JP2010109266A - Solid-state electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a solid-state electrolytic capacitor element which is capable of reducing a leakage current without increasing ESR. <P>SOLUTION: A solid-state electrolytic capacitor includes an anode 2 made of a valve action metal or its alloy, a dielectric layer 3 formed on a surface of the anode 2, an electrolyte layer formed on the dielectric layer 3, a cathode layer 5 formed on the electrolyte layer, and a resin housing 9 covering a capacitor element 10a comprising the anode 2, the dielectric layer 3, the electrolyte layer, and the cathode layer 5. The electrolyte layer includes a first electrolyte region 4a provided on the dielectric layer, a second electrolyte region 4b provided on the first electrolyte region 4a, so as to be brought into contact with the cathode layer 5, and a third electrolyte region 4c provided so as to be brought into contact with the second electrolyte region or the first electrolyte region in a region wherein the cathode layer is not formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor using a valve action metal or an alloy thereof as an anode.

  Conventionally, a solid electrolytic capacitor in which an anode made of a valve metal is anodized in a phosphoric acid aqueous solution, a metal oxide layer as a dielectric is formed on the anode surface, and an electrolyte layer made of manganese dioxide is formed thereon. It has been known.

  On the other hand, a solid electrolytic capacitor in which ESR (equivalent series resistance) is reduced by using a conductive polymer as an electrolyte layer instead of manganese dioxide is known. However, a solid electrolytic capacitor using a conductive polymer as an electrolyte layer has a problem that leakage current is larger than that of a solid electrolytic capacitor using manganese dioxide as an electrolyte layer.

  In order to solve the above problems, Patent Document 1 proposes further forming a conductive polymer layer containing fine powder made of a hard material on the conductive polymer layer.

  In order to further reduce ESR, Patent Document 2 proposes to provide a conductive polymer intermediate layer having a hardness lower than that of the solid electrolyte layer on the surface of the solid electrolyte layer. Patent Document 1 describes that an oxide film can be protected against external mechanical stress and leakage current can be reduced. However, as a result of investigations by the present inventors, suppression of increase in leakage current has been insufficient.

  Further, in Patent Document 2, by forming the conductive polymer intermediate layer from a soft material, the intermediate layer is brought into close contact with the carbon particles, and the contact area between the carbon particles and the intermediate layer is increased, thereby reducing the contact resistance. It is described that the ESR can be reduced by reducing the ESR. However, as a result of studies by the present inventors, it has been found that the effect of reducing ESR is insufficient.

In addition, in both methods of Patent Documents 1 and 2, there is a problem that the capacitance is reduced during high temperature storage.
JP-A-8-213285 JP 2000-133551 A

  An object of the present invention is to provide a solid electrolytic capacitor capable of reducing leakage current without increasing ESR.

  The solid electrolytic capacitor of the present invention includes an anode formed from a valve metal or an alloy thereof, a dielectric layer formed on the surface of the anode, an electrolyte layer formed on the dielectric layer, and the electrolyte. A solid electrolytic capacitor comprising: a cathode layer formed on a layer; and a resin outer body covering a capacitor element composed of the anode, the dielectric layer, the electrolyte layer, and the cathode layer, wherein the electrolyte A first electrolyte region provided on the dielectric layer; a second electrolyte region provided on the first electrolyte region and in contact with the cathode layer; and the cathode In a region where no layer is formed, the second electrolyte region or a third electrolyte region provided so as to be in contact with the first electrolyte region is characterized.

  In the present invention, for example, the electrolyte layer in the region where the cathode layer is not formed on the electrolyte layer includes a first electrolyte region, a second electrolyte region, and a third electrolyte region sequentially provided on the dielectric layer. In some cases, the first electrolyte region and the third electrolyte region are sequentially provided on the dielectric layer. Thus, in the present invention, the second electrolyte region may not be included in the electrolyte layer in the region where the cathode layer is not formed.

  In the present invention, the electrolyte layer is composed of a first electrolyte region, a second electrolyte region, and a third electrolyte region. Therefore, required characteristics can be imparted to each electrolyte region in each electrolyte region. For example, since the first electrolyte region is provided on the dielectric layer, the first electrolyte region can be formed using a material that can improve adhesion to the dielectric layer. In addition, since the second electrolyte region is provided on the first electrolyte region and in contact with the cathode layer, a material capable of improving the adhesion with the cathode layer can be used. .

  The third electrolyte region is formed in the region of the capacitor element where the cathode layer is not formed, and is provided so as to be in contact with the second electrolyte region or the first electrolyte region. When the resin sheathing is formed so as to cover the capacitor element, the stress applied to the inside of the capacitor element can be reduced due to the presence of the cathode layer in the region of the capacitor element in which the cathode layer is formed. However, in the region of the capacitor element where the cathode layer is not formed, it is easily affected by the stress when forming the resin sheathing body, and the leakage current increases due to this stress. In the present invention, in the region where the cathode layer is not formed, the third electrolyte region is provided so as to cover the second electrolyte region or the first electrolyte region. Stress can be reduced and leakage current can be reduced.

