JP2000186183A - Epoxy resin composition for sealing and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for sealing that has excellent reflow resistance, low stressedness, reduced void occurrence and semiconductor devices having a excellent reflow resistance, low stressedness with reduced void occurrence. SOLUTION: This resin composition comprises an epoxy resin, a curing agent and a curing acceleration, an inorganic filler and, in addition, a silicone rubber powder where the silicone rubber powder is covered with a silicone resin. Semiconductor devices are sealed with this epoxy resin composition. In a preferred embodiment, the epoxy resin is at least partially a biphenyl type epoxy resin.

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 used for sealing a semiconductor element and the like, and a semiconductor device sealed using the same.

[0002]

2. Description of the Related Art For protection of electronic components such as semiconductor elements (chips) mounted on a lead frame made of metal and electrically connected to the lead frame using a bonding wire, a pump, or the like, for example, a metal mold is used. This is performed by sealing the entire semiconductor element and a part of the lead frame with resin.

[0003] The epoxy resin composition used for the sealing mainly contains an epoxy resin, a curing agent and an inorganic filler. The inorganic filler is in the form of a powder, and is used for the purpose of reducing the coefficient of thermal expansion and the coefficient of moisture absorption of the molded article (cured resin) of the epoxy resin composition, or improving the thermal conductivity. In recent years, as electronic devices have become smaller and thinner, the mounting form of IC / LSI semiconductor packages mounted thereon has changed from a pin insertion type package represented by a conventional DIP (dual in-line package) to an SOP.
(Small outline packages) and QFPs (quad flat packages) are rapidly transitioning to surface mount packages.

As a result, since the entire package is rapidly exposed to reflow heat as a problem when mounting the surface mount type package, the interface between the sealing resin (cured resin) and the chip and inner lead inside the package is required. Phenomena such as peeling or cracking of the sealing resin portion. It has been pointed out that these phenomena cause a functional deterioration of the semiconductor device itself and a long-term decrease in reliability.

In recent years, the size of chips mounted on packages has been increasing, the reflow resistance has become more severe, and the need to increase the resistance to temperature cycle tests has increased. In this field, it is the greatest challenge to achieve both reflow resistance and low stress of the sealing resin. In order to solve this problem, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, etc.
By adopting a sealing resin design that uses a low-viscosity type epoxy resin and contains a large amount of inorganic filler, the problem of reflow resistance is being solved, but voids occur in such a sealing resin. Secondary problems have been pointed out.

On the other hand, it has been proposed to incorporate silicone rubber powder in order to lower the elasticity of the sealing resin portion to lower the stress, but there is a problem that the reflow resistance is reduced. That is, at the time of reflow, the space between the sealing resin portion and the chip / inner lead is easily separated, and cracks are easily generated in the sealing resin portion.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a sealing material which is characterized by having excellent reflow resistance and low stress, and which is free from voids during molding. An object of the present invention is to provide an epoxy resin composition, and a semiconductor device which is excellent in reflow resistance and low stress property and has few voids.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted various studies to achieve both reflow resistance and low stress, and as a result, there is a problem in the silicone rubber powder to be blended for low stress. I found something. According to this finding, in silicone rubber powder, primary aggregates are liable to secondary agglomeration, and the secondary agglomerated particles remain intact even when compounded due to the low compatibility with the epoxy resin as the base resin. There is a drawback that it tends to remain.
For this reason, peeling occurs between the sealing resin portion and the chip / inner lead during reflow, and cracks occur in the sealing resin portion. Therefore, as a result of various studies to make the silicone rubber powder less likely to undergo secondary aggregation, the present invention was completed.

That is, the epoxy resin composition for sealing according to the present invention comprises an epoxy resin composition comprising an epoxy resin, a curing agent, a curing accelerator, an inorganic filler, and further comprising a silicone rubber powder. It is characterized in that the surface of the silicone rubber powder is coated with a silicone resin. In order to solve the above problems, a semiconductor device according to the present invention is a semiconductor device in which a semiconductor element is sealed using an epoxy resin composition, wherein the epoxy resin composition according to the present invention is used as the epoxy resin composition. Is used.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION (Epoxy resin composition) As an epoxy resin, an epoxy resin generally usable for a sealing material can be used. As epoxy resin, 1
There is no particular limitation as long as it has two or more epoxy groups in the molecule. For example, ortho-cresol novolak epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, phenol novolak epoxy resin, bisphenol type Epoxy resins, triphenolmethane-type epoxy resins, naphthalene skeleton-containing epoxy resins, bromide-containing epoxy resins, and the like.
These may be used alone or in combination. It is preferable that all or a part (for example, 20 to 100 wt%, preferably 50 to 100 wt%) of the epoxy resin is a biphenyl type epoxy resin and / or a dicyclopentadiene type epoxy resin. The biphenyl type epoxy resin and the dicyclopentadiene type epoxy resin are represented by the following general formulas (1) and (2), respectively:

