JPH04370137A - Epoxy resin composition for sealing semiconductor - Google Patents

Abstract

PURPOSE:To provide an epoxy resin composition for semiconductor sealing use, containing a specific epoxy resin, an amorphous silica having specific shape and particle diameter and a specific thermtplastic elastomer and having excellent soldering heat-resistance. CONSTITUTION:The objective epoxy resin composition for sealing semiconductor is composed of (A) 4-20wt.% of an epoxy resin containing >=50wt.% of an epoxy compound of formula (two of R<1> to R<8> are 2,3-epoxypropoxy group and the others are H, 1-4C alkyl or halogen), (B) 3-15wt.% of a phenolic hardener (e.g. bisphenol A) and optionally a curing catalyst, (C) 73-88wt.% of an inorganic filler containing >=80wt.% of amorphous silica composed of (C1) 97-60wt.% of crushed amorphous silica having an average particle diameter of <=10mum and (C2) 3-40wt.% of a spherical amorphous silica having an average particle diameter of <=4mum and smaller than that of the component C1 and (D) 0.2-10wt.% of a polystyrene-based block copolymer (e.g. polystyrene/ polybutadiene/polystyrene block copolymer).

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 that eliminates the problem of package cracks occurring during the soldering process, that is, has excellent solder heat resistance.

0002

[Prior art] Epoxy resins have excellent heat resistance, moisture resistance, electrical properties, adhesive properties, etc., and can be given various properties depending on the formulation, so they are used as industrial materials such as paints, adhesives, and electrical insulation materials. has been done. For example, as methods for encapsulating electronic circuit components such as semiconductor devices, hermetic seals using metals and ceramics, and resin encapsulation using phenolic resins, silicone resins, epoxy resins, etc., have traditionally been used. In view of the balance of physical properties, resin sealing using epoxy resin has become the main method.

Particularly recently, higher density mounting of components on printed circuit boards has been progressing, and instead of the conventional "insertion mounting method" in which lead pins are inserted into holes in the board, a "surface mounting method" in which components are soldered to the surface of the board is being used. ``mounting method'' has become popular. Along with this, packages are also shifting from the conventional DIP (dual inline package) to thin TSOP (thin small outline package) and QFP (quad flat package), which are suitable for high-density mounting and surface mounting. .

[0004] With the shift to the surface mounting method, the soldering process, which did not pose much of a problem in the past, has become a major problem. In the conventional pin insertion mounting method, only the leads are partially heated during the soldering process, but in the surface mounting method, the entire package is immersed in a heating medium and heated. Soldering methods used in the surface mount method include immersion in a solder bath, saturated vapor of an inert liquid, and a solder reflow method in which heating is performed using infrared rays, but in either method, the entire package is heated to a high temperature of 210 to 270 degrees Celsius. It turns out. Therefore, packages sealed with conventional sealing resin,
There was a problem that cracks occurred in the resin part during soldering, reducing reliability and making it unusable as a product.

[0005] The occurrence of cracks in the soldering process is
This is said to be caused by moisture absorbed between post-curing and the mounting process that explosively turns into water vapor and expands during soldering heat, and various improvements to the sealing resin are being considered as countermeasures. .

Conventionally, an orthocresol novolac type epoxy resin was used as the epoxy resin, a phenol novolac resin was used as the curing agent, and an average particle size of 10 to 20 μm was used as the inorganic filler.
Although it has been common to use crushed amorphous silica of 200 m, it has not been possible to avoid the problem of cracks occurring due to heating during surface mounting. Therefore, in order to suppress the occurrence of cracks during the soldering process, an epoxy resin having a biphenyl skeleton was used as the epoxy resin, and crushed amorphous silica with an average particle size of 40 μm or less was used as an inorganic filler.
A method using a combination of spherical amorphous silica with a particle size of μm or less (Japanese Patent Application Laid-open No. 2-99514) has been proposed.