  In the present invention, an anode lead may be provided on the side surface of the anode so as to embed a part thereof. In the present invention, the “side surface” of the anode means the side surface of the outer shape of the anode. As will be described later, the outer shape of the anode is an outer shape that ignores the presence of pores when the anode is formed of a porous body. In general, a cathode layer is not formed on the side surface of the anode in which the anode lead is embedded. Therefore, in such a case, the third electrolyte region is provided on the side surface of the anode.

  When the anode lead is provided so as to be embedded in the side surface of the anode, it becomes more susceptible to stress when the resin sheathing is formed. By providing the third electrolyte region according to the present invention, the stress when forming the resin sheathing in such a case can be further reduced, and the leakage current can be further reduced.

  In the present invention, since the conductive third electrolyte region is provided on the second electrolyte region or the first electrolyte region, the leakage current can be reduced without increasing the ESR. it can.

  In the present invention, it is preferable that the hardness of each of the first electrolyte region and the third electrolyte region is lower than the hardness of the second electrolyte region. By making the hardness of the first electrolyte region lower than the hardness of the second electrolyte region, the first electrolyte region provided on the dielectric layer can be made relatively soft. Adhesion with the first electrolyte region can be enhanced. For this reason, peeling between the dielectric layer and the electrolyte layer is suppressed. In addition, since the stress applied to the dielectric layer through the electrolyte layer can be relaxed, it is possible to suppress a decrease in capacitance and an increase in leakage current during high temperature storage.

  By making the hardness of the third electrolyte region lower than the hardness of the second electrolyte region, it is possible to further reduce the stress applied to the capacitor element when the resin sheathing is formed. For this reason, an increase in leakage current can be further suppressed.

  Moreover, since the adhesiveness between the cathode layer and the second electrolyte region is improved by relatively increasing the hardness of the second electrolyte region, ESR can be further reduced.

  In the present invention, the ratio of the thickness of the third electrolyte region to the thickness of the second electrolyte region (third electrolyte region / second electrolyte region) is preferably in the range of 0.1 to 10. By setting it within such a range, ESR can be further reduced, and leakage current can be further reduced. In addition, it is possible to further reduce the decrease in capacitance during high temperature storage.

  According to the present invention, leakage current can be reduced without increasing ESR.

  Hereinafter, the present invention will be described in more detail based on the embodiments. However, the present invention is not limited to the following embodiments, and can be appropriately modified and implemented without departing from the scope of the invention. Is. In addition, the expression “upper” in the description of the laminated structure in the present specification does not necessarily indicate only the case where it is provided directly on it, but also includes the case where it is provided with another layer interposed therebetween. . For example, in the description that the second layer is formed on the first layer, another layer may be interposed between the first layer and the second layer.

  FIG. 1 is a cross-sectional view showing a solid electrolytic capacitor according to an embodiment of the present invention.

  As shown in FIG. 1, an anode lead 1 is provided on a side surface 2 a of the anode 2 so as to be partially embedded. The anode 2 is formed of a porous body formed by molding a powder made of a valve metal or an alloy thereof so that the outer shape is a substantially rectangular parallelepiped, and then sintering the molded body in a vacuum. . In such a porous body, continuous holes are formed between the sintered powders, and the holes communicate with the outside. In the figure, the pores of the porous body are omitted. Examples of the valve action metal include metals such as niobium, tantalum, titanium, and aluminum. Moreover, as an alloy of valve action metal, the alloy which has these metals as a main component is mentioned.

  FIG. 2 is a perspective view showing the outer shape of the anode 2. As shown in FIG. 2, the anode 2 has a substantially rectangular parallelepiped outer shape. In the figure, the pores of the porous body are omitted. As shown in FIGS. 1 and 2, the anode 2 has a side surface 2a in which the anode lead 1 is embedded, a side surface 2b facing the side surface 2a, and four outer peripheral surfaces 2c sandwiched between the side surfaces 2a and 2b. is doing.

  Referring to FIG. 1, a dielectric layer 3 mainly made of an oxide is formed on the surface of anode 2. The dielectric layer 3 is generally formed by anodizing the surface of the anode 2.

  FIG. 3 is a schematic enlarged cross-sectional view taken along the line AA shown in FIG. As described above, the anode 2 is formed of a porous body, and has fine holes communicating with the outside. As shown in FIG. 3, a dielectric layer 3 is formed on the surface of the anode 2. A dielectric layer 3 is also formed on a part of the surface of the anode lead 1 embedded in the side surface 2 a of the anode 2.

  On the surface of the anode 2, as shown in FIG. 3, a first electrolyte region 4 a is formed so as to be in contact with the dielectric layer 3.

  Referring to FIG. 1, a second electrolyte region 4b is formed on first electrolyte region 4a formed on dielectric layer 3 on outer peripheral surface 2c and side surfaces 2a and 2b of anode 2. Yes. Further, a third electrolyte region 4c is formed on the second electrolyte region 4b on the side surface 2a of the anode.

