A low-density photovoltaic tab and a method of manufacturing the same

Abstract

The application belongs to the technical field of photovoltaic welding strips, and particularly relates to a low-density photovoltaic flat welding strip and a preparation method thereof, the preparation steps being as follows: S1, melting metal copper into liquid form in a furnace, adding silica aerogel into the furnace, and stirring and casting to obtain an ingot; the mass ratio of the metal copper and the silica aerogel is 1:(0.002-0.003); S2, repeatedly rolling to obtain a refined copper strip, removing burrs and flash, and performing multi-pass drawing-annealing treatment through an oval-like flat die to obtain an oval-like processed flat copper wire; S3, surface treatment; S4, pulling the surface-treated flat copper wire out of molten solder alloy, controlling the thickness of the solder alloy layer on the surface of the flat copper wire through an air knife, cooling, and obtaining the low-density photovoltaic flat welding strip. The low-density photovoltaic flat welding strip has low weight per meter, low resistance per meter, and low resistivity, and has a yield strength of 60-70 MPa after annealing, high weldability, high welding utilization rate, and high light utilization rate.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic ribbon technology, specifically relating to a low-density photovoltaic flat ribbon and its preparation method. Background Technology

[0002] Photovoltaic solder ribbon, also known as tinned copper ribbon, is mainly used for connecting photovoltaic module cells. As a crucial raw material in the photovoltaic module welding process, the quality of the solder ribbon directly affects the quality of the photovoltaic module. Round wire photovoltaic solder ribbon consists of round copper wire and a solder alloy layer. The solder alloy layer and the round copper wire are concentric circles, with the solder alloy layer on the outer edge of the round copper wire. Round wire photovoltaic solder ribbon has high light utilization, but its welding reliability and utilization rate are low.

[0003] Photovoltaic flat solder ribbon is a strip-shaped metal electronic component with a width greater than its thickness. It boasts advantages such as good conductivity, high plasticity, corrosion resistance, and excellent high-temperature performance. Furthermore, photovoltaic flat solder ribbon can increase the welding area, thereby enhancing welding efficiency. In traditional photovoltaic flat solder ribbons, the copper base portion is rectangular with relatively flat sides, lacking any elliptical shaping. While this improves welding reliability, it results in poor reflectivity, reducing the light utilization rate of the photovoltaic flat solder ribbon.

[0004] Furthermore, during the research process, the inventors discovered that photovoltaic flat solder strips are primarily produced using hot-dip plating, specifically by drawing pure flat copper wire from molten solder alloy and cooling it to obtain the photovoltaic flat solder strip. Conventional photovoltaic flat solder strips, while meeting the requirement of a tensile strength of 180-190 MPa after annealing, have a yield strength exceeding 70 MPa after annealing, which limits their operational conditions. Summary of the Invention

[0005] To address the problems in the prior art, the present invention provides a low-density photovoltaic flat solder strip and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing low-density photovoltaic flat solder strips, which is achieved by the following technical solution:

[0007] A method for preparing low-density photovoltaic flat bonding strip includes the following steps:

[0008] S1. After melting metallic copper into a liquid state in a furnace, silica aerogel is added to the furnace and stirred to obtain a mixed molten metal. The mixture is then cast to obtain an ingot. The mass ratio of metallic copper to silica aerogel is 1:(0.002-0.003).

[0009] S2. Multiple rolling processes are used to obtain refined copper strips, burrs and flash are removed, and multiple drawing-annealing processes are performed through elliptical flat dies to obtain elliptical flat copper wires.

[0010] S3. Perform surface treatment on flat copper wires that have been treated to resemble ellipses;

[0011] S4. The surface-treated flat copper wire is pulled out from the molten solder alloy. The thickness of the solder alloy layer on the surface of the flat copper wire is controlled by an air knife. After cooling, a low-density photovoltaic flat solder strip is obtained.

[0012] The low-density photovoltaic flat solder strip prepared by this invention has a copper base portion that is a flat copper wire with an elliptical shape on both sides, which makes the photovoltaic flat solder strip have both high solderability and welding utilization rate, as well as high light utilization rate.

[0013] This invention, by adding silica aerogel to a mixed molten metal and controlling the mass ratio of copper to silica aerogel at 1:(0.002-0.003), prepares a low-density photovoltaic flat solder strip. This strip not only has a low basis weight, but also achieves a yield strength below 70 MPa after annealing while maintaining a tensile strength within the 180-190 MPa operating range, thus relaxing the operating conditions for photovoltaic flat solder strips. More importantly, the low-density photovoltaic flat solder strip prepared by this invention also exhibits low resistivity and resistivity.

