A highly conductive adhesive film, its preparation method, and its application in antenna modules.

Abstract

This invention relates to the field of conductive adhesive technology, specifically to a highly conductive adhesive film, its preparation method, and its application in antenna modules. The invention modifies flake silver powder with glutaric acid and mixes it with epoxy resin to prepare component A. Epoxycarbazole is synthesized using N-hydroxyethylcarbazole and epichlorohydrin as raw materials. The epoxycarbazole is then reacted with 2,2-bis(hydroxymethyl)propionic acid to obtain bis(hydroxymethyl)grafted carbazole, which is introduced into a polyurethane prepolymer. After end-capping with 1,2,4-phenyltricarboxylic anhydride, it is mixed with carbon nanotubes to obtain component B. Components A and B are mixed to obtain a mixed adhesive. An active diluent, triethylenetetramine curing agent, anhydrous ethanol, nano-silica, nickel powder, and copper powder are added to the mixed adhesive, and the mixture is dried to form a highly conductive adhesive film. The highly conductive adhesive film prepared according to this invention is applied to the surface of an antenna substrate, and after molding, it is cured at 80–100°C to obtain an antenna module.

Description

Technical Field

[0001] This invention relates to the field of conductive adhesive technology, specifically to a highly conductive adhesive film, its preparation method, and its application in antenna modules. Background Technology

[0002] Conductive adhesive is an adhesive that becomes conductive after drying or curing. Its main function is to connect various conductive materials together, creating a conductive path between them. Currently, conductive adhesive has become an indispensable new material in the electronics industry. There are many types of conductive adhesives, with the most publicly available systems being epoxy-based. They are generally divided into two categories: general conductive adhesives and specialty conductive adhesives. General conductive adhesives only have certain requirements for conductivity and bond strength, while specialty conductive adhesives, in addition to these requirements, also have specific requirements, such as resistance to high and low temperatures, rapid curing, anisotropy, and transparency. Based on the types of conductive materials added, conductive adhesives can be further subdivided into silver-based, gold-based, copper-based, and carbon-based conductive adhesives, among which silver-based conductive adhesives are the most widely used.

[0003] The continuous development of 5G technology has driven a significant increase in 5G frequencies, leading to a dramatic reduction in antenna size within the millimeter-wave range. Electronic devices are also increasingly designed for miniaturization and precision, with more intricate internal component arrangements and smaller available bonding areas. These complex designs demand superior grounding and shielding solutions. Therefore, there is a need to develop a new generation of conductive adhesive solutions. Summary of the Invention

[0004] The purpose of this invention is to provide a highly conductive adhesive film, its preparation method, and its application in antenna modules, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a highly conductive adhesive film, a preparation method thereof, and its application in an antenna module, comprising the following steps:

[0006] Step 1:

[0007] Modified flake silver powder was added to epoxy resin and stirred to obtain component A; carbon nanotubes were added to carboxyl-terminated polyurethane and mixed and stirred to obtain component B; component B was added to component A to obtain a mixed adhesive.

[0008] Step 2:

[0009] By weight, add 2-4 parts of reactive diluent, 4-6 parts of triethylenetetramine curing agent, 10-15 parts of anhydrous ethanol, 3-5 parts of nano-silica, 0-10 parts of nickel powder, and 0-10 parts of copper powder to 100 parts of mixed adhesive to obtain a highly conductive adhesive.

[0010] Furthermore, in step 1, in component A, modified flake silver powder and epoxy resin are mixed in a weight ratio of (3-4):1; in component B, carbon nanotubes and carboxyl-terminated polyurethane are mixed in a weight ratio of 1:(1-1.2).

[0011] Furthermore, in step 1, the preparation method of the modified flake silver powder includes the following steps:

[0012] a. Mix glutaric acid and anhydrous ethanol and stir to obtain a surface activation treatment solution, wherein the mass concentration of glutaric acid in the surface activation treatment solution is 20-25%;

[0013] b. Add flake silver powder to the surface activation treatment solution, sonicate for 10-20 min, filter to collect the solid, rinse with anhydrous ethanol, and then vacuum dry at 40-50℃ to obtain modified flake silver powder.

[0014] Furthermore, in step 1, the preparation method of carboxyl-terminated polyurethane includes the following steps:

[0015] S1: Potassium hydroxide, potassium iodide, and 18-crown-6 are mixed to obtain a catalyst; N-hydroxyethylcarbazole and epichlorohydrin are mixed and added to the above catalyst. The mixture is refluxed for 45-50 hours. After cooling, dichloromethane is added. The mixture is filtered to remove insoluble impurities. The filtrate is then rotary evaporated to remove dichloromethane and obtain epoxy-grafted carbazole.

[0016] S2: Epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid are dispersed in deionized water and reacted at 80-90°C with benzyltriethylammonium chloride as a catalyst to obtain bis(hydroxymethyl)grafted carbazole.

[0017] S3: By weight, 280-330 parts of isophorone diisocyanate and 100 parts of polyethylene glycol 2000 are mixed and reacted at 30-40°C under a nitrogen atmosphere for 2-3 hours using dibutyltin dilaurate as a catalyst; 46-68 parts of bis(hydroxymethyl)-grafted carbazole are added and the reaction is continued for 1-2 hours to obtain an isocyanate-terminated polyurethane prepolymer; the temperature is raised to 40-50°C, 1,2,4-phenyltricarboxylic anhydride is added, and the temperature is raised to 90-100°C and the reaction is continued for 2-3 hours to obtain a carboxyl-terminated polyurethane.

[0018] Furthermore, in S1, the content of each component in the catalyst, by weight, is as follows: 100 parts potassium hydroxide, 2-3 parts potassium iodide, 7-8 parts 18-crown-6;N-hydroxyethylcarbazole, and epichlorohydrin are mixed in a molar ratio of 1:(3-4).

[0019] Furthermore, in S2, epoxy carbazole and 2,2-bis(hydroxymethyl)propionic acid react in a 1:1 molar ratio of epoxy to carboxyl groups.

[0020] Furthermore, in S3, the amount of each component in the polyurethane prepolymer, by weight, is 280-330 parts of isophorone diisocyanate, 100 parts of polyethylene glycol 2000, and 46-68 parts of bis(hydroxymethyl)-grafted carbazole.

[0021] Furthermore, in S3, 1,2,4-phenyltricarboxylic anhydride is added to the polyurethane prepolymer at a molar ratio of 1:1 to 1,2,4-phenyltricarboxylic anhydride and isocyanate groups.

[0022] Furthermore, the application method of the highly conductive adhesive film on the antenna module is as follows: at 80-100℃ and 3-5 kgf / cm²... 2 Under conditions of 1 to 3 m / min, a highly conductive adhesive film is rolled and adhered to the surface of the antenna substrate. The antenna substrate with the highly conductive adhesive film is then molded and assembled to obtain an antenna module.

[0023] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention prepares a highly conductive adhesive film for antenna modules by adding flake silver powder to epoxy resin. Typically, conductive adhesive films often use spherical silver powder, but the conductive pathways are formed through point-to-point contact between the spherical silver powder particles. However, the flake silver powder in this application not only has point-to-point contact but also surface-to-surface contact, which can impart a lower volume resistivity to the conductive adhesive film. This invention uses glutaric acid to modify the flake silver powder, improving its bonding strength with the epoxy resin and enhancing the conductivity of the conductive adhesive film.

[0024] To improve the performance of the conductive adhesive film, this invention uses epoxy resin and modified flake silver powder as component A, and selects polyurethane as component B for toughening modification. After direct blending and curing of polyurethane and epoxy resin, a three-dimensional interpenetrating polymer network structure can be formed, which can better transmit and disperse the stress generated under external force within the material, thereby enhancing strength and toughness. However, epoxy resin and polyurethane have different curing conditions and poor compatibility. Therefore, this invention uses 1,2,4-phenyltricarboxylic anhydride to end-cap the polyurethane prepolymer, utilizing the reaction between carboxyl and epoxy groups to achieve chemical cross-linking and improve the modification effect. Researchers found that the carboxyl-terminated polyurethane used for toughening generates a second phase in the epoxy resin through the sea-island effect, which increases the shear strength of the conductive adhesive. However, the presence of the sea-island effect also hinders the contact between the flake silver powder in the epoxy resin, affecting conductivity. Researchers continued to add carbon nanotubes to the carboxyl-terminated polyurethane component B and blend it with component A. However, the conductivity of the film remained poor. Possible reasons were analyzed: during blending, the carbon nanotubes in component B randomly dispersed into component A, leading to a decrease in the carbon nanotube content in component B and poor conductivity. Therefore, this invention introduces carbazole groups into the carboxyl-terminated polyurethane in component B. Utilizing the strong π-π interaction between the carbazole groups and carbon nanotubes, the carbon nanotubes are firmly adsorbed into the carboxyl-terminated polyurethane, effectively avoiding the aforementioned problem. Furthermore, this invention also incorporates small amounts of nano-silica, copper powder, and nickel powder as reinforcing materials. Nano-silica improves the wear resistance of the conductive film, while copper and nickel powders also possess good conductivity. Adding nano-silica, copper powder, and nickel powder to the conductive film not only improves its strength but also ensures good conductivity. The conductive film prepared by this invention has high shear strength and a volume resistivity below 5 × 10⁻⁶. -4 Ω / cm, high conductivity. Detailed Implementation

[0025] The materials used in this invention and their sources are as follows: Bisphenol A type epoxy resin E-51 is from Henan Chiao Trading Co., Ltd.; flake-shaped nano silver powder (model XFJ45), nano silica (model XFI03), and carbon nanotubes (model XFM31) are all from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; reactive diluent (model LS-622) is from Hubei Green Home Materials Technology Co., Ltd.; copper powder (Cu>99.85%, spherical) and nickel powder (Ni>99.85%, spherical) are both from Hunan Huabang Powder Materials Co., Ltd.

[0026] Example 1: A method for preparing a highly conductive adhesive film, comprising the following steps:

[0027] Step 1:

[0028] S11: Glutaric acid and anhydrous ethanol are mixed and stirred to obtain a surface activation treatment solution, wherein the mass concentration of glutaric acid in the surface activation treatment solution is 25%;

[0029] S12: Add flake silver powder to the surface activation treatment solution, sonicate for 10 min, filter to collect the solid, rinse with anhydrous ethanol, and then vacuum dry at 40℃ to obtain modified flake silver powder.

[0030] Step 2:

[0031] S21: Mix 100g potassium hydroxide, 2g potassium iodide and 8g 18-crown-6 to obtain a catalyst; mix N-hydroxyethylcarbazole and epichlorohydrin in a molar ratio of 1:4, add the above catalyst, reflux for 45h, cool and add dichloromethane, filter to remove insoluble impurities, and rotary evaporate the filtrate to remove dichloromethane to obtain epoxy-grafted carbazole;

[0032] S22: Epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid are dispersed in deionized water and reacted at 80°C with benzyltriethylammonium chloride as a catalyst to obtain bis(hydroxymethyl)grafted carbazole; wherein, epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid react in an epoxy group to carboxyl group molar ratio of 1:1;

[0033] S23: Mix 300g of isophorone diisocyanate and 100g of polyethylene glycol 2000, and react with dibutyltin dilaurate as catalyst at 30℃ under nitrogen atmosphere for 2h; add 52g of bis(hydroxymethyl)-grafted carbazole and continue the reaction for 1h to obtain isocyanate-terminated polyurethane prepolymer; heat to 40℃, add 1,2,4-phenyltricarboxylic anhydride at a molar ratio of 1:1 to isocyanate groups, and continue to heat to 90℃ and react for 2h to obtain carboxyl-terminated polyurethane;

[0034] Step 3:

[0035] S31: Modified flake silver powder is added to epoxy resin at a weight ratio of 3:1 and stirred to obtain component A; carbon nanotubes are added to carboxyl-terminated polyurethane at a weight ratio of 1:1 and stirred to obtain component B; component B is added to component A to obtain a mixed adhesive; the content of each component in the mixed adhesive, by weight percentage, is 80% component A and 20% component B.

[0036] S32: Add 2g of reactive diluent, 4g of triethylenetetramine curing agent, 12g of anhydrous ethanol, 4g of nano-silica, 10g of nickel powder, and 10g of copper powder to 100g of mixed adhesive to obtain a highly conductive adhesive; coat the highly conductive adhesive onto a release film and dry it at 60°C to form a highly conductive adhesive film.

[0037] Example 2: A method for preparing a highly conductive adhesive film, comprising the following steps:

[0038] Step 1:

[0039] S11: Glutaric acid and anhydrous ethanol are mixed and stirred to obtain a surface activation treatment solution, wherein the mass concentration of glutaric acid in the surface activation treatment solution is 25%;

[0040] S12: Add flake silver powder to the surface activation treatment solution, sonicate for 15 min, filter to collect the solid, rinse with anhydrous ethanol, and then vacuum dry at 45℃ to obtain modified flake silver powder.

[0041] Step 2:

[0042] S21: Mix 100g potassium hydroxide, 2g potassium iodide and 8g 18-crown-6 to obtain a catalyst; mix N-hydroxyethylcarbazole and epichlorohydrin in a molar ratio of 1:4, add the above catalyst, reflux for 48h, cool and add dichloromethane, filter to remove insoluble impurities, and rotary evaporate the filtrate to remove dichloromethane to obtain epoxy-grafted carbazole;

[0043] S22: Epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid are dispersed in deionized water and reacted at 85°C with benzyltriethylammonium chloride as a catalyst to obtain bis(hydroxymethyl)grafted carbazole; wherein, epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid react in an epoxy group to carboxyl group molar ratio of 1:1;

[0044] S23: 300g of isophorone diisocyanate and 100g of polyethylene glycol 2000 were mixed and reacted at 35°C under a nitrogen atmosphere for 2.5h with dibutyltin dilaurate as a catalyst; 52g of bis(hydroxymethyl)-grafted carbazole was added and the reaction was continued for 1.5h to obtain an isocyanate-terminated polyurethane prepolymer; the temperature was raised to 45°C and 1,2,4-phenyltricarboxylic anhydride was added at a molar ratio of 1:1 to isocyanate groups, and the temperature was raised to 95°C and the reaction was continued for 2.5h to obtain carboxyl-terminated polyurethane;

[0045] Step 3:

[0046] S31: Modified flake silver powder is added to epoxy resin at a weight ratio of 3.5:1 and stirred to obtain component A; carbon nanotubes are added to carboxyl-terminated polyurethane at a weight ratio of 1:1 and stirred to obtain component B; component B is added to component A to obtain a mixed adhesive; the content of each component in the mixed adhesive, by weight percentage, is 80% component A and 20% component B;

[0047] S32: Add 2g of reactive diluent, 4g of triethylenetetramine curing agent, 12g of anhydrous ethanol, 4g of nano-silica, 10g of nickel powder, and 10g of copper powder to 100g of mixed adhesive to obtain a highly conductive adhesive; coat the highly conductive adhesive onto a release film and dry it at 65°C to form a highly conductive adhesive film.

[0048] Example 3: A method for preparing a highly conductive adhesive film, comprising the following steps:

[0049] Step 1:

[0050] S11: Glutaric acid and anhydrous ethanol are mixed and stirred to obtain a surface activation treatment solution, wherein the mass concentration of glutaric acid in the surface activation treatment solution is 25%;

[0051] S12: Add flake silver powder to the surface activation treatment solution, sonicate for 20 min, filter to collect the solid, rinse with anhydrous ethanol, and then vacuum dry at 50°C to obtain modified flake silver powder.

[0052] Step 2:

[0053] S21: Mix 100g potassium hydroxide, 2g potassium iodide and 8g 18-crown-6 to obtain a catalyst; mix N-hydroxyethylcarbazole and epichlorohydrin in a molar ratio of 1:4, add the above catalyst, reflux for 50h, cool and add dichloromethane, filter to remove insoluble impurities, and rotary evaporate the filtrate to remove dichloromethane to obtain epoxy-grafted carbazole;

[0054] S22: Epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid are dispersed in deionized water and reacted at 90°C with benzyltriethylammonium chloride as a catalyst to obtain bis(hydroxymethyl)grafted carbazole; wherein, epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid react in an epoxy group to carboxyl group molar ratio of 1:1.

[0055] S23: Mix 300g of isophorone diisocyanate and 100g of polyethylene glycol 2000, and react with dibutyltin dilaurate as catalyst at 40℃ under nitrogen atmosphere for 3h; add 52g of bis(hydroxymethyl)-grafted carbazole and continue the reaction for 2h to obtain isocyanate-terminated polyurethane prepolymer; heat to 50℃, add 1,2,4-phenyltricarboxylic anhydride at a molar ratio of 1:1 to isocyanate groups, and continue to heat to 100℃ and react for 3h to obtain carboxyl-terminated polyurethane;

[0056] Step 3:

[0057] S31: Modified flake silver powder is added to epoxy resin at a weight ratio of 4:1 and stirred to obtain component A; carbon nanotubes are added to carboxyl-terminated polyurethane at a weight ratio of 1:1 and stirred to obtain component B; component B is added to component A to obtain a mixed adhesive; the content of each component in the mixed adhesive, by weight percentage, is 80% component A and 20% component B.

