JP2003096268A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for sealing a semiconductor excellent in flowability and filling properties during molding. SOLUTION: The epoxy resin composition for sealing a semiconductor essentially comprises (A) a phenol aralkyl epoxy resin including a diphenylene backbone, (B) a phenol aralkyl phenol resin including a diphenylene backbone, (C) a curing accelerator and (D) an inorganic filler. The inorganic filler comprises molten spherical silica composed of (1) 75-85 wt.% of the molten spherical silica having an average particle size of 60 μm to less than 80 μm and a logarithmic standard deviation of 0.5 or less, (2) 10-20 wt.% of the molten spherical silica having an average particle size of 5 μm to less than 15 μm and a logarithmic standard deviation of 0.5 or less, (3) 2-8 wt.% of the molten spherical silica having an average particle size of 1 μm to less than 5 μm and a logarithmic standard deviation of 0.5 or less, and 2 wt.% or less of a fine particle silica having a particle size of 0.5 μm or less, as measured by a laser diffraction/ scattering method.

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 a semiconductor device using the same.

[0002]

2. Description of the Related Art Conventionally, diodes, transistors, I
In order to protect semiconductor elements such as C and LSI from external stimuli (mechanical, thermal shock, chemical action, etc.), encapsulation molding with an epoxy resin composition is performed in consideration of production cost. It is becoming popular. On the other hand, the recent high integration of semiconductor elements and the accompanying increase in size are in conflict with each other.Recent miniaturization of electronic equipment is required to reduce the size and thickness of semiconductor devices. The mounting method has also changed from the conventional pin insertion type to the surface mounting type, and due to the introduction of lead-free solder to reduce the environmental load, the mounting temperature tends to rise, and the heat generated during surface mounting solder processing Problems such as cracks in semiconductor devices due to impact and peeling between the semiconductor element / lead frame and the cured product of the epoxy resin composition are more likely to occur, and epoxy resin compositions that can impart properties with better thermal shock resistance than before are strong. It has been demanded.

It is considered that these cracks and peeling are caused by water absorption by the semiconductor device itself before the soldering process and explosive vaporization of the water at a high temperature during the soldering process. A technique of reducing water absorption of a cured product of an epoxy resin composition, that is, imparting low water absorption to an epoxy resin composition is often used. The water absorption of the epoxy resin composition is greatly influenced by the constituent resin components. Therefore, as one of the methods of lowering the water absorption, there is a technique of highly filling the inorganic filler to reduce the content of the resin component. However, as the inorganic filler is highly filled, the flowability and filling property of the epoxy resin composition at the time of molding and melting deteriorate. If the fluidity and the filling property of the epoxy resin composition when melted are significantly deteriorated, the solder crack resistance is deteriorated even if the cured product of the epoxy resin composition has low water absorption. Therefore, in order to obtain an epoxy resin composition which is highly filled with an inorganic filler and has a cured product having a property of low water absorption, and which has a good fluidity and a good filling property at the time of melting, There is a demand for an inorganic filler capable of improving the fluidity and filling property of a resin composition.

In addition, a halogen-based flame retardant such as a bromine-containing compound and an antimony compound are usually blended in the epoxy resin composition in order to impart flame retardancy. In recent years, there has been a movement to reduce or eliminate substances that may be harmful due to the emphasis on corporate activities that consider the global environment. Epoxy resin compositions with excellent flame retardancy without using halogen-based flame retardants and antimony compounds. Development is required. As an environment-friendly flame retardant alternative to these, an epoxy resin composition containing a metal hydroxide such as aluminum hydroxide or magnesium hydroxide or red phosphorus has been proposed, but the moisture resistance reliability of a semiconductor device using this, There are some cases where the high-temperature storability is still insufficient, and further there is a problem that an epoxy resin composition that is sufficiently satisfactory in terms of both moldability and curability cannot be obtained, and molding is possible even without using these flame retardants. There is a demand for an epoxy resin composition that satisfies the requirements for curability and curability.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides an epoxy resin composition for semiconductor encapsulation which is excellent in fluidity, filling property, solder crack resistance and flame retardancy during molding, and a semiconductor device using the same. To do.

