Capacitive filtered feedthrough array for an implantable medical device

• US 6,414,835 B1
• Filed: 03/01/2000
• Issued: 07/02/2002
• Est. Priority Date: 03/01/2000
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Strom, James, Wolf, William D., Seifried, Lynn M., Wiklund, Craig L., Fraley, Mary A., Volmering, James E., Haq, Samuel F., Malone, Patrick F.
• Primary Examiner(s): Reichard, Dean A.
• Assistant Examiner(s): Thomas, Eric W.
• Application Number:
  US09/515,385
• Time in Patent Office: 853 Days
• Field of Search: 361/301.2, 361/301.4, 361/302, 361/303, 361/306.3, 361/306.1, 361/307, 361/311, 361/312, 361/313, 361/321--32, 607/5
• 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
• CPC Class Codes: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 1/112 directly combined with via connections
• CPC Class Codes: H05K 1/162 incorporating printed capacitors
• CPC Class Codes: H05K 3/4611 by laminating two or more circuit boards H05K3/4652 takes precedence
• CPC Class Codes: H05K 3/4629 laminating inorganic sheets comprising printed circuits, e.g. green ceramic sheets

Abstract

A capacitive filtered feedthrough assembly is formed in a solid state manner to employ highly miniaturized conductive paths each filtered by a discoid capacitive filter embedded in a capacitive filter array. A non-conductive, co-fired metal-ceramic substrate is formed from multiple layers that supports one or a plurality of substrate conductive paths and it is brazed to a conductive ferrule, adapted to be welded to a case, using a conductive, corrosion resistant braze material. The metal-ceramic substrate is attached to an internally disposed capacitive filter array that encloses one or a plurality of capacitive filter capacitor active electrodes each coupled to a filter array conductive path and at least one capacitor ground electrode. Each capacitive filter array conductive path is joined with a metal-ceramic conductive path to form a feedthrough conductive path. Bonding pads are attached to the internally disposed ends of each feedthrough conductive path, and corrosion resistant, conductive buttons are attached to and seal the externally disposed ends of each feedthrough conductive path. A plurality of conductive, substrate ground paths are formed extending through the co-fired metal-ceramic substrate between internally and externally facing layer surfaces thereof and electrically isolated from the substrate conductive paths. The capacitor ground electrodes are coupled electrically to the plurality of conductive, substrate ground paths and to the ferrule.

Claims

1. A filtered feedthrough assembly adapted to be fitted into an opening of a case of an electronic device, the feedthrough assembly having an internally disposed portion configured to be disposed inside the case and an externally disposed portion configured to be disposed outside the case, the assembly comprising:

an electrically conductive ferrule having a ferrule wall adapted to be fitted into the case opening with an inner wall surface defining a centrally disposed ferrule opening and extending between opposed internally and externally facing ferrule sides;

a multi-layer, co-fired metal-ceramic substrate having opposed internally facing and externally facing substrate surfaces joined by a common substrate edge, the metal-ceramic substrate further comprising;

a plurality of metal-ceramic substrate layers each having internally and externally facing layer surfaces;

a plurality of substrate conductive paths extending through the co-fired metal-ceramic substrate between the internally and externally facing layer surfaces and electrically isolated from one another; and

a further plurality of substrate ground paths extending through the co-fired metal-ceramic substrate between the internally and externally facing layer surfaces and electrically isolated from the substrate conductive paths;

means for hermetically sealing the common substrate edge to the ferrule inner wall within the centrally disposed ferrule opening and electrically coupling the plurality of substrate ground paths to the ferrule;

a discoidal capacitive filter array formed of a ceramic capacitive filter substrate having an internally facing filter substrate side and an externally facing filter substrate side joined by a common filter substrate edge, the capacitive filter array substrate further comprising;

a plurality of filter array conductive paths electrically isolated from one another and extending between the internally facing filter substrate side and the externally facing filter substrate side; and

a plurality of discoidal capacitor filters each comprising at least one capacitor active electrode formed within the filter substrate and extending outward from a filter array conductive path and a common capacitor ground electrode;

means for mechanically joining the externally facing filter substrate side to the internally facing substrate side and electrically joining each filter array conductive path to a substrate conductive path; and

means for electrically coupling the common capacitor ground electrode of the discoidal capacitor filters to the plurality of substrate ground paths;

whereby the filtered feedthrough assembly provides a plurality of miniaturized, electrically isolated, and capacitively filtered, feedthrough conductive paths with low inductance each comprising a substrate conductive path joined to a filter array conductive path and extending between the internally disposed portion and the externally disposed portion when the feedthrough assembly is affixed into an opening in the case of the electronic device.

