Conductive pastes, conductive materials, and semiconductor devices

Abstract

The present invention provides a conductive paste that yields a cured product (conductive material) with excellent conductivity and low elastic modulus. [Solution] The conductive paste of the present invention comprises (A) metal particles and (B) resin particles, wherein the mass ratio (B / A) of resin particles (B) to metal particles (A) is 0.06 or more and 1.0 or less.

Description

[Technical Field]

[0001] The present invention relates to conductive paste, conductive material, and semiconductor device. [Background technology]

[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.

[0003] 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, for example. The paste used to bond the semiconductor elements is required to have properties such as conductivity, and metal nanoparticles are incorporated as components to impart these properties.

[0004] Patent Document 1 discloses a low-silver solids conductive adhesive for use in chip packages, comprising dendritic silver powder and an acrylic resin, wherein the dendritic silver powder is present in an amount greater than 0% by weight and less than 40% by weight.

[0005] Patent Document 2 discloses a conductive adhesive composition containing a conductive filler having a predetermined average particle size and metal particles and silver particles, and thermoplastic resin particles that are solid at 25°C. The document exemplifies nylon particles as the thermoplastic resin particles, and these thermoplastic resin particles are added to suppress peeling of the material to be bonded (paragraph 0041, etc.). In the examples, the amount of thermoplastic resin particles in the conductive adhesive composition is 1 to 5% by mass, and the amount of silver particles is 85% by mass or more. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Taiwan Publication No. 1752819 [Patent Document 2] International Publication No. 2019 / 013231 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in the conventional technologies described in Patent Documents 1 and 2, there was room for improvement in the composition of the conductive material. [Means for solving the problem]

[0008] The inventors of the present invention have discovered that a conductive material obtained from a conductive paste containing resin particles in a predetermined range relative to metal particles exhibits excellent conductivity and elastic modulus, thereby completing the present invention. In other words, the present invention can be described as follows.

[0009] [1](A) Metal particles and, (B) Resin particles and Includes, A conductive paste in which the mass ratio (B / A) of resin particles (B) to metal particles (A) is 0.06 or more and 1.0 or less. [2] The conductive paste according to [1], comprising metal particles (A) in an amount of 20% by mass or more and 65% by mass or less in 100% by mass of the entire conductive paste. [3] The conductive paste according to [1] or [2], wherein the metal particles (A) are in the form of flakes or flaky metal particles. [4] A conductive paste according to any one of [1] to [3], wherein the metal particles (A) include at least one selected from silver-containing particles and copper-containing particles. [5] A conductive paste according to any of [1] to [4], wherein the average particle size of the metal particles (A) is 0.5 μm or more and 20 μm or less. [6] A conductive paste according to any one of [1] to [5], wherein the resin particles (B) are made of a thermoplastic resin. [7] The conductive paste according to any one of [1] to [6], wherein the resin particles (B) are spherical resin particles. [8] The conductive paste according to any one of [1] to [7], wherein the average particle diameter of the resin particles (B) is 1 μm or more and 30 μm or less. [9] The conductive paste according to any one of [1] to [8], further comprising (C) a thermosetting resin.

[10] The conductive paste according to [9], wherein the thermosetting resin (C) includes a phenol novolak type epoxy resin.

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

[10] , wherein the elastic modulus at 250 °C of the cured product of the conductive paste obtained under the following conditions is 5 MPa or more and 300 MPa or less. (Condition) The conductive paste was applied on a Teflon plate, heated from 30 °C to 175 °C over 30 minutes, and then heat-treated at 175 °C for 60 minutes. Thereby, a test piece having a thickness of 0.3 mm and including a cured product of the conductive paste was obtained. In the obtained test piece, the cured product was peeled off from the Teflon plate, set in a measuring device (DMS6100 manufactured by Hitachi High-Technologies Corporation), and dynamic viscoelasticity measurement (DMA) was performed in tensile mode at a frequency of 10 Hz to measure the storage elastic modulus E'(MPa) at 250 °C.

[12] A conductive material obtained by curing the conductive paste according to any one of [1] to

[11] .

[13] A base material, a semiconductor element mounted on the base material via an adhesive layer, and comprising, the adhesive layer is a semiconductor device obtained by curing the conductive paste according to any one of [1] to

[11] .

Effect of the Invention

[0010] According to the present invention, it is possible to provide a conductive paste capable of obtaining a cured product (conductive material) excellent in conductivity and elastic modulus. In other words, it is possible to provide a cured product (conductive material) excellent in the balance between conductivity and elastic modulus.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view schematically showing an example of the semiconductor device of the present embodiment.

Best Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description will be omitted as appropriate. Also, for example, "1 to 10" represents "1 or more" to "10 or less" unless otherwise specified. The notation "(meth)acryl" in the present embodiment represents a concept including both acryl and methacryl. The same applies to similar notations such as "(meth)acrylate".

[0013] The conductive paste of the present embodiment contains metal particles (A) and resin particles (B). The mass ratio (B / A) of the resin particles (B) to the metal particles (A) is 0.06 or more and 1.0 or less. In the conductive paste of the present embodiment, when the mass ratio (B / A) is within the above range, a cured product (conductive material) excellent in conductivity and elastic modulus can be obtained.

