Production process of an extra-fine triangular solder strip

Abstract

The present application relates to the field of photovoltaic technology, in particular to a production process of an extremely fine triangular solder strip. The present application overcomes the problems of incomplete forming appearance of extremely fine special-shaped segmented solder strip, unbalanced processing residual stress, collapse and twisted winding in high-speed winding, and oxidation and blackening. By using modified nano lubricating medium and synchronous pre-rolling, micro deformation volume is reserved at the bottom edge of the copper wire; by using asymmetric rolling and multi-stage constant temperature oil bath diamond composite die continuous drawing, asymmetric cutting angle extremely fine copper base material with bottom square and top pointed is constructed; by implementing segmented non-uniform high-frequency induction temperature difference annealing, adding trace rare earth and nano TiO2 ultrasonic in-situ composite antioxidant composite solder, hot dip plating is carried out, and high-temperature gas phase BTA derivative in-situ oxidation prevention passivation is carried out; water-soluble polyvinyl alcohol / polyethylene glycol viscoelastic damping layer is coated online, and dynamic tension taper coefficient winding is matched, and the product has high appearance fidelity.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, specifically to a production process for an extremely fine triangular solder strip. Background Technology

[0002] With the rapid development of photovoltaic heterojunction cells and gridless technology, the industry's demand for extremely finely segmented triangular solder strips is increasing. However, this type of solder strip faces a deformation and forming challenge in high-speed continuous manufacturing: the mismatch between the abrupt change in the non-uniform cross-section of the "triangular-flat" shape and the rheological behavior of the surface material leads to low fidelity of the wire geometry, instability during winding due to internal residual stress concentration, and easy oxidation and deterioration of the surface photofunctional layer.

[0003] When the cross-section of the solder strip is reduced to an extremely fine specification with a width and height of no more than 0.30 mm, the flow of the copper substrate in the micro-shaped mold is extremely uneven, often resulting in incomplete filling of the top corner and excessively large radius. At the same time, due to the non-uniform structure of the solder strip with alternating "triangular segments" and "flat segments", the significant difference in the width of the two segments will cause severe shear stress concentration during high-speed continuous rolling. In the subsequent hot-dip tinning and continuous winding process, the release of this uneven residual stress can easily cause the wire to fall into the gap, local collapse, and serious twisting and overturning defects.

