Abstract:
A capacitive electrical energy storage structure is fabricated as a thin-film device comprising electrodes on opposite sides of a dielectric layer. In one approach, a high surface area metallic sponge can be incorporated into the structure. The energy storage structure can comprise either single or multiple layers of capacitors connected in series, parallel, or a combination of such arrangements. The multi-layer capacitor structure can be either applied directly to supporting structures of portable or transportable devices or can be fabricated as a film which is applied as a laminate to such structures. Further, a conformal energy storage structure can be produced which is shaped to fit in voids within devices, which voids would otherwise be little used or unused. A high capacity storage thin-film structure can be fabricated on one surface of a substrate with an immediately adjacent, overlapping power consuming electronic circuit such that power is available at very short distance to support operational circuits which cannot tolerate long conductive power supply lines. Portable consumer devices can be fabricated with the interiors of the housings conformally coated with the capacitive structure for providing energy storage as a replacement to rechargeable or disposable batteries. A flexible film of the capacitive structure can be manufactured by a continuous process and this film can be utilized in many different configurations to provide energy storage which is lightweight, configurable to available space, and capable of providing both high energy and high power density.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to electrical energy storage devices and more particularly to capacitor structures having high energy storage and high power delivery capability. 
     BACKGROUND OF THE INVENTION 
     Electronic equipment which is portable or transported must have a source of electrical power that has minimum weight and volume, but maximum capacity for power and energy density. The amount of energy stored and the peak power capability are principle parameters of a prime energy storage device. Compact commercial and military electronic systems have electrical and packaging constraints that are imposed by the volume and weight of the apparatus. These constraints determine the necessary energy and power density of the power source. 
     Examples of current prime energy storage devices include both non-rechargeable and rechargeable technologies. Nickel-cadmium (Ni—Cd) batteries, lithium-ion (Li-ion) batteries, and ultra capacitors are all examples of rechargeable energy storage devices. Rechargeable devices are re-energized by external power sources and are optimum for multi-use applications. Ideal rechargeable systems can store charge for long periods of time (also known as “shelf-life”). Lithium-based thermal batteries are an example of non-rechargeable energy storage devices. A primary energy storage device (non-rechargeable) contains an adequate amount of energy to operate through the life of the device. This type of energy storage device is discarded or destroyed at the end of use. 
     Existing commercial rechargeable energy storage technologies do not meet the power density and peak power requirements of future, high power electronic systems which undergo rapid mode changes during system operation (e.g., cell phone mode changes from idle to transmit). Present thermal batteries, such as used in missiles, generate enormous amounts of heat during activation and thus require insulation or remote packaging away from thermally sensitive electronics, thereby presenting additional design challenges such as thermal management. 
     In addition to the power requirements, existing energy storage technologies are generally packaged without considering the shape of the installation locations. For example, in missile applications electronics are generally packaged as cubic modules. Therefore, when placed into the curved interior of a missile, there are segments of the interior that don&#39;t readily house the typical packaging geometry for current energy storage devices. Additionally, when an energy storage device is situated in an apparatus that has an internal volume other than that of presently used packaging technology, unused space remains (i.e., the arc segments that remain when a square box is placed in a cylindrical housing and volumes associated with structural features such as wings, fins and so forth). Therefore, discretely packaged battery solutions have a further drawback of underutilization of space, which can limit electronics volume and thus overall system performance. 
     A capacitor structure which provides very high storage capacity is described in U.S. Pat. No. 6,226,173 B1 which issued on May 1, 2001 and is entitled “Directionally-Grown Capacitor Anodes.” This patent describes a dendritic sponge which is formed through chemical processing on a body of titanium. This process creates a large surface area which is then coated with a dielectric. By use of selected dopings of the anode, the subsequent dielectric formed on the anode can have a very high dielectric constant. An electrolyte is applied to the opposite side of the dielectric to serve as an electrical conductor (cathode) and to prevent breakdowns by re-oxidizing the dielectric surface at areas of local breakdown. A capacitor formed in this way can have a very high energy and power density per unit weight and volume. 
     Therefore, there is a need for a high energy density and high power density energy storage technology. Further, there is a need for power source technology that can utilize the currently available volumes in commercial and military applications, by, for example, forming the power source integrally with the structure and/or into unique geometric shapes. 
     SUMMARY OF THE INVENTION 
     An electrical energy source provides power for electronic equipment carried within an airborne vehicle. The vehicle has an elongate body section which encloses an interior volume. A multi-layer capacitor structure is provided on a non-planar interior surface of the body section. The capacitor structure has a conformal shape that matches to that of the interior surface of the vehicle. The capacitor structure stores electrical energy for use by the electronic equipment. Terminals are provided which connect the capacitor structure to the electronic equipment for transferring electrical power from the capacitor structure to the electronic equipment. The capacitor structure can be fabricated either directly on the mounting surface or fabricated separately and mounted to the interior surface of the vehicle. 