[0014] [Metal particles (A)] The conductive paste according to the present embodiment contains metal particles (A). The type of the metal particles (A) is not particularly limited, and any metal particles that exhibit conductivity can be used without particular limitation. For example, metal particles of copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimony, or alloys thereof can be included. Among these, due to high conductivity and easy availability, the metal particles (A) preferably contain at least one selected from silver-containing particles and copper-containing particles, and more preferably contain silver-containing particles. The silver-containing particles can cause sintering (sintering) by appropriate heat treatment to form a particle connection structure (sintering structure).

[0015] The metal particles (A) preferably include, for example, spherical, ellipsoidal, flake-shaped, and flaky metal particles. From the viewpoint of reducing the content of metal particles (A) while maintaining good conductivity in the conductive paste, it is preferable that the metal particles include flake-shaped or flaky metal particles, and more preferably that they include flake-shaped metal particles.

[0016] In this embodiment, the conductive paste has a higher ratio of resin particles (B) to metal particles (A) compared to conventional conductive pastes. The presence of resin particles (B) disrupts the orientation of flake-like or flaky metal particles (A) that are aligned in the same direction in a non-contact state, resulting in more contact points between metal particles (A) and the formation of numerous conductive paths. Therefore, conductivity is improved, and the amount of metal particles (A) can be reduced because conductive paths are formed efficiently.

[0017] In this embodiment, the conductive paste has a mass ratio (B / A) within the above range, and conductive paths are efficiently formed, so the amount of metal particles (A) can also be reduced. Specifically, the metal particles (A) can be contained in an amount of preferably 20% to 60% by mass, more preferably 25% to 55% by mass, and even more preferably 30% to 50% by mass, of 100% by mass of the total conductive paste. This makes it possible to reduce the weight of the cured material (conductive material), and further reduce manufacturing costs, including environmental impact and raw material costs.

[0018] In recent years, there has been a growing demand for environmentally friendly materials with low carbon dioxide emissions during the manufacturing process, and conductive pastes are also required to have reduced carbon dioxide emissions during the manufacturing process. On the other hand, conductive pastes containing metal particles (A), such as silver, have excellent conductivity, but the use of silver and other metals with a high environmental impact results in high carbon dioxide emissions during the manufacturing process. Furthermore, the use of precious metals such as silver results in high material costs. The conductive paste of this embodiment can reduce the content of metal particles (A), thereby reducing both environmental impact and manufacturing costs.

[0019] Average particle size D of metal particles (A) 50 From the viewpoint of conductivity, the thickness can preferably be 0.5 μm or more and 20 μm or less, more preferably 1.0 μm or more and 15 μm or less, and even more preferably 1.5 μm or more and 10 μm or less. The average particle size of the metal particles (A) is obtained from the volume-based particle size distribution measured by a flow-type particle image analyzer.

[0020] Average particle size D 50 By setting this to an appropriate value, it is easier to balance thermal conductivity, sinterability, and resistance to heat cycling. Also, the average particle size D 50 Setting this value to an appropriate level can improve the workability of applying / adhering conductive paste, among other things. The particle size distribution of the metal particles (A) (horizontal axis: particle size, vertical axis: frequency) may be unimodal or multimodal.

[0021] The metal particles (A) in this embodiment have an average particle size D based on the volume-based particle size distribution measured by a flow-type particle image analyzer. 50 It is more preferable, and even more preferable, to include two or more different types of flake-shaped silver particles. This further improves the contact rate between the metal particles (A), so that a network is easily formed after sintering of the conductive paste, and the conductivity is further improved. Furthermore, it becomes easier to adjust the viscosity of the conductive paste, allowing for adjustment of the balance between spreadability and thixotropy, and it is also possible to suppress creeping up to the sides and top surfaces of semiconductor devices.

[0022] The metal particles (A) in this embodiment have an average particle size D 50 If it contains two or more different types of flake-like or scale-like metal particles, the average particle size D 50 However, the flake-shaped metal particles are preferably 1 μm or larger, more preferably 2 μm or larger, even more preferably 3 μm or larger, and preferably 6 μm or smaller, more preferably 5 μm or smaller, and even more preferably 4 μm or smaller. Average particle size D 50However, it is preferable to include flake-shaped metal particles that are preferably 4 μm or larger, more preferably 5 μm or larger, even more preferably 6 μm or larger, and preferably 15 μm or smaller, more preferably 12 μm or smaller, and even more preferably 8 μm or smaller. In this embodiment, the metal particles (A) preferably include silver-containing particles.

[0023] The silver-containing particles may be (i) particles consisting substantially of silver only, or (ii) particles consisting of silver and other components. Alternatively, (i) and (ii) may be used in combination as the metal-containing particles.

[0024] (i) Examples of particles consisting substantially of silver include silver particles.

[0025] (ii) Examples of particles consisting of silver and components other than silver include silver-coated resin particles. Silver-coated resin particles are resin particles whose surface is coated with silver. Because silver-coated resin particles are softer than particles made of silver alone, using silver-coated resin particles makes it easier to design the storage modulus to an appropriate value. In the case of silver-coated resin particles, it is sufficient for the silver layer to cover at least a portion of the surface of the resin particle. Of course, the entire surface of the resin particle may also be covered with silver.

