JPH07278261A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin compsn. which has improved moldability and curability, an excellent crack resistance in a sharp change in temp., and a good moisture resistance by compounding a specific epoxy resin, a melt mixture comprising a flexible phenol resin and a specific cure accelerator, and an inorg. filter. CONSTITUTION:An epoxy resin compsn. contains, as the essential components, an epoxy resin contg. 50-100wt.% epoxy resin of formula I (R1 to R8 are each H, halogen, or alkyl), a melt mixture obtd. by thermally melt mixing a phenol resin of formula II (R is a p-xylene group; and n is 1-5) and/or a phenol resin of formula III (R is a residue formed by removing two phenol parts from dicyclopentadienediphenol obtd. by the addition reaction of dicyclopentadiene with phenol or from a terpenediphenol obtd. by the addition reaction of a terpene with phenol; and n is 1-5) with tritolylphosphine as the accelerator for those phenol resins, and an inorg. filler. The compsn. is excellent in resistance to soldering stress and in curability and useful for semiconductor sealing.

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 solder stress resistance and curability in surface mounting of 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 type epoxy resin excellent in heat resistance and moisture resistance is used as a novolak. An epoxy resin composition cured with a type phenolic resin is used. However, in recent years, as the integration of integrated circuits has increased, the size of the chip has gradually increased, and the package has changed from a conventional DIP type to a surface-mounted small and thin flat package, SOP, SOJ, and PLCC. That is, a large chip is enclosed in a small and thin package, and problems such as cracks caused by stress and deterioration of moisture resistance due to these cracks have been greatly highlighted. Especially in the soldering process, the temperature suddenly rises to 200 ° C.
Exposure to the above high temperature causes problems such as cracking of the package and peeling of the chip from the resin, resulting in deterioration of moisture resistance. Therefore, development of a highly reliable encapsulating resin composition suitable for encapsulating these large chips has been desired.

In order to solve these problems, the use of the epoxy resin represented by the formula (1) as the epoxy resin (Japanese Patent Laid-Open No. 64-65116) has been investigated. By using the epoxy resin represented by the formula (1), it is possible to reduce the viscosity of the resin system. Therefore, by adding a larger amount of fused silica powder, the composition has low thermal expansion and low water absorption after molding, and thus has a low solder stress resistance. The sexuality was improved. However,
An increase in elastic modulus due to the addition of a large amount of fused silica powder is one of the harmful effects, and further improvement in solder stress resistance is required. In order to solve this problem, the use of the flexible phenol resin curing agent represented by the formula (2) or the formula (3) has been studied, and it is effective in improving the solder stress resistance.
On the other hand, the reactivity with epoxy resin is poor, the gel time is long, burrs are likely to occur, the hardness at the time of heating is low, and the mold release property is poor, and there are problems such as the presence of white spots due to unreacted components. There was a need for improvement. As a means for solving these problems, there is an increase in the addition amount of the curing accelerator. Generally, when the addition amount of the curing accelerator is increased, the curability is promoted and the above problems are solved. The moisture resistance of the resin composition decreases. Therefore, it has become necessary to develop means for reducing the amount of the curing accelerator added as much as possible and increasing the curability. As a means for this, melting of a novolac type phenolic resin and a curing accelerator has been proposed (JP-A-60-4253). However,
The epoxy resin composition in which the flexible phenol resin curing agent of the formulas (2) and (3) is used in combination does not lead to sufficient improvement in curability, and further improvement is needed.

[0004]

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

[0005]

The present invention provides an epoxy resin containing (A) the epoxy resin represented by the formula (1) in an amount of 50 to 100% by weight in the total amount of epoxy resin,

[0006]

[Chemical 5] (In the formula, R _{1 to} R ₈ are the same or different atoms or groups selected from hydrogen, halogen and alkyl groups)

(B) A flexible phenolic resin curing agent represented by the formula (2) and / or the formula (3) and a tollylphosphine represented by the formula (4) which is a curing accelerator are heated and melted in advance. Molten mixture and

[0008]

[Chemical 6] (R in the formula is paraxylylene, and the value of n is 1 to 5)

[0009]

