JP7571815B2 - Encapsulating composition and semiconductor device - Google Patents

Description

The present invention relates to an encapsulating composition and a semiconductor device.

In recent years, with the miniaturization and high integration of semiconductor packages, there has been concern about heat generation inside the semiconductor package. Heat generation may cause a decrease in the performance of electric or electronic components having the semiconductor package. For this reason, high thermal conductivity is required for materials used in semiconductor packages. For example, there is a demand for high thermal conductivity of the encapsulating material of semiconductor packages.
One method for increasing the thermal conductivity of a sealing material is to use silica and alumina, which is a highly thermally conductive inorganic filler, as an inorganic filler contained in the sealing material (see, for example, Patent Document 1).

Patent No. 4188634

When alumina is used to increase the thermal conductivity of the encapsulant, its fluidity can deteriorate. For example, a semiconductor package that employs a method known as a wire bonding structure, in which a semiconductor element and a substrate are connected via wires, is formed by encapsulating the semiconductor element, substrate, and the wires that electrically connect them with an encapsulant that is a resin composition. In this case, pressure is applied to the wires due to the flow of the encapsulant, which can cause the wires to shift position (wire flow) or result in insufficient protection of the semiconductor element.

One aspect of the present invention has been made in consideration of the above-mentioned conventional circumstances, and aims to provide an encapsulating composition that has excellent flowability when alumina is used as an inorganic filler, and a semiconductor device using the same.

Specific means for achieving the above object are as follows.
<1> A sealing composition containing an epoxy resin, a curing agent, an inorganic filler containing alumina, and a tertiary phosphine oxide.
<2> The sealing composition according to <1>, wherein the tertiary phosphine oxide includes a triarylphosphine oxide.
<3> The sealing composition according to <2>, wherein the triarylphosphine oxide includes triphenylphosphine oxide.
<4> The sealing composition according to any one of <1> to <3>, wherein a content of the tertiary phosphine oxide is 25 parts by mass or less based on 100 parts by mass of the epoxy resin.
<5> The sealing composition according to any one of <1> to <4>, wherein a content of the alumina in the inorganic filler is 50 volume % or more.
<6> A sealing composition containing an epoxy resin, a curing agent, an inorganic filler containing alumina, and an alumina fluidizing agent.
<7> A semiconductor device comprising: a semiconductor element; and a cured product of the encapsulating composition according to any one of <1> to <6>, which encapsulates the semiconductor element.

According to one aspect of the present invention, it is possible to provide a sealing composition that has excellent flowability when alumina is used as an inorganic filler, and a semiconductor device using the same.

Hereinafter, the embodiment for carrying out the encapsulating composition and semiconductor device of the present invention will be described in detail. However, the present invention is not limited to the following embodiment. In the following embodiment, the components (including element steps, etc.) are not essential unless specifically stated. The same applies to the numerical values and their ranges, and do not limit the present invention.
In the present disclosure, the numerical ranges indicated using "to" include the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.
In the present disclosure, each component may contain multiple types of the corresponding substance. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified.
In the present disclosure, the particles corresponding to each component may include multiple types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

<Sealing composition>
A first sealing composition of the present disclosure contains an epoxy resin, a curing agent, an inorganic filler including alumina, and a tertiary phosphine oxide.
A second sealing composition of the present disclosure contains an epoxy resin, a curing agent, an inorganic filler containing alumina, and an alumina fluidizing agent.
Hereinafter, the first sealing composition and the second sealing composition of the present disclosure may be collectively referred to as the sealing composition of the present disclosure.
The sealing composition of the present disclosure has excellent flowability when alumina is used as the inorganic filler, and although the reason for this is not clear, it is presumed to be as follows.
Since the sealing composition of the present disclosure contains a tertiary phosphine oxide or an alumina fluidizing agent, it is considered that the viscosity of the tertiary phosphine oxide decreases or the fluidization of the alumina is promoted by heating the sealing composition, thereby decreasing the viscosity of the sealing composition as a whole. As a result, it is presumed that the fluidity of the sealing composition is improved even when alumina is used as an inorganic filler.
In addition, in conventional sealing compositions, when alumina is used as an inorganic filler to ensure high thermal conductivity, the sealing composition has a low fluidity and the cured product has a high elastic modulus, which is a contradictory property, and it may be difficult to achieve both high thermal conductivity and low fluidity and low elastic modulus of the cured product. According to the sealing composition of the present disclosure, high thermal conductivity is ensured and low fluidity is possible by using alumina as an inorganic filler. Furthermore, even if alumina is used as an inorganic filler, the cured product can have a low elastic modulus.

