JP2016167594A - Conductive material for solar battery module of back contact system, and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive material for a solar battery module of a back contact system capable of effectively enhancing photoelectric conversion efficiency, in the solar battery module of the back contact system.SOLUTION: A conductive material is used for obtaining a solar battery module of a back contact system by electrical connection of a wiring electrode of a resin film having a flexible printed board having a wiring electrode thereon or the wiring electrode having thereon, and an electrode of a solar battery cell having the electrode thereon; and contains conductive particles having a melting point on the outer surface of a conductive section of 300°C or higher, a thermosetting component, and at least one kind of a light reflective material and/or a fluorescent material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive material used for a back contact type solar cell module. The present invention also relates to a back contact type solar cell module using the conductive material.

  Examples of the solar cell module system include a ribbon system and a back contact system. Conventionally, ribbon type solar cell modules have been mainly employed. In recent years, there is an increasing demand for the development of a back contact type solar cell module that can be expected to have high output and high conversion efficiency.

  In the back contact type solar cell module, the solar cell and the flexible printed circuit board are bonded together on the entire surface of the solar cell.

  In Patent Document 1 below, a plurality of solar cells are arranged side by side in the arrangement of the modules with the back surface facing upward, and the P-type electrode and N-type electrode of adjacent solar cells are further electrically connected by an interconnector. The first step of obtaining a series of solar cells connected to each other, and the sealing material, the series of solar cells, the sealing material, and the back side protection member in this order on the front side protection member. The manufacturing method of a solar cell module provided with the 2nd process laminated | stacked and integrated is disclosed. Patent Document 1 describes a method of connecting a wiring electrode of a flexible printed circuit board and an electrode of a solar battery cell with Cu, Ag, Au, Pt, Sn, an alloy containing these, or the like.

  Further, in Patent Document 2 below, one end side of the tab wire is disposed on the surface electrode of the solar battery cell via a conductive adhesive containing spherical conductive particles, and adjacent to the solar battery cell. A step of disposing the other end of the tab wire on the back electrode of the solar battery cell via a conductive adhesive containing conductive particles, and heat-pressing the tab wire to the front electrode and the back electrode. There is disclosed a method for manufacturing a solar cell module including a step of connecting the tab wire to the front electrode and the back electrode by the conductive adhesive. In the tab line, a concavo-convex portion is formed on one surface in contact with the conductive adhesive. The average height (H) of the uneven part and the average particle diameter (D) of the conductive particles satisfy D ≧ H.

  In recent years, it has been proposed to selectively dispose conductive particles on wiring electrodes of a flexible printed circuit board.

  In the following Patent Document 3, a base material, an aluminum wiring disposed on one surface of the base material via an adhesive layer, a solar battery cell having an electrode connected to the aluminum wiring, A method for manufacturing a solar cell module is disclosed that includes a sealing material for sealing a solar battery cell, and a translucent front plate on a surface opposite to the aluminum wiring of the sealing material. The manufacturing method described in Patent Document 3 includes a step of removing the oxide film of the aluminum wiring in advance by a flux, a step of applying aluminum paste solder to the aluminum wiring by printing or a dispenser, the aluminum wiring, and the sun. Connecting the electrodes of the battery cells with the aluminum paste solder. The aluminum paste solder includes aluminum powder and a synthetic resin.

JP 2005-11869 A JP 2012-204388 A JP2013-63443A

  There may be irregularities on the surface of the electrode of the solar battery cell. In addition, irregularities may also exist on the surface of the wiring electrode of the flexible printed board. When the aluminum paste solder described in Patent Document 3 is used, the aluminum paste solder may not sufficiently contact the surface of the electrode due to irregularities on the surface of the electrode. For this reason, the conduction | electrical_connection reliability between electrodes may become low.

  In addition, as described in Patent Document 3, in recent years, since copper wiring electrodes are expensive, there is an increasing demand for using aluminum wiring electrodes. However, an oxide film is easily formed on the surface of the aluminum wiring electrode. For this reason, a decrease in conduction reliability tends to be a big problem. In the conductive materials described in Patent Documents 1 to 3, there is a problem that it is difficult to sufficiently improve the conduction reliability particularly when the aluminum wiring electrodes are electrically connected.

  In a back contact solar cell module, the higher the photoelectric conversion efficiency, the better. With conventional conductive materials, it is difficult to significantly increase the photoelectric conversion efficiency.

  An object of the present invention is to provide a back contact solar cell module conductive material capable of effectively increasing photoelectric conversion efficiency in a back contact solar cell module. Moreover, this invention is providing the solar cell module of a back contact system using the said electrically-conductive material.

  According to a wide aspect of the present invention, the wiring electrode and the electrode of the flexible printed circuit board having the wiring electrode on the surface or the resin film having the wiring electrode on the surface and the solar cell having the electrode on the surface are electrically connected. A conductive material used to obtain a back contact solar cell module by connecting to a conductive particle having an outer surface melting point of 300 ° C. or higher, a thermosetting component, and light reflection Provided is a back contact solar cell module conductive material including at least one of a material and a fluorescent material.

  On the specific situation with the electrically conductive material which concerns on this invention, the said light reflection material is a plate-shaped filler.

  On the specific situation with the electrically-conductive material which concerns on this invention, the said electrically-conductive material contains the said light reflection material.

  On the specific situation with the electrically-conductive material which concerns on this invention, the said fluorescent material is a compound which has an anthracene ring.

  In a specific aspect of the conductive material according to the present invention, the conductive material includes the fluorescent material.

  On the specific situation with the electrically-conductive material which concerns on this invention, content of the said electroconductive particle is 0.1 to 30 weight% in 100 weight% of said electrically-conductive materials.

  On the specific situation with the electrically-conductive material which concerns on this invention, the said thermosetting component contains an epoxy compound.

  On the specific situation with the electrically conductive material which concerns on this invention, the said electroconductive particle is equipped with a base material particle and the electroconductive part arrange | positioned on the surface of the said base material particle.

  On the specific situation with the electrically-conductive material which concerns on this invention, the said base material particle is a resin particle or an organic inorganic hybrid particle.

  On the specific situation with the electrically-conductive material which concerns on this invention, the said electroconductive particle has several protrusion on the outer surface of an electroconductive part.

  On the specific situation with the electrically-conductive material which concerns on this invention, the average height of the said some protrusion in the said electroconductive particle is 10 nm or more and 1000 nm or less.

  On the specific situation with the electrically-conductive material which concerns on this invention, the said wiring electrode of the said flexible printed circuit board or the said resin film is an aluminum wiring electrode.

  According to a wide aspect of the present invention, a flexible printed circuit board or a resin film having a wiring electrode on its surface, a solar battery cell having an electrode on its surface, the flexible printed circuit board or the resin film and the solar battery cell are connected. The connecting part is a conductive material for a back contact solar cell module described above, and the wiring electrode and the electrode are electrically connected by the conductive particles. A back contact solar cell module is provided.

  The back contact solar cell module conductive material according to the present invention includes a conductive particle having an outer surface melting point of 300 ° C. or higher, a thermosetting component, a light reflecting material, and a fluorescent material. Therefore, the photoelectric conversion efficiency of the back contact solar cell module can be effectively increased.

