JP3274265B2 - 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 resistance to soldering stress and curability in surface mounting of a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, electronic components such as diodes, transistors, and integrated circuits have been sealed with a thermosetting resin. In particular, in an integrated circuit, an ortho-cresol novolak type epoxy resin having excellent heat resistance and moisture resistance is used. An epoxy resin composition cured with a mold phenol resin is used. However, in recent years, chips have become larger and larger as integrated circuits have become more highly integrated, and packages have changed from conventional DIP types to small, thin flat packages surface-mounted, SOPs, SOJs, and PLCCs. 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. Especially 200 ° C suddenly in the soldering process
Exposure to the above-mentioned high temperature causes a problem that the moisture resistance is deteriorated due to cracking of the package or separation of the resin and the chip. Therefore, development of a highly reliable encapsulating resin composition suitable for encapsulating these large chips has been desired.

[0003] In order to solve these problems, use of an epoxy resin represented by the formula (1) as an epoxy resin (JP-A-64-65116) has been studied. By using the epoxy resin represented by the formula (1), the viscosity of the resin system can be reduced. Therefore, by adding more fused silica powder, the composition can have low thermal expansion and low water absorption after molding, and can have low soldering stress. The performance has been improved. However,
An increase in the modulus of elasticity due to the addition of a large amount of fused silica powder is another adverse effect, and it is necessary to further improve the solder stress resistance.

In order to solve this problem, the use of a flexible phenolic resin curing agent represented by the formulas (2) and (3) has been studied, which is effective in improving the solder stress resistance.
On the other hand, there are also problems such as poor reactivity with epoxy resin, long gel time, easy occurrence of burrs, low hardness when heated, poor releasability, and white spots due to unreacted components on the molded product surface. , There was a need for improvement. As a means for solving these problems, there is an increase in the addition amount of a curing accelerator. In general, when the addition amount of the curing accelerator is increased, the curability is accelerated and the above-mentioned problems are solved, however, the epoxy The moisture resistance of the resin composition decreases. Therefore, it has become necessary to develop a means for minimizing the amount of the curing accelerator added and improving the curability. Melting of the novolak type phenolic resin and curing accelerator has been proposed as the means (JP 6 1 -4253 JP). However,
Epoxy resin compositions using the flexible phenolic resin curing agents of the formulas (2) and (3) in combination do not lead to a sufficient improvement in curability and require further improvement.

[0005]

DISCLOSURE OF THE INVENTION The present invention is excellent in crack resistance when subjected to thermal stress due to a rapid temperature change in a soldering process, and has a burr caused by differences in moisture resistance and reactivity during molding. An object of the present invention is to provide an epoxy resin composition having improved problems such as white spots, releasability and the like.

[0006]

According to the present invention, there is provided an epoxy resin comprising (A) an epoxy resin represented by the formula (1) in an amount of 50 to 100% by weight based on the total amount of the epoxy resin;

[0007]

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(B) A molten mixture obtained by previously heating and melting a flexible phenol resin curing agent represented by the formula (2) and / or formula (3) and a curing accelerator, tetraphenylphosphonium tetraphenylborate. as well as

[0009]

Embedded image (R in the formula is paraxylylene, and the value of n is 1 to 5)

[0010]

Embedded image (R in the formula represents dicyclopetadiene diphenol obtained by addition reaction of dicyclopetadiene and phenol, terpene diphenol obtained by addition reaction of terpenes and phenol, cyclopentadiene diphenol obtained by addition reaction of cyclopentadiene and phenol, and cyclohexanone. Represents a residue obtained by removing two phenol moieties of each of cyclohexanone diphenols obtained by addition condensation of phenol, and one kind selected from these, and the value of n is 0 to 4)

(C) An epoxy resin composition for semiconductor encapsulation containing an inorganic filler as an essential component.

The biphenyl type epoxy resin represented by the structure of the formula (1) used in the present invention is a bifunctional epoxy resin having two epoxy groups in one molecule, and has a higher melt viscosity than a conventional polyfunctional epoxy resin. And excellent fluidity during transfer molding. 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 solder stress, it is desirable to use the biphenyl type epoxy resin represented by the formula (1) in an amount of 50% by weight or more, preferably 70% by weight or more of the total epoxy resin amount. If it is less than 50% 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, bisphenol type epoxy resin, cresol novolak type epoxy resin,
It refers to a trifunctional epoxy resin such as a phenol novolak type epoxy resin, a triphenolmethane type epoxy resin and an alkyl-modified triphenolmethane type epoxy resin, and a triazine nucleus containing epoxy resin.

