Abstract:
In accordance with the present invention, there is provided multiple embodiments of a concentrated photovoltaic (CPV) receiver cell or die. In each embodiment of the present invention, the receiver die includes a multiplicity of through wafer vias or TWV&#39;s which are etched therethrough to effectively eliminate the bus bars on the top or front surface of the receiver die, connectors such as bus bars instead being effectively moved to the bottom or back surface of the receiver die. The movement of the connectors to the back surface of the receiver die provides the potential for a greater active surface area on the front surface for solar input.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates generally to semiconductor devices, and more particularly to a concentrated photovoltaic (CPV) receiver cell which includes through silicon via (TSV) or through wafer via (TWV) structures etched therethrough to create a connector at the base of the cell, thus providing the cell with greater surface area for solar input. 
     2. Description of the Related Art 
     Photovoltaic cells are a well known means for producing electrical current from electromagnetic radiation. Traditional photovoltaic cells comprise junction diodes fabricated from appropriately doped semiconductor materials. Such devices are typically fabricated as thin, flat wafers with the junction formed parallel to and near one of the flat surfaces. Photovoltaic cells are intended to be illuminated through their so-called “front” surface. Electromagnetic radiation absorbed by the semiconductor produces electron-hole pairs in the semiconductor. These electron-hole pairs may be separated by the electric field of the junction, thereby producing a photocurrent. Currently known photovoltaic cells typically have a generally quadrangular (e.g., square) configuration defining four peripheral side edges, and include a pair of bus bars which are disposed on the top or front surface and extend along respective ones of an opposed pair of the side edges. The bus bars are used to facilitate the electrical connection of the photovoltaic cell to another structure, as described in more detail below. 
     There is currently known in the electrical arts semiconductor devices known as CPV receiver die packages or modules. Currently known CPV modules typically comprise a ceramic substrate having a conductive pattern disposed on one side or face thereof. Attached to the substrate and electrically connected to the conductive pattern are electrical components, including a pair of preformed wire connectors and a packaged diode. Also attached to the substrate and electrically connected to the conductive pattern thereof is a CPV receiver cell or die. The electrical connection between the receiver die and the conductive pattern is often facilitated by a pair of punched thin metal foil or braided ribbon/mesh connectors which extend along and are welded or soldered to respective ones of opposed sides of the receiver die, which typically has a quadrangular or square configuration as indicated above. More particularly, the pair of punched thin metal foils or braided ribbon/mesh connectors are welded or soldered to respective ones of the bus bars on the top or front surface of the receiver die. In certain existing CPV modules, the electrical connection of the receiver die to the conductive pattern is facilitated by the use of multiple wires bonded to the bus bars on the front surface of the receiver die and the bond pads of the conductive pattern of the substrate, the wires being used as an alternative to the aforementioned braided ribbon or mesh interconnects. The CPV module may further include a light concentration means which is adapted to concentrate solar radiation onto the front surface of the receiver die. 
     Current CPV receiver die packages or modules typically generate up to ten amps of electrical current. In order to carry such high current, the above-described ribbons made of metal foil or braided wire mesh, or the above-described multiple bond wire bonds are used to form the interconnection between the bus bars on the front surface of the receiver die and the bond pads of the conductive pattern on the substrate. However, the use of the ribbon/mesh type interconnects or, alternatively, the bond wires give rise to certain deficiencies in currently known CPV modules which detract from their overall utility. More particularly, the ribbon/mesh type interconnects do not have good shape control for automatic pick up, and require the use of specialized welding equipment for the fabrication of the CPV module using the same. Stated another way, it is often difficult to control the shape of the ribbon/mesh type interconnects for automatic pick up and placement, with the fabrication process being mostly done through the use of special welding equipment or manual soldering which is more labor intensive and thus more costly. When wires are used as an alternative to the ribbon/mesh type interconnects, such wires require encapsulation protection for long-term reliability of the CPV module including the same. In addition, in those CPV modules including bond wires, problems may arise in relation to current crowding if too few wires are used. As indicated above, the wires also require encapsulation, over-molding, or other protection from the environment. Moreover, the use of the soldered or welded ribbon/mesh interconnects or bond wires create concerns regarding the electrical current carrying capability of the CPV module including the same. 
