JPH07165878A - Epoxy resin composition for sealing - Google Patents

Abstract

PURPOSE:To obtain a compsn. which hardly allows the occurrence of soldering crack and molding flash by compounding a specific epoxy resin based on a dicyclopentadiene-phenol copolymer with a dicyclopentadiene-phenol copolymer. CONSTITUTION:This compsn. contains an epoxy resin of formula I (wherein i, the number of repeating, is 0-1.0) based on a dicyclopentadiene-phenol copolymer and a dicyclopentadiene-phenol copolymer of formula II (wherein R is H or alkyl; and b is 0 or higher).

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 used for sealing electronic parts such as semiconductors.

[0002]

2. Description of the Related Art Conventionally, a method of sealing electronic parts such as semiconductors with a thermosetting resin composition is generally used. In this case, an epoxy resin composition is most commonly used as the thermosetting resin composition. This epoxy resin composition is, for example, an epoxy resin such as a cresol novolac type epoxy resin, a bisphenol A type epoxy resin or an aliphatic cyclic epoxy resin; a curing agent such as phenol novolac; a curing accelerator such as a tertiary amine or imidazole; silica. , An inorganic filler made of an inorganic powder such as alumina, a coupling agent such as a silane coupling agent, a release agent such as carnauba wax and stearic acid, and a colorant such as carbon black.

Recently, in order to reduce the size and thickness of electronic parts, the semiconductor mounting method is the conventional pin insertion method (DI).
P: dual in-line package, etc.) to a surface mounting method (SOP: small outline package, QFP: quad flat package, etc.). In the case of the surface mounting method, the semiconductor package is subjected to a high temperature treatment (for example, 210 to 270 ° C.) in a soldering process by infrared reflow, and the entire package is heated to a high temperature at that time. In the above-described package sealed with the conventional epoxy resin composition, there are cases in which problems such as cracks and a significant decrease in moisture resistance occur during this process.

The occurrence of cracks in the soldering process
It is said that moisture absorbed between post-curing and mounting is explosively vaporized and expanded by heating in the soldering process. Therefore, as a countermeasure, a method of completely drying the post-cured package, housing it in a container, sealing and shipping it is adopted. However, this method has a drawback that the work of handling the product is complicated.

Further, various improvements of the encapsulating resin composition itself have been studied. For example, JP-A-64-87616,
JP-A-1-108256 proposes a composition in which a biphenyl type epoxy resin is used as an epoxy resin and a general curing agent is used as a curing agent. In addition, JP-A-6
A composition using a dicyclopentadiene / phenol polymer as a curing agent and a general epoxy resin as an epoxy resin is proposed in 2-184020, JP-A-62-104830 and the like. However, with these proposed compositions, sufficient effects have not yet been obtained, and there is room for improvement.

In view of such circumstances, the present inventors have proposed in JP-A-3-166220 a composition containing a biphenyl type epoxy resin and a dicyclopentadiene / phenol polymer. This composition has low hygroscopicity and improved solder cracking properties. However, with the recent increase in the size of semiconductor chips, there has been a demand for further improvement in solder cracking properties in packages and the like that enclose and store large chips. Also,
It has been found that this composition may cause burrs during molding, and there is a problem to be improved in moldability.

[0007]

In view of the above circumstances,
It is an object of the present invention to solve the problem of the prior art of the occurrence of solder cracks in the soldering process, and it is a further object of the present invention to solve the problem of the occurrence of burrs during molding. . That is, an object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation, which can provide a sealed product in which cracks are less likely to occur when exposed to high temperatures in a soldering process and the like. An object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation, which is less likely to cause burrs.

[0008]

[Means for Solving the Problems] In order to solve the problem of reducing the occurrence of solder cracks in the soldering process,
The epoxy resin composition for encapsulation according to the present invention includes a dicyclopentadiene / phenol polymer type epoxy resin (A) represented by the following formula 7 and a dicyclopentadiene / phenol polymer (B) represented by the following formula 8. ) Is contained. In addition, in order to solve the problem of reducing the occurrence of burrs during molding, the encapsulating epoxy resin composition according to the present invention is a novolac-modified compound having a structure represented by the following formula (9). It is desirable to also contain (C).

