JP2013014692A - Anisotropic conductive adhesive film and insulation coated conductive particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic conductive adhesive film which in a circuit connection using the anisotropic conductive adhesive film having a cationic curing type insulating adhesive layer, suppresses the rise of a connection resistance value while maintaining high insulating property in a non-pressurizing direction.SOLUTION: The anisotropic conductive adhesive film 10 includes: the insulating adhesive layer 7; and insulation coated conductive particles 5, dispersed in the insulating adhesive layer 7, and having conductive particles 3 with conductive metal surfaces and insulating fine particles 1 coating the conductive particles 3. The insulating adhesive layer 7 contains an epoxy resin and a cationic curing agent. In a DSC curve determined by the differential scanning calorimetry of the anisotropic conductive adhesive film 10, when a heat generation value of an exothermic peak with a peak temperature in the range of 100 to 150°C is represented by α, and a heat generation value of an exothermic peak with a peak temperature in the range of 200 to 250°C is represented by β, the anisotropic conductive adhesive film is characterized in that α and β satisfy inequality {α/(α+β)}×100≥60.

Description

  The present invention relates to an anisotropic conductive adhesive film and insulating coated conductive particles.

  The method of mounting the liquid crystal driving IC on the glass panel for liquid crystal display can be roughly classified into two types, COG (Chip-on-Glass) mounting and COF (Chip-on-Flex). In COG mounting, an IC for liquid crystal is directly bonded to a glass panel using an anisotropic conductive adhesive film containing conductive particles. On the other hand, in COF mounting, a liquid crystal driving IC is bonded to a flexible tape having metal wiring, and these are bonded to a glass panel using an anisotropic conductive adhesive film containing conductive particles. “Anisotropic conductivity” means maintaining electrical insulation in the non-pressurization direction while electrically connecting the connection terminals in the pressurization direction.

  In recent years, with the increase in definition of liquid crystal display, gold bumps, which are circuit electrodes of liquid crystal driving ICs, are required to have a narrow pitch and a small area. Under such circumstances, there is a problem that the conductive particles of the anisotropic conductive adhesive film flow out between adjacent circuit electrodes and cause a short circuit. In addition, when conductive particles flow out between adjacent circuit electrodes, the number of conductive particles in the anisotropic conductive adhesive film trapped between the gold bumps and the glass panel is reduced, and between the facing circuit electrodes Another problem is that connection resistance rises and connection failure occurs.

  Therefore, as a method for solving these problems, a method of coating the entire surface of the conductive particles with an insulating film (see Patent Document 1) and a method of coating the conductive particles with insulating fine particles (see Patent Documents 2 to 5). ) Has been proposed.

  The dispersibility of the conductive particles in the anisotropic conductive adhesive film is very important for improving the insulating properties. In order to maintain good dispersibility, a kneading method for applying a shearing force to the resin when blending the conductive particles and a method for improving the dispersibility by ultrasonic irradiation are employed. Therefore, it is desirable that the conductive particles coated with the insulating fine particles have the insulating particles adsorbed on the conductive particles with a high adsorption strength that does not drop off from an external impact. In order to obtain a high adsorption strength, methods have been proposed in which reactive functional groups such as ammonium groups and sulfonium groups are introduced into the surface of insulating fine particles to react with the surface of conductive particles (Patent Documents 4 and 5). .

Japanese Patent No. 2779409 Japanese Patent No. 2748705 JP 2009-259804 A International Publication No. 2003/025955 JP 2005-171096 A

  By the way, with the recent thinning of liquid crystal panels, mounting conditions are changing to low pressure and low temperature in order to reduce substrate warpage during mounting. As an insulating adhesive constituting an anisotropic conductive film used for low-temperature mounting, it is effective to employ a cationic curing insulating adhesive. For example, a cationic polymerization initiator is used as a low-temperature curing agent for epoxy resin.

  However, there is a problem that it is difficult to maintain a sufficiently low connection resistance value in a circuit connection using a conventional anisotropic conductive film using a cation curable insulating adhesive.

  Therefore, the present invention suppresses an increase in connection resistance value while maintaining high insulation characteristics in the non-pressurizing direction in circuit connection using an anisotropic conductive adhesive film having a cation curable insulating adhesive layer. The purpose is to do.

  The present invention includes an insulating adhesive layer, conductive particles having conductive metal surfaces dispersed in the insulating adhesive layer, and insulating coated conductive particles having insulating fine particles covering the conductive particles; The present invention relates to an anisotropic conductive adhesive film. The insulating adhesive layer contains an epoxy resin and a cationic curing agent. In the DSC curve obtained by differential scanning calorimetry of the anisotropic conductive adhesive film according to the present invention, the calorific value of the exothermic peak having a peak temperature in the range of 100 ° C to 150 ° C is α, and the peak temperature is 200 ° C to 250 ° C. Α and β satisfy the formula: {α / (α + β)} × 100 ≧ 60, where β is the calorific value of the exothermic peak in the range of ° C.