     As indicated above, the inclusion of the bus bars on the front surface of the receiver cell or die necessitates that the above-described ribbons made of metal, foil or braided wire mesh, or bond wires, be used to facilitate the electrical connection of the receiver die to the bond pads of the conductive pattern on the underlying substrate. In addition to the use of the ribbon/mesh type interconnects or wires giving rise to the deficiencies highlighted above, further penalties in the potential performance of the receiver die are directly attributable to the inclusion of the bus bars on the top or front surface of the receiver die. More particularly, in currently known concentrated photovoltaic receiver cells or dies, a certain percentage of the total area of the front surface of the receiver die is covered by the bus bars. That percentage of the total die area of the front surface covered by the bus bars is typically in the range of from about 8% to about 10%. As will be recognized, the active area of the front surface as a percentage of the overall die area thereof is thus reduced by an amount equal to the percentage of the area covered by the bus bars. In this regard, the active area as a percentage of the overall die area of the front surface could be substantially increased and the receiver die thus made more efficient if the bus bars on the front surface were effectively eliminated from the receiver die. 
     The present invention addresses these and other shortcomings of prior art CPV receiver dies by providing a concentrated photovoltaic receiver cell or die wherein an etching process is used to create through wafer vias or TWV&#39;s through the receiver die. The TWV&#39;s in turn are used to create connectors at the back or bottom surface of the receiver die, thus eliminating the need for the bus bars on the front surface thereof. The movement of the connectors (e.g., bus bars) to the bottom surface of the receiver die provides the potential for a greater active surface area on the front surface for solar input. The movement of the connectors to the bottom surface of the receiver die also effectively eliminates the need for top side connectors such as the aforementioned ribbon/mesh type interconnects or wires, thus allowing for easier top side connection for prisms or other optical input devices. Thus, the receiver die constructed in accordance with the present invention provides an increased top, active surface area ratio, which provides higher wafer utilization and higher power per area efficiency. Additionally, as indicated above, the elimination of the external wires or mesh/ribbon interconnects provides a reliability enhancements and/or manufacturing economies. These and other features of the present invention will be described in more detail below. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided multiple embodiments of a concentrated photovoltaic (CPV) receiver cell or die. In each embodiment of the present invention, the receiver die includes a multiplicity of through wafer vias or TWV&#39;s which are etched therethrough to effectively eliminate the bus bars on the top or front surface of the receiver die, connectors such as bus bars instead being effectively moved to the bottom or back surface of the receiver die. The movement of the connectors to the back surface of the receiver die provides the potential for a greater active surface area on the front surface for solar input. 
     In a first embodiment of the present invention, the bus bars on the front surface of the receiver die are eliminated in favor of two rows or sets of TWV pads. The TWV pads of each set extend along respective ones of an opposed pair of the peripheral edge segments of the receiver die which has a generally quadrangular (e.g., square) configuration. The two sets of TWV pads are further arranged such that each TWV pad of one set is linearly aligned with or disposed in opposed relation to a corresponding TWV pad of the remaining set. Each of these corresponding pairs of the TWV pads is interconnected by one or more fine Ag wires. Though the TWV pads of the two sets thereof included on the front surface of the receiver die collectively take up or cover a prescribed percentage of the available surface area of the front surface, they provide a space savings in comparison to that area which is taken up by the two bus bars in existing CPV receiver die designs. 
