Liquid ACF as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of anisotropic conductive films, and relates to a liquid ACF (anisotropic conductive film) as well as a preparation method and application thereof. The liquid ACF is processed from the following raw materials in parts by weight: 1-10 parts of an epoxy resin curing agent, 20-60 parts of liquid resin, 1-20 parts of conductive particles, 1-20 parts of a thixotropic agent, 0.1-5 parts of a tackifier and 0.1-5 parts of a dispersant. According to the invention, long-term stable dispersion of the conductive particles in a liquid system is realized, and the stability and reliability of the liquid ACF in the use process are ensured. Compared with a conventional solid ACF, the liquid ACF can better infiltrate the surface of an electrode, and uniform distribution of conductive particles is ensured; extra heating is not needed in the coating process, and the problem that the conductive adhesive is cured in advance is avoided; the thickness and the area of the liquid ACF can be easily adjusted through the smearing amount so as to meet the requirements of different application scenes; compared with solid ACF, liquid ACF has extremely low viscosity and can efficiently remove gas in an electrode, so that the adhesive force of colloid is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of anisotropic conductive adhesive films and relates to a liquid ACF and a preparation method and application thereof. Background Art

[0002] Anisotropic Conductive Film (ACF) is a special polymer material that combines conductive, insulating and bonding functions. It establishes a conductive path in the vertical direction (Z axis) through the conductive particles inside, thereby achieving electrode connection between the chip and the substrate. At the same time, these conductive particles are wrapped with resin to ensure the insulation effect on the horizontal plane (X axis and Y axis), effectively preventing short circuits between adjacent electrodes.

[0003] Nowadays, ACF is mostly used in the form of solid tape, which is not only easy to carry but also adaptable to various working environments. However, the application process of ACF is relatively complicated. First, this tape usually needs to be pre-attached to the PET release film, and it needs to be accurately transferred to the target substrate under heating and pressure when it is actually used. The heating step in this process may cause some ACF to cure prematurely, which in turn affects its final conductive properties and bonding quality. Secondly, due to the solid nature of ACF, its viscosity is high, which limits its full contact and infiltration with the substrate surface in a short time, thereby reducing the bonding effect. In addition, the compatibility of ACF with substrates of different materials is also an important consideration. In particular, matching the thickness of ACF with the height of the electrode is the key to ensuring good electrical performance. However, common ACF products on the market usually have only a few fixed thicknesses to choose from, because changing the thickness of ACF often requires adjusting its formulation or production process, which is a time-consuming and costly process.

[0004] Therefore, how to improve the flexibility and adaptability of ACF applications while ensuring its performance has become one of the key directions of current research and development. Summary of the invention

[0005] The present invention aims at the above problems existing in the prior art and provides a liquid ACF.

[0006] One object of the present invention is achieved by the following technical solutions:

[0007] A liquid ACF is made from the following raw materials in parts by weight: 1 to 10 parts of epoxy resin curing agent, 20 to 60 parts of liquid resin, 1 to 20 parts of conductive particles, 1 to 20 parts of thixotropic agent, 0.1 to 5 parts of tackifier and 0.1 to 5 parts of dispersant.

[0008] Preferably, the epoxy resin curing agent includes one or more of a metal salt curing agent and an imidazole curing agent. The metal salt curing agent can be listed as boron trifluoride ethylamine complex, tin tetrachloride, aluminum trichloride, lanthanum trifluoromethanesulfonate, etc.; the imidazole curing agent can be listed as 4-ethyl-2-methyl-imidazole, 2-methylimidazole, 1-benzyl-2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1,2-dimethylimidazole, 2-ethyl-1-methylimidazole, 1,2-diethyl imidazole, 1-ethyl-2-methylimidazole, 2-ethyl-4-methylimidazole, 1-isobutyl-2-methylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole and the like.

[0009] More preferably, the epoxy resin curing agent includes one or more of boron trifluoride ethylamine complex, lanthanum trifluoromethanesulfonate, tin tetrachloride, aluminum trichloride, and 4-ethyl-2-methyl-imidazole.

[0010] Preferably, the liquid resin is a composition of a high-viscosity liquid epoxy resin and a low-viscosity liquid epoxy resin; the viscosity of the high-viscosity liquid epoxy resin is 600-10000 cps, and the viscosity of the low-viscosity liquid epoxy resin is 100-500 cps.

