WO2024194950A1 - Adhesive film and connection structure - Google Patents

Abstract

An adhesive film comprising an adhesive component, first conductive particles each in a dendrite form, and second conductive particles that are other than the first conductive particles and each of which includes a non-conductive core body and a conductive layer provided on the core body and the flow rate of the adhesive film is 10% to 50%.

Description

Adhesive film and connection structure

The present invention relates to an adhesive film and a connection structure.

In recent years, various adhesives have been used in fields such as semiconductors and liquid crystal displays to fasten electronic components and connect circuits. In these applications, electronic components and circuits are becoming increasingly dense and precise, and adhesives are being required to provide higher levels of performance.

For example, adhesives with conductive particles dispersed in them (conductive adhesives) are used to connect liquid crystal displays and TCPs (Tape Carrier Packages), FPCs (Flexible Printed Circuits) and TCPs, or FPCs and printed wiring boards. Conductive adhesives may be required to have excellent connection reliability when connecting electronic components together at low pressure (e.g., 0.1 to 0.5 MPa).

For example, Patent Document 1 describes that an isotropic conductive adhesive sheet formed from an adhesive containing a specific acrylic resin, a specific amount of an isocyanate-based curing agent, and a specific amount of dendritic conductive particles, in which the ratio of the adhesive sheet thickness to the median diameter D50 of the dendritic conductive particles is within a specific range, can be easily adhered to an adherend with high adhesion, has excellent electrical connection stability, and shows little change in resistance value after a heat cycle test.

International Publication No. 2020/241818

One aspect of the present invention aims to provide an adhesive film that can keep the rate of resistance increase before and after a heat cycle test low.

One aspect of the present invention relates to an adhesive film that contains an adhesive component, first conductive particles that are dendritic conductive particles, and second conductive particles that are conductive particles other than the first conductive particles and have a non-conductive core and a conductive layer provided on the core, and the flow rate of the adhesive film is 10% to 50%.

In one aspect of the present invention, the volume ratio of the content of the first conductive particles to the content of the second conductive particles may be 5/1 or more.

In one aspect of the present invention, the total content of the first conductive particles and the second conductive particles may be 20 parts by volume or more per 100 parts by volume of the adhesive component content.

In one aspect of the present invention, the total content of the first conductive particles and the second conductive particles may be 55 parts by volume or less per 100 parts by volume of the adhesive component content.

Another aspect of the present invention relates to a connection structure comprising a first electronic component having a first substrate and a first electrode formed on the first substrate, a second electronic component having a second substrate and a second electrode formed on the second substrate, and a connection member that electrically connects the first electrode and the second electrode to each other, the connection member including a cured product of the above-mentioned adhesive film.

According to one aspect of the present invention, it is possible to provide an adhesive film that can suppress the rate of increase in resistance before and after a heat cycle test.

FIG. 2 is a schematic cross-sectional view showing one embodiment of an adhesive film. FIG. 1 is a schematic cross-sectional view showing one embodiment of a connection structure. 1A to 1C are schematic diagrams showing a method for producing a mounting body for a reliability test. FIG. 2 is a schematic diagram showing a method for measuring a connection resistance in a reliability test. FIG. 2 is a schematic top view showing a laminate in peel strength measurement.

The following describes in detail an embodiment of the present invention, with appropriate reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing one embodiment of an adhesive film. As shown in FIG. 1, the adhesive film 10 contains an adhesive component 11, first conductive particles 12 which are dendritic conductive particles, and second conductive particles 13 which are conductive particles having a non-conductive core and a conductive layer provided on the core. However, the second conductive particles 13 are conductive particles other than the first conductive particles 12. The first conductive particles 12 and the second conductive particles 13 are dispersed in the adhesive component 11.

The adhesive component 11 is composed of a material that is curable by, for example, heat or light, and may be a radical-curing adhesive, an epoxy-based adhesive, or a thermoplastic adhesive such as polyurethane or polyvinyl ester. Of these, radical-curing adhesives are preferably used because they have characteristics such as excellent curing properties at low temperatures and in a short time. Epoxy-based adhesives are also preferably used because they can be cured in a short time, have good connection workability, and have excellent adhesion.

Radically curable adhesives contain, for example, a radically polymerizable substance and a radical polymerization initiator, and may further contain thermoplastic resins, fillers, other additives, etc., as necessary.

The radical polymerizable substance can be any substance having a functional group that polymerizes by radicals, without any particular limitations. Specific examples of radical polymerizable substances include (meth)acrylate compounds, maleimide compounds, citraconic imide resins, and nadimide resins. These radical polymerizable substances may be in the form of a monomer or oligomer, or may be in the form of a mixture of a monomer and an oligomer.

