JP2023007485A - Conductive paste and semiconductor device - Google Patents

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

The present invention relates to conductive pastes and semiconductor devices. More specifically, the present invention relates to a conductive paste used as a semiconductor die attach paste used for bonding and fixing a semiconductor element onto a support member such as a metal frame, and a conductive paste manufactured using the conductive paste. related to semiconductor devices.

2. Description of the Related Art A semiconductor device in which a semiconductor element is mounted on a lead frame and molded with resin is widely used. For example, semiconductor elements such as ICs and LSIs are mounted on a metal piece such as a lead frame, and fixed using a conductive paste called die attach paste. are connected by thin wires (bonding wires), and then these are housed in a package to form a semiconductor product. Optical semiconductor devices using light-emitting diodes (LEDs) and the like, which have been put into practical use for various displays, are transparent after bonding the optical semiconductor element to a predetermined portion on a lead frame or resin substrate with a conductive paste or the like. It is manufactured by sealing with a sealing resin or the like (for example, Patent Document 1).

In the manufacture of semiconductor devices, die attach pastes used to bond semiconductor elements and lead frames and to improve electrical and thermal conductivity between them generally consist of a resin and an electrically conductive filler. It consists of particles with high modulus. If the die attach paste has low thixotropic properties, a phenomenon called bleed-out occurs, in which the resin component contained in the paste oozes out onto the substrate depending on the surface condition of the lead frame. In order to solve this problem, a technique of blending additives has been proposed in order to sufficiently develop thixotropic properties. For example, Patent Literature 2 proposes a technique of adding silicone rubber fine powder as an additive to suppress resin bleeding out.

Japanese Patent Application Laid-Open No. 2003-273407 JP-A-5-335353

As described above, the die attach paste for semiconductors is generally composed of resin and filler. Such a die attach paste needs to be made into a paste by adding a diluent to reduce its viscosity, in other words, in order to ensure good coating workability. However, the inventors of the present invention have found that the organic solvent used as the diluent has a low viscosity, so that the solvent component often spreads due to capillary action caused by fine irregularities on the surface of the lead frame to be joined. rice field. In addition, it was found that the solvent leaked to the bottom surface of the lead frame during the process by bleeding into an unexpected part in the lead frame, and the contamination caused wire bond failure. In addition, the inventors have found that when such a die attach paste is stored for a long period of time, separation and precipitation of components occur in the paste.

The present invention has been made in view of such circumstances, and even when a diluent is added to reduce the viscosity, it suppresses the bleeding out of the diluent, prevents dripping and bleeding, and It is an object of the present invention to provide a conductive paste that can be used as a die attach paste having excellent physical and electrical connection reliability while suppressing separation and precipitation of components in the paste.

Even if the conductive paste contains a diluent, the present inventors found that by using a specific additive, separation and precipitation of components in the paste during storage and bleeding of the diluent when the paste is placed. The inventors have found that out can be suppressed, and have completed the present invention.

According to the present invention, the following conductive paste and semiconductor device are provided.

[1]
a binder resin;
a conductive metal powder;
an alkyl acetalized polyvinyl alcohol;
a diluent;
A conductive paste for bonding electronic components containing
A conductive paste, wherein the content of the alkyl acetalized polyvinyl alcohol is 5 ppm or more and 200 ppm or less with respect to the entire conductive paste.
[2]
a binder resin;
a conductive metal powder;
polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate; and
a diluent;
A conductive paste for bonding electronic components containing
A conductive paste, wherein the content of the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosic acid is 1,000 ppm or more and 15,000 ppm or less based on the entire conductive paste.
[3]
The binder resin is one or more selected from cyanate resins, epoxy resins, (meth)acrylic resins, resins having two or more radically polymerizable carbon-carbon double bonds in one molecule, and maleimide resins. The conductive paste according to [1] or [2] above.
[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]
The conductive paste according to any one of [1] to [4] above, further comprising a curing agent.
[6]
The conductive paste according to [5] above, wherein the curing agent contains 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 contains at least one selected from silver powder, gold powder, platinum powder, and alloys thereof.
[8]
Any one of the above [1] to [7], wherein the conductive metal powder is 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 with respect to the entire conductive paste. The conductive paste described in .
[9]
whether the conductive paste does not contain an inorganic filler different from the conductive metal powder;
Or from the above [1], 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 with respect to the entire conductive paste. The conductive paste according to any one of [8].
[10]
The conductive paste is measured using a BF type viscometer while stirring at a temperature of 25° C. and a shear rate of _0.5 rpm. , preferably 35 Pa·s or more and 70 Pa·s or less, the conductive paste according to any one of the above [1] to [9].
[11]
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. , the conductive paste according to any one of the above [1] to [10].
[12]
The conductive paste is measured using a BF type viscometer while stirring at a temperature of 25 ° C. and a shear rate of _50.0 rpm. The conductive paste according to any one of [1] to [11] above.
[13]
In the conductive paste, using a BF type viscometer, temperature: 25 ° C., shear rate: 0.5 rpm viscosity η _0.5 when measured while stirring at 0.5 rpm, and using a BF type viscometer , temperature: 25 ° C., shear rate: 5.0 rpm viscosity η _5.0 when measured while stirring at 5.0 rpm, and the viscosity ratio Ti ₁ represented by the following formula (1) is 3 or more 7 The conductive paste according to any one of [1] to [12] above, which is:
Ti1= _η0.5 / _η5.0 ( ₁ )
[14]
In the conductive paste, using a BF type viscometer, temperature: 25 ° C., shear rate: 0.5 rpm viscosity η _0.5 when measured while stirring at 0.5 rpm, and using a BF type viscometer , temperature: 25 ° C., shear rate: 50.0 rpm viscosity η _50.0 when measured while stirring at 50.0 rpm, and the viscosity ratio Ti ₂ represented by the following formula (2) is 6 or more and 20 The conductive paste according to any one of [1] to [13] above, preferably 6 or more and 14 or less.
Ti2= _η0.5 / _η50.0 ( ₂ )
[15]
a substrate;
A semiconductor element mounted on the base material via an adhesive layer,
A semiconductor device, wherein the adhesive layer is made of a cured conductive paste according to any one of [1] to [14].

According to the present invention, separation/precipitation of components in the paste during storage and bleeding out of the diluent when the paste is placed are suppressed, making it suitable as a die attach paste with excellent physical and electrical connection reliability. Provided is a conductive paste that can be used for

It is a sectional view showing an example of an electronic device concerning this embodiment. It is a sectional view showing an example of an electronic device concerning this embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
The notation "(meth)acryl" used herein represents a concept that includes both acryl and methacryl. The same applies to similar expressions such as "(meth)acrylate" and "(meth)acrylate".

