Patent Publication Number: US-9842945-B2

Title: Photovoltaic module with flexible circuit

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 14/636,864, filed on Mar. 3, 2015 and entitled “Photovoltaic Module with Flexible Circuit”; which claims priority to U.S. Provisional Patent Application No. 61/952,040, filed on Mar. 12, 2014 and entitled “Photovoltaic Module with Flexible Circuit”; all of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     A solar cell is a device that converts photons into electrical energy. The electrical energy produced by the cell is collected through electrical contacts coupled to the semiconductor material, and is routed through interconnections with other photovoltaic cells to form a photovoltaic module. The interconnections conventionally involve stringing cells together in series or parallel with ribbon bus bars, using two or three ribbons per cell. Automated methods for assembling photovoltaic modules have been developed to improve manufacturability and cost, such as using rollable sheets of solar cells, cell stringing machines and automated lamination. The cell strings are then connected to one or more junction boxes for the entire module using final ribbon runs. The final ribbon connections from the cells to the junction box are typically cut and soldered by hand. 
     A photovoltaic module also includes one or more bypass diodes to protect the module when cells within the module are not operating properly, such as due to damage or shading. A shaded cell reverse biases and consequently draws current from the module instead of producing current, which can result in electrical arcing and even fire, or hot spotting as referred to in the industry. In typical modules, one diode is required for a certain number of cells, such as approximately for every 18-24 solar cells. These diode connections add to the manufacturing steps that are required for assembling a photovoltaic module. Thus, numerous ribbon soldering steps and bypass diode connections are involved in fabricating a photovoltaic module, especially for large modules such as with sixty or more solar cells. 
     SUMMARY OF THE INVENTION 
     A photovoltaic module, and method of making, is disclosed in which a flexible circuit is electrically coupled to a plurality of photovoltaic cells, where the photovoltaic cells are electrically coupled in series to form a series of cells. Each photovoltaic cell has free-standing metallic articles coupled to the top and bottom surfaces of a semiconductor substrate. A cell interconnection element of each photovoltaic cell is electrically coupled to a free-standing metallic article of an adjacent photovoltaic cell, where the interconnection elements of the initial and final cells in the series serve as contact ends for the series of cells. Contact tabs of the flexible circuit are electrically coupled to the contact ends of the series of cells, and a junction box is electrically coupled to a junction box contact region of the flexible circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Each of the aspects and embodiments of the invention described herein can be used alone or in combination with one another. The aspects and embodiments will now be described with reference to the attached drawings. 
         FIG. 1  shows a perspective view of an exemplary electroforming mandrel as disclosed in U.S. patent application Ser. No. 13/798,123. 
         FIG. 2  provides a top view of a metallic article as disclosed in U.S. patent application Ser. No. 14/079,540. 
         FIG. 3  illustrates a cell-to-cell interconnection between an exemplary front mesh and back mesh as disclosed in U.S. patent application Ser. No. 14/079,540. 
         FIG. 4  shows exemplary photovoltaic cells with metallic articles, forming a module assembly. 
         FIG. 5  is a top view of a flexible circuit for a photovoltaic module, in one embodiment. 
         FIGS. 6A and 6B  are top and bottom views, respectively, of another embodiment of a flexible circuit. 
         FIG. 7  depicts an embodiment of a flexible circuit assembled with a photovoltaic module. 
         FIG. 8  is an exploded assembly view of a photovoltaic module with metallic articles and a flexible circuit. 
         FIG. 9  is a flow chart of an exemplary method for forming photovoltaic modules using flexible circuits of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the present disclosure, a photovoltaic module utilizes a flexible circuit for module-level junctions, with solar cells that incorporate free-standing metallic articles. The photovoltaic cells have interconnection elements that are used to form series connections between cells, and to a junction box using the flexible circuit. The flexible circuit can also include diode connections, such that the diode can be housed in the junction box, away from the cells. The flexible circuit reduces the number of terminals that must be soldered compared to ribbon bus bars of conventional cells, making fabrication of the photovoltaic module easily adaptable to automated processes. 
