Conductive resin composition, conductive resin sheet, connection structure, and method for manufacturing connection structure

Abstract

This conductive resin composition contains solder particles, a resin, and a flux. When the melting point of the solder particles is denoted as T0°C, the conductive resin composition excluding the solder particles has a complex viscosity A0 of less than 10Pa·s at T0°C, and has a complex viscosity A1 of not less than 10Pa·s at T0+40°C.

Description

Conductive resin composition, conductive resin sheet, connection structure, and method for manufacturing the connection structure

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

[0002] Conventionally, a conductive resin sheet is used to connect the electrodes of two printed circuit boards, and the conductive resin sheet is made of a composition containing solder particles, a curable resin, and a flux.

[0003] The conductive resin sheet is first placed between two printed circuit boards. The conductive resin sheet is then heated. This softens the curable resin, and the melted solder particles gather and agglomerate between the electrodes (self-agglomeration). The curable resin then hardens around the solder. The agglomerated solder solidifies as the temperature is lowered, forming a solder part. The curable resin forms a cured resin part around the solder part.

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

[0005] International Publication No. 2023 / 145487

[0006] However, conventional conductive resin sheets, including the anisotropic conductive sheet of Patent Document 1, require strict control of the heating rate and other factors to achieve optimal adhesive strength and optimal electrical connection. If the heating rate is not properly controlled, voids and poor curing occur during resin curing, resulting in reduced adhesive strength. Furthermore, the resin hardens faster than the solder particles can fully aggregate between the electrodes, resulting in insufficient electrical connection.

[0007] The present invention provides a conductive resin composition that can more easily improve adhesion reliability and ensure reliable electrical connection, a conductive resin sheet containing the conductive resin composition, a connection structure connected using the conductive resin sheet, and a method for manufacturing the connection structure.

[0008] The present invention [1] is a conductive resin composition containing solder particles, a resin, and a flux, wherein the melting point of the solder particles is T ０ ° C., T of the conductive resin composition excluding the solder particles ０ Complex viscosity A in °C ０ is less than 10 Pa s, and T ０ Complex viscosity A at +40°C １ is 10 Pa·s or more.

[0009] The present invention [2] is a method for manufacturing a solder paste having a melting point T ０ The conductive resin composition according to the above [1], wherein the temperature is 150°C or higher.

[0010] The present invention [3] includes the conductive resin composition according to the above [1] or [2], in which the solder particles contain Sn.

[0011] The present invention [4] is characterized in that the maximum temperature in the temperature range in which the complex viscosity of the conductive resin composition excluding the solder particles is less than 10 Pa·s is T １ °C, minimum temperature T ２ ° C., the T １ ° C. and the T ２ The conductive resin composition according to the above item [1], wherein the temperature difference between the temperature of the conductive resin composition and the temperature of the insulating film is 70°C or more.

[0012] The present invention [5] is the T ０ Complex viscosity A in °C ０ The T ０ Complex viscosity A at +40°C １ The ratio (A １ / A ０ The conductive resin composition according to any one of the above [1] to [4], wherein the ratio (Ratio) is 10 or more.

[0013] The present invention [6] includes a conductive resin sheet containing the conductive resin composition according to any one of the above [1] to [5].

[0014] The present invention [7] includes a connection structure comprising a first substrate, a second substrate arranged at an interval in the thickness direction, and an adhesive layer interposed between the first substrate and the second substrate, wherein each of the first substrate and the second substrate has at least one electrode, a columnar solder portion is arranged between the electrode of the first substrate and the electrode of the second substrate, and the adhesive layer and the columnar solder portion are formed from the conductive resin composition described in any one of [1] to [5] above.

[0015] The present invention [8] includes a method for manufacturing a connection structure, comprising: a first step of preparing a plurality of substrates each having a plurality of electrodes arranged in a planar direction; a second step of preparing a conductive resin sheet by applying the conductive resin composition described in any one of [1] to [5] above; a third step of stacking the two substrates with the conductive resin sheet sandwiched therebetween so that the electrodes of the two substrates face each other, thereby manufacturing a laminate; and 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.

[0016] The present invention [9] includes the method for manufacturing a connection structure according to the above [8], in which the fourth step is carried out in a pressure oven.

[0017] The present invention includes solder particles, a resin, and a flux, and the melting point of the solder particles is T ０ ° C., T of the conductive resin composition excluding the solder particles ０ Complex viscosity A in °C ０ is less than 10 Pa s, and T ０ Complex viscosity A at +40°C １ The conductive resin composition contains a conductive resin composition having a viscosity of 10 Pa·s or more. Therefore, it is possible to more easily improve the adhesive reliability and achieve a reliable electrical connection.

[0018] FIG. 1 is a graph showing the relationship between temperature and complex viscosity of a conductive resin composition excluding solder particles. ０ , T １ , T ２ , and the complex viscosity A ０ , A １2 is a diagram for explaining the above. FIG. 2 shows one embodiment of a conductive resin sheet containing a conductive resin composition. FIG. 3 shows one embodiment of a connection structure connected by the conductive resin sheet shown in FIG. 2. FIGS. 4A to 4E show one embodiment of a method for manufacturing the connection structure shown in FIG. 3. FIG. 4A shows a first step of preparing two substrates each having a plurality of electrodes arranged in the surface direction. FIG. 4B shows a second step of preparing a conductive resin sheet by applying a conductive resin composition. FIG. 4C shows a third step of manufacturing a laminate by stacking a first substrate and a second substrate with a conductive resin sheet sandwiched therebetween so that the electrodes of the two substrates face each other. FIG. 4D shows a fourth step of thermocompression bonding the first substrate and the second substrate to the conductive resin sheet. FIG. 4E shows a fourth step of forming an adhesive layer that solder-connects the first substrate and the second substrate to the conductive resin sheet. FIG. 5 is a graph showing the results of measuring the relationship between temperature and complex viscosity in a conductive resin composition excluding solder particles for each example containing 3,3-dimethylglutaric acid (Example 1-1), glutaric acid (Example 2-1), and malic acid (Comparative Example 1-1) as a flux.

[0019] 1. Conductive Resin Composition The conductive resin composition contains solder particles, a resin component, and a flux. The conductive resin composition has a melting point of the solder particles that is higher than T ０ ° C., the T of the conductive resin composition excluding the solder particles (hereinafter also referred to as the "solder-excluded composition") ０ Complex viscosity A in °C ０ is less than 10 Pa s, and T ０ Complex viscosity A at +40°C １ is 10 Pa·s or more.

[0020] <Solder Particles> From the viewpoint of environmental friendliness, a solder material that does not contain lead (lead-free solder material) is preferably used as the solder material that forms the solder particles. From the viewpoint of further promoting the resin curing action by metal catalytic action, the solder material preferably contains tin (Sn). Examples of solder materials that contain tin include tin and tin alloys. Examples of tin alloys include tin-bismuth alloys (Sn—Bi), tin-silver-copper alloys (Sn—Ag—Cu), and tin-silver alloys (Sn—Ag). Examples of solder materials that are preferably used include tin-silver-copper alloys (Sn—Ag—Cu) and tin-bismuth alloys (Sn—Bi).

[0021] The tin content in the tin-silver-copper alloy is, for example, 90% by mass or more, preferably 95% by mass or more. The silver content in the tin-silver-copper alloy is, for example, 10% by mass or less, preferably 5% by mass or less. The copper content in the tin-silver-copper alloy is, for example, 1% by mass or less, preferably 0.5% by mass or less.

[0022] The tin content in the tin-bismuth alloy is, for example, 80 mass % or less, or preferably 50 mass % or less, and the bismuth content in the tin-bismuth alloy is, for example, 20 mass % or more, or preferably 50 mass % or more.

[0023] The melting point of the solder material (i.e., the melting point of the solder particles) is higher than the softening point of the solid resin described below, and is, 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, it is 280°C or lower, preferably 260°C or lower, and more preferably 240°C or lower. The melting point can be determined by differential scanning calorimetry (DSC) (the same applies hereinafter).

[0024] The shape of the solder particles is not particularly limited, and examples thereof include a spherical shape, a plate shape, and a needle shape. A preferred shape of the solder particles is a spherical shape.

[0025] From the viewpoint of miniaturizing and reducing the height of the connection structure, the average primary particle diameter of the solder particles is, for example, 20 μm or less, preferably 10 μm or less. Also, for example, 0.1 μm or more, preferably 0.5 μm or more. The average primary particle diameter can be measured using a laser diffraction particle size distribution analyzer.

[0026] The solder particles can be used alone or in combination of two or more kinds.

[0027] The solder particles may be either acid-treated or untreated.

[0028] [Acid-Treated Solder Particles] The acid-treated solder particles are obtained by treating solder particles with an acid treating agent. The acid treating agent is a component for removing an oxide film on the surface of the solder particles.

[0029] The acid treating agent has a carboxyl group. Examples of such an acid treating agent include a carboxylic acid treating agent. Examples of the carboxylic acid treating agent include a monocarboxylic acid treating agent, a dicarboxylic acid treating agent, and a trifunctional or higher functional carboxylic acid treating agent.

[0030] The acid treating agent is preferably a dicarboxylic acid treating agent, more preferably an aliphatic dicarboxylic acid treating agent, and even more preferably malic acid.

[0031] The acid treating agents can be used alone or in combination of two or more kinds.

[0032] <Resin Component> The resin component is not particularly limited, but preferably contains a solid resin and a liquid resin. When the resin component contains a solid resin and a liquid resin, the conductive resin sheet has excellent formability and adhesive strength.

[0033] A solid resin does not flow and has no viscosity at 25° C. A liquid resin includes liquids and fluids at 25° C. and has viscosity.

[0034] The solid resin includes thermosetting resins and thermoplastic resins. The solid resin may include either or both of thermosetting resins and thermoplastic resins, but preferably includes only thermosetting resins.

[0035] The liquid resin includes thermosetting resins and thermoplastic resins. The liquid resin may include either or both of thermosetting resins and thermoplastic resins, but preferably includes only thermosetting resins.

[0036] The resin component more preferably comprises a solid thermosetting resin and a liquid thermosetting resin.

[0037] The mass ratio of the solid resin to the 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.

[0038] Alternatively, the resin component may be blended with a known solvent to prepare a varnish containing the resin component. The solid content of the varnish containing the resin component is, for example, 30% to 80% by mass, preferably 40% to 70% by mass.

[0039] The content of the resin component relative to the conductive resin composition is, for example, 20% by mass to 60% by mass, preferably 30% by mass to 50% by mass, and more preferably 33% by mass to 45% by mass.

[0040] The softening point of the solid resin is lower than the melting point of the solder particles. More specifically, in order to soften the solid resin without melting the solder particles in the thermocompression bonding in the sixth step described later, the softening point of the solid resin is lower than the melting point of the solder particles. The softening point of the solid resin is, for example, 40°C or higher, preferably 60°C or higher, and more preferably 80°C or higher, and is, 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.

[0041] The softening point can be measured using a thermomechanical analyzer.

[0042] [Thermosetting Resin] Examples of the thermosetting resin include thermosetting epoxy resin, urea resin, melamine resin, diallyl phthalate resin, silicone resin, phenolic resin, thermosetting acrylic resin, thermosetting polyester, thermosetting polyimide, and thermosetting polyurethane. As the thermosetting resin, preferably, thermosetting epoxy resin is used.

[0043] Examples of thermosetting epoxy resins include thermosetting bisphenol-type epoxy resins (e.g., thermosetting bisphenol A-type epoxy resins, thermosetting bisphenol F-type epoxy resins, and thermosetting bisphenol S-type epoxy resins), thermosetting novolac-type epoxy resins (e.g., thermosetting phenol novolac-type epoxy resins, thermosetting cresol novolac-type epoxy resins, and thermosetting biphenyl-type epoxy resins), thermosetting naphthalene-type epoxy resins, thermosetting fluorene-type epoxy resins (e.g., thermosetting bisarylfluorene-type epoxy resins), and thermosetting triphenylmethane-type epoxy resins (e.g., thermosetting trishydroxyphenylmethane-type epoxy resins). A preferred example of the thermosetting epoxy resin is a thermosetting bisphenol-type epoxy resin. A more preferred example of the thermosetting epoxy resin is a thermosetting bisphenol A-type epoxy resin. The epoxy equivalent of the thermosetting epoxy resin, when it is a liquid resin, is preferably 150 to 240, more preferably 170 to 220. The epoxy equivalent of the thermosetting epoxy resin is preferably 800 to 3,000, more preferably 1,400 to 2,000, in the case of a solid resin.

[0044] These thermosetting resins may be either solid or liquid at room temperature (25° C.).

[0045] The curing temperature of the thermosetting resin is equal to or higher than the melting point of the solder particles, for example, 150°C to 280°C, preferably 160°C to 260°C, and more preferably 170°C to 250°C.

[0046] The thermosetting resins can be used alone or in combination of two or more kinds.

[0047] 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, and even more preferably 90% by mass or more, per 100 parts by mass of the resin component, and is, for example, 100 parts by mass or less.

[0048] [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 (registered trademark)), polycarbonate, polyacetal, polyethylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether sulfone, polyether ether ketone, polyallylsulfone, thermoplastic polyimide, thermoplastic polyurethane, polyaminobismaleimide, polyamideimide, polyetherimide, bismaleimide triazine resin, 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.

[0049] The thermoplastic resins can be used alone or in combination of two or more kinds.

[0050] The content of the thermoplastic resin is, for example, 0 parts by mass or more and, for example, 50 parts by mass or less, and preferably 20 parts by mass or less, per 100 parts by mass of the resin component.

[0051] <Flux> The flux has the effect of removing oxide films on the surfaces of the solder particles and the electrodes (specifically, the first electrode and the second electrode described below). In addition, by selecting the type of flux, the relationship between temperature and complex viscosity can be adjusted.

[0052] The flux is not particularly limited as long as the solder-exclusion composition containing the flux satisfies the requirements of the present invention in terms of the relationship between temperature and complex viscosity. 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 monocarboxylic acid compounds, dicarboxylic acid compounds, and more preferably dicarboxylic acid compounds.

[0053] The monocarboxylic acid compound includes an aliphatic monocarboxylic acid and an aromatic monocarboxylic acid, and the aromatic monocarboxylic acid is preferably 2-phenoxybenzoic acid.

[0054] The dicarboxylic acid compound includes aliphatic dicarboxylic acids and aromatic dicarboxylic acids. The aliphatic dicarboxylic acids include linear saturated dicarboxylic acids, branched saturated dicarboxylic acids, linear unsaturated dicarboxylic acids, and branched unsaturated dicarboxylic acids.

[0055] Examples of the straight-chain saturated dicarboxylic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

[0056] Examples of branched saturated dicarboxylic acids include 3,3-dimethylglutaric acid.

[0057] Examples of the straight-chain unsaturated dicarboxylic acid include fumaric acid.

[0058] Among these, from the viewpoint of improving connection reliability and achieving reliable electrical connection, aliphatic dicarboxylic acids are preferred, linear saturated dicarboxylic acids and branched saturated dicarboxylic acids are more preferred, glutaric acid, adipic acid, pimelic acid and 3,3-dimethylglutaric acid are even more preferred, glutaric acid and 3,3-dimethylglutaric acid are particularly preferred, and 3,3-dimethylglutaric acid is most preferred.

[0059] Furthermore, a salt of the above dicarboxylic acid compound can also be used as the flux.

[0060] The fluxes can be used alone or in combination of two or more kinds.

[0061] Alternatively, the flux may be mixed with a known solvent (e.g., ethanol) to prepare a solution of the flux. The solid content of the flux solution is, for example, 10% by mass to 50% by mass, preferably 20% by mass to 40% by mass.

[0062] The content of the flux 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 the resin component. Furthermore, the content of the flux is, 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 the resin component. By keeping the content of the flux within the above range, it is possible to more easily improve connection reliability and ensure reliable electrical connection.

[0063] The content of the flux is, for example, 1 part by mass or more, or preferably 5 parts by mass or more, per 100 parts by mass of the solder particles, from the viewpoint of further removing the oxide film on the surface of the solder particles.

[0064] The content of the flux relative to the conductive resin composition is, for example, 1 to 10 mass %, or preferably 3 to 7 mass %.

[0065] <Curing Agent> The conductive resin composition may further contain a curing agent. Preferably, the conductive resin composition does not contain a curing agent, or if it contains a curing agent, the content of the curing agent is, for example, less than 20 parts by mass, more preferably less than 10 parts by mass, and even more preferably less than 5 parts by mass, per 100 parts by mass of the resin component. From the viewpoint of achieving a moderate curing rate of the resin component appropriate for the conductive resin composition, the content of the curing agent in the conductive resin composition is preferably less than 3 parts by mass, more preferably less than 1 part by mass, per 100 parts by mass of the resin component. More preferably, the conductive resin composition does not contain a curing agent. In this case, the conductive resin composition consists of solder particles, a resin component, and a flux.

[0066] Examples of the curing agent include an acid anhydride curing agent, an amine curing agent, a phenol curing agent, a cationic initiator, an imidazole catalyst, and DICY (dicyandiamide).

[0067] <Other Additives> The conductive resin composition may contain other additives in an appropriate ratio, if necessary. For example, a curing aid may be used.

[0068] <Relationship between temperature and complex viscosity in a conductive resin composition excluding solder particles> The conductive resin composition exhibits the following characteristics in terms of the relationship between temperature and complex viscosity in a conductive resin composition excluding solder particles. FIG. 1 is a graph showing the change in complex viscosity with respect to the temperature change of the composition excluding solder (temperature-complex viscosity profile). In FIG. 1, T ０ indicates the melting point of the solder particles. ０ °C is, for example, 220 °C. １ ° C. is the maximum temperature in the temperature range where the complex viscosity of the solder-excluded composition is less than 10 Pa s. ２ °C indicates the lowest temperature in the temperature range. ０ Is T ０ 1 shows the complex viscosity of the solder removal composition in ° C. １ is T ０ 1 shows the complex viscosity of the solder exclusion composition at +40° C.

[0069] In the conductive resin composition, the solder-excluded composition, T ０ Complex viscosity A in °C ０ That is, at the melting point of the solder, the non-solder composition has a relatively low viscosity, and the molten solder flows relatively easily in the resin component. ０ Complex viscosity A at +40°C １ is 10 Pa s or more. In other words, when the temperature is 40°C higher than the melting point of the solder, the resin begins to harden and the viscosity of the resin component increases. This makes it easier to improve the adhesive reliability and ensure reliable electrical connection in the conductive resin composition.

[0070] The maximum temperature in the temperature range where the complex viscosity of the solder-exclusion composition is less than 10 Pa·s is defined as T １ °C, minimum temperature T２ °C, T １ °C and T ２ The temperature difference in °C is 70 °C or more, preferably 100 °C or more, and more preferably 130 °C or more. ０ Not only ℃, but also T ０ ℃, T １ °C to T ２ This indicates that the complex viscosity is maintained at a low level of less than 10 Pa s in the temperature range of 70°C or higher, making it easier for the molten solder to flow through the resin component. This makes it easier to improve the adhesive reliability and ensure a reliable electrical connection.

[0071] In addition, the conductive resin composition excluding the solder particles, ０ Complex viscosity A in °C ０ T for ０ Complex viscosity A at +40°C １ The ratio (A １ / A ０ The upper limit of the ratio is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more. The lower limit is preferably 700 or less, more preferably 300 or less, and even more preferably 100 or less. １ / A ０ By setting the ratio within the above range, the temperature-complex viscosity profile of the solder-excluded composition is further optimized, the molten solder flows more easily in the resin component, the columnar solder portion is reliably formed, and the resin component is then reliably cured. This makes it easier to improve the adhesive reliability and ensure reliable electrical connection in the conductive resin composition.

[0072] The complex viscosity of the solder-excluded composition can be measured using a rheometer (manufactured by Anton Paar under the following measurement conditions: atmospheric air, measurement frequency 1 Hz, temperature condition 25 to 300°C, temperature rise rate 10°C / min, and 8 mmφ parallel plates as a measurement jig.

[0073] 2. Method for producing conductive resin composition The conductive resin composition is produced by mixing solder particles, a resin component, a flux, and, if necessary, a curing agent. Specifically, the solder particles, the resin component, the flux, and, if necessary, a curing agent and additives are mixed and stirred as necessary. This produces the conductive resin composition.

[0074] Alternatively, the conductive resin composition may be blended with a known solvent to prepare a varnish of the conductive resin composition. The solid content of the varnish of the conductive resin composition is, for example, 50% by mass to 80% by mass, preferably 60% by mass to 75% by mass.

[0075] Next, the conductive resin sheet obtained using this conductive resin composition will be described in detail.

[0076] 3. Conductive Resin Sheet The conductive resin sheet is formed into a sheet shape from a conductive resin composition. That is, the conductive resin sheet contains a conductive resin composition.

[0077] 2, the conductive resin sheet 1 is disposed on one surface in the thickness direction of the release liner 10. In the conductive resin sheet 1, solder particles 5 are dispersed in the resin component.

[0078] From the viewpoint of making the connection structure smaller and thinner, the thickness of the conductive resin sheet 1 is, for example, 50 μm or less, preferably 25 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less, and for example, 1 μm or more.

[0079] The conductive resin sheet 1 is produced by applying a conductive resin composition (a varnish of the conductive resin composition) to one surface in the thickness direction of the release liner 10, and then drying it as necessary. As drying conditions, the drying temperature is, for example, 40° C. or higher to 100° C. The drying time is, for example, 1 minute to 60 minutes.

[0080] As described above, the release liner 10 is a support for supporting the conductive resin sheet 1. The release liner 10 is, for example, a plastic substrate (plastic film) in the form of a film. The thickness of the release liner 10 is, for example, 1 μm to 100 μm.

[0081] 2, a connection structure 20 is manufactured by connecting two substrates (first substrate 2, second substrate 4), each having an electrode, using the above-described conductive resin sheet 1. When the conductive resin sheet 1 is cured, it forms a columnar solder portion 15 and an adhesive layer 3. In the connection structure 20, the columnar solder portion 15 is disposed between the electrodes 12, 14 of the two substrates 2, 4, and the two substrates 2, 4 are electrically connected. An adhesive layer 3 is disposed between the two substrates 2, 4 and around the columnar solder portion 15. The adhesive layer 3 includes a cured resin 16.

[0082] Specifically, connection structure 20 includes a first substrate 2, a second substrate 4 arranged at an interval in the thickness direction, and an adhesive layer 3 interposed between first substrate 2 and second substrate 4. In other words, connection structure 20 includes, in order toward one side in the thickness direction, first substrate 2, adhesive layer 3, and second substrate 4. More specifically, connection structure 20 includes first substrate 2, adhesive layer 3 arranged directly on the upper surface (one surface in the thickness direction) of first substrate 2, and second substrate 4 arranged directly on the upper surface (one surface in the thickness direction) of adhesive layer 3.

[0083] The adhesive layer 3 bonds the first substrate 2 and the second substrate 4. Specifically, the adhesive layer 3 bonds to the surface of the first substrate 2 excluding the first electrode 12. The adhesive layer 3 also bonds to the surface of the second substrate 4 excluding the second electrode 14.

[0084] The columnar solder portion 15 electrically connects the first electrode 12 and the second electrode 14 that face each other in the thickness direction. The columnar solder portion 15 has a columnar shape (specifically, a cylindrical shape) and is disposed between and in contact with the first electrode 12 and the second electrode 14. The columnar solder portion 15 exhibits anisotropy that exists only between the first electrode 12 and the second electrode 14.

[0085] 5. Method for Manufacturing a Connection Structure One embodiment of a method for manufacturing a connection structure will now be described in detail with reference to FIGS. 4A to 4E.

[0086] The method for manufacturing the connection structure includes a first step of preparing a plurality of substrates each having a plurality of electrodes arranged in the surface direction; a second step of applying a conductive resin composition to prepare a conductive resin sheet 1; a third step of stacking the two substrates 2, 4 with the conductive resin sheet 1 sandwiched between them so that the electrodes of the two substrates 2, 4 face each other, thereby producing a laminate 6; and a fourth step of heating the laminate 6 and melting the solder particles 5 to form columnar solder portions 15 so as to electrically connect the electrodes of the two substrates 2, 4, and hardening the resin component.

[0087] [Step 1] In step 1, a plurality of substrates each having a plurality of electrodes aligned in the surface direction are prepared. This method will be described in detail with respect to the case where two substrates each having a plurality of electrodes aligned in the surface direction are prepared. Specifically, as shown in FIG. 4A, a first substrate 2 and a second substrate 4 are prepared.

[0088] The first substrate 2 has a flat plate shape.

[0089] The first substrate 2 includes a first wired circuit board 11 and a plurality of first electrodes 12 arranged in the surface direction of the first wired circuit board 11. In other words, the first substrate 2 includes the first wired circuit board 11 and a plurality of first electrodes 12 provided on the surface (one surface in the thickness direction) of the first wired circuit board 11.

[0090] The first wired circuit board 11 is made of, for example, an insulating material and a semiconductor material.

[0091] The thickness of the first wired circuit board 11 is, for example, 5 μm to 1000 μm.

[0092] The first electrode 12 is made of a metal.

[0093] The first electrodes 12 are arranged on the first substrate 2 in, for example, a dot pattern.

[0094] More specifically, the first electrodes 12 have a circular shape in a plan view, and the first electrodes 12 are aligned and disposed evenly in the surface direction.

[0095] The thickness of the first electrode 12 is, for example, 0 μm to 20 μm, or preferably 0.001 μm to 5 μm. When the surface of the first substrate 2 and the surface of the first electrode 12 are flush with each other, the thickness of the first electrode 12 is 0 μm.

[0096] 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.

[0097] The distance (pitch) between adjacent first electrodes 12 in the surface direction 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.

[0098] The second substrate 4 has a flat plate shape.

[0099] The second substrate 4 includes a second wired circuit board 13 and a plurality of second electrodes 14 arranged in the surface direction of the second wired circuit board 13. In other words, the second substrate 4 includes the second wired circuit board 13 and a plurality of second electrodes 14 provided on the surface (the other surface in the thickness direction) of the second wired circuit board 13.

[0100] The second wired circuit board 13 is made of, for example, an insulating material or a semiconductor material.

[0101] The thickness of the second wired circuit board 13 is, for example, 5 μm to 1000 μm.

[0102] The second electrode 14 is made of a metal.

[0103] The second electrodes 14 are arranged on the second substrate 4 in, for example, a dot pattern.

[0104] More specifically, the second electrodes 14 have a circular shape in a plan view, and the second electrodes 14 are aligned and disposed evenly in the surface direction.

[0105] The thickness of the second electrode 14 is, for example, 0 μm to 20 μm, or preferably 0.001 μm to 5 μm. When the surface of the second substrate 4 and the surface of the second electrode 14 are flush with each other, the thickness of the second electrode 14 is 0 μm.

[0106] 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.

[0107] Furthermore, the distance (pitch) between adjacent second electrodes 14 in the surface direction is the same as the distance (pitch) between adjacent first electrodes 12 in the surface direction described above.

[0108] [Second Step] In the second step, the conductive resin sheet 1 is prepared as shown in Fig. 4B. Specifically, the conductive resin sheet 1 is prepared in accordance with the above-described method for manufacturing a conductive resin sheet.

[0109] [Step 3] In step 3, as shown in FIG. 4C , the first substrate 2 and the second substrate 4 are laminated with the conductive resin sheet 1 sandwiched therebetween 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 producing a laminate 6.

[0110] Specifically, first, the first substrate 2 and the second substrate 4 are brought close to the conductive resin sheet 1, and the first substrate 2 and the second substrate 4 are brought into contact with the conductive resin sheet 1. More specifically, one thickness-wise surface of the first substrate 2 is brought into contact with the other thickness-wise surface of the conductive resin sheet 1, and the other thickness-wise surface of the second substrate 4 is brought into contact with one thickness-wise surface of the conductive resin sheet 1, so that the first electrode 12 and the second electrode 14 face each other in the thickness direction.

[0111] In this way, the laminate 6 is manufactured.

[0112] [Fourth Step] In the fourth step, first, as shown in FIG. 4D, the first substrate 2 and the second substrate 4 are thermocompression-bonded to the conductive resin sheet 1.

[0113] Specifically, while the laminate 6 is being heated, the first substrate 2 and the second substrate 4 are pressed (thermocompression bonded) against the conductive resin sheet 1 .

[0114] The temperature of the thermocompression bonding is equal to or higher than the softening point of the solid resin and lower than the melting point of the solder particles 5. That is, in this step, the solid resin is softened without melting the solder particles 5. Specifically, the temperature of the thermocompression bonding is, for example, 180°C or lower, preferably 100°C or lower, more preferably 80°C or lower, and, for example, 40°C or higher. The pressure of the thermocompression bonding is, for example, 0.001 MPa to 10 MPa, preferably 0.005 MPa to 5 MPa, more preferably 0.01 MPa to 1 MPa. In the thermocompression bonding, for example, as shown in FIG. 1, the conductive resin composition is ２ ℃ or more T ０ The complex viscosity values ​​are shown below °C.

[0115] This softens the resin component, and the first electrode 12 of the first substrate 2 becomes embedded in the conductive resin sheet 1, and one surface in the thickness direction of the first substrate 2 comes into contact with the conductive resin sheet 1. Also, the second electrode 14 of the second substrate 4 becomes embedded in the conductive resin sheet 1, and the other surface in the thickness direction of the second substrate 4 comes into contact with the conductive resin sheet 1.

[0116] 4E, the laminate 6 is heated. Preferably, the laminate 6 is heated in a pressure oven 25. The pressure oven 25 is an apparatus capable of applying pressure while heating in an enclosed space, and examples thereof include an automatic heating and pressure treatment apparatus, a pressure oven, a voidless pressure oven, an autoclave, and a vacuum pressure reflow apparatus.

[0117] When the laminate 6 is heated, volatile substances may volatilize due to the heating. Such volatile substances may impair electrical connections in the laminate 6. On the other hand, when the laminate 6 is heated using the pressure oven 25, the generation of the volatile substances can be suppressed by applying pressure. As a result, the above-mentioned impediment can be suppressed.

[0118] The heating temperature is equal to or higher than the melting point of the 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, and even more preferably 200°C or higher, and for example, 300°C or lower, preferably 280°C or lower, and more preferably 270°C or lower.

[0119] Such heating melts the solder particles 5. The melted solder particles 5 gather (self-aggregate) between the first electrode 12 and the second electrode 14, which are opposed in the thickness direction, and form columnar solder portions 15 so as to electrically connect the first electrode 12 and the second electrode 14. Meanwhile, the resin component in the conductive resin sheet 1 is expelled by the self-aggregating solder particles 5 and moves to the periphery of the columnar solder portions 15. The thermosetting resin in the resin component then thermally hardens to become the cured resin 16 that bonds the first substrate 2 and the second substrate 4. For example, as shown in FIG. 1 , the conductive resin composition is heated to To°C or higher during heating, causing the solder particles 5 to melt. At this time, the complex viscosity of the conductive resin composition is 10 Pa·s or less, so the molten solder easily self-aggregates and reliably forms columnar solder portions 15. Thereafter, T ０ At +40° C., the complex viscosity of the resin component exceeds 10 Pa·s, so the molten solder does not move any further and remains in the columnar solder portion 15 .

[0120] As a result, the columnar solder portions 15 and the adhesive layer 3 containing the cured resin 16 are formed from the conductive resin sheet 1 between the two base materials (the first substrate 2 and the second substrate 4).

[0121] From the viewpoint of making the connection structure 20 small and low-profile, 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.

[0122] In this manner, the connection structure 20 is manufactured.

[0123] <Effects> The conductive resin composition contains solder particles, resin, and flux. When the melting point of the solder particles is T0°C, the T ０ Complex viscosity A in °C ０ is less than 10 Pa s, and T ０ Complex viscosity A at +40°C １ Therefore, it is possible to more easily improve the adhesive reliability and achieve a reliable electrical connection.

[0124] In detail, the melting point T ０and T which is near the reflow temperature. ０ Complex viscosity A of the solder-exclusion composition at +40°C ０ , A １ When the temperature and the complex viscosity of the conductive resin composition satisfy the above-defined relationship, the temperature-complex viscosity profile of the conductive resin composition can be optimized.

[0125] As explained in the above-mentioned method for manufacturing a connection structure, when using a conductive resin sheet containing a conductive resin composition, in order to accumulate solder particles between electrodes of a substrate and form a columnar solder part, the molten solder particles must be able to move through the resin component. To achieve this, the resin component must maintain an appropriate complex viscosity for an appropriate period of time. In other words, the relationship between temperature and complex viscosity must be appropriate. If the resin component hardens before the columnar solder part is formed, the electrical connection will be insufficient.

[0126] Furthermore, if the relationship between temperature and complex viscosity is not appropriate and the curing speed is not appropriate, voids will occur and curing will be insufficient, resulting in a decrease in adhesive reliability.

[0127] On the other hand, the relationship between temperature and complex viscosity of the conductive resin composition is optimized, which makes it easier to improve connection reliability and ensure reliable electrical connection.

[0128] The conductive resin sheet contains a conductive resin composition, which makes it easier to improve adhesion reliability and ensure reliable electrical connection.

[0129] The connection structure contains a conductive resin composition, which makes it easier to improve adhesion reliability and ensure reliable electrical connection.

[0130] The method for manufacturing the connection structure uses a conductive resin composition, which makes it easier to improve adhesion reliability and ensure reliable electrical connection.

[0131] <Modifications> In the modification examples, the same components and steps as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, the modification examples can achieve the same effects as those in the first embodiment unless otherwise specified. Furthermore, the first embodiment and the modification examples can be combined as appropriate.

[0132] Furthermore, in the above description, the first electrodes 12 and the second electrodes 14 are arranged in a dot pattern, but the arrangement of the first electrodes 12 and the second electrodes 14 is not limited to this.

[0133] Furthermore, in the above description, the first electrode 12 and the second electrode 14 have a circular shape when viewed from above, but the shapes of the first electrode 12 and the second electrode 14 are not limited to this and may be, for example, a square shape when viewed from above.

[0134] In the above description, the second substrate 4 may be, for example, a chip component (for example, a mini / micro LED).

[0135] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Note that "parts" and "%" are by mass unless otherwise specified. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be substituted with the corresponding upper limit values ​​(numeric values ​​defined as "equal to or less than") or lower limit values ​​(numeric values ​​defined as "equal to or more than" or "exceeding") of the blending ratios (content ratios), physical property values, parameters, etc. described in the above "Modes for Carrying Out the Invention."

[0136] 1. Test 1 Evaluation of solder accumulation state and resin viscosity <Details of components> The trade names (names) and abbreviations of the components used in each example and comparative example are described in detail below. Solder particles (name "ST-3"): Sn 96.5% by mass, Ag 3.0% by mass, Cu 0.5% by mass, melting point 217-219°C, spherical shape, average primary particle diameter 3 μm, manufactured by Mitsui Mining & Smelting Co., Ltd. Solder particles (name "ST-7"): Sn 96.5% by mass, Ag 3.0% by mass, Cu 0.5% by mass, melting point 217-219°C, spherical shape, average primary particle diameter 7 μm, manufactured by Mitsui Mining & Smelting Co., Ltd. Solder particles (name "Sn42Bi58 ST-7"): Sn 42% by mass, Bi 58% by mass, melting point 139°C, spherical shape, average primary particle diameter 7 μm, manufactured by Mitsui Mining & Smelting Co., Ltd. 3,3-Dimethylglutaric acid: manufactured by Merck KCaA Glutaric acid: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Adipic acid: manufactured by Tokyo Chemical Industry Co., Ltd. Pimelic acid: manufactured by Tokyo Chemical Industry Co., Ltd. 2-Phenoxybenzoic acid: manufactured by Merck KCaA. Malic acid (name "DL-malic acid"): manufactured by Tokyo Chemical Industry Co., Ltd. Dodecanedioic acid: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Liquid epoxy resin (name "jER828"): bisphenol A type epoxy resin, epoxy equivalent 184 to 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 to 1600 g / eq, solid at 25°C, thermosetting resin, softening point 120 to 130°C, manufactured by Nanya Plastics Co., Ltd. Solid phenolic resin (name "MEH-7851-H"): phenol novolac resin, thermosetting resin, softening point 64 to 85°C, manufactured by UBE Co., Ltd. Curing agent (product name: "Sanaid SI-B3"): thermal cationic polymerization initiator, manufactured by Sanshin Chemical Industry Co., Ltd. Curing agent (product name: "Sanaid SI-B4"): thermal cationic polymerization initiator, manufactured by Sanshin Chemical Industry Co., Ltd. Curing agent (FX-TP-BC-PC-AD-57130): thermal cationic polymerization initiator, manufactured by Nippon Shokubai Co., Ltd.

[0137] <Production of Acid-Treated Solder Particles> Acid-treated solder particles (ST-3 or ST-7) were produced by the following procedure.

[0138] Malic acid as an acid treatment agent was dissolved in distilled water to a concentration of 1 mol / L, and dissolved gas was replaced with nitrogen by bubbling with nitrogen, thereby preparing an aqueous solution of the acid treatment agent.

[0139] Next, 50 g of an aqueous solution of the acid treatment agent was added to 50 g of solder particles (ST-3 or ST-7) in a container, and the container was closed and stirred for 20 minutes. After that, the solder particles were allowed to settle naturally, the supernatant was removed, ethanol was added, and the mixture was stirred until it became homogeneous. The same procedure was then repeated once more.