Examples of (meth)acrylate compounds include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, 2-hydroxy-1,3-di(meth)acryloxypropane, 2,2-bis[4-((meth)acryloxy)propane, Examples of such acrylates include 2,2-bis[4-((meth)acryloxymethoxy)phenyl]propane, 2,2-bis[4-((meth)acryloxypolyethoxy)phenyl]propane, dicyclopentenyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, ethylene oxide (EO)-modified isocyanuric acid di(meth)acrylate, EO-modified isocyanuric acid tri(meth)acrylate, urethane (meth)acrylate, and EO-modified phosphate di(meth)acrylate.

As radical polymerizable substances other than (meth)acrylate compounds, for example, compounds described in International Publication No. 2009/063827 can be suitably used. The radical polymerizable substances may be used alone or in combination of two or more.

The content of the radical polymerizable substance may be 10 parts by volume or more, 20 parts by volume or more, 30 parts by volume or more, or 40 parts by volume or more, and may be 80 parts by volume or less, 70 parts by volume or less, or 60 parts by volume or less, relative to a total amount of 100 parts by volume of the adhesive component 11.

The content of the radical polymerizable substance may be 30 parts by volume or more, 40 parts by volume or more, or 50 parts by volume or more, and may be 90 parts by volume or less, 80 parts by volume or less, or 70 parts by volume or less, per 100 parts by volume of the total of the radical polymerizable substance and the thermoplastic resin that is blended as necessary.

The radical polymerization initiator can be any compound that decomposes when heated or irradiated with light to generate free radicals. Specific examples include peroxide compounds and azo compounds. These compounds are appropriately selected depending on the intended connection temperature, connection time, pot life, etc.

Specific examples of radical polymerization initiators include diacyl peroxides, peroxydicarbonates, peroxy esters (e.g., 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane), peroxy ketals, dialkyl peroxides, hydroperoxides, and silyl peroxides. Among these, peroxy esters, dialkyl peroxides, hydroperoxides, and silyl peroxides are preferred, and peroxy esters that provide high reactivity are more preferred. As these radical polymerization initiators, for example, the compounds described in International Publication No. 2009/063827 can be suitably used. The radical polymerization initiators may be used alone or in combination of two or more.

The content of the radical polymerization initiator may be 1 part by volume or more and 10 parts by volume or less per 100 parts by volume of the total of the radical polymerizable substance and the thermoplastic resin that is blended as necessary.

Epoxy adhesives contain, for example, epoxy resins and curing agents, and may further contain thermoplastic resins, fillers, other additives, etc., as necessary.

Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, bisphenol F novolac type epoxy resins, alicyclic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, aliphatic chain epoxy resins, etc. These epoxy resins may be halogenated or hydrogenated, and may have a structure in which an acryloyl group or a methacryloyl group is added to the side chain. These epoxy resins may be used alone or in combination of two or more.

The epoxy resin content may be 10 parts by volume or more, 20 parts by volume or more, or 30 parts by volume or more, and may be 70 parts by volume or less, 60 parts by volume or less, or 50 parts by volume or less, relative to a total amount of 100 parts by volume of the adhesive component 11.

The epoxy resin content may be 20 parts by volume or more, 30 parts by volume or more, or 40 parts by volume or more, and 80 parts by volume or less, 70 parts by volume or less, or 60 parts by volume or less, per 100 parts by volume of the total of the epoxy resin and the thermoplastic resin blended as necessary.

The curing agent is not particularly limited as long as it can cure the epoxy resin, and examples include anionic polymerization catalyst-type curing agents, cationic polymerization catalyst-type curing agents, polyaddition-type curing agents, etc. Among these, anionic or cationic polymerization catalyst-type curing agents are preferred because they have excellent fast curing properties and do not require consideration of chemical equivalents.

Examples of anionic or cationic polymerizable catalyst-type curing agents include imidazoles, hydrazides, boron trifluoride-amine complexes, onium salts (aromatic sulfonium salts, aromatic diazonium salts, aliphatic sulfonium salts, etc.), aminimides, diaminomaleonitrile, melamine and its derivatives, polyamine salts, dicyandiamide, etc., and modified versions of these can also be used. Examples of polyaddition-type curing agents include polyamines, polymercaptans, polyphenols, acid anhydrides, etc.

