JPH04306224A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition consisting essentially of an epoxy resin, curing agent containing a specific phenolic compound, definite amount of inorganic filler and polystyrene based block copolymer and excellent in resistance to soldering temperature and moisture-proof reliability. CONSTITUTION:The objective composition consisting essentially of (A) epoxy resin such as 1,5-di(2,3-epoxypropoxy)naphthalene, (B) curing agent containing >=50wt.% phenolic compound such as phenol novolak resin expressed by the formula (R<1> to R<4> are H or 1-4C lower alkyl), (C) inorganic filler such as fused silica or alumina of 75-87wt.% based on total amount and (D) polystyrene based block copolymer and prevented in occurrence of package crack in surface mounting process of semiconductor device.

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

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 sealing electronic circuit components such as semiconductor devices, hermetic seals using metals or ceramics, and resin sealing using phenol resins, silicone resins, epoxy resins, and the like have been proposed. However, from the viewpoint of economy, productivity, and balance of physical properties, resin sealing using epoxy resin has become the main method.

On the other hand, recently, the mounting density and automation of components on printed circuit boards have been increasing, and instead of the conventional "insertion mounting method" in which lead pins are inserted into holes in the board, components are soldered onto the surface of the board. The "surface mount method" for attaching devices has become popular. Along with this, the packaging is also conventional DIP.
(dual in-line package) to thin FPP (flat plastic package) 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 surface mounting methods include immersion in a solder bath, solder reflow method that heats with saturated steam of inert gas, and 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, orthocresol novolac type epoxy resin was used as the epoxy resin and phenol novolac resin was used as the curing agent, but this did not avoid the problem of cracks occurring due to solder during surface mounting. Therefore, a method using a triglycidyl ether type epoxy resin of tris(hydroxyphenyl)methane as the epoxy resin and a tris(hydroxyphenyl)methane type phenol resin as the curing agent (Japanese Patent Laid-Open No. 1-171232)
(Japanese Unexamined Patent Publication No. 1-268713), a method using a triglycidyl ether type epoxy resin of tris(hydroxyphenyl)methane as the epoxy resin and a dicyclopentadiene-modified phenol resin as the curing agent (Japanese Patent Application Laid-open No. 1-268713), a method using an average phenol as the curing agent. hydroxyl group equivalent is 2 to 4 meq. /g
A method using a linear phenol resin having phenolic hydroxyl groups at both ends (Japanese Unexamined Patent Publication No. 1-259075) has been proposed.

[0007]

[Problem to be Solved by the Invention] However, although these resins improved by various methods have been effective to some extent against cracks during soldering, they are still not sufficient and have adverse effects on other properties. It often causes In the method of using tris(hydroxyphenyl)methane type phenolic resin as a curing agent, the glass transition temperature of the resin increases due to the high crosslinking density of the resin, but there are problems of increased water absorption and problems of the resin itself becoming brittle. It is occurring. In addition, the curing agent has an average phenolic hydroxyl equivalent of 2 to 4 me.
q. /g, which uses a linear phenolic resin with phenolic hydroxyl groups at both ends, has the problem of a significant drop in the glass transition temperature of the resin, and the large molecular weight of the curing agent, which reduces fluidity and reduces moldability. This is causing a problem.

Furthermore, recent packages have become thinner and more suitable for high-density mounting and surface mounting, as well as larger chip sizes and more pins.If fluidity is insufficient during molding, resin may flow inside the mold cavity. There was a problem in that it could not be filled and unfilled parts occurred.

The object of the present invention is to solve the problem of cracks that occur in the soldering process, to have good moisture resistance reliability, and to have good fluidity during molding so that no unfilling occurs.
That is, the object of the present invention is to provide an epoxy resin composition that has excellent solder heat resistance, moisture resistance reliability, and moldability.

0010

[Means for Solving the Problems] The present inventors have solved the above problems and met the objectives by adding a specific curing agent and a specific proportion of inorganic filler to a specific block copolymer. The inventors have discovered that an epoxy resin composition can be obtained, and have arrived at the present invention.

