Adhesive agent film for circuit connection, method for manufacturing connection structure, conductive material, and connection structure

Abstract

This adhesive agent film for circuit connection includes an adhesive agent component, and has a conductive particle intermixed region in which first conductive particles and second conductive particles having different average particle diameters are intermixed in a direction that is perpendicular to the thickness direction of the adhesive agent film. When D1 (μm) is the average particle diameter of the first conductive particles and D2 (μm) is the average particle diameter of the second conductive particles, the average particle diameter ratio D1 / D2 is less than 1. The second conductive particles each have a nuclear body that is formed from a resin, and a conductive outermost layer that is provided on the nuclear body. When C1 (number / mm2) is the number of first conductive particles per unit area and C2 (number / mm2) is the number of second conductive particles per unit area, the particle number ratio C1 / C2 is 1-13.

Description

Adhesive film for circuit connection, method for manufacturing connection structure, conductive material, and connection structure

[0001] The present invention relates to an adhesive film for circuit connection, a method for producing a connection structure, a conductive material, and a connection structure.

[0002] In recent years, various adhesives have been used to fix electronic components or connect circuits in the fields of semiconductors, liquid crystal displays, etc. In these applications, the trend toward higher density and higher definition is progressing, and adhesives are required to have high adhesive properties and reliability. In particular, as a circuit connecting material, conductive adhesives containing conductive particles are used in connecting a liquid crystal display and a tape carrier package (TCP), connecting a flexible printed circuit (FPC) and a TCP, connecting an FPC and a printed wiring board (PWB), connecting a semiconductor silicon chip and a substrate, connecting an FPC and a touch panel module, connecting FPCs to each other, connecting a COF (Chip On Flex) FPC to a PWB by a COF mounting method, connecting a COF FPC to an FPC, and the like (see, for example, Patent Documents 1 to 3).

[0003] JP-A-60-191228 JP-A-1-251787 International Publication No. 2009 / 063827

[0004] Recently, connection structures obtained by FPC / FPC connection, COF FPC / FPC connection, FPC / PWB connection, or COF FPC / PWB connection via an adhesive film have come to be used as components for terminals such as organic light-emitting diode (OLED) devices, liquid crystal display terminals (smartphones, tablets, smartwatches, etc.), and wearable terminals (terminals worn on the body). When producing such connection structures, from the viewpoint of reducing the load on the mounting components, the adhesive film for circuit connection is required to have excellent connection reliability even when circuit components are connected at low pressure (for example, 1 MPa or less). However, it is difficult to apply sufficient pressure to the conductive particles, and the connection reliability of the connection structure tends to deteriorate. In particular, it is difficult to maintain the desired conductivity when the environmental temperature of the connection structure changes.

[0005] Therefore, the main object of the present invention is to provide an adhesive film for circuit connection, a method for producing a connection structure, and a connection structure that can provide a connection structure with a small resistance increase ratio in a heat cycle test even when mounted at low pressure. Another object of the present invention is to provide a conductive material that can be used to produce the above-mentioned adhesive film for circuit connection.

[0006] One aspect of the present invention relates to the following [1] to

[10] .

[0007] [1] An adhesive film for circuit connection, the adhesive film containing an adhesive component, having a conductive particle mixed region in which first conductive particles and second conductive particles having different average particle diameters are mixed in a direction perpendicular to the thickness direction of the adhesive film, and the average particle diameter of the first conductive particles is D １ (μm), the average particle size of the second conductive particles is D ２ (μm), the average particle size ratio D １ / D ２ is less than 1, the second conductive particles have a core formed of a resin and a conductive outermost layer provided on the core, and the number of particles per unit area of ​​the first conductive particles is C １ (pcs / mm ２ ), the number of particles per unit area of ​​the second conductive particles is C ２ (pcs / mm ２), the particle number ratio C １ / C ２ is 1 to 13. [2] The adhesive film for circuit connection according to [1], wherein the outermost surface of the first conductive particles and the outermost layer of the second conductive particles contain different metals. [3] The adhesive film for circuit connection according to [2], wherein the outermost surface of the first conductive particles contains the metal having the greatest hardness of the different metals. [4] The adhesive film for circuit connection according to [2], wherein the average particle size ratio D １ / D ２ [5] The adhesive film for circuit connection according to any one of [1] to [3], wherein the particle number ratio C is 0.25 to 0.8. １ / C ２ [6] The adhesive film for circuit connection according to any one of [1] to [4], wherein the average particle size ratio D １ / D ２ is 0.25 to 0.8, and the particle number ratio C １ / C ２ [7] The adhesive film for circuit connection according to any one of [1] to [6], wherein the adhesive component contains urethane (meth)acrylate. [8] The adhesive film for circuit connection according to any one of [1] to [6], wherein the adhesive component contains first conductive particles and second conductive particles having different average particle diameters, and the average particle diameter of the first conductive particles is set to D １ (μm), the average particle size of the second conductive particles is D ２ (μm), the average particle size ratio D １ / D ２is less than 1, and the ratio of the number of the first conductive particles to the number of the second conductive particles is 1 to 13. [9] A method for producing a connection structure, comprising the steps of: placing the adhesive film for circuit connection according to any one of claims 1 to 7 between a surface of a first circuit member having a first electrode, on which the first electrode is provided, and a surface of a second circuit member having a second electrode, on which the second electrode is provided; and thermocompression bonding the first circuit member and the second circuit member via the adhesive film for circuit connection at a pressure of 1 MPa or less, thereby electrically connecting the first electrode and the second electrode to each other and bonding the first circuit member and the second circuit member together.

