Patent Publication Number: US-6987660-B2

Title: Spring contact system for EMI filtered hermetic seals for active implantable medical devices

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to feedthrough capacitor terminal pin assemblies and related methods of construction, particularly of the type used in active implantable medical devices (AIMD), such as cardiac pacemakers, implantable hearing devices, implantable cardioverter defibrillators, neurostimulators, drug pumps and the like. Electromagnetic interference (EMI) feedthrough filter capacitors are typically used in such applications to decouple and shield undesirable electromagnetic interference (EMI) signals from the device. More specifically, this invention relates to processes and apparatuses for installing feedthrough capacitors to terminal pin assemblies utilizing conductive, resiliently flexible contact springs. This invention is particularly designed for use in cardiac pacemakers and cardioverter defibrillators. This invention is also applicable to a wide range of other EMI filter applications, such as military or space electronic modules, wherever it is desirable to preclude entry of EMI into a shielded housing. The simplified electrical contact method as described herein is applicable both to hermetically sealed housings and non-hermetically sealed housings and bulkheads. 
   Feedthrough terminal pin assemblies are generally well known in the art for connecting electrical signals through the housing or case of an electronic instrument. For example, in active implantable medical devices, such as cardiac pacemakers, defibrillators or the like, the terminal pin assembly comprises one or more conductive terminal pins supported by an insulator structure for feedthrough passage from the exterior to the interior of the medical device. Many different insulator structures and related mounting methods are known in the art for use in medical devices wherein the insulator structure provides a hermetic seal to prevent entry of body fluids into the housing of the medical device. See, for example, U.S. Pat. No. 5,333,095, the contents of which are incorporated herein. The feedthrough terminal pins are typically connected to one or more lead wires which can undesirably act as an antenna and thus tend to collect stray EMI signals for transmission into the interior of the medical device. In the prior art devices, the hermetic terminal pin subassembly has been combined in various ways with a ceramic feedthrough filter capacitor to decouple interference signals to the housing of the medical device. 
   In prior art devices, a feedthrough capacitor is attached to the ferrule or insulator of the terminal of an active implantable medical device using various attachment methods. For example, thermal-setting conductive adhesives, such as conductive polyimides, solders, welds, brazes and the like, are all used to mechanically and electrically make connections to the feedthrough capacitor. With reference to U.S. Pat. No. 5,333,095, a feedthrough capacitor is surface mounted onto the hermetic terminal subassembly. It is desirable to have a high temperature electrical connection between the lead wires and the inside diameter holes of a feedthrough capacitor. It is also desirable to have a high temperature electrical connection around the outside diameter or perimeter of the capacitor to the ferrule. In most of the prior art applications, including that shown in U.S. Pat. No. 5,333,095, the electrical connection material is a thermal-setting conductive polyimide such as that manufactured by Ablestick. Conductive polyimide is typically inserted using a microsyringe into the annular space between the lead wires and the inside diameter feedthrough holes of the feedthrough capacitor. Multiple centrifuging steps are normally required to pack and densify the thermal-setting conductive polyimide. It is important that the thermal-setting conductive polyimide not have large voids or cavities. 
   Because of the need to inject and then centrifuge the conductive polyimide, it is important that this material not be allowed to flow out underneath the capacitor where it could cause short circuits. Accordingly, in prior art devices there is an insulating washer (typically of a non-conductive polyimide material) that is disposed between the ceramic capacitor and a mounting surface of a terminal pin-supporting alumina insulator. In manufacturing the terminal pin feedthrough subassembly, the capacitor is seated against this non-conductive polyimide washer and then cured. 
   However, complications follow from the use of the conductive polyimide; that is, after the conductive polyimide is centrifuged multiple times, there is usually excess material either on the lead or terminal pin, or on the top surface of the capacitor. This requires multiple cleaning steps after the polyimide is cured at an elevated temperature. These cleaning steps typically consist of microblasting using sodium bicarbonate. No matter what the microblasting medium is, multiple cleaning steps are then required. In a typical application, this would mean multiple cleaning and ultrasonic baths containing de-ionized (DI) water followed by alcohol rinses, and subsequently followed by other cleaning solvents. After all of this, the subassembly is subjected to a bake-out process. To make the outside diameter connection to the ferrule, almost all of the above steps are repeated. 
