JP2003089717A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin composition for semiconductor sealing use having high normal-temperature preservability, moldability, flame retardancy, soldering resistance and moistureproofness reliability and having high environmental safety because of substantially free from any halogen and antimony, in particular compatible with insert mounting and surface mounting designs. SOLUTION: The epoxy resin composition essentially comprises (A) an epoxy resin of formula (1), (B) a phenolic resin of formula (3), (C) a curing promoter of formula (3), and (D) an inorganic filler.

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 is excellent in moldability and solder resistance, and a semiconductor device in which a semiconductor element is encapsulated using the epoxy resin composition.

[0002]

2. Description of the Related Art Epoxy resin compositions for semiconductor encapsulation have been developed and produced in order to protect semiconductor elements such as diodes, transistors and IC chips from mechanical and chemical effects. Items required for this epoxy resin composition are:
Although it is changing depending on the type of semiconductor element, the structure of the semiconductor device, and the environment in which it is used, the required items include storability at room temperature and rapid curing at molding. In the epoxy resin composition, conventionally used curing accelerators include 2-methylimidazole, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, etc. Since the accelerators have a curing-accelerating action even at a relatively low temperature, the epoxy resin composition using them has insufficient storability at room temperature, and therefore, when stored at room temperature, poor filling results from poor fluidity during molding. However, there is a problem such as the occurrence of a wire failure or a disconnection of a gold wire in the semiconductor device, resulting in a defective conduction. For this reason, the epoxy resin composition needs to be stored in a refrigerator and transported in a refrigerator, and it is the current situation that storage and transportation are very expensive. Further, shortening the molding time can be mentioned as one of means for increasing the production efficiency, but for this purpose, fast curing property at the time of molding is required. The above-mentioned curing accelerators that have been conventionally used have a problem that the storage stability of the epoxy resin composition at room temperature is extremely reduced when added in an amount sufficient to achieve rapid curing during molding. . In order to solve this problem, in recent years, so-called latent curing accelerators have been actively researched, which suppress changes in viscosity and fluidity at low temperatures over time and cause a curing reaction only by heating during molding. As a means therefor, it has been proposed to develop latent properties by protecting the active sites of the curing accelerator with ion pairs.
No. 290 proposes latent curing accelerators having a salt structure of various organic acids and phosphonium ions.
However, this phosphonium salt does not have a specific higher-order molecular structure, and the ion pair is easily affected by the external environment. Therefore, in an epoxy resin composition using a low molecular weight epoxy resin or a phenol aralkyl resin in recent years, There is a problem that the storage stability at room temperature decreases.

On the other hand, in terms of reliability after soldering, the adhesiveness of the interface between the cured product of the epoxy resin composition and the base material such as the semiconductor element or the lead frame existing inside the semiconductor device has become very important. There is. If the adhesiveness at this interface is weak, peeling occurs after soldering, and further cracks due to this peeling occur. Further, halogen-based flame retardants, antimony oxide and the like are often blended as flame retardants in the epoxy resin composition. However, halogen-based flame retardants generate halide ions (radicals) at high temperatures, which causes a problem of poor heat resistance such as breakage of gold wires. Also, from the viewpoint of environmental hygiene, there is a demand for an epoxy resin composition which does not use a halogen-based flame retardant, antimony oxide or the like and has excellent flame retardancy.

[0004]

DISCLOSURE OF THE INVENTION The present invention has excellent room temperature storage characteristics, moldability, flame retardancy, solder resistance, and moisture resistance reliability, and substantially does not use halogen-based flame retardants, antimony oxide, etc. The present invention provides an epoxy resin composition for semiconductor encapsulation having high environmental safety, and a semiconductor device obtained by encapsulating a semiconductor element using the epoxy resin composition.

[0005]

Means for Solving the Problems As a result of intensive investigations by the present inventors to improve the room temperature storage characteristics and the rapid curing property, a specific compound was used as a curing accelerator and represented by the general formula (1). It was found that an epoxy resin composition using an epoxy resin and a phenol resin represented by the general formula (3) as a curing agent thereof has extremely excellent characteristics, and the present invention has been completed based on this finding. . That is, the present invention is
An epoxy resin composition comprising (A) an epoxy resin, (B) a phenol resin, (C) a curing accelerator represented by the general formula (2), and (D) an inorganic filler as essential components,
[1] The epoxy resin (A) is an epoxy resin represented by the general formula (1), and [2] the phenol resin (B) is represented by the general formula (3). An epoxy resin composition characterized by being a phenol resin, or [3] the epoxy resin (A) is an epoxy resin represented by the general formula (1), and the phenol resin (B) is a general formula (3). ) An epoxy resin composition, which is a phenol resin represented by

[Chemical 4] (In the formula, R ¹ is an alkyl group having 1 to 4 carbon atoms, and a is 0 to
R ² is an integer of 3, R ² is an alkyl group having 1 to 4 carbon atoms, b is an integer of 0 to 4, and they may be the same or different. n is an average value and is a positive number from 1 to 10. )

[0006]

[Chemical 5] (R ³ in the formula is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl group, which may be the same or different from each other.)

