Abstract:
A system for clamping a plurality of semiconductors that includes: 1) a first endplate and a second endplate that are substantially parallel and oppose each other across a predetermine distance (the predetermined distance being fixed by one or more tension members that extend between the first endplate and the second endplate); and 2) a screw jack that includes a threaded cylinder that moves through a threaded opening in the first endplate upon being rotated such that the threaded cylinder moves toward the second endplate if rotated one direction and away from the second endplate if rotated the opposite direction.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This present application relates generally to systems for providing compression to semiconductor stacks. More specifically, but not by way of limitation, the present application relates to a rigid frame clamping system for compressing a semiconductor stack. 
         [0002]    Semiconductors have many commercial applications, including use in power converters and industrial drives. A common semiconductor system is an integrated gate commutated thyristor (“IGCT”) semiconductor (which will be used herein as an exemplary system, though the invention is so limited). IGCT semiconductors are layered devices, which generally include semiconductors stacked in series (i.e., a semiconductor stack). In operation, IGCT semiconductors require a compressive clamping force, which may be approximately 36 to 44 kN, to press the stack together so that good conductivity is achieved throughout the layers. For the semiconductor stack to operate properly, the compressive force must be applied in a precise amount and location through the stacked semiconductors. 
         [0003]    Commercially available clamps are available for clam ping semiconductor stacks. In general, such semiconductor clamps rely upon compressing the semiconductor stack by tightening nuts on a plurality of threaded rods mounted between two endplates. Specifically, the semiconductor stack is placed between the two endplates, the nuts are tightened, which draws the endplates closer together and compresses the semiconductor stack. 
         [0004]    However, the threaded rod/nut configuration is fraught with inefficiencies. First, the compression force is not delivered in a precise manner to the stacked units. The tightening of a plurality of rods means that the compression is done in an unbalanced manner. Second, the threaded rod/nut configuration makes access and repair to the semiconductor stack difficult. To remove the stacked devices, the entire clamp assembly must be substantially disassembled, which negatively affects repair time, cost, and the required training for the service technicians. Third, the protruding rods of the rod/nut configuration impose a greater length requirement on the clamp assembly. Accordingly, space adjacent to the stack assembly must be allocated to accommodate the extension of the threaded rods. 
         [0005]    Fourth, available clamp assemblies provide limited possibilities for component registration. As used herein, component registration refers to the mounting of semiconductor components to the clamping system such that proper alignment for compression is achieved. As one of ordinary skill in the art will appreciate, for proper operation, the IGCT semiconductors of a system must be precisely aligned along the compression axis, i.e., the axis along which compression is performed. The accompanying components, such as the water-cooled heat sinks, also must be precisely located in relation to the semiconductor, in order to adequately cool the devices. For these reasons, component registration is a significant concern, yet commercially available clamps require additional parts to be added to the clamping system for proper component registration to be achieved. Fifth, current clamps do not allow for water delivery manifolds to be directly mounted to the threaded rods of the clamp assembly. 
         [0006]    Sixth, in operation, IGCT semiconductor systems are mounted within an enclosure via the frame of the clamp. Currently available clamps do not allow for direct mounting to the enclosure. Conventional clumps, because one of the clamping end plates must be free to move in relation to the other end plate, lack a convenient rigid structure with which to mount the system. As such, an additional component must be incorporated into the clamping device to mount the semiconductor stack within the enclosure. 
         [0007]    Seventh, presently available clamps are only adaptable to a single semiconductor stack within one clamp, due to the plurality of the clamping rods and registration concerns. If additional stacks are desired within a single semiconductor application, an auxiliary clamp structure must be added to the assembly. 
         [0008]    All of these factors contribute to additional cost and complexity of employing conventional clamps for use in semiconductor stacks. Thus, there is a need for an improved semiconductor clamp. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0009]    The present application thus may describe a system for clamping a plurality of semiconductors that includes: 1) a first endplate and a second endplate that are substantially parallel and oppose each other across a predetermined distance, the predetermined distance being fixed by one or more tension members; and 2) means for providing a compressive force from one of the endplates. The plurality of semiconductors may be a plurality of integrated gate commutated thyristor semiconductors. 
         [0010]    The means for providing a compressive force may be attached to the first endplate and compress inward toward the second endplate. In some embodiments, the means for providing a compressive force may be a screw jack. The screw jack may include a threaded cylinder that moves through a threaded opening in the first endplate upon being rotated. The screw jack may be rotated via a screw jack head at a first end of the screw jack. The first end of the screw jack may protrude out of an outer surface of the first end plate. A second end of the screw jack may be a ball bearing. 
