Method of manufacturing solar cell module

An aspect of the invention is a method of manufacturing a solar cell module in which wiring members are electrically connected to front and back electrodes on front and back sides of a solar cell with resin adhesion films. The total area of the front electrode is smaller than that of the back electrode. The method includes: arranging the resin adhesion films on the front and back electrodes; arranging a first cushion sheet and a lower press member below the lower resin adhesion film and arranging a second cushion sheet being thicker than the first cushion sheet and an upper press member above the upper resin adhesion film; pressing the press members against each other thereby bonding the resin adhesion films to the solar cell; and releasing the pressure to the press members and moving the first and second cushion sheets away from the solar cell.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to a method of manufacturing a solar cell module including a solar cell string in which wiring members are connected to solar cells by using resin adhesion films.

2. Description of Related Art

Solar cells are expected as a new energy source because they can directly convert clean and inexhaustible sunlight into electricity.

In general, the output power per solar cell is about several watts. For this reason, when such a solar cell is used as a power supply for a house, a building or the like, a solar cell module having multiple solar cells connected to one another to increase the output power thereof is used. A solar cell module includes a solar cell string having multiple solar cells electrically connected to one another with wiring members.

As a method of connecting a wiring member to a solar cell, a method using a resin adhesion film is known (see Patent Document 1, for example). As this conventional technique, there is described a technique of preventing cracks of a solar cell which may otherwise be generated if front and back electrodes thereof are displaced from each other.Patent Document 1: Japanese Patent Application Publication No. 2008-235354

SUMMARY OF THE INVENTION

However, when a solar cell string is manufactured using the above conventional technique, a manufacturing yield is reduced in some cases.

An embodiment of the invention is made in view of the above circumstances, and aims to provide a method of manufacturing a solar cell module with a good yield.

An aspect of the invention relates to a method of manufacturing a solar cell module in which wiring members are electrically connected to electrodes provided on front and back sides of a solar cell by use of resin adhesion films. The electrodes are provided on front and back sides of a substrate of the solar cell respectively. The total area of the electrode on the front surface is smaller than the total area of the electrode on the back surface. The method includes: arranging resin adhesion films on the front and back electrodes, respectively; arranging a first cushion sheet and a lower press member below the lower resin adhesion film in this order and arranging a second cushion sheet and an upper press member above the upper resin adhesion film in this order, the second cushion sheet being thicker than the first cushion sheet; and sticking the resin adhesion films on the front and back electrodes of the solar cell respectively by applying pressure to the lower press member and the upper press member in directions opposed to each other and thereby pressure-bonding the resin adhesion films to the front and back electrodes of the solar cell, and by releasing the pressure to the upper and lower press members to move the members away from each other and moving the first and second cushion sheets away from the resin adhesion films.

According to the aspect of the invention, resin adhesion films can be bonded to front and back electrodes of a solar cell with good adhesion.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention are described in detail with reference to the drawings. Note that the same or equivalent parts in the drawings are given the same reference numerals and are not described again for avoiding duplicate description.

FIG. 1is a cross-sectional view schematically showing a solar cell module according to a first embodiment.FIG. 2is a side view showing a step of bonding conductive resin adhesion films according to the first embodiment.FIG. 3is a schematic cross-sectional view showing a magnified main part of the step of bonding conductive resin adhesion films according to the first embodiment.FIG. 4is a schematic cross-sectional view showing a conductive resin adhesion film used in the first embodiment.

An anisotropic conductive resin adhesion film is used as a resin adhesion film of the first embodiment, for example. As shown in the schematic cross-sectional view ofFIG. 4, conductive resin adhesion film5at least includes resin adhesion component5cand conductive particles5bdispersed in resin adhesion component5c. This resin adhesion component5chaving conductive particles5bdispersed therein is provided on base film5dmade of PET (Polyethylene terephthalate) or the like. Resin adhesion component5cis made of a constituent containing a thermosetting resin such as an epoxy resin, a phenoxy resin, an acrylic resin, a polyimide resin, a polyamide resin, and a polycarbonate resin. One or more of these thermosetting resins are used singularly or in combination. It is preferable to use one or more thermosetting resins selected from a group consisting of an epoxy resin, a phenoxy resin, and an acrylic resin.

