CN116640529A

CN116640529A - Preparation method of anisotropic conductive adhesive film and anisotropic conductive adhesive film

Info

Publication number: CN116640529A
Application number: CN202310709182.9A
Authority: CN
Inventors: 胡友根; 陆喜; 梁嘉俊; 许亚东; 王勇; 刘学斌; 李健辉; 龙浩晖; 孙蓉
Original assignee: Huawei Technologies Co Ltd; Shenzhen Institute of Advanced Electronic Materials
Current assignee: Huawei Technologies Co Ltd; Shenzhen Institute of Advanced Electronic Materials
Priority date: 2023-06-14
Filing date: 2023-06-14
Publication date: 2023-08-25

Abstract

According to the preparation method of the anisotropic conductive adhesive film and the anisotropic conductive adhesive film, the array-distributed conductive microspheres are obtained through the preparation route of the micropore template, the obtained array-distributed conductive microspheres are transferred to the first layer of photo-thermal dual-cured resin adhesive film, the second layer of resin adhesive film is covered on the first layer of resin adhesive film, ultraviolet light pre-curing treatment is carried out on the first layer of resin adhesive film, the pre-curing ensures that the array form of the conductive microspheres is primarily fixed in the resin adhesive film, and the particle array type anisotropic conductive adhesive film is obtained. The use of thermal curing further ensures that the adhesive film obtains good adhesive strength and conductive performance in the bonding process, and compared with the anisotropic conductive adhesive film of a single curing agent system, the obtained particle array type anisotropic conductive adhesive film shows better particle array arrangement, conductive performance and adhesive strength when being applied to bonding electrode assemblies.

Description

Preparation method of anisotropic conductive adhesive film and anisotropic conductive adhesive film

Technical Field

The application relates to the technical field of new materials, in particular to a preparation method of an anisotropic conductive adhesive film and the anisotropic conductive adhesive film.

Background

The anisotropic conductive adhesive film (Anisotropic conductive film, ACF) is widely used for connection of circuit boards in devices such as display panels and camera modules, and has the most remarkable characteristics of conducting circuits in the vertical direction and insulating circuits in the horizontal direction, and has a gluing and fixing function. The main components of the ACF adhesive film are insulating resin and conductive particles. According to the distribution characteristics of conductive particles in the resin, the ACF film can be classified into a particle random distribution type and a particle array type. The conductive particles of the traditional ACF adhesive film are randomly distributed, and the traditional ACF adhesive film can be easily realized through processes such as mixing, coating and the like. The particle array type ACF adhesive film has more advantages in bonding requirements for the ultra-fine pitch electrodes, and can effectively reduce the risk of short circuit. However, the preparation process of the particle array ACF needs to realize the array distribution of the particles in a microscopic scale, and the array morphology of the particles needs to remain basically unchanged in the adhesive film preparation and bonding process, so that great challenges exist in the preparation process and resin formulation selection.

The ACF adhesive film is generally made of epoxy resin or acrylic resin, and a single heat curing system is generally adopted. Epoxy resins provide high bond strength and can withstand long-term reliability testing and are widely used. However, epoxy resins generally have a relatively high hot-pressing temperature (180-250 ℃) and a relatively long hot-pressing time (5-10 seconds), and cause a large thermal stress to the thermally crimped electrode. The acrylic resin solution can solve this problem well, for example, JP2010037539A (Japanese DiRui electronic materials Co., ltd.) uses acrylic compound to prepare ACF adhesive film, and can realize good bonding strength and conduction reliability under the condition of thermal compression bonding at 130 ℃ for 3 s. In addition, the acrylic resin system can be compatible with the photo-curing mode.

In recent years, resin formulations of dual cure systems have been studied to further optimize ACF films, as compared to conventional single cure systems. For example, patent CN111100562a of shenzhen, sambac, inc, adopts sectional heat curing and magnetic curing to prepare dual-curing ACF adhesive film, mainly for solving the problems of reliability of electrode connection and difficult repair. Patent CN102634286B of Shenzhen Feishier Utility Co., ltd. Adopts photo-thermal dual curing technology to prepare ACF adhesive film, wherein the purpose of photo-curing is to avoid using solvent and protect environment. Patent CN104673113a of the university of east China proposes a photo-thermal dual curing ACF adhesive film, which solves the problems that the curing is incomplete by singly adopting a photo-curing mode, the curing temperature is high and the curing time is long by singly adopting a thermal curing mode. However, the above dual curing resins are used for conventional ACF adhesive films in which particles are randomly distributed. The advantage of dual curing is expected to solve the preparation difficulty of the particle array ACF adhesive film.

