Anisotropic conductive composition, anisotropic conductive sheet, connecting structure, and method for manufacturing the connecting structure.

Abstract

To provide an anisotropic conductive composition in which void generation is suppressed, an anisotropic conductive sheet containing the anisotropic conductive composition, a connecting structure connected using the anisotropic conductive sheet, and a method for manufacturing the connecting structure. [Solution] The anisotropic conductive composition comprises solder particles having a flake shape and a resin component, wherein the average aspect ratio of the solder particles is 2 or more.

Description

Technical Field

[0001] The present invention relates to an anisotropic conductive composition, an anisotropic conductive sheet, a connection structure, and a method for manufacturing a connection structure.

Background Art

[0002] Conventionally, an anisotropic conductive sheet has been used for connecting electrodes between two wiring circuit boards. The anisotropic conductive sheet is formed from a composition containing solder particles, a curable resin, and a flux.

[0003] First, the anisotropic conductive sheet is placed between two wiring circuit boards. Next, the anisotropic conductive sheet is heated. As a result, the curable resin once softens, and the melted solder particles gather and aggregate between the electrodes (self-aggregation). Then, the curing of the curable resin progresses around the solder. The aggregated solder solidifies upon subsequent cooling, forming a solder portion. Around the solder portion, the curable resin forms a cured resin portion.

[0004] As such an anisotropic conductive sheet, for example, an anisotropic conductive adhesive film containing minute spherical solder particles, a curable resin, and malic acid as a flux is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the anisotropic conductive adhesive film described in Patent Document 1, tiny spherical solder particles are used to miniaturize and reduce the height of the connected wiring circuit board, i.e., the connecting structure. However, in this case, the surface area of ​​the solder, which is a metal with a high degree of oxidation, becomes very large, resulting in a high degree of oxidation and the generation of voids during the curing of the curable resin. The generation of voids causes a decrease in the adhesive strength of the anisotropic conductive sheet.

[0007] The present invention provides an anisotropic conductive composition in which the generation of voids is suppressed, an anisotropic conductive sheet containing the anisotropic conductive composition, a connecting structure connected using the anisotropic conductive sheet, and a method for manufacturing the connecting structure. [Means for solving the problem]

[0008] The present invention [1] is an anisotropic conductive composition comprising flake-shaped solder particles and a resin component, wherein the average aspect ratio of the solder particles is 2 or more.

[0009] The present invention [2] includes the anisotropic conductive composition described in [1] above, wherein the content ratio of the solder particles is more than 50 parts by mass and 250 parts by mass or less per 100 parts by mass of the resin component.

[0010] The present invention [3] includes the anisotropic conductive composition described in [1] above, which includes flux.

[0011] The present invention [4] includes an anisotropic conductive sheet comprising an anisotropic conductive composition described in any one of the above [1] to [3].

[0012] The present invention [5] includes the anisotropic conductive sheet described in [4] above, wherein the ratio of the average side length of the solder particles to the thickness T of the anisotropic conductive sheet (s / T ratio) is 0.7 or more.

[0013] The present invention [6] includes the anisotropic conductive sheet described in [5] above, wherein the thickness T is 10 μm or less.

[0014] The present invention [7] includes the anisotropic conductive sheet described in [4] above, wherein the initial tack force at 25°C is 100 gf or more.

[0015] The present invention [8] includes a connection structure comprising a first substrate, a second substrate spaced apart in the thickness direction, and an adhesive layer interposed between the first and second substrates, each of the first and second substrates having at least one electrode, a columnar solder portion disposed between the electrode of the first substrate and the electrode of the second substrate, and the adhesive layer and the columnar solder portion being formed from the anisotropic conductive sheet described in [4] above.

[0016] The present invention [9] comprises a first step of preparing a plurality of substrates having a plurality of electrodes arranged in the planar direction, The second step is to prepare the anisotropic conductive sheet described in [4] above, A third step in which the electrodes of the two substrates are facing each other, the anisotropic conductive sheet is sandwiched between the two substrates, and the two substrates are stacked to manufacture a laminate, The method for manufacturing a connection structure includes a fourth step of heating the laminate and melting the solder particles to form columnar solder portions so as to electrically connect the electrodes of the two substrates, and curing the resin component.

[0017] The present invention

[10] includes a method for manufacturing the connection structure described in [9] above, wherein the fourth step is carried out in a pressure oven. [Effects of the Invention]

[0018] The present invention includes an anisotropic conductive composition comprising flake-shaped solder particles and a resin component, wherein the average aspect ratio of the solder particles is 2 or more. Therefore, the generation of voids in the anisotropic conductive composition can be suppressed. [Brief explanation of the drawing]

[0019] [Figure 1]FIG. 1 shows an embodiment of an anisotropic conductive sheet including an anisotropic conductive composition. [Figure 2] FIG. 2 shows an embodiment of a connection structure connected by the anisotropic conductive sheet shown in FIG. 1. [Figure 3] FIGS. 3A to 3E show an embodiment of a method for manufacturing the connection structure shown in FIG. 2. FIG. 3A shows a first step of preparing two substrates each provided with a plurality of electrodes arranged in a plane direction. FIG. 3B shows a second step of preparing an anisotropic conductive sheet by applying an anisotropic conductive composition. FIG. 3C shows a third step of manufacturing a laminate by laminating the first substrate and the second substrate with the anisotropic conductive sheet interposed therebetween so that the electrodes of the two substrates face each other. FIG. 3D shows a step of thermocompression bonding the first substrate, the second substrate, and the anisotropic conductive sheet in the fourth step. FIG. 3E shows a step of forming an adhesive layer for soldering the first substrate, the second substrate, and the anisotropic conductive sheet in the fourth step. [Figure 4] FIGS. 4A to 4C show an embodiment of a method for manufacturing the flake-shaped solder particles of the present invention. FIG. 4A shows a preparation step of preparing a solder material foil. FIG. 4B shows an ultrasonic irradiation device in an ultrasonic irradiation step. FIG. 4C shows an ultrasonic irradiation step of irradiating the solder material foil with ultrasonic waves having a liquid as a medium to break the solder material foil. [Figure 5] FIG. 5 is an image obtained by acquiring an optical microscope image of a cross section in the thickness direction of the anisotropic conductive sheet of Example 1 manufactured in the first step and binarizing the image. [Figure 6] FIG. 6 is an explanatory diagram for explaining an observation range in the evaluation of the generation of voids, the accumulation state of solder, and the generation of bridges.

Embodiments for Carrying Out the Invention

[0020] 1. Anisotropic Conductive Composition The anisotropic conductive composition includes solder particles having a flake shape (hereinafter also referred to as "flake-shaped solder particles") and a resin component.