[0011] Preferably, the high-viscosity liquid epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, novolac epoxy resin, and heterocyclic epoxy resin.

[0012] Preferably, the low-viscosity liquid epoxy resin includes one or more of liquid alicyclic epoxy resin, glycidyl ether epoxy resin, linear phenolic epoxy resin, and aliphatic epoxy resin.

[0013] Preferably, the mass ratio of the high-viscosity liquid epoxy resin to the low-viscosity liquid epoxy resin in the liquid resin is (1-5):(1-5).

[0014] Preferably, the thixotropic agent is fumed silica with a particle size of 1 to 600 nm, more preferably 8 to 500 nm.

[0015] Fumed silica has a high specific surface area and good thixotropy, and can significantly improve the thixotropy of liquid ACF. This enables the liquid ACF to form a stable structure when it is stationary, preventing the sedimentation of the conductive particles, which ensures the uniform distribution of the conductive particles in the liquid ACF and improves the stability and consistency of the product. The present invention uses fumed silica as a thixotropic agent while also serving as an inorganic filler, which can significantly enhance the mechanical properties and thermal stability of the composite material, improve the strength and hardness of the liquid ACF while improving its wear resistance; in a high temperature environment, it can also maintain its structure and performance, preventing the liquid ACF from excessive flow or decomposition.

[0016] Preferably, the viscosity enhancer includes one or more of carboxymethyl cellulose, polyacrylamide, polyvinyl alcohol, latex, and gelatin.

[0017] Preferably, the dispersant includes one or more of polyethylene glycol, polyether amine, polyether polyol and polyacrylic acid.

[0018] Preferably, the conductive particles are a core-shell structure composition with a polymer as the core and a metal layer as the shell, the polymer can be listed as one or more of polymethyl methacrylate, polyaniline, polystyrene, polyacrylamide, polyvinyl chloride, and polyacrylonitrile, and the metal layer can be listed as one or more of nickel layer, gold layer, copper layer, and cobalt layer.

[0019] Preferably, the particle size of the conductive particles is 0.5 to 20 μm, and further 2 to 15 μm.

[0020] The second object of the present invention is achieved by the following technical solutions:

[0021] A method for preparing a liquid ACF comprises the following steps: mixing and stirring an epoxy resin curing agent, a liquid resin, conductive particles, a thixotropic agent, a tackifier and a dispersant uniformly to obtain the liquid ACF.

[0022] The third object of the present invention is achieved by the following technical solutions:

[0023] An application of a liquid ACF comprises coating the liquid ACF on a substrate and / or a carrier, combining the substrate and the carrier through the liquid ACF to form a component, and then performing bonding connection.

[0024] Preferably, the bonding connection temperature is 120-200° C., the pressure is 10-50 MPa, and the time is 1-10 s.

[0025] Liquid ACF is coated on the substrate and / or the carrier, so that the substrate and the carrier are combined to form a component through the liquid ACF; including three situations: (1) liquid ACF is coated on the substrate, so that the liquid ACF on the substrate is in contact with the carrier, and the components are formed after combination; (2) liquid ACF is coated on the carrier, so that the liquid ACF on the carrier is in contact with the substrate, and the components are formed after combination; (3) liquid ACF is coated on both the carrier and the substrate, so that the liquid ACF on the carrier is in contact with the liquid ACF on the substrate, and the components are formed after combination.

[0026] Preferably, the coating thickness of the liquid ACF is 1-100 μm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention innovatively provides a liquid ACF, which is composed of liquid resin, epoxy resin curing agent, thixotropic agent, conductive particles and additives. The liquid ACF has a certain viscosity at room temperature and is in liquid state. When used, it can be evenly applied to the electrode area that needs to be bonded. The subsequent use method is consistent with the traditional solid ACF, which simplifies the operation process. Compared with conventional solid ACF, liquid ACF can better infiltrate the electrode surface, ensure the uniform distribution of conductive particles, improve the conductivity and bonding reliability; it does not require additional heating during the application process, avoiding the problem of premature curing of the conductive glue, and ensuring the stability and consistency of the process; the thickness and area of ​​the liquid ACF can be easily adjusted by the application amount to meet the needs of different application scenarios; compared with solid ACF, liquid ACF has extremely low viscosity, and it can efficiently remove gas from the electrode, thereby improving the adhesion of the colloid.

