WO2020124909A1 - Anisotropic conductive adhesive and conducting film thereof - Google Patents

Abstract

Provided by the present invention are an anisotropic conductive adhesive and a conducting film thereof. The conductive adhesive employs a cationic curing system, and comprises the following components by mass: 10-40 wt% of film-forming resin, 10-40 wt% of epoxy resin and a cationic heat curing agent, 10-40 wt% of acrylic rubber, 3-15 wt% of a solvent and 3-20 wt% of conducting spheres. The mass ratio of the cationic heat curing agent to the epoxy resin is (1-20):60. Provided by the present invention is the anisotropic conductive adhesive, which has quick reactions 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.

For example, in the application of TFT-LCD, a conductive adhesive is used to connect the liquid crystal panel with an external circuit. Among them, when the liquid crystal panel is connected to the flip chip (COF), the printed circuit wiring board (PWB) and the COF, the anisotropic conductive film (ACF) is used for signal transmission. This ACF only allows current to be conducted between the points connected by the ball or only in the Z-axis direction but not in the X and Y-axis directions. Different signals can be transmitted in each channel to ensure high-definition picture quality. Implementability.

Furthermore, the current mainstream ACF products are basically composed of resin, curing agent, conductive particles and additives. According to the type of curing agent, it can be divided into anionic polymerization type, cationic polymerization type and addition polymerization type, etc. Among them, the cationic polymerization type has been widely concerned because of the characteristics of rapid curing at low temperature.

Among them, as a conductive film disclosed in Chinese Patent No. 103459453 A, it uses β-alkyl glycidyl epoxy resin and glycidyl ether epoxy resin as the main body of the resin, which is heated at low temperature by a cationic curing agent. Curing solves the problem of insufficient repairability of the existing cationic system, but does not consider the problem of ACF film formation, and there is room for further improvement in adhesion.

In addition, most of the conductive particles used in current ACF products are conductive gold balls coated with Au/Ni on the outer layer. Traditional conductive gold balls generally use electroless plating to plate gold/nickel on the surface of resin balls with a diameter of 2 to 100 μm. This method consumes a lot of energy. The gold salts used in the production process are mostly cyanide, which is very toxic and the price of gold Expensive, not conducive to cost control.

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 with good film-forming properties and high adhesion.

Technical solution

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

An anisotropic conductive adhesive (ACF), which uses a cationic curing system, including the following components according to the mass ratio: 10-40 wt% film-forming resin, 10-40 wt% epoxy resin, cationic thermal curing Agent, 10-40wt% acrylic rubber, 3-15wt% solvent and 3-20wt% conductive balls. The mass ratio of the cationic thermal curing agent to the epoxy resin is (1-20): 60.

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, when the temperature changes, it has a small volume change rate. Here, the phenoxy resin with a molecular weight in the range of 20,000 to 60,000 is preferred.

Further, in various embodiments, the epoxy resin includes at least one of a glycidyl ether epoxy resin, a glycidyl ester epoxy resin, a glycidyl amine epoxy resin, and an alicyclic epoxy resin Species. The epoxy resin may be used alone or in combination of two or more, and alicyclic epoxy resin is preferred here.

Further, in various embodiments, the cationic thermal curing agent includes at least at least one of cationic thermal curing agents such as aromatic sulfonium salts, aromatic diazonium salts, iodonium salts, phosphonium salts, and selenonium salts. One kind. The preferred combination of the cationic thermal curing agent and the epoxy resin is Vicbase TC3632 curing agent and Daicel 2021P epoxy resin.

Further, in different embodiments, wherein the acrylic rubber is an acrylic rubber with a carboxyl group, its performance parameter requirements are a molecular weight in the range of 100000-1000000 and a glass transition temperature Tg<0°C. Among them, the more carboxyl group content in the rubber is better, which is beneficial to increase the adhesion; in addition, according to the acid value, the carboxyl group-containing acrylic rubber with an acid value> 10 mgKOH/g can be preferentially selected.

