JP3255376B2 - 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, chips have become larger and larger as integrated circuits have become more highly integrated, and packages have become smaller and thinner flat packages that are surface-mounted from conventional DIP types.
It is changing to SOP, SOJ, PLCC. 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. In particular, there has been a problem in that abrupt exposure to a high temperature of 200 ° C. or more in a soldering process causes a crack in a package and a peeling of a resin and a chip to deteriorate moisture resistance. Therefore, development of a highly reliable sealing resin composition suitable for sealing these large chips has been desired.

In order to solve these problems, use of an epoxy resin represented by the formula (1) as an epoxy resin (Japanese Patent Laid-Open Publication No. 64-65116) has been proposed.

[0004]

Embedded image (Wherein R _{1 to} R ₈ are the same or different atoms or groups selected from hydrogen, halogen, and alkyl groups)

[0005] It has been studied. The use of the epoxy resin represented by the formula (1) reduces the viscosity of the resin system. Therefore, by adding more fused silica powder, the composition has low thermal expansion and low water absorption after molding, and thus has a low solder stress resistance. The performance has been improved. However, an increase in the modulus of elasticity due to the incorporation of a large amount of the fused silica powder is another adverse effect, and it is necessary to further improve the solder stress resistance. In order to solve this problem, use of a flexible phenol resin curing agent represented by the formulas (2) and (3) has recently been studied. However, the phenolic resin curing agents represented by the formulas (2) and (3) are inferior in reactivity with the epoxy resin, have a long gel time, easily generate burrs, have a low heat hardness, and have a poor releasability. There were problems such as the presence of white spots due to unreacted components on the surface of the molded article, and thus there was a need for improvement.

As a means for solving these problems, there is an increase in the amount of a hardening accelerator. Generally, when the amount of a hardening accelerator is increased, the curability is accelerated and the above problems are solved. Accordingly, the moisture resistance of the epoxy 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 -425
No. 3). However, the epoxy resin compositions using the flexible phenol resin curing agents of the formulas (2) and (3) have not been sufficiently improved in curability and need to be further improved.

[0007]

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.

[0008]

The present invention relates to (A) an epoxy resin represented by the formula (1):

[0009]

Embedded image (Wherein R _{1 to} R ₈ are the same or different atoms or groups selected from hydrogen, halogen, and alkyl groups)

Is 50 to 100 with respect to the total amount of epoxy resin.
(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 triphenylphosphine;

[0011]

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

[0012]

Embedded image (R in the formula is selected from residues of dicyclopentadiene, terpenes, cyclopentadiene, and cyclohexanone except for two hydrogen atoms, 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 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 and alkyl-modified triphenolmethane type epoxy resin, and triazine nucleus containing epoxy resin. Say.

The molten mixture used in the present invention is a flexible phenolic resin curing agent of formula (2) and / or formula (3) tri
Consists of phenylphosphine . The phenolic resin curing agents represented by the structures of the formulas (2) and (3) are flexible phenolic resin curing agents having a relatively flexible structure in the molecular structure, and have a lower soldering temperature than the phenol novolak resin curing agent. It is possible to reduce the elastic modulus in the vicinity 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 para-xylylene,
The value of n is 1-5. If n exceeds 5, the fluidity during transfer molding tends to decrease, resulting in poor moldability. R in the formula (3) is a residue of dicyclopentadiene, terpenes, cyclopentadiene, and cyclohexanone except for two hydrogen atoms, and among these, a residue of terpenes except for two hydrogen atoms. Is preferred. The value of n is 0
4. If n exceeds 4, the fluidity during transfer molding tends to decrease, and moldability tends to be poor.

[0019] Triphenyl phosphine used in the present invention is Ru der those that promote the reaction of epoxy group and hydroxyl group. G
The addition amount of the triphenylphosphine is 0.1% in the resin composition.
It is preferably from 1 to 0.5% by weight.

[0020] Features of the present invention, triflumizole flexible phenolic resin curing agent represented by the formula (2) and / or formula (3)
That is, a molten mixture in which phenylphosphine is previously melt-mixed is used. Flexible phenolic resin curing agent and Triphe
The procedure for melt-mixing nilphosphine is, for example, as follows, but is not limited thereto. While stirring the flexible phenol resin curing agent that has been melted in advance by heating, triphenylphosphine is gradually added to obtain a molten mixture. At this time, it is preferable that the melting and mixing temperature be higher than the softening point of the flexible phenol resin curing agent and the melting point of triphenylphosphine . The melt mixing time is not particularly limited, but after the melt mixing system becomes transparent,
A time of about 30 minutes is usually sufficient.

