JP5544718B2 - INTERCONNECTOR MATERIAL FOR SOLAR CELL, ITS MANUFACTURING METHOD, AND INTERCONNECTOR FOR SOLAR CELL - Google Patents

Description

  The present invention relates to a solar cell interconnector material suitable for a solar cell interconnector for connecting cells in a solar cell module including a plurality of cells, a manufacturing method thereof, and a solar cell comprising the solar cell interconnector material. The present invention relates to a battery interconnector.

  In recent years, as a power generation method with a small environmental load, a solar cell module is attracting attention and is widely used in various fields. As described in Patent Document 1, for example, the solar cell module includes a plurality of cells made of a semiconductor plate material such as pn-junction silicon, and these cells are electrically connected by a solar cell interconnector and a bus bar. It is set as the structure.

  Here, as an interconnector for electrically connecting cells, for example, as shown in Patent Document 2, a copper rectangular wire made of oxygen-free copper or tough pitch copper is widely used. And connected to the cell via the solder plating layer. Further, as shown in Non-Patent Document 1, an interconnector made of high-purity copper of 6N (purity 99.9999%) has been proposed.

JP 2005-166915 A Japanese Patent Laid-Open No. 11-21660

Hirotoshi Endo, 5 others, “Development of soft solder-plated rectangular wires for solar cells”, Hitachi Cable 26 (2007-1), p. 15-P. 18

  By the way, in the soldering process between the solar cell interconnector and the cell, the solar cell interconnector and the cell are heated to a temperature higher than the liquidus temperature of the solder and then cooled to room temperature. Here, since the thermal expansion coefficient of the cell composed of silicon or the like is different from the thermal expansion coefficient of the solar cell interconnector that is a copper rectangular wire, the cell with the solar cell interconnector extending when the temperature is raised And the solar cell interconnector contracts during cooling, causing a problem that the cell warps. When the cell is warped, there is a problem that the solar cell module cannot be configured or cannot be attached to the frame. Further, the cell may be damaged by this warpage.

Here, in Non-Patent Document 1, a solar cell interconnector made of high purity copper of 6N (purity 99.9999%) has been proposed, and the crystal grain size of 6N high purity copper is coarsened to be soft. Therefore, the warpage during soldering is reduced.
However, recently, in order to produce a solar cell module at a low cost, the thickness of the cell has been reduced, and it is necessary to control the thermal stress generated in the soldering process with higher accuracy than before. Here, the 6N high-purity copper requires a refining treatment step, resulting in high production costs. Further, in the case of ordinary oxygen-free copper, variation in crystal grain coarseness occurs, and the thermal stress at the time of soldering cannot be absorbed uniformly.

  The present invention has been made in view of the above-described circumstances, and is a solar cell interconnector material and a solar cell that can uniformly absorb thermal stress generated during solder bonding and can prevent cell warpage. An object of the present invention is to provide a method for producing an interconnector material for a solar cell and an interconnector for a solar cell constituted by the interconnector material for a solar cell.

  In order to solve the above problems, the solar cell interconnector material according to the present invention is a solar cell interconnector material used as a solar cell interconnector for connecting cells to each other in a solar cell module, In mass parts per million, at least one of Zr and Mg is 3 to 20 ppm, O is 5 ppm or less, the remainder is made of Cu and inevitable impurities, and the average crystal grain size is 300 μm or more. It is a feature.

  Moreover, the solar cell interconnector according to the present invention is a solar cell interconnector for connecting cells in a solar cell module, and is made of the aforementioned solar cell interconnector material, and has a rectangular cross section. A lead-free solder plating layer is formed on at least one of the principal surfaces extending in the extending direction of the rectangular wire.

  According to the interconnector material for solar cells and the interconnector for solar cells having this configuration, at least one kind of Zr and Mg is contained in 3 parts by mass, 3 to 20 ppm, O is 5 ppm or less, and the balance is Cu. And Zr and Mg are present in copper as one of the unavoidable impurities, and by fixing S (sulfur), which is an element that hinders the coarseness of crystal grains, It becomes possible to increase the crystal grain size. By increasing the crystal grain size in this way, the deformation resistance of the solar cell interconnector is reduced, and the occurrence of cell warpage during solder bonding can be suppressed. Moreover, it is possible to suppress variation in crystal grain size due to Zr and Mg, and it is possible to uniformly absorb thermal stress during solder bonding.

