High-voltage electrically insulating designs for use in active implantable medical devices
The high-voltage and/or high-frequency pulse dielectric breakdown strength (DBS) of an implantable medical device is increased by strategically positioning insulation materials on or adjacent to the external surfaces of a filter capacitor. Dielectric breakdown strength is further increased by adding polymeric or ceramic nanoscale metal oxide insulative powders to the insulation materials.
1 . A filtered feedthrough assembly that is attachable to an active implantable medical device (AIMD), the filtered feedthrough assembly comprising:
a) a feedthrough, comprising:
i) an electrically conductive ferrule comprising a ferrule sidewall defining a ferrule opening, the ferrule sidewall extending to a ferrule body fluid side spaced from a ferrule device side;
ii) an insulator hermetically sealed to the ferrule in the ferrule opening, the insulator extending to an insulator body fluid side spaced from an insulator device side, wherein, when the ferrule hermetically sealed to the insulator is attached to an opening in a housing of an AIMD, the ferrule body fluid side adjacent to the insulator body fluid side, and the ferrule device side adjacent to the insulator device side reside outside and inside the AIMD, respectively; and
iii) at least a first terminal pin hermetically sealed to the insulator in a first via hole by a first braze, wherein the first terminal pin extends outwardly beyond the insulator device side; and
b) a filter capacitor, comprising:
i) a dielectric substrate comprising a dielectric substrate peripheral surface extending to a dielectric substrate first end surface spaced from a dielectric substrate second end surface, wherein the dielectric substrate supports at least one active electrode plate interleaved in a capacitive relationship with at least one ground electrode plate, and wherein the dielectric substrate first end surface is adjacent to the insulator and the ferrule device sides; and
ii) at least a first passageway extending through the dielectric substrate to the dielectric substrate first and second end surfaces, wherein the first terminal pin extend through the first passageway and outwardly beyond the dielectric substrate second end surface,
iii) wherein the first terminal pin is electrically connected to one of the active and ground electrode plates in the first passageway; and
c) a polymeric insulating material comprising one or more layers contacted to the dielectric substrate second end surface, wherein the polymeric insulating material comprises insulating nanoparticles.
2 . The filtered feedthrough assembly of claim 1 , wherein the dielectric substrate second end surface is recessed below the ferrule device side, and the polymeric insulating material extends to an inner surface of the ferrule sidewall.
3 . The filtered feedthrough assembly of claim 1 , wherein the dielectric substrate second end surface is spaced above the ferrule device side, and wherein the at least one ground electrode plate extends to the dielectric substrate peripheral surface, and an external ground metallization contacts the ground electrode plate at the peripheral surface, and wherein the polymeric insulating material contacted to the dielectric substrate second end surface contacts the external ground metallization at the dielectric substrate peripheral surface.
4 . The filtered feedthrough assembly of claim 1 , wherein the polymeric insulating material is selected from silicone, polyurethane, polyester, polyethylene, polypropylene, polyimide, polyamide, acrylic, polyacrylates, perfluoroalkoxy (PFA), fluorinated ethylene-propylene (FEP), polyetheretherketone (PEEK), polyamide imide (PAI), polyphenyl sulfone (PPSU), polyetherimide (PEI), polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyoxymethylene (POM), polystyrene (PS), thermoplastic elastomer (TPE), polyethylene terephthalate (PET), ethylene-vinyl acetate (EVA), polyethylene-vinyl acetate (PEVA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), polyoxymethylene (POM) polycarbonate (PC), epoxy, rubber, acetal, polyacetal, polyformaldehyde, phenolic, polysulfide, and combinations thereof.
5 . The filtered feedthrough assembly of claim 1 , wherein the nanoparticles are selected from Al 2 O 3 , BaO, CaO, CeO 2 , MgO, ZnO, ZrO 2 , SiO 2 , TiO 2 , Al 2 SiO 53 , BaTiO 3 , SrTiO 2 , zirconia toughened alumina (ZTA), alumina toughened zirconia (ATZ), yttrium stabilized zirconia (YSZ), yttrium-toughened zirconia (YTZP), aluminum nitride (AlN), silicon nitride (Si 3 N 4 ), boron nitride (BN), carbon nitride (CN), and combinations thereof.
6 . The filtered feedthrough assembly of claim 5 , wherein the nanoparticles range in size from greater than about 100 nanometers (0.1 microns) to about 40,000 nanometers (40 microns).
7 . The filtered feedthrough assembly of claim 5 , wherein a nanoparticle loading in the polymeric insulating material ranges from >0 to about 40%, by weight.
8 . The filtered feedthrough assembly of claim 1 , wherein the polymeric insulating material contacted to the dielectric substrate second end surface is a first polymeric insulating washer.
9 . The filtered feedthrough assembly of claim 8 , wherein the first polymeric insulating washer has opposed first and second sides and a first thermoplastic coating contacts the first side of the first polymeric insulating washer adjacent to the dielectric substrate second end surface.
10 . The filtered feedthrough assembly of claim 9 , wherein the first thermoplastic coating contacting the first side of the first polymeric insulating washer adjacent to the dielectric substrate second end surface is an insulating adhesive.
11 . The filtered feedthrough assembly of claim 9 , wherein a second thermoplastic coating contacts the second side of the first polymeric insulating washer spaced from the dielectric substrate second end surface.
12 . The filtered feedthrough assembly of claim 1 , wherein a second polymeric washer is positioned between the insulator device side and the dielectric substrate first end surface, and wherein the second polymeric washer has at least a washer first opening through which the first terminal pin extends.
13 . The filtered feedthrough assembly of claim 1 , wherein the first terminal pin is a first active terminal pin, and wherein a first electrical connection material connects the first active terminal pin to a capacitor first metallization electrically connected to the at least one active electrode plate in the first passageway.
14 . The filtered feedthrough assembly of claim 1 , wherein the first terminal pin is a first ground terminal pin, and wherein a first electrical connection material connects the first ground terminal pin to a capacitor first metallization electrically connected to the at least one ground electrode plate in the first passageway.
15 . The filtered feedthrough assembly of claim 5 , wherein a nanoparticle loading in the polymeric insulating material ranges from >40% to ≤90% by weight.
16 . The filtered feedthrough assembly of claim 5 , wherein a nanoparticle loading in the polymeric insulating material ranges from >0% to ≤30% by volume.
17 . The filtered feedthrough assembly of claim 5 , wherein a nanoparticle loading in the polymeric insulating material ranges from >40% to ≤99% by volume.