[0011]

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Biphenyl type epoxy resin (wherein, R ^{a to} R ^h are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

[0013]

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A dicyclopentadiene type epoxy resin (where n is an integer of 0 to 6), each having a low viscosity, a high adhesiveness, a low hygroscopicity, and a Is superior to other epoxy resins in that the occurrence of cracks is small. If the proportion of the biphenyl-type epoxy resin and / or the dicyclopentadiene-type epoxy resin is less than 20% by weight, the moisture absorption rate may increase and the reflow resistance level may be insufficient.

The curing agent is not particularly limited as long as it can be generally used for a sealing material and can be used as a curing agent for the epoxy resin. For example, a phenol novolak resin, a phenol resin having a naphthalene skeleton, Polyhydric phenol compounds such as cresol novolak resin, phenol aralkyl resin, naphthol aralkyl resin, dicyclopentadiene-type phenol resin, triphenylmethane-type phenol resin; acid anhydrides such as hexahydrophthalic anhydride; xylenol, resorcinol and formaldehyde And a novolak resin obtained by a condensation reaction with an amine. These may be used alone or in combination.

The mixing ratio of the curing agent is as follows:
The curing agent is preferably set in the range of 0.5 to 1.5 equivalents, more preferably 0.8 to 1.2 equivalents. When the compounding ratio of the curing agent is out of the above range, the reliability is deteriorated, the rigidity at the time of molding is reduced, and the workability tends to be adversely affected. In the epoxy resin composition, a curing accelerator is usually used for promoting the curing. The curing accelerator is not particularly limited as long as it can be generally used for a sealing material and has an action of accelerating the reaction between the epoxy resin and the curing agent. For example, triphenylphosphine (TPP), tributyl Organic phosphines such as phosphine and trimethylphosphine; 2-methylimidazole (2MZ), 2-phenyl-4-methylimidazole,
Imidazoles such as 2-phenylimidazole; 1,8
-Diazabicyclo (5,4,0) undecene-7 (DB
U), tertiary amines such as triethanolamine and benzyldimethylamine. These may be used alone or in combination.

It is preferable that the mixing ratio of the curing accelerator is 0.03 to 1.0% by weight based on the whole sealing resin composition. 0.03wt of curing accelerator
%, The gelation time is prolonged and the workability tends to decrease due to the decrease in rigidity during curing.
If the content exceeds wt%, the composition is cured during molding, and unfilling tends to occur.

In order to reduce the coefficient of thermal expansion and the rate of moisture absorption, to improve the thermal conductivity (heat dissipation), to improve the reliability, and to increase the strength of the cured resin of the sealing portion. Usually, an inorganic filler can be compounded in the epoxy resin composition. The inorganic filler is not particularly limited as long as it can be generally used as an encapsulant and is in the form of a powder. However, fused silica (also referred to as amorphous silica), crystalline silica, alumina, nitrided Silicon, aluminum nitride, and the like can be given. These may be used alone or in combination. The powder of the inorganic filler may have an average particle size that is generally used for a sealing material, for example, an average particle size in the range of 1 to 30 μm. The mixing ratio of the inorganic filler is not particularly limited, but is higher than before, for example, 75 to 92 wt% of the whole composition.
%. Below this range, moisture absorption may increase and reflow resistance may decrease. Above this range, fluidity may decrease, resulting in poor filling (causing unfilled portions), wire sweep or wire breakage (only when wire bonding is performed). ).

The epoxy resin composition of the present invention is blended with a silicone rubber powder so as to reduce the elastic modulus of the cured resin and to provide a low stress property. The silicone rubber powder is a silicone resin. The one whose surface is coated is used. Silicone rubber powder whose surface is coated with silicone resin,
Secondary aggregation is less likely to occur, and the compatibility with the epoxy resin is excellent. For this reason, the cured product of the epoxy resin composition containing the same is less likely to peel off from the chip or inner lead during reflow, and is less likely to crack. As the silicone rubber powder whose surface is coated with the silicone resin, for example, a commercially available product can be used. The surface-coated silicone rubber powder may have an average particle size that is generally used for a sealing material, for example, an average particle size in the range of 0.5 to 20 μm.

The compounding ratio of the silicone rubber powder whose surface is coated with the silicone resin is preferably 0.3 to 5.0% by weight based on the whole sealing resin composition. If the compounding amount is less than 0.3 wt%, a decrease in the elastic modulus of the cured resin material is small, the low stress property is insufficient, and a tendency that voids are easily generated at the time of molding is observed.
Conversely, if the content exceeds 5.0 wt%, the strength of the cured resin itself is greatly reduced, cracks are likely to occur during reflow, and mold release failure from the mold tends to occur.

