Abstract:
A feedthrough filter capacitor assembly comprising a terminal pin connector is described. The terminal pin connector is designed to facilitate an electrical connection between the terminal pin comprising a multitude of compositions to a circuit board of an implantable medical device. The terminal pin connector comprises a clip portion positioned within a connector housing. The connector clip mechanically attaches to the terminal pin of the feedthrough with at least one prong and an exterior surface of the connector housing electrically contacts the circuit board, creating an electrical connection therebetween. The connector housing comprises a material that is conducive to a weld or solder attachment process to the circuit board. The feedthrough filter capacitor assembly is particularly useful for incorporation into implantable medical devices such as cardiac pacemakers, cardioverter defibrillators, and the like, to decouple and shield internal electronic components of the medical device from undesirable electromagnetic interference (EMI) signals.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part of U.S. utility application Ser. No. 13/487,293, filed on Jun. 4, 2012, now U.S. Pat. No. 9,065,224, which claims priority to U.S. provisional application Ser. No. 61/492,828, filed on Jun. 3, 2011. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to a hermetic feedthrough terminal pin assembly, preferably of the type incorporating a filter capacitor. More specifically, this invention relates to a connector assembly comprising a clip positioned within a housing for incorporation into feedthrough filter capacitor assemblies, particularly of the type used in implantable medical devices such as cardiac pacemakers, cardioverter defibrillators, and the like. That is to facilitate connection of the feedthrough terminal pin to a circuit board within the implantable medical device. 
     BACKGROUND OF THE INVENTION 
     Feedthrough assemblies are generally well known in the art for use in connecting electrical signals through the housing or case of an electronic instrument. For example, in an implantable medical device, such as a cardiac pacemaker, defibrillator, or neurostimulator, the feedthrough assembly comprises one or more conductive terminal pins supported by an insulator structure for passage of electrical signals from the exterior to the interior of the medical device. The conductive terminals are fixed into place using a metallization and gold braze process, which provides a hermetic seal between the pin and insulative material. 
     Conventionally, a distal end portion of the terminal pin is electrically connected directly within the implantable medical device. In this case, the distal end portion of the terminal pin is electrically connected directly to an electrical circuit residing within the device by using a soldering or welding attachment process. This connection is readily achievable utilizing platinum or platinum alloy based terminal pins of the prior art. However, the cost of these platinum based terminal pins is prohibitively costly to manufacture. As a result, other lower cost metals such as niobium, tantalum and titanium are increasingly being utilized in replacement of platinum and platinum alloy based terminal pins. These alternative materials provide adequate electrical conduction, however, their specific material properties make them difficult to weld or solder to the electrical contacts of a circuit board. The electrical contacts of the circuit board are typically comprised of gold or copper which are known to be readily solderable and weldable metals. 
     The present invention, therefore, facilitates the electrical connection of the terminal pin to the circuit board by providing a connector that enables an improved connection of the feedthrough terminal pin, regardless of its composition. The terminal pin connector of the present invention comprises a clip that is encompassed within a housing. The clip is positioned circumferentially around the terminal pin and is designed to grip the terminal pin in such a way as to prevent the pin from moving proximally or distally out of the connector. 
     The connector housing comprises an annular sidewall with an outer surface designed to establish physical contact with the circuit board, providing electrical connection therebetween. The outer surface of the connector housing sidewall may be constructed of, or coated with, an electrically conductive material that is conducive to soldering and/or welding attachment processes. Therefore, the present invention provides a feedthrough with an improved electrical connection between its terminal pin or pins and the circuit board of an implantable medical device, for a multitude of terminal pin compositions. 
     SUMMARY OF THE INVENTION 
     In a preferred form, a feedthrough filter capacitor assembly according to the present invention comprises an outer ferrule hermetically sealed to either an alumina insulator or fused glass dielectric material seated within the ferrule. The insulative material is also hermetically sealed to at least one terminal pin. That way, the feedthrough assembly prevents leakage of fluid, such as body fluid in a human implant application, past the hermetic seal at the insulator/ferrule and insulator/terminal pin interfaces. 
