JP3018584B2 - Epoxy resin composition for semiconductor encapsulation - 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 solves the problem of package cracks generated in the soldering step, that is, has excellent solder heat resistance.

[0002]

2. Description of the Related Art Epoxy resins are excellent in heat resistance, moisture resistance, electrical properties, adhesiveness, etc., and can be imparted with various properties by blending and prescription, so that they are used as industrial materials such as paints, adhesives, and electrical insulating materials. Have been. For example, as a method of sealing electronic circuit components such as semiconductor devices, a hermetic seal made of metal or ceramic and a resin seal made of phenol resin, silicone resin, epoxy resin, and the like have been used. In view of the balance of physical properties, resin sealing with epoxy resin is mainly used.

In recent years, in particular, the density of components has been increased in mounting on a printed circuit board. Instead of the conventional "insertion mounting method" in which lead pins are inserted into holes in the board, "surface mounting" in which components are soldered to the board surface is performed. The “mounting method” has become popular. Along with this, the package is also shifting from the conventional DIP (dual inline package) to a thin TSOP (thin small outline package) or QFP (quad flat package) suitable for high-density mounting and surface mounting. .

[0004] With the shift to the surface mounting method, the soldering process, which has not been a problem so far, has become a major problem. In the conventional pin insertion mounting method, the lead portion is only partially heated in the soldering process, but in the surface mounting method, the entire package is immersed in a heating medium and heated. As a soldering method in the surface mounting method, a solder bath immersion, a solder reflow method of heating with a saturated vapor of an inert liquid or infrared rays is used. In any case, the entire package is heated to a high temperature of 210 to 270 ° C. Will be. Therefore, the package sealed with the conventional sealing resin,
There has been a problem that cracks occur in the resin portion at the time of soldering, so that the reliability is reduced and the product cannot be used as a product.

[0005] The occurrence of cracks in the soldering process
It is said that the moisture absorbed between the post-curing and the mounting process explosively evaporates and expands during soldering and heating, and as a countermeasure, various improvements in sealing resins have been studied. .

Conventionally, an orthocresol novolak type epoxy resin is used as an epoxy resin, a phenol novolak resin is used as a curing agent, and an average particle size of 10 to 20 μm is used as an inorganic filler.
Although m-crushed amorphous silica was generally used, the problem of cracking due to heating during surface mounting could not be avoided. Therefore, in order to suppress the occurrence of cracks in the soldering step, an epoxy resin having a biphenyl skeleton is used as the epoxy resin, and crushed amorphous silica having an average particle size of 12 μm or less and an average particle size of 4 μm are used as the inorganic filler.
A method using a combination of spherical amorphous silica having a particle diameter of 0 μm or less (Japanese Patent Laid-Open No. 2-99514) and the like have been proposed.

[0007] However, although the resins improved by these various methods seem to be effective to some extent against cracking during soldering, their heat resistance to soldering is not yet sufficient, and the resin may not be applied to the outside of the package. Even if cracks do not occur, the problem that peeling occurs between the surface of the semiconductor element and the encapsulant and that the moisture resistance reliability is reduced has also become important.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of package cracks generated in the soldering step, that is, to provide an epoxy resin composition for semiconductor encapsulation having excellent solder heat resistance.

[0009]

Means for Solving the Problems The present inventors have solved the above problems by blending a specific epoxy resin with an inorganic filler having a specific shape and particle size, and a specific thermoplastic elastomer. It was found that an epoxy resin composition conforming to the formula (1) was obtained, and the present invention was reached.

