JP2860960B2 - Epoxy resin composition and semiconductor device encapsulated with the composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an epoxy resin composition excellent in moldability, adhesiveness, electrical properties, heat resistance, high-temperature mechanical strength and flame retardancy,
And a resin-sealed semiconductor device sealed with the resin composition.

[Conventional technology]

As a semiconductor encapsulating material, a composition in which a curing accelerator is mixed with a novolak-type phenol-based resin as an epoxy resin and a curing agent is known. This is because novolak-type phenolic resins have better moisture absorption properties and are excellent in moldability as compared with acid anhydride curing.

However, with the recent increase in the degree of integration of semiconductors, changes in package sizes, package shapes, mounting methods, and the like, improvements in reliability including heat resistance, moisture resistance, and low stress have been desired. For example, when the package mounting method has shifted from the pin insertion type to the surface mount type, the package has been exposed to a high temperature of 200 ° C or more during mounting, so if the sealed product was subjected to thermal stress, A large thermal stress is generated due to a difference in thermal expansion coefficient between the sealing resin, the chip, the frame, and the like. For this reason, cracks occur in the package or the chip or the passivation film formed on the chip surface, or the wiring on the chip surface is cut, short-circuited, misaligned, etc., and the fluctuation of the device characteristics and the decrease in the reliability tend to occur. I have. Further, a bromine compound such as a brominated epoxy resin is added to the conventional epoxy resin in order to impart flame retardancy. However, resin-encapsulated semiconductor
When left at a high temperature of not less than ℃ for a long time, bromine contained in the epoxy resin composition is partially decomposed and desorbed, promoting corrosion of the gold-aluminum joint and causing poor connection. Therefore, it is desired to reduce the amount of the bromine compound as much as possible. However, the flame retardancy of the sealed product is reduced and the standard cannot be satisfied.

Conventionally, as a method for increasing the heat resistance of an epoxy resin, means such as polyfunctionalization of an epoxy resin, increasing the molecular weight of a novolak type phenol resin, and polyfunctionalizing an acid anhydride have been used. Regarding the improvement of the flame retardancy of the epoxy resin, it is known to improve the dispersibility by limiting the particle size of antimony trioxide, which is a part of the flame retardant contained in the epoxy resin, as disclosed in JP-A-63-269555. It is proposed in the gazette.
Further, as another method for improving the reliability of the epoxy resin sealing agent, JP-A-59-200443 and JP-A-59-20
As described in each of the publications, a method using a resol type phenol resin as an epoxy resin curing agent has been performed.

Further, a method of using a resol type phenol resin and a novolak type phenol resin in combination with an epoxy resin is described in JP-A-56-79170, JP-A-56-129263, etc. Since it was used as a coating material, there was no need to consider flexibility or resin purity.

[Problems to be solved by the invention]

However, with the polyfunctionalization of the epoxy resin and the increase in the molecular weight of the phenol resin used as a curing agent, the glass transition temperature of the cured product of the resin composition increases, but the adhesiveness and moisture resistance are slightly worse than before. However, it could not be put to practical use as a material for electronic parts. Further, it was very difficult to significantly reduce the amount of a bromine compound that causes corrosion of a gold-aluminum joint only by specifying the particle size of antimony trioxide contained in the epoxy resin composition. On the other hand, when a resol-type phenol resin is used as a curing agent for the epoxy resin, when the resol-type phenol resin is cured, it may produce condensation by-products such as water and formaldehyde, and may have a slightly inferior adhesive property or moisture resistance. When an amount (equivalent) sufficient to completely advance the curing of the epoxy resin is added, the electrical characteristics and heat resistance are significantly reduced.

The present invention has been made in view of such a situation, and the object thereof is to provide a moldability, an adhesive property, an electrical property, a good heat resistance, and a smaller amount of a bromine compound than before. An object of the present invention is to provide an epoxy resin composition capable of imparting flame retardancy and a resin-sealed semiconductor device using the same.