[0007] However, although the resins improved by these various methods seem to be effective to some extent in preventing cracks during soldering, their soldering heat resistance is still insufficient, and they do not cause damage to the outside of the package. The problem of deterioration of moisture resistance reliability due to peeling between the surface of the semiconductor element and the sealing material has also become important even if no cracks occur.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an epoxy resin composition for semiconductor encapsulation that eliminates the problem of package cracks occurring in the soldering process, that is, has excellent solder heat resistance.

[0009]

[Means for Solving the Problems] The present inventors have solved the above problems by blending a specific epoxy resin, an inorganic filler with a specific shape and particle size, and a specific thermoplastic elastomer. The present invention was achieved by discovering that an epoxy resin composition meeting the above requirements can be obtained.

[0010] That is, the present invention provides an epoxy resin (A),
A resin composition comprising a phenolic curing agent (B), amorphous silica (C) and a polystyrene block copolymer (D) as essential components, wherein the epoxy resin (A) has the formula (I )

[0011]

[Case 2]

(However, two of R1 to R8 are 2
, 3-epoxypropoxy group, the rest are hydrogen atoms,
They are selected from C1 to C4 lower alkyl groups or halogen atoms, and do not need to be all the same. ) contains the epoxy resin (a) represented by (a) as an essential component, and the amorphous silica (C) is 97 to 60% by weight of crushed amorphous silica with an average particle size of 10 μm or less and an average particle size of 4 μm or less An inorganic filler consisting of 3 to 40% by weight of spherical amorphous silica, the average particle size of the spherical amorphous silica being smaller than the average particle size of crushed amorphous silica, and containing amorphous silica (C). This is an epoxy resin composition in which the proportion of 73% to 88% by weight of the whole.

The reason why the epoxy resin composition of the present invention has excellent soldering heat resistance is not yet clear, but (1) the epoxy resin (a) has only two epoxy groups in one molecule; (2) The epoxy resin (a) has a rigid naphthalene skeleton. (3) Amorphous silica (
The special combination of shape and particle size of C) shows high strength at high temperatures, reduces local stress and suppresses crack propagation, and (4) the polystyrene block copolymer (D) exhibits high strength over a wide temperature range. The effects of mitigating the strain and stress generated between the semiconductor element and the cured epoxy resin work synergistically, resulting in excellent soldering heat resistance that cannot be expected from the individual contributions of each component. This seems to indicate that

The configuration of the present invention will be explained in detail below.

The epoxy resin (A) in 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, 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- Examples include 1,6-di(2,3-epoxypropoxy)naphthalene, 2,7-di(2,3-epoxypropoxy)naphthalene, and especially 1,5-di(2,3-epoxypropoxy)naphthalene.
Di(2,3-epoxypropoxy)naphthalene, 1,6
-di(2,3-epoxypropoxy)naphthalene,
2,7-di(2,3-epoxypropoxy)naphthalene is preferred.

[0017] There is no particular restriction on the proportion of epoxy resin (a) contained in epoxy resin (A), but in order to exhibit a more sufficient effect, it is necessary to
It is preferable that the epoxy resin (A) contains 50% by weight or more of the following.

[0018] Furthermore, the epoxy resin (A) in the present invention
The rest 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, but preferred specific examples include orthocresol novolac type epoxy resin, phenol novolac type epoxy resin, and bisphenol A. Examples include biphenol type epoxy resin, bisphenol F type epoxy resin, and biphenol type epoxy resin.

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

[0020] Phenolic curing agent (B) in the present invention
is not particularly limited as long as it reacts with the epoxy resin (A) to cure it, but preferred specific examples include phenol novolak resin, cresol novolac resin, phenol aralkyl resin, bisphenol A, bisphenol F, etc. .

In the present invention, a phenolic curing agent (B
) is usually 3 to 15% by weight, preferably 4 to 12% by weight.
Weight%. Furthermore, the compounding 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 from 0.7 to 0.7 from the viewpoint of mechanical properties and moisture resistance.
It is preferably in the range of 1.3, particularly 0.8 to 1.2.

