A method for locally etching a metal and a printing screen for photovoltaic cells

Abstract

The application relates to the technical field of metal mesh etching, in particular to a metal local etching method and a printing screen for photovoltaic cells, and the method comprises the following steps: performing degreasing, washing and drying treatment on a metal mesh to be etched; coating photoresist on the surface of the metal mesh, and pre-baking the metal mesh after coating; aligning a mask with the metal mesh, cross-linking and solidifying the photoresist in the exposed area through an exposure operation to form a protective layer; removing the photoresist in the unexposed area by using an alkaline developing solution; etching the surface of the metal mesh, taking out the metal mesh after the metal of the metal mesh reaches a target line diameter, and performing etching post-treatment; heating the metal mesh, forming a micro gap between the photoresist and the surface of the metal mesh, stripping the photoresist, and cleaning to obtain a local etching metal mesh. The method can control line diameter error and improve pattern precision through the slit coating and visual positioning exposure process, and can meet the production requirements of most fine grid lines.

Description

Technical Field

[0001] This invention relates to the field of metal mesh etching technology, and in particular to a method for partial metal etching and a printing screen for photovoltaic cells comprising a partially etched metal mesh obtained by applying the method. Background Technology

[0002] The metal mesh etching industry is currently developing rapidly with the upgrading of downstream high-end manufacturing demands. In the photovoltaic field, driven by new battery technologies such as HJT and TOPCon, the precision requirements for metal wire diameter have dropped from the traditional 11-13μm to below 8μm. In 2024, the global market size of high-precision metal mesh for photovoltaics reached 400 million yuan, with products with a wire diameter ≤10μm accounting for more than 58%. In terms of process, wet etching is still the mainstream (accounting for about 70%), but high-end photoresist and precision etching equipment still rely on imports, which poses supply chain risks.

[0003] Defects in existing technology:

[0004] 1. Protective materials have limited functionality and cannot simultaneously achieve both corrosion resistance and easy peeling: Existing protective materials are mainly divided into three categories. The first is unmodified polymer films (such as PI films and PEEK films). These materials have limited corrosion resistance and can be penetrated by corrosion liquid in 8wt% ferric chloride solution in just 15 minutes. Moreover, after corrosion, they require chemical solvents such as N-methylpyrrolidone for peeling, which easily leaves residues on the metal surface, leading to ink bleeding and incomplete printing during subsequent printing. The second is spray-coated emulsions (such as acrylic emulsions), which require laser cutting to expose the area to be etched. The process is cumbersome, and the edge accuracy of the cut pattern is low (error ≥ 0.8μm), which cannot meet the etching requirements of fine grid lines below 8μm. The third is adhesive protective films (such as PI films). Although they do not require spraying, they need to be pre-cut according to the pattern. They have poor flexibility when adapting to complex patterns, and the edges are prone to lifting after bonding, causing corrosion liquid to seep into the gaps and affecting the etching accuracy.

[0005] 2. Difficulty in coordinating etching precision and screen strength, resulting in poor compatibility: Existing processes are mostly "overall etching" or "single pattern protective etching". Excessive refinement of the line diameter (such as reducing it to 8μm) will lead to a decrease in screen strength of more than 30%, while the strength retention cannot meet the requirements of fine grid lines.

[0006] Therefore, there is an urgent need for a photoresist, a method for preparing the photoresist, a method for partial metal etching using the photoresist, and a printing screen for photovoltaic cells comprising a partially etched metal mesh obtained by the method for partial metal etching. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention provides a method for partial metal etching and a printing screen for photovoltaic cells comprising a partially etched metal mesh obtained by applying the method for partial metal etching.

[0008] In a first aspect, this application provides a method for localized etching of metal using photoresist, comprising:

[0009] Metal mesh pretreatment: The metal mesh to be etched is degreased, washed with water, and dried;

[0010] Photoresist coating: Photoresist is coated onto the surface of the metal mesh, and the metal mesh is pre-baked after coating;

[0011] Exposure: After aligning the mask with the metal mesh, the photoresist in the exposed area is cross-linked and cured through an exposure operation to form a protective layer;

[0012] Development: Use an alkaline developer to remove the photoresist from the unexposed areas;

[0013] Etching: The surface of the metal mesh is etched. After the metal in the metal mesh reaches the target wire diameter, the metal mesh is removed and post-etching processing is performed.

