JPH09150425A - Anisotropically conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the connection of this film in a short period of time, have excellent storage stability at normal temperature and excellent adhesion within wide temperature range after curing under heat and pressure, and, addition, realize extremely small residual strain at a joint and separation and re-fixing by pressure by heating films fixed by pressure up to the predetermined temperature or higher. SOLUTION: The essential components of this film are polyvinyl butyral resin A having characteristics such as the degree of polymerization of 1,500-2,500, the degree of acetylation of 3mol.% or less, the degree of butyralation of 65mol.% or more, the flow softening point of 200 deg.C or higher, epoxy resin B, microcapsulated imidazole derivative epoxy compound C, solvent D and electroconductive particle E prepared by putting metal covering onto the surface of polymer spherical nuclear material. A paste-like mixture, the mixing ratio in weight of the above components of which satisfies the relationship: A/(B+C)=(10-50)/1,000, is cast on a releasing film and turned into a film by volatilizing solvent.

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, and more particularly to LCD (liquid crystal display).
Connection with a flexible circuit board or TAB film,
The present invention relates to an anisotropic conductive film used for micro-joining a semiconductor IC and an IC-mounted circuit board.

[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 are beginning to be used. (For example, JP-A-59-120436, 6
0-191228, 61-274394, 61-287
974, 62-244242, 63-153534,
63-305591, 64-81878, JP-A 1-4
6549, 1-25178, etc.). Due to the further miniaturization of parts, the connected members that have been connected once due to misalignment or the like in the connection work between the circuits using anisotropic conductive films are peeled and re-pressed without being damaged or damaged (so-called. "Adhesion" is required, the shrinkage of the anisotropic conductive film during the thermosetting reaction and the strain stress of the resin itself in various atmospheres damage the adherend (eg LCD Problems such as cracks in the glass substrate used and warpage of the substrate have arisen.
In order to solve these problems, there is a strong demand for a highly reliable thermosetting anisotropic conductive film having fast curing, long life, moisture resistance, and low distortion.

[0003]

SUMMARY OF THE INVENTION The present invention enables connection in a short time, which was not possible with the conventional thermosetting type,
In addition, it has excellent storage stability at room temperature, has excellent adhesiveness in a wide temperature range (-40 ° C to 100 ° C) after being heated and pressed and cured, and has very little strain (stress) remaining in the joint. It is intended to provide a thermosetting type different conductive film which is small and which can be peeled and re-bonded by heating a pressure-bonded product to a predetermined temperature or higher.

[0004]

The present invention provides a polyvinyl butyral resin (A), an epoxy resin (B) having a naphthalene skeleton, a microencapsulated imidazole derivative epoxy compound (C), a solvent (D) and a polymer spherical nucleus. In a anisotropic conductive film formed by casting a paste-like mixture composed of conductive particles (E) having a metal coating on the surface of a material on a release film and volatilizing the solvent to form a film, the weight ratio of (A) / [ (B) + (C)] = (10-50) / 100
And the degree of polymerization of the polyvinyl butyral resin is 150
An anisotropic conductive film having a acetylation degree of 0 to 2500, an acetylation degree of 3 mol% or less, a butyralization degree of 65 mol% or more, and a flow softening point of 200 ° C. or more.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyvinyl butyral resin used in the present invention has a polymerization degree of 1500 to 2500, an acetylation degree of 3 mol% or less, a butyralization degree of 65 mol% or more, and a flow softening point of 200 ° C. or more. . Degree of polymerization is 150
When it is 0 or less, the resin fluidity at the time of heating and pressurization is large and the adhesive force becomes insufficient. Further, when the degree of polymerization is 2500 or more, the fluidity of the resin is insufficient, and therefore the conductive particles cannot contact the terminals, and the conductivity cannot be obtained. If the degree of acetylation is 3 mol% or more, the compatibility with the adherend (LCD glass substrate or TAB film) deteriorates and the adhesive strength becomes insufficient. If the degree of butyralization is 65 mol% or less, the content of polyvinyl alcohol and polyvinyl acetate in the molecule increases and the adhesive strength becomes insufficient. Further, if the flow softening point is less than 200 ° C., the resin fluidity at the time of heating and pressurization will be large and the inclusion of air bubbles will become large, resulting in insufficient adhesive strength.