[0006]

The present invention provides [1] (A)
The epoxy resin represented by the general formula (1), (B) the phenol resin represented by the general formula (2), (C) the curing accelerator and (D) the inorganic filler are essential, and the inorganic filler is laser diffraction / By scattering method (1) Average particle size of 60 μm or more
Fused spherical silica of less than 80 μm and a logarithmic standard deviation of 0.5 or less 75% by weight to 85% by weight, (2) average particle size 5
10 to 20 wt% of fused spherical silica having a logarithmic standard deviation of 0.5 or less and a μm to 15 μm, (3)
Logarithmic standard deviation of 0.5 when the average particle size is 1 μm or more and less than 5 μm
An epoxy resin composition for semiconductor encapsulation, comprising the following fused spherical silica in an amount of from 2% by weight to 8% by weight, and containing 2% by weight or less of fine silica having a particle size of 0.5 μm or less. ,

[0007]

[Chemical 3] (R is a hydrogen atom or a group selected from an alkyl group having 1 to 4 carbon atoms and may be the same or different. N is an average value and is a positive number of 1 to 5).

[0008]

[Chemical 4] (R is a hydrogen atom or a group selected from an alkyl group having 1 to 4 carbon atoms and may be the same or different. N is an average value and is a positive number of 1 to 5).

[2] The epoxy resin composition for semiconductor encapsulation according to item [1], wherein the fused spherical silica is 70 to 100% by weight in the total inorganic filler, [3] item [1] or [2]. ]
A semiconductor device obtained by encapsulating a semiconductor element using the epoxy resin composition as described in the above item.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin represented by the general formula (1) used in the present invention has a hydrophobic structure between epoxy groups, and the epoxy resin and the phenol resin represented by the general formula (2) are used. The cured product of the epoxy resin composition using is characterized in that it has a low water absorption rate because it contains many hydrophobic structures, and that it has a low elastic modulus in the high temperature range above the glass transition temperature because of its low crosslink density. It reduces thermal stress during surface mount solder processing and has excellent solder crack resistance and adhesion to the base material after solder processing. Further, since the hydrophobic structure between the epoxy groups is a rigid biphenyl skeleton, it has a characteristic that the heat resistance is not deteriorated in spite of the low crosslink density. Specific examples of the epoxy resin represented by the general formula (1) are shown below, but the epoxy resin is not limited to these.

[0011]

[Chemical 5] (N in the formula is an average value and is a positive number of 1 to 5)

The epoxy resin represented by the general formula (1) is
Monomers, oligomers and polymers having an epoxy group in the molecule, such as bisphenol A type epoxy resin, phenol novolac type epoxy resin, orthocresol novolac type epoxy resin, naphthol novolac type epoxy resin, dicyclopentadiene modified phenol type epoxy resin, biphenyl type It may be used in combination with an epoxy resin such as an epoxy resin, a stilbene type epoxy resin, a triphenol methane type epoxy resin, an alkyl modified triphenol methane type epoxy resin and a triazine nucleus-containing epoxy resin. When used in combination, the amount of the epoxy resin represented by the general formula (1) is preferably 70% by weight or more based on the total amount of the epoxy resin. If it is less than 70% by weight, the epoxy resin composition may easily burn or a cured product may be obtained. There is a possibility that the water absorption rate becomes high, or the elastic modulus becomes high, which adversely affects the solder crack resistance.

The phenolic resin represented by the general formula (2) used in the present invention has a hydrophobic structure between hydroxyl groups, and is represented by the epoxy resin represented by the general formula (1) and the general formula (2). The cured product of the epoxy resin composition using the phenolic resin shown has a low water absorption rate because it contains many hydrophobic structures, and also has a low crosslink density, so that the elastic modulus in the high temperature range above the glass transition temperature is high. It has the characteristic of being low, reducing thermal stress during solder reflow during surface mounting, and has excellent solder crack resistance and adhesion to the base material after solder processing. Further, since the hydrophobic structure between the phenyl groups is a rigid biphenyl skeleton, it has a characteristic that the heat resistance is not deteriorated in spite of the low crosslink density. Specific examples of the phenol resin represented by the general formula (2) are shown below, but the invention is not limited thereto.

