JP2009193967A - Lead - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead wire with small thermal expansion and low manufacturing cost. <P>SOLUTION: The lead wire, using a rectangular conductor structured of a clad material made by pinching the both-sides of a thin-plate material for a core with thin-plate materials for a conductor, includes a plated film covering at least side faces of an outer periphery of the rectangular conductor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rectangular conductor having a small thermal expansion, a method for manufacturing the same, and a lead wire.

  As a solar cell, a semiconductor chip in which a silicon crystal is grown on a substrate is used. A connecting lead wire is joined by soldering or the like to a predetermined region (contact region) of the silicon crystal wafer obtained by cutting and dividing the semiconductor chip, and electric power is transmitted (output) through the connecting lead wire.

  Usually, as a lead wire for connection, a solder plating film for connection to a wafer is formed on the surface of a conductor. For example, a flat copper rectangular conductor such as tough pitch copper or oxygen-free copper is used as the conductor, and a Sn—Pb eutectic solder is used as the solder plating film (see, for example, Patent Document 1). In recent years, switching to solder containing no Pb (Pb-free solder) as a constituent material of the 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 soldering the connecting lead wires or a temperature change at the time of using the solar cell. In order to cope with this, there is an increasing need for a connection lead wire having a small thermal expansion and a connection solder plating film having a low melting temperature.

  As an example of a lead wire having a small thermal expansion, a lead frame is formed by a strip (copper-invar (registered trademark) -copper) obtained by cladding a material having a small thermal expansion such as Invar (registered trademark) 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, since the lead frame described in Patent Document 3 performs punching at the time of circuit formation, there is a problem in that a large amount of wasted material is generated, resulting in an increase in manufacturing cost.

  Further, as in the lead frame described in Patent Document 3, a lead wire using a rectangular conductor made of a clad material obtained by clad copper-invar (registered trademark) -copper is connected to a contact region of a silicon crystal wafer. In order to facilitate soldering, if a tensile stress is applied to correct straight lines, the lead wires may be warped. There is a problem in that the warped lead wire cannot be satisfactorily soldered to the silicon crystal wafer.

  An object of the present invention, which was created in view of the above circumstances, is to provide a rectangular conductor having a low thermal expansion and a low manufacturing cost, and a method for manufacturing the same.

  Another object of the present invention is to provide a lead wire using a rectangular conductor with low thermal expansion and low manufacturing cost.

  In order to achieve the above object, the lead wire according to the present invention is a lead wire using a flat conductor composed of a clad material in which both surfaces of a core thin plate material are sandwiched between conductor thin plate materials. A plating film covering at least the side surface is provided.

In the lead wire according to the present invention, the core thin plate material has a coefficient of thermal expansion of 10 (× 10 ⁻⁶ / ° C.) or less, and each of the conductor thin plate materials has a volume resistivity of 5.0 (μΩ · cm) or less.

Furthermore, in the lead wire according to the present invention, it is desirable that the thin sheet material for conductor has a crystal orientation satisfying the following expression (1).
I _R = I (111) / {I (200) + I (111)} ≧ 0.15 (1)
Where I (111): X-ray diffraction intensity of surface (111)
I (200): X-ray diffraction intensity of surface (200)

According to the present invention, the following effects are exhibited.
(1) A rectangular conductor in which the core sheet material is not exposed to the outermost surface can be obtained.
(2) No warpage occurs when a tensile stress is applied to a flat conductor.

It is a cross-sectional view of a flat conductor according to a preferred embodiment of the present invention. It is a cross-sectional view of the lead wire using the flat conductor of FIG. It is a perspective schematic diagram of the cutting device used for the manufacturing method of the flat conductor of FIG. It is the elements on larger scale of the cutting device used for the manufacturing method of the flat conductor of FIG. It is a cross-sectional view of a flat conductor according to another preferred embodiment of the present invention. It is a cross-sectional view of a lead wire using the flat conductor of FIG. It is the elements on larger scale of a cutting device used for the cutting method by a slit method. It is a cross-sectional view of a flat conductor composed of a clad material.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.