  A carbon layer 5a is formed on the second electrolyte region 4b on the first electrolyte region 4a formed on the dielectric layer 3 on the outer peripheral surface 2c and the side surface 2b of the anode 2. A silver layer 5b is formed on the carbon layer 5a. The cathode layer 5 is composed of the carbon layer 5a and the silver layer 5b. At this time, as shown in FIG. 1, the cathode layer 5 is not formed on the third electrolyte region 4c. In the figure, the end of the third electrolyte region 4c is in contact with the cathode layer 5. However, the present invention is not limited to this, and there is a gap between the cathode layer 5 and the end of the third electrolyte region 4c. May be.

  FIG. 4 is a schematic enlarged cross-sectional view taken along the line BB shown in FIG. As shown in FIG. 4, the outer peripheral surface 2 c, which is one surface forming the outer shape of the anode 2, is composed of sintered particles arranged on the outer side of the anode 2. A first electrolyte region 4 a and a second electrolyte region 4 b are sequentially formed on the dielectric layer 3 formed on the outer peripheral surface 2 c toward the cathode layer 5. Further, as shown in FIG. 1, a first electrolyte region 4a and a second electrolyte region 4b are sequentially formed on the side surface 2b as well as on the outer peripheral surface 2c. 3 to 5, the hole of the anode 2 is filled with the first electrolyte region 4a. However, the present invention is not limited to this, and the hole of the anode 2 is not sufficiently filled with the first electrolyte region 4a. In this case, the second electrolyte region 4b may be formed in the gap.

  FIG. 5 is a schematic enlarged cross-sectional view taken along the line C-C shown in FIG. As shown in FIG. 5, the side surface 2 a, which is one surface forming the outer shape of the anode 2, is composed of sintered particles disposed on the outside of the anode 2. As shown in FIG. 5, a first electrolyte region 4a and a second electrolyte region 4b are formed on the dielectric layer 3 on the side surface 2a of the anode 2, and the second electrolyte region 4b is overlaid. In addition, a third electrolyte region 4c is formed. A resin sheathing body 9 is formed on the third electrolyte region 4c. Accordingly, the first electrolyte region 4a, the second electrolyte region 4b, and the third electrolyte region 4c are sequentially formed on the dielectric layer 3 formed on the side surface 2a toward the resin sheathing body 9. Has been. In the present embodiment, the third electrolyte region 4c is formed on the second electrolyte region 4b. However, the first electrolyte region is formed on the dielectric layer formed on the side surface 2a. Only 4a may be formed, and the third electrolyte region 4c may be formed on the first electrolyte region 4a. In this case, the first electrolyte region 4a and the third electrolyte region 4c are sequentially formed on the dielectric layer 3 formed on the side surface 2a toward the resin sheathing body 9.

  In the present embodiment, the electrolyte layer includes a first electrolyte region 4a, a second electrolyte region 4b, and a third electrolyte region 4c.

  The capacitor element 10 a includes an anode 2, an anode lead 1, a dielectric layer 3, electrolyte layers 4 a, 4 b and 4 c, and a cathode layer 5. As shown in FIG. 1, a cathode terminal 7 is connected to the cathode layer 5 of the capacitor element 10 a via a conductive adhesive layer 6. An anode terminal 8 is connected to the anode lead 1 by welding or the like. A resin sheathing body 9 is formed so as to cover the entire capacitor element 10a to which the cathode terminal 7 and the anode terminal 8 are connected. The resin sheathing body 9 is formed so that the ends of the cathode terminal 7 and the anode terminal 8 are exposed.

  The solid electrolytic capacitor 10 of this embodiment is configured as described above.

  In the present embodiment, since the third electrolyte region 4c is provided on the side surface 2a of the anode 2, the stress applied to the capacitor element 10a when the resin sheathing body 9 is formed so as to cover the capacitor element 10a. Can be reduced. The side surface 2a of the anode 2 provided so as to be embedded with the anode lead 1 is particularly susceptible to stress when the resin sheathing 9 is formed, and leakage current increases due to this stress. By providing the third electrolyte region 4c so as to cover the side surface 2a of the anode 2, the stress when forming the resin sheathing body 9 can be reduced, and the leakage current can be reduced.

  Moreover, in the part where the cathode layer 5 on the side surface 2a is not formed, the stress at the time of forming the resin sheathing body 9 is likely to be applied to the side surface 2a, and this stress causes a defect in the dielectric layer and causes leakage current. Increase. In the present embodiment, since the third electrolyte region 4c is formed at a location where the cathode layer 5 is not formed on the side surface 2a, the stress when forming the resin sheathing body 9 can be reduced, and the leakage current can be reduced. can do. In the present embodiment, the region where the cathode layer 5 is not formed on the electrolyte layer is covered with the third electrolyte region 4c, but to the extent that the stress when forming the resin sheathing body 9 can be reduced. It only has to be covered.