[0014]

[Chemical 6] (N in the formula is an average value and is a positive number of 1 to 5)

The phenol resin represented by the general formula (2) is a monomer, oligomer or polymer having a phenolic hydroxyl group in the molecule, such as phenol novolac resin, cresol novolac resin, phenol aralkyl resin, terpene modified phenol resin, dicyclopentadiene. It may be used in combination with a modified phenol resin, a bisphenol A, or a phenol resin such as triphenol methane. When used in combination, the blending amount of the phenol resin represented by the general formula (2) is preferably 70% by weight or more in the total phenol resin. If it is less than 70% by weight, it may be easily burned, the water absorption may be high, or the elastic modulus may be high, which may adversely affect the solder crack resistance. When the epoxy resin represented by the general formula (1) and the phenol resin represented by the general formula (2) are used in combination, low water absorption of the semiconductor device, solder crack resistance in solder treatment after water absorption, Highly reliable characteristics such as adhesion can be obtained. The equivalent ratio of the epoxy groups of all epoxy resins to the phenolic hydroxyl groups of all phenolic resins is preferably in the range of number of epoxy groups / number of phenolic hydroxyl groups = 0.7 to 1.5, and more preferably 0.9 to 1.2. Is. When it is out of the range of 0.7 to 1.5, the curability of the epoxy resin composition is lowered, the glass transition temperature of the cured product is lowered, and the moisture resistance reliability is lowered, which is not preferable.

The curing accelerator used in the present invention includes
Any material that accelerates the curing reaction between the epoxy group and the phenolic hydroxyl group may be used, and those generally used for sealing materials may be widely used. For example, amine compounds such as 1,8-diazabicyclo (5,4,0) undecene-7, organic phosphorus compounds such as triphenylphosphine, tetraphenylphosphonium / tetraphenylborate salts, imidazoles such as 2-methylimidazole. Examples thereof include compounds, which may be used alone or in combination.

The fused spherical silica used in the present invention is (1) fused spherical silica having an average particle size of 60 μm or more and less than 80 μm and a logarithmic standard deviation of 0.5 or less 75% by weight or more and 85% by weight or less by a laser diffraction / scattering method. Hereinafter, (2) fused spherical silica having an average particle size of 5 μm or more and less than 15 μm and a logarithmic standard deviation of 0.5 or less 10% by weight or more and 20% by weight or less,
(3) Constituting 2 wt% to 8 wt% of fused spherical silica having an average particle size of 1 μm to less than 5 μm and a logarithmic standard deviation of 0.5 or less, and containing 2 wt% or less of fine silica of 0.5 μm or less. It is a waste. For the logarithmic standard deviation referred to in the present invention, the value A represented by the following formula was used (see: "Basics of powder engineering" edited by Nikkan Kogyo Shimbun, edited by the Fundamental Editing Committee of Powder Engineering). The smaller the value of A, the narrower the particle size distribution. A = {ln (D2 / D1)} × 0.5 where D1 is the particle diameter when the cumulative residual fraction is 84.1%, and D2 is the particle diameter when the cumulative residual fraction is 15.9%. . The cumulative residual fraction refers to (100-accumulation of particle size frequency). An example of the particle size distribution shown in FIG. 1 is D1 = 54.
If 2 μm and D2 = 97.8 μm, A = {ln (9
7.8 / 54.2)} × 0.5 = 0.3.

When the constitutional requirements of the fused spherical silica having the above-mentioned particle diameter by the laser diffraction / scattering method are not satisfied, the maximum filling property of the fused spherical silica is lowered. The epoxy resin composition using the fused spherical silica having the smallest honey-filling property has a high collision frequency of the fused spherical silica particles when flowing, and the epoxy resin composition cannot obtain sufficient fluidity and filling property, which is preferable. Absent. Further, the fused spherical silica composed of the fused spherical silica having the above-mentioned particle diameter contains 2% by weight or less of fine silica having a particle size of 0.5 μm or less. Since the contact area between the resins increases, the epoxy resin composition has sufficient fluidity,
It is not preferable because the filling property cannot be secured.

