JPH11130938A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor sealing composition excellent in moldability, reliability and high-temperature storability by mixing a polyfunctional epoxy resin and/or a crystalline epoxy resin having a specified melting point with a phenolic resin curing agent, a cure accelerator, a fused silica powder and a specified amount of red phosphorus flame retardant. SOLUTION: This composition is obtained by compounding at least one polyfunctional epoxy resin of formula I or II and/or at least one epoxy resin being a crystalline epoxy resin having a melting point of 50-150 deg.C and represented by any one of formula IV to VIII, a phenolic resin curing agent of formula III and 0.3-5.0 wt.%, based on the composition, red phosphorus flame retardant. In the formulas, R is a 1-12C alkyl; 1 is 1-10; m is 0-3; n is 0-4; and k is 1-6. The red phosphorus flame retardant is desirably one prepared by precoating the surface of red phosphorus with aluminum hydroxide and further coating the resulting surface with a phenolic resin and having a mean particle diameter of 10-70 μm, a maximum particle diameter of 150 μm or below and a red phosphorus content of 60-95 wt.%.

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 high-temperature storage properties. 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 surface on the mounting surface side is resin-sealed, the warpage after resin sealing and the warping in the soldering process at the time of board mounting are small, and the temperature cycle test It is excellent in package cracking resistance and exfoliation resistance in package soldering and soldering processes, and is also excellent in high-temperature storage property. The epoxy resin composition for semiconductor encapsulation and the epoxy resin composition for semiconductor encapsulation. And a semiconductor 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 was developed to meet the demands for more pins, smaller size, and higher speed. 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 is molded and sealed with an epoxy resin composition or the like. Also, on the surface opposite to the element mounting surface of the substrate, solder balls are formed two-dimensionally in parallel so as to be joined to a circuit board on which a package is mounted. Further, a structure using a metal substrate such as a lead frame other than the organic circuit substrate has been devised as a substrate on which the element is mounted.

[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, due to the mismatch of thermal expansion and thermal contraction between the organic substrate or metal substrate and the cured product of the resin composition, or the effect of curing shrinkage during molding and curing of the resin composition, these packages cannot be molded. Warpage tends to occur immediately after. 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. In a package in which substantially only one surface on a substrate is sealed with a resin composition, in order to reduce warpage, the linear expansion coefficient of the substrate and the linear expansion coefficient of the cured resin composition are brought close to each other, and the Two ways to reduce cure shrinkage 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, if the resin composition also has a high glass transition temperature and α ₁ is the same as that of the circuit board, and if the curing shrinkage is zero, the warpage is considered to be almost zero. For this reason, the glass transition temperature is increased by a combination of a polyfunctional epoxy resin and a polyfunctional phenol resin, and α is determined by the amount of the inorganic filler.
_A method of combining ₁ has already been proposed.

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 resin composition and the organic substrate is high. Cracks in the package due to stress caused by rapid vaporization in the package, and peeling at the interface between the device mounting surface of the substrate and the cured product of the resin composition, resulting in a low stress and low moisture absorption of the cured product. With the development, the adhesion to the substrate is also required. Furthermore, due to the mismatch between the thermal expansion coefficient 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 surface mount packages such as QFP and SOP use a crystalline epoxy resin typified by a biphenyl-type epoxy resin and a flexible skeleton to prevent cracks at the time of solder mounting and peeling at each material interface. By using a phenolic resin curing agent in combination and increasing the blending amount of an inorganic filler, measures have been taken to lower the glass transition temperature and lower the moisture absorption. However, at present, this method cannot solve the problem of warpage in a single-sided sealed package.

Next, these epoxy resin compositions contain a halogen-based flame retardant or a combination of a halogen-based flame retardant and antimony trioxide as a flame retardant. Gas and the like are generated to achieve flame retardancy. But,
Since this method uses a halogen or a combination of halogen and antimony, a semiconductor device encapsulated with this resin composition is stored in a high-temperature environment of, for example, 175 ° C. for 2,000 hours. This causes a poor electrical connection between the gold wire and the aluminum pad, which is a major problem. To solve such problems, an epoxy resin composition having a higher glass transition temperature than the environment in which electronic components are used is used, and the diffusion of halogen and antimony halide during high-temperature storage is reduced to improve high-temperature storage properties. A method, a method of adding an ion scavenger, and capturing a halogen or antimony halide during high-temperature storage, and a method of combining these two types have been used. In recent years, the surface mounting, miniaturization, and thinning of electronic components have progressed, and the demand for improved solder cracking resistance during mounting on circuit boards has become strict, and both solder cracking resistance and high-temperature storage properties have been satisfied. Further, a halogen-free and antimony-free resin composition has been demanded from the viewpoint of environmental problems in addition to the problem of high-temperature storage property. There is no halogen-free or antimony-free resin composition that can solve the above-mentioned problems for area mounting type packages such as BGA and CSP, and intensive studies have been made.