     Babayan et al., U.S. patent application Ser. No. 13/798,123, entitled “Free-Standing Metallic Article for Semiconductors” and filed on Mar. 13, 2013, and Babayan et al., U.S. Pat. No. 8,569,096, entitled “Free-Standing Metallic Article for Semiconductors” and issued on Oct. 29, 2013—both of which are owned by the assignee of the present application and are hereby incorporated by reference—disclose electrical conduits for semiconductors such as photovoltaic cells that are fabricated as an electroformed free-standing metallic article. The metallic articles are produced separately from a solar cell and can include multiple elements such as fingers and bus bars that can be transferred stably as a unitary piece and easily aligned to a semiconductor device. The elements of the metallic article are formed integrally with each other in the electroforming process. The metallic article is manufactured in an electroforming mandrel, which generates a patterned metal layer that is tailored for a solar cell or other semiconductor device. For example, the metallic article may have grid lines with height-to-width aspect ratios that minimize shading for a solar cell. The metallic article can replace conventional bus bar metallization and ribbon stringing for cell metallization, cell-to-cell interconnection and module making. The ability to produce the metallization layer for a photovoltaic cell as an independent component that can be stably transferred between processing steps provides various advantages in material costs and manufacturing. 
       FIG. 1  depicts a perspective view of a portion of an exemplary electroforming mandrel  100  in one embodiment of U.S. patent application Ser. No. 13/798,123. The mandrel  100  may be made of electrically conductive material such stainless steel, copper, anodized aluminum, titanium, or molybdenum, nickel, nickel-iron alloy (e.g., Invar), copper, or any combinations of these metals, and may be designed with sufficient area to allow for high plating currents and enable high throughput. The mandrel  100  has an outer surface  105  with a preformed pattern that comprises pattern elements  110  and  112  and can be customized for a desired shape of the electrical conduit element to be produced. In this embodiment, the pattern elements  110  and  112  are grooves or trenches with a rectangular cross-section, although in other embodiments, the pattern elements  110  and  112  may have other cross-sectional shapes. The pattern elements  110  and  112  are depicted as intersecting segments to form a grid-type pattern, in which sets of parallel lines intersect perpendicularly to each other in this embodiment. 
     The pattern elements  110  have a height ‘H’ and width ‘W’, where the height-to-width ratio defines an aspect ratio. By using the pattern elements  110  and  112  in the mandrel  100  to form a metallic article, the electroformed metallic parts can be tailored for photovoltaic applications. For example, the aspect ratio may be between about 0.01 and about 10 as desired, to meet shading constraints of a solar cell. 
     The aspect ratio, as well as the cross-sectional shape and longitudinal layout of the pattern elements, may be designed to meet desired specifications such as electrical current capacity, series resistance, shading losses, and cell layout. Any electroforming process can be used. For example, the metallic article may be formed by an electroplating process. In particular, because electroplating is generally an isotropic process, confining the electroplating with a pattern mandrel to customize the shape of the parts is a significant improvement for maximizing efficiency. Furthermore, although certain cross-sectional shapes may be unstable when placing them on a semiconductor surface, the customized patterns that may be produced through the use of a mandrel allows for features such as interconnecting lines to provide stability for these conduits. In some embodiments, for example, the preformed patterns may be configured as a continuous grid with intersecting lines. This configuration not only provides mechanical stability to the plurality of electroformed elements that form the grid, but also enables a low series resistance since the current is spread over more conduits. A grid-type structure can also increase the robustness of a cell. For example, if some portion of the grid becomes broken or non-functional, the electrical current can flow around the broken area due to the presence of the grid pattern. 
       FIG. 2  shows a top view of an exemplary metallic article  200  that may be produced with the electrically conductive mandrel of  FIG. 1 . The metallic article  200  of  FIG. 2  is disclosed in Babayan et al., U.S. patent application Ser. No. 14/079,540, entitled “Adaptable Free-Standing Metallic Article For Semiconductors” and filed on Nov. 13, 2013; which is owned by the assignee of the present disclosure and is hereby incorporated by reference. The metallic article  200  shows embodiments of various features adapted for a photovoltaic cell. A semiconductor substrate  202  is shown in dashed lines to demonstrate the placement of metallic article on a photovoltaic cell, where the metallic article  200  is configured here as a grid for the front side of the cell. However, the features described herein may be applied to an electrical conduit for the back side of a photovoltaic cell. In this disclosure, reference to semiconductor materials in formation of a semiconductor device or photovoltaic cell may include amorphous silicon, crystalline silicon or any other semiconductor material suitable for use in a photovoltaic cell. The metallic articles may be also applied to other types of semiconductor devices other than photovoltaic cells. Semiconductor substrate  202  is shown in  FIG. 2  as a mono-crystalline cell with rounded corners, also referred to as a pseudosquare shape. In other embodiments, the semiconductor substrate may be multi-crystalline, with a fully square shape. Semiconductor substrate  202  may have electrical conduit lines (not shown) on its surface, such as silver fingers, that carry current generated by substrate  202 . The silver fingers may be screen-printed onto the semiconductor substrate  202  according to conventional methods. For example, the silver fingers may be lines that are perpendicular to the direction of grid lines  210 . The elements of metallic article  200  then serve as electrical conduits to carry electrical current from the silver fingers. In this embodiment of  FIG. 2 , grid lines  210  (horizontal in  FIGS. 2 ) and  220  (vertical in  FIG. 2 ) of metallic article  200  are electrically coupled to the semiconductor substrate  202 , such as by soldering, to collect and deliver the current to interconnection elements  230  and  240 . Interconnection elements  230  and  240  enable cell-to-cell connections for a solar module. Fabricating metallic article  200  with a metal such as copper reduces the cost compared to a cell in which silver is used for all the electrical conduits, and can also improve cell efficiency due to improved conductivity. 
