JP3018779B2 - Epoxy resin composition for semiconductor encapsulation - Google Patents

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 used for encapsulating so-called semiconductor elements such as ICs and LSIs by transfer molding or the like.

[0002]

2. Description of the Related Art Epoxy resins are widely used as various molding materials because of their excellent electrical properties, mechanical properties, heat resistance, adhesiveness, and water resistance as compared with other thermosetting resins. In particular, recently, it has been noted as a molding material for semiconductor encapsulation. By the way, the degree of integration of semiconductor elements is improving year by year, and accordingly, finer wiring, multi-layer wiring, and larger element size are rapidly progressing. On the other hand, a package for protecting a semiconductor element from an external environment is becoming smaller and thinner from the viewpoint of high-density mounting on a printed circuit board. In a resin-encapsulated semiconductor device in which such a large element is encapsulated in a small and thin package, failures such as package cracks, passivation cracks, and aluminum wiring deformation due to thermal stress generated between the element and the sealing material are extremely low. It is easy to happen. As a solution to this, there has been a strong demand for reducing the stress of the molding compound for sealing.

There are the following two methods for reducing the stress. The coefficient of linear expansion of the molding material is reduced to be as close as possible to the coefficient of linear expansion of the semiconductor element (low expansion). Make the elastic modulus of the molding material as small as possible (low elastic modulus). Conventionally, various methods have been studied for the above. First, the reduction in expansion has been studied in the direction of increasing the amount of filler. Regarding the lowering of the elastic modulus, modification with various rubber components has been studied. As a result, epoxy resin molding materials modified with silicone polymers having excellent thermal stability have been widely used at present. Silicone oil is incompatible with the epoxy resin and the curing agent, which are the base resin of the molding material, so that it is dispersed in fine particles (sea-island structure) in the base resin, and a low elastic modulus can be achieved while maintaining heat resistance. However, in the method using the above-mentioned silicone oil, the silicone and the base resin undergo phase separation at the time of molding, and the silicone easily bleeds, so that problems such as mold stains are likely to occur.
As a solution to this problem, a method has been proposed in which silicone and a base resin are preliminarily reacted and used (for example, JP-B-61-48544 and JP-B-62-3).
No. 6050, JP-B-63-32807). Also, a method of dispersing solid silicone fine particles in a sealing material resin in addition to the modified silicone flexible agent has been proposed (JP-A-63-241020, JP-A-63-2410).
No. 21).

[0004]

As described above, if the method of preliminarily reacting the silicone with the base resin and fixing the silicone to the base resin is adopted, the moldability such as mold contamination can be improved, and It is possible to obtain a sealing material having an elastic modulus and high heat resistance. However, it has been found that the method using such a modified silicone resin as a flexible agent exhibits the above-mentioned characteristics and also causes a decrease in mechanical strength.
Further, although the method of dispersing solid silicone fine particles is excellent in mechanical strength, it does not give sufficient characteristics in terms of low stress. The present invention has been made in view of such circumstances, and provides an epoxy resin composition for semiconductor encapsulation with improved mechanical strength without impairing low stress properties and high heat resistance.

[0005]

Means for Solving the Problems The present inventors have found that when a modified silicone resin flexible agent is used in order to satisfy both the low elastic modulus and the mechanical strength, the phase separation structure of the sealing resin is optimized. I thought I needed to control. In other words, by miniaturizing the silicone domain, the domain /
The aim was to increase the total area of the matrix interface and promote the interaction (interdiffusion) of each molecule to further lower the elastic modulus, and to increase the resin strength by increasing the interface strength. To realize this, it was considered effective to use a silicone flexible agent as a block copolymer of silicone and novolak, in particular, a silicone-novolak multi-block copolymer. As a result of intensive studies based on the above findings, the present invention has found that the following composition is effective, and has completed the present invention. That is, the present invention relates to (A) an epoxy resin having two or more epoxy groups in one molecule, (B) a compound having two or more phenolic hydroxyl groups in one molecule, and (C) a reaction between an epoxy group and a phenolic hydroxyl group. (D) a polysiloxane having Si—H groups at both ends represented by the following formula [I] (wherein R ₁ and R ₂ are substituted or unsubstituted carbon atoms having 1 to 3 carbon atoms) A polyvalent alkyl group or a phenyl group, and 1 represents an integer of 0 to 300) and a phenol novolak resin having an allyl group at both terminals, by a polyaddition reaction.

Embedded image (E) An epoxy resin composition for semiconductor encapsulation, comprising an inorganic filler as an essential component.

