Conductive Paste and Semiconductor Device

Abstract

To provide a conductive paste that has high conductivity and improved adhesion to support members such as lead frames, and thus can firmly bond semiconductor devices and support members.SOLUTION: A conductive paste includes (A) silver powder surface-treated with at least one fatty acid selected from oleic acid and sorbitanic acid, and (B) a diluent, and the diluent (B) contains (meth) acrylic monomer and the amount of the fatty acid is from 0.30 mass% to 0.70% by mass of the total amount of the silver and the fatty acid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive paste and a semiconductor device. More specifically, the present invention relates to a conductive paste used as a die attach paste for mounting a semiconductor element on a support member such as a metal frame, and a semiconductor device manufactured using the conductive paste.

Background Art

[0002] Generally, a semiconductor device is manufactured by adhering a semiconductor element such as a semiconductor chip to a support member such as a lead frame or a glass epoxy wiring board with a die bonding material. As such a die bonding material, a heat-curable type conductive paste in which a conductive filler is dispersed in a binder resin, and a sintered type silver paste containing no binder resin are known.

[0003] Generally, a heat-curable type conductive paste can be cured in a relatively low temperature range of about 20 to 200°C as compared with a sintered type silver paste. However, on the other hand, the conductive film obtained using the heat-curable type conductive paste has a problem that its electrical resistivity is higher and its conductivity is lower than that of the conductive film obtained using the sintered type silver paste. That is, since the silver powders are bonded to each other by heating, the conductive film obtained by heating the sintered type silver paste has an electrical resistivity as low as that of bulk silver. In contrast, the conductive film obtained by heating the heat-curable type conductive paste has a relatively high electrical resistivity because a conductive path is formed by the contact of metal powders.

[0004] In view of the above problems in such heat-curable conductive pastes, as a technique for obtaining a conductive film having a low electrical resistivity, for example, in Patent Document 1 and Patent Document 2, it has been proposed to use a conductive paste containing silver powder surface-treated with a liquid fatty acid. Patent Document 1 and Patent Document 2 describe that silver powder surface-treated with a fatty acid has a large contact area between the silver powders, and thus a conductive film with a reduced electrical resistivity can be obtained.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the heat-curable conductive pastes of Patent Document 1 and Patent Document 2 may not have sufficient adhesive strength to lead frames, glass epoxy wiring boards, etc., or voids may concentrate in the vicinity of the adhesive interface, resulting in low adhesive strength. For this reason, when manufacturing a semiconductor device by die-bonding a semiconductor element to a lead frame or the like using a conductive paste and then heating the substrate in a state where the semiconductor device is mounted on the substrate to bond it to the substrate (during reflow soldering), the conductive layer made of the paste may peel off.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a conductive paste having high conductivity and improved adhesion to a support member such as a lead frame, and thus capable of firmly adhering a semiconductor element and a support member.

Means for Solving the Problems

[0008] The inventors of the present invention have found that by adjusting the amount of fatty acid contained in silver powder surface-treated with a fatty acid, a conductive paste with a highly improved balance between conductivity and adhesion to a substrate can be obtained. Further, the inventors have found that a semiconductor device obtained using such a conductive paste is excellent in reliability, and have completed the present invention.

[0009] According to the present invention, (A) silver powder surface-treated with at least one fatty acid selected from oleic acid and sorbitanic acid, and (B) a diluent, A conductive paste comprising: wherein the diluent (B) contains an acrylic monomer, the amount of the fatty acid is 0.30% by mass or more and 0.70% by mass or less based on the total amount of the silver powder and the fatty acid, and a conductive paste is provided.

[0010] Also according to the present invention, a support member, and a semiconductor element mounted on the support member via an adhesive layer, and a semiconductor device is provided. wherein the adhesive layer is made of the above conductive paste.

Advantages of the Invention

[0011] According to the present invention, there are provided a conductive paste with a highly improved balance between conductivity and adhesion to a substrate, and a semiconductor device excellent in reliability obtained using such a conductive paste.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Best Mode for Carrying Out the Invention

[0013] 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 thereof will be omitted as appropriate.

[0014] Hereinafter, embodiments of the present invention will be described.

[0015] (Conductive paste) The conductive paste of this embodiment is a die attach paste used to form a die attach layer for adhering electronic components such as semiconductor elements to a support member such as a lead frame or a wiring board. The conductive paste of this embodiment (A) silver powder surface-treated with at least one fatty acid selected from oleic acid and sorbitanic acid, and (B) a diluent. In the conductive paste of this embodiment, the diluent (B) contains a (meth)acrylic monomer. Further, in the silver powder (a) surface-treated with the fatty acid, the fatty acid is physically adsorbed on the surface of the silver particles. The amount of the fatty acid is 0.30% by mass or more and 0.70% by mass or less based on the total amount of silver and fatty acid. That is, the fatty acid content of the silver powder (A) surface-treated with the fatty acid is 0.30% by mass or more and 0.70% by mass or less.

[0016] The conductive paste of the present embodiment contains a combination of silver powder, which is a conductive metal powder, and a (meth)acrylic monomer as a diluent, and the silver powder is surface-treated with a specific fatty acid. As a result, the die attach layer obtained by heat-treating the conductive paste of the present embodiment has excellent thermal conductivity and high adhesion to the support member. The fatty acid is easily soluble in the diluent. Therefore, when the conductive paste is heated, the fatty acid present on the surface of the silver powder easily evaporates together with the diluent. As a result, in the die attach layer obtained by heating the conductive paste of the present invention, the area of the exposed portion on the surface of the silver powder is increased, and the contact area between the silver powders is increased. Furthermore, the die attach layer obtained by heating the conductive paste has a good contact state between the silver powders, and at least a part of the silver powders are fused and integrated. Such a silver particle connection structure formed by the aggregation of silver powders has high conductivity.

