JP5323310B2 - Connection structure and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection method between a surface electrode and a wiring member of a solar battery cell that has excellent connection reliability, using a connection member instead of solder. <P>SOLUTION: The surface electrode and the wiring member of the solar battery cell are electrically connected by way of a conductive adhesive film. The conductive adhesive film contains an insulating bond and conductive particles. With a ten points average roughness of the surface of the surface electrode contacting the conductive adhesive film being assumed as Rz (&mu;m) and a maximum height as Ry (&mu;m), the conductive particle has average particle size r(&mu;m) being equal to or more than the ten points average roughness Rz, while the thickness t(&mu;m) of the conductive adhesive film is equal to or more than the maximum height Ry. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a method for connecting a surface electrode of a solar battery cell and a wiring member, a conductive adhesive film, and a solar battery module.

  The solar cell module has a structure in which a plurality of solar cells are connected in series and / or in parallel via a wiring member electrically connected to the surface electrode. In producing this solar cell module, solder has been conventionally used to connect the surface electrode of the solar cell and the wiring member (see, for example, Patent Documents 1 and 2). Solder is widely used because it is excellent in connection reliability such as electrical conductivity and fixing strength, is inexpensive and versatile.

On the other hand, from the viewpoint of environmental protection and the like, a method for connecting wirings that does not use solder in a solar cell has been proposed. For example, Patent Documents 3 to 6 disclose methods for connecting wirings with a conductive adhesive such as a conductive paste.
JP 2004-204256 A JP-A-2005-050780 JP 2000-286436 A JP 2001-357897 A Japanese Patent No. 3448924 JP 2005-101519 A

  However, in the connection method using the solder described in Patent Documents 1 and 2, characteristic deterioration of the solar cell is likely to occur. This is because when a solder having a melting point of about 230 to 260 ° C. is melted, a member such as a semiconductor structure in a solar cell is heated, and / or the influence of solder volume shrinkage affects the semiconductor structure and the like. caused by. Further, in the case of wiring connection by solder, it is difficult to control the distance between the electrode and the wiring, so that it is difficult to obtain sufficient dimensional accuracy during packaging. Lowering the dimensional accuracy also leads to a decrease in product yield due to packaging.

  Furthermore, as described in Patent Documents 3 to 5, when the conductive electrode is used to connect the surface electrode of the solar battery cell and the wiring member, the connection between the wirings is performed under high temperature and high humidity conditions. It has been clarified by the present inventors that the reliability greatly decreases with time.

  In addition, as described in Patent Document 6, when a conductive film is used to connect the surface electrode of the solar battery cell and the wiring member, it can be bonded at a low temperature, and thus occurs when solder is used. The bad influence to a photovoltaic cell can be suppressed. However, in the connection method described in Patent Document 6, the influence of the surface state of the adherend is not considered, and the connection reliability is not always sufficient.

  Accordingly, the present invention has been made in view of the above circumstances, and uses a connection member as a substitute for solder, and a method of connecting a surface electrode of a solar battery cell and a wiring member having sufficiently excellent connection reliability. An object is to provide a conductive adhesive film and a solar cell module.

In order to solve the above problems, the present invention is a method of electrically connecting a surface electrode of a solar battery cell and a wiring member via a conductive adhesive film, and the conductive adhesive film is an insulating adhesive. And conductive particles, the surface roughness of the surface electrode in contact with the conductive adhesive film is Rz (μm), and the maximum height is Ry (μm). Provided is a connection method in which r (μm) is 10-point average roughness Rz or more and the thickness t (μm) of the conductive adhesive film is greater than or equal to the maximum height Ry.
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  The present invention also relates to a conductive adhesive film used for electrically connecting a surface electrode of a solar battery cell and a wiring member, comprising an insulating adhesive and conductive particles, The average particle diameter r (μm) of the conductive particles is equal to or greater than the ten-point average roughness Rz, where the ten-point average roughness of the surface in contact with the conductive adhesive film is Rz (μm) and the maximum height is Ry (μm). The conductive adhesive film has a thickness t (μm) equal to or greater than the maximum height Ry.

  In the connection method of the present invention described above, the average particle diameter r of the conductive particles contained in the conductive adhesive film is equal to or greater than the ten-point average roughness Rz on the surface in contact with the conductive adhesive film of the surface electrode of the solar battery cell. This is one of the characteristics. Thereby, the electroconductive particle contained in an electroconductive adhesive film can electrically connect the surface electrode and wiring member of a photovoltaic cell sufficiently reliably.

  Further, the connection method of the present invention has another feature that the thickness t of the conductive adhesive film is equal to or greater than the maximum height Ry on the surface of the surface electrode of the solar battery cell in contact with the conductive adhesive film. Yes. Thereby, a conductive adhesive film can adhere | attach the surface electrode of a photovoltaic cell and a 1st wiring member sufficiently powerfully.

