A locking exhaust screen for BC battery positive UV glue printing and a manufacturing method thereof

Abstract

The application discloses a BC battery positive face UV glue printing lock glue exhaust screen printing plate and a manufacturing method, and relates to the field of precise screen printing screen printing plates. The BC battery positive face UV glue printing lock glue exhaust screen printing plate comprises a three-layer composite integrated structure arranged in sequence from a scraper contact surface to a silicon wafer contact surface, and comprises an upper PI film lock glue layer, a middle metal glue storage layer and a lower electroformed nickel exhaust precise control layer. Each layer is provided with a through hole structure for the UV glue to pass through. The three-layer composite integrated structure is designed. The upper layer of the three-layer composite integrated structure is provided with a conical through hole to realize power-free lock glue during shutdown. The middle layer is used for stable glue output and pressure transmission. The lower layer is provided with a radial exhaust channel to realize synchronous exhaust and form a bubble-free solid glue point. The glue point has high precision, good light transmission and high pressure resistance. The screen printing plate has high interlayer bonding strength, long service life, and can reduce production loss and maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of precision screen printing screen technology, specifically to a locking and venting screen for UV adhesive printing on the front side of BC batteries and its manufacturing method. Background Technology

[0002] BC back-contact solar cells, relying on a zero-shading optical design with no metal grid lines on the front, offer excellent photoelectric conversion performance and are gradually becoming the mainstream technology in the photovoltaic cell field. However, due to the lack of a grid line protective structure on the front of the cell, the cell surface is susceptible to micro-cracks and scratches caused by compression and friction during subsequent testing, sorting, stacking, and module production, directly resulting in poor appearance and reduced conversion efficiency. The industry mainstream approach is to use high-viscosity UV adhesive screen-printed to create a dot matrix protective layer on the front of the cell; the printing screen is a key component ensuring the protective effect of the UV adhesive during molding.

[0003] However, when conventional printing screens are used with high-viscosity UV adhesives, the adhesive is prone to leakage and dripping when the machine is stopped and left to stand still, causing contamination. The printed adhesive dots are also prone to trapping air and generating bubbles. After curing, the adhesive dots collapse and form ring structures, resulting in optical loss. Existing technologies cannot simultaneously solve the core problems of adhesive locking and seepage prevention as well as air venting and shape control.

[0004] To address this, we propose a locking and venting screen for UV adhesive printing on the front side of BC batteries and its manufacturing method. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a locking and venting screen for UV adhesive printing on the front side of BC batteries and a manufacturing method thereof, which can effectively solve the problems of the prior art.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions; This invention discloses a UV adhesive printing screen for BC batteries, comprising: It is a three-layer composite integrated structure arranged sequentially from the squeegee contact surface to the silicon wafer contact surface, including an upper PI film locking layer, a middle metal storage layer and a lower electroformed nickel venting and precision control layer, with through-hole structures for UV adhesive to pass through at corresponding positions in each layer; The upper PI film adhesive layer has a tapered through-hole array with larger upper holes and smaller lower holes arranged on the entire surface. The negative additional pressure generated by the tapered capillary and the surface hydrophobic effect work together to form a powerless adhesive locking mechanism when the machine stops. The intermediate metal adhesive storage layer is provided with an array of adhesive storage through holes, which serve as a space for quantitative storage and pressure transfer of UV adhesive. The lower electroformed nickel venting precision control layer is provided with an array of annular bodies that correspond one-to-one with and are concentrically aligned with the adhesive storage holes of the intermediate metal adhesive storage layer. Each annular body has 4 to 12 equally spaced radial venting channels that extend from the inner diameter to the outer diameter. The width of the radial venting channels is configured to be 5 to 25 μm. The surface tension of the UV adhesive with a viscosity of 2000 to 3000 cps is used to achieve directional separation of gas and adhesive, so that the gas can be discharged through the radial venting channels while the UV adhesive is intercepted. During the printing process, the air trapped inside the adhesive and the residual gas adsorbed on the silicon wafer surface are discharged simultaneously, forming solid adhesive dots without bubbles.

[0007] Furthermore, the upper PI film locking layer is made of polyimide film with a thickness of 2~15μm. The side that contacts the doctor blade is coated with a 0.1~1μm thick fluorocarbon-based or organosilicon low surface energy coating by vapor deposition. The low surface energy coating makes the static contact angle between the UV adhesive and the hole wall greater than 90°. The tapered through-hole is formed by laser processing, with a tapered angle of 5°~30°. The hole diameter on the side that contacts the doctor blade is 80~150μm, and the hole diameter on the side that contacts the intermediate metal adhesive storage layer is 30~60μm. The misalignment deviation between the small hole at the adhesive outlet of the tapered through-hole and the adhesive storage through-hole of the intermediate metal adhesive storage layer on the projection plane does not exceed 50μm.

