filter circuit

Abstract

This filter circuit comprises a resonance circuit, the resonance circuit including an inductance element and a capacitor. The capacitor comprises an element stack, an exterior body, a first external electrode and a second external electrode, and a third external electrode. The element stack is composed of a stack of a plurality of capacitor elements. In a first capacitor element, a first end portion is electrically connected to the first external electrode. In a second capacitor element, a first end portion is electrically connected to the second external electrode. The third external electrode is electrically connected to the cathode portions of the capacitor elements. The configuration provides a filter circuit enabling a decrease in the number of capacitors.

Description

Technical Field

[0001] The present disclosure generally relates to a filter circuit, and more particularly to a filter circuit including a resonance circuit.

Background Art

[0002] The digital signal processing board described in Patent Document 1 includes an LSI to which an element for clock operation is connected, a power input line for supplying power to the LSI, and a decoupling capacitor connected between the power input line and the ground. As the decoupling capacitor, a surface-mounted solid electrolytic capacitor having an ESR of 25 mΩ (100 kHz) or less and an ESL of 800 pH (500 MHz) or less is used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] A filter circuit according to an aspect of the present disclosure includes a resonance circuit. The resonance circuit includes an input terminal, an output terminal, an inductance element, and a capacitor. The inductance element is electrically connected between the input terminal and the output terminal. The capacitor is electrically connected between the inductance element and a conductor of a reference potential. The capacitor is an electrolytic capacitor. The capacitor includes an element laminate, an exterior body, a first external electrode and a second external electrode, and a third external electrode. The element laminate is formed by laminating a plurality of capacitor elements. The exterior body includes a cover [[ID=3�]]sealing member. The first external electrode and the second external electrode are electrically connected to the inductance element. The third external electrode is electrically connected to the conductor of the reference potential. Each of the plurality of capacitor elements includes an anode body, a dielectric layer, and a cathode portion ,ofThe anode body has a porous portion on its surface. The dielectric layer is formed on the surface of at least a portion of the porous portion. The cathode portion covers at least a portion of the dielectric layer. Each of the above-mentioned plurality of capacitor elements At the first end, the anode body From the aforementioned exterior To be exposed. Each of the above-mentioned plurality of capacitor elements At the second end, the anode body is covered by the cathode portion. The plurality of capacitor elements include a first capacitor element and a second capacitor element. In the first capacitor element, the first end is electrically connected to the first external electrode. In the second capacitor element, the first end is electrically connected to the second external electrode. The third external electrode is electrically connected to the cathode portion of the capacitor element.

[0005] This disclosure has the advantage of being able to reduce the number of capacitors. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a circuit diagram of an electrical circuit including a filter circuit according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a plan view showing the same filter circuit mounted on a circuit board. [Figure 3] Figure 3 is a perspective view of the electrolytic capacitor in the filter circuit shown above. [Figure 4] Figure 4 is a perspective view of the electrolytic capacitor shown above. [Figure 5] Figure 5 is a schematic cross-sectional view of the electrolytic capacitor shown above. [Figure 6] Figure 6 is a schematic cross-sectional view of the capacitor element of the electrolytic capacitor shown above. [Figure 7] Figure 7 is a characteristic diagram of the filter circuit shown above. [Figure 8] Figure 8 is a perspective view of an electrolytic capacitor according to Modification 1 of this disclosure. [Figure 9] Figure 9 is a perspective view of an electrolytic capacitor according to Modification 2 of this disclosure. [Figure 10] Figure 10 is a perspective view of an electrolytic capacitor according to Modification 2 of the present disclosure. [Figure 11] Figure 11 is a perspective view of an electrolytic capacitor according to another embodiment of Modification 2 of the present disclosure. [Figure 12] Figure 12 is a perspective view of an electrolytic capacitor according to Modification 3 of the present disclosure. [Figure 13] Figure 13 is a perspective view of an electrolytic capacitor according to Modification 3 of the present disclosure. [Figure 14] Figure 14 is a perspective view of an electrolytic capacitor according to another embodiment of Modification 3 of the present disclosure. [Figure 15] Figure 15 is a perspective view of an electrolytic capacitor according to Modification 4 of this disclosure. [Figure 16] Figure 16 is a perspective view of an electrolytic capacitor according to Modification 4 of this disclosure. [Figure 17] Figure 17 is a perspective view of an electrolytic capacitor according to another embodiment of Modification 4 of the present disclosure. [Figure 18] Figure 18 is a circuit diagram of an electrical circuit including a filter circuit according to Modification 5 of the present disclosure. [Modes for carrying out the invention]

[0007] Before describing the embodiments, the problems in the prior art are briefly outlined below. Conventional electrical circuits sometimes include filter circuits to reduce noise. However, in order to meet the required specifications of the filter circuit, it was sometimes necessary to include many capacitors. In light of the above issues, this disclosure provides a filter circuit that can reduce the number of capacitors.

[0008] The filter circuit according to the embodiment will be described below with reference to the drawings. However, the embodiments described below are only one of many embodiments of this disclosure. The embodiments described below can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. In addition, the figures described in the embodiments below are schematic diagrams, and the ratios of the size and thickness of each component in the figures do not necessarily reflect the actual dimensional ratios.

[0009] (Embodiment) (overview) As shown in Figure 1, the filter circuit 100 of this embodiment includes a resonant circuit 101. The resonant circuit 101 includes an input terminal T1, an output terminal T2, an inductance element 42, and a capacitor 11. The inductance element 42 is electrically connected between the input terminal T1 and the output terminal T2. The capacitor 11 is electrically connected between the inductance element 42 and a conductor W3 (see Figure 2) at a reference potential. The capacitor 11 is an electrolytic capacitor.

[0010] As shown in FIGS. 2 to 6, the capacitor 11 includes an element laminate, an exterior body 14, a first external electrode 21 and a second external electrode 22, and a third external electrode 23 (231 and 232). The element laminate is formed by laminating a plurality of capacitor elements 10. The exterior body 14 includes a sealing member 140 that seals the element laminate. The first external electrode 21 and the second external electrode 22 are electrically connected to an inductance element 42. The third external electrode 23 is electrically connected to a conductor W3 having a reference potential. Each of the plurality of capacitor elements 10 has an anode body 3, a dielectric layer, a cathode portion 6, a first end portion 1a, and a second end portion 2a. The anode body 3 has a porous portion 5 on its surface. The dielectric layer is formed on at least a part of the surface of the porous portion 5. The cathode portion 6 covers at least a part of the dielectric layer. At the first end portion 1a, the anode body 3 is exposed. At the second end portion 2a, the anode body 3 is covered with the cathode portion 6. The plurality of capacitor elements 10 include a first capacitor element 10a and a second capacitor element 10b. In the first capacitor element 10a, the first end portion 1a is electrically connected to the first external electrode 21. In the second capacitor element 10b, the first end portion 1a is electrically connected to the second external electrode 22. The third external electrode 23 is electrically connected to the cathode portion 6 of the capacitor element 10.

[0011] According to the present embodiment, in the first capacitor element 10a and the second capacitor element 10b, the direction in which current flows inside the element is different, and the direction of the magnetic field generated by the current is different. Therefore, the magnetic flux generated in the element laminate is reduced. Thus, the ESL (equivalent series inductance) of the capacitor 11 is reduced.

[0012] Also, in order to reduce the ESL, the number of capacitors 11 can be reduced as compared with the case where a plurality of capacitors having a larger ESL than the capacitor 11 are connected in parallel.

[0013] Also, the first capacitor element 10a and the second capacitor element 10b are alternately laminated. Thereby, the magnetic flux generated in the element laminate can be effectively reduced. Therefore, the ESL can be effectively reduced.

[0014] Furthermore, the first end 1a of the first capacitor element 10a is exposed from the first surface 14a of the outer casing 14, and the first end 1a of the second capacitor element 10b is exposed from the second surface 14b of the outer casing 14, which is opposite to the first surface 14a. This enhances the effect of canceling out magnetic flux between the first capacitor element 10a and the second capacitor element 10b, and can effectively reduce the ESL of the capacitor 11.

[0015] Furthermore, at least a portion of the first external electrode 21 is provided on the first surface 14a of the outer casing 14, and at least a portion of the second external electrode 22 is provided on the second surface 14b of the outer casing 14, which is opposite to the first surface 14a. At least a portion of the third external electrode 23 is provided on the third surface 14c of the outer casing 14, which is different from the first surface 14a and the second surface 14b.

[0016] In the following description of the capacitor 11, the side on which the second surface 14b is provided when viewed from the first surface 14a is defined as "left," and the side on which the first surface 14a is provided when viewed from the second surface 14b is defined as "right." Furthermore, the side on which the fourth surface 14d, opposite to the third surface 14c, is provided when viewed from the third surface 14c is defined as "top," and the side on which the third surface 14c is provided when viewed from the fourth surface 14d is defined as "bottom." In addition, the direction perpendicular to both up / down and left / right is defined as "front / back." As shown in Figure 3, the casing 14 has a fifth surface 14e (front) and a sixth surface 14f (rear). Also, the height of the capacitor 11 means the length of the capacitor 11 in the vertical direction. However, these definitions are not intended to limit the direction in which the capacitor 11 can be used.

[0017] The capacitor 11 is used, for example, mounted on substrate B1 (see Figure 2). The capacitor 11 is mounted on substrate B1 such that the lower surfaces of the first external electrode 21, the second external electrode 22, and the third external electrode 23 are in contact with the surface of substrate B1. In this way, the first external electrode 21, the second external electrode 22, and the third external electrode 23 are electrically connected to substrate B1.

[0018] In the capacitor 11 of this embodiment, at least a portion of the first external electrode 21 and at least a portion of the second external electrode 22 are provided on the side surface of the casing 14, thus reducing the portion inside the capacitor 11 that does not contribute to the capacitance. Therefore, the capacitance of the capacitor 11 can be increased. By increasing the capacitance of the capacitor 11, the number of capacitors 11 can be reduced compared to the case where multiple capacitors with relatively small capacitances are connected in parallel to secure the capacitance.

