JP2000169677A - Epoxy resin composition and semiconductor apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition having small warpage after molding in a package for area mounting and in solder treatment useful for sealing a semiconductor by making a specific epoxy resin, a specified curing agent, a curing promoter and prescribed powder. SOLUTION: This composition comprises (A) an epoxy resin containing at least >=20 wt.% of at least one kind selected from epoxy resins of formula I and formula II (R is a halogen or a 1-12C alkyl; l is 1-10; m is 0 or 1-3; n is 0 or 1-4), (B) a phenol resin curing agent containing (i) 20-90 wt.% in the whole phenol resin of a phenol resin of formula III and (ii) 10-80 wt.% in the whole phenol resin curing agent of a dicyclopentadiene modified phenol resin curing agent of formula IV (k is 1-6), (C) a curing promoter (e.g. triphenylphosphine) and (D) preferably a spherical fused silica.

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 of its mounting surfaces 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. Further, due to the mismatch between the coefficient of linear expansion of the substrate and the cured product of the resin composition, 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, with this approach,
At present, the problem of warpage in a single-sided sealed package cannot be solved.

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 intensive studies, the present inventors have found that a dicyclopentadiene-modified phenol resin curing agent is used in combination with a specific combination of a polyfunctional epoxy resin and a polyfunctional phenol resin curing agent. In that, it is possible to achieve low moisture absorption while reducing the decrease of the glass transition temperature,
It has been clarified that the thermal elasticity at the soldering temperature can be reduced, so that the generated stress is reduced and the adhesion to the circuit board is improved.

That is, the present invention provides (A) a compound represented by the general formula (1):
An epoxy resin containing at least one epoxy resin selected from the group consisting of the epoxy resins represented by (2) in the total epoxy resin in an amount of 20% by weight or more; (B) a general formula (3)
In the total phenolic resin
A phenol resin curing agent containing 10 to 80% by weight of a dicyclopentadiene-modified phenol resin curing agent represented by the general formula (4) in the total phenol resin curing agent, (C) a curing accelerator, A) an epoxy resin composition for semiconductor encapsulation, comprising a fused silica powder, more preferably a curing shrinkage of 0.1 during molding and curing.
5%, linear expansion coefficient alpha ₁ after curing 8～16Ppm /
An epoxy resin composition for encapsulating a semiconductor, wherein the epoxy resin composition has a glass transition temperature of 140 ° C. or higher, and a semiconductor device encapsulated with the epoxy resin composition for encapsulating a semiconductor.

[0010]

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[0011]

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[0012]

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[0013]

Embedded image R in the formulas (1) to (3) is a halogen atom or a
Represents 12 alkyl groups, which may be the same or different from each other. l is 1 to 10, m is 0 or 1 to 3
Is a positive integer of 0 or n is a positive integer of 1 to 4.
K in the formula (4) is a positive integer of 0 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 at least 20% by weight of the total epoxy resin from the viewpoint of glass transition temperature and curing shrinkage. When the content is less than 20% by weight, the crosslinking density of the obtained crosslinked structure decreases, so that the glass transition temperature decreases and the curing shrinkage increases. The epoxy resin of the present invention may be used in combination with another epoxy resin. The epoxy resin that can be used in combination refers to all monomers, oligomers, and polymers having an epoxy group, and includes, for example, bisphenol A type epoxy resin, orthocresol novolak type epoxy resin, and naphthalene type epoxy resin.
These epoxy resins may be used alone or as a mixture.

Among the phenolic resin curing agents of the component (B) used in the present invention, the phenolic resin curing agent represented by the formula (3) 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 use amount of the phenol resin of the formula (3) is 20% in the total phenol resin in terms of the glass transition temperature.
９０90% by weight is required. 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. 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 phenolic resin of the formula (3) can be appropriately used in combination with other phenolic resins, and is not particularly limited, and examples thereof include a phenol novolak resin, a cresol novolak resin, and a naphthol novolak resin.

