JPH11130937A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor sealing composition excellent in moldability, reliability and the suitability for mounting by mixing an epoxy resin containing a specified amount of polyfunctional and dicyclopentadiene-modified epoxy resins with a phenolic resin curing agent containing a specified amount of a polyfunctional phenolic resin, a cure accelerator and fused silica. SOLUTION: This composition is compounded with an epoxy resin containing 20-90 wt.%, based on the total epoxy resin, at least one epoxy resin of formula I or II and 10-80 wt.% dicyclopentadiene-modified epoxy resin and a phenolic resin curing agent containing at least 20 wt.%, based on the total phenolic resin, phenolic resin of formula III. In the formulas, R is a halogen or a 1-12C alkyl; 1 is 1-10; m is 0-3; n is 0-4; and k is 1-6. One having a shrinkage after molding and curing of 0.15% or below, a coefficient α1 of linear expansion after being cured of 8-16 ppm/ deg.C and a glass transition temperature of 140 deg.C or above is desirable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device having excellent moldability, reliability, and mountability. More specifically, a semiconductor device is mounted on one side of a printed wiring board or a metal lead frame. In a so-called area mounting type semiconductor device in which substantially only one side of the mounting surface is resin-sealed, the warpage after resin sealing and the warping in the soldering process at the time of board mounting are small, and in a temperature cycle test. Epoxy resin composition for semiconductor encapsulation which has excellent package crack resistance and package crack resistance and exfoliation resistance in a soldering process, and is excellent in moldability, and a semiconductor encapsulated with the epoxy resin composition for semiconductor encapsulation It concerns the device.

[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 semiconductors has been progressing year by year, and surface mounting of semiconductor packages has been promoted. Packaging packages have been developed and are beginning to move away from packages with traditional structures. A typical example of an area mounting package is a BGA (ball grid array) or a CSP (chip scale package) pursuing further miniaturization.
The surface-mount package represented by is developed to meet the demand for higher pin count and higher speed, which is approaching the limit. The structure is as follows: a rigid circuit board represented by a BT resin / copper foil circuit board (bismaleimide / triazine / glass cloth board) or a flexible circuit board represented by a polyimide resin film / copper foil circuit board; An element is mounted, and only the element mounting surface, that is, one side of the substrate is molded and sealed with an epoxy resin composition or the like. In addition, a solder ball is formed two-dimensionally in parallel on the surface opposite to the element mounting surface of the substrate, and has a feature of joining with a circuit board on which a package is mounted. Furthermore,
As a substrate on which the element is mounted, a structure using a metal substrate such as a lead frame has been devised in addition to the organic circuit substrate.

[0003] The structure of these area mounting type semiconductor packages adopts a single-sided sealing form in which only the element mounting surface of the substrate is sealed with a resin composition and the solder ball forming surface is not sealed. Very rarely, on a metal substrate such as a lead frame, a sealing resin layer of about several tens of μm may exist even on the solder ball forming surface, but a sealing resin layer of several hundred μm to several mm on the element mounting surface. Since the layer is formed, one-sided sealing is substantially achieved. For this reason, due to the mismatch of thermal expansion and thermal contraction between the organic substrate or metal substrate and the cured product of the resin composition, or the effect of curing shrinkage during molding and curing of the resin composition, these packages cannot be molded. Warpage tends to occur immediately after. In addition, when soldering is performed on a circuit board on which these packages are mounted, a heating step of 200 ° C. or more is performed. At this time, package warpage occurs.
A large number of solder balls are not flattened and rise from the circuit board on which the package is mounted, which causes a problem that electrical connection reliability is reduced.

Further, when soldering is performed by soldering by means such as infrared reflow, vapor phase soldering, or solder immersion, moisture present inside the package due to moisture absorption from the cured product of the resin composition and the organic substrate is high. Cracks in the package due to stress caused by rapid vaporization in the package, and peeling at the interface between the device mounting surface of the substrate and the cured product of the resin composition, resulting in a low stress and low moisture absorption of the cured product. With the development, the adhesion to the substrate is also required. Furthermore, due to the mismatch between the coefficient of linear expansion of the substrate and the cured product, peeling of the substrate / cured product interface and package cracking occur even in a temperature cycle test, which is a typical example of a reliability test. In conventional surface mount packages such as QFP and SOP, in order to prevent cracks at the time of solder mounting and peeling at the interface of each material, a molding epoxy resin such as a biphenyl type epoxy resin is used. Attempts to reduce the viscosity and increase the amount of the inorganic filler added have been taken as countermeasures. However, at present, this method cannot solve the problem of warpage in a single-sided sealed package.