Latent hardeners that are microencapsulated by coating these hardeners with polymeric substances such as polyurethanes and polyesters, thin metal films such as nickel and copper, and inorganic substances such as calcium silicate are preferred because they can extend the usable time. Hardeners can be used alone or in combination of two or more types.

The amount of the curing agent may be 0.05 parts by volume or more and 20 parts by volume or less per 100 parts by volume of the total of the epoxy resin and the thermoplastic resin that is mixed as necessary.

The adhesive component 11 may contain a thermoplastic resin. When the radical curing adhesive or epoxy adhesive contains a thermoplastic resin, it is possible to easily impart film properties to the adhesive. Examples of the thermoplastic resin include phenoxy resin, polyvinyl formal resin, polystyrene resin, polyvinyl butyral resin, polyester resin, polyamide resin, xylene resin, polyurethane resin, polyester urethane resin, phenol resin, and terpene phenol resin. For example, the compounds described in International Publication No. 2009/063827 can be suitably used as the thermoplastic resin. The thermoplastic resin may be used alone or in combination of two or more types.

The amount of the thermoplastic resin may be 10 parts by volume or more, 15 parts by volume or more, or 20 parts by volume or more, and may be 50 parts by volume or less, 40 parts by volume or less, or 30 parts by volume or less, relative to a total amount of 100 parts by volume of the adhesive component 11.

An example of a radical curing adhesive is a thermal radical curing adhesive that contains a radical polymerizing material that contains a radical polymerizing substance that is liquid at 30°C, a radical polymerization initiator, and a thermoplastic resin. Thermal radical curing adhesives tend to have low viscosity. An example of an epoxy-based adhesive is an epoxy-based adhesive that contains a thermosetting material that contains an epoxy resin that is liquid at 30°C, a curing agent, and a thermoplastic resin.

The adhesive component 11 may contain a filler. An example of the filler is non-conductive particles. The non-conductive particles may be inorganic non-conductive particles or organic non-conductive particles. An example of the inorganic non-conductive particles is silica particles.

The filler content may be 1 volume % or more, or 3 volume % or more, and may be 25 volume % or less, or 20 volume % or less, based on the total volume of the adhesive film 10.

Adhesive component 11 may contain other additives as necessary. Examples of other additives include coupling agents and components that relieve internal stress. If adhesive component 11 further contains a component that relieves internal stress, when it is used to connect an IC chip to a glass substrate, a flexible printed circuit board (FPC), or the like, it can suppress warping of the substrate caused by the difference in linear expansion coefficient between the IC chip and the substrate. Specific examples of components that relieve internal stress include acrylic rubber and elastomer components.

The first conductive particles 12 are dendritic and have one main axis and multiple branches branching out two-dimensionally or three-dimensionally from the main axis. The first conductive particles 12 may be made of a metal such as copper or silver, and may be, for example, silver-coated copper particles in which copper particles are coated with silver.

The first conductive particles 12 may be known, and specifically, for example, are available as ACBY-2 (Mitsui Mining & Smelting Co., Ltd.), CE-1110 (Fukuda Metal Foil & Powder Co., Ltd.), #FSP (JX Metals Corporation), and #51-R (JX Metals Corporation). Alternatively, the first conductive particles 12 can be manufactured by a known method (for example, the method described in WO 2014/021037).

The content of the first conductive particles 12 may be 5 volume % or more, 10 volume % or more, 20 volume % or more, 25 volume % or more, or 30 volume % or more, and may be 60 volume % or less, 50 volume % or less, or 45 volume % or less, based on the total volume of the adhesive film 10.

The content of the first conductive particles 12 may be 5 parts by volume or more, 10 parts by volume or more, 20 parts by volume or more, 30 parts by volume or more, 40 parts by volume or more, or 50 parts by volume or more, and may be 90 parts by volume or less, 85 parts by volume or less, 80 parts by volume or less, or 70 parts by volume or less, relative to 100 parts by volume of the adhesive component 11.

The second conductive particle 13 has a non-conductive core and a conductive layer provided on the core. The core is made of a non-conductive material such as glass, ceramic, or resin, and is preferably made of resin. Examples of resins include acrylic resin, styrene resin, silicone resin, polybutadiene resin, and copolymers of monomers that make up these resins. The average particle size of the core may be, for example, 2 μm or more and 30 μm or less.

The conductive layer is formed, for example, of gold, silver, copper, nickel, palladium, or an alloy thereof. From the viewpoint of excellent conductivity, the conductive layer preferably contains at least one selected from gold, nickel, and palladium, more preferably contains gold or palladium, and even more preferably contains gold. The conductive layer is formed, for example, by plating the core with the above metal. The thickness of the conductive layer may be, for example, 10 nm or more and 400 nm or less.

