Cyanide-free electroplating silver-coated copper conductive material, preparation method thereof and crystalline silicon solar cell

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides a cyanide-free electroplating silver-coated copper conductive material, a preparation method thereof and a crystalline silicon solar cell. The silver-coated copper electrode provided by the embodiment of the invention comprises a copper core and a copper-tin alloy electroplated layer coated on the surface of the copper core, the surface of the pre-plating material is coated with the silver electroplating layer; the surface of the silver-coated copper material is coated with the self-repairing layer; wherein the self-repairing layer comprises a resin film and a pH response type microcapsule, the microcapsule is embedded in the resin film, and the microcapsule is filled with an ammonium molybdate corrosion inhibitor. The copper-silver interface bonding force can be improved through the copper-tin alloy electroplated layer, and the silver layer material does not contain cyanogen and is environmentally friendly; the corrosion inhibitor in the pH response type microcapsule in the self-repairing film layer on the surface of the silver layer is released under a specific pH condition to form a protection film on the silver layer again, so that the self-repairing purpose is achieved, and the dynamic protection effect is achieved.

Description

Technical Field

[0001] The present application relates to the photovoltaic field, and in particular to a cyanide-free electroplated silver-clad copper conductive material, a preparation method thereof, and a crystalline silicon solar cell. Background Art

[0002] The electrode conductive materials of solar cells generally include silver-coated copper materials; in the traditional manufacturing process of silver-coated copper electrode materials, electroplating solutions containing cyanide (such as potassium silver cyanide) are widely used to deposit the silver layer. Although this process can effectively achieve stable coordination of silver ions and evenly coat silver on the copper substrate, due to the high toxicity of cyanide, it not only poses a health threat to operators, but may also cause serious environmental pollution, especially in the case of improper disposal of waste liquid. In addition, this process requires high-temperature sintering (temperature exceeding 500°C) to enhance the bonding between the silver layer and the copper core, which not only increases energy consumption, but may also cause material deformation or other quality problems related to thermal effects.

[0003] Early attempts to improve the silver-coated copper technology mainly relied on chemical silver plating to form a silver layer on the surface of the copper core, usually using thiosulfate as a chelating agent. However, this method has the problem of insufficient silver layer coverage, which is often less than 90%. This makes the copper base layer easily exposed to the external environment and oxidized, affecting the stability and service life of the electrode. More importantly, the interfacial bonding strength between the silver layer and the copper core is weak, usually less than 50MPa. Under mechanical stress (such as bending) or after experiencing extreme temperature changes, the silver layer is prone to peeling, seriously affecting the electrical properties and structural integrity of the electrode.

[0004] To improve the oxidation resistance of silver-clad copper electrodes, studies have applied a physical protective layer containing organic corrosion inhibitors such as benzotriazole to the surface of the silver layer to form a static antioxidant barrier. While this measure can prevent external oxidizing media from directly contacting the silver layer to a certain extent, such static antioxidant layers are powerless against microcracks that develop within the silver layer. Once microcracks appear in the silver layer, the antioxidant layer cannot self-repair, thus losing its protective function, ultimately leading to further oxidation of the silver layer and a decline in overall performance. Summary of the Invention

[0005] The embodiments of the present application provide a cyanide-free electroplated silver-coated copper conductive material, a preparation method thereof, and a crystalline silicon solar cell, which are at least environmentally friendly and pollution-free; are beneficial for enhancing the interfacial bonding strength between the copper layer and the silver layer, making it difficult to peel off; and are beneficial for dynamically self-repairing tiny cracks in the silver layer, thereby improving the protective performance of the material.

[0006] According to some embodiments of the present application, on one hand, a silver-clad copper electrode is provided, comprising:

[0007] Copper core,

[0008] a copper-tin alloy electroplating layer covering the surface of the copper core;

[0009] a silver electroplating layer covering the surface of the copper-tin alloy electroplating layer;

[0010] The self-repairing layer is coated on the surface of the silver electroplating layer; wherein the self-repairing layer includes a resin film and pH-responsive microcapsules, the pH-responsive microcapsules are embedded in the resin film, and the pH-responsive microcapsules are filled with ammonium molybdate corrosion inhibitor.

[0011] In some embodiments, the content of the pH-responsive microcapsules in the resin film is 3-8 wt %.

[0012] In some embodiments, the ammonium molybdate corrosion inhibitor is an ammonium molybdate aqueous solution with a concentration of 8 to 12 wt %.

[0013] In some embodiments, the pH-responsive microcapsules have a particle size of 1 to 2 μm.

[0014] In some embodiments, the self-healing layer has a thickness of 100-300 nm.

[0015] In some embodiments, the resin film is selected from at least one of a polyurethane resin film, a bisphenol A epoxy resin film, an acrylic film, and a polydimethylsiloxane film.

[0016] In some embodiments, the pH-responsive microcapsules include a core material and a wall material; the core material is an ammonium molybdate corrosion inhibitor; and the wall material swells and ruptures under conditions of pH>8.

[0017] In some embodiments, the wall material is a gelatin-gum arabic composite material.

[0018] In some embodiments, the wall material has a thickness of 180-220 nm.

[0019] In some embodiments, pH-responsive microcapsules are prepared by complex coacervation.

[0020] In some embodiments, the copper core is copper with a purity of ≥99.99%; and the particle size of the copper core is 1-50 μm.

[0021] In some embodiments, the copper-tin alloy electroplating layer is a Cu 3 Sn alloy electroplating layer.

[0022] In some embodiments, the weight ratio of copper to tin in the copper-tin alloy electroplating layer is 1-2:1.

[0023] In some embodiments, the thickness of the copper-tin alloy electroplating layer is 1-2 nm.

[0024] In some embodiments, the thickness of the silver electroplating layer is 0.5-1.2 μm.

[0025] In some embodiments, the grain size of the silver electroplating layer is ≤200 nm.

[0026] In some embodiments, the particle size of the cyanide-free electroplated silver-clad copper conductive material is 1.5 to 51.2 μm.

[0027] According to some embodiments of the present application, the present application further provides a method for preparing the above-mentioned cyanide-free electroplated silver-clad copper conductive material, comprising:

[0028] Step S1: placing the copper core in a copper-tin electroplating solution for pre-electroplating to form a copper-tin alloy electroplating layer on the surface of the copper core as a pre-plating material;

[0029] Step S2: placing the pre-plated material in a silver electroplating solution for silver electroplating to form a silver electroplating layer on the surface of the pre-plated material as a silver-clad copper material; wherein the silver electroplating solution does not contain cyanide;

[0030] Step S3: dispersing pH-responsive microcapsules in liquid resin to form a self-healing material; wherein the pH-responsive microcapsules are filled with ammonium molybdate corrosion inhibitor;

[0031] Step S4: spraying the self-repairing material on the surface of the silver-clad copper material, and after curing, forming a self-repairing layer on the surface of the silver-clad copper material to obtain a cyanide-free electroplated silver-clad copper conductive material; wherein the pH-responsive microcapsules are embedded in the resin film formed by curing the liquid resin.

[0032] In some embodiments, step S0 is further included before step S1, and step S0 includes: sandblasting the surface of the copper core using Al2O3 micropowder, where the particle size of the Al2O3 micropowder is 2 to 5 μm.