FIG. 1 is a cross-sectional view showing a back contact solar cell module obtained by using the back contact solar cell module conductive material according to the first embodiment of the present invention. FIGS. 2A to 2C are cross-sectional views for explaining the respective steps of the first example of the back contact type solar cell module manufacturing method. FIGS. 3A to 3C are cross-sectional views for explaining each step of the second example of the method for manufacturing the back contact solar cell module. FIG. 4 is a cross-sectional view showing an example of conductive particles used in the back contact solar cell module conductive material according to the present invention. FIG. 5 is a cross-sectional view showing a first modification of the conductive particles. FIG. 6 is a cross-sectional view showing a second modification of the conductive particles. FIG. 7 is a cross-sectional view showing a third modification of the conductive particles.

  Details of the present invention will be described below.

(Conductive material for back contact solar cell module)
The back contact solar cell module conductive material according to the present invention includes a conductive particle having an outer surface melting point of 300 ° C. or higher, a thermosetting component, a light reflecting material, and a fluorescent material. 1 type.

  In this invention, since the structure mentioned above is provided, the said wiring electrode and said electrode of the flexible printed circuit board or resin film which has a wiring electrode on the surface, and the photovoltaic cell which has an electrode on the surface are electrically connected. When connected to obtain a back contact solar cell module, the photoelectric conversion efficiency can be considerably increased. In the present invention, a decrease in photoelectric conversion efficiency due to light leakage can be suppressed.

  For example, in a back contact type solar cell module, the wiring electrode and the electrode of the flexible printed circuit board having the wiring electrode on the surface or the resin film having the wiring electrode on the surface and the solar cell having the electrode on the surface are provided. Electrically connected. An oxide film is often formed on the surface of the wiring electrode and the surface of the electrode. In addition, an oxide film may be formed on the surface of the conductive particles.

  The conductive particles preferably have a plurality of protrusions on the outer surface of the conductive part. It is preferable that the conductive particles have base particles and conductive portions arranged on the surface of the base particles. The substrate particles are preferably resin particles or organic-inorganic hybrid particles.

  When the conductive particles have a plurality of protrusions on the outer surface, even if an oxide film is formed on the surface of the wiring electrode, the surface of the electrode, and the surface of the conductive particles, the oxide film is formed by the protrusions. It is pierced. For this reason, the conduction | electrical_connection reliability between electrodes becomes still higher.

  When the conductive particles have base particles and conductive portions arranged on the surfaces of the base particles, the distance between the electrodes can be controlled with high accuracy. In addition, since the conductive particles are easily deformed in response to the change in the interval between the electrodes, the conduction reliability between the electrodes is further enhanced. As a result, the initial energy conversion efficiency and the energy conversion efficiency after the reliability test can be further increased.

  There may be irregularities on the surface of the electrode of the solar battery cell. Further, irregularities may also exist on the surface of the flexible printed circuit board or the wiring electrode of the resin film. For this reason, the space | interval between electrodes may not be uniform. Furthermore, since the flexible printed circuit board or the resin film is relatively flexible, the distance between the electrodes may not be uniform with the deformation of the flexible printed circuit board or the resin film after connection. On the other hand, since the substrate particles are resin particles or organic / inorganic hybrid particles, the repulsive stress due to the deformation of the conductive particles is not excessive in the region where the distance between the electrodes is narrow, It becomes easy to maintain contact stably. As a result, the conduction reliability between the electrodes is further enhanced. Moreover, in the area | region where the space | interval between electrodes is wide, electroconductive particle deform | transforms moderately and it becomes easy to contact electroconductive particle and an electrode. For this reason, the conductive particles have a plurality of protrusions on the outer surface of the conductive portion, thereby further improving the conduction reliability between the electrodes.

  Furthermore, if the conductive particles have a protrusion on the outer surface of the conductive portion, the protrusion is embedded in the electrode. For this reason, even if an impact is applied to the solar cell module, poor connection is less likely to occur. For this reason, conduction | electrical_connection reliability can be improved effectively and the photoelectric conversion efficiency in a solar cell module can be improved further.

  When the average height of the plurality of protrusions in the conductive particle is 10 nm or more and 1000 nm or less, the above effect is effectively exhibited. In particular, when the average height of the plurality of protrusions in the conductive particles is 10 nm or more and 500 nm or less, the above effect is more effectively exhibited. In addition, in order to electrically connect the electrodes of the back contact type solar cell module, it is significant that the conductive particles have protrusions on the outer surface of the conductive portion.

  First, the conductive particles used in the back contact solar cell module will be described more specifically with reference to the drawings. In the following embodiments, different partial configurations can be replaced with each other.

  FIG. 4 is a cross-sectional view showing an example of conductive particles used in the back contact solar cell module conductive material according to the present invention.

  The conductive particles 21 shown in FIG. 4 have base material particles 22 and conductive portions 23 arranged on the surface of the base material particles 22. The conductive part 23 is a conductive layer. The conductive portion 23 covers the surface of the base particle 22. The conductive portion 23 is in contact with the base particle 22. The conductive particle 21 is a coated particle in which the surface of the base particle 22 is coated with the conductive portion 23.

  The conductive particle 21 has a plurality of protrusions 21 a on the outer surface of the conductive portion 23. The conductive portion 23 has a plurality of protrusions 23a on the outer surface.

  The conductive particles 21 have a plurality of core substances 24 on the surface of the substrate particles 22. The conductive portion 23 covers the base particle 22 and the core substance 24. By covering the core substance 24 with the conductive portion 23, the conductive particle 21 has a plurality of protrusions 21 a on the outer surface of the conductive portion 23. The outer surface of the conductive portion 23 is raised by the core substance 24, and a plurality of protrusions 21a and 23a are formed.

  FIG. 5 is a cross-sectional view showing a first modification of the conductive particles.

  A conductive particle 21 </ b> A illustrated in FIG. 5 includes a base particle 22 and a conductive portion 23 </ b> A disposed on the surface of the base particle 22. The conductive portion 23A is a conductive layer. Only the presence or absence of the core substance 24 is different between the conductive particles 21 and the conductive particles 21A. The conductive particles 21A do not have a core substance.

  The conductive particles 21A have a plurality of protrusions 21Aa on the outer surface of the conductive portion 23A. The conductive portion 23A has a plurality of protrusions 23Aa on the outer surface.

  The conductive portion 23A has a first portion and a second portion that is thicker than the first portion. Accordingly, the conductive portion 23A has a protrusion 23Aa on the outer surface (the outer surface of the conductive layer). A portion excluding the plurality of protrusions 21Aa and 23Aa is the first portion of the conductive portion 23A. The plurality of protrusions 21Aa and 23Aa are the second portions where the conductive portion 23A is thick.

  In order to form the protrusions 21Aa and 23Aa like the conductive particles 21A, it is not always necessary to use a core substance.

  FIG. 6 is a cross-sectional view showing a second modification of the conductive particles.

  A conductive particle 21 </ b> B illustrated in FIG. 6 includes a base particle 22 and a conductive portion 23 </ b> B disposed on the surface of the base particle 22. The conductive portion 23B is a conductive layer. The conductive portion 23B includes a first conductive portion 23Bx disposed on the surface of the base particle 22 and a second conductive portion 23By disposed on the surface of the first conductive portion 23Bx.

  The conductive particles 21B have a plurality of protrusions 21Ba on the outer surface of the conductive portion 23B. The conductive portion 23B has a plurality of protrusions 23Ba on the outer surface.

