JP3147402B2 - Epoxy 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 composition for semiconductor encapsulation which is excellent in solder heat resistance, humidity resistance and low stress.

[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 for sealing electronic circuit components such as semiconductor devices, a hermetic seal made of metal or ceramic and a phenol resin, silicone resin,
Resin sealing using an epoxy resin or the like has been proposed. However, resin sealing with epoxy resin is mainly used in terms of balance between economy, productivity, and physical properties.

On the other hand, in recent years, the density and automation of component mounting on a printed circuit board have been advanced, and instead of the conventional "insertion mounting method" in which lead pins are inserted into holes in the board, components are soldered on the surface of the board. “Surface mounting method” has become popular. Along with that, the package is also the conventional D
QFP (Quad Flat Package) suitable for high density mounting and surface mounting from IP (Dual Inline Package)
Package) or SOP (small outline package).

[0005] With the shift to the surface mounting method, the soldering process, which has not been much of a problem in the past, 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. Soldering methods for surface mounting include solder bath immersion and heating with saturated vapor of inert gas (vapor phase method).
And an infrared reflow method are used. In any case, the entire package is heated to a high temperature of 210 to 270 ° C. Therefore, a conventional package sealed with a sealing resin has a problem that cracks occur in the resin portion at the time of soldering and an interface between the chip and the resin is peeled off, so that the reliability is reduced and the package cannot be used as a product.

The generation of cracks in the soldering process and the separation of the interface between the chip and the resin are caused by the fact that the moisture absorbed between the post-curing and the mounting process explosively turns into steam and expands during soldering heating. As a countermeasure, a method of shipping the post-cured package in a completely dried and sealed container is used.

Various studies have been made to improve sealing resins.
For example, adding an epoxy resin having a naphthalene skeleton,
Method for achieving low stress of resin (JP-A-2-88621)
And Japanese Patent Application Laid-Open No. 2-110958).

On the other hand, when a semiconductor is sealed with an epoxy resin, the linear expansion coefficient of the epoxy resin is much larger than that of the semiconductor, so that a thermal stress is applied to the semiconductor element due to a temperature change. There is a problem that current leaks due to sliding, cracks occur in the passivation film or the sealing resin itself, and reliability is reduced.
In order to solve this problem and reduce the stress of the sealing resin, it is effective to lower the coefficient of linear expansion of the sealing resin and to lower the elastic modulus.

In order to reduce the linear expansion coefficient of the sealing resin, there are known a method of selecting the kind of the filler and a method of filling the filler at a high level.

In order to lower the elastic modulus of the sealing resin, a method of adding an elastomer component is effective. For example, a method of adding a styrene-based block copolymer (Japanese Patent Application Laid-open No. Sho 63)
No. 251419) has been proposed.

[0011]

However, the method of enclosing a dry package in a container has disadvantages in that the manufacturing process and the handling of the product are complicated and the product price is high.

[0012] The resins improved by various methods have each been effective little by little, but are still not sufficient. Add an epoxy resin having a naphthalene skeleton,
Method for achieving low stress of resin (JP-A-2-88621)
Japanese Patent Application Laid-Open No. HEI 2-110958) is effective in preventing cracks in the resin portion during soldering, but when a large chip is used, the interface between the chip and the resin is peeled off, and the moisture resistance reliability is reduced. was there.

On the other hand, in order to lower the elastic modulus of the sealing resin, a method of lowering the stress of the epoxy resin by adding a styrene-based block copolymer (Japanese Patent Laid-Open No. 63-251)
419) is effective and effective in preventing cracks in the resin portion during soldering, but did not solve the problem of separation at the interface between the chip and the resin.

An object of the present invention is to solve the problem that the interface between the chip and the resin, which is generated in the soldering step, of the package using such a large chip is separated, and the reliability of the semiconductor element is not reduced and the semiconductor element due to the temperature change can be provided. An object of the present invention is to provide an epoxy composition for semiconductor encapsulation having a small thermal stress, that is, excellent in solder heat resistance, moisture resistance reliability and low stress.

[0015]

Means for Solving the Problems The present inventors have achieved the above object by adding a modified styrene-based block copolymer to an epoxy resin having a specific structure, and have achieved a semiconductor encapsulant meeting the object. The inventors have found that an epoxy composition can be obtained, and have reached the present invention.

