Silver paste etching insulating conductive film and manufacturing method thereof

Abstract

The application discloses a silver paste etching insulating conductive film and a manufacturing method thereof, and relates to the field of flexible electronic manufacturing. The method prints conductive silver paste containing micron-level flaky silver powder on a flexible substrate and solidifies to form a conductive layer. A groove is formed by laser ablation and re-deposited silver nanoparticles are reserved. The silver nanoparticles are converted into an oxidized silver functional layer by ultraviolet ozone low-temperature selective oxidation, and surface organic residues are removed to change the groove sidewall from hydrophobic to hydrophilic. A micro-gravure roller is used for full-width coating of ultraviolet light curing insulating ink. Capillary pressure drives the ink to spontaneously fill the groove without precise alignment. Yield stress stabilizes the thin film in the flat area. Medium-pressure mercury lamp ultraviolet light room temperature curing ensures that the functional layer is not decomposed. The oxidized silver functional layer has both electrochemical migration blocking and interface anchoring effects. The method omits offline cleaning, converts re-deposits from defects into a functional layer, realizes alignment-free filling and low-temperature curing.

Description

Technical Field

[0001] This invention relates to the field of flexible electronics manufacturing, and more particularly to a silver paste etching insulating conductive film and its manufacturing method. Background Technology

[0002] Silver paste conductive films are widely used conductive materials in the field of flexible electronics. Their patterning is typically achieved through laser ablation: after printing and curing silver paste on a flexible substrate, a laser scans and ablates the substrate according to a predetermined pattern, removing unwanted conductive areas to form conductive lines. However, laser ablation inevitably produces silver particle redeposition, which adheres to the sidewalls and adjacent areas of the etched trenches. In existing technologies, redeposition is considered a processing defect and usually requires offline cleaning to remove, increasing the number of process steps and manufacturing costs. Furthermore, when forming an insulating layer on the etched conductive film, existing technologies typically rely on masks, photolithography, or precision alignment devices to define the coating area of ​​the insulating layer. This places high demands on the alignment accuracy of the equipment and also limits the improvement of production efficiency.

[0003] Regarding the curing of the insulation layer, existing technologies mostly employ thermal curing, requiring high curing temperatures and long curing times. This process requirement conflicts with the introduction of heat-sensitive functional layers: for example, if a functional silver oxide layer exists on the sidewalls of the etched trench, the thermal curing temperature may cause it to decompose and fail. Simultaneously, the high curing temperature limits the selection of flexible substrates, making substrates with insufficient temperature resistance unsuitable. Furthermore, existing technologies lack effective methods to improve the wettability of the etched trench sidewalls, often resulting in insufficient filling of the insulation material within the trench, affecting the interfacial bonding quality and electrochemical reliability of the insulation layer. From the perspective of electrochemical migration inhibition, existing technologies mainly rely on the physical sealing effect of the insulation layer to block the migration path of silver ions, but do not block it at the silver ion source level. Therefore, the risk of electrochemical migration leading to a decline in insulation performance remains during long-term use. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a technical solution to address one or more problems in the prior art.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for manufacturing an insulating conductive film by etching with silver paste includes the following steps: S1: Printing silver paste on a flexible substrate and drying and curing it to form a conductive layer, wherein the silver paste comprises micron-sized flake silver powder and an organic carrier; S2: The conductive layer is ablated by laser to form a trench. The laser ablation generates redeposited silver nanoparticles on the sidewalls and bottom of the trench. The redeposited silver nanoparticles are retained without being cleaned or removed. S3: The trench is subjected to ultraviolet ozone treatment in an air atmosphere using a low-pressure mercury lamp emitting dual wavelengths of 185nm and 254nm. The treatment temperature does not exceed 80°C. The ultraviolet ozone treatment oxidizes the redeposited silver nanoparticles into silver oxide, and at the same time oxidizes and decomposes the organic residual carbides and adsorbed hydrocarbons on the surface of the conductive layer. S4: The UV-curable insulating ink with static yield stress is coated onto the conductive layer in a continuous film form using a micro-gravure roller full-width coating method without patterning alignment. The UV-curable insulating ink is spontaneously filled in the grooves by capillary force until it is flush with the surface of the conductive layer, and remains a stable film in the flat area on the surface of the conductive layer. S5: Perform a UV curing step on the UV-curable insulating ink, wherein the surface temperature of the substrate does not exceed 60°C during the curing process.

[0006] The micron-sized flake silver powder has a D50 of 1~10μm, an aspect ratio of ≥10:1, and a silver content of ≥60wt%. The organic carrier is an ethyl cellulose and terpineol system or an acrylate and solvent system. The dry film thickness of the conductive layer is 5~25μm.

[0007] The laser ablation uses a 532nm nanosecond pulsed laser with a pulse width of 8-15ns, a repetition frequency of 20-100kHz, and an average power of 5-20W. Nitrogen is used as the protective gas during the laser ablation process at a flow rate of 5-15L / min. The width W of the trench is 30-100μm, the depth H of the trench is 5-25μm, and the ratio of the depth H to the width W of the trench satisfies H≤W / 2.5.

[0008] The ultraviolet ozone treatment time is 5-30 seconds, and the 254nm irradiation intensity of the low-pressure mercury lamp on the substrate surface is 10-50 mW / cm². 2 The distance between the low-pressure mercury lamp and the substrate surface is 5~20mm, the local ozone concentration in the ultraviolet ozone treatment area is 50~500ppm, the 185nm radiation of the low-pressure mercury lamp accounts for ≥30% of the total ultraviolet radiation power, and the low-pressure mercury lamp is a synthetic quartz lamp tube.

[0009] The static yield stress τ0 of the UV-curable insulating ink is 50~200Pa, the surface tension γ is 28~38mN / m, the power law exponent n<0.3 and the thixotropic recovery time is <5s, and the thickness of the continuous film is 2~5μm.

[0010] The UV-curable insulating ink comprises, by weight, 40-60 parts of bisphenol A type epoxy acrylate oligomer, 10-25 parts of aliphatic polyurethane acrylate oligomer, 10-20 parts of 1,6-hexanediol diacrylate, 5-15 parts of tripropylene glycol diacrylate, 3-10 parts of trimethylolpropane triacrylate, 2-5 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-5 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 3-8 parts of hydrophilic fumed silica, 0.1-0.5 parts of fluorocarbon surfactant, and 0.01-0.05 parts of p-methoxyphenol. The BET specific surface area of ​​the hydrophilic fumed silica is 200±25 m². 2 / g.

[0011] The microgravure roller has a diameter of 20-50 mm, and its rotation direction is opposite to that of the substrate feed direction. The ratio of the linear velocity of the microgravure roller to the substrate feed speed is 0.5-1.5. The surface of the microgravure roller is engraved with cells, the cell count is 120-200 L / cm, the cell depth is 8-15 μm, and the cell shape is a square pyramid. The microgravure roller uses an elastic steel scraper with a contact pressure of 1.5-3.5 N / cm.

[0012] The ultraviolet curing step uses a medium-pressure mercury lamp as the light source. The main emission bands of the medium-pressure mercury lamp include 254nm, 313nm, 365nm, 405nm, and 436nm. The energy density of the ultraviolet curing step is 500~3000mJ / cm². 2 The curing time is 0.1~1s. The flexible substrate is a polyethylene terephthalate film or a polyimide film. The thickness of the flexible substrate is 50~200μm and the surface energy is ≥42mN / m.

[0013] A silver paste etched insulating conductive film, comprising: Flexible substrate; A conductive layer is located on the flexible substrate. The conductive layer is formed of silver paste comprising micron-sized flake silver powder and an organic carrier, and the conductive layer has trenches. A silver oxide layer is located on the sidewalls and bottom of the trench. The silver oxide layer is formed by the oxidation of redeposited silver nanoparticles generated by laser ablation with ultraviolet ozone, and has a thickness of 50~200nm. An insulator, filling the trench with a filling height flush with the surface of the conductive layer; and: An insulating film, covering a flat area on the surface of the conductive layer, has a thickness of 2~5μm; The insulator and the insulating film are formed from a UV-curable acrylate composition.

[0014] The micron-sized flake silver powder has a D50 of 1~10μm and an aspect ratio ≥10:1; the conductive layer has a thickness of 5~25μm; the trench has a width W of 30~100μm and a depth H of 5~25μm; the redeposited silver nanoparticles have a particle size of 20~100nm; the flexible substrate is a polyethylene terephthalate film or a polyimide film; the flexible substrate has a thickness of 50~200μm and a surface energy ≥42mN / m.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (i) By combining laser ablation with retention of silver redeposited material and low-temperature selective oxidation with ultraviolet ozone, the redeposited material generated by laser etching is transformed in situ into a silver oxide functional layer. This transforms the "defects" that require offline cleaning in existing technologies into a functional layer with electrochemical migration blocking capabilities. On the one hand, the offline cleaning process is omitted, simplifying the process flow; on the other hand, the poor solubility of silver oxide cuts off the electrochemical migration failure mechanism at the ion source level, unlike existing technologies that rely solely on the physical sealing of the insulating layer to suppress electrochemical migration without blocking it at the ion source level.

[0016] (ii) By combining the improved wettability of the trench sidewalls through the silver oxide functional layer with the capillary-driven spontaneous filling of the insulating ink, selective filling of the insulating ink within the trench is achieved without the need for a precision alignment device. This transforms alignment accuracy from a hardware constraint to a freedom of material formulation design. In existing technologies, the patterning of the insulating layer relies on masks, photolithography, or precision alignment devices. However, this solution drives selective filling through changes in the interfacial properties of the material system itself, reducing dependence on hardware.

