JP2005191116A - Inner lead for connecting solar cell element and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell module in which stripping of an inner lead for connecting a solar cell element is suppressed while sustaining the output characteristics of the solar cell module. <P>SOLUTION: The inner lead 10 for connecting the solar cell element is set up to connect a plurality of solar cell elements electrically produced by coating a metal foil with solder, and the metal foil 11 is composed by bundling a plurality of number of metal materials. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inner lead for connecting solar cell elements, and also relates to a solar cell module in which a plurality of solar cell elements are electrically connected by the inner lead for connecting solar cell elements.

  A sectional view of a conventional solar cell element is shown in FIG. In FIG. 3, 12 is a semiconductor substrate, 2 is a diffusion layer, 3 is an antireflection film, 4 is a BSF layer, 5 is a front electrode, 6 is a back electrode, and 7 is a solder layer.

  As shown in FIG. 3, the solar cell element 1 is formed of a P-type region and an N-type region. A surface electrode 5 is provided on the surface of the N-type region, and a back electrode is provided on the surface of the P-type region. 6 is provided.

  The electrode formed on the surface of the solar cell element is generally obtained by applying and baking an electrode material on the front and back surfaces of the semiconductor substrate 12 by screen printing.

  FIG. 4 is a view for explaining the surface structure of a general solar cell element.

  As shown in FIG. 4, the surface electrode 5 is formed by a bus bar electrode 8 as a connection electrode of an inner lead for connecting solar cell elements and a finger electrode 9 as a current collecting electrode.

  The solar cell element-connecting inner lead here is for electrically connecting the solar cell elements. Usually, the inner lead of the copper foil having a thickness of about 0.1 mm and a width of about 2 mm is solder-coated. Cut to length and soldered onto the electrode of the solar cell element. For example, when the solar cell element connecting inner leads are connected in series, the light receiving surface side electrodes and the back surface side electrodes of the adjacent solar cell elements are alternately connected.

  Although FIG. 3 shows a view in which the back electrode 6 is uniformly formed on the entire back surface, the back electrode 6 may also be composed of a connecting bus bar electrode and a collecting electrode of the inner lead for connecting solar cell elements. Solder layers 7 are formed on the front and back bus bar electrodes 8 in order to increase the cross-sectional area and reduce resistance loss and to ensure long-term reliability and to facilitate the connection of a plurality of solar cell elements. To do. Further, in order to connect the solar cell elements 1 to each other, the solar cell element connecting inner leads 10 are connected.

  FIG. 5 is a diagram showing a cross section of a solar cell element connecting inner lead used in a conventional solar cell module, FIG. 6 is a cross sectional view for explaining a wiring state of a general solar cell module, and FIG. It is a top view when it sees from the surface for demonstrating the wiring state of a solar cell module.

  The solar cell element connecting inner lead 10 has a configuration in which a solder layer 7 is formed around a flat rectangular copper foil 13 as shown in a schematic diagram of FIG. As shown in FIGS. 6 and 7, one end is wired over almost the entire length of the surface electrode 5, and the plurality of places are welded to the surface electrode 5, whereby the bus bar electrode 8 and the solar cell element connecting inner lead 10 are connected. Connecting. The other end is welded to the bus bar electrode 8 of the back electrode 6 of the adjacent solar cell element 1 so that the solar cell elements 1 are connected to each other. By repeating this, a solar cell module is formed.

  In order to connect the solar cell element 1 and the inner lead 10 for connecting the solar cell element, a method is generally used in which both solders are heated and soldered with a soldering iron or hot air. At this time, it is possible to heat and crimp both separately, but the solar cell element connecting inner lead 10 is wired on the electrode of the solar cell element 1 and heated from above to melt the solder of both. Crimping is more efficient in terms of productivity.

The inner lead 10 for connecting the solar cell element can be welded over the entire length of the bus bar electrode 8 of the solar cell element 1. However, due to the heat applied at the time of welding, the solar cell element 1 is warped due to the difference in thermal shrinkage between the solar cell element 1 and the inner lead 10 for connecting the solar cell element, causing cracks. Further, the bus bar electrode 8 of the solar cell element 1 may be peeled off from the end. Therefore, a method of welding to the solar cell element connecting inner leads 10 at a plurality of locations on the bus bar electrode 8 of the solar cell element 1 is frequently used (for example, see Patent Document 1). According to this method, stress is absorbed to some extent at the unwelded portion, the warpage of the solar cell element 1 can be alleviated, and cracking can be suppressed.
JP 2002-359388 A

  However, in this conventional solar cell module, all stress due to the difference in thermal shrinkage between the solar cell element 1 and the solar cell element connecting inner lead 10 is applied to the welded portion.

