Conductive material, connecting structure, and method for manufacturing the connecting structure

Abstract

To provide a conductive material capable of enhancing solder cohesiveness and storage stability.SOLUTION: The conductive material according to the present invention contains a thermosetting compound, a plurality of solder particles, a flux, and an organic acid. The organic acid has an aliphatic skeleton and has 12 or more carbon atoms. The content of the solder particles is 40 wt.% or more and 90 wt.% or less in 100 wt.% of the conductive material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a conductive material containing solder particles. The present invention also relates to a connection structure using the above conductive material and a method for manufacturing the connection structure.

Background Art

[0002] In recent years, connection methods using a conductive material containing solder particles or the like have been used for connecting substrates and electronic components. In addition, an anisotropic conductive material is sometimes used as the conductive material. In the above anisotropic conductive material, conductive particles are dispersed in a binder resin.

[0003] The above anisotropic conductive material is used to obtain various connection structures. Examples of connection using the above anisotropic conductive material include connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), connection between a semiconductor chip and a flexible printed circuit board (COF (Chip on Film)), connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), and connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)).

[0004] Patent Document 1 below discloses an anisotropic conductive film formed by forming a film of an adhesive resin composition in which conductive particles are dispersed. The above adhesive resin composition includes a base resin made of a polyacetalized resin obtained by acetalizing polyvinyl alcohol, a melamine-based resin, and an ammonium salt. Patent Document 1 also describes that the ammonium salt is preferably one or more selected from the group consisting of ammonium chloride, ammonium sulfate, ammonium phosphate, and ammonium acetate.

[0005] Patent Document 2 discloses conductive fine particles in which a carboxylic acid or carboxylate salt is attached to the surface of conductive substrate particles. The conductive substrate particles are conductive substrate particles formed of tin or an alloy thereof, or conductive substrate particles having a solder layer formed of tin or an alloy thereof on their outermost surface. Furthermore, Patent Document 2 states that it is preferable for a phosphate or phosphate ester to be attached to the surface of the conductive substrate particles.

[0006] Patent Document 3 below discloses an adhesive composition containing (A) an alicyclic epoxy compound and (B1) a cation generator. The (B1) cation generator is a sulfonium phosphate having a structure in which an alkenyl group, an allyl group, or a derivative thereof is bonded to a sulfur atom. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2003-229024 [Patent Document 2] Japanese Patent Publication No. 2011-009184 [Patent Document 3] Japanese Patent Publication No. 2011-111556 [Overview of the project] [Problems that the invention aims to solve]

[0008] Conventional conductive materials, such as those described in Patent Documents 1 to 3, may have poor solder cohesiveness. Furthermore, conventional conductive materials, such as those described in Patent Documents 1 to 3, may have poor storage stability, such as an increase in viscosity over time.

[0009] The object of the present invention is to provide a conductive material that can improve solder cohesiveness and storage stability. Another object of the present invention is to provide a connection structure using the above conductive material and a method for manufacturing the connection structure. [Means for solving the problem]

[0010] A conductive material is provided that comprises a thermosetting compound, a plurality of solder particles, a flux, and an organic acid, wherein the organic acid has an aliphatic skeleton and has 12 or more carbon atoms, and the content of the solder particles is 40% by weight or more and 90% by weight or less in 100% by weight of the conductive material.

[0011] In a particular aspect of the conductive material according to the present invention, the organic acid is a monocarboxylic acid.

[0012] In a specific aspect of the conductive material according to the present invention, the organic acid is an unsaturated monocarboxylic acid.

[0013] In a specific aspect of the conductive material according to the present invention, the organic acid has an amide bond.

[0014] In a particular aspect of the conductive material according to the present invention, the flux is a polycarboxylic acid or a polycarboxylic acid amine salt.

[0015] In a specific aspect of the conductive material according to the present invention, the conductive material either does not contain a thermosetting agent, or contains a thermosetting agent in an amount of 30% by weight or less of the conductive material by 100% by weight.

[0016] In certain aspects of the conductive material according to the present invention, the conductive material does not contain a thermosetting agent.

[0017] In a specific aspect of the conductive material according to the present invention, the particle size of the solder particles is 0.1 μm or more and 10.0 μm or less.

[0018] In a specific aspect of the conductive material according to the present invention, the ratio of the viscosity at 25°C and 0.5 rpm to the viscosity at 25°C and 5 rpm is 2.5 or greater.

[0019] In a particular aspect of the conductive material according to the present invention, the conductive material is a conductive paste.

[0020] According to a broad aspect of the present invention, there is provided a connection structure comprising: a first connection target member having a first electrode on a surface thereof; a second connection target member having a second electrode on a surface thereof; and a connection portion connecting the first connection target member and the second connection target member, wherein a material of the connection portion is the above-described conductive material, and the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

[0021] According to a broad aspect of the present invention, there is provided a method for manufacturing a connection structure, comprising the steps of: using the above-described conductive material to arrange the conductive material on a surface of a first connection target member having a first electrode on a surface thereof; arranging a second connection target member having a second electrode on a surface thereof on a surface of the conductive material opposite to the first connection target member side such that the first electrode and the second electrode face each other; and heating the conductive material to a temperature equal to or higher than the melting point of the solder particles to form, from the conductive material, a connection portion connecting the first connection target member and the second connection target member, and electrically connecting the first electrode and the second electrode by a solder portion in the connection portion.

Effects of the Invention

[0022] The conductive material according to the present invention is a conductive material comprising a thermosetting compound, a plurality of solder particles, a flux, and an organic acid, wherein the organic acid is an organic acid having an aliphatic skeleton and 12 or more carbon atoms, and a content of the solder particles in 100% by weight of the conductive material is 40% by weight or more and 90% by weight or less. Since the conductive material according to the present invention is provided with the above configuration, solder aggregation property and storage stability can be improved.

