Patent Application
20080083995
Next, the epoxy resin composition used in the present invention which produces an encapsulation resin (cured product) having a glass transition temperature of at least 250° C. is described in detail.
The epoxy resin used for the component (A) of the epoxy resin composition of the present invention is not particularly limited. Exemplary typical epoxy resins include novolac epoxy resin, cresol novolac epoxy resin, triphenol alkane epoxy resin, aralkyl epoxy resin, biphenyl skeleton-containing aralkyl epoxy resin, biphenyl epoxy resin, dicyclopentadiene epoxy resin, heterocyclic epoxy resin, naphthalene ring-containing epoxy resin, bisphenol A epoxy compound, bisphenol F epoxy compound, and stilbene epoxy resin, which may be used alone or in combination of two or more. Among these, the preferred are epoxy resins containing an aromatic ring, and the more preferred are polyfunctional epoxy resins having a plurality of epoxy functional groups such as triphenol alkane epoxy resin and cresol novolac epoxy resin.
The epoxy resin may preferably contain a hydrolyzable chlorine at a content of up to 1,000 ppm, and in particular, up to 500 ppm, and sodium and potassium at a content of up to 10 ppm. When the content of the hydrolyzable chlorine is in excess of 1,000 ppm or the sodium or potassium content is in excess of 10 ppm, the semiconductor device may experience loss of moisture resistance when stored under a high temperature, high humidity condition for a prolonged period.
The curing agent component (B) is not a critical component in the present invention. However, a curing agent commonly used in the art may be incorporated at an amount not adversely affecting the object of the present invention.
Exemplary preferable curing agents which may be used for the component (B) include phenol resins such as phenol novolac resin, naphthalene ring-containing phenol resin, aralkyl phenol resin, triphenol alkane phenol resin, biphenyl skeleton-containing aralkyl phenol resin, biphenyl phenol resin, alicyclic phenol resin, heterocyclic phenol resin, naphthalene ring-containing phenol resin, bisphenol A, and bisphenol F, which may be used alone or in combination of two or more.
The curing agent may preferably contain sodium and potassium respectively at a content of up to 10 ppm as in the case of the epoxy resin. When the curing agent has the sodium or potassium content in excess of 10 ppm, the semiconductor device may experience loss of moisture resistance when stored under a high temperature, high humidity condition for a prolonged period.
Amount of the component (B) incorporated in relation to the component (A) is not particularly limited, and an amount effective for curing the epoxy resin commonly used in the art may be employed. When a phenol resin is used for the curing agent, the component (B) is typically used so that molar ratio of the phenolic hydroxy group in the curing agent to 1 mole of the epoxy group in the component (A) is in the range of 0.5 to 1.5, and in particular, 0.8 to 1.2.
The inorganic filler (C) incorporated in the epoxy resin composition of the present invention may be any filler commonly used in the epoxy resin composition. Exemplary such inorganic fillers include silicas such as fused silica, crystalline silica, and cristobalite, alumina, silicon nitride, aluminum nitride, boron nitride, titanium oxide, and glass fiber.
The inorganic filler is not particularly limited for its average particle size, shape, or content. The average particle size, however, is preferably 5 to 30 μm, and the content is preferably 400 to 1,200 parts by weight, and in particular, 500 to 1,000 parts by weight in relation to 100 parts by weight of the total amount of the component (A), (F), and (G), and when the component (B) is used, the total amount of the component (A), (B), (F), and (G).
The inorganic filler incorporated is preferably the one preliminarily subjected to a surface treatment with a coupling agent such as a silane coupling agent and a titanate coupling agent. Preferable examples of such coupling agent include epoxy silanes such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-isocyanate propyltriethoxysilane, γ-ureido propyltriethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; aminosilanes such as N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; and mercaptosilanes such as γ-mercaptopropyltrimethoxysilane; which may be used alone or in combination of two or more. The amount of the coupling agent and the method of the surface treatment are not particularly limited.
In the present invention, the curing reaction between the epoxy resin and the curing agent is promoted by the compound represented by the following formula (1):
wherein R1, R2, and R3 are independently hydrogen atom, an alkyl group containing 1 to 4 carbon atoms, an aryl group such as phenyl group containing 6 to 12 carbon atoms, or hydroxyl group; and R4 to R18 are independently hydrogen atom or an alkyl group or an alkoxy group containing 1 to 4 carbon atoms.
More specifically, sufficient curability and moldability are not realized by the phosphorus compounds commonly used as an accelerator for the epoxy resin composition such as triphenylphosphine, tributylphosphine, tri(p-methylphenyl)phosphine, tri(nonylphenyl)phosphine, triphenylphosphine.triphenylborane, and tetraphenylphosphine.tetraphenylborate.
On the other hand, use of a tertiary amine compound such as triethylamine, benzyldimethylamine, α-methylbenzyldimethylamine, and 1,8-diazabicyclo(5.4.0)undecene-7, and an imidazole compound such as 2-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methylimidazole results in the loss of reliable moisture resistance.
In contrast, use of the compound represented by the formula (1) enables production of the molded article having excellent moldability and reliable moisture resistance.
When an ester solvent such as ethyl acetate or butyl acetate is used for producing the addition compound of a tertiary phosphine and a benzoquinone represented by the formula (1), columnar crystals of about 10 μm are obtained with an extremely small amount the residual solvent. In addition, since the target addition compound of the tertiary phosphine and the benzoquinone is obtained at a high purity, failure in the outer appearance generated by the volatile component of the curing accelerator is avoided and the cured article can be produced at an improved continuous moldability. In this case, the addition reaction may be accomplished at a reaction temperature of 40° C. to 90° C. and preferably 60° C. to 80° C. for 0.5 to 3 hours, and the resulting precipitate may be collected by filtration and washed with an (ester) solvent and dried at 80° C. at a reduced pressure to obtain the addition product having a purity of 98 to 100%.
The curing accelerator of the component (D) may be incorporated at an effective component. More specifically, the compound of formula (1) may be incorporated at 0.1 to 5 parts by weight, and in particular, at 0.5 to 3 parts by weight in relation to 100 parts by weight of the total amount of the components (A), (F), and (G). When incorporated at an amount of less than 0.1 parts by weight, the curing reaction is likely to be retarded and reactivity is likely to be reduced. When incorporated at an amount in excess of 5 parts by weight, curing will proceed too fast to invite molding failures such as wire sweep and insufficient filling.
The compound of formula (1) promotes curing of the epoxy resin by the curing agent. The compound of formula (1), however, is insufficient as a promoter for the curing of the maleimide compound and the alkenyl phenol compound of the components (F) and (G) as described below. Accordingly, simultaneous incorporation of a radical initiator is necessary as a promoter for the curing of the maleimide compound and the alkenyl phenol compound of the components (F) and (G). Exemplary such radical initiators include peroxides such as benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, dilauroyl peroxide, and dibenzoyl peroxide; and azo compounds such as azoisobutyronitrile, 4,4′-azobis(4-cyano valeric acid), and 2,2′-azobis(2,4-dimethyl valeronitrile). Among these, the preferred is dicumyl peroxide in view of the favorable moldability since the temperature for realizing a half life of 1 minute is near the temperature used for the transfer molding.
The radical initiator is incorporated at an amount of 0.05 to 3 parts by weight, and more preferably at 0.1 to 1 parts by weight in relation to 100 parts by weight the total of components (A), (F) and (G). When used at a content of less than 0.05 parts by weight, the composition is less likely to be sufficiently polymerized within the molding time. On the other hand, use in excess of 3 parts by weight is likely to invite increase in the viscosity, which may result in molding failures such as wire sweep and insufficient filling as well as loss of storage ability.
The compound of formula (1) and the radical initiator are used at a weight ratio of the compound of formula (1) to the radical initiator of 0.5 to 6, and preferably 2 to 3.
The component (F) used in the present invention, namely, the compound having at least two maleimide group per molecule is not particularly limited for its structure, and exemplary such compounds include N,N′-4,4′-diphenylmethane bismaleimide and N,N′-(3,3′-dimethyl-4,4′-diphenylmethane)bismaleimide. Preferable example of such maleimide group-containing compound is the bismaleimide represented by the following formula, for example, BMI (product name, manufactured by K.I. Kasei).
The maleimide compound may be added at an amount of 30 to 60 parts by weight, and in particular, at 40 to 50 parts by weight in relation to 100 parts by weight of the total amount of the components (A), (D), (E), and (F). When the amount is less than 30 parts by weight, the glass transition temperature realized by the matrix of the epoxy group and the phenolic hydroxy group is adversely affected, and incorporation at an amount in excess of 60 parts by weight may result in the loss of flow ability, and molding failure such as wire sweep. In view of realizing well balanced properties of the semiconductor encapsulating material, incorporation of approximately 30 to 60 parts by weight, and in particular, approximately 40 to 50 parts by weight is preferable.
Examples of the phenol compound having at least one alkenyl group per molecule (G) include o,o′-diallyl-bisphenol A, o,o′-di(1-propenyl)-bisphenol A, o-allyl phenol novolac resin, o-(1-propenyl)phenol novolac resin, tris-o-allyl phenol alkane phenol resin, and tris-o-(1-propenyl)phenol alkane phenol resin. In view of the reactivity with the maleimide group-containing compound, the phenol compound having at least one alkenyl group is the one containing 1-propenyl group such as o,o′-di(1-propenyl)-bisphenol A, o-(1-propenyl)phenol novolac resin, and o-(1-propenyl)phenol alkane phenol resin because such compound undergoes cyclization by the addition reaction through Diels-Alder reaction with the bismaleimide group, and this is favorable for heat and chemical resistance.
Examples of the alkenyl group-containing phenol compound include o-(1-propenyl)phenol novolac resin (with the product name of 1PP-2 manufactured by Gun Ei Chemical Industry Co., Ltd.) represented by the following formula:
wherein m is 1 to 100, n is 1 to 100, and m+n is 2 to 200.
Amount of the alkenyl group-containing phenol compound is not particularly limited. However, in view of realizing a high glass transition temperature, the alkenyl group is preferably 0.1 to 1.0 mole, and in particular, 0.2 to 0.5 mole in relation to 1 mole of the maleimide group of the component (F).
If desired, the epoxy resin composition for encapsulating a semiconductor device of the present invention may contain various additives other than the components (A) to (G) to the extent that the objects and benefits of the present invention are not adversely affected. Exemplary such additives include a stress reducing agent such as thermoplastic resin, thermoplastic elastomer, organic synthetic rubber, and silicone; a wax such as carnauba wax, higher fatty acid, and synthetic wax; a colorant such as carbon black; a halogen trapping agent; and a flame retardants such as phosphazene compound and zinc molybdate compound.
Exemplary mold releasing agents include carnauba wax, rice wax, polyethylene, oxidized polyethylene, montanic acid; montan wax which is an ester compound of montanic acid with a saturated alcohol, 2-(2-hydroxyethylamino)-ethanol, ethyleneglycol, glycerin, and the like; stearic acid, stearate ester, stearamide, ethylene bisstearamide, and a copolymer of ethylene and vinyl acetate which may be used alone or in combination of two or more.
Such releasing agent may be blended at an amount of 0.1 to 5 parts by weight, and more preferably at 0.3 to 4 parts by weight in relation to 100 parts by weight of the total of the components (A) and (B).
The epoxy resin composition of the present invention can be produced by blending the components (A) to (G) and other additives at the predetermined compositional ratio; fully blending the mixture in a blender, ball mill, or the like to homogeneity; further blending the mixture in molten state with hot rolls, a kneader, an extruder, or the like; cooling for solidification; and pulverizing the solid to an appropriate size.
In fully blending the composition to homogeneity, the composition is preferably preliminarily treated with a silane coupling agent to improve storage stability or as a wetter.
Examples of such silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, N-β(aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl) γ-aminopropyltrimethoxysilane, N-β(aminoethyl) γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, bis(triethoxypropyl) tetrasulfide, and γ-isocyanate propyltriethoxysilane, although the type and amount of the silane coupling agent used for the surface treatment is not particularly limited.
