JP2002294029A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition capable of being filled with molten spherical silica at a high filling ratio. SOLUTION: An epoxy resin composition for sealing a semiconductor comprises (A) an epoxy resin, (B) a phenol resin, (C) a hardening accelerator and (D) a molten spherical silica which remains in an amount of 75-100 wt.% on a sieve having an aperture of 20 μm when it is sieved by a dry method using the sieve, and remains in an amount of 50-97 wt.% on the sieve when it is sieved by a wet method. The content of the molten spherical silica is 88-93 wt.% of the whole epoxy resin composition.

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 fluidity and solder crack resistance, and to a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, diodes, transistors, I
In order to protect semiconductor components such as C and LSI from external stimuli (mechanical / thermal shock, chemical action, etc.), encapsulation molding is performed with an epoxy resin composition in consideration of productivity and cost. Is becoming more common. Contrary to the increase in the size of semiconductor devices in recent years, the size of semiconductor devices has become smaller and thinner due to the recent downsizing of electronic devices, contrary to the increase in size, and furthermore, mounting on printed circuit boards. Since the method has also shifted from the conventional pin insertion type to the surface mount type, cracks in semiconductor devices due to thermal shock during surface mount soldering and peeling at the interface between the semiconductor element / lead frame and the cured epoxy resin composition Such a problem is likely to occur, and an epoxy resin composition having excellent heat resistance is strongly demanded.
It is considered that these solder cracks and peeling are caused by the moisture absorption of the semiconductor device itself before the soldering process and the water vapor explosion at a high temperature during the soldering process.
In order to prevent this, techniques such as imparting low water absorption to the epoxy resin composition are often used, and as one of the techniques for reducing the water absorption, a technique of highly filling the fused silica and reducing the content of the resin component is known. is there. However, when the conventional fused silica is added to the epoxy resin composition at 90% by weight or more,
Dispersibility deteriorates due to aggregation of the small-particle silica, and there is a problem in applying to a sealing material for semiconductors.

[0003]

SUMMARY OF THE INVENTION The present invention provides an epoxy resin composition for semiconductor encapsulation having excellent fluidity, bending strength, and low water absorption, and a semiconductor device having excellent solder crack resistance.

[0004]

Means for Solving the Problems The present invention provides [1] (A)
Epoxy resin, (B) phenolic resin, (C) curing accelerator, (D) When sieved with a dry sieve having an opening of 20 μm, 75 to 100% by weight remains on the sieve, and when sieved with a wet sieve, 50% on the sieve. The epoxy resin composition for encapsulating a semiconductor, characterized in that the epoxy resin composition contains 88 to 93% by weight of the remaining fused spherical silica in the total epoxy resin composition. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein silica of 5 μm or less is adhered, and the semiconductor using the epoxy resin composition for semiconductor encapsulation according to [3] [1] or [2]. A semiconductor device characterized by sealing an element.

[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, and their molecular weight and molecular structure are not particularly limited. For example, biphenyl epoxy resin, bisphenol epoxy resin, stilbene epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, triphenolmethane epoxy resin, alkyl-modified triphenolmethane epoxy resin, naphthol epoxy resin, triazine Nucleus-containing epoxy resin, dicyclopentadiene-modified phenol type epoxy resin, phenol aralkyl type epoxy resin (having a phenylene skeleton, diphenylene skeleton, etc.), naphthol aralkyl resin (phenylene skeleton, diphenylene Down having a skeleton or the like), and these are no problem be used singly or in admixture.
A low-viscosity resin such as a biphenyl-type epoxy resin is preferable for highly filling the fused spherical silica with the fine particles attached.

The phenolic resin used in the present invention includes:
Monomers, oligomers, and polymers generally having two or more phenolic hydroxyl groups in one molecule are not particularly limited in molecular weight and molecular structure. For example, phenol novolak resin, cresol novolak resin, dicyclopentadiene-modified phenol resin And terpene-modified phenolic resins, triphenolmethane-type resins, phenol aralkyl resins (having a phenylene skeleton, diphenylene skeleton, etc.) and naphthol aralkyl resins (having a phenylene skeleton, diphenylene skeleton, etc.), and the like. Can be used. Among them, phenol novolak resin, dicyclopentadiene-modified phenol resin, phenol aralkyl resin (having a phenylene skeleton, diphenylene skeleton, etc.),
A naphthol aralkyl resin (having a phenylene skeleton, a diphenylene skeleton, and the like), a terpene-modified phenol resin, and the like are preferable. The ratio of the number of epoxy groups in all epoxy resins to the number of phenolic hydroxyl groups in all phenolic resins is preferably 0.8 to 1.3.

As the curing accelerator used in the present invention, any one can be used as long as it promotes a curing reaction between an epoxy group and a phenolic hydroxyl group, and those generally used for a sealing material can be used. For example, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, 2-methylimidazole, tetraphenylphosphonium / tetraphenylborate and the like can be mentioned, and these may be used alone or in combination. .

