JP7151156B2 - High thermal conductivity curable composition, high thermal conductivity cured film, laminate and power module - Google Patents

Description

The present invention relates to a highly thermally conductive curable composition, a highly thermally conductive cured film, a laminate and a power module.

Materials (for example, insulating materials) constituting electrical and electronic devices are often required to have heat dissipation properties.
In recent years, in particular, with the development of power modules, various developments have been made on curable compositions with high heat dissipation.

As this type of technology, for example, the technology described in Patent Literature 1 is known. Patent Document 1 describes that a material having high thermal conductivity can be provided by using an epoxy resin or the like having a mesogenic skeleton.
Patent Documents 2 and 3 also describe materials having high thermal conductivity using epoxy resins having a mesogenic skeleton.

JP 2014-139021 A JP 2013-6893 A JP 2013-48257 A

The inventors of the present invention made various studies on epoxy resins having a mesogenic skeleton, such as those described in Patent Documents 1 to 3, and found that they had a problem of relatively low heat resistance. More specifically, the inventors have found that the use of an epoxy resin having a mesogenic skeleton can improve the thermal conductivity, but conversely reduces the heat resistance.

The present invention has been made in view of such circumstances. In other words, an object of the present invention is to provide a highly thermally conductive curable composition having good heat resistance.

As a result of investigation, the present inventors succeeded in obtaining a curable composition with good heat resistance and high thermal conductivity by focusing on a curing system different from epoxy. Specifically, the invention provided below has been completed to achieve the above objects.

According to the invention,
a cyanate compound;
a benzoxazine compound having a structure represented by the following general formulas (B-1) and/or (B-2);
and at least one thermally conductive particle selected from the group consisting of alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide and magnesium oxide.

In general formula (B-1),
a represents an integer of 0 to 3,
R ₁ and R ₂ each independently represent a hydrogen atom or a monovalent organic group, and when a is 2 or more, multiple R ₂ may be the same or different.

Moreover, according to the present invention,
A highly thermally conductive cured film produced using the highly thermally conductive curable composition,
A highly thermally conductive cured film having a coefficient of linear expansion of 36 to 47 ppm/°C at 50 to 150°C is provided.

Moreover, according to the present invention,
a metal layer;
and a cured product of the highly thermally conductive curable composition provided on at least one side of the metal layer.

Moreover, according to the present invention,
the laminate;
and an electronic component provided on the laminate.

INDUSTRIAL APPLICABILITY According to the present invention, a highly thermally conductive curable composition having good heat resistance is provided.

FIG. 2 is a diagram schematically showing an example of the structure of a power module; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The drawings are for illustrative purposes only. The shape and dimensional ratio of each member in the drawings do not necessarily correspond to the actual article.

In this specification, the notation "a to b" in the description of numerical ranges means from a to b, unless otherwise specified. For example, "1 to 5% by mass" means "1% by mass or more and 5% by mass or less".
In the description of a group (atomic group) in the present specification, a description without indicating whether it is substituted or unsubstituted includes both those having no substituent and those having a substituent. For example, the term “alkyl group” includes not only alkyl groups without substituents (unsubstituted alkyl groups) but also alkyl groups with substituents (substituted alkyl groups).
The notation "(meth)acryl" used herein represents a concept that includes both acryl and methacryl. The same applies to similar notations such as "(meth)acrylate".

<High thermal conductivity curable composition>
The highly thermally conductive curable composition of the present embodiment is
a cyanate compound;
a benzoxazine compound containing a structure represented by the following general formulas (B-1) and/or (B-2);
and at least one thermally conductive particle selected from the group consisting of alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide and magnesium oxide.

一般式（Ｂ－１）中、
ａは０～３の整数を表し、
Ｒ_１およびＲ_２はそれぞれ独立に、水素原子または１価の有機基を表し、ａが２以上の場合、複数のＲ_２は同一でも異なっていてもよい。
一般式（Ｂ－２）中、
ｂは０～４の整数を表し、
Ｒ_３は、水素原子または１価の有機基を表し、ｂが２以上の場合、複数のＲ_３は同一でも異なっていてもよい。

In general formula (B-1),
a represents an integer of 0 to 3,
R ₁ and R ₂ each independently represent a hydrogen atom or a monovalent organic group, and when a is 2 or more, multiple R ₂ may be the same or different.
In general formula (B-2),
b represents an integer of 0 to 4,
R ₃ represents a hydrogen atom or a monovalent organic group, and when b is 2 or more, multiple R ₃ may be the same or different.

