Multifunctional alloy nanoparticle composite conductive filler as well as preparation method and application thereof

Abstract

The invention relates to the technical field of conductive adhesives, in particular to a multifunctional alloy nanoparticle composite conductive filler, a preparation method and application thereof. The multifunctional alloy nanoparticle composite conductive filler comprises a silver sheet, Sn-In-Bi alloy nanoparticles and antimony-doped tin oxide nanoparticles in a mass ratio of (40-65): (5-12): (1-7). According to the invention, the multifunctional alloy nanoparticle composite conductive filler is prepared through the cooperation of the silver strip-LMPA-ATO, and the conductive adhesive prepared from the conductive filler has the characteristics of high conductivity, high thermal conductivity and low infrared emissivity, and meets the multi-dimensional functional requirements in a complex environment. The conductive filler shows good compatibility in matrixes (rigid E44 and flexible TPU), particularly, the conductive adhesive prepared from the conductive filler and TPU still keeps flexibility under high filler content, and the electrical stability is still excellent after 2000 cycles, so that the conductive filler has good application prospects in rigid packaging and flexible interconnection scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of conductive adhesive, in particular to a multifunctional alloy nanoparticle composite conductive filler, a preparation method and application thereof. BACKGROUND

[0002] With the development of electronic products towards miniaturization, thinness and flexibility, the traditional high-temperature welding technology has increasingly highlighted the problems of low interconnection yield and poor reliability caused by thermal stress. As a key material for low-temperature interconnection, conductive adhesive (ECA) has the advantage of low processing temperature, but the widely used ECAs at present mostly rely on high proportion of silver filler (usually more than 70wt.%), which not only leads to high cost and mechanical strength reduction, but also has the risk of short circuit caused by electrochemical migration. In addition, the single-function ECAs have been difficult to meet the multi-dimensional demand of heat conduction, infrared stealth and mechanical flexibility of modern electronic devices in complex environments.

[0003] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0004] In view of the above problems of the prior art, the present application aims to provide a multifunctional alloy nanoparticle composite conductive filler, a preparation method and application thereof, and to solve the problem of single function of the existing conductive adhesive.

[0005] In the first aspect of the present application, a multifunctional alloy nanoparticle composite conductive filler is provided, which comprises silver flakes, Sn-In-Bi alloy nanoparticles (LMPA) and antimony-doped tin oxide (ATO) nanoparticles in a mass ratio of (40-65):(5-15):(1-7).

[0006] Optionally, the diameter of the silver flakes is 6-10μm.

[0007] Optionally, the particle size of the Sn-In-Bi alloy nanoparticles is 307±14.4nm, which is made of tin, indium and bismuth in a mass ratio of (10-30):(40-54):(25-35), and comprises BiIn2 phase and β phase, or BiIn2 phase and γ phase.

[0008] Optionally, the Sn-In-Bi alloy nanoparticles are prepared by the following method: Melting tin, indium and bismuth to make Sn-In-Bi alloy; Adding the Sn-In-Bi alloy into polyvinylpyrrolidone aqueous solution, heating to 65-85℃, then shearing, ultrasonic treatment, and finally cooling to obtain the Sn-In-Bi alloy nanoparticles.

[0009] It should be noted that the melting is carried out under the inert gas atmosphere of the vacuum tube furnace.

[0010] Optionally, the shearing process involves stirring at a speed of 2000-3000 r / min for 5-30 min.

[0011] Optionally, the ultrasonic treatment is performed at a frequency of 40kHz and a power of 120W for 20-60 minutes.

[0012] It should be noted that the weight-average molecular weight of polyvinylpyrrolidone (PVP) in the aqueous solution is 1,300,000, and the mass concentration of PVP in the aqueous solution is 3.23 wt.%. In preparing the aqueous solution, PVP is dissolved in deionized water at room temperature until the PVP is completely dissolved.

[0013] Optionally, the cooling is performed by sudden cooling with ice water at 0-4°C until the temperature drops to room temperature. It should be noted that after cooling, the obtained product should be centrifuged, washed with ethanol, filtered, and dried to obtain pure Sn-In-Bi alloy nanoparticles.