     A further embodiment of the present comprises an integrated electronic circuit together with a power supply on a planar substrate. The electronic circuit is formed as a portion of the substrate. A capacitor structure is joined to and is in parallel with the substrate. The capacitor structure stores electrical energy. The capacitor structure is positioned such that it is substantially overlapping with the electronic circuit on the opposite side of the substrate. Power terminals provide connections between the capacitor structure and the electronic circuit for transferring electrical power from the capacitor structure to the electronic circuit. 
     A further embodiment of the present invention is a capacitor stack for providing electrical power to electronic equipment positioned within an interior space of a vehicle. A plurality of planar capacitor structures are bonded together in parallel to form the capacitor stack. The vehicle has a shaped space therein which is at least partially defined by an exterior surface of a housing for the electronic equipment and a portion of a wall of the interior space. Each of the planar capacitor structures has a shape such that the capacitor stack in combination has an exterior configuration substantially corresponding to the shaped space and whereby the capacitor stack can be positioned within the shaped space to substantially fill the shaped space. 
     A further embodiment of the present invention is a power source for a portable electronic device which has a housing and electric power consuming circuitry therein. The housing of the portable electronic device has an interior surface. A film capacitor structure is joined over a majority of the area of the structure to at least a portion of the interior surface of the housing. The capacitor structure has a configuration that conforms to the shape of the interior surface. The capacitor structure can store electrical energy therein. Power terminals are provided which connect the capacitor structure to the power consuming circuitry for transferring electrical power. 
     A further embodiment of the present invention is a method for manufacturing a web of electrically capacitive material which comprises a sequence of processing steps conducted in one or more chambers wherein a metallic layer is applied to a surface of a film, an oxide layer is formed on the surface of the metallic layer, a metallic sponge is formed for the metallic layer, a dielectric oxide is formed on the metallic sponge, an electrolyte is applied to the surface of the dielectric oxide, and a metallic layer is formed on the electrolyte to produce a capacitor electrode, thereby producing a web of capacitive material which can be stored as a roll. 
     A still further embodiment of the present invention is an electrical power source for providing electrical power to equipment carried in an airborne vehicle. The vehicle has an elongate body section which enclosed an interior volume that has one or more structural braces therein. A multi-layer capacitor structure has a majority of the area thereof mounted on a surface of one of the structural braces. The capacitor structure functions to store electrical energy therein. Power terminals are provided for connecting the capacitive structure to the electronic equipment for transferring electrical power. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, reference is made to the following drawings taken in conjunction with the Detailed Description, in which: 
     FIG. 1 is a partially cut away, section view of a tubular body of a missile airframe illustrating the incorporation of a capacitive structure on the interior surface with connections to an electronic device inside the airframe, 
     FIGS. 2A-2H illustrate a sequential process for fabricating the capacitor structure within the airframe body shown in FIG. 1, 
     FIG. 3 is a section view of a semiconductor device having a power consuming amplifier on one side of a substrate and a capacitive energy storage device on the opposite side of the substrate, 
     FIG. 4 is a plan view of the semiconductor structure shown in FIG. 3, 
     FIGS. 5A-5I show the processing steps for fabricating a high capacity capacitor structure on a titanium foil, 
     FIG. 6 is a section and perspective view of a portion of a missile airframe having an interior packaged electronic device, 
     FIG. 7 is an illustration of a set of die cut foil capacitors, 
     FIG. 8 is an illustration of a capacitor stack comprising a plurality of the foils shown in FIG. 7 for producing a shaped capacitor storage structure, 
     FIG. 9 is a completed shaped capacitor stack for conformal installation in a corresponding shaped void, 
     FIG. 10 is an illustration of a control fin arrangement for a missile airframe with a showing of the interior of the fin, 
     FIG. 11 is a section view of the fin shown in FIG. 10 illustrating the incorporation of a capacitive structure on the interior surface of the fin, 
     FIG. 12 is a cutaway view of a portion of a missile airframe showing structural brackets and electronic equipment modules with surfaces which incorporate thin film energy storage structures, 
     FIG. 13 is a perspective view of a case for a cellular telephone wherein the case has a capacitive structure formed on the interior surface for serving as an energy source for the operative electronics of the cellular telephone, 
     FIG. 14 is a section view of a corner of the cellular telephone case shown in FIG. 13, 
     FIG. 15 is an elevation view of equipment for continuous processing of film for producing large volumes of flexible, high capacity, capacitive storage thin film, 
     FIG. 16 is a perspective view of a prime energy storage capacitive structure fabricated by use of the continuously produced film as shown in FIG. 15, 
