Thermally conductive paste, cured product, and semiconductor device

Abstract

The present invention provides: a thermally conductive paste that yields a cured film having high thermal conductivity and a small bonding film thickness; a cured product of the thermally conductive paste; and a semiconductor device comprising the cured product of the thermally conductive paste. The present invention relates to a thermally conductive paste comprising metal particles (A), a thermosetting resin (B), and at least one component selected from the group consisting of a curing agent (C) and a curing accelerator (D). The contained amount of the metal particles (A) is 80 mass% or more in relation to the total amount of the thermally conductive paste. The viscosity of the thermally conductive paste as measured by using an E-type viscometer under the conditions of a temperature of 25°C and a rotational speed of 5 rpm is 200 Pa·s or less. The thixotropy index value (T.I.) of the thermally conductive paste is 5.0 or less, the thixotropy index value being represented by the ratio (viscosity at 1 rpm) / (viscosity at 5 rpm) of the viscosity of the thermally conductive paste as measured by using the E-type viscometer under the conditions of a temperature of 25°C and a rotational speed of 1 rpm to the viscosity of the thermally conductive paste as measured by using the E-type viscometer under the conditions of a temperature of 25°C and a rotational speed of 5 rpm.

Description

Thermally conductive paste, cured product, and semiconductor device

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

[0002] With the increasing capacity, high-speed processing, and miniaturization of semiconductor products, the handling of heat generated during semiconductor product operation, also known as thermal management, is attracting attention.

[0003] One method of thermal management is known to use a thermally conductive paste to dissipate heat generated from semiconductor products to heat dissipation components such as heat sinks (for example, Patent Document 1).

[0004] International Publication No. 2016 / 185936

[0005] It is known that the thermal conductivity of such thermally conductive pastes can be increased by filling them with a high concentration of metal particles. However, when the amount of metal particles is high, the fluidity of the thermally conductive paste decreases, and the bond line thickness (hereinafter referred to as BLT) can become high. A high BLT leads to the problem of increased thermal resistance.

[0006] In view of the above, the object of the present invention is to provide a thermally conductive paste that gives a cured film with high thermal conductivity and a small bonding thickness (BLT).

[0007] As a result of diligent research, the inventors have found that the above problems can be solved by providing a thermally conductive paste containing metal particles and a thermosetting resin, which contains a predetermined amount or more of metal particles, and by setting the viscosity and thixotropy index (T.I.) of the thermally conductive paste to a predetermined value or less, thereby completing the present invention.

[0008] In other words, the present invention is as follows: [1] A thermally conductive paste comprising (A) metal particles, (B) a thermosetting resin, and at least one component selected from the group consisting of (C) a curing agent and (D) a curing accelerator, wherein the content of (A) metal particles is 80% by mass or more of the total amount of the thermally conductive paste, the viscosity of the thermally conductive paste measured using an E-type viscometer at 25°C and a rotation speed of 5 rpm is 200 Pa·s or less, and the thixotropy index value (T.I), expressed as the ratio of the viscosity of the thermally conductive paste measured using an E-type viscometer at 25°C and a rotation speed of 1 rpm to the viscosity of the thermally conductive paste measured at 25°C and a rotation speed of 5 rpm (viscosity at 1 rpm / viscosity at 5 rpm), is 5.0 or less. [2] The thermally conductive paste according to [1], wherein the (A) metal particles include (A1) metal particles with an average particle diameter of 10.0 μm or more. [3] The BET specific surface area of ​​the (A1) metal particles with an average particle diameter of 10.0 μm or more is 1.0 m ２A thermally conductive paste according to [2], wherein the amount is less than or equal to / g. [4] A thermally conductive paste according to [2] or [3], wherein the (A1) metal particles with an average particle diameter of 10.0 μm or more are 50 parts by mass or more per 100 parts by mass of the (A) metal particles. [5] A thermally conductive paste according to any one of [1] to [4], wherein the (A) metal particles further comprise (A2) metal particles with an average particle diameter of 1.0 μm or more and less than 10.0 μm. [6] A thermally conductive paste according to [5], wherein the mass ratio of the (A1) metal particles with an average particle diameter of 10.0 μm or more to the (A2) metal particles with an average particle diameter of 1.0 μm or more and less than 10.0 μm is 70 / 30 to 95 / 5. [7] A thermally conductive paste according to any one of [1] to [6], wherein the (B) thermosetting resin comprises (B1) epoxy resin. [8] The thermally conductive paste according to [7], wherein the (B1) epoxy resin comprises an epoxy resin having a flexible skeleton. [9] The thermally conductive paste according to [8], wherein the epoxy resin having a flexible skeleton comprises at least one selected from an epoxy resin having an aliphatic skeleton, an epoxy resin having a polyalkylene glycol structure, and an epoxy resin having a polyalkylene oxide structure.

[10] The thermally conductive paste according to any one of [1] to [9], wherein the content of the (B) thermosetting resin is 1.0 to 10.0 parts by mass per 100 parts by mass of the (A) metal particles.

[11] The thermally conductive paste according to [7] or [8], wherein the (B1) epoxy resin comprises an epoxy resin that is liquid at room temperature (25°C), and the liquid epoxy resin is contained in an amount of 50% by mass or more relative to the total amount of the (B1) epoxy resin.

[12] The thermally conductive paste according to any one of [1] to

[11] , which is substantially solvent-free.

[13] 400 mm ２A thermally conductive paste according to any one of [1] to

[12] , used for joining an area of ​​the above.

[14] A thermally conductive paste according to any one of [1] to

[13] , wherein the cured film obtained by heating the thermally conductive paste at 180°C for 60 minutes has a thermal conductivity λ in the thickness direction at 25°C of 40 W / m·K or more.

[15] A thermally conductive paste according to any one of [1] to

[14] , further comprising oleic acid.

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

[15] .

[17] A semiconductor device comprising a cured product of the thermally conductive paste according to any one of [1] to

[15] .

[0009] According to the present invention, it is possible to provide a thermally conductive paste that gives a cured film with high thermal conductivity and a small bonding thickness, a cured product of the thermally conductive paste, and a semiconductor device comprising the cured product of the thermally conductive paste.

[0010] The thermally conductive pastes described herein will be explained below based on embodiments. However, the embodiments shown below are illustrative examples for realizing the technical concept of the present invention, and the present invention is not limited to the thermally conductive pastes described below. In this specification, the bonding film thickness refers to the thickness of the coating film after applying the thermally conductive paste to a substrate and heat-treating it under pressure, and can be measured in detail by the method described later.