[Chemical 7] (Wherein R is dicyclopetadienephenol obtained by addition reaction of dicyclopetadiene and phenol, terpene diphenol obtained by addition reaction of terpenes and phenol, cyclopetadiene diphenol obtained by addition reaction of cyclopentadiene and phenol, and cyclohexanone 2 of each of cyclohexanone diphenols that have been addition-condensed with phenol
Represents the residue excluding the phenol part, one selected from these, the value of n is 1 to 5)

[0010]

[Chemical 8]

(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 1
It is a bifunctional epoxy resin having two epoxy groups in the molecule and has a lower melt viscosity than conventional polyfunctional epoxy resins and has excellent fluidity during transfer molding. Therefore,
A large amount of fused silica powder of the composition can be blended, 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 the biphenyl type epoxy resin used, solder stress resistance can be maximized. To obtain the effect of solder stress resistance, the formula (1) is used.
It is desirable to use the biphenyl type epoxy resin represented by the above formula in an amount of 50% by weight or more, preferably 70% by weight or more based on the total amount of the epoxy resin. 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, R _{1 to} R ₈ in the formula are the same or different atoms or groups selected from hydrogen, halogen and alkyl groups, and among these, preferred are R _{1 to} R ₄ are methyl groups,
R _{5 to} R ₈ are hydrogen atoms.

When another epoxy resin is used in combination with the biphenyl type epoxy resin represented by the formula (1), the epoxy resin used means all polymers having an epoxy group. For example, trifunctional epoxy resin such as bisphenol type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, triphenol methane type epoxy resin and alkyl modified triphenol methane type epoxy resin, triazine nucleus-containing epoxy resin, etc. Say.

The melt mixture used in the present invention comprises a flexible phenolic resin curing agent of formula (2) and / or formula (3) and a tollylphosphine of formula (4) which is a curing accelerator. The phenol resin curing agent represented by the structures of the formulas (2) and (3) is a flexible phenol resin curing agent having a relatively flexible structure in its molecular structure, and has a soldering temperature higher than that of the phenol novolac resin curing agent. It is possible to reduce the elastic modulus in the vicinity and to improve the adhesive force between the lead frame and the semiconductor chip. Therefore, it is effective in reducing the stress generated at the time of soldering and preventing the defective peeling from the semiconductor chip or the like. Further, R in the formula (2) is paraxylylene,
The value of n is 1-5. If n exceeds 5, the fluidity at the time of transfer molding tends to deteriorate, and the moldability tends to deteriorate. R in the formula (3) is dicyclopetadiene diphenol obtained by addition reaction of dicyclopetadiene and phenol,
Represents a residue of terpene diphenol obtained by addition reaction of terpenes with phenol, cyclopentadiene diphenol obtained by addition reaction of cyclopentadiene with phenol, and cyclohexanone diphenol obtained by addition condensation of cyclohexanone with phenol, excluding two phenolic moieties. Of these, a residue in which two phenol moieties of terpene diphenol obtained by addition reaction of terpenes with phenol is removed is preferable. The value of n is 1-5. If n exceeds 5, the fluidity at the time of transfer molding tends to deteriorate, and the moldability tends to deteriorate.

The tritolylphosphine used as the curing accelerator in the present invention accelerates the reaction between the epoxy group and the hydroxyl group. The resin composition using this tritolylphosphine is characterized by excellent storage stability. The amount of the curing accelerator added is 0.1 to 0.1% based on the total resin composition.
It is preferably 1.0% by weight. If it is less than 0.1% by weight, the curing is insufficient and sufficient strength cannot be given to the cured product. This is because if it exceeds 1.0% by weight, the curing accelerator that does not participate in the reaction remains in the cured product and adversely affects the reliability and the like.

A feature of the present invention is that the flexible phenol resin curing agent represented by the formula (2) and / or the formula (3) is preliminarily melt-mixed with the tritolylphosphine represented by the formula (4) which is a curing accelerator. It is to use the melt mixture. The procedure for melt-mixing the flexible phenol 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. The flexible phenol resin curing agent and the curing accelerator are heated and melted while stirring under N ₂ substitution. At this time, the melt mixing temperature is 100
-200 degreeC is preferable. The melt-mixing time is not particularly limited, but after the melt-mixing system becomes transparent, 30
About a minute is usually sufficient. This molten mixture may be used in combination with a phenol novolac resin curing agent. The phenol novolac resin curing agent used in combination is an ordinary resin having two or more phenolic hydroxyl groups in one molecule synthesized by a polycondensation reaction of phenols with an aldehyde source such as formaldehyde, for example, phenol novolac resin, cresol novolac resin. It is a resin. By adjusting the amount of this molten mixture, the solder stress resistance can be maximized. In order to bring out the effect of resistance to solder stress, the flexible phenol resin curing agent represented by the formula (2) and / or the formula (3) in the molten mixture is added in an amount of 30% by weight or more based on the total amount of the phenol resin curing agent. , More preferably 50% by weight. If the amount used is less than 30% by weight, the elasticity is low and the adhesion to the lead frame and the semiconductor chip is insufficient, and improvement in solder stress resistance cannot be expected.