The phenolic resin curing agent represented by the general formula (4) is obtained by polymerizing dicyclopentadiene and phenols by an addition reaction. The dicyclopentadiene-modified phenolic resin can reduce the generated stress as compared with the conventional phenol novolak resin because the elastic modulus at the time of the soldering process can be reduced at the heat treatment temperature, and is excellent in the adhesion to the circuit board and the IC chip. Further, since it has a dicyclo skeleton in the molecule, it has excellent moisture absorption resistance. By adjusting the amount of the phenol resin curing agent used, solder crack resistance can be maximized. In order to bring out the effect of the solder crack resistance, the phenol resin curing agent represented by the formula (4) is added in an amount of 10 to 80 in the total phenol resin curing agent.
%, Preferably 30 to 80% by weight. If it is less than 10% by weight, it is difficult to obtain a low elastic modulus at high temperature and high adhesion to a circuit board or an IC chip.
Exceeding the range undesirably increases the warpage of the molded package. The phenolic resins of the formulas (3) and (4) can be appropriately used in combination with other phenolic resins, and are not particularly limited. Examples thereof include a phenol novolak resin, a cresol novolak resin, and a naphthol novolak resin.

The curing accelerator of the component (C) used in the present invention refers to those which can be 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 blending amount 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 ° C.
It is particularly preferable that the curing shrinkage is 0.15% or less. The linear expansion coefficient of the BT resin substrate is 14 ppm /
However, in a composite substrate in which a metal such as a silicon chip or a copper foil circuit is combined with this, 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. Here, the curing shrinkage ratio refers to the ratio between the size of the mold at the molding temperature and the size of the molded product at the molding temperature.

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 a thermomechanical analyzer [Seiko Electronics ( Co., Ltd., TMA-120, 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.

[0026]

The present invention will be specifically described below with reference to examples. << Example 1 >> Epoxy resin represented by formula (5): [softening point 60 ° C., epoxy equivalent 170] 8.3 parts by weight ・ Phenolic resin represented by formula (6): [softening point 107 ° C., hydroxyl equivalent] 97] 3.4 parts by weight ・ Dicyclopentadiene-modified phenol resin curing agent represented by the formula (7): [softening point 106 ° C., hydroxyl equivalent 181] 2.3 parts by weight ・ Triphenylphosphine 0.2 parts by weight ・ Spherical 85.0 parts by weight of fused silica ・ 0.5 parts by weight of carnauba wax ・ 0.3 parts by weight of carbon black After mixing all the above components with a mixer, the surface temperature is adjusted to 30 ° C. using two rolls of 90 ° C. and 45 ° C. The resulting kneaded material sheet was cooled and pulverized to obtain a resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 1 shows the evaluation results.

The structures of formulas (5) to (7) used in Example 1 are shown below.

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<< Examples 2 to 6 >> Based on Example 1 as a basic formulation, the epoxy resins of the formulas (5), (8) and (9) and the formulas (6), (7) and (10) were used. The components were blended in the same proportions as in the basic blend except for the blending ratio of the phenolic resin curing agent, 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 (8) and (9) and the phenol resin of formula (10) used in the above Examples and Comparative Examples are shown below.・ Epoxy resin of formula (8): softening point 65 ° C., epoxy equivalent 210 ・ Epoxy resin having a structure of formula (9) as a main component: melting point 1
05 ° C, epoxy equivalent 195 ・ Phenolic resin of formula (10): softening point 80 ° C, hydroxyl equivalent 104