(First embodiment)
The inventors previously filed a patent application regarding a flat conductor 80 that is a clad material of a copper material 81a-Invar (registered trademark) material 82-copper material 81b shown in FIG. The flat conductor 80 can be obtained by cutting a clad material using a slit method that has been generally used as a method of cutting (cutting) a metal material. Specifically, as shown in FIG. 7, the clad material 70 is continuously cut in a direction perpendicular to the drawing using two pairs of upper and lower rotary blades 71a and 71b (only one set is shown in FIG. 7). Thus, the rectangular conductor 80 shown in FIG. 8 is obtained.

  Here, each edge part 72 of the rotary blades 71a and 71b is sharpened by grinding or the like and finished in a substantially right angle. Therefore, each cut end face (side end face) 83 of the flat conductor 80 obtained by cutting is formed substantially perpendicular to the upper and lower faces, and the copper materials 81a and 81b and the Invar (registered trademark) material 82 are formed on each side end face 83. Is completely exposed. Since each joining part of copper material 81a, 81b and Invar (registered trademark) material 82 is a different material contact part, local battery formation occurs when moisture contacts each joining part. As a result, there is a possibility that corrosion occurs at each joint.

  Therefore, as shown in FIG. 1, the rectangular conductor according to a preferred embodiment of the present invention is composed of a clad material in which both surfaces of a core thin plate material 11 are sandwiched between conductor thin plate materials 12a and 12b. Both side end faces (left and right end faces in FIG. 1) of the thin plate material 11 are covered (wrapped) with the thin plate materials 12a and 12b for conductors, and the core thin plate material 11 is not exposed on the outermost surface. . Both ends of the conductor thin plates 12a and 12b are closed to form a reception portion (closing portion) 13.

  The flat conductor 10 is obtained by cutting a clad material at the positions A and B in the direction of the arrow D1. The core thin plate material 11 and the conductor thin plate materials 12a and 12b in the flat conductor 10 are gently curved in the direction of the arrow D1 at both ends in the width direction (left and right direction in FIG. 1). The lower surface of the plate 12a is formed flat over the entire width direction.

The core thin plate material 11 is made of a member having a thermal expansion coefficient of 10 (× 10 ⁻⁶ / ° C.) or less, for example, an Fe—Ni alloy material, preferably Invar (registered trademark). The conductor thin plates 12a and 12b are made of a member having a volume resistivity of 5.0 (μΩ · cm) or less, such as Cu, Ag, Au, Al, or an alloy material containing such a metal, and cost. Cu or Cu alloy is preferable when performance is important, and Ag or Ag alloy is preferable when low volume resistivity (high conductivity) is important. Furthermore, it is preferable that the core thin plate material 11 has a Vickers hardness of 150 Hv or less, and the conductor thin plate materials 12 a and 12 b have a Vickers hardness of 100 Hv or less.

  The flat rectangular conductor 10 in the best form is formed by combining a core thin plate 11 made of Invar (registered trademark) and conductor thin plates 12a, 12b made of Ag or an Ag alloy.

  The lead wire 20 is obtained by plating the entire outer periphery of the rectangular conductor 10 shown in FIG. 1 with a solder film 21 as shown in FIG. Here, the plating coating of the flat conductor 10 with the solder film 21 may be only a part of the outer periphery of the flat conductor 10 (for example, the upper surface and the lower surface of the flat conductor 10). The lead wire 20 is connected to a predetermined contact region (for example, an Ag plating region) on a cell surface in a silicon crystal wafer (solar cell module (not shown)) and a predetermined contact region on a frame member (for example, a lead frame). By doing so, a solar cell assembly is obtained. Solder films for bonding may also be provided in predetermined contact areas of the cell surface and the lead frame.

