JP7283984B2 - Epoxy resin curing accelerator and epoxy resin composition - Google Patents

Description

The present invention relates to an epoxy resin curing accelerator and an epoxy resin composition. More particularly, the present invention relates to an epoxy resin curing accelerator suitable for producing an epoxy resin-based encapsulant for electronic parts such as semiconductor elements, and an epoxy resin composition containing the same.

As a method for encapsulating semiconductor elements such as ICs, transfer molding of an epoxy resin composition is excellent for low cost and mass production. However, as electronic devices become smaller and lighter, the integration of semiconductors is progressing, and surface mounting is also progressing. has become very strong. In particular, it is important not to impair reliability even when exposed to high temperatures. Conventionally, by increasing the ratio of inorganic fillers in epoxy resin compositions, epoxy resins have low hygroscopicity, high strength, and low thermal expansion to ensure reliability at high temperatures.

In order to aim for reliability at even higher temperatures, it is conceivable to further increase the ratio of inorganic fillers. There were problems such as poor fluidity during molding. Therefore, in order to achieve both curability and fluidity, it has been proposed to use an onium salt with excellent thermal stability as a curing accelerator for epoxy resin (for example, Patent Document 1). Since the resin has excellent thermal stability, the onium salt remains in the resin as an organic ion even after curing, and depending on the curing conditions and application, there is a problem that reliability at high temperatures, which is essential, is insufficient.

JP 2018-104559 A

Therefore, it is desirable to provide an epoxy curing accelerator that exists stably below the curing temperature and rapidly decomposes under curing conditions to cure the epoxy resin, while itself hardly remaining as ions in the cured resin due to decomposition; An object of the present invention is to provide an epoxy resin composition having high reliability at high temperatures while maintaining both curability and fluidity of the epoxy resin composition by using an accelerator.

The present inventors arrived at the present invention as a result of conducting studies to achieve the above object.
That is, the present invention includes an imidazole salt (S) consisting of a cation (A) having imidazole represented by general formula (1) and an anion (B) represented by general formula (2), and the imidazole salt (S ) has a melting point of 170° C. or less; and the epoxy resin curing accelerator (Q), the epoxy resin (E), and two phenolic hydroxyl groups in one molecule It is an epoxy resin composition containing a compound (P) having one or more.

[In Formula (1), R1, R2, R3, and R4 are the same or different and each represents a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, or a hydroxymethyl group. ]

[In formula (2), R5 and R7 are groups in which proton-donating substituents release protons, and they may be the same or different, and R5 and R7 in the same molecule are It combines with silicon atoms to form a chelate structure. R6 is an organic group that bonds with R5 and R7. R9 and R11 are groups in which a proton-donating substituent releases protons, and R9 and R11 in the same molecule are bonded to a silicon atom to form a chelate structure. R10 is an organic group that bonds with R9 and R11. R6 and R10 may be the same or different, and R5, R7, R9 and R11 may be the same or different. R8 represents an organic group having a substituted or unsubstituted aromatic ring or a substituted or unsubstituted heterocyclic ring, or a substituted or unsubstituted aliphatic group. ]

The epoxy resin curing accelerator (Q) of the present invention is a proton-added cation of the imidazole-containing cation (A), but since it has a five-membered ring conjugated structure, it is represented by the general formula (2). A salt can be formed with the anion (B), and as a result, it is possible not to accelerate the curing reaction at low temperatures and heat melting temperatures. Furthermore, the anionic portion has better thermal stability than the chelate structure, and does not accelerate the curing reaction at the temperature at which the mixture of epoxy resin, curing agent and curing accelerator is heated and melted. On the other hand, at a higher molding curing temperature, the epoxy resin composition decomposes quickly and the reaction between the epoxy resin and the curing agent can be accelerated. can. Furthermore, since the cationic moiety is imidazole, it reacts with the epoxy group at the curing temperature and is incorporated into the resin. This provides a decomposition mechanism in which the cationic portion and the anionic portion do not remain as ions in the cured epoxy resin. In general, when imidazoles are used as curing accelerators for epoxy resins, free chlorine is generated, which is a problem. Another advantage is that it is difficult to generate free chlorine by forming a salt with the anion that is used.

