High-energy electrolytic capacitors for implantable defibrillators

• US 20040039421A1
• Filed: 04/28/2003
• Published: 02/26/2004
• Est. Priority Date: 10/02/1998
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Poplett, James M., Tong, Robert R., Christenson, Luke J., OʼPhelan, Michael J.
• Granted Patent: US 7,043,300 B2
• Time in Patent Office: Days
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3782 producing a voltage above the power source level
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: H01G 9/045 based on aluminium
• CPC Class Codes: H01G 9/055 Etched foil electrodes
• CPC Class Codes: Y10T 428/12431 Foil or filament smaller than 6 mils

Abstract

Implantable defibrillators are implanted into the chests of patients prone to suffering ventricular fibrillation, a potentially fatal heart condition. A critical component in these devices is an aluminum electrolytic capacitors, which stores and delivers one or more life-saving bursts of electric charge to a fibrillating heart. To reduce the size of these devices, capacitor manufacturers have developed special aluminum foils, for example core-etched and tunnel-etched aluminum foils. Unfortunately, core-etched foils don'"'"'t work well in multiple-anode capacitors, and tunnel-etched foils are quite brittle and tend to break when making some common types of capacitors. Accordingly, the inventors devised a new foil structure having one or more perforations and one or more cavities with a depth less than the foil thickness. In an exemplary embodiment, each perforation and cavity has a cross-sectional area, with the perforations having a larger, for example, 2 to 100 times larger, average cross-sectional area than the cavities. Other embodiments of the invention include foil assemblies, capacitors, and implantable defibrillators that benefit from properties of the new foil structure.

Claims

1. A foil having a foil thickness and comprising one or more perforations and one or more cavities having a depth less than the foil thickness.

2. The foil of claim 1 wherein the foil has first and second opposing sides, with one or more of the cavities on the first side and one or more of the cavities on the second side and wherein the average depth of the cavities is less than one-half the foil thickness.

3. The foil of claim 2 wherein the average depth of the cavities is about one-third or one-fourth of the foil thickness.

4. The foil of claim 1 wherein the perforations have an average cross-sectional area larger than an average cross-sectional area of the cavities.

5. The foil of claim 4 wherein the average cross-sectional area of the perforations is about 2 to 100 times larger than the average cross-sectional area of the cavities.

6. The foil of claim 1 wherein each perforations has a generally circular cross-section.

7. The foil of claim 1 wherein the foil comprises at least one of aluminum, tantalum, hafnium, niobium, titanium, and zirconium.

8. The foil of claim 1 wherein one or more of the cavaties define a perimeter which circumscribes one or more of the perforations and wherein the foil is at least partly rolled.

9. A foil for a capacitor, comprising:

first and second opposing surfaces which define a foil thickness, with the first opposing surface having one or more cavities each having a maximum depth less than the foil thickness and the second opposing surface having one or more cavities each having a maximum depth less than the foil thickness; and

one or more perforations through the foil.

10. The foil of claim 9 wherein the cavities of the first surface have a first average maximum depth and the cavities of the second surface have a second average maximum depth, with the first and second average maximum depths being less than one-half the foil thickness.

11. The foil of claim 9 wherein the perforations have an average cross-sectional area at least twice an average cross-sectional area of the cavities.

12. An aluminum foil for a capacitor, comprising:

first and second opposing surfaces which define a foil thickness, with the first opposing surface having one or more cavities and the second opposiing surface having one or more cavities, the cavities of the first and second surfaces having an average depth less than one half the foil thickness and having an average cross-sectional area; and

one or more perforations through the foil, with the perforations having an average cross-sectional area at least twice the average cross-sectional area of the cavities.

13. The aluminum foil of claim 12:

wherein the average depth of the cavities is about one-third or one-fourth of the foil thickness;

or

wherein the perforations have an average cross-sectional area about 2 to 100 times larger than the average cross-sectional area of the cavities.

14. A foil assembly comprising two or more foils stacked according to one or more of the following foil sequences:

PP, PPP, PCP, PPCPP, PTP, PTPT, TPT, PTCTP, wherein C denotes a core-etched foil;

T denotes a tunnel-etched foil; and

P denotes a foil having a foil thickness and comprising one or more perforations and one or more cavities having a depth less than the foil thickness.

15. The foil assembly of claim 14:

wherein each P foil has first and second opposing sides, with one or more of the cavities on the first side and one or more of the cavities on the second side and wherein the average depth of the cavities is less than one-half the foil thickness;

or

wherein the perforations have an average cross-sectional area larger than an average cross-sectional area of the cavities;

or

wherein the average cross-sectional area of the perforations is about 2 to 100 times larger than an average maximum cross-sectional area of the cavities;

or

wherein one or more the foils comprises at least one of aluminum, tantalum, hafnium, niobium, titanium, and zirconium.

16. A capacitor comprising a foil having a foil thickness, one or more perforations, and one or more cavities having a depth less than the foil thickness.

