Method for manufacturing composite welding strip, composite welding strip and photovoltaic module

Abstract

This application provides a method for preparing a composite welding strip, the composite welding strip itself, and a photovoltaic module, which can be widely applied in the field of photovoltaic module technology. The method for preparing the composite welding strip includes: sequentially stacking a first copper strip, a conductive metal strip, and a second copper strip to form a symmetrical stack; feeding the symmetrical stack into a hot rolling mill, allowing some metal from the first and second copper strips to flow to the side of the conductive metal strip, forming a first welding strip with a fully sealed structure; wherein the side is the area on the conductive metal strip in the stacked state that does not contact the first and second copper strips; and feeding the first welding strip into a cold rolling mill to form a composite welding strip. This application helps alleviate the corrosion problem of welding strips in related technologies; simultaneously, the symmetrical structure of the upper and lower copper layers in this embodiment helps achieve stress balance and suppresses the possibility of seal failure; the preparation process of this application is simple and helps reduce preparation costs.

Description

Technical Field

[0001] This application relates to the field of photovoltaic module technology, and more specifically, to a method for preparing a composite solder strip, the composite solder strip, and a photovoltaic module. Background Technology

[0002] Photovoltaic solder ribbons are the core conductors in photovoltaic modules, connecting solar cells in series and conducting current. The high cost of pure copper solder ribbons has driven the industry towards composite materials. In related technologies, one embodiment employs complex processes such as aluminum core microalloying and the introduction of a nanoscale zinc interlayer. However, this approach still suffers from the problem of electrochemical corrosion caused by humid air contacting the encapsulation gaps. Another embodiment improves mechanical bonding by altering the geometry of the material interface. This approach increases process complexity and still faces the problem of corrosive media seeping into the interlocking gaps. Summary of the Invention

[0003] The main objective of this application is to provide a method for preparing composite solder strips, composite solder strips, and photovoltaic modules, so as to at least solve the problem of easy corrosion of solder strips in related technologies.

[0004] To achieve the above objectives, according to one aspect of this application, a method for preparing composite solder strips is provided, the method comprising:

[0005] A first copper strip, a conductive metal strip, and a second copper strip are sequentially stacked to form a symmetrical stack; wherein the first copper strip, the conductive metal strip, and the second copper strip all extend along a first direction, and the widths of the first copper strip and the second copper strip along a second direction are both greater than the width of the conductive metal strip along the second direction, and the first direction and the second direction intersect.

[0006] The symmetrical stacked billets are fed into a hot rolling mill so that a portion of the metal from the first copper strip and the second copper strip flows to the side of the conductive metal strip, forming a first weld strip with a fully sealed structure; wherein, the side is the area on the conductive metal strip in the stacked state that does not contact the first copper strip and the second copper strip;

[0007] The first welding strip is fed into a cold rolling mill to form a composite welding strip.

[0008] Optionally, feeding the symmetrical stacked billets into a hot rolling mill to allow a portion of the metal from the first and second copper strips to flow to the side of the conductive metal strip, forming a first weld strip with a fully sealed structure, includes:

[0009] The symmetrical stacked billets are fed into a hot rolling mill, and a preset total reduction rate is applied in a single pass to form a sealing layer on the side of the conductive metal strip, a first copper layer on the upper surface, and a second copper layer on the lower surface, thereby obtaining the first weld strip; wherein, the ratio of the width of the sealing layer along the second direction to the total thickness of the composite weld strip along the third direction is greater than or equal to a first value, the preset total reduction rate is 60%-70%, and the third direction intersects with the first direction.

[0010] Optionally, feeding the first welding strip into a cold rolling mill to form a composite welding strip includes:

[0011] The first welding strip is fed into a cold rolling mill, and a preset reduction rate is applied in a single pass to adjust the thickness of the first welding strip, thereby obtaining a composite welding strip; wherein the preset reduction rate is 15%-20%.

[0012] Optionally, before feeding the symmetrical stacked billets into a hot rolling mill to allow a portion of the metal from the first and second copper strips to flow to the side of the conductive metal strip to form the first weld strip with a fully sealed structure, the method further includes:

[0013] In a protective gas environment, the symmetrical stacked blanks are heated to a first temperature; wherein the first temperature is 410℃-450℃.

[0014] Optionally, after feeding the first welding strip into the cold rolling mill, the method further includes:

[0015] A tin layer with a thickness of a first thickness is plated on the surface of the first solder strip; wherein the first thickness is 5-15 μm.

[0016] Optionally, after feeding the symmetrical stacked billets into the hot rolling mill, the method further includes:

[0017] At a first temperature, atoms at the first interface and the second interface are interdiffused to form an interface bonding layer; wherein, the first interface is the interface between the first copper layer and the conductive metal strip, and the second interface is the interface between the second copper layer and the conductive metal strip.

[0018] The first ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip is adjusted to be within a preset range; wherein the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer, as well as the total thickness, are all thicknesses along the third direction, which intersects with the first direction, and the preset range is 0.15-0.25.

[0019] Optionally, adjusting the ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip to be within a preset range includes:

[0020] The first thickness of the first copper strip and the second copper strip along the third direction is determined, and the second ratio of the first thickness to the second thickness of the conductive metal strip is adjusted to be within a preset ratio range; wherein, the preset ratio range is 1 / 5-1 / 3, and the second thickness is the thickness along the third direction;

[0021] Alternatively, adjust the preset total reduction rate of the hot rolling mill;

[0022] Alternatively, adjust the preset reduction rate of the cold rolling mill;

[0023] Alternatively, the width difference between the first copper strip and the conductive metal strip along the second direction can be adjusted.

