JP4622375B2 - Flat rectangular conductor for solar cell and lead wire for solar cell - Google Patents

Description

  The present invention relates to a rectangular conductor for solar cell and a lead wire for solar cell, and particularly to a rectangular conductor for solar cell and a lead for solar cell, which is less likely to cause deformation or breakage of a silicon crystal wafer when connected to a silicon crystal of a solar cell. It is about the line.

  In a solar cell in which a silicon crystal is grown on a substrate, a connection lead wire is usually joined to a predetermined region of a silicon crystal wafer, and power is transmitted through this.

  In the connection lead wire, a solder plating film for connection to the wafer is formed on the surface of the conductor. For example, there is a conductor using a pure copper flat conductor such as tough pitch copper or oxygen-free copper as a conductor, and Sn—Pb eutectic solder as a solder plating film (for example, see Patent Document 1). In recent years, switching to a solder containing no Pb (Pb-free solder) as a constituent material of a solder plating film has been studied in consideration of the environment (for example, see Patent Document 2).

  By the way, since the silicon crystal wafer occupies most of the material cost among the members constituting the solar cell, the thinning of the silicon crystal wafer is being studied in order to reduce the manufacturing cost. However, when the silicon crystal wafer is thinned, the silicon crystal wafer may be damaged due to a heating process at the time of joining the connecting lead wires or a temperature change when using the solar cell. In order to cope with this, there is an increasing need for a wire material having a small thermal expansion as a connecting lead wire.

As an example of a lead wire having a small thermal expansion, a lead frame is formed by a strip (copper-invar-copper) formed by cladding a material having a low thermal expansion such as Invar (alloy made of Fe64% -Ni36%) with a copper material. (For example, refer to Patent Document 3).
Japanese Patent Laid-Open No. 11-21660 JP 2002-263880 A JP 2002-164560 A

  However, in the lead frame having the above three-layer structure of copper-invar-copper, deformation such as warping may occur due to the crystal orientation of the copper material arranged on both sides of the invar or nonuniform crystal grains. It was. These have been the cause of lowering reliability, such as lower productivity of solar cell modules and lowering of power generation efficiency when used for a long time. In addition, when the copper-invar-copper joint on the side surface is exposed to moisture, there is a risk that it becomes a local battery and corrodes.

  Further, the lead frame using the above invar has a problem that the invar contains about 36% of nickel and is expensive and has a low electrical conductivity.

  Furthermore, since the lead frame using the above-mentioned invar is punched at the time of circuit formation, a large amount of wasted material is generated, resulting in an increase in manufacturing cost.

  Accordingly, an object of the present invention is to provide a rectangular solar cell conductor and a solar cell lead wire that are less likely to be deformed or damaged when the connecting lead wire is joined even when the silicon crystal wafer is thinned. is there.

  Another object of the present invention is to provide a solar cell flat conductor and a solar cell lead wire that are inexpensive and have good electrical conductivity.

  Furthermore, the other object of this invention is to provide the rectangular conductor for solar cells and the lead wire for solar cells which can suppress the raise of manufacturing cost.

In order to solve the above problems, the flat conductor for solar cell of the present invention is an aluminum material or conductivity having a tensile strength of 80 MPa or less and a 0.2% proof stress of 40 MPa or less at room temperature and a purity of 99.0 mass% or more. There is characterized in that by molding the single-layer conductors composed of 60% IACS or more aluminum alloy material into rectangular shape.

Copper plating may be applied to the surface of the conductor formed into the flat rectangular shape .

  Furthermore, a part or all of the surface of the solar cell flat conductor can be plated with solder to form a solar cell lead.

  The solder is preferably lead-free solder.

According to the present invention, since the aluminum material or aluminum alloy material having a normal temperature tensile strength of 80 MPa or less and a 0.2% proof stress of 40 MPa or less is adopted as the conductor, it is possible to suppress deformation or breakage of the silicon crystal wafer. Become. Further, since an aluminum material having a purity of 99.0 mass% or more or an aluminum alloy material having a conductivity of 60% IACS or more is used as the conductor, it can be inexpensive and ensure high conductivity.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
(Flat rectangular conductor for solar cells)
In FIG. 1, one Embodiment of the flat conductor for solar cells of this invention is shown.
This flat conductor 10 for solar cells is formed by forming a soft conductor 1 made of pure aluminum or aluminum alloy into a flat rectangular shape.

