JP2016178303A - Conductive material for solar battery module, and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive material for a solar battery module, which enables the increase in the reliability of connection and the reliability of electrical conduction between electrodes in a solar battery module.SOLUTION: A conductive material for a solar battery module according to the present invention comprises: conductive particles, each including a conductive part having a melting point of 300°C or higher at its outer surface; a thermosetting compound; and a microcapsule type hardener. The conductive material has a viscosity of 50 Pa s or more at 25°C. The conductive material is 1-10 Pa s in minimum melt viscosity when heated from 25°C to 180°C at a temperature rising rate of 10°C/minute. When the conductive material is heated from 25°C to 180°C at a temperature rising rate of 10°C/minute, a length of time during which the viscosity of the conductive material is 10 Pa s or less is 200-1000 seconds.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive material used for a solar cell module. The present invention also relates to a 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.

  Further, in recent years, ribbon type solar cell modules are shifting to a method in which thermocompression bonding is performed slowly over a long time at a low pressure due to the thinning of the cells used. Further, in the back contact type solar cell module, thermocompression bonding is usually performed slowly at a low pressure over a long period of time. When conductive connection is performed using the conductive materials described in Patent Documents 1 to 3, there is a problem that the conductive material is not sufficiently wet and spread, and the connection reliability tends to be low.

  The objective of this invention is providing the electrically-conductive material for solar cell modules which can improve connection reliability and can improve the conduction | electrical_connection reliability between electrodes in a solar cell module. Moreover, this invention is providing the solar cell module using the said electrically-conductive material.

  According to a wide aspect of the present invention, a conductive material used for obtaining a solar cell module by electrically connecting the wiring electrode and the electrode between a wiring electrode and a solar battery cell having the electrode on the surface. And a conductive particle having a melting point of 300 ° C. or more on the outer surface of the conductive part, a thermosetting compound, and a microcapsule-type thermosetting agent, and having a viscosity at 25 ° C. of 50 Pa · s or more. The minimum melt viscosity is 1 Pa · s or more and 10 Pa · s or less when heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min. Provided is a conductive material for a solar cell module, which has a viscosity of 10 Pa · s or less when heated for 200 seconds or more and 1000 seconds or less.

  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 compound 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 processus | protrusion in the said electroconductive particle is 10 nm or more and 500 nm or less.

  On the specific situation with the electrically-conductive material which concerns on this invention, at least one of the material of the said wiring electrode and the material of the said electrode in the said photovoltaic cell is aluminum or copper.

  On the specific situation with the electrically-conductive material which concerns on this invention, this electrically-conductive material is the flexible printed circuit board which has the said wiring electrode on the surface, or the resin film which has the said wiring electrode on the surface, and the photovoltaic cell which has an electrode on the surface. The wiring electrode and the electrode are electrically connected to obtain a solar cell module.

  According to a wide aspect of the present invention, it comprises a wiring electrode, a solar battery cell having an electrode on its surface, and a connection part connecting the wiring electrode and the solar battery cell, and the material of the connection part comprises: There is provided a solar cell module, which is the above-described conductive material for a solar cell module, in which the wiring electrode and the electrode in the solar cell are electrically connected by the conductive particles.

  The conductive material for a solar cell module according to the present invention includes conductive particles whose outer surface has a melting point of 300 ° C. or more, a thermosetting compound, and a microcapsule-type thermosetting agent at 25 ° C. When the viscosity is 50 Pa · s or more and when heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min, the minimum melt viscosity is 1 Pa · s or more and 10 Pa · s or less, and from 25 ° C. to 180 ° C. When heated at a heating rate of 10 ° C./min, the viscosity is 10 Pa · s or less for 200 seconds or more and 1000 seconds or less, thus improving connection reliability and improving conduction reliability between electrodes. be able to.

