JP2509773B2 - Method for producing anisotropic conductive film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrical connection between minute circuits, for example, connection between an LCD (liquid crystal display) and a flexible circuit board, and assembly of electronic parts such as micro-joint between a semiconductor IC and an IC mounting circuit board. The present invention relates to a method for producing an anisotropic conductive film that can be used for the above.

[0002]

2. Description of the Related Art With the recent miniaturization and thinning of electronic devices, the necessity of connecting minute circuits to each other, connecting minute parts to minute circuits, etc. has been dramatically increasing. Anisotropic conductive adhesives and films have been used (for example, JP-A-59-120436, 60-1).
91228, 61-274394, 61-28797.
4, 62-244242, 63-153534, 63-
305591, 64-40784, 64-81878,
JP-A-1-46549, 1-251787, etc.).

An anisotropic conductive film is produced by casting a resin mixture containing a predetermined amount of conductive particles on a release film and drying it. It is sheet-shaped or slit into a certain width. It is made by. The anisotropic conductive film is used on one of the circuits to be connected,
Place a film containing a certain amount of conductive particles formed on the release film, apply predetermined temperature and pressure from the release film side, temporarily press-bond, peel off the release film, and align with the other circuit Then, by thermocompression bonding at a predetermined temperature, pressure, and time, electrical connection between the circuits is made, and at the same time, insulation between adjacent circuits is secured.

The anisotropic conductive film is classified into a thermoplastic type and a thermosetting type, but recently, an epoxy resin type thermosetting type which is more reliable than the thermoplastic type is widely used. It is being used. However, the thermosetting type is excellent in reliability, but it is difficult to control the fluidity during crimping, and it is difficult to peel and re-press after once crimping. Inferior.

Strong adhesion, soft film surface,
For a coating film of an epoxy resin type thermosetting anisotropic conductive film, it is necessary to select a release film that has appropriate workability and adhesiveness required for use, and that has good workability. This is an important element for improving workability in the process of assembling electronic components, such as connecting with an anisotropic conductive film. That is, if the releasability of the release film is too good, the resin mixture is repelled during coating and uniform casting cannot be performed, or an anisotropically conductive film formed in a reel shape by winding with the release film is used. At this time, the anisotropic conductive film itself and the release film may be peeled off at the unwinding portion.

When the releasability is poor, the anisotropic conductive film and the release film may be peeled off at the unwinding portion as described above, or the anisotropic conductive film may be peeled off after the temporary pressure bonding. The adhesive layer of the film may peel off together with the release film, which may cause operational problems, which leads to a decrease in connection yield due to poor connection and a decrease in reliability. There is. Then, in order to avoid the problem of compatibility between release and adhesion, there is a method of sandwiching the adhesive film together with another release film to form a sandwich-like structure, but cost related to lamination, increase in peeling process, etc. The current situation is that problems cannot be avoided.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of various studies in order to solve such problems of the conventional thermosetting anisotropic conductive film, and its object is high. An object of the present invention is to provide a method for producing a thermosetting anisotropic conductive film which improves the above-mentioned problems in use while maintaining connection reliability and has good workability.

[0008]

The present invention provides a reactive elastomer, an epoxy resin, a latent curing agent composed of an imidazole derivative epoxy compound, a coupling agent, a solvent for dissolving them, and a paste-like mixture composed of conductive particles. Tetrafluoroethylene-ethylene copolymer resin (ETF
E) Tetrafluoroethylene-6-fluoropropylene copolymer resin (PEF), perfluoro-alkoxy resin (PF
A method for producing an anisotropic conductive film, which is formed by casting on a fluorine-based release film having a thickness of 25 to 150 μm selected from A) and volatilizing a solvent.

As the release film, there are release paper coated with silicon-based or fluorine-based material, polyester-based film, polymethylpentene resin film, fluorine-based film, etc. Among them, the fluorine-based film is used under the conditions of use. It is preferable because it has sufficient heat resistance below, and has sufficient adhesiveness and appropriate releasability to an anisotropic conductive film having strong adhesiveness and adhesiveness.