[10] A connection structure comprising: a first circuit member having a first electrode; a second circuit member having a second electrode; and a circuit connection portion that electrically connects the first electrode and the second electrode to each other and bonds the first circuit member to the second circuit member, wherein the circuit connection portion comprises a cured product of the adhesive film for circuit connection according to any one of [1] to [7].

[0008] According to the present invention, it is possible to provide an adhesive film for circuit connection, a method for manufacturing a connection structure, and a connection structure that can obtain a connection structure with a small rate of increase in resistance in a heat cycle test even when mounted at low pressure. Furthermore, according to the present invention, it is possible to provide a conductive material that can be used to produce the above-mentioned adhesive film for circuit connection.

[0009] Fig. 1 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection. Fig. 2 is a schematic cross-sectional view showing one embodiment of a circuit connection structure. Fig. 3 is a schematic diagram showing a method for producing a mounting body for reliability testing. Fig. 4 is a schematic diagram showing a method for measuring connection resistance in a reliability test.

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent parts will be designated by the same reference numerals, and duplicated explanations will be omitted. Note that the present invention is not limited to the following embodiment.

[0011] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of another numerical range. Furthermore, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, individually described upper and lower limits can be arbitrarily combined. In the expression "A to B," the numerical values ​​A and B at both ends are included as the lower and upper limits, respectively, in the numerical range. In this specification, for example, the expression "10 or more" means "10" and "a number greater than 10," and this also applies when the numerical values ​​are different. Furthermore, for example, the expression "10 or less" means "10" and "a number less than 10," and this also applies when the numerical values ​​are different. Furthermore, in this specification, "(meth)acrylate" means at least one of acrylate and its corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl" and "(meth)acrylic acid." Furthermore, "A or B" may contain either A or B, or may contain both. Furthermore, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When a plurality of substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified.

[0012] [Adhesive Film for Circuit Connection] The adhesive film for circuit connection of this embodiment contains an adhesive component and has a conductive particle-mixed region in which first conductive particles and second conductive particles having different average particle sizes are mixed in a direction perpendicular to the thickness direction of the adhesive film. When the adhesive film is a single layer, the entire film may be a conductive particle-mixed region, and when the adhesive film has a multi-layer structure, at least one layer may be a conductive particle-mixed region.

[0013] The adhesive film for circuit connection of this embodiment may satisfy all of the following conditions: (a) the average particle size of the first conductive particles is D１ (μm), the average particle size of the second conductive particles is D ２ (μm), the average particle size ratio D １ / D ２ (b) the second conductive particles have a core formed of a resin and a conductive outermost layer provided on the core; (c) the number of particles per unit area of ​​the first conductive particles is C １ (pcs / mm ２ ), the number of second conductive particles per unit area is C ２ (pcs / mm ２ ), the particle number ratio C １ / C ２ is 1 to 13. The number of conductive particles per unit area can be determined by observing the adhesive film at a magnification of 200 times using a metallurgical microscope and measuring the number of conductive particles present in a predetermined area.

[0014] The above-described adhesive film for circuit connection can provide a connection structure with a small resistance increase ratio in a heat cycle test, even when circuit components are mounted at low pressure. The inventors speculate as follows about the reason for this effect. First, a connection structure mounted at low pressure using an adhesive film containing conductive particles is likely to experience an increase in resistance in a heat cycle test because it is difficult to apply sufficient pressure to the conductive particles, resulting in uneven pressure across the connection surfaces of the circuit components. In contrast, the inventors speculate that the above-described adhesive film for circuit connection has a core formed of a resin, and the second conductive particles with a large average particle size preferentially contact the electrodes, thereby absorbing the uneven pressure, while the first conductive particles, mixed at a predetermined particle number ratio, ensure sufficient conductivity, resulting in the formation of a circuit connection that can sufficiently maintain conductivity despite changes in environmental temperature.