FIGS. 1A and 1B are a perspective view and a cross-sectional view showing a ribbon-type solar cell module obtained by using the conductive material for a solar cell module according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a back contact type solar cell module obtained using the conductive material for a solar cell module according to the second embodiment of the present invention. FIGS. 3A to 3C are cross-sectional views for explaining the respective steps of the first example of the method for manufacturing the solar cell module. FIGS. 4A to 4C are cross-sectional views for explaining the respective steps of the second example of the method for manufacturing a solar cell module. FIG. 5 is a cross-sectional view showing an example of conductive particles used in the conductive material for a solar cell module according to the present invention. FIG. 6 is a cross-sectional view showing a first modification of the conductive particles. FIG. 7 is a cross-sectional view showing a second modification of the conductive particles. FIG. 8 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 solar cell module)
The conductive material for a solar cell module according to the present invention includes conductive particles whose melting point on the outer surface of the conductive portion is 300 ° C. or more, a thermosetting compound, and a microcapsule-type thermosetting agent.

  In the conductive material for a solar cell module according to the present invention, the viscosity at 25 ° C. is 50 Pa · s or more. In the conductive material for solar cell module according to the present invention, the minimum melt viscosity is 1 Pa · s or more and 10 Pa · s or less when heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min. In the conductive material for a solar cell module according to the present invention, when heated at a heating rate of 10 ° C./min from 25 ° C. to 180 ° C., the time during which the viscosity is 10 Pa · s or less is 200 seconds or more and 1000 seconds or less. .

  In the present invention, since the above-described configuration is provided, the solar cell module is obtained by electrically connecting the wiring electrode and the electrode of the wiring electrode and the solar cell having the electrode on the surface. Sometimes connection reliability can be improved and conduction reliability between electrodes can be improved. As a result, the initial energy conversion efficiency and the energy conversion efficiency after the reliability test can be increased. By satisfying the above-described viscosity relationship, the conductive material can be appropriately wetted and spread even if it is slowly thermocompression bonded at a low pressure over a long period of time. Generation of voids can be suppressed by appropriately spreading the conductive material. In addition, by suppressing the generation of bubbles that cause voids, it is possible to suppress the positional deviation between the electrodes due to the generation of bubbles, and to suppress the inclination of the solar battery cell.

  In recent years, ribbon-type solar cell modules are shifting to a method in which thermocompression bonding is performed slowly over a long time at a low pressure due to the thinning of the cells used. Further, in the back contact type solar cell module, thermocompression bonding is usually performed slowly at a low pressure over a long period of time. When conducting a conductive connection using the conductive material for a solar cell module according to the present invention, even if the conductive connection is performed at a low pressure, bubbles are less likely to occur during the conductive connection, and voids are less likely to occur at the connection portion. It is possible to improve the reliability of conduction between the two.

  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. In this invention, you may use the flexible printed circuit board which has the said wiring electrode on the surface, or the resin film which has the said wiring electrode on the surface. 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. In addition, irregularities may exist on the surface of the wiring electrode. For this reason, the space | interval between electrodes may not be uniform. Further, when a flexible printed circuit board having the wiring electrode on the surface or a resin film having the wiring electrode on the surface is used, the flexible printed circuit board or the resin film is relatively flexible after connection. In some cases, the distance between the electrodes may not be uniform. 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.

  In particular, when the average height of the plurality of protrusions in the conductive particle is 10 nm or more and 1000 nm or less (preferably 500 nm or less), the above-described effect is more effectively exhibited. Moreover, in order to electrically connect between the electrodes of the solar cell module, it is significant that the conductive particles have protrusions on the outer surface of the conductive portion.

  From the viewpoint of further improving the connection reliability and the conduction reliability, the viscosity of the conductive material at 25 ° C. is 50 Pa · s or more, preferably 500 Pa · s or less, more preferably 300 Pa · s or less.

  The viscosity at 25 ° C. of the conductive material is measured under the conditions of 25 ° C. and 2.5 rpm using an E-type viscometer (“TVB-25H” manufactured by Toki Sangyo Co., Ltd.).

  From the viewpoint of further improving the connection reliability and the conduction reliability, the minimum melt viscosity when the conductive material is heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min is 1 Pa · s or more, preferably 3 Pa. S or more, 10 Pa · s or less, preferably 8 Pa · s or less.

  When the conductive material is heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min, the time during which the viscosity is 10 Pa · s or less is 200 seconds or more, preferably 300 seconds or more, 1000 seconds or less, Preferably it is 800 seconds or less, More preferably, it is 500 seconds or less.