Disclosure of Invention

In view of this, it is necessary to provide an anisotropic conductive film having more excellent particle array arrangement, conductivity and adhesive strength, and a method for preparing the same, aiming at the defects existing in the prior art.

In order to solve the problems, the application adopts the following technical scheme:

the application provides a preparation method of an anisotropic conductive adhesive film, which comprises the following steps:

obtaining conductive microspheres distributed in an array;

obtaining a first layer of resin adhesive film with conductive microspheres distributed in an array;

laminating a second resin adhesive film on the first resin adhesive film;

and performing pre-curing treatment on the first layer of resin adhesive film to obtain the anisotropic conductive adhesive film.

In some embodiments, the step of obtaining the conductive microspheres distributed in the array specifically includes the steps of:

preparing a micropore array template;

modifying the surface of the micropore array template by using a fluorine-containing organic surface modifier to obtain a micropore array template with low surface energy;

and filling the conductive microspheres into each micropore of the micropore array template with low surface energy to obtain the conductive microspheres distributed in an array.

In some of these embodiments, the step of preparing the microwell array template specifically comprises the steps of:

preparing the micropore array template by photoetching or laser etching or soft photoetching or screen printing or electron beam lithography, wherein: the substrate used in the preparation of the micropore array template is a pure silicon substrate or a metal substrate or a ceramic substrate or an organic substrate, the substrate is in a flat plate shape or a roller shape which can be used for continuous preparation, the micropore aperture D1 of the micropore array template is 150 nm-150 mu m, and the pore depth H is 50 nm-150 mu m.

In some embodiments, in the step of modifying the surface of the microwell array template with a fluorine-containing organic surface modifier, the fluorine-containing organic surface modifier is a perfluorosilane or a perfluoropolyether alcohol or a perfluoropolyester or an anti-fingerprint liquid, the modification comprises dip coating, spray coating, or knife coating.

In some embodiments, in the step of filling conductive microspheres into each microwell of the microwell array template with low surface energy to obtain the array distribution of conductive microspheres, the conductive microspheres comprise pure metal microspheres or carbon material microspheres or organic microspheres, and the filling method of the conductive microspheres comprises knife coating or spraying or solution self-assembly.

In some of these embodiments, the conductive microspheres have a particle size D2 of 100nm to 100 μm and D2 < D1,0.5H < D2 < 1.5H.

In some embodiments, the step of obtaining the first layer of resin film with the conductive microspheres distributed in the array specifically includes the following steps:

coating acrylic resin on the release film to obtain an acrylic resin adhesive film;

and coating the acrylic resin adhesive film on the micropore array template, and transferring the conductive microspheres to the acrylic resin adhesive film by stripping the adhesive film to obtain a first layer of resin adhesive film with the conductive microspheres distributed in an array.

In some embodiments, the acrylic resin comprises 0.5-20 parts by weight of photoinitiator, 0.5-20 parts by weight of thermal initiator and 5-200 parts by weight of acrylate; wherein:

the photoinitiator comprises one or more of alkylbenzene ketone, benzil, acyl phosphorus oxide, benzoin and derivatives, benzil, benzophenone, thioxanthone, aryl iodonium salt, alkyl iodonium salt and isopropylbenzene ferrocene hexafluorophosphate;

the thermal initiator comprises one or more of persulfates, hydroperoxides, di-tertiary alkyl peroxides, acyl peroxides, carboxylic acid peroxides, dicarbonates peroxides, azocyano groups, azonitro groups, azoester groups and azohydroxy groups;

the acrylic resin comprises one or more of epoxy acrylate, phosphate ester type acrylate, polyester acrylate, polyurethane acrylate, polyether acrylate, mono-functional acrylate, bi-functional acrylate, tri-functional acrylate and multi-functional acrylate;

in some embodiments, the thickness of the first resin film is 500 nm-20 μm.

In some embodiments, the step of laminating a second resin adhesive film onto the first resin adhesive film specifically includes the steps of:

and coating a second layer of resin adhesive film on the first layer of resin adhesive film, and stripping off the release film on one side of the first layer of resin adhesive film.

In some embodiments, the second resin film is prepared by the following method: and coating a resin adhesive film on the release film to obtain the second layer of resin adhesive film.

In some embodiments, the release force of the release film on the side of the first resin film is smaller than the release force of the release film on the side of the second resin film.

In some embodiments, the thickness of the second resin film is 1 μm to 100 μm.