[0015] The variation in pressure within the connection surface of the circuit component described above is thought to tend to increase when the circuit component has a flexible substrate or when the connection area of ​​the circuit component is large, but even in such cases, the adhesive film for circuit connection described above makes it possible to suppress the resistance increase ratio in a heat cycle test.

[0016] Figure 1 is a schematic cross-sectional view showing one embodiment of an adhesive film. As shown in Figure 1, the adhesive film 1 contains first conductive particles 2, second conductive particles 3 having an average particle size larger than that of the first conductive particles 2, and an adhesive component 4. The second conductive particles 3 have a core 3a formed of a resin and a conductive outermost layer 3b provided on the core 3a. The first conductive particles 2 and the second conductive particles 3 are dispersed in the adhesive component 4 and are mixed in the adhesive film 1 so as to satisfy the above condition (c).

[0017] The first conductive particles 2 can be particles made of one or more metal materials selected from the group consisting of silver, gold, platinum, tin, cobalt, iron, nickel, aluminum, titanium, zinc, copper, and indium.

[0018] The shape of the first conductive particles 2 may be, for example, spherical, approximately spherical, elliptical, angular, or scaly, and may be spherical or approximately spherical from the viewpoint of dispersibility of the conductive particles during mounting.

[0019] From the viewpoint of suitably thinning the adhesive film, the average particle size of the first conductive particles 2 may be 30 μm or less, 25 μm or less, or 22 μm or less, or may be 1 μm or more, 3 μm or more, or 10 μm or more. From the viewpoint described above, the average particle size of the first conductive particles 2 may be 1 to 30 μm, 3 to 30 μm, or 3 to 25 μm.

[0020] In this specification, the average particle size of the conductive particles refers to D50 measured by a particle size distribution measuring device (Microtrac (product name, Nikkiso Co., Ltd.)) using a laser diffraction / scattering method.

[0021] Commercially available products may be used as the first conductive particles 2. Examples of the Ni particles include "SFR-Ni5.0" (product name, Ni particles, average particle size: 6 μm, manufactured by Nippon Atomize Kako Co., Ltd.).

[0022] The second conductive particle 3 has a core 3 a made of a resin and a conductive layer 3 b provided on the core 3 a. Examples of the resin that forms the core include acrylic resin, styrene resin, silicone resin, polybutadiene resin, and copolymers of monomers that constitute these resins. Specific examples of the monomer include divinylbenzene, 1,4-divinyloxybutane, divinyl sulfone, diallyl phthalate, diallyl acrylamide, triallyl (iso)cyanurate, allyl compounds including trimellitate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol, di(delta)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol, hexa(meth)acrylate, pentaerythritol, penta(meth)acrylate, and (poly)methylene glycol di(meth)acrylate compounds including glycerol tri(meth)acrylate. These may be used alone or in combination of two or more.

[0023] The average particle size of the cores may be, for example, 2 μm or more, 30 μm or less, 2 to 30 μm, or 3 to 20 μm.

[0024] The conductive layer is formed of, for example, gold, silver, copper, nickel, palladium, or an alloy thereof. From the viewpoint of excellent conductivity, the conductive layer may contain at least one selected from gold, nickel, and palladium, or may contain gold or palladium, or may contain gold alone. 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, 400 nm or less, 10 to 400 nm, or 50 to 300 nm.

[0025] The shape of the second conductive particles 3 may be, for example, spherical, approximately spherical, angular, or scale-like, and may be spherical or approximately spherical from the viewpoint of dispersibility of the conductive particles during mounting.

[0026] The average particle size of the second conductive particles 3 may be 30 μm or less, 25 μm or less, or 22 μm or less from the viewpoint of suitably thinning the adhesive film, and may be 1 μm or more, 3 μm or more, or 10 μm or more from the viewpoint of connection reliability. From the above viewpoints, the average particle size of the first conductive particles 2 may be 1 to 30 μm, 3 to 30 μm, or 3 to 25 μm.

[0027] The second conductive particles 3 may be commercially available products.

[0028] In the adhesive film of this embodiment, the average particle size of the first conductive particles is D １ (μm), the average particle size of the second conductive particles is D ２ (μm), the average particle size ratio D １ / D ２ is less than 1, but from the viewpoint of suppressing variations in pressure within the connection surface of the circuit member, the average particle size ratio D １ / D ２ may be 0.25 to 0.8, may be 0.3 to 0.7, or may be 0.5 to 0.7.

