JP2002338788A - Epoxy resin composition and hollow package housing semiconductor element using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition suitable for hollow packages which has a higher thermal conductivity compared to conventional compositions and shows a good flow property at transfer molding, and to provide a hollow package housing semiconductor elements. SOLUTION: The epoxy resin composition contains an epoxy resin, a hardener, a curing accelerator, a crystalline silica powder and a globular silica powder. Here, the crystalline silica powder has an average particle size of 0.1 μm or larger but smaller than 30 μm and a content of from 10 to 90 mass % against the total mass of the composition, while the globular silica powder has a sphericity, obtained by the formula: sphericity=(the projected area of the particle)/(the area of a circle having a circumference equal to the projected circumference of the particle), of >=0.8, an average particle size of 0.1 μm or larger but smaller than 30 μm and a content of from 1 to 50 mass % against the total mass of the composition (the total content is <=95 mass % against the total mass of the composition). The composition has a thermal conductivity (λp ) of >=1.2 W/m.k.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition excellent in heat conductivity and moldability suitable for a hollow package for housing a semiconductor element, and a semiconductor element housing hollow package made of the resin composition. .

[0002]

2. Description of the Related Art Conventionally, a CCD (Charge Coupled Device) has been used.
e) and CMOS (Complementary Metal Oxide Semicondu
As a hollow package for accommodating a solid-state imaging device such as a ctor), an inexpensive resin package is used in addition to ceramic. Generally, a resin hollow package is integrated with a resin molded body by insert molding, and a lead frame with both ends opened to the inside and outside of the package is bonded to a semiconductor element fixed to the center of the package with an adhesive. They are electrically connected by wires. Further, the upper surface of the resin molded body has a hermetically sealed structure in which a lid material such as a transparent synthetic resin plate or a glass plate is fixed with an adhesive.

However, in recent years, demands for solid-state image pickup devices such as CCDs and CMOSs have been increasing as the number of pixels and size of video recording devices such as video cameras and digital cameras equipped with such a resin hollow package have increased. Performance is also increasing. That is, as the number of pixels increases and the miniaturization progresses, the amount of heat generated by the semiconductor element increases, which may reduce the function of the imaging element itself.
Therefore, in order to solve such a problem by increasing the heat radiation from the material of the hollow package, a resin hollow package having high thermal conductivity is demanded.

Conventionally, as a means for improving the thermal conductivity of a resin molded product, a method of adding crystalline silica powder having better thermal conductivity than fused silica powder has been used, but crystalline silica powder has a crushed shape. Therefore, it has been pointed out that the flowability of the epoxy resin composition decreases during transfer molding, and the moldability deteriorates.Therefore, in order to improve the thermal conductivity, the filling rate of the inorganic filler is increased. Was said to be difficult.

On the other hand, when the size of the package is reduced, the thickness of the resin molded body becomes thinner, which causes a problem that moisture in the air easily enters the inside of the package through the resin molded body. I was

[0006]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above-mentioned problems, and has a high thermal conductivity and a good fluidity during transfer molding as compared with the prior art. It is an object of the present invention to provide an epoxy resin composition suitable for a hollow package and a resin hollow package for housing a solid-state imaging device such as a CCD and a CMOS.

[0007]

Means for Solving the Problems The present inventors have conducted various studies in order to achieve the above object, and as a result, completed the present invention. That is, the present invention is described below. It contains an epoxy resin, a curing agent, a curing accelerator, crystalline silica powder and spherical silica powder, and the crystalline silica powder has an average particle size of 0.1 μm or more and less than 30 μm, and has a content of 10 mass with respect to the total mass of the composition. % Or more and 90% by mass or less, the spherical silica powder has a sphericity of 0.8 or more determined by the following formula (1), and an average particle size of 0.1 μm or more and 30 or more.
μm, and the content based on the total mass of the composition is 1% by mass or more and 50% by mass or less (provided that the total content of the crystalline silica powder and the spherical silica powder is based on the total mass of the composition) 95% by mass or less.),

[0008]

(Equation 2)

