JP7314489B2 - Phenolic resin, method for producing the same, epoxy resin composition and cured product thereof - Google Patents

Description

The present invention relates to a phenolic resin and a method for producing the same. The present invention also relates to an epoxy resin composition containing the phenol resin and a cured product of the epoxy resin composition. Furthermore, the present invention relates to a semiconductor device having the cured product.

Epoxy resin compositions are widely used in the fields of electrical and electronic parts, structural materials, adhesives, coatings, etc. due to their workability and the excellent electrical properties, heat resistance, adhesiveness, moisture resistance, etc. of their cured products.
In recent years, semiconductor packages have become lighter, thinner, shorter and smaller. Along with this, the package has come to be exposed to high temperatures due to heating in the reflow process of board mounting. If the package absorbs moisture, cracks will occur during the reflow process, affecting the reliability of the semiconductor. Therefore, development of a sealing material having excellent solder heat resistance (reflow resistance) is desired. Therefore, as a sealing material, in addition to low water absorption, a sealing material with low thermal stress and high adhesion is required. Conventionally, an epoxy resin composition using a phenol aralkyl resin as a curing agent has been used as one of such sealing materials. However, an epoxy resin composition using a phenol aralkyl resin as a curing agent has high water absorption and insufficient solder heat resistance (reflow resistance). Moreover, Patent Document 1 discloses an epoxy resin composition in which the curing agent is a cresol aralkyl resin.

JP 2010-100678 A

However, the epoxy resin composition using the cresol aralkyl resin described in Patent Document 1 as a curing agent has room for improvement in curability, moldability (sometimes referred to as moldability in the sense of moldability in molding), flame retardancy, thermal elastic modulus, and the like.

An object of the present invention is to provide a phenolic resin that gives a cured product obtained when used as a curing agent for an epoxy resin, having low water absorption, a low elastic modulus under heat, and excellent curability, moldability, and flame retardancy. Another object of the present invention is to provide an epoxy resin composition containing the phenolic resin and having excellent solder heat resistance (reflow resistance) and a cured product thereof. A further object is to provide a semiconductor device having the cured product.

（一般式（１）中、Ｒは、炭素数１以上６以下の直鎖状若しくは分枝状のアルキル基又は炭素数１若しくは２のアルコキシ基を表し、それぞれ同一又は異なっていてもよい。ｎは、０以上１０以下の整数を表す。） The present invention relates to the following matters.
1. A phenolic resin represented by the following general formula (1) and having a weight average molecular weight in the range of 1200 or more and 1600 or less by gel permeation chromatography (GPC).

(In the general formula (1), R represents a linear or branched alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 or 2 carbon atoms, which may be the same or different. n represents an integer of 0 to 10.)

（一般式（２）中、Ｒは、炭素数１以上６以下の直鎖状若しくは分枝状のアルキル基又は炭素数１若しくは２のアルコキシ基を表す。）

（一般式（３）中、Ｘは、ハロゲン原子又はアルコキシ基を示す。） 2. A method for producing a phenolic resin, wherein a phenolic compound represented by the following general formula (2) and an aromatic compound represented by the following general formula (3) are polycondensed at a reaction temperature of 100° C. or higher and 180° C. or lower with or without an acid catalyst.

(In general formula (2), R represents a linear or branched alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 or 2 carbon atoms.)

(In general formula (3), X represents a halogen atom or an alkoxy group.)

3. An epoxy resin composition containing a phenolic resin and an epoxy resin, a cured product thereof, and a semiconductor device containing the cured product.

According to the present invention, it is possible to obtain a phenolic resin in which the cured product obtained when used as a curing agent for epoxy resins has low water absorption, a low elastic modulus under heat, and excellent curability, moldability, and flame retardancy. Also, an epoxy resin composition containing the phenol resin and having excellent solder heat resistance (reflow resistance) and a cured product thereof can be obtained. Furthermore, a semiconductor device having the cured product can be obtained.

FIG. 1 is a chart of gel permeation chromatography (GPC) analysis of phenolic resin B obtained in Example 2. FIG. 2 is a chart of high performance liquid chromatography (HPLC) analysis of phenolic resin B obtained in Example 2. FIG.

[Phenolic Resin]
The phenolic resin of the present invention is an o-substituted phenolic aralkyl resin represented by the general formula (1).

The phenolic resin of the present invention has a substituent R at the ortho-position (o-position) to the phenolic hydroxyl group. Therefore, the cured product of the epoxy resin composition using the phenolic resin of the present invention as a curing agent has excellent water absorption and moldability, and excellent solder heat resistance (reflow resistance).

