JPH04325517A - Epoxy resin composition for semiconductor sealing - Google Patents

Abstract

PURPOSE:To prevent the formation of package crack in the step of surface mounting of a semiconductor device. CONSTITUTION:An epoxy resin composition essentially consisting of an epoxy resin, a phenolic curing agent and fused silica, wherein the epoxy resin essentially consists of at least either a bifunctional epoxy resin having a biphenyl skeleton or a bifunctional epoxy resin having a naphthalene skeleton, the phenolic curing agent essentially consists of a phenolaralkyl resin, and the fused silica comprises 97-60wt.% broken fused silica of a mean particle size of 10mum and 3-40wt.% spherical fused silica of a mean particle size of 4mum or below, the mean particle size of the spherical fused silica is smaller than that of the broken fused silica, and the inorganic filler containing the fused silica is used in an amount of 75-90wt.% based on the total composition. This composition has excellent soldering-heat resistance and is useful as an epoxy resin for semiconductor sealing.

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 soldering 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 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 TSOP (thin small package) suitable for high-density mounting and surface mounting.
Outline packages) and QFPs (quad flat packages) are on the way.

[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 caused by
This is said to be caused by the moisture absorbed between post-curing and the mounting process becoming explosively vaporized and expanding during soldering heat, and various improvements to the sealing resin are being considered as a countermeasure. .

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.
It was common to use crushed fused silica of m.
The problem of cracks occurring due to heating during surface mounting could not be avoided. Therefore, we used an epoxy resin with a biphenyl skeleton as the epoxy resin, and added fused silica with an average particle size of 1.
A method using a combination of crushed silica with a particle size of 2 μm or less and spherical silica with an average particle size of 40 μm or less (Japanese Patent Application Laid-Open No. 2-99
514) and a method using a combination of tris(hydroxyphenyl)methane and a phenol aralkyl resin as a curing agent (Japanese Patent Application Laid-open No. 1-292029).

[0007]

[Problems to be Solved by the Invention] However, although the resins improved by these various methods have been effective to some extent in preventing cracks during soldering, they are still not sufficient. For example, use an epoxy resin with a biphenyl skeleton, and use fused silica with an average particle size of 12 μm.
In the method of using a combination of crushed silica with an average particle size of 40 μm or less and spherical silica with an average particle size of 40 μm or less, crack resistance is low and sufficient soldering heat resistance cannot be obtained because spherical silica with a large particle size is used. In addition, even when using a combination of tris(hydroxyphenyl)methane and phenol aralkyl resin as a curing agent, conventional orthocresol novolac type epoxy resin or tris(hydroxyphenyl)methane epoxidized product is used as the epoxy resin. The crosslinking density of the cured product is high, so the water absorption rate of the cured product is high, and the cured product itself is hard and brittle, so the degree of soldering heat resistance is low.

An object of the present invention is 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 using fused silica consisting of a combination of a specific epoxy resin, a specific curing agent, and a specific particle size and shape. They discovered that an epoxy resin composition meeting the purpose could be obtained and arrived at the present invention.

[0010] That is, the present invention provides an epoxy resin (A),
A resin composition comprising a phenolic curing agent (B) and fused silica (C) as essential components, the epoxy resin (A) having the formula (I)

[0011]

[C4]

(However, R1 to R8 are hydrogen atoms, C
They are selected from 1 to C4 lower alkyl groups or halogen atoms, and do not need to be all the same. ) Epoxy resin represented by (a1) and formula (II)

0
013]

[C5]

(However, two of R9 to R16 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. ), the phenolic curing agent (B) contains at least one of the epoxy resins (a2) represented by the formula (I) as an essential component;
II)

[0015]

[C6]

(However, R is a hydrogen atom, C1 to C4
are selected from lower alkyl groups or halogen atoms, and do not need to be all the same. Further, n represents an integer of 0 or more. ) is contained as an essential component, and the fused silica (C) is 97 to 60% by weight of crushed fused silica with an average particle size of 10 μm or less and spherical fused silica with an average particle size of 4 μm or less. It consists of 3 to 40% by weight of silica, the average particle size of the spherical fused silica is smaller than the average particle size of the crushed fused silica, and the proportion of the inorganic filler containing fused silica (C) is 75 to 90% by weight of the total. An epoxy resin composition.

