Film-like adhesive and method for producing connection structure

Abstract

Provided is a film-like adhesive 1 for connecting a circuit, the film-like adhesive 1 containing: solder particles 2 having a Bi content of 20-60 mass% and an Sn content of 40-80 mass%; a radically polymerizable compound; and a thermal radical-generating agent, wherein the average particle diameter of the solder particles 2 is 0.6-1.5 times the thickness d1 of the film-like adhesive.

Description

[Technical Field]

[0001] The present specification relates to a film-like adhesive and a method for producing a connection structure. [Background technology]

[0002] In recent years, various adhesives have been used to fix electronic components or connect circuits in fields such as semiconductors and liquid crystal displays. These applications have seen increasing density and resolution, requiring adhesives with high adhesiveness and reliability. In particular, conductive adhesives containing conductive particles (e.g., anisotropic conductive adhesives) have been used as circuit connection materials for connecting liquid crystal displays to tape carrier packages (TCPs), flexible printed circuits (FPCs) to TCPs, FPCs to printed wiring boards (PWBs), semiconductor silicon chips to substrates, FPCs to touch panel modules, FPCs to FPCs, COF (chip-on-flex) FPCs to PWBs using COF mounting, and COF FPCs to FPCs (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 60-191228 [Patent Document 2] Japanese Patent Application Publication No. 1-251787 [Patent Document 3] International Publication No. 2009 / 063827 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, connection structures obtained by FPC / FPC connections, COF FPC / FPC connections, FPC / PWB connections, or COF FPC / PWB connections via film adhesives have come to be used as components for devices such as organic light-emitting diode (OLED) devices, liquid crystal display devices (smartphones, tablets, smartwatches, etc.), and wearable devices (devices worn on the body). These connection structures are required to have low connection resistance in order to improve display quality and reduce power consumption. Furthermore, in recent years, there has been a demand for film adhesives that can be mounted at lower pressures (e.g., 1 MPa or less) in order to reduce the load on mounting components.

[0005] Therefore, a main object of the present invention is to provide a film-like adhesive for circuit connection that can provide a connection structure that exhibits low connection resistance even when mounted at low pressure. [Means for solving the problem]

[0006] One aspect of the present invention relates to a film-like adhesive for circuit connection as shown in [1] below.

[0007] [1] A film-like adhesive for circuit connection, comprising solder particles having a Bi content of 20 to 60 mass % and an Sn content of 40 to 80 mass %, a radical polymerizable compound, and a thermal radical generator, wherein the average particle size of the solder particles is 0.5 to 1.5 times the thickness of the film-like adhesive.

[0008] The film-like adhesive on the side surface allows a connection structure that exhibits low connection resistance to be obtained even when mounting is performed at low pressure (for example, 1 MPa or less). Therefore, the connection structure obtained using the film-like adhesive on the side surface tends to exhibit excellent display quality and reduce power consumption.

[0009] The inventors speculate that the reason for the above-mentioned effect is as follows. First, conventional conductive adhesives using conductive particles electrically connect components through limited physical contact between the conductive particle surface and the electrode surface. In contrast, the film-like adhesive described above uses solder particles of the specific composition, which allows for intimate and extensive physical contact between the electrode surface and the solder particle surface, and also allows for the partial formation of a layer (metallic bond formed by a metal intercalation compound) in which the metal elements of the solder and the metal elements of the outermost electrode plating surface are mixed. Furthermore, in the film-like adhesive described above, the average particle size of the solder particles is 0.5 times or more the thickness of the film-like adhesive, which reduces the amount of adhesive component flow required to capture the solder particles. Therefore, the solder particles can be captured even in low-pressure mounting. For these reasons, it is speculated that the film-like adhesive described above provides the above-mentioned effect.

[0010] However, since the above-mentioned terminals are often placed in high-temperature, high-humidity environments, the connection structure may be required to have high connection reliability, capable of maintaining low connection resistance even in high-temperature, high-humidity environments. In contrast, the connection structure obtained using the film-like adhesive described above tends to exhibit a stable low connection resistance even after high-temperature, high-humidity environmental testing, and tends to have high reliability that allows excellent display quality to be maintained even in harsh environments.

[0011] Furthermore, solder particles of the above composition tend to have a softening point at a low temperature (for example, 130 to 180°C), and therefore, when the film-like adhesive of the above aspect is used, a connection structure that exhibits low connection resistance tends to be obtained even when mounting is performed at a low temperature.

[0012] The film adhesive on the side surface may be any of the film adhesives shown in [2] to [4] below.

[0013] [2] The film-like adhesive according to [1], which has a hardening point lower than the softening point of the solder particles.

[0014] [3] The film-like adhesive according to [1] or [2], wherein the viscosity of the film-like adhesive at the softening point of the solder particles is at least three times the minimum melt viscosity.

[0015] [4] The film-like adhesive according to any one of [1] to [3], wherein the softening point of the solder particles is 130 to 180°C.

[0016] Another aspect of the present invention relates to a method for producing a connection structure, comprising the steps of: placing the film adhesive described in any one of [1] to [4] 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 film adhesive 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.

[0017] The method for manufacturing a connection structure according to the above aspect may be a connection structure in which the first electrode is an electrode having an Au plating layer on its outermost surface, and the second electrode is an electrode having an Au plating layer or an Sn plating layer on its outermost surface. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a film-like adhesive for circuit connection that can obtain a connection structure that exhibits low connection resistance even when mounted at low pressure. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a film adhesive of one embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a film adhesive according to another embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a connection structure according to an embodiment. [Figure 4]FIG. 4 is a schematic cross-sectional view showing a method for manufacturing the connection structure of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] 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." The materials exemplified below may be used singly or in combination of two or more, unless otherwise specified. When multiple substances corresponding to each component are present in the composition, the content of each component refers to the total amount of the multiple substances present in the composition, unless otherwise specified. Numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. "A or B" means that either A or B may be present, or both may be present. "Room temperature" means 25°C, and "normal pressure" means 1 atmosphere.

[0021] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced by the upper or lower limit of another numerical range. In addition, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced by a value shown in the examples.

[0022] In one aspect, the present invention provides a film-like adhesive for circuit connection. Also, in another aspect, the present invention provides the application of a film-like adhesive or a cured product thereof to a connection structure or the manufacture thereof. Also, in one aspect, the present invention provides the application of a film-like adhesive or a cured product thereof to circuit connection. Also, in one aspect, the present invention provides the application of a connection structure for wearable applications.

[0023] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments in any way.

[0024] <Film adhesive> One embodiment of the film-like adhesive is a film-like adhesive for circuit connection, which contains solder particles having a Bi content of 20 to 60 mass % and an Sn content of 40 to 80 mass %, a radical polymerizable compound, and a thermal radical generator, and the average particle size of the solder particles is 0.5 to 1.5 times the thickness of the film-like adhesive.

[0025] In one embodiment, the film-like adhesive may have a hardening point lower than the softening point of the solder particles. In another embodiment, the viscosity of the film-like adhesive at the softening point of the solder particles may be three times or more the minimum melt viscosity. In another embodiment, the softening point of the solder particles may be 130 to 180°C.

[0026] Fig. 1 is a schematic cross-sectional view showing a film-like adhesive according to one embodiment. The film-like adhesive 1 shown in Fig. 1 is an adhesive for circuit connection, and contains (A) solder particles 2 (hereinafter also referred to as "component (A)") having a Bi content of 20 to 60 mass % and an Sn content of 40 to 80 mass %, (B) a radically polymerizable compound (hereinafter also referred to as "component (B)"), and (C) a thermal radical generator (hereinafter also referred to as "component (C)"). In the following description, components other than component (A) contained in the film-like adhesive 1 are referred to as adhesive components.

