Low impedance oxide resistant grounded capacitor for an AIMD

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.

What is claimed is: 
     
       1. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:
 a) an insulator of electrically non-conductive material, the insulator comprising an outer insulator outer surface extending longitudinally from a first an insulator first end to a second an insulator second end, wherein the insulator has at least one conductor bore extending there through to the first and second insulator first and second ends; 
 b) a ferrule of an electrically conductive material, the ferrule comprising a ferrule sidewall defining a ferrule opening, wherein the insulator is hermetically sealed to the conductive ferrule sidewall in the ferrule opening; 
 c) a conductor comprising an electrically conductive material extending from a first conductor first end to a second conductor second end, wherein the conductor is hermetically sealed and disposed through the at least one conductor bore in the insulator and in a non-conductive relation with the conductive ferrule; 
 d) a filter capacitor, comprising:
 i) a dielectric comprising an outer a dielectric outer surface extending longitudinally from a first dielectric first end to a second dielectric second end; 
 ii) at least one active electrode plate supported by the dielectric in an interleaved, partially overlapping relationship with at least one ground electrode plate; and 
 iii) at least one terminal pin bore extending through the dielectric to the first and second dielectric first and second ends, 
 iv) wherein the second dielectric second end is disposed adjacent to the first insulator first end; 
 
 e) a first metallization electrically contacted to the at least one active electrode plate in the terminal in pin bore; 
 f) a first electrical connection electrically coupling the first metallization to the conductor extending through the terminal pin bore in the dielectric; 
 g) a second metallization electrically contacted to the at least one ground electrode plate at at least a portion of the outer dielectric outer surface; and 
 h) a second electrical connection electrically coupling the second metallization to the ferrule, wherein the second electrical connection comprises:
 i) at least one oxide-resistant metal noble-metal addition supported by the ferrule adjacent to the second metallization, wherein the noble-metal metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof; 
 ii) a first conductive material electrically and physically coupling a first portion of the oxide-resistant metal at least one noble-metal addition directly to the ferrule; and 
 iii) a second conductive material electrically and physically coupling a second portion of the oxide-resistant metal at least one noble-metal addition to the second metallization at the outer dielectric outer surface of the filter capacitor, 
 iv) wherein the first and second conductive materials are different. 
 
 
     
     
       2. The assembly of  claim 1 , wherein the oxide-resistant metal at least one noble-metal addition comprises a different material as compared to the ferrule. 
     
     
       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 is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof. 
     
     
       5. The assembly of  claim 1 , wherein the first conductive material is a weld portion of the oxide-resistant metal at least one noble-metal addition electrically and physically coupling to the ferrule. 
     
     
       6. The assembly of  claim 1 , wherein the first conductive material comprises a brazed metal electrically and physically coupling the oxide-resistant metal the at least one noble-metal addition to the ferrule. 
     
     
       7. The assembly of  claim 6 , wherein the brazed metal comprising the oxide-resistant metal addition is selected from the group consisting of 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 the conductor comprises a leadwire. 
     
     
       9. The assembly of  claim 8 , wherein the leadwire is selected from the group consisting of platinum, palladium, silver, and gold. 
     
     
       10. The assembly of  claim 1 , wherein the first side of the insulator is flush with the ferrule adjacent to the second dielectric second end of the filter capacitor. 
     
     
       11. 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 the conductor bore and extending from the first insulator first end to the second insulator second end of the alumina substrate. 
     
     
       12. The assembly of  claim 11 , wherein the platinum fill forms a tortuous and mutually conformal knitline or interface at the hermetic seal to the alumina substrate comprising the insulator, and wherein the hermetic seal has a leak rate that is no greater than 1×10 −7  std cc He/sec. 
     
     
       13. The assembly of  claim 12 , wherein the alumina dielectric substrate and the platinum fill are characterized as the alumina dielectric substrate being in a green state having a first inherent shrink rate during a heat treatment that is greater than a second inherent shrink rate of the platinum fill in the green state during the heat treatment. 
     
     
       14. The assembly of  claim 1 , wherein the oxide-resistant metal the at least one noble-metal addition is selected from the group consisting of a wire, a pad, an L-shaped pad, and an L-shaped pad with cutouts. 
     
     
       15. The assembly of  claim 1 , including a ground wire disposed through both the insulator and the dielectric of the filter capacitor, where the ground wire is not electrically coupled to the at least one active and ground electrode plates, but is electrically coupled to the ferrule. 
     
     
       16. The assembly of  claim 15 , wherein the ferrule comprises an integrally formed conductive peninsula, and wherein the ground wire is electrically coupled to the peninsula. 
     
