JP2008262943A - Circuit board, and differential transmission apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board on which a coil component suitable for suppressing deterioration of impedance characteristics is mounted, and to provide a differential transmission apparatus. <P>SOLUTION: The circuit board having a coil component mounted thereon has a structure in which a terminal electrode formed on a substrate of the coil component is electrically connected to an electrode pad formed on one main surface of the circuit board, the coil component has at least one coil line having a winding axis of a direction perpendicular to the main surface of the circuit board and connected to the terminal electrode, and the electrode pad is not superimposed in plan view on a portion other than a portion extending for connection to the terminal electrode out of the coil line. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a circuit board, and more particularly to a circuit board on which a coil component such as a common mode filter is mounted and a differential transmission device on which the circuit board is mounted.

  Conventionally, noise suppression electronic components such as USB and IEEE1394 in a high-speed transmission line include a ferrite core attached to the outer periphery of an external connection cable, a chip bead inductor mounted on a substrate and connected to the transmission line, a common mode filter, and the like. Ferrite cores and chip bead inductors act as high impedance due to the high magnetic permeability of the ferrite in the noise frequency band to cut off the noise. The common mode filter functions to block noise by providing high impedance due to the high magnetic permeability of the ferrite with respect to common mode noise in differential transmission. Such components are mainly used in personal computers, digital cameras, portable devices, etc., but with the speeding up of data processing, common mode filters that function in the high frequency band of several hundred MHz and even in the GHz band are required. ing. A common mode filter that is assumed to be used in such a high frequency band is disclosed in Patent Document 1, for example. Patent Document 1 discloses a configuration in which stray capacitance generated between electrode pads of a common mode filter is reduced.

JP 2005-317725 A

  In recent years, with the increase in CPU speed, noise-reducing electronic components that support higher-speed transmission such as HDMI and PCI-Express have been demanded. On the other hand, in the high-speed transmission, the influence of the pattern of the board on which the component is mounted cannot be ignored. FIG. 8 shows a pattern of a conventional circuit board and how it is mounted, and FIG. 9 shows a sectional view thereof. Conventionally, the portion (electrode pad) to which the external electrode of the common mode filter is connected in the conductor pattern on the substrate extends to the bottom of the element. The conductor pattern under the element is coupled with the coil pattern inside the element and has a parasitic capacitance. As a result, there is a problem that the impedance to the common mode is lowered and the attenuation of the common mode noise is lowered. Further, particularly for high-speed transmission, there has been a problem that the impedance mismatch with respect to the differential mode becomes large and the loss and distortion of the signal increase. The present invention has been made in view of such a situation, and provides a technique of a circuit board for mounting a coil component such as a noise countermeasure electronic component corresponding to high-speed transmission and suppressing parasitic capacitance.

The circuit board of the present invention is a circuit board on which a coil component is mounted, and a terminal electrode formed on a base of the coil component and an electrode pad formed on one main surface of the circuit board are electrically connected. The coil component has at least one coil line connected to the terminal electrode with a direction perpendicular to a main surface of the circuit board as a winding axis, and the electrode pad includes the coil A portion of the line other than the portion extended for connection to the terminal electrode does not overlap in a plan view.
Accordingly, by reducing the coupling between the pad electrode on the substrate and the coil line of the coil component and reducing the parasitic capacitance, it is possible to suppress the impedance reduction of the coil line and obtain a high noise cutoff characteristic. In addition, the electrode pad that extends inward from the side surface of the base of the coil component is combined with the parasitic impedance equivalent to the stub connected in parallel to the coil, the ground of the circuit board, and other adjacent electrode pads to form the coil component. A parasitic impedance equivalent to a parallel capacitor is generated and the signal is reflected and attenuated, but the signal loss can be reduced by reducing the parasitic impedance due to these electrode pads.

  In addition, a portion of the terminal electrode formed on the base body on the main surface side of the circuit board is other than a portion of the coil line that is extended for connection to the terminal electrode. It is preferable that this portion does not overlap in plan view. According to such a configuration, since the parasitic capacitance formed between the terminal electrode and the coil line is also suppressed, it is possible to further suppress the impedance reduction of the coil line and obtain a high noise cutoff characteristic. Further, the parasitic impedance due to the electrode pad can be further reduced and the signal loss can be reduced.

