Conductive paste and semiconductor device

Abstract

To provide a conductive paste which suppresses separation / precipitation of a component in a paste during storage, and bleed-out of a diluent when the paste is arranged, and is suitably usable as a die attach paste excellent in physical and electric connection reliability.SOLUTION: A conductive paste for electronic component adhesion contains a binder resin, conductive metallic powder, alkyl acetalized polyvinyl alcohol, and a diluent, wherein a content of the alkyl acetalized polyvinyl alcohol is 5 ppm or more and 200 ppm or less with respect to the whole conductive paste.SELECTED DRAWING: Figure 1

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 semiconductors, which is used to bond and fix semiconductor elements onto a support member such as a metal frame, and to a semiconductor device manufactured using the conductive paste. [Background technology]

[0002] Semiconductor devices in which semiconductor elements are mounted on a lead frame and molded with resin are widely used. For example, semiconductor elements such as ICs and LSIs are mounted on metal pieces such as lead frames, fixed using a conductive paste called die attach paste, and then the leads of the lead frame and the electrodes on the semiconductor element are connected with thin wires (bonding wires). These are then housed in a package to form a semiconductor product. Optoelectronic devices using light-emitting diodes (LEDs), which are put into practical use for various displays, are manufactured by bonding optoelectronic semiconductor elements to predetermined parts on a lead frame or resin substrate with conductive paste, and then sealing them with transparent sealing resin (for example, Patent Document 1).

[0003] In the manufacturing of semiconductor devices, die attach paste, used to bond semiconductor elements to lead frames and to improve electrical and thermal conductivity between them, is generally composed of a resin and highly electrically conductive particles as fillers. If the thixotropic properties of the die attach paste are low, a phenomenon called bleed-out occurs, in which the resin components contained in the paste seep into the substrate depending on the surface condition of the lead frame. To solve this problem, techniques have been proposed to incorporate additives to ensure sufficient thixotropic properties. For example, Patent Document 2 proposes a technique to suppress resin bleed-out by adding silicone rubber fine powder as an additive. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-273407 [Patent Document 2] Japanese Patent Application Publication No. 5-335353 [Overview of the project] [Problems that the invention aims to solve]

[0005] As mentioned above, die attach pastes for semiconductors are generally composed of resin and filler. To ensure ease of application, such die attach pastes need to be reduced in viscosity by adding a diluent, in other words, turned into a paste. However, the inventors have found that because the organic solvents used as diluents are low viscosity, the solvent components can often spread due to capillary action caused by fine irregularities on the surface of the lead frame to be bonded. They have also found that bleeding to unexpected parts within the lead frame can cause the solvent to leak to the bottom of the lead frame during the process, or cause wire bonding failures due to contamination. Furthermore, they have found that when such die attach pastes are stored for a long period of time, separation and precipitation of components occur within the paste.

[0006] The present invention has been made in view of these circumstances, and aims to provide a conductive paste that can be used as a die attach paste with excellent physical and electrical connection reliability, even when a diluent is added to reduce viscosity, by suppressing the bleed-out of the diluent, preventing dripping and seeping, and suppressing the separation and precipitation of components in the paste during storage. [Means for solving the problem]

[0007] Even when a diluent is included in the conductive paste, the present inventors have found that by using a specific additive, it is possible to suppress separation and precipitation of components in the paste during storage and bleed-out of the diluent when the paste is disposed, and have completed the present invention.

[0008] According to the present invention, there are provided a conductive paste and a semiconductor device shown below.

[0009] [1] A binder resin, Conductive metal powder, Alkyl acetalized polyvinyl alcohol, A diluent, A conductive paste for bonding electronic components, comprising: The conductive paste, wherein the content of the alkyl acetalized polyvinyl alcohol is 5 ppm or more and 200 ppm or less based on the entire conductive paste. [2] A binder resin, Conductive metal powder, Polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid, A diluent, A conductive paste for bonding electronic components, comprising: The conductive paste, wherein the content of the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid is from 1,000 ppm to 15,000 ppm based on the entire conductive paste. [3] The conductive paste according to [1] or [2] above, wherein the binder resin contains one or more selected from cyanate resins, epoxy resins, (meth)acrylic resins, resins having two or more radical-polymerizable carbon-carbon double bonds in one molecule, and maleimide resins. [4] The conductive paste according to any one of [1] to [3] above, wherein the binder resin contains an epoxy resin having two or more glycidyl groups in one molecule. [5] A conductive paste according to any one of the above [1] to [4], further comprising a hardening agent. [6] The conductive paste according to [5] above, wherein the curing agent comprises one or more selected from aliphatic amines, aromatic amines, dicyandiamides, dihydrazide compounds, acid anhydrides, and phenolic compounds. [7] The conductive paste according to any one of [1] to [6] above, wherein the conductive metal powder comprises at least one selected from silver powder, gold powder, platinum powder and alloys thereof. [8] The conductive paste according to any one of [1] to [7] above, wherein the conductive metal powder is present in an amount of 30% by mass or more and 90% by mass or less, preferably 30% by mass or more and 80% by mass or less, relative to the entire conductive paste. [9] The conductive paste does not contain an inorganic filler different from the conductive metal powder, Alternatively, the conductive paste according to any one of [1] to [8] above, wherein the conductive paste further contains an inorganic filler different from the conductive metal powder, and the content of the inorganic filler is 30% by mass or less of the total conductive paste.

[10] The viscosity of the conductive paste was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 0.5 rpm. 0.5 A conductive paste according to any one of the above [1] to [9], wherein the pressure is 35 Pa·s or more and 100 Pa·s or less, preferably 35 Pa·s or more and 70 Pa·s or less.

[11] A conductive paste according to any one of the above [1] to

[10] , wherein the conductive paste is measured using a BF-type viscometer while being stirred at a temperature of 25°C and a shear rate of 5.0 rpm, and the 5.0 rpm viscosity η5 is 5 Pa·s or more and 30 Pa·s or less.

[12] The viscosity of the conductive paste was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 50.0 rpm. 50.0The conductive paste according to any one of the above [1] to

[11] , having a viscosity of 1 Pa·s or more and 15 Pa·s or less.

[13] In the conductive paste, the 0.5 rpm viscosity η measured while stirring at a temperature of 25°C and a shear rate of 0.5 rpm using a BF type viscometer 0.5 and the 5.0 rpm viscosity η measured while stirring at a temperature of 25°C and a shear rate of 5.0 rpm using a BF type viscometer 5.0 The conductive paste according to any one of the above [1] to

[12] , wherein the viscosity ratio Ti1 represented by the following formula (1) is 3 or more and 7 or less, using these. Ti1 = η 0.5 / η 5.0 (1)

[14] In the conductive paste, the 0.5 rpm viscosity η measured while stirring at a temperature of 25°C and a shear rate of 0.5 rpm using a BF type viscometer 0.5 and the 50.0 rpm viscosity η measured while stirring at a temperature of 25°C and a shear rate of 50.0 rpm using a BF type viscometer 50.0 The conductive paste according to any one of the above [1] to

[13] , wherein the viscosity ratio Ti2 represented by the following formula (2) is 6 or more and 20 or less, preferably 6 or more and 14 or less, using these. Ti2 = η 0.5 / η 50.0 (2)

[15] A base material, A semiconductor element mounted on the base material via an adhesive layer, comprising: The semiconductor device, wherein the adhesive layer is made of a cured product of the conductive paste according to any one of the above [1] to

[14] .

