Conductive pastes, cured products, and semiconductor devices

Abstract

To provide a conductive paste with an improved balance of mounting reliability and thermal conductivity.SOLUTION: A conductive paste includes a (meth)acrylic monomer (A), a (meth)acrylic polymer (B) and a conductive particle (C). In the conductive paste, thermal conductivity λ in a thickness direction measured by a laser flash method at 25°C is 10 W / m K or more, with regard to a 1 mm-thick cured product obtained by raising a temperature of the conductive paste from 30°C to 200°C at a constant rate for 60 minutes and subsequently heating at 200°C for 2 hours. Also, a dynamic storage modulus E' is 20 GPa or less measured by viscosity / elasticity measurement at 25°C in a tension mode at frequency 10 Hz, with regard to a 250 μm-thick cured product obtained by raising the temperature of the conductive paste from 30°C to 200°C at a constant rate for 60 minutes and subsequently heating at 200°C for 2 hours.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a conductive paste, a cured product, and a semiconductor device.

[0002] A semiconductor device, for example, has a structure in which semiconductor elements are stacked on a substrate, and the electrodes of the semiconductor elements are connected to electrodes on the substrate. In such semiconductor devices, a paste-like resin composition is used to bond semiconductor elements to a substrate. That is, the semiconductor elements are stacked on the substrate via an adhesive layer formed from the paste.

[0003] The paste used to bond semiconductor devices requires both electrical and thermal conductivity, and metal nanoparticles are incorporated as components to impart these properties.

[0004] For example, Patent Document 1 describes a thermosetting resin composition comprising (A) plate-type silver fine particles, (B) silver powder having an average particle size of 0.5 to 30 μm, and (C) a thermosetting resin. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-194013 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, semiconductor devices such as semiconductor chips have become smaller and thinner. In these smaller and thinner semiconductor chips, there is an increasing need to make the adhesive layer used to bond the semiconductor elements thinner.

[0007] In addition, semiconductor chips are increasingly required to have high mounting reliability in recent years. However, a problem has arisen where mounting reliability deteriorates as the thickness of the adhesive layer is reduced.

[0008] Furthermore, improved thermal conductivity is required for the adhesive layer of semiconductor chips. This is to efficiently dissipate the heat generated by the semiconductor chip to the outside and prevent thermal runaway of the semiconductor chip.

[0009] This invention was made in view of these circumstances, and aims to provide a conductive paste with an improved balance between mounting reliability and thermal conductivity. [Means for solving the problem]

[0010] According to the present invention, the following conductive paste, cured product, and semiconductor device are provided. [1] (Meth)acrylic monomer (A) and (Meth)acrylic polymer (B) and Conductive particles (C) and In a conductive paste containing, The conductive paste is heated at a constant rate from 30°C to 200°C for 60 minutes, and then heated at 200°C for 2 hours to obtain a 1 mm thick cured product. The thermal conductivity λ in the thickness direction at 25°C, measured by the laser flash method, is 10 W / m·K or higher, and A conductive paste in which the conductive paste is heated at a constant rate from 30°C to 200°C over 60 minutes, followed by heating at 200°C for 2 hours to obtain a cured product with a thickness of 250 μm, and the dynamic storage modulus E' determined by viscoelastic measurement at 25°C, tensile mode, and frequency of 10 Hz is 20 GPa or less. [2] In the conductive paste described in [1] above, A conductive paste in which the conductive particle (C) content is 50% by mass or more and 99% by mass or less. [3] In the conductive paste described in [1] or [2] above, A conductive paste comprising the above (meth)acrylic monomer (A) including a monofunctional (meth)acrylic monomer (A1) and a polyfunctional (meth)acrylic monomer (A2). [4] The conductive paste according to any one of [1] to [3] above, A conductive paste, wherein the glass transition temperature (Tg) of the (meth)acrylic polymer (B) is -75°C or higher and 25°C or lower. [5] The conductive paste according to any one of [1] to [4] above, A conductive paste, wherein the weight average molecular weight of the (meth)acrylic polymer (B) is 5000 or less. [6] The conductive paste according to any one of [1] to [5] above, A conductive paste, wherein the (meth)acrylic polymer (B) has a reactive group. [7] The conductive paste according to any one of [1] to [6] above, A conductive paste, wherein the dynamic storage elastic modulus E' obtained by subjecting a cured product having a thickness of 250 μm obtained by heating the conductive paste from 30°C to 200°C at a constant rate over 60 minutes, followed by heating at 200°C for 2 hours to viscoelasticity measurement at 250°C, in a tensile mode, and at a frequency of 10 Hz is 2 GPa or more. [8] The conductive paste according to any one of [1] to [7] above, A conductive paste, further comprising spacer particles. [9] The conductive paste according to any one of [1] to [8] above, A conductive paste, further comprising a coupling agent.

[10] The conductive paste according to any one of [1] to [9] above, A conductive paste, further comprising a radical polymerization initiator.

[11] The conductive paste according to any one of [1] to

[10] above, A conductive paste, which is for die attachment.

[12] A cured product of the conductive paste according to any one of [1] to

[11] above.

