JP2011056574A - Method and device for joining solar battery module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the warp of a solar battery cell, and to achieve the excellent joined state of the solar battery cell with a string ribbon. <P>SOLUTION: A joining device includes a string ribbon holding implement 4 for abutting a string ribbon 2 comprising a metallic body covered with a solder layer on an electrode of a solar battery cell 1, a YAG laser beam oscillator 5, laser beam emission heads 6a, 6b for irradiating the string ribbon 2 with pulsed laser beam, and optical fibers 7a, 7b for guiding the pulsed laser beam to the laser beam emission heads 6a, 6b from the YAG laser beam oscillator 5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a solar cell module, and more particularly, to a solar cell module joining method and apparatus for soldering a string ribbon to an electrode of a solar cell.

  Conventionally, photovoltaic power generation has attracted attention as a means for producing clean energy that is kind to the global environment. When photovoltaic power generation is introduced, the output is small in one solar battery cell, so that the output is increased using a solar battery module in which a plurality of solar battery cells are connected in series. Thus, what put the photovoltaic cell in a line and connected the photovoltaic cell in series is called strings.

In the step of forming the strings, string ribbons made of copper foil or the like are joined to the solar battery cells by solder. The first half of the string ribbon is soldered to the electrode on the upper surface of the solar cell, and the second half of the string ribbon is soldered to the electrode on the lower surface of the adjacent solar cell.
Conventionally, as a method of joining a string ribbon to a solar battery cell, a method has been proposed in which solder coated on the surface of the string ribbon is melted with hot air (hot air) and soldered (see Patent Document 1). .

JP 2007-273830 A

  Although silicon is used as a raw material for solar cells, there is a problem that the material and manufacturing cost are high, and cost reduction is required. As one of the countermeasures, reduction of the amount of silicon used has been studied, and a technology for thinning the silicon to a thickness of about 200 μm or less is being developed. However, the conventional solar cell and string ribbon joining method requires several seconds to join, so the string ribbon and the entire solar cell are heated, resulting from the difference in thermal expansion between the silicon and the string ribbon at the time of joining. Due to the thermal stress, warpage occurs in the silicon after bonding, and in the worst case, a problem occurs that the solar battery cell is cracked. In particular, as silicon becomes thinner, the problem of warpage has become more prominent.

According to the joining method using hot air disclosed in Patent Document 1, it is possible to suppress the warpage of the solar battery cell by partially applying heat to the string ribbon. However, the joining method disclosed in Patent Document 1 has problems in that preheating is required and it is difficult to control the temperature of the string ribbon at the joint. The temperature of the string ribbon is determined by conditions such as the diameter of the hot air outlet, the air volume, the temperature of the hot air, the distance between the outlet and the string ribbon, the scanning speed of the hot air outlet. Therefore, it is necessary to appropriately control these conditions, and temperature management becomes troublesome. Furthermore, in the joining method disclosed in Patent Document 1, there is a possibility that solder is scattered by hot air.
In the joining method disclosed in Patent Document 1, if the string ribbon temperature at the joint becomes too high, the warpage of the solar battery cell may not be suppressed, and the temperature deviation from the expected range or the scattering of solder may occur. Therefore, there is a possibility that a good bonding state cannot be realized.

  The present invention has been made to solve the above-described problems, and can suppress the warpage of the solar battery cell and can easily realize a good bonding state between the solar battery cell and the string ribbon. It is an object of the present invention to provide a solar cell module joining method and apparatus.

The solar cell module joining method according to the present invention includes a pressing step in which a string ribbon made of a metal body coated with a solder layer is brought into contact with an electrode of a solar cell, and a pulse laser beam is irradiated on the string ribbon to form the solder And a bonding step of melting the layer and soldering the string ribbon to the electrode of the solar battery cell.
Moreover, one structural example of the bonding | joining method of the solar cell module of this invention is further equipped with the alignment process which moves the irradiation position of the said pulsed laser beam relatively with respect to the said string ribbon before the said bonding process. It is characterized by this.
Also, one configuration example of the solar cell module bonding method of the present invention is characterized in that a YAG laser oscillator is used as the laser oscillator that emits the pulse laser beam.
Further, in one configuration example of the solar cell module joining method of the present invention, the pulse laser beam emission condition is such that only the solder layer is melted without melting the metal body which is a base material of the string ribbon. It is set in advance.

  The solar cell module joining apparatus according to the present invention includes a pressing means for bringing a string ribbon made of a metal body covered with a solder layer into contact with an electrode of a solar cell, and irradiating the string ribbon with a pulse laser beam. Laser beam irradiation means for melting the solder layer and soldering the string ribbon to the electrode of the solar battery cell is provided.

  According to the present invention, the use of a pulsed laser that can be bonded with less thermal influence can be used to bond the solar cell and the string ribbon, and at the same time, the solar cell can be prevented from warping. A good bonding state with the string ribbon can be easily realized. Furthermore, in the present invention, since the laser beam can be routed by the optical fiber, the apparatus configuration can be made flexible.

It is a block diagram which shows the structure of the joining apparatus which concerns on embodiment of this invention. It is a perspective view which shows the structure of a photovoltaic cell. It is a top view of the string which connected the several photovoltaic cell in series. It is a flowchart which shows operation | movement of the joining apparatus which concerns on embodiment of this invention. It is a perspective view which shows the state of the photovoltaic cell and string ribbon in the process in the middle of string manufacture in embodiment of this invention. It is a perspective view which shows the state of the photovoltaic cell and string ribbon in the process in the middle of string manufacture in embodiment of this invention. It is a figure which shows the junction part of the photovoltaic cell joined by the joining apparatus which concerns on embodiment of this invention, and a string ribbon. It is a figure which shows the junction part of the photovoltaic cell joined by the joining apparatus which concerns on embodiment of this invention, and a string ribbon. It is a figure which shows the junction part of the photovoltaic cell joined by the joining apparatus which concerns on embodiment of this invention, and a string ribbon.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a bonding apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a solar battery cell, 2 is a string ribbon, 3 is a transport stage for transporting the solar battery cell 1 and the string ribbon 2, 4 is a string ribbon pressing jig serving as pressing means, 5 is a YAG laser oscillator, 6a , 6b are laser emitting heads that irradiate the string ribbon 2 with laser light, 7a and 7b are optical fibers that guide the laser light from the YAG laser oscillator 5 to the laser emitting heads 6a and 6b, and 8 is laser irradiation that is provided on the transport stage 3. This is a through hole. The YAG laser oscillator 5, the laser emission heads 6a and 6b, and the optical fibers 7a and 7b constitute laser light irradiation means.

  FIG. 2 is a perspective view showing the configuration of the solar battery cell 1. As shown in FIG. 2, the solar cell 1 includes a silicon layer 10, transparent conductive films 11a and 11b made of ITO (indium tin oxide) or the like formed on both surfaces of the silicon layer 10, and an upper surface of the transparent conductive film 11a. And a comb-shaped collector electrode 12a formed by firing a silver (Ag) paste, and a comb-shaped collector electrode 12b formed by firing a silver paste on the lower surface of the transparent conductive film 11b.

The silicon layer 10 is composed of a plurality of n-type, i-type, and p-type silicon layers, and its structure is well known as disclosed in, for example, Patent Document 1, and the essence of the present invention. The detailed structure of the silicon layer 10 is not described here.
The collector electrode 12a includes a plurality of finger portions 13a formed in parallel to each other, and a bus bar portion 14a that collects currents flowing through the finger portions 13a. Similarly, the collector electrode 12b includes a finger portion 13b and a bus bar portion 14b.

  FIG. 3 is a plan view of a string in which a plurality of solar cells 1 are connected in series. Adjacent solar cells 1 are connected by two string ribbons 2. The string ribbon 2 is made of a copper foil whose surface is coated with solder. The solder coated on the surface is lead-free solder, for example, SnAgCu solder. The front half of the string ribbon 2 is soldered to the bus bar portion 14 a on the upper surface of the solar cell 1, and the rear half of the string ribbon 2 is soldered to the bus bar portion 14 b on the lower surface of the adjacent solar cell 1.

Hereinafter, the operation of the bonding apparatus according to the present embodiment will be described. FIG. 4 is a flowchart showing the operation of the joining apparatus.
First, a string ribbon conveyance device (not shown) places two string ribbons 2 in parallel at predetermined positions on the conveyance stage 3 (step S1 in FIG. 4).
Subsequently, the solar cell transfer device (not shown) places the solar cell 1 so that the bus bar portion 14b on the lower surface of the solar cell 1 is in contact with the string ribbon 2 and is parallel to the string ribbon 2 (step). S2).

  Furthermore, the string ribbon transport device prepares two new string ribbons 2, and the string ribbon 2 comes into contact with the bus bar portion 14a on the upper surface of the solar cell 1 placed in step S2, and is parallel to the bus bar portion 14a. A new string ribbon 2 is placed so as to become (step S3). FIG. 5 shows the state of the solar battery cell 1 and the string ribbon 2 so far.

  Next, a control device (not shown) uses a drive mechanism (not shown) so that the solar cells 1 and the string ribbon 2 placed in steps S1 to S3 are positioned under the string ribbon pressing jig 4 and the laser emission head 6a. The transfer stage 3 is moved (step S4). In the state after the movement, the solar battery cell 1 and the string ribbon 2 are disposed between the laser emission head 6a and the laser emission head 6b.