[0026] Specifically, in silver-coated resin particles, the silver layer covers preferably 50% or more, more preferably 75% or more, and even more preferably 90% or more of the surface of the resin particles. Particularly preferably, in silver-coated resin particles, the silver layer covers substantially the entire surface of the resin particles. From another perspective, it is preferable that when silver-coated resin particles are cut at a certain cross-section, a silver layer is observed around the entire perimeter of that cross-section.

[0027] From another perspective, the mass ratio of resin to silver in the silver-coated resin particles is, for example, 90 / 10 to 10 / 90, preferably 80 / 20 to 20 / 80, and more preferably 70 / 30 to 30 / 70.

[0028] Examples of "resins" in silver-coated resin particles include silicone resin, (meth)acrylic resin, phenolic resin, polystyrene resin, melamine resin, polyamide resin, and polytetrafluoroethylene resin. Of course, other resins may also be used. Furthermore, only one type of resin may be used, or two or more types of resins may be used in combination. From the viewpoint of elastic properties and heat resistance, silicone resin or (meth)acrylic resin is preferred as the resin. (i) Particles consisting substantially of silver can be obtained from, for example, DOWA Hightech Co., Ltd., Fukuda Metal Foil & Powder Industry Co., Ltd.

[0029] Furthermore, (ii) among the particles consisting of silver and components other than silver, silver-coated resin particles can be obtained from, for example, Mitsubishi Materials Corporation, Sekisui Chemical Co., Ltd., Sanno Co., Ltd., etc.

[0030] [Resin particles (B)] The conductive paste of this embodiment contains resin particles (B).

[0031] The mass ratio (B / A) of resin particles (B) to metal particles (A) can be 0.06 or more and 1.0 or less, preferably 0.08 or more and 0.80 or less, more preferably 0.10 or more and 0.70 or less, even more preferably 0.12 or more and 0.60 or less, even more preferably 0.15 or more and 0.50 or less, and particularly preferably 0.20 or more and 0.50 or less.

[0032] When the mass ratio (B / A) is within this range, the balance between the content of metal particles (A) and resin particles (B) is good, and the contact rate between metal particles (A) can be improved, resulting in excellent conductivity. Furthermore, by using metal particles (A) and resin particles (B) such that the mass ratio (B / A) falls within the specified range, the cured product (conductive material) of the conductive paste exhibits excellent low modulus of elasticity, allowing for stress relief in semiconductor devices equipped with this conductive material and resulting in superior mounting reliability. Moreover, the fact that the mass ratio (B / A) is within the specified range results in excellent adhesion between the substrate and the semiconductor element, leading to superior product reliability of the semiconductor device. In other words, the conductive paste of this embodiment yields a cured product (conductive material) with an excellent balance of conductivity, low modulus of elasticity, and adhesion.

[0033] It is preferable that the resin particles (B) are made of a thermoplastic resin. By using resin particles (B) made of thermoplastic resin, the elastic modulus of the cured conductive paste (conductive material) is reduced compared to alumina or silica. This allows for stress relief in semiconductor devices equipped with this conductive material, resulting in superior mounting reliability.

[0034] Examples of thermoplastic resins include polyvinyl acetal resin, acrylic resin, polyamide resin (e.g., nylon), thermoplastic urethane resin, polyolefin resin (e.g., polyethylene, polypropylene), polycarbonate, polyester resin (e.g., polyethylene terephthalate, polybutylene terephthalate), polyacetal, polyphenylene sulfide, polyether ether ketone, liquid crystal polymer, fluororesin (e.g., polytetrafluoroethylene, polyvinylidene fluoride), modified polyphenylene ether, polysulfone, polyethersulfone, polyarylate, polyamide-imide, polyether-imide, and thermoplastic polyimide. Resin particles made from these thermoplastic resins may be used individually or in combination of two or more types. In this embodiment, it is preferable that the resin particles (B) include resin particles made of nylon.

[0035] The resin particles (B) preferably contain perfectly spherical resin particles. The perfectly spherical resin particles exhibit excellent fluidity and are densely packed between the metal particles (A), resulting in a cured product (conductive material) with superior conductivity.

[0036] "Perfectly spherical" refers to a circularity of 0.8 to 1.0. Circularity is calculated by dividing the circumference of a circle with the same area as the observed particle image by the circumference of the particle image; the closer to 1, the closer to a perfect circle.

[0037] The average particle size of the resin particles (B) can preferably be 1 μm to 30 μm, more preferably 2 μm to 20 μm, and even more preferably 3 μm to 15 μm. The resin particles (B) may contain two or more types of resin particles with different particle sizes. This makes it possible to obtain a cured product (conductive material) with excellent conductivity and elastic modulus.

[0038] The average particle size of resin particles (B) is the particle size D at which the cumulative frequency reaches 50% in the volume-based cumulative frequency distribution curve measured using a laser diffraction particle size distribution analyzer. 50 It refers to.

