Filter circuit

Abstract

Provided is a smaller filter circuit. The filter circuit has an LC circuit, one end of which is connected to a signal path connecting an input terminal and an output terminal, and the other end of which is connected to a reference potential. A filter circuit according to a first embodiment includes a substrate and a plurality of electrodes provided on a main surface or inside of the substrate. The LC circuit includes a first capacitor, a first inductor connected in parallel, and a second capacitor connected in series. The electrodes overlap each other at least partially when viewed in the thickness direction of the substrate. The portion where the electrodes overlap each other is the electrode of the first capacitor or the second capacitor.

Description

Technical Field

[0001] The present invention relates to a filter circuit. Background Art

[0002] In Patent Document 1, a resonance circuit that attenuates a specific frequency is described.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-262349 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, in the resonance device described in Patent Document 1, in order to ensure the capacitance of the capacitor, it is necessary to increase the electrode.

[0008] The present disclosure has been made in view of the above, and an object thereof is to provide a smaller filter circuit.

[0009] Technical Means for Solving the Problems

[0010] A filter circuit according to one aspect of the present disclosure includes an LC circuit. One end of the LC circuit is connected to a signal path that connects an input terminal and an output terminal, and the other end is connected to a reference potential. The filter circuit includes: a substrate; a first electrode provided on one main surface of the substrate; a second electrode provided inside the substrate; and a third electrode provided on the other main surface of the substrate. The LC circuit includes: a first capacitor, one electrode of which is connected to the signal path; a first inductor, one end of which is connected to the signal path; and a second capacitor, one electrode of which is connected to the first capacitor and the first inductor, and the other electrode of which is connected to the reference potential. When viewed in the thickness direction of the substrate, the first electrode and the second electrode overlap at least partially, the second electrode and the third electrode overlap at least partially, a portion of the first electrode that overlaps the second electrode is one electrode of the first capacitor, a portion of the second electrode that overlaps the first electrode is the other electrode of the first capacitor, a portion of the second electrode that overlaps the third electrode is one electrode of the second capacitor, and a portion of the third electrode that overlaps the second electrode is the other electrode of the second capacitor.

[0011] Advantages of the Invention

[0012] According to the present disclosure, a smaller filter circuit can be provided. Brief Description of the Drawings

[0013] Figure 1 It is a schematic diagram showing a module to which the filter circuit according to the first embodiment is applied.

[0014] Figure 2 It is along Figure 1 A cross-sectional view taken along line II-II.

[0015] Figure 3 It is a circuit diagram showing the filter circuit according to the first embodiment.

[0016] Figure 4 It is a schematic diagram showing the main surface of the substrate of the filter circuit according to the first embodiment.

[0017] Figure 5 It is a schematic diagram showing the inside of the substrate of the filter circuit according to the first embodiment.

[0018] Figure 6 It is a schematic diagram showing the main surface of the substrate of the filter circuit according to the first modification example.

[0019] Figure 7 It is a schematic diagram showing the inside of the substrate of the filter circuit according to the first modification example.

[0020] Figure 8 It is a schematic diagram showing the inside of the substrate of the filter circuit according to the second modification example.

[0021] Figure 9 It is a schematic diagram showing the main surface of the substrate of the filter circuit according to the third modification example.

[0022] Figure 10 It is a schematic diagram showing the inside of the substrate of the filter circuit according to the third modification example.

[0023] Figure 11 It is a schematic diagram showing the filter circuit according to the second embodiment.

[0024] Figure 12 It is a circuit diagram showing the filter circuit according to the second embodiment.

[0025] Figure 13 It is a schematic diagram showing the main surface of the substrate of the filter circuit according to the second embodiment.

[0026] Figure 14 It is a schematic diagram showing the inside of the substrate of the filter circuit according to the second embodiment.

[0027] Figure 15 It is a schematic diagram showing the main surface of the substrate of the filter circuit according to the fourth modification example.

[0028] Figure 16 It is a schematic diagram showing the inside of a substrate of a filter circuit according to a fourth modification example.

[0029] Explanation of reference numerals

[0030] 1 Module

[0031] 2 Element

[0032] 3 Conductive bonding material

[0033] 10 Substrate

[0034] 10a Main surface

[0035] 11 Protective film

[0036] 12, 13 Elements

[0037] 20 First pattern

[0038] 21 Main line

[0039] 22 First electrode

[0040] 23 Fourth electrode

[0041] 24 Conductive via hole

[0042] 25 Electrode

[0043] 30 Second pattern

[0044] 31 Transmission line

[0045] 32 Second electrode

[0046] 40 Third electrode

[0047] F1, F2 Filter circuit

[0048] C1 First capacitor

[0049] C2 Second capacitor

[0050] L1 First inductor

[0051] L2 Second inductor

[0052] N1 Node

[0053] N2 Node. Detailed implementation manners

[0054] Hereinafter, the implementation manners of the present invention will be described. In addition, the present invention is not limited by this implementation manner. It is self - evident that each implementation manner is an exemplification, and partial replacement or combination of the structures shown in different implementation manners can be performed.

