Resin composition, method for producing same, conductive adhesive, connection structure, and electronic component

Abstract

Provided are: a resin composition capable of shortening a curing time without impairing adhesion and connection reliability; and a method for producing the same. This resin composition contains: a latent curing agent solution obtained by dissolving a latent curing agent in a liquid first epoxy resin; and a main agent containing a second epoxy resin. In a DSC chart obtained by differential scanning calorimetry, only one exothermic peak is present in the range of 70°C to 150°C, and the viscosity of the first epoxy resin at 25°C is 10 pa·s or less.

Description

Resin composition and method for producing the same, conductive adhesive, connection structure, and electronic component

[0001] The present invention relates to a resin composition and a method for producing the same, a conductive adhesive, a connection structure, and an electronic component.

[0002] BACKGROUND ART Resin compositions containing, as a main component, a compound having an epoxy group or the like have conventionally been used as connecting adhesives for connecting circuit components and circuit boards in electronic devices.

[0003] In recent years, with the expansion of the RFID (Radio Frequency Identification) market, there has been an increasing demand for connecting adhesives that connect circuit components included in RFID media such as RFID tags to circuit boards. From the viewpoint of improving the productivity of electronic devices, RFID media, etc., there is a demand for resin compositions with a short curing time as connecting adhesives that can connect circuit components to circuit boards in a short time.

[0004] As a resin composition with a short curing time, for example, Patent Document 1 proposes a composition that can electrically bond circuits together at a relatively low temperature and in a short time, at a compression temperature of 130°C or less and a compression time of 10 seconds or less, and that has excellent connection reliability and peel strength. Also, for example, Patent Document 2 proposes an anisotropic conductive adhesive that can provide a highly reliable connection even when bonded under thermocompression conditions of 150 to 200°C and 4 to 6 seconds.

[0005] JP 2002-161146 A JP 2009-54377 A

[0006] However, particularly in the field of producing electronic components such as RFID, there is a demand for resin compositions with even shorter curing times in order to further improve productivity.

[0007] Therefore, an object of the present invention is to provide a resin composition that can shorten the curing time without impairing adhesion and connection reliability, and a method for producing the same.

[0008] In view of the above circumstances, the present inventors have conducted extensive research and have found that, in a resin composition containing an epoxy resin as a main component and a latent curing agent, by using a liquid epoxy resin having a predetermined viscosity as a solvent for dissolving the latent curing agent and by producing a resin composition having a characteristic exothermic peak in a DSC chart obtained by differential scanning calorimetry, it is possible to shorten the curing time without impairing adhesion and connection reliability, and have thereby completed the present invention.

[0009] The present invention provides a resin composition comprising a latent curing agent solution in which a latent curing agent is dissolved in a liquid first epoxy resin, and a base resin containing a second epoxy resin, wherein a DSC chart obtained by differential scanning calorimetry shows only one exothermic peak in the range of 70 to 150°C, and the viscosity of the first epoxy resin at 25°C is 10 Pa s or less.

[0010] The present invention also provides a method for producing the resin composition, comprising the steps of: mixing a latent curing agent with a liquid first epoxy resin to prepare a latent curing agent solution in which the latent curing agent is dissolved in the liquid first epoxy resin; and adding the latent curing agent solution to a base resin containing a second epoxy resin and mixing them.

[0011] The present invention also provides a conductive adhesive comprising the resin composition further containing conductive particles.

[0012] The present invention also provides an adhesive structure in which bonded members are bonded together via the conductive adhesive, and an electronic component using the conductive adhesive.

[0013] According to the present invention, it is possible to provide a resin composition that can shorten the curing time without impairing adhesion and connection reliability, a method for producing the same, and a conductive adhesive, connection structure, and electronic component that use the same and have excellent adhesion and connection reliability.

[0014] 1 is a DSC chart of the resin composition obtained in Example 1. FIG. 2 is a DSC chart of the resin composition obtained in Comparative Example 1.

[0015] The present invention will be described below based on preferred embodiments. The resin composition of the present invention is a resin composition comprising a latent curing agent solution in which a latent curing agent is dissolved in a liquid first epoxy resin, and a base resin containing a second epoxy resin, characterized in that a DSC chart obtained by differential scanning calorimetry shows only one exothermic peak in the range of 70 to 150°C, and the viscosity of the first epoxy resin is 10 Pa s or less.

