JP2010258312A - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor reducing a leak current inside a capacitor element, and also to provide a method of manufacturing the same. <P>SOLUTION: In a capacitor element 10, the area of a second surface 10S<SB>2</SB>is larger than that of a first surface 10S<SB>1</SB>and a third surface 10S<SB>3</SB>is formed to be inclined with respect to a counter surface 30S<SB>T</SB>of a resin mold part 30. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor having a resin mold portion and a manufacturing method thereof.

  Conventionally, a solid electrolytic capacitor that is surface-mounted on a printed circuit board or the like has been widely used. In general, a solid electrolytic capacitor includes a capacitor element, an anode lead protruding from the capacitor element, and a resin mold part for sealing the capacitor element. The capacitor element includes a rectangular parallelepiped anode body, a dielectric layer covering the anode body, an electrolyte layer covering the dielectric layer, and a conductive layer covering the electrolyte layer. The capacitor element has a first surface from which the anode lead protrudes and a second surface formed on the opposite side of the first surface.

  Here, a method of increasing the thickness of the portion of the electrolyte layer formed at the edge of the anode body has been proposed (see Patent Document 1). According to this method, the leakage current inside the capacitor element can be reduced by accurately covering the edge of the anode body with the electrolyte layer.

JP 2001-143968 A

  By the way, when sealing a capacitor | condenser element to resin, a capacitor | condenser element is arrange | positioned in a metal mold | die and resin is inject | poured from the injection hole provided in the metal mold | die. Generally, the resin is injected from the injection port of the mold toward the second surface of the capacitor element, and flows between the mold and the capacitor element from the second surface side toward the first surface side. Therefore, a stress may be applied to the third surface that is connected from the second surface to the first surface from the resin, so that the dielectric layer inside the capacitor element may be damaged. As a result, there is a problem that leakage current inside the capacitor element increases.

  Such a problem can occur over almost the entire third surface connected from the second surface to the first surface. Therefore, the method of Patent Document 1 in which only the portion formed at the edge of the anode body is thickened eliminates the problem. I can't.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a solid electrolytic capacitor capable of reducing leakage current inside the capacitor element and a method for manufacturing the same.

  A solid electrolytic capacitor according to a feature of the present invention includes a capacitor element including an anode body, a dielectric layer covering the anode body, and a cathode layer covering the dielectric layer, an anode lead protruding from the capacitor element, a capacitor element, and The capacitor element includes a resin mold portion for sealing the anode lead, and the capacitor element includes a first surface from which the anode lead protrudes, a second surface provided on the opposite side of the first surface, and a first surface and a second surface. The resin mold part has a facing surface facing the third surface, and the area of the second surface is larger than the area of the first surface, and the surface facing the third surface. The gist is that the distance from the second surface gradually increases from the second surface side toward the first surface side.

  In the solid electrolytic capacitor according to the feature of the present invention, the area of the second surface may be 1.02 times or more the area of the first surface.

  In the solid electrolytic capacitor according to the feature of the present invention, the thickness of the cathode layer on the second surface side may be larger than the thickness of the cathode layer on the first surface side.

  In the solid electrolytic capacitor according to the feature of the present invention, the cathode layer includes an electrolyte layer covering the dielectric layer and a conductive layer covering the electrolyte layer, and the thickness of the electrolyte layer on the second surface side is 20 μm or more. Also good.

  In the solid electrolytic capacitor according to the feature of the present invention, the cathode layer includes an electrolyte layer covering the dielectric layer and a conductive layer covering the electrolyte layer, and the thickness of the electrolyte layer is from the first surface side to the second surface side. You may form gradually large toward it.

  A method for manufacturing a solid electrolytic capacitor according to a feature of the present invention includes a step A for forming an anode body by sintering a metal powder molded body in which one end of an anode lead is embedded, and a dielectric layer covering the anode body. Forming a capacitor element by forming a cathode layer covering the dielectric layer; and disposing the capacitor element in a mold so that the anode lead projects out of the capacitor element. And a step D of forming a resin mold portion for sealing the capacitor element by pouring resin from the second surface side provided on the opposite side of the surface. The step C includes an anode body on which a dielectric layer is formed. A step of forming a first electrolyte layer covering the dielectric layer by dipping in a solution containing a predetermined monomer, and a part including a surface from which the anode lead protrudes in the anode body on which the first electrolyte layer is formed Forming a second electrolyte layer in addition to a portion of the anode body by pulling out only the solution from the solution, and in step D, a third surface and a mold connected to the first surface and the second surface of the capacitor element The gist is that the distance from the inner wall gradually increases from the second surface side toward the first surface side.

  ADVANTAGE OF THE INVENTION According to this invention, the solid electrolytic capacitor which can suppress the short circuit between an anode body and an electrolyte layer, and its manufacturing method can be provided.

It is sectional drawing which shows typically the structure of the solid electrolytic capacitor 100 which concerns on 1st Embodiment of this invention. It is sectional drawing in the AA of FIG. It is sectional drawing in the BB line of FIG. It is a figure for demonstrating the manufacturing method of the solid electrolytic capacitor 100 which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the solid electrolytic capacitor 100 which concerns on 1st Embodiment of this invention. It is sectional drawing which shows typically the structure of the solid electrolytic capacitor 100 which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows typically the structure of the solid electrolytic capacitor 100 which concerns on 3rd Embodiment of this invention. It is a figure for demonstrating the measuring method of the size in an Example. It is a figure for demonstrating the measuring method of the size in an Example. It is a figure for demonstrating the measuring method of the size in an Example.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[First Embodiment]
(Configuration of solid electrolytic capacitor)
Hereinafter, a solid electrolytic capacitor according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the structure of the solid electrolytic capacitor 100 according to the first embodiment. 2 is a cross-sectional view taken along line AA in FIG. 3 is a cross-sectional view taken along line BB in FIG.