[0058] S32: Add 2g of reactive diluent, 4g of triethylenetetramine curing agent, 12g of anhydrous ethanol, 4g of nano-silica, 10g of nickel powder, and 10g of copper powder to 100g of mixed adhesive to obtain a highly conductive adhesive; coat the highly conductive adhesive onto a release film and dry it at 70°C to form a highly conductive adhesive film.

[0059] Comparative Example 1: Component A was used to replace the mixed rubber compound, and the remaining parameters were the same as in Example 1.

[0060] Step 1:

[0061] S11: Glutaric acid and anhydrous ethanol are mixed and stirred to obtain a surface activation treatment solution, wherein the mass concentration of glutaric acid in the surface activation treatment solution is 25%;

[0062] S12: Add flake silver powder to the surface activation treatment solution, sonicate for 10 min, filter to collect the solid, rinse with anhydrous ethanol, and then vacuum dry at 40℃ to obtain modified flake silver powder.

[0063] Step 2:

[0064] S21: Modified flake silver powder is added to epoxy resin at a weight ratio of 3:1 to obtain a mixed adhesive.

[0065] S22: Add 2g of reactive diluent, 4g of triethylenetetramine curing agent, 12g of anhydrous ethanol, 4g of nano-silica, 10g of nickel powder, and 10g of copper powder to 100g of mixed adhesive to obtain a highly conductive adhesive; coat the highly conductive adhesive onto a release film and dry it at 60°C to form a highly conductive adhesive film.

[0066] Comparative Example 2: Component B was replaced with carboxyl-terminated polyurethane, and the remaining parameters were the same as in Example 2.

[0067] Step 1:

[0068] S11: Glutaric acid and anhydrous ethanol are mixed and stirred to obtain a surface activation treatment solution, wherein the mass concentration of glutaric acid in the surface activation treatment solution is 25%;

[0069] S12: Add flake silver powder to the surface activation treatment solution, sonicate for 15 min, filter to collect the solid, rinse with anhydrous ethanol, and then vacuum dry at 45℃ to obtain modified flake silver powder.

[0070] Step 2:

[0071] S21: Mix 100g potassium hydroxide, 2g potassium iodide and 8g 18-crown-6 to obtain a catalyst; mix N-hydroxyethylcarbazole and epichlorohydrin in a molar ratio of 1:4, add the above catalyst, reflux for 48h, cool and add dichloromethane, filter to remove insoluble impurities, and rotary evaporate the filtrate to remove dichloromethane to obtain epoxy-grafted carbazole;

[0072] S22: Epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid are dispersed in deionized water and reacted at 85°C with benzyltriethylammonium chloride as a catalyst to obtain bis(hydroxymethyl)grafted carbazole; wherein, epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid react in an epoxy group to carboxyl group molar ratio of 1:1;

[0073] S23: 300g of isophorone diisocyanate and 100g of polyethylene glycol 2000 were mixed and reacted at 35°C under a nitrogen atmosphere for 2.5h with dibutyltin dilaurate as a catalyst; 52g of bis(hydroxymethyl)-grafted carbazole was added and the reaction was continued for 1.5h to obtain an isocyanate-terminated polyurethane prepolymer; the temperature was raised to 45°C and 1,2,4-phenyltricarboxylic anhydride was added at a molar ratio of 1:1 to isocyanate groups, and the temperature was raised to 95°C and the reaction was continued for 2.5h to obtain carboxyl-terminated polyurethane;

[0074] Step 3:

[0075] S31: Modified flake silver powder is added to epoxy resin at a weight ratio of 3.5:1 and stirred to obtain component A; carboxyl-terminated polyurethane is added to component A to obtain a mixed adhesive; the content of each component in the mixed adhesive, by weight percentage, is 80% component A and 20% carboxyl-terminated polyurethane.

[0076] S32: Add 2g of reactive diluent, 4g of triethylenetetramine curing agent, 12g of anhydrous ethanol, 4g of nano-silica, 10g of nickel powder, and 10g of copper powder to 100g of mixed adhesive to obtain a highly conductive adhesive; coat the highly conductive adhesive onto a release film and dry it at 65°C to form a highly conductive adhesive film.

