JP5067994B2 - Epoxy resin composition and semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an epoxy resin composition for semiconductor encapsulation excellent in moldability and a semiconductor device using the same.
[0002]
[Prior art]
Conventionally, in order to protect semiconductor elements such as diodes, transistors, ICs, and LSIs from external stimuli (mechanical, thermal shock, chemical action, etc.), an epoxy resin composition in consideration of production costs It is common to encapsulate with. On the other hand, the recent high integration of semiconductor elements and the accompanying increase in dimensions are contrary to each other, and the recent downsizing of electronic equipment demands a reduction in size and thickness of semiconductor devices, and to the printed circuit board. The mounting method has shifted from the conventional pin insertion type to the surface mounting type, and the introduction of solder that does not contain lead in order to reduce the environmental burden has led to higher mounting temperatures. There is a tendency to cause problems such as cracks in the semiconductor device due to impacts and peeling of the semiconductor element / lead frame from the cured epoxy resin composition, and the epoxy resin composition capable of imparting superior thermal shock resistance characteristics is stronger than before. It has been demanded.
[0003]
These cracks and delamination are thought to occur when the semiconductor device itself absorbs water before soldering and the moisture explosively vaporizes at a high temperature during soldering. To prevent it, the epoxy resin composition A technique of reducing water absorption of a cured product, 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 component. Therefore, as one of the methods for reducing the water absorption, there is a technique of increasing the amount of the inorganic filler and reducing the content of the resin component. However, as the inorganic filler is highly filled, the fluidity and filling properties of the epoxy resin composition during molding and melting deteriorate. When the fluidity and filling property of the epoxy resin composition at the time of melting are remarkably 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 that is highly filled with an inorganic filler and the cured product has low water absorption characteristics, and that has good fluidity and filling properties when melted, the epoxy resin when melted is obtained. There is a need for inorganic fillers that can improve the fluidity and filling properties of resin compositions.
[0004]
The epoxy resin composition usually contains a halogen-based flame retardant such as a bromine-containing compound and an antimony compound 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 importance of corporate activities in consideration of the global environment. Epoxy resin compositions with excellent flame resistance without using halogenated flame retardants and antimony compounds Development is required. As environmentally friendly flame retardants to replace these, epoxy resin compositions containing metal hydroxides such as aluminum hydroxide and magnesium hydroxide and red phosphorus have been proposed, but moisture resistance reliability of semiconductor devices using the same, There are cases where high-temperature storage properties are still insufficient, and 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 without using these flame retardants. There is a need for an epoxy resin composition that satisfies the properties and curability.
[0005]
[Problems to be solved by the invention]
The present invention provides an epoxy resin composition for semiconductor encapsulation excellent in fluidity, filling property, solder crack resistance and flame retardancy during molding, and a semiconductor device using the same.
[0006]
[Means for Solving the Problems]
The present invention
[1] (A) an epoxy resin represented by the general formula (1), (B) a phenol resin represented by the general formula (2), (C) a curing accelerator, and (D) an inorganic filler, which are essential. Filler is measured by laser diffraction / scattering method. (1) Fused spherical silica having an average particle diameter of 60 μm to less than 80 μm and a logarithmic standard deviation of 0.5 or less, 75 wt% to 85 wt%, (2) Average particle diameter of 5 μm or more 10 wt% or more and 20 wt% or less of fused spherical silica having a logarithmic standard deviation of 0.5 or less with a logarithmic standard deviation of 0.5 or less, and (3) 2 wt% of fused spherical silica having an average particle diameter of 1 to 5 μm % To 8% by weight and a fused silica resin containing 2% by weight or less of finely divided silica of 0.5 μm or less , wherein the fused spherical silica is all inorganic. 70-1 in filler Epoxy resin composition for semiconductor encapsulation, which is a 0 wt%,
[0007]
[Chemical 3]
(R is a group selected from a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different from each other. N is an average value and is a positive number of 1 to 5)
[0008]
[Formula 4]
(R is a group selected from a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different from each other. N is an average value and is a positive number of 1 to 5)
[0009]
[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] A semiconductor device comprising a semiconductor element sealed using the epoxy resin composition according to the item [1] or [2].
It is.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The epoxy resin represented by the general formula (1) used in the present invention has a hydrophobic structure between epoxy groups, and an epoxy resin composition using this epoxy resin and a phenol resin represented by the general formula (2). The cured product has a low water absorption because it contains a lot of hydrophobic structures, and has a low cross-link density, so it has a low elastic modulus in the high temperature range that exceeds the glass transition temperature. It is excellent in solder crack resistance and adhesion to the substrate after soldering. Furthermore, since the hydrophobic structure between epoxy groups is a rigid biphenyl skeleton, it has a feature that there is little decrease in heat resistance for a low crosslinking density. Although the specific example of the epoxy resin shown by General formula (1) is shown below, it is not limited to these.
[0011]
[Chemical formula 5]
(Where n is an average value and is a positive number from 1 to 5)
[0012]
The epoxy resin represented by the general formula (1) is a monomer, oligomer or polymer having an epoxy group in the molecule, such as bisphenol A type epoxy resin, phenol novolac type epoxy resin, orthocresol novolak type epoxy resin, naphthol novolak type epoxy resin. , Dicyclopentadiene modified phenol type epoxy resin, biphenyl type epoxy resin, stilbene type epoxy resin, triphenol methane type epoxy resin, alkyl modified triphenol methane type epoxy resin and triazine nucleus-containing epoxy resin There is no problem. The amount of the epoxy resin of the general formula (1) when used in combination is preferably 70% by weight or more in the total epoxy resin, and if it is less than 70% by weight, the epoxy resin composition tends to burn or There is a possibility that the water absorption rate becomes high and the elastic modulus becomes high, and the solder crack resistance is adversely affected.
[0013]
The phenol resin represented by the general formula (2) used in the present invention has a hydrophobic structure between hydroxyl groups, and the epoxy resin represented by the general formula (1) and the phenol represented by the general formula (2). A cured product of an epoxy resin composition using a resin has a low water absorption because it contains a lot of hydrophobic structures, and also has a low cross-link density, so it has a low elastic modulus in a high temperature range exceeding the glass transition temperature. It reduces thermal stress during solder reflow during surface mounting, and has excellent solder crack resistance and adhesion to the substrate after soldering. Furthermore, since the hydrophobic structure between the phenyl groups is a rigid biphenyl skeleton, it has a feature that there is little decrease in heat resistance for a low crosslinking density. Although the specific example of the phenol resin shown by General formula (2) is shown below, it is not limited to this.
[0014]
[Chemical 6]
(Where n is an average value and is a positive number from 1 to 5)
[0015]
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 a phenol novolak resin, a cresol novolak resin, a phenol aralkyl resin, a terpene-modified phenol resin, or a dicyclopentadiene-modified phenol resin. Further, it may be used in combination with phenol resins such as bisphenol A and triphenolmethane. As a compounding quantity of the phenol resin shown by General formula (2) in the case of using together, 70 weight% or more is preferable in all the phenol resins. If it is less than 70% by weight, it tends to burn, the water absorption rate increases, the elastic modulus increases, and solder crack resistance may be adversely affected. When the epoxy resin represented by the general formula (1) and the phenol resin represented by the general formula (2) are used in combination, the semiconductor device has low water absorption, solder crack resistance in the solder treatment after water absorption, Highly reliable characteristics such as adhesion can be obtained. The equivalent ratio of epoxy groups of all epoxy resins to phenolic hydroxyl groups of all phenol resins is preferably in the range of epoxy group number / phenolic hydroxyl group number = 0.7 to 1.5, more preferably 0.9 to 1.2. It is. If 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.
[0016]
As a hardening accelerator used for this invention, what is necessary is just to accelerate | stimulate hardening reaction of an epoxy group and a phenolic hydroxyl group, and what is generally used for the sealing material can be used widely. For example, amine compounds such as 1,8-diazabicyclo (5,4,0) undecene-7, organic phosphorus compounds such as triphenylphosphine and tetraphenylphosphonium / tetraphenylborate salts, and imidazoles such as 2-methylimidazole Examples thereof include compounds, and these may be used alone or in combination.
[0017]
The fused spherical silica used in the present invention is obtained by laser diffraction / scattering method (1) 75% by weight to 85% by weight of fused 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) fused spherical silica having an average particle diameter of 5 μm to less than 15 μm and a logarithmic standard deviation of 0.5 or less, and 10% by weight to 20% by weight or less, and (3) an average particle diameter of 1 μm to less than 5 μm with a logarithmic standard deviation of 0.5. The following fused spherical silica is composed of 2% by weight to 8% by weight and contains 2% by weight or less of fine silica of 0.5 μm or less. As 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 the Basic Editing Committee of Powder Engineering, published by Nikkan Kogyo Shimbun). The smaller the value of A, the narrower the particle size distribution.