Hereinafter, each component constituting the sealing composition will be described. The first sealing composition of the present disclosure contains an epoxy resin, a curing agent, an inorganic filler containing alumina, and a tertiary phosphine oxide, and may contain other components as necessary. The second sealing composition of the present disclosure contains an epoxy resin, a curing agent, an inorganic filler containing alumina, and an alumina fluidizing agent, and may contain other components as necessary.

-Epoxy resin-
The sealing composition contains an epoxy resin. The type of the epoxy resin is not particularly limited, and any known epoxy resin can be used.
Specifically, for example, novolak resins obtained by condensing or co-condensing at least one selected from the group consisting of phenolic compounds (e.g., phenol, cresol, xylenol, resorcin, catechol, bisphenol A, and bisphenol F) and naphthol compounds (e.g., α-naphthol, β-naphthol, and dihydroxynaphthalene) with an aldehyde compound (e.g., formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde) under an acidic catalyst are epoxidized (e.g., phenol novolak type epoxy resins and orthocresol novolak type epoxy resins); bisphenols (e.g., bisphenol A, bisphenol AD, bisphenol F, and bisphenol S) ) and biphenols (e.g., alkyl-substituted and unsubstituted biphenols); epoxidized products of phenol-aralkyl resins; epoxidized products of adducts or polyadditions of phenolic compounds with at least one selected from the group consisting of dicyclopentadiene and terpene compounds; glycidyl ester type epoxy resins obtained by reacting polybasic acids (e.g., phthalic acid and dimer acid) with epichlorohydrin; glycidylamine type epoxy resins obtained by reacting polyamines (e.g., diaminodiphenylmethane and isocyanuric acid) with epichlorohydrin; linear aliphatic epoxy resins obtained by oxidizing olefin bonds with peracids (e.g., peracetic acid); and alicyclic epoxy resins. The epoxy resins may be used alone or in combination of two or more.

From the viewpoint of preventing corrosion of aluminum or copper wiring on elements such as integrated circuits (ICs), the epoxy resin preferably has a high purity and a low amount of hydrolyzable chlorine. From the viewpoint of improving the moisture resistance of the sealing composition, the amount of hydrolyzable chlorine is preferably 500 ppm or less by mass.

Here, the amount of hydrolyzable chlorine is the value obtained by dissolving 1 g of the sample epoxy resin in 30 mL of dioxane, adding 5 mL of 1 mol/L (1N) KOH methanol solution, refluxing for 30 minutes, and then performing potentiometric titration.

The content of the epoxy resin in the sealing composition is preferably 2% by mass to 10% by mass, more preferably 3% by mass to 8% by mass, and further preferably 4% by mass to 6% by mass.
The content of the epoxy resin in the sealing composition excluding the inorganic filler is preferably 30% by mass to 60% by mass, more preferably 35% by mass to 55% by mass, and further preferably 40% by mass to 50% by mass.

- Hardener -
The sealing composition contains a curing agent. The type of the curing agent is not particularly limited, and any known curing agent can be used.
Specific examples of the curing agent include novolak resins obtained by condensing or co-condensing at least one selected from the group consisting of phenolic compounds (e.g., phenol, cresol, resorcin, catechol, bisphenol A, and bisphenol F) and naphthol compounds (e.g., α-naphthol, β-naphthol, and dihydroxynaphthalene) with an aldehyde compound (e.g., formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde) under an acid catalyst; phenol-aralkyl resins; and naphthol-aralkyl resins. One type of curing agent may be used alone, or two or more types may be used in combination.

