Organic silver paste for circuit etching and graphical preparation method thereof

Abstract

The invention belongs to the technical field of conductive materials, and provides organic silver paste for circuit etching and a graphical preparation method of the organic silver paste. The organic silver paste is a two-component system and comprises organic silver paste A and organic silver paste B; wherein the organic silver paste A comprises a silver organic precursor, nano silver powder, fine silver powder, organic film-forming resin, an organic solvent and a dispersion leveling aid, and the organic silver paste B comprises flake silver powder, porous spherical silver powder, organic film-forming resin, an organic solvent and a dispersion thixotropic aid. The organic silver paste is printed to form a film and sintered to form a silver film, and the silver film can be protected by photoresist and realizes circuit transfer through wet etching; the graphical preparation method comprises the following steps: carrying out cleaning and surface activation treatment on a base material, sequentially printing organic silver paste A and organic silver paste B, carrying out heat treatment and sintering densification, forming a positive photoresist pattern on the surface of a silver film, carrying out wet etching after developing and hard baking, and finally removing the photoresist to obtain a silver circuit pattern.

Description

Technical Field

[0001] This invention belongs to the field of conductive materials technology, and relates to an organic silver paste for circuit etching and its patterning preparation method. Background Technology

[0002] With the development of sophisticated electronic devices, miniaturized interconnects, and high-density packaging, the formation of conductive patterns is gradually evolving from traditional thick-film printing to thinner, higher-resolution pattern transfer processes. Among existing conductive metal pastes, gold-based materials are used in some high-end circuits due to their good corrosion resistance and stability; however, their material cost is high, and the accompanying etching systems often rely on halogen-containing or strongly coordinated metal complex systems, posing significant environmental and safety challenges. In contrast, silver-based conductive materials have higher conductivity and a more mature paste preparation system, with obvious advantages in raw material availability and cost. Therefore, conductive silver paste is widely used in electronic interconnects, printed conductors, and other fields.

[0003] However, traditional conductive silver pastes are mostly used for forming thick-film conductors. Typically, the target thickness is achieved through one or more printing processes followed by sintering. Particle accumulation and organic carrier residues can easily lead to problems such as film porosity, surface undulations, and edge burrs, making it difficult to simultaneously achieve thin-film properties and high flatness requirements. When further combined with photoresist for wet etching pattern transfer, defects such as insufficient photoresist adhesion, etching solution penetration along the interface causing bite-edges and undercuts, increased line edge roughness, and localized residues may occur, affecting the yield and consistency of fine lines. On the other hand, some existing technologies attempt to use imageable silver pastes or introduce special photosensitive components into the paste to achieve direct exposure and development. However, these systems are complex, have narrow process windows, are more sensitive to sintering residues and subsequent chemical stability, and are easily affected by fluctuations in substrate, film thickness, and environmental conditions in actual production, making it difficult to consistently obtain high-quality silver films and achieve reliable etching transfer. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an organic silver paste for circuit etching and its patterning preparation method. The organic silver paste is a two-component system, used to form upper and lower stacked silver films. Through the synergistic effect of the organic silver precursor and silver powders of different morphologies, combined with film-forming resins and additives, the film formation quality and sintering density are improved, resulting in a good match between the obtained silver film and the photoresist. This allows for stable transfer of circuit patterns during wet etching, thus balancing conductivity, line edge quality, and manufacturability, thereby meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides an organic silver paste for circuit etching, wherein the organic silver paste is a two-component organic silver paste system, comprising organic silver paste A for forming a first silver film layer and organic silver paste B for forming a second silver film layer; wherein, organic silver paste A comprises an organic silver precursor, nano-silver powder, micro-spherical silver powder, organic film-forming resin, organic solvent, dispersant and / or wetting agent and leveling agent; and organic silver paste B comprises flake silver powder, porous spherical silver powder, organic film-forming resin, organic solvent, dispersant and thixotropic agent; and the organic silver paste A and / or organic silver paste B, after being printed and sintered, form a silver film that can be protected by photoresist and transferred by wet etching.

[0006] Preferably, the organic silver paste A comprises, by mass fraction: an organic silver precursor, calculated as silver, 5-15 wt.%; nano-silver powder, 3-10 wt.%; fine spherical silver powder, 3-10 wt.%; organic film-forming resin, 2-6 wt.%; dispersant and / or wetting agent, 0.2-1.0 wt.%; leveling agent, 0.05-0.3 wt.%; and the balance being organic solvent, wherein the dispersant and / or wetting agent is selected from di(2-ethylhexyl) phosphate, polyoxyethylene alkyl ether phosphate, etc. One or more of the following: ester, 2,4,7,9-tetramethyl-5-decyn-4,7-diol; the leveling agent is a polyether-modified siloxane leveling agent, preferably a polyether-modified polydimethylsiloxane, for example, comprising, by mass fraction: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15% based on silver; and 3%, 3.7%, 4.4%, 5.1%, 5.8%, or 6.5% nano-silver powder. %, 7.2%, 7.9%, 8.6%, 9.3% or 10%; fine spherical silver powder 3%, 3.7%, 4.4%, 5.1%, 5.8%, 6.5%, 7.2%, 7.9%, 8.6%, 9.3% or 10%; organic film-forming resin 2%, 2.4%, 2.8%, 3.2%, 3.6%, 4%, 4.4%, 4.8%, 5.2%, 5.6% or 6%; dispersant and / or wetting agent 0.2%, 0.28%, 0% or 0%; 0.36%, 0.44%, 0.52%, 0.6%, 0.68%, 0.76%, 0.84%, 0.92% or 1.0%; leveling agent 0.05%, 0.075%, 0.1%, 0.125%, 0.15%, 0.175%, 0.2%, 0.225%, 0.25%, 0.275% or 0.3%; organic solvent balance, but not limited to the listed values, other unlisted values ​​within this range also apply.

