Thermally conductive paste

Abstract

This thermally conductive paste contains a polymerizable compound and metal particles. The viscosity η5, as measured at 25°C using a B type viscometer at a rotational speed of 5 rpm, is 8-30 Pa·s. The polymerizable compound includes an epoxy group-containing acrylic resin. The epoxy group-containing acrylic resin has a molecular weight of 10,000 or more. The content of the epoxy group-containing acrylic resin is 0.1-5 parts by mass relative to 100 parts by mass of the thermally conductive paste.

Description

Thermally conductive paste

[0001] This invention relates to a thermally conductive paste.

[0002] Various developments have been made to develop die bond materials for semiconductor devices. One example of this type of technology is the technology described in Patent Document 1. This document describes a die attach material using gold powder and ester alcohol. According to this document, this die attach material can be sintered at a relatively low temperature by sintering under certain conditions.

[0003] Japanese Patent Publication No. 2007-324523

[0004] The inventors of the present invention investigated how to ensure proper adhesion of semiconductor elements to a die when bonding them to a substrate using a thermally conductive paste, particularly in the field of power devices.

[0005] The present invention provides the following thermally conductive paste: [1] A thermally conductive paste comprising a polymerizable compound and metal particles, wherein the viscosity η measured at 25°C using a B-type viscometer at a rotation speed of 5 rpm is ５[1] A thermally conductive paste wherein the thermal pressure is 8 Pa·s or more and 30 Pa·s or less, the polymerizable compound contains an epoxy group-containing acrylic resin, the molecular weight of the epoxy group-containing acrylic resin is 10,000 or more, and the content of the epoxy group-containing acrylic resin is 2.0 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the thermally conductive paste. [2] The thermally conductive paste according to [1], wherein the content of the epoxy group-containing acrylic resin is 2.0 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the thermally conductive paste. [3] The thermally conductive paste according to [1] or [2], wherein the metal particles include one or more of the following: particles using an alloy containing one or more selected from gold, silver, and copper; sinterable metal particles made from an alloy containing one or more selected from gold, silver, and copper; and particles in which an alloy containing one or more selected from gold, silver, and copper is coated on the surface of a base particle. [4] The thermally conductive paste according to any one of [1] to [3], wherein the metal particles include fine metal particles with a particle size of 0.1 μm or more and 0.5 μm or less. [5] The thermally conductive paste according to [4], wherein the content of the fine metal particles is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the thermally conductive paste. [6] The thermally conductive paste according to any one of [1] to [5], wherein the cured product obtained by thermally curing the thermally conductive paste by heating it to 200°C from room temperature for a heating time of 60 minutes and then holding it for 120 minutes has a thermal conductivity at 25°C measured by the laser flash method of 30 W / mK or more and 150 W / mK or less. [7] The thermal conductive paste according to any one of [1] to [6], wherein the cured product obtained by thermally curing the thermal conductive paste by heating it to 200°C from room temperature over a heating time of 60 minutes and then holding it for 120 minutes contains a resin derived from the epoxy group-containing acrylic resin, and the amount of the resin is 2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the cured product. [8] The thermal conductive paste according to any one of [1] to [7], used for bonding semiconductor elements with a thickness of 120 μm or less onto a substrate.

[0006] According to the present invention, it is possible to reduce the tendency for semiconductor elements to crawl onto the die when bonding them to a substrate using a thermally conductive paste.

[0007] This is a schematic diagram of the semiconductor device according to this embodiment. This is a schematic diagram of the creeping and overflow of the thermal conductive paste.

[0008] Embodiments of the present invention will be described in detail below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted where appropriate. Note that the drawings are for illustrative purposes only. The shapes and dimensional ratios of the components in the drawings do not necessarily correspond to actual articles.

[0009] In this specification, the notation "a to b" in descriptions of numerical ranges means a or more and b or less, unless otherwise specified. For example, "1% by mass to 5% by mass" means "1% by mass or more and 5% by mass or less."