(Conductive paste)
The conductive paste of this embodiment is a die attach paste used for forming a die attach layer for bonding an electronic component such as a semiconductor element to a base material such as a lead frame or a wiring board. The conductive paste of the present embodiment contains a binder resin, a conductive metal powder, an alkylacetalized polyvinyl alcohol, and a diluent, and the content of the alkylacetalized polyvinyl alcohol is is 5 ppm or more and 200 ppm or less. In the conductive paste of the present embodiment, the binder resin contained therein is hardened by heat treatment, whereby the conductive metal powders are agglomerated to form a metal powder connection structure. As a result, the die attach layer obtained by heating the conductive paste exhibits electrical conductivity or thermal conductivity, and adhesion to electronic components and substrates.

Since the conductive paste of the present embodiment contains alkyl acetalized polyvinyl alcohol, even if the conductive paste contains a diluent as in the present embodiment, the components in the paste are separated and precipitated during storage. and bleed-out of the diluent when the paste is placed. Therefore, when this conductive paste is placed on the surface of a lead frame in the manufacture of an electronic device, the diluent does not wet and spread. Therefore, the connection between the semiconductor element and the substrate is excellent in physical and electrical connection reliability.
It should be noted that the term “during storage” in the present embodiment refers not only to long-term storage, but also to a period of time during which the conductive paste of the present embodiment is prepared in a manufacturing apparatus and is kept quiet for a long period of time, such as until the actual start of manufacturing. It also includes the state where it is placed.

Here, the lower limit of the content of the alkyl acetalized polyvinyl alcohol contained in the conductive paste of the present embodiment is 5 ppm or more, preferably 10 ppm or more, more preferably 15 ppm with respect to the entire conductive paste. or more, more preferably 20 ppm or more. When the content of the alkyl acetalized polyvinyl alcohol is at least the above lower limit, the separation and precipitation of components can be suppressed while effectively suppressing the occurrence of bleeding.
In addition, the upper limit of the content of the alkyl acetalized polyvinyl alcohol contained in the conductive paste of the present embodiment is 200 ppm or less, preferably 195 ppm or less, more preferably 190 ppm or less with respect to the entire conductive paste. and more preferably 185 ppm or less. When the content of the alkyl acetalized polyvinyl alcohol is equal to or less than the above upper limit value, the viscosity of the conductive paste can be improved.

Further, in one embodiment of the present embodiment, the conductive paste is an electronic component adhesive paste containing a binder resin, conductive metal powder, polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate, and a diluent. , wherein the content of the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosic acid is 1,000 ppm or more and 15,000 ppm or less with respect to the entire conductive paste.

Even if the conductive paste of the present embodiment contains polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate, or if the conductive paste contains a diluent as in the present embodiment, Separation/precipitation of components in the paste and bleeding out of the diluent when the paste is placed are suppressed. Therefore, when this conductive paste is placed on the surface of a lead frame in the manufacture of an electronic device, the diluent does not wet and spread. Therefore, the connection between the semiconductor element and the substrate is excellent in physical and electrical connection reliability.

Here, the lower limit of the content of polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosic acid contained in the conductive paste of the present embodiment is 1000 ppm or more with respect to the entire conductive paste, preferably 1050 ppm or more. , more preferably 1100 ppm or more, and still more preferably 1150 ppm or more. When the content of the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate is at least the above lower limit, it is possible to effectively suppress the occurrence of bleeding and suppress the separation and precipitation of the components.
In addition, the upper limit of the content of polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate contained in the conductive paste of the present embodiment is 15000 ppm or less with respect to the entire conductive paste, preferably 14950 ppm or less. more preferably 14,900 ppm or less, and still more preferably 14,850 ppm or less. When the content of polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid is equal to or less than the above upper limit, the viscosity of the conductive paste can be improved.

Each component used in the conductive paste of this embodiment will be described in detail below.

(binder resin)
As the binder resin used in the conductive paste of the present embodiment, a thermosetting resin is used. One or more selected from resins having two or more heavy bonds in one molecule and maleimide resins can be used. Among these, from the viewpoint of improving the adhesiveness of the conductive paste, it is preferable to contain an epoxy resin, and it is preferable to contain an epoxy resin having two or more glycidyl groups in one molecule.

As epoxy resins used as thermosetting resins, monomers, oligomers, and polymers in general having two or more glycidyl groups in one molecule can be used, and their molecular weights and molecular structures are not particularly limited. Epoxy resins used in the present embodiment include, for example, biphenyl type epoxy resins; bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, tetramethylbisphenol F type epoxy resin; stilbene type epoxy resin; phenol novolac type epoxy resins, novolak type epoxy resins such as cresol novolak type epoxy resins; triphenolmethane type epoxy resins, multifunctional epoxy resins such as alkyl-modified triphenolmethane type epoxy resins; phenol aralkyl type epoxy resins having a phenylene skeleton, biphenylene skeletons Aralkyl-type epoxy resins such as phenol aralkyl-type epoxy resins; dihydroxynaphthalene-type epoxy resins, naphthol-type epoxy resins such as epoxy resins obtained by glycidyl-etherifying a dimer of dihydroxynaphthalene; triglycidyl isocyanurate, monoallyl di triazine nucleus-containing epoxy resins such as glycidyl isocyanurate; and bridged cyclic hydrocarbon compound-modified phenolic epoxy resins such as dicyclopentadiene-modified phenolic epoxy resins. 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, biphenol or derivatives thereof, hydrogenated bisphenol A, hydrogenated bisphenol F, Diols having an alicyclic structure such as hydrogenated biphenol, cyclohexanediol, cyclohexanedimethanol, and cyclohexanediethanol, or their derivatives, aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, and decanediol, or their derivatives, etc. can also be used. The epoxy resin as the thermosetting resin can contain one or more selected from those exemplified above.

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

The cyanate resin used as the 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-cyanatophenyl)propane, 2,2-bis(3,5-dibromo-4-cyanatophenyl)propane, bis(4-cyanatophenyl)ether, bis(4-cyanatophenyl)thioether, bis(4-cyanatophenyl)sulfone, Trimerizing the cyanate groups of tris(4-cyanatophenyl)phosphite, tris(4-cyanatophenyl)phosphate, cyanates obtained by reacting novolac resins with cyanogen halides, and these polyfunctional cyanate resins It can contain one or more selected from prepolymers having a triazine ring formed by The above prepolymer is obtained by polymerizing the above polyfunctional cyanate resin monomer using, for example, an acid such as mineral acid or Lewis acid, a base such as sodium alcoholate or tertiary amines, or a salt such as sodium carbonate as a catalyst. be able to.

