Silver-based conductive paste for flexible electronic device, preparation method and application

Abstract

The invention provides silver-based conductive paste for a flexible electronic device, a preparation method and application, and relates to the technical field of new materials. The preparation method comprises the following steps: carrying out surface modification treatment on original nano silver powder by adopting organic acid to obtain modified nano silver powder; preparing an organic silicon rubber carrier which is composed of an organic solvent, a silane coupling agent and an additive; the modified nano silver powder is mixed with an organic silicon rubber carrier, homogenization treatment is carried out, the silver-based conductive paste is obtained, and the silver-based conductive paste has excellent dispersity and stability. According to the preparation method, agglomeration of the nano-silver particles is effectively prevented, the conductivity and applicability of the nano-silver paste are remarkably improved, and the preparation method is suitable for multiple fields such as electronic packaging.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and more specifically, to a silver-based conductive paste for flexible electronic devices, its preparation method, and its application. Background Technology

[0002] With the rapid development of microelectronics technology, power device packaging, and flexible electronic devices, the demand for conductive pastes with high conductivity, low-temperature sintering, and high reliability is increasing. Nano-silver paste, due to its excellent conductivity, good sintering performance, and ability to achieve high-density connections at low temperatures, has become a key interconnect material in advanced electronic packaging and is widely used in LEDs, IGBT modules, solar cells, flexible circuits, and other fields.

[0003] Currently, nano-silver paste is mainly composed of nano-silver powder, silicone rubber carrier, and additives. However, many technical challenges remain in practical applications: First, due to its large specific surface area and high surface energy, nano-silver powder is prone to agglomeration, leading to uneven dispersion and poor flowability of the paste, affecting printing accuracy and conductivity after sintering; second, the compatibility between traditional organic carrier systems and nano-silver powder is poor, making it difficult to effectively and stably disperse the silver powder, and causing sedimentation or stratification. Summary of the Invention

[0004] The problem that this invention aims to solve is that existing nano-silver pastes are prone to agglomeration during preparation and storage, and the compatibility between traditional organic carrier systems and nano-silver powder is poor, leading to a decline in paste performance.

[0005] To address the aforementioned problems, in a first aspect, the present invention provides a method for preparing a silver-based conductive paste for flexible electronic devices, comprising: Surface modification of raw silver nanoparticles was performed using organic acids to obtain modified silver nanoparticles. An organosilicon rubber carrier is prepared, wherein the organosilicon rubber carrier is composed of an organic solvent, a silane coupling agent, and additives; Modified nano-silver powder was mixed with an organosilicon rubber carrier and homogenized to obtain a silver-based conductive paste.

[0006] Optionally, the surface modification treatment of the original silver nanoparticles with organic acids to obtain modified silver nanoparticles includes: Weigh out the original nano silver powder and organic acid, with the mass ratio of the original nano silver powder to the organic acid being 100:(1-5). Dissolve the organic acid in an organic alcohol solvent and stir to form a homogeneous solution; The original silver nanoparticles were slowly added to the formed homogeneous solution and fully wetted under magnetic stirring. The mixture was then placed in an ultrasonic cleaner and ultrasonically stirred for 60 to 90 minutes at 400W ultrasonic power to ensure that the organic acid fully coated the surface of the original nano silver powder. After sonication, the suspension was transferred to a centrifuge tube and centrifuged at 6000 r / min for 10 to 15 minutes. The supernatant was removed to obtain the precipitate. After washing the precipitate 2-3 times with anhydrous ethanol, it is placed in a vacuum drying oven and dried at 50℃-60℃ for 6-12 hours to obtain modified nano silver powder.

[0007] Optionally, the original silver nanoparticles have an average particle size of 20 nm to 100 nm and a specific surface area of ​​5 m². 2 / g~15m 2 / g, purity ≥99.9%, the original nano silver powder is spherical or near-spherical silver nanoparticles; The organic acid is at least one of succinic acid, citric acid, oleic acid, stearic acid, acetic acid, or benzoic acid.

[0008] Optionally, the preparation of the silicone rubber carrier includes: Weigh the organic solvent according to the proportion and place it in a mixing container. Heat it in a 50°C constant temperature water bath and mechanically stir it at a speed of 300r / min to 500r / min. Add the silane coupling agent and stir until completely dissolved; Then add wetting agent, dispersant, surfactant and plasticizer in sequence, stirring for 15 to 30 minutes after each additive is added until completely dispersed; Finally, add the resin solution and continue stirring for 60 minutes until the system is uniformly transparent or semi-transparent; After being mixed evenly, the mixture is subjected to ultrasonic stirring at a power of 300W to 500W for 30 minutes to obtain an organosilicon rubber carrier.