In the phenolic resin of the present invention, the substituent R is a linear or branched alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 or 2 carbon atoms. Examples of linear or branched alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, cyclopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-hexyl group and isohexyl group. The alkoxy group having 1 or 2 carbon atoms includes a methoxy group and an ethoxy group. From the viewpoint of reducing the water absorption of the cured product of the epoxy resin composition using the phenol resin of the present invention as a curing agent and improving the moldability and curability, the substituent R is preferably a methyl group, an ethyl group, a methoxy group, or an ethoxy group, more preferably a methyl group or a methoxy group, and most preferably a methyl group.

In the phenol resin of the present invention, n is the number of repetitions and represents an integer of 0 or more and 10 or less. The phenolic resin of the present invention is an assembly of molecules with various repeating numbers n. This collection has an average value n' of n. Here, the average value n′ is a value such that the weight average molecular weight (Mw) described later is 1200 or more and 1600 or less, more preferably a value such that the weight average molecular weight (Mw) is 1200 or more and 1500 or less, and still more preferably a value such that the weight average molecular weight (Mw) is 1300 or more and 1500 or less.

In the phenolic resin of the present invention, the weight average molecular weight (Mw) in terms of standard polystyrene by gel permeation chromatography (GPC) measurement is 1200 or more and 1600 or less, more preferably 1200 or more and 1500 or less, still more preferably 1300 or more and 1500 or less. When the weight-average molecular weight (Mw) is within the above range, the cured product of the epoxy resin composition using the phenolic resin of the present invention as a curing agent has a low thermal elastic modulus, excellent solder heat resistance (reflow resistance), exhibits high flame retardancy, prevents blocking of the phenolic resin, and has good handleability.
The weight-average molecular weight (Mw) can be measured, for example, by the method described in Examples below.

A cured product of an epoxy resin using the phenolic resin of the present invention as a curing agent has a low thermal elastic modulus (storage elastic modulus at 270°C). The thermal elastic modulus (storage elastic modulus at 270° C.) is preferably 0.2 GPa or more and 0.7 GPa or less, more preferably 0.3 GPa or more and 0.6 GPa or less. When the storage elastic modulus at 270° C. of the cured product is within the above range, excellent solder heat resistance (reflow resistance) and high flame retardancy can be achieved.
The storage elastic modulus can be measured, for example, by the method described in Examples below.

In the phenol resin of the present invention, the softening point of the phenol resin of the present invention is preferably higher than 60° C. and 80° C. or lower, more preferably 61° C. or higher and 70° C. or lower, from the viewpoint of suppressing the blocking of the phenol resin itself of the present invention, improving the handleability when it is made into an epoxy resin composition, lowering the thermal elastic modulus of the cured product of the epoxy resin composition, and making it excellent in flame retardancy.
The softening point can be measured, for example, by the method described in Examples below.

The phenolic resin represented by the general formula (1) preferably has a hydroxyl equivalent weight of 180 g/eq or more and 190 g/eq or less, and particularly preferably 180 g/eq or more and 185 g/eq or less.

In the phenol resin of the present invention, from the viewpoint of improving the moldability and curability of the cured product of the epoxy resin composition using the phenol resin of the present invention as a curing agent, the melt viscosity of the phenol resin of the present invention at 150 ° C. is preferably 0.05 Pa s or more and 0.2 Pa s or less, and more preferably 0.05 Pa s or more and 0.1 Pa s or less.
The melt viscosity at 150° C. can be measured, for example, by the method described in Examples below.

The phenolic resin of the present invention has a structure in which a benzene ring having one hydroxyl group and one substituent R at the o-position (ortho position) with respect to the hydroxyl group is linked by a xylylene group ( _--CH.sub.2 -- _{C.sub.6H.sub.4 -- CH.sub.2--} ). Examples of the xylylene group (-CH ₂ -C ₆ H ₄ -CH ₂ -) which is a bridging group include 1,2-xylylene group (also referred to as o-xylylene group), 1,3-xylylene group (also referred to as m-xylylene group), and 1,4-xylylene group (also referred to as p-xylylene group).

One of preferred embodiments of the phenolic resin of the present invention is represented by the following general formula (4).

（一般式（４）中、Ｒ及びｎは前記一般式（１）における定義と同じである。）

(In the general formula (4), R and n are the same as defined in the general formula (1).)