  The conductive particles 21B have a plurality of core substances 24 on the surface of the first conductive portion 23Bx. The second conductive portion 23By covers the first conductive portion 23Bx and the core substance 24. The substrate particles 22 and the core substance 24 are arranged with a space therebetween. A first conductive portion 23Bx exists between the base particle 22 and the core substance 24. By covering the core substance 24 with the second conductive portion 23By, the conductive particles 21B have a plurality of protrusions 21Ba on the outer surface of the conductive portion 23B. The surface of the conductive portion 23B and the second conductive portion 23By is raised by the core substance 24, and a plurality of protrusions 21Ba and 23Ba are formed.

  Like the conductive particles 21B, the conductive portion 23B may have a multilayer structure. Further, in order to form the protrusions 21Ba and 23Ba, the core material 24 is disposed on the first conductive portion 23Bx of the inner layer, and the core material 24 and the first conductive portion 23Bx are separated by the second conductive portion 23By of the outer layer. It may be coated.

  FIG. 7 is a cross-sectional view showing a third modification of the conductive particles.

  A conductive particle 21 </ b> C illustrated in FIG. 7 includes a base particle 22 and a conductive portion 23 </ b> C disposed on the surface of the base particle 22.

  The outer shape of the conductive portion 23C is spherical. The conductive particles 21C do not have protrusions on the outer surface of the conductive portion 23C.

  Like the conductive particles 21 </ b> C, the conductive particles may not have protrusions on the outer surface of the conductive portion. Moreover, although electroconductive particle 21,21A, 21B, 21C has the base particle 22, the electroconductive particle does not have a base particle, The whole may be formed of the electroconductive part. For example, the central portion and the outer surface portion of the conductive particles may be formed of a conductive portion, and the central portion of the conductive particles and the outer surface portion of the conductive portion of the conductive particles may be formed of the same material. It may be formed of different materials.

  Back contact solar cell module using a conductive material containing conductive particles 21, 21A, 21B, 21C, etc., preferably using a conductive material containing conductive particles 21, 21A, 21B, 21C Is produced.

  Next, the back contact type solar cell module obtained by using the back contact type solar cell module conductive material according to the first embodiment of the present invention will be described more specifically.

  FIG. 1 is a cross-sectional view showing a back contact solar cell module obtained by using the back contact solar cell module conductive material according to the first embodiment of the present invention. In FIG. 1 to FIG. 3, illustration of the light reflecting material and the fluorescent material is omitted.

  A solar cell module 1 shown in FIG. 1 includes a flexible printed circuit board 2, a solar battery cell 3, and a connection portion 4 that connects the flexible printed circuit board 2 and the solar battery cell 3. The connection part 4 has the 1st connection part formed with the electrically-conductive material containing the electroconductive particle 21, and the 2nd connection part formed with the connection material which does not contain an electroconductive particle. The material of the first connection portion is a conductive material including the conductive particles 21. The material of the second connection portion is a connection material that does not contain conductive particles. Instead of the conductive particles 21, conductive particles 21A, 21B, 21C and the like may be used. The connection part may be formed only of a conductive material containing conductive particles. The material of the connection part may be only a conductive material containing conductive particles.

  Moreover, in the solar cell module 1, the sealing material 5 is arrange | positioned on the surface on the opposite side to the connection part 4 side of the flexible printed circuit board 2. FIG. The sealing material 5 may be a back sheet, or a translucent substrate or the like may be disposed on the surface of the sealing material 5 opposite to the solar battery cell 3 side. A sealing material 6 is disposed on the surface opposite to the connection portion 4 side of the solar battery cell 3. A translucent substrate or the like may be disposed on the surface opposite to the solar cell 3 side of the sealing material 6.

  The flexible printed circuit board 2 has a plurality of wiring electrodes 2a on the surface (upper surface). The solar battery cell 3 has a plurality of electrodes 3a on the front surface (lower surface, back surface). The wiring electrode 2 a and the electrode 3 a are electrically connected by one or a plurality of conductive particles 21. Therefore, the flexible printed circuit board 2 and the solar battery cell 3 are electrically connected by the conductive particles 21. The first connection portion is disposed between the wiring electrode 2a and the electrode 3a. The second connection portion is disposed between a portion of the flexible printed board 2 where the wiring electrode 2a is not provided and a portion where the electrode 3a of the solar battery cell 3 is not provided. The second connection portion may be disposed between the wiring electrode 2a and the electrode 3a.

  Instead of the flexible printed circuit board 2 having the wiring electrode 2a on the surface, a resin film having the wiring electrode on the surface may be used.

  The solar cell module shown in FIG. 1 can be obtained, for example, through the steps shown in FIGS. 2 (a) to 2 (c) below.

  A flexible printed circuit board 2 having wiring electrodes 2a on the surface is prepared. Also, a conductive material 4A containing conductive particles 21 and a binder resin is prepared. In the present embodiment, the binder resin includes a thermosetting compound and a thermosetting agent, and a conductive material 4A having thermosetting properties is used. The conductive material 4A is also a connection material. Next, as shown in FIG. 2A, the conductive material 4A is selectively placed on the wiring electrode 2a of the flexible printed board 2 (first placement step). Instead of the wiring electrode 2a of the flexible printed board 2, the conductive material 4A may be selectively disposed on the electrode 3a of the solar battery cell 3.

  In the present embodiment, in the first arrangement step, the conductive material is not uniformly applied on the entire flexible printed board. As much as possible, it is preferable to dispose the conductive material on the wiring electrode, and it is preferable to dispose the conductive material only on the wiring electrode. However, a conductive material may also be disposed in a portion of the flexible printed board where the wiring electrode is not provided. The smaller the conductive material arranged in the portion of the flexible printed circuit board where the wiring electrodes are not provided, the better.

  Therefore, in the first arrangement step, in the entire conductive material disposed on the flexible printed circuit board or the resin film in 100% by weight, or in the entire conductive material disposed on the solar battery cell in 100% by weight. The amount of the conductive material disposed on or on the wiring electrode is preferably 70% by weight or more, more preferably 90% by weight or more, and further preferably 100% by weight (total amount). However, the conductive material may be uniformly arranged on the flexible printed circuit board or the resin film wiring electrode and on the flexible printed circuit board or the resin film where the wiring electrode is not provided. You may arrange | position a conductive material uniformly on the part in which the electrode of the said photovoltaic cell and the electrode of the said photovoltaic cell are not provided.

  From the viewpoint of further improving the placement accuracy, the placement of the conductive material is preferably performed by printing or application by a dispenser. Therefore, the conductive material is preferably a conductive paste. However, the conductive material may be a conductive film. If a conductive film is used, the excessive flow of the conductive film after arrangement | positioning can be suppressed. On the other hand, it is necessary to prepare a conductive film having a predetermined size.

  Moreover, the photovoltaic cell 3 which has the electrode 3a on the surface is prepared. Moreover, the connection material 4B which does not contain electroconductive particle is prepared. The connecting material 4B includes a thermosetting compound and a thermosetting agent. As shown in FIG.2 (b), the connection material 4B which does not contain electroconductive particle is arrange | positioned on the surface of the side by which the electrode 3a of the photovoltaic cell 3 is provided (2nd arrangement | positioning process). When the conductive material 4A is selectively disposed on the electrode 3a of the solar battery cell 3, the flexible printed board 2 having the wiring electrode 2a on the surface is prepared. A connection material 4B that does not contain conductive particles is disposed on the surface of the flexible printed circuit board 2 on which the wiring electrodes 2a are provided (second disposing step). Note that a connection material that does not include conductive particles may not be disposed.

