Abstract:
A multi-leaded, filter feed-thru assembly for implantable medical devices, such as heart pacemakers, defibrillators, and neurostimulators, which integrates both multi-element semiconductor devices and passive component devices, or multi-element combinations thereof, together with a discoidal capacitive filter device to provide filtration of electromagnetic interference is provided. The assembly additionally provides for the suppression of high voltage transients from defibrillation and electrocautery procedures, as well as providing additional circuit and network functions.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to feed-thru capacitors of the type used in implantable medical devices such as heart pacemakers, defibrillators, and neurostimulators. More specifically, the instant invention relates to a multi-leaded feed-thru assembly combining a capacitive device and additional semi-conductive devices for use in implantable medical devices. Still further, the present invention relates to a multi-leaded feed-thru assembly which integrates both multi-element semiconductor devices and passive component devices, or multi-element combinations thereof, together with a discoidal capacitive filter device to provide filtration of electromagnetic interference (EMI). 
     Conventional feed-thru capacitive devices are known. In particular, ceramic capacitor feed-thru assemblies for use in implantable medical devices are known. With the continued miniaturization of electric devices and the desire for less invasive medical procedures, smaller multi-functional devices have become needed to increase the capabilities of implantable medical devices such as pacemakers while maintaining or even reducing their size and simultaneously increasing their reliability. 
     U.S. Pat. No. 5,735,884, issued to Thompson et al. and incorporated fully herein by reference, discloses a filtering feed-thru assembly for implantable medical devices. The &#39;884 assembly, however, provides poor EMI filter performance due to the use of chip capacitors. While useful for its purpose, the absolute requirement for reliability of these implantable devices mandates that the feed-thru filter must be capable of filtering (i.e., reflecting or absorbing and decoupling) substantially all EMI to prevent damage to the device&#39;s internal circuitry. Failure of the implantable device could result in the loss of function of the medical device and possibly the loss of the patient&#39;s life. 
     U.S. Pat. Nos. 4,424,551 and 5,333,095, issued to Stevenson et al. and incorporated fully herein by reference, also disclose feed-thru filtering capacitive assemblies for use in medical devices. Neither of these assemblies, however, provides for the attachment of semiconductor or passive component devices to such filtering feed-thru devices. This results in an increase in medical device size due to the requirement for downstream assembly of such additional components into the internal circuitry of such a device, in addition to the associated increase in costs. Additionally, neither the &#39;551 nor the &#39;095 assembly provides for suppression of transient voltages at their point of entry (i.e., the end of the electrically conductive leads external to the implantable device). 
     It is, therefore, desirable to provide a multi-leaded feed-thru assembly capable of reliably and thoroughly filtering EMI, as well as, suppressing transient voltages at their point of entry into the implantable medical device and integrating both multi-element semiconductor devices and passive component devices, or multi-element combinations thereof, together with a discoidal capacitive filter. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes and addresses various of the foregoing limitations and drawbacks, and others, concerning the filtration of electromagnetic interference, the suppression of transient voltages, and the integration of additional electronic components into a single assembly for implantable medical devices resulting in the reduction in size and increase in reliability of the medical device. Therefore, the present invention provides a new multi-leaded filtering feed-thru assembly for filtering EMI, such as may be generated by cellular telephones, and suppressing transient voltages, such as may be generated by a defibrillator, as well as allowing for the integration of additional electronic components into the assembly. 
     It is a principle object of the subject invention to provide a filtering feed-thru capacitive device. More particularly, it is an object of the present invention to provide a filtering feed-thru capacitive assembly capable of inclusion in an implantable medical device. 
     Another more particular object of the present invention is to provide a filtering feed-thru assembly capable of filtering EMI as may be experienced by an implanted medical device. In such context, it is a still further object of the present invention to provide a filtering feed-thru assembly capable of suppressing transient voltages as may be experienced by an implanted medical device. 
     It is a further general object of the present invention to provide a filtering feed-thru assembly capable of integration with both multi-element semiconductor devices and passive component devices, or multi-element combinations thereof. In such context, it is a still further object to provide a filtering feed-thru assembly comprising a discoidal capacitive filter. 
     It is a more specific object of the present invention to provide a filtering feed-thru assembly for an implantable medical device, capable of filtering electromagnetic interference from any external signals entering the device, suppressing any transient voltages at their entry point into the device, and capable of integration with both multi-element semiconductor and passive component devices, or multi-element combinations thereof, together with a discoidal capacitive filter. 