  The conductor 1 can reduce the power generation loss of the solar cell as the conductivity becomes higher. Therefore, an aluminum material having a purity of 99.0 mass% or more, particularly 99.5 mass% or more is suitable for the material of the conductor 1. Further, it may be an alloy material of 1050 to 1100 standardized by JIS. Furthermore, the lower the strength and the lower yield strength, the less the load on the silicon crystal wafer during bonding. For this reason, the conductor 1 has a tensile strength of 80 MPa or less, particularly 70 MPa or less, and a 0.2% proof stress of 40 MPa or less, particularly 30 MPa at normal temperature. By selecting such a soft aluminum material or aluminum alloy material, it is possible to reduce the thermal stress during conductor bonding to the silicon crystal wafer.

  The flat conductor 10 for solar cells can be obtained by forming the conductor 1 by die drawing, roll rolling, or a composite process thereof.

  FIG. 2 shows a flat conductor 20 for a solar cell by applying copper plating 2 to the surface of the conductor 1 shown in FIG.

(Solar cell lead wire)
In FIG. 3 , one Embodiment of the lead wire for solar cells of this invention is shown.
This solar cell lead wire 50 is obtained by applying solder plating 12 to the entire surface of the conductor 1 shown in FIG. Moreover, the solder plating 12 can also be given to the whole surface of the conductor 1 which formed the copper plating 2 in the outer layer as shown in FIG. The solder plating 12 is a lead-free product from the environmental aspect, and is performed on the entire outer periphery. The composition is preferably Sn—Zn-based when the conductor 1 alone shown in FIG. 1 is used, and Sn—Ag—Cu-based when the copper plating 2 is applied to the outer layer shown in FIG.

  The plating coating by the solder plating 12 may be only a part of the outer periphery of the flat conductor for solar cells (for example, the upper surface and the lower surface of the flat conductor).

  Moreover, about the lead wire for solar cells, it is preferable to heat-process before or after solder plating so that a desired mechanical characteristic may be acquired.

  A solar cell assembly is obtained by connecting these solar cell leads to a predetermined contact region (for example, an Ag plating region) on the cell surface of a silicon crystal wafer (solar cell module (not shown)). .

(Effects of the flat conductor for the solar cell and the lead wire for the solar cell)
As explained above, the flat conductor for solar cell and the lead wire for solar cell of the embodiment are
Since the aluminum material having a normal temperature tensile strength of 80 MPa or less and a 0.2% proof stress of 40 MPa or less is adopted for the conductor 1, the load applied to the silicon crystal wafer by plastic deformation with a small external force is reduced.

  Further, when the conductor 1 is bonded to the silicon crystal wafer, the conductor 1 is pulled out from the bobbin. At that time, the conductor 1 is not less than work hardened by the influence of the tension, and the strength and the 0.2% proof stress are increased. However, the conductor 1 is made of high-purity aluminum, so that it can be joined while being softened by heating at the time of joining. Further, the strength at the joining temperature (high temperature) and the 0.2% proof stress value are low and good as compared with the copper simple substance and the copper-invar-copper clad material.

  Further, since an aluminum material having a purity of 99.0 mass% or more or an aluminum alloy material having a conductivity of 60% IACS or more is used as the conductor, it is possible to secure high conductivity equivalent to that of pure copper at a low price.

  As described above, by adopting an aluminum material or an aluminum alloy material for the conductor, it is possible to reduce warpage of the silicon crystal wafer while ensuring high conductivity equivalent to that of pure copper, and to prevent deformation or breakage of the silicon crystal wafer. Is possible.