  As shown in FIG. 1, the solid electrolytic capacitor 100 includes a capacitor element 10, an anode lead 20, a resin mold part 30, an anode terminal 40, a cathode terminal 50, and a conductive adhesive layer 60.

  The solid electrolytic capacitor 100 is formed in a flat rectangular parallelepiped shape, for example. The solid electrolytic capacitor 100 is a solid electrolytic capacitor that is surface-mounted on a printed circuit board or the like. Solid electrolytic capacitor 100 has a bottom surface S formed by resin mold part 30. The bottom surface S of the solid electrolytic capacitor 100 is a surface that comes into contact with the surface of a printed circuit board or the like.

  In the following description, the longitudinal direction of the bottom surface S is referred to as “first direction”, the short direction of the bottom surface S is referred to as “second direction”, and the direction perpendicular to the bottom surface S is referred to as “vertical direction”.

  The capacitor element 10 includes an anode body 11, a dielectric layer 12, an electrolyte layer 13, and a conductive layer 14. In the present embodiment, the outer shape of the capacitor element 10 is formed in a quadrangular pyramid shape as shown in FIGS. The square pyramid is a shape of an object including the bottom surface of two objects formed by cutting the square pyramid between a vertex and the bottom surface in a plane parallel to the bottom surface.

As shown in FIGS. 1 and 2, the capacitor element 10 includes a first surface 10S _{1 from} which the anode lead 20 protrudes, a second surface 10S ₂ provided on the opposite side of the first surface 10S ₁ , and a first surface 10S. ₁ and a plurality of third surfaces 10S ₃ connected to the second surface 10S ₂ . The first surface 10S ₁ and the second surface 10S ₂ is substantially perpendicular to the first direction. In addition, each third surface 10S ₃ is inclined with respect to the first direction, and there is a relationship between one third surface 10S ₃ and another third surface 10S ₃ provided on the opposite side of the one third surface 10S ₃ . interval is gradually increased from the second surface 10S ₂ side to the first surface 10S ₁ side.

In the present embodiment, the area of the second surface 10S ₂ is greater than the area of the first surface 10S _1. Thus, the capacitor element 10, the first surface 10S ₁ and the upper surface, and a second surface 10S ₂ is formed in a quadrangular pyramid trapezoidal to bottom. That is, the capacitor element 10 is gradually narrower formed from the second surface 10S ₂ toward the first surface 10S _1. In other words, the capacitor element 10 is tapered from the second surface 10S ₂ side to the first surface 10S ₁ side. The area of the second surface 10S ₂ is preferably not more than 1.02 times the first area of the surface 10S _1.

Further, in the present embodiment, the first surface 10S ₁ and the second surface 10S ₂ each are formed in a square shape, the capacitor element 10 has four third surface 10S _3. On the other hand, the outer shape of the resin mold portion 30 is formed in a substantially rectangular parallelepiped, having four facing surfaces 30S _T opposed to ₃ each of the four third surfaces 10S. Each facing surface 30S _T is formed along the first direction. Thus, each of the third surface 10S _3, as shown in FIGS. 1 and 2, are inclined relative to each opposing face 30S _T, the interval between each of the third surface 10S ₃ and the opposing surface 30S _T is the is gradually increased from the second surface 10S ₂ side to the first surface 10S ₁ side.

Part of the first surface 10S ₁ is formed by the electrolyte layer 13, and the second surface 10S ₂ is formed by the conductive layer 14. The second surface 10S _2, in the step of forming the resin mold portion 30, a surface on which the injection resin is injected.

  The anode body 11 is a porous body formed by sintering a valve action metal powder or an alloy powder containing a valve action metal. As the valve action metal, for example, titanium, tantalum, aluminum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, or the like can be used. Titanium, tantalum, aluminum, and niobium are suitable as materials for the anode body 11 because they have a high dielectric constant and are easily available. Niobium and titanium are particularly preferable because the oxide has a higher dielectric constant than tantalum and aluminum. Moreover, when using the alloy of the above-mentioned valve action metal and another metal as a material of the anode body 11, it is preferable that the ratio of a valve action metal shall be 50% or more.

  The dielectric layer 12 is formed on the surface of the anode body 11 and covers the anode body 11. Here, it should be noted that although not shown, the dielectric layer 12 covers the inner wall surface of the hole of the anode body 11 that is a porous body. In FIG. 1, only the part formed along the external shape of the anode body 11 among the dielectric material layers 12 is shown. The dielectric layer 12 is formed of an oxide of a valve action metal. For example, when the anode body 11 is made of niobium, the dielectric layer 12 formed by the anodic oxidation method is niobium oxide.

  The electrolyte layer 13 is formed on the surface of the dielectric layer 12 and covers the dielectric layer 12. Here, it should be noted that the electrolyte layer 13 covers the dielectric layer 12 that covers the inner wall surface of the hole of the anode body 11 that is a porous body, although not shown. In FIG. 1, only a portion of the electrolyte layer 13 formed along the outer shape of the anode body 11 is shown. The electrolyte layer 13 is composed of a conductive metal oxide such as manganese oxide, or a conductive polymer such as polypyrrole, polyaniline, and polythiophene. Such a conductive polymer is formed by a polymerization method.