[0029] 2. The present invention provides a liquid ACF, which successfully overcomes the main technical difficulty that the conductive particles in the liquid ACF are easy to precipitate in the liquid. In order to solve this problem, the present invention uses multiple components to adjust the viscosity and stability of the system. Specifically, the present invention adopts a combination of a high-viscosity liquid epoxy resin and a low-viscosity liquid epoxy resin as a base resin, which can effectively balance the basic viscosity of the liquid ACF system and the bonding strength after curing; the use of fumed silica as a thixotropic agent can not only effectively improve the thixotropy of the system and prevent the sedimentation of the conductive particles, but also has the function of an inorganic filler, thereby enhancing the mechanical properties and thermal stability of the composite material; by adding a thickener, the viscosity of the system can be further increased to ensure the suspension stability of the conductive particles in the liquid; the use of a dispersant helps to improve the dispersibility of the conductive particles in the liquid resin, prevent aggregation between particles, and can significantly improve the dispersion level of the conductive particles to ensure their uniform distribution in the liquid; by precisely controlling the addition amounts of the thixotropic agent, the thickener and the dispersant, the present invention achieves long-term stable dispersion of the conductive particles in the liquid system, and this precise control not only improves the dispersion effect of the conductive particles, but also ensures the stability and reliability of the liquid ACF during use.

[0030] 3. A liquid ACF provided by the present invention adopts a composite liquid epoxy resin combination and combines the use of multiple additives to achieve an effective balance between the dispersion stability of the conductive particles of the liquid ACF during long-term storage and the bonding strength of the product after hot pressing, and reaches the optimal value. The preferred low-viscosity liquid epoxy resin of the present invention has high heat resistance and mechanical strength, which can significantly improve the bonding strength of the final product. It can still maintain good performance at high temperatures, ensuring the stability and reliability of the liquid ACF during hot pressing; high-viscosity liquid epoxy resin has good toughness and chemical resistance. The compounding with low-viscosity liquid epoxy resin not only enhances the flexibility of the system, but also improves the dispersibility of the conductive particles, preventing the particles from settling and aggregating during storage. By precisely controlling the compounding ratio of the liquid resin, the present invention achieves long-term stable dispersion of conductive particles in the liquid system; at the same time, by optimizing the dosage of thixotropic agent, thickener and dispersant, the dispersion stability and bonding strength of the liquid ACF are further improved, ensuring the excellent performance of the liquid ACF in long-term storage and practical applications.

[0031] 4. The present invention significantly improves the performance and reliability of the final product by adopting the form of liquid ACF. This innovative technology provides a new solution for the field of electronic packaging and assembly and has broad application prospects. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0033] The sources of raw materials in the following examples and comparative examples are as follows:

[0034] Boron trifluoride ethylamine complex: Shanghai Alagong Reagent Co., Ltd.;

[0035] Bisphenol A epoxy resin: OSAKA SODA LX-01, viscosity 7500cps;

[0036] Bisphenol F epoxy resin: OSAKA SODA LX-02F, viscosity 3500cps;

[0037] Liquid alicyclic epoxy resin: CELLOXIDE 2021P, viscosity 200cps;

[0038] Fumed silica: Evonik R972, particle size 12nm;

[0039] Conductive particles: nickel-plated polystyrene microspheres, average particle size 5 μm, Zhenjiang Aibang Ni-500.

[0040] Example 1

[0041] The liquid ACF of this embodiment is made from the following raw materials in parts by weight: 4 parts of boron trifluoride ethylamine complex, 15 parts of bisphenol A epoxy resin, 15 parts of liquid alicyclic epoxy resin, 5 parts of conductive particles, 5 parts of fumed silica, 3 parts of carboxymethyl cellulose and 3 parts of polyethylene glycol.

[0042] The preparation method of the liquid ACF in this embodiment includes the following steps: adding the above raw materials into a 100 mL plastic container and mixing them evenly using a planetary stirrer to obtain liquid ACF glue.

[0043] Example 2

[0044] The liquid ACF of this embodiment is made from the following raw materials in parts by weight: 2 parts of tin tetrachloride, 10 parts of bisphenol F epoxy resin, 10 parts of liquid alicyclic epoxy resin, 3 parts of conductive particles, 3 parts of fumed silica, 1 part of polyacrylamide and 1 part of polyetheramine.