[0024] Optionally, adjusting the preset total reduction rate of the hot rolling mill includes:

[0025] When the preset total reduction rate of the hot rolling mill is the first reduction rate, if the first ratio of the first weld strip obtained is less than the first preset value, the preset total reduction rate of the hot rolling mill is adjusted to the second reduction rate; wherein the second reduction rate is greater than the first reduction rate;

[0026] Adjusting the width difference between the first copper strip and the conductive metal strip along the second direction includes:

[0027] If the width difference is a first difference value, and the first ratio of the first solder strip is less than a first preset value, the width difference is adjusted to a second difference value; wherein the second difference value is less than the first difference value.

[0028] According to another aspect of this application, a composite solder strip is provided, the composite solder strip comprising: a conductive metal layer;

[0029] A first copper layer on the upper surface, a second copper layer on the lower surface, and a sealing layer on the side are symmetrically sealed on the conductive metal layer; wherein the conductive metal layer, the first copper layer, the second copper layer, and the sealing layer all extend along a first direction, the side includes two surface regions arranged opposite each other along a second direction, the upper surface and the lower surface are arranged opposite each other along a third direction, and the first direction, the second direction, and the third direction intersect each other.

[0030] Optionally, an interface bonding layer is further provided between the first copper layer and the conductive metal layer, and between the second copper layer and the conductive metal layer;

[0031] The first ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip is within a preset range; wherein, the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer, as well as the total thickness, are all thicknesses along the third direction, which intersects with the first direction, and the preset range is 0.15-0.25.

[0032] Optionally, a tin layer is further provided on the surface of the first copper layer away from the conductive metal layer, the surface of the second copper layer away from the conductive metal layer, and the surface of the sealing layer away from the conductive metal layer, wherein the thickness of the tin layer is 5-15 μm.

[0033] To achieve the above objectives, according to another aspect of this application, a photovoltaic module is provided in which the cells are interconnected by composite solder strips as described above.

[0034] By applying the technical solution of this application, the width of the copper strip is designed to be greater than the width of the conductive metal strip, so that a fully sealed structure of the weld strip is formed during the hot rolling process, which physically blocks the corrosive medium and helps to alleviate the problem of easy corrosion of the weld strip in related technologies. At the same time, the symmetrical structure of the upper and lower copper layers in the embodiments of this application helps to achieve stress balance and suppress the situation of seal failure. The preparation process of this application is simple and helps to reduce the preparation cost. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 A schematic flowchart of a method for preparing a composite solder strip according to an embodiment of this application is shown.

[0037] Figure 2 A schematic diagram of a composite weld strip cross-sectional structure provided in an embodiment of this application is shown;

[0038] Figure 3 A schematic diagram of a composite welding strip assembly structure according to an embodiment of this application is shown;

[0039] Figure 4 A schematic flowchart of another solder strip preparation process according to an embodiment of this application is shown. Detailed Implementation

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0042] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0043] Photovoltaic solder ribbons are the core conductors in photovoltaic modules, connecting cells in series and conducting current. The high cost of pure copper solder ribbons has driven the industry towards copper-clad aluminum (CCA) composite materials. However, while improved CCA solder ribbons achieve high performance and low cost, their long-term reliability still faces significant challenges.

[0044] The relevant technologies are mainly optimized in two directions, but both have inherent limitations:

[0045] Materials and Interface Strengthening Approach: This approach focuses on improving the copper-aluminum interface itself through materials science methods. One example employs complex processes such as aluminum core microalloying (adding Zr and Sc), introducing a nano-scale zinc (Zn) interlayer, and ultrasonic-assisted rolling to suppress the formation of brittle intermetallic compounds (IMCs). While this approach improves initial bonding strength and processing yield, it is essentially a "passive defense" strategy. It attempts to "strengthen" the copper-aluminum interface to delay failure, but it doesn't change the fact that the aluminum core can still be exposed to humid air through gaps or microscopic defects in the coating. Once moisture intrudes, electrochemical corrosion will still occur. Furthermore, the complex alloying, nano-coating, and precise online process control significantly increase manufacturing costs and technical barriers, weakening the cost advantage of the copper-clad aluminum approach.

[0046] Macroscopic mechanical structure approach: This approach aims to improve mechanical bonding by altering the interface geometry. For example, increasing the copper-aluminum contact area through "embedded" designs such as slots and tenons. While these methods can improve initial peel strength to some extent, they increase process complexity. More importantly, mechanically interlocking structures typically cannot achieve complete sealing of the aluminum core; the interlocking gaps themselves can become rapid channels for corrosive media penetration, failing to address the fundamental issue of long-term weather resistance.

[0047] The problems with the above solutions are as follows: Neither of the two technologies addresses a fundamental design flaw in traditional copper-clad aluminum structures: asymmetry and incomplete sealing. In most structures (such as single-sided copper cladding or circular cross-sections), the aluminum core is exposed or only loosely clad, forming a corrosion galvanic cell in humid and hot environments (copper +0.337V, aluminum -1.662V). Furthermore, asymmetric structures exhibit problems during thermal cycling (-40℃ to 85℃) due to the mismatch in thermal expansion coefficients between copper and aluminum (copper approximately 17 × 10⁻⁶). -6 / ℃, aluminum approximately 23×10 -6 The uneven stress generated by the temperature ( / ℃) accelerates the fatigue delamination of the interface.

[0048] This application stems from a re-examination of fundamental problems in the field of copper-aluminum composite materials, integrating structural mechanics and encapsulation technology. It is understandable that for electrochemical corrosion, the most thorough solution is not "passively reinforcing the interface," but rather "actively eliminating corrosion conditions." Simultaneously, symmetrical structures can counteract internal stress and prevent deformation. Therefore, this invention abandons the path of incremental improvements within traditional frameworks, starting with macroscopic structural design to propose a symmetrical, fully sealed composite structure. This solution does not rely on expensive microalloying materials and nano-coatings, aiming to simultaneously solve the problems of corrosion and thermal fatigue from a physical perspective through a simple, efficient, and reliable structural design, achieving the optimal balance between cost and reliability.