Here, in the present embodiment, the outer shape of the electrolyte layer 13 is formed in a quadrangular pyramid shape. Specifically, the thickness of the electrolyte layer 13, as shown in FIGS. 1 and 2, are formed so as to gradually increase from the first surface 10S ₁ side to the second surface 10S ₂ side. Therefore, the thickness α ₂ of the electrolyte layer 13 on the second surface 10S ₂ side is larger than the thickness α ₁ of the electrolyte layer 13 on the first surface 10S ₁ side. By forming the electrolyte layer 13 in this way, the outer shape of the capacitor element 10 is formed in a quadrangular pyramid shape. The thickness alpha ₂ is preferably 20μm or more.

The conductive layer 14 includes a carbon layer 141 and a silver layer 142. The carbon layer 141 is formed on the surface of the electrolyte layer 13. The carbon layer 141 is formed, for example, by applying a carbon paste. The silver layer 142 is formed on the surface of the carbon layer 141. The silver layer 142 is formed, for example, by applying a silver paste. In the present embodiment, the carbon layer 141 and silver layer 142 is not formed on the first surface 10S ₁ of the capacitor element 10.

Here, it should be noted that the electrolyte layer 13 and the conductive layer 14 constitute a “cathode layer” of the solid electrolytic capacitor 100. In the present embodiment, the carbon layer 141 and the silver layer 142 are uniformly formed. On the other hand, the thickness of the electrolyte layer 13 is formed so as to gradually increase from the first surface 10S ₁ side to the second surface 10S ₂ side. Therefore, as shown in FIGS. 1 and 2, the cathode layer thickness α ₁ on the first surface 10S ₁ side is larger than the cathode layer thickness β on the second surface 10S ₂ side.

The anode lead 20 is disposed along the first direction. Anode lead 20 protrudes from the first surface 10S ₁ of the capacitor element 10. One end of the anode lead 20 is embedded and bonded inside the anode body 11, and the other end of the anode lead 20 is sealed with a resin mold layer 30. The anode lead 20 is made of, for example, the same valve metal as the anode body 11 or an alloy containing the valve metal.

The resin mold part 30 seals the capacitor element 10 and the anode lead 20. The resin mold part 30 is comprised by an epoxy resin, a phenol resin, etc. The resin mold part 30 is formed by, for example, a transfer mold method. As described above, the resin mold portion 30 has a facing surface 30S _T facing the third surface 10S _3.

  The anode terminal 40 is a lead frame formed of a conductive material such as nickel. The anode terminal 40 is drawn from the inside of the resin mold part 30 to the outside. Specifically, one end portion of the anode terminal 40 is connected to the other end portion of the anode lead 20 inside the resin mold portion 30, and the other end portion of the anode terminal 40 is exposed from the resin mold portion 30.

  The cathode terminal 50 is a lead frame formed of a conductive material such as nickel. The cathode terminal 50 is drawn out from the inside of the resin mold part 30. Specifically, one end portion of the cathode terminal 50 is connected to the conductive layer 14 by the conductive adhesive layer 60 inside the resin mold portion 30, and the other end portion of the cathode terminal 50 is exposed from the capacitor element 100. To do.

(Method for manufacturing solid electrolytic capacitor)
Next, a method for manufacturing the solid electrolytic capacitor 100 according to the first embodiment will be described with reference to the drawings.

  First, one end of the anode lead 20 is embedded in a molded body of valve action metal powder or alloy powder containing the valve action metal. The primary particle diameter of the valve action metal powder or the alloy powder containing the valve action metal is, for example, about 0.5 μm, and the secondary particle diameter is, for example, about 100 μm.

  Next, the compact is sintered in a vacuum. Thereby, the anode body 11 which is a porous body having a substantially rectangular parallelepiped outer shape is formed. One end of the anode lead 20 is coupled to the anode body 11.

  Next, a dielectric layer 12 covering the anode body 11 is formed by an anodic oxidation method. Specifically, for example, the anode body 11 is oxidized by applying a constant voltage of about 10 V in an aqueous phosphoric acid solution (about 60 ° C., about 0.01 wt% concentration). The dielectric layer 12 is also formed on the inner wall surfaces of the numerous holes of the anode body 11. The thickness of the dielectric layer 12 is preferably about 10 nm to 500 nm in consideration of the withstand voltage and capacitance of the capacitor element 10, but is not limited thereto.

  Next, an electrolyte layer 13 that covers the dielectric layer 12 is formed by a polymerization method. This polymerization step will be described with reference to FIG.

  First, as shown in FIG. 4A, the anode body 11 on which the dielectric layer 12 is formed is immersed in an oxidizing agent K.

  Next, as shown in FIG. 4B, the anode body 11 on which the dielectric layer 12 is formed is immersed in a solution L containing a predetermined monomer for a predetermined time (for example, about 10 minutes), so that the dielectric A first electrolyte layer 13a covering the layer 12 is formed.

  Next, as shown in FIG. 4C, only the first portion Q1 including the surface from which the anode lead projects out of the anode body 11 on which the first electrolyte layer 13a is formed is pulled up from the solution L.

  Next, as shown in FIG. 4C, the second part Q2 other than the first part Q1 in the anode body on which the first electrolyte layer 13a is formed is kept in the solution L for a predetermined time (for example, about 10 minutes). By immersing, the second electrolyte layer 13b covering the second portion Q2 is formed.

  Next, as shown in FIG. 4D, a part of the second portion Q2 where the second electrolyte layer 13b is formed is pulled up from the solution L, and only the third portion Q3 is left in the solution L for a predetermined time (for example, The third electrolyte layer 13c covering the third portion Q3 is formed by dipping for about 10 minutes).