[0039] The resin particles (B) can be included in the conductive paste in an amount of preferably 1% to 35% by mass, more preferably 2% to 30% by mass, even more preferably 3% to 25% by mass, even more preferably 5% to 20% by mass, and particularly preferably 8% to 20% by mass, based on 100% by mass of the entire conductive paste. This makes it possible to obtain a cured product (conductive material) with excellent conductivity and elastic modulus.

[0040] The conductive paste of this embodiment does not contain or substantially contains inorganic particles such as alumina or silica. Substantially containing inorganic particles means that it is permissible to contain inorganic particles in an amount of 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less, in 100% by mass of the conductive paste.

[0041] [(C) Thermosetting resin] The conductive paste of this embodiment may further include a thermosetting resin (C).

[0042] The thermosetting resin (C) of this embodiment preferably contains one or more selected from the group consisting of polyester resin, epoxy resin, urethane resin, phenolic resin, melamine resin, vinyl resin, (meth)acrylic resin, and silicone resin, and more preferably contains epoxy resin, from the viewpoint of having good conductivity in a conductive paste while reducing the silver content and improving adhesion to the substrate.

[0043] As the epoxy resin used as the thermosetting resin (C) in this embodiment, from the viewpoint of improving the applicability and adhesion of the resulting conductive paste, for example, biphenyl-type epoxy resins; bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, tetramethylbisphenol F-type epoxy resin, modified bisphenol A-type epoxy resin, modified bisphenol F-type epoxy resin; stilbene-type epoxy resins; novolac-type epoxy resins such as phenol novolac-type epoxy resin and cresol novolac-type epoxy resin; polyfunctional epoxy resins such as triphenolmethane-type epoxy resin and alkyl-modified triphenolmethane-type epoxy resin; aralkyl-type epoxy resins such as phenol aralkyl-type epoxy resin having a phenylene skeleton and phenol aralkyl-type epoxy resin having a biphenylene skeleton; dihydroxynaphthalene-type epoxy resin and epoxy resins obtained by glycidyl etherification of a dimer of dihydroxynaphthalene. Preferably, the epoxy resin contains one or more selected from the group consisting of naphthol-type epoxy resins such as naphthol-type epoxy resins; triazine-nucleus-containing epoxy resins such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; bridged cyclic hydrocarbon compound-modified phenol-type epoxy resins such as dicyclopentadiene-modified phenol-type epoxy resins; diglycidyl ethers of bisphenol compounds such as bisphenol A, bisphenol F, and biphenol or their derivatives; diglycidyl ethers of alicyclic diols such as hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated biphenol, cyclohexanediol, cyclohexanedimethanol, and cyclohexanediethanol or their derivatives; diglycidyl ethers of aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, and decanediol or their derivatives; and triglycidyl ethers having a trihydroxyphenylmethane skeleton or an aminophenol skeleton.

[0044] Furthermore, from the viewpoint of more effectively improving the application workability of the conductive paste, the epoxy resin in this embodiment is preferably a liquid epoxy resin that is liquid at 25°C.

[0045] The epoxy resin in this embodiment preferably contains a novolac-type epoxy resin, and more preferably contains a phenol novolac-type epoxy resin. When the thermosetting resin (C) contains this epoxy resin, the resulting cured product exhibits excellent adhesion strength to substrates, semiconductor elements, etc., and also has improved thermal modulus, resulting in excellent wire bonding properties (joining ability).

[0046] The content of the thermosetting resin (C) in the conductive paste of this embodiment can be preferably 5% to 60% by mass, more preferably 10% to 50% by mass, and even more preferably 15% to 40% by mass, when the total amount of the conductive paste is 100% by mass, in order to reduce the silver content while maintaining good conductivity in the conductive paste and to improve the balance of various properties such as adhesion to the substrate.

[0047] [Hardening agent] The conductive paste of this embodiment may contain a curing agent. This can improve the curability of the conductive paste. From the viewpoint of reducing the silver content and improving curability while maintaining good conductivity in the conductive paste, the curing agent of this embodiment preferably contains one or more selected from the group consisting of acid anhydrides and phenol compounds, more preferably contains phenol compounds, and even more preferably contains one or more phenol compounds selected from the group consisting of bisphenols and their derivatives such as bisphenol F, bisphenol A, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetramethylbisphenol S, dihydroxydiphenyl ether, dihydroxybenzophenone, tetramethylbiphenol, ethylidenebisphenol, methylethylidenebis(methylphenol), cyclohexylidenebisphenol, biphenol, etc., and even more preferably contains bisphenol F.

[0048] The content of the hardening agent in the conductive paste of this embodiment can be preferably 0% to 25% by mass, more preferably 0.1% to 20% by mass, even more preferably 1% to 15% by mass, and even more preferably 2% to 10% by mass, when the total amount of the conductive paste is 100% by mass, from the viewpoint of reducing the silver content while maintaining good conductivity in the conductive paste and improving curability.