[0017] The conductive paste of the present embodiment contains silver powder as a conductive metal particle. As a result, the die attach layer obtained by heating the conductive paste has excellent conductivity. Furthermore, the silver powder incorporated in the conductive paste of the present embodiment is silver powder surface-treated with a specific amount of fatty acid. By including such silver powder, the conductive paste of the present embodiment particularly has high adhesion to the support member. Here, the support member to which the conductive paste is applied has a surface treatment agent such as a bleed-out inhibitor or a stress relaxant applied to its surface. This surface treatment agent can act to prevent adhesion between the silver particles and the support member. However, by using silver powder surface-treated with a fatty acid, the fatty acid dissolved in the diluent by heating the conductive paste acts on the surface treatment agent applied to the surface of the support member, and the reduction in adhesion is alleviated. Thereby, the adhesion between the die attach layer obtained by heating the conductive paste and the support member can be improved.

[0018] Each component used in the conductive paste of the present embodiment will be described below. (Silver powder (A)) The silver powder contained in the conductive paste of this embodiment is surface-treated with at least one fatty acid selected from oleic acid and sorbitanic acid, and the fatty acid is physically adsorbed on the surface of the silver particles. The fatty acid content (the amount of fatty acid adsorbed on the surface of silver powder (A)) of the silver powder (A) surface-treated with this fatty acid is 0.30% by mass or more and 0.70% by mass or less with respect to the entire silver powder (A). Such fatty acid-treated silver powder (A) forms a silver particle connection structure that is excellent in conductivity, heat conductivity, and adhesion to the support member by being heat-treated with respect to the conductive paste.

[0019] When the silver powder (A) is silver particles surface-treated with oleic acid, the oleic acid content is 0.30% by mass or more and 0.70% by mass or less with respect to the entire silver powder (A), preferably 0.32% by mass or more and 0.65% by mass or less, and more preferably 0.35% by mass or more and 0.62% by mass or less. When the silver powder (A) is silver particles surface-treated with sorbitanic acid, the sorbitan content is 0.30% by mass or more and 0.70% by mass or less with respect to the entire silver powder (A), preferably 0.35% by mass or more and 0.55% by mass or less, and more preferably 0.37% by mass or more and 0.52% by mass or less.

[0020] The shape of the silver powder (A) is not particularly limited, and examples thereof include spherical, flaky, and scaly shapes. In this embodiment, it is more preferable that the silver powder contains spherical particles. Thereby, the uniformity of the aggregation of the silver powder can be improved. Also, from the viewpoint of reducing costs, an aspect in which the silver powder contains flaky particles can be adopted. Furthermore, from the viewpoint of improving the balance between cost reduction and uniform aggregation, the silver powder may contain both spherical particles and flaky particles.

[0021] The average primary particle size (D 50) is, for example, 0.1 μm or more and 10 μm or less. When the average primary particle diameter of the silver powder is at least the above lower limit value, an excessive increase in the specific surface area can be suppressed, and a decrease in thermal conductivity due to contact thermal resistance can be suppressed. Further, when the average particle diameter of the silver powder is at most the above upper limit value, the formability of the silver particle connection structure between the silver powders can be improved. Further, from the viewpoint of improving the dispensability of the conductive paste, the average primary particle diameter (D 50 ) is more preferably 0.6 μm or more and 2.7 μm or less, and particularly preferably 0.6 μm or more and 2.0 μm or less. The average particle diameter (D 50 ) of the silver powder can be measured, for example, using a commercially available laser particle size distribution analyzer (for example, SALD-7000 manufactured by Shimadzu Corporation).

[0022] Further, the maximum primary particle diameter of the silver powder (A) is not particularly limited, but can be, for example, 1 μm or more and 50 μm or less, more preferably 3 μm or more and 30 μm or less, and particularly preferably 4 μm or more and 18 μm or less. Thereby, it becomes possible to more effectively improve the balance between the uniformity of aggregation and the dispensability of the silver powder. Here, the dispensability of the conductive paste refers to properties such as viscosity and curability required for applying and using this conductive paste on a support member.

[0023] The silver powder (A) surface-treated with the above fatty acid can be obtained by subjecting silver particles to a surface treatment step using a specific fatty acid. As the surface treatment method, a method of drying the solvent after treating the fatty acid diluted in a solvent together with silver particles with a ball mill or the like can be used. The amount of the fatty acid used in the surface treatment step of the silver powder is preferably 1 to 50 parts by mass, more preferably 1 to 20 parts by mass, based on 100 parts by mass of the silver particles. By adjusting the amount of the fatty acid used for the surface treatment, the fatty acid content of the obtained silver powder (A) can be controlled.

[0024] The content of silver powder (A) in the conductive paste is, for example, 40% by mass or more and 90% by mass or less, preferably 50% by mass or more and 80% by mass or less, based on the entire conductive paste. By setting the content to be not less than the above lower limit value, it becomes possible to contribute to the improvement of the thermal conductivity and conductivity of the die attach paste layer obtained by heat-treating the conductive paste. On the other hand, by setting the content to be not more than the above upper limit value, it is possible to contribute to the improvement of the dispensability (coating workability) of the obtained conductive paste and the mechanical strength of the die attach paste layer obtained by heat-treating the conductive paste.