  Next, as shown in FIG. 4E, the third portion Q3 on which the third electrolyte layer 13c is formed is pulled up from the solution L, dried, washed with water, and dried sequentially. Through the above steps, the electrolyte layer 13 constituted by the first electrolyte layer 13a, the second electrolyte layer 13b, and the third electrolyte layer 13c is formed.

  The steps shown in FIGS. 4A to 4E are repeated a plurality of times (for example, about 7 times), thereby increasing the thickness of the electrolyte layer 13 as the distance from the surface from which the anode lead 20 protrudes. As a result, the outer shape of the electrolyte layer 13 is formed in a quadrangular pyramid shape with the surface from which the anode lead 20 projects as the upper surface. Note that the outer shape of the electrolyte layer 13, that is, the slope of the hypotenuse of the quadrangular pyramid can be adjusted by appropriately changing the immersion time in the solution L, the width for pulling up the anode body 11, and the like.

  Next, after applying the carbon paste so as to cover the surface of the electrolyte layer 13 (excluding the surface from which the anode lead 20 protrudes), the carbon paste is dried to form the carbon layer 141 substantially uniformly. Subsequently, after applying the silver paste so as to cover the surface of the carbon layer 141, the silver paste is dried to form the silver layer 142 substantially uniformly. As a result, a conductive layer 14 is formed on the electrolyte layer 13.

Or by being constituted by the anode body 11 and the dielectric layer 12 and the cathode layer (the electrolyte layer 13 and conductive layer 14), the capacitor element 10 having first surface 10S ₁ and the second surface 10S ₂ is formed. Note that the outer shape of the capacitor element 10 is formed in a quadrangular pyramid shape corresponding to the electrolyte layer 13.

  Next, the anode lead 20 is welded to the anode terminal 40, and the cathode terminal 50 is bonded to the conductive layer 14 using a conductive adhesive.

Next, the resin mold portion 30 is formed by a transfer mold method using a box mold. Specifically, as shown in FIG. 5, by arranging the capacitor element 100 in the mold 200, injecting a resin 30M from the injection port 200a of the mold 200 provided ₂ near the second surface 10S.

The following describes the reason for injecting the resin 30M from the first surface 10S ₁ of the opposite anode lead 20 is protruded. First, in the region of the anode body 11 where the anode lead 20 is bonded (hereinafter referred to as “bonded region”), defects and distortions are likely to occur. The dielectric layer 12 is a self-oxidized film formed by anodizing the anode body 11. Therefore, defects and strains are likely to occur in the dielectric layer 12 formed in the vicinity of the coupling region. Accordingly, the pressure received from the injected resin 30M may cause defects or distortion in the dielectric layer 12 near the bonding region. Therefore, generally, the resin 30M, the anode lead 20 is injected from the opposite side of the first surface 10S ₁ projecting.

Injected resin 30M, after hits the second surface 10S _2, flows toward the third surface 10S ₃ on the first surface 10S ₁ side. Incidentally, the interior of the mold 200 is formed in a substantially rectangular shape, a third surface 10S ₃ is inclined with respect to the inner wall of the mold 200, the distance between the third surface 10S ₃ mold inner wall is gradually increased from the second surface 10S ₂ side to the first surface 10S ₁ side.

(Function and effect)
In the capacitor element 10 according to the present embodiment, the area of the second surface 10S ₂ is larger than the area of the first surface 10S _1, the distance between the third surface 10S ₃ and the opposing surface 30S _T, the second surface 10S ₂ side from toward the first surface 10S ₁ side is formed so as to gradually increase.

Therefore, in the manufacturing method of solid electrolytic capacitor 100, a capacitor element 10 is placed in a mold 200, in the step of pouring the resin 30M from the second surface 10S ₂ side of the capacitor element 10, the third from the injected resin 30M it is possible to reduce the stress on the surface 10S _3. As a result, since damage to the dielectric layer 12 can be suppressed, leakage current inside the capacitor element 10 can be reduced.

Further, in the present embodiment, the thickness of the cathode layer β in the second surface 10S ₂ side of the capacitor element 10 is greater than the thickness alpha ₁ of the cathode layer at the first surface 10S ₁ side.

Thus, the strength of the capacitor element 10 in the second surface 10S _2, in particular, it is possible to improve the protection strength of the dielectric layer 12 in the second surface 10S ₂ side. Therefore, it is possible to the second surface 10S ₂ by impact when the resin 30M is abutted, to prevent the dielectric layer 12 in the second surface 10S ₂ side is damaged.

  In the method for manufacturing the solid electrolytic capacitor 100 according to the present embodiment, the step of forming the cathode layer (the electrolyte layer 13 and the conductive layer 14) covering the dielectric layer 12 includes the anode body 11 on which the dielectric layer 12 is formed. In the solution L, the first electrolyte layer 13a covering the dielectric layer 12 is formed, and only the first portion Q1 of the anode body 11 on which the first electrolyte layer 13a is formed is pulled up from the solution L. And a step of forming the second electrolyte layer 13b in the second portion Q2 other than the first portion Q1.

In this way, by lifting the anode body 11 in a plurality of times, the thickness α ₂ of the electrolyte layer 13 on the second surface 10S ₂ side is larger than the thickness α ₁ of the electrolyte layer 13 on the first surface 10S ₁ side. can do. Therefore, it is possible to accurately control the thickness of the electrolyte layer 13 while suppressing an increase in the number of steps. As a result, simply and accurately, it can be larger than the thickness alpha ₁ of the cathode layer the thickness of the cathode layer β in the second surface 10S ₂ side of the first surface 10S ₁ side.

[Second Embodiment]
Next, a solid electrolytic capacitor 100 according to a second embodiment of the present invention will be described with reference to the drawings. In the following, differences from the first embodiment will be mainly described.