[0009]

[Chemical 7]

[0010]

[Chemical 8]

[0011]

[Chemical 9]

The present invention will be described in detail below. Since the dicyclopentadiene / phenol polymer type epoxy resin (A), which is one of the essential components of the epoxy resin composition for encapsulation of the present invention, has a dicyclopentadiene skeleton, the resulting encapsulation product has low hygroscopicity and high It has strength when heated.

The second essential component, a dicyclopentadiene / phenol polymer (B), is a curing agent. By using such a curing agent as an essential component, the hygroscopicity of the cured product becomes small, and the heat resistance is the same as that when general phenol novolac is used as the curing agent. The number of repeating units b in the above formula 8 may be 0 or more, but is preferably in the range of 0 to 5 from the viewpoint of exhibiting effective heat resistance and / or hygroscopicity.

The novolak-modified compound (C) having a structure represented by the above formula 9 which is preferably contained in the present invention is an epoxy compound having a glycidyl ether group, and an epoxy resin and a phenol novolac are reacted with each other. It is a prepolymer obtained by. By using the epoxy resin as a prepolymer in this way, the low molecular weight component (monomer) in the composition is reduced, and as a result, burrs at the time of molding are reduced and molding workability can be improved. it can. In addition, the novolac modified compound (C)
However, when X in the above formula 9 is the following three kinds of organic groups, it is possible to further reduce the occurrence of cracks in the soldering process and the like when mounting the resulting package.
The three kinds of organic groups are an organic group having a biphenyl skeleton represented by the following formula 10, a dicyclopentadiene-based organic group represented by the following formula 11, and a dicyclopentadiene system represented by the following formula 12. There are three types of organic groups.

[0015]

[Chemical 10]

[0016]

[Chemical 11]

[0017]

[Chemical 12]

The method for obtaining the novolac-modified compound (C) having the structure represented by the above-mentioned formula 9 is not particularly limited, and is long at a temperature at which the epoxy resin and the phenol novolac are sufficiently melted (for example, 120 ° C. or more). Examples include a method in which both resins are melt-mixed for a time (for example, 3 hours) in the absence of a catalyst or in the presence of various catalysts to form a prepolymer.

The content ratio of the novolac-modified compound (C) having the structure represented by the above formula 9 in the encapsulating epoxy resin composition is preferably 5 to 50% by weight in all epoxy resins. If it is less than 50%, it cannot be expected to reduce burrs at the time of molding, and if it exceeds 50% by weight, the melt viscosity rapidly rises, which adversely affects the filling property at the time of package molding, resulting in unfilling, wire sweep phenomenon, die pad. Molding defects such as deformation of the above occur frequently.

In the present invention, other epoxy resins may be used in combination as long as the dicyclopentadiene / phenol polymer type epoxy resin (A) is contained as an essential component. For example, any number of commonly used phenol novolac type epoxy resins, orthocresol novolac type epoxy resins and the like can be used in combination as long as the effects of the present invention are not impaired. As for the curing agent, other curing agents such as phenol novolac and cresol novolac may be used in combination as long as the dicyclopentadiene / phenol polymer (B) is contained as an essential component.

The equivalent ratio of the epoxy resin and the curing agent in the encapsulating epoxy resin composition of the present invention is not particularly limited, but it is the number of epoxy groups of all epoxy resins / the number of phenolic hydroxyl groups of all curing agents. Ratio is 0.7 / 1.0 to 1.3 /
It is desirable that it is 1.0, and 0.95 / 1.0-
1.2 / 1.0 is more desirable. If it is less than 0.7 / 1.0, a large amount of phenolic hydroxyl groups remain in the reaction, resulting in a decrease in moisture resistance. If it exceeds 1.3 / 1.0, a large amount of unreacted epoxy groups remain. Therefore, there arises a problem of mold stain such as bleed-out.

The epoxy resin composition for encapsulation of the present invention includes
In addition to the above essential components, a suitable curing accelerator, stress-reducing agent, inorganic filler, coupling agent, release agent, colorant, additive, flame retardant and the like can be added as required.