[0011] That is, the present invention provides an epoxy resin (A),
A resin composition comprising a phenolic curing agent (B), an inorganic filler (C), and a polystyrene block copolymer (D) as essential components, the phenolic curing agent (B) comprising: General formula (I) of

0012

[C4]

(However, R1 to R4 are hydrogen atoms, C
It represents a 1 to C4 lower alkyl group. ) The curing agent contains 50% by weight or more of the phenolic compound (b) represented by
87% by weight of the epoxy resin composition, wherein the epoxy resin (A) has the following general formula (II):

[0014]

[C5]

(However, R1 to R8 are hydrogen atoms, C
It represents a 1 to C4 lower alkyl group or a halogen atom. ) and the following general formula (III):

[0016]

[C6]

(However, two of R1 to R8 are 2
, 3-epoxypropoxy group, the rest are hydrogen atoms,
Represents a C1 to C4 lower alkyl group or halogen atom. It is more preferable that the epoxy resin composition contains one or both of the epoxy resins (a2) represented by (a2) as essential components.

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

The epoxy resin (A) in the present invention is not particularly limited as long as it is a polyfunctional epoxy resin containing two or more epoxy groups in one molecule, but it is usually a polyglycidyl ether of a polyfunctional phenol. Type epoxy resin is used. Specific examples of polyglycidyl ether type epoxy resins of polyfunctional phenols include various novolac type epoxy resins such as cresol novolak type epoxy resins, phenol novolac type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, etc. I can give an example. Among these epoxy resins, cresol novolac type epoxy resins are usually preferably used from the viewpoint of the balance of moisture resistance, heat resistance, and productivity.

In the present invention, the polyglycidyl ether of these polyfunctional phenols may be halogenated for the purpose of imparting flame retardance.

Furthermore, in the present invention, epoxy resin (A
) as the following general formula (II)

[0022]

[Chemical 7]

(However, R1 to R8 are hydrogen atoms, C
It represents a 1 to C4 lower alkyl group or a halogen atom. ) and the following general formula (III):

[0024]

[Chemical formula 8]

(However, two of R1 to R8 are 2
, 3-epoxypropoxy group, the rest are hydrogen atoms,
Represents a C1 to C4 lower alkyl group or halogen atom. It is further preferable to contain one or both of the epoxy resins (a2) represented by (a2) as essential components. By containing an epoxy resin such as epoxy resin (a1) or (a2) which is bifunctional and has a skeleton structure with very high heat resistance, the effect of preventing cracks in the soldering process is further improved.

Preferred specific examples of the epoxy resin (a1) in the present invention include 4,4'-bis(2,3-epoxypropoxy)biphenyl, 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-epoxy propoxy)-3,3',5,5'-tetraethylbiphenyl, 4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetrabutylbiphenyl, etc. , 4'-bis(2,3-epoxypropoxy)biphenyl, and 4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl are particularly preferred.

[0027] Furthermore, the epoxy resin (a2
) is a preferable specific example of 1,5-di(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(2,3-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 1,5-di(2,3-epoxypropoxy)naphthalene, 1,6-
Di(2,3-epoxypropoxy)naphthalene, 2,7
-di(2,3-epoxypropoxy)naphthalene is particularly preferred.

There is no particular restriction on the ratio of the epoxy resins (a1) and (a2) contained in the epoxy resin (A), but in order to exhibit a more sufficient effect, it is necessary to a2) to epoxy resin (A
) is preferably contained in an amount of 30% by weight or more.

In addition, in the present invention, epoxy resin (A
) is usually 4 to 20% by weight, preferably 5 to 15% by weight.
Weight%.

[0030] Phenolic curing agent (B) in the present invention
is the following general formula (I)

[0031]

[Chemical formula 9]

(However, R1 to R4 are hydrogen atoms, C
It represents a 1 to C4 lower alkyl group. It is necessary to contain 50% by weight or more of the phenolic compound (b) represented by ) in the curing agent. By containing 50% by weight or more of the bifunctional, low molecular weight phenolic compound (b) in the curing agent, the crosslinking density of the cured epoxy resin material is moderately reduced and the brittleness, which is a drawback of the cured epoxy resin product, is reduced. As a result, the occurrence of cracks in the soldering process is suppressed, and the melt viscosity of the resin composition is reduced, improving fluidity during molding. If the content of the phenolic compound (b) in the curing agent is less than 50% by weight, a sufficient effect of preventing the occurrence of cracks in the soldering process and fluidity during molding cannot be obtained. For example, the phenol novolac resin conventionally used for semiconductor encapsulation resin has the following general formula (I).

