Abstract:
The disclosed concept relates to electrical isolation between power electronic and cooling and/or mounting components and, in particular, a ceramic layer positioned at the interface of the power electronic and cooling and/or mounting components to provide electrical isolation, as well as, a thermally conductive path to remove heat produced by the power electronic component.

Description:
BACKGROUND 
       [0001]    Field 
         [0002]    The disclosed concept relates generally to power electronic devices, cooling and/or mounting devices therefor and, ceramic coatings applied to the cooling and/or mounting devices. 
         [0003]    Background Information 
         [0004]    It is known in the art to provide cooling and/or mounting devices with power electronic devices for the purpose of removing at least a portion of the heat generated by the power electronic devices, such as diodes. It is also known that in certain instances the power electronic devices may operate at voltages that exceed their isolation rating. Therefore, the cooling and/or mounting devices are also at an elevated potential voltage. It is necessary to isolate the power electronic devices from ground to prevent arcing or ground currents, which can cause noise on a system, degrade or damage a system, and potentially lead to operator injury or death. If the cooling and/or mounting devices use electrically conductive cooling medium, such as water, the entire water circuit can serve as a path to ground thereby resulting in the cooling circuit itself being unsafe. 
         [0005]    Isolation pads and films are known for use in isolating the power electronic devices. However, there are disadvantages associated with many of these pads and films. For example, it has been found that the pads or films can have poor thermal conductivity and/or poor adhesion. In some instances, a thermal grease or epoxy may be required to adhere the pad or film to the surface of the device. The use of an intermediate layer for purposes of enhancing adherence may result in increased contact losses and reduced effective conductivity. 
         [0006]    There is room for improvement in power electronic devices and the cooling and/or mounting devices associated therewith. It would be advantageous for the cooling and/or mounting devices to include a ceramic coating or layer applied to a surface thereof, such that the surface is effective to isolate the cooling and/or mounting devices while providing a means of thermal transfer. 
       SUMMARY 
       [0007]    These needs and others are met by embodiments of the disclosed concept, which are directed to power electronic devices and cooling and/or mounting devices associated therewith, and furthermore to coating compositions for use in applying a protective coating to the surface of the cooling and/or mounting devices to provide effective isolation and thermal transfer. 
         [0008]    As one aspect of the disclosed concept, a power electronic device and cooling device interface is provided. The interface includes a cooling device having a top surface, a ceramic layer applied to the top surface of the cooling device and a power electronic device in contact with the ceramic layer. 
         [0009]    The power electronic device can be selected from a single diode or insulated-gate bipolar transistor, or a plurality of diodes or insulated-gate bipolar transistors. 
         [0010]    The cooling device may be selected from a cold plate, heat spreader or heat sink. 
         [0011]    In certain embodiments, the ceramic layer includes a ceramic coating composition. The ceramic coating composition may be selected from pure ceramic, ceramic-based compositions and ceramic-containing compositions. The ceramic layer can include ceramic selected from boron nitride, alumina, aluminum nitride, silica and mixtures thereof. In certain embodiments, the ceramic coating composition is applied directly to the top surface of the cooling device. In other embodiments, the ceramic coating composition is applied directly to a substrate and the substrate is connected to the top surface of the cooling device. The substrate may be a metal sheet or metal plate. 
         [0012]    In certain embodiments, the ceramic coating composition can be applied to an intermediate coating layer. 
         [0013]    The interface can further include a clamp device to house the power electronic device and, a swivel to contact the clamp device. The swivel is structured to rotate in one direction to apply pressure to the clamp device and to rotate in an opposite direction to release pressure from the clamp device. 
         [0014]    In another aspect of the disclosed concept, a power electronic device and cooling device apparatus is provided. The apparatus includes a cooling device having a top surface and a bottom surface; a power electronic device including a base plate, the base plate having an upper surface and a lower surface, the lower surface of the base plate forming an interface with the top surface of the cooling device; a fastening mechanism having a horizontal portion, a vertical portion and a tip; an aperture having a radial surface and being adapted to receive the vertical portion of the fastening mechanism therein; a ceramic layer applied to the top surface of the cooling device and the radial surface of the aperture; a nut structured to engage the tip of the fastening mechanism. Wherein the aperture is formed to extend vertically through the cooling device, the ceramic layer and the power electronic device. 
