JP2002284857A - Epoxy resin molding material and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin molding material for sealing a semiconductor which has more excellent soldering crack resistance and temperature cycle resistance in their compatibility. SOLUTION: The epoxy resin molding material for sealing a semiconductor comprises an epoxy resin, a phenol resin, an inorganic filler and a curing accelerator, wherein the epoxy resin molding material provides a cured product which has a Charpy impact strength at -65 deg.C (a) and a Charpy impact strength at 260 deg.C (b) to meet an (a)+(b) sum of 5×10<3> N.m/m or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin molding material for semiconductor encapsulation and a semiconductor device using the same.

[0002]

2. Description of the Related Art In recent years, semiconductor devices such as ICs and LSIs have been
Semiconductor devices sealed using an epoxy resin molding material are mainly surface-mounted types such as QFP and TSOP. In addition, as the size of the semiconductor device, the size of the chip, and the pitch become finer, the requirements for solder crack resistance are becoming more stringent. Conventional epoxy resin molding materials have improved solder cracking resistance by increasing the strength and lowering water absorption by increasing the amount of inorganic filler, but cracks tend to occur in large semiconductor devices due to peeling under pads. Also, there is a problem that the temperature cycle resistance is reduced. As described above, with the conventional epoxy resin molding material, it has been difficult to achieve both solder crack resistance and temperature cycle resistance particularly for a large semiconductor device.

In order to improve the solder crack resistance, it is important to improve the adhesion to various members used in a semiconductor device, especially to a lead frame, in addition to the above-described techniques for increasing the strength and reducing the water absorption. In order to improve the adhesion to the lead frame, a method of dimpleting or slitting the lead frame has been proposed and put to practical use. Further, by using a silane coupling agent or adjusting a wax as a release agent, the adhesion can be improved to some extent. However, since solder cracking resistance has been evaluated based on the presence or absence of peeling, stricter requirements for adhesion have been issued, and the stress generated due to the increase in reflow temperature accompanying lead-free has increased. However, conventional techniques alone are becoming insufficient. In addition, in order to improve the temperature cycle resistance, conventionally, silicone oil or the like has been added, or a reaction product of the silicone oil and an epoxy resin, a phenol resin or the like has been added to reduce the elastic modulus. When a silicone oil is used, there occurs a problem that the strength and the adhesion to various members are reduced. Thus, there is a problem that solder crack resistance and temperature cycle resistance are not compatible.

[0004]

SUMMARY OF THE INVENTION The present invention provides an epoxy resin molding compound for semiconductor encapsulation, which can achieve both excellent solder crack resistance and temperature cycle resistance, and a semiconductor device using the same. Things.

[0005]

Means for Solving the Problems The present invention provides [1] (A)
In an epoxy resin molding material containing an epoxy resin, (B) a phenol resin, (C) an inorganic filler, and (D) a curing accelerator, a Charpy impact of the cured product of the epoxy resin molding material at -65 ° C. The sum (a) + (b) of the strength (a) and the Charpy impact strength at 260 ° C. (b) is 5 × 1
[3] An epoxy resin molding material for semiconductor encapsulation characterized by being at least 0 ³ N · m / m ² , [2] a semiconductor element is encapsulated using the epoxy resin molding material for semiconductor encapsulation according to item [1]. A semiconductor device which is stopped.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a method for preventing the occurrence of cracks during soldering and during temperature cycling, a cured product of an epoxy resin molding material itself has a material strength that can withstand the stress generated during processing. A method and a method of reducing the stress generated inside the semiconductor device can be considered. The present inventor particularly focused on the Charpy impact strength as this material strength because impact stress due to steam explosion is generated particularly during soldering, and evaluated the correlation between solder crack resistance and temperature cycle resistance. Charpy impact strength at -65 ° C of the cured product of the epoxy resin molding material (a)
(A) + of the Charpy impact strength (b) at 260 ° C. and
When (b) is adjusted to be 5 × 10 ³ N · m / m ² or more, it is found that cracks generated during the soldering process of the semiconductor device and cracks generated during the temperature cycle are drastically reduced, and the present invention is achieved. Reached.

The epoxy resin used in the present invention includes 1
It refers to all monomers, oligomers and polymers having two or more epoxy groups in the molecule, and is not particularly limited. For example, ortho-cresol novolak epoxy resin, phenol novolak epoxy resin, dicyclopentadiene-modified phenol epoxy resin, bisphenol epoxy resin, biphenyl epoxy resin, stilbene epoxy resin, naphthol epoxy resin,
Triphenolmethane-type epoxy resins, triazine nucleus-containing epoxy resins, terpene-modified phenol-type epoxy resins, phenol-aralkyl-type epoxy resins, and modified resins thereof, and the like, may be used alone or in combination of two or more. . In order to improve the moisture resistance of the epoxy resin molding material, it is desirable that impurity ions such as chlorine ions and sodium ions be as small as possible. For curability, an epoxy equivalent of about 150 to 300 is preferable.