[0025] The silver powder used in the conductive paste of this embodiment may contain silver powder surface-treated with a fatty acid other than oleic acid or sorbitanic acid. Examples of fatty acids other than oleic acid or sorbitanic acid include caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, palmitoleic acid, erucic acid, and the like.

[0026] When using silver particles surface-treated with a fatty acid other than oleic acid or sorbitanic acid, the amount is, for example, 0.05% by mass or more and 1% by mass or less, preferably 0.2% by mass or more and 0.7% by mass or less, based on the total silver powder used.

[0027] In addition to the above silver powder, the conductive paste of this embodiment may contain other conductive metal powders. As other conductive metal powders, gold powder, platinum powder, palladium powder, copper powder, nickel powder, or alloys thereof can be used. When using other conductive metal powders, the amount is, for example, 0.05% by mass or more and 1% by mass or less, preferably 0.2% by mass or more and 0.7% by mass or less, based on the silver powder (A). By using other conductive metal powders in the amount within the above range, the silver powder (A) and other conductive metal powders can form a good metal particle connection structure.

[0028] In the conductive paste of this embodiment, the fatty acid is preferably present in a state of being physically adsorbed on the surface of the silver particles and is not dissolved or dispersed in the diluent described below. When the fatty acid is not present as a free fatty acid, a silver particle linked structure is well formed by heating.

[0029] (Diluent) The conductive paste of this embodiment contains a (meth)acrylic monomer as a diluent. As described above, the conductive paste of this embodiment contains silver powder (A) surface-treated with a specific fatty acid, and the fatty acid present on the surface of this silver powder (A) is easily dissolved in the (meth)acrylic monomer by heating. Therefore, in the die-attach layer obtained by heating the conductive paste of the present invention, the silver powder particles have good contact with each other, and at least a part of the silver powder particles are fused and integrated. The silver particle connection structure formed by the aggregation of such silver powder particles has high conductivity. In addition, the fatty acid dissolved in the (meth)acrylic monomer by heating acts on the surface treatment agent applied to the surface of the support member. The fatty acid acts on the surface treatment agent applied to the surface of the support member to mitigate the reduction in adhesion. As a result, the adhesion between the die-attach layer obtained by heating the conductive paste and the support member can be improved. The above effect is particularly remarkable when the silver powder (A) is silver particles treated with oleic acid or sorbitan acid, and the diluent is a (meth)acrylic monomer.

[0030] Furthermore, the conductive paste of this embodiment contains a diluent, and thus has a viscosity suitable for achieving ease of application to a support member and for filling into fine details.

[0031] In the present embodiment, the content of the (meth)acrylic monomer in the conductive paste is preferably 3% by mass or more, more preferably 4% by mass or more, based on the entire conductive paste. Thereby, the coating workability of the conductive paste and the flatness of the obtained die attach layer can be more effectively improved, and the adhesion between the obtained die attach layer and the support member can be improved. On the other hand, the content of the (meth)acrylic monomer in the conductive paste is preferably 20% by mass or less, more preferably 15% by mass or less, based on the entire conductive paste. Thereby, the occurrence of dripping during the coating operation can be suppressed, the coating workability can be improved, and the adhesion between the obtained die attach layer and the support substrate can be improved. Also, it becomes possible to improve the curability of the conductive paste.

[0032] In the present embodiment, as the (meth)acrylic monomer, a monofunctional (meth)acrylic monomer having only one (meth)acrylic group or a polyfunctional (meth)acrylic monomer having two or more (meth)acrylic groups is used.

[0033] Examples of monofunctional (meth)acrylic monomers include 2-phenoxyethyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethylhexyldiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenol ethylene oxide modified (meth)acrylate, phenylphenol ethylene oxide modified (meth)acrylate, isobornyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, quaternized dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, neopentyl glycol (meth)acrylate benzoate, 1,4-cyclohexanedimethanol mono(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-(meth)acryloyloxyethyl acid phosphate, and 2-(meth)acryloyloxyethyl acid phosphate, etc. can be mentioned. As the monofunctional (meth)acrylic monomer, one or more of the above specific examples can be used in combination.,

[0034] As the monofunctional (meth)acrylic monomer, among the above specific examples, it is preferable to use 2-phenoxyethyl methacrylate. Thereby, the adhesion of the obtained conductive paste to the support member can be improved.,

[0035] Specific examples of the polyfunctional (meth)acrylic monomer include ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, propoxylated bisphenol A di(meth)acrylate, hexane-1,6-diol bis(2-methyl (meth)acrylate), 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-octafluorhexane, 1,4-bis((meth)acryloyloxy)butane, 1,6-bis((meth)acryloyloxy)hexane, triethylene 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, etc.,

[0036] In a preferred embodiment, the conductive paste of the present invention contains a combination of a monofunctional (meth)acrylic monomer and a polyfunctional (meth)acrylic monomer as a diluent. When including a combination of monofunctional / polyfunctional (meth)acrylic monomers, their ratios are, for example, in a molar ratio of monofunctional:polyfunctional of 9:1 to 1:9, preferably 9:1 to 5:5, more preferably 9:1 to 6:4. By using the monofunctional / polyfunctional (meth)acrylic monomer mixture with the above ratios, the adhesion of the resulting conductive paste to the support member can be further improved.

[0037] The conductive paste of this embodiment may contain other diluents in addition to the above-mentioned (meth)acrylic monomers. As other diluents, a reactive diluent or a non-reactive solvent can be used. Here, the reactive diluent refers to a polymerizable monomer that cures by heat treatment to promote the aggregation of silver particles, or when the conductive paste contains a thermosetting resin as a binder resin, it means a compound having a reactive group involved in the cross-linking reaction with this resin. The non-reactive solvent means a solvent that does not have a reactive group having polymerizability or cross-linkability and can volatilize by heat treatment.