The (meth)acrylic resin used as the thermosetting resin is not particularly limited, but for example 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, ethylene glycol di(meth)acrylate, diethylene glycol mono(meth)acrylate, methoxyethyl (meth)acrylate, glycidyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth) (Meth)acrylic resins such as acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate and isoboronol (meth)acrylate, and at least one compound selected from the group consisting of these as a main component (50 % by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more) (meth)acrylic resin obtained by polymerization.

As a resin having two or more radically polymerizable carbon-carbon double bonds in one molecule used as a thermosetting resin, for example, a radically polymerizable (meth)acryloyl group having two or more (meth)acryloyl groups in the molecule ) acrylic resins can be used. In the present embodiment, the acrylic resin may contain a compound having a (meth)acrylic group, which is polyether, polyester, polycarbonate, or poly(meth)acrylate having a molecular weight of 500 to 10,000. When using a resin having two or more radically polymerizable carbon-carbon double bonds in one molecule as the thermosetting resin, the conductive paste should contain a polymerization initiator such as a thermal radical polymerization initiator. can be done.

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

Thermosetting resins also include resins having a biphenyl skeleton. By containing an epoxy resin having a biphenyl skeleton (biphenyl-type epoxy resin), the metal adhesion of the conductive paste can be improved.

The structure of the epoxy resin having a biphenyl skeleton is not particularly limited as long as it has a biphenyl skeleton in its molecular structure and has two or more epoxy groups. are treated with epichlorohydrin, phenol aralkyl type epoxy resins having a biphenylene skeleton, naphthol aralkyl type epoxy resins having a biphenylene skeleton, and the like. It's okay. Among these, those having two epoxy groups in the molecule are particularly preferable because they are excellent in improving 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; Those having two groups (sometimes expressed as having two phenolic nuclei); those having two epoxy groups among naphthol aralkyl type resins having a biphenylene skeleton; and the like.

In the conductive paste of the present embodiment, the lower limit of the content of the binder resin is, for example, 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass with respect to the entire conductive paste. % or more. Thereby, the handleability of the conductive paste can be improved. Also, the viscosity of the conductive paste can be adjusted to a level suitable for use. Moreover, 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 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 base material.

(Conductive metal powder)
The conductive metal powder contained in the conductive paste of the present embodiment agglomerates to form a metal particle connection structure by subjecting the conductive paste to heat treatment. That is, in the die attach paste layer obtained by heating the conductive paste, the metal powders are present in agglomeration with each other. Thereby, electrical conductivity, thermal conductivity, and adhesion to the base material are exhibited.

As the conductive metal powder used in the conductive paste of the present embodiment, silver powder, gold powder, platinum powder, or alloys thereof can be used. It is preferable to use silver powder from the viewpoint of conductivity and ease of handling.

The shape of the conductive metal powder is not particularly limited, but may be, for example, spherical, flaky, or scaly. In this embodiment, the conductive metal powder more preferably contains spherical particles. Thereby, the uniformity of agglomeration of the conductive metal powder can be improved. Moreover, from the viewpoint of cost reduction, it is also possible to adopt a mode in which the conductive metal powder contains flaky particles. Furthermore, from the viewpoint of improving the balance between cost reduction and uniform aggregation, the conductive metal powder may contain both spherical particles and flaky particles.

The average particle size (D ₅₀ ) of the conductive metal powder is, for example, 0.1 μm or more and 10 μm or less. When the average particle size of the conductive metal powder is equal to or greater than the above lower limit, it is possible to improve the formability of the metal particle linked structure between the conductive metal powders. Further, by setting the average particle size of the conductive metal powder to be equal to or less than the above upper limit, it is possible to suppress an excessive increase in the specific surface area and suppress a decrease in thermal conductivity due to contact thermal resistance.
Further, from the viewpoint of improving the dispensability of the conductive paste, the average particle size (D ₅₀ ) of the conductive metal powder is more preferably 0.6 μm or more and 2.7 μm or less, more preferably 0.6 μm or more and 2.0 μm. The following are particularly preferred. The average particle diameter (D ₅₀ ) of the conductive metal powder can be measured, for example, using a commercially available laser particle size distribution analyzer (eg, SALD-7000 manufactured by Shimadzu Corporation).

The maximum particle size of the conductive metal powder 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. This makes it possible to more effectively improve the balance between the uniformity of agglomeration of the conductive metal powder and the dispensability.

The content of the conductive metal powder in the conductive paste is, for example, preferably 30% by mass or more and 90% by mass or less, more preferably 45% by mass or more and 89% by mass or less with respect to the entire conductive paste. , more preferably 60% by mass or more and 88% by mass or less, more preferably 70% by mass or more and 87% by mass or less, and even more preferably 75% by mass or more and 86% by mass or less. By making it equal to or higher than the above lower limit, 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 making it equal to or less than the above upper limit, it is possible to contribute to improvements in the coating workability of the obtained conductive paste and the mechanical strength of the die attach paste layer obtained by heat-treating the conductive paste.

(Alkyl acetalized polyvinyl alcohol)
The conductive paste of this embodiment contains alkyl acetalized polyvinyl alcohol. This makes it possible to suppress the occurrence of bleeding, which is a phenomenon in which the diluent spreads over the base material.

The alkyl acetalized polyvinyl alcohol used in the conductive paste of the present embodiment is alkyl acetalized polyvinyl alcohol synthesized by an acetalization reaction between polyvinyl alcohol and aldehyde. Alkyl acetalized polyvinyl alcohols are composed of 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 aldehydes, formula (III) ) is a resin having In the formula below, 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 is the aldehyde used for acetalization (R ^a —CHO), where R ^a is an alkyl group having ¹ to 10 carbon atoms. R ^b is R ^b in the vinyl ester (R ^b COOCH=CH ₂ ), and R ^b is an alkyl group having 1 to 10 carbon atoms. However, l and/or m may be zero. There is no restriction on the arrangement order of the units, and they may be arranged randomly, arranged in blocks, or arranged in a tapered manner. Also, the bond between repeating units may be Head-to-Tail or Head-to-Head.

In the alkyl acetalized polyvinyl alcohol, l is preferably 25 or more and 40 or less, more preferably 27 or more and 37 or less, still more preferably 30 or more and 35 or less, where the sum of l, m and n is 100. is. When l is within the above numerical range, it is possible to effectively suppress 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.

