Patent Publication Number: US-2022238281-A1

Title: Composite capacitor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of International application No. PCT/JP2020/026830, filed Jul. 9, 2020, which claims priority to Japanese Patent Application No. 2019-193612, filed Oct. 24, 2019, the entire contents of each of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a composite capacitor. 
     BACKGROUND OF THE INVENTION 
     Examples of a document that discloses a composite capacitor are Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2015-519742 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2006-128302 (Patent Document 2). The composite capacitor disclosed in Patent Document 1 includes a first structured surface, a second structured surface, a separator, and an electrolyte. The first and second structured surfaces are carbon-nanotube random arrays. The first and second structured surfaces each include a dielectric coating. The separator is disposed between the first structured surface and the second structured surface. The electrolyte is disposed between the first structured surface and the second structured surface. 
     The composite capacitor disclosed in Patent Document 2 is a variable capacitor including variable capacitance elements connected in series with each other. In the variable capacitor, a lower electrode layer, a thin-film dielectric layer, and an upper electrode layer are sequentially formed on a support substrate. An extending electrode layer connects the upper electrode layer of a variable capacitance element and the upper electrode layer of another variable capacitance element.
     Patent document 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2015-519742   Patent document 2: Japanese Unexamined Patent Application Publication No. 2006-128302   

     SUMMARY OF THE INVENTION 
     In the composite capacitor disclosed in Patent Document 1, plural capacitors are stacked on each other in the extending direction of carbon nanotubes, which are columnar conductors having a nano-size outer diameter. This makes the overall composite capacitor thick. 
     To reduce the overall height of a composite capacitor, as the composite capacitor disclosed in Patent Document 2, for plural capacitors having columnar conductors, an extending electrode layer may be formed on upper electrode layers so as to electrically connect the upper electrode layers. It is however difficult for a capacitor having columnar conductors to deform elastically in the extending direction of the columnar conductors. If an extending electrode layer is formed on upper electrode layers in plural capacitors having columnar conductors, when a mounting substrate having the composite capacitor mounted thereon bends, for example, delamination is likely to occur between the extending electrode layer and the upper electrode layers. 
     The present invention has been made in view of the above-described problems. It is an object of the invention to provide a composite capacitor which can be reduced in the overall height and which can make it less likely to cause delamination. 
     A composite capacitor according to the present invention includes a first capacitor and a second capacitor connected in series with the first capacitor. The first capacitor includes a first support electrode layer, plural first columnar conductors, a first dielectric layer, and a first counter electrode layer. The plural first columnar conductors extend from the first support electrode layer in a thickness direction of the first support electrode layer, and each of the plural first columnar conductors have a nano-size outer diameter. The first dielectric layer covers the first support electrode layer and the plural first columnar conductors. The first counter electrode layer covers the first dielectric layer and opposes the first support electrode layer and the plural first columnar conductors with the first dielectric layer interposed therebetween. The second capacitor includes a second support electrode layer, plural second columnar conductors, a second dielectric layer, and a second counter electrode layer. The second support electrode layer is disposed adjacent to and separate from the first support electrode layer in an in-plane direction of the first support electrode layer. The plural second columnar conductors extend from the second support electrode layer along an extending direction of the plural first columnar conductors. Each of the plural second columnar conductors have a nano-size outer diameter. The second dielectric layer covers, at a side of the second support electrode layer from which the plural second columnar conductors extend, the second support electrode layer and the plural second columnar conductors. The second counter electrode layer covers the second dielectric layer and opposes the second support electrode layer and the plural second columnar conductors with the second dielectric layer interposed therebetween. A connecting conductor layer is bonded to a first surface of the first counter electrode layer, the first surface being positioned at a side of the first counter electrode layer opposite to the first support electrode layer, and is also bonded to a second surface of the second counter electrode layer, the second surface being positioned at a side of the second counter electrode layer opposite to the second support electrode layer. A reinforcement conductor is located between the first counter electrode layer and the second counter electrode layer. The reinforcement conductor is connected to each of the first counter electrode layer, the second counter electrode layer, and the connecting conductor layer. A material forming the reinforcement conductor is identical to a material forming each of the first counter electrode layer and the second counter electrode layer and is different from a material forming the connecting conductor layer. 
     According to the present invention, it is possible to reduce the overall height of a composite capacitor and to make it less likely to cause delamination in the composite capacitor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating a state in which a composite capacitor according to a first embodiment of the invention is mounted on a mounting substrate. 
         FIG. 2  is a sectional view of a composite capacitor according to a second embodiment of the invention. 
         FIG. 3  is a sectional view of a composite capacitor according to a third embodiment of the invention. 
         FIG. 4  is a sectional view of a composite capacitor according to a fourth embodiment of the invention. 
         FIG. 5  is a sectional view of a composite capacitor according to a fifth embodiment of the invention. 