Effect of the Invention

[0010] According to the present invention, separation and precipitation of components in the paste during storage and bleed - out of the diluent when the paste is placed are suppressed, and a conductive paste that can be suitably used as a die attach paste excellent in physical and electrical connection reliability is provided.

Brief Description of the Drawings

[0011] [Figure 1] This is a cross-sectional view showing an example of an electronic device according to this embodiment. [Figure 2] This is a cross-sectional view showing an example of an electronic device according to this embodiment. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below. In this specification, the term "(meth)acrylic" refers to a concept that encompasses both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate" and "(meth)acrylate."

[0013] (Conductive paste) The conductive paste of this embodiment is a die attach paste used to form a die attach layer for bonding electronic components such as semiconductor elements to a substrate such as a lead frame or wiring board. The conductive paste of this embodiment contains a binder resin, conductive metal powder, alkylacetalized polyvinyl alcohol, and a diluent, wherein the content of the alkylacetalized polyvinyl alcohol is 5 ppm to 200 ppm relative to the total conductive paste. When the conductive paste of this embodiment is heat-treated, the binder resin contained therein hardens, causing the conductive metal powders to aggregate with each other and form a metal powder linkage structure. As a result, the die attach layer obtained by heating the conductive paste exhibits conductivity or thermal conductivity, as well as adhesion to electronic components and substrates.

[0014] The conductive paste of this embodiment contains alkylacetalized polyvinyl alcohol, which suppresses the separation and precipitation of components in the paste during storage and the bleed-out of the diluent when the paste is placed, even when the conductive paste contains a diluent as in this embodiment. Therefore, when this conductive paste is placed on the surface of a lead frame during the manufacture of electronic devices, the diluent does not spread. As a result, the connection between the semiconductor element and the substrate is highly reliable both physically and electrically. In this embodiment, "storage time" includes not only long-term storage but also the state in which the conductive paste of this embodiment is prepared in the manufacturing equipment and left undisturbed for a long period of time until actual manufacturing begins.

[0015] Here, the lower limit of the alkylacetalized polyvinyl alcohol content in the conductive paste of this embodiment is 5 ppm or more relative to the total conductive paste, preferably 10 ppm or more, more preferably 15 ppm or more, and even more preferably 20 ppm or more. By having an alkylacetalized polyvinyl alcohol content above the above lower limit, it is possible to effectively suppress the occurrence of bleeding while suppressing the separation and precipitation of components. Furthermore, the upper limit of the alkylacetalized polyvinyl alcohol content in the conductive paste of this embodiment is 200 ppm or less relative to the total conductive paste, but is preferably 195 ppm or less, more preferably 190 ppm or less, and even more preferably 185 ppm or less. By keeping the alkylacetalized polyvinyl alcohol content below the above upper limit, the viscosity of the conductive paste can be improved.

[0016] Furthermore, in one embodiment of this embodiment, the conductive paste is a conductive paste for bonding electronic components comprising a binder resin, conductive metal powder, polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid, and a diluent, wherein the content of the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid may be 1,000 ppm or more and 15,000 ppm or less relative to the entire conductive paste.

[0017] The conductive paste of this embodiment, whether containing polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid, or even if containing a diluent as in this embodiment, suppresses the separation and precipitation of components in the paste during storage and the bleed-out of the diluent when the paste is placed. Therefore, when this conductive paste is placed on the surface of a lead frame during the manufacture of electronic devices, the diluent does not spread. As a result, the connection between the semiconductor element and the substrate is highly reliable both physically and electrically.

[0018] Here, the lower limit of the content of polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid in the conductive paste of this embodiment is 1000 ppm or more relative to the entire conductive paste, preferably 1050 ppm or more, more preferably 1100 ppm or more, and even more preferably 1150 ppm or more. By having a polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid content of 1000 ppm or more relative to the above lower limit, it is possible to effectively suppress the occurrence of bleeding while suppressing the separation and precipitation of components. Furthermore, the upper limit of the content of polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid in the conductive paste of this embodiment is 15,000 ppm or less relative to the entire conductive paste, but is preferably 14,950 ppm or less, more preferably 14,900 ppm or less, and even more preferably 14,850 ppm or less. By keeping the content of polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid below the above upper limit, the viscosity of the conductive paste can be improved.

[0019] The components used in the conductive paste of this embodiment will be described in detail below.

[0020] (Binder resin) The binder resin used in the conductive paste of this embodiment is a thermosetting resin, and one or more of the following thermosetting resins can be used: cyanate resin, epoxy resin, (meth)acrylic resin, a resin having two or more radically polymerizable carbon-carbon double bonds in one molecule, and maleimide resin. Among these, from the viewpoint of improving the adhesion of the conductive paste, it is preferable to include an epoxy resin, and it is preferable to include an epoxy resin having two or more glycidyl groups in one molecule.

[0021] As the epoxy resin used as a thermosetting resin, monomers, oligomers, and polymers in general that have two or more glycidyl groups in one molecule can be used, and their molecular weight and molecular structure are not particularly limited. Examples of epoxy resins used in this embodiment include biphenyl-type epoxy resins; bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and tetramethylbisphenol 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; naphthol-type epoxy resins such as dihydroxynaphthalene-type epoxy resin and epoxy resin obtained by glycidyl etherification of a dimer of dihydroxynaphthalene; triazine-nucleus-containing epoxy resins such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; and bridged cyclic hydrocarbon compound-modified phenol-type epoxy resins such as dicyclopentadiene-modified phenol-type epoxy resin. Furthermore, as epoxy resins, it is also possible to use, for example, bifunctional compounds epoxidized from compounds containing two or more glycidyl groups in one molecule, such as bisphenol compounds or derivatives thereof, including bisphenol A, bisphenol F, biphenol, diols having an alicyclic structure such as hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated biphenol, cyclohexanediol, cyclohexanedimethanol, cyclohexanediethanol or derivatives thereof, aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, decanediol or derivatives thereof, or trifunctional compounds having a trihydroxyphenylmethane skeleton or an aminophenol skeleton. The epoxy resin as a thermosetting resin may include one or more selected from those exemplified above.

[0022] Among these, from the viewpoint of improving the applicability and adhesion of the resulting conductive paste, it is more preferable to include a bisphenol-type epoxy resin, and particularly preferable to include a bisphenol F-type epoxy resin. Furthermore, in this embodiment, from the viewpoint of more effectively improving the applicability of the conductive paste, it is more preferable to include a liquid epoxy resin that is liquid at room temperature (25°C).