The fused spherical silica used in the present invention is preferably contained in the total inorganic filler in an amount of 70 to 100% by weight. If it is less than 70% by weight, sufficient fluidity may not be obtained. . As other inorganic fillers when used in combination,
It may be one generally used as a sealing material, for example, fused crushed silica, fused spherical silica, crystalline silica, chamfered crystalline silica, secondary agglomerated silica, alumina, spherical alumina,
Titanium white, aluminum hydroxide, silicon nitride, aluminum nitride, etc. may be mentioned, and the particle size distribution may be appropriately selected as necessary. The blending amount of the inorganic filler containing fused spherical silica used in the present invention is preferably 70 to 95% by weight based on the total epoxy resin composition. If it is less than 70% by weight, the water absorption is high and the solder crack resistance is deteriorated, which is not preferable. If it exceeds 95% by weight, the fluidity necessary for practical use cannot be secured, which is not preferable.

Regarding the particle size distribution of the fused spherical silica in the present invention, the fused spherical silica is sampled according to JIS M 8100 (powder lump mixture-sampling method), and JIS R
According to 1622-1995 (Preparation of sample for measuring particle size distribution of fine ceramics raw material), fused spherical silica was prepared as a sample for measurement, and JIS R 1629-
1997 (laser diffraction of fine ceramic raw materials
Laser diffraction type particle size distribution analyzer SAL manufactured by Shimadzu Corporation according to the method for measuring particle size distribution by scattering method)
This is a volume-based particle size distribution measured using D-7000 (laser wavelength: 405 nm), using water or the like as a dispersant, and the refractive index of fused spherical silica being a real part 1.45 and an imaginary part 0.00. The average particle diameter is the particle diameter when the volume-based cumulative residual fraction is 50%.

Conventionally, as the inorganic filler to be mixed with the epoxy resin composition for semiconductor encapsulation, generally fused spherical silica,
Although fused crushed silica, crystalline silica, etc. are used, by using fused spherical silica having the characteristics of the present invention, it is possible to improve fluidity and filling property as compared with conventional fillers having various particle size constitutions. An epoxy resin composition containing a large amount of silica can be obtained, and as a result, it contributes to the improvement of the water absorption resistance of the cured product of the epoxy resin composition, and the solder crack resistance of the semiconductor device can be improved.

The epoxy resin composition of the present invention comprises (A)-
In addition to the component (D), if necessary, brominated epoxy resin, antimony oxide, phosphorus compound, flame retardants such as magnesium hydroxide, aluminum hydroxide and boric acid compound, inorganic ion exchanger such as bismuth oxide hydrate, Coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane, colorants such as carbon black and red iron oxide, low stress components such as silicone oil and silicone rubber, natural wax, synthetic wax, It is also possible to add a releasing agent such as higher fatty acid and its metal salt or paraffin, and various additives such as antioxidant.

The epoxy resin composition of the present invention comprises (A)-
It can be obtained by a general method in which the component (D) and other additives are mixed at room temperature using a mixer or the like, melt-kneaded with a kneader such as a roll, kneader, or extruder, cooled, and then pulverized. In order to manufacture a semiconductor device by sealing an electronic component such as a semiconductor element using the epoxy resin composition of the present invention, molding and curing may be performed by a molding method such as a transfer mold, a compression mold or an injection mold.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples.   Epoxy resin A represented by formula (9) (softening point 60 ° C., epoxy equivalent 270)                                                             9.8 parts by weight

[0025]

[Chemical 7]

[0026]   Phenolic resin C represented by formula (10) (softening point 75 ° C., hydroxyl equivalent 195)                                                             7.1 parts by weight

[0027]

[Chemical 8]

1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 0.2 parts by weight γ-glycidoxypropyltrimethoxysilane 0.3 parts by weight carbon black 0.3 parts by weight Carnauba wax 0.3 parts by weight Silica A (79% by weight of fused spherical silica having an average particle size of 72 μm and a logarithmic standard deviation of 0.3, measured by a laser diffraction / scattering method, and an average particle size of 9.6 μm and a logarithmic standard deviation of 0.2). Of 8% by weight of fused spherical silica of 5% by weight of fused spherical silica having an average particle size of 3.9 μm and a logarithmic standard deviation of 0.2 and not containing fine particles of 0.5 μm or less). After mixing all of the above components using a mixer, the mixture was kneaded using a two-roll mill having a surface temperature of 90 ° C. and 45 ° C., cooled and pulverized to obtain an epoxy resin composition. The obtained epoxy resin composition was evaluated by the following methods.