[0029] In the adhesive film of this embodiment, the number of first conductive particles per unit area is C １ (pcs / mm ２ ), the number of second conductive particles per unit area is C ２ (pcs / mm ２ ), the particle number ratio C １ / C ２ is 1 to 13, but from the viewpoint of suppressing variations in pressure within the connection surface of the circuit member, the particle number ratio C １ / C ２ may be 3 or more, 4 or more, 5 or more, or 7 or more, and may be 13 or less, or 8 or less. １ / C ２ may be 3 to 13, 5 to 13, 7 to 13, 3 to 8, or 3 to 5.

[0030] From the viewpoint of obtaining excellent connection reliability, the number of first conductive particles per unit area in the adhesive film C １ (pcs / mm ２ ) is 300 to 5000 pieces / mm ２ and 500 to 5000 pieces / mm ２ and 1000 to 5000 pieces / mm ２ and 2000 to 5000 pieces / mm ２ and 2500 to 5000 pieces / mm ２ It may be.

[0031] From the viewpoint of obtaining excellent connection reliability, the number of second conductive particles per unit area in the adhesive film C ２ (pcs / mm ２ ) is 30 to 2000 pieces / mm ２ and 100 to 2000 pieces / mm ２ and 100 to 1000 pieces / mm ２ It may be.

[0032] In the adhesive film of this embodiment, the outermost surfaces of the first conductive particles and the outermost layers of the second conductive particles may contain different metals, and from the viewpoint of connection reliability, the outermost surfaces of the first conductive particles may contain the metal with the greatest hardness among the different metals. An example of such a metal combination is when the outermost surfaces of the first conductive particles contain Ni and the outermost layers of the second conductive particles contain Au or Pd.

[0033] In this specification, the hardness of a metal means the Mohs hardness.

[0034] The conductive material containing the first conductive particles and the second conductive particles under the above conditions can be used as a constituent material of an adhesive film for circuit connection.

[0035] The adhesive component 4 is composed of a material that is curable by heat or light, and may be a radical-curing adhesive, an epoxy-based adhesive, or a thermoplastic adhesive such as polyurethane or polyvinyl ester. Among 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.

[0036] The radical curing adhesive contains, for example, a radical polymerizable substance and a radical polymerization initiator, and may further contain a thermoplastic resin, a filler, other additives, and the like, as necessary.

[0037] The radical polymerizable substance can be any substance having a functional group that polymerizes by radicals, without any particular limitation. Specific examples include radical polymerizable substances such as (meth)acrylate compounds, maleimide compounds, citraconic acid 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.

[0038] Examples of the (meth)acrylate compound 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] ...

[0033] Examples of suitable 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.

[0039] As the radical polymerizable substance other than the (meth)acrylate compound, for example, the compounds described in WO 2009 / 063827 can be suitably used. The radical polymerizable substance may be used alone or in combination of two or more.

[0040] From the viewpoint of obtaining high connection reliability, the radical polymerizable substance preferably contains either a urethane (meth)acrylate or an isocyanuric acid EO-modified di(meth)acrylate, and more preferably contains both a urethane (meth)acrylate and an isocyanuric acid EO-modified di(meth)acrylate. From the viewpoint of easily obtaining particularly high connection reliability, the ratio thereof may be 3:1 to 1:3 by mass, or may be 2:1 to 1:2, or 1.5:1 to 1:1.5. From the viewpoint of improving heat resistance, a compound having at least one substituent selected from the group consisting of a dicyclopentenyl group, a tricyclodecanyl group, and a triazine ring may be used as the (meth)acrylate compound.

[0041] The content of the radical polymerizable substance may be 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, or 40 parts by mass or more, and may be 90 parts by mass or less, 80 parts by mass or less, or 70 parts by mass or less, relative to 100 parts by mass of the total amount of the adhesive component 4.

[0042] The content of the radical polymerizable substance may be 10 parts by mass or more, 30 parts by mass or more, or 50 parts by mass or more, and may be 90 parts by mass or less, 80 parts by mass or less, or 70 parts by mass or less, relative to 100 parts by mass of the total of the radical polymerizable substance and the thermoplastic resin that is optionally blended.

[0043] The radical polymerization initiator can be any compound that decomposes upon heating or irradiation with light to generate free radicals. Specific examples include peroxide compounds and azo compounds. These compounds are appropriately selected depending on the intended bonding temperature, bonding time, pot life, etc.

[0044] More specific examples of the radical polymerization initiator include diacyl peroxides, peroxydicarbonates, peroxyesters (for example, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane), peroxyketals, dialkyl peroxides, hydroperoxides, and silyl peroxides. Among these, peroxyesters, dialkyl peroxides, hydroperoxides, and silyl peroxides are preferred, and peroxyesters that provide high reactivity are more preferred. As these radical polymerization initiators, for example, compounds described in WO 2009 / 063827 can be suitably used. The radical polymerization initiators can be used alone or in combination of two or more.

