JP2012084560A - Crystalline solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable connection method of a crystalline solar cell module which does not cause the deterioration of generation efficiency and enables a relatively easy connection process.SOLUTION: Crystalline solar cells such as single crystal solar cells or polycrystalline solar cells are connected to form a crystalline solar cell module. A back electrode of each solar cell is joined with an adhesive containing ribbon shaped metal foil and conductive particles. This structure attains high connection reliability and reduces the cost of wiring materials.

Description

  The present invention relates to an apparatus for connecting a wiring member to the surface of a substrate of a crystalline solar cell such as a single crystal solar cell or a polycrystalline solar cell, and particularly a connection method suitable for connecting solar cells having a back electrode. The present invention relates to a crystalline solar cell module using

  The crystalline solar cell module assembly process is a series of solar cell circuits in which a crystal cell substrate (hereinafter simply referred to as “cell”) of a crystalline solar cell such as a single crystal solar cell or a polycrystalline solar cell is connected to a wiring member. Then, it is an assembly mounting process in which an external terminal is attached by sealing with a protective sheet or the like.

  Of these steps, soldering has been widely used as a method for connecting a wiring member to a cell. Lead-containing solder is a good conductor and has a certain strength and environmental reliability, and has a track record of about 20 years. However, when considering the use of lead-free solder from the viewpoint of environmental protection in recent years, a decrease in reliability becomes a problem.

In addition, due to the structure of the crystalline solar cell, a part of the wiring member is arranged on the front side of the solar cell, so if a wide wiring is used, the effective area of the solar cell is reduced due to the shadow of the wiring. In addition, it was necessary to set a limit on the wiring width.
On the other hand, the crystalline solar cell is easily affected by the wiring resistance because the current is larger than that of the thin film solar cell, and it is necessary to increase the cross-sectional area of the wiring in order to reduce the wiring resistance. For this reason, there is a limitation that the wiring thickness cannot be reduced. As a typical design, for example, as described in Patent Document 1, a wiring in which a copper wire having a thickness of about 100 to 250 μm and a width of about 1 to 7.5 mm is coated with solder is used.

On the other hand, in this method, it is inevitable that the wiring covers a part of the effective area of the solar battery cell, and in order to reduce this, a back contact technique is studied as described in Patent Document 2, for example. . In this back contact technology, stress such as thermal expansion is alleviated by soldering a wiring material made of a thin plate-like metal plate for connecting back surfaces to each other. Further, it has been proposed to use a thin plate subjected to mesh processing in order to reduce rigidity.
In these methods, a thick plate whose rigidity cannot be ignored is used as the wiring material. As a result, the connection reliability is lowered and the cost of the wiring material is increased.

JP 2000-49367 A JP 2009-176782 A

  The object of the present invention is to provide a method for connecting a crystalline solar cell that is highly reliable and does not cause a decrease in power generation efficiency by a relatively easy connection process using an inexpensive material. Furthermore, another object is to provide an inexpensive and highly efficient crystalline solar cell module using this connection method.

  In order to achieve the above object, a soft copper or aluminum thin metal foil (thickness 5 μm to 35 μm) is used as a wiring material, and a thermosetting adhesive containing conductive particles on one side of the metal foil is used. Prepare a ribbon-like adhesive tape that has been pre-applied, and stretch it over almost the entire length of one side of two adjacent crystalline solar cells. It was realized by relaxing.

Moreover, in order to achieve the said objective, the stress by thermal expansion was reduced by applying a pressurizing force so that the intermediate part of two adjacent crystalline solar cells might be curved in the pressure welding of a ribbon-shaped adhesive tape.
Moreover, in order to achieve the said objective, the stress by thermal expansion was reduced by applying a pressurizing force so that the intermediate part of two adjacent crystalline solar cells might be curved in the thermosetting of a ribbon-shaped adhesive tape.

Further, in order to achieve the above object, the pressure range of the crystalline solar cell is divided into a plurality of pressure ranges when the ribbon-like adhesive tape is pressed, thereby reducing the stress in the longitudinal direction by reducing the adhesion length contributing to thermal expansion. Reduced.
In order to achieve the above object, the stress in the longitudinal direction can be reduced by reducing the adhesive length that contributes to thermal expansion by dividing the pressure range of the crystalline solar cell into a plurality of parts in the thermosetting of the ribbon-like adhesive tape. Reduced.

  According to the present invention, a connection using a thick plate-like wiring material or a flat copper wire is used instead of a connection using a thick plate-like wiring material or a flat copper wire. It was possible to reduce the generation of thermal stress caused by. Moreover, the flexibility of the wiring could be improved by connecting with an extremely thin metal foil. And, since the connection with the ultra-thin metal foil is performed using a thermosetting adhesive containing conductive particles, the thermal stress is further reduced, so that high connection reliability can be obtained. It was. In addition, the use of ultra-thin metal foil has also realized a reduction in the cost of wiring materials.