An epoxy resin composition having a thermal conductivity (λ _p ) of at least 1.2 W / mk. The density measured in 1-butanol as a medium is 2.1.
0 g / cm ^{3 or} less, and a low-density spherical silica powder having a moisture absorption of 3% or more and an average particle size of 0.1 μm or more and less than 3 μm is contained in the entire composition in an amount of 1% by mass or more and 30% by mass or less (however, The total content of the crystalline silica powder, the spherical silica powder and the low-density spherical silica powder is 95% by mass or less based on the total mass of the composition.) Or an epoxy resin composition for a hollow package containing a semiconductor element, comprising the epoxy resin composition described in the above. A hollow package containing a semiconductor element, which is molded from the epoxy resin composition described in the above item.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The epoxy resin composition of the present invention is an epoxy resin composition containing an epoxy resin, a curing agent, a curing accelerator, crystalline silica powder and spherical silica powder. <Epoxy resin> Examples of the epoxy resin used in the present invention include bisphenol A type, bisphenol F type, and bisphenol AD type epoxy resins; phenol novolak type epoxy resin, orthocresol novolak type epoxy resin; naphthalene skeleton-containing epoxy resin, biphenyl A skeleton-containing epoxy resin is preferably used. Any of these may be used alone or two or more of them may be used in an appropriate ratio. The epoxy equivalent is preferably 300 (g / eq) or less.

<Curing Agent> The curing agent used in the present invention can be used without any particular limitation as long as it is capable of undergoing a curing reaction with the epoxy resin. As the curing agent, a phenol resin is preferable, and as the phenol resin, a phenol novolak resin, an aralkyl phenol resin and the like can be mentioned.

As the curing agent, amines such as diaminodiphenylmethane, diaminodiphenylsulfone and m-phenylenediamine; acid anhydrides such as phthalic anhydride, tetrahydrophthalic anhydride and hexahydrophthalic anhydride; isophthalic dihydrazide; Acid dihydrazide such as adipic acid dihydrazide; dicyandiamide, boron trifluoride and the like;

When the compounding amount of the curing agent is represented by the chemical equivalent ratio, the chemical equivalent ratio to the epoxy resin is 0.5 or more and 1.5 or less, particularly 0.7 or more from the viewpoint of moisture resistance and mechanical properties. It is preferably in the range of 1.2 or less. <Curing Accelerator> As the curing accelerator used in the present invention, one that promotes a crosslinking reaction between the epoxy resin and the curing agent can be used without limitation.

A specific example is 2-methylimi
Dazole, 2-ethyl 4-methylimidazole, 2-d
Imidazoles such as tyl 4-methylimidazoleazine
And triphenylphosphine, tri (p-methylphenyi)
L) Organic phosphines such as phosphine; 1,8-diaza
Bicyclo [5,4,0] undecene-7 phenol salt,
DBU derivatives such as enol novolak salts and carbonates;
Ar-NH-CO-NR _Two(Ar is a substituted or unsubstituted
An aryl group, R is the same or different substituted or
Urea derivatives represented by unsubstituted alkyl groups) and the like.
It is.

These curing accelerators are epoxy resins 10
It is compounded at a ratio of 0.1 to 20 parts by mass, preferably 0.1 to 10 parts by mass with respect to 0 parts by mass. <Inorganic filler> Examples of the inorganic filler used in the present invention include crystalline silica powder and spherical silica powder. As inorganic fillers, in addition to crystalline silica powder and spherical silica powder, alumina powder, aluminum nitride powder, ferrite powder,
Aluminum hydroxide powder, calcium carbonate powder and the like can be used.

The crystalline silica powder used in the present invention has an average particle size of 0.1 μm or more and less than 30 μm, preferably 1 μm
Not less than 25 μm, more preferably not less than 5 μm and not more than 20 μm
Desirably less than. The spherical silica powder has a sphericity determined by the following formula (1) of 0.8 or more, preferably 0.1.
82 or more, more preferably 0.85 or more, and the average particle size is 0.1 to 30 μm, preferably 1 to 30 μm, more preferably 10 to 30 μm
Desirably less than.

[0017]

(Equation 3)

When such crystalline silica powder and spherical silica powder are combined, moldability during transfer molding, that is, fluidity can be improved. The above crystalline silica powder and spherical silica powder usually have a density of 2.20 g / c.
m ³ or more. It is desirable that the crystalline silica powder is blended in an amount of 10% by mass to 90% by mass, preferably 25% by mass to 90% by mass, more preferably 30% by mass to 80% by mass with respect to the total mass of the composition.