By using a melt mixture obtained by melt-mixing the tollylphosphine represented by the formula (4) with a flexible phenol resin curing agent having a slow reaction rate with an epoxy resin as compared with a phenol novolac resin curing agent. It is possible to obtain the same reaction rate as that of the phenol novolac resin curing agent. As a result, even when used in combination with a phenol novolac resin, it is possible to prevent the unreacted flexible phenol resin curing agent from remaining in the cured epoxy resin composition due to the difference in reaction rate, and to prevent unreacted components on the surface of the molded product. It is possible to solve various problems such as the presence of white spots and the decrease in the degree of curing when heated. As a method of using the melt mixture, two or more kinds of melt mixtures produced separately may be used at the time of producing the epoxy resin composition.

As the inorganic filler used in the present invention, fused silica powder, spherical silica powder, crystalline silica powder, secondary agglomerated silica powder, porous silica powder, secondary agglomerated silica powder or silica obtained by pulverizing porous silica powder is used. Examples thereof include powder and alumina, and fused silica powder, spherical silica powder, and a mixture of fused silica powder and spherical silica powder are particularly preferable. Further, the compounding amount of the inorganic filler is 70 to 9 in the total amount of the composition in view of the balance between solder stress resistance and moldability.
Those containing 0% by weight are preferable.

The epoxy resin composition for encapsulation of the present invention contains an epoxy resin, a melted mixture of a flexible phenol curing agent and tritolylphosphine, and an inorganic filler as essential components. Silane coupling agent,
A variety of flame retardants such as brominated epoxy resin, antimony trioxide, hexabromobenzene, colorants such as carbon black and red iron oxide, mold release agents such as natural wax and synthetic wax, and low stress additives such as silicone oil and rubber. There is no problem even if the above-mentioned additive is properly mixed. Further, in order to produce the encapsulating epoxy resin composition of the present invention as a molding material, after the epoxy resin, the melt mixture, the inorganic 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 molding material. These molding materials can be applied to sealing, coating, insulating, etc. of electronic parts or electric parts.

Production Example of Melt Mixture Melt Mixture 1 A flexible phenol resin curing agent represented by the formula (5) (softening point 75 ° C., hydroxyl group equivalent 175 g / eq, n is a mixture of 1 to 4, and is in a weight ratio. 20 for n = 1, 4 for n = 2
0, n = 3 = 30, n = 4 = 10) 600 parts by weight and 150 parts by weight of tritolylphosphine represented by the formula (4).
The mixture was melt-mixed at 0 ° C. for 1 hour (hereinafter referred to as “melt mixture A”).

[0020]

[Chemical 9]

Melt Mixture 2 Flexible phenolic resin curing agent represented by the formula (6) (softening point 120 ° C., hydroxyl group equivalent 174 g / eq, n is 1 to 4)
And n = 1 is 10 and n = 2 is 4 by weight.
0, n = 3 = 30, n = 4 = 20) 600 parts by weight and 1 part of 20 parts by weight of the tritolylphosphine represented by the formula (4).
Melt mixing was carried out at 50 ° C. for 1 hour (hereinafter referred to as “melt mixture B”).

[0022]

[Chemical 10]

Melt Mixture 3 600 parts by weight of a phenol novolac resin curing agent (softening point: 105 ° C., hydroxyl group equivalent: 104 g / eq) and 20 parts by weight of tritolylphosphine represented by the formula (4) at 150 ° C.
It was melt-mixed for a time (hereinafter referred to as a melt mixture C).

