JP6988091B2 - Epoxy resin composition, resin sheet, prepreg, metal foil with resin, metal substrate, and power semiconductor device - Google Patents

Description

The present invention relates to an epoxy resin composition, a resin sheet, a prepreg, a metal foil with a resin, a metal substrate, and a power semiconductor device.

Many electronic and electrical devices such as generators, motors, printed wiring boards, IC chips, etc. are configured to include conductors for conducting electricity and insulating materials. In recent years, with the miniaturization of these devices, the circuit density has increased and the amount of heat generated has increased. Therefore, how to dissipate heat in the insulating material has become an important issue.

As the insulating material used in these devices, a cured resin obtained by curing a thermosetting resin composition is widely used from the viewpoint of insulating property, heat resistance and the like. However, the thermal conductivity of a cured resin product is generally low, which is a major factor that hinders heat dissipation. Therefore, it is desired to develop a cured resin product having high thermal conductivity.

As a cured resin having high thermal conductivity, a cured epoxy resin composition having a mesogen group in its molecular structure has been proposed. In connection with this, a so-called mesogen group-containing epoxy resin having a biphenyl group, a phenol resin, and a resin composition for semiconductor encapsulation containing spherical alumina as essential components are disclosed (for example, Japanese Patent No. 2874089). reference). It has been reported that the cured product of this resin composition has excellent thermal conductivity.
Further, a resin composition containing an epoxy resin having a biphenyl group, a curing agent having a xanthene group, and a filler is disclosed (see, for example, Japanese Patent Application Laid-Open No. 2007-262398). It is reported that the cured product of this resin composition has excellent heat dissipation.

Further, a resin composition containing a mesogen group-containing epoxy resin, a phenol novolac resin containing a compound having a specific structural unit, and a filler is disclosed (see, for example, Japanese Patent Application Laid-Open No. 2013-234313). It has been reported that this resin composition has excellent storage stability before curing and high thermal conductivity after curing.

As a method for achieving high thermal conductivity, there is a method in which particles of high thermal conductive ceramics are filled in a resin composition as a filler to form a composite material. As the high thermal conductive ceramics, alumina, boron nitride, aluminum nitride, silica, magnesium oxide, silicon nitride, silicon carbide and the like are known.

Boron nitride has excellent storage stability and has both high thermal conductivity and electrical insulation. Therefore, in a cured product of a resin composition containing boron nitride particles, both high thermal conductivity and electrical insulation should be achieved. Can be done. However, since the boron nitride particles are scaly in shape, the thermal conductivity in the in-plane direction is higher than the thermal conductivity in the thickness direction. The large aspect ratio derived from the scaly shape of the boron nitride particles has become a problem for high thermal conductivity in the thickness direction of the resin composition.

In addition, since many of the functional groups required for bonding with the resin are present on the side surface of the boron nitride particles, the bondability with the resin is improved as compared with the alumina particles or the like in which the functional groups are present on the entire surface of the particles. Inferior. If the bondability between the resin and the filler is inferior, the thermal conductivity due to the molecular vibration of the resin and the filler decreases, and the thermal conductivity of the cured resin product decreases.

In view of the above problems, it is an object of the present invention to provide an epoxy resin composition having excellent thermal conductivity after curing, a resin sheet, a prepreg, a metal foil with a resin, a metal substrate, and a power semiconductor device using the epoxy resin composition.

The present inventors have arrived at the present invention as a result of diligent studies to solve the above problems. That is, the present invention includes the following aspects.

<1> Containing an epoxy resin monomer, a curing agent, and a filler,
The filler has a particle size D50 corresponding to a cumulative 50% from the small particle size side of the weight cumulative particle size distribution curve of 20 μm or more, and is a ratio of the length in the width direction to the length in the thickness direction of the primary particles. A first filler containing boron nitride particles or an aggregate of the boron nitride particles having an average value of the represented aspect ratios (length in the width direction / length in the thickness direction) of 30 or less, and the particle size D50. An epoxy resin composition comprising boron nitride particles having an aspect ratio of less than 10 μm and an average aspect ratio of 5 or less, or a second filler containing an aggregate of the boron nitride particles.

<2> Containing an epoxy resin monomer, a curing agent, and a filler,
The filler has at least a first peak above 20 μm and a second peak below 10 μm in the particle size distribution curve.
The first peak is composed of the first filler, and the first filler has an aspect ratio (length in the width direction / length in the width direction) expressed by the ratio of the length in the width direction to the length in the thickness direction of the primary particle. Contains boron nitride particles or aggregates of the boron nitride particles having an average value (length in the thickness direction) of 30 or less.
The second peak is composed of a second filler, and the second filler is an epoxy resin composition containing boron nitride particles having an average aspect ratio of 5 or less or an aggregate of the boron nitride particles.

<3> The epoxy resin composition according to <1> or <2>, wherein the curing agent contains a novolak resin obtained by converting a divalent phenol compound into a novolak.

<4> The content ratio of the first filler to the second filler (first filler / second filler) is 4.0 / 6.0 to 9.5 / 0.50 on a volume basis. The epoxy resin composition according to any one of <1> to <3>, which is within the range.

<5> The epoxy resin composition according to any one of <1> to <4>, wherein the content of the filler is 50% by volume to 90% by volume.

<6> The epoxy resin composition according to any one of <1> to <5>, wherein the filler further contains at least one filler selected from the group consisting of alumina, silica and aluminum nitride.

<7> The epoxy resin composition according to any one of <1> to <6>, wherein the epoxy resin monomer contains a compound represented by the following general formula (I).

In the general formula (I), R ^{1 to} R ⁴ independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

<8> The curing agent contains a novolak resin having a structural unit represented by at least one selected from the group consisting of the following general formulas (II-1) and (II-2) <1> to <7. > The epoxy resin composition according to any one of.

In the general formulas (II-1) and (II-2), R ²¹ and R ²⁴ independently represent an alkyl group, an aryl group or an aralkyl group, respectively. R ²² , R ²³ , R ²⁵ and R ²⁶ each independently represent a hydrogen atom, an alkyl group, an aryl group or an aralkyl group. m21 and m22 each independently represent an integer of 0 to 2. n21 and n22 each independently represent an integer of 1 to 7.

<9> The curing agent contains a novolak resin having a structure represented by at least one selected from the group consisting of the following general formulas (III-1) to (III-4) <1> to <8>. The epoxy resin composition according to any one of the above items.

In the general formulas (III-1) to (III-4), m31 to m34 and n31 to n34 independently represent positive integers. Ar ^{31 to} Ar ³⁴ independently represent a group represented by the following general formula (III-a) or a group represented by the following general formula (III-b).

In the general formulas (III-a) and (III-b), R ³¹ and R ³⁴ independently represent a hydrogen atom or a hydroxyl group, respectively. R ³² and R ³³ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

<10> The curing agent contains a monomer which is a phenol compound constituting the novolak resin, and the content of the monomer which is the phenol compound is 5% by mass to 80% by mass in the curing agent <1>. The epoxy resin composition according to any one of <9>.

<11> A resin sheet which is a sheet-shaped molded product of the epoxy resin composition according to any one of <1> to <10>.

<12> A prepreg comprising a fiber base material and the epoxy resin composition according to any one of <1> to <10> impregnated in the fiber base material.

<13> A metal foil with a resin comprising a metal foil and a sheet obtained by using the epoxy resin composition according to any one of <1> to <10> arranged on the metal foil.

<14> Selected from the group consisting of the metal support, the epoxy resin composition according to any one of <1> to <10>, the resin sheet according to <11>, and the prepreg according to <12>. A metal substrate comprising at least one cured product layer and a metal foil in this order.

<15> A semiconductor module in which a metal plate, a solder layer, and a semiconductor chip are laminated in this order, and
With heat dissipation member,
The cured product of the epoxy resin composition according to any one of <1> to <10> arranged between the metal plate of the semiconductor module and the heat radiating member.
Power semiconductor devices including.

According to the present invention, it is possible to provide an epoxy resin composition having excellent thermal conductivity after curing, a resin sheet, a prepreg, a metal foil with a resin, a metal substrate, and a power semiconductor device using the epoxy resin composition.

It is a figure explaining the particle diameter D50 in the weight cumulative particle size distribution curve which took the particle diameter on the horizontal axis, and weight accumulation on the vertical axis. It is a schematic diagram explaining the length in the width direction and the length in the thickness direction in an example of primary particles of boron nitride particles. It is a schematic sectional drawing which shows an example of the structure of the power semiconductor device which concerns on this embodiment. It is a schematic sectional drawing which shows an example of the structure of the power semiconductor device which concerns on this embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.
In the present specification, the term "process" includes not only a process independent of other processes but also the process if the purpose of the process is achieved even if the process cannot be clearly distinguished from the other processes. Is done.

In the numerical range indicated by using "~" in the present specification, the numerical values before and after "~" are included as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. good. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present specification, the content of each component in the composition is the total of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. Means the content of.

In the present specification, the term "layer" refers to the case where the layer is formed in the entire region when the region is observed, and the case where the layer is formed only in a part of the region. Is also included.
As used herein, the term "laminated" refers to stacking layers, and two or more layers may be bonded or the two or more layers may be removable.

<Epoxy resin composition>
The epoxy resin composition of the first embodiment contains an epoxy resin monomer, a curing agent, and a filler, and the filler corresponds to a cumulative 50% from the small particle size side of the weight cumulative particle size distribution curve. The average value of the aspect ratio (length in the width direction / length in the thickness direction) expressed by the ratio of the length in the width direction to the length in the thickness direction of the primary particles having a particle size D50 of 20 μm or more. The first filler containing the boron nitride particles having a value of 30 or less or an aggregate of the boron nitride particles, and the boron nitride particles having a particle size D50 of less than 10 μm and an average aspect ratio of 5 or less. It contains a second filler containing the agglomerates of the boron nitride particles. Hereinafter, the first filler and the second filler are collectively referred to as "specific filler".

The particle size D50 in the present specification means a particle size in which the cumulative weight is 50% in the weight cumulative particle size distribution curve in which the horizontal axis is the particle size and the vertical axis is the weight accumulation. Although the particle size D50 in the weight cumulative particle size distribution curve will be described with reference to FIG. 1, the shape and the like of the weight cumulative particle size distribution curve of the present invention are not limited to this. When the boron nitride particles are present as primary particles, the particle size taken on the horizontal axis is the particle size of the primary particles, and when they are present as aggregates, the particle size taken on the horizontal axis is. The agglomerate diameter.

The epoxy resin composition of the second embodiment contains an epoxy resin monomer, a curing agent, and a filler, and the filler has a first peak of 20 μm or more and a second peak of less than 10 μm in the particle size distribution curve. The first peak is composed of the first filler, and the first filler has an aspect ratio expressed by the ratio of the length in the width direction to the length in the thickness direction of the primary particle. It contains boron nitride particles or aggregates of the boron nitride particles having an average value (length in the width direction / length in the thickness direction) of 30 or less, and the second peak is composed of the second filler. The second filler contains boron nitride particles having an average aspect ratio of 5 or less or an aggregate of the boron nitride particles.

The particle size distribution curve in the present specification means a distribution curve in which the horizontal axis is the particle size and the vertical axis is the frequency. For example, when two types of fillers having a single peak are used, the particle size distribution curve of the filler as a whole has two peaks. When the positions of the peak peaks are close to each other in the two types of fillers, the two peaks appearing on the particle size distribution curve partially overlap, but the position of the peak peaks can generally be confirmed as an inflection point. When the boron nitride particles are present as primary particles, the particle diameter taken on the horizontal axis is the particle diameter of the primary particles, and when they are present as aggregates, the particle diameter is taken on the horizontal axis. Is the aggregate diameter.

By preparing an epoxy resin composition containing an epoxy resin monomer and a curing agent in combination with a specific filler, the thermal conductivity of the cured product of the epoxy resin composition can be improved. The epoxy resin composition may further contain other components, if necessary.

The resin sheet and prepreg constructed by using the epoxy resin composition of the present embodiment exhibit excellent thermal conductivity after curing. Further, the metal substrate provided with the insulating layer obtained by curing the epoxy resin composition of the present embodiment exhibits extremely excellent thermal conductivity.

