JPH11181237A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition little in warpage on a soldering treatment, etc., and having excellent reliability, etc., by compounding a polyfunctional epoxy resin, a crystalline epoxy resin, a phenolic resin-curing agent, molten silica powder and a latent catalyst comprising a phosphonium borate. SOLUTION: This epoxy resin composition comprises (A) an epoxy resin selected from (i) a polyfunctional epoxy resin of formula I or II [R is a halogen or the like; 1 is 1-10; (m) is 0-3; (n) is 0-4] and/or (ii) a crystalline epoxy resin expressed by formula III (R is H, a halogen or a 1-12C alkyl) or the like and having a melting point of 50-150 deg.C, (B) a phenolic resin-curing agent of formula IV, (C) molten silica, and (D) a latent catalyst comprising a phosphonium borate expressed by formula V or the like. The component A preferably comprises 20-90 wt.% of the component Ai and >=10 wt.% of the component Aii.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition for semiconductor encapsulation and a resin-encapsulated semiconductor device having excellent moldability, reliability, and mountability, and more particularly to a printed wiring board and a metal lead frame. The semiconductor element is mounted on one side of
In a so-called area mounting type semiconductor device in which only one surface on the mounting surface side 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. The present invention relates to an epoxy resin composition for semiconductor encapsulation, which has excellent package crack resistance and package crack resistance and peeling resistance in a soldering step, and is excellent in moldability, and a semiconductor 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. Typical area mounting packages are BGA (ball grid array) or CSP (chip size package) pursuing further miniaturization, but these are approaching the limit in conventional surface mounting packages such as QFP and SOP. It has been developed to meet the demand for higher pin counts and higher speeds. 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. Also, on the surface opposite to the element mounting surface of the substrate, solder balls are formed two-dimensionally in parallel so as to be joined to a circuit board on which a package is mounted. Further, a structure using a metal substrate such as a lead frame other than the organic circuit substrate has been devised as a substrate on which the element is mounted.

[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, warpage of the package occurs, and a large number of solder balls do not become flat, and the package is mounted. There is also a problem that the semiconductor device floats from the circuit board to be mounted and lowers the reliability of electrical connection. In a package in which substantially only one surface on a substrate is sealed with a resin composition, in order to reduce warpage, the linear expansion coefficient of the substrate and the linear expansion coefficient of a cured product of the resin composition are brought close to each other, and the resin composition There are two important ways to reduce the cure shrinkage. As a substrate, in an organic substrate, a resin having a high glass transition temperature such as a BT resin or a polyimide resin is widely used, and these have a glass transition temperature higher than around 170 ° C. which is a molding temperature of an 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.

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 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 thermal expansion coefficient of the substrate and the cured product,
In a temperature cycle test, which is a typical example of a reliability test, peeling of the interface between the substrate and the cured product and cracking of the package occur. Conventional surface mount packages such as QFP and SOP use a crystalline epoxy resin typified by a biphenyl-type epoxy resin and a flexible skeleton to prevent cracks at the time of solder mounting and peeling at each material interface. By using a phenolic resin curing agent in combination and increasing the blending amount of an inorganic filler, measures have been taken to lower the glass transition temperature and lower the moisture absorption. However, this method cannot only solve the problem of warpage in the single-sided sealed package, but also causes high viscosity of the resin, so that the gold wires are short-circuited at the time of resin injection, which has been a serious problem.

[0005]

DISCLOSURE OF THE INVENTION The present invention has low warpage after molding in an area mounting package or during soldering, and has particularly excellent adhesiveness to a substrate, so that reliability in a temperature cycle test, soldering, etc. The present invention has been made for the purpose of developing an epoxy resin composition for semiconductor encapsulation, which is excellent in the above-mentioned properties, and furthermore has an effect of preventing a flow of gold wire at the time of resin injection, and a semiconductor device in which a semiconductor element is encapsulated thereby.

