JP4794706B2 - Epoxy resin composition and semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface-mountable epoxy resin composition for semiconductor encapsulation, which is excellent in storage characteristics at room temperature, moldability and reliability of a resin composition, and a semiconductor device encapsulated thereby.
[0002]
[Prior art]
Epoxy resin-based encapsulating resin compositions have been developed and produced in order to protect the IC body from mechanical and chemical effects. The items required for this resin composition are changing depending on the type of IC chip, the structure of the package to be sealed, the environment in which it is used, etc., but the biggest requirement at present is generated when the package is mounted. Crack. As a result of various investigations on this requirement, solder crack resistance was considerably improved by using a biphenyl type epoxy resin which is a crystalline epoxy resin and a resin composition containing more than the theoretical equivalent of the epoxy resin. This crystalline epoxy resin is crystalline at room temperature alone, but when used as a resin composition, the crystallinity is partially lost, so the viscosity increases due to the cross-linking reaction during resin kneading and storage at room temperature, resulting in poor moldability. In addition, since the epoxy resin is added in excess of the theoretical equivalent, curability is lowered and workability is hindered.
[0003]
In order to solve the above problems, for example, triphenylphosphine (hereinafter referred to as TPP) is used as a curing accelerator to reduce the amount added, and tetraphosphonium tetraphenylborate (hereinafter referred to as TPP-K) No. 24399), there is a method for improving the room temperature storage characteristics and curability, but the room temperature storage characteristics and curability cannot be compatible, and it is difficult to say that it is effective. In particular, when it comes to the room temperature storage characteristics, TPP is not limited to TPP-K.
[0004]
[Problems to be solved by the invention]
The present invention has been made as a result of various studies to solve these problems. A specific curing accelerator is used for the biphenyl type epoxy resin, and the blending ratio of the epoxy resin and the phenol resin curing agent is changed. In addition, the epoxy resin composition for semiconductor encapsulation, which is excellent in solder crack resistance by improving the ratio of the epoxy group to the phenolic hydroxyl group and can improve the room temperature storage characteristics while maintaining the curability at the time of molding, and the sealing thereby A stopped semiconductor device is provided.
[0005]
[Means for Solving the Problems]
In the present invention, the epoxy resin represented by the formula (1), the phenol resin curing agent, the curing accelerator and the fused silica powder are essential components, and the curing accelerator represented by the formula (2) is 50 wt% in the total curing accelerator. % Of the epoxy resin and the phenol resin curing agent are mixed in such a proportion that the epoxy group is 1. 27 to 1.4, preferably 50 to 90% by weight of the curing accelerator represented by the formula (2) and 10 to 50% by weight of triphenylphosphine in the total curing accelerator, and the total resin composition The total amount of U and Th in it is 2 ppb or less, which is an epoxy resin composition for semiconductor encapsulation. In addition, the semiconductor device is sealed with these epoxy resin compositions.
[0006]
[Chemical 3]
(R ₁ is a hydrogen atom, a methyl group, an ethyl group, a butyl group, or a halogen atom, and R ₁ may be the same or different.)
[0007]
[Formula 4]
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The epoxy resin represented by the formula (1) of the component (A) used in the present invention has crystallinity because it has a mesogenic skeleton in the main chain and is a relatively low molecule. This epoxy resin exhibits crystallinity and is a diepoxy compound having two epoxy groups in one molecule, so that it is solid at a temperature below the melting point, but becomes a low-viscosity liquid substance at a temperature above the melting point. For this reason, since the epoxy resin composition using these shows low viscosity in a molten state, the fluidity of the resin composition is high at the time of molding, the filling property to a thin package is excellent, and the moldability is good. In addition, since it is a bifunctional epoxy resin, the crosslink density is suppressed, the elastic modulus at high temperature is suppressed, and it is suitable for stress relaxation during reflow, and it solves moldability and solder crack resistance at once. is there.
[0009]
[Chemical formula 5]
(R ₁ is a hydrogen atom, a methyl group, an ethyl group, a butyl group, or a halogen atom, and R ₁ may be the same or different.)
[0010]
In this invention, you may add other epoxy resins, such as an ortho cresol novolak type epoxy resin and a naphthalene type epoxy resin, in the range which does not impair the characteristic of the epoxy resin of Formula (1).
[0011]
The phenol resin curing agent of component (B) used in the present invention is a monomer, oligomer or polymer having at least two phenolic hydroxyl groups capable of forming a crosslinked structure by performing a curing reaction with the above epoxy resin. Examples include phenol novolak resins, paraxylylene-modified phenol resins, phenol aralkyl resins such as metaxylylene / paraxylylene-modified phenol resins, terpene-modified phenol resins, dicyclopentadiene-modified phenol resins, etc., and these can be used alone or in combination. There is no problem. The softening point, hydroxyl group equivalent, etc. are not particularly specified, but the chlorine content in the resin is preferably as low as possible from the viewpoint of long-term reliability.
[0012]
The proportion of the epoxy resin and the phenol curing agent is preferably 1.1 to 1.4 with respect to the phenolic hydroxyl group 1 in view of the balance between moldability and solder crack resistance. In the conventional formulation, the ratio of the epoxy group 1 to the phenolic hydroxyl group 1 has the best balance. However, in the composition formulation of the present invention, if the epoxy group is less than 1.1 with respect to the phenolic hydroxyl group 1, the solder cracking property However, when it exceeds 1.4, the curability is lowered, and the range of 1.1 to 1.4 has the best balance.
[0013]
The curing accelerator of the component (C) used in the present invention is preferably a curing accelerator represented by the formula (2), and the amount used is essentially 50% by weight or more of the total curing accelerator, and curing acceleration The agent has low activity at normal temperature, high activity at high temperature, and a melting point of 200 ° C. to 250 ° C. is preferable in terms of storage stability at room temperature, reactivity, and dispersibility. In these respects, the structure of the formula (2) The curing accelerator is excellent. However, only the curing accelerator of the formula (2) leads to an extremely low reactivity in the kneading temperature range, a low molecular weight reaction at the time of kneading is suppressed, and wrinkles at the time of molding tend to occur. Although the storage stability at room temperature and fluidity are inferior to those of the curing accelerator of formula (2), a balance can be achieved by using triphenylphosphine having a reaction promoting action at low temperatures.
[0014]
[Chemical 6]
[0015]
The curing accelerator used in the present invention contains 50 to 100% by weight of the curing accelerator of formula (2), and may be used in combination with other curing accelerators. The amount of the curing accelerator of the formula (2) in the total curing accelerator is preferably 50 to 90% by weight and the amount of triphenylphosphine is preferably 10 to 50% by weight. When the curing accelerator of the formula (2) is less than 50% by weight, the above effect is not sufficiently exhibited, and the same result as that of the conventional curing accelerator system is obtained. When triphenylphosphine is less than 10% by weight, the usburr property at the time of molding is lowered. Examples of other curing accelerators that can be used in combination include tetraphenylphosphonium / tetraphenylborate, 2-methylimidazole, 1,8-diazabicyclo (5,4,0) undecene-7, and the like.
[0016]
The fused silica powder of component (D) used in the present invention can be used in either a crushed shape or a spherical shape, but in order to increase the blending amount of the fused silica powder and suppress an increase in the melt viscosity of the resin composition. It is preferable to use mainly 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. In addition, malfunctions due to radioactive materials are a problem with memory chips. Therefore, the silica used in the present invention desirably has a total amount of U and Th of 2 ppb or less.
[0017]
In addition to the essential components (A) to (D), the resin composition of the present invention is colored as typified by flame retardants such as brominated epoxy resins and antimony trioxide, coupling agents, and carbon black as necessary. Agents, release agents such as natural wax and synthetic wax, and low stress components such as silicone oil and rubber can be appropriately blended.
In order to obtain a resin composition, after mixing the respective components, the mixture is heated and kneaded with a heating kneader or a hot roll, and then cooled and pulverized to obtain the intended resin composition.
In order to seal an electronic component such as a semiconductor and manufacture a semiconductor device using the epoxy resin composition of the present invention, it may be cured by a conventional molding method such as a transfer mold, a compression mold, or an injection mold. .
[0018]
【Example】
Hereinafter, the present invention will be specifically described with reference to Examples.