[0021] <Flake-Shaped Solder Particles> From an environmental standpoint, lead-free solder materials are preferably used as the solder material that forms flake-shaped solder particles. The solder material preferably contains tin (Sn). Examples of tin-containing solder materials include tin and tin alloys. Examples of tin alloys include tin-bismuth alloy (Sn-Bi), tin-silver-copper alloy (Sn-Ag-Cu), tin-antimony alloy (Sn-Sb), and tin-silver alloy (Sn-Ag). Tin is preferably used as the solder material.

[0022] In tin alloys, the tin content is, for example, 40% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and also, for example, 99% by mass or less.

[0023] The melting point of the solder material (i.e., the melting point of flake-shaped solder particles) is higher than the softening point of the solid resin described later, for example, 120°C or higher, preferably 150°C or higher, more preferably 180°C or higher, and even more preferably 200°C or higher. For example, 280°C or lower, preferably 260°C or lower, more preferably 240°C or lower, and even more preferably 235°C or lower. The melting point is determined by differential scanning calorimetry (DSC) (the same applies hereafter).

[0024] Flake-shaped solder particles have a flake shape. A flake shape is defined as a shape in which, when an anisotropic conductive composition or anisotropic conductive sheet 1 is observed in a cross-section cut in the thickness direction, the exposed solder particles in the cross-section are rectangular or substantially rectangular, having sides (major axis) and thickness (minor axis), and the lengths of the sides and the thickness are different. Typically, the sides and thickness extend in directions perpendicular to each other. Examples of such flake shapes include plate shapes, disc shapes, and needle shapes, with plate shapes and disc shapes being preferred.

[0025] The average side length s of the flake-shaped solder particles is, for example, 1 μm or more and 30 μm or less. From the viewpoint of handling, the average side length s of the flake-shaped solder particles is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. Furthermore, from the viewpoint of suppressing bridging between electrodes, it is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

[0026] The average thickness t of the flake-shaped solder particles is, for example, 0.2 μm or more and 10 μm or less. From the viewpoint of handling, the average thickness t of the flake-shaped solder particles is preferably 0.3 μm or more, more preferably 0.5 μm or more and 0.7 μm or more. Furthermore, from the viewpoint of miniaturizing and lowering the profile of the connection structure, it is preferably 6 μm or less, more preferably 4 μm or less, even more preferably 2 μm or less, and even more preferably 1.5 μm or less.

[0027] The average side length and average thickness t of the flake-shaped solder particles can be calculated by observing multiple flake-shaped solder particles exposed in a cross-section of an anisotropic conductive composition, or an anisotropic conductive sheet 1 manufactured using an anisotropic conductive composition as described below, using an optical microscope, and determining the average.

[0028] The average aspect ratio of flake-shaped solder particles (average side length s / average thickness t) is 2 or greater. If the average aspect ratio of flake-shaped solder particles is less than 2, the suppression of void generation is insufficient. From the viewpoint of suppressing void generation, the average aspect ratio of flake-shaped solder particles is preferably 3 or greater, more preferably 4 or greater, even more preferably 5 or greater, even more preferably 6 or greater, particularly preferably 7 or greater, and most preferably 8 or greater. Also, from the viewpoint of handling, it is preferably 20 or less, more preferably 15 or less.

[0029] Flake-shaped solder particles can be used alone or in combination of two or more types.

[0030] The content ratio of flake-shaped solder particles is, for example, 30 parts by mass or more and 300 parts by mass or less per 100 parts by mass of the resin component described later. From the viewpoint of solder accumulation, the content ratio of flake-shaped solder particles is preferably more than 50 parts by mass, more preferably 80 parts by mass or more, and even more preferably more than 120 parts by mass. Furthermore, from the viewpoint of suppressing the occurrence of bridges between electrodes, it is preferably 250 parts by mass or less, more preferably 220 parts by mass or less, and even more preferably 200 parts by mass or less.

[0031] <Method for manufacturing flake-shaped solder particles> Next, an embodiment of a method for producing flake-shaped solder particles will be described with reference to Figures 4A to 4C.

[0032] A method for manufacturing flake-shaped solder particles comprises a preparation step of preparing a solder material foil 40, and an ultrasonic irradiation step of irradiating the solder material foil 40 with ultrasonic waves using a liquid (specifically, a first liquid 41 and a second liquid 42) as a medium to break the solder material foil 40.

[0033] [Preparation process] In the preparation step, a sheet-shaped solder material foil 40 is prepared, as shown in Figure 4A.

[0034] The thickness of the solder material foil 40 is less than 10 μm, preferably 5 μm or less, more preferably 3 μm or less, even more preferably 2 μm or less, and for example, 0.5 μm or more.

[0035] If the thickness of the solder material foil 40 is less than or equal to the above upper limit, then variations in the length extending in a direction perpendicular to the thickness of the flake-shaped solder particles 50 can be suppressed.

[0036] [Ultrasonic irradiation process] In the ultrasonic irradiation process, the solder material foil 40 is fractured by irradiating it with ultrasonic waves using liquids (first liquid 41 and second liquid 42) as a medium.

[0037] The ultrasonic irradiation process is carried out using the ultrasonic irradiation device 30. The ultrasonic irradiation device 30 will be described in detail below with reference to Figure 4B.

[0038] The ultrasonic irradiation device 30 comprises a first tank 31, a second tank 32 that houses the first tank 31, and an ultrasonic transducer 33.

[0039] The first tank 31 is a container with a smaller volume than the second tank 32. The first tank 31 is, for example, a glass container. The first liquid 41 and the solder material foil 40 are contained in the first tank 31.

[0040] The solder material foil 40 is immersed in the first liquid 41. The first liquid 41 is a medium that comes into contact with the solder material foil 40. The first liquid 41 is not particularly limited as long as it is a medium that propagates ultrasonic waves, but preferably, from the viewpoint of adjusting the viscosity (25°C) of the first liquid 41 as described later, alcohol is used.

[0041] Examples of alcohols include monohydric alcohols and dihydric alcohols. Preferred monohydric alcohols include ethanol and isopropanol (2-propanol). Preferred dihydric alcohols include ethylene glycol.

[0042] The first liquid 41 can be used alone or in combination of two or more. Preferably, from the viewpoint of adjusting the viscosity of the liquid (25°C) described later, a monohydric alcohol and a dihydric alcohol are used in combination as the first liquid 41.

[0043] The viscosity of the first liquid 41 (at 25°C) is, for example, 1 mPa·s to 20 mPa·s, preferably 5 mPa·s to 15 mPa·s.

[0044] If the viscosity (at 25°C) of the first liquid 41 is above the lower limit and below the upper limit, ultrasonic waves can be reliably transmitted to the solder material foil 40. As a result, even finer flake-shaped solder particles 50 can be manufactured (specifically, with a shorter maximum length extending in the direction perpendicular to the thickness).

[0045] The temperature of the first liquid 41 is, for example, 5°C to 25°C, preferably 8°C to 15°C.