[0033] In some embodiments, in step S1, the copper-tin electroplating solution includes: 29-11 g / L SnCl, 4-6 g / L CuSO, and 25-35 g / L sodium citrate.

[0034] In some embodiments, the pre-plating conditions include: a current density of 0.4 to 0.6 A / dm 2 , the electroplating time is 25 to 35 seconds.

[0035] In some embodiments, in step S2, the silver electroplating solution includes: the main salt is AgNO3, and the concentration is 18-22 g / L; the ligands are sodium thiosulfate and disodium edetate, the concentration of sodium thiosulfate is 95-105 g / L, and the concentration of disodium edetate is 9-11 g / L; the additive is polyethylene glycol, and the concentration is 0.5-1.5 g / L.

[0036] In some embodiments, the pH value of the silver plating solution is 8.5-9.5.

[0037] In some embodiments, the silver plating conditions include: a current density of 0.8 to 1.2 A / dm 2 , the temperature is 25-35℃, and the electroplating time is 10-20min.

[0038] In some embodiments, in step S3, the content of the pH-responsive microcapsules in the liquid resin is 3-8 wt%.

[0039] In some embodiments, the liquid resin is selected from at least one of waterborne polyurethane resin, bisphenol A epoxy resin, waterborne acrylic emulsion, and polydimethylsiloxane.

[0040] In some embodiments, the pH-responsive microcapsule comprises a core material and a wall material; the core material is an aqueous solution of ammonium molybdate, and the wall material swells and ruptures under conditions of pH>8.

[0041] In some embodiments, the pH-responsive microcapsules are prepared by a re-coagulation method.

[0042] In some embodiments, the concentration of the ammonium molybdate aqueous solution is 8-12 wt %.

[0043] In some embodiments, the wall material is formed from a gelatin-gum arabic composite material.

[0044] In some embodiments, the wall material has a thickness of 180-220 nm.

[0045] In some embodiments, in step S4, the self-repairing material is sprayed on the surface of the silver-coated copper material and then cured at a temperature of 70 to 90° C. for 8 to 15 minutes to form a self-repairing layer.

[0046] In some embodiments, the copper core has a particle size of 1 to 50 μm.

[0047] In some embodiments, the thickness of the copper-tin alloy electroplating layer is 1-2 nm.

[0048] In some embodiments, the thickness of the silver electroplating layer is 0.5-1.2 μm.

[0049] In some embodiments, the grain size of the silver electroplating layer is ≤200 nm.

[0050] In some embodiments, the self-healing layer has a thickness of 100-300 nm.

[0051] In some embodiments, the pH-responsive microcapsules have a particle size of 1 to 2 μm.

[0052] In some embodiments, the particle size of the cyanide-free electroplated silver-clad copper conductive material is 1.5 to 51.2 μm.

[0053] According to some embodiments of the present application, another aspect of the embodiments of the present application provides a crystalline silicon solar cell, including an electrode; the conductive material of the electrode is the above-mentioned cyanide-free electroplated silver-clad copper conductive material or the cyanide-free electroplated silver-clad copper conductive material prepared by the above-mentioned preparation method.

[0054] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0055] The present application improves the interfacial bonding strength of the two layers by arranging a copper-tin alloy electroplating layer between the copper layer and the silver layer, and the silver layer material does not contain cyanide materials; by arranging a self-repairing film layer on the surface of the silver-clad copper electrode, the corrosion inhibitor in the pH-responsive microcapsule in the resin film is released under specific pH conditions to re-form a protective film on the silver layer, thereby achieving the purpose of self-repair; the silver-clad copper conductive material of the present application has a stable structure, is environmentally friendly, and has a dynamic protective effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] One or more embodiments are exemplified by the figures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a scale limitation. In order to more clearly illustrate the embodiments of the present application or the technical solutions in the traditional technology, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0057] Figure 1 A schematic cross-sectional view of the local structure of cyanide-free electroplated silver-clad copper conductive material particles prepared in an embodiment of the present application;

[0058] Figure 2 Schematic diagram of the partial structure of the self-repairing layer of the cyanide-free electroplated silver-clad copper conductive material prepared in an embodiment of the present application.

[0059] Reference numerals:

[0060] 1. Copper core; 2. Copper-tin alloy electroplating layer; 3. Silver electroplating layer; 4. Self-healing layer; 41. Resin film; 42. pH-responsive microcapsules. DETAILED DESCRIPTION

[0061] As can be seen from the background technology, in the prior art, silver-clad copper conductive materials contain cyanide in the electroplating solution, which causes the electroplated silver layer to contain cyanide, causing pollution and being unfriendly to the environment; the interface bonding force between the electroplated silver layer and the electroplated copper layer is weak and easily peeled off; the surface protective film of the silver layer can only statically protect the silver layer. Once the silver layer is damaged, it cannot automatically repair the tiny cracks on the surface of the silver layer, and cannot protect the oxidation resistance of the silver layer, thereby reducing the overall performance of the conductive material.

[0062] According to some embodiments of the present application, the present application provides a silver-clad copper electrode, such as Figure 1 As shown, including:

[0063] Copper core 1,

[0064] a copper-tin alloy electroplating layer 2, which covers the surface of the copper core 1;

[0065] a silver electroplating layer 3, which covers the surface of the copper-tin alloy electroplating layer 2;

[0066] The self-repairing layer 4 is coated on the surface of the silver electroplating layer 3; wherein the self-repairing layer includes a resin film 41 and a pH-responsive microcapsule 42, wherein the pH-responsive microcapsule 42 is embedded in the resin film 41 and filled with ammonium molybdate corrosion inhibitor. Figure 2 shown.

[0067] When tiny cracks appear on the surface of the silver layer, they are exposed to the outside and produce alkaline corrosive substances such as oxides or hydroxides. The environment at the crack will change, for example, the pH value will increase locally, and the structure of the microcapsule wall material will change, causing the microcapsules to rupture or dissolve, thereby releasing the active corrosion inhibitors contained therein, such as ammonium molybdate. Ammonium molybdate releases molybdate ions according to the change in pH. The molybdate ions can form a dense molybdenum oxide film or composite oxide film on the silver surface. This process not only prevents further oxygen from entering the silver layer and prevents oxidation from spreading, but also fills the cracks through the formation of molybdenum compounds, strengthening the surface structure of the silver layer and achieving self-repair of the damage to the silver layer. The continuous release of molybdenum ions and the continuous deposition of molybdenum compounds constitute a dynamic repair mechanism. If the silver layer is damaged and cracked again, as long as the pH-responsive self-healing layer exists, molybdate ions can continue to be released from the microcapsules, repeating the above repair process, allowing the silver layer to restore its integrity and electrical properties to a certain extent.

[0068] Self-repairing layer working principle:

[0069] Triggering conditions: When the silver layer is microcracked and exposed to a humid / oxidizing environment, the copper core or silver layer undergoes oxidation reaction and the local pH rises (>8).

[0070] Copper oxidation: 2Cu+O2+2H2O→2Cu(OH)2; the release of OH- causes the pH to rise.

[0071] Silver sulfide: 4Ag+2H2S+O2→2Ag2S+2H2O; sulfide hydrolysis produces an alkaline environment.