[0008] As the amount of fused spherical silica conventionally used in an epoxy resin composition for semiconductor encapsulation increases, the water absorption of a cured product of the epoxy resin composition decreases, preventing solder cracking and peeling. However, when this fused spherical silica is blended in the epoxy resin composition in an amount of about 90 to 93% by weight, the small particles of silica present in the fused spherical silica aggregate and it becomes difficult to uniformly disperse the fused spherical silica. However, there is a disadvantage that the fluidity is deteriorated and the moldability is deteriorated.

The fused spherical silica used in the present invention has a particle size of 75 to 100% by weight remaining on the sieve when sieved with a dry sieve having an opening of 20 μm, and 50 to 97% by weight when sieved with a wet sieve. The diameter configuration is good, but it is more preferable that the small particles adhere to the large particles by pre-mixing the fused spherical silica of the small particles that are agglomerated with the large particles with a rotary powder mixing device or the like, and a dry 20 μm mesh is used. When sieved, 75 to 100% by weight of the fused spherical silica having small particles attached on the sieve remains, and when sieved with a wet sieve, the small particles attached to the fused silica are washed away by water and small Desirably, fused spherical silica in which 50 to 97% by weight of fused spherical silica to which no particles are attached remains. By using this fused spherical silica, high filling is possible while maintaining the fluidity of the epoxy resin composition, and the properties such as the strength of the cured product are improved, and as a result, the solder crack resistance of the semiconductor device is improved. Have been found to be possible. If the content is less than 75% by weight on a dry sieve, small particles are present independently, easily agglomerated, and the dispersibility is deteriorated. When the content on the wet sieve is less than 50% by weight or more than 97% by weight, the epoxy resin composition containing the same is not preferable because the fluidity becomes poor and the moldability is reduced.

[0010] Large particles and small particles of fused spherical silica are preliminarily mixed by using a rotary powder mixing device such as a ball mill, a V-type mixer, and a super mixer, so that the aggregation of small particles of fused spherical silica is broken. This is because the particles adhere to the surface of the fused spherical silica, and the dispersibility of the small particles is improved during kneading with the resin component. The compounding amount of the fused spherical silica in which the small particles are adhered to the large particles is 88 to 93 in all the epoxy resin compositions.
% By weight is preferred. If it is less than 88% by weight, the solder crack resistance is poor, and if it exceeds 93% by weight, the fluidity is poor. The maximum particle size of the small particles attached to the fused spherical silica is 1.5 μ
m or less is preferable from the viewpoint of fluidity.

When sieved with a dry sieve having a mesh size of 20 μm as referred to in the present invention, 75 to 100% by weight of the fused spherical silica remains on the sieve and 50 to 97% by weight remains on the sieve when sieved with a wet sieve. It refers to the remaining amount of fused spherical silica after about 10 g of finely weighed and sieved on a dry sieve having an opening of 20 μm, and further sieved with water using the same sieve with water.
Maximum particle size 1.5 attached to fused spherical silica in the present invention
Confirmation of the fused spherical silica having a diameter of not more than μm is performed by fixing the fused spherical silica with a conductive adhesive and then blowing air thereon, and then using a scanning electron microscope (SEM) to remove what remains on the conductive adhesive.

The epoxy resin composition of the present invention comprises (A)
The component (D) is an essential component, but if necessary, a coloring agent such as carbon black, a coupling agent, a release agent such as a natural wax and a synthetic wax, and a low stress such as silicone oil and rubber. Various additives such as additives may be appropriately compounded. Further, the epoxy resin composition of the present invention is prepared by mixing the components (A) to (D) and other additives sufficiently and uniformly using a mixer or the like, and further melt-kneading with a hot roll or a kneader and cooling. It is obtained by subsequent grinding. Various electronic components such as semiconductor elements are encapsulated using the epoxy resin composition of the present invention, and semiconductor devices are manufactured by curing and molding using conventional molding methods such as transfer molding, compression molding, and injection molding. do it.

[0013]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. The mixing ratio is by weight. Example 1 Fused silica A: fused spherical silica 5 having a maximum particle size of 1.1 μm
Parts by weight and 100 parts by weight of fused spherical silica having an average particle size of 22 μm were put into a ball mill and stirred for 30 minutes to give an average particle size of 22 μm.
Attached to μm fused spherical silica. Open this 20
When sieved little by little by a dry method of μm, 78% by weight remained on the sieve, and further, when sieved by water using water, 65% by weight of fused spherical silica remained on the sieve. After fixing the mixed fused silica with a conductive adhesive and then blowing it with air, it was observed by SEM that the average particle size was 2
Fused spherical silica having a maximum particle size of 1.1 μm was adhered to the surface of the 2 μm fused spherical silica. This surface-treated fused spherical silica is referred to as fused silica A. Table 1 shows the particle size composition. Biphenyl type epoxy resin (melting point 105 ° C, epoxy equivalent 195) 4.3 parts by weight Phenol aralkyl resin (softening point 75 ° C, hydroxyl equivalent 175) 3.5 parts by weight 1,8-diazabicyclo (5,4,0) undecene- 7 (hereinafter referred to as DBU) 0.1 part by weight γ-aminopropyltriethoxysilane 0.3 part by weight Carbon black 0.3 part by weight Montanic acid ester 0.2 part by weight Carnauba wax 0.2 part by weight Fused silica A 91.1 parts by weight were mixed at room temperature using a super mixer, and 70 to 10 parts by weight were mixed.
Roll kneading was performed at 0 ° C., followed by cooling and pulverization to obtain an epoxy resin composition. The obtained epoxy resin composition was evaluated by the following method. Table 2 shows the results.

