Nanometer copper paste based on columnar aromatic host-guest interaction and preparation method and application thereof

Abstract

This invention relates to nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons, its preparation method, and its application, belonging to the field of conductive copper paste technology. The nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons of this invention comprises, by weight, the following components: 92-95 parts of columnar aromatic hydrocarbon supramolecular assembly-coated nano-copper powder, 4-8 parts of resin, 2-6 parts of organic solvent, 0.1-1 parts of thixotropic agent, 0.1-1 parts of dispersant, 0.1-1 parts of coupling agent, and 0.1-1 parts of other additives. The columnar aromatic hydrocarbon supramolecular assembly-coated nano-copper powder has a core-shell structure, with the host-guest complex as the shell and the nano-copper powder as the core; the host-guest complex is based on columnar aromatic hydrocarbons grafted with glycidyl methacrylate as the host and benzyl trialkyl quaternary ammonium salt as the guest; the guest is connected to the surface of the nano-copper powder through coordination bonds. The nano-copper paste of this invention has the characteristics of good conductivity, low sintering temperature, strong adhesion, and excellent antioxidant properties.

Description

Technical Field

[0001] This invention relates to the field of conductive copper paste technology, and in particular to nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons, its preparation method and application. Background Technology

[0002] As a substitute for traditional silver paste, nano-copper paste has significant application value in the electronics industry. However, existing nano-copper paste technology faces several key technical bottlenecks: First, nano-copper particles are easily oxidized in air, forming a copper oxide insulating layer, which leads to a sharp decline in conductivity; second, achieving good sintering usually requires high temperatures (typically >300℃) or sintering in a protective atmosphere (such as nitrogen or hydrogen), which limits its application; third, insufficient adhesion between the copper paste and the substrate affects the reliability of the device; fourth, the complete coverage of the conductive phase particles by the cured resin hinders electron transport, increasing the bulk resistance of the electrode.

[0003] Several attempts have been made in the prior art to address these issues. For example, organic protective agents are used to coat copper particles to prevent oxidation, but these agents often form barriers on the particle surface that hinder sintering; low-melting-point alloys or glass powders are added to lower the sintering temperature, but this introduces impurities that reduce conductivity; coupling agents are used to improve adhesion, but the effect is limited and may affect the stability of the slurry.

[0004] Therefore, there is an urgent need to provide a low-temperature sintering nano-copper paste with strong antioxidant properties, good stability, and high conductivity, as well as its preparation method. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons, its preparation method, and its applications. This invention introduces supramolecular assemblies of columnar aromatic hydrocarbons into the nano-copper paste system. Utilizing the host-guest recognition ability and self-organizing properties of columnar aromatic hydrocarbons, a stable protective layer is formed on the surface of the nano-copper powder. Simultaneously, it guides the directional alignment of the nano-copper particles during low-temperature sintering. Furthermore, the tertiary amines decomposed from the guest act as latent curing agents for epoxy resin, curing the epoxy resin after the nano-copper sinters to form a highly efficient conductive network, providing adhesion to the matrix. This solves the problems of poor oxidation resistance, high sintering temperature, insufficient conductivity, and poor room-temperature storage stability of nano-copper pastes in existing technologies.

[0006] The copper paste of this invention achieves self-organized arrangement of nano-copper powder through its internal supramolecular structure. Sintering in air at 200-250°C forms a highly conductive and strong conductive network with a volume resistivity reaching 5 × 10⁻⁶. -6 Its peel strength from the substrate is more than twice that of traditional nano-copper paste, reaching Ω·cm. It also exhibits excellent oxidation resistance and high adhesion to the substrate after sintering.

[0007] This invention is achieved through the following technical solution:

[0008] The first objective of this invention is to provide a nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons, comprising the following components by weight: 92-95 parts of nano-copper powder coated with columnar aromatic hydrocarbon supramolecular assemblies, 4-8 parts of resin, 2-6 parts of organic solvent, 0.1-1 parts of thixotropic agent, 0.1-1 parts of dispersant, 0.1-1 parts of coupling agent, and 0.1-1 parts of other additives;

[0009] The columnar aromatic supramolecular assembly coated with copper nanoparticles has a core-shell structure, with the host-guest complex as the shell and the copper nanoparticles as the core.

[0010] The host-guest complex is based on glycidyl methacrylate-grafted columnar aromatics as the host and benzyl trialkyl quaternary ammonium salt as the guest; the glycidyl methacrylate is covalently grafted onto the hydroxyl groups of the columnar aromatics through an esterification reaction; the host complex is incorporated into the cavity of the columnar aromatics through host-guest interactions; the guest complex is connected to the surface of the nano-copper powder through coordination bonds.

[0011] In one embodiment of the present invention, the particle size of the nano-copper powder is 50 nm - 500 nm.

[0012] In one embodiment of the present invention, the column aromatic hydrocarbon is column[5] aromatic hydrocarbon and / or column[6] aromatic hydrocarbon.

[0013] In one embodiment of the present invention, the benzyl trialkyl quaternary ammonium salt has the structural formula [(C6H5)-CH2N]. + (R)3]X - Where R is methyl or ethyl, X - For Cl - or Br - .

[0014] In one embodiment of the present invention, the resin is one or more selected from epoxy resin, polyurethane resin, acrylic resin and polyester resin; the epoxy resin is one or more selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic glycidyl ether epoxy resin and phenolic epoxy resin.

[0015] In one embodiment of the present invention, the organic solvent is one or more of terpineol, butyl carbitol, butyl carbitol acetate, and 12-ol ester.

[0016] In one embodiment of the present invention, the thixotropic agent is one or more selected from polyamide wax, hydrogenated castor oil, fumed silica, and ethyl cellulose.

[0017] In one embodiment of the present invention, the dispersant is one or more of oleic acid, oleamide, erucamide and BYK111.

[0018] In one embodiment of the present invention, the coupling agent is one or more of KH550, KH560 and phthalate coupling agents.

[0019] In one embodiment of the present invention, the other additives are leveling agents and defoamers;

[0020] The leveling agent is an acrylic leveling agent; the defoamer is an organosilicone defoamer.

[0021] The second objective of this invention is to provide a method for preparing the aforementioned nano-copper paste, comprising the following steps:

[0022] (1) In a nitrogen atmosphere, columnar aromatic hydrocarbons are reacted with glycidyl methacrylate in the presence of a catalyst, a polymerization inhibitor or an initiator to obtain glycidyl methacrylate-grafted columnar aromatic hydrocarbons.

[0023] (2) The columnar aromatic hydrocarbon grafted with glycidyl methacrylate obtained in step (1) is mixed with benzyltrialkyl quaternary ammonium salt in an alcohol solution to form a columnar aromatic hydrocarbon supramolecular assembly;

[0024] (3) Add copper salt and reducing agent to the columnar aromatic supramolecular assembly obtained in step (2), wash and dry to obtain nano-copper powder coated with columnar aromatic supramolecular assembly;

[0025] (4) The nano-copper powder, resin, organic solvent, thixotropic agent, dispersant, coupling agent and other additives coated by the columnar aromatic supramolecular assembly obtained in step (3) are mixed and stirred, and then sieved to obtain the nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons.

[0026] A third objective of this invention is to provide the application of the aforementioned nano-copper paste in the preparation of photovoltaic pastes or electronic pastes.

[0027] In one embodiment of the present invention, the sintering temperature of the gate wires in the electronic circuit is 200 ℃ - 250 ℃.

[0028] In one embodiment of the present invention, the resistivity of the gate lines in the electronic circuit is 5 × 10⁻⁶. - 6 Ω·cm -6.8×10 ⁻6 Ω·cm.

[0029] Mechanism of the invention:

[0030] This invention utilizes a low-temperature curing copper paste prepared by grafting GMA onto columnar aromatics and using benzyltrialkyl quaternary ammonium salt as the guest. Through the supramolecular complex formed by the columnar aromatics and benzyltrialkyl quaternary ammonium salt, the guest molecule (benzyltrialkyl quaternary ammonium salt) simultaneously connects to the surface of the nano-copper powder via coordination bonds, forming a three-layer core-shell structure of "nano-copper-ligand-column aromatics." This creates a dense protective layer on the copper powder surface, achieving oxidation resistance and promoting self-organization and arrangement of the powder particles. Upon heating, the columnar aromatics supramolecular structure detaches, causing the nano-copper particles to desorb and complete sintering, resulting in a highly conductive circuit. Simultaneously, the decomposed tertiary amines promote ring-opening of the epoxy resin, forming a three-dimensional network after the nano-copper sintering, increasing adhesion to the matrix.

[0031] Desorption mechanism: When the guest molecules reach a specific sintering temperature (200℃-250℃), an irreversible Hoffmann elimination reaction occurs, decomposing into electrically neutral olefins and tertiary amine molecules. This causes a sharp drop in their binding force with columnar aromatics, thereby triggering the desorption of the entire supramolecular assembly and exposing the surface of the nano-copper to facilitate sintering.

[0032] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0033] (1) This invention provides a nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons, its preparation method, and its application. The nano-copper paste of this invention comprises nano-copper powder, epoxy-functionalized columnar aromatic hydrocarbon supramolecular assemblies, an organic carrier, and a dispersant. The epoxy-functionalized columnar aromatic hydrocarbons act as supramolecular hosts, guiding the self-organization of nano-copper particles through host-guest interactions. Furthermore, the epoxy groups undergo ring-opening polymerization during sintering to form a three-dimensional cross-linked network, significantly enhancing the mechanical strength and adhesion to the substrate of the sintered body. The tertiary amines derived from the guest in this invention act as latent curing agents for epoxy resins, eliminating the need for additional epoxy resin curing agents.

[0034] (2) Good electrical conductivity: The self-organized sorting structure ensures the efficient formation of conductive pathways, and the resistivity of the sintered body can reach 5×10⁻⁶. - 6 Ω·cm.

[0035] (3) The sintering temperature is significantly reduced: thanks to the self-organized arrangement and the dynamic behavior of supramolecular molecules, the sintering temperature can be reduced to 200 ℃ - 250 ℃.

[0036] (4) Strong adhesion: The epoxy three-dimensional network generated by in-situ catalysis provides mechanical interlocking and chemical bonding, and the adhesion is more than twice that of traditional copper paste.

[0037] (5) Excellent antioxidant properties: The supramolecular composite layer provides excellent antioxidant protection.

[0038] (6) One agent with multiple functions: Through a supramolecular complex structure, it simultaneously solves four key problems: sorting, anti-oxidation, low temperature curing and adhesion, which simplifies the formulation and improves performance stability.

[0039] (7) The slurry can be stored at room temperature: No additional epoxy resin curing agent is added to the system, and it has good stability at room temperature. The viscosity remains almost unchanged after 7 days at room temperature. Attached Figure Description

[0040] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0041] Figure 1 This is a SEM image of the nano-copper powder obtained in Example 2 of the present invention;

[0042] Figure 2 These are 2D (A) and 3D (B) morphological images of the copper paste after screen printing in Embodiment 3 of the present invention;

[0043] Figure 3 These are 2D (A) and 3D (B) morphological images of the copper paste after screen printing in Comparative Example 1 of this invention. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0046] Hydroxyl columnar[5]arene and columnar[6]arene were purchased from Jilin Zhongke Science & Technology Co., Ltd., with CAS numbers 1187983-02-3 and 1207685-12-8, respectively.

[0047] Glycidyl methacrylate was purchased from Weicheng New Materials (Shandong) Co., Ltd., CAS No. 106-91-2;

[0048] Benzyltrimethylammonium chloride was purchased from Yixing Kailida Chemical Co., Ltd., CAS No. 56-93-9;

[0049] Oleylamine was purchased from Aladdin Reagents, CAS No. 112-90-3;

[0050] Ascorbic acid was purchased from Thermo Fisher Scientific, CAS number 50-81-7.

[0051] Example 1

[0052] This embodiment provides a method for preparing nano-copper powder coated with GMA-coated[5] aromatic hydrocarbon and benzyltrimethylammonium chloride, as follows:

[0053] (1) Preparation of Glycidyl Methacrylate (GMA) Grafted Column[5] Aromatics: Weigh 1.0 g (1.2 mmol) of column[5] aromatics and place it in a dry three-necked flask. Add 20 mL of N,N-dimethylformamide (DMF) to dissolve it. Add triethylamine (0.3 g, 3.0 mmol) as a catalyst and hydroquinone (0.01 g) as a polymerization inhibitor. Under nitrogen protection, slowly add glycidyl methacrylate (GMA, 1.7 g, 12 mmol) and control the temperature at 70 °C for 8 h. After the reaction is complete, pour the reaction solution into ice water to precipitate, filter, wash with water and ethanol, and dry under vacuum to obtain GMA-grafted column[5] aromatics.

[0054] (2) 0.1 g of GMA-grafted column[5]arene obtained in step (1) and 0.05 g of benzyltrimethylammonium chloride were dissolved together in 50 mL of ethylene glycol and stirred at room temperature for 4 h to form a host-guest complex solution. 1.7 g of copper sulfate pentahydrate (CuSO4·5H2O) was added to the above solution and stirred to dissolve. Under nitrogen protection and stirring, a reducing agent solution of 0.8 g of sodium borohydride (NaBH4) dissolved in 20 mL of ethylene glycol was rapidly added dropwise. After the addition was completed, the reaction continued for 1 h, and the solution changed from blue to brownish-red, indicating that nano-copper was generated. The reaction solution was centrifuged, washed three times alternately with ethanol and acetone, and dried under vacuum at 40 °C for 12 h to obtain dark brown GMA-column[5]arene and benzyltrimethylammonium chloride-coated nano-copper powder.

[0055] Example 2

[0056] This embodiment provides a method for preparing nano-copper powder coated with GMA-coated[6]arene and benzyltrimethylammonium chloride, as follows:

[0057] (1) 1 mmol of column[6] aromatics was dissolved in anhydrous toluene, and 10 mmol of GMA monomer and 0.1 mmol of ATRP initiator (α-bromoisobutyryl bromide) were added. Under nitrogen protection, a catalyst system (CuBr to PMDETA molar ratio of 1:1) was added, and the reaction was carried out at 70 °C for 24 h. After the reaction was completed, the mixture was passed through a neutral alumina column to remove the catalyst, and then the polymer was precipitated with cold methanol, filtered, and vacuum dried to obtain a white solid product, GMA-grafted column[6] aromatics.

[0058] (2) 0.1 g of GMA-grafted column[6]arene obtained in step (1) and 0.05 g of benzyltrimethylammonium chloride were dissolved together in 50 mL of ethylene glycol and stirred at room temperature for 4 hours to form a host-guest complex solution. 1.7 g of copper sulfate pentahydrate (CuSO4·5H2O) was added to the above solution and stirred to dissolve. Under nitrogen protection and rapid stirring in a 60°C water bath, a reducing agent solution of 0.8 g of sodium borohydride (NaBH4) dissolved in 20 mL of ethylene glycol was rapidly added dropwise. After the addition was completed, the reaction continued for 1 h, and the solution changed from blue to brownish-red, indicating that nano-copper was generated. The reaction solution was centrifuged, washed three times alternately with ethanol and acetone, and dried under vacuum at 40°C for 12 h to obtain dark brown GMA-column[6]arene and benzyltrimethylammonium chloride-coated nano-copper powder.

[0059] Example 3

[0060] This embodiment provides a nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons, which specifically includes the following components by weight:

[0061] 92 conductive phases: GMA-coated[5] aromatics and benzyltrimethylammonium chloride nano-copper powder prepared in Example 1;

[0062] 5 parts resin: 2 parts bisphenol A epoxy resin, 3 parts bisphenol F epoxy resin;

[0063] 0.1 parts leveling agent: methyl methacrylate;

[0064] 0.1 parts defoamer: polysiloxane;

[0065] 0.3 parts coupling agent: KH560;

[0066] 0.2 parts dispersant: oleic acid amide;

[0067] 0.2 parts thixotropic agent: polyamide wax;

[0068] 2.1 parts organic solvent: The volume ratio of butyl carbitol to decyl alcohol ester is 1:1.

[0069] The preparation method of the above-mentioned nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons is as follows:

[0070] (1) Mixed raw materials

[0071] Mix the conductive phase, resin, organic solvent, thixotropic agent, dispersant, coupling agent, leveling agent, and defoamer additive by hand until homogeneous.

[0072] (2) Grinding the mixture

[0073] The mixture was stirred at 1100 rpm until homogeneous, ground, and then sieved to make the fineness of the slurry less than 7 μm, thus obtaining nano-copper slurry based on the host-guest interaction of columnar aromatic hydrocarbons.

[0074] Grid lines were fabricated using the above-mentioned nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons:

[0075] The above-mentioned nano-copper paste was screen-printed into fine grid lines using a screen printing plate. The screen printing parameters were: 520 mesh, 20 μm opening, 65 N printing pressure, and 400 mm / s printing speed. The resulting pattern was placed in an air atmosphere sintering furnace and heated to 250°C for 3 minutes to cure. The electrical properties and adhesion of the resulting grid lines were then tested.

[0076] Example 4

[0077] This embodiment provides a nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons, which is similar to Example 3, except that the conductive phase is the nano-copper powder coated with GMA-column[6] aromatic hydrocarbons and benzyltrimethylammonium chloride prepared in Example 2, and the other components are consistent with those in Example 3.

[0078] The preparation method of the above-mentioned nano-copper paste and grid lines based on the host-guest interaction of columnar aromatic hydrocarbons is consistent with that in Example 3.

[0079] Comparative Example 1

[0080] This comparative example provides a nano copper paste, which is similar to Example 3, except that the nano copper powder coated with GMA-column[5] aromatics and benzyltrimethylammonium chloride in the conductive phase is replaced with nano copper powder coated with oleylamine.

[0081] One part of blocked isocyanate was added as a curing agent for the epoxy resin; the remaining components remained the same as in Example 3.

[0082] The preparation method of the oleylamine-coated copper nanoparticles is as follows: 1.7 g of copper sulfate pentahydrate (CuSO4·5H2O) is added to 50 mL of ethylene glycol solution and stirred to dissolve. Under nitrogen protection and rapid stirring in a 60℃ water bath, a reducing agent solution consisting of 0.8 g of sodium borohydride (NaBH4) dissolved in 20 mL of ethylene glycol is rapidly added dropwise. After the addition is complete, the reaction continues for 1 h, and the solution changes from blue to brownish-red, indicating the formation of copper nanoparticles. 4 mL of oleylamine is added to 20 mL of toluene, and under continuous nitrogen protection, the brownish-red ethylene glycol solution obtained from the above reaction is slowly poured in, stirred rapidly for 10 minutes, allowed to stand, and the upper brownish-red layer is centrifuged, washed three times alternately with ethanol and acetone, and then vacuum dried at 40℃ for 12 h to obtain brownish-red copper nanoparticles.

[0083] The preparation method of the above-mentioned nano-copper paste and gate wire is consistent with that in Example 3.

[0084] Typically, the curing of epoxy resin requires a curing agent to initiate ring-opening of the epoxy groups. In this example, the tertiary amine molecules generated by the thermal decomposition of the guest compound complete the ring-opening curing, while ensuring the room temperature stability of the slurry. This comparative example does not include any guest molecules, meaning that the epoxy resin does not have a curing agent after heating and therefore cannot cure. Thus, a blocked isocyanate needs to be added as a curing agent in the comparative example to verify the effect of the oleylamine-modified nano-copper powder.

[0085] Comparative Example 2

[0086] This comparative example provides a nano copper paste, which is similar to Example 3, except that the nano copper powder coated with GMA-column[5] aromatics and benzyltrimethylammonium chloride in the conductive phase is replaced with nano copper powder coated with ascorbic acid.

[0087] One part of blocked isocyanate was added as a curing agent for the epoxy resin; the remaining components remained the same as in Example 3.

[0088] The preparation method of the ascorbic acid-coated copper nanoparticles is as follows: 1.7 g of copper sulfate pentahydrate (CuSO4·5H2O) is added to 50 mL of ethylene glycol solution and stirred to dissolve. Under nitrogen protection and rapid stirring in a 60℃ water bath, a reducing agent solution consisting of 0.8 g of sodium borohydride (NaBH4) dissolved in 20 mL of ethylene glycol is rapidly added dropwise. After the addition is complete, the reaction continues for 1 h, and the solution changes from blue to brownish-red, indicating the formation of copper nanoparticles. 150 mL of anhydrous acetone is added to the brownish-red reaction solution, the supernatant is discarded by centrifugation, and the precipitate is washed with acetone and centrifuged three times to obtain a preliminarily purified wet precipitate of copper nanoparticles. 0.5 g of ascorbic acid was dissolved in 20 mL of deionized water. The pH of the solution was adjusted to weakly alkaline (pH = 7.5-8.5) using sodium bicarbonate solution. Under nitrogen protection and stirring, the above-mentioned wet precipitate of nano-copper was added. After hydrothermal treatment at 60°C for 2 h, the mixture was centrifuged, washed three times alternately with ethanol and acetone, and vacuum dried at 30°C for 18 h to obtain brownish-red nano-copper powder.

[0089] The preparation method of the above-mentioned nano-copper paste and gate wire is consistent with that in Example 3.

[0090] Comparative Example 3

[0091] This comparative example provides a nano-copper paste, similar to Example 3, except that: the nano-copper powder coated with GMA-column[5]arene and benzyltrimethylammonium chloride in the conductive phase is replaced with nano-copper powder coated with GMA-column[5]arene; 1 part of blocked isocyanate is added as a curing agent for epoxy resin; the remaining components are the same as in Example 3.

[0092] The preparation method of the GMA-column[5] aromatic coated nano-copper powder is similar to that of Example 1, except that: in step (2), benzyltrimethylammonium chloride is not added;

[0093] The preparation method of the above-mentioned nano-copper paste and gate wire is consistent with that in Example 3.

[0094] Comparative Example 4

[0095] This comparative example provides a nano copper paste, similar to Example 3, except that the nano copper powder coated with GMA-column[5] aromatics and benzyltrimethylammonium chloride in the conductive phase is replaced with nano copper powder.

[0096] One part of blocked isocyanate was added as a curing agent for the epoxy resin; the remaining components remained the same as in Example 3.

[0097] The preparation method of the nano-copper powder is as follows: 1.7 g of copper sulfate pentahydrate (CuSO4·5H2O) is added to 50 mL of ethylene glycol solution and stirred to dissolve. Under nitrogen protection and rapid stirring in a 60℃ water bath, a reducing agent solution consisting of 0.8 g of sodium borohydride (NaBH4) dissolved in 20 mL of ethylene glycol is rapidly added dropwise. After the addition is complete, the reaction continues for 1 h, and the solution changes from blue to brownish-red. After centrifugation, washing three times with acetone, and vacuum drying at 40℃ for 12 h, dark brown nano-copper powder is obtained.

[0098] The preparation method of the above-mentioned nano-copper paste and gate wire is consistent with that in Example 3.

[0099] Performance testing

[0100] 1. Figure 1 The image is a 20,000x local scan SEM image of the nano-copper powder coated with GMA-coated[5] aromatics and benzyltrimethylammonium chloride obtained in Example 1. It can be seen that the copper powder has a particle size of 50 nm-500 nm, and the particle surface is smooth and the particles are evenly dispersed.

[0101] Figure 2 These are 2D and 3D morphology images of the gate lines obtained after copper paste screen printing in Example 3. It can be seen that the linewidth of the gate lines is 43.46 μm and the line height is 15.72 μm. The resulting gate lines have less lateral diffusion of conductive particles and are smooth and flat in the longitudinal direction, with a good aspect ratio.

[0102] Figure 3 The images show the 2D and 3D morphology of the grid lines obtained after screen printing with copper paste in Comparative Example 1. It can be seen that the grid line width is 67.53 μm and the line height is 23.84 μm. Furthermore, the conductive particles are severely diffused laterally, the grid line has poor longitudinal flatness, and the aspect ratio is poor.

[0103] 2. The volume resistivity and resistivity change, slurry viscosity stability and adhesion of the above embodiments and comparative examples were tested. The specific test methods are as follows:

[0104] (1) Initial resistivity and resistivity change: The prepared nano-copper paste was screen-printed onto silicon substrates and cured at 250℃ for 3 min. The initial resistivity was then measured. After being placed in a humid and hot environment at 85℃ and 85%RH for 72 h, the resistivity change rate was measured. Resistivity change rate = (resistivity after 72 h - initial resistivity) / initial resistivity × 100%.