  And the effect of these electrical connectivity and adhesiveness acts in a complex manner, and the connection method of the present invention can sufficiently enhance the connection reliability.

  In addition, since the connection method of the present invention does not require the use of solder to connect the surface electrode of the solar cell and the wiring member, the effect of heating the member and volume shrinkage of the conductive adhesive film should be sufficiently reduced. Can do.

  Here, the ten-point average roughness Rz and the maximum height Ry are values derived in accordance with JIS-B0604-1994, and are obtained by observation with an ultradeep shape measurement microscope and calculation with image measurement / analysis software. Derived. The average particle diameter r of the conductive particles is determined by observing the conductive particles with a scanning electron microscope (SEM), randomly extracting 20 particles, measuring the particle diameters of these particles, It is a value calculated as an arithmetic average of particle diameters. Further, the thickness t of the conductive adhesive film is a value measured by a micrometer.

  The elastic modulus of the conductive adhesive film is a value measured as follows. First, an insulating adhesive is applied on a peelable substrate film to form a coating film. The coating is then heated in an oven at 170 ° C. for 20 minutes. Then, a base film is peeled and the film which consists of a heating product of a coating film is obtained. The film is cut into strips having a width of 5 mm and a length of 35 mm to obtain test pieces. About the test piece, the storage elastic modulus in 25 degreeC is measured using a dynamic viscoelasticity measuring apparatus, and let the value be an elastic modulus of a conductive adhesive film.

  In the present invention, the wiring member of the solar battery cell is preferably a film-like conductive member. Thereby, since the distance between the surface electrode of the solar battery cell and the wiring member at the time of connection can be easily controlled, the dimensional accuracy at the time of packaging is further improved.

  In the present invention, the film-like conductive member preferably contains one or more metals selected from the group consisting of Cu, Ag, Au, Fe, Ni, Pb, Zn, Co, Ti, and Mg as a main component. By including these metals, the conductivity of the wiring member is further improved, which leads to further improvement in connection reliability.

  In the present invention, the surface electrode of the solar battery cell is an electrode provided on the surface of one or more wafers selected from the group consisting of a single crystal silicon wafer, a polycrystalline silicon wafer, an amorphous silicon wafer, and a compound semiconductor wafer. There may be. By using such a member as the surface electrode, the above-described effects of the present invention are more effectively exhibited.

  In addition, since the surface of the conventional solar battery cell tends to be rough compared to other electronic device members, according to the present invention, the connection reliability can be further improved significantly, and as a result, for a long time. A high numerical value of the fill factor (hereinafter referred to as “FF”) can be maintained.

  ADVANTAGE OF THE INVENTION According to this invention, the connection method of the surface electrode of a photovoltaic cell and wiring member which has the connection reliability used as a substitute of solder and has the sufficiently excellent connection reliability can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of the conductive adhesive film of the present invention. As shown in FIG. 1, the conductive adhesive film 10 of this embodiment contains at least conductive particles 1 and an adhesive component 2.

  FIG. 2 is a schematic cross-sectional view showing a part of a connection structure obtained by a connection method for connecting a surface electrode of a solar battery cell and a wiring member using the conductive adhesive film of the present invention. This connection structure 200 is obtained by laminating a surface electrode 3 of a solar battery cell, a conductive adhesive film 10 and a wiring member 4 in this order.

  The conductive adhesive film 10 of this embodiment is for connecting the surface electrode 3 of a photovoltaic cell and the wiring member (wiring wire) 4 for connecting a photovoltaic cell in series and / or in parallel. An electrode (surface electrode) for taking out electricity is formed on the front and back surfaces of the solar battery cell.

  Here, as the surface electrode 3, a known material capable of obtaining electrical continuity can be used. Specific examples thereof include, for example, a general silver-containing glass paste, a silver paste in which various conductive particles are dispersed in an adhesive resin, a gold paste, a carbon paste, a nickel paste, an aluminum paste, and firing and vapor deposition. ITO formed by the above. In these, the glass paste electrode containing silver is used suitably from the point which is excellent in heat resistance, electroconductivity, and stability, and a low-cost viewpoint.

  In the case of a solar battery cell, a silver paste and an aluminum paste are applied to a substrate made of at least one of Si single crystal, polycrystal and amorphous by screen printing or the like, and dried and fired as necessary. By doing so, an Ag electrode and an Al electrode are mainly provided as the surface electrodes 3 respectively.

  The conductive adhesive film 10 includes at least an adhesive component 2 and conductive particles 1 dispersed therein. The adhesive component 2 is not particularly limited as long as it exhibits adhesiveness. However, from the viewpoint of further improving connection reliability, the adhesive component 2 is preferably a composition containing a thermosetting resin.

