JPH04218523A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To prevent package cracks from occurring in a surface mounting process of semiconductor devices. CONSTITUTION:A semiconductor sealing epoxy resin composition which is a resin composition, containing an epoxy resin, a curing agent and fused silica as essential components. The epoxy resin contains a bifunctional epoxy resin having a biphenyl skeleton as an essential component and the fused silica is simultaneously composed of 97-60wt.% fused silica in a crushed form having <=10mum average grain size and 3-40wt.% spherical fused silica having <=4mum average grain size. The average grain size of the spherical fused silica is smaller than that of the fused silica in the crushed form. The ratio of an inorganic filler containing the fused silica is 75-90wt.% based on the whole composition. The aforementioned epoxy resin composition is a resin composition, having excellent solder heat resistance and useful as an epoxy resin composition for sealing semiconductors.

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

Conventionally, an orthocresol novolac type epoxy resin was used as the epoxy resin, a phenol novolac resin was used as the curing agent, and an average particle size of 10 to 20 μm was used as the inorganic filler.
It was common to use crushed fused silica of m.
The problem of cracks caused by solder during surface mounting could not be avoided.

[0007] Therefore, a method has been proposed in which an epoxy resin having a biphenyl skeleton is used in combination with a powdered filler having an average particle size of 14 μm or less as an inorganic filler (Japanese Patent Laid-Open Publication No. 87616/1987). However, it cannot be said that the soldering heat resistance is sufficient.

[0008]Also, although there is no description regarding soldering heat resistance,
Coarse silica with an average particle size of 7 to 30 μm and an average particle size of 0.1 to 30 μm
A method using a combination of 3 μm monodispersed spherical silica (
Japanese Unexamined Patent Publication No. 1-263131) has been proposed. However, this method only improves the fluidity of the sealing material, but the level of soldering heat resistance is low.

[0009]

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

0010

[Means for Solving the Problems] The present inventors have solved the above problems by using a specific epoxy resin and fused silica having a specific combination of particle size and shape. 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 curing agent (B) and fused silica (C) as essential components, the resin composition comprising the epoxy resin (A).
) is the following general formula (I)

0012

[Case 2]

(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. ) contains the epoxy resin (a) represented by (a) 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 3 to 40% by weight, 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. It is 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. By being an epoxy resin, the crosslinking density of the cured product is moderately reduced and exhibits low water absorption.
) Even though the crosslinking density of the cured product is low to some extent, the epoxy resin has a highly heat-resistant biphenyl skeleton, so it exhibits toughness (high strength, high elongation) at high temperatures; (3)
(4) Local stress is reduced by combining crushed fused silica and spherical fused silica with a smaller average particle size. It is thought that these effects, such as the possibility of suppressing crack propagation, work synergistically to provide excellent soldering heat resistance that cannot be expected from the individual contributions of each component.

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

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

[0017]

[Chemical formula 3]

(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. ) It is necessary to contain the epoxy resin (a) represented by (a) as an essential component. If the epoxy resin (a) is not contained, the effect of preventing crack generation in the soldering process will not be exhibited.

Preferred specific examples of the epoxy resin (a) 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-epoxypropoxy)-3,3',5,5'-tetraethylbiphenyl, 4,4'-bis(2,3-epoxypropoxy)-3,3 Examples include ',5,5'-tetrabutylbiphenyl, 4,4'-bis(2,3-epoxypropoxy)biphenyl, 4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl is particularly preferred.

There is no particular restriction on the proportion of epoxy resin (a) contained in epoxy resin (A), but in order to exhibit a more sufficient effect, epoxy resin (a) should be added to epoxy resin (A). It is usually necessary to contain 50% by weight or more, preferably 60% by weight or more.

[0021] Furthermore, the epoxy resin (A) in the present invention
The rest is not particularly limited as long as the epoxy resin (a) is contained in the epoxy resin (A) in an amount of 50% by weight or more, but preferred specific examples include orthocresol novolac type epoxy resin, phenol novolac type epoxy resin, and bisphenol A. Examples include bisphenol F 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 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 reacts with the epoxy resin (A) to cure it, but specific examples thereof include phenol novolak resin, cresol novolak resin, and bisphenol A.
phenolic curing agents such as various novolak resins synthesized from resorcinol and formaldehyde; acid anhydrides such as maleic anhydride, phthalic anhydride, and pyromellitic anhydride; and metaphenylene diamine, diaminodiphenylmethane, and diaminodiphenylsulfone. Examples include aromatic amines. Among them, phenolic curing agents are preferably used for encapsulating semiconductor devices from the viewpoint of heat resistance, moisture resistance, and storage stability, and two or more types of curing agents may be used in combination depending on the application.