  Furthermore, in the circuit board, it is preferable that the electrode pad overlaps a part of the terminal electrode formed on the main surface side of the circuit board in a plan view. Thereby, the parasitic impedance of the conductor pattern can be further reduced.

  Further, in the circuit board, it is preferable that the base body and the electrode pad do not overlap in a plan view. According to this configuration, the parasitic capacitance formed between the base including the coil line and the electrode pad can be greatly reduced. Also, the parasitic impedance due to the electrode pad can be greatly reduced.

  Furthermore, it is preferable that the terminal electrode formed on the base is formed on a surface other than the main surface side of the circuit board of the base. As a result, the coupling between the conductor pattern and the coil pattern inside the common mode filter can be further reduced, the parasitic capacitance can be further reduced, and high noise blocking characteristics can be obtained. Further, the parasitic impedance due to the electrode pad can be further reduced, and the signal loss can be reduced.

  Further, in the circuit board, the coil line has a connection part having a width larger than that of the other part at a connection part with the terminal electrode, and the terminal of the connection part and the coil line in the plan view. It is preferable that there is no said pad electrode between parts other than the part extended for the connection with an electrode. Even in the case where the connection portion with the electrode terminal is large, such a configuration can further reduce the coupling between the conductor pattern and the coil pattern inside the common mode filter, further reduce the parasitic capacitance, and obtain a high noise cutoff characteristic. . Further, the parasitic impedance due to the electrode pad can be further reduced and the signal loss can be reduced.

  Furthermore, in the circuit board, the coil component is preferably a common mode filter. Furthermore, it is more preferable that at least two coil lines constituting the common mode filter have the configuration of the coil line. If the common mode filter is applied as the coil component in the above configuration, the common mode impedance is increased by reducing the coupling between the pad electrode on the substrate and the coil line of the common mode filter and reducing the parasitic capacitance, thereby increasing the high common mode. Noise attenuation effect can be obtained. Further, the parasitic impedance between the electrode pads of the adjacent differential signal pair lines can be further reduced, and the loss of the differential signal can be reduced.

  Furthermore, in the circuit board, it is preferable that an electrode pad connected to one of the coil lines does not overlap with another coil line in a plan view. With this configuration, it is possible to further suppress parasitic capacitance in the common mode filter having a plurality of coil lines.

  The differential transmission device of the present invention is characterized in that the circuit board is mounted. The circuit board can be mounted on a device, a cable or the like having a differential transmission transmission and / or reception function to constitute a differential transmission device.

  As described above, according to the circuit board according to the present invention, unnecessary coupling between the electrode pad and the mounted coil component and parasitic impedance of the electrode pad can be reduced. As a result, it is possible to provide a circuit board suitable for high-speed transmission, which can exhibit a high noise blocking characteristic up to a high frequency and can transmit a signal with low loss, and further a differential transmission device equipped with the circuit board.

