Abstract:
Structures for serially connecting at least two capacitors together are described. Serially connecting capacitors together provides device manufactures, such as those selling implantable medical devices, with broad flexibility in terms of both how many capacitors are incorporated in the device and what configuration the capacitor assembly will assume.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims priority based upon provisional application Serial No. 60/433,684 filed Dec. 16, 2002, and 60/434,797 filed Dec. 18, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention generally relates to a capacitor and, more particularly, to at least two side-by-side capacitors connected in series.  
         SUMMARY OF THE INVENTION  
         [0003]    As more and more medical applications are investigated and implemented to aid and assist the human body, devices needed to deliver the desired therapy are becoming increasingly more sophisticated, both functionally and in terms of their structural makeup. Modern implantable devices require power sources that are smaller in size, but powerful enough to meet the therapy requirements. For example, a cardiac defibrillator has a battery powering circuits performing such functions as, for example, the heart sensing and pacing functions. This requires electrical current of about 1 microampere to about 100 milliamperes. From time-to-time, the cardiac defibrillator may require a generally high rate, pulse discharge load component that occurs, for example, during charging of a capacitor assembly in the defibrillator for the purpose of delivering an electrical shock to the heart to treat tachyarrhythmias, the irregular, rapid heartbeats that can be fatal if left uncorrected. This requires electrical current of about 1 ampere to about 4 amperes.  
           [0004]    The current trend in medicine is to make cardiac defibrillators, and like implantable devices, as small and lightweight as possible without compromising power. This, in turn, means that capacitors contained in these devices must be readily adaptable in how they are connected to each other as well as to the battery and the device circuitry. In that light, the present invention relates to structures for serially connecting at least two capacitors together to provide the device manufacture with broad flexibility in terms of both how many capacitors are incorporated in the device and what configuration the capacitor assembly will assume.  
           [0005]    These and other aspects of the present invention will become more apparent to those skilled in the art by reference to the following description and to the appended drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a perspective view looking at the right edges of two side-by-side capacitors connected in series according to the present invention.  
         [0007]    [0007]FIG. 2 is a cross-sectional view taken along line  2 - 2  of FIG. 1.  
         [0008]    [0008]FIG. 3 is an enlarged view of the indicated area of FIG. 2.  
         [0009]    [0009]FIG. 4 is a cross-sectional view taken along line  4 - 4  of FIG. 2.  
         [0010]    [0010]FIG. 5 is a perspective view looking at the right edges of two side-by-side capacitors connected in series according to another embodiment of the present invention.  
         [0011]    [0011]FIG. 6 is a perspective view looking at the left edges of two side-by-side capacitors connected in series according to another embodiment of the present invention.  
         [0012]    [0012]FIG. 7 is a cross-sectional view taken along line  7 - 7  of FIG. 6.  
         [0013]    [0013]FIG. 8 is a partly exploded, perspective view of four side-by-side capacitors connected in series according to another embodiment of the present invention.  
         [0014]    [0014]FIG. 9 is a cross-sectional view taken along line  9 - 9  of FIG. 8. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    Referring now to the drawings, FIGS. 1, 5,  8  and  9  are perspective views showing various embodiments of side-by-side capacitors connected in series according to the present invention. As shown in FIGS.  1  to  4 ,  8  and  9 , a first embodiment of the series connected capacitor assembly  10  comprises a first capacitor  12  and a side-by-side second capacitor  14 . The first capacitor  12  comprises an anode of an anode active material  16  and a cathode of a cathode active material  18  (FIG. 4) housed inside a hermetically sealed casing  20 . The capacitor electrodes are operatively associated with each other by an electrolyte (not shown) contained inside the casing, as will be described in detail hereinafter. It should be pointed out that the capacitors  12 ,  14  can be of either an electrochemical type wherein both the anode and the cathode electrodes are provided by conductive substrates having a capacitive material contacted thereto or, an electrolyte type wherein the cathode electrode is provided by a conductive substrate having capacitive properties. The illustrated capacitors are preferably of the latter type, however, that should not be construed as limiting.  
         [0016]    As particularly shown in FIGS. 2, 3,  8  and  9 , casing  20  is of a metal material comprising mating first and second clamshells or mating casing portions  22  and  24 . Casing portion  22  comprises a surrounding sidewall  26  extending to a face wall  28 . Similarly, casing portion  24  comprises a surrounding sidewall  30  extending to a face wall  32 . The sidewall  26  of the first casing portion  22  is sized to fit inside the periphery of the second sidewall  30  in a closely spaced relationship. This means that the first face wall  28  is somewhat smaller in planar area than the second face wall  32  of casing portion  24 . Also, the height of the second surrounding sidewall  30  of casing portion  24  is less than the height of the first surrounding sidewall  26 . The surrounding sidewall  26  has an inwardly angled lead-in portion  34  that facilitates mating the casing portions  22 ,  24  to each other.  