[Means for solving the problem]

In order to achieve the above object, the present invention provides (a) an epoxy resin composition having two or more functionalities, (b) an epoxy resin curing agent using a novolak-type phenol-based resin and a resole-type phenol-based resin in combination, and (c) silicone. (D) a filler composed of inorganic fine particles; and (c) an epoxy resin composition for semiconductor encapsulation. It is preferable to mix 2 to 20% by weight with respect to the resin composition. When the epoxy resin composition is heated for 100 hours or more with 10 times the amount of hot water at 120 ° C., the extract has an electric conductivity of 100 μs / cm or less, a pH of 3 to 7, and a halogen ion amount of It is good to be below 20ppm.

Further, in the present invention, a resin component is a bifunctional or more functional epoxy resin in an amount of 50 to 90%, and an epoxy resin curing agent using a novolak phenol resin and a resol phenol resin in combination.
The content is preferably 10 to 50% by weight, and the resin composition preferably contains a filler composed of inorganic fine particles in an amount of 55 to 80% by volume with respect to the total composition, and the filler has an average particle diameter of 1 to 30 μm.
m, at least one kind of inorganic particles selected from fused silica, crystalline silica and alumina.

Further, in order to achieve the other object, the present invention provides a resin-sealed electronic device or a resin-sealed semiconductor device sealed with the epoxy resin composition.

The present inventors have conducted various studies on an epoxy resin curing agent that improves the heat resistance, electrical properties, adhesiveness, and moisture resistance of a cured resin while making the curability of the epoxy resin perfect. As a result, not only is a resole-type phenolic resin that has a phenolic hydroxyl group that reacts with an epoxy group and also cures with the curing agent itself as an epoxy resin curing agent, but it is necessary to further react all epoxy groups. It has been found that when a novolak-type phenolic resin having a hydroxyl group is also used in combination, the heat resistance and high-temperature mechanical properties of the cured epoxy resin can be improved without impairing the adhesiveness and moisture resistance.

Also, it was found that when the resol type phenolic resin was blended as a part of the curing agent, even if the amount of the flame retardant, particularly the bromine compound, was reduced, the flame retardant UL standard V-0 could be achieved.

Further, the novolak-type phenolic resin used in combination with the resol-type phenolic resin is used to make the moldability and electrical properties of the epoxy resin composition equal to or higher than those of the conventional epoxy resin.

As the resol-type phenolic resin used in the present invention, a condensation product obtained by reacting phenols such as phenol, cresol, xylenol, and bisphenol A with formaldehyde in the presence of a catalyst is used. As a catalyst that can be used for these synthesis, ammonia, hexamine, amines, oxides or hydroxides of alkali metals, organic metal salts, or a combination of two or more of these can be used.

Among the above-mentioned resins, those which have a small amount of ionic impurities and do not readily hydrolyze the resin cured product with hot water at 120 ° C. to produce no ionic impurities are particularly useful for semiconductor encapsulation. Basically, those having a chemical structure represented by the following general formula (I) or (II) are preferable. However, in producing a resol type phenolic resin, the reaction time is increased to reduce unreacted raw materials, It is desirable that the molecular weight be appropriately large, from 400 to 3,000, from the relationship with the curability and fluidity of the polymer.

Wherein m and n each represent an integer of 1 or more. Also, in order to remove unreacted raw materials and ionic impurities, the reaction product is neutralized with an acid, and then sufficiently washed with water or steam distilled and dried under reduced pressure. Purify using an exchanger or the like.

Novolak type phenolic resin used in the present invention is phenol, cresol, phenol such as xylenol and formaldehyde with paratoluenesulfonic acid, hydrochloric acid,
A condensation product obtained by reacting under an acidic catalyst such as sulfuric acid, perchloric acid, oxalic acid or the like is used and basically has a chemical structure represented by the general formula (III).

(Here, R ₃ represents any one of H and —CH ₃ , and n represents an integer of 1 or more.) The method for adjusting the molecular weight of the resulting novolak-type phenolic resin is as follows. It can be controlled by the molar ratio of aldehyde and formaldehyde and the type and amount of catalyst used, but the molecular weight is
400-3,000 is desirable. Further, it is preferable that ionic impurities or unreacted raw materials are as small as possible to be used for semiconductor encapsulation. For this reason, the reaction product is washed with water or steam distilled and sufficiently dried under reduced pressure. It is also possible to purify using an ion exchange resin, an ion exchanger or the like.