  FIG. 6 is a cross-sectional view schematically showing the structure of the solid electrolytic capacitor 100 according to the second embodiment.

  The anode body 11 is a member having the largest occupied volume ratio in the capacitor element 10 among the constituent elements of the capacitor element 10.

In the present embodiment, the outer shape of the anode body 11 is formed in a quadrangular pyramid shape as shown in FIG. That is, in the capacitor element 10, anode body 11 is tapered from the second surface 10S ₂ side to the first surface 10S ₁ side. Thus, third surface 10S ₃ of the capacitor element 10 is inclined to the first direction, another third provided on the opposite side of the third surface 10S ₃ of the first and one third surface 10S ₃ distance between surface 10S ₃ is a second surface 10S ₂ side gradually decreases toward the first surface 10S ₁ side.

  Such an anode body 11 can be formed by molding a valve metal powder or an alloy powder containing a valve metal using a mold having a quadrangular pyramid internal space.

  In the second embodiment, it should be noted that the thickness of the electrolyte layer 13 is substantially uniform as shown in FIG.

(Function and effect)
The outer shape of the anode body 11 according to the second embodiment is formed in a quadrangular pyramid shape. Thus, by forming the member having the largest occupied volume ratio in the capacitor element 10 in a quadrangular pyramid shape, the outer shape of the capacitor element 10 is formed in a quadrangular pyramid shape.

Therefore, the degree of freedom in designing the capacitor element 10 can be increased. More specifically, the third surface 10S ₃ and a wider range of inclination of the opposing surface 30S _T of the resin mold portion 30 of the capacitor element 10, i.e., the inner wall of the third surface 10S ₃ mold 200 of the capacitor element 10 Can be adjusted over a wide range. As a result, the outer shape of the capacitor element 10 can be easily adjusted to a shape in which stress from the resin 30M is easily reduced.

[Third Embodiment]
Next, a solid electrolytic capacitor 100 according to a third embodiment of the present invention will be described with reference to the drawings. In the following, differences from the first embodiment will be mainly described.

  FIG. 7 is a cross-sectional view schematically showing the structure of the solid electrolytic capacitor 100 according to the third embodiment.

In the present embodiment, the thickness of the conductive layer 14 from the first surface 10S ₁ side is formed so as to gradually increase toward the second surface 10S ₂ side, the outer shape of the conductive layer 14, the quadrangular pyramid trapezoidal Is formed. Specifically, the thickness of the silver layer 142 of the conductive layer 14 is formed so as to gradually increase from the first surface 10S ₁ side to the second surface 10S ₂ side. Therefore, the thickness β of the cathode layer on the second surface 10S ₂ side is larger than the thickness α ₁ of the cathode layer on the first surface 10S ₁ side. By forming the cathode layer in this manner, the outer shape of the capacitor element 10 is formed in a quadrangular pyramid shape.

Such conductive layer 14 can be formed by recoating so as to cover the surface of the carbon layer 141, silver paste on the second surface 10S ₂ side.

  In the third embodiment, it should be noted that the thickness of the electrolyte layer 13 is substantially uniform as shown in FIG.

(Function and effect)
The thickness of the conductive layer 14 according to the third embodiment is formed so as to gradually increase from the first surface 10S ₁ side to the second surface 10S ₂ side. Therefore, the outer shape of the capacitor element 10 can be easily formed into a quadrangular pyramid shape by repeatedly applying the conductive paste.

(Other embodiments)
Although the present invention has been described by using the above-described embodiments, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

For example, in the embodiment described above, the outer shape of the capacitor element 10 is formed in a “square pyramid shape”, but the present invention is not limited to this. The outer shape of the capacitor element 10 according to the present invention, the area of the second surface 10S ₂ is larger than the area of the first surface 10S _1, the distance between the third surface 10S ₃ and the facing surface 30S _T, a second surface 10S it may be a gradually larger shape from a ₂ side to the first surface 10S ₁ side. For example, the external shape of the capacitor element 10 may be a truncated cone or a polygonal trapezoid other than a quadrangular pyramid.

In the above embodiment, the opposing surface 30S T of the third surface 10S ₃ resin mold portion 30 all having the capacitor element 10 _(i.e., the inner wall of the mold 200) is set to be inclined with respect to which It is not limited to. If one third surface 10S ₃ of the capacitor element 10 is long inclined with respect to the opposing surface 30S _T of the resin mold portion 30, it is possible to achieve the effect according to the embodiment.

  Moreover, in the said embodiment, although the anodic oxidation of the anode body 11 was performed using phosphoric acid aqueous solution, this invention is not limited to this, As aqueous solution containing a phosphate ion, ammonium phosphate aqueous solution, sodium phosphate aqueous solution, etc. May be used.

  Although not particularly mentioned in the above embodiment, the resin constituting the resin mold part 30 is antimony oxide, carbana wax, γ-glycidoxypropyltrimethoxysilane and carbon black, waxes, release agents, Various additives such as a colorant, a flame retardant, a coupling agent, and a flexible agent may be added.

 Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  Hereinafter, examples of the solid electrolytic capacitor according to the present invention will be specifically described. However, the present invention is not limited to those shown in the following examples, and may be appropriately changed within the scope not changing the gist thereof. Can be implemented.

  In Examples 1 to 14, the outer shape of the electrolyte layer is formed in a quadrangular pyramid shape, in Examples 15 and 16, the outer shape of the anode body is formed in a quadrangular pyramid shape, and in Example 17, It should be noted that the outer shape of the capacitor layer is formed into a quadrangular pyramid shape by forming the outer shape of the conductive layer into a quadrangular pyramid shape.