     In the receiver die of the first embodiment, each of the TWV&#39;s has a first or top end which extends and is electrically connected to a respective one of the TWV pads on the front surface, and an opposed second or bottom end which extends and is electrically to a connector disposed on the back surface. Thus, like the TWV pads, the TWV&#39;s are also segregated into two sets which extend along and in close proximity to respective ones of the aforementioned opposed pair of the peripheral edge segments of the receiver die. Each of the TWV&#39;s preferably comprises a conductive plug which is surrounded by a suitable passivation to effectively eliminate conductive contact between the conductive plug and the Ge substrate of the receiver die. In the first embodiment, the bottom ends of the TWV&#39;s of each set are electrically connected to respective ones of a pair of bus bars which extend along respective ones of the aforementioned opposed pair of peripheral edge segments of the receiver die in spaced, generally parallel relation to each other. In a variant of the first embodiment, the bottom end of each TWV may extend and be electrically connected to a dedicated pad rather than a bus bar. In this instance, the pads on the back surface of the receiver die will thus also be segregated into two sets which extend along and in close proximity to respective ones of the aforementioned opposed pair of the peripheral edge segments of the receiver die. 
     In a second embodiment of the present invention, the TWV pads included on the front surface of the receiver die are eliminated, with the Ag wires (which extend in spaced, generally parallel relation to each other) instead spanning the entire width of the receiver die, i.e., extending between the aforementioned opposed pair of the peripheral edge segments of the receiver die. In the receiver die of the second embodiment, the TWV&#39;s are, like the TWV&#39;s of the first embodiment, segregated into two sets which extend along and in close proximity to respective ones of the aforementioned opposed pair of the peripheral edge segments of the receiver die. The two sets of TWV&#39;s are further arranged such that each TWV of one set is linearly aligned with or disposed in opposed relation to a corresponding TWV of the remaining set. Additionally, each of the TWV&#39;s (which is identically configured to those of the first embodiment) has a first or top end, with the top ends of the TWV&#39;s of each corresponding pair extending and being electrically connected to respective ones of the opposed end portions of a corresponding one of the Ag wires on the front surface of the receiver die. 
     In addition to the top end, each of the TWV&#39;s of the second embodiment defines a second or bottom end which extends and is electrically to a connector disposed on the back surface of the receiver die. More particularly, in the second embodiment, the bottom ends of the TWV&#39;s of each set are electrically connected to respective ones of a pair of bus bars which extend along respective ones of the aforementioned opposed pair of peripheral edge segments of the receiver die in spaced, generally parallel relation to each other. In one variant of the second embodiment, the bottom end of each TWV may extend and be electrically connected to a dedicated pad rather than a bus bar. In this instance, the pads on the back surface of the receiver die will thus also segregated into two sets which extend along and in close proximity to respective ones of the aforementioned opposed pair of the peripheral edge segments of the receiver die. In another variant of the second embodiment, the TWV&#39;s of both sets may be arranged in a staggered pattern relative to each other such that each Ag wire includes only a single TWV extending into electrical connection thereto. 
     The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These, as well as other features of the present invention, will become more apparent upon reference to the drawings wherein: 
         FIG. 1  is a top perspective view of a CPV receiver cell or die constructed in accordance with a first embodiment of the present invention; 
         FIG. 2  is a bottom plan view of the receiver die shown in  FIG. 1 ; 
         FIG. 3  is an enlarged, partial cross-sectional view of the receiver die shown in  FIG. 1 ; 
         FIG. 4  is a top perspective view of a CPV receiver cell or die constructed in accordance with a second embodiment of the present invention; 
         FIG. 5  is an enlarged, partial top perspective view of the receiver die shown in  FIG. 4 , further illustrating in phantom the through wafer vias or TWV&#39;s thereof; 
         FIG. 6  is an enlarged, partial top perspective view of a first variant of the receiver die of the second embodiment shown in  FIG. 4 , further illustrating in phantom the through wafer vias or TWV&#39;s thereof; and 
         FIG. 7  is a bottom plan view of a second variant of the receiver die of the second embodiment shown in  FIG. 4 , and a first variant of the receiver die of the first embodiment shown in  FIG. 1 . 
     
    
    
     Common reference numerals are used throughout the drawings and detailed description to indicate like elements. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein the showings are for purposes of illustrating preferred embodiments of the present invention only, and not for purposes of limiting the same,  FIGS. 1-3  depict a CPV receiver cell or die  10  constructed in accordance with a first embodiment of the present invention. The receiver die  10  has a generally quadrangular (e.g., square) configuration, and defines a generally planar top or front surface  12  and an opposed, generally planar bottom or back surface  14 . In addition, the receiver die  10  defines four (4) generally straight peripheral edge segments  16 . 