[0014] In a second aspect, the present invention provides a method for preparing a multifunctional alloy nanoparticle composite conductive filler, comprising mixing silver flakes, Sn-In-Bi alloy nanoparticles (LMPA) and antimony-doped tin oxide (ATO) nanoparticles, adding a solvent, stirring under ultrasonic conditions to form a uniform suspension, removing the solvent, and obtaining the multifunctional alloy nanoparticle composite conductive filler.

[0015] Optionally, the solvent is acetone, 1,4-dioxane, or ethyl acrylate, etc.

[0016] It should be noted that the stirring time can be more than 20 minutes until a uniform suspension is formed.

[0017] In a third aspect, the present invention provides an application of a multifunctional alloy nanoparticle composite conductive filler in conductive adhesives.

[0018] In a fourth aspect, the present invention provides a conductive adhesive comprising a matrix and the aforementioned multifunctional alloy nanoparticle composite conductive filler.

[0019] Optionally, the mass ratio of the matrix to the multifunctional alloy nanoparticle composite conductive filler is (20-40):(60-70).

[0020] Optionally, the matrix is ​​epoxy resin (E44) or thermoplastic polyurethane (TPU).

[0021] It should be noted that when the matrix is ​​epoxy resin (E44), a curing agent (dimethylimidazole) also needs to be added. The mass of the curing agent is 0.5% of the mass of the multifunctional alloy nanoparticle composite conductive filler.

[0022] In a fifth aspect, the present invention provides a method for preparing a conductive adhesive, comprising the following steps: dispersing the multifunctional alloy nanoparticle composite conductive filler in a solvent (acetone or dimethylformamide), adding a matrix, heating and stirring to mix, then evaporating the solvent to obtain a paste product, and curing the paste product to obtain the conductive adhesive; Alternatively, the multifunctional alloy nanoparticle composite conductive filler and the matrix are mixed uniformly in a molten state and then processed into a conductive adhesive.

[0023] Optionally, the heating and stirring temperature is 50°C, and the curing temperature is 85°C.

[0024] It should be noted that when the matrix is ​​epoxy resin (E44), a curing agent (dimethylimidazole) needs to be added at the same time as the matrix.

[0025] Beneficial effects: By synergistically producing a multifunctional alloy nanoparticle composite conductive filler through "silver sheet-LMPA-ATO", the conductive adhesive made using this conductive filler simultaneously possesses high conductivity, high thermal conductivity, and low infrared emissivity, meeting the multi-dimensional functional requirements in complex environments.

[0026] This conductive filler exhibits good compatibility in both the rigid E44 and flexible TPU matrices, especially with conductive adhesives made from TPU. It maintains flexibility even with high filler content and demonstrates excellent electrical stability after 2000 cycles, making it a promising candidate for both rigid encapsulation and flexible interconnect applications. Attached Figure Description

[0027] Figure 1 The SEM and DLS particle size distribution diagrams of the LMPA prepared in Example 1 are shown.

[0028] Figure 2 The image shows the XRD pattern of the LMPA prepared in Example 1.

[0029] Figure 3 The images show SEM images and EDS elemental distribution diagrams of the conductive adhesive prepared in Example 1.

[0030] Figure 4 The infrared emissivity curves are for the conductive adhesives prepared in Examples 1 and 2.

[0031] Figure 5 The tensile stress-strain curve of the conductive adhesive prepared in Example 2 is shown.

[0032] Figure 6 This is a photograph of the conductive adhesive prepared in Example 2.

[0033] Figure 7The image shows a SEM image of the nanoparticles prepared in Comparative Example 1.

[0034] Figure 8 The image shows a SEM image of the nanoparticles prepared in Comparative Example 2.