When the D50 of the boron nitride particles or the aggregate of the boron nitride particles as the first filler is 20 μm or more and the D50 of the boron nitride particles or the aggregate of the boron nitride particles as the second filler is less than 10 μm, The second filler is easily filled between the first fillers, and the thermal conductivity is improved.

When the average value of the aspect ratios of the boron nitride particles as the first filler or the primary particles of the aggregates of the boron nitride particles is 30 or less, the anisotropy of the thermal conductivity becomes small, and the thickness direction of the boron nitride particles Thermal conductivity is improved. When the average value of the aspect ratio of the boron nitride particles as the second filler or the primary particles of the aggregate of the boron nitride particles is 5 or less, the anisotropy of the thermal conductivity becomes small, and the anisotropy in the thickness direction of the boron nitride becomes small. Thermal conductivity is improved. In addition, since the number of functional groups on the surface of the boron nitride particles is increased, the bond with the resin is strengthened and the thermal conductivity is improved.

Hereinafter, the materials used for the epoxy resin composition will be described.

(Epoxy resin monomer)
The epoxy resin composition contains at least one epoxy resin monomer. The epoxy resin monomer is not particularly limited, and can be appropriately selected from, for example, epoxy resin monomers generally used for sealing and adhesive epoxy resin compositions.

Above all, the epoxy resin monomer preferably contains an epoxy resin monomer having a mesogen group. Here, the mesogen group refers to an atomic group that facilitates the development of crystallinity or liquid crystallinity by the action of intramolecular interaction. Specific examples thereof include a biphenyl group, a phenylbenzoate group, an azobenzene group, a stilbene group, and derivatives thereof.

It has been found that the epoxy resin monomer having a mesogen group forms a high-order structure with high order, and as a result, the thermal conductivity after curing is improved. It is considered that the epoxy resin monomer having a higher-order structure formed by the presence of boron nitride particles or agglomerates of boron nitride particles becomes an efficient heat conduction path and high heat conductivity can be obtained.

Here, the high-order structure means a structure including a high-order structure in which its components are arranged to form a micro-ordered structure, and corresponds to, for example, a crystal phase and a liquid crystal phase. Whether or not such a high-order structure exists can be easily determined by observing with a polarizing microscope. That is, in the observation in the cross Nicol state, if interference fringes due to polarization elimination are observed, it can be determined that a higher-order structure exists. Higher-order structures usually exist in islands in the resin and form a domain structure. Each of the islands forming the domain structure is called a higher-order structure. The structural units that make up the higher-order structure are generally connected by covalent bonds.

The proportion of the epoxy resin monomer having a mesogen group is preferably 50% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, based on the total amount of the epoxy resin monomer. It is particularly preferable that the epoxy resin monomer is substantially composed of an epoxy resin having a mesogen group. When the proportion of the epoxy resin monomer having a mesogen group is 50% by mass or more in the whole epoxy resin, the high thermal conductivity after curing the epoxy resin composition is improved.

The epoxy resin monomer having a mesogen group preferably contains an epoxy resin monomer represented by the following general formula (I).

In the above general formula (I), R ^{1 to} R ⁴ independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and are preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms. It is more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.
Further ^{, it is preferable that 2 to 4 of R 1 to} R 4 are hydrogen atoms, more preferably 3 or 4 are hydrogen atoms, and further preferably all 4 are hydrogen atoms. .. When ^{any one of R 1 to} R ⁴ is an alkyl group having 1 to 3 carbon atoms, it is preferable that at least one of ^{R 1} and R ^{4 is an alkyl group having 1 to 3 carbon atoms.}

In particular, among the epoxy resin monomers having a mesogen group, the epoxy resin monomer represented by the general formula (I) has been found to form a higher-order structure having high order. By combining the specific filler and the epoxy resin monomer represented by the general formula (I), a smectic structure having high order is exhibited. As a result, the commonly used epoxy resin monomer exhibits high thermal conductivity that cannot be expected from a cured product that is cured by itself without containing a specific filler.

The nematic structure and the smectic structure are each a kind of liquid crystal structure. The nematic structure is a liquid crystal structure in which the major axis of the molecule is oriented in a uniform direction and has an orientation order, but does not have a one-dimensional position order. On the other hand, the smectic structure is a liquid crystal structure having a one-dimensional position order in addition to the orientation order and having a layered structure. Order is higher in smectic structures than in nematic structures. Therefore, the thermal conductivity of the cured product of the epoxy resin composition is also higher when it exhibits a smectic structure.

Examples of preferable forms of the epoxy resin monomer represented by the general formula (I) are described in JP-A-2011-74366. Specific examples of the epoxy resin monomer having a mesogen group are shown, but the present embodiment is not limited thereto.
Epoxy resin monomers having a mesogen group include 4- {4- (2,3-epoxypropoxy) phenyl} cyclohexyl-4- (2,3-epoxypropoxy) benzoate and 4- {4- (2,3-epoxy) benzoate. It preferably contains at least one selected from propoxy) phenyl} cyclohexyl-4- (2,3-epoxypropoxy) -3-methylbenzoate.

Further, the epoxy resin monomer may be in the state of a prepolymer obtained by reacting a part thereof with a curing agent or the like described later. Epoxy resin monomers having a mesogen group are generally easy to crystallize and often have low solubility in a solvent. By partially polymerizing an epoxy resin monomer having a mesogen group, crystallization may be suppressed and moldability may be improved.

The epoxy resin composition may contain other epoxy resin monomers having no mesogen skeleton as the epoxy resin monomers. Examples of other epoxy resin monomers include bisphenol A type epoxy resin monomer, bisphenol F type epoxy resin monomer, bisphenol AD type epoxy resin monomer, hydrogenated bisphenol A type epoxy resin monomer, and hydrogenated bisphenol AD type epoxy resin monomer. , Naphthalene-type epoxy resin monomer and an epoxy resin monomer having one epoxy group called a reactive diluent in one molecule.

The epoxy equivalent of the epoxy resin monomer is not particularly limited. For example, from the viewpoint of thermal conductivity, the average epoxy equivalent is preferably 130 g / eq to 500 g / eq, more preferably 135 g / eq to 400 g / eq, and even more preferably 140 g / eq to 300 g / eq.
The epoxy equivalent is measured by dissolving the precisely weighed epoxy resin in a solvent such as methyl ethyl ketone, adding acetic acid and a tetraethylammonium bromide acetic acid solution, and then potentiometric titration with an acetic acid perchlorate standard solution. An indicator may be used during this titration.

From the viewpoint of moldability and adhesiveness, the total amount of the resin components in the total solid content of the epoxy resin composition is preferably 10% by volume to 50% by volume, preferably 15% by volume to 40% by volume. More preferably, it is more preferably 20% by volume to 35% by volume.
In the present embodiment, the solid content of the epoxy resin molding material means the remaining components obtained by removing the volatile components from the epoxy resin molding material. Further, the resin component refers to an epoxy resin monomer and a curing agent (when the epoxy resin composition contains a curing accelerator described later, a curing accelerator is also included).

When the epoxy resin composition in the present specification contains an epoxy resin monomer, a curing agent, a curing accelerator, a first filler, a second filler, and other optional components other than an organic solvent, the content of the resin component (% by volume). ) Is the value obtained by the following equation. If the corresponding component is not included, it is calculated as 0% by mass. Hereinafter, the content rate (% by volume) of each material used in the epoxy resin composition is a value obtained based on this method.

Resin component content (% by volume) = {((Aw / Ad) + (Bw / Bd) + (Cw / Cd)) / ((Aw / Ad) + (Bw / Bd) + (Cw / Cd) + (D1w / D1d) + (D2w / D2d) + (Ew / Ed))} x 100

Here, each variable is as follows.
Aw: mass composition ratio of epoxy resin monomer (mass%), Bw: mass composition ratio of curing agent (mass%), Cw: mass composition ratio of curing accelerator (mass%), D1w: mass composition of first filler Ratio (% by mass), D2w: mass composition ratio (mass%) of the second filler, Ew: mass composition ratio (mass%) of other optional components (excluding organic solvent), Ad: specific density of epoxy resin monomer, Bd: Relative density of curing agent, Cd: Relative density of curing accelerator, D1d: Relative density of first filler, D2d: Relative density of second filler, Ed: Relative density of other optional components (excluding organic solvent)

(Filler)
The epoxy resin composition contains a filler. The filler has a particle size D50 of 20 μm or more corresponding to the cumulative 50% from the small particle size side of the weight cumulative particle size distribution curve with the particle size on the horizontal axis and the weight accumulation on the vertical axis, and the thickness of the primary particles. Condensation of boron nitride particles or boron nitride particles in which the average value of the aspect ratio (length in the width direction / length in the thickness direction) expressed by the ratio of the length in the width direction to the length in the width direction is 30 or less. It contains a first filler containing an aggregate and a second filler containing boron nitride particles or aggregates of boron nitride particles having a particle size D50 of less than 10 μm and an average aspect ratio of 5 or less.

The entire filler has at least a first peak at 20 μm or more and a second peak at less than 10 μm when a particle size distribution curve is drawn with the particle size on the horizontal axis and the frequency on the vertical axis. The peak of is composed of the first filler, and the first filler has an aspect ratio (length / thickness in the width direction) expressed by the ratio of the length in the width direction to the length in the thickness direction of the primary particle. It contains boron nitride particles or aggregates of the boron nitride particles having an average value of 30 or less in the direction), the second peak is composed of the second filler, and the second filler has the aspect ratio. Includes boron nitride particles or aggregates of the boron nitride particles having an average value of 5 or less.

The thermal conductivity that the content ratio of the first filler to the second filler (first filler / second filler) is 4.0 / 6.0 to 9.5 / 0.50 on a volume basis. It is preferable from the viewpoint of the rate, and 4.0 / 6.0 to 8.0 / 2.0 is more preferable from the viewpoint of the anisotropy of thermal conductivity, and 4.5 / 5.5.0 to 6. 0 / 4.0 is more preferable from the viewpoint of filler filling property.

As a filler, boron nitride particles or boron nitride having a particle diameter D50 of 20 μm or more and an average aspect ratio of 30 or less represented by the ratio of the length in the width direction to the length in the thickness direction of the primary particles. A first filler containing agglomerates of particles, a second filler containing boron nitride particles or agglomerates of boron nitride particles having a particle diameter D50 of less than 10 μm and an average aspect ratio of 5 or less. The content ratio of the first filler to the second filler (first filler / second filler) is in the range of 4.0 / 6.0 to 9.5 / 0.50 on a volume basis. In this case, the improvement in thermal conductivity is remarkable.

From the viewpoint of thermal conductivity, the total content of the filler contained in the epoxy resin composition is preferably 50% by volume to 90% by volume, preferably 60% by volume to 80% by volume, based on the total solid content. It is more preferably 65% by volume to 80% by volume.

When an epoxy resin monomer having a mesogen group is used as the epoxy resin monomer, the presence of a higher-order structure in the epoxy resin composition containing the boron nitride particles can be confirmed as follows.
A cured product (thickness: 0.1 μm to 20 μm) of a composition containing 5% by volume to 10% by volume of boron nitride particles in an epoxy resin monomer having a mesogen group is sandwiched between slide glasses (thickness: about 1 mm). This is observed using a polarizing microscope (for example, manufactured by Olympus Corporation, trade name: BX51). An interference pattern is observed around the boron nitride in the region where the boron nitride particles are present, and no interference pattern is observed in the region where the boron nitride particles are not present. As a result, in the epoxy resin composition containing the epoxy resin monomer having a mesogen group and the boron nitride particles, the cured product of the epoxy resin monomer having a mesogen group centered on the boron nitride particles forms a higher-order structure. It is confirmed. In particular, in the combination of the epoxy resin monomer represented by the general formula (I) and the boron nitride particles, a higher-order structure is effectively formed.

Further, when the above observation is performed on the boron nitride particles having different aspect ratios, the area of the region showing the interference pattern becomes the largest in the case of the boron nitride particles having the average value of the aspect ratios of 5 or less. From this, it can be judged that the effect of forming the higher-order structure of the epoxy resin monomer having a mesogen group is high when the boron nitride particles having an average aspect ratio of 5 or less are used.