[0009] Optionally, the organic solvent is at least one selected from terpineol, butyl carbitol, ethylene glycol, diethylene glycol butyl ether, propylene glycol phenyl ether, or isophorone, and the amount of organic solvent added is 60% to 80% of the total mass of the silicone rubber carrier; The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or vinyltrimethoxysilane, and the amount of silane coupling agent added is 0.5% to 2% of the total mass of the organosilicon rubber carrier.

[0010] Optionally, the step of mixing modified silver nanoparticles with an organosilicon rubber carrier and homogenizing the mixture to obtain a silver-based conductive paste includes: Modified nano-silver powder was slowly and batch-wise added to the prepared organosilicon rubber carrier. While mechanically stirring at a speed of 1000 r / min, 400W ultrasonic treatment was applied and stirring was continued for 120 minutes to achieve preliminary uniform dispersion and obtain a mixed slurry. The mixed slurry was then transferred to a planetary ball mill, and zirconia grinding beads with a diameter of 0.5 mm to 2 mm were added. The mill was then ball-milled at a speed of 300 r / min to 500 r / min for 48 hours. After ball milling, the mixture is passed through a 300-500 mesh sieve to obtain a paste-like nano-silver paste with a fineness of ≤10μm, which is a silver-based conductive paste.

[0011] Secondly, the present invention also provides a silver-based conductive paste for flexible electronic devices, which is prepared by the above-mentioned method for preparing silver-based conductive paste for flexible electronic devices. The silver-based conductive paste includes modified silver nanoparticles and an organosilicon rubber carrier, wherein the mass percentage of modified silver nanoparticles is 70% to 90% and the mass percentage of organosilicon rubber carrier is 10% to 30%.

[0012] Thirdly, the present invention provides an application of a silver-based conductive paste, wherein the silver-based conductive paste is used in flexible electronic devices.

[0013] Optionally, the electronic devices include LEDs, IGBT modules, solar cells, wearable devices, sensors, and displays.

[0014] Optionally, the silver-based conductive paste is coated onto the surface of a substrate and sintered in air or a nitrogen atmosphere at 150°C to 250°C for 30 to 120 minutes, with a sintering temperature of 200°C, to form a conductive silver film bonding layer; the resistivity of the silver film bonding layer is less than 4.8 × 10⁻⁶. -5 Ω·cm, adhesion level 4B or higher.

[0015] This invention provides a silver-based conductive paste for flexible electronic devices, its preparation method, and its application. Compared with existing technologies, it has the following advantages: Surface modification of nano-silver powder with organic acids effectively reduces its surface energy. Combined with ultrasonic and centrifugal treatment, it significantly inhibits the agglomeration behavior of silver powder in subsequent processing and improves dispersion stability. A composite organosilicon rubber carrier system was designed, containing silane coupling agents and various functional additives, which enhances the compatibility between silver powder and organic phase and improves the rheological properties and printability of the paste. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 SEM image of the surface morphology of the modified silver nanopowder prepared in this invention; Figure 2 This is a macroscopic diagram showing the actual application of the nano-silver paste prepared in this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0020] This application provides a method for preparing a silver-based conductive paste for flexible electronic devices, comprising: The original silver nanoparticles were surface modified using organic acids to obtain modified silver nanoparticles.

[0021] Specifically, the original silver nanoparticles have an average particle size of 20nm to 100nm and a specific surface area of ​​5m². 2 / g~15m 2 / g, purity ≥99.9%, the original silver nanoparticles are spherical or near-spherical silver nanoparticles, which is beneficial for improving packing density and the continuity of the conductive network. The organic acid is at least one of succinic acid, citric acid, oleic acid, stearic acid, acetic acid, or benzoic acid. The organic acid forms a coordination or chemisorption with the silver surface through its carboxyl groups, constructing an organic coating layer, achieving steric stabilization, and preventing direct particle contact and agglomeration. Surface chemical modification of the original silver nanoparticles with organic acids can significantly reduce particle surface energy, inhibit agglomeration, and improve its dispersion stability in an organosilicon rubber carrier. Figure 1 It is evident that the surface-treated nano-silver powder exhibits good dispersion uniformity, with no agglomeration between silver powder particles, indicating high dispersion of the surface-treated nano-silver powder.

[0022] An organosilicon rubber carrier is prepared, wherein the organosilicon rubber carrier is composed of an organic solvent, a silane coupling agent, and additives.

