HK1188868A - Solar cell module, manufacturing method for solar cell module, and reel-wound body with tab wire wound therearound - Google Patents

Description

Solar cell module, method for manufacturing solar cell module, and reel-wound body wound with tab wire

Technical Field

The present invention relates to a solar cell module in which a plurality of solar cells are connected to each other by a tab wire, and more particularly, to a tab wire connected to an electrode of a solar cell via a conductive adhesive containing conductive particles, a solar cell module using the tab wire, and a method for manufacturing the solar cell module.

This application claims priority based on japanese patent application No. 2011-64797, which was filed in the japanese country on 23/3/2011, and is incorporated herein by reference.

Background

For example, in a crystalline silicon-based solar cell module, a plurality of adjacent solar cells are connected by a tab line serving as an interconnector (interconnector). The tab wire connects one end side to the front surface electrode of one solar cell and the other end side to the back surface electrode of the adjacent solar cell, thereby connecting the solar cells in series. In this case, one surface side of one end of the tab wire is connected to the front surface electrode of one solar cell, and the other surface side of the other end of the tab wire is connected to the back surface electrode of the adjacent solar cell.

Specifically, in the solar cell, a bus bar (busbar) electrode is formed on a light receiving surface by screen printing (screen print) of silver paste (paste) or the like, and an Ag electrode is formed on a rear surface connection portion of the solar cell. In addition, an Al electrode or an Ag electrode is formed in a region other than the connection portion on the rear surface of the solar cell.

The tab wire is formed by providing solder coating layers on both surfaces of the copper foil in a ribbon shape. Specifically, the tab wire is formed by subjecting a rectangular copper wire having a width of 1 to 3mm, which is obtained by cutting a copper foil having a thickness of about 0.05 to 0.2mm or by rolling a copper wire into a flat shape, to solder plating, dip soldering (dip soldering), or the like.

The tab wire is arranged on each electrode of the solar battery cell, and the solder formed on the surface of the tab wire is melted and cooled by applying heat and pressure with a heat bonder (binder), whereby the solar battery cell and the tab wire are connected (patent document 1).

However, since the connection process is performed at a high temperature of about 260 ℃ during soldering, there is a concern that the connection reliability between the front and rear electrodes of the solar cell and the tab wire may be lowered due to warpage of the solar cell, internal stress generated at the connection portions of the tab wire and the front and rear electrodes, and further, residue of flux (flux).

Therefore, conventionally, a conductive adhesive film that can be connected by thermocompression bonding at a relatively low temperature has been used for connecting the front and rear electrodes of the solar cell to the tab wire (patent document 2). As such a conductive adhesive film, a conductive adhesive film is used in which spherical or flaky conductive particles having an average particle diameter of several μm are dispersed in a thermosetting binder resin composition to form a film.

After the conductive adhesive film is interposed between the front and rear electrodes and the tab wire, the adhesive resin exhibits fluidity and flows out from between the electrodes and the tab wire by applying heat and pressure from above the tab wire by a heat bonding tool, and the conductive particles conduct electricity between the electrodes and the tab wire, and the adhesive resin is thermally cured in this state. This forms a string (string) in which a plurality of solar battery cells are connected in series by tab wires.

A plurality of solar cells in which tab wires are connected to a front surface electrode and a back surface electrode using an electrically conductive adhesive film are sealed with a light-transmitting sealing material such as Ethylene-vinyl acetate (EVA) between a light-transmitting surface protective material such as glass or light-transmitting plastic and a back surface protective material made of a film such as PET (polyethylene Terephthalate).

Documents of the prior art

Patent document

Patent document 1: japanese unexamined patent publication No. 2004-356349;

patent document 2: japanese patent application laid-open No. 2008-135654.

Disclosure of Invention

Problems to be solved by the invention

However, in a structure in which the front and back electrodes of the solar battery cell and the tab wire are bonded using the conductive adhesive film, it is desired to further improve the connection reliability, that is, to electrically connect the tab wire and each electrode of the solar battery cell by a low resistance method using the conductive adhesive film. In particular, since the temperature and humidity environment of the solar cell module changes according to day and night, weather, or four seasons after installation, it is desirable to maintain stable connection even in such environmental changes.

Accordingly, an object of the present invention is to provide a solar cell module, a method for manufacturing the solar cell module, and a reel (reel) wound body around which a tab wire is wound, in which connection reliability is improved when the tab wire is connected to each electrode of a solar cell using a conductive adhesive film.