In addition, when Zr and Mg are less than 3 ppm, the above-described effects cannot be obtained. When the content exceeds 20 ppm, the electrical conductivity of the solar cell interconnector decreases, so the content of Zr and Mg is set to 3 to 20 ppm. More desirably, the content of Zr and Mg is 10 to 15 ppm.
Further, since O (oxygen) is set to 5 ppm or less, loss due to oxidation of easily oxidizable elements Zr and Mg can be prevented. Moreover, the interconnector material for solar cells of this invention can be produced at low cost by adding Zr and Mg to general oxygen-free copper.

  The method for producing a solar cell interconnector according to the present invention is a method for producing a solar cell interconnector used in a solar cell interconnector for connecting cells in a solar cell module, wherein a copper raw material is dissolved. And at least one of Zr and Mg is added to the copper melt that has been subjected to a deoxidation treatment, a deoxidation process in which the oxygen content of the copper melt is 5 ppm or less, Casting to obtain an ingot from the Zr and Mg addition step in which the content of at least one of Mg and Mg is 3 to 20 ppm by mass parts, and the molten copper to which at least one of Zr and Mg is added A process, a processing step of processing the ingot to obtain a copper wire, and a heat treatment of 700 to 800 ° C. for 1 to 10 minutes with respect to the copper wire, and an average crystal grain size of 300 μm or more. And a heat treatment step.

  According to the solar cell interconnector manufacturing method of this configuration, after the deoxidation step in which the oxygen content of the molten copper obtained in the melting step is 5 ppm or less, Zr in which at least one of Zr and Mg is added And Mg addition step, Zr and Mg, which are easily oxidizable elements, can be added with a good yield, and the content of Zr and Mg can be accurately adjusted to 3 to 20 ppm in mass parts per million. Can do. In addition, since a heat treatment step of performing heat treatment at 700 to 800 ° C. for 1 to 10 minutes is provided, the crystal grain size can be sufficiently coarsened without being inhibited by S or the like in this heat treatment step.

Here, it is preferable that the casting process is a continuous casting process for continuously producing an ingot, and the processing process is a continuous rolling process for continuously rolling the ingot.
In this case, by continuously producing the ingot and continuously rolling the ingot, it is possible to produce a rough drawn copper wire, and to produce a solar cell interconnector at a low cost. it can.

  According to the present invention, a thermal battery interconnector material and a solar battery interconnector manufacturing method capable of uniformly absorbing thermal stress generated during solder joining and preventing cell warpage, and this A solar cell interconnector configured by the solar cell interconnector material can be provided.

It is explanatory drawing of the solar cell module provided with the interconnector for solar cells which is this embodiment. It is XX sectional drawing in FIG. It is explanatory drawing of the photovoltaic cell with which the solar cell module of FIG. 1 was equipped. It is YY sectional drawing in FIG. It is the schematic diagram which showed roughly the manufacturing apparatus of the rough drawing copper wire. It is a flowchart which shows the manufacturing method of the interconnector material for solar cells which is this embodiment.

Below, the interconnector for solar cells which concerns on embodiment of this invention is demonstrated with reference to attached drawing.
The solar cell module 30 using the interconnector 32 for solar cells which is this embodiment is shown in FIG. 1, FIG. 3 and 4 show a solar battery cell 31 constituting the solar battery module 30. FIG.
The solar cell module 30 shown in FIGS. 1 and 2 includes a plurality of solar cells 31, a solar cell interconnector 32 that electrically connects these solar cells 31 in series, and a solar cell interconnector 32. Bus bars 35 and 36 to be connected.

  The solar battery cell 31 is made of, for example, pn-junction silicon and has a substantially square plate shape as shown in FIGS. 3 and 4. In this embodiment, the solar battery cell 31 has a side of 130 mm and a thickness of 0.18 mm. used.

The solar battery interconnector 32 according to the present embodiment is disposed on the surface of the solar battery cell 31.
The solar cell interconnector 32 is a rectangular copper wire having a rectangular cross section, and in this embodiment, the width W is 2 mm and the thickness t is 0.2 mm. In this solar cell interconnector 32, as shown in FIG. 4, a lead-free solder plating layer 33 is formed on at least one of two main surfaces extending in the direction in which the copper rectangular wire extends. It is joined to the solar battery cell 31 via a free solder plating layer 33.
The solar cell interconnector 32 has a mass percentage of at least one of Zr and Mg containing 3 to 20 ppm, O; 5 ppm or less, and the remainder being made of Cu and inevitable impurities. Consists of connector material.