     The gridline lines  210  and  220  of  FIG. 2  are shown as approximately perpendicular to each other; however, in other embodiments they may be at non-perpendicular angles to each other. Although both the gridline lines  210  and intersecting gridline lines  220  are capable of carrying electrical current, gridline lines  210  provide the path of least resistance to interconnection elements  230  and  240  and would function as the primary carriers of electrical current. Thus, in this disclosure gridline lines  210  shall also be referred to as bus bars, while the intersecting gridline lines  220  may be referred to as cross members or support members. Cross members  220  provide mechanical support for the free-standing metallic article  200 , both in terms of strength and in maintaining dimensional specifications of the grid. However, cross members  220  can also serve as electrical conduits, such as in providing redundancy if a bus bar  210  should fail. In some embodiments, gridline lines  210  and  220  may have widths  212  and  222 , respectively, that differ from each other such as to optimize mechanical strength or achieve a desired fill factor for the cell. For example, width  212  of gridline lines  210  may be smaller than width  222  of gridline lines  220 , so that gridline lines  220  provide sufficient mechanical stability for metallic article  200  while gridline lines  210  are tailored to achieve as high a fill factor as possible. In other embodiments, width  212  of bus bars  210  may be greater than width  222  of the support members  220 , to achieve the electrical capacity needed for a certain number of bus bars  210 . In further embodiments, certain gridline lines  210  may have different widths than other gridline lines  210 , such as to address mechanical strength or electrical capacity of a particular zone. The pitch of bus bars  210  may also vary from the cross members  220 , or may vary from each other in different regions within metallic article  200  to meet required device conduction requirements. In some embodiments, a coarser or finer mesh pitch may be chosen based on, for example, the silver finger designs of the wafer, the precision of the silver screen printing process, or the type of cell being used. 
     Other free-standing, unitary metallic articles that may be used with the present disclosure have overplated portions, as disclosed in U.S. patent application Ser. No. 14/139,705, entitled “Free-Standing Metallic Article With Overplating” and filed on Dec. 23, 2013; which is owned by the assignee of the present disclosure and is hereby incorporated by reference. Yet further metallic articles may incorporate expansion segments, as disclosed in U.S. patent application Ser. No. 14/079,544, entitled “Free-Standing Metallic Article With Expansion Segment” and filed on Nov. 13, 2013; which is owned by the assignee of the present disclosure and is hereby incorporated by reference. 
       FIG. 3  shows a top view of an exemplary front-to-back cell-to-cell interconnection between two photovoltaic cells as disclosed in U.S. patent application Ser. No. 14/079,540. Cell  300  has a metallic article  310  mounted on the front side, where the metallic article  310  includes an interconnect element  320  at one edge. Metallic article  310  may be, for example, the metallic grid of  FIG. 2  or of the related applications incorporated by reference above. Interconnect  320  is joined to the back side of cell  350 , which has a metallic article  360  configured as a back side mesh. The joining may be achieved by, for example, soldering, welding, ultrasonic, conductive adhesive, or other electrical bonding methods. The interconnect  320  is bonded to the bus bar  370  of metallic article  360  for a series connection between cells  300  and  350 . The interconnect  320  may be integrally formed with the gridlines of the metallic article  310 , or may be a separate piece that is joined to the grid. In certain embodiments, the interconnection elements may extend beyond the edge of the photovoltaic cell such that there is spacing and consequently flexure that is enabled between cells. In some embodiments, both the front metallic article  310  and the back metallic article  360  may have cell-to-cell interconnection elements, such as interconnect  320 . In further embodiments, the back metallic article  360  may have an interconnection element while the front metallic article  310  does not. Interconnection element  320  in this embodiment spans substantially an entire edge of metallic article  310 , such that it is coupled to the plurality of gridlines of the metallic article  310 . Thus, one solder joint with the cell interconnection element  320  enables electrical connection to the entire cell in which the metallic article is used. The interconnection element  320  may or may not extend beyond the top or bottom surface of the semiconductor substrate of a photovoltaic cell, such as to allow for overlap with an adjacent cell, as well as to allow for easy connection to a flexible circuit as shall be described subsequently. 