     According to the invention, a connector is affixed to a distal end portion of at least one of the terminal pins of the feedthrough. The connector comprises a clip that resides within a connector housing. The clip is design to grasp the outer perimeter of the terminal pin, thus preventing the clip from moving in relation to the pin. The connector housing comprises a annular sidewall that surrounds and encompasses the clip therewithin. 
     In a preferred embodiment, the sidewall of the connector housing comprises an electrically conductive interior and external surface that establishes an electrical connection between a circuit board of an implantable medical device and the terminal pin of the feedthrough. The sidewall of the connector housing can either be constructed of an electrically conductive material, or alternatively, a portion of the exterior and interior surfaces of the connector sidewall, such as by a coating composed of an electrically conductive material. It is preferred that the material with which the connector sidewall is constructed or coated, is conducive to solder or welding attachment processes. Once the connector pin and feedthrough assembly are positioned within the implantable medical device, a portion of the exterior surface of the sidewall of the connector is positioned such that it establishes electrical contact within the implantable medical device. More preferably, a portion of the exterior surface of the sidewall of the connector housing is soldered or welded to a circuit board positioned within a medical device. This joined connection, therefore, establishes an electrical connection between the circuit board and the terminal pin of the feedthrough, through the connector housing sidewall. 
     These and other objects and advantages of the present invention will become increasingly more apparent by a reading of the following description in conjunction with the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side view of an embodiment of the feedthrough connector assembly of the present invention. 
         FIG. 2  illustrates an alternate embodiment of the connector feedthrough connector assembly comprising a one-piece housing. 
         FIG. 3  shows a cross-sectional view of an embodiment of the feedthrough connector assembly of the present invention. 
         FIG. 4  shows a perspective view of an embodiment of the connector feature. 
         FIGS. 4A-4C  illustrate different embodiments of the clip portion of the connector feature. 
         FIG. 5A  shows a proximal end view of an embodiment of the connector feature. 
         FIG. 5B  is a cross-sectional view of the connector feature shown in  FIG. 5A . 
         FIG. 5C  shows a distal end view of the connector feature shown in  FIG. 5A . 
         FIG. 6  illustrates an embodiment of the connector feature being joined to a conductor pad of a circuit board. 
         FIG. 7  shows a magnified partial cross-sectional view of an embodiment of the feedthrough connector assembly positioned within an implantable medical device. 
         FIG. 7A  illustrates a cross-sectional view of an embodiment of a feedthrough connector assembly of the present invention positioned within an implantable medical device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings,  FIGS. 1, 2, 3, 7, and 7A  illustrate an embodiment of a feedthrough connector assembly  10  of the present invention. The feedthrough connector assembly  10  is useful with medical devices, preferably an active implantable medical device (AIMD)  12  (FIG,  7 A) such as a pacemaker, cardiac defibrillator, cardioverter defibrillator, cochlear implant, neurostimulator, internal drug pump, deep brain stimulator, hearing assist device, incontinence device, obesity treatment device, Parkinson&#39;s disease therapy device, bone growth stimulator, and the like. As shown, the connector assembly  10  comprises a feedthrough  14  portion and a terminal pin connector portion  16 . 
     The feedthrough  14  portion of the assembly  10  includes terminal pins  18  that provide for coupling, transmitting and receiving electrical signals to and from body tissue, such as a patient&#39;s heart, while hermetically sealing the interior of the medical instrument against ingress of patient body fluids that could otherwise disrupt instrument operation or cause instrument malfunction. 
       FIG. 3  illustrates a cross-sectional view of a preferred embodiment of an internally grounded feedthrough capacitor connector assembly  20  of the present invention. As illustrated the internally grounded feedthrough capacitor connector assembly  20  comprises a filter feedthrough capacitor assembly  22  comprising a capacitor  24  that is attached to the feedthrough portion  14 . Like the feedthrough connector assembly  10 , the feedthrough capacitor connector assembly  20  comprises a connector portion  16 . While not necessary for accomplishing these functions, the filter capacitor  24  is attached to the feedthrough  14  for suppressing or decoupling undesirable electro-magnetic interference (EMI) signals and noise transmission into the interior of the medical device. 