Note that benzoxazine compounds having structures represented by general formulas (B-1) and/or (B-2) are hereinafter simply referred to as “benzoxazine compounds”.

The highly thermally conductive curable composition of the present embodiment includes a cyanate compound (a compound having a functional group represented by —O—CN) and a benzoxazine compound having the general formula (B-1) and / or (B- It is believed that by reacting with the structure represented by 2), a strong chemical structure is formed and the heat resistance is improved compared to conventional epoxy-based compositions.

In addition, the highly thermally conductive curable composition of the present embodiment also has good thermal conductivity (heat dissipation). Although it is presumed, as a result of the reaction of the cyanate compound and the benzoxazine compound (and in some cases, the phenol compound described later), a triazine skeleton, which is a six-membered heteroaromatic ring, is formed, which has thermal conductivity (heat dissipation). ) may be related to the improvement of

Regarding thermal conductivity, when the highly thermally conductive curable composition of the present embodiment is cured to form a film, thermal conductivity in the thickness direction of the film required for the power module described later can also be ensured.

Furthermore, when the highly thermally conductive curable composition of the present embodiment is formed into a cured film, the coefficient of linear expansion tends to be an appropriate value. Here, “easy to set an appropriate value” means that the absolute value of the difference between α and α _Cu can be easily reduced when the thermal expansion coefficient of the cured film is α and the thermal expansion coefficient of copper is α _Cu . be.
A cured product of a conventional epoxy-based composition has a large difference in coefficient of thermal expansion from that of copper, and there was concern that repeated thermal expansion and contraction would likely cause damage, peeling, and the like. The cured film of the highly thermally conductive curable composition of the present embodiment is preferable because it is easy to reduce the difference in thermal expansion coefficient from that of copper as compared with a cured product of a conventional composition. The reason for this is presumed to be that the structure formed by the reaction between the cyanate compound and the benzoxazine compound is rigid.

Just to make sure, the above presumed reasons and the like do not limit the scope of the present invention.

Components and the like of the highly thermally conductive curable composition of the present embodiment will be described.

Cyanate compound The cyanate compound contained in the highly thermally conductive curable composition of the present embodiment is not particularly limited as long as it has a cyanate group (functional group represented by —O—CN).
The cyanate compound preferably has multiple cyanate groups in one molecule. More specifically, the cyanate compound preferably has 2 to 4, more preferably 2 cyanate groups per molecule. By using such a cyanate compound, it is believed that the curing performance can be further improved and the heat resistance is also improved.

From another point of view, the cyanate compound preferably contains a conjugated double bond (a structure having alternating single and double bonds) in its molecule. By using such a cyanate compound, when the composition is cured, a so-called mesogenic structure (a rigid site capable of exhibiting liquid crystallinity) is included in the cured product. When the mesogenic structure is contained in the cured product, it is advantageous from the viewpoint of thermal conductivity, and the thermal conductivity (heat dissipation) can be further enhanced.
As such a cyanate compound, for example, a compound represented by the following general formula (a1) containing a conjugated double bond in the R portion can be mentioned.

As the cyanate compound, those represented by the following general formula (a1) can be preferably mentioned.

In general formula (a1), R is a divalent linking group, preferably a group containing a conjugated double bond.
More specifically, R is a group represented by the general formula -A ¹ -XA ² -. In this general formula, A ¹ and A ² each independently represent a group selected from an aromatic group, a condensed aromatic group, an alicyclic group, and an alicyclic heterocyclic group. Also, X is a single bond or a divalent linking group.

Here, A ¹ or A ² is preferably a hydrocarbon group having 6 to 12 carbon atoms having a benzene ring, a hydrocarbon group having 10 to 20 carbon atoms having a naphthalene ring, or a hydrocarbon group having 12 to 24 carbon atoms having a biphenyl structure. Hydrocarbon groups, hydrocarbon groups of 12 to 36 carbon atoms having 3 or more benzene rings, hydrocarbon groups of 12 to 36 carbon atoms having a condensed aromatic group, alicyclic heterocyclic groups of 4 to 36 carbon atoms, etc. is.