         [0015]    When the fastening mechanism is composed of metal, the ceramic layer can be further applied to a surface of the fastening mechanism. 
         [0016]    Further, when the nut is composed of metal, the ceramic layer can be further applied to at least one of the bottom surface of the cooling device and a surface of the nut. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
           [0018]      FIG. 1A  is a schematic showing an isometric view of a cooling device, in accordance with the prior art; 
           [0019]      FIG. 1B  is a schematic showing an isometric view of the cooling device of  FIG. 1A  with a ceramic coating applied thereto, in accordance with certain embodiments of the disclosed concept; 
           [0020]      FIG. 1C  is a schematic showing a cross-section view of the cooling device of  FIG. 1B , in accordance with certain embodiments of the disclosed concept; 
           [0021]      FIG. 1D  is a schematic showing a cross-section view of the cooling device of  FIG. 1A  with a ceramic coated plate applied thereto, in accordance with certain embodiments of the disclosed concept; 
           [0022]      FIG. 2  is a schematic showing the ceramic coated cooling device of  FIG. 1B  in combination with a plurality of diodes, in accordance with certain embodiments of the disclosed concept; 
           [0023]      FIG. 3  is a schematic showing the ceramic coated cooling device and diode combination shown in  FIG. 2 , with the addition of clamp and swivel devices, in accordance with certain embodiments of the disclosed concept; 
           [0024]      FIG. 3A  is a schematic showing a detailed view of one of the clamp and swivel devices of  FIG. 3 , in accordance with certain embodiments of the disclosed concept; 
           [0025]      FIG. 4  is a schematic showing the ceramic coated cooling device and diode combination shown in  FIG. 3  with the addition of a framework, in accordance with certain embodiments of the disclosed concept; 
           [0026]      FIG. 5A  is a schematic showing the cooling device of  FIG. 1C  with an intermediate layer directly applied thereto and the ceramic coating directly applied to the intermediate layer, in accordance with certain embodiments of the disclosed concept; 
           [0027]      FIG. 5B  is a schematic showing the cooling device of  FIG. 1D  with an intermediate layer directly applied to the plate and the ceramic coating directly applied to the intermediate layer, in accordance with certain embodiments of the disclosed concept; 
           [0028]      FIG. 6  is a schematic showing a metal mounting device for a cooling device and diode combination, in accordance with certain embodiments of the disclosed concept; and 
           [0029]      FIG. 7  is a schematic showing a non-metal mounting device for a cooling device and diode combination, in accordance with certain embodiments of the disclosed concept. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    Directional phrases used herein, such as, for example, left, right, clockwise, counterclockwise, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. 
         [0031]    As employed herein, the statement that two or more parts are “coupled” or “connected” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. 
         [0032]    As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
         [0033]      FIG. 1A  is a schematic showing a cold plate  10  having a top surface  11 , which is employed as a cooling device associated with power electronic devices in accordance with the prior art. Various cooling devices are known in the art, such as, but not limited to liquid cold plates. The liquid associated with a cold plate is referred to as a primary cooling source, which can include, but is not limited to, water, refrigerant or phase change medium. The disclosed concept can be equally applied to a wide variety of cooling devices. 
         [0034]      FIG. 1B  is a schematic showing the cold plate  10  as shown in  FIG. 1A . In addition,  FIG. 1B  includes a ceramic layer  12  formed on the top surface  11  (shown in  FIG. 1A ) of the cold plate  10 . The ceramic layer  12  can be formed by depositing or applying a ceramic coating composition directly to the top surface  11  of the cold plate  10 . As shown in  FIG. 1B , the ceramic layer  12  extends over the entire top surface  11  of the cold plate  10 . However, it is understood that the ceramic layer  12  may be deposited or applied such that it covers only a portion of the top surface  11  of the cold plate  10 . 