[0023] The cyanate resin used as a thermosetting resin is not particularly limited, but examples include 1,3-dicyanatobenzene, 1,4-dicyanatobenzene, 1,3,5-tricyanatobenzene, 1,3-dicyanatonaphthalene, 1,4-dicyanatonaphthalene, 1,6-dicyanatonaphthalene, 1,8-dicyanatonaphthalene, 2,6-dicyanatonaphthalene, 2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene, 4,4'-dicyanatobiphenyl, bis(4-cyanatophenyl)methane, bis(3,5-dimethyl-4-cyanatophenyl)methane, 2,2-bis(4-cyana The prepolymer may include one or more selected from the following: tophenyl)propane, 2,2-bis(3,5-dibromo-4-cyanatophenyl)propane, bis(4-cyanatophenyl)ether, bis(4-cyanatophenyl)thioether, bis(4-cyanatophenyl)sulfone, tris(4-cyanatophenyl)phosphine, tris(4-cyanatophenyl)phosphate, cyanates obtained by the reaction of a novolac resin with a cyanide halide, and prepolymers having a triazine ring formed by trimerizing the cyanate groups of these polyfunctional cyanate resins. The above prepolymer can be obtained by polymerizing the above polyfunctional cyanate resin monomer using, for example, an acid such as a mineral acid or Lewis acid, a base such as a sodium alcoholate or tertiary amine, or a salt such as sodium carbonate as a catalyst.

[0024] The (meth)acrylic resin used as a thermosetting resin is not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-propyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, chloro-2-hydroxyethyl (meth)acrylate, and ethylene glycol di(meth)acrylate. The (meth)acrylic resin may include (meth)acrylic resins such as diethylene glycol mono(meth)acrylate, methoxyethyl (meth)acrylate, glycidyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and isoboronol (meth)acrylate, and (meth)acrylic resins obtained by polymerizing at least one compound selected from the group consisting of these as the main component (50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more).

[0025] As a thermosetting resin having two or more radically polymerizable carbon-carbon double bonds in one molecule, for example, a radically polymerizable (meth)acrylic resin having two or more (meth)acryloyl groups in the molecule can be used. In this embodiment, the acrylic resin may include a polyether, polyester, polycarbonate, or poly(meth)acrylate with a molecular weight of 500 to 10000, and may contain compounds having (meth)acrylic groups. When a thermosetting resin having two or more radically polymerizable carbon-carbon double bonds in one molecule is used, the conductive paste may contain a polymerization initiator such as a thermal radical polymerization initiator.

[0026] The maleimide resin used as a thermosetting resin is not particularly limited, but may include one or more selected from bismaleimide resins such as N,N'-(4,4'-diphenylmethane)bismaleimide, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, and 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane.

[0027] Examples of thermosetting resins include resins having a biphenyl skeleton. By including an epoxy resin having a biphenyl skeleton (biphenyl-type epoxy resin), the metal adhesion of the conductive paste can be improved.

[0028] Epoxy resins having a biphenyl skeleton are not particularly limited in structure as long as they have a biphenyl skeleton in their molecular structure and two or more epoxy groups. Examples include bifunctional epoxy resins obtained by treating biphenol or its derivatives with epichlorohydrin, phenol aralkyl type epoxy resins having a biphenylene skeleton, and naphthol aralkyl type epoxy resins having a biphenylene skeleton. These can be used individually or in combination. Among these, those with two epoxy groups in the molecule are particularly preferred because they exhibit excellent heat resistance. Examples of such epoxy resins include bifunctional epoxy resins obtained by treating biphenol derivatives with epichlorohydrin, such as biphenyl type epoxy resins and tetramethylbiphenyl type epoxy resins; phenol aralkyl type epoxy resins having a biphenylene skeleton with two epoxy groups (sometimes expressed as having two phenolic units); and naphthol aralkyl type resins having a biphenylene skeleton with two epoxy groups.

[0029] In the conductive paste of this embodiment, the lower limit of the binder resin content is, for example, 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more, relative to the total conductive paste. This improves the handling properties of the conductive paste. It also allows the viscosity of the conductive paste to be at a level suitable for use. Furthermore, the upper limit of the binder resin content is, for example, 15% by mass or less, preferably 12% by mass or less, and more preferably 10% by mass or less, relative to the total conductive paste. This improves the balance of various properties of the conductive paste, such as conductivity and adhesion to the substrate.

[0030] (Conductive metal powder) The conductive metal powder contained in the conductive paste of this embodiment aggregates to form a metal particle linkage structure when the conductive paste is subjected to heat treatment. That is, in the die-attach paste layer obtained by heating the conductive paste, the metal powders exist aggregated with each other. This results in conductivity, thermal conductivity, and adhesion to the substrate.

[0031] The conductive metal powder used in the conductive paste of this embodiment can be silver powder, gold powder, platinum powder, or an alloy thereof. From the viewpoint of conductivity and ease of handling, silver powder is preferred.

[0032] The shape of the conductive metal powder is not particularly limited, but examples include spherical, flake-shaped, and flaky shapes. In this embodiment, it is more preferable that the conductive metal powder contains spherical particles. This improves the uniformity of aggregation of the conductive metal powder. Furthermore, from the viewpoint of reducing costs, an embodiment in which the conductive metal powder contains flake-shaped particles can also be adopted. Moreover, from the viewpoint of improving the balance between cost reduction and aggregation uniformity, the conductive metal powder may contain both spherical and flake-shaped particles.

[0033] Average particle size of conductive metal powder (D 50The particle size is, for example, between 0.1 μm and 10 μm. By having the average particle size of the conductive metal powder be greater than or equal to the lower limit, it is possible to improve the formation of metal particle linkage structures between the conductive metal powders. Furthermore, by having the average particle size of the conductive metal powder be less than or equal to the upper limit, it is possible to suppress an excessive increase in specific surface area and reduce the decrease in thermal conductivity due to contact thermal resistance. Furthermore, from the viewpoint of improving the dispensability of conductive paste, the average particle size (D) of the conductive metal powder is important. 50 The average particle size (D) of the conductive metal powder 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. 50 This can be measured using, for example, a commercially available laser particle size analyzer (e.g., Shimadzu Corporation's SALD-7000).

[0034] Furthermore, the maximum particle size of the conductive metal powder is not particularly limited, but can be, for example, 1 μm to 50 μm, more preferably 3 μm to 30 μm, and particularly preferably 4 μm to 18 μm. This makes it possible to more effectively improve the balance between the uniformity of aggregation and the dispensability of the conductive metal powder.

[0035] The content of conductive metal powder in the conductive paste is preferably 30% to 90% by mass of the total conductive paste, more preferably 45% to 89% by mass, even more preferably 60% to 88% by mass, even more preferably 70% to 87% by mass, and even more preferably 75% to 86% by mass. Setting the content above the lower limit contributes to improving the thermal conductivity and electrical conductivity of the die attach paste layer obtained by heat-treating the conductive paste. On the other hand, setting the content below the upper limit contributes to improving the application workability of the resulting conductive paste and the mechanical strength of the die attach paste layer obtained by heat-treating the conductive paste.