  Minimum melt viscosity (minimum value of viscosity) when the conductive material is heated from 25 ° C. to 180 ° C. at a temperature increase rate of 10 ° C./min, and the temperature increase rate from 25 ° C. to 180 ° C. of the conductive material is 10 ° C. / The time when the viscosity is 10 Pa · s or less when heated in minutes is measured using a viscoelasticity measuring apparatus (“ARES-G2” manufactured by TA Instruments).

  The conductive material for a solar cell module according to the present invention is suitably used for obtaining a ribbon type or back contact type solar cell module. The conductive material for a solar cell module according to the present invention is suitably used for obtaining a ribbon-type solar cell module, and is also suitably used for obtaining a back-contact type solar cell module.

  First, the electroconductive particle used for a solar cell module is demonstrated more concretely, referring drawings. In the following embodiments, different partial configurations can be replaced with each other.

  FIG. 5 is a cross-sectional view showing an example of conductive particles used in the conductive material for a solar cell module according to the present invention.

  The conductive particles 21 shown in FIG. 5 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. 6 is a cross-sectional view showing a first modification of the conductive particles.

  A conductive particle 21 </ b> A illustrated in FIG. 6 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. 7 is a cross-sectional view showing a second modification of the conductive particles.

  A conductive particle 21 </ b> B illustrated in FIG. 7 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. 8 is a cross-sectional view showing a third modification of the conductive particles.

  A conductive particle 21 </ b> C illustrated in FIG. 8 includes base material particles 22 and a conductive portion 23 </ b> C disposed on the surface of the base material particles 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 the electroconductive particle 21,21A, 21B, 21C has the base particle 22, the whole may be formed with the electroconductive material. For example, the central portion and the outer surface portion of the conductive particles may be formed of a conductive material, and the central portion of the conductive particles and the outer surface portion of the conductive portion of the conductive particles are formed of the same material. Alternatively, they may be made of different materials.

  A solar cell module is manufactured using a conductive material containing the conductive particles 21, 21A, 21B, 21C and the like, preferably using a conductive material containing the conductive particles 21, 21A, 21B, 21C. .

  Next, the solar cell module obtained by using the conductive material for solar cell module according to the embodiment of the present invention will be described more specifically. In the following drawings, the size, thickness, and the like may be different from the actual size, thickness, and the like for convenience of illustration.

  FIGS. 1A and 1B are a perspective view and a cross-sectional view showing a ribbon-type solar cell module obtained by using the conductive material for a solar cell module according to the first embodiment of the present invention.

  A solar cell module 30 shown in FIGS. 1A and 1B includes a plurality of solar cell module components 31 and an interconnector 32. The plurality of solar cell module components 31 are connected via an interconnector 32.

  In the solar cell module 30, each of the solar cell module components 31 includes a solar cell 41, a connection portion 42, a ribbon 43, a sealing material 44, and a base material 45. The ribbon 43 is a wiring electrode. The connection part 42 connects the ribbon 43 (wiring electrode) and the solar battery cell 41. The ribbon may be a flexible printed circuit board having wiring electrodes on the surface or a resin film having wiring electrodes on the surface. The base material 45 may be a glass substrate or a resin film.

  Ribbons 43 are connected to the surfaces on both sides of the solar battery cell 41 by connecting portions 42, respectively. A laminate of ribbon 43 / connecting part 42 / solar battery cell 41 / connecting part 42 / ribbon 43 is formed. The connection part 42 is formed of a conductive material including the conductive particles 21. The material of the connection part 42 is a conductive material including the conductive particles 21. Instead of the conductive particles 21, conductive particles 21A, 21B, 21C and the like may be used. The solar battery cell 41 has an electrode 41a on the surface. The electrode 41 a and the ribbon 43 (wiring electrode) are electrically connected by the conductive particles 21.

  The base material 45 is laminated | stacked through the sealing material 44 on the surface of the both sides of the laminated body of the ribbon 43 / connecting part 42 / solar cell 41 / connecting part 42 / ribbon 43, respectively. The base material 45 is a pair of base materials, and the laminate is disposed between the pair of base materials 45. The two substrates may be the same or different. Between the pair of base materials 45, the periphery of the laminate is sealed with a sealing material 44.

