JP2006059991A - Solar cell module and manufacturing method thereof - Google Patents

Abstract

[PROBLEMS] To reduce the thermal stress of soldering that occurs when connecting a lead wire and an electrode of a solar battery cell, or the internal stress that occurs in an adhesion portion between a lead wire and a solar battery cell by a simple method. A solar cell module that prevents warpage and breakage of battery cells and has high electrical reliability, long-term durability, and weather resistance is provided by an inexpensive manufacturing method.
In a solar cell module in which at least two solar cells are connected in series or in parallel, the solar cell has a surface electrode on one main surface side and a back electrode on the other main surface side. The electrode of the solar battery cell and the electrode of the solar battery cell adjacent to the solar battery cell are connected by a lead wire, and the lead wire is formed with grooves or irregularities. And a method for manufacturing the same.
[Selection] Figure 1

Description

  The present invention relates to a solar cell module in which solar cells are connected in series or in parallel. In more detail, it is related with the lead wire which connects a photovoltaic cell.

  In order to obtain a predetermined voltage and current, a solar battery cell is configured and used as a solar battery module by connecting a plurality of solar battery cells in series or in parallel. As a connection method in this case, a thick electrode called a bus bar current collecting electrode formed to collect current from the finger current collecting electrode on the light receiving surface side of the solar cell, and a whole surface on the back surface of the solar cell. The electrodes are generally soldered using lead wires (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3). As the lead wire, a copper wire coated with solder is mainly used.

However, in the process of soldering the lead wire to the electrode of the solar battery cell, the solar battery cell is warped due to the difference in thermal expansion coefficient between the lead wire and the solar battery cell, and the solar battery cell is damaged. It was.
In addition, when using copper wire coated with lead-free solder as a lead wire to cope with recent environmental problems, the melting point of lead-free solder must be processed at a higher temperature. Becomes even more serious.

  Further, since the solar cell module is used under severe natural conditions, durability against repeated exposure to a large temperature change is required. However, in the solar cell module manufactured by the conventional method, the internal stress generated in the bonding portion between the lead wire and the electrode of the solar cell impairs the subsequent electrical stability and affects the durability of the solar cell module. There was an effect.

  Moreover, since the lead wire is usually supplied from a reel, it has a curl, and even if it tries to connect to the electrode of the solar battery cell as it is, the lead wire floats and cannot be connected. For this reason, it is necessary to add a mechanism for removing the curl to the lead wire connecting device.

  Also disclosed is a lead wire attachment device that does not induce warpage due to a temperature difference between the lead wire and the solar battery cell during soldering by devising a lead wire holding mechanism and a heating method. (See Patent Document 4). However, as described above, when lead-free solder with a high melting point is used, the temperature difference between soldering and cooling becomes large, so there is a limit to eliminating the warpage of the solar cells on the device side. It was.

  In addition, by using a lead having a plurality of holes formed in a conductive foil or a bundle of a plurality of thin conductive wires as a lead wire, it is a machine especially against deformation from the outside of a solar cell module processed into a film shape. An invention that improves electrical reliability is disclosed (see Patent Document 5). However, it is inferior in terms of strength, workability, handling and the like as compared with a commonly used flat lead wire, and there is no technical advantage to replace the flat lead wire in a crystalline solar cell module.

  On the other hand, in order to prevent damage to solar cells due to thermal stress when soldering lead wires, an invention is disclosed in which the peripheral portion of the solar cells is reinforced with a resin or the like (see Patent Document 6). However, this method requires a step of reinforcing the solar battery cells, and there is a problem that the number of manufacturing steps increases.

