Low-temperature curing type anisotropic conductive adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of conductive adhesives, and particularly discloses a low-temperature curing type anisotropic conductive adhesive which comprises the following components in parts by weight: 15-40 parts of long-chain alkyl modified epoxy resin, 20-40 parts of flexible acrylic resin, 30-50 parts of film-forming resin, 5-20 parts of a free radical polymer, 5-20 parts of an inorganic filler, 1-10 parts of conductive particles, 1-5 parts of an initiator and 1-10 parts of an auxiliary agent. The mass ratio of the long-chain alkyl modified epoxy resin to the flexible acrylic resin is (0.5-1.5): 1. According to the low-temperature curing type anisotropic conductive adhesive and the preparation method thereof provided by the invention, the low-temperature curing type anisotropic conductive adhesive has the characteristics of high bonding strength and low-temperature curing, can maintain connection stability in a long-term use process, and is beneficial to stable operation of an electronic system.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive adhesives, and in particular relates to a low-temperature curing anisotropic conductive adhesive and a preparation method thereof. Background Art

[0002] As the electronics industry is booming, the performance of electronic equipment continues to improve, and the functions are becoming more and more complex, which has prompted the continuous improvement of electronic manufacturing processes. Among them, the interconnection technology of electronic components plays a key supporting role. Traditional interconnection methods, such as welding processes, have been widely used for a long time, but their disadvantages are becoming increasingly significant. On the one hand, the high temperature of welding can easily cause thermal shock to electronic components, causing potential damage to precision chips, flexible circuit boards, etc., shortening the life of the product; on the other hand, when welding with fine pitches, the solder is easy to flow out of control, and the risk of short circuit is high. It is difficult to achieve precise connection under tiny sizes, and it cannot match the development needs of cutting-edge fields such as high-end semiconductors and micro sensors. At the same time, the emergence of isotropic conductive adhesives can solve the problem of high welding temperatures to a certain extent. However, its all-round conductive properties cause new problems such as leakage and electromagnetic interference in complex circuit integration, which is not conducive to the stable operation of electronic systems.

[0003] Epoxy resin, which entered the market first, was first introduced into the field of anisotropic conductive adhesives with its excellent bonding properties, good chemical stability and mechanical strength. In the initial stage of electronic packaging, it can provide stable adhesion for chips and withstand a certain degree of thermal shock and mechanical stress. However, the epoxy group has high curing reaction activity and large shrinkage during the curing process, which can easily lead to internal stress accumulation, causing the conductive adhesive layer to separate from the connected interface, especially when multi-layer chips are stacked and flexible substrates are connected, and debonding occurs frequently; in addition, its curing conditions often require high-temperature and long-term baking, which consumes a lot of energy and is not suitable for new electronic components that are sensitive to temperature, such as organic optoelectronic devices. Acrylate polymers have double bond polymerization reaction characteristics. Although they can achieve light curing and rapid curing at room temperature, they can overcome the problem of high energy consumption of epoxy system curing. However, acrylate system polymers are more flexible than rigid. When subjected to large external forces, the conductive adhesive layer is easy to deform. When subjected to long-term action, the bonding interface is prone to peeling, affecting the connection reliability. Therefore, the electronics industry urgently needs an innovation of anisotropic conductive adhesive with high bonding strength and low-temperature curing to break through the bottleneck of existing technologies. Summary of the invention

[0004] The purpose of the present invention is to overcome the above problems existing in the prior art and to provide a low-temperature curing anisotropic conductive adhesive and a preparation method thereof. The low-temperature curing anisotropic conductive adhesive has the characteristics of high bonding strength and low-temperature curing, can maintain connection stability during long-term use, and is conducive to the stable operation of electronic systems.

[0005] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, the present invention provides a low-temperature curing anisotropic conductive adhesive, comprising the following components in parts by weight: 15-40 parts of a long-chain alkyl modified epoxy resin, 20-40 parts of a flexible acrylic resin, 30-50 parts of a film-forming resin, 5-20 parts of a free radical polymer, 5-20 parts of an inorganic filler, 1-10 parts of conductive particles, 1-5 parts of an initiator, and 1-10 parts of an auxiliary agent;

[0007] The mass ratio of the long-chain alkyl modified epoxy resin to the flexible acrylic resin is (0.5-1.5):1.

