JP2011243659A - Square copper wire, method of manufacturing same, square copper wire for solar cell, and method of manufacturing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a square copper wire of which a difference in thermal expansion that occurs between a silicon wafer and a copper wire and stress are relaxed, and to provide an excellent square copper wire for a solar cell of which, by connecting the silicon wafer with the square copper wire, occurrence of crack is prevented on the silicon wafer for an extended period, for improved power generation efficiency and longer life.SOLUTION: The square copper wire is provided in which a copper strand whose volume resistivity is 2.5 μΩ cm or less and which has been annealed at 300-800°C is applied with cold rolling or cold drawing process of work efficiency 5-15%. Otherwise, the square copper wire in which the copper strand whose volume resistance is 2.5 μΩ cm or less and which has been annealed at 300-800°C is applied with cold rolling or cold drawing process at work efficiency 0-15%, and after that, expansion of 0.5-1% is applied. The square copper wire for a solar cell has the square copper wire provided with a solder layer at least on one surface.

Description

  The present invention relates to a rectangular copper wire and a rectangular copper wire for a solar cell suitable as a lead wire connected to the solar cell, and a method for producing the same.

  A solar cell mainly uses a silicon wafer, and a plurality of silicon wafers are connected in series by lead wires in order to obtain a sufficient electromotive force. FIG. 1 shows a state in which a plurality of silicon wafers 2 are connected by a flat wire 1 (lead wire). This lead wire is generally a rectangular wire plated with solder.

  By the way, the cost of solar cells is mostly silicon wafers, and in recent years, the thickness of silicon wafers has been reduced in order to reduce manufacturing costs. However, when the silicon wafer becomes thin, the strength decreases, and when the silicon wafer 1 is connected by the flat wire 2, the silicon wafer may be warped. That is, a copper wire is mainly used as the flat wire 2, but since the thermal expansion coefficient differs between the lead wire and the silicon wafer as shown in Table 1, the solder of the flat copper wire is melted to form a silicon wafer. In the case of connection, warpage of the silicon wafer 2 does not occur at the time of solder connection as shown in FIG. 2A, but there is a difference in shrinkage when cooled from the solder connection temperature to room temperature, and FIG. As shown in FIG. 3, the silicon wafer 2 is warped, and in the worst case, the wafer may be damaged. In the figure, 4 is a solder layer.

  Similarly, there is a possibility that the silicon wafer is damaged due to thermal stress caused by the thermal cycle when the solar cell is used. For this reason, the need for a lead wire (flat wire) having a small thermal stress generated between the silicon wafer and the silicon wafer is increasing.

  As a lead wire (flat wire) having a small thermal stress generated between a silicon wafer and a clad material in which Fe-36 mass% Ni is a core material and both surfaces thereof are laminated with copper (Patent Document 1). reference). In addition, a method has been proposed in which pure copper is annealed to reduce its yield strength, thereby reducing the thermal stress by yielding the copper wire (see Patent Document 2). This method is expected to reduce the manufacturing cost and increase the power generation efficiency.

Japanese Unexamined Patent Publication No. 60-15937 JP 2006-54355 A

The lead wire made of the clad material as in Patent Document 1 has the effect of reducing the thermal expansion difference and reducing the thermal stress between the silicon wafer and the Fe—Ni alloy having a larger volume resistivity than the copper wire. Since it is used, the power generation efficiency of the solar cell may be reduced.
Moreover, since the copper wire which heat-processed like patent document 2 receives the thermal cycle of the daytime and nighttime in the state where the tensile load at the time of soldering the silicon wafer was connected, the lifetime of a wafer (cell) becomes short. Therefore, there is a need for a lead wire that can maintain the life of the solar cell longer.

In the present invention, cold working such as rolling, drawing (drawing), and tension is applied to the copper wire to relieve the difference in thermal expansion between the silicon wafer (cell) and the copper wire and the stress at the time of solder connection. Is to provide a flat copper wire.
In addition, the present invention provides an excellent solar cell that prevents the generation of cracks in the silicon wafer (cell) over a long period of time, improves the power generation efficiency, and has a long life by connecting the silicon wafer with the flat copper wire. The purpose is to do.

  The rectangular copper wire of the present invention has a volume resistivity of 2.5 μΩ · cm or less, and is subjected to cold rolling or cold drawing at a processing rate of 5 to 15% on a copper wire annealed at 300 to 800 ° C. It is a flat copper wire that has been subjected to wire processing.

  In the method for producing a rectangular copper wire according to the present invention, a copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and the annealed copper wire is cooled at a processing rate of 5 to 15%. It is a manufacturing method of a flat copper wire which performs cold rolling or cold wire drawing.

  The rectangular copper wire of the present invention has a volume resistivity of 2.5 μΩ · cm or less, and a copper wire that has been annealed at 300 to 800 ° C., and has been given an elongation of 0.5 to 1%. It is.

  In the method for producing a rectangular copper wire according to the present invention, a copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and the annealed copper wire is stretched by 0.5 to 1%. Is a method for producing a rectangular copper wire.

  The rectangular copper wire of the present invention has a volume resistivity of 2.5 μΩ · cm or less and is subjected to cold rolling or cold drawing at a processing rate of 0 to 15% on a copper wire annealed at 300 to 800 ° C. It is a flat copper wire which gave 0.5 to 1% of elongation to the copper strand to which the wire processing was performed and the cold rolling or the cold wire drawing was performed.

  In the method for producing a rectangular copper wire according to the present invention, a copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and the annealed copper wire is cooled at a processing rate of 0 to 15%. This is a method for producing a rectangular copper wire, which is subjected to cold rolling or cold wire drawing, and gives 0.5 to 1% elongation to the copper wire subjected to cold rolling or cold wire drawing.

  The rectangular copper wire for solar cells of the present invention is a rectangular copper wire for solar cells in which a solder layer is provided on at least one surface of any one of the above rectangular copper wires.