[0011] [Thermally conductive paste] The thermally conductive paste according to an embodiment of the present invention is a thermally conductive paste comprising (A) metal particles, (B) thermosetting resin, and at least one component selected from the group consisting of (C) curing agent and (D) curing accelerator, wherein the content of (A) metal particles is 80% by mass or more relative to the total amount of the thermally conductive paste, the viscosity of the thermally conductive paste measured using an E-type viscometer at 25°C and a rotation speed of 5 rpm is 200 Pa·s or less, and the thixotropy index value (T.I), expressed as the ratio of the viscosity of the thermally conductive paste measured using an E-type viscometer at 25°C and a rotation speed of 1 rpm to the viscosity of the thermally conductive paste measured at 25°C and a rotation speed of 5 rpm (viscosity at 1 rpm / viscosity at 5 rpm), is 5.0 or less.

[0012] The reason why the thermally conductive paste according to the embodiment of the present invention can produce a cured film with high thermal conductivity and a small bonding thickness is not entirely clear, but the inventors speculate as follows: The thermally conductive paste according to the embodiment of the present invention (A) contains a large amount of metal particles, 80% by mass or more of the total amount of thermally conductive paste, which improves the thermal conductivity of the cured film obtained by curing the thermally conductive paste (hereinafter also simply referred to as the cured film). Furthermore, by setting the viscosity and thixotropy index values ​​to below predetermined values, a cured film with a small bonding thickness can be obtained.

[0013] <Viscosity> The thermal conductive paste according to the embodiment of the present invention has a viscosity of 200 Pa·s or less, as measured using an E-type viscometer at 25°C and a rotation speed of 5 rpm. If it exceeds 200 Pa·s, the bonding thickness of the cured film may become too thick.

[0014] The viscosity measured under conditions of 25°C and 5 rpm is 200 Pa·s or less, preferably 170 Pa·s or less, more preferably 150 Pa·s or less, and even more preferably 100 Pa·s or less, from the viewpoint of reducing the bonding thickness of the cured film. There is no particular limit to the lower limit, but for example, it is 10 Pa·s or more.

[0015] <Thixotropy Index Value> The thermal conductive paste according to the embodiment of the present invention has a thixotropy index value (T.I) of 5.0 or less, which is expressed as the ratio (viscosity at 1 rpm / viscosity at 5 rpm) of the viscosity of the thermal conductive paste measured at 25°C and 1 rpm using an E-type viscometer. If the T.I exceeds 5.0, the bonding film thickness of the cured film may become thicker.

[0016] The T.I. is 5.0 or less, preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.5 or less, from the viewpoint of reducing the bonding thickness of the cured film. There is no particular lower limit, but for example, it is 1.0 or more.

[0017] The viscosity and T.I of the thermally conductive paste can be brought within a predetermined range by setting the composition of the thermally conductive paste and the amounts of each component within the preferred range described below. In particular, (B) setting the type and amount of thermosetting resin within the preferred range described below, and adding preferred additive components such as oleic acid, etc.

[0018] <(A) Metal Particles> The heat-conductive paste according to the embodiment of the present invention contains (A) metal particles (hereinafter also referred to as (A) component) to impart heat conductivity. Examples of metals for the metal particles include silver (Ag), gold (Au), copper (Cu), nickel (Ni), palladium (Pd), platinum (Pt), tin (Sn), and alloys thereof, and silver is preferred from the viewpoint of improving heat conductivity. Silver-containing particles are preferred as metal particles, and examples of silver-containing particles include general silver particles, silver-coated particles obtained by coating the surface of copper particles with silver, and alloys containing silver. From the viewpoint of improving the heat conductivity of the heat-conductive paste, it is preferable to use silver particles containing 50 parts by mass or more of silver per 100 parts by mass of metal particles.

[0019] (A) The content of metal particles is 80% by mass or more of the total amount of thermal conductive paste. If it is less than 80% by mass, the thermal conductivity of the cured film may be insufficient. (A) The content of metal particles is 80% by mass or more of the total amount of thermal conductive paste, preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The upper limit of the content may be, for example, 99% by mass or less.

[0020] - (A1) Metal particles with an average particle diameter of 10.0 μm or more. Component (A) preferably contains metal particles with an average particle diameter of 10.0 μm or more (hereinafter also referred to as component (A1)). Including component (A1) makes it easier to form heat conduction paths in the film thickness direction in the cured film, thereby improving the thermal conductivity.

[0021] The average particle diameter of component (A1) is preferably 10.0 µm or more, more preferably 11.0 µm or more, and still more preferably 13.0 µm or more. In addition, the upper limit of the average particle diameter of component (A1) can be appropriately selected depending on the application of the thermally conductive paste, and is preferably not more than the film thickness required for the cured film, and may be, for example, 100 µm or less, 70 µm or less, or 50 µm or less.

[0022] In addition, the average particle diameter of (A) metal particles is the 50% cumulative diameter measured by a laser diffraction particle size analyzer.

[0023] Component (A1) may have a shape such as a spherical shape, an elliptical spherical shape, a needle shape, a flake (scale) shape, an irregular shape, or the like. From the viewpoint of facilitating formation of a heat conduction path in the film thickness direction of the cured film and further improving the thermal conductivity, a spherical shape is preferred. When component (A1) is flake-shaped or irregularly shaped, the metal particles coordinate in the horizontal direction of the cured film, which may reduce the thermal conductivity in the film thickness direction of the cured film.

[0024] For component (A1), the surface area per mass measured by the BET method (BET specific surface area) is 1.0 m ２ / g or less, preferably 0.9 m ２ / g or less, more preferably 0.8 m ２ / g or less, even more preferably. If the BET specific surface area is not more than the above value, it is preferable because the viscosity and T.I. of the thermally conductive paste can be easily reduced. The lower limit of the BET specific surface area is not particularly limited, and for example, it is preferably 0.01 m ２ / g or more, more preferably 0.02 m ２ / g or more, still more preferably 0.03 m ２ / g or more. The BET specific surface area of component (A1) is preferably 0.01 to 1.0 m ２ / g, more preferably 0.02 to 0.9 m ２ / g, still more preferably 0.03 to 0.8 m ２It is even more preferable that the amount is / g. Furthermore, component (A1) may be metal particles surface-treated with an organic component. By using surface-treated metal particles, the viscosity and thixotropy index value of the thermally conductive paste can be reduced.

[0025] (A1) Commercially available products can be used as components. Specifically, silver particles manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd. (product name: AG-HWQ_15UM, average particle size 14.0 μm, spherical) can be used.

[0026] (A1) One component may be used alone, or two or more components may be used in combination.