     As best seen in  FIG. 3 , the receiver die  10  is fabricated from a number of layers, including a generally planar Ge substrate  18  having at least one active layer  20  applied to one side or face thereof, and a metalized layer  22  or metallization applied to the remaining, opposed side or face thereof. In this regard, the front surface  12  of the receiver die  10  is actually defined by the active layer  20 , with the majority of the back surface  14  being defined by the metalized layer  22 . 
     In the receiver die  10 , two rows or sets of via pads  24 , and more particularly through wafer via or TWV pads  24  are formed on the front surface  12  defined by the active layer  20 . As best seen in  FIG. 1 , the TWV pads  24  of each set extend along respective ones of an opposed pair of the peripheral edge segments  16  defined by the receiver die  10 . The two sets of TWV pads  24  are further arranged such that each TWV pad  24  of one set is linearly aligned with or disposed in opposed relation to a corresponding TWV pad  24  of the remaining set. In  FIG. 1 , thirteen (13) TWV pads  24  are depicted as being included in each set thereof. However, those of ordinary skill in the art will recognize that this number of TWV pads  24  in each set is exemplary only, and may be increased or decreased without departing from the spirit and scope of the present invention. However, it will also be recognized that in the receiver die  10 , the number of TWV pads  24  included in one set will be equal to the number included in the remaining set. Additionally, as shown in  FIGS. 1 and 3 , each of the TWV pads  24  is depicted as having a generally quadrangular (e.g., square) configuration, with one of the peripheral edge segments of each TWV pad  24  of each set extending along and in substantially flush relation to a respective one of the opposed pair of the peripheral edge segments  26  along which the two sets of TWV pads  24  extend as described above. However, those of ordinary skill in the art will also recognize that each of the TWV pads  24  of each set thereof may be formed to have an alternative shape or configuration without departing from the spirit and scope of the present invention. 
     As further seen in  FIGS. 1 and 3 , each of the corresponding pairs of the TWV pads  24  is interconnected by one or more fine Ag wires  26  which are formed on the front surface  12  defined by the active layer  20 , and are arranged so as to extend in spaced, generally parallel relation. In  FIGS. 1 and 3 , two (2) wires  26  are shown as extending between and interconnecting each corresponding pair of the TWV pads  24 . However, those of ordinary skill in the art will recognize that fewer or greater than two wires  26  may be extended between each corresponding pair of TWV pads  24  without departing from the spirit and scope of the present invention. 
     Referring now to  FIGS. 2 and 3 , as indicated above, the majority of the back surface  14  of the receiver die  10  is defined by the metalized layer  22 . In addition to the metalized layer  22 , the back surface  14  is further partially defined by an opposed pair of elongate passivation strips  28  which are formed on that side or face of the substrate  18  having the metalized layer  22  applied thereto. As best seen in  FIG. 2 , the passivation strips  28  extend in spaced, generally parallel relation to each other and to those peripheral edge segments  16  of the opposed pair along which the two sets of TWV pads  24  extend. The passivation strips  28  also extend along and abut respective ones of an opposed pair of the peripheral edge segments defined by the metalized layer  22 . The back surface  14  of the receiver die  10  is further partially defined by an opposed pair of elongate bus bars  30  which also extend in spaced, generally parallel relation to each other and along respective ones of the peripheral edge segments  16  of the opposed pair along which the two sets of the TWV pads  24  extend. As seen in  FIG. 2 , the bus bars  30  also extend along and abut respective ones of the passivation strips  28 , i.e., each passivation strip  28  is captured between the metalized layer  22  and one of the bus bars  30 . The bus bars  30  are each fabricated from a conductive metal material layer which is applied to the same side or face of the substrate  18  having the metalized layer  22  and passivation strips  28  applied thereto. As will be recognized, due to the fabrication of both the metalized layer  22  and bus bars  30  from a conductive metal material, the passivation strips  28  effectively electrically isolate or insulate the bus bars  30  from the metalized layer  22  which is positioned therebetween. As is apparent from the foregoing, the back surface  14  of the receiver die  10  is collectively defined by the metalized layer  22 , passivation strips  28  and bus bars  30 . 
     The receiver die  10  of the present invention further comprises a multiplicity of through wafer vias or TWV&#39;s  32  which are formed therein. More particularly, each of the TWV&#39;s  32  comprises an aperture  34  which has a tapered, generally frusto-conical profile and extends through the substrate  18  and active layer  20 . It is contemplated that the majority of each aperture  34  will be formed by subjecting the substrate  18  to a suitable etching or laser drilling process. Each aperture  34  is effectively lined or coated with a passivation layer  36 . As best seen in  FIG. 3 , a portion of the passivation layer  36  lining the aperture  34  of each TWV  32  is integrally connected to a respective one of the passivation strips  28 . In addition, a portion of the passivation layer  36  lining the aperture  34  of each TWV  32  is integrally connected to a respective one of a pair of elongate, interior passivation strips  38  of the receiver die  10 . The interior passivation strips  38  of the receiver die  10  also extend in spaced, generally parallel relation to each other along respective ones of the opposed pair of the peripheral edge segments  16  along which the two sets of the TWV pads  24  and the two bus bars  30  extend. As best seen in  FIG. 3 , each of the interior passivation strips  38  is used to provide an insulative barrier between the substrate  18  and portions of respective ones of the bus bars  30 . 
     In addition to the aperture  34  and passivation layer  36 , each of the TWV&#39;s  32  comprises a conductive metal plug  40  which is filled into the aperture  34 , and in particular the passivation layer  36  lining the same. When viewed from the perspective shown in  FIG. 3 , the plug  40  of each TWV  32  has a first or top end which extends and is electrically connected to a respective one of the TWV pads  24  on the front surface  12 . In addition to the top end, each plug  40  has an opposed, second or bottom end which extends and is electrically connected to a respective one of the bus bars  30 . Thus, like the TWV pads  24 , the TWV&#39;s  32  are also segregated into two sets which extend along and in close proximity to respective ones of the opposed pair of the peripheral edge segments  16  of the receiver die  10  along which the two sets of TWV pads  24  and the bus bars  30  extend. As will be recognized, the passivation layer  36  of each TWV  32  effectively eliminates conductive contact between the corresponding plug  40  and the surrounding substrate  18 . In the receiver die  10 , it is contemplated that the TWV&#39;s  32  will be formed prior to the formation of the bus bars  30 . In this regard, the metal material filled into the aperture  34  lined with the passivation layer  36  to form the plug  40  may also be used to form a respective one of the bus bars  30 , thus resulting in the plugs  40  of each set of the TWV&#39;s  32  being integrally connected to a respective one of the bus bars  30  in the manner shown in  FIG. 3 . 
     In the receiver die  10  constructed in accordance with the present invention, the TWV pads  24  of the two sets thereof included on the front surface  12  collectively take up or cover a prescribed percentage of the available surface area of the front surface  12 . However, the TWV pads  24  on the front surface provide a space savings in comparison to that area which is taken up by the two bus bars included on the front surface of existing CPV receiver die designs. More particularly, that percentage of the total die area of the front surface  12  which would normally be covered by bus bars in a prior art CPV receiver die design is typically in the range of from about 8% to about 10%. In comparison, that percentage of the total die area of the front surface  12  covered by the TWV pads  24  is typically in the range of from about 0.5% to about 1.0%, thus resulting in a substantial increase in the active area of the front surface  12  as a percentage of the overall die area of such front surface  12 . 
