JP7479872B2 - Thermally conductive adhesive sheet and semiconductor device - Google Patents

Description

The present invention relates to a thermally conductive adhesive sheet and a semiconductor device.

In recent years, with growing awareness of environmental issues, power semiconductor devices have come to be widely used not only for general industrial and electric railway applications, but also for in-vehicle applications. In particular, for in-vehicle components, making each component smaller and lighter within the limited allowable size directly affects the performance of the vehicle, so reducing the size of power semiconductor devices has become a very important issue. In such semiconductor devices, for example, power semiconductor elements are mounted on the die pad of a DBC (Direct Bonded Copper: registered trademark) substrate via highly heat-resistant, high-lead solder. However, restrictions have been put on the use of harmful substances including lead, and there is a demand for lead-free products.

As a highly heat-resistant lead-free bonding material other than high-lead solder, a bonding method using sintered silver paste that bonds nano-order silver filler at a temperature below its melting point is being considered (see, for example, Patent Document 1). Sintered silver paste has high thermal conductivity and is effective for bonding power semiconductor elements that handle large currents. However, from the perspective of making semiconductor devices smaller and thinner, there is a demand for a sheet material that can be used as a bonding material in a thin layer.

Since the thermal conductivity of solder is generally 30 W/m·K, there is a demand for alternative sheet materials with high thermal conductivity, and such sheet materials are available (see, for example, Patent Document 2).

International Publication No. 2015/151136 JP 2016-536467 A

However, there are few sheet materials with high thermal conductivity on the market. This is because, when a sheet material is made to exhibit thermal conductivity on a par with that of a solder material, the reliability characteristics of tests such as thermal cycle tests may deteriorate as a reaction, and the sheet material described in the above-mentioned Patent Document 2 also has room for improvement. Furthermore, in order to exhibit high thermal conductivity characteristics, the particles contained in the sheet must be sintered at a sintering temperature of 250°C or higher, but considering compatibility with organic substrates, oxidation of the copper substrate, and the heat resistance of surrounding components, sintering at an even lower temperature (200°C or lower) is required.
By the way, a sheet material containing nano-sized silver particles has excellent low-temperature sintering properties, but has a problem with temporary adhesion, and a sheet material containing micro-sized silver particles has a problem with sheet properties. Furthermore, in order to express thermal conductivity using silver particles, it is necessary to lower the viscosity of the resin component, which causes a problem with the tackiness of the sheet material, but if the viscosity is set to a level where the tackiness of the sheet material is not a problem, the temporary adhesion decreases.

The present invention has been made in consideration of these circumstances, and aims to provide a semiconductor device in which a semiconductor element is bonded with a highly thermally conductive adhesive sheet that has excellent temporary adhesive properties and sheetability, and has high thermal conductivity even under low-temperature sintering conditions, resulting in a semiconductor device with excellent reliability.

As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following invention.
The present invention was completed based on these findings.

That is, the present disclosure relates to the following:
[1] A thermally conductive adhesive sheet obtained by forming a resin composition containing (A) silver particles, (B) a thermosetting resin, and (C) a binder resin into a sheet,
The thermally conductive adhesive sheet, wherein the (A) silver particles are secondary particles formed by agglomeration of particles including primary particles having an average particle diameter of 10 to 100 nm.
[2] The thermally conductive adhesive sheet according to the above [1], characterized in that the (A) silver particles have a positive thermal expansion coefficient between 150°C and 300°C.
[3] The thermally conductive adhesive sheet according to the above [1] or [2], wherein the (A) silver particles have a tap density of 4.0 to 7.0 g/ ^cm3 .
[4] The thermally conductive adhesive sheet according to any one of the above [1] to [3], wherein the (A) silver particles have a specific surface area, as determined by the BET method, of 0.5 to 1.5 m ² /g.
[5] The thermally conductive adhesive sheet according to any one of [1] to [4] above, wherein the average particle size of the (A) silver particles is 0.5 to 5.0 μm.
[6] The thermally conductive adhesive sheet according to any one of the above [1] to [5], wherein the (B) thermosetting resin is a liquid or solid material having a softening point of 70° C. or lower.
[7] The (B) thermosetting resin is at least one selected from the group consisting of epoxy resins, cyanate resins, maleimide resins and acrylic resins. The thermally conductive adhesive sheet according to any one of [1] to [6].
[8] The thermally conductive adhesive sheet according to any one of the above [1] to [7], wherein the (C) binder resin has a weight average molecular weight of 200,000 to 1,000,000 and a glass transition temperature of −40° C. to 0° C.
[9] The thermally conductive adhesive sheet according to any one of [1] to [8] above, wherein the total content of the (B) thermosetting resin and the (C) binder resin is 5 to 30 mass% and the content of the (A) silver particles is 30 to 95 mass% relative to the total amount of the resin composition.
[10] The thermally conductive adhesive sheet according to any one of [1] to [9] above, in which the elastic modulus after curing of the resin composition is 3 GPa or less, the glass transition temperature (Tg) is 0°C or less, and the thermal expansion coefficient is 50 ppm/°C or less at -50 to -40°C and 140°C to 150°C.
[11] The thermally conductive adhesive sheet according to any one of [1] to [10] above, wherein the thermal conductivity of the cured product obtained by curing the resin composition at 200° C. or less is 30 W / m · K or more.
[12] A semiconductor device comprising: a support member; a cured product of the thermally conductive adhesive sheet according to any one of [1] to [11] above provided on the support member; and a semiconductor element bonded to the support member via the cured product of the thermally conductive adhesive sheet.

According to the present invention, it is possible to provide a semiconductor device in which a semiconductor element is bonded with a highly thermally conductive adhesive sheet, which has excellent temporary adhesion and sheetability, high thermal conductivity even under low-temperature sintering conditions, and can provide a semiconductor device with excellent reliability.

The present invention will now be described in detail with reference to one embodiment.

<Thermal conductive adhesive sheet>
The thermally conductive adhesive sheet of the present embodiment is obtained by forming a resin composition containing (A) silver particles, (B) a thermosetting resin, and (C) a binder resin into a sheet, and is characterized in that the (A) silver particles are composed of secondary particles formed by agglomeration of particles including primary particles having an average particle diameter of 10 to 100 nm.

