Anisotropic conductive adhesive film with wide indentation width and preparation method thereof

Abstract

The present invention belongs to the technical field of conductive adhesives, and relates to an anisotropic conductive adhesive film with a wide indentation width and a preparation method thereof. The anisotropic conductive adhesive film includes the following preparation raw materials: nitrile rubber, thermoplastic resin, low-viscosity acrylate prepolymer with negatively charged groups, multifunctional acrylate monomer, silane coupling agent, conductive particles, silicon dioxide, titanium dioxide, free radical initiator, and polymerization inhibitor; wherein the viscosity of the low-viscosity acrylate prepolymer with negatively charged groups is ≤5000cps (60°C), and the negatively charged groups include one or more of carboxylate and sulfonate groups; the conductive particles are soaked. The present invention solves the problems of insufficient indentation width in traditional ACF by controlling the formula of ACF and optimizing the indentation width, thereby ensuring the reliability and stability of the connection.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive adhesives and relates to an anisotropic conductive adhesive film with a wide indentation width and a preparation method thereof. Background Art

[0002] Anisotropic Conductive Film (ACF) is a special electronic packaging material that can evenly distribute conductive particles with an insulating layer in a thermosetting resin adhesive, which can achieve electrical conduction in a specific direction while maintaining insulation properties in other directions. When ACF is applied to the connection between the glass substrate and the IC chip, the conductive particles are squeezed between the two electrodes through heating and pressurization to form a stable electrical connection. At the same time, since the surface of the conductive particles is coated with a layer of insulating material, those particles that are not captured by the electrodes will not cause a short circuit even if they move to other locations, because the insulating coating between them prevents unnecessary conduction. In addition, the thermosetting adhesive hardens during the heating process, ensuring the firmness and reliability of the connection. Due to its unique physical and electrical properties, ACF is widely used in the connection of flat-panel display panels and IC chips in high-definition televisions, mobile devices, etc., and plays an important role in the trend of miniaturization, lightweight and high performance of modern electronic products.

[0003] The indentation width of ACF refers to the width of the physical trace or imprint formed by ACF in the electrode contact area during the heating and pressurization process. An appropriate indentation width indicates that the conductive particles are in good contact with the electrode, forming a stable conductive path, ensuring the reliability and stability of the connection; if the indentation is too narrow, it may mean that the conductive particles have failed to fully contact the electrode, resulting in poor connection and affecting electrical performance. The main reason for the narrow indentation width is that the fluidity of the ACF colloid is poor during the curing process, which makes it impossible to discharge the colloid. Some conductive particles cannot be deformed under pressure due to the presence of the colloid, resulting in a narrow indentation width. In the use of ACF, in order to ensure the uniformity of the indentation, it is generally required that the indentation width is greater than 2 / 3 of the total width of the electrode to prevent small area failure in the width direction of the electrode from causing overall failure during the reliability process. Summary of the invention

[0004] In view of the shortcomings in the prior art, the present invention provides an anisotropic conductive adhesive film with a wide indentation width and a preparation method thereof, and increases the indentation width by adjusting the formula of ACF.

[0005] One object of the present invention is achieved by the following technical solutions:

[0006] A wide indentation width anisotropic conductive adhesive film, comprising the following raw materials: 5 to 15 parts of nitrile rubber, 5 to 25 parts of thermoplastic resin, 20 to 40 parts of low-viscosity acrylate prepolymer with negatively charged groups, 5 to 15 parts of acrylate monomer, 0.1 to 2 parts of silane coupling agent, 1 to 10 parts of conductive particles, 10 to 30 parts of silicon dioxide, 0.5 to 10 parts of titanium dioxide, 1 to 10 parts of free radical initiator, 0.1 to 1.0 parts of polymerization inhibitor;

[0007] The viscosity of the low-viscosity acrylate prepolymer with negatively charged groups is ≤5000cps (60°C), the negatively charged groups include one or more of carboxylate groups and sulfonate groups, and the viscosity measured at 60°C is ≤5000cps.

[0008] The present invention adds a low-viscosity and negatively charged acrylate prepolymer to the ACF to reduce the colloid viscosity, and the negative charge causes the acrylate prepolymers to repel each other, thereby improving the fluidity when the ACF is heated and flows. The amount of the low-viscosity and negatively charged acrylate prepolymer added is 20 to 40 parts. If too little is added, the fluidity cannot be improved, and if too much is added, the compatibility of the system is affected, resulting in mixed stratification.