[13] base material and A semiconductor element mounted on the substrate via an adhesive layer which is a cured product of the conductive paste described in any of [1] to

[11] above, A semiconductor device equipped with a semiconductor device. [Effects of the Invention]

[0011] According to the present invention, a conductive paste is provided that offers an improved balance between mounting reliability and thermal conductivity. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view showing an example of a semiconductor device according to this embodiment. [Modes for carrying out the invention]

[0013] The present invention will be described below based on embodiments.

[0014] In this embodiment, unless otherwise specified, "A~B" indicating a numerical range means A or greater and B or less.

[0015] In the notation of groups (atomic groups) in this embodiment, notations that do not specify whether they are substituted or unsubstituted include both unsubstituted and substituted groups. For example, "alkyl group" includes not only unsubstituted alkyl groups but also substituted alkyl groups.

[0016] In this embodiment, the term "(meth)acrylic" represents a concept that encompasses both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate."

[0017] In this embodiment, the content of each component in the conductive paste refers to the content relative to the total components of the conductive paste excluding the solvent, if such a solvent is included as described later.

[0018] [Conductive paste] The conductive paste of this embodiment is (Meth)acrylic monomer (A) and (Meth)acrylic polymer (B) and Conductive particles (C) and In a conductive paste containing, The conductive paste is heated at a constant rate from 30°C to 200°C for 60 minutes, and then heated at 200°C for 2 hours to obtain a 1 mm thick cured product. The thermal conductivity λ in the thickness direction at 25°C, measured by the laser flash method, is 10 W / m·K or higher, and The conductive paste is heated at a constant rate from 30°C to 200°C over 60 minutes, and then heated at 200°C for 2 hours to obtain a cured product with a thickness of 250 μm. The dynamic storage modulus E' determined by viscoelastic measurement at 25°C, tensile mode, and frequency of 10 Hz is 20 GPa or less.

[0019] The inventors of this invention conducted studies to improve mounting reliability and found that incorporating a low-stress agent improves mounting reliability. Here, a low-stress agent is an agent that is generally recognized by those skilled in the art as having functions such as reducing the elastic modulus and thereby easing the stress on the cured material. However, the inventors' studies revealed that incorporating a low-stress agent tends to worsen the thermal conductivity of the adhesive layer formed from the conductive paste.

[0020] The conductive paste of this embodiment improves the balance between mounting reliability and thermal conductivity.

[0021] The mechanism by which the conductive paste of this embodiment improves the balance between mounting reliability and thermal conductivity is not clear, but it is presumed to be due to the inclusion of the above-mentioned components (A) and (B), and that the thermal conductivity and flexibility of the cured product formed from the conductive paste are both above a certain level.

[0022] <(meth)acrylmonomer(A)>

[0023] The type of (meth)acrylic monomer (A) is not particularly limited; any monomer having a (meth)acrylic group can be used without any particular restriction.

[0024] (Meth)acrylic monomers (A) are broadly classified into monofunctional (meth)acrylic monomers (A1), which have only one (meth)acrylic group in the molecule, and polyfunctional (meth)acrylic monomers (A2), which have two or more (meth)acrylic groups in the molecule.

[0025] The inclusion of a monofunctional (meth)acrylic monomer (A1) is preferable because it can suppress curing shrinkage, while the inclusion of a polyfunctional (meth)acrylic monomer (A2) is preferable because it can increase the elasticity of the cured product formed from the conductive paste.

[0026] As the monofunctional (meth)acrylic monomer (A1), it is preferable to use a (meth)acrylic acid ester represented by the following formula (1).

[0027] [ka]

[0028] In the above equation (1), R 11 R is a hydrogen or methyl group, 12 R is a monovalent organic group with 1 to 20 carbon atoms. 12 It may contain one or more of the oxygen atom, nitrogen atom, and phosphorus atom, and its R 12 The structure may include hydroxyl groups, carboxyl groups, epoxy groups, oxetanyl groups, amino groups, amide groups, etc.

[0029] The (meth)acrylic acid ester represented by formula (1) above is not particularly limited, but for example, R 12Examples of compounds containing a hydroxyl group in their structure include 1,4-cyclohexanedimethanol monoacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2-methacryloyloxyethyl hexahydrophthalic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-acryloyloxyethyl acid phosphate, and 2-methacryloyloxyethyl acid phosphate.

[0030] Also, R 12Examples of compounds that do not contain a hydroxyl group in their structure include ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isoamyl acrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl acrylate, n-lauryl methacrylate, n-tridecyl methacrylate, n-stearyl acrylate, n-stearyl methacrylate, isostearyl acrylate, ethoxydiethylene glycol acrylate, butoxydiethylene glycol methacrylate, methoxytriethylene glycol acrylate, 2-ethylhexyldiethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypolyethylene glycol methacrylate, methoxy Examples include psidipropylene glycol acrylate, cyclohexyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, nonylphenol ethylene oxide modified acrylate, phenylphenol ethylene oxide modified acrylate, isobornyl acrylate, isobornyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate quaternary, glycidyl methacrylate, and neopentyl glycol acrylate benzoate.

