JP2501143B2 - 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 which solves the problem of package cracks generated in the soldering process, that is, has excellent solder heat resistance.

[0002]

2. Description of the Related Art Epoxy resins are excellent in heat resistance, moisture resistance, electrical characteristics, adhesiveness, etc., and can be given various characteristics by blending formulation, so they are used as industrial materials such as paints, adhesives and electrical insulation materials. Has been done. For example, as a method for sealing electronic circuit parts such as semiconductor devices, hermetic sealing using metal or ceramics and resin sealing using phenol resin, silicone resin, epoxy resin, etc. have been proposed. However, resin sealing with an epoxy resin is mainly used from the viewpoint of the balance of economy, productivity and physical properties.

On the other hand, recently, densification and automation have also been promoted in mounting components on a printed circuit board. Instead of the conventional "insertion mounting method" in which lead pins are inserted into holes in the substrate, the components are soldered on the surface of the substrate. "Surface mounting method" to attach is becoming popular. Along with that, the package will also be DI
P (dual in-line package) is shifting to thin TSOP (thin small outline package) and QFP (quad flat package) suitable for high-density mounting and surface mounting.

With the shift to the surface mounting method, the soldering process, which has not been a problem so far, has become a big 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 dipping method, a solder reflow method of heating with saturated vapor of an inert liquid or infrared rays is used, and in any method, the entire package is heated to a high temperature of 210 to 270 ° C. It will be. Therefore, the package sealed with the conventional sealing resin is
There was a problem that a crack was generated in the resin portion during soldering, the reliability was lowered, and the product could not be used as a product.

The occurrence of cracks in the soldering process is
It is said that moisture absorbed between the post-curing and the mounting process explodes into steam and expands during soldering heating, and various improvements have been made to the encapsulating resin as a countermeasure. .

Conventionally, an ortho-cresol novolac type epoxy resin is used as an epoxy resin, and a phenol novolac resin is used as a curing agent, and an average particle size is 10 to 20 μm as an inorganic filler.
It was common to use crushed fused silica of m.
The problem of cracking due to heating during surface mounting could not be avoided. Therefore, an epoxy resin having a biphenyl skeleton is used as the epoxy resin, and the fused silica has an average particle size of 1
A method of using crushed silica having a particle size of 2 μm or less and spherical silica having an average particle size of 40 μm or less in combination (JP-A-2-99).
514), a method of using a curing agent in combination with tris (hydroxyphenyl) methane and a phenol aralkyl resin (Japanese Patent Laid-Open No. 1-292029).

[0007]

However, the resins improved by these various methods have been effective to some extent against cracks at the time of soldering, but they are still not sufficient. For example, an epoxy resin having a biphenyl skeleton is used as the epoxy resin, and the fused silica has an average particle diameter of 12 μm.
In the method of using the crushed silica having a particle size of m or less and the spherical silica having an average particle size of 40 μm or less in combination, since the spherical silica having a large particle size is used, crack resistance is low and sufficient solder heat resistance cannot be obtained. Also, in the method of using a combination of tris (hydroxyphenyl) methane and phenolaralkyl resin as the curing agent, the conventional orthocresol novolac type epoxy resin or the epoxidized product of tris (hydroxyphenyl) methane is used as the epoxy resin. The degree of cross-linking density of the cured product is high, so that the water absorption rate of the cured product is high, and the cured product itself is hard and brittle, so that the solder heat resistance is low.

An object of the present invention is to provide a semiconductor encapsulating epoxy resin composition that solves the problem of package cracks that occur during the soldering process, that is, has excellent solder heat resistance.

[0009]

The present inventors have solved the above problems by using a specific epoxy resin, a specific curing agent, and a fused silica composed of a combination of a specific particle size and a specific shape. The inventors have found that an epoxy resin composition that meets the purpose can be obtained, and arrived at the present invention.

That is, the present invention relates to an epoxy resin (A),
A resin composition containing a phenolic curing agent (B) and fused silica (C) as essential components, wherein the epoxy resin (A) is of formula (I).

[0011]

Embedded image

(However, R ^{1 to} R ⁸ are hydrogen atoms, and C ₁ to
Selected from a C ₄ lower alkyl group or a halogen atom,
Not all have to be the same. ) Epoxy resin (a ₁ ) represented by the formula (II)

[0013]

Embedded image

(However, two of R ^{9 to} R ¹⁶ are 2, 3
-Epoxypropoxy group, the rest is hydrogen atom, C ₁
Selected from a lower alkyl group of ˜C ₄ or a halogen atom, and all need not be the same. ) At least one of the epoxy resins (a ₂ ) represented by the formula (III) is contained as an essential component, and the phenol-based curing agent (B) has the formula (III)

[0015]

[Chemical 6]

(Wherein R is selected from a hydrogen atom, a C _{1 to} C ₄ lower alkyl group or a halogen atom, and it is not necessary that all are the same. Further, n is an integer of 0 or more). 97 to 60% by weight of crushed fused silica containing the phenolic compound (b) as an essential component and the fused silica (C) having an average particle size of 10 μm or less.
And spherical fused silica having an average particle size of 4 μm or less 3 to 40% by weight
And an average particle diameter of the spherical fused silica smaller than that of the crushed fused silica, and a proportion of the inorganic filler containing the fused silica (C) is 75 to 90% by weight based on the whole epoxy resin composition. is there.

The reason why the epoxy resin composition of the present invention is excellent in solder heat resistance is not yet clear, but (1) the epoxy resin essential to the present invention is a bifunctional one having only two epoxy groups in one molecule. By being an epoxy resin and by appropriately reducing the number of hydroxyl groups in the phenolic compound essential to the present invention, the crosslink density of the cured product is appropriately reduced to exhibit low water absorption, and (2) the crosslink density of the cured product. The epoxy resin has a highly heat-resistant skeleton such as biphenyl or naphthalene even though the content is low to some extent, and therefore exhibits toughness (high strength and high elongation) at high temperature. (3) Fused silica essential to the present invention The combination of the shape and the grain size shows high strength at high temperature, and local stress may be reduced to suppress crack propagation. From given is believed to exhibit excellent solder heat resistance enough not expected.

The structure of the present invention will be described in detail below.

The epoxy resin (A) in the present invention has the formula (I)

[0020]

[Chemical 7]

(However, R ^{1 to} R ⁸ are hydrogen atoms, and C ₁ to
Selected from a C ₄ lower alkyl group or a halogen atom,
Not all have to be the same. ) Epoxy resin (a ₁ ) represented by the formula (II)

[0022]

Embedded image

(However, two of R ^{9 to} R ¹⁶ are 2, 3
-Epoxypropoxy group, the rest is hydrogen atom, C ₁
Selected from a lower alkyl group of ˜C ₄ or a halogen atom, and all need not be the same. ) It is necessary to contain at least one of the epoxy resins (a ₂ ) represented by ( ₄ ) as an essential component. The epoxy resin (a ₁ ) and the epoxy resin (a ₂ ) are both bifunctional epoxy resins having two epoxy groups in one molecule, and it is common that they have a skeleton structure with extremely high heat resistance. Has exactly the same effect.

Preferred examples of the epoxy resin (a ₁ ) in the present invention include 4,4'-bis (2,3-epoxypropoxy) biphenyl and 4,4'-bis (2,3).
-Epoxypropoxy) -3,3 ', 5,5'-tetramethylbiphenyl, 4,4'-bis (2,3-epoxypropoxy) -3,3', 5,5'-tetramethyl-2
-Chlorobiphenyl, 4,4'-bis (2,3-epoxypropoxy) -3,3 ', 5,5'-tetramethyl-
2-bromobiphenyl, 4,4'-bis (2,3-epoxypropoxy) -3,3 ', 5,5'-tetraethylbiphenyl, 4,4'-bis (2,3-epoxypropoxy) -3, 3 ', 5,5'-tetrabutylbiphenyl and the like are mentioned, and 4,4'-bis (2,3-epoxypropoxy) biphenyl, 4,4'-bis (2,3-epoxypropoxy) -3,3 Particularly preferred is', 5,5'-tetramethylbiphenyl.

Further, a preferred specific example of the epoxy resin (a ₂ ) in the present invention is 1,5-di (2,2)
3-epoxypropoxy) naphthalene, 1,5-di (2,3-epoxypropoxy) -7-methylnaphthalene, 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 (2,2
3-epoxypropoxy) -4,8-dimethylnaphthalene, 2-bromo-1,6-di (2,3-epoxypropoxy) naphthalene, 8-bromo-1,6-di (2,3-)
Epoxypropoxy) naphthalene, 2,7-di (2,3
-Epoxypropoxy) naphthalene and the like,
1,5-di (2,3-epoxypropoxy) naphthalene, 1,6-di (2,3-epoxypropoxy) naphthalene and 2,7-di (2,3-epoxypropoxy) naphthalene are particularly preferred.

The ratio of the epoxy resins (a ₁ ) and (a ₂ ) contained in the epoxy resin (A) is not particularly limited, but in order to exert a more sufficient effect, the epoxy resin (a ₁₎ ) And (a ₂ ) at least 50% by weight is preferably contained in the epoxy resin (A).

Further, the epoxy resin (A) in the present invention
Is not particularly limited as long as at least one of the epoxy resins (a ₁ ) and (a ₂ ) is contained in the epoxy resin (A) in an amount of 50% by weight or more, but a preferred specific example is an orthocresol novolac type epoxy resin. , Phenol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, halogenated epoxy resin and the like.

In the present invention, the compounding amount of the epoxy resin (A) is usually 3 to 20% by weight, preferably 4 to 15% by weight.
Is.

Phenolic curing agent (B) in the present invention
Is of formula (III)

[0030]

[Chemical 9]

(Wherein R is selected from a hydrogen atom, a C ₁ -C ₄ lower alkyl group or a halogen atom, and it is not necessary that they are all the same. In addition, n represents an integer of 0 or more). It is necessary to contain the above-mentioned phenolic compound (b) as an essential component.

Phenolic compound (b) in the present invention
Preferable specific examples of the compound include a phenol aralkyl resin obtained by reacting an aralkyl ether and a phenol with a Friedel-Crafts catalyst, and particularly, a compound represented by the formula (IV)

[0033]

[Chemical 10]

A phenol aralkyl resin represented by the formula (n is an integer of 0 or more) is preferably used.

Among these phenol aralkyl resins, a resin having a hydroxyl group equivalent of 130 to 220 is preferably used, and a resin having a hydroxyl group equivalent of 150 to 200 is particularly preferably used. Regarding the softening point of the phenol aralkyl resin, a resin having a temperature of 50 to 110 ° C. is preferably used,
A resin of 60 to 90 ° C. is particularly preferably used.

The ratio of the phenolic compound (b) contained in the phenolic curing agent (B) is not particularly limited, but in order to exert a more sufficient effect, the phenolic compound (b) is mixed with phenol. 5 in the system hardener (B)
It is preferable to contain 0% by weight or more.

The phenolic curing agent (B) in the present invention is cured by reacting the rest with the epoxy resin (A) if the curing agent contains the phenolic compound (b) in an amount of 50% by weight or more. It is not particularly limited as long as it allows it, but preferable specific examples include, for example, phenol novolac resin, cresol novolac resin, tris (hydroxyphenyl) methane, 1,1,2-tris (hydroxyphenyl) ethane, 1,1,3- Examples include tris (hydroxyphenyl) propane, bisphenol A, bisphenol F, and dihydroxybiphenyl.

In the present invention, the compounding amount of the phenolic curing agent (B) is usually 3 to 20% by weight, preferably 4 to.
15% by weight. Further, 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 0.7-from the viewpoint of mechanical properties and moisture resistance.
It is preferably in the range of 1.3, particularly 0.8-1.
It is preferably in the range of 2.

Further, in the present invention, the epoxy resin (A)
A curing catalyst may be used to accelerate the curing reaction of the phenol-based curing agent (B). The curing catalyst is not particularly limited as long as it accelerates the curing reaction, and 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, 1,8-diazabicyclo (5,4,0) undecene-7, Triphenylphosphine, tributylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine,
Examples thereof include organic phosphine compounds such as triphenylphosphine / triphenylborate and tetraphenylphosphine / tetraphenylborate. Among them, organic phosphine compounds are preferable, and triphenylphosphine is particularly preferably used, from the viewpoint of moisture resistance.

