating layer 42 and the conductor width of the spiral conductors 51 and 52 is generated between the spiral conductors 51 and 52. The cut-off frequency of the coil is lowered.
JP-A-8-203737

  As a method of reducing such a capacitance component, a method of increasing the thickness of the insulating layer 42 can be considered. However, this method reduces the magnetic coupling because the distance between the spiral conductors 51 and 52 increases.

  Further, as another method for reducing the capacitance component, a method using a low dielectric constant material as the material of the insulating layer 42 can be considered. However, no low dielectric constant material that satisfies the characteristics required for the insulating layer 42 has been found so far.

  Further, as another method for reducing the capacitance component, a method of narrowing the conductor width of the spiral conductors 51 and 52 is also conceivable. However, narrowing the conductor width increases the DC resistance and also reduces the magnetic coupling. In addition, the reduction of the conductor width has a process limit in the first place.

  The present invention has been made to solve such a problem, and an object of the present invention is to improve the high frequency characteristics of a common mode choke coil by reducing the capacitance component generated between spiral conductors.

  A common mode choke coil according to the present invention is a common mode choke coil including first and second spiral conductors arranged in parallel so as to face each other, and a cavity is formed between the first and second spiral conductors. Is provided. The method for manufacturing a common mode choke coil according to the present invention includes a step of forming a first coil portion in which a first spiral conductor is formed on a first insulating layer, and a step of forming a first coil portion on a second insulating layer. A step of creating a second coil portion in which two spiral conductors are formed, and the first and second via a spacer so that a cavity is formed between the first and second spiral conductors. And a step of laminating the coil portions.

  Thus, in the common mode choke coil according to the present invention, the cavity is formed between the first and second spiral conductors that are magnetically coupled. Therefore, the insulating layer having a relative dielectric constant = 1 is used. Almost the same effect is obtained, and the capacitance component generated between the spiral conductors is very small. In the common mode choke coil according to the present invention, it is preferable that a cavity is provided also in an adjacent portion in the first spiral conductor and an adjacent portion in the second spiral conductor. According to this, it is possible to reduce the capacitive component existing in the first and second spiral conductors themselves.

  The “cavity” in the present invention is provided for the purpose of reducing the capacitance component between the spiral conductors, and therefore, a slight cavity that does not substantially contribute to the reduction of the capacitance component is provided. It is not meant to include such cases.

  A common mode choke coil according to the present invention includes a first insulating layer disposed on the side opposite to the second spiral conductor when viewed from the first spiral conductor, and the second spiral conductor. A second insulating layer disposed on the opposite side of the first spiral conductor and the first and second insulating layers, and the cavity between the first and second spiral conductors. It is preferable to further include a spacer for forming the. According to this, it becomes possible to reliably form a cavity between the first and second spiral conductors by the spacer.

  In this case, the spacer may be a frame-like body that surrounds the outer circumferences of the first and second spiral conductors, and has a porous structure provided between the first and second spiral conductors. It may be an insulator. According to the former, almost all of the space between the first and second spiral conductors is hollow, so that the capacitance component can be made very small. Further, according to the latter, it is possible to reliably prevent a short circuit between the first and second spiral conductors.

  In the present invention, the surface of at least one of the first and second spiral conductors is preferably covered with an insulating thin film. According to this, it is possible to prevent a short circuit between the first and second spiral conductors, and it is possible to improve the reliability of the product because the surface of the conductor is protected.

  The common mode choke coil according to the present invention preferably further includes a pair of magnetic substrates provided on both sides of the first and second coil conductors. According to this, it is possible to further increase the magnetic coupling between the first and second coil conductors.

  As described above, according to the present invention, since the cavity is formed between the spiral conductors that are magnetically coupled, the capacitance component generated between the spiral conductors is greatly reduced. Thereby, it is possible to provide a common mode choke coil having excellent high frequency characteristics such as a cut-off frequency.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic exploded perspective view showing the structure of a common mode choke coil 100 according to a first preferred embodiment of the present invention, and FIG. 2 is a schematic view showing a state in which the common mode choke coil 100 according to the present embodiment is assembled. It is a perspective view.

  As shown in FIG. 1, the common mode choke coil 100 according to this embodiment includes substrates 111 and 112, insulating layers 121 to 124 provided between the substrates 111 and 112, and a conductor pattern formed on a predetermined insulating layer. Is a laminated common mode choke coil. Here, “stacked common mode choke coil” refers to a common mode choke coil in which a plurality of planar conductor patterns are stacked via an insulating layer, and a common mode in which a conductor is wound around a drum. Differentiated from choke coils.

  The material of the substrates 111 and 112 is not particularly limited, but it is preferable to use a material with high magnetic permeability, for example, a magnetic material such as ferrite. This is because magnetic coupling is enhanced by using a magnetic material as the material of the substrates 111 and 112. The material of the insulating layers 121 to 124 is not particularly limited, but it is preferable to use a nonmagnetic material such as polyimide.