A = {ln (D2 / D1)} × 0.5
Here, 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 means (100-integration of particle size frequency).
In the particle size distribution shown in FIG. 1, when D1 = 54.2 μm and D2 = 97.8 μm, A = {ln (97.8 / 54.2)} × 0.5 = 0.3.
[0018]
When the constituent requirements of the fused spherical silica having the above-mentioned particle diameter by the laser diffraction / scattering method are not satisfied, the honey-filling property of the fused spherical silica is lowered. Epoxy resin compositions using fused spherical silica with a minimum honey filling property are preferred because the frequency of collision between fused spherical silicas increases when flowing, and the epoxy resin composition cannot obtain sufficient fluidity and filling properties. Absent.
Further, the fused spherical silica composed of fused spherical silica having the above particle size contains 2% by weight or less of fine silica of 0.5 μm or less. If this value is exceeded, the total specific surface area increases and the fused spherical silica / Since the contact area between the resins increases, the epoxy resin composition is not preferable because sufficient fluidity and filling properties cannot be ensured.
[0019]
The fused spherical silica used in the present invention is desirably contained in an amount of 70 to 100% by weight in the total inorganic filler. If it is less than 70% by weight, sufficient fluidity may not be obtained. . Other inorganic fillers used in combination may be those generally used for sealing materials, such as 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 and the like can 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 in the total epoxy resin composition. If it is less than 70% by weight, the water absorption is increased and the solder crack resistance is lowered, which is not preferable. If it exceeds 95% by weight, it is not preferable because the fluidity necessary for practical use cannot be secured.
[0020]
The particle size distribution of the fused spherical silica in the present invention is obtained by collecting fused spherical silica in accordance with JIS M 8100 (powder mixture-sampling method) and JIS R 1622-1995 (sample for fine ceramic raw material particle size distribution measurement). In accordance with JIS R 1629-1997 (Method for measuring particle size distribution by laser diffraction / scattering method of fine ceramic raw material), manufactured by Shimadzu Corporation Was measured using a laser diffraction particle size distribution analyzer SALD-7000 (laser wavelength: 405 nm) with water or the like as a dispersant and a refractive index of fused spherical silica of real part 1.45 and imaginary part 0.00. Volume-based particle size distribution. The average particle diameter is the particle diameter when the volume-based cumulative residual fraction is 50%.
[0021]
Conventionally, as the inorganic filler to be blended in the epoxy resin composition for semiconductor encapsulation, generally fused spherical silica, fused crushed silica, crystalline silica, etc. are used, but fused spherical silica having the characteristics of the present invention should be used. As a result, it is possible to improve the fluidity and filling properties compared to conventional fillers with various particle sizes, and to obtain an epoxy resin composition with a high blended amount of fused spherical silica, and as a result, a cured product of the epoxy resin composition This contributes to improving the water absorption resistance of the semiconductor device and can improve the solder crack resistance of the semiconductor device.
[0022]
In addition to the components (A) to (D), the epoxy resin composition of the present invention includes flame retardants such as brominated epoxy resin, antimony oxide, phosphorus compound, magnesium hydroxide, aluminum hydroxide, and boric acid compound as necessary. , Inorganic ion exchangers such as bismuth oxide hydrate, coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane, colorants such as carbon black and bengara, silicone oil, silicone rubber Various additives such as a low stress component such as natural wax, synthetic wax, higher fatty acids and metal salts thereof or mold release agents such as paraffin, and antioxidants can also be blended.
[0023]
The epoxy resin composition of the present invention is a mixture of components (A) to (D) and other additives at room temperature using a mixer or the like, and melt-kneaded with a kneader such as a roll, a kneader or an extruder, It is obtained by a general method of grinding after cooling.
In order to seal an electronic component such as a semiconductor element and manufacture a semiconductor device using the epoxy resin composition of the present invention, it may be molded and cured by a molding method such as a transfer mold, a compression mold, or an injection mold.
[0024]
【Example】
Hereinafter, the present invention will be specifically described with reference to Examples.
