JPH1160687A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject compsn. which exhibits a high flowability in molding by compounding an epoxy resin contg. a specified amt. of a crystalline epoxy resin having a specified m.p. with a phenol resin curative contg. a specified amt. of a triphenolmethane-type phenol resin, a cure accelerator and a specified amt. of a fused silica powder. SOLUTION: This compsn. comprises an epoxy resin contg. at least 30 wt.% at least one crystalline epoxy resin represented by formulas I to IV and having an m.p. of 50-150 deg.C, a phenol resin cuative contg. at least 30 wt.% phenol resin represented by formula V, a cure accelerator (e.g. triphenylphosphine) and a fused silica powder in an amt. of 80-90 wt.% of the compsn. In formulas I to III, R is H, a halogen, or a 1-12C alkyl; (l) is 1-10; (m) is 0-3; and (n) is 0-4. This compsn. warps little after molding or during soldering in area mounting packages.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device having excellent moldability, reliability, and mountability. More specifically, a semiconductor device is mounted on one side of a printed wiring board or a metal lead frame. In a so-called area mounting type semiconductor device in which substantially only one of its mounting surfaces is resin-sealed, the warpage after resin sealing and the warping in the soldering process at the time of board mounting are small, and in a temperature cycle test. Epoxy resin composition for semiconductor encapsulation which has excellent package crack resistance and package crack resistance and exfoliation resistance in a soldering process, and is excellent in moldability, and a semiconductor encapsulated with the epoxy resin composition for semiconductor encapsulation It concerns the device.

[0002]

2. Description of the Related Art In recent years, in the market trend of miniaturization, weight reduction, and high performance of electronic equipment, high integration of semiconductors has been progressing year by year, and surface mounting of semiconductor packages has been promoted. Packaging packages have been developed and are beginning to move away from packages with traditional structures. Typical area mounting packages are BGA (ball grid array) or CSP (chip size package) pursuing further miniaturization, but these are approaching the limit in conventional surface mounting packages such as QFP and SOP. It has been developed to meet the demand for higher pin counts and higher speeds. The structure is as follows: a rigid circuit board represented by a BT resin / copper foil circuit board (bismaleimide / triazine / glass cloth board) or a flexible circuit board represented by a polyimide resin film / copper foil circuit board; An element is mounted, and only the element mounting surface, that is, one side of the substrate is molded and sealed with an epoxy resin composition or the like. In addition, a solder ball is formed two-dimensionally in parallel on the surface opposite to the element mounting surface of the substrate, and has a feature of joining with a circuit board on which a package is mounted. Furthermore,
As a substrate on which the element is mounted, a structure using a metal substrate such as a lead frame has been devised in addition to the organic circuit substrate.

[0003] The structure of these area mounting type semiconductor packages adopts a single-sided sealing form in which only the element mounting surface of the substrate is sealed with a resin composition and the solder ball forming surface is not sealed. Very rarely, on a metal substrate such as a lead frame, a sealing resin layer of about several tens of μm may exist even on the solder ball forming surface, but a sealing resin layer of several hundred μm to several mm on the element mounting surface. Since the layer is formed, one-sided sealing is substantially achieved. For this reason, these packages warp immediately after molding due to inconsistency in thermal expansion and thermal shrinkage between the organic or metal substrate and the resin composition, or due to cure shrinkage during molding and curing of the resin composition. Is easy to occur. In addition, when soldering is performed on a circuit board on which these packages are mounted, a heating step of 200 ° C. or more is performed. At this time, warpage of the package occurs, and a large number of solder balls do not become flat, and the package is mounted. There is also a problem that the semiconductor device floats from the circuit board to be mounted and lowers the reliability of electrical connection.

