JP3093051B2 - Epoxy resin composition - Google Patents

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 which is excellent in soldering stress resistance in surface mounting of a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, electronic components such as diodes, transistors, and integrated circuits are sealed with a thermosetting resin. In particular, in an integrated circuit, an O-cresol novolak epoxy resin having excellent heat resistance and moisture resistance is made of novolak. An epoxy resin cured with a mold phenol resin is used. However, in recent years, chips have become larger and larger with the increase in the degree of integration of integrated circuits, and packages have become smaller and thinner flat packages that are surface-mounted from conventional DIP types.
It is changing to SOJ and PLCC. That is, a large chip is sealed in a small and thin package, and cracks are generated due to stress, and problems such as a decrease in moisture resistance due to the cracks have been greatly highlighted. In particular, there is a problem that the package is cracked due to rapid exposure to a high temperature of 200 ° C. or more in the soldering process, and the moisture resistance is deteriorated due to the separation of the resin and the chip. Development of a highly reliable sealing resin composition suitable for sealing these large chips has been desired.

In order to solve these problems, use of an epoxy resin represented by the following formula (1) as an epoxy resin (Japanese Patent Laid-Open No. 64-65116) has been studied.

[0004]

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[0005] The use of the epoxy resin represented by the formula (1) lowers the viscosity of the resin system. Therefore, by blending a larger amount of fused silica powder, the composition has low thermal expansion and low water absorption after molding. In addition, improvement in solder stress resistance was achieved. However, an increase in the modulus of elasticity due to the incorporation of a large amount of the fused silica powder is another adverse effect, and it is necessary to further improve the solder stress resistance.

[0003]

The present invention solves such a problem by using an epoxy resin represented by the formula (1) as an epoxy resin to reduce the elastic modulus, water absorption and thermal expansion coefficient of a molded product. Another object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation in which the use of a curing agent represented by the formula (2) as a curing agent has significantly improved the solder stress resistance of a semiconductor package during mounting on a substrate.

[0004]

The epoxy resin composition of the present invention comprises (A) an epoxy resin represented by the following formula (1):

[0005]

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[0006] 30 to 100 with respect to the total epoxy resin amount
(B) a naphthol resin curing agent represented by the following formula (2):

[0007]

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[0008] 30 to 100% by weight based on the total amount of the curing agent
It is an epoxy resin composition for semiconductor encapsulation which contains a hardener containing (C) an inorganic filler and (D) a hardening accelerator as essential components.

The biphenyl type epoxy resin represented by the structure of the formula (1) is a bifunctional epoxy resin having two epoxy groups in one molecule, and has a lower melt viscosity than conventional polyfunctional epoxy resins during transfer molding. Excellent fluidity. Therefore, a large amount of the fused silica powder of the composition can be blended, an epoxy resin composition having low thermal expansion and low water absorption, and having excellent solder stress resistance can be obtained.

By adjusting the amount of the biphenyl type epoxy resin used, the solder stress resistance can be maximized. In order to obtain the effect of resistance to soldering stress, the biphenyl type epoxy resin represented by the formula (1) is used in an amount of 30% by weight or more, preferably 60% by weight of the total epoxy resin amount.
It is desirable to use not less than weight%. If it is less than 30% by weight, low thermal expansion and low water absorption cannot be obtained, and the solder stress resistance is insufficient. Further, in the formula, R _{1 to} R ₄ are preferably a methyl group, and R _{5 to} R ₈ are preferably a hydrogen atom.

When another epoxy resin is used in addition to the biphenyl type epoxy resin represented by the formula (1), the epoxy resin used generally refers to any polymer having an epoxy group. For example, trifunctional epoxy resins such as bisphenol type epoxy resin, cresol novolak type epoxy resin, phenol novolak type epoxy resin, triphenolmethane type epoxy resin, alkyl-modified triphenolmethane type epoxy resin, and epoxy resin containing triazine nucleus. Say.

