JP7760231B2 - Encapsulating composition, method for producing same, and semiconductor device - Google Patents

Description

The present invention relates to an encapsulating composition, a method for producing the same, and a semiconductor device.

In recent years, with the trend toward miniaturization and high integration, there has been concern about heat generation inside semiconductor packages. Because heat generation can cause a deterioration in the performance of electrical or electronic components that contain semiconductor packages, materials used in semiconductor packages are required to have high thermal conductivity. Therefore, there is a demand for high thermal conductivity encapsulating materials for semiconductor packages.
Furthermore, when sealing a semiconductor package, the sealing material is required to have high fluidity.
For example, when alumina is used as an inorganic filler, the thermal conductivity of the sealing material can be increased, but the fluidity of the sealing material may decrease, and there is a trade-off between increasing the thermal conductivity and improving the fluidity of the sealing material. Therefore, it may be difficult to achieve both high thermal conductivity and improved fluidity at the same time.

An example of an encapsulant using alumina as an inorganic filler is an epoxy resin composition for semiconductor encapsulation, the essential components of which are (A) an epoxy resin, (B) a curing agent, and (D) an inorganic filler containing spherical alumina and spherical silica, in which the spherical alumina includes (d1) a first spherical alumina having an average particle size of 40 μm or more and 70 μm or less, and (d2) a second spherical alumina having an average particle size of 10 μm or more and 15 μm or less, and the spherical silica includes (d3) a first spherical alumina having an average particle size of 4 μm or more and 8 μm or less. An epoxy resin composition for semiconductor encapsulation is known, which comprises (d3) first spherical silica having an average particle size of 0.05 μm or less, (d4) second spherical silica having an average particle size of 0.05 μm or more and 1.0 μm or less, wherein the total amount of (d3) + (d4) is 17% or more and 23% or less of the total inorganic filler, the ratio of (d3)/(d4) is (d3)/(d4) = 1/8 or more and 5/4 or less, and the amount of the inorganic filler is 85% to 95% by mass of the total resin composition (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2006-273920

However, using alumina, a highly thermally conductive filler, can sometimes deteriorate the curing and formability of the sealing material. Therefore, developing a highly thermally conductive sealing material that ensures fluidity, formability, and curing is a difficult task.

The present disclosure has been made in consideration of the above-mentioned conventional circumstances, and aims to provide an encapsulating composition that has excellent curability, fluidity, and moldability, and has excellent thermal conductivity when cured, a method for manufacturing the same, and a semiconductor device using the encapsulating composition.

Specific means for achieving the above object are as follows.
<1> A sealing composition containing an epoxy resin, a curing agent, and an inorganic filler having a porosity of 18% by volume or less.
<2> The sealing composition according to <1>, wherein the inorganic filler has a volume average particle size of 4 μm to 100 μm.
<3> The sealing composition according to <1> or <2>, wherein the inorganic filler contains at least one of alumina and silica.
<4> The sealing composition according to any one of <1> to <3>, wherein the inorganic filler has a specific surface area of 0.7 ^{m 2} /g to 4.0 m ² /g.
<5> A semiconductor device comprising: a semiconductor element; and a cured product of the sealing composition according to any one of <1> to <4>, which seals the semiconductor element.
<6> A step of determining the composition of the inorganic filler so that the porosity is a predetermined value;
a step of mixing the inorganic filler having the composition determined by the step above, an epoxy resin, and a curing agent.

The present disclosure provides an encapsulating composition that has excellent curability, fluidity, and moldability, and has excellent thermal conductivity when cured, as well as a method for producing the same and a semiconductor device using the encapsulating composition.