The molten mixture used in the present invention comprises a flexible phenolic resin curing agent of formula (2) and / or formula (3) and a curing accelerator, tetraphenylphosphonium tetraphenylborate. The phenolic resin curing agents represented by the structures of formulas (2) and (3) are flexible phenolic resin curing agents having a relatively flexible structure in the molecular structure, and are more solder-treated than phenol novolak resin curing agents. It is possible to reduce the elastic modulus near the temperature and improve the adhesion between the lead frame and the semiconductor chip. Therefore, it is effective in preventing a reduction in stress generated at the time of soldering and a resulting peeling defect from a semiconductor chip or the like. Further, R in the formula (2) is paraxylylene, and the value of n is 1 to 5. n is 5
If it exceeds, the fluidity during transfer molding decreases,
Moldability tends to be poor. R in the formula (3) is dicyclopetadiene diphenol obtained by addition reaction of dicyclopetadiene and phenol, terpene diphenol obtained by addition reaction of terpenes and phenol, and cyclopentadiene diphenol obtained by addition reaction of cyclopentadiene and phenol. And the residue of cyclohexanone diphenol obtained by addition condensation of cyclohexanone and phenol, excluding the two phenol moieties of terpene diphenol obtained by addition reaction of terpenes with phenol. Are preferred. The value of n is 0-4
It is. If n exceeds 4, the fluidity during transfer molding tends to decrease, and moldability tends to be poor.

Tetraphenylphosphonium tetraphenylborate, which is a curing accelerator used in the present invention, promotes the reaction between an epoxy group and a hydroxyl group, and is generally used as a semiconductor encapsulating material. The addition amount of this curing accelerator is preferably 0.1 to 1.0% by weight in the resin composition. If it is less than 0.1, a cured product of sufficient strength cannot be obtained, and if it exceeds 1.0, the fluidity decreases and it causes unfilling. A feature of the present invention is to use a molten mixture in which a flexible phenol resin curing agent represented by the formula (2) and / or the formula (3) is melt-mixed in advance with a curing accelerator, tetraphenylphosphonium / tetraphenylborate. That is. The procedure for melt-mixing the flexible phenolic resin curing agent and the curing accelerator is, for example, as follows, but is not limited to this as long as it can be uniformly melt-mixed. A flexible phenol resin curing agent and a curing accelerator are mixed with N ₂
Heat and melt while stirring under displacement. At this time, the melting and mixing temperature is preferably from 150 to 250C. Although the melt mixing time is not particularly limited, it is usually sufficient if the melt mixing time is about 30 minutes after the melt mixing system becomes transparent.

This molten mixture may be used in combination with a phenol novolak resin curing agent. The phenol novolak resin curing agent to be used in combination is an ordinary resin having two or more phenolic hydroxyl groups in one molecule synthesized by a polycondensation reaction between a phenol and an aldehyde source such as formaldehyde, for example, a phenol novolak resin and a cresol novolak. Resin. By adjusting the amount of the molten mixture, the solder stress resistance can be maximized. In order to bring out the effect of resistance to soldering stress, the flexible phenolic resin curing agent represented by the formula (2) and / or (3) in the molten mixture is added in an amount of 30% by weight or more based on the total amount of the phenolic resin curing agent. And more preferably 50% by weight. If the amount is less than 30% by weight, low elasticity and insufficient adhesion to the lead frame and semiconductor chip cannot be expected to improve solder stress resistance. By using a molten mixture obtained by melt-mixing tetraphenylphosphonium / tetraphenylborate with a flexible phenolic resin curing agent whose reaction rate with an epoxy resin is slower than that of a phenol novolak resin curing agent, A reaction rate equivalent to that of the agent can be obtained.
This can prevent the unreacted flexible phenolic resin curing agent from remaining in the epoxy resin composition after curing due to the difference in reaction rate, even when used in combination with the phenol novolak resin, and the unreacted components remain on the molded product surface. Can solve various problems such as the presence of white spots and a decrease in the degree of curing when heated. As the use of the molten mixture, two or more separately prepared molten mixtures may be used at the time of producing the epoxy resin composition.

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. Powders, alumina and the like can be mentioned, 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 preferably 70 to 9 in the total amount of the composition in consideration of the balance between solder stress resistance and moldability.
Those containing 0% by weight are preferred. The epoxy resin composition for encapsulation of the present invention comprises an epoxy resin, a molten mixture of a flexible phenol curing agent and a curing accelerator and an inorganic filler as essential components. Agents, brominated epoxy resins, antimony trioxide, hexabromobenzene, and other flame retardants, colorants 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 Various additives can be appropriately blended. Further, in order to produce the encapsulating epoxy resin composition of the present invention as a molding material, the epoxy resin, the molten mixture, the inorganic filler, and other additives are sufficiently uniformly mixed by a mixer or the like, and then further heated. Alternatively, it can be melt-kneaded in a kneader or the like, cooled and then 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.

Production Example of Melt Mixture Melt Mixture 1 A flexible phenol resin curing agent represented by the formula (4) (a mixture having a softening point of 75 ° C., a hydroxyl equivalent of 175 g / eq, and n of 1 to 4; 20 for n = 1, 4 for n = 2
0, n = 3 = 30, n = 4 = 10) 600 parts by weight and tetraphenylphosphonium / tetraphenylborate 20
The parts by weight were melt-mixed at 200 ° C. for 1 hour (hereinafter referred to as “melt mixture A”).