Conductive particles used as conductive particles5bare metal particles such as gold particles, silver particles, copper particles, or nickel particles, or plated particles such as gold-plated particles, copper-plated particles, or nickel-plated particles which are each formed by covering a surface of a conductive or insulating core particle with a conductive layer such as a metal layer.

In this embodiment, PET is used as base film5d. Resin adhesion layer5aformed of resin adhesion component5cand conductive particles5bis provided on base film5d. The thickness of resin adhesion layer5ais about 0.02 mm.

First of all, solar cell module100manufactured according to the first embodiment is described with reference toFIG. 1.

Solar cell module100includes multiple plate-shaped solar cells1. For example, each solar cell1is formed of a crystalline semiconductor substrate made of monocrystalline silicon, polycrystalline silicon, or the like of about 0.15 mm in thickness, and is shaped like substantially a square having a side of 104 mm or 125 mm. However, solar cell1is not limited to the above, but another solar cell may also be used as solar cell1.

For example, an n-type region and a p-type region are formed in solar cell1so that an interface between the n-type region and the p-type region functions as a junction to form an electric field for isolating carriers. Each of the n-type region and the p-type region may be formed by using, singularly or in combination, semiconductor substrates used for solar cells, such as monocrystalline silicon, polycrystalline silicon, and compound semiconductors including GaAs and InP. An example of a solar cell is one including an intrinsic amorphous silicon layer between a monocrystalline silicon substrate and an amorphous silicon layer having opposite conductivities. This configuration makes it possible to reduce defects at the interface between the monocrystalline silicon substrate and the amorphous silicon layer and improve characteristics of the heterojunction interface.

As shown in a schematic cross-sectional view ofFIG. 6and a plan view ofFIG. 7, electrodes11,12are formed in predetermined regions of front and back sides of solar cell1. These electrodes11,12are electrodes for collecting carriers generated by a photoelectric conversion body of solar cell1. Electrodes11,12include multiple fine line-shaped electrodes11a,12aformed parallel with one another, for example. For example, fine line-shaped electrodes11aon the front surface of solar cell1each have a width of about 100 μm and a thickness of about 60 μm, and about 50 fine line-shaped electrodes11aare formed on the front surface of the substrate at an interval of about 2 mm. On the other hand, fine line-shaped electrodes12aon the back surface thereof each have a width of about 100 μm and a thickness of about 10 μm, and about 240 fine line-shaped electrodes12aare formed on the back surface of the substrate at an interval of about 0.5 mm. These fine line-shaped electrodes11a,12aare formed by screen-printing silver paste and then curing the silver paste at a temperature of a hundred and several tens of degrees, for example. Note that electrodes11,12may include bus bar electrodes in the form of polygonal lines having the same thickness and width as the fine line-shaped electrodes.

As described previously, the number of fine line-shaped electrodes11aof electrode11on the front surface is made smaller than the number of fine line-shaped electrodes12aof electrode12on the back surface for the purpose of increasing the amount of light to be incident on the light-receiving surface of solar cell1. Further, the thickness of each fine line-shaped electrode11aon the front surface is made larger than the thickness of each fine line-shaped electrode12aon the back surface. Thereby, the resistance of electrode11on the front surface is made small, improving the characteristics of the solar cell.