  The first electrolyte region 4a, the second electrolyte region 4b, and the third electrolyte region 4c can be formed from a conductive polymer such as polythiophene or polypyrrole, for example. The first electrolyte region 4a can be formed, for example, by impregnating the anode 2 with a monomer solution for forming a conductive polymer and then polymerizing the anode 2. In the second electrolyte region 4b, the anode 2 on which the first electrolyte region 4a is formed is immersed in a monomer solution of a conductive polymer, and the monomer solution is placed on the outer peripheral surface 2c and the surfaces 2a and 2b of the anode 2. It can form by making it superpose | polymerize after making it adhere. Alternatively, the monomer solution may be applied to and adhered to the outer peripheral surface 2c and the side surfaces 2a and 2b of the anode 2 and then polymerized to form the second electrolyte region 4b.

  The third electrolyte region 4c can be formed by applying a polymer solution of a conductive polymer on the side surface 2a of the anode 2 and then polymerizing it. When the second electrolyte region 4b is not formed on the side surface 2a of the anode 2, the third electrolyte region 4c is formed on the first electrolyte region 4a on the side surface 2a of the anode 2. When the second electrolyte region 4b is formed on the side surface 2a of the anode 2, the third electrolyte region 4c is formed on the second electrolyte region 4b.

  The carbon layer 5a can be formed by applying a carbon paste on the second electrolyte region 4b on the outer peripheral surface 2c of the anode 2 and drying it.

  The silver layer 5b can be formed by applying a silver paste on the carbon layer 5a and drying it.

  The conductive adhesive layer 6 can be formed using a conductive paste.

  The resin sheathing body 9 can be formed by molding a resin such as an epoxy resin after connecting the cathode terminal 7 and the anode terminal 8 to the capacitor element 10a.

  In the present embodiment, the electrolyte layer provided for electrically connecting the dielectric layer 3 and the cathode layer 5 is formed from the first electrolyte region, the second electrolyte region, and the third electrolyte region. It is configured. Therefore, required characteristics can be imparted to each electrolyte region in each electrolyte region.

  When the first electrolyte region, the second electrolyte region, and the third electrolyte region are formed from a conductive polymer, the type, polymerization method, and additive of the conductive polymer that forms each electrolyte region are changed. be able to. For example, an additive made of an organic material such as a resin can be added to the conductive polymer to change the hardness of the conductive polymer layer.

  In the present invention, it is preferable that the hardness of each of the first electrolyte region 4a and the third electrolyte region 4c is lower than the hardness of the second electrolyte region 4b. As a method of making the hardness of each of the first electrolyte region 4a and the third electrolyte region 4c lower than the hardness of the second electrolyte region 4b, the first electrolyte region 4a and the third electrolyte region 4c are formed. For example, a method of adding a resin having elasticity as compared with a conductive polymer such as a silicone resin, for example, an elastomer resin, as an additive to the conductive polymer.

  By making the hardness of the first electrolyte region 4a lower than the hardness of the second electrolyte region 4b, the first electrolyte region 4a in contact with the dielectric layer 3 can be made relatively soft, and the dielectric layer 3 and the first electrolyte region 4a can be improved. For this reason, peeling between the dielectric layer 3 and the electrolyte layer can be suppressed. Furthermore, the stress applied to the dielectric layer 3 through the electrolyte layer can be relieved, and a decrease in capacitance and an increase in leakage current during high temperature storage can be suppressed.

  Further, by making the hardness of the third electrolyte region 4c lower than the hardness of the second electrolyte region 4b, it is possible to reduce the stress applied to the capacitor element 10a when the resin sheathing body 9 is formed. An increase in current can be further suppressed.

  By relatively increasing the hardness of the second electrolyte region 4b, the adhesion between the cathode layer 5 and the second electrolyte region 4b can be improved, and the ESR can be further reduced.

  In the present embodiment, the ratio of the thickness of the third electrolyte region 4c and the thickness of the second electrolyte region 4b (third electrolyte region / second electrolyte region) is in the range of 0.1 to 10. It is preferable. By setting it within such a range, ESR can be further reduced, and leakage current can be further reduced. In addition, it is possible to further reduce the decrease in capacitance during high temperature storage.

  FIG. 2 is a perspective view showing the outer shape of the anode 2 used in this embodiment as described above. As shown in FIG. 2, the anode 2 has a substantially rectangular parallelepiped outer shape. Among the X direction, Y direction, and Z direction, which are dimensional directions of the rectangular parallelepiped, the Y direction is the direction with the shortest dimension. In the present invention, the shortest direction among the dimension directions of the rectangular parallelepiped is defined as the thickness direction.