Further, when soldering is performed by soldering by means such as infrared reflow, vapor phase soldering, or solder immersion, moisture present inside the package due to moisture absorption from the cured product of the resin composition and the organic substrate is high. Cracks may occur in the package due to stress caused by rapid vaporization in the package, and peeling may occur at the interface between the device mounting surface of the substrate and the cured product. Is also required. further,
Due to the mismatch between the coefficient of linear expansion of the substrate and the cured product, peeling of the substrate / cured product interface and package cracking occur even in a temperature cycle test, which is a typical example of a reliability test. Conventional Q
For surface mount packages such as FP and SOP, to prevent cracks at the time of solder mounting and peeling at the interface of each material, crystalline epoxy resin represented by biphenyl type epoxy resin and phenol having a flexible skeleton Measures have been taken to reduce the glass transition temperature and the moisture absorption by using a resin curing agent in combination and increasing the blending amount of the inorganic filler. However, at present, this method cannot solve the problem of warpage in a single-sided sealed package.

In a package in which substantially only one surface of a substrate is sealed with a resin composition, to reduce the warpage, the linear expansion coefficient of the substrate and the linear expansion coefficient of the cured resin composition must be close to each other. Two methods of reducing the cure shrinkage of the composition are important. As the substrate, in the case of an organic substrate, a resin having a high glass transition temperature such as a BT resin or a polyimide resin is widely used, and these have a glass transition temperature higher than around 170 ° C. which is a molding temperature of the epoxy resin composition. Accordingly, in the cooling process from the molding temperature to room contracts only alpha ₁ region of the organic substrate. Therefore, the resin composition is also the same as high and alpha ₁ is a circuit board glass transition temperature, warpage is considered to be substantially zero when further curing shrinkage is zero. Therefore, the glass transition temperature higher by a combination of a polyfunctional epoxy resin and a polyfunctional phenol resin, methods to adjust the alpha ₁ in the amount of the inorganic filler has been proposed.

However, a combination system of a polyfunctional epoxy resin having three or more epoxy groups in one molecule and a polyfunctional phenol resin having three or more phenolic hydroxyl groups in one molecule has a large moisture absorption. That, because each resin viscosity is high, it is not possible to highly fill the inorganic filler and it is difficult to reduce moisture absorption, showing high elasticity even at solder processing temperature,
Due to the high generated stress and the like, the occurrence of package cracks and the occurrence of interface peeling during the soldering process has not been solved. In addition, the gold wire used for electrical connection between the element and the substrate is as thin as tens of μm, and the length of the area mount package is longer than that of the conventional structure package. Due to the high density, the gold wires are deformed unless sealed with a low-viscosity resin composition at the time of molding, and the gold wires come into contact with each other to cause electrical failure. Especially CSP
In such a thin package as described above, it is an essential condition to seal with a resin composition having good filling properties and little deformation of the gold wire.

[0007]

SUMMARY OF THE INVENTION The present invention has a small warpage after molding in an area mounting package or during soldering, and has excellent reliability in a temperature cycle test or soldering.
The object of the present invention is to develop an epoxy resin composition for semiconductor encapsulation having a good filling property and a small deformation of a gold wire, that is, a high fluidity characteristic at the time of molding, and a semiconductor device sealed thereby. .

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventor has found that a combination of a special crystalline epoxy resin and a polyfunctional phenol resin curing agent can reduce the moisture absorption while keeping the glass transition temperature from decreasing. It is possible to increase the filling amount of the inorganic filler because it is possible to achieve a low viscosity,
It is possible to lower moisture absorption and alpha ₁ adjustment, also be possible to reduce the filling improvement and wire deformation amount at the time of molding, the generated stress because it thermal time elastic modulus reduction at soldering temperature decreases, It is clarified that the adhesion to a circuit board is improved.

That is, the present invention relates to (A) a compound represented by the general formula (1):
An epoxy resin represented by (4) and containing at least 30% by weight or more in the total epoxy resin of at least one epoxy resin selected from the group consisting of epoxy resins having a melting point of 50 to 150 ° C .; A) a phenolic resin curing agent containing 30% by weight or more of the phenolic resin in the total phenolic resin, (C) a curing accelerator, and (D) a fused silica powder contained in the total epoxy resin composition in an amount of 80 to 90% by weight. An epoxy resin composition for semiconductor encapsulation, and a semiconductor device encapsulated with the epoxy resin composition for semiconductor encapsulation.