[0004] To address this, a production process for extremely fine triangular welding strips was proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing process for extremely fine triangular welding strips.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a manufacturing process for extremely fine triangular solder strips, the manufacturing process of which is as follows: S1 Pre-rolling and Lubrication: Circular copper wires with a diameter of 0.30-1.60mm are passed through precision rolls at a speed of 100-240m / min. A high-speed circulating pump is turned on, and modified nano-lubricating medium is continuously sprayed online through double-sided atomizing nozzles at the bite point (deformation zone entrance) of the copper wire entering the rolling zone of the rolls. The roll cavity is precision EDM machined so that, in addition to forming the initial cross-sectional trend, a geometric margin of 20μm is reserved on both sides of the base of the forming triangle when rolling the copper wire. S2 temperature-controlled multi-stage drawing: The lubricated rolled copper wire directly enters the primary rolling mill, and the rolling temperature is controlled at 110-130℃ to roll out an asymmetrical preliminary cross-section with a rectangular bottom and a triangular top. The rolled preliminary wire is continuously fed into a three-stage continuous drawing unit composed of diamond composite dies. Each stage of drawing is carried out in a temperature-controlled oil bath at 45℃ and a drawing speed of 100-240m / min. Finally, an asymmetrical structure with a bottom width of 0.3mm and a height of 0.3mm is drawn out to obtain an extremely fine triangular copper substrate. The asymmetric rolling process first locks in the asymmetric initial shape of the bottom rectangle and the top triangle. Then, the multi-stage diamond die is continuously drawn under constant temperature oil bath. By utilizing its thermo-coupling field, the rheological stress and plastic deformation resistance are gently softened and released during the high-speed deep drawing deformation of the copper substrate. This effectively suppresses the anisotropic abnormal slippage of the grains inside the wire during the evolution of the extremely fine asymmetric shape. S3 Segmented Annealing: The ultra-fine triangular copper substrate enters a secondary forming machine with alternating concave and convex rollers, where it is rolled into an alternating segmented structure on a continuous wire. It then passes through a dynamic high-frequency induction annealing device, where a displacement sensor captures the alternation points between the "triangular segments" and "flat segments" in real time. When the triangular segment (narrow cross-section) passes through the induction coil, the induction power current is automatically adjusted to maintain the annealing temperature at 460-480℃ for 0.5 seconds. When the flat segment (wide and flat cross-section) passes through the induction coil, the induction current is automatically increased to raise the annealing temperature to 490-510℃ for 0.4 seconds. The segmented non-uniform heat input counteracts and eliminates the residual work hardening stress that accumulates at the alternating nodes due to the abrupt change in cross-sectional area between the triangular and flat segments, enabling the softened structure of the entire linear shape to achieve mechanical uniformity balance, and directly eliminating the internal disordered torque that subsequently causes twisting. S4 multi-element alloy hot-dip plating: The annealed ultra-fine triangular copper substrate is passed through the tin immersion bath at a speed of 100-240 m / min, the bath temperature is maintained at 260℃, and the online immersion plating time is controlled at 0.8-1.3s. When exiting the bath, excess solder is scraped off by a triangular micro-hole air knife (with a V-shaped micro-hole array gap that matches the geometric profile of the triangular solder strip cross section, and the non-uniform coating thickness is precisely scraped off by the shearing force of the local high-speed nitrogen jet, with a nitrogen pressure of 0.35MPa). The coating thickness is controlled at 15μm to obtain hot-dip plated wire. S5 Vapor Phase Passivation: The hot-dip tin-plated wire drawn from the 260℃ tin-dip bath immediately enters the sealed vapor phase cooling chamber. A protective gas is continuously introduced into the cooling chamber, which consists of 96% N2 by volume flow rate and 4% benzotriazole derivative (5-methylbenzotriazole) aerosol. The vapor phase temperature is maintained at 160℃. After the solder ribbon stays in the chamber for 2 seconds, it is rapidly cooled by cold air. The cold air output temperature is 16℃, and the wind speed is 13-17 m / s. By utilizing the residual heat on the coating surface, vaporized rust-preventive molecules are induced to undergo coordination complexation reactions with the freshly coated metal surface in a closed gas phase, thereby constructing a dense anti-oxidation barrier in situ and achieving the simultaneous integration of internal stress homogenization regulation and anti-oxidation properties. S6 Damping Coating and Tapered Winding: Before entering the winding machine, the finished welding strip after vapor phase passivation is coated with a polymer damping liquid online through an immersion coating tank, and then flash-evaporated with moisture through a micro infrared dryer. The main wavelength of the infrared emitter is 2.5μm (mid-wave infrared matching the water molecule absorption peak); the air temperature inside the drying zone is 110℃; the welding strip passes through the infrared zone online for 0.7-0.9s (continuous drying time), forming a tough damping film with a thickness of 15±2μm on the surface of the welding strip; the online coated welding strip then enters a precision ribbon bobbin, is wound around a plastic I-beam, and is wound to obtain an extremely fine triangular welding strip; After air drying, the polymer composite damping film forms a flexible geometric micro-buffer layer on the surface of the welding strip. With its excellent spatial physical filling ability and anti-extrusion creep stiffness, it compensates for the microscopic spatial collapse gaps that inevitably occur when the triangular and flat segments are stacked and interlaced, thereby locking the lateral degree of freedom of the wire. Under the synergistic effect of dynamically decreasing tapered tension control during winding, the damping layer locks the degree of freedom of the ultra-fine wire in the axial and radial movement of the I-beam shaft, eliminating defects such as wire falling, lateral slippage, and overturning and twisting during the high-speed winding and axial stacking of segmented irregular strips.

[0007] The preferred method for preparing the modified nano-lubricating medium is as follows: 5g of graphene oxide is added to 500mL of anhydrous ethanol and ultrasonically dispersed at 300W for 2h to obtain a uniform suspension; 2.0-3.5mL of 3-aminopropyltriethoxysilane (APTES) is added to the suspension, mechanical stirring is started, the stirring speed is controlled at 500rpm, the reaction temperature is 75℃, and the reaction is continuously refluxed for 5-8h; the mixture is washed three times by alternating centrifugation with anhydrous ethanol and deionized water, and dried in a vacuum oven at 60℃ for 12h to obtain silanized modified graphene; 5g of silanized modified graphene is mixed with 495g of imidazole ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, and put into a fully enclosed planetary ball mill, and continuously ball-milled at 400rpm for 3h to obtain the modified nano-lubricating medium.

[0008] Preferably, during continuous online spraying in S1, the atomizing spray pressure is 0.18-0.22 MPa, the medium flow rate of a single nozzle is 1.5-1.8 L / min, and the medium circulation temperature is controlled at 35℃.

[0009] Preferably, the molten solder in the immersion bath is an antioxidant composite solder.

[0010] The preferred method for preparing the anti-oxidation composite solder is as follows: Weigh the following components by mass percentage (based on a total mass of 10 kg): silver (Ag) 3.0%, copper (Cu) 0.5%, bismuth (Bi) 1.0%-1.5%, cerium (Ce) 0.10%-0.25%, with the balance being tin (Sn). Place these components into a medium-frequency induction melting furnace, heat to 350℃ and electromagnetically stir for 20 min. Reduce the furnace temperature to 260℃ and maintain this temperature for 35 min to release the thermal convection stress within the alloy, forming a multi-element low-eutectic liquid matrix. Weigh 25 g of the alloy with an average particle size of... 20nm titanium dioxide powder was mixed with 2mL of oleic acid surfactant and mechanically stirred at 600rpm for 1.5h at 80℃ to complete the surface oleophilic modification and obtain modified nanoparticles. The modified nanoparticles were added in batches (divided into 5 equal parts, one part was added every 5min) to the above-mentioned multi-element low eutectic liquid at 260℃. At the same time, an ultrasonic probe with a power of 350-500W and a frequency of 20kHz was introduced into the molten pool to continuously disperse the nanoparticles for 30min, so that the nanoparticles formed a micro-uniform dispersion in the alloy liquid, and thus obtained an antioxidant composite solder.

[0011] Preferably, the preparation method of the polymer damping fluid is as follows: 733g of deionized water is added to a reaction vessel with a jacketed heating system, 70g of polyvinyl alcohol (PVA-1799) and 30g of polyethylene glycol (PEG-400) are added, and the mixture is continuously stirred at 450rpm and 90℃ for 4h. The temperature is then lowered to 30℃ to obtain the polymer damping fluid (total solid mass fraction of 12%).

[0012] Preferably, in S3, alternating segmented structures are rolled out on the continuous wire as follows: triangular segments are 70-100mm long, and flat segments are 80-120mm long.

[0013] Preferably, the winding control system in S6 adopts a dynamic tension mode: the initial winding tension is set to 1.2N, and as the winding radius increases, the system automatically decreases dynamically according to a taper coefficient of 0.85. When the entire shaft is full, the end tension decreases to 0.7N, resulting in an extremely fine triangular welding strip.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the rolling and drawing of ultra-fine asymmetric shaped copper substrates, to address the problems of incomplete filling at the apex, surface microcracks, and elastic rebound warping caused by the resistance of metal rheology, ultra-high pressure extreme pressure lubrication of modified graphene / ionic liquid nanocomposite fluid, combined with the lateral geometric volume reservation of the rolls and the thermo-coupling field of multi-stage drawing in constant temperature oil bath, significantly reduced the frictional resistance in the deformation zone and gently released the resistance to plastic deformation. This induced the copper fluid to fill the tiny space at the apex in an isotropic manner. Compared with traditional room temperature cold working and isosceles equilateral paths, this eliminated deformation defects and anisotropic abnormal slippage, and achieved high-fidelity construction of the micro-morphology of asymmetric bottom corners.

[0015] 2. This invention abandons the traditional electroplating process and instead uses an ultrasonic in-situ heat-dissipating plating process with oleophilic modified nano-titanium dioxide and a multi-element tin-based alloy with added rare earth cerium. This allows the nanoparticles to overcome the surface energy barrier and form a highly dispersed micro-network distribution in the molten tin, effectively reducing the surface tension of the molten solder when it spreads on a non-uniform surface. This significantly improves the uniformity of the coating thickness. Furthermore, the trace amounts of rare earth not only effectively refine the matrix grains at the interface, but also work synergistically with the nanoparticles to prevent the oxidation and coarsening of intermetallic compounds at the interface in a long-term humid and hot environment. Compared with conventional tin-lead solder or expensive brush-plated silver, this invention provides extremely fine solder strips with a durable and stable reflectivity without the need for a high-cost silver layer.

[0016] 3. To address the issues of stress accumulation at alternating nodes due to the abrupt changes in the structure between triangular and flat segments, and the potential for slippage and twisting during high-speed overlapping winding, a displacement sensor is used in conjunction with high-frequency induction to implement dynamic temperature difference matching annealing and in-situ vapor phase passivation. Furthermore, a polymer damping film with specific viscoelasticity is applied online before high-speed winding, along with taper tension control. This counteracts and eliminates the work hardening stress accumulated due to abrupt changes in cross-sectional area, achieving a mechanically uniform balance in the softened structure and simultaneously constructing an anti-oxidation barrier. Simultaneously, the damping layer micro-buffer pads fill the stacking gaps and lock the axial and radial degrees of freedom of the wire. Compared to conventional uniform annealing and conventional winding, this eliminates the collapse, slippage, and twisting defects of segmented irregularly shaped strips during high-speed winding and axial stacking. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the production process of the ultra-fine triangular welding strip of this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 This invention provides a manufacturing process for extremely fine triangular welding strips, the technical solution of which is as follows: Example 1 S1 Pre-calendering and lubrication 5g of graphene oxide (G931286, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.) was added to 500mL of anhydrous ethanol and ultrasonically dispersed for 2h at 300W to obtain a uniform suspension. 2.0mL of 3-aminopropyltriethoxysilane (APTES) was added to the suspension, and mechanical stirring was started at 500rpm. The reaction temperature was 75℃, and the reaction was continuously refluxed for 5h. The graphene was washed three times by alternating centrifugation with anhydrous ethanol and deionized water, and dried in a vacuum oven at 60℃ for 12h to obtain silanized modified graphene. 5g of silanized modified graphene was mixed with 495g of imidazole ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and placed in a fully enclosed planetary ball mill. The mixture was continuously ball-milled at 400rpm for 3h to obtain a modified nano-lubricating medium.

[0020] Circular copper busbars with diameters ranging from 0.30 to 1.60 mm are selected. In this embodiment, a circular copper busbar with a diameter of 0.50 mm is used. The busbar passes through a precision roll at a speed of 100 m / min. A high-speed circulating pump is activated, and the modified nano-lubricating medium is continuously sprayed online through double-sided atomizing nozzles at the bite point (deformation zone entrance) of the copper wire entering the rolling zone of the roll. The atomizing spray pressure is 0.18 MPa; the medium flow rate of a single nozzle is 1.5 L / min; and the medium circulation temperature is controlled at 35°C. The roll cavity is precision EDM-processed so that, in addition to forming the initial cross-sectional trend, a geometric margin of 20 μm is deliberately reserved on both sides of the base of the forming triangle when rolling the copper wire.

[0021] S2 Temperature Control Multi-Stage Pulling Asymmetric rolling: The lubricated rolled copper wire directly enters the primary rolling mill, and the rolling temperature is controlled at 110℃ to roll out an asymmetric preliminary cross-section with a rectangular bottom and a triangular top. Temperature-controlled continuous drawing: The rolled prototype wire is continuously fed into a three-stage continuous drawing unit composed of diamond composite dies. Each stage of drawing is carried out in a temperature-controlled oil bath at a temperature of 45℃ and a drawing speed of 100m / min. Finally, an asymmetrical structure with a bottom width of 0.3mm and a height of 0.3mm is drawn out to obtain an extremely fine triangular copper substrate.

[0022] S3 segmented annealing An extremely fine triangular copper substrate enters a secondary forming machine with alternating concave and convex rollers, where it is rolled into alternating segmented structures on a continuous wire: triangular segments are 70mm long and flat segments are 80mm long. It then passes through a dynamic high-frequency induction annealing device, where a displacement sensor captures the alternation points between the triangular and flat segments in real time. When a triangular segment (narrow cross-section) passes through the induction coil, the induction power current is automatically adjusted to maintain the annealing temperature at 460℃ for 0.5s. When a flat segment (wide and flat cross-section) passes through the induction coil, the induction current is automatically increased to raise the annealing temperature to 490℃ for 0.4s.

[0023] S4 multi-element alloy hot-dip galvanizing Weigh the following by weight percentage (based on a total mass of 10 kg): silver (Ag) 3.0%, copper (Cu) 0.5%, bismuth (Bi) 1.0%, cerium (Ce) 0.10%, with the balance being tin (Sn). Place these components into a medium-frequency induction melting furnace, heat to 350℃ and electromagnetically stir for 20 min. Reduce the furnace temperature to 260℃ and hold at that temperature for 35 min to release the thermal convection stress within the alloy, forming a multi-element low-eutectic liquid matrix. Weigh 25 g of titanium dioxide powder with an average particle size of 20 nm, add 2 mL of oleic acid surfactant, and heat at 80℃ with a 6% [missing information - likely a specific concentration or concentration]. The surface was mechanically stirred at 00 rpm for 1.5 h to complete the oleophilic modification and obtain modified nanoparticles. The modified nanoparticles were added in batches (divided into 5 equal parts, one part was added every 5 min) to the above-mentioned multi-element low eutectic liquid at 260°C. At the same time, an ultrasonic probe with a power of 350W and a frequency of 20kHz was introduced into the molten pool to continuously disperse the nanoparticles for 30 min, so that the nanoparticles formed a micro-uniform dispersion in the alloy liquid to obtain an antioxidant composite solder. This solder was directly and continuously transported to the tin immersion bath below through a bottom valve in a closed flow channel for use as the molten bath liquid for hot dipping.

[0024] Hot-dip plating process: The annealed ultra-fine triangular copper substrate is passed through the tin immersion bath at a speed of 100m / min, the bath temperature is maintained at 260℃, and the online immersion plating time is controlled at 0.8s. When exiting the bath, excess solder is scraped off by a triangular micro-hole air knife (with a V-shaped micro-hole array gap that matches the geometric contour of the triangular solder strip cross section (30°-90° apex angle), and the non-uniform coating thickness is precisely scraped off by the shearing force of the local high-speed nitrogen jet, with a nitrogen pressure of 0.35MPa). The coating thickness is controlled at 15μm to obtain hot-dip plated wire.

[0025] S5 vapor phase passivation Hot-dip tin-plated wires drawn from a 260°C tin-dip bath immediately enter a sealed vapor phase cooling chamber. A protective gas is continuously introduced into the cooling chamber, consisting of 96% N2 by volume and 4% benzotriazole derivative (5-methylbenzotriazole) aerosol. The vapor phase temperature is maintained at 160°C. After the solder strip remains in the chamber for 2 seconds, it is rapidly cooled with cold air at an output temperature of 16°C and a velocity of 13 m / s. The protective gas is introduced by placing 5-methylbenzotriazole in a constant-temperature heating tank and maintaining it in a molten state at 160°C. A high-temperature, high-speed nitrogen flow at a flow rate of 15 L / min and a pressure of 0.20 MPa is used for bottom-blowing and bubble carrying, forming a uniform hot aerosol that is continuously introduced into the sealed vapor phase cooling chamber.

[0026] S6 Damping Coating and Tapered Winding 733g of deionized water was added to a jacketed heating reactor, along with 70g of polyvinyl alcohol (PVA-1799) and 30g of polyethylene glycol (PEG-400). The mixture was continuously refluxed and stirred at 450rpm and 90℃ for 4h. After cooling to 30℃, a polymeric damping fluid (total solid mass fraction of 12%) was obtained. At 30℃, the apparent viscosity of this polymeric damping fluid was 200mPa·s, the shear thinning index n<0.65, and the static storage modulus was 20Pa, ensuring that it could be easily flowed and coated under high-speed shear and exhibited extremely high compressive strength when stacked.

[0027] Online coating: Before entering the winding machine, the finished welding strip after vapor phase passivation is coated with polymer damping liquid in an online coating tank, and then the moisture is flashed out in a micro infrared dryer. The main wavelength of the infrared emitter is 2.5μm (mid-wave infrared matching water molecule absorption peak); the air temperature inside the drying zone is 110℃; the welding strip runs through the infrared zone for 0.7s (continuous drying time), forming a tough damping film with a thickness of 15±2μm on the surface of the welding strip.

[0028] Tapered tension winding: After online coating, the solder strip then enters the precision ribbon bobbin and is wound on the plastic I-beam. The winding control system adopts a dynamic tension mode: the initial winding tension is set to 1.2N. As the winding radius increases, the system automatically decreases dynamically according to a taper coefficient of 0.85. When the entire bobbin is full, the end tension decreases to 0.7N, resulting in an extremely fine triangular solder strip.

[0029] Example 2 The preparation method and parameters of Example 1 are the same, except that in S1, the amount of APTES added is 2.5 mL, the reflux time is 6 h, the atomizing spray pressure is 0.19 MPa, and the single nozzle medium flow rate is 1.6 L / min; in S2, the rolling temperature is 120 °C, and the drawing speed is 180 m / min; in S3, the triangular segment length / annealing temperature is 85 mm / 470 °C, and the flat segment length / annealing temperature is 100 mm / 500 °C; in S4, the Bi content is 1.2%, the Ce content is 0.15%, the ultrasonic power is 400 W, the hot-dip galvanizing speed is 180 m / min, and the hot-dip galvanizing time is 1.0 s; in S5, the cold air velocity is 15 m / s; and in S6, the IR continuous drying time is 0.8 s.

[0030] Example 3 The preparation method and parameters of Example 1 are the same, except that in S1, the amount of APTES added is 2.8 mL, the reflux time is 8 h, the atomization spray pressure is 0.22 MPa, and the single nozzle medium flow rate is 1.8 L / min; in S2, the rolling temperature is 130 °C, and the drawing speed is 240 m / min; in S3, the triangular segment length / annealing temperature is 100 mm / 480 °C, and the flat segment length / annealing temperature is 120 mm / 510 °C; in S4, the Bi content is 1.5%, the Ce content is 0.25%, the ultrasonic power is 500 W, the hot-dip galvanizing speed is 240 m / min, and the hot-dip galvanizing time is 1.3 s; in S5, the cold air velocity is 17 m / s; and in S6, the IR continuous drying time is 0.9 s.

[0031] Example 4 The preparation method and parameters of Example 1 are the same, except that in S1, the amount of APTES added is 3.0 mL, the reflux time is 7 h, the atomizing spray pressure is 0.20 MPa, and the single nozzle medium flow rate is 1.7 L / min; in S2, the rolling temperature is 125 °C, and the drawing speed is 220 m / min; in S3, the triangular segment length / annealing temperature is 90 mm / 475 °C, and the flat segment length / annealing temperature is 110 mm / 505 °C; in S4, the Bi content is 1.3%, the Ce content is 0.20%, the ultrasonic power is 450 W, the hot-dip galvanizing speed is 220 m / min, and the hot-dip galvanizing time is 1.2 s; in S5, the cold air velocity is 16 m / s; and in S6, the IR continuous drying time is 0.8 s.

[0032] Comparative Example 1 The preparation method and parameters of Example 2 are the same, except that in S1, the spraying of the modified nano lubricating medium is cancelled and replaced with commercially available conventional copper wire drawing oil (purchased from Zhejiang Changxing Innovation Ultrafine Powder Co., Ltd.).

[0033] Comparative Example 2 Referring to the preparation method and parameters of Example 2, the difference is that in S1, no volume reservation of 20μm on each side of the bottom edge is made, and the asymmetric preliminary cross-section is directly rolled out.

[0034] Comparative Example 3 The preparation method and parameters of Example 2 are the same, except that in S2, the 120°C heating of the primary rolling mill is cancelled and replaced with room temperature (25°C) rolling; the 45°C temperature-controlled oil bath is cancelled and replaced with room temperature drawing.

[0035] Comparative Example 4 The preparation method and parameters of Example 2 are the same, except that in the S4 alloy formula, the amount of Ce added is 0%, and the balance is made up by Sn.

[0036] Comparative Example 5 The preparation method and parameters are the same as in Example 2, except that no modified nanoparticles are added in S4.

[0037] Comparative Example 6 The preparation method and parameters of Example 2 are the same, except that the nano-titanium dioxide was not modified to be oil-loving in S4.

[0038] Comparative Example 7 Referring to the preparation method and parameters of Example 2, the difference is that in S3, the displacement sensor and dynamic sensing adjustment are removed, and the annealing temperature of the triangular segment and the flat segment is uniformly set to 485℃.

[0039] Comparative Example 8 Referring to the preparation method and parameters of Example 2, the difference is that in S6, the online coating and infrared drying steps of the polymer damping liquid are omitted, and tapered tension winding is performed directly.

[0040] Experiment Example 1 Performance Testing Microscopic geometric accuracy (vertex R angle) and morphological fidelity: Triangular segment samples from each embodiment and comparative example were taken, and after resin cold mounting, grinding and polishing, the cross-section was observed using a super depth-of-field three-dimensional microscope, and the vertex R angle of the cross-section was measured; morphological fidelity was calculated by the percentage of overlap between the actual cross-sectional area and the theoretically designed asymmetric cross-sectional area. Spectral reflectance: The hemispherical reflectance of the solder ribbon surface in the visible light band of 380-780nm was measured using a spectrophotometer with an integrating sphere. During the aging test, the sample was placed in a high temperature and high humidity double 85 test chamber at 85℃ / 85% RH for 1000h and its reflectance was measured again to characterize its anti-oxidation and anti-blackening performance. Yield strength fluctuation rate: According to GB / T 228.1 Metallic materials tensile test method, the yield strength of 10 "triangular segments" and 10 "flat segments" on the same coil of welded strip are tested using a universal testing machine, and the maximum deviation rate of the strength of the two segments is calculated to characterize the uniformity of internal stress. Winding twist rate: Under the actual operating conditions of a photovoltaic string welding machine continuously feeding 10,000 meters of wire at a speed of 240m / min, the number of twists and flips is captured and recorded in real time by a high-frequency CCD vision recognition system, and the percentage of defect length to total length is calculated. The results are shown in Table 1.

[0041] Table 1 Performance tests of Examples 1-4 and Comparative Examples 1-8 As shown in Table 1, in Comparative Example 1, the conventional drawing oil ruptured under high-speed, high-pressure extrusion (extremely high hydrodynamic pressure) in an ultra-fine die, failing to provide effective boundary lubrication. This resulted in excessive frictional resistance when the copper substrate flowed towards the sharp corners, preventing the metal fluid from filling the microscopic sharp corners of the diamond die and causing incomplete filling. This demonstrates that the shape-preserving ability of modified graphene / ionic liquid under ultra-high pressure film formation under extreme shear is indispensable. In Comparative Example 2, even with good lubrication, the plastic flow of metal in the die requires volume potential energy. Lacking the 20μm volume reserved on both sides of the bottom edge, the die sidewall could not apply an additional upward extrusion force to the copper material during subsequent drawing, resulting in insufficient metal filling at the sharp corners. This verifies the geometric and rheological synergy of reserved deformation volume + nano-lubrication. In Comparative Example 3, the extremely fine asymmetric cross-section (rectangular at the bottom and triangular at the top) exhibits varying deformation resistance and work hardening rates during cold working. Drawing at room temperature leads to the accumulation of highly uneven anisotropic residual stress within the wire, resulting in severe elastic warping and springback deformation upon demolding. After removing temperature-controlled dynamic recovery, not only is the cross-sectional shape unmaintained, but internal stress also causes self-torsion during unwinding. In Comparative Example 4, without rare-earth element Ce anchoring grain boundaries, coarse intermetallic compounds rapidly form between the tin-based alloy and the copper substrate at the high-temperature, high-humidity aging interface. These coarse grains are easily oxidized to form a black copper oxide / tin suboxide layer that migrates to the surface. In Comparative Example 5, the diffuse reflectance of the tin alloy itself has a physical upper limit. The absence of titanium dioxide nanoparticles prevents the formation of an effective light scattering gain network within the coating, hindering the conversion of direct light into multi-angle reflections. Simultaneously, the increased surface tension due to the lack of nanoparticles results in a thicker and more uneven hot-dip galvanized coating, directly impacting optical utilization. In Comparative Example 6, the unmodified titanium dioxide surface is covered with hydrophilic hydroxyl groups, which are extremely incompatible with molten tin alloy. After the ultrasonic waves are removed, the nanoparticles rapidly undergo secondary agglomeration, forming invisible agglomerated black spots or pits on the coating surface. This not only reduces the overall reflectivity but also disrupts the continuity of the passivation film, leading to further attenuation of reflectivity over time. In Comparative Example 7, the triangular segment has a small cross-sectional area, while the flat segment has a large cross-sectional area. A uniform heat input of 485°C causes localized overheating in the triangular segment (grain coarsening and softening), while the flat segment does not absorb enough heat (retaining a large amount of work-hardened brittleness). This alternating and drastic change in microscopic mechanical properties creates a strong torsional torque within the entire wire. When the wire tension fluctuates slightly, the wire will flip and twist. In Comparative Example 8, during high-speed winding and stacking, because the bottom width of the triangular segment is much smaller than the width of the flat segment, the upper coil is very easy to slip off or get stuck in the geometric width difference of the lower coil, which causes collapse. Without the PVA / PEG damping layer as a strong viscoelastic buffer to physically fill the gap and laterally limit the movement, the microscopic collapse, after thousands of layers of stress accumulation, eventually leads to irreversible and serious wiring disorder and wire torsion defects in the entire axial cable.

[0042] In summary, as can be seen from Comparative Examples 1-3, relying solely on mechanical molds or conventional temperature control cannot overcome the filling and stress rebound barriers of extremely fine asymmetric cross-sections under rheological limits. This application integrates ultra-high pressure nanofluid chemistry and reserved geometric deformation to produce a filling effect. Furthermore, Comparative Examples 7 and 8 demonstrate that the mechanical instability of segmented irregular structures is the root cause of twisting, and conventional annealing and winding cannot balance the thermodynamic differences caused by the abrupt change in cross-section. This application eliminates residual stress fluctuations through dynamic temperature difference induction annealing, and on this basis, uses a water-soluble viscoelastic damping layer to fill the interlayer microscopic physical gaps and resist extrusion distortion. The synergistic effect of internal and external processes greatly reduces the twisting rate. Combined with the improvement of reflective and antioxidant properties by multi-element low eutectic metallurgy and nanopowder modification in Comparative Examples 4-6, the synergistic effect of each step in this application overcomes the wire problems caused by the mismatch between the abrupt change in the "triangular-flat" non-uniform cross-section and the rheological behavior of the surface material.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A manufacturing process for extremely fine triangular welding strips, characterized in that: The production process is as follows: Graphene oxide is silanized and then ball-milled with imidazole ionic liquid to obtain a modified nano-lubricating medium; a circular copper busbar is pre-rolled while the modified nano-lubricating medium is continuously sprayed online; the lubricated and rolled circular copper busbar enters a primary rolling mill to obtain a prototype wire; the prototype wire is drawn in an oil bath and then rolled in a secondary shaping machine to produce a segmented structure with alternating triangular and flat segments, followed by segmented annealing and then hot-dip tin plating in a tin-immersion bath to obtain a hot-dip tin-plated wire, which is then vapor-phase passivated to obtain a finished solder strip; the finished solder strip is coated online with a polymer damping liquid in a dip-coating tank and then tapered-wound to obtain the ultra-fine triangular solder strip.

2. The manufacturing process of an ultra-fine triangular welding strip according to claim 1, characterized in that: The modified nano-lubricating medium is prepared as follows: graphene oxide is added to anhydrous ethanol and ultrasonically dispersed to obtain a suspension; 3-aminopropyltriethoxysilane is added to the suspension and refluxed to obtain silanized modified graphene; the silanized modified graphene is mixed with the imidazole ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and ball-milled to obtain the modified nano-lubricating medium.

3. The production process of an ultra-fine triangular welding strip according to claim 1, characterized in that: The prototype wire has an asymmetrical cross-section with a rectangular bottom and a triangular top.

4. The manufacturing process of an ultra-fine triangular welding strip according to claim 1, characterized in that: The molten bath in the tin-immersion bath is an antioxidant composite solder; the preparation method of the antioxidant composite solder is as follows: silver, copper, bismuth, cerium and tin are weighed according to mass percentage and put into a medium frequency induction melting furnace to form a multi-element low eutectic liquid matrix; modified nanoparticles are added and ultrasonically dispersed to obtain the antioxidant composite solder.

5. The manufacturing process of an ultra-fine triangular welding strip according to claim 4, characterized in that: The modified nanoparticles were obtained by surface oleophilic modification of titanium dioxide powder with oleic acid surfactant.

6. The manufacturing process of an ultra-fine triangular welding strip according to claim 1, characterized in that: The segmented annealing process involves automatically adjusting the induced power supply current when the triangular segment passes through the induction coil to control the annealing temperature at 460-480℃; and automatically increasing the induced current when the flat segment passes through the induction coil to raise the annealing temperature to 490-510℃.

7. The manufacturing process of an ultra-fine triangular welding strip according to claim 1, characterized in that: The polymeric damping fluid is prepared from polyvinyl alcohol and polyethylene glycol.

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