Further, in different embodiments, the main selection principle of the solvent is to have good solubility in the polymer resin and rubber used, which includes methyl ethyl ketone, n-butyl glycidyl ether, toluene and methylene chloride At least one of them. Specifically, 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, 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 pellets, conductive pellets with different particle diameters can be prepared, which fully utilizes the conductivity of the carbon nanotubes, and at the same time greatly reduces the cost relative to the gold-plated pellets.

Further, in different embodiments, it further includes an auxiliary agent of 0.1 to 5 wt%, wherein the auxiliary agent includes at least one of an anti-aging agent, a silane coupling agent, and the like.

Further, in various embodiments, the anti-aging agent includes at least one of anti-aging agents such as amines, phenols, sulfides, and phosphites.

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 and (3-aminopropyl) tri At least one of ethoxysilanes.

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:

Mix all the components except the conductive balls involved in a predetermined ratio uniformly, and then add the conductive balls in a predetermined ratio for mixing, stirring and defoaming to obtain a mixed rubber material;

The mixed glue material is coated on a release film with a thickness of 10-100 um and dried to obtain the anisotropic conductive film according to the present invention.

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 50-100° C. for 3-15 minutes, or use an infrared lamp drying process; the specific may be determined according to actual needs, and is not limited.

Beneficial effect

The invention relates to an anisotropic conductive adhesive, which adopts a cationic curing system, is matched with an alicyclic epoxy resin and is combined with a phenoxy resin, which solves the problem of slow curing of the existing epoxy resin and makes the curing time large Reduced, and at the same time the film formation has also been greatly improved.

Further, by incorporating acrylic rubber with carboxyl terminal and adjusting the ratio between it and the phenoxy resin, the adhesive force at the bonding interface is increased, thereby greatly improving the bonding strength and making the adhesion Achieving optimality greatly reduces the chance of the bonded substrate falling during pre-pressing, thereby improving the through rate of the product.

In addition, it uses polystyrene beads modified with carbon nanotubes on the surface to replace the existing conductive gold balls, which not only meets the conductive effect, but 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 uses a cationic curing system, which includes at least: (A) film-forming resin, (B) epoxy resin, (C) cationic curing agent , (D) acrylic rubber with carboxyl group, (E) solvent, (F) carbon nanotube modified polystyrene beads and (G) other additives.

Among them, as the (A) film-forming resin, a mass ratio range of 10-40 wt% is added. Specifically, phenoxy resin, urea resin, polyimide resin, polyethylene methylal, xylene resin, polyamide resin, polyester resin, polyethylene butyral, and the molecular weight of these resins is preferably located at 100,000 Between -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. For a small volume change rate, phenoxy resins with molecular weights between 20,000 and 60,000 are preferred here.

Among them, as (B) epoxy resin, a mass ratio range of 10-40 wt% is added. Specifically, glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, and alicyclic epoxy resin can be used. 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 can also be used alone It can be used in combination of two or more. Here, alicyclic epoxy resin is preferred.

Among them, as the (C) cationic thermosetting agent, the mass ratio between it and the epoxy resin is (1-20): 60. Specifically, a cationic thermal curing agent such as aromatic sulfonium salt, aromatic diazonium salt, iodonium salt, phosphonium salt, and selenonium salt can be used. The selection of the cationic thermal curing agent 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. The preferred combination of the cationic thermal curing agent and the epoxy resin is Vicbase TC3632 thermal curing agent and Daicel 2021P epoxy resin.

Among them, as (D) acrylic rubber with carboxyl group, the added mass ratio range is 10-40 wt%, and its performance parameters are required to have a molecular weight between 100000-1000000 and a glass transition temperature Tg<0°C. Among them, the more carboxyl group content in the rubber is better, which is beneficial to increase the adhesion, and according to the acid value, the acrylic rubber with acid value>10mgKOH/g can be selected preferentially.

Among them, as the (E) solvent, a mass ratio range of 3 to 15 wt% is added. 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, butyl glycidyl ether, toluene, and methylene chloride. Here, the butyl glycidyl ether with epoxy groups is preferred because it has epoxy groups and the residual solvent can also react with the system for further curing. The solvent is preferably as small as possible to reduce the solvent processing time in the post-process.

