JP2001247652A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor-sealing epoxy resin composition applicable to insertion mounting and surface mounting, which is excellent in room- temperature shelf stability, fluidity, curing characteristics upon molding, and particularly in resistance to solder cracking, although it uses an epoxy resin of a low water absorption and a low viscosity. SOLUTION: The epoxy resin composition comprises, as essential components, (A) an epoxy resin represented by formula (1), (B) a phenolic resin curing agent, (C) a curing accelerator, which is a molecular association comprising a tetra- substituted phosphonium (X), a compound (Y) having two or more phenolic hydroxy groups in a molecule, and a conjugated base of the compound (Y) having two or more henolic hydroxy groups in a molecule, the conjugated base comprising a phenoxide compound formed by removing one hydrogen from the compound (Y) having two or more phenolic hydroxy groups in a molecule, and (D) an inorganic filler, which accounts for 60-92 wt.% of the total epoxy resin composition.

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 encapsulating a semiconductor for insertion mounting and surface mounting, and a semiconductor device having a semiconductor element encapsulated with the epoxy resin composition.

[0002]

2. Description of the Related Art Epoxy resin compositions for encapsulating semiconductors have been developed and manufactured to protect semiconductor elements such as diodes, transistors and IC chips from mechanical and chemical actions. Items required for this epoxy resin composition,
It is changing depending on the type of semiconductor element, the structure of the semiconductor device, and the environment in which it is used. Conventionally, these semiconductor devices have used an epoxy resin composition containing an inorganic filler such as ortho-cresol novolak type epoxy resin, phenol novolak resin, fused silica, and crystalline silica having excellent heat resistance and moisture resistance. . However, in recent years, as semiconductor devices have become more highly integrated, semiconductor devices have become larger and larger, and semiconductor devices have changed from conventional insertion type DIP types to small and thin QFPs, SOPs, SOJs, and surface mountable semiconductor devices.
It is changing to TSOP, TQFP, PLCC. Large semiconductor elements are encapsulated in a small and thin semiconductor device, and cracks occur due to thermal stress and vaporization of absorbed moisture. Have been. In particular, there is a problem that the moisture resistance deteriorates due to the cracking of the semiconductor device or the peeling of the cured product of the epoxy resin composition from the lead frame and the semiconductor element due to the rapid exposure to a high temperature of 200 ° C. or more in the soldering process. Is coming out.

The most effective methods for improving the solder crack resistance are to increase the amount of the inorganic filler and reduce the water absorption and viscosity of the resin component. Simply increasing the amount of inorganic filler to improve solder cracking resistance will reduce the fluidity of the epoxy resin composition and cause poor filling, so it is essential to reduce the viscosity of the resin component It is. Further, the low water-absorbing resin component is less likely to cause a steam explosion even when exposed to a high temperature in the soldering step, and thus has excellent solder crack resistance.
However, when the molecular weight of the resin component is reduced for the purpose of lowering the viscosity of the epoxy resin composition, the molecules are more likely to move, and in the initial stage of the reaction, the crosslinking reaction proceeds promptly, so that the crosslinking reaction partially proceeds during kneading. Certain fluidity is reduced,
Further, for the same reason, there is a disadvantage that the reaction easily occurs even at room temperature, and the storage stability of the epoxy resin composition at room temperature is lowered.
Furthermore, the resin component having a low molecular weight has a high initial reactivity,
Conversely, in the final stage of the reaction, there is a problem that the crosslink density does not sufficiently increase and the curing is not sufficiently performed.

