Composite photovoltaic welding strip and photovoltaic module

Abstract

The embodiment of the utility model discloses a composite photovoltaic welding strip and a photovoltaic module. The welding strip comprises a welding strip base material, the welding strip base material comprises an aluminum layer and a copper layer, and the copper layer comprises a first copper layer arranged on at least part of the peripheral surface of the aluminum layer; the mass ratio of the copper layer to the aluminum layer is 1: 9-9: 1, and the thickness of the first copper layer is larger than or equal to 2 micrometers. According to the solder strip substrate, the mode that only copper is used as the solder strip substrate in the prior art is changed, the aluminum layer is additionally arranged in the solder strip substrate, the usage amount of the copper in the solder strip substrate is reduced, and the cost of the solder strip substrate is reduced. And the mass ratio of the copper layer to the aluminum layer and the thickness of the copper layer are limited, so that the conductivity and the mechanical property of the welding strip base material can meet the requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic, in particular to a multi-layer composite photovoltaic solder ribbon and photovoltaic module. BACKGROUND

[0002] The photovoltaic solder ribbon is an important connecting material in the photovoltaic module, mainly for transmitting and converging the current generated by the cell, and needs excellent electrical conductivity. In addition, the photovoltaic solder ribbon also needs to meet certain mechanical properties. Based on excellent electrical conductivity and mechanical properties, copper becomes the first choice of raw material for the current photovoltaic solder ribbon.

[0003] Specifically, the current photovoltaic solder ribbon uses copper as the base material, and tin-based solder is coated on the surface of the copper base material to form a tin-based solder. The tin-based solder is only used for soldering, and the thickness ratio is small, so the weight ratio of the copper base material is large, usually more than 70%. However, the price of copper is relatively high, which limits the cost reduction of the solder ribbon, and cannot meet the future development needs of the photovoltaic industry for lower manufacturing costs. CONTENT OF THE UTILITY MODEL

[0004] In order to solve the problems of the prior art, the present application provides a composite photovoltaic solder ribbon and a photovoltaic module to reduce the cost of the photovoltaic solder ribbon and solve the problems in the prior art.

[0005] In a first aspect, a composite photovoltaic solder ribbon is provided, the solder ribbon comprising a solder ribbon base material, the solder ribbon base material comprising an aluminum layer and a copper layer, wherein the copper layer comprises a first copper layer disposed on at least part of the outer circumferential surface of the aluminum layer.

[0006] The mass ratio of the copper layer to the aluminum layer is 1:9-9:1, and the thickness of the first copper layer is greater than or equal to 2μm, preferably 2μm-70μm.

[0007] Optionally, the copper layer only comprises the first copper layer disposed on part of the outer circumferential surface of the aluminum layer. Optionally, the thickness of the first copper layer is greater than or equal to 4μm.

[0008] Optionally, the thickness of the first metallurgical bonding layer formed between the first copper layer and the aluminum layer is less than or equal to 10μm.

[0009] Optionally, the copper layer further comprises a second copper layer disposed on the inner circumferential surface of the aluminum layer.

[0010] Optionally, at least one of the thickness of the first metallurgical bonding layer formed between the first copper layer and the aluminum layer and the thickness of the second metallurgical bonding layer formed between the second copper layer and the aluminum layer is less than or equal to 10μm.

[0011] Optionally, the sum of the thicknesses of all metallurgical bonding layers formed between the copper layer and the aluminum layer is less than or equal to 10μm.

[0012] Optionally, the multi-layer composite soldering strip is not broken under a pulling force of no more than 3N in a 180° peeling test scenario.

[0013] Optionally, the multi-layer composite soldering strip is not broken under a pulling force of no more than 5N in a 180° peeling test scenario.

[0014] Optionally, the first copper layer includes a first sub-copper layer and a second sub-copper layer, which are respectively arranged on different outer circumferential surfaces of the aluminum layer, and the thickness of the first sub-copper layer is different from the thickness of the second sub-copper layer. Preferably, the thickness difference between the first sub-copper layer and the second sub-copper layer is greater than or equal to 2μm.

[0015] Optionally, the first sub-copper layer and the second sub-copper layer are respectively arranged on opposite outer circumferential surfaces of the aluminum layer; and / or, the length of the thicker one of the first sub-copper layer and the second sub-copper layer in the cross section is greater than or equal to 150mm.

[0016] Optionally, the tensile strength of the multi-layer composite soldering strip is 85MPa-190MPa, the elongation is 10%-40%, and the yield strength is 40MPa-95MPa. Optionally, the yield strength is 60MPa-72MPa.

[0017] Optionally, the mass ratio of the copper layer to the aluminum layer is 1:4-7:3; and / or, at least part of the copper layer is copper alloy or pure copper or oxygen-free copper; and / or, at least part of the aluminum layer is pure aluminum or aluminum alloy.