The epoxy resin used in the present invention is, for example, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol S type epoxy resin, which has at least two epoxy groups in one molecule. Examples thereof include phenol novolac type epoxy resin and cresol novolac type epoxy resin, which are not limited to these and may be used alone or in combination. Furthermore, in order to obtain high adhesiveness and excellent connection reliability in a wide temperature range (-40 to 100 ° C) after heating and pressurizing and curing, an epoxy resin having a naphthalene skeleton in the molecule is added to these epoxy resins. 1
It is preferable to add 0 to 80% by weight. In particular,
1,6-bis (2,3-epoxypropoxy) naphthalene, a condensate of 2,7-dihydroxynaphthalene and formaldehyde and a reaction product of epicudolhydrin, 2-hydroxynaphthalene and 2,7-dihydroxynaphthalene Examples thereof include a reaction product of a condensate with formaldehyde and epicudolhydrin. If the compounding amount is less than 10% by weight, the glass transition point of the cured product is low and the high temperature region (60 to
Adhesiveness and connection reliability at 100 ° C.) decrease, and when it exceeds 80% by weight, sufficient adhesive strength cannot be obtained at the initial elastic modulus of the cured product.

The microencapsulated imidazole derivative epoxy compound used in the present invention is a microencapsulated product obtained by reacting an isocyanate compound with a reaction product of an imidazole derivative and an epoxy compound, and is commercially available. is there. It is also preferable that this has improved chemical resistance and storage stability. Examples of the epoxy compound used here include glycidyl ether type epoxy resins such as bisphenol A, phenol novolac, bisphenol F, and brominated bisphenol A, diglyceryl dimer acid, diglycidyl phthalate ester, and the like. Examples of the imidazole derivative include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole and 1-benzyl-. 2-methylimidazole, 1-benzyl-2-ethylimidazole, 1-benzyl-2-ethyl-5-methylimidazole, 2-phenyl-4-methyl-5-hydroxydimethylimidazole, 2-phenyl-4,5
Examples thereof include dihydroxymethylimidazole.

The epoxy resin (B) of the present invention and the microencapsulated imidazole derivative epoxy compound (C) which is a latent curing agent and the polyvinyl butyral resin (A).
Weight ratio (A) / [(B) + (C)] = (10-5
0) / 100, which varies depending on the target workability, reliability, etc., but when the polyvinyl butyral resin is less than 10 parts by weight, the initial adhesive force (adhesive force) is insufficient, and when an anisotropic conductive film is used. , The fluidity at the time of melting is large, and the inclusion of bubbles is large. Also, regarding the so-called repairability, which has recently become more necessary, if it is less than 10 parts by weight, the resin softening temperature after curing is high and a high temperature is required at the time of peeling,
It becomes difficult to remove the resin component remaining on the adherend. 5
If the amount exceeds 0 parts by weight, the adhesive strength is sufficient, but the viscosity at the time of melting is high and the fluidity of the resin is insufficient, so that the conductive particles may not be able to contact the terminals and the conductivity may not be obtained. Furthermore, although workability such as repairability is relatively good, compatibility with epoxy resin components, heat resistance, and moisture resistance are insufficient.