         FIG. 6  is a sectional view of a composite capacitor according to a sixth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, composite capacitors according to individual embodiments of the present invention will be described below with reference to the drawings. In the following description of the embodiments, identical or corresponding elements will be designated by like reference numeral and an explanation thereof will not be repeated. 
     First Embodiment 
       FIG. 1  is a sectional view illustrating a state in which a composite capacitor according to a first embodiment of the invention is mounted on a mounting substrate. 
     As shown in  FIG. 1 , a composite capacitor  100  according to the first embodiment of the invention includes a first capacitor  110 A and a second capacitor  110 B. The composite capacitor  100  is mounted on a mounting substrate  10  with a first solder  20 A interposed therebetween on the side of the first capacitor  110 A and with a second solder  20 B interposed therebetween on the side of the second capacitor  110 B. 
     The first capacitor  110 A will first be explained below. As shown in  FIG. 1 , the first capacitor  110 A includes a first support electrode layer  112 A, plural first columnar conductors  114 A, a first dielectric layer  116 A, and a first counter electrode layer  118 A. 
     The first support electrode layer  112 A is bonded to the mounting substrate  10  with the solder  20 A interposed therebetween, for example. The first support electrode layer  112 A may be formed in the shape of a plane, foil, or thin film. The surface of the first support electrode layer  112 A may be formed in an uneven shape. The first support electrode layer  112 A formed in a planar shape is easy to handle during the manufacturing of the composite capacitor  100  and the composite capacitor  100  is thus easy to design. The first support electrode layer  112 A formed in a foil-like shape is easy to handle during the manufacturing of the composite capacitor  100 . The first support electrode layer  112 A formed in a thin-film-like shape can further reduce the height of the composite capacitor  100 . 
     The external shape and the area of the first support electrode layer  112 A as viewed from the thickness direction thereof can suitably be designed in terms of the electrostatic capacity of the first capacitor  110 A. The external shape of the first support electrode layer  112 A is a rectangle, a substantially rectangle having curved corners, or an ellipse, as viewed from the above-described thickness direction. A hole may be formed in the first support electrode layer  112 A as viewed from the above-described thickness direction. 
     As viewed from the above-described thickness direction, the first support electrode layer  112 A may be located farther inward than the first counter electrode layer  118 A, which will be discussed later. If the first support electrode layer  112 A is located farther inward than the first counter electrode layer  118 A, the specific position of the first support electrode layer  112 A can be changed suitably in accordance with stress applied from the mounting substrate  10  to the composite capacitor  100 . 
     To improve the mechanical robustness, the first support electrode layer  112 A preferably has high symmetrical characteristics as viewed from the above-described thickness direction. For example, as viewed from the above-described thickness direction, the first support electrode layer  112 A may have a ring-like external shape or a double-ring-like external shape having concentric two rings. 
     The first support electrode layer  112 A may be formed of multiple layers. If the first support electrode layer  112 A is formed of multiple layers stacked on each other, at least one conductor layer forms the first support electrode layer  112 A. If the first support electrode layer  112 A is formed of multiple layers, it may have a layer different from the conductor layer. This layer may be located on either side of the conductor layer in the above-described thickness direction. This layer may be made of a metal or an insulator. If this layer is made of a metal, the bonding strength with the conductor layer is improved. If this layer is made of an insulator, the bonding strength with the first dielectric layer  116 A, which will be discussed later, can be improved when they contact each other. 
     The material forming the first support electrode layer  112 A is not limited to a particular type. For example, the first support electrode layer  112 A is made of a metal, such as copper. If the first support electrode layer  112 A is formed of multiple layers, the first support electrode layer  112 A may be formed of any material if the above-described conductor layer is made of a metal, such as copper. 
     The plural first columnar conductors  114 A are each supported by the first support electrode layer  112 A. At one side of the first support electrode layer  112 A in the thickness direction thereof, each of the plural first columnar conductors  114 A extends from the first support electrode layer  112 A along the thickness direction. Although in this embodiment each of the plural first columnar conductors  114 A extend from the surface of the first support electrode layer  112 A, they may extend outwardly from the inside of the first support electrode layer  112 A. Additionally, although in this embodiment each of the plural first columnar conductors  114 A are formed of a member different from the first support electrode layer  112 A, they may be formed of a uniform member together with the first support electrode layer  112 A. 
     Each of the plural first columnar conductors  114 A has a nano-size outer diameter. In the present specification, the nano size is 0.1 nm to 1000 nm, for example. Each of the plural first columnar conductors  114 A may have a cylindrical shape or a cylindrical shape with a closed bottom. 
     The material forming the plural first columnar conductors  114 A is not limited to a particular type. In this embodiment, the plural first columnar conductors  114 A are made of a conductive material or a semiconductor material. However, the plural first columnar conductors  114 A may be formed of columnar members made of a semiconductor material or insulating material thinly coated with a metal. 
