JP2002241580A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin composition for sealing a semiconductor having excellent fluidity during molding, solder and temperature cycle resistances. SOLUTION: This epoxy resin for sealing the semiconductor is characterized by having >=0.2 ratio of bulk specific gravity/true specific gravity of the bulk specific gravity to the true specific gravity of rubber particles in the epoxy resin composition consisting essentially of (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) an inorganic filler and (E) the rubber particles.

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 for semiconductor encapsulation having excellent moldability and reliability, and a semiconductor device using the same.

[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 semiconductor elements is progressing year by year, and the size of semiconductor elements is increasing and wiring is becoming finer. When such a semiconductor device is encapsulated with an epoxy resin composition, the cured product of the epoxy resin composition comes into direct contact with the semiconductor device, so that the stress stress is caused by expansion and contraction of the cured product of the epoxy resin composition due to a temperature cycle. This causes problems such as misalignment of wiring, cutting of bonding wires, and destruction of semiconductor elements. For these problems, it is necessary to make the cured product of the epoxy resin composition flexible by reducing the elastic modulus of the cured product of the epoxy resin composition. Also, in the current situation where surface mounting of semiconductor devices has become common, a semiconductor device that has absorbed moisture is exposed to high temperatures during soldering, and cracks occur in the semiconductor device due to the explosive stress of vaporized water vapor, or The occurrence of peeling at the interface between the semiconductor element or lead frame and the cured product of the epoxy resin composition causes defects that greatly impair electrical reliability, and prevention of these defects, that is, improvement of solder resistance is also a major issue. It has become. In order to improve the solder resistance, the epoxy resin composition is blended with a large amount of an inorganic filler to reduce the moisture absorption, lower the thermal expansion, and increase the strength of the semiconductor device. For this reason, use of low-viscosity epoxy resins or crystalline epoxy resins that are crystalline solids at room temperature and become extremely low-viscosity liquid above the melting point. There has been proposed a method for preventing a decrease in fluidity during molding of an epoxy resin composition accompanying the above. However, in an epoxy resin composition manufactured by heating and kneading each component, a cured product of an epoxy resin composition containing a large amount of an inorganic filler increases the elasticity as the strength increases. Increases the stress caused by the stress, which causes a problem in the temperature cycle resistance. In order to achieve both temperature cycle resistance and solder resistance as described above, it is necessary to suppress an increase in elastic modulus even in a system in which a large amount of an inorganic filler is blended. As one of the specific methods, a method of adding various rubber particles for imparting low stress characteristics has been conventionally known. However, conventional rubber particles did not disperse sufficiently in the epoxy resin composition during kneading due to the strong cohesive force of the particles. For this reason, the epoxy resin composition became non-uniform, and the variation in characteristics became large. In addition, when the aggregates of the rubber particles are large, the viscosity in the molten state increases and the fluidity decreases, and defects such as cracks starting from the aggregates during solder reflow may occur. Therefore, development of an epoxy resin composition that satisfies all requirements for fluidity, solder resistance, and temperature cycle resistance has been desired.

[0003]

SUMMARY OF THE INVENTION The present invention provides a semiconductor device which is excellent in fluidity during molding and which is a molded product.
The present invention provides an epoxy resin composition for semiconductor encapsulation excellent in reliability such as temperature cycling resistance and the like, and a semiconductor device using the same.

[0004]

Means for Solving the Problems The present invention provides [1] (A)
In an epoxy resin composition containing an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) an inorganic filler, and (E) rubber particles as essential components, a ratio of a true specific gravity to a bulk specific gravity of the rubber particles. [2] The epoxy resin composition for semiconductor encapsulation having a bulk specific gravity / true specific gravity of 0.2 or more, [2] a rubber composition having a rubber particle content of 0.1 to 5% by weight in the total epoxy resin composition. 1] The epoxy resin composition for semiconductor encapsulation according to the item [1],
[3] A semiconductor device obtained by sealing a semiconductor element using the epoxy resin composition for semiconductor sealing according to the item [1] or [2].