[0019] (detail) (1) Circuit configuration First, with reference to Figure 1, the filter circuit 100 and the electrical circuit EC1 equipped with the filter circuit 100 of this embodiment will be described.

[0020] The electrical circuit EC1 supplies power to the integrated circuit 41. The electrical circuit EC1 includes a filter circuit 100, a DC / DC converter 43, and conductors that constitute a plurality of electrical circuits 30. The plurality of electrical circuits 30 include a first electrical circuit 31 and a second electrical circuit 32.

[0021] The integrated circuit 41 is, for example, a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). The integrated circuit 41 is provided in, for example, a personal computer, a server computer, or a microcontroller.

[0022] The first end of the first circuit 31 is electrically connected to the power supply PS1. That is, the electrical circuit EC1 is electrically connected to the power supply PS1. The second end of the first circuit 31 is electrically connected to the input terminal of the DC / DC converter 43. The power supply PS1 is a DC power supply. The power supply PS1 is, for example, a battery. The power supply PS1 supplies DC power to the DC / DC converter 43.

[0023] The first end of the second circuit 32 is electrically connected to the output terminal of the DC / DC converter 43. The second end of the second circuit 32 is electrically connected to the integrated circuit 41. In other words, the electrical circuit EC1 is electrically connected to the integrated circuit 41. The DC / DC converter 43 converts the DC power input from the power supply PS1 into DC power of a predetermined voltage and outputs it to the integrated circuit 41.

[0024] The filter circuit 100 is provided in the first circuit 31. That is, the filter circuit 100 is electrically connected between the power supply PS1 and the input terminal of the DC / DC converter 43.

[0025] The filter circuit 100 includes a resonant circuit 101. In this embodiment, the filter circuit 100 consists only of the resonant circuit 101.

[0026] The resonant circuit 101 includes an input terminal T1, an output terminal T2, an inductance element 42, and a capacitor 11. The capacitor 11 has two internal capacitors 111 and 112. The two internal capacitors 111 and 112 are housed in one outer casing 14 of the capacitor 11 (see Figure 3). A plurality of first capacitor elements 10a (see Figure 5), described later, constitute the internal capacitor 111, and a plurality of second capacitor elements 10b (see Figure 5) constitute the internal capacitor 112.

[0027] The power supply PS1 is electrically connected to the input terminal T1. The input terminal of the DC / DC converter 43 is electrically connected to the output terminal T2. The input terminal T1 and the output terminal T2 are part of the conductors that make up the first circuit 31. The input terminal T1 and the output terminal T2 may be connectors and may be connected to other connectors provided on the first circuit 31.

[0028] The inductance element 42 is, for example, a coil. The inductance element 42 is electrically connected between the input terminal T1 and the output terminal T2. That is, the first terminal of the inductance element 42 is electrically connected to the input terminal T1, and the second terminal of the inductance element 42 is electrically connected to the output terminal T2.

[0029] The anode of the internal capacitor 111 is electrically connected to the first end of the inductance element 42 via the first external electrode 21. More specifically, the anode of the internal capacitor 111 is electrically connected to the connection point between the first end of the inductance element 42 and the input terminal T1. The cathode of the internal capacitor 111 is electrically connected to a conductor W3 (see Figure 2) at a reference potential via the third external electrode 231. In this embodiment, the reference potential is the ground potential.

[0030] The anode of the internal capacitor 112 is electrically connected to the second end of the inductance element 42 via the second external electrode 22. More specifically, the anode of the internal capacitor 112 is electrically connected to the connection point between the second end of the inductance element 42 and the output terminal T2. The cathode of the internal capacitor 112 is electrically connected to the conductor W3 (see Figure 2) at a reference potential via the third external electrode 232.

[0031] Thus, the resonant circuit 101 constitutes a π-type filter. Specifically, the first external electrode 21 is electrically connected to the first end of the inductance element 42, and the second external electrode 22 is electrically connected to the second end of the inductance element 42.

[0032] Furthermore, in addition to capacitor 11, electrical circuit EC1 includes capacitors 45 and 48. Each of capacitors 45 and 48 is an electrolytic capacitor. Electrical circuit EC1 also includes an inductor 44.

[0033] The inductor 44 is electrically connected between the output terminal of the DC / DC converter 43 and the capacitor 45. The capacitor 45 is electrically connected between the second circuit 32 and the reference potential conductor W3 (ground) (see Figure 2). Together with the capacitor 45, the inductor 44 constitutes a low-pass filter.

[0034] Capacitor 48 is electrically connected between the second circuit 32 and the reference potential conductor W3 (ground). Capacitor 48 smooths the output voltage of the DC / DC converter 43.

[0035] (2) Implementation of capacitor and inductance elements As shown in Figure 2, the capacitor 11 and the inductance element 42 are surface-mounted on the substrate B1. Conductors W1, W2, and W3 are formed on the substrate B1. Conductor W1 includes the input terminal T1 of the resonant circuit 101 (see Figure 1). Conductor W2 includes the output terminal T2 of the resonant circuit 101 (see Figure 1). The potential of conductor W3 is the reference potential (ground potential). Conductor W3 is provided between conductors W1 and W2.

[0036] The capacitor 11 is mounted on the substrate B1 such that its third surface 14c (see Figure 4), which is its bottom surface, faces the surface of the substrate B1. The first external electrode 21 of the capacitor 11 is electrically connected to the conductor W1. The second external electrode 22 is electrically connected to the conductor W2. The third external electrodes 231 and 232 are electrically connected to the conductor W3.

[0037] Since the first external electrode 21 and the second external electrode 22 are equivalent, the first external electrode 21 may be electrically connected to the conductor W2 and the second external electrode 22 to the conductor W1.

[0038] The inductance element 42 has a first electrode 421 that constitutes the first end and a second electrode 422 that constitutes the second end. The first electrode 421 is electrically connected to the conductor W1. The second electrode 422 is electrically connected to the conductor W2.

[0039] (3) Characteristics of Capacitors and Resonant Circuits As described above, capacitor 11 has two internal capacitors 111 and 112. The characteristics of capacitor 11 are defined as the characteristics of the parallel circuit of the two internal capacitors 111 and 112.

[0040] Under the condition that the frequency is between 50 MHz and 1000 MHz, the ESL (Equivalent Series Inductance) of capacitor 11 is 100 pH or less.

[0041] The capacitance of capacitor 11 is 10 [μF] or more.

[0042] As shown in Figure 5, the capacitor 11 has a stacked structure in which a first capacitor element 10a and a second capacitor element 10b are stacked, as a configuration to reduce ESL. More specifically, the capacitor 11 has an alternating stacked structure in which the first capacitor element 10a and the second capacitor element 10b are stacked alternately.

[0043] Furthermore, the capacitor 11 has an end-face current collection structure in which at least a portion of the first external electrode 21 and at least a portion of the second external electrode 22 are provided on the side surface of the outer casing 14, as a configuration for increasing capacitance.

[0044] The solid line portion of Figure 7 represents the damping characteristics of the resonant circuit 101 consisting of the capacitor 11 and the inductance element 42. The dashed line portion of Figure 7 represents the damping characteristics of the resonant circuit according to the comparative example. The resonant circuit according to the comparative example consists of the inductance element 42 and two-terminal conductive aluminum electrolytic capacitors (capacitance 220 μF) provided one on each side of the inductance element 42. In this embodiment, by using a capacitor 11 with a small ESL, the amount of attenuation can be increased over a wider bandwidth.

[0045] (4) Capacitor structure Next, the structure of the capacitor 11 (hereinafter also referred to as electrolytic capacitor 11) of this embodiment will be described with reference to Figures 5 and 6.

[0046] [Electrolytic capacitor] An electrolytic capacitor 11 according to one embodiment of the present disclosure comprises an element stack in which a plurality of capacitor elements 10 are stacked, an outer casing 14, a first external electrode 21, a second external electrode 22, and a third external electrode 23 (231 and 232). The outer casing 14 comprises the element stack cover It includes a sealing member 140. The exterior body 14 of this embodiment further includes a substrate 17. The lower surface of the substrate 17 corresponds to the lower surface (third surface 14c) of the exterior body 14.

[0047] Each of the multiple capacitor elements 10 includes an anode 3 having a porous portion 5 on its surface, a dielectric layer formed on at least a portion of the surface of the porous portion 5, and a cathode portion 6 covering at least a portion of the dielectric layer. Each of the multiple capacitor elements 10 has a first end 1a where the anode 3 is exposed and a second end 2a where the anode 3 is covered by the cathode portion 6, and at least the end face of the first end 1a is exposed from the outer casing 14.

[0048] Multiple capacitor elements 10 include those whose first end 1a faces the first surface 14a of the outer casing 14, and those whose first end 1a faces a second surface 14b different from the first surface 14a of the outer casing 14. Of these, those whose first end 1a faces the first surface 14a of the outer casing 14 are referred to as the first capacitor element 10a, and those whose first end 1a faces a second surface 14b different from the first surface 14a of the outer casing 14 are referred to as the second capacitor element 10b. The first end 1a of the first capacitor element 10a is electrically connected to the first external electrode 21. The first end 1a of the second capacitor element 10b is electrically connected to the second external electrode 22.

[0049] In this configuration, the direction in which current flows through the first capacitor element 10a and the second capacitor element 10b is different. Therefore, the direction of the magnetic field generated by the current is different, and the magnetic flux generated within the element stack is reduced. Thus, ESL is reduced. Preferably, the first surface 14a and the second surface 14b may be mutually opposing surfaces of the outer casing 14. Furthermore, when the first capacitor element 10a and the second capacitor element 10b are stacked alternately, the magnetic flux generated within the element stack can be effectively reduced. Thus, ESL can be effectively reduced.

[0050] The number of first capacitor elements 10a and the number of second capacitor elements 10b may be the same. When the number of first capacitor elements 10a and the number of second capacitor elements 10b are the same, the magnetic field generated by the current flowing through the first capacitor elements 10a and the magnetic field generated by the current flowing through the second capacitor elements 10b cancel each other out without excess or deficiency, reducing the magnetic flux generated within the element stack. Therefore, it is easier to reduce ESL.