The spherical silica powder accounts for 1% by mass to 50% by mass, preferably 5% by mass, based on the total mass of the composition.
Not less than 40% by mass and more preferably not less than 10% by mass.
Desirably, the content is 0% by mass or less. In the present invention, in addition to the crystalline silica powder and the spherical silica powder,
The density measured in butanol as a medium is 2.10 g /
It is preferable to use a low-density spherical silica powder having a density of less than ³ cm ³ and a moisture absorption of 3% or more. Use of the low-density spherical silica powder can impart sufficient moisture resistance to the resin hollow package.

The low-density spherical silica powder has a density measured using 1-butanol as a medium of less than 2.10 g / cm ³ , preferably 1.55 to 2.05 g / cm ³ , more preferably 1.60 to 1 / g. 0.95 g / cm ³ . By using silica having such a density, the moisture resistance of the epoxy resin composition is significantly improved.

The low-density spherical silica powder has a maximum particle size of 100.
μm or less, and the average particle size is 0.1 μm or more and less than 3 μm,
Preferably, one having a thickness of 1 to 2 μm is used. The low-density spherical silica powder accounts for 1 to 30% by mass, preferably 1 to 25% by mass, based on the total mass of the composition.
Below, it is desirable that it is more preferably blended in an amount of 1% by mass or more and 10% by mass or less.

The above-mentioned silica powder (including crystalline silica powder, spherical silica powder and low-density spherical silica powder) is desirably incorporated in a total amount of not more than 95% by mass based on the total mass of the composition. When the crystalline silica powder and the spherical silica powder are mixed in the composition, the minimum amount is 11% by mass or more, preferably 25% by mass, based on the total mass of the composition.
When the crystalline silica powder, the spherical silica powder and the low-density spherical silica powder are blended in the composition, the total amount is 12% by mass or more, preferably 25% by mass, based on the total mass of the composition. % Or more.

In order to suppress the occurrence of soft errors in semiconductors, it is preferable to use silica powder having a uranium content of 1 ppb or less as a radioactive element. <Other compounding agents> In the present invention, montanic acid, stearic acid, behenic acid,
Higher fatty acids such as oleic acid; ester waxes of higher fatty acids such as carnauba wax (carnauba wax); zinc behenate, zinc oleate, magnesium stearate;
Metal salts of higher fatty acids such as barium stearate and aluminum stearate; metal soaps such as zinc stearate can be blended, and these can be used alone or in combination.

In addition to the above, a silane coupling agent may be added to the epoxy resin composition of the present invention, if necessary.
Flame retardants such as brominated epoxy resins and antimony trioxide; coloring agents such as carbon black and phthalocyanine;
A low stress agent may be added. <Production method of composition> The epoxy resin composition of the present invention is obtained by kneading and heating all of these materials with a two-roll or kneader, followed by cooling and pulverization to obtain the desired epoxy resin composition. .

The epoxy resin composition according to the present invention has a cured product having a thermal conductivity (λ _p ) of 1.2 W / m · k or more, preferably 1.3, determined by the following formula (2) by a probe method.
It is at least W / mk, more preferably at least 1.5 W / mk.

[0026]

(Equation 4)

Here, I: current (A) t ₂ , t ₁ : sampling time (s) v ₂ , v ₁ : thermocouple output (mA) K: probe constant H: probe constant The measurement of the thermal conductivity (λ _p ) is specifically performed by a method described later.

The epoxy resin composition according to the present invention has a spiral flow of usually 20 measured by the method described below.
cm or more, preferably 22 cm or more, more preferably 2 cm or more.
It is 5 cm or more, and the melting torque measured by the method described later is usually 1.30 J or less, preferably 1.2 J or less, more preferably 1.1 J or less. The epoxy resin composition of the present invention exhibiting such characteristics has excellent thermal conductivity and excellent fluidity during transfer molding.

The epoxy resin composition of the present invention comprises a CCD,
It shows excellent suitability for a hollow package for accommodating a semiconductor device such as a solid-state imaging device such as a CMOS, but of course, the epoxy resin composition can also be used for other applications generally used. It is. <Hollow Package> Next, the hollow package of the present invention will be described. FIG. 1 shows an example of a cross-sectional view of a hollow package that can be molded with the epoxy resin composition of the present invention.

A hollow package 10 which can be molded from the epoxy resin composition of the present invention usually has a box-shaped package body 1 having an open top, as shown in FIG. And the like, and is sealed via an adhesive 3. Further, an island 4 is provided in the central concave portion of the package body 1,
The semiconductor element 5 mounted thereon is connected to a lead frame via a bonding wire 6. The lead frame is integrally formed by insert molding when forming the package, and the external lead 7 and the internal lead 8 are connected via a lead frame sealed in the package.

A package having such a structure is obtained by transfer molding the above-mentioned epoxy resin composition.
Pressure is 1 to 50 × 10 ⁶ Pa (10 to 500 kg / c
m ² ), molding can be performed under molding conditions of a temperature of 150 to 200 ° C. and a time of 1 to 5 minutes.

[0032]

EXAMPLES Hereinafter, the excellent effects of the present invention will be described with reference to examples, but the present invention is not limited to the examples.
In the present invention, the physical properties of silica were measured as follows. (1) Density The density of silica was measured by the following method. JIS R35
Approximately 5 g of sufficiently crushed and dried silica was weighed in a 50 ml Warden-type specific gravity bottle (mass m _O ) specified in 03 and precisely weighed. The mass of (specific gravity bottle) + (silica) at this time is m
_S. About 10 ml of 1-butanol which had been degassed in advance was added, and ultrasonic stirring was performed for 30 minutes. The pycnometer is then transferred to a vacuum desiccator for at least 30 m.
Placed in a vacuum of mHg for 15 minutes to allow the silica to fully infiltrate 1-butanol. Next, the specific gravity bottle was filled with 1-butanol, covered, and immersed in a constant temperature water bath at 25 ° C. for 15 minutes to measure the mass. At this time (specific gravity bottle) +
The mass of (silica) + (1-butanol) was _defined as m _Sl .

Separately, the following operation was performed for the purpose of measuring the volume of the pycnometer. The specific gravity bottle was filled with water that had been degassed in advance, covered, and immersed in a constant temperature water bath at 25 ° C. for 15 minutes, and then the mass was measured. At this time (specific gravity bottle)
+ The weight of (water) was m _l. The density ρ _S was calculated by the following calculation method.

[0034]

(Equation 5)

Here, m _O : mass of specific gravity bottle (g) m _S : mass of specific gravity bottle + (silica) m _Sl : (specific gravity bottle) + (silica) + (1-butanol) mass) (g) m _l :( pycnometer) + (mass of water) (g) [rho _S: silica density at ^{25 ℃ (g / cm 3)} ρ B: 25 density of 1-butanol at ° C. (= 0 .8
060 g / cm ³ ) ρ _W : density of water at 25 ° C. (= 0.997047 g)
/ Cm ³ ) V: Volume of specific gravity bottle (cm ³ ).

The measurement was repeated twice, and the average was calculated. (2) Moisture absorption rate The moisture absorption rate was measured by the following method. About 5 g of sufficiently dried silica is placed in a container, precisely weighed, and the weight at this time is defined as W ₀ . Next, the container is placed in a thermo-hygrostat at 60 ° C. and 90% RH, and left for 24 hours. The weight at this time is defined as W ₁ . From these W ₀ and W ₁ , the moisture absorption was calculated by the following equation.

[0037]

(Equation 6)

(3) Average Particle Size The average particle size of the low-density spherical silica was measured by the following method. 5 to 50 mg of silica is dispersed in 10 to 2 dispersion media.
0 ml was dispersed using an ultrasonic stirrer. As the dispersion medium, water or polyethylene glycol was used depending on the particle size. Transfer the dispersion to the cell, remove the air bubbles, cover the cell, and use a centrifugal sedimentation method particle size analyzer (CAP manufactured by Horiba, Ltd.)
A-700). The rotation speed of the measuring machine was 500 to 5000 rpm depending on the particle size. The D (MEDIAN) value calculated by the measuring instrument was defined as the average particle size. Also,
Crystalline silica and spherical silica were measured by a laser diffraction method.

[0039]

Example 1 After mixing all raw materials shown in Table 1 with a Henschel mixer, the mixture was heated and kneaded with two rolls at a temperature of 90 to 110 ° C, and then cooled and pulverized to obtain an epoxy resin composition. Using this composition, the following characteristics (1) to (4) were evaluated. The results are shown in Table 1. In Table 1, the mixing ratio of each raw material indicates parts by weight.

