JPH04325516A - Epoxy resin composition for semiconductor sealing - Google Patents

Abstract

PURPOSE:To obtain the title composition excellent in soldering-heat resistance, etc., by mixing an epoxy resin with a specified phenolic curing agent and a specified amount of fused silica of a specified composition. CONSTITUTION:A phenolic curing agent containing at least 50 wt.% phenolic compound of the formula (wherein R<1> to R<4> are H or 1-4C lower alkyl) (e.g. tetramethylbisphenol F) is prepared. Fused silica which comprises 97-60wt.% broken fused silica of a mean particle size of 10mum or below and 3-40wt.% spherical fused silica of a mean particle size of 4mum or below and in which the mean particle size of the spherical fused silica is smaller than that of the broken fused silica is prepared. The title composition is produced by mixing an epoxy resin with the above fused silica and the above phenolic curing agent in such amounts that the inorganic filler containing the fused silica is used in an amount of 75-90wt.% based on the total composition.

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 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
No. 514) and the like have been proposed.

[0007] 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,
In a method in which an epoxy resin having a biphenyl skeleton is used as the epoxy resin, and a combination of crushed silica with an average particle size of 12 μm or less and spherical silica with an average particle size of 40 μm or less is used as fused silica, spherical silica with a large particle size is used. Crack resistance is low and sufficient soldering heat resistance has not yet been achieved.

[0008]

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.

[0009]

[Means for Solving the Problems] The present inventors have solved the above problems by using a specific curing agent 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.

[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 phenolic curing agent (B) having the formula (I)

[0011]

[C4]

(However, R1 to R4 are hydrogen atoms, C
They are selected from 1 to C4 lower alkyl groups, and do not need to all be the same. ) is contained in the curing agent (B) in an amount of 50% by weight or more, 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. Consisting of 3 to 40% by weight of spherical fused silica with an average particle diameter of 4 μm or less, the average particle diameter of the spherical fused silica is smaller than the average particle diameter of crushed fused silica, and the proportion of the inorganic filler containing fused silica (C) is 75 to 90% by weight of the epoxy resin composition, wherein the epoxy resin (A) is of the formula (II).

0
013]

[C5]

(However, R5 to R12 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 (a1) represented by formula (III)

00
15]

[C6]

(However, two of R13 to R20 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 more preferable that the epoxy resin composition contains at least one of the epoxy resins (a2) represented by (a2) as an essential component.

The reason why the epoxy resin composition of the present invention has excellent soldering heat resistance is not yet clear, but (1) the curing agent used in the present invention is a difunctional phenol having only two hydroxyl groups in one molecule. By containing a certain amount or more of the system compound, the crosslinking density of the cured product is moderately reduced, exhibiting low water absorption, and increasing flexibility at high temperatures and improving crack resistance; (2) the present invention; The combination of shape and particle size of fused silica, which is essential for It is thought that it exhibits excellent soldering heat resistance that could not be expected from a single contribution.

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 multifunctional phenols include cresol novolac type epoxy resins, phenol novolac type epoxy resins, and polyglycidyl novolac type resins synthesized from bisphenol A and formaldehyde, naphthol, dihydroxynaphthalene, formaldehyde, and benzaldehyde. An example is ether. Among these epoxy resins, cresol novolac type epoxy resins are particularly 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 formula (II)

[0022]

[C7]

(However, R5 to R12 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 (a1) represented by formula (III)

00
24]

[Chemical formula 8]

(However, two of R13 to R20 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 more preferable to contain at least one of the epoxy resins (a2) represented by (a2) as an essential component. Epoxy resin(
Epoxy resins such as a1) and (a2), which are bifunctional and have a highly heat-resistant biphenyl or naphthyl skeleton, have exactly the same effect in the present invention, and by containing them, cracks can be prevented in the soldering process. The prevention effect will be 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 It is preferable that at least one of a2) is contained in the epoxy resin (A) in an amount of 30% by weight or more.

In the present invention, the blending amount of the epoxy resin (A) is usually 4 to 20% by weight, preferably 5 to 15% by weight.
It is.

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

[0031]

[Chemical formula 9]

(However, R1 to R4 are hydrogen atoms, C
They are selected from 1 to C4 lower alkyl groups, and do not need to all be the same. It is necessary to contain 50% by weight or more of the phenolic compound (b) represented by ) in the curing agent (B). The content of phenolic compound (b) in the curing agent is 50
If it is less than % by weight, the effect of preventing cracks in the soldering process cannot be sufficiently achieved.

For example, a phenol novolac resin conventionally used as a semiconductor encapsulation resin has the formula (IV).

0
034]

[Chemical formula 10]

Although it contains a small amount of the binuclear component represented by
A phenol novolac resin with a softening point of 95° C. contains only about 10% by weight, and this level of content does not sufficiently prevent the occurrence of cracks in the soldering process.

Phenolic compound (b) in the present invention
Preferred specific examples include the binuclear component of phenol novolac resin, bisphenol F, tetramethylbisphenol F, etc., 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 is a curing agent (B) in which the above phenolic compound (b) is combined with the curing agent (B).
), the remainder is not particularly limited as long as it reacts with the epoxy resin to cure it, but preferred specific examples include phenol novolak resin, cresol novolac resin, bisphenol A, resorcinol, and formaldehyde. Examples include various novolak resins made by reacting with.

In the present invention, a phenolic curing agent (B
) is usually 2 to 10% by weight, preferably 3 to 9% 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 hydroxyl group/epoxy group is 0.7 to 1.3 from the viewpoint of mechanical properties and moisture resistance.
It is preferably in the range of 0.8 to 1.2, 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.

Fused silica (C) contained in inorganic filler
There is no particular restriction on the proportion of fused silica (C), but in order to exhibit a more sufficient effect, it is preferable that the inorganic filler contains fused silica (C) in an amount of usually 80% by weight or more, preferably 90% by weight or more.

Further, the inorganic filler in the present invention is not particularly limited as long as it contains the above-mentioned fused silica (C) 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.

[0051]

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

Examples 1 to 12, Comparative Examples 1 to 8 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 8). 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.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

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

A test was also conducted in which the humidified test device was immersed in a solder bath heated to 260° C. for 10 seconds instead of the VPS bath.

As shown in Table 4, 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 5, Comparative Example 1, in which the proportion of the inorganic filler to the whole was smaller than the range of the present invention, had poor solder heat resistance. Furthermore, in Comparative Example 2, in which the content of the phenolic compound (b) was outside the range of the present invention, the soldering heat resistance was poor, and in Comparative Example 6, a good composition was obtained because the torque during melt-kneading was high. It was not possible to evaluate the results. In addition, Comparative Example 3 and Comparative Example 8 in which the proportion of spherical fused silica in fused silica (C) is outside the scope of the present invention,
Comparative Examples 4 and 5, in which the average particle diameters of crushed fused silica and spherical fused silica are outside the scope of the present invention, and Comparative Example 7, in which the average particle diameter of spherical fused silica is larger than the average particle diameter of crushed fused silica. Both have poor solder heat resistance.

[0060]

[Table 4]

[0061]

[Table 5]

Furthermore, as shown in Table 6, by further containing at least one of epoxy resins (a1) and (a2) in the epoxy resin composition of the present invention, the soldering heat resistance is further improved.

[0063]

[Table 6]

[0064]

Effects of the Invention The epoxy resin composition of the present invention has excellent soldering heat resistance for semiconductor encapsulation by using a specific curing agent and fused silica having a specific combination of particle size and shape. .

Claims (2)

[Claims] 1. A resin composition comprising an epoxy resin (A), a phenolic curing agent (B), and fused silica (C) as essential components, wherein the phenolic curing agent (B) has the formula (I) [Chemical 1] (However, R1 to R4 are hydrogen atoms, C1 to C4
lower alkyl groups, not all of which need to be the same. ) is contained in the curing agent (B) in an amount of 50% by weight or more, 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. Consisting of 3 to 40% by weight of spherical fused silica with an average particle diameter of 4 μm or less, the average particle diameter of the spherical fused silica is smaller than the average particle diameter of crushed fused silica, and the proportion of the inorganic filler containing fused silica (C) is Overall 75~
An epoxy resin composition that is 90% by weight. 2. The epoxy resin (A) has the formula (II)
[Chemical formula 2] (However, R5 to R12 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 an epoxy resin represented by formula (III) [Chemical formula 3] (However, two of R13 to R20 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. 2. The epoxy resin composition according to claim 1, which contains at least one of the epoxy resins (a2) represented by (a2) as an essential component.