JPH09165499A - Epoxy resin composition for sealing of semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin compsn. for sealing of a semiconductor which possesses excellent soldering heat resistance, moldability and other properties by incorporating a curing agent, a curing accelerator, an inorg. filler, and a particular a mercaptosilane coupling agent into an epoxy resin. SOLUTION: An epoxy resin (A) (e.g. a bisphenol A type epoxy resin), a phenolic resin curing agent (B) (e.g. phenol novolak resin), a curing accelerator (C) (e.g. 2-methylimidazole), an inorg. filler (D) (e.g. a spherical silica powder), and a mercaptosilane coupling agent (E) represented by the formula are used as indispensable components to obtain an epoxy resin compsn. for sealing of a semiconductor. The component (E) has a mercapto group and an ethoxysilane group as functional groups, and both the groups develop the effect of improving the adhesion in various interfaces and reducing voids. Therefore, the resultant epoxy resin compsn. has high adhesion to various members and has no void, offering good moldability.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is to obtain an epoxy resin composition for semiconductor encapsulation having good adhesion to various members.

[0002]

2. Description of the Related Art Epoxy resin-based semiconductor encapsulating resin compositions have been developed and produced in order to protect IC bodies from mechanical and chemical effects. Items required for it vary depending on the structure of the encapsulated IC package. For example,
High solder heat resistance is required for surface-mountable devices that have great market needs. Therefore, in order to solve the problems, the encapsulating resin composition is being advanced toward higher filling of inorganic fillers, lower viscosity epoxy resins, lower water-absorption curing agents, and higher adhesion-imparting agents. The most important thing to improve the solder resistance is to improve the adhesion to various members inside the semiconductor package. There are many methods for improving the adhesion to the encapsulating resin composition. For example, Japanese Patent Publication 3-1190
Japanese Patent Publication No. 49 discloses that a vinyl group-containing silane coupling agent is effective in improving adhesion, and Japanese Patent Publication No. 4-3403 discloses that methoxy-type mercaptosilane and epoxysilane are effective in improving adhesion. However, both methods are sufficiently effective in improving adhesion, but have problems such as deterioration in moldability, and both reliability centered on solder heat resistance and moldability centered on voids can be achieved. A silane coupling agent has been desired.

[0003]

The present inventors have found that the present invention has good adhesion with various members among the coupling agents in surface-mountable encapsulants and ordinary encapsulants, and further minimizes the occurrence of voids. The purpose is to obtain a high-performance epoxy resin composition for semiconductor encapsulation having good solder heat resistance and moldability by using a silane coupling agent that can be suppressed to the limit.

[0004]

Means for Solving the Problems The present inventor has conducted extensive studies on a silane coupling agent in order to achieve the above object. As a result, it was revealed that the encapsulating resin composition having the following composition was excellent in solder heat resistance and moldability. That is, the present invention comprises an epoxy resin, a phenol resin curing agent, a curing accelerator, an inorganic filler, and a mercaptosilane coupling agent represented by the following formula (S-1) as essential components. It is a resin composition. _{HS-C 3 H 6 -Si -} (- OC 2 H 5) 3 (S-1)

Each composition will be described below. The epoxy resin used in the present invention is a compound having an epoxy group in the molecule, and examples thereof include orthocresol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, triphenolmethane type epoxy resin, and naphthalene type epoxy resin. Examples thereof include epoxy resin and biphenyl type epoxy resin. Further, there is no particular limitation on the polymerization degree and epoxy equivalent of these resins. However, in the case of the surface-mountable encapsulating resin composition, it is required to increase the amount of the inorganic filler compounded, and thus an epoxy resin having a viscosity when melted as low as possible is desired. In order to improve the moisture resistance reliability, it is desirable that chlorine ions, sodium ions and other free ions contained in these epoxy resins be as small as possible.

The phenol resin curing agent used in the present invention is a compound having a phenolic hydroxyl group in the molecule, and examples thereof include phenol novolac, paraxylylene-modified phenol novolac, triphenol methane type phenol novolac and bisphenol A.
There is no problem if these curing agents are modified with silicone. Further, there is no limitation on the degree of polymerization, hydroxyl group equivalent and the like.
Similar to the epoxy resin, a curing agent having a relatively low viscosity tends to be desirable for the surface mounting sealing resin composition. In order to improve the moisture resistance reliability of the resin in these phenols, it is desirable that chlorine ions, sodium ions and other free ions contained as impurities are as small as possible.

The curing accelerator used in the present invention may be any one that accelerates the chemical reaction between the epoxy group and the phenolic hydroxyl group. Commonly used examples include 1,8-diazabicycloundecene, 2-methylimidazole, triphenylphosphine, tetraphenylphosphine / tetraphenylborate and the like. In the case of a formulation containing a low-viscosity epoxy resin and a curing agent, if the reactivity of the curing accelerator is not high, the hardness after molding will be low, and mold release will occur, so the curing reaction may proceed sufficiently under the molding conditions. It is more desirable to select the type and amount of the curing accelerator that can be used.

The inorganic filler used in the present invention includes:
Fused silica powder, spherical silica powder, crystalline silica powder, 2
Examples of the secondary agglomerated silica powder, alumina and the like are preferable, and spherical silica powder is preferable from the viewpoint of improving the fluidity of the encapsulating resin composition. Regarding the shape of the spherical silica powder, in order to improve the fluidity, it is desirable that the shape of the particles themselves be infinitely spherical and that the particle size distribution be broad. Further, there is no problem even if the inorganic filler is surface-treated in advance with the silane coupling agent of the present invention or another silane-based, titanium-based or other surface-treating agent. There is no limitation on the amount of the inorganic filler compounded. There is no particular limitation on the average and maximum particle sizes.

The mercaptosilane coupling agent used in the present invention has a structure represented by the following formula (S-1). _{HS-C 3 H 6 -Si -} (- OC 2 H 5) 3 (S-1)

The above-mentioned coupling agent is an important technical point in the present invention, and therefore will be described in detail. The coupling agent has a mercapto group and an ethoxysilane group as functional groups. Both of them have the effect of improving the adhesiveness of various interfaces and reducing voids. The mercapto group reacts with the epoxy resin among the organic functional groups. Particularly in a system having an amino group, the reactivity of the epoxy group / mercapto group becomes very high. Since the reaction of the base resin of the encapsulation resin with the epoxy resin is high, the strength of the encapsulation resin body is increased, and the solder heat resistance is improved. The mercapto group is further
Highly reactive with metals, especially silver. Among various metals in the IC package, silver is the member having the lowest adhesiveness with the sealing resin. In recent years, the demand for solder crack resistance of surface mount materials is extremely high, and the conditions are also very strict. Under severe evaluation conditions, peeling is likely to occur first at the sealing resin / silver-plated portion with the lowest adhesion among various interfaces.
It is known that the first peeling triggers, the peeling progresses due to the concentration of stress, and an external crack occurs. Due to the adhesiveness of the mercapto group to silver, the sealing resin composition using this has improved adhesiveness to the silver-plated portion, and peeling is less likely to occur during soldering treatment, thus improving solder resistance.

Since the ethoxysilane portion reacts with the silanol on the surface of silica, the strength of the interface between silica and the resin is improved, and the strength of the sealing resin body is increased to improve the solder resistance. However, the reactivity of ethoxysilane with respect to silica is equivalent to that of methoxysilane, and the solder resistance improved by this is not great. However, in the case of methoxysilane, methanol was generated as a by-product, whereas in the case of ethoxysilane, ethanol was found to have less adverse effect on voids. In the case of surface mount materials, internal voids are often generated due to the large number of deer, but most of the causes are volatile components. The most problematic volatile matter is water, both in terms of quality and quantity, but the other major volatile matter is alcohol generated from the coupling agent. Among the volatile components, since the volatile components having a high boiling point and high solubility in the resin do not have a bad influence on the voids, ethanol is less voids than methanol as the generated alcohol. It was found that the encapsulating resin composition using ethoxysilane has the same solder resistance as the encapsulating resin using methoxysilane, but has good moldability, particularly low void property.

Since the silane coupling agent used in the present invention has the above-mentioned characteristics, it provides a high-performance encapsulating resin composition having both solder resistance and moldability. The amount of the silane coupling agent used in the present invention is preferably 0.05 to 1.0 part by weight based on 100 parts by weight of the total composition. If the amount is less than 0.05 parts by weight, the strength does not sufficiently function as a silane coupling agent, so that the strength decreases
Adhesion strength to various interfaces is reduced, and solder resistance is reduced. On the other hand, if it exceeds 1.0 part by weight, the coupling agent, which does not react with the silica surface and is free, occupies most of it, resulting in a decrease in strength and a decrease in solder resistance due to a decrease in adhesiveness at various interfaces. The number of voids increases due to the increase of The coupling agent used in the present invention may be used in combination with another type of silane coupling agent without any problem. The coupling agent used in the present invention may be used as an integral blend or may be used by reacting / treating it on the surface of the inorganic filler.

In addition to the above-mentioned components, the composition of the present invention may optionally contain a coloring agent such as carbon black, a brominated epoxy resin, a flame retardant such as antimony trioxide, other silane coupling agents, silicone oil, A low stress component such as rubber can be added. The epoxy resin composition of the present invention is an epoxy resin, a phenol resin curing agent, a curing accelerator, an inorganic filler, and other additives are mixed at room temperature with a mixer, roll, kneading with a general kneader such as an extruder, After cooling, it can be pulverized to obtain a molding material.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 The following compositions were mixed at room temperature with a mixer, kneaded with a twin roll at 100 ° C., cooled and pulverized to obtain a molding material. The solder heat resistance and the void of the obtained molding material were evaluated, and the results are shown in Table 1. Biphenyl type epoxy resin 8.3 parts by weight Phenol aralkyl type curing agent 8.1 parts by weight Spherical silica powder (average particle size 15 μm) 80.0 parts by weight 1.8-diazabicycloundecene 0.2 parts by weight Silane coupling Agent A 0.5 parts by weight Carbon black 0.3 parts by weight Carnauba wax 0.3 parts by weight Brominated phenol novolac type epoxy resin 1.0 parts by weight Antimony trioxide 1.3 parts by weight

<Evaluation method> -Solder heat resistance: 80 pQFP (thickness: 1.5 mm) was measured at 175 using a tablet of the adjusted sealing resin composition.
Mold at 2 ℃ for 2 minutes. The molded product was post-cured at 175 ° C. for 8 hours and then post-cured to obtain a semiconductor package. The obtained package is 85 ℃, relative humidity 85
% Under the conditions of 168 hours and then at 240 ° C. in an IR reflow furnace. Visually observe external cracks,
Check the peeling condition inside the package with an ultrasonic flaw detector. Of the five packages for each product number, the number of defects (external cracks and peeling of each part) was counted and evaluated. -Void: A QFP package was prepared in the same manner, and the number of internal voids was confirmed with an ultrasonic flaw detector. The void evaluation was performed by counting the number of voids per package.

Except for Example 1, the type and blending amount of the epoxy resin, the phenol resin curing agent, and the silane coupling agent were changed, and the addition amount of the spherical silica powder was changed.
Further, other additives such as carbon black, carnauba wax, brominated phenol novolac type epoxy resin, antimony trioxide, and 1,8-diazabicycloundecene as a curing accelerator must be added. Same as. The epoxy resin, phenol resin curing agent and silane coupling agent used are as follows. -Biphenyl type epoxy resin: Formula (E-1) -Orthocresol novolac type epoxy resin: Formula (E
-2) -Triphenolmethane type epoxy resin: Formula (E-3) -Phenol aralkyl type curing agent: Formula (H-1) -Phenol novolac type curing agent: Formula (H-2) -Spherical silica powder (average particle size) Diameter 15 μm) -Silane coupling agent A: Formula (S-1) -Silane coupling agent B: Formula (S-2) -Silane coupling agent C: Formula (S-3) -Silane coupling agent D: Formula (S-4)

[0017]

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[0018]

Embedded image

HS-C ₃ H ₆ -Si-(-OC ₂ H ₅ ) ₃ (S-1) HS-C ₃ H ₆ -Si-(-OCH ₃ ) ₃ (S-2) _{H 2 N-C 3 H 6} -Si - (- OCH 3) 3 (S-4)

<< Examples 2 to 8 >> Compounds were prepared according to the formulation shown in Table 1, and molding materials were obtained in the same manner as in Example 1 and evaluated in the same manner. << Comparative Examples 1 to 4 >> Compounded according to the formulation in Table 2 and Example 1
A molding material was obtained in the same manner as above and evaluated in the same manner.

Table 1 Example 1 2 3 4 5 6 7 8 Compounding (parts by weight) E-1 8.3 8.3 8.3 8.3 8.3 8.3 E-2 10.2 E-3 9.7 H-1 8.1 8.1 8.1 8.1 8.1 8.1 H-2 6.2 6.7 Spherical silica powder 80 80.4 79.55 80 80 80 80 80 S-1 0.5 0.1 0.95 0.2 0.2 0.2 0.2 0.2 S-2 0.3 S-3 0.3 S-4 0.3 0.3 0.3 Characteristics <Solder heat resistance> Number of external cracks 0 0 0 0 0 0 0 0 0 0 Chip surface peeling number 0 0 0 0 0 0 0 2 2 42 Alloy red frame peeling number 0 0 0 0 0 0 0 1 2 Silver plating part peeling number 0 0 0 0 0 0 2 2 1 <Void number> 2 1 4 3 5 5 4 3

Table 2 Comparative Example 1 2 3 4 Compounding (parts by weight) E-1 8.3 8.3 8.3 8.3 H-1 8.1 8.1 8.1 8.1 Spherical silica powder 80 80.48 79.3 79.98 S-1 0.02 1.2 0.02 S-2 0.5 Characteristics << Solder heat resistance >> External Number of cracks 0 2 2 1 Number of chip surface peelings 0 4 1 0 42 Number of alloy red frame peeling 0 1 2 3 Number of silver plating peeling 0 4 3 4 << Void number >> 12 1 9 16

[0022]

According to the present invention, it is possible to obtain a high-performance epoxy resin composition for semiconductor encapsulation which is excellent in solder heat resistance due to its high adhesion to various members and excellent in moldability due to the absence of voids. You can Therefore, a dry pack-less encapsulating resin composition for surface mounting can be obtained, the reliability of the package can be improved, the moldability can be improved, and the molding cost can be reduced because the molding trouble can be reduced. be able to.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01L 23/31

Claims (1)

[Claims] An epoxy resin, a phenol resin curing agent,
An epoxy resin composition for semiconductor encapsulation, which comprises a curing accelerator, an inorganic filler, and a mercaptosilane coupling agent represented by the following formula (S-1) as essential components. _{HS-C 3 H 6 -Si -} (- OC 2 H 5) 3 (S-1)