CERAMIC-TO-METAL JOINT FOR IMPLANTABLE PULSE GENERATORS

1 . An implantable pulse generator configured for delivering one or more electrical pulses to a target region within a body of a patient, the implantable pulse generator comprising:

a hermetically sealed housing comprising:

a) a ceramic portion comprising a ceramic material, the ceramic portion defining a first inner volume;

b) a case portion defining a second inner volume;

c) an intermediate metal ring positioned between the ceramic portion and the metal case portion, wherein the intermediate metal ring comprises a first side joined to the ceramic portion by either a braze material or a diffusion bond, wherein the braze material or the diffusion bond is substantially free of nickel, and wherein the intermediate metal ring comprises a second side joined to the case portion;

d) a header portion configured to electrically couple to the implantable neurostimulation lead, wherein the header portion comprises a feed through assembly that connects the header portion to the case portion, the feed through assembly electrically coupling components of the header portion and implantable neurostimulation lead to circuitry positioned within the second inner volume defined by the case portion; and

e) a charging coil assembly comprising a charging coil wrapped around an optional ferrite core material, the charging coil assembly is at least partially housed within the first inner volume defined by the ceramic portion,

wherein the charging coil assembly is configured to wirelessly communicate with an external charging device across the ceramic portion to charge a battery positioned within the implantable pulse generator.

2 . The implantable pulse generator of claim 1 , wherein the case portion comprises metal, and wherein the second side of intermediate metal ring is laser welded to the case portion.

3 . The implantable pulse generator of claim 2 , wherein the feed through assembly comprises a multi-pin feed-through assembly comprising a metallic base plate, wherein the metallic base plate is laser-welded to the case portion to create a hermetic seal.

4 . The implantable pulse generator of claim 2 , wherein the case portion comprises Grade 5 Titanium and the intermediate metal ring comprises a different material than the case portion.

5 . The implantable pulse generator of claim 1 , wherein the ceramic portion comprises at least one of zirconia or alumina.

6 . The implantable pulse generator of claim 1 , wherein at least one of the ceramic portion, the case portion, or the intermediate metal ring define one or more alignment guides configured the physically align the intermediate metal ring with the ceramic portion or the case portion during assembly.

7 . The implantable pulse generator of claim 1 , further comprising a humidity sensor configured to monitor an internal humidity within the hermetically sealed housing of the implantable pulse generator.

8 . A method of assembling an implantable pulse generator or portion thereof configured to deliver one or more electrical pulses to a target region within a body of a patient using an implantable neurostimulation lead, the method comprising:

forming a ceramic portion comprising a ceramic material, the ceramic portion defining a first inner volume;

aligning the ceramic portion adjacent to a first side of an intermediate metal ring and joining the ceramic portion to the first side of the intermediate metal ring by brazing or diffusion bonding, wherein the braze material or the diffusion bond is substantially free of nickel and forms a hermetic seal between joined portions of the ceramic portion and the intermediate metal ring; and

joining a second side of the intermediate metal ring to a case portion comprising metal or ceramic material, wherein joined portions of the case portion and the intermediate metal ring form a hermetic seal.

9 . The method of claim 8 , wherein aligning the ceramic portion adjacent to a first side of an intermediate metal ring comprises using one or more alignment guides formed along at least one of the ceramic portion or the intermediate metal ring that are configured the physically align intermediate metal ring with the ceramic portion.

10 . The method of claim 8 , further comprising joining the case portion to a header portion to create a hermetically sealed housing, wherein the header portion comprises a multi-pin feed-through assembly comprising a metallic base plate, wherein the metallic base plate is at least one of laser-welded, brazed, or diffusion bonded to the case portion.

11 . The method of claim 8 , wherein the case portion comprises a ceramic material, and wherein joining the second side of the intermediate metal ring to the case portion comprises at least one of diffusion bonding or brazing.

12 . The method of claim 8 , wherein the case portion comprises a metal, and wherein joining the second side of the intermediate metal ring to the case portion comprises laser welding.