Means for solving the problems

In order to solve the above problem, a solar cell module according to the present invention includes: a plurality of solar cells; and a tab wire connected to the electrodes formed on the surface of each solar cell and the back surface of the adjacent solar cell via a conductive adhesive containing spherical conductive particles, the tab wire having a concave-convex portion formed on a surface thereof contacting the conductive adhesive, the concave-convex portion having an average height H and an average particle diameter D of the conductive particles satisfying D.gtoreq.H.

The method for manufacturing a solar cell module according to the present invention includes: disposing one end side of a tab wire on a front surface electrode of a solar cell via a conductive adhesive containing spherical conductive particles, and disposing the other end side of the tab wire on a back surface electrode of a solar cell adjacent to the solar cell via a conductive adhesive containing conductive particles; and a step of thermally pressing the tab wire to the front surface electrode and the back surface electrode, and connecting the tab wire to the front surface electrode and the back surface electrode via the conductive adhesive, wherein the tab wire has a concave-convex portion formed on a surface thereof contacting the conductive adhesive, and an average height H of the concave-convex portion and an average particle diameter D of the conductive particles satisfy D ≧ H.

The reel-wound body of the present invention is a reel-wound body in which a tab wire is wound on a reel, the tab wire is connected to electrodes formed on the front surface of each solar cell and the back surface of an adjacent solar cell via a conductive adhesive containing spherical conductive particles, and a plurality of the solar cells are connected to each other, the tab wire has a concave-convex portion formed on a surface thereof in contact with the conductive adhesive, and an average height H of the concave-convex portion and an average particle diameter D of the conductive particles satisfy D ≧ H.

Effects of the invention

According to the present invention, in the tab wire, since the average height H of the uneven portion and the average particle diameter D of the conductive particles dispersed in the conductive adhesive satisfy D ≧ H, the conductive particles are held in the recessed portion of the uneven portion and are in contact with the respective electrodes of the solar battery cell. Therefore, in the tab wire, the contact area with each electrode of the solar cell can be increased by the convex portion of the concave-convex portion and the conductive particles, and the on-resistance can be reduced.

Drawings

Fig. 1 is an exploded perspective view illustrating a solar cell module.

Fig. 2 is a sectional view showing a string of solar battery cells.

Fig. 3 is a plan view showing the back electrode and the connection portion of the solar cell.

Fig. 4 is a sectional view showing a joint line on which a conductive adhesive is provided in advance.

Fig. 5 is a sectional view showing a connection state of an electrode of a solar cell and a tab line.

Fig. 6 is a perspective view showing the reel wound body of the joint line.

Fig. 7 is a sectional view showing the conductive adhesive film.

Fig. 8 is a view showing the conductive adhesive film wound in a reel shape.

Fig. 9 is a sectional view showing an example and a comparative example.

Fig. 10 is a plan view showing the example and the comparative example.

Detailed Description

Hereinafter, a solar cell module, a method for manufacturing a solar cell module, and a reel-wound body wound with a tab wire to which the present invention is applied will be described in detail with reference to the drawings.

[ solar cell Module ]

As shown in fig. 1 to 3, a solar cell module 1 to which the present invention is applied includes a string 4 in which a plurality of solar cells 2 are connected in series by a tab wire 3 serving as an interconnector, and a matrix (matrix) 5 in which a plurality of the strings 4 are arranged. The solar cell module 1 is formed by laminating (laminating) the matrix 5 with a sheet 6 of sealing adhesive together with a front cover 7 provided on the light receiving surface side and a back sheet 8 provided on the back surface side, and finally attaching a metal frame 9 of aluminum or the like around the matrix.

As the sealing adhesive, for example, a light-transmitting sealing material such as ethylene-vinyl acetate copolymer resin (EVA) can be used. As the surface cover 7, for example, a light-transmitting material such as glass or light-transmitting plastic can be used. As the back sheet 8, a laminate in which glass or aluminum foil is sandwiched by resin films, or the like can be used.

Each solar cell 2 of the solar cell module includes a photoelectric conversion element 10. As the photoelectric conversion element 10, various photoelectric conversion elements 10 such as a crystalline silicon solar cell module using a single-crystal silicon photoelectric conversion element or a polycrystalline photoelectric conversion element, a thin-film silicon solar cell using a photoelectric conversion element in which a unit made of amorphous (amorphous) silicon and a unit made of microcrystalline silicon or amorphous silicon germanium are stacked, and the like can be used.