In the phenol resin of the present invention, the ratio of the component where n = 0 in the general formula (1) (hereinafter also referred to as "binuclear entity (n = 0)" or simply "binuclear entity" based on the number of phenols) and the component where n = 1 in general formula (1) (hereinafter also referred to as "trinuclear entity (n = 1)" or simply "trinuclear entity") suppresses blocking of the phenol resin itself of the present invention, improves the handling properties when made into an epoxy resin composition, and improves the heat treatment of the cured product of the epoxy resin composition. It is preferably within a specific range from the viewpoint of lowering the elastic modulus and improving flame retardancy. Specifically, the ratio of binuclear nuclei in the phenol resin of the present invention is preferably 15.0% by weight or more and 25.0% by weight or less, more preferably 20.0% by weight or more and 25.0% by weight or less, and most preferably 22.0% by weight or more. In the phenolic resin of the present invention, the trinuclear content is preferably 15.0% to 22.0% by weight, more preferably 18.0% to 21.0% by weight, and most preferably 20.0% to 21.0% by weight. The proportions of binuclear (n=0) and trinuclear (n=1) can be measured, for example, by the method described in Examples below.

In the dinuclear (n=0) component of the phenolic resin of the present invention, the bonding position of the xylylene group ( _--CH.sub.2 -- _{C.sub.6H.sub.4} -- _CH.sub.2-- ) to the benzene ring having one hydroxyl group (phenolic hydroxyl group) and one substituent R at the o-position ( _ortho -position) with respect to the hydroxyl group is such that the ratio of the ortho-position bond to the para-position bond (ortho/para ratio) with respect to the phenolic hydroxyl group is preferably more than 1.05 and 1.20 or less. more preferably 1.06 or more and 1.15 or less, and most preferably 1.06 or more and 1.10 or less.
It is preferable that the ratio of the ortho-position bond to the para-position bond to the phenolic hydroxyl group (ortho/para ratio) is within the above range from the viewpoint of suppressing the blocking of the phenolic resin of the present invention itself, improving the handleability when made into an epoxy resin composition, and lowering the thermal elastic modulus of the cured product of the epoxy resin composition and making it excellent in flame retardancy.
The (ortho/para ratio) of the binuclear (n=0) component can be measured, for example, by the method described in Examples below.

A phenolic resin having the above weight average molecular weight (Mw), hydroxyl equivalent, softening point, ratio of binuclear and trinuclear nuclei, and ortho/para ratio can be obtained by a suitable production method described later.
[Method for producing phenolic resin]
A preferred method for producing the phenolic resin of the present invention is described below.

<Phenol compound>
In this production method, a phenol compound represented by the following general formula (2) and an aromatic compound represented by the following general formula (3) are polycondensed at a reaction temperature of 100° C. or higher and 180° C. or lower in the presence or absence of an acidic catalyst to obtain the phenolic resin of the present invention.

The phenol compound used in the method for producing a phenol resin of the present invention is represented by the following general formula (2).

（一般式（２）中、Ｒは、前記一般式（１）における定義と同じである。）

(In general formula (2), R has the same definition as in general formula (1).)

Examples of the phenol compound represented by formula (2) are not particularly limited, but include 2-methylphenol, 2-ethylphenol, 2-propylphenol, 2-sec-butylphenol, 2-tert-butylphenol, 2-methoxyphenol, 2-ethoxyphenol and the like. Preferred are 2-methylphenol and 2-methoxyphenol, and more preferred is 2-methylphenol.
These phenol compounds can be used individually by 1 type or in combination of 2 or more types.

<Aromatic compound>
The aromatic compound used in the method for producing a phenolic resin of the present invention is represented by the following general formula (3).

（一般式（３）中、Ｘは、ハロゲン原子はアルコキシ基を示す。）

(In general formula (3), X represents an alkoxy group as a halogen atom.)

Examples of the aromatic compound represented by the general formula (3) are not particularly limited, but 1,2-bis(chloromethyl)benzene, 1,2-bis(bromomethyl)benzene, 1,2-bis(methoxymethyl)benzene, 1,2-bis(ethoxymethyl)benzene, 1,3-bis(chloromethyl)benzene, 1,3-bis(bromomethyl)benzene, 1,3-bis(methoxymethyl)benzene, 1,3-bis(ethoxymethyl)benzene, 1,4-bis(chloromethyl). Benzene, 1,4-bis(bromomethyl)benzene, 1,4-bis(methoxymethyl)benzene, 1,4-bis(ethoxymethyl)benzene, and the like. Preferred are 1,4-bis(chloromethyl)benzene, 1,4-bis(bromomethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(ethoxymethyl)benzene, and more preferred are 1,4-bis(chloromethyl)benzene and 1,4-bis(methoxymethyl)benzene.
These aromatic compounds can be used individually by 1 type or in combination of 2 or more types.

<Molar ratio (a1/a2) between phenol compound (a1) and aromatic compound (a2)>
In the method for producing a phenolic resin, when the phenolic compound (a1) represented by the general formula (2) and the aromatic compound (a2) represented by the general formula (3) are reacted, the amount of the phenolic compound (a1) is preferably 1.8 mol or more and 2.3 mol or less, more preferably 1.9 mol or more and 2.2 mol or less, relative to 1 mol of the aromatic compound (a2).
By adopting the production method of the present invention and setting the molar ratio of the phenol compound (a1) and the aromatic compound (a2) within the above range, the weight average molecular weight (Mw) of the phenol resin of the present invention can be set within a predetermined range.