[0010] [Semiconductor Device 100] Figure 1 is a schematic diagram of the semiconductor device 100 according to this embodiment. As shown in Figure 1, the semiconductor device 100 has a configuration in which a semiconductor element 10 is fixed on a substrate 30 via an adhesive layer 20. The semiconductor element 10 is, for example, a power semiconductor that controls a current of 1 A or more. The substrate 30 can be a substrate including a base material portion and a circuit portion formed of rolled copper, or a printed circuit board for mounting existing lead frames, LEDs, power modules, and other electronic components.

[0011] Furthermore, the adhesive layer 20 fixes the semiconductor element 10 and electrically connects the semiconductor element 10 to the substrate 30. In other words, the adhesive layer 20 is electrically conductive. In addition, it is preferable that the adhesive layer 20 has thermal conductivity from the viewpoint of releasing the heat generated by the semiconductor element 10.

[0012] As described later, the thermally conductive paste according to this embodiment can be used, for example, to form the adhesive layer 20 described above.

[0013] [Thermal Conductive Paste] The thermal conductive paste according to this embodiment is a thermal conductive paste containing polymerizable compounds and metal particles, and has a viscosity η measured at 25°C using a B-type viscometer at a rotation speed of 5 rpm. ５ The thermal conductivity is between 8 Pa·s and 30 Pa·s. A semiconductor device refers to, for example, a semiconductor chip. The details of the thermal conductive paste's composition are described below.

[0014] [Polymerizable Compound] The polymerizable compound according to this embodiment includes an acrylic resin. As the acrylic resin, a liquid having two or more acrylic groups in one molecule can be used. Specifically, as the acrylic resin, a polymer or copolymer of acrylic monomers can be used. Here, the polymerization or copolymerization method is not limited, and known methods using general polymerization initiators and chain transfer agents, such as solution polymerization, can be used. Note that one type of acrylic resin may be used alone, or two or more types with different structures may be used. Specifically, as the acrylic resin, acrylic acid polymers, acrylated polybutadiene, etc., may be used.

[0015] Furthermore, it is preferable that the acrylic resin contains reactive groups such as epoxy groups, amino groups, carboxyl groups, and hydroxyl groups in its structure. It is particularly preferable that the acrylic resin contains epoxy groups as reactive groups.

[0016] Examples of commercially available epoxy group-containing acrylic resins mentioned above include ARUFON UG-4040, ARUFON UG-4035, ARUFON UG-4010, ARUFON UG-4070, ARUFON UH-2000, ARUFON UH-2041, ARUFON UH-2170, ARUFON UP-1000, and ARUFON UC-3510, all manufactured by Toagosei Co., Ltd.

[0017] The upper limit of the weight-average molecular weight Mw of the acrylic resin is preferably, for example, 20,000 or less, and more preferably 15,000 or less. The lower limit of the weight-average molecular weight Mw of the acrylic resin is preferably, for example, 10,000 or more, more preferably 11,000 or more, and even more preferably 12,000 or more.

[0018] The lower limit of the polymerizable compound content in the thermal conductive paste is preferably, for example, 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.3 parts by mass or more, even more preferably 1.0 part by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the thermal conductive paste. The upper limit of the polymerizable compound content in the thermal conductive paste is, for example, 5 parts by mass or less, or 3 parts by mass or less, per 100 parts by mass of the thermal conductive paste.

[0019] [Metal particles] In this embodiment, metal particles are used to increase the mechanical strength and thermal conductivity of the hardened body of the thermally conductive paste.

[0020] The metal particles according to this embodiment include one or more of the following: particles using an alloy containing one or more selected from gold, silver, and copper; sinterable metal particles manufactured from an alloy containing one or more selected from gold, silver, and copper; and particles in which an alloy containing one or more selected from gold, silver, and copper is coated on the surface of a base particle.