[0038] Examples of the polymerizable monomer used as the reactive diluent include glycol monomers, epoxy monomers, maleimide monomers, and imide monomers, etc.

[0039] Examples of glycol monomers used as the coincidence monomer include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monoallyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, diethylene glycol monobenzyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol, tetraethylene glycol monomethyl, tetraethylene glycol monoethyl, tetraethylene glycol mono-n-butyl, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol monophenyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol mono-n-butyl ether, and the like. These may be used alone or in combination of two or more.

[0040] When the conductive paste is heat-treated, from the viewpoint of good formation of a silver particle connection structure by aggregation of silver particles contained therein, as the glycol monomer, it is preferable to use tripropylene glycol mono-n-butyl ether or ethylene glycol mono-n-butyl acetate.

[0041] As the epoxy monomer used as the polymerizable monomer, a monofunctional epoxy monomer having only one epoxy group or a polyfunctional epoxy monomer having two or more epoxy groups can be used.

[0042] Examples of the monofunctional epoxy monomer include 4-tert-butylphenyl glycidyl ether, m,p-cresyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, etc. As the monofunctional epoxy monomer, one or more of the above specific examples can be used in combination.

[0043] Examples of the polyfunctional epoxy monomer include bisphenol compounds such as bisphenol A, bisphenol F, and biphenol or their derivatives; diols having an alicyclic structure such as hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated biphenol, cyclohexanediol, cyclohexanedimethanol, and sicylohexanediethanol or their derivatives; bifunctional ones obtained by epoxidizing aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, and decanediol or their derivatives; trifunctional ones having a trihydroxyphenylmethane skeleton or an aminophenol skeleton; polyfunctional ones obtained by epoxidizing phenol novolak resin, cresol novolak resin, phenol aralkyl resin, biphenyl aralkyl resin, naphthol aralkyl resin, etc. As the polyfunctional epoxy monomer, one or more of the above specific examples can be used in combination.

[0044] Examples of the maleimide monomer used as the polymerizable monomer include polytetramethylene ether glycol-di(2-maleimide acetate).

[0045] Examples of the imide monomer used as the polymerizable monomer include acid anhydrides such as pyromellitic dianhydride, diamines such as 4,4'-diaminodiphenyl ether, and the like.

[0046] When the conductive paste of the present embodiment contains the above other diluent, the content of the other diluent in the conductive paste is preferably 3% by mass or more, more preferably 4% by mass or more, based on the total amount of the conductive paste. Thereby, the coating workability of the conductive paste and the flatness of the obtained adhesive layer can be more effectively improved. On the other hand, the content of the other diluent in the conductive paste is preferably 20% by mass or less, more preferably 15% by mass or less, based on the total amount of the conductive paste. Thereby, it is possible to suppress the occurrence of dripping during the coating operation and improve the coating workability. It is also possible to improve the curability of the conductive paste.

[0047] The conductive paste of this embodiment may contain a non-reactive solvent. By containing a non-reactive solvent, the fluidity of the resulting conductive paste can be adjusted to improve handleability and workability. Examples of non-reactive 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, isopalmitic alcohol, isostearyl alcohol, lauryl alcohol, ethylene glycol, propylene glycol or glycerin; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), 2-octanone, isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) or diisobutyl ketone (2,6-dimethyl-4-heptanone); esters such as 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; 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; 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; Low molecular weight volatile silicone oils, or volatile organically modified silicone oils, etc. may be mentioned.;

[0048] The conductive paste of this embodiment may not contain a non-reactive solvent. Here, not containing a non-reactive solvent means substantially not containing it, and refers to the case where the content of the non-reactive solvent in the entire conductive paste is 0.1% by mass or less.

[0049] (Thermosetting resin) The conductive paste of this embodiment may contain a thermosetting resin as a binder resin, if necessary. As the thermosetting resin, one or more selected from polyester resins, epoxy resins, urethane resins, phenol resins, melamine resins, vinyl resins, acrylic resins and silicone resins can be used. Among them, from the viewpoint of improving the adhesion of the conductive paste to the support member, it is preferable to use an epoxy resin.

[0050] As the epoxy resin used as the thermosetting resin, monomers, oligomers, and polymers having two or more glycidyl groups in one molecule can be used in general, and their molecular weights and molecular structures are not particularly limited. As the epoxy resin used in this embodiment, for example, biphenyl type epoxy resin; bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, tetramethyl bisphenol F type epoxy resin; stilbene type epoxy resin; novolac type epoxy resins such as phenol novolac type epoxy resin, cresol novolac type epoxy resin; polyfunctional epoxy resins such as triphenol methane type epoxy resin, alkyl-modified triphenol methane type epoxy resin; aralkyl type epoxy resins such as phenol aralkyl type epoxy resin having a phenylene skeleton, phenol aralkyl type epoxy resin having a biphenylene skeleton; naphthol type epoxy resins such as dihydroxynaphthalene type epoxy resin, epoxy resin obtained by glycidyl etherifying a dimer of dihydroxynaphthalene; triazine nucleus-containing epoxy resins such as triglycidyl isocyanurate, monoallyl diglycidyl isocyanurate; bridged cyclic hydrocarbon compound-modified phenol type epoxy resins such as dicyclopentadiene-modified phenol type epoxy resin can be mentioned. Further, as the epoxy resin, for example, among compounds containing two or more glycidyl groups in one molecule, bisphenol compounds such as bisphenol A, bisphenol F, and biphenol or their derivatives, hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated biphenol, cyclohexanediol, cyclohexanedimethanol, cyclohexanediethanol, etc. having an alicyclic structure, or their derivatives, aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, decanediol, etc. or their derivatives, etc., diglycidyl ones obtained by epoxidizing, trifunctional ones having a trihydroxyphenylmethane skeleton or an aminophenol skeleton can also be used. The epoxy resin as the thermosetting resin can contain one or more selected from those exemplified above.