Two or more kinds of these curing catalysts may be used in combination depending on the use, and the addition amount thereof is the epoxy resin (A).
The range of 0.5 to 5 parts by weight is preferable with respect to 100 parts by weight. The fused silica (C) in the present invention has an average particle size of 10 μm.
A mixture of 97 to 60% by weight of crushed fused silica having a diameter of m or less and 3 to 40% by weight of spherical fused silica having an average particle diameter of 4 μm or less, wherein the average particle size of the spherical fused silica is smaller than the average particle size of the crushed fused silica Is. Here, the average particle size means a particle size (median size) at which the cumulative weight becomes 50%, and is a value measured by using, for example, a laser diffraction type particle size distribution measuring device.

If the average particle size of the crushed fused silica exceeds 10 μm, the solder heat resistance becomes insufficient, and if it is 10 μm or less, no particular limitation is imposed, but from the viewpoint of solder heat resistance, 3 μm or more and 10 μm or less. Those having a thickness of 3 μm or more and less than 7 μm are particularly preferably used. Here, the crushed fused silica may be used in combination of two or more kinds having different average particle sizes as long as the average particle size is 10 μm or less.

The average particle diameter of the spherical fused silica is 4 μm.
If it exceeds 4 μm, the solder heat resistance becomes insufficient, and if it is 4 μm or less, no particular limitation is imposed, but from the viewpoint of solder heat resistance, 0.01 μm or more and 4 μm or less are particularly preferably used. Here, the spherical fused silica has an average particle size of 4
If the average particle size is not more than μm, two or more kinds having different average particle sizes may be used in combination.

In the fused silica (C) of the present invention, it is important that the average particle diameter of the spherical fused silica is smaller than that of the crushed fused silica. If the average particle size of the spherical fused silica is larger than the average particle size of the crushed fused silica, the solder heat resistance is significantly reduced. The average particle size of the spherical fused silica may be smaller than the average particle size of the crushed fused silica, but the average particle size of the spherical fused silica is preferably 2/3 or less of the average particle size of the crushed fused silica, and particularly preferred. Is 1/2 or less.

Further, if the weight ratio of the crushed fused silica and the spherical fused silica is not within 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 fused silica (C) is 75 to 90% by weight, and more preferably 75 to 87% by weight, based on the whole composition. If the ratio of the inorganic filler to the total composition is not within the above range, a cured product having excellent solder heat resistance cannot be obtained. The proportion of the fused silica (C) contained in the inorganic filler is not particularly limited, but in order to exert a more sufficient effect, the fused silica (C) is usually contained in the inorganic filler in an amount of 80% by weight.
The above content, preferably 90% by weight or more, is preferable.

Further, the inorganic filler in the present invention is not particularly limited as long as the above-mentioned fused silica (C) is contained in the inorganic filler in an amount of 80% by weight or more, but a preferable specific example is crystalline silica, Examples thereof include alumina, magnesia, clay, talc, calcium silicate, titanium oxide, antimony oxide, various ceramics and the like.

In the present invention, it is preferable from the viewpoint of moisture resistance reliability that the inorganic filler containing fused silica (C) is surface-treated in advance with a coupling agent such as a silane coupling agent or a titanate coupling agent. As the coupling agent, silane coupling agents such as epoxysilane, aminosilane, mercaptosilane and the like are preferably used.

The epoxy resin composition of the present invention includes a halogenated epoxy resin, a flame retardant such as a halogen compound and a phosphorus compound, a flame retardant aid such as antimony trioxide, a colorant such as carbon black, a silicone rubber and a modified nitrile rubber. , Modified polybutadiene rubber, modified silicone oil and other elastomers, polyethylene and other thermoplastic resins,
A release agent such as a long-chain fatty acid, a metal salt of a long-chain fatty acid, an ester of a long-chain fatty acid, paraffin wax, and modified silicone oil can be optionally added.