The above observation is performed not in the cross Nicol state but in a state where the detector is rotated by 60 ° with respect to the polarizing element. That is, in the cured product of the epoxy resin composition containing no filler, it is judged whether or not the resin forms a higher-order structure depending on whether an interference pattern is observed or a dark field is observed in the observation in the cross Nicol state. can. On the other hand, in the cured product of the epoxy resin composition containing the filler, when the observation is performed in the cross Nicol state, the region of the dark field where no interference pattern is observed is a portion where the resin does not form a higher-order structure, or the filler. It is difficult to determine whether it is the origin.

However, when the detector is rotated 60 ° with respect to the polarizing element, the filler portion has a dark field regardless of the angle between the polarizing element and the analyzer, but the resin does not form a higher-order structure. The part is not a dark field, and it looks bright through light to some extent. This makes it possible to distinguish between the portion where the resin does not form a higher-order structure and the portion derived from the filler.

The epoxy resin composition may further contain at least one other filler selected from the group consisting of alumina, silica and aluminum nitride. Alumina is preferable as the material of other fillers.

The particle diameter D50 of the other fillers is preferably 0.1 μm to 30 μm, more preferably 0.2 μm to 20 μm.

As the other filler, at least one filler selected from the group consisting of alumina, silica and aluminum nitride having a particle size D50 of 0.1 μm to 30 μm is preferable, and alumina having a particle size D50 of 0.2 μm to 20 μm is preferable. Is more preferable.

(First filler)
The first filler has a particle size D50 corresponding to a cumulative 50% from the small particle size side of the weight cumulative particle size distribution curve of 20 μm or more, and has a length in the width direction with respect to the length in the thickness direction of the primary particles. It contains boron nitride particles or aggregates of boron nitride particles having an average aspect ratio represented by a ratio of 30 or less. The first filler is a boron nitride particle having a particle diameter D50 of 20 μm or more and an average aspect ratio of 30 or less represented by the ratio of the length in the width direction to the length in the thickness direction of the primary particles. Alternatively, it is preferably composed of aggregates of boron nitride particles.
Further, the first filler constitutes the first peak in the particle size distribution curve with the particle size on the horizontal axis and the frequency on the vertical axis. The first peak in the particle size distribution curve is located in the region of 20 μm or more.

The first filler may be used alone or in combination of two or more. When two or more kinds of the first fillers are used in combination, for example, when two or more kinds of first fillers having different particle diameters D50 are used, when two or more kinds of first fillers having different crystal forms are used, and when agglomerates are used. In addition, there is a case where two or more kinds of first fillers having different agglomeration forms are used. Furthermore, these combinations may be used.
When two or more types of first fillers having different particle diameters D50 are used, two or more peaks appear in a region of 20 μm or more in the particle size distribution curve of the entire filler.

The particle size D50 of the first filler is 20 μm or more, preferably 20 μm to 100 μm, and more preferably 30 μm to 80 μm from the viewpoint of thermal conductivity and fluidity.

Further, when the D50 of the boron nitride particles or the aggregate of the boron nitride particles is 20 μm or more, the second filler between the first fillers is compared with the aggregate of the boron nitride particles or the boron nitride particles having a D50 of less than 20 μm. Easy to fill with filler.

The particle size D50 of the first filler is measured by using a laser diffraction method, for example, the filler in the epoxy resin composition is extracted, and a laser diffraction scattering particle size distribution measuring device (for example, manufactured by Beckman Coulter, trade name) is used. : Measured using LS230). Specifically, the filler component is extracted from the epoxy resin composition using an organic solvent, nitric acid, aqua regia, etc., sufficiently dispersed by an ultrasonic disperser, etc., and the weight cumulative particle size distribution curve of this dispersion is measured. do. From the obtained weight cumulative particle size distribution curve, a group of particles having a peak of 20 μm or more is taken out and used as the first filler.

The first filler contains boron nitride particles or aggregates of boron nitride particles. Since boron nitride is excellent in storage stability, thermal conductivity and electrical insulation among fillers, the cured product of the epoxy resin composition containing boron nitride particles is excellent in thermal conductivity and electrical insulation. The first filler preferably contains an aggregate of boron nitride particles, and more preferably contains an aggregate in which boron nitride is randomly oriented.

The average aspect ratio of the primary particles of the boron nitride particles as the first filler is 30 or less, preferably 25 or less, more preferably 20 or less, still more preferably 15 or less. .. When the average value of the aspect ratios of the primary particles is 30 or less, the anisotropy of the thermal conductivity becomes small, and the thermal conductivity in the thickness direction of the boron nitride particles is improved. In addition, since the number of functional groups on the surface of the boron nitride particles is increased, the bond with the resin is strengthened and the thermal conductivity is improved.

The lower limit of the average value of the aspect ratios of the first filler is not particularly limited. From the viewpoint of thermal conductivity, it is preferably 1 or more.

For the average value of the aspect ratio, 50 particles were observed using a scanning electron microscope (for example, manufactured by Hitachi, Ltd., trade name: FE-SEM S4700), and (length in the width direction) ÷ (thickness). Calculated by the length in the vertical direction). FIG. 2 is a schematic diagram illustrating a length in the width direction and a length in the thickness direction in an example of primary particles of boron nitride particles. FIG. 2 is a conceptual diagram, and the relative relationship between sizes is not limited to this. FIG. 2 is not limited to the present invention. The length in the width direction means the length of the longest portion in the plane direction of the boron nitride primary particles.

The content of the first filler contained in the epoxy resin composition is not particularly limited. For example, the content of the first filler is preferably 40% by volume to 90% by volume, more preferably 50% by volume to 70% by volume, based on the total volume of the fillers contained in the epoxy resin composition. In the epoxy resin composition, when the content of the first filler is 40% by volume to 90% by volume of the total volume of the fillers, the effect of further increasing the thermal conductivity can be obtained.

The content rate (% by volume) of the first filler in the present specification is a value calculated by the following formula. The variables in the equation are the same as those described above.

Content of the first filler (% by volume) = {(D1w / D1d) / ((Aw / Ad) + (Bw / Bd) + (Cw / Cd) + (D1w / D1d) + (D2w / D2d) + (Ew / Ed))} × 100

(Second filler)
The second filler has a particle size D50 corresponding to a cumulative 50% from the small particle size side of the weight cumulative particle size distribution curve of less than 10 μm, and has a length in the width direction with respect to the length in the thickness direction of the primary particles. Includes boron nitride particles or aggregates of boron nitride particles having an average aspect ratio of 5 or less expressed as a ratio. The second filler is a boron nitride particle having a particle diameter D50 of less than 10 μm and an average aspect ratio of 5 or less represented by the ratio of the length in the width direction to the length in the thickness direction of the primary particles. Alternatively, it is preferably composed of aggregates of boron nitride particles.
The second filler constitutes the second peak in the particle size distribution curve with the particle size on the horizontal axis and the frequency on the vertical axis. The second peak on the particle size distribution curve is located below 10 μm.

The second filler may be used alone or in combination of two or more. When two or more kinds of the second fillers are used in combination, for example, when two or more kinds of second fillers having different particle diameters D50 are used, when two or more kinds of second fillers having different crystal forms are used, and when agglomerates are used. There is a case where two or more kinds of second fillers having different agglomeration forms are used. Furthermore, these combinations may be used.
When two or more types of second fillers having different particle diameters D50 are used, two or more peaks appear in a region of less than 10 μm in the particle size distribution curve of the entire filler.

The particle size D50 of the second filler is less than 10 μm, preferably 0.10 μm or more and less than 10 μm, more preferably 0.50 μm to 8.0 μm, and more preferably 1.0 μm to 5.0 μm. Is even more preferable.

When the particle diameter D50 of the boron nitride particles or the aggregate of the boron nitride particles is less than 10 μm, the second filler is likely to be filled between the first fillers.

The particle size D50 of the second filler is measured by using a laser diffraction method, for example, the filler in the epoxy resin composition is extracted, and a laser diffraction scattering particle size distribution measuring device (for example, manufactured by Beckman Coulter, trade name: It is measured using LS230). Specifically, the filler component is extracted from the epoxy resin composition using an organic solvent, nitric acid, aqua regia, etc., sufficiently dispersed by an ultrasonic disperser or the like, and the particle size distribution curve of this dispersion is measured. From the obtained particle size distribution curve, a group of particles having a peak of less than 10 μm is taken out and used as a second filler.

The second filler contains boron nitride particles or agglomerates of boron nitride particles, preferably contains agglomerates of boron nitride particles, and more preferably contains agglomerates of randomly oriented boron nitride particles.

The second filler is preferably an agglomerate of boron nitride particles. When the second filler is an aggregate of boron nitride, the anisotropy of thermal conductivity derived from the scaly shape is alleviated, and the thickness when the epoxy resin composition is molded into a sheet to form a cured product. Thermal conductivity in the isotropic direction tends to improve.

The average aspect ratio of the primary particles of the boron nitride particles as the second filler is 5 or less, preferably 4 or less, and more preferably 3 or less. When the average value of the aspect ratios of the primary particles is 5 or less, the anisotropy of thermal conductivity becomes small and the thermal conductivity in the thickness direction of boron nitride increases. In addition, since the number of functional groups on the surface of the boron nitride particles is also increased, the bond with the resin is strengthened and the thermal conductivity is increased.

The lower limit of the average aspect ratio of the second filler is not limited. From the viewpoint of thermal conductivity, it is preferably 1 or more.

The content of the second filler contained in the epoxy resin composition is not particularly limited. For example, the content of the second filler is preferably 10% by volume to 90% by volume, preferably 40% by volume to 90% by volume, and 50% by volume of the total volume of the fillers contained in the epoxy resin composition. More preferably, it is from% to 70% by volume. In the epoxy resin composition, when the content of the second filler is 40% by volume to 90% by volume of the total volume of the fillers, the effect of further increasing the thermal conductivity can be obtained.
Further, the content of the second filler may be 10% by volume to 60% by volume or 30% by volume to 50% by volume of the total volume of the fillers contained in the epoxy resin composition.

The content rate (% by volume) of the second filler in the present specification is a value calculated by the following formula. The variables in the equation are the same as those described above.

Content of the second filler (% by volume) = {(D2w / D2d) / ((Aw / Ad) + (Bw / Bd) + (Cw / Cd) + (D1w / D1d) + (D2w / D2d) + (Ew / Ed))} × 100

(Hardener)
The epoxy resin composition contains at least one curing agent. The curing agent is not particularly limited as long as it can cure the epoxy resin monomer. For example, a heavy addition type curing agent such as an acid anhydride curing agent, an amine curing agent, a phenol curing agent, and a mercaptan curing agent, and a catalytic type curing agent such as imidazole can be mentioned. One type of curing agent may be used alone, or two or more types may be used in combination.
Above all, from the viewpoint of heat resistance, it is preferable to use at least one selected from an amine curing agent and a phenol curing agent, and further, from the viewpoint of storage stability, it is more preferable to use at least one type of phenol curing agent. ..

As the amine curing agent, those usually used as a curing agent for epoxy resin monomers can be used without particular limitation, and commercially available ones may be used. Among them, a polyfunctional curing agent having two or more functional groups is preferable from the viewpoint of curability, and a polyfunctional curing agent having a rigid skeleton is more preferable from the viewpoint of thermal conductivity.

Examples of bifunctional amine curing agents are 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diamino-3,3'-dimethoxybiphenyl. , 4,4'-Diaminophenylbenzoate, 1,5-diaminonaphthalene, 1,3-diaminonaphthalene, 1,4-diaminonaphthalene, 1,8-diaminonaphthalene and the like.
Among them, from the viewpoint of thermal conductivity, at least one selected from 4,4'-diaminodiphenylmethane and 1,5-diaminonaphthalene is preferable, and 1,5-diaminonaphthalene is more preferable.

As the phenol curing agent, those usually used as a curing agent for the epoxy resin monomer can be used without limitation. For example, a phenol compound and a phenol novolac resin obtained by novolacizing them can be used.

