JP2001253999A - Epoxy resin molding material and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin molding material for sealing semiconductor which is excellent in adhesion to various members such as lead frames, resistance to soldering crack and resistance to temperature cycling. SOLUTION: This epoxy resin molding material for sealing semiconductor prepared by heat-kneading an epoxy resin composition comprising (A) an epoxy resin, (B) a phenolic resin, (C) an inorganic filler, (D) a hardening accelerator and (E) a vinylidene fluoride-based rubber having a weight average molecular weight of 30,000-70,000 in an amount of 0.02-5 wt.% based on the total weight of the epoxy resin composition features that the dispersed particle diameter of the vinylidene fluoride-based rubber is not larger than 50 μm.

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 having excellent low stress properties and excellent adhesion to various members such as lead frames, 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 mainly sealed with epoxy resin molding materials
Surface mount types such as QFP and SOJ are becoming mainstream.
In addition, the size of the semiconductor device, the size of the semiconductor element, and the fine pitch have been advanced, and requirements for solder crack resistance have also become strict. Conventional epoxy resin molding materials have improved the solder crack resistance by increasing the strength of the inorganic filler and increasing the water absorption rate by increasing the filling of the inorganic filler.However, in large semiconductor devices, peeling under the pad is likely to occur. Also, there is a decrease in temperature cycle resistance. Thus, in the conventional epoxy resin molding material, especially for a large semiconductor device,
It was difficult to achieve both solder crack resistance and temperature cycle resistance.

In order to improve the solder cracking resistance, in addition to the above-described techniques for increasing the strength and lowering the water absorption by increasing the amount of the inorganic filler, various members used in a semiconductor device, particularly a lead frame. It is important to improve the adhesion. For this reason, a method of forming dimples or slits on a 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 the evaluation of the solder crack resistance has been made based on the presence or absence of peeling, stricter requirements have been issued for the adhesion, and the conventional method alone has become 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 is a problem that the strength is reduced and the adhesion to various members is reduced.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to an epoxy resin molding material for semiconductor encapsulation which is excellent in adhesion to various members such as a lead frame, solder crack resistance, and temperature cycle resistance. A semiconductor device is provided.

[0005]

The present invention provides (A) an epoxy resin, (B) a phenolic resin, (C) an inorganic filler,
An epoxy resin composition containing (D) a curing accelerator, and (E) an epoxy resin composition containing 0.02 to 5% by weight of a vinylidene fluoride rubber having a weight average molecular weight of 30,000 to 70,000 in all epoxy resin compositions. In a pulverized molding material, the dispersed particle size of the vinylidene fluoride rubber is 50 μm or less, and an epoxy resin molding material for semiconductor encapsulation, and a semiconductor element is encapsulated using the same. A semiconductor device characterized by the above-mentioned.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The epoxy resin used in the present invention includes all monomers, oligomers and polymers having two or more epoxy groups in one molecule, and is not particularly limited. For example, ortho-cresol novolak type epoxy resin, phenol novolak type epoxy resin,
Dicyclopentadiene-modified phenolic epoxy resin,
Bisphenol-type epoxy resin, biphenyl-type epoxy resin, stilbene-type epoxy resin, naphthol-type epoxy resin, triphenolmethane-type epoxy resin, triazine nucleus-containing epoxy resin, and modified resins thereof, and the like. May be used. 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 epoxy equivalent is preferably about 150 to 300 g / eq.

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,
Examples thereof include a dicyclopentadiene-modified phenol resin, a phenol aralkyl resin, a triphenolmethane resin, and modified resins thereof, and these may be used alone or in combination. 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 g / eq.

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 as a mixture. The shape of the particles may be crushed or spherical without any particular problem, but spherical fused silica having a good balance of flow characteristics, mechanical strength and thermal characteristics is preferred. Further, these inorganic fillers may be surface-treated with a coupling agent.

As the curing accelerator used in the present invention, those generally used in sealing materials 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 as a mixture. These curing accelerators may be dry-blended, melt-blended, or both in the epoxy resin molding material.