Examples of the curing accelerator that can be added to the encapsulating epoxy resin composition of the present invention include 1,8-
Tertiary amines such as diaza-bicyclo (5,4,0) undecene-7, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, tris (dimethylaminomethyl) phenol; 2
-Methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4
-Imidazoles such as methylimidazole and 2-heptadecylimidazole; organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine and phenylphosphine (phosphorus curing accelerator); tetraphenylphosphonium tetraphenylborate, Examples thereof include tetraphenylboron salts such as triphenylphosphine tetraphenylborate, 2-ethyl-4-methylimidazole tetraphenylborate and N-methylmorpholine tetraphenylborate. In the present invention, when the above phosphorus-based curing accelerator is used as the curing accelerator, the moisture resistance reliability is improved.

Examples of the stress reducing agent that can be added to the encapsulating epoxy resin composition of the present invention include silicone polymers. In the case of silicone polymers, a silicone compatibilizer may be added together. desirable. The silicone polymer is preferably a self-curing silicone rubber or gel, and the self-curing silicone rubber or gel has a mixture or a single structure of two kinds of siloxane compounds each having a functional group capable of reacting with each other. Examples thereof include addition polymerization type of vinyl group-containing siloxane. These self-curing silicone rubbers or gels are usually liquid before curing and are of two-part or one-part type. Specifically, there is a type in which polydimethylsiloxane having vinyl groups at both ends and SiH group-containing polydimethylsiloxane are cured with a platinum catalyst or the like. In the present invention, this vinyl-SiH addition type silicone rubber is most suitable. There is. Further, the silicone-based compatibilizer used together with the silicone rubber or gel is preferably a polyoxyalkylene-modified silicone having an epoxy group or a hydrogen group from the viewpoint of reactivity and compatibility, and the compounding ratio is a compatibilizing agent in a weight ratio. / Self-curing silicone rubber = 1/99
It is preferably in the range of 9 to 20/80. If this ratio is less than 1/999, the dispersibility of the silicone rubber is poor and low stress cannot be expected. If it exceeds 20/80, the marking property of the surface of the package molded product is likely to deteriorate. Then, by adding a stress-reducing agent, heat shock resistance can be improved.

Examples of the inorganic filler that can be added to the encapsulating epoxy resin composition of the present invention include those used in ordinary encapsulating epoxy resin compositions such as silica and alumina. Examples of the coupling agent include silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane. Examples of the release agent include carnauba wax, stearic acid, montanic acid and the like, and examples of the colorant include carbon black. However, it is not limited to those illustrated here.

Further, in order to form the encapsulating epoxy resin composition comprising the above-mentioned compounding ingredients as a molding material, the compounding ingredients can be uniformly mixed, and can be produced by a usual process of heating, melting, cooling and crushing. . Examples of the apparatus used at that time include a mixer, a blender, a kneader, and a roll.

[0027]

When the encapsulating epoxy resin composition according to the present invention contains the dicyclopentadiene / phenol polymer type epoxy resin (A) and the dicyclopentadiene / phenol polymer (B), the obtained cured product has high heat resistance. And has a low hygroscopicity. Further, the inclusion of the novolak-modified compound (C) is a prepolymer obtained by reacting the novolak-modified compound (C) with an epoxy resin and a phenol novolac, so that the low molecular weight component (monomer) in the composition decreases, It acts to increase the melt viscosity, and as a result, it is possible to reduce burrs during molding.

The novolac-modified compound (C) is an organic group having a biphenyl skeleton represented by the above formula 10,
In the case of the structure having the dicyclopentadiene-based organic group represented by Formula 11 or the dicyclopentadiene-based organic group represented by Formula 12, the novolac-modified compound (C) may be contained. This has the effect of improving the strength during heating, and as a result, it becomes possible to further reduce the occurrence of cracks during the soldering process during mounting.

Further, the inclusion of a phosphorus-based curing accelerator improves the moisture resistance reliability, and the inclusion of a polyoxyalkylene-modified silicone and a self-curing polyorganosiloxane as a stress reducing agent means that a cured product is obtained. It has the effect of lowering the elastic modulus, and as a result, the heat shock resistance of the resulting packaged product can be improved.