[0055] (First Embodiment)

[0056] Figure 1 It is a schematic diagram showing a module to which the filter circuit according to the first embodiment is applied. Figure 2 It is a cross-sectional view along the line II-II according to the first embodiment. The module 1 according to the first embodiment is an integrated module in which a plurality of integrated circuits and various functional components mounted on the substrate 10 are integrated.

[0057] In the module 1, an element 2 is provided on the main surface of the substrate 10. The element 2 is, for example, a surface mount device (SMD). Further, in the module 1, the filter circuit F1 according to the first embodiment is applied and connected to the element 2. The connection between the filter circuit F1 and the element 2 will be described later.

[0058] Figure 3 It is a circuit diagram showing the filter circuit according to the first embodiment. As Figure 3 shown, the filter circuit F1 according to the first embodiment is a notch filter to which an LC circuit is connected. One end of the LC circuit is connected to a signal path connecting the input terminal IN and the output terminal OUT, and the other end is connected to the ground GND. The LC circuit includes a first capacitor C1, a first inductor L1, and a second capacitor C2. One electrode of the first capacitor C1 is connected to the node N1 on the signal path, and the other electrode of the first capacitor C1 is connected to one electrode of the second capacitor C2. One end of the first inductor L1 is connected to the node N2 on the signal path, and the other end of the first inductor L1 is connected to one electrode of the second capacitor C2. That is, the first inductor L1 is connected in parallel with the first capacitor. One electrode of the second capacitor C2 is connected to the other electrode of the first capacitor C1 and the other end of the first inductor L1, and the other electrode of the second capacitor C2 is connected to the ground GND. That is, the second capacitor C2 is connected in series with the first capacitor C1 and the first inductor L1. Thus, by appropriately adjusting the sum of the capacitances of the first capacitor C1 and the second capacitor C2 and the inductance of the first inductor L1, the signal can be attenuated at a desired attenuation pole through a parallel resonance circuit.

[0059] Here, the capacitance of the first capacitor C1 is 0.03 pF or more. Thus, the capacitance of the first capacitor C1 contributes to the resonance characteristics, and the signal can be attenuated at a desired attenuation pole.

[0060] Here, the capacitances of the first capacitor C1 and the second capacitor C2 are preferably the same. In Figure 3In the filter circuit F1 involved, the larger the sum of the capacitances of the first capacitor C1 and the second capacitor C2 is, the more the frequency of the attenuation pole can be reduced. On the other hand, even if the capacitances of the first capacitor C1 and the second capacitor are different, as long as the sum of the capacitances is the same, the frequency of the attenuation pole remains unchanged. Therefore, by making the capacitances of the first capacitor C1 and the second capacitor C2 the same, it is possible to suppress the increase in the electrode area of the first capacitor C1 or the second capacitor C2 and at the same time reduce the frequency of the attenuation pole.

[0061] As Figure 2 shown, the filter circuit F1 according to the first embodiment includes a substrate 10, a protective film 11, a first pattern 20, a second pattern 30, and a third electrode 40.

[0062] The substrate 10 exemplifies, for example, a ceramic laminated substrate such as a low-temperature co-fired ceramic (LTCC) substrate, a resin multi-layer substrate, a thin film substrate, etc. The base material of the substrate 10 is a dielectric. The substrate 10 has a main surface 10a. In the following description, the thickness direction of the substrate 10 is set as the Z direction, the direction perpendicular to the Z direction is set as the X direction, and the direction perpendicular to the Z direction and the X direction is set as the Y direction.

[0063] Figure 4 is a schematic view of the main surface of the substrate of the filter circuit according to the first embodiment. The first pattern 20 is a pattern of a conductor provided on the main surface 10a of the substrate 10. The first pattern 20 according to the first embodiment has a main line 21, a first electrode 22, a fourth electrode 23, and a via hole 24.

[0064] The main line 21 is a signal path of the filter circuit F1. That is, the main line 21 is at least a part of the line connecting the input terminal and the output terminal of the filter circuit F1. In Figure 4 the example, the main line 21 extends in the X direction, the main line 21 is connected to an output terminal (not shown) at one side in the X direction, and is connected to the first electrode 22 corresponding to the input terminal at the other side in the X direction.

