Patent Publication Number: US-2023135610-A1

Title: Feedthrough With An Integrated Charging Antenna For An Active Implantable Medical Device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application Ser. No. 63/273,355, filed on Oct. 29, 2021. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of medical devices, particularly implantable medical devices. Still more particularly, the present invention relates to a battery- or capacitor-powered active implantable medical device (AIMD) that is designed to deliver electrical stimulation to a patient or to sense biological signals from body tissue. The AIMD of the present invention has a charging antenna that is supported on the insulator for the terminal pin feedthrough. A preferred embodiment has the charging antenna formed of a biocompatible material such as platinum supported on the body fluid side of the feedthrough insulator. 
     2. Prior Art 
     The charging antenna for a medical device, for example, an active implantable medical device (AIMD) typically resides in the device header. This means that the charging antenna requires space in the header in addition to space that is allocated to terminal blocks. As is well known by those skilled in the art, the header terminal blocks are individually electrically connected to a terminal pin that is electrically isolated from the device housing by a feedthrough. The proximal end of the terminal pin is connected to electronic circuits inside the medical device housing while the terminal pin distal end is connected to a terminal block residing in the device header. 
     When a charging antenna is also housed in the header, the antenna requires space in addition to that which is required for the terminal blocks and associated electrical connections to the terminal pins. This additional space in the header typically includes a mechanical frame to support the antenna in its intended shape and position as well as space that is needed to accommodate the charging antenna assembly process. The assembly process includes supporting the charging antenna on its support frame and connecting the antenna to a feedthrough terminal pin. 
     Therefore, there is a desire to reduce the size of a medical device, such as an AIMD, by lessening the amount of space that is needed in the header for the charging antenna. Preferably, the charging antenna is completely removed from the header without adversely affecting its charging functionality. 
     SUMMARY OF THE INVENTION 
     As medical device technologies continue to evolve, active implantable medical devices (AIMD) have gained increased popularity in the medical field. An AIMD is a battery- or capacitor-powered device that is designed to deliver electrical stimulation to a patient or sense biological signals from the patient. To enable an AIMD to stay inside the patient&#39;s body for many years without needing to be replaced, an inductive charging antenna is connected to the capacitor or battery powering the medical device. However, in order to make medical devices and particularly implantable medical devices as small as possible, there is a desire to free up space in the header that is occupied by the charging antenna. In the present invention, the charging antenna is completely removed from the device header. Instead, the charging antenna is supported on the feedthrough insulator. 
     In that respect, the present invention describes several embodiments where the charging antenna is supported on the body fluid side of the feedthrough insulator, on the device side of the insulator and embedded inside the insulator between the body fluid and device sides. If the antenna is supported on the body fluid side, it must be made from a biocompatible material such as platinum. However, if the charging antenna is embedded inside the feedthrough insulator or is supported on the device side of the insulator, it can be made from a less expensive material that is not biocompatible, for example, copper. 
     These and other aspects of the present invention will become increasingly more apparent to those skilled in the art by reference to the following detailed description and to the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a wire formed diagram of a generic human body showing a number of medical devices  100 A to  100 L that can either be implanted in a patient&#39;s body tissue or attached externally to the body. 
         FIG.  2    is a simplified block diagram of an exemplary medical system  10  according to various embodiments of the present invention. 
         FIG.  3    is a plan view looking at the body fluid side of a feedthrough  10  according to the present invention. 
         FIG.  4    is an exploded view of the feedthrough  10  shown in  FIG.  3   . 
         FIG.  5    is a side elevational view of the feedthrough  10  shown in  FIG.  3   . 
         FIG.  6    is a cross-sectional view taken along line  6 - 6  of  FIG.  3   . 
         FIG.  7    is an enlarged view of the indicated section of  FIG.  6   . 
         FIG.  8    is a cross-sectional view taken along line  8 - 8  of  FIG.  3   . 
         FIG.  9    is an enlarged view of the indicated section of  FIG.  8   . 
         FIG.  10    is an enlarged view of the indicated section of  FIG.  8   . 
         FIG.  10 A  is an enlarged view of the indicated section of  FIG.  8   . 
         FIG.  11    is a plan view looking at the device side of the feedthrough  10  shown in  FIG.  3   . 
         FIG.  12    is a plan view looking at the body fluid side of another embodiment of a feedthrough  10 A according to the present invention. 
         FIG.  13    is an exploded view of the feedthrough  10 A shown in  FIG.  12   . 
         FIG.  14    is a side elevational view of the feedthrough  10 A shown in  FIG.  12   . 