  According to the anisotropic conductive film of the present invention, in the circuit connection using the anisotropic conductive adhesive film having a cation curable insulating adhesive layer, while maintaining high insulation characteristics in the non-pressurizing direction. The increase in connection resistance value can be suppressed. A large value of {α / (α + β)} × 100 corresponds to the rapid progress of the cationic curing reaction at a lower temperature. If the curing reaction of the epoxy resin does not proceed sufficiently, the thermal expansion of the adhesive layer in a high-temperature and high-humidity environment increases, and it becomes impossible to maintain the flatness of the conductive particles, leading to an increase in connection resistance. It is believed that there is. As circuit members such as liquid crystal panels are made thinner, there is a tendency to reduce the amount of the cationic curing agent in order to suppress the warpage of the substrate. However, it is considered that when the value of {α / (α + β)} × 100 is large, the curing reaction sufficiently proceeds and the increase in connection resistance is sufficiently suppressed.

  The ratio of α to the calorific value obtained by differential scanning calorimetry with the insulating adhesive layer alone is preferably 68% or more. Thereby, a more excellent effect can be obtained particularly in connection reliability.

  In another aspect, the present invention relates to insulating coated conductive particles having conductive particles having a conductive metal surface and insulating fine particles covering the conductive particles. When 0.5 g of the insulating coated conductive particles according to the present invention is placed in 25 g of 100 ° C. pure water as an eluent for 10 hours, the ammonium ion concentration of the eluate is less than 100 ppm.

  The insulating coated conductive particles according to the present invention can be suitably used for constituting the anisotropic conductive film according to the present invention described above. Since the elution of ammonium ions is small, the value of {α / (α + β)} × 100 can be increased in the cationically curable anisotropic conductive adhesive film.

  The insulating coated conductive particles according to the present invention preferably further have a basic compound having a molecular weight of 100 or more adsorbed on the metal surface. This basic compound preferably has an amino group. Since the basic compound is adsorbed on the metal surface, the adsorption strength between the insulating fine particles and the conductive particles is increased. However, in the presence of a basic compound, the cationic compound may be trapped by the basic compound that has oozed into the adhesive, and the cationic curing reaction may be inhibited. However, according to the knowledge of the present inventors, when the molecular weight of the basic compound is 100 or more, exudation of such a basic compound (for example, ammonium ion) is suppressed. As a result, the cationic curing reaction can sufficiently proceed. And according to the anisotropic conductive film using the insulating coating conductive particles, {α / (α + β)} × 100 ≧ 60 can be easily satisfied.

  It is preferable that the conductive particles have a nickel layer that forms a metal surface, the metal surface has protrusions, and the particle size of the conductive particles is 2.0 to 4.0 μm.

  The insulating fine particles may include organic-inorganic hybrid particles composed of a copolymer containing silicon atoms, and a silane coupling agent having an epoxy group adsorbed on the surface of the organic-inorganic hybrid particles. preferable.

  According to the anisotropic conductive film according to the present invention, in the circuit connection using the anisotropic conductive adhesive film having a cationic curing type insulating adhesive layer, while maintaining high insulation characteristics in the non-pressurizing direction, An increase in connection resistance value can be suppressed. In addition, since the cationic curing reaction proceeds sufficiently even at a low temperature, it is difficult for the resin around the conductive particles to absorb moisture even under a high temperature and high humidity environment. Therefore, a decrease in insulation resistance value is also suppressed.

It is sectional drawing which shows one Embodiment of an anisotropically conductive adhesive film. It is sectional drawing which shows one Embodiment of the circuit connection method by an anisotropic conductive adhesive. It is sectional drawing which shows one Embodiment of a circuit connection structure.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a cross-sectional view showing an embodiment of an anisotropic conductive adhesive film. An anisotropic conductive adhesive film 10 shown in FIG. 1 contains a film-like insulating adhesive layer 7 and a plurality of insulating coated conductive particles 5 dispersed in the insulating adhesive layer 7.

  In the DSC curve obtained by differential scanning calorimetry of the anisotropic conductive adhesive film according to the present invention, the calorific value (first calorific value) of the exothermic peak whose peak temperature is in the range of 100 ° C. to 150 ° C. is α, Α and β satisfy the formula: {α / (α + β)} × 100 ≧ 60, where β is the calorific value (second calorific value) of the exothermic peak whose peak temperature is in the range of 200 ° C. to 250 ° C. .

  The differential scanning calorimetry for obtaining the first calorific value α and the second calorific value β is performed, for example, in the range of 40 ° C. to 250 ° C. at a temperature rising rate of 10 ° C./min. Differential scanning calorimetry provides a DSC curve that shows the relationship between heat flow and temperature. Measurement is performed on a measurement sample of about 10 mg cut from the anisotropic conductive adhesive film.

  The ratio of the first calorific value α to the calorific value γ determined by differential scanning calorimetry of the insulating adhesive layer 7 alone is preferably 68% or more. In the DSC curve of the insulating adhesive layer 7 alone, a single exothermic peak is usually observed. When two or more exothermic peaks are observed, the calorific value γ is the total calorific value thereof.

  The insulating adhesive layer 7 is made of a cationic curable thermosetting resin composition. Preferably, the insulating adhesive layer 7 contains an epoxy resin and a cationic curing agent.

  The insulating adhesive layer 7 preferably contains 3 to 15 parts by mass of a cationic curing agent with respect to 100 parts by mass of the epoxy resin. The cationic curable curing agent is preferably a latent curing agent. The cationic curing agent is selected from, for example, boron trifluoride-amine complex and sulfonium salt.

