A low-temperature curing nickel-doped silver-coated copper paste for solar cells and its preparation and application methods

Abstract

This invention discloses a low-temperature curing nickel-doped silver-coated copper paste for solar cells, and its preparation and application methods, belonging to the field of conductive paste preparation technology. The paste contains 50-80 parts of nickel-doped silver-coated copper powder; wherein the silver content is 85-98 wt%, the nickel content is 2-15 wt%, and the coating layer thickness is 100-500 nm; 10-30 parts of organic solvent, 0.5-5 parts of dispersant, 0.1-2 parts of defoamer, and / or 0.1-2 parts of viscosity modifier. The copper powder is activated in an alkaline activation solution for 4-6 min; then transferred to a silver-nickel binary alloy electroplating solution with a cathode current density of 200-400 mA / cm². 2 The plating process involves plating at room temperature for 3–8 minutes; washing until the conductivity is <10 μS / cm, and drying; then mixing nickel-doped silver-coated copper powder, organic solvent, dispersant, defoamer, and / or viscosity modifier at room temperature according to the formulation ratio. This slurry can be used to prepare conductive and thermally conductive composite materials. This method constructs a nickel-doped silver coating layer on the surface of copper powder through alkali activation and alloy electroplating, reducing silver consumption and achieving synergistic optimization of low-temperature curing and high conductivity.

Description

Technical Field

[0001] This invention belongs to the field of conductive paste preparation technology, specifically relating to a low-temperature curing nickel-doped silver-coated copper paste for solar cells and its preparation and application methods. Background Technology

[0002] In the fabrication process of silicon heterojunction solar cells, conductive paste is required for printing grid electrodes on the back or front of the cell. Traditional pure silver paste, due to its high silver consumption, high cost, and volatile price, has become a major cost bottleneck for improving photoelectric conversion efficiency. How to effectively reduce the silver content in the paste while ensuring good conductivity and reliability is a key problem that the industry urgently needs to solve.

[0003] In recent years, silver-coated copper paste has attracted attention due to the low cost and good conductivity of copper. However, copper is prone to oxidation, which can lead to increased resistivity and decreased reliability after curing. To ensure a certain level of conductivity stability, many existing low-temperature curing silver-coated copper pastes still have relatively high silver consumption, resulting in limited cost reduction or poor performance in resistance to damp heat, making it difficult to meet the requirements of photovoltaic module lifespan and large-scale mass production.

[0004] Based on this, developing a nickel-doped silver-coated copper paste that can be rapidly cured at low temperatures, has good printability and conductivity, significantly reduces silver consumption, and also has excellent oxidation resistance and humid heat stability is of great practical significance for promoting the development of silicon heterojunction solar cells. Summary of the Invention

[0005] The first objective of this invention is to provide a low-temperature curing nickel-doped silver-coated copper paste for solar cells; the second objective is to provide a method for preparing the nickel-doped silver-coated copper paste; and the third objective is to provide the application of the nickel-doped silver-coated copper paste in the preparation of conductive and thermally conductive composite materials.

[0006] The first objective of this invention is achieved as follows: the nickel-doped silver-coated copper paste comprises, by weight: 50-80 parts of nickel-doped silver-coated copper powder; the silver content of the nickel-doped silver-coated copper powder is 85-98 wt%, the nickel content is 2-15 wt%, and the coating thickness is 100-500 nm; 10-30 parts of organic solvent, wherein the organic solvent is any one of isopropanol, n-propanol, or dipropylene glycol monobutyl ether; 0.5-5 parts of dispersant, wherein the dispersant is any one of phosphate esters or polyethers; 0.1-2 parts of defoamer and / or 0.1-2 parts of viscosity modifier.

[0007] The second objective of this invention is achieved as follows: the method for preparing the low-temperature curing nickel-doped silver-coated copper paste includes the following steps: Copper powder coating: Place copper powder in an alkaline activation solution and activate for 4-6 minutes; then transfer it to a silver-nickel binary alloy electroplating solution, setting the cathode current density to 200-400 mA / cm². 2 Plating was carried out at room temperature for 3-8 minutes; the copper powder was washed until the conductivity was <10 μS / cm; and then dried to obtain nickel-doped silver-coated copper powder.

[0008] Slurry preparation: Mix nickel-doped silver-coated copper powder, organic solvent, dispersant, defoamer and / or viscosity modifier at room temperature according to the formula ratio.

[0009] The third objective of this invention is achieved as follows: the application of the low-temperature curing nickel-doped silver-coated copper paste in the preparation of conductive and thermally conductive composite materials includes the following steps: The nickel-doped silver-coated copper paste is mixed with 100 parts of epoxy resin and 10-20 parts of aliphatic amine curing agent, degassed, coated and cured to obtain a composite material with high electrical conductivity, high thermal conductivity and oxidation resistance.