<Evaluation method> (1) Spiral flow Using a mold having a spiral shape in accordance with the EMMI1-66 standard, transfer molding was performed, and the mold temperature was 150 ° C. and the effective pressure was 6.9 × 10 5. ⁶ Pa (70kgf /
cm ² ), and the length of flow in the mold when cured for 180 seconds was measured.

(2) Thermal conductivity Measured using a rapid thermal conductivity meter manufactured by Kyoto Electronics Industry Co., Ltd. First, 105 mm of the prepared epoxy resin composition
(L) × 55 mm (W) × 15 mm (H), and the molded body was left in an atmosphere at 23 ° C. for 12 hours or more. Next, the probe of the rapid thermal conductivity meter was placed on the molded body, and the value after one minute was read to be the thermal conductivity.

(3) Melting torque Labo Plastomill 20R-2 manufactured by Toyo Seiki Seisaku-sho, Ltd.
It was measured using a 00 type. First, the prepared epoxy resin composition was put into a kneading section heated to 160 ° C., and the melting torque of the composition was measured. This melting torque was also used as a criterion for determining the fluidity during transfer molding, similarly to the spiral flow of (1) above.

(4) Appearance of Molded Article Since the appearance of a molded article depends on the shape of the mold and the molding conditions, a method of clarifying the difference in appearance is to mold the mold with a gate size smaller than the cavity volume. Molding was carried out. Conventionally, when molding an epoxy resin composition containing about 70% by mass or more and 90% by mass or less of an inorganic filler by transfer molding, the mold gate dimension is 0.5 cc / mm ² or less with respect to the cavity capacity. It is well known to design with a guideline. However, in the measurement of the present invention, the gate dimension was set to 1.7 cc / mm ² with respect to the cavity capacity.

Specifically, the cavity size 6 shown in FIG.
3.5mm (L) x 12.7mm (W) x 12.7mm
Using the mold of (H), the epoxy resin composition prepared as described above was heated to 110 ° C. by a high frequency preheater, and then subjected to transfer molding at a mold temperature of 180 ° C. and an effective pressure of 2 ° C.
Molded at 9.4 × 10 ⁶ Pa (300 kgf / cm ² )
The appearance of the molded article cured for 120 seconds was visually judged. Judgment was performed by molding 10 molded articles, and was represented by the unfilled and void occurrence rates.

[0045]

Example 2 In Example 1, except that the amount of crystalline silica powder (1) was reduced from 942 parts by weight to 804 parts by weight, and the amount of spherical silica powder (1) was increased from 139 parts by weight to 277 parts by weight. Was performed in the same manner as in Example 1. The results of the evaluation are shown in Table 1.

[0046]

Example 3 Example 1 was repeated except that the amount of crystalline silica powder (1) was reduced from 942 parts by weight to 664 parts by weight, and the amount of spherical silica powder (1) was increased from 139 parts by weight to 417 parts by weight. Was performed in the same manner as in Example 1. The results of the evaluation are shown in Table 1.

[0047]

Example 4 The procedure of Example 1 was repeated, except that the crystalline silica powder (1) was changed to the crystalline silica powder (2). The results of the evaluation are shown in Table 1.

[0048]

Example 5 In Example 1, the crystalline silica powder (1) was changed to the crystalline silica powder (2), the amount was reduced from 942 parts by weight to 804 parts by weight, and the amount of the spherical silica powder (1) was 139 parts by weight. Example 1 was repeated except that the amount was increased to 277 parts by weight. The results of the evaluation are shown in Table 1.

[0049]

Reference Example 1 In the same manner as in Example 1, except that the spherical silica powder (1) was not used and the amount of the crystalline silica powder (1) was increased from 942 parts by weight to 1081 parts by weight. went. The results of the evaluation are shown in Table 1.

[0050]

Reference Example 2 In Example 1, the amount of the crystalline silica powder (1) was reduced from 942 parts by weight to 804 parts by weight, and the spherical silica powder (1) was changed to the spherical silica powder (2) and the amount was 139 parts by weight. Example 1 was repeated except that the amount was increased to 277 parts by weight. The results of the evaluation are shown in Table 1.