[0023] Specifically, the organic solvent is at least one of terpineol, butyl carbitol, ethylene glycol, diethylene glycol butyl ether, propylene glycol phenyl ether, or isophorone, and is added at 60%–80% of the total mass of the silicone rubber carrier. It is used to adjust the viscosity and volatility of the slurry to meet the requirements of different coating processes. The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or vinyltrimethoxysilane, and is added at 0.5%–2% of the total mass of the silicone rubber carrier. The silane coupling agent can react simultaneously with the silver powder surface and the organic resin, enhancing the inorganic-organic interfacial bonding force and improving the adhesion and mechanical strength of the sintered silver film. The additives include wetting agents, dispersants, surfactants, plasticizers, and resin solutions. The wetting agent is at least one of BYK-307, BYK-341, or a polyoxyethylene ether surfactant, and the amount of wetting agent added is 0.5% to 2% of the total mass of the silicone rubber carrier; the dispersant is at least one of Disperbyk-111, EFKA-4050, or sodium polyacrylate, and the amount of dispersant added is 0.5% to 2% of the total mass of the silicone rubber carrier; the surfactant is at least one of Span-80, Tween-80, or sodium dodecyl sulfate, and the amount of surfactant added is 0.5% to 2% of the total mass of the silicone rubber carrier; the plasticizer is at least one of dibutyl phthalate or triphenyl phosphate, and the amount of plasticizer added is 0.5% to 2% of the total mass of the silicone rubber carrier; the resin solution is at least one of ethyl cellulose solution, acrylic resin solution, or epoxy resin solution, and the amount of resin solution added is 17% to 28% of the total mass of the silicone rubber carrier. The above additives work synergistically to improve the wettability, leveling, thixotropy, and storage stability of the slurry.

[0024] Modified nano-silver powder was mixed with an organosilicon rubber carrier and homogenized to obtain a silver-based conductive paste.

[0025] In an optional embodiment of this application, the surface modification treatment of the original silver nanoparticles with organic acids to obtain modified silver nanoparticles includes: The raw silver nanoparticles and organic acid were weighed using an electronic balance, with a mass ratio of raw silver nanoparticles to organic acid of 100:(1-5).

[0026] The organic acid is dissolved in an organic alcohol solvent and stirred to form a homogeneous solution; the organic alcohol solvent can be anisopropanol or anhydrous ethanol, etc.

[0027] The original silver nanoparticles were slowly added to the formed homogeneous solution and thoroughly wetted under magnetic stirring.

[0028] The mixture was then placed in an ultrasonic cleaner and ultrasonically stirred for 60 to 90 minutes at 400W ultrasonic power to ensure that the organic acid fully coated the surface of the original nano silver powder.

[0029] After sonication, the suspension is transferred to a centrifuge tube and centrifuged at 6000 r / min for 10 to 15 minutes. The supernatant is removed to obtain the precipitate.

[0030] After washing the precipitate 2-3 times with anhydrous ethanol, it is placed in a vacuum drying oven and dried at 50℃-60℃ for 6-12 hours to obtain modified nano silver powder.

[0031] In an optional embodiment of this application, the preparation of the silicone rubber carrier includes: Weigh the organic solvent according to the proportion and place it in a mixing container (e.g., a beaker). Heat the mixture in a 50°C constant temperature water bath and mechanically stir it at a speed of 300 r / min to 500 r / min.

[0032] Add the silane coupling agent and stir until completely dissolved.

[0033] Then add wetting agent, dispersant, surfactant and plasticizer in sequence, stirring for 15 to 30 minutes after each additive is added until completely dispersed.

[0034] Finally, add the resin solution and continue stirring for 60 minutes until the system is uniformly transparent or semi-transparent.

[0035] After being mixed evenly, the mixture is subjected to ultrasonic stirring at a power of 300W to 500W for 30 minutes to obtain a uniform and stable organosilicon rubber carrier.

[0036] In an optional embodiment of this application, the step of mixing the modified silver nanoparticles with an organosilicon rubber carrier and homogenizing the mixture to obtain a silver-based conductive paste includes: Modified nano-silver powder was slowly and batch-wise added to the prepared silicone rubber carrier. While mechanically stirring at a speed of 1000 r / min, 400 W ultrasonic treatment was applied and stirring was continued for 120 minutes to achieve preliminary uniform dispersion and obtain a mixed slurry.