[0027] (Component (A): Solder particles) Component (A) contains 20 to 60% by mass of Bi (bismuth) and 40 to 80% by mass of Sn (tin). When the Bi and Sn compositions are within the above ranges, the liquid solder component melted at around 139°C and the solid solder component are mixed during thermocompression bonding. This allows the solder particles to wet and spread over the electrode surfaces while maintaining the distance between the electrodes, forming intimate and widespread physical contact and a partial metallic bond (a layer in which the metal elements of the solder and the metal elements of the outermost electrode plating surface are mixed). From the viewpoint of facilitating the formation of such a metallic bond, component (A) may be solder particles having a Bi content of 21 to 58% by mass and a Sn content of 42 to 79% by mass, or may be solder particles having a Bi content of 21 to 40% by mass and a Sn content of 60 to 79% by mass.

[0028] Component (A) may further contain other metal elements as long as the Bi content and Sn content are within the above-mentioned ranges. Examples of other metal elements include common metal elements that can be contained in solder. The metal elements contained in component (A) may be only Bi and Sn. When the metal elements contained in component (A) are only Bi and Sn (i.e., the total of the Bi content and the Sn content is 100 mass%), a connection structure that exhibits lower connection resistance and higher connection reliability is likely to be obtained.

[0029] The softening point of component (A) is, for example, 130 to 180°C. From the viewpoint of enabling low-temperature mounting, the softening point of component (A) may be 170°C or lower, 160°C or lower, 150°C or lower, or 140°C or lower. From the viewpoint of further improving the ability to capture solder particles, the softening point of component (A) may be 135°C or higher. From these viewpoints, the softening point of component (A) may be 130 to 170°C, 130 to 160°C, 130 to 150°C, or 130 to 140°C, or may be 135 to 170°C, 135 to 160°C, 135 to 150°C, or 135 to 140°C. The softening point of component (A) can be measured using a DSC (differential scanning calorimeter). Specifically, when component (A) is subjected to DSC measurement in a He gas flow at a temperature rise rate of 10°C / min, the first endothermic peak (first endothermic peak) that appears is taken as the softening point of component (A).

[0030] The average particle size of component (A) is 0.5 to 1.5 times the thickness of the film-like adhesive 1. From the viewpoint of further improving the solder particle capture ability and obtaining a connection structure exhibiting lower connection resistance, the average particle size of component (A) is preferably 0.6 times or more, and may be 0.7 times or more, or 0.8 times or more, the thickness of the film-like adhesive 1. From the viewpoint of ease of production and production stability, the average particle size of component (A) may be 1.3 times or less, 1.2 times or less, 1.1 times or less, 1.0 times or less, 0.9 times or less, or 0.8 times or less the thickness of the film-like adhesive 1. From these viewpoints, the average particle size of component (A) is set to 0.5 to 1.3 times, 0.5 to 1.2 times, 0.5 to 1.1 times, 0.5 to 1.0 times, 0.5 to 0.9 times, 0.5 to 0.8 times, 0.6 to 1.5 times, 0.6 to 1.3 times, 0.6 to 1.2 times, 0.6 to 1.1 times, 0.6 to 1.0 times, 0.6 ... the thickness of film-like adhesive 1. It may be 0.9 times, 0.6 to 0.8 times, 0.7 to 1.5 times, 0.7 to 1.3 times, 0.7 to 1.2 times, 0.7 to 1.1 times, 0.7 to 1.0 times, 0.7 to 0.9 times, 0.7 to 0.8 times, 0.8 to 1.5 times, 0.8 to 1.3 times, 0.8 to 1.2 times, 0.8 to 1.1 times, 0.8 to 1.0 times, or 0.8 to 0.9 times.

[0031] The average particle size of component (A) may be, for example, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, 18 μm or more, or 20 μm or more, or 55 μm or less, 30 μm or less, 28 μm or less, or 25 μm or less, or may be 3 to 55 μm, 5 to 30 μm, 10 to 28 μm, 15 to 28 μm, 18 to 25 μm, or 20 to 25 μm. In particular, when the thickness of the film-like adhesive is 25 μm or less, if the average particle size of component (A) is within the above range, the ability to capture solder particles can be further improved, and a connection structure exhibiting lower connection resistance tends to be obtained. A film-like adhesive 1 containing component (A) having an average particle size in the above range can be easily obtained, for example, by using solder particles whose particle size has been adjusted by classification or the like as component (A) used when producing the film-like adhesive 1 (for example, solder particles whose average particle size (D50 value) measured by instrumental analysis such as laser diffraction using a Microtrack measuring device (manufactured by Nikkiso Co., Ltd.) is within the above range).

[0032] The average particle size (D50 value) of component (A) in the film adhesive can be determined, for example, by dissolving the film adhesive in an organic solvent such as methyl ethyl ketone, filtering to separate component (A), and analyzing the resulting component (A) by instrumental analysis such as laser diffraction using, for example, a Microtrac measuring device (manufactured by Nikkiso Co., Ltd.).

[0033] From the viewpoint of achieving higher connection reliability in low-pressure mounting, component (A) preferably does not contain 10 volume % or more of particles with a particle diameter of 55 μm or more, more preferably does not contain 10 volume % or more of particles with a particle diameter of 30 μm or more, and even more preferably does not contain 10 volume % or more of particles with a particle diameter of 25 μm or more. From the same viewpoint, component (A) preferably does not contain 10 volume % or more of particles with a particle diameter of 5 μm or less, more preferably does not contain 10 volume % or more of particles with a particle diameter of 10 μm or less, and even more preferably does not contain 10 volume % or more of particles with a particle diameter of 15 μm or less.

[0034] The content of component (A) may be adjusted appropriately while taking into consideration the required resistance and the need to avoid short circuits due to particle bonding between adjacent electrodes. The content of component (A) may be, for example, 1 to 50 parts by mass, or 10 to 30 parts by mass, per 100 parts by mass of the total amount of the adhesive components.

[0035] (Component (B): radical polymerizable compound) Component (B) is a compound having a radically polymerizable functional group. Examples of component (B) include (meth)acrylate compounds, maleimide compounds, citraconic imide compounds, and nadimide compounds. "(Meth)acrylate compound" refers to a compound having a (meth)acryloyl group. Component (B) may be used in the form of a monomer or oligomer, or a monomer and an oligomer may be used in combination. Component (B) may be used alone or in combination of two or more.

[0036] Specific 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)acryloxymethoxy)phenyl]propane, 2,2-bis[4-((meth)acryloxypolyethoxy)phenyl]propane, dicyclopentenyl (meth)acrylate, tricyclodecanyl (meth)acrylate, tris((meth)acryloyloxyethyl)isocyanurate, isocyanuric acid EO-modified di(meth)acrylate, isocyanuric acid EO-modified tri(meth)acrylate, and urethane (meth)acrylate. As the radical polymerizable compound other than the (meth)acrylate compound, for example, the compounds described in International Publication No. 2009 / 063827 can be suitably used. The (meth)acrylate compound may be used alone or in combination of two or more.

[0037] The (B) component may be a (meth)acrylate compound from the viewpoint of obtaining higher connection reliability. From the viewpoint of obtaining even higher connection reliability, the (B) component 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 of these components 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, the (meth)acrylate compound may be a compound having at least one substituent selected from the group consisting of a dicyclopentenyl group, a tricyclodecanyl group, and a triazine ring.

[0038] The content of component (B) may be 10 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more, per 100 parts by mass of the total amount of adhesive components, from the viewpoints of initial adhesive strength and maintenance of adhesive strength after reliability testing. The content of component (B) may be 90 parts by mass or less, 80 parts by mass or less, or 70 parts by mass or less, per 100 parts by mass of the total amount of adhesive components, from the viewpoints of workability in the transfer step and workability in the connection step. From these viewpoints, the content of component (B) may be 10 to 90 parts by mass, 20 to 80 parts by mass, or 30 to 70 parts by mass.

[0039] (Component (C): Thermal radical generator) Component (C) is a curing agent (such as a thermal radical polymerization initiator) that decomposes when heated to generate free radicals. Examples of component (C) include peroxides (such as organic peroxides) and azo compounds. Component (C) is selected appropriately based on the desired bonding temperature, bonding time, pot life, etc.