       FIG. 4  illustrates a top view of an assembly  400  of photovoltaic cells  410 ,  420 ,  430  and  440  in one embodiment, as would be assembled for a module. Four cells are shown in  FIG. 4 , although any number of cells—such as 4 to 100, or 36 to 96, or 36 to 60—may be utilized in a module as desired. Each neighboring pair of cells is joined together as described in relation to  FIG. 3 . However, in the embodiment of  FIG. 4  each adjacent cell is rotated 90° from the previous cell. For example, cell  420  is rotated 90° clockwise from cell  410  to connect to cell  430 , and cell  430  is rotated 90° clockwise from cell  420  to connect to cell  440 . The cells are connected in series, with a front metallic article of one cell being coupled to the back side metallic article of an adjacent cell as described in relation to  FIG. 3 . Cell  410  in  FIG. 4  provides a positive terminal for the module  400 , while cell  440  provides the negative terminal. Thus, the mesh designs of the metallic articles described herein can be configured with a symmetry that allows for various orientations on a cell, enabling cells within a module to be connected in any sequence as desired. The cells  410 ,  420 ,  430  and  440  are assembled with a gap  460  between them, which allows for flexure of the overall module and also assists with the flow of laminating material when encapsulating the finished module. 
       FIG. 5  shows a top view of an exemplary embodiment of a flexible circuit  500  for use with a module having free-standing metallic articles, such as in  FIG. 4 . Note that the dimensions shown in  FIG. 5  are not to scale, for clarity of the components. Flexible circuit  500  has a first electrical conduit  510 , a second electrical conduit  520 , a third electrical conduit  530  and a fourth electrical conduit  540 , all mounted on a support sheet  550 . Support sheet encompasses the entire length of flexible circuit  500  in this embodiment, and most of its width. Support sheet  550  is an insulating dielectric layer, such as a polymer. The polymer may be, for example, a polyester such as polyethylene terephthalate (PET), or a polyimide. Other low-cost polymers known for use in solar modules may also be utilized. First conduit  510  has a first contact tab  512  that provides a connection to an initial end of a series of cells, and is shown as a negative terminal in this embodiment. Similarly, second conduit  520  has a second contact tab  522  that provides a connection to a final end of a series of cells, shown as a positive terminal in this embodiment. Third and fourth conduits  530  and  540  have third and fourth contact tabs  532  and  542 , respectively, that allow for connection to the series of cells. At least a portion of the conduits  510 ,  520 ,  530  and  540  are attached to the support sheet  550 , where portions of the conduits that are extend beyond the support sheet may be used for electrical connections. The conduits may be attached to support sheet  550  using, for example, adhesives. The flexible module  500  may include one support sheet  550  underneath the electrical conduits  510 ,  520 ,  530  and  540 . In other embodiments support sheets  550  may be both underneath and overlying the conduits, such that the conduits  510 ,  520 ,  530  and  540  are sandwiched between the dielectric material. In such embodiments, a two separate pieces of support sheets  550  may be used, or alternatively, one support sheet  550  may be placed under the conduits and then folded over the conduits. 
     At the opposite ends of the tabs  512 ,  522 ,  532  and  542  of conduits  510 ,  520 ,  530  and  540  are junction box contact pads  514 ,  524 ,  534  and  544 , respectively, which are grouped together in junction box contact region  560  to enable junction box connections for the overall module. The junction box contact pads  514 ,  524 ,  534  and  544  enable connection to bypass diodes. The flexible circuit  500  is configured with four conduits  510 ,  520 ,  530  and  540  for a module having six columns of cells, where a bypass diode, such as diode  581 , may be connected between adjacent pads  514  and  534  for a first pair of cell strings. A second bypass diode  582  may be connected between adjacent pads  534  and  544  for another set of cell strings, and a third bypass diode  583  may be connected between adjacent pads  544  and  524  for a final set of cell strings. Diodes  581 ,  582  and  583  may be located in the junction box area, away from the photovoltaic cells, thus improving safety. Depending on the number of cell strings in a module, the flexible circuit  500  may have different numbers of electrical conduits. For example, a module with only two columns of cells (e.g., module  400  of  FIG. 4 ) may only require two conduits in the flexible circuit  500 , such as conduits  510  and  520 , and may not require a diode. A module with a greater number of cell strings may incorporate more than four electrical conduits in the flexible circuit  500 . 