   All of the foregoing manufacturing steps are highly labor intensive. This was not a significant problem when volumes of implantable medical devices were relatively low. However, in the United States alone, there are over 500,000 pacemakers implanted annually. This market is growing rapidly with the advent of biventricular pacemaking to control congestive heart failure. Thus, high volume manufacturing techniques are needed to control the cost. 
   Accordingly, there is a need for a manufacturing methodology which advantageously lends itself to high-volume manufacturing techniques. Preferably, such a manufacturing methodology would eliminate many of the foregoing labor-intensive manufacturing steps, and especially those related to the use of a non-conductive polyimide material as an insulating washer. By eliminating the conductive polyimide, one also eliminates the non-conductive bonding washer and all the related centrifuging and cleaning steps. The present invention addresses these needs and provides a very low cost manufacturing methodology for EMI filtered hermetic terminal assemblies for active implantable medical devices. 
   SUMMARY OF THE INVENTION 
   The present invention resides in an EMI feedthrough filter terminal assembly for an active implantable medical device, which generally comprises a feedthrough capacitor having an aperture therethrough and first and second sets of electrode plates. The second set of electrode plates are conductively coupled to a housing for the active implantable medical device. A terminal pin at least partially extends through the aperture. A conductive insert is disposed within the aperture for conductively coupling the terminal pin and the first set of electrodes, and for mechanically coupling the terminal pin to the feedthrough capacitor. 
   In a particularly preferred embodiment, the insert comprises a resiliently flexible, conductive contact spring which provides the electrical contact between the inside diameter of the feedthrough hole of a ceramic capacitor and the lead wire or terminal pin. More specifically, the electrical contact spring of the present invention makes contact to an inside diameter metallization of the capacitor where it firmly compresses against both this metallization and the feedthrough terminal pin. This makes a very mechanically and electrically robust electrical connection. The insert contact springs can be made of a conductive, resiliently flexible material such as beryllium, beryllium copper, phosphor bronze, Nitinol or the like. 
   Preferably, the contact spring would be plated with a suitable conductive and non-oxidizable material, such as gold, to prevent oxidation or corrosion from occurring in the electrical contact area. Also, preferably, the terminal pin or lead wire is coated with or otherwise comprised of a conductive and non-oxidizable material. 
   It is desirable to have the contact springs be installed as easily as possible during manufacturing. With the contact spring made of beryllium copper, phosphor bronze or similar materials, a tool is used to push downward on the contact spring during the manufacturing process to solidly insert the spring in place between the lead wire and the inside diameter metallization of the feedthrough capacitor. 
   An adhesive may be used to secure the insert within the aperture. For example, the adhesive may comprise an epoxy preform disposed over the insert and cured within the aperture. 
   Memory shape materials, such as nitinol, provide an additional advantage in that it facilitates the assembly method. That is, it can have one shape at one temperature and a completely different shape at a different temperature. The use of nitinol for the contact springs provides unique benefits. For example, the nitinol spring can very loosely fit and slide into the angular space between the feedthrough capacitor inside diameter and the outside diameter of the terminal pin. In this regard, a chilled fixture can be used where a chilled nitinol spring is inserted. When chilled, the nitinol spring fits very loosely and therefore is easily slid in during a manufacturing operation. However, when the assembly is allowed to warm back up to room temperature, the nitinol expands and therefore tightly compresses between the inside diameter metallization of the ceramic feedthrough capacitor and the outside diameter of the terminal pin. When installed in the human body, the nitinol spring further expands, which provides a reliable and mechanical electrical connection. Inside the human body, the nitinol would be exposed to a steady 37° C. 