     Each of the plural first columnar conductors  114 A includes, for example, carbon nanofibers, another type of nanofibers made of ZnO, for example, or nanorods or nanowires made of ZnO, GaN, or hematite. In this embodiment, specifically, the plural first columnar conductors  114 A are formed of carbon nanotubes, and more specifically, each of the plural first columnar conductors  114 A is formed of multiple, for example, 100 to 200, carbon nanotubes. 
     In this embodiment, the chirality of the carbon nanotubes is not limited to a particular type. The carbon nanotubes may be of a semiconductor type or a metal type. The carbon nanotubes may include both of nanotubes of a semiconductor type and those of a metal type. From the viewpoint of the electrical resistance, the carbon nanotubes preferably have a higher ratio of nanotubes of a metal type than those of a semiconductor type. 
     In this embodiment, the number of layers forming the carbon nanotubes is not particularly restricted. The carbon nanotubes may be of a SWCNT (Single Wall Carbon Nanotube) type formed of one layer or of a MWCNT (Multiwall Carbon Nanotube) type formed of two or more layers. 
     The length of each of the plural first columnar conductors  114 A is not particularly limited. The length of each of the plural first columnar conductors  114 A is preferably long from the viewpoint of the capacitance density per unit area in the planar direction perpendicular to the extending direction of the plural first columnar conductors  114 A. The length of each of the plural first columnar conductors  114 A is several micrometers or longer, 20 μm or longer, 50 μm or longer, 100 μm or longer, 500 μm or longer, 750 μm or longer, 1000 μm or longer, or 2000 μm or longer, for example. 
     The lengths of the plural first columnar conductors  114 A may be different from each other. Forward end portions  115 A of the plural first columnar conductors  114 A are preferably aligned on a virtual plane substantially perpendicular to a thickness direction. This configuration can easily control the electrostatic capacity of the first capacitor  110 A. 
     As one example of the process for disposing the plural first columnar conductors  114 A on the first support electrode layer  112 A, the plural first columnar conductors  114 A may be grown on a substrate, which is not shown, and then, they may be transferred to the first support electrode layer  112 A. 
     The above-described transferring process will be explained specifically. First, catalyst particles are disposed on the above-described substrate. The first columnar conductors  114 A are grown from the surface of the catalyst particles. Each of the plural first columnar conductors  114 A is grown such that a growth end portion is separated from the substrate. 
     Examples of the material forming the substrate are silicon oxide, silicon, gallium arsenide, aluminum, and SUS. 
     If the first columnar conductors  114 A are carbon nanotubes, the catalyst particles are made of Fe, Ni, Co, or an alloy thereof, for example. If the first columnar conductors  114 A contain ZnO, the catalyst particles are made of Pt, Au, or an alloy thereof. To dispose the catalyst particles, a combination of one of CVD (Chemical Vapor Deposition), sputtering, and PVD (Physical Vapor Deposition) and one of lithography and etching may be used. The position of the catalyst particles is suitably selected by patterning. 
     The process for growing the plural first columnar conductors  114 A is not restricted to a particular process. In this embodiment, the plural first columnar conductors  114 A can be grown by CVD or plasma-enhanced CVD, for example. A gas used in CVD or plasma-enhanced CVD may be carbon monoxide, methane, ethylene, acetylene, or a mixture of such a compound and hydrogen or ammonia. 
     When the plural first columnar conductors  114 A are grown with the above-described CVD or plasma-enhanced CVD, for example, if conditions such as the temperature condition and the gas condition are suitably selected, each of the plural first columnar conductors  114 A can be formed to have a length within a desired range and an outer diameter within a desired range. The specific lengths of the plural first columnar conductors  114 A become different from each other depending on the gas concentration, gas flow rate, and temperature variations on the surface of the substrate. 
     The plural first columnar conductors  114 A grown in the above-described manner are bonded at their growth end portions onto the first support electrode layer  112 A. After the plural first columnar conductors  114 A are bonded to the first support electrode layer  112 A, the substrate is removed from the plural first columnar conductors  114 A. In this manner, the plural first columnar conductors  114 A are transferred from the substrate to the first support electrode layer  112 A. 
     The plural first columnar conductors  114 A may be transferred from the substrate to the first support electrode layer  112 A by chemically or mechanically inserting the growth end portions of the plural first columnar conductors  114 A into the first support electrode layer  112 A. With this approach, as shown in  FIG. 1 , the positions of the forward end portions  115 A of the plural first columnar conductors  114 A can be aligned in the arranging direction of the first columnar conductors  114 A. 
     If each of the plural first columnar conductors  114 A is formed of a uniform member together with the first support electrode layer  112 A, instead of the above-described process, one planar electrode layer may be used and the surface of the planar electrode layer may be processed in an uneven form by chemical etching, for example, thereby forming the plural first columnar conductors  114 A and the first support electrode layer  112 A. 
     At the above-described side of the first support electrode layer  112 A in the thickness direction, the first dielectric layer  116 A covers the first support electrode layer  112 A and the plural first columnar conductors  114 A. The first dielectric layer  116 A covers the entire surface of the first support electrode layer  112 A on the side of the plural first columnar conductors  114 A, except for the portions on which the plural first columnar conductors  114 A are disposed. 