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 essential to the present invention is a bifunctional epoxy resin having only two epoxy groups in one molecule. Because it is an epoxy resin and the phenolic compound essential to the present invention has a moderately small amount of hydroxyl groups, the crosslinking density of the cured product is moderately reduced and exhibits low water absorption; (2) the crosslinking density of the cured product; (3) The epoxy resin exhibits toughness (high strength, high elongation) at high temperatures because it has a highly heat-resistant skeleton such as biphenyl or naphthalene, even though the Due to the combination of shape and grain size, it exhibits high strength at high temperatures, and it also reduces local stress and may inhibit crack propagation.The effects work synergistically, and the individual contributions of each are It appears to exhibit unexpectedly excellent soldering heat resistance.

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

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

[0020]

[C7]

(However, R1 to R8 are hydrogen atoms, C
They are selected from 1 to C4 lower alkyl groups or halogen atoms, and do not need to be all the same. ) Epoxy resin represented by (a1) and formula (II)

0
022]

[Chemical formula 8]

(However, two of R9 to R16 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. ) It is necessary to contain at least one of the epoxy resins (a2) represented by (a2) as an essential component. Epoxy resin (a1) and epoxy resin (a2) are both bifunctional epoxy resins having two epoxy groups in one molecule, and they also have a skeleton structure with extremely high heat resistance. It has exactly the same effect.

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.

[0025] 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 It is preferable that at least one of a2) is contained in the epoxy resin (A) in an amount of 50% by weight or more.

[0027] Furthermore, the epoxy resin (A) in the present invention
The rest is not particularly limited as long as at least one of epoxy resins (a1) and (a2) 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 Examples include novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and halogenated epoxy resin.

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

[0029] Phenolic curing agent (B) in the present invention
is the formula (III)

[0030]

[Chemical formula 9]

(However, R is a hydrogen atom, C1 to C4
are selected from lower alkyl groups or halogen atoms, and do not need to be all the same. Further, n represents an integer of 0 or more. ) It is necessary to contain the phenolic compound (b) represented by (b) as an essential component.

Phenolic compound (b) in the present invention
Preferred specific examples include phenol aralkyl resins prepared by reacting aralkyl ethers and phenols with a Friedel-Crafts catalyst, particularly those of formula (IV).

[0033]

[Chemical formula 10]

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

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

There is no particular restriction on the proportion of the phenolic compound (b) contained in the phenolic curing agent (B), but in order to exhibit a more sufficient effect, the phenolic compound (b) should be mixed with phenol. 5 in the system curing agent (B)
It is preferable to contain 0% 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 resin, cresol novolak resin, tris(hydroxyphenyl)methane, 1,1,2-tris(hydroxyphenyl)ethane, Examples include 1,1,3-tris(hydroxyphenyl)propane, bisphenol A, bisphenol F, and dihydroxybiphenyl.

In the present invention, a phenolic curing agent (B
) is usually 3 to 20% by weight, preferably 4 to 15% 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 0.7 to 1.0 from the viewpoint of mechanical properties and moisture resistance.
It is preferably in the range of 3, particularly preferably in the range of 0.8 to 1.2.

[0039] 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.

[0040] 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 fused silica (C) in the present invention has an average particle size of 10μ
Consisting of 97 to 60% by weight of crushed fused silica with a particle diameter of 4 μm or less and 3 to 40% by weight of spherical fused silica with an average particle size of 4 μm or less, and the average particle size of the spherical fused silica is smaller than the average particle size of the crushed fused silica. It is. 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.

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

[0042] The average particle diameter of the spherical fused silica is 4 μm.
If the thickness exceeds 4 μm, the soldering heat resistance becomes insufficient, and if the thickness is 4 μm or less, there is no particular restriction. However, from the viewpoint of soldering 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
Two or more types of particles having different average particle diameters may be used in combination as long as the particle size is less than μm.

In the fused silica (C) in the present invention, it is important that the average particle size of the spherical fused silica is smaller than the average particle size 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 soldering heat resistance will be greatly reduced. The average particle size of the spherical fused silica should be smaller than the average particle size of the crushed fused silica, but preferably the average particle size of the spherical fused silica is 2/3 or less of the average particle size of the crushed fused silica, particularly preferably. is less than 1/2.

Furthermore, if the weight ratio of crushed fused silica to spherical fused 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 fused silica (C) is 75 to 90% by weight, more preferably 75 to 87% by weight, based on the total composition. 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. There is no particular restriction on the proportion of fused silica (C) contained in the inorganic filler, but in order to exhibit a more sufficient effect, the proportion of fused silica (C) in the inorganic filler is usually 80% by weight.
The content is preferably 90% by weight or more.