  The thermosetting resin may be a known one, and examples thereof include an epoxy resin, a phenoxy resin, an acrylic resin, a polyimide resin, a polyamide resin, and a polycarbonate resin. These thermosetting resins are used singly or in combination of two or more. Among these, from the viewpoint of further improving the connection reliability, one or more thermosetting resins selected from the group consisting of epoxy resins, phenoxy resins, and acrylic resins are preferable.

  The adhesive component 2 according to the present embodiment may be a composition containing a known curing agent and curing accelerator as optional components in addition to the thermosetting resin. In addition, this adhesive component 2 is modified with a silane coupling agent, a titanate coupling agent, an aluminate coupling agent or the like in order to improve adhesion and wettability with the surface electrode 3 or the wiring member 4. In order to improve the uniform dispersibility of the conductive particles 1, a dispersant such as calcium phosphate or calcium carbonate may be contained. Further, the adhesive component 2 may contain a rubber component such as acrylic rubber, silicon rubber, urethane, etc. in order to control the elastic modulus and tackiness. The surface electrode 3, the wiring member 4, and the conductive particles 1 In order to suppress migration of contained silver and copper, a chelate material or the like may be contained.

  The elastic modulus of the conductive adhesive film 10 is preferably 0.5 GPa to 4.0 GPa, more preferably 0.9 GPa to 3.5 GPa, from the viewpoint of relaxing warpage of the surface electrode 3 after bonding and compressive stress during bonding. . If the elastic modulus of the conductive adhesive film 10 is 0.5 GPa or more, it is possible to further prevent a decrease in adhesive strength due to inferior film strength, and if it is 4.0 GPa or less, the stress relaxation property is excellent. The warpage and breakage of the surface electrode 3 can be further suppressed.

  The elastic modulus of the conductive adhesive film 10 is measured as follows. First, on the surface of the polyethylene-terephthalate film treated with silicone, an adhesive component that becomes a precursor of the conductive adhesive film 10 is applied by a manipulator (manufactured by YOSHIMISU) to form a coating film. The coating is then dried using an oven at 170 ° C. for 20 minutes. Thereafter, the polyethylene terephthalate film is peeled off to obtain a conductive adhesive film 10 having a film thickness of 25 μm or 35 μm. The obtained conductive adhesive film 10 was cut into a strip having a width of 5 mm and a length of 35 mm, and a dynamic viscoelasticity measuring apparatus (manufactured by Rheometric Scientific, trade name “SOLIDS ANALYZER”, distance between chucks: 2 cm) at 25 ° C. The storage elastic modulus is measured to obtain the elastic modulus of the conductive adhesive film 10.

  The conductive particles 1 are not particularly limited as long as they have conductivity and are solid in the manufacturing environment and use environment of the connection structure 200. Examples of the conductive particles 1 include metal particles such as gold particles, silver particles, copper particles, and nickel particles, or conductive or insulating core particles such as gold plating particles, copper plating particles, and nickel plating particles. The electroconductive particle which coat | covers the surface with electroconductive layers, such as a metal layer, is mentioned.

  Among these, from the viewpoint of relaxing the compressive stress of the conductive particles at the time of connection and improving the connection reliability, particles in which the surface of the core particles is coated with a conductive layer are preferable, and the core particles are plastic particles. More preferably, the conductive layer is metal plating. That is, conductive particles formed by coating the surface of plastic particles with a metal layer are preferable because the particles themselves have high followability to fluctuations such as vibration and expansion after connection.

  From the viewpoint of connection reliability after the adhesive component 2 is cured, the blending amount of the conductive particles 1 dispersed in the conductive adhesive film 10 is 0.5% with respect to the total volume of the conductive adhesive film 10. It is preferable in it being -20 volume%, and it is more preferable in it being 2.0-12 volume%. When the blending amount of the conductive particles 1 is less than 0.5% by volume, the physical contact with the surface electrode 3 tends to decrease, and the connection structure in a reliability test atmosphere (85 ° C. and 85% RH). The connection resistance of 200 tends to decrease. Moreover, since the relative amount of the adhesive component 2 is reduced when the blending amount of the conductive particles 1 exceeds 20% by volume, the adhesive strength of the connection structure 200 is reduced in the reliability test atmosphere (85 ° C. and 85% RH). Tend to.

  Next, the relationship between the surface electrode 3 and the conductive adhesive film 10 will be described in detail. When the average particle diameter of the conductive particles 1 is r (μm), the average particle diameter r is equal to or greater than the ten-point average roughness Rz (μm) of the surface Se of the surface electrode 3. When the film thickness of the conductive adhesive film 10 is t (μm, see FIG. 1), the film thickness t is equal to or greater than the maximum height Ry (μm) of the surface Se of the surface electrode 3.

  The surface Se of the surface electrode 3 may generally have unevenness with a height difference of 3 to 30 μm depending on the application. In particular, the surface electrode 3 in the case of being provided in a solar battery cell tends to be rough, with the height difference of the unevenness being 8 to 18 μm. As a result of intensive studies, the present inventors have found that connection reliability is not sufficient in the conventional solar cell due to the unevenness.

  As a result of further study, the present inventors have found that when a conductive adhesive film 10 in which conductive particles 1 are dispersed in the adhesive component 2 is used as a layer for connecting the surface electrode 3 and the wiring member 4, connection reliability It was clarified that improvement of And it discovered that the relationship between the surface roughness of the surface Se of the surface electrode 3, the average particle diameter of the conductive particles 1 and the film thickness of the conductive adhesive film 10 affects the connection reliability. Specifically, the correlation between the average particle diameter r of the conductive particles 1 and the ten-point average roughness Rz of the surface Se of the surface electrode 3, and the film thickness t of the conductive adhesive film 10 and the surface of the surface electrode 3 It has been found that the correlation with the maximum height Ry of Se affects the connection reliability. In order to improve the connection reliability, the average roughness of the portion with a large height difference on the surface Se of the surface electrode 3 becomes a factor that determines the average particle diameter r of the conductive particles 1, and the height difference on the surface Se of the surface electrode 3. It is considered that the roughness of the largest part of the thickness is a factor that determines the film thickness t of the conductive adhesive film 10.

  That is, when the average particle diameter r of the conductive particles 1 is smaller than the ten-point average roughness Rz of the surface Se of the surface electrode 3, the conductive particles 1 are buried in the recesses on the surface Se, and the surface electrode 3 and the details will be described later. It becomes difficult to contribute to the electrical connection between the wiring members 4 to be described. As a result, connection reliability in the connection structure 200 is not sufficient. Moreover, when the film thickness t of the conductive adhesive film 10 becomes thinner than the maximum height Ry of the surface Se of the surface electrode 3, the conductive adhesive film 10 is filled between the surface electrode 3 and the wiring member 4 without a gap. Becomes difficult, and adhesion between the surface electrode 3 and the wiring member 4 becomes insufficient. As a result, connection reliability in the connection structure 200 is not sufficient.

  The average particle diameter r of the conductive particles 1 is preferably 1 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more larger than the ten-point average roughness Rz of the surface Se of the surface electrode 3. Thereby, the connection failure between the surface electrode 3 and the wiring member 4 can be suppressed more fully. The upper limit of the difference between the average particle diameter r and the ten-point average roughness Rz is preferably Rz μm, and more preferably 2/3 Rz μm. When these differences are Rz μm or less, particularly 2/3 Rz μm or less, the conductive particles 1 are physically and stably disposed in the recesses, so that an advantage of reducing connection resistance is obtained.

  The average particle diameter r of the conductive particles 1 is preferably 3 to 30 μm and more preferably 8 to 25 μm from the viewpoint of improving uniform dispersibility in the adhesive component 2.

  The film thickness t of the conductive adhesive film 10 is preferably 1 μm or more, more preferably 3 μm or more, and particularly preferably 5 μm or more larger than the maximum height Ry of the surface Se of the surface electrode 3. Thereby, the filling of the conductive adhesive film 10 becomes further sufficient, and poor connection can be more sufficiently suppressed. The upper limit of the difference between the film thickness t and the maximum height Ry is preferably 20 μm, and more preferably 10 μm. When these differences are 20 μm or less, particularly 10 μm or less, the fluidity of the resin in the adhesive component 2 and the curability of the resin during thermocompression bonding are further improved, and the advantage that the connection strength is increased is obtained.

  The wiring member 4 is preferably film-shaped, that is, its cross section is rectangular. As a result, the distance from the surface electrode 3 can be easily controlled, so that the dimensional accuracy during packaging is improved.

  The wiring member 4 will not be specifically limited if it contains a metal as a main component. Examples of the metal that is the material of the wiring member 4 include gold, silver, copper, iron, stainless steel, 42 alloy, and solder-plated copper. From the viewpoint of further improving the electrical conductivity, the wiring member 4 preferably contains one or more metals selected from the group consisting of Cu, Ag, Au, Fe, Ni, Pb, Zn, Co, Ti, and Mg. . Moreover, it is preferable that the wiring member 4 is a metal plating layer or a metal electrodeposition layer provided on the surface of an insulating film (not shown) from the viewpoint of further improving flexibility and increasing the dimensional accuracy. However, metal foil may be used depending on the application.

  The material of the insulating film is not particularly limited as long as it exhibits insulating properties. However, from the viewpoint of improving flexibility and improving the dimensional accuracy, it is preferable that the material of the insulating film is a resin as a main component. Examples of this resin include polyimide resin, glass epoxy resin, bismaleimide triazine resin, and polyester resin.

  Next, a connection method according to a preferred embodiment, that is, a method for manufacturing the connection structure 200 will be described. This connection method has the following first step, second step, third step and fourth step.

  In the first step, a first laminate formed by forming the surface electrode 3 on a base material such as a silicon wafer is prepared.

  In the second step, a conductive adhesive film 10 is formed on the surface of the wiring member 4 formed on the insulating film to obtain a second laminate. In the conductive adhesive film 10, a paste-like adhesive component in which the conductive particles 1 are dispersed (hereinafter, a combination of conductive particles and a paste-like adhesive component is also referred to as a “paste-like conductive adhesive”. ) May be obtained through a process of volatilizing the solvent and the like to form a film after coating on the surface of the wiring member 2. Alternatively, the conductive adhesive film 10 may be obtained through a process of being placed on the surface of the wiring member 4 after previously forming a film from a paste-like conductive adhesive by volatilizing a solvent or the like.

  Among these, the latter is preferable from the viewpoint of the film thickness dimensional accuracy of the conductive adhesive film 10 and / or the pressure distribution when the conductive adhesive film 10 is pressure-bonded in the fourth step described later. In this case, after placing the conductive adhesive film 10 on the surface of the wiring member 4, it is preferable to press-bond them in the laminating direction and temporarily press-bond them.

  The paste-like adhesive component is obtained from a composition containing the above-mentioned thermosetting resin and other optional components, and can be used as it is when it is liquid at room temperature (25 ° C.). When the composition is a solid at room temperature, it may be pasted by using a solvent in addition to heating to make a paste. The solvent that can be used is not particularly limited as long as it does not react with the above-described composition and exhibits sufficient solubility.

  Also, when the paste-like conductive adhesive is previously formed into a film shape, the paste-like conductive adhesive is applied on a peelable substrate such as a fluororesin film, a polyethylene terephthalate film, a release paper, or a nonwoven fabric. It can be obtained by impregnating the above-mentioned base material with the adhesive and placing it on a peelable base material and removing the solvent and the like. Thus, when the paste-like conductive adhesive is previously formed into a film shape, it is excellent in handleability and more convenient. In this case, the detachable substrate is peeled and removed immediately before or after the conductive adhesive film 10 is placed on the surface of the wiring member 4.

  The paste-like conductive adhesive is applied using an applicator, roll coater, comma coater, knife coater, doctor blade flow coater, hermetic coater, die coater, lip coater, or the like. At this time, the film thickness t of the conductive adhesive film 10 can be controlled by adjusting the gap of the applicator or the lip coater. The film thickness t of the conductive adhesive film 10 can also be controlled by adjusting the amount of nonvolatile components such as a thermosetting resin contained in the paste-like conductive adhesive.

  In the third step, the first laminate and the second laminate are further laminated such that the surface Se of the surface electrode 3 in the first laminate and the surface of the conductive adhesive film 10 in the second laminate are brought into contact with each other. The obtained third laminated body is obtained. At this time, after the first stacked body and the second stacked body are aligned and stacked, in order to fix the position, the first stacked body and the second stacked body may be pressurized in the stacking direction and temporarily pressed.

  In the fourth step, the third laminated body is heated and pressed in the laminating direction to obtain a connection structure 200 in which at least the surface electrode 3, the conductive adhesive film 10, and the wiring member 4 are laminated in this order. By this fourth step, the surface electrode 3 and the wiring member 4 are bonded by the conductive adhesive film 10, and electrical connection between them is ensured through the conductive adhesive film 10.

  The conditions of the heating temperature and the pressurizing pressure are not particularly limited as long as the electrical connection can be ensured and the surface electrode 3 and the wiring member 4 are bonded by the conductive adhesive film 10. The various conditions for pressurization and heating are appropriately selected depending on the intended use, each component in the adhesive component, and the material of the connection structure 200. For example, the heating temperature may be a temperature at which the thermosetting resin is cured. Further, the pressurizing pressure may be in a range where the surface electrode 3 and the conductive adhesive film 10 are sufficiently in close contact with each other and the surface electrode 3, the wiring member 4 and the like are not damaged. Furthermore, the heating / pressurizing time may be a time such that heat is excessively propagated to the surface electrode 3, the wiring member 4, etc., and those materials are not damaged or deteriorated. Specifically, the condition that the temperature reached by the conductive adhesive film 10 reaches 150 ° C. to 180 ° C. for 15 seconds to 20 seconds under the pressurized condition of 1 MPa to 3 MPa is the electrical connection and adhesive force. It is preferable from the viewpoint of improvement.