[0017] (iii) By combining the yield stress design of the insulating ink with capillary force driving, the ink spontaneously fills the grooves while maintaining the film's self-stability in flat conductive areas due to the yield stress being higher than the capillary driving force, thus suppressing dewetting instability. This combination achieves the unification of full-width printing and selective filling in the same process, unlike existing technologies that require additional processes or devices to limit the coating area of ​​the insulating layer.

[0018] (iv) By combining UV room temperature curing with a silver oxide functional layer, the curing process is completed near room temperature, avoiding the decomposition and damage of the silver oxide functional layer by the thermal curing process, and removing the limitation on the temperature resistance of the substrate. In the prior art, the curing of insulating materials mostly adopts thermal curing, but the low thermal decomposition temperature of silver oxide conflicts with the thermal curing process. This solution eliminates this conflict at the process level by using UV room temperature curing, so that the selection range of flexible substrates is no longer limited by temperature resistance. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to exemplary embodiments.

[0020] I. This invention provides a silver paste etched insulating conductive film and its manufacturing method, which manufactures a conductive film product with alternating conductive lines and insulating bridges on a flexible substrate in a roll-to-roll continuous manner. The process flow includes the following steps: printing conductive silver paste containing micron-sized flake silver powder on a flexible substrate and curing it to form a conductive layer; forming trenches in the conductive layer by laser ablation, retaining the redeposited silver nanoparticles without cleaning; subjecting the redeposited silver nanoparticles to ultraviolet ozone low-temperature selective oxidation treatment to transform them into a silver oxide functional layer, while simultaneously oxidizing and decomposing organic residual carbides on the surface of the conductive layer; covering the entire surface of the conductive layer with ultraviolet-cured insulating ink in the form of a continuous film using a micro-gravure roller full-width coating method, the ink spontaneously filling into the trenches under capillary force and becoming flush with the surface of the conductive layer, while maintaining a stable film in the flat areas of the conductive layer; and curing the insulating ink with ultraviolet light to form a solid insulator filling the trenches and an insulating film covering the surface of the conductive layer.

[0021] The three steps described above—low-temperature selective oxidation with ultraviolet ozone, capillary self-filling in full-width microgravure printing, and room-temperature curing with ultraviolet light—form a causally coupled whole. Ultraviolet ozone oxidation forms a silver oxide functional layer on the trench sidewalls, providing a hydrophilic sidewall prerequisite for capillary self-filling. If thermal curing is used instead, the decomposition of silver oxide at higher temperatures will destroy this functional layer. Therefore, room-temperature curing with ultraviolet light is a necessary condition for the survival of the silver oxide functional layer.

[0022] 2. Raw materials 1. Flexible substrate The flexible substrate is made of polyethylene terephthalate or polyimide, with a thickness of 50~200μm, preferably 75~125μm. Surface roughness Ra≤0.5μm, surface energy≥42mN / m; if insufficient, corona treatment is required. Heat shrinkage rate (longitudinal / transverse)≤1.5% (150℃, 30min). Roll width is 300~1500mm.

[0023] 2. Conductive silver paste The conductive silver paste is a thermosetting type, with micron-sized flake-shaped silver powder, a particle size (D50) of 1~10μm, an aspect ratio ≥10:1, and a silver content ≥60wt%. The organic carrier is either an ethyl cellulose and terpineol system or an acrylate and solvent system. The silver paste viscosity (at 25℃, shear rate 10s) is... -1 The pressure is 5~50 Pa·s. The curing conditions are 120~200℃ and 10~60 min. The sheet resistance after curing is ≤50mΩ / sq (when the film thickness is 10μm), and the film thickness after curing is 5~25μm.

[0024] 3. UV-curable insulating ink (1) Formula composition UV-curable insulating inks are expressed in parts by weight, with each component adjusted independently and no total weight constraint. The specific formulation is as follows: Bisphenol A type epoxy acrylate oligomer: 40-60 parts. Molecular weight 1000-3000 g / mol, functionality 2-4, viscosity 2000-15000 mPa·s (25℃). As a film-forming matrix, it provides hardness, chemical resistance, and insulation, with a volume resistivity greater than 10 Ω·m. 14 Ω·cm.

[0025] Aliphatic polyurethane acrylate oligomer: 10-25 parts. Molecular weight 1500-5000 g / mol, functionality 2-6, glass transition temperature below 0℃. Provides flexibility and adhesion, prevents bending cracking, and has an elongation at break greater than 5%.

[0026] 1,6-Hexanediol diacrylate: 10-20 parts. Functionality 2, molecular weight 226 g / mol, viscosity 7-10 mPa·s. Used as an active diluent monomer to reduce system viscosity and participate in crosslinking reactions.

[0027] Tripropylene glycol diacrylate: 5-15 parts. Functionality 2, molecular weight 300 g / mol, viscosity 15-25 mPa·s. As an active diluent monomer, it provides flexibility and reduces shrinkage.

[0028] Trimethylolpropane triacrylate: 3-10 parts. Functionality 3, molecular weight 296 g / mol, viscosity 100-200 mPa·s. As a multifunctional crosslinking monomer, it improves crosslinking density and hardness.

[0029] 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide: 2-5 parts. It is a type I pyrolysis photoinitiator with a main absorption peak of approximately 278-295 nm, extending to 425 nm. It is suitable for multi-band emission in medium-pressure mercury lamps (313-436 nm) and is responsible for deep curing.

[0030] 2-Hydroxy-2-methyl-1-phenyl-1-propanone: 2-5 parts. It is a type I photoinitiator with main absorption peaks at 247 nm and 285 nm. It is excited by a medium-pressure mercury lamp at the 254 nm wavelength and is responsible for surface and shallow curing.

[0031] Hydrophilic fumed silica: 3-8 parts. BET specific surface area 200±25m². 2 / g, particle size 7~40nm, surface contains silanol groups. As a thixotropic agent, it forms a three-dimensional network structure through hydrogen bonds between surface silanol groups, endowing the system with static yield stress and shear thinning behavior.

[0032] Fluorocarbon surfactant: 0.1~0.5 parts. It is a nonionic perfluoroalkyl ethyl acrylate copolymer or an equivalent short-chain fluorocarbon surfactant (C6 or below). It reduces the surface tension of the ink, ensuring initial spreading of the ink on the substrate surface during printing.

[0033] p-Methoxyphenol: 0.01~0.05 parts. Purity ≥99%. Used as a polymerization inhibitor to prevent thermally initiated polymerization during storage.

[0034] (2) Formula design logic Epoxy acrylates provide rigidity and insulation, while polyurethane acrylates provide flexibility; the combination of the two gives the cured film both hardness and flexural durability. The ratio of the three reactive diluent monomers determines the crosslinking density.

[0035] Fumed silica forms a three-dimensional network structure through hydrogen bonds between surface silanol groups, imparting static yield stress to the system. An addition of 3-8 parts corresponds to a yield stress of approximately 50-200 Pa.

[0036] Fluorocarbon surfactants reduce the surface tension of ink to 28~38mN / m, ensuring that the ink spreads stably on the substrate surface during printing.

[0037] The photoinitiator system of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone covers a wide absorption range of 247~425nm, which matches the multi-band emission of medium-pressure mercury lamps, ensuring complete curing of 2~5μm thick films. If an ultraviolet light-emitting diode is used, 2-hydroxy-2-methyl-1-phenyl-1-propanone has no absorption in the 365nm and 395nm bands, resulting in insufficient curing depth. Therefore, this solution limits the use of medium-pressure mercury lamps.

[0038] (3) Key performance indicators of ink The prepared ink should meet the following performance indicators: Viscosity (25℃, shear rate 100s) -1 ): 200~2000mPa·s, tested using a rotational rheometer.

[0039] Static yield stress τ0 (25℃): 50~200Pa, tested using stress scanning mode, taking the intersection of storage modulus and loss modulus.

[0040] Power law exponent n (shear rate 1~1000s) -1 The value is <0.3, obtained by fitting the steady-state shear flow curve, and the fitting formula is τ=τ0+K·γ. n .

[0041] Thixotropic recovery time (shear rate from 1000s) -1 Reduced to 0.1s -1<5s, using a three-zone thixotropic test.

[0042] Surface tension (25℃): 28~38mN / m, tested using the pendant drop method or the hanging plate method.

[0043] For silver oxide surface contact angles of 30~50°, the seat drop method was used for testing, with a droplet volume of 2μL.

[0044] For silver paste on a flat surface (after UV ozone treatment): contact angle <30°, the seat drop method was used for testing.

[0045] Solid content: ≥95%, is a solvent-free system, close to 100%.

[0046] Storage stability (protected from light at 25°C): ≥6 months without gelation or stratification.

[0047] (4) Key performance indicators of cured film The insulating film cured by ultraviolet light should meet the following performance indicators: Volume resistivity: >10 14 Ω·cm.

[0048] Dielectric strength: >100kV / mm.

[0049] Dielectric constant (1kHz): 3.0~4.0.

[0050] Pencil hardness: ≥2H.

[0051] Adhesion (cross-cut test, for silver film): ≥4B.

[0052] Elongation at break: >5%.

[0053] Bending resistance (R=2mm, 180°): >10,000 cycles without cracking.