   In one embodiment, the insert spring comprises a head having a plurality of resiliently flexible legs extending therefrom and insertable into the aperture. The head is configured to rest on the capacitor surrounding the aperture, and/or extending partially into the aperture. The legs are typically non-planar, so as to physically contact the terminal pin and the aperture metallization of the capacitor. The insert may include barbs which permit the insertion of the insert into the aperture, but impede removal of the insert therefrom. 
   The resiliently flexible, conductive contact spring of the present invention may be advantageously used in connection with the manufacture of a broad variety and range of feedthrough terminal subassemblies for active implantable medical devices. For example, the contact spring of the present invention may be advantageously utilized in connection with, among others, (1) internally grounded feedthrough filter capacitors, such as those shown in U.S. Pat. No. 5,905,627; (2) capacitors utilized in connection with a ferrite slab, as shown and described in U.S. Patent Application Ser. Nos. 60/473,228 and 60/508,426; as well as in connection with (3) applications involving wire bond pads, such as those shown in U.S. Patent Application No. 60/548,770 (the contents of all of which are incorporated herein). 
   Other features and advantages of the present invention will become apparent from the following more-detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate the invention. In such drawings: 
       FIG. 1  is a perspective view of a typical prior art unipolar discoidal feedthrough capacitor; 
       FIG. 2  is an enlarged sectional view taken generally along the line  2 — 2  of  FIG. 1 ; 
       FIG. 3  is a sectional view taken generally along the line  3 — 3  of  FIG. 2 , illustrating the configuration of ground electrode plates within the capacitor; 
       FIG. 4  is a sectional view taken generally along the line  4 — 4  of  FIG. 2 , illustrating the arrangement of active electrode plates within the capacitor; 
       FIG. 5  is a partially fragmented cross-sectional view showing the discoidal feedthrough capacitor or  FIGS. 1–4  mounted to an hermetic terminal assembly of an active implantable medical device; 
       FIG. 6  is a cross-sectional view similar to that of  FIG. 5 , illustrating an hermetic feedthrough terminal comprising a plurality of terminal pins or lead wires and including a capacitor disposed within a capture flange; 
       FIG. 7  is a top-plan view of the assembly of  FIG. 6 ; 
       FIG. 8  is a perspective view of a bipolar internally grounded feedthrough capacitor in accordance with U.S. Pat. No. 5,905,627; 
       FIG. 9  is a sectional view taken generally along the line  9 — 9  of  FIG. 8 , illustrating the configuration of active electrode plates within the capacitor; 
       FIG. 10  is a sectional view taken generally along the line  10 — 10  of  FIG. 8 , illustrating the configuration of ground electrode plates within the capacitor; 
       FIG. 11  is a sectional view taken generally along the line  11 — 11  of  FIG. 8 , illustrating the arrangement of the active and ground electrode plates within the capacitor; 
       FIG. 12  is a perspective view of an hermetic terminal to which the capacitor of  FIGS. 8–11  is mounted; 
       FIG. 13  is a perspective view of the capacitor of  FIG. 8  mounted to the hermetic terminal of  FIG. 12 ; 
       FIG. 14  is a perspective view of an octapolar feedthrough terminal assembly utilizing the contact spring of the present invention in its assembly; 
       FIG. 15  is a sectional view taken generally along the line  15 — 15  of  FIG. 14 , illustrating the configuration of ground electrode plates within the capacitor thereof; 
       FIG. 16  is a sectional view taken generally along the line  16 — 16  of  FIG. 14 , illustrating the configuration of active electrode plates within the capacitor; 
       FIG. 17  is an enlarged perspective view of the conductive, resiliently flexible contact spring of the present invention; 
       FIG. 18  is a fragmented, enlarged sectional view taken generally along the line  18 — 18  of  FIG. 14 , illustrating seating of the contact spring of  FIG. 17  within the annular space between the inside diameter of the feedthrough capacitor and the outside diameter of the terminal pin; 
       FIG. 19  is an enlarged sectional view of the area designated by the number  19  in  FIG. 18 , illustrating an alternative construction of the contact spring of  FIG. 17 ; 
       FIG. 20  is a view similar to  FIG. 19 , illustrating yet another alternative construction of the contact spring of  FIG. 17 ; 