[0009] Preferably, the low-viscosity acrylate prepolymer with negatively charged groups is one or more of polyurethane acrylate with negatively charged groups, polyester acrylate with negatively charged groups, epoxy acrylate with negatively charged groups, modified polyester acrylate with negatively charged groups, and polyether acrylate with negatively charged groups. Further preferably, the viscosity of the low-viscosity acrylate prepolymer with negatively charged groups is 2000-3500 cps (60° C.).

[0010] Preferably, the conductive particles are pre-treated conductive balls, and the pre-treatment includes: soaking the conductive balls in an organic solvent. The present invention pre-treats the conductive balls by soaking them in an organic solvent, so that the polymer molecular chains in the conductive balls absorb the solvent and swell, and some of the molecular chains are broken, which can reduce the hardness of the conductive balls, make them more easily deformed during the bonding process, enhance the bonding indentation, and facilitate the formation of indentations at both ends in the width direction.

[0011] The conductive balls are not particularly limited, and any conductive particles that can be used in anisotropic conductive films and have a conductive effect can be used. Preferably, the conductive balls are core-shell structure compositions with a polymer as the core and a metal layer as the shell, and the polymer can be one or more of polymethyl methacrylate, polyaniline, polystyrene, polyacrylamide, polyvinyl chloride, and polyacrylonitrile, and the metal layer can be one or more of a nickel layer, a gold layer, a copper layer, and a cobalt layer. More preferably, the particle size of the conductive balls is 0.5 to 20 μm, and further 3 to 10 μm.

[0012] In the pretreatment step, preferably, the organic solvent is one or more of methyl ethyl ketone, acetone, toluene, xylene, propyl acetate, ethyl acetate, and butyl acetate.

[0013] In the pretreatment step, preferably, the immersion temperature is 15-45°C, more preferably 20-40°C; the immersion time is 1-10 hours, more preferably 2-8 hours. If the immersion time is too short, the indentation improvement effect is limited, while if the immersion time is too long, the conductive ball will swell excessively, affecting the performance.

[0014] Preferably, the acrylate monomer is a multifunctional acrylate monomer, and more preferably one or more of pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, ditrimethylolpropane tetraacrylate, propoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol hexaacrylate.

[0015] The addition of multifunctional monomers is beneficial to improve the curing modulus of ACF, making the indentation more obvious and easier to press out at both ends of the width direction. The addition amount of multifunctional monomers is 5 to 15 parts. If too little is added, the indentation cannot be improved, and if too much is added, the reliability will deteriorate.

[0016] Preferably, the polymerization inhibitor includes a polyphenol polymerization inhibitor and / or a quinone polymerization inhibitor. Adding a polymerization inhibitor to the ACF formula of the present invention can delay the curing speed and improve the fluidity of the ACF under hot pressing conditions. The amount of polymerization inhibitor added is controlled to be 0.1 to 1 part. If too little polymerization inhibitor is added, the polymerization inhibition effect is not obvious, the monomer polymerizes prematurely, and poor fluidity is caused; and if too much polymerization inhibitor is added, the polymerization reaction will be excessively inhibited, resulting in unclear indentation.

[0017] More preferably, the polymerization inhibitor is a mixture of a polyphenol polymerization inhibitor and a quinone polymerization inhibitor. The polyphenol polymerization inhibitor plays a major role in polymerization inhibition, while the quinone polymerization inhibitor plays a role in polymerization retardation. The two inhibitors cooperate with each other to achieve a better effect of improving fluidity.

[0018] More preferably, the polymerization inhibitor is a mixture of a polyphenol polymerization inhibitor and a quinone polymerization inhibitor in a mass ratio of 1:0.1 to 1. By adjusting the ratio of the two, the fluidity and the reaction rate can be better balanced.

[0019] The polyphenolic polymerization inhibitor is preferably one or more of hydroquinone, p-tert-butylcatechol, 2,6-di-tert-butyl-p-methylphenol, 4,4'-dihydrobiphenyl and bisphenol A. The quinone polymerization inhibitor is preferably one or more of p-benzoquinone, tetrachlorobenzoquinone and 1,4-naphthoquinone.

