Implantable medical device having flat electrolytic capacitor with registered electrode layers

• US 6,009,348 A
• Filed: 06/24/1998
• Issued: 12/28/1999
• Est. Priority Date: 04/03/1998
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Johnson, William L., Lessar, Joseph F., Rorvick, Anthony W., Breyen, Mark D., Pignato, Paul, Bullock, Norma K.
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US09/103,972
• Time in Patent Office: 552 Days
• Field of Search: 29/25.03, 361/509, 361/516, 361/517, 361/518, 361/522, 361/529, 361/523, 361/535, 361/536, 361/525, 607/5
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

An implantable medical device such as a defibrillator is described. The device includes an hermetically sealed housing containing a flat electrolytic capacitor and an energy source such as a battery. The battery is connected to the capacitor and provides charge thereto. The capacitor stores the charge at a relatively high voltage. The charge stored in the capacitor is discharged through a defibrillation lead to a site on or in the heart when fibrillation of the heart is detected by the implantable medical device. Methods of making and using the implantable medical device, the capacitor, and their various components are disclosed.

Claims

1. A method of making an hermetically sealed implantable medical device, comprising the steps of:

(a) providing a housing for the implantable medical device;

(b) providing an energy source for the implantable medical device and disposing the energy source within the housing;

(c) forming a substantially flat aluminum electrolytic capacitor, comprising the steps of;

(i) providing at least one cathode layer formed of cathode foil and having a first perimeter, the at least one cathode layer having at least a first tab projecting from the first perimeter at a first predetermined perimeter location, the at least one cathode layer having top and bottom surfaces;

(ii) providing a plurality of anode layers formed of aluminum anode foil, the plurality of anode layers forming at least a first anode sub-assembly having top and bottom surfaces, at least one of the plurality of anode layers being a first anode layer having a second perimeter and at least a second tab projecting from the second perimeter at a second predetermined perimeter location;

(iii) providing at least a first separator layer formed of separator material;

(iv) vertically stacking the at least one cathode layer, the plurality of anode layers and the first separator layer such that the first separator layer is disposed between the at least one cathode layer and the anode sub-assembly to form a capacitor electrode assembly;

(v) aligning the first tab with a first predetermined registration position in the electrode assembly;

(vi) aligning the second tab with a second predetermined registration position in the electrode assembly;

(vii) placing the electrode assembly in a capacitor case having an open end;

(viii) placing a cover over the open end of the case;

(ix) joining the cover to the case;

(d) disposing the capacitor in the housing;

(e) connecting the capacitor to the power source, and

(f) hermetically sealing the housing.

2. The method of claim 1, wherein the cathode layer providing step is preceded by a step of forming the cathode layer from an aluminum cathode foil.

3. The method of claim 1, wherein the anode layer providing step is preceded by a step of forming the plurality of anode layers from through-etched aluminum anode foil.

4. The method of claim 3, wherein the anode layer forming step further comprises the step of providing aluminum anode foil having a purity of at least about 99.9%.

5. The method of claim 3, wherein the anode layer forming step further comprises the step of providing aluminum anode foil having a specific capacitance selected from the group consisting of at least about 0.3 microfarads/cm², at least about 0.5 microfarads/cm², and at least about 0.8 microfarads/cm² for each anode layer contained therein.

6. The method of claim 3, wherein the anode layer forming step further comprises the step of providing, for each anode layer contained in the capacitor, aluminum anode foil having a thickness selected from the group consisting of from about 20 micrometers to about 300 micrometers, from about 40 micrometers to about 200 micrometers, from about 60 micrometers to about 150 micrometers, and about 70 micrometers to about 140 micrometers.

7. The method of claim 3, wherein the anode layer forming step further comprises the step of attaching the second tab to the second perimeter at the second location in the first anode layer.

8. The method of claim 1, wherein the step of attaching the second tab to the second perimeter at the second location in the first anode layer is preceded by a step of forming the second tab from aluminum strip material.

9. The method of claim 1, wherein the cathode layer providing step is preceded by a step of forming the at least one cathode layer from a highly etched cathode foil.

10. The method of claim 9, wherein the cathode layer forming step further comprises the step of providing cathode foil having a specific capacitance selected from the group consisting of at least about 100 microfarads/cm², at least about 200 microfarads/cm², at least about 250 microfarads/cm², and at least about 300 microfarads/cm².

