Printing screen pattern structure of photovoltaic cell and preparation method of printing screen pattern structure

Abstract

The invention discloses a printing screen graph structure of a photovoltaic cell and a preparation method, and relates to the technical field of cell manufacturing, the printing screen graph structure comprises a positive electrode main grid screen and a positive electrode auxiliary grid screen, the positive electrode auxiliary grid screen is a four-path positive electrode auxiliary grid screen graph, the positive electrode main grid screen is a three-path positive electrode main grid screen graph, and the positive electrode auxiliary grid screen is a three-path positive electrode main grid screen graph. The four positive electrode auxiliary grid screen plate patterns comprise a plurality of parallel transverse grid line patterns of non-edge and non-chamfering areas, chamfering position grid lines, edge vertical grid lines and chamfering inclined grid lines are all transferred to the positive electrode main grid screen plate through the positive electrode auxiliary grid screen plate, and the positive electrode main grid screen plate and the positive electrode auxiliary grid screen plate are each composed of gauze, a screen frame and photo-sensitive glue. According to the invention, the chamfering position grid lines, the edge vertical grid lines and the chamfering inclined grid lines of the four positive electrode and auxiliary grid screen patterns are all transferred to the positive electrode main grid screen, so that the auxiliary grid printing steps and difficulty are reduced, the problems of low product quality and low service life of the screen due to poor printing are solved, the silver paste consumption of the auxiliary grid is reduced, and the production cost is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery manufacturing, and particularly relates to a printing screen pattern structure of a photovoltaic cell and a preparation method. BACKGROUND

[0002] In the field of photovoltaic cell manufacturing, a screen printing process is a core process for forming electrode structures such as positive main electrodes, positive fine electrodes, back main electrodes and back fine electrodes of a cell sheet. The principle is to use the characteristics that a screen pattern part of a screen hole is transparent to paste and a non-pattern part of the screen hole is not transparent to paste. The above-mentioned electrodes can effectively collect and lead out the current generated by the photovoltaic cell, and are of great significance to improve the photoelectric conversion efficiency and performance of the photovoltaic cell.

[0003] With the development of photovoltaic cell technology towards high photoelectric conversion efficiency, the industry has put forward the requirement of 'high height and narrow width' for the design of the grid lines, so as to reduce the light blocking loss and reduce the series resistance. However, this requirement also brings higher challenges to the screen printing process, and problems such as uneven grid line width and height and large morphology difference at different positions are prone to occur, which seriously affects the performance consistency of the cell.

[0004] Especially in the production of N-type TOPCON products, the difficulty of printing precision control is further increased. In order to improve the screen life, the screen manufacturer increases U-shaped adhesive tape at the edge positions of the printing lower knife position and the knife collecting position. The film thickness at the edge and chamfer positions of the screen lower knife position and the knife collecting position is indirectly increased while the screen life is improved. When the printing head starts printing from the lower knife position, the film thickness is thickened after the screen increases the U-shaped adhesive tape, which causes the morphology height at the edge position and the chamfer position to be significantly higher than that at other positions, so that the grid lines at the edge and chamfer positions are worn and fallen off during the cell sheet collecting, carrying and storing processes, and other serious product quality problems occur.

[0005] From the existing screen pattern design, photovoltaic cell printing includes a conventional positive electrode auxiliary grid screen 10 and a conventional positive electrode main grid screen 20 (as shown in FIGS. 1 and 2). Figure 1 and Figure 2 The horizontal grid lines, the edge vertical grid lines and the chamfer inclined grid lines of the conventional positive electrode auxiliary grid screen 10 are integrated on the same screen pattern. The conventional positive electrode main grid screen 20 only includes a main grid basic structure. Under this design, the conventional positive electrode auxiliary grid screen 10 needs to simultaneously undertake the fine printing in the non-edge area and the high-difficulty printing in the edge and chamfer areas. The film thickness unevenness caused by the superposition of the U-shaped adhesive tape further aggravates the auxiliary grid printing failure. In order to solve such failure, the printing parameters need to be frequently adjusted, the doctor blade needs to be replaced or the screen needs to be replaced in the production site. This not only increases the production process complexity and cost, but also greatly reduces the screen life.

[0006] Based on this, the present application provides a printing screen pattern structure of a photovoltaic cell and a preparation method, which can eliminate the disadvantages of the prior art. SUMMARY

[0007] The present application aims to provide a printing screen pattern structure of a photovoltaic cell and a preparation method to solve the problems of uneven film thickness at the edge, poor printing and short screen life caused by U-shaped adhesive tape in the background art.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0009] A printing screen pattern structure of a photovoltaic cell, comprising a positive main grid screen and a positive auxiliary grid screen, the positive auxiliary grid screen is four positive auxiliary grid screen patterns, the positive main grid screen is three positive main grid screen patterns, the four positive auxiliary grid screen patterns comprise a plurality of mutually parallel horizontal grid line patterns in non-edge and non-chamfered area, the positive auxiliary grid screen shifts the chamfered position grid line, the edge vertical grid line and the chamfered inclined grid line of the conventional positive auxiliary grid screen to the positive main grid screen, the three positive main grid screen patterns integrate the main grid pattern of the conventional positive main grid screen and the shifted chamfered position grid line, edge vertical grid line and chamfered inclined grid line, and the positive main grid screen and the positive auxiliary grid screen are both composed of screen gauze, screen frame and photosensitive adhesive.

[0010] Preferably, the screen gauze of the positive main grid screen and the positive auxiliary grid screen both adopts stainless steel screen gauze, and the screen gauze tension of the stainless steel screen gauze is not less than 35N / cm, the screen gauze mesh number of the positive main grid screen is 400-500 mesh, and the screen gauze wire diameter needs to meet the opening rate of 30-40%, and the screen gauze mesh number of the positive auxiliary grid screen is 500-600 mesh.

[0011] Preferably, the screen frame of the positive main grid screen and the positive auxiliary grid screen both adopts aluminum alloy material.

[0012] Preferably, the edge of the positive main grid screen and the positive auxiliary grid screen both reserves a 5-10mm non-pattern area.

[0013] A preparation method of a printing screen pattern structure of a photovoltaic cell, specifically comprising the following steps:

[0014] S1, selecting a screen frame of aluminum alloy material, polishing the surface of the screen frame to remove the oxide layer, then wiping with a cleaning agent to remove oil stains, and then detecting the flatness of the screen frame to ensure that the error is ≤0.1mm / m;

[0015] S2, selecting corresponding mesh number of stainless steel screen gauze for preparing the positive main grid screen and the positive auxiliary grid screen, respectively, fixing the two kinds of screen gauze on the screen stretching equipment, uniformly stretching in the horizontal and vertical directions after pressure maintaining for 10-15 minutes, and then making the screen gauze and the screen frame fit together, coating polyurethane screen adhesive at the contact part of the screen frame and the screen gauze, and heating and curing at a temperature of 60-80℃ for 2-4 hours;

[0016] S3, defatting the screen gauze by using a defatting agent, and then rinsing the screen gauze with pure water, and drying the rinsed screen gauze in an oven at a temperature of 50-60°C for 30 minutes;

[0017] S4, coating the two sides of the two kinds of screen gauze with oil-based photosensitive glue by using an automatic glue coating machine, and drying the screen after coating in a clean environment at a humidity of 40-60% and a temperature of 20-25°C for 30-60 minutes;

[0018] S5, preparing a film containing three positive main grid screen pattern and a film containing four positive auxiliary grid screen pattern, and aligning the two films with the corresponding screen, wherein the two sides of the screen gauze include a printing surface and a non-printing surface, the light transmission area of the film corresponds to the pattern mesh of the printing surface of the screen, and the light shielding area of the film corresponds to the non-printing surface of the screen, and then exposing the screen by using an ultraviolet exposure machine after alignment;

[0019] S6, immersing the exposed screen in a developing solution, dissolving the oil-based photosensitive glue on the surface of the screen which is not exposed, rinsing the developed screen with pure water to remove residual developing solution, and drying the screen at a temperature of 50°C for 30 minutes;

[0020] S7, checking the screen pattern by using a microscope, repairing the screen by using a repair glue if the screen pattern is not qualified, and performing secondary exposure by using an ultraviolet exposure machine if the screen pattern is qualified to enhance the curing degree of the photosensitive glue, coating a hardening agent on the non-printing surface of the screen after exposure, and curing the screen at a temperature of 60-70°C for 1-2 hours to complete the preparation.

[0021] Preferably, the wavelength of the ultraviolet exposure machine is 350-450 nm, the exposure energy of the ultraviolet exposure machine in step S5 is 80-150 mJ / cm 2 , and the exposure energy of the ultraviolet exposure machine in step S7 is 200-300 mJ / cm 2 .

[0022] Preferably, the coating thickness of the polyurethane adhesive in step S2 is 0.1-0.2 mm.

[0023] Preferably, the coating thickness of the oil-based photosensitive glue on the non-printing surface of the screen is greater than that on the printing surface in step S4, the printing surface is the surface of the screen gauze in contact with the silicon wafer, and the non-printing surface is the surface of the screen gauze in contact with the scraper.

[0024] Preferably, the defatting agent in step S3 is an alkaline solution, and the developing solution in step S6 is a sodium carbonate solution with a concentration of 1-3%.

[0025] Preferably, the qualification standard for the screen printing pattern in step S7 is: the screen printing pattern does not have broken lines, pinholes, or rough edges, and the line width error of the screen printing pattern is within ±3μm.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention provides a printing screen pattern structure and preparation method for photovoltaic cells. By transferring the chamfered grid lines, edge vertical grid lines, and chamfered oblique grid lines of the four positive electrode sub-grid screen pattern to the positive electrode main grid screen, the printing steps and difficulty of the sub-grids are reduced. The grid line requirements at different positions of the cell are separated, effectively controlling and reducing the printing height of the edge and chamfered grid lines. This reduces the problems of poor printing leading to low product quality and screen life, and helps to improve production efficiency and product consistency. Furthermore, in photovoltaic cell production, the cost of silver paste is relatively high. By transferring some of the sub-grid lines to the main grid, the amount of silver paste used for the sub-grids can be reduced to a certain extent, thus lowering production costs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a conventional positive electrode subgrid in the prior art.

[0029] Figure 2 This is a schematic diagram of the structure of a conventional positive electrode main grid in the prior art.

[0030] Figure 3 This is a schematic diagram of the positive electrode main grid of the present invention.

[0031] Figure 4 This is a schematic diagram of the positive electrode sub-grid plate of the present invention.

[0032] Figure 5 This is a schematic diagram of the preparation method of the present invention.

[0033] Figure labeling: Conventional positive electrode sub-grid version 10, conventional positive electrode main grid version 20, positive electrode main grid version 30, positive electrode sub-grid version 40. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] In this embodiment, as Figure 3 and Figure 4As shown, a printing screen pattern structure for a photovoltaic cell includes a positive electrode main grid screen 30 and a positive electrode sub-grid screen 40. The positive electrode sub-grid screen 40 has four positive electrode sub-grid patterns, and the positive electrode main grid screen 30 has three positive electrode main grid patterns. The four positive electrode sub-grid patterns include multiple parallel horizontal grid lines in non-edge, non-beveled areas. The pattern of the positive electrode sub-grid screen 40 only contains multiple parallel horizontal fine grid lines. The positive electrode sub-grid screen 40 transfers the beveled grid lines, edge vertical grid lines, and beveled oblique grid lines of the conventional positive electrode sub-grid screen 10 to the positive electrode main grid. On screen 30, transfer refers to the replanning and allocation of electrode patterns during the screen graphic design stage, rather than moving the already formed physical grid lines or paste. The three positive main grid screen graphic integrates the main grid graphic of the conventional positive main grid screen 20 as well as the transferred chamfered grid lines, edge vertical grid lines, and chamfered oblique grid lines. The graphic of the positive main grid screen 30 includes multiple main grid lines as well as vertical grid line arrays and chamfered oblique grid line arrays located on both sides of the main grid lines and connected to the horizontal fine grid lines. Both the positive main grid screen 30 and the positive sub-grid screen 40 are composed of mesh, frame and photosensitive emulsion.

[0036] Specifically, such as Figure 1 and Figure 2 As shown, in conventionally designed screen printing patterns, the vertical and diagonal grid lines at the edges and chamfers of the battery cell, together with the internal horizontal fine grid lines, constitute a complete and concentrated sub-grid pattern. In this invention, the graphic data of the edge vertical grid lines and chamfered diagonal grid lines that originally belonged to the sub-grid pattern are separated and integrated into the graphic data file of the main grid. The film of the main grid screen is made using the new main grid graphic data, and the film of the sub-grid screen is made using the sub-grid graphic data that has been reduced to only horizontal fine grid lines. The simplified sub-grid screen pattern only has regularly arranged horizontal fine grid lines, and the graphic distribution is uniform, without dense edge and chamfer graphics. When coating the photosensitive emulsion, the emulsion flows more uniformly, making it easier to form an emulsion film of uniform thickness. This makes the squeegee pressure transmission and the rheological behavior of the paste more consistent across the entire screen during printing, fundamentally ensuring the uniformity of the film thickness.

[0037] Specifically, photosensitive emulsions are divided into water-based photosensitive emulsions and oil-based photosensitive emulsions. The photosensitive emulsion can be adjusted according to the needs. This method uses oil-based photosensitive emulsions. The oil-based photosensitive emulsion forms the non-printing area, and the mesh openings of the screen not covered by the oil-based photosensitive emulsion form the printed pattern area. During printing, the screen and the silicon wafer surface maintain a small gap or light contact. The paste is poured onto the screen, and pressure is applied and moved along the screen surface by a squeegee, forcing the paste to pass through the mesh openings of the cutout area and adhere to the silicon wafer surface, thereby forming a printed layer consistent with the screen pattern.

[0038] Among them, such as Figure 3As shown, the mesh of both the positive electrode main grid plate 30 and the positive electrode sub-grid plate 40 is made of stainless steel mesh, and the mesh tension of the stainless steel mesh is not less than 35 N / cm. The mesh count of the positive electrode main grid plate 30 is 400-500 mesh, and the mesh wire diameter needs to meet the opening rate of 30-40%. The mesh count of the positive electrode sub-grid plate 40 is 500-600 mesh. The frames of both the positive electrode main grid plate 30 and the positive electrode sub-grid plate 40 are made of aluminum alloy.

[0039] Specifically, the screen pattern must be consistent with the electrode design of the solar cell to ensure that the electrodes can efficiently collect photogenerated carriers after printing. The screen parameters include mesh count, wire diameter, and aperture ratio. The mesh count determines the mesh size; a higher mesh count results in smaller meshes, suitable for fine-line printing. The wire diameter affects mesh strength; wires that are too thin are prone to breakage, while those that are too thick reduce the aperture ratio. The aperture ratio directly affects the amount of ink that passes through. The aperture ratio formula is:

[0040] Among them, such as Figure 3 As shown, a 5-10mm unpatterned area is reserved at the edges of both the positive main grid screen 30 and the positive sub-grid screen 40 to prevent ink overflow and contamination of the silicon wafer edges during printing. The edges of the screen pattern must be smooth to avoid wear on the squeegee. High-tension screens can reduce squeegee pressure and reduce silicon wafer damage.

[0041] Specifically, existing technologies, in order to improve the lifespan of the positive electrode sub-grid screen, add U-shaped tape to the screen's lower and upper cutting positions, thereby increasing the screen film thickness and causing quality problems such as printing defects. On-site, these issues are addressed by replacing the squeegee, adjusting printing parameters, and replacing the screen, which in turn reduces the screen's lifespan. To improve these problems, the chamfered grid lines of the four positive electrode sub-grid screen pattern are transferred to the three positive electrode main grid screen pattern for printing. This eliminates the need for wire pulling and laser opening during screen making, reducing screen production damage and improving the printing defects of the four positive electrode sub-grid screen pattern. This facilitates extending the lifespan of the printing screen. By transferring the edges and chamfered positions of the four positive electrode sub-grid screen pattern to the three positive electrode main grid screen pattern, the printing defects of the positive electrode sub-grid are improved, thus enhancing the quality of the solar cell products.

[0042] In this embodiment, wherein, as Figure 5 As shown, a method for preparing a printing screen pattern structure for a photovoltaic cell specifically includes the following steps:

[0043] Specifically, before starting step S1, the raw materials are prepared: the frame is usually made of high-strength aluminum alloy material such as 6061-T6 with lightweight and low deformation characteristics. The specific size needs to be adjusted according to the specifications of the battery cells. The mesh is made of stainless steel mesh that meets the requirements of tension ≥30N / cm and has low elongation. The mesh parameters (mesh count, wire diameter) need to be selected according to the specific printing precision. For example, 500-600 mesh is used for fine grid screen and 400-500 mesh is used for main grid screen. The oil-based photosensitive emulsion is an organic solvent that is compatible with the printing paste and has high wear resistance. It also includes auxiliary materials such as adhesive for fixing the mesh and the frame, degreasing agent for removing oil stains from the mesh, and developing solution for dissolving unexposed photosensitive emulsion.

[0044] S1. Select an aluminum alloy mesh frame, use sandpaper to sand away the oxide layer on the surface of the mesh frame, then wipe away the oil stains with a cleaning agent, and then check the flatness of the mesh frame to ensure that the error is ≤0.1mm / m, so as to avoid uneven tension of the mesh yarn due to deformation of the mesh frame;

[0045] S2. Select stainless steel mesh of corresponding mesh count to prepare the positive electrode main grid screen 30 and the positive electrode sub-grid screen 40. Fix the two types of mesh on the screen stretching equipment, hold pressure for 10-15 minutes to stabilize the tension, and stretch them evenly in the horizontal and vertical directions with a tension of 35-40 N / cm. High tension can reduce the stretching deformation of the screen during printing, ensure the pattern accuracy, and avoid affecting the consistency of the battery cell efficiency. After stretching, make the mesh adhere to the screen frame. Apply polyurethane adhesive to the contact area between the screen frame and the mesh. The coating thickness of the polyurethane adhesive is 0.1-0.2 mm, and heat and cure at a temperature of 60-80℃ for 2-4 hours to ensure the bonding strength is ≥5 N / cm.

[0046] S3. Use a degreasing agent to degrease the mesh. Degreasing can be achieved by soaking or spraying the mesh surface. The degreasing agent is an alkaline solution that can remove impurities such as grease and dust, and prevent poor adhesion of oily photosensitive adhesive. Then rinse the mesh with pure water and put the rinsed mesh into an oven to dry at a temperature of 50-60℃ for 30 minutes to ensure that the mesh surface is completely dry.

[0047] S4. Use an automatic gluing machine to coat both sides of the two types of mesh with oil-based photosensitive adhesive. After coating, place the screen in a clean environment and dry it for 30-60 minutes at 40-60% humidity and 20-25℃.

[0048] Specifically, the thickness of the oil-based photosensitive emulsion coating on the non-printing side of the screen is greater than that on the printing side. The printing side is the side of the screen that contacts the silicon wafer, while the non-printing side is the side of the screen that contacts the squeegee. The coating thickness on the printing side needs to be adjusted according to the required paste thickness. A slightly thicker coating on the non-printing side can enhance the screen's abrasion resistance. After coating, the screen should be dried in a clean environment to avoid bubbles or cracks in the photosensitive emulsion. The total screen thickness is the sum of the screen thickness and the photosensitive emulsion coating thickness. The total screen thickness determines the printing paste thickness, which is approximately 0.8 times the screen thickness. The mesh size is 3 times the paste particle diameter to avoid clogging the mesh.

[0049] S5. Prepare films containing three positive main grid screen patterns and four positive secondary grid screen patterns. Each film includes electrode patterns. Align the two types of films with their corresponding screens, adding alignment marks along the edges of the printed patterns to ensure an alignment error ≤5μm. The screens have two sides: a printed side and a non-printed side. The light-transmitting areas of the film correspond to the mesh openings on the printed side of the screen, and the light-blocking areas correspond to the non-printed sides of the screen. After alignment, expose the film using a UV exposure machine with a wavelength of 350–450nm and an exposure energy of 80–150mJ / cm². 2 The exposure energy can be adjusted according to the type of photosensitive emulsion. The photosensitive emulsion undergoes a cross-linking reaction and cures after being exposed to light.

[0050] S6. Immerse the exposed screen in the developer solution, which is a sodium carbonate solution with a concentration of 1-3%. The unexposed oil-based photosensitive emulsion on the screen surface is dissolved, exposing the mesh openings and forming a pattern consistent with the film. After development, rinse with pure water to remove residual developer solution and dry at 50°C for 30 minutes.

[0051] S7. Inspect the screen printing pattern under a microscope at 50-100x magnification to ensure it meets the requirements. The acceptable standards are: no broken lines, pinholes, or burrs; and the line width error must be within ±3μm. If the pattern fails to meet the requirements, repair it with adhesive. Severely damaged patterns must be scrapped. If the pattern passes the inspection, perform a second exposure using a UV exposure machine. The wavelength of the UV exposure machine should be 350-450nm, and the exposure energy should be 200-300mJ / cm². 2 To enhance the curing degree of the photosensitive emulsion and improve its wear resistance, a hardener is coated on the non-printing surface of the screen after exposure, and cured at a temperature of 60-70℃ for 1-2 hours to improve the screen's resistance to squeegee wear, thus completing the preparation.

[0052] In summary, this invention achieves functional separation between the sub-grid and main grids by transferring the edge vertical grid lines and chamfered oblique grid lines, traditionally integrated into the four positive electrode sub-grid patterns, to the three positive electrode main grid patterns. This simplifies the sub-grid printing process and indirectly solves the need for applying "U-shaped tape" to reinforce fragile edges, avoiding uneven film thickness caused by the tape. It also avoids losses caused by adjusting parameters and frequently changing the screen, reducing overall production costs and demonstrating good industrial application value and market prospects.

[0053] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A printing screen pattern structure for photovoltaic cells, characterized in that, The device includes a positive main grid pattern (30) and a positive sub-grid pattern (40). The positive sub-grid pattern (40) has four positive sub-grid patterns, and the positive main grid pattern (30) has three positive main grid patterns. The four positive sub-grid patterns include multiple parallel horizontal grid lines in non-edge and non-beveled areas. The positive sub-grid pattern (40) transfers the beveled grid lines, edge vertical grid lines, and beveled oblique grid lines of the conventional positive sub-grid pattern (10) to the positive main grid pattern (30). The three positive main grid patterns integrate the main grid pattern of the conventional positive main grid pattern (20) and the transferred beveled grid lines, edge vertical grid lines, and beveled oblique grid lines. Both the positive main grid pattern (30) and the positive sub-grid pattern (40) are composed of mesh, frame, and photosensitive emulsion.

2. The printing screen graphic structure according to claim 1, characterized in that, The mesh of both the positive electrode main grid (30) and the positive electrode sub-grid (40) is made of stainless steel mesh, and the mesh tension of the stainless steel mesh is not less than 35 N / cm. The mesh count of the positive electrode main grid (30) is 400 to 500 mesh, and the mesh wire diameter needs to meet the opening rate of 30 to 40%. The mesh count of the positive electrode sub-grid (40) is 500 to 600 mesh.

3. The printing screen graphic structure according to claim 1, characterized in that, The frames of both the positive main grid (30) and the positive sub-grid (40) are made of aluminum alloy.

4. The printing screen graphic structure according to claim 1, characterized in that, Both the positive electrode main grid plate (30) and the positive electrode sub-grid plate (40) have a 5-10 mm unpatterned area reserved at their edges.

5. A method for preparing a printing screen pattern structure for a photovoltaic cell according to any one of claims 1-4, characterized in that, Specifically, the following steps are included: S1. Select an aluminum alloy mesh frame, use sandpaper to sand away the oxide layer on the surface of the mesh frame, then wipe away the oil stains with a cleaning agent, and then test the flatness of the mesh frame to ensure that the error is ≤0.1mm / m; S2. Select stainless steel mesh with corresponding mesh count to prepare the positive electrode main grid mesh (30) and the positive electrode sub-grid mesh (40). Fix the two meshes on the mesh pulling device respectively. After holding the pressure for 10 to 15 minutes, stretch them evenly in the transverse and longitudinal directions with a tension of 35 to 40 N / cm. After stretching, make the mesh adhere to the mesh frame. Apply polyurethane adhesive to the contact area between the mesh frame and the mesh, and heat and cure at 60 to 80°C for 2 to 4 hours. S3. Use a degreasing agent to degrease the mesh, then rinse the mesh with pure water, and put the rinsed mesh into an oven to dry at 50-60℃ for 30 minutes. S4. Use an automatic gluing machine to coat both sides of the two types of mesh with oil-based photosensitive adhesive. After coating, place the screen in a clean environment and dry it for 30-60 minutes at 40-60% humidity and 20-25℃. S5. Prepare a film containing three positive main grid screen patterns and a film containing four positive secondary grid screen patterns. Align the two types of films with the corresponding screens respectively. The two sides of the screen include the printing side and the non-printing side. The light-transmitting area of ​​the film corresponds to the pattern mesh of the printing side of the screen, and the light-blocking area of ​​the film corresponds to the non-printing side of the screen. After alignment, perform an exposure operation using an ultraviolet exposure machine. S6. Immerse the exposed screen in the developer solution. The unexposed oily photosensitive emulsion on the screen surface is dissolved. After development, rinse with pure water to remove residual developer solution and dry at 50°C for 30 minutes. S7. Use a microscope to check if the screen pattern is qualified. If it is not qualified, repair it with repair glue. If it is qualified, use a UV exposure machine for secondary exposure to enhance the curing degree of the photosensitive emulsion. After exposure, apply a hardener to the non-printing side of the screen and cure it at a temperature of 60-70℃ for 1-2 hours to complete the preparation.

6. The preparation method according to claim 5, characterized in that, The wavelength of the ultraviolet exploratory machine is 350–450 nm, and the exposure energy of the ultraviolet exploratory machine in step S5 is 80–150 mJ / cm². 2 In step S7, the exposure energy of the ultraviolet exploratory machine is 200–300 mJ / cm². 2 .

7. The preparation method according to claim 5, characterized in that, The coating thickness of the polyurethane adhesive in step S2 is 0.1 to 0.2 mm.

8. The preparation method according to claim 5, characterized in that, In step S4, the thickness of the oil-based photoresist coating on the non-printing side of the screen is greater than the thickness of the oil-based photoresist coating on the printing side. The printing side is the side of the screen that contacts the silicon wafer, and the non-printing side is the side of the screen that contacts the squeegee.

9. The preparation method according to claim 5, characterized in that, The degreasing agent in step S3 is an alkaline solution, and the developing solution in step S6 is a sodium carbonate solution with a concentration of 1-3%.

10. The preparation method according to claim 5, characterized in that, The qualification standard for the screen printing pattern in step S7 is that the screen printing pattern does not have broken lines, pinholes, or rough edges, and the line width error of the screen printing pattern is within ±3μm.

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