[0008] Furthermore, the intermediate metal storage layer is made of nickel alloy or stainless steel and is integrally formed by photolithography electroforming process, with a thickness of 10~100μm; The diameter of the adhesive storage through-hole is 200±20μm, the wall roughness Ra≤0.8μm, the verticality deviation of the wall does not exceed 2°, the center spacing of the adhesive storage through-hole is set according to the required adhesive dot pattern of the BC battery, and the outer diameter of the annular body corresponding to adjacent adhesive dots does not overlap.

[0009] Furthermore, the lower electroformed nickel venting control layer is directly epitaxially grown on the lower surface of the intermediate metal reservoir layer through secondary photolithography electroforming, with an interlayer bonding strength ≥50MPa and a thickness of 5~20μm; The inner diameter of the annular body is 200±20μm, which is exactly the same as the diameter of the glue storage through hole, and the outer diameter is 300~1000μm; The depth of the radial exhaust channel is equal to the thickness of the lower electroformed nickel layer. The channel cross-section is rectangular, the inner wall roughness Ra≤1.2μm, and the channel width remains uniform along the radial direction, dividing the annular body into sector-shaped blocks of equal area.

[0010] Furthermore, the screen printing plate is adapted to screen print UV-isolated adhesive on the front side of BC batteries with a viscosity of 2000~3000cps. The diameter of the solid adhesive dots formed by printing is consistent with the outer diameter of the ring body, the thickness is 5~15μm, the height deviation of the adhesive dots does not exceed ±1μm, the light transmittance after curing is ≥94%, and it can withstand stacking pressure of ≥12MPa without breaking.

[0011] On the other hand, a method for manufacturing a locking and venting screen for UV adhesive printing on the front side of a BC battery includes: Step 1: Prepare the intermediate metal reservoir layer by forming a metal substrate with an array of reservoir vias on a metal substrate using a first photolithography electroforming process; Step 2: Prepare the lower electroformed nickel venting control layer. After plasma activation treatment of the lower surface of the intermediate metal storage layer, perform a second photolithography electroforming to grow a pure nickel layer with concentric rings and equally spaced radial venting channels in situ. Step 3: Process and bond the upper PI film locking layer. Using the through-hole array of the intermediate metal adhesive storage layer as a visual reference, laser process a tapered through-hole array on the pre-treated PI film, and then bond the PI film to the upper surface of the intermediate metal adhesive storage layer.

[0012] Furthermore, the process of the first photolithography electroforming process is as follows: A negative photoresist with the same thickness as the target intermediate layer is spin-coated on the surface of a metal substrate. After pre-baking, it is exposed to ultraviolet light through a high-precision mask. After development, the photoresist in the unexposed areas is removed. Electroforming deposition was performed at 25~40℃ and a current density of 1~3A / dm². After deposition, the remaining photoresist was stripped off, and the intermediate metal reservoir layer was obtained after deburring and ultrasonic cleaning.

[0013] Furthermore, the second photolithography electroforming process employs self-aligned exposure technology. Using the edge of the via in the intermediate metal reservoir layer as an alignment mark, a 5-20 μm thick layer of negative photoresist is spin-coated onto its lower surface. After exposure and development, a ring-shaped structure and radial venting channel pattern are formed. Then, pure nickel electroforming deposition is performed at 22-30°C and a current density of 0.8-1.8 A / dm². After the photoresist is stripped off, a lower electroformed nickel venting precision control layer with a concentricity deviation ≤5 μm from the via is obtained.

[0014] Furthermore, the preprocessing in step 3 follows the following rules: First, a 0.1~1μm thick fluorocarbon-based or organosilicon low surface energy coating is deposited on one side of the PI film by plasma-enhanced chemical vapor deposition, and then the other side is subjected to plasma roughening treatment. The tapered through-hole is laser-drilled using a nanosecond ultraviolet laser, drilling from the side coated with a low surface energy layer to form a tapered through-hole that is larger at the top and smaller at the bottom.

[0015] Furthermore, in step 3, the roughened surface of the PI film is aligned with the upper surface of the intermediate metal adhesive layer by precision hot pressing. The hot pressing is carried out in a vacuum environment with a hot pressing temperature of 120~180℃, a pressure of 0.3~0.8MPa, a holding time of 10~30s, and the film is removed after cooling to room temperature. During the bonding process, use either epoxy resin adhesive or acrylic pressure-sensitive adhesive, and control the adhesive layer thickness to 1~5μm. After bonding, cure at 60~80℃ for 10~20min.

[0016] Compared with the known prior art, the technical solution provided by this invention has the following beneficial effects: This invention employs a three-layer composite integrated structure design: an upper PI film locking layer, a middle metal storage layer, and a lower electroformed nickel venting and precision control layer. It utilizes the negative additional pressure from the upper conical through-hole and the surface hydrophobic effect to achieve power-free glue locking during shutdown, preventing glue dripping and breakage, reducing UV glue material waste and printing defects. The middle metal storage layer serves as a quantitative glue storage and pressure transfer space, stabilizing the glue output and ensuring uniform printing pressure transmission. The annular radial venting channel of the lower electroformed nickel layer utilizes the surface tension of the UV glue to achieve directional separation of air and glue, simultaneously expelling air trapped inside the glue and residual gas on the silicon wafer surface during printing, forming bubble-free solid glue dots. This effectively improves the glue dot forming accuracy, controlling the glue dot height deviation within ±1μm. After curing, the glue dot transmittance is no less than 94%, and it can withstand stacking pressures of over 12MPa without cracking. Simultaneously, the interlayer bonding strength of the three-layer structure is no less than 50MPa, effectively improving the overall lifespan of the screen and the stability of the printing process, thereby reducing equipment downtime and maintenance costs during production. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0018] Figure 1 This is a flowchart illustrating a method for manufacturing a locking and venting screen for UV adhesive printing on the front side of a BC battery. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] The present invention will be further described below with reference to embodiments.

[0021] Example 1: This embodiment provides a locking and venting screen for UV adhesive printing on the front side of a BC battery, such as... Figure 1 As shown, it includes: It is a three-layer composite integrated structure arranged sequentially from the squeegee contact surface to the silicon wafer contact surface, including an upper PI film locking layer, a middle metal storage layer and a lower electroformed nickel venting and precision control layer, with through-hole structures for UV adhesive to pass through at corresponding positions in each layer; The upper PI film locking layer is made of polyimide film with a thickness of 2~15μm. The side that contacts the doctor blade is coated with a 0.1~1μm thick fluorocarbon-based or organosilicon low surface energy coating by vapor deposition. The low surface energy coating makes the static contact angle between the UV adhesive and the hole wall greater than 90°. The tapered through-hole is formed by laser processing with a tapered angle of 5°~30°. The hole diameter on the side that contacts the doctor blade is 80~150μm, and the hole diameter on the side that contacts the middle metal adhesive storage layer is 30~60μm. The misalignment deviation between the small hole at the adhesive outlet of the tapered through-hole and the adhesive storage through-hole of the middle metal adhesive storage layer on the projection plane does not exceed 50μm. The intermediate metal storage layer is made of nickel alloy or stainless steel and is integrally formed by photolithography electroforming process, with a thickness of 10~100μm. The diameter of the gel storage through hole is 200±20μm, the hole wall roughness Ra≤0.8μm, the hole wall verticality deviation does not exceed 2°, the center spacing of the gel storage through hole is set according to the required separation gel dot pattern of BC battery, and the outer diameter of the ring corresponding to adjacent gel dots does not overlap. The upper PI film adhesive layer has a tapered through-hole array with larger upper holes and smaller lower holes arranged on the entire surface. The negative additional pressure generated by the tapered capillary and the surface hydrophobic effect work together to form a powerless adhesive locking mechanism when the machine stops. Specifically, the negative additional pressure ΔP generated by the tapered capillary can be calculated using the modified Laplace formula: Where γ is the surface tension of the UV adhesive (unit: mN / m), and θ is the static contact angle between the UV adhesive and the hole wall. The radius of the larger hole at the top of the tapered through-hole (unit: μm). The radius of the lower orifice is shown in μm. When ΔP > 0, the adhesive is subjected to an upward additional pressure, opposite to the direction of gravity, thus achieving adhesive locking. For UV adhesives with a viscosity of 2000~3000cps and a surface tension of 30~40mN / m, when θ > 90° and the cone angle is 5°~30°, the calculated negative additional pressure is 200~800Pa, which is greater than the pressure generated by the adhesive's own gravity (approximately 50~150Pa), ensuring that the adhesive will not leak from the lower end of the through-hole when the machine stops. When the cone angle is less than 5°, the negative additional pressure is too large, which will cause difficulties in adhesive dispensing during printing; when the cone angle is greater than 30°, the negative additional pressure is less than the gravity of the adhesive, and effective adhesive locking cannot be achieved. The intermediate metal adhesive storage layer has an array of adhesive storage through holes, which serve as a space for quantitative storage and pressure transfer of UV adhesive. The lower electroformed nickel venting control layer is provided with an array of annular bodies that correspond one-to-one with the glue storage through holes of the intermediate metal glue storage layer and are concentrically aligned. Each annular body has 4 to 12 equally spaced radial venting channels that run from the inner diameter to the outer diameter. The width of the radial venting channels is configured to be 5 to 25 μm. The surface tension of the UV glue with a viscosity of 2000 to 3000 cps is used to complete the directional separation of gas and glue, so that the gas can be discharged through the radial venting channels while the UV glue is intercepted. During the printing process, the air trapped inside the glue and the residual gas adsorbed on the silicon wafer surface are discharged simultaneously, forming a solid glue dot without bubbles. The core principle of aerogel directional separation is based on the Laplace pressure difference. For a rectangular cross-section radial exhaust channel, the critical pressure at which the adhesive enters the channel is... =2γcosθ / w, where w is the channel width (unit: μm). When the pressure on the adhesive during printing is less than... At this pressure, the adhesive cannot enter the channel; however, the surface tension of the gas is negligible, and it is not restricted by the pressure, allowing it to freely exit through the channel. For UV adhesives with a viscosity of 2000~3000cps, a surface tension of 30~40mN / m, and a contact angle with the nickel surface of 30°~45°, calculations show that when w≤25μm... The pressure is ≥2.5MPa, which is much greater than the maximum pressure the adhesive experiences during printing (approximately 0.5MPa), therefore the adhesive will not leak out of the channel. When w < 5μm, the resistance of the gas through the channel, R = 12μL / (w³h) (where μ is the gas viscosity, L is the channel length, and h is the channel depth), will increase sharply, causing the venting time to exceed the printing cycle, making synchronous venting impossible. Therefore, controlling the channel width within the range of 5~25μm can simultaneously meet the requirements of gas-adhesive separation and efficient venting. The matching relationship between the width of the radial exhaust channel and the surface tension of the UV adhesive was verified using the Laplace formula. For UV adhesives with a viscosity of 2000~3000cps and a surface tension of 30~40mN / m, when the channel width is ≤25μm, the capillary rise height of the adhesive in the channel is less than the channel depth, and the adhesive cannot seep out through the channel; while the surface tension of the gas is negligible, and it can be discharged smoothly through the channel. When the channel width is <5μm, the gas flow resistance is too large, and the exhaust efficiency is reduced. Therefore, controlling the channel width within the range of 5~25μm can achieve stable gas-adhesive directional separation.

[0022] The lower electroformed nickel venting precision control layer is directly epitaxially grown on the lower surface of the intermediate metal storage layer by secondary photolithography electroforming, with an interlayer bonding strength ≥50MPa and a thickness of 5~20μm; The interlaminar bond strength was determined using the tensile shear test method, with the test standard referring to GB / T228.1-2010. The sample preparation method was as follows: a 10mm × 10mm three-layer composite mesh sample was cut, and the surface of the upper PI film and the lower electroformed nickel layer of the sample were respectively bonded to two stainless steel tensile clamps with epoxy resin. The bonding area was 10mm × 10mm, and the samples were cured at 80℃ for 2 hours after bonding. The test was conducted on a universal testing machine at a tensile speed of 1mm / min. The maximum load F at which interlaminar separation occurred was recorded. The interlaminar bond strength τ = F / S, where S is the bonding area. Five parallel samples were prepared for each batch, and the average value was taken as the final interlaminar bond strength value. During the test, it was necessary to ensure that the direction of the tensile force was parallel to the interlaminar interface to avoid bending stress affecting the test results. The inner diameter of the annular body is 200±20μm, which is exactly the same as the diameter of the gel storage through hole, and the outer diameter is 300~1000μm; The depth of the radial exhaust channel is equal to the thickness of the lower electroformed nickel layer. The channel cross-section is rectangular, the inner wall roughness Ra≤1.2μm, and the channel width is kept uniform along the radial direction, dividing the annular body into sector blocks of equal area. The screen printing is compatible with UV-blocking adhesive for the front of BC batteries with a viscosity of 2000~3000cps. The diameter of the solid adhesive dots formed by printing is consistent with the outer diameter of the ring body, the thickness is 5~15μm, the height deviation of the adhesive dots does not exceed ±1μm, the light transmittance after curing is ≥94%, and it can withstand stacking pressure of ≥12MPa without breaking.

[0023] The process parameters for screen printing using this screen are as follows: squeegee material is polyurethane with a hardness of 70-80 Shore A; squeegee angle is 60°-75°; squeegee pressure is 0.2-0.5 MPa; squeegee speed is 50-150 mm / s; the screen-to-wafer distance is 0.5-2 mm; the ink return blade pressure is 0.1-0.3 MPa; and the printing cycle is 1. UV curing is performed immediately after printing. Nitrogen protection is used during curing, with an oxygen concentration ≤500 ppm in the chamber to prevent oxidation and yellowing of the adhesive surface, thus improving the curing quality and light transmittance of the adhesive dots. The screen removal speed during the printing process should be controlled between 50 and 150 mm / s, and synchronized with the squeegee speed. When the removal speed is below 50 mm / s, the adhesive separation time from the screen is too long, easily leading to blurred edges and excessively large diameter adhesive dots. When the removal speed is above 150 mm / s, the adhesive will be pulled by the screen, forming pointed tips, which can cause the adhesive dots to break in severe cases. For adhesive dots with a thickness of 5-10 μm, a removal speed of 80-120 mm / s is preferred; for adhesive dots with a thickness of 10-15 μm, a removal speed of 50-80 mm / s is preferred. The removal process should maintain a uniform speed to avoid impact vibration and ensure consistent dot height.

[0024] The compatible UV-blocking adhesive for the front of the BC battery is a highly transparent acrylic UV adhesive with a curing wavelength range of 365~405nm, an optimal curing wavelength of 395nm, a curing energy of 500~1500mJ / cm², a curing time of 5~30s, a volume shrinkage rate of ≤2% after curing, a Shore hardness of 60~80D, and a light transmittance of ≥95% in the wavelength range of 400~1100nm. The dynamic viscosity of the UV adhesive at 25℃ is 2000~3000cps. Before use, it needs to be placed in a constant temperature environment of 25℃±1℃ for more than 2 hours, stirred evenly, and degassed to ensure that there are no residual air bubbles in the adhesive. The glue-locking and venting screen in the above embodiments uses a three-layer composite integrated structure design. The upper layer uses tapered through holes to achieve glue-locking without power when the machine is stopped. The middle layer provides stable glue dispensing and pressure transmission. The lower layer uses radial venting channels to simultaneously vent and form bubble-free solid glue dots. The glue dots have high precision, good light transmittance, and strong pressure resistance. The screen has high interlayer bonding strength and long service life, which can reduce production losses and maintenance costs.

[0025] Example 2: At the implementation level, based on Example 1, this example further details the method for manufacturing a locking and venting screen for UV adhesive printing on the front side of a BC battery as described in Example 1: A method for manufacturing a UV adhesive-locking and venting screen for printing on the front side of a BC battery includes: Step 1: Prepare the intermediate metal reservoir layer by forming a metal substrate with an array of reservoir vias on a metal substrate using a first photolithography electroforming process; The process flow for the first photolithography electroforming process is as follows: The metal substrate used to prepare the intermediate metal reservoir layer is a mirror-polished 304 stainless steel substrate with a surface roughness Ra≤0.05μm and a substrate thickness of 0.5~1mm. Before use, the substrate needs to be ultrasonically cleaned for 10min each with acetone, anhydrous ethanol, and deionized water to remove surface oil and impurities. Then, it is immersed in 10% (mass fraction) dilute sulfuric acid for 5min for surface micro-etching activation. After removal, it is immediately rinsed with deionized water and dried with high-purity nitrogen to ensure that there is no oxide layer and water stains on the surface. A negative photoresist with the same thickness as the target intermediate layer is spin-coated on the surface of a metal substrate. After pre-baking, it is exposed to ultraviolet light through a high-precision mask. After development, the photoresist in the unexposed areas is removed. The pre-baking process for negative photoresist is as follows: baking on a precision hot plate at 90~110℃ for 60~120s, followed by natural cooling to room temperature in a dust-free environment to prevent cracking caused by sudden temperature drops. The electroforming solution uses a nickel sulfamate alloy system, with main components of 300~400g / L nickel sulfamate, 30~40g / L boric acid, 10~20g / L nickel chloride, and 5~15g / L cobalt sulfate (used to prepare the nickel alloy layer). The pH value is controlled at 3.5~4.5. During electroforming, continuous filtration with a precision of 5μm and air stirring at 0.1~0.3m / s are employed. When the current density is 1~3A / dm², the deposition rate is 1~3μm / min, corresponding to a deposition time of 3~100min for a target thickness of 10~100μm. Electroforming deposition was carried out at 25~40℃ and current density of 1~3A / dm². After deposition, the remaining photoresist was stripped off, and the intermediate metal reservoir layer was obtained after deburring and ultrasonic cleaning. Step 2: Prepare the lower electroformed nickel venting control layer. After plasma activation treatment of the lower surface of the intermediate metal storage layer, perform a second photolithography electroforming to grow a pure nickel layer with concentric rings and equally spaced radial venting channels in situ. The second photolithography electroforming process uses self-aligned exposure technology. The edge of the through-hole of the intermediate metal reservoir layer is used as the alignment mark. A 5-20 μm thick negative photoresist is spin-coated on its lower surface. Exposure and development form the pattern of the annular body and radial exhaust channels. Then, pure nickel electroforming deposition is performed under the conditions of 22-30℃ and current density of 0.8-1.8A / dm². After the photoresist is stripped off, a lower electroformed nickel exhaust control layer with a concentricity deviation of ≤5 μm from the through-hole of the reservoir is obtained. The self-alignment exposure uses contact ultraviolet exposure at a wavelength of 365 nm and an exposure dose of 150-300 mJ / cm². During exposure, the photomask is tightly bonded to the lower surface of the intermediate metal photoresist layer, utilizing the metal edge of the photoresist via as a natural alignment marker, eliminating the need for additional alignment marks. The development process uses a 2.38% (mass fraction) tetramethylammonium hydroxide aqueous solution at a development temperature of 20-25℃ and a development time of 30-90 seconds. After development, the photoresist is rinsed with deionized water for 30 seconds and then baked at 100-120℃ for 60-90 seconds to enhance the adhesion between the photoresist and the metal surface. The second pure nickel electroforming process uses a high-purity nickel sulfamate electroforming solution, the main components of which are 400~500 g / L nickel sulfamate and 35~45 g / L boric acid. The pH value is controlled at 4.0~4.8. 0.1~0.5 g / L of saccharin is added to the electroforming solution as a brightener and stress reliever. When the current density is 0.8~1.8 A / dm², the deposition rate is 0.8~2.5 μm / min, and the deposition time corresponding to a target thickness of 5~20 μm is 2~25 min. Step 3: Process and bond the upper PI film locking layer. Using the adhesive storage through-hole array of the middle metal adhesive storage layer as a visual reference, laser process a tapered through-hole array on the pre-treated PI film, and then bond the PI film to the upper surface of the middle metal adhesive storage layer. In step 3, the preprocessing follows the following rules: First, a 0.1~1μm thick fluorocarbon-based or organosilicon low surface energy coating is deposited on one side of the PI film by plasma-enhanced chemical vapor deposition, and then the other side is subjected to plasma roughening treatment. The plasma roughening treatment of the PI membrane uses radio frequency oxygen plasma with a power of 200-400W, a treatment time of 60-180s, an oxygen flow rate of 30-60sccm, and a chamber vacuum maintained at 5-15Pa. After roughening treatment, the water contact angle of the PI membrane surface is reduced to below 30°, and a uniform nanoscale uneven structure is formed on the surface to ensure good wetting and mechanical interlocking with the adhesive, thereby improving the interlayer bonding force. The tapered through-hole is laser-drilled using a nanosecond ultraviolet laser, drilling from the side coated with a low surface energy coating to form a tapered through-hole that is larger at the top and smaller at the bottom. The cone angle of the tapered through-hole is precisely controlled by adjusting the laser defocusing amount and the number of scans. Specifically, when the laser defocusing amount is -0.5~0mm (negative defocusing, i.e., the focal point is inside the PI film), the laser energy is distributed in a gradient along the thickness direction of the PI film. The energy density is high near the focal point, resulting in a large aperture; the energy density is low further from the focal point, resulting in a small aperture, thus forming a tapered through-hole. The larger the absolute value of the defocusing amount, the larger the cone angle; the more scans, the smaller the cone angle. For example, with a laser wavelength of 355nm, an average power of 10W, a pulse frequency of 50kHz, and a scanning speed of 1000mm / s, a defocusing amount of -0.2mm and 5 scans can produce a tapered through-hole with a cone angle of approximately 15°; a defocusing amount of -0.4mm and 3 scans can produce a tapered through-hole with a cone angle of approximately 25°. By establishing a pre-defined table of the correspondence between defocusing amount, number of scans, and cone angle, precise control of the cone angle can be achieved, with a deviation not exceeding ±2°. The process parameters for nanosecond ultraviolet laser drilling are as follows: laser wavelength 355nm, pulse width 10~30ns, average laser power 5~20W, pulse frequency 20~100kHz, scanning speed 500~2000mm / s, defocusing amount -0.5~+0.5mm, using a single-pulse superimposed spiral scanning method, with 3~8 scans per hole. During drilling, compressed air at 0.2~0.4MPa is used to vertically blow through the hole opening to promptly remove molten debris and carbonized particles. After drilling, the PI film is ultrasonically cleaned in isopropanol for 5~10 minutes to thoroughly remove residual carbonized layer and dust from the hole wall, ensuring a smooth, burr-free hole wall. Step 3: Align the roughened surface of the PI film with the upper surface of the intermediate metal adhesive layer by precision hot pressing. Perform hot pressing in a vacuum environment. The hot pressing temperature is 120~180℃, the pressure is 0.3~0.8MPa, the holding time is 10~30s, and the film is removed after cooling to room temperature. The vacuum degree of the cavity for precision hot pressing is controlled at 10~100Pa. The hot pressing process adopts a step-by-step pressurization method. First, a pre-pressure of 0.1~0.2MPa is applied and held for 5s to remove residual air between the PI film and the intermediate metal layer. Then, the pressure is uniformly increased to the target pressure of 0.3~0.8MPa. The epoxy resin used is a low-viscosity bisphenol A type epoxy resin, and the curing agent is a modified aliphatic polyamine with a solid content ≥95% and a viscosity of 1000~3000cps at 25℃. The acrylic pressure-sensitive adhesive is a solvent-based acrylic pressure-sensitive adhesive with a solid content ≥40%, a 180° peel strength ≥10N / 25mm, and a temperature resistance range of -40~150℃. During the bonding process, use either epoxy resin adhesive or acrylic pressure-sensitive adhesive, and control the adhesive layer thickness to be 1~5μm. After bonding, cure at 60~80℃ for 10~20min. The completed three-layer composite screen printing plate is fixed to an aluminum alloy frame using a stretching process. The frame size is determined according to the printing press specifications, with common sizes being 320mm×320mm and 450mm×450mm. Polyester mesh is used as an auxiliary support for the stretching, with a mesh count of 100-200 and a wire diameter of 30-50μm. The stretching tension is controlled at 20-30N / cm, and the stretching angle is 0° (i.e., the warp yarns of the mesh are parallel to the edge of the frame). With the upper PI film surface of the three-layer composite screen printing plate facing the mesh, the edges of the screen printing plate are bonded to the mesh using epoxy resin adhesive, with a bonding width of 10-15mm. After bonding, it is cured at 60℃ for 30 minutes. After curing, the excess mesh outside the screen printing plate is removed, resulting in a finished screen printing plate ready for printing. The stretching tension deviation should be controlled within ±2N / cm to ensure uniform screen deformation during printing.

[0026] In summary, the glue-locking and venting screen and its manufacturing method in the above embodiments utilize a three-layer composite integrated structure design consisting of an upper PI film glue-locking layer, a middle metal glue storage layer, and a lower electroformed nickel venting and precision control layer. This design leverages the negative additional pressure from the upper tapered through-hole and the surface hydrophobic effect to achieve power-free glue locking during shutdown, preventing glue dripping and glue breakage, reducing UV glue material waste and printing defects. The middle metal glue storage layer serves as a quantitative glue storage and pressure transfer space, stabilizing the glue output and ensuring uniform printing pressure transmission. The annular radial venting channel of the lower electroformed nickel layer... The UV adhesive surface tension helps to achieve directional separation of air and adhesive, and simultaneously discharges the air trapped inside the adhesive and the residual gas on the silicon wafer surface during the printing process, forming solid adhesive dots without bubbles. This effectively improves the forming accuracy of adhesive dots, controls the height deviation of adhesive dots within ±1μm, and ensures that the light transmittance of the adhesive dots after curing is not less than 94%. The adhesive dots can withstand stacking pressure of more than 12MPa without breaking. At the same time, the interlayer bonding strength of the three-layer structure is not less than 50MPa, which effectively improves the overall service life of the screen and the stability of the printing process, thereby reducing the frequency of equipment downtime and maintenance costs in production. The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A locking and venting screen for UV adhesive printing on the front side of a BC battery, characterized in that, include: It is a three-layer composite integrated structure arranged sequentially from the squeegee contact surface to the silicon wafer contact surface, including an upper PI film locking layer, a middle metal storage layer and a lower electroformed nickel venting and precision control layer, with through-hole structures for UV adhesive to pass through at corresponding positions in each layer; The upper PI film adhesive layer has a tapered through-hole array with larger upper holes and smaller lower holes arranged on the entire surface. The negative additional pressure generated by the tapered capillary and the surface hydrophobic effect work together to form a powerless adhesive locking mechanism when the machine stops. The intermediate metal adhesive storage layer is provided with an array of adhesive storage through holes, which serve as a space for quantitative storage and pressure transfer of UV adhesive. The lower electroformed nickel venting precision control layer is provided with an array of annular bodies that correspond one-to-one with and are concentrically aligned with the adhesive storage holes of the intermediate metal adhesive storage layer. Each annular body has 4 to 12 equally spaced radial venting channels that extend from the inner diameter to the outer diameter. The width of the radial venting channels is configured to be 5 to 25 μm. The surface tension of the UV adhesive with a viscosity of 2000 to 3000 cps is used to achieve directional separation of gas and adhesive, so that the gas can be discharged through the radial venting channels while the UV adhesive is intercepted. During the printing process, the air trapped inside the adhesive and the residual gas adsorbed on the silicon wafer surface are discharged simultaneously, forming solid adhesive dots without bubbles.

2. The venting and sealing screen for UV adhesive printing on the front side of a BC battery according to claim 1, characterized in that, The upper PI film locking layer is made of polyimide film with a thickness of 2~15μm. The side that contacts the doctor blade is coated with a 0.1~1μm thick fluorocarbon-based or organosilicon low surface energy coating by vapor deposition. The low surface energy coating makes the static contact angle between the UV adhesive and the hole wall greater than 90°. The tapered through-hole is formed by laser processing with a tapered angle of 5°~30°. The hole diameter on the side that contacts the doctor blade is 80~150μm, and the hole diameter on the side that contacts the middle metal adhesive storage layer is 30~60μm. The misalignment deviation between the small hole at the adhesive outlet of the tapered through-hole and the adhesive storage through-hole of the middle metal adhesive storage layer on the projection plane does not exceed 50μm.

3. The venting and sealing screen for UV adhesive printing on the front side of a BC battery according to claim 1, characterized in that, The intermediate metal storage layer is made of nickel alloy or stainless steel and is integrally formed by photolithography electroforming process, with a thickness of 10~100μm. The diameter of the adhesive storage through-hole is 200±20μm, the wall roughness Ra≤0.8μm, the verticality deviation of the wall does not exceed 2°, the center spacing of the adhesive storage through-hole is set according to the required adhesive dot pattern of the BC battery, and the outer diameter of the annular body corresponding to adjacent adhesive dots does not overlap.

4. The sealing and venting screen for UV adhesive printing on the front side of a BC battery according to claim 1, characterized in that, The lower electroformed nickel venting control layer is directly epitaxially grown on the lower surface of the intermediate metal storage layer by secondary photolithography electroforming, with an interlayer bonding strength ≥50MPa and a thickness of 5~20μm. The inner diameter of the annular body is 200±20μm, which is exactly the same as the diameter of the glue storage through hole, and the outer diameter is 300~1000μm; The depth of the radial exhaust channel is equal to the thickness of the lower electroformed nickel layer. The channel cross-section is rectangular, the inner wall roughness Ra≤1.2μm, and the channel width remains uniform along the radial direction, dividing the annular body into sector-shaped blocks of equal area.

5. The sealing and venting screen for UV adhesive printing on the front side of a BC battery according to claim 1, characterized in that, The screen printing plate is adapted for screen printing BC battery front UV isolation adhesive with a viscosity of 2000~3000cps. The diameter of the solid adhesive dots formed by printing is consistent with the outer diameter of the ring body, the thickness is 5~15μm, the height deviation of the adhesive dots does not exceed ±1μm, the light transmittance after curing is ≥94%, and it can withstand stacking pressure of ≥12MPa without breaking.

6. A method for manufacturing a UV-sealing and venting screen for printing UV adhesive on the front side of a BC battery as described in any one of claims 1-4, characterized in that, include: Step 1: Prepare the intermediate metal reservoir layer by forming a metal substrate with an array of reservoir vias on a metal substrate using a first photolithography electroforming process; Step 2: Prepare the lower electroformed nickel venting control layer. After plasma activation treatment of the lower surface of the intermediate metal storage layer, perform a second photolithography electroforming to grow a pure nickel layer with concentric rings and equally spaced radial venting channels in situ. The plasma activation treatment uses radio frequency argon plasma with a power of 100-300W, a treatment time of 30-120s, an argon flow rate of 20-50sccm, and a cavity vacuum level maintained at 1-10Pa. After the activation treatment, subsequent photolithography and electroforming processes must be performed within 30 minutes to avoid re-oxidation of the metal surface to form a passivation layer, which would affect the interlayer bonding strength. Step 3: Process and bond the upper PI film locking layer. Using the through-hole array of the intermediate metal adhesive storage layer as a visual reference, laser process a tapered through-hole array on the pre-treated PI film, and then bond the PI film to the upper surface of the intermediate metal adhesive storage layer.

7. The manufacturing method according to claim 6, characterized in that, The process of the first photolithography electroforming process is as follows: A negative photoresist with the same thickness as the target intermediate layer is spin-coated on the surface of a metal substrate. After pre-baking, it is exposed to ultraviolet light through a high-precision mask. After development, the photoresist in the unexposed areas is removed. Electroforming deposition was performed at 25~40℃ and a current density of 1~3A / dm². After deposition, the remaining photoresist was stripped off, and the intermediate metal reservoir layer was obtained after deburring and ultrasonic cleaning.

8. The manufacturing method according to claim 6, characterized in that, The second photolithography electroforming process employs self-aligned exposure technology. Using the edge of the via in the intermediate metal reservoir layer as an alignment mark, a 5-20 μm thick layer of negative photoresist is spin-coated onto its lower surface. After exposure and development, a ring-shaped pattern and radial venting channels are formed. Then, pure nickel electroforming deposition is performed at 22-30°C and a current density of 0.8-1.8 A / dm². After the photoresist is stripped off, a lower electroformed nickel venting control layer with a concentricity deviation of ≤5 μm from the via is obtained.

9. The manufacturing method according to claim 6, characterized in that, The preprocessing in step 3 follows the following: First, a 0.1~1μm thick fluorocarbon-based or organosilicon low surface energy coating is deposited on one side of the PI film by plasma-enhanced chemical vapor deposition, and then the other side is subjected to plasma roughening treatment. The tapered through-hole is laser-drilled using a nanosecond ultraviolet laser, drilling from the side coated with a low surface energy layer to form a tapered through-hole that is larger at the top and smaller at the bottom.

10. The manufacturing method according to claim 9, characterized in that, In step 3, the roughened surface of the PI film is aligned with the upper surface of the intermediate metal adhesive layer by precision hot pressing. The hot pressing is carried out in a vacuum environment with a hot pressing temperature of 120~180℃, a pressure of 0.3~0.8MPa, a holding time of 10~30s, and the film is removed after cooling to room temperature. During the bonding process, use either epoxy resin adhesive or acrylic pressure-sensitive adhesive, and control the adhesive layer thickness to 1~5μm. After bonding, cure at 60~80℃ for 10~20min.

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