JP5329319B2 - Solid electrolytic capacitor - Google Patents

Description

  The present invention relates to a solid electrolytic capacitor including a porous sintered body made of a valve metal such as tantalum or niobium.

  FIG. 7 is a cross-sectional view showing an example of a conventional solid electrolytic capacitor. The solid electrolytic capacitor X shown in the figure includes a porous sintered body 91, an anode wire 92, a dielectric layer 93, a solid electrolyte layer 94, a conductor layer 95, an anode terminal 96A, a cathode terminal 96B, a conducting member 96C, And a resin package 98. An anode wire 92 protrudes from the porous sintered body 91. The dielectric layer 93 is laminated on the surface of the porous sintered body 91. The solid electrolyte layer 94 is laminated on the surface of the dielectric layer 93. The conductor layer 95 is stacked on the solid electrolyte layer 94 and is electrically connected to the solid electrolyte layer 94. The anode terminal 96A is electrically connected to the anode wire 92 through the conducting member 96C. The cathode terminal 96B is bonded to the conductor layer 95. Thereby, the cathode terminal 96 </ b> B is electrically connected to the solid electrolyte layer 94. The resin package 98 seals the porous sintered body 91 and the like.

  The main characteristic of such a solid electrolytic capacitor X is impedance. The solid electrolytic capacitor X is required to have an impedance within a desired range. Conventionally, there has been a problem that impedance varies greatly for each solid electrolytic capacitor X. Such variation in impedance has hindered improvement in yield of the solid electrolytic capacitor X.

JP 2001-358038 A

  The present invention has been conceived under the circumstances described above, and an object thereof is to provide a solid electrolytic capacitor capable of suppressing variations in impedance.

  The solid electrolytic capacitor provided by the present invention includes a porous sintered body made of a valve metal, a dielectric layer laminated on the surface of the porous sintered body, and a solid electrolyte laminated on the dielectric layer. A solid electrolytic capacitor comprising: a capacitor element including a layer; and a conductor layer formed on a surface of the capacitor element and conducting with the solid electrolyte layer. The capacitor element is covered with the conductor layer. It is characterized in that at least one recessed portion is formed.

  In such a configuration, when the conductor layer is formed in the concave portion, the thickness of the conductor layer can be increased. Since the thickness of the conductor layer can be increased, variation in impedance of the solid electrolytic capacitor can be suppressed.

  In a preferred embodiment of the present invention, the capacitor element has one or a plurality of recess forming surfaces in which the recesses are formed, and only one of the recesses is disposed on any of the recess forming surfaces. And the edge of this recessed part is surrounded by the edge of the said recessed part formation surface.

  In a preferred embodiment of the present invention, an edge of the recess is parallel to an edge of the adjacent recess forming surface. Such a configuration is suitable for increasing the size of the recess in plan view while maintaining the same size of the recess formation surface.

  In a preferred embodiment of the present invention, the capacitor element has one or a plurality of recess formation surfaces in which the recesses are formed, and one or a plurality of recess non-formation surfaces in which the recesses are not formed, A conductive plate is further provided which is electrically connected to the conductor layer and faces the surface where the recess is not formed. According to such a configuration, the concave portion is not formed on the surface where the concave portion is not formed, and a step is hardly generated. Therefore, it is easy to attach the conductive plate to the capacitor element.

  In a preferred embodiment of the present invention, an anode wire that is electrically connected to the porous sintered body and protrudes from the recess non-forming surface different from the recess non-forming surface facing the conductive plate is further provided. The capacitor element has a rectangular parallelepiped shape in which each surface has two concave portion-free surfaces and four concave portion-formed surfaces.

  In a preferred embodiment of the present invention, the recess has a flat bottom surface.