In some of these embodiments, the second layer of resin film comprises a thermosetting resin comprising an epoxy resin or an acrylic resin; wherein:

the epoxy resin comprises one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol type glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, epoxy olefin compound or heterocyclic type and mixed type epoxy resin; the thermosetting agent of the epoxy resin comprises a conventional curing agent or a latent curing agent, wherein the conventional curing agent comprises one or more of imidazole compounds, boron trifluoride complexes, organic acid anhydrides, polyamides, tertiary amines, aliphatic polyamines, alicyclic polyamines, aromatic polyamines or modified substances thereof, the latent curing agent comprises one or more of dicyandiamide, microcapsule imidazole, boron trifluoride amine or modified amines, the epoxy resin is 5-200 parts by weight, and the thermosetting agent of the epoxy resin is 0.5-20 parts by weight;

the acrylic resin comprises one or more of epoxy acrylate, phosphate ester type acrylate, polyester acrylate, polyurethane acrylate, polyether acrylate, mono-functional acrylate, bi-functional acrylate, tri-functional acrylate and multi-functional acrylate; the thermosetting agent of the acrylic resin comprises one or a mixture of more of organic peroxide, inorganic peroxide or azo compound, wherein the mass part of the acrylic resin is 5-200 parts, and the mass part of the thermosetting agent of the acrylic resin is 0.5-20 parts.

In some embodiments, the step of pre-curing the first layer of resin film to obtain the anisotropic conductive film specifically includes the following steps:

and irradiating the second resin adhesive film by ultraviolet light, and pre-curing the first resin adhesive film to obtain the required particle array type anisotropic conductive adhesive film.

In some embodiments, the ultraviolet light has an intensity of 0.1 to 50mW cm ^-2 The curing time is 1 s-10 min.

The second object of the application is to provide an anisotropic conductive film prepared by the preparation method of the anisotropic conductive film.

By adopting the technical scheme, the application has the following beneficial effects:

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly explain the embodiments of the present application or the drawings used in the description of the prior art, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1a is a flowchart illustrating steps of a method for preparing an anisotropic conductive film according to an embodiment of the present application;

fig. 1b is a schematic diagram of an anisotropic conductive film according to an embodiment of the present application;

FIG. 2 is an optical micrograph of a microwell array template according to an embodiment of the present application;

FIG. 3 is a three-dimensional confocal laser micrograph of a microwell array template according to an embodiment of the present application;

FIG. 4 shows contact angles before and after surface modification of a silicon wafer according to an embodiment of the present application;

FIG. 5 is an optical micrograph of conductive microspheres filled in a microwell array template according to an embodiment of the present application;

FIG. 6 is a three-dimensional confocal laser micrograph of conductive microspheres filled in a microporous array template according to an embodiment of the present application;

FIG. 7 is a scanning electron micrograph of conductive microspheres according to an embodiment of the present application transferred to a first resin film at an angle of 45 degrees;

FIG. 8 is an optical micrograph of a particle array type anisotropic conductive film according to an embodiment of the present application;

FIG. 9 shows thermal analysis curves (DSC) and cure rates of acrylic resins provided in examples of the present application before and after photo and thermal curing;

FIG. 10 shows a photo-thermal dual-cured particle array type anisotropic conductive film (experimental set) for bonding LCD modules and illuminating a screen (red wire frame is bonding region) according to an embodiment of the present application

FIG. 11 is an optical micrograph of a photo-thermal dual-cured particle array type anisotropic conductive film (experimental group) bonded with FPC and ITO according to an embodiment of the present application;

FIG. 12 is an optical micrograph of an ACF film (control A) bonded with FPC and ITO with a single thermosetting agent according to an embodiment of the present application;

FIG. 13 is an optical micrograph of an ACF film (control B) bonded with FPC and ITO with a single photo-curing agent according to an embodiment of the present application;

FIG. 14 shows the resistance values of the ITO and FPC bonded by the ACF of the experimental and control groups provided in the present application;

fig. 15 is a graph showing peel force test curves and peel strengths of the anisotropic conductive film bonding FPCs and ITO of the experimental and control groups provided in the embodiment of the present application.

Detailed Description

Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present application and should not be construed as limiting the application.

In the description of the present application, it should be understood that the directions or positional relationships indicated by the terms "upper", "lower", "horizontal", "inner", "outer", etc., are based on the directions or positional relationships shown in the drawings, are merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent.

Referring to fig. 1a and fig. 1b, a step flowchart of a method for preparing an anisotropic conductive film according to the present embodiment specifically includes the following steps S110 to S140, and detailed descriptions of specific implementation manners of the steps are described below.