[0021] The coated particles described above are, for example, particles (silicone resin particles) composed of organopolysiloxanes obtained by polymerizing organochlorosilanes such as methylchlorosilane, trimethyltrichlorosilane, and dimethyldichlorosilane, which are then coated with metal. Alternatively, the surface of silicone resin particles, which are composed of a silicone resin with a basic framework of the above-mentioned organopolysiloxanes further cross-linked in three dimensions, is coated with metal.

[0022] In addition, when viewed in terms of shape, the metal particles are preferably composed of at least one or more of spherical particles (including those that are not truly spherical, such as particles with a substantially spherical shape), polygonal particles, flake-shaped particles, dendritic particles, and scaly particles, and particularly preferably composed of spherical and flake-shaped particles, or a combination thereof.

[0023] In the cumulative frequency distribution curve based on volume measured using a laser diffraction particle size distribution measuring device for the metal particles, the particle diameter D50 at a cumulative frequency of 50% is preferably 0.1 μm or more and 500 μm or less, more preferably 0.1 μm or more and 20 μm or less, still more preferably 0.1 μm or more and 10 μm or less, and still more preferably 0.5 μm or more and 10 μm or less. By setting D50 to be not less than the above lower limit value, the mechanical strength can be improved. On the other hand, by setting D50 to be not more than the above upper limit value, the dispersibility of the metal particles in the thermal conductive paste can be improved, and as a result, variations in the mechanical strength are less likely to occur in the cured body of the thermal conductive paste.

[0024] As the upper limit value of the specific surface area of the metal particles, for example, it is preferably 2.10 m ２ / g or less, more preferably 1.05 m ２ / g or less, still more preferably 1.00 m ２ / g or less. Most preferably, it is 0.27 m ２ / g or less. As the lower limit value of the specific surface area of the metal particles, for example, it is preferably 0.10 m ２ / g or more, more preferably 0.20 m ２ / g or more, still more preferably 0.25 m ２ / g or more.

[0025] The lower limit of the metal particle content in the thermal conductive paste is preferably, for example, 65 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 75 parts by mass or more, per 100 parts by mass of thermal conductive paste. This allows the cured product of the thermal conductive paste to exhibit suitable thermal conductivity. The upper limit of the metal particle content in the thermal conductive paste may be, for example, 99 parts by mass or less, or 90 parts by mass or less, per 100 parts by mass of thermal conductive paste. This suppresses a decrease in the adhesive strength between the thermal conductive paste and the adherend.

[0026] [Fine Metal Particles] Furthermore, in the thermal conductive paste according to this embodiment, it is preferable that the metal particles include fine metal particles with an average particle size D50 of 0.1 μm or more and 0.5 μm or less. Specifically, it is preferable that the content of fine metal particles is 5 parts by mass or more and 50 parts by mass or less, more preferably 10 parts by mass or more and 50 parts by mass or less, and even more preferably 20 parts by mass or more and 40 parts by mass or less, per 100 parts by mass of the thermal conductive paste.

[0027] [Other Components] In addition to the components listed above, the thermally conductive paste according to this embodiment may also contain, for example, a stress-reducing agent to relieve stress on the cured product. Specific examples of stress-reducing agents include silicone compounds such as silicone oil and silicone rubber; polybutadiene compounds such as polybutadiene maleic anhydride adducts; polycarbonate nephrodiol dimethacrylate; and acrylonitrile butadiene copolymer compounds. One or more of the above specific examples can be included as the stress-reducing agent. Polybutadiene maleic anhydride adducts and polycarbonate nephrodiol dimethacrylate are particularly preferred as stress-reducing agents.

[0028] The lower limit of the content of the low-stress agent in the thermal conductive paste is preferably, for example, 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the thermal conductive paste. The upper limit of the content of the low-stress agent in the thermal conductive paste is preferably, for example, 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the thermal conductive paste.