[0007] Preferably, the silver organic precursor is selected from one or more of silver carboxylates, silver carboxylates, and silver organic complexes, and is preferably silver neodecanoate and / or silver oxalate.

[0008] Preferably, the D50 of the nano-silver powder is 50-150 nm, and the D50 of the fine spherical silver powder is 0.2-0.8 μm; the organic solvent in the organic silver paste A includes terpineol and diethylene glycol butyl ether, with a mass ratio of terpineol to diethylene glycol butyl ether of 7:3. For example, the D50 of the nano-silver powder can be 50-150 nm, such as 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or 110 nm. The nanometers are 120nm, 130nm, 140nm, or 150nm, and the D50 of the fine spherical silver powder is 0.2-0.8μm, for example, it can be 0.2μm, 0.26μm, 0.32μm, 0.38μm, 0.44μm, 0.5μm, 0.56μm, 0.62μm, 0.68μm, 0.74μm, or 0.8μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0009] Preferably, the organic silver paste B comprises, by mass fraction: 40-65 wt.% flake silver powder; 0-20 wt.% porous spherical silver powder; 0-6 wt.% nano silver powder; 1-5 wt.% organic film-forming resin; 0.2-1.0 wt.% dispersant; 0.2-1.2 wt.% thixotropic agent; and the balance being organic solvent. The D50 of the flake silver powder is 1-3 μm, and the D50 of the porous spherical silver powder is 0.8-2.5 μm. The dispersant is selected from di(2-ethylhexyl) phosphate and polyoxyethylene alkyl ether phosphate. One or more of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, for example, by mass fraction including: flake silver powder 40%, 42.5%, 45%, 47.5%, 50%, 52.5%, 55%, 57.5%, 60%, 62.5% or 65%; porous spherical silver powder 0%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% or 20%; nano silver powder 0%, 0.6%, 1.2%, 1.8%, 2.4%, 3%, 3.6%. 4.2%, 4.8%, 5.4% or 6%; organic film-forming resin 1%, 1.4%, 1.8%, 2.2%, 2.6%, 3%, 3.4%, 3.8%, 4.2%, 4.6% or 5%; dispersant 0.2%, 0.28%, 0.36%, 0.44%, 0.52%, 0.6%, 0.68%, 0.76%, 0.84%, 0.92% or 1.0%; thixotropic agent 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%. 1.0%, 1.1% or 1.2%; balance of organic solvent; the D50 of the flake silver powder is (1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8 or 3.0) μm, and the D50 of the porous spherical silver powder is (0.8, 0.97, 1.14, 1.31, 1.48, 1.65, 1.82, 1.99, 2.16, 2.33 or 2.5) μm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0010] Preferably, the organic film-forming resin is ethyl cellulose or acrylic resin, preferably ethyl cellulose; the organic silver paste A has a solid content of 70-80 wt.% and an apparent viscosity of 20-60 Pa·s at 25°C; the organic silver paste B has a solid content of 75-85 wt.% and an apparent viscosity of 30-90 Pa·s at 25°C; and the thixotropic agent is hydrogenated castor oil, for example, the organic silver paste A may have a solid content of 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%. The apparent viscosity at 25°C is (20, 24, 28, 32, 36, 40, 44, 48, 52, 56 or 60) Pa·s; the solid content of the organic silver paste B is 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84% or 85%, and the apparent viscosity at 25°C is (30, 36, 42, 48, 54, 60, 66, 72, 78, 84 or 90) Pa·s, but is not limited to the listed values, and other unlisted values ​​within this range also apply.