In recent years, electronic and electrical materials, particularly IC encapsulating materials, have recently been required to have fast-curing properties for the purpose of improving production efficiency, as well as to improve physical and physical properties.
There has been an increasing demand for improved preservability for improved handling during storage. Conventionally, epoxy resins for electronic and electric fields have phosphines,
Various compounds such as amines, imidazole compounds, nitrogen-containing heterocyclic compounds such as diazabicycloundecene, and quaternary ammonium, phosphonium or arsonium compounds have been used. These commonly used curing accelerators often exhibit a curing acceleration action even at a relatively low temperature such as room temperature. This causes a decrease in quality as a product, such as an increase in viscosity during production of the epoxy resin composition and during storage of the obtained epoxy resin composition, a decrease in fluidity, and a variation in curability. . In order to solve this problem, recently, research on so-called latent curing accelerators, which suppress changes over time in viscosity and fluidity at low temperatures and cause a curing reaction only by heating during shaping and molding, has been actively conducted. ing. As a means for protecting the active site of the curing accelerator with an ion pair, studies have been made to develop latency, and JP-A-8-41290 discloses a salt structure of various organic acids and phosphonium ions. A latent curing accelerator having the formula: However, this phosphonium salt does not have a specific higher-order molecular structure, and ion pairs are relatively easily affected by the external environment.Therefore, in recent semiconductor encapsulants using low-molecular epoxy resins or phenol aralkyl resins, However, there is a problem that storage stability is deteriorated.

[0005]

DISCLOSURE OF THE INVENTION The present invention uses an epoxy resin having low water absorption and low viscosity, and while being highly filled with an inorganic filler, has room temperature storage properties, fluidity, and curing properties during molding. An object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation which is particularly excellent in solder crack resistance and is compatible with insertion mounting and surface mounting, and a semiconductor device obtained by encapsulating a semiconductor element using the same.

[0006]

The present invention comprises (A) an epoxy resin represented by the formula (1), (B) a phenol resin curing agent, (C) a tetra-substituted phosphonium (X) and a phenolic compound in one molecule. Compound (Y) having two or more hydroxyl groups
And a compound (Y) having a molecular association with a conjugate base of a compound (Y) having two or more phenolic hydroxyl groups in one molecule, wherein the conjugate base has two or more phenolic hydroxyl groups in one molecule. A curing accelerator consisting of a phenoxide-type compound from which one hydrogen has been removed, and (D) an inorganic filler as an essential component, wherein the amount of the inorganic filler is 60 to 92% by weight in the total epoxy resin composition. And a semiconductor device obtained by sealing a semiconductor element using the epoxy resin composition.

Embedded image (Wherein R is a hydrogen atom, a chain or cyclic alkyl group,
A group or atom selected from a phenyl group and a halogen, which may be the same or different.
a is an integer of 1 to 4, and b is an integer of 1 to 3. n is an average value and is a positive number of 1 or more. )

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin represented by the formula (1) used in the present invention is a phenol resin obtained by polymerizing dicyclopentadiene and phenols by an addition reaction.
It is an epoxy resin obtained by glycidyl etherification, and has a lower modulus of elasticity at high temperatures exceeding the glass transition temperature than conventional ortho-cresol novolak epoxy resins. Excellent adhesion. Therefore, it is possible to reduce the thermal stress at the time of surface mounting soldering, and to obtain an epoxy resin composition having excellent solder crack resistance. In addition, the amount of the inorganic filler in the total epoxy resin composition is 6
In order to make it 0 to 92% by weight, as the epoxy resin represented by the formula (1), it is preferable to use a resin having a low softening point, and particularly preferably a resin having a softening point of 40 to 100 ° C. If the temperature is lower than 40 ° C., it is not preferable because the handleability is poor. If the temperature exceeds 100 ° C., there is a possibility that it will not melt at the time of kneading, which is not preferable. Further, R in the formula (1)
Is particularly preferably a hydrogen atom. In addition, there is no problem if used in combination with another epoxy resin as long as the properties of the epoxy resin represented by the formula (1) of the present invention are not impaired. Examples of epoxy resins that can be used in combination include, for example, biphenyl epoxy resin, bisphenol epoxy resin, stilbene epoxy resin, orthocresol novolak epoxy resin, phenol novolak epoxy resin, triphenolmethane epoxy resin, naphthol epoxy resin, and alkyl. Modified triphenolmethane-type epoxy resin, triazine nucleus-containing epoxy resin, dicyclopentadiene-modified phenol-type epoxy resin and the like may be mentioned, and these may be used alone or in combination. In order to bring out the effect of solder crack resistance, the amount of the epoxy resin represented by the formula (1) of the present invention is preferably 30% by weight or more, more preferably 50% by weight or more, based on all the epoxy resins. If it is less than 30% by weight, low elasticity and high adhesion at high temperatures cannot be obtained, and solder crack resistance is insufficient.