[0016] The latent curing agent used in the resin composition of the present invention may be any compound capable of generating a cationic species or a Lewis acid upon heating, such as aromatic sulfonium salts, thiophenium salts, thioranium salts, benzylammonium, pyridinium salts, hydrazinium salts, carboxylic acid esters, sulfonic acid esters, amine imides, etc. Among these, aromatic sulfonium salts are preferred because the compounds are relatively stable and can shorten the curing time.

[0017] The latent curing agent may be a commercially available product. Examples of such commercially available products include SI-L85, SI-L110, SI-L145, SI-L160, SI-H15, SI-H20, SI-H25, SI-H40, SI-H50, SI-60L, SI-80L, SI-100L, SI-B2A, SI-B3, SI-B7, SI-60, SI-80, and SI-100 from the San-Aid (registered trademark) series manufactured by Sanshin Chemical Industry Co., Ltd.; TA-60, TA-100, and TA-110 from San-Apro Co., Ltd.; Adeka Opton CP-66 (counter ion: SbF6) and Adeka Opton CP-77 from ADEKA Corporation; Examples of the latent curing agent include TAG-2678, TAG-2713, and TAG-2172 manufactured by Nippon Soda Co., Ltd., FC-520 manufactured by 3M, and CI-2921, CI-2920, CI-2946, CI-3128, CI-2624, CI-2639, and CI-2064 manufactured by Nippon Soda Co., Ltd. These latent curing agents may be used alone or in combination of two or more.

[0018] The liquid first epoxy resin used in the resin composition of the present invention (hereinafter, sometimes simply referred to as the "first epoxy resin") is a compound having one or more epoxy groups per molecule and a structure containing no nitrogen atoms, and having a viscosity of 10 Pa·s or less, preferably 0.001 to 10 Pa·s, at 25°C. The first epoxy resin is used as a solvent for dissolving the latent curing agent and as a component that also contributes to the curing reaction. Examples of such compounds include glycidyl ether-type epoxy resins such as 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, lauryl glycidyl ether, C12-13 mixed higher alcohol glycidyl ether, p-tert-butylphenyl glycidyl ether, neopentyl glycol diglycidyl ether, higher alcohol glycidyl ether, phenyl glycidyl ether, 2-ethylhexyl glycidyl ether, polypropylene glycol diglycidyl ether, and trimethylolpropane polyglycidyl ether. Among these, compounds having one or two epoxy groups per molecule are preferred because they facilitate uniform dispersion of the base resin and the latent curing agent solution and can shorten the curing time without impairing adhesion and connection reliability. Specific preferred compounds include 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, lauryl glycidyl ether, and p-tert-butylphenyl glycidyl ether.

[0019] The first epoxy resin may be a commercially available product. Examples of such commercially available products include BD(D), HD(D), LA(D), NPG(D), and PG400 from the Epogosey (registered trademark) series manufactured by Yokkaichi Synthetic Co., Ltd., M-1230 from the Epolight (registered trademark) series manufactured by Kyoeisha Chemical Co., Ltd., ED-509S and ED-523L from the Adeka Glysilol (registered trademark) series manufactured by ADEKA Corporation, and SY-35M, PGE, EHG-C, SR-4PG, and SR-TMP manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. These epoxy resins may be used alone as the first epoxy resin, or two or more types may be mixed together.

[0020] The first epoxy resin is a solvent that dissolves the latent curing agent, but can be handled relatively safely compared to commonly used highly hazardous solvents such as benzene, toluene, hexane, methanol, diethyl ether, and propylene carbonate.

[0021] In the latent curing agent solution used in the resin composition of the present invention, the ratio (mass ratio) of the latent curing agent to the first epoxy resin is preferably 10:1 to 1:100, more preferably 5:1 to 1:10, and particularly preferably 1:1 to 1:10. Having the mass ratio of the latent curing agent to the first epoxy resin within the above range enables shortening of the curing time. If the mass ratio of the latent curing agent to the first epoxy resin is such that the latent curing agent is in a higher proportion than the mass ratio of the latent curing agent to the first epoxy resin of 10:1 (e.g., 20:1), the latent curing agent may not dissolve. Furthermore, if the mass ratio of the latent curing agent to the first epoxy resin is such that the first epoxy resin is in a higher proportion than the mass ratio of the latent curing agent to the first epoxy resin of 1:100 (e.g., 1:200), curing may be slow.