[0014] Preferably, the density of the silica aerogel is 0.006-0.01 g / cm³. 3 .

[0015] Preferably, the mass ratio of the metallic copper to the silica aerogel is 1:0.002.

[0016] Preferably, the stirring time in step S1 is 45-90 minutes.

[0017] Preferably, the vertical direction of the elliptical flat mold is a horizontal straight line, and the horizontal direction has elliptical arcs at both ends.

[0018] Preferably, in step S2, each drawing pass reduces the cross-sectional area by 10-15%.

[0019] Preferably, in step S3, the surface treatment includes the following steps:

[0020] Soak the flat copper wire in sodium hydroxide solution, heat and wash, then rinse with deionized water;

[0021] Soak it in hydrochloric acid solution, wash it, and rinse it with deionized water.

[0022] Preferably, the solder alloy is selected from any one of Sn-Pb solder alloy, Sn-Pb-Ag solder alloy, Sn-Pb-Sb solder alloy, Sn-Ag-Cu solder alloy, Sn-Cu solder alloy, Sn-Ag solder alloy, Sn-Sb solder alloy, Sn-In solder alloy, Sn-Bi solder alloy, or Sn-Zn solder alloy.

[0023] Preferably, the air knife is a U-groove air knife.

[0024] Secondly, the present invention provides a low-density photovoltaic flat bonding strip, which is achieved by the following technical solution:

[0025] A low-density photovoltaic flat bonding strip is prepared by the above-described preparation method.

[0026] Preferably, the yield strength of the low-density photovoltaic flat welding strip after annealing is 60-70 MPa.

[0027] Preferably, the low-density photovoltaic flat solder strip is composed of a quasi-elliptical flat copper wire and a solder alloy layer, wherein the solder alloy layer is located on the periphery of the quasi-elliptical flat copper wire; the quasi-elliptical flat copper wire is a horizontal straight line vertically and has quasi-elliptical arcs at both ends horizontally; the width of the quasi-elliptical flat copper wire is 0.22-0.3 mm, and the thickness is 0.15-0.2 mm; the thickness of the vertical portion of the solder alloy layer is 10-15 μm, and the thickness of the horizontal portion does not exceed 5 μm.

[0028] In summary, the present invention has the following beneficial effects:

[0029] 1. The low-density photovoltaic flat solder strip prepared by the present invention has a copper base portion that is a flat copper wire with an elliptical shape on both sides, so that the photovoltaic flat solder strip has both high solderability and welding utilization rate, as well as high light utilization rate.

[0030] 2. This invention, by adding a small amount of silica aerogel to a mixed molten metal and controlling the mass ratio of copper to silica aerogel to be 1:(0.002-0.003), prepares a low-density photovoltaic flat solder strip. This strip not only has a low basis weight, but also achieves a yield strength below 70 MPa after annealing while maintaining a tensile strength within the 180-190 MPa operating range, thus relaxing the operating conditions for photovoltaic flat solder strips. More importantly, the low-density photovoltaic flat solder strip prepared by this invention also exhibits low resistivity and resistivity. Attached Figure Description

[0031] Figure 1 A perspective view of the low-density photovoltaic flat solder strip prepared for the example.

[0032] Figure 2 A front view of the low-density photovoltaic flat ribbon prepared for the example.

[0033] Figure 3 The image shows a magnified cross-sectional view (AA) of the low-density photovoltaic flat ribbon prepared for this example. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the embodiments.

[0035] Example

[0036] The embodiment provides a low-density photovoltaic flat bonding strip, such as Figure 1-3 As shown, the low-density photovoltaic flat solder strip provided by the present invention is a slender article. The low-density photovoltaic flat solder strip is composed of a flat copper wire with a quasi-elliptical shape and a solder alloy layer. The solder alloy layer is located on the periphery of the flat copper wire with a quasi-elliptical shape. The vertical direction of the flat copper wire is a horizontal straight line, and the horizontal direction of the flat copper wire is a quasi-elliptical arc at both ends. The width of the flat copper wire with a quasi-elliptical shape is 0.22-0.3mm, and the thickness of the flat copper wire with a quasi-elliptical shape is 0.15-0.2mm. The thickness of the vertical part of the solder alloy layer is 10-15μm, and the thickness of the horizontal part of the solder alloy layer does not exceed 5μm.