[0006]

The present invention relates to (A) a polyfunctional epoxy resin represented by the general formulas (2) and (3) and / or a compound represented by the formulas (4) to (8) and having a melting point of: 50-150
At least one epoxy resin selected from the group of crystalline epoxy resins at ℃, (B) a phenolic resin curing agent represented by the general formula (1), (C) fused silica powder, and (D)
An epoxy resin composition for encapsulating a semiconductor, comprising a latent catalyst comprising a phosphonium borate represented by the general formula (9) or (10), and a semiconductor device having a semiconductor element encapsulated thereby.

[0007]

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[0008]

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[0009]

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[0010]

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[0011]

Embedded image [R in the formulas (1), (2), (3) and (8) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. l is 1 to 10
Is a positive integer of 0 or 1 to 3, and n is a positive integer of 0 or 1 to 4. ] [Equation (4) ~
R in (7) represents a hydrogen atom, a halogen atom or a carbon atom having 1 carbon atom.
To 12 alkyl groups, which may be the same or different. ]

[0012]

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[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Among the epoxy resins of the component (A) used in the present invention, a resin generally referred to as a triphenolmethane epoxy resin represented by the formula (2) or an epoxy resin represented by the formula (3) is represented by the following formula (1). In combination with a phenolic resin curing agent, the crosslinked density of the cured product is high, the glass transition temperature is high, and the curing shrinkage is small. It is effective in reducing warpage. Specific examples of the formulas (2) and (3) include the following, but are not limited thereto.

[0014]

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[0015]

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The crystalline epoxy resin represented by the formulas (4) to (8) and having a melting point of 50 to 150 ° C. is a diepoxy compound having two epoxy groups in one molecule or an oligomer thereof. Since all of these epoxy resins show crystallinity, they are solid at a temperature lower than the melting point, but become a low-viscosity liquid material at a temperature higher than the melting point. For this reason, the epoxy resin composition using these has a low viscosity in a molten state, so that the fluidity of the resin composition at the time of molding is high, and the filling property into a thin package is excellent. Therefore, it is preferable to use these crystalline epoxy resins when increasing the amount of the fused silica powder to reduce the moisture absorption of the cured product of the obtained epoxy resin composition and improving the solder reflow resistance. .

These crystalline epoxy resins have as few as two epoxy groups in one molecule, and generally have only a low cross-linking density and a cured product with low heat resistance. However, since it has a rigid plane or rod-like skeleton as a structure and has the property of being crystallized, that is, the feature that molecules are easily oriented, the polyfunctional phenol resin curing agent represented by the general formula (1) is used. When used in combination, it is difficult to lower the heat resistance such as the glass transition temperature after curing. For this reason, the semiconductor package sealed with the epoxy resin composition by the combination of the crystalline epoxy resin and the phenol resin curing agent represented by the general formula (1) can reduce the amount of warpage. Further, in a temperature region once exceeding the glass transition temperature, the compound exhibits a low elastic modulus characteristic of a compound having a low functional group, which is effective for reducing stress at a solder processing temperature. This has the effect of preventing the occurrence of package cracks during the soldering process and the occurrence of separation at the interface between the substrate and the resin composition. If the crystalline epoxy resin has a melting point of less than 50 ° C., it tends to fuse in the production process of the epoxy resin composition, and the workability is significantly reduced. Further, a crystalline epoxy resin having a melting point exceeding 150 ° C. has a problem that the uniformity of the material is inferior because the epoxy resin composition is not sufficiently melted in the production step of kneading under heating. The melting point is measured by a differential scanning calorimeter [Seiko Electronics Co., Ltd. SSC520, heating rate 5 ° C./min].
From the endothermic peak temperature. Hereinafter, specific examples of these crystalline epoxy resins are shown, but are not limited thereto.