  Hereinafter, although specific embodiment of this invention is described, this invention is not limited to this embodiment. A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an exploded view of an example of the structure of a common mode filter as an example of a coil component to be mounted in order to explain a circuit board according to an embodiment of the present invention on which the coil component is mounted. FIG. 2 shows how the electrode pads and common mode filter of the circuit board of this embodiment are mounted, and FIG. 3 shows a cross section thereof. The common mode filter shown in FIG. 1 is an example using a planar spiral line as a coil line. Since the common mode filter has a plurality of coil lines and has many terminal electrodes, it is easy to form a parasitic capacitance. The configuration according to the present invention that is effective in suppressing parasitic capacitance is suitable for a common mode filter. In the common mode filter shown in FIG. 1, the planar spiral lines 23 and 24 are arranged to face each other with an insulating layer 19 interposed therebetween, and the lead line 22 is connected to one end of the planar spiral line 23 on the spiral center side by a via 30. The lead-out line 25 is connected to one end on the spiral center side of the planar spiral line 24 by a via 31. Since the planar spiral line easily forms a parasitic capacitance in relation to the pad electrode of the circuit board on which the common mode filter is mounted because of its structure, the configuration according to the present invention is particularly effective. In FIG. 1, a portion of the planar spiral line 23 that is formed perpendicular to the side surface on which the terminal electrode 12 is formed and is connected to the terminal electrode 12 is “for extension of the coil line for connection with the terminal electrode. Corresponds to the “set part”. Similarly, a portion of the planar spiral line 24 that is formed perpendicular to the side surface on which the terminal electrode 11 is formed and is connected to the terminal electrode 11 extends “for connection with the terminal electrode of the coil line. Corresponds to “the part that was made”. Further, the lead-out line 22 and the lead-out line 25 also correspond to the “part of the coil line that is extended for connection with the terminal electrode”. Further, magnetic layers 15 and 16 are arranged on the upper and lower sides to constitute the base of the common mode filter. The common mode filter of this embodiment is an example provided with two coil lines as a coil line connected to the terminal electrode. Terminal electrodes 11, 12, 13, and 14 are formed on the surface of the substrate.

  The planar spiral line 23 is connected to the terminal electrode 12 by a connecting portion 27 formed at one end, wound in a spiral shape while being bent at a right angle, and further connected to a terminal by a connecting portion 26 formed at one end thereof via a lead-out line 22. It is connected to the electrode 13. The connection portion formed in the portion connected to the terminal electrode has a width larger than that of the other portion which is a planar spiral line in order to ensure a good connection, but the width is the width of the planar spiral line. You may connect with a terminal electrode in the same way. The planar spiral line 24 is connected to the terminal electrode 11 by a connection portion 28 formed at one end, wound in a spiral shape while being bent at a right angle, and further connected to a terminal by a connection portion 29 formed at one end thereof via a lead line 25. It is connected to the electrode 14. In the configuration shown in FIG. 1, the outer shape of the planar spiral line is substantially rectangular. However, the outer shape is not limited to this, and may be, for example, a circle or an ellipse. However, in order to efficiently form a coil line in a limited area, a substantially rectangular shape is preferable. Electrode pads 2, 3, 4, and 5 are formed on one main surface of the circuit board 1 of FIG. 2, and terminal electrodes 11, 12, 13, and 14 formed on the base of the common mode filter 10 are respectively provided. It is electrically connected to the electrode pad. The common mode filter 10 has a winding axis in a direction perpendicular to the main surface of the circuit board 1. For example, solder bonding may be used to connect the terminal electrode and the electrode pad.

  The mounting position on the circuit board is indicated by a broken line. The positional relationship between the electrode pad and the electrode of the coil line inside the common mode filter will be described in detail with reference to FIG. A terminal electrode 14 of the common mode filter 10 is connected to the electrode pad 5 of the circuit board 1. The planar spiral line 23 is a planar spiral line that is not connected to the terminal electrode 14. The electrode pad 5 is located outside the boundary 100 of the projection pattern on the circuit board of this line. The electrode pad 5 is overlapped with a portion other than a portion of the planar spiral line extending for connection with the terminal electrode (a portion of the planar spiral line 24 sandwiched between broken lines in FIG. 3) in a plan view. Don't be. Further, the electrode pad 5 connected to the planar spiral line 24 does not overlap with the other planar spiral line 23 in plan view. Therefore, since the electrode pad 5 and the planar spiral lines 23 and 24 are sufficiently separated, the coupling is weakened and the parasitic capacitance is reduced. Thereby, the common mode impedance is increased, and a high common mode noise attenuation effect is obtained. The same applies to the electrode pads 2 to 4.

