RELATED APPLICATIONS  
       [0001]    This application claims priority from Provisional Application No. 60/354,083, filed Jan. 30, 2002. This application is also a continuation-in-part application of U.S. patent application Ser. No. 09/657,123, filed Sep. 7, 2000, entitled INTERNALLY GROUNDED FEEDTHROUGH FILTER CAPACITOR WITH IMPROVED GROUND PLANE DESIGN FOR HUMAN IMPLANT AND OTHER APPLICATIONS. The contents of these prior applications are incorporated herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates generally to EMI filtered connectors. More specifically, the present invention relates to EMI filtered connectors which utilize one or more internally grounded feedthrough capacitors.  
           [0003]    Internally grounded ceramic feedthrough filter capacitors greatly improve the reliability and reduce cost of EMI filters for medical implant terminals. Exemplary internally grounded feedthrough capacitors are shown and described in U.S. Pat. No. 5,905,627 entitled INTERNALLY GROUNDED FEEDTHROUGH FILTER CAPACITOR, the contents of which are incorporated herein.  
           [0004]    Ceramic feedthrough capacitors are used in a wide range of electronic circuit applications as EMI filters. Feedthrough capacitors are unique in that they provide effective EMI filtering over a very broad frequency range. For example, this can be from a few Kilohertz to tens of Gigahertz. The mounting or installation of feedthrough capacitors in a typical electronic circuit is always problematic. For one thing, in order to provide proper shielding and attenuation the EMI filter must be installed as a continuous part of the overall EMI shield. This overall EMI shield is usually metallic. Because of the metallic nature of most EMI shields, the installation of a relatively brittle barium titinate-based ceramic capacitor is inherently problematic. This is due to mismatches in thermal coefficient of expansion and resulting mechanical stresses, which can fracture the relatively brittle monolithic ceramic capacitor and lead to either immediate or latent electrical failures. The internally grounded capacitor described in U.S. Pat. No. 5,905,627 was designed to overcome these difficulties.  
           [0005]    [0005]FIG. 1 illustrates filtered connectors  20   a - 20   l  that are typically used in the military, aerospace, medical, telecommunication and other industries. In an EMI filtered connector, such as those typically used in aerospace, military, telecommunications and medical applications, it is very difficult to install the feedthrough capacitor to the connector housing or back shell without causing excessive mechanical stress to the ceramic capacitor. A number of unique mounting schemes are described in the prior art, which are designs that mechanically isolate the feedthrough capacitor while at the same time provide the proper low impedance ground connection and RF shielding properties. This is important because of the mechanical stresses that are induced in a filtered connector. It is problematic to install a relatively brittle ceramic feedthrough capacitor in a filtered connector because of the resulting mismatch in thermal coefficient of expansion of the surrounding materials, and also the significant axial and radial stresses that occur during connector mating.  
           [0006]    By definition, connectors come in female and male versions to be mated during cable attach. The EMI filtering is typically done in either the female or the male portion, but usually not both. During the insertion or mating of the connector halves, significant mechanical forces are exerted which can be transmitted to the feedthrough capacitor.  
           [0007]    As described in U.S. Pat. No. 5,905,627, the capacitor ground electrode plate is internally attached to one or more lead wires, which can pass all the way through the device or to one or more grounded studs. In the &#39;627 patent, these capacitors were shown uniquely mounted to a variety of implantable medical hermetic terminals such as those used in cardiac pacemakers, implantable defibrillators and the like. By way of example, U.S. Pat. No. 5,905,627 illustrates a rectangular feedthrough capacitor with an internally grounded electrode, which is also shown as FIGS. 2 through 6 herein.  