[(A) Silver Particles]
The (A) silver particles are composed of secondary particles formed by agglomeration of particles including primary particles having an average particle diameter of 10 to 100 nm. The (A) silver particles may be silver particles composed of secondary particles formed by agglomeration of primary particles having the above average particle diameter, or may be silver particles composed of secondary particles formed by agglomeration of particles including primary particles having the above average particle diameter and particles having an average particle diameter larger than the above average particle diameter.
If the average particle size of the primary particles is less than 10 nm, the specific surface area increases and the sheet may become brittle, whereas if it exceeds 100 nm, the sinterability may decrease. From these viewpoints, the average particle size of the primary particles is preferably 10 to 50 nm, and more preferably 20 to 50 nm.
The average particle size of the primary particles can be determined by averaging the particle sizes of 200 silver particles measured by observing the cross sections of spherical silver particles cut with a focused ion beam (FIB) device with a field emission scanning electron microscope (FE-SEM); specifically, it can be measured by the method described in the examples.
The (A) silver particles further comprise silver particles having a positive thermal expansion coefficient in the firing temperature range of 150° C. to 300° C. The thermal expansion coefficient of the (A) silver particles may be 0.2 to 10.0 ppm/° C. or may be 1.5 to 8.0 ppm/° C.
In order to determine the thermal expansion coefficient of silver particles in the present disclosure, a cylindrical pellet-type sample with a diameter of 5 mm and a thickness of 1 mm was prepared by applying a load of 200 kgf to Ag powder silver particles for 1 minute using a mini hydraulic press (manufactured by Specac Corporation). The thermal expansion of the obtained sample was measured using a thermomechanical analysis (TMA) device (manufactured by Seiko Instruments Inc., product name: TMA SS150) under conditions of heating from room temperature to 350°C at a heating rate of 20°C/min, and the thermal expansion coefficient in the firing temperature range of 150°C to 300°C was determined based on the pellet length at 25°C.
The sintering start temperature of silver particles having a positive linear expansion coefficient is the temperature at which contraction begins, that is, the temperature at which the thermal expansion coefficient becomes maximum, and is usually in the range of 150 to 300°C.
When the temperature at which the thermal expansion coefficient is exhibited is within this range, the thermally conductive adhesive sheet has good sinterability and high thermal conductivity because the silver particles expand during sintering, increasing the opportunities for contact between the silver particles.
In particular, a thermally conductive adhesive sheet that contains a binder resin as an essential component has a low proportion of reactive functional groups in the resin composition, and therefore has a small volume exclusion effect associated with resin cure shrinkage, and therefore has a small sintering promotion effect due to the silver particles coming close to each other during sintering, and also has a small degree of freedom for the silver particles, so that by including silver particles with a positive thermal expansion coefficient, high thermal conductivity can be obtained.

The average particle size of the (A) silver particles (secondary particles) is preferably 0.5 to 5.0 μm, more preferably 0.5 to 3.0 μm, and even more preferably 1.0 to 3.0 μm. When the average particle size of the secondary particles is 0.5 μm or more, the storage stability is good, and when it is 5.0 μm or less, the sinterability is improved.
The average particle size of the secondary particles refers to a particle size (50% particle size D50) at which the cumulative volume is 50% in a particle size distribution measured using a laser diffraction particle size distribution measuring device, and specifically, can be measured by the method described in the Examples.

The tap density of the (A) silver particles is preferably 4.0 to 7.0 g/cm ³ , more preferably 4.5 to 7.0 g/cm ³ , and even more preferably 4.5 to 6.5 g/cm ^3. When the (A) silver particles have a tap density of 4.0 g/cm ³ or more, the silver particles can be highly filled in the resin composition, and when the tap density is 7.0 g/cm ³ or less, settling of the silver particles can be prevented during sheet production.
The tap density of the (A) silver particles can be measured using a tap density meter, and specifically, can be measured by the method described in the examples.

The (A) silver particles have a specific surface area, as determined by the BET method, of preferably 0.5 to 1.5 m ² /g, more preferably 0.5 to 1.2 m ² /g, and even more preferably 0.6 to 1.2 m ² /g. If the specific surface area is 0.5 m ² /g or more, the sheet can be prevented from becoming sticky, and if it is 1.5 m ² /g or less, the temporary adhesiveness is improved.
The specific surface area of the (A) silver particles can be measured by a BET single-point method using nitrogen adsorption with a specific surface area measuring device, and specifically, it can be measured by the method described in the examples.

(A) Silver particles are secondary particles formed by agglomeration of particles including nano-sized primary particles, and therefore maintain the high activity of the surfaces of the primary particles and have the ability to sinter (self-sinter) between the secondary particles at low temperatures. In addition, the sintering of the silver particles and the sintering of the silver particles and the bonding material proceed in parallel. Therefore, by using (A) silver particles, it is possible to obtain a thermally conductive adhesive sheet with excellent thermal conductivity and adhesive properties.

The shape of the (A) silver particles is not particularly limited and may be, for example, spherical, flake-like, or scale-like, with spherical shapes being preferred.
In addition, the (A) silver particles may be hollow particles or solid particles. Here, hollow particles refer to particles having voids inside the particles. When the (A) silver particles are hollow particles, it is particularly preferable that voids exist in the center of the silver particles. In addition, solid particles refer to particles having substantially no space inside the particles.

(A) Method for producing silver particles)
(A) The method for producing silver particles is not particularly limited, but for example, includes the steps of adding ammonia water to an aqueous solution containing a silver compound to obtain a silver ammine complex solution, reducing the silver ammine complex in the silver ammine complex solution obtained in the above step with a reducing compound to obtain a silver particle-containing slurry, and adding an organic protective compound to the silver particle-containing slurry obtained in the above step to introduce protective groups into the silver particles.

(Step of Obtaining Silver Ammine Complex Solution)
In this step, aqueous ammonia is added to an aqueous solution containing a silver compound to obtain a silver ammine complex solution.
Examples of silver compounds include silver nitrate, silver chloride, silver acetate, silver oxalate, silver oxide, etc. Among these, silver nitrate and silver acetate are preferred from the viewpoint of solubility in water.

The amount of ammonia added is preferably 2 to 50 mol per mol of silver in the aqueous solution containing the silver compound, more preferably 5 to 50 mol, and even more preferably 10 to 50 mol. When the amount of ammonia added is within the above range, the average particle size of the primary particles can be kept within the above range.

The silver ammine complex solution thus obtained may contain silver powder having an average particle size of 0.5 to 20 μm.

(Step of obtaining silver particle-containing slurry)
In this step, the silver ammine complex in the silver ammine complex solution obtained in the previous step is reduced with a reducing compound to obtain a silver particle-containing slurry.
By reducing the silver ammine complex with a reducing compound, the primary particles of the silver particles in the silver ammine complex are aggregated to form secondary particles (hollow particles) having a void in the center. In addition, when silver powder having an average particle size of 0.5 to 20 μm is added to the silver ammine complex solution in the above process, secondary particles (solid particles) in which the primary particles of the silver particles in the silver ammine complex are aggregated are formed around the silver powder.

By appropriately adjusting the amount of silver in the silver ammine complex and the content of the reducing compound, it is possible to control the aggregation of the primary particles, and the average particle size of the resulting secondary particles can be set within the above-mentioned range.

The reducing compound is not particularly limited as long as it has the reducing power to reduce the silver ammine complex and precipitate silver. Examples of the reducing compound include hydrazine derivatives.
Examples of hydrazine derivatives include hydrazine monohydrate, methyl hydrazine, ethyl hydrazine, n-propyl hydrazine, i-propyl hydrazine, n-butyl hydrazine, i-butyl hydrazine, sec-butyl hydrazine, t-butyl hydrazine, n-pentyl hydrazine, i-pentyl hydrazine, neo-pentyl hydrazine, t-pentyl hydrazine, n-hexyl hydrazine, i-hexyl hydrazine, n-heptyl hydrazine, n-octyl hydrazine, n-nonyl hydrazine, n-decyl hydrazine, n-undecyl hydrazine, n-dodecyl hydrazine, cyclohexyl hydrazine, phenyl hydrazine, 4-methylphenyl hydrazine, benzyl hydrazine, 2-phenylethyl hydrazine, 2-hydrazinoethanol, acetohydrazine, etc. These may be used alone or in combination of two or more.

The content of the reducing compound is preferably 0.25 to 20 mol per mol of silver in the silver ammine complex, more preferably 0.25 to 10 mol, and even more preferably 1.0 to 5.0 mol. When the content of the reducing compound is within the above range, the average particle size of the obtained secondary particles can be within the above range.

(Step of introducing protective groups into silver particles)
In this step, an organic protective compound is added to the silver particle-containing slurry obtained in the previous step to introduce protective groups onto the silver particles.
Examples of the organic protective compound include carboxylic acids, amines, amides, etc. Among them, carboxylic acids are preferred from the viewpoint of enhancing dispersibility.
Examples of carboxylic acids include monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, caprylic acid, octylic acid, nonanoic acid, capric acid, oleic acid, stearic acid, and isostearic acid; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and diglycolic acid; aromatic carboxylic acids such as benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, and gallic acid; and hydroxy acids such as glycolic acid, lactic acid, tartronic acid, malic acid, glyceric acid, hydroxybutyric acid, tartaric acid, citric acid, and isocitric acid.

The amount of organic protective compound is preferably 1 to 20 mmol, more preferably 1 to 10 mmol, and even more preferably 1 to 5 mmol, per 1 mol of silver particles. If the amount of organic protective compound is 1 mmol or more, the silver particles can be dispersed in the resin, and if it is 20 mmol or less, the silver particles can be dispersed in the resin without impairing the sinterability.

The content of the (A) silver particles is preferably 30 to 95% by mass, more preferably 30 to 80% by mass, and even more preferably 35 to 70% by mass, based on the total amount of the resin composition. If the (A) silver particle content is 30% by mass or more, the thermal conductivity can be improved, and if it is 95% by mass or less, the adhesive strength can be improved.

[(B) Thermosetting resin]
The (B) thermosetting resin can be any thermosetting resin generally used for adhesive applications, without any particular limitations. Among them, a liquid or solid material having a softening point of 70° C. or less is preferable, and a resin that is liquid at room temperature (25° C.) is more preferable. From the viewpoint of adhesive applications, the (B) thermosetting resin is preferably at least one selected from the group consisting of epoxy resins, cyanate resins, maleimide resins, and acrylic resins, and more preferably epoxy resins. These may be used alone or in combination of two or more.

Epoxy resins are compounds that have one or more glycidyl groups in the molecule, and when heated, the glycidyl groups react to form a three-dimensional network structure, which then hardens. It is preferable for one molecule to contain two or more glycidyl groups, because a compound with only one glycidyl group cannot exhibit sufficient cured product properties when reacted. Compounds that contain two or more glycidyl groups in one molecule can be obtained by epoxidizing a compound with two or more hydroxyl groups. Examples of such compounds include bisphenol compounds such as bisphenol A, bisphenol F, and biphenol, or derivatives thereof; diols having an alicyclic structure such as cyclohexanediol, cyclohexanedimethanol, and cyclohexanediethanol, or derivatives thereof; bifunctional compounds obtained by epoxidizing aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, and decanediol, or derivatives thereof; trifunctional compounds obtained by epoxidizing compounds having a trihydroxyphenylmethane skeleton or an aminophenol skeleton; and polyfunctional compounds obtained by epoxidizing phenol novolac resins, cresol novolac resins, phenol aralkyl resins, biphenyl aralkyl resins, and naphthol aralkyl resins. However, these are not limited to these.

Among the above epoxy resins, liquid epoxy resins and solid epoxy resins having a softening point of 70° C. or less are preferably used, with liquid epoxy resins being more preferred. Here, liquid epoxy resins refer to epoxy resins that are in a liquid or semi-solid state at room temperature (25° C.), and examples of such resins include epoxy resins that have fluidity at room temperature (25° C.). The viscosity of the liquid epoxy resin at 25° C. is preferably 100,000 mPa·s or less, more preferably 10,000 to 60,000 mPa·s.
The viscosity of the liquid epoxy resin at 25° C. can be measured by a rotational viscometer.

From the viewpoint of fluidity and flexibility, the weight average molecular weight (Mw) of the liquid epoxy resin is preferably 300 to 3,000, and more preferably 500 to 1,000. Here, in this specification, Mw is the value obtained by converting a chromatogram measured by gel permeation chromatography (GPC) into the molecular weight of standard polystyrene.

As the liquid epoxy resin, a biphenyl aralkyl resin is preferable. Note that the biphenyl aralkyl resin is an epoxy resin having a biphenyl skeleton, but the biphenyl skeleton in this embodiment also includes those in which at least one aromatic ring of the biphenyl ring is hydrogenated.

Specific examples of biphenyl aralkyl resins include, for example, 4,4'-bis(2,3-epoxypropoxy)biphenyl, 4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl, 4,4'-(3,3',5,5'-tetramethyl)biphenyl, and epoxy resins obtained by reacting epichlorohydrin with a biphenol compound such as 4,4'-biphenol or 4,4'-(3,3',5,5'-tetramethyl)biphenol. Among these, glycidyl ethers of 4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl and 4,4'-(3,3',5,5'-tetramethyl)biphenyl are preferred. Biphenyl aralkyl resins may be used alone or in combination of two or more.

An example of a commercially available product used as the biphenyl aralkyl resin is YX7105 manufactured by Mitsubishi Chemical Corporation. By using a liquid epoxy resin, particularly a biphenyl aralkyl resin, it is possible to easily maintain the melt viscosity of the resin composition within a suitable range even when the aforementioned (A) silver particles are highly loaded, and it is also possible to obtain a thermally conductive adhesive sheet with excellent heat resistance.

By combining the above liquid epoxy resin with (A) silver particles, good sheet properties are achieved without cracking or peeling, and good temporary adhesion is achieved because moderate tackiness is exhibited at 50-80°C. It is presumed that this is because the surface area of the silver particles retains the liquid components at room temperature, and the resin components soften at the temperature during temporary attachment, resulting in such good sheet properties.

Examples of the curing agent for the epoxy resin include aliphatic amines, aromatic amines, dicyandiamide, dihydrazide compounds, acid anhydrides, and phenolic resins. Examples of the aromatic amine include diaminodiphenylmethane, m-phenylenediamine, diaminodiphenylsulfone, diethyltoluenediamine, trimethylenebis(4-aminobenzoate), polytetramethyleneoxide-di-p-aminobenzoate, and 4,4'-diamino-3,3'-diethyldiphenylmethane. Examples of the dihydrazide compound include carboxylic acid dihydrazides such as adipic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, and p-oxybenzoic acid dihydrazide.
Examples of the acid anhydride include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, dodecenylsuccinic anhydride, a reaction product of maleic anhydride and polybutadiene, a copolymer of maleic anhydride and styrene, etc. Among them, a curing agent containing a sulfone is particularly preferred.

The content of the curing agent is preferably such that the ratio (y)/(x) of the number of reactive functional groups (y) of the curing agent to the number of epoxy groups (x) of the epoxy resin is in the range of 0.3 to 1.5, and more preferably in the range of 0.5 to 1.2. If the ratio (y)/(x) is 0.3 or more, the reliability of the cured product can be improved, and if the ratio (y)/(x) is 1.5 or less, the strength of the cured product can be improved.

In addition, a curing accelerator can be added to accelerate curing. Examples of curing accelerators for epoxy resins include imidazoles, triphenylphosphine or tetraphenylphosphine and their salts, and amine compounds such as diazabicycloundecene and their salts. For example, imidazole compounds such as 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-C11H23-imidazole, and an adduct of 2-methylimidazole and 2,4-diamino-6-vinyltriazine are preferably used. Among them, imidazole compounds with a melting point of 180°C or higher are particularly preferred. From the viewpoint of improving sintering properties, imidazoles that do not contain active hydrogen, such as 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, and 1,2-dimethylimidazole, may be used.

Cyanate resins are compounds that have -NCO groups in their molecules, and when heated, the -NCO groups react to form a three-dimensional network structure, which then hardens. Specific 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, and bis(2,3-dimethyl-4-cyanatophenyl)methane. Examples of the cyanates include 2,2-bis(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, tris(4-cyanatophenyl)phosphite, tris(4-cyanatophenyl)phosphate, and cyanates obtained by reacting novolak resin with cyanogen halide. Prepolymers having triazine rings formed by trimerizing the cyanate groups of these polyfunctional cyanate resins can also be used. The prepolymers are obtained by polymerizing the above polyfunctional cyanate resin monomers using, for example, acids such as mineral acids and Lewis acids, bases such as sodium alcoholates and tertiary amines, and salts such as sodium carbonate as catalysts.

As a curing accelerator for cyanate resin, generally known ones can be used. Examples include organometallic complexes such as zinc octylate, tin octylate, cobalt naphthenate, zinc naphthenate, and iron acetylacetonate, metal salts such as aluminum chloride, tin chloride, and zinc chloride, and amines such as triethylamine and dimethylbenzylamine, but are not limited to these. These curing accelerators may be used alone or in combination of two or more.

Maleimide resins are compounds that contain one or more maleimide groups in one molecule, and are resins that form a three-dimensional network structure and harden when heated by the reaction of the maleimide groups. Examples of bismaleimide resins include N,N'-(4,4'-diphenylmethane)bismaleimide, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, and 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane. More preferred maleimide resins are compounds obtained by reacting dimer acid diamine with maleic anhydride, and compounds obtained by reacting maleimide amino acids such as maleimide acetic acid and maleimide caproic acid with polyols. Maleimide amino acids are obtained by reacting maleic anhydride with amino acetic acid or amino caproic acid, and the polyols are preferably polyether polyols, polyester polyols, polycarbonate polyols, and poly(meth)acrylate polyols, and particularly preferably those that do not contain an aromatic ring.

The acrylic resin used here is a compound having a (meth)acryloyl group in the molecule, and is a resin that forms a three-dimensional network structure and hardens by reacting with the (meth)acryloyl group. It is preferable that the molecule contains one or more (meth)acryloyl groups.
Examples of the acrylic resin include acrylic resins containing epoxy groups, amide groups, amino groups, or hydroxyl groups, polyethers, polyesters, polycarbonates, and poly(meth)acrylates having (meth)acrylic groups. Examples of the epoxy group-containing acrylic resin include acrylic resins obtained by homopolymerization or copolymerization of allyl allyl glycidyl ether, glycidyl methacrylate, and the like. Examples of the amide group- or amino-containing acrylic resin include acrylic resins obtained by homopolymerization or copolymerization of acrylamide, hydroxyethyl acrylamide, N-methylol acrylamide, and the like. Examples of the carboxyl group-containing acrylic resin include acrylic resins obtained by homopolymerization or copolymerization of acrylic acid, methacrylic acid, itaconic acid, and the like. Examples of the hydroxyl group-containing acrylic resin include acrylic resins obtained by homopolymerization or copolymerization of hydroxyethyl acrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, and 1,4-cyclohexane dimethanol monoacrylate, and the like.
Preferred acrylic resins include polyethers, polyesters, polycarbonates, poly(meth)acrylates having a molecular weight of 100 to 10,000, compounds having a (meth)acrylic group, (meth)acrylates having a hydroxyl group, and (meth)acrylamides having a hydroxyl group.

The content of (B) thermosetting resin is preferably 1 to 30 parts by mass, and more preferably 5 to 25 parts by mass, per 100 parts by mass of (A) silver particles. When the content of (B) thermosetting resin is 1 part by mass or more, the adhesive effect of the thermosetting resin can be sufficiently obtained, and when the content of (B) thermosetting resin is 30 parts by mass or less, the decrease in the proportion of silver components is suppressed, high thermal conductivity can be sufficiently ensured, and heat dissipation can be improved.