That is, the present invention provides an epoxy resin (A),
A resin composition comprising a curing agent (B), a filler (C), and a modified styrene-based block copolymer (D) as essential components, wherein the epoxy resin (A) has the following formula (I)

[0017]

Embedded image

(However, two of R ^{1 to} R ⁸ are represented by 2,
Represents a 3-epoxypropoxy group, and the others represent a hydrogen atom, a halogen atom or an alkyl group having 1 to 4 carbon atoms. )
Wherein the proportion of the filler (C) is 60 to 90% by weight of the whole.
Wherein the modified styrenic block copolymer (D) is obtained by copolymerizing or grafting an unsaturated carboxylic acid or a derivative thereof to a styrenic block copolymer. It provides things.

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

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

[0021]

Embedded image

(However, two of R ^{1 to} R ⁸ are 2,
Represents a 3-epoxypropoxy group, and the others represent a hydrogen atom, a halogen atom or an alkyl group having 1 to 4 carbon atoms. )
It is important to contain the epoxy resin (a) having a skeleton represented by the following formula as an essential component from the viewpoint of solder heat resistance and moisture resistance. In the above formula (I), two of R ^{1 to} R ⁸ are a 2,3-epoxypropoxy group, and as other preferable six specific examples, a hydrogen atom, a methyl group, an ethyl group, a propyl group, i-propyl group, n-butyl group, se
Examples thereof include a c-butyl group, a tert-butyl group, a chlorine atom and a bromine atom.

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.

The epoxy resin (A) in the present invention can contain the above-mentioned epoxy resin (a) in combination with another epoxy resin other than the epoxy resin (a). Other epoxy resins that can be used in combination include, for example, cresol novolak type epoxy resin, phenol novolak type epoxy resin, biphenyl type epoxy resin, various novolak type epoxy resins synthesized from bisphenol A and resorcin, and bisphenol A. Type epoxy resin, linear aliphatic epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, halogenated epoxy resin and the like.

The ratio of the epoxy resin (a) contained in the epoxy resin (A) is not particularly limited, and the effect of the present invention is exhibited if the epoxy resin (a) is contained as an essential component. In order to exert a sufficient effect, it is necessary that the epoxy resin (a) is usually contained in the epoxy resin (A) in an amount of 50% by weight or more, preferably 70% by weight or more.

In the present invention, the amount of the epoxy resin (A) is usually 4 to 20% by weight, preferably 6 to 18% by weight.
It is.

The curing agent (B) in the present invention is not particularly limited as long as it is cured by reacting with the epoxy resin (A). Specific examples thereof include a phenol novolak resin, a cresol novolak resin, and a bispheno resin. -Various novolak resins synthesized from phenol A and resorcinol, phenolic hardeners such as various polyhydric phenol compounds, acid anhydrides such as maleic anhydride, phthalic anhydride, pyromellitic anhydride and metaphenylenediamine, diamino And aromatic amines such as diphenylmethane and diaminodiphenylsulfone. For semiconductor encapsulation, a phenol-based curing agent is preferably used from the viewpoint of heat resistance, moisture resistance and storage stability, and two or more curing agents may be used in combination depending on the application.

In the present invention, the amount of the curing agent (B) is usually 2 to 15% by weight, preferably 3 to 10% by weight. Furthermore, the mixing ratio of the epoxy resin (A) and the curing agent (B) is such that the chemical equivalent ratio of (B) to (A) is 0.7 to 1.3, particularly 0, from the viewpoint of mechanical properties and moisture resistance. .8-
It is preferably in the range of 1.2.

In the present invention, the epoxy resin (A)
A curing catalyst may be used for accelerating the curing reaction between the curing agent and the curing agent (B). The curing catalyst is not particularly limited as long as it promotes the curing reaction. For example, 2-methylimidazole,
Imidazole compounds such as 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole, triethylamine, benzyldimethylamine, α-methylbenzyl Tertiary amine compounds such as dimethylamine, 2- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol, 1,8-diazabicyclo (5,4,0) undecene-7, zirconium tetra Organometallic compounds such as methoxide, zirconium tetrapropoxide, tetrakis (acetylacetonato) zirconium, tri (acetylacetonato) aluminum and triphenylphosphine, trimethylphosphine;
Organic phosphine compounds such as triethylphosphine, tributylphosphine, tri (p-methylphenyl) phosphine, and tri (nonylphenyl) phosphine are exemplified. Of these, organic phosphine compounds are preferred from the viewpoint of moisture resistance, and triphenylphosphine is particularly preferably used. These curing catalysts may be used in combination of two or more depending on the use.
The range of 0.5 to 5 parts by weight per 100 parts by weight is preferred.

