JP3480754B2 - Method for producing anisotropic conductive film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical connection between fine circuits, more specifically, a connection between an LCD (Liquid Crystal Display) and a flexible circuit board or a TAB film. The present invention relates to a method for manufacturing an anisotropic conductive film used for micro-joining a semiconductor IC and an IC-mounted circuit board. 2. Description of the Related Art With the recent miniaturization and thinning of electronic equipment, the necessity of connection between minute circuits, connection between minute parts and minute circuits, etc. has been dramatically increased. As a method, anisotropic conductive adhesives and films have begun to be used (for example, see JP-A-59-120436, 60-A).
191228, 61-274394, 61-28797
4, 62-244242, 63-153534, 63-
305591, 64-81878, JP-A-1-4654
9, 1-25178, etc.). Further miniaturization of parts has progressed, and in connection work between circuits using an anisotropic conductive film associated therewith, the connected members once connected without being damaged or damaged due to misalignment or the like are separated and re-pressed (so-called). Damage to the adherend (for example, LCDs) due to the need for “repair”), cure shrinkage during the thermosetting reaction of the anisotropic conductive film, and the strain stress of the resin itself in various atmospheres. There is a problem that the glass substrate used is cracked or the substrate is warped. 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] The present invention enables connection in a short time, which cannot be obtained with the conventional thermosetting type,
It also has excellent storage stability at room temperature, has excellent adhesion in a wide temperature range (-40 ° C to 100 ° C) after curing by heating and pressing, and has extremely small distortion (stress) remaining at the joint. Another object of the present invention is to provide a method for producing a thermosetting anisotropic conductive film which can be peeled off and re-pressed by heating the once-pressed one to a predetermined temperature or higher. According to the present invention, a polymerization degree of 15 is provided.
00 to 2500, acetylation degree is 3 mol% or less, butyralization degree is 65 mol% or more, and flow softening point is 200
Having a nickel film on the surface of a polyvinyl butyral resin (A), an epoxy resin (B), a microencapsulated imidazole derivative epoxy compound (C), a solvent (D), and a polymer spherical nucleus material having a characteristic of not less than ℃. A conductive film (F) having a gold film as an outer layer of the nickel film and having a phosphorus content of 2 to 20% by weight in the nickel film as an essential component;
And the weight ratio is (A) / ((B) + (C)) = (1)
0-50) is a method for producing the anisotropic conductive film of pasty mixture film made to volatilize cast solvent flow on releasing the film is / 100. The degree of polymerization of the polyvinyl butyral resin used in the present invention is from 1500 to 2500.
If it is less than 500, the fluidity of the resin at the time of heating and pressurizing is large, and the adhesive strength becomes insufficient. On the other hand, if the degree of polymerization exceeds 2500, the fluidity of the resin is insufficient, so that the conductive particles cannot come into contact with the terminals and the conductivity cannot be obtained. The acetylation degree of the polyvinyl butyral resin is 3 mol% or less, but 3 mol%.
%, The compatibility with the adherend (LCD glass substrate or TAB film) becomes poor, and the adhesive strength becomes insufficient. The butyralization degree is 65 mol% or more, but if it is less than 65 mol%, the content of polyvinyl alcohol and polyvinyl acetate in the molecule increases, and the adhesive strength becomes insufficient. Further, the flow softening point of the polyvinyl butyral resin is 200 ° C. or higher, but if it is lower than 200 ° C., the fluidity of the resin at the time of heating and pressurization is large, so that bubbles are entrapped and the adhesive strength is insufficient.
The flow softening point was measured by using a Koka type flotte tester (CFT-500, manufactured by Shimadzu Corporation) and measuring 1 g of the sample at 80 ° C.
And the temperature at which the flow rate of the sample reaches 1.0 × 10 ^-3 ml / sec is read with a load of 100 kg / cm ² , an orifice of 1 mmφ × 10 mm, a heating rate of 6 ± 0.5 ° C. Let it be the flow softening point. The weight ratio of the polyvinyl butyral resin (A), the epoxy resin (B) and the microencapsulated imidazole derivative epoxy compound (C) as a latent curing agent is (A) / ((B) + (C)) = (10-50) / 10
0, depending on the target workability, reliability, etc., but when the polyvinyl butyral resin is less than 10 parts by weight,
When the initial adhesive strength (adhesive strength) is insufficient and the anisotropic conductive film is further formed, the flowability at the time of melting is large and the inclusion of bubbles is large. In addition, the so-called repairability, whose necessity has been increasing recently, is less than 10 parts by weight, so that the resin softening temperature after curing is high, a high temperature is required at the time of peeling, and the resin component remaining on the adherend is removed. It becomes difficult. If it exceeds 50 parts by weight, the adhesive strength is sufficient, but the viscosity at the time of melting is high,
The fluidity of the resin is insufficient, so that the conductive particles may not be able to come into contact with the terminals, and thus the conductivity may not be obtained. Furthermore, workability such as repairability is relatively good, but compatibility with epoxy resin components, heat resistance, and moisture resistance are insufficient. The epoxy resin used in the present invention has at least two or more epoxy groups in one molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin And cresol novolak type epoxy resin, and the like, but not limited thereto, and they may be used alone or in combination. The microencapsulated imidazole derivative epoxy compound used in the present invention is a product obtained by microencapsulating a reaction product of an imidazole derivative and an epoxy compound into a fine powder, which is commercially available.