<Acid catalyst>
In the method for producing a phenol resin, the polycondensation reaction can be carried out under an acidic catalyst or without a catalyst. When an acid catalyst is used, the acid catalyst is not particularly limited, and known catalysts such as hydrochloric acid, oxalic acid, sulfuric acid, phosphoric acid and p-toluenesulfonic acid can be used alone or in combination of two or more. On the other hand, carrying out without a catalyst is preferable in that the ionic impurities in the phenol resin to be obtained can be reduced.

<Reaction temperature>
In the method for producing a phenolic resin, the reaction temperature of the polycondensation reaction is 100° C. or higher and 180° C. or lower, preferably 130° C. or higher and 170° C. or lower. By setting the reaction temperature within the above range, the bonding position of the (xylylene group (-CH ₂ -C ₆ H ₄ -CH ₂ -) can be within the above range in terms of the ratio between the ortho-position bond and the para-position bond (ortho/para ratio) with respect to the phenolic hydroxyl group, and when the phenol resin of the present invention is used as a curing agent for an epoxy resin composition, the curability of the epoxy resin composition can be excellent.
<Reaction solvent>
In the method for producing phenolic resin, a solvent may be used for the purpose of facilitating the reaction. Examples of the solvent at this time include water and lower alcohols (C1-C6 aliphatic alcohols). Specific examples include methanol, ethanol, propanol, butanol, pentanol, hexanol and cyclohexanol. The amount of the solvent used is not particularly limited, but it is preferable to coexist with the phenol compound in an amount of 50% by mass or less, more preferably less than 30% by mass, and even more preferably less than 10% by mass, in view of solvent removal costs and recovery costs. On the other hand, it is preferable that the amount of the solvent is 0.1% by mass or more based on the phenolic compound in order to sufficiently exhibit the effect of using the solvent.

<Reaction time>
In the method for producing a phenolic resin, the reaction time is 0.5 to 20 hours, preferably 1 to 15 hours. By setting the reaction time to 0.5 hours, particularly 1 hour or longer, the condensation can be completed more reliably. Further, even if the reaction time is longer than 20 hours, the resulting phenolic resin is not adversely affected, but the condensation is completed and there is no merit. The reaction can be carried out simply by charging all the raw materials at once and then gradually raising the temperature to a predetermined reaction temperature, without violent heat generation during the process.

<Post-processing>
In the method for producing a phenolic resin, when a halogenomethyl aromatic compound is used as the raw material aromatic compound, hydrogen halide gas is generated as the reaction progresses. This gas can be removed out of the system by passing an inert gas such as nitrogen gas through it, or removed under reduced pressure. After the reaction, the phenolic resin of the present invention can be obtained by removing unreacted phenolic compounds and lower alcohols, and depending on the catalyst used, by a method such as distilling off water under reduced pressure.

[Epoxy resin composition and cured product thereof]
The epoxy resin composition of the present invention contains the phenolic resin of the present invention as an epoxy resin curing agent.

Examples of epoxy resins include epoxy resins having two or more epoxy groups in the molecule, such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, cresol novolac type epoxy resins, phenol novolak type epoxy resins, triphenol methane type epoxy resins, glycidyl ether type epoxy resins such as biphenyl type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, and halogenated epoxy resins. These epoxy resins may be used singly or in combination of two or more without any problem.
Preferred epoxy resins include glycidyl ether type epoxy resins, and particularly preferred epoxy resins include biphenyl type epoxy resins.

In the epoxy resin composition of the present invention, the phenol resin plays the role of a curing agent for the epoxy resin, and the epoxy resin composition of the present invention may contain a curing agent other than the phenol resin of the present invention. There is no particular limitation on the types of curing agents other than the phenolic resin of the present invention, and various curing agents can be used depending on the purpose of use of the epoxy resin composition. For example, phenolic resins, amine-based curing agents, amide-based curing agents, acid anhydride-based curing agents, etc. other than general formula (1) can be used.

In the epoxy resin composition of the present invention, the ratio of the phenol resin of the present invention to all the curing agents is preferably higher from the viewpoint of sufficiently increasing the thermal elastic modulus and molding shrinkage of the cured product obtained from the epoxy resin composition. Specifically, the proportion of the phenol resin of the present invention in all curing agents is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass.

