JP2951091B2 - 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 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, thin flat package surface-mounted, SO
It is changing to P, SOJ, PLCC. 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. Especially in the soldering process, 250
Exposure to a high temperature of not less than ° C. has caused the above problem. Development of a highly reliable sealing resin composition suitable for sealing these large chips has been desired.

In order to solve these problems, addition of a thermoplastic oligomer (Japanese Patent Application Laid-Open No. 62-15849) and addition of various silicone compounds (Japanese Patent Application Laid-Open No. JP-115850,
62-116654 and 62-128162), and further modified with silicone (JP-A-62-1368).
No. 60), cracks are generated in the package at the time of soldering, and it has not been possible to obtain a highly reliable epoxy resin composition for sealing.

On the other hand, in order to obtain an epoxy resin composition for semiconductor encapsulation having excellent heat stress resistance during soldering, that is, excellent solder stress resistance, a biphenyl type epoxy resin is used as a resin system (JP-A-64-65116). However, the use of a biphenyl-type epoxy resin has improved the adhesion to the lead frame and the low water absorption, and improved the solder stress resistance, especially the occurrence of cracks. In particular, at a high temperature of 250 ° C. or higher, the solder stress resistance is insufficient because of poor resistance.

[0005]

SUMMARY OF THE INVENTION The present invention provides an epoxy resin composition for semiconductor encapsulation which has excellent solder heat resistance during soldering without deteriorating formability and reliability.

[0006]

The epoxy resin composition of the present invention comprises (A) a co-condensed novolak epoxy resin of paracresol and α-naphthol represented by the following formula (1):

Embedded image (B) an epoxy resin containing 50 to 100% by weight based on the total amount of the epoxy resin (the number of n in the formula is 1 to 6); and (B) a polyfunctional novolak type phenol resin curing agent represented by the following formula (2): 2 for the amount of phenolic resin curing agent
A phenolic resin curing agent containing 5 to 95% by weight,

Embedded image (Wherein R ₁ is an atom or group selected from hydrogen, halogen, and lower alkyl group, and the number of n is 1 to 6). (C) 5 to 10% by weight based on the total amount of the phenol resin curing agent (D) an inorganic filler and (E) a curing accelerator as essential components. It has much better solder heat resistance than the conventional epoxy resin composition.

The co-condensed novolak epoxy resin of para-cresol and α-naphthol used in the present invention is an epoxidized novolak resin obtained by co-condensing para-cresol and α-naphthol from formaldehyde. The amount is desirably 50% by weight or more, and the resin is mainly composed of the structure of the formula (1). n is 1 to 6, 6
If it exceeds, the fluidity becomes poor and the moldability deteriorates. The characteristics are excellent in low water absorption, small in coefficient of linear expansion of resin, excellent in mold releasability during molding, and excellent in solder heat resistance during soldering. The amount of co-condensed novolak epoxy resin of paracresol and α-naphthol is
By adjusting this, the solder heat resistance can be maximized.

In order to achieve the effect of solder heat resistance, it is desirable to use a cocondensed novolak epoxy resin of paracresol and α-naphthol in an amount of 50% by weight or more, preferably 70% by weight or more of the total epoxy resin amount. If the amount is less than 50% by weight, low water absorption and low linear expansion coefficient cannot be sufficiently obtained, and solder heat resistance is insufficient. When an epoxy resin other than the co-condensed novolak epoxy resin of paracresol and α-naphthol is used in combination, the epoxy resin used generally refers to any polymer having an epoxy group. For example, it refers to a bisphenol-type epoxy resin, a cresol novolak-type epoxy resin, a biphenyl-type epoxy resin, a phenol novolak-type epoxy resin, a triphenylmethane-type epoxy resin, a triazine ring-containing epoxy resin, and the like.

The reaction cured product of the polyfunctional novolak type phenolic resin curing agent having the structure represented by the formula (2) and the epoxy resin has the characteristics of obtaining toughness and low water absorption. In particular, it has excellent toughness at high temperature during soldering,
It has a remarkable effect on solder heat resistance when soldering at 60 ° C. In order to bring out the effect of solder heat resistance, it is desirable to use the polyfunctional novolak type phenolic resin curing agent represented by the formula (2) in an amount of 25% by weight or more, preferably 60% by weight or more of the total phenolic resin curing agent. If it is less than 25% by weight, the toughness at the time of heating becomes insufficient, and sufficient solder heat resistance at the time of soldering cannot be obtained. Further, R ₁ in the formula is an atom or a group selected from among hydrogen, halogen, and a lower alkyl group. The lower alkyl group has 1 to 4 carbon atoms, and if it has more than 4, the fluidity will be poor and the moldability will be poor. A methyl group is preferred as the lower alkyl group.