In a package in which substantially only one surface of a substrate is sealed with a resin composition, to reduce warpage, the linear expansion coefficient of the substrate and the linear expansion coefficient of a cured product of the resin composition should be close to each other; Two methods for reducing the cure shrinkage of the resin composition are important. BT for organic substrate
High glass transition temperature resins such as resins and polyimide resins are widely used, and have a glass transition temperature higher than around 170 ° C., which is the molding temperature of the epoxy resin composition. Accordingly, in the cooling process from the molding temperature to room contracts only alpha ₁ region of the organic substrate. Therefore, the resin composition is also the same as high and alpha ₁ is a circuit board glass transition temperature, warpage is considered to be substantially zero when further curing shrinkage is zero. Therefore, the glass transition temperature higher by a combination of a polyfunctional epoxy resin and a polyfunctional phenol resin, methods to adjust the alpha ₁ in the amount of the inorganic filler has been proposed.

However, a combination system of a polyfunctional epoxy resin having three or more epoxy groups in one molecule and a polyfunctional phenol resin having three or more phenolic hydroxyl groups in one molecule has a large moisture absorption. In addition, it shows high elasticity even at the soldering temperature and high generated stress. Therefore, the occurrence of package cracks and the occurrence of interface peeling during the soldering process has not been solved. In order to obtain a package having excellent reliability, it was an essential condition to increase the adhesion between the circuit board or the IC chip and the cured product of the resin composition.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an epoxy resin for semiconductor encapsulation which has a small warpage after molding in an area mounting package or during soldering, and has excellent reliability in a temperature cycle test or soldering. The purpose of the present invention is to develop a composition and a semiconductor device sealed with the composition.

[0008]

Means for Solving the Problems As a result of diligent studies, the present inventor has found that a combination of a specific polyfunctional epoxy resin and a polyfunctional phenol resin curing agent is used in combination with a dicyclopentadiene-modified epoxy resin. It has been clarified that low moisture absorption can be achieved while reducing the glass transition temperature, and that the elastic modulus at the time of soldering can be reduced, resulting in reduced stress and improved adhesion to circuit boards. Things.

That is, the present invention provides (A) a compound represented by the general formula (1):
The total epoxy resin contains at least one epoxy resin selected from the group consisting of the epoxy resins represented by (2) in an amount of 20 to 90% by weight, and the dicyclopentadiene-modified epoxy resin represented by the general formula (3) is a total epoxy resin. An epoxy resin containing 10 to 80% by weight in the resin, (B) a phenolic resin curing agent containing 20% by weight or more of the phenolic resin represented by the general formula (4) in the total phenolic resin, (C) a curing accelerator, (D) ) is a semiconductor encapsulating epoxy resin composition characterized by comprising a fused silica powder, more preferably, 0.15% curing shrinkage during molding curing or less, the linear expansion coefficient alpha ₁ after curing 8 An epoxy resin composition for encapsulating a semiconductor, characterized in that the epoxy resin composition has a glass transition temperature of 140 ° C. or higher at a temperature of from 16 ppm / ° C. The semiconductor device is sealed by the following method.

[0010]

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[0011]

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[0012]

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[0013]

Embedded image R in the formulas (1), (2) and (4) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. l is a positive integer from 1 to 10, m
Is a positive integer of 0 or 1-3, n is 0 or 1-4
Is an integer. K in the formula (3) is a positive integer of 1 to 6.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The epoxy resin represented by the general formula (1) among the epoxy resins of the component (A) used in the present invention is a resin generally referred to as a triphenolmethane type epoxy resin, and specific examples thereof include the following. However, the present invention is not limited to these. In any case, a cured product of the resin composition using the same has characteristics of a high crosslinking density, a high glass transition temperature, and a small cure shrinkage.

[0015]

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The epoxy resin represented by the general formula (2) has a high crosslink density structure and a low curing shrinkage property of the cured product as in the case of the formula (1), but also has a feature that it has a relatively low viscosity. I have. Specific examples include the following, but are not limited thereto.

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The polyfunctional epoxy resin represented by the general formulas (1) and (2) needs to be contained in an amount of 20 to 90% by weight of the total epoxy resin from the viewpoints of glass transition temperature and curing shrinkage. When the content is less than 20% by weight, the crosslink density of the obtained crosslinked structure decreases, so that the glass transition temperature decreases,
Cure shrinkage also increases. On the other hand, if it exceeds 90% by weight, the fluidity at the time of molding is reduced, so that the gold wire is easily deformed and the adhesion to the substrate is reduced.

The epoxy resin represented by the general formula (3)
It is obtained by glycidyl etherification of a phenol resin obtained by polymerizing dicyclopentadiene and phenols by an addition reaction. The dicyclopentadiene-modified epoxy resin can reduce the thermal stress at the soldering temperature and reduce the generated stress, as compared with the conventional orthocresol novolak-type epoxy resin, and has excellent adhesion to a circuit board or an IC chip. Further, since it has a dicyclo skeleton in the molecule, it has excellent moisture absorption resistance. The amount of this epoxy resin used is
By adjusting this, solder crack resistance can be maximized. In order to bring out the effect of solder crack resistance, it is desirable to use the epoxy resin represented by the formula (3) in an amount of 10% by weight or more, preferably 30% by weight or more in the total epoxy resin. If it is less than 10% by weight, it is difficult to obtain a low elastic modulus at a high temperature and high adhesion to a circuit board or an IC chip, and if it exceeds 80% by weight, the warpage of a molded package is undesirably large.

The epoxy resin of the present invention may be used in combination with another epoxy resin. Epoxy resins that can be used in combination include all monomers, oligomers, and polymers having an epoxy group, such as bisphenol A epoxy resin, orthocresol novolac epoxy resin, and naphthol epoxy resin. or,
These epoxy resins may be used alone or in combination.

Among the phenolic resin curing agents of the component (B) used in the present invention, the phenolic resin curing agent represented by the formula (4) is a so-called triphenolmethane type phenolic resin, and specific examples are shown below. .

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When these phenolic resins are used, the crosslink density of the cured product is increased, and a cured product having a high glass transition temperature can be obtained. The amount of the phenol resin of the formula (4) used is 20% in the total phenol resin in terms of the glass transition temperature.
It is necessary to be added in an amount of at least% by weight. If it is less than 20% by weight, the glass transition temperature decreases, the curing shrinkage increases, and the amount of warpage of the molded package increases. The phenolic resin of the formula (4) can be appropriately used in combination with other phenolic resins, and is not particularly limited. Examples thereof include a phenol novolak resin, a cresol novolak resin, and a naphthol type novolak resin.

The curing accelerator of component (C) used in the present invention refers to those which can serve as a catalyst for a crosslinking reaction between the epoxy resin and the phenol resin curing agent, and specifically, amine compounds such as tributylamine. And organic phosphorus compounds such as triphenylphosphine and tetraphenylphosphonium / tetraphenylborate, and imidazole compounds such as 2-methylimidazole, but are not limited thereto. These curing accelerators may be used alone or as a mixture.

The fused silica powder of the component (D) used in the present invention can be used in any of a crushed form and a spherical form. However, the amount of the fused silica powder is increased and the melt viscosity of the resin composition is increased. In order to suppress this, it is preferable to mainly use 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.

The resin composition of the present invention is represented by a brominated epoxy resin, a flame retardant such as antimony trioxide, a coupling agent, and carbon black, if necessary, in addition to the essential components (A) to (D). Coloring agents, release agents such as natural waxes and synthetic waxes, etc., can be appropriately compounded. In order to obtain a resin composition, the components are mixed, heated and kneaded with a heating kneader or a hot roll, and then cooled and pulverized to obtain a desired resin composition. The semiconductor device of the present invention
It is obtained by encapsulating a semiconductor element by transfer molding, compression molding, injection molding or the like using the above-described epoxy resin composition for semiconductor encapsulation.

The semiconductor device of the present invention uses BT as an organic substrate.
When a resin substrate is used, the coefficient of linear expansion (α ₁ ) of the epoxy resin composition after curing is 8 to 16 ppm / ° C., and the glass transition temperature measured by a thermomechanical analyzer (TMA) is 140.
It is particularly preferable that the curing shrinkage is not less than 0.1 ° C and not more than 0.15%. The linear expansion coefficient of the BT resin substrate is 14 ppm
/ ° C., but in a composite substrate in which a metal such as a silicon chip or a copper foil circuit is combined, the linear expansion coefficient changes depending on the area ratio of the chip and the area ratio of the copper foil circuit.
By setting the linear expansion coefficient and the curing shrinkage ratio of the cured product of the resin composition in the above ranges together with the linear expansion coefficient of the substrate, BT
The amount of heat shrinkage of the cured product of the resin composition becomes almost the same in accordance with the amount of heat shrinkage from the molding temperature of the resin substrate to room temperature, and the warpage after molding can be reduced.