[0049] [Coupling agent] The conductive paste of this embodiment may contain a coupling agent. This can improve the adhesion between the conductive paste and the substrate. The coupling agent of this embodiment, from the viewpoint of having good conductivity in a conductive paste while reducing the silver content and improving adhesion to the substrate, is, for example, vinylsilane such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxysilane such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; styrylsilane such as p-styryltrimethoxysilane; methacrylsilane such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; 3-(trimethoxysilyl)propyl methacrylate, 3- It is preferable to include one or more selected from the group consisting of acrylicsilanes such as acryloxypropyltrimethoxysilane; aminosilanes such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; isocyanurate silanes; alkylsilanes; ureidosilanes such as 3-ureidopropyltrialkoxysilane; mercaptosilanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; isocyanate silanes such as 3-isocyanatetopropyltriethoxysilane; and polysulfide silanes such as bis(3-(triethoxysilyl)propyl)tetrasulfide.Among these, from the viewpoint of reducing the silver content while maintaining good conductivity in the conductive paste and improving adhesion to the substrate, the coupling agent of this embodiment more preferably contains one or more selected from the group consisting of epoxysilanes and polysulfide silanes, and even more preferably contains one or more selected from the group consisting of 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropyltrimethoxysilane, and bis(3-(triethoxysilyl)propyl)tetrasulfide.

[0050] The coupling agent content in the conductive paste of this embodiment can be preferably 0.1% to 10% by mass, more preferably 0.5% to 8% by mass, and even more preferably 1% to 5% by mass, when the total amount of the conductive paste is 100% by mass, from the viewpoint of reducing the silver content while maintaining good conductivity in the conductive paste and improving adhesion to the substrate.

[0051] [Hardening agent] The conductive paste of this embodiment may contain a curing aid. This can accelerate the reaction between the epoxy resin and the curing agent. From the viewpoint of further accelerating the reaction between the epoxy resin and the curing agent, the curing aid of this embodiment preferably contains one or more selected from the group consisting of phosphorus atom-containing compounds such as organophosphines, tetrasubstituted phosphonium compounds, phosphobetaine compounds, adducts of phosphine compounds and quinone compounds, and adducts of phosphonium compounds and silane compounds; amidines, tertiary amines and their derivatives such as dicyandiamide, 2-phenyl-4,5-dihydroxymethylimidazole, 1,8-diazabicyclo[5.4.0]undecene-7, and benzyldimethylamine; and nitrogen atom-containing compounds such as quaternary ammonium salts of the above amidines or tertiary amines. It is more preferably selected from the group consisting of amidines, tertiary amines and their derivatives, and even more preferably selected from the group consisting of dicyandiamide derivatives and 2-phenyl-4,5-dihydroxymethylimidazole.

[0052] From the viewpoint of further promoting the reaction between the epoxy resin and the curing agent, the content of the curing aid in the conductive paste of this embodiment can be preferably 0.1% to 10% by mass, more preferably 0.5% to 5% by mass, and even more preferably 1% to 3% by mass, when the total amount of the conductive paste is 100% by mass.

[0053] [Radical polymerization initiator] The conductive paste of this embodiment may contain a radical polymerization initiator. This may, for example, prevent insufficient curing, allow the curing reaction to proceed sufficiently at relatively low temperatures, or further improve adhesive strength. From the viewpoint of allowing the curing reaction to proceed sufficiently, the radical initiator of this embodiment preferably contains one or more selected from the group consisting of peroxides and azo compounds, and more preferably contains a peroxide.

[0054] The radical polymerization initiator of this embodiment preferably contains, from the viewpoint of ensuring sufficient progress of the curing reaction, an organic peroxide such as diacyl peroxide, dialkyl peroxide, or peroxyketal as the peroxide, including 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; and di(2-t-butylperoxyisopropyl)benzene and dicumyl peroxide. It is more preferable to include one or more selected from the group consisting of dialkyl peroxides such as alkyl, 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; and peroxyesters such as 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-hexylperoxybenzoate, t-butylperoxybenzoate, and t-butylperoxy2-ethylhexanonate. Among these, from the viewpoint of ensuring that the curing reaction proceeds sufficiently, the radical polymerization initiator of this embodiment is more preferably to include one or two selected from the group consisting of 1,1-di(t-butylperoxy)cyclohexane and dicumyl peroxide.

[0055] From the viewpoint of ensuring sufficient progress of the curing reaction, the content of the radical polymerization initiator in the conductive paste of this embodiment can be preferably 0.05% to 3% by mass, more preferably 0.10% to 1% by mass, and even more preferably 0.15% to 0.50% by mass, when the total amount of the conductive paste is 100% by mass.

[0056] [solvent] The conductive paste of this embodiment may contain a solvent. This allows for adjustment of the fluidity of the resulting conductive paste, thereby improving handling and workability. From the viewpoint of reducing the silver content while maintaining good conductivity in the conductive paste, and improving handling and workability, the solvent of this embodiment may include, for example, 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, isopalmytil alcohol, isosyl Alcohols such as tearyl 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;It is preferable to include one or more selected from the group consisting of tetrahydrofuran, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, ethoxyethyl ether, ethers such as 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 light oil; nitriles such as acetonitrile or propionitrile; amides such as acetamide or N,N-dimethylformamide; and low molecular weight volatile silicone oil or volatile organic modified silicone oil. Among these, from the viewpoint of reducing the silver content while maintaining good conductivity in the conductive paste and improving handling and workability, the solvent in this embodiment is more preferably ester, and even more preferably ethylene glycol monobutyl ether acetate. ;

[0057] From the viewpoint of reducing the silver content while maintaining good conductivity in the conductive paste, the solvent content in the conductive paste of this embodiment can be preferably 0.1% to 10% by mass, more preferably 0.5% to 5.0% by mass, and even more preferably 1.0% to 3.0% by mass, when the total amount of the conductive paste is 100% by mass.