[0051] Among these, from the viewpoint of improving the coating workability and adhesiveness of the resulting conductive paste, it is more preferable to contain a bisphenol-type epoxy resin, and it is particularly preferable to contain a bisphenol F-type epoxy resin. Further, in the present embodiment, from the viewpoint of more effectively improving the coating workability of the conductive paste, it is more preferable to contain a liquid epoxy resin that is liquid at room temperature (25°C).

[0052] In the conductive paste of the present embodiment, when a thermosetting resin is blended, the lower limit value of the content of the thermosetting resin is, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more with respect to the entire conductive paste. Thereby, the handleability of the conductive paste can be improved. Also, the viscosity of the conductive paste can be adjusted to an appropriate level for use. Further, the upper limit value of the content of the thermosetting resin is, for example, 15% by mass or less, preferably 12% by mass or less, and more preferably 10% by mass or less with respect to the entire conductive paste. Thereby, it is possible to improve the balance of various properties such as the conductivity of the conductive paste and the adhesion to the support member.

[0053] (Hardening agent) The conductive paste of the present embodiment may contain a hardening agent. Thereby, the curability of the conductive paste can be improved. As the hardening agent, for example, one or more selected from aliphatic amines, aromatic amines, dicyandiamide, dihydrazide compounds, acid anhydrides, and phenol compounds can be used. Among these, it is particularly preferable to contain at least one of dicyandiamide and phenol compounds from the viewpoint of improving production stability.

[0054] Examples of the dihydrazide compounds used as the hardening agent include carboxylic acid dihydrazides such as adipic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, and p-oxybenzoic acid dihydrazide. Examples of the acid anhydrides used as the hardening agent include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, dodecenyl succinic anhydride, the reaction product of maleic anhydride and polybutadiene, and the copolymer of maleic anhydride and styrene.

[0055] The phenolic compound used as the hardening agent is a compound having two or more phenolic hydroxyl groups in one molecule. The number of phenolic hydroxyl groups in one molecule is more preferably 2 to 5, and particularly preferably 2 or 3. Thereby, the coating workability of the conductive paste can be more effectively improved, and a crosslinked structure can be formed during curing to make the cured product characteristics of the conductive paste excellent. Examples of the phenolic compound include bisphenols and their derivatives such as bisphenol F, bisphenol A, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol S, dihydroxydiphenyl ether, dihydroxybenzophenone, tetramethylbiphenol, ethylidene bisphenol, methylethylidene bis(methylphenol), cyclohexylidene bisphenol, and biphenol; trifunctional phenols and their derivatives such as tri(hydroxyphenyl)methane and tri(hydroxyphenyl)ethane; and compounds obtained by reacting phenols such as phenol novolak and cresol novolak with formaldehyde, and one or more selected from those having binuclear or trinuclear main bodies and their derivatives. Among these, it is more preferable to contain bisphenols, and particularly preferable to contain bisphenol F.

[0056] In addition, in this embodiment, as the resin having a biphenyl skeleton as a curing agent, a phenolic resin (phenolic compound) having a biphenyl skeleton can be used. Thereby, the conductivity of the conductive paste and the adhesion to the support member can be improved. The phenolic resin having a biphenyl skeleton is not particularly limited in its structure as long as it has a biphenyl skeleton in its molecular structure and has two or more phenolic groups.

[0057] In this embodiment, the content of the curing agent in the conductive paste is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, based on the entire heat conductive paste. Thereby, the curability of the conductive paste can be more effectively improved. On the other hand, the content of the curing agent in the conductive paste is preferably 10% by mass or less, more preferably 7% by mass or less, based on the entire conductive paste. Thereby, the low thermal expansibility and moisture resistance of the adhesive layer formed using the conductive paste can be improved.

[0058] (Other components) In addition to the above-described components, the conductive paste of this embodiment may contain various additional components commonly used in the art, as needed. Examples of the additional components include, but are not limited to, silane coupling agents, curing accelerators, radical polymerization initiators, low stress agents, inorganic fillers, etc., and can be selected according to the desired performance.

[0059] Silane coupling agents are used to improve the adhesion between the conductive paste and the support member. Examples of silane coupling agents include vinyl silanes such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxy silanes such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; styryl silanes such as p-styryltrimethoxysilane; methacryl silanes such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; acrylic silanes such as 3-(trimethoxysilyl)propyl methacrylate and 3-acryloxypropyltrimethoxysilane; amino silanes such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; isocyanurate silane; alkyl silane; ureido silanes such as 3-ureidopropyltrialkoxysilane; mercapto silanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; isocyanate silanes such as 3-isocyanatopropyltriethoxysilane, etc.

[0060] The curing accelerator is used to promote the reaction between an epoxy monomer used as a polymerizable monomer or an epoxy resin used as a binder resin and a curing agent. Examples of the curing accelerator include phosphorus atom-containing compounds such as organic phosphines, tetra-substituted phosphonium compounds, phosphobetaine compounds, adducts of phosphine compounds and quinone compounds, and adducts of phosphonium compounds and silane compounds; amidines such as dicyandiamide, 1,8-diazabicyclo[5.4.0]undecene-7, and benzyldimethylamine, and tertiary amines; and nitrogen atom-containing compounds such as quaternary ammonium salts of the above amidines or the above tertiary amines.