It is preferable to mix the curing agent so that the equivalent of the functional group of the curing agent (for example, a phenolic hydroxyl group in the case of a novolac resin) is 0.5 to 1.5 equivalents per equivalent of the epoxy group of the epoxy resin, and it is particularly preferable to mix the curing agent so that the equivalent is 0.7 to 1.2 equivalents.

- Inorganic filler -
The sealing composition contains an inorganic filler including alumina. When the sealing composition contains an inorganic filler, the moisture absorption of the sealing composition is reduced, and the strength of the sealing composition in a cured state tends to be improved.

The inorganic fillers may be used alone or in combination of two or more kinds.
The use of two or more types of inorganic fillers in combination may, for example, be of two or more types of inorganic fillers differing in components, average particle size, shape, or the like.
The shape of the inorganic filler is not particularly limited, and examples thereof include powder, spheres, fibers, etc. From the viewpoints of flowability during molding of the sealing composition and mold abrasion, a spherical shape is preferred.

The inorganic filler may contain alumina, and may be entirely alumina or may contain alumina and other inorganic fillers in combination. When the inorganic filler contains alumina, the thermal conductivity of the sealing composition tends to be improved.
Other inorganic fillers that can be used in combination with alumina include silica such as spherical silica and crystalline silica, zircon, magnesium oxide, calcium silicate, calcium carbonate, potassium titanate, silicon carbide, silicon nitride, boron nitride, beryllia, zirconia, etc. Furthermore, inorganic fillers having a flame retardant effect include aluminum hydroxide, zinc borate, etc.

When alumina and other inorganic fillers are used in combination as the inorganic filler, it is preferable to use silica as the other inorganic filler in view of its spherical shape.
When alumina and silica are used in combination as the inorganic filler, the content of alumina in the inorganic filler is preferably 50% by volume or more, more preferably 60% by volume or more, and even more preferably 70% by volume or more. The content of alumina in the inorganic filler may be 100% by volume or less, and is preferably 99% by volume or less.

From the viewpoints of moisture absorption, reduction of the linear expansion coefficient, improvement of strength, and solder heat resistance, the content of the inorganic filler is preferably 70% by volume or more, more preferably 73% by volume or more, and even more preferably 76% by volume or more, based on the total volume of the sealing composition. The content of the inorganic filler may be 85% by volume or less.

The average particle size (volume average particle size) of the inorganic filler is preferably 1 μm to 30 μm, more preferably 3 μm to 20 μm, and even more preferably 5 μm to 15 μm. In the present disclosure, the average particle size of the inorganic filler refers to the average particle size of alumina when alumina is used alone as the inorganic filler, and refers to the average particle size of the inorganic filler as a whole when alumina is used in combination with other inorganic fillers as the inorganic filler.
The average particle size of the inorganic filler can be measured by the following method.

The inorganic filler to be measured is added to the solvent (pure water) in the range of 0.02% to 0.08% by mass, and the inorganic filler is dispersed by vibrating it for 1 to 10 minutes in a 110W bath-type ultrasonic cleaner. Approximately 40 mL of the dispersion is poured into a measurement cell and measured at 25°C. A laser diffraction/scattering type particle size distribution measuring device (for example, HORIBA, Ltd., LA920 (product name)) is used as the measuring device to measure the volumetric particle size distribution. The average particle size is determined as the particle size (D50%) when the cumulative amount from the small diameter side in the volumetric particle size distribution is 50%. The refractive index used is that of alumina. When the inorganic filler is a mixture of alumina and other inorganic fillers, the refractive index used is that of alumina.

-Tertiary phosphine oxide-
A first sealing composition of the present disclosure contains a tertiary phosphine oxide.
The tertiary phosphine oxide is not particularly limited, and may be an aliphatic tertiary phosphine oxide, an aromatic tertiary phosphine oxide, etc. The tertiary phosphine oxide may be used alone or in combination of two or more kinds.

Specific examples of tertiary phosphine oxides include triarylphosphine oxides such as triphenylphosphine oxide, diphenyl(p-tolyl)phosphine oxide, tris(alkylphenyl)phosphine oxide, tris(alkoxyphenyl)phosphine oxide, tris(alkylalkoxyphenyl)phosphine oxide, tris(dialkylphenyl)phosphine oxide, tris(trialkylphenyl)phosphine oxide, tris(tetraalkylphenyl)phosphine oxide, tris(dialkoxyphenyl)phosphine oxide, tris(trialkoxyphenyl)phosphine oxide, and tris(tetraalkoxyphenyl)phosphine oxide, trialkylphosphine oxide, dialkylarylphosphine oxide, and alkyldiarylphosphine oxide.