Wiring members120are electrically connected to electrodes11,12. Conductive resin adhesion films5are used to connect wiring members120to electrodes11,12. Conductive resin adhesion films5are pressure-bonded to positions of solar cell1where wiring members120are to be bonded. These conductive resin adhesion films5to be pressure-bonded each have a width which is the same as or slightly smaller than the width of each wiring member120to be connected. For example, if the width of wiring member120is in the range of 0.5 mm to 3 mm, the width of conductive resin adhesion film5is set equal to or smaller than the width of wiring member120within the range of the width of wiring member120, i.e., 0.5 mm to 3 mm. In this embodiment, as shown inFIG. 7, three adhesion resin film layers5aare bonded on each of the front and back sides of solar cell1at positions where wiring members120are to be bonded. Wiring members120are bonded to solar cell1in such a way that resin adhesion films5are respectively arranged on the front and back sides of solar cell1and then pressure is applied to press members in directions opposed to each other. As described previously, the number of fine line-shaped electrodes11aon the front surface of solar cell1is smaller than the number of fine line-shaped electrodes12aon the back surface thereof. For this reason, pressure to be applied to resin adhesion film5on the front surface and pressure to be applied to resin adhesion film5on the back surface when the pressure is applied to the press members in the directions opposed to each other are different. Thus, the inventors of this application have keenly examined a method of bonding resin adhesion films5on the front and back sides of solar cell1and have found a method by which the films can be bonded in good condition. This bonding method is described later.

Wiring members120are connected to electrodes11,12by applying a heat treatment while pressing wiring members120against conductive adhesion films5and thereby thermally curing the adhesion layers of conductive resin adhesion films5.

Note that an example where electrode12on the back surface is formed of fine line-shaped electrodes12ais described in the above description; however, in the case of using a solar cell module of a structure receiving no light on the back surface thereof, a solar cell module of a structure where a metal electrode is provided on the entire back surface is employed.

As shown in the plan views ofFIGS. 1 and 9, each of multiple solar cells1is electrically connected to another adjacent solar cell1with wiring members120made of flat copper foil or the like. Specifically, one end of each wiring member120is connected to electrode11on the upper surface of one of solar cells1whereas the other end is connected to electrode12on the lower surface of another solar cell1adjacent to the one of solar cells1. Solar cell module100has a configuration such that solar cells1are connected in series with wiring members120and a certain output, e.g., an output of 200 W is taken out from solar cell module100to the outside through an output electrode.

As shown inFIG. 1, solar cell string100ais formed by electrically connecting multiple solar cells1to one another with wiring members120made of a conductive material such as copper foil. Solar cell string100ais sealed between translucent or transparent front-surface member41such as glass or translucent or transparent plastic and back-surface member42made of a member such as weather-resistant film, glass, or plastic, with sealing material43such as EVA (ethylene vinylacetate) excellent in weather resistance and humidity resistance.

According to need, solar cell module100described above is fitted in an outer frame (not illustrated) made of aluminum or the like by applying a sealing member to the outer periphery of the module. The outer frame is formed of aluminum, stainless steel, a steel-sheet roll-forming material, or the like. If needed, a terminal box (not illustrated) is provided to the front surface of back-surface member42, for example.

In order to electrically connect wiring members120to solar cells1described above with resin adhesion layers5a, as shown inFIGS. 2 and 3, adhesion films5are first arranged on front and back electrodes11,12of each solar cell1, and then pressure is applied to lower press member61and upper press member62in directions opposed to each other. To apply pressure evenly, first cushion sheet63is disposed between lower press member61and adhesion film5and second cushion sheet64is disposed between upper press member62and adhesion film5. Adhesion films5are pressed against electrodes11,12through first and second cushion sheets63,64.

Resin adhesion layers5aare bonded on front and back electrodes11,12of solar cell1by pressure-bonding conductive adhesion films5on electrodes11,12respectively and then detaching base film5dfrom each resin adhesion layer5a. A resin adhesive used as a resin adhesion component of conductive resin adhesion layer5ais one containing a cross-linking accelerator including mainly an epoxy resin and formulated to rapidly accelerate cross-linkage by a heating process at a temperature of 180° C. and complete curing in approximately 15 seconds. The thickness of conductive resin adhesion film layer5is 0.01 mm to 0.05 mm. The width thereof is preferably the same as or smaller than the width of wiring member120in view of blockage of incident light. Conductive resin adhesion film5used in this embodiment is formed in a strip-shaped film sheet having a width of 1.5 mm and a thickness of 0.02 mm.