[0018] Optionally, the soldering strip further includes a functional layer arranged on the outer circumferential surface of the soldering strip substrate, and the functional layer includes a metal solder layer and / or a conductive adhesive layer and / or a reflective layer arranged on at least part of the outer circumferential surface of the copper layer.

[0019] Optionally, the cross section of the soldering strip is at least one of a rectangle, a circle, a triangle or a special shape, and / or the cross section of the soldering strip substrate is a rectangle, a circle, a triangle or a special shape.

[0020] Optionally, if the cross section of the soldering strip is a circle, the diameter of the soldering strip is 0.1mm-0.35mm.

[0021] Optionally, if the cross section of the soldering strip is a triangle, each side length of the triangle is 0.05mm-0.25mm.

[0022] Optionally, if the cross section of the soldering strip is a rectangle, and the soldering strip is an interconnection soldering strip, the thickness of the interconnection soldering strip is 0.07mm-0.3mm, and the width is 0.4mm-2.5mm.

[0023] Optionally, if the cross section of the solder strip is rectangular, and the solder strip is a busbar, the thickness of the busbar is 0.1mm-0.5mm, and the width of the busbar is 2.5mm-20mm.

[0024] Optionally, the copper layer and the aluminum layer are of the same geometric center type of cladding.

[0025] Optionally, the cross section of the solder strip is rectangular, and the solder strip is a circular wire formed by calendering.

[0026] Optionally, the rectangular shape has two opposite calendered edges, and the thickness of the middle part of the calendered edge is greater than the thickness of the two end parts of the calendered edge.

[0027] Optionally, the thickness difference between the middle part of the calendered edge and the two end parts of the calendered edge is greater than or equal to 5μm.

[0028] Optionally, the solder strip is a reflective solder strip or a concentrated light solder strip.

[0029] In a second aspect, a photovoltaic module is provided, comprising:

[0030] a plurality of cell pieces; and a composite photovoltaic solder strip as claimed in any one of the first aspect for connecting the cell pieces.

[0031] According to the specific embodiments provided in the present application, the present application discloses the following technical effects:

[0032] In the present application, the copper layer is added to the solder strip substrate, reducing the use of copper in the solder strip substrate, reducing the cost of the solder strip substrate, and by limiting the mass ratio of the copper layer to the aluminum layer and the thickness of the copper layer, the electrical conductivity and mechanical properties of the solder strip substrate meet the requirements.

[0033] Further, the solder strip substrate can be provided as a two-layer structure of an aluminum layer plus a first copper layer, and the first copper layer is only provided on part of the outer circumferential surface of the aluminum layer, so that in the case of the same mass of copper, the present application can set a thicker copper layer, thereby avoiding the problem of aluminum leakage due to uneven thickness of the copper layer in the case of thin copper layer.

[0034] Further, in the present application, the thickness of the metallurgical bonding layer formed by the combination surface of the copper layer and the aluminum layer is less than or equal to 10μm, thereby reducing the problem of brittleness of the solder strip substrate and easy breakage of the solder strip substrate due to the metallurgical bonding layer.

[0035] Further, the copper layer further comprises a second copper layer arranged on at least part of the inner circumferential surface of the aluminum layer, so as to form a second copper layer-aluminum layer-first copper layer structure of at least three layers. In this way, even if the intermediate aluminum layer and the metallurgical bonding layer are broken, the solder strip base material can be maintained in an overall non-broken state based on the increased second copper layer, and the overall anti-breaking performance is improved. The relatively high anti-breaking performance can make the 180° peeling test of the solder strip proceed smoothly.

[0036] Further, in the present application, the first copper layer is arranged on different outer circumferential surfaces of the aluminum layer and has different thicknesses. This makes it possible to perform welding at the thicker copper layer later, avoids aluminum leakage, improves the welding strength, and reduces the cost based on the thinner copper layer.

[0037] Of course, implementing any of the solutions of the present application does not necessarily require all the advantages described above to be achieved at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings. In addition, similar numbers in the drawings are used to represent similar components, wherein:

[0039] Figures 1A-1C is a schematic diagram of a solder strip base material with a two-layer structure in the first embodiment of the present application;

[0040] Figure 1D is a schematic diagram of a 180° peeling test in the present application;

[0041] Figure 1E is a schematic diagram of the solder strip base material with different thicknesses of the sub-copper layer in the first embodiment of the present application;

[0042] Figures 2A-2C is another schematic diagram of a solder strip base material with a two-layer structure in the second embodiment of the present application;

[0043] Figures 3A-3C is a schematic diagram of a solder strip base material with a three-layer structure in the third embodiment of the present application;