Japanese Unexamined Patent Publication No. 7-131049 JP-A-8-330615 JP-A-9-55531 Japanese Patent Laid-Open No. 11-87756 JP 2001-135846 A JP 2003-69055 A

  This invention is made | formed in view of the said problem, and arises in the adhesive part of the soldering thermal stress produced when connecting a lead wire to the electrode of a photovoltaic cell, or the lead wire and the electrode of a photovoltaic cell. By reducing the internal stress by a simple method, it is intended to prevent damage to solar cells and to provide a solar cell module with high electrical reliability, long-term durability and weather resistance by an inexpensive manufacturing method. Is.

  In order to achieve the above object, in the present invention, in a solar cell module in which at least two solar cells are connected in series or in parallel, a surface electrode is provided on one main surface side of the solar cell, and the other main surface side A back electrode, and the electrode of the solar battery cell and the electrode of the solar battery cell adjacent to the solar battery cell are connected by a lead wire, and a groove or an unevenness is formed in the lead wire. A solar cell module is provided (claim 1).

Thus, the lead wire in which the groove or the unevenness is formed has stretchability and flexibility, and has sufficient thermal stress due to temperature change and internal stress of the bonding portion between the lead wire and the solar cell electrode. Absorb. Therefore, solar cells connected using lead wires having grooves or irregularities are less likely to warp or crack than solar cells connected using conventional lead wires, and temperature changes and High durability against external force.
In addition, the lead wire in which the groove or the concavo-convex is formed has a higher adhesive force and is difficult to peel off because the area to be bonded to the solar battery cell is increased as compared with the conventional lead wire. Therefore, the solar cell connected using the lead wire in which the groove or the unevenness is formed has a low probability that the bonded portion is peeled off as compared with the solar cell connected using the conventional lead wire, High electrical reliability.
From the above, a solar cell module composed of solar cells connected by a lead wire having grooves or irregularities has high durability against temperature change and external force, and can be used stably for a long time.

  A solar cell module in which the lead wire has a thickness of 50 μm or more and 250 μm or less is preferable.

  Thus, by making the average thickness of the lead wire 50 μm or more and 250 μm or less, the cross-sectional area of the lead wire can be increased, the electrical resistance can be sufficiently reduced, and the lead wire can be thicker than necessary. Absent. In a large-area, high-efficiency solar cell, the generated current increases, so it is more preferable to use a lead wire having a thickness of 100 μm or more in order to prevent loss due to electric resistance.

  Next, in the present invention, a method for manufacturing a solar cell module in which at least two solar cells are connected in series or in parallel, the step of forming a surface electrode on at least one main surface side of the solar cells, Forming a back electrode on the other main surface side, and a lead wire connecting step of connecting the electrode of the solar battery cell and the electrode of the solar battery cell adjacent to the solar battery cell with a lead wire, A method of manufacturing a solar cell module is provided, wherein grooves or irregularities are formed in the lead wire to be connected in the lead wire connecting step.

Thus, by forming grooves or irregularities on the lead wire used to electrically connect the electrode of the solar cell and the electrode of the adjacent solar cell, the lead wire seems to have elasticity and flexibility. Thus, the thermal stress due to the temperature change that occurs when the lead wire and the electrode of the solar battery cell are soldered and the internal stress at the bonding portion between the lead wire and the electrode are sufficiently absorbed. Using such lead wires, connect the surface electrode of the solar cell and the back electrode of the adjacent solar cell, or connect the solar cell and the surface electrodes of the solar cell adjacent to each other or between the back electrodes. When connected, the warpage of the solar cells is reduced compared to the solar cells connected in the same manner using the conventional lead wires, and the solar cells are less likely to be broken in the manufacture of the solar cell module, and the yield can be improved. .
The process of forming grooves or irregularities on the lead wire may be performed any time before the lead wire is connected, or may be performed immediately before the lead wire connecting step.

In the manufacturing method of the solar cell module, the formation of the groove or the unevenness of the lead wire can be performed using a roller or a press plate.
Thus, if a roller or a press plate is used, grooves or irregularities can be formed in the lead wire easily and inexpensively.