By using the curing agent represented by the molecular structure of the formula (2), compared with the conventional phenol novolak resin curing agent, the elastic modulus decreases near the soldering temperature and the adhesion to the lead frame and the semiconductor chip. By improving the force, it is possible to obtain low thermal expansion and low water absorption. Therefore, it is effective for preventing a reduction in stress generated due to a thermal shock at the time of soldering and a peeling defect with a semiconductor chip or the like accompanying the reduction.

By adjusting the amount of the curing agent of the formula (2), the solder stress resistance can be maximized. In order to bring out the effect of resistance to solder stress, it is desirable to use the curing agent represented by the formula (2) in an amount of 30% by weight or more, more preferably 50% by weight or more based on the total amount of the curing agent. If the amount used is less than 30% by weight, low water absorption, low elasticity, etc., and insufficient adhesion to the lead frame and semiconductor chip cannot be expected to improve solder stress resistance. Further, the value of n in the formula is desirably in the range of 1 to 6, and the value of n is 6
If it exceeds, the fluidity during transfer molding tends to decrease, and moldability tends to deteriorate.

When other curing agents other than the curing agent represented by the formula (2) are used in combination, those used generally refer to all polymers having a phenolic hydroxyl group. For example, phenol novolak resins, cresol novolak resins, dicyclopentadiene-modified phenol resins, copolymers of dicyclopentadiene-modified phenol resins with phenol novolak and cresol novolak resins, and para-xylene-modified phenol resins can be used.

The inorganic filler used in the present invention includes fused silica powder, spherical silica powder, crystalline silica powder, secondary aggregated silica powder, porous silica powder, secondary aggregated silica powder or silica obtained by pulverizing porous silica powder. Examples thereof include powder, alumina, and the like, and particularly preferred are fused silica powder, spherical silica powder, and a mixture of fused silica powder and spherical silica powder. The amount of the inorganic filler is 70 to 9 with respect to the total amount of the composition in consideration of the balance between solder stress resistance and moldability.
0% by weight is preferred.

The curing accelerator used in the present invention may be any one which promotes the reaction between an epoxy group and a hydroxyl group, and those generally used for sealing materials can be widely used. Zabicycloundecene (DBU),
Triphenylphosphine (TPP), dimethylbenzylamine (BDMA) and 2-methylimidazole (2M
Z) and the like are used alone or in combination of two or more.

The epoxy resin composition for encapsulation of the present invention comprises an epoxy resin, a curing agent, an inorganic filler and a curing accelerator as essential components. In addition to this, a silane coupling agent and a brominated epoxy resin may be used if necessary. And various additives such as flame retardants such as antimony trioxide and hexabromobenzene, coloring agents such as carbon black and red iron oxide, release agents such as natural wax and synthetic wax, and low stress additives such as silicone oil and rubber. There is no problem if it is appropriately blended.

In order to produce the encapsulating epoxy resin composition of the present invention as a molding material, an epoxy resin, a curing agent,
After the inorganic filler, the curing accelerator, and other additives are sufficiently and uniformly mixed by a mixer or the like, the mixture is further melt-kneaded by a hot roll or a kneader, cooled, and pulverized to obtain a molding material. These molding materials can be applied to sealing, coating, insulating and the like of electronic parts or electric parts.

Hereinafter, the present invention will be described specifically with reference to Examples. Example 1 The following composition: 6.8 parts by weight of an epoxy resin represented by the formula (3) (softening point: 110 ° C., epoxy equivalent: 190)

[0020]

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Orthocresol novolak epoxy resin (softening point: 65 ° C., epoxy equivalent: 200) 4.5 parts by weight Curing agent represented by formula (4) (softening point: 114 ° C., hydroxyl equivalent: 216) 5.3 parts by weight

[0022]

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(N = 1 is 1 while n = 2 is 0.2, n
= 3 or more 0.1) Phenol novolak resin curing agent (softening point 90 ° C, hydroxyl equivalent 104) 3.4 parts by weight Fused silica powder 78.8 parts by weight Triphenylphosphine 0.2 part by weight Carbon black 0.5 part by weight 0.5 part by weight of carnauba wax was mixed at room temperature with a mixer, kneaded at 70 to 100 ° C. with a biaxial roll, cooled and pulverized to obtain a molding material. The obtained molding material was tableted, and a 6 × 6 mm chip was used for a solder crack test at 175 ° C., 70 kg / cm ² and 120 seconds by a low-pressure transfer molding machine.
Sealed in 2p package, and 3 for solder moisture resistance test
A 6 mm chip was sealed in a 16 pSOP package. The sealed test element was subjected to the following solder crack test and solder moisture resistance test.