[0040] From the viewpoints of high reactivity and improved pot life, the 10-hour half-life temperature of component (C) may be 40°C or higher or 60°C or higher. From the viewpoints of high reactivity and improved pot life, the 1-minute half-life temperature of component (C) may be 180°C or lower or 170°C or lower. From the viewpoints of high reactivity and improved pot life, component (C) may be an organic peroxide having a 10-hour half-life temperature of 40°C or higher and a 1-minute half-life temperature of 180°C or lower, or may be an organic peroxide having a 10-hour half-life temperature of 60°C or higher and a 1-minute half-life temperature of 170°C or lower.

[0041] Specific examples of peroxides include diacyl peroxides (such as benzoyl peroxide), peroxydicarbonates, peroxyesters, peroxyketals, dialkyl peroxides, hydroperoxides, and silyl peroxides.

[0042] As component (C), from the viewpoint of suppressing corrosion of electrodes (circuit electrodes, etc.), a curing agent containing chloride ions and organic acids at a concentration of 5000 ppm or less is preferred, and a curing agent that generates little organic acid after thermal decomposition is more preferred. Specific examples of such curing agents include diacyl peroxides, peroxydicarbonates, peroxyesters, dialkyl peroxides, hydroperoxides, and silyl peroxides. From the viewpoint of obtaining high reactivity, at least one selected from the group consisting of diacyl peroxides, peroxydicarbonates, and peroxyesters is preferred, diacyl peroxides and peroxyesters are more preferred, and peroxyesters are even more preferred. Curing agents that generate free radicals when heated may be used alone or in combination of two or more.

[0043] Peroxyesters include cumyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1-cyclohexyl-1-methylethyl peroxy-2-ethylhexanoate, t-hexyl peroxy-2-ethylhexanoate, t Examples of suitable peroxides include 2,5-dimethyl-2,5-di(m-toluoylperoxy)hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di(m-toluoylperoxy)hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, and t-butylperoxyacetate. Examples of diacyl peroxides include dilauroyl peroxide. Among these, from the viewpoint of low-temperature mounting, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane and dilauroyl peroxide are preferred, with dilauroyl peroxide being more preferred. The peroxyester may be used alone or in combination of two or more. As a curing agent that generates free radicals by heat other than the above peroxyester, for example, the compounds described in WO 2009 / 063827 can be suitably used.

[0044] Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(imidazolin-2-yl)propane].

[0045] The component (C) may be used alone or in combination of two or more. The component (C) may be used in combination with a decomposition accelerator, a decomposition inhibitor, etc.

[0046] From the viewpoint of easily obtaining a sufficient reaction rate, the content of the (C) component may be 0.1 part by mass or more, 0.5 part by mass or more, or 1 part by mass or more, and may be 40 parts by mass or less, 30 parts by mass or less, or 20 parts by mass or less, or may be 0.1 to 40 parts by mass, 0.5 to 30 parts by mass, or 1 to 30 parts by mass, relative to 100 parts by mass of the (B) component.

[0047] (Other ingredients) The film adhesive 1 may further contain components (other components) other than the above components (A), (B), and (C). Examples of other components include a (D) phosphate ester-based organic compound (hereinafter also referred to as "component (D)"), a (E) film-forming material (hereinafter also referred to as "component (E)"), a (F) inorganic filler (hereinafter also referred to as "component (F)"), and a (G) silane coupling agent (hereinafter also referred to as "component (G)").

[0048] [Component (D): Phosphate ester organic compound] Component (D) increases the activity of the solder particle surface and the electrode surface, contributing to the improvement of the effect of forming a partial metal bond between the solder particle interface and the electrode interface and creating a close and wide contact interface with the solder particle. To facilitate the achievement of such an effect, component (D) may be a monofunctional or polyfunctional phosphate ester-based radical polymerizable compound. In particular, the above effect is more easily achieved when a radical polymerizable compound having a phosphate ester structure represented by the following general formula (I) or (II) is used as component (D), and the above effect is even more easily achieved when a radical polymerizable compound such as a (meth)acrylate compound is used in combination with a radical polymerizable compound having a phosphate ester structure represented by formula (I) or (II). Note that, in this specification, component (D) is not included in component (B).

[0049] [ka] [In the formula, n represents an integer of 1 to 3, and R represents a hydrogen atom or a methyl group.] [ka] [In the formula, a represents an integer of 1 to 3.]

[0050] The radical polymerizable compound having the phosphoric acid ester structure can be obtained, for example, by reacting phosphoric anhydride with 2-hydroxyethyl (meth)acrylate. Specific examples of the radical polymerizable compound having the phosphoric acid ester structure include mono(2-(meth)acryloyloxyethyl) acid phosphate and di(2-(meth)acryloyloxyethyl) acid phosphate. The radical polymerizable compound having the phosphoric acid ester structure represented by formula (I) or (II) may be used alone or in combination of two or more.

[0051] The content of the radical polymerizable compound having a phosphate ester structure represented by formula (I) or (II) may be 0.1 to 15 parts by mass, or 0.5 to 10 parts by mass, per 100 parts by mass of the total amount of adhesive components, from the viewpoint of facilitating the formation of partial metal bonding between the solder particle interface and the electrode interface. When this content is 0.1 part by mass or more, the effect of partial metal bonding is easily exhibited, and when this content is 15 parts by mass or less, a decrease in workability in the transfer step and thermocompression bonding step due to stickiness can be suppressed.

[0052] The content of component (D) may be 0.1 to 15 parts by mass, or 0.5 to 10 parts by mass, per 100 parts by mass of the total amount of the adhesive components, from the viewpoint of the effect of partial metal bonding and the workability in the transfer process and pressure-bonding process.

[0053] [Component (E): Film-forming material] When the liquid adhesive composition is solidified into a film, component (E) improves the handleability of the film under normal conditions (room temperature and normal pressure), and can impart properties such as tear resistance, crack resistance, and stickiness to the film. Examples of film-forming materials include phenoxy resin, polyvinyl formal resin, polystyrene resin, polyvinyl butyral resin, polyester resin, polyamide resin, xylene resin, and polyurethane resin. Among these, polyester urethane resin and phenoxy resin are preferably used. In particular, when phenoxy resin is used, it tends to have excellent adhesion, compatibility, heat resistance, and mechanical strength. One type of film-forming material may be used alone, or two or more types may be used in combination.

[0054] Examples of phenoxy resins include resins obtained by polyaddition of a bifunctional epoxy resin and a bifunctional phenol, and resins obtained by reacting a bifunctional phenol with an epihalohydrin until the product is polymerized. The phenoxy resin can be obtained, for example, by reacting 1 mole of a bifunctional phenol with 0.985 to 1.015 moles of epihalohydrin in a non-reactive solvent at a temperature of 40 to 120°C in the presence of a catalyst such as an alkali metal hydroxide. From the viewpoint of achieving excellent mechanical and thermal properties, the phenoxy resin may be a copolymer of a bifunctional epoxy resin and a bifunctional phenol. In particular, resins obtained by polyaddition reaction of a difunctional epoxy resin and a difunctional phenol in an equivalent ratio of epoxy group / phenolic hydroxyl group = 1 / 0.9 to 1 / 1.1 in the presence of a catalyst such as an alkali metal compound, an organophosphorus compound, or a cyclic amine compound in an organic solvent (amide, ether, ketone, lactone, alcohol, etc.) with a boiling point of 120°C or higher, heated to 50 to 200°C under conditions of a reaction solids content of 50% by mass or less, tend to have better mechanical and thermal properties. Phenoxy resins may be used singly or in combination of two or more.