[0027] From the viewpoint of improving thermal conductivity, component (A1) is preferably present in amounts of 50 parts by mass or more, more preferably 75 parts by mass or more, and even more preferably 80 parts by mass or more, per 100 parts by mass of component (A). As an upper limit, 100 parts by mass, i.e., the entire amount of component (A), may be component (A1), but it is preferably 95 parts by mass or less, and more preferably 90 parts by mass or less.

[0028] - (A2) Metal particles with an average particle diameter of 1.0 μm or more and less than 10.0 μm. Component (A) preferably further contains, in addition to component (A1), metal particles with an average particle diameter of 1.0 μm or more and less than 10.0 μm (hereinafter also referred to as component (A2)). By including component (A2), the metal particles in the cured film can be densely packed, further improving the thermal conductivity.

[0029] The average particle size of component (A2) is preferably 1.0 μm or larger, preferably 1.5 μm or larger, and more preferably 2.0 μm or larger, from the viewpoint of improving thermal conductivity. Furthermore, since a smaller particle size for component (A2) allows for a higher packing rate, the average particle size of component (A2) is preferably less than 10.0 μm, preferably 6.0 μm or smaller, and more preferably 4.0 μm or smaller, from the viewpoint of high packing rate.

[0030] As the component (A2), commercially available products may also be used. Specifically, silver particles manufactured by DOWA Electronics Co., Ltd. (product name: AG4-8-F, average particle diameter 2.0 μm, spherical shape), (product name: FA182, average particle diameter 2.1 μm, flake shape), etc. can be used.

[0031] As the component (A2), only one type may be used, or two or more types may be used in combination. Furthermore, the component (A2) may be metal particles surface-treated with an organic component. By using surface-treated metal particles, the viscosity and thixotropic index value of the thermally conductive paste can be lowered.

[0032] As the component (A2), those having shapes such as spherical, elliptical spherical, acicular, flake (scale-like), irregular shape, etc. can be used, but it is preferable that the component (A2) includes at least one of "(A2a) spherical metal particles" and "(A2b) flake-shaped metal particles". By including "(A2a) spherical metal particles", it becomes easier to form heat conduction paths in the film thickness direction in the cured film, and the thermal conductivity can be further improved. In addition, by including "(A2b) flake-shaped metal particles", the flake-shaped metal particles are aligned in the horizontal direction of the cured film in the thermally conductive paste, whereby the bonding film thickness can be reduced. More preferably, it is preferable to include both "(A2a) spherical metal particles" and "(A2b) flake-shaped metal particles". By using spherical particles and flake-shaped particles in combination as relatively small-diameter metal particles, it becomes easier to form heat conduction paths in the film thickness direction in the cured film, the thermal conductivity can be improved, and the bonding film thickness of the cured film can be made relatively thin. In the case where both "(A2a) spherical metal particles" and "(A2b) flake-shaped metal particles" are included, it is preferable that "(A2a) spherical metal particles" are contained in a larger amount than "(A2b) flake-shaped metal particles" from the viewpoint of thermal conductivity.

[0033] From the viewpoint of improving thermal conductivity, the component (A2) is preferably blended such that the mass ratio of component (A1) / component (A2) is 70 / 30 to 95 / 5, more preferably 75 / 25 to 90 / 10, and even more preferably 80 / 20 to 85 / 15.

[0034] <(B) Thermosetting Resin> The thermally conductive paste according to an embodiment of the present invention contains (B) a thermosetting resin (hereinafter also referred to as component (B)). The thermosetting resin can be selected from known materials, for example, epoxy resins, urethane resins, vinyl ester resins, silicone resins, phenol resins, urea resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, polyimide resins, etc. can be used. Among these, it is preferable to contain (B1) an epoxy resin.

[0035] (B1) Examples of (B1) epoxy resins include cresol novolac epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, aminophenol epoxy resins, aromatic amine epoxy resins, naphthalene epoxy resins, hydrogenated bisphenol epoxy resins, alicyclic epoxy resins, alcohol ether epoxy resins, cycloaliphatic epoxy resins, fluorene epoxy resins, siloxane-based epoxy resins, etc. Two or more of these may be mixed and used.

[0036] As (B1) the epoxy resin, from the viewpoint of making the cured product have low elasticity, it is preferable to use an epoxy resin having a flexible skeleton. By using an epoxy resin having a flexible skeleton and reducing the elasticity, it is possible to reduce the occurrence of problems such as peeling of the cured film caused by warping generated due to the difference in thermal expansion coefficients between constituent members.

[0037] Examples of epoxy resins having a flexible skeleton include those containing a flexible skeleton such as a polyethylene glycol skeleton, polypropylene glycol skeleton, polyether skeleton, urethane skeleton, polybutadiene skeleton, or nitrile rubber skeleton in a part of the molecule.

[0038] More specifically, epoxy resins with a flexible skeleton include: "epoxy resin compounds in which an aromatic dihydroxy compound and polyalkylene glycol are bonded and have epoxy groups at the ends," obtained by reacting aromatic dihydroxy compounds such as bisphenol A with alkylene oxides such as ethylene oxide and propylene oxide to synthesize compounds having a polyalkylene glycol skeleton, and further epoxidizing the ends of the compounds having a polyalkylene glycol skeleton; "epoxy resin compounds in which an aromatic dihydroxy compound and polyalkylene glycol are bonded and have epoxy groups at the ends," obtained by epoxidizing alkanediols such as propanediol and butanediol, or polyalkylene glycols such as diethylene glycol and polypropylene glycol, and further reacting them with aromatic dihydroxy compounds such as bisphenol A, and epoxidizing the product; and divinyl Examples include epoxy resin compounds having an epoxy group at the terminal end, obtained by diglycidyl etherification of an aliphatic or aromatic skeleton, or by bonding an aromatic dihydroxy compound to an alkanediol or polyalkylene glycol; epoxy resin compounds having an aliphatic skeleton obtained by reacting an aliphatic dicarboxylic acid such as dimer acid or sebacic acid with bisphenol A epoxy resin or other epoxidizing agents; epoxy resin compounds having a polyalkylene glycol structure with an epoxy group at the terminal end, obtained by epoxidizing the terminal end of a polyalkylene glycol such as propylene oxide; and epoxy resin compounds having a polyalkylene oxide structure obtained by diglycidyl etherification of alkylene oxide-modified diol compounds obtained from various diol compounds and various cyclic ether compounds such as ethylene oxide, propylene oxide, tetrahydrofuran, ethyl glycidyl ether, propyl glycidyl ether, and butyl glycidyl ether.In other words, it is preferable that the epoxy resin having a flexible skeleton includes at least one selected from epoxy resins having an aliphatic skeleton, epoxy resins having a polyalkylene glycol structure, and epoxy resins having a polyalkylene oxide structure.