  The conductor pattern formed on the insulating layer is insulated from the internal electrodes 131 to 134 formed on the surfaces of the insulating layers 121 to 123 and the spiral conductors 141 and 142 formed on the surfaces of the insulating layers 122 and 123, respectively. Connection conductors 151 and 152 formed on the surfaces of the layers 121 and 123, respectively, are included. As shown in FIG. 2, the spiral conductors 141 and 142 are both planar coils parallel to the main surfaces of the substrates 111 and 112. These conductor patterns can be formed on the insulating layer by a so-called thin film process such as sputtering, vapor deposition, or plating.

  As shown in FIG. 2, the spiral conductor 141 is provided on the upper surface 122 a of the insulating layer 122, while the spiral conductor 142 is provided on the lower surface 123 b of the insulating layer 123. In FIG. 2, since the lower surface 123 b of the insulating layer 123 is not visible, the spiral conductor 142 is shown separated from the insulating layer 123.

  The upper surface 122a of the insulating layer 122 and the lower surface 123b of the insulating layer 123 are surfaces facing each other. For this reason, if laminated in this state, the spiral conductor 141 and the spiral conductor 142 come into contact with each other. However, in the common mode choke coil 100 according to the present embodiment, the spacer 190 is interposed between the insulating layer 122 and the insulating layer 123. Has been placed. As a result, the spiral conductor 141 and the spiral conductor 142 are held in a state of being separated from each other with a certain distance.

  The spacer 190 used in the present embodiment is a frame-like body that surrounds the outer periphery of the spiral conductors 141 and 142. The thickness of the spacer 190 needs to be set to a thickness exceeding the sum of these thicknesses so that the spiral conductor 141 and the spiral conductor 142 do not contact each other.

  3 is a schematic cross-sectional view of the B cross section shown in FIG.

  As shown in FIG. 3, the spiral conductors 141 and 142 are arranged in parallel so as to face each other, and a cavity 191 formed by a spacer 190 exists between them. With such a structure, since the relative dielectric constant between the spiral conductors 141 and 142 is approximately 1, the capacitance component generated between the two is reduced. Further, in this embodiment, the cavity 191 is also formed between adjacent portions in the same spiral conductor, for example, a portion located relatively on the inner periphery and a portion located relatively on the outer periphery of the spiral conductor 141. Is present. For this reason, the capacitive component existing in the spiral conductors 141 and 142 itself is also reduced.

  Thus, since the spiral conductors 141 and 142 are disposed so as to face each other through the cavity 191, they are magnetically coupled to each other. As shown in FIG. 1, one end of the spiral conductor 141 is connected to the internal electrode 131, and the other end is connected to the internal electrode 133 via the connection conductor 151. One end of the spiral conductor 142 is connected to the internal electrode 132, and the other end is connected to the internal electrode 134 via the connection conductor 152. The internal electrodes 131 to 134 are conductor patterns connected to the external electrodes 101 to 104 shown in FIG. 2 (the illustration of the external electrodes 101 to 104 is omitted in FIG. 1).

  When viewed from the arrow A shown in FIG. 1, the spiral conductors 141 and 142 are both wound counterclockwise (counterclockwise) from one end to the other end. Therefore, if the external electrodes 101 and 102 are a pair of input terminals, the spiral conductors 141 and 142 are magnetically coupled in the same direction. Here, “magnetic coupling in the same direction as each other” means that magnetic coupling is performed so that the magnetic flux is strengthened with respect to the in-phase component and the magnetic flux is canceled with respect to the differential component.

  As described above, in the common mode choke coil 100 according to the present embodiment, since the frame-shaped spacer 190 is disposed between the insulating layer 122 and the insulating layer 123, the cavity 191 is interposed between the spiral conductors 141 and 142. Is formed. As a result, the capacitance component between the spiral conductors 141 and 142 is reduced, so that the high frequency characteristics such as the cut-off frequency are improved, and it is possible to meet the demand for high-speed data transfer.

  Although the manufacturing method of the common mode choke coil 100 according to the present embodiment is not particularly limited, for example, the coil portion C1 and the coil portion C2 shown in FIG. 1 are separately formed, and the cavity 191 is formed between the spiral conductors 141 and 142. As described above, the coil portions C1 and C2 can be laminated through the spacer 190. Here, the coil portion C1 refers to the insulating layers 121 and 122 and the conductor patterns formed on the surfaces thereof, and the coil portion C2 refers to the insulating layers 123 and 124 and the conductor patterns formed on the surfaces thereof. .

  Moreover, in the said embodiment, although a single component is used as the spacer 190 of a frame-shaped body, as shown in FIG. 4 which is a schematic sectional view, if the outer periphery of the substrates 111 and 112 is projected into a frame shape, The spacer 190 as a single component can be omitted. However, in this case, high precision is required for processing the substrates 111 and 112.

  In the common mode choke coil 100 according to the present embodiment, since the spiral conductors 141 and 142 are opposed to each other through the cavity 191, there is a possibility that both are short-circuited when foreign matter enters the cavity. In order to prevent this, as shown in FIG. 5, the surface of at least one of the spiral conductors 141 and 142 (only the spiral conductor 141 in FIG. 5) may be covered with an insulating thin film 192. Further, if both the spiral conductors 141 and 142 are covered with an insulating thin film, the surface of the conductor is physically and chemically protected, so that the reliability of the product can be improved.

