JPH11130940A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor sealing composition showing reduced warpage in a ball grid array type package and being excellent reliability of humidity resistance after soldering by mixing as the essential components a triphenylmethane phenolic resin with an epoxy resin derived by glycidyl- etherifying it and specified amounts of an inorganic filler and a cure accelerator. SOLUTION: There are used a phenolic resin represented by formula I (wherein R1 is a halogen or a 1-10C alkyl; and m is 0-2) and an epoxy resin represented by formula II (wherein R2 is a halogen or a 1-10C alkyl; and n is 0-2). The compounding amount of the inorganic filler is 80-90 wt.% based on the total composition. The epoxy resin of formula II is one prepared by glycidyl-etherifying the phenolic resin of formula I. The inorganic filler used is desirably a broken fused silica powder, a spherical silica powder or a mixture thereof. The cure accelerator used may be anything that can accelerate the curing reaction of epoxy groups with phenolic hydroxyl groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to an epoxy resin composition for semiconductor encapsulation which has a small warpage in a ball grid array type package and which is excellent in reliability and molding workability, and a semiconductor device using the same. Things.

[0002]

2. Description of the Related Art Conventionally, semiconductor devices such as transistors, ICs, and LSIs are mainly used as semiconductor devices sealed with ceramics or plastics. In the above ceramic package, the constituent material itself has heat resistance, and since the moisture permeability is small and hollow, heat resistance,
The semiconductor device has excellent moisture resistance. However, there are disadvantages that the constituent material is more expensive than plastics and the like, and that the productivity of the package is poor. Therefore, among the packages, resin encapsulation using a plastic having excellent cost and productivity has become mainstream except for some high-end products requiring special reliability. An epoxy resin composition (hereinafter, referred to as a resin composition) has been used for such a resin-encapsulated plastic package.
It has been well received by the semiconductor industry for its improved reliability, including improvements from the beginning of development. However, technological innovation in the semiconductor field is unavoidable, and the integration level is increasing and the design rules are becoming finer and the device size is becoming larger.On the other hand, the package size is becoming smaller and thinner in order to increase the mounting density. , The sealing material is increasingly required to have higher reliability. In addition, since the package mounting method has also shifted to surface mounting, which can obtain a higher mounting density than conventional insertion mounting, solder cracks due to thermal shock during soldering during mounting and accompanying Deterioration of reliability such as moisture resistance has become a problem.

On the other hand, as a method of further improving the packaging density of a package, development of a package that replaces the currently mainstream QFP type has been rushed. As described above, as the integration of semiconductors increases, the number of pins in the QFP type further increases, the distance between pins becomes smaller, and the pin diameter becomes smaller, so that the yield and warpage of mounting on a circuit board are reduced. Demands are increasingly stringent. It is generally said that the limit is about 300 pins. In order to solve these problems, a ball grid array (BGA) type package has been developed as a new type package replacing the QFP type. The BGA type package is one in which a semiconductor element is mounted on a substrate such as a maleimide / triazine resin, and only the surface of the substrate on which the element is mounted is sealed with an organic sealing resin. The continuity with the outside of the package is achieved by arranging wiring in the substrate in advance, and
Performed through GA. Therefore, a sufficient distance between the balls can be obtained as compared with the QFP type pins having the same number of pins, so that the yield at the time of mounting on the circuit board can be greatly improved. Conventionally, a liquid resin composition has been used for a BGA type package because of its easy workability, but recently, a transition to a resin composition for transfer molding which is excellent in productivity has been progressing.

However, this BGA type package has several problems. First, since substantially only one side of the substrate is sealed with the resin composition, the difference in thermal expansion coefficient between the cured product of the resin composition and the substrate causes warpage of the package after molding and cooling, which hinders mounting. Cause. Further, the adhesion between the cured product of the resin composition and the substrate is also an important factor, and when the adhesion is reduced, the reliability is reduced due to intrusion of moisture from the peeling interface during use of the semiconductor device. Further, in the case of a multi-ball BGA type package, it is necessary to extend the gold wire in the package from the viewpoint of the structure, and the wire easily flows at the time of sealing. . Therefore, development of a sealing epoxy resin composition that solves such a problem is desired.

[0005]

SUMMARY OF THE INVENTION The present invention solves such a problem by minimizing the warpage of a BGA type package, reducing the flow of wires at the time of sealing, and further improving the reliability of a semiconductor device after soldering. It is an object of the present invention to provide an epoxy resin composition for encapsulating a semiconductor having significantly improved moisture resistance reliability.

[0006]

According to the present invention, there are provided (A) a phenolic resin represented by the formula (1), (B) an epoxy resin represented by the formula (2), and (C) a blending amount in the total resin composition. Is an epoxy resin composition for semiconductor encapsulation, wherein the epoxy resin composition contains 80 to 90% by weight of an inorganic filler and (D) a curing accelerator as essential components.

Embedded image (R ₁ in the formula is the same or different atom or group selected from halogen and an alkyl group having 1 to 10 carbon atoms.
m is 0, 1 or 2. )

[0007]

Embedded image (R ₂ in the formula is the same or different atoms or groups selected from halogen and alkyl groups having 1 to 10 carbon atoms.
n is 0, 1 or 2. )

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The phenolic resin represented by the molecular structure of the formula (1) used in the present invention is a triphenylmethane-type phenolic resin, which also has a phenolic hydroxyl group in the side chain, so When used as a curing agent, it gives the cured product a high crosslink density, a high glass transition temperature, and a very small cure shrinkage characteristic as compared with conventional phenol novolak resins. Further, since a benzene ring is introduced into the side chain, appropriate flexibility and low water absorption can be achieved. Further, compared with the conventional polyfunctional phenolic resin, the molecular weight is small and the melt viscosity is low, which is effective in reducing the wire flow during transfer molding and improving the adhesion to the substrate. Further, since the melt viscosity of the resin is low, a large amount of the inorganic filler can be blended in the resin composition, and low thermal expansion (linear expansion coefficient: 1.1 to 1.3) similar to a BGA type substrate.
(× 10 ⁻⁵ / ° C.), so that the warpage of the BGA type package after molding can be extremely reduced, and the water absorption can be further reduced. When the resin composition containing the phenolic resin of the present invention is applied to a BGA type package, the amount of warpage of the package is significantly reduced, and the adhesion to the substrate and the solder crack resistance are excellent. Further, another phenol resin can be used in combination as long as the properties of the phenol resin represented by the formula (1) are not impaired. Examples of the resin that can be used in combination include a phenol novolak resin, a cresol novolak resin, a dicyclopentadiene-modified phenol resin, a xylylene-modified phenol resin, and a terpene-modified phenol resin. These may be used alone or in combination.

The epoxy resin represented by the formula (2) used in the present invention is obtained by glycidyl etherification of the phenol resin of the formula (1). When applied to a BGA type package similarly to the phenolic resin of the formula (1), the amount of warpage of the package is significantly reduced as compared with the conventional orthocresol novolak type epoxy resin, and further, the adhesion to the substrate and the solder crack resistance Is better. The present invention has an optimal cured physical property for a BGA type package,
By combining a phenolic resin and an epoxy resin having the same resin skeleton structure, a uniform cured product can be obtained, and as a synergistic effect, the amount of warpage of the BGA type package is extremely small, and moisture resistance reliability after soldering is obtained. In addition, it is possible to obtain a resin composition having a very small wire flow during sealing. Further, another epoxy resin can be used in combination as long as the properties of the epoxy resin represented by the formula (2) are not impaired. Examples of resins that can be used in combination include bisphenol A type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, and the like, and these may be used alone or in combination.

As the inorganic filler used in the present invention, generally, crushed silica powder, spherical silica powder formed into a spherical shape by spraying or the like, crystalline silica powder, silicon nitride powder, aluminum nitride powder, alumina powder, Examples thereof include calcium carbonate powder, aggregated silica powder, and porous silica powder. Particularly, it is preferable to use fused silica powder, spherical silica powder, or an appropriate mixture of fused silica powder and spherical silica powder. The amount of the inorganic filler is preferably 80 to 80% in all the resin compositions in order to reduce the warpage in the BGA type package and improve the moisture resistance reliability.
90% by weight is preferred. If it is less than 80% by weight, the obtained cured product has a high linear expansion coefficient, which is different from the linear expansion coefficient of the substrate used for the BGA type package, and the package warpage is undesirably increased. On the other hand, if the amount of the inorganic filler exceeds 90% by weight, the viscosity of the resin composition at the time of encapsulation increases, which causes disadvantages such as the flow of gold wire in the package, which is not preferable.

As the curing accelerator used in the present invention, any one can be used as long as it promotes the curing reaction between the epoxy group and the phenolic hydroxyl group, and those generally used in sealing materials can be widely used. For example, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, dimethylbenzylamine, 2-methylimidazole and the like can be mentioned, and these may be used alone or in combination.

The resin composition of the present invention comprises, in addition to the components (A) to (D), if necessary, a silane coupling agent, a coloring agent such as carbon black and red iron, a releasing agent such as various waxes, and a silicone. Oil, silicone rubber, polyethylene rubber and other low stress additives may be appropriately compounded. Further, the resin composition of the present invention is prepared by sufficiently mixing the components (A) to (D) and other additives using a mixer such as a super mixer, and then mixing the mixture with a hot roll or a kneader. It is obtained by kneading with a melt kneader, cooling and grinding. In order to manufacture a semiconductor device by encapsulating an electronic component such as a semiconductor using the resin composition of the present invention, it is sufficient to cure and mold by a molding method such as a transfer mold, a compression mold, and an injection mold.

[0013]

EXAMPLES Examples and comparative examples of the present invention will be shown below to specifically explain the present invention. The mixing unit is parts by weight. Example 1 The following composition 7.43 parts by weight of a phenol resin represented by the formula (3) (melting point: 150 ° C., hydroxyl equivalent: 141 g / eq)

Embedded image

10.57 parts by weight of an epoxy resin represented by the formula (4) (melting point: 120 ° C., epoxy equivalent: 197 g / eq)

Embedded image 74.00 parts by weight of fused spherical silica powder A (average particle diameter 20 μm, specific surface area 2.5 m ² / g) 7.00 parts by weight of fused spherical silica powder B (average particle diameter 0.5 μm, specific surface area 5.7 m ² / g) 7.00 Parts by weight 1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 0.20 parts by weight Carbon black 0.30 parts by weight Carnauba wax 0.50 parts by weight at room temperature using a super mixer Mix, 70-10
The mixture was kneaded with a biaxial roll at 0 ° C., cooled and pulverized to obtain a resin composition. The obtained resin composition was evaluated by the following method.
Table 1 shows the results.

Evaluation method Spiral flow: using a test mold in accordance with EMMI-I-66, mold temperature 175 ° C., injection pressure 70 kgf /
Spiral flow was measured at cm ² and a curing time of 120 seconds. Unit cm. Production of BGA type package: Using a low pressure transfer molding machine, 175 ° C., pressure 70 kg / cm ² , curing time 1
20 seconds, 357 balls B for testing package warpage, wire flow, solder crack resistance, and solder moisture resistance
A GA-type package (substrate is a maleimide / triazine resin and glass cloth, dimensions 22.5 × 22.5 × 0.85 mm in thickness, hereinafter referred to as a BGA-type 357B package) was formed. Fillability: When the BGA type 357B package was molded, the presence or absence of an unfilled portion was visually observed. Package warpage: The BGA type 357B package was post-mold cured at 175 ° C. for 4 hours. Thereafter, the amount of warpage was measured using a surface roughness meter. The measurement location was the surface sealed with the resin composition, and the probe was run on the diagonal line of the package from end to end. The measurement was performed at two locations in different directions, and the average value was obtained. Unit μm. Measurement of wire flow rate: The BGA type 357B package was measured with a soft X-ray transmission apparatus. The wire flow rate was determined by calculating the percentage of the length of the wire with respect to the length of the wire. The maximum wire flow in each package is taken as the wire flow in that package,
Ten packages were observed for each material and averaged. unit%. Solder crack resistance: The BGA type 357B package was post-mold cured at 175 ° C. for 4 hours. Next, a moisture absorption treatment was performed for 168 hours in a thermo-hygrostat at 85 ° C. and a relative humidity of 60%, and a heat treatment was further performed in an IR reflow furnace at 240 ° C. The obtained package was inspected for defects using an ultrasonic flaw detector. The peeling and cracking of the interface inside the package were regarded as defective, and the number of defective packages with respect to a total of 24 packages was determined and expressed as the number of defectives / total. Solder moisture resistance test: The BGA type 357B package was post-mold cured at 175 ° C. for 4 hours. next,
The sample was subjected to a moisture absorption process in a thermo-hygrostat at 85 ° C. and a relative humidity of 60% for 168 hours, and further heat-treated in a 240 ° C. IR reflow furnace. Thereafter, a pressure cooker test (120
℃, relative humidity 100%), and the open failure of the circuit was measured. The defect rate was determined from the number of defective packages for a total of 24 packages, and the time when the defect rate became 50% was defined as the average life. The unit is time.

Examples 2 and 3 Compounded according to the formulation shown in Table 1, a resin composition was obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. Table 1 shows the results. Comparative Examples 1 to 4 Resins were blended in accordance with the formulation shown in Table 1 to obtain a resin composition in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The softening point of the phenol novolak resin of Comparative Example 3 was 81 ° C.
The hydroxyl equivalent is 104 g / eq, the softening point of the ortho-cresol novolak type epoxy resin of Comparative Example 4 is 55 ° C., and the epoxy equivalent is 195 g / eq. Table 2 shows the results.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

According to the present invention, an epoxy resin composition for semiconductor encapsulation with a small wire flow can be obtained. In particular, when the epoxy resin composition is applied to a ball grid array type package, the warpage of the package is reduced, and after the soldering, Excellent moisture resistance reliability.

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Claims (2)

[Claims] (A) a phenolic resin represented by the formula (1), (B) an epoxy resin represented by the formula (2), and (C) a compounding amount in the total resin composition is 80 to 90% by weight. An epoxy resin composition for semiconductor encapsulation, comprising an inorganic filler and (D) a curing accelerator as essential components. Embedded image (R ₁ in the formula is the same or different atom or group selected from halogen and an alkyl group having 1 to 10 carbon atoms.
m is 0, 1 or 2. ) (R ₂ in the formula is the same or different atoms or groups selected from halogen and alkyl groups having 1 to 10 carbon atoms.
n is 0, 1 or 2. ) 2. A semiconductor device which is encapsulated with the epoxy resin composition for semiconductor encapsulation according to claim 1.