[0031] Examples of polyfunctional (meth)acrylic monomers (A2) include bis(meth)acrylic acid esters. Such bis(meth)acrylic acid esters include 4,4'-isopropylidenediphenol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,6-bis((meth)acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1,4-bis((meth)acryloyloxy)butane, 1,6-bis((meth)acryloyloxy)hexane, triethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, N,N'-di(meth)acryloylethylenediamine, N,N'-(1,2-dihydroxyethylene)bis(meth)acrylamide, or 1,4-bis((meth)acryloyl)piperazine.

[0032] From the perspective of achieving both suppression of curing shrinkage and increased elasticity, it is more preferable that the above monomer (A) includes a monofunctional (meth)acrylic monomer (A1) and a polyfunctional (meth)acrylic monomer (A2).

[0033] When monomer (A) contains both (A1) and (A2), the upper limit of the ratio of (A1) to (A2) is preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less. By having an excess of polyfunctional (meth)acrylic monomer in this way, it is possible to suppress the formation of (meth)acrylic monomers that do not contribute to polymerization, and a strong crosslinked structure can be formed.

[0034] The lower limit of the ratio of the content of (A1) to (A2) is, for example, 0.3 or more, and preferably 0.5 or more.

[0035] The content of (meth)acrylic monomer (A) in the conductive paste is preferably 4% by mass or more, more preferably 6% by mass or more, and even more preferably 8% by mass or more.

[0036] The content of (meth)acrylic monomer (A) in the conductive paste is preferably 27% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0037] The conductive paste of this embodiment may contain only one type of (meth)acrylic monomer (A), or it may contain two or more types.

[0038] <(meth)acrylic polymer (B)> The (meth)acrylic polymer (B) contained in the conductive paste of this embodiment can be obtained by polymerizing any (meth)acrylic monomer using known techniques such as solution polymerization, which utilize common polymerization initiators and chain transfer agents. The (meth)acrylic monomers used can be those exemplified as examples of (meth)acrylic monomers in the section <(meth)acrylic monomer (A)>.

[0039] Examples of commercially available (meth)acrylic polymers (B) include the "ARUFON" series from Toagosei Co., Ltd.

[0040] The (meth)acrylic polymer (B) contained in the conductive paste of this embodiment preferably includes a (meth)acrylic acid polymer.

[0041] The weight-average molecular weight of the (meth)acrylic polymer (B) is preferably 1000 or more, more preferably 1500 or more, and even more preferably 2000 or more. This improves the mechanical strength of the adhesive layer formed from the conductive paste.

[0042] The weight-average molecular weight of the (meth)acrylic polymer (B) is preferably 5000 or less, more preferably 4500 or less, and even more preferably 4000 or less. This improves the flexibility of the adhesive layer formed from the conductive paste and improves adhesion to the substrate. Furthermore, this further improves the balance between mounting reliability and thermal conductivity.

[0043] The weight-average molecular weight of polymer (B) can be measured, for example, by gel permeation chromatography as described below (Method 1). (Method 1) The instrument itself is a TOSOH HLC-8120, and the analytical columns are also manufactured by TOSOH (G1000HXL: 1, G2000HXL: 2, G3000HXL: 1). Using the above-mentioned apparatus and analytical column, GPC measurements were performed with a differential refractometer as the detector under analytical conditions of a flow rate of 1.0 ml / min, elution solvent tetrahydrofuran, and column temperature of 40°C. The molecular weight was then converted using standard polystyrene.

[0044] The glass transition temperature (Tg) of the (meth)acrylic polymer (B) is preferably -75°C or higher, more preferably -70°C or higher, and even more preferably -65°C or higher.

[0045] The glass transition temperature (Tg) of the (meth)acrylic polymer (B) is not particularly limited, but is preferably 25°C or lower, more preferably 22°C or lower, and even more preferably 20°C or lower. This improves the flexibility of the adhesive layer formed from the conductive paste and improves adhesion to the substrate. Furthermore, this further improves the balance between mounting reliability and thermal conductivity.

[0046] The glass transition temperature of polymer (B) can be measured, for example, according to JIS K 7121-2012 (Method for measuring transition temperature of plastics).

[0047] The (meth)acrylic polymer (B) preferably has a reactive group. Examples of reactive groups include isocyanate groups, hydroxyl groups, amino groups, and epoxy groups.

[0048] Polymer (B) containing reactive groups can react and polymerize with various components in the conductive paste. This forms a crosslinked structure, allowing the elastic modulus of the adhesive layer formed from the conductive paste to be within an appropriate range. Furthermore, the reactive groups can react with functional groups present on the surface of the substrate or semiconductor device. This improves adhesion to the substrate or semiconductor device.

[0049] The (meth)acrylic polymer (B) having reactive groups forms a cross-linked structure through various reactions and polymerization with components contained in the conductive paste. This allows the elastic modulus of the adhesive layer formed from the conductive paste to be within an appropriate range. In addition, the reactive groups improve adhesion to substrates, semiconductor devices, etc.

[0050] Examples of commercially available (meth)acrylic polymers (B) having reactive groups include the "ARUFON" series from Toagosei Co., Ltd.

[0051] The content of (meth)acrylic polymer (B) in the conductive paste is preferably 2% by mass or more, more preferably 2.5% by mass or more, and even more preferably 3% by mass or more. This allows the adhesive layer formed from the conductive paste to have appropriate adhesion.

[0052] The content of (meth)acrylic polymer (B) in the conductive paste is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. This allows the viscosity of the paste to be within an appropriate range, improving workability during application.