As the phenol compound, a monofunctional compound such as phenol, o-cresol, m-cresol, p-cresol; a bifunctional compound such as catechol, resorcinol, hydroquinone; 1,2,3-trihydroxybenzene, 1,2, Examples thereof include trifunctional compounds such as 4-trihydroxybenzene and 1,3,5-trihydroxybenzene. Further, a phenol novolac resin obtained by connecting these phenol compounds with a methylene chain or the like to form a novolak can also be used as a curing agent.

The phenolic curing agent is preferably a bifunctional phenol compound such as catechol, resorcinol, or hydroquinone from the viewpoint of thermal conductivity, or a phenol novolac resin in which these are linked by a methylene chain, and these are preferable from the viewpoint of heat resistance. A phenol novolac resin in which a low-molecular-weight bifunctional phenol compound is linked with a methylene chain is more preferable.

Specific examples of the phenol novolak resin include a resin obtained by novolacizing one type of phenol compound such as cresol novolak resin, catechol novolak resin, resorcinol novolak resin, and hydroquinone novolak resin; Examples thereof include resins obtained by novolaking a type or more of phenolic compounds.

When a phenol novolac resin is used as the phenol-based curing agent, the phenol novolac resin has a structural unit represented by at least one selected from the group consisting of the following general formulas (II-1) and (II-2). It preferably contains a compound.

In the general formulas (II-1) and (II-2), R ²¹ and R ²⁴ independently represent an alkyl group, an aryl group or an aralkyl group, respectively. R ²² , R ²³ , R ²⁵ and R ²⁶ each independently represent a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group. m21 and m22 each independently represent an integer of 0 to 2. n21 and n22 each independently represent an integer of 1 to 7.

The alkyl group may be linear, branched, or cyclic.
The aryl group may have a structure containing a hetero atom in the aromatic ring. In this case, it is preferable that the heteroaryl group has a total number of heteroatoms and carbons of 6 to 12.
The alkylene group in the aralkyl group may be chain-shaped, branched-chain-shaped, or cyclic. The aryl group in the aralkyl group may have a structure containing a hetero atom in the aromatic ring. In this case, it is preferable that the heteroaryl group has a total number of heteroatoms and carbons of 6 to 12.

In the above general formulas (II-1) and (II-2), R ²¹ independently represents an alkyl group, an aromatic group, or an aralkyl group, respectively. These alkyl groups, aromatic groups, and aralkyl groups may further have a substituent if possible. Examples of the substituent include an alkyl group (except when R ²² , R ²³ , R ²⁵ and R ²⁶ are an alkyl group), an aromatic group, a halogen atom, a hydroxyl group and the like.
m21 and m22 each independently represent an integer of 0 to 2, and when m21 or m22 is 2, the two R ²¹ or R ²⁴ may be the same or different. m21 and m22 are preferably 0 or 1, and more preferably 0, respectively.
n21 and n22 are the number of structural units represented by the above general formulas (II-1) and (II-2) contained in the phenol novolac resin, and each independently represents an integer of 1 to 7.

In the general formulas (II-1) and (II-2), R ²² , R ²³ , R ²⁵ and R ²⁶ independently represent a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group, respectively. The alkyl group, aryl group, and aralkyl group represented by ^{R 22} , R ²³ , R ^25, and R ^{26 may further have a substituent if possible.} Examples of the substituent include an alkyl group (except when R ²² , R ²³ , R ²⁵ and R ²⁶ are an alkyl group), an aryl group, a halogen atom, a hydroxyl group and the like.

^{R 22} , R ²³ , R ²⁵ and R ²⁶ in the general formulas (II-1) and (II-2) are independently hydrogen atoms, alkyl groups, or aryls from the viewpoint of storage stability and thermal conductivity, respectively. It is preferably a group, more preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms, and even more preferably a hydrogen atom.

Further, from the viewpoint of heat resistance ^{, at least one of R 22} and R ²³ is preferably an aryl group, more preferably an aryl group having 6 to 12 carbon atoms. Further, ^{at least one of R 25} and R ²⁶ is preferably an aryl group, more preferably an aryl group having 6 to 12 carbon atoms.

When the alkyl group or the aryl group has a substituent, the carbon number of the alkyl group or the aryl group does not include the carbon number contained in the substituent.

The phenol curing agent may contain one kind of compound having a structural unit represented by the general formula (II-1) or (II-2) alone, or may contain two or more kinds. It is preferable that the compound contains at least one compound having a structural unit derived from resorcinol represented by the above general formula (II-1).

The compound having a structural unit represented by the general formula (II-1) may further contain at least one kind of a partial structure derived from a phenol compound other than resorcinol. Examples of the partial structure derived from the phenol compound other than resorcinol in the above general formula (II-1) include phenol, cresol, catechol, hydroquinone, 1,2,3-trihydroxybenzene, 1,2,4-trihydroxy. Partial structures derived from benzene and 1,3,5-trihydroxybenzene can be mentioned. The partial structure derived from these may include one kind alone or a combination of two or more kinds.
Further, the compound having a structural unit represented by the above general formula (II-2) may also contain at least one kind of a partial structure derived from a phenol compound other than catechol. Examples of the partial structure derived from the phenol compound other than catechol in the compound having the structural unit represented by the above general formula (I-2) include phenol, cresol, resorcinol, hydroquinone, 1,2,3-trihydroxybenzene, and the like. Partial structures derived from 1,2,4-trihydroxybenzene and 1,3,5-trihydroxybenzene can be mentioned. These partial structures may be used alone or in combination of two or more.

Here, the partial structure derived from the phenol compound means a monovalent or divalent group formed by removing one or two hydrogen atoms from the benzene ring portion of the phenol compound. The position where the hydrogen atom is removed is not particularly limited.

In the compound having a structural unit represented by the general formula (II-1), as a partial structure derived from a phenol compound other than resorcinol, from the viewpoint of thermal conductivity and adhesiveness, phenol, cresol, catechol, hydroquinone, 1, It is preferably a partial structure derived from at least one selected from the group consisting of 2,3-trihydroxybenzene, 1,2,4-trihydroxybenzene, and 1,3,5-trihydroxybenzene, preferably catechol. It is more preferable that the partial structure is derived from at least one selected from the group consisting of and hydroquinone.

Further, in the compound having the structural unit represented by the above general formula (II-1), the content of the partial structure derived from resorcinol is not particularly limited. From the viewpoint of elastic modulus, the content of the partial structure derived from resorcinol with respect to the total mass of the compound having the structural unit represented by the general formula (II-1) is preferably 55% by mass or more, and the glass transition temperature (glass transition temperature). From the viewpoint of Tg) and the linear expansion rate, it is more preferably 80% by mass or more, and further preferably 90% by mass or more from the viewpoint of thermal conductivity.

In the compound having a structural unit represented by the general formula (II-2), as a partial structure derived from a phenol compound other than catechol, from the viewpoint of thermal conductivity and adhesiveness, phenol, cresol, resorcinol, hydroquinone, 1 , 2,3-Trihydroxybenzene, 1,2,4-trihydroxybenzene and 1,3,5-trihydroxybenzene, preferably a partial structure derived from at least one selected from the group consisting of resorcinol and 1,3,5-trihydroxybenzene. More preferably, it is a partial structure derived from at least one selected from hydroquinone.
Further, in the compound having the structural unit represented by the above general formula (II-2), there is no particular limitation on the content ratio of the partial structure derived from catechol. From the viewpoint of elastic modulus, the content ratio of the partial structure derived from catechol to the total mass of the compound having the structural unit represented by the above general formula (II-2) is preferably 55% by mass or more, and the glass transition temperature (glass transition temperature). From the viewpoint of Tg) and the coefficient of linear expansion, it is more preferably 80% by mass or more, and further preferably 90% by mass or more from the viewpoint of thermal conductivity.

Further, when a phenol novolac resin is used as the phenol curing agent, the phenol novolac resin has a structure represented by at least one selected from the group consisting of the following general formulas (III-1) to (III-4). It is more preferable to contain novolak resin.

In the general formulas (III-1) to (III-4), m31 to m34 and n31 to n34 independently indicate positive integers and indicate the number of each structural unit contained. Ar ^{31 to} Ar ³⁴ independently represent a group represented by the following general formula (III-a) or a group represented by the following general formula (III-b).

In the general formulas (III-a) and (III-b), R ³¹ and R ³⁴ independently represent a hydrogen atom or a hydroxyl group, respectively. R ³² and R ³³ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

A curing agent having a partial structure represented by at least one of the general formulas (III-1) to (III-4) can be produced as a by-product by a production method described later for novolacizing a divalent phenol compound. It is a thing.

The partial structures represented by the general formulas (III-1) to (III-4) may be contained as the main chain skeleton of the compound, or may be contained as a part of the side chain. Further, each structural unit constituting the partial structure represented by any one of the above general formulas (III-1) to (III-4) may be randomly included or regularly included. It may be contained in a block shape. Further, in the general formulas (III-1) to (III-4), the substitution position of the hydroxyl group is not particularly limited as long as it is on the aromatic ring.

For each of the general formulas (III-1) to (III-4), a plurality of Ars ^{31 to Ar 34} existing may be all the same atomic group, or may contain two or more kinds of atomic groups. .. In addition, Ar ^{31 to} Ar ³⁴ independently represent a group represented by any one of the above general formulas (III-a) and (III-b).

^{R 31} and R ³⁴ in the general formulas (III-a) and (III-b) are independently hydrogen atoms or hydroxyl groups, and are preferably hydroxyl groups from the viewpoint of thermal conductivity. Further, ^{the replacement positions of R 31} and R ³⁴ are not particularly limited.

Further, in the general formulas (III-a) and (III-b), R ³² and R ³³ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 8 carbon atoms in R ³² and R ³³ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a pentyl group and a hexyl. Groups include groups, heptyl groups, and octyl groups. ^{Further, the substitution positions of R 32} and R ^{33 in} the general formulas (III-a) and (III-b) are not particularly limited.

^{Ar 31 to} Ar ³⁴ in the general formulas (III-a) and (III-b) are groups derived from dihydroxybenzene from the viewpoint of achieving better thermal conductivity (R ^{31 in the general formula (III-a)).} Is a hydroxyl group and R ³² and R ³³ are hydrogen atoms), and at least one selected from a group derived from dihydroxynaphthalene (a group in which R ³⁴ is a hydroxyl group in the general formula (III-b)). Is preferable.

Here, the "group derived from dihydroxybenzene" means a divalent group formed by removing two hydrogen atoms from the aromatic ring portion of dihydroxybenzene, and the position where the hydrogen atom is removed is not particularly limited. Further, "group derived from dihydroxynaphthalene" has the same meaning.

Further, from the viewpoint of productivity and fluidity of the epoxy resin composition, Ar ^{31 to} Ar ³⁴ are more preferably groups derived from dihydroxybenzene, and groups derived from 1,2-dihydroxybenzene (catechol) and groups. It is more preferably at least one selected from the group consisting of groups derived from 1,3-dihydroxybenzene (resorcinol). In particular, from the viewpoint of particularly enhancing thermal conductivity, ^{it is preferable that Ar 31 to} Ar ³⁴ contain at least a group derived from resorcinol. Further, from the viewpoint of particularly enhancing thermal conductivity, the structural unit represented by n31 to n34 preferably contains a group derived from resorcinol.

When the compound having a structure represented by at least one selected from the group consisting of the general formula (III-1) to the above general formula (III-4) contains a structural unit derived from resorcinol, a group derived from resorcinol. The content of the structural unit containing is 55% by mass in the total mass of the compound having a structure represented by at least one of the above general formulas (III-1) to (III-4) from the viewpoint of elastic modulus. The above is preferable, 80% by mass or more is more preferable from the viewpoint of Tg and the linear expansion rate, and 90% by mass or more is further preferable from the viewpoint of thermal conductivity.

The ratio of mx and nx (x is the same value of any one of 31, 32, 33 or 34) in the general formulas (III-1) to (III-4) is mx / nx = 20 from the viewpoint of liquidity. It is preferably / 1 to 1/5, more preferably 20/1 to 5/1, and even more preferably 20/1 to 10/1. Further, the total value (mx + nx) of mx and nx is preferably 20 or less, more preferably 15 or less, and further preferably 10 or less from the viewpoint of fluidity. The lower limit of the total value of mx and nx (mx and nx) is not particularly limited.

mx and nx represent the number of structural units, and indicate how much the corresponding structural units are added to the molecule. Therefore, an integer value is shown for a single molecule. In addition, mx and nx in (mx / nx) and (mx + nx) indicate a rational number which is an average value in the case of an aggregate of a plurality of kinds of molecules.