  In the connection structure 200 thus obtained, the conductive particles 1 dispersed in the conductive adhesive film 10 ensure sufficient electrical connection between the surface electrode 3 and the wiring member 4. Further, the conductive adhesive film 10 bonds the surface electrode 3 and the wiring member 4 with sufficient adhesive strength. As a result, the connection structure 200 is sufficiently excellent in connection reliability. Moreover, since it is not necessary to use solder to ensure electrical connection, the deterioration of the characteristics of the connection structure 200 can be sufficiently suppressed, and a decrease in product yield due to packaging can also be prevented.

  As described above, the conductive adhesive film 10 of the present embodiment can be most suitably used for solar cells. A solar cell includes a plurality of solar cells connected in series and / or in parallel, sandwiched with tempered glass or the like for environmental resistance, and provided with external terminals whose gaps are filled with a transparent resin. Used as a module. The conductive adhesive film 10 of the present embodiment is suitably used for the purpose of connecting a wiring member for connecting a plurality of solar cells in series and / or in parallel with the surface electrode of the solar cells.

  The solar cell module of the present embodiment has a structure in which a plurality of solar cells having a surface electrode are connected via a wiring member electrically connected to the surface electrode as described above. The surface electrode and the wiring member are connected by the conductive adhesive film of this embodiment.

  Here, FIG. 3 is a schematic diagram showing a main part of the solar cell module of the present embodiment, and shows an outline of a structure in which a plurality of solar cells are connected to each other by wiring. 3A shows the front side of the solar cell module, FIG. 3B shows the back side, and FIG. 3C shows the side.

  As shown in FIGS. 3A to 3C, the solar cell module 100 includes a grid electrode 7 and a bus electrode (front electrode) 3a on the front side of the semiconductor wafer 6, and a back electrode 8 and a bus electrode (front electrode) on the back side. A plurality of solar cells each having a surface electrode 3 b are connected to each other by a wiring member 4. The wiring member 4 has one end connected to the bus electrode 3a as the surface electrode and the other end connected to the bus electrode 3b as the surface electrode via the conductive adhesive film 10 of the present invention.

  In the solar cell module 100 having such a configuration, since the surface electrode and the wiring member are connected by the conductive adhesive film of the present embodiment described above, there is no adverse effect on the solar cell and sufficient connection reliability is achieved. Can be obtained. Thereby, the solar cell module 100 has high F.D. due to its excellent connection reliability. F. Can be secured for a long time.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. The present invention can be variously modified without departing from the gist thereof.

  The connection method of the present invention is not only used for manufacturing the above-described solar cell, but also, for example, a tantalum capacitor, an aluminum electrolytic capacitor, a ceramic capacitor, a power transistor, various sensors, a MEMS-related material, a display wiring member for a display material, and the like. In this case, it can be suitably used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
First, a solar battery cell (manufactured by MOTECH, manufactured by a surface electrode (width 2 mm × length 15 cm, Rz: 10 μm, Ry: 14 μm) formed from a silver glass paste on the surface of a polycrystalline silicon wafer. The name “125 square cell polycrystalline MOT T1”, thickness: 250 μm × width 12.5 cm × length 12.5 cm) was prepared.

  Next, an acrylic rubber obtained by copolymerizing 40 parts by mass of butyl acrylate, 30 parts by mass of ethyl acrylate, 30 parts by mass of acrylonitrile, and 3 parts by mass of glycidyl methacrylate (manufactured by Hitachi Chemical Co., Ltd., trade name “KS8200H”, molecular weight: 85 Prepared).

  50 g of phenoxy resin (trade name “PKHC” manufactured by Union Carbide Corporation, weight average molecular weight: 45000) and 125 g of the acrylic rubber were dissolved in 400 g of ethyl acetate to obtain a solution having a solid content of 30% by mass. Next, 325 g of a liquid epoxy resin containing a microcapsule type latent curing agent (manufactured by Asahi Kasei Chemicals, trade name “Novacure HX-3941HP”, epoxy equivalent: 185 g / eq) is added to the above solution, and the solution is further stirred. Thus, a paste-like adhesive component was obtained.

Next, nickel particles (apparent density: 3.36 g / cm ³ ), which are conductive particles having an average particle diameter of 12 μm, were added to the adhesive component described above and dispersed. Thus, a paste-like conductive adhesive containing 5% by volume of conductive particles with respect to the total volume of the adhesive component and the conductive particles was obtained. The average particle diameter of the conductive particles was derived by the method described above through observation with a scanning electron microscope (SEM, manufactured by Hitachi, Ltd., trade name “S-510”). The blending amount of the conductive particles was calculated from the particle volume calculated by regarding the shape of the conductive particles as a sphere having an average particle diameter of the diameter, and the apparent density of the conductive particles.