In an epoxy resin composition using a phenol resin as a curing agent, the ratio of the number of hydroxyl group equivalents of the phenol resin to the number of epoxy group equivalents of the epoxy resin (number of hydroxyl group equivalents/number of epoxy group equivalents) is preferably in the range of 0.5 to 2.0, more preferably in the range of 0.8 to 1.2, and most preferably 1. The functional group equivalent number such as the hydroxyl group equivalent number and the epoxy group equivalent number can be obtained by B/A ([B×C/100]/A when the purity of the compound is C%), where A (g/eq) is the functional group equivalent and B (g) is the charged amount. That is, functional group equivalents such as hydroxyl group equivalents and epoxy group equivalents represent the molecular weight of a compound per functional group, and the number of functional group equivalents represents the number (number of equivalents) of functional groups per compound mass (amount charged).

As the curing accelerator, a known curing accelerator for curing an epoxy resin with a phenol resin can be used. Examples thereof include organic phosphine compounds and boron salts thereof, tertiary amines, quaternary ammonium salts, imidazoles and tetraphenylboron salts thereof, among which triphenylphosphine is preferred from the viewpoint of curability and moisture resistance. Further, in order to achieve higher fluidity, a heat-latent curing accelerator that exhibits activity upon heat treatment is preferred, and a tetraphenylphosphonium derivative such as tetraphenylphosphonium/tetraphenylborate is preferred. The ratio of addition of the curing accelerator to the epoxy resin composition can be the same as that in known epoxy resin compositions, for example, 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the epoxy resin.

The epoxy resin composition of the present invention can suitably contain organic or inorganic fillers. The filler is not particularly limited and may be selected depending on the application. Suitable examples include inorganic fillers such as amorphous silica, crystalline silica, alumina, calcium silicate, calcium carbonate, talc, mica, barium sulfate, and magnesium oxide. In particular, when the epoxy resin composition is used as a semiconductor sealing material, amorphous silica, crystalline silica, and the like are preferably used as the inorganic filler. When the inorganic filler is blended, the blending ratio in the epoxy resin composition [mass of the inorganic filler/mass of the epoxy resin composition containing the inorganic filler] is not limited, but is preferably about 30 to 98% by mass, preferably about 40 to 95% by mass. For applications such as use as a sealing material for semiconductor elements, the content is 60 to 95% by mass, preferably 70 to 95% by mass, more preferably 75 to 90% by mass, and even more preferably 80 to 90% by mass.
If the proportion of the inorganic filler is at least the lower limit of the above range, the water absorption of the cured epoxy resin composition can be reduced. Further, when the proportion of the inorganic filler is equal to or less than the upper limit of the above range, the epoxy resin composition for semiconductor encapsulation can easily obtain fluidity.

The epoxy resin composition of the present invention can further contain additives such as release agents, colorants, coupling agents, flame retardants and the like, which are used in ordinary epoxy resin compositions, and solvents.

The epoxy resin composition of the present invention can be suitably obtained by melting and mixing at least an epoxy resin and a phenol resin using a mixing device such as a twin-screw kneader or a twin roll, if necessary. The resulting epoxy resin composition is preferably pulverized by a pulverizer.

The epoxy resin composition of the present invention can be cured by heat treatment, for example, at 100° C. to 350° C. for 0.01 to 20 hours to obtain a cured product. When the temperature of the curing reaction is 100° C. or higher, curing can be easily performed, and when it is 350° C. or lower, deterioration of performance due to thermal decomposition can be prevented. Further, when the curing reaction time is set to 0.01 hour or more, the reaction can be easily completed, and when it is set to 20 hours or less, productivity can be improved.

The epoxy resin composition of the present invention can be blended with a high proportion of an inorganic filler, has excellent fluidity and moldability, and its cured product has excellent low water absorption, low elastic modulus (especially low elastic modulus under heat), and flame retardancy. Therefore, the epoxy resin composition of the present invention can be particularly suitably used as a semiconductor encapsulant in surface-mounted semiconductor devices.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[1] Synthesis and Evaluation of Phenolic Resin Analysis methods and evaluation methods used in the evaluation of the phenol resin are described below.
[Measurement of softening point]
Softening points were measured using the following equipment.
Equipment used: FP83HT dropping point/softening point measurement system manufactured by Mettler-Toledo, Inc. Measurement conditions: Temperature increase rate of 2° C./min. Measurement method: Measure according to the FP83HT manual. Specifically, a molten sample is poured into a sample cup and cooled to solidify. The cartridge is fitted above and below the cup filled with the sample and inserted into the furnace. The temperature at which the resin softens and flows down the orifice and the lower end of the resin passes through the optical path is detected as the softening point by a photocell.

[Measurement of melt viscosity]
The 150° C. melt viscosity was measured using the following equipment.
Equipment used: BROOKFIELD B-type viscometer DV2T Eiko Seiki Co., Ltd. Measurement temperature: 150°C
Measurement method: Set the furnace temperature of the Brookfield viscometer to 150°C, and weigh a predetermined amount of the sample into a cup.
A cup containing a weighed sample is placed in the furnace to melt the resin, and a spindle is placed from above. Rotate the spindle and read the melt viscosity when the displayed viscosity value becomes stable.

[Weight average molecular weight (Mw)]
The weight average molecular weight (Mw) was determined by polystyrene conversion using the following equipment.
Equipment used: Waters Alliance 2695 (gel permeation chromatographic analysis)
Column: SHODEX LF-804
Guard column: SHODEX KF-G
Dissolving liquid: tetrahydrofuran (THF)
Detector: UV meter, wavelength 254 nm
Flow rate: 1 mL/min Column oven temperature: 40°C

[Composition ratio of 2 and 3 nuclei]
By the following gel permeation chromatography (GPC) analysis, the area ratio (area %) of the resulting binuclear and trinuclear isomers was calculated using analysis software Empower3 Waters. In the calculation of the area ratio (area %) of the binuclear and trinuclear isomers, the linear portion before and after the peak was used as the baseline (0 value), and the peaks were divided by vertical cutting at the lowest point between the peaks of each component. The area ratio (area %) of the obtained binuclear and trinuclear bodies was defined as the composition ratio of the binuclear and trinuclear bodies in the phenolic resin.
Equipment used: Waters Alliance 2695 (gel permeation chromatography analysis) Columns: The following five SHODEX columns were connected in series from upstream to downstream in the following order.
KF-804 x 1
KF-803 x 1
KF-802.5 x 1
KF-802 x 1
KF-801 x 1
In addition, one KF-G manufactured by SHODEX was used as a guard column.
Column oven temperature: 40°C
Solvent: Tetrahydrofuran (THF)
Flow rate: 1.00 mL/min Detector: Waters 2487 Dual λ Absorbance Detector
Detection wavelength: 254 nm
As an example, a gel permeation chromatograph (GPC) analysis chart of the phenolic resin B obtained in Example 2 is shown in FIG. (1) and (2) in FIG. 1 are peaks derived from binuclear and trinuclear bodies, respectively.

[Ortho/para ratio of binuclear bodies]
It was analyzed by the following high performance liquid chromatography (HPLC), and the ortho/para ratio was obtained from the peak area of the binuclear isomer of the phenol resin according to the following formula.
Ortho/para ratio = [op peak area + (o-o' peak area) x 2]/[op peak area + (p-p' peak area) x 2]
Equipment used: RHPLC manufactured by JASCO Corporation
Column: Unifinepak C18
Eluent: Concentration change from water/acetonitrile (volume ratio 80/20) to water/acetonitrile (0/100) in 25 minutes Flow rate: 0.5 mL/min Wavelength: 280 nm
As an example, a chart of high performance liquid chromatography (HPLC) analysis of phenolic resin B obtained in Example 2 is shown in FIG. (1), (2), and (3) in FIG. 2 are the peaks derived from pp', op, and oo' forms, respectively.

[Hydroxyl equivalent]
It was determined by hydroxyl equivalent measurement according to JIS K0070.

[Resin blocking test]
The resin shown in Table 1 was placed in a bag provided with a silica barrier, sealed, and left at 20° C. for 24 hours. After that, the case where no binding between the resins was observed was evaluated as ◯, and the case where the resin was bound was evaluated as X.

[Example 1]
[Synthesis of Resin A]
216 g (2.0 mol) of 2-methylphenol, 160.70 g (0.91 mol) of α,α'-dichloro-p-xylene, and 1.08 g of water were placed in a 1000 mL glass flask equipped with a thermometer, a feed/distillation outlet, a condenser and a stirrer. While removing hydrochloric acid, the temperature was raised to 160° C., and the reaction was carried out at 160° C. for 4 hours. The generated hydrochloric acid was trapped in an alkaline aqueous solution in a glass washing bottle outside the system. After completion of the reaction, the reaction solution was cooled to 95° C., washed with water, heated to 160° C., and subjected to vacuum-steaming treatment to remove unreacted components, thereby obtaining 233 g of Resin A.

[Example 2]
[Synthesis of Resin B]
255 g of Resin B was obtained in the same manner as in Synthesis Example 1 except that the amount of α,α'-dichloro-p-xylene used in Example 1 was changed to 180.03 g (1.03 mol).

[Comparative Example 1]
[Synthesis of Resin C]
283 g of Resin C was obtained in the same manner as in Synthesis Example 1 except that the amount of α,α'-dichloro-p-xylene used in Example 1 was changed to 218.23 g (1.23 mol).

