JP2013152979A - Solar cell module and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low cost solar cell module having a high conversion efficiency in which a wiring material and a thin line electrode can attain a sufficient mechanical bonding strength, and warpage of a solar cell element is reduced, and to provide a manufacturing method therefor.SOLUTION: A solar cell module 100 includes a solar cell element 1, a plurality of thin line electrodes 2a formed on the light-receiving surface 1a of the solar cell element 1, a back electrode formed on the rear surface 1b of the solar cell element 1, and a wiring material 5 for taking out power from the thin line electrodes 2a and the back electrode. A reinforcement electrode 6 wider than the thin line electrodes 2a is provided at an end of the light-receiving surface 1a. The reinforcement electrode 6 and the thin line electrodes 2a are joined to the wiring material 5 using a solder 3. Both sides of the solder joint are covered with a thermosetting resin 4, and a part of the light-receiving surface 1a, not provided with the reinforcement electrode 6 and the thin line electrodes 2a, and the wiring material 5 are bonded by the thermosetting resin 4.

Description

  The present invention relates to a solar cell module in which solar cell elements are connected by a wiring material, and a method for manufacturing the same.

  Conventionally, a solar cell element has a silicon substrate, a thin wire electrode that collects photogenerated carriers generated in the photoelectric conversion region of the silicon substrate, and the light generated carrier that is collected by connecting to the thin wire electrode. Including a light receiving surface current collecting electrode (light receiving surface wiring material connecting electrode) for transmitting to the light source.

  The output wiring material is a strip-like elongated copper foil made of copper (Cu), and the light-receiving surface current collecting electrode (light-receiving surface wiring material connection electrode) is an electrode for joining the copper foil wiring material. The fine wire electrode is fired as a conductive paste containing resin as a binder and particles of a good conductive material such as silver (Ag) as a filler. Usually, the light-receiving surface current collecting electrode and the wiring member are joined by solder as disclosed in Patent Document 1. As the solder, Sn-based Pb-free solder such as Sn-3Ag-0.5Cu (melting point 218 ° C.) or Pb—Sn (melting point 183 ° C.) is used.

  The above-described method for bonding wiring members using a light-receiving surface collecting electrode formed in advance on a silicon substrate has the following two problems. First, silver (Ag) used for the material of the light-receiving surface current collecting electrode is expensive, and a large amount of silver is required to form with a width of 1 to 2 mm, resulting in an increase in manufacturing cost. Secondly, the wiring member is joined over the entire length of the solar battery cell, but the solar cell element may be warped and damaged due to the difference in thermal expansion coefficient between silicon of the solar battery element and copper of the wiring material.

  For this reason, as shown in Patent Document 2, a method has been proposed in which a wiring material is directly bonded to a light receiving surface of a solar cell with a thermosetting adhesive without using a light receiving surface bus electrode. Yes. That is, in this method, a thermosetting resin is disposed so as to intersect with the thin wire electrode of the solar cell, and a wiring material is disposed thereon, and in a pressed state, the adhesive is thermally cured to connect the wiring material. The fine wire electrode and the wiring material are directly connected or electrically connected via conductive particles contained in the thermosetting resin, and the force for maintaining the contact is based on the thermosetting resin.

  In this configuration, the photogenerated carriers collected by the thin wire electrodes flow directly to the wiring material. Moreover, since the light receiving surface collecting electrode is not formed, it can be manufactured at low cost. In addition, since the wiring member is bonded to the silicon substrate with a resin having a Young's modulus of about 1/10 that of solder, the warpage of the solar cell element can be reduced.

JP 2005-217148 A International Publication No. 2009/011209

  As disclosed in Patent Document 2, when a method of adhering a wiring material to a silicon substrate with a thermosetting resin without using a light-receiving surface collecting electrode is used, the thin wire electrode and the wiring material are electrically contacted with each other. Connection will be taken. The electrical resistance due to contact is about 100 times larger than that in the case of solder connection, and since the allowable area is smaller than in the case of solder connection because the contact area between the thin wire electrode and the wiring material is small, the electrical characteristics deteriorate. . Further, since the wiring material is bonded only with the thermosetting resin whose bonding strength is about 1/10 of that of the solder, the bonding reliability is lowered.

  The present invention has been made in view of the above, and the wiring material and the fine wire electrode can obtain sufficient mechanical joint strength, high conversion efficiency, low cost, and further warping of the solar cell element. It aims at obtaining a small solar cell module and its manufacturing method.