[(C) Binder Resin]
The binder resin (C) can be used without any particular limitation as long as it is a resin material for processing the resin composition into a sheet. Examples of the binder resin (C) include silicone oil, acrylic resin, phenoxy resin, nitrile rubber, and acrylic rubber. Among them, acrylic resin is preferred from the viewpoint of good sheetability. These may be used alone or in combination of two or more.

(C) The weight average molecular weight (Mw) of the binder resin is preferably 200,000 to 1,000,000, and more preferably 400,000 to 800,000. If the weight average molecular weight of the binder resin (C) is 200,000 or more, the film-forming properties are improved, and if it is 1,000,000 or less, the viscosity of the compound is suitable for coating.

The glass transition temperature (Tg) of the binder resin (C) is preferably −40° C. to 0° C., and more preferably −30° C. to −5° C. When the glass transition temperature of the binder resin (C) is −40° C. or higher, the sheet surface becomes tack-free and the handling properties are improved, whereas when the glass transition temperature is 0° C. or lower, the film-forming properties are improved.
The glass transition temperature can be measured in accordance with JIS K7121:2012.

The content of (C) binder resin is preferably 5 to 35 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of (A) silver particles. If the content of (C) binder resin is 5 parts by mass or more, a good sheet can be obtained, and if it is 35 parts by mass or less, a decrease in thermal conductivity can be suppressed.

The total content of the (B) thermosetting resin and the (C) binder resin is preferably 5 to 30% by mass, more preferably 6 to 25% by mass, and even more preferably 8 to 20% by mass, based on the total amount of the resin composition. If the total content of the (B) thermosetting resin and the (C) binder resin is 5% by mass or more, the adhesive strength can be improved, and if it is 30% by mass or less, high thermal conductivity can be maintained.

[Diluent]
From the viewpoint of workability, the resin composition used in this embodiment preferably further contains a diluent. Examples of diluents include methyl ethyl ketone, toluene, butyl carbitol, cellosolve acetate, ethyl cellosolve, butyl cellosolve, butyl cellosolve acetate, butyl carbitol acetate, diethylene glycol dimethyl ether, diacetone alcohol, cyclohexanone, N-methyl-2-pyrrolidone (NMP), dimethylformamide, N,N-dimethylacetamide (DMAc), γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, and 3,5-dimethyl-1-adamantanamine (DMA). These may be used alone or in combination of two or more.

When the resin composition used in this embodiment contains a diluent, the content is preferably 3 to 30 parts by mass, more preferably 4 to 25 parts by mass, and even more preferably 4 to 20 parts by mass, per 100 parts by mass of (A) silver particles. If the content of the diluent is 3 parts by mass or more, the viscosity can be reduced by dilution, and if the content is 30 parts by mass or less, the amount of solvent remaining in the sheet is small, and the occurrence of voids when the resin composition is cured is suppressed.

[Other ingredients]
In addition to the above-mentioned components, the resin composition used in this embodiment may contain, as necessary, various additives that are generally added to this type of composition, such as coupling agents, antifoaming agents, surfactants, colorants (pigments, dyes), various polymerization inhibitors, antioxidants, inorganic ion exchangers, and other additives, within the range that does not impair the effects of the present invention. Each of these additives may be used alone or in combination of two or more.

Examples of the coupling agent include silane coupling agents such as epoxy silane, mercapto silane, amino silane, alkyl silane, claydo silane, vinyl silane, and sulfido silane, titanate coupling agents, aluminum coupling agents, and aluminum/zirconium coupling agents.
The colorant includes carbon black and the like.
The inorganic ion exchanger includes hydrotalcite and the like.

The elastic modulus of the cured product of the resin composition is preferably 3 GPa or less, and more preferably 2.8 GPa or less.
The glass transition temperature (Tg) of the cured product of the resin composition is preferably 0° C. or lower, and more preferably −6° C. or lower.
The thermal expansion coefficient of the cured product of the resin composition is preferably 50 ppm/°C or less at -50 to -40°C and 140 to 150°C, and more preferably 48 ppm/°C or less.
The elastic modulus, glass transition temperature and thermal expansion coefficient can all be measured by the methods described in the Examples.

The thermal conductivity of a cured product obtained by curing the above resin composition at 200° C. or less is preferably 30 W/mK or more, and more preferably 32 W/mK or more.
The thermal conductivity can be measured by the method described in the examples.

The thermally conductive adhesive sheet of this embodiment is suitable as an adhesive sheet material useful for applications requiring thermal conductivity, particularly semiconductor bonding applications. In particular, good thermal conductivity is maintained even when the element generates heat.

<Method of manufacturing thermally conductive adhesive sheet>
An example of a method for producing the thermally conductive adhesive sheet of this embodiment is a method in which (A) silver particles, (B) a thermosetting resin, and (C) a binder resin are mixed to form a resin composition, and the resin composition is then molded into a sheet.
The thermally conductive adhesive sheet of this embodiment may be formed on a support film.

The resin composition can be prepared by thoroughly mixing (A) silver particles, (B) thermosetting resin, (C) binder resin, and various other components that are blended as necessary, using a disperse, kneader, centrifugal mixer, or the like.
The above (A) epoxy resin, (B) thermosetting resin, (C) binder resin, and other various components that are blended as necessary can be those described in the above section <Thermal conductive adhesive sheet>.

Next, the resin composition is coated on a support film, dried and formed into a sheet. Coating methods include known methods such as gravure coating, die coating, comma coating, lip coating, cap coating, and screen printing. The drying temperature is preferably 70°C to 120°C, and more preferably 80°C to 100°C. If the drying temperature is 70°C or higher, less solvent remains in the sheet, and the generation of voids when the resin composition is cured is suppressed, and if the drying temperature is 120°C or lower, the film-forming properties are high and handling is easy. A specific example of a coating device is the μ-coat 350 manufactured by Yasui Seiki Co., Ltd.

As the support film, a plastic film such as polyethylene, polypropylene, polyester, polycarbonate, polyarylate, polyacrylonitrile, etc., having a release agent layer on one side thereof is used.
From the viewpoint of ease of handling, the thickness of the support film is usually 10 to 50 μm, and preferably 25 to 38 μm.

The thickness of the thermally conductive adhesive sheet is preferably 10 to 100 μm, and more preferably 10 to 50 μm. By making the thickness of the thermally conductive adhesive sheet 10 μm or more, the handling properties of the sheet are stabilized, and by making the thickness 100 μm or less, tack due to residual solvent in the sheet can be reduced.