[Comparative Example 2]
[Synthesis of Resin D]
321 g of Resin D was obtained in the same manner as in Synthesis Example 1 except that the amount of α,α'-dichloro-p-xylene used in Example 1 was changed to 242.15 g (1.37 mol).

[Comparative Example 3]
[Synthesis of Resin E]
200 g of Resin E was obtained in the same manner as in Synthesis Example 1 except that the amount of α,α'-dichloro-p-xylene used in Example 1 was changed to 135.98 g (0.77 mol).

[Comparative Example 4]
[Synthesis of resin F]
432 g (4.0 mol) of 3-methylphenol, 168.35 g (0.95 mol) of α,α'-dichloro-p-xylene, and 7.66 g of water were placed in a 1000 mL glass flask equipped with a thermometer, a feed/distillate outlet, a condenser and a stirrer. After reacting at 100° C. for 1 hour, the internal temperature was raised to 130° C., and the reaction was further continued for 1 hour. Generated hydrochloric acid was trapped in an alkaline aqueous solution in a glass washing bottle outside the system. After completion of the reaction, the reaction solution was cooled to 95° C., washed with water, heated to 160° C., and subjected to vacuum-steaming treatment to remove unreacted components, thereby obtaining 268 g of Resin F.

[Comparative Example 5]
[Synthesis of Resin G]
432 g (4.0 mol) of 4-methylphenol, 186.07 g (1.05 mol) of α,α'-dichloro-p-xylene, and 8.47 g of water were placed in a 1000 mL glass flask equipped with a thermometer, a feed/distillation outlet, a condenser and a stirrer. After reacting at 100° C. for 1 hour, the internal temperature was raised to 130° C., and the reaction was further continued for 1 hour. Generated hydrochloric acid was trapped in an alkaline aqueous solution in a glass washing bottle outside the system. After completion of the reaction, the reaction solution was cooled to 95° C., washed with water, heated to 160° C., and subjected to vacuum-steaming treatment to remove unreacted components, thereby obtaining 281 g of Resin G.

[Comparative Example 6]
[Synthesis of Resin H]
282 g (3.0 mol) of phenol, 216.49 g (1.24 mol) of α,α'-dichloro-p-xylene, and 9.84 g of water were placed in a 1000 mL glass flask equipped with a thermometer, a feed/distillate outlet, a condenser and a stirrer. After reacting at 100° C. for 1 hour, the internal temperature was raised to 130° C., and the reaction was further continued for 1 hour. Generated hydrochloric acid was trapped in an alkaline aqueous solution in a glass washing bottle outside the system. After completion of the reaction, the reaction solution was cooled to 95° C., washed with water, heated to 160° C., and subjected to vacuum-steaming treatment to remove unreacted components, thereby obtaining 289 g of Resin H.

The evaluation results of Resins A to H are shown in Table 1 below.

[2] Preparation and Evaluation of Epoxy Resin Composition and Cured Product The analysis methods and evaluation methods used in the following evaluation of the epoxy resin composition and cured product will be described.

[Evaluation of moldability]
The epoxy resin composition was evaluated according to the following evaluation criteria.
◯: A compact having the same dimensions was obtained by transfer molding.
x: A molded article having the same dimensions could not be obtained by transfer molding.

[Measurement of liquidity]
The fluidity of the epoxy resin composition was measured using the following equipment.
Equipment used: 60t transfer molding machine manufactured by Takara Seisakusho Co., Ltd. Measurement conditions: mold temperature 175°C, injection pressure 6.8 MPa, holding time 120 seconds Measurement method: The epoxy resin composition was injected into a spiral flow measurement mold according to EMMI-1-66, and the flow length (cm) was measured.

[Measurement of curability]
Curability was measured using the following equipment.
Equipment used: JSR Curastometer WP type manufactured by Orientec Co., Ltd. Measurement conditions: 175°C
Measurement method: Gelling TSX, maximum torque, curing speed (tc(80)) were measured.

[Measurement of mechanical properties (flexural modulus and bending strength)]
The flexural modulus (GPa) and flexural strength (MPa) were measured according to JIS K 7171 using a test piece of the cured product of the epoxy resin composition as an object.
Specimen size: 80mm x 10mm x 4mm
[Measurement of water resistance (water absorption)]
The water absorption (%) was measured in accordance with JIS C6481 using a test piece of the cured product of the epoxy resin composition as an object.
Specimen size: diameter 50 mm x thickness 3 mm
[Measurement of combustibility]
A test piece of a cured product of the epoxy resin composition was used as a target and judged according to UL-94.
Specimen size: 127mm x 13mm x 1mm

[Measurement of storage modulus]
Storage elastic modulus was measured using the following equipment for a test piece of a cured product of the epoxy resin composition.
Equipment used: RSA-G2 manufactured by TA Instruments
Measurement conditions: 30° C. to 270° C., temperature increase rate of 3° C./min. Measurement method: Measurement was performed with a dynamic viscoelasticity measuring device using a test piece of epoxy resin cured material with dimensions of 40 mm × 12 mm × 1 mm, and the storage elastic modulus (GPa) at 30 ° C. and 270 ° C. was obtained.