Hereinafter, embodiments for carrying out the encapsulating composition, the manufacturing method thereof, and the semiconductor device of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, and they do not limit the present invention.
In the present disclosure, 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 stages in this disclosure, 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. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.
In the present disclosure, each component may contain multiple substances corresponding to the component. 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 composition may contain multiple types of particles corresponding to each component. 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>
The sealing composition of the present disclosure contains an epoxy resin, a curing agent, and an inorganic filler having a porosity of 18% by volume or less.
The porosity of an inorganic filler is a value representing the proportion of voids in the bulk volume of the inorganic filler ((void volume/bulk volume of inorganic filler) × 100 (%)). When inorganic fillers of the same material are used, if the weight of the inorganic filler is the same, the bulk volume of the inorganic filler decreases as the porosity decreases. When the bulk volume of the inorganic filler contained in the sealing composition decreases, the value obtained by subtracting the bulk volume of the inorganic filler from the volume of the sealing composition increases, even if the content of the inorganic filler contained in the sealing composition is the same. Hereinafter, this value may be referred to as the "amount of excess resin."
The present inventors focused on the amount of excess resin in the encapsulating composition and investigated the influence of the amount of excess resin on the curability, fluidity, and moldability of the encapsulating composition, as well as on the thermal conductivity of the cured product. As a result, they found that the curability, fluidity, and moldability of the encapsulating composition, as well as the thermal conductivity of the cured product, improved as the amount of excess resin increased (i.e., the porosity of the inorganic filler decreased), and thus completed the present invention.
Although the reason why the curability, fluidity, moldability, and thermal conductivity of the encapsulating composition improve as the amount of excess resin increases is unclear, it is believed that the viscosity of the encapsulating composition decreases as the amount of excess resin increases, improving its fluidity. It is also presumed that the increased amount of excess resin improves the dispersibility of the encapsulating composition during kneading, contributing to the improvement of its curability, moldability, and thermal conductivity when the encapsulating composition is formed.

The components that make up the sealing composition are described below. The sealing composition of the present disclosure contains an epoxy resin, a curing agent, and an inorganic filler, and may also contain other components as needed.

-Epoxy resin-
The sealing composition contains an epoxy resin. The type of epoxy resin is not particularly limited, and any known epoxy resin can be used.
Specifically, for example, novolac resins obtained by condensing or co-condensing at least one selected from the group consisting of phenolic compounds (e.g., phenol, cresol, xylenol, resorcinol, 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 novolac epoxy resins and orthocresol novolac epoxy resins); bisphenols (e.g., bisphenol A, bisphenol AD, bisphenol F, and bisphenol S) ) and biphenols (e.g., alkyl-substituted or unsubstituted biphenols); epoxidized products of phenol-aralkyl resins; epoxidized products of adducts or polyadducts 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 perspective of preventing corrosion of aluminum or copper wiring on elements such as integrated circuits (ICs), a high purity epoxy resin is preferable, and a low amount of hydrolyzable chlorine is preferable. From the perspective 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 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 2.5% by mass to 6% by mass, more preferably 3.5% by mass to 5.5% by mass, and even more preferably 3.5% by mass to 5.0% by mass.
The content of the epoxy resin in the sealing composition excluding the inorganic filler is preferably 40% by mass to 70% by mass, more preferably 45% by mass to 64% by mass, and even more preferably 48% by mass to 55% 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 include novolak resins obtained by condensing or co-condensing at least one selected from the group consisting of phenolic compounds (e.g., phenol, cresol, resorcinol, 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) in the presence of an acid catalyst; phenol-aralkyl resins; biphenyl-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 blend the curing agent so that the equivalent weight of the curing agent's functional group (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 in the epoxy resin, and it is particularly preferable to blend the curing agent so that the equivalent weight is 0.7 to 1.2 equivalents.

-Inorganic filler-
The sealing composition contains an inorganic filler, which tends to reduce the moisture absorption of the sealing composition and improve the strength in a cured state.

The inorganic fillers may be used alone or in combination of two or more.
When two or more inorganic fillers are used in combination, for example, two or more inorganic fillers having different components, average particle diameters, shapes, etc. are used.
The shape of the inorganic filler is not particularly limited, and examples thereof include powder, spheres, fibers, etc. From the viewpoint of flowability during molding of the sealing composition and mold abrasion, a spherical shape is preferred.

In the present disclosure, the porosity of the inorganic filler is 18% by volume or less, preferably 16% by volume or less, more preferably 15% by volume or less, and even more preferably 14% by volume or less. The porosity of the inorganic filler may be 7% by volume or more. When there is one type of inorganic filler, the porosity of the inorganic filler refers to the porosity of one type of inorganic filler. When there are two or more types of inorganic fillers, the porosity of the inorganic filler refers to the porosity of a mixture of two or more types of inorganic fillers.

