JP2003003042A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for sealing a full-mold type power-transistor having properties for improving wet-corrosion resistance of an aluminum-wire and for decreasing the stain of a mold. SOLUTION: The epoxy resin composition for sealing a full-mold type power- transistor comprises (A) an epoxy resin, (B) a phenol resin, (C) a crystal silica, (D) an accelerator and (E) aluminum stearate and other release agents, as essential components. The epoxy resin composition contains 0.30-0.50 wt.% of a total formulated amount of aluminum stearate and other release agents in a total epoxy resin composition, aluminum stearate being 0.01-0.20 wt.% of the total epoxy resin composition, and 75-83 wt.% of a crystalline silica in the total epoxy resin composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-mold type epoxy resin composition for encapsulating a power transistor having excellent moisture resistance and moldability.

[0002]

2. Description of the Related Art A full-mold type power transistor element is a type in which the entire metal heat sink is fully molded with a resin composition for insulation, and the cured product of the resin composition coating the heat sink has thermal conductivity. Therefore, crystalline silica having excellent thermal conductivity is used as the inorganic filler, and the inorganic filler is sealed with an epoxy resin composition that is a combination of an epoxy resin and a phenol resin. In this epoxy resin composition, a natural wax or a synthetic wax is usually used as a release agent. On the other hand, since the power transistor element allows a large current to flow, an aluminum wire having a diameter of 50 to 200 μm is used for electrical connection with the lead pin. This aluminum wire has a problem that it is more likely to be corroded by moisture and impurities than a gold wire.Therefore, element failure due to corrosion of the aluminum wire under the pressure cooker test conditions and mold contamination after continuous molding in the molding process may occur. However, it cannot be said that the current epoxy resin composition is sufficiently satisfactory, and there is a demand for an epoxy resin composition which prevents corrosion of aluminum wires and has less mold stains during molding.

[0003]

SUMMARY OF THE INVENTION The present invention addresses these problems by providing a full-mold type epoxy resin composition for encapsulating a power transistor, which has the characteristics of preventing corrosion of aluminum wires and less of mold contamination during molding. Is provided.

[0004]

The present invention provides (A) epoxy resin, (B) phenol resin, (C) crystalline silica,
An epoxy resin composition comprising (D) a curing accelerator and (E) aluminum stearate and another release agent as essential components, wherein the total amount of aluminum stearate and the other release agent is the total epoxy resin composition. 0.30 to 0.50% by weight, aluminum stearate is 0.01 to 0.20% by weight in the total epoxy resin composition, and crystalline silica is 75 to 83% by weight in the total epoxy resin composition. An epoxy resin composition for encapsulating a power transistor and a semiconductor device characterized by the above.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin used in the present invention is a monomer having two or more epoxy groups in one molecule,
Oligomer or polymer in general, for example, biphenyl type epoxy resin, dicyclopentadiene modified phenol type epoxy resin, bisphenol type epoxy resin, stilbene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenol methane type epoxy compound Examples thereof include alkyl-modified triphenol methane type epoxy resin and triazine nucleus-containing epoxy resin, and these may be used alone or in combination. The resin viscosity is selected to be lower as the filler content increases. In the present invention, a cresol novolac type epoxy resin is usually preferred in terms of balance between moldability and reliability.

The phenolic resin used in the present invention is
For example, phenol novolac resin, cresol novolac resin, dicyclopentadiene modified phenol resin, phenol aralkyl (having a phenylene or diphenylene skeleton) resin, terpene modified phenol resin, triphenol methane compound and the like are mentioned, and phenol novolac resin is particularly preferable. These may be used alone or in combination. The resin viscosity is selected to be lower as the filler content increases.

The aluminum stearate used in the present invention also acts as a mold release agent, and its melting point is not particularly limited, but it is 1 when considering impurities contained therein.
It is preferably about 0 to 125 ° C., and the compounding amount is preferably 0.01 to 0.20% by weight in the total epoxy resin composition, and less than 0.01% by weight is moisture resistance, that is, an effect of preventing corrosion of aluminum wire However, if it exceeds 0.20% by weight, the curing will be delayed and the moldability will be deteriorated.

In the present invention, the relationship between the total amount of the release agent and the improvement of the moisture resistance, that is, the corrosion prevention of the aluminum wire, is a phenomenon found only in the power transistor element using the aluminum wire. No effect of improving the moisture resistance was found in the used semiconductor elements such as SOP and DIP. The total blending amount of aluminum stearate and other release agent is required to be 0.30 to 0.50% by weight in the total epoxy resin composition, and if less than 0.30% by weight, there is a problem in releasability. 0.
If it exceeds 50% by weight, the problem of mold fouling occurs, which is not preferable. Other release agents in the present invention include carnauba wax, ester wax, which have been conventionally used in this technical field.
There are fatty acid wax, fatty acid amide wax, polyethylene wax, zinc stearate wax and the like, but these may be used alone or in combination. Aluminum stearate is 0.01% in the total epoxy resin composition.
It was found that when the total amount of the release agent containing aluminum stearate was 0.30 to 0.50% by weight, the amount of mold stain was extremely small.

The crystalline silica used in the present invention is required to be 75 to 83% by weight in the total epoxy resin composition, and if it is less than 75% by weight, the heat dissipation of the power transistor element becomes low, so that it is not suitable for a full mold type power transistor. When it becomes unsuitable and exceeds 83% by weight, the viscosity of the epoxy resin composition at the time of molding increases and the flowability is deteriorated, which is not preferable. The average particle size of crystalline silica is 10 to 30 μm, and the maximum particle size is 70.
˜150 μm is preferred. If necessary, fused crushed silica, fused spherical silica, alumina, aluminum nitride, silicon nitride and the like which are generally used for semiconductor encapsulation materials may be added.

The curing accelerator used in the present invention is 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-undecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4. -Imidazole compounds such as methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, amine compounds such as 1,8-diazabicyclo (5,4,0) undecene-7, tetra Examples thereof include phenylphosphonium borate salts and phosphorus compounds such as triphenylphosphine, and these may be used alone or in combination.

The epoxy resin composition of the present invention comprises (A)-
The component (E) is an essential component, but in addition to this, various coupling agents typified by silane coupling agents, colorants typified by carbon black, and mold release of natural wax and synthetic wax Agent, brominated epoxy resin, flame retardant such as antimony trioxide, silicone oil,
A low stress additive such as silicone rubber or synthetic rubber, and an ion trapping agent for reducing impurity ions may be appropriately blended. In order to obtain a molding material, all components can be heated and kneaded with a heating kneader or a heating roll, followed by cooling and pulverizing.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 Orthocresol novolac type epoxy resin (epoxy equivalent 200, softening point 60 ° C.) 15.0 parts by weight Phenol novolac resin (hydroxyl group equivalent 105, softening point 80 ° C.) 8.60 parts by weight Crystalline silica (average particle size 25 μm) , Maximum particle size 150 μm) 130.00 parts by weight 1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 0.30 parts by weight Silane coupling agent 0.40 parts by weight Aluminum stearate 0 20 parts by weight Carnauba wax 0.35 parts by weight Carbon black 0.60 parts by weight Brominated epoxy resin 2.00 parts by weight Antimony trioxide 1.60 parts by weight After mixing the above components with a mixer, the barrel temperature 1
The mixture was heated and kneaded with a kneader, a roll or the like at 00 ° C., further cooled and pulverized to obtain an epoxy resin composition. The characteristics were evaluated using this epoxy resin composition. The evaluation results are shown in Table 1.

Evaluation method Spiral flow: Using a spiral flow measuring mold according to EMMI-1-66, the mold temperature was 175 ° C., the injection pressure was 70 kg / cm ² , and the curing time was 2 minutes. Gelation time: put 2 g of molding material on a hot plate at 175 ° C.,
A time period in which the molding material is hardened and peeled off from the hot plate after being spread to a size of about 25 mm square with a spatula and rubbed on the hot plate. Thermal conductivity: A cylindrical test piece having a diameter of 50 mm and a height of 50 mm is molded at a temperature of 170 ° C. and an injection pressure of 70 kg / cm ^2.
Was molded, and the thermal conductivity was measured by the probe method. Moisture resistance reliability: TO-2 using simulated paste with solder paste
A full-mold type TO-220 package mounted on 20 frames and wire-bonded with aluminum wires was molded at a molding temperature of 175 ° C and an injection pressure of 70 kg / cm ² , and
After curing at 75 ℃ for 4 hours, 125 ℃, relative humidity 100%
It was left in the PCT kettle for 200 hours, the package was opened by the hot nitric acid method, and the degree of corrosion of the aluminum wire was observed. The number of packages with corrosion was compared and judged. It is represented by the number of aluminum wire corrosion occurrences. Mold stain: A full mold type TO-220 package was continuously molded for 300 shots at a molding temperature of 175 ° C. and an injection pressure of 70 kg / cm ² , and the mold stain was observed.

Examples 2 to 4 and Comparative Examples 1 to 6 Epoxy resin compositions were prepared in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 1. The fused spherical silica used in Example 2 and Comparative Example 5 has an average particle size of 15 μm and a maximum particle size of 150 μm.

[0015]

[Table 1]

[0016]

According to the present invention, it is possible to obtain a full mold type epoxy resin composition for encapsulating a power transistor, which has characteristics of improving the moisture corrosion resistance of an aluminum wire and having little mold stain.

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Claims (2)

[Claims] 1. An epoxy resin composition containing (A) epoxy resin, (B) phenol resin, (C) crystalline silica, (D) curing accelerator, (E) aluminum stearate and other mold release agents as essential components. The total amount of aluminum stearate and other mold release agent is 0.30 to 0.50% by weight in the total epoxy resin composition, and aluminum stearate is 0.01 to 0.5% in the total epoxy resin composition. 0.20% by weight of crystalline silica is 75 to 83 in the total epoxy resin composition.
An epoxy resin composition for encapsulating a power transistor, wherein the epoxy resin composition is in a weight percentage. 2. A semiconductor device obtained by encapsulating a semiconductor element using the epoxy resin composition according to claim 1.