       FIG. 21  is an enlarged, fragmented sectional view taken generally of the area indicated by the number  21  in  FIG. 20 ; 
       FIG. 22  is a sectional view similar to  FIG. 18 , illustrating an alternative embodiment of the terminal pin subassembly; and 
       FIG. 23  is a sectional view similar to  FIGS. 18 and 22 , illustrating yet another alternative embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1–4  illustrate a prior art unipolar discoidal feedthrough capacitor  100 . The capacitor  100  is typically formed of a dielectric material  102  having disposed therein in an alternating fashion ground electrode plates  104  and active electrode plates  106 . A passageway  108  is provided through the capacitor  100 , which is lined with a metallization layer  110 , typically applied either by thick film processes or by selective electro-plating. The thick film process consists of a silver or silver palladium bearing glass frit which is placed and the fired onto the capacitor  100 . This internal metallization material  110  provides the electrical contact to the active electrode plate set  106 . Metallization  112  is applied about the periphery of the capacitor  100  in a similar manner as the interior metallization  110 . The exterior metallization  112  provides the electrical contact to the ground electrode plate set  104 . 
     FIG. 5  is a cross-sectional view showing the discoidal feedthrough capacitor  100  of  FIG. 1  mounted to an hermetic terminal assembly  114  of an implantable medical device. The assembly  114  shown in  FIG. 5  is typical of most EMI filtered terminals for human implant applications. The terminal assembly  114  typically comprises a conductive ferrule  116  conductively and hermetically attached to a housing  118  of an active implantable medical device by means of a gold braze  120 . A conductive terminal pin or lead  122  extends through the ferrule  116  in non-conductive relation by means of an alumina insulator  124 . An hermetic seal  126  is provided between the alumina insulator  124  and the ferrule  116 , and another gold braze seal  128  is provided between the terminal pin  122  and the insulator  124 . As shown, the hermetic seal  128  extends through the insulator  124  for contact with the interior metallization  110  on the capacitor  100  in a manner as described in detail on U.S. Pat. No. 6,765,779 (the contents of which are incorporated herein). 
   A nonconductive, insulating washer  130  is disposed adjacent to an interior surface of the ferrule  116  and the alumina insulator  124 , and the capacitor  100  is placed adjacent to the insulating washer  130  such that the terminal pin  122  extends through the passageway  108 . 
   Whether or not the capacitor  100  is surface mounted, as shown in  FIG. 5 , or embedded inside the ferrule  116 , there are still basic principles that apply. That is, there must be an electrical connection between the lead wire  122  and the inside diameter metallization  110  of the feedthrough capacitor  100 . This electrical connection material is usually a thermal-setting conductive polymer  132  such as a conductive polyimide, a solder, or the like. It is important that this material  132  be free of voids and flow down into the annular space between the lead wire/terminal pin  122  and the inside diameter (ID) of the feedthrough capacitor  100 . It is also important that this material not migrate or leak out between the capacitor  100  and the hermetic terminal  114  and thus short out to the ferrule  116 . Accordingly, the insulator washer  130  is added which adhesively attaches itself to both the feedthrough capacitor  100  and the mounting surface against the hermetic terminal  114 . This material forms a solid bond thereby preventing material  132  from migrating between the capacitor  100  and the mounting surface and causing short circuits. The placement of electrical material  132  involves the related steps of providing the insulating washer  130  and also a number of clean up steps involving multiple centrifuging of the material  132  followed by curing and cleaning by microblasting, as described above. An electrical connection is also required on the capacitor  100  between its outside diameter metallization  112  and the ferrule  116 . This is shown as material  134  and is also of the group of conductive thermal-setting polymers. 
   In the description of the remaining figures, structure that is functionally equivalent to that described in connection with  FIGS. 1–5  is assigned the same reference number. Accordingly, reference numbers labeled in the drawings and not specifically discussed below may be taken as having the same function and purpose as those components discussed above. 