The insulating adhesive layer 7 preferably contains 20 to 30 parts by mass of an epoxy resin with respect to 100 parts by mass of the insulating adhesive layer. Examples of the epoxy resin include a bisphenol type epoxy resin derived from epichlorohydrin and bisphenol A, bisphenol F, bisphenol AD, etc., an epoxy novolak resin derived from epichlorohydrin and phenol novolac or cresol novolac, and a skeleton containing a naphthalene ring. And various epoxy compounds having two or more glycidyl groups in one molecule, such as naphthalene type epoxy resin having glycidyl, glycidylamine, glycidyl ether, biphenyl, and alicyclic. These can be used alone or in combination of two or more. These epoxy resins are preferably high-purity products in which impurity ions (Na ⁺ , Cl ^{− and the} like), hydrolyzable chlorine and the like are reduced to 300 ppm or less from the viewpoint of preventing electromigration.

  In order to reduce the stress after bonding or to improve the adhesiveness, the insulating adhesive layer 7 is made of rubber components such as butadiene rubber, acrylic rubber, styrene-butadiene rubber, and silicone rubber in addition to the above components. It can also be contained. The insulating adhesive layer 7 contains a filler, softener, accelerator, anti-aging agent, colorant, flame retardant, thixotropic agent, coupling agent, phenol resin, melamine resin, isocyanates, and the like. You can also

  From the viewpoint of film formability, the insulating adhesive layer 7 preferably contains a thermoplastic resin (film-forming polymer) such as a phenoxy resin, a polyester resin, or a polyamide resin. Mixing these film-forming polymers is also preferable from the viewpoint of reducing stress during curing of the reactive resin.

  The insulating coated conductive particles 5 include conductive particles 3 having a conductive metal surface and insulating fine particles 1 covering the conductive particles 3.

  When 0.5 g of the insulating coated conductive particles 5 is placed under pressure in 25 g of 100 ° C. pure water for 10 hours, the ammonium ion concentration of the eluate is preferably less than 100 ppm.

  The insulating fine particles 1 include organic-inorganic hybrid particles composed of a copolymer containing silicon atoms, and a silane coupling agent having an epoxy group adsorbed on the surface of the organic-inorganic hybrid particles. preferable. The insulating fine particles 1 having such a structure do not easily melt in an organic solvent such as toluene, ethyl acetate, methyl ethyl ketone or the like. Therefore, when mixing the insulating coated conductive particles with the adhesive component, the dispersibility of the insulating coated conductive particles in the anisotropic conductive film is improved by irradiating the resin with an ultrasonic wave in an organic solvent. be able to.

  The copolymer having silicon atoms constituting the organic-inorganic hybrid particle has, for example, an acrylic monomer having a (meth) acryl group, a hydrolyzable silyl group (for example, an alkoxysilyl group), and a radically polymerizable unsaturated group. It is a copolymer with a silyl compound. The acrylic monomer preferably comprises methacrylic acid and an acrylic acid alkyl ester. By adsorbing a silane coupling agent having an epoxy group and a hydrolyzable silyl group to the organic / inorganic hybrid particle, the epoxy group is introduced onto the surface of the insulating fine particles 1.

  Since the organic-inorganic hybrid particles composed of the copolymer contain a hydrolyzable silyl group, the hydrolyzable silyl group is hydrolyzed by the action of an acid or an alkali to produce a silanol group. Furthermore, silanol groups react with each other to form a crosslinked structure. Examples of the acid used for the hydrolysis include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as formic acid, acetic acid, p-toluenesulfonic acid, and trichloroacetic acid. Examples of the alkali include potassium hydroxide, sodium hydroxide, ammonia and amine. As a curing catalyst for advancing crosslinking, there are tin-based catalysts such as di-n-butyltin maleate and lauric acid-n-dibutyltin. It is preferable that the curing catalyst is removed by washing by centrifugation after crosslinking. The addition of the curing catalyst may be after particle synthesis or after centrifugation. Desirably, the curing catalyst is added after centrifugation.

  Since the insulating coated conductive particles 5 have the above-described configuration, aggregation of the insulating coated conductive particles is prevented. Furthermore, the insulating fine particles 1 are flattened when heated and pressurized. As a result, particularly excellent effects are achieved in terms of insulation between adjacent circuit electrodes and electrical connection between opposing circuit electrodes when the circuits are connected. Furthermore, it is advantageous in that there are few coating defects due to the insulating fine particles 1 and there are few coating variations.

  The conductive particles 3 may be metal particles made of only metal, or may be composite particles having organic or inorganic core particles and a metal layer covering the core particles. Among these, organic core particles and composite particles having a metal layer covering the organic core particles are preferable. The particle diameter of the conductive particles 3 is preferably 2.0 to 4.0 μm.

  The metal layer is, for example, at least one metal selected from gold, silver, copper, platinum, zinc, iron, palladium, nickel, tin, chromium, titanium, aluminum, cobalt, germanium, and cadmium, or ITO and solder. Various metal compounds. In particular, from the viewpoint of corrosion resistance, the metal layer preferably contains at least one metal selected from nickel, palladium, and gold. It is particularly preferable that the outermost layer of the metal layer is a nickel layer, particularly a nickel plating layer, and the metal surface of the conductive particles 3 is made of nickel.