The filler (C) in the present invention includes fused silica, crystalline silica, silicon nitride, silicon carbide, calcium carbonate, magnesium carbonate, alumina, magnesia, clay, talc, calcium silicate, titanium oxide,
Asbestos, glass fibers and the like can be added.
Among them, fused silica is preferably used from the viewpoint of low stress.

Here, the fused silica means amorphous silica having a true specific gravity of 2.3 or less. The production does not necessarily have to go through a molten state, and any production method can be used. For example, a method of melting crystalline silica, a method of synthesizing from various raw materials, and the like can be mentioned.

In the present invention, the proportion of the filler (C) is
60-90% by weight of the whole in view of moldability and low stress
It is.

In the present invention, it is preferable from the standpoint of reliability that the filler (C) be surface-treated in advance with a coupling agent such as a silane coupling agent or a titanate coupling agent. As the coupling agent, a silane coupling agent such as epoxy silane, amino silane, and mercapto silane is preferably used.

The modified styrenic block copolymer (D) in the present invention is obtained by copolymerizing or grafting an unsaturated carboxylic acid or a derivative thereof to a styrenic block copolymer. The styrene-based block copolymer has an aromatic vinyl hydrocarbon polymer block having a glass transition temperature of usually 25 ° C. or higher, preferably 50 ° C. or higher, and a conjugated diene polymer having a glass transition temperature of 0 ° C. or lower, preferably −25 ° C. or lower. Linear, radial and branched block copolymers composed of united blocks are included. Examples of the aromatic vinyl hydrocarbon include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, 1,3-dimethylstyrene,
There are vinyl naphthalene and the like, and among them, styrene can be preferably used.

The conjugated diene includes butadiene (1,3-butadiene) and isoprene (2-methyl-
Among them, 1,3-butadiene), methyl isoprene (2,3-dimethyl-1,3-butadiene), 1,3-pentadiene and the like, butadiene and isoprene can be preferably used. The proportion of the aromatic vinyl hydrocarbon polymer block as the glass phase block in the styrene-based block copolymer is 10 to 50% by weight, and the proportion of the conjugated diene polymer block as the rubber phase block is 90 to 50% by weight. preferable. There are many combinations of a glass phase block and a rubber phase block, and any of them may be used. However, a triblock copolymer in which a glass phase block is bonded to both ends of an intermediate rubber phase block is preferable. In this case, the number average molecular weight of the glass phase block is preferably 3,000 to 150,000,
Particularly preferably, it is 5,000 to 60,000. The number average molecular weight of the rubber phase block is preferably 5,0.
00 to 300,000, particularly preferably 10,000 to
150,000.

The styrenic block copolymer can be produced by a known living anionic polymerization method, but is not particularly limited thereto, and can also be produced by a cationic polymerization method or a radical polymerization method. The styrene-based block copolymer also includes a hydrogenated block copolymer in which a part of the unsaturated bonds of the above-described block copolymer has 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 styrene-based block copolymer include polystyrene / polybutadiene / polystyrene triblock copolymer (SB
S), polystyrene / polyisoprene / polystyrene triblock copolymer (SIS), hydrogenated copolymer of SBS (SEBS) and hydrogenated copolymer of SIS. Among them, hydrogenated copolymer of SBS (SE
Particularly preferred are hydrogenated copolymers of BS) and SIS.

The modified styrenic block copolymer (D) in the present invention is obtained by copolymerizing or grafting an unsaturated carboxylic acid or a derivative thereof with a styrenic block copolymer, and is usually produced by a grafting reaction. . Here, as the unsaturated carboxylic acid, acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid,
Fumaric acid, itaconic acid, citraconic acid and butenedicarboxylic acid are preferably used. As the derivatives, alkyl esters, glycidyl esters, acid anhydrides, imides and the like are preferably used. Preferred specific examples include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, diglycidyl itaconate, and citraconic acid. Diglycidyl ester, butenedicarboxylic acid diglycidyl ester, butenedicarboxylic acid monoglycidyl ester, maleic anhydride, itaconic anhydride, citraconic anhydride, maleic imide, N-phenylmaleic imide, itaconic imide, citraconic imide, etc. Of these, glycidyl methacrylate, maleic anhydride, N-phenylmaleimide, and maleic imide are preferably used. These unsaturated carboxylic acids or derivatives thereof are
Depending on the application, two or more kinds may be used in combination.