[0039] Among these, it is preferable to use at least one selected from epoxy resins having an aliphatic skeleton, epoxy resins having a polyalkylene glycol structure, and epoxy resins having a polyalkylene oxide structure. That is, it is preferable that the (B1) epoxy resin contains at least one selected from epoxy resins having an aliphatic skeleton, epoxy resins having a polyalkylene glycol structure, and epoxy resins having a polyalkylene oxide structure. The epoxy resin having an aliphatic skeleton may be of the linear aliphatic type or the cyclic aliphatic type, but from the viewpoint of flexibility, linear aliphatic epoxy resins are preferred.

[0040] As the epoxy resin having an aliphatic skeleton, any known aliphatic epoxy resin can be used, and there are no particular limitations. Specific examples of epoxy resins having an aliphatic skeleton include monofunctional aliphatic epoxy resins having one epoxy group in the molecule, such as alkyl alcohol glycidyl ethers [butyl glycidyl ether, 2-ethylhexyl glycidyl ether, etc.] and alkenyl alcohol glycidyl ethers [vinyl glycidyl ether, allyl glycidyl ether, etc.]; difunctional aliphatic epoxy resins having two epoxy groups in the molecule, such as alkylene glycol diglycidyl ether, poly(alkylene glycol) diglycidyl ether, and alkenylene glycol diglycidyl ether; and polyfunctional aliphatic epoxy resins having three or more epoxy groups in the molecule, such as trimethylolpropane, pentaerythritol, dipentaerythritol, and other trifunctional or higher alcohol polyglycidyl ethers [trimethylolpropane triglycidyl ether, pentaerythritol (tri or tetra) glycidyl ether, dipentaerythritol (tri, tetra, penta or hexa) glycidyl ether, etc.].

[0041] Commercially available epoxy resins with a flexible skeleton can also be used. Examples of commercially available products include aliphatic epoxy resin from Mitsubishi Chemical Corporation (product number: YX-7400), glycidyl ether type epoxy resin from Asahi Kasei Corporation (product number: AER9000), and bisphenol A-propylene oxide modified glycidyl ether type epoxy resin from ADEKA Corporation (product number: EP-4000S).

[0042] The content of the epoxy resin having a flexible skeleton is preferably 50% by mass or more, and more preferably 60% by mass or more, relative to the total amount of the epoxy resin (B1), from the viewpoint of reducing the bonding thickness of the cured film. The upper limit of the content may be 100% by mass or 99% by mass or less.

[0043] (B1) In addition to the epoxy resin having a flexible skeleton as described above, it is also preferable to use other epoxy resins in combination. For example, from the viewpoint of further suppressing peeling in reliability tests, it is preferable that the (B1) epoxy resin includes an epoxy resin having a rigid structure such as naphthalene or a biphenyl skeleton, and it is more preferable that it includes an epoxy resin having a naphthalene skeleton. Since epoxy resins having a naphthalene skeleton (naphthalene skeleton epoxy resins) have a moderately rigid structure, it is thought that thermal shrinkage is suppressed, reflow resistance is improved, and peeling in reliability tests can be further suppressed. From the viewpoint of balancing coatability and reliability, the epoxy resin having a rigid structure such as naphthalene or a biphenyl skeleton is preferably 1.0% by mass or more, and more preferably 2.0% by mass or more, relative to the total amount of the (B1) epoxy resin. Furthermore, the upper limit of the content may be 10.0% by mass or less, or 8.0% by mass or less.

[0044] (B1) The epoxy equivalent of the epoxy resin is not particularly limited, but from the viewpoint of lowering the viscosity and T.I of the thermally conductive paste, it is preferably 50 to 500 g / eq, more preferably 60 to 400 g / eq, and even more preferably 70 to 200 g / eq.

[0045] Furthermore, if the epoxy equivalent is small, the wettability with (A) metal particles improves, which can inhibit heat conduction between (A) metal particles in the cured product of the thermally conductive paste, potentially increasing the thermal resistance. Therefore, from the viewpoint of suppressing the increase in thermal resistance, it is preferable that the epoxy equivalent of (B1) epoxy resin be 50 g / eq or more. More preferably, it is 60 g / eq or more, and even more preferably 70 g / eq or more. The upper limit is preferably 500 g / eq or less, more preferably 400 g / eq or less, and even more preferably 200 g / eq or less.

[0046] Furthermore, (B1) epoxy resin preferably contains an epoxy resin that is liquid at room temperature (25°C) from the viewpoint of keeping the viscosity and T.I of the thermal conductive paste below predetermined values ​​and reducing the bonding thickness of the cured film. When multiple epoxy resins are used in combination, (B1) epoxy resin preferably contains 50% by mass or more of the epoxy resin that is liquid at room temperature (25°C) relative to the total amount of (B1) epoxy resin, more preferably 60% by mass or more, and even more preferably 70% by mass or more. Furthermore, from the viewpoint of keeping the viscosity and T.I of the thermal conductive paste below predetermined values ​​and reducing the bonding thickness of the cured film, the epoxy resin that is liquid at room temperature (25°C) preferably contains an epoxy resin with a viscosity of 50,000 mPa·s or less, measured with an HBT viscometer at 25°C and a rotation speed of 50 rpm, more preferably 10,000 mPa·s or less, and even more preferably 2,000 mPa·s or less. While there is no particular lower limit, it is preferable that the viscosity be 10 mPa·s or higher. By setting the viscosity of the epoxy resin within the above range, even if the thermal conductive paste contains substantially no solvent as described later, the viscosity and T.I of the thermal conductive paste can be kept below a predetermined value, and the bonding thickness of the cured film can be reduced.

[0047] (B) The content of the thermosetting resin is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 parts by mass or more, per 100 parts by mass of the metal particles (A). Also, it is preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. (B) The content of the thermosetting resin is preferably 1.0 to 10.0 parts by mass, more preferably 2.0 to 8.0 parts by mass, and even more preferably 3.0 to 6.0 parts by mass, per 100 parts by mass of the metal particles (A). By setting the content within the above range, a thermoconductive paste can be obtained that provides a cured film with high thermal conductivity and a small bonding thickness.

[0048] (B) The content of the thermosetting resin is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more, based on the total amount of the thermal conductive paste. Furthermore, the upper limit is preferably 10.0% by mass or less, more preferably 8.0% by mass or less, and even more preferably 6.0% by mass or less. (B) The content of the thermosetting resin is preferably 1.0 to 10.0% by mass, more preferably 2.0 to 8.0% by mass, and even more preferably 3.0 to 6.0% by mass, based on the total amount of the thermal conductive paste. By setting the content within the above range, a thermal conductive paste can be obtained that provides a cured film with high thermal conductivity and a small bonding thickness.

[0049] <At least one component selected from the group consisting of (C) curing agent and (D) curing accelerator> The thermal conductive paste according to the embodiment of the present invention contains at least one component selected from the group consisting of (C) curing agent and (D) curing accelerator as a component for curing the (B) thermosetting resin described above. That is, either the curing agent or the curing accelerator may be used alone, or both may be used in combination. ((C) curing agent) The (C) curing agent is not particularly limited as long as it cures the (B) thermosetting resin, and for example, a cationic polymerization initiator, a phenolic curing agent, an amine-based curing agent such as an aliphatic amine or aromatic amine, or an acid anhydride curing agent can be used.

[0050] Examples of phenolic curing agents that can be used include bisphenols and their derivatives such as bisphenol F, bisphenol A, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetramethylbisphenol S, dihydroxydiphenyl ether, dihydroxybenzophenone, tetramethylbiphenol, ethylidenebisphenol, methylethylidenebis(methylphenol), cyclohexylidenebisphenol, and biphenol; trifunctional phenols and their derivatives such as tri(hydroxyphenyl)methane and tri(hydroxyphenyl)ethane; compounds obtained by reacting phenols such as phenol novolac and cresol novolac with formaldehyde; and their derivatives.

[0051] As aliphatic amines, aliphatic polyamines such as diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, trimethylhexamethylenediamine, m-xylenediamine, and 2-methylpentamethylenediamine can be used; alicyclic polyamines such as isophoronediamine, 1,3-bisaminomethylcyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, and 1,2-diaminocyclohexane can be used; and piperazine-type polyamines such as N-aminoethylpiperazine and 1,4-bis(2-amino-2-methylpropyl)piperazine can be used. As aromatic amines, aromatic polyamines such as diaminodiphenylmethane, m-phenylenediamine, diaminodiphenylsulfone, diethyltoluenediamine, trimethylenebis(4-aminobenzoate), and polytetramethyleneoxide-di-p-aminobenzoate can be used.

[0052] Examples of acid anhydride-based curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, dodecenyl succinic anhydride, a reaction product of maleic anhydride and polybutadiene, and a copolymer of maleic anhydride and styrene.

[0053] Commercially available curing agents can also be used. Specifically, phenolic curing agents from Meiwa Kasei Co., Ltd. (product names: MEH8005, MEH8000H, allylphenol resin), phenolic curing agents from Gun-ei Chemical Industry Co., Ltd. (product name: PSM4324), amine curing agents from ALBEMARL Co., Ltd. (containing 3,5-diethyltoluene-2,4-diamine and 3,5-diethyltoluene-2,6-diamine) (product names: Etacure 100, Etacure 100 Plus), amine curing agents from Nippon Kayaku Co., Ltd. (4,4'-diamino-3,3'-diethyldiphenylmethane) (product name: Kayahard AA), and acid anhydride curing agents from Mitsubishi Chemical Corporation (product name: YH307) can be used.

[0054] These hardening agents may be used individually or in combination of two or more types.

[0055] The curing agent preferably contains a phenolic curing agent from the viewpoint of suppressing peeling in reliability tests, and more preferably uses both a phenolic curing agent and an amine curing agent in combination.

[0056] (C) The mixing ratio of the curing agent to (B) the thermosetting resin can be the same as when these curing agents are normally used. From the viewpoint of the curing action of (B) the thermosetting resin, preferably it is 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of (B) the thermosetting resin. Furthermore, the upper limit is preferably 30 parts by mass or less, and more preferably 15 parts by mass or less.

[0057] (D) Curing accelerator The thermal conductive paste according to the embodiment of the present invention may contain (D) a curing accelerator, to the extent that it does not impair the effects of the present invention. For example, an imidazole-based curing accelerator can be used as (D) a curing accelerator. Among these, it is preferable to use an imidazole-based curing accelerator.

[0058] The imidazole-based curing accelerator is not particularly limited and includes 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxyimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl- 2-Undecylimidazole, 1-Cyanoethyl-2-ethyl-4-methylimidazole, 1-Cyanoethyl-2-phenylimidazole, 1-Cyanoethyl-2-undecylimidazolium trimellitate, 1-Cyanoethyl-2-phenylimidazolium trimellitate, 2,4-Diamino-6-[2'-Methylimidazolyl-(1')]-Ethyl-s-triazine, 2,4-Diamino-6-[2'-Methylimidazolyl-( 1') ]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adduct, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5- Examples include hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, epoxy-phenol-boric acid ester compounds, and the like.

[0059] When the thermally conductive paste according to the embodiment of the present invention contains (D) a curing accelerator, the blending ratio of (D) the curing accelerator to (B) the thermosetting resin can be the same as when these curing accelerators are normally used. From the viewpoint of the curing action of (B) the thermosetting resin, preferably, the ratio is 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 parts by mass or more, per 100 parts by mass of (B) the thermosetting resin. Furthermore, the upper limit is preferably 10.0 parts by mass or less, and more preferably 9.0 parts by mass or less.

[0060] The thermally conductive paste according to the embodiment of the present invention may contain additives in addition to at least one component selected from the group consisting of (A) metal particles, (B) thermosetting resin, (C) curing agent, and (D) curing accelerator. Examples of additives include (E) thermoplastic resin and (F) solvent.

[0061] <(E) Thermoplastic Resin> The thermally conductive paste according to the embodiment of the present invention may contain (E) thermoplastic resin, to the extent that it does not impair the effects of the present invention. Examples of (E) thermoplastic resin include phenoxy resin, polyurethane resin, polystyrene resin, acrylic resin, polycarbonate resin, polyamide resin, polyamide-imide resin, thermoplastic elastomer, etc. Among these, phenoxy resin is preferred from the viewpoint of improving reflow resistance and suppressing peeling in reliability tests.

[0062] When the thermally conductive paste according to the embodiment of the present invention contains (E) a thermoplastic resin, the content of (E) the thermoplastic resin is preferably 0.01 to 0.20% by mass relative to the total amount of the thermally conductive paste.

[0063] <(F) Solvent> The thermally conductive paste according to the embodiment of the present invention may contain a solvent from the viewpoint of applicability. Examples of solvents include organic compounds having a hydroxyl group and a boiling point of 180 to 265°C, such as terpineol, dihydroterpineol, benzyl alcohol, 2-phenylethyl alcohol, butyl carbitol, butyl carbitol acetate, 2-ethyl-1,3-hexanediol, and texanol. Among these, dihydroterpineol, benzyl alcohol, and butyl carbitol acetate are preferred.