[0022] The second epoxy resin used in the resin composition of the present invention may be any epoxy resin commonly used in adhesives for connecting electronic devices, RFID media, etc., and is usually a compound having two or more epoxy groups in one molecule, but preferably a compound having a structure that does not contain a nitrogen atom. Specific examples of such compounds include novolak resins such as phenol novolak and cresol novolak; polyhydric phenols such as bisphenol A, bisphenol F, bisphenol AD, resorcinol, and bishydroxydiphenyl ether; polyhydric alcohols such as ethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, and polypropylene glycol; polyamino compounds such as ethylenediamine, triethylenetetramine, and aniline; glycidyl-type epoxy resins obtained by reacting epichlorohydrin or 2-methylepichlorohydrin with polycarboxylic compounds such as adipic acid, phthalic acid, and isophthalic acid; aliphatic epoxy resins such as dicyclopentadiene epoxide and butadiene dimer epoxide; and alicyclic epoxy resins such as 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate. Among these, alicyclic epoxy resins are preferred because of their high adhesive strength, excellent heat resistance and electrical insulation, low melt viscosity, and ability to connect at low pressure. To prevent ion migration, it is preferable to use a high-purity product in which impurity ions (Na, Cl, etc.) and hydrolyzable chlorine are reduced.

[0023] These epoxy resins may be used alone as the second epoxy resin, or two or more may be mixed together. In particular, when an alicyclic epoxy resin is used alone and a curing agent solution is added and mixed, the amount of heat generated by the reaction is large in rare cases, and there is a risk that the resin itself may be altered by heat. Therefore, it is more preferable to use an alicyclic epoxy resin in combination with a glycidyl-type epoxy resin. In this case, since a higher content of glycidyl-type epoxy resin increases the curing time, the mass ratio of the alicyclic epoxy resin to the glycidyl-type epoxy resin is preferably 99:1 to 25:75.

[0024] The content of the second epoxy resin in the base resin of the resin composition of the present invention is 50% by mass or less, preferably 20% by mass or less.

[0025] In the resin composition of the present invention, the ratio (mass ratio) of the latent curing agent solution to the main component is preferably 1:1 to 1:100, more preferably 1:1 to 1:10, and particularly preferably 1:1 to 1:5. When the mass ratio of the latent curing agent solution to the main component is within the above range, it becomes possible to shorten the curing time.

[0026] The resin composition of the present invention preferably has a gel time at 150°C of less than 10 seconds, more preferably 0.5 to 8 seconds. By having a gel time within the above range, the curing time can be shortened without further impairing adhesion and connection reliability, and when used as a connecting adhesive, the productivity of electronic devices, RFID media, and the like can be further improved. In the present invention, the gel time refers to the time from when the resin composition begins to be heated at 150°C in accordance with the hot plate method of JIS-C2161:2010, Section 7.1.5, Method A, until the resin composition becomes unable to be stirred due to gelation. A short gel time results in a rapid progress of the curing reaction, and a short curing time until curing is complete. On the other hand, a long gel time results in a slow progress of the curing reaction, and a long curing time until curing is complete. Therefore, a resin composition with a short gel time can connect circuit components and circuit boards in a short time and is useful as a connecting adhesive.

[0027] In the resin composition of the present invention, in a DSC chart obtained by differential scanning calorimetry (DSC), it is preferable that only one exothermic peak exists in the range of 70 to 150°C, more preferably only one in the range of 75 to 130°C, and particularly preferably only one in the range of 80 to 120°C. The inventors believe that by possessing such properties, the curing time can be shortened without impairing adhesion and connection reliability, and when used as a connecting adhesive, the productivity of electronic devices, RFID media, etc. can be further improved. Generally, the latent curing agent is added to the desired epoxy resin in a dissolved state in a solvent. Examples of solvents commonly used to dissolve latent curing agents include γ-butyrolactone (see, for example, paragraph 0033 of JP 2002-161146 A and paragraph 0108 of JP 2016-020476 A). When the resin composition of the present invention is compared with a resin composition produced using γ-butyrolactone as a solvent for a latent curing agent, the temperature of the exothermic peak observed in a DSC chart obtained by differential scanning calorimetry (DSC) in which the temperature is raised from 30°C to 200°C at 5°C / min, and the total heat generation calculated from the area of ​​the exothermic peak, the former has only one exothermic peak in the range of 70 to 150°C, while the latter has at least two exothermic peaks in the range of 70 to 150°C. For example, in Example 1 herein, only one exothermic peak is present near 110°C, and the total heat generation amount is 438.3 J / g (see Figure 1). On the other hand, in Comparative Example 1 herein, the latter has two exothermic peaks (Peak 1 and Peak 2) near 100°C and 115°C, and the total heat generation amount is 384.9 J / g (see Figure 2). From these facts, the present inventors have speculated that by using the first epoxy resin as a solvent for dissolving the latent curing agent, it is possible to reduce the curing reaction, which normally proceeds in two steps, to a one-step reaction, thereby shortening the curing time.

[0028] The resin composition of the present invention may contain known additives as long as they do not affect adhesion, connection reliability, or curing time. Examples of known additives include silane coupling agents, organic solvents, fillers, thixotropic agents, thickeners, viscosity reducers, viscosity modifiers, leveling agents, antioxidants, tackifiers, waxes, heat stabilizers, stabilizers, antistabilizers, foaming agents, organic pigments, inorganic pigments, thermal conductive agents, electrical conductive agents, dyes, antistatic agents, moisture permeable agents, water repellents, hollow foams, flame retardant colorants, water absorbents, moisture absorbents, deodorizers, foam stabilizers, antifoaming agents, antifungal agents, preservatives, anti-algae agents, pigment dispersants, antiblocking agents, and hydrolysis inhibitors. Other resins, such as organic water-soluble compounds, inorganic water-soluble compounds, thermoplastic resins, and thermosetting resins, may also be used in liquid or solid form. Typical additives include stabilizers, electrical conductive agents, thermal conductive agents, and thixotropic agents.

[0029] The resin composition of the present invention can have an extended pot life by further containing a quaternary phosphonium salt represented by the following formula (1) as the stabilizer.

[0030]

[0031] In formula (1), R １ , R ２ , R ３ and R ４ may be the same or different groups, and each independently represents an alkyl group or a phenyl group (—C ６ H ５ R in formula (1) represents １ ~R ４ When X is an alkyl group, it is preferably an alkyl group having 1 to 16 carbon atoms. － represents an anion, for example, F － , Cl － , I － ,Br － , S.O. ４ ２－ , B.F. ４ － , P.F. ４ － , SbF ６ － , (OC ２ H５ ) ２ P=O － , (C ６ H ５ ) ４ B － etc.

[0032] In the resin composition of the present invention, methyl tributyl phosphonium dimethyl phosphate and methyl trioctyl phosphonium dimethyl phosphate are preferred as stabilizers because they can extend the pot life with the addition of a small amount.

[0033] The amount of the quaternary phosphonium salt added as a stabilizer is determined relative to the amount of the latent curing agent, and is preferably an amount such that the mass ratio of the quaternary phosphonium salt to the latent curing agent is 0.001 to 1, and more preferably an amount such that the mass ratio is 0.005 to 0.8. If the mass ratio of the quaternary phosphonium salt to the latent curing agent is less than 0.001, it becomes difficult to achieve an extension effect of the pot life, whereas if this mass ratio exceeds 1, although the pot life is extended, the gel time becomes longer and curing tends to become more difficult.

[0034] When the resin composition of the present invention further contains a quaternary phosphonium salt, the pot life at 25°C is preferably 1 day or more, more preferably 2 days or more, and particularly preferably 3 to 30 days, from the viewpoint of the balance between storage stability and curability.

[0035] When the resin composition of the present invention further contains a quaternary phosphonium salt, the gel time at 150°C is preferably less than 10 seconds, and more preferably 0.5 to 8 seconds, in order to achieve excellent storage stability without impairing adhesion and connection reliability.

[0036] The resin composition of the present invention can contain conductive particles as the aforementioned electrically conductive agent. By including conductive particles, the resin composition of the present invention becomes a one-component conductive adhesive, which is particularly useful as a connecting adhesive that can connect circuit components and circuit boards in a short time without impairing adhesion and connection reliability. Examples of conductive particles include metal particles such as nickel, gold, silver, palladium, copper, and solder, as well as carbon particles that are conductive in themselves. Other examples include particles that are imparted with conductivity by forming a metal coating on the surface of core particles.

[0037] When conductive particles are used as an electrical conductor in the resin composition of the present invention, the average particle size of the conductive particles is preferably 0.1 μm to 1000 μm, and particularly preferably 0.5 to 100 μm. The average particle size of the conductive particles is appropriately selected depending on the specific application of the resin composition of the present invention. However, when the resin composition of the present invention is used as a connecting adhesive, if the average particle size of the conductive particles is too small, electrical conduction becomes difficult, and if the average particle size of the conductive particles is too large, short circuits are likely to occur. The average particle size of the conductive particles can be measured using an electrical resistance method.