[0051] Furthermore, the electrical connection between the element stack and the external electrodes can be achieved by electrically connecting the end face of the first end 1a exposed from the outer casing 14 of each capacitor element 10 to the external electrodes (first external electrode 21 or second external electrode 22). The electrical connection between the end face of the first end 1a and the external electrodes can be achieved, for example, by using an external electrode formed along the first surface 14a or the second surface 14b, or by electrically connecting an intermediate electrode (corresponding to the anode electrode layer 16 described later) formed along the first surface 14a or the second surface 14b to the external electrodes. In this case, since there is no need to interpose other members within the outer casing 14 to connect the first end 1a and the external electrodes (first external electrode 21 or second external electrode 22), it is easy to increase the capacitance of the electrolytic capacitor 11. Furthermore, in the current path from the portion of the anode body 3 where the cathode portion 6 is not formed (anode extraction portion) to the first external electrode 21 or the second external electrode 22, the current path flowing parallel to the stacking plane of the element stack is approximately equal to the length of the anode extraction portion and can be easily shortened. Therefore, the ESL caused by the current path flowing parallel to the stacking plane of the element stack can be further reduced.

[0052] The third external electrodes 23 (231 and 232) are electrically connected to the cathode portion 6 of the capacitor element 10. The third external electrodes 23 (231 and 232) are electrically connected to the cathode portion 6, for example, in the outermost layer (i.e., the bottom or top layer) of the element stack. This allows the cathode terminal to be located on the bottom surface of the electrolytic capacitor 11. On the other hand, by extending the first external electrode 21 or the second external electrode 22 to the bottom surface of the electrolytic capacitor 11, the anode terminal can be located on the bottom surface of the electrolytic capacitor 11. In this case, the current flowing through the extended portion of the first external electrode 21 or the second external electrode 22 flows in the opposite direction to the current flowing through the anode extraction portion. Therefore, the magnetic field generated by the current flowing through the anode extraction portion is canceled out by the magnetic field generated by the current flowing through the extended portion of the first external electrode 21 or the second external electrode 22, further reducing the ESL of the electrolytic capacitor 11. As a result, the extended portion reduces the distance between the cathode terminal and the first and / or second external electrodes, thereby improving the ESL. These synergistic effects significantly reduce the ESL.

[0053] The first end 1a may be electrically connected to a first external electrode 21 or a second external electrode 22 via a contact layer 15. The contact layer 15 can be selectively formed on the end face of the first end 1a of a plurality of capacitor elements 10, for example. The contact layer 15 can connect each of the first end 1a of the plurality of capacitor elements 10 to an intermediate electrode (anode electrode layer 16) or external electrode formed to cover a first surface 14a or a second surface 14b. By using the contact layer 15, the electrical connection between the first end 1a and the external electrode can be ensured. Therefore, the reliability of the electrolytic capacitor 11 can be improved.

[0054] The first external electrode 21 and the second external electrode 22 may face each other in the longitudinal direction of the anode body 3, or they may face each other in the short direction. For example, the first external electrode 21 and the second external electrode 22 may each be located at an end along the short direction of one surface (e.g., the bottom surface) of the outer casing 14, or at an end along the longitudinal direction. In terms of reducing ESL, the first external electrode 21 and the second external electrode 22 may face each other in the short direction of the anode body 3. On the other hand, when the first external electrode 21 and the second external electrode 22 face each other in the longitudinal direction of the anode body 3, it is easy to increase the extension distance of the first external electrode 21 or the second external electrode 22 on the bottom surface of the electrolytic capacitor 11, making it easier to control the distance between the cathode terminal and the anode terminal, and making it easier to control the ESL to a desired value.

[0055] Figure 5 is a schematic cross-sectional view showing the structure of an electrolytic capacitor 11 according to one embodiment of the present disclosure. Figure 6 is a cross-sectional view showing the structure of a capacitor element 10 constituting the electrolytic capacitor 11 of Figure 5. However, the electrolytic capacitor 11 according to the present disclosure is not limited to these.

[0056] As shown in Figures 5 and 6, the electrolytic capacitor 11 comprises a plurality of capacitor elements 10 (10a, 10b). Each capacitor element 10 comprises an anode 3 and a cathode 6. The anode 3 is, for example, a foil (anode foil). The anode 3 has a porous portion 5 on its surface, and a dielectric layer (not shown) is formed on at least a portion of the surface of the porous portion 5. The cathode 6 covers at least a portion of the dielectric layer.

[0057] In the capacitor element 10, the anode 3 is exposed at one end (first end) 1a without being covered by the cathode portion 6, while the anode 3 at the other end (second end) 2a is covered by the cathode portion 6. Hereinafter, the portion of the anode 3 not covered by the cathode portion 6 will be referred to as the first portion 1, and the portion of the anode 3 covered by the cathode portion 6 will be referred to as the second portion 2. The end of the first portion 1 is the first end 1a, and the end of the second portion 2 is the second end 2a. The dielectric layer is formed on the surface of the porous portion 5 formed at least in the second portion 2. The first portion 1 of the anode 3 is also called the anode extraction portion. The second portion 2 of the anode 3 is also called the cathode forming portion.

[0058] More specifically, the second part 2 has a core 4 and a porous part (porous body) 5 formed on the surface of the core 4 by roughening (etching, etc.). On the other hand, the first part 1 may or may not have the porous part 5 on its surface. The dielectric layer is formed along the surface of the porous part 5. At least a portion of the dielectric layer covers the inner wall surface of the pores of the porous part 5 and is formed along that inner wall surface.

[0059] The cathode section 6 comprises a solid electrolyte layer 7 covering at least a portion of the dielectric layer and a cathode extraction layer covering at least a portion of the solid electrolyte layer 7. The surface of the dielectric layer has an uneven shape corresponding to the shape of the surface of the anode 3. The solid electrolyte layer 7 may be formed to fill in such unevenness of the dielectric layer. The cathode extraction layer comprises, for example, a carbon layer 8 covering at least a portion of the solid electrolyte layer 7 and a silver paste layer 9 covering the carbon layer 8.

[0060] The portion of the anode body 3 on which a solid electrolyte layer 7 is formed via a dielectric layer (porous portion 5) is the second portion 2, and the portion of the anode body 3 on which a solid electrolyte layer 7 is not formed via a dielectric layer (porous portion 5) is the first portion 1.

[0061] In the region of the anode body 3 that does not face the cathode portion 6, an insulating separation layer (or insulating member) 12 may be formed to cover the surface of the anode body 3, at least in the portion adjacent to the cathode portion 6. This restricts contact between the cathode portion 6 and the exposed portion (first portion 1) of the anode body 3. The separation layer 12 is, for example, an insulating resin layer.

[0062] In the example shown in Figure 5, four capacitor elements 10 (10a, 10b) are stacked so that their cathode portions 6 (second portion 2) overlap each other. However, there are two types of capacitor elements 10 with different orientations of the first portion 1 of the anode body 3. In Figure 5, in the first capacitor element 10a, the first portion 1 of the anode body 3 is oriented in one direction (to the right in the figure) relative to the second portion 2. In contrast, in the second capacitor element 10b, the first portion 1 of the anode body 3 is oriented in the opposite direction (to the left in the figure) relative to the second portion 2 to the direction in which the first portion 1 of the first capacitor element 10a is oriented. The first capacitor elements 10a and the second capacitor elements 10b are stacked alternately to form a stack of elements. In multiple capacitor elements 10 (10a, 10b), the cathode portions 6 adjacent to each other in the stacking direction are electrically connected via a conductive adhesive layer 13. For example, a conductive adhesive is used to form the adhesive layer 13. The adhesive layer 13 contains, for example, silver.

[0063] The electrolytic capacitor 11 comprises the above-described element stack in which a plurality of capacitor elements 10 (10a, 10b) are stacked, an outer casing 14 including a sealing member 140 that seals the element stack, a first external electrode 21, a second external electrode 22, and a third external electrode 23. In the element stack, the end face of the first end 1a is exposed from the outer casing 14.

[0064] The outer casing 14 has a roughly rectangular shape, and the electrolytic capacitor 11 also has a roughly rectangular shape. The outer casing 14 has a first surface 14a and a second surface 14b opposite to the first surface 14a. In the element stack, the first end 1a of the first capacitor element 10a faces the first surface 14a (i.e., the first end 1a is closer to the first surface 14a than the second end 2a), and the first end 1a of the second capacitor element 10b faces the second surface 14b (i.e., the first end 1a is closer to the second surface 14b than the second end 2a).

[0065] In the electrolytic capacitor 11, each of the multiple first end portions 1a (first portion 1) exposed from the outer casing 14 is electrically connected to a first external electrode 21 extending along a first surface 14a or a second external electrode 22 extending along a second surface 14b. In this case, it is not necessary to bundle the multiple first portions 1 to form the anode of the electrolytic capacitor 11, and it is not necessary to secure the length required to bundle the multiple first portions 1. Therefore, compared to the case where multiple first portions 1 are bundled, the proportion of the first portions 1 in the anode body 3 can be reduced, thereby increasing the capacitance. In addition, the contribution of the first portion 1 to the ESL is reduced. Furthermore, the separation distance between the third external electrode 23 and the first external electrode 21 and / or the second external electrode 22 can be shortened, thus improving the ESL.

[0066] In the electrolytic capacitor 11, each of the end faces of the multiple first end portions 1a exposed from the outer casing 14 is covered with a contact layer 15. An anode electrode layer 16 covers the contact layer 15 and the first surface 14a and the second surface 14b of the outer casing 14. The first external electrode 21 and the second external electrode 22 cover the anode electrode layer 16, thereby electrically connecting the multiple first end portions 1a (first portion 1) to the first external electrode 21 or the second external electrode 22. Specifically, the anode electrode layer 16 covering the first surface 14a of the outer casing 14 is interposed between the contact layer 15 and the first external electrode 21, and the anode electrode layer 16 covering the second surface 14b of the outer casing 14 is interposed between the contact layer 15 and the second external electrode 22.