The epoxy resin composition according to the present invention may contain a release agent. As the release agent, those commonly used for a sealing material can be used. For example, natural carnauba-based, long-chain fatty acids, and their metal soaps, esters, amides, or polyolefins such as polyethylene wax can be used. Even when used alone, two or more kinds are used in combination. May be. In particular,
Carnauba wax, stearic acid and its derivatives, montanic acid and its derivatives, carboxyl group-containing polyolefin and the like are preferably used. These may be used alone or in combination. The compounding ratio of the release agent is preferably 0.05 to 1.5 wt% of the whole composition. When fatty acid amide is used as a release agent, mold stains are less likely to occur.

The sealing epoxy resin composition according to the present invention may optionally contain a coupling agent, a flame retardant, a coloring agent, and the like in an appropriate amount. As a coupling agent,
For example, silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane for silica surface treatment are exemplified. Examples of the flame retardant include halogen compounds such as antimony trioxide and bromo compounds, and phosphorus compounds. Examples of the coloring agent include carbon black, titanium oxide, and organic dyes. The coupling agent, flame retardant, colorant, and the like may be used in combination of two or more.

The epoxy resin composition of the present invention can be produced by uniformly mixing the above-mentioned components with a mixer, a blender or the like, and then kneading with a roll, a kneader or the like. The order of compounding the components is not particularly limited. The epoxy resin composition of the present invention, more specifically,
For example, after mixing and dispersing an epoxy resin, a curing agent, a curing accelerator, an inorganic filler, and other components, the mixture is melt-kneaded with a heating roll or the like, and the kneaded product is cooled and solidified, and then pulverized into a powdery and granular material. Or, if necessary, tableting the crushed material into tablets. (Encapsulation of semiconductor device) The epoxy resin composition obtained in this manner is molded by using a mold, and when solid, powder or granules or tablets are transfer-molded to form a semiconductor element mounted on a lead frame of the semiconductor device. Can be sealed.

As the lead frame, a lead frame made of a copper alloy in terms of electric conductivity and a lead frame made of a 42 alloy alloy in terms of a coefficient of thermal expansion are generally used.

[0025]

EXAMPLES Examples of the present invention and comparative examples outside the scope of the present invention will be shown below, but the present invention is not limited to the following examples. The compounds used in the examples and comparative examples are as follows. As the epoxy resin, ortho-cresol novolak type epoxy resin (manufactured by Sumitomo Chemical Co., Ltd., product number ESCN195XL), bifunctional biphenyl type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., product number YX4000)
H), a dicyclopentadiene type epoxy resin (manufactured by Dainippon Ink Co., Ltd., product number HP7200), and a brominated epoxy resin (manufactured by Sumitomo Chemical Co., Ltd., product number ESB400) were used.

As the curing agent, a phenol novolak type curing agent (Tamanol 752, manufactured by Arakawa Chemical Co., Ltd.) was used. As the curing accelerator, triphenylphosphine (TPP; manufactured by Hokuko Chemical Co., Ltd.) was used. As the inorganic filler, fused silica (average particle size: 15 μm) was used.

As the silicone rubber powder, a silicone rubber powder whose surface is coated with a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., average particle size 5 μm, product number X22
-1139K), silicone rubber powder whose surface is coated with a silicone resin (Shin-Etsu Chemical Co., Ltd., average particle size 12 μm, product number X22-1139G), silicone rubber powder whose surface is not coated with a silicone resin (Toray Dow) Corning Silicone Co., Ltd., average particle size 2 μm, epoxy group-containing, product number E601) was used.

Silicone oil (manufactured by Toray Dow Corning Silicone Co., Ltd., product number S
F8421EG) was used. Natural carnauba wax was used as the wax, γ-glycidoxypropyltriethoxysilane was used as the coupling agent, and antimony trioxide was used as the flame retardant. (Examples 1 to 7 and Comparative Examples 1 to 4)
Mix epoxy resin, curing agent, curing accelerator, inorganic filler, and other components, stir well with a mixer, knead with a heating roll for about 5 minutes, solidify by cooling, pulverize with a pulverizer, and granulate After that, tablet compression was performed to obtain a tablet-like epoxy resin composition.

