JP2001267189A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an expansion of a case or a sealing member due to a solder heat test or the like and to suppress an increase in a leakage current in a solid electrolytic capacitor obtained, by impregnating a capacitor element having an anode member formed with a dielectric film with a conductive polymer as a cathode electrolyte, disposing and sealing the element in a sheathing member. SOLUTION: An outside of the capacitor element impregnated with the conductive polymer is sequentially covered with a first resin layer and a second resin layer. In this case, as a material of the first layer, a material having higher flexibility than that of the second layer is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid state in which a capacitor having an anode member on which a dielectric film is formed is impregnated with a conductive polymer as a cathode electrolyte, and the capacitor element is arranged in an exterior member and sealed. It relates to an electrolytic capacitor.

[0002]

2. Description of the Related Art As a solid electrolytic capacitor, a capacitor element having an anode member on which a dielectric film is formed is impregnated with a conductive polymer as a cathode electrolyte, and the capacitor element is arranged in an exterior member and sealed. The following configuration is known.

In this solid electrolytic capacitor, a capacitor element 11 formed by winding an anode foil having a dielectric film formed thereon and an opposite cathode foil via a separator is impregnated with a conductive polymer as a cathode electrolyte. After being housed in a bottomed cylindrical outer case 15 and sealed with a sealing rubber 16,
A seat plate 18 for surface mounting is mounted. Symbol 17
Reference numerals a and 17b denote anode and cathode extraction terminals.

[0004] Japanese Patent Application Laid-Open No. 11-204377 discloses that in such a solid electrolytic capacitor, a conductive polymer is used in order to suppress gas generation from the conductive polymer by a soldering heat test or the like and to prevent swelling of a case or a sealing member. A technique of coating the outside of an impregnated capacitor element with an epoxy resin or the like is disclosed.

[0005]

However, in a solid electrolytic capacitor in which an epoxy resin layer is formed outside a capacitor element impregnated with a conductive polymer according to the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 11-204377, the solder heat resistance is reduced. When a test is performed, mechanical stress is applied to the capacitor element due to the difference in the coefficient of thermal expansion between the constituent members of the capacitor element containing a conductive polymer and the epoxy resin layer, and the dielectric film is damaged, resulting in a leakage current. It could increase significantly.

The present invention solves the above-mentioned problems in a solid electrolytic capacitor using a conductive polymer as a cathode electrolyte.

[0007]

A solid electrolytic capacitor according to the present invention comprises a capacitor element having an anode member on which a dielectric film is formed, impregnated with a conductive polymer as a cathode electrolyte, and placing the capacitor element in an exterior member. In the solid electrolytic capacitor arranged and sealed, a first resin layer and a second resin layer are sequentially formed outside the capacitor element impregnated with the conductive polymer, and the first resin layer is
It is characterized by being made of a material that is more flexible than the second resin layer.

According to the configuration of the present invention, since the first resin layer made of a highly flexible material is provided in close contact with the outside of the capacitor element, mechanical stress is hardly transmitted to the inside of the capacitor element. As a result, the dielectric film in the capacitor element is hardly damaged.

Further, by forming the first resin layer from such a material, the range of material selection for the second resin layer formed for ensuring airtightness and the like is expanded.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid electrolytic capacitor according to one embodiment of the present invention has a conductive polymer layer formed in a wound type capacitor element 11 as shown in FIG. Is covered with a highly flexible first resin layer 21, and the outside thereof is further covered with a highly airtight second resin layer 22. A sealing member 16 made of stainless steel is mounted and sealed, and a seat plate 18 for surface mounting is mounted.

The wound type capacitor element is obtained by using an aluminum foil subjected to an etching treatment and a chemical conversion treatment as an anode and winding it into a cylindrical shape with a separator paper interposed between the aluminum foil and an opposite cathode foil.

In order to form a conductive polymer layer in a wound type capacitor element, first, 3,4-ethylenedioxythiophene as a monomer which becomes a conductive polymer by oxidative polymerization, and paratoluene as an oxidizing agent A chemical polymerization solution containing iron (III) sulfonate and n-butyl alcohol as a diluent is prepared. Then, after immersing the capacitor element in the chemical polymerization solution, a heat treatment of about 200 ° C. for several minutes is performed, so that 3,4-ethylenedioxythiophene adhered to the anodized foil and the counter cathode foil in the capacitor element. Is formed.

As a material for forming the first resin layer, a thermosetting resin (epoxy resin or the like) having higher flexibility than the second resin layer is suitable. As a material to be used, a thermosetting resin (an acid anhydride epoxy resin or the like) having higher airtightness than the first resin layer is suitable.