[0020] Preferably, the thermoplastic resin includes but is not limited to one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyurethane, polysulfone (PSF), polyethersulfone (PES), polyphenylene ether, polyamide, acrylonitrile-butadiene-styrene (ABS), styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-isoprene-styrene block copolymer (SEPS), styrene-isoprene-styrene block copolymer (SIS), etc.

[0021] Preferably, the silane coupling agent includes one or more of vinyl type (such as vinyl triethoxysilane), chloroalkyl type (γ-chloropropyl triethoxysilane), aminoalkyl type (such as 3-aminopropyl triethoxysilane KH-550), epoxyalkyl type (such as γ-glycidyloxypropyl trimethoxysilane KH-560), and methacrylic acid acyloxyalkyl type (such as γ-methacrylic acid acyloxypropyl trimethoxysilane KH-570).

[0022] Preferably, the free radical initiator includes one or more of a peroxide initiator (such as benzoyl peroxide, potassium persulfate, ammonium persulfate, 2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxide)-hexane, etc.), an azo initiator (such as azobisisobutyronitrile, diisopropyl azodicarboxylate, etc.) and a redox system initiator. The redox system initiator is composed of an oxidant (such as peroxide) and a reductant (such as ferrous sulfate, ascorbic acid, aluminum isopropoxide, etc.).

[0023] Preferably, the wide indentation width anisotropic conductive adhesive film further comprises 0 to 20 parts of other additives, more preferably 0.01 to 20 parts of other additives. Other additives are not particularly limited, and any additive that can be applied to the anisotropic conductive adhesive film to modify its function can be used, such as colorants, adhesion promoters, flame retardants, etc.

[0024] The second object of the present invention is achieved by the following technical solutions:

[0025] A method for preparing anisotropic conductive adhesive film with wide indentation width comprises the following steps:

[0026] The prepared raw materials are added into a solvent and mixed to form a coating liquid, and the anisotropic conductive adhesive film is obtained after coating and cutting.

[0027] Preferably, the solvent can be listed as benzene solvents (toluene, benzene, etc.), ketone solvents (methyl ethyl ketone, acetone, butanone, etc.), alcohol solvents (ethanol, isopropanol, etc.), ester solvents (ethyl acetate, butyl acetate, etc.), etc.

[0028] Preferably, the solid content of the coating liquid is 30-60 wt %.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention adds low-viscosity and negatively charged acrylate prepolymer, polymerization inhibitor, multifunctional acrylate monomer and other components into ACF to form a formula system with other components to improve the colloid fluidity, so that during the heating and pressurizing process of ACF, the conductive particles can better contact with the electrode, forming a wider indentation width, which helps to ensure the stability of the conductive path and the reliability of the connection;

[0031] 2. The polymerization inhibitor of the present invention is further preferably a mixture of a polyphenol polymerization inhibitor and a quinone polymerization inhibitor, wherein the polyphenol polymerization inhibitor plays a major role in polymerization inhibition and the quinone polymerization inhibitor plays a role in polymerization retardation, and the two cooperate with each other to achieve a better effect of improving fluidity;

[0032] 3. The present invention pre-treats the conductive ball by soaking it in an organic solvent, which reduces the hardness of the conductive ball and makes it easier to deform during the bonding process, thereby enhancing the bonding indentation and facilitating the formation of indentations at both ends in the width direction.

[0033] The indentation width of the conductive adhesive film is an important parameter for evaluating the connection quality of ACF. The present invention solves the problem of insufficient indentation width in traditional ACF by controlling the formula of ACF and optimizing the indentation width, thereby ensuring the reliability and stability of the connection. DETAILED DESCRIPTION

[0034] The technical scheme of the present invention is further described below by specific embodiments. It should be understood that the specific embodiments described herein are only used to help understand the present invention and are not intended to be used for specific limitations of the present invention. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0035] In the following examples and comparative examples, the sources of raw materials are as follows:

[0036] Nitrile rubber: Lanzhou Petrochemical NBR 1906;

[0037] Thermoplastic resin: SBS resin, JOP SBS1155;