     The junction box contact pads  514  and  524  allow for an output connection for the junction box, to deliver the current from the entire module. Thus, the flexible circuit  500  allows for a minimal number of solder points between the series of cells and the output for the junction box. In some embodiments, the flexible circuit  500  is designed with a high current capacity such that only one junction box is needed for an entire module, and the first and second contact pads  512  and  522  are the only junction points between the series of cells and the output connection of the junction box. In other embodiments the flexible circuit  500  may be folded over at line  590 , which allows the electrical conduits of flexible circuit  500  to provide a large amount of surface area, for high current-carrying capability, while occupying less space on the overall module. 
     In this embodiment of  FIG. 5 , the junction box contact pads  514 ,  524 ,  534  and  544  are located between the first contact tab  512  and the second contact tab  522 . That is, first contact pad  512 , second contact pad  522 , first junction box contact pad  514  and second junction box contact pad  524  are laterally spaced apart on the support sheet  550 , with the first junction box contact pad  514  and the second junction box contact pad  524  being between the contact tabs  512  and  522 . Thus, the contact tabs  512  and  522  are positioned with enough space between them to be easily laid onto the beginning and ending cells in a series, while the junction box pads  514  and  524  are positioned close together to facilitate junction box wiring. Junction box contact pads in this embodiment are configured as round or oval metal pads, which provide a large area for easy electrical connection. The pads  514 ,  524 ,  534  and  544  may be pre-cleaned, rather than needing to clean the solder connections after backing sheets and other module layers are assembled. Connector  516  of conduit  510  extends along the length of flexible circuit  500  between contact tab  512  and junction box contact pad  514 , to serve as a conduit between tab  512  and pad  514 . Similarly, connector  526  of conduit  520  extends along flexible circuit  500  between contact tab  522  and junction box contact pad  524 . The dashed circles surrounding each contact pad  514 ,  524 ,  534  and  544  represent contact openings in the support sheet  550 , to enable wiring access to the contact pads. Conduits  510 ,  520 ,  530  and  540  are strips of conductive metal, such as copper, and can be made by, for example electroforming, etching, or stamping. The conduits  510  and  520  may be designed with sufficient thickness and surface area to have a high electrical current capacity for an entire photovoltaic module. The current capacity for flexible circuit  500  may be, for example, 4-40 amperes, such as 8-12 amperes. In some embodiments the sheet thickness of conduits  510  and  520  may be, for example, 20-400 μm, such as 100-200 μm. The length ‘L’ of the flexible circuit  500  can be customized to span the edge of the photovoltaic module to which it is being attached. For example, ‘L’ may be on the order of 1 meter for a module of 60 cells. 