     Additional objects and advantages of the invention are set forth in, or will be apparent to those of ordinary skill in the art from, the detailed description as follows. Also, it should be further appreciated that modifications and variations to the specifically illustrated and discussed features and materials hereof may be practiced in various embodiments and uses of this invention without departing from the spirit and scope thereof, by virtue of present reference thereto. Such variations may include, but are not limited to, substitutions of equivalent means, features, and/or materials for those shown or discussed, and the functional or positional reversal of various parts, features, or the like. 
     Still further, it is to be understood that different embodiments, as well as different presently preferred embodiments, of this invention, may include various combinations or configurations of presently disclosed features, elements, or their equivalents (including combinations of features or configurations thereof not expressly shown in the figures or stated in the detailed description). 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention. 
     In one exemplary embodiment of the present invention the assembly comprises a feed-thru filter for a pacemaker or other implantable medical device. Such assembly may have a header, a support plate, with a flange around its outer perimeter for attachment in an opening in the housing of the implantable device. Such attachment can be achieved through any known means but is typically completed by welding or brazing and is preferably a hermetic sealing of the assembly within such opening in the device. 
     Within such header may be a single opening or set of openings through which extend multiple electrically conductive terminal pins. A first end of each of such pins remains external to the implantable medical device when such assembly is connected thereto. Preferably, the opening or set of openings in such header through which such pins pass is hermetically sealed. Within the opening or within each opening in a set of openings may be an electrically insulative support. Such supports, while aiding in sealing the opening or set of openings, may maintain the pins within the opening or set of openings and electrically insulate them from portions of the circuitry of such assembly and such medical device. 
     A discoidal capacitor may be bonded to such header by a conductive polyamide. Such discoidal capacitor may have a second set of openings formed therethrough. Such openings in the capacitor may align with the opening or set of openings through such header when the two are bonded together. This may allow for electrical connection between such discoidal capacitor and such electrically conductive terminal pins. 
     Within such discoidal capacitor may be a first set of electrode plates arranged to be suitable for parallel connections with such pins and a second set of electrode plates arranged to be suitable for series connections with such pins. Such parallel connections with the pins allow-for the filtering of a majority of any electromagnetic interference which may be experienced by such medical devices. Similarly, such series connections with the pins allow for suppression of transient voltage spikes as may be experienced by such implantable devices during defibrillation. In particular, direct current (DC) is reflected or blocked and alternating current (AC) is absorbed and decoupled by the series capacitive electrode plates. 
     On the opposing side of such discoidal capacitor from such header, electrically conductive patterns may be disposed for further connection to additional electronic component elements. Such patterns may also provide for connection to the internal circuitry of such medical device. This may be achieved through either the use of wire bondable pads integrated into such patterns or a second set of terminal pins connected to such discoidal capacitor. In the later instance, the first set of such terminal pins may be used for suppressing transient voltages while the second set may be utilized to filter EMI or vise versa. 
     Should such patterns be used for connection to an additional electrical component, such component may be a multi-element semiconductor and a passive component device, or a multi-element combination thereof. For example, such electrical component may be a semiconductor attached to such discoidal capacitor by solder reflow, a multi-element passive component attached by epoxy bonding and conductive polyamide, or a thick film resistor or inductor attached by firing. 