The amount of the grafting reaction of the unsaturated carboxylic acid or its derivative is from 0.01 to 10 in view of improving the solder heat resistance.
% By weight, and particularly preferably from 0.05 to 5% by weight. Here, the graft reaction means that the unsaturated carboxylic acid or its derivative chemically bonds to the styrene-based block copolymer.

The modified styrenic block copolymer (D) can be prepared by a known method, for example, by reacting a styrenic block copolymer with an unsaturated carboxylic acid or a derivative thereof in a molten state or a solution state in the presence of a radical initiator or It can be obtained by a graft reaction of an unsaturated carboxylic acid or a derivative thereof to a styrene-based block copolymer in the absence. Preferably, it can be manufactured by melt-kneading at 100 to 350 ° C. using a melt-kneading apparatus such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a roll. In addition, when an organic peroxide is added as a radical initiator during melt kneading, the graft reaction can be more effectively performed. Organic peroxides include benzoyl peroxide, 1,1-bis-tert-butylperoxy-3,
3,5-trimethylcyclohexane, n-butyl-4,
4-bis-tert-butylperoxyvalate, te
rt-butylcumyl peroxide, dicumyl peroxide, tert-butylperoxybenzoate, di-tert-butyl peroxide, di (tert-butylperoxy) diisopropylbenzene, 2,5-dimethyl-2,5-di ( tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, tertbutylperoxycumene, and the like. The amount of the organic peroxide to be added is preferably 0.001 to 1 part by weight based on 100 parts by weight of the styrene-based block copolymer.

The amount of the modified styrene-based block copolymer (D) is preferably 0.1 to 10% by weight in the epoxy composition for encapsulating a semiconductor device from the viewpoint of improving the solder heat resistance.
6% by weight is particularly preferred.

Further, a styrene block copolymer can be added to the epoxy composition for encapsulating a semiconductor device of the present invention. The addition amount is preferably 10% by weight or less. Further, the modified styrene-based block copolymer (D) and the styrene-based block copolymer may be used after being pulverized, cross-linked or otherwise pulverized. The modified styrene-based block copolymer (D) and the styrene-based block copolymer can be mixed by any procedure. For example, epoxy resin (A) or curing agent (B)
And a method in which other components are blended after melt-mixing, and a method in which the epoxy resin (A), the curing agent (B), the filler (C) and other components are blended at the same time.

The epoxy composition for encapsulating a semiconductor of the present invention contains a flame retardant such as a halogen compound or a phosphorus compound such as a halogenated epoxy resin, a flame retardant auxiliary such as antimony trioxide, and a coloring agent such as carbon black and iron oxide. Thermoplastic resins such as silicone rubber, silicone oil, modified nitrile rubber, modified polybutadiene rubber, polyethylene,
A releasing 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, an amide of a long-chain fatty acid, paraffin wax and a crosslinking agent such as an organic peroxide can be optionally added.

The epoxy composition for encapsulating a semiconductor of the present invention is preferably melt-kneaded. It is manufactured by doing.

[0044]

The present invention will be described below in detail with reference to examples. In the examples, the number of parts indicates parts by weight, and% indicates% by weight.

Reference Example 1 (Production of Modified Styrene-Based Block Copolymer I) To 100 parts of the styrene-based block copolymer I shown in Table 1, 3 parts of maleic anhydride and 2,5-dimethyl-2,
5-di (tert-butylperoxy) hexane 0.1
Parts were dry blended. This mixture was melt-kneaded using a 30 mmφ single screw extruder at a screw rotation speed of 50 rpm and a cylinder temperature of 230 ° C. to obtain a modified styrene-based block copolymer I.

After the modified styrene block copolymer I was subjected to Soxhlet extraction with an acetone solvent to remove unreacted maleic anhydride, an infrared absorption spectrum and an ultraviolet absorption spectrum were measured to determine a graft reaction amount of maleic anhydride. Quantified. As a result, maleic anhydride was reduced to 1.2.
% Graft reaction.

Reference Example 2 (Production of Modified Styrene Block Copolymer II) As in Reference Example 1, 100 parts of the styrene block copolymer II shown in Table 1 were used, and 2 parts of glycidyl methacrylate and 2,5-dimethyl Using 0.1 part of -2,5-di (tert-butylperoxy) hexane, 1.1% of glycidyl methacrylate was graft-reacted to obtain a modified styrene block copolymer II.

Examples 1-4, Comparative Examples 1-4 The modified styrene block copolymers (D) of Reference Examples 1 and 2 and the styrene block copolymers shown in Table 1 were added to the formulation shown in Table 2. The polymers were dry-blended by a mixer at the composition ratios shown in Table 2. Roll surface temperature 9
The mixture was heated and kneaded for 5 minutes using a mixing roll at 0 ° C., and then cooled and pulverized to produce an epoxy composition for semiconductor encapsulation.

[0049]

[Table 1]

[0050]

[Table 2]

Using this composition, molding was performed at 175 ° C. × 2 minutes by a low pressure transfer molding method.
After post-curing under the condition of 5 hours, the physical properties and moldability of each composition were measured by the following physical property measuring methods.

Solder heat resistance: 160 pins with a chip size of 12 × 12 mm on which a simulated element having Al deposited on the surface is mounted.
Mold 20 QFPs, post cure, 85 ° C / 85%
After humidification for 50 hours at RH, place in a solder bath heated to 260 ° C.
It was immersed for 0 second, and the presence or absence of peeling at the interface between the chip and the resin was examined with an ultrasonic flaw detector. QF at which peeling occurred as failure rate
The proportion of P was determined.

Moisture resistance reliability: Using QFP after solder heat resistance evaluation, Al under the conditions of 121 ° C./100% RH under PCT.
The time at which the cumulative failure rate reaches 50%, where the disconnection of the wiring is regarded as a failure, was determined and defined as the life.

Low stress: 160 with dummy chip mounted
Mold 20 pinQFPs, post cure, -65 ° C
Q that cracks occurred in temperature cycle test of ~ 150 ° C
Assuming that FP was a failure, a time at which the cumulative failure rate became 50% was determined and defined as a life.

Table 3 shows the evaluation results.

[0056]

[Table 3]

As can be seen from Table 3, the epoxy compositions for semiconductor encapsulation of the present invention (Examples 1-4) are excellent in solder heat resistance, moisture resistance reliability and low stress.

On the other hand, in Comparative Examples 1 to 3 containing no modified styrenic block copolymer (D) and Comparative Example 4 containing no epoxy resin (A), solder heat resistance, moisture resistance reliability and low stress resistance were obtained. Inferior to all.

[0059]

The epoxy composition for encapsulating a semiconductor of the present invention contains an epoxy resin having a specific structure, a curing agent, a filler and a modified styrene-based block copolymer. Excellent in stress properties.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 23/31 (56) References JP-A-2-240130 (JP, A) JP-A-2-240131 (JP, A) JP-A-2-240132 (JP, A) JP-A-2-240133 (JP, A) JP-A-3-66723 (JP, A) JP-A-3-68648 (JP, A) JP-A-2-240158 (JP JP, A) JP-A-2-225557 (JP, A) JP-A-1-313552 (JP, A) JP-A-1-240551 (JP, A) JP-A-64-81847 (JP, A) JP-A-2-265916 (JP, A) JP-A-4-202518 (JP, A) JP-A-3-255154 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 63 / 00-63/10 C08G 59/00-59/72 H01L 23/29

Claims (1)

(57) [Claims] 1. A resin composition comprising, as essential components, an epoxy resin (A), a curing agent (B), a filler (C) and a modified styrene-based block copolymer (D). The resin (A) has the following formula (I): (However, two of R ^{1 to} R ⁸ represent a 2,3-epoxypropoxy group, and the other represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 4 carbon atoms.) The resin (a) is contained as an essential component, the ratio of the filler (C) is 60 to 90% by weight of the whole, and the modified styrene-based block copolymer (D) is unsaturated with respect to the styrene-based block copolymer. An epoxy composition for semiconductor encapsulation, which is obtained by copolymerizing or grafting a carboxylic acid or a derivative thereof.