Solder crack test: The sealed test element was subjected to 48 hours and 72 hours under an environment of 85 ° C. and 85% RH.
After the treatment, it was immersed in a solder bath at 260 ° C. for 10 seconds, and external cracks were observed with a microscope. Solder moisture resistance test: Sealed test element was tested at 85 ° C for 8
After being treated for 72 hours in an environment of 5% RH, and then immersed in a solder bath at 260 ° C. for 10 seconds, a pressure cooker test (125 ° C., 100% RH) was performed to measure open circuit failure. Table 1 shows the test results.

Examples 2 to 5 Compounded according to the formulation shown in Table 1, and a molding material was obtained in the same manner as in Example 1. A sealed molded product for a test was obtained from this molding material, and a solder crack test and a solder moisture resistance test were performed using this molded product in the same manner as in Example 1. Table 1 shows the test results.

Comparative Examples 1-4 Compounded according to the recipe in Table 1,
A molding material was obtained in the same manner as in Example 1. A sealed molded product for a test was obtained from this molding material, and a solder crack test and a solder moisture resistance test were performed using this molded product in the same manner as in Example 1. Table 1 shows the test results.

Example 6 The following composition: Epoxy resin represented by formula (3) (softening point: 110 ° C., epoxy equivalent: 190) 3.8 parts by weight ortho-cresol novolak epoxy resin (softening point: 65 ° C., epoxy equivalent: 200) 8 2.6 parts by weight 2.3 parts by weight of a curing agent represented by the formula (5) (softening point 109 ° C., hydroxyl equivalent 200)

[0028]

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(The value of n is a mixture of 1 to 4, and the weight ratio is 0.2 for n = 2 for 1 for n = 1, n for 2
= 3 or more is 0.1. ) Phenol novolak resin curing agent (softening point 90 ° C., hydroxyl equivalent 104) 5.3 parts by weight Fused silica powder 78.8 parts by weight Triphenylphosphine 0.2 parts by weight Carbon black 0.5 parts by weight Carnauba wax 0.5 parts by weight The mixture was mixed at room temperature, kneaded at 70 to 100 ° C. with a biaxial roll, cooled, and pulverized to obtain a molding material. A test sample was prepared from the obtained molding material in the same manner as in Example 1, and a test was performed. Table 2 shows the test results.

Examples 7 to 10 Compounded according to the formulation shown in Table 2 to obtain a molding material in the same manner as in Example 6. A sealed molded product for a test was obtained from this molding material, and a solder crack test and a solder moisture resistance test were performed using this molded product in the same manner as in Example 6. Table 2 shows the test results.

Comparative Examples 5 to 7 Compounded according to the formulation shown in Table 2 and obtained in the same manner as in Example 6. A sealed molded product for a test was obtained from this molding material, and a solder crack test and a solder moisture resistance test were performed using this molded product in the same manner as in Example 6. Table 2 shows the test results.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

According to the present invention, an epoxy resin composition having solder stress resistance, which cannot be obtained by the prior art, can be obtained. When used for encapsulation, coating, insulation, etc. of electronic and electrical components, especially for highly integrated large chip ICs mounted on surface mount packages because of their excellent crack resistance and excellent moisture resistance It is suitable for products that require extremely high reliability.

Claims (1)

(57) [Claims] (A) an epoxy resin represented by the following formula (1): (B) a naphthol resin curing agent represented by the following formula (2): (C) an inorganic filler and (D) an epoxy resin composition for semiconductor encapsulation comprising, as essential components, (C) an inorganic filler and (D) a curing accelerator.