JP2002121357A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition which has little warpage after molding, during ball soldering and after a soldering treatment such as a reflow treatment for sealing an area-packaging semiconductor device, particularly the one which has a high ratio of the area occupied with a semiconductor element. SOLUTION: In an epoxy resin composition for sealing a semiconductor using an epoxy resin, a phenol resin, a curable accelerator and an inorganic filler as main components, the epoxy resin composition for sealing a semiconductor has characteristics of a cured substance from thermosetting of the epoxy resin composition which are a <=10R (wherein R is 7-10×(b+c)), 300<=a<=500 and 0.15<=b+c, wherein a (N/mm2) is a flexural modulus at a molding temperature, b (%) is a curing contraction rate and c (%) is a heat contraction rate from a molding temperature to a room temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called area mounting type semiconductor device in which a semiconductor element is mounted on one surface of a printed wiring board or a metal lead frame, and substantially only one of the mounting surfaces is resin-sealed. The present invention relates to a suitable epoxy resin composition for semiconductor encapsulation and a semiconductor device using the same.

[0002]

2. Description of the Related Art In recent years, in the market trend of miniaturization, weight reduction and high performance of electronic equipment, high integration of semiconductor elements has been progressing year by year, and surface mounting of semiconductor devices has been promoted. In recent years, area-mounted semiconductor devices have been developed, and are beginning to shift from semiconductor devices having conventional structures. Area mounting type semiconductor devices include BGA (ball grid array),
Alternatively, a CSP (chip scale package) or the like pursuing further miniaturization is a typical example.
The surface-mount type semiconductor device represented by the SOP has been developed in order to meet the demand for increasing the number of pins and increasing the speed, which is approaching the limit. As the structure, on one side of a rigid circuit board represented by a BT resin / copper foil circuit board (bismaleimide / triazine resin / glass cloth board) or a flexible circuit board represented by a polyimide resin film / copper foil circuit board A semiconductor element is mounted, and only the semiconductor element mounting surface, that is, only one side of the substrate is molded and sealed with an epoxy resin composition or the like. Further, on the surface opposite to the semiconductor element mounting surface of the substrate, solder balls are formed two-dimensionally in parallel, and are characterized in that they are joined to a circuit board on which a semiconductor device is mounted. Further, as a substrate on which a semiconductor element is mounted, a structure using a metal substrate such as a lead frame has been developed in addition to the above-described organic circuit substrate.

The structure of these area-mounted semiconductor devices is as follows:
A single-sided sealing configuration is adopted in which only the semiconductor element mounting surface of the substrate is sealed with the epoxy resin composition and the solder ball forming surface is not sealed. On a metal substrate such as a lead frame, a sealing resin layer of about several tens of μm may be present even on the surface on which the solder ball is formed, but several hundred μm on the surface on which the semiconductor element is mounted.
Since a sealing resin layer having a thickness of about several mm is formed, substantially single-sided sealing is achieved. For this reason, these semiconductor devices may be affected by mismatch of thermal expansion and thermal shrinkage between the organic substrate or the metal substrate and the cured product of the epoxy resin composition, or the effect of curing shrinkage during molding and curing of the epoxy resin composition. In this case, warpage tends to occur immediately after molding. Also, with the miniaturization of semiconductor devices, the ratio of the semiconductor element area to the resin sealing area is also increasing, and the mismatch between the thermal expansion and thermal contraction between the semiconductor element and the cured product of the epoxy resin composition. Alternatively, warpage is more likely to occur due to the influence of curing shrinkage during molding and curing of the epoxy resin composition. Furthermore, when soldering is performed on a circuit board on which these semiconductor devices are mounted, a heating step of 200 ° C. or more is performed. At this time, the semiconductor device is warped, and many solder balls are not flattened. There is also a problem that the semiconductor device floats up from the circuit board on which the semiconductor device is mounted, and the reliability of the electrical connection is reduced.