FIG. 6 is a cross-sectional view of the capacitor element 10a cut along the XY plane so that the anode lead is included. FIG. 6 corresponds to the capacitor element 10a in the cross section shown in FIG. The thickness t ₂ of the third electrolyte region 4 c is a distance d corresponding to ¼ of the distance D between the outer peripheral surface 2 c of the anode 2 and the outer peripheral surface 2 c facing it in the Y direction which is the thickness direction of the anode 2. The thickness at a position 2 d approaching the center of the anode 2 from the outer peripheral surface 2 c of the anode 2.

The thickness of the second electrolyte region 4b, when the second electrolyte region 4b on the side 2a of the anode 2 is formed, the thickness t ₁ of the second electrolyte region 4b on the side 2a of the anode 2 To do. The thickness t _{1 of} the second electrolyte region 4 b is also a value measured at the position 2 d on the side surface 2 a of the anode 2.

If on the side 2a of the anode 2 second electrolyte region 4b is not formed, the second electrolyte region 4b thickness t ₃ of which are formed on the side surface 2b opposite to the side surface 2a of the anode 2 . The thickness t _{3 is} also a thickness measured at a position 2 d ′ corresponding to the position 2 d on the side surface 2 a of the anode 2.

  The ratio of the thickness of each electrolyte region can be appropriately adjusted by changing the polymerization time when forming the conductive polymer.

  In the present embodiment, as described above, the anode 2 having a substantially rectangular parallelepiped shape is used. However, when the anode 2 has another shape, the outer peripheral surface 2c of the anode 2 is shown in FIG. As shown, the normal line DD of the outer peripheral surface 2c is assumed, and the direction of the shortest distance among the distances between the contacts where the normal line DD contacts the outer peripheral surface 2c facing each other is the thickness direction. Can do. With reference to this thickness direction, the thickness of the second electrolyte region 4b and the thickness of the third electrolyte region 4c can be measured.

  Hereinafter, the present invention will be described based on more specific examples, but the present invention is not limited to the following examples.

(Experiment 1)
[Example 1]
The solid electrolytic capacitor shown in FIG. 1 was produced as follows.

(Step 1)
A niobium metal powder having a primary average particle diameter of about 0.5 μm is molded by embedding a part of the anode lead, and this molded body is sintered in a vacuum, whereby X shown in FIG. An anode 2 made of a niobium porous sintered body having a dimension in the direction of about 4.4 mm, a dimension in the Z direction of about 3.3 mm, and a dimension in the Y direction of about 1.0 mm was formed.

  The anode lead 1 was a niobium lead (diameter 0.5 mm).

(Step 2)
This anode was anodized at a constant voltage of about 10 V for about 10 hours in an about 0.01 wt% phosphoric acid aqueous solution maintained at about 60 ° C., thereby forming a dielectric layer 3 on the surface of the anode 2. .

(Step 3)
After the anode 2 having the dielectric layer 3 formed on the surface is immersed in an oxidizing agent solution, a pyrrole monomer containing 1.0% by weight of a silicone resin (“trade name: Tospearl 120”, manufactured by GE Toshiba Silicones) It was immersed in the solution. As a result, a conductive polymer layer made of polypyrrole containing a silicone resin was formed on the surface of the dielectric layer 3 by a chemical polymerization method. This conductive polymer layer becomes the first electrolyte region 4a.

<Measurement of hardness of first electrolyte region 4a>
Similarly to the first electrolyte region 4a, a conductive polymer is polymerized using a pyrrole monomer solution containing a silicone resin, and this is pulverized and molded to form a plate having a thickness of 8 mm. A molded body was prepared. A test piece having a width and length of 30 mm was cut out from this molded body, and the penetration depth (h) when a predetermined load was applied to the indenter using a desktop durometer (type D) according to JIS-K7215. Thus, the Shore hardness was measured using a formula for calculating hardness. As a result, the Shore hardness of the first electrolyte region 4a was 50.

(Step 4)
After forming the first electrolyte region 4a, the anode 2 is immersed in a pyrrole monomer solution, and in this state, a conductive polymer made of polypyrrole is polymerized by an electrolytic polymerization method to form the second electrolyte region 4b. Formed. The pyrrole monomer solution used here is a solution that does not contain a silicone resin. Using this solution, the Shore hardness of the conductive polymer forming the second electrolyte region was measured in the same manner as described above. The Shore hardness of the second electrolyte region 4b was 95.

  The second electrolyte region 4b is formed on the side surface 2a of the anode 2 as shown in FIG. When the anode 2 is immersed, the second electrolyte region 4b is formed on the side surface 2a of the anode 2 by immersing the side surface 2a of the anode 2 below the liquid level of the pyrrole monomer solution. Can do.

(Step 5)
Next, an oxidant solution is applied onto the second electrolyte region 4b on the side surface 2a of the anode 2, and then pyrrole containing 1.2% by weight of the same silicone resin as used in Step 3 is used. A monomer solution was applied, and a third electrolyte region 4c was formed on the second electrolyte region 4b on the side surface 2a of the anode 2 by chemical polymerization.

  In the same manner as described above, the Shore hardness of the third electrolyte region 4c was measured and found to be 40.