         FIG.  15    is a cross-sectional view taken along line  15 - 15  of  FIG.  12   . 
         FIG.  16    is an enlarged view of the indicated section of  FIG.  15   . 
         FIG.  17    is a cross-sectional view taken along line  17 - 17  of  FIG.  12   . 
         FIG.  18    is an enlarged view of the indicated section of  FIG.  17   . 
         FIG.  19    is an enlarged view of the indicated section of  FIG.  17   . 
         FIG.  20    is a plan view looking at the device side of the feedthrough  10 A shown in  FIG.  12   . 
         FIG.  21    is a plan view looking at the body fluid side of another embodiment of a feedthrough  10 B according to the present invention. 
         FIG.  22    is an exploded view of the feedthrough  10 B shown in  FIG.  21   . 
         FIG.  23    is a side elevational view of the feedthrough  10 B shown in  FIG.  21   . 
         FIG.  24    is a cross-sectional view taken along line  24 - 24  of  FIG.  21   . 
         FIG.  25    is an enlarged view of the indicated section of  FIG.  24   . 
         FIG.  26    is a cross-sectional view taken along line  26 - 26  of  FIG.  21   . 
         FIG.  27    is an enlarged view of the indicated section of  FIG.  26   . 
         FIG.  28    is an enlarged view of the indicated section of  FIG.  26   . 
         FIG.  29    is a plan view looking at the device side of the feedthrough  10 B shown in  FIG.  21   . 
         FIG.  30    is a plan view looking at the body fluid side of another embodiment of a feedthrough  10 C according to the present invention. 
         FIG.  31    is an exploded view of the feedthrough  10 C shown in  FIG.  30   . 
         FIG.  32    is a side elevational view of the feedthrough  10 C shown in  FIG.  30   . 
         FIG.  33    is a cross-sectional view taken along line  33 - 33  of  FIG.  30   . 
         FIG.  34    is a cross-sectional view taken along line  34 - 34  of  FIG.  30   . 
         FIG.  35    is an enlarged view of the indicated section of  FIG.  34   . 
         FIG.  36    is an enlarged view of the indicated section of  FIG.  34   . 
         FIG.  37    is a plan view looking at the device side of the feedthrough  100  shown in  FIG.  30   . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to the drawings,  FIG.  1    is a wire formed diagram of a generic human body illustrating various types of active implantable and external medical devices  100  that can either be implanted in a patient&#39;s body tissue or attached externally to the body. 
     Numerical designation  100 A represents a family of hearing devices which can include the group of cochlear implants, piezoelectric sound bridge transducers, and the like. 
     Numerical designation  100 B represents a variety of neurostimulators and brain stimulators. Neurostimulators are used to stimulate the Vagus nerve, for example, to treat epilepsy, obesity, and depression. Brain stimulators are pacemaker-like devices and include electrodes implanted deep into the brain for sensing the onset of a seizure and also providing electrical stimulation to brain tissue to prevent a seizure from actually occurring. The lead wires associated with a deep brain stimulator are often placed using real time MRI imaging. 
     Numerical designation  100 C shows a cardiac pacemaker which is well-known in the art. 
     Numerical designation  100 D includes the family of left ventricular assist devices (LVADs), and artificial heart devices. 
     Numerical designation  100 E includes a family of drug pumps which can be used for dispensing insulin, chemotherapy drugs, pain medications and the like. 
     Numerical designation  100 F includes a variety of bone growth stimulators for rapid healing of fractures. 
     Numerical designation  100 G includes urinary incontinence devices. 
     Numerical designation  100 H includes the family of pain relief spinal cord stimulators and anti-tremor stimulators. 
     Numerical designation  100 H also includes an entire family of other types of neurostimulators used to block pain. 
     Numerical designation  100 I includes a family of implantable cardioverter defibrillator (ICD) devices and also includes the family of congestive heart failure devices (CHF). This is also known in the art as cardio resynchronization therapy devices, otherwise known as CRT devices. 
     Numerical designation  100 J illustrates an externally worn pack. This pack could be an external insulin pump, an external drug pump, an external neurostimulator or even a ventricular assist device. 
     Numerical designation  100 K illustrates one of various types of EKG/ECG external skin electrodes which can be placed at various locations. 
     Numerical designation  100 L represents external EEG electrodes that are placed on the head. 