[0037] Example 1 provides a method for preparing low-density photovoltaic flat solder strips, the steps of which are as follows:

[0038] S1. Inert gas is introduced into the furnace at a rate of 3m / s. 3 At a rate of / min, 1kg of metallic copper is melted in a furnace until it reaches a liquid state. Then, 2g of silica aerogel (density 0.006g / cm³) is added to the furnace. 3 After stirring for 45 minutes, the mixed metal liquid is taken out and cast into an ingot.

[0039] S2. The ingot is placed in a rolling mill for the first rolling to obtain a copper strip A with a thickness of 0.7 mm. Copper strip A is placed in an annealing furnace and heated to 400℃ for annealing for 7 hours. It is then removed and rolled a second time to obtain a copper strip B with a thickness of 0.5 mm. Copper strip B is placed in an annealing furnace and heated to 650℃, annealing for 1 minute every 50 m. It is then removed and rolled a third time to obtain a copper strip C with a thickness of 0.3 mm. Copper strip C is placed in an annealing furnace and heated to 650℃, annealing for 1 minute every 90 m to obtain a refined copper strip. After removing burrs and flash from the finished copper strip, the strip is placed in a drawing machine at 350℃ and subjected to a first drawing process using heated wire drawing equipment and an elliptical flat die. This first drawing process reduces the cross-sectional area by 15%. After 30 minutes, the drawing process is stopped and held at that temperature for 40 minutes. Following this 40-minute holding period, a second drawing process is performed at 500℃. This second drawing process reduces the cross-sectional area by 15% and is then cooled to 300℃ at a cooling rate of 10℃ / s, held for 60 minutes, and then further cooled at 600℃. The third drawing process was performed at 50℃, and stopped after 40 minutes. The third drawing process reduced the cross-sectional area by 15%, and the wire was cooled to 400℃ at a cooling rate of 15℃ / s and held at that temperature for 60 minutes. After holding at that temperature for 60 minutes, the wire was cooled to 25℃ at a cooling rate of 8℃ / s, resulting in a flat copper wire with an elliptical shape. The flat copper wire with an elliptical shape has a vertical straight line at the top and bottom, and a horizontal arc shape at both ends. The width of the flat copper wire with an elliptical shape is 0.26 mm, and the thickness is 0.18 mm.

[0040] S3. Immerse the oval-shaped flat copper wire in a 1 mol / L sodium hydroxide aqueous solution, heat and wash at 80℃ for 6 hours, rinse three times with deionized water, then immerse it in a 0.1 mol / L hydrochloric acid solution, wash for 3 hours, and rinse three times with deionized water to obtain the surface-treated flat copper wire.

[0041] S4. The surface-treated flat copper wire is passed through a solder furnace containing molten solder alloy. The temperature of the solder furnace is maintained at 250℃. The flat copper wire is pulled out of the solder furnace, and the thickness of the solder alloy layer on the surface of the flat copper wire is controlled by a U-shaped groove air knife. The flat copper wire has a solder alloy layer with a thickness of 13μm on the upper and lower surfaces in the vertical direction and a solder alloy layer with a thickness of less than 3μm in the horizontal direction. It is cooled by a fan, wound into a roller, and vacuum-packed to obtain a low-density photovoltaic flat solder ribbon. The composition of the solder alloy is: Sn 95.9wt%, Ag 3.5wt%, Cu 0.6wt%.

[0042] Example 2 provides a method for preparing low-density photovoltaic flat solder strips, which differs from Example 1 only in that the mass of silica aerogel is 3g.

[0043] Example 3 provides a method for preparing a low-density photovoltaic flat bonding strip, which differs from Example 1 only in that the density of the silica aerogel is 0.01 g / cm³. 3 .

[0044] Example 4 provides a method for preparing low-density photovoltaic flat solder strips, which differs from Example 1 only in that the stirring time in step S1 is 90 min.

[0045] Comparative Example

[0046] Comparative Example 1 provides a method for preparing low-density photovoltaic flat solder strips, which differs from Example 1 only in that the mass of the silica aerogel is 0g.

[0047] Comparative Example 2 provides a method for preparing low-density photovoltaic flat solder strips, which differs from Example 1 only in that the mass of the silica aerogel is 1g.

[0048] Comparative Example 3 provides a method for preparing low-density photovoltaic flat solder strips, which differs from Example 1 only in that the mass of the silica aerogel is 4g.