     An additional conductor layer may be disposed between the first dielectric layer  116 A and the plural first columnar conductors  114 A. This can further reduce the parasitic resistance of the first capacitor  110 A. 
     The material forming the first dielectric layer  116 A is not limited to a particular type. Examples of the material are silicon dioxide, aluminum oxide, silicon nitride, tantalum oxide, hafnium oxide, barium titanate, lead zirconate titanate, and a combination thereof. 
     The process for applying the first dielectric layer  116 A is not restricted to a particular process, and plating, ALD (Atomic Layer Deposition), CVD, MOCVD (Metalorganic Chemical Vapor Deposition), supercritical fluid film deposition, or sputtering, for example, may be used. 
     The first counter electrode layer  118 A covers the first dielectric layer  116 A and opposes the first support electrode layer  112 A and the plural first columnar conductors  114 A with the first dielectric layer  116 A interposed therebetween. In this embodiment, a surface  119 A of the first counter electrode layer  118 A, which is positioned at the opposite side of the first counter electrode layer  118 A as viewed from the first support electrode layer  112 A, has a planar shape. 
     The material forming the first counter electrode layer  118 A is not limited to a particular type, and may be a metal, such as silver, gold, copper, platinum, or aluminum, or an alloy thereof. 
     The process for applying the first counter electrode layer  118 A is not restricted to a particular process, and plating, ALD, CVD, MOCVD, supercritical fluid film deposition, or sputtering, for example, may be used. 
     The second capacitor  110 B will now be explained below. As shown in  FIG. 1 , the second capacitor  110 B includes a second support electrode layer  112 B, plural second columnar conductors  114 B, a second dielectric layer  116 B, and a second counter electrode layer  118 B. The second capacitor  110 B may be configured similarly to the first capacitor  110 A, and the second capacitor  110 B can be manufactured by a method for manufacturing the first capacitor  110 A. That is, the second support electrode layer  112 B, the plural second columnar conductors  114 B, the second dielectric layer  116 B, and the second counter electrode layer  118 B of the second capacitor  110 B may be configured similarly to the first support electrode layer  112 A, the plural first columnar conductors  114 A, the first dielectric layer  116 A, and the first counter electrode layer  118 A, respectively, of the first capacitor  110 A. 
     In the second capacitor  110 B, the second support electrode layer  112 B is bonded to the mounting substrate  10  with the solder  20 B interposed therebetween, for example. The second support electrode layer  112 B is disposed adjacent to and separate from the first support electrode layer  112 A in the in-plane direction of the first support electrode layer  112 A. Each of the plural second columnar conductors  114 B has a nano-size outer diameter. The plural second columnar conductors  114 B extend from the second support electrode layer  112 B along the extending direction of the plural first columnar conductors  114 A. 
     In the second capacitor  110 B, as well as in the first capacitor  110 A, at the side of the second support electrode layer  112 B from which the plural second columnar conductors  114 B extend, the second dielectric layer  116 B covers the second support electrode layer  112 B and the plural second columnar conductors  114 B. The second counter electrode layer  118 B covers the second dielectric layer  116 B and opposes the second support electrode layer  112 B and the plural second columnar conductors  114 B with the second dielectric layer  116 B interposed therebetween. 
     Hereinafter, the overall configuration of the composite capacitor  100  will be described below. As shown in  FIG. 1 , the composite capacitor  100  further includes a connecting conductor layer  120  and a reinforcement conductor  130 . 
     The connecting conductor layer  120  is bonded to the surface  119 A of the first counter electrode layer  118 A, which is positioned at the opposite side of the first counter electrode layer  118 A as viewed from the first support electrode layer  112 A. The connecting conductor layer  120  is also bonded to a surface  119 B of the second counter electrode layer  118 B, which is positioned at the opposite side of the second counter electrode layer  118 B as viewed from the second support electrode layer  112 B. With this configuration, the second capacitor  110 B is connected in series with the first capacitor  110 A. 
     The shape and the thickness of the connecting conductor layer  120  are not particularly limited to a specific shape and thickness. The connecting conductor layer  120  may be formed in the shape of a plane, foil, or thin film. The surface of the connecting conductor layer  120  may be formed in an uneven shape. The connecting conductor layer  120  formed in a planar shape is easy to handle during the manufacturing of the composite capacitor  100  and the composite capacitor  100  is thus easy to design. The connecting conductor layer  120  formed in a foil-like shape is easy to handle during the manufacturing of the composite capacitor  100 . The connecting conductor layer  120  formed in a thin-film-like shape can further reduce the height of the composite capacitor  100 . As the connecting conductor layer  120  is thinner, it is more likely to fuse when an overcurrent flows through the composite capacitor  100 , thereby enabling the connecting conductor layer  120  to serve as a fuse. 