[0065] The first electrode 22 corresponds to one electrode of the first capacitor C1. That is, the first electrode 22 is connected to the main line 21. Here, the first electrode 22 is an electrode whose minimum length in the top view in the Z direction is greater than the width of the main line 21. The width of the main line 21 refers to the average of the lengths in the direction perpendicular to the extending direction of the main line 21. In Figure 4 the example, the width of the main line 21 refers to the width in the Y direction. In addition, the minimum length of the first electrode 22 refers to the minimum distance between two different points on the edge of the first electrode 22. In Figure 4In the example, the so-called minimum length of the first electrode 22 refers to the length in the X direction. In Figure 4 In the example, the first electrode 22 is connected to the main line 21 on one side in the X direction, but this is only an example, and it is sufficient as long as it is connected to the main line 21. In addition, the shape of the first electrode is rectangular, but it is not limited thereto, and it may be other shapes such as circular.

[0066] The fourth electrode 23 is a connection terminal to the element 2. The fourth electrode 23 is provided separately from the first electrode 22. In Figure 4 In the example, three fourth electrodes 23 are provided separately from the first electrode 22 in the X direction, and both ends of the element 2 in the X direction and the Y direction are arranged to overlap with the first electrode 22 or the fourth electrode 23.

[0067] The via hole 24 is a via hole that connects the main line 21 and a transmission line 31 described later. The via hole 24 connects one end from the main line 21 to the transmission line 31 in the Z direction. In Figure 4 In the example, the via hole 24 is provided on the main line 21, but this is only an example.

[0068] Figure 5 FIG. is a schematic diagram showing the inside of a substrate of a filter circuit according to the first embodiment. The second pattern 30 is a pattern of a conductor provided inside the substrate 10. The second pattern 30 according to the first embodiment has a transmission line 31 and a second electrode 32.

[0069] The transmission line 31 is a transmission line that connects the main line 21 and the second electrode 32. Here, the so-called transmission line refers to a layer of a conductor having a shape that linearly extends when viewed from above in the Z direction. In Figure 5 In the example, one end of the transmission line 31 is connected to the via hole 24, and the other end is connected to the second electrode 32.

[0070] In the first embodiment, the transmission line 31 corresponds to the first inductor L1. In Figure 5 In the example, the transmission line 31 is zigzag. Here, the so-called zigzag shape means a shape that extends in one direction and, for a direction intersecting with the one direction, alternately extends in one orientation and the other orientation and meanders. In Figure 5 In the example, while the transmission line 31 extends in the X direction, for the Y direction, it alternately extends in one orientation and the other orientation and meanders. Thus, sufficient inductance can be generated by the transmission line 31.

[0071] The second electrode 32 corresponds to the other electrode of the first capacitor C1 and one electrode of the second capacitor C2. Here, the second electrode 32 is an electrode whose minimum length when viewed from above in the Z direction is greater than the width of the main line 21. The so-called minimum length of the second electrode 32 refers to the minimum distance between two different points on the edge of the second electrode 32. In Figure 5 the example of, the so-called minimum length of the second electrode 32 refers to the length in the X direction. When the second electrode 32 is observed in the Z direction, it overlaps with the first electrode 22 and the third electrode 40. Since the base material of the substrate 10 is a dielectric, the second electrode 32 can generate capacitance between it and the first electrode 22 and act as the first capacitor C1. In addition, the second electrode 32 can generate capacitance between it and the third electrode 40 and act as the second capacitor C2. In addition, the shape of the second electrode 32 is rectangular, but it is not limited thereto, and it may be other shapes such as circular.

[0072] In the first embodiment, the minimum distance in the width direction between the edge in the width direction of the transmission line 31 and the edge of the second electrode 32 is 20 μm or more. Here, the so-called width direction of the transmission line 31 refers to the direction perpendicular to the extension direction of the transmission line 31, and the so-called edge in the width direction of the transmission line 31 refers to the edge that is in the width direction of the transmission line 31 and extends in the extension direction of the transmission line 31. Thus, the transmission line 31 and the second electrode 32 are sufficiently separated, so that parasitic components generated between the transmission line 31 and the second electrode 32 can be suppressed.

[0073] The third electrode 40 corresponds to the other electrode of the second capacitor C2. That is, the third electrode 40 is connected to the ground GND. Here, the third electrode 40 is an electrode whose minimum length when viewed from above in the Z direction is greater than the width of the main line 21. The so-called minimum length of the third electrode 40 refers to the minimum distance between two different points on the edge of the third electrode 40. The third electrode 40 is provided on the other main surface of the substrate 10, that is, the main surface opposite to the main surface 10a. In addition, the third electrode 40 is a conductor film provided to cover the other main surface of the substrate 10, but this is only an example, and it may also be a conductor film provided on a part of the main surface opposite to the main surface 10a.

[0074] Hereinafter, in the module 1 according to the first embodiment, the connection between the filter circuit F1 and the element 2 and the protective film 11 will be described in detail.