Furthermore, the epoxy resin curing accelerator (Q) has a cation (A) having imidazole, and thus has a relatively low melting point. That is, the compounding temperature for heating and melting is close to or lower than the melting point. From this fact, it is possible to design an epoxy resin composition having good fluidity. In other words, by using the epoxy resin curing accelerator (Q), it is possible to improve the reliability of semiconductor devices and the like at high temperatures while maintaining both curability and fluidity of the epoxy resin composition. It is suitable for manufacturing system sealing materials.

The epoxy resin curing accelerator (Q) and the epoxy resin composition of the present invention are described below. The epoxy resin curing accelerator (Q) of the present invention is an imidazole salt (S) consisting of a cation (A) having imidazole represented by the general formula (1) and an anion (B) represented by the general formula (2). characterized by comprising

Cation (A) having imidazole is represented by general formula (1), wherein R1, R2, R3, and R4 are the same or different and are hydrogen atom, methyl group, ethyl group, propyl group , a butyl group, a phenyl group, or a hydroxymethyl group. The hydroxymethyl group is -CH2OH.

The imidazole-containing cation (A) is particularly preferably a hydrogen atom as R2 from the viewpoint that it is incorporated into the resin during curing and provides reliability at high temperatures. Further, from the viewpoint of fluidity, R1 is preferably an alkyl group or a phenyl group, and at least one of R4 and R5 is preferably a hydrogen atom. This is because the imidazole salt has a lower melting point.

Specific examples of the imidazole-containing cation (A) include 1-ethyl-2-methylimidazole cation, 1-propyl-2-methylimidazole cation, 1-butyl-2-methylimidazole cation, 2-phenylimidazole cation, 2 -methylimidazole cation, 2-ethyl-4-methylimidazole cation, 2-phenyl-4-methyl-5-hydroxymethylimidazole cation, 2-phenyl-4,5-dihydroxymethylimidazole cation, 2,4-dimethylimidazole cation , 1,4-dimethyl-2-ethylimidazole cation, 2,4-diethylimidazole cation, 1-methyl-2,4-diethylimidazole cation, and 1,2,4-triethylimidazole cation.

The imidazole-containing cation (A) can be produced, for example, by reacting two kinds of aldehydes and two kinds of amines dropwise and purifying by distillation.

The anion (B) is represented by general formula (2).

[In formula (2), R5 and R7 are groups in which proton-donating substituents release protons, and they may be the same or different, and R5 and R7 in the same molecule are It combines with silicon atoms to form a chelate structure. R6 is an organic group that bonds with R5 and R7. R9 and R11 are groups in which a proton-donating substituent releases protons, and R9 and R11 in the same molecule are bonded to a silicon atom to form a chelate structure. R10 is an organic group that bonds with R9 and R11. R6 and R10 may be the same or different, and R5, R7, R9 and R11 may be the same or different. R8 represents an organic group having a substituted or unsubstituted aromatic ring or a substituted or unsubstituted heterocyclic ring, or a substituted or unsubstituted aliphatic group. ]

Proton donors for the proton-donating substituents R5 to R7 and R9 to R11 in formula (2) include catechol, 1,2-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, and 2,2'-biphenol. , 2,2′-binaphthol, pyrogallol, trihydroxybenzoic acid, gallate, 2,3,4-trihydroxybenzophenone, salicylic acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, chloranil Acid, phenolic compound selected from the group of tannic acid; 2-hydroxybenzyl alcohol, 1,2-cyclohexanediol, 1,2-propanediol, alcoholic compound selected from the group of glycerin; or urea, 1-methyl Urea, 1,3-dimethylurea, 1,3-diaminourea, 1,3-dimethylolurea, allophaneamidethiourea, 1-methylthiourea, 1,3-dimethylthiourea, thiosemicarbazide, thiocarbohydrazide, 4- Urea-based compounds selected from the group of methylthiosemicarbazide and guanylthiourea are preferred. Particularly preferred are the above alcohol compounds. From the viewpoint of fluidity, R8 is preferably a phenyl group or an alkyl group.