Example 1
-13.2 parts by weight of a biphenyl type epoxy resin having the structure of formula (3) as a main component [manufactured by Yuka Shell Epoxy Co., Ltd., trade name YX-4000H, melting point 105 ° C., epoxy equivalent 195]
-Formula (4) phenol novolak resin 5.6 weight part [softening point 80 degreeC, hydroxyl equivalent 105]
-Curing accelerator A of formula (5) 0.3 parts by weight-Triphenylphosphine 0.1 parts by weight-Spherical fused silica I 80.0 parts by weight [U amount 0.1 ppb, Th amount 0.1 ppb, average particle size 15μm]
Carnauba wax 0.5 part by weight Carbon black 0.3 part by weight All the above components were mixed with a mixer, and then kneaded 30 times using two rolls with surface temperatures of 90 ° C and 45 ° C. The kneaded material sheet was cooled and pulverized to obtain a resin composition. The characteristics of the obtained resin composition were evaluated by the following methods. The evaluation results are shown in Table 1.
[0019]
[Chemical 7]
[0020]
[Chemical 8]
[0021]
[Chemical 9]
[0022]
<< Example 2 , Reference Example 3, Examples 4-8, and Comparative Examples 1-5 >>
It compounded according to Table 1 and Table 2, and obtained the resin composition like Example 1, and evaluated similarly. These evaluation results are shown in Tables 1 and 2.
Example 9
Example 1 was used as the basic formulation, blended in place of fused silica II having different amounts of U and Th, 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. The formulation and evaluation results are shown in Table 1. The structures and properties of the curing accelerator B of formula (6), the epoxy resin of formula (7), and fused silica II used in the above examples and comparative examples are shown below.
[0023]
[Chemical Formula 10]
[0024]
Embedded image
[0025]
Formula (7) Cresol novolac type epoxy resin [melting point 55 ° C., epoxy equivalent 201]
Fused silica II
[U amount 1.1 ppb, Th amount 1.6 ppb]
[0026]
"Evaluation methods"
・ Spiral flow:
Using a mold for spiral flow measurement according to EMMI-I-66, measurement was performed at a mold temperature of 175 ° C., an injection pressure of 70 kg / cm ² , and a curing time of 2 minutes.
・ Usvali:
Measures vent burr length during 16pDIP molding.
・ Room temperature storage:
After storing the resin composition at 25 ° C. for 1 week, the spiral flow was measured. The percentage when the initial spiral flow length is 100% is shown in%.
・ Curing property:
Measured using a Shore D hardness meter at a mold temperature of 175 ° C. and a curing time of 2 minutes.
・ Solder resistance:
8 packages of 80pQFP (thickness 1.5mm), left in an environment of 85 ° C and 60% relative humidity for 168 hours, and then processed the package after 10 seconds treatment with IR reflow (240 ° C) and an ultrasonic flaw detector Observe at.
・ U, Th amount:
After ashing the composition, the residual aqueous solution in which silica was volatilized with hydrofluoric acid and antimony was volatilized with hydrochloric acid was measured by ICP-MS (high frequency inductively coupled plasma mass spectrometry).
[0027]
[Table 1]
[0028]
[Table 2]
[0029]
【The invention's effect】
The epoxy resin composition for semiconductor encapsulation of the present invention is excellent in room temperature storage characteristics, and at the same time, improves the curability at the time of molding, and is excellent in solder crack resistance of a semiconductor device using the same.

Claims (4)

(A) An epoxy resin represented by formula (1), (B) a phenol resin curing agent represented by formula (4) , (C) a curing accelerator and (D) fused silica powder as essential components, and formula (2) The curing accelerator represented by the formula (1) contains 50% by weight or more in the total curing accelerator, and the blending ratio of the epoxy resin and the phenol resin curing agent is 1.27 to 1.4 with respect to the phenolic hydroxyl group 1. An epoxy resin composition for encapsulating a semiconductor.
_{(R 1} is a methyl group.)
  2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the curing accelerator represented by the formula (2) is 50 to 90% by weight and triphenylphosphine is 10 to 50% by weight in the total curing accelerator.   The epoxy resin composition for semiconductor encapsulation according to claim 1 or 2, wherein the total amount of U and Th in the total resin composition is 2 ppb or less.   A semiconductor device sealed with the epoxy resin composition for semiconductor sealing according to claim 1, 2 or 3.