[0140] Next, after waiting for the solder particles to settle naturally, the supernatant was removed, acetone was added, and the mixture was stirred until uniform. Next, after waiting for the solder particles to settle naturally, the supernatant was removed, jER828 was added according to the formulations shown in Tables 1 to 4, and the mixture was stirred until uniform.

[0141] Next, the mixture was vacuum dried in a vacuum oven at 25° C. for 2 hours, thereby producing acid-treated solder particles.

[0142] <Production of Conductive Resin Compositions of Examples and Comparative Examples> Conductive resin compositions of Examples and Comparative Examples were produced according to the following procedure.

[0143] Solid epoxy resin (NPES907) or solid phenolic resin (MEH-7851-H) was dissolved in methyl ethyl ketone to prepare a varnish (solids concentration: 60% by mass). 3,3-dimethylglutaric acid, 2-phenoxybenzoic acid, and glutaric acid were dissolved in methyl ethyl ketone to prepare a flux solution (solids concentration: 30% by mass). Malic acid was dissolved in ethanol to prepare a flux solution (solids concentration: 30% by mass). San-Aid SI-B3 and San-Aid SI-B4 were dissolved in methyl ethyl ketone to prepare a curing agent solution (solids concentration: 10% by mass).

[0144] When acid-treated solder particles were used, the above-prepared solder particles (acid-treated), solid epoxy resin or solid phenolic resin, and flux were mixed according to the formulations shown in Tables 1 to 4. Acetone was then added and the mixture was stirred until homogeneous, thereby producing a varnish of the conductive resin composition.

[0145] When using solder particles without acid treatment, the solder particles (without acid treatment), solid epoxy resin or solid phenolic resin, jER828, and flux were mixed according to the formulations shown in Tables 1 to 4. Acetone was then added and stirred until uniform, producing a varnish of the conductive resin composition. The numerical values ​​shown for the formulation of the conductive resin composition in each example in Tables 1 to 4 are parts by mass. Note that a curing agent was further added in Examples 7 to 8 and Examples 10 to 13. In Tables 1 to 4, Examples 1-1 and 1-2 have the same formulation, but the complex viscosity was measured at different temperatures. The same applies to Examples 2-1 and 2-2, Examples 3-1 and 3-2, Examples 4-1 and 4-2, Comparative Examples 1-1 and 1-2, Comparative Examples 2-1 and 2-2, and Comparative Examples 3-1 and 3-2.

[0146] <Manufacturing of Test Connection Structure> Test connection structures containing the conductive resin compositions of each Example and Comparative Example (hereinafter abbreviated as "test connection structures of each Example and Comparative Example") were manufactured by the following procedure: [Step 1] Two substrates were prepared: a dummy wafer with Au electrodes (size 10 mm x 10 mm, electrodes φ 30 μm, distance between electrode ends 30 μm) and alkali-free glass (10 mm x 10 mm).

[0147] [Second Step] The conductive resin composition of each Example and Comparative Example was applied to a release liner using an applicator and dried for 5 minutes at 60° C. Thus, a conductive resin sheet (thickness: 5 μm) was prepared.

[0148] [Step 3] A dummy wafer with an Au electrode, a conductive resin sheet, and alkali-free glass were bonded together in this order in a vacuum at 50° C. The release liner was removed during the bonding process, thereby producing a laminate.

[0149] The obtained laminate was observed with an optical microscope (name "VHX-8000", manufactured by Keyence Corporation) to confirm that no air bubbles were trapped.

[0150] [Step 4] The laminate was placed in a vacuum pressure reflow machine (Model 1200 Table Top Furnace, manufactured by SST International), and after evacuation, the machine was pressurized with nitrogen to 4.5 atmospheres. Then, heating was performed at a heating rate of 100 ° C. / min, a maximum temperature of 260 ° C., and a holding time of 15 minutes. As described above, test connection structures were manufactured for each example and comparative example. In addition, to confirm the effect of the heating temperature on the test connection structure, test connection structures were also manufactured for Examples 1 and 2 and Comparative Example 1, heated not only at the above-mentioned 100 ° C. / min, but also at heating rates of 50 ° C. / min and 25 ° C. / min.

[0151] <Evaluation> [Evaluation of Adhesion Reliability and Solder Accumulation State] Test connection structures were manufactured as described above, and adhesion reliability was evaluated based on the void area ratio, and electrical connection was evaluated based on the solder accumulation rate of the electrodes. Specifically, an optical microscope (named "VHX-8000," manufactured by Keyence Corporation) was used to observe four different fields of view at 900x magnification. Then, based on the following criteria, the area of ​​the area containing bubbles (void area ratio) and the solder accumulation rate of the electrodes in the field of view (electrode solder accumulation rate) were evaluated. Specifically, the electrode solder accumulation rate was calculated by expressing the percentage of electrodes that passed the observation field, with electrodes that were completely covered with solder being considered pass and electrodes that were partially or completely exposed being considered fail. The results are shown in Tables 5 to 8.

[0152] {Evaluation criteria for void area ratio} Level 4: The void area ratio was less than 5%. Level 3: The void area ratio was 5% or more and less than 10%. Level 2: The void area ratio was 10% or more and less than 20%. Level 1: The void area ratio was 20% or more.

[0153] {Evaluation criteria for the solder integration rate of the electrode} Level 4: The solder integration rate of the electrode was 95% or more. Level 3: The solder integration rate of the electrode was 90% or more and less than 95%. Level 2: The solder integration rate of the electrode was 80% or more and less than 90%. Level 1: The solder integration rate of the electrode was less than 80%.

[0154] [Measurement of Complex Viscosity of Solder-Excluded Composition] Each example and comparative example containing a conductive resin composition excluding solder particles from the compositions shown in Tables 1 to 4 was manufactured, and the complex viscosity was measured. According to the formulations shown in Tables 1 to 4 excluding the solder particles, the resin components and flux were mixed. Then, acetone was added to adjust the solids concentration to 70 mass %, and the mixture was stirred until uniform, producing a varnish of the solder-excluded composition. The varnish was then applied to a release liner using an applicator and dried at 60°C for 5 minutes to produce a conductive resin sheet. The thickness after drying was 15±5 μm.

[0155] Measurements were performed using a rheometer (manufactured by Anton Paar under the following measurement conditions: air, measurement frequency 1 Hz, temperature conditions 25 to 300°C, temperature rise rate 10°C / min), and evaluation was performed for each evaluation item in the table. Parallel plates with an 8 mm diameter were used as the measurement jig. The measurement results are shown in Tables 1 to 4. Furthermore, the temperature-complex viscosity profiles of Examples 1-1, 2-1, and Comparative Example 1-1 are shown in Figure 5.