  The method for producing a rectangular copper wire for a solar cell according to the present invention is a method for producing a rectangular copper wire for a solar cell, wherein a solder layer is applied to at least one surface of the rectangular copper wire produced by any one of the above-described methods for producing a rectangular copper wire. It is.

  The flat copper wire for solar cell of the present invention has a volume resistivity of 2.5 μΩ · cm or less and is subjected to cold rolling with a working rate of 0 to 15% on a copper wire annealed at 300 to 800 ° C. A rectangular copper wire for solar cells, in which a solder layer is applied to at least one surface of a flat copper wire that has been subjected to cold wire drawing, and an elongation of 0.5 to 1% is imparted to the rectangular copper wire to which the solder layer has been applied. Is a line.

  In the method for producing a rectangular copper wire for a solar cell of the present invention, a copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and 0 to 15% of the annealed copper wire is processed. Cold rolling or cold wire drawing at a rate, a solder layer is provided on the flat copper wire subjected to the cold rolling or cold wire drawing, and 0.5 to 1 is applied to the rectangular copper wire provided with the solder layer. It is a manufacturing method of the rectangular copper wire for solar cells which provides% elongation.

  The flat copper wire for solar cells of the present invention has a volume resistivity of 2.5 μΩ · cm or less and imparts an elongation of 0.5 to 1% to a copper strand that has been annealed at 300 to 800 ° C. A flat copper wire for a solar cell in which a solder layer is applied to at least one surface of a flat copper wire, and an elongation of 0.5 to 1% is given to the flat copper wire to which the solder layer is applied.

  The manufacturing method of the rectangular copper wire for solar cells of this invention anneals the copper strand whose volume resistivity is 2.5 microhm * cm or less at 300-800 degreeC, and is 0.5-1 to this annealed copper strand. % For a rectangular copper wire, a solder layer is applied to at least one surface of the rectangular copper wire, and a 0.5 to 1% elongation is applied to the rectangular copper wire to which the solder layer is applied. This is a method for producing a flat copper wire.

  The flat copper wire for solar cell of the present invention has a volume resistivity of 2.5 μΩ · cm or less and is subjected to cold rolling or cold treatment at a 0 to 15% processing rate on a copper wire annealed at 300 to 800 ° C. A solder layer is applied to at least one surface of a flat copper wire which has been subjected to cold drawing and has been subjected to cold rolling or cold drawing and has been given an elongation of 0.5 to 1%. A rectangular copper wire for a solar cell in which a 0.5 to 1% elongation is imparted to a rectangular copper wire to which a solder layer is applied.

  In the method for producing a rectangular copper wire for a solar cell of the present invention, a copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and 0 to 15% of the annealed copper wire is processed. This rectangular copper wire is a flat copper wire which has been subjected to cold rolling or cold drawing at a rate and has been given a 0.5 to 1% elongation to a copper wire that has been cold rolled or cold drawn. Is a method for producing a rectangular copper wire for a solar cell, in which a solder layer is applied to at least one surface of the substrate and 0.5 to 1% of elongation is imparted to the rectangular copper wire to which the solder layer is applied.

  In the present invention, “rolling” and “drawing” (including “drawing” in the drawing) mean a process of three-dimensionally processing a copper wire. Further, “providing elongation” includes a process of “tensile processing” and means a step of processing a copper element wire or a rectangular copper wire one-dimensionally in the longitudinal direction.

The present invention provides a rectangular copper wire in which cold working such as rolling, wire drawing (drawing), and tension is applied to a copper wire to reduce the difference in thermal expansion and stress generated between the silicon wafer and the copper wire. it can.
In addition, the present invention provides an excellent solar cell in which a silicon wafer (cell) is connected with the rectangular copper wire, thereby preventing generation of cracks in the silicon wafer for a long period of time, improving power generation efficiency, and extending the life. can do.
Further, the rectangular copper wire of the present invention can be manufactured and provided at a low cost because only simple processing is applied to the copper wire.

FIG. 1 is an explanatory view showing a connection state between a silicon wafer and a rectangular copper wire. FIG. 2 shows a connection state between a silicon wafer and a rectangular copper wire, (A) is an explanatory view showing a state immediately after the connection, and (B) is a wafer due to a difference in thermal shrinkage between the silicon wafer and the rectangular copper wire. It is explanatory drawing explaining curvature. FIG. 3 is a cross-sectional view showing a flat copper wire provided with a solder layer according to an embodiment of the present invention. FIG. 4 is an explanatory diagram for explaining a method of measuring the warpage of the wafer.

  First, the rectangular copper wire of the present invention and the manufacturing method thereof will be specifically described.

Embodiment 1;
In the first embodiment, the volume resistivity of a lead wire (flat copper wire) connecting a plurality of silicon wafers (cells) is 2.5 μΩ · cm or less. When the volume resistivity is larger than 2.5 μΩ · cm, the power generation efficiency of the solar cell is lowered. Therefore, a copper wire having a volume resistivity of 2.5 μΩ · cm or less is used.
In the present invention, an ingot or rough drawn wire having a volume resistivity of 2.5 μΩ · cm or less is cold-worked to obtain a copper wire, and this copper wire is annealed at a temperature of 300 to 800 ° C. for 10 seconds to 1 hour. 5-15% cold rolling or cold wire drawing (when it is not necessary to distinguish between cold rolling and cold wire drawing in the following embodiments, it is simply “cold working”. To make a flat copper wire.

  The copper (including alloy) strand used in the present invention has a volume resistivity of 2.5 μΩ · cm or less. As a material having a volume resistivity of 2.5 μΩ · cm or less, a copper material such as oxygen-free copper (OFC), phosphorous deoxidized copper, tough pitch copper (TPC), high purity copper (purity 99.9999% or more) is preferable.

  A copper wire is manufactured from the copper material ingot or rough drawn wire by a process such as rolling or wire drawing. Next, this copper strand is annealed. The annealing treatment is performed at 300 to 800 ° C. for 10 seconds to 1 hour. When the annealing temperature is lower than 300 ° C., recrystallization does not proceed sufficiently, which is not preferable. Further, when the annealing time is shorter than 10 seconds, it is not preferable because recrystallization does not proceed sufficiently.

