JP2001288253A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor sealing epoxy resin composition being excellent in moldability such as fluidity and curability, adhesion, giving a cured product excellent in high-temperature low-stress properties and soldering resistance, and being excellent in high-temperature storability owing to its excellent flame retardancy exhibited in spite of the absence of a bromine compound and an antimony compound. SOLUTION: There is provided a semiconductor sealing epoxy resin composition consisting essentially of (A) epoxy resins represented by general formulae (1) and/or (2), (B) a phenolic resin represented by general formula (3), (C) an inorganic filler, and (D) a cure accelerator.

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 such as fluidity and curability and excellent solder resistance, and a semiconductor device using the same.

[0002]

2. Description of the Related Art As a method for encapsulating semiconductor elements such as ICs and LSIs, a method by transfer molding of an epoxy resin composition has been employed for a long time as a method suitable for low cost and mass production, and the reliability of epoxy resin or epoxy resin has been long. Improvements have been made by improving phenolic resins as curing agents. However, in the recent market trend of miniaturization, weight reduction and high performance of electronic devices, the integration of semiconductors has been increasing year by year, and the surface mounting of semiconductor devices has been promoted. Demands for resin compositions are becoming more stringent. For this reason, a problem that cannot be solved by the conventional epoxy resin composition has appeared. The biggest problem is that the adoption of the surface mounting of the semiconductor device causes the semiconductor device to be rapidly exposed to a high temperature of 200 ° C. or more in the solder immersion or reflow process, and the moisture absorbed by the semiconductor device explosively evaporates. This is a phenomenon in which a semiconductor device is cracked due to stress, or peeling occurs at each interface with various plated joint portions on a semiconductor element, a lead frame, and inner leads, and reliability is significantly reduced. Further, in recent years, as semiconductor devices have become thinner, the thickness of a cured product of the epoxy resin composition occupying in the semiconductor device has become much thinner.
The semiconductor device for 256MDRAM is a 1 mm thick TSO
P is becoming mainstream. These thin semiconductor devices include:
It is required that the filling property of the epoxy resin composition during molding is good, the gold wire deformation is small, and there is no deformation of semiconductor elements and lead frames (referred to as chip shift or die pad shift). It is necessary to have excellent fluidity during molding. On the other hand, the epoxy resin composition for semiconductor encapsulation contains a compound containing bromine and an antimony compound such as antimony trioxide, antimony pentoxide and antimony pentoxide as a flame retardant component. However, with the increasing awareness of global environmental protection, there is an increasing demand for epoxy resin compositions having flame retardancy without using bromine-containing organic compounds or antimony compounds. Further, when a semiconductor device is stored at a high temperature of 150 to 200 ° C. for a long time, a bromine compound or an antimony compound as a flame retardant is known to cause an increase in the resistance value of a semiconductor element or a break in a gold wire. . From this viewpoint, development of an epoxy resin composition having excellent high-temperature storage characteristics without using a bromine compound or an antimony compound has been awaited.

[0003]

DISCLOSURE OF THE INVENTION The present invention is excellent in moldability such as fluidity and curability, has improved adhesiveness to various members such as semiconductor elements and lead frames, and has a low elastic modulus of a cured product at a high temperature. Semiconductors that have significantly improved the soldering resistance of the semiconductor device when mounted on the board due to the reduction in stress due to the development, and also have excellent flame retardancy, so bromine compounds and antimony compounds have been reduced or eliminated to improve high-temperature storage characteristics. An epoxy resin composition for sealing, and a semiconductor device using the same.

[0004]

The present invention provides (A) an epoxy resin represented by the general formula (1) and / or (2), (B) a phenolic resin represented by the general formula (3),
An epoxy resin composition for semiconductor encapsulation, comprising (C) an inorganic filler and (D) a curing accelerator as essential components, and a semiconductor element encapsulated with the epoxy resin composition. Semiconductor device.