[0055] Examples of bifunctional epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol AD ​​epoxy resins, bisphenol S epoxy resins, biphenyl diglycidyl ether, and methyl-substituted biphenyl diglycidyl ether. Bifunctional phenols are compounds having two phenolic hydroxyl groups. Examples of bifunctional phenols include hydroquinones, bisphenol A, bisphenol F, bisphenol AD, bisphenol S, bisphenol fluorene, methyl-substituted bisphenol fluorene, dihydroxybiphenyl, and methyl-substituted dihydroxybiphenyl. Phenoxy resins may be modified (e.g., epoxy-modified) with a radically polymerizable functional group or other reactive compounds.

[0056] The content of the film-forming material may be 10 to 90 parts by mass or 20 to 60 parts by mass relative to 100 parts by mass of the total amount of the adhesive components.

[0057] [(F) Component: Inorganic filler] Component (F) is, for example, a non-conductive inorganic particle. Examples of component (F) include inorganic particles such as metal oxide particles, such as silica particles, alumina particles, silica-alumina particles, titania particles, and zirconia particles; and metal nitride particles. These may be used alone or in combination.

[0058] Component (F) may be, for example, particles having an average particle size of not more than ¼ of that of component (A).The content of component (F) may be 5 to 60 parts by mass, 10 to 50 parts by mass, 15 to 40 parts by mass, or 20 to 30 parts by mass per 100 parts by mass of the total amount of the adhesive components, from the viewpoint of sufficiently obtaining the effect of improving the electrical properties (connection reliability, etc.) between electrodes due to the addition of a filler.

[0059] However, when solder particles are subjected to high temperature and high pressure loads, they undergo significant melting and flow, resulting in excessive flattening. Therefore, when mounting is performed at high pressure (e.g., 5 MPa or higher), organic particles (e.g., rubber microparticles) may be used as a filler to prevent the connection distance between electrodes from becoming too small. However, in this embodiment, from the perspective of enabling good low-temperature mounting, the content of organic particles may be 5% by mass or less, 1% by mass or less, or even 0% by mass, relative to 100 parts by mass of the total amount of adhesive components. The content of organic particles may be 1 to 5% by mass.

[0060] [Component (G): Silane coupling agent] Component (G) contributes to improving the adhesion (such as adhesion to glass) of the film-like adhesive 1. Examples of component (G) include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and condensates thereof.

[0061] The content of component (G) may be 0.1 to 10 parts by mass, or alternatively 0.25 to 5 parts by mass, relative to 100 parts by mass of the total amount of the adhesive components. When the content of component (G) is 0.1 part by mass or more, the effect of suppressing the occurrence of peeling bubbles at the interface between the circuit component and the circuit connecting material tends to be even greater, and when the content of component (G) is 10 parts by mass or less, the pot life of the film-like adhesive 1 tends to be longer.

[0062] [Other additives] The film-like adhesive 1 may contain other additives as appropriate, such as polymerization inhibitors, softeners, accelerators, antioxidants, colorants, flame retardants, thixotropic agents, coupling agents, adhesion improvers (excluding coupling agents), thickeners, leveling agents, colorants, and weather resistance improvers. The film-like adhesive 1 may further contain other additives. The content of the other additives may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the total amount of the adhesive components.

[0063] Furthermore, the film-like adhesive 1 may contain conductive particles other than component (A) as needed, as long as the effects of the present invention are not impaired. Examples of materials constituting the other conductive particles include metals such as gold (Au), silver (Ag), nickel (Ni), and copper (Cu), as well as carbon. The other conductive particles may also be coated conductive particles, which have a core made of a non-conductive resin, glass, ceramic, plastic, or the like, and are coated with the above-mentioned metals (metal particles, etc.) or carbon. Furthermore, solder particles having a composition other than that of the solder particles, which are component (A), may also be used as the other conductive particles.

[0064] The film-like adhesive 1 contains the aforementioned components (B) and (C), and therefore has radical curing properties. The temperature at which curing of the film-like adhesive 1 is completed (curing point) may be lower than the softening point of component (A). If the curing point of the film-like adhesive 1 is lower than the softening point of component (A), the adhesive components of the film-like adhesive 1 will harden before component (A) softens, and excessive flow of the solder will be suppressed when component (A) melts after the softening point. Therefore, by setting the curing point of the film-like adhesive 1 lower than the softening point of component (A), a connection structure with higher connection reliability can be obtained. The curing point of the film-like adhesive 1 may be 140°C or lower, or may be 135°C or lower, 130°C or lower, 120°C or lower, 110°C or lower, 100°C or lower, or lower than 100°C. The curing point of the film-like adhesive 1 may be 60°C or higher. That is, the curing point of the film-like adhesive 1 may be 60 to 140°C, 60 to 135°C, 60 to 130°C, 60 to 120°C, 60 to 110°C, 60 to 100°C, or 60°C or higher but less than 100°C. The curing point of the film-like adhesive 1 can be adjusted by the type and amount of component (B) and component (C). The curing point of the film-like adhesive 1 is obtained by measuring the melt viscosity curve of the film-like adhesive 1 and confirmed from the viscosity-temperature curve (vertical axis: viscosity, horizontal axis: measurement temperature). Specifically, the temperature at which the thickening (increase in viscosity) associated with curing ends after reaching the minimum melt viscosity (the point with the lowest viscosity) is taken as the curing point of the film-like adhesive 1. The melt viscosity curve measurement can be performed using the method described in the Examples.

[0065] The minimum melt viscosity of the film adhesive 1 is set to 1.0 × 10 5 Pa·s or less, 5.0×10 4 Pa s or less or 1.0×10 4 The minimum melt viscosity of the film adhesive 1 is 1.0×10 Pa·s or less from the viewpoint of excellent filling between electrodes by the adhesive component. 2 Pa·s or more, 5.0×10 2 Pa·s or more, 1.0×10 3 Pa·s or greater or 5.0×10 3 From these viewpoints, the minimum melt viscosity of the film adhesive 1 is 1.0×10 2 ~1.0×10 5 Pa·s, 5.0×10 2 ~5.0×10 4 Pa·s, 1.0×10 3 ~1.0×10 4 Pa s or 5.0 × 10 3 ~1.0×10 4 It may be in Pa·s. The minimum melt viscosity of the film-like adhesive 1, like the curing point described above, is obtained by measuring the melt viscosity curve of the film-like adhesive 1 and confirmed from a viscosity-temperature curve (vertical axis: viscosity, horizontal axis: measurement temperature). The temperature at which the film-like adhesive 1 exhibits its minimum melt viscosity may be, for example, 60°C or higher, 140°C or lower, or may be in the range of 60 to 140°C.

[0066] The film-like adhesive 1 may have a viscosity of at least three times the minimum melt viscosity at the softening point of component (A). In this case, sufficient fluidity of the adhesive components is ensured during melting, while excessive flow of the solder when component (A) melts after the softening point can be further suppressed. This makes it possible to obtain a connection structure with lower connection resistance and higher connection reliability. From the viewpoint of significantly achieving this effect, the viscosity of the film-like adhesive 1 at the softening point of component (A) is preferably at least five times, and may be at least six or seven times, the minimum melt viscosity. The upper limit of the viscosity of the film-like adhesive 1 at the softening point of component (A) is not particularly limited, and may be, for example, 15 times or less, 12 times or less, 11 times or less, or 10 times or less of the minimum melt viscosity. Specifically, the viscosity of the film-like adhesive 1 at the softening point of component (A) is, for example, 1.0 × 10 4 Pa·s or more, 3.0×10 4 Pa s or more, and 1.0 × 10 5 Pa s or less or 7.0 × 10 4 Pa s, and 1.0 × 10 4 ~1.0×10 5 Pa s or 3.0×10 4 ~7.0×10 4 It may be Pa·s.