Specific examples of A ¹ and A ² include phenylene, biphenylene, naphthylene, anthracenylene, cyclohexyl, pyridyl, pyrimidyl and thiophenylene. These may be unsubstituted or may have substituents such as aliphatic hydrocarbon groups, halogen groups, cyano groups and nitro groups.

X is, for example, a single bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -CH ₂ -CH ₂ -, -C=C-, -C≡C-, -CO-O-, - A divalent substituent selected from the group CO-NH-, -CH=N-, -CH=N-N=CH-, -N=N- or -N(O)=N- is preferred.

Alternatively, the cyanate compound may be in the form of polymer, oligomer, or the like. That is, it may be a compound having a cyanate group in the main chain, side chain, end, or the like of a polymer or oligomer. For example, polymers and oligomers containing structural units represented by general formula (a2) below can be mentioned. By using such a polymer or oligomer having an aromatic ring skeleton (that is, a conjugated double bond) as a cyanate compound, thermal conductivity (heat dissipation) can be enhanced.

In general formula (a2), R represents a monovalent substituent, and n represents an integer of 0-3.
Specific examples of the monovalent substituent for R include a monovalent organic group, a halogen atom, a hydroxyl group, a carboxyl group, and the like. Examples of monovalent organic groups include alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkynyl groups, and the like.

The highly thermally conductive curable composition of the present embodiment may contain only one type of cyanate compound, or may contain two or more types.
Although the amount of the cyanate compound in the composition is not particularly limited, for example, the amount of the cyanate compound is 20 to 70% by mass, preferably 30 to 60% by mass, based on the total resin component. In addition, the "resin component" represents a cyanate compound, a benzoxazine compound and a phenol compound (the same shall apply hereinafter).

Benzoxazine compound The benzoxazine compound contained in the highly thermally conductive curable composition of the present embodiment is a compound having a structure represented by general formula (B-1) and/or (B-2), especially Not limited.

In general formula (B-1),
a represents an integer of 0 to 3,
R ₁ and R ₂ each independently represent a hydrogen atom or a monovalent organic group, and when a is 2 or more, multiple R ₂ may be the same or different.
In general formula (B-2),
b represents an integer of 0 to 4,
R ₃ represents a hydrogen atom or a monovalent organic group, and when b is 2 or more, multiple R ₃ may be the same or different.
Note that * represents a bond with another chemical structure.

Specific examples of R ₁ include a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group and an alkynyl group. R ₁ may be substituted with any substituent.
R ₁ is preferably an aryl group, more preferably a phenyl group. It is considered that the heat resistance can be further improved by this.

Specific examples of R ₂ and R ₃ include aliphatic hydrocarbon groups and aromatic hydrocarbon groups.
a is preferably 0 or 1, more preferably 0;
b is preferably 0 or 1, more preferably 0.

The benzoxazine compound preferably has a plurality of structures represented by general formulas (B-1) and/or (B-2) in one molecule. More specifically, the benzoxazine compound preferably has 2 to 4, more preferably 2 structures represented by general formulas (B-1) and/or (B-2) in one molecule. have. By using such a compound, it is believed that the curing performance can be further improved and the heat resistance is also improved.

From another point of view, the benzoxazine compound preferably contains a conjugated double bond (a structure having alternating single and double bonds) in its molecule. By using such a cyanate compound, when the composition is cured, a so-called mesogenic structure (a rigid site capable of exhibiting liquid crystallinity) is included in the cured product. When the mesogenic structure is contained in the cured product, it is advantageous from the viewpoint of thermal conductivity, and the thermal conductivity (heat dissipation) can be further enhanced.
Such benzoxazine compounds include, for example, compounds represented by the following general formula (b1) or (b2) containing a conjugated double bond in the R portion, and compounds in which R in general formula (b1) is One that is a single bond can be mentioned.

Specific embodiments of the benzoxazine compound include compounds represented by the following general formula (b1) or (b2).

In general formula (b1), R ₁ and R ₂ have the same definitions as in general formula (B-1), and R is a single bond or a divalent linking group.
In general formula (b1), two R _1s may be the same or different. Also, when two or more R ₂ are present, each R ₂ may be the same or different.
In general formula (b1), when R is a divalent linking group, specific examples thereof are the same as those for R in general formula (a1).

In general formula (b2), R ₃ has the same definition as in general formula (B-2), and R is a divalent linking group.
In general formula (b1), when two or more R ₃ are present, each R ₃ may be the same or different.
Specific examples of R in general formula (b1) are the same as those of R in general formula (a1).