  In order to solve the above-described problems and achieve the object, the present invention provides a solar cell element, a plurality of thin line electrodes formed on the light receiving surface of the solar cell element, and a back surface of the solar cell element. A solar cell module having a back electrode, a thin wire electrode, and a wiring member for taking out power from the back electrode, the reinforcing electrode provided at the end of the light receiving surface wider than the thin wire electrode, The thin wire electrode and the wiring material are soldered using solder, and both sides of the soldered portion are covered with a thermosetting resin, and the reinforcing electrode and the fine wire electrode on the light receiving surface are not provided. The wiring member is bonded with a thermosetting resin.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that a wiring material and a thin wire | line electrode can obtain sufficient mechanical joining strength, improve conversion efficiency, aim at cost reduction, and also can make the curvature of a solar cell element small.

FIG. 1 is a diagram showing a structure of a solar cell module according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating a joint portion between the solar cell element and the wiring member door of the solar cell module according to the first embodiment. FIG. 3: is sectional drawing which shows the junction part of the solar cell element and wiring material of the solar cell module concerning Embodiment 2 of this invention. FIG. 4 is a diagram showing the relationship between the gelation time of the thermosetting resin according to Embodiment 3 of the present invention and the heating temperature. FIG. 5 is a cross-sectional view illustrating a joint portion between the surface of the wiring material, the solder, and the thermosetting resin according to the third embodiment. FIG. 6 is a diagram showing the relationship between the heating time and the time until the thermosetting adhesive loses fluidity and gels. FIG. 7 is an enlarged schematic view of the cross section of the bonding portion of the wiring material coated with a thermosetting resin and solder, with respect to the bonding portion between the portion other than the reinforcing electrode and the fine wire electrode on the light receiving surface and the wiring material.

  Embodiments of a solar cell module and a manufacturing method thereof according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view of a solar cell module according to Embodiment 1 of the present invention. As shown in FIG. 1, the solar cell module 100 receives light on the light receiving surface 1 a side of a solar cell string 10 in which light receiving surfaces 1 a and back surfaces 1 b of a plurality of solar cell elements 1 are alternately connected using wiring members 5. The surface protection material 11 is disposed, the back surface protection material 12 is disposed on the back surface 1 b side, and the sealing material 13 is disposed between the solar cell string 10 and the protection materials 11 and 12. The reinforcing electrode 6 and the fine wire electrode 2a formed on the light receiving surface 1a are joined to the wiring member 5 with the solder 3, and the side surface of the solder joint portion is covered with the thermosetting resin 4 to form the reinforcing electrode 6 and the fine wire electrode 2a. In a region other than the portion where the wiring is made, the wiring member 5 and the light receiving surface 1a are joined by the thermosetting resin 4.

  FIG. 2 is a perspective view of a string in which a plurality of solar cell elements are connected by a wiring material. As shown in FIG. 2, the solar cell string 10 is formed by connecting a plurality of solar cell elements 1 with wiring members 5. The solar cell element 1 is configured as follows using, for example, p-type silicon having a thickness of about 100 to 200 μm as a substrate. An n-type diffusion layer (impurity diffusion layer: not shown) is formed by phosphorous diffusion on the light-receiving surface 1a side of the p-type silicon substrate serving as a p-type layer, and further prevents reflection of incident light and improves conversion efficiency. An antireflection film made of a silicon nitride film is provided by surface treatment to form a light receiving surface 1a (photoelectric conversion unit region) of the solar cell element 1. Further, a p + layer containing a high-concentration impurity is formed on the back surface 1b of a p-type silicon substrate (hereinafter simply referred to as “substrate”). Further, for the purpose of reflecting incident light and taking out electric power, Similarly, an electrode (back surface electrode 2b) is provided.

  FIG. 3 is a plan view of the solar cell module as seen from the light receiving surface side. As shown in FIG. 3, the reinforcing electrode 6 provided at the end of the light receiving surface 1 a and the wiring member 5 are joined by solder 3. Further, the fine wire electrode 2 a and the wiring member 5 are joined by the solder 3. In a portion where the reinforcing electrode 6 and the thin wire electrode 2a do not exist, the wiring member 5 is bonded to the light receiving surface 1a with the thermosetting resin 4. The side surfaces of the solder joints are covered with the thermosetting resin 4.

  In the present embodiment, the reinforcing electrode 6 is wider than the wiring member 5.

As the material for the wiring material 5, inexpensive copper having a low electric resistance is widely used. The solar cell element 1 is usually made of silicon. Their thermal expansion coefficients are 16 × 10 ⁻⁶ (1 / K) and 3 × 10 ⁻⁶ (1 / K), respectively, and the difference is large. Therefore, a thermal stress is generated in the joint due to the difference in thermal expansion after the solder joint. In the present embodiment, the solder joint portion is a contact portion between the reinforcing electrode 6 and the fine wire electrode 2a, and the solder joint area is small compared to the conventional structure in which the entire wiring member 5 is solder joined, and The thermal stress generated at the joint is reduced by bonding to the light receiving surface 1a with the thermosetting resin 4 having a rigidity lower than that of the solder 3 except for the contact portion between the reinforcing electrode 6 and the thin wire electrode 2a. Can improve the bonding reliability.

  Further, the reinforcing electrode 6 larger than the thin wire electrode 2a is provided at the end of the light receiving surface 1a, and the reinforcing electrode 6 and the wiring material 5 are joined, so that peeling from the end of the wiring material 5 due to repeated thermal stress is caused. Can be prevented.

  On the other hand, the back electrode 2b provided on the back surface 1b of the solar cell element 1 is provided at a position corresponding to the wiring material 5 on the light receiving surface 1a side (a position overlapping the wiring material 5 and the solar cell element 1 in the thickness direction). ing. When the back surface electrode 2b is formed on the entire surface of the back surface 1b, an electrode formed of silver is formed on the line in the same direction as the wiring member 5 and in the longitudinal direction of the solar cell element 1, or an island shape May be formed. In the present embodiment, as shown in FIG. 1, the back electrode 2b is formed in an island shape and joined using the same method as the thin wire electrode 2a on the light receiving surface 1a.

  In the above description, the solar cell module 100 includes the solar cell string 10 formed by connecting a plurality of solar cell elements 1, the protective materials 11 and 12, and the sealing material 13. The solar cell module 1 including the thin wire electrode 2a and the back electrode 2b to which the wiring member 5 is bonded is also referred to as a solar cell module.

  In the above description, the solar cell element 1 has a substantially flat plate shape as an example. However, the solar cell element 1 is not limited to a flat plate shape, and may be, for example, a flexible sheet shape or a cubic shape. Any solar cell element 1 in which the wiring member 5 is joined to the thin wire electrode 2a formed on the surface 1a is applicable.

  In the above description, the solar cell string 10 in which a plurality of solar cell elements 1 are connected by the wiring member 5 is shown. However, the solar cell element 1 may have a single configuration.

  Further, in the above example, a plurality of thin wire electrodes 2a are formed in parallel on the light receiving surface 1a. However, the thin wire electrodes 2a may not be formed in parallel, and a plurality of thin wire electrodes 2a are formed on the light receiving surface 1a. The solar cell element 1 can be applied.

  FIG. 4 is a cross-sectional view of the joint between the wiring member 5 and the light receiving surface 1a side of the solar cell element 1. FIG. FIG. 4A shows a cross section (cross section taken along line AA in FIG. 3) of the joint between the reinforcing electrode 6 and the wiring member 5 on the thin wire electrode 2a. FIG. 4B shows a cross section (cross section taken along the line BB in FIG. 3) of the joint portion between the reinforcing electrode 6 and the wiring member 5 between the thin wire electrodes 2a. FIG. 4C shows a cross section (cross section taken along the line C-C in FIG. 3) at the joint between the thin wire electrode 2 a and the wiring member 5. FIG. 4D shows a cross section (cross section taken along the line DD in FIG. 3) at the bonding portion between the wiring member 5 and the light receiving surface 1a. The wiring member 5 and the reinforcing electrode 6 are joined with the solder 3, and the side surface of the solder joint portion is covered with the thermosetting resin 4. The wiring member 5 and the thin wire electrode 2a are joined with the solder 3, and the side surface of the solder joint is covered with the thermosetting resin 4.

  The solder 3 is Sn-3Ag-0.5Cu (melting point 220 ° C.), Sn-3.5Ag (melting point 221 ° C.), Sn-0.7Cu (melting point 230 ° C.), Sn-8.8Zn (melting point 199 ° C.), etc. Pb-free solder or Pb—Sn (melting point: 183 ° C.) solder may be used.

  The current collector thin wire electrode 2a is joined to the wiring member 5 with the solder 3, whereby the electrical resistance of the joint can be reduced, and a conventional resin adhesive containing conductive particles is used. Compared with the method (Patent Document 2), a large electrical connection area can be obtained, so that it is possible to realize a joint that does not cause deterioration of electrical characteristics.

  As shown in FIG. 4D, the lower surface of the wiring member 5 and the light receiving surface 1 a are bonded with a thermosetting resin 4. As the thermosetting resin 4, an epoxy resin composition containing an organic acid or using an organic acid as a curing agent can be used. As the organic acid curing agent, for example, a phenol curing agent, an acid anhydride curing agent, or a carboxylic acid curing agent can be applied.

  When the solar cell module according to the present embodiment is manufactured, an uncured thermosetting resin 4 (hereinafter referred to as “uncured thermosetting resin 4”) is formed in a region where the wiring member 5 of the light receiving surface 1a provided with the reinforcing electrode 6 and the thin wire electrode 2a is joined. , Referred to as thermosetting adhesive 4a). The thermosetting adhesive 4a may be a liquid or a semi-cured (B stage) film. After the wiring material 5 coated with the solder 3 is disposed at a desired position (a region where the thermosetting adhesive 4a is applied) on the light receiving surface 1a, the wiring material 5 is heated to the melting point of the solder or higher.

  Since the thermosetting adhesive 4a contains an organic acid or uses an organic acid curing agent, the thermosetting adhesive 4a exhibits an action of reducing and removing the oxide film on the solder surface in the process of thermosetting. Thereby, the oxide film on the surface of the solder 3 coated on the wiring material 5 is removed, and the wiring material 5 and the thin wire electrode 2a can be joined with the solder 3.

  Since the organic acid contained in the thermosetting adhesive 4a plays a role of flux, it is not necessary to apply the flux before soldering as in normal soldering and to wash the flux after soldering. . Further, there is no concern that the flux residue remains on the light receiving surface 1a and the residual ions cause deterioration of characteristics. Therefore, a yield can be improved at the time of manufacture of a solar cell module.

  Further, when the thermosetting adhesive 4a is liquefied during heating, the solder 3 is melted, and when solder bonding is started, it is removed to the side surface, and is solidified on the side surface of the solder joint portion to become the thermosetting resin 4. By covering the side surface of the solder joint portion with the thermosetting resin 4, the solder joint portion can be reinforced. The thermosetting resin 4 that covers the solder joint portion reduces the shear stress generated from the thermal expansion difference between the wiring member 5 and the solar cell element 1 and suppresses the generation of cracks caused by fatigue of the solder joint portion. It has the action to do.

  In the present embodiment, since the wiring member 5 is soldered to the thin wire electrode 2a in the light receiving surface 1a and the side surface of the solder joint is covered with the thermosetting resin 4, the electrical connection resistance is low and the reliability is high. Since the bonding is obtained and the portion of the light receiving surface 1a where the thin wire electrode 2a is not provided and the wiring member 5 are bonded with the thermosetting resin 4 having a rigidity lower than that of the solder 3, the conventional structure (Patent Document 1) The warp of the solar cell element 1 can be made smaller than that of Furthermore, since the reinforcing electrode 6 provided at the end of the light receiving surface 1a and the wiring member 5 are connected by the solder 3, the wiring member 5 starts from the end of the light receiving surface 1a even when a large thermal stress is applied. Can be prevented from peeling from the light receiving surface 1a.

Embodiment 2. FIG.
FIG. 5: is a figure which shows the junction part cross section of the reinforcement electrode 6 and the wiring material 5 by the side of the light-receiving surface 1a of the solar cell element 1 of the solar cell module concerning Embodiment 2 of this invention. FIG. 5 shows a cross section of the joint corresponding to the cross section taken along line BB in FIG.

  In the present embodiment, the width of the reinforcing electrode 6 is narrower than that of the wiring member 5. By making the width of the reinforcing electrode 6 narrower than that of the wiring member 5, the thermosetting adhesive 4a discharged to the side surface at the time of solder bonding solidifies, so that the thermosetting resin 4 is only on the side surface of the solder bonding portion. The side surface of the joint portion with the light receiving surface 1a of the reinforcing electrode 6 is also covered. By covering the side surface of the joint portion between the reinforcing electrode 6 and the light receiving surface 1a, the adhesion with the light receiving surface 1a of the reinforcing electrode 6 is improved, and the bonding reliability can be further increased.

Embodiment 3 FIG.
FIG. 6 is a diagram showing the relationship between the heating temperature and the time until the thermosetting adhesive 4a loses fluidity and gels. The time required for gelation of the thermosetting adhesive 4a becomes shorter as the heating temperature is higher. From the viewpoint of productivity, it is desirable to employ a temperature at which the thermosetting adhesive 4a is cured within 10 seconds. In the present embodiment, the heating temperature is 200 ° C.