  The thickness of the insulating thin film 192 is preferably as thin as possible within a range in which a short circuit can be prevented. This is because the thicker the insulating thin film 192, the larger the capacitive component between the spiral conductors 141 and 142, and the less the merit of providing the cavity 191.

  Next, a second preferred embodiment of the present invention will be described.

  FIG. 6 is a schematic exploded perspective view showing the structure of a common mode choke coil 200 according to a preferred second embodiment of the present invention. The external shape of the common mode choke coil 200 according to the present embodiment is as shown in FIG.

  As shown in FIG. 6, the common mode choke coil 200 according to the present embodiment is a common mode choke according to the first embodiment in that a plate-like spacer 290 is used instead of the frame-like spacer 190. This is different from the coil 100. Since the other points are basically the same as those of the common mode choke coil 100 according to the first embodiment, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  The spacer 290 is an insulator having a porous structure. Accordingly, a large number of minute cavities exist inside the spacer 290.

  FIG. 7 is a schematic cross-sectional view of the common mode choke coil 200 according to the present embodiment.

  As shown in FIG. 7, in the common mode choke coil 200 according to the present embodiment, a spacer 290 is interposed between the spiral conductors 141 and 142. Since the spacer 290 is an insulator having a porous structure, a large number of minute cavities (not shown) are formed between them. For this reason, the common mode choke coil 200 according to the present embodiment can also obtain the same effects as the common mode choke coil 100 according to the first embodiment.

  In addition, since the spacer 290 physically exists between the spiral conductors 141 and 142 in the common mode choke coil 200 according to the present embodiment, it is possible to effectively prevent both of them from being short-circuited.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in each of the above embodiments, the substrates are provided on both sides of the pair of coil conductors, but one or both of these substrates may be omitted.

  In the first embodiment, the frame-shaped spacer 190 surrounding the entire outer periphery of the spiral conductors 141 and 142 is used. However, as long as a cavity can be formed between the spiral conductors 141 and 142, the spiral conductors are used. It is not essential to surround the entire outer periphery of 141,142.

1 is a schematic exploded perspective view showing a structure of a common mode choke coil 100 according to a first preferred embodiment of the present invention. 2 is a schematic perspective view showing a state in which a common mode choke coil 100 is assembled. FIG. It is a schematic sectional drawing of the B cross section shown in FIG. 6 is a schematic perspective view showing a modification of the common mode choke coil 100. FIG. 6 is a schematic perspective view showing another modification of the common mode choke coil 100. FIG. It is a substantially exploded perspective view which shows the structure of the common mode choke coil 200 by preferable 2nd Embodiment of this invention. 2 is a schematic cross-sectional view of a common mode choke coil 200. FIG. It is a circuit diagram of a general differential transmission circuit. It is a schematic sectional view of a general common mode choke coil.

Explanation of symbols

11, 12 Signal line 13 Output buffer 14 Input buffer 20, 30 Common mode choke coil 41-43 Insulating layer 51, 52 Spiral conductor 61, 62 Magnetic substrate 100, 200 Common mode choke coil 101-104 External electrodes 111, 112 Substrate 121-124 Insulating layer 122a Upper surface of insulating layer 123b Lower surface of insulating layer 131-134 Internal electrode 141, 142 Spiral conductor 151, 152 Connecting conductor 190, 290 Spacer 191 Cavity 192 Insulating thin film

Claims (8)

  A common mode choke coil comprising first and second spiral conductors arranged in parallel to face each other, characterized in that a cavity is provided between the first and second spiral conductors. Common mode choke coil.   2. The common mode choke coil according to claim 1, wherein a cavity is provided in an adjacent portion in the first spiral conductor and an adjacent portion in the second spiral conductor.   A first insulating layer disposed on the opposite side of the second spiral conductor as viewed from the first spiral conductor; and the first spiral conductor as viewed from the second spiral conductor; Is further provided with a second insulating layer disposed on the opposite side, and a spacer provided between the first and second insulating layers and forming the cavity between the first and second spiral conductors. The common mode choke coil according to claim 1 or 2.   4. The common mode choke coil according to claim 3, wherein the spacer is a frame-like body that surrounds outer peripheries of the first and second spiral conductors.   The common mode choke coil according to claim 3, wherein the spacer is an insulator having a porous structure provided between the first and second spiral conductors.   6. The common mode choke coil according to claim 1, wherein at least one of the first and second spiral conductors is covered with an insulating thin film.   The common mode choke coil according to any one of claims 1 to 6, further comprising a pair of magnetic substrates provided on both sides of the first and second spiral conductors.   A step of creating a first coil portion in which a first spiral conductor is formed on a first insulating layer; and a second coil portion in which a second spiral conductor is formed on a second insulating layer. And a step of laminating the first and second coil portions via a spacer so that a cavity is formed between the first and second spiral conductors. A method for manufacturing a common mode choke coil.

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