LOW IMPEDANCE OXIDE RESISTANT GROUNDED CAPACITOR FOR AN AIMD

• US 20140194964A1
• Filed: 03/10/2014
• Published: 07/10/2014
• Est. Priority Date: 03/20/2008
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Inventors: Woods, Jason, Brendel, Richard L., Stevenson, Robert A., Williams, Christopher M., Naugler, Robert, Frysz, Christine A.
• Granted Patent: US 9,108,066 B2
• Time in Patent Office: Days
• US Class Current: 607/119
• CPC Class Codes: A61N 1/3754 Feedthroughs
• CPC Class Codes: H01G 2/02 Mountings
• CPC Class Codes: H01G 4/228 Terminals
• CPC Class Codes: H01G 4/35 Feed-through capacitors or anti-noise capacitors
• CPC Class Codes: H01G 4/40 Structural combinations of fixed capacitors with other electric elements, the structure mainly consisting of a capacitor, e.g. RC combinations
• CPC Class Codes: H01R 13/7195 with planar filters with openings for contacts
• CPC Class Codes: H03H 1/0007 of radio frequency interference filters
• CPC Class Codes: H03H 2001/0042 Wound, ring or feed-through type capacitor
• CPC Class Codes: H03H 2001/0085 Multilayer, e.g. LTCC, HTCC, green sheets inside PCB filters H05K
• CPC Class Codes: H03H 7/1766 Parallel LC in series path H03H7/1783 takes precedence

Abstract

A hermetically sealed filtered feedthrough assembly for an AIMD includes an insulator hermetically sealed to a conductive ferrule or housing. A conductor is hermetically sealed and disposed through the insulator in non-conductive relation to the conductive ferrule or housing between a body fluid side and a device side. A feedthrough capacitor is disposed on the device side. A first low impedance electrical connection is between a first end metallization of the capacitor and the conductor. A second low impedance electrical connection is between a second end metallization of the capacitor and the ferrule or housing. The second low impedance electrical connection includes an oxide-resistant metal addition attached directly to the ferrule or housing and an electrical connection coupling the second end metallization electrically and physically directly to the oxide-resistant metal addition.

Claims

1. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:

an insulator hermetically sealed to a conductive ferrule or housing;

a conductor hermetically sealed and disposed through the insulator in non-conductive relation to the conductive ferrule or housing between a body fluid side and a device side;

a feedthrough capacitor located on the device side, the feedthrough capacitor comprising a first and a second end metallization, wherein the first end metallization is connected to at least one active electrode plate and wherein the second end metallization is connected to at least one ground electrode plate, wherein the at least one active electrode plate is interleaved and disposed parallel to the at least one ground electrode plate, wherein the at least one active and ground electrode plates are disposed within a capacitor dielectric;

a first low impedance electrical connection between the first end metallization and the conductor; and

a second low impedance electrical connection between the second end metallization and the ferrule or housing, wherein the second low impedance electrical connection comprises an oxide-resistant metal addition attached directly to the ferrule or housing and an electrical connection coupling the second end metallization electrically and physically directly to the oxide-resistant metal addition.

2. The assembly of claim 1, wherein the oxide-resistant metal addition comprises a different material as compared to the ferrule or housing.

3. The assembly of claim 1, wherein the oxide-resistant metal addition comprises a noble metal.

4. The assembly of claim 1, wherein the oxide-resistant metal addition comprises gold, platinum, palladium, silver and combinations thereof.

5. The assembly of claim 1, wherein the oxide-resistant metal addition is laser welded to the ferrule or housing.

6. The assembly of claim 1, wherein the oxide-resistant metal addition comprises a brazed metal.

7. The assembly of claim 6, wherein the brazed metal oxide-resistant metal addition comprises gold, gold-based metal, platinum, platinum based metal, palladium, palladium based metal, silver, silver based metal, gold-palladium, gold-boron, and palladium-silver

8. The assembly of claim 1, wherein a grounding loop is defined on the device side comprising the first low impedance electrical connection and the second low impedance connection from the conductor through the feedthrough capacitor to the ferrule or housing.