     To provide context to the various medical devices  100 A to  100 L illustrated in  FIG.  1   ,  FIG.  2    illustrates a simplified block diagram of an exemplary medical system  200  according to the present invention. The medical system  200  includes a medical device  202 , which can be one of the exemplary medical devices  100 A to  100 L depicted in  FIG.  1   , an external charger  204 , a patient programmer  206 , and a clinician programmer  208 . The exemplary medical device  202  may be an active implantable medical device (AIMD)  210 , which can be implanted in a patient&#39;s body. In some embodiments, the AIMD  210  is coupled to one end of an implantable lead  212 . The other end of the lead  212  includes multiple electrodes  214  through which electrical current is applied to a desired part of the body tissue of a patient. The implantable lead  214  incorporates electrical conductors to provide a path for that current to travel to the body tissue from the AIMD  210 . Although only one implanted lead  212  is shown in  FIG.  2   , it is understood that a plurality of implanted leads may be attached to the AIMD  210 . Furthermore, the type of implanted lead that may be used in the medical system  200  is not limited to the embodiment shown in  FIG.  2   . For example, a paddle lead may be implemented in certain embodiments. 
     The patient programmer  206  and the clinician programmer  208  may be portable handheld devices, such as a smartphone or other custom device, that are used to configure the AIMD  210  so that the AIMD can operate in a desired manner. The patient programmer  206  is used by the patient in whom the AIMD  210  is implanted. The patient may adjust the parameters of electrical stimulation delivered by the AIMD  210 , such as by selecting a stimulation program, changing the amplitude and frequency of the electrical stimulation, and other parameters, and by turning stimulation on and off. 
     The clinician programmer  208  is used by medical personnel to configure the other system components and to adjust stimulation parameters that the patient is not permitted to control, such as setting up stimulation programs among which the patient may choose and setting upper and lower limits for the patient&#39;s adjustments of amplitude, frequency, and other parameters. It is also understood that although  FIG.  2    illustrates the patient programmer  206  and the clinician programmer  208  as two separate devices, they may be integrated into a single programmer in some embodiments. 
     Referring now to  FIGS.  3  to  11   , a first embodiment of a feedthrough  10  according to the present invention is illustrated. The feedthrough  10  comprises a ferrule  12  supporting a ceramic insulator  14 . The insulator  14  resides in an opening in the ferrule  12  and is hermetically sealed to the ferrule by a ring-shaped braze  16 .  FIGS.  3  and  11    are plan views looking at the body fluid side surface and the device side surface, respectively, of the insulator  14  and  FIG.  4    is an exploded view of the feedthrough  10 . 
     The ferrule  12  comprises a surrounding sidewall that is integrally connected to an outwardly extending flange  12 A. When the ferrule  12  is sealed in an opening in the housing for an active implantable medical device, for example the AIMD  210  shown in  FIG.  2   , the flange  12 A is welded to the device housing with the flange edge providing an esthetically contoured transition from the ferrule  12  to the device housing. 
     The ferrule sidewall has a generally rectangular shape formed by opposed ferrule long sides  12 B and  12 C that extend to and meet with opposed ferrule short ends  12 D and  12 E at curved corners. More particularly, end  12 E meets side  12 C at curved corner  12 F, side  12 C meets end  12 D at curved corner  12 G, end  12 D meets side  12 B at curved corner  12 H, and side  12 B meets end  12 E at a curved corner  12 I. 
     The feedthrough insulator  14  is formed from a unitary body of ceramic material in a green-state or it is formed from a plurality of green-state ceramic sheets that are stacked one upon another until a desired thickness is obtained. In any event, the green-state body or laminated green-state ceramic sheets are then subjected to a sintering process to form a unitary ceramic insulator  14  of a desired shape. Sintering a green-state ceramic material is well known to those skilled in the art. 
     A suitable material for the insulator  14  is a ceramic, for example, essentially high purity alumina of the chemical formula Al 2 O 3  or 3% YSZ. “Essentially pure” means that the post-sintered ceramic is at least 96% alumina up to 99.999% alumina. In various embodiments, the post-sintered ceramic container  12  is at least 90% alumina, preferably at least 92% alumina, more preferably at least 94% alumina, and still more preferably at least 96% alumina. Other materials that are suitable for the insulator are selected from zirconia, sapphire, aluminum nitride, alumina toughened zirconia, boron nitride, ceramic-on-ceramic, partially stabilized zirconia, strontium aluminate, yttria-stabilized zirconia, zirconia toughened alumina, zirconia toughened ceramics, celsian (BaAl 2 Si 2 O 8 ), borosilicate sealing glasses, compression sealing glasses, a Li 2 O×Al 2 O 3 ×nSiO 2  glass-ceramic system (LAS system), a MgO×Al 2 O 3 ×nSiO 2  glass-ceramic system (MAS system), a ZnO×Al 2 O 3 ×nSiO 2  glass-ceramic system (ZAS system), and combinations thereof. 