The vinylidene fluoride rubber having a weight average molecular weight of 30,000 to 70,000 used in the present invention will be described in detail below. Examples of the vinylidene fluoride-based rubber of the present invention include a copolymer of vinylidene fluoride and propylene pentafluoride or a copolymer of vinylidene fluoride and propylene hexafluoride. A copolymer of vinylidene and propylene hexafluoride is preferred. Further, in order to make the dispersed particle size of the vinylidene fluoride rubber in the epoxy resin molding material 50 μm or less, the vinylidene fluoride rubber of the present invention is preferably a powder. Since vinylidene fluoride rubber has flexibility, crumbs or pellets are not preferable because they do not disperse finely by a shearing force during ordinary heating and kneading, and it is difficult to obtain a dispersed particle size of 50 μm or less. It is essential that the weight average molecular weight (Mw) is 30,000 to 70,000, more preferably 40,000 to 70,000.
50,000. If the Mw is less than 30,000, bleeding is likely to occur during molding, causing mold contamination and the like, which is not preferable.
If the Mw exceeds 70,000, the viscosity increases, the fluidity decreases, and the low stress property and the adhesiveness become insufficient. It is not preferable because it occurs. The Mw of the vinylidene fluoride rubber of the present invention is determined by gel permeation chromatography (GPC) using polystyrene as a reference substance and using tetrahydrofuran as a developing solvent. As the dispersed particle size in the epoxy resin molding material,
50 μm or less is essential, and more preferably 30 μm or less. For this purpose, it is preferable to use powdered vinylidene fluoride rubber and to select equipment and conditions for reducing the dispersion particle size even during mixing and kneading. If the dispersed particle size exceeds 50 μm, the moldability (bleeding, clouding, fluidity) is poor, which is not preferable. The dispersed particle size of the vinylidene fluoride rubber of the present invention is observed at a magnification of 1,000 to 2,000 using an electron microscope after a cross section of a molded product of the epoxy resin molding material is polished and finished. The compounding amount is 0.02 to 5% by weight, more preferably 0.2 to 3% by weight, based on the entire epoxy resin molding material. If the content is less than 0.02% by weight, the effects of improving water repellency, adhesion to various members, and improving temperature cycle resistance cannot be obtained. If it exceeds 5% by weight, the viscosity becomes too high, the fluidity may be lowered, or the moldability (bleed) may be poor, and the cost may be increased, which is not preferable.

The epoxy resin molding material of the present invention comprises (A)
To (E) 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 trioxide, a coloring agent such as carbon black, a natural wax, and a synthetic wax. Various additives such as a release agent such as wax and low-stress additives such as silicone oil and rubber may be appropriately compounded. The epoxy resin molding material of the present invention is obtained by mixing the components (A) to (E) and other additives sufficiently uniformly at room temperature using a mixer or the like,
Furthermore, it is obtained by melt-kneading with a hot roll or a kneader, 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.

[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 (melting point 105 ° C, epoxy equivalent 195) 8.6 parts by weight Phenol aralkyl resin (softening point 80 ° C, hydroxyl equivalent 174) 7.9 parts by weight Spherical fused silica 80.0 parts by weight 1,8 -Diazabicyclo (5,4,0) undecene-7 (hereinafter referred to as DBU) 0.2 parts by weight vinylidene fluoride rubber (copolymer of vinylidene fluoride and propylene hexafluoride, weight average molecular weight 45,000, powder particles) Diameter of 500 μm or less, hereinafter referred to as (E-1)) 0.5 part by weight Epoxysilane coupling agent 0.5 part by weight Brominated phenol novolak type epoxy resin 1.0 part by weight Antimony trioxide 0.5 part by weight Carbon Black 0.3 parts by weight Carnauba wax 0.5 parts by weight was mixed at room temperature using a mixer and biaxially heated at 70 to 130 ° C. It was kneaded with Lumpur, to obtain a pulverized epoxy resin molding material after cooling. The obtained epoxy resin molding material was evaluated by the following method. Table 1 shows the results.

