Monolithic ceramic capacitor with barium titinate dielectric curie point optimized for active implantable medical devices operating at 37° C.

• US 6,567,259 B2
• Filed: 09/20/2002
• Issued: 05/20/2003
• Est. Priority Date: 05/31/2001
• Status: Expired due to Fees

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch-Sierra, Inc.
• Inventors: Roberts, John E., Haskell, Donald K., Stevenson, Robert A.
• Primary Examiner(s): Dinkins, Anthony
• Application Number:
  US10/251,672
• Publication Number:
  US 20030053284A1
• Time in Patent Office: 242 Days
• Field of Search: 361/302, 361/306.1, 361/303, 361/328, 361/329, 361/330, 333/182, 333/184, 333/185
• US Class Current: 361/302
• CPC Class Codes: A61N 1/3754 Feedthroughs
• CPC Class Codes: H01G 4/35 Feed-through capacitors or anti-noise capacitors

Abstract

A feedthrough filter capacitor assembly for use in active implantable medical devices and a related process for manufacturing a monolithic ceramic capacitor utilizing dielectric materials having a dielectric constant greater than 7000, and preferably in the range of 8500 to 22,000. In the manufacture of the monolithic ceramic capacitor, one or more Curie point shifters and/or other dopants are added to the dielectric material to optimize the dielectric constant at the human body temperature of 37° C. For manufacturing purposes, dopants may be added to the dielectric material to broaden the Curie point peak or point of maximum dielectric constant thereof. The effect is that when such capacitors and terminal assemblies are utilized in a high-voltage defibrillator circuit of an implantable medical device, the dielectric material is optimized so that during the delivery of high-voltage electrical energy, capacitance value of the capacitor drops substantially.

Claims

1. A feedthrough filter capacitor assembly for use in an active implantable medical device, comprising:

at least one conductive terminal pin;

a feedthrough filter capacitor having first and second sets of electrode plates disposed within a dielectric material having a dielectric constant greater than 7000, and a first passageway through which the terminal pin extends in conductive relation with the first set of electrode plates, wherein the feedthrough filter capacitor is optimized for operation within the range of 30°

C. to 40°

C.; and

a conductive ferrule through which the terminal pin passes in non-conductive relation.

2. The feedthrough filter capacitor assembly of claim 1, wherein the feedthrough filter capacitor is optimized for operation and 37°

C.

3. The feedthrough filter capacitor assembly of claim 1, wherein the dielectric constant of the dielectric material is within the range of 8500 to 22,000.

4. The feedthrough filter capacitor assembly of claim 2, wherein the dielectric material of the feedthrough filter capacitor includes at least one dopant used to shift the Curie point to 37°

C.

5. The feedthrough filter capacitor assembly of claim 4, including a Curie point depressor for broadening the temperature bandwidth of the Curie point peak.

6. The feedthrough filter capacitor assembly of claim 4, wherein the at least one dopant is taken from the group of strontium titinate, lead titinate, zirconium dioxide, barium carbonate, zinc oxide, zinc borate, manganese carbonate, and titanium dioxide.

7. The feedthrough filter capacitor assembly of claim 2, wherein the dielectric material of the feedthrough filter capacitor includes at least one dopant used to shift the point of maximum dielectric constant to 37 degrees C.

8. The feedthrough filter capacitor assembly of claim 1, wherein the active implantable medical device is taken from the group of:

cardiac pacemakers, ICD'"'"'s, hearing implants, congestive heart failure treatment devices, atrial defibrillators, bi-ventricular pacemakers, neurostimulators, brain stimulators, bladder control stimulators, artificial eyes, artificial noses, RF muscle actuators, implanted limb manipulation systems, artificial hearts, and ventricular assist devices.

9. The feedthrough filter capacitor assembly of claim 1, including an insulator disposed within the ferrule, for mounting the conductive terminal pin for passage through the conductive ferrule with the conductive terminal pin and the ferrule in non-conductive relation.