[0037] The mixed slurry was then transferred to a planetary ball mill, and zirconia grinding beads with a diameter of 0.5 mm to 2 mm were added. The mill was then ball-milled at a speed of 300 r / min to 500 r / min for 48 hours to further refine the particles and break up micro-agglomerates.

[0038] After ball milling, the material is passed through a 300-500 mesh sieve to remove the grinding media, resulting in a paste-like silver nano-paste with a fineness ≤10μm, moderate viscosity, and uniform dispersion, which is a silver-based conductive paste.

[0039] By modifying the surface of silver nanoparticles with organic acids, combining it with an optimized silicone rubber carrier, and employing a multi-stage mixing process of ultrasonication-stirring-ball milling, a highly dispersible, stable, and conductive silver nanoparticle paste was prepared, meeting the demands of high-end electronic packaging for high-performance interconnect materials. The preparation method is simple, highly operable, effectively inhibits the agglomeration of silver nanoparticles, and significantly improves the dispersibility and stability of the paste. It effectively solves the technical challenge of silver nanoparticles easily agglomerating during preparation and storage, leading to a decline in paste performance.

[0040] This application also provides a silver-based conductive paste for flexible electronic devices, prepared using the above-described method. The silver-based conductive paste comprises modified silver nanoparticles and a silicone rubber carrier, wherein the modified silver nanoparticles comprise 70%–90% by mass, and the silicone rubber carrier comprises 10%–30% by mass. During the curing process, the mixture of modified silver nanoparticles and silicone rubber forms silver nanoparticles that fill the gaps between the silver particles.

[0041] This application also provides an application of a silver-based conductive paste, which is used in flexible electronic devices. The electronic devices include LEDs, IGBT modules, solar cells, wearable devices, sensors, and displays.

[0042] Optionally, the silver-based conductive paste is coated onto the surface of a substrate and sintered in air or a nitrogen atmosphere at 150°C to 250°C for 30 to 120 minutes, with a sintering temperature of 200°C, to form a conductive silver film bonding layer; the resistivity of the silver film bonding layer is less than 4.8 × 10⁻⁶. -5 The adhesion reaches grade 4B or higher, with a resistivity of Ω·cm. Specifically, the nano-silver paste can be applied to the surface of copper, aluminum, ceramic, or flexible polymer substrates by screen printing, doctor blade coating, or dispensing. It is then sintered in air or a nitrogen atmosphere at 150℃~250℃ for 30~120 minutes to form a dense, continuous, and highly conductive silver bonding layer. At a sintering temperature of 200℃, the resistivity of the resulting silver film can be lower than 4.8×10⁻⁶. -5 Ω·cm, strong adhesion (4B grade or higher in cross-cut adhesion test), no obvious cracks or holes. Figure 2 As can be seen, the printed circuit formed by the silver paste bonded tightly to the flexible substrate, without any defects such as peeling, detachment, or voids, indicating that the nano-silver paste has good adhesion to the substrate material. This is due to the surface modification treatment of the silver nanoparticles and the optimization of the silicone rubber carrier, which enabled the silver paste to form a strong interfacial bond with the substrate during the curing process, thereby ensuring the stability and durability of the device during use.

[0043] Through the synergistic effect of surface modification and multi-stage dispersion process, the uniformity, sintering density and interfacial bonding ability of silver paste are improved. The prepared nano silver paste is suitable for low-temperature sintering process, and is particularly suitable for fields with high requirements for conductivity and reliability, such as power electronic device packaging, LED interconnection, flexible circuits and solar cells.

[0044] Example 1 A method for preparing and applying a silver-based conductive paste for flexible electronic devices includes the following steps: (1) Weigh 100g of spherical nano silver powder with an average particle size of 60nm (purity ≥99.9%) and 5g of oleic acid (the mass ratio of silver powder to organic acid is 100:5). Dissolve the oleic acid in 200mL of isopropanol and stir to form a uniform solution.

[0045] (2) Add the nano silver powder slowly to the above solution and wet it fully under magnetic stirring; then place the mixture in an ultrasonic cleaner, set the ultrasonic power to 400W and the frequency to 40kHz, and perform ultrasonic dispersion treatment for 80 minutes to make oleic acid molecules form a hydrophobic coating layer on the surface of the silver powder.

[0046] (3) After sonication, transfer the suspension to a centrifuge tube and centrifuge at 6000 r / min for 12 minutes. Discard the supernatant. Wash the precipitate twice with anhydrous ethanol, 10 mL / g each time, to ensure the removal of unreacted organic matter.

[0047] (4) Place the washed modified silver powder in a vacuum drying oven and dry it for 12 hours at 55°C and a vacuum degree of not less than 0.085MPa to obtain surface-modified nano silver powder with good flowability for later use.