     FIG. 17 is an illustration of the cylindrical capacitive structure shown in FIG. 16 as applied to the interior surface of an airframe, 
     FIG. 18 is a tightly wound cylindrical energy storage capacitor structure made of the film produced as described in reference to FIG. 15, and 
     FIG. 19 is a perspective cut-away view of an airframe having an interior structural member with a layer of capacitive thin-film capacitive laminated to a load-bearing structural member. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides high density energy storage devices in a limited volume with the shapes of the storage devices being adaptable to the available space. Referring now to FIG. 1, there is illustrated a body  30  which comprises a portion of an airframe for a missile. The body  30  has a generally cylindrical configuration, but it could equally well have other configurations. The body  30  has a cylindrical, load bearing external wall  32  made of a material such as steel, titanium, aluminum or a synthetic material such as graphite, kevlar, fiberglass, or other composite laminate or equivalent. A multi-layer capacitive structure  34  is fabricated on the interior surface of the wall  32 . Structure  34  provides for storage of electrical power for operation of electrical and electronic devices within the body  30 . A detailed configuration of each layer of the capacitive structure  34  is illustrated in FIGS. 2A-2H. The body  30  may have, for example, a diameter of 7 inches and the thickness of the wall  32  can be 0.25 inch. 
     The body  30  includes one or more electrical power consuming devices  36  which can be, for example, a microwave transmitter or laser pulse generator. The device  36  is mounted within the interior of the body  30 . The capacitive structure  34  is applied as a continuous layer on the interior of the wall  32 . The structure  34  is terminated by an insulating ring  38  which comprises a material such as teflon, epoxy, cork, or other electrically insulative material. A second interior capacitive structure  40  is fabricated on the interior of the wall  32  and is electrically insulated by a second insulating ring  42 . 
     The first capacitive structure  34  extends along a segment  48  of the body  30  and the second capacitive structure  40  extends along a body segment  50  of the body  30 . In a selected embodiment, the body segment  48  has a length of 24 inches, the capacitive structure  34  has 82 layers (capacitors) with a total thickness of 0.21 inch, has a total capacity at 10.9 farads, stores 400,000 joules of energy and has a peak voltage of 330 volts. In a selected embodiment, the body segment  50  has a length of 24 inches, the capacitor structure has 111 layers with a total thickness of .28 inch, has a capacity of 800 farads, stores 10,000 joules of energy and has a peak voltage of 5.5 volts. In each of the sections  48  and  50  the capacitors in the multiple layers are electrically connected in parallel. Each of the layers has a thickness of approximately 65 microns. The dielectric thickness for the 5.5 volt peak capacitor is approximately 16 nanometers, and for the 330 volt peak capacitor the dielectric thickness is approximately 990 nanometers. 
     The power consuming device  36  is electrically connected to an interior surface, or cathode layer, of the capacitive structure  34  by a terminal  52 , and is further connected electrically to the anode structure wall  32  by conductive pins  54  and  56  which are respectively insulated from the cathode layer of the structure  34  by insulating rings  58  and  60 . These pins can also be configured to provide a parallel connection for all of the capacitive layers wherein each pin is connected to common electrodes. 
     A charging terminal  66  includes a lead  68  that is connected to a wiring harness within the body  30  of the missile. The terminal  66  is connected to the cathode of the capacitive structure  34 . The anode of the structure  34  is electrically connected to the conductive wall  32  which serves as a common terminal for the electrical supply associated with the missile having body  30 . 
     The capacitive structure  34  preferably comprises a substantial number of layered capacitors, for example  96  capacitors connected in parallel. While the airframe which includes body  30  is being stored and transported, there is no electrical power stored within the capacitive structure  34 . When usage of the missile is required, dc electrical power is applied between the wall  32  (anode) and the line  68 , which is connected to the cathode of the capacitive structure  34 . Electrical power is transferred into the capacitive structure  34  until a predetermined voltage level is reached. This may be, for example, 330 volts. After the capacitive structure  34  has been fully charged, the missile is launched and the stored electric energy is provided via terminals  52 ,  54 , and  56  to the electronic device  36 . The capacitive structure  34  has sufficient energy storage capacity to provide the necessary electrical power to device  36  for the duration of a mission for the missile. 
     A sequence of steps for fabricating the capacitive structure  34  are described in reference to FIGS. 2A-2H. These figures are not necessarily to scale or shape, but are drawn to describe the manufacturing process and structure. In FIG. 2A there is shown a layer  80  which comprises a segment of the wall  32 . In a preferred embodiment, this comprises titanium or a titanium alloy (for example, BaTi) having a thickness of approximately .25 inch. Optionally, the layer  80  can be aluminum or steel with a thin layer  82  of titanium (25 microns) which is deposited on the interior surface of the wall  32 . 