[0075] As Figure 2 shown, the element 2 is connected to the first electrode 22 via a conductive bonding material 3 such as solder paste containing a low melting point metal. The element 2 is connected to the fourth electrode 23 via the conductive bonding material 3. In addition, the low melting point metal is called solder, and for example, it is a tin alloy.

[0076] InFigure 1 and Figure 4 In Figure 4 , the region where the protective film 11 is provided is shown as a shaded area. The protective film 11 is a film containing an insulator provided on the main surface 10a. The material of the protective film 11 is, for example, a dielectric used as a resist. In Figure 4 's example, the protective film 11 has a protective film 11a provided so as to surround the element 2 and a protective film 11b provided so as to overlap with the first electrode 22.

[0077] In the region 22a of the first electrode 22, the protective film 11b is not provided. That is, in Figure 4 's example, the first electrode 22 has a region 22a where the surface of the first electrode 22 is exposed from the protective film 11 by not providing the protective film 11 in at least a part. In the region 22a, the conductive bonding material 3 is disposed, and the element is connected to the first electrode 22 via the conductive bonding material 3 in the region 22a. Thus, the first electrode 22 also serves as a connection terminal to the element 2, and thus the filter circuit F1 becomes smaller.

[0078] In the first embodiment, the protective film 11b is provided so as to surround the region 22a. Thus, the region 22a becomes the bottom of the concave protective film 11b. Thus, when the element 2 is mounted, it is possible to suppress the outflow of the conductive bonding material 3 from the region 22a, and the mounting of the element 2 becomes easy.

[0079] As described above, the filter circuit F1 according to the first embodiment has been described, but the filter according to the first embodiment is not limited to Figures 1 to 5 the filter shown. The substrate 10 according to the first embodiment discloses the part having the filter circuit F1, but there may also be circuits other than the filter circuit F1. Hereinafter, modification examples will be described using the drawings, but the description of the same structure as the above description will be omitted.

[0080] (First Modification Example)

[0081] Figure 6 is a schematic view of the main surface of the substrate of the filter circuit according to the first modification example. Figure 7 is a schematic view of the inside of the substrate of the filter circuit according to the first modification example. As Figure 6 shown, the filter circuit according to the first modification example may further include an element 12 as a surface mount element as an inductor. The element 12 is provided on the main surface 10a of the substrate 10. In addition, in Figure 6 , for the protective film, the protective film is not provided in the region of the electrode 25 that is connected to the element 12, and other than that, it is the same as the protective film 11 Figure 4 shown.

[0082] As Figure 6As shown, the first pattern 20A according to the first modification example further includes an electrode 25. In Figure 6 's example, one of the electrodes 25 is provided on the main line 21, and the other of the electrodes 25 is connected to the via hole 24. Thereby, both ends of the element 12 can be connected to a set of electrodes 25 provided in the first pattern 20A. In addition, as Figure 7 shown, the transmission line 31A according to the first modification example is linear and connects the second electrode 32 and the via hole 24.

[0083] (Second Modification Example)

[0084] Figure 8 is a schematic diagram showing the inside of the substrate of the filter circuit according to the second modification example. As Figure 8 shown, in the filter circuit according to the second modification example, when viewed from above in the Z direction, the second electrode 32B overlaps with the first electrode 22 at a part. In addition, the first pattern 20 and the protective film according to the second modification example are the same as the protective film 11 Figure 4 shown. In this case, the region of the first electrode 22 that overlaps with the second electrode 32B when viewed from above in the Z direction corresponds to one electrode of the first capacitor C1. In addition, a capacitor can be formed with the first electrode 22 as one electrode and the third electrode 40 as the other electrode.

[0085] (Third Modification Example)

[0086] Figure 9 is a schematic diagram showing the main surface of the substrate of the filter circuit according to the third modification example. Figure 10 is a schematic diagram showing the inside of the substrate of the filter circuit according to the third modification example. As Figure 9 and Figure 10 shown, regarding the filter circuit according to the third modification example, a part of the main line 21 and the via hole 24 are provided on the element 2 side in the X direction with respect to the first electrode 22, and the second pattern 30C is flipped about the X direction with the second electrode 32 as the center. Thereby, in the third modification example, the transmission line 31 overlaps with the fourth electrode 23 of the first pattern 20. In Figure 9 's example, the main line 21C includes a main line 21a provided on the side opposite to the element 2 side in the X direction with respect to the first electrode 22, and a main line 21b provided on the element 2 side in the X direction with respect to the first electrode 22. Here, the main line 21b is connected to an output terminal (not shown). In addition, the protective film according to the third modification example is the same as the protective film 11 Figure 4 shown.