[0006] One of the components (A) used in the present invention
The epoxy resin having two or more epoxy groups in the molecule is not limited as long as it is generally used in an epoxy resin composition for semiconductor encapsulation, and a phenol novolak epoxy resin and an orthocresol novolak epoxy resin Epoxidized novolak resins of phenols and aldehydes such as naphthol-modified phenol novolak epoxy resins, diglycidyls such as hydroquinone, bisphenol A, bisphenol B, bisphenol F, bisphenol S, biphenol, and alkyl-substituted biphenol A glycidyl ester type epoxy resin obtained by reacting a polybase such as ether, phthalic acid or dimer acid with epichlorohydrin, a polyamine such as diaminodiphenylmethane, isocyanuric acid and epichlorohydrin Glycidylamine-type epoxy resin obtained by the reaction with carboxylic acid, linear aliphatic epoxy resin and alicyclic epoxy resin obtained by oxidizing the olefin bond with a peracid such as peracetic acid, etc., alone or in combination of two or more. Orthocresol novolac epoxy resin having an epoxy equivalent of 220 or less from the viewpoint of heat resistance, moisture resistance and cost is 50% by weight of the whole component (A).
It is preferable to use the above.

[0007] One of the components (B) used in the present invention
Compounds having two or more phenolic hydroxyl groups in the molecule include phenols and aldehydes such as phenol, cresol, xylenol, hydroquinone, resorcinol, catechol, bisphenol A, bisphenol F, biphenol, and naphthol under an acidic catalyst. There are polyphenols such as novolak type phenol resin, bisphenol A, bisphenol F, biphenol, polyparavinylphenol resin, resorcin, catechol, hydroquinone, etc. obtained by condensation reaction, and these are used alone or in combination of two or more. However, from the viewpoint of the balance between cost and properties, it is preferable to use a novolak type phenol resin in an amount of 50% by weight or more based on the entire component (B).

The component (C) used in the present invention is a component necessary for accelerating the curing reaction between the components (A) and (B). For example, 1,8-diazabicyclo (5 , 4, O) undecene-7, tertiary amines such as benzyldimethylamine, triethanolamine, dimethylaminoethanol, triethylenediamine, tris (dimethylaminomethyl) phenol, 2-methylimidazole, 2-phenylimidazole, Phenyl-4
Imidazoles such as -methylimidazole and 2-heptadecylimidazole, organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine and phenylphosphine, tetraphenylphosphonium tetraphenylborate, and 2-ethyl-4-methyl And tetraphenylboron salts such as imidazole tetraphenylborate and N-methylmorpholine tetraphenylborate. These are not limited to one type, and two or more types may be used in combination.

The component (D) used in the present invention is a polysiloxane having Si—H groups at both ends represented by the above formula [I] (wherein R ₁ and R ₂ are substituted or unsubstituted carbon atoms having 1 carbon atom). Represents a monovalent alkyl group or a phenyl group,
Represents an integer of 0 to 300. ) And a phenol novolak resin having an allyl group at both terminals by a polyaddition reaction.
Examples of the phenol novolak resins having an allyl group at both terminals include phenol novolak resins having an allyl group at both terminals represented by the following formula [II] (wherein R ₃ has 1 carbon atom)
To 4 alkyl groups and R ₄ represent an alkyl group having 1 to 4 carbon atoms or an alkoxy group. ) Are preferably used. The molecular weight of the phenol novolak resins containing allyl groups at both ends is preferably larger than the epoxy resin (A) or the phenol resin (B), the number average molecular weight is 900 or more, and the molecular weight distribution Mw / Mn is Those having 2.0 or more are preferably used. The method of synthesizing the component (D) has already been proposed (Japanese Patent Application No. 3-246507, Japanese Patent Application No. 4-49682), but it can be obtained through the following four-stage manufacturing process. First stage: Synthesis reaction of linear high molecular weight phenol novolak resin Second stage: Methylolation reaction of both terminals of novolak resin Third stage: Condensation reaction of novolak resin with methylol group at both terminals with allylphenol Fourth stage: Allyl at both terminals Base novolak resin and both ends Si-
Polyaddition reaction with H-group polysiloxane By these four stages of the production process, it becomes possible to produce a silicone-novolak block copolymer and further a silicone-novolak multiblock copolymer.

Embedded image

The amount of component (D) is such that the amount of silicone in component (D) is 5% of the total amount of (A) + (B) + (D).
It is preferably in the range of from 30% by weight to 30% by weight. If the content is less than 5% by weight, a sufficiently low stress cannot be obtained, and if it exceeds 30% by weight, the mechanical strength of the cured product decreases.