     The sintered insulator  14  comprises a surrounding sidewall extending to an insulator body fluid side surface  14 A and an insulator device side surface  14 B. The insulator sidewall has a shape that substantially matches that of the ferrule  12  except the sidewall has shorter sides and ends so that the insulator fits into an opening bounded by the surrounding sidewall of the ferrule  12 . In that manner, the insulator sidewall has a generally rectangular shape formed by opposed insulator long sides  14 C and  14 D that extend to and meet with opposed insulator short ends  14 E and  14 F at curved corners. More particularly, end  14 F meets side  14 D at curved corner  14 G, side  14 D meets end  14 E at curved corner  14 H, end  14 E meets side  14 C at curved corner  14 I, and side  14 C meets end  14 F at curved corner  14 J. 
     A ring-shaped braze  16 , preferably a gold braze, resides between, and hermetically seals the ferrule  12  to the insulator  14 . However, as is well known by those skilled in the art, before the insulator  14  is brazed to the ferrule  12 , the insulator sidewall is provided with a metallization (not shown) so that the braze wets to the insulator. The metallization typically comprises two metallization layers, a first adhesion layer that is directly applied to the outer surface of the insulator surrounding sidewall, and a second, wetting layer, which is applied on top of the adhesion layer. In a preferred embodiment, the adhesion layer is titanium, and the wetting layer is either molybdenum or niobium. 
     The adhesion and wetting metallization layers may be applied to the insulator sidewall by thin and thick film technologies, such as printing, painting, plating, and deposition processes. Metallization processes include screen printing, pad printing, brush coating, direct bonding, active metal brazing, magnetron sputtering, physical vapor deposition, ion implantation, electroplating, and electroless plating. In an alternate embodiment, both the adhesion and wetting metallization layers may be provided by a single metallization layer. It is noted that in the present drawings, the adhesion and wetting layers are intentionally not shown for the sake of simplicity, however, it is understood that perimeter metallizations are present for each of the ceramic feedthrough insulators according to the present invention. Further, every one of the vias extending through the feedthrough insulators is provided with a suitable metallization. 
     Moreover, while the insulator  14  hermetically sealed to the ferrule  12  are shown having matching generally rectangular shapes, that is by way of example only. Those skilled in the art will readily understand that the insulator  14  hermetically sealed to the ferrule  12  by braze  16  can have a myriad of different shapes that are limited only by the design requirements of the implantable device to which the feedthrough  10  is intended to be connected. 
     A plurality of vias  18 A to  18 AF extend through the thickness of the insulator  14  from the insulator body fluid side surface  14 A to the insulator device side surface  14 B.  FIGS.  8  and  9    show via  18 D as a representative or exemplary one of the vias  18 A to  18 AF. Via  18 D has a device side portion  18 D′ of a first diameter that extends from the device side surface  14 B of the insulator  14  to an annular step  18 D″. At the step  180 ″, the via  18 D widens to a body fluid side portion  180 ′″ having a second diameter that is greater than the first diameter. The body fluid side portion  18 D′″ of the via  18 D extends to the body fluid side surface  14 A of the insulator  14 . The other vias  18 A to  18 C and  18 E to  18 AF are similarly constructed; they each have a step delineating a body fluid side portion from a device side portion. 
     The vias  18 A to  18 AF are arranged in four rows of eight vias. As shown, the first row includes vias  18 A to  18 H, the second row includes vias  181  to  18 P, the third row includes vias  18 Q to  18 X, and the fourth rows includes vias  18 Y to  18 AF. It is understood, however, that the arrangement of the vias in four rows of eight is exemplary. There can be a lesser or greater number of vies than that which is shown, and the vias can be provided in any of a myriad of different arrangements that are specific to an intended use of the feedthrough  10 . The vias  18 A to  18 AF are preferably formed by drilling, punching, cutting, machining, and waterjet cutting through the insulator  14 . 
     As shown in  FIGS.  4 ,  8  and  9   , each via  18 A to  18 AF supports an electrically conductive material  20  and, preferably an electrically conductive platinum-containing material, that is hermetically sealed to the insulator  14  in a major portion of a device side portion (portion  18 D′ for via  18 D) of the via. The conductive material  20  does not extend to the step (step  18 D″ for via  18 D) and is comprised of a platinum-containing material, for example, a substantially closed pore, fritless and substantially pure platinum material that fills a major portion of the device side portion of each of the vias  18 A to  18 AF. The platinum-containing material  20  is hermetically sealed to the insulator  14  and has a leak rate that is not greater than 1×10 −7  std. cc He/sec. 