[0087] As Figure 10As shown, in the third modification example, the width of the portion of the transmission line 31 that overlaps with the fourth electrode 23 is smaller than the minimum length of the fourth electrode 23. Here, the width of the portion of the transmission line 31 that overlaps with the fourth electrode 23 refers to the average of the lengths in the direction perpendicular to the extending direction of the portion of the transmission line 31 that overlaps with the fourth electrode 23 when viewed from above in the Z direction. In addition, the minimum length of the fourth electrode 23 refers to the minimum distance between two different points on the edge of the fourth electrode 23. Thus, it is possible to suppress the generation of parasitic capacitance between the transmission line 31 and the fourth electrode 23.

[0088] In addition, the filter circuit according to the first embodiment is not limited to the modification examples described above.

[0089] For example, the third electrode is not limited to being provided on the main surface opposite to the main surface 10a, and may also be provided on the side opposite to the first electrode 22 with respect to the second electrode 32 inside the substrate 10.

[0090] For example, the first electrode may also overlap only a part of the second electrode. In this case, the region of the first electrode that overlaps with the second electrode when viewed from above in the Z direction corresponds to one electrode of the first capacitor.

[0091] For example, the second electrode may also overlap only a part of the third electrode. In this case, the region of the second electrode that overlaps with the third electrode when viewed from above in the Z direction corresponds to one electrode of the second capacitor.

[0092] For example, the third electrode may also overlap only a part of the second electrode. In this case, the region of the third electrode that overlaps with the second electrode when viewed from above in the Z direction corresponds to the other electrode of the second capacitor.

[0093] As described above, the filter circuit F1 according to the first embodiment is a filter circuit F1 having an LC circuit. One end of the LC circuit is connected to a signal path (main line 21) connecting an input terminal IN and an output terminal OUT, and the other end is connected to a reference potential (ground GND). The filter circuit F1 according to the first embodiment includes a substrate 10, a first electrode 22 provided on one main surface 10a of the substrate 10, a second electrode 32 provided inside the substrate 10, and a third electrode 40 provided on the other main surface of the substrate 10 or inside the substrate 10 on the side opposite to the second electrode 32 with respect to the first electrode 22. The LC circuit includes a first capacitor C1 having one electrode connected to the signal path (main line 21), a first inductor L1 having one end connected to the signal path (main line 21), and a second capacitor C2 having one electrode connected to the first capacitor C1 and the first inductor L1 and the other electrode connected to the reference potential. When viewed in the thickness direction of the substrate 10, the first electrode 22 and the second electrode 32 overlap at least in part. When viewed in the thickness direction of the substrate 10, the second electrode 32 and the third electrode 40 overlap at least in part. The portion of the first electrode 22 that overlaps the second electrode 32 is one electrode of the first capacitor C1. The portion of the second electrode 32 that overlaps the first electrode 22 is the other electrode of the first capacitor C1. The portion of the second electrode 32 that overlaps the third electrode 40 is one electrode of the second capacitor C2. The portion of the third electrode 40 that overlaps the second electrode 32 is the other electrode of the second capacitor C2.

[0094] Accordingly, the first capacitor C1 and the second capacitor C2 are respectively formed by the second electrode 32 and the first electrode 22, and the second electrode 32 and the third electrode 40. Therefore, compared with the case where electrodes are formed on two main surfaces of the substrate 10 to form a capacitor, the area of the electrodes can be reduced without reducing the capacitance, and thus a smaller filter circuit F1 can be provided.

[0095] As a preferred mode, the capacitance of the first capacitor C1 is 0.03 pF or more. Thus, the capacitance of the first capacitor C1 contributes to the resonance characteristics, and therefore the signal can be attenuated at a desired attenuation pole.

[0096] As a preferred mode, the filter circuit F1 further includes a protective film 11 provided on a part of the surface of the first electrode 22. The first electrode 22 has a region 22a where the surface is exposed at least in part. Accordingly, the first electrode 22 also serves as an electrode plate of the first capacitor C1 and a connection terminal of the component 2, and thus a smaller module 1 can be provided.

[0097] As a preferred embodiment, the filter circuit F1 further includes a fourth electrode 23, which is an electrode for mounting another component 2 and is separately provided on one main surface 10a of the substrate 10 from the first electrode 22. Thus, the first electrode 23 also serves as an electrode plate of the first capacitor C1 and a connection terminal of the component 2, and therefore a smaller module 1 can be provided.

[0098] As a preferred embodiment, the first inductor L1 is a transmission line 31 provided on the main surface or inside of the substrate 10, with one end connected to the signal path (main line 21) and the other end connected to the second electrode 32. Thus, the filter circuit F1 can be realized with less space, and therefore a smaller filter circuit F1 can be provided.