Further, those obtained by reacting a microencapsulated imidazole derivative epoxy compound with an isocyanate compound to enhance chemical resistance and storage stability are also suitable. Examples of the epoxy compound used herein include phenol novolak resins, glycidyl ether type epoxy resins such as bisphenol A, bisphenol F and brominated bisphenol A, diglycidyl dimer acid ester, and diglycidyl phthalate ester. Examples of the imidazole derivative include, for example, imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-
Methylimidazole, 1-benzyl-2-ethylimidazole, 1-benzyl-2-ethyl-5-methylimidazole, 2-phenyl-4-methyl-5-hydroxydimethylimidazole, 2-phenyl-4,5-dihydroxymethyl And imidazole. The conductive particles used in the present invention have a nickel film on the surface of a polymer spherical core material, a gold film on the outer layer of the nickel film, and a phosphorous content in the nickel film of 2 to 20. % By weight. The gold film and the nickel film on the surface of the conductive particles have a phosphorous content in nickel of 2 to 20% by weight,
There is no particular limitation. 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. 1 μm is preferred.
In addition, in the method of forming the coating, it is preferable that the coating is uniformly formed in consideration of the adhesive force and conductivity between the coating and the polymer spherical core material serving as the central nucleus. Is desirable. When conductive particles coated with a phosphorous content of less than 2% by weight in a nickel film are used to form an anisotropic conductive film, dispersibility of the conductive particles deteriorates and aggregation occurs. Insulation between adjacent terminals may be reduced, resulting in a short circuit, and there is a restriction on fine circuit connection. Conversely, if it exceeds 20% by weight,
Although the dispersibility is improved, the conductivity is reduced, the connection resistance value is increased, and there is a problem that the long-term connection reliability is reduced. The particle size of the conductive particles used in the present invention is 3 to 15
If the average 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 the variation in the circuit thickness cannot be absorbed during thermocompression bonding. This causes an increase in connection resistance and an open defect.
If the particle size exceeds 15 μm and the average particle size exceeds 10 μm, the particles will contact between adjacent circuits when the circuit pitch (circuit width + circuit interval) is applied to 0.1 mm or less, and insulation between adjacent circuits will occur. There is a danger of deterioration or short circuit. An optimum value may be selected depending on the circuit terminal pitch, terminal thickness variation and the like to be connected within these ranges. For example,
In connection between a liquid crystal display panel and a flexible circuit board (hereinafter, referred to as FPC), which is a main use of an anisotropic conductive film, the conductive particles having a metal coating have a particle size of 3-1.
It is preferably about 5 μm, and the blending amount with respect to the paste mixture is preferably 0.5 to 10% by volume. The compressive breaking strength of the conductive particles is 10 to 10
0 kg / mm ² , compression modulus is 100-1000 kg /
mm ² . If the compression breaking strength is less than 10 kg / mm ² and the compression modulus is less than 100 kg / mm ² , the particles are broken before electrical connection is obtained, and connection cannot be made.
If the compression breaking strength exceeds 100 kg / mm ² and the compression modulus exceeds 1000 kg / mm ² , excessive pressure must be applied to obtain a sufficient area for connecting the terminals. This may damage the body. Since the degree of crushing of the metal-coated particles after thermocompression bonding affects various characteristics such as connection reliability, the compression breaking strength is 10 to 100 kg /
mm ² , and the compression modulus is required to be 100 to 1000 kg / mm ² . The composition of the polymer spherical core material is not particularly limited, and examples thereof include polymers such as epoxy resins, urethane resins, melamine resins, phenol resins, acrylic resins, polyester resins, polystyrene resins, and styrene-butadiene copolymers. These may be used alone or as a mixture. Solvents used in the present invention include acetone, methyl ethyl kent, methyl isobutyl ketone, toluene, xylene, n-butyl alcohol, ethyl acetate, butyl acetate, tetrahydrofuran, methyl cellosolve, ethyl cellosolve, diacetone ether, methyl cellosolve acetate, and ethyl cellosolve. Acetate, dimethylformamide and the like can be mentioned, but the stability of the resin after compounding is influenced by the magnitude of the polarity. Next, the properties required for the release film as the carrier of the anisotropic conductive film are heat resistance, release properties, and a certain degree of adhesion balanced with the release properties, but the workability of the anisotropic conductive film is greatly increased. Since it depends, it is necessary to appropriately select the compounding formulation. Examples of the release film include a polyester film, a polymethylpentene film, a fluorine film, and the like.Among these, the fluorine film has sufficient heat resistance under use conditions, and also has a strong adhesive epoxy resin. It is preferable because sufficient adhesion and releasability are maintained for the coating film. Depending on the composition of the adhesive, a material having good workability is appropriately selected and used from various fluorine-based films. The anisotropic conductive film is prepared by appropriately blending the resin composition and the conductive particles selected and adjusted as described above, mixing and stirring, and casting the mixture on a release film. Various additives such as non-reactive diluent, reactive diluent, and thixotropic, aiming at various properties such as workability such as wettability with the release film and wettability with the release film, and surface viscosity and adhesion during film formation. An imparting agent, a thickening agent, an inorganic filler and the like may be appropriately added. The present invention will be described in detail with reference to embodiments. Example 1 As a reactive elastomer, a polyvinyl butyral resin having a degree of polymerization of 1700, a degree of acetylation of 3 mol% or less, a degree of butyralization of 65 mol% or more, and a flow softening point of 225 ° C. was mixed with toluene / ethyl acetate = 5: 1 (weight ratio). 100 parts by weight of a 10% by weight solution obtained by dissolving in a solution is mixed with a bisphenol A-type epoxy resin (epoxy equivalent: 4000).
/ Eq) of toluene / butyl acetate = 3: 1 (weight ratio), 50 parts by weight of a 50% by weight solution, and 50 parts by weight of a microencapsulated imidazole derivative epoxy compound are rapidly stirred and mixed, and the resulting mixture is mixed with a polystyrene sphere. Addition of 3 parts by weight of nickel / gold plated conductive particles (phosphorus content in nickel film: 10% by weight) to the core material, uniform dispersion, further addition of toluene, 4-fluoroethylene-perfluoroalkyl vinyl ether copolymer The film was cast and dried to a thickness of 25 μm after drying to obtain an anisotropic conductive film. Example 2 As a reactive elastomer, a 10% by weight solution obtained by dissolving a polyvinyl butyral resin having a degree of polymerization of 2350, a degree of acetylation of 3 mol% or less, a degree of butyralization of 65 mol% or more, and a flow softening point of 230 ° C. in ethyl acetate. 10
An anisotropic conductive film was obtained in the same manner as in Example 1 except that 0 parts by weight was used. Example 3 A mixed solution of a polyvinyl butyral resin having a degree of polymerization of 1700, a degree of acetylation of 3 mol% or less, a degree of butyralization of 65 mol% or more, and a flow softening point of 225 ° C. as toluene / ethyl acetate = 5: 1 (weight ratio) as a reactive elastomer. 100 parts by weight of a 10% by weight solution obtained by dissolving in a bisphenol A type epoxy resin (an epoxy equivalent of 4000 g).
/ Eq) of toluene / butyl acetate = 3: 1 (weight ratio) 50% by weight of a mixed solution 100 parts by weight of a solution and a microencapsulated imidazole derivative epoxy compound 50 parts by weight were used in the same manner as in Example 1. An anisotropic conductive film was obtained. Example 4 As a reactive elastomer, a polyvinyl butyral resin having a degree of polymerization of 1700, a degree of acetylation of 3 mol% or less, a degree of butyralization of 65 mol% or more, and a flow softening point of 225 ° C. was mixed with toluene / ethyl acetate = 5: 1 (weight ratio). 500 parts by weight of a 10% by weight solution obtained by dissolving in a solution is mixed with a bisphenol A type epoxy resin (an epoxy equivalent of 4000).
/ Eq) of toluene / butyl acetate = 3: 1 (weight ratio): 50 parts by weight of a 50% by weight solution and 50 parts by weight of a microencapsulated imidazole derivative epoxy compound were used in the same manner as in Example 1. Thus, an anisotropic conductive film was obtained. Examples 5 and 6 In Example 5, nickel / gold plating was performed on polystyrene spherical core material as conductive particles (phosphorus content in nickel film: 5% by weight). In Example 6, phosphorus content in nickel film was 20%.
An anisotropic conductive film was obtained in the same manner as in Example 1 except that the weight% was used. Comparative Examples 1 and 2 In Comparative Example 1, as the reactive elastomer, a degree of polymerization of 30 was used.
