Ceramic-to-metal joint for implantable pulse generators
An implantable pulse generator configured for delivering one or more electrical pulses to a target region within a body of a patient using an implantable neurostimulation lead, the implantable pulse generator comprising a hermetically sealed housing comprising a ceramic portion defining an inner volume configured to receive a charging coil assembly comprising a charging coil wrapped around an optional ferrite core material; an intermediate metal ring; and a case, 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.
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 ceramic portion comprising a first ceramic material, the ceramic portion defining a first inner volume;
a case portion comprising a second ceramic material, the case portion defining a second inner volume;
an intermediate metal ring positioned between the ceramic portion and the case portion, wherein the intermediate metal ring comprises:
a first side joined to the ceramic portion by a first braze material or a first diffusion bond, wherein the first braze material or the first diffusion bond is substantially free of nickel, and
a second side joined to the case portion by a second braze material or a second diffusion bond, wherein the second braze material or the second diffusion bond is substantially free of nickel, wherein the intermediate metal ring defines one or more first alignment guides on the first side configured to physically align the intermediate metal ring with the ceramic portion and one or more second alignment guides on the second side configured to physically align the case portion with the intermediate metal ring during assembly of the implantable pulse generator;
a header portion defining a third inner volume, the header portion being configured to electrically couple to an implantable neurostimulation lead, wherein the header portion comprises a feed-through assembly that connects the header portion to the case portion, and wherein the feed-through assembly electrically couples components of the header portion and the implantable neurostimulation lead to circuitry positioned within the second inner volume; and
a charging-coil assembly comprising a charging coil, wherein the charging-coil assembly is at least partially housed within the first inner volume, wherein the charging-coil assembly is configured to receive wireless power through the first ceramic material from an external charging device to charge a battery at least partially positioned within the second inner volume, and wherein the charging coil extends at least partially around a perimeter of the circuitry positioned within the second inner volume.
2 . The implantable pulse generator of claim 1 , wherein the feed-through assembly comprises a multi-pin feed-through assembly comprising a metallic base plate, and wherein the metallic base plate is coupled to the case portion to create a hermetic seal.
3 . The implantable pulse generator of claim 1 , wherein the ceramic portion comprises zirconia or alumina.
4 . The implantable pulse generator of claim 1 , further comprising a humidity sensor configured to:
monitor an internal humidity within the hermetically sealed housing;
determine, based on the monitored internal humidity, that the hermetically sealed housing is compromised; and
output an indication that a consultation with a physician or replacement of the implantable pulse generator is needed.
5 . The implantable pulse generator of claim 1 , wherein the intermediate metal ring comprises a titanium material ranging from Grade 1 Titanium to Grade 4 Titanium.
6 . The implantable pulse generator of claim 1 , wherein the ceramic portion is coated with a wetting agent comprising one or more of rhodium, hafnium, tantalum, titanium, and platinum, wherein the wetting agent is between the ceramic portion and the first braze material, wherein the wetting agent has a thickness in the range of about 1 to 3 micrometers.
7 . A method of assembling an implantable pulse generator configured to deliver one or more electrical pulses to a target region within a body of a patient via an implantable neurostimulation lead, the method comprising:
forming a ceramic portion comprising a first ceramic material, the ceramic portion defining a first inner volume;
aligning the ceramic portion adjacent to a first side of an intermediate metal ring, wherein the intermediate metal ring comprises a different material than Grade 5 Titanium, and joining the ceramic portion to the first side of the intermediate metal ring by brazing or diffusion bonding, wherein a braze material of the brazing or a diffusion bond of the diffusion bonding is substantially free of nickel and forms a first hermetic seal between the ceramic portion and the intermediate metal ring;
depositing at least a portion of a charging-coil assembly within the first inner volume, wherein the charging-coil assembly comprises a charging coil, and wherein the charging-coil assembly is configured to receive wireless power through the ceramic material from an external charger to charge a battery at least partially housed within a second inner volume defined by a case portion, wherein the case portion comprises a second ceramic material, wherein the charging coil extends at least partially into the second inner volume; and
joining a second side of the intermediate metal ring to the case portion to form a second hermetic seal,
wherein the intermediate metal ring defines one or more first alignment guides on the first side configured to physically align the intermediate metal ring with the ceramic portion and one or more second alignment guides on the second side configured to physically align the intermediate metal ring with the case portion during assembly of the implantable pulse generator.