     The process for manufacturing the capacitive structure for use herein can be the same as that described in U.S. Pat. No. 6,226,173 B1, Ser. No. 09/238,082 filed Jan. 26, 1999, which is incorporated herein by reference. This patent is referred to herein as the &#39;173 patent. The layer  80  serves as the anode of the capacitive structure  34 . 
     As an optional approach, referring to FIG. 2B, the layer  82  is oxidized and this layer is reduced back to metal to form a directional sponge of the layer  82 , as shown in the &#39;173 patent. This optional process produces a metallic sponge which has a substantially greater surface area than the original planar metal layer. 
     In FIG. 2C, which is a preferred alternative to the process described in FIG. 2B, a layer  83  of metal oxide is formed on the exposed surface of the layer  82  for forming a dielectric layer for a capacitor. The dielectric oxide layer can be formed in multiple ways, preferably it is anodically grown in solution. See the &#39;173 patent for a further description. The dielectric layer  83  has a thickness which is a function of the operating voltage of the energy storage device. See the &#39;173 patent for a further description of this process. 
     In the next step, as shown in FIG. 2D, an electrolyte, such as manganese dioxide (MnO 2 ) is processed on the exposed surface of the dielectric oxide layer  83 . The electrolyte fills voids and forms an intimate contact with the previously formed dielectric oxide layer. This electrolyte is shown as layer  84  and it serves two functions. The first is to provide electrical conductivity and thereby function as one plate of a capacitor, and the second function is to supply oxygen to the dielectric where the dielectric breaks down, and therefore it functions as a repair mechanism to maintain the integrity of the dielectric layer of the capacitor. 
     The next step of the fabrication process is shown in FIG. 2E. A layer  86  of graphite is applied such as by sputtering or by being brushed on and dried. The latter process comprises the application of carbon ink which is painted on and thermally cured. The graphite layer  86  is a conductive material which functions as a barrier to the manganese dioxide, which is a very strong oxidizing agent. The manganese dioxide layer  84  cannot be allowed to contact a metal directly, therefore the graphite provides a barrier that protects the succeeding metal layer and provides electrical conductivity. The graphite layer  86  also functions to fill any pores in the surface irregularities of the electrolyte layer  84  because this layer tends to follow the surface features of the underlying sponge of layer  82 , when this optional approach is selected. 
     In FIG. 2F there is shown the application of a layer  88  of silver, which can be a sputtered silver film, a silver epoxy or silver paint. Note that the silver layer  88  is protected from the manganese dioxide layer  84  by the intervening barrier layer  86  of graphite. 
     Referring to FIG. 2G, a layer  90  of tin or solder dip is applied to the surface of the silver layer  88  to protect layer  88  from corrosion. The structure shown in FIG. 2G forms a complete capacitive energy storage device with layer  80  functioning as the anode electrode of a polarized capacitor and layer  92  being the cathode electrode of the capacitive structure. The overall thickness of the structure shown in FIG. 2 is approximately 65 microns. 
     For multiple layers of capacitors connected in series, a layer of titanium or titanium alloy, corresponding to layer  80  shown in FIG. 2A, is deposited on the top of the layer  90  and the processes described in FIGS. 2A-2G are repeated. In this arrangement, the capacitors are electrically connected in series as they are stacked. 
     In a preferred embodiment, such as that shown in FIG. 1,  82  such capacitors are produced and the overall thickness of the multi-layer capacitor stack is approximately .021 inch. Note that the thickness does not include the layer  80  which represents the wall  32  of the airframe body  30 . In this approach to provide parallel connection of capacitive structures, referring to FIG. 2H, a surface insulation layer  92  is applied which can comprise a material such as teflon having a thickness of approximately .005 mil. Subsequent capacitive structures can be applied on the surface of the layer  92  to form a series of capacitor structures that are insulated from each other. This is done by repeating the steps  2 B through  2 H for each capacitor. 
     For connecting the capacitors in structure  34  electrically in parallel, a region at an end of each capacitor anode layer is exposed for connection to all of the other anode layers by a common line and this line is connected to the outer surface of the structure  34 , such as layers  80  or  82  of the innermost capacitor. The cathode layers of each capacitor in structure  34  are likewise interconnected at one end thereof with a second common line which is connected to the inner electrode of the structure  34 , such as layer  90 . 