In the present invention, the mixing ratio of the epoxy resin curing agent is 5 to 95% by weight of the novolak type phenolic resin and 5 to 5% by weight of the resol type phenolic resin based on the total amount of the curing agent.
Preferably it is 95% by weight. When the novolak-type phenolic resin is 5% by weight or less, the resol-type phenolic resin as a curing agent becomes 95% by weight or more, and water and formaldehyde, which are condensation by-products generated during the curing reaction of the resin composition, are cured. Will have a significant effect on For example, minute voids are easily formed inside or at the interface of the cured product, the cured product becomes brittle, and the adhesiveness and moisture resistance decrease.

On the other hand, when the novolak type phenolic resin is 95% by weight or more and the resol type phenolic resin is 5% by weight or less,
It has little effect on improving the heat resistance and high-temperature mechanical strength of the cured resin, and the resol-type phenolic resin cannot be expected to contribute to the improvement of flame retardancy.

The epoxy resin used in the present invention means any epoxy resin containing two or more epoxy groups in one molecule. For example, bisphenol-based resins obtained by reacting bisphenol A or phenol novolak resin with epichlorohydrin Epoxy resins and novolak type epoxy resins, or their brominated epoxy resins, epoxy resins obtained from alicyclic compounds such as cyclohexene, cyclopentadiene, dicyclopentadiene, epoxy resins obtained from vinyl polymers, glycerin Epoxy resins obtained from various polyhydric alcohols or brominated epoxy resins thereof.
Seeds are used. Here, the brominated epoxy resin is used for imparting flame retardancy, and the amount thereof is specified in UV regulation V-0.
The less, the better the less. Also, these epoxy resins must be those from which unreacted raw materials and ionic impurities have been sufficiently removed. It is preferable to mix 0.5 to 1.5 equivalents of a curing agent composed of a novolak type or resol type phenolic resin with respect to the epoxy resin, and the mixing amounts are 50 to 90% by weight of the epoxy resin and 10 to 50% by weight of the curing agent, respectively. Is desirable. When the epoxy resin content is 50% by weight or less, a large amount of hydroxyl groups of the phenol resin remain even after the resin is cured, so that the electrical properties and the moisture resistance are poor. On the other hand, when the blending amount of the epoxy resin is 90% by weight or more, the curing of the epoxy resin is not completely performed, and the heat resistance and the electrical characteristics of the cured product are deteriorated. Furthermore, the composition comprising these epoxy resins and their curing agents must be sufficiently free of ionic impurities in order to be used for semiconductors. In the case of extraction, the object of the present invention can be sufficiently achieved if the electric conductivity of the extract is 100 μs / cm ² or less, the pH is 3 to 7, and the amount of halogen ions is 20 ppm or less.

The epoxy resin composition of the present invention may optionally contain 55 to 80% by volume of an inorganic filler based on the whole composition. The inorganic filler is added for the purpose of improving the thermal expansion coefficient, thermal conductivity, elastic modulus, etc. of the cured product.
If the content is less than 55% by volume, these characteristics cannot be sufficiently improved.
On the other hand, if the content exceeds 80% by volume, the viscosity of the material is significantly increased and the fluidity is reduced. Various compounds can be used as the inorganic filler. It is important to use a thermochemically stable filler for the electronic component material. Specifically, at least one selected from fused silica, crystalline silica, and alumina One type of inorganic particles is desirable. The average particle size of these fillers is preferably in the range of 1 to 30 μm. This is because if the average particle size is less than 1 μm, the viscosity of the resin composition increases and the fluidity significantly decreases,
On the other hand, if it exceeds 30 μm, the resin component and the filler tend to separate from each other at the time of molding, and the cured product becomes non-uniform, causing variations in the physical properties of the cured product and poor filling properties into narrow gaps.

