A method for preparing a photovoltaic ribbon alloy solder

Abstract

The application relates to the technical field of alloy solder, and discloses a preparation method of photovoltaic solder strip alloy solder, specifically as follows: tin particles and copper particles are added into a crucible and placed in a resistance furnace to be smelted under a nitrogen atmosphere, and finally poured into a water-cooled casting mold to obtain a tin-copper solder; the prepared tin-copper solder is placed in a resistance furnace, heated and melted under a nitrogen atmosphere, nickel-cobalt-porous carbon-coated nano titanium dioxide is added, temperature refining is carried out, and finally the alloy solder is poured into a water-cooled casting mold to be prepared. The prepared nickel-cobalt-porous carbon-coated nano titanium dioxide is used as a reinforcing phase of the tin-copper alloy solder, the wetting performance and the mechanical performance of the solder are significantly improved, and the problem that high wettability and high strength cannot be considered together due to poor compatibility between a traditional inorganic nano reinforcing phase and a metal matrix is solved.

Description

Technical Field

[0001] This invention relates to the field of alloy solder technology, and in particular to a method for preparing a photovoltaic solder ribbon alloy solder. Background Technology

[0002] Photovoltaic solder ribbon, also known as tin-plated copper ribbon or tin-coated copper ribbon, is made by coating a layer of alloy solder onto the surface of a copper substrate of a certain specification through processes such as electroplating, vacuum deposition, and hot-dip coating. It is mainly used to connect the cells and conductive busbars in solar photovoltaic modules.

[0003] Traditional tin-lead (Sn-Pb) solders, due to their lead content, pose serious health hazards and environmental pollution problems, and are being replaced by lead-free solders. Among the many lead-free solder systems, tin-copper (Sn-Cu) solders have advantages such as low cost, low impurity sensitivity, good plasticity and conductivity, and the ability to inhibit the dissolution of copper substrates. They have been widely used in photovoltaic ribbon bonding processes. However, they also have problems such as increased melting point leading to process limitations, decreased wetting ability increasing the risk of cold solder joints, poor high-temperature mechanical properties, excessive growth of intermetallic compounds (IMC) inducing brittle fracture, and insufficient long-term service reliability.

[0004] Studies have found that introducing trace amounts of elements such as Ag, Ni, Co, and Zn into the solder matrix can locally control the morphology and grain size of the integrated metallographic structure (IMC). However, the improvement in overall performance by a single method is limited, and excessive doping can easily lead to problems such as new phase agglomeration, melting point changes, and interface embrittlement. Introducing nanoparticles into the solder matrix can utilize the small size effect, high specific surface area, and interfacial activity of the reinforcing phase to exhibit unique advantages in grain boundary pinning, dislocation inhibition, nucleation promotion, and diffusion barrier. This can simultaneously refine the solder microstructure and improve performance. However, ordinary nanoparticles in the solder matrix are prone to uneven dispersion and poor interfacial bonding, which affects the performance improvement effect. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing photovoltaic solder ribbon alloy, comprising the following steps: adding tin particles and copper particles into a crucible and melting them in a resistance furnace, holding the mixture at 400-500℃ for 25-35 minutes under a nitrogen atmosphere, and then pouring it into a water-cooled mold to obtain tin-copper solder.

[0006] The prepared tin-copper brazing filler metal is placed in a resistance furnace and heated to 240-260℃ under a nitrogen atmosphere. Nickel-cobalt-porous carbon-coated nano-titanium dioxide is added, and the temperature is raised to 300-390℃. The ultrasonic power is 500-1000W, the frequency is 20-40kHz, and the ultrasonic vibration lasts for 40-80s. The temperature is then raised to 400-500℃, the ultrasonic power is 500-1000W, the frequency is 20-40kHz, and the ultrasonic vibration lasts for 5-15s. The temperature is held for 25-35min. After the holding period, the filler metal is poured into a water-cooled mold to obtain the alloy solder.

[0007] The raw material formula of the alloy solder, by mass percentage, is: 0.4%-0.9% copper particles, 0.3%-1.5% nickel-cobalt-porous carbon-coated nano titanium dioxide, and the balance tin particles.

[0008] Preferably, the preparation method of the nickel-cobalt-porous carbon-coated nano-titanium dioxide is as follows: Step 1: Using cobalt nitrate hexahydrate and nickel nitrate hexahydrate as metal centers and 5-hydroxyisophthalic acid as organic ligand, a nickel-cobalt bimetallic organic framework is prepared by solvothermal method.

[0009] Step 2: The silicon-trimethoxy functional group in the 3-(2,3-epoxypropoxy)propyltrimethoxysilane structure is hydrolyzed to form silanol, which then undergoes a condensation reaction with the hydroxyl groups on the surface of dried nano-titanium dioxide to generate a siloxane structure, thus preparing epoxy-functionalized titanium dioxide.

[0010] Step 3: Nickel-cobalt-porous carbon-coated nano-titanium dioxide is prepared by undergoing a ring-opening reaction between the epoxy functional groups in epoxy-functionalized titanium dioxide and the hydroxyl functional groups in the nickel-cobalt bimetallic organic framework, followed by carbonization treatment.

[0011] Preferably, the mass ratio of silane coupling agent to nano-titanium dioxide is (0.01~0.05):1.

[0012] Preferably, the molar ratio of cobalt nitrate hexahydrate to nickel nitrate hexahydrate is 1:(1-3).

[0013] Preferably, the carbonization process is as follows: heating to 600-700°C at a heating rate of 1-4°C / min under an inert gas atmosphere, and holding at that temperature for 4-8 hours.

[0014] Preferably, the inert gas is one of argon, nitrogen, and helium.

[0015] Preferably, the method for preparing the dried nano-titanium dioxide is as follows: placing the nano-titanium dioxide in a vacuum drying oven at 50-70℃ and drying it for 10-15 hours to obtain the dried nano-titanium dioxide.

[0016] Preferably, the particle size of the nano-titanium dioxide is 10-100 nm.

[0017] Preferably, the preparation method of the nickel-cobalt bimetallic organic framework is as follows: 5-hydroxyisophthalic acid is dissolved in N,N-dimethylformamide and shaken at room temperature until completely dissolved to obtain solution A.

[0018] Cobalt nitrate hexahydrate and nickel nitrate hexahydrate were added to N,N-dimethylformamide and shaken at room temperature until completely dissolved to obtain solution B. Solution B was poured into solution A and shaken at room temperature for 0.5-2 hours to obtain mixed solution C. Mixed solution C was then transferred to a high-pressure reactor and reacted at 110-130℃ for 4-8 hours. After cooling to room temperature, the mixture was filtered, washed, and vacuum dried at 85-95℃ for 6-10 hours to obtain a nickel-cobalt bimetallic organic framework.

[0019] Preferably, the molar ratio of the organic ligand to the metal center is (0.8-1.2):1.

[0020] Preferably, the crucible is one of a graphite crucible, an alumina crucible, or a silicon carbide crucible.

[0021] The present invention has at least one of the following technical effects: 1. The present invention uses the prepared nickel-cobalt-porous carbon-coated nano-titanium dioxide as the reinforcing phase of tin-copper alloy solder, which significantly improves the wettability and mechanical properties of the solder and improves the problem of poor dispersion and compatibility of traditional nano-reinforcing phases in the solder matrix.

[0022] 2. The nickel-cobalt-porous carbon-coated nano-titanium dioxide composite particles used in this invention are based on the well-known principles of nano-reinforcement and alloying. Each component works synergistically: nickel and cobalt, as known solder alloying elements, improve the wettability between the solder and the matrix, enhancing the solder's mechanical properties and high-temperature stability; the porous carbon coating structure reduces the agglomeration of nanoparticles in the molten solder, improving dispersion uniformity and interfacial bonding; and nano-titanium dioxide, as a known reinforcing phase, further enhances the solder's strength. The combined effect of these components improves the solder's wettability, mechanical properties, and reliability. Attached Figure Description

[0023] Figure 1 This is a TEM image of nickel-cobalt-porous carbon-coated nano-titanium dioxide prepared in Example 1;

[0024] Figure 2 The infrared spectrum of nickel-cobalt-porous carbon-coated nano-titanium dioxide prepared in Example 1;

[0025] Figure 3 The image shows the XPS spectrum of nickel-cobalt-porous carbon-coated nano-titanium dioxide prepared in Example 1. Detailed Implementation

[0026] The present invention will now be described in detail through specific embodiments. However, these illustrative embodiments are for purposes and uses only to illustrate the invention and do not constitute any limitation on the actual scope of protection of the invention, nor are they intended to limit the scope of protection of the invention to these embodiments. All equivalent transformations or simple substitutions made based on the substantive content of this application should fall within the scope of protection of this application. For parameter ranges not mentioned, intermediate values ​​are selected. Furthermore, for mass percentages or weight percentages not explicitly stated or mentioned, they generally refer to the final concentration after addition.

[0027] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] Example 1.

[0029] (1) Preparation of nickel-cobalt-porous carbon-coated nano-titanium dioxide includes the following steps: Step 1: Preparation of nickel-cobalt bimetallic organic framework: Using cobalt nitrate hexahydrate and nickel nitrate hexahydrate as metal centers, 5-hydroxyisophthalic acid as organic ligand, and N,N-dimethylformamide as solvent, nickel-cobalt bimetallic organic framework is prepared by solvothermal method. The specific steps are as follows: 1.1g of 5-hydroxyisophthalic acid is dissolved in 25mL of N,N-dimethylformamide and shaken at room temperature until completely dissolved to obtain solution A, where the molar concentration of 5-hydroxyisophthalic acid is 0.242M.

[0030] 0.58 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 1.17 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) were added to 20 mL of N,N-dimethylformamide and ultrasonically vibrated at room temperature until completely dissolved to obtain solution B. The molar concentration of cobalt nitrate was 0.1 M and the molar concentration of nickel nitrate was 0.2 M. Solution B was poured into solution A and vibrated at room temperature for 1 h to obtain mixed solution C. Mixed solution C was then transferred to a 50 mL stainless steel high-pressure reactor with a polytetrafluoroethylene liner and reacted at 120 °C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed twice with N,N-dimethylformamide, and vacuum dried at 90 °C for 8 h to obtain the nickel-cobalt bimetallic organic framework.

[0031] Step 2: Preparation of epoxy-functionalized titanium dioxide: The silicon-trimethoxy functional group in the 3-(2,3-epoxypropoxy)propyltrimethoxysilane structure is hydrolyzed to form silanol, which then undergoes a condensation reaction with the hydroxyl groups on the surface of nano-titanium dioxide to generate a siloxane structure, thus obtaining epoxy-functionalized titanium dioxide. The specific steps are as follows: Nano-titanium dioxide (particle size of 60 nm) is placed in a vacuum drying oven at 60 °C and dried for 12 h to obtain dried nano-titanium dioxide.

[0032] Hydrochloric acid was added dropwise to 100 mL of deionized water to adjust the pH of the system to 4. 0.2 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane was added, and the mixture was ultrasonically dispersed for 15 min, magnetically stirred for 30 min, and ultrasonically dispersed again for 15 min to ensure complete hydrolysis and dispersion. 10 g of dried nano-titanium dioxide was added, and the mixture was stirred at 70 °C for 1.5 h. After the reaction was completed, the mixture was washed four times with anhydrous ethanol, centrifuged, and dried in a vacuum drying oven at 50 °C until constant weight was obtained to prepare epoxy-functionalized titanium dioxide.

[0033] Step 3: Preparation of Nickel-Cobalt-Porous Carbon-Coated Nano-Titanium Dioxide: The epoxy functional groups in epoxy-functionalized titanium dioxide undergo a ring-opening reaction with the hydroxyl functional groups in the nickel-cobalt bimetallic organic framework. The epoxy ring breaks and forms CO bonds, which are then covalently linked to coat the titanium dioxide surface with the bimetallic organic framework. Following carbonization, nickel-cobalt-porous carbon-coated nano-titanium dioxide is obtained. The specific steps are as follows: Under nitrogen protection, 3g of epoxy-functionalized titanium dioxide and 0.05g of boron trifluoride diethyl ether complex are added to 50mL of N,N-dioxane. In methylformamide, mechanical stirring was performed until homogeneous. 2g of a nickel-cobalt bimetallic organic framework was added, and ultrasonic dispersion was performed for 30min at an ultrasonic power of 800W and a frequency of 20kHz. The system temperature was raised to 50℃, and the reaction was stirred for 6h. Then, the pH of the system was adjusted to 7 using ammonia. The product was then distilled under reduced pressure, filtered, and collected. It was then vacuum dried at 60℃ for 10h, placed in a ceramic boat, and then placed in a tube furnace. The temperature was raised to 650℃ at a heating rate of 2℃ / min and held at this temperature for 6h under argon protection to obtain nickel-cobalt-porous carbon-coated nano-titanium dioxide.

[0034] The prepared nickel-cobalt-porous carbon-coated nano-titanium dioxide was characterized by transmission electron microscopy, infrared spectroscopy, and X-ray photoelectron spectroscopy. The results are as follows: Figures 1-3 As shown, Figure 1 It exhibits a distinct core-shell structure, with a nickel-cobalt-carbon composite shell covering the outer core of nano-titanium dioxide, and the composite particles do not show obvious large-area agglomeration. The core-shell coating structure improves the agglomeration defects of nanoparticles.

[0035] Figure 2 It can be seen from this that ~1250cm -1 A COC stretching vibration peak appears at ~910 cm⁻¹. -1 The presence of a characteristic peak of epoxy groups indicates that epoxy-functionalized titanium dioxide was successfully synthesized.

[0036] Figure 3 As can be seen, the Ni 2p, Co 2p, Ti 2p and C 1s peaks are clearly visible, which is consistent with the elemental composition of the nickel-cobalt-porous carbon-coated nano-titanium dioxide expected to be prepared in this invention.

[0037] (2) Preparation of alloy solder, including the following steps: 98.3g of tin particles and 0.7g of copper particles are added to a graphite crucible and placed in a resistance furnace for melting. Under a nitrogen atmosphere, the temperature is held at 450℃ for 30 minutes. During the holding period, the mixture is mechanically stirred once every 5 minutes. After the holding period, the mixture is poured into a water-cooled mold to obtain tin-copper solder.

[0038] The prepared tin-copper brazing filler metal was placed in a resistance furnace and heated to 250°C under a nitrogen atmosphere to melt it. 1g of nickel-cobalt-porous carbon-coated nano-titanium dioxide was added, and the temperature was further increased. When the melting temperature reached 350°C, an ultrasonic vibrating rod was placed in the molten brazing filler metal and vibrated intermittently for 60s. Every 10s of vibration was followed by a 5s pause, and the temperature was further increased. When the temperature reached 450°C, ultrasonic vibration was applied again for 10s, followed by holding at that temperature for 30min. After holding at that temperature, the molten brazing filler metal was poured into a water-cooled mold to obtain the alloy solder.

[0039] Example 2.

[0040] The difference from Example 1 is that the amount of nickel-cobalt-porous carbon-coated nano-titanium dioxide added is 0.5g; and the amount of Sn particles added is 98.8g.

[0041] Example 3.

[0042] The difference from Example 1 is that the amount of nickel-cobalt-porous carbon-coated nano-titanium dioxide added is 1.5g; and the amount of Sn particles added is 97.8g.

[0043] Example 4.

[0044] The difference from Example 1 is that the amount of nickel-cobalt-porous carbon-coated nano-titanium dioxide added is 0.3g; and the amount of Sn particles added is 99g.

[0045] Example 5.

[0046] The difference from Example 1 is that the amount of Cu particles added is 0.4g; the amount of Sn particles added is 98.6g.

[0047] Example 6.

[0048] The difference from Example 1 is that the amount of Cu particles added is 0.9g; the amount of Sn particles added is 98.1g.

[0049] Example 7.

[0050] The difference from Example 1 is that the amount of nickel nitrate hexahydrate added is 0.58g.

[0051] Example 8.

[0052] The difference from Example 1 is that the amount of nickel nitrate hexahydrate added is 1.75g.

[0053] Example 9.

[0054] The difference from Example 1 is that the amount of 5-hydroxyisophthalic acid added is 0.88g, and the molar ratio of 5-hydroxyisophthalic acid to the metal center is 0.8:1.

[0055] Example 10.

[0056] The difference from Example 1 is that the amount of 5-hydroxyisophthalic acid added is 1.32g, and the molar ratio of 5-hydroxyisophthalic acid to the metal center is 1.2:1.

[0057] Comparative Example 1.

[0058] The difference from Example 1 is that nano-titanium dioxide is used instead of nickel-cobalt-porous carbon-coated nano-titanium dioxide.

[0059] Comparative Example 2.

[0060] The difference from Example 1 is that nickel-cobalt-porous carbon is used instead of nickel-cobalt-porous carbon to coat nano-titanium dioxide.

[0061] The preparation method of nickel-cobalt-porous carbon is as follows: the nickel-cobalt bimetallic organic framework prepared in Example 1 is placed in a ceramic boat and then placed in a tube furnace. The temperature is increased to 650°C at a heating rate of 2°C / min and held at the temperature for 6 hours under argon protection to obtain nickel-cobalt-porous carbon.

[0062] Comparative Example 3.

[0063] The difference from Example 1 is that: nickel-cobalt-porous carbon-coated nano-titanium dioxide is not added, and the amount of Sn particles added is 99.3g.

[0064] Comparative Example 4.

[0065] The difference from Example 1 is that only mechanical grinding and mixing are performed while keeping the amount of nickel-cobalt-porous carbon and nano titanium dioxide the same.

[0066] Performance testing.

[0067] The wetting properties of the alloy solders prepared in the embodiments and comparative examples of this invention were tested according to SJ / T 11390-2019 "Test Methods for Lead-Free Solder". The copper plate size was 30mm × 30mm × 0.30mm. The wetting value (spread rate) was calculated by the following formula: S R = (DH) / D×100%, where S RV represents the wetting value (%), H represents the height of the solder after expansion (mm), and D represents the diameter of the test solder when it is considered as a sphere (mm). D = 1.24V 1 / 3 V is the volume (mm²) of the experimental circular solder. 3 ).

[0068] The tensile strength of the alloy solders prepared in the embodiments and comparative examples of this invention was tested according to GB / T 228.1. The tensile strength was calculated by the following formula: σ=F / S, where σ is the tensile strength (N / mm²). 2 F represents the tensile force (N) at which the specimen breaks, and S represents the average cross-sectional area (mm²) of the central region along the parallel length of the specimen. 2 (Measure at least three points and take the average); the test results are shown in Table 1 below.

[0069] The tensile strength of the alloy solders prepared in the embodiments and comparative examples of this invention at 150℃ was tested according to GB / T 4338-2006 "Metallic materials - High temperature tensile test method". The test results are shown in Table 1.

[0070] The alloy solders prepared in the embodiments and comparative examples of the present invention were placed in a constant temperature and humidity chamber at 85℃ / 85%RH for accelerated aging for 168 hours. Then, the wetting performance was retested according to SJ / T 11390-2019 "Test Method for Lead-Free Solder". The performance retention rate after damp heat aging was calculated. The wetting value retention rate after aging = (wetting value after aging / initial wetting value) × 100%. The test results are shown in Table 1.

[0071] Table 1 Performance test results of alloy solder

[0072]

[0073] The experimental results above show that, by comparing Examples 1 to 4, by changing the amount of nickel-cobalt-porous carbon-coated nano-titanium dioxide added, as the content of nickel-cobalt-porous carbon-coated nano-titanium dioxide increases (from 0.3g to 1.5g), the wettability (wetting value increased from 72.2% to 79.2%) and mechanical properties (tensile strength increased from 35.1N / mm² to 41.9N / mm²) of the solder improve.

[0074] A comparison of Examples 5 and 6 shows that by changing the amount of Cu particles added, as the Cu particle content increases (from 0.4g to 0.9g), the wettability of the solder (wetting value decreases from 79.8% to 76%) decreases, while the mechanical properties (tensile strength increases from 27.4N / mm² to 40.7N / mm²) increase.

[0075] A comparison of Example 1 and Comparative Example 3 shows that by adding nickel-cobalt-porous carbon-coated nano-titanium dioxide, the wettability (wetting value increased from 67.6% to 77.9%) and mechanical properties (tensile strength increased from 30.5 N / mm² to 39.8 N / mm²) of the solder can be significantly improved. 2 ).

[0076] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 2, the wettability and mechanical properties of the solder decrease when nano-titanium dioxide is not coated or added.

[0077] A comparison of Examples 1, 7, and 8 shows that as the molar ratio of Ni to Co increases, the wetting value also increases, indicating that Ni contributes more to wetting and strength than Co.

[0078] A comparison of Examples 1, 9 and 10 shows that the optimal ratio of organic ligand to metal center is 1:1. Too much or too little will cause a decrease in performance.

[0079] A comparison of Example 1 and Comparative Example 4 shows that the core-shell coating structure significantly improves solder wetting properties, mechanical properties, and aging retention compared to mechanical mixing, indicating that the synergistic effect of the core-shell structure is irreplaceable.

[0080] The solder prepared in the example has higher tensile strength at 150°C, higher wetting value retention rate after damp heat aging, and better long-term service reliability, thus improving the problems of traditional SnCu solder being prone to softening at high temperatures and wetting failure after aging.

Claims

1. A method for preparing a photovoltaic solder ribbon alloy, characterized in that, Includes the following steps: Tin and copper particles are added to a crucible and placed in a resistance furnace for melting. Under a nitrogen atmosphere, the temperature is held at 400-500℃ for 25-35 minutes, and then poured into a water-cooled mold to obtain tin-copper brazing filler metal. The prepared tin-copper brazing filler metal is placed in a resistance furnace and heated to 240-260℃ under a nitrogen atmosphere. Nickel-cobalt-porous carbon-coated nano-titanium dioxide is added, and the temperature is raised to 300-390℃. Ultrasonic vibration is performed for 40-80s with an ultrasonic power of 500-1000W and a frequency of 20-40kHz. The temperature is then raised to 400-500℃, and ultrasonic vibration is performed for 5-15s with an ultrasonic power of 500-1000W and a frequency of 20-40kHz. The temperature is held for 25-35 minutes. After the holding period, the filler metal is poured into a water-cooled mold to obtain the alloy solder. The raw material formula of the alloy solder, by mass percentage, is: 0.4%-0.9% copper particles, 0.3%-1.5% nickel-cobalt-porous carbon-coated nano titanium dioxide, and the balance tin particles; The preparation method of the nickel-cobalt-porous carbon-coated nano-titanium dioxide is as follows: Step 1: Using cobalt nitrate hexahydrate and nickel nitrate hexahydrate as metal centers and 5-hydroxyisophthalic acid as organic ligand, a nickel-cobalt bimetallic organic framework was prepared by a solvothermal method. Step 2: The dried nano-titanium dioxide was modified by hydrolyzing a silane coupling agent to generate a siloxane structure, thus obtaining epoxy-functionalized titanium dioxide. The silane coupling agent was 3-(2,3-epoxypropoxy)propyltrimethoxysilane. Step 3: The epoxy functional groups in epoxy-functionalized titanium dioxide undergo a ring-opening reaction with the hydroxyl functional groups in the nickel-cobalt bimetallic organic framework. The ring-opening reaction is catalyzed by boron trifluoride diethyl ether complex and the solvent is N,N-dimethylformamide. Then, carbonization treatment is carried out to obtain nickel-cobalt-porous carbon-coated nano-titanium dioxide. The method for preparing the dried nano-titanium dioxide is as follows: place the nano-titanium dioxide in a vacuum drying oven at 50-70℃ and dry it for 10-15 hours to obtain the dried nano-titanium dioxide; the particle size of the nano-titanium dioxide is 10-100nm.

2. The method for preparing a photovoltaic solder ribbon alloy according to claim 1, characterized in that, The molar ratio of cobalt nitrate hexahydrate to nickel nitrate hexahydrate is 1:(1-3).

3. The method for preparing a photovoltaic solder ribbon alloy according to claim 1, characterized in that, The carbonization process involves heating the temperature to 600-700℃ at a rate of 1-4℃ / min under an inert gas atmosphere and holding it at that temperature for 4-8 hours.

4. The method for preparing a photovoltaic solder ribbon alloy according to claim 3, characterized in that, The inert gas is one of argon, nitrogen, or helium.

5. The method for preparing a photovoltaic solder ribbon alloy according to claim 1, characterized in that, The preparation method of the nickel-cobalt bimetallic organic framework is as follows: Dissolve 5-hydroxyisophthalic acid in N,N-dimethylformamide and shake at room temperature until completely dissolved to obtain solution A; Cobalt nitrate hexahydrate and nickel nitrate hexahydrate were added to N,N-dimethylformamide and shaken at room temperature until completely dissolved to obtain solution B. Solution B was poured into solution A and shaken at room temperature for 0.5-2 hours to obtain mixed solution C. Mixed solution C was then transferred to a high-pressure reactor and reacted at 110-130℃ for 4-8 hours. After cooling to room temperature, the mixture was filtered, washed, and vacuum dried at 85-95℃ for 6-10 hours to obtain a nickel-cobalt bimetallic organic framework.

6. The method for preparing a photovoltaic solder ribbon alloy according to claim 1, characterized in that, The molar ratio of the organic ligand to the metal center is (0.8-1.2):

1.

7. The method for preparing a photovoltaic solder ribbon alloy according to claim 1, characterized in that, The crucible is one of the following: graphite crucible, alumina crucible, and silicon carbide crucible.

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