The photoelectric conversion element 10 is provided with finger electrodes 12 for collecting electricity generated inside and bus bar electrodes 11 for collecting electricity from the finger electrodes 12 on the light receiving surface side. The bus bar electrodes 11 and the finger electrodes 12 are formed by applying Ag paste to the surface of the solar cell 2 to be a light-receiving surface, for example, by screen printing, and then firing the paste. Further, the finger electrodes 12 are formed with a plurality of lines having a width of, for example, approximately 50 to 200 μm substantially in parallel at predetermined intervals, for example, every 2mm, over the entire surface of the light receiving surface. The bus bar electrodes 11 are formed substantially perpendicular to the finger electrodes 12, and a plurality of bus bar electrodes are formed according to the area of the solar battery cells 2.

In the photoelectric conversion element 10, a back electrode 13 made of aluminum or silver is provided on the back surface side opposite to the light receiving surface. As shown in fig. 2 and 3, the back surface electrode 13 is formed on the back surface of the solar cell 2 by, for example, screen printing, sputtering, or the like, using an electrode made of aluminum or silver. The rear surface electrode 13 has a tab wire connection portion 14 to which the tab wire 3 is connected via a conductive adhesive film 17 described later.

In the solar battery cells 2, the bus bar electrodes 11 formed on the front surfaces are electrically connected to the back surface electrodes 13 of the adjacent solar battery cells 2 via the tab wires 3, thereby forming strings 4 connected in series. The tab wire 3 is connected to the bus bar electrode 11 and the rear surface electrode 13 via a conductive adhesive film 17 described later.

[ Joint line ]

As shown in fig. 2, the tab wire 3 is a long conductive base material that electrically connects the adjacent solar battery cells 2X, 2Y, and 2Z. The tab wire 3 is obtained by cutting and rolling a copper foil or an aluminum foil having a thickness of 50 to 300 μm or a thin metal wire of copper, aluminum or the like into a flat plate shape, for example, to obtain a flat-angled copper wire having a width of 1 to 3mm substantially the same as the width of the conductive adhesive film 17. Then, the rectangular copper wire is subjected to gold plating, silver plating, tin plating, solder plating, or the like as necessary, thereby forming the tab wire 3.

[ concave-convex part ]

As shown in fig. 4, the tab wire 3 has a concave-convex portion 18 formed on a surface 3a thereof contacting the conductive adhesive film 17. The uneven portion 18 is formed by a concave portion and a convex portion irregularly formed over the entire surface of the one surface 3a of the tab wire 3, and is formed by extrusion molding of a copper foil in a ribbon shape subjected to plating treatment, etching (etching) of the one surface 3a, or the like.

In the tab wire 3, the average height H of the uneven portion 18 and the average particle diameter D of the conductive particles 23 of the conductive adhesive film 17 described later satisfy D ≧ H. The average height H of the uneven portion 18 is an average of heights from the apex of the concave portion 18b to the apex of the convex portion 18a, and is an average of heights measured at a plurality of places, for example, 10 places. The average height H of the uneven portion 18 can be in the range of 1 to 50 μm, and preferably in the range of 10 to 20 μm.

As shown in fig. 5, in the solar cell module 1, since the average height H of the uneven portion 18 of the tab wire 3 and the average particle diameter D of the conductive particles 23 of the conductive adhesive film 17 satisfy D ≧ H, the contact area with the bus bar electrode 11 and the back surface electrode 13 can be increased by the convex portion 18a of the uneven portion 18 and the conductive particles 23, and the contact resistance can be reduced.

[ peeling treatment ]

The tab wire 3 may have a release-treated layer 19 formed on the other surface 3b opposite to the one surface 3a on which the uneven portion 18 is formed. The release treated layer 19 can be formed by a known method, and for example, can be formed by surface-treating the other surface 3b of the tab wire 3 with a release treating agent such as silicone (silicone), long chain alkyl (alkyl), fluorine, or molybdenum sulfide.

The tab wire 3 is provided with the release treated layer 19 on the other surface 3b, so that the overlapping portion is not adhered even when wound into the wound body 20 as shown in fig. 6. Therefore, when the tab wire 3 is disposed on the bus bar electrode 11 and the back surface electrode 13, it can be smoothly fed out through the reel 21.

[ adhesive film ]

As shown in fig. 7, the conductive adhesive film 17 is a thermosetting adhesive resin layer containing spherical conductive particles 23 at a high density. In addition, the conductive adhesive film 17 preferably has a minimum melt viscosity of 100 to 100000Pa · s for the binder resin from the viewpoint of press-fitting property. When the minimum melt viscosity of the conductive adhesive film 17 is too low, the resin flows during the process from the temporary pressure bonding to the solid curing, which tends to cause poor connection and overflow to the cell light receiving surface, thereby causing a decrease in the light receiving rate. Even if the minimum melt viscosity is too high, a failure is likely to occur at the time of film bonding, and connection reliability may be adversely affected. The lowest melt viscosity can be measured by loading a predetermined amount of sample in a rotary viscometer and raising the temperature at a predetermined rate.

The spherical conductive particles 23 used in the conductive adhesive film 17 are not particularly limited, and examples thereof include metal particles such as nickel, gold, silver, and copper, conductive particles obtained by plating resin particles with gold, conductive particles obtained by insulating and coating the outermost layer of particles obtained by plating resin particles with gold, and the like. The spherical shape in the present invention is not limited to a so-called spherical shape, and includes all forms of the concept that metal particles and resin particles having a generally flat surface or a curved surface, such as a polyhedron, can have a particle diameter, in addition to a spherical shape having a substantially circular or elliptical cross section. The average particle diameter of the conductive particles 23 can be in the range of 1 to 50 μm, and preferably in the range of 10 to 30 μm.

The viscosity of the conductive adhesive film 17 at around room temperature is preferably 10 to 10000kPa · s, more preferably 10 to 5000kPa · s. By setting the viscosity of the conductive adhesive film 17 to be in the range of 10 to 10000kPa · s, when the conductive adhesive film 17 is provided on the one surface 3a of the tab wire 3 and wound around the reel 21, so-called blocking (blocking) due to the protrusion can be prevented, and a predetermined adhesion (tack) force can be maintained.

The composition of the adhesive resin layer of the conductive adhesive film 17 is not particularly limited as long as the above-described characteristics are not impaired, but more preferably contains a film-forming resin, a liquid epoxy resin (epoxy resin), a latent curing agent, and a silane coupling agent.

The film-forming resin corresponds to a high molecular weight resin having an average molecular weight of 10000 or more, and is preferably an average molecular weight of approximately 10000 to 80000 from the viewpoint of film formability. As the film-forming resin, various resins such as an epoxy resin, a modified epoxy resin, a urethane (urethane) resin, and a phenoxy (phenoxy) resin can be used, and among them, a phenoxy resin is particularly preferably used from the viewpoint of the film-forming state, connection reliability, and the like.

The liquid epoxy resin is not particularly limited as long as it has fluidity at room temperature, and any commercially available epoxy resin can be used. As such an epoxy resin, specifically, a naphthalene (naphthalene) type epoxy resin, a biphenyl (biphenyl) type epoxy resin, a phenol novolac (phenol novolac) type epoxy resin, a bisphenol (bisphenol) type epoxy resin, a stilbene (stilbene) type epoxy resin, a triphenolmethane (triphenolmethane) type epoxy resin, an aralkylphenol (phenol aralkyl) type epoxy resin, a naphthol (naphthol) type epoxy resin, a dicyclopentadiene (dicyclopentadiene) type epoxy resin, a triphenylmethane (triphenylmethane) type epoxy resin, and the like can be used. These may be used alone or in combination of two or more. In addition, the resin composition may be used in combination with other organic resins such as acrylic resin as appropriate.

As the latent curing agent, various curing agents such as a heat curing type and a UV curing type can be used. The latent curative is generally non-reactive and is activated to begin reaction upon some trigger (trigger). The trigger may be heat, light, pressure, or the like, and may be selected and used according to the application. In the present application, among them, a latent curing agent of a heat curing type is particularly preferably used, and the latent curing agent is cured by being pressed against the bus bar electrodes 11 and the back surface electrodes 13 by heating. When a liquid epoxy resin is used, a latent curing agent composed of an imidazole (imidazole), an amine (amine), a sulfonium (sulfonium) salt, an onium (onium) salt, or the like can be used.

As the silane coupling agent, epoxy, amino, mercapto, sulfide, ureide, and the like can be used. Among them, in the present embodiment, an epoxy silane coupling agent is particularly preferably used. This improves the adhesion at the interface between the organic material and the inorganic material.

In addition, as other additive composition, inorganic filler (filler) is preferably contained. By containing the inorganic filler, the fluidity of the resin layer at the time of pressure bonding can be adjusted, and the particle capturing ratio can be improved. As the inorganic filler, silica, talc, titanium oxide, calcium carbonate, magnesium oxide, and the like can be used, and the kind of the inorganic filler is not particularly limited.

Fig. 8 is a diagram schematically showing an example of a product form of the conductive adhesive film 17. The conductive adhesive film 17 is formed in a band shape by laminating a pressure-sensitive adhesive resin layer on a release substrate 24. The tape-shaped conductive adhesive film is wound around a reel 25 so that the peeling base 24 is positioned on the outer peripheral side. The release substrate 24 is not particularly limited, and PET (polyethylene Terephthalate), OPP (Oriented Polypropylene), PMP (Poly-4-methyl pentene-1), PTFE (Polytetrafluoroethylene), and the like can be used. The conductive adhesive film 17 may have a structure in which a transparent cover film (cover film) is provided on the adhesive resin layer.

In this case, the tab wire 3 may be used as a cover film to be attached to the adhesive resin layer. The conductive adhesive film 17 is formed by laminating a binder resin layer on the surface 3a of the tab wire 3 on which the uneven portion 18 is formed. In this manner, by laminating and integrating the tab wire 3 and the conductive adhesive film 17 in advance, the adhesive resin layer of the conductive adhesive film 17 is bonded to the tab wire connecting portion 14 of the bus bar electrode 11 and the back surface electrode 13 by peeling the peeling base 24 at the time of actual use, whereby the connection between the tab wire 3 and each of the electrodes 11 and 13 can be achieved.

Although the conductive adhesive film having a film shape has been described above, there is no problem even in the form of a paste. In the present application, the film-shaped conductive adhesive film 17 containing conductive particles or the paste-shaped conductive adhesive paste is defined as "conductive adhesive". When the conductive adhesive paste is used, the conductive adhesive paste may be applied to the surface 3a on which the uneven portion 18 is formed in advance in the tab wire 3, and the conductive adhesive may be attached to the electrodes 11 and 13 of the solar cell 2.

The conductive adhesive film 17 is not limited to a coil shape, and may be a rectangle shape according to the shape of the tab wire connection portion 14 of the bus bar electrode 11 and the back surface electrode 13.

When the reel product is provided as a reel product on which the conductive adhesive film 17 is wound as shown in fig. 8, the viscosity of the conductive adhesive film 17 is set to a range of 10 to 10000kPa · s, whereby the conductive adhesive film 17 can be prevented from being deformed and a predetermined size can be maintained. In addition, even when two or more conductive adhesive films 17 are stacked in a rectangular shape, deformation can be prevented in the same manner, and a predetermined size can be maintained.

In the conductive adhesive film 17, the conductive particles 23, the film-forming resin, the liquid epoxy resin, the latent curing agent, and the silane coupling agent are dissolved in a solvent. As the solvent, toluene (tolumen), ethyl acetate (acetic ether), or a mixed solvent thereof can be used. The resin generation solution obtained by dissolution is applied to a release sheet, and the solvent is volatilized, thereby obtaining the conductive adhesive film 17.

Then, the conductive adhesive film 17 is cut into two front electrodes and two back electrodes by a predetermined length, and is temporarily attached to predetermined positions on the front and back surfaces of the solar cell 2. At this time, the conductive adhesive film 17 is temporarily attached to the tab wire connection portion 14 in which the plurality of bus bar electrodes 11 and the plurality of back electrodes 13 are formed substantially parallel to the surface of the solar cell 2.

Next, the one surface 3a of the tab wire 3 cut to a predetermined length in the same manner is placed on the conductive adhesive film 17 in a superposed manner. Thereafter, the conductive adhesive film 17 is heated and pressurized from above the tab wire 3 at a predetermined temperature and pressure by a heating and bonding machine, whereby the binder resin flows out from between the electrodes 11 and 13 and the tab wire 3, and the conductive particles 23 are sandwiched between the tab wire 3 and the electrodes 11 and 13, and the binder resin is cured in this state. Thus, the conductive adhesive film 17 can bond the tab wire 3 to each electrode, and can bring the convex portion 18a of the concave-convex portion 18 into contact with the bus bar electrode 11 and the rear surface electrode 13 to perform electrical connection.

[ Effect of the invention ]

At this time, in the tab wire 3, since the average height H of the uneven portion 18 and the average particle diameter D of the conductive particles 23 dispersed in the binder resin layer of the conductive adhesive film 17 satisfy D ≧ H, the conductive particles 23 are held in the recessed portions 18b of the uneven portion 18 and are in contact with the bus bar electrode 11 and the back surface electrode 13. Therefore, in the tab wire 3, the contact area with the electrodes 11 and 13 of the solar battery cell 2 due to the convex portions 18a of the concave-convex portions 18 and the conductive particles 23 can be increased, and the on-resistance can be reduced.

In addition, since the conductive adhesive film 17 or the conductive adhesive paste is provided on the surface 3a on which the uneven portion 18 is formed in advance before the tab wire 3 is attached to the electrodes 11 and 13 of the solar cell 2, the step of temporarily attaching the conductive adhesive film 17 to the electrodes 11 and 13 is not required, and the number of manufacturing steps can be reduced.

That is, in the method of temporarily attaching the conductive adhesive film 17 to the electrodes 11 and 13, first, the conductive adhesive film 17 is cut according to the length of each of the electrodes 11 and 13, and is disposed on each of the electrodes 11 and 13, and the adhesive resin layer is temporarily cured by a heat bonder to such an extent that the adhesive resin layer exhibits fluidity without being actually cured, and temporarily attached. Next, the tab wire 3 is arranged on the conductive adhesive film 17, and is heated and pressed by a heating and bonding machine at a predetermined temperature, pressure, and time at which the adhesive resin layer is actually cured.

On the other hand, according to the method of laminating the conductive adhesive on the one surface 3a of the tab wire 3 in advance, the tab wire 3 may be arranged on the electrodes 11 and 13 via the conductive adhesive, and heated and pressed by a heating bonding tool, so that the man-hours in the step of connecting the tab wire 3 can be reduced.

Further, by forming the release treated layer 19 on the other surface 3b of the tab wire 3, the overlapping portion of the wound body 20 of the tab wire 3 wound around the reel 21 is not adhered, and the tab wire 3 can be smoothly fed out from the reel 21 when disposed on the bus bar electrode 11 and the back surface electrode 13.

[ Uniform lamination ]

In addition to the above-described method of disposing the conductive adhesive and the tab wire 3 on the electrodes 11 and 13 of the solar cell 2 and then thermally pressing the tab wire 3 with a heat bonder, the solar cell module 1 may be configured such that the conductive adhesive, the tab wire 3, and a light-transmitting sealing material such as EVA sealing the solar cell 2 are sequentially stacked on the front and back surfaces of the solar cell 2 and then the tab wire 3 is thermally pressed on the electrodes 11 and 13 by collectively performing a lamination process.

Examples

Next, an embodiment of the present invention will be explained. In the examples, as shown in table 1, four kinds of conductive adhesive films containing Ni or not containing conductive particles having different average particle diameters D were used as the conductive adhesives. As the tab wire, various tab wires having different average heights of the convex portions 18a of the concave-convex portions 18 or having no concave-convex portions are used. As shown in FIGS. 9 and 10, two samples 40 of each of these tab wires were connected to each other by thermally pressing two of the Ag electrodes 30 of the glass substrate 31 (thickness: 2.8mm, outer shape: 64 mm. times.28 mm, resistance: 7 m.OMEGA./□ (m.OMEGA./sq)) having the Ag electrode 30 formed on the entire surface thereof via each sample 41 of the conductive adhesive film.

The hot pressing conditions were all 180 ℃ for 15sec and 2 MPa. Further, a silicone rubber (silicon rubber) having a thickness of 200 μm was interposed between the tab wire and the heating bonder as a buffer material so that the pressure was uniformly applied.

After the completion of the sample preparation, the initial resistance value between the two tab wires 40 and the resistance value after the thermal shock test (85 ℃, 85% RH, 500 hr) were measured. The resistance value is measured by a four-terminal method in which a current terminal and a voltage terminal are connected to the two tab wires 40, respectively.

Further, the joint wire 40 used in each of the examples and comparative examples was wound around a reel to form a wound body (see fig. 6), and whether or not the drawing of each wound body was smoothly performed and the drawing characteristics were evaluated.

[ Table 1]

In example 1, the tab wire 3 in which the average height H of the uneven portion 18 formed on the one surface 3a was 10 μm and the release-treated layer 19 was provided on the other surface 3b was used. As the conductive adhesive, adhesive 1 in table 1, that is, conductive adhesive film 17 in which the average particle diameter D of Ni particles to be conductive particles 23 is 10 μm was used. The average height H of the concave-convex portion 18 and the average particle diameter D of the conductive particles 23 in example 1 are D ═ H.

In example 2, the same tab wire 3 as in example 1 was used as the tab wire. As the conductive adhesive, adhesive 2 in table 1, that is, conductive adhesive film 17 in which the average particle diameter D of Ni particles to be conductive particles 23 was 20 μm was used. The average height H of the uneven portion 18 and the average particle diameter D of the conductive particle 23 in example 2 were D > H.

In example 3, the same tab wire 3 as in example 1 was used as the tab wire. As the conductive adhesive, adhesive 3 in table 1, that is, conductive adhesive film 17 in which the average particle diameter D of Ni particles to be conductive particles 23 was 30 μm was used. The average height H of the uneven portion and the average particle diameter D of the conductive particles 23 in example 3 were D > H.