The phenolic resin used in the present invention includes:
It refers to all monomers, oligomers and polymers having two or more phenolic hydroxyl groups in one molecule, and is not particularly limited. For example, phenol novolak resin,
Cresol novolak resin, dicyclopentadiene-modified phenol resin, terpene-modified phenol resin, phenol aralkyl resin, naphthol aralkyl resin, triphenol methane resin, and modified resins thereof, and the like, and these may be used alone or in combination of two or more. You may. In order to improve the moisture resistance of the epoxy resin molding material, it is desirable that impurity ions such as chlorine ions and sodium ions be as small as possible. For curability, the hydroxyl equivalent is preferably about 80 to 250.

It is preferable that the mixing ratio of the epoxy resin and the phenol resin is such that the hydroxyl group in the phenol resin is 0.8 to 1.2 equivalent per 1 equivalent of the epoxy group in the epoxy resin.

Examples of the inorganic filler used in the present invention include fused silica, spherical silica, crystalline silica, secondary aggregated silica, porous silica, silica obtained by pulverizing secondary aggregated silica or porous silica, and alumina. These may be used alone or in combination of two or more. The shape of the particles may be either crushed or spherical without any particular problem, but spherical fused silica having a good balance of flow characteristics, mechanical strength and thermal characteristics is preferably used. The content of the inorganic filler is preferably 75% by weight or more in all the epoxy resin molding materials. Particularly preferred is 83% by weight or more. 7
If it is less than 5% by weight, the effect of improving various properties tends to be significantly reduced. Further, these inorganic fillers may be surface-treated with a coupling agent or the like.

As the curing accelerator used in the present invention, those generally used for a sealing material can be widely used. Representative examples include, for example, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetranaphthoic acid borate, benzyldimethylamine , 2-methylimidazole and the like, and these may be used alone or in combination of two or more. These curing accelerators are
It may be dry-blended, melt-blended, or a combination of both in the epoxy resin molding material.

The epoxy resin molding material of the present invention comprises (A)
To (D) as an essential component, but if necessary, a coupling agent such as a silane coupling agent, a brominated epoxy resin, a flame retardant such as antimony oxide, a coloring agent such as carbon black, a natural wax, and a synthetic wax. Various additives such as a release agent may be appropriately compounded. The epoxy resin molding material of the present invention is prepared by sufficiently mixing the components (A) to (D) and other additives at room temperature with a mixer such as a mixer, and then melting the mixture with a hot roll or a kneader. It is obtained by kneading, cooling and pulverizing. Using the epoxy resin molding material of the present invention to encapsulate electronic components such as semiconductor elements and manufacture semiconductor devices, transfer molding, compression molding, injection molding, and other conventional molding methods can be used to cure and mold. Good. In particular, the epoxy resin molding material of the present invention is suitable for encapsulating large semiconductor devices, and the size of the semiconductor device is, for example, 20 mm × 20 mm or more,
It is suitable for QFP of 4 mm × 24 mm or more.

The epoxy resin molding material of the present invention has a Charpy impact strength at -65 ° C. (a) and a Charpy impact strength at 260 ° C. (b) of a cured product of the epoxy resin molding material.
It is necessary to make adjustment so that the sum (a) + (b) is 5 × 10 ³ N · m / m ² or more. The method is not particularly limited. For example, a specific type effective for improving the impact resistance is used as each of the components (A) to (D), or a method effective for improving the specific impact resistance is used. The use of a certain additive or the like, or the use of a specific manufacturing method, and the like. That is, whichever method is used, as a result, the sum of the Charpy impact strength (a) at -65 ° C. and the Charpy impact strength (b) at 260 ° C. of the cured product of the epoxy resin molding material (a) + ( By adjusting b) to be 5 × 10 ³ N · m / m ² or more, it is possible to obtain an epoxy resin molding material and a semiconductor device which can achieve both excellent solder crack resistance and temperature cycle resistance, compared to the conventional art. . The sum (a) + (b) of the Charpy impact strength at −65 ° C. (a) and the Charpy impact strength at 260 ° C. (b) is 5 × 10 ³ N · m.
If it is less than / m ² , the resistance to solder cracking or the resistance to temperature cycling will be reduced, and it will not be compatible. The additive effective for improving the impact strength used in the present invention is not particularly limited, but for example, an acrylonitrile-butadiene-based copolymer, hydrogenated acrylonitrile-butadiene for improving the temperature cycle resistance at low temperatures. System copolymer, acrylic rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, silicone rubber, fluoro rubber, styrene butadiene block copolymer, styrene isoprene block copolymer, etc. Polyetherimide, polyether sulfone, polyphenylene ether,
And polyarylate. Also, reactive functional groups,
It may have a functional group, side chain, or the like that enhances compatibility with an epoxy resin or a phenol resin. These may be used alone or in combination of two or more. However, in order to achieve both temperature cycling resistance and solder cracking resistance, an additive for improving temperature cycling resistance and an additive for improving solder cracking resistance are used. It is more preferable to use together with an additive. The content is not particularly limited. In addition, the high filling of the inorganic filler is very effective, but with a decrease in fluidity and an increase in viscosity, together with the adjustment of the particle size distribution of the inorganic filler and the viscosity of the resin component,
It is necessary to devise a manufacturing method that improves the wettability between the inorganic filler and the resin component.