  Glossy surface of electrolytic copper foil having a width of 20 cm, a length of 30 cm, and a thickness of 175 μm, which is a wiring member, using a roll coater (trade name “PI-1210” manufactured by Tester Sangyo Co., Ltd.) Was applied to obtain a coating film. The gap of the roll coater was adjusted so that the thickness after the solvent was volatilized from the coating film, that is, the thickness of the conductive adhesive film was 25 μm. This adjustment is performed in advance by changing the gap to produce three types of films having different film thicknesses after removing the solvent, etc., and deriving a relational expression between the gap and the film thickness. It was.

  Next, the solvent was volatilized by placing the coating film on a hot plate and heating at 70 ° C. for 3 minutes. After that, the conductive adhesive film having a thickness of 25 μm is dispersed on the glossy surface of the electrolytic copper foil by cutting into a width of 2 mm by a slitter (trade name “High Precision Gang Unit” manufactured by Toyo Knife Co., Ltd.). The provided laminate was obtained. This laminate was cut to a length of 20 cm to form a rectangle with a width of 2 mm and a length of 20 cm.

  Subsequently, they were laminated so that the surface opposite to the electrolytic copper foil side of the conductive adhesive film and the surface of the surface electrode of the solar battery cell were in contact with each other to obtain a laminate. Subsequently, using a crimping tool (trade name “AC-S300”, manufactured by Nikka Equipment Engineering Co., Ltd.), a heating temperature of 170 ° C., a pressing pressure of 2 MPa, and a heating and pressing time of 20 seconds are applied to the laminate. Under the conditions, heating and pressurization were performed in the stacking direction. Thus, a connection structure was obtained in which the wiring member made of electrolytic copper foil was connected to the surface electrode of the solar battery cell via the conductive adhesive film.

(Example 2)
The connection structure was made in the same manner as in Example 1 except that instead of the electrolytic copper foil, a copper plating film (copper plating thickness: 40 μm) obtained by performing copper plating on the main surface of the resin film as an insulating film was used. Obtained.

(Example 3)
Instead of nickel particles, gold-plated plastic particles (average particle diameter: 20 μm, gold plating thickness: average 200 mm, apparent density: 2.8 g / cm ³ ) formed by coating the surface of plastic particles with gold plating, Rz: 10 μm, Ry: instead of a solar cell provided with a surface electrode formed from a silver glass paste having a surface roughness of 14 μm, Rz: 15 μm, Ry: from a silver glass paste having a surface roughness of 18 μm Except for using a solar cell provided with a surface electrode to be formed (manufactured by MOTECH, trade name “125 square cell polycrystalline MOT T1”, thickness: 250 μm × width 12.5 cm × length 12.5 cm) A connection structure was obtained in the same manner as in Example 1.

(Comparative Example 1)
First, the same photovoltaic cell as in Example 1 was prepared. Next, a solder-plated copper wire (width 2 mm × thickness 250 μm) was prepared, and the solar cell electrode and the solder-plated copper wire were solder-connected. A connection structure was thus obtained.

(Comparative Examples 2 and 3)
A connection structure was obtained in the same manner as in Example 1 except that the average particle diameter of the conductive particles was changed as shown in Table 4.

(Comparative Example 4)
A connection structure was obtained in the same manner as in Example 1 except that the thickness of the conductive adhesive film was changed as shown in Table 6.

  Tables 1 and 2 show the composition of each substance in the adhesive components according to each Example and Comparative Example, Tables 3 and 4 show the types of conductive particles and wiring members, and surface roughness and conductive adhesion of the surface electrodes. The types of film are shown in Tables 5 and 6, respectively. The thickness of the conductive adhesive film and the surface roughness of the surface electrode were measured as follows. The elastic modulus (storage elastic modulus) of the conductive adhesive film was measured as described above.

[Measurement of thickness of conductive adhesive film]
The thickness of the conductive adhesive film was measured with a micrometer (trade name “ID-C112C” manufactured by Mitutoyo Corp.).

[Measurement of surface roughness of surface electrode]
The 10-point average roughness Rz and the maximum height Ry of the surface electrode were derived based on JIS-B0604-1994. The electrode surface was observed with an ultra-deep shape measuring microscope (manufactured by KEYENCE, trade name “VK-8510”), and Rz and Ry were derived by image measurement / analysis software (manufactured by KEYENCE, trade name “VK-H1A7”). .

<Evaluation of each characteristic>
Regarding the connection structures of Examples 1 to 3 and Comparative Examples 1 to 4, peel strength, warpage of the wafer (base material), F.R. F. (1000h) / F. F. (0h) The yield of solar cells was measured as follows. The results are shown in Tables 7 and 8.