[0036] (Alkylacetalized polyvinyl alcohol) The conductive paste of this embodiment contains alkylacetalized polyvinyl alcohol. This suppresses the occurrence of bleeding, which is a phenomenon in which the diluent spreads wet on the substrate.

[0037] The alkylacetalized polyvinyl alcohol used in the conductive paste of this embodiment is an alkylacetalized polyvinyl alcohol synthesized by an acetalization reaction between polyvinyl alcohol and an aldehyde. The alkylacetalized polyvinyl alcohol is a resin having vinyl alcohol units (formula (I)), vinyl ester units (formula (II)), and vinyl acetal units (a structure in which two vinyl alcohol units are acetalized with an aldehyde, formula (III)). In the following formulas, l is the molar ratio of vinyl alcohol units, m is the molar ratio of vinyl ester units, n is the molar ratio of vinyl acetal units, and R a The aldehyde (R) used in acetalization is a -CHO) R in the middle a And R a R is an alkyl group having 1 to 10 carbon atoms. b is vinyl ester (R b R in COOCH=CH2) b And R b l is an alkyl group having 1 to 10 carbon atoms, where l and / or m may be zero. There are no restrictions on the order of the arrangement of each unit; they may be arranged randomly, in blocks, or in a tapered arrangement. The bonds between repeating units may be head-to-tail or head-to-head.

[0038] [ka]

[0039] [ka]

[0040] [ka]

[0041] In the alkylacetalized polyvinyl alcohol described above, when the sum of l, m, and n is set to 100, l is preferably 25 to 40, more preferably 27 to 37, and even more preferably 30 to 35. By keeping l within the above numerical range, the precipitation of solid components and the separation of liquid components in the conductive paste can be effectively suppressed when the conductive paste is stored for a long period of time.

[0042] In the alkylacetalized polyvinyl alcohol described above, when the sum of l, m, and n is set to 100, m is preferably 1 to 10, more preferably 1.1 to 9.7, and even more preferably 1.2 to 9.5. By keeping m within the above numerical range, the precipitation of solid components and the separation of liquid components in the conductive paste can be effectively suppressed when the conductive paste is stored for a long period of time.

[0043] In the alkylacetalized polyvinyl alcohol described above, when the sum of l, m, and n is set to 100, n is preferably 50 to 70, more preferably 51 to 67, and even more preferably 53 to 65. By keeping n within the above numerical range, the precipitation of solid components and the separation of liquid components in the conductive paste can be effectively suppressed when the conductive paste is stored for a long period of time.

[0044] Alkylacetalized polyvinyl alcohol is obtained by alkylacetalizing polyvinyl alcohol with an aldehyde.

[0045] Here, vinyl ester monomers for forming the vinyl ester unit represented by formula (II) include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl pivalate, and vinyl versaticate. Among these, vinyl acetate is preferred due to its availability. From a similar viewpoint, alkylacetalized polyvinyl alcohols preferably contain a methyl group in their molecular structure, and more preferably R in the above general formula (II). b This is a methyl group.

[0046] Aldehydes used to alkylate polyvinyl alcohol include acetaldehyde (including paraacetaldehyde), propionaldehyde, glyoxal, butyraldehyde, n-octylaldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glutaraldehyde, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. Among these, butyraldehyde is particularly preferred from the viewpoint of ease of production. From a similar viewpoint, alkylatelated polyvinyl alcohol preferably contains a butyl group in its molecular structure, and more preferably R in the above general formula (III). a This is a butyl group.

[0047] The weight-average molecular weight of alkylacetalized polyvinyl alcohol is, for example, 6 × 10⁻⁶. 4 The above 15 x 10 4 The following is preferable: 8 × 10 4 The above 12 x 10 4 The following are even more preferable.

[0048] Examples of commercially available alkylacetalized polyvinyl alcohols include S-Rec (manufactured by Sekisui Chemical Co., Ltd.), and various grades are available on the market. More specifically, examples include S-Rec BH-3, S-Rec BX-6, S-Rec KS-1, S-Rec KS-10, and S-Rec KS-3, but these are not the only examples.

[0049] (Polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate) In one embodiment of the present invention, the conductive paste contains polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid. This makes it possible to suppress the separation and precipitation of components in the paste during storage, as well as the occurrence of bleeding, which is the phenomenon in which the diluent spreads over the substrate when the paste is placed, even when the conductive paste contains a diluent as in this embodiment.

[0050] Examples of commercially available polyoxyethylene alkyl ether carboxylic acids include Viewlight LCA-25NH (manufactured by Sanyo Chemical Industries, Ltd.) and Kaocera 8110 (manufactured by Kao Corporation), and examples of commercially available oleyl sarcosinic acid include oleoyl sarcosin 221P (manufactured by NOF Corporation), but are not limited to these.

[0051] Furthermore, the conductive paste of this embodiment may contain known anionic surfactants in addition to the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid mentioned above. The anionic surfactant is not particularly limited, but examples include fatty acid soaps such as potassium laurate, potassium coconut fatty acid, potassium myristate, potassium oleate, potassium oleate diethanolamine salt, sodium oleate, potassium palmitate, potassium stearate, sodium stearate, mixed fatty acid sodium soap, semi-hardened beef tallow fatty acid sodium soap, and castor oil potassium soap; alkyl sulfate ester salts such as sodium dodecyl sulfate, higher alcohol sulfate, dodecyl sulfate triethanolamine, dodecyl sulfate ammonium, polyoxyethylene alkyl ether sulfate sodium, polyoxyethylene alkyl ether sulfate triethanolamine, polyoxyethylene alkylphenyl ether sulfate sodium, and 2-ethylhexyl sulfate sodium; and alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate. Examples include sodium sulfonate; sodium dialkyl sulfosuccinate such as sodium di-2-ethylhexyl sulfosuccinate; sodium alkylnaphthalene sulfonate; sodium alkyldiphenyl ether disulfonate; potassium alkyl phosphate; phosphate ester salts such as sodium polyoxyethylene lauryl ether phosphate; sodium salts of naphthalene sulfonic acid formalin condensate; polycarboxylic acid type polymer anions; sodium acyl(beef tallow) methyl taurate; sodium acyl(coconut) methyl taurate; sodium cocoyl isethionate; sodium α-sulfo fatty acid ester salts; sodium amide ether sulfonate; polyoxyethylene alkyl ether carboxylic acid and its salts; N-acyl amino acids such as oleyl sarcosinate and sodium lauroyl sarcosinate and their salts; and rosinic acid soap.

[0052] (Diluent) In this embodiment, a diluent is added to the conductive paste to achieve an appropriate viscosity, taking into consideration its applicability to semiconductor elements or substrates and its ability to fill into fine details. A non-reactive solvent or a reactive diluent can be used as the diluent. Here, a non-reactive solvent means a solvent that does not have reactive groups involved in the crosslinking reaction of the binder resin, while a reactive diluent means a compound containing reactive groups that are involved in the crosslinking reaction of the binder resin in the conductive paste.