[0038] The shape of the conductive particles is not particularly limited. Generally, the conductive particles may be powder-like, but may also be other shapes, such as fibrous, hollow, plate-like, or needle-like, or may have many protrusions on the particle surface, or may be amorphous. Among these, spherical conductive particles are particularly preferred because of their excellent packing properties.

[0039] When conductive particles having a metal coating formed on the surface of core particles are used as the electrically conductive agent, methods for forming the metal coating on the surface of core particles include, for example, dry methods using vapor deposition, sputtering, mechanochemical methods, hybridization methods, etc., and wet methods using electrolytic plating, electroless plating, etc. Alternatively, a metal coating may be formed on the surface of core particles by combining these methods.

[0040] When conductive particles having a metal coating formed on the surface of core particles are used as the electrically conductive agent, the core particles used may be inorganic or organic. Examples of inorganic core particles include metal particles such as gold, silver, copper, nickel, palladium, and solder, alloys, glass, ceramics, silica, metal or non-metal oxides (including hydrated materials), metal silicates including aluminosilicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal acid salts, metal halides, and carbon. Examples of organic core particles include natural fibers and natural resins, thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylate, polyacrylonitrile, polyacetal, ionomer, and polyester, alkyd resin, phenolic resin, urea resin, benzoguanamine resin, melamine resin, xylene resin, silicone resin, epoxy resin, and diallyl phthalate resin. In the resin composition of the present invention, the particle surfaces are uniformly and densely coated with a metal film, and the particles have oxidation resistance and low resistance during connection. Therefore, it is preferable to use conductive particles in which metal particles such as gold, silver, copper, nickel, palladium, and solder are used as core particles and a metal film of one or more selected from gold, silver, copper, nickel, palladium, and solder is formed on the surface of the metal particles. It is more preferable to use conductive particles in which nickel is used as the core particle and the metal film is formed on the surface of the nickel by electroless plating. The metal film also includes alloys (e.g., nickel-phosphorus alloys and nickel-boron alloys).

[0041] When conductive particles having a metal coating formed on the surface of core particles are used as the electrically conductive agent, the average particle size of the core particles is preferably 0.1 μm to 1000 μm, and particularly preferably 0.5 μm to 100 μm. If the average particle size of the core particles is too small, even conductive particles having a metal coating may have difficulty in conducting electricity, and if the average particle size of the core particles is too large, short circuits may occur. The average particle size of the core particles is a value measured using an electrical resistance method.

[0042] Furthermore, the particle size distribution of the core particles measured by the above-mentioned method has a range. Generally, the range of the particle size distribution of a powder is expressed by the coefficient of variation shown in the following calculation formula (1): Coefficient of variation (%) = (standard deviation / average particle size) × 100 (1) A large coefficient of variation indicates a wide distribution range, while a small coefficient of variation indicates a sharp particle size distribution. It is preferable to use core particles with a coefficient of variation of 50% or less, preferably 30% or less, and particularly preferably 20% or less, from the viewpoint of increasing the effective contribution rate to the connection between the circuit component and the circuit board.

[0043] The shape of the core particles is not particularly limited. Generally, the core particles may be powder-like, but may also be other shapes, such as fibrous, hollow, plate-like, or needle-like, or may have many protrusions on the particle surface or may be amorphous. Among these, spherical core particles are particularly preferred because they have excellent packing properties when used as conductive particles.

[0044] In addition, other physical properties of the core particles are not particularly limited. In the case of core particles made of a resin material, the value of K defined by the following formula (2) is 100 N / mm at 20°C. ２ ~100000N / mm ２ and a recovery rate after 10% compression deformation is in the range of 1% to 100% at 20°C, from the viewpoint of being able to contact the electrodes sufficiently without damaging the electrodes when they are pressed together. ２ ) = (3 / √2) × F × S －３／２ ×R －１／２ ... (2) (In formula (2), F and S are the load value (N) and the compression displacement (mm) at 10% compression deformation of the core material particle when measured with a micro-compression tester (MCTM-500 manufactured by Shimadzu Corporation), respectively, and R is the radius (mm) of the core material particle measured with the micro-compression tester (MCTM-500 manufactured by Shimadzu Corporation).)

[0045] The conductive particles may be surface-treated with a hydrophobizing agent, if necessary, to improve their moisture resistance and corrosion resistance. Examples of the hydrophobizing agent include benzotriazole compounds, titanate coupling agents, higher fatty acids and their derivatives, phosphate esters, and phosphites. These may be used alone or in combination of two or more types as needed.