The phenol novolac resin having a partial structure represented by at least one of the general formulas (III-1) to (III-4) is particularly ^{substituted or unsubstituted dihydroxybenzene in which Ar 31 to} Ar ³⁴ are substituted or unsubstituted and substituted or unsubstituted. When at least one of the dihydroxynaphthalene is used, it tends to be easier to synthesize and a curing agent having a low softening point can be obtained as compared with a phenol resin or the like in which these are simply novolakized. Therefore, by including such a phenol resin as a curing agent, there is an advantage that the epoxy resin composition can be easily manufactured and handled.
Whether or not the phenol novolac resin has a partial structure represented by any of the general formulas (III-1) to (III-4) is determined by the electric field desorption ionization mass spectrometry (FD-MS). It can be determined by whether or not the fragment component contains a component corresponding to the partial structure represented by any of the above general formulas (II-1) to the above general formula (II-4).

The molecular weight of the phenol novolac resin having a partial structure represented by at least one of the general formulas (III-1) to (III-4) is not particularly limited. From the viewpoint of fluidity, the number average molecular weight (Mn) is preferably 2000 or less, more preferably 1500 or less, and even more preferably 350 to 1500. The weight average molecular weight (Mw) is preferably 2000 or less, more preferably 1500 or less, and even more preferably 400 to 1500. Mn and Mw are measured by a conventional method using GPC (gel permeation chromatography).

The hydroxyl group equivalent of the phenol novolac resin having a structure represented by at least one selected from the group consisting of the general formulas (III-1) to (III-4) is not particularly limited. From the viewpoint of the cross-linking density involved in heat resistance, the hydroxyl group equivalent is preferably 50 g / eq to 150 g / eq on average, more preferably 50 g / eq to 120 g / eq, and 55 g / eq to 120 g / eq. It is more preferably eq. In addition, in this specification, a hydroxyl group equivalent means a value measured according to JIS K0070: 1992.

The phenol novolac resin may contain a monomer which is a phenol compound constituting the phenol novolac resin. The content of the monomer which is a phenol compound constituting the phenol novolac resin (hereinafter, also referred to as “monomer content”) is not particularly limited. From the viewpoint of thermal conductivity and moldability, the monomer content is preferably 5% by mass to 80% by mass, more preferably 15% by mass to 60% by mass, and 20% by mass to 50% by mass. It is more preferable to have.

When the monomer content is 80% by mass or less, the number of monomers that do not contribute to cross-linking during the curing reaction decreases, and the high molecular weight substances that contribute to cross-linking occupy a large part, resulting in a higher density structure. It is formed and tends to improve thermal conductivity. Further, when the monomer content is 5% by mass or more, it tends to flow easily during molding, so that the adhesion with the filler is further improved, and more excellent thermal conductivity and heat resistance tend to be achieved.

The content of the curing agent in the epoxy resin composition is not particularly limited. For example, when the curing agent is an amine-based curing agent, the ratio of the equivalent number of active hydrogen of the amine-based curing agent (equivalent number of amine) to the equivalent number of epoxy groups of the epoxy resin monomer (equivalent number of amine / epoxy). The equivalent number of groups) is preferably 0.5 to 2.0, and more preferably 0.8 to 1.2. When the curing agent is a phenolic curing agent, the ratio of the equivalent of the phenolic hydroxyl group of the phenolic curing agent (the equivalent number of the phenolic hydroxyl group) to the equivalent number of the epoxy group of the epoxy resin monomer (the equivalent number of the phenolic hydroxyl group). The number of equivalents / the number of equivalents of the epoxy group) is preferably 0.5 to 2.0, more preferably 0.8 to 1.2.

(Hardening accelerator)
When a phenol curing agent is used in the epoxy resin composition, a curing accelerator may be contained if necessary. By using a curing accelerator together with the phenolic curing agent, the epoxy resin composition can be further sufficiently cured. The type and content of the curing accelerator are not particularly limited, and an appropriate one can be selected from the viewpoint of reaction rate, reaction temperature and storage stability.

As the curing accelerator, a commonly used curing accelerator can be used without particular limitation. The curing accelerator may be commercially available. Specific examples thereof include an imidazole compound, a tertiary amine compound, an organic phosphin compound, and a complex of an organic phosphin compound and an organic boron compound. Above all, from the viewpoint of heat resistance, at least one selected from the group consisting of an organic phosphine compound and a complex of an organic phosphine compound and an organic boron compound is preferable.

Specific examples of the organic phosphine compound include triphenylphosphine, diphenyl (p-tolyl) phosphine, tris (alkylphenyl) phosphine, tris (alkoxyphenyl) phosphine, tris (alkyl / alkoxyphenyl) phosphine, and tris (dialkylphenyl). ) Phosphine, Tris (trialkylphenyl) phosphine, Tris (tetraalkylphenyl) phosphine, Tris (dialkoxyphenyl) phosphine, Tris (trialkoxyphenyl) phosphine, Tris (tetraalkoxyphenyl) phosphine, trialkylphosphine, dialkylarylphosphine , Alkyldialylphosphine and the like.

Specific examples of the complex of the organic phosphin compound and the organic boron compound include tetraphenylphosphonium / tetraphenylborate, tetraphenylphosphonium / tetra-p-tolylborate, tetrabutylphosphonium / tetraphenylborate, and tetraphenylphosphonium. -N-butyltriphenylborate, butyltriphenylphosphonium / tetraphenylborate, methyltributylphosphonium / tetraphenylborate and the like can be mentioned.

The curing accelerator may be used alone or in combination of two or more. As a method for efficiently producing the semi-cured epoxy resin composition and the cured epoxy resin composition described later, two types of curing accelerators having different reaction start temperatures and reaction rates between the epoxy resin monomer and the phenol novolak resin are mixed and used. The method can be mentioned.

For example, it contains an epoxy resin monomer represented by the general formula (I) and a compound having a structural unit represented by at least one selected from the group consisting of the general formulas (II-1) and (II-2). In the case of a reaction with a novolak resin, examples of the curing accelerator include a combination of triphenylphosphine and tetraphenylphosphonium / tetraphenylborate. In the case of the above reaction, the reaction proceeds at 150 ° C. or lower with triphenylphosphine. On the other hand, with tetraphenylphosphonium / tetraphenylborate, the reaction hardly proceeds at 150 ° C or lower. That is, when producing a semi-cured epoxy resin composition, the curing reaction proceeds by applying heat of 150 ° C. or lower to allow triphenylphosphine to act, while preventing tetraphenylphosphonium / tetraphenylborate from acting. It is possible to produce an epoxy resin composition in a state where flexibility and flowability are maintained without excessively allowing the mixture. When producing a cured epoxy resin composition, it is possible to sufficiently proceed the curing reaction by applying heat of 150 ° C. or higher to allow tetraphenylphosphonium and tetraphenylborate to act. The method for producing the semi-cured epoxy resin composition and the cured epoxy resin composition is not limited to this.

When two or more types of curing accelerators are used in combination, the mixing ratio is determined without particular limitation according to the characteristics required for the semi-curing epoxy resin composition (for example, how much flexibility is required). be able to.

When the epoxy resin composition contains a curing accelerator, the content of the curing accelerator in the epoxy resin composition is not particularly limited. From the viewpoint of moldability, the content of the curing accelerator is preferably 0.5% by mass to 1.5% by mass, and 0.5% by mass to 1% by mass, based on the total mass of the epoxy resin monomer and the curing agent. %, More preferably 0.75% by mass to 1% by mass.

(Silane coupling agent)
The epoxy resin composition may further contain at least one of the silane coupling agents. Silane coupling agents form a covalent bond between the surface of the filler and the thermosetting resin that surrounds it (corresponding to a binder agent), efficiently transfer heat, and insulate by preventing the ingress of water. It can play a role of improving reliability.

The type of the silane coupling agent is not particularly limited, and a commercially available product may be used. Considering the compatibility with the epoxy resin monomer represented by the general formula (I) and the curing agent, and reducing the heat conduction defect at the interface between the cured product of the epoxy resin monomer and the boron nitride particles, the epoxy at the end is epoxy. It is preferable to use a silane coupling agent having a group, an amino group, a mercapto group, an epoxide group, or a hydroxyl group.

Specific examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropylmethyldimethoxysilane. , 2- (3,4-Epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-phenyl- Examples thereof include 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-ureidopropyltriethoxysilane. Further, a silane coupling agent oligomer (manufactured by Hitachi Kasei Techno Service Co., Ltd.) represented by a trade name: SC-6000KS2 can be further mentioned. These silane coupling agents may be used alone or in combination of two or more.
The silane coupling agent may be present in a state of covering the surface of the filler or in a state of being separated from the filler.

(Organic solvent)
The epoxy resin composition may further contain at least one of the organic solvents. The inclusion of an organic solvent allows the epoxy resin composition to be adapted to various molding processes. As the organic solvent, those usually used for epoxy resin compositions can be used. Specific examples thereof include alcohol solvents, ether solvents, ketone solvents, amide solvents, aromatic hydrocarbon solvents, ester solvents, nitrile solvents and the like. For example, methyl isobutyl ketone, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, γ-butyrolactone, sulfolane, cyclohexanone, and methylethylketone can be used. These organic solvents may be used alone or in combination of two or more.

(Other ingredients)
The epoxy resin composition may contain other components in addition to the above components, if necessary. Examples of other components include dispersants, plasticizers and the like. As the dispersant, for example, BIC Chemie Japan Co., Ltd., product name: DISPERBYK series (“DISPERBYK” is a registered trademark), Ajinomoto Fine Techno Co., Ltd., product name: Ajispar series (“Ajispar” is a registered trademark). ), Kusumoto Kasei Co., Ltd., trade name: HIPLAAD series (“HIPLAAD” is a registered trademark), and Kao Co., Ltd., trade name: Homogenol series (“Homogenol” is a registered trademark). .. These dispersants may be used alone or in combination of two or more.

<Resin sheet>
The resin sheet of the present embodiment is a sheet-shaped molded body of the epoxy resin composition of the present embodiment. The resin sheet can be produced, for example, by applying the epoxy resin composition of the present embodiment on a support and, if necessary, removing at least a part of the solvent contained therein. Since the resin sheet is formed from the epoxy resin composition of the present embodiment, the cured product is excellent in thermal conductivity and electrical insulation.

The thickness of the resin sheet is not particularly limited and can be appropriately selected depending on the intended purpose. For example, the thickness can be 50 μm to 500 μm, and is preferably 80 μm to 300 μm from the viewpoint of thermal conductivity, electrical insulation, and flexibility.

The resin sheet is, for example, a varnish-like epoxy resin composition (hereinafter, also referred to as “resin varnish”) prepared by adding an organic solvent such as methyl ethyl ketone or cyclohexanone to the epoxy resin composition of the present embodiment on a support. After coating to form a coating layer (epoxy resin composition layer), at least a part of the organic solvent can be removed from the coating layer and dried to produce the product. Examples of the support include a release film such as a PET (polyethylene terephthalate) film.

The application of the resin varnish can be carried out by a known method. Specifically, it can be performed by a method such as a comma coat, a die coat, a lip coat, and a gravure coat. Examples of the method for forming the epoxy resin composition layer having a predetermined thickness include a comma coating method in which an object to be coated is passed between gaps, a die coating method in which a resin varnish having a controlled flow rate is applied from a nozzle, and the like. For example, when the thickness of the coating layer (epoxy resin composition layer) before drying is 50 μm to 500 μm, it is preferable to use the comma coat method.

The drying method is not particularly limited as long as it can remove at least a part of the organic solvent contained in the resin varnish, and can be appropriately selected from the commonly used drying methods according to the organic solvent contained in the resin varnish. In general, a method of heat treatment at about 80 ° C. to 150 ° C. can be mentioned.