       FIGS. 6A and 6B  show top and bottom views, respectively, of another embodiment of a flexible circuit  600 , that uses a smaller support sheet. Dimensions are not shown to scale proportionally, for clarity of the components. For example, the horizontal length ‘L 1 ’ of flexible circuit  600  may be greatly extended relative to the width ‘W 1 ’ shown in  FIGS. 6A-6B . In one exemplary embodiment, the length ‘L 1 ’ of flexible circuit  600  may be configured according to the size of a photovoltaic module, such as on the order of 0.3-2 meters, such as 1 meter, and a nominal width ‘W 1 ’ on the order of 5-30 mm, such as 15-30 mm. Flexible circuit  600  includes four conductive pieces in this embodiment—a first electrical conduit  610 , a second electrical conduit  620 , a third electrical conduit  630  and a fourth electrical conduit  640 . The conduits  610 ,  620 ,  630  and  640  are arranged side by side with isolating gaps between them. First conduit  610  has a contact tab  612  to enable electrical connection between a photovoltaic cell and a junction box contact pad  614  at the opposite end of the conduit  610 . Similarly, second conduit  620  has a contact tab  622  at one end and a junction box contact pad  624  at the opposite end. Third and fourth conduits  630  and  640  have contact tabs  632  and  642 , respectively, and junction box contact pads  634  and  644  at the opposite ends of the conduits. Junction box contact pads  614 ,  624 ,  634  and  644  are positioned near each other in a junction box contact region  660  and along one horizontal edge (top edge in  FIG. 6A ) of the flexible circuit  600 . The contact tabs  612 ,  622 ,  632  and  642  are along an opposite horizontal edge (bottom edge in  FIG. 6A ) of the flexible circuit  600 , for proximity to the photovoltaic cells to which they are to be coupled. In this embodiment, contact tab  612  is approximately flush with the edge of the flexible circuit  600 , for photovoltaic cells that may have an interconnection that extends beyond the body of the cell (e.g., interconnect  320  of  FIG. 3 ). Contact tab  620 , however, has an L-shape such that contact tab  622  extends past the bottom edge of flexible circuit  600  in  FIG. 6A . This type of extending tab may be used, for example, where the photovoltaic cell to which it is connecting does not have an extending interconnect. For example, tab  622  may be used to connect with the back side metallic article  360  of  FIG. 3 , which has flush edges. It can be seen that having a limited number of contact pads, such as only four junction box contact pads  614 ,  624 ,  634  and  644  in  FIG. 6A , for making electrical connections for both the photovoltaic cells and bypass diodes of the entire module enables mechanical and electrical assembly that is easily automatable. 
     Conduits  610 ,  620 ,  630  and  640  are sheets of conductive material, such as copper, having sufficient thickness and surface area to accommodate the electrical current capacity of a photovoltaic module. For example, the sheet thickness of the conduits may be on the order of 20-400 μm, such as 250-350 μm, with a total length ‘L 1 ’ of 300-2000 mm, such as 900-1000 mm, and a width ‘W 1 ’ such as 25-35 mm for a module containing 36-60 cells. Conduits  610 ,  620 ,  630  and  640  may be formed by, for example, electroforming, etching or stamping. 
       FIG. 6B  is a bottom view of the flexible circuit  600 , showing a support sheet  650  covering a portion of the flexible circuit, rather than the entire circuit as with support sheet  550  of  FIG. 5 . Support sheet  650  is an insulating dielectric layer, such as polyethylene terephthalate (PET) or other polyester, or may be a polyimide. For example, support sheet  650  may be PET or polyimide with a thickness of approximately 50 μm. In the embodiment of  FIG. 6B , the support sheet  650  is attached to portions of the first and second conduits  610  and  620  in the junction box contact region ( 660  of  FIG. 6A ), enabling the contact tabs  612 ,  622 ,  632  and  642  to remain exposed for soldering to photovoltaic cells. In other embodiments, the support sheet  650  can extend horizontally further than shown, beyond the junction box contact region  660 , as long as the contact tabs  612  and  622  remain uncovered or exposed through apertures (not shown) cut in the support sheet  650  to allow for electrical connections to be made. Support sheet  650  may be on one face of the flexible circuit  600 , such as the bottom side as shown, or may be on both top and bottom faces of the flexible circuit  600  with apertures cut in the support sheet  650  to enable connections for junction box contact pads  614 ,  624 ,  634  and  644 . In one method of manufacturing the flexible circuit  600 , the conduits  610 ,  620 ,  630  and  640  may be patterned into a single sheet of metal, where multiple sets of the conduits may be laid out on a sheet in some embodiments. Then the support sheet  650  may be glued onto the conduits while the traces (patterns for conduits  610 ,  620 ,  630  and  640 ) are still mechanically connected. The conduit pieces are then separated from each other, with the support sheet  650  maintaining the positioning between the conduit pieces. The support sheet  650  thus may also be used as a manufacturing aid such that the conduit pieces need not be handled separately. 
       FIG. 7  shows bottom view of a portion of an exemplary module  700  that includes a flexible circuit  701  similar to the flexible circuit  600  of  FIGS. 6A-6B . Module  700  has six columns of photovoltaic cells A, B, C, D, E and F in this embodiment, where the cells are connected in series as described in relation to  FIGS. 3 and 4 . The dashed-line arrows indicate the serial routing, such as through front-to-back interconnections between cells using metallic articles as described in  FIGS. 3 and 4 , with positive ‘+’ and negative ‘−’ connections as shown at the top of  FIG. 7 . In other embodiments, conventional cells with ribbon stringing may be used with the flexible circuits of this disclosure. Initial cell  721  of column A is the first cell for the series of cells in the photovoltaic module  700 , and final cell  726  is the last cell in the series. Note that because the electrical terminals provided by flexible circuit  710  are located on one edge of the module, the module  700  is arranged with an even number of cell columns, (six in this embodiment) so that both the positive and negative ends of the cell columns are on edge where the flexible circuit  701  is located. 