The conductive particles having a metal coating on the surface of the polymeric spherical core material have a nickel film on the surface of the polymeric spherical core material, and a gold film as an outer layer of the nickel film. Is a conductive particle having a phosphorus content of 2 to 20% by weight. The gold film and the nickel film on the surface of the conductive particles are not particularly limited except that the phosphorus content in nickel is 2 to 20% by weight. For example, the thickness of the film is not particularly limited, but if it is too thin, the conductivity becomes unstable, and if it is too thick, particle deformation becomes difficult or agglomeration occurs. Therefore, the thickness of each film is 0.01 to 1 μm. Is preferred. In addition, in the method of forming the film, it is preferable that the film is formed uniformly in consideration of the adhesion force and conductivity between the film and the polymeric spherical core material serving as the central nucleus. Is desirable. Phosphorus content in nickel film is 0.5% by weight
When an anisotropic conductive film is formed using conductive particles coated with less than less than the conductive particles, the dispersibility of the conductive particles deteriorates and agglomeration occurs, and the conductive particles reduce the insulation between adjacent terminals and lead to a short circuit. In some cases, there are restrictions on fine circuit connections. On the other hand, when it exceeds 20% by weight, the dispersibility is improved, but the conductivity is lowered, the connection resistance value is increased, and the long-term connection reliability is also lowered.

The diameter of the conductive particles having a metal coating on the surface of the polymeric spherical core material used in the present invention is 3 to 15 μm,
The average particle size is preferably 5 to 10 μm. If the particle size is less than 3 μm and the average particle size is less than 5 μm, it is close to the size of the irregularities on the surface of the circuit to be connected, and variations in the circuit thickness cannot be absorbed during thermocompression bonding, which causes an increase in connection resistance and open defects. Also, the particle size exceeds 15 μm, and the average particle size is 1
If it exceeds 0 μm, when the circuit pitch (circuit width + circuit interval) is 0.1 mm or less, particles may come into contact with each other between adjacent circuits, resulting in deterioration of insulation between adjacent circuits and a risk of short circuit. is there. The optimum value may be selected depending on the circuit terminal pitch, terminal thickness variation, etc., to be connected within these ranges. For example, liquid crystal display panels and flexible circuit boards (hereinafter referred to as F
In the case of connection with PC), the particle diameter of the conductive particles having a metal coating is about 3 to 15 μm, and the compounding amount with respect to the insulating adhesive is preferably 0.5 to 10% by volume.

The conductive particles having a metal coating on the surface of the polymeric spherical core material have a compressive fracture strength of 10 to 100 kg / mm ² .
The compressive elastic modulus is 100 to 1000 kg / mm ² . Compressive fracture strength less than 10 kg / mm ² and compressive elastic modulus 100 kg
If it is less than / mm ² , the particles will be destroyed before electrical connection can be made and connection cannot be made. The compressive breaking strength is 100kg
/ Mm ² and the compression elastic modulus exceeds 1000 kg / mm ² , excessive pressure must be applied to obtain a sufficient area for connecting terminals and the adherend will be damaged. Cause. Since the degree of crushing of the metal-coated particles after thermocompression bonding affects various characteristics such as connection reliability, the compressive fracture strength is 10 to 100 kg / mm ² , and the compressive elastic modulus is 100 to 1000 k.
Must be g / mm ² .

The composition of the polymeric spherical core material is not particularly limited, but examples thereof include polymers such as epoxy resin, urethane resin, melamine resin, phenol resin, acrylic resin, polyester resin, styrene resin and styrene-butadiene copolymer. These may be used alone or as a mixture. For metal coating, Au, Ni, Ag,
Cu, Zn, Sn, In, Al, Pd and the like are mentioned, and these may be combined. Appropriate materials may be selected for the polymeric spherical core material and the metal coating in consideration of the adhesion between the two. The thickness of the metal coating is not particularly limited,
If it is too thin, the conductivity becomes unstable, and if it is too thick, it becomes difficult to deform the particles or agglomerates occur.
The degree is preferred. Further, it is desirable that it is uniformly coated by electroless plating or the like. The amount of conductive particles added is preferably 0.1 to 10% by volume with respect to the total amount of the resin.
If it is less than 0.1% by volume, the connection area is reduced, so that the connection reliability is lowered, and conversely, if it is more than 10% by volume, the insulating property between the adjacent terminals is reduced, which causes a short circuit.

The solvent used in the present invention is acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, xylene, n-butyl alcohol, ethyl acetate, butyl acetate, tetrahydrofuran, methyl cellosolve, ethyl cellosolve, diacetone ether, methyl cellosolve acetate. , Ethyl cellosolve acetate, dimethylformamide, etc. are used, but the stability of each compounding formulation is examined because the size of the polarity affects the resin stability after compounding, and the compounds are used alone or as a mixture.

Next, the characteristics required of the release film which is a carrier of the anisotropic conductive film are heat resistance, releasability, and a certain degree of adhesion which balances with the releasability. Since it greatly affects the properties, it is necessary to select the compounding formulation appropriately. As the release film, there are polyester film, polymethylpentene film, fluorine film, etc. Among them, the fluorine film has sufficient heat resistance under the use conditions and is coated with an epoxy resin having strong adhesion. It is preferable because it maintains sufficient adhesion and releasability to the film. Depending on the composition of the adhesive, one having a good workability is appropriately selected and used from various fluorine-based films.

An anisotropic conductive film is prepared by appropriately mixing the resin mixture selected and adjusted as described above and conductive particles, mixing and stirring, and casting on a release film. Various additives, such as non-reactive diluents and reactivity, aiming at various properties such as solubility, stability, workability such as wettability with release film, surface viscosity during film formation, adhesion, etc. Diluents, thixotropic agents, thickeners, inorganic fillers and the like may be added appropriately.

[0016]

EXAMPLES The present invention will be specifically described with reference to Examples. Example 1 As a reactive elastomer, a polymerization degree of 170
0, acetylation degree 3 mol% or less, butyralization degree 65 m
175 parts by weight of a 10 wt% solution obtained by dissolving a polyvinyl butyral resin having an ol% or more and a flow softening point of 225 ° C. in a toluene / ethyl acetate = 5: 1 (weight ratio) mixed solution, and a bisphenol A type epoxy resin (Epoxy equivalent 4,000 g / eq) toluene / butyl acetate = 3: 1
35 parts by weight of mixed solution 50 parts by weight solution, 15 parts by weight of 1,6-bis (2,3-epoxypropoxy) naphthalene, 100 parts by weight of microencapsulated imidazole derivative epoxy compound {(A) / [(B) + (C)] = 13.2 / 10
0} is rapidly stirred and mixed, and conductive particles (average particle 5 μm) obtained by plating polystyrene spherical core material with Ni / Au
m, phosphorus content in nickel film 10D wt%) 4g,
After being uniformly dispersed, toluene was added, and the mixture was cast and dried on a 4-fluoroethylene-perfluoroalkylvinylether copolymer film so that the thickness after drying was 25 μm to obtain an anisotropic conductive film.

<Examples 2 and 3> As an epoxy resin having a naphthalene skeleton, in Example 2, a reaction product of a condensate of 2,7-dihydroxynaphthalene and formaldehyde and epicudorhydrin, and in Example 3, 2 An anisotropic conductive film was obtained in the same manner as in Example 1 except that a condensate of -hydroxynaphthalene, 2,7-dihydroxynaphthalene and formaldehyde, and a reaction product of epicudrhydrin were used.

Example 4 As a reactive elastomer,
Polyvinyl butyral resin having a degree of polymerization of 1700, an acetylation degree of 3 mol% or less, a butyralization degree of 65 mol% or more, and a flow softening point of 225 ° C. is toluene / ethyl acetate = 5: 1.
(Weight ratio) 100 parts by weight of a 10% by weight solution obtained by dissolving in a mixed solution, 50% by weight of a mixed solution of bisphenol A type epoxy resin (epoxy equivalent: 4,000 g / eq) in toluene / butyl acetate = 3: 1 108 parts by weight of solution,
46 parts by weight of 1,6-bis (2,3 epoxypropoxy) naphthalene and 100 parts by weight of microencapsulated imidazole derivative epoxy compound {(A) / [(B) + (C)] =
An anisotropic conductive film was obtained in the same manner as in Example 1 except that 5.0 / 100} was used. Example 5 As a reactive elastomer, a polymerization degree of 170
0, acetylation degree 3 mol% or less, butyralization degree 65 m
500 parts by weight of a 10 wt% solution obtained by dissolving a polyvinyl butyral resin having a flow softening point of 225 ° C. or more in a toluene / ethyl acetate = 5: 1 (weight ratio) mixed solution is added to a bisphenol A type epoxy resin. (Epoxy equivalent 4,000 g / eq) toluene / butyl acetate = 3: 1
50 parts by weight of mixed solution 34 parts by weight solution, 15 parts by weight 1,6-bis (2,3 epoxypropoxy) naphthalene, 70 parts by weight microcapsulated imidazole derivative epoxy compound {(A) / [(B) + ( C)] = 49.0 / 100}
An anisotropic conductive film was obtained in the same manner as in Example 1 except that was used. << Examples 6 and 7 >> In Example 6, polystyrene spherical core material as conductive particles was plated with Ni / Au (phosphorus content in nickel film was 5% by weight). In Example 7, phosphorus content in nickel film was 20% by weight. An anisotropic conductive film was obtained in the same manner as in Example 1 except that was used.

Comparative Examples 1 and 2 In Comparative Example 1 as a reactive elastomer, the polymerization degree is 300, the acetylation degree is 3 mol% or more, the butyralization degree is 63 ± 3 mol%, and the flow softening point is 11.
Polyvinyl butyral at 5 ° C. was used in Comparative Example 2 to obtain a polymerization degree of 1,
000, degree of acetylation 3 mol% or less, degree of butyral 7
An anisotropic conductive film was obtained in the same manner as in Example 1 except that polyvinyl butyral resin having 0 mol% and a flow softening point of 160 ° C. was used. << Comparative Example 3 >> A reactive elastomer was not used, and a bisphenol A type epoxy resin (epoxy equivalent: 4,000 g /
eq) toluene / butyl acetate = 3: 1 mixed solution 50% by weight 34 parts by weight solution, 1,6-bis (2,3-epoxypropoxy) naphthalene 15 parts by weight, microencapsulated imidazole derivative epoxy compound 70 parts by weight An anisotropic conductive film was obtained in the same manner as in Example 1 except that the parts {(A) / [(B) + (C)] = 0/100} were used.

Comparative Example 4 As a reactive elastomer,
Polyvinyl butyral resin having a degree of polymerization of 1700, an acetylation degree of 3 mol% or less, a butyralization degree of 65 mol% or more, and a flow softening point of 225 ° C. is toluene / ethyl acetate = 5: 1.
(Weight ratio) 600 parts by weight of a 10% by weight solution obtained by dissolving in a mixed solution was mixed with 50 parts by weight of a mixed solution of bisphenol A type epoxy resin (epoxy equivalent: 4,000 g / eq) in toluene / butyl acetate = 3: 1. % Solution of 34 parts by weight and 1,6
-Bis (2,3-epoxypropoxy) naphthalene 15
And 70 parts by weight of the microcapsulated imidazole derivative epoxy compound {(A) / [(B) + (C)] = 58.8 /
An anisotropic conductive film was obtained in the same manner as in Example 1 except that 100} was used. Comparative Example 5 An anisotropic conductive film was obtained in the same manner as in Example 1 except that 15 parts by weight of bisphenol A type epoxy resin (epoxy equivalent of 500 g / eq) was used instead of the epoxy resin having a naphthalene skeleton. . << Comparative Examples 6 and 7 >> In Comparative Example 5, polystyrene spherical core material as conductive particles was plated with Ni / Au (phosphorus content in nickel film: 0% by weight). In Comparative Example 6, phosphorus content in nickel film: 30% by weight. An anisotropic conductive film was obtained in the same manner as in Example 1 except that% was used.