<Semiconductor Device>
The semiconductor device of this embodiment is characterized by having a support member, a cured product of the above-mentioned thermally conductive adhesive sheet provided on the support member, and a semiconductor element bonded to the support member via the cured product of the thermally conductive adhesive sheet.

The semiconductor device of this embodiment can be manufactured, for example, by temporarily attaching the semiconductor device to the joining surface of a silicon chip under conditions of a temperature of 50 to 80°C, a pressure of 0.1 to 1 MPa, and a heating and pressurizing time of 0.1 to 1 minute, mounting the semiconductor device on a support member such as a copper frame, and then heating and pressurizing the semiconductor device under conditions of a temperature of 80°C to 200°C, a pressure of 0.1 to 5 MPa, and a heating and pressurizing time of 0.1 to 1 minute, and then further heating and curing the semiconductor device at 150 to 200°C for 0.5 to 2 hours.

Examples of the support member include a copper frame, a metal substrate such as an aluminum or iron plate, a ceramic substrate, and a glass epoxy substrate.
Examples of the semiconductor element include an IC, an LSI, a diode, a thyristor, and a transistor.

The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples.

(Production of Silver Particles)
[Synthesis Example 1]
40g of silver nitrate was dissolved in 10L of ion-exchanged water to prepare a silver nitrate aqueous solution, to which 203mL of ammonia water with a concentration of 26% by mass was added and stirred to obtain a silver ammine complex aqueous solution. The solution was adjusted to a liquid temperature of 10°C, and 28mL of a 20% by mass aqueous solution of hydrazine monohydrate was dropped over 60 seconds while stirring to precipitate silver particles, thereby obtaining a silver particle-containing slurry. 1% by mass of oleic acid relative to the amount of silver was added to the slurry and stirred for 10 minutes. The slurry was filtered, and the residue was washed with water and methanol, and dried at 60°C in a vacuum atmosphere for 24 hours to obtain silver particles with an average particle size of primary particles: 20nm, an average particle size of secondary particles: 1.1μm, a tap density: 5.2g/ ^cm3 , and a specific surface area: ^1.2m2 /g.
When the cross section of the obtained silver particles was observed with a field emission scanning electron microscope (FE-SEM) (JSM-6700F manufactured by JEOL), it was confirmed that the silver particles were hollow particles having a void in the center.

[Synthesis Example 2]
40g of silver nitrate was dissolved in 10L of ion-exchanged water to prepare a silver nitrate aqueous solution, and 203mL of ammonia water with a concentration of 26% by mass was added thereto and stirred to obtain a silver ammine complex aqueous solution. The solution was adjusted to a liquid temperature of 10°C, and 18mL of a 20% by mass aqueous solution of hydrazine monohydrate was dropped over 60 seconds while stirring to precipitate silver particles, thereby obtaining a silver particle-containing slurry. 1% by mass of oleic acid relative to the amount of silver was added to the slurry and stirred for 10 minutes. The slurry was filtered, and the residue was washed with water and methanol, and dried at 60°C in a vacuum atmosphere for 24 hours to obtain silver particles with an average particle size of primary particles: 20nm, an average particle size of secondary particles: 1.5μm, a tap density of 5.4g/ ^cm3 , and a specific surface area of ^1.1m2 /g.

[Synthesis Example 3]
40g of silver nitrate was dissolved in 10L of ion-exchanged water to prepare a silver nitrate aqueous solution, and 203mL of ammonia water with a concentration of 26% by mass was added thereto and stirred to obtain a silver ammine complex aqueous solution. The solution was adjusted to a liquid temperature of 10°C, and 12mL of a 20% by mass aqueous solution of hydrazine monohydrate was dropped over 60 seconds while stirring to precipitate silver particles, thereby obtaining a silver particle-containing slurry. 1% by mass of oleic acid relative to the amount of silver was added to the slurry and stirred for 10 minutes. The slurry was filtered, and the residue was washed with water and methanol, and dried at 60°C in a vacuum atmosphere for 24 hours to obtain silver particles with an average particle size of primary particles: 20nm, an average particle size of secondary particles: 2.6μm, a tap density: 5.0g/ ^cm3 , and a specific surface area: ^1.0m2 /g.

[Synthesis Example 4]
40g of silver nitrate was dissolved in 10L of ion-exchanged water to prepare a silver nitrate aqueous solution, to which 203mL of ammonia water with a concentration of 26% by mass was added and stirred to obtain a silver ammine complex aqueous solution. 50g of silver powder (product name: Ag-HWQ 1.5μm, manufactured by Fukuda Metal Foil and Powder Co., Ltd.) was added to this aqueous solution to obtain a silver powder-dispersed silver ammine complex aqueous solution. The liquid temperature was adjusted to 10°C, and 28mL of a 20% by mass aqueous solution of hydrazine monohydrate was dropped over 60 seconds while stirring to precipitate silver on the surface of the silver powder, thereby obtaining a silver particle-containing slurry. 1% by mass of oleic acid relative to the amount of silver was added to this slurry and stirred for 10 minutes. This slurry was filtered, and the filter cake was washed with water and methanol and dried at 60°C for 24 hours in a vacuum atmosphere to obtain silver particles having an average primary particle size of 20 nm, an average secondary particle size of 1.9 μm, a tap density of 5.7 g/ ^cm3 , and a specific surface area of 1.0 ^m2 /g.
When the cross section of the obtained silver particles was observed with a field emission scanning electron microscope (FE-SEM) (JSM-6700F manufactured by JEOL Ltd.), it was confirmed that the silver particles were solid particles in which silver aggregated around the silver powder and there was essentially no space inside the particles.

The silver particles obtained in Synthesis Examples 1 to 4 were evaluated by the following method.
[Average particle size of primary particles]
For the measurement of the average particle size of the primary particles, 2.8 mL of a 20 mass % aqueous solution of hydrazine monohydrate was added dropwise over 60 seconds to 1020 mL of the aqueous solution of the silver ammine complex obtained in each of the Synthesis Examples above, followed by solid-liquid separation. The resulting solid was washed with pure water and dried at 60°C for 24 hours in a vacuum atmosphere to obtain silver particles.
The average particle size of the primary particles was determined by taking the number-average of particle sizes of 200 silver particles measured by observing the cross sections of spherical silver particles cut with a focused ion beam (FIB) device (JEM-9310FIB manufactured by JEOL Ltd.) with a field emission scanning electron microscope (FE-SEM) (JSM-6700F manufactured by JEOL Ltd.).

[Average particle size of secondary particles]
The average particle size of the secondary particles was determined from the particle size at which the cumulative volume was 50% (50% particle size D50) in the particle size distribution measured using a laser diffraction particle size distribution measuring device (manufactured by Shimadzu Corporation, product name: SALAD-7500 nano).

[Thermal expansion coefficient]
A load of 200 kgf was applied to the silver particles for 1 minute using a mini hydraulic press (Specac) to obtain a cylindrical pellet-type sample with a diameter of 5 mm and a thickness of 1 mm. The thermal expansion of the sample was measured using a thermomechanical analyzer (TMA) device (Seiko Instruments Inc., product name: TMA SS150) under conditions of heating from room temperature to 350°C at a heating rate of 20°C/min, and the thermal expansion coefficient was determined based on the pellet length at 25°C. The thermal expansion coefficient that was maximum in the firing temperature range of 150°C to 300°C was taken as the maximum thermal expansion coefficient.

[Tap density]
The tap density (TD) was measured using a tap density measuring device (Tap-Pak Volumeter, manufactured by Thermo Scientific) as the mass per unit volume (unit: g/cm ³ ) of silver particles in a vibrated container.

[Specific surface area]
The specific surface area was measured by the BET single point method using nitrogen adsorption, using a specific surface area measuring device (Monosorb, manufactured by QuantaChrome) after degassing at 60° C. for 10 minutes.

(Examples 1 to 8, Comparative Examples 1 to 7)
(1) Preparation of Resin Composition The components of the types and amounts shown in Table 1 were mixed at 25° C. using a planetary mixer (Thinky Corporation, model number: ARV-310) to prepare a resin composition.
In Table 1, blank spaces indicate no blend.

(2) Preparation of a thermally conductive adhesive sheet The above resin composition was applied onto one release surface of a release film (manufactured by Toyobo Co., Ltd., product name: TN-200, thickness 25 μm) by gravure coating using a μ-coat 350 manufactured by Yasui Seiki Co., Ltd. A thermally conductive adhesive sheet having a thickness of 20 μm was formed by the gravure coating method. The drying conditions were a temperature of 80° C. and a speed of 1 m/min.

The details of each component used in preparing the resin composition, as listed in Table 1, are as follows:

[(A) Silver Particles]
(A1): Silver particles obtained in Synthesis Example 1 (average particle size of primary particles: 20 nm, average particle size of secondary particles: 1.1 μm, maximum thermal expansion coefficient: +5.5 ppm/° C., tap density: 5.2 g/cm ³ , specific surface area: 1.2 m ² /g)
(A2): Silver particles obtained in Synthesis Example 2 (average particle size of primary particles: 20 nm, average particle size of secondary particles: 1.5 μm, maximum thermal expansion coefficient: +7.4 ppm/° C., tap density: 5.4 g/cm ³ , specific surface area: 1.1 m ² /g)
(A3): Silver particles obtained in Synthesis Example 3 (average particle size of primary particles: 20 nm, average particle size of secondary particles: 2.6 μm, maximum thermal expansion coefficient: +7.0 ppm/° C., tap density: 5.0 g/cm ³ , specific surface area: 1.0 m ² /g)
(A4): Silver particles obtained in Synthesis Example 4 (average particle size of primary particles: 20 nm, average particle size of secondary particles: 1.9 μm, maximum thermal expansion coefficient: +2.5 ppm/° C., tap density: 5.7 g/cm ³ , specific surface area: 1.0 m ² /g)

[Silver particles other than component (A)]
TC-505C (Tokuriki Honten Co., Ltd., product name, average particle size: 1.93 μm, maximum thermal expansion coefficient: −0.1 ppm/° C., tap density: 6.25 g/cm ³ , specific surface area: 0.65 m ² /g)
Ag-HWQ 1.5 μm (trade name, manufactured by Fukuda Metal Foil and Powder Co., Ltd., average particle size: 1.8 μm, maximum thermal expansion coefficient: −0.6 ppm/° C., tap density: 3.23 g/cm ³ , specific surface area: 0.5 m ² /g)
AgC-221PA (trade name, manufactured by Fukuda Metal Foil and Powder Co., Ltd., average particle size: 7.5 μm, maximum thermal expansion coefficient: −0.1 ppm/° C., tap density: 5.7 g/cm ³ , specific surface area: 0.3 m ² /g)
DOWA Ag nano powder-1 (manufactured by DOWA Electronics Co., Ltd., product name, average particle size: 20 nm, maximum thermal expansion coefficient: -0.1 ppm/°C)

[(B) Thermosetting resin]
Epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name, YX7105, liquid (viscosity at 25°C: 45,000 mPa·s))
Epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name, jER1001, solid (softening point 65°C))
Epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name, jER1009, solid (softening point 140°C))
Acrylic resin: hydroxyethyl acrylamide (HEAA (registered trademark), manufactured by KJ Chemicals Co., Ltd.)
Curing agent: diaminodiphenyl sulfone (manufactured by Mitsui Fine Chemicals, Inc., product name, 4,4-DAS)

[(C) Binder Resin]
Acrylic binder (manufactured by Nippon Carbide Industries Co., Ltd., product name, Nissetsu, weight average molecular weight 500,000, glass transition temperature -10°C)
Acrylic binder (manufactured by Nippon Carbide Industries Co., Ltd., product name: Nissetsu, weight average molecular weight 100,000, glass transition temperature 0° C.)

[Diluent]
- Methyl ethyl ketone (manufactured by Sankyo Chemical Co., Ltd.)

[Other ingredients]
Curing accelerator: Imidazole type (manufactured by Shikoku Chemical Industry Co., Ltd., product name: Curesol 2P4MHZ-PW)
Hardener: Dicumyl peroxide (NOF Corporation, trade name, Percumyl (registered trademark) D)

Using the adhesive sheets (hereinafter simply referred to as adhesive sheets) in which a thermally conductive adhesive sheet was formed on one side of the release films obtained in Examples 1 to 7 and Comparative Examples 1 to 5, the properties of the thermally conductive adhesive sheets were measured and evaluated under the measurement conditions shown below. The evaluation results are shown in Table 1.

<Evaluation items>
(1) Sheet Properties The adhesive sheet was folded 180 degrees, visually observed, and evaluated according to the following criteria.
◯: The thermally conductive adhesive sheets of the folded adhesive sheet were not bonded to each other, and no cracks were found at the bent portions. ×: The thermally conductive adhesive sheets of the folded adhesive sheet were bonded to each other, or cracks occurred at the bent portions.

(2) Temporary adhesion When the thermally conductive adhesive sheet side of the adhesive sheet was pressed against a 6 mm x 6 mm silicon chip and a backside gold chip with a gold vapor deposition layer on the bonding surface under conditions of 65°C, 1 second, and a pressure of 1 MPa, cases where adhesion was possible were judged as ○, and cases where adhesion was impossible were judged as ×.

(3) Elastic Modulus The thermally conductive adhesive sheet was cured at 200°C for 2 hours, and cut into a size of 55 cm length × 1 cm width × 20 μm thickness to prepare a sample. The sample was heated from -50°C to 300°C at a rate of 10°C per minute using a thermomechanical analyzer (manufactured by Seiko Instruments Inc., device name: DMA) to measure the elastic modulus at 25°C.

(4) Glass transition temperature (Tg)
The thermally conductive adhesive sheet was cured at 200°C for 2 hours, and cut into a sample measuring 55 cm long x 1 cm wide x 20 µm thick. The sample was heated from -50°C to 300°C at a rate of 10°C per minute using a thermomechanical analyzer (Seiko Instruments Inc., device name: DMA) to measure the glass transition temperature.

(5) Thermal expansion coefficient The thermally conductive adhesive sheet was cured at 200°C for 2 hours, and cut into a sample measuring 3 cm long x 0.5 cm wide x 20 μm thick. The sample was heated from -50°C to 200°C at a rate of 10°C per minute using a thermomechanical analyzer (Seiko Instruments Inc., device name: TMA/SS), and the deformation of the sample between -50°C to -40°C and between 140°C to 150°C was measured as the thermal expansion coefficient.

(6) Thermal conductivity (cured at 200°C)
The thermally conductive adhesive sheet was cured at 200° C. for 2 hours and cut into a sample measuring 1 cm long x 1 cm wide x 20 μm thick. The thermal conductivity of the sample was measured by a laser flash method in accordance with JIS R 1611:1997 using a thermal conductivity meter (manufactured by Advance Riko Co., Ltd., device name: TC7000).
A thermal conductivity of 30 W/m·K or more was deemed acceptable.

(7) Thermal conductivity (cured at 300°C)
The thermally conductive adhesive sheet was cured at 300° C. for 2 hours and cut into a sample measuring 1 cm long x 1 cm wide x 20 μm thick. The thermal conductivity of the sample was measured by a laser flash method in accordance with JIS R 1611:1997 using a thermal conductivity meter (manufactured by Advance Riko Co., Ltd., device name: TC7000).
A thermal conductivity of 150 W/m·K or more was deemed acceptable.

(8) Hot Adhesive Strength The thermally conductive adhesive sheet side of the adhesive sheet was temporarily attached to a 6 mm x 6 mm silicon chip and a back gold chip with a gold vapor deposition layer on the bonding surface under conditions of 65 ° C., 1 second, and a pressure of 1 MPa, and then the release film of the adhesive sheet was peeled off, and the surface opposite to the surface to which the back gold chip of the thermally conductive adhesive sheet was temporarily attached was mounted on a solid copper frame, heated and pressed at 125 ° C., 5 seconds, and a pressure of 0.1 MPa, and further cured in an oven at 180 ° C. for 1 hour to prepare a sample. The hot die shear strength of the above sample at 260 ° C. was measured using a mount strength measuring device (Besi, device name: 2200 EVO-plus).

(9) Reliability test (heat cycle)
The sample prepared in (8) was heated from -55°C to 150°C in a thermal cycle tester, and then cooled to -55°C (one cycle). This cycle was repeated 1000 times to check the incidence of defects (peeling defects) (number of samples=20).

(A) Examples 1 to 8 use a thermally conductive adhesive sheet formed by molding a resin composition containing silver particles into a sheet shape. All of them have excellent temporary adhesion and sheetability, and even under low-temperature sintering conditions of 200°C or less, they have high thermal conductivity, making it possible to obtain a semiconductor device with excellent reliability.

Claims (12)

A thermally conductive adhesive sheet obtained by forming into a sheet a resin composition containing (A) silver particles, (B) a thermosetting resin, and (C) a binder resin,
the (A) silver particles are hollow secondary particles formed by agglomeration of particles including primary particles having an average particle diameter of 10 to 100 nm,
The (B) thermosetting resin is a liquid or solid material having a softening point of 70° C. or less,
a content of the (B) thermosetting resin is 1 to 30 parts by mass per 100 parts by mass of the (A) silver particles; a content of the (C) binder resin is 5 to 35 parts by mass per 100 parts by mass of the (A) silver particles; and a total content of the (B) thermosetting resin and the (C) binder resin is 5 to 30% by mass with respect to a total amount of the resin composition. The thermally conductive adhesive sheet according to claim 1 , wherein the (A) silver particles have an average secondary particle diameter of 0.5 to 5.0 μm. The thermally conductive adhesive sheet according to claim 1 or 2 , characterized in that the (A) silver particles have a positive thermal expansion coefficient between 150°C and 300°C. The thermally conductive adhesive sheet according to any one of claims 1 to 3 , wherein the (A) silver particles have a tap density of 4.0 to 7.0 g/ ^cm3 . 5. The thermally conductive adhesive sheet according to claim 1 , wherein the silver particles (A) have a specific surface area, as determined by a BET method, of 0.5 to 1.5 m ² /g. The thermally conductive adhesive sheet according to any one of claims 1 to 5 , wherein the (A) silver particles have an average particle size of 0.5 to 5.0 µm. 7. The thermally conductive adhesive sheet according to claim 1 , wherein the thermosetting resin (B) is a liquid or solid material having a softening point of 70° C. or lower. The thermally conductive adhesive sheet according to any one of claims 1 to 7 , wherein the (B) thermosetting resin is at least one selected from the group consisting of epoxy resins, cyanate resins, maleimide resins, and acrylic resins. The thermally conductive adhesive sheet according to any one of claims 1 to 8 , wherein the (C) binder resin has a weight average molecular weight of 200,000 to 1,000,000 and a glass transition temperature of -40°C to 0°C. The elastic modulus of the resin composition after curing is 3 GPa or less, and the glass transition temperature (T
10. The thermally conductive adhesive sheet according to any one of 1 to 9 , wherein the thermal expansion coefficient is 50 ppm/°C or less at -50 to -40°C and 140 to 150°C. The thermally conductive adhesive sheet according to any one of claims 1 to 10 , wherein the resin composition is cured at 200°C or less, and the cured product has a thermal conductivity of 30 W/m·K or more. A semiconductor device comprising: a support member; a cured product of the thermally conductive adhesive sheet according to any one of claims 1 to 11 provided on the support member; and a semiconductor element bonded to the support member via the cured product of the thermally conductive adhesive sheet.