Example 1
A solid electrolytic capacitor according to Example 1 was produced as follows (see FIG. 1).

  First, vacuum sintering is performed with an anode lead inserted in a niobium metal powder having a primary particle size of 0.5 μm, whereby a vertical height of 1.00 mm, a first direction width of 4.40 mm, and a second direction depth of 3 A porous sintered body (anode body) having an outer shape of approximately 30 mm was formed.

  Next, the porous sintered body was immersed in a phosphoric acid aqueous solution (60 ° C., about 0.01 wt%), and held for 10 hours in a state where a voltage of about 10 V was applied. Thus, an oxide film (dielectric layer) was formed on the surface and inside of the porous sintered body.

  Next, the anode body on which the dielectric layer was formed was immersed in an oxidizing agent.

  Next, the entire anode body was immersed in a pyrrole monomer solution for 10 minutes. Subsequently, one third of the anode body on the side from which the anode lead protrudes was held for 10 minutes while being drawn from the liquid surface. Subsequently, two-thirds of the anode body on the side where the anode lead protrudes was held for another 10 minutes in a state where it was pulled out from the liquid surface. Subsequently, the whole anode body was pulled up, and the anode body was sequentially dried, washed with water, and dried.

  The polypyrrole film (electrolyte layer) formation and drying steps described above were repeated seven times. The average thickness a of the electrolyte layer on the surface from which the anode lead protrudes was 10 μm, and the average thickness d of the electrolyte layer on the surface opposite to the surface from which the anode lead protrudes was 20 μm. In addition, the measuring method of average thickness a and d is mentioned later.

  Next, a conductive layer was formed by sequentially applying a carbon paste and a silver paste so as to cover the surface of the polypyrrole film. In the silver paste coating step, the anode body on which the carbon layer was formed was immersed in a silver paste bath for 3 minutes with the surface from which the anode lead protruded exposed.

In the quadrangular frustum-shaped capacitor element formed as described above, the area of the first surface was 3.65 mm ² , and the area of the second surface opposite to the first surface was 3.74 mm ² .

  Next, the anode terminal and the anode lead were connected by welding. Subsequently, a cathode terminal was connected to the silver layer using a conductive adhesive.

  Next, the capacitor element was sealed with resin by a transfer molding method. Specifically, the capacitor element was placed in a substantially rectangular parallelepiped mold, and the resin was injected from the second surface side.

(Example 2)
In Example 2, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 13 μm, and the electrolyte layer on the opposite surface The average thickness d was 25 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 2, the area of the first surface was 3.68 mm ² , and the area of the second surface opposite to the first surface was 3.79 mm ² .

(Example 3)
In Example 3, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is set to 15 μm, and the electrolyte layer on the opposite surface is formed. The average thickness d was 30 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to the third embodiment, the area of the first surface is 3.70 mm ^2, the area of the opposite side of the second surface and the first surface was 3.83Mm ^2.

Example 4
In Example 4, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 6 μm, and the electrolyte layer on the opposite surface The average thickness d was 30 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 4, the area of the first surface was 3.61 mm ² , and the area of the second surface opposite to the first surface was 3.83 mm ² .

(Example 5)
In Example 5, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 10 μm, and the electrolyte layer on the opposite surface The average thickness d was 30 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 5, the area of the first surface was 3.65 mm ² , and the area of the second surface opposite to the first surface was 3.83 mm ² .

(Example 6)
In Example 6, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 12 μm, and the electrolyte layer on the opposite surface The average thickness d was 30 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 6, the area of the first surface is 3.67Mm ^2, the area of the opposite side of the second surface and the first surface was 3.83Mm ^2.

(Example 7)
In Example 7, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 20 μm, and the electrolyte layer on the opposite surface The average thickness d was 30 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 7, the area of the first surface was 3.74 mm ² , and the area of the second surface opposite to the first surface was 3.83 mm ² .

(Example 8)
In Example 8, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is set to 25 μm, and the electrolyte layer on the opposite surface is formed. The average thickness d was 30 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 8, the area of the first surface is 3.79Mm ^2, the area of the opposite side of the second surface and the first surface was 3.83Mm ^2.

Example 9
In Example 9, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 8 μm, and the electrolyte layer on the opposite surface The average thickness d was 15 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 9, the area of the first surface was 3.63 mm ² , and the area of the second surface opposite to the first surface was 3.70 mm ² .

(Example 10)
In Example 10, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 6 μm, and the electrolyte layer on the opposite surface The average thickness d was 12 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 10, the area of the first surface is 3.61Mm ^2, the area of the opposite side of the second surface and the first surface was 3.67Mm ^2.

(Example 11)
In Example 11, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 4 μm, and the electrolyte layer on the opposite surface The average thickness d was 15 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 11, the area of the first surface is 3.60 mm ^2, the area of the opposite side of the second surface and the first surface was 3.70 mm ^2.

(Example 12)
In Example 12, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is set to 6 μm, and the electrolyte layer on the opposite surface The average thickness d was 15 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 12, the area of the first surface was 3.61 mm ² , and the area of the second surface opposite to the first surface was 3.70 mm ² .

(Example 13)
In Example 13, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 11 μm, and the electrolyte layer on the opposite surface The average thickness d was 20 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 13, the area of the first surface was 3.66 mm ² , and the area of the second surface opposite to the first surface was 3.74 mm ² .

(Example 14)
In Example 14, in the step of forming the electrolyte layer, by adjusting the immersion time in the pyrrole monomer solution, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes is 13 μm, and the electrolyte layer on the opposite surface The average thickness d was 20 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 14, the area of the first surface was 3.68 mm ² , and the area of the second surface opposite to the first surface was 3.74 mm ² .