[0046] The second tank 32 is a container with a larger volume than the first tank 31. The second tank 32 is, for example, a glass container. The first tank 31, the second liquid 42, and the ultrasonic transducer 33 are housed in the second tank 32.

[0047] The second liquid 42 is not particularly limited as long as it is a medium that propagates ultrasonic waves. The second liquid 42 is a medium that propagates ultrasonic waves to the first liquid 41 without coming into contact with the solder material foil 40. Water is a preferred example of the second liquid 42.

[0048] The temperature of the second liquid 42 is, for example, 5°C to 25°C, preferably 8°C to 15°C.

[0049] The ultrasonic transducer 33 is not particularly limited as long as it can generate the ultrasonic frequencies described later. In Figure 4B, an ultrasonic transducer housed in the second chamber 32 (for example, an immersion type transducer) is selected as the ultrasonic transducer 33, but the ultrasonic transducer 33 is not limited to this, and for example, a flange type transducer (a flange type transducer placed at the bottom outside the second chamber 32) can also be selected as the ultrasonic transducer 33.

[0050] Then, in order to irradiate the solder material foil 40 with ultrasound using liquids (first liquid 41 and second liquid 42) as a medium, first, the first liquid 41 and the solder material foil 40 are added to the first tank 31, and the solder material foil 40 is immersed in the first liquid 41. As a result, the first liquid 41 and the solder material foil 40 are contained in the first tank 31.

[0051] Next, the first tank 31, the second liquid 42, and the ultrasonic transducer 33 are added to the second tank 32. As a result, the first tank 31, the second liquid 42, and the ultrasonic transducer 33 are contained within the second tank 32.

[0052] Next, ultrasonic waves are generated by the vibration of the ultrasonic transducer 33.

[0053] The ultrasonic irradiation conditions include a frequency of, for example, 10 kHz to 200 kHz, preferably 20 kHz to 180 kHz, and more preferably 30 kHz to 150 kHz.

[0054] By keeping the frequency within the above range, the solder material foil 40 can be reliably fractured. Furthermore, the maximum length extending in the direction perpendicular to the thickness of the flake-shaped solder particles 50 can be kept within an appropriate range, and variations can be suppressed.

[0055] Furthermore, the ultrasonic irradiation conditions include an output power of, for example, 30W to 600W, preferably 50W to 550W, and more preferably 70W to 500W.

[0056] By keeping the output within the above range, the solder material foil 40 can be reliably broken. In addition, the maximum length extending in the direction perpendicular to the thickness of the flake-shaped solder particles 50 can be kept within an appropriate range, and variations can be suppressed.

[0057] Furthermore, the ultrasonic irradiation conditions include an irradiation time of, for example, 1 to 72 hours, preferably 12 to 36 hours, and more preferably 18 to 30 hours.

[0058] The ultrasonic waves generated from the ultrasonic transducer 33 propagate in the following order: second liquid 42, partition wall of first tank 31, and first liquid 41 (if the ultrasonic transducer 33 is a flange-type transducer, the waves propagate in the following order: partition wall of second tank 32, second liquid 42, partition wall of first tank 31, and first liquid 41).

[0059] Next, ultrasonic cavitation occurs in the first liquid 41. The shock waves generated by this ultrasonic cavitation break the solder material foil 40. Specifically, as shown in the enlarged view of Figure 4C, the solder material foil 40 is broken in the thickness direction, and the broken solder material foil 40 is similarly broken in the thickness direction. As this breaking occurs sequentially, the surface of the broken solder material foil 40 is scraped away. This produces flake-shaped solder particles 50.

[0060] As described above, the flake-shaped solder particles 50 produced by the manufacturing method of flake-shaped solder particles exhibit suppressed variation in length in the direction perpendicular to the thickness of the flake-shaped solder particles 50.

[0061] Furthermore, the above-described method for manufacturing flake-shaped solder particles suppresses variations in thickness. Specifically, it is possible to manufacture flake-shaped solder particles with a coefficient of variation in thickness (standard deviation / average thickness) of 0.50 or less.

[0062] <Resin components> The resin component is not particularly limited, but preferably includes a solid resin and a liquid resin. When the resin component includes a solid resin and a liquid resin, the anisotropic conductive sheet 1 exhibits excellent moldability and adhesive strength.

[0063] Solid resins do not flow at 25°C and have no viscosity. Liquid resins, on the other hand, contain liquids and fluids and have viscosity at 25°C.

[0064] Examples of solid resins include thermosetting resins and thermoplastic resins. The solid resin may contain either a thermosetting resin or a thermoplastic resin, or both, but preferably contains only a thermosetting resin.

[0065] Examples of liquid resins include thermosetting resins and thermoplastic resins. The liquid resin may contain either a thermosetting resin or a thermoplastic resin, or both, but preferably contains only a thermosetting resin.

[0066] The resin component more preferably consists of a solid thermosetting resin and a liquid thermosetting resin.

[0067] The mass ratio of solid resin to liquid resin in the resin component is, for example, 0.5 to 1.5, preferably 0.7 to 1.3, and more preferably 0.9 to 1.1.

[0068] Furthermore, the resin component can be mixed with a known solvent to prepare a varnish. The solid content concentration of the resin component varnish is, for example, 30% to 80% by mass, preferably 40% to 70% by mass.

[0069] Furthermore, the content ratio of the resin component is, for example, 10% to 80% by mass, preferably 20% to 70% by mass, and more preferably 30% to 50% by mass, relative to the anisotropic conductive composition.

[0070] Furthermore, the softening point of the solid resin is lower than the melting point of the flake-shaped solder particles. Specifically, in the sixth step of thermocompression bonding described later, from the viewpoint of softening the solid resin without melting the flake-shaped solder particles, the softening point of the solid resin is lower than the melting point of the flake-shaped solder particles. The softening point of the solid resin is, for example, 40°C or higher, preferably 60°C or higher, more preferably 80°C or higher, and also, for example, 200°C or lower, preferably 180°C or lower, more preferably less than 150°C, and even more preferably 140°C or lower.

[0071] The above softening point can be measured using a thermomechanical analyzer. [Thermosetting resin] Examples of thermosetting resins include thermosetting epoxy resins, urea resins, melamine resins, diallyl phthalate resins, silicone resins, phenolic resins, thermosetting acrylic resins, thermosetting polyesters, thermosetting polyimides, and thermosetting polyurethanes. Thermosetting epoxy resins are preferred as the thermosetting resin.