[0067] The film-like adhesive 1 has a thickness of, for example, 5 to 50 μm. When the thickness of the film-like adhesive 1 is 50 μm or less, the amount of flowing adhesive component is not too large, and contamination of the periphery of the connection portion is unlikely. When the thickness of the film-like adhesive 1 is 5 μm or more, the force bonding the adherends together is sufficiently strong, and a sufficient amount of adhesive component is likely to be secured to fill the gaps between the adherends, making it unlikely for voids to form. From these perspectives, the thickness of the film-like adhesive 1 may be, for example, 10 μm or more or 15 μm or more, and may be 40 μm or less or 30 μm or less, or may be 10 to 40 μm, 10 to 30 μm, or 15 to 30 μm. Here, the thickness of the film-like adhesive 1 is the shortest distance from one main surface 1a to the other main surface 1b of the film-like adhesive 1 (the distance indicated by d1 in FIG. 1). Specifically, it can be measured by observation with a laser microscope. As shown in Figure 2, when component (A) having a particle size greater than 1.0 times the thickness of the film adhesive is included, the surface of the film adhesive 1 may be raised by component (A). However, the thickness of the raised portion R1 (e.g., the thickness of the portion where component (A) is located) is not included in the thickness of the film adhesive 1, and the thickness of the flat portion R2 is measured. For example, the thickness of the film adhesive can be determined by removing a portion of the film adhesive formed on the release substrate described below and measuring the height from the exposed portion of the surface of the release substrate to the surface of the film adhesive using a laser microscope. When the particle size of component (A) is greater than the thickness of the film adhesive, this method can be used to confirm a protrusion in the portion where component (A) is present, and the thickness of the film adhesive can be determined by measuring the flat portion without the protrusion. Furthermore, when component (A) having a particle size greater than 1.0 times the thickness of the film adhesive is included, component (A) may be exposed from the surface of the film adhesive 1.

[0068] When one main surface 1a of the film-like adhesive 1 is raised by component (A), the shortest distance from the other main surface 1b (distance shown as d2 in FIG. 2) may be 0.4 times or less, 0.3 times or less, or 0.2 times or less the thickness of the film-like adhesive. Specifically, the shortest distance d2 may be 10 μm or less, 8 μm or less, or 5 μm or less, or may even be 0 μm. In particular, when the thickness of the film-like adhesive is 25 μm, if the shortest distance d2 is in the above range, the ability to capture solder particles can be further improved, and a connection structure exhibiting lower connection resistance tends to be obtained.

[0069] The film-like adhesive 1 is used, for example, to be disposed between a first circuit member having a first electrode and a second circuit member having a second electrode, and to electrically connect the first electrode and the second electrode to each other. Specifically, it can be used as a circuit connecting material, such as an anisotropic conductive adhesive, an isotropic conductive adhesive, silver paste, or silver film.

[0070] A releasable substrate may be provided on a main surface of the film-like adhesive 1. In other words, the film-like adhesive 1 may be provided in the form of a film-like adhesive with a releasable substrate, which comprises a releasable substrate and the film-like adhesive 1 formed on the releasable substrate. Releasable substrates may be provided on both main surfaces of the film-like adhesive 1.

[0071] A film-like adhesive with a peelable substrate can be prepared, for example, by the following method. First, the above-mentioned components (A), (B), and (C), and optionally other components, are added to a solvent (organic solvent) and dissolved or dispersed by stirring, mixing, kneading, or the like to prepare a varnish composition. Next, the varnish composition is applied to a release-treated peelable substrate (such as release paper) using a knife coater, roll coater, applicator, comma coater, die coater, or the like, and the solvent is then volatilized by heating. This results in a film-like adhesive with a peelable substrate.

[0072] The solvent used in preparing the varnish composition may have a boiling point of 50 to 150°C at normal pressure. If the boiling point is 50°C or higher, the solvent will have poor volatility at room temperature and can be used in an open system. If the boiling point is 150°C or lower, the solvent can be easily evaporated, resulting in good reliability after bonding. Specific examples of the solvent include toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, and butyl acetate. These solvents can be used alone or in combination of two or more. The stirring, mixing, and kneading in preparing the varnish composition can be performed using, for example, a mixer, a grinder, a three-roll mill, a ball mill, a bead mill, or a homodisper.

[0073] The release substrate is not particularly limited as long as it has heat resistance sufficient to withstand the heating conditions used to volatilize the solvent. For example, a substrate (e.g., a film) made of oriented polypropylene (OPP), polyethylene terephthalate (PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, polyimide, cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymer, or the like, which has been subjected to a release treatment, can be used.

[0074] The heating conditions for volatilizing the solvent from the varnish composition applied to the substrate are preferably conditions that allow the solvent to volatilize sufficiently. The heating conditions may be, for example, 40°C or higher and 120°C or lower for 0.1 minutes or longer and 10 minutes or shorter. Some of the solvent may remain unremoved in the film adhesive 1. The content of the solvent in the film adhesive 1 may be, for example, 10% by mass or less, based on the total mass of the film adhesive 1.

[0075] <Connection structure and method for manufacturing the same> A method for manufacturing a connection structure according to one embodiment includes the steps of: placing a film adhesive between a surface of a first circuit member having a first electrode on which a first electrode is provided and a surface of a second circuit member having a second electrode on which a second electrode is provided; and thermocompression bonding the first circuit member and the second circuit member via the film adhesive 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. The film adhesive is, for example, the film adhesive according to the above embodiment.

[0076] In one embodiment, the first electrode may be an electrode having an Au plated layer on its outermost surface, and the second electrode may be an electrode having an Au plated layer or an Sn plated layer on its outermost surface.

[0077] A connection structure and a method for producing the same according to one embodiment will be described below by taking as an example a connection structure (circuit connection structure) using the film-like adhesive 1 described above and a method for producing the same.

[0078] Fig. 3 is a schematic cross-sectional view showing a connection structure of one embodiment. The connection structure 100 shown in Fig. 3 includes a first circuit member 10 having a first electrode 15, a second circuit member 20 having a second electrode 25, and a circuit connection portion 30 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.

[0079] The first circuit member 10 and the second circuit member 20 may be the same or different. The first circuit member 10 and the second circuit member 20 may be a glass substrate or a plastic substrate (a plastic substrate made of an organic material such as polyimide, polycarbonate, polyethylene terephthalate, or cycloolefin polymer) on which circuit electrodes are formed; a printed wiring board; a ceramic wiring board; a flexible wiring board; an IC chip such as a drive IC; or the like. Specifically, for example, they may be a printed wiring board (PWB) such as an FR-4 board, or a flexible circuit board (FPC). The flexible circuit board may be a flexible circuit board (COF FPC) used in a COF mounting method. The combination of the first circuit member 10 and the second circuit member 20 is not particularly limited, but may be, for example, a combination in which the first circuit member 10 is a printed wiring board (PWB) or a flexible circuit board (FPC), and the second circuit member 20 is a flexible circuit board (FPC) (including a COF FPC).

[0080] The first electrode 15 is formed on the first substrate 11, and the second electrode 25 is formed on the second substrate 21. The first substrate 11 and the second substrate 21 may be formed of inorganic materials such as semiconductors, glass, and ceramics, organic materials such as polyimide and polycarbonate, or composites such as glass / epoxy. Specifically, for example, when the first circuit member 10 is a printed wiring board, the first substrate 11 may be a glass substrate, and when the first circuit member 10 is a flexible circuit board, the first substrate 11 may be a polyimide film substrate. Similarly, when the second circuit member 20 is a printed wiring board, the second substrate 21 may be a glass substrate, and when the second circuit member 20 is a flexible circuit board, the second substrate 21 may be a polyimide film substrate. In addition, an insulating layer (not shown) may be disposed on the main surface of the first substrate 11 (the surface on which the first electrode 15 is provided) and / or the main surface of the second substrate 21 (the surface on which the second electrode 25 is provided).

[0081] The first electrode 15 and the second electrode 25 face each other and are electrically connected via a circuit connection portion 30. 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. In this case, the electrodes may have a two-layer structure or a three-layer or more structure. Specifically, for example, one or both of the first electrode 15 and the second electrode 25 may be an electrode (circuit electrode) in which a Ni (nickel) plating layer and an Au (gold) plating layer are laminated in this order on a copper circuit (copper foil circuit), or one of the first electrode 15 and the second electrode 25 may be an electrode (circuit electrode) in which a Ni (nickel) plating layer and an Au (gold) plating layer are laminated in this order on a copper circuit (copper foil circuit), and the other may be an electrode having a Sn plating layer on its outermost surface, in which a Sn plating layer is formed on a copper circuit (copper foil circuit). Such an electrode having a Sn plating layer on its outermost surface may be used as an electrode for a COF FPC.