[0008] Furthermore, the preparation method of the long-chain alkyl-modified epoxy resin comprises the following steps:

[0009] Preheat the bisphenol A epoxy resin at 60-70°C, mix it evenly with anhydrous long-chain alkanol, add tertiary amine, raise the temperature to 120-140°C under stirring, react for 6-8h to obtain a crude product, extract and purify the crude product, and dry it under reduced pressure to obtain a long-chain alkyl modified epoxy resin.

[0010] Furthermore, the long-chain alkanol is a C10-C18 normal alkanol.

[0011] Furthermore, the mass ratio of the bisphenol A epoxy resin, the long-chain alkanol and the tertiary amine is (50-70):(80-100):(1-5).

[0012] Furthermore, the flexible acrylic resin is one or more of butyl acrylate copolymer, isooctyl acrylate copolymer, and hydroxy acrylic resin;

[0013] The film-forming resin is bisphenol A type phenoxy resin and / or bisphenol F type phenoxy resin;

[0014] The free radical polymer is a blocked isocyanate containing a double bond;

[0015] The inorganic filler is one or more of nano silicon dioxide, nano titanium oxide, nano magnesium oxide, talc, and calcium carbonate;

[0016] The initiator is a thermal initiator;

[0017] The auxiliary agent is one or more of an inhibitor, a toughening agent, a plasticizer, and a silane coupling agent.

[0018] Furthermore, the blocked isocyanate containing a double bond is one or more of methyl ethyl ketone oxime blocked isocyanate, pyrazole blocked isocyanate, and maleimide blocked isocyanate.

[0019] Furthermore, the thermal initiator comprises a peroxide having a 0.1 hour half-life temperature of 90-105°C.

[0020] Furthermore, the peroxide is one or more of diisopropyl peroxydicarbonate, cumyl peroxyneodecanoate, and tert-butyl peroxypivalate.

[0021] Furthermore, the polymerization inhibitor is one or more of phenol polymerization inhibitors, quinone polymerization inhibitors, nitro compound polymerization inhibitors, aromatic amine polymerization inhibitors, and sulfur-containing compound polymerization inhibitors.

[0022] In a second aspect, the present invention further provides a method for preparing a low-temperature curing anisotropic conductive adhesive, comprising the following steps:

[0023] S1. According to the formula, long-chain alkyl modified epoxy resin, flexible acrylic resin and free radical polymer are stirred, degassed and mixed to obtain a mixed solution 1;

[0024] S2, stirring and degassing the film-forming resin, the inorganic filler, the auxiliary agent and the mixed solution 1 to obtain a mixed solution 2;

[0025] S3, adding conductive particles to the mixed solution 2, vacuum degassing and stirring until uniformly dispersed, then adding an initiator, vacuum degassing and stirring until uniformly dispersed, to obtain a liquid anisotropic conductive adhesive;

[0026] S4. Coat the anisotropic conductive adhesive on the substrate and dry it at 50-60° C. for 5-10 min to obtain an anisotropic conductive adhesive film with a thickness of 20-30 μm.

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

[0028] 1. The present invention provides a low-temperature curing anisotropic conductive adhesive, wherein the raw material components include a long-chain alkyl modified epoxy resin. During the preparation of the long-chain alkyl modified epoxy resin, due to the catalytic effect of tertiary amine, the hydroxyl groups of the long-chain alkanol will attack the epoxy groups in the bisphenol A epoxy resin, and the epoxy groups will undergo a ring-opening reaction. The reaction product contains an ether bond. At the same time, after the hydroxyl groups of the long-chain alkanol combine with the epoxy groups, the epoxy resin molecular chain will be extended. The obtained long-chain alkyl modified epoxy resin can improve the flexibility of the epoxy resin, reduce the curing shrinkage rate, and reduce the internal stress.