         [0035]      FIG. 1C  is a schematic showing a cross-section of the cold plate  10  and the ceramic layer  12  shown in  FIG. 1B . As shown in  FIG. 1C , the ceramic layer  12  is deposited or applied directly onto the top surface  11  (shown in  FIG. 1A ) of the cold plate  10 . 
         [0036]    In an alternate embodiment, the ceramic layer  12  can be formed by depositing or applying a ceramic coating composition to a substrate, such as, a metal sheet or metal plate, and connecting the ceramic coated substrate to the cold plate  10 .  FIG. 1D  is a schematic showing a cross-section of the cold plate  10  and the ceramic layer  12  shown in  FIG. 1B . In addition,  FIG. 1D  includes a substrate  13 , which can be constructed of metal. As shown in  FIG. 1D , the ceramic layer  12  is directly deposited or applied to a top surface of the substrate  13 , and a bottom surface of the substrate  13  is connected or coupled to the top surface  11  of the cold plate  10 . Various mechanisms for connecting or coupling one substrate to another are known in the art. In certain embodiments, the substrate  13  is connected to the cold plate  10  by welding. In  FIG. 1D , the substrate  13  covers the entire top surface of the cold plate  10 . However, it is contemplated and understood that the substrate  13  may cover only a portion of the top surface of the cold plate  10 . In addition, there may be a recess formed in the top surface of the cold plate  10 , such that the substrate  13  is placed within the recess and therefore, the substrate  13  is flush with the top surface of the cold plate  10 . 
         [0037]    Deposition or application of the ceramic coating composition, e.g., to the cold plate  10  or the substrate  13 , to form a ceramic layer  12  can be accomplished using various conventional apparatus and techniques known in the art, such as, spraying, brushing, wiping and the like. The disclosed concept includes the use of pure ceramic compositions, ceramic-based compositions and ceramic-containing compositions. Suitable ceramics for use can be selected from a wide variety of ceramics known in the art, such as, but not limited to, boron nitride, alumina, aluminum nitride, silica and mixtures thereof. In certain embodiments, the ceramic composition is Thermolon®, which is commercially available from Porcelain Industries. 
         [0038]      FIG. 2  is a schematic showing the cold plate  10  and the ceramic layer  12 , as shown in  FIG. 1B . In addition,  FIG. 2  includes a creep barrier  14  and a plurality of diodes  16  positioned on the top surface  11  (shown in  FIG. 1A ) to interface with the cold plate  10  and to contact the ceramic layer  12 . The diodes  16  are located within the area that is formed and encompassed by the creep barrier  14 . There are three diodes shown in  FIG. 2 , however, it is contemplated that there can be more or less than three diodes in certain other embodiments of the disclosed concept. For example, there can be a single diode or a plurality of diodes. Furthermore, it is understood that the diodes  16  are representative of a power electronic device for use in accordance with certain embodiments of the disclosed concept; however, it is contemplated that a variety of other power electronic devices are known in the art and can be employed in the disclosed concept. For example, one or more insulated-gate bipolar transistors may be used. 
         [0039]    Although, as shown in  FIG. 2 , the ceramic layer  12  extends over the entire top surface  11  of the cold plate  10 , it is understood that the ceramic layer  12  may be deposited or applied to the cold plate  10  such that it covers only the portion of the top surface  11  that is encompassed by the creep barrier  14  (and the portion of the surface of the cold plate  10  that extends beyond the creep barrier  14  is not covered by the ceramic layer  12 ). Further, it is understood that in certain embodiments, the creep barrier  14  may be absent. Furthermore, although  FIG. 2  shows a plurality of diodes  16 , it is contemplated that there are a wide variety of power electronic devices known in the art, which are associated with cooling devices, and the disclosed concept can be equally applied to the wide variety of power electronic devices. 