[0010] Compared with the prior art, the technical solution described in this invention has the following advantages: 1. The selected activation conditions can completely reduce the oxide layer on the surface of copper powder, exposing fresh copper atoms. The fresh copper surface and the deposited silver-nickel alloy can form a copper-silver-nickel ternary metal bonding interface, and the bonding strength is much higher than that of physical adsorption.

[0011] 2. Because nickel is dissolved in the grain boundaries of the silver layer, it hinders the growth of silver grains, refines the grains of the alloy layer, and forms a dense barrier structure. During the electrodeposition process, nickel will preferentially fill the defect sites of the silver layer growth, significantly reduce the porosity of the coating layer, cut off the channels for water and oxygen to diffuse to the copper nucleus, and reduce the oxidation rate of the copper nucleus by more than 30% in humid or high-temperature environments.

[0012] 3. Due to the higher density of the alloy coating, the coating thickness can be reduced from the traditional >500nm to 100~500nm under the same anti-oxidation effect, thereby effectively reducing the consumption of silver.

[0013] 4. The slurry system employs high shear dispersion and optimized dispersant formulation to achieve excellent suspension stability and low viscosity characteristics, facilitating spraying, screen printing, or dispensing processes.

[0014] 5. The slurry is directly compatible with existing epoxy / amine curing systems, the process is simple, and no additional formula adjustments are required.

[0015] 6. The component has good electrical conductivity after curing (volume resistivity ≤ 6.5 μΩ·cm).

[0016] In summary, the technical solution of this invention constructs a nickel-doped silver coating layer on the surface of copper powder through alkaline activation and silver-nickel alloy electroplating, which solves the oxidation failure problem of traditional silver-coated copper powder at the atomic scale, while reducing the amount of silver consumed and achieving synergistic optimization of low-temperature curing and high conductivity. Attached Figure Description

[0017] Figure 1 The volume resistivity of the nickel-doped silver-coated copper paste prepared in Example 1 after being formulated and cured with an amine curing agent, in the initial state and after aging in air at 100°C for 72 hours; Figure 2 The volume resistivity of the nickel-doped silver-coated copper paste prepared in Example 2 after being formulated and cured with an amine curing agent, in the initial state and after aging in air at 100°C for 72 hours; Figure 3 The volume resistivity of the nickel-doped silver-coated copper paste prepared in Example 3, after being formulated and cured with an amine curing agent, is measured in its initial state and after aging in air at 100°C for 72 hours. Detailed Implementation

[0018] The present invention will be further described below, but this is not intended to limit the invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the scope of protection of the present invention.

[0019] The nickel-doped silver-coated copper paste comprises, by weight: 50-80 parts of nickel-doped silver-coated copper powder; the silver content of the nickel-doped silver-coated copper powder is 85-98 wt%, the nickel content is 2-15 wt%, and the coating thickness is 100-500 nm; 10-30 parts of organic solvent, wherein the organic solvent is any one of isopropanol, n-propanol, or dipropylene glycol monobutyl ether; 0.5-5 parts of dispersant, wherein the dispersant is any one of phosphate esters or polyethers; 0.1-2 parts of defoamer and / or 0.1-2 parts of viscosity modifier.

[0020] The dispersant is preferably a polyether phosphate.

[0021] The defoamer is preferably a siloxane type.

[0022] The viscosity modifier is preferably polyacrylate.

[0023] The nickel-doped silver-coated copper paste has a curing temperature of ≤180℃ and a resistivity of ≤6.5 μΩ·cm.

[0024] The method for preparing the low-temperature curing nickel-doped silver-coated copper paste includes the following steps: Copper powder coating: Place copper powder in an alkaline activation solution and activate for 4-6 minutes; then transfer it to a silver-nickel binary alloy electroplating solution, setting the cathode current density to 200-400 mA / cm². 2Plating was carried out at room temperature for 3-8 minutes; the copper powder was washed until the conductivity was <10 μS / cm; and then dried to obtain nickel-doped silver-coated copper powder.

[0025] Slurry preparation: According to the formula ratio, mix nickel-doped silver-coated copper powder, organic solvent (selected from isopropanol, n-propanol or dipropylene glycol monobutyl ether), dispersant (polyether phosphate), defoamer (siloxane type) and / or viscosity modifier (polyacrylate) at room temperature.

[0026] In the copper powder coating process, the alkaline activation solution consists of 10 g / L Na₂S₂O₄ and 5 g / L NaOH. The silver-nickel binary alloy electroplating solution consists of 30 g / L AgNO₃, 2 g / L NiSO₄, 40 g / L KCN complexing agent, and 10 g / L KOH. The drying process refers to vacuum drying at 60°C for 3 hours.

[0027] In the slurry preparation process, the mixing involves placing each component of the slurry in a high-speed disperser and dispersing it at a speed of 2000~5000 rpm for 10~20 minutes. The room temperature refers to 25±5 ℃. After mixing, a sieving process can be added, allowing the slurry to be filtered through a 200-mesh sieve.

[0028] The application of the low-temperature curing nickel-doped silver-coated copper paste in the preparation of conductive and thermally conductive composite materials includes the following steps: The nickel-doped silver-coated copper paste is mixed with 100 parts of epoxy resin and 10-20 parts of aliphatic amine curing agent, degassed, coated and cured to obtain a composite material with high electrical conductivity, high thermal conductivity and oxidation resistance.

[0029] The aliphatic amine curing agent is any one of triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, and hexamethylenediamine.

[0030] Example 1

[0031] The nickel-doped silver-coated copper paste contains, by weight: 60 parts nickel-doped silver-coated copper powder, 20 parts isopropanol; 1.5 parts polyether phosphate; 0.5 parts siloxane defoamer and 0.5 parts polyacrylate.

[0032] preparation: Copper powder coating: 100g of copper powder was placed in 500mL of alkaline activation solution and stirred at 300rpm for 5min. The alkaline activation solution consisted of 10g / L Na2S2O4 and 5g / L NaOH. The powder was then transferred to a 1L electroplating tank containing a silver-nickel binary alloy electroplating solution, and the cathode current density was set to 300 mA / cm². 2The silver-nickel binary alloy electroplating solution, composed of 30 g / L AgNO3, 2 g / L NiSO4, 40 g / L KCN complexing agent, and 10 g / L KOH, was plated at room temperature for 3 min. The solution was washed until the conductivity was <10 μS / cm. The copper powder was then vacuum dried at 60℃ for 3 h to obtain nickel-doped silver-coated copper powder.

[0033] Slurry preparation: According to the formula ratio, nickel-doped silver-coated copper powder, isopropanol, polyether phosphate, siloxane defoamer and / or polyacrylate are placed in a high-speed disperser and dispersed at 2000 rpm for 15 min, with the temperature controlled at 25±5℃. Then, the slurry is passed through a 200-mesh sieve to obtain a uniform and stable slurry.

[0034] Slurry performance testing: Viscosity test: Brookfield viscometer at 25 ℃; Oxidation test: After aging in air at 100 ℃ for 72 h, the integrity of the copper powder coating layer was observed by SEM; Conductivity assessment: After the slurry was prepared and cured with the amine curing agent system, the resistivity of the cured body was tested using the four-probe method. The volume resistivity in the initial state and after aging in air at 100 ℃ for 72 h is as follows: Figure 1 As shown.

[0035] application: The prepared nickel-doped silver-coated copper paste was mixed with 100 parts of epoxy resin and 15 parts of triethylenetetramine, degassed, coated and cured to obtain a composite material with high electrical conductivity, high thermal conductivity and oxidation resistance.

[0036] Example 2

[0037] The nickel-doped silver-coated copper paste contains, by weight: 65 parts nickel-doped silver-coated copper powder, 25 parts n-propanol; 2 parts polyether phosphate; 1 part siloxane defoamer and 1 part polyacrylate.

[0038] preparation: Copper powder coating: 100g of copper powder was placed in 500mL of alkaline activation solution and stirred at 300rpm for 4min. The alkaline activation solution consisted of 10g / L Na2S2O4 and 5g / L NaOH. The powder was then transferred to a 1L electroplating tank containing a silver-nickel binary alloy electroplating solution, and the cathode current density was set to 200 mA / cm². 2 The silver-nickel binary alloy electroplating solution, composed of 30 g / L AgNO3, 2 g / L NiSO4, 40 g / L KCN complexing agent, and 10 g / L KOH, was plated at room temperature for 6 min. The solution was washed until the conductivity was <10 μS / cm. The copper powder was then vacuum dried at 60℃ for 3 h to obtain nickel-doped silver-coated copper powder.

[0039] Slurry preparation: According to the formula ratio, nickel-doped silver-coated copper powder, n-propanol, polyether phosphate, siloxane defoamer and / or polyacrylate are placed in a high-speed disperser and dispersed at 3000 rpm for 15 min, with the temperature controlled at 25±5℃. Then, the mixture is passed through a 200-mesh sieve to obtain a uniform and stable slurry.

[0040] Slurry performance test: Same as Example 1, results are as follows Figure 2 As shown.

[0041] application: The prepared nickel-doped silver-coated copper paste was mixed with 100 parts of epoxy resin and 15 parts of tetraethylenepentamine, degassed, coated and cured to obtain a composite material with high electrical conductivity, high thermal conductivity and oxidation resistance.

[0042] Example 3

[0043] The nickel-doped silver-coated copper paste contains, by weight: 70 parts nickel-doped silver-coated copper powder, 15 parts dipropylene glycol monobutyl ether, 2.5 parts polyether phosphate, 1.5 parts siloxane defoamer, and 1.5 parts polyacrylate.

[0044] preparation: Copper powder coating: 100g of copper powder was placed in 500mL of alkaline activation solution and stirred at 300rpm for 6min. The alkaline activation solution consisted of 10g / L Na2S2O4 and 5g / L NaOH. The powder was then transferred to a 1L electroplating tank containing a silver-nickel binary alloy electroplating solution, and the cathode current density was set to 400 mA / cm². 2 The silver-nickel binary alloy electroplating solution, composed of 30 g / L AgNO3, 2 g / L NiSO4, 40 g / L KCN complexing agent, and 10 g / L KOH, was plated at room temperature for 4 min. The solution was washed until the conductivity was <10 μS / cm. The copper powder was then vacuum dried at 60℃ for 3 h to obtain nickel-doped silver-coated copper powder.

[0045] Slurry preparation: According to the formula ratio, nickel-doped silver-coated copper powder, dipropylene glycol monobutyl ether, polyether phosphate, siloxane defoamer and / or polyacrylate are placed in a high-speed disperser and dispersed at 4000 rpm for 10 min, with the temperature controlled at 25±5 ℃. Then, the slurry is passed through a 200-mesh sieve to obtain a uniform and stable slurry.

[0046] Slurry performance test: Same as Example 1, results are as follows Figure 3 As shown.

[0047] application: The prepared nickel-doped silver-coated copper paste was mixed with 100 parts of epoxy resin and 15 parts of hexamethylenediamine, degassed, coated and cured to obtain a composite material with high electrical conductivity, high thermal conductivity and oxidation resistance.

Claims

1. A low-temperature curing nickel-doped silver-coated copper paste for solar cells, characterized in that, The nickel-doped silver-coated copper paste comprises, by weight: 50-80 parts of nickel-doped silver-coated copper powder; the silver content of the nickel-doped silver-coated copper powder is 85-98 wt%, the nickel content is 2-15 wt%, and the coating thickness is 100-500 nm; 10-30 parts of organic solvent, wherein the organic solvent is any one of isopropanol, n-propanol, or dipropylene glycol monobutyl ether; 0.5-5 parts of dispersant, wherein the dispersant is any one of phosphate esters or polyethers; 0.1-2 parts of defoamer and / or 0.1-2 parts of viscosity modifier.

2. The low-temperature curing nickel-doped silver-coated copper paste according to claim 1, characterized in that, The dispersant is a polyether phosphate.

3. The low-temperature curing nickel-doped silver-coated copper paste according to claim 1, characterized in that, The defoamer is of the siloxane type.

4. The low-temperature curing nickel-doped silver-coated copper paste according to claim 1, characterized in that, The viscosity modifier is polyacrylate.

5. A method for preparing low-temperature curing nickel-doped silver-coated copper paste according to any one of claims 1 to 4, characterized in that, The process includes the following steps: Copper powder coating: Place copper powder in an alkaline activation solution and activate for 4-6 minutes; then transfer it to a silver-nickel binary alloy electroplating solution, setting the cathode current density to 200-400 mA / cm². 2 Plating at room temperature for 3-8 minutes; washing until conductivity <10 μS / cm; drying to obtain nickel-doped silver-coated copper powder; Slurry preparation: Mix nickel-doped silver-coated copper powder, organic solvent, dispersant, defoamer and / or viscosity modifier at room temperature according to the formula ratio.

6. The preparation method according to claim 5, characterized in that, In the copper powder coating process, the alkaline activation solution consists of 10 g / L Na2S2O4 and 5 g / L NaOH.

7. The preparation method according to claim 5, characterized in that, In the copper powder coating process, the composition of the silver-nickel binary alloy electroplating solution is: 30 g / L AgNO3, 2 g / L NiSO4, 40 g / L KCN complexing agent, and 10 g / L KOH.

8. The preparation method according to claim 5, characterized in that, In the copper powder coating process, the drying refers to vacuum drying at 60°C for 3 hours.

9. The preparation method according to claim 5, characterized in that, In the slurry preparation process, the mixing involves placing each component of the slurry in a high-speed disperser and dispersing it at a speed of 2000~5000 rpm for 10~20 minutes.

10. The application of the low-temperature curing nickel-doped silver-coated copper paste according to any one of claims 1 to 4 in the preparation of conductive and thermally conductive composite materials, characterized in that, The process includes the following steps: The nickel-doped silver-coated copper paste is mixed with 100 parts of epoxy resin and 10-20 parts of aliphatic amine curing agent, degassed, coated and cured to obtain a composite material with high electrical conductivity, high thermal conductivity and oxidation resistance.

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