9.8 parts by weight of epoxy resin A represented by formula (9) (softening point 60 ° C., epoxy equivalent 270)
[Chemical 7]
[0026]
Phenol resin C represented by the formula (10) (softening point 75 ° C., hydroxyl group equivalent 195) 7.1 parts by weight
[Chemical 8]
[0028]
1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 0.2 part by weight γ-glycidoxypropyltrimethoxysilane 0.3 part by weight carbon black 0.3 part by weight carnauba wax 0 .3 parts by weight silica A (79% by weight fused spherical silica having an average particle size of 72 μm and logarithmic standard deviation of 0.3 measured by laser diffraction / scattering method, fused spherical particles having an average particle size of 9.6 μm and logarithmic standard deviation of 0.2 82.0 parts by weight of all of the above-mentioned components, comprising 16% by weight of silica, 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 silica of 0.5 μm or less) The components were mixed using a mixer, then kneaded using two rolls having surface temperatures 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.
[0029]
Evaluation Method Spiral Flow: Using a mold for spiral flow measurement according to EMMI-1-66, measurement was performed at a mold temperature of 175 ° C., an injection pressure of 6.9 Mpa, and a curing time of 120 seconds. The unit is cm.
Solder crack resistance: Using a multi-plunger molding machine, 80 pQFP (thickness 2.0 mm, chip size 6 mm × 6 mm) was molded under 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 as post-cure at 175 ° C. for 8 hours were treated in an environment of 85 ° C. and 85% relative humidity for 168 hours, and then IR reflow treatment (maximum 260 ° C. for 10 seconds) was performed. The external cracks of the package after treatment with a microscope and the presence or absence of internal peeling and cracks were 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.
Fillability: 144 pLQFP using a multi-plunger molding machine under conditions of a mold temperature of 180 ° C., an injection pressure of 9.8 MPa, and a curing time of 60 seconds (package size is 20 mm × 20 mm, thickness is 1.4 mm, dimensions of the simulated semiconductor element) Is 12 mm × 12 mm, the lead frame is made of Cu), and the unfilled number of times is 5 times or more, ×, 1-4 times are indicated by Δ, and no occurrence is indicated by ○.
Flame retardancy: Using a low-pressure transfer molding machine, test specimens were molded at a mold temperature of 175 ° C., 9.8 MPa, and a curing time of 120 seconds, treated as post-cure at 175 ° C. for 8 hours, and then subjected to UL-94 vertical test. (Test specimen thickness 1.6 mm and 3.2 mm) was performed, and the flame retardancy was judged.
[0030]
Examples 1 to 4, 6, 7 and Comparative Examples 1 to 8
According to the composition of Table 1 and 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. The results are shown in Tables 1 and 2.
The characteristics of the raw materials used other than 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 (Mitsui Chemicals, XL-225, softening point 75 ° C., hydroxyl equivalent 175)
Fused silica B (Fused silica with an average particle diameter of 1.6 μm measured by the laser diffraction / scattering method and no peak with a logarithmic standard deviation of 0.5 or less)
Fused silica C (fused silica with an average particle size of 22 μm measured by laser diffraction / scattering method and no peak with a logarithmic standard deviation of 0.5 or less)
[0031]
[Table 1]
[0032]
[Table 2]
[0033]
【Effect of the invention】
The epoxy resin composition of the present invention is excellent in fluidity and filling property at the time of molding, and contributes to improvement of solder crack resistance and flame retardancy of a semiconductor device using the epoxy resin composition.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the particle size of a particle size distribution and the cumulative residual fraction.

Claims (2)

(A) An epoxy resin represented by the general formula (1), (B) a phenol resin represented by the general formula (2), (C) a curing accelerator and (D) an inorganic filler are essential, and the inorganic filler is By laser diffraction / scattering method (1) Fused 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, 75 wt% to 85 wt%, (2) Average particle size of 5 μm to less than 15 μm (3) 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, An epoxy resin composition for encapsulating a semiconductor comprising fused spherical silica composed of 8% by weight or less and 2% by weight or less of fine silica of 0.5 μm or less, wherein the fused spherical silica is contained in all inorganic fillers 77.0 / (7 .0 + 10.0) epoxy resin composition for semiconductor encapsulation, which is a × 100 to 100 wt%.
(R is a group selected from a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different from each other. N is an average value and is a positive number of 1 to 5)
(R is a group selected from a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different from each other. N is an average value and is a positive number of 1 to 5) A semiconductor device comprising a semiconductor element sealed with the epoxy resin composition according to claim 1.