Method for producing solid electrolytic capacitor
View Patent ↗The invention relates to a method for producing a solid electrolytic capacitor with excellent LC value, comprising sequentially stacking a dielectric oxide film, a semiconductor layer and an electrode layer on a sintered body of conductive powder to which an anode lead is connected and then encapsulating the whole with an outer jacket resin, wherein surface area of a cathode plate used in forming the semiconductor layer on the dielectric oxide film by applying current between the conductor having the dielectric oxide film thereon used as anode and the cathode plate provided in electrolysis solution is made larger by 10 times or more than its apparent surface area to thereby efficiently form the semiconductor layer, a capacitor produced by the method, and electronic circuits and electronic devices using the capacitor.
1. A method of producing solid electrolytic capacitors, comprising sequentially stacking a dielectric oxide film, a semiconductor layer and an electrode layer on a sintered body of conductive powder to which an anode lead is connected and then encapsulating the sequential stack with an outer jacket resin, wherein the semiconductor layer is formed by electrolysis which comprises immersing the sintered body having the dielectric oxide film thereon in an electrolysis solution and applying current between the sintered body having the dielectric oxide film thereon and a cathode plate in contact with the electrolysis solution, the cathode plate being a cathode plate with its surface area having been made larger by 10 times or more than its apparent surface area,
wherein said cathode plate comprises a wall of a container holding said electrolysis solution and used to form the semiconductor layer.
2. The method of producing solid electrolytic capacitors according to claim 1 , wherein by connecting the sintered body of conductive powder to the cathode plate provided in a container holding said electrolysis solution and used to form the semiconductor layer or to a wall of the container, the surface area of the cathode is made larger by 10 times or more than the apparent surface area of the cathode.
3. The method of producing solid electrolytic capacitors according to claim 1 , wherein the conductor is a metal or alloy consisting mainly of at least one selected from the group consisting of tantalum, niobium, titanium and aluminium, niobium oxide, or a mixture of two or more of these metals, alloys and niobium oxide.
4. The method of producing solid electrolytic capacitors according to claim 1 , wherein the material of the anode lead is tantalum, aluminium, niobium and titanium or an alloy mainly containing these valve-action metals.
5. The method of producing solid electrolytic capacitors according to claim 1 , wherein the anode lead is in form of line, foil or sheet.
6. The method of producing solid electrolytic capacitors according to claim 1 , wherein the semiconductor layer is at least one selected from organic semiconductor layer and inorganic semiconductor layer.
7. The method of producing solid electrolytic capacitors according to claim 6 , wherein the organic semiconductor is at least one selected from the group consisting of an organic semiconductor consisting of benzopyrroline tetramer and chloranile, an organic semiconductor mainly consisting of tetrathiotetracene, an organic semiconductor mainly consisting of tetracyanoquinodimethane and an organic semiconductor mainly consisting of an electroconductive polymer prepared by doping a dopant to a polymer having a repeating unit represented by formula (1) or (2)
(In the formula, R 1 to R 4 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, X represents an oxygen atom, a sulfur atom or a nitrogen atom, R 5 , which is present only when X is a nitrogen atom, represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 1 with R 2 or R 3 with R 4 may combine with each other to form a ring).
8. The method of producing solid electrolytic capacitors according to claim 7 , wherein the electroconductive polymer having the repeating unit represented by formula (1) is an electroconductive polymer having as repeating unit a structural unit represented by formula (3)
(In the formula, R 6 and R 7 each independently represents a hydrogen atom, a linear or branched, saturated or unsaturated alkyl group having 1 to 6 carbon atoms, or a substituent forming at least one 5- to 7-membered saturated hydrocarbon ring structure containing two oxygen atoms, in which said alkyl groups are bonded at arbitrary positions with each other. Also, examples of the ring structure include those having a vinylene or phenylene bond which may be substituted).
9. The method of producing solid electrolytic capacitors according to claim 7 , wherein the electroconductive polymer is selected from polyaniline, polyoxyphenylene, polyphenylene sulfide, polythiophene, polyfuran, polypyrrole, polymethylpyrrole, and substituted derivatives thereof and copolymers thereof.
10. The method of producing solid electrolytic capacitors according to claim 8 , wherein the electroconductive polymer is poly(3,4-ethylenedioxythiophene).
11. The method of producing solid electrolytic capacitors according to claim 6 , wherein the electroconductivity of the semiconductor is within a range of 10 −2 to 10 3 S/cm.
12. A solid electrolytic capacitor produced by the method described in claim 1 .
13. An electronic circuit using the solid electrolytic capacitor described in claim 12 .
14. An electronic device using the solid electrolytic capacitor described in claim 12 .
15. The production method of the solid electrolytic capacitor as claimed in claim 1 wherein the cathode is a sintered body of conductive powder.