  FIG. 8 is a cross-sectional view of a bus bar electrode formed on the surface of a semiconductor substrate of a general solar cell element, and FIG. 9 is a state when an inner lead for connecting a solar cell element is wired on the electrode in a conventional solar cell module. It is sectional drawing for demonstrating.

  The cross-section of the solar cell element 1 on which the electrode is formed by applying and baking the electrode material and covering the bus bar electrode 8 and the solder formed on the surface of the semiconductor substrate 12 is high at the center as shown in FIG. It has a shape that becomes lower as it goes. Here, as shown in FIG. 5, in order to connect the solar cell element connecting inner lead 10 having a plate-like copper foil 13 at the center, the sun is formed on the surface electrode 5 formed on the surface of the semiconductor substrate 12 of the solar cell element 1. Even if the battery element connecting inner lead 10 is arranged and heated from above the solar cell element connecting inner lead 10, the copper foil 13 does not follow the shape of the surface electrode 5, but the surface as shown in FIG. Necking of solder occurs at the welding point of the electrode 5 and the inner lead 10 for connecting the solar cell element. As the width of the solder layer 7 becomes narrow in this way, the solder layer 7 becomes weak, and a situation in which peeling or cracking easily occurs due to the influence of the stress. In addition, since the solar cell module is usually used outdoors for a long time, the temperature is higher than the ambient temperature during the day, and the temperature is lower than the ambient temperature during the night. It is also affected by seasonal changes. The thermal expansion and contraction of the solar cell element connecting inner lead 10 are repeated by this temperature cycle, so that a large stress is applied to the welded portion, cracking and peeling progress, and the surface electrode 5 and the inner lead for connecting the solar cell element. 10 may be peeled off, the characteristics of the solar cell module may deteriorate, or the resistance may become extremely high in some cases, and heat may be generated to melt the filler (not shown) of the solar cell module. there were.

  In order to suppress the constriction of the solder welded portion between the surface electrode 5 and the solar cell element connecting inner lead 10, the width of the solar cell element connecting inner lead 10 may be made smaller than the width of the surface electrode 5. Since the resistance loss of the element connecting inner lead 10 becomes large, the solar cell element connecting inner lead 10 must be thickened to increase the cross-sectional area.

  However, when the solar cell element connecting inner lead 10 becomes thick, when the solar cell element connecting inner lead 10 is welded to the surface electrode 5 with hot air or the like, heat is hardly transmitted to the solder layer 7 of the surface electrode 5, It took time to weld the surface electrode 5 and the inner lead 10 for connecting the solar cell element, and there was a problem that the elongation due to thermal expansion of the inner lead 10 for connecting the solar cell element was further increased. When the inner lead 10 for connecting solar cell elements is welded to the surface electrode 5 in a stretched state, a larger compressive stress is applied to the welded portion when the inner lead 10 for connecting solar cell elements contracts. is there.

  Further, as another method for suppressing the constriction of the solder welded portion, the thickness of the copper foil 13 may be reduced so as to easily follow the shape of the surface electrode 5. However, in this method, the resistance loss of the solar cell element connecting inner lead 10 becomes large, and thus the width of the solar cell element connecting inner lead 10 must be increased to increase the cross-sectional area. If it does in this way, the neck of a welding part will become still bigger.

  The object of the present invention has been made in view of the problems of such a conventional solar cell module, while maintaining the output characteristics of the solar cell module, from the solar cell element of the inner lead for solar cell element connection. An object of the present invention is to provide an inner lead for connecting a solar cell element in which peeling is suppressed.

  Another object of the present invention is to provide a highly reliable solar cell module in which a plurality of solar cell elements are electrically connected using the solar cell element connecting inner lead.

  In order to achieve the above object, the solar cell element connecting inner lead of the present invention is a solar cell element connection formed by coating a metal foil with solder provided to electrically connect a plurality of solar cell elements. An inner lead for a metal, wherein the metal foil is formed by bundling a plurality of metal materials.

  At this time, the metal foil configured by bundling the plurality of metal materials is characterized in that each metal material is arranged in a line in the width direction of the metal foil.

  Further, in the inner lead for connecting another solar cell element of the present invention, the metal foil configured by bundling the plurality of metal materials is composed of stranded wires each of which is made of a metal wire. It is characterized by.

  Furthermore, in another solar cell element connecting inner lead of the present invention, the metal material is copper.