[0011] Preferably, the silver film formed by organic silver paste A and / or organic silver paste B under sintering conditions of 600°C and 20-40 min satisfies the following: total dry film thickness of 1.0-2.0 μm, and can achieve circuit pattern transfer by wet etching under photoresist protection. For example, the silver film formed under sintering conditions of 600°C and (20, 22, 24, 26, 28, 30, 32, 34, 36, 38 or 40) min satisfies the following: total dry film thickness of (1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0) μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] Secondly, the present invention provides a method for fabricating circuit patterns using the aforementioned organic silver paste for circuit etching, comprising the following steps: S1, cleaning and surface activation treatment of the substrate; S2, printing a first silver film layer on the surface of the substrate using the organic silver paste A and performing pre-baking and medium-temperature heat treatment; S3, printing a second silver film layer on the surface of the first silver film layer using the organic silver paste B and performing pre-baking and medium-temperature heat treatment; S4, sintering and densifying the double-layer silver film; S5, forming a photoresist pattern on the surface of the silver film and performing wet etching using the photoresist pattern as a resist layer; S6, removing the photoresist to obtain the circuit silver pattern.

[0013] In the preparation of silver paste A, the organic silver precursor stabilizes the silver element in the organic phase through coordination or ionic bonds, enabling the precursor and silver powder to form a uniformly dispersed system under shearing. The dispersant, through adsorption on the silver powder surface, alters interparticle interactions and inhibits re-agglomeration, maintaining particle distribution during storage and printing shearing. The leveling agent primarily reduces film defects caused by local wetting differences by adjusting the surface tension gradient and interfacial energy. The film-forming resin forms a continuous organic network after solvent evaporation, providing physical fixation for the silver powder and precursor, and providing an initial bonding framework for structural evolution in subsequent heat treatment stages. In the preparation of silver paste B, flake-shaped silver powder provides a conductive framework pathway primarily based on surface contact, while porous spherical silver powder provides pore structures and surface sites, enabling the system to form a multi-scale porous structure of particle accumulation during film formation. The thixotropic agent, through the formation of reversible weak interactions, ensures the silver paste maintains shape stability during static storage and exhibits a flowable state during squeegee printing shearing, thereby achieving screen transfer and boundary shaping.

[0014] In the first silver film printing and pre-baking / medium-temperature heat treatment step, solvent evaporation causes the film-forming resin to vitrify or gel and fix the particle stacking structure. Subsequent heat treatment triggers ligand removal and thermal decomposition of the silver organic precursor, transforming silver species from a coordinated state into metallic silver atoms or clusters, which then nucleate and grow on the silver powder surface or in the interparticle spaces. This process provides a fine-scale silver phase at particle contact points and within pores, forming interparticle bridges and altering pore connectivity. Simultaneously, the resin and organic additives undergo thermal decomposition and volatilization, generating and escaping small molecules. In the second silver film printing and pre-baking / medium-temperature heat treatment step, the flake-like silver powder is oriented under the shearing action of the squeegee, forming a flake-to-flake and flake-to-sphere contact network. The porous structure of the porous spherical silver powder provides adsorption and penetration sites, making it easier for the precursor decomposed silver or nano-silver in the upper film to deposit and bridge in the pore regions, thereby altering the pore morphology and connectivity of the upper film.

[0015] During the sintering densification step, residual organic matter further decomposes and escapes, and surface diffusion occurs between metallic silver particles, driving neck growth and pore shrinkage. The fine silver phase formed by the decomposition of nano-silver and precursor has a higher chemical potential at high curvature, preferentially undergoing diffusion and coalescence, promoting neck formation and accelerating the transformation of interparticle contact into metallurgical bonding; flake silver powder undergoes diffusion welding at the contact surface to form a continuous conductive path, and the pore structure of porous spherical silver powder undergoes pore wall migration and partial closure during sintering, ultimately reducing the pore connectivity inside the silver film, and transforming the charge transport path from particle contact type to continuous metallic phase transport type. In the photoresist coating, exposure, and development steps, the photoresist forms a continuous polymer film after spin coating. Exposure triggers photochemical transformation of the photosensitive components in the positive photoresist, generating structural units that can be dissolved in alkaline developer; under the action of tetramethylammonium hydroxide (TMAH) developer, the exposed areas undergo alkaline catalytic dissolution or ionization dissolution and are removed, while the unexposed areas remain insoluble, thus forming a resist pattern.