[0005]

Embedded image (R in the formula (1) is the same or different group selected from alkyl groups having 1 to 4 carbon atoms, a is an integer of 0 to 3,
b is an integer of 1 to 2, m and n are average values, and a positive number of 1 to 10)

[0006]

Embedded image (R in the formula (2) is the same or different group selected from alkyl groups having 1 to 4 carbon atoms, a is an integer of 0 to 4,
b is an integer of 1 to 2, n is an average value, and a positive number of 1 to 10)

[0007]

Embedded image (M and n in the formula (3) are average values and positive numbers of 1 to 10)

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The epoxy resin used in the present invention is at least one selected from the group consisting of epoxy resins represented by the general formulas (1) and (2). The epoxy resins represented by the general formulas (1) and (2) are characterized in that epoxides of naphthols are contained in the molecule. Examples of the epoxy resin represented by the general formula (1) include those obtained by co-condensing a phenol and a naphthol or a naphthalene diol with formaldehyde, and further glycidyl etherizing the novolak resin. , Naphthol or naphthalene diols are generally random copolymerized. As naphthol, α-naphthol, β-
Any of naphthols may be used. In addition, the ratio of n / (m + n) is desirably 0.25 or more for this purpose. As the epoxy resin represented by the general formula (2), for example, a naphthol resin obtained by polymerizing bis (methoxymethyl) benzene with naphthol or naphthalene diol by a Friedel-Crafts alkylation reaction and further glycidyl etherizing the naphthol resin is used. Is mentioned. As the naphthol, either α-naphthol or β-naphthol may be used. The cured product of the epoxy resin composition using the epoxy resin represented by the general formula (1) or (2) has a higher temperature than the glass transition temperature as compared with the case of using the conventional ortho-cresol novolak type epoxy resin. High strength at the time and low moisture absorption. Therefore, it is excellent in solder resistance at the time of soldering after moisture absorption of surface mounting. Further, the naphthalene skeleton has many aromatic rings and thus has excellent flame retardancy. Depending on the combination with the curing agent, good flame retardancy can be exhibited without blending a flame retardant.

The epoxy resins represented by the general formulas (1) and (2) may be used in combination with other epoxy resins as long as their properties are not impaired. By adjusting, solder resistance and flame retardancy can be maximized. In order to obtain these effects, the total amount of the epoxy resins represented by the general formulas (1) and (2) is preferably at least 30% by weight, more preferably at least 50% by weight in the total epoxy resin. Three
If the content is less than 0% by weight, sufficient strength at low temperatures and low hygroscopicity may not be obtained, and the solder crack resistance may be insufficient, and the flame retardancy tends to decrease. Other epoxy resins that can be used in combination with the epoxy resins represented by the general formulas (1) and (2) include all monomers, oligomers and polymers having an epoxy group in the molecule, such as bisphenol-type epoxy resins and biphenyls Epoxy resin, stilbene epoxy resin, phenol novolak epoxy resin, orthocresol novolak epoxy resin, triphenolmethane epoxy resin, alkyl-modified triphenolmethane epoxy resin, dicyclopentadiene-modified phenol epoxy resin, containing triazine nucleus Examples include an epoxy resin and a phenol aralkyl type epoxy resin (having a phenylene skeleton, a biphenylene skeleton, and the like), and these may be used alone or in combination.