2. The filtered feedthrough assembly of claim 1, wherein the case of the electronic device and the ferrule are formed of metallic materials amenable to being welded together, the electrically conductive ferrule further comprises a welding flange extending outwardly of the ferrule wall away from the ferrule opening for a predetermined distance defining a flange width, and the flange formed with a stress relieving thickness for absorbing stress caused by thermal welding energy applied to the ferrule and flange in the process of welding the flange to the case.

3. The filtered feedthrough assembly of claim 2, wherein the co-fired metal-ceramic substrate ceramic material comprises one of the group consisting essentially of alumina, aluminum nitride, beryllium oxide, and silicon dioxide that has a coefficient of thermal expansion (CTE) compatible with the CTE of the material of the ferrule.

4. The filtered feedthrough assembly of claim 3, wherein the ferrule is formed of a conductive material selected from the group consisting of niobium, titanium, titanium alloys such as titanium-6Al-4V or titanium-vanadium, platinum, molybdenum, zirconium, tantalum, vanadium, tungsten, iridium, rhodium, rhenium, osmium, ruthenium, palladium, silver, and alloys, mixtures and combinations thereof.

5. The filtered feedthrough assembly of claim 1, wherein:

the metal-ceramic substrate further comprises a plurality of planar ceramic layers shaped in a green state to have a layer thickness and a plurality of substrate conductive path via holes and common ground via holes extending therethrough between an internally facing layer surface and an externally facing layer surface, the plurality of ceramic layers assembled together and co-fired from the green state to form the substrate;

each of the plurality of substrate conductive paths extending through the co-fired metal-ceramic substrate between the internally and externally facing layer surfaces and electrically isolated from one another further comprise a plurality of electrically conductive vias extending through via holes of the plurality of layer thicknesses and a plurality of electrically conductive traces formed on certain of the internally or externally facing layer surfaces such that the conductive traces join the conductive vias to form each substrate conductive path; and

each of the further plurality of substrate ground paths extending through the co-fired metal-ceramic substrate between the internally and externally facing layer surfaces comprise a plurality of electrically conductive vias extending through via holes of the plurality of layer thicknesses and at least one conductive trace formed on certain of the internally or externally facing layer surfaces and extending to the substrate edge to enable electrical joinder of the ground vias in common and to the ferrule through the means for hermetically sealing the common substrate edge to the ferrule inner wall within the centrally disposed ferrule opening.

6. The filtered feedthrough assembly of claim 5, wherein the means for hermetically sealing the common substrate edge to the ferrule inner wall within the centrally disposed ferrule opening and electrically coupling the plurality of substrate ground paths to the ferrule comprises a substrate-ferrule braze joint formed of a conductive braze material.

7. The filtered feedthrough assembly of claim 5, wherein each of the plurality of substrate conductive paths extending through the co-fired metal-ceramic substrate between the internally and externally facing layer surfaces further comprise:

a substrate conductor braze pad on the substrate internally facing side comprising part of the means for mechanically joining the externally facing filter substrate side to the internally facing substrate side and electrically joining each filter array conductive path to a substrate conductive path;

a substrate conductor braze pad on the substrate externally facing side; and

an externally disposed bonding button mechanically supported on the externally facing metal-ceramic substrate side and electrically connected with an electrical path of the metal-ceramic substrate through the braze pad on the substrate externally facing side.

8. The filtered feedthrough assembly of claim 7, wherein the externally disposed bonding buttons are formed of a conductive material selected from the group consisting of niobium, platinum or a platinum-iridium alloy, titanium, titanium alloys such as titanium-6Al-4V or titanium-vanadium, molybdenum, zirconium, tantalum, vanadium, tungsten, iridium, rhodium, rhenium, osmium, ruthenium, palladium, silver, and alloys, mixtures and combinations thereof.

9. The filtered feedthrough assembly of claim 7, wherein the exterior facing surface of the metal-ceramic substrate is formed with a plurality of spaced apart button cavities aligned with the plurality of substrate conductor paths extending through the externally facing ceramic layer of the metal-ceramic substrate, each conductor hole receiving a substrate conductor braze pad and an externally disposed bonding button therein.

10. The filtered feedthrough assembly of claim 7, wherein the substrate conductive paths are formed of a conductive paste applied by screen printing to said ceramic layers in the green state to form the traces and fill the via holes, the conductive paste selected from the group consisting of copper, tungsten, molybdenum and gold.

11. The filtered feedthrough assembly of claim 7, wherein:

each filter array conductive path further comprises a filter array hole extending between the internally facing filter substrate side and the externally facing filter substrate side and through at least one capacitor active electrode; and

the means for mechanically joining the externally facing filter substrate side to the internally facing substrate side and electrically joining each filter array conductive path to a substrate conductive path comprises reflow solder filling the filter array holes and mechanically bonded with the substrate conductor braze pads on the substrate internally facing side, whereby the reflow solder within each filter array hole forms at least part of a filter array conductive path.