[0072] Examples of thermosetting epoxy resins include thermosetting bisphenol-type epoxy resins (e.g., thermosetting bisphenol A-type epoxy resin, thermosetting bisphenol F-type epoxy resin, and thermosetting bisphenol S-type epoxy resin), thermosetting novolac-type epoxy resins (e.g., thermosetting phenol novolac-type epoxy resin, thermosetting cresol novolac-type epoxy resin, and thermosetting biphenyl-type epoxy resin), thermosetting naphthalene-type epoxy resin, thermosetting fluorene-type epoxy resin (e.g., thermosetting bisarylfluorene-type epoxy resin), and thermosetting triphenylmethane-type epoxy resin (e.g., thermosetting trishydroxyphenylmethane-type epoxy resin). Preferably, thermosetting bisphenol-type epoxy resin is used as the thermosetting epoxy resin. More preferably, thermosetting bisphenol A-type epoxy resin is used as the thermosetting epoxy resin. The epoxy equivalent of the thermosetting epoxy resin is preferably 150 to 240, and more preferably 170 to 220, in the case of a liquid resin. The epoxy equivalent of the thermosetting epoxy resin is preferably 800 to 3000, and more preferably 1400 to 2000, in the case of a solid resin.

[0073] Furthermore, these thermosetting resins may be in either a solid or liquid state at room temperature (25°C).

[0074] The curing temperature of the thermosetting resin is the same as or higher than the melting point of the flake-shaped solder particles, for example, 150°C to 280°C, preferably 160°C to 260°C, and more preferably 220°C to 250°C.

[0075] Thermosetting resins can be used alone or in combination of two or more types.

[0076] The content of the thermosetting resin is, for example, 30 parts by mass or more, preferably 50 parts by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, or, for example, 100 parts by mass or less, per 100 parts by mass of the resin component.

[0077] [Thermoplastic resin] Examples of thermoplastic resins include thermoplastic epoxy resins, thermoplastic phenolic resins, phenoxy resins, polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymers, etc.), thermoplastic acrylic resins, thermoplastic polyesters, polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide (nylon®), polycarbonate, polyacetal, polyethylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyallylsulfone, thermoplastic polyimides, thermoplastic polyurethanes, polyaminobismaleimide, polyamideimide, polyetherimide, bismaleimide triazine resins, polymethylpentene, fluorinated resins, liquid crystal polymers, olefin-vinyl alcohol copolymers, ionomers, polyarylates, acrylonitrile-ethylene-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, and butadiene-styrene copolymers.

[0078] Thermoplastic resins can be used alone or in combination of two or more types.

[0079] The content ratio of thermoplastic resin is, for example, 0 parts by mass or more, and for example, 50 parts by mass or less, preferably 20 parts by mass or less, per 100 parts by mass of resin component.

[0080] <Flux> The anisotropic conductive composition preferably contains flux. The flux has the effect of removing the oxide film from the surface of the flake-shaped solder particles and the surface of the electrodes (specifically, the first electrode and the second electrode described later).

[0081] The flux is not particularly limited as long as it has the effect of removing the oxide film from the surface of the flake-shaped solder particles and the surface of the electrode. Examples of such fluxes include organic acids, preferably carboxylic acids. Examples of carboxylic acids include monocarboxylic acid compounds, dicarboxylic acid compounds, and tricarboxylic acid compounds, preferably dicarboxylic acid compounds.

[0082] Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acids and aromatic dicarboxylic acids. Aliphatic dicarboxylic acids include linear saturated dicarboxylic acids, branched saturated dicarboxylic acids, linear unsaturated dicarboxylic acids, and branched unsaturated dicarboxylic acids.

[0083] Examples of linear saturated dicarboxylic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

[0084] Examples of branched saturated dicarboxylic acids include 3,3-dimethylglutaric acid.

[0085] Examples of linear unsaturated dicarboxylic acids include fumaric acid.

[0086] Among these, from the viewpoint of effectively removing flake-shaped solder particles and the oxide film on the electrode, aliphatic dicarboxylic acid is preferred, more preferably linear saturated dicarboxylic acid or branched saturated dicarboxylic acid. Further preferred are glutaric acid, adipic acid, pimelic acid, and 3,3-dimethylglutaric acid, particularly preferred are glutaric acid and 3,3-dimethylglutaric acid, and most preferably is 3,3-dimethylglutaric acid.

[0087] Furthermore, the salts of the dicarboxylic acid compounds mentioned above can also be used as flux.

[0088] Flux can be used alone or in combination of two or more types.

[0089] Alternatively, the flux can be prepared as a solution by mixing it with a known solvent (e.g., ethanol). The solid content concentration of the flux solution is, for example, 10% to 50% by mass, preferably 20% to 40% by mass.

[0090] The flux content is, for example, 3 parts by mass or more, preferably 6 parts by mass or more, more preferably 9 parts by mass or more, and particularly preferably 13 parts by mass or more, per 100 parts by mass of resin component. Alternatively, it may be, for example, 30 parts by mass or less, preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and particularly preferably 17 parts by mass or less, per 100 parts by mass of resin component. By setting the flux content within the above range, flake-shaped solder particles and the oxide film on the electrodes can be effectively removed.

[0091] Furthermore, from the viewpoint of further removing the oxide film on the surface of the flake-shaped solder particles, the flux content is, for example, 1 part by mass or more, preferably 5 parts by mass or more, and also, for example, 15 parts by mass or less, preferably 10 parts by mass or less, per 100 parts by mass of flake-shaped solder particles.

[0092] Furthermore, the flux content is, for example, 1% to 10% by mass, preferably 3% to 7% by mass, relative to the anisotropic conductive composition.

[0093] <Hardening agent> The anisotropic conductive composition may further contain a curing agent. Preferably, it does not contain a curing agent, or if it does, the curing agent content is, for example, less than 20 parts by mass per 100 parts by mass of the resin component. The curing agent content is preferably less than 5 parts by mass, more preferably less than 3 parts by mass, and even more preferably less than 1 part by mass.

[0094] Examples of curing agents include acid anhydride-based curing agents, amine-based curing agents, phenol-based curing agents, cationic initiators, imidazole catalysts, and DICY (dicyandiamide).

[0095] <Other additives> The anisotropic conductive composition may contain other additives in appropriate proportions as needed. For example, it may contain a curing aid.

[0096] 2. Method for producing an anisotropic conductive composition An anisotropic conductive composition is manufactured by mixing flake-shaped solder particles, a resin component, a flux as needed, and a curing agent and additives as needed. Specifically, the flake-shaped solder particles, the resin component, the flux as needed, and the curing agent and additives as needed are mixed and stirred as necessary. This produces an anisotropic conductive composition.

[0097] Furthermore, the anisotropic conductive composition can be prepared as a varnish by blending it with a known solvent. The solid content concentration of the anisotropic conductive composition varnish is, for example, 50% to 80% by mass, preferably 60% to 75% by mass.

[0098] Next, we will describe in detail the anisotropic conductive sheet 1 obtained using this anisotropic conductive composition.

[0099] 3. Anisotropic conductive sheet The anisotropic conductive sheet 1 is formed in sheet form from an anisotropic conductive composition. In other words, the anisotropic conductive sheet 1 contains an anisotropic conductive composition.