As the compounding amount of the above components (A), (B) and (D), (total number of epoxy groups) / (total number of phenolic hydroxyl groups) in the three components is 0.8 to 1.2. It is preferable to mix them in such a manner as to obtain a balanced cured product.

The inorganic filler (E) used in the present invention is an essential component for lowering the coefficient of linear expansion of the cured product. Examples thereof include fused silica, crystalline silica, alumina, zircon, calcium silicate, and carbonate. Calcium, silicon carbide,
Powders such as silicon nitride, boron nitride, beryllia, magnesia, zirconia, mullite, titania, etc. and single crystal fibers such as silicon carbide, silicon nitride, and alumina, glass fibers, etc. can be given. To fused silica. Also, regarding the shape of the filler,
Both rectangular and spherical shapes can be used. The spherical filler is preferably used as a part or all of the filler in order to give high fluidity. It is preferable that the compounding amount of the component (E) is 50 to 85% by volume of the whole composition. If it is less than 50% by volume, the coefficient of linear expansion of the cured product becomes large, and the package crack resistance is poor. 85% by volume
In the case described above, the fluidity is extremely reduced, and molding cannot be carried out under the usual molding pressure.

Further, the composition of the present invention comprises a flame retardant such as a brominated epoxy resin and antimony trioxide, a release agent such as a higher fatty acid, a metal salt of a higher fatty acid, an ester wax, a coloring agent such as carbon black, Coupling agents such as epoxy silane, amino silane, alkyl silane, organic titanate and aluminum alcoholate can be used as needed.

As a general method for producing a molding material using the above-described raw materials, a raw material mixture having a predetermined compounding amount is sufficiently mixed by a mixer or the like, and then heated rolls are used.
A molding material can be obtained by kneading with an extruder or the like, cooling, and pulverizing.

As a method for sealing a semiconductor using the molding material obtained in the present invention, a low pressure transfer molding method is the most general method, but it is also possible to use a method such as injection molding or casting.

【Example】

Hereinafter, the present invention will be described with reference to Examples.
The scope of the present invention is not limited to these examples.

Example 1 First, the component (D) used in Example 1 was synthesized. (Synthesis of o-cresol novolak resin) 500 g (4.62 m) of o-cresol was placed in 11 separable flasks equipped with a stirrer, a condenser, a Dean-Stark trap, and a thermometer.
ol), 193 g of paraformaldehyde (5.54 mol)
l), xylene (92 ml) and 2-n-butoxyethanol (92 ml) were added, the mixture was stirred, heated to 50 ° C., and oxalic acid (23.3 g) was added. Then heated to 100 ° C,
After completely dehydrating the condensed water with a Dean-Stark trap over 2 hours, the mixture was stirred at 150 ° C. for 20 hours. After completion of the reaction, the solvent was distilled off by heating and reducing the pressure. The obtained resin had a yield of 423 g (98% yield), Mn = 1900, and Mw =
7,600, Mw / Mn = 3.96, the shape was a yellow transparent solid.

(Synthesis of o-cresol novolak resin containing methylol groups at both ends) 400 g of o-cresol novolak resin previously synthesized in 51 separable flasks equipped with a stirrer, a cooling tube, a thermometer, and a dropping funnel (2. 11
× 10 _- ¹ mol), sodium hydroxide 64g was added and this performs stirred with methanol 1600ml completely dissolved. Then heat to 50 ° C and add 35%
1400 g of formaldehyde solution (formalin) (16.
7 mol) was dropped from the dropping funnel over about 1 hour.
After completion of the dropwise addition, stirring was performed for 4 hours while maintaining the reaction temperature at 50 ° C. After completion of the reaction, the reaction solution was carefully neutralized with acetic acid, and then poured into a large amount of distilled water to precipitate a crude product. After the precipitate was separated by filtration, the precipitate was washed three times with distilled water, and reprecipitated three times with acetone (good solvent) / distilled water (poor solvent). Thereafter, vacuum drying was performed at room temperature. The obtained resin had a yield of 299 g (72% yield), Mn = 3200, and Mw = 7.
400, Mw / Mn = 2.3, the shape was a reddish brown solid.