[0099] As a preferred embodiment, the first inductor L1 is a transmission line 31 provided on the main surface or inside of the substrate 10, with one end connected to the signal path (main line 21) and the other end connected to the second electrode 32. In the thickness direction of the substrate 10, a part of the transmission line 31 overlaps with the fourth electrode 23. The width of the overlapping part of the transmission line 31 and the fourth electrode 23 is smaller than the minimum width of the fourth electrode 23. Thus, the generation of parasitic capacitance between the transmission line 31 and the fourth electrode 23 can be suppressed.

[0100] As a preferred embodiment, the shape of the transmission line 31 is zigzag when observed in the thickness direction of the substrate 10. Thus, the filter circuit F1 can be realized with less space, and therefore a smaller filter circuit F1 can be provided.

[0101] As a preferred embodiment, the minimum distance in the width direction between the edge in the width direction of the transmission line 31 and the edge of the second electrode 32 is 20 μm or more. Thus, the generation of parasitic capacitance between the transmission line 31 and the second electrode 32 can be suppressed.

[0102] As a preferred embodiment, the first inductor L1 is a component provided on one main surface 10a of the substrate 10. In this case, a small filter circuit F1 can also be provided.

[0103] (Second Embodiment)

[0104] Figure 11 is a schematic diagram showing the filter circuit according to the second embodiment. As Figure 12 shown, the difference between the filter circuit F2 according to the second embodiment and the first embodiment is that a component 13 is mounted on the main line as the second inductor. Hereinafter, the filter circuit F2 according to the second embodiment will be described with reference to the drawings, but the description of the same points as those in the first embodiment will be omitted.

[0105] Figure 12This is a circuit diagram showing the filter circuit according to the second embodiment. As Figure 12 shown, the difference between the filter circuit F2 according to the second embodiment and the filter circuit F1 according to the first embodiment is that a second inductor L2 is inserted into the signal path connecting the input terminal IN and the output terminal OUT. One end of the second inductor L2 is connected to the node N1 on the signal path, and the other end of the second inductor L2 is connected to the node N2 on the signal path. In this case, it is also possible to appropriately adjust the sum of the electrostatic capacitances of the first capacitor C1 and the second capacitor C2 and the inductance of the first inductor L1, so that the signal is attenuated at a desired attenuation pole through the parallel resonance circuit. In addition, by inserting the second inductor L2 into the signal path connecting the input terminal IN and the output terminal OUT, the frequency of the attenuation pole can be reduced.

[0106] Figure 13 This is a schematic diagram showing the main surface of the substrate of the filter circuit according to the second embodiment. Figure 13 This is a diagram showing the filter circuit according to the second embodiment with the component 13 removed. In the second embodiment, the main line 21D includes the main line 21a and the main line 21b. In Figure 13 the example, the main line 21a is connected to an input terminal (not shown), and the main line 21b is connected to an output terminal (not shown). In the second embodiment, one end of the first electrode 22D in the one end of the X direction is connected to one end of the main line 21b. In addition, one end of the fourth electrode 23D in the one end of the X direction is connected to one end of the main line 21a. In Figure 13 the example, the via hole 24D is provided on the main line 21a, but this is only an example.

[0107] Figure 14 This is a schematic diagram showing the inside of the substrate of the filter circuit according to the second embodiment. In Figure 14 the example, one end of the transmission line 31D is connected to the via hole 24D, and the other end is connected to the second electrode 32.

[0108] In the second embodiment, as Figure 14 shown, the transmission line 31D overlaps with the main line 21 of the first pattern 20D and the fourth electrode 23D. In the second embodiment, similar to the third modification example, the overlapping portion of the transmission line 31D and the fourth electrode 23D is smaller than the minimum length of the fourth electrode 23D. Thus, the parasitic capacitance generated between the transmission line 31D and the fourth electrode 23D can be suppressed.

[0109] Hereinafter, the connection between the main line 21 and the component 13 and the protective film 11A in the filter circuit F2 according to the second embodiment will be described in detail. In Figure 11 and Figure 13In the figure, the area where the protective film 11 is provided is shown as a shaded area.

[0110] In Figure 13 In the example of, the protective film 11 also has a protective film 11c provided on the fourth electrode 23D. Similar to the protective film 11b for the first electrode 22D, the protective film 11c is provided in a frame shape so as to overlap the edge of the fourth electrode 23D when viewed from above in the Z direction. Here, at least a part of the fourth electrode 23D has a region 23Da where the surface of the fourth electrode 23D is exposed from the protective film 11. In Figure 13 In the example of, in the region 23Da, similar to the region 22Da of the first electrode 22D, a conductive bonding material is disposed, and the element is connected to the fourth electrode 23D via the conductive bonding material in the region 23Da.