[0022] Furthermore, in the present invention, epoxy resin (A)
A curing catalyst may be used to promote the curing reaction between the curing agent and the phenolic curing agent (B). The curing catalyst is not particularly limited as long as it promotes the curing reaction, and examples thereof include 2-methylimidazole, 2-phenylimidazole, and 2-phenyl-
Imidazole compounds such as 4-methylimidazole and 2-heptadecylimidazole, tertiary amine compounds such as triethylamine, benzyldimethylamine, α-methylbenzyldimethylamine, 1,8-diazabicyclo(5,4,0)undecene-7, Triphenylphosphine, tributylphosphine, tri(p-methylphenyl)
Examples include organic phosphine compounds such as phosphine, tri(nonylphenyl)phosphine, triphenylphosphine/triphenylborate, and tetraphenylphosphine/tetraphenylborate. Among them, from the viewpoint of moisture resistance, organic phosphine compounds are preferred, and triphenylphosphine is particularly preferably used.

[0023] These curing catalysts may be used in combination of two or more depending on the application, and the amount added is determined by the amount of the epoxy resin (A).
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 with an average particle size of 10 μm or less and 3 to 40% by weight of spherical amorphous silica with an average particle size of 4 μm or less. The average particle size of the spherical amorphous silica is smaller than the average particle size of the crushed amorphous silica. The average particle size herein means the particle size (median diameter) that accounts for 50% of the cumulative weight, and is a value measured using, for example, a laser diffraction particle size distribution analyzer.

[0025] The average particle size of crushed amorphous silica is 10 μm.
If it exceeds 10 μm, the soldering heat resistance becomes insufficient, and if it is 10 μm or less, there is no particular restriction, but from the viewpoint of soldering heat resistance, 3 μm or more and 10 μm or less are preferably used, especially 3 μm or more and less than 7 μm. Those are preferably used.

[0026] Furthermore, the average particle size of the spherical amorphous silica is 4μ.
If it exceeds m, the soldering heat resistance becomes insufficient, and if it is 4 μm or less, there is no particular restriction, but from the viewpoint of soldering heat resistance, 0.01 μm or more and 4 μm or less are particularly preferably used.

In the amorphous silica (C) used in 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. If the average particle size of the spherical amorphous silica is larger than the average particle size of the crushed amorphous silica, the soldering heat resistance will be 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.

Furthermore, in the present invention, if the weight ratio of crushed amorphous silica to spherical amorphous silica is not within the above range, a cured product with excellent soldering 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 of the entire composition.
and more preferably 75 to 85 in the entire composition.
Weight%. If the ratio of the inorganic filler to the entire composition is not within the above range, a cured product with excellent soldering heat resistance cannot be obtained.

Amorphous silica (C
) There is no particular restriction on the proportion of amorphous silica (C), but in order to exhibit a more sufficient effect, the inorganic filler should normally contain 80% by weight or more, preferably 90% by weight or more of amorphous silica (C). preferable.

Further, the inorganic filler in the present invention is not particularly limited as long as it contains the above-mentioned amorphous silica (C) in an amount of 80% by weight or more, but as a preferred specific example, crystalline silica 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 used after being surface-treated with a coupling agent such as a silane coupling agent or a titanate coupling agent from the viewpoint of moisture resistance reliability. . As the coupling agent, silane coupling agents such as epoxysilane, aminosilane, and mercaptosilane are preferably used.

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

[0034] Examples of the aromatic vinyl hydrocarbons include styrene, α-methylstyrene, o-methylstyrene, and p-methylstyrene.
-Methylstyrene, 1,3-dimethylstyrene, vinylnaphthalene, etc. Among them, styrene is preferably used.

As the conjugated diene, butadiene (
1,3-butadiene), isoprene (2-methyl-1,
Among them, butadiene and isoprene are preferably used.

The proportion of the aromatic vinyl hydrocarbon polymer block, which is 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, which is the rubber phase block, is 10 to 50% by weight. 90-5
0% by weight is preferred.