  As shown in FIG.1 and FIG.2, the solar cell interconnector 32 is joined to the surface and the back surface of the solar cell 31, and electrically connects the adjacent solar cells 31 to each other. The solar cell interconnector 32 is configured to be connected to the positive bus bar 35 and the negative bus bar 36, respectively. The solar cell interconnector 32 and the bus bars 35 and 36 are provided in the solar cell module 30. All the solar cells 31 are connected in series.

Next, the manufacturing apparatus of the rough drawn copper wire 23 used as the raw material of the interconnector material for solar cells which is this embodiment is demonstrated with reference to FIG .
The roughing copper wire manufacturing apparatus 1 includes a melting furnace A, a holding furnace B, a casting rod C, a belt-wheel continuous casting machine D, a continuous rolling apparatus E, and a coiler F. Yes.

  In this embodiment, a shaft furnace having a cylindrical furnace body is used as the melting furnace A. A plurality of burners (not shown) are arranged in a multistage shape in the vertical direction at the lower part of the furnace body. And the electrolytic copper which is a raw material is inserted from the upper part of a furnace main body, is melt | dissolved by the combustion of the said burner, and a copper molten metal is made continuously.

  The holding furnace B is for temporarily storing the molten copper produced in the melting furnace A while holding it at a predetermined temperature, and sending a certain amount of the molten copper to the casting iron C.

  The cast iron C is for transferring the molten copper sent from the holding furnace B to the tundish 11 disposed above the belt-wheel continuous casting machine D. The cast iron C is sealed with, for example, an inert gas such as Ar 2 or a reducing gas. The cast iron C is provided with a stirring means (not shown) for stirring the molten copper with an inert gas.

A pouring nozzle 12 is disposed on the end of the tundish 11 in the direction of the flow of the molten copper, and the molten copper in the tundish 11 is supplied to the belt-wheel continuous casting machine D through the pouring nozzle 12. The
The belt-wheel type continuous casting machine D includes a cast wheel 13 having a groove formed on the outer peripheral surface thereof, and an endless belt 14 that is circulated so as to contact a part of the outer peripheral surface of the cast wheel 13. The molten copper supplied through the pouring nozzle 12 is poured into the space formed between the groove and the endless belt 14 and cooled to continuously cast the bar-shaped ingot 21. .

  The belt-wheel type continuous casting machine D is connected to a continuous rolling device E. The continuous rolling device E continuously rolls the bar-shaped ingot 21 produced from the belt-wheel continuous casting machine D to produce a rough drawn copper wire 23 having a predetermined outer diameter. The rough-drawn copper wire 23 produced from the continuous rolling device E is wound around a coiler via the cleaning / cooling device 15 and the flaw detector 16.

The cleaning / cooling device 15 cleans the surface of the rough-drawn copper wire 23 produced from the continuous rolling device E with a cleaning agent such as alcohol.
The flaw detector 16 detects flaws in the roughing copper wire 23 sent from the cleaning / cooling device 15.

The manufacturing method of the interconnector material for solar cells which is this embodiment using the manufacturing apparatus of the rough drawn copper wire 23 set as such will be described with reference to FIGS. 4 and 5.
First, 4N (purity 99.99%) electrolytic copper is charged into the melting furnace A and melted to obtain a molten copper (melting step S1). In this melting step S1, the oxygen content of the molten copper is set to 20 ppm or less by adjusting the air-fuel ratio of the plurality of burners of the shaft furnace to make the inside of the melting furnace A a reducing atmosphere.

The molten copper obtained by the melting furnace A is transferred to the tundish through the holding furnace B and the casting iron C.
Here, the molten copper passing through the cast iron C sealed with an inert gas or a reducing gas is stirred by the aforementioned stirring means, thereby promoting the reaction between the molten copper and the inert gas or the reducing gas. Thus, the oxygen content is reduced to 5 ppm or less (deoxidation step S2).

  In this way, at least one of Zr and Mg is continuously added to the molten copper whose oxygen content is reduced to 5 ppm or less, and the content of Zr and Mg is adjusted to 3-20 ppm (Zr and Mg). Addition step S3). In addition, it is preferable to adjust content of Zr and Mg to 10-15 ppm.

