Conductive resin composition

Abstract

To provide a conductive resin composition enabling proper aggregation of solder particles on an electrode and achieving excellent electrical conduction even under conditions of a slow heating rate.SOLUTION: A conductive resin composition comprises a thermosetting resin, a curing agent for curing the thermosetting resin, solder particles, and a flux, wherein, a flux without a hydroxyl group is used as the flux, and the mass of the flux relative to the mass of the solder particles is adjusted to 5 mass% or more in terms of solid content.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive resin composition, and particularly to a conductive resin composition used when mounting an electronic element on a wiring board.

Background Art

[0002] With the recent increase in the density of printed wiring boards due to the miniaturization, thinning, and lightening of electronic devices, the development and improvement of conductive connection materials have been promoted as technologies used for the electrical connection of electronic components, for example, the electrical connection between a wiring board and an electronic element or the electrical connection between wiring boards. Such a conductive connection material is applied between members to be electrically connected and heat-pressed, thereby enabling electrical connection in a lightweight and space-saving manner. Specifically, although the conductive connection material itself is insulating, a conductive path is formed by sandwiching and pressing the conductive particles contained in the conductive connection material between electrodes by heat-pressing. As a result, electrical connection between members becomes possible. On the other hand, in the region where no pressure is applied without being sandwiched between electrodes even after heat-pressing, the conductive particles remain dispersed, so the insulating property is maintained. Thus, a so-called anisotropic conductive connection structure is formed (for example, Patent Document 1).

[0003] On the other hand, it is known that solder particles have the property of aggregating on electrodes when melted in a liquid resin. Then, by utilizing such properties of solder particles, the solder particles dispersed in a curable resin in a fluid state are melted and self-aggregated on the electrodes, and solder is disposed only between the electrodes to be connected, while ensuring insulation between adjacent electrodes. Such an anisotropic conductive connection material has also been developed (for example, Patent Document 2). Such an anisotropic conductive connection material is used for applications in which a plurality of electrodes are collectively electrically connected, such as COG mounting and FOG mounting.

[0004] However, in the case of using a hot plate or the like with a high heating rate to melt solder particles, the conventional anisotropic conductive adhesive exhibits good solder aggregability. However, when using a box furnace or the like with a low heating rate to melt solder particles, the curing reaction of the epoxy resin proceeds before the melting point of the solder particles is reached, and the solder particles do not aggregate properly on the electrodes, resulting in the problem that good conduction cannot be achieved.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Under such circumstances, it is a technical problem to provide a conductive resin composition that can properly aggregate solder particles on electrodes even when the heating rate is slow, enabling good conduction.

[0007] Therefore, an object of the present invention is to provide a conductive resin composition that can properly aggregate solder particles on electrodes even when the heating rate is slow, enabling good conduction.

Means for Solving the Problems

[0008] As a result of intensive research, the inventors have found that by blending a thermosetting resin, a curing agent for curing the thermosetting resin, solder particles, and a flux in a conductive resin composition, using a flux that does not contain a hydroxy group as the flux, and adjusting the mass of the flux with respect to the mass of the solder particles to 5% by mass or more in terms of solid content, the above-mentioned problems can be solved. That is, the gist of the present invention is as follows.

[0009] [1] A thermosetting resin, A curing agent for curing the thermosetting resin, solder particles, and flux A conductive resin composition containing the same, wherein the flux does not contain a hydroxy group, and the mass of the flux relative to the mass of the solder particles is 5% by mass or more in terms of solid content. The conductive resin composition is characterized by this. [2] The conductive resin composition according to [1], wherein the flux is an aliphatic dicarboxylic acid. [3] The conductive resin composition according to [1] or [2], wherein when the flux is heated at a heating rate of 5 ° C. / min, the viscosity at the melting point of the solder particles is 1000 dPa·S or less. [4] The conductive resin composition according to any one of [1] to [3], wherein the thermosetting resin contains an epoxy resin that is liquid at room temperature and an epoxy resin that is solid at room temperature. [5] The conductive resin composition according to any one of [1] to [4], wherein the content of the solder particles is 20 to 70% by mass in terms of solid content with respect to the total mass of the conductive resin composition. [Advantages of the Invention]

[0010] According to the present invention, in the conductive resin composition, even when the heating rate is slow, the solder particles can be appropriately aggregated on the electrode, enabling good electrical conduction.

[0011] [Conductive Resin Composition] According to one aspect of the present invention, a conductive resin composition (hereinafter, also referred to as "the conductive resin composition of the present invention") is provided. The conductive resin composition of the present invention contains a thermosetting resin, a curing agent for curing the thermosetting resin, solder particles, and flux as essential components. Hereinafter, each component of the conductive resin composition of the present invention will be described in detail. Note that commercially available products may be used for each component, or appropriately synthesized products may be used.

[0012] (Thermosetting Resin) The thermosetting resin functions as a binder for the solder particles described later and also has the function of hardening to fix the wiring board and the electronic element. Examples of the thermosetting resin include epoxy resin, phenolic resin, melamine resin, unsaturated polyester resin, maleimide resin, polyurethane resin, silicone resin, cyanate resin, acrylic resin, etc. Among these, epoxy resin and acrylic resin are preferably used, and epoxy resin is particularly preferably used.

[0013] As the epoxy resin, any resin having two or more epoxy groups in one molecule can be used without limitation. For example, epoxy resins having a bisphenol skeleton such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, hydrogenated bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol S type epoxy resin; phenolic novolak type epoxy resin, cresol novolak type epoxy resin, novolak type epoxy resin of bisphenol A, biphenyl type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, phosphorus-containing epoxy resin, anthracene type epoxy resin, norbornene type epoxy resin, adamantane type epoxy resin, fluorene type epoxy resin; aminophenol type epoxy resin, aminocresol type epoxy resin, alkylphenol type epoxy resin, etc. described later can be mentioned. The above-mentioned epoxy resins can be used alone or in combination of two or more.

[0014] Examples of the polyfunctional epoxy resin include EP-3300E manufactured by ADEKA Corporation, which is a hydroxybenzophenone type liquid epoxy resin, jER 630 manufactured by Mitsubishi Chemical Corporation, which is an aminophenol type liquid epoxy resin (para-aminophenol type liquid epoxy resin), ELM-100 manufactured by Sumitomo Chemical Co., Ltd., etc., jER 604 manufactured by Mitsubishi Chemical Corporation, which is a glycidylamine type epoxy resin, YH-434 manufactured by Nippon Steel Chemical & Material Co., Ltd., Sumiepoxy ELM-120 manufactured by Sumitomo Chemical Industry Co., Ltd., D.E.N.431 manufactured by Dow Chemical Company, which is a phenol novolak type epoxy resin, and the like. These polyfunctional epoxy resins can be used alone or in combination of two or more kinds.

[0015] Among the above-mentioned epoxy resins, from the viewpoint of making the conductive resin composition in a paste form, it is preferable to use a liquid one. Specifically, a liquid epoxy resin having a bisphenol skeleton is preferable, and a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a bisphenol E type epoxy resin are more preferable. Examples of these commercially available products include ZX-1059 (a mixture of bisphenol A type and bisphenol F type epoxy resins) manufactured by Nippon Steel Chemical & Material Co., Ltd., jER 828, jER 834, jER 1001 (bisphenol A type epoxy resin), jER 807, jER 4004P (bisphenol F type epoxy resin) manufactured by Mitsubishi Chemical Corporation, R710 (bisphenol E type epoxy resin) manufactured by Air Water, Inc., and the like.

[0016] In addition to the epoxy resin that is liquid at normal temperature described above, the thermosetting resin preferably includes an epoxy resin that is solid (for example, powdery) at normal temperature. Specifically, a solid epoxy resin having a bisphenol skeleton is preferable, and a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a bisphenol E type epoxy resin are more preferable. Examples of these commercially available products include YX4000 (biphenyl type epoxy resin, pulverized grade) manufactured by Mitsubishi Chemical Corporation, and the like.

[0017] The acrylic resin is not particularly limited as long as it is a resin having a (meth)acrylic group. Examples thereof include trifunctional methacrylate monomers such as trimethylolpropane trimethacrylate and epoxy acrylate having a trimethylpropane skeleton. Among these, monofunctional (meth)acrylate, bifunctional (meth)acrylate, polyfunctional (meth)acrylate having three or more functional groups, epoxy (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate having two or more functional groups can be preferably used.

[0018] Examples of monofunctional (meth)acrylates include aliphatic (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, butoxyethyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octylheptyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate; alicyclic (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, 3-methyl-3-oxetanylmethyl (meth)acrylate, 1-adamantyl (meth)acrylate; aromatic (meth)acrylates such as phenyl (meth)acrylate, nonylphenyl (meth)acrylate, p-cumylphenyl (meth)acrylate, o-biphenyl (meth)acrylate, 1-naphthyl (meth)acrylate, 2-naphthyl (meth)acrylate, benzyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-3-(o-phenylphenoxy)propyl (meth)acrylate, 2-hydroxy-3-(1-naphthoxy)propyl (meth)acrylate, 2-hydroxy-3-(2-naphthoxy)propyl (meth)acrylate; 2-tetrahydrofurfuryl (meth)acrylate,Examples of the heterocyclic (meth)acrylate include N-(meth)acryloyloxyethylhexahydrophthalimide and 2-(meth)acryloyloxyethyl-N-carbazole.

[0019] Examples of the bifunctional (meth)acrylate include aliphatic (meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 2-methyl-1,3-propanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, glycerin di(meth)acrylate, and tricyclodecane dimethanol (meth)acrylate; alicyclic (meth)acrylates such as cyclohexane dimethanol (meth)acrylate and tricyclodecane dimethanol (meth)acrylate; aromatic (meth)acrylates such as bisphenol A di(meth)acrylate, bisphenol F di(meth)acrylate, bisphenol AF di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, and fluorene-type di(meth)acrylate; and heterocyclic (meth)acrylates such as isocyanuric acid di(meth)acrylate.

[0020] Examples of polyfunctional (meth)acrylates having three or more functional groups include aliphatic (meth)acrylates such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ethoxylated glycerin tri(meth)acrylate, and heterocyclic (meth)acrylates such as isocyanuric acid tri(meth)acrylate.

[0021] The content of the thermosetting resin in the conductive resin composition of the present invention is not particularly limited as long as the effects of the present invention are achieved, but in terms of solid content conversion, it is preferably 20 to 70% by mass. When the content of the thermosetting resin is 20% by mass or more, the adhesion between the wiring board and the electronic element and the insulation reliability of the cured product can be made good. On the other hand, when the content of the thermosetting resin is 70% by mass or less, the amount of solder particles required for connection can be ensured.

[0022] (Curing agent) The conductive resin composition of the present invention contains a curing agent for curing the above-described thermosetting resin. As the curing agent, known curing agents generally used for curing curable resins can be used. Specific examples of the curing agent include amines, imidazoles, polyfunctional phenols, acid anhydrides, isocyanates, and polymers containing these functional groups. The curing agent may be used alone or in combination of two or more.

[0023] Examples of the amines include dicyandiamide and diaminodiphenylmethane. Examples of the imidazoles include alkyl-substituted imidazoles and benzimidazoles. The imidazoles may also be imidazole latent curing agents such as imidazole adducts. Examples of the polyfunctional phenols include hydroquinone, resorcinol, bisphenol A and its halogen compounds, and novolac and resole resins which are condensates of these with aldehydes. Examples of the acid anhydrides include phthalic anhydride, hexahydrophthalic anhydride, methyl nadic anhydride, and benzophenone tetracarboxylic acid. Examples of the isocyanates include tolylene diisocyanate and isophorone diisocyanate. As the isocyanates, those masked with phenols or the like can also be used.