     In an exemplary embodiment of the present invention, the electrically conductive platinum-containing material is initially in the form of a paste or ink of a substantially pure platinum fill that is disposed within the major portion of a device side portion (portion  18 D′ for via  18 D) of the via with the ceramic material of the insulator being in the green-state, as described above. Upon sintering the green-state ceramic material, whether the ceramic is a unitary body or a stack of ceramic sheets, the paste or ink of the platinum-containing material is co-sintered with the green-state ceramic to form a platinum-filled via portion with the platinum being hermetically sealed to the insulator without the aid of a metallization contacting the insulator in the via. A suitable process for forming a platinum-containing via in a ceramic substrate is described in U.S. Pat. No. 8,653,384 to Tang et al., which is assigned to the assignee of the present invention and incorporated herein by reference. 
     According to another embodiment of the present invention, in lieu of the substantially pure platinum material  20 , the major portion of the device side portion (portion  18 D′ for via  18 D) of each of the vias  18 A to  18 AF is filled with a composite reinforced metal ceramic (CRMC) material. The CRMC material is a platinum-containing material that comprises, by weight %, from about 10:90 ceramic:platinum to about 90:10 ceramic:platinum or, from about 70:30 ceramic:platinum to about 30:70 ceramic:platinum. The ceramic is preferably alumina. 
     As shown in  FIGS.  3 ,  8  and  9   , a terminal pin  22  extends through the body fluid side portion (portion  18 D′″ for via  18 D) of each of the vias  18 A to  18 AF and into the device side portion (portion  18 D′ for via  18 D) to abut the conductive material  20 . The terminal pin  22  is hermetically secured in place in the body fluid side portion and part of the device side portion of each of the vias  18 A to  18 AF by a braze  24 , preferably a gold braze  24 . With the terminal pin  22  abutting the platinum-containing material  20 , an electrically conductive pathway is established through each of the vias  18 A to  18 AF from the body fluid side surface  14 A to the device side surface  14 B of the insulator  14 . 
       FIG.  11    illustrates that a pair of vias  26  and  28  are arranged side-by-side adjacent to side  140  of the insulator  14  and side  12 C of the ferrule  12 . These vias  26  and  28  are spaced from vias  18 AB and  18 AC. 
     Referring back to  FIG.  3   , an electrically conductive trace  30  serving as an inductive charging antenna is supported on the body fluid side surface  14 A of the insulator. Since the antenna trace  30  will be exposed to body fluids, and the like, it must be a biocompatible material. Suitable biocompatible materials include platinum, platinum alloys, gold, gold alloys, rhodium, titanium, molybdenum, and mixtures thereof, and the antenna trace  30  may be applied to the insulator by thin and thick film technologies, such as printing, screen printing, pad printing, painting, plating, brush coating, direct bonding, active metal brazing, magnetron sputtering, physical vapor deposition, ion implantation, electroplating, and electroless plating. 
     The antenna trace  30  has a first leg portion  30 A that is received in the via  26  where it is hermetically sealed to the insulator  14 . The antenna trace  30  has a first lateral portion  30 B that extends along the body fluid side surface  14 A of the insulator from the first leg portion  30 A and between the insulator side  14 D and vias  18 AB,  18 AA,  18 Z and  18 Y to a curved turn spaced from the insulator end  14 E. There, the first lateral portion  30 B of the antenna trace  30  forms a second lateral portion  30 C that extends about half-way along the length of but spaced from the insulator end  14 E. A little more than half-way along the length of the insulator end  14 E, the second lateral trace portion  30 C curves toward the opposite insulator end  14 F and forms into a rectangularly-shaped serpentine trace portion  30 D extending along the body fluid side surface  14 A between the second and third rows of vias  181  to  18 P and  18 Q to  18 X. A short distance spaced from the end  14 F of insulator  14 , the rectangularly-shaped serpentine portion  30 D of the antenna trace  30  makes a curved turn and forms into a third lateral trace portion  30 D that extends along the body fluid side surface, spaced from the insulator side  14 D. A short distance from the insulator side  14 D, the third lateral trace portion  30 D makes another curved turn and forms a fourth lateral trace portion  30 F that extends between but spaced from vias  18 AC to  18 AF and the insulator side  14 D to meet via  28 . At via  28 , the fourth lateral trace portion  30 F forms a second leg portion  30 G that resides in the via  28  where it is hermetically sealed to the insulator  14 . The distal ends of the leg portions  30 A and  30 G reside at the device side surface  14 B of the insulator  14  and are configured for subsequent electrical connection to electronic circuits (not shown) housed inside the AIMD  210 . 