[0053] The conductive paste of this embodiment may contain only one type of (meth)acrylic polymer (B), or it may contain two or more types.

[0054] <Conductive particles (C)> The type of conductive particle (C) is not particularly limited; any conductive material can be used without any restrictions.

[0055] The shape of the conductive particles (C) is not particularly limited, and for example, spherical, elliptical, flaky, and scaly shapes can be used. From the viewpoint of improving the dispersibility of the conductive particles (C), the shape of the conductive particles (C) is preferably spherical. Further, from the viewpoint of improving conductivity, the shape of the conductive particles (C) is preferably flaky.

[0056] From the viewpoint of improving the balance between the conductivity of the adhesive layer and the dispersibility of the conductive particles (C), it is preferable that the conductive particles (C) include both spherical particles and flaky particles.

[0057] The material of the conductive particles (C) is not particularly limited, and for example, metal particles such as silver particles, gold particles, and copper particles; metal-coated particles such as silver-coated particles can be used.

[0058] Commercial products of metal particles such as silver particles can be obtained from, for example, Tokuriki Honten Co., Ltd., Fukuda Metal Foil & Powder Co., Ltd., DOWA Hightech Co., Ltd., etc. Further, commercial products of metal-coated particles such as silver-coated particles can be obtained from, for example, Mitsubishi Materials Corporation, Sekisui Chemical Co., Ltd., Sanyo Co., Ltd., etc.

[0059] The particle diameter D at 50% cumulative in the volume-based particle size distribution of the conductive particles (C) 50 is preferably 0.3 µm or more, more preferably 0.5 µm or more, still more preferably 0.8 µm or more.

[0060] The D of the conductive particles (C) 50 is preferably 5 µm or less, more preferably 4.5 µm or less, still more preferably 4 µm or less.

[0061] The D of the conductive particles (C) 50 can be determined by performing particle image measurement using, for example, a flow-type particle image analyzer FPIA (registered trademark)-3000 manufactured by Sysmex Corporation. More specifically, the particle diameter of the conductive particles (C) can be determined by measuring the volume-based median diameter using the aforementioned apparatus. This method for determining particle size is the D of the spacer particle, which will be described later. 50 The same conditions can be applied to this as well.

[0062] The content of conductive particles (C) in the conductive paste is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. This improves both electrical conductivity and thermal conductivity.

[0063] The content of conductive particles (C) in the conductive paste is preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less. This allows the viscosity of the conductive paste to be within an appropriate range, improving workability.

[0064] The conductive paste of this embodiment may contain only one type of conductive particle (C), or it may contain two or more types.

[0065] <Optional ingredients> The conductive paste of this embodiment may contain components other than those described above (A) to (C) as optional components.

[0066] The conductive paste of this embodiment may contain spacer particles as an optional component. The spacer particles function to control the film thickness of the adhesive layer formed from the conductive paste, and their inclusion allows for precise control of the film thickness.

[0067] The material of the spacer particles is not particularly limited, but it is preferable that they contain a resin component. Specifically, it is preferable that they contain polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polytetrafluoroethylene, polystyrene, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyimide, polysulfone, polyphenylene oxide, polyacetal, etc.

[0068] From the viewpoint of heat resistance and elastic modulus of the spacer particles, it is preferable that the spacer particles contain a crosslinkable resin. Specifically, it is more preferable that they contain crosslinkable resins such as epoxy resin, phenolic resin, melamine resin, unsaturated polyester resin, divinylbenzene polymer, divinylbenzene-styrene copolymer, divinylbenzene-acrylic acid ester copolymer, diallyl phthalate polymer, triallyl isocyanurate polymer, and benzoguanamine polymer. Of these resins, the most preferred are crosslinkable resins whose main chain is a divinylbenzene skeleton. Specific examples of crosslinkable resins with a divinylbenzene skeleton as the main chain include divinylbenzene polymers, divinylbenzene-styrene copolymers, divinylbenzene-acrylic acid ester copolymers, and diallyl phthalate polymers. The crosslinkable resin having a divinylbenzene skeleton as its main chain has a low risk of ionic impurities being introduced during its manufacturing process. Therefore, using spacer particles containing the crosslinkable resin having a divinylbenzene skeleton as its main chain further improves mounting reliability.

[0069] Particle size D at 50% accumulation in the volume-based particle size distribution of spacer particles 50 The thickness is 5 μm or more, preferably 7 μm or more, and more preferably 10 μm or more. This makes it possible to form an adhesive layer with high accuracy in thickness even when the thickness of the adhesive layer is set to be thin, thereby improving the mounting reliability of semiconductor devices.

[0070] Spacer particle D 50 The thickness is 100 μm or less, preferably 90 μm or less, and more preferably 80 μm or less. This makes it possible to form an adhesive layer with high accuracy in terms of film thickness even when the adhesive layer thickness is set to be thin, thereby improving the mounting reliability of semiconductor devices.