[0010]

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Embedded image R in the formulas (1) to (3) represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 12 carbon atoms, which may be the same or different. R in the formulas (5) and (6) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms;
They may be the same or different, and l is 1 to
A positive integer of 10, m is 0 or a positive integer of 1 to 3, and n is 0 or a positive integer of 1 to 4.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Among the epoxy resins of the component (A) used in the present invention, the epoxy resins represented by the general formulas (1) to (4) are respectively a hydroquinone type epoxy compound [formula (1)] and a stilbene type epoxy compound [formula (1). 2)], a bisphenol F type epoxy compound [formula (3)], and an aralkyl-modified biphenyl type epoxy resin [formula (4)], a crystalline epoxy resin having an internal melting point of 50 to 150 ° C. Specific examples thereof are shown below, but the present invention is not limited thereto.

[0012]

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[0013]

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[0014]

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[0015]

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Since all of these epoxy resins exhibit crystallinity, they are solid at a temperature lower than the melting point, but become a low-viscosity liquid substance at a temperature higher than the melting point. For this reason, in the case of a crystalline epoxy resin having a melting point of less than 50 ° C., fusion tends to occur in the production process of the epoxy resin composition, and workability is significantly reduced. In addition, a crystalline epoxy resin having a melting point exceeding 150 ° C. has a problem that the uniformity of the material is poor because the epoxy resin composition is not sufficiently melted in a manufacturing process of kneading under heating. The melting point can be determined from the endothermic peak temperature (heating rate 5 ° C./min) with a differential scanning calorimeter [SSC / 5200 manufactured by Seiko Denshi Co., Ltd.].

These crystalline epoxy resins have as few as two epoxy groups in one molecule, and have a low crosslink density when combined with a phenol novolak resin or a phenol resin curing agent having a flexible skeleton. Only a cured product having a low viscosity. However, it has a rigid planar or rod-like skeleton as a structure, and has the property of being crystallized, that is, the feature that molecules are easily oriented, so that the general formula (5)
When the polyfunctional phenol resin curing agent represented by the formula (1) is used in combination, it is difficult to lower the heat resistance such as the glass transition temperature even if the crosslink density of the crosslinked structure by the cured polyfunctional phenol resin is reduced. On the other hand, in a combination of a normal bifunctional non-crystalline epoxy resin and a polyfunctional phenol resin, the crosslink density is reduced and the glass transition temperature is significantly reduced. Furthermore, when a crystalline epoxy resin and a polyfunctional phenol resin are combined, a low elastic modulus characteristic of a low functional group resin is exhibited in a temperature region once exceeding the glass transition temperature. It is effective for conversion. This has the effect of preventing the occurrence of package cracks during the soldering process and the occurrence of peeling at the interface between the substrate and the cured product of the resin composition. Further, since the resin composition has a low viscosity in a molten state, the fluidity of the resin composition during molding is high, and the filling property into a thin package is excellent. The crystalline epoxy resin having a melting point of 50 to 150 ° C. needs to be contained in the total epoxy resin in an amount of 30% by weight or more. If the content is less than 30% by weight, it is difficult to obtain the effect of lowering the elasticity or lowering the viscosity during heating, and therefore, high adhesion to the substrate is not exhibited, which is not preferable.

The epoxy resin of the present invention may be used in combination with another epoxy resin. The epoxy resin that can be used in combination refers to all monomers, oligomers, and polymers having an epoxy group, and includes, for example, bisphenol A type epoxy resin, orthocresol novolak type epoxy resin, and naphthalene type epoxy resin. or,
These epoxy resins may be used alone or in combination.

Among the phenolic resin curing agents of component B used in the present invention, the phenolic resin curing agent represented by the formula (5) is a so-called triphenolmethane-type phenolic resin, and specific examples are shown below.

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When these phenolic resin curing agents are used, the crosslink density of the cured product increases, and a cured product having a high glass transition temperature can be obtained. The amount of the phenolic resin of the formula (5) needs to be 30% by weight or more based on the total phenolic resin in view of the glass transition temperature. 30% by weight
If it is less than 10, the glass transition temperature decreases, the curing shrinkage ratio increases, and the amount of warpage of the molded package increases.
The phenolic resin of the formula (5) can be appropriately used in combination with other phenolic resins, and is not particularly limited, and examples thereof include a phenol novolak resin, a cresol novolak resin, and a naphthol novolak resin.