The resulting epoxy resin composition of the present invention is effective for use in encapsulating various semiconductor devices. An exemplary method used for the encapsulation is low pressure transfer molding. The curing and molding of the epoxy resin composition of the present invention can be accomplished, for example, by treating the composition at 150 to 200° C. for 30 to 300 seconds, and then conducting the post curing at 180 to 260° C. for 2 to 16 hours. Post curing at a high temperature for a long time is preferable for realizing a high glass transition temperature.
In the semiconductor device encapsulated by an encapsulation resin (cured product) of the resin composition for encapsulating a semiconductor device according to the present invention, it is effective that the encapsulation (cured product) resin preferably has a glass transition temperature (Tg) of at least 250° C., and preferably at least 280° C. The semiconductor device (thickness of the semiconductor device, 0.58 mm; thickness of the encapsulating layer, 0.30 mm) shown in
In
As described above, the semiconductor device of the present invention in which the encapsulation resin has a glass transition temperature (Tg) of at least 250° C. is well adapted for on-vehicle and security card applications since the resin used for encapsulation has a high chemical resistance.
In the present invention, glass transition temperature was measured by setting a test piece in a thermal delatometer and elevating the temperature to 300° C. at a temperature elevation rate of 5° C./minutes under the load of 19.6 mN. A graph showing change in size in relation to the temperature was prepared, and arbitrary two points A1 and A2 on the curve that gives the tangent line at a temperature less than the inflection point, and arbitrary two points B1 and B2 on the curve that gives the tangent line at a temperature in excess of the inflection point were selected. The temperature of the point of intersection of the line including A1 and A2 and the line including B1 and B2 was used for the glass transition temperature.
Next, the present invention is described in further detail by referring to the Examples and Comparative Examples which by no means limit the scope of the present invention.
The components shown in Tables 1 and 2 were homogeneously mixed in molten state by using heated dual rolls, and the mixture was cooled and pulverized to produce the epoxy resin composition. The epoxy resin composition was molded at 175° C., 6.9 N/mm2, and a molding time of 120 seconds to produce a test piece of 5×5×15 mm. The test piece was subjected to post curing under respective conditions and evaluated for its glass transition temperature.
The test piece was placed in a thermal delatometer (Rigaku TMA8140C), and change in size was measured by elevating the temperature to 300° C. at a temperature elevation rate of 5° C./minutes under the load of 19.6 mN. The change in size was plotted in relation to the temperature, and arbitrary two points A1 and A2 on the curve that gives the tangent line at a temperature less than the inflection point, and arbitrary two points B1 and B2 on the curve that gives the tangent line at a temperature in excess of the inflection point were selected. The temperature of the point of intersection of the line including A1 and A2 and the line including B1 and B2 was used for the glass transition temperature.
The semiconductor device shown in
A test piece (100×10×0.8 mm) was produced by molding at 175° C. for 90 seconds. After the post-curing for a predetermined time, the test piece was immersed in gasoline at 30° C. for 1 week. Change in weight after 1 week was measured.
Spherical molten silica (manufactured by Tatsumori Ltd.; average particle size, 15 μm)
832.0 g of triphenylphosphine (manufactured by Hokko Chemical Industry Co., Ltd.) was dissolved in 1800.0 g of butyl acetate, and the mixture was stirred at 80° C. for 30 minutes. A solution of 352.0 g of 1,4-benzoquinone in 1800 g of butyl acetate was added dropwise at 145 g/minute, and after completing the addition, the mixture was stirred for 1 hour for aging. The mixture was then cooled to room temperature, and the precipitate was collected by filtration, washed, and dried at a reduced pressure to obtain 982.7 g of an adduct of the triphenylphosphine and the 1,4-benzoquinone.
dicumyl peroxide (Percumyl D manufactured by NOF Corporation)
a bismaleimide represented by the following formula (BMI, manufactured by K.I. Kasei)
o-(1-propenyl)phenol novolac resin represented by the following formula:
wherein m/n is 1/1.
Japanese Patent Application No. 2006-273061 is incorporated herein by reference.
Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-273061 | Oct 2006 | JP | national |