[0046] The resin composition of the present invention may contain boron nitride, aluminum oxide, titanium oxide, silica, etc. as the thermal conductive agent. These may be used alone or in combination of two or more. Furthermore, there are no particular restrictions on the particle shape, size, amount, etc.

[0047] The method for producing the resin composition of the present invention comprises the steps of: mixing a latent curing agent with a first epoxy resin to prepare a latent curing agent solution in which the latent curing agent is dissolved in the first epoxy resin; and adding the latent curing agent solution to a base resin containing a second epoxy resin and mixing them to obtain the resin composition of the present invention as a one-component resin composition.

[0048] In the step of preparing the latent curing agent solution, the latent curing agent and the first epoxy resin can be mixed using a general device to dissolve the latent curing agent in the first epoxy resin. Examples of such devices include a planetary mixer, a two-roll mill, a three-roll mill, a bead mill, and a ball mill. However, a planetary mixer with a rotary and revolutionary vacuum degassing mixer is suitable because it can simultaneously mix the materials and remove air bubbles from the paste in a short time.

[0049] In the step of adding the latent curing agent solution to the base agent and mixing them, the base agent and the latent curing agent solution can be mixed using a common device. Examples of such devices include a planetary mixer, a two-roll mill, a three-roll mill, a bead mill, and a ball mill. There are no particular limitations on the device as long as it can mix uniformly, but a planetary mixer with a vacuum degassing mixer is suitable because it can simultaneously knead the paste and remove air bubbles in a short time.

[0050] In the method for producing a resin composition of the present invention, the latent curing agent solution and known additives may be added to and mixed with the base compound, if necessary. When mixing the latent curing agent solution and the base compound at high speed, heat is generated. If this heat causes the temperature of the latent curing agent solution and the base compound to exceed a predetermined temperature during mixing, the curing reaction may begin. Therefore, it is preferable to add the additives to the base compound and mix them uniformly to form a mixed solution before adding the latent curing agent solution to the base compound, or to prepare a uniform solution of the latent curing agent solution and the additives, and then add the solution to the base compound.

[0051] In the method for producing a resin composition of the present invention, by mixing a latent curing agent solution, conductive particles as an electrical conductor, and a main component, the resulting resin composition becomes a one-component conductive adhesive, which is particularly useful as a connecting adhesive that can connect circuit components and circuit boards in a short time without impairing adhesion and connection reliability.

[0052] The conductive adhesive of the present invention is made of a resin composition containing the conductive particles described above. The content of the conductive particles in the conductive adhesive is preferably 1 to 70 mass %, and more preferably 5 to 30 mass %, from the viewpoints of adhesion and connection reliability.

[0053] The conductive adhesive of the present invention can be used in various forms such as a paste or a sheet.

[0054] The conductive adhesive of the present invention can provide highly reliable electrode connections in electronic components such as miniaturized IC chips and light-emitting diodes, as well as in circuit boards.

[0055] Examples of adhesive structures in which bonded members are bonded together via the conductive adhesive of the present invention include RFID-related products such as IC cards and IC tags in which an IC chip is bonded to a substrate having an electrode, and light-emitting electronic components in which a light-emitting diode is bonded to a substrate having an electrode.

[0056] As a method for bonding electronic components using the conductive adhesive of the present invention, known methods can be used. For example, a method can be used in which the conductive adhesive of the present invention is applied to the surface of a substrate on which an electrode has been formed, using a coating device such as a slit coater, roll coater, spin coater, screen printing method, metal mask printing method, dispenser, or jet dispenser, so as to have a film thickness of 0.1 to 100 μm, and the electronic component is placed on the substrate so that a portion of the electronic component is located above the electrode, and the resulting laminate is heated and pressurized.

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0058] Example 1 The amounts of latent curing agent (manufactured by San-Apro Co., Ltd., trade name: TA-100) and 1,6-hexanediol diglycidyl ether (manufactured by Yokkaichi Synthetic Co., Ltd., trade name: EPOGOSE® HD(D)) (solvent A), which is a solvent for dissolving the latent curing agent, shown in Table 1, were thoroughly mixed using a rotary and revolutionary vacuum degassing mixer to prepare a latent curing agent solution. The viscosity of solvent A at 25°C was 0.1 Pa·s. Furthermore, the amounts of base agent (manufactured by Mitsubishi Chemical Corporation, trade name: jER828), viscosity modifier (manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil® 200), and conductive particles (manufactured by Nippon Chemical Industry Co., Ltd., trade name: Bright 6GNM5-NiS) as an electrical conductive agent, in which a gold coating is formed on the surface of nickel core particles by electroless plating, were mixed using a rotary and revolutionary vacuum degassing mixer to prepare a base agent mixture. Thereafter, the latent curing agent solution was added to the main component mixture in a weight ratio of 15% and kneaded to obtain a resin composition.