     A further embodiment of the present invention is illustrated in FIGS. 3 and 4. A semiconductor device  102  comprises a substrate which has an electronic circuit designed for a specific application on one side of the substrate, and a capacitive electrical power storage structure fabricated on the opposite side. In the present illustrated embodiment, the functional electronic circuit is a millimeter wave integrated circuit high power amplifier (MMIC HPA)  104 , and on the opposite side of the substrate is a power storage structure  106 . The power storage structure is a capacitor which stores electrical energy for powering the circuit  104 . The device  102  includes a substrate  108  which can be silicon, gallium arsenide, silicon carbide, or other suitable semiconductor material that can be optionally surfaced area enhanced by etching grooves or channels as shown to increase the effective plate area. Fabricated into the substrate  108  is a first electrode layer  110  which preferably comprises titanium or a titanium-based alloy. 
     Immediately above layer  110  is a dielectric layer  112  comprising an oxide of the metal comprising layer  110 , in which is produced thermally, anodically or by mechanical application over the electrode layer. A solid electrolyte  114  is applied as a layer over the dielectric layer  112 . An example of the electrolyte is manganese dioxide, as in the previously described embodiment. 
     Immediately on the surface of the electrolyte layer  114  there is formed a graphite layer  116  which, just as previously described, serves as a barrier to the manganese dioxide with respect to an overlying electrode. Overlying the layer  116  is a metalization layer  118 , preferably made of gold, having a thickness of approximately 25 microns. 
     The cathode electrode layer  118  is connected by a wire bond  124  to a pad  128  which is connected to a via  130  that is in turn connected to a pad  131  on the opposite surface of the substrate  108 . A wire bond  132  is connected between pad  131  and a component of the circuit  104 . The anode electrode layer  110  is connected to a via  133  which is connected to a pad  134 . A wire bond  135  connects from pad  134  to a further component of circuit  104 . 
     Note that each of the downward extending units of the power structure  106  has a width of approximately 1 mil. This downwardly extending unit includes a U-shaped portion of the electrode layer  110 , an interior U-shaped portion of the layer  112 , and a downward extension of the electrolyte layer  114 . These U-shaped channels are one example of a technique to enhance the effective plate surface area. Other options for surface enhancement include V-channels, or other methodologies which provide additional anode surface area beyond that of a flat plate configuration. 
     The power storage structure  106  is electrically connected directly to the circuit  104  for providing power thereto. In an application where the circuit  104  is an MMIC HPA, for example an RF transmitter, circuit  104  may need to operate by generating pulses with extremely fast rise times, such as less than 10 nanoseconds. Such pulses are designed to be transmitted from an antenna and may require substantial energy and such energy must be readily available to the circuit  104 . 
     The power storage structure  106  can be connected to the circuit  104  by means of through-the-substrate connecting lines or around-the-edge connecting lines of sufficient size to carry the required electrical power. With the configuration shown in FIG. 3, the power structure can be located immediately adjacent and parallel to the circuit  104 . Thus, the propagation distance from the structure  106  to the circuit  104  is only a fraction of an inch. As a result, stored electrical power can be rapidly transferred from the power storage semiconductor structure  106  to the circuit  104  for utilization therein. 
     The boundary of the power structure  106  on the substrate  108  is defined by an insulating ring  120  which extends around the periphery of the conductive layers  114  and  116 . 
     Referring to FIG. 4, there is shown a plan view of the semiconductor device  102  illustrating the cathode electrode layer  118 , the insulating ring  120  and an exterior conductive area  122  which can comprise the anode of the power structure  106 . 
     A still further embodiment of the present invention is a foil configuration power storage structure which is fabricated as shown in the steps  5 A- 5 I. The fabrication process begins in FIG. 5A. A foil substrate  138  comprises titanium or an alloy such as BaTi which has a thickness of 1-3 mils. 
     Referring to FIG. 5B, an oxide layer  140  of thermally grown TiO 2  (or optionally BaTiO x ) is produced for a desired metal sponge depth, which is preferably in the range of 1000-5000 microns. Details of this process are shown in the above incorporated &#39;173 patent. 
     Referring now to FIG. 5C, the oxide layer  140  is reduced to a metallic sponge layer  140 A by use of the processes described in the &#39;173 patent, thereby leaving CaO material  140 B within the crevices of layer  140 A. This step is performed by the application of Ca vapor at a temperature of approximately 900 degrees C. 
     The next step in the process is shown in FIG. 5D. A layer  142  of gold film (or other equivalent conductive metal) is sputter applied to a thickness of approximately 25 microns on the back side of the foil layer  138  to form a contact for later assembling a stacked unit. 
     Referring to FIG. 5E, the material  140 B shown in FIG. 5D is leached in distilled water to remove the CaO reactant from the directional metal sponge and this is followed by a distilled water bath. 