Incidentally, the thickness t ₂ of the third electrolyte part 4c which is defined as described above, the ratio between the thickness t ₁ of the second electrolyte region 4b was 1.0. The thickness t ₂ of the second electrolyte region 4b thickness t ₁ and the third electrolyte region 4c is a scanning electron microscope (SEM), it can be measured by observing the cross section of the element.

  The method for forming the third electrolyte region 4c is not limited to the above method. For example, after a paste is applied to the surface where the third electrolyte region 4c is not desired (for example, the outer peripheral surface other than the side surface 2a of the anode 2) to form a mask, it is immersed in an oxidant solution, and then a silicone resin is placed. By immersing in a fixed amount of pyrrole monomer solution, a conductive polymer layer made of silicone resin-containing polypyrrole can be formed by a chemical polymerization method. In this case, the resist can then be removed by ultrasonic cleaning in acetone.

  In the present invention, the third electrolyte region 4 c may be formed in a portion other than the side surface 2 a of the anode 2. For example, the outer peripheral surface 2c of the anode 2 may be formed around the side surface 2a.

(Step 6)
Next, a carbon paste is applied and dried so as to cover the second electrolyte region 4b on the outer peripheral surface 2c and the side surface 2b, thereby forming the carbon layer 5a. Next, a silver paste is applied on the carbon layer 5a and then dried to form the silver layer 5b.

  Next, the cathode terminal 7 is connected to the silver layer 5b through the conductive adhesive layer 6, and the anode terminal 8 is welded to the anode lead 1, thereby electrically connecting each terminal to the capacitor element 10a. did.

(Step 7)
Next, a resin outer package is formed so as to cover the capacitor element 10a by a transfer molding method using a resin composition based on an epoxy resin so that the end of the cathode terminal 7 and the end of the anode terminal 8 are exposed. 9 was formed.

  As described above, the solid electrolytic capacitor 10 of this example was produced.

[Example 2]
FIG. 7 is a cross-sectional view showing the solid electrolytic capacitor of this example. As shown in FIG. 7, in this embodiment, the second electrolyte region 4b is not formed on the side surface 2a of the anode 2, and the first electrolyte region 4a on the side surface 2a of the anode 2 is not formed. A third electrolyte region 4c is formed on the top.

  The solid electrolytic capacitor of this example is manufactured so that the liquid level of the monomer solution does not exceed the side surface 2a of the anode 2 when the anode 2 is immersed in the pyrrole monomer solution in Step 4 of Example 1 above. did.

[Comparative Example 1]
FIG. 8 is a cross-sectional view showing a solid electrolytic capacitor of Comparative Example 1. In the comparative example 1, the second electrolyte region 4b is not formed without performing the step 4 of the above-mentioned example 1. Other than that was carried out similarly to the said Example, and produced the solid electrolytic capacitor.

[Comparative Example 2]
FIG. 9 is a cross-sectional view showing a solid electrolytic capacitor of Comparative Example 2. In Comparative Example 2, the third electrolyte region 4c is not formed without performing Step 5 of Example 1 above. Other than that was carried out similarly to the said Example 1, and produced the solid electrolytic capacitor.

[Comparative Example 3]
FIG. 10 is a cross-sectional view showing a solid electrolytic capacitor of Comparative Example 3. In Comparative Example 3, the third electrolyte region 4c is not formed on the second electrolyte region 4b of the side surface 2a of the anode 2 in Step 1 of Example 1, but other than the side surface 2a of the anode 2. A third electrolyte region 4c was formed on the second electrolyte region 4b on the outer peripheral surface 2c. Other than that was carried out similarly to the said Example 1, and produced the solid electrolytic capacitor.

[Comparative Example 4]
In Step 5 of Example 1 above, instead of forming the third electrolyte region 4c, an insulating silicone resin (trade name “TSE3250”, manufactured by GE Toshiba Silicones) was used to form the silicone resin layer. 3 is formed at the location where the electrolyte region 4c is formed. The ratio of the thickness t ₁ and the thickness t ₂ of the silicone resin layer in this case the second electrolyte region 4b was 1.0 in the same manner as in Example 1.

<Measurement of leakage current>
About each solid electrolytic capacitor of Examples 1-2 and Comparative Examples 1-4, the voltage of 2.5V was applied and the electric current after 5 minutes was measured as a leakage current. The measurement results are shown in Table 1.

<Measurement of ESR>
About each solid electrolytic capacitor of Examples 1-2 and Comparative Examples 1-4, ESR in 100 kHz was measured. The measurement results are shown in Table 1.

<Evaluation of capacity maintenance rate in long-term reliability test>
About each solid electrolytic capacitor of Examples 1-2 and Comparative Examples 1-4, the voltage of 2.5V was applied in 105 degreeC atmosphere, and the high temperature load test (reliability test) was done. The high temperature load test was conducted for 1000 hours. The capacitance at a frequency of 120 Hz before and after the test was measured with an LCR meter, and the capacity retention rate was calculated by the following equation. Note that the closer this value is to 100, the smaller the deterioration of the capacitance in the reliability test.