There are many combinations of the glass phase block and the rubber phase block, and any of them may be used. Particularly preferred are triblock copolymers in which phase blocks are combined. The number average molecular weight of the glass phase block in this case is preferably 1,000 to 100,000, particularly preferably 2,000.
The number average molecular weight of the rubber phase block is preferably 5,000 to 200,000, particularly preferably 10,000 to 100,000.

[0038] The polystyrene block copolymer (D) also includes a hydrogenated block copolymer in which a part of the unsaturated bonds of the above block copolymer is reduced by hydrogenation.

Preferably, 25% or less of the aromatic double bonds in the aromatic vinyl hydrocarbon polymer block and 80% or more of the aliphatic double bonds in 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), a hydrogenated copolymer of SIS, a polystyrene/polyisoprene diblock copolymer, a 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 it is less than 0.2% by weight, there will be little effect of improving soldering heat resistance, and if it exceeds 10% by weight, the fluidity will decrease and molding will become difficult, making it impractical.

Furthermore, 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 aid 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 a paraffin wax can be optionally added.

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

[0044]

[Examples] The present invention will be specifically explained below with reference to Examples.

Examples 1 to 9, Comparative Examples 1 to 7 The formulations shown in Table 1 and the polystyrene block copolymer (D) shown in Table 2 were prepared in Tables 3, 4 (Examples) and Table 4, respectively. 5.Table 6
Dry blending was carried out using a mixer at the composition ratio shown in (Comparative Example). This was melt-kneaded using a twin-screw extruder with a barrel set temperature of 90°C, and then 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 soldering 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 x 17 x 1.7 mm, chip size: 9 x 9 x 0.5 mm) was heated at 175°C for 120 seconds using a low-pressure transfer molding machine. Molded,
It was cured at 175°C for 12 hours. This test device 1
After humidifying the six devices at 85° C./85% RH for a predetermined time, they were immersed in a solder bath heated to 260° C. for 10 seconds, and devices with cracks were judged as defective. Furthermore, among the devices immersed in the solder bath, the devices in which no cracks occurred were internally observed using an ultrasonic flaw detector to check for peeling on the surface of the semiconductor element.

[0054]

[Table 7]

[0055]

[Table 8]

As seen in Table 7, the epoxy resin compositions of the present invention (Examples 1 to 9) have excellent soldering heat resistance. In particular, in Examples 3 to 8, it was found that when the humidification conditions were made stricter, the crushed amorphous silica having a smaller average particle size had better soldering heat resistance. On the other hand, Table 8
As shown in Comparative Example 1 which does not contain epoxy resin (a), Comparative Example 2 which does not contain spherical amorphous silica, the average particle size of spherical amorphous silica is the average particle size of crushed amorphous silica. Comparative Example 5, which is larger, Comparative Example 6, and Comparative Example 7 in which the average particle diameters of crushed amorphous silica and spherical amorphous silica are out of the range of the present invention, respectively, have poor solder heat resistance. Furthermore, in Comparative Example 2, which does not contain spherical amorphous silica, and Comparative Examples 3 and 4, which do not contain polystyrene-based block copolymer (D), peeling was observed on the surface of the semiconductor element even in devices where package cracks did not occur. .

[0057]

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

Claims (1)

[Claims] 1. A resin composition comprising an epoxy resin (A), a phenolic curing agent (B), an amorphous silica (C), and a polystyrene block copolymer (D) as essential components. , the epoxy resin (A) has the formula (I
) [Chemical formula 1] (However, two of R1 to R8 are 2,3-epoxypropoxy groups, and the rest are hydrogen atoms, C1 to C4
are selected from lower alkyl groups or halogen atoms, and do not need to be all the same. ) contains the epoxy resin (a) represented by (a) as an essential component, and the amorphous silica (C) is 97 to 60% by weight of crushed amorphous silica with an average particle size of 10 μm or less and an average particle size of 4 μm or less An inorganic filler consisting of 3 to 40% by weight of spherical amorphous silica, the average particle size of the spherical amorphous silica being smaller than the average particle size of crushed amorphous silica, and containing amorphous silica (C). An epoxy resin composition for semiconductor encapsulation, in which the proportion of the composition is 73 to 88% by weight.