[0058] [(meth)acryl monomer]

[0059] The conductive paste of this embodiment may contain a (meth)acrylic monomer. The type of (meth)acrylic monomer is not particularly limited; any monomer having a (meth)acrylic group can be used without any particular restriction.

[0060] (Meth)acrylic monomers are broadly classified into two types: monofunctional (meth)acrylic monomers, which have only one (meth)acrylic group in their molecule, and polyfunctional (meth)acrylic monomers, which have two or more (meth)acrylic groups in their molecule.

[0061] Examples of monofunctional (meth)acrylic monomers 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, cyclohexyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate quaternary derivative, glycidyl methacrylate, or neopentyl glycol acrylate benzoate.

[0062] Examples of polyfunctional (meth)acrylic monomers 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, neopentyl glycol di(meth)acrylate, N,N'-di(meth)acryloylethylenediamine, or 1,4-bis((meth)acryloyl)piperazine.

[0063] From the viewpoint of adjusting the viscosity of the conductive paste, the content of (meth)acrylic monomer in the conductive paste of this embodiment can preferably be 1 part by mass or more and 25 parts by mass or less, more preferably 2 parts by mass or more and 20 parts by mass or less, and even more preferably 3 parts by mass or more and 15 parts by mass or less.

[0064] [Other ingredients] The conductive paste of this embodiment may use known components such as polymerization inhibitors, defoamers, surfactants, and colorants as other components. The content of these other components can be arbitrarily set according to the physical properties to be imparted to the conductive paste.

[0065] <Conductive paste> The method for preparing the conductive paste in this embodiment is not particularly limited, but for example, after pre-mixing the above-mentioned components, the paste can be obtained by kneading using a three-roller system and then vacuum degassing. In this case, the long-term workability of the conductive paste can be improved by appropriately adjusting the preparation conditions, such as performing the pre-mixing under reduced pressure.

[0066] The thermal modulus at 250°C of the cured conductive paste obtained under the following conditions can be 5 MPa or more and 300 MPa or less, preferably 7 MPa or more and 200 MPa or less, and more preferably 8 MPa or more and 170 MPa or less. The cured product obtained from the conductive paste of this embodiment has excellent wire bonding properties (joining ability) because its thermal modulus is within the above range.

[0067] (conditions) The conductive paste was applied to a Teflon plate, and the temperature was increased from 30°C to 175°C over 30 minutes, followed by heat treatment at 175°C for 60 minutes. This yielded a test specimen containing a cured conductive paste with a thickness of 0.3 mm. The cured material was peeled off the Teflon plate and placed in a measuring device (Hitachi High-Tech Science Corporation, DMS6100). Dynamic viscoelasticity measurement (DMA) was performed in tensile mode at a frequency of 10 Hz to measure the storage modulus E' (MPa) at 250°C.

[0068] <Application> The 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. In this embodiment, LED refers to a light-emitting diode.

[0069] Examples of semiconductor devices using LEDs include bullet-shaped LEDs, surface-mount (SMD) LEDs, COB (Chip On Board) LEDs, and power LEDs.

[0070] Specifically, the types of semiconductor packages mentioned above include CMOS image sensors, hollow packages, MAP (Mold Array Package), QFP (Quad Flat Package), SOP (Small Outline Package), CSP (Chip Size Package), QFN (Quad Flat Non-leaded Package), SON (Small Outline Non-leaded Package), BGA (Ball Grid Array), LF-BGA (Lead Flame BGA), FC-BGA (Flip Chip BGA), MAP-BGA (Molded Array Process BGA), eWLB (Embedded Wafer-Level BGA), Fan-In type eWLB, Fan-Out type eWLB, and others.

[0071] <Conductive materials> The conductive material of this embodiment includes a cured product of the conductive paste of this embodiment. The conductive material of this embodiment can be obtained, for example, by sintering the conductive paste of this embodiment. By changing the shape of the conductive material, it can be applied to various components in the automotive and electrical fields that require heat dissipation.

[0072] <Semiconductor device> An example of a semiconductor device using the conductive paste according to this embodiment will be described below. Figure 1 is a schematic cross-sectional view showing an example of a semiconductor device according to this embodiment.

[0073] The semiconductor device 100 of this embodiment comprises a substrate 30 and a semiconductor element 20 mounted on the substrate 30 via an adhesive layer 10, the adhesive layer 10 including a cured product of the conductive paste of this embodiment. The semiconductor element 20 and the substrate 30 are electrically connected, for example, via a bonding wire 40. The semiconductor element 20 is also sealed, for example, with a sealing resin 50.