(Example 15)
In Example 15, the outer shape of the anode body was formed in a quadrangular pyramid shape. Specifically, the dimension of the surface from which the anode lead protrudes has an average height of 0.97 mm in the vertical direction and an average depth of 3.20 mm in the second direction, and the dimension of the surface opposite to the surface from which the anode lead protrudes. The average height was 1.00 mm and the average depth in the second direction was 3.30 mm. The average width in the first direction was 4.4 mm.

  Further, in the step of forming the electrolyte layer, by immersing the entire anode body in the pyrrole monomer solution for 30 minutes, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes becomes 30 μm, and the average of the electrolyte layer on the opposite surface The thickness d was 30 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 15, the area of the first surface is 3.62Mm ^2, the area of the opposite side of the second surface and the first surface was 3.83Mm ^2.

(Example 16)
In Example 16, the outer shape of the anode body was formed in a quadrangular pyramid shape. Specifically, the dimension of the surface from which the anode lead projects is 0.97 mm in the vertical average height and the average depth in the second direction is 3.20 mm, and the dimension of the surface opposite to the surface from which the anode lead projects is the average height in the vertical direction. The average depth in the second direction was 3.30 mm.

  Further, in the step of forming the electrolyte layer, by immersing the entire anode body in the pyrrole monomer liquid for 10 minutes, the average thickness a of the electrolyte layer on the surface from which the anode lead protrudes becomes 10 μm, and the average of the electrolyte layer on the opposite surface The thickness d was 10 μm.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 16, the area of the first surface was 3.44 mm ² , and the area of the second surface opposite to the first surface was 3.65 mm ² .

(Example 17)
In Example 17, in the step of forming the electrolyte layer, the entire anode body was immersed in the pyrrole monomer solution for 30 minutes, and then the entire anode body was pulled up, and the anode body was sequentially dried, washed with water, and dried. The average thickness a of the electrolyte layer on the surface from which the anode lead protrudes was 30 μm, and the average thickness d of the electrolyte layer on the opposite surface was 30 μm.

  In Example 17, in the silver paste application step, the anode body on which the carbon layer was formed was immersed in a silver paste bath for 2 minutes with the surface from which the anode lead protruded exposed. Subsequently, one third of the anode body on the side from which the anode lead protrudes was held for 30 seconds while being drawn from the bath surface. Subsequently, two-thirds of the anode body on the side from which the anode lead protrudes was held for another 30 seconds in a state of being pulled out from the bath surface.

  Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Example 17, the area of the first surface is 3.70 mm ^2, the area of the opposite side of the second surface and the first surface was 3.83Mm ^2.

(Comparative Example 1)
In Comparative Example 1, in the step of forming the electrolyte layer, the entire anode body was immersed in a pyrrole monomer solution for 30 minutes, and then the entire anode body was pulled up, and the anode body was sequentially dried, washed with water, and dried. Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Comparative Example 1, the area of the first surface and the area of the second surface were both 3.83 mm ² .

(Comparative Example 2)
In Comparative Example 2, in the step of forming the electrolyte layer, the entire anode body was immersed in a pyrrole monomer solution for 10 minutes, and then the entire anode body was pulled up, and the anode body was sequentially dried, washed with water, and dried. Other steps were performed in the same manner as in Example 1.

In the capacitor element according to Comparative Example 2, the area of the first surface and the area of the second surface were both 3.65 mm ² .

(Size measurement)
FIG. 8 is a diagram for explaining a method for measuring the average thickness of the electrolyte layers according to Examples 1 to 17 and Comparative Examples 1 and 2. Specifically, for Examples 1 to 14 and Comparative Examples 1 and 2, as shown in FIG. 8, the average thickness of the electrolyte layer at two measurement positions a and the average of the electrolyte layer at four measurement positions b The thickness, the average thickness of the electrolyte layer at four measurement positions c, and the average thickness of the electrolyte layer at three measurement positions d were measured. The average thickness of the electrolyte layer was measured in a SEM (scanning electron microscope) photograph of a cut surface perpendicular to the second direction so as to include the anode lead. The average thickness of the electrolyte layer at the measurement positions a to d shown in FIG. 8 and the ratio of the area of the second surface to the area of the first surface (“area ratio” in the table) are shown in the table below.

 FIG. 9 is a diagram for explaining a method of measuring the average depth and the average height of the anode bodies according to Examples 15 and 16. Specifically, for Example 15 and Example 16, as shown in FIG. 9, the average depth and average height of the anode body at one measurement position e and the average depth of the anode body at two measurement positions f. The average height, the average depth and average height of the anode body at two measurement positions g, and the average depth and average height of the anode body at one measurement position h were measured. The size of the anode body was measured in an optical micrograph of a cut surface perpendicular to the second direction so as to include the anode lead and an optical micrograph of the cut surface perpendicular to the vertical direction so as to include the anode lead. The measurement results are shown in the table below.

  Moreover, about Example 15 and Example 16, the average thickness of the electrolyte layer in the two measurement positions a and the average thickness of the electrolyte layer in the three measurement positions d were measured (refer FIG. 8). The average thickness of the electrolyte layer was measured in a SEM photograph of a cut surface perpendicular to the second direction so as to include the anode lead. Regarding Example 15 and Example 16, the measurement results of the average thicknesses a and d of the electrolyte layer and the ratio of the area of the second surface to the area of the first surface (“area ratio” in the table) are shown in the table below. .

