JP2963260B2 - 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 having excellent solder stress resistance.

[0002]

2. Description of the Related Art Most highly integrated IC devices are sealed by a resin sealing method using an epoxy resin sealing material which is excellent in reliability, cost and mass productivity. As an epoxy resin sealing material, a resin composition composed of an orthocresol novolak epoxy resin and a novolak type phenol resin having excellent heat resistance, moisture resistance, and moldability is used. However, with the recent high integration and multifunctionality,
Highly integrated IC packages tend to have smaller and thinner packages due to larger elements and more streamlined mounting, and are smaller and thinner than conventional DIP types in SOJ, SOP, and QF.
There is a rapid shift to P, TSOP type surface mount packages.

This means that the package itself is exposed to a high temperature of 215 to 260 ° C. at the time of soldering, unlike the conventional DIP type, and the surface mount type package in which a large chip is sealed in a small and thin package has a large stress. This causes cracking of the package resin and separation of the chip interface, which is a fatal problem for the reliability of the IC package. A highly reliable encapsulating resin composition suitable for encapsulating these surface mount packages is desired.

In order to solve these problems, addition of thermoplastic oligomers (Japanese Patent Laid-Open No. 62-15849) and addition of various silicone compounds (Japanese Patent Laid-Open No. No. 115850, 62
-116654, 62-128162),
Furthermore, a method such as silicone modification (Japanese Unexamined Patent Publication No. 62-136860) is used, but in any case, a crack occurs in the package at the time of soldering, and a highly reliable epoxy resin composition for semiconductor encapsulation is obtained. Did not reach.

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 (Japanese Patent Application Laid-Open No. 64-65116). Publication) has been studied, but the use of a biphenyl type epoxy resin improves the adhesion to the lead frame and low water absorption, and improves the solder stress resistance, and in particular, reduces the occurrence of cracks.
Since the heat resistance is inferior, the solder stress resistance is insufficient particularly at a high temperature such as 250 ° C. or higher.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation which has excellent solder heat resistance during soldering without deteriorating formability and reliability.

[0007]

According to the present invention, there is provided (A) a co-condensed novolak epoxy resin of orthocresol and β-naphthol represented by the following formula (1):
An epoxy resin containing 0 to 100% by weight,

[0008]

Embedded image (N = 1-6)

(B) a curing agent containing a phenolic resin curing agent represented by the following formula (2) in an amount of 30 to 100% by weight based on the total amount of the curing agent;

[0010]

Embedded image

(Wherein R ₁ and R ₂ are the same or different atoms or groups selected from hydrogen, halogen and lower alkyl groups, n = 1 to 6) (C) inorganic filler and (D) curing An epoxy resin composition for semiconductor encapsulation containing an accelerator as an essential component,
It has extremely excellent soldering heat resistance compared to conventional epoxy resin compositions.

The co-condensed novolak epoxy resin of ortho-cresol and β-naphthol used in the present invention is an epoxidized product of a novolak resin obtained by co-condensing ortho-cresol and β-naphthol from formaldehyde. The amount is desirably 50% by weight or more, and the compound mainly has the structure of the formula (1). Further, n is 1 to 6, and when n exceeds 6, the fluidity during molding is poor. Formula (1) has characteristics of excellent low water absorption, a small coefficient of linear expansion of the resin, and excellent releasability at the time of molding, and shows good results in solder heat resistance at the time of soldering. By adjusting the amount of the ortho-cresol and β-naphthol co-condensed novolak epoxy resin, solder heat resistance can be maximized by adjusting the amount.

In order to obtain the effect of solder heat resistance, ortho-cresol and β-naphthol co-condensed novolak epoxy resin are 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 water absorption and low coefficient of linear expansion cannot be sufficiently obtained, and solder heat resistance is insufficient. When an epoxy resin other than ortho-cresol and β-naphthol co-condensed novolak epoxy resin is used in combination, the epoxy resin used generally refers to any polymer having an epoxy group. For example, bisphenol type epoxy resin, cresol novolak type epoxy resin, biphenyl type epoxy resin, phenol novolak type epoxy resin, triphenolmethane type epoxy resin, and alkyl modified triphenolmethane type epoxy resin.
It refers to a functional epoxy resin, a triazine nucleus-containing epoxy resin and the like.