[0006]

DISCLOSURE OF THE INVENTION The present invention has low warpage after molding in an area mounting package or during soldering, and has particularly excellent adhesion to a substrate, so that reliability in a temperature cycle test, soldering, etc. The present invention has been made for the purpose of developing a halogen-free and antimony-free epoxy resin composition for semiconductor encapsulation which is excellent in heat resistance and high-temperature storage property.

[0007]

The present invention relates to (A), a polyfunctional epoxy resin represented by the general formula (1) or (2) and / or a polyfunctional epoxy resin represented by the formula (4) to (8) and having a melting point of 50: At least one epoxy resin selected from the group of crystalline epoxy resins at a temperature of up to 150 ° C., (B) a phenolic resin curing agent represented by the general formula (3), (C) a curing accelerator, (D) fused silica powder, And (E) an epoxy resin composition for encapsulating a semiconductor, comprising 0.3 to 5.0% by weight of a red phosphorus-based flame retardant in the total epoxy resin composition, and a semiconductor element mounted on one surface of the substrate The semiconductor device is characterized in that substantially only one surface on the substrate surface side on which the semiconductor element is mounted is sealed with the semiconductor sealing epoxy resin composition. Preferably, a red phosphorus-based flame retardant coats the surface of red phosphorus in advance with aluminum hydroxide, and further coats the surface with a phenol resin, having an average particle size of 10 to 70 μm and a maximum particle size of 150 μm or less. The epoxy resin composition for semiconductor encapsulation as described above, wherein the content of red phosphorus in the flame retardant is 60 to 95% by weight.

[0008]

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[0009]

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[0010]

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[0011]

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[0012]

Embedded image R in the formulas (1), (2), (3) and (8) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. l is a positive integer of 1 to 10, m is 0 or a positive integer of 1 to 3, and n is 0
Alternatively, it is a positive integer of 1 to 4. R in the formulas (4) to (7) represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The resin generally referred to as a triphenolmethane epoxy resin represented by the formula (1) or the epoxy resin represented by the formula (2) used in the present invention is cured by a combination with a phenol resin curing agent of the formula (3). Since the epoxy resin composition has a high cross-linking density, a high glass transition temperature, and a small curing shrinkage, it is effective in reducing warpage in sealing an area-mounted semiconductor package, which is an application of the present epoxy resin composition. Specific examples of the formulas (1) and (2) include the following, but are not limited thereto.

[0014]

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[0015]

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The crystalline epoxy resin represented by the formulas (4) to (8) and having a melting point of 50 to 150 ° C. is a diepoxy compound having two epoxy groups in one molecule or an oligomer thereof. Since all of these epoxy resins show crystallinity, they are solid at a temperature below the melting point,
It becomes a low-viscosity liquid substance at temperatures above the melting point. For this reason, the epoxy resin composition using these has a low viscosity in a molten state, so that the fluidity of the resin composition at the time of molding is high, and the filling property into a thin package is excellent. Therefore, it is preferable to use these crystalline epoxy resins when increasing the amount of the fused silica powder to reduce the moisture absorption of the cured product of the obtained epoxy resin composition and improving the solder reflow resistance. .

In these crystalline epoxy resins, the number of epoxy groups in one molecule is as small as 2 to at most several, and generally, only a cured product having a low crosslinking density and low heat resistance can be obtained. However, since it has a rigid plane or rod-like skeleton as a structure and has the property of being crystallized, that is, the feature that molecules are easily oriented, the polyfunctional phenol resin curing agent represented by the general formula (3) is used. When used in combination, it is difficult to lower the heat resistance such as the glass transition temperature after curing. For this reason, the semiconductor package sealed with the epoxy resin composition by the combination of the crystalline epoxy resin and the phenol resin curing agent represented by the general formula (3) can reduce the amount of warpage. Further, in a temperature region once exceeding the glass transition temperature, the compound exhibits a low elastic modulus characteristic of a compound having a low functional group, which is effective for reducing stress at a solder processing temperature. 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.

If the crystalline epoxy resin has a melting point of less than 50 ° C., it tends to fuse in the production process of the epoxy resin composition, and the workability is significantly reduced. Also, 150 ° C
A crystalline epoxy resin having a melting point exceeding the above range has a problem that the uniformity of the material is poor because the epoxy resin composition is not sufficiently melted in the production step of kneading under heating. The melting point is measured by a differential scanning calorimeter [Seiko Electronics Co., Ltd. S
SC520, heating rate 5 ° C./min]. Specific examples of these crystalline epoxy resins are shown below, but the invention is not limited thereto.

[0019]

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[0020]

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[0021]

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From the viewpoint of reducing package warpage, increasing fluidity during molding, and achieving solder resistance during mounting, the polyfunctional epoxy resins represented by the above general formulas (1) and (2) are all It is particularly preferable that the total epoxy resin contains 20 to 90% by weight in the epoxy resin and further contains the crystalline epoxy resin represented by the formulas (4) to (8) and having a melting point of 50 to 150 ° C in the total epoxy resin. preferable.

The phenolic resin curing agent represented by the general formula (3) used in the present invention is a so-called triphenolmethane-type phenolic resin, and specific examples are shown below, but are not limited thereto.

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When these phenolic resins are used, the crosslinked density of the cured product increases, and a cured product having a high glass transition temperature can be obtained. For this reason, the warpage of the package sealed with the obtained epoxy resin composition can be reduced. Equation (3)
The phenol resin can be appropriately used in combination with other phenol resins, and is not particularly limited. Examples thereof include a phenol novolak resin, a cresol novolak resin, and a naphthalene-type novolak resin.

The curing accelerator of the component (C) used in the present invention refers to those which can serve as a catalyst for a crosslinking reaction between the epoxy resin and the phenol resin curing agent, and specifically includes 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 red phosphorus flame retardant of component (E) used in the present invention includes red phosphorus alone, but is liable to be oxidized and is unstable and has difficulty in handling. Is coated with aluminum hydroxide, and the surface thereof is further coated with a phenol resin. The content of red phosphorus in the coated red phosphorus flame retardant is preferably from 60 to 95% by weight, and if the content of red phosphorus is less than 60% by weight, it is necessary to incorporate a large amount into the resin composition. If added in a large amount, the fluidity is undesirably reduced. If it exceeds 95% by weight, there is a problem in the oxidation stability of red phosphorus. As the particle diameter of the red phosphorus flame retardant, those having an average particle diameter of 10 to 70 μm and a maximum particle diameter of 150 μm or less are preferable. Average particle size is 1
If it is less than 0 μm, the fluidity of the resin composition will decrease,
If it exceeds 0 μm, the dispersibility of the flame retardant deteriorates, which is not preferable. On the other hand, when the maximum particle size exceeds 150 μm, there is a problem in the filling property of the package, which is not preferable. These red phosphorus-based flame retardants include, for example, Nova Red and Nova Excel of Rin Kagaku Kogyo Co., Ltd., which can be easily obtained from the market. The content of red phosphorus in the entire resin composition is preferably from 0.3 to 5.0% by weight, and if it is less than 0.3% by weight, the flame retardancy is insufficient. The red phosphorus-based flame retardant is flammable, and the flame retardant itself oxidizes to exhibit flame retardancy.
When the ratio exceeds, the flame retardant acts to assist combustion due to too much flame retardant, resulting in insufficient flame retardancy.

The resin composition of the present invention may be used, if necessary, in addition to the essential components (A) to (E), a silicone additive, a coupling agent, an ion scavenger for reducing impurities, and carbon black. A representative coloring agent, a release agent such as a natural wax and a synthetic wax, and the like 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. The semiconductor device of the present invention can be obtained by using the above-described epoxy resin composition for semiconductor encapsulation and encapsulating the semiconductor element by transfer molding, compression molding, injection molding or the like.

[0029]

The present invention will be specifically described below with reference to examples. << Example 1 >> An epoxy resin having a structure represented by the formula (9) as a main component: [Epicoat 1032H, trade name, manufactured by Yuka Shell Epoxy Co., Ltd., softening point 60 ° C, epoxy equivalent 170] 4.6 weight Parts: Biphenyl epoxy resin having a structure represented by the formula (10) as a main component: [YX-4000H, manufactured by Yuka Shell Epoxy Co., Ltd., melting point: 105 ° C., epoxy equivalent: 195] 4.6 parts by weight A phenolic resin represented by the formula (11): [Mehwa Kasei Co., Ltd., trade name MEH-7500, softening point 107 ° C, hydroxyl equivalent 97] 4.8 parts by weight ・ Red phosphorus flame retardant: (Red phosphorus After the surface is coated with aluminum hydroxide, the surface is further treated with a phenol resin. The content of red phosphorus is 75% by weight, the average particle size is 40 μm, and the maximum particle size is 120 μm.) 1.0 part by weight Triphenylphosphine: 0.2 parts by weight ・ Spherical fused silica: 84.0 parts by weight ・ Carnauba wax: 0.5 parts by weight ・ Carbon black: 0.3 parts by weight After mixing all the above components with a mixer, the surface temperature becomes 90 ° C. The mixture was kneaded 30 times using two rolls at 45 ° C., and the obtained kneaded material sheet was cooled and pulverized to obtain a resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 1 shows the evaluation results.