  The annealed copper element wire is then subjected to cold working at a working rate of 5 to 15% and formed into a flat copper wire. The processing rate of cold working is 5 to 15%. If the processing rate is less than 5%, the processing rate is insufficient, so that a sufficient effect cannot be obtained. If the processing rate exceeds 15%, the Young's modulus and strength of the flat copper wire are increased. In particular, if a solder layer is provided on the surface of this flat copper wire and a silicon wafer (cell) is soldered via this solder layer, the thermal stress may increase at the time of soldering and the silicon wafer may be destroyed. It is not preferable to make the value larger than 15%.

  In the first embodiment, the annealed copper wire is subjected to cold working with a working rate of 5 to 15% to form a flat copper wire, and this flat copper wire has a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the silicon wafer. Can be finished. Therefore, it is possible to provide a flat rectangular copper wire excellent in connecting a plurality of silicon wafers (cells).

Embodiment 2;
In the second embodiment, similarly to the first embodiment, a copper material having a volume resistivity of 2.5 μΩ · cm or less is used, and the copper material is cold-worked to form a copper wire. The same annealing treatment as that in the first embodiment is performed. Next, the annealed copper element wire is stretched by 0.5 to 1% by cold tension to obtain a rectangular copper wire.

In the second embodiment, residual stress is generated in the rectangular copper wire by giving an elongation of 0.5 to 1% to the annealed copper wire to obtain a rectangular copper wire.
The reason why the annealed copper element wire is subjected to 0.5 to 1% cold tensile processing is to impart a residual stress in the direction opposite to the thermal expansion to the rectangular copper wire, so that the cold tension is less than 0.5%. Sufficient residual stress cannot be imparted by processing, and cold tensile processing exceeding 1% is not preferable because it becomes a plastic region.
In this way, the residual stress applied to the rectangular copper wire acts as a residual stress in the opposite direction to the thermal expansion of the rectangular copper wire when a plurality of silicon wafers (cells) are soldered. The difference in thermal expansion between the two can be reduced, and the amount of warpage of the silicon wafer can be reduced. Therefore, it is possible to provide an excellent flat copper wire that can prevent cracking of the silicon wafer (cell).

Embodiment 3;
In the third embodiment, 0-15% cold rolling or cold wire drawing is added to an annealed copper wire having a volume resistivity of 2.5 μΩ · cm or less, and 0.5 0.5 by cold tensile processing. It is a flat copper wire which gave ~ 1% elongation.

  In the third embodiment, a copper material having a volume resistivity of 2.5 μΩ · cm or less is used, and the copper material is cold-worked to obtain a copper wire, which is the same as in the first embodiment. After the annealing treatment, 5 to 15% of cold rolling or cold drawing is performed to obtain a flat copper wire. Subsequently, this flat rectangular copper wire is stretched by 0.5 to 1% by cold tensile processing to obtain a rectangular copper wire.

  In the third embodiment, the annealed copper wire is subjected to 5 to 15% cold working to obtain a flat copper wire, and this flat copper wire has a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the silicon wafer. Can be finished. Next, 0.5 to 1% of cold tensile processing is performed to form a flat copper wire, thereby generating a residual stress in the flat copper wire. Therefore, when connecting a plurality of silicon wafers (cells), the thermal expansion coefficients of the silicon wafer and the rectangular copper wire are approximate, and residual stress acting in the opposite direction to the thermal expansion of the rectangular copper wire is applied. Therefore, the difference in thermal expansion between the silicon wafer and the flat copper wire is alleviated, and the amount of warpage of the silicon wafer is reduced. Therefore, it is possible to provide an excellent flat copper wire that does not cause cracks in the silicon wafer.

  Next, the rectangular copper wire for solar cells and the manufacturing method thereof will be specifically described.

Embodiment 4;
Embodiment 4 is a rectangular copper wire for solar cells in which a solder layer is provided on the rectangular copper wire.
The rectangular copper wire of Embodiment 4 employs the rectangular copper wire manufactured in Embodiments 1 to 3 above. The solder layer may be provided on the entire surface of the flat copper wire, or may be provided only on the surface connected to the silicon wafer (cell).

  The solder layer can be applied to a required position of a flat copper wire by, for example, a plating method or a dipping method. As the “solder” for forming the solder layer, Sn-based solder can be used. In addition, it is preferable to use the solder which added 0.1 mass% or more of Pb, In, Bi, Ag, and Cu as a 2nd component. In particular, in order to prevent environmental pollution, it is desirable to use a solder such as Pb-free Sn—Ag, Sn—Ag—Cu, Sn—Cu, or Sn—Ag—In.

Embodiment 4-1;
The annealed copper wire is subjected to 5-15% cold rolling or cold drawing to form a flat copper wire, and a solder layer is provided on the flat copper wire. Since this flat copper wire with a solder layer is provided with a solder layer on a flat copper wire finished to a thermal expansion coefficient substantially equal to that of the silicon wafer, the rectangular copper wire has a thermal expansion coefficient substantially equal to that of the silicon wafer. When a plurality of silicon wafers (cells) are connected via a solder layer, the cell can be connected without being damaged over time.

Embodiment 4-2;
Further, the annealed copper element wire is subjected to 0.5 to 1% cold tensile processing, and a solder layer is provided on the rectangular copper wire that leaves residual stress in the rectangular copper wire. When a plurality of silicon wafers (cells) are soldered with a rectangular copper wire in which residual stress remains in the rectangular copper wire, the residual stress acts as a stress in the direction opposite to the thermal expansion of the rectangular copper wire. The thermal expansion difference between the two is reduced, the amount of warpage of the silicon wafer (cell) is reduced, and cracks can be prevented.