[0007]

[Chemical 6] (In the formula, R ¹ is an alkyl group having 1 to 4 carbon atoms, and a is 0 to
R ² is an integer of 3, R ² is an alkyl group having 1 to 4 carbon atoms, b is an integer of 0 to 4, and they may be the same or different. n is an average value and is a positive number from 1 to 10. )
[4] The epoxy resin composition according to any one of items [1] to [3], wherein the total amount of antimony atoms contained in the epoxy resin composition is less than 0.1% by weight, and [5] the epoxy resin composition. [1] to [4], wherein a semiconductor element is sealed with the epoxy resin composition according to any one of [1] to [4].

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having two or more epoxy groups in one molecule, for example, an epoxy represented by the general formula (1). Resin, bisphenol type epoxy resin, stilbene type epoxy resin, orthocresol novolac type epoxy resin, phenol novolac type epoxy resin, triphenolmethane type epoxy resin, alkyl modified triphenolmethane type epoxy resin, naphthol type epoxy resin, triazine nucleus-containing epoxy Examples thereof include resins and dicyclopentadiene-modified phenolic epoxy resins. These may be used alone or in combination of two or more. Among these epoxy resins, the epoxy resin represented by the general formula (1) is preferable. In the general formula (1), R ¹ is an alkyl group having 1 to 4 carbon atoms, a is an integer of 0 to 3, R ² is an alkyl group having 1 to 4 carbon atoms, and b is an integer of 0 to 4. , They may be the same or different from each other. n is an average value and is 1 to 1.
A positive number of 0, preferably a positive number of 1 to 4, more preferably 1
Is a positive number of -3. The compounding amount of the epoxy resin represented by the general formula (1) is preferably 50% by weight or more, more preferably 70% by weight or more, based on the whole epoxy resin.
If it is less than 50% by weight, it may easily burn. or,
When the phenol resin represented by the general formula (3) is used or the compounding amount of the inorganic filler is increased, even if the compounding amount of the epoxy resin represented by the general formula (1) in all epoxy resins is lowered, Flame resistance is maintained.

The phenol resin used in the present invention is 1
A general term for monomers, oligomers, and polymers having two or more phenolic hydroxyl groups in the molecule, for example, phenolic resin represented by the general formula (3), phenol novolac resin, cresol novolac resin, phenol aralkyl resin, naphthol aralkyl. Examples thereof include resins, triphenol methane resins, terpene modified phenol resins, dicyclopentadiene modified phenol resins, and these may be used alone or in combination of two or more. These phenolic resins can be used without limitation in molecular weight, softening point, hydroxyl group equivalent and the like. Among these phenol resins, the phenol resin represented by the general formula (3) is preferable. R ¹ in the general formula (3) is an alkyl group having 1 to 4 carbon atoms, a is an integer of 0 to 3, and R ² is
An alkyl group having 1 to 4 carbon atoms, b is an integer of 0 to 4, and they may be the same or different from each other. n is an average value and is a positive number of 1 to 10, preferably a positive number of 1 to 4, and more preferably a positive number of 1 to 3. The amount of the phenol resin represented by the general formula (3) is preferably 50% by weight or more, more preferably 70% by weight based on the total phenol resin.
It is more than weight%. If it is less than 50% by weight, it may easily burn. Further, when the epoxy resin represented by the general formula (1) is used or the compounding amount of the inorganic filler is increased, the compounding amount of the phenol resin represented by the general formula (3) in all phenolic resins is lowered. Also, flame retardance is maintained. The equivalent ratio of all epoxy resins and all phenol resins used in the present invention is preferably 0.5 to 2, particularly preferably 0.7.
~ 1.5. When it is out of the range of 0.5 to 2, the curability, the moisture resistance and the like may decrease.

