Solder strip, photovoltaic module and soldering method for back contact cells

Abstract

This application relates to the field of photovoltaic module manufacturing technology, and more particularly to a welding method for a solder ribbon, a photovoltaic module, and a back contact cell. The solder ribbon provided in this application includes, from the inside out, a conductor base strip, a low-melting-point alloy layer, and an insulating layer. The insulating layer melts during the welding of the back contact cell to cover the molten low-melting-point alloy layer. After the electrode to be welded on the back contact cell passes through the insulating layer and enters the low-melting-point alloy layer, the insulating layer solidifies to cover the low-melting-point alloy layer and the electrode connected to it, thus providing insulation and preventing short circuits between the positive and negative electrodes due to slight solder ribbon misalignment.

Description

Technical Field

[0001] This application relates to the field of photovoltaic module manufacturing technology, specifically to a welding method for a solder strip, a photovoltaic module, and a back contact cell. Background Technology

[0002] In the photovoltaic industry, back-contact solar cells have alternating positive and negative electrodes on their back side, with a spacing of only 0.5mm-2mm between them. To achieve electrode connection in back-contact solar cells, welding is required.

[0003] The solder strip consists of a conductor base strip and a low-melting-point alloy coating the conductor base strip. However, because the distance between the positive and negative electrodes of the back contact cell is extremely small, and the solder strip is a conductor from the inside out, misalignment of the solder strip during welding can easily lead to a short circuit between the positive and negative electrodes. Summary of the Invention

[0004] This application provides a solder strip with an insulating layer on its outer surface. After the electrode to be soldered to the back contact cell enters the low-melting-point alloy layer through the insulating layer, it solidifies to cover the low-melting-point alloy layer and the electrode connected to the low-melting-point alloy layer, thus playing an insulating role and avoiding the problem of short circuit between the positive and negative electrodes after slight displacement of the solder strip.

[0005] In a first aspect, this application provides a solder strip, comprising:

[0006] Conductor baseband;

[0007] A low-melting-point alloy layer is provided, which covers the outer surface of the conductor base strip;

[0008] An insulating layer is provided on the outer surface of the insulating layer covering the low-melting-point alloy layer. The insulating layer is configured to melt to cover the molten low-melting-point alloy layer when welding the back contact cell, and to solidify to cover the low-melting-point alloy layer and the electrode connected to the low-melting-point alloy layer after the electrode to be welded to the back contact cell enters the low-melting-point alloy layer through the insulating layer.

[0009] Optionally, the welding strip provided in this application also includes a thermoplastic adhesive layer, which is disposed on the outer surface of the insulating layer. The thermoplastic adhesive layer is configured to melt when welding the back contact cell to fill the gap between the insulating layer and the back contact cell.

[0010] Optionally, in the solder strip provided in this application, the insulating layer is a polytetrafluoroethylene coating with reflective dispersible particles.

[0011] Optionally, in the solder ribbon provided in this application, the reflectivity of the reflective dispersion particles is ≥90%, and the volume resistivity of the reflective dispersion particles is ≥1×10¹. 4 Ω.cm.

[0012] Optionally, in the solder strip provided in this application, the thickness of the conductor base strip is a, where 100μm≤a≤200μm;

[0013] The thickness of the low-melting-point alloy layer is b, where 10μm≤b≤30μm;

[0014] The thickness of the insulating layer is c, where 5μm≤c≤15μm;

[0015] The thickness of the thermoplastic adhesive layer is d, where 3μm≤d≤10μm.

[0016] Secondly, this application provides a welding method for back contact solar cells, using the welding strip provided above, the method comprising the following steps:

[0017] Align and make contact between the electrode to be welded on the back contact cell and the welding strip;

[0018] The welding strip is heated, and both the low-melting-point alloy layer and the insulating layer of the welding strip melt. The insulating layer covers the low-melting-point alloy layer, and the electrode to be welded, which is in back contact with the battery cell, enters the low-melting-point alloy layer through the insulating layer so that the low-melting-point alloy layer and the electrode to be welded are connected.

[0019] Cool to room temperature to allow the insulating layer and the low-melting-point alloy layer to solidify. The solidified insulating layer covers the low-melting-point alloy layer and the electrode connected to the low-melting-point alloy layer.

[0020] Optionally, in the welding method for back contact solar cells provided in this application, aligning and contacting the electrode to be welded on the back contact solar cell with the solder strip includes:

[0021] The welding strip is placed in the welding strip placement groove on the welding strip positioning plate, and the welding strip is attracted by the welding strip; wherein the depth of the welding strip placement groove is e, and the thickness of the welding strip is h, where 1:3≤e:h≤1:2;

[0022] Orient the electrode to be welded, which is in back contact with the battery cell, toward the welding strip positioning plate, and align the electrode and welding strip using an infrared vision system;

[0023] Move the back contact cell toward the solder strip so that the back contact cell comes into contact with the thermoplastic adhesive layer of the solder strip.

[0024] Optionally, in the welding method for the back contact cell provided in this application, heating the solder strip further includes:

[0025] The thermoplastic adhesive layer of the solder ribbon melts to fill the gap between the insulating layer and the back contact cell.

[0026] Optionally, in the welding method for the back contact cell provided in this application, heating the solder strip includes:

[0027] The solder ribbon is heated by a laser generated by a continuous semiconductor laser. The laser wavelength is 800nm ​​to 1100nm, the laser power is set to 50W to 200W, the laser scanning speed is 50mm / s to 200mm / s, and the laser spot is elliptical. The major axis of the ellipse is aligned with the length of the solder ribbon. The length of the major axis of the ellipse is 1.5 to 2.0 times the length of the solder ribbon, and the length of the minor axis of the ellipse is 0.8 to 1.2 times the width of the solder ribbon.

[0028] Thirdly, this application provides a photovoltaic module, including a back contact cell and the aforementioned solder strip connected to the back contact cell;

[0029] Alternatively, it can be manufactured using the welding method for the back contact battery cells provided above.

[0030] In the welding method of the welding ribbon, photovoltaic module and back contact cell provided in this application, the welding ribbon includes a conductor base strip, a low melting point alloy layer and an insulating layer from the inside to the outside. The insulating layer melts to cover the molten low melting point alloy layer when welding the back contact cell. After the electrode to be welded on the back contact cell enters the low melting point alloy layer through the insulating layer, it solidifies to cover the low melting point alloy layer and the electrode connected to the low melting point alloy layer, which plays an insulating role and can avoid the problem of short circuit between the positive electrode and the negative electrode after the welding ribbon is slightly offset. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] Figure 1 This is a schematic diagram of the structure of the solder strip in this application;

[0033] Figure 2 This is a schematic diagram of the structure of the welding strip positioning plate used in the welding method for the back contact solar cell of this application. Figure 1 ;

[0034] Figure 3 This is a schematic diagram of the structure of the welding strip positioning plate used in the welding method for the back contact solar cell of this application. Figure 2 ;

[0035] Figure 4 This is a schematic diagram of the structure of the welding strip positioning plate used in the welding method for the back contact solar cell of this application. Figure 3 ;

[0036] Figure 5 This is a schematic diagram of the back contact battery cell, solder ribbon, and solder ribbon positioning plate being aligned in the welding method of the back contact battery cell of this application.

[0037] 100 - Solder strip, 110 - Conductor base strip, 120 - Low melting point alloy layer, 130 - Insulation layer, 140 - Thermoplastic adhesive layer;

[0038] 200-Welding strip positioning plate, 210-Positioning plate body, 220-Welding strip placement groove, 230-Adsorption hole, 240-Negative pressure connector, 250-Negative pressure channel;

[0039] 300-back contact battery cell;

[0040] 400-electrode.

[0041] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0042] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0043] In photovoltaic module manufacturing technology, to improve light-receiving efficiency, back-contact solar cells typically have a current-collecting structure located on the back side. This structure includes alternating positive and negative electrodes. Electrodes of the same polarity within the same back-contact solar cell need to be connected in parallel via solder ribbons to collect current. Electrodes of different polarities between adjacent back-contact solar cells need to be connected in series via solder ribbons to form a continuous circuit. Due to the small gap and dense arrangement of the positive and negative electrodes, and the fact that the solder ribbons are conductors from the inside out, misalignment of the solder ribbons during welding can easily lead to a short circuit between the positive and negative electrodes.

[0044] In view of this, this application proposes a welding strip. The welding strip includes a conductor base strip, a low-melting-point alloy layer covering the outer surface of the conductor base strip, and an insulating layer covering the outer surface of the low-melting-point alloy layer. When welding the back contact solar cell, the insulating layer melts and covers the molten low-melting-point alloy layer, providing insulation and protective covering to the welding area before forming a conductive connection. After the electrode to be welded on the back contact solar cell passes through the insulating layer into the low-melting-point alloy layer, the insulating layer solidifies and covers the low-melting-point alloy layer and the electrode connected to it, thereby forming a connection structure that combines internal conductivity and external insulation after welding, avoiding the risk of short circuits.

[0045] This application provides a solder strip 100, such as Figure 1As shown, the assembly includes a conductor base strip 110, a low-melting-point alloy layer 120, and an insulating layer 130. The solder strip 100 also includes the low-melting-point alloy layer 120, which covers the outer surface of the conductor base strip 110. The solder strip 100 also includes an insulating layer 130, which covers the outer surface of the low-melting-point alloy layer 120. The insulating layer 130 is configured to melt and cover the molten low-melting-point alloy layer 120 during the soldering of the back contact cell 300, and to solidify and cover the low-melting-point alloy layer 120 and the electrode 400 connected to the low-melting-point alloy layer 120 after the electrode to be soldered to the back contact cell 300 enters the low-melting-point alloy layer 120 through the insulating layer 130.

[0046] The conductor base strip 110 serves as the primary carrier for current conduction and also as the supporting structure for the entire weld strip 100. The melting point of the conductor base strip 110 is much higher than that of the low-melting-point alloy layer 120. When the low-melting-point alloy layer 120 melts and welds, the conductor base strip 110, acting as a supporting structure, maintains the elongated shape of the weld strip 100. The conductor base strip 110 can be made of metals with high conductivity, such as aluminum or copper.

[0047] The conductor base strip 110 plays a major role in conducting electricity and bearing force in the solder strip 100. It is used to establish a low-resistance current channel between the electrodes 400 to be welded to the back contact cell 300, and to maintain the stability of the overall shape of the solder strip 100 during the welding heating and cooling process, so as to avoid significant bending or collapse of the solder strip 100 during laying, alignment and welding. The conductor base strip 110 is located on the innermost side of the solder strip 100, forming a central load-bearing skeleton. Its outer surface is directly bonded to the low melting point alloy layer 120, and the low melting point alloy layer 120 forms a layered coating relationship with the insulating layer 130, so that the three form a composite structure distributed from the inside to the outside. During welding, they work together to locally cooperate with the electrodes 400 to be welded to the back contact cell 300.

[0048] The low-melting-point alloy layer 120 is a fusible weldable functional layer covering the outer surface of the conductor base strip 110. Also known as a fusible alloy, it refers to a metallic alloy with a melting point below 300°C. The low-melting-point alloy layer 120 is typically composed of a specific ratio of low-melting-point metallic elements such as bismuth (Bi), tin (Sn), lead (Pb), cadmium (Cd), and indium (In). The melting point of the low-melting-point alloy layer 120 is much lower than that of the conductor base strip 110, making it suitable as a welding material.

[0049] When the solder strip 100 is welded to the back contact cell 300, the low-melting-point alloy layer 120 can enter a flowable liquid state when heated, and form wetting, spreading, and metallurgical bonding with the electrode 400 to be welded on the back contact cell 300, thereby establishing a stable electrical connection. At the same time, the interface reconstruction after melting increases the contact area and reduces the contact resistance. The low-melting-point alloy layer 120 is located on the outer periphery of the conductor base strip 110 and the inner side of the insulating layer 130. During the welding process, after the insulating layer 130 softens, melts through, or ruptures due to heat, it directly interacts with the electrode 400, and after cooling, it forms a solid connection interface with the electrode 400, enabling the electrode 400 to be welded and conduct.

[0050] The thickness of the low-melting-point alloy layer 120 is typically 10 μm to 30 μm, which is relatively small compared to the conductor substrate 110. The low-melting-point alloy layer 120 can be formed by electroplating, spraying, hot dipping, rolling lamination, or offset transfer.

[0051] The insulating layer 130 is a functional coating covering the outer surface of the low-melting-point alloy layer 120. When the solder ribbon 100 is slightly offset before welding, it can prevent short circuit between the solder ribbon 100 and the non-target electrode 400. After welding, it solidifies and covers the low-melting-point alloy layer 120 and the electrode 400 connected to the low-melting-point alloy layer 120, so that the low-melting-point alloy layer 120 is conductive inside the welding connection area and the insulating layer 130 is insulating outside the welding connection area, thereby improving the electrical isolation stability of the electrode 400 welding connection area.

[0052] The insulating layer 130 is located outside the low-melting-point alloy layer 120. During the welding process, it is first softened, melted or partially cracked by heat, so that the electrode 400 to be welded can penetrate or contact the low-melting-point alloy layer 120 under the combined action of pressure and heat. After welding is completed, the insulating layer 130 re-solidifies and covers the low-melting-point alloy layer 120 and the electrode 400 connected thereto, thereby forming a continuous insulating protective shell outside the conductive interface.

[0053] The insulating layer 130 can be a polyimide-based insulating coating, a fluorinated polymer coating, or a composite ceramic polymer coating. The insulating layer 130 can be made into a continuous uniform coating, a locally thickened coating, or a functional coating with a micro-textured surface.

[0054] The welding strip provided in this application includes, from the inside out, a conductor base strip 110, a low-melting-point alloy layer 120, and an insulating layer 130. The insulating layer 130 melts during welding of the back contact cell 300 to cover the molten low-melting-point alloy layer 120. After the electrode 400 to be welded on the back contact cell 300 enters the low-melting-point alloy layer 120 through the insulating layer 130, it solidifies to cover the low-melting-point alloy layer 120 and the electrode 400 connected to the low-melting-point alloy layer 120, thus providing insulation and preventing short circuits between the positive and negative electrodes after slight displacement of the welding strip 100.

[0055] In some embodiments, such as Figure 1 As shown, a thermoplastic adhesive layer 140 is also provided on the outer surface of the insulating layer 130. The thermoplastic adhesive layer 140 is configured to melt during the welding of the back contact cell 300 to fill the gap between the insulating layer 130 and the back contact cell 300.

[0056] During welding, as the temperature rises, the thermoplastic adhesive layer 140 softens, temporarily fixing the welding ribbon 100 and facilitating subsequent alignment and positioning of the electrode 400 of the back contact cell 300 with the welding ribbon 100. During the welding process of the welding ribbon 100, the thermoplastic adhesive layer 140 melts upon heating, exhibiting a certain degree of fluidity and wettability, which can fill the gap between the welding ribbon 100 and the electrode 400 of the back contact cell 300. After welding is completed, the thermoplastic adhesive layer 140 cools and solidifies, forming physical anchor points that further enhance the welding strength.

[0057] The thermoplastic adhesive layer 140 can melt first and flow into the micro gap between the insulating layer 130 and the back contact cell 300 when welding the back contact cell 300, so as to improve the adhesion between the welding ribbon 100 and the back of the back contact cell 300, reduce the risk of displacement caused by local suspension, edge lifting and uneven pressure, and provide a stable interface basis for the reliable connection between the subsequent low melting point alloy layer 120 and the electrode 400 to be welded.

[0058] The thermoplastic adhesive layer 140 is disposed on the outermost side of the insulating layer 130, directly facing the back of the back contact cell 300, and forms a coaxial multi-layer covering structure with the insulating layer 130. During welding preheating, hot pressing positioning or local heating, the thermoplastic adhesive layer 140 softens and flows before the inner insulating layer 130, and enters the gap area between the outer surface of the insulating layer 130 and the surface of the back contact cell 300, thereby forming a continuous attachment interface.

[0059] The thermoplastic adhesive layer 140 may be made of thermoplastic polyurethane, or it may be composed of ethylene-vinyl acetate copolymer, polyolefin hot melt material, or modified polyamide hot melt layer. The thermoplastic adhesive layer 140 may be in the form of a continuous film, a micro-array coating, or locally thickened edges.

[0060] Under the action of a heating device, a hot pressing device, or a local welding heat source, the thermoplastic adhesive layer 140 first softens and becomes fluid. It can fill the gaps formed between the insulating layer 130 and the back contact cell 300 due to surface micro-undulations, assembly errors, and warping of the back contact cell 300, thereby forming a more continuous contact interface between the outer surface of the solder ribbon 100 and the back side of the back contact cell 300. As the temperature further increases, the thermoplastic adhesive layer 140 maintains the initial constraint on the position of the solder ribbon 100, works with the insulating layer 130 to suppress the offset and slippage of the solder ribbon 100, and provides more stable support for the conductive connection between the inner low-melting-point alloy layer 120 and the electrode 400. After the welding process is completed and cooled, the thermoplastic adhesive layer 140 re-cures, continuing to cover and lock the outside of the insulating layer 130, thereby reducing interface loosening caused by heat shrinkage, vibration, or subsequent handling processes.

[0061] The thermoplastic adhesive layer 140 not only improves the initial adhesion between the solder ribbon 100 and the back contact cell 300, but also suppresses local warping and displacement during the welding process, reduces the void residue around the electrode 400 of the back contact cell 300, and makes the final connection interface more uniform and stable, thereby helping to improve the mechanical reliability and electrical connection consistency of the interconnect structure.

[0062] In some embodiments, such as Figure 1 As shown, in the solder strip 100 provided in this application, the insulating layer 130 is a polytetrafluoroethylene coating with reflective dispersing particles.

[0063] The insulating layer 130, on the one hand, covers the low-melting-point alloy layer 120 before welding, preventing the solder ribbon 100 from making conductive contact with the electrode 400 to be welded in the non-target area of ​​the back contact cell 300, thereby reducing the risk of short circuit between electrodes 400 of different polarities; on the other hand, since the insulating layer 130 is provided with reflective dispersion particles, the reflective dispersion particles can scatter and reflect the incident light, thereby reducing the shading loss of the back contact cell 300 when the solder ribbon 100 covers the electrode area on the back of the back contact cell 300, and improving the light utilization efficiency.

[0064] Polytetrafluoroethylene (PTFE) coatings can be in the form of pure PTFE, or in the form of PTFE-polyimide composite coatings, PTFE-fluororubber composite coatings, or PTFE-modified insulating films. PTFE coatings can be used stably for extended periods in environments ranging from -196℃ to 260℃. PTFE coatings resist corrosion from strong acids, strong alkalis, and most organic solvents. PTFE coatings possess excellent electrical insulation properties and outstanding dielectric properties, unaffected by ambient temperature and frequency, making them ideal insulating materials.

[0065] The reflective dispersing particles can be selected from titanium dioxide, aluminum oxide, zinc oxide, silicate microparticles, or other inorganic particles with high reflectivity and good dispersibility, either as a single substance or a mixture thereof.

[0066] In some embodiments, the size and density of the reflective dispersion particles can be set according to the specific requirements of the insulation layer 130, so that the reflectivity of the reflective dispersion particles is ≥90% and the volume resistivity of the reflective dispersion particles is ≥1×10¹. 4 Ω.cm.

[0067] In some embodiments, such as Figure 1 As shown, in the solder strip 100 provided in this application, the thickness of the conductor base strip 110 is a, 100μm≤a≤200μm;

[0068] The thickness of the low-melting-point alloy layer is b, where 10μm≤b≤30μm;

[0069] The thickness of the insulating layer is c, where 5μm≤c≤15μm;

[0070] The thickness of the thermoplastic adhesive layer is d, where 3μm≤d≤10μm.

[0071] The thickness 'a' of the conductor base strip 110 satisfies 100μm≤a≤200μm. This thickness range makes the conductor base strip 110 a thin metal base strip with excellent flexibility and formability. Compared to traditional rigid metal base strips with a thickness of 1.0mm or 1.5mm, the thickness of 100μm≤a≤200μm ensures low resistance and good conductivity while providing sufficient mechanical strength, tensile strength, and processing stability for the solder strip 100, and also significantly reduces the overall weight.

[0072] The thickness range of the conductor base strip 110 can be matched according to the component welding process, the width of the solder strip and the current load of the electrode 400. When a scenario with high mechanical strength requirements is used, it can be set to close to 200μm, while in a scenario that emphasizes compliant fit and lightweight, it can be set to close to 100μm.

[0073] Although thin, copper or aluminum substrates with a thickness of over 100μm can still provide sufficient cross-sectional area to carry medium currents and serve as the primary heat conduction path to rapidly diffuse heat laterally.

[0074] The thickness of the low-melting-point alloy layer 120 is b, 10μm≤b≤30μm, which is less than the thickness of the conductor base 110 but greater than that of conventional ultra-thin surface layers. This allows for sufficient solder reserve while ensuring rapid melting, compensating for minor surface roughness differences in the electrode 400 and enhancing post-weld bonding strength. The low-melting-point alloy layer 120 enables electrode 400 welding connections at lower temperatures (typically below 300°C, compared to 1500°C for steel), effectively preventing thermal damage to the conductor base 110 or surrounding sensitive components and reducing the probability of thermal warping of the back contact cell 300.

[0075] The insulation layer 130 has a thickness of c, where 5μm ≤ c ≤ 15μm, making it an extremely thin insulation layer with extremely low thermal resistance (a core advantage): according to the thermal resistance formula R = d / (λ⋅A), the smaller the insulation layer thickness d, the lower the thermal resistance. Compressing the insulation layer to below 15μm means that heat can be conducted almost unimpeded to the low-melting-point alloy layer 120, facilitating the melting and welding of the low-melting-point alloy layer 120. The thickness d of the thermoplastic adhesive layer 140 is limited to 3μm to 10μm and can be a thin layer of thermoplastic polyurethane, a hot-melt layer, or a polyolefin hot-melt film. The thickness d of the thermoplastic adhesive layer 140 is less than that of the insulation layer 130, which is sufficient to form a stable adhesive interface after heating and compensate for the micro-undulations on the surface of the solar cell, thereby improving the initial bonding strength between the solder ribbon 100 and the back contact solar cell 300 and the continuity of the interface after welding.

[0076] This application provides a welding method for back contact battery cells, such as... Figures 1 to 5 As shown, using the solder strip 100 provided above, the method includes the following steps:

[0077] Align and make contact between the electrode 400 to be welded on the back contact cell 300 and the welding strip 100;

[0078] The welding ribbon 100 is heated, and both the low melting point alloy layer 120 and the insulating layer 130 of the welding ribbon 100 melt. The insulating layer 130 covers the low melting point alloy layer 120, and the electrode 400 to be welded, which is in back contact with the battery cell 300, enters the low melting point alloy layer 120 through the insulating layer 130, so that the low melting point alloy layer 120 and the electrode 400 to be welded are connected.

[0079] Cool to room temperature to allow the insulating layer 130 and the low-melting-point alloy layer 120 to solidify. The solidified insulating layer 130 covers the low-melting-point alloy layer 120 and the electrode 400 connected to the low-melting-point alloy layer 120.

[0080] The low-melting-point alloy layer 120 of the solder strip 100 can melt and be welded at temperatures below 300°C, effectively preventing warping or microcracks (hidden cracks) in the back contact cell 300 caused by drastic temperature changes, thereby improving the structural integrity and long-term reliability of the back contact cell 300. The lower welding temperature is also more favorable for the precision electrodes 400 on the back contact cell 300, preventing excessive material diffusion or performance degradation of the electrodes 400 due to high temperatures, and ensuring stable electrical performance at the weld joint.

[0081] The low-melting-point alloy layer 120 in the solder ribbon 100 can act as a small stress buffer layer after cooling and solidification. It can absorb and release the stress caused by the difference in thermal expansion coefficients between the back contact cell 300 and the solder ribbon 100, further reducing the risk of cracks near the welding point.

[0082] Since the electrodes 400 of the back contact cell 300 are all located on the back side, the solder ribbons 100 can be arranged flat on the same plane, making the stress distribution more uniform and significantly improving the mechanical strength and anti-microcrack performance of the back contact cell 300.

[0083] Before welding, the welding ribbon 100 is laid on the area to be welded of the back contact cell 300, ensuring accurate contact between the electrode 400 and the corresponding position of the welding ribbon 100. Then, the welding ribbon is locally heated using a hot press head, laser heating head, or hot air heating device, so that the low melting point alloy layer 120 preferentially reaches a molten state, and the insulating layer 130 softens simultaneously and forms a coating state, thereby providing an entry channel for the electrode 400 to penetrate. By controlling the heating temperature above the melting point of the low melting point alloy layer 120 without significantly damaging the substrate and functional layers of the back contact cell 300, the low melting point alloy layer 120 fully wets the surface of the electrode 400 and forms a stable metallurgical bond, while avoiding overheating that could lead to cell warping, grid line ablation, or encapsulation interface degradation.

[0084] After electrode 400 passes through insulating layer 130 and enters low-melting-point alloy layer 120, it is kept at a low temperature for a short time to complete interface wetting and conductive connection. Then it is naturally cooled or controlled to room temperature, allowing the molten insulating layer 130 to re-solidify and seal the connection area between the melting point alloy layer 120 and electrode 400. Since the insulating layer 130 forms a peripheral isolation between the low-melting-point alloy layer 120 and electrode 400 after solidification, it can suppress short circuits between adjacent electrodes and improve the long-term environmental stability of the solder joint.

[0085] Using the welding method of the back contact cell of this application, since the solder ribbon 100 itself has the functions of conductivity, fusion confinement and insulating encapsulation, reliable welding can be completed under a lower heat load, which is conducive to improving the yield of the back contact cell 300.

[0086] It should be noted that before aligning the electrode 400 with the solder ribbon 100, the back contact cell 300 can be placed in a plasma cleaner and treated with argon plasma for 40 to 60 seconds to remove the oxide layer on the surface of the electrode 400. After removing the oxide layer, the surface of the electrode 400 becomes more hydrophilic. This allows the molten low-melting-point alloy layer 120 to spread and wet the surface of the electrode 400 more evenly and fully during subsequent welding. This effectively avoids defects such as incomplete soldering and cold soldering, and significantly improves the mechanical reliability of the solder joint.

[0087] It is worth noting that after the back contact cell 300 cools to room temperature, electroluminescence detection and insulation resistance testing are generally required to determine the welding quality.

[0088] Electroluminescence detection can see through the interior of the solder strip 100, identify the welding condition between the low-melting-point alloy layer 120 and the electrode 400, and accurately identify micro-defects.

[0089] Insulation resistance testing can detect whether there are micro-short circuits or leakage paths between electrodes caused by solder splashes, residues, or positioning deviations, thereby reducing the risk of electric arcs, fires, and other safety accidents in the entire photovoltaic module under high-voltage operating conditions.

[0090] In some embodiments, aligning and contacting the electrode 400 to be welded to the back contact cell 300 with the solder ribbon 100 includes:

[0091] The welding strip 100 is placed into the welding strip placement groove 220 on the welding strip positioning plate 200, and the welding strip positioning plate 200 adsorbs the welding strip 100 into the welding strip placement groove 220; wherein, the depth of the welding strip placement groove 220 is e, and the thickness of the welding strip 100 is h, where 1:3≤e:h≤1:2;

[0092] The electrode 400 to be welded, which is in back contact with the battery cell 300, is oriented toward the welding strip positioning plate 200, and the electrode 400 and the welding strip 100 are aligned using an infrared vision system.

[0093] Move the back contact cell 300 toward the solder ribbon 100 so that the back contact cell 300 comes into contact with the thermoplastic adhesive layer 140 of the solder ribbon 100.

[0094] The welding strip 100 is first supported and limited by the welding strip positioning plate 200. The welding strip placement groove 220 performs preliminary positioning of the welding strip 100. During further positioning, the adsorption effect of the welding strip positioning plate 200 on the welding strip 100 can be achieved by vacuum adsorption or electrostatic adsorption to ensure that the welding strip 100 does not warp, shift or bounce during handling and alignment.

[0095] For example, such as Figures 2 to 4As shown, the welding strip positioning plate 200 includes a positioning plate body 210, on which a welding strip placement groove 220 is provided, and the welding strip placement groove 220 is connected to a negative pressure mechanism for adsorbing the welding strip 100.

[0096] Based on the mechanical structure limiting the welding strip placement groove 220, the negative pressure mechanism firmly fixes the welding strip 100 within the groove 220 through adsorption force. This effectively prevents any slight movement, warping, or bouncing of the welding strip 100 during welding preparation. Compared to directly clamping the welding strip 100 using tools such as grippers, negative pressure adsorption is a soft-contact fixing method, avoiding pressure damage, scratches, or deformation of the welding strip 100 caused by improper mechanical clamping force.

[0097] The mechanical mechanism of the welding strip placement groove 220 is fixed, and the forced adsorption fixation of the negative pressure mechanism forms a reliable fixed state of the welding strip 100. This ensures that the position of the welding strip 100 remains unchanged throughout the entire process from positioning to welding, providing a stable foundation for the subsequent heating and welding process and guaranteeing the uniformity and reliability of the weld quality.

[0098] The positioning method formed by the welding strip placement groove 220 and the negative pressure mechanism can minimize secondary contamination or damage to the welding strip surface after cleaning or before welding, ensure the activity of the welding interface, and thus guarantee the final welding strength.

[0099] Specifically, the negative pressure mechanism includes an adsorption hole 230, a negative pressure channel 250, and a negative pressure connector 240. The negative pressure channel 250 is located inside the positioning plate body 210, and each welding strip placement groove 220 is provided with an adsorption hole 230 that communicates with the negative pressure channel 250. One end of the negative pressure connector 240 is connected to the negative pressure channel 250, and the other end is used to connect to a negative pressure source.

[0100] By providing a negative pressure channel 250 within the positioning plate body 210 and an adsorption hole 230 within the solder ribbon placement groove 220, with the adsorption hole 230 directly connected to the bottom of the solder ribbon placement groove 220, the suction force generated by the negative pressure source acts on the solder ribbon 100 placed within the solder ribbon placement groove 220 through the negative pressure channel 250 and the adsorption hole 230. This design ensures that the solder ribbon 100 can be quickly and firmly adsorbed in a predetermined position, preventing displacement, warping, or bouncing during transport or welding preparation.

[0101] The negative pressure channel 250 is integrated inside the positioning plate body 210, making the entire welding strip positioning plate 200 compact in structure, which is convenient for automated equipment to grasp and operate, while avoiding interference from external pipelines to the welding area.

[0102] The depth of the solder strip placement groove 220 is e, and the thickness of the solder strip 100 is h, where 1:3 ≤ e:h ≤ 1:2. By strictly controlling the ratio of the depth e of the solder strip placement groove 220 to the thickness h of the solder strip 100, a balance between "limiting" and "adsorption" is achieved.

[0103] When the groove depth e is at least 1 / 3 of the solder strip thickness h, the sidewalls of the solder strip placement groove 220 can effectively physically shield and limit the solder strip 100. This can prevent the solder strip 100 from sliding laterally when affected by slight external vibrations or airflow, ensuring the alignment accuracy of the solder strip 100 with the electrode 400 of the back contact cell 300.

[0104] When the depth e of the solder ribbon placement groove 220 does not exceed 1 / 2 of the thickness h of the solder ribbon 100, after the solder ribbon 100 is placed in the solder ribbon placement groove 220, more than half of its upper surface is still exposed above the plane of the positioning plate body 210. The upper surface of the solder ribbon 100 maintains a height difference with the surface of the positioning plate body 210, allowing the negative pressure adsorption holes 230 to act directly on the bottom surface of the solder ribbon 100. Furthermore, the solder ribbon 100 will not sink to the bottom due to the solder ribbon placement groove 220 being too deep, preventing adsorption force attenuation or poor contact.

[0105] If the solder strip placement groove 220 is too deep (e.g., e>h), the solder strip 100 may be deeply embedded in the solder strip placement groove 220, resulting in insufficient adsorption force or difficulty in being contacted by the subsequent electrode 400 to be welded; if the solder strip placement groove 220 is too shallow (e.g., e<1 / 3h), it will not play a good limiting and positioning role.

[0106] Compared to traditional mechanical clamping methods, in this embodiment, the welding strip placement groove 220 combined with the negative pressure adsorption hole 230 is a soft contact fixation method, which avoids excessive clamping force causing deformation or damage to the low melting point alloy layer on the surface of the welding strip, thereby ensuring the integrity of the welding interface.

[0107] By controlling the depth e of the solder strip placement groove 220 and the thickness h of the solder strip 100 to be between 1:3 and 1:2, such as 1:2.8 or 1:2.2, the solder strip 100 can be partially embedded in the solder strip placement groove 220 while retaining sufficient exposed height. This is beneficial for the infrared vision system to identify the outline of the solder strip 100, and also avoids the solder strip 100 from being excessively restricted due to the solder strip placement groove 220 being too deep, which would affect the subsequent contact with the electrode 400.

[0108] After the electrode 400 to be welded on the back contact cell 300 is aligned with the welding ribbon positioning plate 200, the electrode 400 and the welding ribbon 100 are coordinately registered using an infrared vision system. The infrared vision system can identify the boundary based on the reflection difference of the electrode 400 and the surface thermal radiation characteristics of the welding ribbon 100, thereby correcting the lateral and angular deviations between the electrode 400 and the welding ribbon 100. Subsequently, the back contact cell 300 is brought close to the welding ribbon 100 along a predetermined pressing direction, so that the electrode 400 first contacts the thermoplastic adhesive layer 140 and forms an initial position. The thermoplastic adhesive layer 140 softens or partially melts after being heated, which can fill the tiny gaps between the electrode 400 and the welding ribbon 100.

[0109] Through the aforementioned alignment and contact methods, the adsorption and limiting of the solder ribbon positioning plate 200, the matching of the depth of the solder ribbon placement groove 220 with the thickness of the solder ribbon 100, and the precise identification of the infrared vision system work together to stably maintain the solder ribbon 100 at a predetermined height and position, allowing the electrode 400 to contact the thermoplastic adhesive layer 140 in a controllable posture. First, mechanical positioning eliminates macroscopic displacement of the solder ribbon 100, then visual alignment eliminates minor deviations between the electrode 400 and the solder ribbon 100. Subsequently, the preliminary contact of the thermoplastic adhesive layer 140 achieves interface buffering and initial adhesion between the electrode 400 and the solder ribbon 100, thereby improving assembly consistency before welding, reducing the risk of electrode misalignment, damage, and poor connection, and providing a reliable foundation for subsequent heating and melting, conductive connection, and post-weld coating stability. This ultimately improves the yield and connection reliability of the back contact cell 300 welding.

[0110] In some embodiments, heating the solder ribbon 100 further includes melting the thermoplastic adhesive layer 140 of the solder ribbon 100 to fill the gap between the insulating layer 130 and the back contact cell 300.

[0111] After the solder ribbon 100 is aligned and in contact with the electrode 400 to be welded to the back contact cell 300, the solder ribbon 100 is heated in a controlled manner using hot pressing or infrared heating, causing the thermoplastic adhesive layer 140 to soften preferentially and melt and flow. The thermoplastic adhesive layer 140 can be made of a material system with a melting point lower than that of the insulating layer 130 but higher than that of the ambient temperature, and its thickness d is preferably controlled within the range of 3μm to 10μm, so as to ensure sufficient wetting and leveling ability while avoiding excessive thickness that would lead to adhesive overflow or increased thermal resistance.

[0112] After the thermoplastic adhesive layer 140 changes from a solid state to a viscous flow state, it spreads along the outer periphery of the insulating layer 130 and the microscopic undulations on the surface of the back contact cell 300 due to its own fluidity. Under the action of external pressure, it can enter the local gaps between the insulating layer 130 and the back contact cell 300, thereby forming a continuous filling interface. When the temperature drops, it solidifies again, which can seal the gap between the insulating layer 130 and the back contact cell 300 and play a role in interface buffering and adhesion stabilization.

[0113] It should be noted that the heating temperature, holding time and pressure of the thermoplastic adhesive layer 140 can be matched and set according to the softening point of the thermoplastic adhesive layer 140, the total thickness of the solder strip 100 and the surface condition of the back contact cell 300, so as to ensure that the thermoplastic adhesive layer 140 is fully melted without causing the insulation layer 130 to fail or the low melting point alloy layer 120 to be excessively lost.

[0114] In some embodiments, heating the solder strip 100 includes:

[0115] The solder ribbon 100 is heated by a laser generated by a continuous semiconductor laser. The laser wavelength is 800nm ​​to 1100nm, the laser power is set to 50W to 200W, the laser scanning speed is 50mm / s to 200mm / s, and the laser spot is elliptical. The major axis of the ellipse is aligned with the length of the solder ribbon 100. The length of the major axis of the ellipse is 1.5 to 2.0 times the length of the solder ribbon, and the length of the minor axis of the ellipse is 0.8 to 1.2 times the width of the solder ribbon.

[0116] The laser emitted by the continuous semiconductor laser is preferably selected in the near-infrared band of 800nm ​​to 1100nm, which matches the absorption characteristics of the solder ribbon 100, so that the heat can be transferred to the low melting point alloy layer 120 and the insulating layer 130 in a more concentrated manner, thereby avoiding the decrease in energy utilization caused by wavelength deviation.

[0117] By controlling the laser power to 50W to 200W, preferably 80W to 150W, it is possible to ensure rapid heating of the welding strip 100 while suppressing overheating and ablation, allowing the insulating layer 130 to soften first and cover the molten low-melting-point alloy layer 120, while providing a stable thermal window for the electrode 400 to be welded to penetrate the insulating layer 130.

[0118] Setting the laser scanning speed to 50mm / s to 200mm / s, preferably 80mm / s to 160mm / s, allows the laser dwell time on the surface of the solder strip 100 to be coordinated with the thickness of the solder strip 100 and the thermal conductivity of the material, thus avoiding local heat accumulation that could lead to solder flow or carbonization of the insulating layer.

[0119] Setting the laser spot to an ellipse with its major axis aligned with the length of the welding strip 100, and with the major axis being 1.5 to 2.0 times the length of the welding strip and the minor axis being 0.8 to 1.2 times the width of the welding strip, allows the laser to form a continuous and uniform heating zone along the length of the welding strip 100, covering the effective welding area in the width direction of the welding strip 100, thus reducing temperature differences and uneven melting at the edge of the welding strip 100.

[0120] The near-infrared laser generated by the continuous semiconductor laser, after passing through a grating, produces an elliptical spot that acts on the solder ribbon 100. The heat is continuously distributed along the length of the solder ribbon, first softening or melting the outer insulating layer 130 and forming a protective coating on the inner low-melting-point alloy layer 120. Then, during the pressing of the electrode 400, the low-melting-point alloy layer 120 partially cracks and forms a conductive contact with the electrode 400. Due to the matching of power, scanning speed, and spot size, the surface temperature rise of the solder ribbon 100 can be maintained within a range suitable for melting but without damaging the layered structure of the solder ribbon 100. This achieves coordinated melting and controlled re-solidification of the low-melting-point alloy layer 120 and the insulating layer 130, thereby ensuring that the welding area has a stable electrical connection and can form a continuous coating on the low-melting-point alloy layer 120 and the electrode 400 after cooling, reducing the risk of short circuits and improving the mechanical stability and insulation reliability of the post-weld connection.

[0121] The following will compare specific examples of the welding method for the back contact battery cell according to this application with specific examples of traditional welding methods.

[0122] Specific example 1:

[0123] Preparation of back contact solar cell 300: An N-type back contact solar cell 300 with a thickness of 140 μm is used. The width of the electrode 400 is 0.8 mm, and the spacing between the electrodes 400 is 1.2 mm. The back contact solar cell 300 is placed in a plasma cleaner and treated with argon plasma for 60 seconds to remove the oxide layer on the electrode surface.

[0124] Preparation of solder strip 100: Pure copper with a width of 0.6 mm and a thickness of 0.15 mm was selected as the conductor base strip 110, and the average contact resistance of a single solder strip was 0.4 mΩ. SnBiAg was electroplated onto the surface of the conductor base strip 110 as a low-melting-point alloy layer 120 (Sn64Bi35Ag1, melting point 145℃), with a thickness of 20 μm. A white polyimide coating was then applied to the surface of the low-melting-point alloy layer 120 as an insulating layer 130. Titanium dioxide particles with a particle size of 0.3 μm (40% by mass) were dispersed in the insulating layer 130. The insulating layer 130 had a thickness of 10 μm, a reflectivity of 92%, and a volume resistivity of 5 × 10¹. 4 Ω.cm; A thermoplastic polyurethane elastomer coating is applied to the outermost layer as a thermoplastic adhesive layer 140 with a thickness of 5μm.

[0125] Fabrication of the welding strip positioning plate 200: Made of stainless steel and manufactured through precision machining. The surface of the welding strip positioning plate 200 is provided with welding strip placement grooves 220 that correspond to the arrangement of the electrodes 400 of the back contact cell 300. The depth of the welding strip placement grooves 220 is 0.08 mm (approximately 43% of the total thickness of the welding strip 100, which is 0.185 mm), and the width of the welding strip placement grooves 220 is 0.7 mm (117% of the width of the welding strip 100).

[0126] Pre-positioning and pre-fixing of welding strips 100: Place the twelve welding strips 100 sequentially into the groove 220 of the welding strip positioning plate 200, then place the welding strip positioning plate 200 on the heating platform, heat to 90°C, apply 0.2MPa pressure, hold the pressure for 10 seconds, soften the thermoplastic adhesive layer 140, and temporarily fix the welding strips 100 in the welding strip placement groove 220.

[0127] Back contact cell 300 alignment and bonding: Place the back contact cell 300 face down above the solder ribbon positioning plate 200, and align it using an infrared vision system to align the electrode 400 on the back of the back contact cell 300 with the solder ribbon 100 on the solder ribbon positioning plate 200 (alignment deviation ±0.08mm). After alignment, gently press down the back contact cell 300 to bring the electrode 400 into contact with the thermoplastic adhesive layer 140 on the surface of the solder ribbon 100.

[0128] Laser scanning welding: A continuous semiconductor laser with a wavelength of 980nm is used, the laser power is set to 120W, the scanning speed is 150mm / s, and the spot is elliptical (major axis 1.0mm, minor axis 0.6mm), with the major axis parallel to the weld strip 100. Under nitrogen protection (oxygen content 50ppm), single-scan welding is performed along the centerline of the weld strip 100.

[0129] Cooling and Inspection: After soldering, the entire assembly is transferred to a cooling platform to cool to room temperature. Electroluminescence testing is performed, and no microcracks or cold solder joints are found. Insulation resistance testing is performed, and the resistance value is >200MΩ.

[0130] Specific example 2:

[0131] The procedure is essentially the same as in Example 1, except that the laser power is adjusted to 80W, the scanning speed is adjusted to 100mm / s, and the spot is rectangular (major axis 1.2mm, minor axis 0.7mm). Electroluminescence detection was performed after welding, and no microcracks or incomplete welds were found. Insulation resistance testing was conducted, and the resistance value was >200MΩ.

[0132] Specific example 3:

[0133] The method is basically the same as in Example 1, except that the reflective insulating layer in the middle of the composite welding strip is a white polytetrafluoroethylene coating, with dispersed barium sulfate particles of 0.4 μm in diameter and a reflectivity of 91%. Electroluminescence detection was performed after welding, and no hidden cracks or incomplete welds were found; insulation resistance testing was performed, and the resistance value was >200MΩ.

[0134] Comparative Example 1

[0135] Traditional infrared welding was used, with ordinary reflective welding strips (without insulation layer), a welding temperature of 220℃, and a welding time of 15 seconds. Results: The fragmentation rate was 7%. Electroluminescence detection revealed multiple microcracks. Insulation resistance testing revealed a short circuit at electrode 400 in three back-contact cell 300, resulting in a yield of only 85%.

[0136] Comparative Example 2

[0137] A conductive adhesive bonding method was adopted, using commercially available silver-filled epoxy conductive adhesive, with a curing temperature of 150℃ and a curing time of 15 minutes. Results: The average contact resistance of a single solder strip was 2.8 mΩ, significantly higher than the 0.4 mΩ in Example 1; after 1000 hours of damp heat aging, the contact resistance of a single solder strip increased to 5.2 mΩ, with a power decrease of 4.5%. Soldering a single 300mm back contact solar cell required 15 minutes, resulting in low production efficiency.

[0138] Comparative Example 3

[0139] A laser spot welding scheme was adopted, with a circular laser spot of 0.4 mm in diameter, and spot welding was performed every 2 mm along the weld strip. Results: The average contact resistance of a single weld strip was 1.5 mΩ, which was higher than that of Example 1; after 2000 thermal cycles, some spot welds fell off, and the welding strength decreased significantly.

[0140] The specific examples and comparative data are recorded in Table 1 below.

[0141]

[0142] As shown in Table 1, the embodiments of the present invention are significantly superior to the comparative examples in terms of welding yield, fragmentation rate, contact resistance, welding speed, and long-term reliability. In particular, they have achieved unexpected technical effects in eliminating short-circuit risks, reducing fragmentation rate, and improving welding efficiency.

[0143] This application proposes a photovoltaic module, including a back contact cell 300 and the aforementioned solder ribbon 100 connected to the back contact cell 300; or, manufactured using the aforementioned soldering method for the back contact cell 300.

[0144] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0145] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A welding strip, characterized in that, For back-contact cell welding, the welding strip (100) comprises: Conductor baseband (110); A low-melting-point alloy layer (120) is provided to cover the outer surface of the conductor base strip (110); An insulating layer (130) is provided covering the outer surface of the low-melting-point alloy layer (120). The insulating layer (130) is configured to melt to cover the molten low-melting-point alloy layer (120) when welding the back contact cell (300), and to solidify to cover the low-melting-point alloy layer (120) and the electrode (400) connected to the low-melting-point alloy layer (120) after the electrode (400) to be welded to the back contact cell (300) enters the low-melting-point alloy layer (120) through the insulating layer (130).

2. The welding strip according to claim 1, characterized in that, It also includes a thermoplastic adhesive layer (140) which covers the outer surface of the insulating layer (130) and is configured to melt when welding adjacent back contact cells (300) to fill the gap between the insulating layer (130) and the back contact cells (300).

3. The welding strip according to claim 1, characterized in that, The insulating layer (130) is a polytetrafluoroethylene coating with reflective dispersible particles.

4. The welding strip according to claim 3, characterized in that, The reflectivity of the reflective dispersion particles is ≥90%, and the volume resistivity of the reflective dispersion particles is ≥1×10¹. 4 Ω.cm.

5. The welding strip according to claim 2, characterized in that, The thickness of the conductor base strip (110) is a, 100μm≤a≤200μm; The thickness of the low-melting-point alloy layer (120) is b, 10μm≤b≤30μm; The thickness of the insulating layer (130) is c, where 5μm≤c≤15μm; The thickness of the thermoplastic adhesive layer (140) is d, 3μm≤d≤10μm.

6. A welding method for back contact battery cells, characterized in that, Using the welding strip according to any one of claims 1 to 5, the welding method comprises the following steps: Align and make contact between the electrode (400) to be welded on the back contact cell (300) and the welding strip (100); When the solder strip (100) is heated, both the low-melting-point alloy layer (120) and the insulating layer (130) of the solder strip (100) melt. The insulating layer (130) covers the low-melting-point alloy layer (120). The electrode (400) to be welded of the back contact cell (300) enters the low-melting-point alloy layer (120) through the insulating layer (130) so that the low-melting-point alloy layer (120) and the electrode (400) to be welded are connected. Cool to room temperature to allow the insulating layer (130) and the low-melting-point alloy layer (120) to solidify, the solidified insulating layer (130) covering the low-melting-point alloy layer (120) and the electrode (400) connected to the low-melting-point alloy layer (120).

7. The welding method for the back contact battery cell according to claim 6, characterized in that, The step of aligning and contacting the electrode (400) to be welded on the back contact cell (300) with the solder strip (100) includes: The welding strip (100) is placed in the welding strip placement groove (220) on the welding strip positioning plate (200), and the welding strip placement groove (220) adsorbs and fixes the welding strip (100); wherein, the depth of the welding strip placement groove (220) is e, and the thickness of the welding strip (100) is h, where 1:3≤e:h≤1:2; The electrode (400) to be welded on the back contact cell (300) is oriented toward the welding strip positioning plate (200), and the electrode (400) and the welding strip (100) are aligned by an infrared vision system. The back contact cell (300) is moved toward the solder strip (100) so that the back contact cell (300) comes into contact with the thermoplastic adhesive layer (140) of the solder strip (100).

8. The welding method for the back contact battery cell according to claim 6, characterized in that, The heating of the solder strip (100) further includes: The thermoplastic adhesive layer (140) of the solder ribbon (100) melts to fill the gap between the insulating layer (130) and the back contact cell (300).

9. The welding method for back contact battery cells according to claim 6, characterized in that, The heating of the solder strip (100) includes: The solder ribbon (100) is heated by a laser generated by a continuous semiconductor laser; wherein the wavelength of the laser is 800nm ​​to 1100nm, the power of the laser is set to 50W to 200W, the scanning speed of the laser is 50mm / s to 200mm / s, the laser spot is elliptical, the major axis of the ellipse is aligned with the length direction of the solder ribbon (100), the length of the major axis of the ellipse is 1.5 to 2.0 times the length of the solder ribbon, and the length of the minor axis is 0.8 to 1.2 times the width of the solder ribbon.

10. A photovoltaic module, characterized in that, Includes a back contact cell (300) and a solder strip (100) as described in any one of claims 1-5 connected to the back contact cell (300). Alternatively, it can be manufactured using the welding method for the back contact battery cells as described in any one of claims 6-9.

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