  In a preferred embodiment of the present invention, the concave portion has a side surface that forms an obtuse angle with respect to the bottom surface. According to such a configuration, for example, when the concave portion is formed by a mold or the like and then the mold is separated from the concave portion, the convex portion of the mold and the side surface of the concave portion are not easily rubbed. Therefore, it can suppress as much as possible that the said side surface of the said recessed part becomes a smooth surface which emits metallic luster. Thereby, it can be avoided that the aqueous solution does not easily penetrate from the side surface when the dielectric layer or the solid electrolyte layer is formed.

  In a preferred embodiment of the present invention, the recess is arcuate in cross-sectional view.

  In preferable embodiment of this invention, the depth of the said recessed part is 13-30 micrometers.

  In a preferred embodiment of the present invention, the depth of the recess is 2.6 to 6.0% of the dimension of the capacitor element in the direction in which the recess is recessed.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is sectional drawing which shows an example of the solid electrolytic capacitor concerning 1st Embodiment of this invention. It is a perspective view which shows the structure of a part of solid electrolytic capacitor shown in FIG. It is a figure which shows one process of manufacturing the solid electrolytic capacitor shown in FIG. It is a figure which shows the relationship between the depth of the recessed part of a solid electrolytic capacitor shown in FIG. 1, and an impedance. It is a figure which shows the relationship between the depth of the recessed part of the solid electrolytic capacitor shown in FIG. 1, and the thickness of a conductor layer. It is sectional drawing which shows an example of the solid electrolytic capacitor concerning 2nd Embodiment of this invention. It is sectional drawing which shows an example of the conventional solid electrolytic capacitor.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of the solid electrolytic capacitor according to the first embodiment of the present invention. The solid electrolytic capacitor A1 shown in the figure includes a capacitor element 1, a conductor layer 3, an anode terminal 41, a cathode terminal 42, a conducting member 43, and a resin package 6. FIG. 2 is a perspective view showing only the capacitor element 1 shown in FIG.

  As shown in FIG. 1, the capacitor element 1 includes a porous sintered body 11, an anode wire 12, a dielectric layer 13, and a solid electrolyte layer 14. The porous sintered body 11 has a structure in which a large number of pores are formed. The porous sintered body 11 is made of, for example, tantalum or niobium. The anode wire 12 protrudes from the porous sintered body 11. The anode wire 12 is made of, for example, tantalum or niobium. The dielectric layer 13 is laminated on the surface of the porous sintered body 11 and is formed on the surface of the porous sintered body 11. The dielectric layer 13 is made of an oxide of a valve metal such as tantalum pentoxide or niobium pentoxide. The solid electrolyte layer 14 is laminated on the dielectric layer 13 and is formed so as to fill the pores of the porous sintered body 11. The solid electrolyte layer 14 is made of, for example, manganese dioxide or a conductive polymer. When the solid electrolyte layer 14 is used, charges are stored at the interface between the solid electrolyte layer 14 and the dielectric layer 13.

  As shown in FIG. 2, the capacitor element 1 has a rectangular parallelepiped shape. Capacitor element 1 has four concave portion forming surfaces 1a in which concave portions 15 are formed and two concave portion non-forming surfaces 1c in which concave portions 15 are not formed. The anode wire 12 protrudes from one of the recess-unformed surfaces 1c.

  Each recess forming surface 1a has a rectangular edge 1b. In each recess forming surface 1a, one or a plurality of recesses 15 are formed. In the present embodiment, only one recess 15 is formed in any recess forming surface 1a. Each recess 15 has a rectangular edge 153. The edge 153 of each recess 15 is surrounded by the edge 1b of the recess forming surface 1a where the recess 15 is formed. The edge 153 of each recess 15 is parallel to the adjacent edge 1b of the recess forming surface 1a where the recess 15 is formed.

  As clearly shown in FIG. 1, each recess 15 has a bottom surface 151 and a side surface 152. Each bottom surface 151 has a flat shape. Each side surface 152 forms an obtuse angle with the bottom surface 151. That is, the side surface 152 is inclined with respect to the bottom surface 151 so that the concave portion 15 is squeezed toward the bottom surface 151.