[0071] The particle size distribution of the spacer particles is preferably set to a narrow width, which allows for more precise control of the film thickness of the adhesive layer formed from the conductive paste. The coefficient of variation (Cv) can be used as an indicator of the particle size distribution of spacer particles. The coefficient of variation (Cv) is calculated by dividing the standard deviation by the arithmetic mean, and represents the relative variability of the values. It is preferable to set the coefficient of variation (Cv) to be small, as this allows for more precise control of the film thickness of the adhesive layer formed from the conductive paste. Specifically, the coefficient of variation Cv of the particle size distribution of the spacer particles is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less.

[0072] The coefficient of variation Cv of the particle size distribution of spacer particles can be calculated by dividing the standard deviation of the particle size distribution of the spacer particles by the arithmetic mean of the particle sizes of the spacer particles.

[0073] It is preferable for the spacer particles to have high strength. This makes it difficult for the spacer particles to break even when external force is applied to the adhesive layer formed from the conductive paste, thus maintaining the thickness of the adhesive layer. Specifically, the compressive fracture strength of the spacer particles is 3 kg / mm². 2 Preferably 4 kg / mm 2 It is more preferable that it be 5 kg / mm 2 It is even more preferable that the above conditions are met.

[0074] The compressive fracture strength of the spacer particles can be measured according to JIS Z 8844:2019 (Method for measuring fracture strength and deformation strength of fine particles).

[0075] The content of spacer particles in the conductive paste is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more.

[0076] The content of spacer particles in the conductive paste is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less.

[0077] The conductive paste of this embodiment may contain only one type of spacer particle, or it may contain two or more types.

[0078] The conductive paste of this embodiment may contain a coupling agent as an optional component. The inclusion of a coupling agent improves the adhesion of the conductive paste to the substrate.

[0079] Various silane compounds such as epoxysilane, mercaptosilane, aminosilane, alkylsilane, ureidosilane, vinylsilane, and (meth)acrylsilane can be used as coupling agents. Examples of these include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane (3-glycidyloxypropyltrimethoxysilane), γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, vinyltriacetoxysilane, phenylaminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-anilinopropyltrimethoxysilane, γ-anilinopropylmethyldimethoxysilane, γ-[bis(β-hydroxyethyl)]aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(A Examples of silane coupling agents include minoethyl)-γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-(β-aminoethyl)aminopropyldimethoxymethylsilane, N-(trimethoxysilylpropyl)ethylenediamine, N-(dimethoxymethylsilylisopropyl)ethylenediamine, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, hexamethyldisilane, vinyltrimethoxysilane, 3-isocyanatetopropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-(trimethoxysilyl)propyl methacrylate, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, or hydrolysates thereof.

[0080] The content of the coupling agent in the conductive paste is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.15% by mass or more. Furthermore, the content of the coupling agent in the conductive paste is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0081] The conductive paste of this embodiment may contain only one coupling agent, or it may contain two or more coupling agents.

[0082] The conductive paste of this embodiment may contain a radical polymerization initiator as an optional component. The inclusion of a radical polymerization initiator generates radicals within the system, promoting the polymerization of monomers (A), etc.

[0083] Examples of radical polymerization initiators include azo compounds and peroxides, with the use of peroxides being preferable.

[0084] Examples of peroxides include, Examples of organic peroxides include diacyl peroxides, dialkyl peroxides, and peroxyketals, and more specifically, ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; Peroxyketals such as 1,1-di(t-butylperoxy)cyclohexane and 2,2-di(4,4-di(t-butylperoxy)cyclohexyl)propane; Hydroperoxides such as p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide; Dialkyl peroxides such as bis(1-phenyl-1-methylethyl)peroxide, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, and di-t-butyl peroxide; Diacyl peroxides such as dibenzoyl peroxide and di(4-methylbenzoyl) peroxide; Peroxydicarbonates such as di-n-propyl peroxydicarbonate and diisopropyl peroxydicarbonate; Examples include peroxyesters such as 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-hexylperoxybenzoate, t-butylperoxybenzoate, and t-butylperoxy2-ethylhexanonate. Furthermore, compounds having two or more peroxy groups in one molecule, such as 1,1-bis(1,1-dimethylethylperoxy)cyclohexane, can also be cited.

[0085] The content of the radical polymerization initiator in the conductive paste is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.15% by mass or more. Furthermore, the content of the radical polymerization initiator in the conductive paste is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0086] The conductive paste of this embodiment may contain only one radical polymerization initiator, or it may contain two or more radical polymerization initiators.

[0087] The conductive paste of this embodiment may contain a stress-reducing agent as an optional component. In this embodiment, the stress-reducing agent is an agent that can relieve stress when an external force is applied to the adhesive layer formed from the conductive paste. This stress-reducing agent is not particularly limited as long as it can reduce stress, but for example, acrylic rubber, silicone rubber, urethane rubber, styrene-butadiene rubber, butadiene rubber, and modified versions thereof can be used.

[0088] The stress-reducing agent preferably has reactive groups that can react with other components such as (meth)acrylic monomer (A) or (meth)acrylic polymer (B). Examples of reactive groups include those found in (meth)acrylic polymer (B), as described above.

[0089] The content of the low-stress agent in the conductive paste is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and even more preferably 1% by mass or more. Furthermore, the content of the low-stress agent in the conductive paste is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0090] The conductive paste of this embodiment may contain only one type of low-stress agent, or it may contain two or more types.

