JPH07118366A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin composition which can give a cured molding reduced in thermal expansion and water absorptivity, improved in adhesion to a lead frame and a semiconductor chip and reduced in stress in the molding by mixing an inorganic filler with a specified epoxy resin, a curing agent and a cure accelerator. CONSTITUTION:The composition is prepared by mixing 85-92wt.%, based on the total epoxy resin composition, inorganic filler (e.g. spherical silica powder or a mixture of a fused silica powder with a spherical silica powder) with an epoxy resin mixture in which the total amount of the epoxy resin of formula I (wherein Rs, which may be the same or different from each other, are each an atom or a group selected from among H, halogen or alkyl) is at least 80wt.% based on the total epoxy resin weight, and in which the weight ratio, formula I/formula II (wherein R1 to R5, which may be the same or different from each other, are each an atom or a group selected from among H, halogen and alkyl) is 2/8 to 8/2, a curing agent in which the amount of the phenolic resin of formula III (wherein n=1-6) is at least 20wt.% based on the total phenolic resin curing agent, and a cure accelerator for accelerating the curing reaction of the epoxy group with the hydroxyl group and optionally additives, and melt-kneading the resulting mixture.

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 resistance to solder stress in surface mounting semiconductor devices.

[0002]

2. Description of the Related Art Conventionally, electronic parts such as diodes, transistors and integrated circuits have been sealed with a thermosetting resin. Especially in integrated circuits, orthocresol novolac epoxy resin, which is excellent in heat resistance and moisture resistance, is replaced with phenol novolac. An epoxy resin composition which is cured with a resin and contains an inorganic filler such as fused silica or crystalline silica as a filler is used. However, in recent years, as the integration of integrated circuits has increased, the size of chips has gradually increased, and the package has changed from the conventional DIP type to surface-mounted small and thin QFP and SO.
It has changed to P, SOJ, TSOP, TQFP, PLCC. That is, a large chip is enclosed in a small and thin package, and cracks are generated due to thermal stress, and problems such as deterioration of moisture resistance due to these cracks are greatly highlighted. In particular, when exposed to a high temperature of 200 ° C. or higher in the soldering process, moisture resistance is deteriorated due to cracking of the package and peeling of the chip from the resin. Therefore,
It is desired to develop a highly reliable resin composition for semiconductor encapsulation suitable for encapsulating these large chips.

[0003]

The present invention addresses the above problems by adding an inorganic filler to the total epoxy resin composition in an amount of 8%.
By including 5 to 92% by weight, low thermal expansion and low water absorption of the molded product are achieved, and the epoxy resin represented by the formula (1) and the formula (2) and the curing agent are represented by the formula (3). By blending a specified amount of curing agent,
A semiconductor encapsulation that significantly improves the solder stress resistance of the semiconductor package when mounted on a board by reducing the water absorption, improving the adhesion to the lead frame and semiconductor chip, and reducing the stress by lowering the elastic modulus of the molded product at high temperatures. An epoxy resin composition for stopping is provided.

[0004]

According to the present invention, 85 to 92% by weight of the total epoxy resin composition (A) is an inorganic filler,
The total amount of the epoxy resin represented by the formula (1) and the epoxy resin represented by the formula (2) in the total amount of the epoxy resin (B) is 8
0% by weight or more, and the weight ratio is the formula (1) / the formula (2)
= 2/8 to 8/2 epoxy resin,

[0005]

[Chemical 4]

[0006]

[Chemical 5]

(C) A curing agent containing 20% by weight or more of the phenol resin represented by the formula (3) in the total amount of the phenol resin curing agent, and

[0008]

[Chemical 6]

(D) An epoxy resin composition for semiconductor encapsulation containing a curing accelerator as an essential component, which has excellent solder crack resistance as compared with conventional resin compositions.

Examples of the inorganic filler used in the present invention include fused silica powder, spherical silica powder, crystalline silica powder, secondary agglomerated silica powder, porous silica powder, alumina and the like. In particular, spherical silica powder and fused silica powder. A mixture of powder and spherical silica powder is preferred. Further, the blending amount of the inorganic filler is preferably 85 to 92% by weight, and more preferably 87 to 90% by weight in the total epoxy resin composition in view of the balance between solder crack resistance, moldability and fluidity. If the amount of inorganic filler is less than 85% by weight, low thermal expansion,
Low water absorption cannot be obtained and solder crack resistance is insufficient.
Further, if the amount of the inorganic filler exceeds 92% by weight, there is a problem such as displacement of the die pad and the gold wire in the semiconductor package due to the high viscosity.