0, a polyvinyl butyral resin having a degree of acetylation exceeding 3 mol%, a butyral degree of 63 mol%, and a flow softening point of 115 ° C. In Comparative Example 2, a polymerization degree of 1000, an acetylation degree of 3 mol% or less, and a butyral degree of 70 mol
%, And an anisotropic conductive film was obtained in the same manner as in Example 1, except that a polyvinyl butyral resin having a flow softening point of 160 ° C. was used. Comparative Example 3 As a reactive elastomer, a polyvinyl butyral resin having a degree of polymerization of 1700, a degree of acetylation of 3 mol% or less, a degree of butyralization of 65 mol% or more, and a flow softening point of 225 ° C. was mixed with toluene / ethyl acetate = 5: 1 (weight ratio). 50 parts by weight of a 10% by weight solution obtained by dissolving in a solution was mixed with a bisphenol A type epoxy resin (epoxy equivalent 4000 /
eq) 100 parts by weight of a 50% by weight solution of a mixed solution of toluene / butyl acetate = 3: 1 (weight ratio) and 50 parts by weight of a microencapsulated imidazole derivative epoxy compound were used in the same manner as in Example 1. An anisotropic conductive film was obtained. Comparative Example 4 As a reactive elastomer, a polyvinyl butyral resin having a degree of polymerization of 1700, a degree of acetylation of 3 mol% or less, a degree of butyralization of 65 mol% or more, and a flow softening point of 225 ° C. was mixed with toluene / ethyl acetate = 5: 1 (weight ratio). 1000 parts by weight of a 10% by weight solution obtained by dissolving in a solution,
Bisphenol A type epoxy resin (epoxy equivalent 400
0 / eq) toluene / butyl acetate = 3: 1 (weight ratio)
An anisotropic conductive film was obtained in the same manner as in Example 1 except that 100 parts by weight of a mixed solution of 50% by weight of the above solution and 50 parts by weight of a microencapsulated imidazole derivative epoxy compound were used. Comparative Examples 5 and 6 In Comparative Example 5, nickel / gold plating was performed on a polystyrene spherical core material as conductive particles (phosphorus content in nickel film: 0% by weight). In Comparative Example 6, phosphorus content in nickel film was 30%.
An anisotropic conductive film was obtained in the same manner as in Example 1 except that the weight% was used. With respect to the anisotropic conductive films obtained in these Examples and Comparative Examples, the results of evaluating the storage stability, adhesive strength, repairability, and connection reliability are shown in Tables 1 and 2.
Shown in Evaluation method The thickness of the anisotropic conductive film used as the test piece was 25
μm. Storage preservation: Anisotropic conductive film is kept at room temperature (23 ° C.)
After leaving at 0 ° C., it was confirmed that the sample melted on a hot plate at 120 ° C. Further, using this test piece, TAB and sheet resistance 30
When a 1.1 mm-thick glass (hereinafter referred to as ITO glass) having an indium / tin oxide conductive film of Ω formed on the entire surface is connected, the initial connection resistance value is 2 at all terminals.
If it was less than Ω, it was evaluated as ○, and if it exceeded 2 Ω, it was evaluated as ×. Adhesion: Evaluated by a 90 ° peel test. As an adherend, copper foil / polyimide = 35/75 μm 0.4
TAB with tin plating of μm (pitch 0.10 mm,
(200 terminals) and ITO glass were used. Repairability: The test piece once bonded by thermocompression 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. Connection reliability: -40 ° C / 30 minutes, 25 ° C / 5 minutes, 80 ° C
After 250 cycles of a temperature recycle test at 25 ° C. for 5 minutes, the connection resistance between adjacent terminals was measured. [Table 1] [Table 2] According to the present invention, it is possible to obtain an anisotropic conductive film having an extremely good balance between adhesion and workability, high reliability and low connection resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification symbol FI H01B 5/16 H01B 5/16 H01R 11/01 501 H01R 11/01 501E (58) Fields surveyed (Int.Cl. ⁷ , DB Name) H01B 13/00 501 H01B 5/16 H01B 5/00 H01B 1/22 B29C 41/30 C08J 5/18 CFC H01R 11/01

Claims (1)

(57) [Claims 1] A polymerization degree is 1500 to 2500, an acetylation degree is 3 mol% or less, and a butyralization degree is 65 mol%.
As described above, the surface of the polyvinyl butyral resin (A), the epoxy resin (B), the microencapsulated imidazole derivative epoxy compound (C), the solvent (D), and the polymer spherical core material having a flow softening point of 200 ° C. or more are described. A conductive film (F) having a nickel film, a gold film as an outer layer of the nickel film, and a phosphorus content of 2 to 20% by weight in the nickel film as an essential component; (A) /
((B) + (C) ) = (10~50) pasty mixture production side of the anisotropic conductive film, characterized in that the membrane manufactured to volatilize cast solvent flow on releasing the film is / 100
Law .