[0091] The conductive paste of this embodiment may contain a solvent as an optional component. The inclusion of a solvent reduces the viscosity of the conductive paste, improving its workability.

[0092] Examples of solvents include alcohols such as 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 glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, methyl methoxybutanol, α-terpineol, β-terpineol, hexylene glycol, benzyl alcohol, 2-phenylethyl alcohol, isopalmityl alcohol, isostearyl alcohol, lauryl alcohol, ethylene glycol, propylene glycol, or glycerin; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol (4-hydroxy-4-methyl-2- Ketones such as 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-diacetone Esters such as xyethane, tributyl phosphate, tricresyl phosphate, or tripentyl phosphate; ethers such as tetrahydrofuran, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, ethoxyethyl ether, 1,2-bis(2-diethoxy)ethane, or 1,2-bis(2-methoxyethoxy)ethane; ester ethers such as 2-(2-butoxyethoxy)ethane acetate;Examples include 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; silicone oils such as volatile organic modified silicone oils; and others.

[0093] The solvent content in the conductive paste can be arbitrarily set according to the desired viscosity.

[0094] The conductive paste of this embodiment may contain only one solvent, or it may contain two or more solvents.

[0095] Other optional components that can be included in the conductive paste include known additives such as curing agents, curing accelerators, polymerization inhibitors, defoaming agents, surfactants, and dicyandiamide derivatives. The content of these optional components can be arbitrarily set according to the physical properties to be imparted.

[0096] The conductive paste of this embodiment may contain only one of the above-mentioned optional components, or it may contain two or more.

[0097] <Method for manufacturing conductive paste> The conductive paste of this embodiment can be obtained by mixing the above-mentioned components.

[0098] For example, the mixture can be prepared by pre-mixing each component, kneading it using a three-roll mill, and then degassing it under vacuum.

[0099] <Physical properties of conductive paste> The conductive paste of this embodiment forms a cured product that possesses a certain level of thermal conductivity and flexibility.

[0100] in particular, The conductive paste of this embodiment is heated at a constant rate from 30°C to 200°C for 60 minutes, and then heated at 200°C for 2 hours to obtain a 1 mm thick cured product. The thermal conductivity λ in the thickness direction at 25°C, measured by the laser flash method, is 10 W / m·K or higher, and The dynamic storage modulus E' of the conductive paste of this embodiment, obtained by heating the paste at a constant rate from 30°C to 200°C for 60 minutes, and then heating it at 200°C for 2 hours to obtain a cured product with a thickness of 250 μm, is determined to be 20 GPa or less by viscoelastic measurement at 25°C, tensile mode, and frequency of 10 Hz.

[0101] Preferably, the thermal conductivity λ measured by the above method is 12 W / m·K or higher, and the dynamic storage modulus E' measured by the above method is 18 GPa or lower. It is more preferable that the thermal conductivity λ measured by the above method is 15 W / m·K or higher, and the dynamic storage modulus E' measured by the above method is 16 GPa or lower.

[0102] This improves the balance between thermal conductivity and flexibility of the adhesive layer formed from the conductive paste, thereby enhancing the mounting reliability of semiconductor devices.

[0103] The thermal conductivity λ measured by the above method is preferably 12 W / m·K or higher, and more preferably 15 W / m·K or higher. This improves the thermal conductivity of the adhesive layer formed from the conductive paste, allowing heat to be released more efficiently from within the semiconductor device.

[0104] The dynamic storage modulus E' measured by the above method is preferably 18 GPa or less, and more preferably 16 GPa or less. This improves the flexibility of the adhesive layer formed from the conductive paste and improves its adhesion to the substrate.

[0105] Since semiconductor devices require mounting reliability under a wide range of temperature conditions, from room temperature to high temperatures, it is preferable that the elastic modulus of the adhesive layer formed from the conductive paste is maintained even under high-temperature conditions.

[0106] Specifically, the dynamic storage modulus E' obtained by viscoelastic measurement of a 250 μm thick cured product obtained by heating the conductive paste of this embodiment from 30°C to 200°C at a constant rate for 60 minutes, followed by heating at 200°C for 2 hours, at 250°C, in tensile mode, and at a frequency of 10 Hz, is preferably 2 GPa or more, more preferably 4 GPa or more, and even more preferably 6 GPa or more.

[0107] <Applications of conductive paste> The applications of the conductive paste in this embodiment are not particularly limited, but it is preferably used for die-attachment applications in semiconductor devices, where semiconductor elements are bonded to a support such as a substrate.

[0108] [Cured product] The cured product of this embodiment is the cured product of the conductive paste described above.

[0109] The curing method for obtaining the cured product of this embodiment is not particularly limited, but for example, the cured product can be obtained by curing components such as (meth)acrylic monomer (A) with heat or light.

[0110] The heat treatment temperature for the conductive paste is preferably 150°C or higher, more preferably 175°C or higher, and even more preferably 200°C or higher. Furthermore, the heat treatment temperature of the conductive paste is preferably 500°C or lower, more preferably 400°C or lower, and even more preferably 300°C or lower.

[0111] [Semiconductor device] The semiconductor device of this embodiment comprises a substrate and a semiconductor element mounted on the substrate via an adhesive layer which is a cured product of the conductive paste described above.