The solder film 21 is composed of Sn—Pb eutectic solder or Pb free solder, and preferably Sn—Ag—Cu Pb free solder. The Sn—Ag—Cu-based Pb-free solder may further contain In and / or P. The In content is preferably 1 to 10% by weight, and the P content is preferably 0.005 to 0.015% by weight. For example, Sn-Ag-Cu Pb-free solder
Sn-3 (or 4) Ag-0.5Cu-0.01P,
Sn-3 (or 4) Ag-0.5Cu-3In,
Sn-3 (or 4) Ag-0.5Cu-3In-0.01P,
Sn-3 (or 4) Ag-0.5Cu-5In,
Sn-3 (or 4) Ag-0.5Cu-5In-0.01P,
Sn-3 (or 4) Ag-0.5Cu-8In,
Sn-3 (or 4) Ag-0.5Cu-8In-0.01P,
(The unit is weight%).

  In general, Pb-free solder has a higher melting temperature than Sn—Pb eutectic solder, so there is a concern about damage to the connection member (cell surface and lead frame contact area) due to solder bonding. However, among Pb-free solders, Sn-3Ag-0.5Cu solder and Sn-4Ag-0.5Cu solder (both units are weight%) have a feature that the melting temperature is low. Moreover, by further including In and / or P in these solders, the melting temperature of the solder can be further lowered.

  For this reason, by using these Sn-Ag-Cu Pb-free solders, it is possible to reduce the risk of deformation or breakage of the silicon cell during solder bonding. Here, the reason why the content of In is set to 1 to 10% by weight is that when the content exceeds 10% by weight, the viscosity of the molten solder becomes high and the soldering workability decreases. Further, by setting the P content to 0.005 to 0.015% by weight, it is possible to prevent oxidative discoloration of the solder during the soldering operation, so that the reliability of connection (soldering) can be improved.

  The film thickness of the solder film 21 is 1/30 to 1/3, preferably 1/10 to 1/3, of the thickness of the flat conductor 10.

  The lead wire 20 of the best form is a flat conductor 10 formed by combining a thin sheet material for core 11 made of Invar (registered trademark) and thin sheet materials for conductor 12a, 12b made of Ag or an Ag alloy. A Sn—Ag—Cu-based solder film 21 is plated on the outer periphery to a thickness of 1/5 of the thickness of the flat conductor 10.

  Next, the operation of the present embodiment will be described.

  In the rectangular conductor 10 according to the present embodiment, since the entire outer periphery of the core thin plate material 11 is covered with the conductor thin plate materials 12a and 12b, the outermost surface of the core thin plate material 11 is dissimilar to the clad material. The material contact is not exposed at all. As a result, even if the flat conductor 10 comes into contact with moisture, local battery formation does not occur on the outermost surface of the flat conductor 10, and corrosion does not occur. Therefore, the flat conductor 10 having good corrosion resistance is obtained.

  In addition, in the flat conductor 10 according to the present embodiment, since a local battery does not occur on the outermost surface, the lead conductor can be formed without plating the entire outer periphery of the flat conductor 10 with the solder film 21. It can be used. Therefore, the plating coating of the flat conductor 10 with the solder film 21 is sufficient for only a part of the flat conductor 10 (in the vicinity of the contact portion with each contact region). As a result, the cost of the lead wire 20 can be reduced. Furthermore, when a solder film for bonding is provided in a predetermined contact area of the cell surface and the lead frame, the rectangular conductor 10 can be applied as it is as a lead wire having good corrosion resistance.

  Furthermore, since the lead wire 20 using the flat conductor 10 according to the present embodiment has good corrosion resistance, the solar cell assembly is used for a long time by configuring the solar cell assembly using the lead wire 20. In this case, the long-term reliability can be improved without fear of causing a decrease in power generation efficiency.

  Next, the manufacturing method of the flat conductor which concerns on this Embodiment is demonstrated based on an accompanying drawing.

  The manufacturing method of the flat conductor 10 according to the present embodiment cuts a clad material formed by sandwiching both surfaces of a core thin plate material with a conductor thin plate material using a slit method.

Specifically, first, the both sides of the core thin plate material are sandwiched between the conductor thin plate materials, and then cold rolling and heat treatment are repeated as appropriate, and as shown in FIG. Get. At this time, a Vickers hardness of 150 Hv or less is used as the core thin plate material, and a Vickers hardness of 100 Hv or less is used as the conductor thin plate material. In addition, as the thin plate material for the core, one having a thermal expansion coefficient of 10 (× 10 ⁻⁶ / ° C.) or less is used, and as the thin plate material for the conductor, one having a volume resistivity of 5.0 (μΩ · cm) or less is used.

  Next, as shown in FIGS. 3 and 4, the obtained clad material 30 is cut using a cutting device 31 having two pairs of upper and lower rotary blades 31a and 31b, and one rotary blade 31a and 31a is connected to the other. While moving in the direction of the rotary blades 31b, 31b (the direction of the arrow D2 in FIG. 3), it is caused to travel in the direction of the arrow D3. At this time, each edge portion 32 of at least one of the rotary blades 31a and 31b (only the rotary blade 31a in FIG. 4) is subjected to curved surface processing (R processing) with a radius r, and each edge portion 32 is curved. Chamfered into a shape. The radius r is 1/50 or more (r ≧ t / 50) of the plate thickness t of the clad material 30. The rotating blade to be moved is the one that has been subjected to curved surface processing. When both of the rotating blades 31a and 31b are subjected to R machining, even if both the rotating blades 31a and 31b are moved toward each other, Good.

  By using the cutting device 31 to cut the clad material 30 with adjusted hardness, a cutting sag 41 is generated in the cutting part 35. By this cutting sag 41, the conductor thin plate material (conductor thin plate material 12b in FIG. 1) and the core thin plate material (core thin plate material 11 in FIG. 1) in the clad material 30 face toward the rotary blade 31b. It is deformed so as to be dragged (entrained) by the edge part 32 of the rotary blade 31a that moves. When each plate material is deformed, the amount of deformation is greater in the soft conductor thin plate material than in the core thin plate material. As a result, the conductor thin plate is deformed so as to cover the side surface of the core thin plate, and the flat conductor 10 shown in FIG. 1 is obtained.

  The reason why the Vickers hardness of the core thin plate material 11 is defined as 150 Hv or less and the Vickers hardness of the conductor thin plate materials 12 a and 12 b is defined as 100 Hv or less will be described below. By setting each Vickers hardness to a specified value or less, flexibility is imparted to the clad material 30 and toughness is improved, so that at the time of cutting, the cut portion 35 becomes sticky and the cutting sag 41 tends to occur. If each Vickers hardness exceeds a specified value, the rigidity of the clad material 30 becomes too high, and the cutting sag 41 hardly occurs in the cutting part 35, and the closing part 13 shown in FIG. 1 cannot be obtained.

  Moreover, at each edge part 32 of at least one rotary blade 31a, 31b (only the rotary blade 31a in FIG. 4), it is 1/50 or more of the plate | board thickness t of the clad material 30, Preferably it is 1 / 30-1 / 10. By performing curved surface processing with a radius r having a size, the angle of the cut edge in the cut portion 35 of the clad material 30 becomes an obtuse angle. Therefore, a sufficient cutting sag 41 can be generated in the cutting part 35. As a result, as shown in FIG. 1, the conductor thin plate material that has been cut and sag 41 can cover the entire core thin plate material 11, particularly the side end surfaces. When the size of the radius r is less than 1/50 of the plate thickness t, the cutting sag 41 hardly occurs in the cutting part 35, and the closing part 13 shown in FIG. 1 cannot be obtained.

  The cutting device (or cutting device) is not particularly limited to the rotary blades 31a and 31b using the slit method, and a pair of cutting blades (or cutting blades) such as a punching machine using upper and lower molds. The same effect can be obtained if the method is used for cutting and cutting. In the case of a punching machine, a curved surface with a radius r having a size of 1/50 or more of the plate thickness t of the clad material 30 is applied to the edge of at least one of the upper and lower molds.

  The manufacturing method of the flat conductor 10 of the best mode is that each edge portion 32 of at least one of the rotary blades 31a and 31b has a radius r having a size of 1/30 to 1/10 of the plate thickness t of the clad material 30. Using the cutting device 31 shown in FIG. 3 formed by curved surface processing, the core thin plate material 11 having a Vickers hardness of 110 to 130 Hv and the conductive thin plate materials 12 a and 12 b having a Vickers hardness of 60 to 80 Hv are formed in combination. The clad material 30 is cut.

  Next, the operation of the present embodiment will be described.

  In the manufacturing method of the flat conductor 10 according to the present embodiment, the cut end surface of the core thin plate material can be covered with the conductor thin plate material at the same time by merely cutting the clad material 30. That is, the rectangular conductor 10 having the closing portion 13 in which both side end surfaces of the core thin plate material 11 shown in FIG. 1 are wrapped with the respective conductive thin plate materials 12a and 12b without performing special processing other than the cutting processing. Obtainable. Therefore, it becomes possible to manufacture the flat conductor 10 with low thermal expansion and good corrosion resistance at low cost.

  Next, another embodiment of the present invention will be described with reference to the accompanying drawings.

(Second Embodiment)
A cross-sectional view of a flat conductor according to another preferred embodiment of the present invention is shown in FIG.

As shown in FIG. 5, the flat conductor 50 according to the present embodiment has both sides of a core thin plate 51 having a thermal expansion coefficient of 10 (× 10 ⁻⁶ / ° C.) or less and a volume resistivity of 5.0 ( [mu] [Omega] .cm) or less, it is composed of a clad material sandwiched between thin conductor plates 52a and 52b. The conductor thin plate member 52a, 52b has a isotropic crystal orientation at random, the following (1) the value of I _R shown in the expression is 0.15 or more, preferably 0.20 to 0 70, particularly preferably 0.35 to 0.70.

I _R = I (111) / {I (200) + I (111)} ≧ 0.15 (1)
Where I (111): X-ray diffraction intensity of surface (111)
I (200): X-ray diffraction intensity of the surface (200) As the core thin plate material 51 and the conductor thin plate materials 52a and 52b, the core thin plate material 11 and the conductor thin plate material of the flat conductor 10 according to the previous embodiment. The same thing as 12a, 12b is applicable.

  The rectangular conductor 50 according to the present embodiment is manufactured by the same manufacturing method (slit method) and punching method as the rectangular conductor 80 shown in FIG. 8, and is not particularly limited.

Rectangular conductor 50 of the best mode comprises a core sheet material 51 composed of invar (registered trademark), consists of Ag or an Ag alloy, and, I _R value is thin conductors of 0.35 to 0.70 It is formed by combining the plate materials 52a and 52b.

  A lead wire 60 is obtained as shown in FIG. 6 by plating the entire outer periphery of the flat conductor 50 shown in FIG. 5 with the solder film 21 shown in FIG. Here, the plating coating of the flat conductor 50 with the solder film 21 may be only a part of the outer periphery of the flat conductor 50 (for example, the upper surface and the lower surface of the flat conductor 50). The lead wire 60 is connected to a predetermined contact region (for example, an Ag plating region) on the cell surface of the silicon crystal wafer (solar cell module (not shown)) and a predetermined contact region of the frame member, so that the solar cell An assembly is obtained.

BEST MODE lead 60 includes a core sheet material 51 composed of invar (registered trademark), consists of Ag or an Ag alloy, and, I _R value is thin conductors of 0.35 to 0.70 The Sn—Ag—Cu-based solder film 21 is plated on the outer periphery of the flat conductor 50 formed by combining the plate materials 52 a and 52 b with a film thickness that is 1/5 of the thickness of the flat conductor 50.

  Next, the operation of the present embodiment will be described.

Conductor thin plate material 52a, the reason for defining the I _R value of 52b to 0.15 or more will be described below. The in-plane orientation (normal orientation of the clad material surface) of the crystal grains of the conductor thin plates 52a and 52b is mainly dominated by the plane (111) and the plane (200). As described in the previous embodiment, the clad material is obtained by appropriately repeating the cold rolling and heat treatment on the core thin plate material 51 sandwiched between the conductor thin plate materials 52a and 52b. It is.