8 . The method of claim 7 , 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, and wherein the metallic base plate is laser-welded, brazed, or diffusion-bonded to the case portion.
9 . The method of claim 7 , wherein joining the second side of the intermediate metal ring to the case portion comprises laser welding.
10 . The method of claim 7 , wherein joining the ceramic portion to the first side of the intermediate metal ring comprises brazing using a gold braze material.
11 . The method of claim 10 , further comprising sputtering a braze wetting agent comprising niobium on the ceramic portion prior to brazing.
12 . An implantable neurostimulator device configured for delivering one or more electrical pulses to a target region within a body of a patient via an implantable neurostimulation lead comprising a plurality of neurostimulation electrodes electrically coupleable to the implantable neurostimulator device, the implantable neurostimulator device comprising:
a ceramic portion comprising a first ceramic material and forming a first part of a housing of the implantable neurostimulator device, wherein the ceramic portion defines a first inner volume;
a case portion comprising a second ceramic material, the case portion forming a second part of the housing of the implantable neurostimulator device, wherein the case portion defines a second inner volume;
an intermediate metal ring comprising a different material than Grade 5 Titanium, the intermediate metal ring being positioned between the ceramic portion and the case portion and forming a third part of the housing of the implantable neurostimulator device, wherein the intermediate metal ring comprises a first side joined to the ceramic portion by a first braze material or a first diffusion bond, wherein the first braze material or the first diffusion bond is substantially free of nickel, wherein the intermediate metal ring comprises a second side joined to the case portion by a laser-weld joint or by a second braze material or a second diffusion bond, wherein the second braze material or the second diffusion bond is substantially free of nickel, and wherein the ceramic portion, the case portion, and the intermediate metal ring collectively define a third inner volume of the housing, and wherein the intermediate metal ring defines one or more first alignment guides with the first part of the housing configured to physically align the intermediate metal ring with the ceramic portion and one or more second alignment guides with the second part of the housing configured to physically align the intermediate metal ring with the case portion during assembly of the implantable pulse generator;
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, brazed or diffusion bonded to the case portion to provide a hermetic seal between the header portion and the case portion, wherein the multi-pin feed-through assembly electrically couples components of the header portion and the implantable neurostimulation lead to electronic circuitry at least partially positioned within the second inner volume; and
electronic circuitry disposed within the third inner volume of the housing, wherein the electronic circuitry is configured to generate the one or more electrical pulses delivered to the target region within the body of the patient via the implantable neurostimulation lead, wherein the electronic circuitry comprises:
a printed circuit board at least partially housed within the second inner volume, 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 the implantable neurostimulator device during a recharge cycle of the implantable neurostimulator device or while delivering the one or more electrical pulses; and
a charging-coil assembly comprising a charging coil defining a central coil axis, wherein the charging-coil assembly is housed within the first inner volume so that the central coil axis is substantially parallel to a normal defined by a major plane of the implantable neurostimulator device, and wherein the charging-coil assembly is configured to receive wireless power through the ceramic material from an external charging device to charge the rechargeable battery;
wherein the implantable neurostimulator device is hermetically sealed and defines a total volume of less than 10 cubic centimeters, and
wherein the charging coil extends at least partially around a perimeter of the printed circuit board positioned within the second inner volume.
13 . The implantable neurostimulator device of claim 12 , wherein the implantable neurostimulator device has a leachable nickel content of less than about 300 micrograms per day (μg/day).
14 . The implantable neurostimulator device of claim 12 , 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 the printed circuit board or the case portion during assembly of the implantable neurostimulator device.
15 . The implantable neurostimulator device of claim 14 , wherein the at least two alignment guides of the metallic base plate comprise at least two alignment apertures defined by the metallic base plate.