[0045] The content of the radical polymerization initiator may be 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the total of the radical polymerizable substance and the thermoplastic resin blended as needed.

[0046] The epoxy adhesive contains, for example, an epoxy resin and a curing agent, and may further contain a thermoplastic resin, a filler, other additives, and the like, as necessary.

[0047] Examples of epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, bisphenol F novolac epoxy resins, alicyclic epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, hydantoin epoxy resins, isocyanurate epoxy resins, and aliphatic chain epoxy resins. 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 a side chain. These epoxy resins may be used alone or in combination of two or more.

[0048] The content of the epoxy resin may be 10 parts by mass or more, 30 parts by mass or more, or 50 parts by mass or more, and may be 90 parts by mass or less, 80 parts by mass or less, or 70 parts by mass or less, relative to 100 parts by mass of the total amount of the adhesive component 4.

[0049] The content of the epoxy resin may be 10 parts by mass or more, 30 parts by mass or more, or 50 parts by mass or more, and may be 90 parts by mass or less, 80 parts by mass or less, or 70 parts by mass or less, relative to 100 parts by mass in total of the epoxy resin and the thermoplastic resin blended as necessary.

[0050] The curing agent is not particularly limited as long as it can cure the epoxy resin, and examples thereof 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 are fast-curing agents and do not require consideration of chemical equivalents.

[0051] 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. Modified versions of these can also be used. Examples of polyaddition-type curing agents include polyamines, polymercaptans, polyphenols, acid anhydrides, etc.

[0052] These curing agents are preferably microencapsulated by coating them with a polymeric substance such as a polyurethane or polyester, a thin metal film such as nickel or copper, or an inorganic substance such as calcium silicate, because this extends the usable time. The curing agents may be used singly or in combination of two or more.

[0053] The content of the curing agent may be 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the total of the epoxy resin and the thermoplastic resin blended as needed.

[0054] The adhesive component 4 may contain a thermoplastic resin. When the radical curing adhesive or epoxy adhesive contains a thermoplastic resin, it can 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. As the thermoplastic resin, for example, compounds described in International Publication No. 2009 / 063827 can be suitably used. The thermoplastic resin may be used alone or in combination of two or more.

[0055] The content of the thermoplastic resin may be 10 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more, and may be 60 parts by mass or less, 50 parts by mass or less, or 40 parts by mass or less, relative to 100 parts by mass of the total amount of the adhesive component 4.

[0056] An example of a radical-curing adhesive is a thermal radical-curing adhesive containing a radical-polymerizable material containing a radical-polymerizable 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 containing a thermosetting material containing an epoxy resin that is liquid at 30°C, a curing agent, and a thermoplastic resin.

[0057] A filler may be blended into the adhesive component 4. Examples of fillers include non-conductive particles. The non-conductive particles may be inorganic non-conductive particles or organic non-conductive particles. Examples of inorganic non-conductive particles include silica particles.

[0058] The content of the filler may be 1% by mass or more, or 10% by mass or more, and may be 50% by mass or less, or 30% by mass or less, based on the total mass of the adhesive film 1 .

[0059] The adhesive component 4 may contain other additives as needed. Examples of other additives include coupling agents and components that relieve internal stress. When the adhesive component 4 further contains a component that relieves internal stress, warping of the substrate caused by the difference in linear expansion coefficient between the IC chip and the substrate can be suppressed when the adhesive component 4 is used to connect an IC chip to a glass substrate, a flexible printed circuit board (FPC), or the like. Specific examples of components that relieve internal stress include acrylic rubber and elastomer components.

[0060] The thickness of the adhesive film 1 (d shown in FIG. 1) may be, for example, 50 μm or less, 45 μm or less, or 40 μm or less, or 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The width of the conductive particle-containing region in the thickness direction of the adhesive film may be within the above range.

[0061] The adhesive film 1 can be obtained, for example, by applying a paste-like adhesive composition to a resin film such as a PET (polyethylene terephthalate) film or a fluororesin film, and then drying it. The paste-like adhesive composition can be obtained, for example, by heating or dissolving in a solvent a mixture containing the adhesive component 4, the first conductive particles 2, and the second conductive particles 3. As the solvent, for example, a solvent having a boiling point of 50°C or higher and 150°C or lower under atmospheric pressure (e.g., toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, butyl acetate, etc.) can be used.

[0062] The adhesive film 1 may be composed of multiple adhesive layers. In this case, a layer containing a mixture of the first conductive particles 2 and the second conductive particles 3 may constitute at least one of the multiple adhesive layers.

[0063] The adhesive film 1 can be cured, for example, by 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.

[0064] The adhesive film 1 can be adhered to an adherend by applying heat and pressure in combination. 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 longer and 120 seconds or shorter.