As described above, the number of fine line-shaped electrodes11aon the front surface of solar cell1is smaller than the number of fine line-shaped electrodes12aon the back surface thereof. For this reason, as shown inFIG. 10, when the pressure is applied to the press members in the directions opposed to each other, the total contact surface area of electrode11and resin adhesion layer5aprovided on the front surface side of solar cell1differs from the total contact surface area of electrode12and resin adhesion layer5aprovided on the back surface side of solar cell1.

The difference in the total contact surface area makes pressure application uneven so that the resin adhesion film having a smaller contact surface area receives more pressure. If the pressure is applied to the electrode12in a concentrated manner, there is a drawback that resin adhesion layer5ain the electrode11is broken as shown in a x part, causing bonding failure.

Further, to apply pressure evenly, first cushion sheet63is disposed between lower press member61and adhesion film5and second cushion sheet64is disposed between upper press member62and adhesion film5. However, because the number of fine line-shaped electrodes11aon the front surface differs from the number of fine line-shaped electrodes12aon the back surface, the total surface area in which cushion sheet63contacts the electrode differs from the total surface area in which cushion sheet64contacts the electrode.

Because the number of electrodes11on the front surface is smaller, the area in which cushion sheet64contact electrode11is smaller than the area in which cushion sheet63contacts electrode12on the back surface. Since the pressure is applied to press members61,62in the directions opposed to each other, the pressure applied to each fine line-shaped electrode11aon the front surface is larger than each fine line-shaped electrode12aon the front surface if cushion sheets63,64are of the same material and thickness. This pressure difference sometimes causes adhesion film5on the front surface side to be partially pressure-bonded to fine line-shaped electrodes11aand produces a portion where resin adhesion layer5ais thin. If such a thin portion exists in resin adhesion layer5a, there may be a case where resin adhesion layer5aat this portion is broken when base film5dis detached, and is exfoliated from fine line-shaped electrode11atogether with base film5dwithout being detached from base film5d, thus causing bonding failure of resin adhesion layer5aas shown in the x part ofFIG. 10.

To cope with this, the inventors of this application have examined the thickness of cushion sheets63,64so that the pressure can be applied to fine line-shaped electrodes11aevenly, and thus have found the way to solve this bonding failure.

Using a silicone rubber sheet as each of first and second cushion sheets63,64, the condition of how resin adhesion layer5ais bonded to front and back electrodes11,12of solar cell1is checked as the thickness of each of these silicone rubber sheets is changed.

Solar cell1used in this embodiment is formed of a crystalline semiconductor substrate made of monocrystalline silicon having a thickness of 0.15 mm, and is shaped like substantially a square having a side of 125 mm. Electrodes11,12are formed in predetermined regions of front and back sides of solar cell1. Electrodes11,12include multiple fine line-shaped electrodes11a,12aformed parallel with one another, for example. For example, about 50 fine line-shaped electrodes11aare formed on the front surface of the substrate at a pitch of about 2 mm, and each fine line-shaped electrode11aon the front surface of solar cell1has a width of about 100 μm and a thickness of about 60 μm. On the other hand, about 240 fine line-shaped electrodes12aare formed on the back surface of the substrate at a pitch of about 0.5 mm, and each fine line-shaped electrode12aon the back surface thereof has a width of about 100 μm and a thickness of about 10 μm.

Resin adhesion films5are arranged on front and back electrodes11,12of solar cell1described above. Then, first cushion sheet63made of a silicone rubber sheet and lower press member61are arranged below lower resin adhesion film5in this order, and second cushion sheet64made of a silicone rubber sheet and upper press member62are arranged above upper resin adhesion film5in this order. Pressure is applied to lower press member61and upper press member62in directions opposed to each other, and thereby resin adhesion films5are pressure-bonded to front and back electrodes11,12of solar cell1. Here, lower press member61and upper press member62pinch these components with a pressure of 0.50 MPa.