As a method for synthesizing the imidazole salt (S), for example, a method of reacting the cation (A) having imidazole, alkoxysilanes, and the proton donor capable of forming a chelate bond with a silicon atom at a constant ratio. are mentioned.

Here, examples of the alkoxysilanes include phenyltrimethoxysilane, phenyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, hexyltrimethoxysilane, and hexyltriethoxysilane. , and tetraethoxysilane.

The melting point of the imidazole salt (S) of the present invention is 170° C. or lower, but the lower limit is preferably -50° C. or higher from the viewpoint of ease of handling. More preferably, the melting point has an upper limit of 130°C or lower and a lower limit of -30°C or higher. More preferably -20°C to 100°C, most preferably 0°C to 70°C. If it exceeds 170°C, the viscosity increases and the fluidity deteriorates.

The epoxy resin composition of the present invention is characterized by comprising an epoxy resin (E), a compound (P) having two or more phenolic hydroxyl groups in one molecule, and the epoxy resin curing accelerator (Q). .

Epoxy resin (E) is generally a monomer, oligomer, or polymer having two or more epoxy groups in one molecule, and its molecular weight and molecular structure are not particularly limited. Novolac type epoxy resin, hydroquinone type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, stilbene type epoxy resin, triphenolmethane type epoxy resin, alkyl-modified triphenolmethane type epoxy resin, triazine nucleus containing epoxy resin, dicyclopentadiene-modified phenol type epoxy resin, phenol aralkyl type epoxy resin having a phenylene and/or biphenylene skeleton, naphthol type epoxy resin, naphthalene type epoxy resin, naphthol aralkyl type epoxy resin having a phenylene and/or biphenylene skeleton etc., and these may be used singly or in combination.

Examples of the epoxy resin (E) include those manufactured by DIC Corporation: HP-4032, HP-4700, HP-7200, HP-820, HP-4770, HP-5000, EXA-850, EXA-830, EXA- 1514, EXA-4850 series; manufactured by Nippon Kayaku Co., Ltd.: EPPN-201L, BREN-105, EPPN-502H, EOCN-1020, NC-2000-L, XD-1000, NC-7000L, NC-7300L, EPPN -501H, NC-3000; XY-4000 manufactured by Mitsubishi Chemical Corporation.

Compounds (P) having two or more phenolic hydroxyl groups in one molecule are general monomers, oligomers, and polymers having two or more phenolic hydroxyl groups in one molecule, and their molecular weight and molecular structure are not particularly limited. but for example, phenol novolak resin, cresol novolak resin, triphenolmethane type phenol resin, terpene-modified phenol resin, dicyclopentadiene-modified phenol resin, phenol aralkyl resin having a phenylene and/or biphenylene skeleton, phenylene and/or biphenylene skeleton Naphthol aralkyl resins, bisphenol compounds and the like having

Examples of the compound (P) having two or more phenolic hydroxyl groups include Meiwa Kasei Co., Ltd.: HF series, MEH-7500 series, MEH-7800 series, MEH-7851 series, MEH-7600 series, MEH-8000 Series: TriP-PA, BisP-TMC, BisP-AP, OC-BP, TekP-4HBPA, CyRS-PRD4 manufactured by Honshu Chemical Industry Co., Ltd., and the like.

By curing the epoxy resin composition of the present invention, a cured epoxy resin is finally obtained. The amount of the epoxy resin curing accelerator (Q) is adjusted according to the reactivity of the epoxy resin and the curing agent, and is usually 1 to 25 parts by weight, preferably 2 to 20 parts by weight, per 100 parts by weight of the epoxy resin. is. The optimum compounding amount may be set according to the required curing properties.