The high thermal conductivity curable composition of the present embodiment may contain only one kind of benzoxazine compound, or may contain two or more kinds.
Although the amount of the benzoxazine compound in the composition is not particularly limited, it is, for example, 30 to 80% by mass, preferably 40 to 70% by mass, based on the total resin component.

- Thermally conductive particles The highly thermally conductive curable composition of the present embodiment contains at least one thermally conductive particle selected from the group consisting of alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide and magnesium oxide. .
Among these, from the viewpoint of thermal conductivity, the thermally conductive particles preferably contain boron nitride or aluminum nitride.
The boron nitride can comprise monodisperse particles, agglomerated particles or mixtures thereof of scaly boron nitride.
Moreover, from the viewpoint of the balance between thermal conductivity and insulation, at least one of magnesium oxide and alumina may be used.
The shape of the thermally conductive particles is not particularly limited, but can usually be spherical.

The particle size of the thermally conductive particles is not particularly limited, but for example, the median diameter (D ₅₀ ) value is preferably 1 to 200 μm, more preferably 2 to 100 μm. The median diameter can be calculated, for example, based on a weight cumulative particle size distribution measured using a laser diffraction method.

The highly thermally conductive curable composition of the present embodiment may contain only one type of thermally conductive particles, or may contain two or more types thereof.
The case of containing two or more types of thermally conductive particles specifically includes the case of containing two or more types of thermally conductive particles having different elemental compositions, or the case of containing two or more types of thermally conductive particles having the same elemental composition but different particle sizes. It may contain conductive particles. In the latter case, the thermally conductive particles may have at least two peaks or at least three peaks in their particle size distribution curve.

The amount of thermally conductive particles is 50-90% by volume, preferably 60-90% by volume, more preferably 60-85% by volume, based on the total solids volume of the composition. As another aspect, the total content of the thermally conductive particles is, for example, 1 to 90% by mass, 5 to 85% by mass, preferably 10 to 85% by mass, based on the mass of the total solid content of the composition. %. Thermal conductivity can be improved by making it more than the said lower limit. By making it below the said upper limit, the fall of processability can be suppressed.

- Phenol-based compound The highly thermally conductive curable composition of the present embodiment preferably contains a phenol-based compound.
According to the findings of the present inventors, the inclusion of a phenolic compound in the highly thermally conductive curable composition of the present embodiment seems to facilitate the formation of a mesogenic structure in the cured product, and thermal conductivity ( heat dissipation) can be further enhanced. Although it is speculation, the reason for this is thought to be that phenol acts as a catalyst for the cyanate compound, facilitating the formation of the triazine skeleton.

Any compound having a phenolic hydroxyl group can be used as the phenolic compound. For example, a known phenol resin can be used.
Phenol resins include reaction products of phenol compounds and aldehyde compounds such as phenol novolak resins, cresol novolak resins, bisphenol novolak resins, and resol-type phenol resins; and a reaction product with at least one compound selected from the group consisting of compounds and dihaloalkyl compounds.

Also, the phenolic compound may be a low-molecular-weight phenolic compound instead of a phenolic resin. As the low-molecular-weight phenolic compound, a phenolic compound containing 2 to 5 phenolic hydroxyl groups in one molecule is preferred.
More specifically, bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, terpene diphenol, 4,4′-biphenol, 2,2′-biphenol, 3,3′,5,5′-tetramethyl-[ 1,1′-biphenyl]-4,4′-diol, hydroquinone, resorcinol, naphthalenediol, tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, dihydroxy Benzene, dihydroxynaphthalene and the like can be mentioned.

The highly thermally conductive curable composition of the present embodiment may contain only one type of phenolic compound, or may contain two or more types.
The amount of the phenolic compound in the composition is not particularly limited, but is preferably 1 to 20 parts by mass, more preferably 1 to 5 parts by mass when the total amount of the cyanate compound and the benzoxazine compound is 100 parts by mass. Department. By including an appropriate amount of phenolic compound in the composition, a mesogenic structure is likely to be formed when the composition is cured, and the thermal conductivity tends to be further improved.

