Electrolytic capacitor with fractal surface

• US 5,822,177 A
• Filed: 07/11/1996
• Issued: 10/13/1998
• Est. Priority Date: 07/11/1995
• Status: Expired due to Term

• Current Assignee: Biotronik Mess-Und Therapiegeraete GmbH & Company Ingenieurbuero Berlin (Biotronik SE & Company KG)
• Original Assignee: Biotronik Mess-Und Therapiegeraete GmbH & Company Ingenieurbuero Berlin (Biotronik SE & Company KG)
• Inventors: Popp, Thomas, Bolz, Armin
• Primary Examiner(s): Kincaid, Kristine L.
• Assistant Examiner(s): Dinkins, Anthony
• Application Number:
  US08/678,138
• Time in Patent Office: 824 Days
• Field of Search: 361/500, 361/503, 361/508-512, 361/514, 361/537, 361/516, 361/517, 361/519, 361/520, 361/523-526, 361/528-530, 361/532, 361/535, 29/25.03, 607/13, 607/9, 607/11
• US Class Current: 361/508
• CPC Class Codes: H01G 9/042 characterised by the material H01G11/22 takes precedence
• CPC Class Codes: H01G 9/048 characterised by their structure H01G11/22 takes precedence

Abstract

An electrolytic capacitor, in particular a tantalum electrolytic capacitor, is provided with a metal anode, in particular a sintered tantalum anode (1), a non-conducting insulating layer applied on it by means of molding the metal anode (1) for forming the dielectric of the electrolytic capacitor, an electrolyte in liquid, pasty or solid form, which forms the cathode of the electrolytic capacitor, and a flat cathode contact (5, 17) for providing current to the electrolyte. The flat cathode contact (5, 7) is provided with an electrically conducting, fractal surface coating (6), at least in the area of its contact surface with the electrolyte.

Claims

1. An electrolytic capacitor, comprising:

a metal anode;

a non-conducting insulating layer applied to the metal anode by forming the metal anode for producing a dielectric of the electrolyte capacitor;

an electrolyte in liquid, pasty or solid form constituting a cathode of the electrolytic capacitor; and

a flat cathode contact for supplying current to the electrolyte, wherein

the flat cathode contact is provided with an electrically conducting, fractal surface coating.

2. The electrolytic capacitor in accordance with claim 1, wherein the fractal surface coating is a material selected from the group consisting of iridium, tantalum and aluminum.

3. The electrolytic capacitor in accordance with claim 1, wherein the flat cathode contact comprises a material selected from the group consisting of titanium, tantalum and aluminum.

4. An electrolytic capacitor comprising:

a metal anode;

a non-conducting insulating layer applied to the metal anode by forming the metal anode for producing a dielectric of the electrolytic capacitor;

an electrolyte in liquid, pasty or solid form constituting a cathode of the electrolytic capacitor; and

a flat cathode contact for supplying current to the electrolyte, wherein

the flat cathode contact is provided with an electrically conducting, fractal surface coating;

wherein the fractal surface coating is a material selected from the group consisting of iridium, tantalum and aluminum;

wherein the fractal surface coating of the cathode contact is applied by cathode sputtering at a value of a pressure distance product during the cathode sputtering of approximately 0.5 mbar-cm.

5. An electrolytic capacitor, comprising:

a metal anode;

a non-conducting insulating layer applied to the metal anode by forming the metal anode for producing a dielectric of the electrolytic capacitor;

an electrolyte in liquid, pasty or solid form constituting a cathode of the electrolytic capacitor; and

a flat cathode contact for supplying current to the electrolyte, wherein

the flat cathode contact is provided with an electrically conducting, fractal surface coating;

further comprising a porous, electrically insulating separating foil saturated with the electrolyte and inserted between the molded metal anode and the flat cathode contact.

6. An electrolytic capacitor, comprising:

a metal anode;

a non-conducting insulating layer applied to the metal anode by forming the metal anode for producing a dielectric of the electrolytic capacitor;

an electrolyte in liquid, pasty or solid form constituting a cathode of the electrolytic capacitor; and

a flat cathode contact for supplying current to the electrolyte, wherein

the flat cathode contact is provided with an electrically conducting, fractal surface coating;

wherein the cathode contact is a cylindrical housing, cup (5) provided with the fractal surface coating on an interior thereof and into which the metal anode is inserted in an insulating manner with an electrolyte-saturated separating foil interposed therebetween, and wherein the metal anode is a cylindrical sinter anode made of tantalum powder.

7. The electrolytic capacitor in accordance with claim 6, wherein the sinter anode is connected with a connecting wire passed in an insulated manner through a cover of the housing cup, an end thereof at an anode side thereof is pressed into the sinter anode or connected with tantalum anode shells in an electrically conducting manner.

8. An electrolytic capacitor, comprising:

a metal anode;

a non-conducting insulating layer applied to the metal anode by forming the metal anode for producing a dielectric of the electrolytic capacitor;

an electrolyte in liquid, pasty or solid form constituting a cathode of the electrolytic capacitor; and

a flat cathode contact for supplying current to the electrolyte, wherein

the flat cathode contact is provided with an electrically conducting, fractal surface coating;

wherein the cathode contact includes a fractally coated cathode foil.

9. The electrolytic capacitor in accordance with claim 8, further comprising an electrolyte-saturated separating foil and a cathode cup into an interior which two tantalum anode shells with inserted sinter anodes made of tantalum powder have been inserted in an insulating manner, and wherein, the cathode contact comprises the cathode foil which is provided on both sides with the fractal coating and is arranged between two facing flat longitudinal sides of the anode and a respective interposition of the electrolyte-saturated separating foil.

10. The electrolytic capacitor in accordance with claim 9, wherein the cathode foil is welded on its edge with the cathode cup.

11. The electrolytic capacitor in accordance with claim 9, wherein the cathode cup is connected with a cathode connecting wire for the electrical contact with the cathode contact.

12. The electrolytic capacitor in accordance with claim 8, wherein said fractally coated cathode foil is disposed in a housing cup with the interposition of an electrolyte-saturated separating foil, wound together with the molded comprising a foil.

13. The electrolytic capacitor in accordance with claim 12, wherein the anode foil is wound such that the anode foil is folded upon itself into several layers.

14. The electrolytic capacitor in accordance with claim 13, wherein the anode foil is provided with perforations.

15. An electrolytic capacitor, comprising:

a metal anode;

a non-conducting insulating layer applied to the metal anode by molding the metal anode for producing a dielectric of the electrolytic capacitor;

an electrolyte in liquid, pasty or solid form constituting a cathode of the electrolytic capacitor; and

a flat cathode contact for supplying current to the electrolyte, wherein

the flat cathode contact is provided with an electrically conducting, fractal surface coating;

wherein the anode is a sintered tantalum anode doped with nitrogen by means of a heat treatment process after sintering.

16. A process for producing a tantalum anode for an electrolytic capacitor in accordance with claim 15, comprising the steps:

charging the anode with a nitrogen atmosphere after sintering;

pumping out the nitrogen atmosphere,

tempering the resulting tantalum anode at temperatures between 1000° and

2000°

C. and at a process pressure on the order of magnitude of 10_-5 mbar.