[0065] The adhesive film for circuit connection of this embodiment can be used as a circuit connecting material for low pressure mounting (for example, a pressure of 1 MPa or less). ２ Even in the above cases, a connection structure with a small rate of increase in resistance in a heat cycle test can be obtained by low-pressure mounting.

[0066] [Method for manufacturing connection structure] The method for manufacturing a connection structure of this embodiment includes: step A of placing the adhesive film for circuit connection of this embodiment described above between the surface on which the first electrode of a first circuit member having a first electrode is provided and the surface on which the second electrode of a second circuit member having a second electrode is provided; and step B of thermocompression bonding the first circuit member and the second circuit member via the adhesive film for circuit connection at a pressure of 1 MPa or less, thereby electrically connecting the first electrode and the second electrode to each other and bonding the first circuit member and the second circuit member together.

[0067] Hereinafter, a method for producing a circuit connection structure will be described, taking as an example an embodiment in which the adhesive film 1 is used as the adhesive film for circuit connection of this embodiment.

[0068] 2 is a schematic cross-sectional view showing one embodiment of a connection structure obtained using an adhesive film 1. As shown in FIG. 2, the circuit connection structure 100 includes a first circuit board 11 and a first circuit member 10 having a first electrode 15 formed on the main surface of the first circuit board 11, a second circuit board 21 and a second circuit member 20 having a second electrode 25 formed on the main surface of the second circuit board 21, and a circuit connection portion disposed between the first circuit member 10 and the second circuit member 20, electrically connecting the first electrode 15 and the second electrode 25 to each other via first conductive particles 2 and second conductive particles 3, and bonding the first circuit member 10 and the second circuit member 20 together. The circuit connection portion is composed of a cured product of the adhesive film 1 and includes a cured product 5 of an adhesive component and first conductive particles 2 and second conductive particles 3 dispersed in the cured product 5.

[0069] The first circuit member 10 and the second circuit member 20 may be the same or different from each other. The first circuit member 10 and the second circuit member 20 may be a glass substrate or a plastic substrate on which electrodes are formed, a printed wiring board, a ceramic wiring board, a flexible wiring board, an IC chip, or the like. The first circuit member 10 and the second circuit member 20 may be formed from an inorganic material such as a semiconductor, glass, or ceramic, an organic material such as polyimide or polycarbonate, or a composite such as glass / epoxy. Among these, since the adhesive film 1 for circuit connection can be suitably used for FPC / PWB connection, FPC / PWB connection for COF, FPC / FPC connection, and FPC / PET (PET substrate) connection, the first circuit member 10 may be, for example, a plastic substrate made of an organic material such as polyimide, polycarbonate, polyethylene terephthalate, or cycloolefin polymer, and the second circuit member 20 may be, for example, formed from a printed wiring board, an inorganic material such as a semiconductor, glass, or ceramic, an organic material such as polyimide or polycarbonate, or a composite such as glass / epoxy.

[0070] The first electrode 15 and the second electrode 25 may be electrodes containing metals such as gold, silver, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, aluminum, molybdenum, and titanium, or oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), and indium gallium zinc oxide (IGZO). The first electrode 15 and the second electrode 25 may be electrodes formed by laminating two or more of these metals, oxides, and the like. An electrode formed by laminating two or more of these metals, oxides, and the like may have two or more layers, or three or more layers. When the first circuit member 10 is an FPC, the first electrode 15 may be an electrode having a Sn-plated layer or an Au-plated layer on its outermost surface. When the second circuit member 20 is a printed wiring board, the second electrode 25 may be an electrode having a Ni-plated layer, an Au-plated layer, a Ni / Au-plated layer, a Cu layer, or an Ag layer on its outermost surface.

[0071] In the connection structure of this embodiment, the first conductive particles 2 and the second conductive particles 3 are used in combination in a predetermined ratio, so that the first electrode 15 and the second electrode 25 can be suitably connected.

[0072] In step A, the adhesive film 1 for circuit connection may be laminated onto one of the first circuit member 10 and the second circuit member 20, and then the other circuit member may be placed on the laminated adhesive film 1 for circuit connection so that the first electrode 15 and the second electrode 25 face each other.

[0073] The heating temperature during thermocompression bonding in step B can be set as appropriate, and may be, for example, 50 to 250°C, or 100 to 200°C. In the case of low-pressure mounting, the pressure may be, for example, 1 MPa or less, or 0.5 to 1.0 MPa, calculated as an area pressure for the area where the adhesive film for circuit connection contacts the electrode. The heating and pressurizing time may be in the range of 0.5 to 120 seconds.