Embodiment 4-3;
Further, 0-15% cold rolling or cold drawing is applied to the annealed copper wire, and a solder layer is provided on the rectangular copper wire that has been given 0.5-1% elongation by cold drawing. . Since this flat copper wire has a thermal expansion coefficient approximate to that of a silicon wafer and a residual stress acting in the opposite direction to the thermal expansion of the flat copper wire is applied, a plurality of silicon wafers (cells) are connected via a solder layer. ), The difference in thermal expansion between the silicon wafer and the rectangular copper wire is alleviated, the amount of warpage of the silicon wafer is reduced, and an excellent effect of not causing cracks in the aged wafer is obtained.

Embodiment 5;
The flat copper wire for solar cell of the fifth embodiment is a flat copper wire for solar cell obtained by applying a solder layer to the flat copper wire manufactured in the first embodiment and then giving an elongation of 0.5 to 1%. The solder layer may be provided on the entire surface of the flat copper wire, or may be provided only on the surface connected to the wafer.

  The flat copper wire for solar cell of Embodiment 5 is annealed and subjected to cold rolling or cold drawing of 0 to 15% processing rate on a copper wire having a volume resistivity of 2.5 μΩ · cm or less. Use flat rectangular copper wire. A solder layer is applied to at least one surface of the flat copper wire, and then an elongation of 0.5 to 1% is imparted to the flat copper wire to which the solder layer has been applied.

The reason why 0.5 to 1% elongation is given after the solder layer is provided on the flat copper wire is to reduce the warpage of the flat copper wire, and this elongation is given if the flat copper wire is not warped. Although the process to do can be omitted, when warping is observed in the flat copper wire, an appropriate elongation is applied after the solder layer is provided.
If the elongation is less than 0.5%, an effect sufficient to reduce warpage cannot be obtained, and if an elongation exceeding 1% is imparted, the elongation of the material is lost, which is not preferable. .
The reason why the tensile process is performed after the solder layer is provided is that the flat copper wire may be warped by the heat when the solder layer is formed by plating or the like. The process can be omitted.

Embodiment 6;
The flat copper wire for solar cell of the sixth embodiment is a flat copper wire for solar cell obtained by applying a solder layer to the flat copper wire manufactured in the second embodiment and then giving 0.5 to 1% elongation. The solder layer may be provided on the entire surface of the flat copper wire, or may be provided only on the surface connected to the wafer.

The flat copper wire for solar cell of Embodiment 6 gives an elongation of 0 to 15% processing rate to a flat copper wire having a volume resistivity of 2.5 μΩ · cm or less that has been annealed, and then the flat copper wire. It is a rectangular copper wire for a solar cell in which a solder layer is applied to at least one surface of the wire, and an elongation of 0.5 to 1% is given to the rectangular copper wire to which the solder layer is applied.
The reason why 0.5 to 1% elongation is applied after the solder layer is provided is to correct the warpage generated in the flat copper wire by the heat when the solder layer is provided as in the fifth embodiment. When the elongation is less than 0.5%, a sufficient effect for correcting the warp cannot be obtained, and when an elongation exceeding 1% is imparted, the elongation of the material is lost.

Embodiment 7;
The rectangular copper wire for solar cells of the seventh embodiment is a rectangular copper wire for solar cells obtained by applying a solder layer to the rectangular copper wire produced in the third embodiment and then giving an elongation of 0.5 to 1%. The solder layer may be provided on the entire surface of the flat copper wire, or may be provided only on the surface connected to the wafer.

The flat copper wire for solar cell of the seventh embodiment is subjected to cold working at a processing rate of 0 to 15% on the annealed copper element wire having a volume resistivity of 2.5 μΩ · cm or less, and the cold working is performed. An elongation of 0.5 to 1% is imparted to the applied wire, then a solder layer is applied to at least one surface of the flat copper wire, and then 0.5 to 1% to the flat copper wire to which the solder layer is applied Is a rectangular copper wire for solar cells to which the elongation of
The reason why 0.5 to 1% elongation is applied after the solder layer is provided is to correct the warpage generated in the flat copper wire by the heat when the solder layer is provided as in the fifth embodiment. If the elongation is less than 0.5%, a sufficient effect for correcting the warp cannot be obtained, and if an elongation exceeding 1% is imparted, the elongation of the material is lost.

  Next, the manufacturing method of the flat copper wire of this invention and the flat copper wire for solar cells is demonstrated in detail based on an Example.

Production of flat copper wire;
The copper (including alloy) strand used in the present invention employs a volume resistivity of 2.5 μΩ · cm or less. Examples of materials having a volume resistivity of 2.5 μΩ · cm or less include copper strands such as oxygen-free copper (OFC), phosphorous deoxidized copper, tough pitch copper (TPC), and high-purity copper (purity 99.9999% or more). .

In the manufacture of a flat copper wire, first, a copper rough wire is manufactured from a copper material having a volume resistivity of 2.5 μΩ · cm or less. As a method for producing a copper rough wire, there are a belt & wheel method, a twin belt method, a dip forming method, a hot extrusion method, an upcast method and the like.
The rough drawn wire is drawn and rolled into a flat cross-sectional shape (rolling method). This rolling method is suitable for producing a continuous flat copper wire.
In order to manufacture rectangular copper wires of various widths, a copper material (ingot) having a volume resistivity of 2.5 μΩ · cm or less is rolled into a strip-shaped copper plate, and the copper strip is slit to form a rectangular copper wire. It is also possible to adopt the method.

  These flat copper wires are annealed by an energization method or a batch method. When performing annealing continuously, the energization method is more efficient and preferable. Here, the annealing treatment is performed at a temperature of 300 to 800 ° C. for 10 seconds to 1 hour.

After the annealing treatment, this flat copper wire is cold worked. Processing methods include cold rolling or cold drawing, or a combination of these. A processing method for finishing to a desired material and shape is selected.
When the shape of the flat copper wire is determined, elongation (tensile processing) is applied instead of rolling or wire drawing. Cold tensioning is performed by a leveler method, for example.