12. The filtered feedthrough assembly of claim 11, wherein the filter array conductive paths further comprise a plurality of internally disposed bonding pads adhering to the reflow solder filling the plurality of filter array holes on the internally facing side of the capacitive filter array.

13. The filtered feedthrough assembly of claim 12, wherein the internally disposed bonding pads are formed of a conductive material selected from the group consisting of copper, nickel, gold and aluminum and alloys, mixtures and combinations thereof.

14. The filtered feedthrough assembly of claim 7, wherein:

each capacitive filter comprises a plurality of capacitor active electrodes formed within the filter substrate and extending outward from a filter array conductive path, a further plurality of capacitor ground electrodes formed within the filter substrate and extending inward from the filter substrate edge, and a termination layer overlying the filter substrate edge electrically coupling the capacitor ground electrodes together.

15. The filtered feedthrough assembly of claim 14, wherein:

each filter array conductive path further comprises a filter array hole extending between the internally facing filter substrate side and the externally facing filter substrate side and through the plurality of capacitor active electrodes, and a hole metallization layer within the hole electrically coupling the capacitor active electrodes together; and

the means for mechanically joining the externally facing filter substrate side to the internally facing substrate side and electrically joining each filter array conductive path to a substrate conductive path comprises reflow solder filling the filter array holes and mechanically bonded with the hole metallization layer and the substrate conductor braze pads on the substrate internally facing side, whereby the reflow solder within each filter array hole forms at least part of a filter array conductive path.

16. The filtered feedthrough assembly of claim 1, wherein:

the filter conductive paths further comprise a plurality of internally disposed bonding pads supported along the Internally facing filter substrate side, each internally disposed bonding pad electrically conducted with a filter array conductive path of the capacitive filter array; and

the substrate conductive paths further comprise a plurality of externally disposed bonding buttons supported along the externally facing metal-ceramic substrate side, each externally disposed bonding button electrically conducted with a substrate conductive path.

17. The filtered feedthrough assembly of claim 16, wherein the internally disposed bonding pads are formed of a conductive material selected from the group consisting of copper, nickel, gold and aluminum and alloys, mixtures and combinations thereof.

18. The filtered feedthrough assembly of claim 16, wherein the externally disposed bonding buttons are formed of a conductive material selected from the group consisting of niobium, platinum or a platinum-iridium alloy, titanium, titanium alloys such as titanium-6Al-4V or titanium-vanadium, molybdenum, zirconium, tantalum, vanadium, tungsten, iridium, rhodium, rhenium, osmium, ruthenium, palladium, silver, and alloys, mixtures and combinations thereof.

19. A filtered feedthrough assembly adapted to be fitted into an opening of a case of an electronic device, the feedthrough assembly having an internally disposed portion configured to be disposed inside the case and an externally disposed portion configured to be disposed outside the case, the assembly comprising:

an electrically conductive ferrule having a ferrule wall adapted to be fitted into the case opening with an inner wall surface defining a centrally disposed ferrule opening and extending between opposed internally and externally facing ferrule sides;

a multi-layer, co-fired metal-ceramic substrate having opposed internally facing and externally facing substrate surfaces joined by a common substrate edge, the metal-ceramic substrate further comprising a plurality of metal-ceramic substrate layers each having internally and externally facing layer surfaces and a plurality of substrate conductive paths extending through the co-fired metal-ceramic substrate between the internally and externally facing layer surfaces and electrically isolated from one another;

means for hermetically sealing the common substrate edge to the ferrule inner wall within the centrally disposed ferrule opening and electrically coupling the plurality of substrate ground paths to the ferrule;

a discoidal capacitive filter array formed of a ceramic capacitive filter substrate having an internally facing filter substrate side and an externally facing filter substrate side joined by a common filter substrate edge, the capacitive filter array substrate further comprising;

a plurality of filter array conductive paths electrically isolated from one another and extending between the internally facing filter substrate side and the externally facing filter substrate side each formed of reflow solder filling a;

filter array hole; and

a plurality of discoidal capacitor filters each comprising at least one capacitor active electrode formed within the filter substrate and extending outward from a filter array conductive path and a common capacitor ground electrode;

means for mechanically joining the externally facing filter substrate side to the internally facing substrate side and electrically joining each filter array conductive path to a substrate conductive path comprising the reflow solder forming the plurality of filter array conductive paths; and

means for electrically coupling the common capacitor ground electrode of the discoidal capacitor filters to the ferrule;

whereby the filtered feedthrough assembly provides a plurality of miniaturized, electrically isolated, and capacitively filtered, feedthrough conductive paths each comprising a substrate conductive path joined to a filter array conductive path and extending between the internally disposed portion and the externally disposed portion when the feedthrough assembly is affixed into an opening in the case of the electronic device.