     FIGS. 6–13  illustrate several additional and different types of feedthrough terminal assemblies  214  and  314  which may advantageously utilize the conductive insert, usually in the form of a resiliently flexible contact spring  136  ( FIG. 17 ) of the present invention.  FIG. 6  is a prior art terminal assembly  214  taken from U.S. Pat. No. 6,275,369. It has a capture flange  138  in order to facilitate the placement of thermal-setting conductive adhesive  134  disposed between the ferrule  116  and the outside diameter metallization  112  of the feedthrough capacitor  200 .  FIG. 7  is the top view of the feedthrough filter assembly of  FIG. 6 , illustrating that this is a quadpolar or four-hole device. 
     FIG. 8  is a perspective view of a bipolar internally grounded capacitor  300  in accordance with U.S. Pat. No. 5,905,627.  FIGS. 9–11  illustrate the active electrode plates  106  of the capacitor  300  of  FIG. 8 , and the ground electrode plates  104 . It is noteworthy that the ground electrode plates  104  do not extend to the outside or perimeter of the ceramic capacitor  300 . The capacitor  300  of  FIG. 8  is designed for mounting onto a hermetic terminal subassembly  140  with a grounded pin  142  as shown in  FIG. 12 . Pin  142  is solidly welded or brazed into the ferrule  116  of the hermetic terminal subassembly  140 . 
     FIG. 13  shows the capacitor  300  of  FIGS. 8–11  mounted to the ferrule of  FIG. 12 . One can see that electrical connection material  132  has been placed to make electrical attachment to the capacitor inside diameter metallization  110 ,  112  and each of the lead and ground wires  122  and  142 . As mentioned before, an adhesively backed insulating washer  130  has been first disposed between the capacitor  300  and the ferrule  116 . This is important so that the electric connection material  132  does not leak out underneath the ceramic capacitor  300  and short over to the ferrule  116 . 
     FIG. 14  illustrates a novel octapolar feedthrough terminal assembly  414  which utilizes the contact spring  136  of the present invention. The capacitor  400  shown in  FIG. 14  is an internally grounded capacitor similar to  FIGS. 8–11  but with more lead wires or terminal pins  122 . The ground pin  142  has been gold brazed or welded directly to the ferrule  116  of the hermetic terminal subassembly  140 . The other eight lead wires  122  pass through the ferrule  116  in insulative relationship. The octapolar feedthrough capacitor  400 , in this case, has not been seated down against an insulating washer as has been described in prior art embodiments. Electrical contact between the capacitor inside diameter metallization  110  and the outside surface of the lead wires  122  is accomplished by inserting the contact spring  136  of the present invention as shown. An insertion tool is used to slide the contact spring  136  down along the lead wire  122  and then ram it firmly into the space between the inside diameter metallization  110  and the lead wire  122 . The same is true for connection between the ground lead  142  and associated ground metallization  112 . 
     FIG. 15  illustrates the ground electrode plate set  104  of the capacitor  400  shown in  FIG. 14 , and  FIG. 16  illustrates the eight active electrode plate sets  106 . At times herein, the active electrodes  106  are referred to as a first set of electrode plates, and the ground electrode plate set  104  are referred to as a second set of electrode plates. 
     FIG. 17  is an enlarged perspective view of an insert  136  embodying the invention. As one can see, there is a top head portion  144  which is an integral part of the overall spring design. The contact springs  136  are typically constructed of beryllium, beryllium copper, phosphor bronze, nitinol or the like. Active implantable medical devices have both shock and vibration standards. For example, pacemakers must be able to withstand rough handling or even being dropped on the floor or street by a doctor. Shock standards vary between 1000 and 1500 Gs. Accordingly, referring now back to the structure shown in  FIG. 14 , it is important that the feedthrough capacitor  400  be firmly retained by the insert contact springs  136 . It is thus important that the contact spring  136  be designed so that it firmly pinches down against lead and ground wires  122  and  142 . This is where the top head portion  144  of the contact spring  136  is very important. As long as the contact spring  136  grips very tightly on the lead wire  122 , then the flange or head  144  will retain the ceramic capacitor  400  such that it cannot come loose during shock and vibration loading. 