[0044] Figures 4A-4C is another schematic diagram of a solder strip base material with a three-layer structure in the fourth embodiment of the present application. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] As described in the background section, existing photovoltaic solder ribbons use copper substrates, which are costly. Therefore, this application creatively provides a novel composite photovoltaic solder ribbon. The ribbon includes a substrate comprising an aluminum layer and a copper layer, wherein the copper layer includes a first copper layer disposed on at least a portion of the outer peripheral surface of the aluminum layer; the mass ratio of the copper layer to the aluminum layer is 1:9 to 9:1, and the thickness of the first copper layer is greater than or equal to 2 μm. This application provides a solder ribbon substrate formed by a multilayer structure of copper and aluminum. By adding an aluminum layer, the cost is reduced, and by limiting the thickness and mass of the copper layer, the conductivity and mechanical properties of the solder ribbon substrate are ensured to meet requirements.

[0047] In some embodiments of this application, the mass ratio of copper layer to aluminum layer is further limited to 1:4 to 7:3, in order to reduce the possibility that if the proportion of copper layer is too small, the copper layer will be too thin, which may easily lead to aluminum leakage and high resistance during the production process, thereby seeking a better balance between the performance of the solder ribbon substrate and low cost.

[0048] In some embodiments of this application, the solder strip can be a reflective solder strip or a focusing solder strip. In some embodiments of this application, the solder strip can be an interconnect solder strip or a busbar solder strip.

[0049] In some embodiments of this application, the cross-section of the solder strip is rectangular, circular, triangular, or irregular. The cross-section of the solder strip substrate is also rectangular, circular, triangular, or irregular.

[0050] In some embodiments of this application, the cross-section of the solder strip is circular, and the diameter of the solder strip is 0.1 mm to 0.35 mm. It should be noted that in this application, when the cross-section of the solder strip is circular, the diameter of the solder strip is the same as the thickness of the solder strip.

[0051] In some embodiments of this application, the cross-section of the solder strip is triangular, with each side of the triangle having a length of 0.05mm to 0.25mm. Its thickness can be the height of the triangle, which can be calculated based on the side lengths.

[0052] In some embodiments of this application, the cross-section of the solder strip is rectangular, and the solder strip is an interconnect solder strip with a thickness of 0.07mm to 0.3mm and a width of 0.4mm to 2.5mm.

[0053] In some embodiments of this application, the cross-section of the solder strip is rectangular, and the solder strip is a busbar solder strip with a thickness of 0.1 mm to 0.5 mm and a width of 2.5 mm to 20 mm.

[0054] In some embodiments of this application, the tensile strength of the multilayer composite welding strip is 85MPa to 190MPa, the elongation is 10% to 40%, and the yield strength is 40MPa to 95MPa.

[0055] In some embodiments of this application, at least a portion of the copper layer is a copper alloy, pure copper, or oxygen-free copper, thereby providing better electrical conductivity and mechanical properties.

[0056] At least a portion of the aluminum layer is pure aluminum or an aluminum alloy. Considering the overall conductivity and strength of the solder strip, in a preferred embodiment of this application, the aluminum alloy is at least one of an aluminum-iron alloy, an aluminum-copper alloy, or an aluminum-magnesium alloy. Specifically, 0.3% to 0.8% iron, 0.1% to 0.5% copper, or 0.04% to 0.15% magnesium can be added to the aluminum to form the corresponding aluminum alloy, thereby providing better conductivity and mechanical properties.

[0057] Depending on the specific requirements, the solder strip may also include a functional layer disposed on the outer peripheral surface of the solder strip substrate, specifically a functional layer disposed on at least a portion of the outer peripheral surface of the first copper layer. These functional layers may specifically include a metal solder layer and / or a conductive adhesive layer and / or a reflective layer disposed on at least a portion of the outer peripheral surface of the copper layer.

[0058] The metal solder layer can be composed of one or more elements such as tin, lead, bismuth, silver, and copper. The conductive adhesive layer includes a dielectric and conductive particles. The conductive particles can be one or more metals such as silver, copper, tin, and nickel, or one or more non-metals such as graphite and carbon nanotubes. The thickness of the metal solder layer or conductive adhesive layer can be set from 0.5 μm to 35 μm.

[0059] In some embodiments of this application, the functional layer is a reflective layer to form a reflective solder ribbon. Specifically, multiple grooves can be formed on the surface of the solder ribbon substrate to create reflective structures such as triangles between the grooves, thereby improving light utilization and increasing component power. The height of the triangle can be 10μm to 40μm, and the apex angle can be 115° to 125°.