[0074] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0075] <Synthesis of polyurethane acrylate (UA1)> 2,500 parts by mass (2.50 mol) of poly(1,6-hexanediol carbonate) (trade name: Duranol T5652, manufactured by Asahi Kasei Chemicals Corporation, number average molecular weight 1,000) and 666 parts by mass (3.00 mol) of isophorone diisocyanate (manufactured by Sigma-Aldrich Co.) were uniformly added dropwise over 3 hours to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser with a calcium chloride drying tube, and a nitrogen gas inlet tube. Next, nitrogen gas was sufficiently introduced into the reaction vessel, and the reaction vessel was heated to 70 to 75°C to allow the mixture to react. 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, followed by the addition of 238 parts by mass (2.05 mol) of 2-hydroxyethyl acrylate (Sigma-Aldrich), and the mixture was allowed to react for 6 hours at 70°C in an air atmosphere. This yielded polyurethane acrylate (UA1). The weight-average molecular weight of polyurethane acrylate (UA1) was 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: GPC-8020 manufactured by Tosoh Corporation Detector: RI-8020 manufactured by Tosoh Corporation Column: Gelpack GLA160S + GLA150S manufactured by Resonaq Techno Service Co., Ltd. Sample concentration: 120 mg / 3 mL Solvent: tetrahydrofuran Injection volume: 60 μL Pressure: 2.94 × 10 Pa (30 kgf / cm) Flow rate: 1.00 mL / min

[0076] (Preparation of Solution A1) As thermoplastic resins, 5.36 parts by mass of phenoxy resin A (manufactured by Tomoe Engineering Co., Ltd., product name: PKHC) and 4.77 parts by mass of phenoxy resin B (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: ZX-1356-2) were used, and as radical polymerizable substances, 10.59 parts by mass of polyurethane acrylate (UA1) synthesized as described above, 0.69 parts by mass of isocyanuric acid EO-modified di- and triacrylate (manufactured by Toa Gosei Co., Ltd., product name: M-315), and dimethyloltricyclodecane diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., product name: DC Solution A1 was obtained by mixing 0.78 parts by mass of EO-modified phosphate dimethacrylate (manufactured by Nippon Kayaku Co., Ltd., product name: PM-21), 0.39 parts by mass 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, 7.22 parts by mass of silica particles (manufactured by Admatechs Co., Ltd., product name: SE-2050, average particle size: 0.5 μm) as a filler, and 2.0 parts by mass of toluene as a solvent. The adhesive component contained in Solution A1 (hereinafter also referred to as "adhesive component a1")

[0077]

[0078] <Preparation of Conductive Particles> The following conductive particles were prepared. Conductive Particle B1: "SFR-Ni5.0" (manufactured by Nippon Atomize Kako Co., Ltd., product name, Ni particles, average particle size: 6 μm) Conductive Particle B2: Ni particles (average particle size: 3 μm) Conductive Particle B3: Ni particles (average particle size: 10 μm) Conductive Particle B4: Conductive particles having a plastic core surface plated with Au (average particle size: 10 μm) Conductive Particle B5: Conductive particles having a plastic core surface plated with Ni (average particle size: 5 μm) Conductive Particle B6: Conductive particles having a plastic core surface plated with Ni and an outermost surface displacement plated with Pd (average particle size: 5 μm)

[0079] <Preparation of Adhesive Film> (Example 1) Conductive particles B1 and conductive particles B4 were dispersed in solution A1 so that the mass ratio of adhesive component a1:first conductive particles:second conductive particles was 100:6:1.3, to obtain a mixed solution. The obtained mixed solution was applied to a 50 μm thick fluororesin film, and the solvent was removed by hot air drying at 70° C. for 5 minutes, to obtain a 35 μm thick adhesive film formed on the fluororesin film (adhesive film with fluororesin film).

[0080] (Examples 2 to 8 and Comparative Examples 1 to 3) The adhesive films of Examples 2 to 8 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the blending ratios of adhesive component a1, the first conductive particles, and the second conductive particles, and the types of the first conductive particles and the second conductive particles were changed as shown in Table 2 or Table 3.

[0081]

[0082]