The phenolic resin represented by the general formula (3) used in the present invention includes, for example, those obtained by co-condensing xylene glycol and naphthaldehyde with phenol under an acid catalyst. The cured product of the epoxy resin composition using the phenolic resin represented by the general formula (3) has a low modulus of elasticity in a high temperature region exceeding the glass transition temperature, and has low moisture absorption. Thermal stress during attachment can be reduced, and it has features that are excellent in solder crack resistance and adhesion to a substrate after soldering. In addition, the structure contained in the molecule has high flame retardancy, and is good even when the flame retardant is not reduced or blended in combination with the naphthalene skeleton-containing epoxy resin represented by the general formulas (1) and (2). Expresses flame retardancy. M and n in the general formula (3) are average values and are positive numbers of 1 to 10. More preferably, m and n = 1 to 5. If either m or n exceeds 10, the fluidity is poor, which is not preferable. The ratio of m / (m + n) is preferably from 0.1 to 0.9. If it is less than 0.1, the effect of lowering the elastic modulus and moisture absorption at high temperatures is small, and the flame retardancy is reduced. If it exceeds 0.9, the curability tends to be reduced. The melt viscosity of the phenol resin represented by the general formula (3) at 150 ° C. is as follows:
0.1 to 1.5 poise is preferred. If it is less than 0.1 poise, a problem occurs in the crosslinking property, which is not preferable. If it exceeds 1.5 poise, the fluidity at the time of melting is undesirably reduced. The melt viscosity at 150 ° C. of the phenolic resin represented by the general formula (3) of the present invention was measured using an ICI viscometer (Cone & Co.).
(Plate type). The phenolic resin represented by the general formula (3) may be used in combination with other phenolic resins as long as its properties are not impaired. However, by adjusting the amount of these phenolic resins, the solder crack resistance is improved. Can be maximized. In order to bring out the effect of the solder crack resistance, it is desirable to use the phenol resin represented by the general formula (3) in an amount of 30% by weight or more, preferably 50% by weight or more in the total phenol resin. If it is less than 30% by weight, low elasticity, low moisture absorption, and sufficient adhesiveness at high temperatures may not be obtained, and the solder crack resistance may be insufficient, and the flame retardancy may be reduced. The phenolic resin that can be used in combination with the phenolic resin represented by the general formula (3) refers to all monomers, oligomers, and polymers having a phenolic hydroxyl group in the molecule, such as phenol novolak resin, cresol novolak resin, phenol aralkyl resin, and terpene. Modified phenolic resins, dicyclopentadiene-modified phenolic resins, triphenolmethane-type resins, and the like may be mentioned, and these may be used alone or in combination.

The inorganic filler used in the present invention includes:
For example, fused silica, crystalline silica, alumina, silicon nitride and the like can be mentioned, and these may be used alone or in combination. In particular, in order to highly fill the inorganic filler, it is preferable to use spherical fused silica and to broaden the particle size distribution of the spherical fused silica because the melt viscosity of the epoxy resin composition during molding can be reduced. Further, as the inorganic filler, a material which has been previously surface-treated with a silane coupling agent may be used. The blending amount of the inorganic filler is preferably from 75 to 93% by weight in the entire epoxy resin composition. 75% by weight
If the value is less than the above range, the moisture absorption of the semiconductor device obtained by molding increases, the strength at the solder processing temperature decreases, and cracks easily occur in the semiconductor device during the solder processing, which is not preferable.
On the other hand, if the content exceeds 93% by weight, the fluidity of the epoxy resin composition during molding decreases, and unfilling, chip shift, and pad shift tend to occur, which is not preferable.

The curing accelerator used in the present invention is a catalyst for a cross-linking reaction between an epoxy resin and a phenol resin. Examples of the curing accelerator include amines such as tributylamine and 1,8-diazabicyclo (5,4,0) undecene-7. Compound, triphenylphosphine, tetraphenylphosphonium
Organic phosphorus compounds such as tetraphenyl borate salt;
Examples thereof include imidazole compounds such as methylimidazole, and these may be used alone or in combination.

The epoxy resin composition of the present invention comprises (A)
In addition to the component (D), a flame retardant such as a brominated epoxy resin or antimony trioxide may be contained as needed, but the stability of the electrical characteristics of the semiconductor device at a high temperature of 150 to 200 ° C. In required applications, the content of bromine atoms and antimony atoms is preferably less than 0.2% by weight in the total epoxy resin composition, and more preferably not completely contained. Any content is 0.2
If the content is not less than the weight%, the resistance value of the semiconductor device increases with time when left at high temperature, and eventually, a defect that the gold wire of the semiconductor element is broken occurs. Also, from the viewpoint of environmental protection,
Each content of bromine atom and antimony atom is 0.2
It is desirable that the content be less than 10% by weight and not contained as much as possible.
The content of bromine atoms can be measured by elemental analysis such as fluorescent X-ray analysis and ion chromatography. The content of antimony atoms can be measured by elemental analysis such as atomic absorption analysis, emission analysis, X-ray fluorescence spectroscopy, and ion chromatography. In addition to the components (A) to (D), the epoxy resin composition of the present invention may contain, if necessary, an inorganic ion exchanger such as bismuth oxide hydrate, a low stress agent represented by a polysiloxane compound, and a cup. Ring agent,
Colorant represented by carbon black, natural wax,
Various additives such as a synthetic wax, a higher fatty acid and a releasing agent such as a metal salt thereof or paraffin, and an antioxidant can be appropriately compounded. The epoxy resin composition of the present invention,
The components (A) to (D), other additives, and the like are mixed at room temperature using a mixer, melt-kneaded in a kneader such as a roll, kneader, or extruder, cooled, and pulverized. Using the epoxy resin composition of the present invention to seal electronic components such as semiconductor elements and manufacture semiconductor devices, transfer molding, compression molding, and injection molding may be performed by conventional molding methods such as molding. .

[0014]

The present invention will be specifically described below with reference to examples.
The mixing ratio is by weight. Example 1 5.9 parts by weight of an epoxy resin A represented by the formula (4) (softening point: 70 ° C., epoxy equivalent: 220, melt viscosity at 150 ° C .: 1.0 poise)

Embedded image

5.1 parts by weight of a phenolic resin E represented by the formula (5) (softening point 70 ° C., hydroxyl equivalent 175, melt viscosity at 150 ° C. 0.9 poise, m: n = 66: 34)

Embedded image 88.0 parts by weight of spherical fused silica 0.2 parts by weight of triphenylphosphine 0.3 parts by weight of carbon black 0.5 parts by weight of carnauba wax were mixed using a mixer.
The mixture was kneaded 30 times using two rolls at 5 ° C., cooled and pulverized to obtain an epoxy resin composition. The obtained epoxy resin composition was evaluated by the following method. Table 1 shows the results.

Evaluation method Spiral flow: Using a mold for spiral flow measurement in accordance with EMMI-1-66, a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 70 kg / cm ² and a curing time of 2 minutes.
The unit is cm. Curability: mold temperature 175 ° C, injection pressure 70kg / c
Molding was performed with m ² and a curing time of 2 minutes, and the Bacol hardness 10 seconds after the mold opening was measured. Bending strength at heating / bending elastic modulus at heating: The bending strength and flexural modulus at 240 ° C. were measured according to JIS K 6911.
The unit is N / mm ² . Flame retardancy: Using a transfer molding machine, mold temperature 17
A test piece was molded at 5 ° C., an injection pressure of 70 kg / cm ² , and a curing time of 2 minutes, and a UL-94 vertical test (test piece thickness 1/16
inch). Solder resistance: Using a transfer molding machine, mold temperature 1
75 ° C, injection pressure 70kg / cm ² , curing time 2 minutes 1
00 pin TQFP (Package size is 14 × 14m
m, thickness 1.4 mm, silicon chip size is 8.
(0 × 8.0 mm, lead alloy made of 42 alloy) was molded and post-cured at 175 ° C. for 8 hours. It is left for 168 hours in an environment of 85 ° C. and 85% relative humidity, and then 240 ° C.
For 10 seconds. Observation was performed with a microscope, and the crack occurrence rate [(number of external crack occurrence packages) / (total number of packages) × 100] was expressed in%. Further, the ratio of the peeling area between the chip and the cured product of the epoxy resin composition was measured using an ultrasonic flaw detector, and the peeling rate [(peeling area) /
(Chip area) × 100] is shown in%. High temperature storage characteristics: using a transfer molding machine, a mold temperature of 175 ° C., an injection pressure of 70 kg / cm ² , and a curing time of 2 minutes.
The OP was molded and post-cured at 175 ° C. for 8 hours. 185
The sample was placed in a constant temperature bath at a temperature of ° C., and the resistance value between the pins was measured at regular intervals. The thermostatic bath processing time when the number of packages whose resistance value increased by 10% or more from the initial resistance value became 8 or more out of 15 was indicated as high-temperature storage characteristics. If this time is long, it indicates that the high-temperature stability is excellent. The unit is h
r. Bromine atom, antimony atom content: pressure 60 kg / cm
^The resulting molded product was compression-molded to a diameter of 40 mm and a thickness of 5 to 7 mm in ² , and the content of bromine atoms and antimony atoms in all the epoxy resin compositions was quantified using a fluorescent X-ray analyzer. The unit is% by weight.