[0029] In addition to the components described above, the thermally conductive paste according to this embodiment may also contain, for example, a silane coupling agent to improve adhesion between the thermally conductive paste and the substrate. Specific examples of silane coupling agents include vinylsilanes such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxysilanes such as 3-glycidyloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; styrylsilanes such as p-styryltrimethoxysilane; methacrylsilanes such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; and 3-acryloxypropyltrimethoxysilane. Acrylic silanes such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and other aminosilanes can be used; isocyanurate silanes; alkyl silanes; ureidosilanes such as 3-ureidopropyltrialkoxysilane; mercaptosilanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; isocyanate silanes such as 3-isocyanatetopropyltriethoxysilane; and 3-(trimethoxysilyl)propyl methacrylate can be used. As a silane coupling agent, one or more of the above specific examples can be used in combination.

[0030] The lower limit of the silane coupling agent content in the thermally conductive paste is preferably, for example, 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.2 parts by mass or more, per 100 parts by mass of the thermally conductive paste. The upper limit of the silane coupling agent content in the thermally conductive paste is preferably, for example, 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the thermally conductive paste.

[0031] In addition to the components described above, the thermally conductive paste according to this embodiment may also contain, for example, a diluent. For example, a reactive diluent or a non-reactive solvent can be used as the diluent. Here, a reactive diluent means a polymerizable monomer that hardens upon heat treatment to promote the aggregation of metal particles, or, if the conductive paste contains a thermosetting resin as a binder resin, a compound having a reactive group that participates in the crosslinking reaction with this resin. A non-reactive solvent means a solvent that does not have polymerizable or crosslinkable reactive groups and can volatilize upon heat treatment.

[0032] Examples of polymerizable monomers used as reactive diluents include glycol monomers, acrylic monomers, epoxy monomers, maleimide monomers, and imide monomers.

[0033] Examples of glycol monomers used as polymerizable monomers include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monoallyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, and diethylene glycol monobenzyl ether. Examples include triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol, tetraethylene glycol monomethyl, tetraethylene glycol monoethyl, tetraethylene glycol mono-n-butyl, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol monophenyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, and tripropylene glycol mono-n-butyl ether. These may be used individually or in combination of two or more.

[0034] As the acrylic monomer used as the coincidence monomer, a monofunctional acrylic monomer having only one (meth)acrylic group or a polyfunctional acrylic monomer having two or more (meth)acrylic groups can be used.

[0035] Examples of monofunctional acrylic monomers include 2-phenoxyethyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethylhexyldiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate. (T) Acrylate, Methoxydipropylene glycol (meth)acrylate, Cyclohexyl (meth)acrylate, Tetrahydrofurfuryl (meth)acrylate, Benzyl (meth)acrylate, Phenoxyethyl (meth)acrylate, Phenoxydiethylene glycol (meth)acrylate, Phenoxypolyethylene glycol (meth)acrylate, Nonylphenol ethylene oxide modified (meth)acrylate, Phenylphenol ethylene oxide modified (meth)acrylate, Isobornyl (meth)acrylate, Dimethylaminoethyl (meth)acrylate, Diethylaminoethyl (meth)acrylate, Dimethylaminoethyl (meth)acrylate quaternary, Glycidyl (meth)acrylate, Neopentyl glycol (meth)acrylate benzoate, 1,Examples thereof include 4-cyclohexanedimethanol mono(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-(meth)acryloyloxyethyl acid phosphate, and 2-(meth)acryloyloxyethyl acid phosphate. As the monofunctional acrylic monomer, one or more of the above specific examples can be used in combination.,

[0036] The lower limit of the content of the diluent in the thermally conductive paste is preferably, for example, 3 parts by mass or more, more preferably 4 parts by mass or more, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of the thermally conductive paste. The upper limit of the content of the diluent in the thermally conductive paste is preferably, for example, 20 parts by mass or less, more preferably 17 parts by mass or less, and still more preferably 15 parts by mass or less with respect to 100 parts by mass of the thermally conductive paste.,