  The metal surface of the conductive particle 3 preferably has a protrusion.

  As a method for forming a metal layer on the surface of the core particle, there are displacement plating, electroplating, sputtering and the like in addition to electroless plating.

  The organic core particles are not particularly limited, but, for example, acrylic resins such as polymethyl methacrylate and polymethyl acrylate, polyolefin resins such as polyethylene, polypropylene, polyisobutylene and polybutadiene, and copolymers of divinylbenzene and acrylic acid These particles can be used as organic core particles.

  The conductive particles 3 preferably have at least one surface functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an alkoxyl group, and an alkoxycarbonyl group. These surface functional groups include, for example, at least one selected from the group consisting of a mercapto group, a sulfide group, and a disulfide group on a conductive particle on which carboxybenzotriazole is adsorbed on the metal surface of the conductive particle and then adsorbed with benzotriazole. It can introduce | transduce easily by the method of making the compound which has group contact.

  It is preferable that a basic compound having a molecular weight of 100 or more is adsorbed on the metal surface of the conductive particles 3. In this case, the insulating fine particles 1 can be adsorbed to the conductive particles 3 through this basic compound.

  The basic compound preferably has an amino group, and more preferably has two or more amino groups. The more amino groups, the higher the adsorption strength between the insulating fine particles and the conductive particles.

  The molecular weight of the basic compound is preferably 100 or more, more preferably 1000 or more, still more preferably 10,000 or more, and even more preferably 50000 or more, from the point that it is difficult to fall off from the conductive particles and is difficult to elute into the insulating adhesive layer. is there. When the molecular weight of the basic compound is increased, the falling off of the insulating fine particles and the dropping of the basic compound itself are more effectively prevented. The molecular weight of the basic compound is usually 200000 or less.

  The amino group not only easily binds to the metal surface of the conductive particle, but also has high reactivity with the surface functional group of the conductive particle such as a carboxyl group. Further, a chemical bond is formed between the surface functional group of the conductive particle and the epoxy group on the surface of the insulating fine particle, and the bond between the conductive particle and the insulating fine particle becomes strong. As a result, the coating with the insulating fine particles becomes uniform, and the insulating fine particles are firmly held by the conductive particles. This is considered as a factor that prevents the insulating fine particles from falling off.

  The basic compound having an amino group is, for example, a polyamine selected from polyethyleneimine, pentaethylenehexamine, bis (hexamethylene) triamine, tetraethylenepentamine, hexamethylenediamine, and 1,5-diaminopentane. Among these, polyethyleneimine is preferable. Since polyethyleneimine has the highest charge density among polyamines, it can be firmly bonded to conductive particles having surface functional groups. Therefore, it is considered that the bond between the conductive particles having a surface functional group and the insulating fine particles covering the conductive particles can be further strengthened.

  The surface potential (zeta potential) of the conductive particles having a surface functional group and insulating fine particles having a hydroxyl group or the like on the surface is usually negatively charged as long as the pH is in a neutral region. When a basic compound having an amino group having a positive surface potential is adsorbed on the surface of the conductive particles, the amino group chemically bonds with the epoxy group of the insulating fine particles, and the insulating fine particles are more unlikely to peel off.

  Insulating coated conductive particles are, for example, insulating a conductive compound (preferably conductive particles having a surface functional group) with a basic compound attached to the metal surface and conductive particles with a basic compound attached to the metal surface. And a step of bringing the fine particles into contact with each other. By such a method, it is possible to produce insulating coated conductive particles with fewer coating defects and in which insulating fine particles are not easily detached.

  The anisotropic conductive adhesive film 10 includes, for example, a step of applying a liquid composition containing an insulating adhesive, insulating coated conductive particles, and an organic solvent for dissolving or dispersing them to a peelable substrate, And a step of removing the organic solvent at a temperature not higher than the activation temperature of the curing agent from the liquid composition thus obtained.

  As another embodiment, a paste-like anisotropic conductive adhesive containing the insulating adhesive and the insulating coated conductive particles 5 can also be suitably used for circuit connection.

  FIG. 2 is a cross-sectional view showing an embodiment of a circuit connection method using an anisotropic conductive adhesive film. As shown in FIG. 2, a first circuit member 20 having a substrate 21 and an electrode 22 provided on the substrate, and a second circuit member 30 having a substrate 31 and an electrode 32 provided on the substrate 31. Are disposed so that the electrodes 22 and 32 face each other, and the anisotropic conductive adhesive film 10 is disposed between the first circuit member 20 and the second circuit member 30. By heating and pressurizing the whole in this state, a connection structure 100 in which the first circuit member 20 and the second circuit member 30 are connected to each other as shown in the sectional view of FIG. 3 is obtained.

  Examples of these circuit members include a glass substrate, a tape substrate such as polyimide, a bare chip such as a driver IC, and a rigid package substrate.