[0100] As shown in Figure 1, the anisotropic conductive sheet 1 is arranged on one side in the thickness direction of the release liner 10. In the anisotropic conductive sheet 1, flake-shaped solder particles 5 are dispersed in the resin component.

[0101] The anisotropic conductive sheet 1 preferably has an s / T ratio (ratio of the average side length s of the flake-shaped solder particles to the thickness T of the anisotropic conductive sheet) of 0.7 or more, more preferably 1.1 or more, even more preferably 1.5 or more, and also preferably 2.2 or less, more preferably 2.0 or less, and even more preferably 1.8 or less. By having an s / T ratio within the above range, miniaturization and reduction of the profile can be further achieved.

[0102] The thickness of the anisotropic conductive sheet 1 is, for example, 50 μm or less, preferably 25 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, even more preferably 8 μm or less, particularly preferably 6 μm or less, and also, for example, 1 μm or more, from the viewpoint of miniaturizing and lowering the height of the connecting structure.

[0103] The anisotropic conductive sheet 1 is manufactured by applying an anisotropic conductive composition (anisotropic conductive composition varnish) to one side in the thickness direction of a release liner 10, and then drying it as necessary. As for the drying conditions, the drying temperature is, for example, 40°C to 100°C. The drying time is, for example, 1 minute to 60 minutes.

[0104] The release liner 10 is a support for supporting the anisotropic conductive sheet 1, as described above. The release liner 10 is, for example, a film-shaped plastic substrate (plastic film). The thickness of the release liner 10 is, for example, 1 μm to 100 μm.

[0105] The initial tack force of the anisotropic conductive sheet 1 at 25°C is, for example, 80 gf or more, preferably 100 gf or more, more preferably 120 gf or more, and even more preferably 140 gf or more. Having an initial tack force above the above lower limit provides excellent initial adhesion between wiring circuit boards. Furthermore, from the viewpoint of ease of rework, the initial tack force is, for example, 500 gf or less, preferably 400 gf or less, and more preferably 300 gf or less.

[0106] The initial tack force of the anisotropic conductive sheet 1 can be measured by performing a probe tack test using the tacking tester TAC1000 (manufactured by Lesca).

[0107] 4. Connection Structure As shown in Figure 2, the connecting structure 20 is manufactured by connecting two wiring circuit boards (first board 2, second board 4) equipped with electrodes using the anisotropic conductive sheet 1 described above. When the anisotropic conductive sheet 1 hardens, it forms columnar solder portions 15 and an adhesive layer 3. In the connecting structure 20, the columnar solder portions 15 are positioned between the electrodes 12 and 14 of the two boards 2 and 4, and the two boards 2 and 4 are electrically connected. The adhesive layer 3 is positioned between the two boards 2 and 4 and around the columnar solder portions 15. The adhesive layer 3 contains a hardening resin 16.

[0108] Specifically, the connecting structure 20 comprises a first substrate 2, a second substrate 4 spaced apart in the thickness direction, and an adhesive layer 3 interposed between the first substrate 2 and the second substrate 4. In other words, the connecting structure 20 comprises the first substrate 2, the adhesive layer 3, and the second substrate 4 in order toward one side in the thickness direction. More specifically, the connecting structure 20 comprises the first substrate 2, an adhesive layer 3 directly positioned on the upper surface (one side in the thickness direction) of the first substrate 2, and a second substrate 4 directly positioned on the upper surface (one side in the thickness direction) of the adhesive layer 3.

[0109] The adhesive layer 3 adheres to the first substrate 2 and the second substrate 4. Specifically, the adhesive layer 3 adheres to the surface of the first substrate 2, excluding the first electrode 12. The adhesive layer 3 also adheres to the surface of the second substrate 4, excluding the second electrode 14.

[0110] Furthermore, the columnar solder portion 15 electrically connects the first electrode 12 and the second electrode 14, which are opposite each other in the thickness direction. The columnar solder portion 15 has a columnar shape (specifically, a cylindrical shape), is positioned between the first electrode 12 and the second electrode 14, and is in contact with them. The columnar solder portion 15 exhibits anisotropy that exists only between the first electrode 12 and the second electrode 14.

[0111] 5. Method for manufacturing a connecting structure An embodiment of a method for manufacturing a connecting structure will be described in detail below with reference to Figures 3A to 3E.

[0112] The method for manufacturing the connecting structure comprises a first step of preparing two (or more) substrates 2 and 4; a second step of preparing an anisotropic conductive sheet 1; a third step of stacking the two substrates 2 and 4 with the anisotropic conductive sheet 1 in between so that the electrodes of the two substrates 2 and 4 face each other, thereby manufacturing a laminate 6; and a fourth step of heating the laminate 6 to form columnar solder portions 15 and to cure the resin components.

[0113] [1st step] In the first step, the first substrate 2 and the second substrate 4 are prepared as shown in Figure 3A.

[0114] The first substrate 2 has a flat plate shape.

[0115] The first substrate 2 comprises a first wiring circuit board 11 and a plurality of first electrodes 12 arranged in the planar direction of the first wiring circuit board 11. In other words, the first substrate 2 comprises a first wiring circuit board 11 and a plurality of first electrodes 12 provided on the surface (one side in the thickness direction) of the first wiring circuit board 11.

[0116] The first wiring circuit board 11 is formed from, for example, an insulating material and a semiconductor material.

[0117] The thickness of the first wiring circuit board 11 is, for example, 5 μm to 1000 μm.

[0118] The first electrode 12 is made of metal.

[0119] The first electrode 12 is arranged on the first substrate 2, for example, as a dot pattern.

[0120] More specifically, the first electrode 12 has a circular shape in plan view. Furthermore, the multiple first electrodes 12 are evenly aligned and arranged in the planar direction.

[0121] The thickness of the first electrode 12 is, for example, 0 μm to 20 μm, preferably 0.001 μm to 5 μm. If the surface of the first substrate 2 and the surface of the first electrode 12 coincide, the thickness of the first electrode 12 is 0 μm.

[0122] The diameter of the first electrode 12 is, for example, 1 μm to 200 μm, preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm, and even more preferably 1 μm to 20 μm.

[0123] Furthermore, in the planar direction, the distance (pitch) between adjacent first electrodes 12 is, for example, 3 μm to 400 μm, preferably 5 μm to 200 μm, more preferably 7 μm to 100 μm, and even more preferably 10 μm to 40 μm.

[0124] The second substrate 4 has a flat plate shape.

[0125] The second substrate 4 comprises a second wiring circuit board 13 and a plurality of second electrodes 14 arranged in the planar direction of the second wiring circuit board 13. In other words, the second substrate 4 comprises a second wiring circuit board 13 and a plurality of second electrodes 14 provided on the surface (other than the thickness direction) of the second wiring circuit board 13.

[0126] The second wiring circuit board 13 is formed from, for example, an insulating material or a semiconductor material.

[0127] The thickness of the second wiring circuit board 13 is, for example, 5 μm to 1000 μm.