  Next, the control device lowers the string ribbon pressing jig 4 and presses the string ribbon pressing jig 4 from above against the string ribbon 2 placed in step S3, and the string ribbon placed in steps S1 and S3. 2 is pressed so as not to move (step S5).

  Subsequently, the control device emits a predetermined pulse laser beam from the YAG laser oscillator 5, and as shown in FIG. 1, the laser beam passes from the laser emission heads 6a and 6b through the optical fibers 7a and 7b to the solar battery cell 1. The string ribbon 2 on the upper surface and the lower surface is irradiated. At this time, the pulse laser beam emitted from the laser emission head 6 b reaches the string ribbon 2 on the lower surface of the solar battery cell 1 through the laser irradiation through hole 8 provided in the conveyance stage 3. By melting the solder coated on the surface of the string ribbon 2 by irradiation with the pulse laser beam, the string ribbon 2 placed in step S1 is soldered to the bus bar portion 14b on the lower surface of the solar battery cell 1, and step S3 The string ribbon 2 placed in step 1 is soldered to the bus bar portion 14a on the upper surface of the solar battery cell 1 (step S6).

  Since it is necessary to irradiate the string ribbon 2 at a desired joint location with the pulse laser beam, the carrier stage 3 or the laser emission head 6a is operated by the operation of the drive mechanism based on the instruction of the control device before the pulse laser beam irradiation. , 6b may be moved so as to align the pulse laser beam with the string ribbon 2 at a desired joint location. For example, the control device photographs the solar battery cell 1 and the string ribbon 2 with a camera, recognizes the string ribbon 2 by image recognition processing, and performs alignment so that the laser beam strikes a desired position of the string ribbon 2. Just do it.

  Further, when soldering a plurality of locations on one string ribbon 2, the control device may move the transfer stage 3 or the laser emission heads 6a and 6b and repeat the process of step S6.

Furthermore, since it is necessary to solder two string ribbons 2 to the upper surface and lower surface of the solar battery cell 1, when trying to solder a total of four string ribbons 2 at a time, the laser emission heads 6a and 6b respectively Two pieces are required.
However, it is also possible to perform soldering with the laser emitting heads 6a and 6b one by one by moving the transport stage 3 or the laser emitting heads 6a and 6b.

Next, returning to step S2, as shown in FIG. 6, in the solar cell transport device, the bus bar portion 14b on the lower surface of the solar cell 1 comes into contact with the latter half of the string ribbon 2 placed in step S3, In addition, a new solar battery cell 1 is placed so as to be parallel to the string ribbon 2. The subsequent steps are as described above.
Thus, the steps S2 to S6 are repeated until the manufacture of the strings is completed (YES in step S7).

  As described above, in the present embodiment, the conventional problem is improved by using a pulse laser that can be bonded with less thermal influence. Here, in the bonding method of the present embodiment, the YAG laser is used, but the base material of the string ribbon 2 is not melted, and the plating on the surface of the string ribbon 2 is mainly melted. It is characterized by performing solder joints. When a YAG laser is used, sufficient solder joint strength between the string ribbon 2 plating and the solar cell 1 electrode can be obtained by optimizing the laser energy even with a very short joining process time of the order of several milliseconds. It was confirmed by experiment that In the joining method in which the base material of the string ribbon 2 is melted and welded to the electrode of the solar battery cell 1, the silicon of the solar battery cell 1 may be damaged, and there is a problem in the joining stability.

  7A to FIG. 7F, FIG. 8A to FIG. 8F, FIG. 9A, and FIG. 9B are solar cells 1 joined by the joining apparatus of this embodiment. It is a figure which shows the junction part of and a string ribbon. These drawings show images taken by an SEM (scanning electron microscope). 7A, FIG. 7D, FIG. 8A, and FIG. 8D are images of the joint portion taken from directly above, FIG. 7B, FIG. 7E, and FIG. ), FIG. 8 (E) is a photograph of the joint portion taken from an oblique upper angle of 45 °, FIG. 7 (C), FIG. 7 (F), FIG. 8 (C), FIG. 8 (F), FIG. FIG. 9B is a photograph of a cross section of the joint. FIG. 9A is an enlarged view of FIG. 8F, and FIG. 9B is an enlarged view of the same part as in FIGS. 8F and 9A. The magnifications of FIGS. 7C, 7F, 8C, 8F, and 9A are 500 times, and the magnification of FIG. 9B is 2000 times.

  7 (A) to FIG. 7 (F), FIG. 8 (A) to FIG. 8 (F), FIG. 9 (A), and FIG. 9 (B), 20 is a copper foil that is a base material of the string ribbon 2, 21 is a solder plating coated on the surface of the copper foil.