[0111] In the second embodiment, the region 22Da is on the fourth electrode side of the first electrode 22D when viewed from above in the Z direction. More specifically, when viewed from above in the Z direction, the fourth electrode 23D exists in the direction where the geometric center of the region 22Da is located with respect to the geometric center of the first electrode 22D. Thereby, the area of the region where the element 13 and the first electrode 22D overlap when viewed from above in the Z direction can be reduced, and thus the generation of parasitic components between the element 13 and the first electrode 22D can be suppressed.

[0112] In the second embodiment, similar to the region 22Da, the region 23Da is on the first electrode side of the fourth electrode 23D when viewed from above in the Z direction. More specifically, when viewed from above in the Z direction, the first electrode 22D exists in the direction where the geometric center of the region 23Da is located with respect to the geometric center of the fourth electrode 23D. Thereby, the area of the region where the element 13 and the fourth electrode 23D overlap when viewed from above in the Z direction can be reduced, and thus the generation of parasitic components between the element 13 and the fourth electrode 23D can be suppressed.

[0113] As described above, the filter circuit F2 according to the second embodiment has been described, but the filter according to the second embodiment is not limited to Figures 11 to 14 the filter shown. Hereinafter, modification examples will be described with reference to the drawings.

[0114] (Fourth Modification Example)

[0115] Figure 15 is a schematic diagram of the main surface of the substrate of the filter circuit according to the fourth modification example. Figure 16 is a schematic diagram of the inside of the substrate of the filter circuit according to the fourth modification example. As Figure 16As shown, the filter circuit according to the fourth modification example sets the transmission line 31E as an L-shaped line to increase the areas of the electrodes of the first capacitor C1 and the second capacitor C2, that is, the first electrode 22E and the second electrode (not shown). In this case, the capacitance of the first capacitor C1 increases, instead of reducing the inductance of the transmission line 31E, that is, the first inductor L1. Therefore, in this case, the electrical signal can also be attenuated at a specific frequency (attenuation pole).

[0116] As described above, the filter circuit according to the second embodiment is a filter circuit further having a second inductor L2 inserted into a signal path (main line 21D) between one electrode of the first capacitor C1 and the first inductor L1. Another element 13 is the second inductor L2. In this case, a small-sized filter circuit can also be provided.

[0117] As a preferred mode, when viewed in the thickness direction of the substrate, the fourth electrode 23D is disposed in a direction with respect to the geometric center of the first electrode 22D toward the geometric center of the region 22Da. Thereby, the parasitic capacitance generated between the another element 13 and the fourth electrode 23D can be suppressed.

[0118] In addition, the above-described embodiments are for facilitating the understanding of the present disclosure and are not for limiting the interpretation of the present invention. The present disclosure can be changed / improved without departing from its gist, and the equivalents thereof are also included in the present disclosure.

[0119] The present disclosure can adopt the following structure as described above or in place of the above.

[0120] (1) A filter circuit having an LC circuit, one end of the LC circuit is connected to a signal path connecting an input terminal and an output terminal, and the other end is connected to a reference potential,

[0121] wherein the filter circuit includes:

[0122] A substrate;

[0123] A first electrode disposed on one main surface of the substrate;

[0124] A second electrode disposed inside the substrate; and

[0125] A third electrode disposed on the other main surface of the substrate, or disposed inside the substrate on a side opposite to the second electrode with respect to the first electrode,

[0126] The LC circuit includes:

[0127] A first capacitor, one electrode of which is connected to the signal path;

[0128] The first inductor, one end of which is connected to the signal path; and

[0129] The second capacitor, one electrode of which is connected to the first capacitor and the first inductor, and the other electrode of which is connected to the reference potential,

[0130] When observed in the thickness direction of the substrate, at least a part of the first electrode and the second electrode overlap each other,

[0131] When observed in the thickness direction of the substrate, at least a part of the second electrode and the third electrode overlap each other,

[0132] The part of the first electrode that overlaps with the second electrode is one electrode of the first capacitor,

[0133] The part of the second electrode that overlaps with the first electrode is the other electrode of the first capacitor,

[0134] The part of the second electrode that overlaps with the third electrode is one electrode of the second capacitor,

[0135] The part of the third electrode that overlaps with the second electrode is the other electrode of the second capacitor.

[0136] (2)The filter circuit according to (1), wherein,

[0137] The capacitance of the first capacitor is 0.03 pF or more.

[0138] (3)The filter circuit according to (1) or (2), wherein,

[0139] The filter circuit further includes a protective film, and the protective film is provided on a part of the surface of the first electrode,

[0140] At least a part of the first electrode has a region where the surface is exposed from the protective film.

[0141] (4)The filter circuit according to (3), wherein,

[0142] The filter circuit further includes a fourth electrode, and the fourth electrode is an electrode for mounting another component and is provided separately from the first electrode on one main surface of the substrate.