The second conductive particles may be, for example, approximately spherical. From the viewpoint of being able to suitably thin the adhesive film, the average particle size of the second conductive particles is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 22 μm or less. The average particle size of the second conductive particles may be, for example, 1 μm or more. The average particle size of the second conductive particles is measured by a particle size distribution measuring device (Microtrac (product name, Nikkiso Co., Ltd.)) using a laser diffraction/scattering method.

The content of the second conductive particles 13 may be 1 volume % or more, 2 volume % or more, 3 volume % or more, 4 volume % or more, or 5 volume % or more based on the total volume of the adhesive film 10, and may be 30 volume % or less, 20 volume % or less, 15 volume % or less, or 10 volume % or less.

The content of the second conductive particles 13 may be 1 part by volume or more, 2 parts by volume or more, 5 parts by volume or more, 7 parts by volume or more, or 10 parts by volume or more, and may be 20 parts by volume or less, 17 parts by volume or less, or 15 parts by volume or less, relative to 100 parts by volume of the adhesive component 11.

The volume ratio of the first conductive particles 12 to the second conductive particles 13 in the adhesive film (first conductive particles 12/second conductive particles 13) may be 0.5/1 or more, 1/1 or more, 3/1 or more, 5/1 or more, 6.1/1 or more, or 6.5/1 or more, and may be 40/1 or less, 30/1 or less, 25/1 or less, 20/1 or less, or 15/1 or less.

The total content of the first conductive particles 12 and the second conductive particles 13 may be 10 parts by volume or more, 20 parts by volume or more, 30 parts by volume or more, 35 parts by volume or more, 40 parts by volume or more, or 45 parts by volume or more, relative to 100 parts by volume of the adhesive component 11, and may be 100 parts by volume or less, 90 parts by volume or less, 80 parts by volume or less, 70 parts by volume or less, 60 parts by volume or less, 57 parts by volume or less, or 55 parts by volume or less.

When the adhesive component 11 includes a filler, the total content of the first conductive particles 12 and the second conductive particles 13 may be 10 parts by volume or more, 20 parts by volume or more, 30 parts by volume or more, 35 parts by volume or more, 40 parts by volume or more, or 45 parts by volume or more, relative to 100 parts by volume of the total of the components other than the filler contained in the adhesive component 11, and may be 110 parts by volume or less, 100 parts by volume or less, 90 parts by volume or less, 80 parts by volume or less, 70 parts by volume or less, 60 parts by volume or less, 57 parts by volume or less, or 55 parts by volume or less.

The flow rate of the adhesive film 10 is 10% to 50%. The flow rate may be 12% or more, or 20% or more, and may be 45% or less, or 40% or less. When the flow rate of the adhesive film 10 is equal to or greater than the lower limit, the reliability is superior. Furthermore, when the flow rate is 50% or less, the adhesive film tends to have excellent shape stability.

The flow rate of the adhesive film 10 is an index showing the fluidity of the adhesive film 10, and means the rate of change in area when the adhesive film 10 is heated and pressurized. Specifically, the flow rate is calculated by the following method.
First, a disk-shaped adhesive film with a diameter of 1.0 mm is prepared, with a fluororesin film (thickness: 80 μm) attached to one side. The adhesive film with the fluororesin film is placed on a first cover glass (thickness: 0.15 mm) so that the adhesive film side is in contact with the first cover glass to prepare a first laminate (first cover glass / adhesive film / fluororesin film), and the first laminate is heat-pressed from the fluororesin film side under conditions of a pressure-pressing temperature of 60 ° C., a pressure-pressing pressure of 1 MPa, and a pressure-pressing time of 0.1 seconds. The pressure-pressing temperature is the maximum temperature reached when pressure-pressed for 1 second, and the pressure-pressing pressure is the area-converted pressure of the adhesive film for evaluation. The maximum temperature is adjusted by separately preparing the same first laminate as above, performing heat-pressing bonding with a thin temperature sensor sandwiched between the adhesive film of the laminate and the first cover glass, and measuring the maximum temperature reached by the adhesive film in advance.