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 preferred specific examples include crystalline silica, Examples include alumina, magnesia, clay, talc, calcium silicate, titanium oxide, antimony oxide, and various ceramics.

In the present invention, it is preferable from the viewpoint of moisture resistance reliability that the inorganic filler containing fused silica (C) is previously surface-treated 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, and mercaptosilane are preferably used.

The epoxy resin composition of the present invention includes halogenated epoxy resins, flame retardants such as halogen compounds and phosphorus compounds, flame retardant aids such as antimony trioxide, colorants such as carbon black, silicone rubber, and modified nitrile rubber. , elastomers such as modified polybutadiene rubber and modified silicone oil, thermoplastic resins such as polyethylene, long chain fatty acids, metal salts of long chain fatty acids, esters of long chain fatty acids, paraffin wax, modified silicone oil and other mold release agents. Can be 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.

[0050]

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

Examples 1 to 12, Comparative Examples 1 to 8 The compositions shown in Tables 1 and 2 were mixed in the composition ratios shown in Table 3 (Examples 1 to 12) and Table 4 (Comparative Examples 1 to 8). It was blended using a mixer. 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.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

Using this epoxy resin composition, the following soldering heat resistance test, bending test, and water absorption measurement were conducted.

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 molded using a low-pressure transfer molding machine at 175°C for 120 seconds. 1
Cured at 75°C for 12 hours. After humidifying the 16 test devices in an 85°C/85%RH atmosphere for a predetermined time, they were immersed in a VPS (vapor phase solder reflow) bath heated to 215°C for 90 seconds to remove cracked devices. It was marked as defective.

Bending test: ASTM (D790-58T)
A test piece conforming to the above was molded using a low-pressure transfer molding machine at 175°C for 120 seconds, and cured at 175°C for 12 hours. Using this test piece, the ambient temperature was 215°C.
A bending test was conducted in accordance with ASTM (D790-58T), and the bending strength and bending deflection rate were calculated.

Water absorption measurement: 80 used for soldering heat resistance test
The water absorption rate was measured when the pinQFP device was humidified for a predetermined period of time in an 85° C./85% RH atmosphere.

As shown in Table 5, the epoxy resin compositions of the present invention (Examples 1 to 12) have excellent soldering heat resistance. On the other hand, as shown in Table 6, epoxy resin (a
Comparative Example 1, which does not contain 1) and (a2), and Comparative Example 2, which does not contain phenolic compound (b), have poor soldering heat resistance. In addition, Comparative Examples 3 and 4 in which the average particle diameters of crushed fused silica and spherical fused silica are outside the scope of the present invention, respectively, and the ratio of spherical fused silica in fused silica (C) is outside the scope of the present invention. Comparative example 5 and comparative example 6,
Comparative Example 7 in which the average particle size of the spherical fused silica was larger than the average particle size of the crushed fused silica had poor solder heat resistance. Furthermore, even in Comparative Example 8, in which the proportion of the inorganic filler to the whole was smaller than the range of the present invention, the soldering heat resistance was deteriorated.

[0061]

[Table 5]

[0062]

[Table 6]

[0063]

Effects of the Invention The epoxy resin composition of the present invention is an excellent solder for semiconductor encapsulation because it uses a specific epoxy resin, a specific curing agent, and fused silica having a specific combination of particle size and shape. Has heat resistance.

Claims (1)

[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)
is the formula (I) [Formula 1] (However, R1 to R8 are hydrogen atoms, C1 to C4
are selected from lower alkyl groups or halogen atoms, and do not need to be all the same. ), and epoxy resin (a1) represented by formula (II) [Chemical formula 2] (However, two of R9 to R16 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. ), the phenolic curing agent (B) is represented by the formula (III) [Chemical formula 3] (where R is a hydrogen atom, C1 to C4 It contains as an essential component a phenolic compound (b) selected from a lower alkyl group or a halogen atom, all of which do not need to be the same, and n represents an integer of 0 or more. Fused silica (C) has an average particle size of 10μ
Consisting of 97 to 60% by weight of crushed fused silica with a particle diameter of m or less and 3 to 40% by weight of spherical fused silica with an average particle size of 4 μm or less,
An epoxy resin composition in which the average particle size of spherical fused silica is smaller than the average particle size of crushed fused silica, and the proportion of an inorganic filler containing fused silica (C) is 75 to 90% by weight.