Abstract:
A method for forming a plurality of strips to be used for formulating high-breakdown strength and high-temperature capacitors is disclosed. The method includes forming a metalized substrate having a particular pattern, masking a portion of the metalized substrate, coating the metalized substrate with a dielectric material and removing the masking material and thus the dielectric layer from a portion of the metalized layer to form a contact surface. In lieu of placing a masking material on the metalized substrate, the exposed contact area can be formed by shielding a portion of the metalized substrate while depositing the dielectric layer.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention described and disclosed in this application is for a method of forming long strips of dielectric coated metalized film that are used to form high-breakdown strength and high-temperature capacitors. 
         [0003]    2. Description of Related Art 
         [0004]    U.S. Pat. No. 7,460,352, the contents of which is hereby incorporated by reference, discloses a method of forming high energy density wound capacitors using long strips of metalized substrate coated with a dielectric. As shown in  FIG. 2  of the patent the strips include an insulating substrate  22 , metalized layers  23  and  25  on each side of the substrate and dielectric layers  24 ,  26 . The dielectric material is deposited on the metalized film. In order to provide an electrical contact area without the dielectric coating, a mask is positioned over a portion of the film as it is transported and coated with the dielectric, thus leaving an exposed edge of the metalized substrate, see column 4, lines 19-24. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The invention disclosed in this application is for a method to manufacture a long, narrow dielectric coated metalized polymer film by taking a wide polymer film with a metal pattern on both sides, then masking certain regions of the film so the dielectric is not deposited in these regions, or coating the film with a lift-off mask in certain regions so that after the dielectric is deposited it can be removed later from those regions as the lift-off mask is removed. In both approaches, the wide polymer film is comprised of multiple narrow strips with metal regions that are either exposed or can be exposed for the purpose of electrical contact. The narrow strips may be slit (or singulated) from the wide polymer film and then wound into capacitors. For the lift-off mask approach, the mask may be removed before or after slitting. The end result is a long narrow strip of dielectric coated metalized polymer film with a strip of uncoated metalized polymer on both sides. 
         [0006]    By starting with a wide strip of metalized film according to a given metal pattern and forming plural strips of a metalized substrate coated with a dielectric in certain regions and uncoated in certain other regions, a cheaper and more efficient method of producing the final capacitor is achieved. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0007]      FIG. 1  is a top view of a portion of the metalized substrate. 
           [0008]      FIG. 2  is a cross section of a strip formed according to an embodiment of the invention prior to being coated with the dielectric. 
           [0009]      FIG. 3  is a perspective view showing various embodiments of the various devices used to place the masking material on the metalized substrate. 
           [0010]      FIG. 4  is a perspective view showing the formation of plural strips by slitting and shielding strands 
           [0011]      FIG. 5  is a perspective view showing the second slitting step and mask removal. 
           [0012]      FIG. 6  is a cross sectional view of the finish strip according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]      FIG. 1  illustrates an example of a metalized substrate with a particular pattern required for a narrow capacitor electrode. The pattern is repeated over the width of the substrate on both sides. The film includes an insulating substrate  21  which may be formed from a variety of materials as disclosed in U.S. Pat. No. 7,460,352, and a metalized coating  12  on each side of the substrate  21 . On portions of the strip the metal coating is thicker as shown at  15  in  FIGS. 1 and 2 . 
         [0014]    The pattern of the film can be described by reference to  FIG. 1 . At the left side portion of film  10  there is a first uncoated portion  21  of the substrate. A number of sections  12  represent portions of the film that are coated with a metal layer of a first thickness. Sections  15  of the film represent portions of the film that are coated with a layer of metal thicker than that of layer  12 . The film is formed as a roll of material having the pattern of  FIG. 1  along its width and length as shown in  FIG. 3 . 
         [0015]    Portions  13  which are intermediate between the metalized portions of the film represent areas of the substrate that are not coated with a metal. Right edge portion  21  of the substrate is also not coated with a metal. The film as described to this point is commercially available from Steiner Film Inc. or other vendors in various patterns. The materials used for the various components of the film are described in U.S. Pat. No. 7,460,352 and other materials known in the art may be used. 