Brief Description of Drawings

[0023] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a connection structure using the conductive material according to a first embodiment of the present invention. [Figure 2]Figs. 2(a) to 2(c) are cross-sectional views for explaining each step of an example method for producing a connection structure using the conductive material according to the first embodiment of the present invention. Mode for Carrying Out the Invention

[0024] Hereinafter, the present invention will be described in detail.

[0025] (Conductive Material) The conductive material according to the present invention comprises a thermosetting compound, a plurality of solder particles, a flux, and an organic acid. In the conductive material according to the present invention, the organic acid is an organic acid having an aliphatic skeleton and 12 or more carbon atoms. In the conductive material according to the present invention, the content of the solder particles in 100% by weight of the conductive material is 40% by weight or more and 90% by weight or less.

[0026] In the conductive material according to the present invention, since the above configuration is provided, solder aggregation property and storage stability can be improved.

[0027] According to the present invention, storage stability can be improved, and an increase in viscosity over time can be suppressed even when the conductive material is stored at room temperature or the like.

[0028] From the viewpoint of exerting the effect of the present invention more effectively, the conductive material is preferably liquid at 25°C, and is preferably a conductive paste.

[0029] From the viewpoint of more efficiently arranging solder on an electrode, the viscosity (ηA) of the conductive material immediately after production at 25°C and 5 rpm is preferably 30 Pa·s or more, more preferably 50 Pa·s or more, and preferably 400 Pa·s or less, more preferably 300 Pa·s or less. The viscosity (ηA) can be appropriately adjusted depending on the types and blending amounts of the blending components.

[0030] The ratio (initial thixotropic index) of the viscosity (ηB) of the conductive material immediately after manufacturing at 25°C and 0.5 rpm to the viscosity (ηA) of the conductive material immediately after manufacturing at 25°C and 5 rpm is preferably 2.0 or higher, more preferably 2.5 or higher, and even more preferably 3.0 or higher. The above ratio (ηB / ηA) is preferably 5.0 or lower, more preferably 4.5 or lower, and even more preferably 4.0 or lower. When the above ratio (ηB / ηA) is above the lower limit and below the upper limit, the plaqueability (especially printability) of the conductive material can be improved.

[0031] The viscosity (ηA) and viscosity (ηB) mentioned above can be measured using an E-type viscometer. Examples of E-type viscometers include the "TVE22L" manufactured by Toki Sangyo Co., Ltd.

[0032] From the viewpoint of further improving the storage stability of the conductive material, the viscosity (ηC) of the conductive material at 25°C and 5 rpm after 24 hours is preferably 40 Pa·s or more, more preferably 50 Pa·s or more, preferably 400 Pa·s or less, and more preferably 300 Pa·s or less.

[0033] The ratio of the viscosity (ηD) of the conductive material at 25°C and 0.5 rpm after 24 hours to the viscosity (ηC) of the conductive material at 25°C and 5 rpm after 24 hours (thixotropic index after 24 hours) is preferably 2.0 or higher, more preferably 2.5 or higher, and even more preferably 3.0 or higher. The ratio (ηD / ηC) is preferably 5.0 or lower, more preferably 4.5 or lower, and even more preferably 4.0 or lower. When the ratio (ηD / ηC) is above the lower limit and below the upper limit, the plaqueability (especially printability) of the conductive material can be improved over a long period of time.

[0034] The viscosity (ηC) and viscosity (ηD) described above can be measured using an E-type viscometer on conductive material left standing for 24 hours under conditions of 25°C and 50%RH. Examples of E-type viscometers include the "TVE22L" manufactured by Toki Sangyo Co., Ltd.

[0035] The conductive material described above can be used as a conductive paste, a conductive film, or the like. Preferably, the conductive paste is an anisotropic conductive paste, and preferably the conductive film is an anisotropic conductive film. From the viewpoint of more efficiently arranging solder on the electrodes, the conductive material is preferably a conductive paste. The conductive material is suitably used for the electrical connection of electrodes. Preferably, the conductive material is a circuit connection material.

[0036] The following describes each component contained in the conductive material mentioned above. In the following description, "(meth)acrylic" refers to either "acrylic" or "methacrylic," or both.

[0037] (thermosetting compound) The above conductive material includes a thermosetting compound. The above thermosetting compound is a compound that can be cured by heating.

[0038] The thermosetting compound described above is not particularly limited. Examples of the thermosetting compound include oxetane compounds, epoxy compounds, episulfide compounds, (meth)acrylic compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. From the viewpoint of further improving the curability and viscosity of the conductive material and further effectively enhancing conductivity reliability, the thermosetting compound preferably contains an epoxy compound or an episulfide compound, and more preferably an epoxy compound. The thermosetting compound may be used alone or in combination of two or more.

[0039] The epoxy compound described above is a compound having at least one epoxy group. Examples of the epoxy compound include bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, phenol novolac type epoxy compound, biphenyl type epoxy compound, biphenyl novolac type epoxy compound, biphenol type epoxy compound, naphthalene type epoxy compound, fluorene type epoxy compound, phenol aralkyl type epoxy compound, naphthol aralkyl type epoxy compound, dicyclopentadiene type epoxy compound, anthracene type epoxy compound, epoxy compound having an adamantane skeleton, epoxy compound having a tricyclodecane skeleton, naphthylene ether type epoxy compound, and epoxy compound having a triazine core as its skeleton. Only one of the epoxy compounds may be used, or two or more may be used in combination.

[0040] From the viewpoint of improving the heat resistance of the cured product and enhancing the insulation reliability between electrodes that should not be connected, the epoxy compound is preferably a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, or a phenol novolac type epoxy compound, and more preferably a phenol novolac type epoxy compound.

[0041] The epoxy compound described above is liquid or solid at room temperature (25°C). If the epoxy compound is solid at room temperature, it is preferable that its melting point is below the melting point of the solder particles. By using the preferred epoxy compound described above, the viscosity increases when the connecting members are bonded together. This suppresses misalignment between the first connecting member and the second connecting member when acceleration is applied due to impacts such as those during transport. Furthermore, the heat generated during curing significantly reduces the viscosity of the conductive material, allowing for efficient aggregation of solder particles.

[0042] In 100% by weight of the above conductive material, the content of the above thermosetting compound is preferably 4% by weight or more, more preferably 6% by weight or more, even more preferably 10% by weight or more, preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 25% by weight or less. When the content of the above thermosetting compound is above the lower limit and below the upper limit, the effects of the present invention can be exhibited more effectively, and the insulation reliability between electrodes that should not be connected and the conductivity reliability between electrodes that should be connected can be improved more effectively. Furthermore, when the content of the above thermosetting compound is above the lower limit, the impact resistance can be improved.

[0043] In 100% by weight of the above conductive material, the content of the epoxy compound is preferably 4% by weight or more, more preferably 6% by weight or more, even more preferably 10% by weight or more, preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 25% by weight or less. When the content of the epoxy compound is above the lower limit and below the upper limit, the effects of the present invention can be exhibited more effectively, and the insulation reliability between electrodes that should not be connected and the conductivity reliability between electrodes that should be connected can be improved more effectively. Furthermore, when the content of the epoxy compound is above the lower limit, the impact resistance can be improved.

[0044] (Solder particles) The above conductive material contains a plurality of solder particles. The above solder particles are formed of solder in both their central portion and outer surface. The above solder particles are particles in which both the central portion and outer surface are solder. If conductive particles comprising base particles formed from a material other than solder and a solder portion arranged on the surface of the base particles are used instead of the above solder particles, the conductive particles will not easily accumulate on the electrodes. In addition, with the above conductive particles, the solderability between conductive particles is low, so conductive particles that have moved onto the electrodes tend to move off the electrodes more easily, and the effect of suppressing displacement between electrodes also tends to be low.

[0045] The solder described above is preferably a metal with a melting point of 450°C or less (low melting point metal). The solder particles described above are preferably metal particles with a melting point of 450°C or less (low melting point metal particles). The low melting point metal particles described above are particles containing a low melting point metal. The low melting point metal refers to a metal with a melting point of 450°C or less. The melting point of the low melting point metal is preferably 400°C or less, more preferably 300°C or less. The solder particles described above are preferably low melting point solder with a melting point of less than 300°C.

[0046] The melting point of the solder particles is preferably 80°C or higher, more preferably 120°C or higher, even more preferably 130°C or higher, preferably 400°C or lower, more preferably 300°C or lower, and even more preferably 220°C or lower. When the melting point of the solder particles is above the lower limit and below the upper limit, the solder particles can be arranged on the electrode more efficiently, and the insulation reliability and conductivity reliability can be more effectively improved.

[0047] The melting point of the solder particles mentioned above can be determined by differential scanning calorimetry (DSC). Examples of differential scanning calorimetry (DSC) equipment include the "EXSTAR DSC7020" manufactured by SII Corporation.

[0048] The average particle diameter of the solder particles is preferably 0.1 μm or more, more preferably 1.0 μm or more, preferably 20.0 μm or less, more preferably 10.0 μm or less, and even more preferably 8.0 μm or less. When the average particle diameter of the solder particles is above the lower limit and below the upper limit, the effects of the present invention can be exhibited even more effectively. In conventional conductive materials containing solder particles with a relatively small average particle diameter, it is difficult to sufficiently suppress variations in the transfer area, but in the present invention, even when the average particle diameter of the solder particles is relatively small, variations in the transfer area can be effectively suppressed. Furthermore, when the average particle diameter of the solder particles is above the lower limit and below the upper limit, the solder particles can be arranged on the electrode more efficiently, and the conductivity reliability and connection reliability can be further effectively improved. The average particle diameter of the solder particles may be 2 μm or less, 1 μm or less, or less than 1 μm. In the present invention, the effects of the present invention can be effectively achieved even when the average particle diameter of the solder particles is considerably small.

[0049] The average particle size of the solder particles is preferably the number-average particle size. The average particle size of the solder particles can be determined, for example, by performing a laser diffraction particle size distribution measurement.

[0050] The content of solder particles in 100% by weight of the conductive material is 40% by weight or more and 90% by weight or less. Preferably, the content of solder particles in 100% by weight of the conductive material is 43% by weight or more, more preferably 45% by weight or more, even more preferably 50% by weight or more, preferably 85% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. If the content of solder particles is above the lower limit, the solder cohesiveness can be further improved. If the content of solder particles is below the upper limit, the arrangement properties (especially printability) of the conductive material can be improved.

[0051] (Flux) The conductive material described above includes flux. Using flux allows for more efficient placement of solder on the electrodes. The flux is not particularly limited; any flux commonly used in soldering and the like can be used.

[0052] Examples of the fluxes mentioned above include zinc chloride, mixtures of zinc chloride and inorganic halides, mixtures of zinc chloride and inorganic acids, molten salts, phosphoric acid, phosphate amine salts, derivatives of phosphoric acid, polycarboxylic acids, polycarboxylic acid amine salts, organic halides, hydrazine, amine compounds different from both phosphate amine salts and polycarboxylic acid amine salts, and rosin. Only one of these fluxes may be used, or two or more may be used in combination.

[0053] Examples of the molten salts mentioned above include ammonium chloride.

[0054] Examples of the above-mentioned phosphate amine salts include acid phosphate amine salts. Examples of the above-mentioned acid phosphate amine salts include alkyl acid phosphate amine salts, and more specifically, examples of ethyl acid phosphate bis(2-ethylhexylamine salt), butyl acid phosphate bis(2-ethylhexylamine salt), butyl acid phosphate bis(dimethyldodecylamine), butyl acid phosphate bis(2-ethylhexylamine), etc.

[0055] The above polycarboxylic acid has two or more carboxyl groups. The above polycarboxylic acid may be a dicarboxylic acid or a tricarboxylic acid. Examples of the above polycarboxylic acid include citric acid, malonic acid, succinic acid, glutamic acid, glutaric acid, adipic acid, pimelic acid, malic acid, suberic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, isophthalic acid, terephthalic acid, and trimellitic acid.

[0056] Examples of the above-mentioned polyvalent carboxylic acid amine salts include cyclohexylamine glutarate, cyclohexylamine adipicate, benzylamine glutarate, and benzylamine adipicate.

[0057] Examples of the above-mentioned amine compounds that are different from both phosphate amine salts and polyvalent carboxylic acid amine salts include dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, and carboxybenzotriazole.

[0058] The above-mentioned rosins include activated rosins and inactivated rosins. The above-mentioned rosins are rosins whose main component is abietic acid. The above-mentioned rosins include abietic acid and acrylic-modified rosins.

[0059] The flux described above preferably contains a polycarboxylic acid, phosphoric acid, a polycarboxylic acid amine salt, or a phosphoric acid amine salt. The flux is more preferably a polycarboxylic acid or a polycarboxylic acid amine salt, and even more preferably a polycarboxylic acid amine salt. By using these preferred fluxes, the insulation reliability between electrodes that should not be connected and the conductivity reliability between electrodes that should be connected can be more effectively improved.

[0060] The activation temperature (melting point) of the flux is preferably 50°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, preferably 350°C or lower, more preferably 300°C or lower, even more preferably 250°C or lower, even more preferably 200°C or lower, and even more preferably 180°C or lower. When the activation temperature of the flux is above the lower limit and below the upper limit, the flux effect is exerted more effectively, and solder can be placed on the electrode more efficiently.

[0061] The melting point of the above flux can be determined by differential scanning calorimetry (DSC). Examples of differential scanning calorimetry (DSC) equipment include the "EXSTAR DSC7020" manufactured by SII Corporation.

[0062] Furthermore, it is preferable that the boiling point of the flux is 400°C or lower.

[0063] The flux may be dispersed in the conductive material or may be attached to the surface of the solder particles.

[0064] In 100% by weight of the conductive material, the flux content is preferably 5% by weight or more, more preferably 8% by weight or more, preferably 20% by weight or less, and more preferably 15% by weight or less. When the flux content is above the lower limit and below the upper limit, oxide films are less likely to form on the surface of the solder and electrodes, and the oxide films formed on the surface of the solder and electrodes can be removed more effectively.

[0065] (organic acid) The above-mentioned conductive material contains an organic acid. By using the above-mentioned organic acid, the thixotropy of the conductive material can be improved.

[0066] The above organic acid is an organic acid having an aliphatic skeleton and 12 or more carbon atoms. The number of carbon atoms in the above organic acid is preferably 14 or more, more preferably 16 or more, preferably 24 or less, and more preferably 22 or less. When the number of carbon atoms in the above organic acid is above the lower limit and below the upper limit, the thixotropy of the conductive material can be improved.

[0067] Examples of organic acids having an aliphatic skeleton and 12 or more carbon atoms include palmitoleic acid, elaidic acid, linoleic acid, linolenic acid, stearic acid, lauric acid, myristic acid, palmitic acid, oleic acid, and N-oleoylsarcosine. These organic acids may be used individually or in combination of two or more.

[0068] From the viewpoint of improving the thixotropy of the conductive material, the organic acid is preferably an organic acid having one carboxyl group. From the viewpoint of further improving the storage stability of the conductive material, the organic acid is preferably a monocarboxylic acid. From the viewpoint of improving oxygen barrier properties, the organic acid is preferably having an unsaturated bond. From the viewpoint of improving oxygen barrier properties and further improving the storage stability of the conductive material, the organic acid is preferably an unsaturated monocarboxylic acid. From the viewpoint of improving oxygen barrier properties, the number of unsaturated bonds in the organic acid is preferably 1 or more, more preferably 2 or more, preferably 6 or less, and more preferably 4 or less.

[0069] From the viewpoint of reducing outgassing when conductive materials are heated, it is preferable that the above-mentioned organic acid has an amide bond. The above-mentioned organic acid may have one amide bond, two amide bonds, or two or more amide bonds. Examples of organic acids having an amide bond include N-myristoyl sarcosine, N-lauroyl sarcosine, and N-oleoyl sarcosine.

[0070] From the viewpoint of exhibiting the effects of the present invention more effectively, the above organic acid preferably contains lauric acid, myristic acid, palmitic acid, oleic acid, or N-oleoylsarcosine, more preferably contains oleic acid or N-oleoylsarcosine, and particularly preferably contains N-oleoylsarcosine.

[0071] In 100% by weight of the conductive material, the content of the organic acid is preferably 0.5% by weight or more, more preferably 1.0% by weight or more, preferably 10% by weight or less, and more preferably 5.0% by weight or less. When the content of the organic acid is above the lower limit and below the upper limit, the thixotropy of the conductive material can be improved.

[0072] (Other ingredients) The above conductive material may optionally contain various additives such as fillers, bulking agents, softeners, plasticizers, thixotropes, leveling agents, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, and flame retardants.

[0073] From the viewpoint of further improving storage stability, it is preferable that the conductive material does not contain a thermosetting agent, or contains a thermosetting agent in an amount of 30% by weight or less per 100% by weight of the conductive material. From the viewpoint of further improving storage stability, the content of the thermosetting agent in 100% by weight of the conductive material is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 5% by weight or less. From the viewpoint of further improving storage stability, it is most preferable that the conductive material does not contain a thermosetting agent.

[0074] Examples of the above-mentioned thermosetting agents include imidazole curing agents, thiol curing agents, amine curing agents, phenol curing agents, acid anhydride curing agents, thermal cation initiators, and thermal radical generators. Only one of these thermosetting agents may be used, or two or more may be used in combination.

[0075] (Connection structure and method for manufacturing the connection structure) The connection structure according to the present invention comprises a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and a connection portion connecting the first connection target member and the second connection target member. In the connection structure according to the present invention, the material of the connection portion is the conductive material described above. In the connection structure according to the present invention, the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

[0076] A method for manufacturing a connection structure according to the present invention comprises the step of placing the conductive material described above on the surface of a first connection target member having a first electrode on its surface. A method for manufacturing a connection structure according to the present invention comprises the step of placing a second connection target member having a second electrode on the surface of the conductive material opposite to the first connection target member side, such that the first electrode and the second electrode face each other. A method for manufacturing a connection structure according to the present invention comprises the step of heating the conductive material above the melting point of the solder particles to form a connection portion connecting the first connection target member and the second connection target member using the conductive material, and electrically connecting the first electrode and the second electrode by the solder portion in the connection portion.

[0077] The connection structure and method for manufacturing the connection structure according to the present invention use a specific conductive material, which allows for good formation of a solder joint between the first electrode and the second electrode. Furthermore, it is difficult for a portion of the solder to be placed in areas (spaces) where electrodes are not formed, and the amount of solder placed in these areas can be significantly reduced. Therefore, the conductivity reliability between the first electrode and the second electrode can be improved. Moreover, electrical connections between laterally adjacent electrodes that should not be connected can be prevented, thereby improving insulation reliability.

[0078] The connection structure and method for manufacturing the connection structure according to the present invention use a specific conductive material, which makes it easier for solder to accumulate between the first electrode and the second electrode, allowing for efficient solder placement on the electrode (line). Furthermore, it is difficult for a portion of the solder to be placed in areas (spaces) where electrodes are not formed, significantly reducing the amount of solder placed in these areas. Consequently, the conductivity reliability between the first electrode and the second electrode can be improved. Moreover, electrical connections between laterally adjacent electrodes that should not be connected can be prevented, thereby improving insulation reliability.

[0079] Furthermore, in order to efficiently arrange solder on the electrodes and to significantly reduce the amount of solder placed in areas where electrodes are not formed, it is preferable to use a conductive paste rather than a conductive film as the conductive material.

[0080] Furthermore, using conductive paste instead of conductive film makes it easy to adjust the thickness of the connection and solder joints by changing the amount of conductive paste applied. On the other hand, with conductive film, there is a problem in that in order to change or adjust the thickness of the connection joint, it is necessary to prepare conductive film of different thicknesses or conductive film of a predetermined thickness. In addition, with conductive film, compared to conductive paste, it is not possible to sufficiently lower the melt viscosity of the conductive film at the solder melting temperature, which tends to inhibit solder aggregation.

[0081] The thickness of the solder joint between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, preferably 100 μm or less, and more preferably 80 μm or less. The solder wetted area on the electrode surface (the area in contact with solder out of 100% of the exposed area of ​​the electrode) is preferably 50% or more, more preferably 70% or more, and preferably 100% or less.

[0082] Specific embodiments of the present invention will be described below with reference to the drawings.

[0083] Figure 1 is a schematic cross-sectional view showing a connection structure using a conductive material according to the first embodiment of the present invention.

[0084] The connection structure 1 shown in Figure 1 comprises a first connection target member 2, a second connection target member 3, and a connection portion 4 connecting the first connection target member 2 and the second connection target member 3. The material of the connection portion 4 is the conductive material described above. The connection portion 4 is formed from the conductive material described above. In this embodiment, the conductive material includes a thermosetting compound, a plurality of solder particles, a flux, and an organic acid.

[0085] The connecting portion 4 has a solder portion 4A where multiple solder particles are gathered and joined together, and a cured portion 4B where a thermosetting compound has been heat-cured.

[0086] The first connection target member 2 has a plurality of first electrodes 2a on its surface (top surface). The second connection target member 3 has a plurality of second electrodes 3a on its surface (bottom surface). The first electrodes 2a and the second electrodes 3a are electrically connected by a solder portion 4A. Therefore, the first connection target member 2 and the second connection target member 3 are electrically connected by a solder portion 4A. In the connection portion 4, between the first electrodes 2a and the second electrodes 3a, there are no solder particles in a region different from the solder portion 4A (the hardened portion 4B). In a region different from the solder portion 4A (the hardened portion 4B), there are no solder particles separated from the solder portion 4A. However, if the amount is small, solder particles may be present in a region different from the solder portion 4A (the hardened portion 4B) between the first electrodes 2a and the second electrodes 3a.

[0087] As shown in Figure 1, in the connection structure 1, multiple solder particles accumulate between the first electrode 2a and the second electrode 3a. After the multiple solder particles melt, the molten solder particles wet and spread across the surface of the electrodes before solidifying, forming a solder portion 4A. As a result, the contact area between the solder portion 4A and the first electrode 2a, and between the solder portion 4A and the second electrode 3a, becomes larger. In other words, by using solder particles, the contact area between the solder portion 4A and the first electrode 2a, and between the solder portion 4A and the second electrode 3a, becomes larger compared to the case where conductive particles with an outer surface made of metal such as nickel, gold, or copper are used. This also improves the conductivity reliability and connection reliability of the connection structure 1. Note that flux generally becomes gradually deactivated by heating.

