WO2020124931A1 - Anisotropic conductive adhesive and conductive film thereof - Google Patents

Abstract

The present invention provides an anisotropic conductive adhesive and a conductive film thereof. The conductive adhesive uses a thermal-cured epoxy resin system as a base, and comprises the following components in percentage by mass: 10-40wt% of epoxy resin, 0.5-10wt% of thermal curing agent, 10-40wt% of film forming resin, 10-40wt% of rubber containing carboxyl or hydroxyl, 0.1-5wt% of silane-based coupling agent, 0.1-5wt% of antioxidant, 1-10wt% of conductive ball, and the balance being a solvent. The present invention provides an anisotropic conductive adhesive that has a fast reaction speed and a short curing time.

Description

Anisotropic conductive adhesive and conductive film Technical field

The present invention relates to the field of semiconductor technology, and in particular, to a conductive adhesive and its conductive film for electrical connection between semiconductor electronic components.

Background technique

It is known that the development of semiconductor electronic components is becoming more and more miniaturized and refined. Correspondingly, the electrical connection between small-sized semiconductor devices also poses a huge challenge for the conductive adhesive used to connect and conduct circuits.

Among them, it is not only required that the conductive adhesive has high adhesion and reliability, but also to accurately turn on the micro circuit, especially to achieve the anisotropic conduction of the micro circuit, such as vertical conduction of the upper and lower circuits, and horizontal insulation. , That is, anisotropic conductive adhesive.

At the same time, in addition to improving the performance of the conductive adhesive itself, the application process must also be able to meet the requirements of the production process. The most important point is that the anisotropic conductive adhesive needs to be cured in a very short time, usually less than 15s, to complete the bonding of the circuit board, thereby improving production efficiency and increasing output.

In this regard, the anisotropic conductive adhesives commonly used in the industry can be divided into two categories from the main components: the first type is a system of thermosetting epoxy resin mixed with conductive gold balls; the second type is a thermosetting acrylic resin Mixed conductive gold ball system.

However, there are still many problems in the actual development and application of these two types of conductive adhesives, which are mainly summarized in the following aspects:

First, for epoxy resin systems, the biggest problem is that the curing time is too long and the curing temperature is too high;

Second, for acrylate systems, there is mainly the problem of warpage after curing;

Third, the bonding strength is not enough. It is not enough to only increase the degree of adhesion inside the glue. It is also necessary to consider how to increase the adhesion at the interface of the glued substrate;

Fourth, the conductive particles used are mainly gold balls, that is, the surface of the resin beads is coated with a layer of gold. On the one hand, the technology of gold plating is difficult, the process of producing gold balls is complicated, on the other hand, the price of gold balls is very high. Not conducive to reducing production costs;

Therefore, it is indeed necessary to develop a new type of anisotropic conductive adhesive to overcome the defects in the prior art.

technical problem

One aspect of the present invention is to provide an anisotropic conductive adhesive, which has a fast reaction speed and a short curing time.

Technical solution

The technical scheme adopted by the present invention is as follows:

An anisotropic conductive adhesive (ACF), which is based on a thermosetting epoxy resin system; including the following components by mass ratio: 10-40 wt% epoxy resin, 0.5-10 wt% thermal curing agent , 10-40wt% film-forming resin, 10-40wt% rubber, 0.1-5wt% silane-based coupling agent, 0.1-5wt% anti-aging agent, 1-10wt% conductive ball and the remaining solvent.

Further, in various embodiments, the epoxy resin includes BPA type epoxy resin, BPF type epoxy resin, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, bisphenol S type epoxy resin At least one of resin, glycidylamine type epoxy resin, Hein type epoxy resin, phenol novolak type epoxy resin, alicyclic epoxy resin, and naphthalene ring epoxy resin. Wherein, in different embodiments, the selection of the epoxy resin may be used alone, or two or more types may be used in combination. In a specific embodiment, among them, a general-purpose BPA type epoxy resin is preferred.

Further, in different embodiments, the thermal curing agent includes one of imidazoles, amines, thiols, dicyandiamides, acid anhydrides, and latent curing agents.

Further, in different embodiments, the latent curing agent includes one of amine addition molding, imidazole addition molding, microcapsule-coated imidazole type, thermal cationic type, and other latent curing agents.