     More particularly, the feedthrough  14  of the feedthrough connector assembly  10  and the feedthrough filter capacitor assembly  22 , comprises a ferrule  26  defining an insulator-receiving bore surrounding an insulator  28 . Suitable electrically conductive materials for the ferrule  26  include titanium, tantalum, niobium, stainless steel or combinations of alloys thereof, the former being preferred. The ferrule  26  may be of any geometry, non-limiting examples being curved, round, rectangle, and oblong. A surrounding flange  30  extends from the ferrule  26  to facilitate attachment of the feedthrough  14  to a casing  32  of the implantable medical device  12  as previously described ( FIGS. 7 and 7A ). The method of attachment may be by laser welding, soldering or other suitable methods. 
     The insulator  28  is of a ceramic material such as of alumina, zirconia, zirconia toughened alumina, aluminum nitride, boron nitride, silicon carbide, glass or combinations thereof. Preferably, the insulating material is alumina, which is highly purified aluminum oxide, and comprises a sidewall  34  extending to a first upper side  36  and a second lower side  38 . The insulator  28  is also provided with bores  40  that receive the terminal pins  18  passing therethrough. A layer of metal  42 , referred to as metallization, is applied to the insulator sidewall  34  and a bore sidewall  44  of the terminal pin bores  40  to aid a braze material  46  in hermetically sealing between the ferrule  26  and the sidewall  34  of the insulator  28  and between the terminal pins  18  and the bore sidewall  44  of the insulator  28 , respectively. Specifically, the metallization layer  42  is preferably applied to a portion of the outer surface of the insulator sidewall  34  and a portion of the surface of the inside sidewall  44  of the terminal pin bores  40 . These surfaces are intended to contact and bond with the ferrule  26  and terminal pins  18  respectively of the feedthrough assembly  14 , establishing a hermetic seal therebetween. 
     As further shown in  FIG. 3 , the feedthrough filter capacitor assembly  22  includes the filter capacitor  24  that provides for filtering undesirable EMI signals before they can enter the device housing via the terminal pins  18 . The filter capacitor  24  comprises a ceramic or ceramic-based dielectric monolith  48  having multiple capacitor-forming conductive electrode plates formed therein. The capacitor dielectric  48  preferably has a circular cross-section matching the cross-section of the ferrule  26  and supports a plurality of spaced-apart layers of first or “active” electrode plates  50  in spaced relationship with a plurality of spaced apart layers of second or “ground” electrode plates  52 . Alternatively, the capacitor dielectric  48  may have an oval or rectangular cross-section that approaches the cross-section shape of the ferrule  26 . The filter capacitor  24  is preferably joined to the feedthrough  14  adjacent to the insulator upper side  36  by a bead  54  of conductive material, such as a solder or braze ring, or a thermal-setting conductive adhesive, and the like. The dielectric  48  includes lead bores  56  provided with an inner surface metallization layer. The terminal pins  18  pass therethrough and are conductively coupled to the active plates  50  by a conductive braze material  58  contacting between the terminal pins  18  and the bore metallization. In a similar manner, the ground plates  52  are electrically connected through an outer surface metallization  60  and the conductive material  54  to the ferrule  26 . 
     As shown in  FIGS. 1, 3, 6, 7 and 7A , the terminal pin connector  16  of the present invention is attached to at least one terminal pin  18  of the feedthrough  14 . The terminal pin connector  16  may be attached to the terminal pin  18  of either an unfiltered feedthrough assembly  14 , as shown in  FIGS. 1-2, 6, 7 and 7A , or the feedthrough filter capacitor assembly  22 , as illustrated in  FIG. 3 . More specifically, the connector portion  16  is attached to a distal end portion  62  of the terminal pin  18 . For identification purposes, the distal end portion  62  of the terminal pin  18  is defined as the portion of the terminal pin  18  that resides within the active implantable medical device (AIMD)  12 . 