[0035] Figure 9 The image shows a SEM image of the nanoparticles prepared in Comparative Example 3. Detailed Implementation

[0036] This invention provides a multifunctional alloy nanoparticle composite conductive filler, its preparation method, and its applications. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0037] Low-melting-point alloy particles, due to their low-temperature melting characteristics, have been attempted as auxiliary fillers for ECAs to reduce the amount of silver used. However, the preparation of low-melting-point alloy particles currently mostly uses organic alcohol solvents, which not only have problems with toxicity and flammability, but also have uneven particle size (often greater than 2μm), affecting the construction of conductive networks. In addition, existing ECAs have single functions and lack an integrated solution that simultaneously possesses high conductivity, high thermal conductivity, infrared stealth, and flexible adaptability, which limits their application in high-end fields such as flexible electronics and high-frequency communications.

[0038] This embodiment provides a multifunctional alloy nanoparticle composite conductive filler, comprising silver flakes, Sn-In-Bi alloy nanoparticles (LMPA), and antimony-doped tin oxide (ATO) nanoparticles in a mass ratio of (40-65):(5-15):(1-7). The mass ratio can be 40:5:1, 65:15:1, 50:10:5, 40:10:2, 45:8:4, 40:12:6, 60:6:4, 50:9:7, 55:8:4, or any value within the range.

[0039] This embodiment utilizes a synergistic process of "silver sheet-LMPA-ATO" to create a multifunctional alloy nanoparticle composite conductive filler. The conductive adhesive made using this filler exhibits both high conductivity (e.g., resistivity of 2.98 × 10⁻⁶) and high conductivity (e.g., resistivity 2.98 × 10⁻⁶). -4 With characteristics such as high Ω·cm, high thermal conductivity (e.g., 5.57 W / (m·K)) and low infrared emissivity (e.g., 0.27), it meets the multi-dimensional functional requirements in complex environments.

[0040] Research has found that Sn-In-Bi alloys possess latent heat of phase change and have certain applications in thermal management. ATO, a commonly used infrared stealth material, can significantly improve the conductivity of conductive adhesives when added in small amounts. Combining LMPA with ATO allows LMPA to melt and fuse with Ag sheets to construct a three-dimensional conductive and thermally conductive network. ATO, with its advantageous particle size (20-60nm), fills the network gaps, further enhancing conductivity and thermal conductivity. Therefore, the addition of LMPA and ATO can simultaneously provide high conductivity, high thermal conductivity, and infrared stealth properties.

[0041] In some embodiments, the average diameter of the silver sheet is 6-10 μm. Studies on different silver sheet sizes have found that a diameter of 6-10 μm is more conducive to the formation of a conductive network at low Ag content. Table 1 shows the resistivity of different silver sheet diameters.

[0042] Table 1. Resistivity of silver sheets with different diameters

[0043] In some embodiments, the Sn-In-Bi alloy nanoparticles have a particle size of 300±14.4 nm and are made of tin, indium, and bismuth in a mass ratio of (10-30):(40-54):(25-35), comprising BiIn2 phase and β phase, or BiIn2 phase and γ phase, that is, comprising BiIn2 and β phase, or BiIn2 and γ phase. The mass ratio can be 20:50:30, 30:40:30, 25:40:35, 15:50:29, 20:45:30, 26:48:29, 30:45:32, or any value within the range.

[0044] LMPA is melted and combined with Ag sheets to construct a three-dimensional conductive and thermally conductive network. This also enhances the mechanical properties of the conductive adhesive.

[0045] In some embodiments, the Sn-In-Bi alloy nanoparticles are prepared by the following method: Tin, indium, and bismuth are melted to form a Sn-In-Bi alloy; The Sn-In-Bi alloy was added to an aqueous solution of polyvinylpyrrolidone, heated to 65-85°C, then sheared, ultrasonicated, and finally cooled to obtain the Sn-In-Bi alloy nanoparticles.

[0046] Through mechanical shearing and ultrasonic cavitation, the surface of the molten alloy is oxidized under shear force and broken into fine particles in the fluid. Polyvinylpyrrolidone in the solution is adsorbed onto the surface of the particles, encapsulating them and greatly preventing particle aggregation. Ultrasonic induction of directional fluid movement promotes the uniform distribution of cavitation bubbles, enhancing the uniformity of particle formation.

[0047] It should be noted that melting takes place in an inert gas atmosphere within a vacuum tube furnace.