Further, in different embodiments, the combination of the epoxy resin and the curing agent is BPA-type epoxy resin and ADEKA latent curing agent I.

Further, in various embodiments, the film-forming resin includes phenoxy resin, urea resin, polyimide resin, polyvinyl methylal, xylene resin, polyamide resin, polyester resin, poly At least one of ethylene butyral, and the molecular weight of the selected film-forming resin is in the range of 10,000-100,000.

Further, in different embodiments, the selected film-forming resin preferably contains more hydroxyl groups or carboxyl groups, which is beneficial to improve the adhesion of the adhesive; at the same time, the selected film-forming resin must have a sufficiently strong Heat resistance, with a small volume change rate when temperature changes, phenoxy resin with molecular weight between 20,000 and 60,000 is preferred here.

Further, in different embodiments, wherein the rubber is a carboxyl/hydroxyl group rubber, its performance parameters are required to have a molecular weight between 100000-1000000 and a glass transition temperature Tg<0°C. Among the rubbers selected, the more the hydroxyl/carboxyl group content is, the better the adhesion is; in addition, the rubber with acid value> 10 mgKOH/g can be preferentially selected according to the acid value. Specifically, it may be an acrylic rubber with a carboxyl group/hydroxyl group or a nitrile rubber with a carboxyl terminal.

Further, in different embodiments, the preferred ratio of the carboxyl/hydroxyl-containing rubber to the phenoxy resin selected from the film-forming resin is 1:1, but it is not limited thereto.

Further, in various embodiments, the silane coupling agent includes vinyl silane, amino silane, methacryloxy silane, A151 (vinyl triethoxy silane), A171 (vinyl trimethoxy) Silane), A172 (vinyl tris(β-methoxyethoxy) silane), 2,3 epoxypropylpropyl trimethoxysilane, amino functional trimethoxysilane, (3-aminopropyl) tri One of ethoxysilane. Specifically, (3-aminopropyl) triethoxysilane is preferred, but not limited to.

Further, in different embodiments, the anti-aging agent includes one of anti-aging agents such as amines, phenols, sulfides, and phosphites. Specifically, the anti-aging agent is preferably an amine anti-aging agent, which may specifically be N-phenyl-2-naphthylamine, but is not limited thereto.

Further, in various embodiments, the conductive spheres include polystyrene beads modified with carbon nanotubes, the surface of which is uniformly coated with the carbon nanotubes. By adjusting the particle size of the polystyrene beads, conductive beads with different particle diameters can be prepared, that is, the conductivity of the carbon nanotubes is fully utilized, and the cost is greatly reduced compared with the gold-plated beads.

Further, in different embodiments, the main selection principle of the solvent is to have good solubility in the polymer resin and rubber used, which may specifically be selected from methyl ethyl ketone, n-butyl glycidyl ether, toluene and One of dichloromethane. Further, it is preferably an epoxy-containing n-butyl glycidyl ether, because it has an epoxy group, and the residual solvent can also react with the system for further curing.

Further, another aspect of the present invention is to provide a conductive film, which includes a release film. The anisotropic conductive adhesive according to the present invention is attached to the release film.

Further, another aspect of the present invention is to provide a method for preparing the conductive film according to the present invention, including the following steps:

Disperse the phenoxy resin in the solvent at a predetermined concentration, and then add the silane coupling agent, anti-aging agent, and rubber in a predetermined ratio in sequence, and perform the steps of mixing, stirring, and defoaming to obtain a pre-mixed rubber material;

After the epoxy resin and the curing agent are mixed in a predetermined ratio, they are added to the pre-mixed glue material to obtain a medium-mixed glue material;

Disperse the conductive balls in the middle-mix rubber material at a predetermined ratio, and then perform the steps of mixing, stirring and defoaming to obtain the final mixed rubber material;

The final mixed rubber material is coated on a release film with a thickness of 10 to 100 um and dried, and then the anisotropic conductive film according to the present invention is obtained.

Further, in different embodiments, the material of the release film includes one of PET, PTFT, or a composite film material.

Further, in different embodiments, the coating method of the final mixed adhesive material includes one of film forming methods such as knife coating, spin coating, and screen printing.