  The depth L1 of the recess 15 is preferably 13 to 30 μm, for example. The dimension L2 of the capacitor element 1 in the vertical direction in FIG. 1 is 500 μm. Therefore, the depth L1 is preferably 2.6 to 6.0% of the dimension L2. The size of the dimension L2 varies depending on the type of the capacitor element 1. In the capacitor element 1 considered to be the smallest, the dimension L2 is 350 μm.

  As shown in FIG. 1, the conductor layer 3 is formed on the surface of the capacitor element 1 and is electrically connected to the solid electrolyte layer 14. Furthermore, the conductor layer 3 covers the recess 15. The conductor layer 3 is composed of, for example, a graphite layer and a silver layer.

  The anode terminal 41 is a plate-like member made of, for example, copper or nickel. The anode terminal 41 is electrically connected to the anode wire 12 through the conductive member 43. The anode terminal 41 is used for surface mounting the solid electrolytic capacitor A1 on, for example, a circuit board. The cathode terminal 42 is a plate-like member made of, for example, copper or nickel, and is disposed so as to face the non-recessed surface 1 c of the capacitor element 1. The cathode terminal 42 is electrically connected to the conductor layer 3 through, for example, a conductive paste (not shown). Thereby, the cathode terminal 42 is electrically connected to the solid electrolyte layer 14. The cathode terminal 42 is used for surface mounting the solid electrolytic capacitor A1 on a circuit board, for example.

  The resin package 6 is made of, for example, an epoxy resin. The resin package 6 covers the capacitor element 1 and the like, and is for protecting the capacitor element 1 and the like.

  Next, a method for manufacturing the solid electrolytic capacitor A1 according to the present embodiment will be described.

  First, a rectangular parallelepiped porous sintered body 11 is formed. In the step of forming the porous sintered body 11, for example, pressure molding is performed in a state in which a part of the anode wire 12 is made to enter a fine powder of a valve metal such as tantalum or niobium. When performing pressure molding, as shown in FIG. 3, a mold 7 having a tapered convex portion 71 is used. And a sintering process is performed with respect to the pressure-molded body obtained by pressure molding. By this sintering treatment, the valve action fine powders are sintered, and a porous sintered body 11 having a large number of pores is formed. Further, the porous sintered body 11 is formed with a recess 15 ′ by using the mold 7 having the protrusion 71. Since the convex portion 71 is tapered, it is easy to remove the mold 7 from the concave portion 15 ′ after the convex portion 17 is pushed into the porous sintered body 11 to form the concave portion 15 ′.

  Next, the dielectric layer 13 shown in FIG. 1 is formed. The dielectric layer 13 is formed, for example, by subjecting the porous sintered body 11 to anodization in a state where the porous sintered body 11 is immersed in a chemical conversion solution of a phosphoric acid aqueous solution. Next, the porous sintered body 11 on which the dielectric layer 13 is formed is immersed in, for example, an aqueous solution of manganese nitrate. Thereafter, the porous sintered body 11 is pulled up and fired. By repeating this dipping and sintering steps, the solid electrolyte layer 14 is formed.

  Through the above steps, the capacitor element 1 shown in FIG. 1 is formed.

  Next, a graphite layer is formed on the surface of the capacitor element 1. Then, a silver layer is formed by immersing in a solution of silver paste and solidifying by drying. In this way, the conductor layer 3 shown in FIG. 1 is formed. Then, by forming the anode terminal 41, the conductive member 43, the cathode terminal 42, and the resin package 6, the solid electrolytic capacitor A1 can be formed.

  Next, the operation of the solid electrolytic capacitor A1 according to this embodiment will be described.

  In the solid electrolytic capacitor A <b> 1, the capacitor element 1 is formed with a recess 15 covered with the conductor layer 3. When the conductor layer 3 is formed in the recess 15, the thickness of the conductor layer 3 can be increased. Since the thickness of the conductor layer 3 can be increased, variation in impedance of the solid electrolytic capacitor A1 can be suppressed.