[0018]

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[0019]

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[0020]

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Further, from the viewpoint of reducing package warpage, increasing fluidity during molding, and achieving solder resistance during mounting, the polyfunctional epoxy resins represented by the general formulas (3) and (4) are all used. It is particularly preferable that the total epoxy resin contains 20 to 90% by weight in the epoxy resin and further contains the crystalline epoxy resin represented by the formulas (5) to (9) and having a melting point of 50 to 150 ° C in the total epoxy resin. preferable. The epoxy resin used in the present invention can be appropriately used in combination with other epoxy resins and is not particularly limited. For example, in addition to the above, bisphenol F type epoxy resin, bisphenol A type epoxy resin, orthocresol novolak type Epoxy resins, naphthol type epoxy resins and the like can be mentioned. These epoxy resins may be used alone or as a mixture.

Formula (1) of the component (B) used in the present invention
Is a so-called triphenolmethane-type phenol resin, and specific examples are shown below, but are not limited thereto.

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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. For this reason, the warpage of the package sealed with the obtained epoxy resin composition can be reduced. The phenolic resin of the formula (1) can be appropriately used in combination with other phenolic resins, and is not particularly limited. Examples thereof include phenol novolak resins, cresol novolak resins, and naphthol novolak resins.

The fused silica powder of the component (C) 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 latent catalyst comprising the phosphonium borate represented by the general formulas (9) and (10) as the component (D) used in the present invention is disclosed in JP-A-8-295721. It does not disclose the application as a catalyst with a specific phenol resin or a specific epoxy resin for the purpose of application to a structure in which one side is directly sealed to an organic substrate as described above. The latent catalyst composed of phosphonium borate used in the present invention has a melting point of 250 ° C. or less, does not show catalytic activity at room temperature, does not progress the curing reaction, and exhibits very strong catalytic activity at high temperatures. . Therefore, the resin composition has a high preservability at room temperature, exhibits catalytic activity when the semiconductor is heat-sealed and molded, and highly cures the epoxy resin composition.

A conventional curing accelerator can be used in combination with the latent catalyst comprising phosphonium borate as the component (D) for use in the present invention. Specific examples include, but are not limited to, amine compounds such as tributylamine, organic phosphorus compounds such as triphenylphosphine and tetraphenylphosphonium / tetraphenylborate salts, and imidazole compounds such as 2-methylimidazole. Not something. These curing accelerators may be used alone or as a mixture.

The resin composition of the present invention may be, if necessary, a brominated epoxy resin, a flame retardant such as antimony trioxide, a coupling agent, or carbon black, 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. Using the epoxy resin composition of the present invention to encapsulate electronic components such as semiconductors and manufacture semiconductor devices, transfer molding, compression molding, and injection molding can be performed by conventional molding methods such as injection molding. Good.

[0028]

The present invention will be specifically described below with reference to examples. << Example 1 >> An epoxy resin having a structure represented by the formula (11) as a main component: [manufactured by Yuka Shell Epoxy Co., Ltd., Epicoat 1032H, softening point 60 ° C, epoxy equivalent 170] 4.6 weight Part: Biphenyl-type epoxy resin having a structure represented by the formula (12) as a main component: [YX-4000H, manufactured by Yuka Shell Epoxy Co., Ltd., melting point 105 ° C., epoxy equivalent 195] 4.6 parts by weight A phenolic resin represented by the formula (13): [Mehka Kasei Co., Ltd., trade name: MEH-7500, softening point 107 ° C, hydroxyl equivalent 97] 4.8 parts by weight • Latency represented by the formula (9) Catalyst 0.4 parts by weight ・ Spherical fused silica 84.7 parts by weight ・ Carnauba wax 0.5 parts by weight ・ Carbon black 0.3 parts by weight After mixing all the above components by a mixer, the surface temperature is 90 ° C. and 45 ° C. of 30 times kneaded using this roll, the kneaded product sheet obtained by pulverizing after cooling to obtain a resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 1 shows the evaluation results.

<< Example 2 and Comparative Examples 1-2 >> Example 1
Was used as a basic blend, the type of catalyst was changed, and the other components were blended in the same ratio as the basic blend, 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. << Examples 3 to 9 and Comparative Example 3 >> Based on Example 1, the components were mixed at the same ratio as the basic compounding, while changing the types of epoxy resin and phenolic resin and the amounts thereof, and carrying out. 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 1 shows the formulation and evaluation results.