Among these, the tertiary phosphine oxide preferably includes a triarylphosphine oxide, and more preferably includes a triphenylphosphine oxide.
The proportion of triarylphosphine oxide in the tertiary phosphine oxide is preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, and further preferably 70% by mass to 100% by mass.
Furthermore, the proportion of triphenylphosphine oxide in the triarylphosphine oxide is preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, and even more preferably 70% by mass to 100% by mass.

The content of the tertiary phosphine oxide is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the epoxy resin. The content of the tertiary phosphine oxide may be 1 part by mass or more per 100 parts by mass of the epoxy resin.

- Alumina fluidizer -
A second sealing composition of the present disclosure contains an alumina flow agent.
In this disclosure, an alumina fluidizer refers to a compound that meets the following characteristics:
An epoxy resin, a curing agent, and alumina are mixed so that the alumina content is 75% by volume to prepare a first sealing composition, and the viscosity of the first sealing composition at 175°C is measured using a flow property evaluation device (Shimadzu Corporation, CFT-100D (product name)). Next, 5 parts by mass of a predetermined compound is added to 100 parts by mass of the first sealing composition to prepare a second sealing composition, and the viscosity of the second sealing composition at 175°C is measured using a flow property evaluation device (Shimadzu Corporation, CFT-100D (product name)). When the reduction rate of the viscosity of the second sealing composition relative to the viscosity of the first sealing composition (((viscosity of the first sealing composition-viscosity of the second sealing composition)/viscosity of the first sealing composition)×100(%)) is 10% or more, the predetermined compound is considered to be an alumina fluidizer.

As a result of intensive research, the present inventors have discovered a method for evaluating compounds that can improve the fluidity of sealing compositions that use alumina as an inorganic filler. The above method makes it possible to easily find compounds (alumina fluidizers) that improve the fluidity of sealing compositions when alumina is used as an inorganic filler.

The melting temperature of the alumina fluidizer is not particularly limited, and from the viewpoint of becoming liquid at the sealing temperature when the sealing composition is used to seal a semiconductor package, the melting temperature is preferably equal to or lower than the sealing temperature, more preferably equal to or lower than 165°C, and even more preferably equal to or lower than 160°C.
From the viewpoint of storage stability of the sealing composition, it is preferable that the alumina fluidizer does not contain a functional group that accelerates the curing reaction of the epoxy resin. Examples of the functional group that accelerates the curing reaction of the epoxy resin include a carboxy group, an amino group, and a hydroxyl group.

The content of the alumina fluidizing agent is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the epoxy resin. The content of the alumina fluidizing agent may be 1 part by mass or more per 100 parts by mass of the epoxy resin.

(Cure Accelerator)
The sealing composition may further contain a curing accelerator. The type of the curing accelerator is not particularly limited, and any known curing accelerator may be used.
Specifically, cycloamidine compounds such as 1,8-diaza-bicyclo[5.4.0]undecene-7, 1,5-diaza-bicyclo[4.3.0]nonene, and 5,6-dibutylamino-1,8-diaza-bicyclo[5.4.0]undecene-7; cycloamidine compounds with maleic anhydride, 1,4-benzoquinone, 2,5-toluquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, 2,6-dimethylbenzoquinone, and 2,3-dimethoxy-5-methyl-1,4-benzoquinone; quinone compounds such as phenyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, etc., compounds having intramolecular polarization obtained by adding compounds having a π bond such as diazophenylmethane and phenol resin; tertiary amine compounds such as benzyldimethylamine, triethanolamine, dimethylaminoethanol, tris(dimethylaminomethyl)phenol, etc., and derivatives of tertiary amine compounds; 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, Examples of the curing accelerator include imidazole compounds such as thiimidazole, derivatives of imidazole compounds, organic phosphine compounds such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, tris(4-methylphenyl)phosphine, diphenylphosphine, and phenylphosphine, and phosphorus compounds having intramolecular polarization obtained by adding a compound having a π bond such as maleic anhydride, the above-mentioned quinone compound, diazophenylmethane, and phenolic resin to an organic phosphine compound, tetraphenylboron salts such as tetraphenylphosphonium tetraphenylborate, triphenylphosphine tetraphenylborate, 2-ethyl-4-methylimidazole tetraphenylborate, and N-methylmorpholine tetraphenylborate, and derivatives of tetraphenylboron salts, and adducts of phosphine compounds such as triphenylphosphonium-triphenylborane and N-methylmorpholine tetraphenylphosphonium-tetraphenylborate with tetraphenylboron salts. One type of curing accelerator may be used alone, or two or more types may be used in combination.