[0029] 2. In the present invention, the long-chain alkyl group in the long-chain alkyl-modified epoxy resin has greater flexibility and steric hindrance, can increase the free rotation ability of the molecular chain, and provide flexibility. The flexible acrylate molecule itself contains a flexible acrylate segment. After the two are blended, the flexible segments can be interlaced and entangled with each other to form a flexible network structure in the adhesive layer; the epoxy group in the long-chain alkyl-modified epoxy resin can chemically react with the active group in the flexible acrylate, and when an initiator is used to cure the mixed system of the long-chain alkyl-modified epoxy resin and the flexible acrylate, the initiator can simultaneously initiate the nucleophilic addition reaction of the long-chain alkyl-modified epoxy resin and the free radical polymerization reaction of the acrylate, thereby improving the curing effect. Multiple chemical reactions influence each other and proceed in coordination to form an interpenetrating network structure in the reaction system, which not only retains the high strength and good adhesion of the epoxy resin, but also exerts the flexibility of the acrylate, thereby significantly improving the toughness and adhesion performance of the anisotropic conductive adhesive film. In addition, the long-chain alkyl-modified epoxy resin provided by the present invention is mixed with the flexible acrylate in a specific mass ratio to better promote the synergistic effect between the two, thereby forming an anisotropic conductive adhesive film with high flexibility and high cross-linking degree.

[0030] 3. The blocked isocyanate containing double bonds of the present invention is in a closed state at room temperature and cannot react with other active groups in the system, thereby avoiding the premature curing reaction of the anisotropic conductive adhesive during storage, thereby ensuring that the anisotropic conductive adhesive has a long storage time at room temperature and is not prone to gelling or deterioration. However, as the temperature rises, the initiator will decompose to produce free radicals, which will then trigger a free radical polymerization reaction of the double bonds. At the same time, the opened isocyanate groups can react chemically with the hydroxyl groups in the long-chain alkyl modified epoxy resin and the carboxyl groups in the acrylic resin, further promoting the formation of a cross-linked structure and accelerating the curing speed. The interaction of multiple chemical reactions helps to reduce the temperature required for curing. Therefore, the present invention uses a blocked isocyanate containing double bonds, which can not only improve the storage performance, but also ensure low-temperature curing.

[0031] 4. The initiator of the present invention selects peroxide with a half-life temperature of 90-105°C for 0.1 hours. When the half-life temperature of the initiator is low, it is easy to decompose during storage, and the effective ingredients are greatly reduced during the bonding process, which is easy to be incomplete. When the half-life temperature of the initiator is high, the activity of the initiator is insufficient during the low-temperature bonding process, and it is impossible to induce the monomer to reach a higher reaction rate under low temperature and short time conditions. Therefore, a suitable initiator can ensure a higher reaction rate at a lower temperature. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Preparation Example 1

[0034] Preparation Example 1 provides a method for preparing a long-chain alkyl-modified epoxy resin, comprising the following steps:

[0035] After preheating 50 g of bisphenol A epoxy resin at 60° C., mix it evenly with 80 g of anhydrous lauryl alcohol, add 1 g of tertiary amine, raise the temperature to 120° C. with a stirring speed of 300 rpm, and react for 8 hours to obtain a crude product. The crude product is extracted and purified with deionized water and dried under reduced pressure to obtain a long-chain alkyl modified epoxy resin.

[0036] Preparation Example 2

[0037] Preparation Example 2 provides a method for preparing a long-chain alkyl-modified epoxy resin, comprising the following steps:

[0038] After preheating 60 g of bisphenol A epoxy resin at 65° C., mix it evenly with 90 g of anhydrous n-decanol, add 3 g of tertiary amine, raise the temperature to 130° C. with a stirring speed of 500 rpm, and react for 7 hours to obtain a crude product. The crude product is extracted and purified with deionized water and dried under reduced pressure to obtain a long-chain alkyl-modified epoxy resin.