11. The method of claim 9, wherein the cathode layer forming step further comprises the step of providing cathode foil having a thickness selected from the group consisting of from about 10 micrometers to about 200 micrometers, from about 15 micrometers to about 150 micrometers, from about 20 micrometers to about 100 micrometers, from about 25 micrometers to about 75 micrometers, and about 30 micrometers.

12. The method of claim 9, wherein the cathode layer forming step further comprises the step of providing cathode foil having a purity of at least about 99%.

13. The method of claim 1, wherein the anode layer providing step is preceded by a step of selecting a plurality of non-notched anode layers and at least one notched anode layer for inclusion in the anode sub-assembly.

14. The method of claim 1, wherein the first separator layer providing step is preceded by a step of forming the first separator layers from Kraft paper.

15. The method of claim 1, wherein the anode layer providing step is preceded by a step of selecting a plurality of non-notched anode layers and at least one notched anode layer for inclusion in the anode sub-assembly.

16. The method of claim 1, wherein the anode layer providing step is preceded by a step of cold welding the plurality of anode layers together to form the anode sub-assembly.

17. The method of claim 1, wherein the anode layer providing step and the separator layer providing step are preceded by a step of pressure bonding the first separator layer to the anode sub-assembly.

18. The method of claim 1, wherein the anode layer providing step and the separator layer providing step are preceded by a step of covering the top and bottom surfaces of the anode sub-assembly with the first separator layer and a second separator layer.

19. The method of claim 18, further comprising the subsequent step of securing a free edge of the first separator layer with tape, adhesive or stitching or by ultrasonic paper welding.

20. The method of claim 1, wherein the cathode layer providing step and the separator layer providing step are preceded by a step of covering the top and bottom surfaces of the at least one cathode layer with the first separator layer and a second separator layer.

21. The method of claim 20, further comprising the subsequent step of securing a free edge of the first separator layer with tape, adhesive or stitching or by ultrasonic paper welding.

22. The method of claim 1, wherein the anode layer providing step and the separator layer providing step are preceded by a step of forming the first anode layer and a step of forming the first separator layer and a second separator layer, the first and second separator layers each defining third perimeters of substantially equal lengths and substantially equal third surface areas, the second perimeter of the first anode layer defining a second surface area, the second surface area being less than the third surface area.

23. The method of claim 1, wherein the cathode layer providing step and the separator layer providing step are preceded by a step of forming the at least one cathode layer and a step of forming the first separator layer and a second separator layer, the first and second separator layers each defining third perimeters of substantially equal lengths and substantially equal third surface areas, the first perimeter of the at least one cathode layer defining a first surface area, the first surface area being less than the third surface area.

24. The method of claim 1, wherein the separator layer providing step is preceded by a step of forming the first separator layer and a second separator layer such that the physical dimensions of the first and second separator layers are greater than those of the anode layers.

25. The method of claim 1, wherein the separator layer providing step is preceded by a step of forming the first separator layer and a second separator layer such that the physical dimensions of the first and second separator layers are greater than those of the at least one cathode layer.

26. The method of claim 1, wherein the step of vertically stacking the at least one cathode layer, the plurality of anode layers and the separator layer further comprises providing a stacking fixture for registration of the layers therein as the layers are stacked in the fixture.

27. The method of claim 1, wherein the steps of vertically aligning the first and second tabs further comprises providing a stacking fixture for registration of the tabs as the layers are stacked in the fixture.

28. The method of claim 1, further comprising the step of wrapping the stacked electrode assembly with an outer wrap.

29. The method of claim 28, further comprising the step of securing the outer wrap to the stacked electrode assembly with tape.

30. The method of claim 1, wherein the vertical stacking step is accomplished using robotic assembly means.

31. The method of claim 1, wherein the vertical aligning step is accomplished using robotic assembly and camera means.

32. The method of claim 1, further comprising the steps of providing a second cathode layer formed of cathode foil and having a third perimeter, providing a second separator layer formed of separator material, the second cathode layer having at least a third tab projecting from the third perimeter at a third predetermined perimeter location, the second cathode layer having top and bottom surfaces, vertically stacking the second cathode layer and the second separator layer on the stacked electrode assembly such that the second separator layer is disposed between the top surface of the anode sub-assembly and the bottom surface of the second cathode layer, aligning the third tab with a third predetermined registration position in the electrode stack, and vertically aligning the first tab and the third tab such that the first predetermined registration location of the electrode assembly coincides vertically with the third predetermined registration location of the electrode assembly.