That is, the present invention provides an epoxy resin (A),
A resin composition containing a phenolic curing agent (B), an amorphous silica (C) and a polystyrene block copolymer (D) as essential components, wherein the epoxy resin (A) has the formula (I) )

[0011]

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(However, two of R ^{1 to} R ⁸ are 2, 3
An epoxypropoxy group, the rest being hydrogen atoms, C ₁
Selected from lower alkyl group or a halogen atom -C _4, need not all be identical. )) As an essential component, and the amorphous silica (C) is 97 to 60% by weight of crushed amorphous silica having an average particle size of 10 μm or less, and the average particle size is 4 μm or less. An inorganic filler comprising 3 to 40% by weight of spherical amorphous silica, wherein the average particle diameter of the spherical amorphous silica is smaller than the average particle diameter of the crushed amorphous silica, and the amorphous silica (C) Is 73 to 88% by weight of the total epoxy resin composition.

The reasons why the epoxy resin composition of the present invention is excellent in solder heat resistance are not yet clear, but (1) the epoxy resin (a) has only two epoxy groups in one molecule, so that the cured product has The crosslinking density is appropriately reduced, the polystyrene-based block copolymer (D) exhibits low water absorption by hydrophobizing the resin, and (2) the epoxy resin (a) has a rigid naphthalene skeleton. And toughness (high strength, high elongation) at high temperature due to the fact that the crosslink density of the cured product is appropriately low. (3) High temperature due to the special combination of amorphous silica (C) shape and particle size And (4) the polystyrene-based block copolymer (D) can be used in a semiconductor device and an epoxy resin cured product in a wide temperature range. From the effect the contribution of each single work synergistically, such that have the effect of relieving the strain stress generated between is believed to exhibit excellent solder heat resistance enough not have been predicted.

Hereinafter, the configuration of the present invention will be described in detail.

The epoxy resin (A) of the present invention contains the epoxy resin (a) represented by the above formula (I) as an essential component.

Preferred specific examples of the epoxy resin (a) in the present invention include 1,5-di (2,3-epoxypropoxy) naphthalene and 1,5-di (2,3-epoxypropoxy) -7-methyl Naphthalene, 1,6-di (2,3-epoxypropoxy) naphthalene, 1,6-
Di (2,3-epoxypropoxy) -2-methylnaphthalene, 1,6-di (2,3-epoxypropoxy) -8
-Methylnaphthalene, 1,6-di (2,3-epoxypropoxy) -4,8-dimethylnaphthalene, 2-bromo-1,6-di (2,3-epoxypropoxy) naphthalene, 8-bromo-1, Examples thereof include 6-di (2,3-epoxypropoxy) naphthalene and 2,7-di (2,3-epoxypropoxy) naphthalene, and particularly 1,5-di (2,3-epoxypropoxy) naphthalene, 6-
Di (2,3-epoxypropoxy) naphthalene, 2,
7-Di (2,3-epoxypropoxy) naphthalene is preferred.

The proportion of the epoxy resin (a) contained in the epoxy resin (A) is not particularly limited, but in order to achieve a more satisfactory effect, the epoxy resin (a)
Is preferably contained in the epoxy resin (A) in an amount of 50% by weight or more.

The epoxy resin (A) of the present invention
The residue is not particularly limited as long as the epoxy resin (a) is contained in the epoxy resin (A) in an amount of 50% by weight or more. Preferred specific examples are ortho-cresol novolak epoxy resin, phenol novolak epoxy resin, and bisphenol A Type epoxy resin, bisphenol F type epoxy resin, biphenol type epoxy resin and the like.

In the present invention, the amount of the epoxy resin (A) is usually 4 to 20% by weight, preferably 5 to 15% by weight.
It is.

The phenolic curing agent (B) in the present invention
Is not particularly limited as long as it is cured by reacting with the epoxy resin (A), but preferred specific examples include phenol novolak resin, cresol novolak resin, phenol aralkyl resin, bisphenol A, bisphenol F and the like. .

In the present invention, the amount of the phenolic curing agent (B) is usually 3 to 15% by weight, preferably 4 to 15% by weight.
It is 12% by weight. Furthermore, the mixing ratio of the epoxy resin (A) and the phenolic curing agent (B) is such that the chemical equivalent ratio of hydroxyl group / epoxy group is 0. 0 from the viewpoint of mechanical properties and moisture resistance.
It is preferably in the range of 7 to 1.3, particularly 0.8 to 1.2.