The curing accelerator represented by the general formula (2) used in the present invention is a molecule of tetra-substituted phosphonium (X) and pyrogallol (ie 1,2,3-trihydroxybenzene) and a conjugate base of pyrogallol. The conjugate base is a phenoxide type compound in which one hydrogen is removed from pyrogallol. General formula (2) of the present invention
The curing accelerator represented by 2 is 2 even if used alone.
You may use together more than one kind. The substituent of the tetra-substituted phosphonium (X) which is one of the constituents of the curing accelerator represented by the general formula (2) of the present invention is not limited at all, and the substituents may be the same or different. May be. For example, a tetra-substituted phosphonium ion having a substituted or unsubstituted aryl group or alkyl group as a substituent is preferable because it is stable against heat and hydrolysis. In particular,
Tetraphenylphosphonium, tetratolylphosphonium, tetraethylphenylphosphonium, tetramethoxyphenylphosphonium, tetranaphthylphosphonium, tetrabenzylphosphonium, ethyltriphenylphosphonium, n-butyltriphenylphosphonium,
2-hydroxyethyltriphenylphosphonium, trimethylphenylphosphonium, methyldiethylphenylphosphonium, methyldiallylphenylphosphonium,
Tetra-n-butylphosphonium etc. can be illustrated.

The curing accelerator represented by the general formula (2) of the present invention has a phosphonium-phenoxide type salt in its structure as described above.
The difference from the organic acid anion salt type compound is that in the curing accelerator represented by the general formula (2) of the present invention, the higher order structure by hydrogen bond surrounds the ionic bond. In the conventional phosphonium-organic acid anion salt type compound, the reactivity is controlled only by the strength of the ionic bond, whereas in the curing accelerator represented by the general formula (2) of the present invention, At room temperature, the enclosure of anions with a higher-order structure protects the active sites, while at the molding stage, the higher-order structures collapse, exposing the active sites and giving the so-called latent property that develops reactivity. .

By the way, when the compound represented by the general formula (2) of the present invention is used as a curing accelerator in an epoxy resin composition containing antimony oxide, the phenolic hydroxyl group of pyrogallol is coordinated with an antimony atom. As a result, the activity as a curing accelerator decreases. Therefore, in the epoxy resin composition of the present invention, by using the epoxy resin represented by the general formula (1) and the phenol resin represented by the general formula (3) alone or in combination, antimony oxide is not used. Flame retardancy is maintained. That is, in the present invention, when the content of antimony atoms in the total epoxy resin composition is less than 0.1% by weight, the effect of the compound represented by the general formula (2) of the present invention as a curing accelerator is obtained. It is preferable to fully draw it out, and it is more preferable that it is not completely contained.

The method for producing the curing accelerator represented by the general formula (2) of the present invention is not limited at all, but two typical methods can be mentioned. The first is a method in which a tetra-substituted phosphonium / tetra-substituted borate (Y) is reacted with pyrogallol at a high temperature and then a thermal reaction is further performed in a solvent having a boiling point of 60 ° C. or higher. The second is a method of reacting pyrogallol, an inorganic base or an organic base, and a tetra-substituted phosphonium halide. The substituents of the tetra-substituted phosphonium halide used are not particularly limited, and the substituents may be the same or different from each other. For example, a tetra-substituted phosphonium ion having a substituted or unsubstituted aryl group or alkyl group as a substituent is preferable because it is stable against heat and hydrolysis. Specifically, tetraphenylphosphonium, tetratolylphosphonium, tetraethylphenylphosphonium, tetramethoxyphenylphosphonium, tetranaphthylphosphonium, tetrabenzylphosphonium, ethyltriphenylphosphonium, n-butyltriphenylphosphonium, 2-hydroxyethyltriphenylphosphonium, Examples include trimethylphenylphosphonium, methyldiethylphenylphosphonium, methyldiallylphenylphosphonium, and tetra-n-butylphosphonium. As the halide, chloride and bromide can be exemplified, and the tetra-substituted phosphonium halide may be selected from the characteristics such as price and moisture absorption and the availability, and any of them can be used.

There is no problem even if it is used in combination with another curing accelerator as long as the characteristics of the curing accelerator represented by the general formula (2) of the present invention are not impaired. Other curing accelerators that can be used in combination are not particularly limited, and examples thereof include triphenylphosphine and 1,8-diazabicyclo (5,4,4).
0) Undecene-7, 2-methylimidazole and the like can be mentioned, and these may be used alone or in combination of two or more. As the compounding amount of the curing accelerator represented by the general formula (2) of the present invention, about 0.2 to 20 parts by weight is added per 100 parts by weight of the total amount of all epoxy resins and all phenolic resins. The other characteristics are well-balanced and suitable.