In the above alkyl acetalized polyvinyl alcohol, when the sum of l, m and n is 100, m is preferably 1 or more and 10 or less, more preferably 1.1 or more and 9.7 or less, and still more preferably It is 1.2 or more and 9.5 or less. When m is within the above numerical range, it is possible to effectively suppress 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.

In the alkyl acetalized polyvinyl alcohol, n is preferably 50 or more and 70 or less, more preferably 51 or more and 67 or less, still more preferably 53 or more and 65 or less, where the sum of l, m and n is 100. is. When n is within the above numerical range, it is possible to effectively suppress 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.

Alkyl acetalized polyvinyl alcohol is obtained by alkyl acetalizing polyvinyl alcohol with an aldehyde.

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, and pivaline. Examples include vinyl acid and vinyl versatate. Among these, vinyl acetate is preferable from the viewpoint of availability. From the same point of view, the alkyl acetalized polyvinyl alcohol preferably contains a methyl group in its molecular structure, and more preferably ^Rb in the above general formula (II) is a methyl group.

Aldehydes used for alkylacetalizing 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, β-phenylpropionaldehyde and the like. Among them, butyraldehyde is particularly preferable from the viewpoint of ease of production. From the same point of view, the alkyl acetalized polyvinyl alcohol preferably contains a butyl group in its molecular structure, and more preferably R ^a in the above general formula (III) is a butyl group.

The weight average molecular weight of the alkyl acetalized polyvinyl alcohol is, for example, preferably 6×10 ⁴ or more and 15×10 ⁴ or less, more preferably 8×10 ⁴ or more and 12×10 ⁴ or less.

Examples of commercially available alkyl acetalized polyvinyl alcohol include S-Lec (manufactured by Sekisui Chemical Co., Ltd.), and various grades are available from the market. More specifically, S-LEC BH-3, S-LEC BX-6, S-LEC KS-1, S-LEC KS-10, S-LEC KS-3, and the like can be mentioned, but the present invention is not limited to these.

(polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate)
The conductive paste in one embodiment of the invention comprises polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate. As a result, even if the conductive paste contains a diluent as in the present embodiment, the separation and precipitation of components in the paste during storage and the diluent when the paste is placed wet the base material. It is possible to suppress the occurrence of bleeding, which is a spreading phenomenon.

Examples of commercially available polyoxyethylene alkyl ether carboxylic acids include Beaurite LCA-25NH (manufactured by Sanyo Chemical Industries, Ltd.) and Kaosera 8110 (manufactured by Kao Corporation). Examples thereof include oleoyl sarcosine 221P (NOF Corporation), but are not limited thereto.

In addition, the conductive paste of the present embodiment can contain a known anionic surfactant in addition to the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinic acid. Examples of anionic surfactants include, but are not limited to, potassium laurate, potassium coconut fatty acid, potassium myristate, potassium oleate, potassium oleate diethanolamine salt, sodium oleate, potassium palmitate, potassium stearate, and sodium stearate. , mixed fatty acid soda soap, semi-hardened tallow fatty acid soda soap, castor oil potash soap; sodium dodecyl sulfate, sodium higher alcohol sulfate, triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, sodium polyoxyethylene alkyl ether sulfate, polyoxy Alkyl sulfate ester salts such as triethanolamine ethylene alkyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, sodium 2-ethylhexyl sulfate; sodium alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate; sodium di-2-ethylhexyl sulfosuccinate, etc. Sodium dialkylsulfosuccinate; Sodium alkylnaphthalenesulfonate; Sodium alkyldiphenylether disulfonate; Potassium alkylphosphate; Carboxylic acid type polymer anions; sodium acyl (beef tallow) methyl taurate; sodium acyl (coconut) methyl taurate; sodium cocoyl isethionate; α-sulfo fatty acid ester sodium salt; sodium amide ether sulfonate; carboxylic acids and their salts; N-acyl amino acids such as oleyl sarcosinate and sodium lauroyl sarcosinate and their salts; and rosin acid soaps.

(diluent)
A diluent is added to the conductive paste of the present embodiment in order to give the conductive paste an appropriate viscosity in consideration of the applicability to the semiconductor element or base material and the filling property in detail. As diluents, non-reactive solvents or reactive diluents can be used. Here, the non-reactive solvent means a solvent that does not have a reactive group that participates in the cross-linking reaction of the binder resin, and the reactive diluent means the solvent that is involved in the cross-linking reaction of the binder resin contained in the conductive paste. It means a compound with a participating reactive group.

By containing a non-reactive solvent, the conductive paste of the present embodiment can adjust the fluidity of the conductive paste to be obtained, and can improve handleability and workability. Non-reactive solvents include 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, methylmethoxybutanol, α-terpineol, β-terpineol, Alcohols such as xylene glycol, benzyl alcohol, 2-phenylethyl alcohol, isopalmityl alcohol, isostearyl alcohol, lauryl alcohol, ethylene glycol, propylene glycol or glycerin; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol ( 4-hydroxy-4-methyl-2-pentanone), 2-octanone, isophorone (3,5,5-trimethyl-2-cyclohexene-1-one) or diisobutyl ketone (2,6-dimethyl-4-heptanone), etc. ketones; 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, Esters such as 1,2-diacetoxyethane, tributyl phosphate, tricresyl phosphate or tripentyl phosphate; tetrahydrofuran, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, ethoxyethyl ethers, ethers such as 1,2-bis(2-diethoxy)ethane or 1,2-bis(2-methoxyethoxy)ethane; ester ethers such as acetic acid 2-(2-butoxyethoxy)ethane; 2-( Ether alcohols such as 2-methoxyethoxy)ethanol; toluene, xylene, n-para Hydrocarbons such as fin, isoparaffin, dodecylbenzene, turpentine oil, kerosene or light oil; Nitriles such as acetonitrile or propionitrile; Amides such as acetamide or N,N-dimethylformamide; Alternatively, volatile organically modified silicone oil and the like can be mentioned.

In the present 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, relative to the entire conductive paste. , more preferably 0.5% by mass or more. Thereby, it is possible to more effectively improve the workability of applying 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 with respect to the entire conductive paste, more preferably 35% by mass or less, and 30% by mass or less. It is more preferable that the content is 25% by mass or less. As a result, it is possible to suppress the occurrence of dripping or the like during the application work, thereby improving the application workability.

By containing a reactive diluent, the conductive paste of the present embodiment can improve curability while adjusting the fluidity of the obtained conductive paste. Reactive diluents used as diluents include, for example, glycol monomers, acrylic monomers, epoxy monomers, maleimide monomers, and the like.