[0024] In the present invention, the amount of curing agent (B) blended is usually 3 to 15% by weight, preferably 4 to 10% by weight. Further, the compounding ratio of the epoxy resin (A) and the curing agent (B) is preferably such that the chemical equivalent ratio of hydroxyl group/epoxy group is in the range of 0.7 to 1.3 from the viewpoint of mechanical properties and moisture resistance.
In particular, it is preferably in the range of 0.8 to 1.2.

[0025] Furthermore, in the present invention, epoxy resin (A)
A curing catalyst may be used to promote the curing reaction of and curing agent (B). The curing catalyst is not particularly limited as long as it promotes the curing reaction, and examples include 2-methylimidazole and 2-methylimidazole.
- Imidazole compounds such as phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecyl imidazole, triethylamine, benzyldimethylamine, α-methylbenzyldimethylamine, 1,8-
3 such as diazabicyclo(5,4,0) undecene-7
class amine compounds, triphenylphosphine, tributylphosphine, tri(p-methylphenyl)phosphine,
Examples include organic phosphine compounds such as 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.

[0026] These curing catalysts may be used in combination of two or more types 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 size of 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 should be 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, the average particle size of the crushed fused silica is 10μ
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 m.

[0028] Furthermore, the average particle diameter of the spherical fused silica is 4 μm.
If it exceeds 4 μm, the soldering heat resistance becomes insufficient, and if it is 4 μm or less, there is no particular restriction, but in consideration of moldability, 0.1 μm or more and 4 μm or less are particularly preferably used. Here, the average particle size of spherical fused silica is 4μ
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 m.

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 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 77 to 88% by weight. If the proportion of the inorganic filler to the whole 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, it is necessary to add fused silica (C)
in the inorganic filler, usually 80% by weight or more, preferably 90% by weight.
It is preferable to contain it in an amount of % by weight or more.

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

In the present invention, it is preferable from the viewpoint of 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.

[0035]

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

Examples 1 to 12, Comparative Examples 1 to 9 The formulations shown in Table 1 were mixed in a mixer at the composition ratios shown in Table 2 (Examples 1 to 12) and Table 3 (Comparative Examples 1 to 9). Blend 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.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

Using this epoxy resin composition, the following soldering heat resistance test was conducted.

Solder heat resistance test: 32 80-pin QFP devices (package size: 17 x 17 x 1.7 mm, chip size: 9 x 9 x 0.5 mm) were molded using a low pressure transfer molding machine at 175°C for 120 seconds. It was molded and cured at 180°C for 5 hours. After humidifying this test device in an 85°C/85%RH atmosphere for a predetermined time,
16 pieces were immersed in a solder bath heated to 260°C for 10 seconds,
The remaining 16 devices were immersed in a VPS (vapor phase solder reflow) bath heated to 215° C. for 90 seconds, and each device with cracks was judged as defective.

As seen in Table 4, the epoxy resin compositions of the present invention (Examples 1 to 12) have excellent soldering heat resistance. On the other hand, in Comparative Example 2, in which the content of epoxy resin (a) was outside the range of the present invention, the solder heat resistance was poor, and in Comparative Example 6, the torque during melt-kneading was high, resulting in a good composition. It was not possible to obtain and evaluate the results. Also,
Comparative Examples 5 and 7 in which the average particle diameters of crushed fused silica and spherical fused silica are outside the scope of the present invention, respectively, and Comparative Examples in which the proportion of spherical fused silica in fused silica (C) is outside the scope of the present invention Comparative Example 3, Comparative Example 8, and Comparative Example 4 in which the average particle size of the spherical fused silica was larger than the average particle size of the crushed fused silica, all had poor solder heat resistance. Comparative Example 1 in which the proportion of the inorganic filler to the whole is lower than the range of the present invention
Comparative Example 9 has poor solder heat resistance and exceeds the range of the present invention.
However, since the torque during melt-kneading was high, a good composition could not be obtained and could not be evaluated.

[0043]

[Table 4]

[0044]

[Table 5]

Furthermore, as shown in Table 6, when the humidification conditions are made even stricter, the average particle diameter of the crushed fused silica increases to 7 μm.
It can be seen that cracks begin to appear in some parts of the package for compositions with a particle size of m or more, and compositions in which the average particle size of crushed fused silica is less than 7 μm have even better solder heat resistance.

[0046]

[Table 6]

[0047]

EFFECTS OF THE INVENTION The epoxy resin composition of the present invention has excellent solder heat resistance for semiconductor encapsulation due to the use of a specific epoxy resin and fused silica having a specific combination of particle size and shape.

Claims (1)

[Claims] Claim 1: Epoxy resin (A), curing agent (B),
A resin composition containing fused silica (C) as an essential component, wherein the epoxy resin (A) has the following general formula (I) [Formula 1] (wherein R1 to R8 are hydrogen atoms, C1 ~C4
are selected from lower alkyl groups or halogen atoms, and do not need to be all the same. ) contains the epoxy resin (a) represented by (a) as an essential component, and the 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 3 to 40% by weight, 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% of the total.
% by weight of the epoxy resin composition.