In the present invention, the epoxy resin (A)
A curing catalyst may be used to accelerate the curing reaction between the phenolic curing agent (B) and the phenolic curing agent (B). The curing catalyst is not particularly limited as long as it promotes the curing reaction. For example, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-
Imidazole compounds such as 4-methylimidazole and 2-heptadecylimidazole, tertiary amine compounds such as triethylamine, benzyldimethylamine, α-methylbenzyldimethylamine, and 1,8-diazabicyclo (5,4,0) undecene-7; Triphenylphosphine, tributylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine,
Organic phosphine compounds such as triphenylphosphine / triphenylborate and tetraphenylphosphine / tetraphenylborate are exemplified. Of these, organic phosphine compounds are preferred from the viewpoint of moisture resistance, and triphenylphosphine is particularly preferably used.

Depending on the application, two or more of these curing catalysts may be used in combination.
The range of 0.5 to 5 parts by weight per 100 parts by weight is preferred.

The amorphous silica (C) in the present invention is composed of 97 to 60% by weight of crushed amorphous silica having an average particle size of 10 μm or less and 3 to 40% by weight of spherical amorphous silica having an average particle size of 4 μm or less. And the average particle size of the spherical amorphous silica is smaller than the average particle size of the crushed amorphous silica. Here, the average particle diameter means a particle diameter (median diameter) at which the cumulative weight becomes 50%, and is a value measured using, for example, a laser diffraction type particle size distribution analyzer.

The average particle size of the crushed amorphous silica is 10 μm.
If the heat resistance exceeds 10 mm, the solder heat resistance becomes insufficient, and if it is 10 μm or less, there is no particular limitation. However, those having a solder heat resistance of 3 μm or more and 10 μm or less are preferably used, and particularly 3 μm or more and less than 7 μm. Is preferably used.

The average particle size of the spherical amorphous silica is 4 μm.
If m is exceeded, the solder heat resistance becomes insufficient. If it is 4 μm or less, there is no particular limitation. However, from 0.01 μm or more and 4 μm or less from the viewpoint of solder heat resistance.

In the amorphous silica (C) of the present invention, it is important that the average particle size of the spherical amorphous silica is smaller than the average particle size of the crushed amorphous silica. When the average particle size of the spherical amorphous silica is larger than the average particle size of the crushed amorphous silica, the solder heat resistance is greatly reduced. The average particle size of the spherical amorphous silica may be smaller than the average particle size of the crushed amorphous silica, but preferably the average particle size of the spherical amorphous silica is 2 times the average particle size of the crushed amorphous silica. / 3 or less, particularly preferably 1/2 or less.

Further, in the present invention, when the weight ratio of the crushed amorphous silica to the spherical amorphous silica is not in the above range, a cured product having excellent solder heat resistance cannot be obtained.

In the present invention, the proportion of the inorganic filler containing amorphous silica (C) is 73 to 88% by weight in the whole composition.
And more preferably 75 to 85 in the whole composition.
% By weight. If the ratio of the inorganic filler to the entire composition is not in the above range, a cured product having excellent solder heat resistance cannot be obtained.

The proportion of the amorphous silica (C) contained in the inorganic filler is not particularly limited. However, in order to exert a more satisfactory effect, the amorphous silica (C) is contained in the inorganic filler. Usually, it is preferable that the content is 80% by weight or more, preferably 90% by weight or more.

The inorganic filler in the present invention is not particularly limited as long as the amorphous silica (C) is contained in an amount of 80% by weight or more in the inorganic filler. Examples include silica, alumina, magnesia, clay, talc, calcium silicate, titanium oxide, antimony oxide, and various ceramics.