[0128] The second electrode 14 is made of metal.

[0129] The second electrode 14 is arranged on the second substrate 4, for example, as a dot pattern.

[0130] More specifically, the second electrode 14 has a circular shape in plan view. Furthermore, multiple second electrodes 14 are evenly aligned and arranged in the planar direction.

[0131] The thickness of the second electrode 14 is, for example, 0 μm to 20 μm, preferably 0.001 μm to 5 μm. If the surface of the second substrate 4 and the surface of the second electrode 14 coincide, the thickness of the second electrode 14 is 0 μm.

[0132] The diameter of the second electrode 14 is, for example, 1 μm to 200 μm, preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm, and even more preferably 1 μm to 20 μm.

[0133] Furthermore, in the planar direction, the distance (pitch) between adjacent second electrodes 14 is the same as the distance (pitch) between adjacent first electrodes 12 in the planar direction as described above.

[0134] [Second process] In the second step, an anisotropic conductive sheet 1 is prepared as shown in Figure 3B. Specifically, the anisotropic conductive sheet 1 is prepared in accordance with the manufacturing method of the anisotropic conductive sheet described above.

[0135] [3rd step] In the third step, as shown in Figure 3C, the first substrate 2 and the second substrate 4 are stacked with an anisotropic conductive sheet 1 in between, so that the first electrode 12 of the first substrate 2 and the second electrode 14 of the second substrate 4 face each other, thereby manufacturing a laminate 6.

[0136] More specifically, first, the first substrate 2 and the second substrate 4 are brought close to the anisotropic conductive sheet 1, so that the first substrate 2 and the second substrate 4 come into contact with the anisotropic conductive sheet 1. More specifically, in the thickness direction, one side of the first substrate 2 in the thickness direction is brought into contact with the other side of the anisotropic conductive sheet 1 in the thickness direction, and the other side of the second substrate 4 in the thickness direction is brought into contact with one side of the anisotropic conductive sheet 1 in the thickness direction, so that the first electrode 12 and the second electrode 14 face each other.

[0137] This allows for the manufacture of the laminate 6.

[0138] [4th step] In the fourth step, first, the first substrate 2 and the second substrate 4 are heat-pressed together with the anisotropic conductive sheet 1, as shown in Figure 3D.

[0139] Specifically, the laminate 6 is heated while the first substrate 2 and the second substrate 4 are pressed (thermocompressed) toward the anisotropic conductive sheet 1.

[0140] The temperature for thermocompression bonding is above the softening point of the solid resin and below the melting point of the flake-shaped solder particles 5. In other words, in this step, the solid resin is softened without melting the flake-shaped solder particles 5. Specifically, the thermocompression bonding temperature is, for example, 180°C or lower, preferably 100°C or lower, more preferably 80°C or lower, and also, for example, 40°C or higher. The thermocompression bonding pressure is, for example, 0.001 MPa to 10 MPa, preferably 0.005 MPa to 5 MPa, more preferably 0.01 MPa to 1 MPa.

[0141] As a result, the resin components soften, the first electrode 12 of the first substrate 2 becomes embedded in the anisotropic conductive sheet 1, and one side of the first substrate 2 in the thickness direction comes into contact with the anisotropic conductive sheet 1. In addition, the second electrode 14 of the second substrate 4 becomes embedded in the anisotropic conductive sheet 1, and the other side of the second substrate 4 in the thickness direction comes into contact with the anisotropic conductive sheet 1.

[0142] Next, as shown in Figure 3E, the laminate 6 is heated. Preferably, the laminate 6 is heated in a pressure oven 25. The pressure oven 25 is a device that can heat and pressurize in a sealed space, and examples include an automatic heating and pressurizing apparatus, a pressurizing oven, a voidless pressurizing oven, an autoclave, and a vacuum pressurizing reflow apparatus.

[0143] When the laminate 6 is heated, volatile substances may be released due to the heating. Such volatile substances may interfere with electrical connections in the laminate 6. On the other hand, when the laminate 6 is heated using a pressure oven 25, the generation of the above-mentioned volatile substances can be suppressed by pressurization. As a result, the above-mentioned interference can be suppressed.

[0144] The heating temperature is above the melting point of the flake-shaped solder particles 5. Specifically, the heating temperature is, for example, 100°C or higher, preferably 130°C or higher, more preferably 150°C or higher, even more preferably 200°C or higher, even more preferably 220°C or higher, and also, for example, 300°C or lower, preferably 280°C or lower, and more preferably 270°C or lower.

[0145] This heating process melts the flake-shaped solder particles 5. The melted flake-shaped solder particles 5 gather (self-aggregate) between the first electrode 12 and the second electrode 14, which are opposite each other in the thickness direction, forming a columnar solder portion 15 that electrically connects the first electrode 12 and the second electrode 14. Meanwhile, the resin component in the anisotropic conductive sheet 1 is displaced by the self-aggregating flake-shaped solder particles 5 and moves to the periphery of the columnar solder portion 15. Subsequently, the thermosetting resin in the resin component heat-cures to become a cured resin 16 that adheres the first substrate 2 and the second substrate 4.

[0146] This forms a columnar solder portion 15 and an adhesive layer 3 containing a curing resin 16 between the two substrates (first substrate 2 and second substrate 4) from the anisotropic conductive sheet 1.

[0147] From the viewpoint of miniaturizing and reducing the height of the connecting structure 20, the thickness of the adhesive layer 3 is less than 50 μm, preferably 25 μm or less, more preferably less than 15 μm, even more preferably 5 μm or less, and for example, 1 μm or more.

[0148] Based on the above, the connecting structure 20 is manufactured.

[0149] <Effects and Effects> The anisotropic conductive composition contains solder particles having a flake shape and a resin component, and the average aspect ratio of the solder particles is 2 or more. Therefore, the generation of voids in the anisotropic conductive composition can be suppressed.

[0150] By using an anisotropic conductive composition containing flake-shaped solder particles with an average aspect ratio of 2 or more, the surface area of ​​the solder, which is a highly oxidized metal, can be reduced compared to using minute spherical solder particles, thereby lowering the degree of oxidation. As a result, the generation of voids during the curing of the resin component can be suppressed.

[0151] The anisotropic conductive sheet 1 contains an anisotropic conductive composition. Therefore, the generation of voids during the curing of the resin component can be suppressed.

[0152] The connecting structure 20 contains an anisotropic conductive composition. Therefore, the generation of voids during the curing of the resin component can be suppressed.

[0153] The manufacturing method for the connecting structure involves using an anisotropic conductive composition. Therefore, the generation of voids during the curing of the resin component can be suppressed.

[0154] <Variation> In the modified examples, components and processes similar to those in the first embodiment are given the same reference numerals, and their detailed descriptions are omitted. Furthermore, the modified examples can achieve the same effects and advantages as the first embodiment, unless otherwise specified. Moreover, the first embodiment and the modified examples can be combined as appropriate.

[0155] Furthermore, in the above description, the first electrode 12 and the second electrode 14 are arranged as a dot pattern, but the arrangement of the first electrode 12 and the second electrode 14 is not limited to this.

[0156] Furthermore, in the above description, the first electrode 12 and the second electrode 14 have a circular shape in plan view, but the shape of the first electrode 12 and the second electrode 14 is not limited to this, and for example, they may be rectangular in plan view.

[0157] Furthermore, in the above description, the second substrate 4 may be, for example, a chip component (e.g., a mini / microLED). [Examples]

[0158] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, "parts" and "%" are based on mass. Furthermore, specific numerical values ​​such as blending ratios (content), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than") of the blending ratios (content), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0159] 1. Manufacturing of flake-shaped solder particles Flake-shaped solder particles were manufactured using the following procedure.

[0160] <Details of ingredients> This section details the names and abbreviations of the components used in the manufacture of flake-shaped solder particles. EtOH: Ethanol EG: Ethylene glycol

[0161] <Manufacturing of flake-shaped solder particles> (Flake-shaped solder particles 1) [Preparation process] As shown in Figure 4A, tin foil (127mm x 127mm, 1.3μm thick, manufactured by Narika Co., Ltd.) was prepared as the solder material foil 40.

[0162] [Ultrasonic irradiation process] An ultrasonic irradiation apparatus 30, as shown in Figure 4B, was prepared. A conical flask was used as the first tank 31. A glass water tank was used as the second tank 32. An ultrasonic transducer 33, named "WF1973" and manufactured by WAVE FACTORY, was used. A liquid mixture of 140 mL of EG and 60 mL of EtOH was used as the first liquid 41. Water was used as the second liquid 42.

[0163] The first liquid 41 and solder material foil 40 were added to the first tank 31, and the solder material foil 40 was immersed in the first liquid 41. As a result, the first liquid 41 and solder material foil 40 were contained in the first tank 31.

[0164] Next, the first tank 31, the second liquid 42, and the ultrasonic transducer 33 were added to the second tank 32. As a result, the first tank 31, the second liquid 42, and the ultrasonic transducer 33 were contained within the second tank 32.

[0165] Next, ultrasonic waves were generated by the vibration of the ultrasonic transducer 33 based on the ultrasonic irradiation conditions shown in Table 1. By irradiating the solder material foil 40 with ultrasonic waves using liquids (first liquid 41 and second liquid 42) as a medium, the solder material foil 40 was fractured, and flake-shaped solder particles 50 were produced.

[0166] (Flake-shaped solder particles 2) As shown in Table 1, flake-shaped solder particles 2 were manufactured in a separate lot using the same manufacturing method as flake-shaped solder particles 1.

[0167] [Table 1]

[0168] 2. Manufacturing and evaluation of test connection structures <Details of ingredients> The trade names (names) and abbreviations of the components listed in Table 2 used in each example and comparative example are described in detail below. 3,3-Dimethylglutaric acid (hereinafter also referred to as "dimethylglutaric acid"): Manufactured by Merck KCaA. Liquid epoxy resin (name "jER828"): Bisphenol A type epoxy resin, epoxy equivalent 184-194 g / eq, liquid at 25°C, thermosetting resin, manufactured by Mitsubishi Chemical Corporation. Solid epoxy resin (name "NPES907"): Bisphenol A type epoxy resin, epoxy equivalent 1500-1600 g / eq, solid at 25°C, thermosetting resin, softening point 120-130°C, manufactured by Nanya Plastics Co., Ltd. Spherical solder particles: Sn 96.5% by mass, Ag 3.0% by mass, Copper 0.5% by mass, Cu alloy, melting point 217-219℃, spherical shape, average primary particle diameter: 1 μm, maximum particle size Dmax: 2.9 μm [(Obtained by classifying solder particles (name "Sn96.5Ag3Cu0.5 ST-3"): spherical shape, average primary particle diameter: 3 μm, manufactured by Mitsui Mining & Smelting Co., Ltd.)]

[0169] <Manufacturing of anisotropic conductive compositions> Using the manufactured flake-shaped solder particles 1, 2, or spherical solder particles, anisotropic conductive compositions for each example and comparative example were prepared according to the following procedure.

[0170] First, the manufactured flake-shaped solder particles were washed using the following procedure. The dispersion containing the flake-shaped solder particles was irradiated with ultrasound, then allowed to stand to allow the solder particles to settle naturally. After removing the supernatant, ethanol was added and the mixture was stirred until homogeneous. The same procedure was then repeated once more. Next, after the flake-shaped solder particles had settled naturally, the supernatant was removed, acetone was added and the mixture was stirred until homogeneous. The same procedure was then repeated once more. Next, after the flake-shaped solder particles had settled naturally, the supernatant was removed, and the mixture was allowed to stand at room temperature for 5 minutes to air dry.

[0171] Next, flake-shaped solder particles or spherical solder particles, resin components, and flux were mixed according to the formulation described in Table 1. Then, methyl ethyl ketone was added and the mixture was stirred until homogeneous to produce an anisotropic conductive composition varnish (solid content concentration 70% by mass). NPES907 was prepared beforehand by dissolving it in methyl ethyl ketone to form a varnish (solid content concentration 50% by mass). The flux was also prepared beforehand by dissolving it in acetone to form a flux solution (solid content concentration 20% by mass). The values ​​for each component listed in the table represent the solid content.

[0172] <Manufacturing of test connection structures> The test connection structures for each example and comparative example were manufactured using the following procedure.

[0173] (1st step) The anisotropic conductive compositions of each example and comparative example were applied to a release liner using an applicator and dried at 60°C for 5 minutes to prepare anisotropic conductive sheets. The thickness (sheet thickness) T of the anisotropic conductive sheets is shown in Table 2.

[0174] (2nd process) Two substrates were prepared: a dummy wafer with Au electrodes (10mm x 10mm in size, 50μm square electrode, 50μm distance between electrode ends) and alkali-free glass (10mm x 10mm).

[0175] (3rd step) A dummy wafer with an Au electrode, an anisotropic conductive sheet, and alkali-free glass were bonded in sequence at 50°C under vacuum conditions. The release liner was removed during bonding. This produced a laminate. The resulting laminate was then observed using an optical microscope (name "VHX-8000", manufactured by Keyence Corporation) to confirm the absence of trapped air bubbles.

[0176] (4th step) The laminate was placed in a vacuum pressure reflow apparatus (named "Model 1200 Table Top Furnace," manufactured by SST International), and after vacuuming, it was pressurized with nitrogen to 4.5 atmospheres. Then, the temperature was increased at a rate of 100°C / min, with a maximum temperature of 270°C for Examples 1-4 and 260°C for Comparative Example 1, followed by a holding time of 1 minute. This produced test connection structures for each example and comparative example, in which a dummy wafer with an Au electrode, an adhesive layer (anisotropic conductive sheet), and alkali-free glass were laminated in one direction in the thickness direction.