Further, in different embodiments, the drying treatment method is to heat it at 50 to 100° C. for 3 min to 15 min, or use an infrared lamp drying process; the specific may be determined according to actual needs and is not limited.

Beneficial effect

The present invention relates to an anisotropic conductive adhesive, which is based on a thermosetting epoxy resin system and solves the problem of slow curing of epoxy resin by selecting a suitable mix ratio between epoxy resin and thermal curing agent Problem, making the optimal curing time reduced to less than 15s.

Further, by incorporating a suitable ratio of nitrile rubber with carboxyl terminal and/or acrylic rubber with carboxyl/hydroxyl group, the adhesion at the bonding interface is increased, thereby greatly improving the bonding strength and making the adhesion force reach Optimally, it greatly reduces the chance of the bonded substrate falling during pre-pressing, thereby improving the straight-through rate of the product.

In addition, it uses small balls modified with carbon nanotubes on the surface to replace the existing conductive gold balls. While obtaining the same conductive effect, it also greatly reduces its overall production cost.

BRIEF DESCRIPTION

In order to more clearly explain the technical solutions in the embodiments of the present invention, the drawings required in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, without paying any creative work, other drawings can also be obtained based on these drawings.

FIG. 1 is a schematic layout diagram of a test structure for testing the conduction resistance and insulation resistance of an anisotropic conductive adhesive according to the present invention.

Embodiments of the invention

The technical solution of the anisotropic conductive adhesive and its conductive film according to the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

An embodiment of the present invention provides an anisotropic conductive adhesive, which is based on a thermosetting epoxy resin system; which contains at least: (A) epoxy resin, (B) thermal curing agent, ( C) Film-forming resin, (D) rubber with carboxyl/hydroxyl groups, (E) silane-based coupling agent, (F) anti-aging stabilizer, (G) carbon nanotube modified polystyrene beads, and (H ) Solvent.

Among them, as (A) epoxy resin, the added mass ratio range: 10 to 40 wt%. Specifically, BPA type epoxy resin, BPF type epoxy resin, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, bisphenol S type epoxy resin, glycidyl amine type epoxy resin, Hein One or more types of epoxy resins, phenol novolac epoxy resins, alicyclic epoxy resins, and naphthalene epoxy resins.

The selection of the epoxy resin mainly needs to consider two factors: the first is the viscosity of the epoxy resin; the second is the matching reaction between the epoxy resin and the curing agent, that is, the curing rate. The epoxy resin selected here may be used alone or in combination of two or more quantities. Here, the general-purpose BPA epoxy resin is preferred.

Among them, as the (B) thermosetting agent, a mass ratio range of 0.5 to 10 wt% is added. Specifically, one of imidazoles, amines, thiols, dicyandiamides, acid anhydrides, and latent thermal curing agents can be used. The latent thermal curing agent includes amine addition molding, imidazole addition molding, microcapsule-coated imidazole type, thermal cationic type, and other latent thermal curing agents.

The selection of the thermal curing agent mainly needs to consider two major issues: first, the curing rate; second, normal temperature and low temperature can not initiate a cross-linking reaction, which affects the storage characteristics of the product. After a lot of experimental screening, it is found that ADEKA latent curing agent I and BPA epoxy resin have a good matching effect, and can be cured completely within 15S at high temperature.

Among them, as the (C) film-forming resin, a mass ratio range of 10-40 wt% is added. Specifically, one of phenoxy resin, urea resin, polyimide resin, polyvinyl methylal, xylene resin, polyamide resin, polyester resin, and polyvinyl butyral can be used. The molecular weight of these resins It is preferably between 100000-1000000. The resin selected here is more suitable if it can contain more hydroxyl groups or carboxyl groups, which is beneficial to improve the adhesion of the adhesive; at the same time, the selected resin must have sufficient heat resistance, when the temperature changes, it has more Phenoxy resin with a molecular weight between 20,000 and 60,000 is preferred here for small volume change rate.

Among them, as (D) rubber with carboxyl group/hydroxyl group, the mass ratio range is 10-40 wt%. Specifically, acrylic rubber with carboxyl groups/hydroxyl groups and/or nitrile rubber with carboxyl groups at the ends can be selected. The molecular weight is required to be between 100000-1000000 and the glass transition temperature Tg<0°C. Among them, the more the content of hydroxyl/carboxyl groups in the rubber, the better, which is beneficial to increase the adhesion, and the rubber with acid value>10mgKOH/g can be preferentially selected according to the acid value. Further, the preferred ratio of the selected phenoxy resin and rubber is 1:1, and the adhesion performance is excellent.