[0059] Example 2 The amounts of latent curing agent (manufactured by San-Apro Co., Ltd., trade name: TA-100) and lauryl glycidyl ether (manufactured by Yokkaichi Synthetic Co., Ltd., trade name: EPOGOSE (registered trademark) LA (D)) (solvent B) that dissolve the latent curing agent were thoroughly mixed using a rotary and revolutionary vacuum defoaming mixer to prepare a latent curing agent solution. The viscosity of solvent B at 25°C was 0.1 Pa·s. Furthermore, the amounts of base agent (manufactured by Mitsubishi Chemical Corporation, trade name: jER828), viscosity modifier (manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil (registered trademark) 200), and conductive particles (manufactured by Nippon Chemical Industry Co., Ltd., trade name: Bright 6GNM5-NiS) as an electrical conductor, in which a gold coating was formed on the surface of nickel core particles by electroless plating, were mixed using a rotary and revolutionary vacuum defoaming mixer to prepare a base agent mixture. Thereafter, the latent curing agent solution was added to the main component mixture in a weight ratio of 15% and kneaded to obtain a resin composition.

[0060] (Examples 3 to 6) The amounts of latent curing agent and solvent for dissolving the latent curing agent shown in Table 1 were thoroughly mixed using a planetary vacuum degassing mixer to prepare a latent curing agent solution. The amounts of base agent, viscosity modifier, and electrical conductive agent shown in Table 1 were also mixed using a planetary vacuum degassing mixer to prepare a base agent mixture. The latent curing agent solution was then added to the base agent mixture and mixed, yielding a resin composition.

[0061] Comparative Example 1 The amounts of latent curing agent (manufactured by San-Apro Co., Ltd., product name: TA-100) and γ-butyrolactone (manufactured by Tokyo Chemical Industry Co., Ltd.) (solvent C), which is a solvent for dissolving the latent curing agent, shown in Table 1 were thoroughly kneaded with a rotary-revolving vacuum degassing mixer to prepare a latent curing agent solution. Also shown in Table 1 were the amounts of base agent (manufactured by Mitsubishi Chemical Corporation, product name: jER828), viscosity modifier (manufactured by Nippon Aerosil Co., Ltd., product name: Aerosil (registered trademark) 200), and conductive particles (manufactured by Nippon Chemical Industry Co., Ltd., product name: Bright 6GNM5-NiS) as an electrically conductive agent, in which a gold coating was formed on the surface of nickel core particles by electroless plating, and these were kneaded with a rotary-revolving vacuum degassing mixer to prepare a base agent mixture. Thereafter, 6% by weight of the latent curing agent solution was added to the base agent mixture and kneaded to obtain a resin composition.

[0062] (Comparative Example 2) A latent curing agent solution was prepared by thoroughly kneading the amounts of latent curing agent and the solvent for dissolving the latent curing agent shown in Table 1 with a planetary vacuum degassing mixer. Furthermore, a main component, viscosity modifier, and electrical conductive agent were kneaded with the planetary vacuum degassing mixer in the amounts shown in Table 1 to prepare a main component mixed liquid. The latent curing agent solution was then added to the main component mixed liquid and kneaded to obtain a resin composition.

[0063]

[0064] <Evaluation 1> <DSC Chart> For the resin compositions obtained in Example 1 and Comparative Example 1, a differential scanning calorimetry (DSC) apparatus (manufactured by Rigaku Corporation, apparatus name: Thermo plus EVO2 DSC8231) was used to measure a DSC chart by raising the temperature from 30°C to 200°C at 5°C / min in an air atmosphere using a 5 mg sample weight. The temperature at which the maximum value of the exothermic peak appeared was determined from the obtained DSC chart. The total heat generation amount was calculated from the area of ​​the exothermic peak. The DSC chart of the resin composition obtained in Example 1 is shown in Figure 1, and the DSC chart of the resin composition obtained in Comparative Example 1 is shown in Figure 2. The resin compositions used were prepared within 3 hours. <Gel Time at 150°C> In accordance with the hot plate method of JIS-C2161:2010, Section 7.1.5, Method A, 1 ml of the resin compositions obtained in Examples 1 to 6 and Comparative Examples 1 and 2 was placed on a hot plate at 150°C, and the time (seconds) until gelation was measured while stirring. The results are shown in Table 2. The resin compositions used were those prepared within 3 hours.