[0067] In the example shown in Figure 5, the element stack is supported by a substrate 17. The substrate 17 is, for example, a laminated substrate with conductive wiring patterns formed on its front and back surfaces, and the wiring patterns on the front and back surfaces are electrically connected by through-holes. The wiring patterns on the front surface are electrically connected to the cathode portion 6 of the capacitor element 10 stacked in the bottom layer, and the wiring patterns on the back surface (third surface 14c) are electrically connected to the third external electrodes 23 (231 and 232). Thus, the third external electrodes 23 and the cathode portion 6 of each capacitor element 10 of the element stack are electrically connected via the substrate 17. In this case, the number, shape, and arrangement of the third external electrodes 23 can be arbitrarily set depending on the wiring pattern on the back surface. The third external electrodes 23 can be formed on the substrate 17 by, for example, plating, and the substrate 17 on which the third external electrodes 23 are formed can be treated as a single component.

[0068] At least a portion of the third external electrode 23 is exposed on the bottom surface of the electrolytic capacitor 11. The exposed portion of the third external electrode 23 on the bottom surface constitutes the cathode terminal of the electrolytic capacitor 11. In the example of Figure 5, two third external electrodes 23 are provided spaced apart, and the third external electrodes 23 are exposed in multiple regions.

[0069] A portion of the first external electrode 21 is bent along the bottom surface of the casing 14 and exposed on the bottom surface of the electrolytic capacitor 11. Similarly, a portion of the second external electrode 22 is bent along the bottom surface of the casing 14 so as to face the bent portion of the first external electrode 21 and is exposed on the bottom surface of the electrolytic capacitor 11. The exposed portions of the first external electrode 21 and the second external electrode 22 on the bottom surface constitute the anode terminals of the electrolytic capacitor 11. In other words, in this embodiment, the electrolytic capacitor 11 has two spaced-apart anode terminals. A cathode terminal may be located between the two spaced-apart anode terminals.

[0070] The ESL of the electrolytic capacitor 11 depends on the distance L1 between the first external electrode 21 and the third external electrode 23 at the bottom surface, and the distance L2 between the second external electrode 22 and the third external electrode 23 at the bottom surface. The shorter the distances L1 and L2, the smaller the ESL tends to be. To reduce the ESL, multiple third external electrodes 23 may be placed at the bottom surface. In this case, one of the multiple third external electrodes 23 (third external electrode 231) may be placed close to the first external electrode 21, and another of the multiple third external electrodes 23 (third external electrode 232) may be placed close to the second external electrode 22. This can effectively reduce the ESL. The distances L1 and L2 may be, for example, 0.4 mm to 1.1 mm. Furthermore, "having multiple third external electrodes 23" means that the third external electrodes 23 are exposed in multiple spaced-apart regions, and is not limited to cases where the multiple third external electrodes 23 are spaced apart. Two or more of the multiple third external electrodes 23 may be formed continuously within the casing 14 and electrically connected. The multiple third external electrodes 23 may be provided on different surfaces of the casing 14, such as one being provided on the top surface and another on the bottom surface.

[0071] As shown in Figure 4, when viewed from the direction normal to the third surface 14c (bottom surface), the distance L1 between the edge 2310 of the third external electrode 23 that faces the first external electrode 21 and the first external electrode 21 is preferably shorter than the distance L3 between the line segment S1 that is perpendicular to the direction in which the first surface 14a and the second surface 14b are aligned (left-right direction) and bisects the outer casing 14 and the edge 2310 of the third external electrode 23. In this embodiment, when multiple third external electrodes 23 are provided, the edge 2310 of the third external electrode 23 that faces the first external electrode 21 refers to the edge of the third external electrode 231 that has an edge facing the first external electrode 21 among the multiple third external electrodes 23.

[0072] Furthermore, when viewed from the direction normal to the third surface 14c (bottom surface), the distance L2 between the edge 2320 of the third external electrode 23 that faces the second external electrode 22 and the second external electrode 22 is preferably shorter than the distance L4 between the line segment S1 that is perpendicular to the direction in which the first surface 14a and the second surface 14b are aligned (left-right direction) and bisects the outer casing 14 and the edge 2320 of the third external electrode 23. In this embodiment, when multiple third external electrodes 23 are provided, the edge 2320 of the third external electrode 23 that faces the second external electrode 22 refers to the edge of the third external electrode 232 that has an edge facing the second external electrode 22 among the multiple third external electrodes 23.

[0073] In the electrolytic capacitor 11, the direction of the current flowing through the first capacitor element 10a is opposite to the direction of the current flowing through the second capacitor element 10b. As a result, the magnetic field generated by the current flowing through the first capacitor element 10a and the magnetic field generated by the current flowing through the second capacitor element 10b cancel each other out, reducing the magnetic flux generated in the electrolytic capacitor 11. Consequently, the ESL (Electromagnetic Saturation Level) is reduced.

[0074] On the other hand, in the parts of the first part 1 and the second part 2 where the capacitor elements 10 do not overlap (the parts not covered by the cathode extraction layer in Figure 5), no magnetic field cancellation effect occurs. However, in the electrolytic capacitor 11 of this embodiment, it is easy to shorten the length of the first part 1. Therefore, the contribution of ESL caused by this part is reduced. Furthermore, since the first external electrode 21 and the second external electrode 22 extend along the bottom surface of the outer casing 14, the contribution of ESL caused by this part can be further reduced. Due to these effects, the ESL of the electrolytic capacitor 11 can be significantly improved.

[0075] The components of the electrolytic capacitor 11 according to the above embodiment will be described in more detail below.

[0076] (Anode 3) The anode 3 may include valve metals, alloys containing valve metals, and compounds containing valve metals (such as intermetallic compounds). These materials can be used individually or in combination of two or more. As valve metals, aluminum, tantalum, niobium, titanium, etc., can be used. The anode 3 may be a foil of a valve metal, an alloy containing a valve metal, or a compound containing a valve metal, or it may be a porous sintered body of a valve metal, an alloy containing a valve metal, or a compound containing a valve metal.

[0077] When a metal foil is used for the anode 3, a porous portion 5 is usually formed on the surface of at least the second portion 2 of the anode foil in order to increase the surface area. The second portion 2 has a core portion 4 and a porous portion 5 formed on the surface of the core portion 4. The porous portion 5 may be formed by roughening the surface of at least the second portion 2 of the anode foil by etching or the like. It is also possible to place a predetermined masking member on the surface of the first portion 1 and then perform a roughening treatment such as etching. Alternatively, it is also possible to roughen the entire surface of the anode foil by etching or the like. In the former case, an anode foil is obtained in which the surface of the first portion 1 does not have a porous portion 5, but the surface of the second portion 2 has a porous portion 5. In the latter case, a porous portion 5 is formed on the surface of the first portion 1 in addition to the surface of the second portion 2. As for the etching treatment, any known method may be used, for example, electrolytic etching. The masking member is not particularly limited, but an insulator such as a resin is preferred. The masking member is removed before the formation of the solid electrolyte layer 7, but it may be a conductor containing a conductive material.

[0078] When the entire surface of the anode foil is roughened, the surface of the first portion 1 has a porous portion 5. As a result, the adhesion between the porous portion 5 and the sealing member 140 is not sufficient, and air (specifically, oxygen and moisture) may enter the inside of the electrolytic capacitor 11 through the contact area between the porous portion 5 and the sealing member 140. To suppress this, the porous first portion 1 may be compressed in advance to flatten the holes in the porous portion 5. This suppresses the entry of air into the inside of the electrolytic capacitor 11 through the porous portion 5 from the first end portion 1a exposed from the sealing member 140, and the reduction in the reliability of the electrolytic capacitor 11 due to such air intrusion.

[0079] (Dielectric layer) The dielectric layer is formed, for example, by anodizing the valve metal on the surface of at least the second portion 2 of the anode body 3 by chemical conversion treatment or the like. The dielectric layer contains an oxide of the valve metal. For example, when aluminum is used as the valve metal, the dielectric layer contains aluminum oxide. The dielectric layer is formed along the surface of the second portion 2 (including the inner wall surface of the pores of the porous portion 5) on which the porous portion 5 is formed. However, the method of forming the dielectric layer is not limited to this, and it is sufficient to form an insulating layer that functions as a dielectric on the surface of the second portion 2. The dielectric layer may also be formed on the surface of the first portion 1 (for example, on the porous portion 5 on the surface of the first portion 1).

[0080] (Cathode part 6) The cathode section 6 comprises a solid electrolyte layer 7 that covers at least a portion of the dielectric layer, and a cathode extraction layer that covers at least a portion of the solid electrolyte layer 7.

[0081] (Solid electrolyte layer 7) The solid electrolyte layer 7 includes, for example, a conductive polymer. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. The solid electrolyte layer 7 can be formed, for example, by chemical polymerization and / or electrolytic polymerization of raw material monomers on a dielectric layer. Alternatively, it can be formed by coating a dielectric layer with a solution containing a conductive polymer or a dispersion containing a conductive polymer. The solid electrolyte layer 7 may also contain a manganese compound.

[0082] (Cathode extraction layer) The cathode extraction layer comprises, for example, a carbon layer 8 and a silver paste layer 9. The carbon layer 8 only needs to be conductive and can be made using a conductive carbon material such as graphite. The carbon layer 8 is formed, for example, by applying carbon paste to at least a portion of the surface of the solid electrolyte layer 7. For the silver paste layer 9, for example, a composition containing silver powder and a binder resin (such as epoxy resin) can be used. The silver paste layer 9 is formed, for example, by applying silver paste to the surface of the carbon layer 8. Note that the configuration of the cathode extraction layer is not limited to this and is acceptable as long as it has a current collection function.

[0083] (separation layer 12) An insulating isolation layer 12 may be provided to electrically isolate the first portion 1 from the cathode portion 6. The isolation layer 12 may be provided close to the cathode portion 6 so as to cover at least a portion of the surface of the first portion 1. It is preferable that the isolation layer 12 is in close contact with the first portion 1 and the sealing member 140. This can suppress the intrusion of air into the electrolytic capacitor 11. The isolation layer 12 may be disposed on the first portion 1 via a dielectric layer.