     Referring now to FIG. 5F, the layer  140 C of titanium metallic sponge is subject to an anodization process to produce a layer  144  of titanium oxide (TiO 2 ). A sufficient voltage is applied during the anodization process to assure that there is minimum leakage such that at the operating voltage of the resulting capacitor, there will be little loss of stored charge. An applicable anodization process is described in the &#39;173 patent and in the patents referenced therein. 
     Referring now to FIG. 5G, an electrolyte layer  146  of MnO 2  is applied through the sponge layer  140 C and into contact with the dielectric oxide layer  144 . In FIG. 5H, a layer  148  of graphite is applied through the metal sponge  140 C for contact with the electrolyte layer  146 . 
     In a final step, referring to FIG. 5I, a layer  150  of gold is sputter applied to the top of layer  140 C for forming a cathode capacitor terminal. 
     Referring now to FIG. 6, there is shown a portion of an airframe  180  having a cylindrical casing  182  and an electronic module  184  mounted within the casing  182 . The module  184  has a rectangular configuration and when positioned within the casing  182  forms arc-shaped voids  186 ,  188 ,  190  and  192 . Most sub-assemblies used within a missile airframe, as well as power sources such as batteries, have a rectangular or round configuration that is not adaptable for utilization within the voids  186 - 192 . If such a module or battery is of sufficiently small size to fit within one of the voids, it will not only be of minimal size and effectiveness, it will still leave a substantial unused volume within the void. One aspect of the present invention is the design and utilization of an energy storage structure which is shaped to have a configuration that will fit within such a void and thereby optimize the utilization of such spaces. 
     As described above in reference to FIG. 5, a foil-based energy storage structure can be fabricated in accordance with the present invention. This device has a thin, planar structure which can be die-cut in any planar configuration. 
     Referring to FIG. 7, there are shown die-cut sections  200 ,  202 ,  204  and  206 , each of which has opposite planar surfaces. The opposite surfaces are respectively the anode and cathode of each energy storage capacitor. Each of the sections  200 - 206  has an arc configuration corresponding to a section of one of the voids, such as  186  shown in FIG.  6 . The lower surfaces of the sections  200 - 206  have respective silk-screened solder paste layers  200 A,  202 A,  204 A and  206 A. The upper surfaces have silk-screened solder paste layers  200 B,  202 B,  204 B and  206 B. 
     Referring now to FIG. 8, there is shown a stacked capacitor device  208  comprising the group of die-cut sections  200 - 206 . These sections are assembled in a holding fixture  210  which is heated to reflow the solder paste to connect the sections  200 - 204  physically as a stacked unit  208  wherein the sections are electrically connected in series. 
     Referring to FIG. 9, there is shown a completed energy storage device  211  which has the stack capacitor unit  208  enclosed by a nonconductive cover or housing  212 . This housing provides environmental protection and electrical insulation for all the individual sections and the device  211  as a whole. The first of the enclosed die-cut sections has a first lead  214  connected to a surface such as  200 A (see FIG. 7) and a second conductive lead  216  connected to a second surface, such as  206 B of the last of the sections. The leads  214  and  216  are connected to a wiring harness within the airframe. The composite energy storage device  211  is positioned within a void, such as  186  shown in FIG.  6 . The outer configuration of the device  211  matches the shape of the void  186 , thereby optimizing the use of the available space. 
     Referring now to FIG. 10, there is shown a missile airframe  250  having a fin  252 . The fin  252  has an interior volume  254 . A section view of the fin  252  is shown in FIG.  11 . An aerodynamically configured fin has the interior volume  254  which has a complex configuration based on the structural requirements of the airframe  250  and the aerodynamic requirements of the fin and the missile surfaces. It is difficult to make productive use of the volume  254 . However, in the present invention, a multi-layer capacitor structure  256  is formed on the interior surfaces of the fin  252 . The capacitor structure  256  is fabricated in the same manner as described in FIGS. 2A-2H for the structure  34  shown in FIG.  1 . By building the thin-film capacitor structure  256  within a fin, such as  252 , additional energy storage capacity is provided to the airframe  250  without the requirement to use additional space. 
     A still further illustration of applying the present invention is shown in FIG.  12 . An airframe  270  has an exterior casing  272  which corresponds to the casing  32  shown in FIG.  1 . The interior of the airframe  270  includes various spars, ribs and brackets that provide structural support to the airframe as well as providing mounting locations for interior components, such as electronic modules. Within the airframe  270 , plates  274 ,  276  and  278  are mounted, such as by welding, to the interior of the casing  272 , and together form a bracket. A plate  280  is mounted to the plates  274  and  278  and is connected to structural plates  282  and  284 . A plate  286  is connected to the plates  282  and  284  opposite plate  280 . A rectangular electronic module  288  is mounted on an exposed surface of the plate  286 . 