           [0008]    More particularly, an internally grounded feedthrough filter capacitor assembly is generally designated in FIG. 6 by the reference number  22 . The feedthrough filter capacitor assembly  22  comprises, generally, at least one conductive terminal pin  24  and a conductive ferrule  26  through which the terminal pin passes in non-conductive relation. An insulator  28  supports each conductive terminal pin  24  from the conductive ferrule  26  in electrically insulated relation, and the assembly of the terminal pins, the conductive ferrule and the insulators comprises a terminal pin sub-assembly  30 . The feedthrough filter capacitor assembly  22  further includes a feedthrough filter capacitor  32  that has first and second sets of electrode plates  34  and  36 . A first passageway  38  is provided through the feedthrough filter capacitor  32  through which the terminal pin  24  extends in conductive relation with the first set of electrode plates  34 . The feedthrough filter capacitor  32  further includes a second passageway  40  into which a ground lead  42  extends. The ground lead  42  is conductively coupled to the second set of electrode plates  36  and the conductive ferrule  26 . Typically, the conductive ferrule  26  is conductively mounted to a conductive substrate  44  that may comprise, for example, the housing for an implantable medical device.  
           [0009]    The internally grounded feedthrough filter capacitor assembly  22  eliminates the need for external conductive connections between the capacitor and a ground by connecting the internal ground plates to a ground pin, tubelet, or similar ground lead structure. This is a particularly convenient and cost effective approach for certain implantable cardioverter defibrillators (ICDs) that already employ a grounded terminal pin in order to use the titanium housing of the implanted ICD as one of the cardiac electrodes. As there is no external electrical connection, the need for external capacitor metalization around the capacitor perimeter or outside diameter has been eliminated. This not only reduces expensive metallization firing or plating operations, but also eliminates the joining of materials which are not perfectly matched in thermal coefficient of expansion.  
           [0010]    The feedthrough filter capacitor  32  comprises a monolithic, ceramic internally grounded bipolar feedthrough filter capacitor having three passageways extending therethrough. The outer two passageways are configured to receive therethrough respective conductive terminal pins  24 , and the internal diameter of the first passageways  38  are metallized to form a conductive link between the first sets of electrode plates  34 . As is well understood in the art, the first sets of electrode plates  34  are typically silk-screened onto ceramic plates forming the feedthrough filter capacitor  32 . These plates  34  are surrounded by an insulative ceramic material that need not metallized on its exterior surfaces.  
           [0011]    Similarly, a second set of electrode plates  36  is provided within the feedthrough filter capacitor  32 . The inner diameter of the central or second passageway  40  through the feedthrough filter capacitor  32  is also metallized to conductively connect the second set of electrode plates  36  which comprise the ground plane of the feedthrough filter capacitor  32 . The second passageway  40  is configured to receive therethrough the ground lead  42  which, in this particular embodiment, comprises a ground pin.  
           [0012]    With reference to FIG. 5, the terminal pin subassembly  30  comprises a plate-like conductive ferrule  26  having three apertures therethrough that correspond to the three passageways through the feedthrough filter capacitor  32 . The conductive terminal pins  24  are supported through the outer apertures by means of an insulator  28  (which also may be hermetic), and the ground pin  42  is supported within the central aperture by a suitable conductor  46  such as a solder, an electrically conductive thermal setting material or welding/brazing.  
           [0013]    The feedthrough filter capacitor  32  is placed adjacent to the non-body fluid side of the conductive ferrule  26  and a conductive attachment is effected between the metallized inner diameter of the first and second passageways  38  and  40  through the feedthrough filter capacitor  32  and the respective terminal pins  24  and ground lead  42 . As was the case described above in connection with the attachment of the ground lead  42  to the conductive ferrule  26 , the conductive connection  48  between the terminal pins  24  and the ground lead  42  with the feedthrough filter capacitor  32  may be effected by any suitable means such as a solder or an electrically conductive thermal setting material or brazing. The result is the feedthrough filter capacitor assembly  22  illustrated in FIG. 6 which may then be attached to the conductive substrate  44 .  
           [0014]    EMI filtered connectors are typically manufactured using monolithic ceramic capacitor arrays  50   a  and  50   b . Examples of these multi-hole capacitor arrays are shown in FIG. 7. Planar arrays can vary in the number of feedthrough holes from one all the way up to several hundred in some cases. In the planar arrays  50   a  and  50   b  shown in FIG. 7, both the inside diameter of the feedthrough holes  52  and the entire outside perimeter  54  are metallized. The purpose of the metallization is to connect the electrode plates in parallel and to provide a surface for electrical attachment to the capacitor. The metallization usually consists of a fired-on silver loaded glass frit, plating, or the like (sometimes gold terminations are used). The general material used for the dielectric is barium titinate. Accordingly, these devices, when fired, are very brittle (and mechanically weak). In an EMI filtered connector, the brittle ceramic capacitor does not match the thermal coefficient of expansion of the surrounding connector metallic material (such as the connector housing or back shell). Because of this, mechanical stresses are introduced during capacitor installation, mechanical connector mating and during temperature cycling.  
           [0015]    [0015]FIG. 8 is a cross-sectional view of a typical filtered connector  56  in a π filter configuration. As can be seen the two ceramic discoidal capacitors  58  are directly attached to the inside diameter of the connector. This results in an area of high stress concentration, which can lead to fractures of the monolithic ceramic capacitor. These fractures can result in either immediate or latent electrical failure. A number of manufacturers of filtered connectors have gone to great lengths to mechanically isolate the ceramic feedthrough capacitor. FIG. 9 is an illustration of such a system, which shows spring contact fingers  60 ,  62  which isolate the capacitors  58  (disposed on either side of an intermediate ferrite inductor  64 ) mechanically, both for the ground connections to the connector  56  and the connection between the lead wire  66  and the capacitor inside diameter. This allows the capacitors  58  to structurally float thereby making them much less sensitive to damage during connector insertion or during thermal cycling.  
           [0016]    [0016]FIG. 10 is a connector manufactured by Amphenol utilizing beryllium copper contact resistance clips  68 , which provide the ground spring as previously described in FIG. 9. FIG. 10 also illustrates that a beryllium copper EMI grounding spring  70  has been used at the inside diameter contact of the ceramic capacitor. This assembly has been very successful in the industry; however, it is quite complicated and expensive to manufacture. FIG. 10 further illustrates a machine aluminum alloy shell  72 , a stainless steel socket hood  74 , front removable machine copper alloy contacts  76 , a silicone rubber interfacial seal  78 , a high temperature dielectric insert  80 , a monolithic planar capacitor array  82 , sealing and stress isolating elastomeric gaskets  84 , a fixed rear nation contact  86 , and a ferrite inductor  88 .  
           [0017]    [0017]FIG. 11 illustrates yet another prior art Amphenol connector which has utilized grounding springs  68  and  70  in order to isolate the monolithic ceramic capacitor array from the mechanical stresses due to the connector itself. Components illustrated in FIG. 11 that are equivalent to the components of the connector of FIG. 10 show the same reference number.  
           [0018]    In summary, FIGS. 8 through 11 illustrate various methods of installing ceramic capacitor arrays inside of a connector back shell or housing. As can be seen, the capacitors as installed in FIG. 8 are subject to damage caused by both mechanical and thermal stresses. Solutions as indicated in FIGS. 9, 10 and  11 , are effective; however, they are expensive, complicated and not very volumetrically efficient.  
           [0019]    Accordingly, there is a need for novel filter connectors which utilize the internally grounded feedthrough capacitor as described above in a variety of filtered connector applications. Modification of the connector is needed to adapt it to be compatible with the internally grounded capacitors. Such modifications must provide a low impedance electrical connection that will operate to several gigahertz while at the same time mechanically isolating the ceramic capacitor so that excessive mechanical stresses do not result. The present invention fulfills these needs and provides other related advantages.  
