Method and apparatus for high voltage aluminum capacitor design

• US 20060023400A1
• Filed: 07/15/2005
• Published: 02/02/2006
• Est. Priority Date: 07/16/2004
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Sherwood, Gregory J.
• Granted Patent: US 7,224,575 B2
• Time in Patent Office: Days
• US Class Current: 361/503
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: H01G 9/0032 formation of the dielectric layer
• CPC Class Codes: H01G 9/10 Sealing, e.g. of lead-in wires
• CPC Class Codes: Y10T 29/43 Electric condenser making
• CPC Class Codes: Y10T 29/435 Solid dielectric type

Abstract

Structure and method providing a capacitor connected to a component, including a capacitor stack made from one or more substantially planar cathode layers, one or more substantially planar anode layers, one or more substantially planar separator layers, and a solitary electrolyte. Additionally, the capacitor includes a case with a first aperture sized for passage of the capacitor stack and a second aperture, and one or more conductors connecting the capacitor stack to the component, with at least one conductor passing through the second aperture of the case, the at least one conductor sealingly connected to the second aperture. Further, the capacitor case is filled with a solitary electrolyte, and the capacitor stack is adapted to deliver to electronics from about 5.3 joules per cubic centimeter of capacitor stack volume to about 6.3 joules per cubic centimeter of capacitor stack volume, at a voltage of between about 465 volts to about 565 volts.

Claims

1. A capacitor for connection to a component, comprising:

a capacitor stack, including one or more substantially planar cathode layers, one or more substantially planar anode layers, one or more substantially planar separator layers, and a unitary electrolyte;

a case with a feedthrough hole and a first aperture sized for passage of the capacitor stack;

a lid sealingly substantially conforming to the first aperture and sealingly connected to the first aperture; and

a feedthrough assembly connected to the capacitor stack and passing through the second aperture of the case and sealingly connected to the feedthrough hole,

wherein the case is filled with the unitary electrolyte, and the capacitor is adapted to deliver to the component from about 5.3 joules per cubic centimeter of capacitor stack volume to about 6.3 joules per cubic centimeter of capacitor stack volume, at a voltage of between about 465 volts to about 620 volts.

2. The apparatus of claim 1, wherein the capacitor stack is adapted to deliver an electrical pulse to the component at between approximately 490 volts and approximately 540 volts.

3. The apparatus of claim 2, wherein the capacitor stack is adapted to deliver an electrical pulse at approximately 515 volts.

4. The apparatus of claim 1, wherein the capacitor stack is adapted to deliver from about 5.5 joules per cubic centimeter of capacitor stack volume to about 6.1 joules per cubic centimeter of capacitor stack volume.

5. The apparatus of claim 4, wherein the capacitor stack is adapted to deliver about 5.8 joules per cubic centimeter of capacitor stack.

6. The apparatus of claim 1, wherein the capacitor stack includes from about 16 substantially planar cathode layers to about 22 substantially planar cathode layers, and from about 52 substantially planar anode layers to about 64 substantially planar anode layers, and one or more substantially planar separator layers.

7. The apparatus of claim 6, wherein the capacitor stack includes approximately 20 substantially planar cathode layers, and approximately 58 substantially planar anode layers.

8. The apparatus of claim 1, wherein the anode includes anode foils comprising an aluminum substrate at least partially encased in an aluminum oxide (Al₂O₃).

9. The apparatus of claim 8, wherein the aluminum oxide is formed at between approximately 600 volts and approximately 760 volts.

10. The apparatus of claim 1, wherein the cathode includes an aluminum substrate and a titanium coating.

11. The apparatus of claim 10, wherein the titanium coating is between approximately 0.5 nanometers and approximately 6.0 nanometers thick.

12. The apparatus of claim 1, wherein the capacitor stack has a mass of between approximately 10.7 grams and approximately 11.8 grams.

13. The apparatus of claim 1, wherein the anode has a capacitance of between approximately 0.70 and approximately 0.85 microfarads per square centimeter when charged at approximately 550 volts.

14. The apparatus of claim 1, wherein the anode and cathode layers include at least one member of the group including aluminum, tantalum, hafnium, niobium, titanium, and zirconium.

15. The apparatus of claim 1, wherein a plurality of anode connection members define a first surface, and a plurality of cathode connection members define a second surface, and the feedthrough assembly is connected to the first surface.

16. The apparatus of claim 1, wherein the capacitor case is electrically conductive.

17. The apparatus of claim 16, wherein a conductor connects the capacitor case to the cathode of the capacitor stack.

18. The apparatus of claim 17, wherein a terminal is connected to the case and is adapted for connection to the component.

19. The apparatus of claim 1, wherein a plurality of anode connection members define a first surface, and a plurality of cathode connection members define a second surface, and the feedthrough assembly is connected to the first surface.

20. The apparatus of claim 19, wherein a conductor connects the capacitor case to the second surface of the capacitor stack.

21. A method of producing an apparatus for use in a patient, comprising:

etching an anode foil;

anodizing the anode foil;

assembling the anode foil, at least one cathode foil and one or more separators into a capacitor stack adapted to deliver from about 5.3 joules per cubic centimeter of capacitor stack volume to about 6.3 joules per cubic centimeter of capacitor stack volume at a voltage of between about 465 volts to about 620 volts;

inserting the stack into a capacitor case;

inserting the capacitor case into a device housing adapted for implant in a patient;

connecting the capacitor to a component; and

sealing the device housing.

22. The method of claim 21, wherein anodizing includes forming a hydrous oxide layer on an aluminum foil.

23. The method of claim 21, wherein anodizing the anode foil includes forming a dielectric layer from about 600 nanometers to about 800 nanometers.

24. The method of claim 21, further comprising:

forming a hydrous oxide layer on an anode foil;

anodizing the anode foil in a bath containing an aqueous solution of approximately 10 to approximately 120 grams per liter boric acid and approximately 2 to approximately 50 parts per million phosphate as electrolyte at a pH of 4.0 to 6.0 and a temperature of approximately 85 degrees Celsius to approximately 95 degrees Celsius, whereby said foil can be anodized to approximately 760 V without scintillation; and

interrupting the anodizing process to stabilize the anode foil in a mildly alkaline bath.

25. The method of claim 24, wherein the anodization occurs from approximately 600 volts to approximately 760 volts.

26. The method of claim 25, wherein the anodization occurs from about 650 volts to about 720 volts.

27. The method of claim 26, wherein the anodization occurs from about 670 volts to about 710 volts during formation.

28. The method of claim 21, wherein the mildly alkaline bate bath includes an approximately 0.001 to approximately 0.05M borax solution having a pH of approximately 8.5 to approximately 9.5 and a temperature of at least 80 degrees Celsius.

29. The method of claim 28, wherein the borax solution is buffered by approximately 0.005 molar to approximately 0.05 molar sodium carbonate solution.

30. The method of claim 29, wherein interrupting includes removing the anode foil from the bath more than once, and dipping the anode in the mildly alkaline bath at least twice.

31. The method of claim 21, wherein the resistivity of said electrolyte is approximately 1500-3600 ohm-centimeters.

32. The method of claim 21, wherein the pH of the boric acid solution is attained by the addition of a reagent selected from one of the group including ammonium and alkali metal hydroxides and ammonium and alkali metal salts.

33. The method of claim 29, wherein said reagent is selected from the group consisting of sodium hydroxide and borax.

34. The method of claim 21, wherein the phosphate is phosphoric acid.