[0112] An example of a semiconductor device according to this embodiment will be described with reference to Figure 1. Figure 1 is a cross-sectional view showing a semiconductor device 100 according to this embodiment. The semiconductor device 100 according to this embodiment comprises a substrate 30 and a semiconductor element 20 mounted on the substrate 30 via an adhesive layer 10 which is a cured product of a conductive paste.

[0113] The semiconductor element 20 and the substrate 30 are electrically connected, for example, via bonding wires 40. The semiconductor element 20 is also sealed, for example, with a sealing resin 50.

[0114] The thickness of the adhesive layer 10 is not particularly limited, but is, for example, 5 μm or more and 100 μm or less.

[0115] In the example shown in Figure 1, the substrate 30 is a lead frame composed of a die pad 32 and an outer lead 34. In this case, the semiconductor element 20 is mounted on the die pad 32 via a die attach layer 10. The semiconductor element 20 is electrically connected to the outer lead 34, for example, via a bonding wire 40. The substrate 30, which is the lead frame, is composed of, for example, a 42 alloy or a Cu frame.

[0116] The substrate 30 may be an organic substrate or a ceramic substrate. As the organic substrate, substrates known to those skilled in the art, such as those coated with epoxy resin, cyanate resin, or maleimide resin, are preferred. Furthermore, the surface of the substrate 30 may be coated with silver or the like to improve adhesion with the die attach paste.

[0117] The planar shape of the semiconductor element 20 is not particularly limited, but for example, it is rectangular. In this embodiment, for example, a rectangular semiconductor element 20 having a chip size of 0.5 × 0.5 mm or more and 15 × 15 mm or less can be used.

[0118] The semiconductor device 100 can be manufactured, for example, by the following procedure.

[0119] First, the conductive paste described above is applied to the die pad 32 (substrate 30), and the semiconductor element 20 is mounted on top of the applied conductive paste. The method for applying the conductive paste is not particularly limited, but examples include dispensing, printing, and inkjet methods.

[0120] Next, the conductive paste is heat-treated to harden it. This forms an adhesive layer 10 on the die pad 32 (substrate 30). The temperature conditions for the heat treatment can be set appropriately depending on the composition of the conductive paste.

[0121] Next, the semiconductor element 20 and the outer lead 34 (substrate 30) are electrically connected using bonding wires 40, and the semiconductor element 20 is sealed with sealing resin 50 to obtain the semiconductor device 100.

[0122] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. [Examples]

[0123] [Preparation of conductive paste] A conductive paste was prepared by uniformly mixing each component according to the formulation shown in Table 1. The units for the content of each component in Table 1 are parts by mass.

[0124] The details of the components shown in Table 1 are as follows:

[0125] <Monomer (A)> • Light ester PO (2-phenoxyethyl methacrylate, manufactured by Kyoeisha Chemical Co., Ltd.) • Light ester 1.6HX (1.6-hexanediol dimethacrylate, manufactured by Kyoeisha Chemical Co., Ltd.) • Light Ester EG (ethylene glycol dimethacrylate, manufactured by Kyoeisha Chemical Co., Ltd.) • Light ester TMP (trimethylolpropane trimethacrylate, Kyoeisha Chemical Co., Ltd.)

[0126] <Polymer (B)> ARUFON UG-4010 (Acrylic acid polymer containing epoxy groups, glass transition temperature: -57°C, weight-average molecular weight: 2900, manufactured by Toagosei Co., Ltd.)

[0127] <Conductive particles (C)> ·AG-DSB-114 (silver particles, D 50 (0.7μm, manufactured by DOWA High-Tech Co., Ltd.) ·HKD-12 (silver particles, D 50 (7.6 μm, manufactured by Fukuda Metal Foil Powder Co., Ltd.)

[0128] <Optional ingredients> • Percadox BC (radical polymerization initiator, dialphakmyl peroxide, manufactured by Agzo Pharmaceuticals) • Low-stress agent 1 (Low-stress agent, 1,4-Cyclohexanedicarboxylic acid, di-2-propenyl ester, polymer with 1,2-propanediol, manufactured by Kanto Chemical Co., Ltd.) • SP-239 (Spacer particles, divinylbenzene polymer, D 50 :39μm, Coefficient of Variation Cv: 5%, Compressive Breaking Strength: 11kg / mm 2 (Manufactured by Sekisui Chemical Co., Ltd.)

[0129] [Evaluation of the physical properties of hardened materials] <Thermal conductivity> The conductive paste obtained by the above method was applied to a Teflon® plate, and the temperature was raised at a constant rate from 30°C to 200°C over 60 minutes, followed by heating at 200°C for 2 hours to obtain a cured sample with a thickness of 1 mm. The obtained cured sample was peeled off the Teflon® plate, and the thermal conductivity λ in the thickness direction at 25°C was measured by the laser flash method. The results are shown in Table 1.

[0130] <modulus of elasticity> The conductive paste obtained by the above method was applied to a Teflon® plate, and the temperature was increased at a constant rate from 30°C to 200°C over 60 minutes, followed by heating at 200°C for 2 hours to obtain a cured sample with a thickness of 250 μm. The obtained cured sample was peeled off the Teflon® plate, and the dynamic storage modulus E' was measured at 25°C (or 250°C), in tensile mode, and at a frequency of 10 Hz. The results are shown in Table 1.