33. The method of claim 1, further comprising the steps of providing a second anode sub-assembly comprising a plurality of anode layers formed of aluminum anode foil, the second anode sub-assembly having top and bottom surfaces, at least one of the plurality of anode layers of the second anode sub-assembly being a second anode layer having a fourth perimeter and at least a fourth tab projecting from the fourth perimeter at a fourth predetermined perimeter location, providing a second separator layer formed of separator material, vertically stacking the second anode sub-assembly and the second separator layer in the stacked electrode assembly such that the second separator layer is disposed beneath the bottom surface of the cathode layer and the top surface of the second anode sub-assembly, aligning the fourth tab with a fourth predetermined registration position in the electrode stack, and vertically aligning the second tab and the fourth tab such that the second predetermined registration location of the electrode assembly coincides vertically with the fourth predetermined registration location of the electrode assembly.

34. The method of claim 1, further comprising the step of electrically connecting the at least one cathode layer to the case.

35. An hermetically sealed implantable medical device having a housing, an energy source disposed within the housing and a substantially flat aluminum electrolytic capacitor connected to the energy source and disposed within the housing, the capacitor comprising:

(a) at least one cathode layer formed of cathode foil and having a first perimeter, the at least one cathode layer having at least a first means for aligning projecting from the first perimeter at a first predetermined perimeter location, the at least one cathode layer having top and bottom surfaces;

(b) a plurality of anode layers formed of aluminum anode foil, the plurality of anode layers forming an anode sub-assembly having top and bottom surfaces, at least one of the plurality of anode layers being a first anode layer having a second perimeter and at least a second means for aligning projecting from the second perimeter at a second predetermined perimeter location;

(c) at least a first separator layer formed of separator material, the at least one cathode layer, the plurality of anode layers and the first separator layer being vertically stacked to form an electrode assembly such that the first separator layer is between the at least one cathode layer and the anode sub-assembly, the first aligning means being aligned with a first predetermined registration position in the electrode assembly, the second aligning means being aligned with a second predetermined registration position in the electrode assembly;

(d) a case having an open end for receiving the electrode assembly therein, and

(e) a cover disposed over the open end of the case and in sealing engagement therewith;

wherein the capacitor and the energy source are connected to one another and disposed within the housing, and the housing is hermetically sealed.

36. The device of claim 35, wherein the cathode layer is formed from aluminum cathode foil.

37. The device of claim 35, wherein the anode layers are formed of through-etched aluminum anode foil.

38. The device of claim 35, wherein each anode layer has a specific capacitance selected from the group consisting of at least about 0.3 microfarads/cm², at least about 0.5 microfarads/cm², and at least about 0.8 microfarads/cm².

39. The device of claim 35, wherein the each anode layer has a thickness selected from the group consisting of from about 20 micrometers to about 300 micrometers, from about 40 micrometers to about 200 micrometers, from about 60 micrometers to about 150 micrometers, and from about 70 micrometers to about 140 micrometers.

40. The device of claim 35, wherein the cathode layer is formed from a highly etched cathode foil.

41. The device of claim 35, wherein the cathode layer is formed from a cathode foil having a specific capacitance selected from the group consisting of at least about 100 microfarads/cm , at least about 200 microfarads/cm², at least about 250 microfarads/cm², and at least about 300 microfarads/cm².

42. The device of claim 35, wherein the cathode layer is formed from foil having a thickness selected from the group consisting of from about 10 micrometers to about 200 micrometers, from about 15 micrometers to about 150 micrometers, from about 20 micrometers to about 100 micrometers, from about 25 micrometers to about 75 micrometers, and about 30 micrometers.

43. The device of claim 35, wherein the anode sub-assembly comprises a plurality of non-notched anode layers and at least one notched anode layer.

44. The device of claim 35, wherein the anode layers in the anode sub-assembly are cold welded together.

45. The device of claim 35, wherein at least one of the first separator layer is pressure bonded to the anode sub-assembly.

46. The device of claim 35, wherein the top and bottom surfaces of the anode sub-assembly are covered by the first separator layer and a second separator layer.

47. The device of claim 35, wherein the top and bottom surfaces of the cathode layer are covered by the first separator layer and a second separator layer.

48. The device of claim 35, wherein the separator layer has a perimeter extending beyond the perimeter of the anode sub-assembly.

49. The device of claim 35, wherein the separator layer has a perimeter extending beyond the perimeter of the cathode layer.