[0018]

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Melt mixture 2 A flexible phenol resin curing agent represented by the formula (5) (a mixture having a softening point of 120 ° C., a hydroxyl equivalent of 17 g / eq, n of 0 to 3 and a weight ratio of n = 0 to 10). , N = 1 is 4
0, n = 2 = 30, n = 3 = 20) 600 parts by weight and tetraphenylphosphonium / tetraphenylborate 20
The parts by weight were melt-mixed at 200 ° C. for 1 hour (hereinafter referred to as a melt mixture B).

[0020]

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Melt Mixture 3 Twenty parts by weight of tetraphenylphosphonium / tetraphenylborate was melt-mixed with 600 parts by weight of a phenol novolak resin curing agent (softening point: 105 ° C., hydroxyl equivalent: 104 g / eq) at 200 ° C. for 1 hour (hereinafter referred to as melting). Mixture C).

[0022]

The present invention will be specifically described below with reference to examples. Example 1 The following composition 3,3 ′, 5,5′-tetramethylbiphenol diglycidyl ether (melting point 107 ° C., epoxy equivalent 190 g / eq) 12 parts by weight Melt mixture A 6.2 parts by weight Phenol novolak resin curing agent ( Softening point 105 ° C, hydroxyl equivalent 104g / eq) 2 parts by weight Fused silica powder 78.8 parts by weight Carbon black 0.5 part by weight Carnauba wax 0.5 part by weight is mixed at room temperature with a mixer, and the mixture is mixed at 70-100 ° C. The mixture was kneaded with a biaxial roll, cooled and pulverized to obtain a molding material. The obtained molding material is tableted, and a low pressure transfer molding machine is used to seal a 6 × 6 mm chip in a 52p package at 175 ° C., 70 kg / cm ² , 120 seconds for solder cracking test. 3 x 6 for testability
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. Table 1 shows the evaluation results.

Evaluation test Solder crack test: A sealed test element was heated at 85 ° C. for 8 hours.
48 hours and 72 hours of treatment were performed in an environment of 5% RH, and then 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, and then subjected to a pressure cooker test (1
(25 ° C., 100% RH) to determine the oven failure of the circuit. Moldability test: 16 pDIP was molded using a transfer molding machine at 175 ° C. and 70 kg / cm ² , and the Bacol hardness was measured 10 seconds after release from the mold. The obtained molded product was checked for burrs (vents), releasability, and appearance. Gel time: Measured on a hot plate at 175 ° C.

Examples 2 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. 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. The flexible phenol resin curing agent used in Comparative Examples 1, 3, and 4 has a structure represented by the formula (4) (softening point: 7).
5 ° C., a hydroxyl group equivalent of 175 g / eq, n is a mixture of 1 to 4, and n = 1 = 20, n = 2 = 40, n
= 3 = 30, n = 4 = 10). The flexible phenolic resin curing agent used in Comparative Examples 1, 3, and 4 has a structure represented by the formula (5) (softening point: 120 ° C., hydroxyl equivalent: 17 g / eq, n
Is a mixture of 0 to 3, and n = 0 is 10 by weight,
n = 1 is 40, n = 2 is 30, and n = 3 is 20). 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.

[0025]

[Table 1]

[0026]

According to the present invention, the moldability and curability of a composition comprising a flexible phenolic resin curing agent and an epoxy resin, which could not be obtained by the prior art, can be improved, and a rapid increase in the soldering process can be achieved. It has excellent crack resistance when subjected to thermal stress due to temperature change, and also has good moisture resistance.
When used for insulation or the like, it is particularly suitable for a product that requires extremely high reliability in a highly integrated large chip IC mounted on a surface mount package.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // H01L 23/29 H01L 23/30 R 23/31 (56) References JP-A-6-322073 (JP, A) JP JP-A-6-184280 (JP, A) JP-A-5-343570 (JP, A) JP-A-5-175369 (JP, A) JP-A-4-173828 (JP, A) JP-A-2-102217 (JP) JP-A-61-89221 (JP, A) JP-A-4-363316 (JP, A) JP-A-61-4253 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C08G 59/24 C08G 59/62 C08G 59/68 C08L 63/02 H01L 23/29

Claims (1)

(57) [Claims] 1. An epoxy resin containing (A) an epoxy resin represented by the formula (1) in an amount of 50 to 100% by weight based on the total amount of the epoxy resin. (B) a molten mixture obtained by previously heating and melting a flexible phenolic resin curing agent represented by the formula (2) and / or formula (3) and a curing accelerator, tetraphenylphosphonium / tetraphenylborate; 2] (R in the formula is paraxylylene, and the value of n is 1 to 5) (R in the formula represents dicyclopetadiene diphenol obtained by addition reaction of dicyclopetadiene and phenol, terpene diphenol obtained by addition reaction of terpenes and phenol, cyclopentadiene diphenol obtained by addition reaction of cyclopentadiene and phenol, and cyclohexanone. A residue of the cyclohexanone diphenol obtained by addition condensation of phenol, excluding the two phenolic moieties. One of these is selected. The value of n is 0 to 4.) (C) Inorganic filler is essential An epoxy resin composition for encapsulating a semiconductor, comprising: a component.