     Referring now to  FIG. 7 , there is shown a bottom plan view of a receiver die  10   a  which is formed as a first variant of the receiver die  10  shown and described above in relation to  FIGS. 1-3 . The primary distinction between the receiver dies  10 ,  10   aa  ties in the substitution of the bus bars  30  of the receiver die  10  with two rows or sets of pads  42 . The pads  42  of each set extend along and in close proximity to respective ones of the opposed pair of the peripheral edge segment  16  of the receiver die  10   a  along which the TWV pads  24  extend. In the receiver die  10   a , the bottom end of each TWV  32 , and in particular the plug  40  thereof: extends and is electrically connected to a respective one of the pads  42  of a corresponding set thereof. Thus, each TWV pad  24  of each set is electrically connected to a respective one of the pads  42  of a corresponding set by a respective one of the TWV&#39;s  32 . Accordingly, the number of pads  42  corresponds to the number of TWV&#39;s  32 , which in turn corresponds to the number of TWV pads  24  included in the receiver die  10   a . In  FIG. 7 , each of the pads  42  is shown as having a generally circular configuration. However, those of ordinary skill in the art will recognize that the pads  42  may be formed to have other shapes (e.g., quadrangular or square) without departing from the spirit and scope of the present invention. 
     A further distinction between the receiver dies  10 ,  10   a  lies in the configuration of the passivation strips  28   a  of the receiver die  110   a  in comparison to the passivation strips  28  of the receiver die  10 . More particularly, in the receiver die  10   a , each of the passivation strips  28   a  extends along and abuts a respective one of an opposed pair of the peripheral edge segments defined by the metalized layer  22 . However, each of the passivation strips  28   a  also extends along and in substantially flush relation to a respective one of the opposed pair of the peripheral edge segments  16  along which the TWV pads  24  extend. As such, as seen in  FIG. 7 , each set of the pads  42  is effectively positioned upon an extends along the approximate center of a respective one of the two passivation strips  28   a . The passivation strips  28   a  thus effectively facilitate the electrical isolation or insulation of the pads  42  of each set from the metalized layer  22  which is positioned between the two sets of pads  42 . 
     Referring now to  FIGS. 4 and 5 , there is shown a CPV receiver cell or die  100  constructed in accordance with a second embodiment of the present invention. The receiver die  100  has a generally quadrangular (e.g., square) configuration, and defines a generally planar top or front surface  112  and an opposed, generally planar bottom or back surface  114 . In addition, the receiver die  100  defines four (4) generally straight peripheral edge segments  116 . Like the receiver die  10 , the receiver die  100  is fabricated from a number of layers, including a generally planar Ge substrate  118  having at least one active layer  120  applied to one side or face thereof, and a metalized layer  122  or metallization applied to the remaining, opposed side or face thereof. In this regard, the front surface  112  of the receiver die  100  is defined by the active layer  120 , with the majority of the back surface  114  being defined by the metalized layer  122 . In the receiver die  100 , a multiplicity of fine Ag wires  126  are formed on the front surface  112  defined by the active layer  120 , and are arranged so as to extend in spaced, generally parallel relation between an opposed pair of the peripheral edge segments  116 . 
     As best seen in  FIG. 5 , as indicated above, the majority of the back surface  114  of the receiver die  100  is defined by the metalized layer  122 . In addition to the metalized layer  122 , the back surface  114  is further partially defined by an opposed pair of elongate passivation strips  128  which are formed on that side or face of the substrate  118  having the metalized layer  122  applied thereto. The passivation strips  128  extend in spaced, generally parallel relation to each other and to those peripheral edge segments  116  of the opposed pair between which the wires  126  extend. The passivation strips  128  also extend along and abut respective ones of an opposed pair of the peripheral edge segments defined by the metalized layer  122 . The back surface  114  of the receiver die  100  is further partially defined by an opposed pair of elongate bus bars  130  which also extend in spaced, generally parallel relation to each other and along respective ones of the peripheral edge segments  116  of the opposed pair between which the wires  126  extend. The bus bars  130  also extend along and abut respective ones of the passivation strips  128 , i.e., each passivation strip  128  is captured between the metalized layer  122  and one of the bus bars  130 . The bus bars  130  are each fabricated from a conductive metal material layer which is applied to the same side or face of the substrate  118  having the metalized layer  122  and passivation strips  128  applied thereto. As will be recognized, due to the fabrication of both the metalized layer  122  and bus bars  130  from a conductive metal material, the passivation strips  128  effectively electrically isolate or insulate the bus bars  130  from the metalized layer  122  which is positioned therebetween. As is apparent from the foregoing, the back surface  114  of the receiver die  100  is collectively defined by the metalized layer  122 , passivation strips  128  and bus bars  130 . 