In the present invention, the glass transition temperature, the coefficient of linear expansion,
The cure shrinkage is measured by the following method. Glass transition temperature (Tg) and coefficient of linear expansion (α ₁ ): A test piece obtained by transfer-molding the resin composition at 175 ° C. for 2 minutes is post-cured at 175 ° C. for 8 hours, and then thermo-mechanical analyzer (Seiko Electronics ( (TMA-120, Inc., heating rate 5 ° C./min). Curing shrinkage: 180 ° C mold temperature of test piece, 7
Transfer molding was performed at an injection pressure of 5 kg / cm ² for 2 minutes, and post-curing was further performed at 175 ° C. for 8 hours. The cavity dimensions of the mold heated to 180 ° C. and the dimensions of the molded article heated to 180 ° C. were measured with calipers, and the curing shrinkage was represented by the ratio of molded article dimension / mold cavity dimension.

[0027]

The present invention will be specifically described below with reference to examples. << Example 1 >> An epoxy resin having a structure represented by the formula (5) as a main component: [manufactured by Yuka Shell Epoxy Co., Ltd., Epicoat 1032H, softening point 60 ° C., epoxy equivalent 170] 5.6 parts by weight Dicyclopentadiene-modified epoxy resin having the structure of (3) as a main component: [HP-7200, manufactured by Dainippon Ink and Chemicals, Inc., melting point 65 ° C., epoxy equivalent 250] 3.8 parts by weight Formula (6) A phenolic resin represented by: [Mehka Kasei Co., Ltd., MEH-7500, softening point 107 ° C., hydroxyl equivalent 97] 4.6 parts by weight ・ Triphenylphosphine 0.2 parts by weight ・ Spherical fused silica 85.0 parts by weight・ 0.5 parts by weight of carnauba wax ・ 0.3 parts by weight of carbon black After mixing all the above components by a mixer, the mixture was kneaded 30 times using two rolls having a surface temperature of 90 ° C. and 45 ° C. to obtain a mixture. And the kneaded material sheet was pulverized after cooling, the resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 1 shows the evaluation results.

[0028]

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[0029]

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<< Examples 2 to 6 >> Based on Example 1 as a basic formulation, in addition to the formula (5), the epoxy resin of the formulas (7) and (8) and the epoxy resin of the formula (6) and the formula (9) A phenolic resin curing agent was used, the mixing ratio was changed, and the other components were mixed at the same ratio as the basic mixing, and mixed and kneaded in the same manner as in Example 1 to obtain a resin composition. Evaluation was performed in the same manner as in Example 1. Table 1 shows the formulation and evaluation results. << Comparative Examples 1 to 5 >> Example 1 was used as a basic compound, and the components were mixed at the same ratio as the basic compound except that the mixing ratio of the epoxy resin and the phenol resin curing agent was changed in the same manner as in the example. The mixture was mixed and kneaded in the same manner as in Example 1 to obtain a resin composition. Evaluation was performed in the same manner as in Example 1. Table 2 shows the formulation and evaluation results.

The structures and properties of the epoxy resins of formulas (7) and (8) and the phenol resin of formula (9) used in the above Examples and Comparative Examples are shown below.

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Embedded image ・ Epoxy resin of formula (7): softening point 65 ° C., epoxy equivalent 210 ・ Epoxy resin of formula (8): liquid, viscosity (25 ° C.) 55 Pois
e, epoxy equivalent 168 ・ phenolic resin of formula (9): softening point 80 ° C., hydroxyl equivalent 104

<< Evaluation Method >> Glass transition temperature (Tg) and coefficient of linear expansion (α ₁ ): Determined by the methods described above.・ Heat elastic modulus: Flexural elastic modulus at 240 ° C is JIS-K6
It was measured under the test conditions of 911. Curing shrinkage: According to the method described above. Package warpage: 225-pin BGA package (substrate is a 0.36 mm thick BT resin substrate, package size is 24 × 24 mm, thickness 1.17 mm, silicon chip is 9 × 9 mm, thickness 0.35 mm, chip and circuit board Is bonded with a gold wire having a diameter of 25 μm) at a mold temperature of 180 ° C. and 75 kg /
perform transfer molding for 2 minutes at an injection pressure of cm ^2,
Further post-curing was performed at 175 ° C. for 8 hours. After cooling to room temperature, the displacement in the height direction was measured diagonally from the gate of the package using a surface roughness meter, and the value with the largest variation difference was defined as the amount of warpage. Solder Resistance: The molded product package used for measuring the package warpage was left for 168 hours in an environment of 85 ° C. and 60% relative humidity, and then immersed in a 240 ° C. solder bath for 10 seconds.
The package was observed using an ultrasonic flaw detector, and the number of internal cracks and the number of peels at the interface between the substrate and the resin composition were represented by% of (number of generated packages) / (total number of packages).