[0016] Preferably, the pre-baking temperature is 120-140℃ for 5-10 min, and the medium-temperature heat treatment temperature is 220-280℃ for 8-15 min; the sintering densification includes: holding at 350℃ for 8-12 min, then raising the temperature to 790-810℃ and holding for 20-40 min, followed by furnace cooling. For example, the pre-baking temperature can be (120, 122, 124, 126, 128, 130, 132, 134, 136, 138 or 140)℃ for (5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10) min, and the medium-temperature heat treatment temperature can be (220, 226, 232, 238, 244, 250, 256, 262, 268)℃. The sintering densification process includes holding at 350°C for (8.0, 8.4, 8.8, 9.2, 9.6, 10.0, 10.4, 10.8, 11.2, 11.6, or 12.0) min, followed by heating to (790, 792, 794, 796, 798, 800, 802, 804, 806, 808, or 810)°C for (20, 22, 24, 26, 28, 30, 32, 34, 36, 38, or 40) min, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0017] Preferably, the photoresist used to form the photoresist pattern on the silver film surface is a positive photoresist, developed with TMAH developer and hard baked at a temperature of 120-130°C for 8-15 minutes; the wet etching solution is a ferric nitrate nonahydrate solution with a concentration of 250-500 g / L and a pH of 2-3, at an etching temperature of 30-35°C and an etching time of 30-120 seconds; after development with TMAH developer, rinsing is performed with deionized water, for example at temperatures of (120, 121, 122, 123, 124, 125, 126, 127, 128, 129, or 130)°C for times of (8, 8.7, 9.4, 10.1, 10.8, 11.5, 12.2, 12.9, 13.6). The etching solution used in the wet etching process is a ferric nitrate nonahydrate solution with a concentration of (250, 275, 300, 325, 350, 375, 400, 425, 450, 475 or 500) g / L, a pH of (2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0), an etching temperature of (30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5 or 35) °C, and an etching time of (30, 39, 48, 57, 66, 75, 84, 93, 102, 111 or 120) s, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The organic silver paste for circuit etching provided by the present invention adopts a two-component system. Through the synergistic dispersion and film formation of silver organic precursor and silver powder with different morphologies, the printed silver film achieves interparticle bridging and metallurgical bonding during heat treatment and sintering, reducing pore connectivity and interface defects caused by organic residues, thereby improving film continuity and electrical connection stability; the silver film is compatible with positive photoresist processes, and hard baking after development can improve etching resistance and inhibit the penetration of etching solution along the interface; wet etching using an ammonia and hydrogen peroxide system can achieve controllable removal of silver film in unprotected areas, and a clear silver circuit pattern is obtained after resist removal, which is convenient to implement in existing printing, sintering and photolithography etching production lines, and is suitable for stable preparation and fine processing of conductive patterns. Attached Figure Description

[0019] Figure 1 This is a micrograph of a silver circuit pattern obtained by using organic silver paste and a patterning preparation method in Example 1 of the present invention; Figure 2 for Figure 1 A magnified photomicrograph of a portion of the silver circuit pattern shown. Detailed Implementation

[0020] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0021] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0022] Example 1 This embodiment provides an organic silver paste for circuit etching and a method for its patterning preparation, specifically including: An organic silver paste for circuit etching is a two-component organic silver paste system, comprising organic silver paste A and organic silver paste B; The organic silver paste A comprises, by mass fraction: 5 wt.% silver neodecanoate (calculated as silver); 10 wt.% silver nanoparticles with a D50 of 50 nm; 3 wt.% fine spherical silver powder with a D50 of 0.8 μm; 6 wt.% ethyl cellulose; 0.2 wt.% di(2-ethylhexyl) phosphate; 0.3 wt.% polyether-modified polydimethylsiloxane; the balance being a mixed organic solvent of terpineol and diethylene glycol butyl ether (mass ratio 7:3); the organic silver paste A has a solid content of 70 wt.% and an apparent viscosity of 60 Pa·s at 25°C; The organic silver paste B comprises, by mass fraction: 65 wt.% flake silver powder with a D50 of 1 μm; 0 wt.% porous spherical silver powder with a D50 of 2.5 μm; 6 wt.% nano silver powder; 1 wt.% ethyl cellulose; 1.0 wt.% polyoxyethylene alkyl ether phosphate; 0.2 wt.% hydrogenated castor oil; the balance being a mixed organic solvent of terpineol and diethylene glycol butyl ether (mass ratio 7:3); the organic silver paste B has a solid content of 75 wt.% and an apparent viscosity of 90 Pa·s at 25°C; The method for preparing the circuit pattern of this organic silver paste includes the following steps: S1, Cleaning and surface activation treatment of the substrate; S2, the organic silver paste A is used to print a first silver film layer on the surface of the substrate and then pre-baking and medium-temperature heat treatment are performed; the pre-baking temperature is 120°C and the time is 10 min, and the medium-temperature heat treatment temperature is 280°C and the time is 8 min. S3, the organic silver paste B is used to print a second silver film layer on the surface of the first silver film layer to form a second silver film layer and then pre-baking and medium-temperature heat treatment are performed; the pre-baking temperature is 140°C and the time is 5 min, and the medium-temperature heat treatment temperature is 220°C and the time is 15 min; S4, the double-layer silver film is sintered and densified, and the total dry film thickness of the sintered silver film is 2.0 μm; the sintering and densification includes: holding at 350℃ for 12 min, then raising the temperature to 790℃ and holding for 40 min, followed by furnace cooling; S5, a photoresist pattern is formed on the surface of the silver film, and the photoresist pattern is used as a resist layer for wet etching; the photoresist is a positive photoresist, developed with TMAH developer and hard baked, the hard baking temperature is 130℃ and the time is 8min; the etching solution for wet etching is ferric nitrate nonahydrate solution with a concentration of 250g / L, pH of 2, etching temperature of 30℃ and etching time of 30s, and after development with TMAH developer, it is rinsed with deionized water. S6, remove the photoresist to obtain the silver pattern of the circuit.