  The molten copper whose components have been adjusted in this way is supplied to the belt-wheel continuous casting machine D via the pouring nozzle 12, and the bar-shaped ingot 21 is continuously produced (casting step S4). Here, in the casting step S4, since the space formed between the groove formed in the casting wheel 13 and the endless belt 14 has a trapezoidal shape, the bar-shaped ingot 21 having a substantially trapezoidal cross section is formed. Will be produced.

  This bar-shaped ingot 21 is supplied to a continuous rolling device E and subjected to roll rolling, and a rough drawn copper wire 23 having a predetermined outer diameter (in this embodiment, a diameter of 8 mm) is produced (processing step S5). This roughing copper wire 23 is cleaned and cooled by the cleaning / cooling device 15, and the flaw detector 16 is inspected for the presence or absence of damage.

  The thus drawn rough drawn copper wire 23 with a diameter of 8 mm is drawn to produce a copper wire with a diameter of 1 mm. Thereafter, it is formed into a flat shape having a thickness of 200 μm and a width of 2 mm by a rolling mill, and heat treatment is performed at 700 to 800 ° C. for 1 to 10 minutes to obtain a solar cell interconnector material (heat treatment step S6). By this heat treatment step S6, the average crystal grain size of the solar cell interconnector material becomes 300 μm or more.

  A plating layer is formed while the solar cell interconnector material is continuously immersed in a SnAgCu plating bath. A lead-free solder plating layer 33 is formed on the surface of the solar cell interconnector material, and the solar cell interconnector 32 according to this embodiment is manufactured. In the present embodiment, the composition of the lead-free solder plating layer 33 is Sn-3.0 mass% Ag-0.5 mass% Cu.

  The solar cell module 30 including the solar cell interconnector 32 configured as described above is used by being disposed outdoors, and sunlight or the like is applied to the solar cells 31 and the generated electricity is used for solar cells. Collected by the interconnector 32 and the bus bars 35, 36.

  According to the solar cell interconnector 32 of the present embodiment, at a mass percentage, at least one of Zr and Mg is contained at 3 to 20 ppm, O; 5 ppm or less, and the balance is made of Cu and inevitable impurities. Since it is made of a copper material, Zr and Mg can fix S (sulfur) present in copper as one of inevitable impurities and promote the coarsening of the crystal grain size. Thus, by making a crystal grain diameter 300 micrometers or more, the deformation resistance of the interconnector 32 for solar cells becomes small, and generation | occurrence | production of the curvature of the photovoltaic cell 31 at the time of solder joining can be suppressed. Moreover, it is possible to suppress variation in crystal grain size due to Zr and Mg, and it is possible to uniformly absorb thermal stress during solder bonding.

  Moreover, since the casting process S4 is a continuous casting process by the belt-wheel continuous casting machine D and the processing process S5 is a continuous rolling process by the continuous rolling device E, the interconnector material for solar cells is manufactured at low cost. can do. Furthermore, in this embodiment, since it is a general oxygen-free copper-based copper material of 4N (purity 99.99%), it is not necessary to perform a special refining process, and further, manufacturing of an interconnector material for solar cells Cost can be reduced.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, although the size of the solar battery cell has been described with one side being 130 mm and the thickness being 0.1 mm, the size of the solar battery cell is not particularly limited. However, in a thin solar cell having a thickness of 0.2 mm or less, cracks are likely to occur due to warpage during solder joining, and thus the effect of the solar cell interconnector according to the present embodiment becomes significant.

  Further, as a method for producing an interconnector material for solar cells, the casting process S4 is described as a continuous casting process by the belt-wheel type continuous casting machine D, and the processing process S5 is described as a continuous rolling process by the continuous rolling apparatus E. For example, in the casting step S4, a cylindrical ingot is produced, and in the processing step S5, a rough drawn copper wire is obtained from the cylindrical ingot, and a solar cell is obtained from the rough drawn copper wire. An interconnector material may be manufactured.

In addition, although it has been described that the solar cell interconnector material is immersed and energized in a plating bath to form a lead-free solder plating layer, the present invention is not limited to this, and the lead-free solder plating layer is formed by other plating methods. May be formed. In addition, this lead-free solder plating layer should just be formed in at least one of the main surfaces extended in the extension direction of the interconnector material for solar cells (copper flat wire).
Furthermore, the composition of the lead-free solder plating layer is not limited to Sn-3.0 mass% Ag-0.5 mass% Cu, but may be other compositions.