[0061] Specifically, azo compounds, peroxides, etc. can be used as the radical polymerization initiator.

[0062] Examples of the low stress agent include silicone compounds such as silicone oil and silicone rubber; polybutadiene compounds such as polybutadiene maleic anhydride adducts; and acrylonitrile-butadiene copolymer compounds.

[0063] Examples of the inorganic filler include fused silica such as fused crushed silica and fused spherical silica; silica such as crystalline silica and amorphous silica; silicon dioxide; alumina; aluminum hydroxide; silicon nitride; and aluminum nitride.

[0064] (Preparation of Conductive Paste) The conductive paste of this embodiment (i) a step of surface-treating silver particles with oleic acid or sorbitanic acid, and (ii) It can be produced by a step of mixing the surface-treated silver powder, a diluent, and, if necessary, the above components. For the mixing in the above (ii), after premixing each of the above components, kneading can be performed using a three-roll mill, and further vacuum degassing can be used. At this time, the long-term workability of the conductive paste can be improved by appropriately adjusting the preparation conditions, such as performing the premixing under reduced pressure.

[0065] The conductive paste of this embodiment can adjust its viscosity according to the application. The viscosity of the conductive paste can be controlled by adjusting the type of binder resin used, the type of diluent, their blending amounts, and the like. The lower limit value of the viscosity of the conductive paste of this embodiment is, for example, 10 Pa·s or more, preferably 20 Pa·s or more, and more preferably 30 Pa·s or more. Thereby, the workability of the conductive paste can be improved. On the other hand, the upper limit value of the viscosity of the conductive paste is, for example, 1×10 3 Pa·s or less, preferably 5×10 2 Pa·s or less, and more preferably 2×10 2 Pa·s or less. Thereby, the coatability can be improved.

[0066] (Application) The application of the conductive paste of this embodiment will be described. The conductive paste according to this embodiment is used, for example, for adhering a substrate and a semiconductor element. Here, examples of the semiconductor element include a semiconductor package, an LED, and the like. Compared with the conventional paste-like adhesive composition, the conductive paste according to this embodiment can improve the connection reliability and the appearance. Thereby, it can be suitably used for applications in which a semiconductor element with a large heat generation amount is mounted on a substrate. In this embodiment, LED refers to a Light Emitting Diode.

[0067] Specific examples of the semiconductor device using an LED include a bullet-type LED, a Surface Mount Device (SMD) LED, a Chip On Board (COB), a Power LED, and the like.

[0068] Specific examples of the types of the semiconductor packages include CMOS image sensors, cavity 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 the like.

[0069] An example of a semiconductor device using the conductive paste according to the present embodiment will be described below. FIG. 1 is a cross-sectional view showing an example of a semiconductor device according to the present embodiment. The semiconductor device 100 according to the present embodiment includes a support member 30 and a semiconductor element 20 mounted on the support member 30 via an adhesive layer 10 which is a cured product of a conductive paste. The semiconductor element 20 and the support member 30 are electrically connected via, for example, a bonding wire 40 or the like. Further, the semiconductor element 20 is sealed with, for example, a sealing resin 50.

[0070] Here, the lower limit value of the thickness of the adhesive layer 10 is preferably, for example, 5 μm or more, and more preferably 10 μm or more. Thereby, the heat capacity of the cured product of the conductive paste can be improved, and the heat dissipation performance can be improved. Further, the upper limit value of the thickness of the adhesive layer 10 is preferably, for example, 50 μm or less, and more preferably 30 μm or less. Thereby, the conductive paste can exhibit suitable adhesive strength while improving the heat dissipation performance.

[0071] In FIG. 1, the support member 30 is, for example, a lead frame. In this case, the semiconductor element 20 is to be mounted on the die pad 32 or the support member 30 via the adhesive layer 10. Further, the semiconductor element 20 is electrically connected to the outer lead 34 (support member 30) via, for example, the bonding wire 40. The support member 30 which is a lead frame is composed of, for example, 42 alloy, a Cu frame.

[0072] The support member 30 may be an organic substrate or a ceramic substrate. As the organic substrate, those composed of, for example, an epoxy resin, a cyanate resin, a maleimide resin, etc. are preferable. Note that the surface of the support member 30 may be coated with a metal such as silver or gold. Thereby, the adhesiveness between the adhesive layer 10 and the support member 30 can be improved.

[0073] FIG. 2 is a modified example of FIG. 1 and is a cross-sectional view showing an example of the semiconductor device 100 according to the present embodiment. In the semiconductor device 100 according to this modified example, the support member 30 is, for example, an interposer. On the other surface of the support member 30 which is an interposer, opposite to the surface on which the semiconductor element 20 is mounted, for example, a plurality of solder balls 52 are formed. In this case, the semiconductor device 100 is to be connected to another wiring substrate via the solder balls 52.

[0074] (Method for manufacturing a semiconductor device) An example of the method for manufacturing the semiconductor device according to the present embodiment will be described. First, a conductive paste is applied on the support member 30, and then the semiconductor element 20 is disposed thereon. That is, the support member 30, the paste-like adhesive composition, and the semiconductor element 20 are laminated in this order. The method for applying the conductive paste is not limited, but specifically, dispensing, printing method, inkjet method, etc. can be used.