  In the obtained connection structure 100, the insulating fine particles 1 are peeled off at the contact portions of the insulating coated conductive particles 5 with the electrodes, and the opposing electrodes are electrically connected. On the other hand, the insulating property is maintained by interposing the insulating fine particles 1 between adjacent electrodes on the same substrate.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these.

(Example 1, insulating coated conductive particles 1)
1. Conductive particles (nuclear particles)
10 g of plastic core particles having an average particle diameter of 2.6 μm made of a copolymer of divinylbenzene and acrylic acid having an adjusted degree of crosslinking were prepared. This plastic core particle has a carboxyl group on its surface. The hardness of the plastic core particles (compression modulus when the particle diameter was displaced by 20% at 200 ° C., 20% K value) was 280 kgf / mm ² .

(Formation of nickel plating layer with protrusions)
A 30% by mass polyethyleneimine aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) containing polyethyleneimine having a molecular weight of 70000 was diluted to 0.3% by mass with ultrapure water. 10 g of the plastic core particles were added to 300 mL of this 0.3% by mass polyethylene aqueous solution, and the mixture was stirred at room temperature for 15 minutes. The plastic core particles were taken out by filtration using a φ3 μm membrane filter (Millipore), and the taken out plastic core particles were put in 300 g of ultrapure water and stirred at room temperature for 5 minutes. Next, the plastic core particles are removed by filtration using a φ3 μm membrane filter (Millipore), and the plastic core particles on the membrane filter are washed twice with 200 g of ultrapure water to remove the unadsorbed polyethyleneimine. As a result, plastic core particles adsorbed with polyethyleneimine were obtained.

  A colloidal silica dispersion having an average particle diameter of 100 nm was diluted with ultrapure water to obtain a 0.33% by mass silica particle dispersion (total amount of silica: 1 g). The plastic core particles adsorbed with polyethyleneimine were put therein and stirred at room temperature for 15 minutes. Thereafter, plastic core particles were taken out by filtration using a φ3 μm membrane filter (Millipore). Since silica was not extracted from the filtrate, it was confirmed that substantially all silica particles were adsorbed on the plastic core particles. The plastic core particles on which the silica particles were adsorbed were placed in 200 g of ultrapure water and stirred at room temperature for 5 minutes. Thereafter, the plastic core particles were taken out by filtration using a φ3 μm membrane filter (Millipore), and the plastic core particles on the membrane filter were washed twice with 200 g of ultrapure water. The washed plastic core particles were dried by heating at 80 ° C. for 30 minutes and 120 ° C. for 1 hour in order to obtain composite particles composed of the plastic core particles and silica particles adsorbed on the surface thereof. .

  After taking 1 g of the composite particles and irradiating them with ultrasonic waves having a resonance frequency of 28 kHz and an output of 100 W for 15 minutes, a palladium catalyst containing 8 mass% of Atotech Nene Gantt 834 (manufactured by Atotech Japan Co., Ltd.), which is a palladium catalyst. The solution was added to 100 mL and stirred at 30 ° C. for 30 minutes while irradiating ultrasonic waves. Thereafter, the composite particles were taken out by filtration using a φ3 μm membrane filter (Millipore), and the taken out composite particles were washed with water. The composite particles after washing with water were added to a 0.5% by mass dimethylamine borane solution adjusted to pH 6.0 to obtain composite particles whose surface was activated.

The composite particles whose surface was activated were immersed in distilled water and subjected to ultrasonic dispersion to obtain a suspension. While stirring this suspension at 50 ° C., nickel sulfate hexahydrate 50 g / L, sodium hypophosphite monohydrate 20 g / L, dimethylamine borane 2.5 g / L and citric acid 50 g / L were added. The electroless plating solution A mixed and adjusted to pH 7.5 was gradually added to form an electroless nickel plating layer on the composite particles. The phosphorus content in the nickel plating layer was about 7%. The thickness of the nickel was adjusted by sampling and atomic absorption, and the addition of the electroless plating solution A was stopped when the thickness of the nickel plating layer reached 750 mm. After filtration, washing with 100 mL of pure water was performed for 60 seconds to obtain conductive particles 1 having a nickel plating layer having protrusions on the surface. When the height of the protrusion of the nickel plating layer was observed by SEM, it was 100 nm, which was almost the same as the particle size of the silica particles adsorbed on the plastic core particles. The coverage by the protrusions was measured by image analysis of the SEM image, and was about 40%. Further, the saturation magnetization per unit volume was measured by using BHV-525 manufactured by Riken Denshi and the specific gravity system, and found to be 0.5 emu / cm ³ .

