Abstract:
A connector block providing electrical coupling to electronic componentry of an implantable medical device. The implantable medical device has a case containing the electronic componentry. A preformed electrically conductive “wireform” mounted with respect to a structurally rigid polymer frame forming a plurality of electrical contacts. Potting is formed in situ with liquid thermoset polymer substantially filling any voids in the connector block and forming a thermoset polymer gasket between the connector block and the case.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to implantable medical devices and, more particularly, to connector blocks for implantable medical devices.  
       BACKGROUND OF THE INVENTION  
       [0002]     Implantable medical devices for producing a therapeutic result in a patient are well known. Examples of such implantable medical devices include implantable drug infusion pumps, implantable neurostimulators, implantable cardioverters, implantable cardiac pacemakers, implantable defibrillators and cochlear implants. Some of these devices, if not all, and other devices either provide an electrical output or otherwise contain electrical circuitry to perform their intended function.  
         [0003]     Such implantable medical devices, when implanted, are subjected to a harsh environment in contact with bodily fluids. Such bodily fluids can be corrosive to the implantable medical device. Typically, implantable medical devices are hermetically sealed, often in a titanium case, in order to protect the implantable medical device from the harmful effects of the bodily fluids with which the implantable medical device comes into contact.  
         [0004]     Often, however, it is necessary and/or desirable to make an electrical connection to and/or form such an implantable medical device. As an example, it may be necessary to use an electrical connection to feed electrical power into the implantable medical device. Alternatively or in addition, it may be necessary to use an electrical connection to bring a therapeutic electrical signal outside of the implantable medical device in order to properly place an electrode or lead at a location in the body of the patient where the therapeutic electrical signal can provide the best result.  
         [0005]     In any of these circumstances, it may be necessary to breach the otherwise hermetically sealed case of the implantable medical device in order to make an electrical connection. Since these electrical connections breach the otherwise hermetically sealed case, the electrical connection may be prone to contamination by bodily fluids which could lead to infiltration of bodily fluids into the implantable medical device and possibly result in a premature failure of the device.  
         [0006]     This problem is exacerbated in newer electrically stimulating devices utilizing recharging technology where the implanted secondary coil and electrical contacts are located outside of the titanium case. The problem is further exacerbated by an increase in the number of excitation electrodes for use in patient therapy, therefore resulting in an increase in the number of electrical connections made outside of the titanium case. With the implanted secondary coil and the greater number of electrical contacts located outside of the titanium case, the greater the problem of making a secure, reliable connection without risking compromise of the implantable medical device and possible subsequent premature failure. Failure of an implanted medical device could lead not only to necessary surgery to explant the device but could jeopardize the patient&#39;s well being by making the therapeutic advantages of the medical device unavailable to the patient until explantation and re-implantation could occur.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     Thus, it is extremely desirable to be able to make an electrical connection with an implantable medical device which not only can reliably electrical connect a plurality of lead wires but also reliably protect the implantable medical device from the ravages of the body.  
         [0008]     Thus in an embodiment, the present invention provides a connector block providing electrical coupling to electronic componentry of an implantable medical device. The implantable medical device has a case containing the electronic componentry. A preformed electrically conductive “wireform” mounted with respect to a structurally rigid polymer frame forming a plurality of electrical contacts. Potting is formed in situ with liquid thermoset polymer substantially filling any voids in the connector block and forming a thermoset polymer gasket between the connector block and the case.  
         [0009]     In another embodiment, the present invention provides an implantable medical device having a case and electronic componentry contained in the case. A connector block provides electrical coupling to the electronic componentry. A preformed electrically conductive “wireform” mounted with respect to a structurally rigid polymer frame forming a plurality of electrical contacts. Potting is formed in situ with liquid thermoset polymer substantially filling any voids in the connector block and forming a thermoset polymer gasket between the connector block and the case.  
         [0010]     In another embodiment, the present invention provides a method of forming a connector block providing electrical coupling to electronic componentry of an implantable medical device. The implantable medical device has a case containing the electronic componentry. The connector block has a structurally rigid polymer frame and a preformed electrically conductive “wireform” mounted with respect to the frame forming a plurality of electrical contacts. The connector block is mounted to the case. A plurality of lead wires are connected to the plurality of electrical contacts. The connector block is potted with liquid thermoset polymer substantially filling any voids in the connector block and forming a thermoset polymer gasket between the connector block and the case.  