  Next, the flexible printed circuit board 2 obtained in the first arrangement step and provided with the conductive material 4A is bonded to the solar battery cell 3 obtained in the second arrangement step and provided with the connection material 4B. The process of matching is performed. That is, as shown in FIG. 2 (c), the flexible printed circuit board 2 and the solar cell are connected so that the wiring electrode 2 a of the flexible printed circuit board 2 and the electrode 3 a of the solar battery cell 3 are electrically connected by the conductive particles 21. The battery cell 3 is bonded together (bonding process). A conductive material 4A including conductive particles 21 is disposed between the wiring electrode 2a and the electrode 3a. A connecting material 4B that does not include conductive particles is disposed between a portion of the flexible printed circuit board 2 where the wiring electrode 2a is not provided and a portion of the solar battery cell 3 where the electrode 3a is not provided.

It is preferable to pressurize in the said bonding process. By the pressurization, the protrusions effectively break through the oxide film on the surface of the conductive portion or the surface of the electrode. As a result, the conduction reliability can be further improved. The pressure of the pressurization is preferably 1.0 × 10 ³ Pa or more, and preferably 1.0 × 10 ⁶ Pa or less. When the pressure of the pressurization is not less than the above lower limit and not more than the above upper limit, the conduction reliability between the electrodes is further enhanced.

  As described above, the connection portion 4 is formed by the conductive material 4A and the connection material 4B. Moreover, the solar cell module 1 shown in FIG. 1 is obtained by arrange | positioning the sealing material 5 and the sealing material 6 as needed.

  Moreover, in the said bonding process, it is preferable to heat 4A of conductive materials and the connection material 4B. By heating, the conductive material 4 </ b> A and the connection material 4 </ b> B can be cured to form the cured connection portion 4.

  The heating temperature is preferably 50 ° C. or higher, more preferably 80 ° C. or higher, still more preferably 100 ° C. or higher, preferably 200 ° C. or lower, more preferably 170 ° C. or lower. When the temperature of the heating is not less than the above lower limit and not more than the above upper limit, curing can be sufficiently advanced and connection reliability can be effectively increased.

  The heating time from the start of heating to the completion of heating is preferably 30 seconds or longer, more preferably 60 seconds or longer. The heating time from the start of heating to the completion of heating is preferably 1200 seconds or less, more preferably 600 seconds or less. When the heating time is not less than the above lower limit and not more than the above upper limit, curing can sufficiently proceed and connection reliability can be effectively improved.

  The solar cell module shown in FIG. 1 can also be obtained, for example, through the steps shown in FIGS. 3 (a) to 3 (c) below.

  A flexible printed circuit board 2 having wiring electrodes 2a on the surface is prepared. Also, a conductive material 4A containing conductive particles 21 and a binder resin is prepared. As shown in FIG. 3A, the conductive material 4A is selectively placed on the wiring electrode 2a of the flexible printed circuit board 2 (first placement step). Instead of the wiring electrode 2a of the flexible printed board 2, the conductive material 4A may be selectively disposed on the electrode 3a of the solar battery cell 3.

  Moreover, the connection material 4B which does not contain electroconductive particle is prepared. The connecting material 4B is disposed on the portion of the flexible printed board 2 where the wiring electrode 2a is not provided (second disposing step). In the first arrangement step and the second arrangement step, the first arrangement step may be performed first, or the second arrangement step may be performed first. The first arrangement step and the second arrangement step may be performed simultaneously.

  Moreover, as shown in FIG.3 (b), the photovoltaic cell 3 which has the electrode 3a on the surface is prepared. When the conductive material 4A is selectively disposed on the electrode 3a of the solar battery cell 3, the flexible printed board 2 having the wiring electrode 2a on the surface is prepared.

  Next, the step of bonding the flexible printed circuit board 2 on which the conductive material 4A and the connection material 4B are arranged and the solar cell 3 obtained in the first and second arrangement steps is performed. As shown in FIG. 3 (c), the flexible printed circuit board 2 and the solar battery cell are connected so that the wiring electrode 2 a of the flexible printed circuit board 2 and the electrode 3 a of the solar battery cell 3 are electrically connected by the conductive particles 21. 3 are bonded together (bonding process).

  As described above, the connection portion 4 is formed by the conductive material 4A and the connection material 4B. Moreover, the solar cell module 1 shown in FIG. 1 is obtained by arrange | positioning the sealing material 5 and the sealing material 6 as needed.

  As an electrode (wiring electrode) provided on the flexible printed circuit board or the resin film and an electrode provided on the solar battery cell, a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a silver electrode, Metal electrodes such as a molybdenum electrode and a tungsten electrode can be mentioned. Especially, a copper electrode (copper wiring electrode) or an aluminum electrode (aluminum wiring electrode) is preferable, and an aluminum electrode (aluminum wiring electrode) is especially preferable. It is particularly preferable that the wiring electrode provided on the flexible printed board or the resin film is an aluminum wiring electrode, or the electrode provided on the solar battery cell is an aluminum electrode. In this case, only one of the wiring electrode provided on the flexible printed circuit board or the resin film and the electrode provided on the solar battery cell may be formed of aluminum, both of which are aluminum. May be formed. The wiring electrode provided on the flexible printed circuit board or the resin film may be an aluminum wiring electrode, and the electrode provided on the solar battery cell may be an aluminum electrode. In the case of using an aluminum electrode (aluminum wiring electrode), the effect of the present invention is further exhibited, and in particular, the effect due to the protrusion of the conductive particles is further exhibited.

  Hereinafter, other details of the conductive particles, the conductive material, and the solar cell module will be described. In the following description, “(meth) acryl” means one or both of “acryl” and “methacryl”, and “(meth) acrylate” means one or both of “acrylate” and “methacrylate”. To do.

(Conductive particles)
The conductive particles may be entirely formed of a conductive portion (conductive material). It is preferable that the said electroconductive particle is equipped with base material particle and the electroconductive part arrange | positioned on the surface of this base material particle.

  Examples of the substrate particles include resin particles, inorganic particles excluding metal particles, organic-inorganic hybrid particles, and metal particles. The substrate particles are preferably substrate particles excluding metal particles, and more preferably resin particles, inorganic particles excluding metal particles, or organic-inorganic hybrid particles.

  The substrate particles are preferably resin particles formed of a resin. When connecting the electrodes, the conductive particles are generally compressed after the conductive particles are arranged between the electrodes. When the substrate particles are resin particles, the conductive particles are easily deformed by compression, and the contact area between the conductive particles and the electrode is increased. For this reason, the conduction | electrical_connection reliability between electrodes becomes high.

  Various organic materials are suitably used as the resin for forming the resin particles. Examples of the resin for forming the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; Alkylene terephthalate, polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene Oxide, polyacetal, polyimide, polyamideimide, polyether ether Tons, polyethersulfone, and polymers such as obtained by polymerizing various polymerizable monomers one or more having an ethylenically unsaturated group is used. By polymerizing one or more of various polymerizable monomers having an ethylenically unsaturated group, it is possible to design and synthesize resin particles having any compression property suitable for a conductive material.