The content of the curing accelerator is preferably 0.1% to 8% by mass based on the total amount of the epoxy resin and the curing agent.

(Ion trapping agent)
The sealing composition may further include an ion trapping agent.
The ion trapping agent that can be used in the present disclosure is not particularly limited as long as it is an ion trapping agent that is generally used in sealing materials used in the manufacture of semiconductor devices. Examples of the ion trapping agent include compounds represented by the following general formula (II-1) or (II-2).

Mg _1-a Al _a (OH) ₂ (CO ₃ ) _a/2・uH ₂ O (II-1)
(In general formula (II-1), a is 0<a≦0.5, and u is a positive number.)
BiO _b (OH) _c (NO ₃ ) _d (II-2)
(In the general formula (II-2), b is 0.9≦b≦1.1, c is 0.6≦c≦0.8, and d is 0.2≦d≦0.4.)

Ion trapping agents are commercially available. For example, "DHT-4A" (Kyowa Chemical Industry Co., Ltd., product name) is a commercially available example of the compound represented by general formula (II-1). For example, "IXE500" (Toagosei Co., Ltd., product name) is a commercially available example of the compound represented by general formula (II-2).

Other examples of ion trapping agents include hydrous oxides of elements selected from magnesium, aluminum, titanium, zirconium, antimony, and the like.
The ion trapping agent may be used alone or in combination of two or more kinds.

When the sealing composition contains an ion trapping agent, the content of the ion trapping agent is preferably 1 part by mass or more per 100 parts by mass of epoxy resin from the viewpoint of realizing sufficient moisture resistance reliability. From the viewpoint of fully exerting the effects of other components, the content of the ion trapping agent is preferably 15 parts by mass or less per 100 parts by mass of epoxy resin.

The average particle size of the ion trapping agent is preferably 0.1 μm to 3.0 μm, and the maximum particle size is preferably 10 μm or less. The average particle size of the ion trapping agent can be measured in the same manner as for the inorganic filler.

(Coupling Agent)
The sealing composition may further contain a coupling agent. The type of the coupling agent is not particularly limited, and any known coupling agent may be used. Examples of the coupling agent include a silane coupling agent and a titanium coupling agent. The coupling agent may be used alone or in combination of two or more types.

Examples of silane coupling agents include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-[bis(β-hydroxyethyl)]aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-(β- aminoethyl) aminopropyl dimethoxymethyl silane, N-(trimethoxysilylpropyl) ethylenediamine, N-(dimethoxymethylsilyl isopropyl) ethylenediamine, methyltrimethoxysilane, methyltriethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyl trimethoxysilane, γ-chloropropyl trimethoxysilane, hexamethyldisilane, γ-anilinopropyl trimethoxysilane (N-phenyl-3-aminopropyl trimethoxysilane), vinyltrimethoxysilane and γ-mercaptopropyl methyldimethoxysilane.

Examples of titanium coupling agents include isopropyl triisostearoyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, isopropyl tri(N-aminoethyl-aminoethyl) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl phosphite) titanate, bis(dioctyl pyrophosphate)oxyacetate titanate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl tridodecyl benzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctyl phosphate) titanate, isopropyl tricumyl phenyl titanate, and tetraisopropyl bis(dioctyl phosphite) titanate.