[0039] Preparation Example 3

[0040] Preparation Example 3 provides a method for preparing a long-chain alkyl-modified epoxy resin, comprising the following steps:

[0041] After preheating 70 g of bisphenol A epoxy resin at 70° C., mix it evenly with 100 g of anhydrous n-octadecyl alcohol, add 5 g of tertiary amine, raise the temperature to 140° C. at a stirring speed of 600 rpm, and react for 6 hours to obtain a crude product. The crude product is extracted and purified with deionized water and dried under reduced pressure to obtain a long-chain alkyl modified epoxy resin.

[0042] Comparative Preparation Example 1

[0043] Comparative Preparation Example 1 provides a method for preparing a long-chain alkyl-modified epoxy resin, comprising the following steps:

[0044] After preheating 50 g of bisphenol A epoxy resin at 60°C and mixing evenly with 80 g of hexanol, 1 g of tertiary amine was added, and the temperature was raised to 120°C with a stirring speed of 300 rpm. After reacting for 8 hours, a crude product was obtained. The crude product was extracted and purified with deionized water and dried under reduced pressure to obtain a long-chain alkyl modified epoxy resin.

[0045] Comparative Preparation Example 2

[0046] Comparative Preparation Example 1 provides a method for preparing a long-chain alkyl-modified epoxy resin, comprising the following steps:

[0047] After preheating 50 g of bisphenol A epoxy resin at 60 ° C, mix it evenly with 80 g of n-eicosanol, add 1 g of tertiary amine, raise the temperature to 120 ° C with a stirring speed of 300 rpm, and react for 8 hours to obtain a crude product. The crude product is extracted and purified with deionized water and dried under reduced pressure to obtain a long-chain alkyl modified epoxy resin.

[0048] Example 1

[0049] This embodiment provides a low-temperature curing anisotropic conductive adhesive, comprising the following components by weight: 40 parts of long-chain alkyl modified epoxy resin, 40 parts of flexible acrylic resin, 40 parts of bisphenol A type phenoxy resin, 20 parts of pyrazole blocked isocyanate, 13 parts of inorganic filler, 1 part of conductive particles, 5 parts of initiator, and 6 parts of auxiliary agent;

[0050] Among them, the long-chain alkyl modified epoxy resin is prepared by Preparation Example 1; the flexible acrylic resin is a hydroxy acrylic resin (model MR14896A); the pyrazole blocked isocyanate is 2-[(3,5-dimethyl-1-H-pyrazolyl) carboxyamino] ethyl acrylate; the inorganic filler is nano-silicon dioxide; the conductive particles are nickel-plated polystyrene microspheres with an average particle size of 5 μm; the initiator is diisopropyl peroxydicarbonate; the auxiliary agent is obtained by mixing 2,5-di-tert-butyl-p-benzoquinone and KH550 in a mass ratio of 1:1;

[0051] This embodiment also provides a method for preparing a low-temperature curing anisotropic conductive adhesive, comprising the following steps:

[0052] S1, long-chain alkyl modified epoxy resin, flexible acrylic resin and pyrazole blocked isocyanate are stirred and degassed to uniformly obtain a mixed solution 1;

[0053] S2, stirring and degassing the bisphenol A type phenoxy resin, the inorganic filler, the auxiliary agent and the mixed solution 1 to obtain a mixed solution 2;

[0054] S3, adding conductive particles to the mixed solution 2, vacuum degassing and stirring until uniformly dispersed, then adding an initiator, vacuum degassing and stirring until uniformly dispersed, to obtain a liquid anisotropic conductive adhesive;

[0055] S4. Coat the anisotropic conductive adhesive on the substrate and dry it at 50° C. for 10 min to obtain an anisotropic conductive adhesive film with a film thickness of 30 μm.