    Furthermore, the solar cell module of the present invention is characterized in that a plurality of solar cell elements are electrically connected using the solar cell element connecting inner lead according to any one of claims 1 to 4.

  According to the inner lead for connecting a solar cell element of the present invention, it is an inner lead for connecting a solar cell element, which is provided to electrically connect a plurality of solar cell elements, and is formed by coating a metal foil with solder. The metal foil is configured by bundling a plurality of metal materials, and while securing the same cross-sectional area as a conventional copper foil, while heating the inner lead for connecting the solar cell element, The flexibility in the short direction when fixing to the surface electrode 5 provided on the surface of the semiconductor substrate by soldering can be enhanced. Therefore, as shown in FIG. 2, the inner lead for connecting the solar cell element can easily follow the shape of the electrode, and the welding area at the welding point can be increased, thereby effectively suppressing the peeling of the inner lead for connecting the solar cell element. Will be able to.

  According to another solar cell element connecting inner lead of the present invention, the metal foil configured by bundling the plurality of metal materials is arranged in a line in the width direction of the metal foil. By doing so, since the flexibility in the short direction of the inner lead for connecting the solar cell element is improved, the welding area between the inner lead for connecting the solar cell element and the electrode is improved, and the adhesion strength is improved. Will be able to.

  Moreover, you may make it arrange | position a metal strand wire in the inner lead for a solar cell element connection at this time. By using a stranded wire structure, the expansion and contraction of the inner lead for connecting the solar cell element can be suppressed, so the stress generated at the welding point is alleviated and the peeling of the inner lead for connecting the solar cell element is effectively suppressed. Will be able to.

  Further, since the metal is made of copper, the inner lead for connecting the solar cell element has good conductivity and is easy to solder.

  In addition, the inner lead for connecting the solar cell element of the present invention has an aspect ratio (height / width) in which the electrode area of the bus bar electrode is reduced and the thickness is increased to prevent resistance loss, particularly in order to improve the characteristics of the solar cell element. When the solar cell module using a solar cell element having a large bus bar electrode is used, the effect is particularly effectively exhibited.

  Moreover, according to the solar cell module of the present invention, a plurality of solar cell elements are electrically connected using the solar cell element connecting inner lead according to any one of claims 1 to 4, so that the solar cell element The peeling of the connecting inner lead can be effectively suppressed, and a more reliable solar cell module can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 3 shows a cross-sectional view of a solar cell element according to the present invention. Moreover, FIG. 2 is sectional drawing for demonstrating a state when the inner lead for solar cell element connection is wired on the electrode among the solar cell modules concerning this invention.

  2 and 3, 12 is a semiconductor substrate, 2 is an n-type diffusion layer, 3 is an antireflection film, 4 is a BSF layer, 5 is a front electrode, 6 is a back electrode, 7 is a solder layer, 8 is a bus bar electrode, 9 is a finger electrode, 10 is an inner lead for connecting a solar cell element, and 11 is a metal foil.

  In the present invention, the basic structure of the solar cell element is the same as the conventional one. Here, a case where a P-type silicon substrate is used as the semiconductor substrate 12 will be described as an example.

The semiconductor substrate 12 is made of single crystal silicon or polycrystalline silicon having a thickness of about 0.3 mm. This semiconductor substrate 12 contains about 1 × 10 ¹⁶ to 10 ¹⁸ atoms · cm ⁻³ of one conductivity type semiconductor impurity such as boron (B) and has a specific resistance of about 1 to 5 Ω · cm.

The semiconductor substrate 12 is placed in a diffusion furnace and heated using phosphorus oxychloride (POCl ₃ ) or the like, whereby phosphorus atoms are added to the surface portion of the semiconductor substrate 12 by 1 × 10 ¹⁶ to 10 ¹⁸ atoms · cm ^−3. The diffusion layer 2 having a thickness of about 0.3 to 0.4 μm is formed by diffusing to a certain extent.

Next, the antireflection film 3 is formed on the surface side of the semiconductor substrate 12. The antireflection film 3 is made of, for example, a silicon nitride film (SiN _x ) or the like, and has a thickness of 500 to 1000 nm and a refractive index of 1 by a plasma CVD method using a mixed gas of silane (SiH ₄ ) and ammonia (NH ₃ ). .90 to 2.30 or so. The antireflection film 3 is provided to prevent light from being reflected from the surface of the semiconductor substrate 12 and to effectively take light into the semiconductor substrate 12.