Capacity retention ratio = (capacitance after reliability test / capacitance before reliability test) × 100
The measurement results are shown in Table 1.

  As shown in Table 1, in the solid electrolytic capacitors of Examples 1 and 2 according to the present invention, the leakage current and ESR are low, and the capacity retention rate is high.

  In Comparative Example 1 in which the second electrolyte region 4b is not formed, the leakage current and ESR are high, and the capacity retention rate is low. In particular, the leakage current is remarkably increased. This is because by providing the second electrolyte region 4b, the adhesion between the carbon layer 5a and the silver layer 5b formed thereon is improved, the stress applied to the anode 2 can be reduced, and the leakage current is reduced. It seems to be due to what can be done.

  In Comparative Example 2 in which the third electrolyte region 4c is not formed, the leakage current is particularly large. This is because, when the resin sheathing body 9 is molded, by providing the third electrolyte region on the side surface 2a of the anode 2 where stress is particularly likely to be applied, the stress can be relieved and an increase in leakage current can be suppressed. It seems to be due to.

  In Comparative Example 3 in which the third electrolyte region 4c is provided not on the side surface 2a of the anode 2 but in other portions, the leakage current is remarkably increased. This also shows that by providing the third electrolyte region 4c, it is possible to reduce the stress when molding the resin, and to suppress an increase in leakage current.

  In Comparative Example 4 in which a silicone resin layer is provided instead of the third electrolyte region 4c, an increase in leakage current is suppressed as compared with Comparative Example 2. This seems to be because the stress during resin molding could be reduced by providing a silicone resin layer on the side surface 2a of the anode 2. However, ESR is higher than those in Examples 1 and 2, and the silicone resin layer does not have conductivity, so it seems that ESR cannot be sufficiently reduced.

  As described above, in the solid electrolytic capacitors of Examples 1 and 2 according to the present invention, both the leakage current and the ESR are low, and a high capacity retention rate is obtained. This is because the first electrolyte region 4a mainly suppresses separation between the dielectric layer 3 and the electrolyte layer in the long-term reliability test, and the second electrolyte region 4b mainly reduces the interface resistance with the cathode layer 5. This is probably because the third electrolyte region 4c can mainly reduce the stress on the capacitor element when the resin sheathing is formed.

(Experiment 2)
Example 3
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that in Step 5 of Example 1, a pyrrole monomer solution containing 1.0% by weight of a silicone resin was used.

  The Shore hardness of the third electrolyte region 4c produced in this example was 50.

Example 4
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that in Step 5 of Example 1 above, a pyrrole monomer solution containing 0.8% by weight of a silicone resin was used.

  The Shore hardness of the third electrolyte region 4c produced in this example was 60.

Example 5
In Step 3 of Example 1, the first electrolyte region 4a is formed using a pyrrole monomer solution containing no silicone resin. In Step 4, the first electrolyte region 4a is immersed in a pyrrole monomer solution containing 1.0% by weight of a silicone resin. A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the second electrolyte region 4b was formed by polymerization by electrolytic polymerization.

  The Shore hardness of the first electrolyte region 4a and the second electrolyte region 4b formed in the present example was 80 and 30, respectively.

Example 6
In Step 3 of Example 1, the first electrolyte region 4a was formed using a pyrrole monomer solution containing 1.2% by weight of a silicone resin. In Step 4, 1.0% by weight of the silicone resin was contained. The second electrolyte region 4b was formed by being immersed in a pyrrole monomer solution and polymerized by an electrolytic polymerization method. In step 5, the third electrolyte region 4c was formed using a pyrrole monomer solution not containing a silicone resin. A solid electrolytic capacitor was produced in the same manner as in Example 1 except for the above.

  The shore hardness of each of the first electrolyte region 4a, the second electrolyte region 4b, and the third electrolyte region 4c formed in this example was 40, 30, and 80.

<Evaluation of characteristics of solid electrolytic capacitors>
In the same manner as described above, the leakage current, ESR, and capacity retention rate of each solid electrolytic capacitor were measured, and the results are shown in Table 2.

  As shown in Table 2, in Examples 1 and 3-4, the Shore hardness of the first electrolyte region 4a and the Shore hardness of the third electrolyte region 4c are lower than the Shore hardness of the second electrolyte region 4b. The leakage current and ESR are particularly low, and the capacity retention rate is also high. This is because the first electrolyte region 4a is softer than the second electrolyte region 4b, and the adhesion between the dielectric layer 3 and the electrolyte layer is further improved, so that the dielectric layer 3 and the electrolyte layer are separated from each other. It is considered that the stress applied to the dielectric layer 3 through the electrolyte layer can be relieved and the decrease in capacitance and the increase in leakage current during high temperature storage can be further effectively suppressed.

  Further, since the third electrolyte region 4c is softer than the second electrolyte region 4b, the stress applied to the capacitor element 10a when the resin sheathing body 9 is formed can be reduced, and the increase in leakage current is more effective. It is thought that it can be suppressed.