  A second embodiment of the present invention will be described with reference to FIG. Since the electrode pad and the common mode filter are the same as in the first embodiment except for the positional relationship, the description thereof is omitted. The electrode pad 5 is not positioned between the boundary 100 of the projection pattern on the circuit board 1 of the planar spiral line 24 and the boundary 101 of the projection pattern on the circuit board of the connecting portion 29. That is, in a plan view, there is no pad electrode between the connection portions 26 and 29 and a portion of the planar spiral line other than the portion extended for connection with the terminal electrode. This positional relationship can also be said that the tip of the pad electrode does not protrude inside the substrate from the projection pattern on the circuit board of the connection portion. As a result, the parasitic impedance of the electrode pad is further reduced, the loss for high-frequency components in the differential mode is also reduced, and the effect of high-speed transmission without distortion to the signal wave system is obtained.

  Next, a third embodiment of the present invention will be described with reference to FIG. Since the electrode pad and the common mode filter are the same as in the first embodiment except for the positional relationship, the description thereof is omitted. The electrode pad 5 is located outside the boundaries 102 and 103 of the projection pattern on the circuit board of the substrate of the common mode filter 10. That is, the base of the common mode filter and the electrode pad do not overlap in plan view. Therefore, the coupling between the electrode pad 5 and the base of the common mode filter including the planar spiral lines 23 and 24 is weakened, and the parasitic capacitance is reduced. Thereby, the common mode impedance is increased and a high common mode noise attenuation effect is obtained.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. Since the configuration of the terminal electrode is the same as that of the first embodiment except that the positional relationship between the electrode pad and the common mode filter is different, the description thereof is omitted. In the configuration shown in FIG. 6, the electrode pad 5 is not overlapped with the planar spiral lines 23 and 24 in a plan view, and is formed on the main surface side of the circuit board 1 of the base of the common mode filter among the terminal electrodes. The portion of the planar spiral line other than the portion extended for connection to the terminal electrode (the portion of the planar spiral line 24 in FIG. 6) does not overlap in plan view. The portion of the terminal electrode formed on the main surface side of the circuit board 1 of the base of the common mode filter similarly has no overlap with the planar spiral line 23. Therefore, the parasitic capacitance caused by the pad electrode can be further reduced.

  Further, the pad electrode is located on the outer side, and has a portion 202 that is in contact with a portion 201 that is not in contact with the electrode pad 5 on one surface 200 of the terminal electrode 14. Specifically, the electrode pad 5 overlaps a part of the terminal electrode formed on the main surface side of the circuit board in plan view. As a result, the parasitic impedance of the electrode pad is further reduced, the loss for high-frequency components in the differential mode is also reduced, and the effect of transmitting to the signal wave system at high speed without distortion is obtained.

  A fifth embodiment of the present invention will be described with reference to FIG. Since the configuration of the terminal electrode is the same as that of the first embodiment except that the positional relationship between the electrode pad and the common mode filter is different, the description thereof is omitted. The terminal electrode is formed on the side surface and the upper surface of the base of the common mode filter, that is, the surface other than the main surface side of the circuit board. The terminal electrode 14 and the electrode pad 5 are located outside the boundaries 102 and 103 of the projection pattern on the circuit board of the base of the common mode filter. Therefore, the coupling between the electrode pad 5 and the common mode filter including the planar spiral lines 23 and 24 is further weakened, and the parasitic capacitance is reduced. Thereby, the common mode impedance is increased and a high common mode noise attenuation effect is obtained. Actually, when the configuration of the present invention in FIG. 7 and the conventional configuration in FIG. 9 are compared, the signal loss at 6 GHz is reduced by 1 dB in the configuration of the present invention.

  The above circuit board is an example in which a common mode filter is mounted as a coil component, but the coil component is not limited to this. For example, an inductor having one coil line may be used. Also in this case, the effect of suppressing parasitic capacitance and suppressing impedance variation is exhibited. The coil line is not limited to a planar spiral line, and a helical line having a winding axis in a direction perpendicular to the main surface of the circuit board may be used. In this case, a coil pattern is formed on a plurality of insulating layers and stacked, and the coil pattern formed on each insulating layer is connected by a via electrode to constitute a helical coil wound in the stacking direction. .

  For example, a normal printed wiring board (PCB) may be used as the circuit board according to the present invention. The circuit board may be a single layer board or a multilayer board. The coil component may be of an array type in which a plurality of coil portions are formed in one chip, such as a common mode filter array.