  Next, a BSF layer 4 is formed on the back surface by applying and baking an aluminum paste, and the aluminum remaining on the surface is removed. Thereafter, a silver paste is applied to the front and back surfaces of the semiconductor substrate 12 by a screen printing method or the like and baked at 600 to 800 ° C. for about 1 to 30 minutes, whereby the front electrodes 5 and the back electrodes 6 including the finger electrodes 9 and the bus bar electrodes 8 are formed. Form.

  The structure of the back surface of the solar cell element 1 may be configured by an output extraction electrode (bus bar electrode) made of silver and a current collecting electrode made of aluminum in addition to the structure shown in FIG. In this structure, the BSF layer can be formed simultaneously with the formation of the collecting electrode.

  On the surface of the front electrode 5 and the back electrode 6, in order to increase the area of the electrode and reduce the resistance, and to protect the surface of the electrode and ensure long-term reliability, wiring characteristics when connecting a plurality of elements are further provided. For the purpose of improving, the solder layer 7 is formed. The solder layer 7 is formed by immersing the solar cell element 1 in molten solder.

  Thereafter, as shown in FIGS. 6 and 7, one end of the solar cell element connecting inner lead 10 is wired over almost the entire length on the surface electrode 5, and a plurality of locations are welded to the surface electrode 5, whereby the bus bar electrode 8 and The solar cell element connecting inner lead 10 is connected. The other end is welded to the bus bar electrode 8 of the back electrode 6 of the adjacent solar cell element 1 so that the solar cell elements 1 are connected to each other. By repeating this, a solar cell module is formed.

  In order to connect the solar cell element 1 and the inner lead 10 for connecting the solar cell element, a method is generally used in which both solders are heated and soldered with a soldering iron or hot air. At this time, it is possible to heat and crimp both separately, but the solar cell element connecting inner leads 10 are wired on the surface electrode 5 formed on the surface of the semiconductor substrate 12 of the solar cell element 1, It is more efficient in terms of productivity to heat and heat the solder to melt and melt the solder.

  The inner lead 10 for connecting the solar cell element can be welded over the entire length of the bus bar electrode 8 of the solar cell element 1. However, due to the heat applied at the time of welding, the solar cell element 1 is warped due to the difference in thermal shrinkage between the solar cell element 1 and the inner lead 10 for connecting the solar cell element, causing cracks. Further, the bus bar electrode 8 of the solar cell element 1 may be peeled off from the end. Therefore, a method of welding with the solar cell element connecting inner leads 10 at a plurality of locations on the bus bar electrode 8 of the solar cell element 1 is frequently used. According to this method, the stress is absorbed to some extent at the unwelded portion, the warpage of the solar cell element 1 can be alleviated, and cracking can be suppressed.

  FIG. 1 is a sectional view showing one embodiment of an inner lead for connecting a solar cell element used in a solar cell module according to the present invention, and FIG. 10 is an inner lead for connecting a solar cell element used in the solar cell module according to the present invention. The figure which showed the cross section of other Example, FIG. 11 is the figure which showed the cross section of the further another Example of the inner lead for a solar cell element used for the solar cell module concerning this invention.

  The solar cell element connecting inner lead according to the present invention is characterized in that a plurality of metal materials are in contact with each other or are bundled with a certain distance therebetween.

  As shown in FIGS. 10 and 11, the copper foil 11 may be divided in the longitudinal direction of the cross section (thickness direction of the solar cell element connecting inner lead 10) to have a structure in which a plurality of layers are stacked. Even in such a structure, since the thickness of one metal foil 11 is thinner than the conventional one, the surface electrode provided on the surface of the semiconductor substrate 12 of the solar cell element 1 while heating the inner lead 10 for connecting the solar cell element. 5 can be increased in flexibility in the short direction when fixed by soldering, and the inner lead 10 for connecting the solar cell elements can easily follow the shape of the surface electrode 5 to increase the welding area of the welding point. Therefore, peeling of the solar cell element connecting inner lead 10 can be effectively suppressed.

  The metal material is made of a highly conductive metal such as silver, copper, aluminum, or iron, and is preferably made of copper in consideration of its conductivity and ease of solder coating. is there.

  By doing so, solder is applied to the surface electrode 5 provided on the surface of the semiconductor substrate 12 of the solar cell element 1 while heating the inner lead 10 for connecting the solar cell element while ensuring the same cross-sectional area as the conventional copper foil. Flexibility in the short direction when fixing with attachment can be enhanced. Therefore, as shown in FIG. 2, the solar cell element connecting inner lead 10 can easily follow the shape of the surface electrode 5, and the welding area at the welding point can be increased. The peeling of the battery element connecting inner lead 10 can be effectively suppressed. In FIG. 2, the solder layer on the surface electrode 5 of the solar cell element and the solder layer of the inner lead 10 for connecting the solar cell element are shown separately for the sake of explanation, but in actuality, both solders are melted and welded together. Therefore, there is no boundary between them.