Four types of silicone rubber sheets of 200 μm, 300 μm, 400 μm, and 450 μm thicknesses are prepared. The first and second cushion sheets are pinched and pressed between lower press member61and upper press member62, using a silicone rubber sheet of 200 μm thickness as first cushion sheet63and a silicone rubber sheet of 200 μm, 300 μm, 400 μm, or 450 μm thickness as second cushion sheet64. Table 1 shows this result.

When silicone rubber sheets of the same thickness are used as first and second cushion sheets63,64on the upper and lower sides, the pressure applied on fine line-shaped electrodes11aof upper electrode11is larger, causing bonding failure of resin adhesion layer5a. On the other hand, when upper second cushion sheet64having a thickness of 300 μm, 400 μm, or 450 μm is employed, i.e., when the thickness of second cushion sheet64is larger than the thickness of lower first cushion sheet63(200 μm), second cushion sheet62is bent or deformed more than first cushion sheet63and follows the shape of the front surface of solar cell1. Hence, it is possible to apply the pressure to fine line-shaped electrodes11aevenly and prevent the concentration of the pressure. As a result, it can be confirmed that resin adhesion layers5aare reliably bonded to front and back electrodes11,12of solar cell1.

As described above, making the thickness of upper second cushion sheet64larger than the thickness of lower first cushion sheet63causes second cushion sheet64to follow the shape of the front surface of solar cell1, and thereby makes it possible to apply the pressure to fine line-shaped electrodes11aevenly and reliably bond resin adhesion layers5ato front and back electrodes11,12of solar cell1. The thickness of upper second cushion sheet64is preferably 1.2 times or larger than, or more preferably 1.5 times or larger than the thickness of lower first cushion sheet63. Because too thick cushion sheet64increases the material ratio of the cushion sheets, the thickness of cushion sheet64is preferably 1.5 times or larger than and 2.5 times or smaller than the thickness of cushion sheet63.

In addition, although a silicone rubber sheet is used in the above embodiment, the same effect can be obtained by using another elastic sheet.

Further, although electrodes11,12are formed using silver paste, electrodes11,12formed by plating or the like also bring about the same effect.

Next, a description is given of a method of bonding wiring members120to solar cell1on which conductive resin adhesion films5are bonded.

Wiring members120are placed on conductive resin adhesion layers5a,5awhich are bonded to the front and back sides of solar cell1. Then, as shown inFIG. 8, wiring members120are pressure-bonded to and fixed provisionally on electrodes11,12. In the step of provisionally fixing wiring members120, for example, heater blocks80,80are pressed with a pressure of about 0.5 MPa to press wiring members120,120toward solar cell1. Thereafter, wiring members120are provisionally fixed by heating heater blocks80,80to a low temperature such that the resin adhesion component would not be thermally cured, e.g., to a temperature of approximately 90° C. After that, solar cells1on which wiring members120are provisionally fixed are aligned to form a string. Solar cells1on which wiring members120are provisionally fixed are then conveyed in sequence by conveyer82.

Subsequently, the string in which wiring members120are provisionally fixed is heated while the wiring members are pressed toward solar cells1again, thereby curing the resin adhesion component and fully pressure-bonding wiring members120to solar cells1.

The string in which multiple solar cells1are connected to one another with wiring members120is sandwiched between front-surface member41made of glass and back-surface member42made of a material such as weather-resistant film, glass, or transparent plastic via translucent or transparent sealing-material sheets43a,43bsuch as EVA. Then, solar cells1are sealed between front-surface member41and back-surface member42by a laminating device by use of the sealing-material sheets. Thereafter, the string thus sealed is put in a furnace and heated at a temperature of approximately 150° C. for about 10 minutes. This accelerates the cross-linking reaction and enhances the adhesion between sealing material43(sealing-material sheets) and front- and back-surface members41,42. As a result, the solar cell module as shown inFIG. 1is manufactured.

Note that, the above embodiment describes an example where three wiring members120arranged on each solar cell1are used to connect solar cells1to each other. However, the number of wiring members120is not limited to three. The invention is applicable to any case where wiring members120are arranged on front and back sides of solar cell1irrespective of the number of wiring members120.