[0037] In addition to the above components, the thermally conductive paste according to this embodiment may also contain, for example, a solvent. Specifically, the solvent may be methyl carbitol, ethyl carbitol, butyl carbitol, methyl carbitol acetate, ethyl carbitol acetate, butyl carbitol acetate, acetylacetone, methyl isobutyl ketone (MIBK), anone, diacetone alcohol, ethyl cellosolve, methyl cellosolve, butyl cellosolve, ethyl cellosolve acetate, methyl cellosolve acetate, butyl cellosolve acetate, ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene Alcohols such as glycerol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, methyl methoxybutanol, α-terpineol, β-terpineol, γ-terpineol, terpineol (a mixture of α, β, and γ), dihydroterpineol, hexylene glycol, benzyl alcohol, 2-phenylethyl alcohol, isopalmytil alcohol, isostearyl alcohol, lauryl alcohol, ethylene glycol, propylene glycol, or glycerin; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), 2-octanone, isophorone (3,5,5-trimethyl-2-cyclohexen-1-one), or diisobutyl ketone (2,6-dimethyl-4-heptanone);Ethyl acetate, butyl acetate, diethyl phthalate, dibutyl phthalate, acetoxyethane, methyl butyrate, methyl hexanoate, methyl octanoate, methyl decanoate, methyl cellosolve acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, 1,2-diacetoxyethane, tributyl phosphate, tricresyl phosphate or tripentyl phosphate esters; tetrahydrofuran, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, etoxy Ethers such as ethyl ether, 1,2-bis(2-diethoxy)ethane, or 1,2-bis(2-methoxyethoxy)ethane; ester ethers such as 2-(2-butoxyethoxy)ethane acetate; ether alcohols such as 2-(2-methoxyethoxy)ethanol; hydrocarbons such as toluene, xylene, n-paraffin, isoparaffin, dodecylbenzene, turpentine oil, kerosene, or diesel fuel; nitriles such as acetonitrile or propionitrile; amides such as acetamide or N,N-dimethylformamide; low molecular weight volatile silicone oils, or volatile organic modified silicone oils can be used. As a solvent, one or more of the above specific examples can be used in combination.

[0038] The lower limit of the solvent content in the thermal conductive paste is preferably, for example, 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the thermal conductive paste. The upper limit of the solvent content in the thermal conductive paste is preferably, for example, 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the thermal conductive paste.

[0039] In this embodiment, the thermally conductive paste has a large molecular weight of polymerizable compound. Therefore, when used as a die bonding material for mounting semiconductor chips on a substrate, for example, the resin material contained in the thermally conductive paste does not spread first toward the edges of the semiconductor chip. As a result, the resin material and metal particles spread more easily together, suppressing variations in the density of the metal particles while preventing the thermally conductive paste from creeping up or overflowing.

[0040] [Physical Properties of Thermally Conductive Paste] The thermally conductive paste according to this embodiment has a viscosity η measured at 25°C using a B-type viscometer at a rotation speed of 5 rpm. ５ It is preferable that the pressure is between 8 Pa·s and 30 Pa·s, and more preferably between 10 Pa·s and 20 Pa·s.

[0041] Furthermore, the cured product obtained by thermally curing the thermal conductive paste according to this embodiment by heating it from room temperature to 200°C over a 60-minute heating period and then holding it for 120 minutes preferably has a thermal conductivity at 25°C measured by the laser flash method of 30 W / mK or more and 150 W / mK or less, and more preferably 50 W / mK or more and 150 W / mK or less.

[0042] Furthermore, the cured product obtained by heat-curing the thermally conductive paste according to this embodiment by heating it from room temperature to 200°C over a 60-minute heating period and then holding it for 120 minutes contains a resin portion, and the resin portion content is preferably 2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the cured product.

[0043] The resin content can be calculated, for example, by subtracting the mass of metal particles contained in the thermal conductive paste from the total mass of the cured product. The mass of the metal particles can be obtained by removing them using methods such as washing the thermal conductive paste with an organic solvent or heating the thermal conductive paste to burn and decompose only the organic components, and then measuring the mass of the metal particles.