[0056] Example 2

[0057] This embodiment provides a low-temperature curing anisotropic conductive adhesive, comprising the following components by weight: 15 parts of long-chain alkyl modified epoxy resin, 30 parts of flexible acrylic resin, 30 parts of bisphenol F type phenoxy resin, 5 parts of pyrazole blocked isocyanate, 20 parts of inorganic filler, 5 parts of conductive particles, 1 part of initiator, and 10 parts of auxiliary agent;

[0058] Among them, the long-chain alkyl modified epoxy resin is prepared by Preparation Example 2; the flexible acrylic resin is a hydroxy acrylic resin (model MR14896A); the pyrazole blocked isocyanate is 2-[(3,5-dimethyl-1-H-pyrazolyl)carboxyamino]ethyl acrylate; the inorganic filler is nano-titanium oxide; the conductive particles are nickel-plated polystyrene microspheres with an average particle size of 5 μm; the initiator is tert-butyl peroxypivalate; the auxiliary agent is a mixture of 2,5-di-tert-butyl-p-benzoquinone and KH550 in a mass ratio of 1:1:

[0059] This embodiment also provides a method for preparing a low-temperature curing anisotropic conductive adhesive, comprising the following steps:

[0060] S1, long-chain alkyl modified epoxy resin, flexible acrylic resin and pyrazole blocked isocyanate are stirred and degassed to uniformly obtain a mixed solution 1;

[0061] S2, stirring and degassing the bisphenol F type phenoxy resin, the inorganic filler, the auxiliary agent and the mixed solution 1 to obtain a mixed solution 2;

[0062] S3, adding conductive particles to the mixed solution 2, vacuum degassing and stirring until uniformly dispersed, then adding an initiator, vacuum degassing and stirring until uniformly dispersed, to obtain a liquid anisotropic conductive adhesive;

[0063] S4. Coat the anisotropic conductive adhesive on the substrate and dry it at 55° C. for 8 minutes to obtain an anisotropic conductive adhesive film with a thickness of 25 μm.

[0064] Example 3

[0065] This embodiment provides a low-temperature curing anisotropic conductive adhesive, comprising the following components by weight: 30 parts of long-chain alkyl modified epoxy resin, 20 parts of flexible acrylic resin, 50 parts of bisphenol A type phenoxy resin, 10 parts of pyrazole blocked isocyanate, 5 parts of inorganic filler, 10 parts of conductive particles, 3 parts of initiator, and 1 part of auxiliary agent;

[0066] Among them, the long-chain alkyl-modified epoxy resin is prepared by Preparation Example 3; the flexible acrylic resin is a hydroxy acrylic resin (model MR14896A); the pyrazole blocked isocyanate is 2-[(3,5-dimethyl-1-H-pyrazolyl)carboxyamino]ethyl acrylate; the inorganic filler is nano-silicon dioxide; the conductive particles are nickel-plated polystyrene microspheres with an average particle size of 5 μm; the initiator is diisopropyl peroxydicarbonate; the auxiliary agent is obtained by mixing 2,5-di-tert-butyl-p-benzoquinone and KH550 in a mass ratio of 1:1;

[0067] This embodiment also provides a method for preparing a low-temperature curing anisotropic conductive adhesive, comprising the following steps:

[0068] S1, long-chain alkyl modified epoxy resin, flexible acrylic resin and pyrazole blocked isocyanate are stirred and degassed to uniformly obtain a mixed solution 1;

[0069] S2, stirring and degassing the bisphenol A type phenoxy resin, the inorganic filler, the auxiliary agent and the mixed solution 1 to obtain a mixed solution 2;

[0070] S3, adding conductive particles to the mixed solution 2, vacuum degassing and stirring until uniformly dispersed, then adding an initiator, vacuum degassing and stirring until uniformly dispersed, to obtain a liquid anisotropic conductive adhesive;

[0071] S4. Coat the anisotropic conductive adhesive on the substrate and dry it at 60° C. for 5 minutes to obtain an anisotropic conductive adhesive film with a thickness of 20 μm.

[0072] Comparative Example 1

[0073] This comparative example provides a low-temperature curing anisotropic conductive adhesive, and its raw material components are specifically referred to Example 1. The difference between this comparative example and Example 1 is that the long-chain alkyl-modified epoxy resin is replaced by an equal mass of bisphenol A epoxy resin;

[0074] This comparative example also provides a method for preparing a low-temperature curing anisotropic conductive adhesive. The preparation method is carried out with reference to the preparation method of Example 1, except that an equal mass of bisphenol A epoxy resin is used in step S1 to replace the long-chain alkyl modified epoxy resin.