It is the top view which mounted the cell matrix of the 1st Example of this invention on the cover glass. It is the schematic which shows the module cross section of the 1st Example of this invention. It is a top view which shows the back electrode of the cell of the 1st Example of this invention. FIG. 3 is a perspective view of the cell string according to the first embodiment of the present invention with the ribbon tape removed. It is a perspective view which shows the cell string of the 1st Example of this invention. 1 is a perspective view of a ribbon tape according to a first embodiment of the present invention. It is a perspective view of the ribbon tape of the other Example of this invention. It is a perspective view of the ribbon tape of the other Example of this invention.

Hereinafter, a first mode for carrying out the present invention will be described with reference to FIGS.
FIG. 1 is a plan view showing a state in which a cell matrix 5 formed by connecting cells to each other is placed on a cover glass 6 in a module manufacturing process of a crystalline solar cell according to the present invention. FIG. 1 shows a state in which the cell 1 (solar cell) is viewed from the back side (non-light-receiving surface). A cell string 5a is formed by connecting the electrodes on the back surface of the plurality of cells 1 in a row with a ribbon tape 2 which is a metal foil. A combination of a plurality of cell strings 5a arranged side by side is called a cell matrix 5. At the end of the cell string 5a, the pass bar 3 and the electrode of the cell 1 are connected by the ribbon tape 2, and the lead wires 4 lead out the wiring to the outside of the cell matrix 5.

A cross section of the solar cell module cut at the cell string 5a is shown in FIG. In FIG. 2, the upper side is the front side (light receiving surface). The electrodes at the back end portions of the plurality of cells 1 are connected by a ribbon tape 2 to form a cell string 5a. A pass bar 3 connected by the ribbon tape 2 is connected to one end, and a lead wire 4 is connected to the other end. Then, another cell string 5a is connected by the pass bar 3 in the depth direction of the drawing. The cell matrix 5 made of these is covered with a cover glass 6 on the front side and a back sheet 8 on the back side. The gap between the cover glass 6 and the cell matrix 5 and between the back sheet 8 and the cell matrix 5 is made of the sealing resin 7. Filled and sealed.
Further, the outside of the cell matrix 5 is protected in a frame shape by an aluminum frame 9, and a gap between the frame 9 and the back sheet 8 or the sealing resin 7 is protected by a caulking material 10.

  FIG. 3 shows a comb-like electrode 101 which is the back electrode of the cell 1. The back surface 100 of the cell 1 is passivated with an oxide film and an insulating material, and positive and negative comb-like electrodes 101 and 102 are formed there. Comb-like electrodes 101 and 102 are formed by printing and sintering a silver paste containing fine silver particles as a main component, mixed with a slight organic thickener, an organic solvent, and a low melting glass frit by screen printing. Yes. Each comb-like electrode 101 and 102 has a large number of comb-tooth portions 101b and 102b arranged alternately, and one end thereof is connected by common electrodes 101a and 102a, respectively.

In the actual connection process, the cells 1 are sequentially connected by the ribbon tape 2, but in order to show the structure of the cell string 5a, the cell string 5a with the ribbon tape 2 removed is shown in FIG. In this figure, for the sake of simplicity, the number of comb-tooth portions 101b and 102b is shown smaller than the actual number.
A large number of cells 1 are arranged in a straight line so that the common electrode 102a of the next cell 1 is arranged adjacent to the common electrode 101a of the cell 1. Further, a pass bar 3 is arranged at this end to form a cell string 5a.

  FIG. 5 shows a state in which the cell strings are connected by the ribbon tape 2. Here, the ribbon tape 2 is a copper foil tape having a width of 4 mm and a length of 150 mm and a thickness of 0.035 mm, and is connected so as to straddle the common electrodes 101 a and 102 a of the two cells 1. Further, the ribbon tape 2 is given a deflection 2a in the gap portion of the cell 1. This is to give relief to the stress of the connecting portion. When the ribbon tape 2, which is a copper foil tape, is pressed against the cell 1, the intermediate portion is pushed down to form the flexure 2a.

The ribbon tape 2 has the structure shown in FIG. An elongated CF 200b having a width of 1 mm, a length of 145 mm, and a thickness of 0.025 mm is attached to one side of the ribbon-shaped copper foil 200a. The CF 200b is a tape obtained by kneading conductive nickel particles with a thermosetting adhesive into a film shape, and is manufactured by temporarily pressing the CF 200b onto the copper foil 200a immediately before the ribbon tape 2 is connected.
Thereafter, the ribbon tape 2 is adhered to the cell 1 by placing the CF tape 200b of the ribbon tape 2 downward and straddling the two cells 1 and applying pressure. The cell 1 to which the ribbon tape 2 is adhered is further heated under pressure to cure the thermosetting adhesive with the conductive nickel particles being pressed into the common electrodes 101a and 102a and the copper foil 200a. 1 is electrically connected to each other.

  As a result, the back surface connection of the solar cell can be realized simply and at low cost. In addition, the electrical connection between the cells is made of fine conductive nickel particles, and the mechanical connection is made of a thermosetting adhesive, making it possible to perform low-temperature bonding compared to solder connection in conventional solar cells. Become. Furthermore, since stress relaxation due to the flexibility of the resin can also be expected, it can be expected that it will be more resistant to thermal stress over a long period of time and improve reliability.