  In this case, a roller or a press plate may be disposed in the lead wire feeding portion, and the lead wire may be connected while forming a groove or an unevenness in the lead wire fed out.

As described above, in-line processing may be performed in which a roller or a press plate is disposed in the lead wire feeding portion and the lead wire is connected while forming a groove or an unevenness in the lead wire to be fed out.
Since the lead wire is usually supplied from a reel, it has a curl, and even if an attempt is made to connect to the electrode of the solar battery cell as it is, the lead wire floats and cannot be connected. Therefore, conventionally, it has been necessary to add a mechanism for removing the curl to the lead wire connecting device. However, the above-mentioned in-line processing can remove the curl simultaneously with the processing of the lead wire.
The apparatus for forming grooves or irregularities on the lead wire is not limited to a roller or a press plate as long as it can form grooves or irregularities on the lead wire.

  As described above, according to the present invention, when a solar cell is connected using a lead wire having grooves or irregularities, the lead wire and the electrode of the solar cell are soldered. Thermal stress, or thermal stress caused by temperature change of the outside air, or internal stress generated at the bonding part between the lead wire and solar cell electrode can be reduced, and electrical reliability, long-term durability and weather resistance are high. A solar cell module can be provided at low cost.

Hereinafter, although this invention is demonstrated in detail, this invention is not limited to these.
The solar cell module of the present invention is a solar cell module in which at least two solar cells are electrically connected, for example, in series, and has a surface electrode on one main surface side of the solar cell, and the other main surface side The back electrode of the solar battery cell and the back electrode of the solar battery cell adjacent to the solar battery cell are connected by a lead wire, and grooves or irregularities are formed on the lead wire. It is what.

  In FIG. 1, the schematic of the part to which the adjacent photovoltaic cell is connected in series is shown. The dotted line shows that it is located on the back side of the solar battery cell. Solar cells 101 and 101 ′ are generally commercially available crystalline silicon solar cells, and light receiving surface finger electrodes 102, light receiving surface bus bar electrodes 103, back surface aluminum electrodes 104, and back surface silver pad electrodes 105 are formed by screen printing. Is formed. The bus bar electrode 103 on the light receiving surface of the solar battery cell 101 and the silver pad electrode 105 ′ on the back surface of the solar battery cell 101 ′ are electrically connected by a lead wire 106 with a material such as solder or a conductive adhesive. .

Here, the lead wire 106 according to the present invention is formed with grooves or irregularities. The lead wire in which the groove or the unevenness is formed has stretchability and flexibility, and exhibits a function of sufficiently absorbing thermal stress due to temperature change and internal stress of the bonded portion. Accordingly, solar cells connected using lead wires having grooves or irregularities are less likely to warp and crack than solar cells connected using conventional lead wires. Therefore, the durability against temperature change and external force is high.
In addition, a lead wire in which grooves or irregularities are formed has a larger surface area than a conventional lead wire, and an area to be bonded to a solar battery cell is increased. Therefore, the adhesive force is difficult to peel off. Therefore, the solar cell connected using the lead wire in which the groove or the unevenness is formed has a low probability that the bonded portion is peeled off as compared with the solar cell connected using the conventional lead wire, High electrical reliability.
As described above, the solar battery module including the solar battery cells connected by the lead wires having grooves or irregularities as in the present invention is highly durable against temperature change and external force, and can be used stably for a long time. can do.

  The shape of the groove and the unevenness of the lead wire 106 according to the present invention is not particularly limited. For example, the cross-sectional shape is a smooth or uneven wavy line shown in FIG. 4 or a smooth shape shown in FIG. Or a shape having irregularities, or those having grooves locally formed as shown in FIG. Further, as the outer surface shape of the lead wire 106, as shown in FIG. 7, grooves or irregularities are formed perpendicular to the lead wire drawing direction, a lattice shape as shown in FIG. As shown, rounded depressions are arranged.