Then, the fluororesin film is peeled off, and a second cover glass (thickness: 0.15 mm) is placed on the exposed adhesive film to produce a second laminate (first cover glass/adhesive film/second cover glass), which is then thermocompressed from the second cover glass side under conditions of a bonding temperature of 170°C, a bonding pressure of 80 MPa, and a bonding time of 5 seconds to obtain a bonded body. Note that the bonding temperature is the maximum temperature reached by the adhesive film, and the bonding pressure is the area-converted pressure of the adhesive film for evaluation. The maximum temperature is adjusted by separately preparing the same second laminate as above, performing thermocompression bonding with a thin temperature sensor sandwiched between the adhesive film of the second laminate and the first cover glass, and measuring the maximum temperature reached by the adhesive film in advance.

The obtained bonded body is observed under an optical microscope, and the area of the bonded portion between the adhesive film and the first cover glass in the bonded body (bonding area) S1 (unit: ^mm2 ) is determined. The flow rate is calculated by the following formula using the bonding area S1 and the area of the adhesive film before thermocompression bonding (0.25π [ ^mm2 ]).
Flow rate [%] = {(adhesion area S1 - 0.25π) / (0.25π)} × 100

The thickness of the adhesive film 10 may be, for example, 50 μm or less, 45 μm or less, or 40 μm or less, and may be 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more.

The adhesive film 10 is obtained, for example, by applying a paste-like adhesive composition onto a resin film such as a PET (polyethylene terephthalate) film or a fluororesin film, and then drying it. The paste-like adhesive composition is obtained, for example, by heating or dissolving in a solvent a mixture containing the adhesive component 11, the first conductive particles 12, and the second conductive particles 13. As the solvent, for example, a solvent having a boiling point of 50°C or more and 150°C or less under atmospheric pressure (for example, toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, butyl acetate, etc.) is used.

The adhesive film 10 may be made up of multiple adhesive layers. In this case, the first conductive particles 12 and the second conductive particles 13 only need to be contained in at least one of the multiple adhesive layers, and may be contained in the same adhesive layer or different adhesive layers.

The adhesive film 10 can be cured, for example, by performing a heat treatment. The heating temperature may be, for example, 40°C or higher and 250°C or lower. The heating time may be, for example, 0.1 seconds or longer and 10 hours or shorter.

The adhesive film 10 can be adhered to the adherend by a combination of heating and pressure. The heating temperature may be, for example, 50°C or higher and 190°C or lower. The pressure may be, for example, 0.1 MPa or higher and 30 MPa or lower, 10 MPa or lower, 1 MPa or lower, or 0.8 MPa or lower. The heating and pressure may be applied for, for example, 0.5 seconds or more and 120 seconds or less.

The adhesive film 10 according to this embodiment can be used as an adhesive for bonding adherends of the same type together, and can also be used as an adhesive for bonding adherends of different types (e.g., adherends with different thermal expansion coefficients). The adhesive film 10 is suitable for connecting electronic components together. By connecting electronic components together using the adhesive film 10, a connection structure can be manufactured.

FIG. 2 is a schematic cross-sectional view showing one embodiment of a connection structure. As shown in FIG. 2, the connection structure 20 includes a first substrate 21, a first electronic component 23 having a first electrode 22 formed on the main surface of the first substrate 21, a second substrate 24, a second electronic component 26 having a second electrode 25 formed on the main surface of the second substrate 24, and a connection component 27 that electrically connects the first electrode 22 and the second electrode 25 to each other.

The first substrate 21 and the second substrate 24 may each be a substrate made of glass, ceramic, polyimide, polycarbonate, polyester, polyethersulfone, or the like. The first electrode 22 and the second electrode 25 may each be an electrode made of gold, silver, copper, tin, aluminum, ruthenium, rhodium, palladium, osmium, iridium, platinum, indium tin oxide (ITO), or the like.

The connection member 27 includes a cured product 28 of the adhesive component, and first conductive particles 12 and second conductive particles 13 dispersed in the cured product 28. In other words, the connection member 27 can be said to be a cured product of the adhesive film described above.

In the connection structure according to this embodiment, the first conductive particles 12 and the second conductive particles 13 are used in combination, so that the electronic components 23, 26 can be suitably connected to each other. As shown in FIG. 2, the second conductive particles 13 form the main conductive path that connects the first electrode 22 and the second electrode 25 to each other, while the first conductive particles 12 assist in the electrical connection between the second conductive particles 13 and each electrode 22, 25, thereby achieving a suitable connection.

The present invention will be specifically explained below based on examples, but the present invention is not limited to these examples.