  FIG. 4 is a diagram showing the relationship between the depth L1 of the recess 15 and the impedance of the solid electrolytic capacitor A1. FIG. 5 is a diagram illustrating the relationship between the depth L1 of the recess 15 and the thickness of the conductor layer 3 actually formed in the recess 15.

  As shown in FIG. 4, it can be confirmed that the impedance of the solid electrolytic capacitor A1 decreases when the depth L1 is 13 μm or more. Moreover, as shown in FIG. 5, the tendency for the thickness of the conductor layer 3 to become large when the depth L1 is 13 micrometers or more can be confirmed. From these tendencies, it can be said that when the depth L1 is 13 μm or more, the effect of reducing the variation in impedance of the solid electrolytic capacitor A1 is particularly easily manifested. On the other hand, when the depth L1 increases, the volume of the porous sintered body 11 decreases and the capacity of the solid electrolytic capacitor A1 decreases. Therefore, in the solid electrolytic capacitor A1, it is preferable that the depth L1 is not excessively increased and the depth L1 is 30 μm or less. That is, it can be said that the depth L1 is very preferably 13 to 30 μm. The depth L1 is 13 to 30 μm or less because the capacitor element 1 is 2.1 × 1.3 × 1.0 mm size (the solid electrolytic capacitor A1 is 3.2 × 1.6 × 1.1 mm size). It is particularly suitable when it is smaller.

  Further, the depth L1 of the recess 15 is 2.6 to 6.0% of the dimension L2, and is extremely smaller than the dimension L2. Therefore, even if the recess 15 is formed, the strength of the porous sintered body 11 is not easily reduced.

  The edge 153 of the recess 15 is parallel to the end edge 1b of the recess forming surface 1a. This is suitable for increasing the size of the recess 15 in plan view while maintaining the size of the recess forming surface 1a at the same level. Thereby, the dispersion | variation in the impedance of solid electrolytic capacitor A1 can further be suppressed.

  The cathode terminal 42 is disposed so as to face the non-recessed surface 1c. Further, there is no step formed when the recess 15 is formed on the recess-unformed surface 1c. Therefore, it is easy to stably arrange the cathode terminal 42 on the non-recessed surface 1c.

  The side surface 152 of the recess 15 forms an obtuse angle with respect to the bottom surface 151. Therefore, after forming the recess 15 ′ with the mold 7 shown in FIG. 3, when the mold 7 is separated from the recess 15 ′, the protrusion 71 of the mold 7 and the side surface 152 ′ of the recess 15 ′ are rubbed. Hard to fit. Therefore, it is possible to suppress as much as possible that the side surface 152 ′ of the recess 15 ′ becomes a smooth surface that emits metallic luster. This makes it difficult for the aqueous phosphoric acid solution to penetrate from the side surface 152 'when forming the dielectric layer 13, or makes it difficult for the aqueous manganese nitrate solution to penetrate from the side surface 152' when forming the solid electrolyte layer 14. You can avoid doing it.

  FIG. 6 shows a cross-sectional view of a solid electrolytic capacitor according to a second embodiment of the present invention. In the figure, the same or similar elements as those of the above embodiment are denoted by the same reference numerals as those of the above embodiment.

  The solid electrolytic capacitor A2 shown in the figure is different from the solid electrolytic capacitor A1 according to the first embodiment in that the recess 15 has an arcuate shape in a cross-sectional view. The depth L1 of the recess 15 in the solid electrolytic capacitor A2 is also preferably 13 to 30 μm. Further, the depth L1 of the recess 15 is preferably 2.6 to 6.0% of the dimension L2 of the capacitor element 1 in the vertical direction of FIG. Even with such a configuration, variation in impedance can be suppressed as in the first embodiment. Moreover, according to this structure, the intensity | strength of the porous sintered compact 11 can be maintained with high. Further, there is an effect similar to that of the first embodiment shown in FIG. 3 in which it is easy to remove the mold 7 from the recess 15 ′ after forming the recess 15 ′.

  The scope of the present invention is not limited to the embodiment described above. The specific configuration of each part of the solid electrolytic capacitor according to the present invention can be varied in design in various ways. In the said embodiment, although the cathode terminal 42 showed the example which conduct | electrically_connects with the conductor layer 3 via an electrically conductive paste in the downward direction of FIG.1 and FIG.6, this invention is not limited to this. For example, the cathode terminal 42 may be electrically connected to the conductor layer 3 via, for example, a conductive paste in the upper part of FIGS. In this case, the shape of the cathode terminal 42 may be changed as appropriate. Alternatively, the cathode terminal 42 and the conductor layer 3 may be electrically connected by a wire. By doing so, it can be expected that the fuse function is exhibited.

A1, A2 Solid electrolytic capacitor 1 Capacitor element 11 Porous sintered body 12 Anode wire 13 Dielectric layer 14 Solid electrolyte layer 1a Recessed surface 1b Edge 1c Recessed surface 15, 15 'Recessed surface 151 Bottom surface 152 Side surface 153 Edge 3 Conductor layer 41 Anode terminal 42 Cathode terminal (conductive plate)
43 Conducting member 6 Resin package 7 Mold 71 Protrusion L1 Depth L2 Dimensions

Claims (10)

Capacitor element including a porous sintered body made of a valve metal, a dielectric layer laminated on the surface of the porous sintered body, and a solid electrolyte layer laminated on the dielectric layer, and the capacitor element A solid electrolytic capacitor comprising a conductor layer formed on a surface of the conductive layer and electrically connected to the solid electrolyte layer.
The capacitor element is formed with at least one recess covered with the conductor layer ,
The capacitor element has one or a plurality of recess forming surfaces in which the recesses are formed,
In any one of the recess forming surfaces, only one of the recesses is disposed, and the edge of the recess is surrounded by the edge of the recess forming surface,
The area of the recess in plan view is larger than the area of the surrounding surface that is defined by the edge and the edge and surrounds the recess in plan view.
The solid electrolytic capacitor, wherein a thickness of a portion of the conductor layer covering the recess is thicker than a thickness of a portion of the conductor layer covering the surrounding surface . The recess has a bottom surface covered with the conductor layer, and the dimension of the portion formed on the bottom surface of the conductor layer in the depth direction of the recess is larger than the depth of the recess. The solid electrolytic capacitor according to claim 1. Edge of the recess is parallel to the edge of the recessed surface adjacent solid electrolytic capacitor according to claim 1 or 2. The capacitor element has one or a plurality of recess formation surfaces in which the recesses are formed, and one or a plurality of recess non-formation surfaces in which the recesses are not formed,
4. The solid electrolytic capacitor according to claim 1, further comprising a conductive plate that is electrically connected to the conductor layer and faces the non-recessed surface. 5. An anode wire that is electrically connected to the porous sintered body and protrudes from the recess-unformed surface different from the recess-unformed surface facing the conductive plate;
5. The solid electrolytic capacitor according to claim 4, wherein the capacitor element has a rectangular parallelepiped shape in which each surface has two non-recessed surfaces and four recessed surface.   The solid electrolytic capacitor according to claim 1, wherein the recess has a flat bottom surface.   The solid electrolytic capacitor according to claim 6, wherein the concave portion has a side surface that forms an obtuse angle with respect to the bottom surface.   The solid electrolytic capacitor according to claim 1, wherein the recess has an arcuate shape in a cross-sectional view.   The solid electrolytic capacitor according to claim 1, wherein a depth of the concave portion is 13 to 30 μm.   10. The solid electrolytic capacitor according to claim 1, wherein the depth of the recess is 2.6 to 6.0% of a dimension of the capacitor element in a direction in which the recess is recessed.

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