As the fluorine-based release film, tetrafluorofluoroethylene resin (TFF), ETFE, FEP, P
FA, vinylidene fluoride resin (PVE), trifluorochloroethylene resin, etc. are mentioned, and one surface of these is physically or chemically treated to give a difference in releasability between the front and back. Although the present invention is used, the present inventors have examined various fluorine-based films in accordance with resin blending, and
By using one type selected from FEP and PFA as a release film, an anisotropic conductive film having thermosetting type reliability and good thermoplastic type workability was found.

The thickness of these films is 25 to 150.
μm is optimal. If the fluorine-based release film is less than 25 μm, wrinkles will form on the entire film, making post-processing such as film winding and slitting impossible, and since the film itself is not stiff, it will be temporarily pressed. The workability when doing is significantly deteriorated. If it exceeds 150 μm, the film thickness error (variation) becomes large, and it becomes difficult to control the thickness of the coated film. Further, the increase in thickness causes the cost to increase because the fluorine-based film is originally expensive.

The reactive elastomer is polyvinyl butyral resin, and the total solid content of the latent curing agent composed of the epoxy resin and the imidazole derivative epoxy compound is 100 parts by weight (hereinafter, all addition parts are parts by weight). 20 to 70 parts are used in combination.

The epoxy resin used in the present invention is an epoxy resin having at least two epoxy groups in one molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, dimer acid diglycidyl ester, phthalic acid diglycidyl ester, tetrabromobisphenol A type epoxy resin. Resins, bisphenol hexafluoroacetone glycidyl ether, triglycidyl isocyanurate, tetraglycidyl diaminodiphenylmethane, etc. may be used alone or in admixture of two or more, but they are compatible with other compounds such as latent curing agents. A good bisphenol A type epoxy resin is preferably used.

Any solvent can be used as long as it can completely dissolve the above-mentioned reactive elastomer and epoxy resin. Specifically, acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene,
Examples include xylene, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, ethyl acetate, tetrahydrofuran, methyl cellosolve, ethyl cellosolve, diacetone ether, methyl cellosolve acetate, ethyl cellosolve acetate, dimethylformamide, and dimethylacetamide. Depending on the high polarity, the stability of the resin solution after compounding may be affected.
It is used as a mixture of two or more species.

The imidazole derivative epoxy compound is
It is an adduct of an imidazole compound and an epoxy compound. As the imidazole compound, imidazole,
2-methylimidazole, 2-ethylimidazole, 2
-Ethyl-4 methyl imidazole, 2-phenyl imidazole, 2-phenyl-4-methyl imidazole, 1-
Benzyl-2-methylimidazole, 1-benzyl-2
-Ethylimidazole, 1-benzyl-2-ethyl-5
-Methylimidazole, 2-phenyl-4-methyl-5
-Hydroxymethylimidazole, 2-phenyl-4,
5-dihydroxymethyl imidazole etc. are mentioned.
Examples of the epoxy compound include glycidyl ether type epoxy resins such as bisphenol A, phenol novolac, bisphenol F, and brominated bisphenol A, diglycidyl ester of dimer acid, diglycidyl ester of phthalic acid.

The reaction product of the above-mentioned imidazole derivative and epoxy compound can be obtained as a fine powder, but it is preferable to further mix it with an isocyanate compound to improve the storage stability and to microcapsulate it.

The coupling agent is preferably a silane coupling agent. For example, olefin functional silane, epoxy functional silane, acrylic functional silane, monoaminosilane, diaminosilane, triaminosilane, terminal trialkoxysilane, complex reactive aminosilane, mercapto functional silane, isocyanate functional silane, and the like. , 1 due to the required characteristics of anisotropic conductive film
They may be used alone or in combination of two or more.

As conductive particles, plastic beads plated with metal, solder, or various alloys are often used. These may be appropriately used depending on the type of adherend and are not particularly limited.