Step S110: obtaining the conductive microspheres distributed in an array.

In this embodiment, in the step of obtaining the conductive microspheres distributed in the array, the following steps S111 to S113 are specifically included, and the implementation manner of each step is described in detail below.

Step S111: and preparing a micropore array template.

In this embodiment, the step of preparing the microwell array template specifically includes the following steps: preparing the micropore array template by photoetching or laser etching or soft photoetching or screen printing or electron beam lithography, wherein: the substrate used in the preparation of the micropore array template is a pure silicon substrate or a metal substrate or a ceramic substrate or an organic substrate, the substrate is in a flat plate shape or a roller shape which can be used for continuous preparation, the micropore aperture D1 of the micropore array template is 150 nm-150 mu m, and the pore depth H is 50 nm-150 mu m.

In some specific embodiments, the microwell array is obtained using industry standard photolithographic processes using planar monocrystalline silicon as a template substrate. The micropore array is hexagonal periodic pattern, the pore diameter of the micropore is 4 μm, and the pore depth is 4 μm.

Step S112: and modifying the surface of the micropore array template by using a fluorine-containing organic surface modifier to obtain the micropore array template with low surface energy.

In this embodiment, the fluorine-containing organic surface modifier is a perfluorosilane or a perfluoropolyether alcohol or a perfluoropolyester or an anti-fingerprint liquid, and the modification includes dip coating, spray coating, or knife coating.

In some specific embodiments, the modifier used is commercial anti-fingerprint liquid, model H005 (Shenzhen Hongzhi Co., ltd.) and dip coating is used as the surface modification method.

Step S113: and filling the conductive microspheres into each micropore of the micropore array template with low surface energy to obtain the conductive microspheres distributed in an array.

In this embodiment, the conductive microsphere includes a pure metal microsphere, a carbon material microsphere or an organic microsphere, and the filling method of the conductive microsphere includes knife coating, spraying or solution self-assembly.

Further, the particle diameter D2 of the conductive microsphere is 100 nm-100 μm, D2 is less than D1,0.5H is less than D2 and less than 1.5H, so as to ensure that the microsphere can be filled into the micropores and can be transferred to the first layer of resin adhesive film from the micropores.

In some specific embodiments, the conductive microspheres are organic gold-plated microspheres with a particle size of about 3 μm, and the microspheres are filled into the microporous template by knife coating.

Step S120: a first layer of resin adhesive film with conductive microspheres distributed in an array is obtained.

In some embodiments, in the step of obtaining the first resin film layer with the conductive microspheres distributed in the array, the following steps S121 to S122 are specifically included, and the implementation manner of each step is described in detail below.

Step S121: and coating the acrylic resin on the release film to obtain the acrylic resin adhesive film.

In some embodiments, the acrylic resin comprises 0.5-20 parts by weight of photoinitiator, 0.5-20 parts by weight of thermal initiator and 5-200 parts by weight of acrylate; wherein: the photoinitiator comprises one or more of alkylbenzene ketone, benzil, acyl phosphorus oxide, benzoin and derivatives, benzil, benzophenone, thioxanthone, aryl iodonium salt, alkyl iodonium salt and isopropylbenzene ferrocene hexafluorophosphate; the thermal initiator comprises one or more of persulfates, hydroperoxides, di-tertiary alkyl peroxides, acyl peroxides, carboxylic acid peroxides, dicarbonates peroxides, azocyano groups, azonitro groups, azoester groups and azohydroxy groups; the acrylic resin comprises one or more of epoxy acrylate, phosphate acrylate, polyester acrylate, polyurethane acrylate, polyether acrylate, mono-functional acrylate, bi-functional acrylate, tri-functional acrylate and multi-functional acrylate.

Step S122: and coating the acrylic resin adhesive film on the micropore array template, and transferring the conductive microspheres to the acrylic resin adhesive film by stripping the adhesive film to obtain a first layer of resin adhesive film with the conductive microspheres distributed in an array.

In some embodiments, the thickness of the first resin film is 500 nm-20 μm.

Step S130: and coating a second layer of resin adhesive film on the first layer of resin adhesive film. In some embodiments, the step of laminating a second resin adhesive film onto the first resin adhesive film specifically includes the steps of: and coating a second layer of resin adhesive film on the first layer of resin adhesive film, and stripping off the release film on one side of the first layer of resin adhesive film.

Specifically, the second layer of resin adhesive film is prepared by the following method: and coating a resin adhesive film on the release film to obtain the second layer of resin adhesive film. The thickness of the second layer of resin adhesive film is 1-100 mu m.

Further, the release force of the release film on one side of the first resin adhesive film is smaller than that of the release film on one side of the second resin adhesive film.

In some specific embodiments, the release force of the release film on the side of the first resin adhesive film is 5-10 g, and the release force of the release film on the side of the second resin adhesive film is 15-20 g.

In some of these embodiments, the second layer of resin film comprises a thermosetting resin comprising an epoxy resin or an acrylic resin; wherein: the epoxy resin comprises one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol type glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, epoxy olefin compound or heterocyclic type and mixed type epoxy resin; the thermosetting agent of the epoxy resin comprises a conventional curing agent or a latent curing agent, wherein the conventional curing agent comprises one or more of imidazole compounds, boron trifluoride complexes, organic acid anhydrides, polyamides, tertiary amines, aliphatic polyamines, alicyclic polyamines, aromatic polyamines or modified substances thereof, the latent curing agent comprises one or more of dicyandiamide, microcapsule imidazole, boron trifluoride amine or modified amines, the epoxy resin is 5-200 parts by weight, and the thermosetting agent of the epoxy resin is 0.5-20 parts by weight; the acrylic resin comprises one or more of epoxy acrylate, phosphate ester type acrylate, polyester acrylate, polyurethane acrylate, polyether acrylate, mono-functional acrylate, bi-functional acrylate, tri-functional acrylate and multi-functional acrylate; the thermosetting agent of the acrylic resin comprises one or more of persulfates, hydroperoxides, di-tertiary alkyl peroxides, acyl peroxides, peroxycarboxylic acid esters, peroxydicarbonates, azocyano groups, azonitro groups, azoester groups and azohydroxyl groups, wherein the mass portion of the acrylic resin is 5-200 portions, and the mass portion of the thermosetting agent of the acrylic resin is 0.5-20 portions.

Step S140: and performing pre-curing treatment on the first layer of resin adhesive film to obtain the anisotropic conductive adhesive film.

In some embodiments, the step of pre-curing the first layer of resin film to obtain the anisotropic conductive film specifically includes the following steps: and irradiating the second resin adhesive film by ultraviolet light, and pre-curing the first resin adhesive film to obtain the required particle array type anisotropic conductive adhesive film.

Further, the ultraviolet light intensity is 0.1-50 mW cm ^-2 The curing time is 1 s-10 min.

According to the preparation method of the anisotropic conductive adhesive film and the anisotropic conductive adhesive film, provided by the application, the conductive microspheres distributed in an array are obtained, the first layer of resin adhesive film with the conductive microspheres distributed in an array is obtained, the second layer of resin adhesive film is arranged on the first layer of resin adhesive film, the first layer of resin adhesive film is subjected to pre-curing treatment, the anisotropic conductive adhesive film is obtained, the array form of the conductive microspheres is ensured to be primarily fixed in the resin adhesive film through pre-curing, the good bonding strength and the good conductive performance of the adhesive film are further ensured in the bonding process through thermal curing, and compared with the anisotropic conductive adhesive film of a single curing agent system, the obtained particle array anisotropic conductive adhesive film shows better particle array arrangement, conductive performance and bonding strength when being applied to bonding electrode assemblies.

The above technical scheme of the present application will be described in detail with reference to specific embodiments.

TABLE 1 resin component of ACF and parts by mass

Example 1

The present example is an experimental group, i.e., a particle array ACF film prepared based on photo-thermal dual cure acrylic resin.

And (3) using the planar monocrystalline silicon as a template substrate, and adopting the industry standard photoetching and etching process to obtain the micropore array. The shape of the micropore array is a hexagonal periodic pattern, the pore diameter of the micropores is 4 μm, and the pore depth is 4 μm, as shown in fig. 2 and 3. The microporous template is dip-coated with an anti-fingerprint liquid (model H005, shenzhen Hongzhen Co., ltd.) and subjected to surface modification to obtain a silicon-based template with a superhydrophobic surface (FIG. 4). The microspheres were then filled into the microporous template by knife coating (fig. 5 and 6). A first layer of acrylic resin film containing both light and heat curing agents was prepared according to the formulation of example 1 of table 1. The adhesive film was covered on the surface of the microporous template, and the array of conductive microspheres was transferred to the first layer of acrylic adhesive film (fig. 7). An epoxy adhesive film was prepared according to the second resin adhesive film formulation of example 1 of table 1, and then coated onto the first resin adhesive film. Finally, pre-curing the acrylic resin adhesive film by using ultraviolet light, wherein the ultraviolet light intensity is 20mW cm < -2 >, and the curing time is 30-60 s. A final particle array ACF film prepared based on photo-thermal dual cure acrylic resin was obtained (fig. 8).

