JP2002284853A - Wax-containing melt mixture, epoxy resin composition, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device-sealing epoxy resin composition excellent in adhesiveness and releasability. SOLUTION: The composition is characterized in that it comprises (A) an inorganic filler, (B) a wax-containing melt mixture, and (C) a hardening accelerator.

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 for semiconductor encapsulation having excellent releasability and a semiconductor device having excellent adhesion.

[0002]

2. Description of the Related Art Conventionally, electronic components such as diodes, transistors, and integrated circuits are mainly sealed with an epoxy resin composition. A wax is blended in the resin composition to improve the continuous moldability and the appearance of the product, and the wax oozes out of the resin at the time of molding to help release from the mold. However, while the wax in the epoxy resin composition aids in releasing from a mold, it causes peeling off of a semiconductor element or a lead frame or other members in a semiconductor device, thereby deteriorating moisture resistance such as corrosion. May cause. In response to such problems, selection of a wax having a good balance between releasability and adhesion, selection of an epoxy resin and a phenol resin having a good curability, and an increase in the amount of a curing accelerator have been put to practical use.

However, in recent years, the surface mounting and miniaturization of electronic components have been advanced, and there has been a strict demand for improved solder crack resistance when mounted on a circuit board. Further, there has been a demand for a lead-free solder. It is becoming stricter, and there is a demand for an epoxy resin composition having low water absorbing properties. To reduce water absorption, there is a method of increasing the amount of inorganic filler or a method of reducing the water absorption of epoxy resin and phenol resin.
In the former, the balance between the releasability and the adhesiveness is lost due to the decrease in the amount of resin, and in the latter, the curability is reduced and the releasability is deteriorated due to the decrease in the number of functional groups. For this reason, there is a demand for an epoxy resin composition having both releasability and adhesion.

[0004]

An object of the present invention is to provide an epoxy resin composition and a semiconductor device having excellent mold releasability at the time of molding by using a molten mixture of wax having specific properties for solving such problems. It is an object of the present invention to provide a semiconductor device having excellent adhesion to members inside the semiconductor device.

[0005]

The present invention relates to [1] a wax which causes phase separation from a cured product of a mixture of a wax, an epoxy resin, a phenol resin and a curing accelerator, wherein the wax, the epoxy resin and the phenol resin are used. [2] The wax-containing melt mixture according to [1], wherein the wax-containing melt mixture has a wax particle size of 0.1 to 10 µm. 3] An epoxy resin composition for semiconductor encapsulation comprising (A) an inorganic filler, (B) a molten mixture containing a wax and (C) a curing accelerator, [4]
The epoxy resin composition for semiconductor encapsulation according to item [3], wherein the inorganic filler is a fused spherical silica having an average particle diameter of 10 to 30 µm and contained 85 to 93% by weight of the total epoxy resin composition. [5] A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition according to the item [3] or [4].

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having two or more epoxy groups in one molecule, such as biphenyl type epoxy resin, bisphenol type epoxy resin, phenol novolak type epoxy resin and cresol novolak type epoxy resin. Resins, triphenolmethane-type epoxy compounds, dicyclopentadiene-modified epoxy resins and the like can be mentioned, and they may be used alone or in combination. Examples of the phenol resin used in the present invention include a phenol novolak resin, a phenol aralkyl (including a phenylene and / or diphenylene skeleton) resin, a terpene-modified phenol resin, and a triphenolmethane-type resin. You may. The ratio of the number of epoxy groups in the epoxy resin to the number of hydroxyl groups in the phenol resin is preferably 0.8 to 1.2.

The curing accelerator used in the present invention may be any one that promotes the curing reaction between the epoxy group and the phenolic hydroxyl group, and those generally used for a sealing material can be widely used. For example, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, 2-methylimidazole and the like can be mentioned, and they may be used alone or in combination. The inorganic filler used in the present invention, fused silica, crystalline silica, alumina, silicon nitride and the like, among them, low thermal expansion fused silica is preferable, in order to highly fill the fused silica,
Those having a wide particle size distribution and a spherical shape are preferred. Crystalline silica, alumina, silicon nitride, and the like may be blended as long as the properties of the fused silica are not impaired. The blending amount is preferably from 85 to 93% by weight in the total epoxy resin composition from the balance between moldability and reliability.