[0065] <Evaluation 2> <Production of IC Tag> The resin compositions prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were applied by a dispenser method to an area including the entire aluminum wiring on a substrate (size: 2.5 cm long, 8 cm wide) with aluminum wiring formed on a PET film, so that the thickness after curing was 100 μm, and an IC having a gold bump was placed on the coating. The resin composition was cured by heating at a temperature of 190°C under a pressure of 1 N for 2 seconds, thereby connecting the substrate and the IC, and an IC tag was produced as an adhesive structure. The resin composition used was prepared within 3 hours. <Adhesion> The die shear strength of the produced IC tag was measured. The die shear strength was measured using a digital force gauge to determine the strength (N) when peeling the IC chip from the substrate. The results are shown in Table 2. The die shear strength results in the table indicate the following: ◯: 10N or more ×: Less than 10N <Connection reliability> The communication strength of the manufactured IC tag and the communication strength of the IC tag after a high temperature and high humidity test (85°C, 85RH, 168 hours) were measured, and the IC tag was evaluated as a pass rate (%), with a difference between the former and the latter being within 2 dBm. The communication strength was measured using the Tagformance (registered trademark) Pro system manufactured by Voyantic. The results are shown in Table 2. The connection reliability results in the table indicate the following: ◯: 70% or more △: 30% or more but less than 70% ×: Less than 30%

[0066]

[0067] 1 and 2, the resin composition obtained in Example 1 had only one exothermic peak near 110 ° C., with a total heat release of 438.3 J / g, and the resin composition obtained in Comparative Example 1 had two exothermic peaks, one near 100 ° C. (peak 1 in FIG. 2) and one near 115 ° C. (peak 2 in FIG. 2), with a total heat release of 384.9 J / g. Table 2 confirms that the resin compositions obtained in Examples 1 to 6 had shorter gel times than the resin compositions obtained in Comparative Examples 1 and 2. Furthermore, it was confirmed that the adhesive structures produced using the resin compositions of Examples 1 to 6 had equivalent adhesion and superior connection reliability compared to the adhesive structures produced using the resin compositions of Comparative Examples 1 and 2.

Claims

1. A resin composition comprising a latent curing agent solution in which a latent curing agent is dissolved in a liquid first epoxy resin, and a base material containing a second epoxy resin, wherein a DSC chart obtained by differential scanning calorimetry shows only one exothermic peak in the range of 70 to 150°C, and the viscosity of the first epoxy resin at 25°C is 10 Pa·s or less.

2. The resin composition according to claim 1, which has only one exothermic peak in the range of 75 to 130° C. in a DSC chart obtained by differential scanning calorimetry.

3. The resin composition according to claim 1, wherein the latent hardener is an aromatic sulfonium salt.

4. A resin composition according to claim 1, wherein in the latent hardener solution, the ratio of the latent hardener to the first epoxy resin is, by mass, the former:the latter = 10:1 to 1:

100.

5. The resin composition according to claim 1, which has a gel time at 150° C. of less than 10 seconds.

6. The resin composition according to any one of claims 1 to 5, further comprising conductive particles.

7. The resin composition according to claim 6, wherein said conductive particles are metal particles selected from the group consisting of nickel, gold, silver, palladium, copper and solder.

8. The resin composition according to claim 6, wherein the conductive particles are core particles having a metal film formed on the surface thereof by electroless plating.

9. The resin composition according to claim 8, wherein the core particles are metal particles selected from the group consisting of nickel, gold, silver, palladium, copper and solder.

10. A method for producing a resin composition according to any one of claims 1 to 5, comprising the steps of: mixing a latent curing agent with a liquid first epoxy resin to prepare a latent curing agent solution in which the latent curing agent is dissolved in the liquid first epoxy resin; and adding the latent curing agent solution to a base material containing a second epoxy resin and mixing them.

11. A conductive adhesive comprising the resin composition according to claim 6.

12. A bonded structure in which bonded members are bonded together via the conductive adhesive of claim 11.

13. An electronic component using the conductive adhesive of claim 11.

14. The electronic component according to claim 13, which is selected from the group consisting of IC cards, IC tags, and light-emitting electronic components.

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