         [0011]     In a preferred embodiment, the thermoset polymer gasket comprises a biocompatible thermoset polymer.  
         [0012]     In a preferred embodiment, the present invention further provides a thermoplastic polymer urethane cover covering any exposed portions of the connector block with the connector block installed onto the implantable medical device.  
         [0013]     In a preferred embodiment, the thermoset polymer provides electrical isolation between the plurality of electrical contacts.  
         [0014]     In a preferred embodiment, the frame forms a chimney near at least one of the plurality of electrical contacts, the chimney forming a void allowing the liquid thermoset polymer to penetrate and at least partially fill the chimney.  
         [0015]     In a preferred embodiment, the liquid thermoset polymer at least partially filling the chimney provides a bonding surface for like thermoset polymers.  
         [0016]     In a preferred embodiment, a grommet is adapted to be inserted into the chimney bonding with the liquid thermoset polymer in the chimney.  
         [0017]     In a preferred embodiment, the grommet comprises a thermoset polymer compatible with the thermoset polymer at least partially filling the chimney.  
         [0018]     In a preferred embodiment, the thermoset polymer comprises silicone rubber.  
         [0019]     In a preferred embodiment, the thermoset polymer gasket formed by the liquid thermoset polymer forms a skirt that is thinner than reasonably achievable by the polymer frame.  
         [0020]     In a preferred embodiment, the polymer is treated with an adhesion promoter.  
         [0021]     In a preferred embodiment, a set screw mates with the polymer frame at the at least one of the plurality of electrical contacts for securing a mating lead wire to the connector block.  
         [0022]     In a preferred embodiment, the potting forms an internal strain relief for a lead wire coupled to the connector block.  
         [0023]     In a preferred embodiment, the plurality of electrical contacts are linearly arranged. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  illustrates an implantable medical device implanted in a patient;  
         [0025]      FIG. 2  is a block diagram of an implantable medical device illustrating energy transfer from an external charging device;  
         [0026]      FIG. 3  is a top view of a base laminate used in an internal antenna in an implantable medical device;  
         [0027]      FIG. 4  is a side cross-sectional view the base laminate of  FIG. 3 ;  
         [0028]      FIG. 5  is a top view of coil ready coreless laminate formed from the base laminate of  FIGS. 3 and 4 ;  
         [0029]      FIG. 6  is an perspective view of the laminate of  FIG. 5  having received a secondary charging coil;  
         [0030]      FIG. 7  is an illustration of a pressure lamination process securing cover sheets to the laminated substrate;  
         [0031]      FIG. 8  illustrates the attachment of support feet in a first step in an overmolding process;  
         [0032]      FIGS. 9A, 9B ,  9 C,  9 D and  9 E illustrate the injection molding of a second step in an overmolding process;  
         [0033]      FIG. 10  is an exploded view of an internal antenna showing both the overmolded laminated substrate and a cover;  
         [0034]      FIG. 11  is a perspective view of an internal antenna for use with an implantable medical device;  
         [0035]      FIG. 12  illustrates an interior view of a housing of an implantable medical device showing the positioning of a power source;  
         [0036]      FIG. 13  is a perspective view of a battery support for an implantable medical device;  
         [0037]      FIG. 14  is a cross-sectional view of an implantable medical device showing the placement and support of a battery;  
         [0038]      FIG. 15  is a perspective view an internal antenna about to be mated with a housing of implantable medical device;  
         [0039]      FIG. 16  is a detailed view of a portion of  FIG. 15  illustrating an engagement tab;  
         [0040]      FIG. 17  is another detailed view of an engagement tab for an internal antenna;  
         [0041]      FIG. 18  is a top view of a portion of a housing for implantable medical device illustrating bottom rail engagement and fill hole;  
         [0042]      FIG. 19  is a detailed view of internal antenna mounted to housing illustrating sealing implantable medical device using an adhesive needle;  
         [0043]      FIG. 20  is a cross-sectional view of a portion of internal antenna and housing illustrating a flow channel for an adhesive sealant;  
         [0044]      FIG. 21  is an exploded view of a connector block for use with an implantable medical device;  
         [0045]      FIG. 22  is a cross-sectional view of the connector block of  FIG. 21 ;  
         [0046]      FIG. 23  is a partial cross-section view of the connector block of  FIG. 21  illustrating a chimney; and  
         [0047]      FIG. 24  is an exploded view illustrating the assembly of internal antenna, housing and connector block of implantable medical device. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0048]      FIG. 1  shows implantable medical device  10  for example, a drug pump, implanted in patient  12 . The implantable medical device  10  is typically implanted by a surgeon in a sterile surgical procedure performed under local, regional, or general anesthesia. Before implanting the medical device  10 , a catheter  14  is typically implanted with the distal end position at a desired location, or therapeutic delivery site  16 , in the body of patient  12  and the proximal end tunneled under the skin to the location where the medical device  10  is to be implanted. Implantable medical device  10  is generally implanted subcutaneously at depths, depending upon application and device  10 , of from 1 centimeter (0.4 inches) to 2.5 centimeters (1 inch) where there is sufficient tissue to support the implanted system. Once medical device  10  is implanted into the patient  12 , the incision can be sutured closed and medical device  10  can begin operation.  