[0064] On the other hand, in the embodiment of the present invention, it is preferable that the thermally conductive paste substantially does not contain (F) solvent, from the viewpoint of reducing voids during heat curing of the thermally conductive paste or during heating of the cured product such as reflow treatment. If voids occur, the thermal conductivity and reliability may deteriorate. In this specification, "substantially solvent-free" means that no solvent is intentionally added to the thermally conductive paste. The (A) metal particles or (B) thermosetting resin contained in the thermally conductive paste may already contain (F) solvent. Since it is difficult to remove the (F) solvent contained in the (A) metal particles or (B) thermosetting resin used in the thermally conductive paste, the solvent that is inevitably contained in the (A) metal particles or (B) thermosetting resin may also be contained in the thermally conductive paste.

[0065] Specifically, a thermally conductive paste being substantially solvent-free means that the amount of solvent contained in the thermally conductive paste is less than 5% by mass of the total amount of the thermally conductive paste, and may be 3% by mass or less, 2% by mass or less, or 1% by mass or less.

[0066] <Other Additives> The thermally conductive paste according to the embodiment of the present invention may further contain other additives such as fatty acids, titanate coupling agents, antioxidants, flame retardants, dispersants, surfactants, leveling agents, thixotropic agents, defoaming agents, and ion scavenging agents. In particular, from the viewpoint of reducing the viscosity and T.I. of the thermally conductive paste, it is preferable to contain at least one of fatty acids and titanate coupling agents, and more preferable to contain fatty acids and titanate coupling agents.

[0067] Examples of fatty acids include high- and intermediate fatty acids. High-grade fatty acids are fatty acids with 15 or more carbon atoms, and include straight-chain saturated fatty acids such as pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid, octadecanoic acid (stearic acid), 12-hydroxyoctadecanoic acid (12-hydroxystearic acid), eicosanoic acid (arachidic acid), docosanoic acid (behenic acid), tetracosanoic acid (lignoceric acid), hexacosanoic acid (cerotic acid), and octacosanoic acid (montanic acid); branched-chain saturated fatty acids such as 2-pentylnonanoic acid, 2-hexyldecanoic acid, 2-heptyldodecanoic acid, and isostearic acid; and unsaturated fatty acids such as palmitoleic acid, oleic acid, isoleic acid, elaidic acid, linoleic acid, linolenic acid, ricinoleic acid, gadolenic acid, erucic acid, and seracolleic acid. Intermediate fatty acids are fatty acids with 6 to 14 carbon atoms, and examples include straight-chain saturated fatty acids such as hexanoic acid (caproic acid), heptanoic acid, octanoic acid (caprylic acid), nonanoic acid (pelargonic acid), decanoic acid (capric acid), undecanoic acid, dodecanoic acid (lauric acid), tridecanoic acid, and tetradecanoic acid (myristic acid); branched-chain saturated fatty acids such as isohexanoic acid, isoheptanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, 2-propylheptanoic acid, isodecanoic acid, isoundecanoic acid, 2-butyloctanoic acid, isododecanoic acid, and isotridecanoic acid; and unsaturated fatty acids such as 10-undecenoic acid. Among these, higher fatty acids are preferred, and oleic acid is more preferred.

[0068] The thermally conductive paste according to the embodiment of the present invention preferably further contains oleic acid.

[0069] Examples of titanate coupling agents include isopropyltriisostearoyl titanate, isopropyltris(dioctyl pyrophosphate) titanate, isopropyltri(N-aminoethyl-aminoethyl) titanate, tetraoctylbis(ditridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl phosphite) titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, and bis(dioctyl Examples of titanate coupling agents include pyrophosphate ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacrylate isostearoyl titanate, isopropyl toridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacrylic titanate, isopropyl tri(dioctyl phosphate) titanate, isopropyl tricumylphenyl titanate, and tetraisopropyl bis(dioctyl phosphite) titanate.

[0070] If the thermally conductive paste according to the embodiment of the present invention contains other additives, the content of the other additives is preferably 0.01 to 0.5% by mass relative to the total amount of the thermally conductive paste.

[0071] <Method for Manufacturing Thermally Conductive Paste> The method for manufacturing the thermally conductive paste according to the embodiment of the present invention is not particularly limited, and the paste can be manufactured by putting each component in a predetermined proportion into a mixer such as a meteorite agitator, dissolver, bead mill, raika mill, pot mill, three-roll mill, rotary mixer, twin-screw mixer, etc., and mixing them.

[0072] In the embodiment of the present invention, the heat-conductive paste preferably has a heat conductivity λ in the thickness direction at 25°C of the cured film obtained by heating at 180°C for 60 minutes, which is 40 W / m·K or more. A heat conductivity λ of 40 W / m·K or more indicates high heat conductivity. A heat conductivity λ of 50 W / m·K or more is more preferable, and a heat conductivity λ of 60 W / m·K or more is even more preferable. There is no particular upper limit to the heat conductivity λ, but for example, it is 200 W / m·K or less.

[0073] The thermal conductivity λ can be calculated as follows. First, the thermal diffusivity α in the thickness direction of the cured film obtained using the laser flash method is measured at 25°C. Next, the specific heat Cp of the cured film is measured by differential scanning calorimetry (DSC). Furthermore, the density ρ of the cured film is measured in accordance with JIS K 6911. Using these values, the thermal conductivity λ is calculated based on the following equation (1): Thermal conductivity λ [W / (m·K)] = α [m ２ / sec]×Cp[J / kg・K]×ρ[g / cm ３ ]...(1)

[0074] The heat-conductive paste according to the embodiment of the present invention can be suitably used for large-area bonding because its cured product can withstand reliability tests such as heat cycle tests. For example, the bonding area can be 400 mm². ２ It may be greater than or equal to 900 mm ２ The above is also acceptable. When large-area bonding is performed with a thermally conductive paste, warping and other issues tend to occur, especially due to differences in the coefficients of thermal expansion between the constituent members. However, the thermally conductive paste according to the embodiment of the present invention has low elasticity, even when bonding large areas, and can suppress delamination in reliability tests. The thermally conductive paste according to the embodiment of the present invention is 900 mm ２ It is preferable to use this for joining large areas as described above.