     The electronic circuits housed inside the medical device are configured to deliver electrical stimulation therapy to body tissue via an implantable lead, for example, the exemplary lead  212  shown in  FIG.  2   , connected to a terminal block (not shown) in the device header and to sense electrical biological signals from the body tissue through the same or a different implantable lead. Transmission of electrical stimulation therapy and sensed biological signals pass back and forth from the device electronic circuits to the exemplary lead electrodes  214  in contact with the body tissue. This transmission is along terminal pins that are supported in the feedthrough  10 . In the various feedthrough embodiments according to the present invention, the electrically conductive material  20  contacting terminal pin  22  forms an electrically conductive pathway that is functionally equivalent to a terminal pin as a wire having a length that extends outwardly from both the body fluid and device side surfaces  14 A,  14 B of the insulator  14 . 
     While the rectangularly-shaped serpentine portion  30 D of the antenna trace  30  is shown extends between the second and third rows of vias  18 I to  18 P and  18 Q to  18 X, it is within the scope of the present invention that the antenna portion  30 D can extend along the body fluid side surface  14 A of the insulator  14  in a different pattern. For example, the rectangularly-shaped serpentine portion  30 D can extends between the first and second rows of vias  18 A to  18 H and  18 I to  18 P, or between the third and fourth rows of vias  18 Q to  18 X and  18 Y to  18 AF. It can also extend between side  14 C of the insulator and vias  18 A to  18 H or between the insulator side  14 D and vias  18 Y and  18 AF. 
       FIGS.  12  to  20    illustrate a second embodiment of a feedthrough  10 A according to the present invention.  FIGS.  12  and  20    are plan views looking at the body fluid side surface  14 A and the device side surface  14 B, respectively, of the insulator  14  and  FIG.  13    is an exploded view of the feedthrough  10 A. Except for the shape of its antenna trace  32 , feedthrough  10 A has the same structure as the feedthrough  10  shown in  FIGS.  3  to  11   . 
     Looking at  FIG.  12   , in a similar manner as with the antenna trace  30  for feedthrough  10 , the electrically conductive trace  32  serving as a charging antenna is supported on the body fluid side surface  14 A of the insulator. Since the antenna trace  32  will be exposed to body fluids, and the like, it must be a biocompatible material. Suitable biocompatible materials include platinum, platinum alloys, gold, gold alloys, rhodium, titanium, molybdenum, and mixtures thereof, and the antenna trace  32  may be applied to the insulator by thin and thick film technologies, such as printing, screen printing, pad printing, painting, plating, brush coating, direct bonding, active metal brazing, magnetron sputtering, physical vapor deposition, ion implantation, electroplating, and electroless plating. 
     The antenna trace  32  has a first leg portion  32 A that is received in via  26  where it is hermetically sealed to the insulator. The antenna trace  32  has a first lateral portion  32 B that extends along the body fluid side surface  14 A between and spaced from the insulator side  14 D and the vias  18 AB,  18 AA,  18 Z and  18 Y from the first leg portion  32 A to a curved turn spaced from the insulator end  14 E. There, the first lateral portion  32 B of the antenna trace  32  forms a second lateral portion  32 C that extends along the body fluid side surface  14 A, spaced inwardly from the insulator end  14 E. A short distance from insulator side  14 C, the antenna trace portion  32 C curves toward the insulator end  14 F. There, the second lateral portion  32 C forms a third lateral portion  32 D that extends along the body fluid side surface  14 A between and spaced from the first row of vias  18 A to  18 H and the insulator side  14 C and toward the opposite insulator end  14 F. Spaced a short distance from the insulator end  14 F, the antenna trace portion  32 D makes a curved turn and forms a fourth lateral portion  32 E that extends along the body fluid side surface  14 A. Spaced inwardly from the insulator side  14 D, the fourth lateral portion  32 E makes another curved turn toward the insulator side  14 D. There, the fourth lateral portion  32 E forms a fifth lateral portion  32 F that extends along the body fluid side surface  14 A between but spaced from the vias  18 AC to  18 AF and the insulator side  14 D to meet via  28 . At the via  28 , the antenna trace  32  forms a second leg portion  32 G that resides in the via  28  where it is hermetically sealed to the insulator. The distal ends of the leg portions  32 A and  32 G reside at the device side surface  14 B of the insulator  14  and are configured for subsequent electrical connection to electronic circuits (not shown) housed inside the AIMD  210 . 
       FIGS.  21  to  29    illustrate a third embodiment of a feedthrough  10 B according to the present invention.  FIGS.  21  and  29    are plan views looking at the body fluid side surface  14 A and the device side surface  14 B, respectively, of the insulator  14  and  FIG.  22    is an exploded view of the feedthrough  10 B. Except for the shape and location of its antenna trace  34 , feedthrough  10 B has the same structure as the feedthrough  10  shown in  FIGS.  3  to  11    and the feedthrough  10 A shown in  FIGS.  12  to  20   . While the antenna trace  30  for the feedthrough  10  and the antenna trace  32  for the feedthrough  10 A are supported on the body fluid side surface  14 A of the insulator  14 , the electrically conductive trace  34  serving as a charging antenna can also be embedded inside the insulator, located between the body fluid side and device side surfaces  14 A and  14 B, respectively. Since the embedded antenna trace  34  will not be exposed to body fluids, and the like, can be of a biocompatible material selected from platinum, platinum alloys, gold, gold alloys, rhodium, titanium, molybdenum, and mixtures thereof, or a material that is not biocompatible selected from copper, copper alloys, platinum, platinum alloys, gold, gold alloys, and mixtures thereof. 
     In any event, the antenna trace  34  may be applied to a green-state ceramic sheet before the final laminated stack-up thickness is obtained prior to the laminated sheets being subjected to a sintering process. The biocompatible or non-biocompatible material comprising the antenna trace  34  may be deposited by thin and thick film technologies, such as printing, screen printing, pad printing, painting, plating, brush coating, direct bonding, active metal brazing, magnetron sputtering, physical vapor deposition, ion implantation, electroplating, and electroless plating. 
     The antenna trace  34  has a first leg portion  34 A that is received in via  26 A where it is hermetically sealed to the insulator  14 . The antenna trace  34  has a first lateral portion  34 B that extends from the first leg portion  34 A between the insulator body fluid and device side surfaces  14 A,  14 B and spaced from the insulator side  14 D and the vias  18 AB,  18 AA,  18 Z and  18 Y to a curved turn spaced from the insulator end  14 E. There, the first lateral portion  34 B of the antenna trace  34  forms a second lateral portion  34 C that extends between the insulator body fluid and device side surfaces  14 A,  14 B, spaced inwardly from the insulator end  14 E. A short distance from insulator side  14 C, the antenna trace portion  34 C curves toward the insulator end  14 F. There, the second lateral portion  34 C forms a third lateral portion  34 D that extends between the insulator body fluid and device side surfaces  14 A,  14 B and spaced from the first row of vies  18 A to  18 H and the insulator side  14 C toward the opposite insulator end  14 F. Spaced a short distance from the insulator end  14 F, the antenna trace portion  34 D makes a curved turn into a fourth lateral portion  34 E that extends between the insulator body fluid and device side surfaces  14 A,  14 B. Spaced inwardly from the insulator side  14 D, the fourth lateral portion  34 E makes another curved turn toward the insulator side  14 D. There, the fourth lateral portion  34 E forms a fifth lateral portion  34 F that extends between the insulator body fluid and device side surfaces  14 A,  14 B and spaced from the vias  18 AC to  18 AF and the insulator side  14 D to meet via  28 A. At via  28 A, the antenna trace  34  forms a second leg portion  34 G that resides in the via  28 A where it is hermetically sealed to the insulator  14 . The distal ends of the leg portions  34 A and  34 G reside at the device side surface  14 B of the insulator  14  and are configured for subsequent electrical connection to electronic circuits (not shown) housed inside the AIMD  210 . 
       FIGS.  30  to  37    illustrate a fourth embodiment of a feedthrough  10 C according to the present invention.  FIGS.  30  and  37    are plan views looking at the body fluid side surface  14 A and the device side surface  14 B, respectively, of the insulator  14  and  FIG.  31    is an exploded view of the feedthrough  10 C. In this embodiment, the electrically conductive trace  36  serving as a charging antenna is supported on the device side surface  14 B of the insulator. This means that there is no need for the vias  26  and  28  shown with respect to the first and second feedthroughs  10 A and  10 B and the vias  26 A and  28 A shown for the third feedthrough  10 B. Also, since the antenna trace  36  will not be exposed to body fluids, it does not need to be made from a biocompatible material. Suitable material for the antenna trace  36  supported on the device side surface  14 B of the insulator include copper, copper alloys, platinum, platinum alloys, gold, gold alloys, and mixtures thereof. Otherwise, the feedthrough  100  has the same structure as the feedthrough  10  shown in  FIGS.  3  to  11   , the feedthrough  10 A shown in  FIGS.  12  to  20    and the feedthrough  10 B shown in  FIGS.  21  to  29   . 