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 mono-isopropyl ether, ethylene glycol mono-n-butyl ether, and 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 mono-isopropyl 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 individually by 1 type, and may be used in combination of 2 or more type.

When the conductive paste is heat-treated, the metal powder contained therein aggregates with each other to favorably form a metal particle connection structure. From this viewpoint, the glycol monomer is tripropylene glycol mono-n-butyl ether or ethylene glycol mono-n. -Butyl ether is preferably used.

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

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-ethylhexyl diethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, cyclohexyl (meth) acrylate ) 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 product, 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 succinate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethylhexahydrophthalate, 2-(meth)acryloyl Oxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-(meth)acryloyloxyethyl acid phosphate, and 2-(meth)acrylic Loyl oxyethyl acid phosphate and the like can be mentioned. As the monofunctional acrylic monomer, one or a combination of two or more of the above specific examples can be used.

Among the above specific examples, 2-phenoxyethyl methacrylate is preferably used as the monofunctional acrylic monomer. This can improve the adhesion of the resulting conductive paste to the substrate.

Specific examples of 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′-isopropylidenediphenol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,6-bis((meth)acryloyloxy)-2,2, 3,3,4,4,5,5-octafluorohexane, 1,4-bis((meth)acryloyloxy)butane, 1,6-bis((meth)acryloyloxy)hexane, triethylene glycol di(meth) ) acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, N,N'-di(meth)acryloylethylenediamine, N,N'-(1,2-dihydroxyethylene)bis(meth) acrylamide, 1,4-bis((meth)acryloyl)piperazine and the like.

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

Monoepoxy monomers include t-butylphenyl glycidyl ether, m,p-cresyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, and the like. As the monoepoxy monomer, one or a combination of two or more of the above specific examples can be used.

Polyfunctional epoxy monomers include bisphenol compounds such as bisphenol A, bisphenol F and biphenol, or derivatives thereof; diols having an alicyclic structure or derivatives thereof; aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, decanediol, or difunctional epoxidized derivatives thereof; trihydroxyphenylmethane skeleton, trifunctional ones having an aminophenol skeleton; polyfunctional ones obtained by epoxidizing phenol novolak resins, cresol novolak resins, phenol aralkyl resins, biphenyl aralkyl resins, naphthol aralkyl resins, and the like. As the polyfunctional epoxy monomer, one or a combination of two or more of the above specific examples can be used.

Maleimide monomers used as reactive diluents include polytetramethylene ether glycol-di(2-maleimide acetate).

In the present embodiment, the content of the reactive diluent in the conductive paste is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, relative to the entire conductive paste. . Thereby, it is possible to more effectively improve the workability of applying 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, more preferably 15% by mass or less, relative to the entire conductive paste. As a result, it is possible to suppress the occurrence of dripping or the like during the application work, thereby improving the application workability. It also becomes possible to improve the curability of the conductive paste.

(curing agent)
The conductive paste of this embodiment may contain a curing agent. Thereby, the curability of the conductive paste can be improved. As the curing agent, for example, one or more selected from aliphatic amines, aromatic amines, dicyandiamides, dihydrazide compounds, acid anhydrides, and phenolic compounds can be used. Among these, containing at least one of dicyandiamide and a phenol compound is particularly preferable from the viewpoint of improving production stability.

Dihydrazide compounds used as curing agents include carboxylic acid dihydrazide such as adipic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, and p-oxybenzoic acid dihydrazide. Acid anhydrides used as curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, dodecenylsuccinic anhydride, a reaction product of maleic anhydride and polybutadiene, anhydride Examples include copolymers of maleic acid and styrene.

A phenolic compound used as a curing 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 the number of phenolic hydroxyl groups in one molecule is particularly preferably 2 or 3. As a result, it is possible to more effectively improve the workability of applying the conductive paste, and to form a crosslinked structure at the time of curing, thereby making it possible to improve the properties of the cured product of the conductive paste. Examples of the above phenol compounds include bisphenol F, bisphenol A, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetramethylbisphenol S, dihydroxydiphenyl ether, dihydroxybenzophenone, tetramethylbiphenol, ethylidenebisphenol, and methylethylidenebis(methylphenol). , cyclohexylidenebisphenol, biphenol and other phenolic resins having a biphenyl skeleton and their derivatives, trifunctional phenols and their derivatives such as tri(hydroxyphenyl)methane and tri(hydroxyphenyl)ethane, phenol novolak, cresol novolak, etc. It can contain one or more selected from compounds obtained by reacting phenols and formaldehyde, which are mainly composed of binuclear compounds or trinuclear compounds, and derivatives thereof. Among these, it is more preferable to contain a phenol resin having a biphenyl skeleton, and it is particularly preferable to contain bisphenol F.

In the present 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, with respect to the entire conductive paste. 0.14% by mass or more is more preferable. Thereby, the curability of the conductive paste can be improved more effectively. 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, and 1% by mass or less with respect to the entire conductive paste. is more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less. This makes it possible to improve the low thermal expansion property and moisture resistance of the adhesive layer formed using the conductive paste.

(Inorganic filler)
In the conductive paste of the present embodiment, the content of the inorganic filler different from the conductive metal powder is preferably 30% by mass or less with respect to the entire conductive paste. Here, the inorganic filler different from the conductive metal powder refers to a material different from the conductive metal powder described above, and examples thereof include fused silica such as fused crushed silica and fused spherical silica; crystalline silica; silica, such as amorphous silica; silicon dioxide; alumina; aluminum hydroxide; silicon nitride;
In addition, the content of the inorganic filler different from the conductive metal powder is preferably 30% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, particularly preferably 10% by mass or less, with respect to the entire conductive paste. It does not contain inorganic fillers unlike conductive metal powders. As a result, the balance of various properties such as the conductivity of the conductive paste and the adhesion to the substrate is improved, and when the conductive paste is stored for a long time, precipitation of solid components in the conductive paste and liquid components Separation can be effectively suppressed. Here, not containing an inorganic filler different from the conductive metal powder means substantially not containing, and the content of the inorganic filler different from the conductive metal powder with respect to the entire conductive paste is 0.1. It refers to the case where it is less than mass %.

(other ingredients)
In addition to the components described above, the conductive paste of the present embodiment may, if necessary, contain various additional components commonly used in this field. Further components include, but are not limited to, silane coupling agents, curing accelerators, radical polymerization initiators, stress reducing agents, etc., and can be selected according to desired performance.