With reference toFIGS. 19 and 20, a description is given of an example of a method of connecting wiring members to electrodes of a solar cell by use of conductive resin adhesion films as a resin adhesive.

First, resin adhesion layers5a,5aare bonded on electrodes11,12of solar cell1by pressure-bonding conductive resin adhesion films5on electrodes11,12respectively and then detaching the base film from the resin adhesion layer5aof each adhesion film5. Then, as shown inFIG. 19, while wiring members120,120are arranged above and below solar cell1on which resin adhesion layers5a,5aare bonded, heater blocks40,40press them to press wiring members120toward solar cell1. Thereafter, wiring members120are provisionally fixed on solar cell1by heating heater blocks40,40to a temperature such that the resin adhesion component of resin adhesion layer5awould not be thermally cured and such that solar cells1,1are aligned.

After that, the process proceeds to the step of fully pressure-bonding wiring members120. Specifically, as shown inFIG. 20, solar cells1,1on which wiring members120are provisionally pressure-bonded are pressed with high temperature and high pressure by heater blocks40,40. Here, sheets70,71having a releasing function are placed between heater blocks40and provisionally-bonded solar cells1,1. Wiring members120are pressed toward solar cell1by using heater blocks40,40heated to a temperature high enough to thermally cure the resin adhesion component or higher. Thereby, the resin adhesion component is thermally cured, and electrodes11,12of solar cell1and wiring members120are connected with resin adhesion layers5a, thus forming a solar cell string. A sheet made of PTFE (polytetrafluoroethylene) may be used as sheets70,71.

Next, a second embodiment is described. A solar cell and a solar cell module according to the second embodiment are the same or similar to as solar cell1and solar cell module100according to the first embodiment.

In the second embodiment, multiple solar cells1described above are electrically connected to one another with wiring members120made of a conductive material such as flat copper foil by use of conductive resin adhesion layers5aas a resin adhesive. To this end, as shown inFIGS. 11 and 12, conductive resin adhesion layers5aare first bonded on each of front and back electrodes11,12of solar cell1at positions where wiring members120are to be connected. More specifically, conductive resin adhesion layers5aare bonded to cover all multiple fine line-shaped electrodes11a,12a. An anisotropic conductive adhesion film is used as conductive resin adhesion layers5a. The thickness of each conductive resin adhesion layer5ais 0.01 mm to 0.05 mm. The width thereof is preferably the same as or smaller than the width of wiring member120in view of blockage of incident light. The anisotropic conductive adhesion film used in this embodiment is formed in a strip-shaped film sheet having a width of 1.5 mm and a thickness of about 0.02 mm.

As shown inFIG. 13, each of multiple solar cells1is electrically connected to another adjacent solar cell1with wiring members120. Specifically, wiring members120are arranged on conductive resin adhesion layers5a,5abonded on each of the front and back sides of solar cell1, in such a way that one end of each wiring member120is connected to electrode11on the upper surface of one of solar cells1whereas the other end is connected to electrode12on the lower surface of another solar cell1adjacent to the one solar cell1. Then, as shown inFIG. 14, wiring members120are pressure-bonded to conductive resin layers5a,5aand provisionally fixed on electrodes11,12. In the step of provisionally fixing wiring members120, for example, heater blocks80,80are pressed with a pressure of about 0.5 MPa to press wiring members120,120toward solar cell1. Thereafter, wiring members120are provisionally fixed by heating heater blocks80,80to a low temperature such that the resin adhesion component would not be thermally cured, e.g., to a temperature of approximately 90° C. After that, solar cells1,1on which wiring members120are provisionally fixed are aligned to form a string. Solar cells1on which wiring members120are provisionally fixed are then conveyed in sequence by conveyer82.

Here, any suitable method may be used for the pressure-bonding and heating according to situations, including a method in which a metal block incorporating therein a heater is pressed with a certain pressure and heated to a certain temperature and a method in which a press member such as a press pin and blowing hot air are used to press with a certain pressure and heat to a certain temperature, for example.