The phenol resin curing agent represented by the formula (2) is obtained by modifying para-xylene in the skeleton. In the formula, n is 1 to 6, and R ₁ and R ₂ are the same or different atoms or groups selected from hydrogen, halogen, and lower alkyl groups. Among these, when n exceeds 6, the fluidity during molding is poor. When the lower alkyl group has 1 to 4 carbon atoms and exceeds 4, the fluidity during molding is poor. Each of R ₁ and R ₂ is preferably a hydrogen atom. Features include low elastic modulus above the glass transition temperature and low internal stress during soldering.
In addition, it has characteristics such as excellent adhesion to the chip and the lead frame and low water absorption. The amount of the phenol resin curing agent used is preferably at least 30% by weight, more preferably at least 60% by weight, based on the total amount of the curing agent.
If it is less than 30% by weight, the adhesion to the lead frame and the low water absorption are not improved, and the solder stress resistance is insufficient.

When a phenol resin curing agent other than the phenol resin curing agent represented by the formula (2) is used in combination, the phenol resin curing agent used generally refers to any polymer having a phenolic hydroxyl group. For example, phenol novolak resins, cresol novolak resins, dicyclopentadiene-modified phenol resins, co-condensates of dicyclopentadiene-modified phenol resins with phenol novolak and cresol novolak resins, and para-xylene-modified phenol resins 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, and 1,8-diazabicyclo [5,4,0] -7-undecene (DBU);
And imidazole compounds such as secondary amine, 2-methylimidazole, 2-phenylimidazole and 2-ethyl-4-methylimidazole. These can be used alone or in combination of two or more.

The composition of the present invention may further contain 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.

In order to produce the encapsulating epoxy resin composition of the present invention as a molding material, an epoxy resin, a curing agent,
After a curing accelerator, a filler, 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.

[0020]

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

Example 1 Co-condensed novolak epoxy resin of orthocresol and β-naphthol (n is a mixture of 70% by weight of n = 3 and 30% by weight of n = 4, epoxy equivalent 225, softening point 84 ° C.) 13.5 parts by weight A phenolic resin curing agent represented by the following formula (3) (n is a mixture of 30% by weight for n = 2 and 70% by weight for n = 3, hydroxyl equivalent 175, softening point 75 ° C.) 5 parts by weight

[0022]

Embedded image

75 parts by weight of fused silica powder 0.2 parts by weight of triphenylphosphine 0.3 parts by weight of carbon black 0.5 parts by weight of carnauba wax are mixed at room temperature with a mixer, and kneaded at 70-100 ° C. with a biaxial roll. After cooling, the obtained molding material was converted into a tablet, and the resulting molding material was tabletted, and a low pressure transfer molding machine was used to package a 6 × 6 mm chip in a 52p package for solder crack testing at 175 ° C., 70 kg / cm ² and 120 seconds. And a 3 × 6 mm chip was sealed in a 16 pSOP package for a solder moisture resistance test. 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 at 85 ° C, 85
% RH environment and then immersed in a solder bath at 260 ° C. for 10 seconds, followed by a pressure cooker test (12
5 ° C., 100% RH), and the open failure of the circuit was measured. 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.

[0027]

[Table 1]

[0028]

According to the present invention, a resin composition having excellent heat resistance, low water absorption and flexibility can be obtained. As a sealing material for highly integrated IC packages that are surface-mounted on a printed circuit board, they are extremely excellent in solder heat resistance during soldering.

Claims (1)

(57) [Claims] (A) an epoxy resin containing a co-condensed novolak epoxy resin of orthocresol and β-naphthol represented by the following formula (1) in an amount of 30 to 100% by weight based on the total epoxy resin amount: (N = 1-6) (B) a curing agent containing a phenolic resin curing agent represented by the following formula (2) in an amount of 30 to 100% by weight based on the total amount of the curing agent; (Wherein R ₁ and R ₂ are the same or different atoms or groups selected from hydrogen, halogen, and lower alkyl groups;
n = 1 to 6) An epoxy resin composition for semiconductor encapsulation comprising (C) an inorganic filler and (D) a curing accelerator as essential components.