The porosity of the inorganic filler is a value measured by the following method.
The sealing composition is placed in a crucible and left at 800°C for 4 hours to be incinerated. The particle size distribution of the resulting ash is measured using a laser diffraction/scattering particle size distribution analyzer (e.g., HORIBA, Ltd., LA920) applying the refractive index of alumina. The porosity ε is calculated from the particle size distribution using the Ouchiyama formula below. The Ouchiyama formula is described in detail in the following literature.
N. Ouchiyama and T. Tanaka, Ind. Eng. Chem. Fundament. , 19, 338 (1980)
N. Ouchiyama and T. Tanaka, Ind. Eng. Chem. Fundament. , 20, 66 (1981)
N. Ouchiyama and T. Tanaka, Ind. Eng. Chem. Fundament. , 23, 490 (1984)

The inorganic filler preferably contains at least one of alumina and silica, and more preferably contains alumina from the viewpoint of high thermal conductivity. The inorganic filler may be entirely alumina, or alumina may be used in combination with other inorganic fillers. When the inorganic filler contains alumina, the thermal conductivity of the sealing composition tends to be improved. Examples of silica include spherical silica and crystalline silica.
Examples of inorganic fillers other than silica that can be used in combination with alumina include zircon, magnesium oxide, calcium silicate, calcium carbonate, potassium titanate, silicon carbide, silicon nitride, boron nitride, aluminum nitride, beryllia, zirconia, etc. Furthermore, examples of inorganic fillers having a flame retardant effect include aluminum hydroxide, zinc borate, etc.

When alumina and silica are used in combination as inorganic fillers, the alumina content in the inorganic filler is preferably 50% by volume or more, more preferably 70% by volume or more, and even more preferably 85% by volume or more. The alumina content in the inorganic filler may also be 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 60% by volume or more, more preferably 70% by volume or more, and even more preferably 75% by volume or more, of the entire sealing composition. The content of the inorganic filler may be 95% by volume or less.

From the viewpoint of high thermal conductivity, the average particle size of the inorganic filler is preferably 4 μm to 100 μm, more preferably 7 μm to 70 μm, and even more preferably 7 μm to 40 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.
The thermal conductivity of the cured product of the sealing composition tends to increase as the average particle size of the inorganic filler increases.
The average particle size of the inorganic filler can be measured by the following method.

The inorganic filler to be measured is added to a solvent (pure water) in a range of 1% to 5% by weight, along with 1% to 8% by weight of surfactant, and the mixture is vibrated in a 110W ultrasonic cleaner for 30 seconds to 5 minutes to disperse the inorganic filler. Approximately 3 mL of the dispersion is poured into a measurement cell and measured at 25°C. A laser diffraction/scattering particle size distribution analyzer (e.g., HORIBA, Ltd., LA920) is used to measure the volumetric particle size distribution. The average particle size is calculated as the particle size (D50%) at which the cumulative total from the smallest diameter side in the volumetric particle size distribution reaches 50%. The refractive index used is that of alumina. If the inorganic filler is a mixture of alumina and other inorganic fillers, the refractive index used is that of alumina.

From the viewpoint of fluidity and moldability, the specific surface area of the inorganic filler is preferably 0.7 ^{m 2} /g to 4.0 m ² /g, more preferably 0.9 m ² /g to 3.0 m ² /g, and even more preferably 1.0 ^m 2 /g to 2.5 m ² /g.
The fluidity of the sealing composition tends to increase as the specific surface area of the inorganic filler decreases.
In the present disclosure, the specific surface area of an inorganic filler refers to the specific surface area of alumina when, for example, alumina is used alone as the inorganic filler, and refers to the specific surface area of a mixture of inorganic fillers when alumina is used in combination with other inorganic fillers as the inorganic filler.
The specific surface area (BET specific surface area) of an inorganic filler can be measured from the nitrogen adsorption capacity in accordance with JIS Z 8830:2013. Quantachrome's AUTOSORB-1 (trade name) can be used as an evaluation device. When measuring the BET specific surface area, it is preferable to first perform a pretreatment to remove moisture by heating, since moisture adsorbed on the sample surface and in the structure is thought to affect the gas adsorption capacity.
In the pretreatment, a measurement cell containing 0.05 g of a measurement sample is depressurized to 10 Pa or less using a vacuum pump, heated to 110°C, and held for 3 hours or more, and then naturally cooled to room temperature (25°C) while maintaining the depressurized state. After this pretreatment, measurements are performed at an evaluation temperature of 77 K and an evaluation pressure range of less than 1 in terms of relative pressure (equilibrium pressure relative to saturated vapor pressure).