The curing reaction of the resin sheet (epoxy resin composition layer) has hardly progressed. Therefore, although it has flexibility, it lacks flexibility as a sheet. Therefore, when the support such as the PET film is removed, the sheet may not be self-supporting and may be difficult to handle.

Therefore, from the viewpoint of improving handleability, the resin sheet is preferably a semi-hardened epoxy resin composition layer constituting the resin sheet. That is, the resin sheet is preferably a semi-cured epoxy resin composition that is a B-stage sheet that is further heat-treated until the epoxy resin composition layer is in a semi-cured state (B-stage state). By semi-curing the epoxy resin composition layer, it is possible to obtain a resin sheet having excellent thermal conductivity and electrical insulation, and excellent flexibility and pot life as a B stage sheet.

The B-stage sheet in the present embodiment, a viscosity of ^{10 4 Pa · s~10 5 Pa ·} s at room temperature (25 to 30 ° C.), is ^{10 2 Pa · s~10 3 Pa ·} s at 100 ° C. It means a resin sheet formed from an epoxy resin composition. Further, the cured epoxy resin composition after curing, which will be described later, is not melted by heating. The viscosity is measured by DMA (dynamic viscoelasticity measuring device; frequency 1 Hz, load 40 g: heating rate 3 ° C./min).

The conditions for heat-treating the resin sheet are not particularly limited as long as the epoxy resin composition layer can be put into the B stage state. The above conditions can be appropriately selected depending on the composition of the epoxy resin composition. The heat treatment is preferably performed by a method selected from hot vacuum pressing, hot roll laminating and the like in order to reduce voids in the epoxy resin composition layer generated when the resin varnish is applied. This makes it possible to efficiently manufacture a B stage sheet having a flat surface.

Specifically, for example, the epoxy resin composition layer is heated and pressurized under reduced pressure (for example, 1 kPa) at a temperature of 100 ° C. to 200 ° C. for 1 minute to 3 minutes at a press pressure of 1 MPa to 20 MPa. It can be semi-cured to the B stage state.

It is preferable that the epoxy resin composition is applied onto the support, two dried resin sheets are bonded together, and then the above heating and pressure treatment is performed to semi-cure the resin sheet to the B stage state. At this time, it is desirable to bond the coated surfaces of the epoxy resin composition layer (the surfaces where the epoxy resin composition layer is not in contact with the support) to each other. When the epoxy resin composition layers are bonded so as to be in contact with each other, both sides of the obtained resin sheet in the B stage state (that is, the surface that appears when the support is peeled off) become flatter, and the adhesiveness to the adherend is improved. It will be good. The metal substrate described later produced using such a resin sheet exhibits high thermal conductivity and insulating properties.

The thickness of the B stage sheet can be appropriately selected according to the purpose. For example, it can be 50 μm to 500 μm, and is preferably 80 μm to 300 μm from the viewpoint of thermal conductivity, electrical insulation, and flexibility. It can also be produced by hot-pressing while laminating two or more layers of resin sheets.

The residual ratio of the volatile components in the B stage sheet is preferably 2.0% by mass or less, preferably 1.0% by mass or less, from the viewpoint of suppressing the formation of bubbles due to the generation of outgas when the epoxy resin composition layer is cured. It is more preferably present, and further preferably 0.8% by mass or less. The solvent residual ratio is determined from the mass change before and after drying the sample obtained by cutting the B stage sheet into 40 mm × 40 mm in a constant temperature bath preheated to 190 ° C. for 2 hours.

Further, the resin sheet may have a cured epoxy resin composition layer obtained by curing the epoxy resin composition layer. The resin sheet having the cured epoxy resin composition layer can be produced by curing the uncured resin sheet or the B stage sheet. The curing treatment method can be appropriately selected depending on the composition of the epoxy resin composition, the purpose of the cured epoxy resin composition, and the like, but is preferably heat and pressure treatment.

For example, it is formed from a cured epoxy resin composition by heating an uncured resin sheet or B stage sheet at 100 ° C. to 250 ° C. for 1 hour to 10 hours, preferably 130 ° C. to 230 ° C. for 1 hour to 8 hours. A resin sheet can be obtained. The heat treatment is preferably performed while applying a pressure of 1 MPa to 20 MPa.

The resin sheet having the cured epoxy resin composition layer obtained by the above method has high thermal conductivity and high heat resistance. Examples of the method for producing a resin sheet having a cured epoxy resin composition layer include the following methods. First, the B stage sheet is sandwiched between two copper foils (thickness 80 to 120 μm) having a matte surface on one side so as to be in contact with each other, and pressure is applied at a temperature of 130 ° C. to 230 ° C. for 3 minutes to 10 minutes. Heat and pressurize at 1 MPa to 20 MPa to adhere copper foil to both sides of the B stage sheet. Subsequently, the B stage sheet is heated at 130 ° C. to 230 ° C. for 1 to 8 hours. Then, the copper foil portion of the resin sheet is removed by an etching treatment to obtain a resin sheet having a cured epoxy resin composition layer.

<Prepreg>
The prepreg of the present embodiment has a fiber base material and the epoxy resin composition of the present embodiment impregnated with the fiber base material. The prepreg of the present embodiment having such a configuration is excellent in thermal conductivity and electrical insulation. Further, the epoxy resin composition containing the filler has improved thixotropic properties. Therefore, it is possible to suppress the sedimentation of the filler in the coating step and the impregnation step described later when producing the prepreg. Therefore, it is possible to suppress the occurrence of the light and shade distribution of the filler in the thickness direction of the prepreg. As a result, a prepreg having excellent thermal conductivity and electrical insulation can be obtained.

The fiber base material constituting the prepreg is not particularly limited to a fiber base material such as a normal woven fabric or a non-woven fabric as long as it is usually used in manufacturing a metal foil-coated laminated board and a multilayer printed wiring board. Used.

The opening of the fiber base material is not particularly limited. From the viewpoint of thermal conductivity and electrical insulation, the opening is preferably 5 times or more the particle size D50 of the filler. Further, when the particle size distribution curve of the filler has a plurality of peaks, it is more preferable that the mesh size is 5 times or more the average particle diameter of the filler corresponding to the peak having the maximum particle diameter.

The material of the fiber base material is not particularly limited. Specifically, inorganic fibers such as glass, alumina, boron, silica-alumina glass, silica glass, tilano, silicon carbide, silicon nitride, and zirconia, aramid, polyether ether ketone, polyetherimide, polyether sulfone, carbon, Examples include organic fibers such as cellulose and mixed abstracts thereof. Of these, glass fiber woven fabrics are preferably used. As a result, for example, when a printed wiring board is constructed using a prepreg, it is possible to obtain a printed wiring board that is flexible and can be arbitrarily bent. Further, it is possible to reduce the dimensional change of the printed wiring board due to the temperature change, moisture absorption and the like in the manufacturing process.

The thickness of the fiber base material is not particularly limited. From the viewpoint of imparting better flexibility, it is more preferably 30 μm or less, and from the viewpoint of impregnation property, it is preferably 15 μm or less. The lower limit of the thickness of the fiber base material is not particularly limited, but is usually about 5 μm.

The impregnation amount (content rate) of the epoxy resin composition of the present embodiment in the prepreg is preferably 50% by mass to 99.9% by mass in the total mass of the fiber base material and the epoxy resin composition.

The prepreg is produced by impregnating a fiber base material with the epoxy resin composition of the present embodiment prepared in the same manner as above and removing at least a part of an organic solvent by heat treatment at 80 ° C to 150 ° C. can do.

Further, there is no particular limitation on the method of impregnating the fiber base material with the epoxy resin composition. For example, a method of applying by a coating machine can be mentioned. Specifically, a vertical coating method in which the fiber base material is passed through the epoxy resin composition and pulled up, and a fiber base in which the epoxy resin composition is applied to the support film and then the fiber base material is pressed against the epoxy resin composition. A horizontal coating method for impregnating a material can be mentioned. The horizontal coating method is preferable from the viewpoint of suppressing uneven distribution of the filler in the fiber base material.

The prepreg in the present embodiment may be used after its surface has been smoothed in advance by hot pressure treatment with a press, a roll laminator, or the like before laminating or pasting. The treatment conditions such as the heating temperature, the degree of decompression, and the press pressure in the hot pressurization treatment of the prepreg are the same as the conditions mentioned in the heating and pressurizing treatment of the B stage sheet.

The solvent residual ratio in the prepreg is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and further preferably 0.8% by mass or less.

The solvent residual ratio is determined from the mass change before and after drying when the sample obtained by cutting the prepreg into 40 mm × 40 mm is dried in a constant temperature bath preheated to 190 ° C. for 2 hours.

<Metal foil with resin>
The metal foil with resin of the present embodiment includes a metal foil and a sheet obtained by using the epoxy resin composition of the present embodiment arranged on the metal foil. The resin-attached metal foil is an example of a laminated board having an adherend and a semi-cured epoxy resin composition layer or a cured epoxy resin composition layer arranged on the adherend, and is an example of a laminated board having a printed wiring board. It can be used to make.

The metal foil with resin is configured by using two metal foils as an adherend in a laminated board. Specifically, one metal foil, a semi-cured epoxy resin composition layer or a cured epoxy resin composition layer, and the other metal foil are laminated in this order.
The details of the metal foil, the semi-curable epoxy resin composition layer, and the cured epoxy resin composition layer constituting the metal foil with resin are as described above.

<Metal substrate>
The metal substrate of the present embodiment includes a metal foil, at least one cured product layer (cured epoxy resin composition layer) selected from the group consisting of the epoxy resin composition of the present embodiment, the resin sheet, and the prepreg. The metal support and the metal support are laminated in this order. The metal substrate is an example of the laminated board, and can be used for manufacturing a printed wiring board.

The metal substrate is configured by using a metal foil and a metal support as an adherend in the laminated board. Specifically, the metal substrate is configured by laminating the metal foil, the cured epoxy resin composition layer, and the metal support in this order.
The details of the metal foil and the cured epoxy resin composition layer constituting the metal substrate are as described above.

The metal support is not particularly limited from the commonly used metal supports and can be appropriately selected. Specific examples thereof include an aluminum plate and an iron plate. The thickness of the metal support is not particularly limited. From the viewpoint of workability, the thickness of the metal support is preferably 0.5 mm or more and 5 mm or less.

Further, from the viewpoint of increasing productivity, it is preferable that the metal support is manufactured in a size larger than necessary, mounts electronic components, and then cut to a size to be used. Therefore, it is desirable that the metal support used for the metal substrate has excellent cutting processability.

When aluminum is used as the metal support, aluminum or an alloy containing aluminum as a main component can be selected as the material. Many types of aluminum or alloys containing aluminum as a main component are available depending on their chemical composition and heat treatment conditions. Above all, it is preferable to select a type having high workability such as easy cutting and excellent strength.

<Power semiconductor device>
The power semiconductor device of the present embodiment is a semiconductor module in which a metal plate, a solder layer, and a semiconductor chip are laminated in this order, a heat dissipation member, and a book arranged between the metal plate and the heat dissipation member of the semiconductor module. A cured product of the epoxy resin composition of the embodiment, and the like.
In the power semiconductor device, only the semiconductor module portion may be sealed with a sealing material or the like, or the entire power semiconductor module may be molded with a molding resin or the like. Hereinafter, an example of a power semiconductor device will be described with reference to the drawings, but the present invention is not limited thereto. Further, the size of the members in each figure is conceptual, and the relative relationship between the sizes of the members is not limited to this.

FIG. 3 is a schematic cross-sectional view showing an example of the configuration of a power semiconductor device. In FIG. 3, a cured product 102 of a resin sheet is arranged between a metal plate 106 in a semiconductor module in which a metal plate 106, a solder layer 110, and a semiconductor chip 108 are laminated in this order, and a heat dissipation base substrate 104, and the semiconductor module is formed. Is sealed with a sealing material 114.
Further, FIG. 4 is a schematic cross-sectional view showing another example of the configuration of the power semiconductor device. In FIG. 4, a cured product 102 of a resin sheet is arranged between a metal plate 106 in a semiconductor module in which a metal plate 106, a solder layer 110, and a semiconductor chip 108 are laminated in this order, and a heat dissipation base substrate 104, and the semiconductor module is formed. And the heat dissipation base substrate 104 are molded with the mold resin 112.