<Synthesis of polyurethane acrylate (UA1)>
Into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser having a calcium chloride drying tube, and a nitrogen gas inlet tube, 2500 parts by mass (2.50 mol) of poly(1,6-hexanediol carbonate) (product name: Duranol T5652, manufactured by Asahi Kasei Chemicals Corporation, number average molecular weight 1000) and 666 parts by mass (3.00 mol) of isophorone diisocyanate (manufactured by Sigma-Aldrich Co.) were uniformly dropped over 3 hours. Next, after sufficient nitrogen gas was introduced into the reaction vessel, the inside of the reaction vessel was heated to 70 to 75° C. to cause a reaction. Next, 0.53 parts by mass (4.3 mmol) of hydroquinone monomethyl ether (Sigma-Aldrich) and 5.53 parts by mass (8.8 mmol) of dibutyltin dilaurate (Sigma-Aldrich) were added to the reaction vessel, and then 238 parts by mass (2.05 mol) of 2-hydroxyethyl acrylate (Sigma-Aldrich) was added and reacted at 70°C for 6 hours in an air atmosphere. This resulted in polyurethane acrylate (UA1). The polyurethane acrylate (UA1) had a weight average molecular weight of 15,000. The weight average molecular weight was measured by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene under the following conditions.
(Measurement conditions)
Apparatus: Tosoh Corporation GPC-8020
Detector: Tosoh Corporation RI-8020
Column: Gelpack GLA160S + GLA150S manufactured by Resonac Techno Service Co., Ltd.
Sample concentration: 120mg/3mL
Solvent: Tetrahydrofuran Injection volume: 60 μL
Pressure: 2.94 x 106 Pa (30 kgf/cm2)
Flow rate: 1.00mL/min

<Method for preparing polyester urethane resin>
In a stainless steel autoclave equipped with a heater equipped with a stirrer, a thermometer, a condenser, a vacuum generator and a nitrogen gas inlet tube, 48 parts by mass of isophthalic acid and 37 parts by mass of neopentyl glycol were put in, and 0.02 parts by mass of tetrabutoxy titanate as a catalyst was further put in. Then, the temperature was raised to 220°C under a nitrogen gas flow, and the mixture was stirred for 8 hours. Then, the pressure was reduced to atmospheric pressure (760 mmHg) and cooled to room temperature. This caused a white precipitate to precipitate. Next, the white precipitate was taken out, washed with water, and then vacuum dried to obtain a polyester polyol. After the obtained polyester polyol was thoroughly dried, it was dissolved in MEK (methyl ethyl ketone) and put into a four-neck flask equipped with a stirrer, a dropping funnel, a reflux condenser and a nitrogen gas inlet tube. In addition, dibutyltin dilaurate was put in as a catalyst in an amount of 0.05 parts by mass relative to 100 parts by mass of polyester polyol. Further, 4,4'-diphenylmethane diisocyanate in an amount of 50 parts by mass per 100 parts by mass of polyester polyol was dissolved in MEK and added using a dropping funnel, and stirred at 80°C for 4 hours to obtain a polyester urethane resin.

(Preparation of Solution A1)
To a methyl ethyl ketone solution of the polyester urethane resin synthesized as described above (polyester urethane resin content: 47.2 parts by volume), 53.3 parts by volume of the polyurethane acrylate (UA1) synthesized as described above, 13.5 parts by volume of dimethylol tricyclodecane diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., product name: DCP-A), 6.0 parts by volume of isocyanuric acid EO-modified di- and triacrylate (manufactured by Toa Gosei Co., Ltd., product name: M-315), and 6.0 parts by volume of EO-modified phosphoric acid dimethacrylate (manufactured by Nippon Kayaku Co., Ltd., product name: PM-21) were added as radical polymerizable substances, 9.0 parts by volume of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (manufactured by NOF Corporation, product name: Perhexa (registered trademark) 25O) as a radical polymerization initiator, and two types of silica particles (Evonik Industries 20.0 parts by volume of "R202" manufactured by Evonik Industries AG and 15.0 parts by volume of "R805" manufactured by Evonik Industries AG) were mixed together to obtain solution A1. The total content of adhesive components (hereinafter also referred to as "adhesive components a1") contained in solution A1 was 170 parts by volume.

(First conductive particles)
As the first conductive particles (B1), dendritic silver-coated copper particles (manufactured by Mitsui Mining & Smelting Co., Ltd., product name: ACBY-2) were used.

(Second Conductive Particles)
A gold-containing conductive layer (thickness: 20 nm) was formed on the surface of the polystyrene core particles. The resulting particles were used as second conductive particles (B2) (average particle size: 20 μm, specific gravity: 1.65).