When the sealing composition contains a coupling agent, the content of the coupling agent is preferably 3% by mass or less based on the total sealing composition, and from the viewpoint of exerting its effect, it is preferable that the content of the coupling agent is 0.1% by mass or more.

(Release Agent)
The sealing composition may further contain a release agent. The type of the release agent is not particularly limited, and a known release agent may be used. Specific examples include higher fatty acids, higher fatty acid esters, carnauba wax, and polyethylene wax. The release agent may be used alone or in combination of two or more types.
When the sealing composition contains a release agent, the content of the release agent is preferably 10 mass % or less based on the total amount of the epoxy resin and the curing agent, and from the viewpoint of exerting its effect, it is preferably 0.5 mass % or more.

(Colorants and Modifiers)
The sealing composition may contain a colorant (e.g., carbon black). The sealing composition may also contain a modifier (e.g., silicone and silicone rubber). The colorant and modifier may each be used alone or in combination of two or more kinds.

When conductive particles such as carbon black are used as the colorant, the conductive particles preferably have a content of particles having a particle diameter of 10 μm or more of 1 mass % or less.
When the sealing composition contains conductive particles, the content of the conductive particles is preferably 4 mass % or less based on the total amount of the epoxy resin and the curing agent.

<Method of producing sealing composition>
The method for producing the encapsulating composition is not particularly limited, and can be performed by a known method. For example, the encapsulating composition can be produced by thoroughly mixing a mixture of raw materials in a predetermined amount using a mixer or the like, kneading the mixture using a hot roll, an extruder, or the like, and then cooling, pulverizing, or the like. The state of the encapsulating composition is not particularly limited, and may be in a powder, solid, liquid, or the like.

<Semiconductor Device>
The semiconductor device of the present disclosure includes a semiconductor element and a cured product of the sealing composition of the present disclosure that seals the semiconductor element.

There are no particular limitations on the method for encapsulating a semiconductor element using the encapsulating composition, and any known method can be used. For example, the transfer molding method is common, but compression molding method, injection molding method, etc. may also be used.

The semiconductor device disclosed herein is suitable for use as an IC, LSI (Large-Scale Integration), etc.

The following describes examples of the present invention, but the present invention is not limited to these. In addition, the numerical values in the table mean "parts by mass" unless otherwise specified.

(Examples 1 to 5 and Comparative Examples 1 to 3)
The materials shown in Tables 1 and 2 were premixed (dry blended), kneaded for about 15 minutes with a biaxial roll (roll surface temperature: about 80° C.), and then cooled and pulverized to produce a powdered sealing composition. In Tables 1 and 2, "-" indicates that the corresponding component is not included.

-Epoxy resin-
Epoxy resin 1: biphenyl type epoxy resin, epoxy equivalent: 192 g/eq
Epoxy resin 2: bisphenol type crystalline epoxy resin, epoxy equivalent: 192 g/eq
Epoxy resin 3: bisphenol F type epoxy resin, epoxy equivalent: 158 g/eq
- Hardener -
Curing agent 1: Multifunctional phenolic resin, triphenylmethane type phenolic resin with a hydroxyl group equivalent of 104 g/eq -Curing accelerator-
・Phosphorus-based curing accelerator - Coupling agent -
Coupling agent: N-phenyl-3-aminopropyltrimethoxysilane (silane coupling agent)
- Release agent -
・Montan acid ester - colorant -
・Carbon black - ion trapping agent -
・Hydrotalcite-based ion trapping agent -modifier-
Modifier 1: Silicone (epoxy modified silicone resin)
-Tertiary phosphine oxide-
・Tertiary phosphine oxide: Triphenylphosphine oxide - inorganic filler -
Alumina 1: Volume average particle size is 11.7 μm
Alumina 2: Volume average particle size is 13.5 μm
Alumina 3: Volume average particle size is 0.6 μm
Silica 1: Volume average particle size is 21.7 μm
Silica 2: Volume average particle size is 0.1 μm
Silica 3: Volume average particle size is 14.5 μm
Silica 4: Volume average particle size is 0.6 μm

<Evaluation of thermal conductivity>
Using the encapsulating composition obtained above, a semiconductor element was encapsulated in a compression molding machine under the conditions of a mold temperature of 175°C to 180°C, a molding pressure of 7 MPa, and a curing time of 150 seconds to prepare a test piece for evaluating thermal conductivity. The thermal conductivity of the test piece was then measured by a xenon flash (Xe-flash) method. The results are shown in Table 3.

<Liquidity>
(Evaluation of Spiral Flow (SF))
Using a spiral flow measurement mold conforming to EMMI-1-66, the prepared encapsulating composition was molded with a transfer molding machine under conditions of a mold temperature of 180° C., a molding pressure of 22.5 MPa, and a curing time of 300 seconds to determine the flow distance. The results are shown in Table 3.
(Disk Flow (DF) Evaluation)
Using a flat plate mold for measuring disk flow having an upper mold of 200 mm (W) x 200 mm (D) x 25 mm (H) and a lower mold of 200 mm (W) x 200 mm (D) x 15 mm (H), 5 g of the sealing composition weighed with an upper plate balance was placed on the center of the lower mold heated to 180 ° C., and after 5 seconds, the upper mold heated to 180 ° C. was closed and compression molded under conditions of a load of 78 N and a curing time of 90 seconds, and the major axis (mm) and minor axis (mm) of the molded product were measured with a caliper, and the average value (mm) was taken as the disk flow. The results are shown in Table 3.

<High temperature elastic modulus>
The sealing composition was heated at 175°C for 10 minutes to obtain a cured product measuring 10 mm x 50 mm x 3 mm. The elastic modulus of the obtained cured product was measured using a dynamic viscoelasticity measuring device (TA Instruments'"RSAIII"). The measurement was performed at a temperature increase rate of 10°C/min from 30°C to 300°C. The elastic modulus (MPa) measured at 260°C is shown in Table 3 as the high temperature elastic modulus.

As is clear from the evaluation results in Table 3, the sealing compositions of Examples 1 to 5, which contain alumina as an inorganic filler and tertiary phosphine oxide, have superior fluidity compared to the sealing composition of Comparative Example 1, which contains alumina as an inorganic filler and does not contain tertiary phosphine oxide. In addition, the sealing compositions of Examples 1 to 5 have superior thermal conductivity compared to the sealing compositions of Comparative Examples 2 and 3, which do not contain alumina as an inorganic filler.

The disclosure of Japanese Patent Application No. 2017-254884, filed on December 28, 2017, is incorporated herein by reference in its entirety.
All publications, patent applications, and standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or standard was specifically and individually indicated to be incorporated by reference.

Claims (3)

The composition contains an epoxy resin, a curing agent, an inorganic filler containing alumina, and a tertiary phosphine oxide ,
the tertiary phosphine oxide comprises triphenylphosphine oxide;
the content of the tertiary phosphine oxide is 1 part by mass to 25 parts by mass relative to 100 parts by mass of the epoxy resin,
The content of the alumina in the inorganic filler is 50 volume % to 100 volume % . The composition contains an epoxy resin, a curing agent, an inorganic filler containing alumina, and an alumina fluidizing agent ,
the alumina fluidizing agent has a melting temperature of 165° C. or lower and does not contain a carboxy group, an amino group, or a hydroxyl group; and when a first sealing composition is prepared by mixing the epoxy resin, the curing agent, and the alumina so that the alumina content is 75 volume %, the viscosity of the first sealing composition is measured at 175° C., and a second sealing composition is prepared by adding 5 parts by mass of the alumina fluidizing agent to 100 parts by mass of the first sealing composition, and the viscosity of the second sealing composition is measured at 175° C., a reduction rate of the viscosity of the second sealing composition relative to the viscosity of the first sealing composition ((viscosity of the first sealing composition−viscosity of the second sealing composition)/viscosity of the first sealing composition)×100(%)) is 10% or more;
The content of the alumina fluidizer is 1 part by mass to 25 parts by mass relative to 100 parts by mass of the epoxy resin,
The content of the alumina in the inorganic filler is 50 volume % to 100 volume % . A semiconductor device comprising: a semiconductor element; and a cured product of the encapsulating composition according to claim 1 or 2 , which encapsulates the semiconductor element.