Table 1 Example 1 2 3 4 5 6 << Type and blending amount (parts by weight) of epoxy resin >> Epoxy resin of formula (5) 5.6 7.6 2.4 2.4 7.6 Epoxy resin of formula (7) 4.0 Epoxy resin of formula (3) 3.8 1.4 4.8 6.0 4.7 1.3 Epoxy resin of formula (8) 2.4 2.4 << Type and amount of blending agent (parts by weight) >> Phenolic resin of formula (6) 4.6 2.5 2.2 4.0 1.1 1.3 Phenolic resin of formula (9) 2.5 2.2 3.4 3.8 "evaluation" Tg (℃) 193 188 185 191 184 187 α 1 (ppm / ℃) 13 13 13 13 13 13 thermal time elastic modulus ^{(N / mm 2) 3050 2650} 2100 2900 2150 2550 cure shrinkage (%) 0.06 0.07 0.07 0.06 0.09 0.08 Package warpage (μm) 32 35 37 33 40 38 Solder resistance: Number of cracks (%) 0 0 0 0 0 0 Number of peels (%) 0 0 0 0 0 0

Table 2 Comparative Example 1 2 3 4 5 << Type and blending amount (parts by weight) of epoxy resin >> Epoxy resin of formula (5) 8.9 7.9 1.9 Epoxy resin of formula (7) 9.6 Epoxy resin of formula (3) 4.9 0.9 4.7 formula Epoxy resin of (8) 4.9 2.9 << Type and blending amount (parts by weight) of curing agent >> Phenolic resin of formula (6) 5.1 4.4 4.2 Phenolic resin of formula (9) 5.2 4.5 << Evaluation >> Tg (° C) 198 195 137 160 165 α ₁ (ppm / ° C) 13 13 13 13 13 Thermal elasticity (N / mm ² ) 3450 3300 1750 2850 1950 Curing shrinkage (%) 0.05 0.06 0.23 0.18 0.16 Package warpage (μm) 30 35 113 90 72 Solder resistance: number of cracks (%) 80 60 70 200 0 Number of peelings (%) 50 30 40 100

[0035]

The epoxy resin composition for semiconductor encapsulation of the present invention is also excellent in moldability such as gold wire deformation, and the area mounting type semiconductor device sealed with the epoxy resin composition for semiconductor encapsulation can be used at room temperature. Also, the warpage in the soldering process is small, and the reliability such as solder resistance and temperature cycle resistance is high.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 3/36 C08K 3/36 H01L 23/29 H01L 23/30 R 23/31

Claims (3)

[Claims] (A) at least one epoxy resin selected from the group consisting of the epoxy resins represented by the general formulas (1) and (2) in an amount of 20 to 90% by weight in the total epoxy resin;
A dicyclopentadiene-modified epoxy resin represented by the general formula (3):
Epoxy resin, (B) a phenol resin curing agent containing at least 20% by weight of the phenol resin represented by the general formula (4) in the total phenol resin, (C) a curing accelerator, and (D) a fused silica powder. Characteristic epoxy resin composition for semiconductor encapsulation. Embedded image Embedded image Embedded image Embedded image R in the formulas (1), (2) and (4) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. l is a positive integer from 1 to 10, m
Is a positive integer of 0 or 1-3, n is 0 or 1-4
Is a positive integer. K in the formula (3) is a positive integer of 1 to 6. Wherein% cure shrinkage during molding curing 0.15, the linear expansion coefficient alpha ₁ after curing is 8~16ppm / ℃, and claim 1 having a glass transition temperature of 140 ° C. or higher
The epoxy resin composition for semiconductor encapsulation according to the above. 3. A semiconductor element is mounted on one side of a substrate, and substantially only one side on the substrate side on which the semiconductor element is mounted is sealed with the epoxy resin composition according to claim 1 or 2. A semiconductor device characterized by the above-mentioned.