[0044] [Method for Manufacturing Thermally Conductive Paste] The method for manufacturing thermally conductive paste according to this embodiment will now be described. The method for manufacturing thermally conductive paste includes a mixing step of mixing the above-mentioned raw material components to produce a mixture, and a defoaming step of removing air contained in the mixture.

[0045] <Mixing Process> In the mixing process, the raw material components described above are mixed to produce a mixture. The mixing method is not limited; for example, a three-roll mixer or a blender can be used. This is how the raw material components are mixed to obtain a mixture.

[0046] <Defoaming Process> In the defoaming process, air contained in the mixture is removed. The method for removing air contained in the mixture is not limited and can be done, for example, by letting the mixture stand under vacuum. This results in obtaining a thermally conductive paste.

[0047] [Applications] The applications of the thermal conductive paste according to this embodiment will now be described. The thermal conductive paste according to this embodiment is used, for example, to bond a substrate to a semiconductor element. Here, examples of semiconductor elements include semiconductor packages and LEDs. Compared to conventional thermal conductive pastes, the thermal conductive paste according to this embodiment can suppress both fillet creep and overflow. As a result, it can be more suitably used for bonding semiconductor elements with a thickness of 140 μm or less, and especially 120 μm or less.

[0048] The present invention will be described in detail below using examples, but the present invention is not limited in any way to the descriptions of these examples.

[0049] Table 1 shows the values ​​of parts by mass of each raw material component relative to 100 parts by mass of the thermally conductive paste for each example and comparative example. (Polymerizable compound) ・Polymerizable compound 1: Acrylic resin with epoxy groups (manufactured by Toagosei Co., Ltd.: ARUFON UG-4035, Mw: 11,000) (Diluent) ・Diluent 1: 2-Phenoxyethyl methacrylate ・Diluent 2: 1,4-Cyclohexanedimethanol monoacrylate (Stress agent) ・Stress agent 1: Polybutadiene maleic anhydride adduct (Coupling agent) ・Coupling agent 1: Epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.) ・Coupling agent 2: 3-Methacrylopropyltrimethoxysilane (Metal particles) ・Metal particle 1: Silver powder (average particle size D50: 0.7 μm) ・Metal particle 2: Silver powder (average particle size D50: 0.7 μm) ・Metal particle 3: Silver powder (average particle size D50: 7 μm) ・Metal particle 4: Silver powder (average particle size D50: 7.6 μm) • Metal particles 5: Silver-coated powder (average particle size D50: 11.4 μm) • Fine metal particles 1: Silver powder (average particle size D50: 0.4 μm) (Solvent) • Solvent 1: 2-Ethylhexyl glycol

[0050]

[0051] <Preparation of Thermally Conductive Paste> Thermally conductive paste was obtained for each example and comparative example by the following procedure. First, each raw material component, excluding the metal particles, from the blending amounts shown in Table 1, was kneaded with the solvent at room temperature in a three-roll mill. Then, the solvent and metal particles were kneaded in a three-roll mill and degassed to obtain a thermally conductive paste.

[0052] <Measurement> The following values ​​were measured for the thermally conductive paste of each example and comparative example. The measured values ​​are shown in Table 1.

[0053] (Viscosity: η ５ ) The value measured at 25°C using a B-type viscometer at a rotation speed of 5 rpm is η ５ That's what I decided.

[0054] (Thixotropy: η) ０．５ / η ５ ) The value measured at 25°C using a B-type viscometer at a rotation speed of 0.5 rpm is η ０．５ And from the measured values, η ０．５ / η ５ The value was calculated.

[0055] (Volume Resistivity) The thermally conductive pastes of each example and comparative example were heated from room temperature to 200°C over a 60-minute heating period, and then held for 120 minutes to obtain cured products. The volume resistivity of the surface of the obtained cured products was measured using a four-electrode DC method with a milliohmmeter (manufactured by HIOKI Corporation), using electrodes spaced 40 mm apart.