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having two or more epoxy groups in one molecule, such as bisphenol A type epoxy resin and bisphenol F type epoxy resin. , Biphenyl epoxy resin, stilbene epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, naphthol novolak epoxy resin, triphenolmethane epoxy resin, alkyl-modified triphenolmethane epoxy resin, dicyclopentadiene-modified phenol Epoxy resin, phenol aralkyl type epoxy resin (having a phenylene skeleton, biphenylene skeleton, etc.), naphthol aralkyl type epoxy resin (having a phenylene skeleton, biphenylene skeleton, etc.), Pen-modified phenol type epoxy resins, hydroquinone type epoxy resin, triazine nucleus-containing epoxy resins, but are not limited thereto. These epoxy resins can be used alone or
It may be used in combination of more than one kind. In order to improve the solder resistance of the semiconductor device, the amount of the inorganic filler in the epoxy resin composition is increased, and the cured product of the obtained epoxy resin composition has low moisture absorption, low thermal expansion, and high heat resistance. In order to achieve strength, it is particularly preferable to use 30% by weight or more of a crystalline epoxy resin which exhibits crystallinity at ordinary temperature and becomes a liquid having an extremely low viscosity when the melting point is exceeded. As a crystalline epoxy resin, the melting point is 70 to 150 ° C.
Is preferred in terms of handling workability and workability during kneading. The melting point of the crystalline epoxy resin in the present invention,
Using a differential scanning calorimeter (manufactured by Seiko Denshi Kogyo Co., Ltd.), the temperature at the top of the endothermic peak of crystal melting when the temperature was raised from room temperature at 5 ° C./min.

[0006] The phenolic resin used in the present invention refers to all monomers, oligomers and polymers having two or more phenolic hydroxyl groups in one molecule.
Phenol novolak resin, cresol novolak resin, phenol aralkyl resin (having phenylene skeleton, biphenylene skeleton, etc.), naphthol aralkyl resin (having phenylene skeleton, biphenylene skeleton, etc.), terpene-modified phenol resin, dicyclopentadiene-modified phenol resin, triphenol Examples include, but are not limited to, methane type resins and bisphenol compounds. These phenol resins may be used alone or in combination of two or more. These phenolic resins can be used without any limitation in molecular weight, softening point, hydroxyl equivalent, etc., but phenol resins having a softening point of 90 ° C. or lower and a relatively low viscosity are preferred. If the softening point is 90 ° C. or higher, the effect of lowering the viscosity of the epoxy resin may be reduced.
The softening point of the phenolic resin in the present invention is determined according to JIS K
It was measured according to the ring and ball method of 2406. The equivalent ratio of the epoxy group of all epoxy resins to the phenolic hydroxyl group of all phenol resins is preferably 0.5 to 2.0, particularly preferably 0.7 to 1.5. If the ratio is outside the range of 0.5 to 2.0, the curability, the moisture resistance reliability and the like may be reduced.

The curing accelerator used in the present invention includes:
A substance that can serve as a catalyst for a crosslinking reaction between an epoxy resin and a phenol resin. Specific examples thereof include amine compounds such as tributylamine and 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, Examples include organic phosphorus compounds such as tetraphenylphosphonium / tetraphenylborate salts, and imidazole compounds such as 2-methylimidazole, but are not limited thereto. These curing accelerators can be used alone or
It may be used in combination of more than one kind.

The inorganic filler used in the present invention includes, for example, fused silica, crystalline silica, alumina, silicon nitride, aluminum nitride and the like. These inorganic fillers may be used alone or in combination of two or more. When increasing the amount of the inorganic filler, fused silica is generally used. Fused silica can be used in either crushed or spherical form.However, in order to increase the amount of the fused silica and to suppress an increase in the melt viscosity of the epoxy resin composition, it is better to mainly use a spherical form. preferable. In order to further increase the blending amount of the fused spherical silica, it is desirable to adjust the particle size distribution of the fused spherical silica to be wider. The inorganic filler that has been surface-treated with a silane coupling agent or the like in advance may be used.

The rubber particles used in the present invention include, for example, butadiene styrene rubber, butadiene acrylonitrile rubber, polyurethane rubber, polyisoprene rubber,
Examples include, but are not limited to, acrylic rubber, fluorine rubber, silicone rubber, and the like. These may be used alone or in combination of two or more. In addition, in order to impart affinity with epoxy resin and phenol resin, in addition to organic substituents such as methyl group and phenyl group, C, O,
An organic substituent having an N, S atom or the like may be present in the crosslinked structure. Examples of the organic substituent having a C, O, N, S atom or the like include a vinyl group, a phenethyl group, a hydroxy group, a carboxyl group, an acryl group, an alkoxy group, an epoxy group, a polyether group, a caprolactone group,
Examples include, but are not limited to, amino groups, ureido groups, isocyanate groups, and mercapto groups. The ratio of the true specific gravity to the bulk specific gravity of the rubber particles of the present invention is the bulk specific gravity /
The true specific gravity is preferably 0.2 or more. More preferably, it is 0.
3 to 0.7. If it is less than 0.2, the cohesion of the rubber particles becomes too strong, the epoxy resin composition is not sufficiently dispersed in the kneading during kneading, and the epoxy resin composition becomes non-uniform, and the characteristics are varied. Aggregation without dispersion increases viscosity in a molten state and decreases fluidity, and causes unfavorable problems such as cracks starting from agglomerates of rubber particles during solder reflow.
The bulk specific gravity of the rubber particles used in the present invention was measured using a powder tester PT-E manufactured by Hosokawa. 100cm ³
Put the sample powder into a container that is more than 100 cm ³ by attaching a cover to the container and tap it 180 times, then remove the cover, remove the sample powder more than 100 cm ³ , and remove 100 cm ³ of weight. Was measured to determine the bulk specific gravity of the rubber particles. The true specific gravity of the rubber particles used in the present invention was determined by using a pycnometer method. The maximum particle size of the rubber particles of the present invention is preferably 100 μm or less. If it exceeds 100 μm, rubber particles may be clogged in the mold during molding of the semiconductor device, and unfilling may occur. The average particle size of the rubber particles of the present invention is preferably 50 μm or less. If it exceeds 50 μm, the flowability of the epoxy resin composition is impaired, and the strength is undesirably reduced. The maximum particle size and the average particle size of the rubber particles in the present invention were measured by dispersing the rubber particles in water using a surfactant and using a Coulter counter. The content of the rubber particles of the present invention is preferably from 0.1 to 5% by weight in the entire epoxy resin composition. If it is less than 0.1% by weight, the effect of the modification is small, and the effect of reducing the elastic modulus may not be seen. Also, 5
Exceeding the weight percentage may reduce the strength. Further, other flexibility-imparting agents may be added as long as the properties of the rubber particles of the present invention are not impaired. Examples of the flexibility-imparting agent that can be used in combination include, but are not limited to, liquid synthetic rubbers such as liquid organopolysiloxane and liquid polybutadiene. These may be used alone or in combination of two or more.

The epoxy resin composition of the present invention comprises (A)
The component (E) is an essential component, but if necessary, a flame retardant such as a brominated epoxy resin or antimony oxide,
Various additives such as a silane coupling agent, a release agent such as a natural wax and a synthetic wax, and a coloring agent such as carbon black may be appropriately compounded. The epoxy resin composition of the present invention is obtained by mixing the components (A) to (E), other additives, and the like using a mixer or the like, then kneading the mixture using a heating kneader or a hot roll, cooling, and pulverizing. Obtained. In order to manufacture a semiconductor device by encapsulating an electronic component such as a semiconductor element using the epoxy resin composition of the present invention, it is sufficient to cure and mold by a molding method such as a transfer mold, a compression mold, and an injection mold.