Evaluation method Spiral flow: Measurement was performed using a mold for measuring spiral flow according to EMMI-1-66 at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, and a curing time of 120 seconds. Hot bending strength: The hot bending strength was measured (at 260 ° C.) according to JIS K 6911. The unit is N / mm ² . Boiling water absorption rate: Using a transfer molding machine, a disk having a diameter of 50 mm and a thickness of 3 mm was formed at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, and a curing time of 180 seconds.
It was post-cured in 8 hours, left in boiling water for 24 hours, and the change in weight was measured to determine the water absorption. The unit is% by weight. Solder crack resistance: 80 pQFP (2.0 mm thick, chip size 6 mm × 6 mm) was molded using a multi-plunger molding machine under the conditions of a mold temperature of 175 ° C., an injection pressure of 9.8 MPa, and a curing time of 120 seconds. . Six packages treated at 175 ° C for 8 hours as post cure
The treatment was performed for 168 hours in an environment of 5 ° C. and a relative temperature of 85%, followed by an IR reflow treatment (maximum 260 ° C. for 10 seconds). After processing with a microscope, external cracks of the package were observed, and the presence or absence of internal peeling and cracks was observed with an ultrasonic flaw detector, and the number of defective packages was counted. When the number of defective packages is n, n / 6 is displayed.

Examples 2 and 3, Comparative Examples 1 to 5 Fused silicas B to E were prepared as follows. Fused silica B: fused spherical silica 1 having a maximum particle size of 1.1 μm
0 parts by weight and 100 parts by weight of fused spherical silica having an average particle size of 22 μm were charged into a V-type mixer and stirred for 30 minutes.
Attached to 2 μm fused spherical silica. Open this 2
When the mixture was sieved little by little with a dry method of 0 μm, 97% by weight remained on the sieve, and when the mixture was sieved wet with water, 58% by weight of fused spherical silica remained on the sieve. Further, after fixing the mixed fused silica with a conductive adhesive and observing the blown air with a SEM, the maximum particle size of 1.1 μm was formed on the surface of the fused spherical silica having an average particle size of 22 μm.
m of fused spherical silica. This surface-treated fused spherical silica is referred to as fused silica B. Table 1 shows the particle size composition. Fused Silica C: Fused silica having an average particle diameter of 24 μm was sieved little by little by a dry method with an opening of 20 μm.
% By weight and further sieved with water using water, 71% by weight of fused spherical silica remained on the sieve. After fixing this fused silica with a conductive adhesive, the air blown was observed by SEM to find that the average particle size was 24 μm.
There was no deposit on the surface of the fused spherical silica. It is called fused silica C. Table 1 shows the particle size composition. Fused silica D: fused spherical silica 1 having a maximum particle size of 1.1 μm
5 parts by weight and 100 parts by weight of fused spherical silica having an average particle size of 22 μm were put into a V-type mixer and stirred for 30 minutes to give an average particle size of 2 parts.
Attached to 2 μm fused spherical silica. Open this 2
When the mixture was sieved little by little with a dry method of 0 μm, 70% by weight remained on the sieve, and when the mixture was sieved with water using water, 46% by weight of fused spherical silica remained on the sieve. Further, after fixing the mixed fused silica with a conductive adhesive and observing the blown air with a SEM, the maximum particle size of 1.1 μm was formed on the surface of the fused spherical silica having an average particle size of 22 μm.
m of fused spherical silica. This surface-treated fused spherical silica is referred to as fused silica D. Table 1 shows the particle size composition. Fused Silica E: Fused spherical silica having an average particle size of 28 μm was sieved little by little in a dry manner with a mesh size of 20 μm, 100% by weight remained on the sieve, and further sieved in a wet manner using water. 98% by weight of fused spherical silica remained.
After fixing fused silica having an average particle size of 28 μm with a conductive adhesive, air was blown and observed by SEM. As a result, there was no deposit on the surface of the fused spherical silica having an average particle size of 28 μm. It is called fused silica E. Table 1 shows the particle size composition. According to the formulation in Table 2, 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 2 shows the results.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, an epoxy resin composition for semiconductor encapsulation having good flowability and excellent moldability can be obtained even when the fused spherical silica is highly filled. Excellent bending strength and solder crack resistance.

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Claims (3)

[Claims] Claims: 1. An epoxy resin, (B) a phenolic resin, (C) a curing accelerator, and (D) a sieve with a dry sieve having a mesh size of 20 μm. An epoxy resin composition for encapsulating a semiconductor, comprising 50 to 97% by weight of fused spherical silica remaining on the sieve when sieved at 88 to 93% by weight of the total epoxy resin composition. 2. The fused spherical silica has a maximum particle size of 1.5 μm.
The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the following silica is adhered. 3. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition for semiconductor encapsulation according to claim 1 or 2.