In the present invention, the inorganic filler containing amorphous silica (C) is preferably surface-treated with a coupling agent such as a silane coupling agent or a titanate coupling agent before use in terms of moisture resistance reliability. . As the coupling agent, a silane coupling agent such as epoxy silane, amino silane, and mercapto silane is preferably used.

The polystyrene-based block copolymer (D) of the present invention has an aromatic vinyl hydrocarbon polymer block having a glass transition temperature of 25 ° C. or higher, preferably 50 ° C. or higher, and a glass transition temperature of 0 ° C. or lower, preferably It means a linear, radial or branched block copolymer composed of a conjugated diene polymer block at -25 ° C or lower.

The aromatic vinyl hydrocarbon includes styrene, α-methylstyrene, o-methylstyrene and p-methylstyrene.
-Methylstyrene, 1,3-dimethylstyrene, vinylnaphthalene and the like, among which styrene is preferably used.

The conjugated diene includes butadiene (1,3-butadiene) and isoprene (2-methyl-
Examples thereof include 1,3-butadiene), methyl isoprene (2,3-dimethyl-1,3-butadiene), and 1,3-pentadiene. Of these, butadiene and isoprene are preferably used.

The proportion of the aromatic vinyl hydrocarbon polymer block as the glass phase block in the polystyrene block copolymer (D) is 10 to 50% by weight, and the proportion of the conjugated diene polymer block as the rubber phase block is 10 to 50% by weight. 90-5
0% by weight is preferred.

There are many combinations of a glass phase block and a rubber phase block, and any one of them may be used. A diblock copolymer in which a glass phase block and a rubber phase block are bonded one by one, Triblock copolymers with attached phase blocks are particularly preferred. In this case, the number average molecular weight of the glass phase block is preferably 1,000 to 100,000, particularly preferably 2,000.
The number average molecular weight of the rubber phase block is preferably from 5,000 to 200,000, and particularly preferably from 10,000 to 100,000.

The polystyrene-based block copolymer (D) also includes a hydrogenated block copolymer in which some of the unsaturated bonds in the above-mentioned block copolymer have been reduced by hydrogenation.

Here, it is preferable that 25% or less of the aromatic double bond of the aromatic vinyl hydrocarbon polymer block and 80% or more of the aliphatic double bond of the conjugated diene polymer block are hydrogenated.

Preferred specific examples of the polystyrene block copolymer (D) include polystyrene / polybutadiene / polystyrene triblock copolymer (SBS), polystyrene / polyisoprene / polystyrene triblock copolymer (SIS), and SBS. Hydrogenated copolymer (SEB
S), hydrogenated copolymer of SIS, polystyrene / polyisoprene diblock copolymer, hydrogenated copolymer of polystyrene / polyisoprene diblock copolymer (SEP) and the like.

In the present invention, the blending amount of the polystyrene block copolymer (D) is usually 0.2 to 10% by weight, preferably 0.5 to 5% by weight. If the amount is less than 0.2% by weight, the effect of improving solder heat resistance hardly appears. If the amount is more than 10% by weight, the fluidity is reduced and molding becomes difficult, which is not practical.

Further, the epoxy resin composition of the present invention contains a halogen compound such as a halogenated epoxy resin, a flame retardant such as a phosphorus compound, a flame retardant auxiliary such as antimony trioxide,
Colorants such as carbon black, elastomers such as silicone rubber, modified nitrile rubber, and modified polybutadiene rubber, thermoplastic resins such as polyethylene, long-chain fatty acids,
A release agent such as a metal salt of a long-chain fatty acid, an ester of a long-chain fatty acid, an amide of a long-chain fatty acid, or paraffin wax can be arbitrarily added.

The epoxy resin composition of the present invention is preferably melt-kneaded, and is manufactured by melt-kneading using a known kneading method such as a kneader, a roll, a single-screw or twin-screw extruder and a co-kneader. You.