10. A feedthrough filter capacitor assembly for use in active implantable medical devices, comprising:

at least one conductive terminal pin;

a conductive ferrule through which the terminal pin passes in non-conductive relation;

a feedthrough filter capacitor having first and second sets of electrode plates disposed within a dielectric material having a dielectric constant greater than 7000, and a first passageway through which the terminal pin extends in conductive relation with the first set of electrode plates, wherein the feedthrough filter capacitor is optimized for operation at 37°

C.; and

a ground lead which extends into a second passageway through the feedthrough filter capacitor, wherein the ground lead is conductively coupled to the second set of electrode plates and the conductive ferrule.

11. The feedthrough filter capacitor assembly of claim 10, including an insulator disposed within the ferrule, for mounting the conductive terminal pin for passage through the conductive ferrule with the conductive terminal pin and the ferrule in non-conductive relation.

12. The feedthrough filter capacitor assembly of claim 10, including means for hermetically sealing passage of the terminal pin through the conductive ferrule.

13. The feedthrough filter capacitor assembly of claim 10, wherein the dielectric constant of the dielectric material is within the range of 8500 to 22,000.

14. The feedthrough filter capacitor assembly of claim 13, wherein the dielectric material of the feedthrough filter capacitor includes at least one dopant used to shift the point of maximum dielectric constant to 37 degrees C.

15. The feedthrough filter capacitor assembly of claim 14, including a Curie point depressor for broadening the temperature bandwidth of the Curie point peak.

16. The feedthrough filter capacitor assembly of claim 15, wherein the at least one dopant is taken from the group of strontium titinate, lead titinate, zirconium dioxide, barium carbonate, zinc oxide, zinc borate, manganese carbonate, and titanium dioxide.

17. The feedthrough filter capacitor assembly of claim 13, wherein the dielectric material of the feedthrough filter capacitor includes at least one dopant used to shift the Curie point to 37°

C.

18. A process for manufacturing a monolithic chip capacitor for use in an active implantable medical device, comprising the steps of:

providing a dielectric material having a dielectric constant greater than 7000;

adding one of more Curie point shifters to the dielectric material to optimize the monolithic chip capacitor dielectric constant at the human body temperature of 37°

C.; and

processing the dielectric material with the added shifters into a finished monolithic chip capacitor having first and second sets of electrode plates disposed therein.

19. The process of claim 18, including the step of adding a dopant to broaden the Curie point peak of the dielectric material.

20. The process of claim 18, wherein the monolithic chip capacitor comprises a feedthrough filter capacitor.

21. The process of claim 18, wherein the monolithic chip capacitor is optimized for use in an electromagnetic interference filter.

22. The process of claim 18, including the step on installing the capacitor in a high-voltage defibrillator circuit of an implantable medical device.

23. The process of claim 22, wherein the dielectric material is further optimized so that during the delivery of high-voltage electrical energy, capacitance value of the monolithic chip capacitor drops to less than 65% of its initial value.

24. The process of claim 23, wherein the capacitance value of the monolithic chip capacitor drops to less than 20% of the initial value.

25. The process of claims 23, wherein the high-voltage electrical energy comprises a bi-phasic or mono-phasic fast rise time defibrillation pulse.

26. A process for manufacturing a monolithic chip capacitor for use in an active implantable medical device, comprising the steps of:

providing a dielectric material having a dielectric constant greater than 7000;

adding one or more Curie point shifters to the dielectric material to shift the point of maximum dielectric constant to 37 degrees C.;

adding a dopant to broaden the Curie point peak of the dielectric material;

optimizing the dielectric material so that during the delivery of high-voltage electrical energy, capacitance value of the monolithic chip capacitor drops to less than 65% of its initial value; and

processing the dielectric material with the added shifters and dopant into a finished monolithic chip capacitor having first and second sets of electrode plates disposed therein.

27. The process of claim 26, wherein the monolithic chip capacitor comprises a feedthrough filter capacitor.

28. The process of claim 27, wherein the monolithic chip capacitor is optimized for use in an electromagnetic interference filter.

29. The process of claim 28, including the step on installing the capacitor in a high-voltage defibrillator circuit of an implantable medical device.

30. The process of claim 26, wherein the capacitance value of the monolithic chip capacitor drops to less than 20% of the initial value.

31. The process of claim 26, wherein the high-voltage electrical energy comprises a bi-phasic or mono-phasic fast rise time defibrillation pulse.