     A bracket  294  is mounted to the interior of the casing  272  and provides support for an elongate module  296 . 
     There are numerous unused surfaces available within the airframe  270  for fabrication of thin-film capacitive structures as described above. These include surfaces  272 A on the interior of the casing  272 ,  276 A on the interior of the plate  276 ,  280 A on the interior surface of the plate  280 , and  284 A on the surface of the plate  284 . By applying thin-film capacitor structures at these various surfaces, the unused volume within the airframe  270  can be utilized to store additional electrical power. The plates further provide the structural basis for supporting the capacitive structures and also serve as a common cathode for all of the capacitors. The plates shown in the airframe  270  can be made of aluminum, titanium, steel, other metals or may be made of synthetic materials as listed above. Such synthetic materials would require an additional electrical lead because the substrate would not be conductive. 
     A capacitive structure  272 B is fabricated on the interior surface of the casing  272  on the surface  272 A. A thin-film capacitive structure  276 B is fabricated on the surface  276 A of the plate  276 . A thin-film planar capacitive structure  286 B is fabricated on the surface  286 A of the plate  286 . 
     A still further embodiment of the present invention is shown in FIGS. 13 and 14. There is shown in these figures a portion of a housing  310  for a cellular telephone. An opposed matching portion completes the housing and the electronic components are included between the two housing pieces. The housing  310  is a structural plastic layer  312  which provides the structural integrity for the housing  310 . Plastic layer  312  is an electrical insulator. On the immediately interior surface of the layer  312  there is provided a first electrode  314  (anode) which is applied as a thin layer of titanium or titanium alloy which covers most of the interior surfaces of the housing  310 . The housing includes a plurality of upstanding members such as member  316 , which has a rectangular outer configuration with a rectangular center hole for receiving a push-button key. The upstanding member  316  has a top surface  316 A and four side surfaces  316 B. The electrode layer  314  extends to cover the top and side surfaces of all of the members, such as  316  and the surfaces  316 A and  316 B. 
     A dielectric layer  318  is applied to the surface of the electrode  314 . The dielectric layer is a metal oxide anodically formed and having a thickness based on the voltage rating of the energy storage device. The dielectric layer extends to cover all of the available interior surfaces of the housing  310  where the layer  312  is present, including on the sides and top of the upstanding members such as  316 . 
     A second electrode  320  is fabricated on the surface of the dielectric layer  318  and likewise extends to cover all of the available surface area within the interior of the housing  310 . The electrode  320  serves as the cathode of the capacitive structure which comprises layers  314 ,  318  and  320 . Electrode  320  comprises successive layers of MnO 2 , graphite, silver and tin and in combination these layers comprise the cathode of the storage device. 
     The upper limit of the electrode  314  is defined by a masking layer  322 . An insulating layer  324  extends along the edges of the dielectric layer  318  and electrode  320  to provide electrical insulation between layers  314  and  320  (anode and cathode). 
     An electrical conducting terminal  332  is isolated by insulation  334  so that it is electrically connected to the electrode layer  314  but electrically isolated from the electrode  320 . An electrical terminal  336  is connected directly to the electrode layer  320  to provide electrical connection to the capacitive energy storage structure. 
     The combination of the layers  314 ,  318  and  320  comprise an energy storage film which has an overall thickness of approximately 1.0 mils. This electrical storage film can store electrical power for operating the cell telephone through the terminals  332  and  336 . These terminals can likewise be used to initially store electrical power into the storage film. The storage film can be repeatedly recharged to provide electrical power for the cell telephone. In contrast to a battery, the capacitive storage film can be very quickly charged, on the order of seconds, as opposed to the charging time of many minutes or hours required for rechargeable batteries. 
     Options for the design of the energy storage film shown in FIGS. 13 and 14 include a plurality of capacitive layers stacked one on the other to provide additional electrical storage capacity. A still further option is to include the fabrication process wherein a metallic sponge is formed, as described above, for the dielectric and corresponding electrodes such that there is greater surface area and therefore greater electrical energy storage. The second half of the housing for enclosing the cellular telephone can likewise have a similar coating to provide additional energy storage capability. 
     Specific application examples for utilization of the invention as described in reference to FIGS. 13 and 14 include power tool housings, laptop computer cases, cellular telephone cases, handheld GPS cases, media player cases such as compact disk, DVD and MP3, hand held games, and any other portable electrically powered device. 