  The average thickness of the lead wire 106 according to the present invention is preferably 50 μm or more and 250 μm or less. This is to reduce the specific resistance and facilitate handling. That is, when the thickness is 50 μm or more and 250 μm or less, the cross-sectional area of the lead wire can be increased, the electric resistance can be sufficiently reduced, and the thickness is not increased more than necessary. In particular, in a large-area, high-efficiency solar cell of 125 mm square or more, it is preferable to use a lead wire having an average thickness of 100 μm or more in order to generate a large current of 5 A or more and prevent resistance loss. In addition, the lead wire in which the grooves or irregularities are formed has a distribution in the in-plane thickness depending on the processing pattern, but the thickness distribution is preferably within ± 30% with respect to the average thickness. In this way, the strength of the lead wire itself can be maintained, and the specific resistance is not adversely affected.

  As a material of the lead wire 106 according to the present invention, a material having low specific resistance and mechanical strength is desirable. As such a material, workable and inexpensive copper is preferably used. Further, the surface can be subjected to rust prevention treatment, and a thin metal layer such as silver, palladium, gold, nickel, solder, or tin may be plated or deposited on the surface.

  As a method for manufacturing the solar cell module according to the present invention, the method according to the present invention is a method for manufacturing a solar cell module in which at least two solar cells are electrically connected, for example, in series. A step of forming a surface electrode on one main surface side of the cell, a step of forming a back electrode on the other main surface side, the surface electrode of the solar cell and the back electrode of the solar cell adjacent to the solar cell. And a lead wire connecting step of connecting the lead wire and the lead wire in the lead wire connecting step.

  The substrate of the solar battery cell 101 may be amorphous silicon or silicon polycrystal, but a silicon single crystal is preferable because the photovoltaic conversion efficiency can be increased. This silicon single crystal substrate can be obtained by cutting a silicon single crystal grown by a conventional CZ method, FZ method or the like into a desired size.

  On the silicon wafer obtained as described above, the light-receiving surface finger electrode 102 and the light-receiving surface bus bar electrode 103 which are surface electrodes are formed on one main surface side of the solar battery cell by screen printing. Similarly, the back surface aluminum electrode 104 and the back surface silver pad electrode 105 which are back surface electrodes are formed on the other main surface side of the solar battery cell by screen printing.

  Next, the light receiving surface bus bar electrode 103 of the solar battery cell 101 and the back surface silver pad electrode 105 ′ of the adjacent solar battery cell 101 ′ are electrically connected to each other through the solder or conductive adhesive using the lead wire 106. The lead wire connecting process is performed.

  By forming grooves or irregularities in the lead wire used here, the lead wire becomes stretchable and flexible, and occurs when the lead wire and the solar cell electrode are soldered in the lead wire connecting step. The thermal stress and the internal stress at the bonding portion between the lead wire and the electrode are sufficiently absorbed. Solar cells connected using such lead wires are less warped of the solar cells than solar cells connected using conventional lead wires, and the solar cells are cracked in the solar cell module manufacturing process. It becomes difficult, and the yield of a solar cell module manufacturing process can be improved.

  The formation of the groove or unevenness of such a lead wire can be performed by, for example, a roller, a press plate, or a file.

  The process of forming grooves or irregularities on the lead wire may be performed any time before the lead wire is actually connected, or may be performed immediately before the lead wire connecting step. Further, a machined mechanism such as a patterned roller 201 illustrated in FIG. 2 or FIG. 3 or a patterned press machine 301 is provided at a lead wire feeding portion supplied from a reel in the lead wire connecting process. In addition, it is possible to perform in-line from the processing of the lead wire to the connection of the solar battery cell.