The compounding ratio of the epoxy resin (E) and the compound (P) having two or more phenolic hydroxyl groups in one molecule is also not particularly limited, but the compound ( It is preferably used so that the phenolic hydroxyl group of P) is 0.5 to 2 equivalents, more preferably 0.7 to 1.5 equivalents. As a result, the various properties of the epoxy resin composition are further improved while maintaining a suitable balance of the various properties.

The epoxy resin composition of the present invention preferably further contains an inorganic filler (H).
When the epoxy resin composition of the present invention is used for encapsulation of electronic parts such as semiconductor elements, it is added to the epoxy resin composition for the purpose of improving the solder resistance of the resulting semiconductor device. The type is not particularly limited, and those commonly used for sealing materials can be used.

In addition, the content of the inorganic filler (H) is not particularly limited, but per 100 parts by weight of the total amount of the epoxy resin (E) and the compound (P) having two or more phenolic hydroxyl groups in one molecule, It is preferably 200 to 2400 parts by weight, more preferably 400 to 1400 parts by weight. The content of the inorganic filler (H) can be used even outside the above range, but if it is less than the above lower limit, the reinforcing effect of the inorganic filler (H) may not be sufficiently exhibited. If the content of H) exceeds the above upper limit, the fluidity of the epoxy resin composition is reduced, and there is a risk of insufficient filling during molding of the epoxy resin composition (for example, during the manufacture of semiconductor devices). be.

The epoxy resin composition of the present invention preferably further contains other functional compounds (functional additives).

Functional additives include, for example, 3-glycidyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane and phenyltrimethoxysilane. Coupling agents represented by alkoxysilanes such as , titanate esters and aluminate esters; colorants such as carbon black; brominated epoxy resins, antimony oxide, aluminum hydroxide, magnesium hydroxide, zinc oxide and phosphorus low stress components such as silicone oil and silicone rubber; natural waxes such as carnauba wax, synthetic waxes such as polyethylene wax; higher fatty acids such as stearic acid and zinc stearate, metal salts of the higher fatty acids and Release agents such as paraffin; ion catchers such as magnesium, aluminum, titanium, and bismuth; various additives such as bismuth antioxidants; modified compounds such as benzoxazine, cyanate ester, and bismaleimide that improve heat resistance. .

The epoxy resin composition of the present invention can also contain resin components other than the epoxy resin (E) and the compound (P) having two or more phenolic hydroxyl groups in one molecule.
Other resin components include epoxy resins using acid anhydrides, polyimide resin components, nanocomposite components, cyanate ester resin components, and the like.

Other functional compounds are described in "Review Epoxy Resin Vol. 1", "Review Epoxy Resin Vol. 1", Epoxy Resin Technology Association, 2003; Electronics Mounting Society Journal, 14, 204, 2011; journal of Applied Polymer Science , 109, 2023-2028, 2008; Polymer Preprints, Japan, 60, 1K19, 2011; Neckwork Polymer, 33, 130, 2012; Polym. Int. 54, 1103-1109, 2005; Journal of Applied Polymer Science, 92, 2375-2386, 2004; Neckwork Polymer, 29, 175, 2008; 6), 217, 2009.

The epoxy resin composition of the present invention is obtained by uniformly mixing the above components and, if necessary, other additives using a mixer. It can also be obtained by heating and kneading using a kneader such as a twin-screw extruder, followed by cooling and pulverization. In addition, when the epoxy resin composition obtained above is in the form of powder, in order to improve workability in use, it can be used after being pressurized into tablets by a press or the like.

The epoxy resin composition of the present invention can be used, for example, when various electronic components such as semiconductor elements are encapsulated to manufacture semiconductor devices, conventional methods such as transfer molding, compression molding and injection molding can be used. Curing molding may be performed by a molding method.

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples, but the present invention is not limited to these. Hereinafter, unless otherwise specified, % means % by weight, and part means part by weight.
Details of the epoxy resin curing accelerator (hereinafter referred to as curing accelerator) used in Examples and Comparative Examples are shown below.