2. Insulating fine particles In a 500 mL three-necked flask, 7.5 g of a silane coupling agent having a radical polymerizable unsaturated group and an alkoxysilyl group (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-5103) and methacrylic acid (Wako Pure Chemical Industries, Ltd. ( 6.9 g), methyl acrylate (Wako Pure Chemical Industries, Ltd.) 4.1 and g, 2,2′-azobis (isobutyronitrile) 0.36 g, and acetonitrile 350 g These were mixed. After replacing dissolved oxygen with nitrogen (100 mL / min) over 1 hour, the polymerization reaction was allowed to proceed for 6 hours while heating to 80 ° C. to obtain organic-inorganic hybrid particles having a primary particle size of 300 nm. The dispersion containing the organic-inorganic hybrid particles is placed in a 20 mL container, and 3000 r. p. m. The unreacted monomer was removed by centrifugation for 30 minutes (manufactured by Kokusan Co., Ltd .: H-103N). Further, 20 mL of methanol was added, and the mixture was ultrasonically dispersed and centrifuged again. As a curing catalyst, an aqueous ammonia solution (28% by mass) containing an equimolar amount of ammonia with respect to the amount of carboxyl groups was added, and methanol was added and ultrasonically dispersed to advance the crosslinking reaction. After centrifugation again, the aqueous ammonia solution was removed, and the organic-inorganic hybrid particles were dispersed in 30 g of methanol. Thereto, 5 g of a silane coupling agent having a glycidyl group was added and adsorbed on the surface of the fine particles to obtain insulating fine particles having a glycidyl group on the surface.

3. Insulating coated conductive particles <Step of forming surface functional groups>
10 g of the conductive particles prepared as described above were added to 300 g of a carboxybenzotriazole methanol solution (concentration: 2% by mass), and three-motor (trade name: BL3000, manufactured by Shinto Kagaku Co., Ltd.) was used under ultrasonic irradiation. Stirring (600 rpm) was performed at room temperature (25 ° C.) for 1 hour. 7.5 g of mercaptoacetic acid was added to the stirring vessel, and the mixture was further stirred for 1 hour, filtered through a φ3 μm membrane filter (manufactured by Millipore: coated type membrane filter), and 10 g of conductive particles having a carboxyl group as a surface functional group were obtained. Obtained.

<Step of adsorbing basic compound to conductive particles>
Next, a 30% by mass polyethyleneimine aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd., trade name: 30% polyethyleneimine P-70 solution) containing polyethyleneimine having a weight average molecular weight of 70,000 is diluted with ultrapure water to obtain 0.3. A mass% polyethyleneimine aqueous solution was obtained. 10 g of the above functional group-containing conductive particles are added to this 0.3% by weight polyethyleneimine aqueous solution, stirred for 15 minutes at room temperature (25 ° C.), filtered through a 3 μm membrane filter, and the conductive particles having polyethyleneimine adsorbed on the surface. Got. The conductive particles were mixed with 200 g of ultrapure water, stirred at room temperature (25 ° C.) for 5 minutes, and filtered. The particles obtained by filtration were washed twice with 200 g of ultrapure water on the membrane filter to remove polyethyleneimine not adsorbed on the particles.

<Process for coating conductive particles with insulating fine particles>
50 g of a 2% by weight insulating fine particle dispersion obtained by diluting insulating fine particles with 2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise to 10 g of conductive particles adsorbed with the polymer electrolyte. While stirring at room temperature (25 ° C.) for 30 minutes, the conductive particles were covered with insulating fine particles. Conductive particles coated with insulating fine particles (insulating coated conductive particles) were taken out by filtration. The taken insulating coated conductive particles are put in a mixed solution of 50 g of silicone oligomer having an epoxy group and a weight average molecular weight of 1000 (manufactured by Hitachi Chemical Coated Sand Co., Ltd .: SC-6000) and 150 g of methanol, and 1 at room temperature (25 ° C.). The mixture was stirred for a period of time, and the insulating coated conductive particles were taken out by filtration. Finally, the insulating coated conductive particles were stirred in toluene (manufactured by Wako Pure Chemical Industries, Ltd.) for 3 minutes and filtered.

<Classification process>
The obtained insulating coated conductive particles were vacuum dried at 150 ° C. for 1 hour. Thereafter, aggregates were removed using a swirling air flow classifier (Seishin Enterprise Co., Ltd.).

(Example 2, insulating coated conductive particles 2)
In the step of adsorbing the basic compound to the conductive particles, a 30% by mass polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 10,000 (Wako Pure Chemical Industries, Ltd.) was used instead of the 30% by mass polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 70,000. Insulating coated conductive particles 2 were produced in the same manner as the insulating coated conductive particles 1 except that Kogyo Co., Ltd., trade name: 30% polyethyleneimine P-70 solution) was used.

(Example 3, insulating coated conductive particles 3)
In the step of adsorbing the basic compound to the conductive particles, a 30% by mass polyethyleneimine aqueous solution (Wako Pure Chemical Industries, Ltd.) containing polyethyleneimine having a weight average molecular weight of 600 is used instead of the 30% by mass polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 70,000. Insulating coated conductive particles 3 were produced in the same manner as the insulating coated conductive particles 1 except that Kogyo Co., Ltd. was used.

(Example 4, insulating coated conductive particles 4)
In the step of adsorbing the basic compound to the conductive particles, a polyfunctional aziridine chemite (2,2-bishydroxymethylbutanol-tris [3- (1-) is used instead of 30 mass% polyethyleneimine containing polyethyleneimine having a weight average molecular weight of 70,000. Insulating coated conductive particles 4 were produced in the same manner as in the insulating coated conductive particles 1 except that aziridinyl) proposal], manufactured by Nippon Shokubai Co., Ltd., trade name: PZ-33, molecular weight: 425) was used.