     The external shape of the connecting conductor layer  120  as viewed from the above-described thickness direction is a rectangle, a substantially rectangle having curved corners, or an ellipse. If the corners of the connecting conductor layer  120  as viewed from the thickness direction are curved, stress in the connecting conductor layer  120  is eased and the mechanical robustness is improved. A hole may be formed in the connecting conductor layer  120  as viewed from the thickness direction. To improve the mechanical robustness, the connecting conductor layer  120  preferably has high symmetrical characteristics as viewed from the thickness direction. 
     As viewed from the above-described thickness direction, the portion of the connecting conductor layer  120  which contacts the first counter electrode layer  118 A may be located farther inward than the first counter electrode layer  118 A. The portion of the connecting conductor layer  120  which contacts the second counter electrode layer  118 B may be located farther inward than the second counter electrode layer  118 B. 
     The connecting conductor layer  120  may have a dumbbell-like external shape. One end portion of the dumbbell is positioned on the surface  119 A of the first counter electrode layer  118 A, while the other end portion of the dumbbell is positioned on the surface  119 B, which is the opposite side of the second counter electrode layer  118 B as viewed from the second support electrode layer  112 B. That is, the central axis of the dumbbell is located between the first support electrode layer  112 A and the second support electrode layer  112 B, as viewed from the above-described thickness direction. With this configuration, the portion of the connecting conductor layer  120  corresponding to this central axis can effectively ease stress in the above-described in-plane direction. Additionally, when an overcurrent flows through the composite capacitor  100 , the portion of the connecting conductor layer  120  corresponding to this central axis can easily fuse and thus also serve as a fuse. 
     The material forming the connecting conductor layer  120  is not restricted to a particular type. The connecting conductor layer  120  may be made of a metal, such as copper, a semiconductor material, or a ceramic material. If the connecting conductor layer  120  is made of a metal, the bonding strength with the first counter electrode layer  118 A and the second counter electrode layer  118 B can be improved. If the connecting conductor layer  120  is made of a semiconductor material, a metal bonding layer may be formed between the connecting conductor layer  120  and each of the first counter electrode layer  118 A and the second counter electrode layer  118 B in advance. With the provision of the metal bonding layer, the bonding strength between the connecting conductor layer  120  and each of the first counter electrode layer  118 A and the second counter electrode layer  118 B can be improved. If the connecting conductor layer  120  is made of a ceramic material, which is a relatively hard material, the robustness in response to stress applied from another member can be enhanced. 
     The reinforcement conductor  130  is located between the first counter electrode layer  118 A and the second counter electrode layer  118 B. The reinforcement conductor  130  is connected to each of the first counter electrode layer  118 A, the second counter electrode layer  118 B, and the connecting conductor layer  120 . 
     The reinforcement conductor  130  is made of the same material as the first counter electrode layer  118 A and the second counter electrode layer  118 B. This can improve the mechanical robustness of the overall composite capacitor  100  and also enhances the efficiency of heat dissipation from the reinforcement conductor  130 . 
     The reinforcement conductor  130  may be formed of a uniform member together with the first counter electrode layer  118 A and the second counter electrode layer  118 B. If the reinforcement conductor  130  is formed of a uniform member together with the first counter electrode layer  118 A and the second counter electrode layer  118 B, the manufacturing of the composite capacitor  100  can be facilitated. If the reinforcement conductor  130  is formed of a uniform member together with the first counter electrode layer  118 A, the boundary between the first counter electrode layer  118 A and the reinforcement conductor  130  is positioned on the side surface of the first support electrode layer  112 A closer to the second capacitor  110 B and at one side of the above-described thickness direction of the first support electrode layer  112 A. If the reinforcement conductor  130  is formed of a uniform member together with the second counter electrode layer  118 B, the boundary between the second counter electrode layer  118 B and the reinforcement conductor  130  is positioned on the side surface of the second support electrode layer  112 B closer to the first capacitor  110 A and at one side of the above-described thickness direction of the second support electrode layer  112 B. The material forming the reinforcement conductor  130  is different from the material of the connecting conductor layer  120 . 
     In this embodiment, the dimension of an in-plane central portion  131  of the reinforcement conductor  130  in the above-described thickness direction is smaller than the dimension of a first region  132 A in the thickness direction where the reinforcement conductor  130  and the first counter electrode layer  118 A contact each other and is also smaller than the dimension of a second region  132 B in the thickness direction where the reinforcement conductor  130  and the second counter electrode layer  118 B contact each other. 
     In this embodiment, in the above-described thickness direction, an end portion  133 A of the first region  132 A on the side of the first support electrode layer  112 A is positioned closer to the first support electrode layer  112 A than the forward end portions  115 A of the plural first columnar conductors  114 A are. Additionally, the end portion  133 A is positioned closer to the first support electrode layer  112 A than an average position PA of the centers of the plural first columnar conductors  114 A in the above-described thickness direction is. 