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<< Evaluation Method >> Glass transition temperature (Tg) and coefficient of linear expansion (α1): Based on the above-mentioned methods.・ 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 thickness 0.36 mm, BT resin used for core material, package size 24 × 24 mm, thickness 1.17 mm,
Silicon chip is 9 × 9mm in size and 0.35m in thickness
m, 25 μm between the chip and the bonding pad of the circuit board
transfer molding was performed at a mold temperature of 180 ° C. and an injection pressure of 75 kg / cm ² for 2 minutes, and further post-cured 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 amount of epoxy resin (parts by weight) >> Epoxy resin of formula (5) 8.3 4.5 4.1 2.1 2.3 Epoxy resin of formula (8) 8.6 Epoxy resin of formula (9) 4.5 4.1 6.2 6.7 << Type and amount (parts by weight) of curing agent >> Phenolic resin of formula (6) 3.4 4.2 1.5 2.2 1.4 4.2 Phenolic resin of formula (7) 2.3 0.8 2.8 3.2 2.9 0.8 Phenolic resin of formula (10) 1.5 1.4 "evaluation" Tg (℃) 191 193 183 190 185 181 α 1 (ppm / ℃) 13 13 13 13 13 13 thermal time elastic modulus ^{(N / mm 2) 2960 3130} 2800 3030 2560 2720 cure shrinkage (%) 0.05 0.07 0.07 0.07 0.09 0.08 Package warpage (μm) 28 30 36 37 41 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 amount of epoxy resin (parts by weight) >> Epoxy resin of formula (5) 8.9 7.8 Epoxy resin of formula (8) 9.6 Epoxy resin of formula (9) 4.9 9.2 8.4 << Curing Kind of agent and blending amount (parts by weight) >> Phenolic resin of formula (6) 5.1 4.4 4.3 1.1 Phenolic resin of formula (7) 3.1 0.5 2.8 Phenolic resin of formula (10) 3.1 1.7 << Evaluation >> Tg (° C) 198 195 145 171 162 α ₁ (ppm / ° C) 13 13 13 13 13 Thermal elasticity (N / mm ² ) 3450 3300 1860 3050 2110 Curing shrinkage (%) 0.05 0.06 0.25 0.15 0.18 Package warpage (μm) 30 35 107 78 91 Solder resistance: number of cracks (%) 90 80 70 30 0 Number of peelings (%) 50 60 40 100

[0033]

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.

[Procedure amendment]

[Submission date] December 8, 1998 (1998.12.
8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

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Embedded image R in the formulas (1) to (3) is a halogen atom or a
Represents 12 alkyl groups, which may be the same or different from each other. l is 1 to 10, m is 0 or 1 to 3
Is a positive integer of 0 or n is a positive integer of 1 to 4.
K in the formula (4) is a positive integer of 1 to 6.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

[0013]

Embedded image R in the formulas (1) to (3) is a halogen atom or a
Represents 12 alkyl groups, which may be the same or different from each other. l is 1 to 10, m is 0 or 1 to 3
Is a positive integer of 0 or n is a positive integer of 1 to 4.
K in the formula (4) is a positive integer of 1 to 6.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // C08G 59/32 H01L 23/30 R 59/62 F term (reference) 4J002 CC06X CD03W CD05W CD06W CD07W CE00Y DJ017 EN026 EU116 EW016 EW176 FD017 FD090 FD130 FD14X FD14Y FD156 GJ02 GQ00 4J036 AC02 AE07 AF36 DA04 DA05 DC05 DC41 DD07 FA05 FB06 FB08 GA04 JA07 4M109 AA01 BA01 CA21 EA02 EB03 EB04 EB06 EB07 EB08 EC03 EC01 EC01

Claims (3)

[Claims] (A) an epoxy resin containing at least one epoxy resin selected from the group consisting of the epoxy resins represented by the general formulas (1) and (2) in a total epoxy resin content of 20% by weight or more; ) The phenol resin represented by the general formula (3) is contained in the total phenol resin in an amount of 20 to 90% by weight, and the dicyclopentadiene-modified phenol resin curing agent represented by the general formula (4) is contained in the total phenol resin curing agent by 1%.
An epoxy resin composition for semiconductor encapsulation, comprising a phenol resin curing agent containing 0 to 80% by weight, (C) a curing accelerator, and (D) a fused silica powder. Embedded image Embedded image Embedded image Embedded image R in the formulas (1) to (3) is a halogen atom or a
Represents 12 alkyl groups, which may be the same or different from each other. l is 1 to 10, m is 0 or 1 to 3
Is a positive integer of 0 or n is a positive integer of 1 to 4.
K in the formula (4) is a positive integer of 0 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 side of the substrate 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.