[0023] Figure 1 The image shows a micrograph of a silver circuit pattern obtained by printing a film onto a substrate surface using the organic silver paste of the present invention, sintering and densifying it, and then using a photoresist pattern protection and wet etching process. The image shows multiple parallel lines and the continuity of the pattern in the corner areas. The lines are consistent in direction, and the lines at the corners remain intact. No obvious broken lines or large areas of residual metal film are observed, indicating that the silver film can achieve stable line transfer during the patterning process.

[0024] Figure 2 for Figure 1 The magnified micrograph of the central line area shows that the silver lines are formed by continuous accumulation of metallic phases. The line boundaries are clear, and there are no obvious collapses or peeling features at the edges. The non-line areas outside the lines are the exposed areas of the substrate after being etched away. This shows that wet etching has a removal effect on the silver film in areas not protected by photoresist, and there are no obvious large residues or through gaps at the edges of the lines.

[0025] Example 2 This embodiment provides an organic silver paste for circuit etching and a method for its patterning preparation, specifically including: An organic silver paste for circuit etching is a two-component organic silver paste system, comprising organic silver paste A and organic silver paste B; The organic silver paste A comprises, by mass fraction: 15 wt.% silver oxalate (calculated as silver); 3 wt.% nano-silver powder with a D50 of 150 nm; 10 wt.% micro-spherical silver powder with a D50 of 0.2 μm; 2 wt.% acrylic resin; 1.0 wt.% polyoxyethylene alkyl ether phosphate; 0.05 wt.% polyether-modified polydimethylsiloxane; the balance being a mixed organic solvent of terpineol and diethylene glycol butyl ether (mass ratio 7:3); the organic silver paste A has a solid content of 80 wt.% and an apparent viscosity of 20 Pa·s at 25°C; The organic silver paste B comprises, by mass fraction: 40 wt.% flake silver powder with a D50 of 3 μm; 20 wt.% porous spherical silver powder with a D50 of 0.8 μm; 0 wt.% nano silver powder; 5 wt.% acrylic resin; 0.2 wt.% 2,4,7,9-tetramethyl-5-decyn-4,7-diol; 1.2 wt.% hydrogenated castor oil; the balance being a mixed organic solvent of terpineol and diethylene glycol butyl ether (mass ratio 7:3); the organic silver paste B has a solid content of 85 wt.% and an apparent viscosity of 30 Pa·s at 25°C; The method for preparing the circuit pattern of this organic silver paste includes the following steps: S1, Cleaning and surface activation treatment of the substrate; S2, the organic silver paste A is used to print a first silver film layer on the surface of the substrate and then pre-baking and medium-temperature heat treatment are performed; the pre-baking temperature is 140°C and the time is 5 min, and the medium-temperature heat treatment temperature is 220°C and the time is 15 min. S3, the organic silver paste B is used to print a second silver film layer on the surface of the first silver film layer to form a second silver film layer and then pre-baking and medium-temperature heat treatment are performed; the pre-baking temperature is 120°C and the time is 10 min, and the medium-temperature heat treatment temperature is 280°C and the time is 8 min. S4, the double-layer silver film is sintered and densified, and the total dry film thickness of the sintered silver film is 1.0 μm; the sintering and densification includes: holding at 350℃ for 8 min, then raising the temperature to 810℃ and holding for 20 min, followed by furnace cooling. S5, a photoresist pattern is formed on the surface of the silver film, and the photoresist pattern is used as a resist layer for wet etching; the photoresist is a positive photoresist, developed with TMAH developer and hard baked, the hard baking temperature is 120℃ and the time is 15min; the etching solution for wet etching is ferric nitrate nonahydrate solution with a concentration of 500g / L, pH of 3, etching temperature of 35℃ and etching time of 120s, and after development with TMAH developer, it is rinsed with deionized water. S6, remove the photoresist to obtain the silver pattern of the circuit.

[0026] Example 3 This embodiment provides an organic silver paste for circuit etching and a method for its patterning preparation, specifically including: An organic silver paste for circuit etching is a two-component organic silver paste system, comprising organic silver paste A and organic silver paste B; The organic silver paste A comprises, by mass fraction: 10 wt.% of a mixture of silver neodecanoate and silver oxalate (calculated as silver); 6 wt.% of nano-silver powder with a D50 of 100 nm; 6 wt.% of fine spherical silver powder with a D50 of 0.5 μm; 4 wt.% of ethyl cellulose; 0.5 wt.% of 2,4,7,9-tetramethyl-5-decyn-4,7-diol; 0.15 wt.% of polyether-modified polydimethylsiloxane; and the balance being a mixed organic solvent of terpineol and diethylene glycol butyl ether (mass ratio 7:3); the organic silver paste A has a solid content of 75 wt.% and an apparent viscosity of 40 Pa·s at 25 °C; The organic silver paste B comprises, by mass fraction: 50 wt.% flake silver powder with a D50 of 2 μm; 10 wt.% porous spherical silver powder with a D50 of 1.5 μm; 3 wt.% nano silver powder; 3 wt.% ethyl cellulose; 0.6 wt.% di(2-ethylhexyl) phosphate; 0.8 wt.% hydrogenated castor oil; the balance being a mixed organic solvent of terpineol and diethylene glycol butyl ether (mass ratio 7:3); the organic silver paste B has a solid content of 80 wt.% and an apparent viscosity of 60 Pa·s at 25°C; The method for preparing the circuit pattern of this organic silver paste includes the following steps: S1, Cleaning and surface activation treatment of the substrate; S2, the organic silver paste A is used to print a first silver film layer on the surface of the substrate and then pre-baking and medium-temperature heat treatment are performed; the pre-baking temperature is 130°C and the time is 8 min, and the medium-temperature heat treatment temperature is 250°C and the time is 12 min; S3, the organic silver paste B is used to print a second silver film layer on the surface of the first silver film layer and then pre-baking and medium-temperature heat treatment are performed; the pre-baking temperature is 130°C and the time is 8 min, and the medium-temperature heat treatment temperature is 250°C and the time is 12 min. S4, the double-layer silver film is sintered and densified, and the total dry film thickness of the sintered silver film is 1.5μm; the sintering and densification includes: holding at 350℃ for 10min, then raising the temperature to 800℃ and holding for 30min, followed by furnace cooling. S5, a photoresist pattern is formed on the surface of the silver film, and the photoresist pattern is used as a resist layer for wet etching; the photoresist is a positive photoresist, developed with TMAH developer and hard baked, the hard baking temperature is 125℃ and the time is 12min; the etching solution for wet etching is ferric nitrate nonahydrate solution with a concentration of 300g / L, pH of 2.4, etching temperature of 32℃ and etching time of 80s; after development with TMAH developer, it is rinsed with deionized water. S6, remove the photoresist to obtain the silver pattern of the circuit.

[0027] Example 4 This embodiment provides an organic silver paste for circuit etching and a method for its patterning preparation, specifically including: An organic silver paste for circuit etching is a two-component organic silver paste system, comprising organic silver paste A and organic silver paste B; The organic silver paste A comprises, by mass fraction: 8 wt.% silver neodecanoate (calculated as silver); 8 wt.% nano-silver powder with a D50 of 120 nm; 8 wt.% fine spherical silver powder with a D50 of 0.6 μm; 5 wt.% ethyl cellulose; 0.8 wt.% di(2-ethylhexyl) phosphate; 0.2 wt.% polyether-modified polydimethylsiloxane; the balance being a mixed organic solvent of terpineol and diethylene glycol butyl ether (mass ratio 7:3); the solid content of the organic silver paste A is 78 wt.%, and the apparent viscosity at 25°C is 50 Pa·s; The organic silver paste B comprises, by mass fraction: 60 wt.% flake silver powder with a D50 of 2.5 μm; 5 wt.% porous spherical silver powder with a D50 of 2.0 μm; 4 wt.% nano silver powder; 4 wt.% ethyl cellulose; 0.4 wt.% polyoxyethylene alkyl ether phosphate; 0.5 wt.% hydrogenated castor oil; the balance being a mixed organic solvent of terpineol and diethylene glycol butyl ether (mass ratio 7:3); the organic silver paste B has a solid content of 82 wt.% and an apparent viscosity of 70 Pa·s at 25°C; The method for preparing the circuit pattern of this organic silver paste includes the following steps: S1, Cleaning and surface activation treatment of the substrate; S2, the organic silver paste A is used to print a first silver film layer on the surface of the substrate and then pre-baking and medium-temperature heat treatment are performed; the pre-baking temperature is 135°C and the time is 6 min, and the medium-temperature heat treatment temperature is 260°C and the time is 10 min. S3, the organic silver paste B is used to print a second silver film layer on the surface of the first silver film layer and then pre-baking and medium-temperature heat treatment are performed; the pre-baking temperature is 135°C and the time is 6 min, and the medium-temperature heat treatment temperature is 260°C and the time is 10 min. S4, the double-layer silver film is sintered and densified, and the total dry film thickness of the sintered silver film is 1.8μm; the sintering and densification includes: holding at 350℃ for 11min, then raising the temperature to 805℃ and holding for 35min, followed by furnace cooling. S5, a photoresist pattern is formed on the surface of the silver film, and the photoresist pattern is used as a resist layer for wet etching; the photoresist is a positive photoresist, which is developed with TMAH developer and hard baked at a temperature of 128°C for 10 min; the etching solution for wet etching is ferric nitrate nonahydrate solution with a concentration of 400 g / L, a pH of 2.7, an etching temperature of 34°C, and an etching time of 60 s; after development with TMAH developer, the film is rinsed with deionized water. S6, remove the photoresist to obtain the silver pattern of the circuit.

[0028] Comparative Example 1 This comparative example provides an organic silver paste for circuit etching and its patterning preparation method. The difference between this example and Example 1 is that organic silver paste A and organic silver paste B are premixed into a single silver paste in the same mass ratio, and the single silver paste is used for the subsequent two printings. Other process parameters and operating conditions are exactly the same as in Example 1.

[0029] Comparative Example 2 This comparative example provides an organic silver paste for circuit etching and its patterning preparation method. The difference between this example and Example 1 is that no silver organic precursor is added to the organic silver paste A, and an equal amount of fine spherical silver powder is used to supplement the solid components. Other process parameters and operating conditions are exactly the same as in Example 1.

[0030] Comparative Example 3 This comparative example provides an organic silver paste for circuit etching and its patterning preparation method. The difference between this example and Example 1 is that porous spherical silver powder is not added to the organic silver paste B, but is replaced by an equal amount of flake silver powder. Other process parameters and operating conditions are exactly the same as in Example 1.

[0031] Comparative Example 4 This comparative example provides an organic silver paste for line etching and its patterning preparation method. The difference between this example and Example 1 is that after forming the positive photoresist pattern and completing TMAH development, no hard baking process is performed. Other process parameters and operating conditions are exactly the same as in Example 1.

[0032] The organic silver pastes prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to performance testing, and the testing methods are as follows: The sheet resistance test method is as follows: Prepare a continuous silver film test piece sintered in the same batch and process as the circuit (without photolithography to avoid the influence of linear geometry on the results), and use the four-probe method to determine the sheet resistance of the silver film; use a four-probe sheet resistance tester to measure the voltage drop between the probes under constant current and automatically calculate the sheet resistance value by the instrument according to the four-probe theory, and take measurements at the center and four corners of the test piece and take the average value.

[0033] The surface roughness testing method is as follows: using the sintered silver film surface as the test surface, a stylus-type surface roughness meter is used for measurement. Before testing, the instrument is calibrated using a standard roughness sample block; the sample is fixed on the platform, and the stylus is scanned in a straight line along a single direction on the sample surface. The scanning direction is consistent with the visible texture direction of the sample or repeated in the same direction to ensure comparability; the roughness evaluation parameter Rz is selected in the instrument, and the sampling length and evaluation length are set simultaneously, and filtering is enabled to remove the influence of macroscopic morphological fluctuations on roughness; measurements are taken once at the center and at different positions around the sample, the Rz value of each measuring point is recorded, and the average value is calculated. Finally, the surface roughness result is given in μm.

[0034] The line width and line spacing test method is as follows: After photolithography etching and resist removal, the dimensions of the silver circuit pattern are measured using an optical microscope with a scale eyepiece or micrometer. A suitable magnification is selected to ensure that the feature to be measured occupies a sufficient proportion in the field of view and that the boundary is clear. The scale is aligned with the edge of the circuit to read the number of scale divisions. The actual values ​​of line width and line spacing are then calculated based on the pre-calibrated "actual length corresponding to unit scale". Multiple measurements are taken along different areas of the same pattern, and the average value is recorded.

[0035] The test results are shown in Table 1.

[0036] Table 1. Organic silver paste and its patterning test results in Examples 1-4 and Comparative Examples 1-4

[0037] As shown in Table 1, compared with Example 1, Comparative Example 1 has increased sheet resistance, increased surface roughness, decreased line width, and increased line spacing; Comparative Example 2 has increased sheet resistance, increased surface roughness, decreased line width, and increased line spacing; Comparative Example 3 has increased sheet resistance, increased surface roughness, decreased line width, and increased line spacing; and Comparative Example 4 has increased sheet resistance, unchanged surface roughness, decreased line width, and increased line spacing.

[0038] This is because in Comparative Example 1, when A and B were premixed into a single silver paste, the wetting and interstitial effects of the underlying fine silver / precursor on the substrate were disturbed by the flake particles, resulting in increased local porosity and undulations in the film, uneven sintering necks, and increased sheet resistance. The photoresist adhered poorly to the rough surface, and lateral etching penetration led to narrower linewidths and larger line spacing. In Comparative Example 2, after removing the silver organic precursor, the lack of in-situ generated fine silver phase bridging during the heat treatment stage meant that particle contact mainly relied on direct powder sintering, resulting in slower neck formation and higher pore connectivity, increasing sheet resistance and roughness. Pores and interface channels made it easier for the etching solution to penetrate, reducing linewidth retention. In Comparative Example 3, after replacing the porous spherical silver powder with flake silver powder, multi-scale stacking and porosity control were weakened, resulting in uneven distribution of interstitial and diffusion channels in the upper film, reduced sintering densification efficiency, increased sheet resistance, and greater surface undulations. Locally weakly bonded areas were more easily etched laterally during etching, leading to larger line spacing. In Comparative Example 4, after removing the hard baking after development, the residual solvent of the photoresist and the micropore channels did not shrink sufficiently, resulting in low interface adhesion. The etching solution penetrated along the interface, causing intensified side etching under the mask, leading to a decrease in linewidth and an increase in line spacing. However, the sintering conditions of the silver film remained unchanged, and the sheet resistance and roughness were basically the same.