[0156]

[0157]

[0158]

[0159]

[0160]

[0161]

[0162]

[0163]

[0164] 2. Test 2 Evaluation of Electrical Connection of Test Connection Structure <Production of Test Connection Structure Containing Conductive Resin Composition> After producing a conductive resin sheet containing a conductive resin composition having the composition shown in Table 9 according to the procedure of Example 1, the test connection structure of Example 5 was produced using the same procedure except that two dummy wafers with Au electrodes were used as the two substrates in the first step. For Example 6 and Comparative Example 4, the test connection structure was produced using the same procedure except that two FPC boards (electrode φ 100 μm, electrode end distance 200 μm) were used as the two substrates in the first step. In Examples 5 and 6, the heating in the fourth step of producing the test connection structure was carried out at a heating rate of 100 ° C. / min. The numerical values ​​shown for the formulation of the conductive resin composition of each example in Table 9 are parts by mass. The dummy wafer with Au electrodes used in Example 5 is referred to as a silicon wafer substrate in Table 9.

[0165] <Evaluation> [Evaluation of Electrical Connection-1] After the test connection structure of Example 5 was embedded in resin, the laminate cross section was exposed by mechanical polishing, and the electrical connection of the counter electrodes was evaluated using an optical microscope (name "VHX-8000", manufactured by Keyence Corporation) according to the following criteria. The results are shown in Table 9. Level 2: Connection of the counter electrodes by solder was observed. Level 1: Connection of the counter electrodes by solder was not observed.

[0166] [Evaluation of Electrical Connection - 2] For the test connection structure of Example 6, the electrical resistance value between the opposing electrodes was evaluated using a digital multimeter (name "PC500a", manufactured by Sanwa Electric Measurement Co., Ltd.). The electrical connection of the opposing electrodes was evaluated according to the following criteria. The results are shown in Table 9. Level 2: The electrical resistance value was a positive value (a value exceeding 0). Level 1: The electrical resistance value was 0 or less.

[0167]

[0168] <Discussion> The results of Experiments 1 and 2 show that, compared to the solder removal composition containing malic acid (Comparative Example 1), the solder removal composition containing dimethylglutaric acid as a flux (Example 1-1) and the solder removal composition containing glutaric acid (Example 2-1) have significantly different relationships between temperature and complex viscosity, as shown in Figure 5. Furthermore, in the solder removal compositions of Examples 1-1 and 2-1, the above-mentioned T ０ Complex viscosity A at 220°C (a temperature close to the melting point of the solder particles) ０ is less than 10 Pa s, and T ０ Complex viscosity A at +40°C (260°C) １ As a result, it is shown that the conductive resin compositions of Examples 1-1 and 2-1 can obtain adhesive reliability and electrical connection. Also, in Examples 12 and 13, which used low-melting-point solder particles (melting point 139°C), T ０ Complex viscosity A at 138°C (a temperature close to the melting point of low-melting-point solder particles) ０ is less than 10 Pa s, and T ０ Complex viscosity A at +40°C (178°C) １ is 10 Pa·s or more, and as a result, it has been shown that these conductive resin compositions can provide adhesive reliability and electrical connection.

[0169] Furthermore, as will be shown in the examples below, the conductive resin compositions of Examples 1-1 and 2-1 have a wider margin (tolerance) for the temperature rise, and are shown to be able to obtain improved adhesion reliability and reliable electrical connection even under temperature rise conditions of 50°C / min and 25°C / min. That is, from the above, it has been shown that by optimizing the relationship between temperature and complex viscosity in the solder-excluded composition, a conductive resin composition can be obtained that can more easily achieve improved connection reliability and reliable electrical connection.

[0170] The above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be interpreted as limiting. Modifications of the present invention that are obvious to those skilled in the art are intended to be included in the scope of the following claims.

[0171] The conductive resin composition, conductive resin sheet, connection structure, and method for producing a connection structure of the present invention are suitably used, for example, in the production of electronic devices.

[0172] REFERENCE SIGNS LIST 1 conductive resin sheet 2 first substrate 4 second substrate 5 solder particles 6 laminate 10 release liner 12 first electrode 14 second electrode 15 columnar solder portion 20 connection structure 25 pressure oven

Claims

1. A conductive resin composition comprising solder particles, a resin, and a flux, wherein the melting point of the solder particles is T ０ ° C., the T of the conductive resin composition excluding the solder particles ０ Complex viscosity A at °C ０ is less than 10 Pa s, and T ０ Complex viscosity A at +40°C １ The conductive resin composition has a viscosity of 10 Pa·s or more.

2. The melting point T of the solder particles ０ The conductive resin composition according to claim 1, wherein the temperature is 150°C or higher.

3. The conductive resin composition according to claim 2, wherein the solder particles contain Sn.

4. The maximum temperature in the temperature range at which the complex viscosity of the conductive resin composition excluding the solder particles is less than 10 Pa·s is defined as T １ °C, minimum temperature T ２ ° C., the T １ ° C. and the T ２ The conductive resin composition according to claim 1 , wherein the temperature difference in ° C. is 70° C. or more.

5. Said T ０ Complex viscosity A at °C ０ The above T ０ Complex viscosity A at +40°C １ The ratio (A １ / A ０ The conductive resin composition according to claim 1 , wherein the ratio (R) is 10 or more.

6. A conductive resin sheet comprising the conductive resin composition according to any one of claims 1 to 5.

7. A connection structure comprising a first substrate, a second substrate arranged at a distance in the thickness direction, and an adhesive layer interposed between the first substrate and the second substrate, each of the first substrate and the second substrate having at least one electrode, a columnar solder portion being 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 conductive resin composition according to any one of claims 1 to 5.

8. A method for manufacturing a connection structure, comprising: a first step of preparing a plurality of substrates each having a plurality of electrodes arranged in a planar direction; a second step of preparing a conductive resin sheet by applying the conductive resin composition according to any one of claims 1 to 5; a third step of stacking the two substrates with the conductive resin sheet sandwiched therebetween so that the electrodes of the two substrates face each other, thereby producing a laminate; and 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 hardening the resin component.

9. The method for producing a connection structure according to claim 8, wherein the fourth step is carried out in a pressure oven.

Images