Evaluation method Spiral flow: Using a mold for spiral flow measurement according to EMMI-1-66, mold temperature 175 ° C.
It was measured at an injection pressure of 6.9 MPa and a curing time of 120 seconds.
The unit is cm. Solder crack resistance: 80 pQFP (thickness: 2.0 mm, 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. . Post-cure 6 packages that were treated at 175 ℃ for 8 hours
It was treated for 168 hours in an environment of 5 ° C. and 85% relative humidity, and then subjected to IR reflow treatment (maximum 260 ° C. for 10 seconds). The number of defective packages was counted by observing external cracks of the package after processing with a microscope and observing internal peeling and cracks with an ultrasonic flaw detector. When the number of defective packages is n, it is displayed as n / 6. Fillability: 144 pLQFP (package size is 20 mm ×, using a multi-plunger molding machine under the conditions of a mold temperature of 180 ° C., an injection pressure of 9.8 MPa, and a curing time of 60 seconds.
20mm, thickness 1.4mm, size of simulated semiconductor device is 1
2 mm × 12 mm, the lead frame is made of Cu) was continuously molded 10 times, and the number of unfilled times was represented by x when it was 5 or more, Δ when 1 to 4 times, and ◯ when no occurrence. Flame retardance: A low-pressure transfer molding machine was used to mold a test piece at a mold temperature of 175 ° C., 9.8 MPa, and a curing time of 120 seconds, and post-curing was performed at 175 ° C. for 8 hours, followed by a UL-94 vertical test. (Test piece thickness 1.6 mm and 3.2 mm) was performed to determine flame retardancy.

Examples 1 to 7 and Comparative Examples 1 to 7 Epoxy resin compositions were obtained in the same manner as in Example 1 according to the formulations shown in Tables 1 and 2 and evaluated in the same manner as in Example 1.
The results are shown in Tables 1 and 2. The characteristics of the raw materials used other than those in Example 1 are shown below. Biphenyl type epoxy resin B (manufactured by Japan Epoxy Resin Co., Ltd., YX-4000, softening point 105 ° C., epoxy equivalent 193) Phenol aralkyl resin D (manufactured by Mitsui Chemicals, Inc., XL
-225, softening point 75 ° C., hydroxyl equivalent 175) fused silica B (fused silica having an average particle size of 1.6 μm measured by a laser diffraction / scattering method and having no peak with a logarithmic standard deviation of 0.5 or less) Spherical silica) Fused silica C (fused silica having an average particle size of 22 μm measured by a laser diffraction / scattering method and a logarithmic standard deviation of 0.
(Fused spherical silica with no peak below 5)

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

The epoxy resin composition of the present invention is excellent in fluidity and filling during molding, and contributes to improvement of solder crack resistance and flame retardancy of a semiconductor device using the same.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the particle size of the particle size distribution and the cumulative residual fraction.

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Claims (3)

[Claims] 1. An epoxy resin represented by the general formula (1) (A), a phenol resin represented by the general formula (2) (B),
(C) A curing accelerator and (D) an inorganic filler are essential, and the inorganic filler has a logarithmic standard deviation of 0.5 according to (1) an average particle diameter of 60 μm to 80 μm measured by a laser diffraction / scattering method.
The following fused spherical silica 75% by weight or more and 85% by weight or less, and (2) fused spherical silica 10% by weight or more and 2 with an average particle size of 5 μm or more and less than 15 μm and a logarithmic standard deviation of 0.5 or less.
0% by weight or less, (3) Fused spherical silica having an average particle size of 1 μm or more and less than 5 μm and a logarithmic standard deviation of 0.5 or less 2% by weight or more and 8% by weight or less and 0.5 μm or less An epoxy resin composition for semiconductor encapsulation, comprising a fused spherical silica in an amount of not more than wt%. [Chemical 1] (R is a hydrogen atom or a group selected from an alkyl group having 1 to 4 carbon atoms and may be the same or different. N is an average value and is a positive number of 1 to 5.) Chemical 2] (R is a hydrogen atom or a group selected from an alkyl group having 1 to 4 carbon atoms and may be the same or different. N is an average value and is a positive number of 1 to 5). 2. The fused spherical silica is contained in a total inorganic filler of 7
The epoxy resin composition for semiconductor encapsulation according to claim 1, which is 0 to 100% by weight. 3. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition according to claim 1.