  1 and 2 show an example in which a plurality of metal materials are arranged in a line in the longitudinal direction of the solar cell element connecting inner lead 10, but the present invention is not limited to this and the scope of the present invention is not limited thereto. The structure can be changed within.

  In any case, the metal material is made of a highly conductive metal such as silver, copper, aluminum, or iron, but considering its conductivity, ease of handling, and material cost. It is preferable to be made of copper.

  1 and 2, the shape of the cross section of the metal material is described as a circle, but the present invention is not limited thereto, and may be an ellipse, polygon, or thin line structure.

  Moreover, you may make it arrange | position a metal twisted wire in the inner lead 10 for a solar cell element connection at this time. By using a stranded wire structure, the expansion and contraction of the solar cell element connecting inner lead 10 can be suppressed. Therefore, the stress generated at the welding point is alleviated, and the peeling of the solar cell element connecting inner lead 10 is effective. Can be suppressed.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to this. For example, it is possible to wire different solar cell element connecting inner leads on the front and back electrodes, and connect the solar cell element connecting inner leads to the back side, the front side, or between the solar cell elements. It is.

  Two bus bar electrodes are shown on the solar cell element, but may be one or three or more.

  Moreover, it is also possible to use a solar cell element whose entire surface is coated with solder without distinguishing the bus bar electrode as the back electrode of the solar cell element.

  In the above description, an electrode obtained by applying and baking an electrode material has been described as an example, but the present invention is not limited to this. For example, even if the upper end of the electrode is obtained by sputtering or vapor deposition using a photolithographic method, the solder coated on the surface of the electrode has a substantially semicircular shape because of wettability. The effect is demonstrated.

  Further, the solder type may be Sn-Pb so-called 6-4 solder or so-called lead-free solder which does not contain Pb.

  Further, the present invention effectively exhibits the effect even if the solar cell module has a structure in which a solar cell element having no solder layer on the electrode of the solar cell element is connected to the inner lead for connecting the solar cell element.

It is the figure which showed the cross section of one Example of the inner lead for solar cell element connection used for the solar cell module concerning this invention. It is sectional drawing for demonstrating a state when the inner lead for solar cell element connection is wired on the electrode among the solar cell modules concerning this invention. It is the figure which showed the cross section of the general solar cell element. It is a figure for demonstrating the surface structure of a general solar cell element. It is the figure which showed the cross section of the inner lead for a solar cell element connection used for the conventional solar cell module. It is sectional drawing for demonstrating the wiring state of a common solar cell module. It is a top view when it sees from the surface for demonstrating the wiring state of a common solar cell module. It is sectional drawing of the bus-bar electrode formed in the semiconductor substrate surface of a common solar cell element. It is sectional drawing for demonstrating a state when the inner lead for solar cell element connection is wired on the electrode among the conventional solar cell modules. It is the figure which showed the cross section of the other Example of the inner lead for a solar cell element used for the solar cell module concerning this invention. It is the figure which showed the cross section of the further another Example of the inner lead for a solar cell element used for the solar cell module concerning this invention.

Explanation of symbols

1: Solar cell element 2: Diffusion layer 3: Antireflection film 4: BSF layer 5: Front electrode 6: Back electrode 7: Solder layer 8: Bus bar electrode 9: Finger electrode 10: Inner lead 11 for connecting solar cell element: Metal Foil 12: Semiconductor substrate 13: Copper foil

Claims (5)

Provided for electrically connecting a plurality of solar cell elements, is an inner lead for connecting solar cell elements formed by coating a metal foil with solder, wherein the metal foil is formed by bundling a plurality of metal materials An inner lead for connecting a solar cell element. 2. The solar cell element connection according to claim 1, wherein each of the metal foils configured by bundling the plurality of metal materials is arranged in a line in the width direction of the metal foil. For inner lead. 2. The solar cell element connecting inner according to claim 1, wherein each of the metal foils configured by bundling the plurality of metal materials is formed of a stranded wire in which each metal material is formed of a metal wire. Lead. The inner lead for solar cell element connection according to any one of claims 1 to 3, wherein the metal material is copper. A solar cell module, wherein a plurality of solar cell elements are electrically connected using the solar cell element connecting inner lead according to claim 1.

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