[0105] (2) Slurry viscosity stability: The slurry was sealed and left at room temperature (25℃) for 7 days, and the viscosity was tested. Viscosity change rate = (viscosity after 7 days - initial viscosity) / initial viscosity × 100%.

[0106] (3) Adhesion: Refer to GB / T 17473.4-2008.

[0107] The test results are shown in Table 1 below:

[0108] Table 1

[0109]

[0110] Examples 3 and 4: The present invention preferably uses columnar aromatics [5] because of their cavity size (approximately 4.7 Å), their assemblies are better matched with the size of the hydrophobic segments (such as benzene rings and dodecyl chains) of the p-benzyltrimethylammonium chloride guest molecule, and can form a supramolecular protective layer with a higher binding constant and greater stability. At the same time, this "tight fit" effect makes the dissociation of host-guest interaction more rapid and thorough when thermal triggering occurs, thereby achieving a better intelligent desorption effect and finally obtaining a sintered body with better conductivity and adhesion. In contrast, columnar aromatics [6] have a larger cavity (approximately 6.7 Å), and their assemblies are relatively loosely bound to the guest, resulting in slightly worse protective effect and desorption efficiency.

[0111] Example 3 and Comparative Examples 1 and 2: The interaction between columnar aromatic hydrocarbons and guest supramolecular structures fundamentally solves the technical bottleneck of traditional organic protective agents hindering the formation of conductive networks after sintering due to carbonization residues, significantly reducing volume resistivity. Through a synergistic mechanism of forming a dense protective layer, intelligent cleaning desorption, and promoting dense sintering, the interaction between columnar aromatic hydrocarbons and guest structures is significantly improved. After the copper paste solidifies, the rigid columnar aromatic hydrocarbon molecules dispersed in the matrix become entangled with the polymer chains, forming a denser micronetwork throughout the material. This dense network greatly extends the path for oxygen and water vapor to penetrate from the external environment to the surface of the copper particles. The rigid structure of the columnar aromatic hydrocarbons inhibits the migration of conductive particles and enhances thermomechanical stability. Comparative Examples 1 and 2 involve uncontrollable physical desorption due to thermal decomposition of the coating, which may result in premature loss of protection and oxidation or delayed desorption, affecting the sintering of copper powder. Furthermore, residual organic matter hinders the formation of the conductive network.

[0112] Example 3 and Comparative Example 3: Modification of nano-copper powder using only columnar aromatics relies mainly on the point-to-point adsorption of functional groups such as hydroxyl groups of the columnar aromatics onto the copper surface, forming a disordered, loose, and unevenly covered physical adsorption layer. The binding force is weak, easily destroyed by washing or thermal disturbance, and the antioxidant capacity is limited. The desorption process is random and uncontrollable physical desorption, which may lead to premature loss of protection and oxidation. Although it can provide some antioxidant protection, the protective layer is not stable enough and tends to remain at the copper interface after sintering, resulting in poor conductivity.

[0113] Example 3 and Comparative Example 4: The surface of the nano-copper powder in Comparative Example 4 is uncoated, and the conductive pathways are blocked by the oxide layer. It is loose, porous, and has weak adhesion. The interface is a weak point and is easily affected by the environment, leading to failure. There are a large number of defects and interface separation forming point contacts, resulting in a significant electron tunneling effect and high resistance.

[0114] In summary, the columnar aromatic hydrocarbon-guest supramolecular assembly not only provides antioxidant protection at the nanoscale, but its induced self-organizing and sequencing behavior also significantly improves the rheology and printability of the nano-copper paste on a macroscopic scale. Compared to uncoated or conventionally coated nano-copper pastes (Comparative Examples 1-4), the paste of this invention (Example 3) exhibits: superior dispersion stability and uniformity, ensuring a smooth and even printed film; more ideal shear-thinning behavior and thixotropy, resulting in sharp printed line edges and a good aspect ratio, facilitating the printing of fine lines below 40 μm; and consistent sintering shrinkage behavior of copper powder and resin, effectively preventing the formation of defects such as cracks and voids. These synergistic effects ensure that the final conductive pattern has high line control, high uniformity, and high consistency, meeting the stringent requirements of printed electronics technology for line control capabilities.