[0024] From the viewpoints of the curing rate of the conductive resin composition and the strength of the cured product after curing, the content of the curing agent in the conductive resin composition of the present invention is preferably 3 to 15 parts by mass, more preferably 4 to 10 parts by mass, and particularly preferably 5 to 8 parts by mass in terms of solid content based on 100 parts by mass of the thermosetting resin.

[0025] The curing rate of the conductive resin composition can be controlled by adjusting the type and blending amount of the curing agent and, if desired, the curing accelerator. However, from the viewpoint of imparting anisotropy to the conductive resin composition, it is preferable that the reaction temperature (curing temperature) of the thermosetting resin is higher than the melting point of the solder particles described later, and more preferably 5°C or higher. The "anisotropic" conductive resin composition refers to a property that, when the solder particles are melted, the solder particles gather on the electrodes, melts the solder particles dispersed in the curable resin in a fluid state and self-assembles on the electrodes, and can arrange the solder only between the electrodes to be connected, and can ensure insulation between adjacent electrodes. As described above, when the reaction temperature (curing temperature) of the thermosetting resin is higher than the melting point of the solder particles, the solder particles dispersed in the composition can be self-assembled before the thermosetting resin cures.

[0026] (Solder particles) The conductive resin composition of the present invention contains solder particles. As the solder particles, conventionally known ones can be used without particular limitation, and examples include gold, silver, nickel, copper, lead, low melting point solder particles, and the like. The solder particles may be composite particles in which non-conductive particles such as glass, ceramic, and plastic as nuclei are coated with solder, or composite particles having the non-conductive particles and solder particles. When the solder particles are the above-mentioned composite particles or heat-meltable metal particles, the solder particles are melted and deformed by heating, so that the contact area with the electrode increases during connection, and particularly high reliability can be obtained.

[0027] As the solder particles, it is preferable to use solder particles that melt by heating at 140°C. Among them, low melting point solder particles are more preferable, and Sn-Pb-based and Sn-Bi-based low melting point solder particles are more preferable.

[0028] Also, as the lead-free solder particles, solder particles containing no lead are preferable. The lead-free solder particles mean solder particles having a lead content of 0.10 mass% or less as defined in JIS Z 3282:2017 (Solder - Chemical Composition and Shape).

[0029] As the lead-free solder particles, low melting point solder particles composed of one or more metals selected from tin, bismuth, indium, copper, silver, and antimony are preferably used. In particular, from the viewpoints of cost, handleability, and balance of bonding strength, an alloy of tin (Sn) and bismuth (Bi) is preferably used.

[0030] The content ratio of Bi in such low melting point solder particles is appropriately selected within the range of 20 to 65% by mass, preferably 35 to 65% by mass, and more preferably 55 to 60% by mass. By setting the content ratio of Bi in the low melting point solder particles to 20% by mass or more, the melting point of the low melting point solder particles can be set to 140°C or lower. Therefore, by setting the content ratio of Bi in the low melting point solder particles within the range of 20 to 65% by mass, the low melting point solder melts at a lower temperature than the thermosetting resin, and sufficient conductive connection can be obtained even with heating at a relatively low temperature.

[0031] The solder particles are preferably spherical. Here, spherical means that at a magnification at which the shape of the solder particles can be confirmed, it contains 90% or more of those having a ratio of the major axis to the minor axis of spherical powder of 1 to 1.5. Also, the solder particles preferably have an average particle diameter of 1 to 100 μm, more preferably 3 to 80 μm, and even more preferably 5 to 60 μm. In this specification, the average particle diameter refers to the median diameter (D50) measured using a laser diffraction particle size distribution analyzer.

[0032] Also, the solder particles preferably have a specific surface area of 300 to 2000 cm 2 / g, and more preferably 500 to 1500 cm 2 / g. By using solder particles having a specific surface area within the above range, the stability of the conductive connection between the electrodes of the wiring board and the electronic elements is improved. The specific surface area of the solder particles means the value measured by the BET method. Specifically, an inert gas (for example, nitrogen gas) with a known size of one molecule is adsorbed on the surface of the measurement sample, and the specific surface area can be obtained from the adsorption amount and the occupied area of the inert gas.

[0033] The blending amount of the solder particles is preferably 20 to 70% by mass, more preferably 30 to 60% by mass, and particularly preferably in the range of 35 to 55% by mass with respect to the solid content in the conductive resin composition. By setting the content of the solder particles to 20% by mass or more, sufficient electrical connection can be ensured while securing the adhesion between the wiring board and the electronic element. Further, by setting the content of the solder particles to 70% by mass or less, sufficient adhesion can be ensured while securing the electrical connection property.

[0034] (Flux) From the viewpoint of enhancing the stability of electrical connection, the conductive resin composition of the present invention contains a flux that does not contain a hydroxy group, in addition to a thermosetting resin, a curing agent, and solder particles. If the flux contains a hydroxy group, it is considered that the reaction between the flux and the epoxy resin proceeds even at a low temperature. Therefore, when the conductive resin composition contains a flux containing a hydroxy group, it is considered that the increase in viscosity below the melting point of the solder particles is promoted. On the other hand, since the flux does not contain a hydroxy group, the increase in viscosity below the melting point of the solder particles can be suppressed, and the aggregability of the solder particles can be made good. In the present specification, the "hydroxy group" with respect to the flux is a concept excluding the hydroxy group constituting the carboxy group. That is, "not containing a hydroxy group" with respect to the flux means that the flux may contain a carboxy group.

[0035] As the flux, a known flux used in the conductive resin composition can be used. For example, 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, a derivative of phosphoric acid, an organic halide, hydrazine, an organic acid, rosin, etc. can be mentioned. The flux may be used alone or in combination of two or more.

[0036] Among the above-mentioned fluxes, organic acids can be preferably used. Preferred organic acids include, in addition to monocarboxylic acids, polycarboxylic acids such as dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids. Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid, arachidic acid, behenic acid, lignoceric acid, etc. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, diglycolic acid, etc. Examples of tricarboxylic acids include benzene-1,2,5-tricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,3-propanetricarboxylic acid, etc. Examples of tetracarboxylic acids include benzophenonetetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, etc. Among these carboxylic acids, aliphatic dicarboxylic acids (dibasic acids) are preferred, and succinic acid, glutaric acid, and adipic acid are particularly preferred.

[0037] The melting point of the flux is preferably 90 to 220 °C, more preferably 130 to 200 °C, and even more preferably 133 to 186 °C. The conductive resin composition containing solder particles is generally used by heating it to a temperature equal to or higher than the melting point of the solder particles. When the melting point of the flux is within the above range, the flux can be melted during the heating of the conductive resin composition, and as a result, the stability of the conductive connection can be further enhanced.

[0038] The content of the flux in the conductive resin composition is 5% by mass or more in terms of solid content based on the mass of the solder particles, preferably 8 to 50% by mass, and particularly preferably 8 to 30% by mass. By the content of the flux being within the above-mentioned range, the conductive connectivity of the conductive resin composition can be made good.

[0039] (Filler) The conductive resin composition may contain a filler as necessary to increase the physical strength of the cured product and the like. As the filler, known inorganic or organic fillers can be used, and in particular, barium sulfate, spherical silica, hydrotalcite, and talc are preferably used. Further, metal oxides or metal hydroxides such as aluminum hydroxide can be used as extender pigment fillers to obtain flame retardancy.

[0040] In order to enhance the dispersibility in the conductive resin composition, the filler may be surface-treated. By using a surface-treated filler, its aggregation can be suppressed. The surface treatment method is not particularly limited, and known and commonly used methods may be used. However, it is preferable to treat the surface of the inorganic filler with a surface treatment agent having a curable reactive group, for example, a coupling agent having a curable reactive group as an organic group.

[0041] As the coupling agent, coupling agents such as silane-based, titanate-based, aluminate-based, and zirconate-based coupling agents can be used. Among them, silane-based coupling agents are preferable. Examples of such silane-based coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, N-(2-aminomethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-anilinopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and the like. The coupling agent may be used alone or in combination of two or more.

[0042] When the conductive resin composition of the present invention is heated at a heating rate of 5 °C / min, it is preferable that the viscosity at the melting point of the solder particles described above is 1000 dPa·s or less. By the viscosity of the conductive resin composition being within such a range, a decrease in the aggregability of the solder particles can be suppressed.

[0043] The conductive resin composition of the present invention can be produced by blending and stirring the above-described respective components at a predetermined blending ratio and by a known and commonly used method.

[0044] The conductive resin composition of the present invention can be used for the electrical connection between members in electronic components. For example, it can be used for the electrical connection between a printed wiring board and an electronic element or for the electrical connection between printed wiring boards, and is particularly suitably used for an electronic element mounting substrate such as chip on board (COB) in which an electronic element such as a bare chip or an LED chip is directly mounted on a substrate and connected. Among them, it can be suitably used for applications in which a plurality of elements are mounted on a wiring board with a fine pitch between adjacent electrode intervals and electrical connection is performed collectively.

Examples

[0045] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, the numerical values of each component all represent "parts by mass".

[0046] [Preparation of Conductive Resin Composition] The respective components shown in Table 1 below were blended in the amounts shown in the same table and mixed at 400 rpm for 10 minutes using a stirrer (FBLh600M, manufactured by Tokyo Glass Kikai Co., Ltd.) to prepare the conductive resin compositions of Examples 1 to 5 and Comparative Examples 1 to 7. The details of each component in Table 1 are as follows. Liquid epoxy resin 1: A mixture of bisphenol A type and bisphenol F type epoxy resins (ZX-1059, manufactured by Nippon Steel Chemical & Material Co., Ltd.) Liquid epoxy resin 2: A mixture of bisphenol A type and bisphenol F type epoxy resins (jER 828, manufactured by Mitsubishi Chemical Corporation) Solid epoxy resin: Biphenyl-type epoxy resin (YX4000 pulverized grade, manufactured by Mitsubishi Chemical Corporation) Flux 1: Adipic acid (manufactured by Wako Pure Chemical Industries, Ltd., melting point 151 - 154 °C) Flux 2: Glutaric acid (manufactured by Kanto Chemical Co., Inc., melting point 95 - 98 °C) Flux 3: Succinic acid (manufactured by Hayashi Pure Chemical Industries, Ltd., melting point 185 °C) Flux 4: L-Tartaric acid (manufactured by Hayashi Pure Chemical Industries, Ltd., melting point 192 °C) Hardener: Dicyandiamide (DICY) Solder particles: Sn42Bi58 (DS10, manufactured by Mitsui Mining & Smelting Co., Ltd.)

[0047]

Table 1

[0048] [Measurement of viscosity of conductive resin composition] A 20 mm diameter sensor and plate were attached to a rheometer MARS40 (manufactured by HAAKE), and the conductive resin compositions of the examples and comparative examples were each set. Then, the viscosity of the conductive resin composition was measured under the conditions of a gap of 0.2 mm, a heating rate of 5 °C / min, a shear rate of 26.181 / S, and a measurement temperature range of 30 - 230 °C. The results are shown in Table 1.

[0049] [Evaluation of solder particle aggregation] The conductive resin compositions of the examples and comparative examples were each applied to a glass plate using a metal mask, and an LED chip KPG-0603SEC-E-TT (chip size: 650 μm × 350 μm, electrode area: 175 μm × 275 μm, electrode distance: 200 μm, electrode height: 3 μm, forward voltage 2.5 V) was mounted using tweezers to prepare a substrate for evaluating solder particle aggregation.