     A continuous process for producing capacitive energy storage film (web) in accordance with the present invention is shown in FIG.  15 . The film is fabricated on a polymer sheet  350  which is stored in an unprocessed roll  352  that is supported on a rotating rod  354 . The sheet  350  may have, for example, a length of 2000 feet, a width of 2.0 feet, and have a film thickness of 1.0 mils. The sheet of film  350  is fed into a processing chamber  356  which includes a plurality of inlet and outlet lines such as  358  and  360 . The sheet  350  is processed within the chamber  356  and is then transferred to a take-up roll  362  that is supported by a rod  364  which can be driven to pull the sheet  352  through the chamber  356 . 
     For the complete processing operation for the sheet  350 , refer to FIGS. 2A-2H as well as FIG.  15 . The preferred capacitive structure in this embodiment does not utilize the sponge metal processing step described as an option in FIGS. 2A-2H. The processing for the sheet  350  is the same as that described in the FIGS. 2A-2H, but with the film  350  replacing the supporting structure  80  shown in FIGS. 2A-2H. The processing chamber  356  is replicated with multiple such chambers to provide each of the processing steps shown in FIGS. 2A-2H. The sheet  350  on roll  352  is initially processed through a chamber, such as  356 , to perform a processing operation to apply a titanium layer to the surface of the film. The process is operated continuously to produce the roll  362  which comprises the film with the titanium layer applied thereto. The roll  362  is then placed in the position of roll  352  and applied through another processing chamber to perform the next sequential step which is forming a layer of titanium oxide on the surface of the titanium layer. After this process is completed for the entire roll, the take-up roll, is them transferred to the input of a further processing chamber to perform the process described in FIG.  2 D. 
     The entire length of the sheet  350  is fed through each chamber for performing each sequential processing step. This includes the processes shown in FIGS. 2E,  2 F,  2 G and a final application of an overlying insulator in step  2 H. The resulting product is a roll of processed film having 2000 linear feet of capacitive material which can be used many ways, with specific examples as shown in the following figures. This is a production process which can produce the capacitive structure in a way that is less expensive and more rapid manner than direct application of the capacitive layers to structural members of an airframe, such as described in reference to FIG.  1 . 
     As an option to the processing of feeding the sheet  350  through a processing chamber, the sheet  350  could be placed entirely within a chamber statically for each processing step. 
     Referring to FIG. 16, a capacitive energy storage device  372  is made with the flexible thin-film produced in accordance with the processes described in reference to FIG. 15. A length of film  374  is wrapped about a cylindrical form (not shown), and a binding material, such as epoxy, is applied to the touching surfaces of the film to fix the shape and size of the energy storage device  372 . The interior surface of the cylindrical device  372  is etched through the surface insulation to form a contact pad  376  to which is connected a line  378 . Likewise, on the exterior surface of the cylindrical device  372  an etching step is performed to expose the outer electrode and a contact pad  380  is formed and it is connected a conducting line  382 . The lines  378  and  382  provide a path for the initial charging of the capacitive energy storage device  372 , as well as for supplying power from the device to an electronic apparatus. 
     Referring to FIG. 17, the energy storage device  372  is positioned on the interior of a cylindrical airframe  390  and is bonded to the interior surface of the airframe  390  by a material such as epoxy. The lines  378  and  382  are connected to the wiring harness within the airframe for receiving and supplying electrical power. The configuration shown in FIG. 17 is an alternative to the direct fabrication of the capacitive structure on the interior casing wall of the airframe  390 . 
     A still further embodiment of a capacitive energy storage device in accordance with the present invention is a device  400  illustrated in FIG. 18. A length of film  402 , such as prepared in accordance with the description in reference to FIG. 15, is tightly wrapped in a solid cylindrical structure with an interior conductive pad (not shown) connected to a conductive line  404  and an exterior conductive pad  406  connected to a conductive line  408 . The energy storage device  400  can then be inserted into a cylindrical void area or used in an available space. 
     Referring now to FIG. 19, an airframe  420 , having a cylindrical configuration, includes an interior flat structural plate  422  which is connected by brackets to the interior surface of the airframe  420 . A film  424 , which is fabricated as described in reference to FIG. 15, is mounted on the planar surface of the structure  422  by a bonding agent such as epoxy. Electrical connections are made to the film  424  by a first pad (not shown) which is connected to a line  426 . A pad  428  is formed by etching through the outer insulating layer of the film  424  and is connected to a line  430 . The lines  426  and  430  are connected to a wiring harness within the airframe  420  for receiving electrical power for storage in the film  424  and later providing electrical power to devices within the airframe  420 . Optionally, the capacitive structure can be fabricated on the surface of plate  422  as described above in reference to FIGS. 2A-2H. 
     Although several embodiments of the invention have been illustrated in the accompanying drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention.