JP2000273278A - Production of epoxy resin holding material for semiconductor sealing use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing the subject molding material with good flowability even with the high content of an inorganic filler therein, slight in void development in semiconductor seal molding therewith. SOLUTION: This method for producing an epoxy resin molding material for semiconductor sealing use comprises premixing the total compounding materials essentially including an epoxy resin solid at room temperature, a phenolic resin, a curing promoter, and an inorganic filler, and also including other component(s) followed by kneading the compounding materials under molten state; wherein it is characteristic that >=50 wt.% of the respective amounts of the epoxy resin and phenolic resin to be compounded represent powder <250 μm in particle size, the premixing is conducted within such a temperature range as not to soften nor melt them followed by conducting the melt kneading.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an epoxy resin molding material which has good fluidity even when the filling rate of an inorganic filler is high, and causes less voids during semiconductor encapsulation molding.

[0002]

2. Description of the Related Art For sealing semiconductor elements such as ICs and LSIs, epoxy resin molding materials that can be transfer molded are widely used from the viewpoint of reliability and productivity. Epoxy resin molding material is composed of epoxy resin, phenolic resin, curing accelerator, silica filler, release agent, flame retardant, coupling agent, etc. Usually, a predetermined amount of the constituent materials is weighed and stirred with a Henschel mixer or the like. A manufacturing method in which all components are uniformly mixed and dispersed by pre-mixing using a mixer and then melt-kneading using a heating kneader such as a single-screw extruder, a twin-screw extruder, a heating roll, or a continuous kneader. Has been adopted.

On the other hand, in response to the trend toward smaller and lighter electronic devices and higher functionality, semiconductor packages have become smaller and thinner.
As the pitch is increasingly narrowed, there is a strong demand for epoxy resin molding materials for semiconductor encapsulation to improve solder heat resistance and moisture resistance related to the reliability of the semiconductor package after encapsulation. Therefore, for the purpose of reducing the stress and moisture absorption inside the semiconductor package, the components of the epoxy resin molding material have shifted to materials having a high content of the inorganic filler. However, this transition lowers the fluidity during the encapsulation molding, resulting in an increase in molding defects such as lead frame deformation, gold wire deformation, and voids. On the contrary,
Attempts to optimize the shape and particle size distribution of the inorganic filler, or to minimize the viscosity of resin components such as epoxy resin and phenolic resin in the temperature range where sealing molding is performed, maintain fluidity and maintain filling properties. While attempts have been made to improve the above, while these studies have been continued, the problem of void reduction is in a situation where it is increasingly close-up as a problem that is difficult to solve.

[0004] Voids of an epoxy resin molding material having a high content of an inorganic filler can be reduced by increasing the degree of kneading of the molding material during the melt-kneading process and promoting compatibility between the resin components of the material and dispersion of the inorganic filler. It is well known that increasing the degree of kneading during the melt-kneading process promotes the curing reaction of the molding material due to the heat history applied in the process, resulting in impairing the fluidity of the molding material. For this reason, a method is used in which, among the blended components, raw materials that do not undergo a curing reaction in the premixing stage are combined, and melt-kneaded after melting and mixing at a temperature higher than the temperature at which these raw materials are melted or softened (for example, Japanese Patent Application Laid-Open No. 149454, JP-A-Hei 4
Alternatively, by selecting a kneader and optimizing kneading conditions, the progress of the curing reaction in the kneader can be minimized, and the phase between different resin components can be reduced. A method of promoting dissolution and dispersion of the inorganic filler (for example, Japanese Patent Application Laid-Open No. 9-52228) is disclosed.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an epoxy molding material for semiconductor encapsulation which has good fluidity and has very few voids, even if the content of the inorganic filler is high. Is to do.

[0006]

The present invention has been studied in view of such circumstances, and as a result, it has been newly found that voids are greatly reduced only by promoting compatibility between resin components.
Furthermore, the present inventors have found a specific method for reducing voids in an epoxy resin molding material having a large content of an inorganic filler without advancing a curing reaction. That is, the present invention
Epoxy resin and phenolic resin used in a method for producing an epoxy resin molding material for semiconductor encapsulation which is preliminarily mixed with a raw material containing at least an epoxy resin, a phenolic resin, a curing accelerator and an inorganic filler which are solid at room temperature and then melt-kneaded Producing an epoxy molding material for semiconductor encapsulation, characterized in that 50% by weight or more of the respective compounding amounts are powdered with a particle size of less than 250 μm, which are premixed in a temperature range in which they do not melt or soften, and then melt-kneaded. Is the way.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The epoxy resin used in the present invention is not particularly limited as long as it has two or more epoxy groups in one molecule and is a solid at room temperature. For example, bisphenol type epoxy resin, biphenyl type Epoxy resins, phenol novolak-type epoxy resins, cresol novolak-type epoxy resins, alkyl-modified triphenolmethane-type epoxy resins, and the like can be used, and these may be used alone or in combination. However, when using a crystalline epoxy resin, it is necessary to use a resin having a melting point in the range of 50 ° C. to 150 ° C. in an amount of 70% by weight or more of the total epoxy resin. The reason for this is that if the melting point is lower than 50 ° C., the resin temperature rises due to frictional heat generated at the time of pre-mixing and melting starts, resulting in extremely poor workability and productivity. This is because of inferior results.

On the other hand, if the melting point exceeds 150 ° C.,
A very high temperature is required to melt the epoxy resin in the kneading machine.However, when melting and kneading the pre-mixed epoxy resin composition in the kneading machine, it is difficult to suppress the progress of the curing reaction. In other words, it is because the fluidity during sealing molding cannot be maintained satisfactorily. Regarding the use amount of the crystalline epoxy resin to be 70% by weight or more of the total epoxy resin, if the amount is less than 70% by weight, the viscosity of the produced molding material is not sufficiently reduced and the fluidity is reduced. This is because it often happens. The melting point can be easily known by an ordinary measuring method for judging the melting temperature of the resin in the glass capillary from the appearance or a measuring method using a differential scanning calorimeter.

The phenolic resin used in the present invention is not particularly limited as long as it is solid at room temperature.
For example, phenol novolak resin, cresol novolak resin, dicyclopentadiene-modified phenol resin,
Examples thereof include phenol aralkyl resins, naphthol aralkyl resins, and terpene-modified phenol resins, and these may be used alone or as a mixture.

In the present invention, it is preferable that the particle diameters of the epoxy resin and the phenolic resin in the pre-mixing are both smaller, but the content of the powder having a particle size of at least less than 250 μm is 5 to the respective compounding amounts of the epoxy resin and the phenolic resin.
It is necessary to account for 0% by weight or more. This is because when the powder particles are large, even if the epoxy resin and the phenol resin are sufficiently mixed in the pre-mixing process, it takes time for the two to be compatible in the kneader, and the curing reaction proceeds during the time. That's why. In order to determine the particle size distribution of the resin to be blended, a dry sieving method is used in which the weight distribution is measured using a sieve driven by ultrasonic waves, sound waves, rotational vibration, air flow, or the like. At this time, when the powder has cohesiveness, a method of performing measurement by mixing a small amount of a neutralizing agent such as white carbon into the powder to be measured is preferable. In addition, the powder to be measured is dispersed in a poor solvent containing a small amount of a surfactant, and the volume particle size distribution of the powder is measured by a laser light scattering method. The method of converting into may be used.

The inorganic filler used in the present invention includes fused silica powder, crystalline silica powder, alumina, silicon nitride and the like. These may be used alone or in combination. In addition, the inorganic filler that has been previously surface-treated with a silane coupling agent may be used. When using fused silica powder, use a spherical shape,
The content of silica is preferably 60 to 94% by weight in the whole composition, and more preferably 85 to 94% by weight in consideration of the balance between moldability and reliability. The reason for this is that in the conventional manufacturing method, an extremely large shear energy was required in the melt-kneading process in order to sufficiently compatibilize the resin component mixed with a large amount of silica. Has progressed and the fluidity of the molding material has been impaired, but in the present invention, the resin component is atomized in the raw material stage, so that a considerable uniform mixing state is already attained in the pre-mixing stage. In the process, the shear energy required for the compatibility of the resin components is reduced. For this reason, even if the silica content is 85 to 94% by weight or more, the fluidity of the molding material can be kept good.

The curing accelerator used in the present invention serves as a catalyst for a curing reaction for crosslinking the epoxy resin and the phenol resin, and includes an amine compound, an organic sulfonic acid compound,
Examples thereof include imidazole compounds, and these may be used alone or in combination. The epoxy resin molding material for semiconductor encapsulation obtained in the present invention is, in addition to the essential components described above, if necessary, a surface treatment agent used for a filler such as γ-glycidoxypropyltrimethoxysilane, carbon black , A release agent such as carnauba wax, a low stress agent such as silicone oil, a flame retardant such as antimony trioxide, and the like.

The premixer used in the present invention includes:
A Henschel mixer with multiple blades attached to the rotating shaft, a torrero mixer with scrapers attached to the central shaft and dispersers attached to the side, a planetary mixer with planetary motion while the central shaft rotates, In addition to mixers with strong agitation, such as kneaders with two rotating shafts, mainly shearing, such as colloid mills, pot-type or continuous ball mills, raikai, roll mills, and closed multi-stage shearing extruders. Although a strong mixer can be used, it is preferable to use a mixer having a strong stirring action and a mixer having a large shearing action. The method is particularly preferred.
Further, it is preferable to provide a cooling mechanism so that the mixing operation can be performed in a temperature range where the resin component does not melt or soften. The melt-kneading used in the present invention is not particularly limited, but a single-screw extruder including a co-kneader, a twin-screw extruder, a heating roll, a continuous kneader, a Banbury mixer and the like can be used.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Example 1 Epoxy resin [3,3 ′, 5,5′-tetramethylbiphenol diglycidyl ether resin, melting point 103 ° C., epoxy equivalent 195, median diameter 230 μm based on weight by sieving method] 4.2 parts by weight, phenol Resin [15
Melt viscosity at 0 ° C. 0.3 Pa. s, hydroxyl equivalent 17
5, weight-based median diameter 150 μm by sieving method]
4.3 parts by weight, 1.0 part by weight of brominated bisphenol A type epoxy resin, 0.2 parts by weight of triphenylphosphine, 88.0 parts by weight of spherical fused silica powder, 0.5 parts of γ-glycidoxypropyltrimethoxysilane 0.5 Parts by weight,
0.3 parts by weight of carbon black, carnauba wax
A mixture consisting of 0.5 parts by weight and 1.0 part by weight of antimony trioxide was used as a basic compound A, which was premixed with a Henschel mixer (capacity: 15 liters, rotation speed: 1,000 rpm) set at room temperature for 2 minutes. In the same direction, a twin screw extruder (screw diameter D = 30 mm, extruder shaft length = 1 m, kneading disc length = 6D,
The mixture was heated and kneaded at a screw rotation speed of 300 rpm and a discharge rate of 20 kg / h). After making the ejected material a 2 mm thick sheet,
It was cooled and pulverized to obtain an epoxy resin molding material. The fluidity and the number of voids of the obtained material were evaluated according to the following methods. The results are shown in Table 1.

<Evaluation Method> Fluidity: The spiral flow value of the epoxy resin molding material for semiconductor encapsulation was measured using a transfer molding machine equipped with a spiral flow measurement mold in accordance with EMMI-I-66. . The transfer molding conditions were a mold temperature of 175 ° C., an injection pressure of 70 kg / cm ² , and a dwell time of 120 seconds. Number of voids: 160pQFP (Body size 28mm X
A semiconductor package having a length of 28 mm, a package thickness of 3.6 mm, and an IC chip size of 15 mm X 15 mm) is sealed and molded, and the major axis diameter remaining in the semiconductor package is 0.1 mm.
The number of voids described above was observed with an ultrasonic flaw detector, and the number of voids per package was counted. The transfer sealing molding conditions for the semiconductor package were a mold temperature of 175 ° C., an injection time of 15 seconds, a dwell time of 120 seconds, and a material preheating temperature of 80 ° C.

Example 2 The same basic compound A as in Example 1 was preliminarily mixed for 2 minutes at a rotation speed of a Henschel mixer of 500 rpm, and the mixture was heated and kneaded by a twin-screw extruder in the same direction. Table 1 shows the evaluation results of the fluidity and the number of voids of the obtained epoxy resin molding material. Example 3 In the same manner as in Example 2, the basic compound A was preliminarily mixed with a Henschel mixer, and then continuously ball-milled (screw rotation speed 500 rpm, ball diameter 10 mm, discharge amount 20 kg /
In h), premixing was further performed, and the mixture was heated and kneaded with a twin-screw extruder in the same direction. Table 1 shows the evaluation results of the fluidity and the number of voids of the obtained epoxy resin molding material.

Example 4 In the same manner as in Example 2, the basic compound A was preliminarily mixed with a Henschel mixer, and then a closed multi-stage shearing extruder (rotating blade diameter 80 mm, number of blades 4 sets, blade rotation speed 300 rpm, discharge rate) The mixture was further premixed at 20 kg / h) and heated and kneaded with a co-meshing twin screw extruder. Table 1 shows the evaluation results of the fluidity and the number of voids of the obtained epoxy resin molding material.

Comparative Examples 1 to 4 Of the basic compound A, only the epoxy resin and the phenol resin were used.
Compound B, which had been replaced with 80 μm, was preliminarily mixed and kneaded in the same manner as in Examples 1 to 4. Table 1 shows the evaluation results of the fluidity and the number of voids of the obtained epoxy resin molding material.

Examples 5-8, Comparative Examples 5-8 Epoxy resin [3,3 ', 5,5'-tetramethylbiphenol diglycidyl ether resin, melting point 103 ° C, epoxy equivalent 195, weight-based by sieving method Median diameter 230 μm] 7.9 parts by weight, phenol resin [15
Melt viscosity at 0 ° C. 0.3 Pa. s, hydroxyl equivalent 17
5, weight-based median diameter 150 μm by sieving method]
8.0 parts by weight, 1.5 parts by weight of brominated bisphenol A type epoxy resin, 0.4 parts by weight of triphenylphosphine, 80.0 parts by weight of spherical fused silica powder, 0.4 gamma-glycidoxypropyltrimethoxysilane 0.4 Parts by weight,
0.3 parts by weight of carbon black, carnauba wax
A composition having a low content of silica powder composed of 0.5 parts by weight and 1.0 part by weight of antimony trioxide was defined as a basic compound C. Of the basic compound C, only the epoxy resin and the phenol resin were weighed. The reference median diameter is 330 each
Preliminary mixing and heat kneading were performed in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 4 together with the compound D substituted for those having μm and 280 μm. Table 2 shows the evaluation results of the fluidity and the number of voids of the obtained epoxy resin molding material.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

As described above, according to the present invention, even if the filling rate of the inorganic filler is high, the resin component is uniformly mixed without causing the curing reaction to proceed. An epoxy molding compound is obtained, and as a result,
In the encapsulation molding of a semiconductor package, it is possible to stably produce an epoxy molding material for semiconductor encapsulation which has good flowability, has few voids, and is excellent in moldability.

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Claims (2)

[Claims] 1. A method for producing an epoxy resin molding material for semiconductor encapsulation in which a raw material containing at least an epoxy resin, a phenol resin, a curing accelerator and an inorganic filler which is solid at room temperature is preliminarily mixed and kneaded. 50% by weight or more of the respective blending amounts of the epoxy resin and the phenol resin are powder having a particle size of less than 250 μm, and they are premixed in a temperature range where they do not melt or soften, and then melt-kneaded. Manufacturing method of epoxy molding material. 2. The epoxy resin is a crystalline epoxy resin having a melting point of 50 to 150 ° C., containing 70% by weight or more in the total epoxy resin, and the inorganic filler is a fused spherical silica powder. The method for producing an epoxy resin molding material for semiconductor encapsulation according to claim 1, wherein the amount of the resin composition is at least 10 wt%.