[0060] The configurations of the above embodiments ensure that the mechanical and electrical properties of the solder strip still meet the requirements even with the addition of aluminum and reduced costs. In a preferred embodiment of this application, the configurations of the above embodiments can be satisfied simultaneously, thereby achieving solder strips with superior mechanical and electrical properties.

[0061] In some embodiments of this application, the functional layer may also be a light-concentrating layer to form a light-concentrating solder ribbon.

[0062] The following will explain some of the structural settings of the solder strip with reference to the attached diagram.

[0063] Example 1:

[0064] Embodiment 1 of this application provides a two-layer structured solder strip substrate, such as... Figure 1A , 1B As shown in Figure 1C, the solder strip substrate includes an aluminum layer 10 and a copper layer 11, wherein the copper layer 11 includes a first copper layer 111, which is disposed on all the outer peripheral surfaces of the aluminum layer 10, thereby forming a copper-clad aluminum substrate structure.

[0065] 1A, 1B, and 1C are schematic diagrams showing that the cross-section of the solder strip substrate is circular, rectangular, and triangular, respectively.

[0066] Solder ribbons are not prone to bending during actual use, so the bending resistance of the solder ribbon substrate is usually not a major concern. However, to inspect the welding quality between the solder ribbon and the solar cell, a 180° peel test is performed on the solder ribbon. During the test, the solder ribbon is welded to the solar cell, and then a tensile force is applied to the solder ribbon in the direction indicated by the arrow. Figure 1D As shown, the solder ribbon 1 is pulled off the solar cell 2, and the welding quality between the solder ribbon and the solar cell is evaluated based on the peeling condition of the solder ribbon. However, the applicant found that the solder ribbon substrate formed by copper-clad aluminum often breaks during the subsequent 180° peel test, making it difficult to conduct the 180° peel test smoothly. When the first copper layer 111 comes into contact with the aluminum layer 10, a reaction occurs at the interface where the two are bonded, forming a new layer, namely the first metallurgical bonding layer 101. The applicant's research found that this metallurgical bonding layer 101 is more brittle than the first copper layer 111 and the aluminum layer 10, and is more prone to breakage when bent. Therefore, this application creatively proposes to focus on the first metallurgical bonding layer 101 and limit its thickness to less than or equal to 10 μm, thereby reducing the bending resistance of the solder ribbon substrate. Specifically, this application can adjust the solder ribbon substrate formation process, such as annealing temperature and annealing time, so that the thickness of the first metallurgical bonding layer 101 is less than or equal to 10 μm.

[0067] In some embodiments of this application, it is desirable that the thickness of the first copper layer on different outer peripheral surfaces of the distributed aluminum layer is uniform, such as... Figure 1A , 1B As shown in Figure 1C. However, in alternative embodiments, such as... Figure 1EAs shown (the first metallurgical bonding layer is omitted in the figure), the first copper layer 111 includes a first sub-copper layer 1111 and a second sub-copper layer 1112, which are respectively disposed on different outer peripheral surfaces of the aluminum layer 10. The thickness of the first sub-copper layer 1111 is different from that of the second sub-copper layer 1112 (the thickness of the first sub-copper layer 1111 is greater than that of the second sub-copper layer 1112 in the figure). This thickness difference does not include thickness errors caused by process precision issues. Specifically, the thickness difference between the first sub-copper layer 1111 and the second sub-copper layer 1112 is greater than or equal to 2μm. The advantage of this setting is that the thicker sub-copper layer can be used as a welding surface to weld with the battery cell in subsequent welding, while the sub-copper layer that is not used as a welding surface is set thinner. In this way, under the same conditions, the same mass of copper can be used to meet the thickness requirements for welding and reduce the amount of copper used in the solder strip substrate.

[0068] In a further embodiment, the thicker of the first sub-copper layer 1111 and the second sub-copper layer 1112, which is the sub-copper layer subsequently used for welding, has a cross-sectional length greater than or equal to 150 mm, thereby meeting the welding length requirements.

[0069] The outer peripheral surfaces corresponding to the first sub-copper layer 1111 and the second sub-copper layer 1112 can be selected as needed. In a preferred embodiment, the first sub-copper layer 1111 can be disposed on the outer peripheral surface corresponding to subsequent welding, while the second sub-copper layer 1112 is disposed on all other outer peripheral surfaces. Considering process errors, the area where the first sub-copper layer is disposed can be expanded to ensure that the placement of the first sub-copper layer can completely correspond to subsequent welding. Figure 1E For example, the aluminum layer 10 has an upper outer peripheral surface 102, left and right outer peripheral surfaces 103, and a lower outer peripheral surface 104. The upper outer peripheral surface 102 corresponds to the subsequent welding. In this case, the first sub-copper layer 1111 can be only disposed on the upper outer peripheral surface 102, while the second sub-copper layer 1112 is disposed on the left and right outer peripheral surfaces 103 and the lower outer peripheral surface 104. However, in a preferred embodiment, the first sub-copper layer 1111 (not shown in the figure) can also be disposed in a portion of the upper outer peripheral surface 102 and the left and right outer peripheral surfaces 103 near the upper outer peripheral surface 102. Unlike the one shown in 1E, in an alternative embodiment, the first sub-copper layer 1111 and the second sub-copper layer 1112 can be disposed on the opposite outer peripheral surfaces of the aluminum layer 10.