[0088] In the connection structure 1 shown in Figure 1, the entirety of the solder portion 4A is located in the opposing region between the first and second electrodes 2a and 3a. Also, in the connection structure 1 shown in Figure 1, the entirety of the cured material portion 4B is located in the opposing region between the first and second electrodes 2a and 3a. In the above connection structure, most of the solder portion is located in the opposing region between the first and second electrodes, and a portion of the solder portion may protrude laterally from the opposing region between the first and second electrodes. The solder portion that protrudes laterally from the opposing region between the first and second electrodes is a part of the solder portion and not solder particles separated from the solder portion. In this embodiment, the amount of solder particles separated from the solder portion can be reduced, but solder particles separated from the solder portion may be present in the cured material portion. Also, in the above connection structure, most of the cured material portion is located in the opposing region between the first and second electrodes, and a portion of the cured material portion may protrude laterally from the opposing region between the first and second electrodes.

[0089] When viewing the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connection portion, and the second electrode, it is preferable that the solder portion in the connection portion occupies 50% or more of the area of ​​the opposing portions of the first electrode and the second electrode. The area of ​​the portion in which the solder portion in the connection portion is located within 100% of the area of ​​the opposing portions of the first electrode and the second electrode is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, particularly preferably 80% or more, and most preferably 90% or more. By satisfying the above preferred configuration, the conductivity reliability can be further enhanced.

[0090] Next, with reference to Figure 2, an example of a method for manufacturing a connecting structure 1 using a conductive material according to one embodiment of the present invention will be described.

[0091] First, a first connection target member 2 having a first electrode 2a on its surface (top surface) is prepared. Next, as shown in Figure 2(a), a conductive material 11 containing a thermosetting compound 11B, a plurality of solder particles 11A, flux, and an organic acid is placed on the surface of the first connection target member 2 (first step).

[0092] A conductive material 11 is placed on the surface of the first connection target member 2 on which the first electrode 2a is provided. After the placement of the conductive material 11, solder particles 11A are placed both on the first electrode 2a (line) and on the region (space) where the first electrode 2a is not formed. Note that the conductive material may be placed only on the surface of the first electrode.

[0093] Methods for arranging the conductive material 11 include coating with a dispenser, screen printing, and ejection with an inkjet device.

[0094] Furthermore, a second connection target member 3 having a second electrode 3a on its surface (bottom surface) is prepared. Next, as shown in Figure 2(b), the second connection target member 3 is placed on the conductive material 11 on the surface of the first connection target member 2, on the surface of the conductive material 11 opposite to the first connection target member 2 side (second step). The second connection target member 3 is placed on the surface of the conductive material 11 from the side of the second electrode 3a. At this time, the first electrode 2a and the second electrode 3a are facing each other.

[0095] Next, the conductive material 11 is heated to a temperature above the melting point of the solder particles 11A (third step). Preferably, the conductive material 11 is heated to a temperature above the curing temperature of the thermosetting compound 11B. During this heating, the solder particles 11A that were present in areas where electrodes were not formed gather between the first electrode 2a and the second electrode 3a (self-aggregation effect). If a conductive paste is used instead of a conductive film, the solder particles 11A gather even more effectively between the first electrode 2a and the second electrode 3a. The solder particles 11A also melt and join together. The thermosetting compound 11B also heats harden. As a result, as shown in Figure 2(c), a connection portion 4 connecting the first connection target member 2 and the second connection target member 3 is formed by the conductive material 11. The connection portion 4 is formed by the conductive material 11, a solder portion 4A is formed by the joining of multiple solder particles 11A, and a cured portion 4B is formed by the heat hardening of the thermosetting compound 11B. If the solder particles 11A have moved sufficiently, it is not necessary to maintain a constant temperature from the time the movement of solder particles 11A not located between the first electrode 2a and the second electrode 3a begins until the movement of solder particles 11A between the first electrode 2a and the second electrode 3a is completed.

[0096] In this embodiment, it is preferable not to apply pressure in the second and third steps. In this case, the weight of the second connection target member 3 is added to the conductive material 11. Therefore, when the connection portion 4 is formed, the solder particles 11A gather more effectively between the first electrode 2a and the second electrode 3a. If pressure is applied in at least one of the second and third steps, the tendency for the solder particles 11A to gather between the first electrode 2a and the second electrode 3a to be inhibited increases.

[0097] Furthermore, in this embodiment, since no pressure is applied, even if the first connection target member 2 and the second connection target member 3 are superimposed while the alignment of the first electrode 2a and the second electrode 3a is misaligned, the misalignment can be corrected and the first electrode 2a and the second electrode 3a can be connected (self-alignment effect). This is because the molten solder that has self-aggregated between the first electrode 2a and the second electrode 3a becomes more energetically stable when the contact area between the solder and other components of the conductive material is minimized, and a force acts to create an aligned connection structure, which is the connection structure with the smallest contact area. In this case, it is desirable that the conductive material has not hardened and that the viscosity of components other than the solder particles of the conductive material is sufficiently low at that temperature and time.

[0098] In this way, the connection structure 1 shown in Figure 1 is obtained. Note that the second and third steps may be performed consecutively. Alternatively, after performing the second step, the laminate of the first connection target member 2, the conductive material 11, and the second connection target member 3 may be moved to the heating section and the third step may be performed. To perform the heating, the laminate may be placed on a heating member, or the laminate may be placed in a heated space.

[0099] The heating temperature in the third step described above is not particularly limited.

[0100] The heating method in the third step described above includes heating the entire connecting structure using a reflow oven or oven to a temperature above the melting point of the solder particles and above the curing temperature of the thermosetting compound, or locally heating only the connecting portion of the connecting structure.