[0075] Next, the conductive paste is cured by pre-curing and then post-curing. Through heat treatments such as pre-curing and post-curing, silver particles in the conductive paste aggregate, and a heat conduction layer in which the interfaces between a plurality of silver particles disappear is formed in the adhesive layer 10. Thereby, the support member 30 and the semiconductor element 20 are adhered via the adhesive layer 10. Next, the semiconductor element 20 and the support member 30 are electrically connected using a bonding wire 40. Next, the semiconductor element 20 is encapsulated with a sealing resin 50. Thereby, a semiconductor device can be manufactured.

[0076] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can also be adopted.

Example

[0077] Hereinafter, the present invention will be described with reference to examples and comparative examples, but the present invention is not limited thereto.

[0078] In Examples 1 to 7 and Comparative Examples 1 to 3, a conductive paste was prepared with the formulations and amounts shown in Table 1 below. In each example and comparative example, the average primary particle size and the fatty acid content (the amount of fatty acid present on the surface of the silver powder after treatment, mass%) of the silver powder used were measured. The average primary particle size was measured using a laser particle size distribution analyzer (manufactured by Shimadzu Corporation, SALD-7000, etc.). The fatty acid content was calculated from the mass of the residue after firing the silver powder at 800°C for 30 minutes using TG / DTA measurement.

[0079] (Silver powder 1) · Silver particle shape: Flake · Average primary particle size: 3.06 μm · Oleic acid content (the amount of oleic acid present on the surface of silver powder 1): 0.37 mass%

[0080] (Silver powder 2) · Silver particle shape: Flake · Average primary particle size: 2.52 μm · Oleic acid content (the amount of oleic acid present on the surface of silver powder 2): 0.61% by mass

[0081] (Silver powder 3) · Silver particle shape: Flake · Average primary particle size: 2.72 μm · Oleic acid content (the amount of oleic acid present on the surface of silver powder 3): 0.73% by mass

[0082] (Silver powder 4) · Silver particle shape: Flake · Average primary particle size: 3.71 μm · Sorbitan acid content (the amount of sorbitan acid present on the surface of silver powder 4): 0.37% by mass

[0083] (Silver powder 5) · Silver particle shape: Flake · Average primary particle size: 3.90 μm · Sorbitan acid content (the amount of sorbitan acid present on the surface of silver powder 5): 0.51% by mass

[0084] (Silver powder 6) · Silver particle shape: Flake · Average primary particle size: 3.44 μm · Sorbitan acid content (the amount of sorbitan acid present on the surface of silver powder 6): 0.71% by mass

[0085] (Silver powder 7) · Silver particle shape: Flake · Average primary particle size: 3.25 μm · Oleic acid content (the amount of oleic acid present on the surface of silver powder 7): 0.35% by mass

[0086] (Silver powder 8) As silver powder 8, untreated silver powder was used. · Average primary particle size: 1.23 μm · Fatty acid content: 0.00% by mass

[0087] Furthermore, the components used in the examples and comparative examples are shown below. (Diluent) · Diluent 1: 2 - phenoxyethyl methacrylate (monofunctional methacrylic monomer), manufactured by Kyoeisha Chemical Co., Ltd., "Light Ester PO" · Diluent 2: 1,6 - hexanediol dimethacrylate (bifunctional (meth)acrylic monomer), manufactured by Kyoeisha Chemical Co., Ltd., "Light Ester 1,6Hx" (Low stress agent) · Low stress agent 1: Epoxidized polybutadiene, manufactured by Daicel Corporation · Low stress agent 2: Acrylic polymer, manufactured by Toagosei Co., Ltd. · Low stress agent 3: Allyl resin, manufactured by Kanto Chemical Co., Inc. (Thermosetting resin) · Thermosetting resin 1: Bisphenol - F - diglycidyl ether, manufactured by Nippon Kayaku Co., Ltd., "RE - 303SL" (Curing catalyst) · Curing catalyst 1: Imidazole, manufactured by Shikoku Chemicals Corporation, "Curezol 2PZ - PW" (Radical polymerization initiator) · Radical polymerization initiator 1: Di - alpha - cumyl peroxide, manufactured by Kayaku Akzo Co., Ltd., "Perkadox BC"

[0088] [Examples 1 - 7, Comparative Examples 1 - 3] (Preparation of varnish - like resin composition) First, components with the compounding amounts described in the "Varnish composition" of Table 1 were kneaded with a three - roll mill at room temperature to prepare a varnish - like mixture. Next, the obtained varnish - like mixture was used in the compounding amount described in the "paste composition" of Table 1, mixed with silver powder, and kneaded with a three - roll mill at room temperature to obtain a paste - like composition (conductive paste).

[0089] (Measurement of physical properties of conductive paste) The conductive pastes of each example and each comparative example were measured for the following physical properties, and the adhesion of the conductive paste to the support member was evaluated.

[0090] <Elastic modulus (room temperature)> The conductive paste obtained above was applied onto a Teflon plate, and the temperature was raised from 30°C to 200°C over 60 minutes, followed by heat treatment at 200°C for 120 minutes. As a result, a test piece of the conductive paste with a thickness of 0.3 mm after heat treatment was obtained. The obtained heat-treated body was peeled off from the Teflon plate, set in a measuring device (DMS6100 manufactured by Hitachi High-Tech Science Corporation), and dynamic viscoelasticity measurement (DMA) was performed in tension mode at a frequency of 1 Hz. Thereby, the storage elastic modulus E'(MPa) at 25°C was measured. <Elastic modulus (250°C)> Test pieces were prepared under the same conditions as the measurement method of the elastic modulus at room temperature, and the storage elastic modulus at 250°C was measured.