[0131] [Implementation reliability evaluation] <Preparation of test specimens> The conductive paste obtained by the above method was applied to the surface of a copper frame, and a silicon chip measuring 5 mm in length and 5 mm in width and 200 μm thick was mounted on top of the applied conductive paste. The thickness of the conductive paste layer (adhesive layer) with the silicon chip mounted was determined by the amount of D of the compounded spacer particles (D). 50 It followed the value. Next, the temperature was raised from 30°C to 200°C at a rate of 2.83°C / min in an oven under a nitrogen atmosphere, and then the specimen was heat-treated at 200°C for 2 hours to obtain the test piece.

[0132] <Void occurrence rate> The conductive paste layer of the test specimens obtained by the above method was peeled off, and air bubbles in the adhesive layer were observed using an X-ray transmission device. The ratio of the area of ​​air bubbles (voids) to the area of ​​the 5 × 5 mm chip was evaluated according to the following evaluation criteria. The results are shown in Table 1. A: The area ratio of bubbles is 5% or less. B: The area ratio of the bubbles is greater than 5% and less than or equal to 10%. C: The area ratio of the bubbles is greater than 10%.

[0133] <msl> The test specimens obtained using the above method were sealed with an epoxy sealant, heat-treated in a 175°C oven for 4 hours to perform post-molding curing, and a package structure with a length of 14 mm, a width of 14 mm, and a thickness of 0.8 mm was obtained. The package structure obtained by the above method was placed in a constant temperature and humidity chamber at a temperature of 60°C and a relative humidity of 60% for 40 hours, and then passed through a reflow oven at 260°C at a speed of 67 cm / min three times to obtain a package structure that had undergone MSL (Moisture Sensitivity Level) testing. The delamination state of the heat-tested package structures obtained by the above method was observed and evaluated according to the following evaluation criteria. The results are shown in Table 1. Acceptable: No delamination occurred between the conductive paste layer and the copper frame, or between the sealant and the copper frame. Failure: Delamination occurred between the conductive paste layer and the copper frame and / or between the sealant and the copper frame.

[0134] [Table 1]

[0135] As shown in Table 1, the semiconductor device using the conductive paste of the embodiment exhibited good thermal conductivity and good MSL results. This indicates that the conductive paste of this embodiment improves the balance between mounting reliability and thermal conductivity. [Explanation of Symbols]

[0136] 10 Adhesive layer 20 Semiconductor elements 30 Base material 32 die pads 34 Outer lead 40 Bonding Wires 50 Sealing resin 100 Semiconductor Devices< / msl>

Claims

1. (Meth)acrylic monomer (A) and (Meth)acrylic polymer (B) and Conductive particles (C) and In a conductive paste containing, The conductive paste is heated at a constant rate from 30°C to 200°C over 60 minutes, and then heated at 200°C for 2 hours to obtain a 1 mm thick cured product. The thermal conductivity λ in the thickness direction at 25°C, measured by the laser flash method, is 10 W / m·K or higher, and The conductive paste is heated at a constant rate from 30°C to 200°C for 60 minutes, and then heated at 200°C for 2 hours to obtain a cured product with a thickness of 250 μm. The dynamic storage modulus E', determined by viscoelastic measurement at 25°C, tensile mode, and frequency of 10 Hz, is 20 GPa or less. A conductive paste wherein the (meth)acrylic monomer (A) comprises a monofunctional (meth)acrylic monomer, a difunctional (meth)acrylic monomer, and a trifunctional or more functional (meth)acrylic monomer.

2. In the conductive paste according to claim 1, A conductive paste in which the conductive particle (C) content is 50% by mass or more and 99% by mass or less.

3. In the conductive paste according to claim 1 or 2, A conductive paste wherein the glass transition temperature (Tg) of the (meth)acrylic polymer (B) is -75°C or higher and 25°C or lower.

4. In the conductive paste according to claim 1 or 2, A conductive paste wherein the weight-average molecular weight of the (meth)acrylic polymer (B) is 5000 or less.

5. In the conductive paste according to claim 1 or 2, A conductive paste wherein the (meth)acrylic polymer (B) has a reactive group.

6. In the conductive paste according to claim 1, A conductive paste in which the conductive paste is heated at a constant rate from 30°C to 200°C for 60 minutes, and then heated at 200°C for 2 hours to obtain a cured product with a thickness of 250 μm, the dynamic storage modulus E' determined by viscoelastic measurement at 250°C, tensile mode, and frequency of 10 Hz is 2 GPa or higher.

7. A conductive paste according to claim 1 or 2, Furthermore, a conductive paste containing spacer particles.

8. A conductive paste according to claim 1 or 2, Furthermore, a conductive paste containing a coupling agent.

9. A conductive paste according to claim 1 or 2, Furthermore, a conductive paste containing a radical polymerization initiator.

10. A conductive paste according to claim 1 or 2, A conductive paste used for die attachment.

11. A cured product of a conductive paste according to claim 1 or 2.

12. base material and A semiconductor element mounted on the substrate via an adhesive layer which is a cured product of the conductive paste described in claim 1 or 2, A semiconductor device equipped with a semiconductor device.

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