[0048] In some embodiments, the shearing process involves stirring at a speed of 1500-3000 r / min for 5-30 min.

[0049] In some implementations, ultrasonic treatment involves sonicating at a frequency of 30-50 kHz and a power of 100-150 W for 20-60 minutes. Ultrasound can promote particle uniformity; excessively high frequencies or power can disrupt the encapsulation behavior of polyvinylpyrrolidone and increase the probability of particle collisions, thus greatly enhancing particle aggregation.

[0050] It should be noted that the weight-average molecular weight of polyvinylpyrrolidone in the aqueous solution is 1,300,000, and the mass concentration of polyvinylpyrrolidone in the aqueous solution is 3.23 wt.%. When preparing the aqueous solution, polyvinylpyrrolidone is dissolved in deionized water at room temperature until the PVP is completely dissolved.

[0051] In some embodiments, the cooling is performed by sudden cooling with ice water at 0-10°C until the temperature drops to room temperature. It should be noted that after cooling, the resulting product is centrifuged, washed with ethanol, filtered, and dried to obtain pure Sn-In-Bi alloy nanoparticles.

[0052] In a second aspect, the present invention provides a method for preparing a multifunctional alloy nanoparticle composite conductive filler, comprising mixing silver flakes, Sn-In-Bi alloy nanoparticles (LMPA) and antimony-doped tin oxide (ATO) nanoparticles, adding a solvent, stirring under ultrasonic conditions to form a uniform suspension, removing the solvent, and obtaining the multifunctional alloy nanoparticle composite conductive filler.

[0053] In some embodiments, the solvent is a solvent that is easily removed at low temperatures, such as acetone, 1,4-dioxane, or ethyl acrylate.

[0054] It should be noted that the stirring time can be more than 20 minutes until a uniform suspension is formed.

[0055] In a third aspect, the present invention provides an application of a multifunctional alloy nanoparticle composite conductive filler in conductive adhesives.

[0056] In a fourth aspect, the present invention provides a conductive adhesive comprising a matrix and the aforementioned multifunctional alloy nanoparticle composite conductive filler.

[0057] In some embodiments, the mass ratio of the matrix to the multifunctional alloy nanoparticle composite conductive filler is (20-40):(60-70), such as 20:60, 30:70, 40:60, 25:65, 30:65, 20:70, 25:70, 40:65, 28:67, 38:64, or any value within the range.

[0058] Optionally, the matrix is ​​epoxy resin (E44) or thermoplastic polyurethane (TPU).

[0059] It should be noted that when the matrix is ​​epoxy resin (E44), a curing agent (dimethylimidazole) also needs to be added. The mass of the curing agent is 0.5% of the mass of the multifunctional alloy nanoparticle composite conductive filler.

[0060] In a fifth aspect, the present invention provides a method for preparing a conductive adhesive, comprising the following steps: dispersing the multifunctional alloy nanoparticle composite conductive filler in a solvent (acetone or dimethylformamide), adding a matrix, heating and stirring to mix, then evaporating the solvent to obtain a paste product, and curing the paste product to obtain the conductive adhesive; Alternatively, the multifunctional alloy nanoparticle composite conductive filler and the matrix are mixed uniformly in a molten state and then processed into a conductive adhesive.

[0061] Optionally, the heating and stirring temperature is 50°C, and the curing temperature is 85°C.

[0062] It should be noted that when the matrix is ​​epoxy resin (E44), a curing agent (dimethylimidazole) needs to be added at the same time as the matrix.

[0063] Example 1 1. Preparation of Sn-In-Bi alloy nanoparticles: Weigh out 0.1g of metal raw materials (0.02g of Sn, 0.0484g of In, and 0.0316g of Bi) according to the ratio of 20wt.%Sn, 48.4wt.%In, and 31.6wt.%Bi, place them in a crucible, put them in a vacuum tube furnace, introduce argon gas (argon gas flow rate of 50mL / min), heat to 400℃ to completely melt the metal, hold at that temperature for 30min, and then cool naturally to room temperature to obtain a blocky Sn-In-Bi alloy.