  The surface of the solder 3 has irregularities due to different solidification temperatures of the solder composition (see, for example, lead-free solder mounting technology, Corona, p79). Usually, the adhesive force of the thermosetting resin 4 is determined by the anchor effect due to the unevenness of the surface. Therefore, in order to increase the adhesive force of the wiring material 5 coated with the solder 3, the thermosetting adhesive 4a is gelled in a state where the surface of the solder 3 is uneven, that is, the solder 3 is not melted. There is a need to.

  FIG. 7 is an enlarged schematic view of the cross section of the bonding portion of the wiring member 5 coated with the thermosetting resin 4 and the solder 3 with respect to the bonding portion between the portion other than the reinforcing electrode 6 and the thin wire electrode 2a of the light receiving surface 1a and the wiring member 5. It is. FIG. 7A shows a state where the wiring member 5 in which the solder 3 is coated on the thermosetting adhesive 4a is pressed. FIG.7 (b) shows the state which the thermosetting adhesive 4a gelatinized by heating. FIG. 7C shows a state where the solder is melted. FIG. 7D shows a state after cooling.

  As shown in FIG. 7 (a), the wiring material 5 coated with the solder 3 is pressed against the thermosetting adhesive 4a so that the surface of the thermosetting adhesive 4a follows the unevenness of the surface of the solder 3. Unevenness is formed. When the thermosetting adhesive 4a shown in FIG. 7B is gelled, the solder 3 is not melted and is in contact with the gelled thermosetting adhesive 4b. When the temperature further rises and the solder 3 is melted, the melted solder 3a is melted in the irregularities of the gelled thermosetting adhesive 4b as shown in FIG. After cooling shown in FIG. 7 (d), the gelled thermosetting adhesive 4a is completely cured, and the solder 3 is solidified in the unevenness of the thermosetting resin 4, so that the wiring material 5 And the adhesive force between the thermosetting resin 4 are improved.

  When implemented with Sn-3Ag-0.5Cu (melting point 218 ° C.) having a melting point higher than 200 ° C., which is the temperature at which the thermosetting adhesive 4a gels in 10 seconds, a solder material having a low melting point, for example, melting point 183 ° C. Compared with Sn-58Bi, an adhesion strength of 3 times or more was obtained.

  Thus, by making the thermosetting adhesive 4a gel at a temperature lower than the melting point of the solder 3, the anchor effect of the thermosetting resin 4 is enhanced, and the adhesive force between the wiring member 5 and the thermosetting resin 4 is increased. Can be improved.

  As described above, the solar cell module and the manufacturing method thereof according to the present invention are useful in that the warpage of the solar cell element can be reduced, and in particular, a solar cell using a large-sized solar cell element that is easily affected by the warp. Suitable for application to modules.

DESCRIPTION OF SYMBOLS 1 Solar cell element 1a Light-receiving surface 1b Back surface 2a Fine wire electrode 2b Back surface electrode 3 Solder 3a Molten solder 4 Thermosetting resin 4a Thermosetting adhesive (Uncured thermosetting resin)
4b Gelled thermosetting adhesive 5 Wiring material 6 Reinforcing electrode 10 Solar cell string 11, 12 Protective material 100 Solar cell module

Claims (4)

A solar cell element, a plurality of thin line electrodes formed on the light receiving surface of the solar cell element, a back electrode formed on the back surface of the solar cell element, and power from the thin line electrode and the back electrode A solar cell module having a wiring material to be extracted,
Reinforcing electrodes provided wider at the end of the light receiving surface than the thin wire electrodes,
The reinforcing electrode and the fine wire electrode and the wiring member are soldered using solder, and both sides of the soldered part are covered with a thermosetting resin,
A portion of the light receiving surface where the reinforcing electrode and the fine wire electrode are not provided and the wiring member are bonded with the thermosetting resin.   The solar cell module according to claim 1, wherein a width of the reinforcing electrode is narrower than a width of the wiring member.   3. The solar cell module according to claim 1, wherein a melting point of the solder is higher than a temperature at which the thermosetting resin gels. 4. It is a manufacturing method of the solar cell module according to claim 3,
Contacting the wiring material coated with the solder with the uncured thermosetting resin;
The step of causing the uncured thermosetting resin brought into contact with the wiring material to gel at a temperature lower than the melting point of the solder;
Heating and melting the solder above its melting point;
And a step of cooling the solder to below the melting point and solidifying the solder.

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