The type of the inorganic filler used in the present invention is not particularly limited, and those generally used for sealing materials can be used. Examples thereof include fused crushed silica, fused spherical silica, crystalline silica, secondary agglomerated silica, alumina, titanium white, aluminum hydroxide, talc, clay, and glass fiber. You may use together more than one kind. Fused spherical silica is particularly preferable. It is preferable that the shape is infinitely spherical, and the filling amount can be increased by mixing particles having different particle sizes. The compounding amount of the inorganic filler is preferably 200 to 2400 parts by weight per 100 parts by weight of the total amount of all epoxy resins and all phenolic resins. If it is less than 200 parts by weight, the reinforcing effect due to the inorganic filler may not be sufficiently exhibited or may burn. On the other hand, if it exceeds 2400 parts by weight,
There is a possibility that the fluidity of the epoxy resin composition will decrease, resulting in defective filling during molding. Particularly, the compounding amount of the inorganic filler is 100, which is the total amount of all epoxy resins and all phenolic resins.
If it is 250 to 1400 parts by weight per part by weight, the moisture absorption of the cured product of the epoxy resin composition will be low, the occurrence of solder cracks can be prevented, and the viscosity of the epoxy resin composition upon melting will be low. Therefore, there is no possibility of causing deformation of the gold wire inside the semiconductor device, which is more preferable. or,
It is preferable that the inorganic filler is thoroughly mixed in advance.
An inorganic filler pretreated with a coupling agent or the like may be used.

The epoxy resin composition of the present invention comprises (A)-
In addition to the component (D), a flame retardant such as a brominated epoxy resin may be contained if necessary, but applications in which stability of electrical characteristics of a semiconductor device at a high temperature of 150 to 200 ° C. is required Then, the content of bromine atoms is preferably less than 0.1% by weight in the total epoxy resin composition, and more preferably not completely contained. If the content of bromine atoms is 0.1% by weight or more, the resistance value of the semiconductor device may increase with time when left at high temperature, and eventually a failure may occur in which the gold wire of the semiconductor element is broken. . From the viewpoint of environmental protection, if the content of bromine atoms is less than 0.1% by weight,
It is desirable that it is not contained as much as possible. The epoxy resin composition of the present invention includes, in addition to the components (A) to (D), if necessary, a coupling agent such as γ-glycidoxypropyltrimethoxysilane, a coloring agent such as carbon black, and a phosphorus compound. Various additives such as flame retardants, low-stress components such as silicone oils and silicone rubbers, natural waxes, synthetic waxes, release agents such as higher fatty acids and their metal salts or paraffins, and antioxidants can be added. The epoxy resin composition of the present invention is obtained by mixing components (A) to (D), other additives, and the like at room temperature with a mixer, kneading with a kneader such as a roll or an extruder, and cooling and pulverizing. can get. In order to manufacture a semiconductor device by sealing an electronic component such as a semiconductor element using the epoxy resin composition of the present invention, it may be cured and molded by a molding method such as a transfer mold, a compression mold, an injection mold. In particular, the epoxy resin composition of the present invention is suitable for semiconductor devices compatible with insertion mounting and surface mounting.

[0017]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. [Synthesis Example of Molecular Association] 189 g of pyrogallol (1.5
Mol) and 210 g (0.5 mol) of tetraphenylphosphonium tetraphenylborate (Y) were charged in a 3 L separable flask and reacted at 200 ° C. for 3 hours. The benzene distillate in this reaction is 97% of the theoretical amount.
It was weight% (that is, benzene distillation rate was 97%). The crude product of this reaction was finely pulverized, charged into a separable flask, 2-propanol was added in an amount 3 times the weight of the crude product charged, and the internal temperature was 82.4 ° C. (boiling point temperature of 2-propanol). Stir for 5 hours. After that, most of 2-propanol was removed, and low boiling point components were further removed under reduced pressure with heating. The obtained product was named compound C1.

[Production Example of Epoxy Resin Composition] The mixing ratio is parts by weight. (Example 1) 80 parts by weight of a resin containing an epoxy resin represented by the formula (4) as a main component (epoxy equivalent: 275, melting point: 105 ° C)

[Chemical 7] Phenol novolac resin (hydroxyl group equivalent 104, softening point 73 ° C.) 30 parts by weight Compound C1 4.0 parts by weight Fused spherical silica (average particle size 15 μm) 600 parts by weight Carbon black 5 parts by weight Carnauba wax 5 parts by weight are mixed and heated. Using a roll, the mixture was kneaded at 95 ° C. for 8 minutes, cooled, and then pulverized to obtain an epoxy resin composition. The obtained epoxy resin composition was evaluated by the following methods. The results are shown in Table 1.
Shown in.