[0038] Low viscosity acrylate prepolymer with negatively charged groups: CN997 NS, Sartomer, viscosity: 3500cps@60℃, negatively charged group is carboxylate group; CN982, Sartomer, viscosity 4500cps@60℃, negatively charged group is sulfonate group;

[0039] Low viscosity non-negatively charged acrylate prepolymer: CN9023, Sartomer, viscosity 3000cps@60℃;

[0040] High viscosity non-negatively charged acrylate prepolymer: CN9004 NS, Sartomer, viscosity 21000cps@60℃;

[0041] Multifunctional monomer: pentaerythritol tetraacrylate, Changxing EM241; ethoxylated pentaerythritol tetraacrylate, Changxing EM2411;

[0042] Common monomer: tricyclodecane dimethanol diacrylate, Changxing EM2204;

[0043] Free radical initiator: 2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxy)-hexane, Nouryon TRIGONOX141; dibenzoyl peroxide, Perkadox GB-50;

[0044] Silane coupling agent: Lingtai LT1640; Japan Shin-Etsu KBM-403;

[0045] Conductive ball: nickel-plated polymer ball, average particle size 5μm, Zhenjiang Aibang Ni-500;

[0046] Silicon dioxide: average particle size 20nm, Brofos-SiO2-S820;

[0047] Titanium dioxide: average particle size 21nm, P25;

[0048] Hydroquinone, p-benzoquinone, 1,4-naphthoquinone: MacLean;

[0049] Adhesion promoter: BYK-4512, colorant: Fluor V-7709s.

[0050] Example 1

[0051] The raw materials of the anisotropic conductive film of this embodiment are:

[0052] 10 parts of nitrile rubber, 18 parts of thermoplastic resin, 21 parts of low-viscosity acrylate prepolymer with negatively charged groups (CN997 NS, Sartomer), 8 parts of multifunctional monomer (pentaerythritol tetraacrylate), 1 part of silane coupling agent (Lingtai LT1640), 5 parts of conductive particles, 12 parts of silicon dioxide, 1 part of titanium dioxide, 2 parts of free radical initiator (2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxide)-hexane), inhibitor: 0.3 parts of hydroquinone, 0.2 parts of p-benzoquinone, 1 part of adhesion promoter (BYK-4512), 0.3 parts of colorant (Fulu V-7709s);

[0053] The conductive particles are pretreated conductive balls, and the pretreatment steps are: immersing 5 parts of the conductive balls in 20 parts of methyl ethyl ketone at a immersion temperature of 30° C. for 5 hours; after the immersion, taking out the conductive balls and draining them.

[0054] The preparation method of the anisotropic conductive adhesive film includes: weighing the raw materials according to the above weight parts, adding toluene, stirring and mixing at 30°C to form a coating liquid (solid content is 50wt%), coating the coating liquid on a PET film at a temperature of 70°C (3min), and cutting to obtain an anisotropic conductive adhesive film loaded on the PET film with a thickness of 10μm.

[0055] Example 2

[0056] The raw materials of the anisotropic conductive film of this embodiment are:

[0057] 12 parts of nitrile rubber, 20 parts of thermoplastic resin, 25 parts of low viscosity acrylate prepolymer with negatively charged groups (CN982, Sartomer), 10 parts of multifunctional monomer (ethoxylated pentaerythritol tetraacrylate), 1.2 parts of silane coupling agent (Japan Shin-Etsu KBM-403), 6 parts of conductive particles, 14 parts of silicon dioxide, 1.8 parts of titanium dioxide, 3 parts of free radical initiator (dibenzoyl peroxide), inhibitor: 0.4 parts of hydroquinone, 0.3 parts of 1,4-naphthoquinone, 1.5 parts of adhesion promoter (BYK-4512), 0.5 parts of colorant (Fulu V-7709s).

[0058] The conductive particles are pretreated conductive balls, and the pretreatment steps are: immersing 6 parts of the conductive balls in 25 parts of methyl ethyl ketone at a immersion temperature of 30° C. for 6 hours; after the immersion, taking out the conductive balls and draining them.

[0059] The preparation method of the anisotropic conductive adhesive film includes: weighing the raw materials according to the above weight parts, adding toluene, stirring and mixing at 30°C to form a coating liquid (solid content is 45wt%), coating the coating liquid on a PET film at a temperature of 75°C (4 minutes), and cutting to obtain an anisotropic conductive adhesive film loaded on the PET film, with a thickness of 15μm.