A silane coupling agent is used to improve the adhesion between the conductive paste and the substrate. Examples of silane coupling agents include vinylsilanes such as vinyltrimethoxysilane and vinyltriethoxysilane; 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidide; epoxysilanes such as xypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane; styryls such as p-styryltrimethoxysilane; silane; methacrylsilanes such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane; methacrylic acid 3-(trimethoxy Acrylsilanes such as silyl)propyl, 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane; , 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane, etc. Aminosilanes; Isocyanurate silanes; Alkylsilanes; Ureidosilanes such as 3-ureidopropyltrialkoxysilane; mercaptosilanes such as dimethoxysilane and 3-mercaptopropyltrimethoxysilane; isocyanatesilanes such as 3-isocyanatopropyltriethoxysilane; and the like.

The curing accelerator is used to accelerate the reaction between the epoxy resin used as the binder resin, or the epoxy monomer used as the reactive diluent when a reactive diluent is used, and the curing agent. Examples of curing accelerators include phosphorus atom-containing compounds such as organic phosphines, tetrasubstituted phosphonium compounds, phosphobetaine compounds, adducts of phosphine compounds and quinone compounds, adducts of phosphonium compounds and silane compounds; 2-methylimidazole , 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and other imidazole compounds; dicyandiamide, 1,8-diazabicyclo[5.4.0]undecene-7, benzyl Amidines such as dimethylamine and tertiary amines; and nitrogen atom-containing compounds such as quaternary ammonium salts of the above amidines or the above tertiary amines.

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

Examples of the low-stress agent 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 copolymer compounds; and allyl ester resins. can.

When the conductive paste of the present embodiment contains a low-stress agent, the content of the low-stress agent in the conductive paste is preferably 1% by mass or more with respect to the entire conductive paste, and 2% by mass or more. It is more preferable that the content is 3% by mass or more. Thereby, the curability of the conductive paste can be improved more effectively. 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, and 6% by mass or less with respect to the entire conductive paste. is more preferably 4% by mass or less. This makes it possible to improve the low thermal expansion property and moisture resistance of the adhesive layer formed using the conductive paste.

(Preparation of conductive paste)
The method of preparing the conductive paste is not particularly limited. For example, after premixing the above components, the mixture is kneaded using three rolls and then vacuum defoamed to obtain a paste-like composition. can be done. At this time, the long-term workability of the conductive paste can be improved by appropriately adjusting the preparation conditions, for example, performing premixing under reduced pressure.

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 to be used, the type of diluent, the blending amount thereof, and the like. In addition, the conductive paste of the present embodiment can suppress the separation and precipitation of the components during long-term storage, thereby reducing the change in viscosity during long-term storage of the conductive paste.

The conductive paste of the present embodiment was measured using a BF type viscometer at a temperature of 25° C. and a shear rate of _0.5 rpm. It is preferably 35 Pa·s or more, more preferably 38 Pa·s or more, and particularly preferably 40 Pa·s or more, in any case after standing still for 24 hours. As a result, when the conductive paste is adhered, it can be prevented from spreading excessively on the substrate, and short-circuiting with a chip of another system can be prevented. The upper limit of the 0.5 rpm viscosity η _0.5 is preferably 100 Pa·s or less, more preferably 90 Pa·s or less, still more preferably 80 Pa·s or less, and still more preferably 70 Pa·s. s or less, more preferably 65 Pa·s or less, and still more preferably 60 Pa·s or less. Thereby, workability can be improved.

The conductive paste of the present embodiment is measured using a BF type viscometer at a temperature of 25° C. and a shear rate of _5.0 rpm. It is preferably 5 Pa·s or more, more preferably 8 Pa·s or more, and particularly preferably 10 Pa·s or more, in any case after standing still for 24 hours. As a result, when the conductive paste is adhered, it can be prevented from spreading excessively on the substrate, and short-circuiting with a chip of another system can be prevented. The upper limit of the _5.0 rpm viscosity η5.0 is preferably 30 Pa·s or less, more preferably 25 Pa·s or less, and particularly preferably 20 Pa·s or less. Thereby, workability can be improved.

The conductive paste of the present embodiment is measured using a BF type viscometer at a temperature of 25° C. and a shear rate of _50.0 rpm. It is preferably 1 Pa·s or more, more preferably 1.5 Pa·s or more, and particularly preferably 2 Pa·s or more in any case after standing still for 24 hours. As a result, when the conductive paste is adhered, it can be prevented from spreading excessively on the substrate, and short-circuiting with a chip of another system can be prevented. The upper limit of the _50.0 rpm viscosity η50.0 is preferably 15 Pa·s or less, more preferably 10 Pa·s or less, and particularly preferably 7 Pa·s or less. Thereby, workability can be improved.

In the conductive paste of the present embodiment, the lower limit of the viscosity ratio Ti ₁ of the above η _0.5 and the above η _5.0 represented by the following formula (1) is is preferably 3 or more, more preferably 3.5 or more, and still more preferably 4 or more.
Ti1= _η0.5 / _η5.0 ( ₁ )
When Ti ₁ is equal to or higher than the above lower limit, it is possible to prevent the conductive paste from spreading excessively on the substrate when adhered, and to prevent a short circuit with a chip of another system.
In addition, the upper limit of Ti ₁ is preferably 7 or less, more preferably 6.5 or less, and still more preferably 6 or less both immediately after production and after standing for 24 hours after production. . When Ti ₁ is equal to or less than the above upper limit, workability can be made more suitable when the conductive paste is adhered onto the base material.

In the conductive paste of the present embodiment, the lower limit of the viscosity ratio Ti ₂ of the above η _0.5 and the above η _50.0 represented by the following formula (2) is is preferably 6 or more, more preferably 6.5 or more, and still more preferably 7 or more.
Ti2= _η0.5 / _η50.0 ( ₂ )
When _Ti2 is equal to or higher than the above lower limit, it is possible to prevent the conductive paste from spreading excessively on the substrate when adhered, and to prevent a short circuit with a chip of another system.
In addition, the upper limit of Ti ₂ is preferably 20 or less, more preferably 17 or less, still more preferably 14 or less, both immediately after production and after standing for 24 hours after production. It is preferably 13.5 or less, more preferably 13 or less. When Ti ₂ is equal to or less than the above upper limit value, workability in bonding the conductive paste onto the base material can be made more suitable.

(Application)
Applications of the conductive paste of the present embodiment will be described.
The conductive paste according to this embodiment is used, for example, to bond a substrate and a semiconductor element. Here, examples of semiconductor elements include semiconductor packages and LEDs.
The conductive paste according to the present embodiment can improve connection reliability and appearance as compared with conventional conductive pastes. As a result, it can be suitably used for mounting a semiconductor element that generates a large amount of heat on a substrate. In addition, in this embodiment, LED shows a light emitting diode (Light Emitting Diode).

Specific examples of semiconductor devices using LEDs include bullet-type LEDs, surface mount device (SMD) LEDs, COBs (Chip On Boards), and power LEDs.

The types of the semiconductor packages include, specifically, CMOS image sensors, hollow packages, MAPs (Mold Array Packages), QFPs (Quad Flat Packages), SOPs (Small Outline Packages), CSPs (Chip Size Packages), 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 eWLB, and Fan-Out eWLB.

An example of a semiconductor device using the conductive paste according to this embodiment will be described below.
FIG. 1 is a cross-sectional view showing an example of a semiconductor device according to this embodiment.
A semiconductor device 100 according to this embodiment includes a base material 30 and a semiconductor element 20 mounted on the base material 30 via an adhesive layer 10 that is a cured product of a conductive paste. Semiconductor element 20 and base material 30 are electrically connected, for example, via bonding wires 40 or the like. Also, the semiconductor element 20 is sealed with a sealing resin 50, for example.

Here, the lower limit of the thickness of the adhesive layer 10 is preferably, for example, 5 μm or more, 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 can be improved. Also, 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. As a result, the conductive paste can exhibit suitable adhesion while improving heat dissipation.

In FIG. 1, the base material 30 is, for example, a lead frame. In this case, the semiconductor element 20 is mounted on the die pad 32 or the base material 30 with the adhesive layer 10 interposed therebetween. In addition, the semiconductor element 20 is electrically connected to the outer leads 34 (the base material 30) via bonding wires 40, for example. The base material 30, which is a lead frame, is composed of, for example, a 42 alloy Cu frame.

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, or the like. Note that the surface of the base material 30 may be coated with a metal such as silver or gold, for example. Thereby, the adhesiveness between the adhesive layer 10 and the substrate 30 can be improved.

FIG. 2 is a modification of FIG. 1 and is a cross-sectional view showing an example of the semiconductor device 100 according to this embodiment. In semiconductor device 100 according to this modification, base material 30 is, for example, an interposer. A plurality of solder balls 52, for example, are formed on the other surface of the substrate 30, which is an interposer, opposite to the surface on which the semiconductor element 20 is mounted. In this case, the semiconductor device 100 will be connected to another wiring board through the solder balls 52 .

(Method for manufacturing semiconductor device)
An example of a method for manufacturing a semiconductor device according to this embodiment will be described.
First, a conductive paste is applied onto the substrate 30, and then the semiconductor element 20 is arranged thereon. That is, the base material 30, the conductive paste, and the semiconductor element 20 are laminated in this order. Although the method for applying the conductive paste is not limited, specifically, dispensing, printing, ink-jetting, and the like can be used.

The conductive paste is then cured by pre-curing and then post-curing the conductive paste. By heat treatment such as pre-curing and post-curing, the silver particles in the conductive paste are aggregated to form a thermally conductive layer in the adhesive layer 10 in which the interfaces between the silver particles disappear. Thereby, the substrate 30 and the semiconductor element 20 are adhered via the adhesive layer 10 . Next, the semiconductor element 20 and the base material 30 are electrically connected using bonding wires 40 . Then, the semiconductor element 20 is sealed with the sealing resin 50 . Thereby, a semiconductor device can be manufactured.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can also be adopted.

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited to these.

Components used in Examples and Comparative Examples are shown below.
(Alkyl acetalized polyvinyl alcohol)
- Alkyl acetalized polyvinyl alcohol 1 (A1): a compound represented by the following chemical formula (IV) (l: 33, m: 3, n: 64, molecular weight: 110000)
- Alkyl acetalized polyvinyl alcohol 2 (A2): S-Lec BH-3 (manufactured by Sekisui Chemical Co., Ltd., used as a 10% butyl carbitol solution)

(polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate)
- Polyoxyethylene alkyl ether carboxylic acid 1 (B1): sodium polyoxyethylene alkyl ether carboxylate (manufactured by Sanyo Chemical Industries, Ltd., Beaulight LCA-25NH)
- Polyoxyethylene alkyl ether carboxylic acid 2 (B2): polyoxyethylene alkyl ether carboxylic acid (manufactured by Kao Corporation, Kaosera 8110)
- Oleyl sarcosinate 1 (B3): oleyl sarcosinate (manufactured by NOF Corporation, oleoyl sarcosine 221P)

(binder resin)
- Binder resin 1: bisphenol F type epoxy resin (manufactured by Nippon Kayaku, RE-403S, epoxy equivalent 165 g / eq)
(Low stress agent)
-Low stress agent 1: Acrylic acid polymer (UG-4035 manufactured by Toagosei Co., Ltd.)
(diluent)
- Diluent 1: butyl carbitol (manufactured by Sankyo Chemical Co., Ltd., containing butyl carbitol as a solvent for alkyl acetalized polyvinyl alcohol 2)
(curing agent)
-Curing agent 1: Bisphenol F (DIC-BPF manufactured by DIC)
(Silane coupling agent)
-Silane coupling agent 1: sulfide silane (manufactured by Osaka Soda Co., Ltd., Cabras-4)
(Conductive metal powder)
- Silver powder 1: flaky silver powder (average particle size: 0.7 μm, manufactured by Ames, SF-65S)

(Examples 1 to 10, Comparative Examples 1 to 10)
<Preparation of conductive paste>
First, a varnish-like mixture was prepared by kneading the components in the blending amounts described in Tables 1 and 2 under "Varnish" at room temperature using a three-roll mill. Next, the obtained varnish-like mixture was mixed with silver powder in the amount described in "Paste" in Tables 1 and 2, and kneaded at room temperature with a three-roll mill to obtain the paste in each example and each comparative example. A paste composition (conductive paste) was obtained.

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

<Adhesion strength>
The conductive paste obtained above is applied onto a silver lead frame, and then a silver-plated silicon chip of length 2.0 mm×width 2.0 mm×thickness 350±5 μm is placed on the conductive paste. Then, the temperature was raised from 25° C. to 150° C. over 30 minutes, followed by heat treatment at 150° C. for 2 hours to obtain a cured product, which was used as a test piece. For this test piece, the die shear strength at 260° C. between the silver lead frame and the silicon chip was measured. Results are shown in Tables 1 and 2.

<Viscosity>
For the conductive paste of each example and comparative example, the viscosity at room temperature of 25° C. was measured using a BF type viscometer (manufactured by BROOKFIELD ENGINEERING, model DV3T) immediately after preparation of the conductive paste and after standing for 24 hours. . As for the order of measurement at this time, first, the viscosity was measured for 6 minutes at a shear rate of 0.5 rpm. Then, after increasing the shear rate to 5.0 rpm, the 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 the viscosity was measured for 1 minute at the shear rate of 50.0 rpm. The viscosities at each shear rate were set to η _0.5 , η _5.0 and η _50.0 , respectively. The unit of viscosity is Pa·s.
Also, using the measured viscosities, the viscosity ratio Ti ₁ and the viscosity ratio Ti ₂ were calculated according to the following equations (1) and (2).
Ti1= _η0.5 / _η5.0 ( ₁ )
Ti2= _η0.5 / _η50.0 ( ₂ )

<Presence or absence of bleeding after applying the conductive paste>
The conductive paste of each example and comparative example was applied on a silver lead frame activated by argon treatment (200 W, 180 sec), and the wetting and spreading of the paste at the moment of application was observed with a metallurgical microscope (U-PMTVC, manufactured by OLYNPUS). ) was used to observe.
Immediately after application, the paste spreads out and forms a circular shape, which can be seen as a circular object through which light does not transmit when observed with a metallurgical microscope. _A0 was the diameter of the circular object through which no light was transmitted. Twenty-four hours after the paste was applied, the paste, which had been wetted and spread immediately after the application, appeared as a circular object through which light was semi-transmitted with a metallurgical microscope. The diameter of the circular object through which the light was semi _- transmitted was defined as A1.
In addition, the paste was applied separately from the _one for which A1 was measured, and _A0 was measured again. Thereafter, the temperature was raised from 25° C. to 150° C. over 30 minutes, and heat treatment was performed at 150° C. for 2 hours to obtain a cured product. After this cured product was allowed to stand for 24 hours, the paste, which had spread even further immediately after the application, was seen as a circular object through which light was semi-transmitted with a metallurgical microscope. The diameter of the circular object through which the light was semi-transmitted was defined as _A2 .
Here, it means that the more A ₁ or A ₂ is larger than A ₀ , the more wetting and spreading (bleeding) of the paste occurs. If A ₁ /A ₀ or A ₂ /A ₀ is 1, the result is "○", if A ₁ /A ₀ or A ₂ /A ₀ is greater than 1 and 1.1 or less, "△", A If ₁ /A ₀ or A ₂ /A ₀ is greater than 1.1, it is shown in Tables 1 and 2 as "x".

<Separation/Precipitation>
The conductive pastes of each example and comparative example were allowed to stand at room temperature. After standing, the paste was observed after 12 hours and 24 hours. A case where separation or precipitation did not occur was evaluated as "○", a case where solid component precipitation occurred was evaluated as "precipitation", and a case where liquid component separation occurred was evaluated as "separation".

The conductive pastes of Examples showed little or no bleeding, and neither separation nor sedimentation of components occurred even after long-term storage. Moreover, when used for adhesion between a lead frame and a silicon chip, excellent adhesion strength was exhibited.

100 semiconductor device 10 adhesive layer 20 semiconductor element 30 base material 32 die pad 34 outer lead 40 bonding wire 50 sealing resin 52 solder ball

Claims (15)

a binder resin;
a conductive metal powder;
an alkyl acetalized polyvinyl alcohol;
a diluent;
A conductive paste for bonding electronic components containing
A conductive paste, wherein the content of the alkyl acetalized polyvinyl alcohol is 5 ppm or more and 200 ppm or less with respect to the entire conductive paste. a binder resin;
a conductive metal powder;
polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosinate; and
a diluent;
A conductive paste for bonding electronic components containing
A conductive paste, wherein the content of the polyoxyethylene alkyl ether carboxylic acid or oleyl sarcosic acid is 1,000 ppm or more and 15,000 ppm or less based on the entire conductive paste. The binder resin is one or more selected from cyanate resins, epoxy resins, (meth)acrylic resins, resins having two or more radically polymerizable carbon-carbon double bonds in one molecule, and maleimide resins. Conductive paste according to claim 1 or 2, comprising. The conductive paste according to claim 1 or 2, wherein the binder resin contains an epoxy resin having two or more glycidyl groups in one molecule. 3. The conductive paste according to claim 1, further comprising a curing agent. The conductive paste according to claim 5, wherein the curing agent contains one or more selected from aliphatic amines, aromatic amines, dicyandiamides, dihydrazide compounds, acid anhydrides, and phenolic compounds. The conductive paste according to claim 1 or 2, wherein the conductive metal powder contains at least one selected from silver powder, gold powder, platinum powder, and alloys thereof. The conductive paste according to claim 1 or 2, wherein the conductive metal powder is in an amount of 30% by mass or more and 90% by mass or less with respect to the entire conductive paste. whether 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, and the content of the inorganic filler is 30% by mass or less with respect to the entire conductive paste.
The conductive paste according to claim 1 or 2. The conductive paste is measured using a BF type viscometer while stirring at a temperature of 25° C. and a shear rate of _0.5 rpm. The conductive paste according to claim 1 or 2, which is 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. , The conductive paste according to claim 1 or 2. The conductive paste is measured using a BF type viscometer while stirring at a temperature of 25 ° C. and a shear rate of _50.0 rpm. The conductive paste according to claim 1 or 2, which is In the conductive paste, using a BF type viscometer, temperature: 25 ° C., shear rate: 0.5 rpm viscosity η _0.5 when measured while stirring at 0.5 rpm, and using a BF type viscometer , temperature: 25 ° C., shear rate: 5.0 rpm viscosity η _5.0 when measured while stirring at 5.0 rpm, and the viscosity ratio Ti ₁ represented by the following formula (1) is 3 or more 7 The conductive paste according to claim 1 or 2, which is:
Ti1= _η0.5 / _η5.0 ( ₁ ) In the conductive paste, using a BF type viscometer, temperature: 25 ° C., shear rate: 0.5 rpm viscosity η _0.5 when measured while stirring at 0.5 rpm, and using a BF type viscometer , temperature: 25 ° C., shear rate: 50.0 rpm viscosity η _50.0 when measured while stirring at 50.0 rpm, and the viscosity ratio Ti ₂ represented by the following formula (2) is 6 or more and 20 The conductive paste according to claim 1 or 2, which is:
Ti2= _η0.5 / _η50.0 ( ₂ ) a substrate;
A semiconductor element mounted on the base material via an adhesive layer,
3. A semiconductor device, wherein the adhesive layer comprises a cured product of the conductive paste according to claim 1.

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