  When the clad material is manufactured, if the plane (200) becomes dominant due to the in-plane orientation of the texture of recrystallized grains in the conductor thin plate materials 52a and 52b, in other words, if IR becomes less than 0.15, recrystallization will occur. The grains become coarse. As a result, if the lead wire 60 using the flat conductor 50 shown in FIG. 5 is to be soldered to the contact region of the silicon crystal wafer and applied with a tensile stress, the lead wire 60 is straightened. The line 60 is likely to be warped.

In the rectangular conductor 50 of the present embodiment, by defining the conductive thin plate material 52a, 52 b I _R value of 0.15 or more, warpage when correcting linearly by the tensile stress load Will not occur. Therefore, the lead wire 60 using this flat conductor 50 has good solderability.

  Further, the flat conductor 50 according to the present embodiment is a core thin plate material 51 having a small thermal expansion at the center and a thin plate for conductors 52a and 52b having a low volume resistivity (good conductivity) at the outer peripheral portion. It is configured. For this reason, even if the silicon crystal wafer constituting the solar cell assembly is thinned, there is no possibility that the silicon crystal wafer is damaged at the time of solder bonding between the silicon crystal wafer and the lead wire 60 using the flat conductor 50, and The power obtained by the solar cell assembly can be output with almost no loss.

  Further, in the flat conductor 50 according to the present embodiment, since the dissimilar material contact portion between the core thin plate material 51 and the conductor thin plate materials 52a and 52b exists on the outermost surface thereof, the flat conductor 50 has a moisture content. If contact is made, corrosion due to the use of local batteries may occur. For this reason, in the lead wire 60 using the flat conductor 50 according to the present embodiment, the entire outer periphery of the flat conductor 50 is plated with the solder film 21 unless corrosion due to local battery formation is not particularly problematic. It is preferable. As a result, there is no possibility that the lead wire 60 is corroded due to the local battery.

  Moreover, since the lead wire 60 using the flat conductor 50 according to the present embodiment has good solderability with the silicon crystal wafer, the productivity of the solar cell assembly can be improved.

(Third embodiment)
A flat conductor according to still another preferred embodiment of the present invention will be described with reference to FIG.

The basic configuration of a flat conductor (not shown) according to the present embodiment is the same as that of the flat conductor 10 shown in FIG. 1, and the conductor thin plates 12a and 12b are further random and isotropic. has a crystal orientation, the following (1) the value of I _R shown in the expression is 0.15 or more, preferably from 0.20 to 0.70, particularly preferably those of from 0.35 to 0.70 is there.

I _R = I (111) / {I (200) + I (111)} ≧ 0.15 (1)
Where I (111): X-ray diffraction intensity of surface (111)
I (200): X-ray diffraction intensity of surface (200) The rectangular conductor according to the present embodiment is manufactured by the same manufacturing method as the rectangular conductor 10 according to the first embodiment described above.

The flat conductor of the best form is composed of Invar (registered trademark), is composed of a core thin plate 11 having a Vickers hardness of 110 to 130 Hv, Ag or an Ag alloy, has a Vickers hardness of 60 to 80 Hv, and I It is formed by combining conductor thin plates 12a and 12b having _R values of 0.35 to 0.70. The lead wire (not shown) in the best form is Sn-Ag-Cu-based solder film 21 with a thickness of 1/5 of the thickness of the flat conductor on the outer periphery of the flat conductor in the best form described above. (See FIG. 1) is plated.

  Also in the flat conductor according to the present embodiment, the same effects as those of the flat conductors 10 and 50 according to the first and second embodiments described above can be obtained. Specifically, it is a flat conductor that has good corrosion resistance and is unlikely to warp when it is attempted to straighten by applying a tensile stress.

  Also, the lead wire using the flat conductor according to the present embodiment has the same effects as the lead wires 20 and 60 using the flat conductor 10, 50 according to the first and second embodiments described above. can get. Specifically, the solder film 21 is low in cost because it is sufficient to cover only a part of the rectangular conductor (in the vicinity of the contact portion with each predetermined contact region), and soldering is performed because warpage hardly occurs. Leads to good lead.