<< Evaluation Method >> The anisotropic conductive films obtained in these Examples and Comparative Examples were evaluated for storage stability, adhesive strength, repairability and long-term reliability. The results are shown in Tables 1 and 2. Show. The anisotropic conductive films used as the test pieces all had a thickness of 25 μm, and the adherends were TAB (pitch 0.10 mm, number of terminals 200 with tin plating of 0.4 μm on copper foil / polyimide = 35/75 μm). And an indium / tin oxide conductive film having a sheet resistance value of 30 Ω and having a thickness of 1.1 mm (hereinafter referred to as ITO glass). -Storage stability: After the anisotropic conductive film was left at room temperature (23 ° C) and 40 ° C, it was confirmed that the anisotropic conductive film was melted on a hot plate of 120 ° C, and the sample was used to connect TAB and ITO glass. In this case, if the initial connection resistance value was 2Ω or less at all terminals, it was evaluated as ○, and if it exceeded 2Ω, it was evaluated as ×. -Adhesive strength: evaluated by a 90 ° peel test. Repairability: A test piece that was once joined by thermocompression bonding was heated to 150 ° C. on a hot plate and peeled off, and it was observed whether the connected member could be peeled off without damage. *: Peeled without any damage, ○: Peeled without damage, X: Damaged when peeled.・ Connection reliability: -40 ° C / 30 minutes, 25 ° C / 5 minutes, 80
250 ° C / 30 minutes, 25 ° C / 5 minutes temperature cycle test
After cycling, the connection resistance between adjacent terminals was measured. Those whose resistance could not be measured were regarded as poor conduction (OPEN).

Table 1 Example 1 2 3 4 5 6 7 Storage stability Room temperature ○ ○ ○ ○ ○ ○ ○ 40 ℃ ○ ○ ○ ○ ○ ○ ○ Adhesion room temperature 790 730 680 640 930 810 800 (g / cm) 60 ℃ 830 870 840 740 820 720 840 Repairability ○ ○ ○ ○ ※ ○ ○ Connection reliability Initial 1.4 1.5 1.4 1.3 1.9 1.7 1.6 (Ω) After processing 1.8 1.8 2.0 1.7 2.6 2.1 2.0

Table 2 Comparative Example 1 2 3 4 5 6 7 Storage stability Room temperature ○ ○ ○ × ○ ○ ○ 40 ℃ ○ ○ ○ × ○ ○ ○ Adhesive strength Room temperature 400 890 820 470 520 740 760 (g / cm) 60 ℃ 430 680 540 280 300 820 790 Repairability ○ ○ ○ ※ ○ ○ ○ Connection reliability Initial 1.7 3.9 1.8 2.4 3.1 OPEN OPEN (Ω) After processing 2.4 OPEN 2.7 OPEN OPEN OPEN OPEN OPEN

[0025]

EFFECTS OF THE INVENTION According to the present invention, it can be used for fine micro-bonding with a pitch of 0.05 or less, and has a very good balance of adhesion and workability and high reliability.
An anisotropic conductive film having a low connection resistance was obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C09J 163/00 JFP C09J 163/00 JFP H01B 5/16 H01B 5/16 H01R 4/04 H01R 4 / 04 // H05K 3/36 H05K 3/36 A B29K 25:00 303: 06 B29L 7:00

Claims (3)

[Claims] 1. A polyvinyl butyral resin (A), an epoxy resin (A) having a polymerization degree of 1500 to 2500, an acetylation degree of 3 mol% or less, a butyralization degree of 65 mol% or more, and a flow softening point of 200 ° C. or more. B), the microcapsulated imidazole derivative epoxy compound (C), the solvent (D), and the conductive particles (E) having a metal coating on the surface of the polymeric spherical core material as essential components, and the weight ratio is (A) / [(B) + (C)] = (10 to 50)
An anisotropic conductive film, characterized in that a paste-like mixture of 100/100 is cast on a release film to volatilize a solvent to form a film. 2. The conductive particles have a nickel film on the surface of the polymeric spherical core material, and further have a gold film on the outer layer of the nickel film,
The anisotropic conductive film according to claim 1, wherein the phosphorus content in the nickel film is 2 to 20% by weight. 3. The anisotropic conductive film according to claim 1, wherein the epoxy resin contains 10 to 80% by weight of an epoxy resin having a naphthalene skeleton in the molecule.