[0048] (5) Prepare the silicone rubber carrier according to the following formula: 65wt% propylene glycol phenyl ether; 2.0wt% sodium dodecyl sulfate (surfactant); 15wt% epoxy resin (resin solution); 2.0wt% γ-aminopropyltriethoxysilane (silane coupling agent); 2.0wt% EFKA-4050 (dispersant); 2.0wt% BYK-307 (wetting agent); 2.0wt% triphenyl phosphate (plasticizer).

[0049] (6) Add propylene glycol phenyl ether to a beaker, heat it in a 50°C constant temperature water bath, and mechanically stir it at 400 r / min. First, add γ-aminopropyltriethoxysilane and stir continuously for 30 min until completely dissolved. Then, add EFKA-4050, BYK-307, triphenyl phosphate, and sodium dodecyl sulfate in sequence. After each additive is added, continue stirring for 20 min to ensure uniform dispersion of the system. Finally, slowly add epoxy resin solution and continue stirring for 90 min until the system is transparent and homogeneous. Then, perform ultrasonic dispersion treatment on the mixed system (power 400W, time 40 min) to obtain a high-stability organosilicon rubber carrier.

[0050] (7) Weigh 80.0g of modified silver powder and 20.0g of silicone rubber carrier according to the mass ratio of modified nano silver powder to silicone rubber carrier of 80:20; place the silicone rubber carrier in a stirring container and turn on high-speed mechanical stirring (speed 1000r / min); add the silver powder slowly in batches, and at the same time start the ultrasonic equipment (probe type, power 400W) to realize the composite dispersion process of stirring and ultrasonication at the same time; after the addition is completed, continue to process for 120 minutes to ensure that the silver powder is fully wetted and initially dispersed.

[0051] (8) Transfer the mixed slurry to a planetary ball mill, load it with zirconia grinding beads (0.8 mm in diameter, with a filling rate of about 65%), and ball mill for 48 hours at a speed of 400 r / min to further break up micro-agglomerates and improve the uniformity of the slurry.

[0052] (9) After ball milling, the paste is filtered through a 350-mesh nylon screen to remove grinding beads and impurities, resulting in a paste-like nano silver paste with a fineness of ≤10μm and good thixotropic properties.

[0053] (10) The prepared nano-silver paste was screen-printed onto a flexible polyethylene terephthalate (PET) substrate, with the film thickness controlled at 15–25 μm; subsequently, it was sintered in air at 150°C for 90 minutes to form conductive lines (i.e., silver film bonding layers or printed circuits); the resistivity of the resulting silver film was measured to be 4.5 × 10⁻⁶. -5 With an adhesion rating of 5B (Ω·cm), the resistance change rate is less than 6% after repeated bending 10,000 times under a bending radius of 3mm, and no cracks are generated. It exhibits excellent flexibility and reliability and is suitable for the construction of semiconductor devices or circuits in flexible electronics fields such as wearable devices, flexible sensors, and foldable displays.

[0054] Example 2 This embodiment provides a method for preparing and applying a silver-based conductive paste for flexible electronic devices, including the following steps: (1) Weigh 100.0g of spherical nano silver powder (purity ≥99.9%) with an average particle size of 100nm and 2.5g of stearic acid (the mass ratio of silver powder to organic acid is 100:2.5). Dissolve the stearic acid in 220mL of anhydrous ethanol and heat it in a water bath to 60℃ to aid dissolution and form a clear solution.

[0055] (2) Under stirring conditions, the nano silver powder was slowly added to the above solution to prevent clumping; then the mixture was placed in an ultrasonic disperser, the ultrasonic power was set to 400W and the frequency to 40kHz, and ultrasonic treatment was performed for 90 minutes to form a steric hindrance coating layer on the surface of the silver powder with long-chain hard fatty acids.

[0056] (3) After sonication, the suspension was transferred to a centrifuge tube and centrifuged at 6000 r / min for 15 minutes. The supernatant was discarded. The precipitate was washed twice with ethanol at 10 mL / g each time, and centrifuged under the same conditions each time.

[0057] (4) Place the washed modified silver powder in a vacuum drying oven and dry it for 10 hours at 60°C and a vacuum degree of not less than 0.08MPa to obtain surface modified nano silver powder with good flowability and strong anti-agglomeration ability, for later use.

[0058] (5) Prepare the silicone rubber carrier according to the following formula: Isophorone (solvent) 63.0wt%; Tween-80 (surfactant) 1.0wt%; acrylic resin solution (resin solution) 18.0wt%; γ-glycidyl etheroxypropyltrimethoxysilane (KH-560, coupling agent) 2.0wt%; Disperbyk-111 (dispersant) 2.0wt%; BYK-341 (wetting agent) 2.0wt%; dibutyl phthalate (DBP, plasticizer) 2.0wt%.

[0059] (6) Add isophorone to a three-necked flask, place it in a constant temperature water bath at 50°C, and mechanically stir at 400 r / min; first add γ-glycidyl etheroxypropyltrimethoxysilane, and continue stirring for 30 min until completely dissolved; then add Disperbyk-111 (dispersant), BYK-341 (wetting agent), dibutyl phthalate (DBP, plasticizer) and Tween-80 (surfactant) in sequence, and continue stirring for 20 min after each additive is added to ensure uniform dispersion of the system; finally, slowly add acrylic resin solution and continue stirring for 90 min until the system is transparent and homogeneous; then perform ultrasonic dispersion treatment on the mixed system (power 400W, time 40 min) to obtain a highly stable organosilicon rubber carrier.

[0060] (7) Weigh 90.0g of modified silver powder and 10.0g of silicone rubber carrier according to the mass ratio of modified nano silver powder to silicone rubber carrier of 90:10; place the silicone rubber carrier in a stainless steel stirring vessel and turn on high-speed stirring (speed 1000r / min); slowly add the silver powder in six batches, and at the same time start the ultrasonic probe (power 400W) to perform ultrasonic dispersion while adding materials; after all materials are added, continue to treat under ultrasonic + stirring conditions for 120 minutes to ensure uniform wetting of the high solid content system.

[0061] (8) Transfer the mixed slurry to a planetary ball mill, add zirconia grinding beads (1.0 mm in diameter, about 60% filling rate), and ball mill for 48 hours at a speed of 500 r / min to effectively break the micro-agglomeration phenomenon under high concentration and improve the homogeneity of the slurry.

[0062] (9) After ball milling, the grinding media is removed by filtering through a 400-mesh stainless steel screen to obtain a paste-like nano silver paste with a solid content of up to 90 wt%, moderate viscosity, and no particle feel.

[0063] (10) The obtained silver paste was coated onto an aluminum nitride ceramic substrate (AlN) by printing or dispensing. After attaching a copper chip, the substrate was sintered in air at 180°C for 120 minutes to form a sintered layer (i.e., a silver film bonding layer or printed circuit). Testing showed that the sintered layer was dense and free of pores, with good interfacial bonding and a volume resistivity of 4.1 × 10⁻⁶. -5 With a thermal conductivity greater than 200 W / (m·K) and a shear strength exceeding 35 MPa, it meets the technical requirements for high thermal conductivity and high reliability interconnect materials in high-power IGBT modules, laser packaging, etc., and is suitable for semiconductor devices such as those required for IGBT modules or laser packaging.

[0064] Example 3 This embodiment provides a method for preparing and applying a silver-based conductive paste for flexible electronic devices, including the following steps: (1) Weigh 100.0g of spherical nano silver powder (purity ≥99.9%) with an average particle size of 80nm and 1g of citric acid (the mass ratio of silver powder to organic acid is 100:1). Dissolve the citric acid in 250mL of anhydrous ethanol and stir until completely dissolved to form a transparent solution.

[0065] (2) The nano silver powder was slowly added to the above organic acid solution and fully wetted under stirring conditions. Then the mixture was placed in an ultrasonic disperser, the ultrasonic power was set to 400W and the frequency was 40kHz, and ultrasonic treatment was performed for 90 minutes to achieve uniform modification of the silver powder surface.

[0066] (3) After sonication, the suspension was transferred to a centrifuge tube and centrifuged at 6000 r / min for 15 minutes. The supernatant was discarded. The precipitate was washed twice with anhydrous ethanol, each time with 12 mL / g of silver powder. The same centrifugation conditions were performed each time.

[0067] (4) Place the washed precipitate in a vacuum drying oven and dry it for 10 hours at a temperature of 60°C and a vacuum degree of not less than 0.08MPa to obtain surface-functionalized modified nano silver powder for later use.

[0068] (5) Prepare the silicone rubber carrier according to the following formula: diethylene glycol butyl ether (solvent) 76.0wt%; Tween-80 (surfactant) 1.0wt%; ethyl cellulose solution (resin solution) 17.0wt%; γ-glycidyl etheroxypropyltrimethoxysilane (KH-560, coupling agent) 1.0wt%; sodium polyacrylate (dispersant) 1.0wt%; polyoxyethylene ether (surfactant) 2.0wt%; dibutyl phthalate (DBP, plasticizer) 2.0wt%.