         [0011]    In some embodiments, the one or more tension members may be rigid rods that connect to an inner face of each of the endplates, the one or more tension members being substantially perpendicular to each of the endplates. In some embodiments, the one or more tension members may be four tension members. The tension members may be located in predetermined locations based upon registering the semiconductors and/or other semiconductor system components along a compression axis. The system may further include registration brackets attached to the semiconductors and/or other semiconductor system components. The registration brackets may engage the one or more of the tension members such that the semiconductors and/or other semiconductor system components are fixed in the compression axis and while being able to slide along the length of the one or more tension members. 
         [0012]    The system may further include a spring washer attached to one of the endplates. The spring washer may include a ball bearing. The compression of the spring washer may indicate the clamping force applied to the plurality of semiconductors. The system further may include fixed registration brackets that allow for fixed registration of semiconductor system components to the tension members such that, when the fixed registration bracket is engaged, the semiconductor system component does not slide along the length of the tension members. The system further may include mounting apertures in at least one of the endplates. The mounting apertures may include an opening through the endplate through which the system may be directly mounted to an enclosure. 
         [0013]    The present application further may describe a system for clamping a plurality of semiconductors that includes: 1) a first endplate and a second endplate that are substantially parallel and oppose each other across a predetermine distance (the predetermined distance being fixed by one or more tension members that extend between the first endplate and the second endplate); and 2) a screw jack that includes a threaded cylinder that moves through a threaded opening in the first endplate upon being rotated such that the threaded cylinder moves toward the second endplate if rotated one direction and away from the second endplate if rotated the opposite direction. In some embodiments, the system further may include a spring washer attached to the second endplate such that the compression of the spring washer indicates the clamping force applied to the plurality of semiconductors. The screw jack may be rotated via a screw jack head at a first end of the screw jack, the first end of the screw jack protruding out of an outer surface of the first end plate. A second end of the screw jack may include a ball bearing that is configured to engage one of the plurality of semiconductors. The system further may include registration brackets attached to the semiconductors and/or other semiconductor system components, the registration brackets engaging one or more of the tension members such that the semiconductors and/or other semiconductor system components are fixed in the compression axis while being able to slide along the length of the one or more tension members. 
         [0014]    These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a view a rigid frame of a semiconductor clamping system according to an exemplary embodiment of the present application. 
           [0016]      FIG. 2  is a view of the rigid frame clamping system according to an exemplary embodiment of the present application. 
           [0017]      FIG. 3  is a view of a IGCT semiconductor system within a rigid frame clamping system according to an exemplary embodiment of the present application. 
           [0018]      FIG. 4  is a view of registration locations according to exemplary embodiments of the present application. 
           [0019]      FIG. 5  is a view of registration locations according to exemplary embodiments of the present application. 
           [0020]      FIG. 6  is a view of system mounting apertures according to exemplary embodiment of the present application. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring now to the figures, where the various numbers represent like parts throughout the several views,  FIG. 1  demonstrates a rigid frame  100  which may be used in a rigid frame clamping system according to exemplary embodiments of the present application. The rigid frame  100  may include two endplates  102  and a plurality of tension members  104 . The two endplates  102  may be rectangular plates, which are parallel to and oppose each other. The plurality of tension members  104  may include four rods, each of which may have a rectangular cross-section. Those of ordinary skill in the art will appreciate that more or less tension members of different cross-sectional design may be used. The tension members  104  may rigidly connect the inner face of each of the endplates  102 . The tension members  104  may be substantially perpendicular to the endplates  102 . The four tension members  104  may be located at predetermined locations based upon component registration requirements as discussed in more detail below. 
         [0022]    Each of the tension members  104  may be pinned to the endplate  102  by pins  106 . Specifically, the end of the tension member  104  may insert into an opening in the endplate  102  and a pin  106  may be inserted through the edge of the endplate  104  such that the pin  106  passes through the tension member  104  and terminates in the endplate  102 . Those of ordinary skill in the art will appreciate that other methods of connecting the tension member  104  to the endplate  102  also may be used. 
         [0023]    The rigid frame  100  may be made of a rigid, non-conducting material, such as a fiberglass composite laminate, glastic engineering material, fully insulated metal or other similar material. The non-conducting quality of the material may electrically isolate all of the semiconductor components that come in contact with the rigid frame  100 . 
         [0024]    Each of the endplates  102  may include an opening through the approximate center of the endplate  102  that aligns with the central axis of the semiconductor stack. A screw jack opening  108  may be substantially circular in shape and, as discussed in more detail below, be used in conjunction with the installation of a screw jack (not shown in  FIG. 1 ). A corresponding washer opening  110  through the opposing endplate  102  may be substantially rectangular in shape and, as discussed in more detail below, be used in conjunction with the installation of a bellville or spring washer. The positioning and quantity of the screw jack openings  108  and the washer openings  110  may vary. 
         [0025]      FIG. 2  demonstrates a view of a rigid frame clamping system  200 . The rigid frame clamping system  200  may include the previous described rigid frame  100 . The rigid frame clamping system  200  may further include a bellville or spring washer  202  (hereinafter “the bellville washer  202 ”). The bellville washer  202  may be any commercially available bellville or spring washer. Using the washer opening  110 , the Bellville washer  110  may be attached to the endplate  102  by conventional methods. The bellville washer  202  may be constructed such that the displacement inward of its springs or coils indicates the compressive force that is acting on the bellville washer  202 . At the end opposite of the end attached to the endplate  102 , the bellville washer  202  may have a washer ball bearing  203 . 
         [0026]    Mounted within the screw jack opening  108  may be mechanical means for providing a compressive force into the rigid frame  100 , which in some embodiments may include screw jack  204 . The screw jack  204  may be a screw jack that extends inward into the rigid frame  100  (and out of the inner face of the endplate  102 ) upon the clockwise rotation of a screw jack head  206 . The screw jack head  206  may be allen-wrench compatible, though other head configurations may be used. Those of ordinary skill in the art will appreciate that other mechanical means may be used beside the specified screw jack  204  to provide the described functionality. Similar to the bellville washer  202 , at the end of the screw jack  204  that extends inward into the rigid frame  100  may be a screw jack ball bearing (not visible in  FIG. 2 ). 
         [0027]    In operation, as shown in  FIG. 3 , an IGCT semiconductor system  300  may be housed and compressed within the rigid frame clamping system  200 . As is known in the art, an IGCT semiconductor system  300  may include a series of IGCT semiconductors  302 , which may be stacked in series between the screw jack  206  and the bellville washer  204 . The IGCT semiconductor system  300  further may include other semiconductor components as described below. The other semiconductor system components may include a series of gate drives  304 . In addition, attached to the front of the IGCT semiconductors  302  (and partially obscuring the view of the IGCT semiconductors  302 ) may be a plurality of power resistors  305  and heat sinks  306  attached thereto. The heat sinks  306  may remove excess heat from the system. The heat sinks  306  may be water-cooled. A supply of water may be delivered to each of the heat sinks  306  by a water deliver manifold  308 . Other semiconductor system components may include a plurality of capacitors  310 , which may be mounted to the top of the power resistors  305 . Those of ordinary skill in the art will appreciate that the described components and their positioning may be altered and still efficiently accommodated by alternative embodiments of the present application. 
         [0028]    The screw jack ball bearing may engage the IGCT semiconductors at one end of the stack at a preformed dimple. The washer ball bearing  203  may engage the IGCT semiconductor at the other end of the stack at a second preformed dimple. Thus engaged, the screw jack  206  may be rotated such that the screw jack  206  extends into the rigid frame  100 . The distance between the endplates  102  remains fixed due to the tension members  104  such that the extension of the screw jack  206  compresses the IGCT semiconductor stack. Specifically, the extension of the screw jack  206  may place the tension member  104  in a state of tension, which may act to compress the IGCT semiconductor stack. The screw jack  206  is the only component that must be adjusted to apply an even compressive force to the semiconductor stack. As the IGCT semiconductor stack is compressed, the bellville washer  202  may be compressed. The compression of the bellville washer  202  will cause it to deflect inward. The extent of the deflection may be used to calibrate the amount of compressive force applied to the semiconductor stack. In this manner, a known compressive force may be evenly applied to the semiconductor stack at precise points. 
         [0029]    As shown in the exemplary embodiments of  FIGS. 1 ,  2  and  3 , the tension members  104  may be positioned to substantially equalize and balance the compressive load and allow for efficient registration locations for the component parts of the IGCT semiconductor system  300 . Specifically, the tension members  104  may be positioned such that the components of the IGCT semiconductor system  300  may be aligned in the correct position along the compression axis by registering themselves directly to the tension members  104 .  FIG. 4  provides examples of this functionality. As shown in blown-up section in top-left corner of  FIG. 4 , gate drive registration brackets  402  may register the gate drives  304  to the rigid frame  100 . Specifically, each of the gate drives  304  may have two gate drive registration brackets  402  on each of its sides. The gate drive registration bracket  402  may include any type of bracket that fixes the gate drive  304  to the tension member  104  in a predetermined location along the compression axis, while still allowing the gate drive  304  to slide back and forth along the tension member  104 . In some embodiments, the gate drive registration bracket  402  may include a “C” shaped bracket that may engage the tension member  104 . This design may allow the gate drive  304  to be fixed in relation to the compression axis and still slide along the tension member  104 . 