[0060] Example 3

[0061] The raw materials of the anisotropic conductive film of this embodiment are:

[0062] 10 parts of nitrile rubber, 18 parts of thermoplastic resin, 21 parts of low viscosity acrylate prepolymer with negatively charged groups (CN997 NS, Sartomer), 8 parts of multifunctional monomer (pentaerythritol tetraacrylate), 1 part of silane coupling agent (Lingtai LT1640), 5 parts of conductive particles, 12 parts of silicon dioxide, 1 part of titanium dioxide, 2 parts of free radical initiator (2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxy)-hexane), inhibitor: 0.5 parts of hydroquinone, 1 part of adhesion promoter (BYK-4512), 0.3 parts of colorant (Fulu V-7709s).

[0063] The preparation method of the conductive particles and the preparation method of the anisotropic conductive adhesive film are the same as those in Example 1.

[0064] Example 4

[0065] The raw materials of the anisotropic conductive film of this embodiment are:

[0066] 10 parts of nitrile rubber, 18 parts of thermoplastic resin, 21 parts of low viscosity acrylate prepolymer with negatively charged groups (CN997 NS, Sartomer), 8 parts of multifunctional monomer (pentaerythritol tetraacrylate), 1 part of silane coupling agent (Lingtai LT1640), 5 parts of conductive particles, 12 parts of silicon dioxide, 1 part of titanium dioxide, 2 parts of free radical initiator (2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxide)-hexane), inhibitor: 0.5 parts of p-benzoquinone, 1 part of adhesion promoter (BYK-4512), 0.3 parts of colorant (Fulu V-7709s)

[0067] The preparation method of the conductive particles and the preparation method of the anisotropic conductive adhesive film are the same as those in Example 1.

[0068] Comparative Example 1

[0069] The raw materials of the anisotropic conductive adhesive film of Comparative Example 1 are:

[0070] 10 parts of nitrile rubber, 18 parts of thermoplastic resin, 21 parts of low viscosity acrylate prepolymer with negatively charged groups (CN997 NS, Sartomer), 8 parts of multifunctional monomer (pentaerythritol tetraacrylate), 1 part of silane coupling agent (Lingtai LT1640), 5 parts of conductive particles, 12 parts of silicon dioxide, 1 part of titanium dioxide, 2 parts of free radical initiator (2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxy)-hexane), 1 part of adhesion promoter (BYK-4512), 0.3 parts of colorant (Fulu V-7709s).

[0071] The preparation method of the conductive particles and the preparation method of the anisotropic conductive adhesive film are the same as those in Example 1.

[0072] Comparative Example 2

[0073] The raw materials of the anisotropic conductive adhesive film of Comparative Example 2 are:

[0074] 10 parts of nitrile rubber, 18 parts of thermoplastic resin, 21 parts of low-viscosity non-negatively charged acrylate prepolymer (CN9023, Sartomer), 8 parts of multifunctional monomer (pentaerythritol tetraacrylate), 1 part of silane coupling agent (Lingtai LT1640), 5 parts of conductive particles, 12 parts of silicon dioxide, 1 part of titanium dioxide, 2 parts of free radical initiator (2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxide)-hexane), inhibitor: 0.3 parts of hydroquinone, 0.2 parts of benzoquinone, 1 part of adhesion promoter (BYK-4512), 0.3 parts of colorant (Fulu V-7709s).

[0075] The preparation method of the conductive particles and the preparation method of the anisotropic conductive adhesive film are the same as those in Example 1.

[0076] Comparative Example 3

[0077] The raw materials of the anisotropic conductive adhesive film of Comparative Example 3 are:

[0078] 10 parts of nitrile rubber, 18 parts of thermoplastic resin, 21 parts of high viscosity non-negatively charged acrylate prepolymer (CN9004 NS, Sartomer), 8 parts of multifunctional monomer (pentaerythritol tetraacrylate), 1 part of silane coupling agent (Lingtai LT1640), 5 parts of conductive particles, 12 parts of silicon dioxide, 1 part of titanium dioxide, 2 parts of free radical initiator (2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxide)-hexane), inhibitor: 0.3 parts of hydroquinone, 0.2 parts of benzoquinone, 1 part of adhesion promoter (BYK-4512), 0.3 parts of colorant (Fulu V-7709s).

