Welding-aid material for photovoltaic module, preparation method of welding-aid material and series welding composite lamination welding process

Abstract

The invention belongs to the technical field of photovoltaic welding, and particularly provides a welding aid material for a photovoltaic module, a preparation method of the welding aid material and a series welding composite lamination welding process. The preparation method of the soldering-aid material for the photovoltaic module comprises the following steps: A, enabling MAL-PEG-NH2 and 2-formylphenylboronic acid to react to prepare a precursor, and then enabling the precursor to react with a furan derivative to prepare an inhibitor; and B, uniformly mixing the solvent and the inhibitor, then adding the activating agent, the film-forming agent, the surfactant, the pH regulator, the antioxidant, the corrosion inhibitor and the rheological agent, and uniformly mixing to obtain the water-based paint. The prepared welding-aid material for the photovoltaic module has the advantages that generation of interlayer IMC is inhibited, and the welding strength is improved.

Description

Technical Field

[0001] The present application belongs to the field of photovoltaic welding technology, and in particular relates to a flux material for photovoltaic modules, a preparation method thereof, and a string welding composite lamination welding process. Background Art

[0002] The photovoltaic module cell welding process involves welding individual solar cells in series to form a cell string, which forms the basic component of a solar panel. The conversion efficiency of a solar panel depends on the quality of its electrical performance, and the performance of the cell string is affected by the quality of the welding of the individual cells and the string.

[0003] Flux plays a crucial role in the photovoltaic soldering process, removing oxides, preventing reoxidation, reducing surface tension, and promoting solder wetting and spreading. Currently, fluxes can be categorized by composition into organic fluxes, inorganic fluxes, and hybrid organic-inorganic fluxes; by activity into strong, medium, and weakly active fluxes; and by cleaning method into solvent-cleanable, water-cleanable, and no-clean types.

[0004] As performance requirements for photovoltaic modules continue to rise, research on fluxes has deepened. For example, patent application publication number CN107322188A discloses a flux for photovoltaic ribbon welding, comprising zinc chloride, ammonium chloride, hydroxy acid, citric acid, triisopropanolamine, dibutylamine, cetyltrimethylammonium bromide, acrylic resin, silicon-modified acrylic resin, sorbitol, triethanolamine, a humectant, and deionized water. The flux comprises the following components, calculated by mass percentage: zinc chloride, ammonium chloride, hydroxy acid, citric acid, triisopropanolamine, dibutylamine, cetyltrimethylammonium bromide, acrylic resin, silicon-modified acrylic resin, sorbitol, triethanolamine, a humectant, and the remainder being deionized water. By doing so, the flux reduces the surface tension of the solder, improves wettability, reduces post-weld slag, and enhances photovoltaic welding quality.

[0005] For example, the patent document with application publication number CN116493808A discloses a water-based flux for photovoltaic cell welding, which includes the following raw materials in percentage by weight: 0.5-2% activator, 0.05-1% surfactant, 0.05-0.2% corrosion inhibitor, 1-5% auxiliary agent, 0.1-0.5% defoaming agent, and 92-99% deionized water. The flux improves the deoxidation welding fluxing ability, has a lower residual crystallization effect, improves the work efficiency of the photovoltaic module factory, and the lower product raw material cost helps the efficiency of the photovoltaic module factory.

[0006] The flux used in the aforementioned photovoltaic welding process has a weak inhibitory effect on the growth of IMCs during welding, and the amount of atomic migration at the interface between the substrate and the solder is large. Therefore, how to improve the flux's ability to inhibit the growth of intermetallic compounds during welding is an urgent problem to be solved. Summary of the Invention

[0007] In response to the above problems, in order to further suppress the IMC growth and interface atomic migration during the welding process of photovoltaic modules, the present application provides a flux material for photovoltaic modules, a preparation method thereof, and a series welding composite lamination welding process.

[0008] This application first provides a method for preparing a flux material for a photovoltaic module, comprising the following steps: A: MAL-PEG-NH2 and 2-formaldehyde phenylboronic acid are reacted to prepare a precursor, which is then reacted with a furan derivative to prepare an inhibitor; B: Take the solvent and inhibitor and mix them evenly, then add the activator, film-forming agent, surfactant, pH adjuster, antioxidant, corrosion inhibitor and rheological agent and mix them evenly.

[0009] Furthermore, in step A, the molar ratio of MAL-PEG-NH2 to 2-formylphenylboronic acid is 1:(2-2.5).

[0010] Furthermore, in step A, the mass ratio of the precursor to the furan derivative is (5-10):1.

[0011] Furthermore, in step A, n of the PEG chain in the MAL-PEG-NH2 molecule is less than 6000.

[0012] Furthermore, in the step A, the furan derivative is prepared from phenylphosphoryl dichloride and furfurylamine.

[0013] Furthermore, in step B, the solvent is one or more of ethylene glycol monobutyl ether, propylene glycol methyl ether, n-octanol, tetrahydrofurfural, glycerol, diethylene glycol, and ethanol; And / or, in step B, the activator is one or more of methylsuccinic acid, DL-malic acid, lactic acid, oxalic acid, sebacic acid, azelaic acid, citric acid, salicylic acid, palmitic acid, adipic acid, benzoic acid, and stearic acid; And / or, in step B, the film-forming agent is a rosin-type film-forming agent; And / or, in step B, the surfactant is a nonionic surfactant; And / or, in step B, the antioxidant is a phenolic antioxidant; And / or, in step B, the corrosion inhibitor is benzotriazole; And / or, in step B, the rheological agent is one or more of hydrogenated castor oil, ethyl cellulose, and polyamide wax.

[0014] The present application provides a flux material for photovoltaic modules, which is prepared using the above-mentioned preparation method.

[0015] The present application also provides a series welding composite lamination welding process, comprising the following steps: S1: Install the interconnecting strip on the welding machine; S2: Use coating equipment to evenly apply the photovoltaic module flux material on the surface of the soldering pattern cells or interconnecting bars, and use hot air for preliminary curing; and / or, using a coating device to evenly apply silver glue or solder paste or a photovoltaic module flux material on the surface of the battery or the surface of the interconnect bar, and using hot air for preliminary curing; the battery is one of an HJT / topcon / BC battery, a perovskite battery, and an HJT / Topcon perovskite tandem battery; The photovoltaic module flux material is prepared by the above-mentioned preparation method; S3: The interconnecting strips and the battery grid lines are stacked and pre-welded to form a string; then the welding is strengthened by lamination vacuum heat welding.

[0016] Furthermore, in step S1, the interconnection bar is a SnPb-coated interconnection bar or a SnPbBi-coated low-temperature interconnection bar.

[0017] Furthermore, in step S3, the pre-welding is performed by infrared welding, hot air welding or electromagnetic welding.

[0018] Compared with the prior art, this application has the following beneficial effects: 1. The flux material of this application is compounded with multiple components, including solvents, inhibitors, activators, film formers, surfactants, pH adjusters, antioxidants, corrosion inhibitors, and rheological agents. It can undergo physical and chemical reactions with the surface of the base metal, forming an adsorption film with excellent wettability, which wets the metal surface. During the welding process, it can dissolve and remove oxides on the base surface, wet and spread with the solder, reduce the formation of intermetallic compounds, and thus improve the weld strength and enhance the performance of the photovoltaic module.

[0019] 2. The inhibitor in this application is prepared by first reacting MAL-PEG-NH2 with 2-formylphenylboronic acid to form a precursor, which is then reacted with a furan derivative to form a dynamic cross-linked network, thereby enhancing the adsorption effect of the adsorption film. During the welding process, as the temperature rises, the DA bonds in the dynamic cross-linked network break, and the dynamic cross-linked network disintegrates, further enhancing the wetting and spreading effect on the base metal surface. At the same time, it also forms a carbon skeleton structure, inhibiting and hindering atomic migration between the solder and the base metal, further reducing the formation of interlayer IMCs, and improving welding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are SEM images of the solder joint cross sections of Examples 1-2 and Control Groups 1-2 of the present application. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0022] This application has conducted extensive experimental research on the wetting properties of flux and the different mechanisms for inhibiting IMC formation. Specifically, this application provides a method for preparing a flux material for photovoltaic modules, comprising the following steps: A: MAL-PEG-NH2 and 2-formaldehyde phenylboronic acid are reacted to prepare a precursor, which is then reacted with a furan derivative to prepare an inhibitor; B: Take the solvent and inhibitor and mix them evenly, then add the activator, film-forming agent, surfactant, pH adjuster, antioxidant, corrosion inhibitor and rheological agent and mix them evenly.

[0023] Furthermore, in step A, the molar ratio of MAL-PEG-NH2 to 2-formylphenylboronic acid is 1:(2-2.5).

[0024] Furthermore, in step A, the mass ratio of the precursor to the furan derivative is (5-10):1.

[0025] Furthermore, in step A, n of the PEG chain in the MAL-PEG-NH2 molecule is less than 6000.

[0026] Furthermore, in the step A, the furan derivative is prepared from phenylphosphoryl dichloride and furfurylamine.

[0027] In some specific embodiments, in step A, the molar ratio of MAL-PEG-NH2 to 2-formylphenylboronic acid can be 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, or 1:2.5. More preferably, in step A, a molar ratio of MAL-PEG-NH2 to 2-formylphenylboronic acid of 1:2.2 can achieve better experimental results.

[0028] In some specific embodiments, in step A, the mass ratio of the precursor to the furan derivative can be 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, or 10:1. More preferably, under normal circumstances, in step A, when the mass ratio of the precursor to the furan derivative is 6.5:1, better experimental results can be achieved.

[0029] In some specific embodiments, in step A, n of the PEG chain in the MAL-PEG-NH2 molecule can be 400, 600, 800, 1000, 1200, 2000, 2500, or 3000. More preferably, under normal circumstances, in step A, when n of the PEG chain in the MAL-PEG-NH2 molecule is 800, better experimental results can be obtained.

[0030] Furthermore, in step B, the solvent is one or more of ethylene glycol monobutyl ether, propylene glycol methyl ether, n-octanol, tetrahydrofurfural, glycerol, diethylene glycol, and ethanol; And / or, in step B, the activator is one or more of methylsuccinic acid, DL-malic acid, lactic acid, oxalic acid, sebacic acid, azelaic acid, citric acid, salicylic acid, palmitic acid, adipic acid, benzoic acid, and stearic acid; And / or, in step B, the film-forming agent is a rosin-type film-forming agent; And / or, in step B, the surfactant is a nonionic surfactant; And / or, in step B, the antioxidant is a phenolic antioxidant; And / or, in step B, the corrosion inhibitor is benzotriazole; And / or, in step B, the rheological agent is one or more of hydrogenated castor oil, ethyl cellulose, and polyamide wax.

[0031] In some specific embodiments, under normal circumstances, in step B, when the organic acid consists of DL-malic acid and salicylic acid, better experimental results can be obtained. More preferably, in step B, the organic acid consists of DL-malic acid and salicylic acid in a mass ratio of 5:3.

[0032] In some specific embodiments, in step B, the solvent is preferably selected from ethylene glycol monobutyl ether, propylene glycol methyl ether, n-octanol, and tetrahydrofurfural. More preferably, under normal circumstances, the solvent is ethylene glycol monobutyl ether, propylene glycol methyl ether, n-octanol, and tetrahydrofurfural in a mass ratio of 1:2:3:3, which results in better experimental results.

[0033] In some specific embodiments, more preferably, in step B, the film-forming agent is ice white rosin.

[0034] In some specific embodiments, more preferably, in step B, when octylphenol polyoxyethylene ether is selected as the surfactant, the effect is better.

[0035] In some specific embodiments, more preferably, in step B, when hydroquinone is selected as the antioxidant, better experimental results can be obtained.

[0036] The present application provides a flux material for photovoltaic modules, which is prepared using the above-mentioned preparation method.

[0037] The present application also provides a series welding composite lamination welding process, comprising the following steps: S1: Install the interconnecting strip on the welding machine; S2: Use coating equipment to evenly apply the photovoltaic module flux material on the surface of the soldering pattern cells or interconnecting bars, and use hot air for preliminary curing; and / or, using a coating device to evenly apply silver glue or solder paste or a photovoltaic module flux material on the surface of the battery or the surface of the interconnect bar, and using hot air for preliminary curing; the battery is one of an HJT / topcon / BC battery, a perovskite battery, and an HJT / Topcon perovskite tandem battery; The photovoltaic module flux material is prepared by the above-mentioned preparation method; S3: The interconnecting strips and the battery grid lines are stacked and pre-welded to form a string; then the welding is strengthened by lamination vacuum heat welding.

[0038] Furthermore, in step S1, the interconnection bar is a SnPb-coated interconnection bar or a SnPbBi-coated low-temperature interconnection bar.

[0039] Furthermore, in step S3, the pre-welding is performed by infrared welding, hot air welding or electromagnetic welding.

[0040] Generally, in step S1, better technical effects can be achieved when the interconnection bars are SnPbBi coated low-temperature interconnection bars.

[0041] Preferably, the photovoltaic module welding process of the present application can be applied to the welding of OBBtopcon / HJT cells and XBC / perovskite cells.

[0042] Example 1 The method for preparing the flux material for photovoltaic modules of this embodiment includes the following steps: A: Add 100 mL of anhydrous ethanol, 0.05 mol of MAL-PEG-NH2 (n of the PEG chain is 800), and 0.11 mol of 2-formaldehyde phenylboronic acid to a 500 mL four-necked flask equipped with a stirrer, thermometer, dropping funnel, and condenser. Mix well, then add sodium borohydride and a small amount of PBS buffer solution. React at room temperature under nitrogen to prepare the precursor. Then, 5 g of the precursor and 0.77 g of a furan derivative (5-hydroxymethylfurfural) were dissolved in 150 mL of anhydrous ethanol in a round-bottom flask, and a Lewis acid catalyst was added. The mixture was refluxed for 5 h to obtain the inhibitor. B: Take 45g of solvent (composed of 5g of ethylene glycol monobutyl ether, 10g of propylene glycol methyl ether, 15g of tetrahydrofurfuryl alcohol, and 15g of n-octanol), mix 2g of inhibitor evenly, then add 8g of activator (composed of 5g of DL-malic acid and 3g of salicylic acid), 30g of film-forming agent (ice white rosin), 1g of surfactant (octylphenol polyoxyethylene ether-10), pH adjuster, 1g of antioxidant (hydroquinone), 1g of corrosion inhibitor (benzotriazole), and 5g of rheological agent (hydrogenated castor oil) and continue mixing evenly.

[0043] The photovoltaic module welding process of this embodiment includes the following steps: S1: Install SnPbBi coated low temperature interconnect strips on the welding machine; S2: Use coating equipment to evenly apply the flux material for photovoltaic modules on the surface of the cell or the surface of the interconnect bar, and use hot air for preliminary curing; the cell is one of HJT / topcon / BC cell, perovskite cell, or HJT\Topcon perovskite tandem cell; S3: The interconnection strips and the battery grid lines are stacked and pre-welded to form a string; then lamination vacuum heat welding is used to strengthen the welding. The lamination temperature is 150°C and the lamination time is 20 minutes.

[0044] Example 2 The method for preparing the flux material for photovoltaic modules of this embodiment includes the following steps: A: Add 100 mL of anhydrous ethanol, 0.05 mol of MAL-PEG-NH2 (n of the PEG chain is 800), and 0.11 mol of 2-formylphenylboronic acid to a 500 mL four-necked flask equipped with a stirrer, thermometer, dropping funnel, and condenser. Mix well, then add sodium borohydride and a small amount of PBS buffer solution. React at room temperature under nitrogen to prepare the precursor. Then, 5 g of the precursor and 0.77 g of the furan derivative were dissolved in 150 mL of anhydrous ethanol in a round-bottom flask, and a Lewis acid catalyst was added. The reaction was refluxed for 5 h to obtain the inhibitor. B: Take 45g of solvent (composed of 5g of ethylene glycol monobutyl ether, 10g of propylene glycol methyl ether, 15g of tetrahydrofurfuryl alcohol, and 15g of n-octanol), mix 2g of inhibitor evenly, then add 8g of activator (composed of 5g of DL-malic acid and 3g of salicylic acid), 30g of film-forming agent (ice white rosin), 1g of surfactant (octylphenol polyoxyethylene ether-10), pH adjuster, 1g of antioxidant (hydroquinone), 1g of corrosion inhibitor (benzotriazole), and 5g of rheological agent (hydrogenated castor oil) and continue mixing evenly.

[0045] The furan derivative of this example was prepared by the following steps: 100 mL of tetrahydrofuran, 0.2 mol of triethylamine, and 0.3 mol of furfurylamine were added to a 500 mL three-necked flask and mixed evenly. The mixture was then placed in an ice-water bath. Under nitrogen protection, 100 mL of a tetrahydrofuran solution containing 0.1 mol of phenylphosphoryl dichloride was slowly added dropwise. After 30 minutes of addition, the mixture was reacted for 6 hours, filtered, precipitated with petroleum ether, and the resulting precipitate was washed and dried.

[0046] The photovoltaic module welding process of this embodiment includes the following steps: S1: Install SnPbBi coated low temperature interconnect strips on the welding machine; S2: Use coating equipment to evenly apply the flux material for photovoltaic modules on the surface of the cell or the surface of the interconnect bar, and use hot air for preliminary curing; the cell is one of HJT / topcon / BC cell, perovskite cell, or HJT\Topcon perovskite tandem cell; S3: The interconnection strips and the battery grid lines are stacked and pre-welded to form a string; then lamination vacuum heat welding is used to strengthen the welding. The lamination temperature is 150°C and the lamination time is 20 minutes.

[0047] Control group 1 The preparation method of the solder flux material of this control group includes the following steps: taking 45g of solvent (composed of 5g of ethylene glycol monobutyl ether, 10g of propylene glycol methyl ether, 15g of tetrahydrofurfuryl alcohol, and 15g of n-octanol) and 2g of MAL-PEG-NH2, mixing them evenly, and then adding 8g of activator (composed of 5g of DL-malic acid and 3g of salicylic acid), 30g of film-forming agent (ice white rosin), 1g of surfactant (octylphenol polyoxyethylene ether-10), pH adjuster, 1g of antioxidant (hydroquinone), 1g of corrosion inhibitor (benzotriazole), and 5g of rheological agent (hydrogenated castor oil) and continuing to mix evenly to obtain the solder flux material.

[0048] The photovoltaic module welding process of this control group includes the following steps: S1: Install SnPbBi coated low temperature interconnect strips on the welding machine; S2: Use coating equipment to evenly apply flux material on the surface of the cell or interconnect bar, and use hot air for preliminary curing; the cell is one of HJT / topcon / BC cell, perovskite cell, or HJT\Topcon perovskite tandem cell; S3: The interconnection strips and the battery grid lines are stacked and pre-welded to form a string; then lamination vacuum heat welding is used to strengthen the welding. The lamination temperature is 150°C and the lamination time is 20 minutes.

[0049] Control group 2 The preparation method of the flux material for photovoltaic modules of this control group includes the following steps: A: Add 100 mL of tetrahydrofuran, 0.2 mol of triethylamine, and 0.3 mol of furfurylamine to a 500 mL three-necked flask and mix thoroughly. Then, place in an ice-water bath. Under nitrogen, slowly add dropwise 0.1 mol of phenylphosphoryl dichloride in 100 mL of tetrahydrofuran. After 30 minutes of complete addition, react for 6 hours, filter, and precipitate with petroleum ether. Wash and dry the resulting precipitate to obtain a furan derivative. B: Take 45g of solvent (composed of 5g of ethylene glycol monobutyl ether, 10g of propylene glycol methyl ether, 15g of tetrahydrofurfuryl alcohol, and 15g of n-octanol) and 2g of furan derivative and mix them evenly. Then add 8g of activator (composed of 5g of DL-malic acid and 3g of salicylic acid), 30g of film-forming agent (ice white rosin), 1g of surfactant (octylphenol polyoxyethylene ether-10), pH adjuster, 1g of antioxidant (hydroquinone), 1g of corrosion inhibitor (benzotriazole), and 5g of rheological agent (hydrogenated castor oil) and continue mixing evenly.

[0050] The photovoltaic module welding process of this control group includes the following steps: S1: Install SnPbBi coated low temperature interconnect strips on the welding machine; S2: Use coating equipment to evenly apply flux material on the surface of the cell or interconnect bar, and use hot air for preliminary curing; the cell is one of HJT / topcon / BC cell, perovskite cell, or HJT\Topcon perovskite tandem cell; S3: The interconnection strips and the battery grid lines are stacked and pre-welded to form a string; then lamination vacuum heat welding is used to strengthen the welding. The lamination temperature is 150°C and the lamination time is 20 minutes.

[0051] Performance testing 1. Welding performance test was carried out according to GB / T9491-2021 standard. The cross-section of the solder joints obtained from the soldering materials of Examples 1-2 and Control Groups 1-2 was observed by electron scanning electron microscopy. The results are as follows: Figure 1As shown, it can be seen that the flux material of the present application effectively inhibits the growth of the IMC layer of the solder joint, refines the solder joint structure to a certain extent, and obtains a better welding effect.

[0052] Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a flux material for a photovoltaic module, characterized in that: The steps include: A: MAL-PEG-NH2 and 2-formaldehyde phenylboronic acid are reacted to prepare a precursor, which is then reacted with a furan derivative to prepare an inhibitor; B: Take the solvent and inhibitor and mix them evenly, then add the activator, film-forming agent, surfactant, pH adjuster, antioxidant, corrosion inhibitor and rheological agent and mix them evenly.

2. The method for preparing a flux material for photovoltaic modules according to claim 1, wherein: In step A, the molar ratio of MAL-PEG-NH2 to 2-formylphenylboronic acid is 1:(2-2.5).

3. The method for preparing a flux material for photovoltaic modules according to claim 1, wherein: In step A, the mass ratio of the precursor to the furan derivative is (5-10):

1.

4. The method for preparing a flux material for a photovoltaic module according to claim 1, wherein: In step A, the n of the PEG chain in the MAL-PEG-NH2 molecule is less than 6000.

5. The method for preparing a flux material for photovoltaic modules according to claim 3, wherein: In step A, a furan derivative is prepared from phenylphosphoryl dichloride and furfurylamine.

6. The method for preparing a flux material for a photovoltaic module according to claim 1, wherein: In step B, the solvent is one or more of ethylene glycol monobutyl ether, propylene glycol methyl ether, n-octanol, tetrahydrofurfural, glycerol, diethylene glycol, and ethanol; And / or, in step B, the activator is one or more of methylsuccinic acid, DL-malic acid, lactic acid, oxalic acid, sebacic acid, azelaic acid, citric acid, salicylic acid, palmitic acid, adipic acid, benzoic acid, and stearic acid; And / or, in step B, the film-forming agent is a rosin-type film-forming agent; And / or, in step B, the surfactant is a nonionic surfactant; And / or, in step B, the antioxidant is a phenolic antioxidant; And / or, in step B, the corrosion inhibitor is benzotriazole; And / or, in step B, the rheological agent is one or more of hydrogenated castor oil, ethyl cellulose, and polyamide wax.

7. A flux material for photovoltaic modules, characterized by: The method is as described in any one of claims 1 to 6.

8. A series welding composite lamination welding process, characterized in that: The steps include: S1: Install the interconnecting strip on the welding machine; S2: Use coating equipment to evenly apply the photovoltaic module flux material on the surface of the soldering pattern cells or interconnecting bars, and use hot air for preliminary curing; and / or, using a coating device to evenly apply silver glue or solder paste or a photovoltaic module flux material on the surface of the battery or the surface of the interconnect bar, and using hot air for preliminary curing; the battery is one of an HJT / topcon / BC battery, a perovskite battery, and an HJT / Topcon perovskite tandem battery; The photovoltaic module flux material is prepared by the preparation method according to any one of claims 1 to 6; S3: The interconnecting strips and the battery grid lines are stacked and pre-welded to form a string; then the welding is strengthened by lamination vacuum heat welding.

9. The string welding composite lamination welding process according to claim 8, characterized in that: In the step S1, the interconnection bar is a SnPb-coated interconnection bar or a SnPbBi-coated low-temperature interconnection bar.

10. The string welding composite lamination welding process according to claim 8, characterized in that: In step S3, the pre-welding is performed by infrared welding, hot air welding or electromagnetic welding.

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