JP2000281750A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition which has good moldability and can give a cured product showing excellent soldering resistance even in soldering after moisture absorption by mixing an epoxy resin with a phenolic resin, a fused silica powder, a cure accelerator, and a mold release by melting under heating and adding another mold release to the resultant mixture. SOLUTION: This composition is prepared by melt-mixing an epoxy resin composition essentially consisting of an epoxy resin, a phenolic resin, a fused silica powder, a cure accelerator, and at least one mold release and containing at least either an epoxy resin of formula I and a phenolic resin of formula II under heating, and adding a mold release selected from among a long-chain fatty acid amide ester, a long-chain fatty acid metal salt, a polyolefin oxide, and a paraffin oxide to the resultant mixture. In the formulae, R is H, a halogen or a 1-9C alkyl; and (n)is 1-5 on the average. The phenolic resin used is one having a hydroxyl equivalent of 130-210. The fused silica powder is used in an amount of, desirably, 75-93 wt.% based on the entire composition and is desirably a spherical one.

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 which has excellent moldability and solder resistance and is particularly suitable for thin semiconductor devices, and a semiconductor device using the same.

[0002]

2. Description of the Related Art Transfer molding of an epoxy resin composition is suitable as a method for encapsulating semiconductor elements such as ICs and LSIs at a low cost and suitable for mass production. The phenol resin has been improved to improve the characteristics. However, in the recent market trend of miniaturization, weight reduction and high performance of electronic devices, the integration of semiconductors has been increasing year by year, and the surface mounting of semiconductor devices has been promoted. Demands for resin compositions are becoming more stringent. For this reason, a problem that cannot be solved by the conventional epoxy resin composition has appeared. The biggest problem is that
Due to the adoption of surface mounting, the semiconductor device is rapidly exposed to a high temperature of 200 ° C. or more in a solder immersion or reflow process, and cracks are generated in the semiconductor device due to stress when moisture absorbed explosively evaporates. This is a phenomenon in which peeling occurs at the interface between each of the plated portions on the element, the lead frame, and the inner lead and the cured product of the resin composition, and the reliability is significantly reduced.

In recent years, the thickness of a resin composition occupying in a semiconductor device has been further reduced with the reduction in thickness of the semiconductor device. For example, in a semiconductor device for 64M or 256M DRAM, a 1 mm thick TSOP has become mainstream. It is getting. These thin semiconductor devices are required to have a resin composition that has good filling properties at the time of molding, has little deformation of gold wires, and has no deformation of semiconductor elements or lead frames (referred to as chip shift or die pad shift). The composition needs to have excellent fluidity during molding. In order to achieve both improvement in reliability due to soldering and improvement in fluidity during molding, the amount of fused silica powder in the epoxy resin composition is increased to reduce moisture absorption, increase strength, and reduce thermal expansion. And improving the solder resistance, and using a resin having a low melt viscosity to maintain a low viscosity and high fluidity during molding is becoming common. On the other hand, the adhesiveness at the interface between a cured product of an epoxy resin composition and a substrate such as a semiconductor element or a lead frame existing inside a semiconductor device has become very important in reliability by soldering. If the adhesive force at the interface is weak, peeling occurs at the interface with the base material after the soldering, and further, cracks occur in the semiconductor device due to the peeling. Many proposals have been made on epoxy resins and phenolic resins from the viewpoint of improving the adhesive strength at the interface. Particularly, epoxy resins of the general formula (1) and phenolic resins of the general formula (2) have a high flexibility. It is known that it is characterized by low moisture absorption and is suitable (JP-A-5-343570, JP-A-6-80763, JP-A-8-143648, etc.).