[0051]

Reference Example 3 In Example 1, the amount of the crystalline silica powder (1) was reduced from 942 parts by weight to 664 parts by weight, and the spherical silica powder (1) was changed to the spherical silica powder (2) and the amount was changed to 139 parts by weight. The procedure was the same as in Example 1, except that the amount was increased to 417 parts by weight. The results of the evaluation are shown in Table 1.

[0052]

REFERENCE EXAMPLE 4 In Example 1, the amount of the crystalline silica powder (1) was reduced from 942 parts by weight to 804 parts by weight, and the spherical silica powder (1) was changed to the spherical silica powder (3) and the amount was 139 parts by weight. Example 1 was repeated except that the amount was increased to 277 parts by weight. The results of the evaluation are shown in Table 1.

From the results shown in Table 1, it is found that the epoxy resin composition (Examples 1 to 5) obtained by mixing the crystalline silica powder and the spherical silica powder having a sphericity of 0.8 or more was 1.2 W / m · k. A composition not containing spherical silica powder (Reference Example 1) having the above thermal conductivity, a low melting torque, and no appearance defect rate of a molded product, and having a sphericity of less than 0.8. Compared with compositions containing spherical silica powder (Reference Examples 2 to 4),
It turns out that transfer moldability is favorable.

Reference Examples 2 and 4 are compositions in which a crystalline silica powder and a spherical silica powder having a small sphericity were blended. Although the thermal conductivity was 1.6 W / m · k or more, the spherical silica powder had a spherical shape. Due to the low degree, poor appearance of the molded article occurs.

[0055]

[Table 1]

[0056]

The epoxy resin composition of the present invention has a high thermal conductivity and is suitable as a material for a resin hollow package for housing a solid-state imaging device such as a CCD or CMOS.
Further, the epoxy resin composition of the present invention is excellent in flowability and therefore excellent in moldability during transfer molding.

[Brief description of the drawings]

FIG. 1 shows a cross-sectional view of an example of a hollow package for housing a semiconductor element.

FIG. 2A shows a transfer molding die (only a lower die) used for evaluating the appearance of a molded product, and FIG. 2B shows a cross-sectional view taken along the line AA in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Package body 2 ... Lid material 3 ... Adhesive 4 ... Island 5 ... Semiconductor element 6 ... Bonding wire 7 ... External lead part 8 ... Internal lead part 10 ... Hollow package 11 ... Cavity 12 ... Gate 13 ... Runner 14 ... Cold Slug well 15… Lower mold 16… Upper mold

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 23/29 H01L 23/30 R 23/31 F term (Reference) 4J002 CC042 CC122 CD031 CD051 CD061 DD076 DE118 DE148 DE238 DF018 DJ018 EF126 EN056 EN076 EQ026 EU117 EU207 EW017 FA088 FD018 FD090 FD142 FD146 FD157 FD160 4J036 AA01 AD08 AF06 DA01 DA02 DA05 DB15 DC03 DC35 DC40 DC46 DD05 DD07 FA03 FA05 FB07 FB08 GA19 JA15 4E109 EA03 EB03 EB03 EB08

Claims (4)

[Claims] 1. An epoxy resin, a curing agent, a curing accelerator, a crystalline silica powder and a spherical silica powder, wherein the crystalline silica powder has an average particle size of 0.1 μm or more and 30 μm or more.
Less than 10 and the content relative to the total mass of the composition is 10
The spherical silica powder has a sphericity of 0.
8 or more, the average particle size is 0.1 μm or more and less than 30 μm, and the content relative to the total mass of the composition is 1% by mass.
Not less than 50% by mass (provided that the total content of the crystalline silica powder and the spherical silica powder is not more than 95% by mass with respect to the total mass of the composition). An epoxy resin composition having a thermal conductivity (λ _p ) of 1.2 W / m · k or more. 2. A low-density spherical silica powder having a density of less than 2.10 g / cm ³ measured using 1-butanol as a medium, a moisture absorption of 3% or more, and an average particle size of 0.1 μm or more and less than 3 μm. 1% by mass or more and 30% by mass or less in the composition (however, the content of crystalline silica powder, spherical silica powder and low-density spherical silica powder is 95% by mass or less based on the total mass of the composition. The epoxy resin composition according to claim 1, wherein: 3. An epoxy resin composition for a hollow package containing a semiconductor element, comprising the epoxy resin composition according to claim 1 or 2. 4. A hollow package containing a semiconductor element, which is molded from the epoxy resin composition according to claim 1.