[
0033

[Chemical formula 10]

(However, R1 to R4 represent hydrogen atoms.) Contains a small amount of dinuclear component represented by the formula (R1 to R4 represent hydrogen atoms), but in the case of phenol novolac resin with a softening point of 83°C, it is 15% by weight.
1 for phenol novolak resin with a softening point of 95°C.
The content is only around 0% by weight, and with this level of content, it is not possible to obtain a sufficient effect of preventing the generation of cracks in the soldering process and fluidity during molding.

Phenolic compound (b) in the present invention
Preferred specific examples include the binuclear component of phenol novolak resin, bisphenol F, and tetramethylbisphenol F, and two or more of them may be used at the same time as long as the total amount is 50% by weight or more.

In addition, the phenolic curing agent (B) in the present invention can contain the above-mentioned phenolic compound (b) in an amount of 50% by weight or more, with the remainder being an epoxy resin (A).
), but preferred specific examples include phenol novolak resins, cresol novolak resins, various novolak resins synthesized from bisphenol A and resorcinol, and compounds of the following general formula (IV )

[0037]

[Chemical formula 11]

(However, R is a hydrogen atom or C1 to C
4 represents a lower alkyl group, all of which do not need to be the same, and m represents an integer of 0 or more. ) or the following general formula (V
)

[0039]

[Chemical formula 12]

(However, R is a hydrogen atom or C1 to C
4 represents a lower alkyl group, all of which do not need to be the same, and n represents an integer of 0 or more. ) and various phenolic resins.

In the present invention, a phenolic curing agent (B
) is usually 2 to 10% by weight, preferably 3 to 8% by weight. Furthermore, the compounding ratio of the epoxy resin (A) and the phenolic curing agent (B) is such that the chemical equivalent ratio of (B) to (A) 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.

[0042] Furthermore, in the present invention, epoxy resin (A)
A curing catalyst may be used to promote the curing reaction of 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, 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.

[0043] Two or more of these curing catalysts may be used in combination 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. Preferred specific examples of the inorganic filler (C) in the present invention include fused silica, crystalline silica, alumina, magnesia, talc, and various ceramics, with fused silica being particularly preferably used.

[0044] Furthermore, two or more of these inorganic fillers may be used in combination depending on the purpose.

The proportion of the inorganic filler (C) in the present invention in the entire epoxy resin composition is 75 to 87% by weight, more preferably 75 to 85% by weight. If the inorganic filler (C) is less than 75% by weight, the soldering heat resistance will be insufficient, and if it exceeds 87% by weight, the fluidity will be insufficient.

In the present invention, it is preferable from the viewpoint of reliability that the inorganic filler (C) is previously surface-treated with a coupling agent such as a silane coupling agent or a titanate coupling agent. Epoxysilane as a coupling agent,
Silane coupling agents such as aminosilane and mercaptosilane are preferably used.

Furthermore, in the present invention, it is important to contain the polystyrene block copolymer (D) as an essential component.

The polystyrene block copolymer (D) contains 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 -25°C. Includes linear, radial, and branched block copolymers consisting of conjugated diene polymer blocks having a temperature of 0.degree. C. or less.

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 a glass phase block and a rubber phase block, and any of them may be used. For example, a diblock copolymer in which one glass phase block and one rubber phase block are bonded, and a diblock copolymer in which one glass phase block and one rubber phase block are combined, 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.

The polystyrene block copolymer (D) also includes a hydrogenated block copolymer in which some of the unsaturated bonds of the above block copolymer are reduced by hydrogenation.

Here, it is preferable that 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 improvement in soldering heat resistance and moisture resistance reliability, and if it exceeds 10% by weight, the fluidity will decrease, making molding difficult and impractical.

In the present invention, it is not yet clear why the polystyrene block copolymer (D) contributes to improving soldering heat resistance and moisture resistance reliability, but the polystyrene block copolymer makes the cured epoxy resin hydrophobic. This is due to the synergistic effect of two effects: the conjugated diene polymer block in the polystyrene block copolymer reduces the internal stress generated between the semiconductor chip and the cured epoxy resin over a wide temperature range. It is estimated that
In the epoxy resin composition of the present invention, the effect of this polystyrene block copolymer, the effect of the phenolic compound (b) mentioned above, and the low water absorption effect due to high loading of the inorganic filler (C) are synergistic. It is presumed that these effects showed excellent soldering heat resistance that could not have been expected from each individual contribution.

The epoxy resin composition of the present invention contains halogen compounds such as halogenated epoxy resins, flame retardants such as phosphorus compounds, flame retardant aids such as antimony trioxide, colorants such as carbon black, silicone rubber, and modified nitrile. Optionally add release agents such as rubber, elastomers such as modified polybutadiene rubber, thermoplastic resins such as polyethylene, long chain fatty acids, metal salts of long chain fatty acids, esters of long chain fatty acids, amides of long chain fatty acids, paraffin wax, etc. can do.

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.

[0059]

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

Examples 1 to 9, Comparative Examples 1 to 5 The formulations shown in Table 1 and the polystyrene block copolymers shown in Table 2 were mixed in a mixer at the composition ratios shown in Tables 3 and 4, respectively.
Dry blended using. 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.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

[Table 3]

[0064]

[Table 4]

Using this composition, the following soldering heat resistance test, moisture resistance reliability test, and moldability were confirmed.

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. Further, after 24 hours of humidification, 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 from the chip.

Moisture resistance reliability test: A simulated element with aluminum wiring was mounted on an 80-pin QFP device, molded using a low-pressure transfer molding machine at 175° C. for 120 seconds, and cured at 175° C. for 12 hours. After humidifying this test device at 85°C/85%RH for a predetermined time,
It was immersed in a solder bath heated to 60°C for 10 seconds. PCT was performed on the test device after being immersed in solder under the conditions of 143° C./100% RH regardless of the occurrence of cracks, and the characteristic life in Weibull distribution was determined.

Moldability (Fillability): After molding, the 80-pin QFP device used in the solder heat resistance test was observed visually and using a microscope to check for any unfilled parts.

As seen in Table 5, the epoxy resin compositions of the present invention (Examples 1 to 9) are excellent in soldering heat resistance, moisture resistance reliability, and moldability. On the other hand, Comparative Example 1 in which the content of the phenolic compound (b) is outside the range of the present invention
In Comparative Example 4, the soldering heat resistance was poor, and there were also problems in moldability. Furthermore, in Comparative Examples 2 and 3, which did not contain the polystyrene block copolymer (D), the moisture resistance reliability was very poor, the soldering heat resistance was also poor, and peeling occurred on the chip surface. Furthermore, in Comparative Example 5 in which the content of the inorganic filler was outside the range of the present invention, both solder heat resistance and moisture resistance reliability were poor.

[0070]

[Table 5]

[0071]

Effects of the Invention The epoxy resin composition of the present invention has excellent soldering heat resistance, moisture resistance reliability, and moldability because it contains a specific curing agent, a specific proportion of inorganic filler, and a polystyrene block copolymer. ing.

Claims (2)

[Claims] 1. A resin composition comprising an epoxy resin (A), a phenolic curing agent (B), an inorganic filler (C), and a polystyrene block copolymer (D) as essential components. , the phenolic curing agent (B) has the following general formula (I) [Formula 1] (wherein R1 to R4 are hydrogen atoms, C1 to C4
represents a lower alkyl group. ) An epoxy resin composition containing 50% by weight or more of a phenolic compound (b) represented by (b) in a curing agent, and in which the proportion of the inorganic filler (C) is 75 to 87% by weight. 2. The epoxy resin (A) has the following general formula (II): (wherein R1 to R8 are hydrogen atoms, C1 to C4
represents a lower alkyl group or a halogen atom. ) and the following general formula (I
II) [Chemical formula 3] (However, two of R1 to R8 are 2,3-epoxypropoxy groups, and the rest are hydrogen atoms, C1 to C4
represents a lower alkyl group or a halogen atom. 2. The epoxy resin composition according to claim 1, which contains one or both of the epoxy resins (a2) represented by (a2) as essential components.