However, the resin composition using the epoxy resin represented by the general formula (1) or the phenol resin represented by the general formula (2) as a curing agent has a low functional group density such as an epoxy group or a phenolic hydroxyl group and has a low flexibility. Due to the presence of a rigid biphenyl structure between the functional groups that are the reaction points, curing during molding is slow due to the effect of steric hindrance,
Therefore, there are observed such phenomena that the hardness at the time of heating is low and the molded product adheres to the mold at the time of release from the mold, or the molded product is damaged. In order to improve the molding workability, an epoxy resin composition with further improved releasability has been desired.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a resin having good moldability and excellent in soldering resistance which does not cause cracks or peeling from a substrate in a cured semiconductor device even in a soldering process after moisture absorption. It has been made for the purpose of the composition.

[0006]

That is, the present invention provides (A) an epoxy resin, (B) a phenolic resin, (C) a fused silica powder, (D) a curing accelerator, and (E) a long-chain fatty acid, One or more release agents selected from fatty acid amides are essential components, and at least one selected from an epoxy resin represented by the general formula (1) or a phenol resin represented by the general formula (2) is included. An epoxy for semiconductor encapsulation, wherein the epoxy resin composition is heated and melt-mixed, and further comprising (F) at least one selected from long-chain fatty acid esters, long-chain fatty acid metal salts, polyolefin oxides, and paraffin oxides. A resin composition and a semiconductor device formed by sealing a semiconductor element using the resin composition.

Embedded image (R in the formula is a hydrogen atom, a halogen atom, or a carbon atom 1
A group selected from the alkyl groups from 1 to 9, which may be the same or different, and n is an average value and a positive number of 1 to 5)

[0007]

Embedded image (R in the formula is a hydrogen atom, a halogen atom, or a carbon atom 1
A group selected from the alkyl groups from 1 to 9, which may be the same or different, and n is an average value and a positive number of 1 to 5)

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having an epoxy group, for example, crystalline epoxy resins such as biphenyl type epoxy resin, stilbene type epoxy resin, hydroquinone type epoxy resin and bisphenol F type epoxy resin. And bisphenol A type epoxy resin, orthocresol novolak type epoxy resin, dicyclopentadiene modified phenol type epoxy resin, triphenolmethane type epoxy resin, naphthol type epoxy resin, epoxy resin represented by the general formula (1), and the like. These epoxy resins may be used alone or in combination. Among them, a preferred epoxy resin is an epoxy resin represented by the general formula (1). The epoxy resin represented by the general formula (1) is an epoxy resin having two or more epoxy groups in one molecule, and is characterized by having a hydrophobic structure between epoxy groups. The cured product of the phenolic resin has a low cross-linking density and a large hydrophobic structure, and thus has a low moisture absorption rate. Therefore, the thermal stress during molding of the epoxy resin composition or the solder after moisture absorption of a semiconductor device as a molded product. Reduces thermal stress generated during processing and has excellent adhesion to substrate. On the other hand, since the hydrophobic structure between the epoxy groups is a rigid biphenyl skeleton, it has a feature that the heat resistance is not significantly reduced despite the low crosslinking density. Specific examples of the epoxy resin represented by the general formula (1) are shown below, but are not limited thereto.

Embedded image In order to increase the filling amount of the fused silica powder in the epoxy resin composition, the above-mentioned crystalline epoxy resin which exhibits crystallinity at room temperature and extremely lowers the melt viscosity at the molding temperature is preferable.

The phenolic resin used in the present invention refers to all monomers, oligomers and polymers having a phenolic hydroxyl group, such as phenol novolak resin,
Cresol novolak resin, xylylene-modified phenol resin, terpene-modified phenol resin, dicyclopentadiene-modified phenol resin, bisphenol A, triphenolmethane, phenol resin represented by the general formula (2), and the like can be given. The hydroxyl equivalent is preferably 130 to 21 in order to improve the low hygroscopicity of the cured product of the resin composition and the adhesion to the substrate.
Phenolic resins in the range of 0 are preferred. These epoxy resins may be used alone or as a mixture. Among these phenol resins, a phenol resin represented by the general formula (2) is preferable. The characteristics of the epoxy resin represented by the general formula (2) are exactly the same as those described for the epoxy resin represented by the general formula (1), and the epoxy resin represented by the general formula (1) and the epoxy resin represented by the general formula (2)
When the phenol resin is combined with the phenol resin, the greatest effect is obtained in reliability such as low moisture absorption of the semiconductor device, solder resistance after solder absorption after moisture absorption, and adhesion. As the phenolic resin represented by the formula (2) used in the present invention, those having the following structures are specifically shown, but are not limited thereto.

Embedded image It is essential that the epoxy resin composition of the present invention contains at least one or more of the epoxy resin represented by the general formula (1) and the phenol resin represented by the general formula (2).

Examples of the fused silica powder used in the present invention include natural silica melted in a flame, and synthetic silica obtained by hydrolyzing tetramethoxysilane, tetraethoxysilane and the like. Further, there are spherical silica and crushed silica depending on the shape and production method. The blending amount of the fused silica powder is 75 to 9 in the total resin composition.
3% by weight is preferred. If the content is less than 75% by weight, the amount of moisture absorbed by the cured product of the resin composition increases, and the strength at the soldering temperature is reduced. On the other hand, if it exceeds 93% by weight, the fluidity during molding of the resin composition decreases,
Unfilling, chip shift, and pad shift are likely to occur, which is not preferable. Particularly, in order to highly fill the fused silica powder, a spherical one is preferable. Further, a broad particle size distribution is effective for reducing the melt viscosity of the resin composition during molding.

[0011] The curing accelerator used in the present invention refers to those which can serve as a catalyst for the crosslinking reaction between the epoxy resin and the phenol resin. Specific examples include tributylamine,
1,8-diazabicyclo (5,4,0) undecene-7
And the like, an organic phosphorus-based compound such as triphenylphosphine, tetraphenylphosphonium / tetraphenylborate salt, and an imidazole compound such as 2-methylimidazole. These may be used alone or as a mixture.

The release agents used in the present invention include, as a first group, long-chain fatty acids such as stearic acid, montanic acid and palmitic acid, N-stearylstearic acid amide, ethylenebisstearic acid amide, N, N'-diamine. It is selected from long-chain fatty acid amides such as stearyl sebacic amide and m-xylylene bisstearyl amide. The first group of release agents is preliminarily mixed with the epoxy resin composition and melted or dispersed in the composition by heating and kneading. These release agents are epoxy resins of the general formula (1) or general formula (2)
Excellent compatibility with phenolic resins, lowering the melt viscosity of the resin composition during heating and kneading, improving the uniformity of the resin composition and improving the fluidity during molding of the obtained resin composition, Although there is an effect of improving the filling property of the thin semiconductor device, on the other hand, the migration of the release agent to the surface of the mold is small, and a sufficient release effect cannot be obtained with these alone. On the other hand, when these release agents are mixed with the powder obtained by cooling and pulverizing the heat-kneaded epoxy resin composition, a melt from these release agents contaminates the mold during molding, and the molded product The surface is also contaminated.

The release agent used in the present invention includes, as a second group, long-chain fatty acid esters such as carnauba wax and montanic acid ester, and calcium salts and zinc salts of long-chain fatty acids such as stearic acid and montanic acid. It is selected from metal salts of chain fatty acids, and oxidized polyolefins and oxidized paraffins. Of the release agents of the second group, when melted and dispersed by heating and kneading with the epoxy resin composition, the release agents having high compatibility with the resin may transfer to the mold surface or the molded product surface during molding. Due to the difficulty, the releasability becomes insufficient. On the other hand, with a release agent having low compatibility (such as a long-chain fatty acid ester or a metal salt of a long-chain fatty acid), uniform dispersion in the epoxy resin composition is difficult. The problem of contaminating the product surface or reducing the adhesion to the base material by concentrating on the interface between the base material in a semiconductor device such as a semiconductor element and a lead frame and the cured product of the epoxy resin composition And cannot be blended in large amounts. In order to solve the problems of the second group of release agents,
The release agent of the group is added as a powder to the powder obtained by kneading and kneading the epoxy resin composition containing the heat-kneaded release agent of the first group, followed by pulverization, and is mixed and mixed well. It is necessary. According to this method, the release agent is efficiently transferred to the surface of the mold, has excellent releasability, and hardly dissolves in the resin. It is also possible to add a part of the release agent of the second group of the present invention simultaneously with the first group and knead with the epoxy resin composition by heating.

The resin composition of the present invention comprises, in addition to the components (A) to (F), if necessary, a flame retardant such as a brominated epoxy resin or antimony trioxide, a low stress agent represented by a polysiloxane compound, A coupling agent, a coloring agent represented by carbon black, and the like can be appropriately compounded. In order to manufacture an electronic device such as a semiconductor device by encapsulating an electronic component using the resin composition of the present invention, it is only necessary to cure and mold by a conventional molding method such as transfer molding, compression molding and injection molding.

Hereinafter, the present invention will be described specifically with reference to Examples. The mixing unit is parts by weight. Example 1 5.9 parts by weight of an epoxy resin of the formula (3) (epoxy equivalent 270, softening point 60 ° C.)

Embedded image

Phenol aralkyl resin (XL225-LL, manufactured by Mitsui Chemicals, Inc., softening point 75 ° C., hydroxyl equivalent 175; hereinafter referred to as phenol aralkyl resin) 4.0 parts by weight Spherical fused silica powder 87.2 parts by weight triphenylphosphine 0.2 parts by weight Stearic acid 0.1 parts by weight Zinc stearate 0.2 parts by weight Brominated epoxy resin 0.5 parts by weight Antimony trioxide 1.3 parts by weight Silane coupling agent 0.5 parts by weight Carbon black After mixing 3 parts by weight using a mixer, the surface temperature was 90 ° C and 4 ° C.
The mixture was kneaded 30 times using two rolls at 5 ° C., and the obtained kneaded material sheet was cooled and pulverized to obtain a resin composition powder. Next, 0.2 parts by weight of zinc stearate was added to the resin composition powder, and mixed sufficiently using a mixer. The obtained resin composition was evaluated by the following method. Table 1 shows the results.

Evaluation method Spiral flow: Using a mold for measuring spiral flow according to EMMI-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.
The unit is cm. Releasability: 100-pin TQFP (package size is 14
(× 14 mm, thickness 1.4 mm, silicon chip size 8.0 × 8.0 mm, lead frame made of 42 alloy)
Was subjected to transfer molding at a mold temperature of 175 ° C., an injection pressure of 75 kg / cm ² and a curing time of 2 minutes. After the molding, the releasability from the mold when the mold was opened was evaluated. ○ indicates good releasability, and × indicates occurrence of mold adhesion or runner breakage. Mold stain: The epoxy resin composition was continuously molded 100 times under the above conditions using a mold evaluated for mold release properties, and the surface of the mold after molding was visually observed. When the discoloration was recognized on the mold surface, it was indicated by x, and when there was no change, it was indicated by o. Solder Resistance: The 100-pin TQFP molded product obtained in the release property evaluation was post-cured at 175 ° C. for 8 hours. The semiconductor package was left for 168 hours in an environment of 85 ° C. and 85% relative humidity, and then immersed in a 240 ° C. solder bath for 10 seconds. Observe external cracks with a microscope, and determine the number of cracks ((number of packages in which cracks occur) / (number of all packages) × 10
0) was expressed in%. Further, the ratio of the peeling area between the chip and the resin composition was measured using an ultrasonic flaw detector, and the peeling rate ((peeling area) / (chip area) × 100) was calculated as 5%.
The average value of the packages was determined and expressed in%.

Examples 2 to 5 Each component was blended in the proportions shown in Table 1 to obtain a resin composition in the same manner as in Example 1, and evaluated in the same manner as in Example 1. Table 1 shows the results. Comparative Examples 1 to 5 According to the ratios shown in Table 2, Comparative Example 1 is a resin composition not containing a release agent, and Comparative Example 2 was prepared by mixing each component not containing a release agent, The mixture was kneaded 30 times using two rolls at 90 ° C. and 45 ° C., and the obtained kneaded material sheet was cooled and pulverized to obtain a resin composition powder, and 0.3% by weight of carnauba wax was added to the resin composition powder. Comparative Example 3 is a resin composition obtained by adding 0.3 parts by weight of a carnauba wax and then mixing the respective components containing 0.3 parts by weight of carnauba wax. A resin composition obtained by kneading 30 times using two rolls at a temperature of 30 ° C., cooling and pulverizing the obtained kneaded material sheet, and Comparative Example 4 in which each component containing no release agent was mixed. Thereafter, the mixture was kneaded 30 times using two rolls having a surface temperature of 90 ° C. and 45 ° C. to obtain a kneaded material. The sheet is cooled and then crushed to obtain a resin composition powder,
Comparative Example 5 is a resin composition obtained by adding 0.2 parts by weight of carnauba wax and 0.1 parts by weight of stearic acid to this resin composition powder, and thoroughly mixing using a mixer.
Is obtained by mixing each component not containing a release agent, kneading 30 times using two rolls having a surface temperature of 90 ° C. and 45 ° C., cooling the obtained kneaded material sheet, and pulverizing the resin composition. Powder, and zinc stearate 0.2% is added to the resin composition powder.
It is a resin composition obtained by adding parts by weight and sufficiently mixing using a mixer. The properties of the epoxy resin and the phenol resin used in other than Example 1 are shown below. An epoxy resin having the formula (4) as a main component (an epoxy equivalent of 19)
5, mp 105 ° C.), phenolic resin of formula (5) (hydroxyl equivalent 195, softening point 70 ° C.). The structures of the formulas (4) and (5) are shown below.

Embedded image

[0019]

Embedded image

The release agents used in the examples and comparative examples are as follows:
As described above, the release agent added and blended during the heat kneading is the first
Table 1 and Table 2 show the group and the release agent added and mixed after the heat kneading as a second group.

[Table 1]

[0021]

[Table 2]

[0022]

When the resin composition of the present invention is used, a semiconductor device which is excellent in mold releasability and sealed is excellent in hot strength and low hygroscopicity, and therefore excellent in solder resistance after moisture absorption.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08K 5/20 C08K 5/20 C08L 23/26 C08L 23/26 61/18 61/18 63/00 63/00 BC A 91/06 91/06 H01L 23/29 H01L 23/30 R 23/31 F-term (reference) 4J002 CC02X CC04X CC05X CC07X CD02W CD03W CD04W CD05W CD06W CD07W DJ016 EF058 EN027 EP018 EQ027 EU117 EW017 EW177 EY017 FA086 FD016J00 4J036 AA01 AA02 AC01 AD07 AD08 AD10 AD12 AJ14 DA01 DA02 DA04 DA05 DC05 DC06 DC40 DC41 DD07 DD09 FA10 FA12 FB07 FB08 GA04 JA07 4M109 AA01 BA01 CA21 EA02 EB03 EB04 EB06 EB07 EB08 EB09 EB13 EC01 EC03 EC20

Claims (2)

[Claims] 1. A resin selected from (A) an epoxy resin, (B) a phenolic resin, (C) a fused silica powder, (D) a curing accelerator, and (E) a long-chain fatty acid or a long-chain fatty acid amide.
An epoxy resin composition containing at least one release agent as an essential component and containing at least one selected from the epoxy resin represented by the general formula (1) or the phenol resin represented by the general formula (2) is heated and melted. And (F) a long-chain fatty acid ester, a long-chain fatty acid metal salt, an oxidized polyolefin,
An epoxy resin composition for semiconductor encapsulation comprising at least one selected from oxidized paraffins. Embedded image (R in the formula is a hydrogen atom, a halogen atom, or a carbon atom 1
Which may be the same or different, and n is an average value and is a positive number of 1 to 5) (R in the formula is a hydrogen atom, a halogen atom, or a carbon atom 1
A group selected from the alkyl groups from 1 to 9, which may be the same or different, and n is an average value and a positive number of 1 to 5) 2. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition for semiconductor encapsulation according to claim 1.