The flexibility of the resin material can be quantified by numerical values such as Rockwell hardness, tensile strength, and elongation at break. The resin material constituting the first resin layer has a Rockwell hardness of M. 100 or less on scale, 5k tensile strength
Those having a g-weight / mm ² or more and an elongation at break of 4% or more are suitable.

Further, the first resin layer may be made of a resin having adhesiveness to the outer periphery of the capacitor element on which the conductive polymer is adhered and having a surface resistivity of 10 ¹³ Ω or more. preferable.

The capacitor elements on which the first and second resin layers are formed are provided with anode and cathode extraction terminals 17a, 17a.
With the sealing rubber 16 attached to the base of b, it is housed in an aluminum outer case 15 having a bottomed cylindrical shape. After the opening is subjected to horizontal drawing and curling, the rated voltage is applied. An aging process for several tens of minutes to several hours is performed to complete the capacitor.

The inventor of the present application has proposed a solid electrolytic capacitor having a first and a second resin layer formed according to the above-described embodiment of the present invention [Example] and a second resin layer without forming the first resin layer. And a solid electrolytic capacitor [Comparative Example] in which only a layer made of the same material was formed, and a VPS method (215 ° C. × 90
Seconds × 2 times).

Table 1 shows various characteristics before the soldering heat test, and Table 2 shows variations in leakage current before and after the soldering heat test.

[0019]

[Table 1]

[0020]

[Table 2]

The capacitor element used in the above Examples and Comparative Examples has a rating of 20 V-22 μF and an outer diameter of 6.3 m.
m × L6.0 mm, and in Table 1, C is 1
The capacitance at 20 Hz, tan δ indicates the tangent of the loss angle at 120 Hz, and ESR indicates the equivalent series resistance at 100 kHz. Each characteristic value is an average of 50 samples.

The LC yield in Table 1 indicates the number of non-defective products / the number of samples (50 each) when the leakage current after 60 seconds from the application of the rated voltage is 88 μA or less is regarded as a non-defective product.
Table 2 shows the minimum value and the maximum value of the leakage current (LC) of the 50 samples each of the example and the comparative example before and after the soldering heat test, after 60 seconds after applying the rated voltage. It is a thing.

As can be seen from Table 1, the solid electrolytic capacitor according to the embodiment of the present invention has almost the same initial characteristics as the comparative example, and as can be seen from Table 2, the solid electrolytic capacitor according to the embodiment of the present invention. In the capacitor, compared to the comparative example,
The increase in leakage current due to the solder heat resistance test is remarkably suppressed.

In the above embodiment, the polymer of 3,4-ethylenedioxythiophene was used as the material of the cathode electrolyte, but other conductive polymers (for example, pyrrole, thiophene, aniline, or derivatives thereof were oxidized). (Polymerized polymer) may be used.

In the above embodiment, a wound-type capacitor element is used. However, a capacitor element using a tantalum sintered body having a dielectric film formed thereon as an anode member may be used.

[0026]

According to the present invention, a capacitor element having an anode member on which a dielectric film is formed is impregnated with a conductive polymer as a cathode electrolyte, and the capacitor element is disposed in an exterior member and sealed. In electrolytic capacitors,
Swelling of the case and the sealing member due to a solder heat resistance test and the like is prevented, and an increase in leakage current is also suppressed.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a conventional solid electrolytic capacitor.

[Explanation of symbols]

 Reference Signs List 11 capacitor element 15 exterior member (exterior case) 16 sealing rubber 17a anode extraction terminal 17b cathode extraction terminal 18 seat plate 21 first resin layer 22 second resin layer

Claims (3)

[Claims] 1. A solid electrolytic capacitor in which a capacitor element having an anode member on which a dielectric film is formed is impregnated with a conductive polymer as a cathode electrolyte, and the capacitor element is disposed in an exterior member and hermetically sealed. A first resin layer and a second resin layer are sequentially formed outside the capacitor element impregnated with the conductive polymer, and the first resin layer has higher flexibility than the second resin layer. A solid electrolytic capacitor comprising a material. 2. A capacitor obtained by winding an anode foil having a dielectric film formed thereon and an opposite cathode foil via a separator is impregnated with a conductive polymer as a cathode electrolyte, and the capacitor element is housed in an outer case. The solid electrolytic capacitor according to claim 1, wherein the capacitor is sealed. 3. The solid electrolytic capacitor according to claim 1, wherein the conductive polymer is a polymer obtained by oxidative polymerization of thiophene or a derivative thereof.