[0053] The conductive paste of this embodiment can be improved in terms of handling and workability by adjusting the fluidity of the resulting conductive paste by including a non-reactive solvent. 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, diethylene glycol monobutyl ether (butyl carbitol), propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, methyl methoxybutanol, α-terpineol, β-terpineol, hexylene glycol, benzyl alcohol, 2-phenylethyl alcohol, isopalmityl alcohol, isostearyl alcohol, lauryl alcohol, ethylene glycol, propylene glycol, or glycerin; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexyl Ketones such as sanone, 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, propionic acid Esters such as ethylene 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;Examples include ester ethers such as 2-(2-butoxyethoxy)ethane acetate; ether alcohols such as 2-(2-methoxyethoxy)ethanol; hydrocarbons such as toluene, xylene, n-paraffin, isoparaffin, dodecylbenzene, turpentine oil, kerosene, or diesel fuel; nitriles such as acetonitrile or propionitrile; amides such as acetamide or N,N-dimethylformamide; and low molecular weight volatile silicone oils or volatile organic modified silicone oils.

[0054] In this embodiment, the content of the non-reactive solvent in the conductive paste is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, relative to the total conductive paste. This can more effectively improve the application workability of the conductive paste and the flatness of the resulting adhesive layer. On the other hand, the content of the non-reactive solvent in the conductive paste is preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less, relative to the total conductive paste. This can suppress the occurrence of dripping during application and improve the application workability.

[0055] The conductive paste of this embodiment can be improved in terms of curability while adjusting the fluidity of the resulting conductive paste by including a reactive diluent. Examples of reactive diluents used as diluents include glycol monomers, acrylic monomers, epoxy monomers, and maleimide monomers.

[0056] Examples of glycol monomers used as reactive diluents include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monoallyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, and diethylene glycol monobenzyl ether. Examples include triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol, tetraethylene glycol monomethyl, tetraethylene glycol monoethyl, tetraethylene glycol mono-n-butyl, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol monophenyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, and tripropylene glycol mono-n-butyl ether. These may be used individually or in combination of two or more.

[0057] When a conductive paste is heat-treated, it is preferable to use tripropylene glycol mono-n-butyl ether or ethylene glycol mono-n-butyl ether as the glycol monomer, from the viewpoint of ensuring that the metal powders contained therein aggregate and form a good metal particle linkage structure.

[0058] As the acrylic monomer used as a reactive diluent, monofunctional acrylic monomers having only one (meth)acrylic group, or polyfunctional acrylic monomers having two or more (meth)acrylic groups can be used.

[0059] Examples of monofunctional acrylic monomers include 2-phenoxyethyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethylhexyldiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate. (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, dimethylaminoethyl (meth)acrylate quaternary, glycidyl (meth)acrylate, neopentyl glycol (meth)acrylate benzoate, 1,Examples include 4-cyclohexanedimethanol mono(meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-(meth)acryloyloxyethyl acid phosphate, and 2-(meth)acryloyloxyethyl acid phosphate. As monofunctional acrylic monomers, one or more of the above specific examples can be used in combination.

[0060] As the monofunctional acrylic monomer, it is preferable to use 2-phenoxyethyl methacrylate from the above specific examples. This improves the adhesion of the resulting conductive paste to the substrate.

[0061] Specifically, polyfunctional acrylic monomers 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'-isopropylidene diphenol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, and 1,6-bis((meth)acryloyloxy)-2,2,3,3,4,4,5,5-octa Examples include fluorohexane, 1,4-bis((meth)acryloyloxy)butane, 1,6-bis((meth)acryloyloxy)hexane, triethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, N,N'-di(meth)acryloylethylenediamine, N,N'-(1,2-dihydroxyethylene)bis(meth)acrylamide, or 1,4-bis((meth)acryloyl)piperazine.

[0062] As the epoxy monomer used as a reactive diluent, monoepoxy monomers having only one epoxy group, or polyfunctional epoxy monomers having two or more epoxy groups can be used.

[0063] Examples of monoepoxy monomers include t-butylphenyl glycidyl ether, m,p-cresyl glycidyl ether, phenyl glycidyl ether, and cresyl glycidyl ether. One or more of the above specific examples can be used as monoepoxy monomers.

[0064] Examples of polyfunctional epoxy monomers 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 psidilohexanediethanol, or their derivatives; bifunctional compounds obtained by epoxidizing aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, and decanediol, or their derivatives; trifunctional compounds having a trihydroxyphenylmethane skeleton or an aminophenol skeleton; and polyfunctional compounds obtained by epoxidizing phenol novolac resin, cresol novolac resin, phenol aralkyl resin, biphenyl aralkyl resin, naphthol aralkyl resin, etc. One or more of the above specific examples can be used as polyfunctional epoxy monomers.

[0065] Examples of maleimide monomers used as reactive diluents include polytetramethylene ether glycol-di(2-maleimide acetate).

[0066] In this embodiment, the content of the reactive diluent in the conductive paste is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more, relative to the total conductive paste. This more effectively improves the application workability of the conductive paste and the flatness of the resulting adhesive layer. On the other hand, the content of the reactive diluent in the conductive paste is preferably 20% by mass or less, and more preferably 15% by mass or less, relative to the total conductive paste. This suppresses dripping during application and improves application workability. It also improves the curability of the conductive paste.

[0067] (Hardening agent) The conductive paste of this embodiment may contain a curing agent. This can improve the curability of the conductive paste. As the curing agent, one or more selected from aliphatic amines, aromatic amines, dicyandiamides, dihydrazide compounds, acid anhydrides, and phenol compounds can be used. Among these, it is particularly preferable to include at least one of dicyandiamides and phenol compounds from the viewpoint of improving manufacturing stability.

[0068] Examples of dihydrazide compounds used as curing agents include carboxylic acid dihydrazides such as adipic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, and p-oxybenzoic acid dihydrazide. Examples of acid anhydrides used as curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, dodecenyl succinic anhydride, reaction products of maleic anhydride and polybutadiene, and copolymers of maleic anhydride and styrene.

[0069] The phenolic compounds used as curing agents are compounds having two or more phenolic hydroxyl groups in one molecule. More preferably, the number of phenolic hydroxyl groups in one molecule is 2 to 5, and particularly preferably, the number of phenolic hydroxyl groups in one molecule is 2 or 3. This allows for more effective improvement of the application workability of the conductive paste, and also enables the formation of a cross-linked structure during curing, resulting in superior cured product properties of the conductive paste. The above-mentioned phenolic compounds may include, for example, phenolic resins having a biphenyl skeleton, such as bisphenol F, bisphenol A, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetramethylbisphenol S, dihydroxydiphenyl ether, dihydroxybenzophenone, tetramethylbiphenol, ethylidenebisphenol, methylethylidenebis(methylphenol), cyclohexylidenebisphenol, and biphenol, and their derivatives; trifunctional phenols such as tri(hydroxyphenyl)methane and tri(hydroxyphenyl)ethane, and their derivatives; and compounds obtained by reacting phenols such as phenol novolac and cresol novolac with formaldehyde, where the main compound is dinuclear or trinuclear, and their derivatives. Among these, it is more preferable to include phenolic resins having a biphenyl skeleton, and it is particularly preferable to include bisphenol F.