[0049] Performance testing

[0050] For the low-density photovoltaic flat solder strips prepared in Examples 1-4 and Comparative Examples 1-3 of this invention, the weight per meter, resistivity at 20℃, resistance per meter, tensile strength after annealing (annealing voltage 31V), and yield strength after annealing (annealing voltage 31V) of the low-density photovoltaic flat solder strips were tested according to the group standard T / CPIA0005—2022 Photovoltaic Tin-coated Solder Strips. The test results are shown in Table 1.

[0051] Table 1 Test Data

[0052] Weight in grams (g) Resistivity at 20℃ (Ω·mm² / m) meter resistance (mΩ) Tensile strength after annealing (MPa) Yield strength after annealing (MPa) Example 1 0.356 0.02158 539.3 186.3 66.8 Example 2 0.348 0.02167 542.6 185.5 65.5 Example 3 0.361 0.02151 538.1 185.8 67.2 Example 4 0.354 0.02156 538.9 186.6 66.3 Comparative Example 1 0.385 0.02178 545.5 183.3 73.4 Comparative Example 2 0.373 0.02147 537.8 182.9 70.8 Comparative Example 3 0.339 0.02181 546.6 186.6 64.2

[0053] The following details this application based on the test data in Table 1.

[0054] The test data from Example 1 and Comparative Example 1 show that the addition of silica aerogel gives the low-density photovoltaic flat welding strip a lower weight per unit weight, resistivity at 20°C, and resistance per unit weight. Furthermore, while meeting the requirement that the tensile strength after annealing is in the range of 180-190 MPa, the yield strength after annealing is below 70 MPa, resulting in a wide range of operating conditions.

[0055] The test data from Examples 1-2 and Comparative Examples 2-3 show that when the mass ratio of metallic copper to silica aerogel is 1:(0.002-0.003), the prepared low-density photovoltaic flat ribbon also has low microresistivity and resistivity.

[0056] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a low-density photovoltaic flat solder strip, characterized in that, Includes the following steps: S1. After melting metallic copper into a liquid state in a furnace, silica aerogel is added to the furnace and stirred to obtain a mixed molten metal. The mixture is then cast to obtain an ingot. The mass ratio of metallic copper to silica aerogel is 1:(0.002-0.003). S2. Multiple rolling processes are used to obtain refined copper strips, burrs and flash are removed, and multiple drawing-annealing processes are performed through elliptical flat dies to obtain elliptical flat copper wires. S3. Perform surface treatment on flat copper wires that have been treated to resemble ellipses; S4. The surface-treated flat copper wire is pulled out from the molten solder alloy. The thickness of the solder alloy layer on the surface of the flat copper wire is controlled by an air knife. After cooling, a low-density photovoltaic flat solder strip is obtained.

2. The method for preparing a low-density photovoltaic flat solder strip according to claim 1, characterized in that, The density of the silica aerogel is 0.006-0.01 g / cm³. 3 .

3. The method for preparing a low-density photovoltaic flat solder strip according to claim 2, characterized in that, The mass ratio of the metallic copper to the silica aerogel is 1:0.

002.

4. The method for preparing a low-density photovoltaic flat solder strip according to claim 1, characterized in that, The stirring time in step S1 is 45-90 minutes.

5. The method for preparing a low-density photovoltaic flat solder strip according to claim 1, characterized in that, The vertical direction of the elliptical flat mold is a horizontal straight line at the top and bottom, and the horizontal direction at both ends is an elliptical arc.

6. The method for preparing a low-density photovoltaic flat solder strip according to claim 5, characterized in that, In step S2, each drawing pass reduces the cross-sectional area by 10-15%.

7. The method for preparing a low-density photovoltaic flat solder strip according to claim 1, characterized in that, The air knife is a U-shaped groove air knife.

8. A low-density photovoltaic flat welding strip, characterized in that, It is prepared by any one of claims 1-7.

9. A low-density photovoltaic flat welding strip according to claim 8, characterized in that, The yield strength of the low-density photovoltaic flat welding strip after annealing is 60-70 MPa.

10. A low-density photovoltaic flat bonding strip according to claim 8, characterized in that, The low-density photovoltaic flat solder strip is composed of a flat copper wire with an elliptical shape and a solder alloy layer. The solder alloy layer is located on the periphery of the flat copper wire with an elliptical shape. The flat copper wire with an elliptical shape is a horizontal straight line vertically and has elliptical arcs at both ends horizontally. The width of the flat copper wire with an elliptical shape is 0.22-0.3mm and the thickness is 0.15-0.2mm. The thickness of the solder alloy layer in the vertical direction is 10-15μm, and the thickness of the solder alloy layer in the horizontal direction is no more than 5μm.

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