   In the illustrated embodiment, the insert spring  136  includes a plurality of legs  152  extending downwardly therefrom. These legs are preferably comprised of a resiliently flexible material so as to have spring-like characteristics in order to be squeezed in the annular space between the terminal pin  122  and the inner aperture metallization  110 , as illustrated in  FIG. 18 . Preferably, the legs  152  are non-planar so as to facilitate physical contact between terminal pin  122  and the first set of active electrode plates  106 , through the inner metallization  110 . 
   Although the insert  136  has been described as such, it will be readily understood by those skilled in the art that the inserts could be formed into various geometries, such as a spiral or helix spring, V-shape spring, etc. The important aspect of the insert  136  is that it form an electrical and mechanical connection between the terminal pin  122  and the internal metallization  110 . 
   To secure the insert  136  within the aperture, an adhesive may be used. For example, referring back to  FIG. 14 , one can see an optional epoxy pre-form  146  that can be dropped in place around two or three or even all of the nine lead and ground wires  122 ,  142 . This epoxy pre-form  146  is cured to form a bonding material between the lead/ground wire  122 ,  142  and the top  144  of the contact spring  136 . After curing, the epoxy material  146  establishes shear strength between the lead/ground wires  122 ,  142  and the contact spring  136 . This would act to improve the shock and vibration handling capability of the assembly. 
   As mentioned above, the insert  136  can be comprised of a memory shape alloy material, such that it has one shape at one temperature, and a completely different shape at a different temperature. Nitinol is such a memory shape material which can be designed such that the insert spring  136  can fit very loosely and slide into the angular space between the capacitor inside metallization  110  and outside diameter of the terminal pin  122  when either at an elevated temperature well above body temperature; or a lower temperature, preferably significantly below room temperature. Thus, when the assembly is at room temperature or body temperature, approximately 37° C., the insert  136  fits very tightly between the terminal pin  122  and the capacitor so as to establish a mechanical and electrical connection. 
     FIG. 18  is an enlarged cross-sectional view taken from  FIG. 14 . In this view, one can see that the contact spring  136  has been seated into the annular space between the inside diameter metallization  110  of the feedthrough capacitor  400  and the outside diameter of a terminal pin  122 . As previously mentioned, it is desirable that the legs  152  of the contact spring  132  solidly contact the outside diameter of the pin  122  and also solidly contact the inside diameter metallization  110  of the feedthrough capacitor  400 . 
     FIG. 19  illustrates an alternative embodiment of the contact spring  136  previously described in  FIGS. 17 and 18 . In this case, the bottom of the legs  152  of the contact spring  136  comes to sharp points  148  which dig into the lead wire  122 . This is to improve the shock and vibration loading characteristics of the assembly. 
     FIGS. 20 and 21  illustrate yet a different embodiment of the contact spring  136  insert assembly previously described in  FIGS. 17–19 . In this embodiment, one or more sharp notches or barbs  150  have been formed in the legs  152  of the contact spring  136 . These sharp barbs  150  are designed to dig into the inside diameter metallization  110  of the feedthrough capacitor  400 . The barbs  150  are formed such that they permit the insertion of the insert spring  136  into the aperture, but impede removal of the insert  136  therefrom. If this type of contact spring  136  is used, this becomes a one-way insertion. That is, there would be no way to remove the ceramic capacitor  400  without breaking it. There is no reason to remove the feedthrough capacitor  400  once it is installed. It is generally more desirable to have the maximum resistance to both shock and vibration loads. 