[0008] The phenolic resin curing agent used in the present invention is capable of undergoing a curing reaction with the above-mentioned epoxy resin to form a crosslinked structure, a monomer, an oligomer having two or more phenolic hydroxyl groups in one molecule, and Refers to polymers in general. For example, phenol novolak resin, cresol novolak resin, phenol aralkyl resin, triphenol methane type resin, naphthol aralkyl resin, terpene-modified phenol resin, dicyclopentadiene-modified phenol resin and the like, and these may be used alone or in combination. Good. These phenol resins can be used without any limitation in molecular weight, softening point, hydroxyl equivalent, and the like. In order to make the amount of the inorganic filler in the entire epoxy resin composition 60 to 92% by weight, it is preferable to use a phenol resin curing agent having a low softening point, and the softening point is particularly preferably 55 to 130 ° C. Are preferred. If the temperature is lower than 55 ° C., it is not preferable because the handleability is poor. If the temperature exceeds 130 ° C., it may not melt during kneading, which is not preferable. The ratio of the total epoxy resin of the present invention to the total phenol resin curing agent acting as a curing agent is preferably 1 to 1.5 phenolic hydroxyl groups per 1 epoxy group.

The molecular association as the curing accelerator (C) used in the present invention includes a tetrasubstituted phosphonium (X), a compound (Y) having two or more phenolic hydroxyl groups in one molecule, and a phenol in one molecule. A molecular association with a conjugate base of a compound (Y) having two or more neutral hydroxyl groups,
The conjugate base has two phenolic hydroxyl groups per molecule.
It is a phenoxide-type compound obtained by removing one hydrogen from a compound (Y) having at least one hydrogen atom. The substituent of the tetra-substituted phosphonium (X), which is one of the components of the molecular assembly of the present invention, is not limited at all, and the substituents may be the same or different. For example, a tetra-substituted phosphonium ion having a substituted or unsubstituted aryl 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, trimethylphenylphosphonium,
Examples thereof include methyldiethylphenylphosphonium, methyldiallylphenylphosphonium, and tetra-n-butylphosphonium.

[0010] The constituent component of the molecular assembly of the present invention, 1
As the compound (Y) having two or more phenolic hydroxyl groups in the molecule, for example, bis (4-hydroxy-3,
5-dimethylphenyl) methane (commonly known as tetramethylbisphenol F), 4,4′-sulfonyldiphenol,
4,4′-isopropylidene diphenol (commonly known as bisphenol A), bis (4-hydroxyphenyl) methane, bis (2-hydroxyphenyl) methane, (2-hydroxyphenyl)-(4-hydroxyphenyl) methane, and these Inner bis (4-hydroxyphenyl) methane, bis (2-hydroxyphenyl) methane, and a mixture of three kinds of (2-hydroxyphenyl)-(4-hydroxyphenyl) methane (for example, manufactured by Honshu Chemical Industry Co., Ltd.
Bisphenols such as bisphenol FD);
-Benzenediol, 1,3-benzenediol, 1,
Dihydroxybenzenes such as 4-benzenediol,
Trihydroxybenzenes such as 1,2,4-benzenetriol; various isomers of dihydroxynaphthalenes such as 1,6-dihydroxynaphthalene; various kinds of biphenols such as 2,2′-biphenol and 4,4′-biphenol Examples include compounds such as isomers. Further, the conjugate base as another component is a phenoxide-type compound obtained by removing one hydrogen from the compound (Y).

Although the molecular aggregate of the present invention has a phosphonium-phenoxide type salt in its structure as described above, the difference from the phosphonium-organic acid anion salt type compound in the prior art is that the molecular associate of the present invention is different. In the aggregate, the higher-order structure due to the hydrogen bond surrounds the ionic bond. In the salt of the prior art, the reactivity is controlled only by the strength of the ionic bond, whereas in the molecular aggregate of the present invention, the enclosing by the higher-order structure of the anion protects the active site at normal temperature, while In the molding stage, the active sites are exposed due to the collapse of the higher-order structure, and so-called latency, which expresses reactivity, is imparted.

The method for producing the molecular aggregate of the present invention includes the following:
Although not limited at all, two typical methods can be mentioned. The first is a tetra-substituted phosphonium / tetra-substituted borate (Z) and two phenolic hydroxyl groups in one molecule.
This is a method in which a compound (Y) having at least one compound is reacted at a high temperature and then thermally reacted in a solvent having a boiling point of 60 ° C. or more. The second is a compound (Y) having two or more phenolic hydroxyl groups in one molecule, an inorganic base or an organic base,
This is a method of reacting with a tetra-substituted phosphonium halide. The substituent of the tetra-substituted phosphonium halide to be used is not limited at all, 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 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, tetra-n-butylphosphonium and the like. Examples of the halide include chloride and bromide. The halide may be selected from the properties of the tetra-substituted phosphonium halide, such as the price and moisture absorption, and the availability thereof, and any of them may be used.

The compounding amount of the molecular aggregate of the present invention is preferably 0.1 to 1% by weight in the total epoxy resin composition.
Usually, the mixture can be mixed at a moderately high temperature, for example, at 70 to 150 ° C. If it is less than 0.1% by weight, sufficient curability may not be obtained at the time of heat molding. If it exceeds 1% by weight, curing may be too fast and fluidity may be reduced at the time of molding, which may cause poor filling. is there. Also, there is no problem if used in combination with other curing accelerators as long as the properties of the molecular aggregate of the present invention are not impaired. Examples of the curing accelerator that can be used in combination include triphenylphosphine, 1,8-diazabicyclo (5,4,0) undecene-7, 2-methylimidazole, and the like, and these may be used alone or in combination. . When used in combination, the amount of the molecular aggregate of the present invention is desirably 40% by weight or more in the total curing accelerator. 40
If the amount is less than the weight percentage, the object of the present invention may not be sufficiently achieved.

The inorganic filler used in the present invention includes:
Fused crushed silica, fused spherical silica, crystalline silica, secondary crystalline silica, alumina and the like can be mentioned, and fused spherical silica is particularly desirable from the viewpoint of improving the fluidity of the epoxy resin composition. The shape of the spherical silica is desirably a true sphere in order to improve the fluidity, and the particle size distribution is desirably broad. The amount of the inorganic filler is preferably 60 to 9 in the total epoxy resin composition in consideration of the balance between solder crack resistance, moldability and fluidity.
2% by weight is preferred. If the content is less than 60% by weight, it is not preferable because the water absorption and the thermal expansion cannot be reduced and the solder crack resistance becomes insufficient. Exceeding 92% by weight is not preferable because the viscosity is increased to cause problems such as deformation of gold wires and die pads inside the semiconductor device.

The epoxy resin composition of the present invention comprises (A)
In addition to the component (D), if necessary, a coupling agent such as γ-glycidoxypropyltrimethoxysilane, a coloring agent such as carbon black, a brominated epoxy resin, a flame retardant such as antimony oxide, a phosphorus compound, and a silicone oil. And various additives such as a low-stress component such as silicone rubber, a natural wax, a synthetic wax, a higher fatty acid and a metal salt thereof, a releasing agent such as paraffin, and an antioxidant. The epoxy resin composition of the present invention comprises (A)
(D) The component and other additives are mixed at room temperature using a mixer, kneaded with a kneader such as a roll or an extruder, cooled, and pulverized. In order to manufacture a semiconductor device by encapsulating an electronic component such as a semiconductor element using the epoxy resin composition of the present invention, it is sufficient to cure and mold by a molding method such as a transfer mold, a compression mold, and an injection mold. In particular, the epoxy resin composition of the present invention is suitable for a semiconductor device compatible with insertion mounting and surface mounting.