[0049] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0050] Figure 1 This is a schematic flowchart of a method for preparing a composite solder strip according to an embodiment of this application. The method for preparing the composite solder strip includes:

[0051] Step S100: The first copper strip, the conductive metal strip, and the second copper strip are stacked sequentially to form a symmetrical stack; wherein the first copper strip, the conductive metal strip, and the second copper strip all extend along the first direction, and the width of the first copper strip and the second copper strip along the second direction is greater than the width of the conductive metal strip along the second direction, and the first direction and the second direction intersect.

[0052] Step S200: The symmetrical stacked billets are fed into a hot rolling mill so that some of the metal from the first copper strip and the second copper strip flows to the side of the conductive metal strip to form a first weld strip with a fully sealed structure; wherein, the side is the area on the conductive metal strip in the stacked state that does not contact the first copper strip and the second copper strip.

[0053] In step S300, the first welding strip is fed into a cold rolling mill to form a composite welding strip.

[0054] In this application, the conductive metal strip can be made of aluminum. The solder strip is prepared using symmetrical stacking, where the first copper strip, the conductive metal strip, and the second copper strip can be placed centered to facilitate the subsequent formation of a fully sealed structure. The first direction is as follows: Figure 2 The middle direction is shown as X, and the second direction is as follows. Figure 3 The central direction is shown as Y, and the second direction is shown as Z. In some embodiments, as... Figure 3 The schematic diagram of the billet assembly stage shows that the width of the first copper strip 201 is greater than the width of the conductive metal strip 202. The widths of the first copper strip and the second copper strip 203 are the same, or the width difference between the first copper strip and the second copper strip is within a preset width difference range, so that the position of the subsequently generated weld strip corresponds to the intermetallic compound of the sealing layer, maintaining the symmetrical structure of the weld strip. The upper and lower first copper strips and the second copper strip each extend beyond the edge of the conductive metal strip, forming a margin in width. The margin of the copper strip can laterally cover the two side boundaries of the conductive metal strip in the subsequent hot rolling process, providing a structural basis for the subsequent side covering (i.e., sealing layer). The hot rolling mill is used for hot rolling composite to form a fully sealed structure. Part of the metal in the first copper strip and the second copper strip includes the metal in the areas of the first copper strip and the second copper strip that do not correspond to the conductive metal strip, that is, the part of the first copper strip that is wider than the width of the conductive metal strip. The side of the conductive metal strip is the surface of the conductive metal strip that is arranged opposite to it along the second direction. In another embodiment, the side is the surface area of ​​the conductive metal strip that does not contact the first copper strip and the second copper strip. It should be noted that... Figure 2 The cross-sectional shape of the solder strip shown is flat, which is an example only. This application does not limit the specific shape of the solder strip cross-section. For example, in some other embodiments, the cross-sectional shape of the solder strip can be designed as circular.

[0055] It is understood that in this application, the conductive metal strips of the symmetrically stacked blanks are located in the middle position, with the first copper strip and the second copper strip placed on the upper and lower surfaces of the conductive metal strip, respectively. The three strips maintain their corresponding positions and are not offset during stacking, thus forming an original composite structure with a mirror-symmetric relationship in a third direction. This stacking method, combined with the subsequent integrated hot and cold rolling process, ensures that the physical positional relationship between the upper and lower copper strips and the conductive metal strip is stably maintained, achieving structural symmetry.

[0056] This application forms a continuous, gapless, fully sealed structure by covering the side of the conductive metal strip. This structure completely blocks the contact path between the humid and hot environment and the side of the conductive metal strip, effectively avoiding electrochemical corrosion and thermal fatigue delamination caused by the exposure of the aluminum core. At the same time, through symmetrical structural design and hot-cold composite rolling process, the overall structural stability and conductivity of the welding strip are ensured, ultimately achieving long-term reliable operation of the copper-aluminum composite welding strip under high humidity and heat and multiple thermal cycles.

[0057] Optionally, the symmetrically stacked billets are fed into a hot rolling mill so that a portion of the metal from the first and second copper strips flows to the side of the conductive metal strip, forming a first weld strip with a fully sealed structure, including:

[0058] The symmetrical stacked billets are fed into a hot rolling mill, and a preset total reduction rate is applied in a single pass to form a sealing layer on the side of the conductive metal strip, a first copper layer on the upper surface, and a second copper layer on the lower surface, thus obtaining a first weld strip; wherein, the ratio of the width of the sealing layer along the second direction to the total thickness of the composite weld strip along the third direction is greater than or equal to a first value, the preset total reduction rate is 60%-70%, and the third direction intersects with the first direction.

[0059] like Figure 2 The cross-sectional structure of the weld strip shown has an upper and lower surface of the conductive metal strip that are oppositely arranged along a third direction. In this application, the side surface includes two surface areas; therefore, the sealing layer in this application includes two segments: a first sealing sub-layer and a second sealing sub-layer. In the embodiments of this application, the first copper layer 101, the first sealing sub-layer 106, the second copper layer 103, and the second sealing sub-layer 107 are interconnected and sealed on the surface of the conductive metal strip 102. It can be understood that a single pass refers to the process in which the rolled material passes through a pair of rotating rolls once, resulting in plastic deformation. The percentage reduction in thickness is calculated as: (thickness before rolling - thickness after rolling) / thickness before rolling × 100%. In hot rolling, the reduction per pass can usually be designed to be a large value (because the metal is soft), promoting metal flow to form a fully sealed structure; while in cold rolling, because the material has hardened, the reduction per pass is usually small, requiring multi-pass rolling combined with intermediate annealing to achieve the target thickness of the weld strip. This application utilizes an integrated cold-rolling and hot-rolling process to achieve symmetrical and fully sealed weld strip structures, effectively suppressing the risks of electrochemical corrosion and thermal fatigue delamination, thus providing dual protection for structural integrity and environmental durability. The first numerical value in this application can be 0.08.

[0060] Optionally, the first weld strip is fed into a cold rolling mill to form a composite weld strip, comprising:

[0061] The first weld strip is fed into a cold rolling mill, and a preset reduction rate is applied in a single pass to adjust the thickness of the first weld strip, thereby obtaining a composite weld strip; wherein, the preset reduction rate is 15%-20%.

[0062] In this embodiment, the first weld strip with a fully sealed structure formed by hot rolling is fed into a cold rolling mill, and a preset reduction rate of 15%-20% is applied in a single pass of the cold rolling mill. By precisely controlling the deformation amount, the thickness of the weld strip is stably adjusted and the surface roughness is controllably optimized. This helps to ensure that the fully sealed structure between the copper strip and the conductive metal strip remains intact during plastic deformation, thereby effectively improving the dimensional accuracy, surface finish and electrical connection consistency of the composite weld strip.

[0063] Optionally, before feeding the symmetrically stacked billets into a hot rolling mill to allow a portion of the metal from the first and second copper strips to flow to the side of the conductive metal strip to form the first weld strip of the fully sealed structure, the method further includes:

[0064] In a protective gas environment, the symmetrical stacked billets are heated to a first temperature, which is 410℃-450℃.

[0065] In this embodiment, the protective gas can be an inert gas. By heating the symmetrical stacked billet, which is formed by sequentially stacking the first copper strip, the conductive metal strip, and the second copper strip, to a specific temperature range of 410°C-450°C in the protective gas environment, the formation of a dense oxide film due to oxidation at the copper-aluminum interface during the heating process is effectively suppressed. This ensures that the metal surface remains clean and active before hot rolling, thereby enabling the metal of the first and second copper strips to flow fully and atomically bond to the side area of ​​the conductive metal strip during the subsequent hot rolling process, achieving a fully sealed encapsulation of the aluminum core.

[0066] Optionally, after feeding the first welding strip into the cold rolling mill, the method further includes:

[0067] A tin layer with a first thickness is plated on the surface of the first solder strip; wherein the first thickness is 5-15 μm.

[0068] In this embodiment, after the first solder strip is hot-rolled to form a fully sealed structure, it is fed into a cold rolling mill to complete the deformation process. Then, a tin layer with a thickness of 5-15μm is plated on its surface to make the tin layer uniformly cover the entire surface of the solder strip. By utilizing the excellent anti-oxidation properties of tin and the good wettability between tin and silver paste, the contact between the copper and conductive metal strip exposed interface and the humid and hot environment is effectively isolated, avoiding the problem of reduced solderability caused by surface oxidation before welding. At the same time, by precisely controlling the thickness of the tin layer in the range of 5-15μm, sufficient protection and welding wetting ability are ensured, while avoiding thermal expansion mismatch or excessive diffusion during welding caused by an excessively thick tin layer, which affects the conductivity.

[0069] Optionally, after feeding the symmetrically stacked billets into the hot rolling mill, the method further includes:

[0070] At a first temperature, atoms at the first interface and the second interface are interdiffused to form an interface bonding layer; wherein, the first interface is the interface between the first copper layer and the conductive metal strip, and the second interface is the interface between the second copper layer and the conductive metal strip.

[0071] The first ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip is adjusted to be within a preset range; wherein, the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer, as well as the total thickness, are all thicknesses along a third direction, which intersects with the first direction, and the preset range is 0.15-0.25.

[0072] In this application, the material of the sealing layer is the same as that of the first copper layer and the second copper layer. Therefore, the first interface in this application also includes the interface between the sealing layer and the conductive metal strip. The interface bonding layer 104 is a layer of intermetallic interface surrounding the surface of the conductive metal strip, such as... Figure 2 As shown, the tin layer 105 is disposed on the outer surface.

[0073] Optionally, adjusting the first ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip to be within a preset range includes:

[0074] The first thickness of the first copper strip and the second copper strip along the third direction is determined, and the second ratio of the first thickness to the second thickness of the conductive metal strip is adjusted to be within a preset ratio range; wherein, the preset ratio range is 1 / 5-1 / 3, and the second thickness is the thickness along the third direction;

[0075] Alternatively, adjust the preset total reduction rate of the hot rolling mill;

[0076] Alternatively, adjust the preset reduction rate of the cold rolling mill;

[0077] Alternatively, the width difference between the first copper strip and the conductive metal strip along the second direction can be adjusted.

[0078] In this application, the first thickness sum is the original thickness sum of the copper strip. This application can adjust the first ratio of the final first weld strip by adjusting the original thickness relationship between the copper strip and the conductive metal strip. In other embodiments, this application can also adjust the first ratio of the generated first weld strip by adjusting the preset total reduction rate of the hot rolling mill or the preset reduction rate of the cold rolling mill. In other embodiments, this application can also adjust the width difference between the first copper strip and the conductive metal strip to adjust the first ratio of the generated first weld strip. Of course, the width difference between the second copper strip and the conductive metal strip along the second direction can also be adjusted to adjust the first ratio to be within a preset range. That is, the method of adjusting the first ratio provided by this application includes: adjusting the original thickness ratio of the first copper strip, the second copper strip and the conductive metal strip; adjusting the preset total reduction rate applied in the hot rolling process, the preset total reduction rate being 60%~70%; adjusting the preset reduction rate applied in the cold rolling process, the preset reduction rate being 15%~20%; and adjusting the width difference between the first copper strip, the second copper strip and the conductive metal strip. Those skilled in the art can select one or more of the above methods according to actual needs, and adjust the first ratio so that the first ratio is within a preset range.

[0079] Optionally, adjusting the preset total reduction rate of the hot rolling mill includes:

[0080] When the preset total reduction rate of the hot rolling mill is the first reduction rate, if the first ratio of the first weld strip obtained is less than the first preset value, the preset total reduction rate of the hot rolling mill is adjusted to the second reduction rate; wherein the second reduction rate is greater than the first reduction rate;

[0081] Adjusting the width difference between the first copper strip and the conductive metal strip along the second direction includes:

[0082] If the width difference is a first difference value, and the first ratio of the first solder strip is less than a first preset value, the width difference is adjusted to a second difference value; wherein the second difference value is less than the first difference value.

[0083] For the adjustment of the hot rolling mill, when the first ratio of the first weld strip obtained after passing through the hot rolling mill is too small, the preset total reduction rate of the hot rolling mill needs to be increased. For the cold rolling mill, the same reduction rate adjustment strategy as the hot rolling mill is adopted. For the initial width difference between the first copper strip and the conductive metal strip, if the first ratio is too small, the width difference is reduced to the second difference. In this application, the first preset value is related to the left endpoint value of the preset interval, that is, the first preset value can be 0.15, 0.14, or 0.16. This application does not limit the specific value of the first preset value.

[0084] In this embodiment, a stacked blank is formed by symmetrically stacking a first copper strip, a conductive metal strip, and a second copper strip. During hot rolling, some metal from the copper strips on both sides flows to the side of the conductive metal strip, forming a fully sealed structure that effectively isolates the aluminum core from the humid and hot environment. Subsequently, at a first temperature, atomic-level interdiffusion occurs between the first and second interfaces, forming a continuous and dense interface bonding layer, achieving metallurgical bonding between the copper layer and the conductive metal strip. Furthermore, by precisely controlling the ratio of the sum of the thickness of the first copper layer, the thickness of the interface bonding layer, and the thickness of the second copper layer to the total thickness of the composite weld strip within a preset range of 0.15-0.25, it is ensured that the interface bonding layer has sufficient bonding strength to resist the risk of delamination caused by thermal cycling and mechanical stress, while avoiding the problems of increased brittleness and decreased conductivity caused by excessively thick bonding layers, thus achieving a balance between conductivity, low cost, and structural stability.

[0085] According to another aspect of this application, a composite solder strip is provided, the composite solder strip comprising: a conductive metal layer;

[0086] A first copper layer on the upper surface of the conductive metal layer, a second copper layer on the lower surface, and a sealing layer on the side are symmetrically sealed; wherein the conductive metal layer, the first copper layer, the second copper layer, and the sealing layer all extend along a first direction, the side includes two surface regions arranged opposite each other along a second direction, the upper surface and the lower surface are arranged opposite each other along a third direction, and the first direction, the second direction, and the third direction intersect each other.

[0087] Optionally, an interface bonding layer is further provided between the first copper layer and the conductive metal layer, and between the second copper layer and the conductive metal layer;

[0088] The first ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip is within a preset range; wherein, the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer, the third thickness, and the total thickness are all thicknesses along a third direction, which intersects with the first direction, and the preset range is 0.15-0.25.

[0089] Optionally, a tin layer is further provided on the surface of the first copper layer away from the conductive metal layer, the surface of the second copper layer away from the conductive metal layer, and the surface of the sealing layer away from the conductive metal layer, with the thickness of the tin layer being 5-15 μm.

[0090] To achieve the above objectives, according to another aspect of this application, a photovoltaic module is provided in which the cells are interconnected by composite solder strips as described above.

[0091] To enable those skilled in the art to better understand the technical solution of this application, the implementation process of the composite solder strip preparation method of this application will be described in detail below with reference to specific embodiments.

[0092] This invention aims to fundamentally address the long-term weather resistance issues caused by structural defects in existing copper-clad aluminum solder strips, particularly electrochemical corrosion under humid and hot environments and thermomechanical fatigue failure under temperature cycling. It provides a photovoltaic composite solder strip with a simple structure, controllable manufacturing process, superior cost, and ultra-high reliability and excellent electrical performance.

[0093] To achieve the above objectives, the present invention employs the following core methods in combination:

[0094] Symmetrical fully sealed "sandwich" structure: A creatively designed strictly symmetrical composite structure of "upper copper layer - aluminum core - lower copper layer". Its core feature is that, through precision plastic processing, it ensures that the upper and lower copper layers not only cover the aluminum core in the vertical direction, but also achieve metallurgical bonding and complete closure on both sides of the solder strip, thereby completely sealing the aluminum core in a continuous copper shell, achieving 360-degree no exposure.

[0095] The coordinated design of functional layer thickness and width: The total thickness of the copper layers on both sides is precisely controlled to be 15%-25% of the total thickness of the solder strip to balance conductivity and cost. More importantly, during billet assembly, the initial width of the upper and lower copper strips is made greater than the initial width of the aluminum strip. This design ensures that during rolling, the excess copper material can flow laterally fully, completely wrapping the sides of the aluminum core and forming a tight seal.

[0096] Highly efficient integrated solid-state composite process: Utilizing large-deformation hot rolling composite as the core process. Under specific temperature and pressure conditions, atomic diffusion (forming a metallurgical bond) at the copper-aluminum interface and side sealing are simultaneously achieved in a single or double pass, resulting in an extremely simple and efficient process path.

[0097] The effects achieved by this application include:

[0098] Effect 1: Extremely high long-term environmental reliability. The fully sealed structure physically and completely blocks any path for corrosive media such as water and oxygen to contact the aluminum core, eliminating the basis for electrochemical corrosion. The symmetrical structure allows the stress generated by the difference in thermal expansion to self-balance at the upper and lower interfaces, greatly suppressing the initiation of unilateral warping, delamination, and fatigue cracks. Its protection mechanism is upgraded from "passive resistance" to "active isolation".

[0099] Effect 2: Excellent electrical and soldering performance. The optimized copper layer thickness creates low-resistance parallel conductive channels parallel to the aluminum core. Because the aluminum core is perfectly protected, its bulk resistance does not deteriorate during long-term use, resulting in extremely high overall stability of the solder strip resistance. The outer pure copper layer provides ideal solderability with battery silver paste.

[0100] Effect 3: Significant cost and process advantages. This structural design does not rely on microalloying such as Al-Zr-Sc or nano-Zn coatings; the core functions can be achieved using conventional 1060 aluminum and T2 oxygen-free copper. The one-piece hot rolling process replaces the complex processes of multi-step coating, laser welding, ultrasonic rolling, and triggered annealing, resulting in a shorter production process, lower energy consumption and equipment investment, easier yield control, and strong overall cost competitiveness.

[0101] like Figure 2 As shown, the main body of the solder strip has a three-layer composite structure: an upper copper layer (first copper layer), an aluminum core layer (conductive metal layer / strip), and a lower copper layer (second copper layer). The upper and lower copper layers are completely closed at the side fusion zone, forming a continuous copper sealing edge. The aluminum core layer is completely encapsulated with no exposed surface. The interface bonding zone / layer is a dense metallurgical bonding layer. Figure 3 This diagram illustrates the design of raw material width during the billet assembly stage. It clearly shows that to achieve side sealing, the initial width of the copper strip must be greater than the initial width of the aluminum strip during billet assembly. Figure 4 This is a process flow diagram of the preparation method of the present invention.

[0102] This invention is prepared using an integrated process of "continuous hot rolling composite - cold rolling finishing", the process is as follows: Figure 4 As shown, the core steps are as follows:

[0103] ① Raw material preparation and surface treatment: Prepare annealed 1060 pure aluminum strip and T2 oxygen-free copper strip respectively. Degrease and alkaline wash the mating surfaces, and use "mechanical grinding with wire brush + non-electrolytic pickling" for online activation to completely remove the oxide film.

[0104] ② Symmetrical stacking: The strips are precisely stacked in the order of "wide copper strip - narrow aluminum strip - wide copper strip" to form symmetrical stacked blanks. This step is the structural basis for achieving side sealing.

[0105] ③ Protective heating: Under a nitrogen protective atmosphere, the stacked billets are rapidly heated to 410℃-450℃.

[0106] ④ Hot Rolling Composite and Sealing (Core Step): The heated billet is fed into a four-roll precision hot rolling mill, where a total reduction of 60%-70% is applied in a single pass. Under the action of high temperature, high pressure and large shear strain, the following are simultaneously achieved: a) interdiffusion of atoms at the copper-aluminum interface to form a metallurgical bond; b) a relatively wide copper layer of metal flows laterally, converging and welding on the side of the aluminum core to form a fully sealed structure.

[0107] ⑤ Online quenching and cold rolling finishing: The composite strip is immediately water-cooled after rolling. Then, it undergoes a cold rolling pass with a reduction rate of 15%-20% to precisely control the final thickness, improve dimensional accuracy and surface finish.

[0108] ⑥ Surface tin plating and slitting: The composite strip is continuously electroplated with tin (tin layer thickness 5-15μm), and finally slitted to the target length (e.g. 2.0mm) and wound up.

[0109] The following experiments illustrate the effectiveness of the solder strip of this application. Using the above parameters and processes, the solder strip of the present invention (Example S) was prepared and compared with a traditional copper-clad aluminum solder strip (Comparative Example C1) and a sample with a simulated material optimization route (Comparative Example C2). The results are shown in Table 1.

[0110] Table 1

[0111]

[0112] Data Analysis: Electrical Performance: Due to the formation of parallel low-resistivity pathways, the present invention exhibits the lowest initial resistivity, superior to the comparative example C2 which uses complex materials. Reliability: In dual 85°C damp heat aging and salt spray tests, the present invention demonstrates a comprehensive and significant lead. The extremely low resistivity change rate (+2.5%) and extremely high peel strength retention rate (95%) directly prove the superior effect of the "fully sealed" structure in eradicating corrosion. The excellent stability after thermal cycling confirms the effectiveness of the symmetrical structure in resisting thermal fatigue. Cost: While achieving top-tier long-term reliability, the present invention's overall manufacturing cost is far lower than that of C2, which relies on special materials and complex processes, making it highly competitive in terms of cost-effectiveness.

[0113] In some embodiments, the welding strip provided in this application includes an aluminum or aluminum alloy core layer, and copper or copper alloy layers symmetrically bonded to the upper and lower surfaces of the core layer via metallurgical bonding; the upper and lower copper or copper alloy layers are fused along both sides of the core layer to form a continuous sealing edge, so that the aluminum core layer is completely covered and sealed without any exposed surface. The total thickness of the upper and lower copper or copper alloy layers accounts for 15%-25% of the total thickness of the composite welding strip (i.e., a preset range). The width of the sealing edge is not less than 8% of the total thickness of the composite welding strip (i.e., a first value).

[0114] The adjustment of the first ratio in this application can be achieved through the coordinated control of multiple process parameters. The basic principle is as follows:

[0115] ① Copper and aluminum have different resistance to deformation at high temperatures: aluminum is softer and has a greater elongation. The aluminum layer is thinned more during hot rolling with large deformation, thus relatively increasing the proportion of copper layer thickness.

[0116] ②The cold rolling stage mainly plays a role in dimensional finishing, and can also make minor adjustments to the thickness ratio (usually within 1% to 3%).

[0117] ③ By rationally designing the original billet size and rolling process parameters, the final copper layer thickness ratio can be precisely controlled within the target range of 15% to 25%.

[0118] Those skilled in the art can adjust the first ratio by one or a combination of the following methods.

[0119] ①Method 1: Control the thickness ratio of the original copper strip to the aluminum strip through design.

[0120] During the billet assembly stage, the ratio of the thickness of the first and second copper strips to the thickness of the conductive metal strip (aluminum strip) is directly set. Based on the principle of constant volume before and after rolling and the coordination relationship between copper and aluminum deformation, the required original thickness ratio can be determined through theoretical calculation or finite element simulation, so that after 60%~70% hot rolling and 15%~20% cold rolling, the total thickness of the copper layer falls within the range of 15%~25%.

[0121] Example parameters: When the target copper layer thickness accounts for 20%, if the final total solder strip thickness is 0.20mm, then the total copper layer thickness is 0.04mm (approximately 0.02mm at the top and bottom). Experiments have verified that the above target can be achieved with an original copper strip thickness to aluminum strip thickness ratio between 1:5 and 1:3 (adjusted slightly based on the reduction rate).

[0122] Method 2: Dynamic control is achieved through online adjustment of the total hot rolling reduction rate.

[0123] In the hot rolling process, when the total reduction rate per pass varies within the range of 60% to 70%, it will have a significant impact on the proportion of copper layer thickness. The higher the total reduction rate, the more obvious the thinning of the aluminum layer and the higher the proportion of copper layer thickness.

[0124] Specific implementation method: Equip the hot rolling mill with an online thickness monitoring device to measure the total thickness and the thickness of each layer of the first weld strip after hot rolling in real time. If the measured copper layer thickness ratio is too low (e.g., below 15%), the total reduction rate can be increased from 65% to 68%~70%; if it is too high (e.g., above 25%), the total reduction rate can be reduced to 60%~62%. Through closed-loop feedback control, ensure that the copper layer thickness ratio of the first weld strip after hot rolling is within the target range (e.g., 17%~23%), leaving room for fine-tuning in subsequent cold rolling.

[0125] ③Method 3: Compensation adjustment through cold rolling reduction rate.

[0126] When the first weld strip after hot rolling enters the cold rolling mill, a cold rolling reduction rate of 15% to 20% is applied. The cold rolling stage will also cause a slight change in the copper layer thickness ratio (usually within 1% to 3%). When the copper layer thickness ratio after hot rolling is close to but slightly exceeds the 15% to 25% boundary, it can be corrected by appropriately increasing or decreasing the cold rolling reduction rate.

[0127] Specific procedures: If the copper layer thickness after hot rolling accounts for 24.5% (close to the upper limit), a smaller cold rolling reduction rate (e.g., 12%) can be used to reduce the final percentage to below 24%. If the copper layer thickness after hot rolling accounts for 15.8% (close to the lower limit), a larger cold rolling reduction rate (e.g., 20%) can be used to increase the final percentage to 16%~17%.

[0128] ④ Method 4: Indirect control through the width difference design between copper strip and aluminum strip.

[0129] In this application, the copper strip width is greater than that of the conductive metal strip / aluminum strip (WCu > WAl). During hot rolling, a portion of the excess copper flows laterally to form a side sealing layer, while the remainder contributes to the copper layer thickness on both the upper and lower surfaces. By adjusting the width difference (e.g., 0.1 mm to 2.0 mm), the distribution ratio of copper to the side sealing layer can be controlled, thereby indirectly affecting the proportion of copper layer thickness.

[0130] Example: When it is necessary to increase the percentage of copper layer thickness, the width difference can be appropriately reduced (so that more copper material is retained on the upper and lower surfaces). When it is necessary to reduce the percentage of copper layer thickness, the width difference can be increased (so that more copper material flows to the side sealing layer).

[0131] ⑤ Method 5: Multi-pass hot rolling or cold rolling + intermediate annealing.

[0132] In some embodiments, composite weld strips can be prepared using a single-pass hot rolling followed by a single-pass cold rolling process. However, in other embodiments, multi-pass rolling can be employed: Multi-pass hot rolling: The total reduction rate is applied gradually in 2-3 passes, with the copper layer thickness ratio measured after each pass and the reduction parameters for the next pass adjusted. Multi-pass cold rolling + intermediate annealing: The cold rolling stage is performed in 2 passes, with a reduction rate of 5%-10% per pass. Short-term annealing at 400°C-450°C is performed between passes to eliminate work hardening. The final thickness ratio is finely adjusted through cumulative deformation.

[0133] The following table compares and analyzes the adjustment parameters of the five methods described above through specific examples. As shown in Table 2, it can be seen that by adjusting the original thickness ratio, width difference, hot rolling reduction rate, and cold rolling reduction rate, the final copper layer thickness ratio can be flexibly controlled within the target range of 15% to 25%. Examples 1 to 5 all fall within the preset range of this application, while Comparative Examples 1 and 2 exceed the range due to improper parameter selection.

[0134] Table 2

[0135]

[0136] The method for preparing composite solder strip according to the embodiments of this application includes the following steps: providing a copper strip with a width of WCu and an aluminum strip with a width of WAl, wherein WCu>WAl; cleaning and activating the bonding surface, and symmetrically assembling the strip in the order of copper-aluminum-copper; heating to 410℃-450℃ under a protective atmosphere and hot rolling, with a total reduction rate of 60%-70%, to achieve interface metallurgical bonding and side sealing in one step; and then performing cold rolling finishing and surface tin plating.

[0137] It should be noted that the above are merely illustrative examples and do not specifically limit the methods, steps, or execution logic provided in this application.

[0138] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0139] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0140] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0141] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0142] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0143] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0144] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0145] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a composite solder strip, characterized in that, The method for preparing the composite solder strip includes: A first copper strip, a conductive metal strip, and a second copper strip are sequentially stacked to form a symmetrical stack; wherein the first copper strip, the conductive metal strip, and the second copper strip all extend along a first direction, and the widths of the first copper strip and the second copper strip along a second direction are both greater than the width of the conductive metal strip along the second direction, and the first direction and the second direction intersect. The symmetrical stacked billets are fed into a hot rolling mill so that a portion of the metal from the first copper strip and the second copper strip flows to the side of the conductive metal strip, forming a first weld strip with a fully sealed structure; wherein, the side is the area on the conductive metal strip in the stacked state that does not contact the first copper strip and the second copper strip; The first welding strip is fed into a cold rolling mill to form a composite welding strip.

2. The method for preparing the composite solder strip according to claim 1, characterized in that, The step of feeding the symmetrical stacked billets into a hot rolling mill to allow a portion of the metal from the first and second copper strips to flow to the side of the conductive metal strip, forming a first weld strip with a fully sealed structure, includes: The symmetrical stacked billets are fed into a hot rolling mill, and a preset total reduction rate is applied in a single pass to form a sealing layer on the side of the conductive metal strip, a first copper layer on the upper surface, and a second copper layer on the lower surface, thereby obtaining the first weld strip; wherein, the ratio of the width of the sealing layer along the second direction to the total thickness of the composite weld strip along the third direction is greater than or equal to a first value, the preset total reduction rate is 60%-70%, and the third direction intersects with the first direction.

3. The method for preparing the composite solder strip according to claim 1, characterized in that, The step of feeding the first welding strip into a cold rolling mill to form a composite welding strip includes: The first welding strip is fed into a cold rolling mill, and a preset reduction rate is applied in a single pass to adjust the thickness of the first welding strip, thereby obtaining a composite welding strip; wherein the preset reduction rate is 15%-20%.

4. The method for preparing the composite solder strip according to claim 1, characterized in that, Before feeding the symmetrical stacked billets into the hot rolling mill to allow a portion of the metal from the first and second copper strips to flow to the side of the conductive metal strip, forming the first weld strip with a fully sealed structure, the method further includes: In a protective gas environment, the symmetrical stacked blanks are heated to a first temperature; wherein the first temperature is 410℃-450℃.

5. The method for preparing the composite solder strip according to claim 1, characterized in that, After feeding the first welding strip into the cold rolling mill, the method further includes: A tin layer with a thickness of a first thickness is plated on the surface of the first solder strip; wherein the first thickness is 5-15 μm.

6. The method for preparing the composite welding strip according to claim 2, characterized in that, After feeding the symmetrical stacked billets into the hot rolling mill, the method further includes: At a first temperature, atoms at the first interface and the second interface are interdiffused to form an interface bonding layer; wherein, the first interface is the interface between the first copper layer and the conductive metal strip, and the second interface is the interface between the second copper layer and the conductive metal strip. The first ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip is adjusted to be within a preset range; wherein the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer, as well as the total thickness, are all thicknesses along the third direction, which intersects with the first direction, and the preset range is 0.15-0.

25.

7. The method for preparing the composite solder strip according to claim 6, characterized in that, The adjustment of the first ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip to be within a preset range includes: The first thickness of the first copper strip and the second copper strip along the third direction is determined, and the second ratio of the first thickness to the second thickness of the conductive metal strip is adjusted to be within a preset ratio range; wherein, the preset ratio range is 1 / 5-1 / 3, and the second thickness is the thickness along the third direction; Alternatively, adjust the preset total reduction rate of the hot rolling mill; Alternatively, adjust the preset reduction rate of the cold rolling mill; Alternatively, the width difference between the first copper strip and the conductive metal strip along the second direction can be adjusted.

8. The method for preparing the composite solder strip according to claim 7, characterized in that, The adjustment of the preset total reduction rate of the hot rolling mill includes: When the preset total reduction rate of the hot rolling mill is the first reduction rate, if the first ratio of the first weld strip obtained is less than the first preset value, the preset total reduction rate of the hot rolling mill is adjusted to the second reduction rate; wherein the second reduction rate is greater than the first reduction rate; Adjusting the width difference between the first copper strip and the conductive metal strip along the second direction includes: If the width difference is a first difference value, and the first ratio of the first solder strip is less than a first preset value, the width difference is adjusted to a second difference value; wherein the second difference value is less than the first difference value.

9. A composite welding strip, characterized in that, The composite welding strip includes: a conductive metal layer; A first copper layer on the upper surface, a second copper layer on the lower surface, and a sealing layer on the side are symmetrically sealed on the conductive metal layer; wherein the conductive metal layer, the first copper layer, the second copper layer, and the sealing layer all extend along a first direction, the side includes two surface regions arranged opposite each other along a second direction, the upper surface and the lower surface are arranged opposite each other along a third direction, and the first direction, the second direction, and the third direction intersect each other.

10. The composite welding strip according to claim 9, characterized in that, An interface bonding layer is further provided between the first copper layer and the conductive metal layer, and between the second copper layer and the conductive metal layer; The first ratio of the sum of the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer to the total thickness of the composite solder strip is within a preset range; wherein, the thicknesses of the first copper layer, the interface bonding layer, and the second copper layer, as well as the total thickness, are all thicknesses along the third direction, which intersects with the first direction, and the preset range is 0.15-0.

25.

11. The composite welding strip according to claim 9, characterized in that, A tin layer is further provided on the surface of the first copper layer away from the conductive metal layer, the surface of the second copper layer away from the conductive metal layer, and the surface of the sealing layer away from the conductive metal layer, and the thickness of the tin layer is 5-15 μm.

12. A photovoltaic module, characterized in that, The photovoltaic module interconnects the cells using composite solder strips as described in any one of claims 9 to 11.

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