[0075] Comparative Example 2

[0076] This comparative example provides a low-temperature curing anisotropic conductive adhesive, and its raw material components are specifically referred to Example 1. The only difference between this comparative example and Example 1 is that the long-chain alkyl-modified epoxy resin is prepared by Comparative Preparation Example 1;

[0077] This comparative example also provides a method for preparing a low-temperature curing anisotropic conductive adhesive. The preparation method is carried out with reference to the preparation method of Example 1, except that the long-chain alkyl-modified epoxy resin in step S1 is prepared by Comparative Preparation Example 1.

[0078] Comparative Example 3

[0079] This comparative example provides a low-temperature curing anisotropic conductive adhesive, and its raw material components are specifically referred to Example 1. The only difference between this comparative example and Example 1 is that the long-chain alkyl-modified epoxy resin is prepared by Comparative Preparation Example 2;

[0080] This comparative example also provides a method for preparing a low-temperature curing anisotropic conductive adhesive. The preparation method is carried out with reference to the preparation method of Example 1, except that the long-chain alkyl-modified epoxy resin in step S1 is prepared by Comparative Preparation Example 2.

[0081] Comparative Example 4

[0082] This comparative example provides a low-temperature curing anisotropic conductive adhesive, and its raw material components are specifically referred to Example 1. The only difference between this comparative example and Example 1 is that an equal mass of styrene acrylic resin (rigid acrylic resin) is used to replace the flexible acrylic resin (hydroxy acrylic resin).

[0083] This comparative example also provides a method for preparing a low-temperature curing anisotropic conductive adhesive. The preparation method is carried out with reference to the preparation method of Example 1, except that in step S1, an equal mass of styrene acrylic resin (rigid acrylic resin) is used to replace the flexible acrylic resin (hydroxy acrylic resin).

[0084] Comparative Example 5

[0085] This comparative example provides a low-temperature curing anisotropic conductive adhesive, and its raw material components are specifically referred to Example 1. The only difference between this comparative example and Example 1 is that an equal mass of double-bond-containing isocyanate (ethyl isocyanate acrylate) is used to replace the pyrazole-blocked isocyanate (2-[(3,5-dimethyl-1-H-pyrazolyl)carboxyamino]ethyl acrylate).

[0086] This comparative example also provides a method for preparing a low-temperature curing anisotropic conductive adhesive. The preparation method is carried out with reference to the preparation method of Example 1, except that an equal mass of double-bond-containing isocyanate (ethyl isocyanate acrylate) is used in step S1 to replace the pyrazole-blocked isocyanate (2-[(3,5-dimethyl-1-H-pyrazolyl)carboxyamino]ethyl acrylate).

[0087] Comparative Example 6

[0088] This comparative example provides a low-temperature curing anisotropic conductive adhesive, and its raw material components are specifically referred to Example 1. The only difference between this comparative example and Example 1 is that an equal mass of 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane (0.1 hour half-life temperature is 128° C.) is used to replace the initiator (diisopropyl peroxydicarbonate);

[0089] This comparative example also provides a method for preparing a low-temperature curing anisotropic conductive adhesive. The preparation method is carried out with reference to the preparation method of Example 1, except that an equal mass of 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane (0.1 hour half-life temperature is 128°C) is used in step S3 to replace the initiator (diisopropyl peroxydicarbonate).

[0090] Comparative Example 7

[0091] This comparative example provides a low-temperature curing anisotropic conductive adhesive, and its raw material components are specifically referred to Example 1. The only difference between this comparative example and Example 1 is that the addition amount of the long-chain alkyl modified epoxy resin is 10 parts, and the addition amount of the flexible acrylic resin is 30 parts;

[0092] This comparative example also provides a method for preparing a low-temperature curing anisotropic conductive adhesive, and the preparation method is carried out with reference to the preparation method of Example 1.