  When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, as the polymerizable monomer having an ethylenically unsaturated group, a non-crosslinkable monomer and And a crosslinkable monomer.

  Examples of the non-crosslinkable monomer include styrene monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid, and maleic anhydride; (Meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl ( Alkyl (meth) acrylates such as (meth) acrylate and isobornyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate, glycidyl (meth) acrylate, dicycle Oxygen atom-containing (meth) acrylates such as pentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, 1,3-adamantanediol di (meth) acrylate; Nitrile-containing monomers such as acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether; acid vinyl esters such as vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate; ethylene, propylene, isoprene, butadiene, etc. Unsaturated hydrocarbons such as: trifluoromethyl (meth) acrylate, pentafluoroethyl (meth) acrylate, halogen-containing monomers such as vinyl chloride, vinyl fluoride, and chlorostyrene.

  From the viewpoint of further improving compression characteristics, aliphatic (meth) acrylate is preferable, and cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate Dicyclopentanyl (meth) acrylate or 1,3-adamantanediol di (meth) acrylate is more preferable.

  Examples of the crosslinkable monomer include tetramethylolmethane tetra (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and dipenta Erythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) Polyfunctional (meth) acrylates such as acrylate, (poly) tetramethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate; triallyl (iso) cyanure And silane-containing monomers such as triallyl trimellitate, divinylbenzene, diallyl phthalate, diallylacrylamide, diallyl ether, γ- (meth) acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, vinyltrimethoxysilane It is done.

  From the viewpoint of further improving the compression characteristics, polyfunctional (meth) acrylate is preferable, and (poly) tetramethylene glycol di (meth) acrylate or 1,4-butanediol di (meth) acrylate is more preferable.

  The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method. Examples of this method include a method of suspension polymerization in the presence of a radical polymerization initiator, and a method of polymerizing by swelling a monomer together with a radical polymerization initiator using non-crosslinked seed particles.

  In the case where the substrate particles are inorganic particles or organic-inorganic hybrid particles excluding metal particles, examples of the inorganic material that is a material of the substrate particles include silica and carbon black. The inorganic substance is preferably not a metal. The particles formed from the silica are not particularly limited. For example, after forming a crosslinked polymer particle by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups, firing may be performed as necessary. The particle | grains obtained by performing are mentioned. Examples of the organic / inorganic hybrid particles include organic / inorganic hybrid particles formed of a crosslinked alkoxysilyl polymer and an acrylic resin.

  When the substrate particles are metal particles, examples of the metal that is a material of the metal particles include silver, copper, nickel, silicon, gold, and titanium. However, the substrate particles are preferably not metal particles.

  The average particle diameter of the substrate particles is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 10 μm or more, preferably 500 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. The average particle diameter of the substrate particles may be 20 μm or less. When the average particle diameter of the base particles is not less than the above lower limit and not more than the above upper limit, when the electrodes are connected using conductive particles, the contact area between the conductive particles and the electrodes becomes sufficiently large, and the conductive particles are conductive. Aggregated conductive particles are less likely to be formed when the layer is formed. Further, the distance between the electrodes connected via the conductive particles does not become too large, and the conductive portion is difficult to peel from the surface of the base particle. From the viewpoint of absorbing the influence of unevenness on the circuit surface of the solar battery cell or flexible printed board, the average particle diameter of the base particles is preferably 10 μm or more and 50 μm or less.

  The “average particle diameter” of the substrate particles indicates a number average particle diameter. The average particle diameter of the resin particles is obtained by observing 50 arbitrary resin particles with an electron microscope or an optical microscope and calculating an average value.

  The thickness of the conductive part is preferably 5 nm or more, more preferably 10 nm or more, further preferably 20 nm or more, particularly preferably 50 nm or more, preferably 1000 nm or less, more preferably 800 nm or less, still more preferably 500 nm or less, particularly Preferably it is 400 nm or less, Most preferably, it is 300 nm or less. When there are a plurality of conductive portions, the thickness of the conductive portion indicates the thickness of the entire plurality of conductive portions. When the thickness of the conductive part is equal to or greater than the lower limit, the conductivity of the conductive particles is further improved. When the thickness of the conductive part is not more than the above upper limit, the difference in the coefficient of thermal expansion between the base particle and the conductive part becomes small, and the conductive part becomes difficult to peel from the base particle.

  Examples of a method for forming the conductive part on the surface of the substrate particle include a method for forming the conductive part by electroless plating and a method for forming the conductive part by electroplating.

  The conductive part preferably contains a metal. The metal that is the material of the conductive part is not particularly limited. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, tungsten, molybdenum and cadmium, and alloys thereof. Is mentioned. Further, tin-doped indium oxide (ITO) may be used as the metal. As for the said metal, only 1 type may be used and 2 or more types may be used together.

  The melting point of the outer surface of the conductive part is 300 ° C. or higher. When the melting point of the outer surface of the conductive part is less than 300 ° C., the conductive part may melt during thermosetting of the connection part. The outer surface of the conductive part is preferably not solder. Solder is inferior in contact with the aluminum electrode. The melting point of the outer surface of the conductive part is preferably 350 ° C. or higher, more preferably 400 ° C. or higher, and still more preferably 450 ° C. or higher.

  The conductive particles have a plurality of protrusions on the outer surface of the conductive part. Since the core substance is embedded in the conductive portion, protrusions can be easily formed on the outer surface of the conductive portion. An oxide film is often formed on the surface of the electrode connected by the conductive particles. When conductive particles having protrusions are used, the oxide film is effectively excluded by the protrusions by placing the conductive particles between the electrodes and pressing them. For this reason, an electrode and electroconductive particle contact more reliably and the connection resistance between electrodes becomes still lower. Furthermore, the protrusion effectively eliminates the binder resin between the conductive particles and the electrode. For this reason, the conduction | electrical_connection reliability between electrodes becomes high.

  As a method for forming protrusions on the surface of the conductive particles, a method of forming a conductive portion by electroless plating after attaching a core substance to the surface of the base particles, and electroless plating on the surface of the base particles After the conductive part is formed by the method, the core material is attached, and the conductive part is further formed by electroless plating, and the conductive part is formed by adding the core substance in the middle stage of forming the conductive part by electroless plating. And the like. As another method of forming the protrusion, a method of forming a core material by reaction in a plating bath during electroless plating formation without adding a core material, and forming a conductive layer together with the core material by electroless plating Etc. As a method for attaching the core substance to the surface of the substrate particles, a conventionally known method can be adopted. Since the core substance is embedded in the conductive portion, it is easy for the conductive portion to have a plurality of protrusions on the outer surface. However, the core substance is not necessarily used in order to form protrusions on the surfaces of the conductive particles and the conductive part. The core substance is preferably disposed inside or inside the conductive part.

  Examples of the material of the core substance include a conductive substance and a non-conductive substance. Examples of the conductive material include conductive non-metals such as metals, metal oxides, and graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene. Examples of the nonconductive material include silica, alumina, and zirconia. Among them, metal is preferable because conductivity can be increased and connection resistance can be effectively reduced. The core substance is preferably metal particles.