   With reference to  FIG. 14 , the capacitor  400  is an internally grounded feedthrough capacitor such that the ground pin  142  is conductively coupled to the second set of ground electrode plates  104 , as illustrated in  FIG. 15 . In this case, a contact spring insert  136  can be used to establish both a mechanical and an electrical connection between the ground terminal pin or lead wire  142  and the metallization  112  surrounding the aperture through the capacitor  400  which is conductively coupled to the second set of ground electrode plates  104 . 
     FIG. 22  illustrates an alternative embodiment of the feedthrough capacitor terminal assembly  414  of  FIG. 14 . In  FIG. 22 , the leads or terminal pins  122  have been cut off such that they do not extend above the feedthrough capacitor  100 . A modified contact spring  136  is shown inserted into the annular space between the inside diameter metallization  110  and the outside surface of the lead wire  122 . The head  144  of the contact spring  136  assembly has been enlarged and thickened to provide a convenient surface for wire bonding. Wire bond attachments by the customer are normally done by ultrasonic or thermal bonding techniques. In this case, it is desirable that the entire contact spring  136  be plated with an ultra pure or soft gold plating suitable for wire bonding. One skilled in the art will realize that if one were to modify the contact spring  136  shown in  FIG. 17 , one could co-braze a wide variety of wire bond caps to the top head portion  144  thereby providing an alternative way of manufacturing the assembly shown in  FIG. 22 . 
   In reference to U.S. patent application Ser. No. 10/812,967, which illustrates a variety of wire bond pads, any of these wire bond pads could be integrated with the contact spring  136  as described herein. In addition, any of the substrates shown therein could be placed on top of the feedthrough capacitor  100  which will improve both the shock and vibration loading resistance. This is illustrated by  FIG. 23  where one of the novel wire bond caps of pending U.S. patent application Ser. No. 10/812,967 is shown on top of the feedthrough capacitor  100 . 
   In  FIG. 23 , one can see that in accordance with the present invention, a contact spring  136  has been placed between the capacitor inside diameter metallization  110  and the outside surface diameter of terminal pin  122 . In this case, the lead terminal pin  122  has been lengthened to protrude only slightly above the ceramic capacitor  100 . A wire bond pad  154  is shown disposed on top of the lead  122 . In a preferred embodiment, this wire bond pad  154  would be laser welded through a hole  156  to form laser weld material  158  which makes a very highly reliable mechanical and electrical connection between wire bond pad  154  and lead  122 . It would be preferable if this wire bond pad  154  were of Kovar or a similar alloy with ultra pure or soft gold plating. An optional connective material  160  is shown which connects the wire bond pad  154  to the contact spring top head portion  144 . As one can see, in this case the contact spring  136  does not need to withstand high shock and vibration loads. This is because the mass of the ceramic capacitor  100  is firmly retained by the laser weld connection  158 . In this case, a contact spring  136  could be used which does not have to dig into the terminal pin  122 . 
   All of the aforementioned novel contact spring assemblies require that a good electrical connection be made between the insert contact spring  136  and lead wire  122 . This is not a problem if the lead wire  122  is of the group of platinum, platinum iridium, gold or other non-corroding noble alloys. However, if tantalum, niobium or titanium pins were to be used, then some pretreatment is necessary. Referring now back to  FIG. 20 , this assembly could be a problem if the lead wire  122  was of the group of titanium, tantalum or niobium. In this case, the lead wire  122  would have to be pretreated either by plating, sputtering, plasma arc deposition or the like, such that it was over coated with a conductive but non-oxidizable material such as silver or gold, which would make a reliable electrical connection to the contact spring  136 . 
   It will be appreciated by those skilled in the art that the present invention provides a manufacturing methodology which advantageously renders itself to high volume manufacturing techniques by eliminating many of the labor-intensive manufacturing steps, including the use of a non-conductive polyimide material as an insulating washer. This eliminates all the related centrifuging including steps. Those skilled in the art will realize that there are a number of ways to design springs and inserts through more reliable electrical connections between the capacitor plates  104  or  106  and the terminal pins  122  or  142 . 
   Although several particular embodiments of the invention have been described in detail for purposes of illustration, various modifications of each may be made without departing from the spirit and scope of the invention.