Further, in the composition of the present invention, a flexibilizing agent composed of a silicone compound for toughening or lowering the elastic modulus of the cured product can be used. The flexible agent can be used. The amount of the plasticizer is 2 to 20 with respect to the total resin composition.
% By weight. This is because when the amount of the plasticizer is less than 2% by weight, there is almost no effect on toughening or low elasticity of the cured product, and when it is more than 20% by weight, the spiral flow becomes extremely short, This is because the floating agent emerges on the surface of the cured resin, and consequently the stain on the molding die becomes remarkable. As the solubilizer, the epoxy resin composition and the incompatible type can reduce the elastic modulus of the cured product without lowering the glass transition temperature.
It is useful to use a terminal or side chain amino group, hydroxyl group, epoxy group, carboxyl group, modified silicone resin-based flexible agent from the viewpoint of water resistance and high purity.

In addition to the composition of the present invention, if necessary, a curing catalyst for accelerating the curing reaction of the resin, a coupling agent for increasing the adhesion between the resin component and the filler, a dye or pigment for coloring, Various additives such as a release agent for improving the releasability of the cured product from the mold can be used as long as the object of the invention is not impaired. Examples of the curing catalyst include phosphorus-containing organic basic compounds such as triphenylphosphine and tetraphenylphosphonium tetraphenylborate, tertiary amines such as tetrasubstituted boron salts thereof, benzyldimethylamine, and 1,8-diazabicyclo (5,4, 0) -undecene,
It is preferable to use at least one kind such as imidazole and the like, and as the coupling agent, at least one kind such as epoxysilane and aminosilane.

Fillers, plasticizers and their respective additives, as well as the resin component, contain a large amount of ionic impurities, which significantly lowers the reliability of various products. Therefore, when each of these additives is extracted for 100 hours or more with 10 times the volume of 120 ° C. hot water, the electric conductivity of the extract is 100 μs / cm or less, and the pH is 3 to
7. It is necessary that the extraction amount of halogen ions is 20 ppm or less.

(Operation)

The heat resistance and the high-temperature mechanical strength of the epoxy resin composition of the present invention are superior to conventional molding resins,
This is because, as a part of the epoxy resin curing agent, a resol-type phenol-based resin that cures itself is used, and this resin also plays a significant role in improving heat resistance. The novolak-type phenolic resin used in combination as a curing agent is used to completely cure the epoxy resin, and prevents the adhesiveness of the cured resin from the novolak-type phenolic resin from deteriorating in moisture resistance. Act like so.

〔Example〕

Hereinafter, the present invention will be specifically described according to Examples,
The present invention is not limited to these.

Production Example 1 [Resole-type phenol resin synthesis 1] 500 g of phenol, 30% formalin in 5 flasks
550 g and zinc acetate 5 g were added, and the mixture was gradually heated with stirring and heated at 90 ° C. for 2 hours with reflux. Thereafter, the pressure in the flask was reduced to 20 mmHg to remove condensed water and unreacted components. Next, 300 g of acetone was added to the reaction product to dissolve the reaction product, and ion-exchanged water 3 was further added, followed by vigorous stirring at 50 ° C. for 30 minutes. After cooling, the upper aqueous layer was removed. The reaction product was dissolved again in 300 g of acetone, ion-exchanged water 3 was added to the solution, and the mixture was vigorously stirred at 50 ° C. for 30 minutes. After cooling, the upper aqueous layer was removed. After repeating this operation five times, the reaction product was dried at 40 ° C. for 48 hours while depressurizing to obtain a desired resol-type phenol resin (A).

The resol type phenol resin (A) thus obtained has a number average molecular weight of 710, a softening temperature of 75 ° C, a free phenol content of 0.3% by weight, and a gel time of 180 ° C (JIS-K-5
909, by the hot plate method) was 45 seconds. In addition, 50 g of ion-exchanged water was added to 5 g of resol type phenol resin, and
After heating for a time and examining the characteristics of the extract, the pH of the extract was 3.
8.Electric conductivity 55μs / cm, ionic impurity Cl ion
2.5 ppm, Br ion and NH ₄ ion were 1 ppm or less.