• Silica particles The highly thermally conductive curable composition of the present embodiment preferably contains silica particles.
By including silica particles in the composition, sedimentation, uneven distribution, etc. of the thermally conductive particles in the composition can be suppressed, and the uniformity of the distribution of the thermally conductive particles when the composition is cured can be improved. can be increased (details are unknown, but it is presumed to be an effect due to the charge of silica particles). This can also improve performance such as thermal conductivity.
Any silica particles may be used, and fumed silica and colloidal silica can be used. Fumed silica is preferred in terms of cost and performance.

The particle size of silica particles is, for example, 1 to 100 nm, preferably 2 to 50 nm. This diameter is considered to further enhance the uniformity of the distribution of the thermally conductive particles described above.
In addition, the particle size here means the primary particle average size according to the laser diffraction method.

Further, the silica particles have an apparent specific gravity of, for example, 10 to 200 g/L, preferably 20 to 100 g/L. By setting this value, it is considered that the uniformity of the distribution of the thermally conductive particles described above can be further improved.
The apparent specific gravity here can be measured based on ISO 787/XI.

As the silica particles, for example, fumed silica AEROSIL (registered trademark) of Nippon Aerosil Co., Ltd. can be used.
The highly thermally conductive curable composition of the present embodiment may contain only one type of silica particles, or may contain two or more types.
The amount of silica particles in the composition is not particularly limited, but is, for example, 0.1 to 5% by mass, preferably 0.2 to 3% by mass, based on the total solid content of the composition.

• Other Components The highly thermally conductive curable composition of the present embodiment may contain various components other than those described above as long as the object of the present invention is not impaired. For example, resins, curing accelerators, release additives, silane coupling agents, antioxidants, surface modifiers (leveling agents and surfactants), and the like may be included. These may be used alone, or may be used in combination of two or more.

Examples of resins include epoxy resins, phenoxy resins, polyimide resins, benzoxazine resins, unsaturated polyester resins, phenol resins, melamine resins, silicone resins, bismaleimide resins, and acrylic resins.
Curing accelerators include imidazoles, organic phosphorus compounds, organic metal salts, tertiary amines, phenol compounds, organic acids and the like.
Release additives include oxidized and non-oxidized polyolefins, carnauba wax, montanic acid esters, montanic acid and stearic acid.
Silane coupling agents include, for example, epoxy silane coupling agents, amino silane coupling agents, mercapto silane coupling agents, ureido silane coupling agents, cationic silane coupling agents, titanate coupling agents, A silicone oil type coupling agent and the like can be mentioned.

・ Supplement about the ratio of each component
In the highly thermally conductive curable composition of the present embodiment, particularly by appropriately adjusting the amount of the cyanate compound and the amount of the benzoxazine compound, the thermal conductivity can be further increased (a mesogenic structure is formed in the cured product. may be easier to arrange properly). In addition, the mechanical properties, durability, etc. of the cured product can be further enhanced.

Specifically, m _a is the number of moles of cyanate groups possessed by the cyanate compound in the composition, and groups of structures represented by general formulas (B-1) and/or (B-2) possessed by the benzoxazine compound are _{m b /} m _a is preferably 0.8 to 1.2, more preferably 0.9 to 1.1.

-Method for producing composition Examples of the method for producing the highly thermally conductive curable composition of the present embodiment include the following methods.
A resin varnish (a varnish-like thermosetting resin composition) can be prepared by dissolving, mixing, and stirring each component other than the thermally conductive particles in a solvent. For this mixing, various mixers such as an ultrasonic dispersion system, a high-pressure collision dispersion system, a high-speed rotation dispersion system, a bead mill system, a high-speed shear dispersion system, and a rotation-revolution dispersion system can be used.

Although the solvent used above is not particularly limited, it is typically an organic solvent. Examples thereof include ketone solvents such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone, ether solvents such as propylene glycol monomethyl ether, and ester solvents such as propylene glycol monomethyl ether acetate and butyl acetate.

In addition, thermally conductive particles are added to the resin varnish obtained as described above, and kneaded using a triple roll or the like to obtain a highly thermally conductive curable composition in a B-stage state (semi-cured state). Obtainable. By adding the thermally conductive particles during kneading, the thermally conductive particles can be more uniformly dispersed in the composition.
Of course, the thermally conductive particles may be added during kneading or during mixing of the resin varnish.
From the viewpoint of dispersibility, the thermally conductive particles are preferably dispersed in a predetermined solvent (nanoparticle dispersion) and added to the resin varnish.