[0083] 3( a) and 3(b), the adhesive films with fluororesin film of Examples 1 to 8 and Comparative Examples 1 to 3 were cut into 150 mm × 100 mm pieces, and a 1.5 mm wide adhesive film 31 was prepared using a plotter. The adhesive film 31 was placed in the approximate center of a 20 mm × 40 mm printed wiring board (PWB) 32 (having circuit electrodes in which Ni / Au plating was applied to copper wiring with a line width of 200 μm, a pitch of 200 μm, and a thickness of 1 μm) so that the adhesive film 31 was in contact with the PWB 32, and the adhesive film 31 was thermocompression bonded from the fluororesin film side using a thermocompression bonding device (manufactured by Ohashi Manufacturing Co., Ltd., BD-07) under conditions of a bonding temperature of 70°C, a bonding pressure of 1 MPa, and a bonding 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 20 mm x 40 mm flexible circuit board (COF FPC) (having circuit electrodes with Sn-plated copper wiring) 33 was prepared, and this was placed on top of the laminate of PWB 32 and adhesive film 31 so as to cover the adhesive film 31, and thermocompression bonding was performed from the side of COF FPC 33 using a thermocompression bonding device (manufactured by Ohashi Manufacturing Co., Ltd., BD-07) under conditions of a compression temperature of 170°C, a compression pressure of 1 MPa, and a compression time of 6 seconds, thereby obtaining a mounting body for evaluation.

[0084] An ammeter and a voltmeter were connected to the resulting assembly as shown in Figure 4, and the connection resistance (initial connection resistance) was measured using the four-terminal method. Furthermore, using a TSA-43EL manufactured by Espec Corporation, the assembly was subjected to a heat cycle test in which the following heat cycle was repeated 500 times: holding at -40°C for 30 minutes, heating to 100°C over 10 minutes, holding at 100°C for 30 minutes, and cooling to -40°C over 10 minutes. The connection resistance (post-test connection resistance) was then measured in the same manner as above. The resistance increase ratio was calculated using the following formula. The results are shown in Tables 2 and 3. Reliability (resistance increase ratio) = [maximum post-test connection resistance] / [maximum initial connection resistance]

[0085] REFERENCE SIGNS LIST 1...adhesive film, 2...first conductive particles, 3...second conductive particles, 4...adhesive component, 5...cured product of adhesive component, 10...first circuit member, 11...first circuit board, 15...first electrode, 20...second circuit member, 21...second circuit board, 25...second electrode, 31...adhesive film, 32...PWB, 33...FPC for COF, 100...circuit connection structure.

Claims

1. An adhesive film used for connecting circuits, the adhesive film includes an adhesive component, and has a conductive particle mixed region in which first conductive particles and second conductive particles having different average particle diameters are mixed in a direction perpendicular to the thickness direction of the adhesive film, and the average particle diameter of the first conductive particles is D １ (μm), the average particle size of the second conductive particles is D ２ (μm), the average particle size ratio D １ / D ２ is less than 1, the second conductive particles have a core body formed of a resin and a conductive outermost layer provided on the core body, and the number of particles per unit area of ​​the first conductive particles is C １ (pcs / mm ２ ), the number of particles per unit area of ​​the second conductive particles is C ２ (pcs / mm ２ ), the particle number ratio C １ / C ２ The adhesive film for circuit connection, wherein 2. The adhesive film for circuit connection according to claim 1, wherein the outermost surface of the first conductive particles and the outermost layer of the second conductive particles comprise different metals.

3. The adhesive film for circuit connection according to claim 2, wherein the outermost surface of the first conductive particles contains the metal having the greatest hardness among the different metals.

4. Average particle size ratio D １ / D ２ The adhesive film for circuit connection according to claim 1, wherein the viscosity is 0.25 to 0.

8.

5. The particle number ratio C １ / C ２ The adhesive film for circuit connection according to claim 1, wherein the molecular weight is 3 to 13.

6. Average particle size ratio D １ / D ２ is 0.25 to 0.8, and the particle number ratio C １ / C ２ The adhesive film for circuit connection according to claim 3, wherein the molecular weight is 3 to 13.

7. The adhesive film for circuit connection according to claim 1, wherein the adhesive component contains a urethane (meth)acrylate.

8. The conductive material contains first conductive particles and second conductive particles having different average particle diameters, and the average particle diameter of the first conductive particles is D １ (μm), the average particle size of the second conductive particles is D ２ (μm), the average particle size ratio D １ / D ２ is less than 1; and a ratio of the number of the first conductive particles to the number of the second conductive particles is 1 to 13.

9. A method for manufacturing a connection structure, comprising the steps of: placing an adhesive film for circuit connection according to any one of claims 1 to 7 between a surface of a first circuit member having a first electrode, on which the first electrode is provided, and a surface of a second circuit member having a second electrode, on which the second electrode is provided; and thermocompressing the first circuit member and the second circuit member via the adhesive film for circuit connection at a pressure of 1 MPa or less, thereby electrically connecting the first electrode and the second electrode to each other and bonding the first circuit member and the second circuit member together.

10. A connection structure comprising: a first circuit member having a first electrode; a second circuit member having a second electrode; and a circuit connection portion that electrically connects the first electrode and the second electrode to each other and bonds the first circuit member to the second circuit member, wherein the circuit connection portion comprises a cured body of an adhesive film for circuit connection according to any one of claims 1 to 7.

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