<Method for producing imidazole salt (S-1)>
240 parts of triethoxyphenylsilane (manufactured by Tokyo Chemical Industry Co., Ltd.) and 252 parts of pyrogallol (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to 1,000 parts of methanol in a three-neck glass round-bottomed flask equipped with a dropping funnel and a reflux tube. After dissolving in parts, 144 parts of 2-phenylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise to obtain an imidazole salt represented by the following formula (s1). Purification was performed by filtering, washing with methanol several times, and drying to obtain an imidazole salt (S-1).

<Method for producing imidazole salt (S-2)>
The imidazole salt ( S-2) was obtained.

<Method for producing imidazole salt (S-3)>
Represented by the following formula (s3) by using 110 parts of 2-ethyl-4-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) instead of 2-phenylimidazole in the method for producing imidazole salt (S-1). An imidazole salt (S-3) was obtained.

<Method for producing imidazole salt (S-4)>
By using 96 parts of 1,2-dimethylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) instead of 2-phenylimidazole in the method for producing imidazole salt (S-1), imidazole represented by the following formula (s4) Salt (S-4) was obtained.

<Method for producing imidazole salt (S-5)>
By using 206 parts of trimethoxyhexylsilane (manufactured by Tokyo Chemical Industry Co., Ltd.) instead of triethoxyphenylsilane in the method for producing imidazole salt (S-1), and removing the solvent with an evaporator instead of filtering. , an imidazole salt (S-5) represented by the following formula (s5) was obtained.

<Production Example of Salt (S'-1) Used in Comparative Example>

<Method for producing salt (S'-1)>
A stirring autoclave was charged with 108 parts of dimethyl carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.) and 500 parts of methanol as a solvent. After reacting for 80 hours, a methanol solution of the intermediate DBU derivative methyl carbonate (S'-1-1) was obtained. 240 parts of triethoxyphenylsilane (manufactured by Tokyo Chemical Industry Co., Ltd.), 252 parts of pyrogallol (manufactured by Tokyo Chemical Industry Co., Ltd.), and sodium After adding 30 parts of a 28% methanol solution of methoxide (manufactured by Tokyo Kasei Kogyo Co., Ltd.) into 900 parts of methanol, a salt represented by the following formula (s'1) was obtained. Purification was performed by filtering, washing with methanol several times, and drying to obtain a salt (S'-1).

<Method for producing salt (S'-2)>
A stirring autoclave was charged with 216 parts of dimethyl carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.) and 500 parts of methanol as a solvent, and 84 parts of 2-methyl-2-imidazoline (manufactured by Tokyo Chemical Industry Co., Ltd.) was added thereto. The mixture was charged and reacted at a reaction temperature of 125° C. for 80 hours to obtain a methanol solution of the intermediate imidazolinium methyl carbonate (S′-2-1). Thereafter, a salt (S'-2) represented by the following formula (s'2) was obtained in the same manner as the salt (S'-1) production method.

<Method for producing salt (S'-3)>
419 parts of tetraphenylphosphonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to 1,000 A salt (S'-3) represented by the following formula (s'3) was obtained by using 2,3-dihydronaphthalene instead of pyrogallol.

Example 1
Epoxy resin 1: Nippon Kayaku Co., Ltd., trade name NC3000 (softening point 58 ° C., epoxy equivalent 273) 100 parts; Phenol resin-based curing agent 1: Meiwa Kasei Co., Ltd., trade name MEH-7500 (softening point 110° C., hydroxyl equivalent weight 97) 33 parts; 7 parts of the epoxy resin curing accelerator obtained in each of the above examples; After uniformly pulverizing and mixing 4 parts of antimony trioxide and 1 part of carbon black, the mixture was melt-kneaded for 10 minutes using a hot roll at 130° C., cooled and pulverized to obtain a sealing material. The obtained epoxy resin composition was evaluated by the following methods. Table 2 shows the results. Table 1 shows the melting points of curing accelerators.

<Performance evaluation>
<Liquidity (flow value)>
For the obtained epoxy resin composition, the flow value (unit: cm) of spiral flow at 175° C. (70 kg/cm 2 ) was measured according to the method of EMMI 1-66 and used as an index of fluidity. A higher flow value indicates better fluidity.

<Gel time>
Using a Curastometer Model 7 (manufactured by A&D Co., Ltd., trade name), under the conditions of a temperature of 175 ° C., a resin die P-200 and an amplitude angle of ± 1/4 °, each of the above epoxy resins The curing torque was measured for the composition, and the gel time (in seconds) was defined as the point at which the curing torque rises.

<Curability (curing torque)>
In the measurement with the above curastometer, the value of curing torque (unit: kgf·cm) 300 seconds after the start of measurement was used as an index of curability (strength and hardness at demolding).
<Melting point>
A sample was placed on a test stand made of SUS, the temperature was gradually increased, and the temperature at which the sample melted was visually observed.
<Chlorine content, amount of ions>
The cured sample after the curability measurement was pulverized with a mixer, put into 30 g of deionized water, heated at 170° C. for 30 hours, and the chloride ion content and ion amount in the extracted water were calculated. Ion chromatography was used to determine the chloride ion content, and the electrical conductivity of the extract was substituted for the ion content.

Examples 2-5, Comparative Examples 1-4
Table 1 shows the melting points of curing accelerators. Further, an epoxy resin composition was obtained in the same manner as in Example 1 according to the formulation shown in Table 2, and evaluated in the same manner as in Example 1. Table 2 shows the results.
Raw materials used in other than Example 1 are shown below.

Epoxy resin 2: manufactured by Mitsubishi Chemical Corporation, trade name XY-4000H (softening point 80°C, epoxy equivalent 192)

Phenolic resin-based curing agent 2: Meiwa Kasei Co., Ltd., trade name MEH-7851SS (softening point 67 ° C., hydroxyl equivalent 203)

Curing accelerator 1: manufactured by Tokyo Chemical Industry Co., Ltd., 2-phenylimidazole

As is clear from Table 2, in the epoxy resin compositions of Examples 1 to 5 of the present invention, the flow value of the sealant after melt-kneading is large and the fluidity is excellent, and the curing is excellent compared to the comparative examples. It can be seen that the torque is high and the curability is excellent. Furthermore, as a measure of reliability at high temperature, it can be seen that the chloride ion content and electrical conductivity after extraction are also low.

On the other hand, Comparative Examples 1 and 2 have low curing torque, which indicates curability, and high electrical conductivity, which indicates high temperature reliability. Comparative Example 3 has a short flow value, which indicates fluidity, and a high electrical conductivity, which indicates high-temperature reliability. Comparative Example 4 has a low curing torque, which indicates curability, and a high chloride ion content, which indicates high temperature reliability. Thus, the comparative examples do not satisfy all of the fluidity, curability and high-temperature reliability as the examples.

The epoxy resin curing accelerator (Q) of the present invention provides an epoxy resin composition suitable for semiconductor devices with high reliability at high temperatures while maintaining both the curability and fluidity of the epoxy resin composition. It is suitable for manufacturing epoxy resin-based encapsulants for electronic parts.

Claims (5)

An imidazole salt (S) consisting of a cation (A) having imidazole represented by the general formula (1) and an anion (B) represented by the general formula ( 2-1) or (2-2) , the imidazole salt An epoxy resin curing accelerator (Q), wherein (S) has a melting point of 170° C. or lower.

[In Formula (1), R1, R2, R3, and R4 are the same or different and each represents a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, or a hydroxymethyl group. ]

[ In formulas (2-1) and (2-2), R8 represents an unsubstituted aromatic group or an unsubstituted aliphatic group . ] The epoxy resin curing accelerator (Q) according to claim 1 , wherein the imidazole salt (S) has a melting point of 130°C or less. 3. The epoxy resin curing accelerator (Q) according to claim 1 or 2, wherein R2 in general formula (1) is a hydrogen atom. An epoxy resin composition containing the epoxy resin curing accelerator (Q) according to any one of claims 1 to 3 , an epoxy resin (E), and a compound (P) having two or more phenolic hydroxyl groups in one molecule. . A cured product obtained by curing the epoxy resin composition according to claim 4 .