  The flat copper wire thus manufactured is immersed in a plating bath to cover the solder plating layer. Although the solder alloy has been described above, Sn-based solder (Sn—Pb, Sn—Ag, Sn—Ag—Cu, Sn—Cu, etc.) is used in this embodiment. If the solder bath temperature is too high, the processing applied to the flat copper wire may be lost due to the annealing effect. Therefore, the melting point of the solder alloy is + 50 ° C. or lower, preferably + 20 ° C. or lower, and the dipping time is also short.

Examples 1-3
Tough pitch copper is used as a copper material with a volume resistivity of 2.5 μΩ · cm or less, the copper is drawn into a rough drawn wire by the belt and wheel method, and then annealed at 400 ° C. by energization heating. % Was rolled to obtain a rectangular copper wire having a width of 2.0 mm and a thickness of 0.16 mm (hereinafter referred to as a rectangular wire before plating). This pre-plated rectangular copper wire is immersed in a Sn-3% Ag-0.5% Cu bath maintained at 250 ° C., and a solder plating layer having a thickness of about 40 μm is provided on the entire rectangular copper wire. Copper wire was created.

Evaluation of the produced flat copper wire for solar cells was performed as follows.
(1) Measurement of heat shrinkage The length of a 150 mm long pre-plated rectangular copper wire when heated to 250 ° C. and then the length when cooled to room temperature (heat shrinkage) were measured. It was described in.

(2) Measurement of warpage and cracking of silicon wafer Next, various solder-plated rectangular wires were soldered to a 150 × 150 × 0.2 mm silicon wafer and cooled to room temperature. Investigated about.
As shown in FIG. 4, the amount of warpage was measured with a laser displacement meter or the like as the maximum value of the warpage of the silicon wafer when both ends of the wafer were placed on a horizontal plane. The results are shown in Table 2.
For evaluation of wafer cracks, those with no cracks were judged as “good” and “○” was marked on the table, and those with cracks were judged as “impossible” and “x” on the table. Marked. The results are shown in Table 2.

(3) Determination of Life of Silicon Wafer The life of the wafer was evaluated by a thermal fatigue test of 10,000 cycles at 25 ° C. to 100 ° C.
Judgment is made by judging that the cracks did not occur as `` good '' and marking the table with `` ○ '', and those with cracks or those that cannot be evaluated as `` impossible '' A mark “×” was given, and a crack in the wafer surface was judged as “impossible (crack generation)” and given a “△” mark. The results are shown in Table 2.

Examples 4-6
Oxygen-free copper is used as a copper material with a volume resistivity of 2.5 μΩ · cm or less, drawn into a copper rough wire by the belt and wheel method, annealed by heat treatment at 400 ° C. by energization heating, and 5-15 % Cold rolling was performed to obtain a rectangular copper wire before plating having a width of 2.0 mm and a thickness of 0.16 mm. This pre-plated rectangular copper wire is immersed in a bath of Sn-3% Ag-0.5% Cu in which the bathtub is kept at 250 ° C., and a solder plating layer having a thickness of about 40 μm is provided on the entire rectangular copper wire. A flat copper wire was prepared.

  Evaluation of the produced flat copper wire for solar cells was performed by measuring and evaluating the amount of thermal shrinkage, warpage, cracking and life of the silicon wafer, and the results are shown in Table 2.

Comparative Examples 7-10
Using the same tough pitch copper as in Example 1 and making the cold rolling rate 2%, 3%, 20% and 30%, a rectangular copper wire was prepared in the same process as in Example 1, The plating layer was provided on the same conditions, and the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

Comparative Examples 11-14
A rectangular copper wire was prepared in the same process as in Example 4 except that the same oxygen-free copper as in Example 4 was used and the cold rolling rate was 2%, 3%, 20%, and 30%. A plating layer was provided under the same conditions as in Example 4, and the same evaluation as in Example 4 was performed. The results are shown in Table 2.

Conventional Example 15
A rectangular copper wire is prepared using the same tough pitch copper as in Example 1, and a rectangular copper wire with a cold rolling rate of 99% is prepared without annealing, and the plating layer is formed under the same conditions as in Example 1. The same measurement and evaluation as in Example 1 were performed. The results are shown in Table 2.

Conventional Example 16
A flat copper wire is prepared using the same tough pitch copper as in Example 1, a flat copper wire is prepared by performing the same annealing treatment as in Example 1, and a plating layer is provided under the same conditions as in Example 1. Example 1 The same measurement and evaluation were performed. The results are shown in Table 2.

Conventional Example 17
A flat copper wire is prepared using the same oxygen-free copper as in Example 4, and a flat copper wire with a cold rolling rate of 99% is prepared without annealing, and the plating layer is formed under the same conditions as in Example 4. The same measurement and evaluation as in Example 4 were performed. The results are shown in Table 2.

Conventional Example 18
A flat copper wire is prepared using the same oxygen-free copper as in Example 4, a flat copper wire is prepared by performing the same annealing treatment as in Example 4, and a plating layer is provided under the same conditions as in Example 4. The same measurement and evaluation as in No. 4 were performed. The results are shown in Table 2.

As is apparent from Table 2, the flat copper wires of Examples 1 to 6 were subjected to cold rolling with a working rate of 5 to 15% on the annealed copper wires. As described above, since a predetermined amount of processing rate is given to the copper wire, the amount of thermal shrinkage is small compared to the conventional examples 16 and 18 in which the cold rolling is not performed after the heat treatment.
Moreover, the solder plating coated rectangular copper wire using these rectangular copper wires was connected to the silicon wafer as compared with the conventional examples 15 and 17 in which the annealing treatment was not performed and the processing rate of a predetermined amount or more was given. The wafer warpage at the time was small, and the wafer did not crack.
In addition, since the load applied to the wafer is small, the life against heat cycle is also good.

  On the other hand, Comparative Examples 9, 10, 13, and 14 were subjected to cold rolling processing with a processing rate greater than 15%, and all of them had a small amount of thermal shrinkage, but because the applied stress was large, it was applied to the wafer. Cracking occurred. In Comparative Examples 7, 8, 11, and 12 that were subjected to cold rolling with a processing rate of less than 5%, the wafer surface was not cracked during solder connection, but the wafer surface was fine with respect to the thermal cycle. Cracks occurred and none of them satisfied the object of the present invention.