(Synthesis of o-cresol novolak resin containing allyl groups at both ends) A 4-allyl-encapsulated flask was equipped with a stirrer, a condenser, a thermometer, and a dropping funnel.
794 g of 2-methoxyphenol (eugenol)
(4.84 mol) 1,4-dioxane 1200 ml,
4.90 g (0.49 mol) of hydrochloric acid was added, and
And stirred under reflux. 290 g of an o-cresol novolak resin containing a methylol group at both ends synthesized earlier in this solution
(0.0906 mol) in 1,4-dioxane 900 m
solution was dissolved in the dropping funnel from the dropping funnel to 100 ml / 30.
Carefully dripped at a rate of minutes. After the completion of the dropwise addition, reflux stirring was performed for 1 hour. After completion of the reaction, unreacted eugenol was completely removed under reduced pressure at 200 ° C./30 mmHg. Complete removal was confirmed by GPC. The obtained resin has a yield of 2
90 g (yield 92%), Mn = 2300, Mw = 940
0, Mw / Mn = 4.1, the shape was a black solid.

(Synthesis of Silicone-Novolak Block Copolymer) 40 g of o-cresol novolak resin containing allyl groups at both ends was previously synthesized in 11 separable flasks equipped with a stirrer, a cooling tube, a thermometer, and a dropping funnel. 0.
014 mol), 40 g of methyl isobutyl ketone, and 0.04 ml of 2-ethylhexanol chloroplatinate solution, and the mixture was heated to 80 ° C. and stirred. Both ends S of degree of polymerization 78
100.9 g of i-H group polysiloxane (0.0174 m
ol) in 100 g of methyl isobutyl ketone,
The solution was added dropwise over 1 hour. After the completion of the dropwise addition, the reaction was performed for 6 hours. After completion of the reaction, methyl isobutyl ketone was removed under reduced pressure. The obtained resin has a yield of 75 g (yield 93
%), Mn = 4800, Mw = 13000, Mw / Mn
= 2.7, the shape was a black solid.

Next, materials were manufactured. (A) 50 parts by weight of an orthocresol novolak type epoxy resin having an epoxy equivalent of 200 and a softening point of 76 ° C, an epoxy equivalent of 400, a softening point of 69 ° C and a bromine content of 48 as a component.
20 parts by weight of a brominated bisphenol A-type epoxy resin (weight%), a hydroxyl equivalent of 106 as the component (B), and a softening point of 82
Phenol novolak resin at 49 ° C., 1.0 part by weight of triphenylphosphine as component (C), 40 parts by weight of the above silicone-novolak block copolymer as component (D), and 450 parts by weight of fused silica as component (E). Parts, 1.5 parts by weight of carnauba wax, 8 parts by weight of antimony trioxide, 1.5 parts by weight of carbon black, 3-
5 parts by weight of glycidoxypropyltrimethoxysilane was blended and kneaded using a 10-inch diameter heating roll at a kneading temperature of 80 to 90 ° C. and a kneading time of 15 minutes. The molding material of Example 1 was produced by cooling and pulverizing the sheet-like kneaded material.

Examples 2 to 4 A molding material was prepared in the same manner as in Example 1 except that the component (D) in Example 1 was changed as shown in Table 1.

Comparative Example 1 A molding material was prepared in the same manner as in Example 1 except that the component (D) was omitted. Comparative Example 2 First, a silicone-modified phenol resin was prepared. (Synthesis of allyl group-containing phenol novolak resin) 500 g (5.31 mol) of phenol, 174 g (1.06 mol) of eugenol, and 156 g (4.46 mol) of paraformaldehyde were placed in 11 separable flasks equipped with a stirrer, a condenser, and a thermometer. And add 50 minutes of stirring
C. and 6.7 g of oxalic acid was added. Then 100
C. and stirred for 6 hours. After completion of the reaction, 100
Unreacted monomers were removed by heating and reducing the pressure under the conditions of -200 ° C / 20 mmHg. The obtained resin has a yield of 566.
g (91% yield), Mn = 760, Mw / Mn = 1.
8. The shape was a yellow transparent solid.

(Synthesis of Silicone-Modified Phenolic Resin)
36 g of allyl group-containing o-cresol novolak resin (0.0383 mol) previously synthesized in 11 separable flasks equipped with a stirrer, a cooling pipe, a thermometer, and a dropping funnel.
l), 290 ml of methyl isobutyl ketone, and 0.06 ml of a 2-ethylhexanol solution of chloroplatinic acid were added.
C. and stirred. 90 g (0.0155 mol) of a polysiloxane having a Si-H group at both ends at a polymerization degree of 78 was dissolved in 90 g of methyl isobutyl ketone, and added dropwise to the above solution over 1 hour. After the completion of the dropwise addition, the reaction was performed for 6 hours. After completion of the reaction, methyl isobutyl ketone was removed under reduced pressure. The obtained resin had a yield of 111 g (88% yield) and Mn = 200.
0, Mw / Mn = 4.8, the shape was a black solid.