(Example 5, insulating coated conductive particles 5)
Insulating coating, except that in the step of adsorbing the basic compound to the conductive particles, pentaethylenehexamine (manufactured by Kanto Chemical Co., Inc.) was used in place of the 30 mass% polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 70,000. Insulating coated conductive particles 5 were produced in the same manner as the conductive particles 1.

(Example 6, insulating coated conductive particles 6)
In the step of adsorbing the basic compound to the conductive particles, bis (hexamethylene) triamine (manufactured by Kanto Chemical Co., Inc.) was used in place of the 30% by mass polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 70,000. Insulating coated conductive particles 6 were produced in the same manner as the insulating coated conductive particles 1.

(Example 7, insulating coating conductive particles 7)
In the step of adsorbing the basic compound to the conductive particles, insulation was performed except that tetraethylenepentamine (manufactured by Kanto Chemical Co., Inc.) was used in place of the 30 mass% polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 70,000. Insulating coated conductive particles 7 were produced in the same manner as the coated conductive particles 1.

(Example 8, insulating coated conductive particles 8)
In the step of adsorbing the basic compound to the conductive particles, insulation was performed except that hexamethylenediamine (manufactured by Wako Pure Chemical Industries, Ltd.) was used in place of the 30 mass% polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 70,000. Insulating coated conductive particles 8 were produced in the same manner as the coated conductive particles 1.

(Example 9, insulating coated conductive particles 9)
In the step of adsorbing the basic compound to the conductive particles, 1,5-diaminopentane (manufactured by Kanto Chemical Co., Inc.) was used in place of the 30 mass% polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 70,000. Insulating coated conductive particles 9 were produced in the same manner as the insulating coated conductive particles 1.

(Comparative Example 1, insulating coated conductive particles 10)
Insulating coated conductive except that ethylenediamine (manufactured by Wako Pure Chemical Industries, Ltd.) was used in place of the 30 mass% polyethyleneimine aqueous solution containing polyethyleneimine having a weight average molecular weight of 70,000 in the step of adsorbing the basic compound to the conductive particles Insulating coated conductive particles 10 were produced in the same manner as the particles 1.

(Anisotropic conductive adhesive film)
Copolymer of 5 parts by mass of phenoxy resin (manufactured by Union Carbide: PKHC), acrylic rubber (40 parts by mass of butyl acrylate, 30 parts by mass of ethyl acrylate, 30 parts by mass of acrylonitrile, and 3 parts by mass of glycidyl methacrylate, weight average molecular weight: 85 10 parts by mass and 15 parts by mass of an epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd .: YL-983U) are dissolved in 10 parts by mass of ethyl acetate, and the total concentration of phenoxy resin, acrylic rubber and epoxy resin is 30 masses. % Solution was obtained.

  To this solution, 2 parts by mass of a cationic curing agent (sulfonium salt, Sanshin Chemical Industry Co., Ltd .: SI-60) was added to prepare an adhesive solution. 30 parts by mass of an ethyl acetate dispersion (10% by mass) of a silica filler (manufactured by Nippon Aerosil Co., Ltd .: Aerosil R805) was added to this adhesive solution and stirred. Furthermore, 20 parts by mass of the insulating coated conductive particles were mixed with an adhesive solution, and ultrasonic dispersion was performed. This dispersion was applied to a silicone-treated polyethylene terephthalate film separator (thickness 40 μm) with a roll coater and dried at 80 ° C. for 5 minutes to form an anisotropic conductive adhesive film having a thickness of 23 μm.

  Using the produced anisotropic conductive adhesive film, a chip (1.7 mm × 17 mm, thickness: 0.5 mm) with gold bumps (area: 30 μm × 90 μm, space 10 μm, height: 15 μm, number of bumps: 362) and Connection with a glass substrate with ITO circuit (Geomatec, thickness: 0.7 mm) was performed as follows.

The anisotropic conductive adhesive film is cut into a predetermined size (2 mm × 19 mm), the surface opposite to the separator is directed to the glass substrate with the ITO circuit, and the ITO circuit of the glass substrate with the ITO circuit is formed on the surface. On the other hand, it was attached by applying pressure at 0.98 MPa (10 kgf / cm ² ) while heating to 80 ° C. The separator was peeled from the attached anisotropically conductive adhesive film. After that, the surface with the gold bumps of the chip is directed to the surface opposite to the surface with the glass substrate with the ITO circuit of the anisotropic conductive adhesive film, and in that state, with the gold bumps of the chip and the ITO circuit The alignment with the glass substrate was performed. Next, heating and pressurization were performed under the conditions of 170 ° C., 70 MPa, and 5 seconds to perform the main connection, thereby obtaining a mounting sample.

(Measurement of calorific value)
A 10 mg sample cut from the anisotropic conductive adhesive film was placed in an aluminum cell and sealed under pressure. Then, differential scanning calorimetry was performed in the range of 40 ° C. to 250 ° C. at a rate of temperature increase of 10 ° C./min using DSC (manufactured by TA Instruments: Q1000). From the obtained DSC curve, the calorific value (first calorific value) α of the exothermic peak having a peak in the range of 100 ° C. to 150 ° C. and the calorific value of the exothermic peak having the peak in the range of 200 ° C. to 250 ° C. 2 calorific value) β was determined. A value of {α / (α + β)} × 100 was calculated from the obtained α and β.