The epoxy resin represented by the molecular structure of the formula (1) is obtained by glycidyl etherification of a phenol resin obtained by polymerizing dicyclopentadiene and phenol by an addition reaction, and is a conventional orthocresol novolak epoxy resin. Compared with, it has a very low water absorption, has a low elastic modulus at high temperatures exceeding the glass transition temperature, and has excellent adhesiveness to metals such as lead frames. Therefore, the thermal stress at the time of soldering of surface mounting can be reduced, and the epoxy resin composition excellent in solder crack resistance can be obtained. The value of n is 0 to 6 and it is a mixture thereof, and if it exceeds 6, the fluidity is lowered and the moldability is deteriorated. The biphenyl type epoxy resin represented by the structure of the formula (2) is a bifunctional epoxy resin having two epoxy groups in one molecule, has a lower melt viscosity than the conventional orthocresol novolac epoxy resin, and is excellent in transfer molding. Excellent fluidity. Therefore, a large amount of fused silica powder can be blended in the composition, low thermal expansion and low water absorption can be achieved, and an epoxy resin composition excellent in solder stress resistance can be obtained. By adjusting the amount of epoxy resin used, solder crack resistance can be maximized. The total amount of the epoxy resins represented by the formulas (1) and (2) is preferably 80% by weight or more, more preferably 90% by weight or more based on the total amount of the epoxy resin. 80
If it is less than wt%, low water absorption and adhesiveness cannot be obtained sufficiently,
Solder crack resistance is insufficient. Next, the epoxy resins represented by the formulas (1) and (2) have a weight ratio of formula (1) / formula (2) = 2/8 to 8/2, preferably formula (1) / formula (2). ) = 3/7 to 7/3. The ratio of formula (1) is 20
When it is less than wt%, low water absorption, which is an advantage of the formula (1),
Low elasticity and high adhesiveness are not sufficiently obtained, and when the ratio of the formula (1) exceeds 80% by weight, the low viscosity which is the advantage of the formula (2) cannot be obtained and the flowability during transfer molding is adversely affected. give. When the other epoxy resin is used in combination with the epoxy resin represented by the formula (1) or (2), the epoxy resin to be used is a monomer, an oligomer or a polymer having an epoxy group in general. For example, naphthalene type epoxy compound, bisphenol type epoxy compound, phenol novolac type epoxy resin, cresol novolac type epoxy resin,
Examples thereof include triphenol methane type epoxy compounds, alkyl-modified triphenol methane type epoxy compounds, and triazine nucleus-containing epoxy resins.

The phenol resin curing agent represented by the formula (3) is a polycondensation product of phenol and P-xylylene glycol dimethyl ether, and has characteristics of low water absorption and excellent flexibility. In particular, it is excellent in flexibility at high temperature during soldering, and has a remarkable effect on solder heat resistance during soldering at 250 to 260 ° C. By adjusting the amount of the phenol and P-xylylene glycol dimethyl ether polycondensation phenol resin curing agent used, solder heat resistance can be maximized. In order to bring out the effect of solder heat resistance, the phenol resin curing agent represented by the formula (3) is contained in an amount of 20% by weight or more, preferably 30% by weight of the total curing agent.
The above uses are preferred. If it is less than 20% by weight, the flexibility becomes insufficient and the solder heat resistance during soldering cannot be sufficiently obtained. The value of n is 1 to 6 and is a mixture of these,
If it exceeds, the fluidity is lowered and the moldability is deteriorated. When used in combination with other than the phenol resin curing agent represented by the formula (3), it mainly refers to all polymers having a phenolic hydroxyl group. For example, phenol novolac resin, cresol novolac resin, dicyclopentadiene modified phenol resin, copolymer of dicyclopentadiene modified phenol resin and phenol novolac or cresol novolac resin, naphthalene modified phenol resin and the like can be used. As the compounding amount of these curing agents, the ratio of the number of epoxy groups in the epoxy resin to the number of hydroxyl groups in the curing agent is 0.8 to 1.2, and preferably an equivalent amount.

The curing accelerator used in the present invention may be any one as long as it accelerates the curing reaction between the epoxy group and the hydroxyl group, and those generally used for sealing materials can be widely used. For example, 1,8-diazabicycloundecene, triphenylphosphine, dimethylbenzylamine, 2-methylimidazole and the like are used alone or in combination of two or more. The epoxy resin composition of the present invention contains an inorganic filler, an epoxy resin, a curing agent and a curing accelerator as essential components, but in addition to this, a silane coupling agent, a brominated epoxy resin, antimony trioxide, and hexa may be added if necessary. Flame retardants such as brombenzene, colorants such as carbon black and red iron oxide, mold release agents such as natural wax and synthetic wax, and various additives such as low-stress additives such as silicone oil and rubber may be appropriately blended. There is no.
Further, in order to produce the encapsulating epoxy resin composition of the present invention as a molding material, after the epoxy resin, the curing agent, the curing accelerator, the filler, and other additives are sufficiently uniformly mixed by a mixer or the like, Further, it can be melt-kneaded with a hot roll or a kneader, cooled, and then pulverized to obtain a sealing material. These molding materials can be applied to coating, insulation, sealing, etc. of transistors, integrated circuits, etc., which are electric or electronic parts.