[0030]

EXAMPLES Specific examples and comparative examples of the present invention will be shown below. (Examples 1 to 9 and Comparative Examples 1 and 2) The raw materials shown in Tables 1 to 3 were blended in the proportions shown in the same table, and further 290 parts by weight of fused silica having an average particle diameter of 14 μm was used as an inorganic filler and coupled. 2 parts by weight of γ-aminopropyltriethoxysilane as a release agent and 1 part of carnauba wax as a release agent.
Parts by weight, 1 part by weight of carbon black as a coloring agent, and the resulting mixture is heated at a kneading temperature of 85.
The mixture was kneaded at 8 ° C for 8 minutes. Then, it was pulverized to about 5 mmφ to prepare a semiconductor-sealing resin composition (epoxy resin molding material).

Details of each raw material shown in Tables 1 to 3 will be described. The dicyclopentadiene / phenol polymer type epoxy resin (A) is represented by the above formula 7, and has an epoxy equivalent of 262 and a melting point (softening point) of 65 ° C., “EXA7200” (Dainippon Ink and Chemicals, Inc.). (Trade name of) was used. The biphenyl type epoxy resin is represented by the following formula 13 (where a is 0 in the formula), epoxy equivalent 195, melting point 105 ° C. epoxy resin “YX4000H” (trade name of Yuka Shell Epoxy Co., Ltd.). Was used. As the cresol novolac type epoxy resin, an epoxy resin “ESCN195XL” (trade name of Sumitomo Chemical Co., Ltd.) having an epoxy equivalent of 195 and a melting point of 70 ° C. was used.

[0032]

[Chemical 13]

The structural formula of the dicyclopentadiene / phenol polymer (B) represented by the above formula 8 is represented by the following formula 14 and has an average molecular weight of 550 and an OH equivalent of 18
0, melting point 101 ° C, phenolic hardener "DPR500
0 ”(trade name of Mitsui Toatsu Chemicals, Inc.) was used. As a curing agent other than (B), phenol novolac "Tamanol 752" having an OH equivalent of 104 and a melting point of 82 ° C is used.
(Trade name of Arakawa Chemical Industry Co., Ltd.) was used.

[0034]

[Chemical 14]

The following three kinds of compounds (C-1, C-2 and C-3) were synthesized as the novolac modified compound (C) shown in the column of epoxy resin in Tables 1 to 3 by the method shown below. Used.

(Synthesis of C-1) The above-mentioned biphenyl type epoxy resin "YX4000H" --- 390 parts by weight The above-mentioned phenol novolac "Tamanol 752" --- 105 parts by weight Triphenylphosphine (TPP) ---- 0. By heating a mixture of 3 parts by weight or more of raw materials at 150 ° C. for 4 hours, X is an organic group having a biphenyl skeleton represented by the above formula 10 (e in the formula is 0). A novolac-modified compound having a structure represented by Formula 9 (C-
1) was synthesized.

(Synthesis of C-2) Epoxy resin “ZX-1257” having the structure of the following formula 15: 514 parts by weight [“ZX-1257” is a trade name of Toto Kasei Co., Ltd.] The above-mentioned phenol novolac “Tamanol” 752 ”--105 parts by weight Triphenylphosphine (TPP) --0.4 parts by weight A mixture of the above raw materials is heated at 150 ° C. for 4 hours, whereby X is represented by the above formula 11. A novolac-modified compound (C-2) having a structure represented by the above formula 9, which is a cyclopentadiene-based organic group, was synthesized. The epoxy resin “ZX-1257” is an epoxy resin having a structure of the following formula 15 and having an epoxy equivalent of 257 and a melting point (softening point) of 52 ° C.

[0038]

[Chemical 15]

(Synthesis of C-3) The above-mentioned dicyclopentadiene / phenol polymer type epoxy resin “EXA7200” ─ 364 parts by weight The above-mentioned phenol novolac “Tamanol 752” ─ 105 parts by weight Triphenylphosphine (TPP) ─ ─ A mixture of 0.3 parts by weight or more of the raw materials is heated at 150 ° C. for 4 hours, whereby X is a dicyclopentadiene-based organic group represented by the above formula 12; The novolak modified compound (C-3) having the structure shown below was synthesized.