In example 4, the tab wire 3 in which the average height H of the uneven portion 18 formed on the one surface 3a was 20 μm and the release-treated layer 19 was provided on the other surface 3b was used. As the conductive adhesive, adhesive 2 in table 1, that is, conductive adhesive film 17 in which the average particle diameter D of Ni particles to be conductive particles 23 was 20 μm was used. The average height H of the concave-convex portion 18 and the average particle diameter D of the conductive particles 23 in example 4 are D ═ H.

In example 5, the same tab wire as in example 4 was used as the tab wire. As the conductive adhesive, adhesive 3 in table 1, that is, conductive adhesive film 17 in which the average particle diameter D of Ni particles to be conductive particles 23 was 30 μm was used. The average height H of the uneven portion 18 and the average particle diameter D of the conductive particles 23 in example 5 were D > H.

In example 6, the tab wire 3 in which the average height H of the uneven portion 18 formed on the one surface 3a was 10 μm and the release treated layer 19 was not provided on the other surface 3b was used. As the conductive adhesive, adhesive 1 in table 1, that is, conductive adhesive film 17 in which the average particle diameter D of Ni particles to be conductive particles 23 is 10 μm was used. The average height H of the concave-convex portion 18 and the average particle diameter D of the conductive particles in example 6 are D ═ H.

In comparative example 1, a tab wire having no uneven portion (H ═ 0) formed on one surface and a release-treated layer provided on the other surface was used. As the conductive adhesive, adhesive 1 in table 1, that is, conductive adhesive film 17 in which the average particle diameter D of Ni particles to be conductive particles 23 is 10 μm was used. The average height H of the uneven portion and the average particle diameter D of the conductive particles 23 in comparative example 1 were D > H.

In comparative example 2, the same tab wire 3 as in example 1 was used as the tab wire. As the conductive adhesive, the adhesive 4 in table 1, that is, an insulating adhesive film containing no conductive particles 23 was used.

In comparative example 3, the same tab wire 3 as in example 4 was used as the tab wire. As the conductive adhesive, adhesive 1 in table 1, that is, conductive adhesive film 17 in which the average particle diameter D of Ni particles to be conductive particles 23 is 10 μm was used. The average height H of the uneven portion 18 and the average particle diameter D of the conductive particle 23 in comparative example 1 are D < H.

Table 2 shows the initial resistance values of the respective samples, the resistance values after the thermal shock test (85 ℃, 85% RH, 500 hr), and the evaluation of the drawing characteristics of the wound body of the tab wire used in the respective samples.

[ Table 2]

As shown in table 2, in each example, the connection resistance between the tab wire and the Ag electrode 30 was low in both the initial value and the value after the thermal shock test, and the drawing characteristics of the wound body of the tab wire were also good, and there was no problem in practical use. This is because the average height H of the uneven portion 18 of the tab wire 3 and the average particle diameter D of the Ni particles of the conductive adhesive film 17 satisfy D ≧ H, and therefore, the Ni particles are held in the concave portion 18b of the uneven portion 18 and come into contact with the Ag electrode 30. Therefore, in the tab wire 3 of each example, the contact area with the Ag electrode 30 due to the convex portion 18a of the concave-convex portion 18 and the Ni particles is increased, and the on-resistance can be reduced.

In particular, when the average height H of the uneven portion 18 of the tab wire 3 is equal to the average particle diameter D of the Ni particles of the conductive adhesive film 17 (D ═ H) (examples 1, 4, and 6), the connection resistance is suppressed to be low, which is preferable.

Further, according to the examples, it is understood that the average particle diameter (D) of the conductive particles 23 (Ni particles) can be suitably used in the range of 10 to 30 μm. Further, according to the respective embodiments, it is understood that the average height H of the concave and convex portions 18 of the tab wire 3 can be suitably used in the range of 10 to 20 μm.

In comparative example 1, since no uneven portion was provided on the tab wire, the initial value of the connection resistance with the Ag electrode 30 was high, and the value after the thermal shock test was also large, which was problematic in practical use. In comparative example 2, since the insulating adhesive film was used for connecting the tab wire 3 and the Ag electrode 30, the initial value of the connection resistance and the value after the thermal shock test could not be measured, and thus, the connector could not be used in practical applications. In comparative example 3, since the average particle diameter D of the Ni particles was smaller than the average height H of the uneven portion of the tab wire, the Ni particles were not sandwiched between the concave portion of the tab wire and the Ag electrode and did not contribute to the conduction, and therefore, the connection resistance after the thermal shock test was increased greatly, which was a practical problem.