Evaluation method Spiral flow: Using a mold for spiral flow measurement according to EMMI-1-66, the mold temperature was 175 ° C., the injection pressure was 6.9 MPa, and the curing time was 120 s. The spiral flow is a fluidity parameter, and the larger the value, the better the fluidity. The unit is cm. Shore D hardness: mold temperature 175 ° C, injection pressure 6.9MP
a, the molding time was 120 s, and the Shore D hardness value measured 10 seconds after the mold was opened was defined as the curability. The Shore D hardness is an index of curability, and the larger the value, the better the curability. Storage property at 30 ° C .: After storage at 30 ° C. for 1 week, spiral flow was measured and expressed as a percentage of the spiral flow immediately after preparation. Units%. Flame retardance: UL-94 vertical test method (sample thickness 1/16 in
ch). Solder resistance: Mold temperature 1 using transfer molding machine
1 at 75 ° C, injection pressure 6.9 MPa, curing time 120s
Eight flat packages of 4 mm × 20 mm × 2.7 mm were molded. Post cure at 175 ° C for 4 hours, 8
After leaving it in a thermo-hygrostat at 5 ° C. and a relative humidity of 85% for 168 hours to absorb moisture, it was immersed in a solder bath at 240 ° C. for 30 seconds, and cracks outside the package were observed. When the number of defective packages is n, it is displayed as n / 8. Moisture resistance reliability: Using a transfer molding machine, mold temperature 175 ° C., injection pressure 6.9 MPa, curing time 120 s 16 pDIP (chip size 3.0 mm × 3.5 mm)
Was molded. Post cure at 175 ° C for 4 hours, then pressure cooker test (125 ° C, 2.4 x 10
⁵ Pa) was performed to measure the failure occurrence time when the circuit open failure was measured every 50 hours. The unit is hours. Antimony atom content rate: 40 m diameter at a pressure of 5.9 MPa
m, the thickness was 5 to 7 mm, and the obtained molded product was quantified for the content of antimony atoms in the total epoxy resin composition using a fluorescent X-ray analyzer. The unit is% by weight.

(Examples 2 to 7 and Comparative Examples 1 to 6) According to the formulations shown in Table 1, epoxy resin compositions were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1. The orthocresol novolac type epoxy resin used in the examples and comparative examples has an epoxy equivalent of 210 and a softening point of 65 ° C. As the phenol resin of the general formula (3), the one represented by the formula (5) (hydroxyl group equivalent 199, softening point 70 ° C.) was used. The curing accelerator used in the comparative example is a compound represented by the formula (6).

[Chemical 8]

[0021]

[Chemical 9] (In the formula, the symbol Ph represents a phenyl group.)

[0022]

[Table 1]

[0023]

INDUSTRIAL APPLICABILITY The epoxy resin composition of the present invention is excellent in room-temperature storage characteristics for semiconductor encapsulation, fast curing property, moldability, flame retardancy, and substantially safe from the environment because it does not contain halogen or antimony. The semiconductor device using the same is excellent in solder resistance and moisture resistance reliability and is particularly useful as a device for insertion mounting and surface mounting.

Claims (5)

[Claims] 1. An epoxy resin represented by the general formula (1), a phenol resin (B), a curing accelerator represented by the general formula (2), and an inorganic filler (D). An epoxy resin composition comprising an essential component. [Chemical 1] (In the formula, R ¹ is an alkyl group having 1 to 4 carbon atoms, and a is 0 to
R ² is an integer of 3, R ² is an alkyl group having 1 to 4 carbon atoms, b is an integer of 0 to 4, and they may be the same or different. n is an average value and is a positive number from 1 to 10. ) [Chemical 2] (R ³ in the formula is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl group, which may be the same or different from each other.) 2. An epoxy resin (A), a phenol resin (B) represented by the general formula (3), and a general formula (2) (C).
An epoxy resin composition comprising a curing accelerator represented by the formula (1) and an inorganic filler (D) as essential components. [Chemical 3] (In the formula, R ¹ is an alkyl group having 1 to 4 carbon atoms, and a is 0 to
R ² is an integer of 3, R ² is an alkyl group having 1 to 4 carbon atoms, b is an integer of 0 to 4, and they may be the same or different. n is an average value and is a positive number from 1 to 10. ) 3. An epoxy resin represented by the general formula (1) (A), a phenol resin represented by the general formula (3) (B),
(C) a curing accelerator represented by the general formula (2), and (D)
An epoxy resin composition comprising an inorganic filler as an essential component. 4. The antimony atom contained in the total epoxy resin composition is less than 0.1% by weight.
Or the epoxy resin composition described in 3. 5. A semiconductor device obtained by encapsulating a semiconductor element using the epoxy resin composition according to any one of claims 1 to 4.