[0093] Comparative Example 8

[0094] This comparative example provides a low-temperature curing anisotropic conductive adhesive, and its raw material components are specifically referred to Example 1. The difference between this comparative example and Example 1 is that the addition amount of the long-chain alkyl modified epoxy resin is 30 parts, and the addition amount of the flexible acrylic resin is 10 parts;

[0095] This comparative example also provides a method for preparing a low-temperature curing anisotropic conductive adhesive, and the preparation method is carried out with reference to the preparation method of Example 1.

[0096] Performance Testing

[0097] The performance tests were conducted on the low temperature curing anisotropic conductive adhesives prepared in Examples 1-3 and Comparative Examples 1-8. The relevant test items are as follows, and the relevant test results are shown in Tables 1 and 2.

[0098] Physical property evaluation of anisotropic conductive film: The anisotropic conductive film stored at 2°C for 60 days was placed at room temperature.

[0099] After 30 minutes of warming at 25℃, the anisotropic conductive film sample was connected to the printed circuit board and FPC under the initial pressing conditions (65℃, 1 second, 1.0MPa) and the final pressing conditions (150℃, 5 seconds, 3.5MPa). The bonding strength test was carried out at 90°, 1cm width, and 50mm / min stretching speed. The individual adjacent electrodes on the TFT were designed to be U-shaped and bonded to the electrodes on the FPC, and the test lines were led out. The connection resistance was measured by the diode method, the FPC was torn off, the residual glue outside the bonding area was removed, the glue after bonding was scraped, the DSC was tested and compared with that before bonding, and the reaction rate was calculated.

[0100] Based on the product characteristics of the anisotropic conductive adhesive film and the product usage environment, the anisotropic conductive adhesive film prepared in the above embodiment was subjected to a high temperature and high humidity (85°C, 85RH%, 250H) test and a cooking (100°C, 4H) test;

[0101] Table 1 Test results of reliability of adhesive films obtained from Examples 1-3 and Comparative Examples 1-8

[0102]

[0103] Note: “—” indicates that after the reliability test, interface peeling occurred between the adhesive layer and the substrate, and the performance could not be tested.

[0104] Table 2 Test results of the reaction rate of the adhesive films obtained in Examples 1-3 and Comparative Examples 1-8 (bonding condition: 3.5 MPa / 5s)

[0105]

[0106]

[0107] From the test results in Table 1, it can be seen that by comparing Example 1 with Comparative Example 1, the use of long-chain alkyl-modified epoxy resin can improve the high temperature and high humidity resistance of the anisotropic conductive adhesive; by comparing Example 1 with Comparative Examples 2 and 3, it can be seen that by selecting an alkyl alcohol that is too long or too short, the obtained long-chain alkyl-modified epoxy resin is not conducive to forming an excellent flexible network structure with other components, so that the high temperature and high humidity resistance of the anisotropic conductive adhesive film cannot be well improved; by comparing Example 1 with Comparative Example 4, it can be seen that the use of flexible acrylic resin can improve the high temperature and high humidity resistance of the anisotropic conductive adhesive. The bonding strength and high temperature and high humidity resistance of the anisotropic conductive adhesive are improved; by comparing Example 1 with Comparative Example 5 and Comparative Example 6, it can be seen that the use of a blocked isocyanate containing a double bond and an initiator with a half-life temperature of 90-105°C for 0.1 hours can improve the reaction rate of the anisotropic conductive adhesive and maintain good conductivity under high temperature and high humidity conditions; by comparing Example 1 with Comparative Example 7 and Comparative Example 8, it can be seen that the long-chain alkyl-modified epoxy resin and the flexible acrylate are mixed in a specific mass ratio, and the synergistic effect is enhanced, which helps to improve the high temperature and high humidity resistance of the anisotropic conductive adhesive film.

[0108] Based on the data in Table 1 and Table 2, the anisotropic conductive adhesive film of the present invention is blended with a long-chain alkyl modified epoxy resin and a flexible acrylic resin in a specific ratio, which can reduce the shrinkage rate of the adhesive film and reduce the internal stress. At the same time, the flexible acrylic resin can improve the toughness of the adhesive layer and improve the adhesion performance. After high temperature and high humidity treatment, it still has a high bonding strength. In the anisotropic conductive adhesive film of the present invention, a blocked isocyanate containing a double bond and an initiator with a 0.1 hour half-life temperature of 90-105°C are used, which can be cured at low temperature and maintain a high reaction rate.