     
       17. The assembly of  claim 1 , wherein the feedthrough capacitor has a resonant frequency above 400 MHz. 
     
     
       18. The assembly of  claim 1 , wherein the feedthrough capacitor has a capacitance of from 300 picofarads to 10,000 picofarads. 
     
     
       19. The assembly of  claim 1 , wherein the second conductive material is selected from a solder and a thermal-setting conductive adhesive. 
     
     
       20. The assembly of  claim 1 , wherein the first and second conductor first and second ends are spaced from the respective first and second insulator first and second ends. 
     
     
       21. The assembly of  claim 1 , wherein the at least one oxide-resistant metal noble-metal addition is received in a pocket in the ferrule. 
     
     
       22. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:
 a) a ferrule comprising a conductive peninsula or extension; 
 b) an insulator hermetically sealed to the conductive ferrule; 
 c) 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; 
 d) 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; 
 e) a first low impedance electrical connection between the first end metallization and the conductor; 
 f) 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 peninsula or extension; and 
 g) 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. 
 
     
     
       23. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:
 a) an insulator of electrically non-conductive material, the insulator comprising an outer insulator surface extending longitudinally from a first an insulator first end to a second an insulator second end, wherein the insulator has at least one conductor bore extending there through to the first and second insulator first and second ends; 
 b) a ferrule of an electrically conductive material, the ferrule comprising' a ferrule sidewall including a peninsula and defining a ferrule opening, wherein the insulator is hermetically sealed to the conductive ferrule in the ferrule opening; 
 c) a conductor comprising an electrically conductive material extending from a first conductor first end to a second conductor second end, wherein the conductor is hermetically sealed and disposed through the at least one conductor bore in the insulator and in a non-conductive relation with the conductive ferrule; 
 d) a filter capacitor located adjacent to the first insulator first end, the filter capacitor comprising:
 i) a dielectric comprising an outer a dielectric outer surface extending longitudinally from a first dielectric first end to a second dielectric second end; 
 ii) at least one active electrode plate supported by the dielectric in an interleaved, partially overlapping relationship with at least one ground electrode plate; and 
 iii) at least one terminal pin bore extending through the dielectric to the first and second dielectric first and second ends, 
 iv) wherein the second dielectric second end is disposed adjacent to the first insulator first side; 
 
 e) a first metallization electrically contacted to the at least one active electrode plate in the terminal pin bore; 
 f) a first electrical connection electrically coupling the first metallization to the conductor extending through the terminal pin bore in the dielectric; 
 g) a second metallization electrically contacted to the at least one ground electrode plate at the outer dielectric outer surface; 
 h) a ground conductor disposed through the filter capacitor in non-conductive relation with the at least one ground and active electrode plates, wherein the ground conductor is electrically coupled to the conductive peninsula; and 
 i) a second electrical connection electrically coupling the second metallization to the ferrule, wherein the second electrical connection comprises:
 i) at least one noble-metal addition supported by the ferrule adjacent to the second metallization, wherein the noble-metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof; 
 ii) a first conductive material electrically and physically coupling a first portion of the oxide-resistant metal noble-metal addition to the ferrule; and 
 iii) a second conductive material electrically and physically coupling a second portion of the noble metal noble-metal addition to the second metallization at the outer dielectric surface of the filter capacitor, 
 iv) wherein the first and second conductive materials are different. 
 
 
     
     
       24. The assembly of  claim 23 , wherein the first conductive material is a weld portion of the oxide-resistant metal noble-metal addition electrically and physically coupling to the ferrule. 
     
     
       25. The assembly of  claim 23 , wherein the first conductive material comprises a brazed metal electrically and physically coupling the oxide-resistant metal noble-metal addition to the ferrule. 
     
     
       26. The assembly of  claim 23 , wherein the second conductive material is selected from a solder and a thermal-setting conductive adhesive. 
     