         [0017]    With the first and second casing portions  22 ,  24  mated to each other, the distal end of the second surrounding sidewall  30  contacts the first surrounding sidewall  26  a short distance toward the face  28  from the bend forming the lead-in portion  34 . The casing portions  22 ,  24  are hermetically sealed to each other by welding the sidewalls  26 ,  30  together at this contact location. The weld is provided by any conventional means; however, a preferred method is by laser welding.  
         [0018]    The anode active material  16  is typically of a metal selected from the group consisting of tantalum, aluminum, titanium, niobium, zirconium, hafnium, tungsten, molybdenum, vanadium, silicon, germanium, and mixtures thereof in the form of a pellet. As is well known by those skilled in the art, the anode metal in powdered form, for example tantalum powder, is compressed into a pellet having an anode wire  36  embeded therein and extending there from, and sintered under a vacuum at high temperatures. The porous body is then anodized in a suitable electrolyte to fill its pores with the electrolyte and to form a continuous dielectric oxide film on the sintered body. The assembly is then reformed to a desired voltage to produce an oxide layer over the sintered body and anode wire. The anode can also be of an etched aluminum or titanium foil.  
         [0019]    The cathode electrode is spaced from the anode electrode housed inside the casing and comprises the cathode active material  18 . The cathode active material has a thickness of about a few hundred Angstroms to about 0.1 millimeters directly coated on the inner surface of the face walls  28 ,  32  (FIGS.  2  to  4 ) or, it is coated on a conductive substrate (not shown) in electrical contact with the inner surface of the face walls. In that respect, the face walls  28 ,  32  may be of an anodized-etched conductive material, have a sintered active material with or without oxide contacted thereto, be contacted with a double layer capacitive material, for example a finely divided carbonaceous material such as graphite or carbon or platinum black, a redox, pseudocapacitive or an under potential material, or be an electroactive conducting polymer such as polyaniline, polypyrole, polythiophene, and polyacetylene, and mixtures thereof.  
         [0020]    According to one preferred aspect of the present invention, the redox or cathode active material  18  includes an oxide of a first metal, the nitride of the first metal, the carbon nitride of the first metal, and/or the carbide of the first metal, the oxide, nitride, carbon nitride and carbide of the first metal having pseudocapacitive properties. The first metal is preferably selected from the group consisting of ruthenium, cobalt, manganese, molybdenum, tungsten, tantalum, iron, niobium, iridium, titanium, zirconium, hafnium, rhodium, vanadium, osmium, palladium, platinum, nickel, and lead.  
         [0021]    The cathode active material  18  may also include a second or more metals. The second metal is in the form of an oxide, a nitride, a carbon nitride or carbide, and is not essential to the intended use of the conductive face walls  28 ,  32  as a capacitor electrode, and the like. The second metal is different than the first metal and is selected from one or more of the group consisting of tantalum, titanium, nickel, iridium, platinum, palladium, gold, silver, cobalt, molybdenum, ruthenium, manganese, tungsten, iron, zirconium, hafnium, rhodium, vanadium, osmium, and niobium. In a preferred embodiment of the invention, the cathode active material  18  includes an oxide of ruthenium or oxides of ruthenium and tantalum.  
         [0022]    The mating casing portions  22 ,  24 , and the electrically connected conductive substrate if it is provided, are preferably selected from the group consisting of tantalum, titanium, nickel, molybdenum, niobium, cobalt, stainless steel, tungsten, platinum, palladium, gold, silver, copper, chromium, vanadium, aluminum, zirconium, hafnium, zinc, iron, and mixtures and alloys thereof. Preferably, the face and sidewalls of the casing portions have a thickness of about 0.001 to about 2 millimeters.  
         [0023]    The exemplary electrolytic type capacitor shown in FIGS.  1  to  4 ,  8  and  9  has the cathode active material  18  preferably coating the face walls  28 ,  32  spaced from the respective sidewalls  26 ,  30 . Such a coating is accomplished by providing the conductive face walls  28 ,  32  with a masking material in a known manner so that only an intended area of the face walls is contacted with active material. The masking material is removed from the face walls prior to capacitor fabrication. Preferably, the cathode active material  18  is substantially aligned in a face-to-face relationship with the major faces of the anode active material  16 .  