         [0040]      FIG. 3  is a schematic showing the cold plate  10 , ceramic layer  12 , creep barrier  14  and plurality of diodes  16  shown in  FIG. 2 . In addition,  FIG. 3  shows a plurality of threaded swivels  20  and a corresponding plurality of clamps  24 . Each one of the combined plurality of threaded swivels  20  and clamps  24  is positioned to house a corresponding one of the plurality of diodes  16 .  FIG. 3A  is a schematic showing a detailed view of one of the plurality of clamps  24 . As shown in  FIG. 3A , each one of the clamps  24  includes an upper surface  25  and a plurality of legs  23 , each of which extends downwardly from a corresponding corner of the upper surface  25 . One end of each of the plurality of legs  23  is attached or coupled to the upper surface  25  and the other end of each of the plurality of legs  23  is in contact with the surface of the baseplate of the diode. 
         [0041]      FIG. 4  is a schematic showing the cold plate  10 , ceramic layer  12 , creep barrier  14 , plurality of diodes  16 , plurality of legs  23  and plurality of threaded swivels  20  shown in  FIG. 3 . In addition,  FIG. 4  includes a framework  22 . The framework  22  has a top canopy  26  and a plurality of extensions  28 , each extending downwardly from the top canopy  26 . One end of each of the extensions  28  is attached or coupled to a corner of the canopy  26 . In certain embodiments, the canopy  26  and the plurality of extensions  28  are a single integrated or molded piece. An opposite end of each of the plurality of extensions  28  is structured to correspond and connect or fasten to a corner portion of the top surface  11  of the cold plate  10 . Various means of connecting or fastening one surface to another are well known in the art. In certain embodiments, each of the plurality of extensions  28  can include an aperture  29 , which aligns with an aperture formed in the top surface  11  (shown in  FIG. 1A ) of the cold plate  10 . A fastening mechanism (not shown), such as, a bolt, can be inserted within each of the apertures to secure the framework  22  to the cold plate  10 . The canopy  26  also includes a plurality of swivel apertures (not shown) formed therein and a plurality of nuts  32 , which are structured to receive each of the plurality of threaded swivels  20 . As shown in  FIG. 4 , each of the plurality of threaded swivels  20  is inserted into each of the corresponding plurality of nuts  32  to secure an interface between the plurality of diodes  16  and the cold plate  10 . For example, as each of the plurality of threaded swivels  20  is rotated into one of the plurality of nuts  32  and tightened, a tip of each of the plurality of the threaded swivels  20  contacts and presses downward on the each of the corresponding plurality of clamps  24 , which causes pressure to be applied to the plurality of diodes  16  in contact with the cooling plate  10 . Each of the plurality of threaded swivels  20  is rotated in one direction to apply pressure to each of the corresponding plurality of clamps  24  and is rotated in an opposite direction to release the pressure. 
         [0042]    In accordance with certain embodiments of the disclosed concept, the ceramic coating composition is deposited or applied directly onto the top surface  11  of the cold plate  10  to form the ceramic layer  12  (shown  FIG. 1C ). In certain other embodiments, the ceramic coating composition is deposited or applied directly onto a substrate  13 , which is connected to the top surface  11  of the cold plate  10  (shown in  FIG. 1D ). Alternately, in these embodiments, the surface to be coated (e.g., the top surface  11  or the substrate  13 ) can be pre-treated prior to depositing or applying the ceramic coating composition. For example, there may be deposited or applied an intermediate layer such that the ceramic coating composition is deposited or applied to the intermediate layer instead of being directly to the top surface  11  of the cold plate  10  or the substrate  13 . The intermediate layer may serve various functions, such as, but not limited to, providing enhanced adhesive properties to adhere the ceramic coating composition to the top surface  11  of the cold plate  10  or the substrate  13 . Various materials are known in the art for providing adhesive properties to enhance adherence between two surfaces, which can be used in the disclosed concept. 