2E4MZ in the curing accelerator column of Tables 1 to 3
Represents 2-ethyl-4-methylimidazole, TPP
Indicates triphenylphosphine. The stress reducing agent used in Example 9 was self-curing with 10 parts by weight of a hydrogen group-containing polyoxyalkylene-modified silicone (hydrogen equivalent 2500, Toshiba Silicone Co., Ltd., product number MDT-20) which is a compatibilizer. And 90 parts by weight of polyorganosiloxane (manufactured by Toray Dow Corning Silicone Co., Ltd., product number SE1821), which is a conductive silicone rubber, were used. The polyorganosiloxane is a two-component type vinyl or SiH addition type silicone rubber.

The resin composition for semiconductor encapsulation (epoxy resin molding material) obtained above was molded at 170 to 175 ° C. for 90 seconds using a transfer molding machine, and then 17
Post-curing was performed at 5 ° C. for 6 hours to obtain samples for evaluation of the following moisture absorption rate, strength at heat, solder crack resistance, heat shock resistance, and moisture resistance reliability after moisture absorption soldering. Various performances were measured and evaluated by the following methods, and the obtained results are shown in Tables 1 to 3.

(1) Burr The encapsulating resin composition (epoxy resin molding material) of each Example and Comparative Example was used at 170 to 175 ° C. using a transfer molding machine and a mold for evaluating burrs having a slit of 20 μm.
Was molded for 90 seconds, and the length of the burr generated in the 20 μm slit was measured and evaluated.

(2) Moisture absorption rate A disk having a diameter of 50 mm and a thickness of 3.0 mm was prepared as an evaluation sample under the above-mentioned conditions.
The moisture absorption rate was calculated from the weight change when moisture was absorbed at 85% RH for 72 hours.

(3) Heat strength 100 mm × 10 mm × 4 mm bending test sample was prepared under the above-mentioned conditions, and this test sample was used to measure J
A bending test was performed in an atmosphere of 240 ° C. in accordance with ISK-6911, and the bending strength during heating was determined from the obtained fracture stress value, which was taken as the strength during heating.

(4) Solder cracking property A semiconductor chip having a size of 8 mm × 17 mm × 0.4 mm is mounted on a lead frame made of 42 alloy using silver paste, and then this semiconductor chip has an outer width of 4 mm.
Using a 00 mil 26-pin SOP molding die, sealing molding and post-curing were performed under the above-mentioned conditions with the sealing resin compositions of Examples and Comparative Examples to obtain an evaluation sample.
The sample for evaluation in which the obtained semiconductor chip is sealed is allowed to absorb moisture at 85 ° C. and 85% RH for 72 hours, and then, 26
It was immersed in a solder bath at 0 ° C. for 10 seconds and evaluated. The evaluation method was performed by observing the appearance of the sample and observing the inside of the sample with an ultrasonic probe. The obtained results are shown in Tables 1 to 3.
Is expressed as (number of samples with cracks) / (total number of samples immersed for 10 seconds).

(5) Heat shock resistance As in the case of the above (4) solder crack resistance test, an evaluation sample in which a semiconductor chip is sealed is prepared, and this evaluation sample is subjected to a low temperature in a liquid phase. Side -65 ° C 5
For 500 minutes, a heating / cooling cycle test was performed at 150 ° C. for 5 minutes on the high temperature side for 500 cycles. The presence of cracks in the samples that underwent this cycle test was examined. The evaluation method was performed by observing the appearance of the sample. The obtained results are shown in Tables 1 to 3 (number of samples with cracks).
It is shown as / (total number of samples subjected to cycle test).