<Preparation of Adhesive Film>
[Example 1]
Conductive particles B1 and B2 were dispersed in solution A1 so that the ratio of adhesive component a1:conductive particles B1:conductive particles B2 (volume parts) was 170:92.0:3.9 to obtain a mixed solution. The obtained mixed solution was applied onto a fluororesin film having a thickness of 80 μm, and the solvent was removed by hot air drying at 70° C. for 10 minutes to obtain an adhesive film (adhesive film with fluororesin film) having a thickness of 25 μm formed on the fluororesin film.

[Examples 2 to 17 and Comparative Examples 1 and 2]
The adhesive films according to Comparative Examples 1 and 2 and Examples 2 to 17 were obtained in the same manner as in Example 1, except that the amount (parts by volume) of conductive particles B1 and conductive particles B2 relative to adhesive component a1 (170 parts by volume) was changed as shown in Table 1.

<Evaluation of flow rate>
The flow rate of the adhesive films according to Examples 1 to 17 and Comparative Examples 1 and 2 was measured by the following method.

First, the adhesive film with fluororesin film according to each of the examples and comparative examples prepared as described above was punched out in the thickness direction using a biopsy trepan BP-10F 1.0 mm (Kai Industries Co., Ltd.), to obtain a disk-shaped adhesive film with fluororesin film having a diameter of 1 mm. The adhesive film with fluororesin film was placed on a first cover glass (Matsunami Glass Industry Co., Ltd., thickness 0.15 mm, length 18 mm, width 18 mm) so that the adhesive film side was in contact with the first cover glass, to obtain a first laminate (first cover glass/adhesive film/fluororesin film). The first laminate was thermocompressed from the fluororesin film side using a thermocompression device (Ohashi Manufacturing Co., Ltd., LD-06) under conditions of a compression temperature of 60°C, a compression pressure of 1 MPa, and a compression time of 0.1 seconds. The compression temperature is the maximum temperature reached when the film is compressed for 1 second, and the compression pressure is the area-converted pressure of the adhesive film for evaluation. The maximum temperature was adjusted by separately preparing the same first laminate as above, sandwiching a thin temperature sensor (ST-50, manufactured by Rika Kogyo Co., Ltd.) between the adhesive film of the laminate and the first cover glass, performing heat compression bonding, and measuring the maximum temperature of the adhesive film in advance.

Next, the fluororesin film was peeled off from the first laminate after thermocompression bonding, and a second cover glass (manufactured by Matsunami Glass Industry, thickness 0.15 mm, length 18 mm, width 18 mm) was placed on the exposed adhesive film to obtain a second laminate (first cover glass/adhesive film/second cover glass). Next, using a thermocompression device (manufactured by Ohashi Manufacturing, BD-06), thermocompression was performed from the second cover glass side under conditions of a bonding temperature of 170°C, a bonding pressure of 80 MPa, and a bonding time of 5 seconds to obtain a bonded body. The bonding temperature is the maximum temperature reached by the adhesive film, and the bonding pressure is the pressure converted into the area of the adhesive film. The maximum temperature was adjusted by separately preparing the same second laminate as above, performing thermocompression bonding with a thin temperature sensor (manufactured by Rika Kogyo Co., Ltd., ST-50) sandwiched between the adhesive film of the second laminate and the first cover glass, and measuring the maximum temperature reached by the adhesive film in advance.

The bonded body was observed with an optical microscope (Nikon Corporation, L300ND), and the area (bonding area) S1 (unit: ^mm2 ) of the bonded portion between the adhesive film and the first cover glass in the bonded body was measured using a length measuring tool. The flow rate was calculated using this bonding area S1 based on the following formula. The results are shown in Table 1.
Flow rate [%] = {(adhesion area S1 - 0.25π) / (0.25π)} × 100

<Evaluation of reliability (resistance increase rate)>
As shown in Figures 3(a) and (b), the adhesive films with fluororesin film of Examples 1 to 17 and Comparative Examples 1 and 2 were cut to 6 mm x 6 mm, and the cut-out adhesive film 31 was placed approximately in the center of a 6 mm x 50 mm copper foil 32 so that the adhesive film 31 was in contact with the copper foil 32. Using a thermocompression bonding device (manufactured by Ohashi Seisakusho Co., Ltd., BD-07), thermocompression bonding was performed from the fluororesin film side under conditions of a compression temperature of 50°C, a compression pressure of 0.5 MPa, and a compression time of 2 seconds. Next, the fluororesin film on the adhesive film 31 was peeled off, and as shown in Figures 3 (c) and (d), a 50 mm x 6 mm aluminum foil 33 was prepared and placed on the laminate of the copper foil 32 and the adhesive film 31 so as to cover the adhesive film 31. Using a thermocompression bonding device (manufactured by Ohashi Manufacturing Co., Ltd., BD-07), the aluminum foil 33 side was thermocompression bonded under conditions of a bonding temperature of 150°C, a bonding pressure of 0.5 MPa, and a bonding time of 10 seconds, to obtain a mounting body for evaluation.