[0014] Photoresist stripping: The metal mesh is heated to create micro-gaps between the photoresist and the surface of the metal mesh. The photoresist is then stripped off and cleaned to obtain a partially etched metal mesh.

[0015] By adopting the above-mentioned approach, a new precision etching process based on the exposure and development of photosensitive materials is optimized, significantly different from existing non-photosensitive protective pattern preparation methods such as laser cutting and mechanical trimming. Based on the metal local etching method of this application, metal etching is completed with line diameter error controlled within ±0.3μm, and the pattern accuracy is improved by 40% compared to existing processes (±0.5μm), meeting the requirements for fabricating fine gate lines below 8μm.

[0016] In one specific implementation, the metal mesh can be made of stainless steel wire or tungsten wire, with an initial wire diameter of 11-13 μm and a mesh count of 300-700.

[0017] In one specific implementation, a slit coater is used to coat the photoresist, with the slit width adjusted to 50-100μm, the coating speed to 5-10mm / s, the vacuum adsorption pressure to -0.08MPa, and the coating thickness controlled to 10-15μm.

[0018] By adopting the above scheme, a slit coating machine is used to achieve photoresist coating, which can uniformly coat the photoresist onto the surface of the metal mesh.

[0019] In one specific implementation, the mask includes a protected area and an etched area, wherein the light transmittance of the protected area is ≤5%, the light transmittance of the etched area is ≥90%, and the edges of both the protected area and the etched area are provided with a gradient light-transmitting area with a width of not less than 5μm.

[0020] By adopting the above scheme, the mask design can achieve differentiated line diameter control, taking into account both the precision and strength of the local etched metal mesh, which can meet the needs of high-precision screen printing of new photovoltaic cells; in addition, a 5μm gradient light-transmitting zone is set at the edge of the area to be protected and the area to be etched to avoid overexposure that would cause the edge of the pattern to become blurred.

[0021] In one specific implementation method, an ultraviolet (UV) exposure machine is used for the exposure operation. The UV wavelength of the UV exposure machine is 365nm, the energy density is controlled at 300-500mJ / cm², and the exposure time is controlled at 20-30s.

[0022] Furthermore, before the exposure operation, the positioning holes on the metal mesh are identified by an industrial camera, and the mask position is adjusted to ensure that the positioning error is ≤0.3μm.

[0023] In one specific implementation, the alkaline developer is a 0.5wt% Na2CO3 solution, the temperature is 30°C, and the developing operation is spray developing for 30-60 seconds at a pressure of 0.1MPa.

[0024] In one specific implementation, the etching and post-etching process includes:

[0025] Immerse the developed metal mesh in the etching solution, stir at room temperature, and etch for 15-20 minutes;

[0026] The wire diameter of the metal in the metal mesh is monitored in real time. When the wire diameter in the area to be corroded reaches 8-9 μm, the metal mesh is removed.

[0027] Rinse with deionized water for at least 5 minutes to remove residual etching solution;

[0028] Dry in a hot air oven at 45-55℃ for at least 8 minutes to obtain a semi-finished metal mesh with a finer wire diameter.

[0029] In one specific implementation, the photosensitive adhesive peeling process includes:

[0030] Place the dried metal mesh semi-finished product into a constant temperature box, set the temperature to 50-60℃, and keep it at that temperature for at least 5 minutes.

[0031] Use a tool to clamp the photoresist at the edge of the metal mesh and slowly peel it off horizontally;

[0032] The metal mesh was wiped with a lint-free cloth dampened with a small amount of isopropyl alcohol to remove residual adhesive, resulting in the final partially etched metal mesh.

[0033] In one specific implementation, the photoresist used in the metal local etching method provided in this application, based on a total mass of 100%, comprises:

[0034] 88-92% of the substrate;

[0035] 5-7% of the primary functional modifier is used to form a protective film with the substrate;

[0036] 2.5-4% of a secondary functional modifier is used to assist in the stripping of photoresist;

[0037] 0.5-1% of additives;

[0038] The substrate includes epoxy acrylate adhesive.

[0039] Furthermore, the epoxy acrylate adhesive is selected from one or more of bisphenol A epoxy acrylate and phenolic epoxy acrylate; the parameters of the epoxy acrylate adhesive are: styrene content 18-22% by mass, acid value 15-20 mgKOH / g (test standard GB / T 2895-2008), viscosity (25℃, NDJ-1 type rotational viscometer) 8000-12000 mPa. s, solid content ≥98%, epoxy equivalent 200-300 g / eq.

[0040] By adopting the above solution, using epoxy acrylate adhesive as the substrate, the basic exposure and development performance of the photoresist can be guaranteed. After curing, the photoresist forms a continuous and dense protective film with a resolution of ≤2μm, which is suitable for fine grid line pattern requirements.

[0041] By adopting the above scheme, the photoresist is synergistically modified by the first functional modifier and the second functional modifier, achieving both enhanced corrosion resistance and temperature-controlled stripping. The photoresist of this application has significantly improved corrosion resistance compared to existing PI films. Furthermore, based on the second functional modifier, the photoresist stripping does not require chemical solvents, and the residual rate is ≤0.1%, avoiding damage to the steel wire surface.

[0042] In one specific implementation, the first functional modifier is Al2O3 nano-ceramic particles with a particle size of 30-50 nm.

[0043] By adopting the above scheme, Al2O3 nano-ceramic particles, as the first functional modifier, can form Al2O3 acrylate adhesive in combination with the substrate (epoxy acrylate adhesive). As a basic film-forming agent, it can ensure the basic exposure and development performance of the photoresist. After the photoresist is cured, it forms a continuous and dense protective film with a resolution of ≤2μm, which is suitable for fine grid line pattern requirements.

[0044] In one specific implementation, the second functional modifier is a polycaprolactone temperature-controlled peeling agent.

[0045] Furthermore, polycaprolactone temperature-controlled stripping agent, with a number-average molecular weight of 2000-4000 g / mol and a melting point of 50-60℃, is used to assist photoresist in rapid stripping under temperature-controlled conditions, reducing the residue rate.

[0046] By adopting the above scheme, polycaprolactone temperature-controlled release agent, as the second functional modifier, has good compatibility with the substrate at room temperature (25℃) and does not affect film formation; when the temperature is raised to 50-60℃, the molecular chain undergoes a phase change, and the polycaprolactone temperature-controlled release agent changes from solid to semi-liquid, thereby forming a tiny gap between the photoresist and the metal surface, making the photoresist easy to peel off, with a residual rate of ≤0.1% after manual peeling.

[0047] Furthermore, the above-mentioned photoresist is prepared as follows:

[0048] Based on the photoresist described above, weigh the substrate, first functional modifier, second functional modifier and additives according to the mass fraction, and disperse them in a high-speed disperser for 25-30 minutes. The speed of the high-speed disperser should not be less than 3000 r / min.

[0049] By adopting the above scheme, the photoresist prepared by the method of this application uses epoxy acrylate adhesive as the substrate, and is compounded with 5-7 wt% Al2O3 nano-ceramic particles and 2-4 wt% polycaprolactone temperature-controlled release agent. Among them, the Al2O3 nano-ceramic particles can form a reinforcing skeleton after the photoresist is cured, so that the photoresist can withstand the etching solution for ≥120 min, and the corrosion resistance is significantly improved compared with existing materials. The polycaprolactone temperature-controlled release agent can undergo a phase transition at 50-60℃, so that the photoresist and the steel wire surface form a micro gap, which can achieve manual peeling with a residue rate of ≤0.1%, without relying on chemical solvents.

[0050] Furthermore, the auxiliary agent is a photoinitiator, specifically 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0051] Secondly, this application also provides a printing screen for photovoltaic cells, comprising a partially etched metal mesh and a polyester mesh obtained by the aforementioned partial metal etching method, wherein the partially etched metal mesh and the polyester mesh are composite, and the tension of the screen is 10-25 N / cm.

[0052] By adopting the above scheme, the local etched metal mesh and polyester mesh are more tightly bonded, the bonding interface has better resistance to solvents, and the screen printing stencil is more stable and less prone to cracking during use.

[0053] In summary, this application has the following beneficial effects:

[0054] This application utilizes slit coating and visual positioning exposure processes to control the line diameter error within ±0.3μm, improving the pattern accuracy by 40% compared to existing processes (±0.5μm), thus meeting the fabrication requirements for fine gate lines below 8μm.

[0055] This application can achieve differentiated wire diameter control through mask design to meet the needs of different photovoltaic cells, taking into account both precision and strength, and filling the technological gap in the production of high-precision screen printing plates for new photovoltaic cells; for example, nickel screen is adapted to TOPCon cells, and steel wire screen is adapted to PERC cells.

[0056] Compared with the prior art, this application uses a bifunctional modified photoresist in the etching process. The photoresist is synergistically modified by Al2O3 nano-ceramic particles and polycaprolactone, which simultaneously achieves corrosion resistance enhancement and temperature-controlled self-peeling. The photoresist in this application has significantly improved corrosion resistance compared with existing PI films. Peeling does not require chemical solvents, and the residue rate is ≤0.1%, avoiding damage to the metal surface. Attached Figure Description

[0057] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a flowchart of a method for localized etching of metal provided in an embodiment of the present invention. Detailed Implementation

[0059] To further aid in understanding the technical solution of the present invention, several specific embodiments are provided to describe the technical solution of the present invention in more detail. All described embodiments are only some embodiments of the present invention, not all of them; embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The following embodiments are further illustrations of the present invention, but the present invention is not limited thereto.

[0060] like Figure 1 As shown, the present invention provides a method for local etching of metal, comprising:

[0061] S1. Metal mesh pretreatment: The metal mesh to be etched is degreased, washed with water and dried.

[0062] S2. Photoresist coating: Photoresist is coated onto the surface of the metal mesh, and the metal mesh is pre-baked after coating;

[0063] S3. Exposure: After aligning the mask with the metal mesh, the photoresist in the exposed area is cross-linked and cured through the exposure operation to form a protective layer;

[0064] S4. Development: Use alkaline developer to remove photoresist from unexposed areas;

[0065] S5. Etching: The surface of the metal mesh is etched. After the metal in the metal mesh reaches the target wire diameter, the metal mesh is removed and post-etching processing is performed.

[0066] S6. Photoresist stripping: The metal mesh is heated to create micro-gaps between the photoresist and the surface of the metal mesh. The photoresist is then stripped off and cleaned to obtain a partially etched metal mesh.

[0067] Furthermore, the metal mesh to be etched undergoes degreasing, washing, and drying processes, as follows:

[0068] Degreasing: After stretching the metal mesh to be etched, immerse it in a 3wt% Na2CO3 solution and clean it with ultrasonic cleaning at a constant temperature of 40℃ (frequency 40kHz) for at least 10 minutes to remove surface oil and oxide layer.

[0069] Wash with water: Rinse with deionized water for at least 3 minutes to remove residual degreasing agent;

[0070] Drying: Dry in a hot air oven at a temperature of not less than 50°C for at least 5 minutes to ensure that the surface of the metal mesh is dry (moisture content ≤0.5%), so as to avoid bubbles when coating photoresist later.

[0071] Example 1:

[0072] To prepare a bifunctional modified photoresist, the mass fractions of each component in this embodiment are as follows: 90% epoxy acrylate adhesive, 6% Al2O3 nano-ceramic particles, 3% polycaprolactone, and 1% photoinitiator. The above components are dispersed in a high-speed disperser for 30 minutes at a speed of 3000 r / min to obtain a uniform bifunctional modified photoresist.

[0073] The Al2O3 nanoceramic particles have a particle size of 40 nm, and the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0074] The epoxy acrylate adhesive is selected from bisphenol A epoxy acrylate, and the parameters of the epoxy acrylate are as follows: styrene content 18-22% by mass, acid value 15-20 mg KOH / g (test standard GB / T 2895-2008), viscosity (25℃, NDJ-1 type rotational viscometer) 8000-12000 mPa. s, solid content ≥98%, epoxy equivalent 200-300 g / eq;

[0075] The polycaprolactone is a polycaprolactone homopolymer with a number average molecular weight of 2000-3000 g / mol, a melting point of 58-60℃, a linear molecular structure, and an industrial-grade purity (≥99%).

[0076] Example 2:

[0077] The photoresist prepared in Example 1 was used for localized etching of metal.

[0078] In this embodiment, the metal mesh to be etched is an electroformed nickel mesh. The local etching process of the electroformed nickel mesh is as follows:

[0079] (1) Pre-treated electroformed nickel mesh (initial wire diameter of electroformed nickel mesh 11μm, mesh number 520 mesh), degreased by 3wt% Na2CO3 solution, ultrasonically cleaned, and dried at 50℃;

[0080] (2) Slit coating (width 80μm, speed 8mm / s) of dual-function modified photoresist, thickness 12μm;

[0081] (3) Use a mask (3% transmittance in the area to be protected and 95% transmittance in the area to be corroded), visual positioning error 0.2μm, and ultraviolet exposure (energy density 400mJ / cm², exposure time 25s).

[0082] (4) Develop with 0.5wt% Na2CO3 solution for 45s, then expose twice (energy density 250mJ / cm², exposure time 12s).

[0083] (5) Etch at room temperature for 18 minutes with etching solution to refine the wire diameter of electroformed nickel mesh to 8μm, then wash and dry.

[0084] (6) Keep warm at 55℃ for 5 minutes, peel off the photoresist by hand, and wipe away the residue with isopropyl alcohol.

[0085] Example 3:

[0086] Bifunctional modified photoresist was prepared. In this embodiment, the mass fractions of each component of the photoresist were as follows: 88.5% epoxy acrylate adhesive, 7% Al2O3 nano-ceramic particles, 4% polycaprolactone, and 0.5% photoinitiator. The above components were dispersed in a high-speed disperser for 25 minutes at a speed of 3000 r / min to obtain the bifunctional modified photoresist.

[0087] The Al2O3 nanoceramic particles have a particle size of 35 nm, and the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0088] The epoxy acrylate adhesive is selected from a mixture of bisphenol A epoxy acrylate and phenolic epoxy acrylate, with a mass ratio of bisphenol A epoxy acrylate to phenolic epoxy acrylate of 7:3. The parameters of the epoxy acrylate adhesive are: styrene content 18-22%, acid value 15-20 mg KOH / g (test standard GB / T 2895-2008), viscosity (25℃, NDJ-1 type rotational viscometer) 8000-12000 mPa. s, solid content ≥98%, epoxy equivalent 200-300 g / eq;

[0089] The polycaprolactone is a diol-modified polycaprolactone with a number average molecular weight of 3000-4000 g / mol, a melting point of 55-57℃, a diol-modified branched structure, industrial-grade purity (≥99%), and is a pale yellow transparent liquid that is completely miscible with an epoxy acrylate mixture (bisphenol A: phenolic resin = 7:3).

[0090] Example 4:

[0091] The photoresist prepared in Example 3 was used for localized etching of the metal.

[0092] In this embodiment, the metal mesh to be etched is a stainless steel wire mesh. The local etching process of the stainless steel wire mesh is as follows:

[0093] (1) Pre-treatment of 304 stainless steel wire mesh (the initial wire diameter of the stainless steel wire mesh is 12μm and the mesh count is 600 mesh), degreasing with 3wt% Na2CO3 solution, ultrasonic cleaning, and drying at 50℃;

[0094] (2) Slit coating (width 60μm, speed 6mm / s) of dual-function modified photoresist, thickness 10μm;

[0095] (3) A mask was used (5% transmittance in heavily doped regions and 92% transmittance in undoped regions), with a visual positioning error of 0.3 μm and ultraviolet exposure (energy density 350 mJ / cm², exposure time 22 s).

[0096] (4) Develop with 0.5wt% Na2CO3 solution for 50s, then expose a second time (energy 220mJ / cm², time 10s).

[0097] (5) Etch at room temperature for 16 minutes with etching solution to refine the wire diameter of stainless steel wire mesh to 7μm, then wash and dry.

[0098] (6) Keep warm at 58℃ for 5 minutes, peel off the photoresist by hand, and wipe away the residue with isopropyl alcohol.

[0099] Comparative Example 1:

[0100] The etching process of electroformed nickel mesh using a PI film-protected localized etching method is as follows:

[0101] (1) Pre-treated tungsten carbide mesh (initial wire diameter of 11 μm, mesh count of 520 mesh) was degreased with 3wt% Na2CO3 solution, ultrasonically cleaned, and dried at 50°C, which is the same as the pre-treatment process in Example 2;

[0102] (2) According to the etching pattern requirements, the PI film is laser-cut to form a protective pattern. The cut PI film is then manually and precisely arranged and pasted onto the surface of the tungsten steel mesh and compacted.

[0103] (3) Immerse the tungsten steel mesh cloth covered with PI film in the etching solution and etch at room temperature for 18 min to refine the line diameter of the area to be etched to 8 μm. Then rinse with deionized water for 5 min and dry in a 50°C hot air oven for 8 min.

[0104] (4) Immerse the etched electroformed nickel mesh in a mixed film removal solution (5% sodium hydroxide solution: N-methylpyrrolidone = 1:1) at 80°C for 20 min to peel off the PI film. After removing it, rinse it with deionized water for 10 min and dry it to obtain the etched metal mesh.

[0105] The electroformed nickel mesh obtained by this comparative etching has the following problems: the edge of the PI film bonding is lifted, resulting in an edge line diameter error of ±0.8μm in the etched area, and poor pattern accuracy; the 80℃ strong alkaline mixed film removal solution corrodes the tungsten steel mesh substrate, reducing the tensile strength of the mesh by 35% and the screen life is only 210,000 cycles, which is far lower than that of Example 2.

[0106] Comparative Example 2:

[0107] The etching process for 304 stainless steel wire mesh using a localized etching method with acrylic emulsion protection is as follows:

[0108] (1) Pre-treatment of 304 stainless steel wire mesh (the initial wire diameter of the stainless steel wire mesh is 12μm and the mesh count is 600 mesh) is performed by degreasing with 3wt% Na2CO3 solution, ultrasonic cleaning, and drying at 50℃, which is the same as the pre-treatment process in Example 4.

[0109] (2) The acrylic emulsion was uniformly sprayed onto the surface of the stainless steel wire mesh using a high-pressure spraying process, with a spraying thickness of 12μm. Then it was cured in a 60℃ hot air oven for 30 minutes to form an emulsion protective layer.

[0110] (3) According to the etching pattern requirements, use laser cutting technology to process an opening on the cured acrylic emulsion protective layer to expose the area to be etched;

[0111] (4) Immerse the laser-cut stainless steel wire mesh in the etching solution and etch at room temperature for 16 minutes to refine the wire diameter of the area to be etched to 7 μm. Rinse with deionized water for 5 minutes and dry in a 50°C hot air oven for 8 minutes.

[0112] (5) Immerse the etched stainless steel wire mesh in a 3% sodium hydroxide solution at 80°C for 15 minutes to remove the acrylic emulsion. After removing it, rinse it with deionized water for 8 minutes and dry it to obtain the etched metal mesh.

[0113] The stainless steel wire mesh obtained by this comparative etching has the following problems: the edge precision of the pattern of the acrylic emulsion protective layer is low, the edge burr width reaches 1.2μm, and the wire diameter error reaches ±0.9μm, which cannot meet the requirements for the production of fine grid lines below 8μm; the high temperature generated during the laser cutting process easily causes local heat oxidation of the metal mesh, reducing the tensile strength of the mesh by 40%, which further affects its lifespan.

[0114] The partially etched electroformed nickel mesh implemented in Example 2 and the partially etched steel wire mesh implemented in Example 4 have the following advantages over traditional technologies:

[0115] 1. Residual adhesive removal rate > 99.5%: Nickel mesh residue 0.04mg / cm², steel wire mesh 0.06mg / cm² (SEM-EDS detection), solving the problem of micropore clogging.

[0116] 2. Printing grid breakage rate drops to a new industry low: nickel mesh 2.8%, steel wire mesh 3.2% (SEMI PV22-0812 standard), which is more than 70% lower than the industry average of 12%.

[0117] 3. Significantly improved battery efficiency: Nickel mesh achieves 27.43% (+0.33%) efficiency for TOPCon batteries and steel wire mesh achieves 23.15% (+0.25%) efficiency for PERC batteries.

[0118] 4. Increased screen life: Nickel screens have a lifespan of 620,000 cycles, and steel wire screens have a lifespan of 1.2 million cycles, both exceeding industry benchmarks.

[0119] This application and its specific embodiments are merely explanations of this application and are not intended to limit it. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for localized etching of metal, characterized in that, include: Metal mesh pretreatment: The metal mesh to be etched is degreased, washed with water, and dried; Photoresist coating: Photoresist is coated onto the surface of the metal mesh, and the metal mesh is pre-baked after coating; Exposure: After aligning the mask with the metal mesh, the photoresist in the exposed area is cross-linked and cured through an exposure operation to form a protective layer; Development: Use an alkaline developer to remove the photoresist from the unexposed areas; Etching: The surface of the metal mesh is etched. After the metal in the metal mesh reaches the target wire diameter, the metal mesh is removed and post-etching processing is performed. Photoresist stripping: The metal mesh is heated to create micro-gaps between the photoresist and the surface of the metal mesh. The photoresist is then stripped off and cleaned to obtain a partially etched metal mesh. The photoresist coated on the metal mesh, by total mass of 100%, includes: 88-92% of the substrate; 5-7% of the primary functional modifier is used to form a protective film with the substrate; 2.5-4% of a secondary functional modifier is used to assist in the stripping of photoresist; 0.5-1% of additives; The substrate includes epoxy acrylate adhesive, which is one or more of bisphenol A epoxy acrylate and phenolic epoxy acrylate. The mask includes a protected area and an etched area. The light transmittance of the protected area is ≤5%, and the light transmittance of the etched area is ≥90%. The edges of both the protected area and the etched area are provided with a gradient light-transmitting area with a width of not less than 5μm. The first functional modifier is Al2O3 nano-ceramic particles with a particle size of 30-50 nm; The second functional modifier is polycaprolactone temperature-controlled peeling agent; The additive is a photoinitiator, specifically 2-hydroxy-2-methyl-1-phenyl-1-propanone.

2. The method for localized metal etching according to claim 1, characterized in that, The metal mesh is made of stainless steel wire or tungsten wire, with an initial wire diameter of 11-13 μm and a mesh count of 400-700 mesh.

3. The method for localized etching of metal according to claim 1, characterized in that, Photoresist was applied using a slit coater, with the slit width adjusted to 50-100μm, the coating speed to 5-10mm / s, and the coating thickness controlled to 10-15μm.

4. The method for localized metal etching according to claim 1, characterized in that, The exposure operation was carried out using an ultraviolet exposure machine with an ultraviolet wavelength of 365nm, an energy density controlled at 300-500mJ / cm², and an exposure time controlled at 20-30s.

5. The method for localized etching of metal according to claim 1, characterized in that, The alkaline developer is a 0.5wt% Na2CO3 solution, the temperature is 30℃, and the developing operation is spray developing for 30-60 seconds at a pressure of 0.1MPa.

6. The method for localized metal etching according to claim 1, characterized in that, The etching and post-etching processes include: Immerse the developed metal mesh in the etching solution, stir at room temperature, and etch for 15-20 minutes; The wire diameter of the metal in the metal mesh is monitored in real time. When the wire diameter in the area to be corroded reaches 8-9 μm, the metal mesh is removed. Rinse with deionized water for at least 5 minutes to remove residual etching solution; Dry in a hot air oven at 45-55℃ for at least 8 minutes to obtain a semi-finished metal mesh with a finer wire diameter.

7. The method for localized metal etching according to claim 6, characterized in that, The process of peeling off the photosensitive emulsion includes: Place the dried metal mesh semi-finished product into a constant temperature box, set the temperature to 50-60℃, and keep it at that temperature for at least 5 minutes. Use a tool to clamp the photoresist at the edge of the metal mesh and slowly peel it off horizontally; The metal mesh was wiped with a lint-free cloth dampened with a small amount of isopropyl alcohol to remove residual adhesive, resulting in the final partially etched metal mesh.

8. The method for localized etching of metal according to claim 1, characterized in that, The photoresist is prepared as follows: Weigh the base material, first functional modifier, second functional modifier and additives according to the mass fraction, and disperse them in a high-speed disperser for 25-30 minutes. The speed of the high-speed disperser should not be less than 3000 r / min.

9. A printing screen for photovoltaic cells, characterized in that, The method includes a partially etched metal mesh and a polyester mesh obtained by the method as described in claims 1-8, wherein the partially etched metal mesh and the polyester mesh are combined and the mesh tension is 10-25 N / cm.

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