[0075] [Cured product of thermally conductive paste] This disclosure also relates to a cured product of a thermally conductive paste according to an embodiment of the present invention. The thermally conductive paste according to an embodiment of the present invention can be printed or applied to a desired portion of a substrate or the like by a conventionally known method such as screen printing, and then heated to a predetermined temperature to form a cured product. The heating temperature of the thermally conductive paste can be 120 to 300°C, preferably 150 to 250°C, and more preferably 180 to 210°C. The heating time can be appropriately changed depending on the heating temperature, but for example it can be 15 to 120 minutes, preferably 30 to 90 minutes. The heating of the thermally conductive paste may be carried out while applying pressure as appropriate. For example, it may be carried out while applying pressure of 0.1 to 1.0 MPa in the thickness direction of the thermally conductive paste.

[0076] The thickness of the cured product may be, for example, 500 μm or less, 300 μm or less, 150 μm or less, 100 μm or less, or 50 μm or less, from the viewpoint of reducing thermal resistance. Furthermore, there is no particular lower limit to the thickness of the cured product, but for example, it is 10.0 μm or more.

[0077] [Semiconductor Device] This disclosure also relates to a semiconductor device comprising a cured product of a thermally conductive paste according to an embodiment of the present invention. The cured film obtained by curing the thermally conductive paste according to an embodiment of the present invention has high thermal conductivity and a small bonding thickness, making it suitable for bonding components together in a semiconductor device.

[0078] For example, a semiconductor device comprising a semiconductor element, a cured film of a thermally conductive paste according to an embodiment of the present invention, and a lid in this order, wherein the semiconductor element and the lid are joined by the cured film. In this case, the thickness of the cured film is preferably 150 μm or less, and more preferably 100 μm or less, from the viewpoint of reducing thermal resistance. The lower limit of the thickness is, for example, 10 μm.

[0079] Another example is a semiconductor device comprising, for instance, a lid, a cured film of a thermally conductive paste according to an embodiment of the present invention, and a heat sink in this order, wherein the lid and the heat sink are joined by the cured film. In this case, the thickness of the cured film is preferably 150 μm or less, and more preferably 100 μm or less, from the viewpoint of reducing thermal resistance. The lower limit of the thickness is, for example, 10 μm.

[0080] The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples.

[0081] The following raw materials were used to prepare the thermally conductive pastes of the examples and comparative examples.

[0082] (A) Component (metal particles) The following a1 to a3 shown in Table 1 were used.

[0083]

[0084] (A) The average particle size of the metal particles was defined as the 50% cumulative diameter measured with a laser diffraction particle size analyzer (product name: Microtrac MT3000II, manufactured by Microtrac Bell Co., Ltd.).

[0085] (A) Surface area per unit mass (BET specific surface area) (m²) of metal particles measured by the BET method ２ The specific surface area ( / g) was measured using a fully automated specific surface area analyzer, Macsoeb (manufactured by MOUNTEC Corporation). After pre-drying at 100°C and flowing nitrogen gas for 10 minutes, the measurement was performed using the BET single-point method by nitrogen gas adsorption.

[0086] (B) Component (Thermosetting Resin) b1: Aliphatic epoxy resin (Product code: YX-7400, manufactured by Mitsubishi Chemical Corporation, viscosity 200 mPa·s) Epoxy equivalent 270 g / eq. b2: Naphthalene skeleton epoxy resin (Product code: HP-4710, manufactured by DIC Corporation, solid) Epoxy equivalent 170 g / eq. b3: Aminophenol type epoxy resin (Product code: 630D, manufactured by Mitsubishi Chemical Corporation, viscosity 750 mPa·s) Epoxy equivalent 90 g / eq. b4: Epoxy resin in which a polyalkylene oxide structure is added to the epoxy resin and bisphenol A skeleton (Product code: AER9000, manufactured by Asahi Kasei Corporation, viscosity 900 mPa·s) Epoxy equivalent 380 g / eq.

[0087] The viscosity of the resin is shown as measured using a Brookfield HBT viscometer at 25°C and 50 rpm.

[0088] The structural formulas for b1, b2, and b4 are shown below.

[0089]

[0090] [In general formula (b1), n ​​is an integer between 1 and 15.]

[0091]

[0092]

[0093] [R in general formula (b4)] ２０ is a glycidyl group, R ２１ and R ２２ These are methyl groups, R ２３ The propylene group (-CH ２ -CH(CH ３ )-,-CH(CH ３ ) - CH ２ -), n21 is an integer between 1 and 15, and n22 is an integer between 1 and 15.

[0094] (C) Hardener c1: Amine-based hardener (Product code: Kayahard AA, manufactured by Nippon Kayaku Co., Ltd.) c2: Phenolic hardener (Product code: MEH8000H, manufactured by Meiwa Kasei Co., Ltd.)

[0095] (D) Curing accelerator (curing catalyst) d1: 2-ethyl-4-methylimidazole (Catalog number: 2E4MZ, manufactured by Shikoku Chemicals Co., Ltd.) d2: 2-phenyl-4-methyl-5-hydroxymethylimidazole (Catalog number: 2P4MHZ_PW, manufactured by Shikoku Chemicals Co., Ltd.)

[0096] (E) Thermoplastic resin e1: Phenoxy resin (Product code: PKHH, manufactured by Gabriel)

[0097] (G) Other additives g1: Titanate coupling agent (product code: KR46B, manufactured by Ajinomoto Fine Techno Co., Ltd.) g2: Oleic acid (manufactured by Wako Pure Chemical Industries, Ltd.)

[0098] [Examples 1-12, Comparative Examples 1-2] A thermally conductive paste was produced by mixing and dispersing each raw material using a roll mill to achieve the blending ratios shown in Tables 2-3 below. The thermally conductive pastes of Examples 1-12 and Comparative Examples 1-2 were substantially solvent-free. In Tables 2-3, the values ​​for each raw material represent parts by mass.

[0099] [Evaluation] <Measurement of Thermal Conductivity> The obtained thermal conductive paste was applied to a copper substrate to form a coating film, and a 10 mm x 10 mm silicon chip was placed on top of the coating film. Then, the film was heat-treated at 180°C for 60 minutes while applying a pressure of 0.2 MPa in the thickness direction to cure it, and a cured film with a thickness of 50 μm was obtained. The thermal conductive paste was cured in the above manner, and the silicon chip was bonded to the substrate. Next, the thermal diffusion coefficient α in the thickness direction of the heat-treated body was measured by the laser flash method. The measurement temperature was 25°C. In addition, the specific heat Cp was measured by differential scanning calorimetry (DSC) measurement. Furthermore, the density ρ was measured in accordance with JIS K 6911. Using these values, the thermal conductivity λ was calculated based on the following formula: Thermal conductivity λ [W / (m·K)] = α [m ２ / sec]×Cp[J / kg・K]×ρ[g / cm ３ ]

[0100] <Viscosity of Thermally Conductive Paste> The viscosity of the thermally conductive paste was measured at 25°C and a rotation speed of 5 rpm using an E-type viscometer (model number: TV-25 (cone plate: No. 6)) manufactured by Toki Sangyo Co., Ltd.