[0064] Weigh 1g of PVP (weight average molecular weight 1,300,000), add it to 30mL of deionized water, and stir at room temperature for 1h until completely dissolved to form a 3.23wt.% PVP aqueous solution.

[0065] The obtained Sn-In-Bi alloy was added to a PVP aqueous solution and heated to 70°C. The mixture was stirred until the Sn-In-Bi alloy was completely melted. A high-speed rotary mill was started, and the mixture was sheared at 2800 r / min for 20 min. Then, an ultrasonic instrument was turned on, and the mixture was ultrasonically treated at 40 kHz frequency and 120 W power for 30 min. After the treatment, the suspension was quickly placed in an ice-water bath (0-4°C) and rapidly cooled to room temperature to obtain a suspension containing Sn-In-Bi alloy nanoparticles.

[0066] The cooled suspension containing Sn-In-Bi alloy nanoparticles was placed in a centrifuge tube and centrifuged at 8000 r / min for 15 min to remove the supernatant. 10 mL of ethanol was added to wash the precipitate, and the centrifugation-washing operation was repeated 3 times. Finally, the precipitate was placed in a vacuum drying oven at 40℃ and dried for 12 h to obtain Sn-In-Bi alloy nanoparticles.

[0067] The results obtained from SEM and dynamic light scattering (DLS) tests are as follows: Figure 1 As shown, the left image is a SEM image of LMPA nanoparticles, and the right image is a particle size distribution map of DLS. Figure 1 It can be seen that the Sn-In-Bi alloy nanoparticles obtained in this embodiment have a particle size of 307±14.4 nm and are uniform. The obtained Sn-In-Bi alloy nanoparticles were subjected to powder diffraction, and the results are as follows... Figure 2 As shown, the Sn-In-Bi alloy nanoparticles in this embodiment contain BiIn2 phase and In... 0.2 Sn 0.8 Phase, indicating that indium exists in the BiIn2 phase and In 0.2 Sn 0.8 The phase is distributed in bismuth and tin.

[0068] 2. Preparation of multifunctional alloy nanoparticle composite conductive fillers: Weigh 5g of silver flakes (average size 6.8μm), 1g of Sn-In-Bi alloy nanoparticles, and 0.5g of ATO nanoparticles, place them in an agate mortar, and mix and grind for 10min. Then transfer the mixture to a beaker, add 5mL of acetone, and stir magnetically for 20min under ultrasonic (30kHz, 80W) to form a uniform suspension. Place the suspension in a 50℃ rotary evaporator to evaporate and remove the acetone, obtaining a multifunctional alloy nanoparticle composite conductive filler.

[0069] 3. Preparation of conductive adhesive: Weigh 0.65g of multifunctional alloy nanoparticle composite conductive filler, add 0.35g of E44 epoxy resin and 0.00325g of dimethylimidazole (curing agent), and stir on a heating plate at 50℃ for 30min to form a gel-like product.

[0070] The gel-like product was uniformly coated onto a glass substrate (100 μm thick) and cured in an oven at 85 °C for 2 h to obtain the conductive adhesive (E44-based). The obtained conductive adhesive (E44-based) was subjected to scanning electron microscopy and EDS elemental analysis, and the results are as follows: Figure 3 As shown, the left image is a scanning electron microscope (SEM) image of the conductive adhesive (E44-based), and the right image is an EDS elemental distribution map. From... Figure 3 As can be seen from the data, the Ag, In, Sn, Bi, and Sb elements in the conductive adhesive obtained in this embodiment are uniformly distributed, proving that the conductive network is completely constructed.

[0071] Performance testing: A four-probe measurement system was used for testing, and the resistivity was 2.98 × 10⁻⁶. -4 The thermal conductivity was measured in Ω·cm using a TPS2500S thermal conductivity analyzer, and was 5.57 W / (m·K). The infrared emissivity in the 3-14 μm band was measured to be 0.27 using a Bruker Vertex70V spectrometer.