The curing accelerator of the component (C) used in the present invention refers to those which can be a catalyst for a crosslinking reaction between the epoxy resin and the phenol resin curing agent, and specifically, amine compounds such as tributylamine. And organic phosphorus compounds such as triphenylphosphine and tetraphenylphosphonium / tetraphenylborate, and imidazole compounds such as 2-methylimidazole, but are not limited thereto. These curing accelerators may be used alone or as a mixture.

The fused silica powder of the component (D) used in the present invention can be used in any of a crushed form and a spherical form. However, the amount of the fused silica powder is increased and the melt viscosity of the resin composition is increased. In order to suppress this, it is preferable to mainly use spherical silica. In order to further increase the content of the spherical silica, it is desirable to adjust the particle size distribution of the spherical silica to be wider. The fused silica powder of the present invention must be contained in the total epoxy resin composition in an amount of 80 to 90% by weight. If it is less than 80% by weight, the heat shrinkage during the cooling process from the molding temperature to room temperature becomes too large compared to the heat shrinkage of the substrate, and the package warpage at room temperature becomes large. Further, since the package absorbs a large amount of moisture, the package is likely to be cracked or peeled off at the interface between the substrate and the resin composition during the soldering process after the moisture absorption. 90% by weight
If the ratio exceeds, the viscosity of the resin composition at the time of molding is too high, so that the gold wire deformation tends to occur.

The resin composition of the present invention is represented by a brominated epoxy resin, a flame retardant such as antimony trioxide, a coupling agent, and carbon black, if necessary, in addition to the essential components (A) to (D). Coloring agents, release agents such as natural waxes and synthetic waxes, etc., can be appropriately compounded. In order to obtain a resin composition, the components are mixed, heated and kneaded with a heating kneader or a hot roll, and then cooled and pulverized to obtain a desired resin composition. Using the epoxy resin composition of the present invention to encapsulate electronic components such as semiconductors and manufacture semiconductor devices, transfer molding, compression molding, and injection molding can be performed by conventional molding methods such as injection molding. Good.

[0024]

The present invention will be specifically described below with reference to examples. Example 1 Hydroquinone-type epoxy resin having a structure represented by the formula (6) as a main component Melting point 144 ° C., epoxy equivalent 175 7.7 parts by weight ・ Phenolic resin represented by the formula (7) [Meiwa Kasei Co., Ltd. ), MEH-7500, softening point 107 ° C, hydroxyl equivalent 97] 4.3 parts by weight ・ Triphenylphosphine 0.2 parts by weight ・ Spherical fused silica 87.0 parts by weight ・ Carnauba wax 0.5 parts by weight ・ Carbon black 0.3 parts by weight After the above components were mixed by a mixer, the mixture was kneaded 30 times using two rolls having a surface temperature of 90 ° C. and 45 ° C., and the obtained kneaded material sheet was cooled and pulverized to obtain a resin. The composition was used. The properties of the obtained resin composition were evaluated by the following methods. The evaluation results are shown in Tables 1 to 4.

[0025]

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<< Examples 2 to 5 >> Based on Example 1 as a basic compound, the type of the crystalline epoxy resin was changed,
Example 1 by changing the blending amount of the phenol resin curing agent
Was mixed and kneaded in the same manner as in the above to obtain a resin composition. Evaluation was performed in the same manner as in Example 1. Table 1 shows the formulation and evaluation results. Example 6 and Comparative Examples 1 to 3 Mixing and kneading in the same manner as in Example 1 except that the mixing ratio of the crystalline epoxy resin was changed and the type of the non-crystalline epoxy resin was changed, based on Example 1. Thus, a resin composition was obtained. Evaluation was performed in the same manner as in Example 1. Table 2 shows the formulation and evaluation results. << Example 7 and Comparative Examples 4 and 5 >> A resin composition was prepared by mixing and kneading in the same manner as in Example 1 except that Example 1 was used as a basic compounding agent and the amount of the phenolic resin curing agent of the formula (7) was changed. I got Evaluation was performed in the same manner as in Example 1. Table 3 shows the formulation and evaluation results. Example 8 and Comparative Example 6 Based on Example 1 as a basic compound, changing the compounding ratio of the inorganic filler, and changing the compounding ratio of the crystalline epoxy resin and the phenol resin curing agent accordingly,
Mixing and kneading were performed in the same manner as in Example 1 to obtain a resin composition. Evaluation was performed in the same manner as in Example 1. Table 4 shows the formulation and evaluation results.