[0115] In traditional slurries (Comparative Examples 1-4), a curing agent must be added to ensure the final curing of the epoxy resin. These curing agents are physically mixed with the epoxy resin in the slurry but are not chemically isolated. The high reactivity of the epoxy resin causes slow pre-crosslinking with the curing agent during slurry storage, resulting in unstable viscosity, short shelf life, and severely impacting the industrial application of the product. Furthermore, in Comparative Example 4, the nano-copper powder has high surface energy and unsaturated surface atomic coordination, continuously releasing copper ions with strong Lewis acidity in the slurry system. These copper ions exhibit significant catalytic ring-opening activity towards epoxy groups, leading to uncontrolled pre-crosslinking of the slurry during storage, manifested as a sharp increase in viscosity, loss of fluidity, and ultimately, product spoilage.

[0116] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons, characterized in that, By weight, it includes the following components: 92-95 parts of columnar aromatic supramolecular assembly coated with nano-copper powder, 4-8 parts of resin, 2-6 parts of organic solvent, 0.1-1 parts of thixotropic agent, 0.1-1 parts of dispersant, 0.1-1 parts of coupling agent and 0.1-1 parts of other additives; The columnar aromatic supramolecular assembly coated with copper nanoparticles has a core-shell structure, with the host-guest complex as the shell and the copper nanoparticles as the core. The host-guest complex is based on columnar aromatics grafted with glycidyl methacrylate as the host and benzyl trialkyl quaternary ammonium salt as the guest; the guest is connected to the surface of the nano copper powder through coordination bonds.

2. The nano-copper paste according to claim 1, characterized in that, The particle size of the nano-copper powder is 50 nm - 500 nm; And / or, the column aromatics are column[5] aromatics and / or column[6] aromatics.

3. The nano-copper paste according to claim 1, characterized in that, The structural formula of the benzyltrialkyl quaternary ammonium salt is [(C6H5)-CH2N]. + (R)3 ]X - Where R is methyl or ethyl, X - For Cl - or Br - .

4. The nano-copper paste according to claim 1, characterized in that, The resin is one or more of epoxy resin, polyurethane resin, acrylic resin and polyester resin; the epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic glycidyl ether epoxy resin and phenolic epoxy resin.

5. The nano-copper paste according to claim 1, characterized in that, The organic solvent is one or more of terpineol, butyl carbitol, butyl carbitol acetate, and 12-ol ester.

6. The nano-copper paste according to claim 1, characterized in that, The thixotropic agent is one or more of polyamide wax, hydrogenated castor oil, fumed silica, and ethyl cellulose.

7. The nano-copper paste according to claim 1, characterized in that, The dispersant is one or more of oleic acid, oleamide, erucamide, and BYK111.

8. The nano-copper paste according to claim 1, characterized in that, The coupling agent is one or more of KH550, KH560 and phthalate coupling agents; And / or, the other additives are leveling agents and defoamers; the leveling agent is an acrylic leveling agent; the defoamer is an organosilicone defoamer.

9. The method for preparing nano-copper paste according to any one of claims 1-8, characterized in that, Includes the following steps: (1) In a nitrogen atmosphere, columnar aromatic hydrocarbons are reacted with glycidyl methacrylate in the presence of a catalyst, a polymerization inhibitor or an initiator to obtain glycidyl methacrylate-grafted columnar aromatic hydrocarbons. (2) The columnar aromatic hydrocarbon grafted with glycidyl methacrylate obtained in step (1) is mixed with benzyltrialkyl quaternary ammonium salt in an alcohol solution to form a columnar aromatic hydrocarbon supramolecular assembly; (3) Add copper salt and reducing agent to the columnar aromatic supramolecular assembly obtained in step (2), wash and dry to obtain nano-copper powder coated with columnar aromatic supramolecular assembly; (4) The nano-copper powder, resin, organic solvent, thixotropic agent, dispersant, coupling agent and other additives coated by the columnar aromatic supramolecular assembly obtained in step (3) are mixed and stirred, and then sieved to obtain the nano-copper paste based on the host-guest interaction of columnar aromatic hydrocarbons.

10. The application of the nano-copper paste according to any one of claims 1-8 in the preparation of photovoltaic paste or electronic paste.

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