[0091] <Die shear strength after moisture absorption (length 5 mm × width 5 mm × thickness 350 μm silicon chip)> Curing conditions: The conductive paste obtained above was applied onto a copper frame, and a silicon chip with a length of 2 mm × a width of 2 mm was mounted thereon to a thickness of 20 μm. Thereafter, the temperature was raised to 175°C in 30 minutes under a nitrogen atmosphere and left for 5 hours (1 hour of curing and post-mold cure) to obtain test pieces. Moisture absorption conditions: The obtained test pieces were left in an environment of a temperature of 120°C and a relative humidity of 100% for 24 hours, and the taken-out samples were passed through a reflow process at 260°C three times. Measurement conditions for die shear strength: The test pieces after moisture absorption treatment were placed on a 260°C plate for 20 seconds, and in that state, the chip peel strength was measured with a bond tester (DAGE 4000P type). Figure 3 is a schematic diagram showing the measurement method of the chip peel strength. The silicon chip 220 is adhered via a conductive paste 210 onto a copper frame 200 surface-treated with a bleed-out inhibitor. A jig 230 was pressed against the side surface of the silicon chip 220, and the die shear strength was measured as the maximum stress when a force was applied in the arrow direction shown in Figure 3 under the conditions of a measurement speed of 50 μm / second and a measurement height of 50 μm, and this was taken as the adhesive strength. The die shear strength is shown in Table 1. The unit of the die shear strength is "N". The larger the value of the die shear strength, the stronger the adhesion between the silicon chip and the copper frame.

[0092] <Reliability (Package Peel Test)> The conductive paste obtained above was applied onto a copper frame, and on top of that, a 200-μm-thick silicon chip with a length of 8 mm × width of 8 mm was mounted and made 20-μm thick. Then, the temperature was raised to 175°C over 30 minutes under a nitrogen atmosphere and left for 1 hour to obtain test pieces. Seven test pieces were prepared. Then, it was sealed with an epoxy molding compound to obtain a package. Thereafter, post-mold cure was performed at 175°C for 4 hours to obtain a package structure. This package structure has a length of 14 mm, a width of 14 mm, and a thickness of 0.8 mm. Then, the obtained package structure was placed in the following environment. Environment 1: Temperature 85°C, Relative Humidity 85%, 168 hours The package structure exposed to the conditions of Environment 1 was taken out, and the presence or absence of peeling of the silicon chip from the copper frame in the package structure was confirmed. The number of package structures with peeling observed was shown in Table 1 as the number of peeled ones. The reliability is shown in Table 1 according to the following evaluation criteria. Number of peeled ones 0: ◎ (Good) Number of peeled ones 1 - 3: ○ (Slightly inferior, but no problem for use) Number of peeled ones 4 - 7: △ (Inferior)

[0093]

Table 1

[0094] The conductive pastes of the examples and comparative examples had conductivity that enabled them to be used as die attach pastes. Among the examples, Examples 1, 2, 6, and 7, which used silver powders 1, 2, or 7 with an oleic acid content of 0.30 to 0.70% by mass, had better reliability in the package peel test than Comparative Example 1, which used silver powder 3 with an oleic acid content of 0.73% by mass, and Comparative Example 3, which used untreated silver powder 8 with an oleic acid content of 0.00% by mass. Examples 3 and 4, which used silver powders 4 or 5 with a sorbitan acid content of 0.30 to 0.70% by mass, had better reliability in the package peel test than Comparative Example 2, which used a silver powder with a sorbitan acid content of 0.71% by mass, and Comparative Example 3, which used untreated silver powder 8 with a sorbitan acid content of 0.00% by mass.

Explanation of Signs

[0095] 100 Semiconductor device 10 Adhesive layer 20 Semiconductor element 30 Support member 32 Die pad 34 Outer lead 40 Bonding wire 50 Encapsulating resin 52 Solder ball 200 Copper frame 210 Conductive paste 220 Silicon chip 230 Fixture

Claims

1. A conductive paste comprising: (A) silver powder surface-treated with at least one fatty acid selected from oleic acid and sorbitanic acid; and (B) a diluent, wherein the diluent (B) contains a (meth)acrylic monomer, and the amount of the fatty acid is 0.30% by mass or more and 0.70% by mass or less based on the total amount of the silver powder and the fatty acid.

2. The conductive paste according to claim 1, wherein the diluent (B) contains neither free oleic acid nor free sorbitanic acid dissolved or dispersed therein.

3. The conductive paste according to claim 1 or 2, wherein the average primary particle diameter of the silver powder (A) surface-treated with the fatty acid is 0.1 µm or more and 10 µm or less.

4. The conductive paste according to any one of claims 1 to 3, wherein the silver powder (A) surface-treated with the fatty acid is in an amount of 40% by mass or more and 90% by mass or less based on the entire conductive paste.

5. The conductive paste according to any one of claims 1 to 4, wherein the (meth)acrylic monomer contains a monofunctional (meth)acrylic monomer, a polyfunctional (meth)acrylic monomer, or a combination thereof.

6. The conductive paste according to any one of claims 1 to 5, wherein the diluent (B) further contains at least one selected from glycol monomers, epoxy monomers, maleimide monomers, and imide monomers.

7. The conductive paste according to any one of claims 1 to 6, further comprising a thermosetting resin (C).

8. The conductive paste according to claim 7, wherein the thermosetting resin (C) contains at least one selected from polyester resins, epoxy resins, urethane resins, phenol resins, melamine resins, vinyl resins, acrylic resins, and silicone resins.

9. The conductive paste according to any one of claims 1 to 8, further comprising a curing agent.

10. A semiconductor device comprising: a support member; and a semiconductor element mounted on the support member via an adhesive layer, wherein the adhesive layer is made of the conductive paste according to any one of claims 1 to 9.

Images