         SUMMARY OF THE INVENTION  
         [0020]    The present invention resides in an improved EMI filtered connector which provides the proper degree of both thermal and mechanical isolation of an array of feedthrough filter capacitors from the connector housing and yet at the same time provides a low impedance RF connection so that a high degree of EMI filtering effectiveness is maintained. The EMI filtered connector of the present invention comprises, generally, a plurality of conductive terminal pins, a grounded conductive connector housing through which the terminal pins pass in non-conductive relation, and an array of feedthrough filter capacitors each having a distinct first set of electrode plates, a non-distinct second set of electrode plates, and a first passageway through which a respective terminal pin extends in conductive relation with the first set of electrode plates. As used herein, a distinct set of electrode plates refers to a set of electrode plates which are distinctly separate and associated with a particular capacitor of the feedthrough filter capacitor array. A non-distinct set of electrode plates refers to those plates which are common to two or more of the distinct capacitors in the array of feedthrough filter capacitors. At least one ground lead is conductively coupled to the conductive connector housing, and extends into a second passageway through the array of feedthrough filter capacitors in conductive relation with the second set of electrode plates.  
           [0021]    In a preferred form of the invention, the outer peripheral surface of the array of feedthrough filter capacitors is non-conductive. Further, an insulator is disposed in or adjacent to the connector, for mounting the conductive terminal pins for passage through the conductive connector with the conductive terminal pins and the connector is non-conductive relation. The insulator may provide means for hermetically sealing passage of the terminal pins through the connector housing, as well as means for hermetically sealing passage of the ground lead through the connector housing.  
           [0022]    The array of feedthrough filter capacitors may be symmetrical about the ground lead or asymmetrical. The ground lead may form a portion of the connector housing. Further, an insulative washer may be disposed between the array of feedthrough filter capacitors and the connector housing.  
           [0023]    In one illustrated embodiment, a grounding ring is conductively coupled to the ground lead and to the connector housing. The grounding ring is secured to the ground lead utilizing a conductive washer and a retaining clip. As shown, a plurality of ground leads in conductive relation with the second set of electrode plates are provided, wherein all of the ground leads are conductively coupled to the grounding ring.  
           [0024]    A plurality of arrays of feedthrough filter capacitors may be provided within a single grounded conductive connector. In this case, each of the plurality of arrays of feedthrough capacitors may be provided with its own non-distinct second set of electrode plates.  
           [0025]    A novel feature of the internally grounded feedthrough capacitor is the elimination of all electrical and mechanical attachments to the outside diameter or the perimeter of the feedthrough capacitor. This allows the filtered capacitor to float on the connector pins thereby eliminating the problems with conventional connectors. The result is a more cost effective and much more reliable filtered connector assembly.  
           [0026]    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  
       [0027]    The accompanying drawings illustrate the invention. In such drawings:  
         [0028]    [0028]FIG. 1 illustrates prior art filtered connectors that are typically used in the military, aerospace, medical, telecommunication and other industries;  
         [0029]    [0029]FIG. 2 illustrates a prior art internally grounded feedthrough capacitor in accordance with U.S. Pat. No. 5,905,627;  
         [0030]    [0030]FIG. 3 illustrates the active electrode plate pattern of the capacitor of FIG. 2;  
         [0031]    [0031]FIG. 4 illustrates the ground electrode plate pattern of the capacitor of FIG. 2;  
         [0032]    [0032]FIG. 5 illustrates a hermetically sealed terminal which includes the capacitor of FIG. 2;  
         [0033]    [0033]FIG. 6 illustrates the internally grounded capacitor of FIG. 2 mounted to a hermetic seal terminal and housing of an implantable defibrillator;  
         [0034]    [0034]FIG. 7 shows examples of typical prior art multi-hole capacitor arrays;  