[0070] In this embodiment, the content of the curing agent in the conductive paste is preferably 0.10% by mass or more, more preferably 0.12% by mass or more, and even more preferably 0.14% by mass or more, relative to the total conductive paste. This makes it possible to more effectively improve the curability of the conductive paste. On the other hand, the content of the curing agent in the conductive paste is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less, relative to the total conductive paste. This makes it possible to improve the low thermal expansion and moisture resistance of the adhesive layer formed using the conductive paste.

[0071] (Inorganic filler) In this embodiment, it is preferable that the conductive paste contains an inorganic filler different from conductive metal powder at a content of 30% by mass or less relative to the entire conductive paste. Here, the inorganic filler different from conductive metal powder refers to a material different from the conductive metal powder mentioned above, and examples of such materials 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. Furthermore, the content of inorganic fillers other than conductive metal powder is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably no inorganic fillers other than conductive metal powder are included in the conductive paste. This improves the balance of various properties of the conductive paste, such as conductivity and adhesion to the substrate, and effectively suppresses the precipitation of solid components and separation of liquid components in the conductive paste when the conductive paste is stored for a long period of time. Here, "no inorganic fillers other than conductive metal powder" means substantially none, and refers to a case where the content of inorganic fillers other than conductive metal powder relative to the entire conductive paste is 0.1% by mass or less.

[0072] (Other ingredients) The conductive paste of this embodiment may, in addition to the components described above, optionally contain various further components commonly used in the art. These further components may include, but are not limited to, silane coupling agents, curing accelerators, radical polymerization initiators, and stress reducers, and can be selected according to the desired performance.

[0073] Silane coupling agents are used to improve the adhesion between conductive paste and substrate. Examples of silane coupling agents include vinylsilanes such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxysilanes such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; styrylsilanes such as p-styryltrimethoxysilane; methacrylsilanes such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; and methacrylates such as 3-(trimethoxysilyl)propyl and 3-acryloxypropyltrimethoxysilane. Examples include krillsilanes; 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; sulfidosilanes such as bis(trimethoxysilylpropyl)monosulfide and bis(triethoxysilylpropyl)monosulfide; mercaptosilanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; and isocyanate silanes such as 3-isocyanatetopropyltriethoxysilane.

[0074] Curing accelerators are used to accelerate the reaction between the epoxy resin used as a binder resin, or the epoxy monomer used as a reactive diluent when a reactive diluent is used, and the curing agent. Examples of curing accelerators include phosphorus-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; imidazole compounds such as 2-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 2-phenyl-4,5-dihydroxymethylimidazole; amidines and tertiary amines such as dicyandiamide, 1,8-diazabicyclo[5.4.0]undecene-7, and benzyldimethylamine; and nitrogen-containing compounds such as quaternary ammonium salts of the above amidines or tertiary amines.

[0075] Specifically, azo compounds, peroxides, and the like can be used as radical polymerization initiators.

[0076] Examples of low-stress agents that can be used include silicone compounds such as silicone oil and silicone rubber; polybutadiene compounds such as polybutadiene maleic anhydride adducts; acrylic acid polymers such as acrylonitrile butadiene copolymers; and allyl ester resins.

[0077] When the conductive paste of this embodiment contains a low-stress agent, the content of the low-stress agent in the conductive paste is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, relative to the total conductive paste. This can more effectively improve the curability of the conductive paste. On the other hand, the content of the low-stress agent in the conductive paste is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, and even more preferably 4% by mass or less, relative to the total conductive paste. This can improve the low thermal expansion and moisture resistance of the adhesive layer formed using the conductive paste.

[0078] (Preparation of conductive paste) The method for preparing the conductive paste is not particularly limited, but for example, after pre-mixing the above-mentioned components, a paste-like composition can be obtained by kneading using a three-roll mill 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.

[0079] The viscosity of the conductive paste of this embodiment can be adjusted 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, and the amounts of these components used. Furthermore, the conductive paste of this embodiment can suppress the separation and precipitation of components during long-term storage, thereby reducing viscosity changes when the conductive paste is stored for a long period of time.

[0080] The conductive paste of this embodiment measured the viscosity at 0.5 rpm η using a BF type viscometer at a temperature of 25°C and a shear rate of 0.5 rpm. 0.5 The lower limit of the viscosity is preferably 35 Pa·s or higher, more preferably 38 Pa·s or higher, and particularly preferably 40 Pa·s or higher, both immediately after fabrication and after 24 hours of standing. This prevents the conductive paste from spreading too much on the substrate when bonded, and prevents short circuits with other chip systems. 0.5 The upper limit is preferably 100 Pa·s or less, more preferably 90 Pa·s or less, even more preferably 80 Pa·s or less, even more preferably 70 Pa·s or less, even more preferably 65 Pa·s or less, and even more preferably 60 Pa·s or less. This improves workability.

[0081] The conductive paste of this embodiment measured its viscosity at 5.0 rpm η using a BF-type viscometer at a temperature of 25°C and a shear rate of 5.0 rpm. 5.0The lower limit of the viscosity is preferably 5 Pa·s or higher, more preferably 8 Pa·s or higher, and particularly preferably 10 Pa·s or higher, both immediately after fabrication and after 24 hours of standing. This prevents the conductive paste from spreading too much on the substrate when bonded, and prevents short circuits with other chip systems. 5.0 The upper limit is preferably 30 Pa·s or less, more preferably 25 Pa·s or less, and particularly preferably 20 Pa·s or less. This improves workability.

[0082] The conductive paste of this embodiment was measured using a BF-type viscometer at a temperature of 25°C and a shear rate of 50.0 rpm, and its viscosity at 50.0 rpm was η 50.0 The lower limit of the viscosity is preferably 1 Pa·s or more, more preferably 1.5 Pa·s or more, and particularly preferably 2 Pa·s or more, both immediately after fabrication and after 24 hours of standing. This prevents the conductive paste from spreading too much on the substrate when bonded, and prevents short circuits with other chips. Also, the viscosity η at 50.0 rpm is 50.0 The upper limit is preferably 15 Pa·s or less, more preferably 10 Pa·s or less, and particularly preferably 7 Pa·s or less. This improves workability.

[0083] The conductive paste of this embodiment is represented by the following formula (1) η 0.5 and the above η 5.0 The lower limit of the viscosity ratio Ti1 is preferably 3 or higher, more preferably 3.5 or higher, and even more preferably 4 or higher, both immediately after production and after 24 hours of standing. Ti1=η 0.5 / η 5.0 (1) By ensuring that Ti1 is above the lower limit mentioned above, it is possible to prevent the conductive paste from spreading too much on the substrate when it is bonded, thereby preventing short circuits with other chips. Furthermore, the upper limit of Ti1 is preferably 7 or less, more preferably 6.5 or less, and even more preferably 6 or less, both immediately after manufacturing and after 24 hours of standing. Keeping Ti1 below the upper limit makes it possible to improve the workability when bonding the conductive paste to the substrate.

[0084] The conductive paste of this embodiment is represented by the following formula (2) η 0.5 and the above η 50.0 The lower limit of the viscosity ratio Ti2 is preferably 6 or higher, more preferably 6.5 or higher, and even more preferably 7 or higher, both immediately after production and after 24 hours of standing. Ti2 = η 0.5 / η 50.0 (2) By ensuring that Ti2 is above the lower limit mentioned above, it is possible to prevent the conductive paste from spreading too much on the substrate when it is bonded, thereby preventing short circuits with other chips. Furthermore, the upper limit of Ti2 is preferably 20 or less, more preferably 17 or less, even more preferably 14 or less, even more preferably 13.5 or less, and even more preferably 13 or less, both immediately after production and after 24 hours of standing. Keeping Ti2 below the above upper limit makes it possible to improve the workability when bonding the conductive paste to the substrate.

[0085] (Application) The applications of the conductive paste of this embodiment will now be described. The conductive paste according to this embodiment is used, for example, to bond a substrate to a semiconductor element. Examples of semiconductor elements include semiconductor packages and LEDs. The conductive paste according to this embodiment offers improved connection reliability and appearance compared to conventional conductive pastes. This makes it suitable for applications involving the mounting of semiconductor elements with high heat generation onto a substrate. In this embodiment, LED refers to a Light Emitting Diode.

[0086] Examples of semiconductor devices using LEDs include bullet-shaped LEDs, surface-mount (SMD) LEDs, COB (Chip On Board) LEDs, and power LEDs.

[0087] 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, and Fan-Out type eWLB.

[0088] An example of a semiconductor device using the conductive paste according to this embodiment will be described below. Figure 1 is a cross-sectional view showing an example of a semiconductor device according to this embodiment. The semiconductor device 100 according to this embodiment comprises a substrate 30 and a semiconductor element 20 mounted on the substrate 30 via an adhesive layer 10 which is a cured conductive paste. 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.

[0089] Here, the lower limit of the thickness of the adhesive layer 10 is preferably, for example, 5 μm or more, and more preferably 10 μm or more. This improves the heat capacity of the cured conductive paste and enhances heat dissipation. The upper limit of the thickness of the adhesive layer 10 is preferably, for example, 50 μm or less, and more preferably 30 μm or less. This allows the conductive paste to exhibit suitable adhesion while improving heat dissipation.

[0090] 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.

[0091] The substrate 30 may be an organic substrate or a ceramic substrate. The organic substrate is preferably made of, for example, epoxy resin, cyanate resin, maleimide resin, etc. The surface of the substrate 30 may be coated with a metal such as silver or gold. This improves the adhesion between the adhesive layer 10 and the substrate 30.

[0092] Figure 2 is a modified example of Figure 1 and is a cross-sectional view showing an example of the semiconductor device 100 according to this embodiment. In the semiconductor device 100 according to this modified example, the substrate 30 is, for example, an interposer. On the substrate 30 which is an interposer, a plurality of solder balls 52 are formed on the other side opposite to the side on which the semiconductor element 20 is mounted. In this case, the semiconductor device 100 is connected to another wiring board via the solder balls 52.

[0093] (Method of manufacturing semiconductor devices) An example of a method for manufacturing a semiconductor device according to this embodiment will be described. First, a conductive paste is applied to the substrate 30, and then the semiconductor element 20 is placed on top of it. In other words, the substrate 30, conductive paste, and semiconductor element 20 are layered in this order. The method for applying the conductive paste is not limited, but specifically, dispensing, printing, inkjet methods, etc., can be used.

[0094] Next, the conductive paste is cured by pre-curing and then post-curing. Through heat treatment such as pre-curing and post-curing, the silver particles in the conductive paste aggregate, and a heat-conducting layer is formed in the adhesive layer 10, where the interfaces between multiple silver particles disappear. As a result, the substrate 30 and the semiconductor element 20 are bonded together via the adhesive layer 10. Next, the semiconductor element 20 and the substrate 30 are electrically connected using bonding wires 40. Then, the semiconductor element 20 is sealed with sealing resin 50. This allows for the manufacture of a semiconductor device.

[0095] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. [Examples]

[0096] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0097] The components used in the examples and comparative examples are shown below. (Alkylacetalized polyvinyl alcohol) -Alkylacetalized polyvinyl alcohol 1 (A1): Compound represented by the following chemical formula (IV) (l: 33, m: 3, n: 64, molecular weight: 110,000) - Alkyl acetalized polyvinyl alcohol 2(A2): Esrec BH-3 (manufactured by Sekisui Chemical Co., Ltd., used as a 10% butyl carbitol solution)

[0098] [ka]

[0099] (Polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate) -Polyoxyethylene alkyl ether carboxylic acid 1(B1): Sodium polyoxyethylene alkyl ether carboxylic acid (manufactured by Sanyo Chemical Industries, Ltd., Viewlight LCA-25NH) -Polyoxyethylene alkyl ether carboxylic acid 2(B2): Polyoxyethylene alkyl ether carboxylic acid (manufactured by Kao Corporation, Kaocera 8110) -Oleyl sarcosinate 1(B3): Oleyl sarcosinate (manufactured by NOF Corporation, Oleyl sarcosinate 221P)

[0100] (Binder resin) - Binder resin 1: Bisphenol F type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., RE-403S, epoxy equivalent 165 g / eq) (Stress-reducing agent) - Low-stress agent 1: Acrylic acid polymer (manufactured by Toagosei Co., Ltd., UG-4035) (Diluent) -Diluent 1: Butyl carbitol (manufactured by Sankyo Chemical Co., Ltd., contains butyl carbitol, which is the solvent for alkyl acetalized polyvinyl alcohol 2) (Hardening agent) - Hardener 1: Bisphenol F (DIC Corporation, DIC-BPF) (Silane coupling agent) -Silane coupling agent 1: Sulfide silane (manufactured by Osaka Soda Co., Ltd., Cabras-4) (Conductive metal powder) -Silver powder 1: Flake-type silver powder (average particle size: 0.7 μm, manufactured by Ames, SF-65S)

[0101] (Examples 1-10, Comparative Examples 1-10) <Preparation of conductive paste> First, a varnish-like mixture was prepared by kneading the components listed in Tables 1 and 2 under "Varnish" at room temperature using a three-roll mill. Next, silver powder was mixed into the obtained varnish-like mixture in the amounts listed under "Paste" in Tables 1 and 2, and kneaded at room temperature using a three-roll mill to obtain the paste-like compositions (conductive pastes) for each example and comparative example.

[0102] The conductive pastes of each example and each comparative example were evaluated for the following items.