         [0049]     Implantable medical device  10  operates to infuse a therapeutic substance into patient  12 . Implantable medical device  10  can be used for a wide variety of therapies such as pain, spasticity, cancer, and many other medical conditions.  
         [0050]     The therapeutic substance contained in implantable medical device  10  is a substance intended to have a therapeutic effect such as pharmaceutical compositions, genetic materials, biologics, and other substances. Pharmaceutical compositions are chemical formulations intended to have a therapeutic effect such as intrathecal antispasmodics, pain medications, chemotherapeutic agents, and the like. Pharmaceutical compositions are often configured to function in an implanted environment with characteristics such as stability at body temperature to retain therapeutic qualities, concentration to reduce the frequency of replenishment, and the like. Genetic materials are substances intended to have a direct or indirect genetic therapeutic effect such as genetic vectors, genetic regulator elements, genetic structural elements, DNA, and the like. Biologics are substances that are living matter or derived from living matter intended to have a therapeutic effect such as stem cells, platelets, hormones, biologically produced chemicals, and the like. Other substances may or may not be intended to have a therapeutic effect and are not easily classified such as saline solution, fluoroscopy agents, disease diagnostic agents and the like. Unless otherwise noted in the following paragraphs, a drug is synonymous with any therapeutic, diagnostic, or other substance that is delivered by the implantable infusion device.  
         [0051]     Implantable medical device  10  can be any of a number of medical devices such as an implantable pulse generator, implantable therapeutic substance delivery device, implantable drug pump, cardiac pacemaker, cardioverter or defibrillator, as examples.  
         [0052]     Electrical power for implantable medical device  10  can be contained in implantable medical device itself. Power source for implantable medical device  10  can be any commonly known and readily available sources of power such as a chemical battery, electrical storage device, e.g., capacitor, a mechanical storage device, e.g., spring, or can be transcutaneously supplied in real time, or some combination.  
         [0053]     In order to achieve a transcutaneous transfer of energy, either to charge or recharge an implanted battery or to supply real time power supply, or some combination, an inductive charging technique using an external primary coil and an internal secondary coil can be utilized.  
         [0054]      FIG. 2  illustrates an embodiment of implantable medical device  10  situated under cutaneous boundary  18 . Charging regulation module  20  controls the charging of rechargeable power source  22 . Power source  22  powers electronics module  24  which, in turn, controls therapy module  26 . Again, charging regulation and therapy control is conventional. Implantable medical device  10  also has internal telemetry coil  28  configured in conventional manner to communicate through external telemetry coil  30  to an external programming device (not shown), charging unit  32  or other device in a conventional manner in order to both program and control implantable medical device and to externally obtain information from implantable medical device  10  once implantable medical device has been implanted. Internal telemetry coil  28 , rectangular in shape with dimensions of 1.85 inches (4.7 centimeters) by 1.89 inches (4.8 centimeters) constructed from 150 turns of 43 AWG wire, is sized to be larger than the diameter of secondary charging coil  34 . Secondary coil  34  is constructed with 182 turns of 30 AWG wire with an inside diameter of 0.72 inches (1.83 centimeters) and an outside diameter of 1.43 inches (3.63 centimeters) with a height of 0.075 inches (0.19 centimeters). Magnetic shield  36  is positioned between secondary charging coil  34  and housing  38  and sized to cover the footprint of secondary charging coil  34 .  
         [0055]     Internal telemetry coil  28 , having a larger diameter than secondary coil  34 , is not completely covered by magnetic shield  36  allowing implantable medical device  10  to communicate with the external programming device with internal telemetry coil  28  in spite of the presence of magnetic shield  36 .  
         [0056]     Rechargeable power source  24  can be charged while implantable medical device  10  is in place in a patient through the use of external charging device  40 . In a preferred embodiment, external charging device  40  consists of charging unit  32  and external antenna  42 . Charging unit  32  contains the electronics necessary to drive primary coil  44  with an oscillating current in order to induce current in secondary coil  34  when primary coil  44  is placed in the proximity of secondary coil  34 . Charging unit  32  is operatively coupled to primary coil by cable  46 . In an alternative embodiment, charging unit  32  and external antenna  42  may be combined into a single unit. Antenna  42  may also optionally contain external telemetry coil  30  which may be operatively coupled to charging unit  32  if it is desired to communicate to or from implantable medical device  10  with external charging device  40 . Alternatively, external antenna  42  may optionally contain external telemetry coil  30  which can be operatively coupled to an external programming device, either individually or together with external charging unit  32 .  
         [0057]     Repositionable magnetic core  48  can help to focus electromagnetic energy from primary coil  30  to more closely be aligned with secondary coil  34 . Energy absorptive material  50  can help to absorb heat build-up in external antenna  42  which will also help allow for a lower temperature in implantable medical device  10  and/or help lower recharge times. Thermally conductive material  52  is positioned covering at least a portion of the surface of external antenna  42  which contacts cutaneous boundary  18  of patient  12 . Thermally conductive material  52  positioned on the surface of external charging device  40  in order to distribute any heat which may be generated by external charging device  40 .  
         [0058]     Secondary coil  34  is located in internal antenna  54  that is separable from housing  38 . Magnetic shield  56  is positioned between secondary coil  34  and housing  38  and inside the diameter of internal telemetry coil  28  to help isolate the remainder of implantable medical device  10  from electromagnetic energy from external charging device  40 .  
         [0059]     In  FIG. 3  and  FIG. 4 , construction of internal antenna  54  begins with base laminate  58 .  
         [0060]     Base laminate  58  is constructed of a plurality of layers, preferably three layers, of Metglas™ material  59  secured together by a suitable adhesive, such as Pyralux® acrylic adhesive. Each layer of Metglas™ material  59  is approximately 0.001 inch (0.0254 millimeters) thick. Eight eddy current grooves  60  are radially etched by laser into one side of the layers of Metglas™ material  59  at approximately equal radial spacings. An insulative layer of polyimide is adhesively secured to each side of Metglas™ laminate resulting in a base laminate  58  approximately 0.15 inches (3.8 millimeters) thick. Base laminate  58  is approximately 1.54 inches (39 millimeters) square with two rounded corners to facilitate subsequent assembly.  
         [0061]     Lead wires  62  are placed ( FIG. 5 ) onto base laminate  58  with ends positioned at locations adapted to connect with wires from a coil to added to base laminate  58 . Lead wires  62  are placed inboard and, generally, away from cutouts for hub  64  and feet  66 . Preferably, lead wires  62  are flat 0.004 inch (0.10 millimeters) and round 0.015 inch (0.38 millimeters) in locations  70  and  72  exiting base laminate  58 . Preferably, lead wires  62  are made from niobium ribbon wire. Once positioned, lead wires  62  are secured in place by adhesively securing another layer  63  of polyimide to the side of base laminate  58  onto which lead wires  62  have been positioned. The resulting structure forms a coil ready coreless laminate  68  ready to receive a coil of wire that forms secondary coil  34 . Pre-placing lead wires  62  onto base laminate  58  reduces stress from normal movement of lead wires  62  and aids in further assembly.  
         [0062]     Prior to being placed onto the surface of coil ready coreless laminate  68 , secondary coil  34  is preferably coated in a siloxane coating process. Secondary coil  34  is placed in a vacuum chamber that is then evacuated to 0.10 torr vacuum and held for ten (10) minutes. 10 sccm of Hexamethyldisiloxane, 30 sccm of Nitrous oxide and 1 sccm of Argon are pumped into the chamber. Approximately 150 watts of power to ignite the plasma for thirty (30) seconds.  