As described above, the cured product 102 of the resin sheet, which is the sheet-shaped molded product of the resin composition of the present embodiment, is used as a heat-dissipating adhesive layer between the semiconductor module and the heat-dissipating base substrate 104 as shown in FIG. Is possible. Further, even when the entire power semiconductor device is molded as shown in FIG. 4, it can be used as a heat radiating material between the heat radiating base substrate 104 and the metal plate 106.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

The materials used for producing the epoxy resin composition and their abbreviations are shown below.
(Epoxy resin monomer)
-Resin monomer A:

[4- {4- (2,3-epoxypropoxy) phenyl} cyclohexyl-4- (2,3-epoxypropoxy) benzoate, epoxy equivalent: 212 g / eq, manufactured by the method described in JP-A-2011-74366. ]

(First filler)
HP-40 [boron nitride particles, manufactured by Mizushima Ferroalloy Co., Ltd., average particle diameter: 40 μm, average aspect ratio: 15]

(Second filler)
MBN-010T [boron nitride particles, manufactured by Mizushima Ferroalloy Co., Ltd., average particle diameter: 1 μm, average aspect ratio: 3]

(Other fillers)
-AA-18 [Alumina particles, manufactured by Sumitomo Chemical Co., Ltd., average particle diameter: 18 μm]
-AA-3 [Alumina particles, manufactured by Sumitomo Chemical Co., Ltd., average particle size: 3 μm]
-AA-04 [Alumina particles, manufactured by Sumitomo Chemical Co., Ltd., average particle diameter: 0.40 μm]
-SP-3 [Boron Nitride Particles, manufactured by Denki Kagaku Kogyo Co., Ltd., average particle diameter: 5 μm, average aspect ratio: 10

(Hardener)
-CRN [Catechol resorcinol novolak (charged mass ratio: 5/95) resin, manufactured by Hitachi Kasei Co., Ltd., containing 50% by mass of cyclohexanone]

<CRN synthesis method>
In a 3 L separable flask equipped with a stirrer, a cooler and a thermometer, 627 g of resorcinol, 33 g of catechol, 316.2 g of 37 mass% formaldehyde, 15 g of oxalic acid, and 300 g of water were put and 100 while heating in an oil bath. The temperature was raised to ° C. Reflux was carried out at around 104 ° C., and the reflux temperature was maintained for 4 hours. Then, the temperature in the flask was raised to 170 ° C. while distilling off water, and the temperature was maintained at 170 ° C. for 8 hours. After the reaction, the mixture was concentrated under reduced pressure for 20 minutes to remove water and the like in the system to obtain the desired phenol novolac resin (CRN).
Moreover, when the structure of the obtained CRN was confirmed by FD-MS, the existence of all the partial structures represented by the general formulas (III-1) to (III-4) was confirmed.

Under the above reaction conditions, a compound having a partial structure represented by the general formula (III-1) is first produced, and when this is further dehydrated, the compounds of the general formulas (III-1) to (III-4) are formed. It is considered that a compound having a partial structure represented by at least one of them is produced.

For the obtained CRN, Mn and Mw were measured as follows.
Mn and Mw were measured using high-speed liquid chromatography manufactured by Hitachi, Ltd., trade name: L6000, and data analysis device manufactured by Shimadzu Corporation, trade name: C-R4A. As the GPC column for analysis, Tosoh Corporation, trade names: G2000HXL and G3000HXL were used. The sample concentration was 0.2% by mass, tetrahydrofuran was used as the mobile phase, and the measurement was performed at a flow rate of 1.0 mL / min. A calibration curve was prepared using a polystyrene standard sample, and Mn and Mw were calculated using polystyrene-equivalent values.

For the obtained CRN, the hydroxyl group equivalent was measured as follows.
The hydroxyl group equivalent was measured by the acetyl chloride-potassium hydroxide titration method. Since the color of the solution is dark, the end point of the titration was determined by potentiometric titration instead of the coloration method using an indicator. Specifically, after acetyl chloride-acetylating the hydroxyl group of the measurement resin in a pyridine solution, the excess reagent was decomposed with water, and the produced acetic acid was titrated with a potassium hydroxide / methanol solution.

The obtained CRN is a mixture of compounds having a partial structure represented by at least one of the general formulas (III-1) to (III-4), and Ar is in the general formula (III-a). R ³¹ is a hydroxyl group, and R ³² and R ³³ are a group derived from 1,2-dihydroxybenzene (catechol) and a group derived from 1,3-dihydroxybenzene (resorcinol), which are hydrogen atoms. It was a phenol resin (hydroxyl equivalent 62 g / eq, number average molecular weight 422, weight average molecular weight 564) containing 35% by mass of a monomer component (resorcinol) as an agent.

(Hardening accelerator)
-TPP: Triphenylphosphine [manufactured by Wako Pure Chemical Industries, Ltd., trade name]

(Additive)
KBM-573: N-Phenyl-3-aminopropyltrimethoxysilane [silane coupling agent, manufactured by Shin-Etsu Chemical Co., Ltd., trade name]

(solvent)
・ MEK: Methyl ethyl ketone ・ CHN: Cyclohexanone

(Support)
-PET film [Made by Teijin DuPont Co., Ltd., Product name: A53, Thickness 50 μm]
-Copper foil [manufactured by Furukawa Electric Co., Ltd., thickness: 105 μm, GTS grade]

(Example 1) <Preparation of epoxy resin composition>
Resin monomer A is 7.59% by mass, the first filler (HP-40) is 37.85% by mass, the second filler (MBN-010T) is 4.24% by mass, and CRN is 4.47% by mass. 0.08% by mass of TPP and 45.77% by mass of CHN were mixed to obtain an epoxy resin varnish as an epoxy resin composition containing a solvent.

The density of the first filler in the total volume of the filler contained in the epoxy resin composition is set ^{to 2.20 g / cm 3} for the density of boron nitride and 1.20 g / cm ^{3 for} the density of the mixture of the resin monomer A and CRN. When the content was calculated, it was 90% by volume. As for the content of the first filler in the filler, a particle group having a peak of 20 μm or more was taken out from the weight cumulative particle size distribution curve and used as the first filler. Moreover, when the ratio of the filler (the sum of the first filler and the second filler) to the total solid content of the epoxy resin composition was calculated, it was 70% by volume.

<Preparation of semi-cured epoxy resin composition>
The epoxy resin varnish was applied onto a PET film using an applicator so that the thickness after drying was 200 μm, and then dried at room temperature (20 ° C to 30 ° C) for 5 minutes and further at 130 ° C for 5 minutes. .. Then, hot pressurization (press temperature: 165 ° C., vacuum degree: 1 kPa, press pressure: 15 MPa, pressurization time: 2 minutes) was performed by a vacuum press to obtain a sheet-shaped semi-cured epoxy resin composition.

<Preparation of cured epoxy resin composition with copper foil>
After peeling off the PET film of the semi-cured epoxy resin composition obtained above, the matte surface of the copper foil is sandwiched between two copper foils so as to face the semi-cured epoxy resin composition, respectively, and vacuum pressed. (Press temperature: 180 ° C., vacuum degree: 1 kPa, press pressure: 15 MPa, pressurization time: 6 minutes). Then, under atmospheric pressure conditions, it was heated at 150 ° C. for 2 hours and at 210 ° C. for 4 hours to obtain a cured epoxy resin composition with a copper foil.

<Measurement of thermal conductivity>
(Thermal conductivity in the thickness direction)
The copper foil of the cured epoxy resin composition with a copper foil obtained above was etched and removed to obtain a sheet-shaped cured epoxy resin composition (cured resin sheet). The obtained cured resin sheet was cut into 10 mm × 10 mm to obtain a sample. After blackening this sample with a graphite spray, the thermal diffusivity was evaluated by a xenon flash method (trade name: LFA447 nanoflash manufactured by NETZSCH). From the product of this value, the density measured by the Archimedes method, and the specific heat measured by DSC (differential scanning calorimetry device; trade name: DSC Pyris1 manufactured by PerkinElmer), the thickness direction of the cured resin sheet The thermal conductivity was calculated.
The results are shown in Table 1.

(In-plane thermal conductivity)
The copper foil of the cured epoxy resin composition with a copper foil obtained above was etched and removed to obtain a sheet-shaped cured epoxy resin composition (cured resin sheet). The obtained cured resin sheet was cut into 5 mm × 30 mm to obtain a sample. After blackening the sample with a graphite spray, the thermal diffusivity was evaluated by the optical exchange method (trade name: Laser-PIT manufactured by ULVAC-RIKO, Inc.). The thermal conductivity of the cured resin sheet in the in-plane direction was determined from the product of this value, the density measured by the Archimedes method, and the specific heat measured by DSC (trade name: DSC Pyris1 manufactured by PerkinElmer). ..

(Confirmation of smectic structure formation)
The copper foil of the cured epoxy resin composition with a copper foil obtained above was etched and removed to obtain a sheet-shaped cured epoxy resin composition (cured resin sheet). The obtained cured resin sheet was cut into 10 mm × 10 mm to obtain a sample. This sample is subjected to X-ray diffraction (X-ray analyzer manufactured by Rigaku Co., Ltd.) in the range of tube voltage 40 kV, tube current 20 mA, 2θ = 2 ° to 30 ° using _{CuK α 1 wire, and 2θ = 2 ° to 10} The formation of smectic structures was confirmed by the presence or absence of diffraction peaks in the ° range.

(Example 2)
Resin monomer A is 7.05% by mass, the first filler (HP-40) is 15.61% by mass, the second filler (MBN-010T) is 15.61% by mass, and the filler (AA-18: 7). .04% by mass, AA-04: 7.04% by mass) in total 14.08% by mass, CRN 4.14% by mass, TPP 0.07% by mass, and CHN 43.44% by mass. An epoxy resin varnish was obtained as an epoxy resin composition containing a solvent.

Fillers contained in the epoxy resin composition, where the density of boron nitride is 2.20 g / cm ³ , the density of alumina is 3.98 g / cm ^3, and the density of the mixture of resin monomer A and CRN is 1.20 g / cm ^3. When the contents of the first filler and the second filler in the total volume of the above were calculated, they were both 40% by volume. Moreover, when the ratio of the filler to the total solid content of the epoxy resin composition was calculated, it was 70% by volume.

A semi-cured epoxy resin composition and a cured epoxy resin composition were prepared in the same manner as in Example 1 except that the epoxy resin varnish obtained above was used, and evaluated in the same manner as described above.
The results are shown in Table 1.

(Example 3)
The tree resin monomer A is 7.05% by mass, the first filler (HP-40) is 15.61% by mass, the second filler (MBN-010T) is 15.61% by mass, and the filler is (AA-3). : 7.04% by mass, AA-04: 7.04% by mass) in total 14.08% by mass, CRN 4.14% by mass, TPP 0.07% by mass, and CHN 43.44% by mass. Then, an epoxy resin varnish was obtained as an epoxy resin composition containing a solvent.

The density of the boron nitride 2.2 g / cm ^3, the density of a mixture of a density of the alumina 3.98 g / cm ³ and the resin monomers A and CRN as 1.20 g / cm ^3, a filler contained in the epoxy resin composition When the contents of the first filler and the second filler in the total volume of the above were calculated, they were both 40% by volume. Moreover, when the ratio of the filler to the total solid content of the epoxy resin composition was calculated, it was 70% by volume.

A semi-cured epoxy resin composition and a cured epoxy resin composition were prepared in the same manner as in Example 1 except that the epoxy resin varnish obtained above was used, and evaluated in the same manner as described above.
The results are shown in Table 1.

(Comparative Example 1)
<Preparation of epoxy resin composition>
Resin monomer A is 5.98% by mass, filler (AA-04: 7.29% by mass, AA-18: 48.08% by mass, AA-3: 17.48% by mass) is 72.85% by mass in total. CRN is 3.48% by mass, TPP is 0.06% by mass, KBM-573 is 0.08% by mass, and solvent (MEK: 14.47% by mass, CHN: 3.08% by mass) is 17.55 in total. By mixing by mass%, an epoxy resin varnish was obtained as an epoxy resin composition containing a solvent.

The density of the alumina 3.98 g / cm ^3, and the density of the mixture of the resin monomers A and CRN as 1.20 g / cm ^3, containing the first filler in the total volume of the filler contained in the epoxy resin composition When the rate was calculated, it was 0% by volume. Moreover, when the ratio of the filler to the total solid content of the epoxy resin composition was calculated, it was 74% by volume.

<Preparation of semi-cured epoxy resin composition>
The epoxy resin varnish was applied onto a PET film using an applicator so that the thickness after drying was 200 μm, and then dried at room temperature (20 ° C to 30 ° C) for 15 minutes and further at 130 ° C for 5 minutes. .. Then, hot pressurization (press temperature: 130 ° C., vacuum degree: 1 kPa, press pressure: 1 MPa, pressurization time: 1 minute) was performed by a vacuum press to obtain a sheet-shaped semi-cured epoxy resin composition.

<Preparation of cured epoxy resin composition with copper foil>
After peeling off the PET film of the semi-cured epoxy resin composition obtained above, the matte surface of the copper foil is sandwiched between two copper foils so as to face the semi-cured epoxy resin composition, respectively, and subjected to vacuum pressing. Vacuum heat crimping (press temperature: 180 ° C., vacuum degree: 1 kPa, press pressure: 4 MPa, pressurization time: 5 minutes). Then, under atmospheric pressure conditions, the mixture was heated at 140 ° C. for 2 hours, 165 ° C. for 2 hours, and further at 190 ° C. for 2 hours to obtain a cured epoxy resin composition with a copper foil.

The cured epoxy resin composition with a copper foil obtained above was used and evaluated in the same manner as in Example 1.

(Comparative Example 2)
Resin monomer A is 7.93% by mass, the first filler (HP-40) is 35.10% by mass, and the filler (AA-3: 7.95% by mass, AA-04: 7.95% by mass) is further added. A total of 15.90% by mass, CRN 4.67% by mass, TPP 0.08% by mass, and CHN 36.32% by mass were mixed to obtain an epoxy resin varnish as an epoxy resin composition containing a solvent.

Fillers contained in the epoxy resin composition, where the density of boron nitride is 2.20 g / cm ³ , the density of alumina is 3.98 g / cm ^3, and the density of the mixture of resin monomer A and CRN is 1.20 g / cm ^3. When the content of the first filler in the total volume of was calculated, it was 80% by volume. Moreover, when the ratio of the filler to the total solid content of the epoxy resin composition was calculated, it was 70% by volume.

A semi-cured epoxy resin composition and a cured epoxy resin composition were prepared in the same manner as in Example 1 except that the epoxy resin varnish obtained above was used, and evaluated in the same manner as described above.
The results are shown in Table 1.

(Comparative Example 3)
Resin monomer A is 5.70% by mass, the second filler (MBN-010T) is 25.19% by mass, and the filler (AA-3: 5.73% by mass, AA-04: 5.73% by mass) is further added. A total of 11.46% by mass, CRN 3.35% by mass, TPP 0.06% by mass, and CHN 54.24% by mass were mixed to obtain an epoxy resin varnish as an epoxy resin composition containing a solvent.

The density of the boron nitride 2.2 g / cm ^3, the density of a mixture of a density of the alumina 3.98 g / cm ³ and the resin monomers A and CRN as 1.20 g / cm ^3, a filler contained in the epoxy resin composition When the content of the second filler in the total volume of was calculated, it was 80% by volume. Moreover, when the ratio of the filler to the total solid content of the epoxy resin composition was calculated, it was 70% by volume.

A semi-curable epoxy resin composition and a cured epoxy resin composition were produced in the same manner as in Example 1 except that the epoxy resin varnish obtained above was used.

(Comparative Example 4)
Resin monomer A is 7.05% by mass, the first filler (HP-40) is 15.61% by mass, and further the filler (SP-3: 15.61% by mass, AA-3: 7.04% by mass, AA). -04: 7.04% by mass) in total 14.08% by mass, CRN 4.14% by mass, TPP 0.07% by mass, and CHN 43.44% by mass, and an epoxy resin composition containing a solvent. An epoxy resin varnish was obtained as a product.

Fillers contained in the epoxy resin composition, where the density of boron nitride is 2.20 g / cm ³ , the density of alumina is 3.98 g / cm ^3, and the density of the mixture of resin monomer A and CRN is 1.20 g / cm ^3. When the content of the first filler in the total volume of was calculated, it was 40% by volume. Moreover, when the ratio of the filler to the total solid content of the epoxy resin composition was calculated, it was 70% by volume.

A semi-cured epoxy resin composition and a cured epoxy resin composition were prepared in the same manner as in Example 1 except that the epoxy resin varnish obtained above was used, and evaluated in the same manner as described above.
The results are shown in Table 1.

(Comparative Example 5)
Resin monomer A is 5.70% by mass, other fillers (SP-3: 25.19, AA-3: 5.73% by mass, AA-04: 5.73% by mass) are total 36.65% by mass, CRN. Was mixed at 3.35% by mass, TPP at 0.06% by mass, and CHN at 54.24% by mass to obtain an epoxy resin varnish as an epoxy resin composition containing a solvent.

The density of the boron nitride 2.2 g / cm ^3, the density of a mixture of a density of the alumina 3.98 g / cm ³ and the resin monomers A and CRN as 1.20 g / cm ^3, the total solid content of the epoxy resin composition When the ratio of the filler to the total volume of was calculated, it was 70% by volume.

A semi-cured epoxy resin composition and a cured epoxy resin composition were prepared in the same manner as in Example 1 except that the epoxy resin varnish obtained above was used, and evaluated in the same manner as described above.
The results are shown in Table 1.

(Comparative Example 6) The resin monomer A is 8.13% by mass, the first filler (HP-40) is 40.40% by mass, the filler (SP-3) is 4.49% by mass, and the CRN is 4.77. Epoxy resin varnish was obtained as an epoxy resin composition containing a solvent by mixing% by mass, 0.08% by mass of TPP, and 42.13% by mass of CHN.

The density of the boron nitride 2.2 g / cm ^3, the density of a mixture of a density of the alumina 3.98 g / cm ³ and the resin monomers A and CRN as 1.20 g / cm ^3, a filler contained in the epoxy resin composition When the content of the first filler in the total volume of was calculated, it was 90% by volume. Moreover, when the ratio of the filler to the total solid content of the epoxy resin composition was calculated, it was 70% by volume.

A semi-cured epoxy resin composition and a cured epoxy resin composition were prepared in the same manner as in Example 1 except that the epoxy resin varnish obtained above was used, and evaluated in the same manner as described above.
The results are shown in Table 1.

From the above results, the particle size D50 corresponding to the cumulative 50% from the small particle size side of the weight cumulative particle size distribution curve is 20 μm or more, and the ratio of the length in the width direction to the length in the thickness direction of the primary particles. The first filler containing the boron nitride particles or the aggregates of the boron nitride particles having an average value of the aspect ratio (length in the width direction / length in the thickness direction) represented by 30 or less, and the particle diameter. The epoxy resin composition containing boron nitride particles having a D50 of less than 10 μm and an average aspect ratio of 5 or less or a second filler containing an aggregate of the boron nitride particles is anisotropic after curing. It was found that the particles are small and exhibit high thermal conductivity.

Claims (14)

Contains an epoxy resin monomer, a curing agent, and a filler,
The epoxy resin monomer contains an epoxy resin monomer having a mesogen group, and the epoxy resin monomer contains.
The filler has a particle size D50 corresponding to a cumulative 50% from the small particle size side of the weight cumulative particle size distribution curve of 20 μm or more, and is a ratio of the length in the width direction to the length in the thickness direction of the primary particles. A first filler containing boron nitride particles or an aggregate of the boron nitride particles having an average value of the represented aspect ratios (length in the width direction / length in the thickness direction) of 30 or less, and the particle size D50. Includes a boron nitride particle having an aspect ratio of less than 10 μm and an average aspect ratio of 5 or less, or a second filler containing an aggregate of the boron nitride particles.
The filler contains alumina, and the content ratio of the first filler to the first filler (first filler / second filler) is 4.0 / 6.0 to 8.0 / 2 on a volume basis. Epoxy resin composition within the range of 0.0. Contains an epoxy resin monomer, a curing agent, and a filler,
The epoxy resin monomer contains an epoxy resin monomer having a mesogen group, and the epoxy resin monomer contains.
The filler has at least a first peak above 20 μm and a second peak below 10 μm in the particle size distribution curve.
The first peak is composed of the first filler, and the first filler has an aspect ratio (length in the width direction / length in the width direction) expressed by the ratio of the length in the width direction to the length in the thickness direction of the primary particle. Contains boron nitride particles or aggregates of the boron nitride particles having an average value (length in the thickness direction) of 30 or less.
The second peak is composed of the second filler, and the second filler contains boron nitride particles having an average aspect ratio of 5 or less or an aggregate of the boron nitride particles.
The filler contains alumina, and the content ratio of the first filler to the first filler (first filler / second filler) is 4.0 / 6.0 to 8.0 / 2 on a volume basis. Epoxy resin composition within the range of 0.0. The epoxy resin composition according to claim 1 or 2, wherein the content of the filler is 50% by volume to 90% by volume. The epoxy resin composition according to any one of claims 1 to 3, wherein the filler further contains at least one filler selected from the group consisting of silica and aluminum nitride. The epoxy resin composition according to any one of claims 1 to 4, wherein the epoxy resin monomer contains a compound represented by the following general formula (I).

[In the general formula (I), R ^{1 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ] The epoxy resin composition according to any one of claims 1 to 5, wherein the curing agent contains a novolak resin in which a bifunctional phenol compound is linked with a methylene chain. Any of claims 1 to 6, wherein the curing agent contains a novolak resin having a structural unit represented by at least one selected from the group consisting of the following general formulas (II-1) and (II-2). The epoxy resin composition according to claim 1.

[In the general formulas (II-1) and (II-2), R ²¹ and R ²⁴ independently represent an alkyl group, an aryl group or an aralkyl group, respectively. R ²² , R ²³ , R ²⁵ and R ²⁶ each independently represent a hydrogen atom, an alkyl group, an aryl group or an aralkyl group. m21 and m22 each independently represent an integer of 0 to 2. n21 and n22 each independently represent an integer of 1 to 7. ] Any one of claims 1 to 7, wherein the curing agent contains a novolak resin having a structure represented by at least one selected from the group consisting of the following general formulas (III-1) to (III-4). The epoxy resin composition according to item 1.

[In the general formulas (III-1) to (III-4), m31 to m34 and n31 to n34 independently represent positive integers, respectively. Ar ^{31 to} Ar ³⁴ independently represent a group represented by the following general formula (III-a) or a group represented by the following general formula (III-b). ]

[In the general formulas (III-a) and (III-b), R ³¹ and R ³⁴ independently represent a hydrogen atom or a hydroxyl group, respectively. R ³² and R ³³ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ] The curing agent contains a monomer which is a phenol compound constituting the novolak resin, and the content of the monomer is 5% by mass to 80% by mass in the curing agent. Any one of claims 6 to 8. The epoxy resin composition according to item 1. A resin sheet which is a sheet-shaped molded product of the epoxy resin composition according to any one of claims 1 to 9. A prepreg comprising a fiber base material and the epoxy resin composition according to any one of claims 1 to 9, which is impregnated with the fiber base material. A metal foil with a resin comprising a metal foil and a sheet obtained by using the epoxy resin composition according to any one of claims 1 to 9 arranged on the metal foil. At least one selected from the group consisting of the metal support, the epoxy resin composition according to any one of claims 1 to 9, the resin sheet according to claim 10 , and the prepreg according to claim 11. A metal substrate comprising two cured product layers and a metal foil in this order. A semiconductor module in which a metal plate, a solder layer, and a semiconductor chip are laminated in this order,
With heat dissipation member,
The cured product of the epoxy resin composition according to any one of claims 1 to 9, which is arranged between the metal plate of the semiconductor module and the heat radiating member.
Power semiconductor devices including.

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