     One of ordinary skill in the art would recognize that any combination of additional electronic component, such discoidal capacitor, and connection type to the internal circuitry of such implantable devices is possible. Additionally, such terminal pins may be located in-line or on a bolt circle and such insulative supports may constitute either a single multi-hole support or individual supportive elements. Finally, such header may either provide only a supportive plate for the remainder of the assembly or may constitute a canister to contain the entire assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
     FIG. 1 is an overhead perspective view of an exemplary embodiment of the present invention illustrating a filtering feed-thru assembly with electrically conductive pins located on a bolt circle and wire bondable pads for connection to a circuit and to ground; 
     FIG. 2 is a schematic diagram of the exemplary embodiment of FIG. 1 showing parallel capacitors for filtering electromagnetic interference and series capacitors for suppressing transient voltages; 
     FIG. 3 is a cross-sectional view of the exemplary embodiment of FIG. 1 taken along line A—A showing at least two of the electrically conductive pins extending through the header and supported by an electrically insulative support, as well as an exemplary discoidal capacitor and an additional electronic component; 
     FIG. 4 is a cross-sectional view of the exemplary embodiment of FIG. 1 taken along line B—B showing at least two of the electrically conductive pins extending through the header (shown to be a canister) and supported by an electrically insulative support, as well as an exemplary discoidal capacitor and an additional electronic component connected via a conductive polyamide; 
     FIG. 5 is an overhead perspective view of the exemplary embodiment of FIG. 1 taken along line C—C of FIG. 4 showing an exemplary electrically conductive pattern on the upper surface of the discoidal capacitor connecting the electrically conductive pins, the additional electronic component, and the wire bondable pads; 
     FIG. 6 is a perspective side view of a second exemplary embodiment of the present invention illustrating a filtering feed-thru assembly with a first set of electrically conductive pins located in-line and a second set of electrically conductive pins for connection to the internal circuitry of the implantable medical device; 
     FIG. 7 is a schematic diagram of the exemplary embodiment of FIG. 6 showing parallel capacitors for filtering electromagnetic interference and series capacitors for suppressing transient voltages; 
     FIG. 8 is an overhead perspective view of the exemplary embodiment of FIG. 6 taken along line D—D of FIG. 6 showing an exemplary electrically conductive pattern on the upper surface of the discoidal capacitor connecting a first set of the in-line electrically conductive pins and the additional electronic component and the second set of in-line electrically conductive pins for connection to the internal circuitry of the implantable device; 
     FIG. 9 is a side perspective view of a third exemplary embodiment of the present invention illustrating a filtering feed-thru assembly with electrically conductive pins located in-line and wire bondable pads for connection to internal circuitry of an implantable medical device; 
     FIG. 10 is a schematic diagram of the exemplary embodiment of FIG. 9 showing parallel capacitors for filtering electromagnetic interference; and 
     FIG. 11 is an overhead perspective view of the exemplary embodiment of FIG. 9 taken along line E—E of FIG. 9 showing an exemplary electrically conductive pattern on the upper surface of the discoidal capacitor connecting the in-line electrically conductive pins, the additional electronic component, and the wire bondable pads. 
    
    
     Repeat use of reference characters throughout the present specification and appended drawings is intended to represent the same or analogous features or elements of the invention. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to presently preferred embodiments of the invention, examples of which are fully represented in the accompanying drawings. Such examples are provided by way of an explanation of the invention, not limitation thereof In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention, without departing from the spirit and scope thereof. For instance, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Still further, variations in selection of materials and/or characteristics may be practiced, to satisfy particular desired user criteria. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the present features and their equivalents. 
     As disclosed above, the present invention is particularly concerned with a multi-leaded feed-thru filter assembly capable of reliably and thoroughly filtering EMI, as well as, suppressing transient voltages and integrating both multi-element semiconductor devices and passive component devices, or multi-element combinations thereof, together with a discoidal capacitor. FIG. 1 depicts a first preferred embodiment of the present invention including an exemplary filtering feed-thru assembly  100  having a header  120 , a three-sided canister, with a flange  122  around its outer perimeter for attachment in an opening in the housing of the implantable device (not shown). 
     Disposed upon the header  120  is an exemplary discoidal capacitor  124 . On the upper surface of the discoidal capacitor  124  is an electrically conductive pattern  126  to be discussed in detail later. In electrical communication with the pattern  126  is an electronic component  128 . In accordance with the first embodiment this additional electronic component  128  may be a semiconductor attached to such discoidal capacitor  124  by solder reflow, a multi-element passive component attached by epoxy bonding and conductive polyamide, or a thick film resistor or inductor attached by firing. 
     As best seen in FIGS. 3 and 4, the header  120  is a supportive surface for the remainder of the assembly  100 . The header has an opening  130  through which pass a corresponding set of terminal pins  132 . Each terminal pin  132  has a respective first  132 ( a ) and second end opposite the first end thereof. The first end  132 ( a ) of each terminal pin remains external to the implantable device (not shown) when the assembly  100  is connected thereto. The terminal pins  132  are maintained in the opening  130  by an exemplary electrically insulative support  134 . The support  134  may be either a single multi-hole support or a set of individual supports in an embodiment where a set of individual openings exists in the header  120 . 