     As illustrated in  FIGS. 3, 4, 4A-4C and 5A-5C , the terminal pin connector  16  comprises a clip  64  that resides within a connector housing  66 . The clip  64  is designed to be positioned around the perimeter of the terminal pin  18  such that the clip  64  grasps the exterior surface of the terminal pin  18 . In one embodiment shown in  FIGS. 4A-4C, and 5B , the clip  64  comprises a clip base portion  68  with at least one prong  70  extending from the base  68 . As shown, the clip base portion  68  comprises an annular sidewall  72  which encompasses a clip base portion throughbore  74 . This throughbore  74  is the opening through which the terminal pin  18  longitudinally extends. The base throughbore  74  is dimensioned such that the terminal pin  18  of a multitude of diameters can pass therethrough. 
     As shown in  FIGS. 3 and 4A-4C , the clip  64  comprises at least one prong or finger  70  that extends from the base portion  68 . As shown, the prong or prongs  70  are preferably angled inwardly towards a longitudinal axis A-A ( FIG. 5B ) that extends longitudinally through the throughbore  74  of the base portion  68 . This inward orientation enables the prong or prongs  70  to contact and compress against the exterior surface of the perimeter of the terminal pin  18  gripping the pin  18  therewithin. In addition, the inward orientation of the prong  70  creates a wedging relationship between the terminal pin  18  and the base clip annular sidewall  72 . As the end of the prong  70  compresses against the sidewall of the terminal pin  18 , the pin  18  becomes wedged between the prong  70  and the bottom edge of the sidewall  72 . Such a wedging relationship helps prevent the terminal pin  18  from disengaging with the clip  64 . 
     As the terminal pin  18  is introduced through the base portion  68  of the clip  64 , the space between the prong(s)  70  expands to thereby allow the terminal pin  18  to proceed therebetween. The prong(s)  70  of the clip  64  are preferably designed to allow the terminal pin  18  to proceed in one direction between the prong end(s) such that the terminal pin  18  is prohibited from moving in the reverse direction. In a preferred embodiment, the terminal pin  18  proceeds in a distal direction through the throughbore  74  of the clip  64  residing within the connector housing  66 . Once positioned within the throughbore  74 , the angled prong orientation grips the pin  18  and prevents it from moving in the reverse proximal direction. 
       FIG. 3  illustrates an alternative embodiment of a clip  64  and connector housing  66  assembly of the present invention. As shown, a single prong  70  extends from the base portion  68  of the clip  64 . In addition, the connector housing  66  comprises an opening  67  that partially extends through the thickness of the housing  66  from a first housing end  59  towards a second housing end  69 . The opening  67  has a first diameter that extends through the first housing end  59 . The opening  67  extends axially along longitudinal axis A-A through a portion of the housing thickness to an end wall  65  located at the second housing end  69 , thereby forming a blind hole  67  within the connector housing  66 . As defined herein a “blind hole” is a hole that is formed such as by reaming, drilling, or milling to a specified depth without breaking through the end wall  65  of the work piece. 
     In a preferred embodiment, at least a portion of the distal end  62  of the terminal pin  18  is positioned within the blind hole  67  that extends along longitudinal axis A-A. In a preferred embodiment, the distal end  62  of the terminal pin  18  is positioned within the blind hole  67  proximate an interior surface  63  of the end wall  65 . 
     In addition, a single prong  70  is shown extending distally from the annular sidewall  72 . In a preferred embodiment, the end of the prong  70  contacts a portion of an exterior surface of the terminal pin  18  along the distal end portion  62  that resides within the opening  67 . This is to help prevent inadvertent movement of the terminal pin  18  along the longitudinal axis A-A out from within the connector opening  67 . The prong  70  is preferably angled inwardly towards the central axis A-A that extends longitudinally through the throughbore  74  of the base portion  68  and into the blind hole  67 . As previously mentioned, this inward orientation enables the prong  70  to contact and compress against the exterior surface of the perimeter of the terminal pin  18  gripping the pin  18  therewithin. Furthermore, the prong  70  creates a wedging relationship between the exterior surface of the terminal pin  18  and the annular sidewall  72 . 