Subsequently, a step of fully pressure-bonding wiring members120is carried out. The full pressure-bonding step is described with reference toFIGS. 15 to 18. In the step of fully pressure-bonding and fixing wiring members120, as shown in FIGS.15and16, provisionally-fixed solar cell string100ais conveyed on conveyer belt60to a position between upper heater blocks40aand lower heater blocks40bserving as a press member carrying out the pressure-bonding step. Conveyer belt60has slits61at positions opposed to wiring members120. Lower silicone rubber sheets75bas a second cushion sheet and lower heater blocks40bare disposed facing these slits61. Moreover, upper silicone rubber sheets75aas a first cushion sheet are disposed between solar cell string100aand upper heater blocks40a. At the time of pressing, lower silicone rubber sheets75band lower heat blocks40bare inserted into slits61. When the full pressure-bonding step is carried out, upper heater blocks40aand lower heater blocks40bmove in directions indicated by the arrows A to apply pressure to solar cell1with silicone rubber sheets75a,75binterposed therebetween.

In this embodiment, silicone rubber sheets75a,75bof the same material are interposed between upper heater blocks40aand wiring members120and between lower heater blocks40band wiring members120. Since silicone rubber sheets75a,75bhave cushioning properties, they are used to absorb an influence of unevenness caused by electrodes11,12, for example, achieving even application of pressure. Further, since silicone rubber sheets75a,75bhave cushioning properties, the breakage of solar cell11during the step can also be suppressed.

When provisionally-fixed solar cell string100ais conveyed toward a position between upper and lower heater blocks40a,40b, upper and lower heater blocks40a,40bare moved away from solar cell1, as shown inFIG. 16. Likewise, silicone rubber sheets75a,75bare also moved away from solar cell1.

Once solar cell1and wiring members120to be fully pressure-bonded and fixed arrive at the position between upper and lower heater blocks40a,40b, upper and lower heater blocks40a,40bmove in the directions indicated by the arrows A shown inFIG. 16to pressure-bond wiring members120and solar cell1with silicone rubber sheets75a,75binterposed therebetween. Then, as shown inFIG. 17, upper and lower heater blocks40a,40bpress wiring members120and solar cell1with silicone rubber sheets75a,75binterposed therebetween, with a pressure larger than that in the provisional pressure-bonding step, e.g., with a pressure of about 5 MPa, to press wiring members120,120toward solar cell1. In this event, lower heater blocks40band silicone rubber sheets75blocated closer to conveyer belt60protrude toward solar cell1through slits61in conveyer belt60to press wiring members120and solar cell1. Thereafter, wiring members120are fully pressure-bonded and fixed by heating upper and lower heater blocks40a,40bto a temperature high enough to thermally cure the resin adhesion component, e.g., to a temperature equal to or higher than 120° C. and equal to or lower than 200° C. Thereby, solar cells1on which wiring members120are fixed with thermally-cured resin adhesion layers5are electrically connected and aligned.

After the full pressure-bonding step is over, upper and lower heater blocks40a,40bmove away from solar cell1by moving in directions indicated by the arrows B. In this event, silicone rubber sheets75a,75balso move in directions away from solar cell1.

In the full pressure-bonding step described above, upper and lower silicone rubber sheets75a,75bstick to the front and back surfaces of solar cell1with a certain force. Owing to this, when upper and lower heater blocks40a,40bmove in the directions indicated by the arrows B shown inFIG. 18to move away from solar cell1, a force occurs on the upper side of solar cell1and a force occurs on the lower side of solar cell1balance out. This prevents solar cell string100afrom being lifted upward.

Here, if solar cell string100ais lifted upward as shown inFIG. 21, this causes failure such as bending of wiring member120and connection failure of wiring member120.

In the meantime, in the case of the technique shown inFIG. 20, sheets70,71having a releasing function, such as a sheet made of PTFE (polytetrafluoroethylene), are placed between heater blocks40and provisionally-bonded solar cells1,1. The sheets made of such a material do not have enough cushioning properties and thus may cause the breakage of solar cell1in the full pressure-bonding step.