[0074] In Figure 1, the substrate 30 is, for example, a lead frame. In this case, the semiconductor element 20 is mounted on the die pad 32 or the substrate 30 via an adhesive layer 10. The semiconductor element 20 is also electrically connected to the outer lead 34 (substrate 30) via, for example, a bonding wire 40. The substrate 30, which is the lead frame, is composed of, for example, a 42 alloy or a Cu frame.

[0075] The conductive paste of this embodiment can be used to manufacture the semiconductor device of this embodiment. For example, the conductive paste of this embodiment can be used as an "adhesive" between a substrate and a semiconductor element to manufacture the semiconductor device of this embodiment.

[0076] In other words, the semiconductor device of this embodiment comprises, for example, a substrate and a semiconductor element mounted on the substrate via an adhesive layer obtained by sintering the conductive paste described above by heat treatment. The semiconductor device of this embodiment is less susceptible to deterioration of the adhesion of the adhesive layer even under heat cycling. In other words, the semiconductor device of this embodiment has high reliability. Examples of semiconductor devices include ICs, LSIs, power semiconductor devices, and various other types of devices. Examples of substrates include various semiconductor wafers, lead frames, BGA substrates, mounted substrates, heat spreaders, and heat sinks.

[0077] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted as long as they do not impair the effects of the present invention. [Examples]

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0079] [Examples 1-9, Comparative Examples 1-2] Following the formulations shown in Table 1, each component was pre-mixed, then kneaded using a three-roll mill, and finally degassed under vacuum to prepare a conductive paste. The units for the content of each component in Table 1 are parts by mass.

[0080] The details of the components shown in Table 1 are as follows: [Epoxy resin] • Epoxy resin 1: Diglycidyl ether of bisphenol F epichlorohydrin (manufactured by Nippon Kayaku Co., Ltd., RE-403S, epoxy equivalent 160 g / eq) • Epoxy resin 2: Phenolic novolac type epoxy resin (DIC Corporation, N770)

[0081] [Hardening agent] • Phenolic curing agent: Bisphenol F (DIC Corporation, DIC-BPF, melting point 90°C)

[0082] [Acrylic monomer] · Acrylic monomer: Ethylene glycol dimethacrylate (manufactured by Kyoeisha Chemical Co., Ltd., Light Ester EG)

[0083] [Coupling agent] · Coupling agent: 3-Glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-403E)

[0084] [Hardening aid] · Hardening aid 1: Dicyandiamide derivative (manufactured by ADEKA Corporation, EH-3636AS) · Hardening aid 2: 2-Phenyl-4,5-dihydroxymethylimidazole (manufactured by Shikoku Chemicals Corporation, 2PHZ-PW)

[0085] [Radical polymerization initiator] · Peroxide: 1,1-Di(tert-butylperoxy)cyclohexane (Perhexa CS, manufactured by NOF Corporation)

[0086] [Metal particles] · Silver filler 1: Manufactured by Fukuda Metal Foil & Powder Co., Ltd., HKD-11, median diameter D 50 : 2.5μm, flaky · Silver filler 2: Manufactured by Fukuda Metal Foil & Powder Co., Ltd., HKD-10A, median diameter D 50 : 8μm, flaky · Silver filler 3: Manufactured by Fukuda Metal Foil & Powder Co., Ltd., HKD-13A, median diameter D 50 : 6.0μm, flaky · Silver filler 4: Silver powder surface-treated with fatty acid, manufactured by Tokuryu Honten Co., Ltd., TKR-88, median diameter D 50 : 3.3μm, flaky

[0087] [Resin particles] · Resin particles: Nylon, SP-500, average particle diameter D 50 : 5μm, manufactured by Toray Industries, Inc.

[0088] [Solvent] • Solvent: Tripropylene glycol mono-n-butyl ether (product name: BFTG, manufactured by Nippon Emulsifier Co., Ltd.)

[0089] [Adhesion strength] A conductive paste was applied to a silver lead frame, and then a silver-plated silicon chip measuring 2.0 mm in length, 2.0 mm in width, and 350 ± 5 μm in thickness was placed on the conductive paste. The sample was then heated from 25°C to 175°C over 30 minutes, and then heat-treated at 175°C for 1 hour to obtain a cured sample. The die shear strength between the silver lead frame and the silicon chip of this cured sample was measured at 260°C and a shear rate of 500 μm / second using a Dage4000 (Nordson Advanced Technologies). The results are shown in Table 1. Furthermore, the failure mode of the conductive paste cured material that was destroyed in the die-sher strength measurement test was visually confirmed. If delamination occurred at the interface between the copper frame and the conductive paste cured material, it was classified as "LF interface"; if cracks were present in the die-attach paste cured material itself, it was classified as "cohesive failure"; and if both types of delamination were observed, it was classified as "cohesive failure / LF interface," as shown in Table 1.

[0090] [Vertical volume resistance] A conductive paste was applied to a copper frame, and a 2.5 mm square silver-plated copper chip was mounted on it. The sample was then heated from 25°C to 175°C at a rate of 5°C / min under a nitrogen atmosphere with a residual oxygen concentration of less than 1000 ppm, followed by heat treatment at 175°C for 60 minutes to obtain a cured sample. The paste thickness of this cured sample was measured using a thickness gauge, and then the resistance was measured by placing a terminal on the surface of the chip and the surface of the copper frame using a milliohmmeter, and the volume resistivity was calculated. The unit is Ω·cm. The results are shown in Table 1.