  Since the lead wire is usually supplied from a reel, it has a curl, and even if an attempt is made to connect to the electrode of the solar battery cell as it is, the lead wire floats and cannot be connected. Therefore, conventionally, it has been necessary to add a mechanism for removing the curl to the lead wire connecting device. However, if the above in-line processing is performed, it is possible to remove the curl simultaneously with the processing of the lead wire, and it is possible to connect the lead wire very easily and efficiently.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

Hereinafter, the present invention will be specifically described by way of examples.
Example 1
(Lead wire processing)
A flat copper wire coated with solder having a width of 2 mm, a thickness of 150 μm, and a length of 300 mm is obtained by combining two rollers having a pattern capable of forming the cross-sectional shape of FIG. 4 and the outer surface shape of FIG. processed. By selecting an appropriate pattern and gap between the rollers, a flat copper wire shaped to have a thickness of 150 μm, an interval between adjacent irregularities of 2 mm, and an elevation difference of irregularities of 0.5 mm is obtained. It was set as the lead wire using.

(Solar cell connection)
As the substrate of the solar battery cell, a single crystal silicon substrate having a 150 mm pseudo square and a thickness of 250 μm was used. The light-receiving surface bus bar electrode 103 of the solar battery cell 101 formed by the screen printing method is melted with solder covering the lead wire on one end of the lead wire 106 processed as described above on a hot plate heated to 200 ° C. Attached. The other end of the lead wire 106 was attached to the back surface silver pad electrode 105 ′ of the adjacent solar cell 101 ′ by melting the solder covering the lead wire on a hot plate heated to 200 ° C. Here, the warpage of the solar battery cell 101 was measured and found to be 0.2 mm.

(modularization)
About the solar cell connected above, the hot plate which heated the one end to 200 degreeC using the lead wire processed and prepared like the above with respect to the back surface silver pad electrode 105 of the solar cell 101 The solder covering the lead wire was melted and attached. Similarly, one end of the lead wire was attached to the light-receiving surface bus bar electrode 103 ′ of the solar battery cell 101 ′ by melting the solder covering the lead wire on a hot plate heated to 200 ° C. The dimensions of the white plate glass, EVA, and back sheet were selected so that the other ends of these two lead wires were taken out to the outside, and the solar cells were modularized to obtain a solar cell module. Using this solar cell module as a sample, a temperature and humidity cycle test (humidity 85%, −40 ° C. to 90 ° C., cycle time 6 hours) was performed 200 cycles, and the cell characteristics before and after the test were measured. The fill factor before the test was 78.4%, while the fill factor after the test was unchanged at 78.4%.

(Tensile test)
Moreover, in order to evaluate durability by a tensile test, solar cells were connected using lead wires processed with a roller in the same manner as described above. As the substrate of the solar battery cell, a single crystal silicon substrate having a 150 mm pseudo-square shape and a thickness of 400 μm was used. One end of the processed lead wire 106 was attached to the light-receiving surface bus bar electrode 103 of the solar battery cell 101 formed by the screen printing method by melting the solder covering the lead wire on a hot plate heated to 200 ° C. . The other end of the lead wire 106 was attached to the back surface silver pad electrode 105 ′ of the adjacent solar cell 101 ′ by melting the solder covering the lead wire on a hot plate heated to 200 ° C. Using the solar cell thus obtained as a sample, the attached lead wire was pulled at an angle of 90 degrees with respect to the solar cell, and the force required for peeling was measured. The substrate was destroyed at 3.5 N. No separation between the lead wire and the bus bar electrode was observed.

(Comparative Example 1)
(Solar cell connection)
Except for using a flat copper wire covered with solder having a width of 2 mm, a thickness of 150 μm, and a length of 300 mm as the lead wire 106 without being processed, the same method as in Example 1 (connection of solar cells), When the solar cells 101 and 101 ′ were connected and the warpage of the solar cells 101 was measured, it was 0.5 mm.

(modularization)
The solar cell connected in the same manner as in (modularization) of Example 1 except that a flat copper wire covered with solder having a width of 2 mm, a thickness of 150 μm, and a length of 300 mm was used as the lead wire 106 without being processed. When the battery cell was modularized and the temperature and humidity cycle test was performed, the fill factor before the test was 78.2%, while the fill factor after the test was 77.7%, a 0.7% decrease in relative value. did.

(Tensile test)
Further, except that a flat copper wire covered with solder having a width of 2 mm, a thickness of 150 μm and a length of 300 mm was used as the lead wire 106 without being processed, the same method as in the (tensile test) of Example 1 was used. When the battery cell was connected and the tensile test was performed, it peeled between the lead wire and the bus bar electrode while being broken at 3.2N.

  From the above results, the solar cell module obtained by the production method of the present invention has less warpage and higher durability against external force and temperature change than the solar cell module obtained by the conventional production method. As shown, it is excellent in electrical stability and long-term durability / weather resistance.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

For example, in the said Example, although the example was given and demonstrated about the case of the series which connects the surface electrode of a photovoltaic cell, and the back surface electrode of an adjacent photovoltaic cell, surface electrodes of the photovoltaic cell adjacent to a photovoltaic cell Needless to say, the back electrodes may be connected in parallel.
Moreover, as a lead wire, you may use a well-known wiring material other than a flat copper wire.
In addition to solder, a conductive adhesive or the like may be used as means for connecting solar cells using lead wires.
In addition, the process for imparting stretchability and flexibility to the lead wire is not limited to the groove or unevenness of the form shown above, and may be a process of forming various patterns / shapes having the same effect on the lead wire as grooves or unevenness. All are included in the present invention.
The apparatus for forming grooves or irregularities on the lead wire may be any device that can form grooves or irregularities on the lead wire, and is not limited to a roller, a press plate, or a file.

It is the top view and sectional drawing which show the connection part at the time of connecting two adjacent photovoltaic cells in series. It is a schematic diagram of lead wire processing using a roller. It is a schematic diagram of lead wire processing using a press plate. It is an example of the cross-sectional shape of a lead wire. It is another example of the cross-sectional shape of a lead wire. It is another example of the cross-sectional shape of a lead wire. It is an example of the outer surface shape of a lead wire. It is another example of the outer surface shape of a lead wire. It is another example of the outer surface shape of a lead wire.

Explanation of symbols

101, 101 '... solar cell, 102 ... light-receiving surface finger electrode,
103, 103 '... light receiving surface bus bar electrode,
104 ... back surface aluminum electrode, 105, 105 '... back surface silver pad electrode, 106 ... lead wire,
201 ... roller with a pattern formed thereon, 202 ... reel of lead wire,
301: A press machine on which a pattern is formed.

Claims (5)

  In the solar cell module in which at least two solar cells are connected in series or in parallel, the solar cell has a surface electrode on one main surface side and a back electrode on the other main surface side, and the solar cell A solar battery comprising a cell electrode and a solar battery cell electrode adjacent to the solar battery cell connected by a lead wire, wherein the lead wire is formed with grooves or irregularities. module.   The solar cell module according to claim 1, wherein the lead wire has a thickness of 50 μm or more and 250 μm or less.   A method for manufacturing a solar cell module in which at least two solar cells are connected in series or in parallel, wherein at least a step of forming a surface electrode on one main surface side of the solar cell, and another main surface side Forming a back electrode; and a lead wire connecting step of connecting the electrode of the solar battery cell and the electrode of the solar battery cell adjacent to the solar battery cell with a lead wire, and connecting in the lead wire connecting step A method of manufacturing a solar cell module, wherein grooves or irregularities are formed in a lead wire to be formed.   4. The method for manufacturing a solar cell module according to claim 3, wherein the formation of the groove or unevenness of the lead wire is performed by a roller or a press plate.   5. The lead wire connecting step, wherein a roller or a press plate is disposed in a lead wire feeding portion, and the lead wire is connected while forming grooves or irregularities in the lead wire to be fed out. The manufacturing method of the solar cell module of description.

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