         [0035]    [0035]FIG. 8 is a cross-sectional view of a typical prior art filtered connector in a n filter configuration, with direct OD (outer diameter) attach and resultant high mechanical stress to the capacitors;  
         [0036]    [0036]FIG. 9 is a cross-sectional view of a prior art feedthrough capacitor with spring attachments;  
         [0037]    [0037]FIG. 10 is a cross-sectional view of a prior art Amphenol filtered connector;  
         [0038]    [0038]FIG. 11 is a cross-sectional view of a prior art Amphenol filtered connector with EMI grounding springs;  
         [0039]    FIGS.  12 A- 12 F illustrate a sub D-type filtered connector with twenty-five pins and utilizing an internally grounded feedthrough capacitor;  
         [0040]    [0040]FIG. 13 shows an hermetic connector with a novel grounding ring for providing one or more grounded pins for the internally grounded capacitor;  
         [0041]    FIGS.  14 A- 14 E show an hermetically sealed connector with internally grounded feedthrough capacitor with novel locking clips and retaining ring;  
         [0042]    FIGS.  15 A- 15 F illustrate a circular quadpolar connector with an internally grounded feedthrough capacitor; and  
         [0043]    FIGS.  16 A- 16 I illustrate how two or more individual internally grounded feedthrough capacitors can be used to provide filtering in a very large connector array or connector block. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0044]    The present invention relates to a method for mounting a monolithic ceramic capacitor to an electronic connector in a manner which provides the proper degree of both thermal and mechanical isolation from the connector housing and yet at the same time provides a low impedance RF connection so that a high degree of EMI filtering effectiveness (attenuation) is maintained. A feature of the present invention is that an internally grounded electrode plate can be grounded at multiple points (not just at its outside diameter or perimeter). This overcomes a serious deficiency in prior art filtered connectors that are physically large. In a large conventional prior art filtered connector, the pins closest to the center are a relatively long distance from the outside diameter or perimeter ground. This creates inductance which tends to reduce the filtering efficiency (attenuation in dB) of these pins. This situation is remedied by the use of a grounded pin near to the center of the array. A multipoint ground attachment assures that the capacitor ground plane will present a very low RF impedance to ground which guarantees that the feedthrough capacitor will operate as a broadband filter with a high level of attenuation. Moreover, use of an internal ground eliminates the outer diameter (OD) termination on the capacitor, and also eliminates of the need for an electrical/mechanical connection between the shielded case or housing and the capacitor OD (or perimeter in the case of rectangular feedthrough).  
         [0045]    In the following description of the preferred embodiments, elements which are functionally equivalent to those described above in connection with the internally grounded feedthrough filter capacitor assembly  22  of FIGS.  2 - 6  will share common reference numbers in increments of  100 . Thus, the D-type filter connector of FIGS.  12 A- 12 F is referred to generally by the reference number  122 , the hermetic connector of FIGS. 13 and 14A- 14 E is designated generally by the reference number  222 , the circular quadpolar connector of FIGS.  15 A- 15 F is designated generally by the reference number  322 , and the connector shown in FIGS.  16 A- 16 I is designated by the reference number  422 .  
         [0046]    In accordance with the invention, EMI filtered connectors  122 - 422  are provided which utilize one or more internally grounded feedthrough capacitors  132 - 432 . Novel filtered connectors incorporating internally grounded feedthrough capacitors provide a number of very important advantages including:  
         [0047]    1. The elimination of the capacitor&#39;s OD or perimeter termination;  
         [0048]    2. Reduced cost because of elimination of the metallization and firing steps for the OD termination;  
         [0049]    3. Greatly reduced mechanical stress because the capacitor is free to float on its pins;  
         [0050]    4. The capacitor is much more rugged and resistant to both thermal shock and mechanical stresses due to mismatches in thermal coefficients of expansion;  
         [0051]    5. Capacitor installation is greatly simplified;  
         [0052]    6. Reliability is improved; and  
         [0053]    7. The capacitor is much less subject to damage during the insertion stresses created during connector mating.  
         [0054]    With reference to FIGS.  12 A- 12 F, there is shown a sub D-type filtered connector  122  utilizing an internally grounded capacitor  132 . A novel feature of this approach is that two of the ground pins  142  (the one furthest from the left and the one furthest from the right) are grounded right to the metallic case  144  of the connector itself (the pins may be attached by welding, brazing, soldering, conductive adhesives, swadging, press-in or the like). The capacitor feedthrough holes  138 ,  140  are then attached to each one of the pins  124 ,  142  (including the two grounded pins  142 ). The attachment to the ground pins  142  connects the capacitor ground electrode plate stack  136  in accordance with the principles of the internally grounded capacitor. These pin to capacitor feedthrough hole attachments can be made by automated wave soldering processes, conductive adhesives, spring contact fingers, or the like. This novel connector design method allows the capacitor  132  to float entirely on the pins  124 ,  142  with no mechanical connection at all between the capacitor outside perimeter and the case itself. This completely eliminates the need for capacitor outside perimeter metallization which is itself an expensive process. The active feedthrough holes  138  of the capacitor of FIG. 12 are connected to the other connector pins  124  which provides effective EMI filtering. In FIG. 12F, the ground electrode plate is cut away so that the active electrode plates are partially exposed. A plurality of ground and active electrode plate sets  136 ,  134  are stacked up to achieve the desired capacitance value.  
         [0055]    Generally, the active area of each capacitor is adjusted by controlling the area of the active electrode plate (silk screen design and metal laydown control). Those pins that have a smaller active electrode area will have less capacitance. The voltage rating of the capacitor is dependant upon the dielectric thickness between the electrode plates and the width and accuracy of the capacitor margin areas. In order to manufacture such large planar array capacitors successfully, accurate registration of the active and ground electrode plates is critical. In order to accomplish this, large planar array capacitors are typically manufactured using full or modified wet stack techniques which includes automated silk screening of the electrodes. Accurate hole drilling is also critical. A significant amount of process “art” is involved in this manufacturing operation, particularly in light of the non-linear shrinkage characteristics of the large ceramic arrays wherein the hole to hole spacing may vary.  
         [0056]    [0056]FIGS. 13 and 14A- 14 E illustrate a novel military-style filtered hermetic connector  222  incorporating an internally grounded feedthrough capacitor  232 . In this case, a special grounding ring  256  is slipped over the connector pins  224 ,  242 . In FIG. 13, two different grounding ring options are illustrated which shows that the designer can select any of the pins to be grounded. An attachment is made of the grounding ring  256 ,  256 ′ to the connector housing  244 . This attachment can be either through welding, brazing, soldering, press fit and the like. An electrical connection is also made from the grounding ring  256 ,  256 ′ to two or more of the connector housing pins  242 . As one can see the grounding ring  256 ,  256 ′ could ground as many pins  242  as desired around the circumference of the connector housing  244 . Further, an insulative washer  257  is disposed between the capacitor array  232  and the connector housing  226 . In the section view of FIG. 14E, the ground electrode is partially cut away to reveal the active electrodes.  
         [0057]    There are a number of other methods for providing grounded pins  242  for use in an internally grounded filtered connector  222 . For example, the grounding ring  256  as shown in FIG. 13 could be omitted and instead the inside diameter of the connector housing  244  could be machined in such a way to ground one or more of the connector pins. FIGS.  14 A- 14 E illustrate such a connector, which has a number of ground pins  242 , which are integral to the connector housing  244 .  
         [0058]    Internally grounded feedthrough capacitors  232  can be attached in a variety of unique ways. One such way is shown in FIGS.  14 A- 14 E wherein conductive rubber washers  258  are used along with a retaining clip  260 . An alternative to the retaining clip  260  and conductive rubber washer  258  is to use a push nut which exerts a spring force against the capacitor to seat it to the ground post(s).  
         [0059]    FIGS.  15 A- 15 F illustrate a smaller quadpolar hermetic connector  322  wherein the pins  324  are glass sealed into the connector housing  344 . There is a centered ground pin  342  which is brazed or welded and becomes an integral part of the housing. This pin  342  may also be formed during housing manufacturing or screw machine manufacturing of the pin. It is not necessary that this ground pin  342  protrude all the way through the connector. In other words, the connector could be a tripolar connector wherein the ground pin  342  is only used to connect to the ground electrode plates  336  of the feedthrough capacitor  332 . In the sectional view of FIG. 15F, the ground electrode  336  is partially cut away to reveal the active electrodes.  
         [0060]    FIGS.  16 A- 16 I illustrate how two or more individual internally grounded feedthrough capacitors  432  can be used to provide filtering in a very large connector array or connector block  422 . One or more grounded pins  442  are provided for convenient attachment to the internal ground electrode plates  436  of each feedthrough capacitor. The array that is shown in FIGS.  16 A- 16 I uses two internally grounded feedthrough capacitors  432 . It will be obvious to one experienced in the art that four, six or even more capacitors could be used depending on the number of pins and the geometry of the connector. In the section view, the ground electrode is partially cut away to reveal the active electrodes.  
         [0061]    It is important that the number of ground pins  442  and their spacing be adjusted such that the internal inductance of the ground electrode not be too high. The grounding pin  442  does cause a small amount of inductance which appears in series with the feedthrough capacitor equivalent circuit. It is a matter of geometry and design to make sure that this inductance is small enough so that the capacitor&#39;s self-resonant frequency is always above 10 GHz. This is important for military and space applications, which typically specify attenuation up to 10 GHz. For implantable medical device applications the upper frequency is 3 GHz. This is because of the body&#39;s tendency to both reflect and absorb EMI fields above 3 GHz.  
         [0062]    From the foregoing it will be appreciated that a novel feature of the present invention is that the internally grounded electrode plate can be grounded at multiple points (not just at its outside diameter or perimeter). This overcomes a serious deficiency in prior art filtered connectors that are physically large. In a large conventional prior art filtered connector, the pins closest to the center are a relatively long distance from the outside diameter or perimeter ground. This creates inductance which tends to reduce the filtering efficiency (attenuation in dB) of these pins. This situation is remedied with the novel internal grounded connector by the addition of a grounded pin near to the center of the array. This multipoint ground attachment assures that the capacitor ground plane will present a very low RF impedance to ground which guarantees that the feedthrough capacitor will operate as a broadband filter with a high level of attenuation.  
         [0063]    Another novel feature of the internal ground is the elimination of the OD termination and also the elimination of the need for an electrical/mechanical connection between the shielded case or housing and the capacitor OD (or perimeter in the case of rectangular feedthrough).  
         [0064]    A variety of alternate methods of grounding the pins for the internally grounded feedthrough capacitor(s) to be mounted in filtered connectors will be apparent to those skilled in the art. There are literally thousands of connector configurations in the market place. L, PI, T and other low pass EMI filter circuit configurations simply involve adding one or more inductors, ferrite beads, or ferrite slabs to the concepts that have been described herein. The illustrations herein are intended to demonstrate novel methods of adapting the internally grounded feedthrough capacitor to filtered connector applications but are not intended to limit the scope of the invention.
An EMI filtered connector includes a plurality of conductive terminal pins, a grounded conductive connector housing through which the terminal pins pass in non-conductive relation, and an array of feedthrough filter capacitors. Each of the feedthrough filtered capacitors has a distinct first set of electrode plates, a non-distinct second set of electrode plates, and a first passageway through which a respective terminal pin extends in conductive relation with the first set of electrode plates. At least one ground lead is conductively coupled to the conductive connector housing and extends into a second passageway through the array of feedthrough filter capacitors in conductive relation with the second set of electrode plates. An insulator is disposed in or adjacent to the connector for mounting the conductive terminal pins for passage through the conductive connector with the conductive terminal pins and the connector in non-conductive relation. The outer peripheral surface of the array of feedthrough filter capacitors is non-conductive.