[Examples 3 and 4] and [Comparative Examples 7 to 11]
Epoxy resin (YX-4000 manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 187 g/eq), filler (Kikuros MSR-2212 manufactured by Tatsumori Co., Ltd.), and curing accelerator (TPP manufactured by Hokko Chemical Industry Co., Ltd.) were blended in the proportions shown in Table 2, kneaded, cooled, and pulverized using a twin-screw kneader. By doing so, an epoxy resin composition was obtained. Using this epoxy resin composition, fluidity and curability were measured. Also, a test piece was prepared with a transfer molding machine using a 40Φ tablet prepared using the obtained epoxy resin composition. The moldability at this time was evaluated according to the above evaluation criteria. The test piece was post-cured at 180° C. for 8 hours to obtain a cured epoxy resin. Physical properties were evaluated using this cured epoxy resin.
These evaluation results are shown in Table 3.

As is clear from the results shown in Table 3, by using the phenolic resin of the present invention having a substituent at the 2-position and adjusted to a specific molecular weight, Comparative Example 11 using a phenolic resin having no substituent (corresponding to Curing Agent 5 in Patent Document 1) is superior in low water absorption and low thermal elastic modulus, and satisfies various physical properties such as moldability, flame retardancy, and heat resistance. On the other hand, in Comparative Examples 7 and 8 using the phenolic resin of Comparative Example 1 (corresponding to curing agent 4 in Patent Document 1) and Comparative Example 2 having a molecular weight exceeding the range of the present invention even if it has a substituent at the 2-position as in the present invention, the results of increasing the thermal elastic modulus and impairing the flame retardancy due to polymerization were obtained. As described above, the phenolic resin of Comparative Example 3, which has a substituent at the 2-position as in the present invention but has a molecular weight less than the range of the present invention, has poor handling properties because the phenolic resin itself easily binds to each other. In addition, the phenolic resins of Comparative Example 4 (corresponding to curing agent 2 in Patent Document 1) and Comparative Example 5 (corresponding to curing agent 3 in Patent Document 1) using a phenolic resin having a substituent at the 3- or 4-position different from that of the present invention were significantly reduced in moldability, and some epoxy resin cured products could not be obtained (Comparative Examples 9 and 10). Since it is necessary to increase the molecular weight in order to obtain a cured epoxy resin product, when the phenolic resins of Comparative Examples 4 and 5 are used, it is not possible to obtain a highly fluid epoxy resin composition due to the increase in viscosity and softening point.

As described above, the phenol resin of the present invention is easy to handle, and by using the phenol resin of the present invention, it is possible to obtain an epoxy resin composition having good moldability and cured physical properties, low water absorption, flame retardancy, and a low thermal elastic modulus, and a cured product thereof. Therefore, according to the present invention, it is possible to provide a phenolic resin which is excellent in reflow reliability and can be suitably used in an epoxy resin composition for a semiconductor sealing material.

Claims (8)

A phenolic resin represented by the following general formula (1), having a weight average molecular weight by gel permeation chromatography (GPC) in the range of 1200 or more and 1600 or less, a softening point of more than 60°C and 80°C or less, and a binuclear content of 20.0% or more and 25.0% or less by weight.

(In the general formula (1), R represents a linear or branched alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 or 2 carbon atoms, which may be the same or different. n represents an integer of 0 to 10.) The phenolic resin according to claim 1, which has a melt viscosity at 150°C of 0.2 Pa·s or less. The method for producing a phenolic resin according to claim 1, wherein a phenol compound represented by the following general formula (2) and an aromatic compound represented by the following general formula (3) are polycondensed at a reaction temperature of 100°C or higher and 180°C or lower in the presence of an acid catalyst or in the absence of a catalyst.

(In general formula (2), R represents a linear or branched alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 or 2 carbon atoms.)

(In general formula (3), X represents a halogen atom or an alkoxy group.) An epoxy resin composition comprising the phenolic resin according to claim 1 or 2 and an epoxy resin. 5. The epoxy resin composition of claim 4, further comprising a curing accelerator. 6. The epoxy resin composition according to claim 4, further comprising an inorganic filler. A cured product of the epoxy resin composition according to any one of claims 4 to 6. A semiconductor device comprising the cured product according to claim 7 .