50. The device of claim 35, wherein the implantable medical device is selected from the group consisting of a PCD, an AID, an ICD, a defibrillator, an implantable pulse generator and a pacemaker.

51. The device claim 35, wherein the energy source is selected from the group consisting of a battery, an electrochemical cell, a primary electrochemical cell, a secondary or rechargeable electrochemical cell, an electrochemical cell comprising a lithium-containing anode, an electrochemical cell comprising a silver vanadium oxide-containing cathode, an electrochemical cell comprising a (CF_n)_x, containing cathode, an electrochemical cell comprising a cathode containing a mixture of silver vanadium oxide and (CF_n)_x, a spirally wound electrochemical cell, an electrochemical cell having a plurality of plate-shaped electrodes, and an electrochemical cell having at least one serpentine electrode disposed therewithin.

52. The device of claim 35, wherein the plurality of anode layers are connected electrically to the case.

53. The device of claim 35, wherein the at least one cathode layer is electrically connected to the case.

54. The device of claim 35, wherein the case is connected electrically to neither the at least one cathode layer nor to the plurality of anode layers.

55. The method of claim 54, further comprising the step of electrically connecting the at least one cathode layer to the case.

56. The method of claim 54, wherein the case providing step further comprises the step of providing an aluminum or aluminum alloy case.

57. A method of registering layers in an electrode assembly for a substantially flat electrolytic capacitor suitable for use in an hermetically sealed implantable medical device, comprising the steps of:

(a) providing at least one cathode layer formed of cathode foil and having a first perimeter, the at least one cathode layer having at least a first means for aligning projecting from the first perimeter at a first predetermined perimeter location, the at least one cathode layer having top and bottom surfaces;

(b) providing a plurality of anode layers formed of anode foil, the plurality of anode layers forming an anode sub-assembly having top and bottom surfaces, at least one of the plurality of anode layers being a first anode layer having a second perimeter and at least a second means for aligning projecting from the second perimeter at a second predetermined perimeter location;

(c) providing at least a first separator layer formed of separator material;

(d) vertically stacking the at least one cathode layer, the plurality of anode layers and the separator layer to form an electrode assembly such that the first separator layer is disposed between the at least one cathode layer and the anode sub-assembly, and

(e) aligning the first aligning means with a first predetermined registration position in the electrode assembly;

(f) aligning the second aligning means with a second predetermined registration position in the electrode assembly, and

(g) placing the electrode assembly in a case of the substantially flat electrolytic capacitor.

58. The method of claim 57, wherein the cathode layer providing step is preceded by a step of forming the cathode layer from an aluminum cathode foil.

59. The method of claim 57, wherein the anode layer providing step is preceded by a step of forming the plurality of anode layers from through-etched aluminum anode foil.

60. The method of claim 57, wherein the anode layer forming step further comprises the step of providing aluminum anode foil having a specific capacitance selected from the group consisting of at least about 0.3 microfarads/cm², at least about 0.5 microfarads/cm², and at least about 0.8 microfarads/cm² for each anode layer contained therein.

61. The method of claim 57, wherein the anode layer forming step further comprises the step of providing aluminum anode foil having a thickness selected from the group consisting of from about 20 micrometers to about 300 micrometers, from about 40 micrometers to about 200 micrometers, from about 60 micrometers to about 150 micrometers, and from about 70 micrometers to about 140 micrometers.

62. The method of claim 57, wherein the cathode layer providing step is preceded by a step of forming the at least one cathode layer from a highly etched cathode foil.

63. The method of claim 57, wherein the cathode layer forming step further comprises the step of providing cathode foil having a specific capacitance selected from the group consisting of at least about 100 microfarads/cm², at least about 200 microfarads/cm², at least about 250 microfarads/cm², and at least about 300 microfarads/cm².

64. The method of claim 57, wherein the cathode layer forming step further comprises the step of providing cathode foil having a thickness selected from the group consisting of from about 10 micrometers to about 200 micrometers, from about 15 micrometers to about 150 micrometers, from about 20 micrometers to about 100 micrometers, from about 25 micrometers to about 75 micrometers, and about 30 micrometers.

65. The method of claim 57, wherein the anode layer providing step is preceded by a step of selecting a plurality of non-notched anode layers and at least one notched anode layer for inclusion in the anode sub-assembly.