     Flexible circuit  701  has a first conduit  710  with a contact tab  712  that extends from flexible circuit  701  in this embodiment, to overlap an edge of cell  721  and be electrically coupled to, for example, a metallic article conductor on the back side of cell  721 . In other embodiments, contact tab  712  may be coupled to bus bar ribbons of cell  721 . Final cell  726  may be electrically coupled to second conduit  720  of flexible circuit  701  through, for example, an interconnection element (not shown) extending from the front side of cell  726 , or through bus bar ribbons. The interconnection element of cell  726  may be the interconnection element strip  320  of  FIG. 3 , which enables one solder joint to electrically connect the flexible circuit  701  to cell  726  compared to multiple solder joints for multiple bus bar ribbons. Flexible circuit  701  also includes third conduit  730  that is electrically coupled to cell  723  of column C, and fourth conduit  740  that is electrically coupled to cell  725  of column E. Diodes (not shown) may be coupled between adjacent pairs of junction box pads at ends of conduits  710 ,  720 ,  730 , and  740  in junction box region  760 , similar to the diodes  581 ,  582  and  583  described in relation to  FIG. 5 . 
     For the module-level connections, it can be seen that only four attachment points—junction box contact pads of conduits  710 ,  720 ,  730  and  740  in junction box region  760 —are required for coupling the cell strings and diodes of module  700  to a junction box. By having the four contact pads (not shown for clarity) grouped together in one area, junction box connections are simplified compared to having multiple ribbons that must be routed and threaded into the junction box area and soldered by hand. Regarding manufacturability, the flexible circuit  701  only needs to be laid into position on the module  700  and soldered onto the interconnection elements of cells  721 ,  723 ,  725  and  726 , and therefore is conducive to automated processes. Flexible circuits are generally low cost components, which further reduces cost of the overall module. In some embodiments, the contact pads of conduits  710 ,  720 ,  730  and  740  can be large metal pads for easy access inside the junction box. Also, while conventional modules require the back sheet of a module to be cut (e.g., slitted) to allow for a junction box ribbon to be manually pushed through the back EVA and backsheet before lamination, the flexible circuits described herein allow for pre-punching holes in the back EVA and backsheet to expose the flexible circuit contact points for direct soldering or for welding the contact leads from the junction box. 
       FIG. 8  is an exploded assembly view of a photovoltaic module assembly  800  using the flexible circuits and solar cells with free-standing metallic articles as disclosed herein. A photovoltaic module layer  830  has photovoltaic cells  832  connected in series, with initial contact end  834  and final contact end  835  of the series of cells  832  being electrically coupled to flexible circuit  836 . The photovoltaic cells  832 , made with free-standing metallic articles, are assembled onto the module sheet  840 , which may be a material such as ethylene vinyl acetate (EVA). The cells  832  may be laid into place and have interconnection elements coupled together to adjacent cells as described above, using manual or automated methods. For example, the cell-to-cell interconnections may be made using automated soldering and heating methods. The flexible circuit  836  may also be coupled to contact ends  834  and  835  of the series of cells  832  using automated soldering and heating methods, since the contact tabs of the flexible circuit  836  need only to be laid onto contact ends  834  and  835  rather than requiring threading and cutting of multiple bus bar ribbons as in conventional modules. The cells  832  can be sandwiched between EVA sheets  820  and  840 , to encapsulate the cells  832 . Backing sheet  850 , such as a polyvinyl fluoride (PVF) film (e.g., Tedlar®, or Tedlar-polyester-Tedlar), encloses the back side of the assembly  800 . A glass sheet  810  covers the front of the assembly, to provide protection from environmental conditions. The entire layered stack may be put in a laminator, where heat and vacuum are applied to laminate the assembly. To complete the module, output connection wires  860  are routed from the flexible circuit  836 , through holes  842  and  852  in EVA layer  850  and back sheet  850 , respectively, to junction box  870  on the back of the module assembly  800 . 