(Curing accelerator)
The sealing composition may further contain a curing accelerator. The type of the curing accelerator is not particularly limited, and known curing accelerators can 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 containing 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, and the like, 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, and tris(dimethylaminomethyl)phenol, and derivatives of tertiary amine compounds; 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-5-methylimidazole, 2-phenyl-6-methylimidazole, 2-phenyl-7-methylimidazole, 2-phenyl-8-methylimidazole, 2-phenyl-9-methylimidazole, 2-phenyl-1,4-methylimidazole, 2-phenyl-1,4-methylimidazole, 2-phenyl-1,4-methylimidazole, 2-phenyl-2-methylimidazole, 2-phenyl-2-methylimidazole, 2-phenyl-3-methylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-5-methylimidazole, 2-phenyl-1,4-methylimidazole, 2-phenyl-2-methylimidazole, 2-phenyl-4 ...1,4-methylimidazole, 2- 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; phosphorus compounds having intramolecular polarization obtained by adding a compound having a π bond such as maleic anhydride, the above-mentioned quinone compounds, diazophenylmethane, and phenolic resins to an organic phosphine compound; tetraphenylboron salts such as tetraphenylphosphonium tetraphenylborate, triphenylphosphine tetraphenylborate, 2-ethyl-4-methylimidazole tetraphenylborate, and N-methylmorpholine tetraphenylborate; and adducts of phosphine compounds and tetraphenylboron salts such as triphenylphosphonium-triphenylborane and N-methylmorpholine tetraphenylphosphonium-tetraphenylborate. 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 relative to the total amount of epoxy resin and curing agent.

(Ion trapping agent)
The sealing composition may further contain an ion trapping agent.
The ion trapping agent usable in the present disclosure is not particularly limited as long as it is an ion trapping agent that is commonly 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 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" (trade name, Kyowa Chemical Industry Co., Ltd.) is a commercially available example of a compound represented by general formula (II-1). For example, "IXE500" (trade name, Toagosei Co., Ltd.) is a commercially available example of a 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 in order to achieve sufficient moisture resistance reliability. In order to fully utilize the effects of the 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 inorganic fillers.

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

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-aminopropyltriethoxysilane, trimethoxysilane, γ-(β-aminoethyl)aminopropyldimethoxymethylsilane, N-(trimethoxysilylpropyl)ethylenediamine, N-(dimethoxymethylsilylisopropyl)ethylenediamine, methyltrimethoxysilane, methyltriethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, hexamethyldisilane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, and γ-mercaptopropylmethyldimethoxysilane.

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.

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

(Release agent)
The sealing composition may further contain a release agent. The type of release agent is not particularly limited, and known release agents can be used. Specific examples include higher fatty acids, carnauba wax, and polyethylene wax. One type of release agent may be used alone, or two or more types may be used in combination.
When the sealing composition contains a release agent, the content of the release agent is preferably 10% by 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% by 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.

When conductive particles such as carbon black are used as the colorant, the content of conductive particles having a particle diameter of 10 μm or more is preferably 1% by mass or less.
When the sealing composition contains conductive particles, the content of the conductive particles is preferably 3 mass % or less based on the total amount of the epoxy resin and the curing agent.