  FIG. 10 is a diagram for explaining a method for measuring the thickness of the conductive layer according to Example 17. Specifically, for Example 17, as shown in FIG. 10, the average thickness of the conductive layer at two measurement positions i, the average thickness of the conductive layer at four measurement positions j, and the four measurement positions. The average thickness of the conductive layer at k and the average thickness of the conductive layer at three measurement positions 1 were measured. The thickness of the conductive layer was measured in a SEM (scanning electron microscope) photograph of a cut surface perpendicular to the second direction so as to include the anode lead. The average thickness of the electrolyte layer at the measurement positions i to 1 shown in FIG. 10 and the ratio of the area of the second surface to the area of the first surface (“area ratio” in the table) are shown in the table below.

(Measurement of leakage current and equivalent series resistance)
For each of Examples 1 to 17 and Comparative Examples 1 and 2, a leakage current (LC) value 5 minutes after application of voltage 2.5 V and an equivalent series resistance (ESR) value at 100 kHz were measured. The measurement results are shown in the table below. The values shown in the table below are normalized by the values in Example 1.

  As shown in the above table, in Examples 1 to 17, the LC value could be reduced as compared with Comparative Examples 1 and 2. In Examples 1 to 17, the distance between the capacitor element and the inner wall of the mold can be increased toward the first surface side by making the area of the second surface larger than the area of the first surface. This is because. That is, the stress received from the resin injected into the third surface of the capacitor element can be relaxed. On the other hand, in Comparative Examples 1 and 2, the distance between the capacitor element and the inner wall of the mold is uniform. Therefore, the dielectric layer was damaged by the stress received from the resin injected into the third surface, and the leakage current increased.

  It should be noted that the LC values were improved also in Examples 15 and 16. Since the thicknesses of the electrolyte layers and the conductive layers in Examples 15 and 16 are the same as those in Comparative Examples 1 and 2, the distance between the capacitor element and the inner wall of the mold is gradually increased from the second surface side toward the first surface side. It was confirmed that the LC value can be reduced only by increasing the value to a small value.

  Here, it was confirmed that the leakage current is reduced as the area ratio is larger, that is, as the area of the second surface is larger than the area of the first surface. In particular, it was found that the leakage current can be effectively reduced when the area of the second surface is 1.02 times or more the area of the first surface.

  This is because the inclination of the third surface of the capacitor element with respect to the inner wall of the mold can be increased as the area of the second surface is made larger than the area of the first surface. This is because the stress applied to can be reduced.

  Moreover, it was confirmed that the leakage current decreases as the average thickness of the electrolyte layer on the second surface side increases. In particular, it has been found that the leakage current can be effectively reduced when the average thickness of the electrolyte layer on the second surface is 20 μm or more.

  This is because the protective strength of the dielectric layer on the second surface side could be improved by increasing the thickness of the electrolyte layer or conductive layer on the second surface side.

DESCRIPTION OF SYMBOLS 10 ... Capacitor element 11 ... Anode body 12 ... Dielectric layer 13 ... Electrolyte layer 14 ... Conductive layer 141 ... Carbon layer 142 ... Silver layer 20 ... Anode lead 30 ... Resin mold part 30M ... Resin 40 ... Anode terminal 50 ... Cathode terminal 60 ... Conductive adhesive layer 100 ... Solid electrolytic capacitor 200 ... Mold L ... Solution

Claims (6)

A capacitor element including an anode body, a dielectric layer covering the anode body, and a cathode layer covering the dielectric layer;
An anode lead protruding from the capacitor element;
A resin mold part for sealing the capacitor element and the anode lead;
The capacitor element is
A first surface from which the anode lead protrudes;
A second surface provided on the opposite side of the first surface;
A third surface connected to the first surface and the second surface;
The resin mold portion has a facing surface facing the third surface,
The area of the second surface is larger than the area of the first surface,
The solid electrolytic capacitor is characterized in that an interval between the third surface and the facing surface is gradually increased from the second surface side toward the first surface side. 2. The solid electrolytic capacitor according to claim 1, wherein an area of the second surface is 1.02 times or more of an area of the first surface. 3. The solid electrolytic capacitor according to claim 1, wherein a thickness of the cathode layer on the second surface side is larger than a thickness of the cathode layer on the first surface side. The cathode layer is
An electrolyte layer covering the dielectric layer;
A conductive layer covering the electrolyte layer,
4. The solid electrolytic capacitor according to claim 1, wherein a thickness of the electrolyte layer on the second surface side is 20 μm or more. 5. The cathode layer is
An electrolyte layer covering the dielectric layer;
A conductive layer covering the electrolyte layer,
5. The solid electrolytic capacitor according to claim 1, wherein a thickness of the electrolyte layer is gradually increased from the first surface side toward the second surface side. 6. A step of forming an anode body by sintering a molded body of metal powder in which one end of the anode lead is embedded,
Forming a dielectric layer covering the anode body;
Forming a capacitor element by forming a cathode layer covering the dielectric layer; and
The capacitor element is arranged in a mold, and the capacitor element is sealed by pouring resin from a second surface side provided on the opposite side of the capacitor element from the first surface from which the anode lead protrudes. And a step D of forming a resin mold part,
Step C includes
Forming a first electrolyte layer covering the dielectric layer by immersing the anode body on which the dielectric layer is formed in a solution containing a predetermined monomer;
Forming a second electrolyte layer in addition to the portion of the anode body by pulling out only a portion of the anode body on which the first electrolyte layer is formed, including the surface from which the anode lead protrudes, from the solution. Including
In step D,
The distance between the third surface connected to the first surface and the second surface of the capacitor element and the inner wall of the mold gradually increases from the second surface side toward the first surface side. A method for producing a solid electrolytic capacitor.

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