     In a preferred embodiment, a recess  71 , such as the recess illustrated in  FIG. 3 , may partially extend within an external terminal pin surface about the distal pin portion  62  thereof. More preferably, the recess  71  is positioned such that it annularly extends around the circumference of the pin  18  within the distal pin portion  62 . The recess  71  preferably enhances the grip of the prong  70  along the pin&#39;s exterior surface by providing a groove within the exterior pin surface for the end of the prong  70  to be positioned therewithin. Thus, the recess  71  helps prevent the pin  18  from becoming disengaged from the clip  64 . In addition, the recess  71  helps prevent the connector housing  66  from undesirably moving in a distal axial direction such that it might slide off the distal end of the terminal pin  18 . 
     Alternatively, in lieu of the recess  71 , an outwardly extending ridge  73  may be constructed about the distal portion  62  of the terminal pin  18 . Like the recess  71 , the ridge  73  may be positioned such that it annularly extends around the circumference of the pin  18  within the distal end portion  62 . Like the recess  71 , the outwardly extending ridge  73  helps prevent disengagement of the clip  64  from the terminal pin  18 . In a preferred embodiment, when the pin  18  is positioned within the connector housing  66 , the ridge  73  is preferably positioned proximal of the end of the prong  70 . This way, the ridge  73  enhances the grip of the prong  70  on the exterior surface of the pin  18  and helps prevent unintentional distal axial movement of the connector housing  66  that would disengage it from the terminal pin  18 . 
     The connector clip  64  is preferably composed of an electrically conductive material, such as an electrically conductive metal. The connector clip  64  is designed to provide an electrical connection between the terminal pin  18  of the feedthrough  14  and the connector housing  66 . In a preferred embodiment, the clip  64  may be constructed from copper, tin, stainless steel, aluminum, titanium, gold, platinum, palladium, palladium alloys, associated alloys and combinations thereof. 
     As shown in  FIGS. 1, 4, 4A-4C, 5A-5C, 7 and 7A , the connector housing  66  comprises an annular sidewall  76  which encompasses a housing throughbore  78  or blind opening  67  ( FIG. 3 ) that extends longitudinally therethrough. In the embodiment shown, the housing  66  is designed similarly to that of a tube having an opening that extends from a proximal housing end  80  to a distal housing end  82 . The connector housing  66  comprises a sidewall thickness  84  that extends from an interior sidewall surface  86  to an exterior sidewall surface  88 . In a preferred embodiment, the terminal pin connector  16  has a length  90  ranging from about 0.25 inches to about 2.0 inches and a throughbore diameter  92  that ranges from about 0.1 inches to about 0.25 inches. 
     An individual clip  64  is preferably positioned within the throughbore  78  or blind hole  67  ( FIG. 3 ) of each connector housing  66 . This orientation prevents the clip  64  from moving within or out of the housing  66 . Furthermore, this embodiment allows each of the terminal pins  18  to be bent in individual orientations. Alternatively, as shown in the embodiment of  FIG. 2 , the connector housing may be constructed of a one-piece housing body  94 . In this embodiment, the connector housing body  94  comprises a one-piece construction having a plurality clips  64  positioned within each of the individual housing thoughbores  78 . The housing throughbores  78  may be arranged in a linear orientation or they may be arranged in the form of a circle, oval, triangle, star or the like to match the cross-sectional form of the feedthrough  14 . 
     The exterior surface of the sidewall  88  of the connector housing  66  or one-piece housing body embodiment  94 , is preferably constructed with at least one planar surface portion  93 . As shown in  FIG. 4 , the illustrated embodiment of the connector housing  66  comprises four planar surface portions, a top planar surface  96 , a bottom planar surface  98 , a left side planar surface  100  and a right side planar surface  102  that extend at least part way along the longitudinal length of the housing  66 . Alternatively, the connector housing  66  may comprise fewer or more exterior surface planar portions. 