     In this embodiment, in the above-described thickness direction, an end portion  133 B of the second region  132 B on the side of the second support electrode layer  112 B is positioned closer to the second support electrode layer  112 B than the forward end portions  115 B of the plural second columnar conductors  114 B are. Additionally, the end portion  133 B is positioned closer to the second support electrode layer  112 B than an average position PB of the centers of the plural second columnar conductors  114 B in the above-described thickness direction is. 
     In this embodiment, a surface  134  of the reinforcement conductor  130 , which is positioned at the opposite side of the reinforcement conductor  130  as viewed from the connecting conductor layer  120 , is curved so as to project toward the connecting conductor layer  120 . In this embodiment, when the region between the first capacitor  110 A and the second capacitor  110 B is divided into four regions in the direction from the first capacitor  110 A to the second capacitor  110 B, a portion  135  on the surface  134  which is closest to the connecting conductor layer  120  is located within the two central regions of these four regions. More specifically, the portion  135  on the surface  134  which is closest to the connecting conductor layer  120  is positioned at the center between the first capacitor  110 A and the second capacitor  110 B. 
     As viewed from the above-described thickness direction, within the region between the first capacitor  110 A and the second capacitor  110 B, the reinforcement conductor  130  contacts at least part of the first counter electrode layer  118 A and at least part of the second counter electrode layer  118 B. 
     The process for forming the reinforcement conductor  130  is not restricted to a particular process, and plating, ALD, CVD, MOCVD, supercritical fluid film deposition, or sputtering, for example, may be used. To form the reinforcement conductor  130  as a uniform member together with the first counter electrode layer  118 A and the second counter electrode layer  118 B, the reinforcement conductor  130 , the first counter electrode layer  118 A, and the second counter electrode layer  118 B may be formed in the following manner. A member constituted by the first counter electrode layer  118 A and the second counter electrode layer  118 B continuously disposed in the horizontal direction may be formed and be then ground with a dicer, for example, at the supported side of this member. If the reinforcement conductor  130  is formed in this manner, the shape of the reinforcement conductor  130 , that is, the thickness of the reinforcement conductor  130 , can easily be adjusted, which further facilitates the adjustment to the equivalent series resistance of the composite capacitor  100 . 
     As shown in  FIG. 1 , when the composite capacitor  100  of this embodiment is mounted on the mounting substrate  10 , the plural first columnar conductors  114 A and the plural second columnar conductors  114 B extend in the vertical direction with respect to the mounting substrate  10 . When a mechanical force is applied to the first capacitor  110 A and the second capacitor  110 B in the extending direction of the plural first columnar conductors  114 A and the plural second columnar conductors  114 B, elastic deformation is less likely to occur in the first capacitor  110 A and the second capacitor  110 B. Because of this configuration, when, due to thermal stress, for example, the mounting substrate  10  having the composite capacitor  100  mounted thereon is curved in a projecting form on the opposite side of the composite capacitor  100 , the connecting conductor layer  120  and each of the first counter electrode layer  118 A and the second counter electrode layer  118 B pull each other, and such a pulling force is concentrated between the connecting conductor layer  120  and each of the first counter electrode layer  118 A and the second counter electrode layer  118 B. Such a pulling force especially acts on the interface between the connecting conductor layer  120  and the first counter electrode layer  118 A and the interface between the connecting conductor layer  120  and the second counter electrode layer  118 B which face the portion between the first capacitor  110 A and the second capacitor  110 B. 
     In view of this issue, as described above, the composite capacitor  100  according to the first embodiment of the invention includes the reinforcement conductor  130 . The reinforcement conductor  130  is located between the first counter electrode layer  118 A and the second counter electrode layer  118 B. The reinforcement conductor  130  is connected to the first counter electrode layer  118 A, the second counter electrode layer  118 B, and the connecting conductor layer  120 . The material forming the reinforcement conductor  130  is the same as the first counter electrode layer  118 A and the second counter electrode layer  118 B and is different from the material of the connecting conductor layer  120 . 
     With this configuration, the overall height of the composite capacitor  100  can be reduced, and also, the delamination is less likely to occur between the connecting conductor layer  120  and each of the first counter electrode layer  118 A and the second counter electrode layer  118 B. 
     In this embodiment, the dimension of the in-plane central portion  131  of the reinforcement conductor  130  in the above-described thickness direction is smaller than the dimension of the first region  132 A in the thickness direction where the reinforcement conductor  130  and the first counter electrode layer  118 A contact each other and is also smaller than the dimension of the second region  132 B in the thickness direction where the reinforcement conductor  130  and the second counter electrode layer  118 B contact each other. 
     With this configuration, the portion of the reinforcement conductor  130  positioned near the interface between the connecting conductor layer  120  and the first counter electrode layer  118 A can firmly connect the connecting conductor layer  120  and the first counter electrode layer  118 A, while the portion of the reinforcement conductor  130  positioned near the interface between the connecting conductor layer  120  and the second counter electrode layer  118 B can firmly connect the connecting conductor layer  120  and the second counter electrode layer  118 B. Additionally, at the central portion  131 , the reinforcement conductor  130  can absorb stress acting on the composite capacitor  100  when the mounting substrate  10  is distorted. 
     In this embodiment, the surface  134  of the reinforcement conductor  130 , which is positioned at the opposite side of the reinforcement conductor  130  as viewed from the connecting conductor layer  120 , is curved so as to project toward the connecting conductor layer  120 . 
     Since the surface  134  is smoothly curved, the mechanical robustness of the reinforcement conductor  130  is improved. 
     In this embodiment, when the region between the first capacitor  110 A and the second capacitor  110 B is divided into four regions in the direction from the first capacitor  110 A to the second capacitor  110 B, on the surface  134 , which is positioned at the opposite side of the reinforcement conductor  130  as viewed from the connecting conductor layer  120 , the portion  135  of the surface  134  which is positioned closest to the connecting conductor layer  120  is located within the two central regions of these four regions. 
     With this configuration, stress acting on the composite capacitor  100  when the mounting substrate  10  bends and is distorted can be absorbed at the portion of the connecting conductor layer  120  which contact the reinforcement conductor  130 . This can improve the mechanical robustness of the composite capacitor  100 . 
     In this embodiment, in the above-described thickness direction, the end portion  133 A of the first region  132 A on the side of the first support electrode layer  112 A is positioned closer to the first support electrode layer  112 A than the forward end portions  115 A of the plural first columnar conductors  114 A are. In the above-described thickness direction, the end portion  133 B of the second region  132 B on the side of the second support electrode layer  112 B is positioned closer to the second support electrode layer  112 B than the forward end portions  115 B of the plural second columnar conductors  114 B are. 
     With this configuration, even when the plural first columnar conductors  114 A are curved from the supported side to the end portions  115 A and are positioned toward the side surface of the first counter electrode layer  118 A and even when the plural second columnar conductors  114 B are curved from the supported side to the end portions  115 B and are positioned toward the side surface of the second counter electrode layer  118 B, the reinforcement conductor  130  can cover the forward end portions  115 A of the plural first columnar conductors  114 A and the forward end portions  115 B of the plural second columnar conductors  114 B. It is thus less likely that the composite capacitor  100  is broken in a short-circuiting mode, which may be caused by short-circuiting between any of the above-described forward end portions  115 A and  115 B and another member. 
     In this embodiment, the end portion  133 A of the first region  132 A on the side of the first support electrode layer  112 A is positioned closer to the first support electrode layer  112 A than the average position PA of the centers of the plural first columnar conductors  114 A in the above-described thickness direction is. The end portion  133 B of the second region  132 B on the side of the second support electrode layer  112 B is positioned closer to the second support electrode layer  112 B than the average position PB of the centers of the plural second columnar conductors  114 B in the above-described thickness direction is. 
     As a result of forming the reinforcement conductor  130  other than the central portion  131  to be thick, parasitic resistance components in a conductive path connecting the first capacitor  110 A and the second capacitor  110 B can be reduced. 
     Second Embodiment 
     Hereinafter, a composite capacitor according to a second embodiment of the invention will be described below. The composite capacitor according to the second embodiment of the invention is different from the composite capacitor  100  according to the first embodiment of the invention in that it further includes an insulating section. An explanation of elements configured similarly to those of the first embodiment of the invention will not be repeated. 
       FIG. 2  is a sectional view of a composite capacitor according to the second embodiment of the invention. As shown in  FIG. 2 , a composite capacitor  200  according to the second embodiment of the invention further includes an insulating section  240  disposed in a gap between the first capacitor  110 A and the second capacitor  110 B. Dielectric breakdown, which may be caused by a short-circuiting mode between the first capacitor  110 A and the second capacitor  110 B of the composite capacitor  200 , is thus less likely to occur in the composite capacitor  200 . The mechanical robustness of the composite capacitor  200  can also be improved. 
     In this embodiment, the insulating section  240  closely contacts the surface  134  of the reinforcement conductor  130 . As viewed from the above-described in-plane direction, the portion of the insulating section  240  surrounded by the first capacitor  110 A, the second capacitor  110 B, and the reinforcement conductor  130  contacts the first support electrode layer  112 A, the first counter electrode layer  118 A, the second support electrode layer  112 B, and the second counter electrode layer  118 B. 
     The material forming the insulating section  240  is not limited to a particular type. An example of the material forming the insulating section  240  is a ceramic material, such as alumina and hafnium. 
     The process for forming the insulating section  240  is not restricted to a particular process, and plating, ALD, CVD, MOCVD, supercritical fluid film deposition, or sputtering, for example, may be used. The insulating section  240  may be formed by applying a paste material containing an insulating material and then by drying the paste material. 