[0011]

The present invention will be specifically described below with reference to examples.
The unit of the compounding amount is part by weight. Example 1 Biphenyl type epoxy resin (YX4000H manufactured by Yuka Shell Epoxy Co., Ltd., melting point: 105 ° C, epoxy equivalent: 195) 7.8 parts by weight Phenol aralkyl resin (XL225 manufactured by Mitsui Chemicals, Inc., softening point: 75 ° C) (Hydroxyl equivalent 175) 7.0 parts by weight 1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 0.2 part by weight Spherical fused silica 83.5 parts by weight Rubber particles 1 (silicone rubber, Bulk specific gravity / true specific gravity = 0.61) 1.0 part by weight Carnauba wax 0.2 part by weight Carbon black 0.3 part by weight was mixed using a mixer.
The mixture was kneaded using two rolls at 5 ° C., cooled and pulverized to obtain an epoxy resin composition. The properties of the obtained epoxy resin composition were evaluated by the following methods. Table 1 shows the results.

Evaluation method Spiral flow: Using a mold for spiral flow measurement in accordance with EMMI-1-66, a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 6.9 N / mm ² and a curing time of 120 seconds. The unit is cm. Flexural strength: JIS defines flexural strength at 25 ° C or 240 ° C
It was measured according to K 6911. The unit is N / mm ² . Flexural modulus: JI is the flexural modulus at 25 ° C or 240 ° C
It was measured according to SK6911. The unit is N / m
m ² . Temperature cycle resistance: 100-pin TQFP package (package size is 14 x 14 mm, thickness is 1.4 mm, silicon chip size is 8.0 x 8.0 mm, lead frame is made of 42 alloy), mold temperature is 175 ° C, Transfer molding was performed with an injection pressure of 7.5 N / mm ² and a curing time of 120 seconds, and post-curing was performed at 175 ° C. for 8 hours. The obtained package was repeatedly treated in an environment of −60 ° C./30 minutes to 150 ° C./30 minutes, and the presence or absence of external cracks was observed. The time during which external cracks occurred in 50% or more of the obtained packages was measured and indicated as "50% failure occurrence time". The unit is hr. Solder resistance: 100-pin TQFP package (package size: 14 x 14 mm, thickness: 1.4 mm, silicon chip size: 8.0 x 8.0 mm, lead frame made of 42 alloy), mold temperature: 175 ° C, injection Pressure 7.5
Transfer molding was performed at N / mm ² and a curing time of 120 seconds, and post-curing was performed at 175 ° C. for 8 hours. The obtained package was left in an environment of 85 ° C. and a relative humidity of 85% for 168 hours, and the difference in weight before and after moisture absorption was divided by the weight before moisture absorption to obtain a moisture absorption rate, and the result was expressed in%. After that 240
C. for 10 seconds. External cracks were observed with a microscope, and the crack occurrence rate [(number of crack occurrence packages) / (total number of packages) × 100] was expressed in%.
Also, observe this package using an ultrasonic flaw detector,
The percentage of occurrence of peeling at the interface between the chip (SiN-coated product) and the cured product of the epoxy resin composition [(number of peeling occurrence packages) / (total number of packages) × 100] was expressed in%.

Examples 2 to 5 and Comparative Examples 1 to 3 According to the formulations shown in Table 1, an epoxy resin composition was obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. Table 1 shows the results. Table 2 shows the material of the rubber particles and the ratio of the true specific gravity to the bulk specific gravity used in Examples and Comparative Examples.

[Table 1]

[0014]

[Table 2]

[0015]

The epoxy resin composition of the present invention has excellent fluidity at the time of molding and has both high strength and low elastic modulus. A semiconductor device using the epoxy resin composition has solder resistance and Excellent reliability such as temperature cycle resistance.

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Claims (3)

[Claims] 1. An epoxy resin composition comprising (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) an inorganic filler, and (E) rubber particles as essential components. The epoxy resin composition for semiconductor encapsulation wherein the ratio of the true specific gravity to the bulk specific gravity is 0.2 or more in terms of bulk specific gravity / true specific gravity. 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the content of the rubber particles is 0.1 to 5% by weight in the total epoxy resin composition. 3. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition for semiconductor encapsulation according to claim 1 or 2.