[0079] The preparation method of the conductive particles and the preparation method of the anisotropic conductive adhesive film are the same as those in Example 1.

[0080] Comparative Example 4

[0081] The raw materials of the anisotropic conductive adhesive film of Comparative Example 4 are:

[0082] 10 parts of nitrile rubber, 18 parts of thermoplastic resin, 21 parts of low viscosity acrylate prepolymer with negatively charged groups (CN997 NS, Sartomer), 8 parts of ordinary monomer (Changxing EM2204), 1 part of silane coupling agent (Lingtai LT1640), 5 parts of conductive particles, 12 parts of silicon dioxide, 1 part of titanium dioxide, 2 parts of free radical initiator (2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxide)-hexane), inhibitor: 0.3 parts of hydroquinone, 0.2 parts of benzoquinone, 1 part of adhesion promoter (BYK-4512), 0.3 parts of colorant (Fulu V-7709s).

[0083] The preparation method of the conductive particles and the preparation method of the anisotropic conductive adhesive film are the same as those in Example 1.

[0084] Comparative Example 5

[0085] The raw materials of the anisotropic conductive adhesive film of Comparative Example 5 are:

[0086] 10 parts of nitrile rubber, 18 parts of thermoplastic resin, 21 parts of low viscosity acrylate prepolymer with negatively charged groups (CN997 NS, Sartomer), 8 parts of multifunctional monomer (pentaerythritol tetraacrylate), 1 part of silane coupling agent (Lingtai LT1640), 5 parts of conductive balls (without soaking pretreatment), 12 parts of silicon dioxide, 1 part of titanium dioxide, 2 parts of free radical initiator (2,5-dimethyl-2,5-bis-(2-ethylhexanoyl peroxide)-hexane), inhibitor: 0.3 parts of hydroquinone, 0.2 parts of benzoquinone, 1 part of adhesion promoter (BYK-4512), 0.3 parts of colorant (Fulu V-7709s)

[0087] The preparation method of the anisotropic conductive adhesive film is the same as that of Example 1.

[0088] The anisotropic conductive adhesive films of Examples 1-4 and Comparative Examples 1-5 were bonded at 160°C, 3MPa, and 5s. After bonding, a peel strength tester was used to measure the bonding force (gf / cm) at a peel angle of 90° and a peel speed of 50mm / min. A pre-designed electrode with detectable on-resistance was selected on the FPC, and an on-resistance test was performed using a resistance meter. The indentation was observed using a DIC microscope, and the length of the indentation area was measured from top to bottom along the Y-axis direction of the electrode. The measured value is the indentation width. The results are shown in Table 1:

[0089] Table 1 ACF performance of Examples 1-4 and Comparative Examples 1-5

[0090] Example Indentation width (μm) Adhesion force (gf / cm) On-resistance(Ω) Example 1 833 1332 2.2 Example 2 838 1340 2.3 Example 3 820 1290 2.8 Example 4 778 1329 2.6 Comparative Example 1 533 1225 3.9 Comparative Example 2 732 1179 2.9 Comparative Example 3 639 1136 3.1 Comparative Example 4 758 1286 2.5 Comparative Example 5 725 1358 2.8

[0091] As can be seen from Table 1, the ACF prepared by the formula of the present invention has a wide indentation width after connection. Example 3 and Example 4 respectively use hydroquinone and para-benzoquinone as inhibitors. Compared with the comparative example 1 without adding the inhibitor, hydroquinone or para-benzoquinone as the inhibitor can significantly widen the indentation width. Compared with Example 1, the indentation width of Example 3 with hydroquinone as the inhibitor is slightly reduced, and the bonding force is reduced; the indentation width of Example 4 with para-benzoquinone as the inhibitor is significantly reduced, indicating that the composite use of hydroquinone and para-benzoquinone in a certain proportion has a better effect of improving the indentation width.