[0069] (6) Diethylene glycol butyl ether was added to a three-necked flask and placed in a constant temperature water bath at 50°C. The mixture was mechanically stirred at 400 r / min. First, γ-glycidyl etheroxypropyltrimethoxysilane was added and stirred for 30 min until fully dissolved. Then, sodium polyacrylate, polyoxyethylene ether, dibutyl phthalate and Tween-80 were added in sequence. After each component was added, the mixture was stirred for 20 min. Finally, ethyl cellulose solution was slowly added dropwise and stirred for 90 min until the system was completely transparent and homogeneous. Then, ultrasonic dispersion was performed (power 400 W, time 40 min) to obtain a high-stability organosilicon rubber carrier.

[0070] (7) Weigh 88.0g of modified silver powder and 12.0g of silicone rubber carrier according to the mass ratio of modified nano silver powder to silicone rubber carrier of 88:12; place the silicone rubber carrier in a stirring container and turn on the mechanical stirring (speed 1000r / min); slowly add the modified silver powder in five batches, and turn on the ultrasonic equipment (power 400W) at the same time, and stir ultrasonically while adding the material; after all the materials are added, continue to stir for 120 minutes under the same conditions to achieve preliminary uniform dispersion.

[0071] (8) Transfer the mixed slurry to a planetary ball mill, add zirconium oxide grinding beads (1.0 mm in diameter, with a filling rate of about 60%), and ball mill for 48 hours at a speed of 450 r / min to achieve deep homogenization and nanoscale dispersion.

[0072] (9) After ball milling, the slurry is filtered through a 400-mesh stainless steel screen to remove the grinding media and obtain a paste-like nano silver paste with a fineness of ≤10μm and a suitable viscosity.

[0073] (10) The obtained nano-silver paste was coated onto a copper-plated ceramic substrate (DBC) using a dispensing process, and then sintered in air at 200°C for 60 minutes to form a conductive connection layer (i.e., a silver film connection layer or printed circuit). Testing showed that the sintered silver layer was dense and pore-free, with an adhesion (cross-cut test) rating of 5B and a volume resistivity of 3.9 × 10⁻⁶. -5 With a strength of Ω·cm, it exhibits excellent conductivity and interfacial bonding strength, making it suitable for low-temperature interconnect processes in high-reliability semiconductor devices such as IGBT modules and LED packages.

[0074] In summary, compared with existing technologies, it has the following beneficial effects: 1. Surface modification of nano-silver powder with organic acids effectively reduces its surface energy. Combined with ultrasonic and centrifugal treatment, it significantly inhibits the agglomeration behavior of silver powder in subsequent processing and improves dispersion stability.

[0075] 2. A composite silicone rubber carrier system was designed, which includes silane coupling agents and various functional additives. This enhances the compatibility between silver powder and the organic phase, improves the rheological properties and printability of the paste, and results in a tightly bonded printed circuit to the substrate.

[0076] 3. A multi-stage dispersion process of "ultrasound-high-speed stirring-planetary ball milling" is adopted to achieve uniform dispersion of nano-silver powder in the carrier and obtain a highly dense sintered structure.

[0077] 4. The prepared nano-silver paste can be well sintered at relatively low temperatures, exhibits excellent electrical conductivity, and is suitable for heat-sensitive substrates.

[0078] 5. The process is controllable and repeatable, making it suitable for large-scale production. It is widely used in semiconductor devices such as electronic packaging and power modules, as well as in fields such as sensors and flexible electronics, and has good industrialization prospects.

[0079] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a silver-based conductive paste for flexible electronic devices, characterized in that, include: Surface modification of raw silver nanoparticles was performed using organic acids to obtain modified silver nanoparticles. An organosilicon rubber carrier is prepared, wherein the organosilicon rubber carrier is composed of an organic solvent, a silane coupling agent, and additives; Modified nano-silver powder was mixed with an organosilicon rubber carrier and homogenized to obtain a silver-based conductive paste.