         [0030]    In similar fashion, the other components of the IGCT semiconductor system  300  may be registered onto the rigid frame  100 . For example, as demonstrated in the other blown-up section of  FIG. 4 , heat sink registration brackets  404  may register the heat sinks  306  to the rigid frame  100 . Each of the heat sinks  306  may have a single or multiple heat sink registration brackets  404  on a bottom surface. In this manner, the heat sinks  306  may sit on one of the tension member  104 , thus being aligned and fixed into place in relation to the compression axis. The heat sink registration bracket  402  may include any type of bracket that fixes the gate drive  304  to the tension member  104  (i.e., fixed into place along the compression axis), while still allowing the heat sink  402  to slide back and forth along the tension member  104 . As shown in  FIG. 4 , the heat sink registration bracket  404  may include a bracket with a slot into which a side of the tension member  104  may insert. The fit between the tension member  104  and the slot may be a snug one. 
         [0031]    Given the registration of the components as described above, installation of the component parts of the IGCT semiconductor system  300  in the rigid frame clamping systems  200  may be completed in an efficient manner. For example, to install the components, the pins  106  of one of the endplates  102  may be removed such that the endplate  102  is disconnected from the tension members  104 . With the ends of the tension members  104  free at one end, the gate drive  304 , for example, may be installed by sliding the gate drive registration brackets  402  onto the two relevant tension members  104 . In some embodiments, the gate drive  304  may have two gate drive registration brackets  402  on each of its sides. Each of the relevant tension members  104  may be inserted into the slot of the gate drive registration bracket  402  and the gate drive  304  may slide down the tension members  104  into position. With the predetermined positioning of the tension members  104 , the gate drives  304  may be supported, and fixed in the appropriate position along the compression axis, as shown. 
         [0032]    To take another example, the heat sinks  306  (and related hardware) may be installed in much the same manner. In addition, if one of the heat sinks  306  is part of a pre-assembled unit of semiconductor components, which may include, for example, the gate drive  304 , the IGCT semiconductor, and other components, the pre-assembled unit may be efficiently installed at once by engaging the brackets to the relevant tension members  104  and sliding the unit down the tension members  104  into position. In this manner, the components may be efficiently installed while fixing their position along the compression axis. 
         [0033]    Access to components already installed in the IGCI semiconductor system  300  also is enhanced. The compression force of the rigid frame clamping system  200  may be released simply by turning the screw jack  206  in the counter-clockwise direction. Once the clamp released, the components may slide lengthwise along tension members to either be removed or spread out, which may allow for convenient removal, replacement or repair of any of the component parts. 
         [0034]    Because the tension members  104  are rigid and do not change position in relation to the endplates  104  (as conventional clamps do), some of the components may be fixed to the tension members  104  (i.e., fixed in such a manner that the component is not allowed to slide along the length of the tension member  104 ). An example of a component that may be registered in this manner is the water delivery manifolds  308 , which, as illustrated in  FIG. 5 , may be fixed to the bottom of the rigid frame clamping system  200 . The water delivery manifolds  308  may be attached by conventional methods to crosspieces  502 . Each end of the cross piece  502  may attach to one of the tension members  104 . Further, because of the nature of the water delivery manifold component  308  (i.e., because the water delivery manifold  308  does not have to be aligned and compressed along the compression axis), this type of registration may be effective. Because the tension members  104  are rigid and do not change position in relation to the endplates  102 , this type of registration may be possible. The registration of the water delivery manifolds  308  in this manner may allow for them to the conveniently replaced or repaired, while remaining an integral part of the IGCT semiconductor system  300 . 
         [0035]      FIG. 6  illustrates system mounting apertures  602  in one of the endplates  102 . Because the position of the endplates  102  in relation to each other does not change (which is different than the rod/nut assembly of known systems), the endplates  102  may be conveniently mounted directly to a system enclosure (not shown) without specialized hardware. As such, the end plates may be directly mounted to the enclosure using standard hardware and procedures. Mounting may be done by bolting or pinning the endplates  102  via the system mounting apertures  602  directly to the enclosure. 
         [0036]    It should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.