Example 2

This example is control group a, an ACF film prepared based on a single thermally cured acrylic resin.

And (3) using the planar monocrystalline silicon as a template substrate, and adopting the industry standard photoetching and etching process to obtain the micropore array. The micropore array is hexagonal periodic pattern, the pore diameter of the micropore is 4 μm, and the pore depth is 4 μm. The microporous template is dip-coated by adopting anti-fingerprint liquid (model H005, shenzhen Hongzhen Co., ltd.) and subjected to surface modification to obtain the silicon-based template with the superhydrophobic surface. The microspheres are then filled into the microporous template by knife coating. A first layer of acrylic resin film was formulated according to the formulation of example 2 of table 1, and contained a single thermosetting agent. Covering the adhesive film on the surface of the microporous template, and transferring the conductive microspheres arranged in an array to the first layer of acrylic resin adhesive film. An epoxy adhesive film was prepared according to the second resin adhesive film formulation of example 2 of table 1, and then coated onto the first resin adhesive film. An ACF film prepared based on a single thermally cured acrylic resin was obtained.

Example 3

This example is control group B, an ACF adhesive film prepared based on a single photo-cured acrylic resin.

And (3) using the planar monocrystalline silicon as a template substrate, and adopting the industry standard photoetching and etching process to obtain the micropore array. The micropore array is hexagonal periodic pattern, the pore diameter of the micropore is 4 μm, and the pore depth is 4 μm. The microporous template is dip-coated by adopting anti-fingerprint liquid (model H005, shenzhen Hongzhen Co., ltd.) and subjected to surface modification to obtain the silicon-based template with the superhydrophobic surface. The microspheres are then filled into the microporous template by knife coating. A first layer of acrylic resin film was prepared according to the formulation of example 3 of table 1, which contained a single photo-curing agent. Covering the adhesive film on the surface of the microporous template, and transferring the conductive microspheres arranged in an array to the first layer of acrylic resin adhesive film. An epoxy adhesive film was prepared according to the second resin adhesive film formulation of example 3 of table 1, and then coated onto the first resin adhesive film. Finally, pre-curing the acrylic resin adhesive film by using ultraviolet light, wherein the ultraviolet light intensity is 20mW cm < -2 >, and the curing time is 30-60 s. An ACF film prepared based on a single photo-cured acrylic resin was obtained.

Example 4

Using a metal substrate as a template substrate, an industry standard screen printing was used to obtain a microwell array. The micropore array is in a triangular periodic pattern, the pore diameter of the micropores is 150nm, and the pore depth is 50nm. And dip-coating the microporous template by using perfluorinated silane, and carrying out surface modification on the microporous template to obtain the silicon-based template with the superhydrophobic surface. The microspheres are then filled into the microporous template by spraying.

Preparing acrylic resin from 0.5 part by mass of alkyl benzene ketone, 0.5 part by mass of organic peroxide and 5 parts by mass of epoxy acrylate; covering the surface of the micropore template with a glue film, and transferring the conductive microspheres arranged in an array to an acrylic resin glue film to obtain a first resin glue film; preparing a second layer of resin adhesive film from 5 parts by weight of bisphenol A epoxy resin and 0.5 part by weight of imidazole compound, and then coating the second layer of resin adhesive film onto the first layer of resin adhesive film. Finally, pre-curing the acrylic resin adhesive film by using ultraviolet light with the intensity of 50mW cm ^-2 Curing time of 1sParticle array type anisotropic conductive adhesive film based on photo-thermal dual curing.

Example 5

The ceramic substrate is used as a template substrate, and the micropore array is prepared by adopting electron beam lithography of industry standard. The micropore array is in a triangular periodic pattern, the pore diameter of the micropores is 150 mu m, and the pore depth is 150 mu m. And spraying the microporous template with perfluoropolyether, and carrying out surface modification on the microporous template to obtain the silica-based template with the superhydrophobic surface. Then, the microspheres are filled into the microporous template by adopting a solution self-assembly mode.

