A kind of electroless nickel-phosphorus plating solution for photovoltaic copper grid line and / or flexible circuit and its plating method and application

Abstract

This invention discloses a chemical nickel-phosphorus plating solution for photovoltaic copper grid lines and / or flexible circuits, along with its plating method and applications. The plating solution uses nickel sulfate hexahydrate and sodium hypophosphite monohydrate as the main salts, employing a complex system of multi-component organic acids and phosphonic acid complexing agents, and incorporating brighteners, accelerators, stabilizers, dispersants, and pH buffers. The pH of the plating solution is 3.0–5.0. The plating method involves a three-step pretreatment process: organic solution degreasing, acid washing to remove oxidation, and activation of micron-sized zinc particles. Plating is performed at 78–92°C and a plating rate of 18–24 μm / h. The resulting plating layer has complete coverage, a bright and smooth appearance, and the phosphorus content can be controlled within the range of 0–13 wt%. This invention solves key technical problems such as difficulty in copper surface activation, poor uniformity of fine wire coverage, and a narrow range for phosphorus content control. It can significantly improve the oxidation resistance and welding reliability of copper grid lines and effectively reduce copper diffusion, possessing significant engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of electroplating technology and photovoltaic cell and flexible circuit manufacturing, specifically relating to a chemical nickel-phosphorus plating solution for photovoltaic copper grid lines and / or flexible circuits, as well as its plating method and application. Background Technology

[0002] With the development of the photovoltaic industry, copper grid lines are gradually replacing traditional silver grid lines to reduce costs. However, copper is prone to oxidation, has poor corrosion resistance, and its diffusion significantly affects device stability. Therefore, depositing a dense, uniform nickel-phosphorus plating layer with good conductivity and barrier properties on copper grid lines is of great significance.

[0003] Electroless nickel-phosphorus plating offers advantages such as uniform deposition, no need for external current, and strong adaptability to complex geometries. It can form a continuous, dense plating layer on the fine structure of copper grid lines, providing an excellent barrier layer and solder interface. However, existing electroless nickel-phosphorus plating processes have the following problems when applied to copper grid lines: (1) It is difficult to directly induce autocatalytic deposition on the copper surface, and effective activation treatment is required; (2) The copper grid lines are narrow, and the plating solution must have good dispersion ability to ensure uniform coverage; (3) The plating rate is low, which makes it difficult to meet industrial needs; (4) The plating solution is not stable enough and is prone to decomposition; (5) The phosphorus content is difficult to control, which affects the effectiveness of the diffusion barrier layer.

[0004] Based on the above problems, it is of great significance to develop a chemical nickel-phosphorus plating system and process that is suitable for copper grid lines, with high stability, high deposition rate, moderate phosphorus content, and uniform and bright coating.

[0005] Furthermore, in flexible circuit applications, electroless nickel plating primarily serves as a functional interlayer between the copper conductor and the external environment. It acts as an excellent diffusion barrier and corrosion-resistant protective layer, inhibiting copper oxidation and migration, and improving the stability of flexible circuits in complex environments such as humidity and heat. Simultaneously, the nickel layer improves the soldering performance and contact reliability of the chip pad area, enhancing the conductivity stability and mechanical durability of flexible circuits during long-term use. For roll-to-roll manufacturing processes of flexible circuits, electroless nickel plating also offers advantages such as requiring no external current, uniform thickness, and suitability for large-area continuous processing. Therefore, it possesses significant process adaptability and application value in flexible circuit metallization systems. Summary of the Invention

[0006] The purpose of this invention is to provide a chemical nickel-phosphorus plating solution for photovoltaic copper grid lines and / or flexible circuits, as well as its plating method and application, to solve the problems in the prior art such as difficulty in activating copper grid lines, poor uniformity of plating coverage, narrow range of control for plating rate and phosphorus content, and insufficient stability of plating solution, so as to achieve the deposition of a bright, smooth, and fully covered nickel-phosphorus alloy plating layer on the copper layer.

[0007] To solve the above-mentioned technical problems and achieve the above-mentioned technical effects, the present invention is implemented through the following technical solution: A chemical nickel-phosphorus plating solution for photovoltaic copper grid lines and / or flexible circuits, comprising the following components by mass concentration: Nickel sulfate hexahydrate (NiSO4·6H2O) 15~35 g / L; Sodium hypophosphite monohydrate (NaH2PO2·H2O) 15~50g / L; Complexing agent 2~30g / L; Accelerator 1~10g / L; Brightener 5~50mg / L; Stabilizer 5~50mg / L; Dispersant 0.01~1g / L; pH adjuster 5~20g / L; The remainder is deionized water.

[0008] Furthermore, the complexing agent may be selected from any one or a combination of sodium citrate, malic acid, lactic acid, and ethylenediaminetetramethylenephosphonic acid.

[0009] Furthermore, the pH of the electroless nickel-phosphorus plating solution is 3.0~5.0.

[0010] The concentration of ethylenediaminetetramethylenephosphonic acid in the complexing agent is 0.5~2 g / L, which is used to deeply complex nickel ions and inhibit the self-decomposition of the plating solution.

[0011] Furthermore, the accelerator is selected from any one or a combination of two of succinic acid and propionic acid.

[0012] Furthermore, the brightener is selected from any one or a combination of two of copper sulfate and propyne onium salt.

[0013] Furthermore, the stabilizer is selected from any one or a combination of sodium thiosulfate, potassium iodide, and thiourea.

[0014] Furthermore, the dispersant is selected from sodium dodecyl sulfonate.

[0015] Furthermore, the pH adjuster is selected from sodium acetate.

[0016] A method for electroless nickel-phosphorus plating on the surface of photovoltaic copper grid lines and / or flexible circuit copper substrates using the above-mentioned electroless nickel-phosphorus plating solution includes the following steps: Step 1, Degreasing treatment: The copper attached to the polyester polymer film was immersed in isopropanol (IPA) as a copper substrate and ultrasonically cleaned at 40~60℃ for 1~5 minutes to remove organic contaminants on the surface of the copper substrate. After removal, it was thoroughly rinsed with deionized water. Step 2, Acid washing and activation: Immerse the degreased copper substrate in a dilute sulfuric acid solution with a volume fraction of 8% to 20% for 20 to 120 seconds at room temperature to remove the copper oxide layer on the surface of the copper substrate and expose the fresh metallic copper surface. Rinse with deionized water immediately after removal. Step 3: Activation of zinc particles: The acid-washed and activated copper substrate is immersed in an activation solution containing micron-sized zinc particles to form an activation nucleus, which induces the subsequent autocatalytic deposition of nickel and phosphorus. The substrate is treated at room temperature for 30-90 seconds and then rinsed with deionized water. In the activation solution, the particle size of the micron-sized zinc particles is 1~20μm, the content of the micron-sized zinc particles is 5~50g / L, the activation solution uses water as the dispersion, and the pH of the activation solution is controlled within the range of 11~13 by adding an appropriate amount of sodium hydroxide. Step 4: Electroless nickel-phosphorus plating: After the zinc particles are activated, the copper substrate is quickly transferred into the above-mentioned electroless nickel-phosphorus plating solution preheated to 78~92℃ for plating. The plating time is determined according to the target thickness, and the plating rate is 18~24μm / h, so that a nickel-phosphorus layer is formed on the surface of the copper substrate. During the plating process, the pH of the electroless nickel-phosphorus plating solution is kept stable at 3.8~5.0, and an appropriate amount of sodium acetate solution can be added. After the plating is completed, the substrate is taken out, rinsed with deionized water, and dried.

[0017] Furthermore, in step 3, the particle size of the micron-sized zinc particles can be selected as 2-10 μm.

[0018] Furthermore, in step 3, the content of the micron-sized zinc particles can be selected from 0.5 to 5 g / L.

[0019] Furthermore, in step 3, the pH of the activation solution can be selected as pH=12.

[0020] Furthermore, in step 3, the activation solution can be prepared into a suspension by adding sodium dodecyl sulfonate and / or gelatin.

[0021] Furthermore, in step 3, the content of sodium dodecyl sulfonate and / or gelatin in the activation solution is 1~2 g / L.

[0022] Furthermore, in step 4, the preheating temperature of the electroless nickel-phosphorus plating solution can be selected as 78~88℃.

[0023] Furthermore, in step 4, the pH of the electroless nickel-phosphorus plating solution can be stabilized within the range of 4.0 to 4.5.

[0024] Furthermore, in step 4, after the plating is completed, the thickness of the nickel-phosphorus layer is 0.05~50μm.

[0025] Furthermore, this method controls the phosphorus content in the electroless nickel-phosphorus plating solution by adjusting the mass ratio of the main salt (the mass ratio of nickel sulfate hexahydrate to sodium hypophosphite monohydrate) and the concentration of the complexing agent. After plating, the phosphorus content accounts for 0 to 13 wt% of the nickel-phosphorus layer content.

[0026] Application of the above-mentioned plating method in the preparation of photovoltaic copper grid line blocking layer.

[0027] Application of the above-mentioned plating method in the fabrication of a key functional nickel layer on a copper substrate for flexible circuits.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a composite complexing agent system, with different complexing agents affecting Ni. 2+ Different complexing abilities can lead to the formation of gradient complex structures after compounding, preventing free Ni from... 2+ Excessive concentration fluctuations reduce the risk of self-decomposition and "battery bursting," extend the service life of the plating solution, and regulate the deposition rate and optimize coating quality. Through synergistic effects, comprehensive optimization of "stability + reactivity + coating performance" is achieved.

[0029] Since the copper substrate itself cannot serve as a catalytic site for nickel growth, the nickel-phosphorus plating process is slow, especially for dense copper grid lines in solar cells, where the unactivated copper substrate cannot be fully covered. This invention, through zinc particle activation, significantly reduces the plating time of the nickel-phosphorus coating, improves the uniformity of the nickel plating, and increases process efficiency. Furthermore, compared to the high cost of palladium activation solutions, the cost of the zinc particle activation solution in this invention is significantly reduced, contributing to cost reduction in the process.

[0030] In summary, the nickel-phosphorus electroless plating solution and nickel-phosphorus layer plating method provided by this invention, while ensuring high stability of the plating solution, achieve precise control over plating rate, phosphorus content, and coating structure, significantly improving the density and uniform coverage of the nickel-phosphorus coating. This system is particularly suitable for photovoltaic copper grid lines with fine linewidth and high aspect ratio, effectively solving the problems of slow plating initiation and localized incomplete plating, forming a continuous, bright, and highly adhesive functional coating. Furthermore, compared to traditional precious metal activation processes, this invention has significant advantages in cost control and process feasibility, and possesses promising prospects for industrial application.

[0031] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is an image showing the appearance of the sample in Example 1 of the present invention under a video microscope.

[0033] Figure 2 This is the EDS energy dispersive spectroscopy (EDS) analysis diagram of the sample in Example 3 of the present invention.

[0034] Figure 3 This is an EDS elemental distribution diagram of the sample in Example 3 of the present invention. Detailed Implementation

[0035] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to provide a clearer understanding of the invention's purpose, features, and advantages. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the invention, but are merely illustrative of the essential spirit of the invention's technical solution.

[0036] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0037] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0038] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0039] The singular forms “a” and “the” used in this specification and the appended claims include plural references unless otherwise expressly stated herein. It should be noted that the term “or” is generally used to mean “and / or” unless otherwise expressly stated herein.

[0040] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Unless otherwise specified, all reagents and materials used in the present invention are commercially available.

[0041] This invention provides a chemical nickel-phosphorus plating solution for photovoltaic copper grid lines and / or flexible circuits, the components of which include nickel sulfate hexahydrate (NiSO4·6H2O), sodium hypophosphite monohydrate (NaH2PO2·H2O), complexing agent, accelerator, brightener, stabilizer, dispersant, pH adjuster, and deionized water as solvent.

[0042] In the electroless nickel-phosphorus plating solution, the content of nickel sulfate hexahydrate (NiSO4·6H2O) is 15~35 g / L.

[0043] In the electroless nickel-phosphorus plating solution, the content of sodium hypophosphite monohydrate (NaH2PO2·H2O) is 15~50 g / L.

[0044] In the electroless nickel-phosphorus plating solution, the content of the complexing agent is 2~30g / L, and it can be selected from any one or a combination of sodium citrate, malic acid, lactic acid, and ethylenediaminetetramethylenephosphonic acid.

[0045] In one preferred embodiment, the concentration of ethylenediaminetetramethylenephosphonic acid in the complexing agent is 0.5~2g / L, which is used to deeply complex nickel ions and inhibit the self-decomposition of the plating solution.

[0046] In one preferred embodiment, the concentration of sodium citrate in the complexing agent is 2~20 g / L.

[0047] In one preferred embodiment, the concentration of malic acid in the complexing agent is 1~15g / L.

[0048] In one preferred embodiment, the concentration of lactic acid in the complexing agent is 1~15 mL / L.

[0049] In the electroless nickel-phosphorus plating solution, the content of the accelerator is 1~10g / L, and it can be selected from any one or a combination of two of succinic acid and propionic acid.

[0050] In the electroless nickel-phosphorus plating solution, the brightener content is 5~50 mg / L, and it can be selected from any one or a combination of two of copper sulfate and propyne onium salt.

[0051] In the electroless nickel-phosphorus plating solution, the content of the stabilizer is 5~50 mg / L, and it can be selected from any one or a combination of sodium thiosulfate, potassium iodide, and thiourea.

[0052] In the electroless nickel-phosphorus plating solution, the content of the dispersant is 0.01~1g / L, and it can be selected from sodium dodecyl sulfonate.

[0053] In the electroless nickel-phosphorus plating solution, the pH adjuster content is 5~20 g / L, and it can be selected from sodium acetate.

[0054] The pH of the electroless nickel-phosphorus plating solution is 3.0~5.0.

[0055] The present invention also provides a method for electroless nickel-phosphorus plating on the surface of photovoltaic copper grid lines and / or flexible circuit copper substrates using the above-mentioned electroless nickel-phosphorus plating solution, comprising the following steps: Step 1, Degreasing treatment: The copper attached to the polyester polymer film is immersed in isopropanol (IPA) as a copper substrate and ultrasonically cleaned at 40~60℃ for 1~5 minutes to remove organic contaminants on the surface of the copper substrate. After removal, it is thoroughly rinsed with deionized water.

[0056] Step 2, Acid washing and activation: Immerse the degreased copper substrate in a dilute sulfuric acid solution with a volume fraction of 8% to 20% for 20 to 120 seconds at room temperature to remove the copper oxide layer on the surface of the copper substrate, exposing the fresh metallic copper surface. After removal, rinse immediately with deionized water.

[0057] Step 3: Activation of zinc particles: The acid-washed and activated copper substrate is immersed in an activation solution containing micron-sized zinc particles to form an activation nucleus, which induces the subsequent autocatalytic deposition of nickel and phosphorus. The substrate is treated at room temperature for 30-90 seconds and then rinsed with deionized water.

[0058] Furthermore, the particle size of the micron-sized zinc particles is 1~20μm. As an example, the particle size of the micron-sized zinc particles is preferably 2-10μm.

[0059] Furthermore, the content of the micron-sized zinc particles is 5~50 g / L. As an example, the content of the micron-sized zinc particles is preferably 0.5~5 g / L.

[0060] Furthermore, the activation solution uses water as a dispersion, and the pH of the activation solution is controlled within the range of 11-13 by adding an appropriate amount of sodium hydroxide. As an example, the pH of the activation solution is preferably controlled within the range of 11-12, and preferably pH=12.

[0061] Furthermore, sodium dodecyl sulfonate and / or gelatin can be added to the activation solution to prepare a suspension. As an example, the content of sodium dodecyl sulfonate and / or gelatin is 1-2 g / L.

[0062] Step 4: Electroless nickel-phosphorus plating: The copper substrate, after being activated by zinc particles, is rapidly transferred to the aforementioned electroless nickel-phosphorus plating solution preheated to 78-92°C, preferably 78-88°C, for plating at a rate of 18-24 μm / h, so as to form a nickel-phosphorus layer on the surface of the copper substrate. The plating time is determined according to the target thickness, preferably the thickness of the nickel layer is 0.05-50 μm. During the plating process, the pH of the electroless nickel-phosphorus plating solution is kept stable at 3.8-5.0, preferably stable at 4.0-4.5, and sodium acetate solution can be added as needed. After plating is completed, the substrate is removed, rinsed with deionized water, and dried.

[0063] Furthermore, this method controls the phosphorus content in the electroless nickel-phosphorus plating solution by adjusting the mass ratio of nickel sulfate hexahydrate to sodium hypophosphite monohydrate (main salt mass ratio) and the concentration of the complexing agent. After plating, the phosphorus content accounts for 0 to 13 wt% of the nickel-phosphorus layer content.

[0064] The present invention also provides an application of the above-mentioned plating method in the preparation of a photovoltaic copper grid barrier layer.

[0065] The present invention also provides an application of the above-mentioned plating method in the preparation of a key functional nickel layer on a copper substrate for flexible circuits.

[0066] This invention performs electroless nickel-phosphorus plating by preparing the following three embodiments of electroless nickel-phosphorus plating solutions and plating methods, and observes the surface morphology of the generated copper grid lines or copper substrates, as well as calculating the phosphorus content. Example 1

[0067] 1. Prepare the electroless nickel-phosphorus plating solution according to the following concentrations: Nickel sulfate hexahydrate 35 g / L, sodium hypophosphite monohydrate 40 g / L, sodium citrate 2 g / L, malic acid 1 g / L, lactic acid 1 mL / L, ethylenediaminetetramethylenephosphonic acid 1 g / L, succinic acid 2 g / L, copper sulfate 15 mg / L, propyneonium salt 40 mg / L, thiourea 2 mg / L, sodium dodecyl sulfonate 40 mg / L, sodium acetate 10 g / L.

[0068] Adjust the pH of the electroless nickel-phosphorus plating solution to 4.2 using ammonia or dilute sulfuric acid.

[0069] Sodium citrate, malic acid, lactic acid, and ethylenediaminetetramethylenephosphonic acid are used as complexing agents.

[0070] Succinic acid is used as an accelerator.

[0071] Copper sulfate and propyne onium salt are used as brighteners.

[0072] Thiourea is used as a stabilizer. Sodium dodecyl sulfonate is used as a dispersant.

[0073] Sodium acetate is used as a pH adjuster.

[0074] 2. Perform electroless nickel-phosphorus plating on the photovoltaic copper grid wires according to the following plating process: Step 1, Degreasing treatment: The copper grid structure attached to the polyester polymer film was immersed in isopropanol and ultrasonically cleaned at 50°C for 60 seconds to remove organic contaminants from the surface of the copper grid structure. After removal, it was thoroughly rinsed with deionized water.

[0075] Step 2, Acid washing and activation: After degreasing, the copper grid structure attached to the polyester polymer film is immersed in a 10% (v / v) dilute sulfuric acid solution and treated at room temperature for 20 seconds to remove the copper oxide layer on the surface of the copper grid structure, exposing the fresh metallic copper surface. After removal, it is immediately rinsed with deionized water.

[0076] Step 3, Zinc particle activation: After acid washing and activation, the copper grid structure attached to the polyester polymer film is immersed in an activation solution containing 10μm zinc particles. The activation solution is a 5g / L suspension containing micron-sized zinc particles, the pH is adjusted to 12, and the treatment is carried out at room temperature for 90s. After removal, it is rinsed with deionized water.

[0077] Step 4: Electroless nickel-phosphorus plating: After the zinc particles are activated, the copper grid structure film is quickly transferred into the above-mentioned electroless nickel-phosphorus plating solution preheated to 84~85℃. The plating time is 5 minutes and the plating rate is 21 μm / h, so that a nickel-phosphorus layer is formed on the surface of the copper grid structure. During the plating process, the pH is kept stable at 4.2~4.3, and an appropriate amount of sodium acetate solution can be added. After the plating is completed, the film is taken out, rinsed with deionized water and dried.

[0078] 3. Coating results: See Figure 1 As shown, in this embodiment, the nickel-phosphorus plating layer on the surface of the copper grid line after electroless nickel-phosphorus plating is completely covered without any missed plating. The plating layer has a bright and smooth appearance, and a nickel-phosphorus plating layer with a thickness of about 2μm is obtained. After EDS energy dispersive spectroscopy content conversion, the phosphorus content in the obtained nickel-phosphorus plating layer is about 2.3wt%. Example 2

[0079] 1. Prepare the electroless nickel-phosphorus plating solution according to the following concentrations: Nickel sulfate hexahydrate 30 g / L, sodium hypophosphite monohydrate 50 g / L, sodium citrate 2 g / L, malic acid 5 g / L, lactic acid 1 mL / L, ethylenediaminetetramethylenephosphonic acid 2 g / L, succinic acid 2 g / L, propionic acid 1 mL / L, copper sulfate 15 mg / L, propyne onion salt 40 mg / L, sodium thiosulfate 2 mg / L, potassium iodide 1 mg / L, sodium dodecyl sulfate 40 mg / L, sodium acetate 5 g / L.

[0080] Adjust the pH of the electroless nickel-phosphorus plating solution to 3.8 using ammonia or dilute sulfuric acid.

[0081] Sodium citrate, malic acid, lactic acid, and ethylenediaminetetramethylenephosphonic acid are used as complexing agents.

[0082] Propionic acid and succinic acid are used as accelerators.

[0083] Copper sulfate and propyne onium salt are used as brighteners.

[0084] Sodium thiosulfate and potassium iodide are used as stabilizers. Sodium dodecyl sulfonate is used as a dispersant.

[0085] Sodium acetate is used as a pH adjuster.

[0086] 2. Perform electroless nickel-phosphorus plating on the photovoltaic copper grid wires according to the following plating process: Step 1, Degreasing treatment: The copper substrate was immersed in isopropanol and ultrasonically cleaned at 50°C for 60 seconds to remove organic contaminants from the surface of the copper grid structure. After removal, it was thoroughly rinsed with deionized water.

[0087] Step 2, Acid washing and activation: After degreasing, the copper substrate is immersed in a 10% (v / v) dilute sulfuric acid solution and treated at room temperature for 50 seconds to remove the copper oxide layer on the surface of the copper substrate, exposing the fresh metallic copper surface. After removal, it is immediately rinsed with deionized water.

[0088] Step 3, Zinc particle activation: After acid washing and activation, the copper substrate was immersed in an activation solution containing micron-sized zinc particles with a concentration of 5 g / L, a zinc particle size of 5 μm, and a pH of 12. The solution was treated at room temperature for 70 seconds, and then rinsed with deionized water.

[0089] Step 4: Electroless nickel-phosphorus plating: After the zinc particles are activated, the copper substrate is quickly transferred into the above-mentioned electroless nickel-phosphorus plating solution preheated to 88°C. The plating time is 3 minutes and the plating rate is 23 μm / h, so that a nickel-phosphorus layer is formed on the surface of the copper substrate. During the plating process, the pH is kept stable at 3.8, and an appropriate amount of sodium acetate solution can be added. After the plating is completed, the substrate is taken out, rinsed with deionized water, and dried.

[0090] 3. Coating results: In this embodiment, the nickel-phosphorus coating on the copper substrate after electroless nickel-phosphorus plating is complete and without obvious defects. The coating has a bright and smooth appearance and a nickel-phosphorus coating with a thickness of about 1 μm. After EDS energy dispersive spectroscopy content conversion, the phosphorus content in the obtained nickel-phosphorus coating is about 5.2 wt%. Example 3

[0091] 1. Prepare the electroless nickel-phosphorus plating solution according to the following concentrations: Nickel sulfate hexahydrate 20 g / L, sodium hypophosphite monohydrate 45 g / L, sodium citrate 5 g / L, malic acid 2 g / L, lactic acid 1 mL / L, succinic acid 1 g / L, propionic acid 1 mL / L, copper sulfate 15 mg / L, propyne onion 45 mg / L, sodium thiosulfate 2 mg / L, potassium iodide 1 mg / L, sodium dodecyl sulfate 40 mg / L, sodium acetate 10 g / L.

[0092] Adjust the pH of the electroless nickel-phosphorus plating solution to 4.4 using ammonia or dilute sulfuric acid.

[0093] Sodium citrate, malic acid, and lactic acid are used as chelating agents.

[0094] Succinic acid and propionic acid are used as accelerators.

[0095] Copper sulfate and propyne onium salt are used as brighteners.

[0096] Sodium thiosulfate and potassium iodide are used as stabilizers. Sodium dodecyl sulfonate is used as a dispersant.

[0097] Sodium acetate is used as a pH adjuster.

[0098] 2. Perform electroless nickel-phosphorus plating on the photovoltaic copper grid wires according to the following plating process: Step 1, Degreasing treatment: The copper grid structure film was immersed in isopropanol and ultrasonically cleaned at 50°C for 60 seconds to remove organic contaminants from the surface of the copper grid structure. After removal, it was thoroughly rinsed with deionized water.

[0099] Step 2, Acid washing and activation: After degreasing, the copper grid structure film is immersed in a 10% (v / v) dilute sulfuric acid solution and treated at room temperature for 50 seconds to remove the copper oxide layer on the surface of the copper grid structure, exposing the fresh metallic copper surface. After removal, it is immediately rinsed with deionized water.

[0100] Step 3, Zinc particle activation: After acid washing and activation, the copper grid structure film is immersed in an activation solution containing micron-sized zinc particles with a concentration of 5 g / L, a zinc particle size of 5 μm, and a pH of 12. The solution is treated at room temperature for 70 seconds and then rinsed with deionized water.

[0101] Step 4: Electroless nickel-phosphorus plating: After the zinc particles are activated, the copper grid structure film is quickly transferred into the above-mentioned electroless nickel-phosphorus plating solution preheated to 80°C. The plating time is 10 min and the plating rate is 20 μm / h, so that a nickel-phosphorus layer is formed on the surface of the copper grid structure. During the plating process, the pH is kept stable at 4.4, and an appropriate amount of sodium acetate solution can be added. After the plating is completed, the film is taken out, rinsed with deionized water and dried.

[0102] 3. Coating results: In this embodiment, the copper grid wire surface after electroless nickel-phosphorus plating has a complete nickel-phosphorus coating, with a bright and smooth appearance, resulting in a nickel-phosphorus coating approximately 3 μm thick. See also Figure 2 As shown, after EDS (Energy Dispersive X-ray Diode) content conversion, the phosphorus content in the obtained nickel-phosphorus coating is approximately 12.6 wt%. (See also...) Figure 3 As shown, the nickel and phosphorus in the obtained nickel-phosphorus coating are uniformly distributed. Figure 3 The copper element originates from the base copper layer, and the carbon element originates from the polyester polymer film layer (excluding the nickel-phosphorus layer).

[0103] As can be seen from the results of the above embodiments, the nickel-phosphorus electroless plating solution and nickel-phosphorus layer plating method provided by the present invention, while ensuring the high stability of the plating solution, achieves precise control of plating rate, phosphorus content, and coating structure, significantly improving the density and uniform coverage of the nickel-phosphorus coating. This system is particularly suitable for photovoltaic copper grid lines with fine linewidth and high aspect ratio, effectively solving the problems of slow plating initiation and localized incomplete plating, forming a continuous, bright, and highly adhesive functional coating. Furthermore, compared with traditional precious metal activation processes, the present invention has significant advantages in cost control and process feasibility, and possesses promising prospects for industrial application.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A chemical nickel-phosphorus plating solution for photovoltaic copper grid lines and / or flexible circuits, characterized in that, It contains the following components by mass concentration: Nickel sulfate hexahydrate 15~35g / L, sodium hypophosphite monohydrate 15~50g / L, complexing agent 2~30g / L, accelerator 1~10g / L, brightener 5~50mg / L, stabilizer 5~50mg / L, dispersant 0.01~1g / L, pH adjuster 5~20g / L, balance deionized water; The complexing agent is selected from any one or a combination of sodium citrate, malic acid, lactic acid, and ethylenediaminetetramethylenephosphonic acid; The pH of the electroless nickel-phosphorus plating solution is 3.0~5.

0.

2. The electroless nickel-phosphorus plating solution according to claim 1, characterized in that, The concentration of ethylenediaminetetramethylenephosphonic acid in the complexing agent is 0.5~2 g / L, which is used to deeply complex nickel ions and inhibit the self-decomposition of the plating solution.

3. The electroless nickel-phosphorus plating solution according to claim 1, characterized in that, The accelerator is selected from any one or a combination of two of succinic acid and propionic acid.

4. The electroless nickel-phosphorus plating solution according to claim 1, characterized in that, The stabilizer is selected from any one or a combination of sodium thiosulfate, potassium iodide, and thiourea.

5. A method for electroless nickel-phosphorus plating on the surface of photovoltaic copper grid lines and / or flexible circuit copper substrates using the electroless nickel-phosphorus plating solution as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1, Degreasing treatment: The copper attached to the polyester polymer film was immersed in isopropanol as a copper substrate and ultrasonically cleaned at 40~60℃ for 1~5 minutes to remove organic contaminants on the surface of the copper substrate. After removal, it was rinsed thoroughly with deionized water. Step 2, Acid washing and activation: Immerse the degreased copper substrate in a dilute sulfuric acid solution with a volume fraction of 8% to 20% for 20 to 120 seconds at room temperature to remove the copper oxide layer on the surface of the copper substrate and expose the fresh metallic copper surface. Rinse with deionized water immediately after removal. Step 3: Activation of zinc particles: The acid-washed and activated copper substrate is immersed in an activation solution containing micron-sized zinc particles to form an activation nucleus, which induces the subsequent autocatalytic deposition of nickel and phosphorus. The substrate is treated at room temperature for 30-90 seconds and then rinsed with deionized water. Step 4: Electroless nickel-phosphorus plating: The copper substrate, after being activated by zinc particles, is rapidly transferred into the electroless nickel-phosphorus plating solution preheated to 78-92°C as described in any one of claims 1-5 for plating at a plating rate of 18-24 μm / h, so as to form a nickel-phosphorus layer on the surface of the copper substrate. During the plating process, the pH of the electroless nickel-phosphorus plating solution is kept stable in the range of 3.8-5.0 by adding sodium acetate solution. After the plating is completed, the substrate is removed, rinsed with deionized water, and dried.

6. The plating method according to claim 1, characterized in that, In the activation solution, the particle size of the micron-sized zinc particles is 1~20μm, the content of the micron-sized zinc particles is 5~50g / L, the activation solution uses water as the dispersion, and the pH of the activation solution is controlled within the range of 11~13 by adding sodium hydroxide.

7. The plating method according to claim 1, characterized in that, After plating, the thickness of the nickel-phosphorus layer is 0.05~50μm.

8. The plating method according to claim 1, characterized in that, The phosphorus content in the electroless nickel-phosphorus plating solution is controlled by adjusting the mass ratio of nickel sulfate hexahydrate to sodium hypophosphite monohydrate and the concentration of the complexing agent. After plating, the phosphorus content is in the range of 0-13 wt% of the nickel-phosphorus layer content.

9. The application of the plating method as described in any one of claims 5 to 8 in the preparation of a photovoltaic copper grid barrier layer.

10. The application of the plating method as described in any one of claims 5 to 8 in the fabrication of a key functional nickel layer on a copper substrate for flexible circuits.

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