[0044]

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

Examples 1 to 9 and Comparative Examples 1 to 7 The blends shown in Table 1 and the polystyrene block copolymer (D) shown in Table 2 were used in Tables 3 and 4 (Examples) and Table 4, respectively. 5. Dry blending was performed by a mixer at the composition ratio shown in Table 6 (Comparative Example). This is the barrel setting temperature 90 ° C
After melt-kneading using a twin screw extruder, the mixture was cooled and pulverized to produce an epoxy resin composition.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

[0050]

[Table 5]

[0051]

[Table 6]

Using this composition, the following solder heat resistance test was conducted, and the results are shown in Tables 7 and 8.

Solder heat resistance test: An 80-pin QFP device (package size: 17 × 17 × 1.7 mm, chip size: 9 × 9 × 0.5 mm) was tested at 175 ° C. × 120 seconds using a low-pressure transfer molding machine. Molded,
Cured at 175 ° C. for 12 hours. This test device 1
After the six pieces were humidified at 85 ° C./85% RH for a predetermined period of time, they were immersed in a solder bath heated to 260 ° C. for 10 seconds, and the cracked device was determined to be defective. In addition, among the devices immersed in the solder bath, devices in which cracks did not occur were internally observed with an ultrasonic flaw detector to check whether or not the semiconductor element surface had peeled off.

[0054]

[Table 7]

[0055]

[Table 8]

As shown in Table 7, the epoxy resin compositions of the present invention (Examples 1 to 9) have excellent solder heat resistance. In particular, in Examples 3 to 8, when the humidification conditions were strict, it was found that those having a smaller average particle size of the crushed amorphous silica were more excellent in solder heat resistance. In contrast, as shown in Table 8, Comparative Example 1 not containing the epoxy resin (a), Comparative Example 2 not containing the spherical amorphous silica, and the average particle size of the spherical amorphous silica was crushed amorphous. In Comparative Example 5 larger than the average particle size of the fusible silica, Comparative Example 6 and Comparative Example 7 in which the average particle sizes of the crushed amorphous silica and the spherical amorphous silica were respectively out of the range of the present invention, the solder heat resistance was low. bad. Comparative Example 2 containing no spherical amorphous silica or Comparative Example 3 containing no polystyrene-based block copolymer (D),
In Comparative Example 4, peeling was observed on the surface of the semiconductor element even in a device in which a package crack did not occur.

[0057]

The epoxy resin composition of the present invention has excellent solder heat resistance and is useful as an epoxy resin composition for semiconductor encapsulation.

────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI // H01L 23/29 H01L 23/30 R 23/31 (56) References JP-A-4-325515 (JP, A) JP JP-A-4-136024 (JP, A) JP-A-3-119050 (JP, A) JP-A-4-306224 (JP, A) JP-A-4-226123 (JP, A) JP-A-4-50222 (JP) JP-A-2-99552 (JP, A) JP-A-1-266152 (JP, A) JP-A-4-202521 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C08L 63/00-63/10 C08L 53/00-53/02 C08K 3/36 C08G 59/24 C08G 59/62 H01L 23/29

Claims (1)

(57) [Claims] 1. A resin composition comprising, as essential components, an epoxy resin (A), a phenolic curing agent (B), an amorphous silica (C), and a polystyrene block copolymer (D). And the epoxy resin (A) has the formula (I): (However, two of R ^{1 to} R ⁸ are 2,3-epoxypropoxy groups and the rest are selected from a hydrogen atom, a C ₁ -C ₄ lower alkyl group or a halogen atom, and all must be the same.) Epoxy resin (a) represented by
As an essential component, and the amorphous silica (C) is a crushed amorphous silica 9 having an average particle size of 10 μm or less.
7 to 60% by weight and 3 to 40% by weight of spherical amorphous silica having an average particle diameter of 4 μm or less, wherein the average particle diameter of the spherical amorphous silica is smaller than that of the crushed amorphous silica, and The ratio of the inorganic filler containing the crystalline silica (C) is 73
An epoxy resin composition for encapsulating a semiconductor, which is 88% by weight.