[0101] The first and second connection targets described above are not particularly limited. Specifically, the first and second connection targets include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors and diodes, as well as electronic components such as resin films, printed circuit boards, flexible printed circuit boards, flexible flat cables, rigid-flexible circuit boards, glass epoxy circuit boards and glass circuit boards. It is preferable that the first and second connection targets are electronic components.

[0102] Preferably, at least one of the first and second connection target members is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board. Preferably, the second connection target member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board. Resin films, flexible printed circuit boards, flexible flat cables, and rigid flexible circuit boards have the properties of being highly flexible and relatively lightweight. When a conductive film is used to connect such connection target members, solder particles tend not to accumulate on the electrodes. In contrast, by using a conductive paste, even when using a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board, solder particles can be efficiently collected on the electrodes, thereby sufficiently improving the conductivity reliability between electrodes. When using a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board, the effect of improving conductivity reliability between electrodes by not applying pressure is obtained even more effectively compared to when using other connection target members such as semiconductor chips.

[0103] Examples of electrodes provided on the above-mentioned connection target member include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the above-mentioned connection target member is a flexible printed circuit board, the electrodes are preferably gold electrodes, nickel electrodes, tin electrodes, silver electrodes, or copper electrodes. When the above-mentioned connection target member is a glass substrate, the electrodes are preferably aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, or tungsten electrodes. In the case of aluminum electrodes, the electrodes may be made solely of aluminum, or they may be electrodes in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

[0104] In the connection structure according to the present invention, it is preferable that the first electrode and the second electrode are arranged in an area array or peripheral configuration. The effects of the present invention are more effectively demonstrated when the first electrode and the second electrode are arranged in an area array or peripheral configuration. An area array is a structure in which electrodes are arranged in a grid pattern on the surface of the member to be connected. A peripheral configuration is a structure in which electrodes are arranged on the outer periphery of the member to be connected. In the case of a structure in which electrodes are arranged in a comb shape, it is sufficient for solder particles to aggregate along a direction perpendicular to the comb, whereas in the area array or peripheral configuration, it is necessary for solder particles to aggregate uniformly across the entire surface on which the electrodes are arranged. Therefore, while conventional methods tend to result in uneven solder amounts, the method of the present invention makes it possible to aggregate solder particles uniformly across the entire surface.

[0105] The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to the following examples.

[0106] The following materials were prepared.

[0107] (thermosetting compound) Thermosetting compound 1 (phenol novolac type epoxy compound, DOW "DEN431", viscosity 1400 mPa·s at 51.7°C) Thermosetting compound 2 (phenol novolac type epoxy compound, DOW "DEN438", viscosity 35,000 mPa·s at 51.7°C)

[0108] (Solder particles) Solder particle 1 (SnAgCu solder particle, manufactured by Mitsui Mining & Smelting Co., Ltd., "Sn96.5Ag3Cu0.5 DS10", average particle size 10.0 μm, melting point: 219℃) Solder particles 2 (SnAgCu solder particles, manufactured by Mitsui Mining & Smelting Co., Ltd., "Sn96.5Ag3Cu0.5 ST-3", average particle size 3.0 μm, melting point: 219℃) Solder particles 3 (SnAgCu solder particles, manufactured by Mitsui Mining & Smelting Co., Ltd., "Sn96.5Ag3Cu0.5 ST-2", average particle size 2.0 μm, melting point: 219℃) Solder particles 4 (SnBi solder particles, manufactured by Mitsui Mining & Smelting Co., Ltd., "Sn42Bi58 DS10", average particle size 10.0 μm, melting point 139°C) Solder particles 5 (SnBi solder particles, manufactured by Mitsui Mining & Smelting Co., Ltd., "Sn42Bi58 ST-3", average particle size 3.0 μm, melting point 139°C) Solder particles 6 (SnBi solder particles, manufactured by Mitsui Mining & Smelting Co., Ltd., "Sn42Bi58 ST-2", average particle size 2.0 μm, melting point 139°C)

[0109] (Flux) Benzylamine adipic acid salt (prepared according to Synthesis Example 1 below; melting point 180°C, boiling point of adipic acid 338°C, boiling point of benzylamine 185°C) Benzylamine glutarate salt (prepared according to Synthesis Example 2 below; melting point 108°C, boiling point of glutaric acid 200°C, boiling point of benzylamine 185°C)

[0110] (Synthesis Example 1) In a glass bottle, 24 g of water (the reaction solvent) and 13.89 g of adipic acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed and dissolved until homogeneous at room temperature. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixture. The resulting mixture was placed in a refrigerator at 5°C to 10°C and left overnight. The precipitated crystals were separated by filtration, washed with water, and vacuum-dried to obtain benzylamine adipic acid salt.

[0111] (Synthesis Example 2) In a glass bottle, 24 g of water (the reaction solvent) and 13.212 g of glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were added and dissolved until homogeneous at room temperature. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixture. The resulting mixture was placed in a refrigerator at 5-10°C and left overnight. The precipitated crystals were separated by filtration, washed with water, and vacuum-dried to obtain flux 1.

[0112] (organic acid) N-oleoyl sarcosine (unsaturated monocarboxylic acid with amide bond, 21 carbon atoms) Oleic acid (unsaturated monocarboxylic acid, 18 carbon atoms) Palmitic acid (monocarboxylic acid, 16 carbon atoms) Myristic acid (monocarboxylic acid, 14 carbon atoms) Lauric acid (monocarboxylic acid, 12 carbon atoms) Octanoic acid (monocarboxylic acid, 8 carbon atoms)

[0113] (Example 1~ 7, Reference example 8~ 12 and Comparative Examples 1,2) Preparation of conductive materials (anisotropic conductive paste): A conductive material (anisotropic conductive paste) was obtained by blending the components shown in Tables 1-4 below in the amounts shown in Tables 1-4 below.