[0092] Comparative Example 2 adds a low-viscosity, non-negatively charged acrylate prepolymer, and Comparative Example 3 adds a high-viscosity, non-negatively charged acrylate prepolymer. Compared with Comparative Examples 2 and 3, Example 1 adds a low-viscosity, negatively charged acrylate prepolymer, which can effectively improve fluidity and increase the indentation width. Comparison between Comparative Example 4 and Example 1 shows that the multifunctional monomer added in the present invention can improve the indentation width.

[0093] In Comparative Example 5, conductive balls without soaking treatment are directly added. The conductive balls in Comparative Example 5 have a relatively high hardness and are not easily deformed during the bonding process, which is not conducive to the formation of indentations at both ends in the width direction.

[0094] 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.

[0095] 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.

[0096] 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. An anisotropic conductive film with a wide indentation width, characterized in that: The preparation material comprises the following raw materials: 5 to 15 parts of nitrile rubber, 5 to 25 parts of thermoplastic resin, 20 to 40 parts of low-viscosity acrylate prepolymer with negatively charged groups, 5 to 15 parts of acrylate monomer, 0.1 to 2 parts of silane coupling agent, 1 to 10 parts of conductive particles, 10 to 30 parts of silicon dioxide, 0.5 to 10 parts of titanium dioxide, 1 to 10 parts of free radical initiator, and 0.1 to 1.0 parts of polymerization inhibitor; The viscosity of the low-viscosity acrylate prepolymer with negatively charged groups is ≤5000 cps (60° C.), and the negatively charged groups include one or more of carboxylate groups and sulfonate groups.

2. The anisotropic conductive adhesive film with a wide indentation width according to claim 1, characterized in that: The low-viscosity acrylate prepolymer with negatively charged groups is one or more of polyurethane acrylate with negatively charged groups, polyester acrylate with negatively charged groups, epoxy acrylate with negatively charged groups, modified polyester acrylate with negatively charged groups, and polyether acrylate with negatively charged groups; The viscosity of the low-viscosity acrylate prepolymer with negatively charged groups is 2000-3500 cps (60° C.).

3. The anisotropic conductive adhesive film with a wide indentation width according to claim 1, characterized in that: The conductive particles are pre-treated conductive balls, and the pre-treatment includes: immersing the conductive balls in an organic solvent.

4. The anisotropic conductive adhesive film with a wide indentation width according to claim 3, characterized in that: The organic solvent is one or more of methyl ethyl ketone, acetone, toluene, xylene, propyl acetate, ethyl acetate, and butyl acetate; The soaking temperature is 15-45° C., and the soaking time is 1-10 hours.

5. The anisotropic conductive adhesive film with a wide indentation width according to claim 1, characterized in that: The acrylate monomer is a multifunctional acrylate monomer, and the multifunctional acrylate monomer is one or more of pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, ditrimethylolpropane tetraacrylate, propoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol hexaacrylate.

6. The anisotropic conductive adhesive film with a wide indentation width according to claim 1, characterized in that: The polymerization inhibitor includes polyphenol polymerization inhibitor and / or quinone polymerization inhibitor.

7. The anisotropic conductive adhesive film with a wide indentation width according to claim 1, characterized in that: The polymerization inhibitor is a mixture of a polyphenol polymerization inhibitor and a quinone polymerization inhibitor in a mass ratio of 1:0.1-1.

8. The anisotropic conductive adhesive film with a wide indentation width according to claim 6 or 7, characterized in that: The polyphenol inhibitor is one or more of hydroquinone, p-tert-butylcatechol, 2,6-di-tert-butyl-p-methylphenol, 4,4'-dihydrobiphenyl and bisphenol A; the quinone inhibitor is one or more of p-benzoquinone, tetrachlorobenzoquinone and 1,4-naphthoquinone.

9. The anisotropic conductive adhesive film with a wide indentation width according to claim 1, characterized in that: The thermoplastic resin includes one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyurethane, polysulfone, polyethersulfone, polyphenylene oxide, polyamide, acrylonitrile-butadiene-styrene, styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, styrene-isoprene-styrene block copolymer; And / or, the free radical initiator includes one or more of a peroxide initiator, an azo initiator and a redox system initiator.

10. The method for preparing anisotropic conductive adhesive film with wide indentation width according to claim 1, characterized in that: The following steps are involved: The prepared raw materials are added into a solvent and mixed to form a coating liquid, and the anisotropic conductive adhesive film is obtained after coating and cutting.