         [0024]    A preferred coating process is in the form of an ultrasonically generated aerosol as described in U.S. Pat. Nos. 5,894,403; 5,920,455; 6,224,985; and 6,468,605, all to Shah et al. These patents are assigned to the assignee of the present invention and incorporated herein by reference. In that manner, the ultrasonically generated active material contacted to the conductive surfaces has a majority of its particles with diameters of less than about 10 microns. This provides an internal surface area for the active material of about 10 m 2 /gram to about 1,500 m 2 /gram.  
         [0025]    A separator (not shown) of electrically insulative material is provided between the anode active material  16  and the cathode active material  18  to prevent an internal electrical short circuit between them. The separator material also is chemically unreactive with the anode and cathode active materials and both chemically unreactive with and insoluble in the electrolyte. In addition, the separator material has a degree of porosity sufficient to allow flow therethrough of the electrolyte during the electrochemical reaction of the capacitor  12 . Illustrative separator materials include woven and non-woven fabrics of polyolefinic fibers including polypropylene and polyethylene or fluoropolymeric fibers including polyvinylidene fluoride, polyethylenetetrafluoroethylene, and polyethylenechlorotrifluoroethylene laminated or superposed with a polyolefinic or fluoropolymeric microporous film, non-woven glass, glass fiber materials and ceramic materials. Suitable microporous films include a polyethylene membrane commercially available under the designation SOLUPOR® (DMS Solutech), a polytetrafluoroethylene membrane commercially available under the designation ZITEX® (Chemplast Inc.), a polypropylene membrane commercially available under the designation CELGARD® (Celanese Plastic Company, Inc.), and a membrane commercially available under the designation DEXIGLAS® (C. H. Dexter, Div., Dexter Corp.). Cellulose based separators also typically used in capacitors are contemplated by the scope of the present invention. Depending on the electrolyte used, the separator can be treated to improve its wettability, as is well known by those skilled in the art.  
         [0026]    A suitable electrolyte for the capacitors  12 ,  14  is described in U.S. Pat. No. 6,219,222 to Shah et al., which includes a mixed solvent of water and ethylene glycol having an ammonium salt dissolved therein. U.S. Pub. Nos. 20030090857 and 20030142464 describe other electrolytes for the present capacitors. The electrolyte of the former publication comprises water, a water-soluble inorganic and/or organic acid and/or salt, and a water-soluble nitro-aromatic compound while the latter relates to an electrolyte having de-ionized water, an organic solvent, isobutyric acid and a concentrated ammonium salt. These publications and patent are assigned to the assignee of the present invention and incorporated herein by reference. The electrolyte is provided inside the hermetically sealed casing through a fill opening closed by a hermetic closure  38  (FIG. 1), as is well known by those skilled in the art.  
         [0027]    The casing  20 , including the portions  22 ,  24 , being of a conductive metal serves as one terminal for making electrical connection between the capacitor and its load. A pin  40  (FIGS. 2, 8 and  9 ) is welded to the sidewall  26  to provide the negative terminal for the first capacitor  12 . Pin  40  also provides the negative terminal for the side-by-side capacitor assembly  10 , as will be described in detail hereinafter.  
         [0028]    The other electrical terminal or contact for the first capacitor  12  comprises the anode wire  36  extending from the anode active material  16  and connected to the anode lead  42  extending through the first surrounding sidewall  26 . A sleeve  44  is mounted on the distal end of the anode lead  42 . The sleeve  44  provides for serially connecting the first capacitor  12  to the second capacitor  14 , as will be described in detail hereinafter.  
         [0029]    As shown in FIGS. 2 and 3, the anode lead  42  is electrically insulated from the metal casing  20  by an insulator glass-to-metal seal  46 . The glass-to-metal seal  46  comprises a ferrule  48  defining an internal cylindrical through bore or passage  50  of constant inside diameter. Outwardly facing annular steps  52 A and  52 B are provided at the respective upper and lower ferrule ends. The upper step  52 A is of an outer diameter sized to fit in a closely spaced relationship in an annular opening  54  in the first casing sidewall  26  with the remaining body of the ferrule butted against the inner surface of the sidewall. The ferrule  48  is secured therein by welding, and the like.  
         [0030]    As shown in FIGS. 2, 8 and  9 , the anode active material  16  has a notch  56  that provides clearance for the glass-to-metal seal  46 . The anode wire  36  is embedded in the anode active material  16  extends outwardly from the notch  56 . A distal end  36 A is bent into a position generally parallel to the longitudinal axis of ferrule  48 . A proximal end  42 A of the anode lead  42  is bent into a J-hook shape to align parallel with the distal end  36 A of the anode wire  36 . The distal end  36 A of the anode wire is then welded to the proximal end  42 A of the anode lead to electrically connect the anode to the lead  42 .  
         [0031]    An insulative glass  58  provides a hermetic seal between the inside of the ferrule  48  and the anode lead  42 . The glass is, for example, ELAN® type  88  or MANSOL™ type  88 . The anode lead  42  preferably comprises the same material as the anode active material  16 . In that manner, the portion of the anode lead  42  extending outside the capacitor  12  for connection to a load is hermetically sealed from the interior of the capacitor and insulated from the mating casing portions  22 ,  24  serving as the terminal for the cathode.  
         [0032]    The second capacitor  14  illustrated in drawing FIGS.  1  to  4 ,  8  and  9  is similar to the first capacitor  12  in terms of its mechanical structure as well as its chemistry. As previously discussed, however, the capacitors  12 ,  14  need not be chemically similar. For example, the first capacitor  12  can be of an electrolytic type while the second capacitor  14  can be of the electrochemical type. Preferably, the capacitors  12 ,  14  are both of the electrolytic type.  
         [0033]    The second capacitor  14  comprises an anode active material  60  and a cathode active material  62  (FIG. 3) housed inside a hermetically sealed casing  64  and operatively associated with each other by an electrolyte (not shown). Casing  64  is similar to casing  20  of capacitor  12  and comprises mating third and fourth portions  66  and  68  (FIG. 1). Casing portion  66  comprises a surrounding sidewall  70  extending to a face wall  72 . Similarly, casing portion  68  comprises a surrounding sidewall  74  extending to a face wall  76 . The sidewall  70  of the third casing portion  66  is sized to fit inside the periphery of the fourth sidewall  74  in a closely spaced relationship. The height of the fourth surrounding sidewall  74  is less than that of the third surrounding sidewall  70  and its inwardly angled lead-in portion  78 . Laser welding the contacting sidewalls  70 ,  74  together hermetically seals the third and fourth mated casing portions  66 ,  68  to each other.  
         [0034]    The cathode active material  62  is supported on the inner surfaces of the face walls  72 ,  76  opposite the major faces of the anode active material  60 . In that manner, the casing  64 , being of a conductive metal, serves as one terminal for making electrical connection between the capacitor  14  and its load.  
         [0035]    The other electrical terminal or contact is provided by a conductor or lead  80  extending from within the capacitor  14  connected to the anode active material  60  and through the third surrounding sidewall  70 . The anode active material  60  is similar in construction to the anode of capacitor  12  and includes a notch that provides clearance for a glass-to-metal seal  82 . An anode wire  84  embedded in the anode active material  60  extends outwardly from the notch to a distal end welded to the proximal end of the anode lead  80  to electrically connect the anode to the lead.  
         [0036]    The glass-to-metal seal  82  electrically insulates the anode lead  80  from the metal casing  64  and comprises a ferrule  86  provided with an annular step of reduced diameter fitted in a closely spaced relationship in an annular opening in the first casing sidewall  70 . The remaining ferrule body is butted against the inner surface of the sidewall with the ferrule  86  being secured therein by welding. An insulative glass  88  hermetically seals between the cylindrical inner surface of the ferrule  86  and the anode lead  80 .  
         [0037]    A separator (not shown) of electrically insulative and ionically conductive material segregates the anode active material  60  from the cathode active material  62 . The electrolyte is provided inside the hermetically sealed casing  64  through a fill opening closed by a hermetic closure  90 .  
         [0038]    The thusly constructed first and second capacitors  12 ,  14  are then positioned back-to-back or side-by-side. In this configuration, the face wall  32  of the casing portion  24  of the first capacitor  12  is aligned with and proximate to the face wall  76  of the casing portion  68  of the second capacitor  14 . An adhesive  94  (FIG. 3), for example, a double-sided polyimide tape, is intermediate the casing portions  24 ,  68  to secure them together. A suitable tape for this purpose is commercially available from E. I. Du Pont De Nemours and Company Corporation under the trademark KAPTON®. If desired, the capacitors  12 ,  14  are provided with a paralyene coating by a vacuum deposition process about their entire outer surface prior to being aligned in the side-by-side orientation.  