Below, the result of the confirmation experiment performed in order to confirm the effectiveness of this invention is demonstrated.
The confirmation experiment is the interconnector material for solar cells (Invention Example 1-9) which is the embodiment described above, and the Zr and Mg-containing copper materials in which the Zr, Mg and O contents deviate from the present invention as comparative examples, As a conventional example, 4N (purity 99.99%) oxygen-free copper was prepared, and a test piece having a thickness of 0.2 mm, a width of 2 mm, and a length of 150 mm was prepared.

The test piece was heat-treated at 700 ° C. for 10 minutes, and then the crystal grain size and 0.2% proof stress were measured.
The crystal grain size was measured by S4300SE manufactured by Hitachi High-Technology Co., Ltd., with a viewing area of 5000 mm ² and the average crystal grain size at 10 locations and the difference between the maximum crystal grain size and the minimum crystal grain size. Moreover, based on JIS Z2241, the tensile test was done using AG-5kNX by Shimadzu Corporation, and 0.2% yield strength was measured.

  The confirmation experiment results are shown in Table 1.

As shown in Table 1, according to Inventive Example 1-9, the average crystal grain size is set to 300 μm or more by the heat treatment at 700 ° C. × 10 min, and the difference between the maximum crystal grain size and the minimum crystal grain size is also 60 μm or less. It was confirmed that the variation in crystal grain size was small. The 0.2% proof stress was 50 MPa or less , and it was confirmed that the 0.2% proof stress was sufficiently softened.
On the other hand, in Comparative Example 1-3 and the conventional example, the average crystal grain size is as small as 100 to 180 μm even by heat treatment at 700 ° C. × 10 min, and the difference between the maximum crystal grain size and the minimum crystal grain size is 200 It was as large as 250 μm, and it was confirmed that there was a large variation in crystal grain size. The 0.2% proof stress was 75 to 85 MPa, and it was confirmed that the softening was insufficient.

  Therefore, according to the present invention example, since the average crystal grain size is as large as 300 μm or more and the variation is small, it can be confirmed that the thermal stress at the time of soldering can be sufficiently absorbed and the cell warpage can be prevented. It was done.

30 Solar cell module 31 Solar cell 32 Solar cell interconnector 33 Lead-free solder plating layer S1 Dissolution step S2 Deoxidation step S3 Zr and Mg addition step S4 Casting step S5 Processing step S6 Heat treatment step

Claims (5)

Solar cell interconnector material used as a solar cell interconnector connecting cells in a solar cell module,
In mass parts per million, at least one of Zr and Mg is 3 to 20 ppm, O is 5 ppm or less, the remainder is made of Cu and inevitable impurities, and the average crystal grain size is 300 μm or more. A characteristic interconnector material for solar cells.   2. The solar cell interconnector material according to claim 1, comprising 10 to 15 ppm of at least one of Zr and Mg in parts by mass. A method for producing an interconnector material for solar cells used in an interconnector for solar cells that connects cells in a solar cell module,
A melting step of obtaining a molten copper by melting a copper raw material,
A deoxidation step in which the oxygen content of the molten copper is 5 ppm or less;
Zr and Mg addition step of adding at least one of Zr and Mg to the deoxidized copper melt so that the content of at least one of Zr and Mg is 3 to 20 ppm by mass parts per million When,
A casting step of obtaining an ingot from the molten copper to which at least one of Zr and Mg is added;
A processing step of processing the ingot to obtain a copper wire;
A heat treatment step of performing heat treatment at 700 to 800 ° C. for 1 to 10 minutes on the copper wire and setting an average crystal grain size to 300 μm or more;
The manufacturing method of the interconnector material for solar cells characterized by comprising.   The said casting process is a continuous casting process which produces an ingot continuously, The said process process is a continuous rolling process which continuously rolls the said ingot. A method for producing an interconnector material for a solar cell. A solar cell interconnector for connecting cells in a solar cell module,
The interconnector material for solar cell according to claim 1 or claim 2, wherein the cross section is a rectangular wire having a rectangular shape,
A lead-free solder plating layer is formed on at least one of main surfaces extending in the extending direction of the flat wire.

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