Here, the outer size of the solar battery cell 1 is 6 inches, the thickness of the silicon layer 10 is 175 μm, the thickness of the bus bar portions 14 a and 14 b made of silver is 20 μm, and the thickness of the copper foil that is the base material of the string ribbon 2 The thickness of the solder plating composed of Sn ₃ Ag _0.5 Cu coated on the surface of the copper foil is 40 μm. Further, the pulse width of the pulse laser beam emitted from the YAG laser oscillator 5 is 10 msec, the distance (work distance) between the laser emission heads 6 a and 6 b and the string ribbon 2 on which the pulse laser beam is incident is 40 mm, The focused spot diameter of the pulse laser beam is 0.4 mm.

  7A to 7C show the case where the laser energy is 13.1 J / pulse, FIGS. 7D to 7F show the case where the laser energy is 11.3 J / pulse, 8A to 8C show the case where the laser energy is 9.5 J / pulse, and FIGS. 8D to 8F, FIGS. 9A and 9B are lasers. The case where energy is 7.5 J / pulse is shown.

  7A to 7F and FIGS. 8A to 8C show that the base material of the string ribbon 2 has melted. On the other hand, most of the base material of the string ribbon 2 is obtained under the condition that the laser energy shown in FIGS. 8D to 8F, 9A, and 9B is 7.5 J / pulse. It can be seen that the best results are obtained because the soldering is realized by melting the solder plating on the surface of the string ribbon 2 without melting.

As described above, in the present embodiment, a pulse laser capable of joining with less thermal influence is used for joining the solar battery cell 1 and the string ribbon 2. In this embodiment, since the laser output can be easily managed, it is possible to easily set the laser beam emission conditions for obtaining a good bonding state. Moreover, in this Embodiment, since the heating by laser beam irradiation can be limited to the location centering on a junction part, the curvature of the photovoltaic cell 1 can be suppressed. In the present embodiment, preheating as in the joining method disclosed in Patent Document 1 is unnecessary, and solder is not scattered by hot air. As a result, in this Embodiment, the curvature of the photovoltaic cell 1 can be suppressed, and at the same time, a favorable joined state between the photovoltaic cell 1 and the string ribbon 2 can be easily realized. Furthermore, in the present embodiment, since the laser light can be routed by the optical fibers 7a and 7b, the apparatus configuration can be made flexible.
Needless to say, the manufacturing process shown in FIG. 4 is an example, and the manufacturing process is not limited to this.

  The present invention can be applied to a technique of soldering a string ribbon to an electrode of a solar battery cell.

  DESCRIPTION OF SYMBOLS 1 ... Solar cell, 2 ... String ribbon, 3 ... Conveying stage, 4 ... String ribbon holding jig, 5 ... YAG laser oscillator, 6a, 6b ... Laser emission head, 7a, 7b ... Optical fiber, 8 ... For laser irradiation Through-hole, 10 ... silicon layer, 11a, 11b ... transparent conductive film, 12a, 12b ... collecting electrode, 13a, 13b ... finger part, 14a, 14b ... bus bar part.

Claims (8)

A pressing step of bringing a string ribbon made of a metal body covered with a solder layer into contact with an electrode of a solar battery cell;
A joining step of irradiating the string ribbon with pulse laser light to melt the solder layer, and soldering the string ribbon to the electrode of the solar battery cell. In the joining method of the solar cell module of Claim 1,
Furthermore, the joining method of the solar cell module characterized by including the alignment process which moves the irradiation position of the said pulsed laser beam relatively with respect to the said string ribbon before the said joining process. In the joining method of the solar cell module of Claim 1,
A solar cell module joining method, wherein a YAG laser oscillator is used as the laser oscillator for emitting the pulse laser beam. In the joining method of the solar cell module of Claim 1,
The method for joining solar cell modules, wherein the pulse laser beam emission conditions are set in advance so as to melt only the solder layer without melting the metal body that is the base material of the string ribbon. A pressing means for bringing a string ribbon made of a metal body covered with a solder layer into contact with an electrode of a solar battery cell;
A solar cell module joining apparatus comprising: laser beam irradiation means for irradiating the string ribbon with a pulse laser beam to melt the solder layer and soldering the string ribbon to the electrode of the solar cell. . In the joining apparatus of the solar cell module of Claim 5,
Furthermore, the joining apparatus of the solar cell module provided with the positioning means to which the irradiation position of the said pulse laser beam is moved relatively with respect to the said string ribbon. In the joining apparatus of the solar cell module of Claim 5,
The said laser beam irradiation means has a YAG laser oscillator as a laser oscillator which radiate | emits the said pulse laser beam, The joining apparatus of the solar cell module characterized by the above-mentioned. In the joining apparatus of the solar cell module of Claim 5,
The apparatus for joining solar cell modules is characterized in that the emission condition of the pulse laser light is set in advance so as to melt only the solder layer without melting the metal body which is a base material of the string ribbon.