Among them, as the (E) silane-based coupling agent, a mass ratio range of 0.1 to 5 wt% is added. Specifically, vinyl silane, amino silane, methacryloxy silane, A151 (vinyl triethoxy silane), A171 (vinyl trimethoxy silane), A172 (vinyl tri (β-methoxy) Ethoxy) silane), 2,3 epoxypropylpropyl trimethoxysilane, amino functional trimethoxysilane, (3-aminopropyl) triethoxysilane. Here, (3-aminopropyl) triethoxysilane is preferred.

Among them, as (F) anti-aging agent, the added mass ratio range: 0.1 ~ 5wt%. Specifically, amines, phenols, sulfides, phosphites and other types of anti-aging agents can be selected. Preference is given here to amine anti-aging agents, for example, N-phenyl-2-naphthylamine, but not limited to.

Among them, as (G) carbon nanotube modified polystyrene beads, the added mass ratio range: 1-10wt%. The surface of the polystyrene beads is uniformly coated with carbon nanotubes, and then by adjusting the particle size of the polystyrene beads, conductive beads with different particle diameters can be prepared, thereby making full use of the carbon nanotubes Electrical conductivity, while greatly reducing costs.

Here, as the (H) solvent, it is the balance. The main selection principle is to have good solubility in the polymer resin and rubber used, and it can be specifically selected from methyl ethyl ketone, n-butyl glycidyl ether, toluene, and methylene chloride. N-butyl glycidyl ether with epoxy groups is preferred here, because it has epoxy groups, and the residual solvent can also react with the system for further curing.

Further, another aspect of the present invention is to provide a conductive film, which includes a release film. The anisotropic conductive adhesive according to the present invention is attached to the release film.

Further, another embodiment of the present invention provides a method for preparing the conductive film according to the present invention, which includes the following steps:

Step1: First disperse the phenoxy resin in the solvent at a predetermined concentration, and then add the silane coupling agent, anti-aging agent and rubber in order according to a predetermined ratio, and perform the steps of mixing, stirring and defoaming, Obtain a pre-mixed rubber material; after mixing the epoxy resin with a curing agent at a predetermined ratio, quickly add to the pre-mixed rubber material to obtain a medium-mixed rubber material; and then modify the carbon nanotube-modified polystyrene Balls (CNT) are dispersed in the medium-mix rubber material in a predetermined ratio, and the processes of rubber mixing, stirring and defoaming are performed again to ensure full mixing;

Step2: Apply the above-mentioned defoaming material of Step 1 to the release film of 10-100um thick, and then apply the coating and dry it. The release film can be made of PET, PTFT or its composite film, and can be processed. Wherein the coating method can be formed by knife coating, spin coating, screen printing and other processes, and the drying can be heated at 50-100° C. for 3 min-15 min, or using an infrared lamp drying process.

Step3: Cut the large ACF film made in the above Step2, and obtain ACF films with different widths according to requirements, such as 1.2mm width, but not limited to.

Further, the following will list different embodiments and their experimental results to further describe the performance of the anisotropic conductive adhesive according to the present invention.

Among them, the above-mentioned test method of bonding strength is that the anisotropic conductive adhesive film in each embodiment column in the above list is affixed to the connection point of the PCBA circuit board. The length of the conductive film is 42mm and the width is 2mm. Press (pressure 0.3Mpa, temperature 120℃, time 2s), tear off the release film (PET material), paste the COF on it, and then pass this pressure (pressure 0.3Mpa, temperature 180℃, time 10s) to complete For the preparation of the sample, a tensile machine was used, perpendicular to the PCBA board, and the COF was pulled upward at 90 degrees to determine the bonding strength.

Among them, the above-mentioned test method for conducting impedance and insulation impedance is to adopt the layout structure shown in FIG. 1, and stick the anisotropic conductive adhesive film in each embodiment column in the above list on it. Specifically, for the insulation resistance, the conductive glue is directly pasted, and the insulation resistance is tested by the four-probe method after the hot pressing process described above; for the conduction resistance, it is necessary to stick ITO glass on the glue. To verify whether the upper and lower continuity, also use the four-probe method to test.