[0077] Comparative Example 3: Carboxyl-terminated polyurethane was prepared without the use of bis(hydroxymethyl)-grafted carbazole, with all other parameters being the same as in Example 3.

[0078] Step 1:

[0079] S11: Glutaric acid and anhydrous ethanol are mixed and stirred to obtain a surface activation treatment solution, wherein the mass concentration of glutaric acid in the surface activation treatment solution is 25%;

[0080] S12: Add flake silver powder to the surface activation treatment solution, sonicate for 20 min, filter to collect the solid, rinse with anhydrous ethanol, and then vacuum dry at 50°C to obtain modified flake silver powder.

[0081] Step 2:

[0082] 300g of isophorone diisocyanate and 100g of polyethylene glycol 2000 were mixed and reacted at 40℃ under a nitrogen atmosphere for 3 hours with dibutyltin dilaurate as a catalyst. 29g of 2,2-bis(hydroxymethyl)propionic acid was added and the reaction was continued for 2 hours to obtain an isocyanate-terminated polyurethane prepolymer. The temperature was raised to 50℃, and 1,2,4-phenyltricarboxylic anhydride was added at a molar ratio of 1:1 to isocyanate groups. The temperature was raised to 100℃ and the reaction was continued for 3 hours to obtain a carboxyl-terminated polyurethane.

[0083] Step 3:

[0084] S31: Modified flake silver powder is added to epoxy resin at a weight ratio of 4:1 and stirred to obtain component A; carbon nanotubes are added to carboxyl-terminated polyurethane at a weight ratio of 1:1 and stirred to obtain component B; component B is added to component A to obtain a mixed adhesive; the content of each component in the mixed adhesive, by weight percentage, is 80% component A and 20% component B.

[0085] S32: Add 2g of reactive diluent, 4g of triethylenetetramine curing agent, 12g of anhydrous ethanol, 4g of nano-silica, 10g of nickel powder, and 10g of copper powder to 100g of mixed adhesive to obtain a highly conductive adhesive; coat the highly conductive adhesive onto a release film and dry it at 70°C to form a highly conductive adhesive film.

[0086] Experiments: Samples prepared according to the schemes in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. Volume resistivity testing: Method 5011 of standard GJB548A-1996 was used. Highly conductive adhesive was coated onto a standard glass slide measuring 2.54cm × 7.62cm, and after drying, a conductive adhesive film sample was formed. The resistance of the sample was tested using an RTS-8 four-point probe. Each group of samples was tested 5 times, and the average value was recorded. Shear strength testing: Standard GB7124-86 (A1 / A1 overlap) was used. The overlap specimen was LY12CZ aluminum alloy with a length of (100±0.2)mm, a width of (25±0.2)mm, and a thickness of (2±0.1)mm. The test was conducted using an electronic universal testing machine at a tensile speed of 5mm / min. Five samples were tested in each group, and the average value was taken. The experimental results are shown in Table 1.

[0087] Table 1. Test results of various properties of conductive adhesive film

[0088] project <![CDATA[Volume resistivity (10 -4 Ω / cm)]]> Shear strength (MPa) Example 1 4.82 13.8 Example 2 4.64 14.3 Example 3 4.25 14.7 Comparative Example 1 4.15 10.2 Comparative Example 2 19.36 13.4 Comparative Example 3 8.47 12.1

[0089] Conclusions: Data from Examples 1-3 show that the conductive adhesive prepared by this invention exhibits good conductivity and high shear strength. Data from Example 1 and Comparative Example 1 indicate that the addition of carboxyl-terminated polyurethane effectively improves the shear strength of the conductive adhesive film. Data from Example 2 and Comparative Example 2 show that when only carboxyl-terminated polyurethane is added, the second phase generated by the carboxyl-terminated polyurethane in the epoxy resin system through the sea-island effect increases the shear strength of the conductive adhesive, but hinders the contact between the silver powder fillers, thus reducing conductivity. Data from Example 3 and Comparative Example 3 show that using bis(hydroxymethyl)-grafted carbazole to prepare carboxyl-terminated polyurethane improves both conductivity and shear strength.