[0072] Example 2 The difference between this embodiment and Embodiment 1 is that the preparation of the conductive adhesive is different. The preparation of the conductive adhesive in this embodiment includes: Weigh 0.65g of the multifunctional alloy nanoparticle composite conductive filler prepared in Example 1, add 0.35g of TPU particles, and place in a twin-screw extruder. Melt-blend for 10min at 180℃ and 100r / min, then extrude and granulate. Then press through a flatbed thermoforming machine at 190℃ and 10MPa pressure for 5min to prepare a conductive adhesive (TPU-based) with a thickness of 100μm.

[0073] Performance testing: The elongation at break was 420% using a universal testing machine (tensile rate 50 mm / min), which is comparable to that of pure TPU (450%). After 2000 tensile-bending cycles (strain 0-20%) using a self-assembled cyclic device, the resistance change rate after the cycles was less than 5%, indicating excellent electrical stability.

[0074] The conductive adhesives prepared in Examples 1 and 2 were subjected to infrared emissivity measurements, and the results are as follows: Figure 4 As shown. From Figure 4 It can be seen that the infrared emissivity of the power-generating gels obtained in Examples 1 and 2 is less than 0.3, and both have infrared stealth properties.

[0075] The conductive adhesive obtained in Example 2 was subjected to a tensile stress-strain test, and the results are as follows: Figure 5 As shown. From Figure 5 As can be seen, the elongation at break of the conductive adhesive in this embodiment is close to that of pure TPU, proving that it has excellent flexibility.

[0076] When the conductive adhesive of this embodiment is applied to a screen-printed circuit, the brightness of the LED light remains essentially unchanged after multiple bends at different angles. The result is as follows: Figure 6 As shown, a) is a schematic diagram of the screen-printed circuit, b) is a physical image of the screen-printed circuit after being powered on, c) is a physical image of the screen-printed circuit after being powered on (bent state one), and d) is a physical image of the screen-printed circuit after being powered on (bent state one). This illustrates the electrical stability of the conductive adhesive in this embodiment and its feasibility for low-temperature applications.

[0077] Comparative Example 1 The preparation of Sn-In-Bi alloy nanoparticles in this comparative example differs from that in Example 1 in that the preparation conditions for Sn, In, and Bi particles are different. In this comparative example, no mechanical stirring is used, and the microparticles are prepared by ultrasound.

[0078] Weigh out 0.1g of metal raw materials (Sn: 0.027g, In: 0.045g, Bi: 0.028g), place them in a crucible, put them in a vacuum tube furnace, introduce argon gas (flow rate 50mL / min), heat to 400℃ to completely melt the metal, hold at that temperature for 30min, and then let it cool naturally to room temperature to obtain a blocky Sn-In-Bi alloy.

[0079] Weigh 1g of PVP (weight average molecular weight 1,300,000), add it to 30mL of deionized water, and stir at room temperature for 1h until completely dissolved to form a 3.23wt.% PVP aqueous solution.

[0080] The obtained Sn-In-Bi alloy was added to a PVP aqueous solution and heated to 70°C. The mixture was stirred until the Sn-In-Bi alloy was completely melted. An ultrasonic instrument was turned on and ultrasonically treated at a frequency of 40kHz and a power of 120W for 30 minutes. After treatment, the suspension was quickly placed in an ice-water bath (0-4°C) and rapidly cooled to room temperature to obtain a suspension containing Sn-In-Bi alloy particles.

[0081] The cooled suspension containing Sn-In-Bi alloy nanoparticles was placed in a centrifuge tube and centrifuged at 8000 r / min for 15 min to remove the supernatant. 10 mL of ethanol was added to wash the precipitate, and the centrifugation-washing operation was repeated 3 times. Finally, the precipitate was placed in a vacuum drying oven at 40℃ and dried for 12 h to obtain Sn-In-Bi alloy particles.

[0082] Characterization by SEM showed that the Sn-In-Bi alloy nanoparticles obtained in this comparative example had a particle size of 20 μm, as shown in the results below. Figure 7 As shown.

[0083] Comparative Example 2 The preparation of Sn-In-Bi alloy nanoparticles in this comparative example differs from that in Example 1 in that: no polyvinylpyrrolidone was added in this comparative example, and the obtained Sn-In-Bi alloy was added to deionized water.

[0084] Weigh out 0.1g of metal raw materials (Sn: 0.027g, In: 0.045g, Bi: 0.028g), place them in a crucible, put them in a vacuum tube furnace, introduce argon gas (flow rate 50mL / min), heat to 400℃ to completely melt the metal, hold at that temperature for 30min, and then let it cool naturally to room temperature to obtain a blocky Sn-In-Bi alloy.

[0085] The obtained Sn-In-Bi alloy was added to 30 mL of deionized water and heated to 70 °C. The mixture was stirred until the Sn-In-Bi alloy was completely melted. A high-speed rotary mill was started and sheared at 2800 r / min for 20 min. Then, an ultrasonic instrument was turned on and ultrasonically treated at 40 kHz frequency and 120 W power for 30 min. After treatment, the suspension was quickly placed in an ice-water bath (0-4 °C) and rapidly cooled to room temperature to obtain a suspension containing Sn-In-Bi alloy nanoparticles.

[0086] The cooled suspension containing Sn-In-Bi alloy nanoparticles was placed in a centrifuge tube and centrifuged at 8000 r / min for 15 min to remove the supernatant. 10 mL of ethanol was added to wash the precipitate, and the centrifugation-washing operation was repeated 3 times. Finally, the precipitate was placed in a vacuum drying oven at 40℃ and dried for 12 h to obtain Sn-In-Bi alloy nanoparticles.

[0087] The Sn-In-Bi alloy nanoparticles obtained in Comparative Example 2 exhibited large-scale agglomeration, making it impossible to measure their particle size using dynamic light scattering (DLS). The results are as follows: Figure 8 As shown.

[0088] Comparative Example 3 The preparation of Sn-In-Bi alloy nanoparticles in this comparative example differs from that in Example 1 in that the total amount of Sn, In, and Bi added is different; the total amount of Sn, In, and Bi added in this comparative example is 1g.

[0089] Weigh out 1g of metal raw materials (Sn: 0.27g, In: 0.45g, Bi: 0.28g), place them in a crucible, put them in a vacuum tube furnace, introduce argon gas (flow rate 50mL / min), heat to 400℃ to completely melt the metal, hold for 30min, and then cool naturally to room temperature to obtain a blocky Sn-In-Bi alloy.

[0090] Weigh 1g of PVP (weight average molecular weight 1,300,000), add it to 30mL of deionized water, and stir at room temperature for 1h until completely dissolved to form a 3.23wt.% PVP aqueous solution.

[0091] The obtained Sn-In-Bi alloy was added to a PVP aqueous solution and heated to 70°C. The mixture was stirred until the Sn-In-Bi alloy was completely melted. A high-speed rotary mill was started, and the mixture was sheared at 2800 r / min for 20 min. Then, an ultrasonic instrument was turned on, and the mixture was ultrasonically treated at 40 kHz frequency and 120 W power for 30 min. After the treatment, the suspension was quickly placed in an ice-water bath (0-4°C) and rapidly cooled to room temperature to obtain a suspension containing Sn-In-Bi alloy nanoparticles.

[0092] The cooled suspension containing Sn-In-Bi alloy nanoparticles was placed in a centrifuge tube and centrifuged at 8000 r / min for 15 min to remove the supernatant. 10 mL of ethanol was added to wash the precipitate, and the centrifugation-washing operation was repeated 3 times. Finally, the precipitate was placed in a vacuum drying oven at 40℃ and dried for 12 h to obtain Sn-In-Bi alloy nanoparticles.

[0093] Characterization by SEM showed that the Sn-In-Bi alloy nanoparticles obtained in this comparative example had a particle size of 5 μm, as shown in the results below. Figure 9 As shown.

[0094] Comparative Example 4 Weigh 5g of silver sheet (6.8μm), add 0.35g of E44 epoxy resin and 0.00325g of dimethylimidazole (curing agent), and stir on a 50℃ heating plate for 30min to form a gel-like product.