Evaluation method Spiral flow: Using a mold for spiral flow measurement in accordance with EMMI-1-66, a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 70 kg / cm ² and a curing time of 2 minutes.
The unit is cm. Moldability (bleed): 160pQFP was molded using a low-pressure transfer molding machine at a mold temperature of 175 ° C., a pressure of 70 kg / cm ² and a curing time of 1.5 minutes, and the state of the surface of the obtained package was visually observed. Then, the presence or absence of bleed was judged by ○, Δ, and ×. Dispersion particle size of vinylidene fluoride rubber: A 160 pQFP cross section used for evaluation of moldability was polished and finished, and then subjected to 1000 to 2000 using an electron microscope.
Observed at times. Solder crack resistance: 208 pQFP (3.2 mm thick) was molded using a low-pressure transfer molding machine at a mold temperature of 175 ° C., a pressure of 70 kg / cm ² , and a curing time of 2 minutes. The treatment was performed for 8 hours (the number of samples was 12). The obtained package was absorbed in an atmosphere at 85 ° C. and a relative humidity of 60% for 168 hours, and then subjected to an IR reflow treatment at 240 ° C. The inside of the package after the treatment was observed using an ultrasonic flaw detector, and the solder crack resistance (and adhesion) was evaluated by the number of packages having peeling or cracks on the chip surface or the pad back surface. Temperature cycle resistance: 208 pQFP (3.2 mm thick) was molded using a low-pressure transfer molding machine at a mold temperature of 175 ° C., a pressure of 70 kg / cm ² , and a curing time of 2 minutes. Time processing was performed (the number of samples was 12). After the obtained package absorbs moisture for 192 hours in an atmosphere at 30 ° C. and a relative humidity of 60%, a temperature cycle resistance test is performed at −65 ° C. to 150 ° C. for 1000 cycles in accordance with MIL standard 883C.
The inside of the package after the test was observed using an ultrasonic flaw detector, and the temperature cycle resistance was evaluated based on the number of packages having peeling or cracking on the chip surface or the pad back surface.

Examples 2 to 4 and Comparative Examples 1 to 6 According to the formulations shown in Tables 1 and 2, an epoxy resin molding material was obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1.
The results are shown in Tables 1 and 2. In Example 2, a copolymer of vinylidene fluoride and propylene pentafluoride (weight average molecular weight: 44,000, powder particle size: 500 μm or less.
(Referred to as (E-2)). In Comparative Example 1, a copolymer of vinylidene fluoride and propylene hexafluoride (weight average molecular weight 25,000, powder particle size 500 μm or less.
(E-3) is referred to in Comparative Example 2 as a copolymer of vinylidene fluoride and propylene hexafluoride (weight average molecular weight 75,000, powder particle size 500 μm or less.
4)), in Comparative Example 3, vinylidene fluoride and 6
Copolymer with propylene fluoride (weight average molecular weight 450
00, pellet form. Hereinafter, this is referred to as (E-5).

[Table 1]

[0015]

[Table 2]

[0016]

According to the present invention, it is possible to obtain an epoxy resin molding material for semiconductor encapsulation having excellent adhesion to various members such as a lead frame, solder crack resistance, and temperature cycle resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 23/29 H01L 23/30 R 23/31 F-term (Reference) 4J002 BD143 CC03X CC06X CC11X CD04W CD05W CD06W CD07W CD13W CD18W DE146 DJ016 EN067 EU117 EV207 EW147 EY017 FD016 FD157 GQ05 4J036 AD08 AD18 AF06 AF07 DB15 FA05 FB02 FB07 JA07 4M109 AA01 EA03 EB03 EB04 EB06 EB07 EB08 EB09 EB12 EB13 EB19 EC03 EC05

Claims (3)

[Claims] 1. An epoxy resin, (B) a phenolic resin, (C) an inorganic filler, (D) a curing accelerator, and (E) 0.02 to 5% by weight of the total epoxy resin composition. In a molding material obtained by heating, kneading and pulverizing an epoxy resin composition containing a vinylidene fluoride rubber having a weight average molecular weight of 30,000 to 70,000, the dispersed particle size of the vinylidene fluoride rubber is 50 μm or less. Epoxy resin molding material for semiconductor encapsulation. 2. A vinylidene fluoride rubber having a weight average molecular weight of 30,000 to 70,000 is a copolymer of vinylidene fluoride and propylene pentafluoride or a copolymer of vinylidene fluoride and propylene hexafluoride. The epoxy resin molding material for semiconductor encapsulation according to claim 1. 3. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin molding material according to claim 1.