(6) Moisture absorption reliability after moisture absorption soldering (USPC
BT) A semiconductor chip (evaluation semiconductor element) of 8 mm × 17 mm × 0.4 mm size with a glass-based protective film, which is provided with a comb-shaped aluminum wiring circuit having a line width of 3 μm, and a lead alloy made of 42 alloy and silver. It is mounted using a paste, and then this semiconductor chip is sealed with the sealing resin composition of each Example and Comparative Example under the above conditions using a 26-pin SOP molding die having an outer width of 400 mils. A static evaluation and post-curing were performed to obtain a sample for evaluation. The obtained evaluation sample in which the obtained semiconductor element for evaluation is sealed is 8
After absorbing moisture at 5 ° C. and 85% RH for 72 hours, it was immersed in a solder bath at 260 ° C. for 10 seconds. Then 138.5 ° C, 85
A continuous energization test of 20 V for 300 hours was performed under the condition of% RH. With respect to the samples that had been subjected to this energization test, their resistance values were examined, and those having a large change in resistance value from the initial value before the test were regarded as defective. The obtained results are shown in Tables 1 to 3 as (defective number) / (total sample number tested).

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

As is clear from Tables 1 to 3, in the examples of the present invention, the occurrence of solder cracks in the soldering process is less than in the comparative examples. In addition, in Examples 2 to 9 which also contained the novolac-modified compound (C) having the structure represented by the above Formula 9, the occurrence of burrs during molding was less than that of Example 1 and Comparative Example. .

[0052]

Since the epoxy resin composition for encapsulation of the present invention is constituted as described above, it has the following effects.

According to the encapsulating epoxy resin composition of the first aspect of the present invention, cracks are less likely to occur when the resulting encapsulating product (package) is exposed to a high temperature in a soldering process or the like. Produce an effect.

According to the encapsulating epoxy resin composition of the second aspect of the invention, in addition to the effect of the first aspect of the invention, the molding workability is improved because less burr is generated during the molding. Has the effect.

According to the encapsulating epoxy resin composition of the invention described in claims 3 to 7, in addition to the effect of the invention of claim 1, cracks are generated when exposed to a high temperature in a soldering process or the like. Further, it has the effect of being less likely to occur.

According to the epoxy resin composition for encapsulation of the eighth aspect of the present invention, in addition to the above effects, the moisture resistance reliability of the obtained encapsulation product (package) is improved.

According to the epoxy resin composition for encapsulation of the ninth aspect of the present invention, in addition to the above effects, there is an effect that the heat shock property of the resulting encapsulated product (package) is improved.

Claims (9)

[Claims] 1. A seal containing a dicyclopentadiene / phenol polymer epoxy resin (A) represented by the following formula 1 and a dicyclopentadiene / phenol polymer (B) represented by the following formula 2. Stopping epoxy resin composition. [Chemical 1] [Chemical 2] 2. The encapsulating epoxy resin composition according to claim 1, which also contains a novolac-modified compound (C) having a structure represented by the following formula 3. [Chemical 3] 3. The epoxy resin composition for encapsulation according to claim 2, wherein X in Formula 3 is an organic group having a biphenyl skeleton represented by Formula 4 below. [Chemical 4] 4. The encapsulating epoxy resin composition according to claim 2, wherein X in Formula 3 is a dicyclopentadiene-based organic group represented by Formula 5 below. [Chemical 5] 5. The encapsulating epoxy resin composition according to claim 2, wherein X in Formula 3 is a dicyclopentadiene-based organic group represented by Formula 6 below. [Chemical 6] 6. The encapsulating material according to claim 2, wherein the content ratio of the novolac-modified compound (C) is 5 to 50% by weight based on the whole epoxy resin. Epoxy resin composition. 7. The ratio of the number of epoxy groups of all epoxy resins / the number of phenolic hydroxyl groups of all curing agents is 0.7 / 1.0 to 1.
It is 3 / 1.0, The epoxy resin composition for closure in any one of Claim 1 to 6 characterized by the above-mentioned. 8. The epoxy resin composition for encapsulation according to claim 1, which contains a phosphorus-based curing accelerator. 9. A polyoxyalkylene-modified silicone and a self-curing polyorganosiloxane as a stress reducing agent, and a polyoxyalkylene-modified silicone /
Weight ratio of self-curing polyorganosiloxane is 1/999
The epoxy resin composition for encapsulation according to any one of claims 1 to 8, wherein the epoxy resin composition is 20 to 80/80.