66. The method of claim 57, wherein the anode layer providing step is preceded by a step of selecting a plurality of non-notched anode layers and at least one notched anode layer for inclusion in the anode sub-assembly.

67. The method of claim 57, wherein the anode layer providing step is preceded by a step of cold welding the plurality of anode layers together to form the anode sub-assembly.

68. The method of claim 57, wherein the anode layer providing step and the separator layer providing step are preceded by a step of pressure bonding the first separator layer to the anode sub-assembly.

69. The method of claim 57, wherein the anode layer providing step and the separator layer providing step are preceded by a step of covering the top and bottom surfaces of the anode sub-assembly with the first separator layer and a second separator layer.

70. The method of claim 57, wherein the cathode layer providing step and the separator layer providing step are preceded by a step of covering the top and bottom surfaces of the at least one cathode layer with the first separator layer and a second separator layer.

71. The method of claim 57, wherein the anode layer providing step and the separator layer providing step are preceded by a step of forming the first anode layer and a step of forming the first separator layer and a second separator layer, the first and second separator layers each defining third perimeters of substantially equal lengths and substantially equal third surface areas, the second perimeter of the first anode layer defining a second surface area, the second surface area being less than the third surface area.

72. The method of claim 57, wherein the cathode layer providing step and the separator layer providing step are preceded by a step of forming the at least one cathode layer and a step of forming the first separator layer and a second separator layer, the first and second separator layers each defining third perimeters of substantially equal lengths and substantially equal third surface areas, the first perimeter of the at least one cathode layer defining a first surface area, the first surface area being less than the third surface area.

73. The method of claim 57, wherein the separator layer providing step is preceded by a step of forming the first separator layer and a second separator layer such that the physical dimensions of the first and second separator layers are larger than those of the anode layers.

74. The method of claim 57, wherein the separator layer providing step is preceded by a step of forming the first separator layer and a second separator layer such that the physical dimensions of the first and second separator layers are larger than those of the at least one cathode layer.

75. The method of claim 57, wherein the step of vertically stacking the at least one cathode layer, the plurality of anode layers and the separator layer further comprises providing a stacking fixture for registration of the layers therein as the layers are stacked in the fixture.

76. The method of claim 57, wherein the steps of aligning the first and second aligning means further comprises providing a stacking fixture for registration of the first and second aligning means as the layers are stacked in the fixture.

77. The method of claim 57, wherein the vertical stacking step is accomplished using robotic assembly and camera means.

78. The method of claim 57, further comprising the steps of providing a second cathode layer formed of cathode foil and having a third perimeter, providing a second separator layer formed of separator material, the second cathode layer having at least a third means for aligning projecting from the third perimeter at a third predetermined perimeter location, the second cathode layer having top and bottom surfaces, vertically stacking the second cathode layer and the second separator layer on the stacked electrode assembly such that the second separator layer is disposed between the top surface of the anode sub-assembly and the bottom surface of the second cathode layer, aligning the third aligning means with a third predetermined registration position in the electrode assembly, and vertically aligning the first aligning means and the third aligning means such that the first predetermined registration location of the electrode assembly coincides vertically with the third predetermined registration location of the electrode assembly.

79. The method of claim 57, further comprising the steps of providing a second anode sub-assembly comprising a plurality of anode layers formed of aluminum anode foil, the second anode sub-assembly having top and bottom surfaces, at least one of the plurality of anode layers of the second anode sub-assembly being a second anode layer having a fourth perimeter and at least a fourth means for aligning projecting from the fourth perimeter at a fourth predetermined perimeter location, providing a second separator layer formed of separator material, vertically stacking the second anode sub-assembly and the second separator layer in the stacked electrode assembly such that the second separator layer is disposed beneath the bottom surface of the cathode layer and the top surface of the second anode sub-assembly, aligning the fourth aligning means with a fourth predetermined registration position in the electrode assembly, and vertically aligning the second aligning means and the fourth aligning means such that the fourth predetermined registration location of the electrode assembly coincides vertically with the fourth predetermined registration location of the electrode assembly.

80. The method of claim 79, further comprising the step of disposing the substantially flat aluminum electrolytic capacitor in a housing of an hermetically sealed implantable medical device.

81. The method of claim 57, further comprising the step of sealing the substantially flat aluminum electrolytic capacitor with a cover.

82. The method of claim 81, further comprising the step of providing one of a PCD, an ICD, a pacemaker, an IPG, an AID and a defibrillator as the hermetically sealed implantable medical device.