JP3093050B2 - 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, ortho-cresol novolak epoxy resin having excellent heat resistance and moisture resistance is made of a novolak type. An epoxy resin composition cured with a phenol resin is used.
However, in recent years, the chip has been gradually increased in size with the increase in the degree of integration of integrated circuits, and the package has been changed from the conventional DIP type to a small and thin QFP, SOP, S
OJ and PLCC are changing. That is, a large chip is sealed in a small and thin package, and cracks are generated by stress, and problems such as a decrease in moisture resistance due to the cracks have been greatly highlighted. In particular, in the soldering process, the above problem occurs due to rapid exposure to a high temperature of 250 ° C. or more, and a highly reliable sealing material suitable for sealing these large chips. Development of resin compositions 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 fused silica powder is another adverse effect, and it is necessary to further improve the solder stress resistance.

[0006]

The present invention solves such a problem by using an epoxy resin represented by the formula (1).
Low water absorption and low linear expansion are achieved, and the curing agent represented by the formula (2) is used for low water absorption and flexibility. An object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation with significantly improved stress properties.

[0007]

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

[0008]

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[0009] 30 to 100 with respect to the total epoxy resin amount
(B) a phenolic resin curing agent containing 30 to 100% by weight of a total amount of the phenolic resin curing agent represented by the following formula (2);

[0010]

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An epoxy resin composition for semiconductor encapsulation comprising (C) an inorganic filler and (D) a curing accelerator as essential components. It has extremely excellent solder heat resistance as compared with conventional epoxy resin compositions.

The 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 that of a conventional polyfunctional epoxy resin 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. The amount of the epoxy resin used can be adjusted to improve the solder stress resistance. In order to obtain the effect of resistance to soldering stress, it is desirable to use the biphenyl type epoxy resin represented by the formula (1) in an amount of 30% by weight or more, preferably 60% by weight or more of the total epoxy resin amount. 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, R _{1 to} R ₄ in the formula are a methyl group,
R _{5 to} R ₈ are preferably a hydrogen atom.

When another epoxy resin is used in addition to the epoxy resin represented by the formula (1), the epoxy resin used generally refers to all polymers 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), the elastic modulus decreases near the soldering temperature and the adhesion to the lead frame and the semiconductor chip as compared with the conventional phenol novolak resin curing agent and the like. The force can be improved, and low thermal expansion and low water absorption can be obtained. Therefore, it is effective in 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 controlling the amount of the curing agent represented by the molecular structure of the formula (2), the solder stress resistance can be improved. 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 60% 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. If the value of n exceeds 6, the fluidity during transfer molding tends to decrease, and moldability tends to deteriorate.

Further, in the formula, R _{1 to} R ₈ are preferably hydrogen or a methyl group, and R ₉ is preferably an aromatic ring having a naphthalene ring. When other curing agents other than the phenolic resin curing agent represented by the formula (2) are used in combination, those used generally refer to polymers generally having a phenolic hydroxyl group. For example, phenol novolak resin, cresol novolak resin, dicyclopentadiene-modified phenol resin, copolymer of dicyclopentadiene-modified phenol resin with phenol novolak and cresol novolak resin, terpene-modified phenol resin, para-xylene-modified phenol resin, naphthol resin, etc. 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 grinding 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 that promotes the reaction between an epoxy group and a hydroxyl group, and those generally used for a sealing material can be widely used. Desen (D
BU), triphenylphosphine (TPP), dimethylbenzylamine (BDMA), 2-methylimidazole (2MZ) or the like is 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. Various additives such as flame retardants such as antimony trioxide and hexabromobenzene, coloring agents such as carbon black and red iron oxide, mold 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 addition, in order to manufacture the epoxy resin composition for sealing of the present invention as a molding material, an epoxy resin, a curing agent, an inorganic filler, a curing accelerator, and other additives are sufficiently and uniformly mixed by a mixer or the like. Alternatively, the mixture may be melt-kneaded with 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: 3.8 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) 8.7 parts by weight Curing agent represented by the formula (4) (softening point 118 ° C., hydroxyl equivalent 180) 2.3 parts by weight

[0022]

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(N = 1 is 1 while n = 2 is 0.2, n =
3 is 0.1, and n = 4 to 6 is 0.1. Phenol novolak resin curing agent (softening point 90 ° C., hydroxyl equivalent 104) 5.2 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 parts were 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 to 4 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.

Example 6 The following composition: Epoxy resin represented by formula (3) (softening point: 110 ° C., epoxy equivalent: 190) 4.4 parts by weight orthocresol novolak epoxy resin (softening point: 65 ° C., epoxy equivalent: 200) 8 2.6 parts by weight Curing agent represented by formula (5) (softening point 110 ° C., hydroxyl equivalent 155)

[0027]

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(The value of n is a mixture of 1 to 4. The weight ratio of n is 1 for n = 1, 1.5 for n = 2, n
= 3 is 0.5 and n = 4 to 6 is 0.1. ) Phenol novolak resin curing agent (softening point 90 ° C., hydroxyl equivalent 104) 4.9 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 parts were 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 and obtained molding materials 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 formed 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 in Table 2, and a molding material was 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.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

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 phenolic resin curing agent represented by the following formula (2) in an amount of 30 to 100% by weight based on the total epoxy resin amount;
A phenolic resin curing agent, including An epoxy resin composition for semiconductor encapsulation, comprising (C) an inorganic filler and (D) a curing accelerator as essential components.