Further toughness can be obtained by using bisphenol A together with a polyfunctional novolak type phenolic resin curing agent represented by the formula (2) in an amount of 5 to 10% by weight based on the total amount of the phenolic resin curing agent. If the amount of bisphenol A is less than 5% by weight, the effect of toughening is small, and if it exceeds 10% by weight, the curability is reduced. When other polyphenols are used in combination with the polyfunctional novolak type phenolic resin curing agent and bisphenol A, those used include the whole polymer having various phenolic hydroxyl groups. For example, a phenol novolak resin, a cresol novolak resin, a co-condensate of a dicyclopentadiene-modified phenol resin with a phenol novolak resin and a cresol novolak resin,
A para-xylene-modified phenol resin or the like can be used.

Examples of the inorganic filler used in the present invention include fused silica powder, spherical silica powder, crystalline silica powder, secondary aggregated silica powder, silica powder obtained by pulverizing porous silica powder, and alumina. Powders, spherical silica powders and mixtures of fused silica powder and spherical silica powder are preferred. In addition, as the compounding amount of the inorganic filler,
From the balance between solder stress resistance and moldability, it is desirable that the total resin composition contains 70 to 90% by weight.

Further, 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 a sealing material can be widely used. For example, organic phosphine compounds such as triphenylphosphine (TPP), tributylphosphine, and tri (4-methylphenyl) phosphine; tributylamine;
Tertiary amines such as triethylamine, benzyldimethylamine, trisdimethylaminomethylphenol, 1,8-diazabicyclo [5,4,0] -7-undecene (DBU), 2-methylimidazole, 2-phenylimidazole, 2-ethyl And imidazole compounds such as -4-methylimidazole. These can be used alone or in combination of two or more.

The composition of the present invention may further comprise a coloring agent such as carbon black, a release agent such as carnauba wax and synthetic wax, a flame retardant such as brominated epoxy and antimony trioxide, and a γ- Coupling agents such as glycidoxypropyltrimethoxysilane and rubber components such as silicone rubber and polybutadiene can be added. The epoxy resin composition of the present invention is prepared by uniformly mixing an epoxy resin, a curing agent, an inorganic filler, a curing accelerator, and other additives with a mixer or the like, and then hot-melting and kneading with a general kneading device such as a roll or an extruder. By cooling, pulverizing, a molding material can be obtained.

[0014]

The present invention will be specifically described below with reference to examples.

Example 1 A co-condensed novolak epoxy resin of paracresol and α-naphthol represented by the following formula (1) (n is a mixture of 80% by weight of n = 1 and 20% by weight of n = 2, epoxy equivalent: 200) , Softening point 65 ° C) 13 parts by weight

[0016]

Embedded image

A polyfunctional novolak-type phenol resin curing agent represented by the following formula (3) (n is a mixture of 35, 48, 14, and 3% by weight, respectively, where n = 1, 2, 3, and 4; a hydroxyl equivalent of 106; 6.29 parts by weight)

[0018]

Embedded image

Bisphenol A 0.35 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 is mixed at room temperature with a mixer, The mixture was kneaded with a biaxial roll at 100 ° C., cooled and pulverized to obtain a molding material. The obtained molding material is tableted, and a low pressure transfer molding machine is used to enclose a 6 × 6 mm chip in a 52p package for a solder crack test at 175 ° C., 70 kg / cm ² for 120 seconds, and for a solder moisture resistance test. A 3 × 6 mm chip was sealed in a 16pSOP 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 at 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 at 85 ° C, 85
The samples were treated for 48 hours and 72 hours in an environment of% RH, then immersed in a solder bath at 260 ° C. for 10 seconds, and then subjected to a pressure cooker test (125 ° C., 100% RH) to measure the open failure of the circuit. 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 molded product in which a test element was sealed with this molding material was obtained, 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 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 molded product in which a test element was sealed with this molding material was obtained, 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.

[0022]

[Table 1]

[0023]

The epoxy resin composition of the present invention does not deteriorate moldability, improves solder stress resistance, and does not generate cracks during soldering, as compared with conventional epoxy resin compositions. . Furthermore, since it has low water absorption, the solder moisture resistance is greatly improved. As apparent from these, the present resin composition is useful as a semiconductor encapsulating material having excellent moldability, reliability, and resistance to soldering stress during soldering.

Claims (1)

(57) [Claims] (A) A co-condensed novolak epoxy resin of paracresol and α-naphthol represented by the following formula (1): (B) an epoxy resin containing 50 to 100% by weight based on the total amount of the epoxy resin (the number of n in the formula is 1 to 6); and (B) a polyfunctional novolak type phenol resin curing agent represented by the following formula (2): 2 for the amount of phenolic resin curing agent
A phenolic resin curing agent containing 5 to 95% by weight; (Wherein R ₁ is an atom or group selected from hydrogen, halogen, and lower alkyl group, and the number of n is 1 to 6). (C) 5 to 10% by weight based on the total amount of the phenol resin curing agent An epoxy resin composition for semiconductor encapsulation, comprising, as essential components, bisphenol A, (D) an inorganic filler and (E) a curing accelerator.