  Moreover, since it can connect using cheap copper foil, reduction of member cost can also be anticipated. Conventionally, a crystalline solar cell has been difficult to connect with a copper foil because of a large current. However, since the common electrodes 101a and 102b can be connected widely, the current density can be lowered. Moreover, the effect that the thin wiring using copper foil was attained is also great.

  As described above, the first embodiment using the ribbon tape 2 in which the CF 200b is bonded to the copper foil 200a has been described. However, the present invention can be expected to have the respective effects by changing the ribbon tape 2 as follows.

  The ribbon tape 2A of FIG. 7 is coated with CF201b obtained by kneading a thermosetting adhesive containing conductive nickel particles on one side of a long ribbon-like copper foil 201a having a width of 5 mm and a thickness of 0.035 mm. It is the connection tape which affixed and protected the peeling film 201c. CF201b is applied to a wide copper foil, a wide release film 201c is attached, and then cut into a desired tape width by a splitter, and formed into a long adhesive film, whereby the copper foil 200 is individually cut out and the CF200b is pasted each time. There is an advantage that the ribbon tape 2A can be obtained at a lower cost than the case of attaching.

  The ribbon tape 2B of FIG. 7 is a ribbon tape 2B in which an adhesive 202b is applied to the surface of a copper foil 202a on which rib-shaped protrusions 202ab are formed in advance by knurling and protected with a release film 202c. This tape is also processed with a splitter to a width of 5 mm, and is wound around a reel and supplied. The copper foil with unevenness similar to the ribbon tape 2B is a member that has been frequently used for the purpose of preventing static electricity and reducing electromagnetic waves, and has an advantage that it can be obtained at low cost because expensive fine nickel particles are unnecessary.

  Furthermore, since the bonding with the cell 1 is based on adhesion as compared with the first embodiment, even if an excessive stress is generated during use, the adhesion portion is deformed and it is easy to avoid breakage. Further, since the copper foil 202a is provided with irregularities in advance, the copper foil 202a can be easily deformed, and thermal stress can be easily relaxed without providing the bending 2a shown in the first embodiment, and also in the longitudinal direction. In order to show flexibility, thermal stress relaxation in the width direction of the cell string 5a can be expected.

  The ribbon tape 2C shown in FIG. 7 was previously cut with a cross-shaped cut by pressing, and then the adhesive 203b was applied to the surface of the copper foil 203a on which the crown-shaped protrusion 203ab was formed by burring, and was protected with a release film 203c. Ribbon tape 2C. Since sharp protrusions can be formed as compared with the ribbon tape 2B, there is an advantage that the connection of the cell 1 to the common electrodes 101a and 102a is further ensured. Further, since the protrusions 203ab are provided in a staggered arrangement on the copper foil 203a, the copper foil 202a can be easily deformed. Therefore, in this embodiment, thermal stress can be easily relaxed.

On the other hand, as in the ribbon tape 2D shown in FIG. 8, a method of sticking a large number of strip-shaped CF200c that is relatively shorter than the first embodiment is also possible. In this case, since the amount of expensive CF used can be reduced, the material cost can be reduced, and the copper foil 200a in the non-bonded portion can be easily deformed because the bonded portion is intermittent and has a short distance. There is an advantage that the thermal stress due to the difference in the material of the foil 200a can be reduced.
Furthermore, in these examples, the base material of the ribbon tape is a copper foil, but in order to make it cheaper, for example, an aluminum foil having a thickness of 0.01 mm can be used.

  DESCRIPTION OF SYMBOLS 1 ... Cell (solar cell), 2 ... Ribbon tape (metal foil), 3 ... Pass bar, 4 ... Lead wire, 5 ... Cell matrix, 6 ... Cover glass, 7 ... sealing resin, 8 ... backsheet, 9 ... frame, 10 ... caulking material.

Claims (6)

In a crystalline solar cell module in which crystalline solar cells such as single crystal solar cells and polycrystalline solar cells are connected,
A crystalline solar cell module characterized by being joined by a ribbon-like metal foil straddling the back electrode of a solar cell. In the crystalline solar cell module according to claim 1,
The crystalline solar battery module, wherein the ribbon-like metal foil connecting the solar battery cells is joined to the electrode of the solar battery cell by an adhesive film containing conductive particles. In the crystalline solar cell module according to claim 1,
The ribbon-shaped metal foil that connects the solar cells is pressed against the electrode of the solar cell by an adhesive, and is joined to the electrode of the solar cell by a protrusion provided on the ribbon-shaped metal foil. A crystalline solar cell module. In the crystalline solar cell module according to claim 2,
The crystalline solar battery module, wherein the ribbon-like metal foil for connecting the solar cells is formed by previously applying an adhesive containing conductive particles to the entire surface of one side. In the crystalline solar cell module according to claim 2,
The crystalline solar cell module, wherein the ribbon-like metal foil connecting the solar cells is formed by attaching an adhesive film containing conductive particles before joining. In the crystalline solar cell module according to claim 5,
The crystalline solar cell module, wherein the ribbon-shaped metal foil connecting the solar cells is formed by cutting out and pasting a plurality of adhesive films containing conductive particles into a rectangular shape before joining.

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