  FIG. 2 is a cross-sectional view showing a back contact type solar cell module obtained using the conductive material for a solar cell module according to the second embodiment of the present invention.

  A solar cell module 1 shown in FIG. 2 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. 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.

  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. 2 can be obtained through the steps shown in FIGS. 3A to 3C below, for example. The solar cell module shown in FIG. 1 can also be obtained through the same process.

  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. 3A, 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.3 (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. 3 (c), the flexible printed circuit board 2 and the solar cell are electrically connected by the conductive particles 21 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. 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 pressurizing pressure is preferably 1.0 × 10 ³ Pa or more, more preferably 9.8 × 10 ⁴ 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. 2 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, still more preferably 200 seconds or longer, particularly preferably 300 seconds or longer. The heating time from the start of heating to the completion of heating is preferably 1200 seconds or less, more preferably 1000 seconds or less, still more preferably 800 seconds or less, particularly preferably 600 seconds or less, and most preferably 500 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. 2 can also be obtained through the steps shown in FIGS. 4A to 4C below, for example. The solar cell module shown in FIG. 1 can also be obtained through the same process.

  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. 4A, 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.

  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.4 (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. 4C, the flexible printed circuit board 2 and the solar battery cell are connected so that the wiring electrode 2a of the flexible printed circuit board 2 and the electrode 3a 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. 2 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. Moreover, since the effect of the present invention is further exerted, at least one of the material for the wiring electrode and the material for the electrode in the solar battery cell is preferably aluminum or copper, and is preferably aluminum. More preferred. When one of the material of the wiring electrode and the material of the electrode in the solar battery cell is aluminum, the other may be copper. The material of the wiring electrode may be aluminum, and the material of the electrode in the solar battery cell may be aluminum.

  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 material, or may be formed entirely of a conductive portion. 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 part, a protrusion can be easily formed on the outer surface of the conductive part. 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 of attaching the core substance to the surface of the substrate particles, a conventionally known method can be employed. 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, still more preferably 200 nm or more, preferably 600 nm or less, more preferably 500 nm or less. It is. 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 projection is a virtual line of the conductive portion (dashed line shown in FIG. 5) on the assumption that there is no projection on the line (dashed line L1 shown in FIG. 5) connecting the center of the conductive particles and the tip of the projection. 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. 5, 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.

10% 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.

  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: Compressive displacement from the origin load value to the reverse load value when applying a load L2: Unloading displacement from the reverse load value to the origin load value 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.

  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 is preferably 0.1% by weight or more, preferably 30% by weight in 100% by weight of the conductive material. It is as follows. 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, it is preferable that the thermosetting component and the thermosetting compound contain an epoxy compound.

  In the present invention, the thermosetting agent contained in the conductive material is a microcapsule type thermosetting agent. The thermosetting agent contained in the connection material is also preferably a microcapsule type thermosetting agent.

  Specific examples of the microcapsule type thermosetting agent include dicyandiamide microencapsulated product, hydrazide compound microencapsulated product, imidazole compound microencapsulated product, triazine ring compound microencapsulated product, methyl (meth) acrylate resin or Latent thermosetting agents (eg, “EPCAT-P” and “EPCAT-PS” manufactured by Nippon Kayaku Co., Ltd.) coated with triphenylphosphine (thermosetting agent) by a shell formed of styrene resin or the like, polyurea A latent thermosetting agent coated with a thermosetting agent such as amine or a thermosetting agent such as modified imidazole is dispersed in an epoxy resin by a shell formed of a polymer or radical polymer, and is crushed and pulverized. Latent thermosetting agent, thermoplastic A latent thermosetting agent dispersed and contained in the molecule, and an imidazole latent thermosetting agent coated with a tetrakisphenol compound (for example, “TEP-2E4MZ” and “HIPA manufactured by Nippon Soda Co., Ltd.) -2E4MZ "), a latent curing agent obtained by encapsulating an imidazole-based curing agent with an isocyanate compound (for example," Novacure HX3941HP "," Novacure HXA3922HP "," Novacure HXA3932HP ", and" Novacure HXA3042HP "manufactured by Asahi Kasei E-Materials) Etc. As for the said microcapsule type thermosetting agent, only 1 type may be used and 2 or more types may be used together.