  Further, an insulating adhesive film having the same composition as the anisotropic conductive adhesive film was prepared except that the insulating coated conductive particles were not included, and the DSC curve thereof was also obtained under the same conditions as described above. In the obtained DSC curve, one exothermic peak was observed, and the calorific value γ was determined to be 98 J / g.

(Ion concentration measurement)
0.5 g of insulating coated conductive particles and 25 g of pure water as an eluent were put in a pressure-resistant pot, covered, and placed in a constant temperature bath at 100 ° C. for 10 hours. Thereafter, the eluate was passed through a filter having a diameter of 0.08 μm to remove solids. The cation and anion concentrations were measured by ion chromatography (DIONEX-LC25 Ion Chromatography). From the measurement results, the concentration of ammonium ions (NH ₄ ⁺ ) was determined.

(Conductivity evaluation)
The connection resistance value of the mounted sample was measured by the 4-terminal method. A constant current (1 mA) was applied between the chip electrode and the substrate electrode using a constant current power supply device (R-6145 manufactured by Advantest Co., Ltd.), and the potential difference at the connection portion at that time was determined as a digital multimeter manufactured by Advantest Co., Ltd. It measured using (R-6557) and converted into resistance value. Further, the mounting sample was put into a high-temperature and high-humidity tank at 85 ° C. and 85 RH%, taken out after 500 hours, and the connection resistance value after the reliability test was measured by the same method as described above.

(Insulation characteristics evaluation)
A voltage of direct current (DC) 50V was applied to the connection part of the circuit of the mounting sample for 1 minute, and the insulation resistance after the application was measured with a multimeter using a two-terminal measurement method. Here, the insulation resistance means a resistance between adjacent circuit electrodes.

(Dropping test)
A glass bottle containing a dispersion obtained by dispersing 0.5 g of insulating coated conductive particles in 5 g of ethyl acetate was immersed in an ultrasonic bath for 30 minutes. Insulating coated conductive particles before ultrasonic treatment or insulating coated conductive particles taken out from the dispersion after ultrasonic treatment were placed on an SEM sample stage, and 25 images were taken. The area covered with insulating fine particles existing in concentric circles from the center of the grain to 60% of the projected area was measured. The change in the coating area before and after the ultrasonic treatment was evaluated as follows. The results are shown in Table 2.
A: 0 to 10%
B: 10-30%
C: 30-50%
D: Over 50%

(appearance)
The anisotropic conductive adhesive film in the mounting sample was observed at 2500 times from the glass substrate side using an optical microscope (KEYENCE) to observe whether or not floating occurred around the conductive particles.
A: No floating B: With floating

  The evaluation results are shown in Tables 1 and 2. From these evaluation results, according to the anisotropic conductive adhesive film of the example in which the first heat generation amount α and the second heat generation amount β satisfy α / (α + β) × 100 ≧ 60, the anisotropic conductive film of Comparative Example 1 is used. Compared with the adhesive film, a remarkable improvement was confirmed particularly in terms of insulation characteristics after the reliability test.

  DESCRIPTION OF SYMBOLS 1 ... Insulating fine particle, 3 ... Conductive particle, 5 ... Insulation covering conductive particle, 7 ... Insulating adhesive layer, 10 ... Anisotropic conductive adhesive film.

Claims (7)

An insulating adhesive layer, and insulating coated conductive particles having conductive particles having a conductive metal surface and insulating fine particles covering the conductive particles dispersed in the insulating adhesive layer. A conductive adhesive film,
The insulating adhesive layer contains an epoxy resin and a cationic curing agent,
In the DSC curve obtained by differential scanning calorimetry of the anisotropic conductive adhesive film, the calorific value of the exothermic peak having a peak temperature in the range of 100 ° C to 150 ° C is α, and the peak temperature is in the range of 200 ° C to 250 ° C. An anisotropic conductive adhesive film in which α and β satisfy the formula: {α / (α + β)} × 100 ≧ 60, where β is the calorific value of the exothermic peak in FIG.   The anisotropic conductive adhesive film according to claim 1, wherein a ratio of α to a calorific value obtained by differential scanning calorimetry of the insulating adhesive layer alone is 68% or more. Insulating coated conductive particles having conductive particles having a conductive metal surface and insulating fine particles covering the conductive particles,
Insulating coated conductive particles, wherein 0.5 g of the insulating coated conductive particles is placed in 25 g of 100 ° C. pure water as an eluent for 10 hours, and the ammonium ion concentration of the eluted solution is less than 100 ppm.   The insulating coated conductive particles according to claim 3, further comprising a basic compound having a molecular weight of 100 or more adsorbed on the metal surface.   The insulating coated conductive particles according to claim 4, wherein the basic compound has an amino group.   The conductive particle has a nickel layer that forms the metal surface, the metal surface forms a protrusion, and the particle size of the conductive particle is 2.0 to 4.0 μm. The insulating coating conductive particles according to any one of -5.   The insulating fine particles include organic-inorganic hybrid particles composed of a copolymer containing silicon atoms, and a silane coupling agent having an epoxy group adsorbed on the surface of the organic-inorganic hybrid particles. Item 7. The insulating coated conductive particle according to any one of Items 3 to 6.

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