         [0039]    The capacitors  12 ,  14  are then electrically connected in series by a connecting tab  96 . The tab  96  has a foot portion  96 A secured to the surrounding sidewall  70  of casing portion  68 , such as by welding, adjacent to the anode lead  42  for the first capacitor  12 . An arm portion  96 B of the tab has an opening that receives the sleeve  44  mounted on the distal end of the anode lead  42  in a surrounding relationship. A weld (not shown) then finishes the connection of the tab  96  to the sleeve  44  of the anode lead  42 .  
         [0040]    The positive polarity anode lead  42  of the first capacitor  12  is now connected to the negative polarity casing  64  of the second capacitor  14 . The series connected side-by-side capacitors  12 ,  14  are then connectable to a load (not shown). Connecting the negative polarity terminal pin  40  of the first capacitor  12  and the sleeve  86  mounted on the positive polarity terminal lead  80  of the second capacitor  14  does this.  
         [0041]    [0041]FIG. 5 shows another embodiment for serially connecting side-by-side capacitors  100  and  102  according to the present invention. The capacitors  100 ,  102  are identical to the previously described capacitors  12 ,  14  in every respect except for the collared sleeve  104  mounted on the anode lead  106  of capacitor  102 . This structure is particularly shown in FIG. 9 where the sleeve  86  mounted on the anode lead  80  for the capacitor  14  (FIG. 2) has been replaced by the collared sleeve  104 . The collar  104  serves as a stop for properly aligning the arm portion  108 A of a tab  108  when connecting it to the anode lead  80 . The foot of tab  108  is connected to the casing  110  of an adjacent capacitor  120 .  
         [0042]    [0042]FIGS. 6 and 7 illustrate another embodiment for serially connecting side-by-side capacitors  120  and  122  according to the present invention. The capacitors  120 ,  122  are identical to the previously described capacitors  12 ,  14  in every respect except for the structure serially connecting the anode lead  124  of one to the casing  126  of the other.  
         [0043]    The anode terminal lead  124  of capacitor  120  is provided with a sleeve  128  at its distal end thereof. The sleeve  128  supports a channel member  130  comprising a pair of spaced apart sidewalls  130 A,  130 B joined together by a closing end wall  130 C. The channel  130  is open opposite the end wall  130 C. The sidewalls  130 A,  130 B and end wall  130 C meet at a bottom wall provided with an opening  132  that snuggly receives the sleeve  128  of the anode lead  124 . The sleeve  128  and channel member  130  are connected together, such as by crimping. Alternatively, a solder or weld (not shown) is used to make the connection.  
         [0044]    An angled terminal pin  134  is provided with an enlarged base  136  secured to the sidewall  138  of the casing  126  for capacitor  122 , such as by welding. A distal portion  134 A of the terminal pin  134  is formed by a right-angled bend. That way, when the capacitors  120 ,  122  are brought together into the side-by-side orientation contacting the double-sided adhesive tape  140 , the distal portion  134 A of the terminal pin  134  is received in the channel member  130  between its sidewalls  130 A,  130 B. Crimping, soldering or welding the channel sidewalls onto the terminal pin  134  then makes the connection between the capacitors  120 ,  122 .  
         [0045]    [0045]FIG. 9 illustrates an embodiment of the present invention where the sleeve  44  mounted on the positive polarity anode lead  42  of capacitor  12  is connected to the negative polarity casing  64  of capacitor  14  by the tab  96 . The collared sleeve  104  mounted on the positive polarity lead  80  of capacitor  102  is connected to the negative polarity casing of capacitor  120  by the tab  108  resting against the collar. The sleeve  128  on the positive polarity terminal lead  124  of capacitor  120  is, in turn, connected to the negative polarity casing  126  of the capacitor  122  by the angled terminal pin  134  received in the channel member  130 . A positive polarity terminal lead  142  provided with a distal sleeve  144  is electrically insulated from the casing  126  for the capacitor  122  by a glass-to-metal seal  146 . The terminal lead  142  and glass-to-metal seal  144  are similar to those that have been previously described.  
         [0046]    Thus, according to the present invention, adjacent capacitors are connectable in series by connecting the anode terminal lead from one to the casing of the next. The anode terminal lead can be connected to the next capacitor&#39;s casing by a sleeve  44 /tab  96  structure, a collared sleeve  104 /tab  108  structure, or a sleeve  128 /channel member  130  structure. That way, any number of capacitors is serially connected together to increase the delivered capacity of the assembly. This is particularly important in advanced implantable medial devices, such as cardiac defibrillators, where delivered capacity coupled with reduced package volume is paramount in the minds of design engineers.  
         [0047]    It is appreciated that various modifications to the inventive concepts described herein may be apparent to those of ordinary skill in the art without departing from the spirit and scope of the present invention as defined by the appended claims.