[0101] <Thixotropy Index Value> The viscosity of the thermally conductive paste was measured using an E-type viscometer (model number: TV-25 (cone plate: No. 6)) manufactured by Toki Sangyo Co., Ltd. at 25°C, 1 rpm and 25°C, 5 rpm. Using these measurements, the thixotropic index value (T.I.), expressed as viscosity at 1 rpm / viscosity at 5 rpm, was calculated.

[0102] <Bonding Film Thickness (BLT)> The obtained thermally conductive paste was applied to a copper substrate to form a coating film, and a 10 x 10 mm silicon chip was placed on top of the coating film. Then, the film was heat-treated at 180°C for 60 minutes while applying pressure of 0.2 MPa in the thickness direction to cure it. The thickness of the cured material was measured using a micrometer (Mitutoyo Co., Ltd., part number MDC-25MJ), and the BLT was calculated by subtracting the previously measured silicon chip and copper substrate thicknesses, and evaluated according to the following criteria: ○ (Excellent): Bonding film thickness (BLT) of 100 μm or less △ (Good): Bonding film thickness (BLT) of more than 100 μm to 150 μm × (Unacceptable): Bonding film thickness (BLT) of more than 150 μm

[0103] <Measurement of Elastic Modulus> The obtained thermally conductive paste was applied to a glass plate and heat-treated at 180°C for 60 minutes to cure it. This resulted in a cured thermally conductive paste with a film thickness of 0.3 mm. The cured material obtained under the above conditions was peeled off the glass plate and set in a measuring device (Hitachi High-Tech Corporation, model number DMA7100), and dynamic viscoelasticity measurement (DMA) was performed in tensile mode at a frequency of 10 Hz. This allowed for the measurement of the storage modulus E' (GPa) at 25°C.

[0104]

[0105]

[0106] As shown in Tables 2-3, the thermally conductive pastes of Examples 1-12 yielded cured films with high thermal conductivity and small bonding thickness. Furthermore, the thermally conductive pastes of Examples 1-12 also had low elastic modulus, and in all examples, the storage modulus of the cured product was confirmed to be 3.0 GPa. On the other hand, the thermally conductive paste of Comparative Example 1, whose viscosity exceeded a predetermined value, resulted in a larger bonding thickness. Similarly, the thermally conductive paste of Comparative Example 2, whose T.I. exceeded a predetermined value, also resulted in a larger bonding thickness.

[0107] The thermally conductive paste according to an embodiment of the present invention provides a cured film with high thermal conductivity and a small bonding thickness. Furthermore, the present invention provides a thermally conductive paste that provides a cured film with high thermal conductivity and a small bonding thickness (BLT).

[0108] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2025-056612 filed on 28 March 2025, the contents of which are incorporated herein by reference.

Claims

1. A thermally conductive paste comprising (A) metal particles, (B) a thermosetting resin, and at least one component selected from the group consisting of (C) a curing agent and (D) a curing accelerator, wherein the content of (A) metal particles is 80% by mass or more of the total amount of the thermally conductive paste, the viscosity of the thermally conductive paste measured using an E-type viscometer at 25°C and a rotation speed of 5 rpm is 200 Pa·s or less, and the thixotropy index value (T.I), expressed as the ratio of the viscosity of the thermally conductive paste measured using an E-type viscometer at 25°C and a rotation speed of 1 rpm to the viscosity of the thermally conductive paste measured at 25°C and a rotation speed of 5 rpm (viscosity at 1 rpm / viscosity at 5 rpm), is 5.0 or less.

2. The thermally conductive paste according to claim 1, wherein the (A) metal particles include (A1) metal particles with an average particle diameter of 10.0 μm or more.

3. The BET specific surface area of ​​the metal particles with an average particle diameter of 10.0 μm or more (A1) is 1.0 m². ２ The thermally conductive paste according to claim 2, wherein the amount is less than or equal to / g.

4. The thermally conductive paste according to claim 2 or 3, wherein the amount of metal particles (A1) with an average particle diameter of 10.0 μm or more is 50 parts by mass or more per 100 parts by mass of the metal particles (A).

5. The thermally conductive paste according to any one of claims 1 to 4, wherein the (A) metal particles further comprise (A2) metal particles having an average particle diameter of 1.0 μm or more and less than 10.0 μm.

6. The thermally conductive paste according to claim 5, wherein the mass ratio of (A1) metal particles with an average particle diameter of 10.0 μm or more and (A2) metal particles with an average particle diameter of 1.0 μm or more and less than 10.0 μm is 70 / 30 to 95 / 5.

7. The thermally conductive paste according to any one of claims 1 to 6, wherein the (B) thermosetting resin comprises (B1) epoxy resin.

8. The thermally conductive paste according to claim 7, wherein the (B1) epoxy resin comprises an epoxy resin having a flexible skeleton.

9. The thermally conductive paste according to claim 8, wherein the epoxy resin having a flexible skeleton comprises at least one selected from an epoxy resin having an aliphatic skeleton, an epoxy resin having a polyalkylene glycol structure, and an epoxy resin having a polyalkylene oxide structure.

10. The thermally conductive paste according to any one of claims 1 to 9, wherein the content of the thermosetting resin (B) is 1.0 to 10.0 parts by mass per 100 parts by mass of the metal particles (A).

11. The thermally conductive paste according to claim 7 or 8, wherein the (B1) epoxy resin comprises a liquid epoxy resin at room temperature (25°C), and the liquid epoxy resin is present in an amount of 50% by mass or more relative to the total amount of the (B1) epoxy resin.

12. A thermally conductive paste according to any one of claims 1 to 11, which is substantially solvent-free.

13. 400 mm ２ A thermally conductive paste according to any one of claims 1 to 12, used for joining the above-mentioned area.

14. The thermal conductive paste according to any one of claims 1 to 13, wherein the cured film obtained by heating the thermal conductive paste at 180°C for 60 minutes has a thermal conductivity λ in the thickness direction at 25°C of 40 W / m·K or more.

15. A thermally conductive paste according to any one of claims 1 to 14, further comprising oleic acid.

16. A cured product of a thermally conductive paste according to any one of claims 1 to 15.

17. A semiconductor device comprising a cured product of a thermally conductive paste according to any one of claims 1 to 15.

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