[0045] The preparation method of the liquid ACF in this embodiment is the same as that in Example 1.

[0046] Example 3

[0047] The liquid ACF of this embodiment is made from the following raw materials in parts by weight: 8 parts of 4-ethyl-2-methyl-imidazole, 20 parts of bisphenol A epoxy resin, 20 parts of liquid alicyclic epoxy resin, 10 parts of conductive particles, 10 parts of fumed silica, 5 parts of polyvinyl alcohol and 5 parts of polyacrylic acid.

[0048] The preparation method of the liquid ACF in this embodiment is the same as that in Example 1.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that the epoxy resin component in the raw material only uses bisphenol A epoxy resin, and the rest is the same as Example 1.

[0051] The liquid ACF of this comparative example is made from the following raw materials in parts by weight: 4 parts of boron trifluoride ethylamine complex, 30 parts of bisphenol A epoxy resin, 5 parts of conductive particles, 5 parts of fumed silica, 3 parts of carboxymethyl cellulose and 3 parts of polyethylene glycol.

[0052] The preparation method of the liquid ACF in this comparative example is the same as that in Example 1.

[0053] Comparative Example 2

[0054] The difference between this comparative example and Example 1 is that the epoxy resin component in the raw material uses only liquid alicyclic epoxy resin, and the rest is the same as Example 1.

[0055] The liquid ACF of this comparative example is made from the following raw materials in parts by weight: 4 parts of boron trifluoride ethylamine complex, 30 parts of liquid alicyclic epoxy resin, 5 parts of conductive particles, 5 parts of fumed silica, 3 parts of carboxymethyl cellulose and 3 parts of polyethylene glycol.

[0056] The preparation method of the liquid ACF in this comparative example is the same as that in Example 1.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 is that no thixotropic agent component is added to the raw materials, and the rest is the same as Example 1.

[0059] The liquid ACF of this comparative example is made from the following raw materials in parts by weight: 4 parts of boron trifluoride ethylamine complex, 15 parts of bisphenol A epoxy resin, 15 parts of liquid alicyclic epoxy resin, 5 parts of conductive particles, 3 parts of carboxymethyl cellulose and 3 parts of polyethylene glycol.

[0060] The preparation method of the liquid ACF in this comparative example is the same as that in Example 1.

[0061] Comparative Example 4

[0062] The difference between this comparative example and Example 1 is that no viscosity enhancer component is added to the raw materials, and the rest is the same as Example 1.

[0063] The liquid ACF of this comparative example is made from the following raw materials in parts by weight: 4 parts of boron trifluoride ethylamine complex, 15 parts of bisphenol A epoxy resin, 15 parts of liquid alicyclic epoxy resin, 5 parts of conductive particles, 5 g of fumed silica and 3 parts of polyethylene glycol.

[0064] The preparation method of the liquid ACF in this comparative example is the same as that in Example 1.

[0065] Comparative Example 5

[0066] The difference between this comparative example and Example 1 is that no dispersant component is added to the raw materials, and the rest is the same as Example 1.

[0067] The liquid ACF of this comparative example is made from the following raw materials in parts by weight: 4 parts of boron trifluoride ethylamine complex, 15 parts of bisphenol A epoxy resin, 15 parts of liquid alicyclic epoxy resin, 5 parts of conductive particles, 5 g of fumed silica and 3 parts of carboxymethyl cellulose.

[0068] The preparation method of the liquid ACF in this comparative example is the same as that in Example 1.

[0069] Comparative Example 6

[0070] The difference between this comparative example and Example 1 is that no thixotropic agent, viscosity enhancer and dispersant component are added to the raw materials, and the rest is the same as Example 1.

[0071] The liquid ACF of this comparative example is made from the following raw materials in parts by weight: 4 parts of boron trifluoride ethylamine complex, 15 parts of bisphenol A epoxy resin, 15 parts of liquid alicyclic epoxy resin and 5 parts of conductive particles.

[0072] The preparation method of the liquid ACF in this comparative example is the same as that in Example 1.