9. The assembly of claim 8, wherein the total resistance of the grounding loop is less than 1 milliohm.

10. The assembly of claim 8, wherein the total inductance of the grounding loop is less than 10 nanohenries.

11. The assembly of claim 8, wherein the total inductance of the grounding loop is less than 1 nanohenries.

12. The assembly of claim 1, wherein the conductor comprises a leadwire.

13. The assembly of claim 12, wherein the leadwire comprises platinum, palladium, silver or gold.

14. The assembly of claim 1, wherein the insulator is flush with the ferrule or housing on the device side.

15. The assembly of claim 1, wherein the insulator comprises an alumina substrate comprised of at least 96% alumina and the conductor comprises a substantially closed pore and substantially pure platinum fill disposed within a via hole and extending between the body fluid side and the device side of the alumina substrate.

16. The assembly of claim 15, including a hermetic seal between the platinum fill and the alumina substrate, wherein the platinum fill forms a tortuous and mutually conformal knitline or interface between the alumina substrate and the platinum fill, wherein the hermetic seal has a leak rate that is no greater than 1×

10<sup>−

7</sup> std cc He/sec.

17. The assembly of claim 16, wherein an inherent shrink rate during a heat treatment of the alumina dielectric substrate in a green state is greater than that of the platinum fill in the green state.

18. The assembly of claim 1, wherein the oxide-resistant metal addition comprises a wire, a pad, an L-shaped pad or an L-shaped pad with cutouts.

19. The assembly of claim 1, including a ground wire disposed through both the insulator and the feedthrough capacitor, where the ground wire is not electrically coupled to the at least one active and ground electrode plate.

20. The assembly of claim 19, wherein the ferrule or housing comprises an integrally formed conductive peninsula, where the ground wire is electrically coupled to the peninsula.

21. The assembly of claim 1, wherein the feedthrough capacitor comprises a resonant frequency above 400 MHz.

22. The assembly of claim 1, wherein the feedthrough capacitor comprises a capacitance of between 300 picofarads and 10,000 picofarads.

23. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:

an insulator hermetically sealed to a conductive ferrule;

a conductor hermetically sealed and disposed through the insulator in non-conductive relation to the conductive ferrule between a body fluid side and a device side;

a feedthrough capacitor located on the device side, the feedthrough capacitor comprising a first and a second end metallization, wherein the first end metallization is connected to at least one active electrode plate and wherein the second end metallization is connected to at least one ground electrode plate, wherein the at least one active electrode plate is interleaved and disposed parallel to the at least one ground electrode plate, wherein the at least one active and ground electrode plates are disposed within a capacitor dielectric;

a first low impedance electrical connection between the first end metallization and the conductor;

an oxide-resistant metal addition attached directly to the ferrule; and

a second low impedance electrical connection coupling the second end metallization electrically and physically directly to the oxide-resistant metal addition.

24. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:

a ferrule comprising a conductive peninsula or extension;

an insulator hermetically sealed to the conductive ferrule;

a conductor hermetically sealed and disposed through the insulator in non-conductive relation to the conductive ferrule between a body fluid side and a device side;

a feedthrough capacitor located on the device side, the feedthrough capacitor comprising a first and a second end metallization, wherein the first end metallization is connected to at least one active electrode plate and wherein the second end metallization is connected to at least one ground electrode plate, wherein the at least one active electrode plate is interleaved and disposed parallel to the at least one ground electrode plate, wherein the at least one active and ground electrode plates are disposed within a capacitor dielectric;

a first low impedance electrical connection between the first end metallization and the conductor;

a ground conductor disposed through the feedthrough capacitor in non-conductive relation with the at least one ground and active electrode plates, where the ground conductor is electrically coupled to the conductive peninsular or extension; and

an oxide-resistant metal addition attached directly at one end to the ground conductor and connected at the other end to the second end metallization of the feedthrough capacitor.