[0103] <Adhesion Strength> The conductive paste obtained above 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 temperature was raised from 25°C to 150°C over 30 minutes, and then heat-treated at 150°C for 2 hours to obtain a cured body, which was used as a test specimen. The die shear strength between the silver lead frame and the silicon chip at 260°C was measured for this test specimen. The results are shown in Tables 1 and 2.

[0104] <Viscosity> For each example and comparative example of conductive paste, the viscosity at room temperature (25°C) was measured using a BF-type viscometer (BROOKFIELD ENGINEERING, model DV3T) immediately after preparation and after 24 hours of standing. The measurement procedure was as follows: First, viscosity was measured for 6 minutes at a shear rate of 0.5 rpm. Next, the shear rate was increased to 5.0 rpm, and viscosity was measured for 2 minutes at a shear rate of 5.0 rpm. Similarly, the shear rate was increased to 50.0 rpm, and viscosity was measured for 1 minute at a shear rate of 50.0 rpm. The viscosity at each shear rate was expressed as η. 0.5 η 5.0 η 50.0 The unit of viscosity is Pa·s. Furthermore, using the measured viscosity, the viscosity ratios Ti1 and Ti2 were calculated according to the following equations (1) and (2). Ti1=η 0.5 / η 5.0 (1) Ti2 = η 0.5 / η 50.0 (2)

[0105] <Presence or absence of bleeding after applying conductive paste> The conductive pastes of each example and comparative example were applied to silver lead frames activated by argon treatment (200W, 180sec), and the wetting spread of the paste at the moment of application was observed using a metallurgical microscope (U-PMTVC, manufactured by OLYNPUS). Immediately after application, the paste spreads and forms a circular shape, which, when observed under a metallurgical microscope, appears as a circular object that does not transmit light. The diameter of this circular object that does not transmit light was defined as A0. 24 hours after application, the paste, which has spread further than immediately after application, appears as a circular object that partially transmits light under a metallurgical microscope. The diameter of this partially transmittance circular object was defined as A1. In addition, a paste was applied separately from the one used to measure A1, and A0 was measured again. Then, the temperature was raised from 25°C to 150°C over 30 minutes, and a hardened body was obtained by heat treatment at 150°C for 2 hours. After the hardened body was left to stand for 24 hours, the paste, which had spread further from immediately after application, appeared as semi-transparent circular objects under a metallurgical microscope. The diameter of these semi-transparent circular objects was defined as A2. Here, the greater A1 or A2 is than A0, the more paste wetting (bleeding) occurs. The results are shown in Tables 1 and 2 as follows: "○" if A1 / A0 or A2 / A0 is 1, "△" if A1 / A0 or A2 / A0 is greater than 1 and less than or equal to 1.1, and "×" if A1 / A0 or A2 / A0 is greater than 1.1.

[0106] <Separation and precipitation> The conductive pastes of each example and comparative example were left to stand at room temperature. The pastes were observed 12 hours and 24 hours after standing. "○" indicated that no separation or precipitation occurred, "precipitation" indicated that precipitation of solid components occurred, and "separation" indicated that separation of liquid components occurred.

[0107] [Table 1]

[0108] [Table 2]

[0109] The conductive pastes used in the examples exhibited little to no bleeding, and no separation or precipitation of components occurred even after long-term storage. Furthermore, when used to bond the lead frame to the silicon tip, they showed excellent adhesive strength. [Explanation of Symbols]

[0110] 100 Semiconductor Equipment 10 Adhesive layer 20 Semiconductor elements 30 Base material 32 die pads 34 Outer lead 40 Bonding Wires 50 Sealing resin 52 Solder ball

Claims

1. Binder resin and Conductive metal powder and Alkyl acetalized polyvinyl alcohol and Diluent and A conductive paste for bonding electronic components, including A conductive paste in which the content of alkylacetalized polyvinyl alcohol is 5 ppm or more and 200 ppm or less relative to the entire conductive paste.

2. Binder resin and Conductive metal powder and Polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid, Diluent and A conductive paste for bonding electronic components, including A conductive paste in which the content of the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid is 1,000 ppm or more and 15,000 ppm or less relative to the entire conductive paste.

3. The conductive paste according to claim 1 or 2, wherein the binder resin comprises one or more selected from cyanate resin, epoxy resin, (meth)acrylic resin, resin having two or more radically polymerizable carbon-carbon double bonds in one molecule, and maleimide resin.

4. The conductive paste according to claim 1 or 2, wherein the binder resin comprises an epoxy resin having two or more glycidyl groups in one molecule.

5. A conductive paste according to claim 1 or 2, further comprising a curing agent.

6. The conductive paste according to claim 5, wherein the curing agent comprises one or more selected from aliphatic amines, aromatic amines, dicyandiamides, dihydrazide compounds, acid anhydrides, and phenolic compounds.

7. The conductive paste according to claim 1 or 2, wherein the conductive metal powder comprises at least one selected from silver powder, gold powder, platinum powder, and alloys thereof.

8. The conductive paste according to claim 1 or 2, wherein the conductive metal powder is present in an amount of 30% by mass or more and 90% by mass or less relative to the entire conductive paste.

9. The conductive paste does not contain an inorganic filler different from the conductive metal powder, Alternatively, the conductive paste further contains an inorganic filler different from the conductive metal powder, wherein the content of the inorganic filler is 30% by mass or less of the total conductive paste. The conductive paste according to claim 1 or 2.

10. The viscosity η at 0.5 rpm of the conductive paste was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 0.5 rpm. ０．５ A conductive paste according to claim 1 or 2, wherein the pressure is 35 Pa·s or more and 100 Pa·s or less.

11. The viscosity η at 5.0 rpm of the conductive paste was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 5.0 rpm. ５ The conductive paste according to claim 1 or 2, wherein the pressure is 5 Pa·s or more and 30 Pa·s or less.

12. The viscosity η at 50.0 rpm of the conductive paste was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 50.0 rpm. ５０．０ A conductive paste according to claim 1 or 2, wherein the pressure is 1 Pa·s or more and 15 Pa·s or less.

13. The viscosity η at 0.5 rpm of the conductive paste was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 0.5 rpm. ０．５ The viscosity at 5.0 rpm (η) was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 5.0 rpm. ５．０ The viscosity ratio Ti, expressed by the following equation (1), is given by the following formula: １ A conductive paste according to claim 1 or 2, wherein the ratio is 3 or more and 7 or less. Three １ =the ０．５ / or ５．０ (1)

14. The viscosity η at 0.5 rpm of the conductive paste was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 0.5 rpm. ０．５ The viscosity at 50.0 rpm (η) was measured using a BF-type viscometer while stirring at a temperature of 25°C and a shear rate of 50.0 rpm. ５０．０ The viscosity ratio Ti, expressed by the following equation (2), is obtained using the above. ２ A conductive paste according to claim 1 or 2, wherein the ratio is 6 or more and 20 or less. Three ２ =the ０．５ / or ５０．０ (2)

15. Substrate and The system comprises a semiconductor element mounted on the substrate via an adhesive layer, The adhesive layer is made of a cured product of the conductive paste described in claim 1 or 2, wherein the semiconductor device is a semiconductor device.

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