Furthermore, the highly thermally conductive curable composition of the present embodiment can also be obtained by uniformly mixing each component in the form of a solid (powder, etc.).

<High Thermal Conductivity Cured Film, Laminate and Power Module>
A cured product can be obtained by curing the above-described highly thermally conductive curable composition.
For example, a highly thermally conductive cured film of a cured product of a highly thermally conductive curable composition can be provided on the metal layer surface of a substrate having a metal layer thereon. That is, it is possible to obtain a laminate comprising a metal layer and a cured product of a highly thermally conductive curable composition provided on at least one side of the metal layer.
Since the cured product or cured film here has high thermal conductivity, it can be preferably used as a heat dissipating member or the like.

A cured product or cured film can preferably be provided on the copper layer. In other words, in the above "laminate comprising a metal layer and a cured product of a highly thermally conductive curable composition provided on at least one side of the metal layer", the metal layer is preferably a copper layer.
As described above, when the highly thermally conductive curable composition of the present embodiment is formed into a cured film, the difference in coefficient of thermal expansion from copper tends to be smaller than that of a cured product of a conventional composition. Therefore, when the cured film is provided on the copper layer, damage, peeling, etc. due to repeated thermal expansion and contraction can be suppressed.

Quantitatively expressing that “the difference in thermal expansion coefficient is small”, the linear expansion coefficient at 50 to 150 ° C. of the highly thermally conductive cured film produced using the above-described highly thermally conductive curable composition is, for example, 30. ~50 ppm/°C, preferably 36-47 ppm/°C.

The laminate may have layers other than these two layers as long as it has a metal layer and a cured film of a highly thermally conductive curable composition. Moreover, the laminated body may be in a mode in which, for example, the cured film of the highly thermally conductive curable composition is sandwiched from above and below by metal layers of the same or different kind.

The film formation, curing conditions, etc. will be supplemented.
When the highly thermally conductive curable composition is in the form of a varnish, for example, the composition is applied to the surface of an appropriate substrate (for example, the above-described substrate having a metal layer on its surface), and the solvent is dried. and heat curing to obtain a cured film or cured product.
The method of applying the composition is not particularly limited, and can be carried out by spin coating using a spinner, spray coating using a spray coater, bar coating, dipping, printing, roll coating, inkjet method, or the like.
Drying can be performed by heat treatment by any method such as a hot plate, hot air, or oven. The heating temperature is usually 80-150°C, preferably 90-140°C. The heating time is usually 30 to 600 seconds, preferably 30 to 450 seconds.
Thermal curing can also be performed by heating in any manner. A laminate including other members (base material) may be formed by pressing at the same time as heating. When pressing, the conditions can be 1 to 100 MPa, 120 to 260° C., and 10 to 300 minutes. Heating can combine two or more stages of different conditions, and the above conditions such as pressure, temperature, and time can be applied to each stage.

In addition, when the properties of the highly thermally conductive curable composition are in a B-stage state (semi-cured state), a cured film or cured product can be obtained using a known thermosetting resin molding technique. For example, a cured film or cured product can be obtained by compression molding, transfer molding, injection molding, or the like.

Alternatively, the cured film or cured product can be obtained by impregnating a suitable substrate with the highly thermally conductive curable composition and thermally curing it.

A power module to which the above cured product or cured film is applied will be described.
FIG. 1 is a cross-sectional view showing the configuration of the power module 11. As shown in FIG.
The power module 11 can comprise a metal base laminate 100 (comprising a metal substrate 101 , an insulating layer 102 and a metal layer 103 ) and electronic components provided on the metal base laminate 100 .

A power semiconductor element or the like can be used as the electronic component. Power semiconductor devices typically use wide bandgap materials such as SiC, GaN, Ga ₂ O ₃ and diamond, and are designed to be used at high voltages and high currents. is. Of course, other electronic components may be mounted on the metal base laminate 100 besides the power semiconductor element.
The metal-based laminate 100 can function as a heat spreader for heat from electronic components (various types of heat generating elements) that generate heat during operation.

The metal substrate 101 typically serves to dissipate heat accumulated in the metal base laminate 100 . The metal substrate 101 is not particularly limited as long as it is a heat-dissipating metal substrate, and is, for example, a copper substrate, a copper alloy substrate, an aluminum substrate, or an aluminum alloy substrate, preferably a copper substrate or an aluminum substrate, more preferably a copper substrate. By using a copper substrate or an aluminum substrate, the heat dissipation of the metal substrate 101 can be improved.