Production Example 2 [Synthesis 2 of resol type phenol resin] In a flask of No. 5, 570 g of phenol A, 75 g of formaldehyde, 800 g of paraformaldehyde and 10 g of an aqueous sodium hydroxide solution were added, and the mixture was gradually heated with stirring and refluxed at 90 ° C. for 4 hours. Heated. The reaction was stopped by adding ion-exchanged water 3 and neutralized with acetic acid, after which the organic matter and water were separated. The organic matter was dissolved in 150 g of acetone, ion-exchanged water 0.7 was added to the solution, and the mixture was vigorously stirred at 50 ° C. for 30 minutes. After cooling, the upper aqueous layer was removed. After repeating this operation five times, the reaction product was dried at 40 ° C. for 24 hours while reducing the pressure to obtain the desired resol-type phenol resin (B).

The resol type phenol resin (B) thus obtained has a number average molecular weight of 680, a softening temperature of 78 ° C., a free bisphenol A content of about 7% by weight, and a gelation time of 180 ° C. of 25%.
Seconds. The resole-type phenolic resin was subjected to extraction liquid properties in the same manner as in Production Example 1. As a result, the pH of the extraction liquid was 4.5, the electric conductivity was 25 μs / cm, and the ionic impurities Cl.
The content of ions was 2.8 ppm, and the content of Br ions and NH ₄ ions was 1 ppm or less.

[Examples 1 to 12] As resin components, o-cresol novolak type epoxy resin (epoxy equivalent 195, softening temperature 75 to 80 ° C), brominated bisphenol A type epoxy resin (epoxy equivalent 394,
Softening temperature 65 ° C), novolak type phenol resin as curing agent (hydroxyl equivalent 106, softening temperature 65 ° C) and Production Example 1
Alternatively, the purified resole phenolic resin obtained in Production Example 2, a side chain epoxy-modified silicone resin (molecular weight 73,600, epoxy equivalent 3,900) as a solubilizing agent, various compounds shown in Table 1 as a curing catalyst, and a filler as a filler 30/70 mixture of square fused silica having an average particle diameter of 6 μm and spherical fused silica having an average particle diameter of 30 μm, antimony trioxide powder as a flame retardant aid, epoxysilane as a coupling agent, montanic acid as a release agent Using an ester wax and carbon black as a coloring agent, molding materials were prepared in the mixing ratios shown in Table 1. Each material was kneaded using a 20-inch diameter biaxial roll and kneaded at a roll surface temperature of about 65 to 80 ° C. for about 10 minutes.

[Comparative Examples 1 to 9] In Comparative Example 1, an o-cresol novolak type epoxy resin containing a large amount of ionic impurities as an epoxy resin (epoxy equivalent 210, softening temperature 73 ° C, pH in the extract characteristics at 120 ° C / 20 hours, pH 4.0, electric conductivity 105μs / cm, ionic impurity Cl ion 42ppm, Br ion 25ppm)
With respect to the other components, molding materials were prepared in the same manner as described above, using the same raw materials as in the above-mentioned Examples, at the compounding ratios shown in Table 1. In Comparative Examples 2 to 9, molding materials were produced under the same conditions using the same raw materials as in the above-mentioned Example.

The moldability of each molding material obtained in this way at 180 ° C, and a molded product that was molded at a mold temperature of 180 ° C, a molding pressure of 7 kg / cm ² , a molding time of 90 seconds, and post-cured at 180 ° C for 6 hours Of various physical properties and molded products of 100
50 g of ion-exchanged water was added to the g, and the mixture was heated at 120 ° C. for 120 hours. Thereafter, the pH, electric conductivity and extracted ionic impurities of the water were compared. These results are summarized in Table 1. In addition, all the compounding ratios in Table 1 are represented by parts by weight. In addition, the curing catalyst indicated by the symbol in the table is
DBU: 1,8-diazabicyclo (5,4,0) -undecene, TPP
-K: tetraphenylphosphonium tetraphenylborate, 2P4MHZ: 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2P4BHZ: 2-phenyl-4-benzyl-5-hydroxymethylimidazole.