Examples 20-22
5 to 15% after using tough pitch copper as a copper material with a volume resistivity of 2.5 μΩ · cm or less, drawing into copper rough wire by belt & wheel method, annealing by conducting heat treatment at 400 ° C. by current heating Was subjected to cold wire drawing to obtain a rectangular copper wire before plating having a width of 2.0 mm and a thickness of 0.16 mm. This pre-plated rectangular copper wire is immersed in a bath of Sn-3% Ag-0.5% Cu in which the bathtub is kept at 250 ° C., and a solder plating layer having a thickness of about 40 μm is provided on the entire rectangular copper wire. A flat copper wire was prepared.

  Measurement and evaluation of the produced flat copper wire for solar cell were performed in the same manner as in Example 1, and the results are shown in Table 3.

Examples 23-25
Oxygen-free copper is used as a copper material with a volume resistivity of 2.5 μΩ · cm or less, drawn into a copper rough wire by the belt and wheel method, annealed by heat treatment at 400 ° C. by energization heating, and 5-15 % Cold drawing was performed to obtain a rectangular copper wire before plating having a width of 2.0 mm and a thickness of 0.16 mm. This pre-plated rectangular copper wire is immersed in a bath of Sn-3% Ag-0.5% Cu in which the bathtub is kept at 250 ° C., and a solder plating layer having a thickness of about 40 μm is provided on the entire rectangular copper wire. A flat copper wire was prepared.

  The measurement and evaluation of the created flat copper wire for solar cell were performed in the same manner as in Example 1, and the thermal shrinkage, warpage, cracking and life of the silicon wafer were measured and evaluated, and the results are shown in Table 3.

Comparative Examples 26-29
A rectangular copper wire was prepared in the same process as in Example 20, except that the same tough pitch copper as in Example 20 was used and the cold drawing rate was 2%, 3%, 20%, and 30%. A plating layer was provided under the same conditions as in Example 20, and the same measurement and evaluation as in Example 20 were performed. The results are also shown in Table 3.

Comparative Examples 30-33
Using the same oxygen-free copper as in Example 23 and making the cold drawing rate 2%, 3%, 20%, and 30%, a rectangular copper wire was prepared in the same process as in Example 23. A plating layer was provided under the same conditions as in Example 23, and the same measurements and evaluations as in Example 23 were performed. The results are also shown in Table 3.

Conventional examples 34-37
The same processing, measurement, and evaluation as in Conventional Examples 15 to 18 were performed except that cold drawing was performed instead of the cold rolling of Conventional Examples 15 to 18 shown in Table 2. The results are also shown in Table 3.

As is apparent from Table 3, the rectangular copper wires of Examples 20 to 25 are subjected to 5 to 15% cold drawing on the annealed copper material. As described above, since a predetermined amount of processing rate is imparted to the copper material, the amount of thermal shrinkage is small as compared with the conventional examples 35 and 37 in which the cold wire drawing is not performed after the heat treatment.
Moreover, the solder plating coated rectangular copper wire using these rectangular copper wires was connected to the silicon wafer as compared with the conventional examples 34 and 36 in which the annealing treatment was not performed and a processing rate of a predetermined amount or more was given. The wafer warpage at the time was small, and the wafer did not crack.
In addition, since the load applied to the wafer is small, the life against heat cycle is also good.

  On the other hand, Comparative Examples 28, 29, 32, and 33 were subjected to cold drawing greater than a processing rate of 15%, and all of them had a small amount of heat shrinkage. However, since the applied stress was large, the wafer was cracked. In Comparative Examples 26, 27, 30, and 31 subjected to cold wire drawing with a processing rate of less than 5%, although cracks were not generated in the wafer during solder connection, fine cracks were formed on the surface with respect to the thermal cycle. None of these were satisfied with the object of the present invention.

Examples 40-63
After drawing copper rough wire made of tough pitch copper by belt & wheel method, annealing by conducting heat treatment at 400 ° C by energization heating, then cold rolling with a processing rate of 0-15%, did. This flat copper wire is subjected to a tensile process that gives 0.5 to 1% elongation before solder plating and then subjected to solder plating, or a tensile process that gives 0.5 to 1% elongation after solder plating, A rectangular copper wire for solar cells having a final cross-sectional shape of width 2.0 mm and thickness 0.16 mm was manufactured. The solder layer was immersed in a Sn-3% Ag-0.5% Cu solder bath maintained at 250 ° C. to a thickness of about 40 μm.

  The same measurement and evaluation as in Example 1 were performed on the flat rectangular copper wires for solar cells manufactured under the conditions of Examples 40 to 63, and the results are shown in Table 4.

Examples 64-87
After drawing an oxygen-free copper copper-drawn wire with a belt and wheel method, and conducting annealing at 400 ° C. by energization heating, it was subjected to cold rolling with a processing rate of 0 to 15% to obtain a rectangular wire. did. This flat copper wire is subjected to a tensile process that gives 0.5 to 1% elongation before solder plating and then subjected to solder plating, or a tensile process that gives 0.5 to 1% elongation after solder plating, A rectangular copper wire for solar cells having a final cross-sectional shape of width 2.0 mm and thickness 0.16 mm was manufactured. The solder layer was immersed in a Sn-3% Ag-0.5% Cu solder bath maintained at 250 ° C. to a thickness of about 40 μm.

  The same measurement and evaluation as in Example 1 were performed on the flat rectangular copper wires for solar cells manufactured under the conditions of Examples 64-87, and the results are shown in Table 4.