       FIG. 9  is a flow chart  900  of an exemplary method for manufacturing a solar cell module using a flexible circuit and metallic articles as described above. In other embodiments, conventional ribbon bus bar connections may be used with the flexible circuits disclosed herein. In a step  910 , a plurality of photovoltaic cells is provided, each with a free-standing metallic article coupled to a semiconductor substrate material. In some embodiments, the free-standing metallic articles are electroformed on an electrically conductive mandrel in step  912 , where the electrically conductive mandrel has a preformed pattern in which at least a portion of the metallic articles are formed, and the metallic articles are separated from the mandrel. Step  910  may also include, in step  914 , electrically coupling a first metallic article to the top surface of the semiconductor substrate, and a second metallic article to the bottom surface of the semiconductor substrate. In step  920 , the plurality of photovoltaic cells are electrically coupled in series to form a series of cells. The series connection includes electrically coupling a cell interconnection element of each photovoltaic cell to a free-standing metallic article of an adjacent photovoltaic cell. For example, the cell interconnection element may couple the front metallic article to a back metallic article of the neighboring cell. The cell interconnection element of an initial cell in the series of cells serves as a first contact end for the series of cells, and the interconnection element for a final cell in the series cells serves as a second contact end for the series of cells. 
     In step  930 , a flexible circuit comprising a first contact tab, a second contact tab, and a junction box contact region is provided. The flexible circuit may include first and second electrical conduits, which may be fabricated by stamping or electroforming, where the first electrical conduit includes the first contact tab, and the second electrical conduit includes the second contact tab. In some embodiments the flexible circuit may also include a first bypass diode conduit and a second bypass diode conduit, with each diode contact conduit having contact tabs and junction box contact pads. The flexible circuit may also include a support sheet attached to at least a portion of the first and second conduits, as well as the bypass diode conduits. The support sheet may have apertures through the sheet at the first and second junction box contact pads. In step  940  the first contact tab of the flexible circuit is electrically coupled to the first contact end of the series of cells, and the second contact tab of the flexible circuit is electrically coupled to the second contact end of the series of cells. In some embodiments, the bypass diode tabs may be electrically coupled to the series of cells in step  945 . In step  950  the junction box region of the flexible circuit is electrically coupled to a junction box, which can include coupling the first and second junction box contact pads to the junction box with, for example, output connection wires. Step  950  may also include electrically coupling a diode to the junction box pads of the bypass diode conduits. 
     Note that additional steps may be inserted into the method of  FIG. 9  to complete the entire module, and the order of steps may be performed in a different order than what is shown. For example, the module assembly process may begin with providing a glass cover panel, and then placing an EVA sheet on the glass. A cell circuit assembly with flexible circuit may be laid onto the first EVA sheet, where the cell circuit assembly may be fabricated in accordance with the steps of flow chart  900 . Then a second EVA sheet with punched holes for wire routing may be placed over the cell assembly. The EVA sheets may be laminated onto the cells to encapsulate the photovoltaic cells. A backsheet with punched holes for wire routing is placed over the assembly, and the junction box is attached to finish the module. 
     Steps  920 ,  940  and  950  may be automated, such that no manual coupling of components is needed. Automated processes may include, for example, pick and place methods, use of lamination machines, and automated soldering methods. In some embodiments of step  920  the photovoltaic cells may be electrically coupled together by soldering the front interconnect tab to the back contact edge pads, to series connect the cells. In other embodiments, steps  930 ,  940  and  945  may involve soldering the flexible circuit to a multi-cell circuit cell assembly using automated or manual processes. For an exemplary 60-cell circuit, a flexible circuit tab solders to the back of the first cell from the tab, and another flexible circuit tab solders cell number 60 from the front cell tab to the flex circuit. The additional conduit tabs are soldered to the back of the twentieth cell and the back of the fortieth cell. 
     It can be seen that the free-standing electroformed metallic article described herein is applicable to various cell types and may be inserted at different points within the manufacturing sequence of a solar cell. Furthermore, the electroformed electrical conduits may be utilized on either the front surface or rear surface of a solar cell, or both. In addition, although the embodiments herein have primarily been described with respect to photovoltaic applications, the methods and devices may also be applied to other semiconductor applications. Furthermore, the flow chart steps may be performed in alternate sequences, and may include additional steps not shown. Although the descriptions have described for full size cells, they may also be applicable to half-size or quarter-size cells. For example, the metallic article design may have a layout to accommodate the cell having only one or two chamfered corners instead of all four corners being chamfered as in a mono-crystalline full pseudosquare. 
     While the specification has been described in detail with respect to specific embodiments of the invention, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the scope of the present invention, which is more particularly set forth in the appended claims. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.