[0084] The separation layer 12 may include, for example, a resin, as exemplified by the sealing member 140 described later. The dielectric layer formed in the porous portion 5 of the first part 1 may be compressed and densified to provide insulation.

[0085] The separation layer 12 that adheres to the first part 1 is obtained, for example, by attaching a sheet-like insulating material (such as resin tape) to the first part 1. When using an anode foil having a porous portion 5 on its surface, the porous portion 5 of the first part 1 may be compressed and flattened before the insulating material is attached to the first part 1. It is preferable that the sheet-like insulating material has an adhesive layer on the surface that is attached to the first part 1.

[0086] Alternatively, a liquid resin may be applied to or impregnated into the first part 1 to form an insulating member that adheres closely to the first part 1. In the method using a liquid resin, the insulating member is formed to fill the irregularities on the surface of the porous part 5 of the first part 1. The liquid resin easily penetrates into the depressions on the surface of the porous part 5, and insulating members can be easily formed within the depressions as well. As the liquid resin, a curable resin composition as exemplified in the fourth step described later can be used.

[0087] (Sealing member 140) The sealing member 140 of the outer casing 14 preferably contains, for example, a cured product of a curable resin composition, and may also contain a thermoplastic resin or a composition containing the same.

[0088] The sealing member 140 can be formed, for example, using molding techniques such as injection molding. The sealing member 140 can be formed, for example, by filling a predetermined location with a curable resin composition or thermoplastic resin (composition) using a predetermined mold so as to cover the capacitor element 10.

[0089] The curable resin composition may include, in addition to the curable resin, fillers, curing agents, polymerization initiators, and / or catalysts. Thermosetting resins are examples of curable resins. The curing agents, polymerization initiators, catalysts, etc., are appropriately selected depending on the type of curable resin.

[0090] As the curable resin composition and thermoplastic resin (composition), those exemplified in the third step described below can be used.

[0091] From the viewpoint of adhesion between the separation layer 12 and the sealing member 140, it is preferable that the insulating member and the sealing member 140 each contain resin. The sealing member 140 adheres more easily to the insulating member containing resin than the first portion 1 containing the valve metal or the dielectric layer containing the oxide of the valve metal.

[0092] It is more preferable that the separation layer 12 and the sealing member 140 contain the same resin. In this case, the adhesion between the separation layer 12 and the sealing member 140 is further improved, thereby further suppressing the intrusion of air into the electrolytic capacitor 11. Examples of the same resin contained in the separation layer 12 and the sealing member 140 include epoxy resin.

[0093] From the viewpoint of increasing the strength of the sealing member 140, it is preferable that the sealing member 140 contains a filler. On the other hand, it is preferable that the separation layer 12 contains a filler with a smaller particle size than the sealing member 140, and more preferably that it does not contain a filler. When forming the separation layer 12 by impregnating the first part 1 with a liquid resin, it is preferable that the liquid resin contains a filler with a smaller particle size than the sealing member 140, and more preferably that it does not contain a filler. In this case, it is easier to impregnate the liquid resin into the depths of the recesses on the surface of the porous part 5 of the first part 1, and it is easier to form the separation layer 12. In addition, it is easier to form a separation layer 12 with a small thickness so that multiple capacitor elements 10 can be stacked.

[0094] (Contact layer 15) The contact layer 15 may be formed to cover the end face of the first end 1a of the anode body 3. Preferably, the contact layer 15 may be formed to cover only the surface of the first end 1a exposed from the sealing member 140, without covering the surface of the sealing member 140 (and the separation layer 12), which is made of resin material, as much as possible.

[0095] The contact layer 15 may contain a metal with a lower ionization tendency than the metal constituting the anode 3. For example, if the anode 3 is aluminum (Al) foil, the contact layer 15 can be made of a material containing, for example, Zn, Ni, Sn, Cu, or Ag. In this case, the formation of a strong oxide film on the surface of the contact layer 15 is suppressed, making the electrical connection more reliable compared to the case where the exposed portion of the anode 3 at the first end 1a is directly connected to the external electrode.

[0096] An alloy layer may be formed at the interface between the contact layer 15 and the anode 3. For example, if the anode 3 is aluminum (Al) foil, Cu, Zn, or Ag can form an alloy layer at the interface due to intermetallic bonding with Al, since their interatomic distances are close to those of Al. This can make the bonding strength with the anode 3 stronger. The contact layer 15 may be composed of a single element metal of the above elements, an alloy such as bronze or brass, or a laminate of multiple single-element metal layers (for example, a laminated structure of Cu layers and Ag layers).

[0097] When forming the contact layer 15, it is preferable that the sealing member 140 does not contain a filler, or, if the sealing member 140 contains a filler, that the Young's modulus of the filler is smaller than that of the contact layer 15. This suppresses the formation of the contact layer 15 on the surface of the sealing member 140, and allows the contact layer 15 to be selectively formed on the end face of the first end 1a. .

[0098] The contact layer 15 can be formed by, for example, a cold spray method, thermal spraying, plating, vapor deposition, etc. In the cold spray method, for example, solid metal particles are made to collide with the surface of the sealing member 140 (first surface 14a and / or second surface 14b), including the exposed surface of the first end 1a, thereby fixing the metal particles to the surface by plastic deformation and forming a contact layer 15 containing the metal that constitutes the metal particles on the end face of the first end 1a. In this case, if the Young's modulus of the metal particles is greater than the Young's modulus of the constituent material of the sealing member 140 (e.g., filler), the plastic deformation of the metal particles that collide with the surface of the sealing member 140 can be suppressed, and their adhesion to the surface of the sealing member 140 can be suppressed. At least a portion of the energy from the collision is used to break the sealing member 140, and a portion of the resin is scraped off. As a result, a contact layer 15 can be selectively formed on the end face of the first end 1a of the anode body 3, and the surface of the sealing member 140 (first surface 14a and / or second surface 14b) can be roughened.

[0099] (Anode electrode layer 16) An anode electrode layer 16 may be interposed between the contact layer 15 and the external electrode (first external electrode 21 or second external electrode 22). The anode electrode layer 16 covers the first surface 14a or the second surface 14b of the outer casing 14 and, if necessary, can be electrically connected to the first end 1a of the (multiple) capacitor elements 10 via the contact layer 15.

[0100] The anode electrode layer 16 may include a conductive resin layer mixed with conductive particles. The conductive resin layer can be formed by applying and drying a conductive paste containing conductive particles and resin material to the first surface 14a or the second surface 14b of the outer casing 14. The resin material is suitable for bonding the outer casing 14 and the materials constituting the anode 3 (contact layer 15), and the bonding strength can be increased by chemical bonding (e.g., hydrogen bonding). As conductive particles, for example, metal particles such as silver and copper, or conductive inorganic material particles such as carbon can be used.

[0101] The anode electrode layer 16 may be a metal layer. In that case, the anode electrode layer 16 may be formed using electrolytic plating, electroless plating, sputtering, vacuum deposition, chemical vapor deposition (CVD), cold spray, or thermal spraying.

[0102] The anode electrode layer 16 may cover a portion of the surface (e.g., the top or bottom surface) of the outer casing 14 that is perpendicular to the first surface 14a and the second surface 14b.

[0103] The surface roughness Ra of the outer casing 14 covered by the anode electrode layer 16 may be 5 micrometers or more. In this case, the contact area between the anode electrode layer 16 and the outer casing 14 increases, and the adhesion between the anode electrode layer 16 and the outer casing 14 is improved by the anchoring effect, thereby further enhancing reliability.

[0104] (external electrode) The first to third external electrodes 21 to 23 are preferably metal layers. The metal layer is, for example, a plating layer. The metal layer includes, for example, at least one selected from the group consisting of nickel (Ni), copper (Cu), zinc (Zn), tin (Sn), silver (Ag), and gold (Au). For the formation of the first to third external electrodes 21 to 23, film deposition techniques such as electroplating, electroless plating, sputtering, vacuum deposition, chemical vapor deposition (CVD), cold spraying, and thermal spraying may be used.

[0105] The first to third external electrodes 21 to 23 may, for example, have a laminated structure of a Ni layer and a tin layer. At least the outer surface of the first to third external electrodes 21 to 23 should be made of a metal with excellent wettability with solder. Examples of such metals include Sn, Au, Ag, and Pd.

[0106] The first external electrode 21 and the second external electrode 22 may be formed by bonding a Cu cap, which has a Sn coating pre-formed on it, to the anode electrode layer 16.

[0107] The first external electrode 21 and the second external electrode 22 both constitute the anode terminal of the electrolytic capacitor 11. When mounting the electrolytic capacitor 11 onto the substrate 17, both the first external electrode 21 and the second external electrode 22 must be connected to the electrodes on the substrate 17. However, the first external electrode 21 and the second external electrode 22 may be electrically connected via the surfaces of the outer casing 14 other than the first surface 14a and the second surface 14b. In this case, when mounting the electrolytic capacitor 11 onto the substrate 17, it is sufficient to connect either the first external electrode 21 or the second external electrode 22 to the electrodes on the substrate 17.

[0108] [Manufacturing method for electrolytic capacitor 11] An electrolytic capacitor 11 according to one embodiment of the present disclosure can be manufactured by a manufacturing method that includes, for example, a first step of preparing an anode 3, a second step of obtaining a plurality of capacitor elements 10, a third step of obtaining an element stack formed by stacking the plurality of capacitor elements 10, a fourth step of covering the element stack with a sealing member 140, a fifth step of forming the end face of the first portion 1 and exposing it from the sealing member 140, and a sixth step of electrically connecting the end face of the first portion 1 to an external electrode. The manufacturing method may further include a step of placing a separation layer 12 (insulating member) on a part of the anode 3 (separation layer placement step). The steps of the manufacturing method for the electrolytic capacitor 11 will be described below.