Accordingly, the second embodiment described above makes it possible to suppress the breakage of solar cell1and prevent solar cell1from being lifted upward after the full pressure-bonding step, and thereby to improve the manufacturing yield of a solar cell module.

As described previously, the sheets placed between heater blocks40a,40band solar cell1preferably have cushioning properties in order to suppress the breakage of solar cell during the full pressure-bonding step. In addition, in order to prevent solar cell from being lifted upward after the full pressure-bonding step, sheet75bprovided below solar cell1preferably has adhesive strength at least equal to or larger than sheet75aprovided above solar cell1. As such a combination of upper sheet75aand lower sheet75b, a fluorinated rubber sheet or a PET sheet may be used as upper sheet75aand a silicone rubber sheet, an acrylic rubber sheet, or the like may be used as lower sheet75b, in addition to the combination of the silicone rubber sheets described in the above embodiment.

Meanwhile, the adhesive strength of silicone rubber sheets75a,75bbecomes larger as the temperature at the time of pressure-bonding becomes higher. Using these characteristics, it is preferable to make the actual temperature of lower heater block40bhigher than the actual temperature of upper heater block40aand thereby make the adhesive strength of lower silicone rubber sheet75bslightly larger in order to prevent solar cell1from being lifted upward. By making the actual temperature of lower heater block40bhigher than the actual temperature of upper heater block40ain this manner, the same sheet can be used for upper sheet75aand lower sheet75b.

Besides, conveyer belt60is placed below solar cell1. Hence, even when silicone rubber sheet75bsticks to the lower side of solar cell1, solar cell1is supported by conveyer belt60and thus silicone rubber sheet75bis detached from solar cell1, preventing further downward movement of solar cell1. As a result, it is possible to prevent solar cell string100afrom being lifted and from being moved downward of conveyer belt60.

One of methods of making different the actual temperatures of upper and lower heater blocks40a,40bis a method of making the heating temperature of lower heater block40bhigher than the heating temperature of upper heater block40a. Another method is a method of making the thermal capacity of lower heater block40blarger than the thermal capacity of upper heater block40awhile keeping the heating temperatures of the heaters the same. Since the actual temperature becomes higher as the thermal capacity becomes larger with the same temperatures of the heaters, the actual temperature of lower heater block40bcan be made higher.

Note that, although the second embodiment described above employs an anisotropic conductive adhesion film as a resin adhesion film, one containing no conductive particles may also be used as a resin film. When a resin adhesive containing no conductive particles is used, an electrical connection is established by bringing a part of the front surface of electrode11(12) into direct contact with the front surface of wiring member120. In this case, it is preferable to use wiring member120made by forming a conductive film softer than electrode11(12), such as tin (Sn) or solder, on the front surface of a conductor such as a copper foil plate, and to establish a connection by making a part of electrode11(12) penetrate the conductive film.

Further, resin adhesion layer5ausing adhesive paste in the form of paste may be employed instead of resin adhesion layer5aformed of an adhesion film in the form of film. For example, anisotropic conductive paste may be used to connect the wiring member.

While sandwiched between transparent sealing-material sheets43a,43bsuch as EVA, a string in which multiple solar cells1are connected to one another with wiring members120in this manner is sandwiched between front-surface member41made of glass and back-surface member42made of a material such as weather-resistant film, glass, or transparent plastic so that they overlap one another. Then, solar cells1are sealed between front-surface member41and back-surface member42by a laminating device by use of the sealing-material sheets. Thereafter, the string thus sealed is put in a furnace and heated at a temperature of approximately 150° C. for about 10 minutes. This accelerates the cross-linking reaction and enhances the adhesion between sealing material43(sealing-material sheets) and front- and back-surface members41,42. As a result, the solar cell module as shown inFIG. 1is manufactured.

It should be understood that the embodiments disclosed herein are exemplary in all points and do not limit the invention. The scope of the invention is defined not by the descriptions of the embodiments described above but by claims, and it is intended that the scoped of the invention includes equivalents of claims and all modifications within the scope of claims.

EXPLANATION OF REFERENCE NUMERALS