[0177] <Measurement and Evaluation> [Calculation of the aspect ratio of flake-shaped solder particles] For each example and comparative example manufactured in the first step, the anisotropic conductive sheets were cut in the thickness direction using a freeze microtome to expose the cross-sections. Optical microscope images of the thickness-direction cross-sections were then acquired. Image analysis was performed on the acquired images. After binarizing the images, the length and thickness of the exposed edges of each of the 20 flake-shaped solder particles in the image were measured using the Fit elipse (ellipse approximation) function of the image analysis software ImageJ. Based on the measurement results, the average edge length s and average thickness t were calculated. The average aspect ratio (average edge length s / average thickness t) was then calculated from these average values. Table 2 shows the average edge length s, average thickness t, and average aspect ratio of the flake-shaped solder particles for each example. Table 2 also shows the average edge length / thickness of the anisotropic conductive sheet (s / T). Figure 5 shows the binarized optical microscope image of the cross-section of the anisotropic conductive sheet of Example 1.

[0178] [Probe Tack Test] Test specimens were prepared using the following apparatus and conditions, and the initial tack force was evaluated. The results are shown in Table 2. Specifically, first, a polyester film (product name "Lumirror", thickness 50 μm, manufactured by Toray Industries, Inc.) was laminated with double-sided adhesive tape (product name "No. 5000NS", manufactured by Nitto Denko Corporation). Next, an anisotropic conductive sheet was laminated to the double-sided adhesive tape to obtain a laminate. A 2 kg hand roller was used for lamination. After this, a test specimen measuring 2 cm × 2 cm was cut from the laminate. Next, the tack (gf) of the surface of the anisotropic conductive sheet on the test specimen at 25°C was measured using a tacking tester (product name "TAC1000", manufactured by Resca Corporation). In this measurement, a SUS403 probe (diameter 5 mm) was used, the probe pressing speed was set to 120 mm / min, the pressing pressure to 0.5 N, the pressing time to 3 seconds, and the probe peeling speed to 2 mm / second.

[0179] [Void generation evaluation] For each example and comparative example, the test connection structure was observed using an optical microscope (named "VHX-8000," manufactured by Keyence Corporation) to check for void formation at three locations (specifically, observation ranges (1) to (3) shown in Figure 6) from the alkali-free glass side. Observations were performed at a magnification of 500x, with each measurement range covering an area of ​​630 μm × 500 μm in plan view. The formation of voids was then evaluated based on the following criteria. The results are shown in Table 2.

[0180] {Evaluation Criteria for Void Generation} A: The area of ​​the region containing air bubbles (voids) was less than 20% of the observation area. B: The area of ​​the region containing air bubbles (voids) was 20% or more of the observation area.

[0181] [Observation of the solder accumulation state] For each example and comparative example, the solder accumulation state at electrodes aligned in the plane direction of the Au electrode-equipped dummy wafer at three locations (specifically, observation ranges (1) to (3) shown in Figure 6) was observed from the alkali-free glass side using an optical microscope (named "VHX-8000," manufactured by Keyence Corporation). The observation was performed at a magnification of 500x, with each observation range covering an area of ​​630 μm × 500 μm in plan view. The solder accumulation state was then evaluated based on the following criteria. The results are shown in Table 2.

[0182] {Evaluation criteria for solder integration} A: In the observation area, the percentage of electrodes where 50% or more of the surface area is covered with solder is 90% or more. B: Among the multiple electrodes present in the observation area, the percentage of electrodes where 50% or more of the surface area is covered with solder is between 70% and 90%. C: Among the multiple electrodes present in the observation area, the percentage of electrodes whose surface area is covered with solder at a rate of 50% or more is between 50% and 70%. D: Among the multiple electrodes present in the observation area, the percentage of electrodes where 50% or more of the surface area is covered with solder is less than 50%.

[0183] [Evaluation of bridge occurrence] For each example and comparative example, the test connection structure was observed using optical microscopy (VHX-8000, KEYENCE) to check for the presence or absence of bridge formation between electrodes aligned in the plane direction of the Au electrode-equipped dummy wafer at three locations (specifically, observation ranges (1) to (3) shown in Figure 6) from the alkali-free glass side. The observation was performed at a magnification of 500x, with each observation range covering an area of ​​630 μm × 500 μm in plan view. The presence or absence of bridge formation was then evaluated based on the following criteria. The results are shown in Table 2.

[0184] {Evaluation Criteria for Bridge Occurrence} A: No bridges were observed within the observed area. B: A bridge was observed within the observation area.

[0185] [Table 2] [Explanation of Symbols]

[0186] 1. Anisotropic conductive sheet 2. First substrate 3 Adhesive layer 4. Second circuit board 5. Flake-shaped solder particles 6 Laminate 10. Release Liner 12 1st electrode 14 2nd electrode 15 Columnar solder section 20 Connection Structures 25 Pressure Oven

Claims

1. It contains solder particles having a flake shape and a resin component, An anisotropic conductive composition wherein the average aspect ratio of the solder particles is 2 or more.

2. The anisotropic conductive composition according to claim 1, wherein the content ratio of the solder particles is more than 50 parts by mass and 250 parts by mass or less, based on 100 parts by mass of the resin component.

3. An anisotropic conductive composition according to claim 1, comprising flux.

4. An anisotropic conductive sheet comprising the anisotropic conductive composition according to any one of claims 1 to 3.

5. The anisotropic conductive sheet according to claim 4, wherein the ratio of the average side length s of the solder particles to the thickness T of the anisotropic conductive sheet (s / T ratio) is 0.7 or more.

6. The anisotropic conductive sheet according to claim 5, wherein the thickness T is 10 μm or less.

7. The anisotropic conductive sheet according to claim 4, wherein the initial tack force at 25°C is 100 gf or more.

8. The device comprises a first substrate, a second substrate spaced apart in the thickness direction, and an adhesive layer interposed between the first and second substrates. Each of the first and second substrates is provided with at least one electrode, A columnar solder portion is arranged between the electrode of the first substrate and the electrode of the second substrate. A connecting structure wherein the adhesive layer and the columnar solder portion are formed from the anisotropic conductive sheet described in claim 4.

9. The first step involves preparing multiple substrates, each having multiple electrodes arranged in the planar direction. A second step of preparing the anisotropic conductive sheet described in claim 4, A third step involves stacking the two substrates with the anisotropic conductive sheet in between so that the electrodes of the two substrates face each other, thereby manufacturing a laminate. A method for manufacturing a connection structure, comprising: a fourth step of heating the laminate and melting the solder particles to form columnar solder portions so as to electrically connect the electrodes of the two substrates, and curing the resin component.

10. The method for manufacturing a connecting structure according to claim 9, wherein the fourth step is carried out in a pressure oven.

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