  Examples of the metal include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium and cadmium, and tin-lead. Examples include alloys composed of two or more metals such as alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. Of these, nickel, copper, silver or gold is preferable. The metal that is the material of the core substance may be the same as or different from the metal that is the material of the conductive part. The material of the core substance preferably includes nickel. Examples of the metal oxide include alumina, silica and zirconia.

  The shape of the core material is not particularly limited. The shape of the core substance is preferably a lump. Examples of the core substance include a particulate lump, an agglomerate in which a plurality of fine particles are aggregated, and an irregular lump.

  The average diameter (average particle diameter) of the core substance is preferably 0.001 μm or more, more preferably 0.05 μm or more, preferably 0.6 μm or less, more preferably 0.4 μm or less. The average diameter of the core substance may be 0.9 μm or less, or 0.2 μm or less. When the average diameter of the core substance is not less than the above lower limit and not more than the above upper limit, the connection resistance between the electrodes is effectively reduced.

  The “average diameter (average particle diameter)” of the core substance indicates a number average diameter (number average particle diameter). The average diameter of the core material is obtained by observing 50 arbitrary core materials with an electron microscope or an optical microscope and calculating an average value.

  The number of the protrusions per one conductive particle is preferably 10 or more, more preferably 200 or more, and still more preferably 500 or more. The number of the protrusions may be 3 or more, or 5 or more. The upper limit of the number of protrusions is not particularly limited. The upper limit of the number of protrusions can be appropriately selected in consideration of the particle diameter of the conductive particles. The number of the protrusions is preferably 1500 or less, more preferably 1000 or less.

  From the viewpoint of further improving the conduction reliability, the average height of the plurality of protrusions is preferably 10 nm or more, more preferably 50 nm or more, further preferably 200 nm or more, preferably 1000 nm or less, more preferably 600 nm or less. More preferably, it is 500 nm or less. The average height of the plurality of protrusions may be 300 nm or less. When the average height of the protrusions is not less than the above lower limit and not more than the above upper limit, the connection resistance between the electrodes is effectively reduced.

  The height of the protrusion is the imaginary line of the conductive portion (the broken line shown in FIG. 4) on the line connecting the center of the conductive particles and the tip of the protrusion (broken line L1 shown in FIG. 4) when there is no protrusion. L2) Indicates the distance from the top (on the outer surface of the spherical conductive particles assuming no projection) to the tip of the projection. That is, in FIG. 4, the distance from the intersection of the broken line L1 and the broken line L2 to the tip of the protrusion is shown.

  From the viewpoint of further improving the conduction reliability, the ratio of the average height of the plurality of protrusions to the thickness of the conductive portion is preferably 1 or more, more preferably 2 or more, preferably 7 or less, more preferably 6 It is as follows.

Conduction from the viewpoint of the reliability further increased, the compression modulus when the conductive particles are compressed 10% (10% K value), preferably 1100 N / mm ² or more, more preferably 1300 N / mm ² or more, even more preferably 1500 N / mm ² or more, more preferably 1600 N / mm ² or more, even more preferably 1800 N / mm ² or more, particularly preferably 2000N / mm ² or more, preferably 5000N / mm ² or less, more preferably the 4500N / mm ^2, more preferably not more than 4000 N / mm ^2.

  The compression elastic modulus (10% K value) of the conductive particles can be measured as follows.

  Using a micro-compression tester, the conductive particles are compressed under the conditions of 25 ° C., compression speed of 2.6 mN / sec, and maximum test load of 10 gf on the end face of a cylindrical indenter (diameter 50 μm, made of diamond). The load value (N) and compression displacement (mm) at this time are measured. From the measured value obtained, the compression elastic modulus can be obtained by the following formula. As the micro compression tester, for example, “Fischer Scope H-100” manufactured by Fischer is used.

K value (N / mm ² ) = (3/2 ^1/2 ) · F · S ⁻³ / ² · R ^−1/2
F: Load value when the conductive particles are 10% compressively deformed (N)
S: Compression displacement (mm) when the conductive particles are 10% compressively deformed
R: radius of conductive particles (mm)

  The compression elastic modulus universally and quantitatively represents the hardness of the conductive particles. By using the compression elastic modulus, the hardness of the conductive particles can be expressed quantitatively and uniquely.

  The fracture strain of the conductive particles is 55% or more. From the viewpoint of further improving the conduction reliability, the fracture strain of the conductive particles is preferably 55% or more, more preferably 60% or more, still more preferably 65% or more, and particularly preferably 70% or more. In the case of not breaking, the breaking strain substantially exceeds 70%.

  The fracture strain can be measured as follows.

  Using a micro-compression tester, the conductive particles are compressed under the conditions of 25 ° C., compression speed of 2.6 mN / sec, and maximum test load of 10 gf on the end face of a cylindrical indenter (diameter 50 μm, made of diamond). It is a value obtained from the following equation from the measured value of the compression displacement when the conductive particles are destroyed in the compression process.

Fracture strain (%) = (B / D) × 100
B: Compression displacement (mm) when the conductive particles are broken
D: Diameter of conductive particles (mm)

  For example, the compression elastic modulus and the fracture strain can be controlled within the above range by the composition of the monomer constituting the base particle.

  From the viewpoint of further improving the conduction reliability, the compression recovery rate when the conductive particles are compressed by 10% is preferably 40% or more, more preferably 45% or more, and further preferably 50% or more, preferably 80% or less, more preferably 70% or less, and still more preferably 60% or less.

  From the viewpoint of further improving the conduction reliability, the compression recovery rate when the conductive particles are compressed by 50% is preferably 3% or more, more preferably 5% or more, still more preferably 7% or more, preferably It is 18% or less, more preferably 15% or less, and still more preferably 10% or less.

  The compression recovery rate can be measured as follows.

  Spread conductive particles on the sample stage. For each dispersed conductive particle, using a micro-compression tester, 10% of the conductive particles at 25 ° C. in the center direction of the conductive particles on the end surface of a cylindrical (diameter 50 μm, made of diamond) smooth indenter Alternatively, a load (reverse load value) is applied until 50% compression deformation occurs. Thereafter, unloading is performed up to the origin load value (0.40 mN). The load-compression displacement during this period is measured, and the compression recovery rate can be obtained from the following equation. The load speed is 0.33 mN / sec. As the micro compression tester, for example, “Fischer Scope H-100” manufactured by Fischer is used.

Compression recovery rate (%) = [(L1-L2) / L1] × 100
L1: Compression displacement from the load value for origin to the reverse load value when applying a load L2: Unloading displacement from the reverse load value to the load value for origin when releasing the load

  For example, the compression recovery rate can be controlled within the above range by the composition of the monomers constituting the substrate particles.

  The average particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 10 μm or more, preferably 500 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. The average particle diameter of the conductive particles may be 20 μm or less. When the average particle diameter of the conductive particles is not less than the above lower limit and not more than the above upper limit, the contact area between the conductive particles and the electrode becomes sufficiently large when the electrodes are connected using the conductive particles, and the conductive Aggregated conductive particles are less likely to be formed when the layer is formed. In addition, the interval between the electrodes connected via the conductive particles does not become too large, and the conductive portion is difficult to peel from the surface of the conductive particles. From the viewpoint of absorbing the influence of unevenness on the circuit surface of the solar battery cell or flexible printed circuit board, the average particle diameter of the conductive particles is preferably 10 μm or more and 50 μm or less.

  The “average particle size” of the conductive particles indicates a number average particle size. The average particle diameter of the resin particles is obtained by observing 50 arbitrary resin particles with an electron microscope or an optical microscope and calculating an average value.

  From the viewpoint of enhancing the conduction reliability between the electrodes and the photoelectric conversion efficiency in the solar cell module, the content of the conductive particles in the conductive material of 100% by weight is 0.1% by weight or more and 30% by weight or less. In 100% by weight of the conductive material, the content of the conductive particles is preferably 0.3% by weight or more, more preferably 0.5% by weight or more, preferably 20% by weight or less, more preferably 10% by weight. Hereinafter, it is more preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less. When the content of the conductive particles is not less than the above lower limit and not more than the above upper limit, the conduction reliability between the electrodes is further enhanced.

(Thermosetting component)
The conductive material includes a thermosetting compound (a curable compound that can be cured by heating) and a thermosetting agent. The connection material preferably includes a thermosetting component. The connection material preferably includes a thermosetting compound (a curable compound that can be cured by heating) and a thermosetting agent.

  Examples of the thermosetting compound include epoxy compounds, episulfide compounds, (meth) acrylic compounds, phenolic compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. As for the said thermosetting compound, only 1 type may be used and 2 or more types may be used together.

  From the viewpoint of further improving the conduction reliability, the thermosetting component preferably contains an epoxy compound.

  Examples of the thermosetting agent include imidazole curing agents, amine curing agents, phenol curing agents, polythiol curing agents, and other thiol curing agents, acid anhydrides, and thermal cationic curing initiators (thermal cationic curing agents). As for the said thermosetting agent, only 1 type may be used and 2 or more types may be used together.

  The imidazole curing agent is not particularly limited, and 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2, 4-Diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine and 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s- Examples include triazine isocyanuric acid adducts.

  The thiol curing agent is not particularly limited, and examples thereof include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate. .

  The amine curing agent is not particularly limited, and hexamethylene diamine, octamethylene diamine, decamethylene diamine, 3,9-bis (3-aminopropyl) -2,4,8,10-tetraspiro [5.5]. Examples include undecane, bis (4-aminocyclohexyl) methane, metaphenylenediamine, and diaminodiphenylsulfone.

  Examples of the thermal cationic curing initiator include iodonium cationic curing agents, oxonium cationic curing agents, and sulfonium cationic curing agents. Examples of the iodonium-based cationic curing agent include bis (4-tert-butylphenyl) iodonium hexafluorophosphate. Examples of the oxonium-based cationic curing agent include trimethyloxonium tetrafluoroborate. Examples of the sulfonium-based cationic curing agent include tri-p-tolylsulfonium hexafluorophosphate.

  The content of the thermosetting agent is not particularly limited. Each content of the thermosetting agent is preferably 5 parts by weight or more with respect to 100 parts by weight of the thermosetting compound in the conductive material and 100 parts by weight of the thermosetting compound in the connection material. Is 10 parts by weight or more, preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and still more preferably 20 parts by weight or less. When the content of the thermosetting agent is not less than the above lower limit and not more than the above upper limit, the conductive paste and the connection material can be sufficiently thermoset.

  In 100% by weight of the conductive material, the content of the thermosetting component and the total content of the thermosetting compound and the thermosetting agent are each preferably 10% by weight or more, more preferably 30% by weight. More preferably, it is 50% by weight or more, particularly preferably 70% by weight or more, preferably 99.99% by weight or less, more preferably 99.9% by weight or less. When the content of the thermosetting component and the total content of the thermosetting compound and the thermosetting agent are not less than the above lower limit and not more than the above upper limit, conductive particles are efficiently disposed between the electrodes. The connection reliability is further increased.

(Light reflecting material and fluorescent material)
The conductive material includes at least one of a light reflecting material and a fluorescent material. The said light reflecting material reflects the light which reached the light reflecting material in a connection part, and raises the photoelectric conversion efficiency of a solar cell module. The said fluorescent material improves the photoelectric conversion efficiency of a solar cell module by exhibiting a fluorescence effect | action. The conductive material may include the light reflecting material, may include the fluorescent material, or may include both the light reflecting material and the fluorescent material.

  Examples of the light reflecting material include glass beads, mica, talc, boron nitride, zinc oxide, titanium oxide, aluminum oxide, and montmorillonite. As for the said light reflection material, only 1 type may be used and 2 or more types may be used together.

  From the viewpoint of effectively increasing the photoelectric conversion efficiency, the light reflecting material is preferably a plate-like filler. From the viewpoint of effectively increasing the photoelectric conversion efficiency, the light reflecting material is preferably a plate-like filler. The aspect ratio (major axis / thickness) of the plate-like filler is preferably 10 or more, and preferably 50 or less.

  Examples of the fluorescent material include polycyclic aromatic hydrocarbons such as a compound having an anthracene ring, a compound having a naphthalene ring, and a compound having a phenanthrene ring. As for the said fluorescent material, only 1 type may be used and 2 or more types may be used together.

  From the viewpoint of effectively increasing the photoelectric conversion efficiency, the fluorescent material is preferably a compound having an anthracene ring.

  Examples of the compound having an anthracene ring include 9,10-dihydroxyanthracene, 2-anthracenecarboxylic acid, 2,3-anthracene dicarboxylic acid, 2,3-anthracene dicarboxylic acid anhydride, benzanthracene, 9-cyanoanthracene, and 9 , 10-bis (phenylethynyl) anthracene and the like.

  In 100% by weight of the conductive material, the total content of the light reflecting material and the fluorescent material is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and preferably 50% by weight. Hereinafter, it is more preferably 30% by weight or less. Further, in 100% by weight of the conductive material, the content of the light reflecting material is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, preferably 50% by weight or less, more preferably 30% by weight or less. The total content of the conductive material in 100% by weight of the conductive material is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and preferably 50% by weight or less. Preferably it is 30 weight% or less. When the content of the light reflecting material and the fluorescent material is not less than the lower limit and not more than the upper limit, the photoelectric conversion efficiency is further increased.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

(Examples 1-11, 14, 15 and Comparative Example 1)
(1) Preparation of electroconductive particle The copolymer particle (average particle diameter of 20 micrometers) formed with styrene and isobornyl acrylate was prepared. A palladium catalyst and a nickel core material were attached to the copolymer particles, and then electroless nickel plating was performed to produce conductive particles having a plurality of protrusions on the nickel surface. The thickness of the nickel layer was 0.1 μm, and the average height of the protrusions was 450 nm.

(2) Preparation of conductive material (conductive paste) The components shown in Tables 1 and 2 below are blended in the amounts shown in Tables 1 and 2 below, and stirred for 5 minutes at 2000 rpm using a planetary stirrer. Thus, a conductive material was obtained.

(3) Production of connection material (paste) Of the components of the conductive material produced as described above, a material in which conductive particles, a reflective material, and a fluorescent material were not blended was used as the connection material.

(4) Production of Solar Cell Module A flexible printed circuit board (L / S = 50 μm / 50 μm) having an aluminum wiring electrode on its surface was prepared. Moreover, the photovoltaic cell (L / S = 50micrometer / 50micrometer) which has a copper electrode on the surface was prepared.

  A conductive material was selectively applied on the wiring electrode of the flexible printed board by using a screen printer to partially form a conductive material layer having a thickness of 50 μm. All of the conductive material on the flexible printed circuit board was disposed on the wiring electrode. That is, the amount of the conductive material disposed on the wiring electrode was 100% by weight out of 100% by weight of the entire conductive material disposed on the flexible printed board.

  Moreover, the connection material was apply | coated to the surface of the side by which the electrode of the photovoltaic cell was provided over the whole by screen printing, and the connection material layer with a thickness of 100 micrometers was formed.

  Next, the flexible printed circuit board and the solar battery cell were bonded together so that the aluminum wiring electrode of the flexible printed circuit board and the copper electrode of the solar battery cell were electrically connected by conductive particles. At this time, the flexible printed circuit board and the solar battery cell were placed in a vacuum laminate for 5 minutes in an atmosphere of 150 ° C. so as to be sandwiched between the glass substrate and the EVA film. The conductive material layer and the connection material layer were cured by heating during laminating to form a connection portion. A solar cell module was obtained in which the aluminum wiring electrode of the flexible printed board and the copper electrode of the solar cell were electrically connected by conductive particles.

(Example 12)
A solar cell module was obtained in the same manner as in Example 1 except that the electrode of the solar cell was changed from a copper electrode to an aluminum electrode.

(Example 13)
A solar cell module was obtained in the same manner as in Example 1 except that the connecting material was not used.

(Example 16)
A solar cell module was obtained in the same manner as in Example 1 except that the conductive material was applied not only on the wiring but on the entire surface without using the connection material.

(Example 17)
A solar cell module was obtained in the same manner as in Example 1 except that the conductive particles were changed to spherical copper powder (conductive particles) having an average particle diameter of 20 μm.

(Evaluation)
(1) Compressive elastic modulus of conductive particles (10% K value)
The compression modulus (10% K value) of the obtained conductive particles was measured by the above-described method using a micro compression tester (“Fischer Scope H-100” manufactured by Fischer).

(2) Fracture strain of conductive particles The fracture strain of the obtained conductive particles was measured by the above-described method using a micro-compression tester (“Fischerscope H-100” manufactured by Fischer).

(3) Compression recovery rate of conductive particles The compression recovery rate when the obtained conductive particles were compressed by 10% and the compression recovery rate when compressed by 50% were measured by the above-described method using a micro compression tester (Fischer Corporation). It was measured using “Fischer Scope H-100”).

  Conductive particles were sprayed on the sample stage. For each dispersed conductive particle, using a micro-compression tester, 10% of the conductive particles at 25 ° C. in the center direction of the conductive particles at the end face of a cylindrical (diameter 50 μm, diamond) smooth indenter Alternatively, a load (reverse load value) was applied until 50% compression deformation occurred. Thereafter, unloading was performed up to the load value for origin (0.40 mN). The load-compression displacement during this period was measured, and the compression recovery rate was determined from the above formula.

(4) Initial energy conversion efficiency The energy conversion efficiency in the obtained solar cell module was measured. The initial energy conversion efficiency was determined according to the following criteria.

[Evaluation criteria for initial energy conversion efficiency]
XX: Energy conversion efficiency exceeds 23% XX: Energy conversion efficiency exceeds 20% and 23% or less O: Energy conversion efficiency exceeds 18% and 20% or less △: Energy conversion efficiency exceeds 16% 18 % Or less ×: Energy conversion efficiency is 16% or less

(5) Energy conversion efficiency after reliability test About the obtained solar cell module, cycle test of −40 ° C. to 90 ° C., holding time 30 minutes, temperature change rate 87 ° C./hour is performed 200 cycles with a cycle tester. After doing, energy conversion efficiency was measured. The energy conversion efficiency after the reliability test was determined according to the following criteria.

[Evaluation criteria for energy conversion efficiency after reliability test]
XX: Energy conversion efficiency exceeds 23% XX: Energy conversion efficiency exceeds 20% and 23% or less O: Energy conversion efficiency exceeds 18% and 20% or less △: Energy conversion efficiency exceeds 16% 18 % Or less ×: Energy conversion efficiency is 16% or less

  The results are shown in Tables 1 to 3 below.

  In addition, the number of protrusions per conductive particle in Examples 1 to 16 and Comparative Example 1 was about 300 to about 900.

DESCRIPTION OF SYMBOLS 1 ... Solar cell module 2 ... Flexible printed circuit board 2a ... Wiring electrode 3 ... Solar cell 3a ... Electrode 4 ... Connection part 4A ... Conductive material 4B ... Connection material 5 ... Sealing material 6 ... Sealing material 21, 21A, 21B, 21C: Conductive particles 21a, 21Aa, 21Ba ... Protrusions 22 ... Base particles 23, 23A, 23B, 23C ... Conductive portions 23a, 23Aa, 23Ba ... Protrusions 23Bx ... First conductive portions 23By ... Second conductive portions 24 ... Core material

Claims (13)

A flexible printed circuit board having a wiring electrode on its surface or a resin film having a wiring electrode on its surface, and a solar cell having an electrode on its surface, electrically connecting the wiring electrode and the electrode, A conductive material used to obtain a solar cell module,
A conductive material for a solar cell module of a back contact system, comprising conductive particles having an outer surface melting point of 300 ° C. or higher, a thermosetting component, and at least one of a light reflecting material and a fluorescent material. .   The conductive material for a back contact solar cell module according to claim 1, wherein the light reflecting material is a plate-like filler.   The back contact type solar cell module conductive material according to claim 1 or 2, comprising the light reflecting material.   The conductive material for a back contact solar cell module according to any one of claims 1 to 3, wherein the fluorescent material is a compound having an anthracene ring.   The back contact type solar cell module conductive material according to any one of claims 1 to 4, comprising the fluorescent material.   The back contact solar cell module according to any one of claims 1 to 5, wherein a content of the conductive particles is 0.1 wt% or more and 30 wt% or less in 100 wt% of the conductive material. Conductive material.   The conductive material for a solar cell module according to any one of claims 1 to 6, wherein the thermosetting component contains an epoxy compound.   The back contact type solar cell module electroconductivity according to any one of claims 1 to 7, wherein the conductive particles include base particles and a conductive portion disposed on a surface of the base particles. material.   The conductive material for a back contact solar cell module according to claim 8, wherein the substrate particles are resin particles or organic-inorganic hybrid particles.   The conductive material for a back contact solar cell module according to any one of claims 1 to 9, wherein the conductive particles have a plurality of protrusions on an outer surface of a conductive portion.   11. The conductive material for a back contact solar cell module according to claim 10, wherein an average height of the plurality of protrusions in the conductive particles is 10 nm or more and 1000 nm or less.   The conductive material for a back contact solar cell module according to any one of claims 1 to 11, wherein the wiring electrode of the flexible printed circuit board or the resin film is an aluminum wiring electrode. A flexible printed circuit board or resin film having wiring electrodes on the surface;
A solar battery cell having an electrode on its surface;
A connecting portion connecting the flexible printed circuit board or the resin film and the solar battery cell;
The material of the connection portion is a conductive material for a back contact solar cell module according to any one of claims 1 to 12,
A back contact type solar cell module in which the wiring electrode and the electrode are electrically connected by the conductive particles.

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