The evaluation of the physical properties of the epoxy resin compositions of Examples and Comparative Examples and the molded articles thereof were performed as follows. Internal voids: The internal voids are evaluated for each resin composition by using an evaluation package (QFP package. Size: 15 mm)
10 mm × 19 mm × 2.4 mm) were produced, and internal voids generated in these packages were observed. The package for evaluation is a TEG chip for evaluation (size: 7.6 mm
A lead frame for a 60-pin QFP mounted with a 7.6 mm x 0.35 mm) was transfer-molded with each epoxy resin composition using a 60-pin QFP mold, and was molded at 175 ° C for 6 hours.
It was made after-curing (post-curing) for a time. The molding conditions were a temperature of 170 ° C., an injection time of 10 seconds, and a pressurization time of 12
The injection pressure was 70 kgf / cm ² for 0 seconds. The internal voids of the obtained package were observed from both front and back surfaces of each package with an ultrasonic microscope M-700II (manufactured by Canon Inc.). Count and calculate the average number of occurrences per package.
Those with less than 0.5 pieces were judged as good (○). In any case, the smaller the average number of generated pieces, the better the moldability.

Reflow resistance: The reflow resistance was evaluated by counting the number of packages having the following defects in the packages prepared for the evaluation of internal voids. After pre-drying the package at 125 ° C. for 24 hours, the package is left in a thermo-hygrostat at 85 ° C. and 60% relative humidity for 168 hours to perform a moisture absorption process, and then a reflow process (using a hot air having a peak of 245 ° C.) Type far-infrared ray reflow furnace). The appearance of the package after this treatment was visually observed, and the number of packages in which cracks had occurred outside was counted to show the number of defective products per 10 packages. Samples with 5 or more defectives were judged as defective (x), and samples with less than 5 defectives were judged as good (O). It means that the smaller the number of defective products, the better the solder heat resistance, and it is unlikely that defects will occur even if the package is subjected to a reflow treatment in a moisture absorbing state.

Low stress index: A package prepared for evaluating internal voids was subjected to a three-point bending test with an autograph tester to determine a flexural modulus (E). The coefficient of linear expansion (α1) at 70 to 120 ° C. was determined using a TMA measuring device. The product of the respective values (α1 × E = low stress index) is obtained by calculation, and those higher than 2500 are determined as defective (×).
And 2500 or less were judged as good (良). . The smaller the low stress index, the better the low stress property.

The above results are shown in Tables 1 to 3.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

As shown in Tables 1 to 3, the package sealed with the epoxy resin composition of the example has less internal voids and the reflow resistance than the package sealed with the comparative example. The properties were almost equal to or better than those of the comparative examples, and were low stress properties and excellent.

[0037]

According to the present invention, when a semiconductor device is sealed using the epoxy resin composition for sealing according to the present invention, reflow resistance and low stress are excellent, and voids are generated during molding. Less is. According to the epoxy resin composition of the second or third aspect, the reflow resistance is further improved.

According to the epoxy resin composition of the fourth aspect of the present invention, in addition to the above effects, low stress properties are sufficient, voids are hardly generated, cracks are hardly generated during reflow, and mold release defects are generated. It becomes difficult to do. Since the semiconductor device according to the fifth aspect of the present invention performs semiconductor encapsulation by using the epoxy resin composition according to the present invention, the semiconductor device has few internal voids, and has excellent reflow resistance and low stress. Can be.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 23/29 H01L 23/30 R 23/31 F term (Reference) 4J002 CC033 CC043 CC053 CC063 CD031 CD041 CD051 CD061 CD071 CD121 CP032 DE147 DF017 DJ007 DJ017 EU116 EU136 EW146 FB092 FB262 FD012 FD017 FD143 FD156 FD170 GQ05 4J036 AD07 AE07 DB21 DC05 DC06 DC12 DC41 DC46 DD07 FB08 JA07 4M109 AA01 BA01 EA03 EB17 EB19 EC03

Claims (5)

[Claims] 1. An epoxy resin composition comprising an epoxy resin, a curing agent, a curing accelerator, and an inorganic filler, and further comprising a silicone rubber powder, wherein the surface of the silicone rubber powder is coated with a silicone resin. An epoxy resin composition for sealing, characterized in that: 2. The epoxy resin composition for sealing according to claim 1, wherein at least a part of the epoxy resin is a biphenyl type epoxy resin. 3. The epoxy resin composition for sealing according to claim 1, wherein at least a part of the epoxy resin is a dicyclopentadiene type epoxy resin. 4. The method according to claim 1, wherein the proportion of the silicone rubber powder whose surface is coated with the silicone resin is in the range of 0.3 to 5.0% by weight based on the solid content of the epoxy resin composition. The epoxy resin composition for sealing according to any one of the above. 5. A semiconductor device in which a semiconductor element is sealed with an epoxy resin composition, wherein the epoxy resin composition according to claim 1 is used as the epoxy resin composition. A semiconductor device.