[0143] (5)The filter circuit according to (4), wherein,

[0144] The filter circuit further has a second inductor, and the second inductor is inserted into the signal path between one electrode of the first capacitor and the first inductor,

[0145] The additional element is the second inductor.

[0146] (6)The filter circuit according to (4) or (5), wherein

[0147] When observed in the thickness direction of the substrate, the fourth electrode is disposed in a direction toward the geometric center of the region with respect to the geometric center of the first electrode.

[0148] (7)The filter circuit according to any one of (4) to (6), wherein

[0149] The first inductor is a transmission line disposed on the main surface or inside of the substrate, having one end connected to the signal path and the other end connected to the second electrode.

[0150] In the thickness direction of the substrate, a part of the transmission line overlaps with the fourth electrode.

[0151] The width of the part of the transmission line overlapping with the fourth electrode is smaller than the minimum width of the fourth electrode.

[0152] (8)The filter circuit according to any one of (1) to (6), wherein

[0153] The first inductor is a transmission line disposed on the main surface or inside of the substrate, having one end connected to the signal path and the other end connected to the second electrode.

[0154] (9)The filter circuit according to (7) or (8), wherein

[0155] The shape of the transmission line is zigzag when observed in the thickness direction of the substrate.

[0156] (10)The filter circuit according to any one of (7) to (9), wherein

[0157] The minimum distance in the width direction between the edge in the width direction of the transmission line and the edge of the second electrode is 20 μm or more.

[0158] (11)The filter circuit according to any one of (1) to (6), wherein

[0159] The first inductor is an element disposed on the one main surface of the substrate.

[0160] According to the present disclosure, a filter circuit capable of obtaining desired filter characteristics can be realized.

Claims

1. A filter circuit comprising an LC circuit, one end of the LC circuit being connected to a signal path connecting an input terminal and an output terminal, and the other end of the LC circuit being connected to a reference potential, in, The filter circuit comprises: substrate; A first electrode is provided on a main surface of the substrate; a second electrode disposed inside the substrate; and a third electrode disposed on the other main surface of the substrate, or disposed on the inside of the substrate on the side opposite to the first electrode relative to the second electrode, The LC circuit comprises: a first capacitor having one electrode connected to the signal path; a first inductor having one end connected to the signal path; and a second capacitor having one electrode connected to the first capacitor and the first inductor and another electrode connected to a reference potential, The first electrode and the second electrode overlap at least partially when viewed in the thickness direction of the substrate, The second electrode and the third electrode overlap at least partially when viewed in the thickness direction of the substrate, The portion of the first electrode that overlaps with the second electrode is one electrode of the first capacitor. The portion of the second electrode that overlaps with the first electrode is another electrode of the first capacitor. The portion of the second electrode that overlaps with the third electrode is one electrode of the second capacitor. A portion of the third electrode that overlaps with the second electrode serves as another electrode of the second capacitor.

2. The filter circuit according to claim 1, wherein: The electrostatic capacitance of the first capacitor is greater than or equal to 0.03 pF.

3. The filter circuit according to claim 1 or 2, wherein: The filter circuit further includes a protective film provided on a portion of the surface of the first electrode. The first electrode has a region in which at least a portion of its surface is exposed from the protective film.

4. The filter circuit according to claim 3, wherein: The filter circuit further includes a fourth electrode, which is an electrode for mounting another element and is provided on one main surface of the substrate so as to be separated from the first electrode.

5. The filter circuit according to claim 4, wherein: The filter circuit further includes a second inductor inserted into the signal path between one electrode of the first capacitor and the first inductor. The other element is the second inductor.

6. The filter circuit according to claim 4 or 5, wherein: When viewed in the thickness direction of the substrate, the fourth electrode is provided in a direction toward a geometric center of the region relative to a geometric center of the first electrode.

7. The filter circuit according to any one of claims 4 to 6, wherein: The first inductor is a transmission line provided on the main surface or inside the substrate, one end of which is connected to the signal path and the other end of which is connected to the second electrode. In the thickness direction of the substrate, a portion of the transmission line overlaps with the fourth electrode. A width of a portion of the transmission line overlapping the fourth electrode is smaller than a minimum width of the fourth electrode.

8. The filter circuit according to any one of claims 1 to 6, wherein: The first inductor is a transmission line provided on the main surface or inside the substrate, one end of which is connected to the signal path and the other end of which is connected to the second electrode.

9. The filter circuit according to claim 7 or 8, wherein: The transmission line has a zigzag shape when viewed in the thickness direction of the substrate.

10. The filter circuit according to any one of claims 7 to 9, wherein: A minimum distance between an edge in the width direction of the transmission line and an edge of the second electrode in the width direction is 20 μm or more.

11. The filter circuit according to any one of claims 1 to 6, wherein: The first inductor is an element provided on the one main surface of the substrate.

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