[0082] When the first electrode 15 is an electrode having an Au plating layer on its outermost surface and the second electrode 25 is an electrode having an Au plating layer or an Sn plating layer on its outermost surface, close and wide physical contact and partial metal bonding with the (A) component are easily formed during production, which tends to result in lower connection resistance and higher connection reliability.

[0083] The circuit connection portion 30 includes an insulating material 31 and solder particles (or a molten and solidified product thereof) 2. The insulating material 31 is the adhesive component in the film-like adhesive 1 of the above embodiment or a cured product thereof. The solder particles 2 connecting the first electrode 15 and the second electrode 25 are a molten and solidified product of component (A) contained in the film-like adhesive 1, and are in close and wide physical contact with the surfaces of the first electrode 15 and the second electrode 25, forming a partial metal bond. The circuit connection portion 30 is formed from the film-like adhesive 1 of the above embodiment. Therefore, it can also be said that the circuit connection portion 30 includes the film-like adhesive 1 of the above embodiment or a cured product thereof.

[0084] The connection structure 100 is, for example, a connection structure for a display input circuit or as a connector replacement circuit.

[0085] 4 is a schematic cross-sectional view showing a method for manufacturing the connection structure 100. The method for manufacturing the connection structure 100 includes, for example, a step (arrangement step) of arranging the film-like adhesive 1 of the above embodiment between the surface of the first circuit member 10 on which the first electrode 15 is provided and the surface of the second circuit member 20 on which the second electrode 25 is provided, and a step (thermocompression bonding step) of thermocompression bonding the first circuit member 10 and the second circuit member 20 together via the film-like adhesive 1, thereby electrically connecting the first electrode 15 and the second electrode 25 to each other and bonding the first circuit member 10 and the second circuit member 20 together.

[0086] The placement step includes, for example, a step (transfer step) of transferring the film-like adhesive 1 from a film-like adhesive with a peelable substrate to the first circuit member 10. In the transfer step, for example, the film-like adhesive with a peelable substrate is placed on the first circuit member 10 so that the surface on which the film-like adhesive 1 faces faces the surface of the first circuit member 10 on which the first electrodes 15 are provided, and the film-like adhesive 1 is transferred to the first circuit member 10 by thermocompression bonding from the peelable substrate side. After transfer, the peelable substrate is peeled from the film-like adhesive, and then the process proceeds to the thermocompression bonding step.

[0087] The heating temperature in the transfer step is not particularly limited, but may be a temperature that reaches a temperature of 50 to 80°C after thermocompression bonding for a predetermined number of seconds. The pressure is not particularly limited as long as it does not damage the first circuit member 10, but may be 0.1 to 2 MPa. Heating and pressure may be applied for a period of 0.3 to 3 seconds.

[0088] In the thermocompression bonding step, the first circuit member 10 and the second circuit member 20 are thermocompression bonded (heated and pressurized) in opposing directions (the directions indicated by arrows A and B in FIG. 4(a)). The pressure during thermocompression bonding is, for example, 10 MPa or less, and may be 5 MPa or less or 3 MPa or less. With the film-like adhesive of the above embodiment, a connection structure with low connection resistance can be obtained even when the pressure during thermocompression bonding is 1 MPa or less. Therefore, the pressure during thermocompression bonding may be 1 MPa or less, or may be 0.8 MPa or less or 0.5 MPa or less. The pressure during thermocompression bonding may be, for example, 0.3 MPa or more. The temperature during thermocompression bonding is, for example, 130 to 180°C, and may be 170°C or less or 150°C or less from the viewpoints of reducing the load on the mounting members (the first circuit member 10 and the second circuit member 20) and preventing excessive flow of solder particles. The film-like adhesive of the above embodiment tends to provide a connection structure with low connection resistance even when the temperature during thermocompression bonding is 140 to 150° C. The above pressure is the pressure per area of ​​the film-like adhesive (area of ​​the bonded portion), and the above temperature is the temperature reached by the film-like adhesive when thermocompression bonding is performed for a predetermined number of seconds. [Example]

[0089] The present invention will be specifically described below based on examples, but the present invention is not limited thereto.

[0090] Example 1 5 parts by mass of urethane acrylate (product name: UN-952, manufactured by Negami Chemical Industrial Co., Ltd.) and 10 parts by mass of isocyanuric acid EO-modified diacrylate (product name: M-215, manufactured by Toagosei Co., Ltd.), which are radical polymerizable compounds; 2 parts by mass of a reaction product of a 6-hexanolide addition polymer of 2-hydroxyethyl methacrylate and phosphoric anhydride (product name: PM-21, manufactured by Nippon Kayaku Co., Ltd.), which is a phosphate ester-based organic compound; 3 parts by mass of a peroxyester (product name: Perhexa 25O, manufactured by NOF Corporation), which is a thermal radical generator; 15 parts by mass of silica filler (product name: AEROSIL R202, manufactured by Nippon Aerosil Co., Ltd.), which is an inorganic filler; and 35 parts by mass of a polyester urethane resin (product name: UR8240, manufactured by Toyobo Co., Ltd.), which is a film-forming material, were mixed and stirred in methyl ethyl ketone to obtain Solution A.

[0091] Solder particles (product name: Sn72Bi28 Type 5) manufactured by Mitsui Mining & Smelting Co., Ltd. were classified to remove solder particles with a particle size of 15 μm or less and solder particles with a particle size of 25 μm or more, thereby obtaining solder particles A (Bi content: 28% by mass, Sn content: 72% by mass, average particle size: 20 μm, softening point: 139°C). The average particle size of solder particles A was confirmed by measuring the D50 value of solder particles A using a microtrack measuring device. The obtained solder particles A were dispersed in the solution A prepared above. In this case, the amount of solder particles A added was 30 parts by mass relative to 100 parts by mass of the nonvolatile content (components other than methyl ethyl ketone) in solution A. This resulted in a coating solution for forming a film-like adhesive. The softening point of the solder particles was calculated from the value of the first endothermic peak in DSC. DSC measurements of the solder particles were performed using a differential scanning calorimeter (product name: Q-1000) manufactured by TA Instruments, at a temperature rise rate of 10°C / min in a He gas flow in the range of 30 to 200°C.

[0092] The coating solution obtained above was applied using a coating device to a polyethylene terephthalate (PET) film (thickness: 50 μm) that had been release-treated on one side. The coating film was dried with hot air at 70°C to form an anisotropically conductive film-like adhesive (thickness: 25 μm) on the PET film. This resulted in the film-like adhesive with a peelable substrate of Example 1 (ratio of the average particle size of the solder particles to the thickness of the film-like adhesive: r = 0.8). The thickness of the film-like adhesive was measured using a laser microscope. Specifically, the thickness of the film-like adhesive was determined by removing a portion of the film-like adhesive on the PET film and measuring the height from the exposed portion of the surface of the PET film to the surface of the film-like adhesive.