The present invention will be specifically described below with reference to examples. Example 1 3.4 parts by weight of an epoxy resin represented by the formula (4) (softening point: 65 ° C., epoxy equivalent: 250 g / eq)

[0015]

[Chemical 7] (The value of n is a mixture showing 0 to 2, and the weight ratio thereof is 1 for n = 0 and 0.4 for n = 1 and 0.2 for n = 2.
5)

3.4 parts by weight of the epoxy resin represented by the formula (5) (melting point: 110 ° C., epoxy equivalent: 190 g / eq)

[0017]

[Chemical 8]

2.1 parts by weight of a phenol resin curing agent represented by the formula (6) (softening point 80 ° C., hydroxyl group equivalent 170 g / eq)

[0019]

[Chemical 9] (The value of n is a mixture showing 1 to 3, and the weight ratio is 1 for n = 1 and 3 for n = 2 and 1 for n = 3)

Phenol novolac resin curing agent (softening point 105 ° C., hydroxyl group equivalent 100 g / eq) 2.1 parts by weight fused silica powder (average particle size 10 μm, specific surface area 2.0 m ² / g) 88 parts by weight triphenylphosphine 0.2 parts by weight carbon black 0.3 parts by weight Carnauba wax 0.5 parts by weight were mixed in a mixer at room temperature, kneaded at 70 to 100 ° C. with a biaxial roll, cooled and pulverized to obtain a molding material. The molding material obtained by crushing was 175 ° C., 70 kg / cm ² ,
The spiral flow was measured under the condition of 120 seconds. Further, the obtained molding material was tabletted, and a 6 × 6 mm chip was tested for solder cracking test under the conditions of 175 ° C., 70 kg / cm ² , 120 seconds with a low-pressure transfer molding machine.
Sealed in 2pQFP and 3x for solder moisture resistance test
A 6 mm chip was encapsulated in 16 pSOP. The following solder cracking property test and solder moisture resistance test were conducted on the sealed test element. The evaluation results are shown in Table 1.

Solder cracking property test: The sealed test element was treated in an environment of 85 ° C. and 85% RH for 48 hours and 72 hours, then immersed in a solder bath at 260 ° C. for 10 seconds, and external cracks were observed with a microscope. did. Solder moisture resistance test: Sealed test element at 85 ℃, 85%
It is treated for 72 hours in an environment of RH and then immersed in a solder bath at 260 ° C for 10 seconds, and then subjected to a pressure cooker test (12
5 ° C., 100% RH) was performed to measure the open defect of the circuit. Examples 2 to 10 Compounding was performed according to the formulation shown in Table 1, and molding materials were obtained in the same manner as in Example 1. The ortho-cresol novolak epoxy resin (referred to as EOCN) used in Example 10 has a softening point of 65.
C., epoxy equivalent is 200 g / eq. Using this molding material, a sealed molded product for testing was obtained, and a solder cracking resistance test and a solder moisture resistance test were conducted in the same manner as in Example 1 using this molded product. The evaluation results are shown in Table 1.

Comparative Examples 1 to 6 Compounding was carried out according to the formulation shown in Table 2, and molding materials were obtained in the same manner as in Example 1. Using this molding material, a sealed molded product for testing was obtained, and a solder cracking resistance test and a solder moisture resistance test were conducted in the same manner as in Example 1 using this molded product. The evaluation results are shown in Table 2.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

According to the present invention, it is possible to obtain an epoxy resin composition having a solder stress resistance which could not be obtained by the prior art. Therefore, when the epoxy resin composition is subjected to thermal stress due to a rapid temperature change due to the soldering process. Has very good crack resistance and good moisture resistance, so when used for encapsulation, coating, insulation, etc. of electronic and electrical parts, especially highly integrated large chip IC mounted in surface mount package It is suitable for products that require high reliability.

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Claims (1)

[Claims] 1. A total of 85 to 85 of (A) the total epoxy resin composition.
92% by weight is an inorganic filler, the total amount of the epoxy resin represented by the formula (1) and the epoxy resin represented by the formula (2) in the total amount of the epoxy resin (B) is 80% by weight or more, and the weight thereof is An epoxy resin having a ratio of formula (1) / formula (2) = 2/8 to 8/2, [Chemical 2] (C) a curing agent containing 20% by weight or more of the phenol resin represented by the formula (3) in the total amount of the phenol resin curing agent; (D) An epoxy resin composition for semiconductor encapsulation containing a curing accelerator as an essential component.