     The antenna trace  36  begins at a first end  36 A which is spaced from but adjacent to the via  18 AB and the insulator side  14 D. From there antenna trace  36  has a first lateral portion  36 B that extends along the device side surface  14 B between and spaced from the insulator side  14 D and the vias  18 AB,  18 AA,  18 Z and  18 Y to a curved turn spaced from the insulator end  14 E. There, the first lateral portion  36 B of the antenna trace  36  forms a second lateral portion  36 C that extends along the device side surface  14 B, spaced inwardly from the insulator end  14 E. A short distance from insulator side  14 C, the antenna trace portion  36 C curves toward the insulator end  14 F. There, the second lateral portion  36 C forms a third lateral portion  36 D that extends along the device side surface  14 B between and spaced from the first row of vias  18 A to  18 H and the insulator side  14 C and toward the opposite insulator end  14 F. Spaced a short distance from insulator end  14 F, the antenna trace portion  36 D makes a curved turn and forms a fourth lateral portion  36 E that extends along the device side surface  14 A. Spaced inwardly from the insulator side  14 D, the fourth lateral portion  36 E makes another curved turn and extends toward the insulator side  14 D. There, the fourth lateral portion  36 E forms a fifth lateral portion  36 F that extends along the device side surface  14 B between but spaced from the vias  18 AC to  18 AF and the insulator side  14 D to terminate at a second end  36 G of the antenna trace  36 . The first and second ends  36 A and  36 G are spaced from but adjacent to each other at the device side surface  14 B of the insulator  14  and are configured for subsequent electrical connection to electronic circuits (not shown) housed inside the AIMD  210 . 
     Thus, various embodiments for an inductive charging antenna  30 ,  32 ,  34  and  36  supported on or embedded inside the insulator  14  for the feedthrough of a medical device  202  have been described. However, the scope of the present invention charging antennas is not intended to be limited to the specific structures shown in the drawings. For example, while the rectangularly-shaped serpentine portion  30 D of the charging antenna  30  in  FIGS.  3  to  11    is shown extending between the second and third rows of vias  18 I to  18 P and  18 Q to  18 X on the body fluid side surface  14 A of the feedthrough insulator  14 , that is by way of example only. The same antenna configuration can reside of the device side surface  14 B of the insulator or be embedded inside the insulator. Further, the serpentine-shaped portion  30 D need not have a rectangular shape. Instead, that portion of the charging antenna trace may have a curved or sinusoidal shape or have several curved or sinusoidal trace sections that are connected to an intermediate lateral trace section. Further, the illustrated feedthroughs  10 ,  10 A,  10 B and  10 C can have more or less vias than the  32  shown, and the vias need not be aligned in rows of an equal number. Still further, the charging antenna can weave between and among the vias in virtually any pattern that is limited only by the requirements of the medical device into which the feedthrough will be built. Moreover, feedthrough embodiments  10 A and  10 C can encircle or surround any number of feedthrough vias or, regardless the number of vias, the charging antenna can surround the feedthrough vias as an embedded antenna disposed between the body fluid and device side surfaces of the insulator  14 . 
     Referring back to  FIG.  2   , with the medical device  202 , for example, the AIMD  210  implanted in body tissue, the external charger  204  of the medical device system  200  is configured to provide inductive charging current to the various charging antennas  30 ,  32 ,  34  and  36 . The charging antennas are connected to electronic circuits housed inside the medical device  202 . In addition to controlling the delivery of electrical stimulation to a patient and to receiving sensed biological signals from body tissue, the electronic circuits control inductive charging of the battery or capacitor power source (not shown) that provides electrical power for those functionalities, among others. The electrical energy power source can be a capacitor or a rechargeable battery, for example, a hermetically sealed rechargeable Li-ion battery. An exemplary rechargeable electrical energy power source is a lithium-ion electrochemical cell comprising a carbon-based or Li 4 Ti 5 O 12 -based anode and a lithium metal oxide-based cathode, such as of LiCoO 2  or lithium nickel manganese cobalt oxide (LiNi a Mn b Co 1-a-b O 2 ). 
     Inductive charging power may be delivered to the charging antennas  30 ,  32 ,  34  and  36  from an external charging pad  216  containing a transmitting coil (not shown) connected to the external charger  204 . In some embodiments, the external charging pad  216  is a hand-held device that is connected to the external charger  204  by a multiconductor cable which includes (power conductors and control lines). In another embodiment, the external charging pad  216  is an internal component of the external charger  204 . 
     It is appreciated that various modifications to the inventive concepts described herein may be apparent to those skilled in the art without departing from the spirit and scope of the present invention as defined by the hereinafter appended claims.