[0093] Example 2 Solder particles (product name: Sn72Bi28 DS10) manufactured by Mitsui Mining & Smelting Co., Ltd. were classified to remove solder particles with a particle size of 12 μm or less and solder particles with a particle size of 20 μm or more, thereby obtaining solder particles B (Bi content: 28% by mass, Sn content: 72% by mass, average particle size: 16 μm, softening point: 139°C). The average particle size of solder particles B was confirmed by measuring the D50 value of solder particles B using a microtrack measuring device. An anisotropic conductive film-like adhesive (thickness: 20 μm) was formed on a PET film in the same manner as in Example 1, except that solder particles B were used instead of solder particles A and the coating conditions were changed so that the thickness of the film-like adhesive obtained after drying was 20 μm. This resulted in a film-like adhesive with a peelable substrate of Example 2 (ratio of the average particle size of the solder particles to the thickness of the film-like adhesive = 0.8). The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0094] Example 3 50 g of phenoxy resin (product name: PKHC, manufactured by Union Carbide Corporation) was dissolved in a mixed solvent of toluene / ethyl acetate (mass ratio: 50 / 50) to prepare a phenoxy resin solution with a solid content of 40%. 35 parts by mass of this phenoxy resin solution (14 parts by mass of phenoxy resin), 14 parts by mass of isocyanuric acid EO (ethylene oxide) modified diacrylate (trade name: M-215, manufactured by Toagosei Co., Ltd.) and 14 parts by mass of urethane acrylate (trade name: U-2PPA, manufactured by Shin-Nakamura Chemical Co., Ltd.), which are radical polymerizable compounds, 3 parts by mass of 2-methacryloyloxyethyl acid phosphate (trade name: Light Ester P-2M, manufactured by Kyoeisha Chemical Co., Ltd.), which is a phosphate ester organic compound, 2 parts by mass of 3-methacryloxypropyltrimethoxysilane (trade name: KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), which is a silane coupling agent, and 2 parts by mass of peroxyester (trade name: Perhexa 25O, manufactured by NOF Corporation), which is a thermal radical generator, were mixed to obtain solution B.

[0095] An anisotropic conductive film-like adhesive (thickness: 25 μm) was formed on a PET film in the same manner as in Example 1, except that solution B obtained above was used instead of solution A. This resulted in a film-like adhesive with a peelable substrate of Example 3 (ratio of average particle size of solder particles to thickness of film-like adhesive: 0.8). The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0096] Example 4 An anisotropic conductive film-like adhesive (thickness: 28 μm) was formed on a PET film in the same manner as in Example 2, except that the coating conditions were changed so that the thickness after drying would be 28 μm. This resulted in a film-like adhesive with a peelable substrate of Example 4 (ratio of average particle size of solder particles to thickness of film-like adhesive: r=0.6). The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0097] Example 5 An anisotropic conductive film-like adhesive (thickness: 32 μm) was formed on a PET film in the same manner as in Example 2, except that the coating conditions were changed so that the thickness after drying would be 32 μm. This resulted in a film-like adhesive with a peelable substrate of Example 5 (ratio of average particle size of solder particles to thickness of film-like adhesive: r=0.5). The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0098] Example 6 Solder particles (product name: Sn72Bi28 Type 5) manufactured by Mitsui Mining & Smelting Co., Ltd. were classified to remove solder particles with a particle size of 20 μm or less and solder particles with a particle size of 25 μm or more, thereby obtaining solder particles C (Bi content: 28 mass %, Sn content: 72 mass %, average particle size: 22 μm, softening point: 139°C). The average particle size of solder particles C was confirmed by measuring the D50 value of solder particles C using a microtrack measuring device. The obtained solder particles C and methyl ethyl ketone were added to and dispersed in solution A prepared in Example 1 to obtain a coating liquid. In this case, the amount of solder particles C added was 30 parts by mass relative to 100 parts by mass of the nonvolatile content (components other than methyl ethyl ketone) in solution A, and the amount of methyl ethyl ketone added was 20 parts by mass.

[0099] The coating solution obtained above was applied to a polyethylene terephthalate (PET) film (thickness: 50 μm) with one side treated for release using a coating device, resulting in a coating film with a thickness of 22 μm. The resulting coating film was dried with hot air at 70°C to form an anisotropically conductive film-like adhesive (thickness: 20 μm) on the PET film. This resulted in the film-like adhesive with a peelable substrate of Example 6 (ratio of average particle size of solder particles to thickness of film-like adhesive: r = 1.1). The thickness of the film-like adhesive was the thickness d1 of the flat portion of the film-like adhesive (the portion corresponding to R2 in Figure 2), and was measured in the same manner as in Example 1.

[0100] Example 7 Solder particles (product name: Sn42Bi58 Type 5) manufactured by Mitsui Mining & Smelting Co., Ltd. were classified to remove solder particles with a particle size of 15 μm or less and solder particles with a particle size of 25 μm or more, thereby obtaining solder particles D (Bi content: 58 mass %, Sn content: 42 mass %, average particle size: 20 μm, softening point: 139°C). The average particle size of solder particles D was confirmed by measuring the D50 value of solder particles D using a microtrack measuring device. An anisotropic conductive film-like adhesive (thickness: 25 μm) was formed on a PET film in the same manner as in Example 1, except that solder particles D obtained above were used instead of solder particles A. This resulted in a film-like adhesive with a peelable substrate of Example 7 (ratio of average particle size of solder particles to thickness of film-like adhesive: 0.8). The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0101] Example 8 The mixture contained 10 parts by mass of a radical polymerizable compound, a carbonate-based urethane acrylate (product name: UN-5500, manufactured by Negami Chemical Industrial Co., Ltd.), 5 parts by mass of an isocyanuric acid EO-modified diacrylate (product name: M-215, manufactured by Toagosei Co., Ltd.), and 5 parts by mass of dimethyloltricyclodecane diacrylate (product name: DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.), and 2-methacryloyloxyethyl acid phosphate (product name: L-methacryloyloxyethyl acid phosphate), a phosphate ester-based organic compound. A methyl ethyl ketone solution containing 1 part by mass of urethane filler (product name: MM-101SM, manufactured by Negami Chemical Co., Ltd.), 10 parts by mass of diacyl peroxide (product name: Perloil L, manufactured by NOF Corporation) as a thermal radical generator (free radical generator), and 31 parts by mass of polyester urethane resin (product name: UR4800, manufactured by Toyobo Co., Ltd.) as an insulating resin was mixed and stirred to obtain solution C.

[0102] An anisotropic conductive film-like adhesive (thickness: 25 μm) was formed on a PET film in the same manner as in Example 1, except that solution C obtained above was used instead of solution A. This resulted in a film-like adhesive with a peelable substrate of Example 8 (ratio of average particle size of solder particles to thickness of film-like adhesive: r=0.8). The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0103] Example 9 Phenoxy resin (product name: PKHC, manufactured by Union Carbide Corporation) was dissolved in a mixed solvent of toluene and ethyl acetate (mass ratio: 50 / 50) to prepare a phenoxy resin solution with a solid content of 40%. Ten parts by mass of this phenoxy resin solution (4 parts by mass of phenoxy resin) was mixed with 10 parts by mass of radically polymerizable compounds, namely, urethane acrylate (product name: UN-952, manufactured by Negami Chemical Industrial Co., Ltd.) and 10 parts by mass of EO-modified isocyanuric acid diacrylate (product name: M-215, manufactured by Toagosei Co., Ltd.), and 2 parts by mass of a phosphate ester-based organic compound, a reaction product of 6-hexanolide addition polymer of 2-hydroxyethyl methacrylate and phosphoric anhydride (product name: PM-21, manufactured by Nippon Kayaku Co., Ltd.). Parts by mass of the cellulose acetate copolymer, 0.1 parts by mass of a polymerization inhibitor (product name: LA-7RD, ADEKA Corporation), 3 parts by mass of a thermal radical generator peroxyester (product name: Perhexa 25O, NOF Corporation), 15 parts by mass of organic fine particles (product name: EXL-2655, Rohm and Haas Japan Co., Ltd.), and 20 parts by mass of a film-forming polyester urethane resin (product name: UR4800, Toyobo Co., Ltd.) were mixed in methyl ethyl ketone and stirred to obtain solution D.