  The manufacturing method of the coil component represented by the common mode filter is not particularly limited. An example of the manufacturing method will be described with reference to FIG. The magnetic layers 15 and 16 are provided by processing a sintered sintered ferrite substrate to a predetermined thickness and size. Insulating layers 17 to 21 made of a heat-resistant resin such as polyimide, planar spiral lines 23 and 24 made of silver or copper, and lead lines 22 and 25 are laminated on the ferrite substrate as the magnetic layer 15 by photolithography. . The lead line and the planar spiral line are electrically connected by vias or the like. A ferrite substrate is bonded thereon as the magnetic layer 15. For example, the bonding is performed using an adhesive. After cutting, electrode terminals 11 to 14 are formed outside the chip by plating, sputtering, coating, or the like. For the insulating layers 117 to 21, the planar spiral lines 23 and 24, and the lead lines 22 and 25, an LTCC process in which a silver paste is printed on a ceramic green sheet, laminated, and fired may be applied. The coil component according to the present invention may be manufactured by a multilayer flexible substrate in which thin sheets of polyimide or the like on which an electrode pattern is formed are bonded and laminated.

  The circuit board can be widely applied to devices having a differential transmission transmission and / or reception function, and differential transmission devices such as cables. By mounting the circuit board of the present invention on a DVD player, a digital TV, an HDTV, a display, a projector or the like that performs differential transmission, it contributes to high performance of these devices.

1 shows an exploded structure of a common mode filter for explaining an embodiment of a circuit board of the present invention. It is a figure which shows the external appearance of one Embodiment of the circuit board of this invention. It is a figure which shows the cross section of one Embodiment of the circuit board of this invention. It is a figure which shows other embodiment of the circuit board of this invention. It is a figure which shows other embodiment of the circuit board of this invention. It is a figure which shows the cross section of other embodiment of the circuit board of this invention. It is a figure which shows the cross section of other embodiment of the circuit board of this invention. It is a figure which shows the external appearance of the form of the conventional circuit board. It is a figure which shows the cross section of the form of the conventional circuit board.

Explanation of symbols

1: Circuit board 2-5: Electrode pad 10: Common mode filters 11-14, 200-202: Terminal electrode 15, 16: Magnetic layers 17-21: Insulating layer 23, 24: Planar spiral line 22, 25: Lead line 26 to 29: connection portion 30, 31: via 6, 8: winding end 100 to 103 of coil pattern: boundary line of projection onto circuit board

Claims (9)

A circuit board on which coil components are mounted,
The terminal electrode formed on the base of the coil component and the electrode pad formed on one main surface of the circuit board are electrically connected,
The coil component has at least one coil line connected to the terminal electrode, the winding axis being a direction perpendicular to the main surface of the circuit board,
The circuit board according to claim 1, wherein the electrode pad does not overlap a portion of the coil line other than a portion extending for connection with the terminal electrode in a plan view.   Of the terminal electrodes formed on the base, a portion formed on the main surface side of the circuit board is a portion other than a portion of the coil line that is extended for connection to the terminal electrode. The circuit board according to claim 1, wherein the circuit boards do not overlap in plan view.   The circuit board according to claim 1, wherein the electrode pad overlaps a part of a portion of the terminal electrode formed on the main surface side of the circuit board in a plan view. The circuit board according to claim 1, wherein the base body and the electrode pad do not overlap in plan view.   The circuit board according to claim 1, wherein the terminal electrode formed on the base is formed on a surface other than a main surface side of the circuit board. The coil line has a connection portion having a width larger than other portions in the connection portion with the terminal electrode,
The said pad electrode does not exist between the said connection part and parts other than the part extended for the connection with the said terminal electrode among the said coil lines in planar view, It is characterized by the above-mentioned. The circuit board according to any one of 5.   The circuit board according to claim 1, wherein the coil component is a common mode filter.   The circuit board according to claim 7, wherein an electrode pad connected to one coil line of the coil lines does not overlap with another coil line in a plan view.   A differential transmission device on which the circuit board according to claim 7 is mounted.

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