As is clear from Table 1, the resin composition of the present invention uses a novolak-type phenol resin and a resol-type phenol resin as a curing agent in combination, so that the electrical properties and adhesiveness of the cured resin are the same as those of a conventional epoxy resin molding material. It can be seen that the heat resistance and the mechanical strength at high temperatures are improved while maintaining substantially the same. Furthermore, when Example 2 and Comparative Example 4 are compared, the flame retardancy is improved with the same blending amount of the brominated epoxy resin due to the blending of the resol type phenol resin. As for the moldability, molding can be performed under the same conditions as those of commonly used epoxy resin-based molding materials. In the resin composition containing the flexibilizer of the present invention, if the blending amount of the flexibilizer is 2% by weight or less, there is almost no effect on lowering the elastic modulus of the resin. The spiral flow is significantly reduced.

Next, using a part of the above molding material, a silicone chip having zigzag wiring of aluminum formed on the surface is mounted on a copper-based lead frame, and a gold wire (φ30 μm) is formed on the chip surface between the aluminum electrode and the lead frame. The semiconductor device that was wire-bonded was sealed and subjected to various reliability tests. The results are shown in Tables 3 and 4.

As is clear from Tables 3 and 4, the sealed product of the present invention is superior to the comparative example in moisture resistance reliability, high-temperature storage characteristics, and crack resistance of the package during reflow. Further, as is apparent from the results of Comparative Example 1, when the purity of the molding material is poor, various reliability of the package is significantly reduced. Therefore, the purity of the molding material is a very important factor for the reliability of the package.

[Effect of the Invention] A molding material using an epoxy resin composition using a curing agent in which a novolak-type phenol resin and a resol-type phenol resin of the present invention are used together has good moldability similar to that of a conventional epoxy resin. A semiconductor device sealed with a molding material is excellent in various reliability such as humidity resistance, high-temperature storage characteristics, and reflow resistance. Therefore, the present invention can provide an epoxy resin composition useful not only as a sealing material for electronic and electrical equipment, but also as an adhesive or insulating material for electronic and electrical equipment that requires high heat resistance and good adhesiveness. Is evident.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // (C08L 63/00 83:04) (72) Inventor Yasuhide Sugawara 4026 Kuji-cho, Hitachi City, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research, Ltd. In-house (72) Inventor Hiroyuki Horazoji 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory, Ltd. Takashi Urano 1772-1, Okukabo, Yuki-shi, Ibaraki Pref. Hitachi Chemical Co., Ltd. Minami-Yuki Plant (56) References JP-A-63-183917 (JP, A) JP-A-63-230731 (JP, A) 59-79170 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 63/00-63/10 C08G 59/62 H01L 23/29

Claims (8)

(57) [Claims] 1. An epoxy resin composition having (a) a bifunctional or higher functional epoxy resin, (b) an epoxy resin curing agent using a novolak type phenolic resin and a resol type phenolic resin in combination, and (c) a solubilizing agent comprising a silicone compound. And (d) a filler comprising inorganic fine particles. An epoxy resin composition for semiconductor encapsulation, comprising: 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the compounding amount of the plasticizer comprising the silicone compound is 2 to 20% by weight based on the total resin composition. . 3. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the amount of the filler composed of the inorganic fine particles is 55 to 80% by volume based on the whole composition. 4. The filler according to claim 3, wherein the filler comprising the inorganic fine particles is at least one kind of inorganic particles selected from fused silica, crystalline silica and alumina having an average particle diameter of 1 to 30 μm. Epoxy resin composition for semiconductor encapsulation. 5. The method according to claim 1, wherein the epoxy resin composition has a 10-fold amount of 120.
2. The extract according to claim 1, wherein the extract has an electric conductivity of 100 μs / cm or less, a pH of 3 to 7, and a halogen ion content of 20 ppm or less when heated with hot water at 100 ° C. for 100 hours or more. Epoxy resin composition for semiconductor encapsulation. 6. A resin-sealed electronic device which is sealed with the epoxy resin composition for semiconductor sealing according to claim 1. 7. The resin-encapsulated electronic device according to claim 6, wherein the electronic device is transfer-molded with an epoxy resin composition for encapsulating a semiconductor. 8. A resin-encapsulated semiconductor device, which is encapsulated by the epoxy resin composition for encapsulating a semiconductor according to claim 1.