In a semiconductor device in which substantially only one surface on a substrate is sealed with an epoxy resin composition, in order to reduce warpage, the thermal expansion coefficient of the substrate and the thermal expansion coefficient of a cured product of the epoxy resin composition are determined. Two approaches are important: approaching and reducing curing shrinkage during molding and curing of the epoxy resin composition. That is, it is necessary to reduce the curing shrinkage during the molding and curing of the epoxy resin composition and the heat shrinkage from the molding temperature to room temperature in order to reduce the warpage. As the substrate, resins having a high glass transition temperature (hereinafter, referred to as Tg), such as BT resin and polyimide resin, are widely used for organic substrates, and these are used at temperatures around 170 ° C., which is the molding temperature of the epoxy resin composition. Also have a high Tg. Accordingly, during the cooling process from the molding temperature to room temperature, the organic substrate contracts only in the region of α1. Therefore, if the cured product of the epoxy resin composition has a high Tg and the same α1 as that of the organic substrate, and if the curing shrinkage is zero, the warpage is considered to be almost zero. For this reason, a method has already been proposed in which Tg is increased by combining a polyfunctional epoxy resin and a polyfunctional phenol resin, and α1 is adjusted by the amount of the inorganic filler.

On the other hand, in a semiconductor device in which the ratio of the semiconductor element area to the resin sealing area is large, it is important to make the thermal expansion coefficients of the semiconductor element and the cured product of the epoxy resin composition close to each other. However, since the thermal expansion of the semiconductor element is too small, it is difficult to equalize the thermal expansion of the semiconductor element and the cured product of the epoxy resin composition. Was unable to solve the problem.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an area mounting type semiconductor device, particularly, an area mounting type semiconductor device having a large ratio of an occupied area of a semiconductor element. An object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation with a small warpage after a soldering process such as a reflow process, and a semiconductor device using the same.

[0007]

The present invention relates to an epoxy resin composition comprising (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, and (D) an inorganic filler as main components. The properties of a cured product obtained by heating and curing the epoxy resin composition indicate that the flexural modulus at the molding temperature is a (N / m
m ² ), when the curing shrinkage is b (%) and the heat shrinkage from the molding temperature to room temperature is c (%), a ≦ 10 ^R (where:
R = 7−10 × (b + c)), 300 ≦ a ≦ 50
The present invention relates to an epoxy resin composition for semiconductor encapsulation, characterized by satisfying 00, 0.15 ≦ b + c, and an area mounting type semiconductor device obtained by encapsulating a semiconductor element using the same. The ratio of the semiconductor element area to 25
% Of the semiconductor device.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies, the present inventor measured a cured product obtained by heat-curing an epoxy resin composition containing components (A) to (D) as a main component at a molding temperature. It has been found that the flexural modulus has a large effect on warpage. In other words, by lowering the flexural modulus at the molding temperature, a phenomenon occurs in which the stress generated from the difference in the thermal expansion coefficient between the semiconductor element and the cured product of the epoxy resin composition is relaxed,
It has been found that the warpage is reduced. Furthermore, it was found that the bending elasticity at the molding temperature, the curing shrinkage, and the heat shrinkage from the molding temperature to room temperature have a composite effect on the warpage. When the flexural modulus at the molding temperature of the cured product is a (N / mm ² ), the curing shrinkage is b (%), and the heat shrinkage from the molding temperature to room temperature is c (%), a ≤
10 ^R (where R = 7−10 × (b + c)), 3
By satisfying 00 ≦ a ≦ 5000 and 0.15 ≦ b + c, a so-called area-mounted semiconductor device in which substantially only one surface on a substrate is sealed with an epoxy resin composition,
It has been found that the warpage is reduced in an area-mounted semiconductor device having a large ratio of the occupied area of the semiconductor element.