  As described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various other things are assumed.

  Further, the rectangular conductor of the present invention can be used as a lead for a solar cell assembly, and can also be used as a conductor for transmitting a high frequency signal of 1 GHz or more. In particular, the rectangular conductor of the present invention can be expected to be applied to a wireless LAN or the like whose transmission characteristics are significantly deteriorated due to thermal expansion.

  Next, although this invention is demonstrated based on an Example, this invention is not limited to this Example.

(Example 1)
Made Invar (registered trademark), a width of 2.0 mm, and the thin core plate thickness is 0.030mm material, made of Cu, a width of 2.0 mm, the plate thickness of 0.060 mm, I _R 0.60 A flat conductor having a width of 2.0 mm and a plate thickness of 0.150 mm and having the structure shown in FIG. 1 was prepared.

  A solder film having a film thickness of 0.035 mm was formed around the flat conductor to produce a lead wire having the structure shown in FIG.

(Example 2)
Except I _R of the conductor-sheet metal is 0.40, the same procedure as in Example 1 to prepare a flat conductor, then to produce a lead.

(Comparative Example 1)
Except I _R of the conductor-sheet metal is 0.12, the same procedure as in Example 1 to prepare a flat conductor, then to produce a lead.

(Comparative Example 2)
Except I _R of the conductor-sheet metal is 0.03, the same procedure as in Example 1 to prepare a flat conductor, then to produce a lead.

  In order to solder the lead wires of Examples 1 and 2 and Comparative Examples 1 and 2 to the contact area on the cell surface of the silicon crystal wafer, a tensile stress of 210 MPa was applied to each lead wire. The results at the time of stress loading are shown in Table 1.

As shown in Table 1, the leads of Examples 1 and 2, because I _R of the conductor-sheet metal is 0.15 or more (0.60,0.40), lead by the stress load straight It was corrected and no warping occurred (becomes flat). As a result, the lead wires of Examples 1 and 2 could be satisfactorily soldered to the silicon crystal wafer.

Straightening contrast, leads of Comparative Examples 1 and 2, because I _R of the conductor-sheet metal is less than 0.15 (0.12,0.03), in a straight line leads by stress loads Attempting to do so caused a big warp. As a result, the lead wires of Comparative Examples 1 and 2 could not be well soldered to the silicon crystal wafer.

10 Flat conductor 11 Thin plate material for core 12a, 12b Thin plate material for conductor

Claims (9)

  In a lead wire using a flat conductor composed of a clad material in which both surfaces of a core thin plate material are sandwiched between conductor thin plate materials, a plating film covering at least the side surface of the outer periphery of the flat conductor is provided. Lead. The core sheet material has a thermal expansion coefficient of 10 (× 10 ⁻⁶ / ° C.) or less, and each conductor sheet material has a volume resistivity of 5.0 (μΩ · cm) or less. The lead wire according to claim 1. The lead wire according to claim 1, wherein the thin sheet material for conductor has crystal orientation satisfying the following expression (1).
I _R = I (111) / {I (200) + I (111)} ≧ 0.15 (1)
Where I (111): X-ray diffraction intensity of surface (111)
I (200): X-ray diffraction intensity of surface (200)   The lead wire according to any one of claims 1 to 3, wherein the core sheet material has a Vickers hardness of 150 Hv or less, and the conductor sheet material has a Vickers hardness of 100 Hv or less.   The lead wire according to any one of claims 1 to 4, wherein the core thin plate material is made of an Fe-Ni alloy material, and the conductor thin plate material is made of Cu, Ag, Au, Al, or an alloy material containing a metal thereof.   The lead wire according to any one of claims 1 to 5, wherein the plating film is a Sn-Pb solder film.   6. The lead wire according to claim 1, wherein the plating film is a Pb-free solder film.   The lead wire according to claim 7, wherein the Pb-free solder film is composed of a Sn-Ag-Cu alloy.   The lead wire according to claim 8, wherein the Sn-Ag-Cu alloy further contains In and / or P.

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