         [0063]     In  FIG. 6 , secondary coil  34  is then placed onto the surface of coil ready coreless laminate  68  and electrically connected to lead wires  62  at locations  70  and  72  by welding or, preferably, opposed welding. Cross-over copper wire  74  from secondary coil  34  makes electrical connection at location  72 . The resulting substrate  80  is then sandwiched between a cover sheet  76  of polyimide secured with a thermoset adhesive as illustrated in  FIG. 7 . Substrate  80  is placed into a press between polyimide cover sheets  76  which, of course, can be added either before or after substrate  80  is placed into the press. A thermoset adhesive, preferably Pyralux® acrylic adhesive, is located between substrate  80  and cover sheets  76 . A liquid thermoset polymer, such as liquid silicone rubber, is added to the press outside of cover sheets  76 . Heat, preferably approximately 340 degrees Fahrenheit, and pressure, preferably approximately 1,200 pounds per square inch (8,274 pascals), are applied in the press forcing liquid thermoset polymer again cover sheets  76  which are, in turn, pressed against substrate  80 . The use of a liquid material in the press allows the press to apply force evenly against the irregular upper surface of substrate  80 . The thermoset polymer is allowed to cure under heat and pressure for approximately five (5) minutes forming an at least partially cured silicone rubber sheet on either side of substrate  80  and allowed to cool for approximately twenty (20) minutes. The assembly can then be removed from the mold and the silicone rubber sheets removed (peeled) away and discarded leaving the laminated substrate  80 .  
         [0064]     This process can increase the efficiency of laminating a plurality of articles. The press is only used during while the liquid thermoset polymer is being pressed to substrate  80 . Once the liquid thermoset polymer has cured, e.g., approximately five (5) minutes, the laminated substrate  80  may be removed from the press. The laminated substrate  80  can continue to be allowed to cool outside of the press, e.g., for approximately twenty (20) minutes. As soon as the first laminated substrate  80  is removed from the press, the press may be used again to produce a second laminated substrate  80 . Since the laminated substrate  80  need only remain in the press during the initial stages (first five (5) minutes) for curing, the press may be used to produce a second laminated substrate  80  while the first laminated substrate  80  continues to cool. The early re-use of the press, as compared with having to along laminated substrate to remain in the press for the entire cooling time, is a consider savings in equipment time and allows a greatly increased efficiency of operation.  
         [0065]     Laminated substrate  80  is then overmolded to seal laminated substrate in an environment better able to withstand the harmful effects of bodily fluids after implantation. The overmolding takes place in two steps. In the first step shown in  FIG. 8 , a plurality of support feet  82  are placed on one side, preferably the underside, of laminated substrate  80 . Support feet  82  may be molded onto the underside of laminated substrate  80  using conventional molding techniques. Alternatively, support feet  82  may be adhesively attached, e.g., with glue, may be ultrasonically staked or may be otherwise mechanically attached, e.g., by threaded fastener. Support feet  82  may be equally spaced somewhat near each of the four corners of laminated substrate  80 . In a preferred embodiment, support feet have a circular cross-section. Preferably hub  84  is also molded, or otherwise mechanically attached, to laminated substrate surrounding a central hole in laminated substrate.  
         [0066]     The second part of the overmolding process is illustrated in  FIGS. 9A, 9B ,  9 C and  9 D. In  FIG. 9A , laminated substrate  90  with support feet  82  and hub  84  is placed into an injection mold. Injection material  85 , preferably polysulfone, is introduced into the mold through five (5) injection holes ( 86 A,  86 B,  86 C,  86 D and  86 E) from one side of the injection mold. Please note that the  FIGS. 9A, 9B ,  9 C and  9 D represent a cross-sectional view of the injection mold. Although a total of five (5) injection holes are utilized, only three (3) are visible in the cross-sectional view. One (1) injection hole is used for the hub (injection hole  86 B). Four (4) injection holes are equally spaced as illustrated in  FIG. 9E . Note that injection holes  86 D and  86 E are not visible in the cross-sectional view in  FIG. 9A . Injection material  85  begins to flow into the underside of laminated substrate  80  through injection holes  86 A and  86 C. Injection material  85  also begins to flow through hub  84  and spreads out over the topside of laminated substrate  80  through injection hole  86 B. In  FIG. 9B , injection material  85  continues to flow into the injection mold through the five (5) injection holes ( 86 A,  86 B,  86 C,  86 D and  86 E) in a manner such that the amount of injection material  85  flowing over the topside of laminated substrate  80  and the amount of injection material  85  flowing over the underside of laminated substrate  80  is such that mechanical forces against laminated substrate  80  are evened out from topside and underside. Generally, this is expected to occur when injection material  85  flows at approximately the same rate over the topside of laminated substrate  80  as over the underside of laminated substrate  90 . That is, injection material  85  on the topside of laminated substrate  80  is forcing against the topside of laminated substrate  80  with about the same amount of force that injection material  85  is forcing against the underside of laminated substrate  80 . The general evening of molding forces for topside to underside helps stabilize laminated substrate  80  during the molding process and helps to eliminate warping of laminated substrate  80 . In  FIG. 9C , injection material  85  continues to flow evenly over the topside and the underside of laminated substrate  80 . In  FIG. 9D , injection material  85  has filled the injection mold essentially filling all of the cavity of the injection mold resulting in an overmolded laminated substrate  80 . Injection holes  86 A,  86 B,  86 C,  86 D and  86 E are chosen in size such to facilitate the even flow of injection material  85 . If injection material  85  does not flow evenly over both the topside and the underside of laminated substrate  80 , the resultant overmolded part can warp following cooling.  
         [0067]     As shown in  FIGS. 9A, 9B ,  9 C and  9 D, injection material  85  flows around support feet  82  and encircles each of circular support feet  82 . As injection material  85  cools following the injection molding process, injection material  85  has a tendency to shrink. Typically, shrinkage of injection material may create a crack or a gap which may create an area into which bodily fluids could subsequently gain entry following implantation. However, by encircling each of support feet  82 , such shrinkage of injection material  85  will actually cause injection material to form more tightly around support feet  82  creating an even stronger bond and helping to ensure that bodily fluids can not gain entry following implantation. This same technique holds true for hub  84 . Hub  84  has a circular cross-section and has surrounding a indentation which allow injection material  85  to surround hub  84  and shrink more tightly to hub  84  as injection material  85  cools creating a stronger bond and less likelihood of leaks.  
         [0068]     Overmolded cover  90 , created in  FIGS. 9A, 9B ,  9 C and  9 D, by overmolding laminated substrate  88  in an injection mold, is shown in  FIG. 10  with polysulfone cover  85 . Cover  90  is mechanically joined with overmolded substrate  88  in a conventional manner to complete the assembly of internal  54  (shown in  FIG. 11 ).  
         [0069]      FIG. 12  shows housing  38  of portion of implantable medical device  10  holding power source  22 , electronics module  24  and other components. Power source (preferably a battery)  22  is located in area  92  in housing  38 . It is desirable that battery  22  be reasonably secured within housing  38  but at the same be allowed to expand and contract with use. Chemical batteries, such as battery  22 , may have a tendency to expand as the battery  22  is charged and subsequently contract as the battery  22  ceases to be charged. Such expansion and contraction in a battery  22  which is very tightly secured in housing  38  might cause battery  22  to either come loose from its attachments and/or compromise its electrical connections. Therefore, in a preferred embodiment battery  22  is held in a manner which allows battery  22  to expand, e.g., during charging, and subsequently contract, e.g., following charging, without compromising mechanical and/or electrical connections. Spacer  94 , seen more clearly in  FIG. 13 , supports battery  22  around the periphery of battery  22  while cutout  96  in the central portion of spacer  94  allows battery  22  to expand without compromise. In a preferred embodiment, battery  22  has a rectangular shape with major and minor sides. Preferably, spacer  94  supports a major side of battery  22  while allowing cutout  96  to allow expansion of the major side of battery  22 . In a preferred embodiment, spacer  94  is constructed with a layer of polyimide approximately 0.001 inch (0.0254 millimeters) thick. Preferably, spacer  94  is secured in an inside surface of housing  38  with a suitable adhesive (see  FIG. 14 ). As can be seen in  FIG. 14 , battery  22 , fits inside battery cup  97  supported by spacer  94 , is allowed to expand, e.g., during charge, as illustrated by expansion dotted lines  98 . During a subsequent operation of assembly of implantable medical device  10 , epoxy  100  is introduced into housing  38  to help secure battery  22 . Battery cup  97  and spacer  94  will help to ensure that epoxy  100  does not fill the space created by spacer  94 .  