[0016]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. [Synthesis example of molecular aggregate] Bisphenol FD manufactured by Honshu Chemical Industry Co., Ltd. Trade name of an isomer mixture of bis (monohydroxyphenyl) methane. It corresponds to compound (Y). 300 g (1.5 mol) and 329 g of tetraphenylphosphonium / tetraphenylborate (Z)
(0.5 mol) in a 3 L separable flask,
The reaction was performed at 200 ° C. for 3 hours. The amount of benzene distilled in this reaction was 97% by weight of the theoretical amount (that is, the benzene distillation rate was 97%). The crude product from this reaction is finely pulverized, charged into a separable flask, and 2-propanol is added in an amount 3 times the charged weight of the crude product, and the internal temperature is 82.4 ° C.
(Boiling point temperature of 2-propanol) for 1.5 hours. Thereafter, most of the 2-propanol was removed, and a low-boiling component was further removed under heating and reduced pressure. The obtained product was designated as compound C1. The solvent is heavy methanol, and C1
Was measured by ¹ H-NMR. The peaks around 4.8 ppm and 3.3 ppm are the peaks of the solvent, 6.4 ppm.
The group of peaks at about 7.1 ppm is the starting material bisphenol F [moles (a) based on 1 mol of (X)] and a phenoxide-type conjugate base [(X) 1 Number of moles per mole (b)]
The peak group around 7.6 to 8.0 ppm is assigned to the phenyl proton of the tetraphenylphosphonium group, and the molar ratio is (a +
b) / (X) = 2.2 / 1 was calculated.

[Production Example of Epoxy Resin Composition] The blending ratio is by weight. (Example 1) 10.20 parts by weight of an epoxy resin represented by the formula (2) (epoxy equivalent: 250, softening point: 65 ° C)

Embedded image Phenol novolak resin curing agent (hydroxyl equivalent 105, softening point 60 ° C) 2.80 parts by weight Paraxylylene-modified phenolic resin curing agent (hydroxyl equivalent 175, softening point 95 ° C) 2.80 parts by weight Compound C1 0.60 parts by weight Melting and crushing Silica 45.00 parts by weight Fused spherical silica 35.00 parts by weight γ-glycidoxypropyltrimethoxysilane 0.50 parts by weight Carbon black 0.30 parts by weight Brominated phenol novolak epoxy resin 0.50 parts by weight Antimony trioxide 2.00 parts by weight of carnauba wax 0.30 parts by weight were mixed by a mixer, kneaded at 100 ° C. using a biaxial roll, cooled and pulverized to obtain an epoxy resin composition. The obtained epoxy resin composition was evaluated by the following method. Table 1 shows the results.

Evaluation method Spiral flow: Spiral flow was measured using a mold for measuring spiral flow according to EMMI-1-66 at a mold temperature of 175 ° C., an injection pressure of 70 kg / cm ² , and a curing time of 2 minutes. Spiral flow is a parameter of fluidity, and the larger the value, the better the fluidity. The unit is cm. Room temperature storage: After storing at 25 ° C., the spiral flow was measured. The percentage with respect to the spiral flow immediately after the preparation was determined, and the result was expressed in days until the flow residual ratio became 90%. Gel time: After melting on a hot plate heated to 175 ° C., the time until hardening was measured while kneading with a spatula. The unit is seconds. Shore D hardness: mold temperature 175 ° C, injection pressure 70kg /
The composition was molded in 2 cm ² and a curing time of 2 minutes, and the value of Shore D hardness measured 10 seconds after opening the mold was taken as the curability. Shore D hardness is an index of curability, and the larger the numerical value, the better the curability. Solder crack resistance: using a transfer molding machine, mold temperature 175 ° C, injection pressure 70 kg / cm ² , curing time 2
Eight 80 QFP (1.5 mm thick) are molded in
After 8 hours at 5 ° C, 85 ° C, relative humidity 60
% For 168 hours, and then treated by IR reflow (240 ° C.) for 10 seconds. The obtained packages were visually observed and observed with an ultrasonic flaw detector, and the number of packages in which external cracks, peeling on the chip, and peeling under the pad occurred was indicated as n / 8.