[0091] [modulus of elasticity] A conductive paste was applied to a Teflon plate and heated from 30°C to 175°C over 30 minutes, followed by heat treatment at 175°C for 60 minutes. This yielded a test specimen containing a cured conductive paste with a thickness of 0.3 mm. The cured material was peeled from the Teflon plate and placed in a measuring device (Hitachi High-Tech Science Corporation, DMS6100). Dynamic viscoelasticity measurements (DMA) were performed in tensile mode at a frequency of 10 Hz to measure the storage modulus E' (MPa) at room temperature (25°C) and 250°C. The results are shown in Table 1.

[0092] [Viscosity measured at 5 rpm (25°C), thixotropic index] The viscosity of the conductive paste immediately after preparation was measured using a BF-type viscometer (device name: DV3T, manufactured by Brookfield) at the following measurement temperatures and rotation speeds. The results are shown in Table 1. η0.5: Rotational speed 0.5 rpm, shear rate 1.92 s -1 , measurement temperature 25℃ η5: Rotational speed 5 rpm, shear rate 19.2 s -1 , measurement temperature 25℃ Furthermore, the thixotropic index (η0.5 / η5) was calculated. The results are shown in Table 1.

[0093] [Table 1]

[0094] As shown in Table 1, Comparative Example 1, a conductive paste containing many metal particles (silver filler) and no resin particles, exhibited excellent conductivity, but its high elastic modulus meant that there was room for improvement in mounting reliability when used as an adhesive layer for semiconductor devices. Furthermore, Comparative Example 2, a conductive paste that did not use resin particles, had excellent low elastic modulus, but its high longitudinal volume resistivity meant there was room for improvement in conductivity, and its low adhesion strength resulted in low product reliability when used as an adhesive layer for semiconductor devices. The conductive paste of Comparative Example 2 also had low viscosity, which caused problems with moldability. In contrast, the conductive paste of the present invention according to the examples had an excellent balance of conductivity and low modulus of elasticity due to the mass ratio (B / A) of resin particles (B) to metal particles (A) (silver filler) being 0.06 or more and 1.0 or less. Furthermore, due to its excellent low modulus of elasticity and adhesion, it exhibited excellent mounting reliability and product reliability. In other words, the cured product (conductive material) obtained from the conductive paste of the present invention had an excellent balance of conductivity, low modulus of elasticity, and adhesion. [Explanation of Symbols]

[0095] 100 Semiconductor Equipment 10 Adhesive layer 20 Semiconductor elements 30 Base material 32 die pads 34 Outer lead 40 Bonding Wires 50 Sealing resin

Claims

1. (A) Metal particles and (B) Resin particles and Includes, A conductive paste in which the mass ratio (B / A) of resin particles (B) to metal particles (A) is 0.06 or more and 1.0 or less.

2. The conductive paste according to claim 1, wherein metal particles (A) are contained in an amount of 20% by mass or more and 60% by mass or less in 100% by mass of the entire conductive paste.

3. The conductive paste according to claim 1, wherein the metal particles (A) include flake-shaped or flaky metal particles.

4. The conductive paste according to claim 1, wherein the metal particles (A) include at least one selected from silver-containing particles and copper-containing particles.

5. The conductive paste according to claim 1, wherein the average particle size of the metal particles (A) is 0.5 μm or more and 20 μm or less.

6. The conductive paste according to claim 1, wherein the resin particles (B) are made of a thermoplastic resin.

7. The conductive paste according to claim 1, wherein the resin particles (B) include perfectly spherical resin particles.

8. The conductive paste according to claim 1, wherein the average particle size of the resin particles (B) is 1 μm or more and 30 μm or less.

9. The conductive paste according to claim 1, further comprising (C) a thermosetting resin.

10. The conductive paste according to claim 9, wherein the thermosetting resin (C) comprises a phenol novolac type epoxy resin.

11. The conductive paste according to claim 1, wherein the thermal modulus at 250°C of the cured product of the conductive paste obtained under the following conditions is 5 MPa or more and 300 MPa or less. (conditions) The conductive paste is applied to a Teflon plate, and the temperature is increased from 30°C to 175°C over 30 minutes, followed by heat treatment at 175°C for 60 minutes. This yields a test specimen containing a cured conductive paste with a thickness of 0.3 mm. The cured material is peeled off the Teflon plate from the obtained test specimen and placed in a measuring device (Hitachi High-Tech Science Corporation, DMS6100). Dynamic viscoelasticity measurement (DMA) is performed in tensile mode at a frequency of 10 Hz to measure the storage modulus E' (MPa) at 250°C.

12. A conductive material obtained by curing a conductive paste according to any one of claims 1 to 11.

13. Substrate and The system comprises a semiconductor element mounted on the substrate via an adhesive layer, The adhesive layer is formed by curing a conductive paste according to any one of claims 1 to 11, wherein the semiconductor device is a semiconductor device.

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