Description of the reference numerals

1: a solar cell module;

2: a solar cell unit;

3: a joint line;

4: stringing;

5: a matrix;

6: a sheet material;

7: a surface cover;

8: a back sheet;

9: a metal frame;

10: a photoelectric conversion element;

11: a bus electrode;

12: a finger electrode;

13: a back electrode;

14: a joint line connecting portion;

17: a conductive adhesive film;

18: a concave-convex portion;

19: stripping the treatment layer;

20: a wound body;

21: coiling;

23: conductive particles;

24: stripping the substrate;

25: coiling;

30: an Ag electrode;

31: a glass substrate.

Claims (15)

1. A solar cell module is provided with:

a plurality of solar cells; and

a tab wire connected to the electrodes formed on the front surface of the solar cell and the back surface of the adjacent solar cell via a conductive adhesive containing spherical conductive particles to connect the plurality of solar cells to each other,

in the tab wire, a surface in contact with the conductive adhesive is formed with a concavo-convex portion, and an average height (H) of the concavo-convex portion and an average particle diameter (D) of the conductive particles satisfy that the average particle diameter (D) of the conductive particles is not less than the average height (H) of the concavo-convex portion.

2. The solar cell module of claim 1,

the conductive adhesive is integrally formed in advance on the surface on which the uneven portion is formed before the tab wire is disposed on the front surface electrode and the rear surface electrode.

3. The solar cell module of claim 2,

the tab wire has a release-treated layer formed on the other surface on which the uneven portion is not formed.

4. The solar cell module according to any one of claims 1 to 3,

the conductive particles have an average particle diameter (D) of 10 to 30 μm,

the average height (H) of the uneven portion is 10 to 20 μm.

5. The solar cell module according to any one of claims 1 to 4,

the conductive particles are Ni.

6. A method for manufacturing a solar cell module includes:

disposing one end side of a tab wire on a front surface electrode of a solar cell via a conductive adhesive containing spherical conductive particles, and disposing the other end side of the tab wire on a back surface electrode of a solar cell adjacent to the solar cell via a conductive adhesive containing conductive particles; and

a step of thermally pressing the tab wire to the front surface electrode and the back surface electrode and connecting the tab wire to the front surface electrode and the back surface electrode via the conductive adhesive,

in the tab wire, a surface in contact with the conductive adhesive is formed with a concavo-convex portion, and an average height (H) of the concavo-convex portion and an average particle diameter (D) of the conductive particles satisfy that the average particle diameter (D) of the conductive particles is not less than the average height (H) of the concavo-convex portion.

7. The method for manufacturing a solar cell module according to claim 6,

the conductive adhesive is integrally formed in advance on the surface on which the uneven portion is formed, before the step of disposing the tab wire on the front surface electrode and the back surface electrode.

8. The method for manufacturing a solar cell module according to claim 6 or claim 7,

the tab wire is wound in a coil shape before the step of disposing the tab wire on the front surface electrode and the back surface electrode.

9. The method for manufacturing a solar cell module according to any one of claims 6 to 8,

the conductive particles have an average particle diameter (D) of 10 to 30 μm,

the average height (H) of the uneven portion is 10 to 20 μm.

10. The method for manufacturing a solar cell module according to any one of claims 6 to 9,

the conductive particles are Ni.

11. A wound body on a reel, wherein a tab wire is wound around the reel, the tab wire being connected to electrodes formed on the front surface of a solar cell and the back surface of an adjacent solar cell via a conductive adhesive containing spherical conductive particles, and the plurality of solar cells are connected to each other,

in the tab wire, a surface in contact with the conductive adhesive is formed with a concavo-convex portion, and an average height (H) of the concavo-convex portion and an average particle diameter (D) of the conductive particles satisfy that the average particle diameter (D) of the conductive particles is not less than the average height (H) of the concavo-convex portion.

12. The reel package according to claim 11,

in the tab wire, the conductive adhesive is integrally formed in advance on a surface on which the uneven portion is formed.

13. The reel package according to claim 11 or claim 12,

in the tab wire, a release treated layer is formed on the other surface on which the uneven portion is not formed.

14. The reel package according to any one of claims 11 to 13,

the conductive particles have an average particle diameter (D) of 10 to 30 μm,

the average height (H) of the uneven portion is 10 to 20 μm.

15. The reel package according to any one of claim 11 to claim 14,

the conductive particles are Ni.