In the present invention, the molding temperature refers to a mold temperature at which the epoxy resin composition is cured by heating.
The temperature is in the range of 60 to 190 ° C., but is not limited to this temperature range. The value of a was measured according to JIS K 6911. The value of b + c was determined using a transfer molding machine at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa,
With a curing time of 90 seconds, a disk having a diameter of 100 mm and a thickness of 3 mm was molded, and the inner diameter of the mold cavity at 175 ° C. and the outer diameter of the disk at room temperature (25 ° C.) were measured. (1
Inner diameter of mold cavity at 75 ° C .− (outer diameter of disk at 25 ° C.)｝ / (Inner diameter of mold cavity at 175 ° C.)]
It calculated from the formula of x100. Units%. In addition, about the molded product to be used, evaluation is made without post-curing treatment. In the relationship of a, b and c, a is 10 ^R or 500
Exceeding 0 is not preferable because warpage increases. or,
When a is less than 300, the cured product at the time of molding and curing becomes soft, so that the releasability from the mold is deteriorated and the moldability is undesirably reduced. Furthermore, if b + c is less than 0.15,
It is not preferable because the curing shrinkage during the molding and curing becomes small, the releasability from the mold becomes poor, and the moldability decreases. The method for adjusting the physical properties as described above is not particularly limited, but the amount of the inorganic filler is adjusted by a combination of resin components, or the elastic modulus of the cured product is adjusted by blending a low stress component such as silicone oil or rubber. And the like.

The epoxy resin composition of the present invention has warpage in a so-called area-mounted semiconductor device in which substantially only one surface of a substrate is sealed, particularly in an area-mounted semiconductor device having a large ratio of an occupied area of a semiconductor element. Very small and optimal. In a semiconductor device having a large ratio of the occupied area of a semiconductor element, a phenomenon in which a bending elastic modulus at a molding temperature is reduced to reduce a stress generated due to a difference in a thermal expansion coefficient between the semiconductor element and a cured product of the epoxy resin composition. This is because warpage is reduced. In particular, in a semiconductor device in which the ratio of the semiconductor element occupation area to the resin sealing area is 25% or more, the effect of reducing the warpage is exerted to the maximum. 25
%, The stress generated due to the difference in the coefficient of thermal expansion between the semiconductor element and the cured product of the epoxy resin composition is small, so that the curing shrinkage and the heat shrinkage of the epoxy resin composition dominantly warp. As a factor, the flexural modulus at the molding temperature of the epoxy resin composition does not affect the warpage. The resin sealing area in the present invention is:
It is the area of the sealing portion formed by covering the semiconductor element with the epoxy resin composition, that is, the sum of the area of the semiconductor element and the area of the contact portion between the epoxy resin composition and the wiring board. The ratio of the occupied area of the semiconductor element is calculated by {(semiconductor element area) / (resin sealed area)} × 100 from the resin sealing area of the semiconductor device and the semiconductor element area (unit%). .

The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having an epoxy group, such as triphenolmethane epoxy resin, alkyl-modified triphenolmethane epoxy resin, biphenyl epoxy resin, bisphenol Epoxy resin, stilbene epoxy resin, ortho-cresol novolak epoxy resin, phenol novolak epoxy resin, phenol aralkyl epoxy resin, epoxy resin containing triazine nucleus, epoxy resin containing naphthalene skeleton, dicyclopentadiene-modified phenol epoxy resin, etc. And these may be used alone or as a mixture.

The phenolic resin used in the present invention refers to all monomers, oligomers and polymers having at least two or more phenolic hydroxyl groups capable of forming a crosslinked structure by curing reaction with the epoxy resin. Phenol novolak resin, cresol novolak resin, para-xylylene-modified phenol resin, phenol aralkyl resin such as meta-xylylene / para-xylylene-modified phenol resin, resin containing a naphthalene skeleton, terpene-modified phenol resin, dicyclopentadiene-modified phenol resin, triphenol methane resin, etc. These may be used alone or as a mixture.