[0024]

EXAMPLES 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 104 ° C, epoxy group equivalent 190 g / eq) 12 parts by weight Melt mixture A 6.2 parts by weight Phenol novolac resin curing Agent (softening point 105 ° C., hydroxyl group 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 0.5 parts by weight are mixed with a mixer at room temperature to 70 to 100. The mixture was kneaded with a biaxial roll at ℃, cooled and pulverized to obtain a molding material. The obtained molding material is made into a tablet, and a 6 x 6 mm chip is sealed in a 52p package for a solder crack test under conditions of 175 ° C, 70 kg / cm ² and 120 seconds with a low-pressure transfer molding machine, and solder moisture resistance. 3 × 6mm for sex test
The chip was encapsulated in a 16p SOP package. The following solder crack test and solder moisture resistance test were performed on the sealed test element. The evaluation results are shown in Table 1.

Solder crack test: The sealed test element was subjected to an environment of 85 ° C. and 85% RH for 48 hours and 72 hours.
After processing, 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
72Hr treatment in an environment of% RH, then after dipping in a solder bath at 260 ° C for 10 seconds, a pressure cooker test (1
At 25 ° C. and 100% RH), the oven failure of the circuit was measured. Moldability test: 160 pDIP was molded using a transfer molding machine at 175 ° C. and 70 kg / cm ² , and mold release 1
Bacol hardness was measured after 0 seconds. The obtained molded product was checked for burr (vent), releasability and appearance. Gel time: measured on a hot plate at 175 ° C.

Examples 2 and 3 Compounding was carried out according to the formulation shown in Table 1, and a molding material was obtained in the same manner as in Example 1. Using this molding material, a molded product sealed for testing was obtained, and a solder crack test and a solder moisture resistance test were carried out in the same manner as in Example 1 using this molded product. The ortho-cresol novolac type epoxy resin of Example 4 had a softening point of 65.
C., epoxy group equivalent is 200 g / eq. The evaluation results are shown in Table 1. Comparative Examples 1 to 6 Compounding was carried out according to the prescription of Table 2, 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, 4, and 5 has the structure of formula (5) (softening point 7
5 ° C., hydroxyl group equivalent 175 g / eq, n is a mixture of 1 to 4, and in weight ratio, n = 1 is 20, n = 2 is 40, n
= 3 = 30, n = 4 = 10). The flexible phenol resin curing agent used in Comparative Example 2 has the structure of formula (6) (softening point 120 ° C., hydroxyl group equivalent 170 g / eq, n is 1).
To 4 in a weight ratio of n = 1 to 10, n =
2 is 40, n = 3 is 30, and n = 4 is 20). Using this molding material, a molded product sealed for testing was obtained, and a solder crack test and a solder moisture resistance test were carried out in the same manner as in Example 1 using this molded product. The evaluation results are shown in Table 2.

[0027]

[Table 1]

[0028]

[Table 2]

[0028]

According to the present invention, it is possible to improve the moldability and curability of a composition comprising a flexible phenol resin curing agent and an epoxy resin, which could not be obtained by the prior art, and to achieve a rapid improvement in the soldering process. It has excellent resistance to cracking when it is subjected to thermal stress due to temperature changes, and because it has good resistance to moisture, it can be used for sealing and coating electronic and electrical parts.
When used for insulation or the like, it is suitable for products that require extremely high reliability, especially in highly integrated large chip ICs mounted in surface mount packages.

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Claims (2)

[Claims] 1. An epoxy resin comprising (A) an epoxy resin represented by the formula (1) in an amount of 50 to 100% by weight in the total amount of epoxy resin, (Wherein R _{1 to} R ₈ are the same or different atoms or groups selected from hydrogen, halogen and alkyl groups) (B) Flexible phenol represented by formula (2) and / or formula (3) A molten mixture obtained by previously heating and melting a resin curing agent and a tollylphosphine that is a curing accelerator represented by the formula (4), and (R in the formula is paraxylylene, and the value of n is 1 to 5) (R in the formula is dicyclopetadiene phenol 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 and phenol Represents a residue obtained by removing each of the two phenol moieties of cyclohexanone diphenol that is addition-condensed with, and one selected from these, the value of n is 1 to 5). (C) An epoxy resin composition for semiconductor encapsulation, which comprises an inorganic filler as an essential component. 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein R in the formula (3) is a residue of terpene diphenol obtained by addition reaction of terpenes with phenol, excluding two phenol moieties.