     
       27. The assembly of  claim 23 , wherein the second conductive material does not contact the conductive material. 
     
     
       28. An implantable medical device, comprising:
 a) a thermally or electrically conductive AIMD housing containing at least one of tissue-stimulating and biological-sensing circuits for the AIMD, wherein the housing has an opening providing passage from a body fluid side outside the housing to a device side inside the housing; and 
 b) a filtered feedthrough assembly hermetically sealed in the housing opening, the filtered feedthrough assembly comprising:
 i) an insulator of electrically non-conductive material, the insulator comprising an outer insulator outer surface extending from a body fluid side an insulator body fluid side end to a device side an insulator device side end, wherein the insulator has at least one conductor bore extending there through to the body fluid and device side insulator body fluid and device side ends; 
 ii) a ferrule of an electrically conductive material electrically and physically connected to the housing in the housing opening, the ferrule comprising a ferrule sidewall having an inner a ferrule inner sidewall surface defining a ferrule opening and an outer a ferrule outer sidewall surface hermetically sealed to the device housing, wherein the insulator is received in the ferrule opening and hermetically sealed to the ferrule at the inner ferrule inner surface; 
 iii) a conductor comprising an electrically conductive material extending from a body fluid side conductor body fluid side end to a device side conductor device side end, wherein the conductor is hermetically sealed and disposed through the at least one conductor bore in the insulator and in a non-conductive relation with the conductive ferrule; 
 iv) a filter capacitor, comprising:
 A) a dielectric comprising an outer a dielectric outer surface extending from a first dielectric first end to a second dielectric second end; 
 B) at least one active electrode plate supported by the dielectric in an interleaved, partially overlapping relationship with at least one ground electrode plate; and 
 C) at least one terminal pin bore extending through the dielectric to the first and second dielectric first and second ends, 
 D) wherein the second end of the capacitor dielectric is located adjacent to the device side of the insulator; 
 
 v) a first metallization electrically contacted to the at least one active electrode plate in the terminal pin bore; 
 vi) a first electrical connection electrically coupling the first metallization to the conductor in the terminal pin bore extending through the dielectric; 
 vii) a second metallization electrically contacted to the at least one ground electrode plate at the outer dielectric outer surface; and 
 viii) a second electrical connection electrically coupling the second metallization to the ferrule, wherein the second electrical connection comprises:
 A) at least one oxide-resistant metal noble-metal addition supported by the ferrule adjacent to the second metallization, wherein the at least one noble-metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof; 
 B) a first conductive material electrically and physically coupling a first portion of the oxide-resistant metal at least one noble-metal addition directly to the ferrule hermetically sealed to the device housing; and 
 C) a second conductive material electrically and physically coupling a second portion of the oxide-resistant metal at least one noble-metal addition to the second metallization at the outer dielectric outer surface of the filter capacitor, 
 D) wherein the first and second conductive materials are different. 
 
 
 
     
     
       29. The implantable medical device of  claim 28 , wherein the first conductive material is a weld portion of the oxide-resistant metal at least one noble-metal addition electrically and physically coupling to the ferrule. 
     
     
       30. The implantable medical device of  claim 28 , wherein the first conductive material comprises a brazed metal electrically and physically coupling the oxide-resistant metal at least one noble-metal addition to the ferrule. 
     
     
       31. The implantable medical device of  claim 28 , wherein the second conductive material is selected from a solder and a thermal-setting conductive adhesive. 
     
     
       32. The implantable medical device of  claim 28 , wherein the second conductive material, does not contact the ferrule. 
     
     
       33. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:
 a) an insulator of electrically non-conductive material, the insulator comprising an outer insulator outer surface extending from a first an insulator first end to a second an insulator second end, wherein the insulator has at least one conductor bore extending there through to the first and second insulator first and second ends; 
 b) a ferrule of an electrically conductive material, the ferrule comprising a ferrule sidewall defining a ferrule opening, wherein the insulator is hermetically sealed to the conductive ferrule sidewall in the ferrule opening; 
 c) a conductor comprising an electrically conductive material extending from a first conductor first end to a second conductor second end, wherein the conductor is hermetically sealed and disposed through the at least one conductor bore in the insulator and in a non-conductive relation with the conductive ferrule; 
 d) a filter capacitor, comprising:
 i) a dielectric comprising an outer a dielectric outer surface extending from a first dielectric first end to a second dielectric second end; 
 ii) at least one active electrode plate supported by the dielectric in an interleaved, partially overlapping relationship with at least one ground electrode plate; and 
 iii) at least one terminal pin bore extending through the dielectric to the first and second dielectric first and second ends, 
 iv) wherein the second dielectric second end is disposed adjacent to the first insulator first end; 
 
 e) a first metallization electrically contacted to the at least one active electrode plate in the terminal pin bore; 
 f) a first electrical connection electrically coupling the first metallization to the conductor extending through the terminal pin bore in the dielectric; 
 g) a second metallization electrically contacted to the at least one ground electrode plate at the outer dielectric outer surface; and 
 h) a second electrical connection electrically coupling the second metallization to the ferrule, wherein the second electrical connection comprises:
 i) at least one noble-metal addition supported by the ferrule adjacent to the second metallization, wherein the at least one noble-metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof; 
 ii) a weld portion of the oxide-resistant metal at least one noble-metal addition electrically and physically coupling to the ferrule; and 
 iii) a solder or thermal-setting material electrically and physically coupling a second portion of the oxide-resistant metal at least one noble-metal addition to the second metallization at the outer dielectric outer surface of the filter capacitor.