     The receiver die  100  further comprises a multiplicity of through wafer vias or TWV&#39;s  132  which are formed therein and identically configured to the above-described TWV&#39;s  32  of the receiver die  10  (i.e., formed from an aperture  34  lined with a passivation layer  36  and filled with a conductive metal plug  40 ). A portion of the passivation layer lining the aperture of each TWV  132  is integrally connected to a respective one of the passivation strips  128 . In addition, a portion of the passivation layer lining the aperture of each TWV  132  is integrally connected to a respective one of a pair of elongate, interior passivation strips of the receiver die  100  which, though not shown in  FIGS. 4 and 5 , are identically configured to and minor the functional attributes of the interior passivation strips  38  of the receiver die  10 . In this regard, the interior passivation strips of the receiver die  100  also extend in spaced, generally parallel relation to each other along respective ones of the opposed pair of the peripheral edge segments  116  between which the wires  126  extend. 
     In the receiver die  100 , the TWV&#39;s  132  are segregated into two sets which extend along and in close proximity to respective ones of the opposed pair of the peripheral edge segments  116  of the receiver die  100  between which the wires  126  extend. The two sets of TWV&#39;s  132  are further arranged such that each TWV  132  of one set is linearly aligned with or disposed in opposed relation to a corresponding TWV  132  of the remaining set. In this regard, the plugs of the TWV&#39;s  132  of each corresponding pair each have a first or top end which extends and is electrically connected to an end portion of a respective one on the wires  126 , i.e., each of the wires  126  has a corresponding pair of the TWV&#39;s  132  electrically connected to respective ones of the opposed end portions thereof. In addition to the top end, the plug of each TWV  132  has an opposed, second or bottom end which extends and is electrically connected to a respective one of the bus bars  130 . As in the receiver die  10 , in the receiver die  100 , it is also contemplated that the TWV&#39;s  132  will be formed prior to the formation of the bus bars  130 , thus resulting in the plugs of each set of the TWV&#39;s  132  being integrally connected to a respective one of the bus bars  130 . 
     In the receiver die  100 , the complete elimination of any bus bars on the front surface as occurs in existing CPV receiver die designs provides a substantial increase in the active area of the front surface  112  as a percentage of the overall die area of such front surface  112 . As indicated above, that percentage of the total die area of the front surface  112  which would normally be covered by bus bars in a prior art CPV receiver die design is typically in the range of from about 8% to about 10%. This loss of active area is, in large measure, eliminated in the receiver die  100  as a result of the bus bars  130  effectively being moved from the front surface  112  to the back surface  114 . 
     Referring now to  FIG. 6 , there is shown a partial top perspective view of a receiver die  100   a  which is formed as a first variant of the receiver die  100  shown and described above in relation to  FIGS. 4 and 5 . The sole distinction between the receiver dies  100 ,  100   a  lies in the number and arrangement of the TWV&#39;s  132  of the receiver die  100   a  in comparison to those of the receiver die  100 . More particularly, in the receiver die  100   a , the TWV&#39;s  132  of both sets are arranged in a staggered pattern relative to each other such that each wire  126  includes only a single TWV  132  extending into electrical connection with one of the opposed end portions thereof, i.e., each wire  126  includes only a single TWV  132  electrically connected thereto. 
     It is also contemplated that the structural features of the receiver die  10   a  shown in  FIG. 7  and described above as a variant to the receiver die  10  may also be applied to either of the receiver dies  100 ,  100   a . In this regard, the bus bars  130  of the receiver dies  100 ,  100   a  may be substituted with the two rows or sets of pads  42  electrically connected to the bottom ends of the plugs of respective ones on the TWV&#39;s  132 , with the passivation strips  128  being substituted with the passivation strips  28   a.    
     This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.