         [0016]    As an example, the final strip shown in  FIG. 2  in cross section may be about 50 mm wide and the width of the thicker metal layer  15  may be 5 mm. The thickness of the substrate  21  may be 12.7 um. The deposited metal may be aluminum with a resistance of twenty ohm/sq in the thinner portion and a resistance of 2 ohm/sq in the thicker portion. 
         [0017]    In order to create areas where the dielectric does not cover the film, a masking material  14  is applied over the area of the film where the metal layer will be exposed, for example at the middle section of metal layer  15  as shown in  FIG. 1 . The masking material may be ink, polyvinyl alcohol, PMMA, photoresist or any other material that will separate from the metal coating after the dielectric layer has been applied as explained below. 
         [0018]    The masking material may be applied to the film by any one of a plurality of known coating techniques. Such techniques are illustrated in  FIG. 3  and include an ink jet  45 , solid tape dispensers  44 , a liquid dispensing nozzle  46 , a material dispenser in combination with a slotted shield  43 , or printing devices such as a gravure type printer  42 . The film is moved under the dispensing device by a roller system  40 ,  41  that unwinds the film, applies the mask and rewinds the film as shown in  FIG. 3 . The mask may be applied ex-situ before loading in the coating system or in-situ in the coating system. The masking material is applied to both sides of the film. 
         [0019]    The next step in the process is to apply a layer of dielectric material to both sides of the film. Thus can be done in accordance with the disclosure in U.S. Pat. No. 7,460,352 or by any other known method. The dielectric material may be formed from amorphous oxides, amorphous nitrides, or multi-layer stacks of amorphous oxides and nitrides. 
         [0020]    After dielectric deposition, the film is removed from the web coater and slit into first narrower sections  53  using a mechanical slitter or a laser saw as shown in  FIG. 4 . The slits will go through portion  13  of the substrate  21  that is not coated with metal. After this step, the strips  53  are slit along the thicker portion of the metalized layer  15  as shown in  FIG. 5 . The masking material along with dielectric material is then removed from both sides of the film by any suitable means. The masking material could also be removed prior to slitting.  FIG. 5  illustrates rolls of tape  57 ,  59  that can be run over the surface of the film to strip off the dielectric and masking material. Other methods to remove the masking and dielectric material include immersion in a solvent with ultrasonic agitation. As the mask lifts off and dissolves, the dielectric material above the mask also releases from the substrate exposing the metalized edge. 
         [0021]    The final composition of the strip is shown in  FIG. 6  and includes the substrate  21 , metalized coatings  12  on both sides of the substrate, and dielectric layer  31  on both sides of the metalized strip. A portion of the thick section  15  of the metal layer is left uncovered on both sides by the dielectric after the masking material and the dielectric layer on top of it is removed. Also, the metalized layers  12  do not extend to the right edge of the strip as illustrated in  FIG. 6 . 
         [0022]    Although the above described embodiment has the metalized layers and the dielectric on both sides of the substrate, the substrate could be metalized and then coated with a dielectric on one side only, using a mask or a masking material to form the metalized area for electrical contact. 
         [0023]    The strip is now ready to be rolled into a final configuration as a capacitor as described in U.S. Pat. No. 7,460,352. 
         [0024]    As an alternative to mask application and removal, the exposed metalized area  15  may be formed by shielding the strip during the deposition of the dielectric layer as shown in  FIG. 4 . A dielectric coating device  51  deposits a layer of dielectric material onto the film coming off of roller  59 . A solid mask device  52  using a plurality of thin shielding strands prevents dielectric material from being deposited on certain areas of the film thus creating the exposed metal areas. 
         [0025]    The above description is illustrative of embodiments of the invention. Various modifications will be evident to those skilled in the art without departing from the invention the scope of which is defined by the following claims. Furthermore the dimensions of the film and the thickness of the various layers as shown are for illustration only and can be varied according to the particular materials used and the desired characteristics of the final capacitor. 
         [0026]    Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.