[0109] (1st step) In the first step, an anode body 3 with a dielectric layer formed on its surface is prepared. More specifically, an anode body 3 is prepared comprising a first portion 1 including one end and a second portion 2 including the other end opposite to the first end, with a dielectric layer formed on the surface of at least the second portion 2. The first step includes, for example, the steps of forming a porous portion 5 on the surface of the anode body 3 and forming a dielectric layer on the surface of the porous portion 5. More specifically, the anode body 3 used in the first step has a first portion 1 including the end to be removed (the one end mentioned above) and a second portion 2 including a second end 2a (the other end mentioned above). It is preferable to form a porous portion 5 on the surface of at least the second portion 2.

[0110] When forming the porous portion 5 on the surface of the anode 3, it is sufficient to create irregularities on the surface of the anode 3, which can be done, for example, by roughening the surface of the anode foil by etching (e.g., electrolytic etching).

[0111] The dielectric layer can be formed by chemical conversion treatment of the anode 3. Chemical conversion treatment can be performed, for example, by immersing the anode 3 in a conversion solution to impregnate the surface of the anode 3 with the conversion solution, and by applying a voltage between the anode 3 as the anode and the cathode immersed in the conversion solution. If the surface of the anode 3 has a porous portion 5, the dielectric layer will be formed along the uneven shape of the surface of the porous portion 5.

[0112] (Separation layer arrangement process) When manufacturing an electrolytic capacitor 11 equipped with a separation layer 12 (insulating material), the step of placing the separation layer 12 (insulating material) may be performed after the first step and before the second step. In this step, the insulating material is placed on a part of the anode 3. More specifically, in this step, the insulating material is placed on the first part 1 of the anode 3 via a dielectric layer. The insulating material is , the It is positioned to isolate part 1 from the cathode part 6 which will be formed in a later process.

[0113] In the separation layer placement step, a sheet-like insulating material (such as resin tape) may be attached to a part of the anode 3 (for example, the first part 1). Even when using an anode 3 with a porous portion 5 formed on its surface, the insulating material can be firmly attached to the first part 1 by compressing and flattening the surface irregularities of the first part 1. It is preferable that the sheet-like insulating material has an adhesive layer on the surface that is attached to the first part 1.

[0114] In addition to the above, in the separation layer arrangement step, an insulating member may be formed by applying or impregnating a part of the anode 3 (for example, the first part 1) with a liquid resin. For example, the liquid resin may be applied or impregnated and then cured. In this case, an insulating member that adheres closely to the first part 1 can be easily formed. As the liquid resin, a curable resin composition as exemplified in the fourth step (formation of the sealing member 140), a resin solution obtained by dissolving the resin in a solvent, etc., can be used.

[0115] If a porous portion 5 is formed on the surface of the anode 3, it is preferable to apply or impregnate a liquid resin to a part of the surface of the porous portion 5 of the anode 3 (for example, the surface of the first portion 1). In this case, an insulating member can be easily formed to fill the irregularities on the surface of the porous portion 5 of the first portion 1. The liquid resin can easily enter into the depressions on the surface of the porous portion 5, and an insulating member can be easily formed in the depressions as well. As a result, the porous portion 5 on the surface of the anode 3 is protected by the insulating member, and when the anode 3 is partially removed together with the sealing member 140 in the fourth step, the collapse of the porous portion 5 of the anode 3 is suppressed. Because the surface of the porous portion 5 of the anode 3 and the insulating member are firmly adhered to each other, when the anode 3 is partially removed together with the sealing member 140 in the fourth step, the peeling of the insulating member from the surface of the porous portion 5 of the anode 3 is suppressed.

[0116] (2nd process) In the second step, a cathode portion 6 is formed on the anode body 3 to obtain a capacitor element 10. If an insulating member is provided in the sixth step, the cathode portion 6 is formed in the portion of the anode body 3 where the insulating member is not provided in the second step to obtain a capacitor element 10. More specifically, in the second step, at least a portion of the dielectric layer formed on the surface of the second portion 2 of the anode body 3 is covered with the cathode portion 6.

[0117] The step of forming the cathode portion 6 is, for example, a dielectric layer The process includes the steps of forming a solid electrolyte that covers at least a portion of the solid electrolyte layer 7, and forming a cathode extraction layer that covers at least a portion of the solid electrolyte layer 7.

[0118] The solid electrolyte layer 7 can be formed, for example, by chemical polymerization and / or electrolytic polymerization of raw material monomers on a dielectric layer. Alternatively, the solid electrolyte layer 7 may be formed by applying a treatment solution containing a conductive polymer and then drying it. The treatment solution may further contain other components such as a dopant. For example, poly(3,4-ethylenedioxythiophene) (PEDOT) can be used as the conductive polymer. For example, polystyrene sulfonic acid (PSS) can be used as the dopant. The treatment solution is a dispersion or solution of the conductive polymer. Examples of dispersion media (solvents) include water, organic solvents, or mixtures thereof.

[0119] The cathode extraction layer can be formed, for example, by sequentially stacking a carbon layer 8 and a silver paste layer 9 on a solid electrolyte layer.

[0120] (3rd step) In the third step, multiple capacitor elements 10 are stacked to obtain an element stack. In this step, for example, multiple capacitor elements 10 are stacked alternately with the cathode portions 6 of the capacitor elements 10 overlapping each other via a conductive adhesive, such that the first portion 1 faces opposite sides between adjacent capacitor elements 10, thereby obtaining an element stack.

[0121] Subsequently, the element stack is placed on a laminated substrate (substrate 17) having wiring patterns formed on its front and back surfaces via a conductive adhesive. A third external electrode 23 is pre-formed on the side of the laminated substrate opposite to the side on which the element stack is placed. Upon placement, the third external electrode 23 connects to the wiring patterns formed on the laminated substrate, and to the wiring patterns on the front and back surfaces. and It is electrically connected to the cathode portion 6 of the capacitor element 10 that constitutes the element stack via a through-hole.

[0122] Alternatively, for example, an electrical connection between the element stack and the third external electrode 23 may be made by attaching a plate-shaped third external electrode 23, processed into a predetermined shape, to the surface of the cathode portion 6 exposed in the bottom or top layer of the element stack via a conductive paste or the like.

[0123] The third external electrode 23 may be formed using electroplating, electroless plating, physical vapor deposition, chemical vapor deposition, cold spray, and / or thermal spraying.

[0124] (4th step) In the fourth step, the element laminate is covered with a sealing member 140. At this time, the entire third external electrode 23 is not covered by the sealing member 140, and at least a portion of the third external electrode 23 is exposed. The sealing member 140 can be formed using injection molding or the like. For example, the sealing member 140 can be formed by filling a curable resin composition or thermoplastic resin (composition) into predetermined locations on the element laminate using a predetermined mold.

[0125] The curable resin composition may include, in addition to the curable resin, fillers, curing agents, polymerization initiators, and / or catalysts. Examples of curable resins include epoxy resins, phenolic resins, urea resins, polyimides, polyamide-imides, polyurethanes, diallyl phthalates, and unsaturated polyesters. Examples of thermoplastic resins include polyphenylene sulfide (PPS) and polybutylene terephthalate (PBT). A thermoplastic resin composition containing both a thermoplastic resin and a filler may also be used.

[0126] As fillers, for example, insulating particles and / or fibers are preferred. Examples of insulating materials constituting the filler include insulating compounds (oxides, etc.) such as silica and alumina, glass, and mineral materials (talc, mica, clay, etc.). The sealing member 140 may contain one of these fillers, or a combination of two or more.

[0127] (5th step) In the fifth step, after the fourth step, the end face of the first portion 1 is formed and exposed from the sealing member 140. More specifically, at both ends of the element stack, at least the anode body 3 is partially removed together with the sealing member 140, so that at least the first end 1a of the anode body 3 (specifically, the end face of the first end 1a) is exposed from the sealing member 140 on both the first surface 14a and the second surface 14b. Methods for exposing the first end 1a from the sealing member 140 include, for example, after covering the capacitor element 10 with the sealing member 140, polishing the surface of the sealing member 140 or cutting off a part of the sealing member 140 so that the first end 1a is exposed from the sealing member 140. Alternatively, a part of the first portion 1 may be cut off together with a part of the sealing member 140. In this case, the first end portion 1a, which does not contain the porous portion 5 and has a surface on which no natural oxide film has been formed, can be easily exposed from the sealing member 140, and a low-resistance and highly reliable connection state can be obtained between the first portion 1 and the external electrode. Dicing is preferred as the method of cutting the sealing member 140. As a result, the exposed end surface of the first end portion 1a of the first portion 1 appears on the cut surface. Since the element stack has two types of capacitor elements 10 with different orientations of the first portion 1, when separating a part of the first portion 1 together with a part of the sealing member 140, it is necessary to cut in two places. One of the two cut surfaces becomes the first surface 14a, and the other becomes the second surface 14b.

[0128] In the fifth step, the anode 3 and insulating member may be partially removed along with the sealing member 140 at both ends of the element stack, exposing the end face of the first end 1a and the end face of the insulating member from the sealing member 140. In this case, the anode 3 and the insulating member each have end faces that are flush with the sealing member 140. This makes it easy to expose the end faces of the anode 3 and the insulating member, which are flush with the surface of the sealing member 140, from the sealing member 140.

[0129] In the fifth step, the end face of the anode body 3 (first end 1a), which does not have a native oxide film formed on it, can be easily exposed from the sealing member 140, and a connection state with low resistance and high reliability can be obtained between the anode body 3 (more specifically, the first part 1) and the external electrode.

[0130] (6th step) In the sixth step, the end face of the anode body 3 (first end 1a) exposed from the outer casing 14 is electrically connected to an external electrode. In this step, for example, the first external electrode 21 is formed to cover the first surface 14a of the outer casing 14, and the second external electrode 22 is formed to cover the second surface 14b, and each external electrode is electrically connected to the end face of the first end 1a. The electrical connection between the end face of the first end 1a and the external electrode may be made by bonding, or by electroplating, electroless plating, physical vapor deposition, chemical vapor deposition, cold spray, and / or thermal spraying.

[0131] Prior to forming the first external electrode 21 and the second external electrode 22, a step of forming a contact layer 15 on the end face of the first end 1a, and / or a step of forming an anode electrode layer 16 that covers the first surface 14a or the second surface 14b of the outer casing 14 may be performed. When forming the anode electrode layer 16, the first external electrode 21 and the second external electrode 22 are formed to cover the anode electrode layer 16.

[0132] (Step of forming the contact layer 15) The contact layer 15 can be formed by methods such as cold spraying, thermal spraying, plating, or vapor deposition. The contact layer 15 may be formed so as not to cover the first surface 14a and the second surface 14b of the outer casing 14, but to selectively cover the end surface of the first end 1a.

[0133] When using the cold spray method, the contact layer 15 is formed by impacting the end face of the first end 1a with metal particles at high speed. The metal particles may be of a metal with a lower ionization tendency than the metal constituting the anode 3. For example, if the anode 3 is an Al foil, Cu particles can be used as such metal particles. In this case, the Cu particles that impact the end face of the first end 1a at high speed can penetrate the native oxide film (Al oxide film) formed on the end face, and a metallic bond between Al and Cu can be formed. As a result, an alloy layer of Al and Cu can be formed at the interface between the contact layer 15 and the first end 1a. On the other hand, the surface of the contact layer 15 is formed by the Cu layer, which is a non-valve metal. Composition Since Cu has a lower ionization tendency than Al, the surface of the contact layer 15 is less prone to oxidation, ensuring reliable electrical connection with the external electrode (or anode electrode layer 16).

[0134] The cold spray method is a technique that uses compressed gases such as air, nitrogen, and helium to accelerate metal particles ranging in size from a few micrometers to tens of micrometers to subsonic to supersonic speeds, causing them to collide with a substrate while still in a solid state, thereby forming a metal coating. While some aspects of the adhesion mechanism of metal particles in the cold spray method remain unclear, it is generally believed that the collision energy of the metal particles causes plastic deformation of the metal particles or the metal substrate, exposing a new surface on the metal surface and thus activating it.

[0135] In the cold spray method described above, metal particles can also collide with the first surface 14a and the second surface 14b of the outer casing 14, which is made of a non-metallic material, and with the end face of the separation layer 12 (insulating member). When the substrate into which the metal particles collide is a resin substrate, the bonding between the metal particles and the resin substrate is considered to be primarily mechanical, with the plastically deformed metal particles fitting into the irregularities on the surface of the resin substrate. Therefore, in order to deposit a metal film on the surface of a resin substrate, the following conditions must be met: (ia) the resin substrate must have sufficient hardness so that the collision energy is efficiently used for the plastic deformation of the metal particles; (iia) a metal material and processing conditions must be selected that facilitate the plastic deformation of the metal particles; and (iiia) the resin substrate must not be easily damaged by the collision energy.

[0136] Conversely, if metal particles are not fixed to the resin substrate, the basic conditions are: (ib) to give the resin substrate elasticity so that impact energy is not converted into plastic deformation energy; (iib) to select a metal material and processing conditions that are less prone to plastic deformation within the range in which a contact layer 15 can be formed on the end face of the first end 1a; and (iiib) to reduce the strength of the resin substrate so that the substrate is destroyed at an impact below the level at which plastic deformation occurs.

[0137] Generally, when the Young's modulus of metal particles is smaller than that of the components constituting the resin substrate (e.g., filler), plastic deformation during collisions between metal particles tends to be promoted, while when it is larger, plastic deformation during collisions between metal particles tends to be suppressed. In the latter case, the collision energy of the metal particles causes brittle fracture of the resin substrate, and the surface of the resin substrate is scraped away.

[0138] Therefore, by making the Young's modulus of the metal particles (which can also be called the contact layer 15) greater than the Young's modulus of the filler contained in the resin substrate, it is possible to create a state in which the metal particles are less likely to adhere to the resin substrate. As a result, the formation of the contact layer 15 on the first surface 14a and the second surface 14b of the outer casing 14, and on the end surface of the separation layer 12 (insulating member) is suppressed, and it becomes possible to selectively form the contact layer 15 on the end surface of the first end 1a. In addition, by causing the metal particles to collide with the first surface 14a and the second surface 14b of the outer casing 14, the effect of roughening the first surface 14a and the second surface 14b can be obtained.

[0139] For example, if the sealing member 140 of the outer casing 14 is filled with silica having a Young's modulus of 94 GPa, then Cu particles and Ni particles can be used as metal particles that have a larger Young's modulus and are easily bonded with Al. However, the bonding state also changes depending on the shape, size, and temperature of the metal particles, as well as the size and filling rate of the silica filled into the resin material, so this is not the only option.

[0140] (Step of forming the anode electrode layer 16) The anode electrode layer 16 may be formed to cover the end face of the first end 1a or the contact layer 15, and to cover the first surface 14a and the second surface 14b of the outer casing 14. Furthermore, if a separation layer 12 is provided, the anode electrode layer 16 may be formed to cover the end face of the separation layer 12 (insulating member).

[0141] The anode electrode layer 16 may be formed by applying a conductive paste containing conductive particles and a resin material. Specifically, the anode electrode layer 16 is formed by applying a conductive paste (e.g., silver paste) to each end face using a dipping method, transfer method, printing method, dispensing method, etc., and then curing it at a high temperature.

[0142] Other methods include electroplating, electroless plating, sputtering, vacuum deposition, and chemical deposition (C The anode electrode layer 16, which is a metal layer, may be formed by the VD method, cold spray method, or thermal spray method.

[0143] (Variation 1) Hereinafter, a modified example 1 concerning the external electrodes will be described with reference to Figure 8. Components similar to those in the embodiment are denoted by the same reference numerals and their description is omitted.

[0144] The capacitor 11 of this modified example 1 differs from the embodiment in that it has four third external electrodes 23. The main parts of two of the third external electrodes 23 are provided on the fifth surface 14e (front surface) of the casing 14. The main parts of the remaining two third external electrodes 232 are provided on the sixth surface 14f (rear surface) of the casing 14.

[0145] Each third external electrode 23 has length in the vertical direction. The upper end of each third external electrode 23 is bent toward the center of the outer casing 14. The lower end of each third external electrode 23 is also bent toward the center of the outer casing 14. As a result, a portion of each third external electrode 23 is provided on the third surface 14c (bottom surface). Another portion of each third external electrode 23 is provided on the fourth surface 14d (top surface).

[0146] (Modification 2) Hereinafter, a modified example 2 concerning the external electrodes will be described with reference to Figures 9 and 10. Components similar to those in the embodiment are denoted by the same reference numerals and their description is omitted.

[0147] The capacitor 11 of this modified example 2 differs from the embodiment in the configuration of the two third external electrodes 23 (231 and 232). The main part of the third external electrode 231 is provided on the fifth surface 14e (front surface) of the casing 14. The main part of the third external electrode 232 is provided on the sixth surface 14f (rear surface) of the casing 14.

[0148] The two third external electrodes 23 have length in the vertical direction. The upper end of each third external electrode 23 is bent toward the center of the outer casing 14. The lower end of each third external electrode 23 is also bent toward the center of the outer casing 14. As a result, a portion of each third external electrode 23 is provided on the third surface 14c (bottom surface). Another portion of each third external electrode 23 is provided on the fourth surface 14d (top surface).

[0149] Furthermore, as a further variation of this modified example 2, the two third external electrodes 23 in Figure 10 may be connected on the third surface 14c (bottom surface), as shown in Figure 11, to form a single third external electrode 23.

[0150] (Variation 3) Hereinafter, a third modified example relating to the external electrodes will be described with reference to Figures 12 and 13. Components similar to those in the embodiment are denoted by the same reference numerals and their description is omitted.

[0151] The capacitor 11 of this modified example 3 differs from the embodiment in the configuration of the first external electrode 21 and the second external electrode 22. The first external electrode 21 and the second external electrode 22 are formed in a downwardly convex U shape. The first external electrode 21 and the second external electrode 22 cover a part of the third surface 14c (bottom surface), a part of the fifth surface 14e (front surface), and a part of the sixth surface 14f (rear surface) of the outer casing 14. The first external electrode 21 and the second external electrode 22 further cover a part of the fourth surface 14d (top surface).

[0152] Furthermore, the shape of the third external electrode 23 is the same as in the embodiment. That is, the third external electrode 23 is also formed in a downwardly convex U-shape, covering a part of the third surface 14c (bottom surface), a part of the fifth surface 14e (front surface), and a part of the sixth surface 14f (rear surface). The third external electrode 23 further covers a part of the fourth surface 14d (top surface).

[0153] As a further variation of this Modification 3, instead of the two third external electrodes 23 in Figure 13, four third external electrodes 23 may be provided, as shown in Figure 14. The configuration of the four third external electrodes 23 is the same as the configuration shown in Figure 8, so a detailed explanation is omitted.

[0154] (Modification 4) Hereinafter, a fourth modified example concerning the external electrode will be described with reference to Figures 15 and 16. Components similar to those in the embodiment are denoted by the same reference numerals and their description is omitted.

[0155] The capacitor 11 in this modified example 4 differs from the embodiment in the configuration of the first external electrode 21, the second external electrode 22, and the two third external electrodes 23.

[0156] The configurations of the first external electrode 21 and the second external electrode 22 are the same as those shown in Figure 12, so their explanation is omitted. The configurations of the two third external electrodes 23 are the same as those shown in Figure 10, so their explanation is omitted.

[0157] Furthermore, as a further variation of this modified example 4, the two third external electrodes 23 in Figure 16 may be connected on the third surface 14c (bottom surface), as shown in Figure 17, to form a single third external electrode 23.

[0158] (Variation 5) Below, a modified example 5 of the circuit configuration of the filter circuit 100 using capacitor 11 will be described with reference to Figure 18.

[0159] The resonant circuit 101 constitutes an L-type filter. Specifically, the first end of the inductance element 42 is electrically connected to the input terminal T1. The first external electrode 21 of the capacitor 11 is electrically connected to the second end of the inductance element 42, and the second external electrode 22 is also electrically connected to the second end of the inductance element 42. More specifically, the first external electrode 21 and the second external electrode 22 are electrically connected to the connection point between the second end of the inductance element 42 and the output terminal T2.

[0160] In this way, by constructing an L-type filter using capacitor 11 with a relatively small ESL, the signal attenuation can be increased over a relatively wide bandwidth.

[0161] The resonant circuit 101 may further include a second inductance element separate from the inductance element 42 (the first inductance element). The first end of the second inductance element may be electrically connected to the second external electrode 22, and the second end of the second inductance element may be electrically connected to the output terminal T2. In other words, the resonant circuit 101 may constitute a T-type filter.

[0162] (Other modifications of the embodiment) The following lists other modifications of the embodiment. These modifications may be implemented in appropriate combinations. Furthermore, these modifications may be implemented in appropriate combinations with the modifications described above.

[0163] In this embodiment, the number of capacitors 11 having an alternating stacked structure and an end-face current collection structure is one. However, the filter circuit 100 may have multiple capacitors 11. Also, a parallel circuit of multiple capacitors 11 may be electrically connected between the circuit 30 and the conductor W3 at the reference potential.

[0164] As power supply PS1, an AC power supply and an AC / DC converter that converts the AC power input from the AC power supply into DC power and outputs it may be used.

[0165] The number of pairs of the first capacitor element 10a and the second capacitor element 10b is not limited to two pairs, but may be one pair or three or more pairs. Furthermore, the arrangement is not limited to the alternating stacking of the first capacitor element 10a and the second capacitor element 10b, but may consist of a first stacked structure made up of multiple first capacitor elements 10a and a second stacked structure made up of multiple second capacitor elements 10b, which may be stacked alternately.

[0166] The outer casing 14 may include a case for housing the sealing member 140.

[0167] (summary) Based on the embodiments described above, the following aspects are disclosed.

[0168] The filter circuit (100) according to the first embodiment includes a resonant circuit (101). The resonant circuit (101) includes an input terminal (T1), an output terminal (T2), an inductance element (42), and a capacitor (11). The inductance element (42) is electrically connected between the input terminal (T1) and the output terminal (T2). The capacitor (11) is electrically connected between the inductance element (42) and a conductor (W3) at a reference potential. The capacitor (11) is an electrolytic capacitor. The capacitor (11) includes an element stack, an outer casing (14), a first external electrode (21), a second external electrode (22), and a third external electrode (23). The element stack is composed of a plurality of capacitor elements (10) stacked on top of each other. The outer casing (14) is the element stack cover Includes a sealing member (140). The first external electrode (21) and the second external electrode (22) are electrically connected to the inductance element (42). The third external electrode (23) is electrically connected to the reference potential conductor (W3). Each of the plurality of capacitor elements (10) includes an anode (3), a dielectric layer, and a cathode (6). ,of The anode (3) has a porous portion (5) on its surface. The dielectric layer is formed on at least a portion of the surface of the porous portion (5). The cathode (6) covers at least a portion of the dielectric layer. Each of the multiple capacitor elements (10) At the first end (1a), the anode body (3) From the exterior (14)To be exposed. Each of the multiple capacitor elements (10) At the second end (2a), the anode (3) is covered by the cathode (6). The plurality of capacitor elements (10) include a first capacitor element (10a) and a second capacitor element (10b). In the first capacitor element (10a), the first end (1a) is electrically connected to the first external electrode (21). In the second capacitor element (10b), the first end (1a) is electrically connected to the second external electrode (22). The third external electrode (23) is electrically connected to the cathode (6) of the capacitor element (10).

[0169] According to the above configuration, the ESL of capacitor (11) can be reduced. Therefore, compared to the case where multiple capacitors with a larger ESL than capacitor (11) are connected in parallel to reduce the ESL, the number of capacitors can be reduced.

[0170] Furthermore, in the filter circuit (100) according to the second embodiment, in the first embodiment, at least a portion of the first external electrode (21) is provided on the first surface (14a) of the casing (14). At least a portion of the second external electrode (22) is provided on the second surface (14b) of the casing (14) opposite to the first surface (14a). At least a portion of the third external electrode (23) is provided on the third surface (14c) of the casing (14), which is different from the first surface (14a) and the second surface (14b).

[0171] With the above configuration, the capacitance of capacitor (11) can be increased. Therefore, the number of capacitors can be reduced compared to the case where multiple capacitors with relatively small capacitances are connected in parallel to obtain the required capacitance.

[0172] Furthermore, in the filter circuit (100) according to the third embodiment, in the second embodiment, when viewed from the direction normal to the third surface (14c), the distance (L1) between the edge (2310) of the third external electrode (23) that faces the first external electrode (21) and the first external electrode (21) is shorter than the distance (L2) between the line segment (S1) and the edge (2310) of the third external electrode (23). The line segment (S1) is perpendicular to the direction in which the first surface (14a) and the second surface (14b) are aligned and divides the outer casing (14) into two equal parts.

[0173] With the above configuration, the distance (L1) between the third external electrode (23) and the first external electrode (21) is relatively short, which improves the ESL of the capacitor (11).

[0174] Furthermore, in the filter circuit (100) according to the fourth embodiment, in any one of the first to third embodiments, the output terminal (T2) is electrically connected to the input terminal of the DC / DC converter (43).

[0175] According to the above configuration, the noise in the input power of the DC / DC converter (43) can be reduced.

[0176] Furthermore, in the filter circuit (100) according to the fifth embodiment, in any one of the first to fourth embodiments, the first external electrode (21) is electrically connected to the first end of the inductance element (42). The second external electrode (22) is electrically connected to the second end of the inductance element (42).

[0177] According to the above configuration, a π-type filter can be constructed with a single capacitor (11), thus reducing the number of capacitors compared to the case where a π-type filter is constructed using two capacitors.

[0178] Furthermore, in the filter circuit (100) according to the sixth embodiment, in any one of the first to fifth embodiments, the equivalent series inductance of the capacitor (11) is 100 pH or less when the frequency is between 50 MHz and 1000 MHz.

[0179] The above configuration allows for a reduction in the number of capacitors.

[0180] Furthermore, in the filter circuit (100) according to the seventh embodiment, in any one of the first to sixth embodiments, the capacitance of the capacitor (11) is 10 [μF] or more.

[0181] The above configuration allows for a reduction in the number of capacitors.

[0182] Configurations other than those in the first embodiment are not essential to the filter circuit (100) and can be omitted as appropriate.

[0183] Furthermore, the configuration according to the following eighth aspect may be realized without requiring the configuration of the first aspect. The filter circuit (100) according to the eighth aspect includes a resonant circuit (101). The resonant circuit (101) includes an input terminal (T1), an output terminal (T2), an inductance element (42), and a capacitor (11). The inductance element (42) is electrically connected between the input terminal (T1) and the output terminal (T2). The capacitor (11) is electrically connected between the inductance element (42) and a conductor (W3) at a reference potential. Under the condition that the frequency is 50 [MHz] or more and 1000 [MHz] or less, the equivalent series inductance of the capacitor (11) is 100 [pH] or less.

[0184] The above configuration allows for a reduction in the number of capacitors. [Explanation of Symbols]

[0185] 1a 1st end 2a Second end 3. Anode 5 Porous part 6. Cathode section 10 Capacitor element 10a First capacitor element 10b Second capacitor element 11 Capacitors 14 Exterior 14a First face 14b Second side 14c Third side 21 First external electrode 22 Second external electrode 23 Third external electrode 42 Inductance Elements 43 DC / DC Converters 100 filter circuit 101 Resonant circuit 140 Sealing member 2310 Edge L1, L2 distance S1 line segment T1 input terminal T2 output terminal W3 conductor

Claims

1. The resonant circuit includes an input terminal, an output terminal, an inductance element electrically connected between the input terminal and the output terminal, and a capacitor electrically connected between the inductance element and a conductor of a reference potential. The capacitor is an electrolytic capacitor, The aforementioned capacitor is A stack of elements in which multiple capacitor elements are stacked, An outer casing including a sealing member that covers the aforementioned element laminate, A first external electrode electrically connected to the first end on the input side of the inductance element, and a second external electrode electrically connected to the second end on the output side of the inductance element, It comprises a third external electrode electrically connected to the conductor of the reference potential, Each of the aforementioned plurality of capacitor elements is an anode body having a porous portion on its surface, A dielectric layer formed on at least a portion of the surface of the porous portion, The dielectric layer includes a cathode portion covering at least a part of the dielectric layer, At the first end of each of the plurality of capacitor elements, the anode body is exposed from the outer casing. At the second end of each of the plurality of capacitor elements, the anode body is covered by the cathode portion. The plurality of capacitor elements include a first capacitor element whose first end is electrically connected to the first external electrode, and a second capacitor element whose first end is electrically connected to the second external electrode. The third external electrode is electrically connected to the cathode portion of the capacitor element. The first external electrode and the second external electrode extend along the bottom surface of the outer casing. Filter circuit.

2. At least a portion of the first external electrode is provided on the first surface of the outer casing, At least a portion of the second external electrode is provided on the second surface of the outer casing that is opposite to the first surface, At least a portion of the third external electrode is the first surface and the second surface of the outer casing It is provided on a third surface that is different from the surface, The filter circuit according to claim 1.

3. Viewed from the direction normal to the third surface, the distance between the edge of the third external electrode facing the first external electrode and the first external electrode is shorter than the distance between the line segment perpendicular to the direction in which the first and second surfaces are aligned and bisecting the exterior body and the edge of the third external electrode. The filter circuit according to claim 2.

4. The input terminal of the DC / DC converter is electrically connected to the output terminal. The filter circuit according to any one of claims 1 to 3.

5. Under the condition that the frequency is between 50 MHz and 1000 MHz, the equivalent series inductance of the capacitor is 100 pH or less. A filter circuit according to any one of claims 1 to 4.

6. The capacitance of the aforementioned capacitor is 10 μF or more. The filter circuit according to any one of claims 1 to 5.

7. When L1 is the distance between the third external electrode and the first external electrode on the bottom surface of the capacitor, and L2 is the distance between the third external electrode and the second external electrode, the values ​​of L1 and L2 are between 0.4 mm and 1.1 mm. A filter circuit according to any one of claims 1 to 6.

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