<Method of manufacturing sealing composition>
The method for producing a sealing composition according to the present disclosure includes the steps of: determining a composition of an inorganic filler so that the porosity is a predetermined value; and mixing the inorganic filler having the composition determined in the step, an epoxy resin, and a curing agent. The predetermined porosity is preferably 18% by volume or less, more preferably 16% by volume or less, even more preferably 15% by volume or less, and particularly preferably 14% by volume or less.
The method for determining the composition of the inorganic filler so that the porosity is a predetermined value is not particularly limited. When the inorganic filler has a spherical shape, the porosity of the inorganic filler can be calculated based on the particle size distribution of the inorganic filler. Therefore, the particle size distributions of multiple inorganic fillers may be measured and accumulated in advance, the porosity of the inorganic filler may be determined according to the characteristics of the sealing composition, and the composition of the inorganic filler may be determined by combining multiple inorganic fillers so that the porosity is the predetermined value.
As a method for calculating the void ratio of the inorganic filler based on the particle size distribution of the inorganic filler, a method of calculation using the above-mentioned Ouchiyama formula can be mentioned.
Next, the inorganic filler, the composition of which is determined so as to have a predetermined porosity, the epoxy resin, the curing agent, and other components used as needed are thoroughly mixed using a mixer or the like, and then the mixture is kneaded using a hot roll, an extruder, etc., and then subjected to treatments such as cooling and pulverization, thereby producing an encapsulating composition. The state of the encapsulating composition is not particularly limited, and may be in the form of a powder, solid, liquid, etc.

<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 semiconductor elements using the encapsulating composition, and any known method can be used. For example, transfer molding is common, but compression molding, injection molding, and other methods may also be used.

The semiconductor device disclosed herein is suitable 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. Furthermore, unless otherwise specified, the numerical values in the tables refer to "parts by mass."

(Examples 1 to 6 and Comparative Examples 1 to 3)
The components shown below were premixed (dry blended) in the mixing ratios (parts by mass) shown in Table 1 or Table 2, then kneaded in a twin-screw kneader, cooled and pulverized to produce powdered sealing compositions.

(A) Epoxy Resin A1: Bisphenol-type crystalline epoxy resin, epoxy equivalent: 192 g/eq
A2: Biphenyl type epoxy resin, epoxy equivalent: 192 g/eq
A3: Bisphenol F type epoxy resin, epoxy equivalent: 158 g/eq
(B) Curing agent B1: Triphenylmethane type phenolic resin, triphenylmethane type phenolic resin with a hydroxyl group equivalent of 104 g/eq. (C) Curing accelerator C1: Phosphorus-based curing accelerator (an adduct of tributylphosphine and benzoquinone)
(D) Filler (inorganic filler)
D1: Alumina filler with an average particle size (D50, particle size corresponding to 50% of the cumulative volume from the smallest diameter side) of 10.4 μm and a specific surface area of 1.5 m ² /g. D2: Alumina filler with an average particle size of 1.6 μm and a specific surface area of 3.3 m ² /g. D3: Alumina filler with an average particle size of 43.9 μm and a specific surface area of 0.15 m ² /g. D4: Alumina filler with an average particle size of 0.7 μm and a specific surface area of 8.0 m ² /g. D5: Silica filler with a specific surface area of 200 m ² /g. D6: Alumina filler with an average particle size of 11.7 μm and a specific surface area of 2.2 m ² /g, a 9/1 (mass ratio) mixture of silica filler and alumina filler.

<Porosity, specific surface area and average particle size>
The porosity, specific surface area and average particle size of the inorganic filler were measured by the methods described above. The results are shown in Table 3 or Table 4.

<Curability>
The curability was evaluated based on the gel time measured using a gelation tester as follows.
0.5 g of the sealing composition obtained above was placed on a hot plate heated to 175°C, and the sample was uniformly spread into a circle of 2.0 cm to 2.5 cm using a jig at a rotation speed of 20 to 25 rpm. The time from when the sample was placed on the hot plate until the sample lost its viscosity, became gelled, and could be peeled off from the hot plate was measured, and this was measured as the gel time (sec).
The results are shown in Table 3 or Table 4. When the same amount of catalyst (amount of curing accelerator) is used per 100 parts by mass of epoxy, the shorter the gel time, the better the curability.