  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 agents (thermal cationic curing initiators). As for the said thermosetting agent, only 1 type may be used and 2 or more types may be used together.

  Since the connecting material can be cured more rapidly at a low temperature, the thermosetting agent is an imidazole curing agent, an amine curing agent, a phenol curing agent, a thiol curing agent, an acid anhydride, or a thermal cation curing agent. Is preferred. As for the said thermosetting agent, only 1 type may be used and 2 or more types may be used together. Moreover, since the storage stability of a connection material can be improved, a microcapsule type hardening | curing agent is preferable. Since the storage stability of the connecting material can be improved, it is preferable that the capsule thickness of the microcapsule is thick.

  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 agent include iodonium-based cationic curing agents, oxonium-based cationic curing agents, and sulfonium-based 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 microcapsule type thermosetting agent and the thermosetting agent is preferably 100 parts by weight of the thermosetting compound in the conductive material and 100 parts by weight of the thermosetting compound in the connecting material. Is 5 parts by weight or more, more preferably 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 microcapsule-type thermosetting agent and the thermosetting agent is not less than the above lower limit and not more than the above upper limit, the conductive paste and the connecting 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.

  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 1-5,7,8,10,11 and Comparative Examples 1-4)
(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) Preparation of connection material (paste) The material which did not mix | blend electroconductive particle was used as a connection material among the components of the conductive material produced above.

  In Examples 1 to 9 and Comparative Examples 1 to 6, back contact type solar cell modules were produced, and in Examples 10 and 11 and Comparative Example 7, ribbon type solar cell modules were produced.

(4-1) Production of Ribbon Type Solar Cell Module A solar cell having silver wiring on the front surface and the back surface was prepared (bus bar electrode: front surface 2 lines, back surface 2 lines, each line width 3 mm). A copper ribbon wire (width 3 mm, thickness 0.3 mm) was prepared. A conductive material was selectively applied onto the bus bar electrode using a dispenser to form a conductive material layer having a thickness of 50 μm. Next, the ribbon wire and the solar battery cell were bonded together so that the ribbon wire and the silver electrode of the solar battery cell were electrically connected by the conductive particles. At this time, the ribbon wire 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 copper electrode of the ribbon wire and the silver electrode of the solar cell were electrically connected by conductive particles.

(4-2) Production of back contact type solar cell module A flexible printed circuit board (L / S = 50 μm / 50 μm) having aluminum wiring electrodes 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 6)
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 9
A solar cell module was obtained in the same manner as in Example 1 except that the connecting material was not used.

(Comparative Example 5)
A solar cell module was obtained in the same manner as in Example 1 except that the conductive material (conductive paste) was changed to the solder paste.

(Comparative Example 6)
A solar cell module was obtained in the same manner as in Example 1 except that the conductive material (conductive paste) was changed to Ag paste.

(Comparative Example 7)
Same as Example 10 except that no conductive material (conductive paste) is used, the ribbon wire is changed to a solder-coated Cu ribbon wire (solder coated ribbon), and the ribbon wire and the solar battery cell are connected by solder. Thus, a solar cell module was obtained.

(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) Viscosity of conductive material at 25 ° C. (η25)
The viscosity (η25) at 25 ° C. of the conductive material was measured using an E-type viscometer (“TVB-25H” manufactured by Toki Sangyo Co., Ltd.) under the conditions of 25 ° C. and 2.5 rpm.

(5) The minimum melt viscosity (ηmin) when the conductive material is heated from 25 ° C. to 180 ° C. at a rate of temperature increase of 10 ° C./min, and the conductive material is heated from 25 ° C. to 180 ° C. at a rate of temperature increase of 10 ° C./min. Time when viscosity when heated is 10 Pa · s or less (T)
When the conductive material is heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min and when the conductive material is heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min The time (T) during which the viscosity of the resin was 10 Pa · s or less was measured using a viscoelasticity measuring apparatus (“ARES-G2” manufactured by TA Instruments).