The structures and properties of other epoxy resins of formulas (11), (12), (14) to (18) and phenolic resins of formulas (13) and (19) used in the above Examples and Comparative Examples are as follows. Show.

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[0031]

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[0032]

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An epoxy resin having a structure of the formula (14) as a main component: a melting point of 144 ° C. and an epoxy equivalent of 175. An epoxy resin having a structure of the formula (15) as a main component: a melting point of 52 ° C. and an epoxy equivalent of 225. Epoxy resin having a structure of 16) as a main component: melting point 133 ° C., epoxy equivalent 182 ・ Epoxy resin having a structure of formula (17) as a main component: melting point 82 ° C., epoxy equivalent of 190 ・ mainly a structure of formula (18) Epoxy resin as a component: softening point 65 ° C., epoxy equivalent 210 ・ phenol resin of formula (19): softening point 80 ° C., hydroxyl equivalent 104

<< Evaluation Method >> Spiral flow: Using a mold for measuring spiral flow according to EMMI-I-66, using 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. -Glass transition temperature (Tg) and coefficient of linear expansion (α ₁ ): 1
The test piece obtained by transfer molding at 75 ° C. for 2 minutes was post-cured at 175 ° C. for 8 hours, and measured by a thermomechanical analyzer [TMA-120 manufactured by Seiko Denshi Co., Ltd., heating rate 5 ° C./min].・ Heat elastic modulus: Flexural elastic modulus at 240 ° C is JIS-K6
It was measured according to 911. 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.

Package warpage: 225-pin BGA package (substrate 0.36 mm thick, bismaleimide
Triazine / glass cloth substrate, package size 2
4 × 24 mm, thickness 1.17 mm, silicon chip size 9 × 9 mm, thickness 0.35 mm, the chip and the bonding pad of the circuit board are bonded with a gold wire having a diameter of 25 μm). 75kg / cm
Perform transfer molding for 2 minutes at ² injection pressure, 8 hours at 175 ° C., and post-cured. 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. Gold wire deformation: 225 molded by evaluating package warpage
The pin BGA package was observed with a soft X-ray fluoroscope, and the deformation rate of the gold wire was represented by (flow amount) / (gold wire length) in%.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

The epoxy resin composition for semiconductor encapsulation of the present invention has a small warpage in the area mounting type semiconductor device using the same at room temperature and in the soldering process, and has a good effect on the gold wire for connection between the chip and the substrate. On the other hand, it can be molded without any influence and has excellent adhesion with a solder resist layer formed on a substrate, so that it has excellent reliability such as solder resistance and temperature cycle resistance.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08G 59/68 C08G 59/68 C08K 3/36 C08K 3/36 H01L 23/29 H01L 23/30 R 23/31

Claims (2)

[Claims] 1. A polyfunctional epoxy resin represented by the general formulas (2) and (3) and / or a crystalline epoxy represented by the formulas (4) to (8) and having a melting point of 50 to 150 ° C. At least one epoxy resin selected from the group of resins, (B)
A phenolic resin curing agent represented by the general formula (1), (C)
Fused silica powder, and (D) general formula (9) or (10)
An epoxy resin composition for encapsulating a semiconductor, comprising a latent catalyst comprising a phosphonium borate represented by the formula: Embedded image Embedded image Embedded image Embedded image Embedded image [R in the formulas (1), (2), (3) and (8) represents a halogen atom or an alkyl group having 1 to 12 carbon atoms, and may be the same or different. l is 1 to 10
Is a positive integer of 0 or 1 to 3, and n is a positive integer of 0 or 1 to 4. ] [Equation (4) ~
R in (7) represents a hydrogen atom, a halogen atom or a carbon atom having 1 carbon atom.
To 12 alkyl groups, which may be the same or different. ] 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.