[0109] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0110] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A low temperature curing anisotropic conductive adhesive, characterized in that: The invention comprises the following components in parts by weight: 15-40 parts of long-chain alkyl modified epoxy resin, 20-40 parts of flexible acrylic resin, 30-50 parts of film-forming resin, 5-20 parts of free radical polymer, 5-20 parts of inorganic filler, 1-10 parts of conductive particles, 1-5 parts of initiator, and 1-10 parts of auxiliary agent; The mass ratio of the long-chain alkyl modified epoxy resin to the flexible acrylic resin is (0.5-1.5):

1.

2. The low temperature curing anisotropic conductive adhesive according to claim 1, characterized in that: The preparation method of the long-chain alkyl modified epoxy resin comprises the following steps: Preheat the bisphenol A epoxy resin at 60-70°C, mix it evenly with anhydrous long-chain alkanol, add tertiary amine, raise the temperature to 120-140°C under stirring, react for 6-8h to obtain a crude product, extract and purify the crude product, and dry it under reduced pressure to obtain a long-chain alkyl modified epoxy resin.

3. The low temperature curing anisotropic conductive adhesive according to claim 2, characterized in that: The long-chain alkanol is a C10-C18 normal alkanol.

4. The low temperature curing anisotropic conductive adhesive according to claim 2, characterized in that: The mass ratio of the bisphenol A epoxy resin, the long-chain alkanol and the tertiary amine is (50-70):(80-100):(1-5).

5. The low temperature curing anisotropic conductive adhesive according to claim 1, characterized in that: The flexible acrylic resin is one or more of butyl acrylate copolymer, isooctyl acrylate copolymer, and hydroxy acrylic resin; The film-forming resin is bisphenol A type phenoxy resin and / or bisphenol F type phenoxy resin; The free radical polymer is a blocked isocyanate containing a double bond; The inorganic filler is one or more of nano silicon dioxide, nano titanium oxide, nano magnesium oxide, talc, and calcium carbonate; The initiator is a thermal initiator; The auxiliary agent is one or more of an inhibitor, a toughening agent, a plasticizer, and a silane coupling agent.

6. The low temperature curing anisotropic conductive adhesive according to claim 5, characterized in that: The blocked isocyanate containing a double bond is one or more of methyl ethyl ketone oxime blocked isocyanate, pyrazole blocked isocyanate and maleimide blocked isocyanate.

7. The low temperature curing anisotropic conductive adhesive according to claim 5, characterized in that: The thermal initiator includes a peroxide having a 0.1 hour half-life temperature of 90-105°C.

8. The low temperature curing anisotropic conductive adhesive according to claim 7, characterized in that: The peroxide is one or more of diisopropyl peroxydicarbonate, cumyl peroxyneodecanoate, and tert-butyl peroxypivalate.

9. The low temperature curing anisotropic conductive adhesive according to claim 5, characterized in that: The polymerization inhibitor is one or more of phenol polymerization inhibitors, quinone polymerization inhibitors, nitro compound polymerization inhibitors, aromatic amine polymerization inhibitors, and sulfur-containing compound polymerization inhibitors.

10. A method for preparing the low temperature curing anisotropic conductive adhesive according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. According to the formula, long-chain alkyl modified epoxy resin, flexible acrylic resin and free radical polymer are stirred, degassed and mixed to obtain a mixed solution 1; S2, stirring and degassing the film-forming resin, the inorganic filler, the auxiliary agent and the mixed solution 1 to obtain a mixed solution 2; S3, adding conductive particles to the mixed solution 2, vacuum degassing and stirring until uniformly dispersed, then adding an initiator, vacuum degassing and stirring until uniformly dispersed, to obtain a liquid anisotropic conductive adhesive; S4. Coat the anisotropic conductive adhesive on the substrate and dry it at 50-60° C. for 5-10 min to obtain an anisotropic conductive adhesive film with a thickness of 20-30 μm.

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