Examples 2 to 5, Comparative Examples 1 to 4 Epoxy resin compositions were obtained in the same manner as in Example 1 according to the formulations 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 materials used in the examples and comparative examples are shown below. Naphthol aralkyl type epoxy resin B represented by the formula (6) (softening point: 65 ° C., epoxy equivalent: 260, melt viscosity at 150 ° C .: 1.2 poise)

Embedded image

The naphthalene type epoxy resin C represented by the formula (7) (softening point 70 ° C., epoxy equivalent 175, 150 ° C.)
Melt viscosity at 1.8 poise)

Embedded image

Biphenyl type epoxy resin D (melting point 105
° C, epoxy equivalent 195, Yuka Shell Epoxy Co., Ltd.
Phenolic resin F represented by the formula (8) (softening point 71 ° C.,
(Hydroxyl equivalent 184, melt viscosity at 150 ° C. 0.9 poise, m: n = 77: 23)

Embedded image

Phenol resin G represented by the formula (9) (softening point 77 ° C., hydroxyl equivalent 175, melt viscosity at 150 ° C. 0.7 poise, m: n = 72: 28)

Embedded image

The phenolic resin H represented by the formula (10)
(Softening point 79 ° C., hydroxyl equivalent 175, melt viscosity at 150 ° C. 0.6 poise, m: n = 68: 32)

Embedded image

Brominated phenol novolak type epoxy resin (softening point: 84 ° C., epoxy equivalent: 285, bromine atom content: 35% by weight, BREN-S, manufactured by Nippon Kayaku Co., Ltd.)

[Table 1]

[0023]

[Table 2]

[0024]

The epoxy resin composition for semiconductor encapsulation of the present invention has excellent moldability such as fluidity and curability, and excellent adhesion to various members such as semiconductor elements and lead frames. Because of the low modulus of elasticity, low stress has been achieved, and semiconductor devices using this have excellent solder resistance when mounted on a substrate and excellent flame retardancy even without the addition of bromine and antimony compounds. Excellent in high temperature storage characteristics.

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Claims (4)

[Claims] (A) an epoxy resin represented by the general formula (1) and / or (2); (B) a phenolic resin represented by the general formula (3); (C) an inorganic filler; D) An epoxy resin composition for semiconductor encapsulation comprising a curing accelerator as an essential component. Embedded image (R in the formula (1) is the same or different group selected from alkyl groups having 1 to 4 carbon atoms, a is an integer of 0 to 3,
b is an integer of 1 to 2, m and n are average values, and positive numbers of 1 to 10) (R in the formula (2) is the same or different group selected from alkyl groups having 1 to 4 carbon atoms, a is an integer of 0 to 4,
b is an integer of 1 to 2, n is an average value, and a positive number of 1 to 10) (M and n in the formula (3) are average values and positive numbers of 1 to 10) 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the phenol resin represented by the general formula (3) has a melt viscosity at 150 ° C. of 0.1 to 1.5 poise. 3. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein each of the total epoxy resin compositions contains less than 0.2% by weight of bromine atoms and antimony atoms. 4. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition according to claim 1.