(Examples 2 to 4, Comparative Examples 1 to 4) An epoxy resin composition was obtained in the same manner as in Example 1 according to the composition shown in Table 1, and evaluated in the same manner as in Example 1. Table 1 shows the results. Other raw materials used in the examples other than Example 1 were ortho-cresol novolak type epoxy resin (softening point 60
° C, epoxy equivalent 200), triphenylphosphine as a curing accelerator, and tetraphenylphosphonium tetraphenylborate.

[Table 1]

[0020]

According to the present invention, a semiconductor seal for insertion mounting and surface mounting which is excellent in room temperature storage properties, fluidity, and curing properties at the time of molding while using an epoxy resin having low water absorption and low viscosity. An epoxy resin composition for stopping is obtained, and a semiconductor device using the same is excellent in solder crack resistance and can greatly improve productivity.

Claims (8)

[Claims] (A) an epoxy resin represented by the formula (1), (B) a phenol resin curing agent, (C) a tetra-substituted phosphonium (X) and two phenolic hydroxyl groups in one molecule.
And a compound (Y) having two or more phenolic hydroxyl groups in one molecule and a conjugate base, wherein the conjugate base has two or more phenolic hydroxyl groups in one molecule. A curing accelerator consisting of a phenoxide-type compound obtained by removing one hydrogen from the compound (Y) having at least one compound, and (D) an inorganic filler as an essential component, wherein the inorganic filler is contained in the total epoxy resin composition in an amount of 60 to 92%. % By weight of the epoxy resin composition. Embedded image (Wherein R is a hydrogen atom, a chain or cyclic alkyl group,
A group or atom selected from a phenyl group and a halogen, which may be the same or different.
a is an integer of 1 to 4, and b is an integer of 1 to 3. n is an average value and is a positive number of 1 or more. ) 2. An epoxy resin (A) represented by the formula (1)
The epoxy resin composition according to claim 1, which has a softening point of 40 to 100C. 3. The epoxy resin composition according to claim 1, wherein the phenol resin curing agent (B) has a softening point of 55 to 130 ° C. 4. A compound (Y) having two or more phenolic hydroxyl groups in one molecule is selected from dihydroxybenzenes, trihydroxybenzenes, bisphenols, biphenols, dihydroxynaphthalenes, phenol novolak resins, and phenol aralkyl resins. The epoxy resin composition according to any one of claims 1 to 3, which is at least one member selected from the group consisting of: 5. The method according to claim 5, wherein the molecular aggregate reacts the tetra-substituted phosphonium / tetra-substituted borate (Z) with the compound (Y) having two or more phenolic hydroxyl groups in one molecule at a high temperature, and further reacts the compound. The epoxy resin composition according to any one of claims 1 to 4, which is obtained by a thermal reaction in a solvent having a boiling point of 60 ° C or higher. 6. The molecular aggregate obtained by reacting a compound (Y) having two or more phenolic hydroxyl groups in one molecule, an inorganic base or an organic base, and a tetra-substituted phosphonium halide. Item 5. The epoxy resin composition according to any one of Items 1 to 4. 7. The epoxy resin composition according to claim 1, wherein the tetra-substituted phosphonium (X) is tetraphenylphosphonium. 8. A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition according to claim 1.