<Liquidity>
The resulting sealing composition was passed through a two-tier sieve (top sieve: 2.38 mm, bottom sieve: 0.5 mm), and 7 g of the sample remaining on the bottom sieve was weighed. The sealing composition was placed on a smooth mold heated to 180°C, and an 8 kg smooth mold also heated to 180°C was placed on the sample and left for 60 seconds. The average values (mm) of the major and minor axes (mm) of the resulting disk-shaped molded product were then calculated, and this average value (mm) was designated as the disk flow (DF).
The results are shown in Table 3 or Table 4. The longer the disk flow, the better the fluidity.

<Moldability>
15 g of the obtained sealing composition was placed on a mold set at 180° C. on a hot press plate and molded for 90 seconds. After molding, the length of the portion where the sealing composition flowed the longest was measured using a vernier caliper in slits of 50 μm, 30 μm, 20 μm, 10 μm, 5 μm, and 2 μm made in the mold, and this measurement value was defined as the burr length.
The results are shown in Table 3 or Table 4. The shorter the burr, the better the formability.

<Thermal conductivity>
Using the encapsulating composition obtained above, test specimens for evaluating thermal conductivity were prepared using a vacuum hand press molding machine under conditions of a mold temperature of 175°C to 180°C, a molding pressure of 7 MPa, and a curing time of 600 seconds. The thermal diffusivity of the molded test specimens in the thickness direction was then measured. The thermal diffusivity was measured using a laser flash method (apparatus: LFA467 nanoflash, manufactured by NETZSCH). Pulsed light irradiation was performed under conditions of a pulse width of 0.31 (ms) and an applied voltage of 247 V. The measurement was performed at an ambient temperature of 25°C ± 1°C. The density of the test specimens was also measured using an electronic hydrometer (AUX220, manufactured by Shimadzu Corporation). The theoretical specific heat of the encapsulating composition calculated from the literature values of the specific heat of each material and the blending ratio was used to determine the specific heat.
The thermal conductivity value was then obtained by multiplying the thermal diffusivity by the specific heat and density using equation (1).
λ=α×Cp×ρ...Formula (1)
(In formula (1), λ represents thermal conductivity (W/(m·K)), α represents thermal diffusivity (m ² /s), Cp represents specific heat (J/(kg·K)), and ρ represents density (kg/m ³ ).)
The results are shown in Table 3 or Table 4.

As is clear from the evaluation results in Tables 3 and 4, the sealing compositions of Examples 1 to 6, in which the porosity of the inorganic filler is 18% by volume or less, have superior curability, fluidity, and formability compared to the sealing compositions of Comparative Examples 1 to 3, in which the porosity of the inorganic filler exceeds 18% by volume. Furthermore, the thermal conductivity of the cured products of the sealing compositions of Examples 1 to 6 is equal to or higher than that of the cured products of the sealing compositions of Comparative Examples 1 to 3.

The disclosure of Japanese Patent Application No. 2017-254885, filed on December 28, 2017, is incorporated herein by reference in its entirety.
All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims (4)

The composition contains an epoxy resin, a curing agent, and an inorganic filler having a porosity of 18% by volume or less,
the inorganic filler comprises alumina and silica;
The content of alumina in the inorganic filler is 50% by volume to 99% by volume,
The solid or powdered sealing composition has a particle size (D50%) of 11.7 μm to 100 μm when the cumulative particle size distribution from the smallest diameter side in the volumetric particle size distribution of the inorganic filler is 50%. 2. The sealing composition according to claim 1, wherein the inorganic filler has a specific surface area of 0.7 ^{m 2} /g to 4.0 m ² /g. 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. determining the composition of the inorganic filler so that the porosity is 18% by volume or less ;
a step of mixing the inorganic filler having the composition determined by the step, an epoxy resin, and a curing agent;
the inorganic filler comprises alumina and silica;
The content of alumina in the inorganic filler is 50% by volume to 99% by volume,
The method for producing a solid or powdered sealing composition, wherein the inorganic filler has a particle diameter (D50%) of 11.7 μm to 100 μm when the cumulative particle diameter from the smallest diameter side in the volume-based particle size distribution reaches 50%.