[0114] (evaluation) (1) Initial thixotropic index, and (2) Storage stability The viscosity of the obtained conductive material was measured using an E-type viscometer (TVE22L, manufactured by Toki Sangyo Co., Ltd.).

[0115] Viscosity (ηA) of the above conductive material immediately after preparation at 25°C and 5 rpm. Viscosity (ηB) of the above conductive material immediately after preparation at 25°C and 0.5 rpm. Viscosity (ηC) of the above conductive material at 25°C and 5 rpm after 24 hours. Viscosity (ηD) of the above conductive material at 25°C and 0.5 rpm after 24 hours.

[0116] From the measurement results, the ratio (ηB / ηA) (initial thixotropic index) and the ratio (ηD / ηC) (thixotropic index after 24 hours) were calculated. Furthermore, the ratio ((ηD / ηC) / (ηB / ηA)) was calculated. More specifically, ηC and ηD were determined by measuring the viscosity of the conductive material after it had been left for 24 hours at 25°C and 50%RH. The initial thixotropic index and storage stability were judged according to the following criteria.

[0117] [Criteria for determining the initial thixotropic index] ○○: Ratio (ηB / ηA) is 3.0 or higher ○: Ratio (ηB / ηA) is 2.5 or greater and less than 3.0 ×: Ratio (ηB / ηA) is less than 2.5

[0118] [Criteria for determining storage stability] ○○: The ratio ((ηD / ηC) / (ηB / ηA)) is 0.90 or higher. ○: The ratio ((ηD / ηC) / (ηB / ηA)) is 0.60 or greater and less than 0.90. ×: Ratio ((ηD / ηC) / (ηB / ηA)) is less than 0.60

[0119] (3) Solder cohesiveness Fabrication of connection structures: As the first and second connection target members, a glass epoxy substrate (material: FR-4, thickness: 0.5 mm) having a Cu / Au electrode pattern with an L / S ratio of 60 μm / 90 μm on its surface was prepared. A conductive material (anisotropic conductive paste) immediately after fabrication was screen printed onto the upper surface of the first connection target member to a thickness of 100 μm, forming a conductive material (anisotropic conductive paste) layer. Next, the second connection target member was laminated on the upper surface of the conductive material (anisotropic conductive paste) layer so that the electrodes faced each other. The weight of the second connection target member was added to the conductive material (anisotropic conductive paste) layer. From that state, the conductive material (anisotropic conductive paste) layer was heated to a temperature of 260°C (for solder particles 1-3) or 180°C (for solder particles 4-6) to cure the conductive material (anisotropic conductive paste) layer, and a connection structure having a connection part connecting the first connection target member and the second connection target member was obtained. No pressure was applied during heating.

[0120] Evaluation of solder cohesion: In the obtained connection structure, microscopic images of the opposing portions of the first electrode and the second electrode were acquired using an optical microscope (OLYMPUS BX53M) in the stacking direction between the first electrode, the connection portion, and the second electrode. Next, the acquired microscopic images were processed using the image processing software "ImageJ" to convert the amount of side balls formed around the opposing portions of the first electrode and the second electrode (solder portion in the connection portion) into pixel values. Solder cohesiveness was determined according to the following criteria.

[0121] [Criteria for determining solder cohesiveness] ○○: Pixel value less than 1500 ○: Pixel value is between 1500 and 3000 ×: Pixel value is 3000 or higher

[0122] The composition of the conductive materials and the results are shown in Tables 1-4 below.

[0123] [Table 1]

[0124] [Table 2]

[0125] [Table 3]

[0126] [Table 4] [Explanation of Symbols]

[0127] 1…Connection structure 2…First connection target member 2a...First electrode 3…Second connection target member 3a...Second electrode 4…Connection part 4A...Solder section 4B…Cured product part 11…Conductive materials 11A... Solder particles 11B...Thermosetting compound

Claims

1. A conductive material comprising a thermosetting compound, multiple solder particles, flux, and an organic acid. The organic acid comprises N-myristoyl sarcosine, N-lauroyl sarcosine, or N-oleoyl sarcosine. A conductive material wherein the content of solder particles in 100% by weight of the conductive material is 40% by weight or more and 90% by weight or less.

2. The conductive material according to claim 1, wherein the flux is a polycarboxylic acid or a polycarboxylic acid amine salt.

3. The conductive material according to claim 1 or 2, which either does not contain a thermosetting agent or contains a thermosetting agent in an amount of 30% by weight or less in 100% by weight of the conductive material.

4. The conductive material according to claim 3, which does not contain a thermosetting agent.

5. The conductive material according to claim 1 or 2, wherein the particle size of the solder particles is 0.1 μm or more and 10.0 μm or less.

6. The conductive material according to claim 1 or 2, wherein the ratio of the viscosity at 25°C and 0.5 rpm to the viscosity at 25°C and 5 rpm is 2.5 or more.

7. A conductive material according to claim 1 or 2, which is a conductive paste.

8. A first connection target member having a first electrode on its surface, A second connection target member having a second electrode on its surface, It comprises a connecting portion that connects the first member to be connected and the second member to be connected, The material of the connecting portion is the conductive material described in claim 1 or 2. A connection structure in which the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

9. A step of placing the conductive material described in claim 1 or 2 on the surface of a first connection target member having a first electrode on its surface, A step of arranging a second connection target member having a second electrode on its surface on the surface of the conductive material opposite to the first connection target member side, such that the first electrode and the second electrode face each other. A method for manufacturing a connection structure, comprising the steps of: heating the conductive material to a point above the melting point of the solder particles to form a connection portion connecting the first connection target member and the second connection target member using the conductive material; and electrically connecting the first electrode and the second electrode with the solder portion in the connection portion.

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