[0050] Each evaluation substrate produced according to the above-described procedure was heated in a box oven to 180°C at a heating rate of 15°C / min and heated for 30 minutes to aggregate solder particles on the electrode portion of the LED chip. Next, the degree of coating of the electrodes by the solder particles was observed using an optical microscope from the back side (i.e., the side opposite to the side on which the LED chip was mounted) of each evaluation substrate, and the aggregation of the solder particles was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1. ○: The coating of the electrodes by the solder particles is 60% or more, and the aggregation of the solder particles on the electrodes is extremely good. △: The coating of the electrodes by the solder particles is 30% or more and less than 60%, and the aggregation of the solder particles on the electrodes is good. ×: The coating of the electrodes by the solder particles is less than 30%, and the aggregation of the solder particles on the electrodes is poor.

[0051] [Evaluation of LED Lighting Conductivity (Conductivity)] The conductive resin compositions of the examples and comparative examples were each applied through a metal mask (mask thickness: 100 μm, opening: 400 μm × 200 μm) onto a rigid substrate (substrate: FR-4) having electrode PADs (electrode area: 200 μm × 200 μm, electrode pitch: 130 μm, electrode height: 8 μm, electrode surface: flash Au plating treatment) to a thickness of 80 μm using a scraper. Next, an LED chip (chip size: 380 μm × 200 μm, electrode area: 80 μm × 130 μm, electrode pitch: 150 μm, electrode height: 3 μm, forward voltage: 3.0 V) was placed on each of the applied conductive resin compositions using a chip mounter (ACT-1000, manufactured by Actes Kyo San Co., Ltd.) such that the electrodes of the LED chip and the electrodes on the rigid substrate overlapped. Then, the temperature was raised to 180°C at a heating rate of 15°C / min using a box oven and heated for 30 minutes to bond the LED chip and the rigid substrate, thereby producing an evaluation substrate for LED lighting conductivity (conductivity).

[0052] A forward voltage of 2.5 V was applied to the electrode portions of each evaluation substrate fabricated according to the above-described procedure using a 7011DC signal source (manufactured by Hioki E.E. Corporation), and the presence or absence of LED lighting was visually observed. The LED lighting conduction (conductivity) was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1. 〇: All 10 LEDs on the evaluation substrate were lit, and the conductivity was extremely good. △: Among the 10 LEDs on the evaluation substrate, 7 to 9 LEDs were lit, and the conductivity was good. ×: Among the 10 LEDs on the evaluation substrate, only 0 to 6 LEDs were lit, and the conductivity was poor.

[0053] From the evaluation results shown in Table 1, it can be seen that for each of the conductive resin compositions of Examples 1 to 5, good aggregation of solder particles on the electrode and good conductivity are compatible. On the other hand, for each of the conductive resin compositions of Comparative Examples 1 to 7, it can be seen that good aggregation of solder particles on the electrode and good conductivity are not compatible.

Claims

1. thermosetting resin, a curing agent for curing the thermosetting resin; Solder particles, and Flux A conductive resin composition comprising: The flux does not contain a hydroxy group, The conductive resin composition, characterized in that the mass of the flux relative to the mass of the solder particles is 5 mass % or more in terms of solid content.

2. The conductive resin composition according to claim 1 , wherein the flux is an aliphatic dicarboxylic acid.

3. 2. The conductive resin composition according to claim 1, wherein the conductive resin composition has a viscosity of 1000 dPa·S or less at the melting point of the solder particles when heated at a temperature increase rate of 5° C. / min.

4. 2. The conductive resin composition according to claim 1, wherein the thermosetting resin comprises an epoxy resin that is liquid at room temperature and an epoxy resin that is solid at room temperature.

5. 2. The conductive resin composition according to claim 1, wherein the content of the solder particles is 20 to 70 mass % in terms of solid content with respect to the total mass of the conductive resin composition.

Images