[0054] (5) Ink preparation process The ink preparation is carried out according to the following steps: Epoxy acrylate oligomers and polyurethane acrylate oligomers are added to a stainless steel mixing tank with a heating jacket at a temperature of 40-50°C.

[0055] Add 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate, and stir at low speed with an anchor impeller at 200-500 rpm for 10-20 minutes.

[0056] Add 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone, and continue stirring until completely dissolved at 300-600 rpm for 10-15 minutes. This step and subsequent steps should be performed in the dark.

[0057] Add fumed silica slowly in 3-4 portions, with 5-minute intervals between each addition. After each addition, disperse the silica using a high-speed disperser at 1000-2000 rpm for 5-10 minutes. Adding in batches is crucial; adding it all at once will cause severe agglomeration.

[0058] Disperse at high speed until no visible agglomerates are visible, increase the rotation speed to 2000~3000 rpm, and the total dispersion time is 30~60 min.

[0059] The three-roll mill is used for dispersion in 2-3 stages, with the roller spacing gradually adjusted to 10μm.

[0060] Add fluorocarbon surfactant and p-methoxyphenol, and stir at low speed with an anchor-type agitator at 300-500 rpm for 5-10 minutes until homogeneous.

[0061] Vacuum degassing, vacuum degree ≤ -0.08MPa, time 15~30min, rotation speed 100~200rpm.

[0062] Filtered with a 200-mesh (75μm) stainless steel filter.

[0063] Fill into opaque containers, seal and store away from light at a temperature of 15~25℃.

[0064] Perform the entire process in the dark (ambient light < 50 lux or use a yellow safety lamp) to prevent the photoinitiator from being activated by ambient ultraviolet light. Perform rheological property testing within 4 hours of preparation.

[0065] III. Process Steps 1. Silver paste printing and curing (1) Substrate preparation Incoming material inspection includes checking the appearance of the substrate roll, measuring its thickness and surface energy (dyne pen, ≥42mN / m). If the surface energy is <42mN / m, online corona treatment is performed at a power density of 2~5W·min / m. 2 The substrate is treated with an ionizer to eliminate surface static electricity, with a residual voltage <100V. The unwinding tension is set to 30~50N, with tension fluctuation ≤±1N throughout the entire process.

[0066] (2) Silver paste printing Roll-to-roll screen printing is used, with a 300-400 mesh stainless steel screen and an emulsion thickness of 15-20 μm. The squeegee hardness is 60-70 degrees Shore A, the angle is 60-75°, the pressure is 2-5 bar, the printing speed is 1-3 m / min, and the screen spacing is 1.5-2.5 mm. The wet film thickness is 15-25 μm. Conductive patterns are printed according to the product design documents, with a 30-100 μm gap between adjacent lines, which is the subsequent groove width W.

[0067] (3) Drying and curing A three-zone hot air convection oven was used. The first zone was 80℃ for 30-60 seconds; the second zone was 110℃ for 30-60 seconds; and the third zone was 130-200℃ for 60-120 seconds. The total drying time was 120-240 seconds. The dry film thickness after drying was 5-25 μm, and the residual volatile matter was <3 wt%. After curing, sheet resistance (four-probe method), adhesion (cross-cut adhesion test, ≥4B), and film thickness (step tester) were performed. After curing, the substrate was cooled to ≤40℃ using cooling rollers.

[0068] The surface of the cured silver paste conductive film is a dense silver film containing a small amount of organic residual carbides (thermal decomposition products of ethyl cellulose and adsorbed hydrocarbons), with low surface energy and a water contact angle >90°, exhibiting liquefaction.

[0069] 2. Laser ablation forms grooves. (1) Laser parameters A nanosecond pulsed Nd:YAG laser (frequency-doubled output) is used, with a wavelength of 532 nm (preferred) or 1064 nm. The absorption rate of silver at 532 nm is approximately 3-4 times that at 1064 nm, resulting in higher ablation efficiency. The pulse width is 8-15 ns, the repetition rate is 20-100 kHz, and the average power is 5-20 W. Beam quality M... 2 ≤1.5. A galvanometer scanning method is used, coupled with a telecentric F-θ field lens, with a focal length of 100~160mm. The focused spot diameter is 20~35μm (1 / e). 2 Diameter). Scanning speed 200~1000 mm / s. Single pulse energy density 2~8 J / cm². 2 The production line has a conveyor belt speed of 1~6m / min and achieves continuous processing through a flying marking mode. It is equipped with automatic focus tracking to compensate for substrate Z-axis offset.

[0070] (2) Protective gas Nitrogen gas is used as the protective gas at a flow rate of 5-15 L / min, with the purging direction coaxial with the scanning direction. Only nitrogen gas is permitted; compressed air must not be used. Compressed air contains approximately 21% oxygen, which would cause partial oxidation of the redeposited material into silver oxide, resulting in uncontrollable composition. Subsequent ultraviolet ozone oxidation requires the redeposited material to be pure metallic silver, and nitrogen protection ensures this condition.

[0071] (3) Design of ablation parameters The ablation depth is defined as burning through the silver paste layer to the substrate surface, i.e., the trench depth H equals the thickness of the cured silver paste film, typically 5~25 μm. The trench width W is 30~100 μm. The scanning strategy employs single scanning or multiple parallel scanning (line spacing = spot diameter × 0.5~0.8). A negative pressure dust extraction port is installed below the trench, with a flow rate of 50~100 m³ / h. 3 / h, equipped with a high-efficiency air filter.

[0072] (4) Post-ablation state Silver nanoparticles, with a particle size of 20–100 nm, are redeposited on the bottom and sidewalls of the trench, forming a loose, grayish-black layer with a thickness of 50–500 nm. The redeposited material is composed of metallic silver, and trace amounts of carbides may be attached to its surface.

[0073] Redeposition is an unavoidable byproduct of laser ablation. This method does not remove it through cleaning, but rather retains and functionalizes it; this is one of the fundamental differences between this invention and existing technologies.

[0074] 3. Ultraviolet ozone low-temperature selective oxidation (1) Equipment and process parameters The ultraviolet ozone oxidation station uses low-pressure mercury lamps as the light source, employing synthetic quartz tubes to emit dual wavelengths of 185nm and 254nm. The 185nm radiation accounts for ≥30%, and the 254nm wavelength deviation is ≤±2nm. The lamps are arranged in an array parallel to the substrate's conveying direction, with a spacing of 20-50mm and a quantity of 4-20 lamps. The distance between the lamps and the substrate surface is 5-20mm. The 254nm irradiance on the substrate surface is 10-50mW / cm². 2 Effective treatment length: 0.3~1.0m. Treatment time: 5~30s. Treatment temperature: room temperature to 80℃. Atmosphere: air (containing O2 ≥ 20.9 vol%), local ozone concentration: 50~500 ppm.

[0075] Equipped with an infrared thermometer to monitor the substrate surface temperature in real time, with an over-temperature alarm threshold of 80℃. The inner wall of the processing chamber is covered with an aluminum foil reflective surface, and the exhaust gas is treated by an ozone decomposition catalyst, resulting in an ozone concentration of <0.1ppm.

[0076] The oxidation process is complete when the trench sidewalls change color from grayish-black to brownish-black. The oxide layer thickness is 50~200nm.

[0077] (2) Photochemical reaction mechanism The ultraviolet ozone oxidation process involves the following photochemical reaction chain: Primary photolysis (185nm): O2 + hν(185nm) → O( 3 P)+O( 3 P); A 185nm photon has an energy of 6.7 eV, exceeding the dissociation energy of an oxygen molecule (5.1 eV), thus dissociating oxygen into two ground-state oxygen atoms (O). 3 P).

[0078] Ozone formation (three-body reaction): O( 3 P) + O2 + M → O3 + M; M is a third agent (nitrogen or oxygen), which carries away excess energy to stabilize ozone molecules. This reaction occurs rapidly in air at normal pressure, with a time constant of <1 ms.

[0079] Ozone photolysis (254nm): O3 + hν(254nm) → O2 + O( 1 D); The photon energy at 254 nm is 4.9 eV, exceeding the photolysis threshold of ozone (approximately 1.0 eV), thus dissociating ozone into oxygen and excited-state atomic oxygen (O). 1 D). O( 1 D) is the most reactive species in the system with the strongest oxidizing power, with an oxidation potential of 2.8 eV, which is higher than that of ozone (2.07 eV).

[0080] Silver surface oxidation: 2Ag+O( 1 D)→Ag2O (main pathway); 2Ag + O3 → Ag2O + O2 (minor path); O( 1 D) and O3 work together on the silver surface to oxidize metallic silver into silver oxide.

[0081] 185nm is responsible for generating ozone and directly breaking the chemical bonds of organic pollutants on the surface; 254nm is responsible for photolyzing ozone into O(n). 1 D) and directly break the chemical bonds of organic pollutants. The two wavelengths work together to form a steady-state cycle of ozone generation and photolysis.

[0082] (3) Selective oxidation principle Ultraviolet ozone treatment can selectively oxidize the redeposited silver nanoparticles on the trench sidewalls without significantly affecting the dense silver film of the conductive circuit. The physical basis for this is due to the following two factors: Geometric exposure differences The nano-silver particles (20~100nm in diameter) are discrete particles with their entire surface area exposed to an oxidizing atmosphere. Oxidation follows a contraction core model, with the oxidation front advancing simultaneously from all directions toward the particle center. Particles with a diameter of 50nm only need to advance about 25nm to be completely oxidized.

[0083] The dense silver film has only its upper surface exposed. Oxidation follows the planar front model, and the oxidation front needs to advance from the film surface down the entire film thickness (typically 10 μm = 10000 nm), which is three orders of magnitude different from the 25 nm of nanoparticles.

[0084] Surface energy and curvature effect Nanoparticles, due to their high curvature, possess significantly higher surface energy than bulk silver (Gibbs-Thomson effect), resulting in a greater thermodynamic driving force and lower activation energy for oxidation reactions. When the particle size is <100 nm, the surface atomic ratio is >10%, exhibiting a significant accelerating effect.

[0085] Considering the two factors mentioned above, within a UV ozone treatment time of 5-30 seconds, nano-silver particles (thickness <200nm) can be completely oxidized to silver oxide, while the dense silver film only forms an extremely thin oxide layer on its surface that is much thinner than the redeposited particle silver oxide layer, which has no substantial impact on conductivity.

[0086] (4) The role of the silver oxide functional layer The silver oxide functional layer on the sidewalls and bottom of the trench has the following three functions: Chemical anchoring Hydroxyl groups on the surface of silver oxide form hydrogen bonds with polar groups in acrylic inks, while the nano-roughness of silver oxide provides a mechanical interlocking effect. The two work together to provide interfacial bonding force, which is superior to that of metallic silver surfaces covered with organic residues.

[0087] Electrochemical migration blocking Silver oxide is a sparingly soluble oxide (Ksp≈2×10⁻⁶). -8 Under humid and electric field conditions, it does not release free silver ions, thus cutting off the growth path of silver dendrites at the ion source level. This blocking mechanism is independent of the physical sealing of the insulating layer.

[0088] Improved wettability UV ozone treatment improves wettability through a dual mechanism: First, it removes organic residual carbides and adsorbed hydrocarbons from the sintered surface of the silver paste. Ultraviolet ozone oxidizes and decomposes organic matter into carbon dioxide and water, exposing the high surface energy of the silver / silver oxide surface.

[0089] Second, the redeposited nano-silver is oxidized into silver oxide. Silver oxide is a polar metal oxide with high surface energy.

[0090] The two work together to reduce the contact angle of the insulating ink to the trench sidewall from >90° (silver paste sintered surface containing organic residues) to 30~50° (clean silver oxide surface), achieving a qualitative change from hydrophobic to hydrophilic.

[0091] (5) Collateral effects on the substrate The UV ozone treatment simultaneously induces slight photo-oxidation of the exposed polyethylene terephthalate (PET) surface at the bottom of the trench, slightly increasing the surface energy and thus improving ink adhesion. This effect is a byproduct. While the 185nm photon energy exceeds the ester bond energy of PET, the limited dose received by the substrate bottom surface is due to the trench width of only 30–100 μm and the processing time of only 5–30 s. If the trench depth is greater (>20 μm) and the processing time is longer (>20 s), a narrow-band filter with a cutoff of 185nm can be added.

[0092] 4. Microgravure full-width printing and capillary self-filling (1) Microgravure printing process The micro-gravure roller coating method is used in reverse printing mode, where the roller rotates in the opposite direction to the belt feed, so that the ink forms a thinner meniscus and a more uniform coating is obtained.

[0093] The microgravure roller has a diameter of 20-50mm, and the steel core surface is coated with ceramic before laser engraving of the cells. The cell count is 120-200 lines / cm, the depth is 8-15μm, the cells are pyramidal, and the volume is 2-6cm³. 3 / m 2 The doctor blade is made of elastic steel sheet, with a thickness of 0.15~0.20mm, a hardness of HRC52~56, a reverse angle of 30~60°, and a contact pressure of 1.5~3.5N / cm. The ratio S of the printing roller linear speed to the belt speed is 0.5~1.5. The belt speed is 1~6m / min. The impression roller is an elastic rubber pressure roller with a Shore degree of 70~80 and a pressure of 1~3bar.

[0094] Wet film thickness: 2~5μm. Since the ink is solvent-free, the dry film thickness is approximately equal to the wet film thickness. Coating width is the same as the substrate width; no patterning alignment is performed. Tension is controlled at 30~50N, with an accuracy of ≤±1N. A closed ink chamber is used for ink supply, and the ink temperature is controlled at 25±2℃.

[0095] Before using the ink, stir it slowly to restore its uniformity. Measure the viscosity to confirm it is within the range of 200~2000 mPa·s, and measure the yield stress to confirm it is within the range of 50~200 Pa.

[0096] (2) Capillary self-filling mechanism After full-width microgravure printing is completed but before UV curing, the ink selectively and spontaneously fills the surface of the conductive film, based on the matching relationship between capillary pressure and yield stress: Capillary self-filling in the groove region After UV ozone oxidation treatment, a silver oxide functional layer is formed on the sidewalls of the trenches, reducing the contact angle of the insulating ink to 30-50°, making it hydrophilic. The geometry of the trenches generates capillary pressure Pc, which is calculated using the following formula: Pc = 2γ·cosθ / W; Where γ is the surface tension of the ink, θ is the contact angle between the ink and the silver oxide surface, and W is the groove width.

[0097] Substituting typical parameters into the calculation: γ = 35 mN / m = 0.035 N / m, θ = 40°, W = 50 μm = 50 × 10 -6 m, then: Pc=2×0.035×cos(40°) / (50×10 -6 )≈1072Pa; The static yield stress τ0 of the ink is 50~200Pa, which is much smaller than the capillary pressure Pc (Pc / τ0≈5~40). The capillary driving force is much greater than the yield stress, and the ink is spontaneously drawn into the grooves and filled to be flush with the surface of the conductive layer.

[0098] The capillary filling time can be estimated using the Lucas-Washburn equation: t fill =2μL 2 / (γ·r·cosθ); Substituting the parameters: μ≈1~10Pa·s (apparent viscosity of ink at low shear rate), L=H=15μm (fill depth = groove depth), γ=0.035N / m, r=W / 2=25μm (hydraulic radius), cosθ=cos(40°)≈0.77, then t fill ≈0.7~7ms.

[0099] Capillary filling is completed in milliseconds, far faster than production line cycle time (seconds), and has no limitations on production line speed. The time interval between printing completion and UV curing is 1~30s, providing ample safety margin.

[0100] The Lucas-Washburn equation is strictly applicable to Newtonian fluids, but when the driving pressure is much greater than the yield stress (in this scheme, Pc / τ0≈5~40), the yield stress correction factor is close to 1, and the equation is still a reasonable approximation.

[0101] Self-stabilization of thin films in flat regions In the flat areas of the conductive circuit, the ink is covered as a continuous film of 2~5μm. In flat areas, there is no capillary driving force, the Laplace pressure is close to zero, and the static yield stress τ0 is much greater than the Laplace pressure. The ink maintains a stable film, does not flow, and does not dewet.

[0102] The dual behavior of capillary self-filling and film self-stabilization enables full-width printing and selective filling to be achieved in the same process, which is determined by the matching relationship between material formulation and groove geometry, without the need for a precision alignment device.

[0103] 5. UV curing (1) Curing equipment and parameters The UV curing station uses a medium-pressure mercury lamp (iron-doped), with main emission wavelengths of 254, 313, 365, 405, and 436 nm. The lamp power is 120~300 W / cm². The irradiance on the substrate surface is 500~2000 mW / cm². 2 Energy density 500~3000 mJ / cm³ 2 The number of lamp groups is 1 to 4, and the distance between them and the substrate is 50 to 150 mm. The curing time is 0.1 to 1 second.

[0104] A cooling roller (water-cooled, roller surface temperature 20~25℃) is installed on the back of the substrate to control the substrate surface temperature below 60℃. The atmosphere is air, with optional nitrogen protection (oxygen concentration <1000ppm) to eliminate oxygen inhibition effect and improve surface curing degree.

[0105] (2) Curing temperature and stability of silver oxide Silver oxide begins to decompose slowly at approximately 100°C and completely decomposes at 300°C. In this process station, the substrate surface temperature is controlled to ≤60°C using cooling rollers, far below the decomposition initiation temperature. Within the curing time window (<1s), the thermal decomposition rate of silver oxide is negligible, and the functional layer remains intact.

[0106] After curing, samples can be taken for X-ray photoelectron spectroscopy. The 3d5 / 2 binding energy of Ag(I) in silver oxide is 367.4 eV. If this binding energy remains unchanged, it confirms that the silver oxide has not decomposed.

[0107] If a thermosetting method is used (such as thermosetting polyimide above 300℃ or epoxy above 150℃), the curing temperature is far higher than the decomposition temperature of silver oxide, leading to the complete decomposition and failure of the functional layer. Therefore, UV curing at room temperature is a necessary condition for the survival of the silver oxide functional layer.

[0108] (3) Determination of curing effect The curing effect is judged by the following indicators: pencil hardness ≥ 2H, cross-cut adhesion ≥ 4B (3M 600 tape peel), insulation resistance (between adjacent conductive lines, 50μm spacing) > 10. 10 Ω (10V DC).

[0109] IV. Product Structure After Curing After UV curing, the product has the following layered structure: 1. Conductive circuit area: silver paste layer (5~25μm) + extremely thin silver oxide layer on the surface (natural oxidation on dense silver film, which has no substantial impact on conductivity) + UV-cured insulating film (2~5μm, residual layer in flat areas).

[0110] 2. Insulation gap area: Silver oxide functional layer (50~200nm) on the sidewall of the trench + UV-cured insulator inside the trench (filled to be flush with the surface of the conductive layer) + Silver oxide functional layer (same thickness) on the bottom of the trench.

[0111] The total thickness of the product is approximately 60~230μm. The width of the conductive lines is 50~500μm, with a spacing of 30~100μm. Insulation resistance >10 Ω·cm. 9 Ω (500V DC). Withstand voltage > 500V sAC (1min). Bending life (R=2mm) > 10000 cycles.

[0112] The 2-5 μm insulating film remaining in flat areas does not affect the electrical function of the conductive circuit. If it is necessary to expose the pad area, the following methods can be used: Method 1 (Preferred): Pre-clean the pad area at a lower power in the laser ablation station to remove the silver paste layer down to the substrate surface, forming an exposed window. During full-width printing, the ink has weak adhesion to the exposed substrate and can be removed by subsequent wiping.

[0113] Method 2: After UV curing, the cured insulating film in the pad area is removed by high-power laser ablation.

[0114] V. Key Process Constraints 1. Trench width to depth ratio The ratio of groove width W to depth H should be controlled within the range of 2.5:1 to 20:1. If the ratio is too small (<2.5:1), the groove width-to-depth ratio will be too large, making it difficult for air bubbles in the ink to escape, resulting in incomplete filling and residual air bubbles. If the ratio is too large (>20:1), the groove will be too shallow, resulting in insufficient insulation distance. The groove width W should be ≥30μm.

[0115] 2. Matching of capillary pressure and yield stress The static yield stress τ0 of the ink must be less than the capillary pressure Pc generated by the trench, i.e., Pc > τ0. If τ0 ≥ Pc, the ink cannot be driven into the trench by capillary force, the trench will not be filled, and the insulating bridge will be missing. At the same time, the contact angle between the ink and the silver oxide surface must be < 90°, which is a necessary condition for the capillary pressure to be positive (i.e., the spontaneous filling direction).

[0116] 3. Ultraviolet ozone treatment time The UV ozone treatment time should be ≥5 seconds to ensure complete oxidation of the nano-silver and sufficient removal of organic residues. Insufficient treatment time will result in incomplete oxidation, with residual metallic silver posing a risk of electrochemical migration and insufficient improvement in wetting.

[0117] 4. Temperature constraint After the silver oxide functional layer is formed (i.e., after ultraviolet ozone oxidation treatment), the surface temperature of the substrate at each work station must be <80℃. 80℃ is lower than the decomposition initiation temperature of silver oxide (approximately 100℃), and is also the upper limit of the safe heat deformation limit for polyethylene terephthalate substrates.

[0118] 5. Matching wet film thickness with trench depth For microgravure printing, the wet film thickness (2~5μm) must be greater than or equal to the groove depth H to ensure sufficient filling. Since the ink is a solvent-free system, the dry film is approximately equal to the wet film, and the wet film thickness must meet the volume required to fill the grooves.

[0119] VI. Parameter Linkage Relationship The following interrelationships exist among the various process parameters in this method: 1. When the conveyor belt speed is increased, the ultraviolet ozone treatment time is shortened accordingly. It is necessary to increase the number of lamps or increase the irradiation intensity to maintain a treatment time of ≥5s.

[0120] 2. As the conveyor belt speed increases, the UV curing energy density decreases accordingly. Therefore, it is necessary to increase the number of lamps or increase the power to maintain the energy density between 500 and 3000 mJ / cm³. 2 Within the range.

[0121] 3. When the groove width decreases, the capillary pressure Pc increases, allowing the use of inks with higher yield stress (more resistant to sagging), but it should be noted that the groove width must not be less than 30μm.

[0122] 4. When the amount of fumed silica added increases, the yield stress τ0 increases. It is necessary to confirm that τ0 is still < Pc, otherwise the ink cannot fill the groove.

[0123] 5. When the ink viscosity increases, the amount of microgravure transfer decreases and the wet film becomes thinner. It is necessary to confirm that the wet film thickness is still ≥ the groove depth H, otherwise the filling amount will be insufficient.

[0124] VII. Overall Production Line Layout and Environmental Control 1. Production line layout The production line is arranged sequentially along the conveyor belt direction as follows: unwinding machine, silver paste printing station, drying and curing station, laser ablation station, ultraviolet ozone oxidation station, microgravure printing station, ultraviolet curing station, online inspection station, and rewinding machine. The total length of the production line is approximately 7.5~13.0m.

[0125] The tension throughout the line is kept constant at 30~50N, with fluctuations ≤±1N. The conveyor speed at each station is uniformly 1~6m / min, driven uniformly by the main drive roller.

[0126] 2. Environmental control The ambient temperature is 22~28℃, the ambient humidity is 40~60%RH, and the cleanliness level is ISO Class 7 (Class 10,000 cleanroom) or better. Static electricity control uses ionizers and grounded guide rollers, with residual voltage on the substrate surface <100V. The UV ozone station has an independent exhaust system, with ozone emission concentration <0.1ppm.

[0127] 3. Online testing Online inspection points are set up at the exit of each workstation: after drying and curing, the dry film thickness is measured; after laser ablation, the groove width and depth are measured; after ultraviolet ozone oxidation, color changes are monitored with a colorimeter, and samples are taken periodically for XPS confirmation; after microgravure printing, the fill integrity is measured; after ultraviolet curing, the hardness, adhesion, insulation resistance, and sheet resistance are measured. Continuous full-width linear CCD inspection is used to detect appearance defects.

[0128] VIII. Rolling and Storage The winding tension should be 30~50N, with taper tension control and alignment accuracy ≤±0.5mm. If the cured film surface is slightly sticky, insert a polyethylene release film during winding. Storage conditions: temperature 15~30℃, relative humidity <70%RH, protected from light.

[0129] To verify the actual impact of each core technical feature on product performance, experiments were designed for systematic investigation. Each time, only one technical feature parameter was changed while the others remained constant, and the significance was determined by comparing changes in key performance indicators. All test methods were performed in accordance with currently effective national or international standards.

[0130] IX. Basis for Variable Selection The core technical features of this method form a causal chain: micron-sized flake silver powder provides the physical prerequisite for selective oxidation; ultraviolet ozone oxidation transforms the redeposited silver into a silver oxide functional layer, changing the trench sidewalls from hydrophobic to hydrophilic; the hydrophilic sidewalls of silver oxide make spontaneous capillary filling possible; the trench width determines the magnitude of capillary pressure; ultraviolet light room temperature curing ensures that the functional layer does not decompose.

[0131] Silver powder particle size is a physical prerequisite for the selective oxidation mechanism. Selective oxidation depends on the order-of-magnitude difference in oxidation kinetics between the redeposited nanoparticles and the dense silver film: nanoparticles follow a contracting core model, and can be completely oxidized with a propagation distance of only about 25 nm; dense silver films follow a planar front model, and can be propelled over a distance in the micrometer range.

[0132] The duration of ultraviolet ozone treatment directly controls the integrity of the formation of the silver oxide functional layer. Insufficient treatment time results in incomplete oxidation of redeposited particles, insufficient decomposition of organic residues, and incomplete improvement in wettability and inhibition of electrochemical migration. Excessive treatment time leads to excessive growth of the oxide layer on the surface of the dense silver film, which may increase sheet resistance.

[0133] The width of the groove directly determines the magnitude of the capillary pressure and is inversely proportional to it. If the groove width is too small, the depth-to-width ratio increases, making it difficult for air bubbles to escape; if it is too large, the capillary pressure decreases to near the yield stress, resulting in insufficient filling driving force.

[0134] Based on the above assessment, the ultraviolet ozone treatment time and trench width were selected as the two experimental variables.

[0135] 10. General Rules for Experimental Sample Preparation Except for the variables specifically specified in each experiment, all samples were prepared under the following uniform conditions: The flexible substrate is made of polyethylene terephthalate film with a thickness of 125 μm, a surface roughness Ra≤0.5 μm, and a surface energy ≥42 mN / m. The substrate is cut into sheet samples of 200 mm × 200 mm.

[0136] The conductive silver paste is a thermosetting silver paste made from micron-sized flake silver powder. The silver powder particle size (D50) is 5μm, the aspect ratio of the flake silver powder is ≥10:1, and the silver content is 75wt%. The organic carrier is an ethyl cellulose and terpineol system. Conductive patterns are printed using screen printing with a 300-mesh stainless steel screen, an emulsion thickness of 18μm, a squeegee hardness of 65 Shore A, a squeegee angle of 70°, a squeegee pressure of 3 bar, and a screen spacing of 2mm. The printed pattern is a comb-like cross-line pattern, with the spacing between adjacent lines set according to experimental requirements. The wet film thickness is approximately 20μm.

[0137] After printing, the film was dried and cured in a three-zone hot air oven: 80℃ for 45 seconds in the first zone, 110℃ for 45 seconds in the second zone, and 150℃ for 90 seconds in the third zone. The cured dry film thickness was approximately 15 μm. The sheet resistance after curing was measured using the four-probe method as the initial value, and the adhesion was confirmed to be ≥4B using the cross-cut adhesion test.

[0138] Laser ablation was performed using a nanosecond pulsed Nd:YAG laser (frequency-doubled output) with a wavelength of 532 nm, a pulse width of 10 ns, a repetition rate of 50 kHz, an average power of 10 W, and a beam quality of M. 2 ≤1.5, focused spot diameter approximately 25μm, scanning speed 500mm / s, single pulse energy density approximately 5J / cm² 2 Nitrogen gas was used as the protective gas at a flow rate of 10 L / min, and the purging direction was coaxial with the scanning direction. A negative pressure dust suction port was installed at the bottom of the trench, with a flow rate of 75 m³ / min. 3 / h, equipped with a high-efficiency air filter. The trench depth is equal to the thickness of the silver paste cured film (approximately 15μm).

[0139] Ultraviolet ozone treatment uses a low-pressure mercury lamp (dual wavelengths 185nm and 254nm), a synthetic quartz lamp tube, with 185nm radiation accounting for ≥30%, a lamp tube distance of 10mm from the sample surface, and a 254nm irradiance intensity of 30mW / cm² on the substrate surface.2 The process is carried out in an air atmosphere at a temperature of room temperature (25°C) to no more than 80°C.

[0140] The insulating ink is formulated using the aforementioned recipe, and its key performance indicators are: viscosity (at 25°C, shear rate 100s). -1 The static yield stress τ0 is approximately 100 Pa, the surface tension is approximately 35 mN / m, and the contact angle with the silver oxide surface is approximately 40°.

[0141] Full-width microgravure printing employs a microgravure roller coating method, using a reverse printing mode. The roller diameter is 30mm, the cell count is 150 lines / cm, the cell depth is 12μm, and the cells are pyramidal. The squeegee is a flexible steel sheet, 0.18mm thick, with a hardness of HRC54, a reverse angle of 45°, and a contact pressure of 2.5N / cm. The ratio of roller linear speed to belt speed is S=1.0. The wet film thickness is approximately 3μm.

[0142] UV curing uses a medium-pressure mercury lamp (iron-doped) with a lamp power of 200W / cm², and the irradiance on the substrate surface is approximately 1000mW / cm². 2 Energy density approximately 1500 mJ / cm³ 2 The distance between the lamp assembly and the substrate is 100mm. A water-cooled cooling roller is installed on the back of the substrate, with a roller surface temperature of 22℃ and a substrate surface temperature ≤60℃.

[0143] Experiment 1: The Effect of Ultraviolet Ozone Treatment Time 1. Variable setting Set five processing time levels: (1) Group B0: 0s (no ultraviolet ozone treatment, used as a blank control); (2) Group B1: 5s; (3) Group B2: 15s; (4) Group B3: 30s; (5) Group B4: 60s.

[0144] All samples used the same micron-sized flake silver powder (D50=5μm) and the same laser ablation parameters (groove width 50μm, depth approximately 15μm), with only the UV ozone treatment time varying. After treatment, full-width microgravure printing and UV curing were performed.

[0145] 2. Test Items and Methods (1) Contact angle of trench sidewall The contact angle of the redeposited surface with the insulating ink was measured using the seated drop method at various treatment times. The insulating ink was used as the test liquid, with a droplet volume of 2 μL and a test temperature of 25 °C. At least 5 locations were measured for each group, and the average value was taken.

[0146] Expected results: The contact angle of group B0 is >90°, gradually decreasing with increasing treatment time, dropping to 30-50° in the range of 5-30s, and slowing down at 60s.

[0147] (2) Analysis of silver oxidation state X-ray photoelectron spectroscopy was used to analyze the silver oxidation state of the redeposited material on the trench sidewalls at different treatment times. The trench area was tested (due to its small size, a large-area analysis mode was used, with a spot size of approximately 400 μm to ensure coverage of the trench area). The Ag(I)3d5 / 2 binding energy of 367.4 eV was used as the criterion for silver oxide formation.

[0148] Expected result: Group B0 shows pure Ag 0 Characteristics: Groups B2 and B3 are dominated by Ag(I), while group B4 is similar to group B3.

[0149] (3) Changes in sheet resistance of conductive lines The four-probe method was used to measure the rate of change of sheet resistance of the conductive circuit before and after processing at each processing time.

[0150] Expected results: The rate of change of sheet resistance is small in the range of 5~30s, and may increase at 60s.

[0151] (4) Trench filling integrity After full-width microgravure printing and UV curing, cross-sectional samples were prepared from samples processed at each time point. The filling of the insulator within the trenches was observed using an optical microscope. The following indicators were evaluated: Fill rate: The percentage of the trench cross-sectional area filled by insulators, as observed and statistically analyzed in cross-section.

[0152] Bubbles / voids: Whether there are bubbles or voids in the trench.

[0153] Fill height: The height difference between the top surface of the insulator and the surface of the conductive layer, preferably flush.

[0154] Expected results: Group B0 trenches are not filled or are not completely filled; Groups B1 to B3 are completely filled; Group B4 is consistent with Groups B2 to B3.

[0155] (5) Insulation resistance Insulation resistance between adjacent conductive lines was measured using samples cured with UV light. The test voltage was 500V DC, and the resistance value was read after 60 seconds of voltage application. A three-electrode system was used: two adjacent conductive lines served as the measuring electrode and the grounding electrode, respectively, with a protective electrode placed outside the measuring electrode to eliminate the influence of surface leakage current. At least three pairs of adjacent lines were measured for each sample, and the average value was taken.

[0156] The test temperature was 23℃±2℃, and the relative humidity was 50%±5%. Before the test, the sample was placed in the test environment for more than 24 hours to achieve temperature and humidity equilibrium.

[0157] Expected results: The insulation resistance of group B0 is significantly lower, while groups B1-B3 reach 10. 9 Above Ω, group B4 is similar to group B3.

[0158] (6) Accelerated Electrochemical Migration Test Specialized comb-shaped electrode samples were prepared for accelerated electrochemical migration experiments. The conductive circuitry of the samples was designed as a comb-shaped cross structure with a line width of 200 μm and a line spacing of 50 μm. The cross-line areas were laser-ablated and treated with UV ozone for various processing times before being filled with insulating ink and cured with UV light.

[0159] The sample was placed in a constant temperature and humidity test chamber at a temperature of 85℃±2℃ and a relative humidity of 85%±5%. A DC bias voltage of 10V was applied between adjacent conductive lines for 500 hours. The insulation resistance between adjacent lines was measured every 24 hours during the test. The change curve of insulation resistance over time was recorded.

[0160] After the experiment, the decreasing trend of insulation resistance was used as the criterion for whether electrochemical migration had occurred.

[0161] Expected results: The insulation resistance of group B0 may drop sharply in the later stage, while groups B2 and B3 will remain stable.

[0162] Experiment 12: The Influence of Trench Width 1. Variable setting Set five horizontal groove widths: (1) Group C1: 20 μm (below the range described in this method); (2) Group C2: 30μm (lower limit); (3) Group C3: 50μm (preferred value); (4) C4 group: 100μm (upper limit).

[0163] (5) Group C5: 150 μm (above the range described in this method) The trench depth was uniformly approximately 15 μm. The aspect ratios (H / W) for each group were as follows: Group C1 0.75:1, Group C2 0.5:1, Group C3 0.3:1, Group C4 0.15:1, and Group C5 0.1:1. All samples used the same micron-sized flake silver powder (D50 = 5 μm), the same UV ozone treatment time (15 s), the same insulating ink and printing process, and the same UV curing conditions.

[0164] 2. Test Items and Methods (1) Trench filling integrity Cross-sectional samples were prepared using the same method as in Experiment 1 and observed using an optical microscope. The fill ratio, air bubbles / voids, and fill height were evaluated.

[0165] Expected results: Group C1 may not be completely filled; Groups C2 to C4 will be completely filled; Group C5 may have insufficient filling drive.

[0166] (2) Calculation of theoretical capillary pressure Based on the measured surface tension γ of the ink, the contact angle θ with the silver oxide surface, and the groove width W for each group, the capillary pressure Pc = 2γcosθ / W was calculated. Simultaneously, the static yield stress τ0 of the ink was measured to verify whether the matching condition Pc > τ0 was satisfied.

[0167] The surface tension of the ink was measured using the pendant drop method: an ink droplet was formed using a micro-sampler, and the droplet profile image was captured using optical projection. The surface tension was calculated by fitting the image using the Yang-Laplace equation. The test temperature was 25℃, and at least three measurements were taken, with the average value taken.

[0168] The static yield stress of the ink was measured using a rotational rheometer with a conical clamp (1° cone angle, 40mm diameter), in stress scanning mode, logarithmically increasing stress, a scanning range of 0.1~1000Pa, and a frequency of 1Hz. The stress value corresponding to the intersection of the storage modulus G' and the loss modulus G'' was taken as the static yield stress τ0. The test temperature was 25℃.

[0169] Expected results: Pc in groups C1 to C4 is significantly greater than τ0, while Pc in group C5 may be close to τ0.

[0170] (3) Insulation resistance The insulation resistance between adjacent conductive lines was measured using the same three-electrode system and method as in Experiment 1. The test voltage was 500V DC, and the reading was taken after 60 seconds.

[0171] Expected results: The insulation resistance of groups C1 and C5 may be too low, while groups C2 to C4 will reach 10. 9 Ω and above.

[0172] (4) Dielectric strength Measure the dielectric strength (withstand voltage) between adjacent conductive lines. Apply AC voltage in a continuously increasing manner at a rate of 500V / s until breakdown occurs. Record the voltage value at breakdown and divide it by the trench width to obtain the dielectric strength (kV / mm). Measure at least 3 pairs of adjacent lines for each sample and take the average value.

[0173] The test is conducted in an insulating oil medium to prevent surface flashover. A ball-to-ball electrode or flat electrode system is used, with the upper electrode having a diameter of 25 mm and the lower electrode grounded.

[0174] Expected results: The dielectric strength of groups C2 to C4 will reach over 100kV / mm, while groups C1 and C5 may be lower.

[0175] (5) Film stability in flat areas The surface morphology of the insulating film in the flat area of ​​the conductive circuit after UV curing was observed using a white light interferometer to assess whether dewetting, pinholes, or uneven thickness had occurred. The measurement area was 100 mm × 100 mm, and the sampling resolution was 10 μm. The uniformity of film thickness and the number of surface defects were recorded.

[0176] Expected results: The insulating film in the flat areas of each group should maintain a uniform thickness of 2~5μm and be free of dewetting pinholes.

[0177] XIII. Experimental Data Processing Data for each group were recorded as mean ± standard deviation. A t-test was used to compare two groups, and a one-way ANOVA was used to compare multiple groups. The significance level was p < 0.05.

[0178] XIV. Exemplary Description Because the above experimental methods are objective and reasonable, a selection of experimental groups were chosen as examples. Except for specifically specified variables, all other parameters remained consistent.

[0179] 1. Example 1: Time Variable in Ultraviolet Ozone Treatment Experimental Group 1 (Conventional Group) The flexible substrate is made of polyethylene terephthalate film with a thickness of 125 μm, a surface roughness Ra of 0.3 μm, and a surface energy of 45 mN / m.

[0180] The conductive silver paste is a thermosetting type, with micron-sized flake silver powder, a particle size D50 of 5μm, an aspect ratio of 12:1, and a silver content of 75wt%. The organic carrier is an ethyl cellulose and terpineol system. The viscosity of the silver paste is (25℃, shear rate 10s). -1 The value is 15 Pa·s.

[0181] The silver paste printing was performed using screen printing with a 300-mesh stainless steel screen, an emulsion thickness of 18μm, a squeegee hardness of 65 Shore A, a squeegee angle of 70°, a squeegee pressure of 3 bar, a screen spacing of 2mm, and a printing speed of 2m / min. The printed pattern consisted of comb-like intersecting lines, with conductive lines 300μm wide and adjacent lines spaced 50μm apart. The wet film thickness was 20μm.

[0182] The silver paste was cured using a three-zone hot air oven: the first zone was 80℃ for 45 seconds, the second zone was 110℃ for 45 seconds, and the third zone was 150℃ for 90 seconds. The cured dry film thickness was 15μm.

[0183] Laser ablation was performed using a nanosecond pulsed Nd:YAG laser (frequency-doubled output) with a wavelength of 532 nm, a pulse width of 10 ns, a repetition rate of 50 kHz, an average power of 10 W, and a beam quality of M. 2 The wavelength is 1.3, the focused spot diameter is 25 μm, the scanning speed is 500 mm / s, and the single-pulse energy density is 5 J / cm². 2 The protective gas was nitrogen, with a flow rate of 10 L / min, and the purging direction was coaxial with the scanning direction. The ablation depth was equal to the thickness of the solidified silver paste film, with a trench depth H of 15 μm and a trench width W of 50 μm. After ablation, the redeposited silver nanoparticles were retained on the trench sidewalls and bottom without being removed by cleaning.

[0184] The ultraviolet ozone treatment uses a low-pressure mercury lamp (dual wavelengths 185nm and 254nm), a synthetic quartz lamp tube, with 35% of the radiation at 185nm. The distance between the lamp tube and the substrate surface is 10mm, and the irradiance at 254nm on the substrate surface is 30mW / cm². 2 The processing time is 15 seconds, and the surface temperature of the substrate is 25~48℃ during the process, which is carried out in an air atmosphere.

[0185] The formulation of the UV-curable insulating ink is as follows: 50 parts of bisphenol A type epoxy acrylate oligomer (molecular weight 2000 g / mol, functionality 3), 18 parts of aliphatic polyurethane acrylate oligomer (molecular weight 3000 g / mol, functionality 4), 15 parts of 1,6-hexanediol diacrylate, 10 parts of tripropylene glycol diacrylate, 6 parts of trimethylolpropane triacrylate, 3 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 3 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 5 parts of hydrophilic fumed silica (BET specific surface area 200 m²). 2 / g), 0.3 parts fluorocarbon surfactant, and 0.03 parts p-methoxyphenol. The ink performance indicators are: viscosity (25℃, shear rate 100s) -1 The static yield stress τ0 is 100 Pa, the power law exponent n is 0.25, the surface tension γ is 35 mN / m, and the contact angle θ on the silver oxide surface is 40°.

[0186] Microgravure printing employs a microgravure roller coating method in reverse printing mode (the roller rotation direction is opposite to the belt feed direction). The roller diameter is 30mm, and the steel core surface is ceramic-coated followed by laser engraving of the cells. The cell count is 150 lines / cm, the cell depth is 12μm, and the cells are pyramidal. The elastic steel squeegee is 0.18mm thick, with a hardness of HRC54, a reverse angle of 45°, and a contact pressure of 2.5N / cm. The ratio of roller linear speed to belt feed speed (S) is 1.0. The wet film thickness is 4μm. Full-width coating is used, without patterned alignment.

[0187] UV curing uses a medium-pressure mercury lamp (iron-doped) with a lamp power of 200W / cm², and the irradiance on the substrate surface is 1000mW / cm². 2 Energy density 1500 mJ / cm³ 2 The distance between the lamp assembly and the substrate is 100mm. A water-cooled cooling roller is installed on the back of the substrate, with a roller surface temperature of 22℃. During the curing process, the surface temperature of the substrate does not exceed 55℃.

[0188] Experimental Group 2 (Conventional Group) The difference between this experimental group and experimental group one is that the ultraviolet ozone treatment time is 5 seconds.

[0189] Experimental Group 3 (Conventional Group) The difference between this experimental group and experimental group one is that the ultraviolet ozone treatment time is 30 seconds.

[0190] Experimental group four (control group) The difference between this experimental group and Experimental Group 1 is that the UV ozone treatment time is 0s (no UV ozone treatment is performed, and the substrate directly enters the next station).

[0191] 2. Example 2: Variation in trench width Experimental Group 1 (Conventional Group) The difference between this experimental group and Experimental Group 1 of Example 1 is that the trench width is 30μm (the laser scanning path spacing is adjusted accordingly, and the conductive line width remains 300μm).

[0192] Experimental Group 2 (Conventional Group) The difference between this experimental group and Experimental Group 1 of Example 2 is that the groove width is 50μm.

[0193] Experimental Group 3 (Conventional Group) The difference between this experimental group and Experimental Group 1 of Example 2 is that the groove width is 100μm.

[0194] Experimental group four (control group) The difference between this experimental group and Experimental Group 1 of Example 2 is that the groove width is 20μm.

[0195] Experimental group 5 (control group) The difference between this experimental group and Experimental Group 1 of Example 2 is that the groove width is 150μm.

[0196] 3. Blank control group The blank control group uses existing technology and processes, and the specific procedures are as follows: The flexible substrate, conductive silver paste, silver paste printing and curing process are exactly the same as those in Experiment 1 of Example 1.

[0197] The laser ablation process was exactly the same as that in Experiment 1 of Example 1, with a trench width of 50 μm and a trench depth of 15 μm.

[0198] Following laser ablation, plasma cleaning was used to remove the redeposited silver nanoparticles from the sidewalls and bottom of the trench. The plasma cleaning employed oxygen plasma with a radio frequency power of 100W, a processing time of 60 seconds, and a working pressure of 0.3Pa. After cleaning, the exposed dense silver film surface (containing residual organic carbides) on the sidewalls and bottom of the trench was left untreated with ultraviolet ozone.

[0199] The insulating layer coating was applied using a precision alignment screen printing method. Alignment was achieved using a charge-coupled device (CCD) vision system with an accuracy of ±10 μm. A 200-mesh stainless steel screen was used, and the emulsion thickness was 15 μm. The insulating ink was a two-component epoxy resin thermosetting insulating ink (not the UV-curable acrylic ink described in this invention), patterned and applied to the groove areas using screen printing. Curing was performed in a 150°C hot air convection oven for 30 minutes.

[0200] 4. Experimental Data Recording The test results of the final product performance parameters for each experimental group are shown in the table below. Sheet resistance was measured at five locations using the four-probe method, and the average value was taken. Insulation resistance was measured using a three-electrode system, with a DC voltage of 500V applied for 60 seconds, and the reading was taken at a test temperature of 23℃±2℃. Fill rate was obtained through cross-sectional observation and statistical analysis.

[0201] The data is summarized into the following table (Table 1): Table 1. Summary Table of Experimental Data

[0202] The experimental results of each embodiment are analyzed below to explore the underlying reasons for the performance trends at the molecular level.

[0203] XV. Analysis of the Influence of Ultraviolet Ozone Treatment Time Example 1 shows a phased change characteristic. The untreated group has an extremely low fill rate and significantly low insulation resistance; from 5s to 15s, the fill rate and insulation resistance increase significantly; from 15s to 30s, the increase slows down but the sheet resistance increases slightly.

[0204] In the untreated state, the surface of the redeposited particles is covered with organic carbides and adsorbed hydrocarbons, exhibiting lignophalism (contact angle > 90°) and negative capillary pressure, preventing spontaneous ink filling. Simultaneously, metallic silver can release silver ions under humid conditions and an electric field, forming an electrochemical migration ion source.

[0205] In the 5s treatment stage, the photochemical reaction chain has been initiated but not fully completed. Organic matter removal and silver oxide formation have been partially completed, and the contact angle has decreased to the hydrophilic range, but metallic silver nuclei still remain inside the particles, and the filling rate and insulation resistance have not yet reached their optimal levels.

[0206] During the 15s processing stage, the redeposited particles are completely oxidized to silver oxide, and the organic matter is fully decomposed. The contact angle stabilizes within the hydrophilic range, the capillary pressure is sufficiently greater than the yield stress, and the ink is completely filled. As a sparingly soluble oxide, silver oxide does not release silver ions, thus cutting off electrochemical migration at the ion source level.

[0207] The increase slows down between 15s and 30s because the particles are almost completely oxidized. The slight increase in sheet resistance is due to the continued slow growth of the oxide layer on the surface of the dense silver film. Silver oxide is a semiconductor, and the increase in thickness slightly reduces the effective conductive cross-sectional area.

[0208] XVI. Analysis of the Influence of Trench Width Example 2 shows that all groups of trench widths within the defined range achieved near-complete filling, and the insulation resistance was on the same order of magnitude; the control groups below the lower limit and above the upper limit both showed a decrease in filling rate and a decrease in insulation resistance, but the mechanisms of decrease were different.

[0209] Capillary pressure is inversely proportional to groove width. Within the defined range, the capillary pressure of each group is significantly greater than the yield stress, satisfying the matching condition. However, there are slight differences in filling rate among the groups, stemming from the competition between capillary pressure and the difficulty of bubble removal.

[0210] The highest filling rate is achieved at 50 μm, representing the optimal balance between capillary driving force and bubble removal capability. At 30 μm, the capillary pressure increases, but the increased aspect ratio leads to increased resistance to bubble removal. At 100 μm, bubble removal is easier, but the decreased capillary pressure weakens the driving force in the later stages.

[0211] The filling rate of the 20μm group decreased significantly because the aspect ratio was too large, and the air bubbles were trapped at the bottom of the groove and could not be discharged, forming cavitation, which led to a decrease in filling rate and a shortening of insulation distance.

[0212] The 150μm group experienced a more severe decrease in filling rate, but the mechanism was different. The capillary pressure dropped significantly to near the yield stress level, and the ink front stalled due to pressure decay during its advancement, leaving the bottom of the groove unfilled.

[0213] The sheet resistance of each group is basically the same, indicating that the trench width does not affect the oxidation behavior of ultraviolet ozone on the conductive circuit. The oxidation behavior depends on the particle size and the microstructure of the dense silver film.

[0214] XVII. Comparative Analysis of Blank Control Group The blank control group had a sheet resistance that was basically the same as that of the conventional group, but its insulation resistance was significantly lower than that of all conventional groups, and its fill rate was also lower than that of the optimal group.

[0215] There are two reasons for the low insulation resistance: First, plasma cleaning removes the redeposited material, but the exposed metallic silver on the sidewalls is not converted into silver oxide, which can release silver ions and trigger electrochemical migration; second, the volume shrinkage rate of thermosetting epoxy is higher than that of UV-cured acrylate, which may produce microcracks that provide channels for silver ion migration.

[0216] The low fill rate is due to the lack of capillary self-filling driving force in precision alignment screen printing. The ink is deposited by gravity and pressed in by the doctor blade pressure. The thermosetting epoxy ink has high viscosity and poor fluidity, and the air bubbles are not fully expelled.

[0217] In summary, the two variables affect product performance at different levels: processing time determines the integrity of functional layer formation (molecular reaction kinetics level), while trench width determines the capillary pressure magnitude and bubble removal capacity (mesoscopic geometry level). They correspond to different stages of the causal chain, and their influence dimensions do not overlap.

[0218] The technical features described above can be combined in any way. For the sake of brevity, not all possible combinations of the technical features described above are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for manufacturing an insulating conductive film by etching with silver paste, characterized in that: Includes the following steps: S1: Printing silver paste on a flexible substrate and drying and curing it to form a conductive layer, wherein the silver paste comprises micron-sized flake silver powder and an organic carrier; S2: The conductive layer is ablated by laser to form a trench. The laser ablation generates redeposited silver nanoparticles on the sidewalls and bottom of the trench. The redeposited silver nanoparticles are retained without being cleaned or removed. S3: The trench is subjected to ultraviolet ozone treatment in an air atmosphere using a low-pressure mercury lamp emitting dual wavelengths of 185nm and 254nm. The treatment temperature does not exceed 80°C. The ultraviolet ozone treatment oxidizes the redeposited silver nanoparticles into silver oxide, and at the same time oxidizes and decomposes the organic residual carbides and adsorbed hydrocarbons on the surface of the conductive layer. S4: The UV-curable insulating ink with static yield stress is coated onto the conductive layer in a continuous film form using a micro-gravure roller full-width coating method without patterning alignment. The UV-curable insulating ink is spontaneously filled in the grooves by capillary force until it is flush with the surface of the conductive layer, and remains a stable film in the flat area on the surface of the conductive layer. S5: Perform a UV curing step on the UV-curable insulating ink, wherein the surface temperature of the substrate does not exceed 60°C during the curing process.

2. The method according to claim 1, characterized in that, The micron-sized flake silver powder has a D50 of 1~10μm, an aspect ratio of ≥10:1, and a silver content of ≥60wt%. The organic carrier is an ethyl cellulose and terpineol system or an acrylate and solvent system. The dry film thickness of the conductive layer is 5~25μm.

3. The method according to claim 1, characterized in that, The laser ablation uses a 532nm nanosecond pulsed laser with a pulse width of 8-15ns, a repetition frequency of 20-100kHz, and an average power of 5-20W. Nitrogen is used as the protective gas during the laser ablation process at a flow rate of 5-15L / min. The width W of the trench is 30-100μm, the depth H of the trench is 5-25μm, and the ratio of the depth H to the width W of the trench satisfies H≤W / 2.

5.

4. The method according to claim 1, characterized in that, The ultraviolet ozone treatment time is 5-30 seconds, and the 254nm irradiation intensity of the low-pressure mercury lamp on the substrate surface is 10-50 mW / cm². 2 The distance between the low-pressure mercury lamp and the substrate surface is 5~20mm, the local ozone concentration in the ultraviolet ozone treatment area is 50~500ppm, the 185nm radiation of the low-pressure mercury lamp accounts for ≥30% of the total ultraviolet radiation power, and the low-pressure mercury lamp is a synthetic quartz lamp tube.

5. The method according to claim 1, characterized in that, The static yield stress τ0 of the UV-curable insulating ink is 50~200Pa, the surface tension γ is 28~38mN / m, the power law exponent n<0.3 and the thixotropic recovery time is <5s, and the thickness of the continuous film is 2~5μm.

6. The method according to claim 1, characterized in that, The UV-curable insulating ink comprises, by weight, 40-60 parts of bisphenol A type epoxy acrylate oligomer, 10-25 parts of aliphatic polyurethane acrylate oligomer, 10-20 parts of 1,6-hexanediol diacrylate, 5-15 parts of tripropylene glycol diacrylate, 3-10 parts of trimethylolpropane triacrylate, 2-5 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-5 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 3-8 parts of hydrophilic fumed silica, 0.1-0.5 parts of fluorocarbon surfactant, and 0.01-0.05 parts of p-methoxyphenol. The BET specific surface area of ​​the hydrophilic fumed silica is 200±25 m². 2 / g.

7. The method according to claim 1, characterized in that, The microgravure roller has a diameter of 20-50 mm, and its rotation direction is opposite to that of the substrate feed direction. The ratio of the linear velocity of the microgravure roller to the substrate feed speed is 0.5-1.

5. The surface of the microgravure roller is engraved with cells, the cell count is 120-200 L / cm, the cell depth is 8-15 μm, and the cell shape is a square pyramid. The microgravure roller uses an elastic steel scraper with a contact pressure of 1.5-3.5 N / cm.

8. The method according to claim 1, characterized in that, The ultraviolet curing step uses a medium-pressure mercury lamp as the light source. The main emission bands of the medium-pressure mercury lamp include 254nm, 313nm, 365nm, 405nm, and 436nm. The energy density of the ultraviolet curing step is 500~3000mJ / cm². 2 The curing time is 0.1~1s. The flexible substrate is a polyethylene terephthalate film or a polyimide film. The thickness of the flexible substrate is 50~200μm and the surface energy is ≥42mN / m.

9. A silver paste etched insulating conductive film, prepared by the method according to any one of claims 1 to 8, comprising: Flexible substrate; A conductive layer is located on the flexible substrate. The conductive layer is formed of silver paste comprising micron-sized flake silver powder and an organic carrier, and the conductive layer has trenches. A silver oxide layer is located on the sidewalls and bottom of the trench. The silver oxide layer is formed by the oxidation of redeposited silver nanoparticles generated by laser ablation with ultraviolet ozone, and has a thickness of 50~200nm. An insulator is filled in the trench with a filling height flush with the surface of the conductive layer; as well as An insulating film, covering a flat area on the surface of the conductive layer, has a thickness of 2~5μm; The insulator and the insulating film are formed from a UV-curable acrylate composition.

10. The conductive film according to claim 9, characterized in that, The micron-sized flake silver powder has a D50 of 1~10μm and an aspect ratio ≥10:1; the conductive layer has a thickness of 5~25μm; the trench has a width W of 30~100μm and a depth H of 5~25μm; the redeposited silver nanoparticles have a particle size of 20~100nm; the flexible substrate is a polyethylene terephthalate film or a polyimide film; the flexible substrate has a thickness of 50~200μm and a surface energy ≥42mN / m.

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