     In accordance with the present embodiment, the exemplary discoidal capacitor  124  is bonded to the supportive surface of the header  120  with a conductive polyamide  136 . The capacitor  124  has a set of openings  138  disposed therethrough, in the present embodiment arranged in a bolt circle, for passage of the terminal pins  132 . The set of openings  138  in the discoidal capacitor are aligned with the opening  130  in the header  120  to allow for passage of the terminal pins  132  through the bonded pair. Within the set of openings  138  in the discoidal capacitor  124 , the terminal pins  132  are maintained in electrical communication by use of the same conductive polyamide  136  used to bond the header  120  and the discoidal capacitor  124 . 
     Within the exemplary discoidal capacitor  124  is a first set of electrode plates (not shown) arranged to be in parallel connection with the terminal pins  132  and a second set of electrode plates (not shown) arranged to be in series connection with the terminal pins  132 . The electrode plates are diagrammatically represented by the arrangement of FIG. 2, and those of ordinary skill in the art will understand the details thereof without additional discussion, which details form no particular aspect of the subject invention beyond the disclosure herewith. Such parallel connections with the pins  132  allow for the filtering of a majority of any electromagnetic interference which may be experienced by such medical devices. Similarly, such series connections with the pins  132  allow for suppression of transient voltage spikes as may be experienced by such implantable devices during defibrillation. To be more specific, direct current (DC) transients are reflected away or blocked from the device while alternating current (AC) transients are absorbed and decoupled by the series capacitive electrode plates. 
     As shown in FIGS. 1 and 5, on the opposing side of the discoidal capacitor  124  from the header  120 , an exemplary electrically conductive pattern  126  is disclosed for connection of additional electronic components. The disclosed pattern  126  also provides for connection to the internal circuitry of the medical device. In the present embodiment this is achieved through the use of wire bondable pads  140  integrated into the pattern  126 . Notably, the center wire bondable pad  142  preferably is a ground. FIG. 2 depicts a schematic diagram of the assembly  100  including the terminal pins  132 , the parallel and series capacitive electrode plates and the wire bonded pads  140  and  142  on the upper surface of the discoidal capacitor  124 . 
     In a second exemplary preferred embodiment of the present invention, as shown in FIGS. 6-8, an additional capacitive device  244  has been placed between the header  220  and the discoidal capacitor  224 . The method of bonding, a conductive polyamide  236 , is identical to that previously described. This additional capacitor  244  has a first set of electrode plates arranged to be in parallel connection with the first set of preferably in-line terminal pins  232  and a second set of electrode plates arranged to be in series connection with the pins  232 . The addition of another capacitive device  244  capable of both filtering EMI and suppressing transient voltages aids in the reliability of the device. 
     As in the previous embodiment, an electrically conductive pattern  226  is disposed on the upper surface of the discoidal capacitor  224  allowing for the connection of an additional electronic component  228  to the assembly  200 . In the present preferred embodiment, however, the discoidal capacitor  224  has two sets of openings therethrough. See, for example, FIG.  8 . The first set of openings  238  is identical in form and purpose as that disclosed in the prior embodiment. The second set of openings  248  is for passage of an second set of terminal pins  246  through the discoidal capacitor. This second set of pins  246  replaces the wire bonded pads  140  and  142  of the first preferred embodiment as can be seen in the schematic diagram of FIG.  7 . 
     In a third exemplary preferred embodiment of the present invention, as seen in FIGS. 9-11, an additional capacitive device  344  has been placed between the header  320  and the discoidal capacitor  324 . The method of bonding, a conductive polyamide  336 , is identical to that previously described. This additional capacitor  344  has a set of electrode plates arranged to be in parallel connection with the in-line terminal pins  332 . In this embodiment, there are no series connections with the pins  332  which allows for a thinner assembly  300  and reduced production costs. The absence of the series capacitors can clearly be seen in the schematic diagram of the assembly as shown in FIG.  10 . 
     As seen in FIG. 11, an electrically conductive pattern  326  is disposed on the upper surface of the discoidal capacitor  324  allowing for the connection of an additional electronic component  328  to the assembly  300 . In the present preferred embodiment, the disclosed pattern  326  also provides for connection to the internal circuitry of the medical device through the use of wire bondable pads  340  integrated into the pattern  326 . 
     Although several preferred embodiments of the invention have been described using specific terms and devices, such descriptions are for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or the scope of the present invention, which is set forth in the following claims. In addition, it should be understood that aspects of various other embodiments may be interchanged both in whole or in part. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.