Formula (8) used in the above Examples and Comparative Examples
The structures and properties of the epoxy resins of (13) and (14) and (15) are shown below.

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[0028]

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An epoxy resin having a structure of the formula (8) as a main component: a melting point of 52 ° C. and an epoxy equivalent of 225. An epoxy resin having a structure of the formula (9) as a main component: a melting point of 1.
33 ° C., epoxy equivalent 182 ・ Epoxy resin having the structure of formula (10) as a main component: melting point
82 ° C., epoxy equivalent 190 ・ Epoxy resin having a structure of formula (11) as a main component: softening point 65 ° C., epoxy equivalent 200 ・ Epoxy resin having a structure of formula (12) as a main component: softening point 60 ° C., epoxy Equivalent 170-Epoxy resin having the structure of formula (13) as a main component: liquid,
Viscosity (25 ° C) 55 Poise, epoxy equivalent 168 ・ Phenolic resin of formula (14): softening point 80 ° C, hydroxyl equivalent 104 ・ Phenolic resin of formula (15): softening point 78 ° C, hydroxyl equivalent 175

<< Evaluation Method >> Spiral flow: Using a mold for measuring spiral flow according to EMMI-1-66, using a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 70 kg / cm ² and a curing time of 2 minutes. -Glass transition temperature (Tg) and coefficient of linear expansion (α ₁ ): 1
The test piece obtained by transfer molding at 75 ° C. for 2 minutes was further cured at 175 ° C. for 8 hours, and measured by a thermomechanical analyzer [TMA-120 manufactured by Seiko Denshi Co., Ltd., heating rate 5 ° C./min].・ Heat elastic modulus: Flexural elastic modulus at 240 ° C is JIS-K6
It was measured under the test conditions of 911. Package warpage: 225-pin BGA package (substrate is a 0.36 mm thick BT resin substrate, package size is 24 × 24 mm, thickness 1.17 mm, silicon chip is 9 × 9 mm, thickness 0.35 mm, chip and circuit board Is bonded with a gold wire having a diameter of 25 μm) at a mold temperature of 180 ° C. and 75 kg /
Perform transfer molding for 2 minutes at an injection pressure of cm ² ,
Further post-curing was performed at 175 ° C. for 8 hours. After cooling to room temperature, the displacement in the height direction was measured diagonally from the gate of the package using a surface roughness meter, and the value with the largest variation difference was defined as the amount of warpage. Solder Resistance: The molded product package used for measuring the package warpage was left for 168 hours in an environment of 85 ° C. and 60% relative humidity, and then immersed in a 240 ° C. solder bath for 10 seconds.
The package was observed using an ultrasonic flaw detector, and the number of internal cracks and the number of peels at the interface between the substrate and the resin composition were represented by% of (number of generated packages) / (total number of packages). Gold wire deformation: 225 molded by evaluating package warpage
The pin BGA package was observed with a soft X-ray fluoroscope, and the deformation rate of the gold wire was represented by (flow amount) / (gold wire length) in%.

Table 1 Example 1 2 3 4 << Type and blending amount (parts by weight) of epoxy resin >> Epoxy resin of formula (6) 7.7 Epoxy resin of formula (8) 8.4 Epoxy resin of formula (9) 7.8 Formula (10) 7.9 << Type and blending amount (parts by weight) of curing agent >> Phenolic resin of formula (7) 4.3 3.6 4.2 4.1 << Evaluation >> Spiral follow (cm) 104 118 95 120 Tg (° C) 155 154 159 148 α ₁ (Ppm / ° C) 10 10 10 10 Thermal elastic modulus (N / mm ² ) 2060 2010 2250 2000 Package warpage (μm) 31 31 30 38 Solder resistance: Number of cracks (%) 0 0 0 0 Number of peelings (%) 000 00 0 Gold wire change (%) 3 2 4 2