Preparing acrylic resin from 20 parts by weight of benzil, 20 parts by weight of inorganic peroxide and 200 parts by weight of phosphate type acrylic ester; covering the surface of the micropore template with a glue film, and transferring the conductive microspheres arranged in an array to an acrylic resin glue film to obtain a first resin glue film; preparing a second layer of resin adhesive film from 200 parts by weight of bisphenol F type epoxy resin and 20 parts by weight of dicyandiamide, and then coating the second layer of resin adhesive film onto the first layer of resin adhesive film. Finally, pre-curing the acrylic resin adhesive film by using ultraviolet light with the intensity of 0.1mW cm ^-2 The curing time is 10min, and the particle array type anisotropic conductive adhesive film based on photo-thermal dual curing is used.

Example 6

Using an organic substrate as a template substrate, and adopting electron beam lithography of industry standard to prepare and obtain the micropore array. The shape of the micropore array is a square periodic pattern, the pore diameter of the micropores is 100 mu m, and the pore depth is 100 mu m. And spraying the microporous template with perfluoropolyether alcohol, and carrying out surface modification on the microporous template to obtain the silicon-based template with the superhydrophobic surface. Then, the microspheres are filled into the microporous template by adopting a solution self-assembly mode.

Preparing acrylic resin from 10 parts by weight of acyl phosphorus oxide, 10 parts by weight of azo compound and 100 parts by weight of polyester acrylate; covering the surface of the micropore template with a glue film, and transferring the conductive microspheres arranged in an array to an acrylic resin glue film to obtain a first resin glue film; 100 parts by weight of polyphenol type glycidyl ether epoxy resin,The microcapsule imidazole with the mass portion of 10 portions is prepared into a second layer of resin adhesive film, and then the second layer of resin adhesive film is covered on the first layer of resin adhesive film. Finally, pre-curing the acrylic resin adhesive film by using ultraviolet light with the intensity of 10mW cm ^-2 The curing time is 5min, and the particle array type anisotropic conductive adhesive film based on photo-thermal dual curing is used.

Effect evaluation of examples

Example 1 (experimental group) is a particle array ACF film prepared based on a photo-thermal dual cure acrylic resin. The light and heat dual-curing acrylic resin can realize the step-by-step curing of acrylic acid, and the ultraviolet light pre-curing can preliminarily fix the conductive particles distributed in an array on the resin adhesive film, so that the array distribution of the particles is prevented from being damaged due to the melting and flowing of the resin adhesive film in the subsequent hot-pressing process. As shown in fig. 9, the stepwise curing of the photo-thermal dual-cured acrylic resin was analyzed using DSC. From the data of the curing absorption enthalpy change and the curing rate, the acrylic resin of the formula is cured to different degrees after ultraviolet irradiation and after heating.

The ACF film prepared in the embodiment is actually applied to bonding of an LCD module, as shown in fig. 10, an LCD screen can be normally lightened, which indicates that the prepared ACF film has good conductive performance and adhesive performance.

The morphology of the ACF film bonded FPC and the ITO electrode was observed, as shown in fig. 11, and example 1 (experimental group) after thermocompression bonding, the array morphology of the particles remained due to the pre-curing effect of uv irradiation, and the convex marks of the particles on the ITO were observed, indicating that the thermal curing process provided better adhesion. As shown in fig. 12 (comparative group a), in example 2, an ACF film prepared based on a single thermosetting acrylic resin, since the array type conductive particles were not pre-cured, the array morphology of the ordered particles was destroyed, i.e., the particles were randomly distributed, although the thermosetting could provide a good bonding effect (particle protrusion) after thermocompression bonding, and the ACF film was not a particle array type ACF film. As shown in fig. 13, example 3 (control B), an ACF film prepared based on a single photo-cured acrylic resin, pre-curing with uv light can help the array particles to maintain the array morphology after thermocompression bonding, but no significant particle protruding mark was observed.

As shown in fig. 14 and 15, the resistance and peel strength after bonding of the ACF film of the embodiment were tested. The resistance measurement was performed by a four-probe method (shown in the inset in fig. 14). The resistances of example 1 (experimental group) and example 2 (control group a) were 1.5 to 2.0Ω, and the resistance of example 3 (control group B) was about 3Ω. The peel strength of example 1 (experimental group) was about 9N/cm, while the peel strength of example 2 (control group A) and example 3 (control group B) was about 4N/cm. It can be seen that the particle array type ACF adhesive film prepared based on the photo-thermal dual curing acrylic resin prepared in example 1 (experimental group) was applied to bonding experiments to obtain more excellent conductive properties and adhesive strength than those of example 2 and example 3 of the control group.