[0090] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0091] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a highly conductive adhesive film, characterized in that: Includes the following steps: Step 1: Modified flake silver powder was added to epoxy resin and stirred to obtain component A; carbon nanotubes were added to carboxyl-terminated polyurethane and mixed and stirred to obtain component B; component B was added to component A to obtain a mixed adhesive. Step 2: By weight, add 2-4 parts of reactive diluent, 4-6 parts of triethylenetetramine curing agent, 10-15 parts of anhydrous ethanol, 3-5 parts of nano-silica, 0-10 parts of nickel powder, and 0-10 parts of copper powder to 100 parts of mixed adhesive to obtain a highly conductive adhesive; coat the highly conductive adhesive onto a release film and dry it at 60-70°C to obtain a highly conductive adhesive film. In step 1, in component A, modified flake silver powder and epoxy resin are mixed in a weight ratio of (3-4):1; in component B, carbon nanotubes and carboxyl-terminated polyurethane are mixed in a weight ratio of 1:(1-1.2). In step 1, the preparation method of carboxyl-terminated polyurethane, Includes the following steps: S1: Potassium hydroxide, potassium iodide, and 18-crown-6 are mixed to obtain a catalyst; N-hydroxyethylcarbazole and epichlorohydrin are mixed and added to the above catalyst. The mixture is refluxed for 45-50 hours. After cooling, dichloromethane is added. The mixture is filtered to remove insoluble impurities. The filtrate is then rotary evaporated to remove dichloromethane and obtain epoxy-grafted carbazole. S2: Epoxycarbazole and 2,2-bis(hydroxymethyl)propionic acid are dispersed in deionized water and reacted at 80-90°C with benzyltriethylammonium chloride as a catalyst to obtain bis(hydroxymethyl)grafted carbazole. S3: By weight, 280-330 parts of isophorone diisocyanate and 100 parts of polyethylene glycol 2000 are mixed and reacted at 30-40°C under a nitrogen atmosphere for 2-3 hours using dibutyltin dilaurate as a catalyst; 46-68 parts of bis(hydroxymethyl)-grafted carbazole are added and the reaction is continued for 1-2 hours to obtain an isocyanate-terminated polyurethane prepolymer; the temperature is raised to 40-50°C, 1,2,4-phenyltricarboxylic anhydride is added, and the temperature is raised to 90-100°C and the reaction is continued for 2-3 hours to obtain a carboxyl-terminated polyurethane.

2. The method for preparing a highly conductive adhesive film according to claim 1, characterized in that: In step 1, the method for preparing modified flake silver powder includes the following steps: a. mixing glutaric acid and anhydrous ethanol and stirring to obtain a surface activation treatment solution, wherein the mass concentration of glutaric acid in the surface activation treatment solution is 20-25%; b. Add flake silver powder to the surface activation treatment solution, sonicate for 10-20 min, filter to collect the solid, rinse with anhydrous ethanol, and then vacuum dry at 40-50℃ to obtain modified flake silver powder.

3. The method for preparing a highly conductive adhesive film according to claim 1, characterized in that: In S1, the components of the catalyst are mixed by weight as follows: 100 parts potassium hydroxide, 2-3 parts potassium iodide, 7-8 parts 18-crown-6;N-hydroxyethylcarbazole, and epichlorohydrin in a molar ratio of 1:(3-4).

4. The method for preparing a highly conductive adhesive film according to claim 1, characterized in that: In S2, epoxy carbazole and 2,2-bis(hydroxymethyl)propionic acid react at a molar ratio of epoxy to carboxyl groups of 1:

1.

5. The method for preparing a highly conductive adhesive film according to claim 1, characterized in that: In S3, the amount of each component in the polyurethane prepolymer, by weight, is 280-330 parts isophorone diisocyanate, 100 parts polyethylene glycol 2000, and 46-68 parts bis(hydroxymethyl) grafted carbazole.

6. The method for preparing a highly conductive adhesive film according to claim 1, characterized in that: In S3, 1,2,4-phenyltricarboxylic anhydride is added to the polyurethane prepolymer at a molar ratio of 1:1 to 1,2,4-phenyltricarboxylic anhydride and isocyanate groups.

7. The highly conductive adhesive film prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the highly conductive adhesive film as described in claim 7 in an antenna module, characterized in that: At 80–100℃ and 3–5 kgf / cm² 2 Under conditions of 1 to 3 m / min, a highly conductive adhesive film is rolled and adhered to the surface of the antenna substrate. The antenna substrate with the highly conductive adhesive film is then molded and assembled to obtain an antenna module.