[0104] An anisotropic conductive film-like adhesive (thickness: 25 μm) was formed on a PET film in the same manner as in Example 1, except that solution D obtained above was used instead of solution A. This resulted in a film-like adhesive with a peelable substrate of Example 9 (ratio of average particle size of solder particles to thickness of film-like adhesive: r=0.8). The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0105] (Comparative Example 1) Solder particles (Bi content: 28% by mass, Sn content: 72% by mass, average particle size: 5 μm, softening point: 139°C, product name: ST-5) manufactured by Mitsui Mining & Smelting Co., Ltd. were prepared as solder particles E. The average particle size of solder particles E was confirmed by measuring the D50 value of solder particles E using a microtrack measuring device. An anisotropic conductive film-like adhesive (thickness: 25 μm) was formed on a PET film in the same manner as in Example 1, except that solder particles E were used instead of solder particles A. This resulted in a film-like adhesive with a peelable substrate of Comparative Example 1 (ratio of average particle size of solder particles to thickness of film-like adhesive: r = 0.2). The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0106] (Comparative Example 2) An anisotropic conductive film-like adhesive (thickness: 25 μm) was formed on a PET film in the same manner as in Comparative Example 1, except that solution B was used instead of solution A. This resulted in a film-like adhesive with a peelable substrate (ratio of the average particle size of the solder particles to the thickness of the film-like adhesive = 0.2) of Comparative Example 2. The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0107] (Comparative Example 3) 13 parts by mass of a carbonate-based urethane acrylate (product name: UN-5500, manufactured by Negami Chemical Industrial Co., Ltd.), 10 parts by mass of tris(acryloxyethyl) isocyanurate (product name: M-315, manufactured by Toagosei Co., Ltd.), and 5 parts by mass of dimethyloltricyclodecane diacrylate (product name: DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.), which are radical polymerizable compounds, 1 part by mass of 2-2-methacryloyloxyethyl acid phosphate (product name: Light Ester P-2M, manufactured by Kyoeisha Chemical Co., Ltd.), which is a phosphate ester-based organic compound, 5 parts by mass of benzoyl peroxide (product name: Niper BMT-K, manufactured by NOF Corporation), which is a thermal radical generator, and 33 parts by mass of a polyester urethane resin (product name: UR4800, manufactured by Toyobo Co., Ltd.), which is a film-forming material, were mixed in methyl ethyl ketone to obtain a methyl ethyl ketone solution. Thereafter, 3 parts by mass of polystyrene fine particles (trade name: PB-3006W, manufactured by Matsuura Corporation, average particle size: 6 μm) were mixed with the obtained methyl ethyl ketone solution to obtain a solution E.

[0108] An anisotropic conductive film-like adhesive (thickness: 25 μm) was formed on a PET film in the same manner as in Comparative Example 1, except that solution E was used instead of solution A. This resulted in a film-like adhesive with a peelable substrate (ratio of average particle size of solder particles to thickness of film-like adhesive = 0.2) of Comparative Example 3. The thickness of the film-like adhesive was measured in the same manner as in Example 1.

[0109] <Evaluation> (Viscosity measurement of film adhesive) The hardening point, minimum melt viscosity (viscosity A), and viscosity at the softening point of the solder particles (139° C.) (viscosity B) of the film-like adhesives of Examples 1 to 9 and Comparative Examples 1 to 3 were measured by the following methods.

[0110] First, the film adhesive was cut into several pieces and passed through a hot roll laminator heated to 40°C to prepare 500 μm thick viscosity measurement samples. The resulting samples were subjected to melt viscosity curve measurements using a shear viscosity measurement device (product name: ARES-G2, manufactured by TA Instruments) at a measurement frequency of 10 Hz, a heating rate of 10°C / min, and a measurement temperature range of 0°C to 250°C, resulting in a viscosity-temperature curve (vertical axis: viscosity, horizontal axis: measurement temperature) for the film adhesive. From the resulting viscosity-temperature curve, the hardening point of the film adhesive, the minimum melt viscosity (viscosity A), the viscosity at the softening point of the solder particles (139°C) (viscosity B), and the temperature T0 showing the minimum melt viscosity were determined. The results are shown in Table 1.

[0111] (Evaluation of connection structure) A first member was prepared as an adherend simulating a circuit component, comprising a ceramic substrate with a gold electrode (10 mm × 5 mm, single electrode) on its surface. The film-like adhesive with a peelable substrate obtained above was then cut to a width of 1.5 mm and attached to the gold electrode of the first member from the film-like adhesive side. Next, a thermocompression bonding device (heating method: constant heat type, manufactured by Nikka Setsubi Engineering Co., Ltd.) was used to heat and pressurize the PET film side (thermocompression bonding) so that the film-like adhesive reached a temperature of 70°C. The compression time was 1 second, and the pressure applied was 1 MPa per total area of ​​the film-like adhesive (area of ​​the bonded portion). After the resulting bonded body returned to room temperature, the PET film was peeled off from the bonded body, yielding a laminate comprising the film-like adhesive provided on the first member.

[0112] As the second member, a flexible circuit board (FPC) having circuit electrodes plated with Ni / Au on a copper circuit with a line width of 100 μm, a pitch of 200 μm, and a thickness of 35 μm was prepared. The second member was placed on the film-like adhesive side (opposite the first member) of the laminate obtained above, and pressurized (thermocompression bonding) while heating the film-like adhesive to a temperature of 140 ° C. using a thermocompression bonding device (heating method: constant heat type, manufactured by Nikka Setsubi Engineering Co., Ltd.). The pressure was 0.5 MPa or 5 MPa per total area of ​​the film-like adhesive (area of ​​the adhesive portion). In this way, connection structure A (compression pressure 0.5 MPa) and connection structure B (compression pressure 5 MPa) were produced.

[0113] The connection resistance value per circuit terminal of the connection structures A and B obtained above was measured using a four-terminal method. The measurement current was 1 mA, and the measurement voltage V (mV) was measured to calculate the initial resistance per connection terminal. A reliability test was then performed by placing connection structures A and B in a thermostatic chamber maintained at 85°C and 85% RH for 250 hours. After the test, connection structures A and B were removed from the thermostatic chamber and the connection resistance value was measured using the same method as above. The initial connection resistance and the connection resistance after the reliability test were evaluated according to the following criteria. The results are shown in Table 1. [Initial connection resistance] The average value of the connection resistance value (initial resistance value) measured at multiple electrodes in the connection structure immediately after manufacture was designated as X (Ω), and those where X was 0.01Ω or less were designated as "A", those where X was 0.05Ω or less were designated as "B", and those where X was more than 0.05Ω were designated as "C". [Connection resistance after reliability test] The average connection resistance value measured for multiple electrodes in the connection structure after the reliability test was defined as Y (Ω), and the rate of increase from the initial resistance value calculated using the formula: Y / X was 2 or less, which was rated as "A", more than 2 but less than 5, which was rated as "B", and more than 5, which was rated as "C".

[0114] [Table 1] [Explanation of symbols]

[0115] 1...film-like adhesive, 2...solder particles, 10...first circuit member, 11...first substrate, 15...first electrode, 20...second circuit member, 21...second substrate, 25...second electrode, 30...circuit connection portion, 31...insulating material, 100...connection structure.

Claims

1. A film-like adhesive for circuit connection, The solder paste contains solder particles having a Bi content of 20 to 60 mass % and a Sn content of 40 to 80 mass %, a radical polymerizable compound, and a thermal radical generator, A film-like adhesive, wherein the average particle size of the solder particles is 0.5 to 1.0 times the thickness of the film-like adhesive.

2. The film-like adhesive according to claim 1 , which has a hardening point lower than the softening point of the solder particles.

3. 3. The film-like adhesive according to claim 1, wherein the viscosity of the film-like adhesive at the softening point of the solder particles is at least three times the minimum melt viscosity.

4. 4. The film-like adhesive according to claim 1, wherein the softening point of the solder particles is 130 to 180°C.

5. a step of placing the film adhesive according to any one of claims 1 to 4 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 film-like adhesive 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.

6. the first electrode is an electrode having an Au plating layer on its outermost surface, The method for manufacturing a connection structure according to claim 5 , wherein the second electrode is an electrode having an Au-plated layer or an Sn-plated layer on its outermost surface.

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