(6) Presence / absence of voids The obtained solar cell module (one cell of 6-inch cells) was observed with an X-ray void inspection apparatus, and voids were evaluated. The presence or absence of voids was determined according to the following criteria.

[Judgment criteria for occurrence of voids]
○○: No void at the connection part ○: Less than 100 voids with a maximum diameter of less than 50 μm exist at the connection part Δ: More than 100 voids with a maximum diameter of less than 50 μm exist at the connection part However, there is no void with a maximum diameter of 50 μm or more in the connection part. ×: There is a void with a maximum diameter of 50 μm or more in the connection part.

(7) 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

(8) Energy conversion efficiency after reliability test (connection reliability)
The obtained solar cell module was subjected to 200 cycles of a cycle test at −40 ° C. to 90 ° C., a holding time of 30 minutes, and a temperature change rate of 87 ° C./hour with a cycle tester, and then the energy conversion efficiency was measured. The energy conversion efficiency after the reliability test was determined according to the following criteria.

[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

(9) Energy conversion efficiency after condensation freezing test (weather resistance reliability)
The obtained solar cell module was subjected to 20 cycles of a cycle test at −40 ° C. and a humidity of 0% RH to 85 ° C. and a humidity of 85% RH for a holding time of 30 minutes, and then the energy conversion efficiency was measured. did. The energy conversion efficiency after the condensation freezing test was determined according to the following criteria.

[Criteria for energy conversion efficiency after condensation freeze 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 and 2 below.

  In addition, the number of protrusions per single particle in Examples 1 to 11 and Comparative Examples 1 to 4 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 30 ... Solar cell module 31 ... Solar cell module component 32 ... Interconnector 41 ... Solar cell 41a ... Electrode 42 ... Connection part 43 ... Ribbon 44 ... Sealing material 45 ... Base material

Claims (10)

A conductive material used to obtain a solar cell module by electrically connecting the wiring electrode and the electrode with a wiring electrode and a solar cell having an electrode on the surface,
Including conductive particles having a melting point of 300 ° C. or more on the outer surface of the conductive part, a thermosetting compound, and a microcapsule-type thermosetting agent,
The viscosity at 25 ° C. is 50 Pa · s or more,
When heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min, the minimum melt viscosity is 1 Pa · s or more and 10 Pa · s or less,
A conductive material for a solar cell module, wherein the time during which the viscosity is 10 Pa · s or less is 200 seconds or more and 1000 seconds or less when heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min.   The conductive material for a solar cell module according to claim 1, wherein the content of the conductive particles is 0.1 wt% or more and 30 wt% or less in 100 wt% of the conductive material.   The conductive material for a solar cell module according to claim 1, wherein the thermosetting compound contains an epoxy compound.   The conductive material for a solar cell module according to any one of claims 1 to 3, wherein the conductive particles include base particles and conductive portions arranged on the surfaces of the base particles.   The conductive material for a solar cell module according to claim 4, wherein the substrate particles are resin particles or organic-inorganic hybrid particles.   The conductive material for a solar cell module according to any one of claims 1 to 5, wherein the conductive particles have a plurality of protrusions on an outer surface of a conductive portion.   The conductive material for a solar cell module according to claim 6, wherein an average height of the plurality of protrusions in the conductive particles is 10 nm or more and 500 nm or less.   The conductive material for a solar cell module according to any one of claims 1 to 7, wherein at least one of the wiring electrode material and the electrode material in the solar battery cell is aluminum or copper.   A flexible printed circuit board having the wiring electrode on the surface or a resin film having the wiring electrode on the surface, and a solar battery cell having the electrode on the surface, and electrically connecting the wiring electrode and the electrode to form a solar cell The conductive material for a solar cell module according to any one of claims 1 to 8, which is used for obtaining a module. A wiring electrode;
A solar battery cell having an electrode on its surface;
A connecting portion connecting the wiring electrode and the solar battery cell,
The material of the connection part is a conductive material for a solar cell module according to any one of claims 1 to 9,
The solar cell module in which the said wiring electrode and the said electrode in the said photovoltaic cell are electrically connected by the said electroconductive particle.

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