The obtained silicone-modified phenolic resin was blended as a flexibilizer component so as to have the same silicone concentration as in Example 1, and a molding material was prepared in the same manner as in Example 1.

Comparative Example 3 A commercially available silicone rubber fine powder having an average particle size of 5 μm (KMP
594) was blended as a flexible agent component so that the silicone concentration was the same as in Example 1, and a molding material was produced in the same manner as in Example 1.

The above seven types of molding materials were evaluated for glass transition temperature, flexural modulus, flexural strength and elongation at break. Table 2 shows the results. The methods for producing the cured molding material and evaluating the properties are as follows.

[0028]

[Table 1]

[0029]

[Table 2]

(1) Preparation of cured molding material Using a low-pressure transfer press, a mold temperature of 175 ° C.
A test piece was prepared by molding under the conditions of a molding pressure of 70 kg / cm ² and a molding time of 120 seconds, followed by post-curing at 175 ° C. for 6 hours.

(2) Characteristic Evaluation (2-1) Glass Transition Temperature Using a thermomechanical analyzer, the temperature was raised at a rate of 5 ° C./min and 19 m
The measurement was performed on a test piece of mx 4 mm x 4 mm. The glass transition temperature was determined from the inflection point of the linear expansion curve. (2-2) Flexural modulus According to JIS-K-6911, using a bending tester,
The measurement was performed on a test piece of 0 mm × 70 mm × 3 mm. (2-3) Flexural strength Measured in the same manner as in (2-2). (2-4) Elongation at break was measured by the same method as in (2-2). From the results shown in Table 2, Comparative Example 2 has low flexural strength and is inferior in toughness, while Comparative Examples 1 and 3 have high flexural modulus and are insufficient in low stress property. In contrast, Examples 1 to 4
It can be seen that the composition provides a cured product having low elastic modulus, high strength, and high heat resistance, which is not found in the prior art.

[0032]

The composition of the present invention has low stress, high strength and high heat resistance as compared with the conventional composition, so that a highly reliable product can be obtained by encapsulating a semiconductor component using the composition. And its industrial value is great.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Shigeo Sase, 1500 Ogawa, Oji, Shimodate, Ibaraki Prefecture Inside the Shimodate Research Laboratory (72) Inventor Atsushi Fujioka 1500 Ogawa, Oji, Shimodate, Ibaraki Shimodate Research Institute Co., Ltd. (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 23/29 C08G 59/62 C08K 3/00 C08L 63/00 H01L 23/31

Claims (5)

(57) [Claims] (A) an epoxy resin having two or more epoxy groups in one molecule; (B) a compound having two or more phenolic hydroxyl groups in one molecule; and (C) a reaction between an epoxy group and a phenolic hydroxyl group. (D) a polysiloxane having Si—H groups at both ends represented by the following formula [I] (wherein R ₁ and R ₂ are substituted or unsubstituted carbon atoms having 1 to 3 carbon atoms) A polyvalent alkyl group or a phenyl group, and l represents an integer of 0 to 300) and a phenol novolak resin having an allyl group at both ends by a polyaddition reaction, and a silicone-novolak block copolymer and 1) (E) An epoxy resin composition for semiconductor encapsulation, comprising an inorganic filler as an essential component. 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the component (A) is a novolak type epoxy resin having an epoxy equivalent of 220 or less. 3. The component (B) has a number average molecular weight of 300 to 60.
The novolak type phenol resin of claim 1 or 2.
The epoxy resin composition for semiconductor encapsulation according to the above. 4. A phenol novolak resin having an allyl group at both terminals used for the component (D) is reacted with the following formula [I]
Phenol novolac resins having allyl groups at both terminals represented by I] (wherein R ₃ is an alkyl group having 1 to 4 carbon atoms, R ₄ represents an alkyl group or an alkoxy group having 1 to 4 carbon atoms, m represents an integer of 1 or more.) and the epoxy resin composition for semiconductor encapsulation according to any one of claims 1 to 3. Embedded image 5. A phenol novolak resins having allyl groups at both terminals to be used in the component (D), the number-average molecular weight of 900 or more, a molecular weight distribution Mw / Mn allyl groups at both ends which is 2.0 or more Phenol novolak tree with
The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the epoxy resin composition is a fat .