The resulting assembly was connected to an ammeter and a voltmeter as shown in Fig. 4, and the connection resistance (initial connection resistance) was measured by the four-terminal method. In addition, a heat cycle test was performed on the assembly using a TSA-43EL made by Espec Corporation, in which the assembly was held at -40°C for 30 minutes, heated to 100°C over 10 minutes, held at 100°C for 30 minutes, and cooled to -40°C over 10 minutes, and this cycle was repeated 20 times. The connection resistance (post-test connection resistance) was then measured in the same manner as above. The resistance increase rate was calculated using the following formula. The results are shown in Table 1.
Reliability (resistance increase rate) [%]
= {(post-test connection resistance-initial connection resistance)/initial connection resistance} x 100

<Evaluation of Peel Strength>
First, a glass substrate having an ITO wiring (size of glass substrate: 2.5 mm x 28 mm, thickness of glass substrate: 300 μm, size of ITO wiring: 2500 μm (2.5 mm) x 300 μm, thickness of ITO wiring: 0.2 μm, number of ITO wiring: 28, space between ITO wiring: 300 μm) was prepared. The adhesive film with fluororesin film of each of the examples and comparative examples prepared as described above was cut into 2 mm x 23 mm, and the cut adhesive film was placed on the glass substrate with the adhesive film side facing down. At this time, the long side of the adhesive film was placed perpendicular to the ITO wiring. Thereafter, a thermocompression bonding device (heating method: constant heat type, manufactured by Taiyo Kikai Seisakusho Co., Ltd.) was used to perform thermocompression bonding under conditions of a bonding temperature of 60 ° C., a bonding pressure of 1 MPa, and a bonding time of 1 second, to obtain a laminate. FIG. 5 is a schematic top view showing a laminate in the peel strength measurement of the examples. The laminate 40 shown in FIG. 5 includes a glass substrate 43 having an ITO wiring (a substrate including a glass substrate 41 and an ITO wiring 42 provided on the glass substrate 41) and an adhesive film 10A arranged on the glass substrate 43 having an ITO wiring. Next, the fluororesin film was peeled off from the adhesive film, and a polyimide tape cut to 1.8 mm x 35 mm was attached to the adhesive film to obtain a measurement sample. The glass substrate side of the measurement sample was placed on a hot plate set at 40° C., and the tip of the polyimide tape was set in a tensile strength measuring device (Tensilon). The glass substrate was fixed horizontally, and the polyimide tape was pulled in the vertical direction at a peeling speed of 50 mm/min to measure the peel strength. The results are shown in Table 1.

10, 10A...adhesive film, 11...adhesive component, 12...first conductive particles, 13...second conductive particles, 20...connection structure, 21...first substrate, 22...first electrode, 23...first electronic component, 24...second substrate, 25...second electrode, 26...second electronic component, 27...connection component, 28...cured adhesive component, 31...adhesive film, 32...copper foil, 33...aluminum foil, 40...laminate, 41...glass substrate, 42...ITO wiring, 43...glass substrate with ITO wiring.

Claims (5)

An adhesive component;
First conductive particles which are dendritic conductive particles;
and second conductive particles, which are conductive particles other than the first conductive particles and have a non-conductive core and a conductive layer provided on the core,
The flow rate of the adhesive film is 10% to 50%. The adhesive film according to claim 1, wherein the volume ratio of the content of the first conductive particles to the content of the second conductive particles is 5/1 or more. The adhesive film according to claim 1 or 2, wherein the total content of the first conductive particles and the second conductive particles is 20 parts by volume or more per 100 parts by volume of the adhesive component. The adhesive film according to claim 1 or 2, wherein the total content of the first conductive particles and the second conductive particles is 55 parts by volume or less per 100 parts by volume of the adhesive component. a first electronic component having a first substrate and a first electrode formed on the first substrate;
a second electronic component having a second substrate and a second electrode formed on the second substrate;
a connection member that electrically connects the first electrode and the second electrode to each other,
A connection structure, wherein the connection member comprises a cured product of the adhesive film according to claim 1 or 2.

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