[0030]

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<< Examples 2 to 8 >> Based on Example 1 as the basic formulation, the epoxy resins of the formulas (9) and (10) and the formula (1)
By changing the type of phenolic resin and the amount of the phenolic resin in 1), the other components are blended in the same ratio as the basic blending,
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 1 shows the formulation and evaluation results. << Examples 9 to 13, Comparative Examples 1 to 3 >> Based on Example 1 as a basic composition, the amount of the red phosphorus-based flame retardant was changed by changing the type of the flame retardant, and the other components were blended at the same ratio as the basic composition. Then, the mixture was mixed and kneaded in the same manner as in Example 1 to obtain a resin composition. Evaluation was performed in the same manner as in Example 1. Tables 2 and 3 show the formulation and evaluation results.

The formula (1) used in the above Examples and Comparative Examples
The structures and properties of the epoxy resins and phenol resins of 2) to (16) are shown below.

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[0033]

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Epoxy resin having a structure represented by formula (12) as a main component: melting point 144 ° C., epoxy equivalent 175 ・ Epoxy resin having a structure represented by formula (13) as a main component: melting point 103 ° C., epoxy equivalent 225 ・ Epoxy resin having a structure represented by formula (14) as a main component: melting point 133 ° C., epoxy equivalent 182 ・ Epoxy resin having a structure represented by formula (15) as a main component: melting point 82 ° C., epoxy equivalent 190 ・An epoxy resin having a structure represented by the formula (16) as a main component: a softening point of 65 ° C., an epoxy equivalent of 210 orthocresol novolac type epoxy resin (OCN)
Epoxy resin): Softening point 63 ° C, epoxy equivalent 200 ・ Phenol novolak resin: Softening point 80 ° C, hydroxyl equivalent 104

<< 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. Curing shrinkage: 180 ° C mold temperature of test piece, 7
Transfer molding was performed at an injection pressure of 5 kg / cm ² for 2 minutes, and post-curing was further performed at 175 ° C. for 8 hours. The cavity dimensions of the mold heated to 180 ° C. and the dimensions of the molded article heated to 180 ° C. were measured with calipers, and the curing shrinkage was represented by the ratio of molded article dimension / mold cavity dimension.

Package warpage: 225-pin BGA package (substrate is 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 The bonding pad of the circuit board is bonded with a gold wire having a diameter of 25 μm) at a mold temperature of 180 ° C.
Transfer molding was performed at an injection pressure of 75 kg / cm 2 for 2 minutes, and post-curing was further 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. 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%.・ High temperature storage: Seal the test element in 80 QFP of 14 × 20 mm and 2 mm in thickness, leave it at high temperature (175 ° C.), and place between lead pin-gold wire-AL pad-AL circuit-AL pad-gold wire-lead pin By measuring the electric resistance value and measuring the start time of the resistance value rise, the connection failure of the internal circuit due to high temperature storage was evaluated. -Flame resistance: UL-94 vertical test (sample thickness 1.0mm)

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

The epoxy resin composition for semiconductor encapsulation of the present invention has a small warpage in the area mounting type semiconductor device using the same at room temperature and in the soldering process, and has a high reliability such as solder resistance and temperature cycle resistance. It has excellent storage properties and high-temperature storage properties.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 3/02 C08K 3/02 3/36 3/36 9/02 9/02 9/04 9/04 H01L 23/29 H01L 23 / 30 R 23/31

Claims (3)

[Claims] 1. A polyfunctional epoxy resin represented by the general formulas (1) and (2) and / or a crystalline epoxy represented by the formulas (4) to (8) and having a melting point of 50 to 150 ° C. At least one epoxy resin selected from the group of resins,
(B) a phenolic resin curing agent represented by the general formula (3),
(C) a curing accelerator, (D) fused silica powder, and (E)
0.3 to 5. Red phosphorus flame retardant in the total epoxy resin composition.
An epoxy resin composition for encapsulating a semiconductor, comprising 0% by weight. Embedded image Embedded image Embedded image Embedded image Embedded image R in the formulas (1), (2), (3) and (8) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. l is a positive integer of 1 to 10, m is 0 or a positive integer of 1 to 3, and n is 0
Alternatively, it is a positive integer of 1 to 4. R in the formulas (4) to (7) represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. 2. A red phosphorus-based flame retardant, in which the surface of red phosphorus is coated in advance with aluminum hydroxide, and the surface is further coated with a phenol resin, having an average particle size of 10 to 70 μm and a maximum particle size of 15 μm.
2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the content is 0 μm or less, and the content of red phosphorus in the coated flame retardant is 60 to 95% by weight. 3. A semiconductor element is mounted on one side of a substrate, and substantially only one side on the side of the substrate on which the semiconductor element is mounted is sealed with the epoxy resin composition for semiconductor encapsulation according to claim 1 or 2. A semiconductor device characterized by being performed.