The curing accelerator used in the present invention includes:
It refers to a compound that can serve as a catalyst for a crosslinking reaction between the epoxy resin and the phenol resin, for example, amine compounds such as 1,8-diazabicyclo (5,4,0) undecene-7, tributylamine, triphenylphosphine, and tetraphenylphosphine. Examples include, but are not limited to, organophosphorus compounds such as phonium tetraphenylborate salts, and imidazole compounds such as 2-methylimidazole. These may be used alone or as a mixture.

The kind of the inorganic filler used in the present invention is not particularly limited, and those generally used for a sealing material can be used. For example, fused silica,
Examples thereof include crystalline silica, secondary aggregated silica, alumina, titanium white, aluminum hydroxide, talc, clay, and glass fiber, with fused silica being particularly preferred. Fused silica can be used in any of a crushed form and a spherical form. However, in order to increase the blending amount and suppress an increase in the melt viscosity of the epoxy resin composition, it is more preferable to mainly use the spherical silica. In order to further increase the content of the spherical silica, it is desirable to adjust the particle size distribution of the spherical silica to be wider. Further, as the inorganic filler, a material which has been surface-treated with a coupling agent or the like in advance may be used.

The epoxy resin composition of the present invention comprises (A)
In addition to the component (D), if necessary, brominated epoxy resins, antimony oxide, flame retardants such as phosphorus compounds, inorganic ion exchangers, coupling agents, coloring agents represented by carbon black, natural waxes, synthetic waxes, Release agents such as higher fatty acids and metal salts thereof or paraffin, low stress components such as silicone oil and rubber, and various additives such as antioxidants can be appropriately compounded. In particular, when low-stress components such as silicone oil and rubber are compounded, the elastic modulus decreases,
This is preferable because warpage is reduced. The epoxy resin composition of the present invention is obtained by mixing the components (A) to (D) and other additives using a mixer or the like, and then heating the kneader, a hot roll,
It is obtained by heating and kneading with a kneading machine such as an extruder, cooling and pulverizing. Using the epoxy resin composition of the present invention, to seal electronic components such as semiconductor elements, and to manufacture a semiconductor device, transfer molding, compression molding, injection molding and other conventional molding methods such as curing molding Good. In particular, the epoxy resin composition of the present invention is suitable for sealing area-mounted semiconductor devices,
Further, it is most suitable for sealing an area-mounted semiconductor device in which the ratio of the occupied area of the semiconductor element is large.

[0016]

The present invention will be specifically described below with reference to examples.
The mixing ratio is by weight. Example 1 8.7 parts by weight of an epoxy resin containing a resin represented by the formula (1) as a main component (melting point: 105 ° C., epoxy equivalent: 195)

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A phenol resin represented by the formula (2) (softening point: 105 ° C., hydroxyl equivalent: 97) 4.3 parts by weight

Embedded image Triphenylphosphine 0.15 parts by weight Spherical fused silica (average particle size 15 μm) 86.25 parts by weight Carbon black 0.3 part by weight Carnauba wax 0.3 part by weight was mixed with a mixer. The mixture was kneaded using two rolls at a temperature of ℃, cooled and pulverized to obtain an epoxy resin composition. The obtained epoxy resin composition was evaluated by the following method. Table 1 shows the results.