[Peel strength measurement]
The edge part of the tab electrode (electrolytic copper foil or copper plating film) in the obtained connection structure was bent vertically, and fixed to a chuck of a peel strength measuring device (trade name “STA-1150” manufactured by ORIENTEC). Thereafter, the tab electrode was pulled up at a pulling speed of 2 cm / second, and the peel strength was measured. In the table, “wafer cracking” means that the peel strength was not measured because the peel strength was high, and the wafer was cracked before completely peeling (peeling) the tab electrode.

[Wafer warpage measurement]
The obtained connection structure was placed on a smooth surface with the wafer facing down, and one end (one side) of the rectangular wafer was fixed to the smooth surface. Since the wafer has a convex surface on the side opposite to the electrode side, when one end of a rectangular wafer is fixed to a smooth surface, one end facing the surface is raised. The distance from the smooth surface of the one end which floated up was measured 5 points | pieces using the focal depth meter, and the arithmetic mean value was computed. The ratio (%) of the arithmetic average value to the length of one side of the wafer was derived as the amount of warpage. In addition, since the measurement limit lower limit is 0.3%, when it is smaller than that, it is indicated as “<0.3” in the table.

[F. F. (1000h) / F. F. (Measurement of (0h)]
The IV curve of the obtained connection structure was measured using a solar simulator (trade name “WXS-155S-10”, AM: 1.5G, manufactured by Wacom Denso Co., Ltd.). In addition, after the connection structure was allowed to stand for 1000 hours in a high-temperature and high-humidity atmosphere at 85 ° C. and 85% RH, the IV curve was measured in the same manner. From each IV curve, F.R. F after each was derived and left in a high temperature and high humidity atmosphere. F. F. before standing under high temperature and high humidity conditions. F. F. divided by. F. (1000h) / F. F. (0h) was used as an evaluation index. In general, F.I. F. (1000h) / F. F. When the value of (0h) is 0.95 or less, it is determined that the connection reliability is low.

[Solar cell yield measurement]
First, 10 connection structures were produced. The state of each connection structure was observed, and the number of ten pieces excluding those in which cracking or peeling was observed was evaluated as a yield (%).

It is a schematic cross section which shows a part of electroconductive adhesive film which concerns on embodiment. It is a schematic cross section which shows a part of connection structure which concerns on embodiment. It is a schematic diagram which shows the principal part of the solar cell module which concerns on embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Conductive particle, 2 ... Adhesive component, 3 ... Surface electrode, 3a ... Bus electrode (surface electrode), 3b ... Bus electrode (surface electrode), 4 ... Wiring member, 6 ... Semiconductor wafer, 7 ... Grid electrode, 8 ... back electrode, 10 ... conductive adhesive film, 100 ... solar cell module, 200 ... connection structure.

Claims (12)

A method of electrically connecting a bus electrode of a solar battery cell and a wiring member through a conductive adhesive film,
The conductive adhesive film contains an insulating adhesive and conductive particles,
The ten-point average roughness of the surface of the bus electrode in contact with the conductive adhesive film is Rz (μm), and the maximum height is Ry (μm).
The conductive particles have an average particle diameter r (μm) equal to or greater than the ten-point average roughness Rz, and a thickness t (μm) of the conductive adhesive film is equal to or greater than the maximum height Ry.
The difference between the between the thickness t and the maximum height Ry is Ri der less 17 .mu.m,
The connection method , wherein the ten-point average roughness Rz is 10 to 15 μm .   The connection method according to claim 1, wherein the wiring member is a film-like conductive member.   The connection according to claim 1 or 2, wherein the wiring member contains, as a main component, one or more metals selected from the group consisting of Cu, Ag, Au, Fe, Ni, Pb, Zn, Co, Ti, and Mg. Method.   The bus electrode is an electrode provided on the surface of one or more wafers selected from the group consisting of a single crystal silicon wafer, a polycrystalline silicon wafer, an amorphous silicon wafer, and a compound semiconductor wafer. The connection method according to any one of the above.   The connection method according to claim 1, wherein the average particle diameter r is 1 μm or more larger than the ten-point average roughness Rz.   The average particle diameter r is larger than the ten-point average roughness Rz, and the difference between the average particle diameter r and the ten-point average roughness Rz is equal to or less than Rz. The connection method described.   The connection method as described in any one of Claims 1-6 whose said average particle diameter r is 3-30 micrometers.   The connection method according to claim 1, wherein the thickness t is 1 μm or more larger than the maximum height Ry.   The connection method according to claim 1, comprising a step of laminating the conductive adhesive film on the bus electrode. The bus electrode, a glass paste containing silver is applied to the surface of the wafer is obtained by drying and firing, the connection method according to any one of claims 1-9. The insulating adhesive contains a thermosetting resin, the connection method according to any one of claims 1-10. The connection method according to claim 11 , wherein the thermosetting resin includes an epoxy resin.

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