Comparative Examples 88-115
After drawing copper rough drawn wire made of tough pitch copper or oxygen-free copper by the belt & wheel method, conducting heat treatment at 400 ° C by current heating and annealing, then cold rolling with a processing rate of 0-18% A flat copper wire was used. This flat copper wire is subjected to a tensile process that gives an elongation of less than 0.5% before solder plating, or an elongation of more than 1%, and then solder plated, or an elongation of less than 0.5% after solder plating, or Tensile processing giving an elongation greater than 1% was performed, and a flat copper wire for a solar cell having a final cross-sectional shape of width 2.0 mm and thickness 0.16 mm was manufactured. The processing conditions are listed in Table 4. Moreover, the solder layer was applied to a thickness of about 40 μm by being immersed in a solder bath of Sn-3% Ag-0.5% Cu maintained at 250 ° C.
The same measurement and evaluation as in Example 1 were performed on the flat rectangular copper wires for solar cells manufactured under the conditions of Comparative Examples 88 to 115, and the results are also shown in Table 4.

Conventional examples 116-119
Conventional examples 116 to 119 were subjected to the same processing as conventional examples 15 to 18 on the copper wire, and the same measurement and evaluation as in Example 1 were performed. The results are also shown in Table 4.

As is clear from Table 4, the rectangular copper of Examples 40 to 87, in which the annealed copper material was cold-rolled with a processing rate of 0 to 15% and then subjected to a tensile process of 0.5 to 1%. The wire does not give a predetermined amount of processing rate to the copper material, and has a smaller amount of thermal shrinkage than the conventional examples 117 and 119 that are not subjected to tensile processing.
Moreover, the solder plated coated rectangular copper wires using these rectangular copper wires are not subjected to heat treatment, are given a processing rate of a predetermined amount or more, and are compared with the conventional examples 116 and 118 which are not subjected to tensile processing. Therefore, the warpage of the wafer when connected to the silicon wafer was small, and the wafer did not crack.
In addition, since the load applied to the wafer is small, the life against heat cycle is also good.

  As shown in Table 4, the flat copper wire subjected to 0.5 to 1% tensile processing has a small amount of heat shrinkage. A plurality of silicon wafers connected by solder-plated rectangular copper wires (samples 40 to 87) using these copper wires are less warped, are not cracked, and have a smaller load on the silicon wafer than the conventional example. . For this reason, the lifetime with respect to a heat cycle was also favorable. Further, when the annealed conductor is used as it is (samples 40 to 45, 64 to 69) and when the conductor is subjected to cold rolling or cold wire drawing (samples 46 to 63, 70 to 87), The amount of warp tends to decrease when cold rolling or cold wire drawing is applied.

  On the other hand, Comparative Examples 88, 89, 92, 93, etc. subjected to a tensile process with an elongation of less than 0.5% are insufficient in the tensile process, and the tensile process has an elongation of more than 1%. The comparative examples 90, 91, 94, 95, etc. subjected to are increased in elongation due to excessive tensile processing, and all of them do not improve the amount of warpage, cause trouble in solder connection with the wafer, and crack. The generation and lifetime of the product did not satisfy the object of the present invention.

Examples 120-143
After drawing copper rough drawn wire made of tough pitch copper by the belt and wheel method, conducting heat treatment at 400 ° C by electrical heating and annealing, and then subjecting it to cold wire drawing at a processing rate of 0 to 15%, rectangular copper wire It was. This flat copper wire is subjected to a tensile process that gives 0.5 to 1% elongation before solder plating and then subjected to solder plating, or a tensile process that gives 0.5 to 1% elongation after solder plating, A rectangular copper wire for solar cells having a final cross-sectional shape of width 2.0 mm and thickness 0.16 mm was manufactured. The solder layer was immersed in a Sn-3% Ag-0.5% Cu solder bath maintained at 250 ° C. to a thickness of about 40 μm.

  The same measurement and evaluation as Example 1 were performed on the flat rectangular copper wires for solar cells manufactured under the conditions of Examples 120 to 143, and the results are shown in Table 5.

Examples 144-167
After drawing copper rough drawn wire made of oxygen-free copper by the belt and wheel method, annealing by conducting heat treatment at 400 ° C by energization heating, and then performing cold wire drawing at a processing rate of 0 to 15% to make flat copper A line. This flat copper wire is subjected to a tensile process that gives 0.5 to 1% elongation before solder plating and then subjected to solder plating, or a tensile process that gives 0.5 to 1% elongation after solder plating, A rectangular copper wire for solar cells having a final cross-sectional shape of width 2.0 mm and thickness 0.16 mm was manufactured. The solder layer was immersed in a Sn-3% Ag-0.5% Cu solder bath maintained at 250 ° C. to a thickness of about 40 μm.

  The same evaluation as Example 1 was performed on the flat rectangular copper wires for solar cells manufactured under the conditions of Examples 144 to 167, and the results are shown in Table 5.

Comparative Examples 168-185
After drawing copper rough drawn wire made of tough pitch copper or oxygen-free copper by the belt & wheel method, annealing by conducting heat treatment at 400 ° C by energization heating, then cold drawing with a processing rate of 0-18% A flat rectangular copper wire was used. This flat copper wire is subjected to a tensile process that gives an elongation of less than 0.5% before solder plating, or an elongation of more than 1%, and then solder plated, or an elongation of less than 0.5% after solder plating, or Tensile processing giving an elongation greater than 1% was performed, and a flat copper wire for a solar cell having a final cross-sectional shape of width 2.0 mm and thickness 0.16 mm was manufactured. The processing conditions are listed in Table 5. Moreover, the solder layer was applied to a thickness of about 40 μm by being immersed in a solder bath of Sn-3% Ag-0.5% Cu maintained at 250 ° C.

  The same measurement and evaluation as in Example 1 were performed on the flat rectangular copper wires for solar cells manufactured under the conditions of Comparative Examples 168 to 185, and the results are also shown in Table 5.

Conventional examples 196 to 199
Conventional examples 196 to 199 were subjected to the same processing as conventional examples 34 to 37 on copper wires, and the same measurement and evaluation as in Example 1 were performed. The results are also shown in Table 5.

As is apparent from Table 5, the rectangular copper of Examples 120 to 167, in which the heat-treated copper material was cold-drawn at a processing rate of 0 to 15% and then subjected to a tensile process of 0.5 to 1%. The wire does not give a predetermined amount of processing rate to the copper material, and the heat shrinkage is smaller than that of the conventional examples 197 and 199 where the wire drawing is not performed.
In addition, the solder plated coated rectangular copper wires using these rectangular copper wires are not annealed, are given a processing rate of a predetermined amount or more, and are not subjected to wire drawing. In comparison, the warpage of the wafer when connected to the silicon wafer was small, and no cracks occurred in the wafer.
In addition, since the load applied to the wafer is small, the life against heat cycle is also good.

As shown in Table 5, the flattened copper wire subjected to 0.5 to 1% tensile processing had a small amount of heat shrinkage. A plurality of silicon wafers connected by solder-plated rectangular copper wires (samples 120 to 167) using these copper wires are less warped, are not cracked, and have a smaller load on the silicon wafer than the conventional example. . For this reason, the lifetime with respect to a heat cycle was also favorable.
Further, when the heat-treated conductor is used as it is (samples 120 to 125, 144 to 149) and the case where the conductor is subjected to cold rolling or cold wire drawing (samples 126 to 143, 150 to 167), The amount of warp tends to decrease when cold rolling or cold wire drawing is applied.

The present invention can provide a rectangular copper wire in which cold working such as rolling, wire drawing, and tension is applied to a copper wire to reduce a difference in thermal expansion and stress generated between the silicon wafer and the rectangular copper wire.
In addition, the present invention can provide an excellent solar cell that does not cause cracks in the silicon wafer over a long period of time, has good power generation efficiency, and has a long life by connecting the silicon wafer with the rectangular copper wire. .
Furthermore, since simple processing is added to the copper wire, it can be manufactured at low cost.

1. 1. Solder-plated rectangular copper wire for solar cells 2. Silicon wafer Flat conductor for solar cells (flat wire)
4). Solder plating layer

Claims (14)

  Rectangular copper having a volume resistivity of 2.5 μΩ · cm or less and a copper wire annealed at 300 to 800 ° C. subjected to cold rolling or cold drawing at a working rate of 5 to 15%. line.   A rectangular copper wire having a volume resistivity of 2.5 μΩ · cm or less and an elongation of 0.5 to 1% applied to a copper wire annealed at 300 to 800 ° C.   A copper wire having a volume resistivity of 2.5 μΩ · cm or less and annealed at 300 to 800 ° C. is subjected to cold rolling or cold drawing at a processing rate of 0 to 15%, A rectangular copper wire obtained by imparting an elongation of 0.5 to 1% to a copper wire that has been rolled or cold-drawn.   The flat copper wire for solar cells in which the solder layer is provided in the at least one surface of the flat copper wire in any one of Claims 1-3.   Rectangular copper having a volume resistivity of 2.5 μΩ · cm or less and a copper wire annealed at 300 to 800 ° C. subjected to cold rolling or cold drawing at a processing rate of 0 to 15%. A rectangular copper wire for a solar cell, in which a solder layer is applied to at least one surface of the wire and an elongation of 0.5 to 1% is imparted to the rectangular copper wire to which the solder layer is applied.   Solder layer on at least one surface of a rectangular copper wire having a volume resistivity of 2.5 μΩ · cm or less and an elongation treatment of 300 to 800 ° C. imparted with an elongation of 0.5 to 1%. The rectangular copper wire for solar cells which gave 0.5 to 1% of elongation to the rectangular copper wire to which the solder layer was applied.   A copper wire having a volume resistivity of 2.5 μΩ · cm or less and annealed at 300 to 800 ° C. is subjected to cold rolling or cold drawing at a working rate of 0 to 15%, A rectangular copper wire in which a solder layer is applied to at least one surface of a flat copper wire obtained by applying elongation of 0.5 to 1% to a copper wire that has been rolled or cold drawn. A rectangular copper wire for a solar cell having an elongation of 0.5 to 1%.   A rectangular wire having a volume resistivity of 2.5 μΩ · cm or less annealed at 300 to 800 ° C., and subjected to cold rolling or cold drawing at a 5 to 15% processing rate on the annealed copper wire. Copper wire manufacturing method.   A method for producing a rectangular copper wire, in which a copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C. and an elongation of 0.5 to 1% is imparted to the annealed copper wire.   A copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and the annealed copper wire is subjected to cold rolling or cold drawing at a work rate of 0 to 15%, A method for producing a rectangular copper wire, which imparts 0.5 to 1% elongation to a copper wire subjected to cold rolling or cold wire drawing.   The manufacturing method of the rectangular copper wire for solar cells which applies a solder layer to the at least one surface of the rectangular copper wire manufactured with the manufacturing method of the flat copper wire in any one of Claims 8-10.   A copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and the annealed copper wire is subjected to cold rolling or cold drawing at a work rate of 0 to 15%, Manufacturing of a rectangular copper wire for a solar cell in which a solder layer is provided on a flat copper wire subjected to cold rolling or cold drawing, and a 0.5 to 1% elongation is imparted to the flat copper wire provided with the solder layer. Method.   A copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and a 0.5 to 1% elongation is imparted to the annealed copper wire to obtain a flat copper wire. A method for producing a rectangular copper wire for solar cells, wherein a solder layer is applied to at least one surface of a copper wire, and an elongation of 0.5 to 1% is imparted to the rectangular copper wire to which the solder layer is applied.   A copper wire having a volume resistivity of 2.5 μΩ · cm or less is annealed at 300 to 800 ° C., and the annealed copper wire is subjected to cold rolling or cold drawing at a work rate of 0 to 15%, A copper wire that has been cold-rolled or cold-drawn is formed into a flat copper wire having an elongation of 0.5 to 1%. A solder layer is applied to at least one surface of the flat copper wire, and the solder layer is applied. The manufacturing method of the rectangular copper wire for solar cells which provides 0.5 to 1% of elongation to the done rectangular copper wire.

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