[0056] (Thermal conductivity) The thermal conductivity at 25°C was measured and calculated from the laser flash method, specific gravity, and specific heat of the cured products obtained by heating the thermal conductive paste of each example and comparative example to 200°C from room temperature over a heating time of 60 minutes and then holding for 120 minutes.

[0057] (Evaluation) The creeping and overflow of the thermal conductive paste when semiconductor elements were mounted on a substrate was evaluated using the thermal conductive paste of each example and comparative example. Figure 2 shows a schematic diagram of the creeping and overflow of the thermal conductive paste. First, the thermal conductive paste was applied to the substrate so that the paste thickness before curing was 25 μm to 50 μm, and then a semiconductor element 10 with dimensions of 4 mm × 4 mm and a thickness D of 100 μm (a silicon substrate cut out of the planar shape from an unprocessed silicon wafer) was placed on it. After that, the thermal conductive paste was heated to 200°C over a heating time of 60 minutes from room temperature and held for 120 minutes to heat-cur, and then cut to obtain a cross-section. As shown in Figure 2, an image of the cross-section was obtained, and the length W of the adhesive layer 20 that protruded horizontally from the edge of the semiconductor element 10 was measured. ｘ The length W of the adhesive layer 20 is the length of the adhesive layer 20 that extends vertically up from the bottom surface of the semiconductor element 10. ｙ The difference between the thickness D of the semiconductor element 10 and the difference between the thickness D ｙ ) is 50 μm or larger, W ｘ This indicates that it was 100 μm or less, and "Bad" is (D-W ｙ ) is less than 50 μm, W ｘ This indicates that the particle size was over 100 μm.

[0058] In summary, it was confirmed that the thermally conductive paste according to the example containing 2.0 parts by mass or more of epoxy group-containing acrylic resin can reduce fillet creep and overflow.

[0059] This application claims priority based on Japanese Patent Application No. 2024-231263, filed on 26 December 2024, and incorporates all of its disclosures herein.

[0060] 100 Semiconductor device 10 Semiconductor element 20 Adhesive layer 30 Substrate

Claims

1. A thermally conductive paste containing polymerizable compounds and metal particles, wherein the viscosity η is measured at 25°C using a B-type viscometer at a rotation speed of 5 rpm. ５ A thermally conductive paste wherein the thermal pressure is 8 Pa·s or more and 30 Pa·s or less, the polymerizable compound contains an epoxy group-containing acrylic resin, the molecular weight of the epoxy group-containing acrylic resin is 10,000 or more, and the content of the epoxy group-containing acrylic resin is 2.0 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the thermally conductive paste.

2. The content of the epoxy group-containing acrylic resin is 2.0 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the thermal conductive paste, as described in claim 1.

3. The thermally conductive paste according to claim 1 or 2, wherein the metal particles include one or more of the following: particles made using an alloy containing one or more selected from gold, silver, and copper; sinterable metal particles manufactured from an alloy containing one or more selected from gold, silver, and copper; and particles in which an alloy containing one or more selected from gold, silver, and copper is coated on the surface of a base particle.

4. The thermally conductive paste according to claim 1 or 2, wherein the metal particles include fine metal particles with a particle size of 0.1 μm or more and 0.5 μm or less.

5. The thermal conductive paste according to claim 4, wherein the content of the fine metal particles is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the thermal conductive paste.

6. The thermal conductive paste according to claim 1 or 2, wherein the thermal conductive paste is heated from room temperature to 200°C over a 60-minute heating period, and then held for 120 minutes to heat-cur the cured product, the cured product having a thermal conductivity of 30 W / mK or more and 150 W / mK or less as measured by the laser flash method.

7. The heat-conductive paste according to claim 1 or 2, wherein the heat-conductive paste is heated from room temperature to 200°C over a 60-minute heating period, and then held for 120 minutes to obtain a cured product which contains a resin derived from the epoxy group-containing acrylic resin, and the amount of the resin is 2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the cured product.

8. A thermally conductive paste according to claim 1 or 2, used for bonding semiconductor elements with a thickness of 120 μm or less onto a substrate.

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