Method for reducing diameter of tungsten filament of tungsten filament screen cloth

Abstract

The invention provides a method for reducing the diameter of a tungsten filament of tungsten filament screen cloth, which reduces the risk of injury to operators and is good in environmental friendliness. The size precision control of the tungsten filament reducing process is high; the corrosion degree of equipment is reduced, and the maintenance cost is reduced. The method is characterized in that a mixed solution containing potassium ferricyanide, potassium hydroxide and deionized water is adopted as an etching solution for reducing the tungsten filament, the mass percent of potassium ferricyanide in the etching solution is 5%-20%, and the mass percent of potassium hydroxide in the etching solution is 3%-10%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar photovoltaic screen processing, in particular to a diameter reduction method of tungsten wire of tungsten wire screen. BACKGROUND

[0002] In the screen printing process of solar photovoltaic cells, the screen plate is one of the most critical components. Tungsten wire, with its excellent high-temperature performance and outstanding mechanical strength, plays a crucial role in the field of screen printing and has become one of the important choices for making high-precision screen plates.

[0003] Tungsten has the following four characteristics:

[0004] (1) High hardness: Tungsten is a high-hardness metal material with high Mohs hardness; in the process of screen printing, it can maintain good shape and stable structure, and is not easy to deform or damage, which can ensure the precision and quality of printing;

[0005] (2) Good high-temperature resistance: The production process of photovoltaic cells may involve some high-temperature processes, and tungsten has a very high melting point. In a high-temperature environment, the tungsten screen plate will not soften or deform, and can maintain good performance;

[0006] (3) Good chemical stability: It is not easy to react with the ingredients in the printing paste, and can resist the corrosion of some corrosive substances in the paste during printing, prolonging the service life of the screen plate;

[0007] (4) Low roughness and good surface flatness: The surface roughness of tungsten screen plate is low and the flatness is good, which is conducive to the uniform distribution and smooth flow of the paste on the screen plate. In the screen printing process, it can ensure that the paste can uniformly pass through the mesh, reducing the paste hanging phenomenon.

[0008] These characteristics make tungsten particularly suitable for making high-mesh, low-wire-diameter screens. High-mesh screens can perfectly meet the stringent requirements of photovoltaic cells for printing precision, allowing conductive paste to pass through the mesh and be accurately printed on the silicon wafer, thereby forming front and back electrodes, which greatly helps to improve the photoelectric conversion efficiency of solar cells.

[0009] With the growing global demand for clean energy, the production scale of solar cells continues to expand, and the demand for high-quality, high-precision photovoltaic printing screen plates tungsten wire screen cloth is also increasing. With the continuous development of photovoltaic technology, low-wire-diameter screen plates will become one of the key technologies to achieve higher efficiency and lower cost solar cells.

[0010] As an extremely effective microfabrication technology, chemical etching can achieve high-precision processing of tungsten wires. Through chemical etching, the wire diameter and surface morphology of tungsten wires can be precisely controlled to meet the needs of different application scenarios. In the prior art, tungsten wire etching is mostly carried out by using strong acid (such as HNO3 and HF) or high-temperature molten salt method, which has the following defects: high corrosiveness, dangerous operation; surface microcracks or roughening are easily produced; etching uniformity is difficult to control, affecting the performance of subsequent devices, and the existing alkaline etching solution is safer, but the etching rate is low, and there is a lack of surface smoothness control means.

[0011] Therefore, there is an urgent need to develop a chemical etching method for reducing the diameter of tungsten wires with safety. SUMMARY

[0012] To solve the above problems, the present application provides a method for reducing the diameter of tungsten wires of tungsten wire mesh cloth, which reduces the risk of injury to operators and has good environmental friendliness; the size precision control of the tungsten wire diameter reduction process is high; and the corrosion degree of the equipment is reduced, and the maintenance cost is reduced.

[0013] A method for reducing the diameter of tungsten wires of tungsten wire mesh cloth, characterized in that a mixed solution containing potassium ferricyanide, potassium hydroxide and deionized water is used as an etching solution to reduce the diameter of tungsten wires, the mass percentage of potassium ferricyanide in the etching solution is 5%-20%, and the mass percentage of potassium hydroxide is 3%-10%.

[0014] Further characterized in that:

[0015] Before the tungsten wires of the tungsten wire mesh cloth are reduced in diameter, the tungsten wire mesh cloth is sequentially subjected to acetone ultrasonic cleaning and dilute hydrochloric acid soaking to remove oxidation, and then washed with water and dried;

[0016] During the diameter reduction operation, the tungsten wire mesh cloth to be treated is completely immersed in the etching solution, and etching is carried out at a temperature of 30-50°C for 5-40 minutes;

[0017] After the etching operation is completed, the tungsten wire mesh cloth is taken out, washed with deionized water for 3-5 minutes, washed with ethanol for 2-3 minutes, and then dried in an oven at 50-70°C for 10-20 minutes to obtain tungsten wires with smooth surfaces.

[0018] Further characterized in that:

[0019] The etching solution also comprises a surfactant composition, after the potassium ferricyanide and potassium hydroxide of the etching solution are configured in place, part of deionized water is added first, then 0.1%-1% of the surfactant composition in mass percentage is added, wherein the surfactant composition is composed of a non-ionic surfactant and a small amount of anionic surfactant, then the remaining mass of deionized water is added, so that the total mass of the etching solution reaches 100% of the set mass, and then the surfactant is uniformly dispersed in the etching solution through stirring;

[0020] The mass percentage of the anionic surfactant in the surfactant composition is not more than 10%;

[0021] The non-ionic surfactant and the anionic surfactant are independently added or mixed and then added when the surfactant composition is added;

[0022] The stirring speed during mixing of the etching solution is 200-300 revolutions per minute, and the stirring time is 5-20 minutes;

[0023] After the surfactant is added, the pH value of the etching solution obtained by stirring is controlled to be between 10 and 13, and the pH value is adjusted by adjusting the content of potassium hydroxide, that is, the higher the content of potassium hydroxide, the higher the pH value, and the lower the content of potassium hydroxide, the lower the pH value;

[0024] The etching process is carried out under stirring to ensure uniform contact between the etching solution and the tungsten wire surface and ensure uniform etching;

[0025] During etching, the etching solution is placed in a container, the bottom of the container is provided with a stirring device, the stirring speed of the stirring paddle of the stirring device is 100-200 revolutions per minute, the tungsten wire mesh is clamped by a clamp that does not react with the etching solution and is immersed below the liquid level of the etching solution, and the tungsten wire mesh is arranged above the stirring paddle, which ensures uniform contact between the etching solution and the surface of each tungsten wire.

[0026] After the present application is adopted, a potassium ferricyanide-potassium hydroxide synergistic oxidation system is provided to realize rapid and uniform etching; the etching solution in an alkaline environment is more uniform in dissolving metal, avoiding local over-etching or material damage that may be caused by traditional acid etching; the operation is simple, the process parameters are controllable, and it is suitable for industrial production; the etching solution itself and the etching process have little harm to the human body, thereby making the entire reducing process environmentally friendly and safe, and the wastewater treatment difficulty is low. DETAILED DESCRIPTION

[0027] The application discloses a diameter-reducing method for tungsten wires of a tungsten wire mesh cloth, and adopts a mixed solution containing potassium ferricyanide, potassium hydroxide, a surfactant composition and deionized water as an etching liquid to perform diameter-reducing treatment on the tungsten wires, the mass percentage of the potassium ferricyanide in the etching liquid is 5%-20%, the mass percentage of the potassium hydroxide is 3%-10%, the mass percentage of the surfactant composition is 0.1%-1%, and the rest is the deionized water.

[0028] In specific implementation, the method comprises the following steps:

[0029] S1, before diameter-reducing the tungsten wires of the tungsten wire mesh cloth, the tungsten wire mesh cloth is sequentially subjected to ultrasonic cleaning with acetone, immersion in dilute hydrochloric acid (5wt%) for removing oxidation, and then is subjected to water washing and drying;

[0030] S2, before step S1 is completed, the etching liquid is prepared, part of the deionized water is first added, then 0.1%-1% of the surfactant composition in mass percentage is added, the surfactant composition is composed of a non-ionic surfactant and a small amount of an anionic surfactant, then the rest of the deionized water is added, so that the total mass of the etching liquid reaches 100% of the set mass, then the surfactant is uniformly dispersed in the etching liquid by stirring, the stirring speed during mixing of the etching liquid is 200-300 revolutions per minute, and the stirring time is 5-20 minutes;

[0031] The mass percentage of the anionic surfactant in the surfactant composition is not more than 10%;

[0032] The non-ionic surfactant and the anionic surfactant are independently added or are added after being mixed together when the surfactant composition is added;

[0033] After the surfactant is added, the pH value of the obtained etching liquid is controlled to be between 10 and 13, the pH value is adjusted by adjusting the content of the potassium hydroxide, the higher the content of the potassium hydroxide, the higher the pH value, and the lower the content of the potassium hydroxide, the lower the pH value;

[0034] S3, during diameter-reducing operation, the tungsten wire mesh cloth to be treated is completely immersed in the etching liquid, and etching is performed at a temperature of 30-50 DEG C for 5-40 minutes;

[0035] S4, after the etching operation is completed, the tungsten wire mesh cloth is taken out, is first washed with deionized water for 3-5 minutes, is then washed with ethanol for 2-3 minutes, and is then dried in an oven at 50-70 DEG C for 10-20 minutes, so that the tungsten wires are obtained.

[0036] In a preferred embodiment, the etching process in step S3 is performed under stirring, so that the etching liquid uniformly contacts the surface of the tungsten wires and the uniformity of etching is ensured.

[0037] In the etching process, the etching solution is placed in a container, the bottom of the container is provided with a stirring device, the stirring speed of the stirring paddle of the stirring device is 100-200 revolutions per minute, the tungsten wire mesh cloth is clamped by a clamp which does not chemically react with the etching solution and is immersed below the liquid level of the etching solution, and the tungsten wire mesh cloth is arranged above the stirring paddle, which ensures that the etching solution uniformly contacts the surface of each tungsten wire.

[0038] In the specific embodiment 1, the composition of the solution is KOH 5%, K3[Fe(CN)6] 3%, surfactant 0.1%, and the balance is deionized water in terms of mass percentage, the etching conditions are 30°C constant temperature for 10 minutes without stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20 μm, the wire diameter after etching is 10.32 μm, and the etching value is 0.88 μm.

[0039] In the specific embodiment 2, the composition of the solution is KOH 5%, K3[Fe(CN)6] 7%, surfactant 0.1%, and the balance is deionized water in terms of mass percentage, the etching conditions are 40°C constant temperature for 20 minutes without stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20 μm, the wire diameter after etching is 7.75 μm, and the etching value is 3.45 μm.

[0040] In the specific embodiment 3, the composition of the solution is KOH 20%, K3[Fe(CN)6] 10%, surfactant 0.1%, and the balance is deionized water in terms of mass percentage, the etching conditions are 50°C constant temperature for 30 minutes without stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20 μm, the wire diameter after etching is 5.84 μm, and the etching value is 5.36 μm.

[0041] In the specific embodiment 4, the composition of the solution is KOH 15%, K3[Fe(CN)6] 3%, surfactant 0.1%, and the balance is deionized water in terms of mass percentage, the etching conditions are 40°C constant temperature for 40 minutes without stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20 μm, the wire diameter after etching is 6.79 μm, and the etching value is 4.41 μm.

[0042] In the specific embodiment 5, the composition of the solution is KOH 15%, K3[Fe(CN)6] 7%, surfactant 0.1%, and the balance is deionized water in terms of mass percentage, the etching conditions are 20°C constant temperature for 15 minutes without stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20 μm, the wire diameter after etching is 7.04 μm, and the etching value is 4.16 μm.

[0043] Specific embodiment 6, the composition of the liquid is made according to the mass percentage of KOH 10%, K3[Fe(CN)6]10%, surfactant 0.1%, the balance is deionized water, the etching conditions are 30℃ constant temperature for 20 minutes, no stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20μm, the wire diameter after etching is 7.85μm, and the etching value is 3.35μm.

[0044] Specific embodiment 7, the composition of the liquid is made according to the mass percentage of KOH 20%, K3[Fe(CN)6]3%, surfactant 0.1%, the balance is deionized water, the etching conditions are 50℃ constant temperature for 20 minutes, no stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20μm, the wire diameter after etching is 8.86μm, and the etching value is 2.34μm.

[0045] Specific embodiment 8, the composition of the liquid is made according to the mass percentage of KOH 20%, K3[Fe(CN)6]7%, surfactant 0.1%, the balance is deionized water, the etching conditions are 30℃ constant temperature for 30 minutes, no stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20μm, the wire diameter after etching is 8.00μm, and the etching value is 3.20μm.

[0046] Specific embodiment 9, the composition of the liquid is made according to the mass percentage of KOH 20%, K3[Fe(CN)6]10%, surfactant 0.1%, the balance is deionized water, the etching conditions are 40℃ constant temperature for 10 minutes, no stirring, the wire diameter of the tungsten wire mesh cloth before etching is 11.20μm, the wire diameter after etching is 6.96μm, and the etching value is 4.24μm.

[0047] The experimental data of specific embodiment 1 to specific embodiment 9 are as follows:

[0048] Serial No. Before Etching - Line Width / μm After Etching - Line Width / μm Etching Value / μm Example 1 11.20 10.32 0.88 Example 2 11.20 7.75 3.45 Example 3 11.20 5.84 5.36 Example 4 11.20 6.79 4.41 Example 5 11.20 7.04 4.16 Example 6 11.20 7.85 3.35 Example 7 11.20 8.86 2.34 Example 8 11.20 8.00 3.20 Example 9 11.20 6.96 4.24

[0049] The above experiments prove that the etching liquid with potassium ferricyanide and potassium hydroxide as main components can effectively etch the tungsten wire mesh cloth with a small amount of reagent, successfully achieve the purpose of reducing the diameter, and more accurately match the production process requirements of solar photovoltaic cells, thereby effectively improving the photoelectric conversion efficiency of solar photovoltaic cells.

[0050] The beneficial effects are as follows: it gives a potassium ferricyanide-potassium hydroxide synergistic oxidation system, realizes rapid and uniform etching; the etching solution in the alkaline environment is more uniform in dissolving metal, avoiding local over-etching or material damage that may be caused by traditional acid etching; it is simple to operate, and the process parameters are controllable, and is suitable for industrial production; the etching solution itself and the etching process have little harm to human body, thereby making the entire reducing process environmentally friendly and safe, and the wastewater treatment difficulty is low.

[0051] It is apparent to those skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0052] Furthermore, it should be understood that although the present specification is described in terms of embodiments, not every embodiment according to the present specification need necessarily contain every feature described. The description herein is intended for purposes of illustration only and is not necessary limiting. Those skilled in the art will readily recognize a variety of non- limiting embodiments contemplated that can be made by applying the teachings of the present specification in a non- limiting manner, with only minimal experimentation required to generate other desirable structures, systems, and procedures similar to those described herein. Accordingly, all such changes come within the intent and scope of the present application as defined by the following claims.

Claims

1. A method for reducing the diameter of tungsten wires in a tungsten wire mesh, characterized in that: It uses a mixed solution containing potassium ferricyanide, potassium hydroxide, and deionized water as an etching solution to reduce the diameter of tungsten wire. The mass percentage of potassium ferricyanide in the etching solution is 5%-20%, and the mass percentage of potassium hydroxide is 3%-10%.

2. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 1, characterized in that: Before the tungsten wires in the tungsten wire mesh are reduced in diameter, the tungsten wire mesh is subjected to ultrasonic cleaning with acetone, soaking in dilute hydrochloric acid to remove oxidation, and then washing and drying with water.

3. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 2, characterized in that: During the diameter reduction operation, the tungsten wire mesh to be treated is completely immersed in the etching solution and etched for 5-40 minutes at a temperature of 30℃-50℃.

4. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 3, characterized in that: After the etching process is completed, remove the tungsten wire mesh, rinse it with deionized water for 3-5 minutes, clean it with ethanol for 2-3 minutes, and then dry it in an oven at 50℃-70℃ for 10-20 minutes to obtain a smooth tungsten wire.

5. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 1, characterized in that: The etching solution also includes a surfactant composition. After the potassium ferricyanide and potassium hydroxide in the etching solution are prepared, some deionized water is added first, followed by 0.1%-1% by mass of the surfactant composition. The surfactant composition is a mixture of nonionic surfactant and a small amount of anionic surfactant. Then, the remaining mass of deionized water is added to make the total mass of the etching solution reach 100% of the set mass. Then, the surfactant is evenly dispersed in the etching solution by stirring.

6. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 5, characterized in that: The anionic surfactant accounts for no more than 10% of the mass of the surfactant composition.

7. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 5, characterized in that: When adding surfactant compositions, nonionic surfactants and anionic surfactants are added independently, or a mixture of both is added.

8. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 5, characterized in that: The stirring speed during etching solution mixing is 200-300 rpm, and the stirring time is 5-20 minutes.

9. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 5, characterized in that: After adding the surfactant, the pH value of the etching solution obtained by stirring is controlled between 10 and 13.

10. The method for reducing the diameter of tungsten wires in a tungsten wire mesh according to claim 3, characterized in that: The etching process is carried out under stirring conditions.