The thickness of the metal substrate 101 can be appropriately set as long as the object of the present invention is not impaired.
The upper limit of the thickness of the metal substrate 101 is, for example, 20.0 mm or less, preferably 5.0 mm or less. By using the metal substrate 101 having a thickness equal to or less than this numerical value, the thickness of the metal-based laminate 100 as a whole can be reduced. In addition, it is possible to improve the workability of the metal-based laminate 100 in external shape processing, cutting processing, and the like.
Also, the lower limit of the thickness of the metal substrate 101 is, for example, 0.1 mm or more, preferably 1.0 mm or more, and more preferably 2.0 mm or more. By using the metal substrate 101 having a value equal to or greater than this value, the heat dissipation of the metal-based laminate 100 as a whole can be improved.

The insulating layer 102 typically contains a cured product of the above thermosetting resin composition.

The metal layer 103 is provided on the insulating layer 102 and processed for circuits. Examples of the metal forming the metal layer 103 include one or more selected from copper, copper alloys, aluminum, aluminum alloys, nickel, iron, tin, and the like. Among these, the metal layer 103 is preferably a copper layer or an aluminum layer, and particularly preferably a copper layer. By using copper or aluminum, the circuit workability of the metal layer 103 can be improved. For the metal layer 103, a metal foil that is available in plate form or a metal foil that is available in roll form may be used.

The lower limit of the thickness of the metal layer 103 is, for example, 0.01 mm or more, preferably 0.10 mm or more, and more preferably 0.25 mm or more. If it is more than such a numerical value, heat generation of the circuit pattern can be suppressed even in applications requiring a high current.
Also, the upper limit of the thickness of the metal layer 103 is, for example, 2.0 mm or less, preferably 1.5 mm or less, and more preferably 1.0 mm or less. If it is less than such a numerical value, it is possible to improve the circuit workability and to reduce the thickness of the substrate as a whole.

An example of the power module 11 is, as shown in FIG. A power semiconductor element 2 is mounted. The power semiconductor element 2 is electrically connected to the metal layer 103b through the bonding wire 7. As shown in FIG. Power semiconductor element 2 , bonding wires 7 , and metal layers 103 a and 103 b are sealed with sealing material 6 .

The power module 11 may also include other electronic components such as chip capacitors 8 and chip resistors 9 mounted on the metal layer 103 of the metal base laminate 100 . Moreover, the power module 11 may have a structure in which the metal substrate 101 is connected to the heat dissipation fins 5 via a known thermally conductive grease 4 . Moreover, the power module 11 may include the solder resist 10 .

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can be adopted. Moreover, the present invention is not limited to the above-described embodiments, and includes modifications, improvements, etc. within the scope of achieving the object of the present invention.
Examples of reference forms are added below.
1.
a cyanate compound;
a benzoxazine compound having a structure represented by the above general formula (B-1) and/or (B-2);
at least one thermally conductive particle selected from the group consisting of alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide and magnesium oxide;
A highly thermally conductive curable composition comprising:
In general formula (B-1),
a represents an integer of 0 to 3,
R ₁ and R ₂ each independently represent a hydrogen atom or a monovalent organic group, and when a is 2 or more, multiple R ₂ may be the same or different.
In general formula (B-2),
b represents an integer of 0 to 4,
R ₃ represents a hydrogen atom or a monovalent organic group, and when b is 2 or more, multiple R ₃ may be the same or different.
2.
1. A highly thermally conductive curable composition according to
A highly thermally conductive curable composition, wherein at least one compound selected from the group consisting of the cyanate compound and the benzoxazine compound contains a conjugated double bond.
3.
1. or 2. A highly thermally conductive curable composition according to
A highly thermally conductive curable composition further comprising a phenolic compound.
4.
1. ~3. A highly thermally conductive curable composition according to any one of
A highly thermally conductive curable composition further comprising silica particles.
5.
1. ~ 4. A highly thermally conductive cured film produced using the highly thermally conductive curable composition according to any one of
A highly thermally conductive cured film having a linear expansion coefficient of 36 to 47 ppm/°C at 50 to 150°C.
6.
a metal layer;
provided on at least one side of the metal layer; ~ 4. A cured product of the highly thermally conductive curable composition according to any one of
A laminate comprising:
7.
6. A laminate according to
A laminate, wherein the metal layer is a copper layer.
8.
6. or7. A laminate according to any one of
and an electronic component provided on the laminate.