         [0070]      FIGS. 15 through 20  illustrate the mechanical connection of internal antenna  54  to housing  38  to achieve an integrated implantable medical device  10  that will be able to withstand the ravages of bodily fluids once implanted. Housing  38  has a recharge rail  102  extending around three sides that is adapted to slideably mate with a complementary rail  104  on internal antenna  54 . However, electrical connector wires  106  inhibit rail  104  of internal antenna  54  from engaging recharge rail  102  from the open end. While electrical connector wires could be bent and then reformed to the illustrated position following installation of internal antenna  54  onto housing  38 , this is not desirable from a reliability standpoint, due to the bending and straightening of wires  106 , it is also inefficient. Recharge rail  102  has a drop opening  108  allowing tab  110  of internal antenna  54  to drop into opening  108  and then allow rail  104  to slidably engage recharge rail  102  which are configured to slidably engage over a portion of the sliding distance. This “drop and slide” engagement allows internal antenna  54  to drop avoiding interference with electrical connection wires  106  and still slidably securely engage to housing  38 . Detent  112  provides tactile feedback to the installer to know when proper sliding engagement is achieved. Following engagement, locking tab  114  may be purposely bent up to engage the rear of rail  104  preventing internal antenna  54  from disengaging with housing  38 . It is to be recognized and understood that all of these engaging and locking mechanisms preferably exist on both sides of implantable medical device  10  in complementary fashion even though the drawings illustrate only one side.  
         [0071]     An adhesive channel  116  is formed around the perimeter of housing  38 . Fill hole  118  communicates through both internal antenna  54  and housing  38  to allow an adhesive needle  120  to be inserted. Adhesive needle  120  may then be used to fill adhesive channel  116 , through fill hole  118 , with adhesive providing another layer of sealing for implantable medical device  10 .  
         [0072]     Once internal antenna  54  is secured to housing  54 , electrical connector wires  106  may be connected using connector block  122  as shown in  FIGS. 21, 22 ,  23  and  24 . Rigid polysulfone frame  124  provides structural rigidity to connector block  122 . Frame  124  is laid out in linear fashion so that all electrical connections are in a linear row. Wire frame  126  is stamped out of a conductive material, preferably a metal. Since rigid frame  124  is laid out linearly, wire frame  126  can be stamped with a plurality of linear connector areas. Wire frame  126  is joined with rigid frame  124  and mated with electrical connector wires  106 . Frame cover  128  fits over rigid frame  124 . Once assembled, a biocompatible thermoset polymer, such as silicone rubber, can be injected into connector block  122  substantially filling any voids in connector block  122  forming a thermoset polymer gasket helping to prevent infiltration of body fluids into implantable medical device  10 . The thermoset polymer (not shown) also provides electrical isolation between the electrical contacts of wire frame  126 .  
         [0073]     Connector block  122  has a plurality of openings  130  allowing an external electrical connection with implantable medical device  10 . Chimneys  132  form a void near the external electrical contact openings allowing the thermoset polymer to at least partially fill chimney  132  to further seal and secure an electrical connection opening into implantable medical device  10 . Such thermoset polymer also provides a strain relief for the lead used for the external electrical connection. Grommets  134 , which are compatible with thermoset polymer, additionally secure and electrically isolate the external electrical connection. A set screw  136  may be used to mechanically secure the external wire to connector block  122 . As thermoset polymer substantially fills voids within connector block  122 , thermoset polymer forms a skirt, when cured, that is usually thinner than is reasonably possible to be created with rigid frame  124  or thermoplastic cover  128 . The thinner skirt achieved with the thermoset polymer allows an even stronger and more secure seal against the intrusion of body fluids.  
         [0074]     In a preferred embodiment, rigid frame is treated before assembly with an adhesion promoter to create a stronger bond between rigid frame  124  and thermoset polymer. The surface of polysulfone rigid frame  124  is cleaned with a detergent, preferably Micro 90™ detergent, rinsed first in D.I. water and then rinsed in IPA. Polysulfone rigid frame  124  is plasma treated by first being placed in a vacuum chamber that is then evacuated to 0.10 torr vacuum and held for ten (10) minutes. 10 sccm of Hexamethyldisiloxane, 30 sccm of Nitrous oxide and 1 sccm of Argon are pumped into the chamber. Approximately 150 watts of power to ignite the plasma for thirty (30) seconds. Rigid frame  124  is then coated by being dipped into a twenty percent (20%) solution of RTV medical silicone adhesive and heptane by weight for approximately two (2) seconds. Rigid frame  124  is then removed from the dip and cured in an oven at 150 degrees Centigrade for eight (8) hours.  
         [0075]     Thus, embodiments of the connector block for an implantable medical device are disclosed. One skilled in the art will appreciate that the present invention can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the present invention is limited only by the claims that follow.