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

[0050]

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

Examples 1-12, Comparative Examples 1-8 The formulations shown in Table 1 and Table 2 were converted into Table 3 (Examples 1 to 1).
2) and the composition ratios shown in Table 4 (Comparative Examples 1 to 8) were blended using a mixer. This is barrel setting temperature 9
After melt-kneading with a twin-screw extruder at 0 ° C., cooling and pulverization were performed to produce an epoxy resin composition.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

Using this epoxy resin composition, a solder heat resistance test, a bending test, and a water absorption rate measurement described below were carried out.

Solder heat resistance test: 80 pin QFP device (package size: 17 × 17 × 1.7 mm, chip size: 9 × 9 × 0.5 mm) was molded under the condition of 175 ° C. × 120 seconds using a low-voltage transfer molding machine. Then 1
Cured at 75 ° C. for 12 hours. The 16 test devices were humidified in an atmosphere of 85 ° C / 85% RH for a predetermined time, and then heated to 215 ° C to produce VPS (vapor phase
It was immersed in a solder reflow bath for 90 seconds to make a device with cracks defective.

Bending test: ASTM (D790-58T)
The test piece conforming to the above standard was molded using a low-pressure transfer molding machine under the condition of 175 ° C. × 120 seconds and cured at 175 ° C. for 12 hours. Using this test piece, the ambient temperature was 215 ° C.
The bending test was performed by the method according to ASTM (D790-58T), and the bending strength and the bending deflection rate were calculated.

Water absorption measurement: 80 used in solder heat resistance test
The water absorption was measured when the pinQFP device was humidified at 85 ° C./85% RH for a predetermined time.

As shown in Table 5, the epoxy resin compositions of the present invention (Examples 1 to 12) have excellent solder heat resistance. On the other hand, as shown in Table 6, Comparative Example 1 not containing the epoxy resins (a ₁ ) and (a ₂ ) and Comparative Example 2 not containing the phenolic compound (b) have poor solder heat resistance. Further, the average particle diameters of the crushed fused silica and the spherical fused silica are out of the range of the present invention. Comparative Examples 3 and 4, the ratio of the spherical fused silica in the fused silica (C) is out of the range of the present invention. Comparative Example 5 and Comparative Example 6,
In Comparative Example 7 in which the average particle size of the spherical fused silica is larger than the average particle size of the crushed fused silica, the solder heat resistance is poor.
Further, even in Comparative Example 8 in which the ratio of the inorganic filler to the whole is less than the range of the present invention, the solder heat resistance is deteriorated.

[0061]

[Table 5]

[0062]

[Table 6]

[0063]

The epoxy resin composition of the present invention is excellent in solder for semiconductor encapsulation by using a specific epoxy resin, a specific curing agent, and fused silica composed of a combination of specific particle size and shape. Has heat resistance.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 23/31

Claims (1)

(57) [Claims] 1. A resin composition comprising an epoxy resin (A), a phenolic curing agent (B), and fused silica (C) as essential components, wherein the epoxy resin (A) has the formula (I). ) [Chemical 1] (However, R ^{1 to} R ⁸ are selected from a hydrogen atom, a C _{1 to} C ₄ lower alkyl group or a halogen atom, and it is not necessary that all are the same.)
(A ₁ ) and the formula (II): (However, two of R ^{9 to} R ¹⁶ are 2,3-epoxypropoxy groups, and the rest are selected from a hydrogen atom, a C _{1 to} C ₄ lower alkyl group or a halogen atom, and all must be the same. Of the epoxy resin (a ₂ ) represented by
The phenolic curing agent (B) is represented by the formula (III): (However, R is selected from a hydrogen atom, a C _{1 to} C ₄ lower alkyl group or a halogen atom, and it is not necessary that all are the same. In addition, n represents an integer of 0 or more.) The compound (b) is contained as an essential component, and the fused silica (C) has an average particle size of 10 μm or less and 97 to 60% by weight of crushed fused silica and an average particle size of 4 μm.
The average particle size of the spherical fused silica is 3 to 40% by weight, the average particle size of the spherical fused silica is smaller than that of the crushed fused silica, and the proportion of the inorganic filler containing the fused silica (C) is 75% of the total. ~ 90 wt% epoxy resin composition.