[0014]

The present invention will be specifically described below with reference to examples.
The mixing ratio is by weight. Example 1 Biphenyl type epoxy resin (melting point 105 ° C, epoxy equivalent 195) 5.8 parts by weight Phenol aralkyl resin (softening point 80 ° C, hydroxyl equivalent 174) 5.2 parts by weight Spherical fused silica 83.0 parts by weight triphenylphosphine 0.2 parts by weight Hydrogenated acrylonitrile-butadiene copolymer 1.5 parts by weight Polyetherimide 1.5 parts by weight Epoxysilane coupling agent 0.5 parts by weight Brominated phenol novolak type epoxy resin 1.0 parts by weight 0.5 parts by weight of antimony oxide, 0.3 parts by weight of carbon black, 0.5 parts by weight of carnauba wax are mixed at room temperature using a mixer, kneaded at 90 to 130 ° C. using a biaxial roll, cooled and ground. Thus, an epoxy resin molding material was obtained. The obtained epoxy resin molding material was evaluated by the following method. Table 1 shows the results.

Evaluation method Charpy impact strength: based on JIS K 6911,
Using a low pressure transfer molding machine, molding temperature 175
° C, pressure 7N / mm^TwoCharpy with a curing time of 120 seconds
The impact test specimen is molded and post-mold cured.
At 175 ° C. for 8 hours. The obtained test piece
Charpy impact at measurement temperature of -65 ° C and 260 ° C using
The strength was measured, and (a) + (b) was determined. unit
Is Nm / m ^Two. Solder crack resistance: using low-pressure transfer molding machine
Molding temperature 175 ° C, pressure 7N / mm^Two, Curing time 1
208pQFP in 20 seconds (dummy chip size 9mm
× 9mm × thickness 350μm, package size 28mm
× 28mm × 3.2mm thick) and further
8 hours treatment at 175 ° C.
(The number of samples is 12). 85 obtained packages
After absorbing moisture for 168 hours in an atmosphere at 60 ° C. and a relative humidity of 60%, 2
An IR reflow treatment at 60 ° C. was performed. Use ultrasonic flaw detector
And observe the inside of the package after processing.
Is a defective package with peeling or cracks on the back of the pad
The solder crack resistance (and adhesion) was determined by the number of samples. Temperature cycle resistance: Using low pressure transfer molding machine
Molding temperature 175 ° C, pressure 7N / mm^Two, Curing time 1
208pQFP in 20 seconds (dummy chip size 9mm
× 9mm × thickness 350μm, package size 28mm
× 28mm × 3.2mm thick) and further
8 hours treatment at 175 ° C.
(The number of samples is 12). 30 packages obtained
After absorbing moisture for 192 hours in an atmosphere at 60 ° C and a relative humidity of 60%,
Temperature cycle test was performed at -65 ° C to 150 ° C for 200 cycles.
Cycle, 500 cycles, 1000 cycles
The number of packages that have peeled or cracked
The temperature cycle resistance was determined.

Examples 2 to 6, Comparative Examples 1 to 4 Epoxy resin molding materials were obtained in the same manner as in Example 1 according to the formulations in Tables 1 and 2, and evaluated in the same manner as in Example 1.
The results are shown in Tables 1 and 2. In Examples 3 and 4, an epoxy-modified silicone rubber and polyether sulfone were used. In Example 6, kneading was performed at 120 to 130 ° C. using a biaxial kneader.

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, there is provided an epoxy resin molding material for semiconductor encapsulation and a semiconductor device which are both excellent in solder crack resistance and temperature cycling resistance, and which are particularly suitable for large semiconductor devices. Obtainable.

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Claims (2)

[Claims] 1. An epoxy resin molding material comprising (A) an epoxy resin, (B) a phenolic resin, (C) an inorganic filler, and (D) a curing accelerator, wherein the cured product of the epoxy resin molding material is The sum (a) + (b) of the Charpy impact strength at -65 ° C. (a) and the Charpy impact strength at 260 ° C. (b) is 5 × 10 ³ N · m / m ² or more. Epoxy resin molding compound for semiconductor encapsulation. 2. A semiconductor device, wherein a semiconductor element is sealed using the epoxy resin molding material for semiconductor sealing according to claim 1.