[0095] The gel-like product was evenly coated onto a glass substrate (100 μm thick) and cured in an oven at 85°C for 2 hours to obtain E44-based conductive adhesive.

[0096] Performance testing: A four-probe measurement system was used for testing, and the resistivity was approximately 10. 3 Ω·cm, no conductive path formed; thermal conductivity was 1.06 W / (m·K) as measured by a TPS2500S thermal conductivity analyzer; infrared emissivity in the 3-14μm band was approximately 0.6 as measured by a Bruker Vertex70V spectrometer.

[0097] In summary, this invention utilizes a synergistic process of "silver sheet-LMPA-ATO" to create a multifunctional alloy nanoparticle composite conductive filler. The conductive adhesive made using this filler exhibits both high conductivity (resistivity 2.98 × 10⁻⁶) and high resistivity (2.98 × 10⁻⁶). -4With its high thermal conductivity (5.57 W / (m·K)) and low infrared emissivity (0.27), this conductive filler meets the multi-dimensional functional requirements of complex environments. It exhibits good compatibility with both rigid E44 and flexible TPU matrices, especially with conductive adhesives made from TPU. Even with high filler content, it maintains flexibility and demonstrates excellent electrical stability after 2000 cycles, making it promising for applications in both rigid encapsulation and flexible interconnection scenarios.

[0098] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A multifunctional alloy nanoparticle composite conductive filler, characterized in that, It includes silver flakes, Sn-In-Bi alloy nanoparticles, and antimony-doped tin oxide nanoparticles with a mass ratio of (40-65):(5-12):(1-7).

2. The multifunctional alloy nanoparticle composite conductive filler according to claim 1, characterized in that, The average diameter of the silver sheet is 6-10 μm.

3. The multifunctional alloy nanoparticle composite conductive filler according to claim 1, characterized in that, The Sn-In-Bi alloy nanoparticles have a particle size of 300±14.4 nm and are made of tin, indium and bismuth in a mass ratio of (10-30):(40-54):(25-35), including BiIn2 phase and β phase, or BiIn2 phase and γ phase.

4. A multifunctional alloy nanoparticle composite conductive filler according to claim 1 or 3, characterized in that, The Sn-In-Bi alloy nanoparticles were prepared by the following method: Tin, indium, and bismuth are melted to form a Sn-In-Bi alloy; The Sn-In-Bi alloy was added to an aqueous solution of polyvinylpyrrolidone, heated to 65-85°C, then sheared, ultrasonicated, and finally cooled to obtain the Sn-In-Bi alloy nanoparticles.

5. The multifunctional alloy nanoparticle composite conductive filler according to claim 4, characterized in that, The shearing process involves stirring at a speed of 1500-3000 r / min for 5-30 min; The ultrasonic treatment is performed at a frequency of 30-50kHz and a power of 100-150W for 20-60 minutes.

6. The multifunctional alloy nanoparticle composite conductive filler according to claim 4, characterized in that, The cooling process involves sudden cooling with ice water at 0-4°C until the temperature drops to room temperature.

7. A method for preparing a multifunctional alloy nanoparticle composite conductive filler, characterized in that, Silver flakes, Sn-In-Bi alloy nanoparticles, and antimony-doped tin oxide nanoparticles were mixed, a solvent was added, and the mixture was stirred under ultrasonic conditions to form a uniform suspension. The solvent was then removed to obtain the multifunctional alloy nanoparticle composite conductive filler.

8. Application of a multifunctional alloy nanoparticle composite conductive filler in conductive adhesives.

9. A conductive adhesive, characterized in that, It includes a matrix and a multifunctional alloy nanoparticle composite conductive filler as described in any one of claims 1-6.

10. A method for preparing a conductive adhesive, characterized in that, The process includes the following steps: dispersing the multifunctional alloy nanoparticle composite conductive filler according to any one of claims 1-6 in a solvent, adding a matrix, heating and stirring to mix, then evaporating the solvent to obtain a paste product, and curing the paste product to obtain the conductive adhesive; Alternatively, the multifunctional alloy nanoparticle composite conductive filler and the matrix are mixed uniformly in a molten state and then processed into a conductive adhesive.

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