Evaluation method Spiral flow: Using a mold for measuring spiral flow according to EMMI-1-66, a mold temperature of 175 ° C.
The measurement was performed at an injection pressure of 6.9 MPa and a curing time of 120 seconds. Curability: Measured using a Shore D hardness meter at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, and a curing time of 90 seconds. Flexural modulus at molding temperature a: As described above, JIS K
It was measured according to 6911. Using a transfer molding machine, a cured product was molded at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, and a curing time of 90 seconds, and the flexural modulus was measured at 175 ° C. The unit is N / mm ² . b + c: As described above, a disk having a diameter of 100 mm and a thickness of 3 mm was formed using a transfer molding machine at a mold temperature of 175 ° C., an injection pressure of 6.9 MPa, and a curing time of 90 seconds, and a mold at 175 ° C. The inner diameter of the cavity and the room temperature (25
C)), the outer diameter of the disc was measured at [{(inner diameter of mold cavity at 175 ° C.) − (Outer diameter of disc at 25 ° C.)} /
(Inner diameter of mold cavity at 175 ° C.)] × 100. Units%. Package warpage: Using a transfer molding machine, mold temperature 175 ° C., injection pressure 6.9 MPa, curing time 90
In seconds, 192pBGA (0.36mm thick BT resin substrate, chip size 9.0mm × 9.0mm × thickness 0.3)
5mm, package size 16.0mm x 16.0m
m, resin sealing area: 15.5 mm × 15.5 mm, thickness of sealing resin: 0.8 mm), and post-cured at 175 ° C. for 2 hours. After cooling to room temperature, the displacement in the height direction was measured using a surface roughness meter diagonally from the gate of the package, and the largest value of the displacement difference was defined as the amount of warpage. Unit is μ
m. The ratio of the area occupied by the semiconductor element of the package used in this evaluation is ｛(9.0 mm × 9.0 mm) / (1
(5.5 mm × 15.5 mm)｝ 100 = 34%. Releasability: The releasability from the mold was examined during the molding of 192pBGA. Those that did not release smoothly from the mold were judged to be defective.

Examples 2 to 5 and Comparative Examples 1 to 5 Epoxy resin compositions were prepared according to Tables 1 and 2 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. The epoxy resins, phenolic resins, and additives used in Examples and Comparative Examples are shown below. An epoxy resin represented by the formula (3) (softening point: 60 ° C.,
Epoxy equivalent 170),

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An epoxy resin represented by the formula (4) (softening point: 60 ° C., epoxy equivalent: 245);

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A phenolic resin represented by the formula (5) (softening point: 87 ° C., hydroxyl equivalent: 210);

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A phenolic resin represented by the formula (6) (softening point: 83 ° C., hydroxyl equivalent: 175);

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Phenol novolak resin (softening point 80
° C, hydroxyl equivalent 105), silicone rubber (average particle size 5
μm).

[Table 1]

[0024]

[Table 2]

[0025]

According to the present invention, there can be obtained an epoxy resin composition which has excellent moldability and is suitable for encapsulating an area-mounted semiconductor, particularly for encapsulating an area-mounted semiconductor device having a large ratio of an occupied area of a semiconductor element. In a semiconductor device using this, the warpage after molding is small, and the warpage after soldering such as solder balling and reflow processing during mounting is very small.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship among the flexural modulus (a), the curing shrinkage (b), and the heat shrinkage (c) at the molding temperature of the epoxy resin compositions of Examples and Comparative Examples.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M109 AA01 BA01 BA04 CA21 CA22 DB17 EA02 EB03 EB04 EB06 EB07 EB08 EB09 EB13 EB18 EB19 EC04 GA10

Claims (3)

[Claims] 1. An epoxy resin composition containing (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, and (D) an inorganic filler as main components, wherein the epoxy resin composition is heat-cured. The properties of the cured product are as follows: a (N / mm ² ), the flexural modulus at the molding temperature, b (%), the curing shrinkage,
When the heat shrinkage from the molding temperature to room temperature is c (%), a ≦ 10 ^R (where R = 7−10 × (b + c)), 300 ≦ a ≦ 5000, 0.15 ≦ b + c An epoxy resin composition for semiconductor encapsulation, wherein 2. A semiconductor device is mounted on one surface of a substrate, and substantially only one surface on the substrate surface side on which the semiconductor device is mounted is sealed with the epoxy resin composition according to claim 1. Semiconductor device. 3. The semiconductor device according to claim 2, wherein the ratio of the semiconductor element area to the resin sealing area is 25% or more.