     As illustrated in  FIG. 6 , the planar surface portion  93  of the exterior surface  88  of the housing  66  is designed to establish intimate electrical contact with an electrical contact pad  104  of a circuit board  106  of the medical device  12 . As such, the connector housing  66  may be composed of an electrically conductive material or alternatively, is coated with an electrically conductive material, such as a metal. 
     In an embodiment, the exterior surface  88  of the connector housing  66  comprises a coating of an electrically conductive material. In a preferred embodiment, the coating is conducive for use in the joining processes of soldering or welding. The coating may comprise, but not be limited to, copper, tin, stainless steel, aluminum, titanium, gold, platinum, palladium, palladium alloys, associated alloys and combinations thereof. 
     Alternatively, a portion of the exterior surface  88  and a portion of the interior surface  86  of the sidewall  76  of the connector housing  66  may be constructed of an electrically conductive material, particularly a material that is conducive to the joining processes of soldering and/or welding. In either case, the connector housing  66  preferably enables an electrically conductive pathway that extends through at least a portion of the thickness  84  of the housing sidewall from the inner surface  86  of the housing  66  to the outer surface  88 . The connector housing  66  is designed such that an electrical connection is made between the terminal pin.  18  of the feedthrough  14  portion and the circuit board  106  of the AIMD  12 . 
     Once the connector feedthrough assembly  10  or filtered feedthrough connector assembly  20  is positioned within the AIMD  12 , the exterior surface  88  of the connector housing  66  may be electrically joined to an electrically conductive pad or area  104  of the circuit board of the AIMD  12  by a weld  107 . As shown in  FIG. 6 , a joining instrument  108 , such as a laser welding or soldering instrument, may be utilized to join a portion of the exterior housing surface  88  to the circuit board pad  104 . Although it is preferred that the exterior surface of the housing  66  of the connector  16  is permanently joined to the electrical contact pad  104  of the circuit board  106 , the exterior surface  88  of the housing  66  of the connector may be placed in contact with the surface of the electrical contact pad  104 , without the joining weld  107 , such that it may be easily removed. For example, once the terminal pin connector(s) are positioned over the terminal pin(s), the terminal pin(s) may be bent such that the exterior surface  88  of the housing  66  is in a removeable contactable relationship with the surface of the electrical contact pad  104  of the circuit board  106 . 
     The feedthrough connector assembly  10  or filtered feedthrough connector assembly  20  is preferably designed to be utilized with a “clam shell” style medical device casing  32 . A “clam shell” type medical device casing  32  is one in which two opposing case halves come together to form the full casing In one embodiment, as illustrated in  FIG. 7A , the feedthrough connector assembly  10  or filtered feedthrough connector assembly  20  is positioned within an inlet  110  of a first half  112  of the casing  32 . The flange  30  is typically welded to casing half within the inlet  110  and the terminal pin connector(s)  16 , attached to their respective terminal pins  18 , are positioned on the circuit board pad(s)  104  of the circuit board  106 . In a second embodiment, the terminal pin connector(s)  16  may be first positioned and joined either by welding or soldering  107  on the circuit board pad(s)  104  of the circuit board  106 . After the terminal pin connector(s)  16  are positioned on their respective circuit board pad(s)  104 , the terminal pins  18 , are positioned within the terminal pin connector(s)  16 . Once the terminal pins  18  are correctly positioned, the flange  30  of the feedthrough  14  is preferably welded to the first case half  112 . In either embodiment, a second case half or case lid  114  ( FIG. 7 ) is positioned adjacent to the first case half  112  such that their respective inlets  110  and sidewalls oppose each over. The respective first and second halves of the casing  32  are typically welded together establishing a hermetic seal therewithin. 
     It is appreciated that various modifications to the invention concepts described herein may be apparent to those of ordinary skill in the art without departing from the scope of the present invention as defined by the appended claims.