[0019]

EXAMPLES The present invention will now be described in more detail based on examples. Parts represent parts by weight.

The anisotropic conductive films used as the test pieces all had a thickness of 25 μm, and the adhesive strength was evaluated by a 90 ° peel test.

Example 1 As a reactive elastomer, K-polyvinyl butyral resin flakes having a degree of acetylation of 3 mol% or more and a degree of butyralization of 68% (manufactured by Monsanto Co.) were added to a mixed solution of toluene and methyl ethyl ketone = 2/1 with stirring. Then 4
A 0 wt% resin solution was made.

20 parts of bisphenol type epoxy resin Epicoat 828 (produced by Yuka Shell Co., Ltd.) was mixed with 100 parts of this solution. Separately from this, Epoxy resin Epicoat 10
04 (made by Yuka Shell Co., Ltd.) 60 parts of methyl ethyl ketone 3
It was dissolved in 0 part and added to the above-mentioned reactive elastomer and mixed uniformly. To this mixed solution, 40 parts of HX3742 (manufactured by Asahi Kasei Corporation) was mixed as a reaction product of an imidazole derivative and an epoxy compound. Furthermore, as a silane coupling agent, trialkoxysilane X-12-666
2% (made by Shin-Etsu Chemical Co., Ltd.) was added to the resin solid content and mixed.

Further, the conductive particles have an average particle size of 10 μm.
m, the maximum particle diameter of 15 μm, 90 g of tin-lead solder are uniformly dispersed, and a fluorine-based release film having a thickness of 100 μm is ETF.
A coating film was formed on E (manufactured by Asahi Glass Co., Ltd.) so that the thickness after drying was 25 μm, dried at 50 ° C. for 1 hour, and wound with a release film to obtain an anisotropic conductive film.

Examples 2 and 3 Anisotropic conductive films were produced in the same manner as in Example 1 except that FEP was used in Example 2 and PFA was used in Example 3 as the release film. The release films used in the examples all have a thickness of 100 μm.

Comparative Examples 1 to 3 Anisotropic conductive films were produced in the same manner as in Example 1 except that the thickness of the fluorine-based release film was 20 μm. Comparative Examples 4 to 6 An anisotropic conductive film was produced in exactly the same manner as in Example 1 except that the thickness of the fluorine-based release film was 200 μm.

With respect to the reel-shaped anisotropic conductive films obtained in these Examples and Comparative Examples, the unwinding stability when using the anisotropic conductive film and the releasability of the fluorine-based release film were evaluated. The results are shown in Table 1.

When the anisotropic conductive film is used, the unwinding stability is evaluated by continuously winding 100 m of the anisotropic conductive film roll formed on the reel at room temperature (23 ° C.), and releasing the fluorine-based release film. It was observed whether the film and the anisotropic conductive film peeled off. The peel strength of the fluorine-based release film was evaluated by measuring the load when the release film was peeled by 90 ° from the anisotropically conductive film that was temporarily pressure-bonded. The adherend is copper foil 3
A two-layer flexible circuit board (pitch 0.18 mm, number of terminals 200) obtained by plating 5 μm with nickel 5 μm and gold 0.5 μm was used.

[0028]

[Table 1]

[0029]

According to the present invention, it is possible to provide an anisotropic conductive film having excellent balance of adhesion and workability, high reliability, and low connection resistance.

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Claims (1)

(57) [Claims] 1. A tetrafluoroethylene-ethylene copolymerization of a latent mixture of a reactive elastomer, an epoxy resin, an imidazole derivative epoxy compound, a coupling agent, a solvent that dissolves these, and a paste-like mixture containing conductive particles. Resin, tetrafluoroethylene-6-fluoropropylene copolymer resin, perfluoro-alkoxy resin, cast on a fluorine-based release film having a thickness of 25 to 150 μm, and formed into a film by volatilizing the solvent. A method for producing an anisotropic conductive film, comprising: