Conductive material, connection structure, and method for manufacturing connection 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 conductive material and a method for manufacturing the connection structure. [Background technology]

[0002] In recent years, a method of connecting a substrate and an electronic component using a conductive material containing solder particles or the like has been used. In addition, an anisotropic conductive material may be used as the conductive material. In the anisotropic conductive material, conductive particles are dispersed in a binder resin.

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

[0004] The following Patent Document 1 discloses an anisotropic conductive film formed by forming an adhesive resin composition in which conductive particles are dispersed. The adhesive resin composition contains 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] The following Patent Document 2 discloses conductive fine particles in which a carboxylic acid or a carboxylate is attached to the surface of a conductive base particle. The conductive base particle is a conductive base particle formed of tin or an alloy thereof, or a conductive base particle having a solder layer formed of tin or an alloy thereof on the outermost surface. Patent Document 2 also describes that it is preferable that a phosphate or a phosphoric acid ester is further attached to the surface of the conductive base particle.

[0006] The following Patent Document 3 discloses an adhesive composition containing (A) an alicyclic epoxy compound and (B1) a cation generator. (B1) The 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] JP 2003-229024 A [Patent Document 2] JP 2011-009184 A [Patent Document 3] JP 2011-111556 A Summary of the Invention [Problem to be solved by the invention]

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

[0009] An object of the present invention is to provide a conductive material capable of improving solder cohesion and storage stability. Another object of the present invention is to provide a connection structure using the conductive material and a method for manufacturing the connection structure. [Means for solving the problem]

[0010] According to a broad aspect of the present invention, there is provided a conductive material comprising a thermosetting compound, a plurality of solder particles, a flux, and an organic acid, the organic acid having an aliphatic skeleton and having 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.

[0011] In a specific 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 specific aspect of the conductive material according to the present invention, the flux is a polyvalent carboxylic acid or a polyvalent carboxylic acid amine salt.

[0015] In a specific aspect of the conductive material according to the present invention, the conductive material does not contain a heat curing agent, or contains 30% by weight or less of a heat curing agent relative to 100% by weight of the conductive material.

[0016] In a particular aspect of the conductive material according to the present invention, the conductive material does not include a thermal curing agent.

[0017] In a specific aspect of the conductive material according to the present invention, the solder particles have a particle size of 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 specific 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 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, wherein the material of the connection portion is the conductive material described above, 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-mentioned conductive material to place the conductive material on a surface of a first connection target member having a first electrode on its surface; placing a second connection target member having a second electrode on its surface opposite the first connection target member side of the conductive material so that the first electrode and the second electrode face each other; and heating the conductive material to a temperature 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 a solder portion in the connection portion. Effect of the Invention

[0022] The conductive material according to the present invention is a conductive material containing a thermosetting compound, a plurality of solder particles, a flux, and an organic acid, the organic acid having an aliphatic skeleton and a carbon number of 12 or more, and 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. Since the conductive material according to the present invention has the above configuration, it is possible to improve solder cohesion and storage stability. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a connection structure using a conductive material according to a first embodiment of the present invention. [Diagram 2]2(a) to (c) are cross-sectional views illustrating the steps of an example of a method for producing a connection structure using the conductive material according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The present invention will be described in detail below.

[0025] (Conductive materials) The conductive material according to the present invention includes 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 has an aliphatic skeleton and has 12 or more carbon atoms. In the conductive material according to the present invention, 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.

[0026] Since the conductive material according to the present invention has the above-mentioned configuration, it is possible to improve the solder cohesion and storage stability.

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

[0028] In order to more effectively exert the effects of the present invention, the conductive material is preferably in a liquid state at 25° C., and is preferably a conductive paste.

[0029] From the viewpoint of disposing the solder on the electrodes more efficiently, the viscosity (ηA) of the conductive material immediately after preparation 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 by the types and amounts of the blended components.

[0030] The ratio (initial thixotropic index) of the viscosity (ηB) of the conductive material immediately after preparation at 25°C and 0.5 rpm to the viscosity (ηA) of the conductive material immediately after preparation at 25°C and 5 rpm is preferably 2.0 or more, more preferably 2.5 or more, and even more preferably 3.0 or more. The ratio (ηB / ηA) is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. When the ratio (ηB / ηA) is equal to or greater than the lower limit and equal to or less than the upper limit, the arrangement property (particularly printability) of the conductive material can be improved.

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

[0032] From the viewpoint of further enhancing 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, and is preferably 400 Pa s or less, 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 more, more preferably 2.5 or more, and even more preferably 3.0 or more. The ratio (ηD / ηC) is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. When the ratio (ηD / ηC) is equal to or more than the lower limit and equal to or less than the upper limit, the positionability (particularly printability) of the conductive material can be improved over a long period of time.

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

[0035] The conductive material can be used as a conductive paste, a conductive film, or the like. The conductive paste is preferably an anisotropic conductive paste, and the conductive film is preferably an anisotropic conductive film. From the viewpoint of more efficiently disposing the solder on the electrodes, the conductive material is preferably a conductive paste. The conductive material is preferably used for electrically connecting the electrodes. The conductive material is preferably a circuit connecting material.

[0036] Each component contained in the conductive material will be described below. In the following description, "(meth)acrylic" means either or both of "acrylic" and "methacrylic".

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

[0038] The thermosetting compound 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 increasing the conduction reliability, the thermosetting compound preferably contains an epoxy compound or an episulfide compound, and more preferably contains an epoxy compound. The thermosetting compound may be used alone or in combination of two or more kinds.

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

[0040] From the viewpoint of increasing the heat resistance of the cured product and increasing the insulation reliability between electrodes that must 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 is liquid or solid at room temperature (25°C), and when the epoxy compound is solid at room temperature, the melting temperature of the epoxy compound is preferably equal to or lower than the melting point of the solder particles. By using the preferred epoxy compound, the viscosity becomes high at the stage where the connection target members are bonded together, so that it is possible to suppress the positional deviation between the first connection target member and the second connection target member when acceleration is applied due to an impact during transportation, etc. Furthermore, the viscosity of the conductive material can be significantly reduced by the heat during curing, and the aggregation of the solder particles can be efficiently promoted.

[0042] In 100% by weight of the conductive material, the content of the 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 thermosetting compound is equal to or more than the lower limit and equal to or less than the upper limit, the effect of the present invention can be more effectively exhibited, and the insulation reliability between electrodes that should not be connected and the conduction reliability between electrodes that should be connected can be more effectively improved. In addition, when the content of the thermosetting compound is equal to or more than the lower limit, the impact resistance can be improved.

[0043] In 100% by weight of the 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 equal to or more than the lower limit and equal to or less than the upper limit, the effect of the present invention can be more effectively exhibited, and the insulation reliability between electrodes that should not be connected and the conduction reliability between electrodes that should be connected can be more effectively improved. In addition, when the content of the epoxy compound is equal to or more than the lower limit, the impact resistance can be improved.

[0044] (solder particles) The conductive material includes a plurality of solder particles. The solder particles are formed of solder at both the center and the outer surface. The solder particles are particles in which both the center and the outer surface are solder. When conductive particles having a base particle formed of a material other than solder and a solder portion arranged on the surface of the base particle are used instead of the solder particles, the conductive particles are less likely to gather on the electrode. In addition, the conductive particles have low solder bonding between the conductive particles, so that the conductive particles that have moved onto the electrode tend to move out of the electrode, and the effect of suppressing positional deviation between the electrodes also tends to be low.

[0045] The solder is preferably a metal having a melting point of 450°C or less (low melting point metal). The solder particles are preferably metal particles having a melting point of 450°C or less (low melting point metal particles). The low melting point metal particles are particles containing a low melting point metal. The low melting point metal refers to a metal having 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 are preferably a low melting point solder having 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, and 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 equal to or higher than the lower limit and equal to or lower than the upper limit, the solder particles can be more efficiently arranged on the electrodes, and the insulation reliability and conduction reliability can be more effectively improved.

[0047] The melting point of the solder particles can be determined by differential scanning calorimetry (DSC), such as "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, and 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 equal to or greater than the lower limit and equal to or less than the upper limit, the effect of the present invention can be more effectively exhibited. Although it is difficult to sufficiently suppress the variation in the transfer area with a conventional conductive material containing solder particles with a relatively small average particle diameter, the present invention can effectively suppress the variation in the transfer area even when the average particle diameter of the solder particles is relatively small. In addition, when the average particle diameter of the solder particles is equal to or greater than the lower limit and equal to or less than the upper limit, the solder particles can be more efficiently arranged on the electrodes, and the conduction reliability and connection reliability can be more 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, even if the average particle diameter of the solder particles is quite small, the effect of the present invention can be effectively exhibited.

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

[0050] 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. The content of the solder particles in 100% by weight of the conductive material is preferably 43% by weight or more, more preferably 45% by weight or more, even more preferably 50% by weight or more, and preferably 85% by weight or less, more preferably 80% by weight or less, even more preferably 70% by weight or less. When the content of the solder particles is equal to or more than the lower limit, the solder cohesion can be further improved. When the content of the solder particles is equal to or less than the upper limit, the arrangement (particularly printability) of the conductive material can be improved.

[0051] (Flux) The conductive material includes a flux. By using the flux, the solder can be arranged on the electrode more efficiently. The flux is not particularly limited. As the flux, a flux generally used for solder joints or the like can be used.

[0052] Examples of the flux include zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, phosphoric acid, an amine salt of phosphoric acid, a derivative of phosphoric acid, a polycarboxylic acid, an amine salt of a polycarboxylic acid, an organic halide, hydrazine, an amine compound different from both the amine salt of phosphoric acid and the amine salt of a polycarboxylic acid, and rosin, etc. Only one type of the flux may be used, or two or more types may be used in combination.

[0053] The molten salt may, for example, be ammonium chloride.

[0054] The above-mentioned phosphoric acid amine salts include acid phosphate amine salts, etc. The above-mentioned acid phosphate amine salts include alkyl acid phosphate amine salts, etc., more specifically, 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 polycarboxylic acid has two or more carboxy groups. The polycarboxylic acid may be a dicarboxylic acid or a tricarboxylic acid. Examples of the 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 polyvalent carboxylic acid amine salt include cyclohexylamine glutaric acid salt, cyclohexylamine adipate salt, benzylamine glutaric acid salt, and benzylamine adipate salt.

[0057] Examples of the amine compound different from both the amine salt of a phosphoric acid and the amine salt of a polycarboxylic acid include dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, and carboxybenzotriazole.

[0058] The rosin may be activated rosin or non-activated rosin. The rosin is a rosin containing abietic acid as a main component. The rosin may be abietic acid or acrylic modified rosin.

[0059] The flux preferably contains a polycarboxylic acid, phosphoric acid, a polycarboxylic amine salt, or a phosphoric amine salt. The flux is more preferably a polycarboxylic acid or a polycarboxylic amine salt, and even more preferably a polycarboxylic amine salt. By using these preferable fluxes, it is possible to more effectively improve the insulation reliability between electrodes that should not be connected and the conduction reliability between electrodes that should be connected.

[0060] The activation temperature (melting point) of the flux is preferably 50° C. or higher, more preferably 70° C. or higher, and even more preferably 80° C. or higher, and is 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 equal to or higher than the lower limit and equal to or lower than the upper limit, the flux effect is more effectively exerted, and the solder can be more efficiently disposed on the electrodes.

[0061] The melting point of the flux can be determined by differential scanning calorimetry (DSC). An example of a DSC device is "EXSTAR DSC7020" manufactured by SII Corporation.

[0062] The flux preferably has a boiling point of 400° C. or lower.

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

[0064] In 100% by weight of the conductive material, the content of the flux is preferably 5% by weight or more, more preferably 8% by weight or more, and preferably 20% by weight or less, more preferably 15% by weight or less. When the content of the flux is equal to or more than the lower limit and equal to or less than the upper limit, it becomes more difficult for an oxide film to be formed on the surfaces of the solder and the electrodes, and further, the oxide film formed on the surfaces of the solder and the electrodes can be removed more effectively.

[0065] (organic acid) The conductive material contains an organic acid, and the use of the organic acid can improve the thixotropy of the conductive material.

[0066] The organic acid has an aliphatic skeleton and a carbon number of at least 12. The carbon number of the organic acid is preferably at least 14, more preferably at least 16, and is preferably at most 24, more preferably at most 22. When the carbon number of the organic acid is at least the lower limit and at most 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, N-oleoyl sarcosine, etc. The above organic acids may be used alone 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 carboxy 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 the oxygen barrier property, the organic acid is preferably one having an unsaturated bond. From the viewpoint of improving the oxygen barrier property and further improving the storage stability of the conductive material, the organic acid is preferably an unsaturated monocarboxylic acid. From the viewpoint of improving the oxygen barrier property, the number of unsaturated bonds in the organic acid is preferably 1 or more, more preferably 2 or more, and is preferably 6 or less, more preferably 4 or less.

[0069] From the viewpoint of reducing outgassing when the conductive material is heated, the organic acid preferably has an amide bond. The organic acid may have one amide bond, two amide bonds, or more than two 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 exerting the effects of the present invention more effectively, the organic acid preferably contains lauric acid, myristic acid, palmitic acid, oleic acid, or N-oleoyl sarcosine, more preferably contains oleic acid or N-oleoyl sarcosine, and particularly preferably contains N-oleoyl sarcosine.

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

[0072] (Other ingredients) The conductive material may contain various additives, as necessary, such as a filler, an extender, a softener, a plasticizer, a thixotropic agent, a leveling agent, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a lubricant, an antistatic agent, and a flame retardant.

[0073] From the viewpoint of further improving storage stability, it is preferable that the conductive material does not contain a heat curing agent, or contains 30% by weight or less of the heat curing agent in 100% by weight of the conductive material. From the viewpoint of further improving storage stability, the content of the heat curing 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 heat curing agent.

[0074] Examples of the heat curing agent include imidazole curing agents, thiol curing agents, amine curing agents, phenolic curing agents, acid anhydride curing agents, thermal cationic initiators, and thermal radical generators. The heat curing agents may be used alone or in combination of two or more.

[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 part 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 part 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 part in the connection part.

[0076] The method for manufacturing a connection structure according to the present invention includes a step of using the conductive material described above to place the conductive material on a surface of a first connection target member having a first electrode on its surface. The method for manufacturing a connection structure according to the present invention includes a step of placing a second connection target member having a second electrode on its surface opposite to the first connection target member side of the conductive material, such that the first electrode and the second electrode face each other. The method for manufacturing a connection structure according to the present invention includes a step of forming a connection part connecting the first connection target member and the second connection target member from the conductive material by heating the conductive material to a melting point of the solder particles or higher, and electrically connecting the first electrode and the second electrode with a solder part in the connection part.

[0077] In the connection structure and the method for manufacturing the connection structure according to the present invention, a specific conductive material is used, so that a solder part can be well formed between the first electrode and the second electrode. In addition, a part of the solder is unlikely to be disposed in an area (space) where no electrode is formed, and the amount of solder disposed in the area where no electrode is formed can be significantly reduced. Therefore, the reliability of the conduction between the first electrode and the second electrode can be improved. Moreover, it is possible to prevent an electrical connection between laterally adjacent electrodes that should not be connected, and thus the reliability of the insulation can be improved.

[0078] In the connection structure and the method for manufacturing the connection structure according to the present invention, a specific conductive material is used, so that the solder is likely to gather between the first electrode and the second electrode, and the solder can be efficiently arranged on the electrodes (lines). In addition, a part of the solder is unlikely to be arranged in an area (space) where no electrodes are formed, and the amount of solder arranged in the area where no electrodes are formed can be significantly reduced. Therefore, the reliability of the conduction between the first electrode and the second electrode can be improved. Moreover, it is possible to prevent electrical connection between laterally adjacent electrodes that should not be connected, and the reliability of the insulation can be improved.

[0079] Furthermore, in order to efficiently place the solder on the electrodes and significantly reduce the amount of solder placed in areas where no electrodes are formed, it is preferable to use a conductive paste as the conductive material rather than a conductive film.

[0080] In addition, if a conductive paste is used instead of a conductive film, the thickness of the connection and solder parts can be easily adjusted by changing the amount of conductive paste applied. On the other hand, in the case of a conductive film, in order to change or adjust the thickness of the connection, it is necessary to prepare a conductive film of a different thickness or a conductive film of a specified thickness. In addition, compared to a conductive paste, a conductive film cannot sufficiently reduce the melt viscosity of the conductive film at the melting temperature of the solder, and the cohesion of the solder tends to be easily inhibited.

[0081] The thickness of the solder between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, and preferably 100 μm or less, more preferably 80 μm or less. The solder wetted area on the surface of the electrode (the area in contact with the 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] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

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

[0084] The connection structure 1 shown in Fig. 1 includes 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 connection portion 4 has a solder portion 4A in which a plurality of solder particles are gathered and joined together, and a cured portion 4B in which a thermosetting compound is thermally cured.

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

[0087] As shown in FIG. 1, in the connection structure 1, a plurality of solder particles are gathered between the first electrode 2a and the second electrode 3a, and after the plurality of solder particles melt, the molten solder particles wet and spread over the surface of the electrodes, and then solidify to form the solder portion 4A. Therefore, the connection area between the solder portion 4A and the first electrode 2a, and between the solder portion 4A and the second electrode 3a is increased. That is, by using the 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 is increased compared to the case where conductive particles whose outer surface is a metal such as nickel, gold, or copper are used. This also increases the conduction reliability and connection reliability in the connection structure 1. In addition, flux is generally gradually deactivated by heating.

[0088] In the connection structure 1 shown in FIG. 1, all of the solder portion 4A is located in the region between the first and second electrodes 2a, 3a. In the connection structure 1 shown in FIG. 1, all of the hardened portion 4B is located in the region between the first and second electrodes 2a, 3a. In the connection structure, most of the solder portion is located in the region between the first and second electrodes, and a part of the solder portion may protrude laterally from the region between the first and second electrodes. The solder portion protruding laterally from the region between the first and second electrodes is a part of the solder portion, and is not a solder particle separated from the solder portion. In the present embodiment, the amount of solder particles separated from the solder portion can be reduced, but the solder particles separated from the solder portion may be present in the hardened portion. In the connection structure, most of the hardened portion is located in the region between the first and second electrodes, and a part of the hardened portion may protrude laterally from the region between the first and second electrodes.

[0089] When the portion where the first electrode and the second electrode face each other is viewed in the lamination direction of the first electrode, the connection portion, and the second electrode, the solder portion in the connection portion is preferably disposed in 50% or more of the 100% area of ​​the portion where the first electrode and the second electrode face each other. Of the 100% area of ​​the portion where the first electrode and the second electrode face each other, the area of ​​the portion where the solder portion in the connection portion is disposed 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. When the solder portion in the connection portion satisfies the above-mentioned preferred aspects, the electrical connection reliability can be further improved.

[0090] Next, with reference to FIG. 2, an example of a method for producing the connection 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 (upper surface) is prepared. Next, as shown in Fig. 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 on which the first electrode 2a of the first connection target component 2 is provided. After the conductive material 11 is placed, solder particles 11A are placed on both the first electrode 2a (lines) and the area (space) where the first electrode 2a is not formed. The conductive material may be placed only on the surface of the first electrode.

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

[0094] Also, a second connection target member 3 having a second electrode 3a on its surface (lower surface) is prepared. Next, as shown in FIG. 2(b), in the conductive material 11 on the surface of the first connection target member 2, a second connection target member 3 is placed 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 second electrode 3a side. At this time, the first electrode 2a and the second electrode 3a are made to face each other.

[0095] Next, the conductive material 11 is heated to a temperature equal to or higher than the melting point of the solder particles 11A (third step). Preferably, the conductive material 11 is heated to a temperature equal to or higher than the curing temperature of the thermosetting compound 11B. During this heating, the solder particles 11A that existed in the area where no electrode is formed gather between the first electrode 2a and the second electrode 3a (self-aggregation effect). When a conductive paste is used instead of a conductive film, the solder particles 11A gather more effectively between the first electrode 2a and the second electrode 3a. In addition, the solder particles 11A melt and bond to each other. In addition, the thermosetting compound 11B is thermally cured. As a result, as shown in FIG. 2(c), the connection portion 4 that connects 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, the solder portion 4A is formed by bonding the multiple solder particles 11A, and the thermosetting compound 11B is thermally cured to form the cured portion 4B. As long as the solder particles 11A move sufficiently, it is not necessary to maintain the temperature constant from the time when the movement of the solder particles 11A that are not located between the first electrode 2a and the second electrode 3a begins to the time when the movement of the solder particles 11A to 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 step and the third step. In this case, the weight of the second connection target member 3 is added to the conductive material 11. Therefore, when the connection part 4 is formed, the solder particles 11A are more effectively gathered between the first electrode 2a and the second electrode 3a. Note that, if pressure is applied in at least one of the second step and the third step, the action of the solder particles 11A to gather between the first electrode 2a and the second electrode 3a tends to be inhibited.

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

[0098] In this manner, the connection structure 1 shown in FIG. 1 is obtained. The second step and the third step may be performed consecutively. After the second step, the obtained laminate of the first connection target member 2, the conductive material 11, and the second connection target member 3 may be moved to a 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 is not particularly limited.

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

[0101] The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members 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 boards, glass epoxy boards, and glass boards. The first and second connection target members are preferably electronic components.

[0102] At least one of the first connection target member and the second connection target member is preferably a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate. The second connection target member is preferably a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate. Resin films, flexible printed circuit boards, flexible flat cables, and rigid flexible substrates 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 gather on the electrodes. In contrast, by using a conductive paste, even if a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate is used, solder particles can be efficiently gathered on the electrodes, thereby sufficiently improving the conduction reliability between the electrodes. When a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate is used, the effect of improving the conduction reliability between the electrodes by not applying pressure can be obtained more effectively than when other connection target members such as semiconductor chips are used.

[0103] Examples of the electrodes provided on the connection target members 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 connection target members are flexible printed circuit boards, the electrodes are preferably gold electrodes, nickel electrodes, tin electrodes, silver electrodes, or copper electrodes. When the connection target members are glass substrates, the electrodes are preferably aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, or tungsten electrodes. When the electrodes are aluminum electrodes, they may be electrodes made of aluminum only, or 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, the first electrode and the second electrode are preferably arranged in an area array or peripheral arrangement. When the first electrode and the second electrode are arranged in an area array or peripheral arrangement, the effect of the present invention is more effectively exerted. The area array is a structure in which the electrodes of the connection target member are arranged in a lattice shape on the surface on which the electrodes are arranged. The peripheral is a structure in which the electrodes are arranged on the outer periphery of the connection target member. In the case of a structure in which the electrodes are arranged in a comb shape, it is sufficient that the solder particles are aggregated along a direction perpendicular to the comb, whereas in the area array or peripheral structure, the solder particles need to be uniformly aggregated over the entire surface on which the electrodes are arranged. Therefore, while the amount of solder is likely to be non-uniform in the conventional method, the method of the present invention can uniformly aggregate the solder particles over the entire surface.

[0105] The present invention will be specifically described below with reference to examples and comparative examples, but 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 35000 mPa s at 51.7°C)

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

[0109] (Flux) Adipic acid benzylamine 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) Glutaric acid benzylamine 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) 24 g of water as a reaction solvent and 13.89 g of adipic acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved at room temperature until homogenous. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed solution. The obtained mixed solution 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 adipic acid benzylamine salt.

[0111] (Synthesis Example 2) 24 g of water as a reaction solvent and 13.212 g of glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved at room temperature until homogenous. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed solution. The obtained mixed solution was placed in a refrigerator at 5 to 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, carbon number 21) Oleic acid (unsaturated monocarboxylic acid, carbon number 18) Palmitic acid (monocarboxylic acid, carbon number 16) Myristic acid (monocarboxylic acid, carbon number 14) Lauric acid (monocarboxylic acid, carbon number 12) Octanoic acid (monocarboxylic acid, carbon number 8)

[0113] (Examples 1 to 12 and Comparative Examples 1 and 2) Preparation of conductive material (anisotropic conductive paste): The components shown in Tables 1 to 4 below were mixed in the amounts shown in Tables 1 to 4 below to obtain conductive materials (anisotropic conductive pastes).

[0114] (evaluation) (1) Initial thixotropic index, and (2) Storage stability The following 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 leaving the conductive material for 24 hours under conditions of 25°C and 50% RH. The initial thixotropic index and storage stability were evaluated according to the following criteria.

[0117] [Initial thixotropic index criteria] ○○: Ratio (ηB / ηA) is 3.0 or more ○: Ratio (ηB / ηA) is 2.5 or more and less than 3.0 ×: Ratio (ηB / ηA) is less than 2.5

[0118] [Criteria for storage stability] ○○: Ratio ((ηD / ηC) / (ηB / ηA)) is 0.90 or more ○: Ratio ((ηD / ηC) / (ηB / ηA)) is 0.60 or more and less than 0.90 ×: Ratio ((ηD / ηC) / (ηB / ηA)) is less than 0.60

[0119] (3) Solder cohesion Fabrication of connection structures: A glass epoxy board (material: FR-4, thickness: 0.5 mm) having a Cu / Au electrode pattern with an L / S of 60 μm / 90 μm on the surface was prepared as the first and second connection target members. The conductive material (anisotropic conductive paste) immediately after preparation was printed to a thickness of 100 μm on the upper surface of the first connection target member by screen printing to form 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 face each other. The weight of the second connection target member is added to the conductive material (anisotropic conductive paste) layer. From this state, the conductive material (anisotropic conductive paste) layer was heated to a temperature of 260° C. (in the case of solder particles 1 to 3) or 180° C. (in the case of solder particles 4 to 6) to harden 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] Solder cohesion rating: For the resulting connection structure, an optical microscope (OLYMPUS "BX53M") was used to obtain a microscopic image of the portion where the first electrode and the second electrode face each other in the lamination direction of the first electrode, the connection portion, and the second electrode. Next, the obtained microscopic image was processed using the image processing software "ImageJ," and the amount of side balls formed around the portion where the first electrode and the second electrode face each other (solder portion in the connection portion) was converted into a pixel value. Solder cohesion was evaluated according to the following criteria.

[0121] [Criteria for solder cohesion] XX: Pixel value is less than 1500 ○: Pixel value is 1500 or more and less than 3000 ×: Pixel value is 3000 or more

[0122] The compositions of the conductive materials and the results are shown in Tables 1 to 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 connecting member 3a...Second electrode 4…Connection 4A…Solder part 4B…Cured product part 11...Conductive materials 11A…Solder particles 11B...Thermosetting compound

Claims

1. A conductive material comprising 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 in 100% by weight of the conductive material is 40% by weight or more and 90% by weight or less. A conductive material.

2. The conductive material according to claim 1, wherein the organic acid is a monocarboxylic acid.

3. The conductive material according to claim 1 or 2, wherein the organic acid is an unsaturated monocarboxylic acid.

4. The conductive material according to claim 1 or 2, wherein the organic acid has an amide bond.

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

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

7. The conductive material according to claim 6, which does not contain a thermosetting agent.

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

9. 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. The conductive material according to claim 1 or 2.

10. The conductive material according to claim 1 or 2, which is a conductive paste.

11. 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, wherein the material of the connection portion is the conductive material according to claim 1 or 2, And a connection structure in which the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

12. A step of disposing the conductive material on the surface of a first connection target member having a first electrode on its surface using the conductive material according to claim 1 or 2; A step of disposing 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 of the conductive material so that the first electrode and the second electrode face each other. A method for manufacturing a connection structure, comprising: forming a connection portion that connects the first connection target member and the second connection target member with the conductive material by heating the conductive material to a temperature equal to or higher than the melting point of the solder particles; and electrically connecting the first electrode and the second electrode with a solder portion in the connection portion.

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