[0070] Figure 1E Taking a rectangular solder strip substrate as an example, in actual production, the rectangular solder strip substrate may be formed by rolling a circular solder strip substrate. Therefore, it is necessary to set the requirements for the first sub-copper layer and the second sub-copper layer in advance during the formation process of the circular solder strip substrate according to the requirements of the rectangular solder strip substrate.

[0071] In an optional embodiment, Figure 1EThe rectangle in the figure has two opposing rolled edges (the top and bottom edges in the figure), and the thickness of the middle part of the rolled edge is greater than the thickness of the two ends of the rolled edge. Specifically, the thickness difference between the middle part of the rolled edge and the two ends of the rolled edge is greater than or equal to 5 μm.

[0072] In other embodiments of this application, when there is no thickness difference in the copper layer, the copper layer and the aluminum layer can overlap in a geometrically centered manner.

[0073] Example 2

[0074] Embodiment 2 of this application provides another two-layer structured solder strip substrate, such as Figure 2A , 2B As shown in Figures 2C and 2C, the solder strip substrate includes an aluminum layer 20 and a copper layer 21, wherein the copper layer 21 includes a first copper layer 211, which is disposed on only a portion of the outer peripheral surface of the aluminum layer 11, thereby forming a partially copper-clad aluminum substrate structure.

[0075] in Figure 2A , 2B Figures 2C and 2C show the cross-sections of the solder strip substrate as circular, rectangular, and triangular, respectively.

[0076] In some embodiments, a first copper layer 211 may be selectively provided on a portion of the outer peripheral surface corresponding to the subsequent welding surface, so that the first copper layer 211 forms a welding surface for subsequent welding with the battery cell. The outer peripheral surface that does not correspond to the welding surface may not have the first copper layer provided. For example Figure 2B In the process, the upper outer peripheral surface 201 of the aluminum layer 20 corresponds to the subsequent welding surface, and a first copper layer 211 is disposed thereon. The first copper layer 211 is used for subsequent welding with the battery cell. The left and right outer peripheral surfaces 202 and the lower outer peripheral surface 203 of the aluminum layer 20 do not correspond to the subsequent welding surface, and the first copper layer 211 may not be disposed thereon.

[0077] Of course, in this application, a first copper layer can also be set on the outer peripheral surface that does not correspond to the subsequent welding surface based on other needs. This application does not limit the specific selection of the outer peripheral surface, and it can be done according to the requirements.

[0078] Compared to setting the first copper layer 211 on the entire outer periphery of the aluminum layer 20, setting the first copper layer 211 only on a portion of the outer periphery of the aluminum layer 20 has the advantage of forming a thicker first copper layer 211 using the same mass of copper, under the same conditions. This first copper layer 211 is subsequently used for welding, which can improve the welding strength and prevent exposed aluminum from directly welding to the battery cell, thus avoiding problems such as poor welding and poor conductivity.

[0079] Similar to Embodiment 1, the solder strip substrate in Embodiment 2 also includes a metallurgical bonding layer formed at the interface between the first copper layer 211 and the aluminum layer 20. Figure 2A ,2B (not shown in 2C), and the thickness of the metallurgical bonding layer is preferably less than or equal to 10 μm.

[0080] For the solder strip substrate in Embodiment 2, taking a rectangular cross-section as an example, it can be formed by pressing copper plates and aluminum plates together, or it can be formed by pouring high-temperature molten aluminum onto copper plates. This application does not impose any specific restrictions on this.

[0081] Example 3

[0082] Embodiment 3 of this application provides a three-layer structured solder strip substrate, such as... Figure 3A , 3B As shown in Figures 3C and 3C, the solder strip substrate includes an aluminum layer 30 and a copper layer 31. The copper layer 31 includes a first copper layer 311 and a second copper layer 312. The first copper layer 311 is disposed on all the outer peripheral surfaces of the aluminum layer 30, and the second copper layer 312 is disposed on all the inner peripheral surfaces of the aluminum layer 30, thereby forming a copper-clad aluminum-aluminum-clad copper substrate structure.

[0083] It should be noted that the inner circumferential surface in this application is a concept relative to the outer circumferential surface. An inner circumferential surface only exists when an object is hollow. For solid objects, there is only an outer circumferential surface, not an inner circumferential surface. For example... Figure 1A , 1B Aluminum layers in 1C, 2A, 2B, and 2C.

[0084] 3A, 3B, and 3C are schematic diagrams showing that the cross-section of the solder strip substrate is circular, rectangular, and triangular, respectively.

[0085] As mentioned above, copper-clad aluminum structures are prone to breakage during 180° peel tests. To address this, this application further provides a three-layer cladding structure. A second copper layer 312 is disposed on the inner circumferential surface of the aluminum layer 30, i.e., the innermost layer is the second copper layer 312, sandwiching the aluminum layer 30 between the first copper layer 311 and the second copper layer 312. Based on this, the first metallurgical bonding layer 301 on the bonding surface between the aluminum layer 30 and the first copper layer 311, and the second metallurgical bonding layer 302 on the bonding surface between the aluminum layer 30 and the second copper layer 312, are also sandwiched between the first copper layer 311 and the second copper layer 312. This ensures that even if the first metallurgical bonding layer 301 and the second metallurgical bonding layer 302 break during a 180° peel test, the presence of the first copper layer 311 and the second copper layer 312 will prevent the overall solder strip substrate from breaking (only during metallographic observation will the breakage of the first metallurgical bonding layer 301 and the second metallurgical bonding layer 302 between the two copper layers be observed; the solder strip substrate appears intact to the naked eye).

[0086] Furthermore, in this application, the thicknesses of the first metallurgical bonding layer 301 and the second metallurgical bonding layer 302 can be set. Specifically, at least one of the thicknesses of the first metallurgical bonding layer 301 and the second metallurgical bonding layer 302 is less than or equal to 10 μm. In a preferred embodiment, the sum of the thicknesses of the first metallurgical bonding layer 301 and the second metallurgical bonding layer 302 is less than or equal to 10 μm.

[0087] Considering that the main function of the second copper layer 312 is to serve as an inner metallurgical bonding layer to improve the fracture resistance of the solder strip substrate, and another main function of the first copper layer 311 is to be welded to the battery cell, the thickness of the first copper layer 311 is greater than the thickness of the second copper layer 312. In a specific embodiment, the difference between the thickness of the first copper layer 311 and the thickness of the second copper layer 312 is not less than 2μm.

[0088] It should be noted that, in this application, another aluminum layer may be further provided on the inner circumferential surface of the second copper layer 312, and a third copper layer may be provided on the inner circumferential surface of the other aluminum layer. These layers are stacked sequentially to form more interlocking structures, thereby further enhancing the fracture resistance of the solder strip substrate.

[0089] This application does not specifically limit the number of layers. In a preferred embodiment, the entire solder strip substrate can remain unbroken during a 180° peel test under a tensile force of no more than 3N, and further, under a tensile force of no more than 5N (the metallurgical bonding layer may break).

[0090] In other embodiments of this application, the first copper layer and the second copper layer can be set in the same manner as in Embodiment 1. The setting method is similar and will not be described in detail here.

[0091] It should be noted that in other embodiments of this application, when there is no thickness difference in the copper layer, the copper layer and the aluminum layer are encased in a geometrically centered manner.

[0092] Example 4

[0093] Embodiment 4 of this application provides another three-layer structured solder strip substrate, such as Figure 4A , 4B As shown in 4C, the solder strip substrate includes an aluminum layer 40 and a copper layer 41. The copper layer 41 includes a first copper layer 411 and a second copper layer 412. The first copper layer 411 is only disposed on the outer peripheral surface of a portion of the aluminum layer 40, and the second copper layer 412 is disposed on the inner peripheral surface of the aluminum layer 40, thereby forming a partially copper-clad aluminum-aluminum-clad copper substrate structure.

[0094] Similar to Embodiment 2, a first copper layer 411 can be provided on a portion of the outer peripheral surface corresponding to the subsequent welding surface, so that the first copper layer 411 forms a welding surface for subsequent welding with the battery cell. The first copper layer 411 may not be provided on the outer peripheral surface that does not correspond to the welding surface.

[0095] Of course, in this application, a first copper layer can also be set on the outer peripheral surface that does not correspond to the subsequent welding surface based on other needs. This application does not limit the specific selection of the outer peripheral surface, and it can be done according to the requirements.

[0096] Compared to setting the first copper layer 411 on the entire outer periphery of the aluminum layer 40, setting the first copper layer 411 only on a portion of the outer periphery of the aluminum layer 40 has the advantage of forming a thicker first copper layer 411 using the same mass of copper, under the same conditions. This first copper layer 411 is subsequently used for welding, which can improve the welding strength and prevent exposed aluminum from directly welding to the battery cell, thus avoiding problems such as poor welding and poor conductivity.

[0097] It should be noted that the thickness mentioned in this application is defined according to the following rules:

[0098] If the cross-section is circular, the thickness is defined as follows: if it is solid (such as the aluminum layer in Examples 1 and 2, and the second copper layer in Examples 3 and 4), the thickness is its own diameter; if it is hollow (such as the first copper layer in Example 1, and the aluminum layer in Examples 3 and 4), the thickness is the difference between its own outer radius and inner radius.

[0099] If the cross-section is rectangular, the thickness is defined as follows: if it is solid (such as the aluminum layer in Examples 1 and 2, and the second copper layer in Examples 3 and 4), the thickness is the thickness between its upper outer circumferential surface and its lower outer circumferential surface; if it is hollow (such as the first copper layer in the examples, and the aluminum layer in Examples 3 and 4), the thickness is the thickness between its outer circumferential surface and its corresponding inner circumferential surface.

[0100] If the cross-section is triangular, the thickness is defined as follows: if it is solid (such as the aluminum layer in Examples 1 and 2, and the second copper layer in Examples 3 and 4), the thickness is the height of its own triangle; if it is hollow (such as the first copper layer in each example, and the aluminum layer in Examples 3 and 4), the thickness is half the difference between the height of the triangle formed by its own outer circumference and the height of the triangle formed by its own inner circumference.

[0101] The above embodiments one to four illustrate, by way of example, some of the solder strip substrate arrangements of this application. In addition to the above embodiments, this application may include more solder strip substrate structural arrangements, and this application does not impose specific limitations on these, as long as they satisfy the inventive concept of this application.

[0102] Example 5

[0103] Corresponding to the above embodiments, Embodiment 5 of this application provides a photovoltaic module, the photovoltaic module comprising:

[0104] Multiple battery cells;

[0105] And the composite photovoltaic ribbon described above for connecting the solar cells.

[0106] Example 6

[0107] Regarding the aforementioned composite photovoltaic ribbon, Embodiment Six of this application also provides a specific preparation process:

[0108] Removing the oxide layer: Specifically, steel wire can be used to remove the oxide layer from the surface of the coarse aluminum rod (such as 9mm to 16mm in diameter) and the copper foil, so that the two can be tightly bonded in the subsequent wire drawing process.

[0109] Coating welding: Copper foil with the oxide layer removed is wrapped around the outer circumference of the rough aluminum rod to cover it, and the joints of the copper foil are welded together using high-temperature argon arc welding. During the copper foil coating process, the speed is generally a few meters to tens of meters per minute. The higher the proportion of copper by mass, the slower the coating speed.

[0110] Multi-stage wire drawing: The coated coarse aluminum rod is passed through multiple wire drawing machines to gradually draw the coated and welded coarse aluminum rod into fine wires. The wire drawing speed is usually 800m / min to 2000m / min. After drawing, a round wire is formed.

[0111] Calendering: The drawn round wire is calendered into strip (the cross-section of the strip is rectangular) using a calendering machine. Specifically, the calendering machine sets the calendering width according to the required strip width range.

[0112] Annealing: The rolled strip (or round wire if the final product is round) is subjected to online short-circuit or in-line annealing to modify the material's mechanical properties to meet requirements, including tensile strength, yield strength, and elongation. The annealing current, annealing temperature, and annealing time not only affect the material's mechanical properties but also the thickness of the metallurgical bonding layer at the copper-aluminum interface. Higher annealing currents, temperatures, and times result in a thicker metallurgical bonding layer. In this application, the thickness of the metallurgical bonding layer has a significant impact on the performance of the weld strip substrate; therefore, the annealing current, annealing temperature, and annealing time must be reasonably set according to the required thickness of the metallurgical bonding layer. In one specific embodiment, the annealing time is 0.5s to 4s.

[0113] Applying flux and tinning: Apply flux to the surface of the annealed material, and then immerse it in a molten tin bath for tinning.

[0114] Cooling: Cool the material with conventional air or pass it through a low-temperature cooling pipe to rapidly reduce the surface temperature of the material.

[0115] Rewinding: Wrap the material around the shaft, and replace the shaft after it has reached a certain length.

[0116] In one specific embodiment of this application, the process from calendering to winding is completed on the same production line, so the speed of each step is the same, typically 60m / min to 150m / min.

[0117] Depending on the desired finished product, the above process can be adjusted, and this application does not impose specific limitations on it. For example, if the final product is circular, it can be directly annealed after multiple drawing stages without calendering. However, if the final product is a wider rectangular busbar, multiple calendering stages are required. After annealing, other related functional layers can be coated or prepared as needed, such as a reflective layer or a conductive adhesive layer.

[0118] If the desired finished product is a partial coating as described in Example 2 above, then during the coating welding process, the copper foil does not need to completely cover the thick aluminum rod.

[0119] If the desired finished product is the three-layer structure described in Examples 3 and 4 above, then aluminum foil needs to be wrapped around a thick copper rod, and then copper foil needs to be wrapped around the aluminum foil, followed by processes such as wire drawing, rolling, and annealing.

[0120] The technical solution provided by this utility model has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. Furthermore, those skilled in the art will recognize that, based on the ideas of this utility model, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A composite photovoltaic welding strip, characterized in that, The solder strip includes a solder strip substrate, which includes an aluminum layer and a copper layer, wherein the copper layer includes a first copper layer disposed on at least a portion of the outer peripheral surface of the aluminum layer; the mass ratio of the copper layer to the aluminum layer is 1:9 to 9:1, and the thickness of the first copper layer is greater than or equal to 2 μm.

2. The composite photovoltaic welding strip according to claim 1, characterized in that, The thickness of the first metallurgical bonding layer formed between the first copper layer and the aluminum layer is less than or equal to 10 μm.

3. The composite photovoltaic welding strip according to claim 1, characterized in that, The copper layer also includes a second copper layer disposed on the inner circumferential surface of the aluminum layer.

4. The composite photovoltaic welding strip according to claim 3, characterized in that, The thickness of the first metallurgical bonding layer formed between the first copper layer and the aluminum layer, and the thickness of the second metallurgical bonding layer formed between the second copper layer and the aluminum layer, are both less than or equal to 10 μm. or, The sum of the thicknesses of all metallurgical bonding layers formed between the copper layer and the aluminum layer is less than or equal to 10 μm.

5. The composite photovoltaic welding strip according to any one of claims 1 to 4, characterized in that, The welding strip did not break under a tensile force of no more than 3N in a 180° peel test scenario.

6. The composite photovoltaic welding strip according to any one of claims 1 to 4, characterized in that, The first copper layer includes a first sub-copper layer and a second sub-copper layer, which are respectively disposed on different outer peripheral surfaces of the aluminum layer. The thickness of the first sub-copper layer is different from that of the second sub-copper layer.

7. The composite photovoltaic welding strip according to claim 6, characterized in that, The first sub-copper layer and the second sub-copper layer are respectively disposed on the opposite outer peripheral surfaces of the aluminum layer; And / or, The thicker of the first and second sub-copper layers has a cross-sectional length greater than or equal to 150 mm.

8. The composite photovoltaic welding strip according to any one of claims 1 to 4, characterized in that, The tensile strength of the welding strip is 85MPa to 190MPa, the elongation is 10% to 40%, and the yield strength is 40MPa to 95MPa. And / or, The mass ratio of the copper layer to the aluminum layer is 1:4 to 7:3; And / or, At least a portion of the copper layer is pure copper, oxygen-free copper, or a copper alloy; And / or, At least a portion of the aluminum layer is pure aluminum or an aluminum alloy; And / or, The solder strip further includes a functional layer disposed on the outer peripheral surface of the solder strip substrate, the functional layer including a metal solder layer and / or a conductive adhesive layer and / or a reflective layer disposed on at least a portion of the outer peripheral surface of the copper layer; And / or, The cross-section of the welding strip is rectangular, circular, or triangular; And / or, The cross-section of the welding strip substrate is rectangular, circular, or triangular; And / or, The copper layer and the aluminum layer are geometrically centered and overlapped. And / or, The welding strip is a reflective welding strip or a focused welding strip.

9. The composite photovoltaic welding strip according to any one of claims 1 to 4, characterized in that, If the cross-section of the welding strip is circular, the diameter of the welding strip is 0.1mm to 0.35mm; If the cross-section of the welding strip is triangular, the length of each side of the triangle is 0.05mm to 0.25mm; If the cross-section of the solder strip is rectangular, and the solder strip is an interconnect solder strip, the thickness of the interconnect solder strip is 0.07mm to 0.3mm, and the width is 0.4mm to 2.5mm; If the cross-section of the solder strip is rectangular and the solder strip is a busbar solder strip, the thickness of the busbar solder strip is 0.1mm to 0.5mm and the width is 2.5mm to 20mm.

10. The composite photovoltaic welding strip according to any one of claims 1 to 4, characterized in that, The cross-section of the welding strip is rectangular, and the welding strip is formed by rolling a round wire.

11. The composite photovoltaic welding strip according to claim 10, characterized in that, The rectangle has two opposite rolled edges, and the thickness of the middle portion of the rolled edges is greater than the thickness of the two ends of the rolled edges.

12. A photovoltaic module, characterized in that, The photovoltaic module includes: Multiple battery cells; And a composite photovoltaic ribbon as described in any one of claims 1 to 11 for connecting the solar cells.

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