Among them, as (F) carbon nanotube modified polystyrene beads, the added mass ratio range: 3-20 wt%. 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 fully utilizing carbon The conductivity of the nanotubes also greatly reduces the cost.

Among them, as the (G) auxiliary agent, an anti-aging agent, a silane coupling agent, etc. may be added, depending on requirements, and there is no limitation. If it needs to be added, the added mass ratio is 0.1-5wt%. The anti-aging agent may be one of amines, phenols, sulfides, phosphites and other anti-aging agents. The silane coupling agent can be selected from vinyl silane, amino silane, methacryloxy silane, A151 (vinyl triethoxy silane), A171 (vinyl trimethoxy silane), A172 (vinyl trimethoxy silane) (β-methoxyethoxy) silane), 2,3 epoxypropylpropyl trimethoxysilane, amino functional group trimethoxysilane, (3-aminopropyl) triethoxysilane, etc.

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, all components except the conductive ball involved are uniformly mixed according to a predetermined ratio, and then a predetermined ratio of the conductive ball is added to perform mixing, stirring and defoaming to obtain a mixed rubber material.

Step2: Apply the mixed rubber material defoamed in Step 1 above to the release film with a thickness of 10-100um, then apply 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 present invention relates to an anisotropic conductive adhesive, which uses a cationic curing system, an alicyclic epoxy resin combined with a phenoxy resin, which solves the problem of slow curing of existing epoxy resins, resulting in a large curing time Reduced, and at the same time the film formation has also been greatly improved.

Further, by incorporating acrylic rubber with carboxyl terminal and adjusting the ratio between it and the phenoxy resin, the adhesive force at the bonding interface is increased, thereby greatly improving the bonding strength and making the adhesion Achieving optimality greatly reduces the chance of the bonded substrate falling during pre-pressing, thereby improving the through rate of the product.

In addition, it uses polystyrene beads modified with carbon nanotubes on the surface to replace the existing conductive gold balls, which not only meets the conductive effect, but 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, which uses a cationic curing system, and includes the following components according to mass ratio:

   10～40wt% film-forming resin;

   10～40wt% epoxy resin;

   Cationic thermal curing agent;

   10～40wt% acrylic rubber;

   3-15wt% solvent; and

   3～20wt% conductive ball;

   Wherein the cationic thermal curing agent includes at least one of cationic thermal curing agents such as aromatic sulfonium salts, aromatic diazonium salts, iodonium salts, phosphonium salts, selenonium salts; wherein the cationic thermal curing agent The mass ratio of curing agent to the epoxy resin is (1-20): 60.
2. An anisotropic conductive adhesive according to claim 1, wherein the epoxy resin comprises glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin and alicyclic At least one of the group epoxy resins.
3. The anisotropic conductive adhesive according to claim 1, wherein the conductive ball comprises polystyrene beads modified with carbon nanotubes, the surface of which is uniformly coated with the carbon nanotubes.
4. 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 At least one of amide resin, polyester resin, and polyvinyl butyral, and the molecular weight of the selected resin is in the range of 10,000-100,000.
5. The anisotropic conductive adhesive according to claim 1, wherein the acrylic rubber is an acrylic rubber with a carboxyl group, and the required performance parameters include a molecular weight in the range of 100000-1000000 and a glass transition temperature Tg<0 ℃ and acid value>10mgKOH/g.
6. The anisotropic conductive adhesive according to claim 1, wherein the solvent includes at least one of methyl ethyl ketone, n-butyl glycidyl ether, toluene and methylene chloride.
7. The anisotropic conductive adhesive according to claim 1, further comprising 0.1 to 5 wt% of an auxiliary agent, wherein the auxiliary agent includes at least one of an anti-aging agent, a silane coupling agent and the like.
8. An anisotropic conductive adhesive according to claim 7, wherein the anti-aging agent includes at least one of amines, phenols, sulfides and phosphite anti-aging agents.
9. An anisotropic conductive adhesive according to claim 7, wherein the silane 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 At least one of (3-aminopropyl) triethoxysilane.
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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