[0072] Repair process:

[0073] pH-responsive release: The microcapsule wall material (e.g., gelatin-gum arabic) swells and ruptures in an alkaline environment, releasing ammonium molybdate ((NH4)2MoO4(NH4)2MoO4).

[0074] Corrosion inhibitor function:

[0075] Molybdate ion (MoO4 2- ) reacts with silver / copper ions to form a dense passivation film.

[0076] 2Ag+MoO4 2- +2H2O→Ag2MoO4+2H2O (silver molybdate protective layer).

[0077] Cu2+MoO4 2- →CuMoO4 (copper molybdate inhibits further oxidation).

[0078] Dynamic repair effect:

[0079] The passivation film fills the cracks and prevents oxygen and moisture from penetrating;

[0080] The repair efficiency is ≥90% (verified by electrochemical impedance spectroscopy EIS test).

[0081] The present application improves the interfacial bonding strength between copper and silver by arranging a copper-tin alloy electroplating layer between the copper layer and the silver layer, and the silver layer material does not contain cyanide-related toxic substances; by arranging a self-repairing film layer on the surface of the silver-clad copper conductive material, the corrosion inhibitor in the microcapsule in the resin film is released according to the change of environmental pH to re-form a protective film on the silver layer, thereby achieving the purpose of self-repair; the positive electrode structure of the silver-clad copper electrode of the present application is stable, environmentally friendly, and has a dynamic protective effect.

[0082] To further optimize the self-healing effect, the microcapsule content in the resin film layer is controlled. In some embodiments, the pH-responsive microcapsules 42 are present in the resin film 41 at a concentration of 3 to 8 wt%, such as 3%, 4%, 5%, 6%, 7%, or 8%, or any range therebetween. This concentration of microcapsules is sufficient to cover and respond to all potentially damaged areas on the silver layer without affecting migration and diffusion pathways. This ensures that the self-healing layer retains good mechanical properties and is not susceptible to damage.

[0083] To further optimize the self-healing effect, the corrosion inhibitor content is controlled. In some embodiments, the concentration of the ammonium molybdate aqueous solution is 8 to 12 wt %, for example, any value among 8%, 9%, 10%, 11%, 12%, or any range therebetween, and another example is 10 wt %. Controlling the concentration of the ammonium molybdate corrosion inhibitor within this range helps promote the ammonium molybdate's repair effect on the microcracked surface of the silver layer and ensures suitable mechanical strength.

[0084] To optimize the dispersion of the microcapsules within the resin film, their particle size is controlled. In some embodiments, the pH-responsive microcapsules 42 have a particle size of 1 to 2 μm, such as any value among 1.2, 1.5, 1.8, and 2.0 μm, or any range therebetween. These appropriately sized microcapsules facilitate rapid response and release, helping to quickly repair damaged areas. Furthermore, their uniform dispersion within the resin film ensures the film's toughness.

[0085] To enhance the protective effect of the resin film on the electrode, the film thickness is appropriately controlled. In some embodiments, the thickness of the self-healing layer 4 is 100 to 300 nm, for example, any value among 100, 120, 150, 180, 200, 230, 250, 280, and 300 nm, or any range therebetween. Controlling the thickness of the self-healing film within this range facilitates the distribution density and uniformity of the microcapsules within the film, ensuring appropriate penetration and diffusion pathways, and ensuring that the repair reactants can promptly and effectively reach the microcracks in the silver layer, thereby improving the repair effect and efficiency.

[0086] To enhance the protective effect of the silver-coated copper conductive material, a suitable base resin material is selected. In some embodiments, the resin film 41 is selected from at least one of a polyurethane resin film, a bisphenol A epoxy resin film, an acrylic film, and a polydimethylsiloxane film. The resin selected as the outermost protective film for the conductive material exhibits excellent weather and chemical resistance. It also exhibits high adhesion and flexibility, resisting peeling from the surface of the silver-coated copper conductive material, thereby helping to maintain the material's structural integrity and functionality. Furthermore, it exhibits high wear and impact resistance, protecting the conductive material from damage and maintaining stable material performance.

[0087] To optimize the release function of the microcapsules, appropriate microcapsule materials are selected. In some embodiments, the pH-responsive microcapsules 42 include a core material and a wall material. The core material is an ammonium molybdate corrosion inhibitor, and the wall material swells and ruptures under conditions of pH > 8. That is, when the pH of the environment reaches 8 or above, the wall material of the microcapsule automatically swells and ruptures, thereby releasing the ammonium molybdate inside. The wall material having the above-mentioned function is, for example, a gelatin-gum arabic composite material. The core material is an ammonium molybdate corrosion inhibitor. The thickness of the wall material is 180 to 220 nm, for example, any value among 180, 190, 200, 210, and 220 nm, or a range between any two values. The gelatin-gum arabic wall material is sensitive to pH and undergoes structural changes under specific pH conditions, causing the wall material to swell and rupture, thereby releasing the corrosion inhibitor, thereby repairing the damage to the silver layer. The wall material thickness within the above range not only ensures a certain mechanical strength to encapsulate the core material corrosion inhibitor, but also ensures that the corrosion inhibitor can be easily released from the capsule, with an appropriate response speed.

[0088] To optimize the structural stability and conductivity of the silver-clad copper material and improve its structure, in some embodiments, the copper core 1 is copper with a purity of ≥99.99%; the particle size of the copper core 1 is 1 to 50 μm, for example, any value of 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 μm, or a range between any two values; the copper-tin alloy electroplating layer 2 is a Cu3Sn alloy electroplating layer; the thickness of the copper-tin alloy electroplating layer is 1 to 2 nm, for example, any value of 1, 1.2, 1.5, 1.8, or 2.0 nm, or a range between any two values. The weight ratio of copper to tin in the copper-tin alloy electroplating layer 2 is (1 to 2):1, for example, 1.6:1. By adding a copper-tin transition layer with an appropriate copper-tin ratio between the copper layer and the silver layer and controlling the appropriate layer thickness, the interfacial bonding between the copper and silver layers can be improved, preventing peeling and enhancing the stability of the overall electrode structure.

[0089] To optimize the silver-clad copper structure and improve the silver layer microstructure, in some embodiments, the thickness of the silver electroplated layer 3 is 0.5 to 1.2 μm, for example, any value among 0.5, 0.8, 1.0, and 1.2 μm, or any range therebetween. The grain size of the silver electroplated layer is ≤ 200 nm. This silver layer is cyanide-free, non-toxic, and environmentally friendly, and its grains are small and highly dense.

[0090] In some embodiments, the copper core particle size is as follows: 5 μm Al2O3 is used for sandblasting, and the initial copper powder particle size is 1 to 50 μm (conventional copper powder range); the total particle size after silver plating is as follows: the copper core + silver layer (0.5 to 1.2 μm) is ≈ 1.5 to 51.2 μm; the effect of the self-healing coating is as follows: the polyurethane layer (100 to 300 nm) has a negligible effect on the total particle size (only the surface coating); the final conductive material particle size range is 1.5 to 51.2 μm (dominated by the initial size of the copper core). The above-mentioned particle size of the conductive material helps to uniformly distribute the conductive material in the conductive slurry, which is beneficial to improving the electrode performance.

[0091] According to some embodiments of the present application, another aspect of the present application provides a method for preparing a cyanide-free electroplated silver-clad copper conductive material, comprising:

[0092] Step S1: placing the copper core 1 in a copper-tin electroplating solution for pre-electroplating to form a copper-tin alloy electroplating layer 2 on the surface of the copper core 1 as a pre-plating material;

[0093] Step S2: placing the pre-plated material in a silver electroplating solution for silver electroplating to form a silver electroplating layer 3 on the surface of the pre-plated material as a silver-clad copper material; wherein the silver electroplating solution does not contain cyanide;

[0094] Step S3: dispersing pH-responsive microcapsules 42 in liquid resin to form a self-healing material; wherein the pH-responsive microcapsules 42 are filled with ammonium molybdate corrosion inhibitor;

[0095] Step S4: spraying the self-repairing material on the surface of the silver-coated copper material, and after curing, forming a self-repairing layer 4 on the surface of the silver-coated copper material to obtain a cyanide-free electroplated silver-coated copper conductive material; wherein the pH-responsive microcapsules 42 are embedded in the resin film 41 formed by curing the liquid resin. Figure 2 shown.

[0096] The present application successfully produces a pollution-free, structurally stable, and self-repairing protective layer electroplated silver-clad copper conductive material using the above method. The method is simple and easy to operate.

[0097] To improve electroplating adhesion, the copper surface is roughened. In some embodiments, step S1 is preceded by step S0, which includes sandblasting the copper substrate using Al2O3 powder with a particle size of 2 to 5 μm, at a sandblasting pressure of 0.3 to 0.6 MPa, for a duration of 10 to 30 seconds. Under these sandblasting conditions, the copper surface is roughened using the powder of the aforementioned size, resulting in a good roughening effect and helping to improve electroplating adhesion.

[0098] In order to improve the quality of electroplated copper-tin alloy, the electroplating solution and electroplating conditions are regulated; in some embodiments, in step S1, the copper-tin electroplating solution includes: SnCl29-11g / L, CuSO44-6g / L, sodium citrate 25-35g / L; for example: SnCl29.5-10.5g / L, CuSO44.5-5.5g / L, sodium citrate 28-32g / L; for another example: SnCl210g / L, CuSO45g / L, sodium citrate 30g / L. The pre-plating conditions include: a current density of 0.4-0.6A / dm 2 , the plating time is 25 to 35 seconds; for example, the current density is 0.45 to 0.55A / dm 2 , the plating time is 28 to 32 seconds; for example: the current density is 0.5A / dm 2 The copper-tin layer was electroplated using the above electroplating solution formulation under the above conditions to obtain a nanoscale copper-tin alloy electroplated layer with appropriate copper and tin contents and a target thickness. The copper-tin alloy electroplated layer was uniform and dense, which helped to improve the bonding strength between copper and silver.

[0099] In order to improve the quality of the electroplated silver layer and ensure that the silver layer is free of cyanide pollutants, the electroplating solution and electroplating conditions are regulated; in some embodiments, in step S2, the silver electroplating solution includes: the main salt is AgNO3, and the concentration is 18-22 g / L; for example, 19-21 g / L; for example, 20 g / L; the ligands are sodium thiosulfate and disodium edetate, and the concentration of sodium thiosulfate is 95-105 g / L, for example, 98-102 g / L, for example, 100 g / L; the concentration of disodium edetate is 9-11 g / L; for example, 9.5-10.5 g / L; for example, 10 g / L; the additive is polyethylene glycol, and the concentration is 0.5-1.5 g / L; for example, 0.8-1.2 g / L; for example, 1.0 g / L; the pH value of the silver electroplating solution is 8.5-9.5. Silver plating conditions include: current density of 0.8 to 1.2 A / dm 2 (Pulse power supply, duty cycle 50%), such as 0.8, 0.9, 1.0, 1.1, 1.2A / dm 2 The temperature is 25-35°C, and the plating time is 10-20 minutes, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 minutes, or a range therebetween. The complexing agent is selected to be cyanide-free to ensure that the silver layer is cyanide-free. Polyethylene glycol has a grain refinement effect. A suitable temperature prevents thiosulfate decomposition, and a suitable plating time controls the silver layer thickness to an accuracy of ±0.05 μm.

[0100] To improve the quality and effectiveness of the self-healing coating, in some embodiments, in step S3, the pH-responsive microcapsules are present in the liquid resin at a concentration of 3 to 8 wt%. The microcapsules have a particle size of 1 to 2 μm. This concentration is sufficient to cover and respond to all potentially damaged areas on the silver layer without affecting migration and diffusion pathways, while also ensuring that the protective film retains good mechanical properties and is not susceptible to damage.

[0101] In some embodiments, the liquid resin is selected from at least one of a waterborne polyurethane resin (e.g., Bayer Bayhydrol UH2606), a bisphenol A epoxy resin (e.g., Hexion EPON resin), a waterborne or solvent-based acrylic emulsion (e.g., BASFAcronal series), and polydimethylsiloxane (Wacker SILRES SY231). These resins are liquid before spraying and form a solid film after curing.

[0102] In some embodiments, the pH-responsive microcapsule 42 includes a core material and a wall material; the core material is an ammonium molybdate corrosion inhibitor, and the wall material swells and ruptures under conditions of pH>8. The wall material is a gelatin-gum arabic composite material. The concentration of the ammonium molybdate aqueous solution is 8 to 12 wt%, for example, 10 wt%; the thickness of the wall material is 180 to 220 nm. The microcapsules are prepared using the above-mentioned complex coacervation method. The above-mentioned gelatin-gum arabic wall material is sensitive to pH value, and its structure changes under a specific pH environment. The wall material will swell and rupture to release the corrosion inhibitor, thereby achieving the purpose of repairing the damage to the silver layer; the wall material thickness is within the above-mentioned range, which can not only ensure a certain mechanical strength to encapsulate the core material corrosion inhibitor, but also ensure that the corrosion inhibitor can be released from the capsule more easily.

[0103] In some embodiments, pH-responsive microcapsules are prepared by complex coacervation; this method is an existing technology, and the wall thickness and particle size of the microcapsules can be controlled by adjusting the core material, wall material, process parameters, etc. according to actual needs.

[0104] For example, (1) core material solution preparation: dissolve ammonium molybdate in deionized water to prepare an 8-12 wt% solution, for example, 10 wt%;

[0105] (2) Wall material dissolution: Gelatin (positively charged) and gum arabic (negatively charged) are dissolved in warm water (40-60°C) at a mass ratio of 1:1, with a concentration of 3-8 wt%, for example, 5 wt% at 50°C;

[0106] (3) Mixing and emulsification: slowly add the core material solution into the wall material solution and homogenize at high speed (10000 rpm, 5 min) to form an O / W emulsion;

[0107] (4) pH adjustment and coagulation: add dilute hydrochloric acid to adjust the pH to 3-5 (near the isoelectric point of gelatin), for example, pH = 4; gelatin and gum arabic undergo complex coagulation due to charge neutralization, wrapping the core material droplets;

[0108] (5) Curing and cross-linking: adding glutaraldehyde (cross-linking agent, 0.3-0.8 wt%, for example, 0.5 wt%), stirring at 40-60° C. for 1-3 h (for example, 50° C. for 2 h) to cross-link and cure the wall material;

[0109] (6) washing and drying;

[0110] (7) The microcapsules were separated by centrifugation, washed with water to remove unreacted products, and dried under vacuum at 40° C. to obtain microcapsules with a wall thickness of 180 to 220 nm (e.g., 200 nm) and a particle size of 1 to 2 μm.

[0111] In some embodiments, in step S4, the self-repairing material is sprayed on the surface of the intermediate electrode and then cured at a temperature of 70-90° C. for 8-15 minutes to form the self-repairing layer 4. The above temperature is conducive to the curing efficiency and effect.

[0112] In some embodiments, the particle size of the copper core 1 is 1 to 50 μm; the thickness of the copper-tin alloy electroplating layer 2 is 1 to 2 nm; the thickness of the silver electroplating layer 3 is 0.5 to 1.2 μm; the grain size of the silver electroplating layer 3 is ≤200 nm; the thickness of the self-repairing layer 4 is 100 to 300 nm; the particle size of the cyanide-free electroplated silver-clad copper conductive material is 1.5 to 51.2 μm; and the particle size of the pH-responsive microcapsule 42 is 1 to 2 μm.

[0113] According to some embodiments of the present application, another aspect of the present application provides a conductive silver paste, comprising a conductive material; the conductive material is the aforementioned silver-coated copper conductive material or the silver-coated copper conductive material obtained by the aforementioned preparation method. The silver-coated copper material, as the conductive body, can replace pure silver to reduce costs and is in granular form.

[0114] According to some embodiments of the present application, another aspect of the present application provides a crystalline silicon solar cell, comprising an electrode; the conductive material of the electrode is the aforementioned cyanide-free electroplated silver-coated copper conductive material or the cyanide-free electroplated silver-coated copper conductive material prepared by the aforementioned preparation method. For example, the conductive material of the electrode of a PERC cell or a TOPCon / BC cell is the aforementioned silver-coated copper material.

[0115] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0116] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0117] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0118] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0119] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0120] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0121] In the accompanying drawings corresponding to the embodiments of the present application, the thickness and area of ​​the layers are exaggerated for better understanding and ease of description. When describing a component (such as a layer, film, region or substrate) on another component or on the surface of another component, the component can be "directly" located on the surface of the other component, or there can be a third component between the two components. On the contrary, when describing a component on the surface of another component or when another component is formed or provided on the surface of a component, it means that there is no third component between the two components. In addition, when describing a component as "approximately" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a partial edge of the entire surface.

[0122] In the description of the embodiments of the present application, when a component "includes" another component, unless otherwise specified, other components are not excluded, and other components may be further included. In addition, when a component such as a layer, film, region, or plate is referred to as being "on / located on" another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therebetween. In addition, when a component such as a layer, film, region, or plate is "directly located on" another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it means that no other components are located therebetween.

[0123] The terms used herein in the description of the various embodiments are intended only to describe the specific embodiments and are not intended to be limiting. As used in the description of the various embodiments and the appended claims, "part" is intended to include the plural form unless the context clearly indicates otherwise. A component includes a layer, film, region, or plate.

[0124] The following detailed description of the various embodiments of the present application is provided in conjunction with the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the various embodiments of the present application to facilitate a better understanding of the present application. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0125] Example 1

[0126] The method for preparing a cyanide-free electroplated silver-clad copper conductive material comprises the following steps:

[0127] Step S0, sandblasting: using Al2O3 micropowder with a particle size of 5 μm to roughen the surface of copper powder (purity ≥99.99%, particle size 40 μm), the sandblasting pressure is 0.45 MPa, and the time is 20 s;

[0128] Step S1, pre-plating Cu3Sn layer: placing the copper core 1 in a copper-tin electroplating solution for pre-plating to form a nano-scale copper-tin alloy electroplating layer 2 on the surface of the copper core 1 as a pre-plating material;

[0129] Copper-tin electroplating solution formula: SnCl2 10g / L, CuSO4 5g / L, sodium citrate 30g / L;

[0130] Pre-plating conditions: current density 0.5A / dm 2 , electroplating time 30s; the thickness of the copper-tin alloy electroplating layer 2 is 1.5nm;

[0131] Step S2: Electroplating a cyanide-free silver layer: Plating the pre-plated material from step S1 in a silver electroplating solution for silver electroplating to form a silver electroplating layer 3 on the surface of the pre-plated material as a silver-clad copper material; wherein the silver electroplating solution does not contain cyanide;

[0132] The plating solution formula includes: the main salt is AgNO3, the concentration is 20g / L; the complexing agent is sodium thiosulfate (concentration 100g / L) + disodium ethylenediaminetetraacetic acid (concentration 10g / L); the additive is polyethylene glycol (PEG-6000), the concentration is 1g / L, and the pH value is adjusted to 8.5-9.5 with ammonia water;

[0133] Electroplating conditions: current density 1.0A / dm 2(pulse power supply, duty cycle 50%), temperature 25° C., electroplating time 15 min; the thickness of the silver electroplating layer 3 is 0.8 μm, and the grain size is ≤ 200 nm.

[0134] Step S3-1, preparation of pH-responsive microcapsules 42: (1) core material solution preparation: dissolve ammonium molybdate in deionized water to prepare a 10 wt% solution; (2) wall material dissolution: gelatin (positively charged) and gum arabic (negatively charged) are dissolved in warm water (50°C) at a mass ratio of 1:1 to a concentration of 5 wt%; (3) mixing and emulsification: slowly add the core material solution to the wall material solution and homogenize at high speed (10000 rpm, 5 min) to form an O / W emulsion; (4) pH Adjusting coagulation: adding dilute hydrochloric acid to adjust the pH to 4.0 (near the isoelectric point of gelatin), gelatin and gum arabic undergo complex coagulation due to charge neutralization, wrapping the core material droplets; (5) Curing and cross-linking: adding glutaraldehyde (cross-linking agent, 0.5wt%), stirring at 50℃ for 2h to cross-link and solidify the wall material; (6) Washing and drying: (7) Centrifuging and separating the microcapsules, washing with water to remove unreacted products, and vacuum drying at 40℃ to obtain microcapsules with a wall material thickness of 200nm and a particle size of 1.5μm.

[0135] Step S3-2, preparing a self-healing material: dispersing the pH-responsive microcapsules 42 in a waterborne polyurethane resin (Bayer Bayhydrol), with the microcapsules accounting for 5 wt% of the waterborne polyurethane;

[0136] Step S4: spraying a self-repairing layer: spraying a self-repairing material on the surface of the silver-coated copper material, curing at 80°C for 10 minutes, forming a self-repairing layer 4 on the surface of the silver-coated copper material in step S2, controlling the layer thickness to be 200nm, and obtaining a cyanide-free electroplated silver-coated copper conductive material; Figure 1 wherein the pH-responsive microcapsules are embedded in the resin film 1 formed by curing the liquid resin, as shown in FIG. Figure 2 shown.

[0137] Example 2

[0138] The method for preparing a cyanide-free electroplated silver-clad copper conductive material comprises the following steps:

[0139] Step S0, sandblasting: using Al2O3 micropowder with a particle size of 5 μm to roughen the surface of copper powder (purity ≥99.99%, particle size 30 μm); the sandblasting pressure is 0.3 MPa, and the time is 30 s;

[0140] Step S1, pre-plating Cu3Sn layer: placing the copper core 1 in a copper-tin electroplating solution for pre-plating to form a nano-scale copper-tin alloy electroplating layer 2 on the surface of the copper core 1, which is recorded as the pre-plating material;

[0141] Copper-tin electroplating solution formula: SnCl29g / L, CuSO44g / L, sodium citrate 25g / L;

[0142] Pre-plating conditions: current density 0.4A / dm 2 , electroplating time 25s; the thickness of the copper-tin alloy electroplating layer 2 is 1nm;

[0143] Step S2: Electroplating a cyanide-free silver layer: Plating the pre-plated material from step S1 in a silver electroplating solution for silver electroplating to form a silver electroplating layer 3 on the surface of the pre-plated material, which is referred to as a silver-clad copper material; wherein the silver electroplating solution does not contain cyanide;

[0144] The plating solution formula includes: the main salt is AgNO3, the concentration is 18g / L; the complexing agent is sodium thiosulfate (concentration 95g / L) + disodium ethylenediaminetetraacetic acid (concentration 9g / L); the additive is polyethylene glycol (PEG-6000), the concentration is 0.5g / L, and the pH value is adjusted to 8.5-9.5 with ammonia water;

[0145] Electroplating conditions: current density is 0.8A / dm 2 (pulse power supply, duty cycle 50%), temperature 25° C., electroplating time 10 min; the thickness of the silver electroplating layer 3 is 0.5 μm, and the grain size is ≤ 200 nm.

[0146] Step S3-1, preparation of pH-responsive microcapsules 42: (1) core material solution preparation: dissolve ammonium molybdate in deionized water to prepare a 10 wt% solution; (2) wall material dissolution: gelatin (positively charged) and gum arabic (negatively charged) are dissolved in warm water (50°C) at a mass ratio of 1:1 to a concentration of 5 wt%; (3) mixing and emulsification: slowly add the core material solution to the wall material solution and homogenize at high speed (10000 rpm, 5 min) to form an O / W emulsion; (4) pH Adjusting coagulation: adding dilute hydrochloric acid to adjust the pH to 4.0 (near the isoelectric point of gelatin), gelatin and gum arabic undergo complex coagulation due to charge neutralization, wrapping the core material droplets; (5) Curing and cross-linking: adding glutaraldehyde (cross-linking agent, 0.5wt%), stirring at 50℃ for 2h to cross-link and solidify the wall material; (6) Washing and drying: (7) Centrifuging and separating the microcapsules, washing with water to remove unreacted products, and vacuum drying at 40℃ to obtain microcapsules with a wall material thickness of 200nm and a particle size of 1.5μm.

[0147] Step S3-2, preparing a self-healing material: dispersing the pH-responsive microcapsules 42 in an aqueous polyurethane resin (Bayer Bayhydrol series), with the microcapsules accounting for 5 wt% of the aqueous polyurethane;

[0148] Step S4: spraying a self-repairing layer: spraying a self-repairing material on the surface of the silver-coated copper material, curing at 80°C for 10 minutes, forming a self-repairing layer 4 on the surface of the silver-coated copper material in step S2, controlling the layer thickness to be 200nm, and obtaining a cyanide-free electroplated silver-coated copper conductive material; Figure 1wherein the pH-responsive microcapsules are embedded in the resin film 1 formed by curing the liquid resin, as shown in FIG. Figure 2 shown.

[0149] Example 3

[0150] The method for preparing a cyanide-free electroplated silver-clad copper conductive material comprises the following steps:

[0151] Step S0, sandblasting: using Al2O3 micropowder with a particle size of 5 μm to roughen the surface of copper powder (purity ≥99.99%, particle size 50 μm); the sandblasting pressure is 0.6 MPa, and the time is 10 s;

[0152] Step S1, pre-plating Cu3Sn layer: placing the copper core 1 in a copper-tin electroplating solution for pre-plating to form a nano-scale copper-tin alloy electroplating layer 2 on the surface of the copper core 1, which is recorded as the pre-plating material;

[0153] Copper-tin electroplating solution formula: SnCl2 11g / L, CuSO4 6g / L, sodium citrate 35g / L;

[0154] Pre-plating conditions: current density 0.6A / dm 2 , electroplating time 35s; the thickness of the copper-tin alloy electroplating layer 2 is 2nm;

[0155] Step S2: Electroplating a cyanide-free silver layer: Plating the pre-plated material from step S1 in a silver electroplating solution for silver electroplating to form a silver electroplating layer 3 on the surface of the pre-plated material, which is referred to as a silver-clad copper material; wherein the silver electroplating solution does not contain cyanide;

[0156] The plating solution formula includes: the main salt is AgNO3, the concentration is 22g / L; the complexing agent is sodium thiosulfate (concentration is 105g / L) + disodium ethylenediaminetetraacetic acid (concentration is 11g / L); the additive is polyethylene glycol (PEG-6000), the concentration is 1.5g / L, and the pH value is adjusted to 8.5-9.5 with ammonia water;

[0157] Electroplating conditions: current density is 1.2A / dm 2 (pulse power supply, duty cycle 50%), temperature 35° C., electroplating time 20 min; the thickness of the silver electroplating layer 3 is 1.2 μm, and the grain size is ≤ 200 nm.

[0158] Step S3-1, preparation of pH-responsive microcapsules 42: (1) core material solution preparation: dissolve ammonium molybdate in deionized water to prepare a 10 wt% solution; (2) wall material dissolution: gelatin (positively charged) and gum arabic (negatively charged) are dissolved in warm water (50°C) at a mass ratio of 1:1 to a concentration of 5 wt%; (3) mixing and emulsification: slowly add the core material solution to the wall material solution and homogenize at high speed (10000 rpm, 5 min) to form an O / W emulsion; (4) pH Adjusting coagulation: adding dilute hydrochloric acid to adjust the pH to 4.0 (near the isoelectric point of gelatin), gelatin and gum arabic undergo complex coagulation due to charge neutralization, wrapping the core material droplets; (5) Curing and cross-linking: adding glutaraldehyde (cross-linking agent, 0.5wt%), stirring at 50℃ for 2h to cross-link and solidify the wall material; (6) Washing and drying: (7) Centrifuging and separating the microcapsules, washing with water to remove unreacted products, and vacuum drying at 40℃ to obtain microcapsules with a wall material thickness of 200nm and a particle size of 1.5μm.

[0159] Step S3-2, preparing a self-healing material: dispersing the pH-responsive microcapsules 42 in an aqueous polyurethane resin (Bayer Bayhydrol series), with the microcapsules accounting for 5 wt% of the aqueous polyurethane;

[0160] Step S4: spraying a self-repairing layer: spraying a self-repairing material on the surface of the silver-coated copper material, curing at 80°C for 10 minutes, forming a self-repairing layer 4 on the surface of the silver-coated copper material in step S2, controlling the layer thickness to be 200nm, and obtaining a cyanide-free electroplated silver-coated copper conductive material; Figure 1 wherein the pH-responsive microcapsules are embedded in the resin film 1 formed by curing the liquid resin, as shown in FIG. Figure 2 shown.

[0161] Example 4

[0162] The difference between Example 4 and Example 1 is that the amount of microcapsules added in step S3-2 is replaced with 3 wt%.

[0163] Example 5

[0164] The difference between Example 5 and Example 1 is that the amount of microcapsules added in step S3-2 is replaced with 8 wt%.

[0165] Example 6

[0166] The difference between Example 6 and Example 1 is that the concentration of gelatin and gum arabic after mixing in step S3-1 (2) is replaced with 3 wt%, and (5) the stirring time for curing and cross-linking is 1 h; microcapsules with a wall thickness of 180 nm and a particle size of 1.2 μm are obtained.

[0167] Example 7

[0168] The difference between Example 7 and Example 1 is that the concentration of gelatin and gum arabic after mixing in step S3-1 (2) is replaced with 8 wt%; (5) the stirring time for curing and cross-linking is 3 h; and microcapsules with a wall thickness of 220 nm and a particle size of 1.8 μm are obtained.

[0169] Example 8

[0170] The difference between Example 8 and Example 1 is that the concentration of the ammonium molybdate aqueous solution in step S3-1(1) is replaced with 8 wt%.

[0171] Example 9

[0172] The difference between Example 9 and Example 1 is that the concentration of the ammonium molybdate aqueous solution in step S3-1(1) is replaced with 12 wt%.

[0173] Example 10

[0174] The difference between Example 10 and Example 1 is that the resin material of the self-repairing layer in step S3-2 is replaced by water-based acrylic emulsion (BASF Acronal).

[0175] Example 11

[0176] The difference between Example 11 and Example 1 is that the resin material of the self-repairing layer in step S3-2 is replaced with bisphenol A epoxy resin (Hexion EPON resin).

[0177] Example 12

[0178] The difference between Example 12 and Example 1 is that the resin material of the self-repairing layer in step S3-2 is replaced by polydimethylsiloxane (Wacker SILRES SY231).

[0179] Example 13

[0180] The difference between Example 13 and Example 1 is that the thickness of the self-repairing layer in step S4 is replaced with 100 nm.

[0181] Example 14

[0182] The difference between Example 14 and Example 1 is that the thickness of the self-repairing layer in step S4 is replaced with 300 nm.

[0183] Example 15

[0184] The difference between Example 15 and Example 1 is that the particle size of the copper core in step S1 is replaced with 1 μm.

[0185] Example 16

[0186] The difference between Example 16 and Example 1 is that the particle size of the copper core in step S1 is replaced with 10 μm.

[0187] Comparative Example 1

[0188] The difference between Comparative Example 1 and Example 1 is that there is no self-repairing layer in step S3, and a silver-clad copper material is formed after the silver plating layer is completed.

[0189] Comparative Example 2

[0190] The difference between Comparative Example 2 and Example 1 is that there is no self-repairing layer in step S3, but epoxy resin is coated, and the resin does not contain microcapsules, forming an ordinary epoxy resin protective film.

[0191] Performance testing:

[0192] The structural stability and electrical properties of the silver-clad copper electrodes of each embodiment and each comparative example were tested using the following testing methods. The results are shown in Table 1.

[0193] 1. Silver layer bonding strength

[0194] Standard: ASTM D4541;

[0195] Equipment: PosiTest AT automatic tensile tester;

[0196] Conditions: 20mm diameter aluminum ingot bonding surface, vertical tension rate 1mm / min;

[0197] Standard: Take a minimum of 10 tests, and the failure mode must be cohesive fracture (not interfacial delamination).

[0198] 2. Determination of self-repair efficiency

[0199] Step (1) scratching the silver layer (depth 1 μm × length 100 μm);

[0200] Step (2) soaking in 0.1M Na2SO4 and 0.01M H2O2 solution (pH = 9);

[0201] Step (3) In situ observation:

[0202] Equipment: Zeiss SEM with EDS (accelerating voltage 5 kV);

[0203] Indicator: time for the Mo content at the scratch to reach 5at.% (repair rate);

[0204] Electrochemical verification: CHI760E electrochemical workstation, monitoring the impedance recovery rate of the scratched area (1kHz).

[0205] 3. Electrode resistivity (four-probe method)

[0206] Equipment: Keithley 2400 source meter and Signatone four-probe station;

[0207] Conditions: 25℃ dry environment, current 10mA, take the average value of 5 points;

[0208] 4. Power attenuation rate

[0209] Aging conditions: 85°C / 85% RH, 2000h, IV test every 48h (AM1.5 light);

[0210] Equipment: SAN-EI XES-40S1 solar simulator and Keysight B2900A SMU.

[0211] Table 1

[0212]

[0213] It can be seen from the data in Table 1 that: the bonding strength of the silver layer in the silver-clad copper conductive material prepared in each embodiment of the present application is ≥80 MPa (ASTM D4541 standard); the self-healing layer releases molybdate ions when the pH is >8 (oxidizing environment), and the repair efficiency is ≥90%; the electrode resistivity is ≤2.2 μΩ·cm (the difference with the pure silver electrode is <10%); the power attenuation after the component wet heat test (85°C / 85% RH, 2000h) is ≤1.0% (industry standard ≤2.5%); since the silver plating solution does not contain cyanide, the silver-clad copper conductive material does not contain cyanide, complies with EU RoHS and REACH regulations, and is environmentally friendly.

[0214] In contrast, the silver-clad copper surface in Comparative Example 1 has no self-healing layer, is easily corroded, has poor oxygen resistance, and has poor electrochemical properties; dynamic oxidation protection is missing, and Cu2O spots (diameter > 10μm) appear on the electrode surface after the wet heat test, resulting in a resistance jump and a power attenuation rate of 3.3%, which is significantly greater than the embodiments of the present application.

[0215] In comparative example 2, the crack propagation of the ordinary epoxy resin film could not be suppressed (the fracture toughness of the resin was only 1.5 MPa·m 0 · 5 ), when the microcrack width is greater than 5 μm, the copper core oxidation is accelerated, and the power attenuation rate reaches 1.2%. Although the effect is improved, it is not as obvious as that of the embodiment of the present application, and as time goes by, the protection effect of the embodiment of the present application becomes more obvious.

[0216] The present application improves the interfacial bonding strength of the two layers by arranging a copper-tin alloy electroplating layer between the copper layer and the silver layer, and the silver layer material does not contain cyanide materials; by arranging a self-repairing film layer on the surface of the silver-clad copper electrode, the corrosion inhibitor in the pH-responsive microcapsule in the resin film is released under specific pH conditions to re-form a protective film on the silver layer, thereby achieving the purpose of self-repair; the silver-clad copper conductive material of the present application has a stable structure, is environmentally friendly, and has a dynamic protective effect.

[0217] Those skilled in the art will appreciate that the above-described embodiments are specific examples for implementing the present application, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present application. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined in the claims.

Claims

1. A cyanide-free electroplated silver-clad copper conductive material, characterized in that: The cyanide-free electroplated silver-clad copper conductive material comprises: Copper core (1), a copper-tin alloy electroplating layer (2) coated on the surface of the copper core (1); a silver electroplating layer (3) coated on the surface of the copper-tin alloy electroplating layer (2); A self-repairing layer (4) is coated on the surface of the silver electroplating layer (3); wherein the self-repairing layer comprises a resin film (41) and pH-responsive microcapsules (42), the pH-responsive microcapsules (42) are embedded in the resin film (41), and the pH-responsive microcapsules (42) are filled with an ammonium molybdate corrosion inhibitor.

2. The cyanide-free electroplated silver-clad copper conductive material according to claim 1, wherein The content of the pH-responsive microcapsules (42) in the resin film (41) is 3 to 8 wt%; And / or, the ammonium molybdate corrosion inhibitor is an ammonium molybdate aqueous solution with a concentration of 8 to 12 wt%.

3. The cyanide-free electroplated silver-clad copper conductive material according to claim 1, wherein The pH-responsive microcapsule (42) has a particle size of 1 to 2 μm; And / or, the thickness of the self-repairing layer (4) is 100-300 nm.

4. The cyanide-free electroplated silver-clad copper conductive material according to claim 1, wherein The resin film (41) is selected from at least one of a polyurethane resin film, a bisphenol A epoxy resin film, an acrylic film and a polydimethylsiloxane film; And / or, the pH-responsive microcapsule (42) comprises a core material and a wall material; the core material is the ammonium molybdate corrosion inhibitor; and the wall material swells and ruptures under the condition of pH>8.

5. The cyanide-free electroplated silver-clad copper conductive material according to claim 4, wherein: The wall material is a gelatin-gum arabic composite material; and / or, the thickness of the wall material is 180 to 220 nm; And / or, the pH-responsive microcapsules (42) are prepared by a complex coacervation method.

6. The cyanide-free electroplated silver-clad copper conductive material according to any one of claims 1 to 5, characterized in that: The copper core (1) is copper with a purity of ≥99.99%; the particle size of the copper core (1) is 1 to 50 μm; And / or, the copper-tin alloy electroplating layer (2) is a Cu3Sn alloy electroplating layer; And / or, the weight ratio of copper to tin in the copper-tin alloy electroplating layer (2) is (1-2):1; and / or, the copper-tin alloy electroplating layer (2) has a thickness of 1 to 2 nm; and / or, the thickness of the silver electroplating layer (3) is 0.5 to 1.2 μm; and / or, the grain size of the silver electroplating layer (3) is ≤200 nm; And / or, the particle size of the cyanide-free electroplated silver-clad copper conductive material is 1.5 to 51.2 μm.

7. A method for preparing the cyanide-free electroplated silver-clad copper conductive material according to any one of claims 1 to 6, characterized in that: include: Step S1: placing the copper core (1) in a copper-tin electroplating solution for pre-electroplating to form a copper-tin alloy electroplating layer (2) on the surface of the copper core (1) as a pre-plating material; Step S2: placing the pre-plated material in a silver electroplating solution for silver electroplating to form a silver electroplating layer (3) on the surface of the pre-plated material as a silver-clad copper material; wherein the silver electroplating solution does not contain cyanide; Step S3: dispersing pH-responsive microcapsules (42) in liquid resin to form a self-repairing material; wherein the pH-responsive microcapsules (42) are filled with ammonium molybdate corrosion inhibitor; Step S4: spraying the self-repairing material onto the surface of the silver-coated copper material, and after curing, forming a self-repairing layer (4) on the surface of the silver-coated copper material to obtain the cyanide-free electroplated silver-coated copper conductive material; wherein the pH-responsive microcapsules (42) are embedded in the resin film (41) formed by curing the liquid resin.

8. The preparation method of the cyanide-free electroplated silver-clad copper conductive material according to claim 7, wherein The step S0 is included before the step S1. The step S0 includes: sandblasting the surface of the copper core with Al2O3 powder. The particle size of the Al2O3 powder is 2 to 5 μm.

9. The method for preparing the cyanide-free electroplated silver-clad copper conductive material according to claim 7 or 8, wherein In step S1, the copper-tin electroplating solution includes: 29-11 g / L SnCl, 4-6 g / L CuSO, and 25-35 g / L sodium citrate; And / or, the pre-plating conditions include: current density of 0.4 to 0.6 A / dm 2 , the electroplating time is 25 to 35 seconds.

10. The method for preparing the cyanide-free electroplated silver-clad copper conductive material according to claim 7 or 8, wherein: In step S2, the silver electroplating solution includes: a main salt of AgNO3, with a concentration of 18 to 22 g / L; a complexing agent of sodium thiosulfate and disodium edetate, with a concentration of sodium thiosulfate of 95 to 105 g / L and a concentration of disodium edetate of 9 to 11 g / L; and an additive of polyethylene glycol, with a concentration of 0.5 to 1.5 g / L. and / or, the pH value of the silver electroplating solution is 8.5 to 9.5; And / or, the silver electroplating conditions include: current density of 0.8 to 1.2 A / dm 2 , the temperature is 25-35℃, and the electroplating time is 10-20min.

11. The method for preparing the cyanide-free electroplated silver-clad copper conductive material according to claim 7 or 8, wherein: In the step S3, the content of the pH-responsive microcapsules (42) in the liquid resin is 3 to 8 wt%; And / or, the liquid resin is selected from at least one of waterborne polyurethane resin, bisphenol A epoxy resin, waterborne acrylic emulsion and polydimethylsiloxane; And / or, the pH-responsive microcapsule (42) comprises a core material and a wall material; the core material is an aqueous solution of ammonium molybdate, and the wall material swells and ruptures under the condition of pH>8.

12. The method for preparing a cyanide-free electroplated silver-clad copper conductive material according to claim 11, wherein: The pH-responsive microcapsules (42) are prepared by a re-coagulation method; and / or, the concentration of the ammonium molybdate aqueous solution is 8 to 12 wt%; and / or, the wall material is formed of a gelatin-gum arabic composite material; And / or, the thickness of the wall material is 180-220 nm.

13. The method for preparing the cyanide-free electroplated silver-clad copper conductive material according to claim 7 or 8, wherein: In the step S4, the self-repairing material is sprayed on the surface of the silver-coated copper material, and then cured at a temperature of 70 to 90° C. for 8 to 15 minutes to form the self-repairing layer (4); and / or, the thickness of the self-repairing layer (4) is 100 to 300 nm; and / or, the pH-responsive microcapsule (42) has a particle size of 1 to 2 μm; And / or, the particle size of the cyanide-free electroplated silver-clad copper conductive material is 1.5 to 51.2 μm.

14. The method for preparing the cyanide-free electroplated silver-clad copper conductive material according to claim 7 or 8, wherein: The particle size of the copper core (1) is 1 to 50 μm; and / or, the copper-tin alloy electroplating layer (2) has a thickness of 1 to 2 nm; and / or, the thickness of the silver electroplating layer (3) is 0.5 to 1.2 μm; And / or, the grain size of the silver electroplating layer (3) is ≤200 nm.

15. A crystalline silicon solar cell comprising an electrode; characterized in that: The conductive material of the electrode is the cyanide-free electroplated silver-clad copper conductive material according to any one of claims 1 to 6 or the cyanide-free electroplated silver-clad copper conductive material prepared by the preparation method according to any one of claims 7 to 14.

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