17. The capacitor of claim 16 wherein the foil has first and second opposing sides, with one or more of the cavities on the first side and one or more of the cavities on the second side and wherein the average depth of the cavities is less than one-half the foil thickness.

18. The capacitor of claim 17 wherein the average depth of the cavities is about one-third or one-fourth of the foil thickness.

19. The capacitor of claim 16:

wherein the perforations have an average cross-sectional area larger than an average cross-sectional area of the cavities;

or

wherein the perforations have generally circular cross-sections;

or

wherein the foil comprises at least one of aluminum, tantalum, hafnium, niobium, titanium, and zirconium.

20. The capacitor of claim 16 wherein at least a portion of the foil is rolled.

21. The capacitor of claim 16 wherein the foil is part of an anode structure.

22. A capacitor comprising:

a foil having first and second opposing surfaces which define a foil thickness, with the first opposing surface having one or more cavities each having a maximum depth less than the foil thickness and the second opposing surface having one or more cavities each having a maximum depth less than the foil thickness; and

one or more perforations through the foil.

23. The capacitor of claim 22:

wherein the cavities of the first surface have a first average depth and the cavities of the second surface have a second average depth, with the first and second average depths being less than one-half the foil thickness;

or

wherein the perforations have an average cross-sectional area at least twice an average maximum cross-sectional area of the cavities;

or

wherein at least a portion of the foil is rolled.

24. An aluminum electrolytic capacitor comprising:

at least one aluminum anode foil having first and second opposing surfaces which define a foil thickness, with the first opposing surface having one or more cavities and the second opposing surface having one or more cavities, the cavities of the first and second surfaces having an average maximum depth less than one half the foil thickness and having an average maximum cross-sectional area; and

one or more perforations through the aluminum anode foil, with the perforations having an average maximum cross-sectional area at least twice the average maximum cross-sectional area of the cavities.

25. The aluminum electrolytic capacitor of claim 24:

wherein the average depth of the cavities is about one-third or one-fourth the foil thickness;

or

wherein the perforations have an average maximum cross-sectional area about 2 to 100 times larger than the average maximum cross-sectional area of the cavities.

26. A capacitor comprising:

at least one perforated-core-etched foil;

or

at least one perforated-core-etched foil adjacent at least one core-etched foil;

or

at least one perforated-core-etched foil, at least one core-etched foil; and

at least one tunnel-etched foil.

27. The capacitor of claim 26 wherein each perforated core-etched foil comprises:

first and second opposing surfaces which define a foil thickness, with the first opposing surface having one or more cavities each having a maximum depth less than the foil thickness and the second opposiing surface having one or more cavities each having a maximum depth less than the foil thickness; and

one or more perforations through the foil.

28. The capacitor of claim 27 wherein the cavities of the first surface have a first average depth and the cavities of the second surface have a second average depth, with the first and second average depths being less than one-half the foil thickness.

29. A capacitor comprising one or more tunnel-etched foils between two or more perforated-core-etched foils.

30. A defibrillator comprising:

one or more leads for sensing electrical signals of a patient or for applying electrical energy to the patient;

a monitoring circuit for monitoring heart activity of the patient through one or more of the leads; and

a therapy circuit for delivering electrical energy through one or more of the leads to a heart of the patient, wherein the therapy circuit includes one or more capacitors which include a foil that comprises;

first and second opposing surfaces which define a foil thickness, with the first opposing surface having one or more cavities each having a maximum depth less than the foil thickness and the second opposiing surface having one or more cavities each having a maximum depth less than the foil thickness; and

one or more perforations through the foil.

31. The defibrillator of claim 30 wherein the cavities of the first surface have a first average maximum depth and the cavities of the second surface have a second average maximum depth, with the first and second average maximum depths being less than one-half the foil thickness.

32. A method of processing a foil, the method comprising:

perforating a foil having a foil thickness; and

forming one or more surface cavities in the foil, the surface cavities having an average depth less than the foil thickness.

33. The method of claim 32, wherein perforating the foil occurs after forming the one or more surface cavities.

34. The method of claim 32 wherein the foil has first and second opposing sides and forming one or more surface cavities in the foil comprises forming one or more of the cavities on the first side and one or more of the cavities on the second side, with the cavities having an average depth less than one-half the foil thickness.

35. The method of claim 32 wherein the average depth of the cavities is about one-third or one-fourth of the foil thickness.

36. The method of claim 32 wherein forming the perforations or forming the cavities comprising using electromagnetic, chemical, or mechanical energy.

37. The method of claim 32 wherein the foil comprises at least one of aluminum, tantalum, hafnium, niobium, titanium, and zirconium.

38. A method of making a perforated-core-etched foil for a capacitor, the method comprising:

forming one or more holes in a core-etched foil;

or

forming one or more surface cavities in a perforated foil having a foil thickness, with the surface cavities having an average depth less than the foil thickness.