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 phenol resin curing agent represented by the formula (2) and / or (3) in the molten mixture is added in an amount of 30% by weight based on the total amount of the phenol resin curing agent. More preferably, it is desirable to use 50% by weight or more. 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 melting and mixing triphenylphosphine with a flexible phenol resin curing agent having a lower reaction rate with an epoxy resin than a phenol novolak resin curing agent, A reaction rate equivalent to the above 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 the 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 hardness 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 the total amount of the composition from the balance between solder stress resistance and moldability.
~ 90% by weight is preferred.

The epoxy resin composition for encapsulation of the present invention comprises an epoxy resin, a flexible phenol curing agent and triphenylphospho.
The molten mixture with the fins and the inorganic filler are essential components, but if necessary, a silane coupling agent, a brominated epoxy resin, an antimony trioxide, a flame retardant such as hexabromobenzene, carbon black, red iron oxide And various additives such as a release agent such as natural wax and synthetic wax, and a low stress additive such as silicone oil and rubber.

In order to produce the encapsulating epoxy resin composition of the present invention as a molding material, an epoxy resin, a molten mixture, an inorganic filler, and other additives are sufficiently mixed by a mixer or the like. Furthermore, it can 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.

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 20 parts by weight of triphenylphosphine were melt-mixed at 120 ° C. for 5 minutes (hereinafter referred to as melt-mixing A).

[0028]

Embedded image

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 20 parts by weight of triphenylphosphine were melt-mixed at 170 ° C. for 5 minutes (hereinafter referred to as melt-mixing B).

[0030]

Embedded image

Melt Mixture 3 60 parts by weight of triphenylphosphine 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 120 ° C. for 5 minutes (hereinafter referred to as melt mixture C). ).

[0032]

The present invention will be specifically described below with reference to examples. Example 1 The following composition 12 parts by weight of an epoxy resin represented by the formula (6) (softening point: 107 ° C., epoxy equivalent: 190 g / eq)

[0033]

Embedded image

Melt Mixture A 6.2 parts by weight Phenol novolak resin curing agent (softening point 105 ° C., hydroxyl equivalent 104 g / eq) 2 parts by weight Fused silica powder 78.8 parts by weight Carbon black 0.5 parts by weight Carnauba wax 0 The mixture was mixed at room temperature with a mixer, kneaded with a biaxial roll at 70 to 100 ° C., cooled, and pulverized to obtain a molding material. The obtained molding material is tabletted, a 6 × 6 mm chip is sealed in a 52p package for a solder crack test at 175 ° C., 70 kg / cm ² , and 120 seconds using a low-pressure transfer molding machine. A 3 × 6 mm chip was sealed in a 16 pSOP package for a sex test. 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), and the open defect of the circuit was measured. Moldability test: using a transfer molding machine at 175 ° C. and 70 kg / cm ² , molding 16pDIP,
After a second, the Bacol hardness was measured. The obtained molded product was checked for bends, burrs, releasability, and appearance. Gel time: Measured on a hot plate at 175 ° C.

Examples 2 and 3 The components were blended 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 Compounds were prepared according to the formulation shown in Table 1 and molding materials were obtained in the same manner as in Example 1. The flexible phenol resin curing agent used in Comparative Examples 1, 3, and 4 is a compound represented by the formula (4) (a mixture having a softening point of 75 ° C., a hydroxyl equivalent of 175 g / eq, n of 1 to 4, and a weight of 1 to 4). N = 1 = 20, n = 2 = 40,
n = 3 = 30, n = 4 = 10). The flexible phenol resin curing agent used in Comparative Examples 1, 3, and 4 is represented by the formula (5) (softening point: 120 ° C., hydroxyl equivalent: 17 g / e).
q, n is a mixture of 0 to 3, and n = 0 is 10, n = 1 is 40, n = 2 is 30, and n = 3 is 20 in weight ratio.
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.

[0038]

[Table 1]

[0039]

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.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01L 23/31 (58) Investigated field (Int.Cl. ⁷ , DB name) C08G 59/62 C08G 59/40 C08K 3/00 C08L 63/02 H01L 23/29

Claims (1)

(57) [Claims] (A) an epoxy resin represented by the formula (1): An epoxy resin containing 50 to 100% by weight of the total epoxy resin (wherein R _{1 to} R ₈ are the same or different atoms or groups selected from hydrogen, halogen, and alkyl groups); A molten mixture obtained by previously heating and melting a flexible phenol resin curing agent represented by (2) and / or formula (3) and triphenylphosphine; (R in the formula is paraxylylene, and the value of n is 1 to 5) (R in the formula is selected from residues of dicyclopentadiene, terpenes, cyclopentadiene, and cyclohexanone except for two hydrogen atoms, and the value of n is 0 to 4.)
(C) An epoxy resin composition for semiconductor encapsulation, comprising an inorganic filler as an essential component.