In summary, the application provides a particle array type anisotropic conductive film based on photo-thermal dual curing and a preparation method thereof. The use of the photo-thermal dual-curing acrylic resin formula can ensure that the array form of the conductive particles is primarily fixed in the resin adhesive film through the pre-curing of ultraviolet light, and then the thermosetting is used for further ensuring that the adhesive film has good adhesive strength and conductive performance in the bonding process. Compared with an anisotropic conductive adhesive film of a single curing agent system, the photo-thermal dual-cured ACF adhesive film shows more excellent particle array arrangement, conductivity and bonding strength.

It will be understood that the technical features of the above-described embodiments may be combined in any manner, and that all possible combinations of the technical features in the above-described embodiments are not described for brevity, however, they should be considered as being within the scope of the description provided in the present specification, as long as there is no contradiction between the combinations of the technical features.

The foregoing description of the preferred embodiments of the present application has been provided for the purpose of illustrating the general principles of the present application and is not to be construed as limiting the scope of the application in any way. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other embodiments of the present application as will occur to those skilled in the art without the exercise of inventive faculty, are intended to be included within the scope of the present application.

Claims

1. The preparation method of the anisotropic conductive adhesive film is characterized by comprising the following steps of:

obtaining conductive microspheres distributed in an array;

laminating a second resin adhesive film on the first resin adhesive film;

2. The method for preparing the anisotropic conductive film according to claim 1, wherein in the step of obtaining the conductive microspheres distributed in an array, the method specifically comprises the following steps:

preparing a micropore array template;

3. The method for preparing the anisotropic conductive film according to claim 2, wherein the step of preparing the micro-pore array template comprises the steps of:

4. The method of preparing an anisotropic conductive film according to claim 2, wherein in the step of modifying the surface of the microporous array template with a fluorine-containing organic surface modifier to obtain a microporous array template with low surface energy, the fluorine-containing organic surface modifier is a perfluorosilane or a perfluoropolyether alcohol or a perfluoropolyester or an anti-fingerprint liquid, and the modification includes dip coating, spray coating or blade coating.

5. The method of claim 1 or 2, wherein in the step of filling conductive microspheres into each microwell of the microwell array template with low surface energy to obtain conductive microspheres distributed in an array, the conductive microspheres comprise pure metal microspheres or carbon material microspheres or organic microspheres, the surface of the conductive microspheres is coated with a metal layer, and the filling method of the conductive microspheres comprises knife coating or spraying or solution self-assembly.

6. The method for preparing an anisotropic conductive film according to claim 3, wherein the particle diameter D2 of the conductive microspheres is 100 nm-100 μm, D2 is less than D1, and 0.5H is less than D2 is less than 1.5H.

7. The method for preparing the anisotropic conductive film according to claim 1 or 2, wherein in the step of obtaining the first resin film layer in which the conductive microspheres are distributed in an array, the method comprises the steps of:

8. The method for preparing an anisotropic conductive film according to claim 7, wherein the acrylic resin comprises 0.5 to 20 parts by mass of photoinitiator, 0.5 to 20 parts by mass of thermal initiator and 5 to 200 parts by mass of acrylate; wherein:

the acrylic resin comprises one or more of epoxy acrylate, phosphate acrylate, polyester acrylate, polyurethane acrylate, polyether acrylate, mono-functional acrylate, bi-functional acrylate, tri-functional acrylate and multi-functional acrylate.

9. The method of claim 8, wherein the first resin film has a thickness of 500nm to 20 μm.

10. The method of preparing an anisotropic conductive film according to claim 1, wherein in the step of laminating a second resin film layer onto the first resin film layer, the method comprises the steps of:

11. The method for preparing the anisotropic conductive film according to claim 10, wherein the second resin film is prepared by the following method: and coating a resin adhesive film on the release film to obtain the second layer of resin adhesive film.

12. The method of claim 11, wherein the release force of the release film on the first resin film side is less than the release force of the release film on the second resin film side.

13. The method for preparing an anisotropic conductive film according to claim 11, wherein the thickness of the second resin film is 1 μm to 100 μm.

14. The method of preparing an anisotropic conductive film according to claim 11, wherein the second resin film comprises a thermosetting resin comprising an epoxy resin or an acrylic resin; wherein:

15. The method for preparing an anisotropic conductive film according to claim 1, wherein the step of obtaining the anisotropic conductive film by pre-curing the first resin film comprises the steps of:

16. The method for preparing an anisotropic conductive film according to claim 15, wherein the ultraviolet light has an intensity of 0.1 to 50mW cm ^-2 The curing time is 1 s-10 min.

17. An anisotropic conductive film prepared by the method of any one of claims 1 to 16.