[0073] The colloid viscosity and initial conductive particle content of the liquid ACF glue of the above-mentioned embodiment and comparative example were detected, and then the liquid ACF was allowed to stand at room temperature for 3 months, and the conductive particle content in the upper and lower layers of the colloid was detected respectively; the liquid ACF after standing was coated on a substrate, and hot pressed for 5s at 160°C and 40MPa for bonding to the carrier, and the bonding strength was tested with a thrust machine, and the conductive function was tested. The specific test results are shown in Table 1.

[0074] Table 1 Performance test results of embodiments and comparative examples

[0075]

[0076] As shown in Table 1, it can be seen from Examples 1 to 3 that the liquid ACF prepared within the scope of the technical solution of the present invention still has good dispersion stability of the conductive particles after long-term standing, and can be normally conducted. It can be seen from the comparative examples that the colloid viscosity of the liquid ACF prepared without using raw materials within the scope of the technical solution has greatly decreased. After long-term standing, the content of conductive particles in the lower colloid has greatly increased, and the content of conductive particles in the upper colloid has greatly decreased. Obvious coagulation phenomenon has occurred, and good bonding strength and conduction function cannot be guaranteed after bonding connection.

[0077] The various aspects, embodiments, and features of the present invention should be considered to be illustrative in all aspects and not limiting of the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0078] In the preparation method of the present invention, the order of each step is not limited to the order listed. For those skilled in the art, without creative work, the order of each step is also within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0079] Finally, it should be noted that the specific embodiments described herein are merely examples of the present invention, and are not intended to limit the implementation methods of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described, or replace them in a similar manner. It is not necessary and impossible to provide all examples of all implementation methods here. However, these obvious changes or modifications derived from the essential spirit of the present invention still fall within the scope of protection of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A liquid ACF, characterized in that: The liquid ACF is processed from the following raw materials in parts by weight: 1 to 10 parts of epoxy resin curing agent, 20 to 60 parts of liquid resin, 1 to 20 parts of conductive particles, 1 to 20 parts of thixotropic agent, 0.1 to 5 parts of tackifier and 0.1 to 5 parts of dispersant.

2. A liquid ACF according to claim 1, characterized in that: The epoxy resin curing agent includes one or more of a metal salt curing agent and an imidazole curing agent.

3. A liquid ACF according to claim 2, characterized in that: The epoxy resin curing agent includes one or more of boron trifluoride ethylamine complex, lanthanum trifluoromethanesulfonate, tin tetrachloride, aluminum trichloride, and 4-ethyl-2-methyl-imidazole.

4. A liquid ACF according to claim 1, characterized in that: The liquid resin is a composition of a high-viscosity liquid epoxy resin and a low-viscosity liquid epoxy resin; the viscosity of the high-viscosity liquid epoxy resin is 600-10000 cps, and the viscosity of the low-viscosity liquid epoxy resin is 100-500 cps.

5. A liquid ACF according to claim 4, characterized in that: The high-viscosity liquid epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, phenolic epoxy resin, and heterocyclic epoxy resin; And / or, the low-viscosity liquid epoxy resin includes one or more of liquid alicyclic epoxy resin, glycidyl ether epoxy resin, linear phenolic epoxy resin, and aliphatic epoxy resin.

6. A liquid ACF according to claim 4, characterized in that: The mass ratio of the high-viscosity liquid epoxy resin to the low-viscosity liquid epoxy resin in the liquid resin is (1-5):(1-5).

7. A liquid ACF according to claim 1, characterized in that: The thixotropic agent is fumed silicon dioxide with a particle size of 1 to 600 nm.

8. The liquid ACF according to claim 1, characterized in that: The viscosity enhancer includes one or more of carboxymethyl cellulose, polyacrylamide, polyvinyl alcohol, latex, and gelatin; And / or, the dispersant includes one or more of polyethylene glycol, polyether amine, polyether polyol, and polyacrylic acid; And / or, the conductive particles are core-shell structure compositions with a polymer as a core and a metal layer as a shell.

9. A method for preparing a liquid ACF according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: mixing and stirring epoxy resin curing agent, liquid resin, conductive particles, thixotropic agent, tackifier and dispersant evenly to obtain liquid ACF.

10. An application of a liquid ACF as claimed in any one of claims 1 to 8, characterized in that: The application includes coating a liquid ACF on a substrate and / or a carrier, combining the substrate and the carrier through the liquid ACF to form a component, and then performing bonding connection.

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