13 . The method of claim 8 , further comprising depositing a charging coil assembly within as least a portion of the first inner volume defined by the ceramic portion, wherein the communication assembly comprises a charging coil wrapped around an optional ferrite core material, the charging coil assembly being housed within the first inner volume defined by the ceramic portion, wherein the charging coil assembly is configured to wirelessly communicate with an external charger by a wireless signal delivered across the ceramic portion to charge a battery housed within the device.

14 . The method of claim 8 , wherein joining the ceramic portion to the first side of the intermediate metal ring comprises brazing using a gold braze material.

15 . The method of claim 14 , further comprising sputtering a braze wetting agent comprising niobium on the ceramic portion prior to brazing.

16 . The method of claim 8 , wherein joining the ceramic portion to the first side of the intermediate metal ring comprises diffusion bonding.

17 . An implantable neurostimulator device configured for delivering one or more electrical pulses to a target region within a body of a patient using an implantable neurostimulation lead comprising a plurality of neurostimulation electrodes electrically coupleable to the device, the implantable neurostimulator device comprising:

a) a ceramic portion comprising a ceramic material and forming part of a housing of the implantable neurostimulator device, wherein the ceramic portion defines a first inner volume;

b) a metal case portion forming part of the housing of the implantable neurostimulator device, wherein the metal case portion defines a second inner volume;

c) an intermediate metal ring positioned between the ceramic portion and the metal case portion and forming part of the housing of the implantable neurostimulator device, wherein the intermediate metal ring comprises a first side joined to the ceramic portion by either a braze material or a diffusion bond, wherein the braze material and the diffusion bond are substantially free of nickel, the intermediate metal ring having a second side joined to the metal case portion by a laser-weld joint, wherein the ceramic portion, metal case portion, and intermediate metal ring collectively define a third internal volume of the housing;

d) a header portion configured to electrically couple to the implantable neurostimulation lead, wherein the header portion comprises a multi-pin feed-through assembly comprising a metallic base plate, wherein the metallic base plate of the multi-pin feed-through assembly is laser-welded to the metal case portion to provide a hermetic seal between the header portion and the metal case portion, wherein the multi-pin feed-through electrically couples components of the header portion and implantable neurostimulation lead to electronic circuitry at least partially positioned within the second inner volume defined by the metal case portion; and

e) electronic circuitry disposed within the third internal volume of the housing, wherein the circuitry is configured to generate the one or more electrical pulses delivered to the target region within a body of a patient using the implantable neurostimulation lead, wherein the electronic circuitry comprises:

i) a printed circuit board being at least partially housed within the second inner volume defined by the metal case portion, the printed circuit board having a rechargeable battery and a temperature sensor electrically coupled thereto, wherein the temperature sensor is configured to detect a temperature of a portion the implantable neurostimulator device during at least one of a recharge cycle of implantable neurostimulator device or during the delivery of one or more electrical pulses to a target region within a body of a patient using an implantable neurostimulation lead; and

ii) a charging coil assembly comprising a charging coil defining a central coil axis and a ferrite core material, wherein the charging coil of the charging coil assembly is wrapped around a ferrite core material such that the ferrite core material is aligned with the central coil axis,

wherein the charging coil assembly is housed within the first inner volume defined by the ceramic portion so that the central coil axis is substantially perpendicular to a normal defined by a major plane of the implantable neurostimulator device, and wherein the charging coil assembly is configured to wirelessly communicate with an external charging device across the ceramic portion to charge the rechargeable battery positioned within the implantable neurostimulator device;

wherein the implantable neurostimulator device is hermetically sealed and defines a total device volume of less than 10 cubic centimeters, and wherein the implantable neurostimulator device is configured to be fully implanted within a body of a patient and adapted for sacral nerve stimulation treatment.

18 . The implantable neurostimulator device of claim 17 , wherein the implantable neurostimulator device has a leachable nickel content is less than 300 μg/day.

19 . The implantable neurostimulator device of claim 17 , wherein at least one of the ceramic portion, the metal case portion, or the intermediate metal ring define one or more alignment guides configured the physically align intermediate metal ring with the ceramic portion or the case portion during assembly.

20 . The implantable neurostimulator device of claim 17 , wherein the metallic base plate of the multi-pin feed-through assembly comprises at least two alignment guides configured to physically align the multi-pin feed-through assembly with at least one of the printed circuit board or the metal case portion during assembly of the implantable neurostimulator device.