The invention relates to an anisotropic conductive adhesive, which is based on a thermosetting epoxy resin system and solves the problem of slow curing of epoxy resin by selecting a suitable ratio of epoxy resin and curing agent The problem reduced the curing time to less than 15s.

Further, by incorporating a suitable ratio of nitrile rubber with carboxyl terminal and/or acrylic rubber with carboxyl/hydroxyl group, the adhesion at the bonding interface is increased, thereby greatly improving the bonding strength and making the adhesion force reach Optimally, it greatly reduces the chance of the bonded substrate falling during pre-pressing, thereby improving the straight-through rate of the product.

In addition, it uses small balls modified with carbon nanotubes on the surface to replace the existing conductive gold balls. While obtaining the same conductive effect, it also greatly reduces its overall production cost.

The technical scope of the present invention is not limited to the content in the above description. Those skilled in the art can make various modifications and modifications to the above embodiments without departing from the technical idea of the present invention, and these modifications and modifications should belong to Within the scope of the invention.

Claims (10)

1. An anisotropic conductive adhesive based on a thermosetting epoxy resin system; including the following components according to mass ratio:

   10～40wt% epoxy resin;

   0.5～10wt% thermal curing agent;

   10～40wt% film-forming resin;

   10～40wt% rubber with carboxyl group or hydroxyl group;

   0.1～5wt% silane coupling agent;

   0.1～5wt% anti-aging agent;

   1～10wt% conductive ball; and

   Remaining solvent;

   The epoxy resin includes BPA epoxy resin, BPF epoxy resin, glycidyl ether epoxy resin, glycidyl ester epoxy resin, bisphenol S epoxy resin, glycidyl amine epoxy resin , At least one of Hein epoxy resin, phenol novolac epoxy resin, alicyclic epoxy resin and naphthalene epoxy resin.
2. An anisotropic conductive adhesive according to claim 1, wherein the thermal curing agent comprises one of imidazoles, amines, thiols, dicyandiamides, acid anhydrides and latent curing agents Wherein the latent curing agent includes one of amine addition molding, imidazole addition molding, microcapsule-coated imidazole type, thermal cationic type and other latent curing agents.
3. An anisotropic conductive adhesive according to claim 2, wherein the combination of the epoxy resin and the curing agent is a BPA epoxy resin and ADEKA latent curing agent I.
4. An anisotropic conductive adhesive according to claim 1, wherein the conductive ball comprises carbon nanotube modified polystyrene beads, the surface of which is uniformly coated with the carbon nanotube.
5. An anisotropic conductive adhesive according to claim 1, wherein the film-forming resin comprises phenoxy resin, urea resin, polyimide resin, polyvinyl methylal, xylene resin, poly One of amide resin, polyester resin and polyethylene butyral, and the molecular weight of the selected resin is between 10,000 and 100,000.
6. An anisotropic conductive adhesive according to claim 1, wherein the carboxyl/hydroxyl-containing rubber includes carboxyl/hydroxyl-containing acrylic rubber and/or carboxyl-terminated nitrile rubber, wherein the required performance parameters Including molecular weight between 100000-1000000, glass transition temperature Tg<0℃ and acid value>10mgKOH/g.
7. An anisotropic conductive adhesive according to claim 1, wherein the silane-based coupling agent includes vinyl silane, amino silane, methacryloxy silane, A151 (vinyl triethoxy silane ), A171 (vinyl trimethoxysilane), A172 (vinyl tri(β-methoxyethoxy) silane), 2,3 epoxypropylpropyl trimethoxysilane, amino functional trimethoxysilane and One of (3-aminopropyl) triethoxysilane.
8. An anisotropic conductive adhesive according to claim 1, wherein the anti-aging stabilizer includes an anti-aging agent among amines, phenols, sulfides and phosphites.
9. An anisotropic conductive adhesive according to claim 1, wherein the solvent comprises one of methyl ethyl ketone, n-butyl glycidyl ether, toluene and methylene chloride.
10. A conductive film comprising a release film, wherein the anisotropic conductive adhesive according to claim 1 is attached to the release film.

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