  Even when the conductor is designed to have a resistance equivalent to that of a conventional pure copper wire, deformation or destruction of the silicon crystal wafer at the time of conductor bonding can be reduced to a level equivalent to or lower than that of the copper-invar-copper clad wire. In addition, by making the conductor aluminum, it is possible to contribute to weight reduction of the solar cell module, and even if the electric resistance value of the conductor is the same, the weight can be reduced to about ½.

  In order to confirm the effect of the present invention, a plurality of conductors having different mechanical characteristics were prototyped and verified. Further, as a comparative example, a material having a normal temperature tensile strength and a 0.2% proof stress outside the ranges specified in the present invention was produced. Furthermore, as a prior art, a solder-plated rectangular soft copper wire and a solder-plated copper-invar-copper-clad soft rectangular wire (2: 1: 2) were also prototyped. Furthermore, in the evaluation of the conductors of the examples, a type having a size of width 2.0 mm × thickness 0.15 mm and a copper single resistance type were also manufactured. Sn, Ag-Cu plating was applied to the conductors of Examples, Comparative Examples, and the prior art. In the examples, 1 μm pure copper plating was applied on the aluminum conductor.

  The evaluation was performed by observing the warp of the silicon crystal wafer. If a flat wire is soldered to the center of a silicon crystal wafer of length 100mm x width 100mm x thickness 2mm, the warp of the silicon crystal wafer is equivalent to that of a conventional copper-invar-copper-clad soft flat wire. ◎ if less, x if inferior. Table 1 shows examples (present invention), and Table 2 shows comparative examples and evaluation results of conventional techniques.

  No. in Table 1 1 to No. 7 has the same dimensions as the pure copper wire (No. 19, 20). These have an electrical resistance of about 1.7 times higher than that of copper wire. However, the conductor has a tensile strength of 80 MPa or less at room temperature and a 0.2% proof stress of 40 MPa or less, and the warp of the silicon crystal wafer is equivalent to the conventional copper-invar-copper clad soft rectangular wire (No. 19) or It was confirmed that it was smaller than that. Furthermore, it was found that the warpage of the silicon crystal wafer was remarkably reduced by setting the normal temperature tensile strength to 70 MPa or less and the 0.2% proof stress to 30 MPa (No. 1 to No. 3).

  No. 8 to No. No. 10 has the same electrical resistance as that of pure copper wires (No. 19 and 20). 1 to No. The thickness of the conductor shown in Fig. 7 is 1.7 times thicker. In these cases, the warp of the silicon crystal wafer can be reduced to the same level as that of the conventional copper-invar-copper-clad soft rectangular wire (No. 18), although the conductor thickness is increased by 1.7 times. I was able to confirm.

  On the other hand, no. 11 to No. In the plated wire No. 17, the tensile strength and the 0.2% proof stress are 80 and 40 MPa or more at room temperature, respectively, so that the warp of the silicon crystal wafer is not less than the conventional copper-invar-copper clad soft rectangular wire (No. 18). Became bigger.

It is sectional drawing which shows one Embodiment of the flat conductor for solar cells of this invention. It is sectional drawing which shows other embodiment of the flat conductor for solar cells of this invention. It is sectional drawing which shows one Embodiment of the lead wire for solar cells of this invention .

DESCRIPTION OF SYMBOLS 1 Conductor 2 Copper plating 3 Copper sheath 5 Copper thin plate material 7 Coupling part 12 Solder plating 10, 20, 30, 40 Solar cell rectangular conductor 50, 60, 70 Lead wire for solar cell

Claims (4)

Tensile strength at room temperature is less and 0.2% proof stress 80MPa equal to or less than 40 MPa, a single-layer conductors having a purity 99.0Mass% more aluminum material or conductivity consists 60% IACS or more aluminum alloy material flat A rectangular conductor for solar cells, characterized in that it is shaped into a shape.   The flat conductor for a solar cell according to claim 1, wherein a copper plating is applied to a surface of the conductor formed into the flat rectangular shape. Claim 1 for a solar cell lead wire, wherein a part or the whole of the surface of any one solar cell flat conductor according plated with solder 2. 4. The solar cell lead wire according to claim 3 , wherein the solder is lead-free solder.

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