The wax used in the present invention may be any wax having a property of causing phase separation from a cured product of a mixture of the wax and an epoxy resin, a phenol resin and a curing accelerator. Those which assist the mold and which do not deteriorate the appearance of the surface of the molded product are preferred. If compatible, the wax does not exude, causing poor mold release. If the wax bleeds completely and cannot be dispersed in the resin, oil floating and poor appearance of the flow mark occur. The particle size of the wax in the wax-containing molten mixture is:
0.1 to 10 μm is preferred.
If the thickness exceeds μm, unevenness due to bleeding occurs, causing poor appearance and peeling from semiconductor elements, etc., which is not preferable. The wax having the property of causing phase separation without bleeding from the cured product of the mixture of the wax and the epoxy resin, the phenol resin and the curing accelerator is used for each epoxy resin composition and the epoxy resin, the phenol resin and the curing accelerator. In each case, evaluation and selection may be made by the following method. As the wax selected, either a natural or synthetic wax may be used, and usually, fatty acids, polyolefins, fatty acid esters, fatty acid amides, fatty acid metal salts and the like are preferable.

Evaluation of phase separation of wax: The ratio of the number of epoxy groups in the epoxy resin to the number of hydroxyl groups in the phenol resin was 1 and 1 part by weight of the wax was added to 100 parts by weight of the total of the epoxy resin and the phenol resin. And the epoxy resin, phenol resin and wax in this ratio
After melt-mixing at a temperature of ° C, a curing accelerator is blended and mixed quickly, and cured in a 150 ° C oven. The cured product was observed with an optical microscope, and evaluated based on the presence or absence of a wax dispersed phase. Since the behavior of phase separation differs depending on the molecular structure of the epoxy resin or phenolic resin and the molecular structure of the wax, if the molecular structure of any of the epoxy resin, phenolic resin, or wax is different, it is necessary to evaluate each combination. . . Measurement of wax particle size: Place a mixture of epoxy resin, hardener, and wax on a slide at 150 ° C
Was melted on a hot plate and left for 2 minutes, and then the particle size of the wax was measured with an optical microscope.

[0010] The wax-containing melt mixture can be obtained by dispersing a wax, an epoxy resin and a phenol resin using a melt mixer. Examples of the melt mixer include a homogenizer, a Nanomizer (manufactured by Nanomizer), and a CLEARMIX (manufactured by M Technique). The epoxy resin composition using this wax-containing molten mixture has excellent mold release properties during molding, and excellent adhesion to a semiconductor element or a lead frame in the obtained semiconductor device, and also has an appearance of the semiconductor device. Even if there is no problem and the amount of resin is significantly reduced by highly filling the inorganic filler, molding can be performed without any problem, and at the same time, the solder crack resistance is excellent. Without using a wax-containing molten mixture, when an epoxy resin composition consisting of an epoxy resin, a phenolic resin, a curing accelerator, an inorganic filler and a wax that causes phase separation is formed and molded,
If the balance between the releasability and the adhesion is deteriorated and the inorganic filler is highly filled, unsatisfactory release and separation from members such as a semiconductor element and a lead frame in a semiconductor device occur, which is not preferable.

The epoxy resin composition of the present invention may contain, if necessary, a flame retardant such as a brominated epoxy resin, antimony trioxide, a coupling agent, a silicone, in addition to a wax-containing melt mixture, an inorganic filler and a curing accelerator. Low stress components such as oil and rubber can be appropriately compounded. The epoxy resin composition of the present invention is obtained by mixing the ground wax-containing molten mixture, the inorganic filler, the curing accelerator and the remaining components, kneading with a heating kneader or a hot roll, and subsequently cooling and grinding. be able to. In order to manufacture a semiconductor device by encapsulating a semiconductor element using the epoxy resin composition of the present invention, a conventional molding method such as transfer molding, compression molding, and injection molding may be used.

[0012]

The present invention will be specifically described below with reference to examples.
The mixing ratio is by weight. Example 1 Biphenyl-type epoxy resin [YX-4000H, melting point 105 ° C, epoxy equivalent 195, manufactured by Yuka Shell Epoxy Co., Ltd.] 4.0 parts by weight Phenol aralkyl resin [XL-225 manufactured by Mitsui Chemicals, Inc.] Softening point 75 ° C, hydroxyl equivalent 175] 3.6 parts by weight 1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 0.1 part by weight Spherical fused silica (average particle size 25 μm) 92.0 parts by weight Carnauba wax 0.3 parts by weight The phase separation of the epoxy resin, phenol aralkyl resin and carnauba wax shown in Table 1 was observed in accordance with the above-described evaluation method of phase separation. As a result, phase separation occurred in this combination. Heat the above epoxy resin, phenol aralkyl resin, carnauba wax components to 110 ° C.,
In the molten state, the mixture was mixed at 15000 rpm for 3 minutes using a clear mix, cooled and pulverized (referred to as treatment 1), and the remaining spherical fused silica and DBU were mixed.
The mixture was kneaded 30 times using two rolls at a temperature of 45 ° C. and a temperature of 45 ° C. The resulting kneaded material sheet was cooled and pulverized to obtain a resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 1 shows the evaluation results.

Evaluation Method Evaluation of the phase separation of the wax and measurement of the dispersed particle diameter of the wax are performed by the above-described methods. The obtained resin composition was tableted, and was then 175 ° C., 6.9 with a low-pressure transfer molding machine.
Under the conditions of MPa and 120 seconds, a 6 mm × 6 mm test element for solder crack resistance test was sealed in 80 pQFP. Moldability was determined based on the presence or absence of molding defects at this time.
The sealed test element was subjected to the following solder crack resistance test and appearance inspection. Solder crack resistance test: Sealed test elements (10 packages) were placed in an atmosphere of 85 ° C. and 85% relative humidity for 7 days.
After leaving it for 2 hours, it was immersed in solder (260 ° C.) and the presence or absence of peeling on the chip in the package was observed.

Examples 2 and 3, Comparative Examples 1 to 3 The components were blended according to Table 1, and the phase separation was observed in the same manner as in Example 1 to obtain a resin composition, which was similarly evaluated. The wax component of Comparative Example 1 was polyethylene powder, and the wax component of Comparative Example 3 was stearic acid. In Comparative Example 2, a resin composition was manufactured by an ordinary method. Treatment 2: The components of the epoxy resin, the phenol aralkyl resin and the wax were heated to 110 ° C., mixed in a molten state with Clearmix at 10,000 rpm for 1 minute, cooled and pulverized. Treatment 2 was blended with the remaining components in the table to give a resin composition in the same manner as in Example 1. Table 1 shows the evaluation results.

[0015]

[Table 1]

[0016]

According to the present invention, it is possible to obtain an epoxy resin composition having excellent releasability at the time of molding and a semiconductor device having excellent adhesion to members in the semiconductor device.

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Claims (5)

[Claims] 1. A wax which causes a phase separation from a cured product of a mixture of a wax, an epoxy resin, a phenol resin and a curing accelerator, wherein the wax is a molten mixture comprising the wax, an epoxy resin and a phenol resin. Wax-containing melt mixture. 2. The wax-containing melt mixture according to claim 1, wherein the wax particle diameter in the wax-containing melt mixture is 0.1 to 10 μm. 3. An epoxy resin composition for semiconductor encapsulation comprising (A) an inorganic filler, (B) a wax-containing melt mixture, and (C) a curing accelerator. 4. An inorganic filler having an average particle size of 10 to 30 μm.
Of fused spherical silica in the total epoxy resin composition
The epoxy resin composition for semiconductor encapsulation according to claim 3, which contains 93% by weight. 5. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition according to claim 3 or 4.