     In this embodiment, too, it is possible to reduce the overall height of the composite capacitor  200  by using the reinforcement conductor  130  having a predetermined configuration and also to make it less likely to cause delamination between the connecting conductor layer  120  and each of the first counter electrode layer  118 A and the second counter electrode layer  118 B. 
     Hereinafter, composite capacitors according to third through sixth embodiments of the invention will be described below. Each of the composite capacitors according to the third through sixth embodiments of the invention is different from the composite capacitor  100  according to the first embodiment of the invention in the configuration of the external shape of the reinforcement conductor. An explanation of elements configured similarly to those of the first embodiment of the invention will not be repeated. 
     Third Embodiment 
       FIG. 3  is a sectional view of a composite capacitor according to the third embodiment of the invention. As shown in  FIG. 3 , in a composite capacitor  300  according to the third embodiment of the invention, at the central portion  131  of a reinforcement conductor  330 , a surface  334  of the reinforcement conductor  330 , which is positioned at the opposite side of the reinforcement conductor  330  as viewed from the connecting conductor layer  120 , is parallel with the above-described in-plane direction. 
     With this configuration, when a mounting substrate bends and is distorted, the central portion  131  having a uniform thickness of the reinforcement conductor  330  can absorb stress acting on the composite capacitor  300 . This further improves the mechanical robustness of the composite capacitor  300 . Additionally, the thickness of the central portion  131  can easily be adjusted, which makes it easy to control the value of the equivalent series resistance of the conductive path formed by the reinforcement conductor  330  and the connecting conductor layer  120 . 
     Fourth Embodiment 
       FIG. 4  is a sectional view of a composite capacitor according to the fourth embodiment of the invention. As shown in  FIG. 4 , in a composite capacitor  400  according to the fourth embodiment of the invention, a reinforcement conductor  430  has a U-like external shape having a cavity on the side of the support electrode layer. With this configuration, as in the composite capacitor  300  according to the third embodiment of the invention, in the composite capacitor  400  according to the fourth embodiment of the invention, at the central portion  131  of the reinforcement conductor  430 , the surface  434  is parallel with the above-described in-plane direction. 
     Fifth Embodiment 
       FIG. 5  is a sectional view of a composite capacitor according to the fifth embodiment of the invention. As shown in  FIG. 5 , as in the composite capacitor  300  according to the third embodiment of the invention, in a composite capacitor  500  according to the fifth embodiment of the invention, at the central portion  131  of a reinforcement conductor  530 , the surface  534  is parallel with the above-described in-plane direction. Moreover, in this embodiment, the surface  534  of the reinforcement conductor  530  other than the central portion  131  is curved to project toward the first support electrode layer  112 A and the second support electrode layer  112 B. 
     Sixth Embodiment 
       FIG. 6  is a sectional view of a composite capacitor according to the sixth embodiment of the invention. As shown in  FIG. 6 , in a composite capacitor  600  according to the sixth embodiment of the invention, a reinforcement conductor  630  includes a first reinforcement conductor  630 A and a second reinforcement conductor  630 B that are separate from each other. The first reinforcement conductor  630 A contacts the first counter electrode layer  118 A and the connecting conductor layer  120 . The second reinforcement conductor  630 B contacts the second counter electrode layer  118 B and the connecting conductor layer  120 . 
     In the composite capacitors  300 ,  400 ,  500 , and  600  according to the third through sixth embodiments of the invention, too, it is possible to reduce the overall heights of the composite capacitors  300 ,  400 ,  500 , and  600  by using the reinforcement conductors  330 ,  430 ,  530 , and  630  each having a predetermined configuration and also to make it less likely to cause delamination between the connecting conductor layer  120  and each of the first counter electrode layer  118 A and the second counter electrode layer  118 B. 
     In the above-described embodiments, some of the configurations may be combined with each other within a technically possible range. 
     The above-disclosed embodiments are provided only for the purposes of illustration, but are not intended to be exhaustive or to limit the invention to the precise forms disclosed. It is intended that the scope of the invention be defined, not by the foregoing description, but by the following claims. The scope of the present invention is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10  mounting substrate 
               20 A first solder 
               20 B second solder 
               100 ,  200 ,  300 ,  400 ,  500 ,  600  composite capacitor 
               110 A first capacitor 
               110 B second capacitor 
               112 A first support electrode layer 
               112 B second support electrode layer 
               114 A first columnar conductor 
               114 B second columnar conductor 
               115 A,  115 B forward end portion 
               116 A first dielectric layer 
               116 B second dielectric layer 
               118 A first counter electrode layer 
               118 B second counter electrode layer 
               119 A,  119 B surface 
               120  connecting conductor layer 
               130 ,  330 ,  430 ,  530 ,  630  reinforcement conductor 
               131  central portion 
               132 A first region 
               132 B second region 
               133 A,  133 B end portion 
               134 ,  334 ,  434 ,  534  surface 
               135  portion 
               240  insulating section 
               630 A first reinforcement conductor 
               630 B second reinforcement conductor