         [0043]      FIG. 5A  shows a cross-section view of the cold plate  10  and ceramic layer  12  shown in  FIG. 1C . In addition,  FIG. 5A  includes an intermediate layer  34  deposited or applied to the top surface  11  (shown in  FIG. 1A ) of the cold plate  10  and the ceramic layer  12  is then formed on top of the intermediate layer  34 , such as, by depositing or applying the ceramic coating composition onto an outer surface of the intermediate layer  34 . Alternately,  FIG. 5B  shows a cross-section view of the cold plate  10 , ceramic layer  12  and substrate  13  shown in  FIG. 1D . In addition,  FIG. 5B  includes the intermediate layer  34  deposited or applied to the substrate  13  and the ceramic layer  12  is then formed on top of the intermediate layer  34 , such as, by depositing or applying the ceramic coating composition onto an outer surface of the intermediate layer  34 . 
         [0044]    In certain embodiments of the disclosed concept, a fastening mechanism, such as, one or more bolts or the like can be employed to mount a cooling device, e.g., a cold plate, with a power electronic device, e.g., a diode. The use of the one or more bolts as the fastening mechanism requires that one or more corresponding mounting holes or apertures are formed within the cold plate and the diode. As such, the one or more bolts contact the diode baseplate and as a result, bypass a ceramic coating that may be applied to the surface of the cold plate and provide a path to ground. In accordance with the disclosed concept, the surface of the mounting apertures, e.g., an internal radial surface, can be coated with a ceramic composition to form a ceramic coating on the surface of the mounting apertures. 
         [0045]    In certain embodiments, the one or more bolts are composed or constructed of metal. In these embodiments, the one or more metal bolts can be coated with the ceramic composition. In other embodiments, the one or bolts may be composed of a non-metal material, such as, but not limited to, plastic or fiberglass. 
         [0046]      FIG. 6  shows a power electronic device and associated cooling device combination  50  in accordance with certain embodiments of the disclosed concept. The combination  50  includes a diode  52 , a cold device  54 , a mounting aperture  56 , a metal bolt  58  and a metal nut  60 . The diode  52  consists of a case  62  and a metal baseplate  64 . The metal baseplate  64  can be composed of a wide variety of metals and metal alloys. In certain embodiments, the metal baseplate  64  is composed of alumina silica carbide. The mounting aperture  56  extends through the metal baseplate  64  and the cold device  54 . The metal bolt  58  has a horizontal portion, a vertical portion and a tip. The horizontal portion of the metal bolt  58  is in contact with the metal baseplate  64 . The vertical portion of the metal bolt  58  extends through the mounting aperture  56 . The tip of the metal bolt  58  has fitted thereon the metal nut  60  to secure the metal bolt  58  within the mounting aperture  56  and, the interface between the diode  52  and the cold device  54 . A ceramic coating composition is deposited or applied to a top surface of the cold device  54  such that the ceramic coating layer  66  is formed at the interface. In addition, the ceramic coating layer  66  is formed on each of two side surfaces of the cold device  54 , which form the mounting aperture  56  and its radial surface. Thus, the radial surface of the aperture  56  has applied thereto the ceramic coating layer  66 . Furthermore, the ceramic coating layer  66  is applied to a bottom surface of the cold device  54 , such that the metal nut  60  contacts the ceramic coating layer  66 . 
         [0047]    As shown in  FIG. 6 , since the metal bolt  58  and metal nut  60  are used, all surfaces that contact these metal components are ceramic coated with the ceramic coating layer  66 . However, if the bolt and the nut are not composed of metal, it is not necessary to ceramic coat the bottom surface of the cold device  54  that contacts the nut. 
         [0048]      FIG. 7  shows the combination  50  shown in  FIG. 6  including the diode  52 , cold device  54 , mounting aperture  56 , case  62 , metal baseplate  64  and ceramic coating layer  66 . However, in  FIG. 7 , a non-metal bolt  58 A and a non-metal nut  60 A are used. Thus, as shown in  FIG. 7 , the ceramic coating layer  66  is only applied to the interface of the metal baseplate  64  of the diode  52  and the cold device  54 , and to the interface of the cold device  54  and the mounting aperture  56 . 
         [0049]    While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.