[0039] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An organic silver paste for circuit etching, characterized in that, The organic silver paste is a two-component organic silver paste system, comprising organic silver paste A for forming a first silver film layer and organic silver paste B for forming a second silver film layer; wherein, organic silver paste A contains an organic silver precursor, nano-silver powder, micro-spherical silver powder, organic film-forming resin, organic solvent, dispersant and / or wetting agent and leveling agent; organic silver paste B contains flake silver powder, porous spherical silver powder, organic film-forming resin, organic solvent, dispersant and thixotropic agent; organic silver paste A and / or organic silver paste B, after being printed and sintered, form a silver film that can be protected by photoresist and transferred by wet etching.

2. The organic silver paste for circuit etching according to claim 1, characterized in that, The organic silver paste A comprises, by mass fraction: 5-15 wt.% silver organic precursor, calculated as silver; 3-10 wt.% nano silver powder; 3-10 wt.% micro-spherical silver powder; 2-6 wt.% organic film-forming resin; 0.2-1.0 wt.% dispersant and / or wetting agent; 0.05-0.3 wt.% leveling agent; and the balance of organic solvent.

3. An organic silver paste for circuit etching according to claim 1 or 2, characterized in that, The silver organic precursor is selected from one or more of silver carboxylates, silver carboxylates, and silver organic complexes, preferably silver neodecanoate and / or silver oxalate.

4. An organic silver paste for circuit etching according to claim 1 or 2, characterized in that, The nano-silver powder has a D50 of 50-150 nm, and the micro-spherical silver powder has a D50 of 0.2-0.8 μm; the organic solvent in the organic silver paste A includes terpineol and diethylene glycol butyl ether, with a mass ratio of terpineol to diethylene glycol butyl ether of 7:3; the dispersant and / or wetting agent is selected from one or more of di(2-ethylhexyl) phosphate, polyoxyethylene alkyl ether phosphate, and 2,4,7,9-tetramethyl-5-decyn-4,7-diol; the leveling agent is a polyether-modified siloxane leveling agent, preferably polyether-modified polydimethylsiloxane.

5. The organic silver paste for circuit etching according to claim 1, characterized in that, The organic silver paste B comprises, by mass fraction: 40-65 wt.% flake silver powder; 0-20 wt.% porous spherical silver powder; 0-6 wt.% nano silver powder; 1-5 wt.% organic film-forming resin; 0.2-1.0 wt.% dispersant; 0.2-1.2 wt.% thixotropic agent; and the balance being organic solvent. The D50 of the flake silver powder is 1-3 μm, and the D50 of the porous spherical silver powder is 0.8-2.5 μm.

6. An organic silver paste for circuit etching according to claim 1, 2, or 5, characterized in that, The organic film-forming resin is ethyl cellulose or acrylic resin, preferably ethyl cellulose; the organic silver paste A has a solid content of 70-80 wt.% and an apparent viscosity of 20-60 Pa·s at 25°C; the organic silver paste B has a solid content of 75-85 wt.% and an apparent viscosity of 30-90 Pa·s at 25°C; the thixotropic agent is hydrogenated castor oil.

7. The organic silver paste for circuit etching according to claim 1, characterized in that, The silver film formed by the organic silver paste A and / or the organic silver paste B under sintering conditions of 600℃ and 20-40min meets the following requirements: total dry film thickness of 1.0-2.0μm, and the circuit pattern can be transferred by wet etching under the protection of photoresist.

8. A method for fabricating circuit patterns using organic silver paste for circuit etching according to claim 1, characterized in that, The process includes the following steps: S1, cleaning and surface activation of the substrate; S2, printing a first silver film layer on the substrate surface using the organic silver paste A and performing pre-baking and medium-temperature heat treatment; S3, printing a second silver film layer on the surface of the first silver film layer using the organic silver paste B and performing pre-baking and medium-temperature heat treatment; S4, sintering and densifying the double-layer silver film; S5, forming a photoresist pattern on the silver film surface and using the photoresist pattern as a resist layer for wet etching. S6, remove the photoresist to obtain the silver pattern of the circuit.

9. The method for fabricating circuit patterns using organic silver paste for circuit etching according to claim 8, characterized in that, The pre-baking temperature is 120-140℃ and the time is 5-10 min; the medium-temperature heat treatment temperature is 220-280℃ and the time is 8-15 min. The sintering densification process includes: holding at 350°C for 8-12 minutes, then raising the temperature to 790-810°C and holding for 20-40 minutes, followed by furnace cooling.

10. The method for fabricating circuit patterns using organic silver paste for circuit etching according to claim 8, characterized in that, The photoresist used to form the photoresist pattern on the silver film surface is a positive photoresist. It is developed with TMAH developer and hard baked at a temperature of 120-130℃ for 8-15 minutes. The etching solution used for wet etching is a ferric nitrate nonahydrate solution with a concentration of 250-500 g / L and a pH of 2-3. The etching temperature is 30-35℃ and the etching time is 30-120 seconds. After development with TMAH developer, the film is rinsed with deionized water.

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