2. The method for preparing silver-based conductive paste for flexible electronic devices as described in claim 1, characterized in that, The surface modification treatment of the original silver nanopowder with organic acid to obtain modified silver nanopowder includes: Weigh out the original nano silver powder and organic acid, with the mass ratio of the original nano silver powder to the organic acid being 100:(1-5). Dissolve the organic acid in an organic alcohol solvent and stir to form a homogeneous solution; The original silver nanoparticles were slowly added to the formed homogeneous solution and fully wetted under magnetic stirring. The mixture was then placed in an ultrasonic cleaner and ultrasonically stirred for 60 to 90 minutes at 400W ultrasonic power to ensure that the organic acid fully coated the surface of the original nano silver powder. After sonication, the suspension was transferred to a centrifuge tube and centrifuged at 6000 r / min for 10 to 15 minutes. The supernatant was removed to obtain the precipitate. After washing the precipitate 2-3 times with anhydrous ethanol, it is placed in a vacuum drying oven and dried at 50℃-60℃ for 6-12 hours to obtain modified nano silver powder.

3. The method for preparing silver-based conductive paste for flexible electronic devices as described in claim 1, characterized in that, The original silver nanoparticles have an average particle size of 20nm to 100nm and a specific surface area of ​​5m². 2 / g~15m 2 / g, purity ≥99.9%, the original nano silver powder is spherical or near-spherical silver nanoparticles; The organic acid is at least one of succinic acid, citric acid, oleic acid, stearic acid, acetic acid, or benzoic acid.

4. The method for preparing the silver-based conductive paste for flexible electronic devices as described in claim 1, characterized in that, The preparation of the organosilicon rubber carrier includes: Weigh the organic solvent according to the proportion and place it in a mixing container. Heat it in a 50°C constant temperature water bath and mechanically stir it at a speed of 300r / min to 500r / min. Add the silane coupling agent and stir until completely dissolved; Then add wetting agent, dispersant, surfactant and plasticizer in sequence, stirring for 15 to 30 minutes after each additive is added until completely dispersed; Finally, add the resin solution and continue stirring for 60 minutes until the system is uniformly transparent or semi-transparent; After being mixed evenly, the mixture is subjected to ultrasonic stirring at a power of 300W to 500W for 30 minutes to obtain an organosilicon rubber carrier.

5. The method for preparing the silver-based conductive paste for flexible electronic devices as described in claim 4, characterized in that, The organic solvent is at least one of terpineol, butyl carbitol, ethylene glycol, diethylene glycol butyl ether, propylene glycol phenyl ether, or isophorone, and the amount of organic solvent added is 60% to 80% of the total mass of the silicone rubber carrier. The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or vinyltrimethoxysilane, and the amount of silane coupling agent added is 0.5% to 2% of the total mass of the organosilicon rubber carrier.

6. The method for preparing the silver-based conductive paste for flexible electronic devices as described in claim 1, characterized in that, The process of mixing modified silver nanoparticles with an organosilicon rubber carrier and homogenizing the mixture to obtain a silver-based conductive paste includes: Modified nano-silver powder was slowly and batch-wise added to the prepared organosilicon rubber carrier. While mechanically stirring at a speed of 1000 r / min, 400W ultrasonic treatment was applied and stirring was continued for 120 minutes to achieve preliminary uniform dispersion and obtain a mixed slurry. The mixed slurry was then transferred to a planetary ball mill, and zirconia grinding beads with a diameter of 0.5 mm to 2 mm were added. The mill was then ball-milled at a speed of 300 r / min to 500 r / min for 48 hours. After ball milling, the mixture is passed through a 300-500 mesh sieve to obtain a paste-like nano-silver paste with a fineness of ≤10μm, which is a silver-based conductive paste.

7. A silver-based conductive paste for flexible electronic devices, characterized in that, The silver-based conductive paste for flexible electronic devices is prepared by the method described in any one of claims 1-6. The silver-based conductive paste comprises modified silver nanoparticles and an organosilicon rubber carrier, wherein the mass percentage of modified silver nanoparticles is 70% to 90% and the mass percentage of organosilicon rubber carrier is 10% to 30%.

8. An application of a silver-based conductive paste, characterized in that, The silver-based conductive paste of claim 7 is used in flexible electronic devices.

9. The application of the silver-based conductive paste as described in claim 8, characterized in that, The electronic devices include LEDs, IGBT modules, solar cells, laser packages, wearable devices, sensors, and displays.

10. The application of the silver-based conductive paste as described in claim 8, characterized in that, The silver-based conductive paste is coated onto the surface of a substrate and sintered at 150°C to 250°C in air or a nitrogen atmosphere for 30 to 120 minutes, with a sintering temperature of 200°C, to form a conductive silver film bonding layer; the resistivity of the silver film bonding layer is less than 4.8 × 10⁻⁶. -5 Ω·cm, adhesion level 4B or higher.

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