Table 2 Example Comparison Example 1 6 1 2 3 << Type and amount of epoxy resin (parts by weight) >> Epoxy resin of formula (6) 7.7 2.7 1.5 Epoxy resin of formula (11) 5.3 6.5 Epoxy resin of formula (12) 7.6 Epoxy resin of formula (13) 7.6 << Type and blending amount (parts by weight) of curing agent >> Phenolic resin of formula (8) 4.3 4.0 4.0 4.4 4.4 << Evaluation >> Spiral follow (cm) 104 92 61 67 134 Tg (° C) ) 155 164 169 193 119 α ₁ (ppm / ° C) 10 10 9 9 10 Thermal elastic modulus (N / mm ² ) 2060 2280 2340 3600 2070 Package warpage (μm) 31 28 68 24 70 Solder resistance: number of cracks (%) 0 50 60 20 Number of peelings (%) 0 40 30 10 Change in gold wire (%) 3 5 14 18 3

Table 3 Example Comparative Example 1 7 4 5 << Type and blending amount of epoxy resin ( parts by weight) >> Epoxy resin of formula (6) 7.7 7.6 7.5 6.0 << Type and blending amount of curing agent (parts by weight) >> Formula (7) ) 4.3 1.6 1.1 Phenolic resin of formula (14) 2.8 3.4 Phenolic resin of formula (15) 6.0 << Evaluation >> Spiral follow (cm) 104 115 106 96 Tg (° C) 155 146 144 127 α ₁ (ppm / ° C) ) 10 9 10 10 Thermal elastic modulus (N / mm ² ) 2060 2040 1980 1150 Package warpage (μm) 31 35 65 156 Solder resistance: Number of cracks (%) 0 30 0 Number of peelings (%) 0 50 0 Gold wire change (%) 3 3 5 5

Table 4 Example Comparative Example 18 86 << Type and blending amount of epoxy resin ( parts by weight) >> Epoxy resin of formula (6) 7.7 10.9 13.5 << Type and blending amount of curing agent (parts by weight) >> phenol of formula (7) resin 4.3 6.1 7.5 "amount of the inorganic filler" fused silica (parts by weight) 87 82 78 "evaluation" spiral follow (cm) 104 137 158 Tg ( ℃) 155 150 148 α 1 (ppm / ℃) 10 15 17 thermal Elasticity at time (N / mm ² ) 2060 1530 1130 Package warpage (μm) 31 41 168 Solder resistance: Number of cracks (%) 0 0 60 Number of peels (%) 0 0 60 Change in gold wire (%) 3 2 2

[0035]

The epoxy resin composition for semiconductor encapsulation of the present invention is also excellent in moldability such as gold wire deformation, and the area mounting type semiconductor device sealed with the epoxy resin composition for semiconductor encapsulation can be used at room temperature. Also, the warpage in the soldering process is small, and the reliability such as solder resistance and temperature cycle resistance is high.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 23/31

Claims (2)

[Claims] (A) represented by the general formulas (1) to (4),
And an epoxy resin containing at least one epoxy resin selected from the group consisting of crystalline epoxy resins having a melting point of 50 to 150 ° C. in the total epoxy resin in an amount of 30% by weight or more,
(B) a phenolic resin curing agent containing at least 30% by weight of the phenolic resin represented by the general formula (5) in the total phenolic resin, (C) a curing accelerator, and (D) a total of 80 to 90 in the total epoxy resin composition. An epoxy resin composition for encapsulating a semiconductor, comprising a fused silica powder contained by weight%. Embedded image Embedded image R in the formulas (1) to (3) represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 12 carbon atoms, which may be the same or different. R in the formulas (4) and (5) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms,
They may be the same or different, and l is 1 to
A positive integer of 10, m is 0 or a positive integer of 1 to 3, and n is 0 or a positive integer of 1 to 4. 2. A semiconductor device is mounted on one surface of a substrate, and substantially only one surface on the substrate surface side on which the semiconductor device is mounted is sealed with the epoxy resin composition according to claim 1. Semiconductor device.