  Moreover, since the adhesiveness between the cathode layer 5 and the electrolyte layer is improved by making the second electrolyte region 4b relatively hard, it is considered that ESR can be further reduced.

  In Examples 5 and 6, the hardness of the first electrolyte region 4a and the hardness of the third electrolyte region 4c are higher than the hardness of the second electrolyte region 4b. For this reason, compared with Example 1 and 3-4, there are few effects of reduction of leakage current and ESR, and the capacity maintenance rate is also low. However, compared with Comparative Examples 1 to 4 shown in Table 1, the capacity retention rate is high, the leakage current and the ESR are low, and excellent effects are obtained even in long-term reliability.

(Experiment 3)
[Examples 7 to 19]
As shown in Table 3, the thickness _{t 2} of the third electrolyte region 4c, the ratio between the thickness _{t 1} of the second electrolyte region 4b, 0.05,0.08,0.10,0.20, Solid electrolysis was performed in the same manner as in the above example except that 0.50, 0.80, 1.50, 2.00, 3.00, 5.00, 10.00, 11.00, and 14.00. A capacitor was produced. The thickness t ₁ of the second electrolyte region 4b was controlled by adjusting the position of the side surface 2a of the anode 2 immersed in the pyrrole monomer solution and the polymerization time in Step 4 of Example 1 above. The thickness t ₂ of the third electrolyte region 4c is at the time of applying on the second electrolyte region 4b on the side 2a of the anode 2, it was controlled by adjusting the thickness of the coating film thickness and the polymerization time . When application thickness became thick, application was repeated several times.

  In the same manner as described above, the leakage current, ESR, and capacity retention rate of each solid electrolytic capacitor were measured, and the measurement results are shown in Table 3.

As is apparent from the results shown in Table 3, the thickness t ₂ of the third electrolyte region 4c, the ratio of the thickness t ₁ of the second electrolyte region 4b (third electrolyte region / second electrolyte region) In Examples 9 to 17 in the range of 0.1 to 10, both the leakage current and ESR are low, and it can be seen that the capacity retention rate after the long-term reliability test is particularly high.

Further, from the results shown in Table 3, the thickness _{t 2} of the third electrolyte region 4c, the ratio of the thickness _{t 1} of the second electrolyte region 4b is, in the case in the range of 0.5 to 2.0, It can be seen that the leakage current and ESR can be reduced more effectively and the capacity retention rate can be increased.

Sectional drawing which shows the solid electrolytic capacitor of one Embodiment (Example 1) according to this invention. The perspective view which shows the anode in embodiment shown in FIG. Sectional drawing which shows between AA shown in FIG. Sectional drawing which shows between BB shown in FIG. Sectional drawing which shows between CC shown in FIG. Sectional drawing which shows the capacitor | condenser element in embodiment shown in FIG. Sectional drawing which shows the solid electrolytic capacitor of other embodiment (Example 2) according to this invention. Sectional drawing which shows the solid electrolytic capacitor of the comparative example 1. FIG. Sectional drawing which shows the solid electrolytic capacitor of the comparative example 2. Sectional drawing which shows the solid electrolytic capacitor of the comparative example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Anode lead 2 ... Anode 2a ... Side surface of anode 2b ... Side surface opposite to side surface of anode 2c ... Outer peripheral surface of anode 3 ... Dielectric layer 4a ... First electrolyte region 4b ... Second electrolyte region 4c ... Third 5 ... cathode layer 5a ... carbon layer 5b ... silver layer 6 ... conductive adhesive layer 7 ... cathode terminal 8 ... anode terminal 9 ... resin sheathing body 10 ... solid electrolytic capacitor 10a ... capacitor element

Claims (4)

An anode formed from a valve metal or an alloy thereof;
A dielectric layer formed on the surface of the anode;
An electrolyte layer formed on the dielectric layer;
A cathode layer formed on the electrolyte layer;
A solid electrolytic capacitor comprising a resin sheath covering a capacitor element composed of the anode, the dielectric layer, the electrolyte layer, and the cathode layer;
A first electrolyte region provided on the dielectric layer; a second electrolyte region provided on the first electrolyte region and in contact with the cathode layer; A solid electrolytic capacitor comprising a third electrolyte region provided in contact with the second electrolyte region or the first electrolyte region in a region where the cathode layer is not formed.   The region where the cathode layer is not formed is a side surface of the anode, and an anode lead is provided on the side surface of the anode so as to embed a part thereof. Solid electrolytic capacitor.   3. The solid electrolytic capacitor according to claim 1, wherein the hardness of each of the first electrolyte region and the third electrolyte region is lower than the hardness of the second electrolyte region. 4.   The ratio of the thickness of the third electrolyte region to the thickness of the second electrolyte region (third electrolyte region / second electrolyte region) is in the range of 0.1 to 10. The solid electrolytic capacitor according to any one of 1 to 3.

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