Embodiments of the present invention will be described in detail based on examples and comparative examples. In addition, the present invention is not limited to the examples.

<Preparation of thermally conductive particles>
Aggregated boron nitride, which is a kind of thermally conductive particles, was produced by the following procedure.
A mixture obtained by mixing melamine borate and scaly boron nitride powder was added to an aqueous ammonium polyacrylate solution and mixed for 2 hours to prepare a slurry for spraying. Next, this slurry was supplied to a spray granulator and sprayed under conditions of an atomizer rotation speed of 15000 rpm, a temperature of 200° C. and a slurry supply rate of 5 ml/min to produce composite particles. Then, the obtained composite particles were sintered at 2000° C. in a nitrogen atmosphere to obtain agglomerated boron nitride.

<Preparation of highly thermally conductive curable composition containing no thermally conductive particles>
Resin components (cyanate compound, benzoxazine compound, phenol compound, etc.) were mixed in a mortar according to the proportions shown in Table 1 to obtain compositions of Examples 1-4.
On the other hand, as comparative compositions, epoxy resins and the like shown in Table 2 were melt-mixed on a hot plate, cooled and pulverized to obtain compositions of Comparative Examples 1-3.

<Preparation of highly thermally conductive curable composition containing thermally conductive particles>
First, a resin component (a mixture of a cyanate compound, a benzoxazine compound, a phenol compound, etc.) shown in Table 1 was added to a solvent, cyclohexanone, and stirred to obtain a solution.
Next, in this solution (25.9 parts by mass in terms of resin component), silica particles (manufactured by Nippon Aerosil Co., Ltd., product number: RX-200, primary particle diameter: about 12 nm) 0.7 parts by mass and thermally conductive particles 73.4 parts by mass of (agglomerated boron nitride described above) was added and premixed.
After that, they were uniformly mixed in a planetary mixer (planetary mixer) to obtain a varnish-like composition containing thermally conductive particles.

On the other hand, for the composition for comparison, first, the resin component shown in Table 2 was added to cyclohexanone in the amount shown in Table 2, and the mixture was stirred to obtain a thermosetting resin composition solution. Next, silica particles (manufactured by Nippon Aerosil Co., Ltd., product number: RX-200) and thermally conductive particles (the above aggregated boron nitride) were added to this solution in the amounts shown in Table 2 and premixed. After that, they were mixed in a planetary mixer (planetary mixer) to obtain a varnish-like composition in which the thermally conductive particles were uniformly dispersed.

<Preparation of resin molding (not including thermally conductive particles)>
The resin components shown in Table 1 or Table 2 are mixed in a mortar and pressed at a pressure of 10 MPa at 220° C. for 2 hours to form a disk-shaped molded body with a diameter of 1 cm and a thickness of 1 mm (softening point measurement only by the resin component sample) was obtained. (However, in Example 2, the pressing pressure was 10 MPa, the pressure was 160° C. for 1 hour, and then the pressing pressure was 220° C. for 2 hours.)

<Production of laminate (including thermally conductive particles)>
(1) Application of a highly thermally conductive curable composition on a copper foil First, a copper foil with a thickness of 18 μm with one side roughened (manufactured by Fukuda Metal Foil & Powder Co., Ltd., surface-treated electrolytic copper foil CF-T8G- UN-18), was prepared. Using a hand applicator, the prepared varnish-like highly thermally conductive curable composition was applied to a thickness of 500 μm on the roughened surface of this. This was heated on a hot plate set at 120° C. for 5 minutes to dry the solvent.
As a result, a copper foil having a coating film of a highly thermally conductive curable composition was obtained.

(2) Pressing, formation of laminate, in order from the bottom, a backing plate, a cushion material, a SUS (stainless steel) plate, a copper foil with a coating film of the highly thermally conductive curable composition of (1) above (coating surface (upper surface) and a copper foil (same as used in (1) above) were overlaid and pressed together. For the press, a device "Labo Press" manufactured by Toyo Seiki Seisakusho Co., Ltd. was used, and the temperature was 220 ° C. and the pressure was 10 MPa for 2 hours (however, in Example 2, the press pressure was 10 MPa and the pressure was 160 ° C. for 1 hour. After that, it was further pressed at 220° C. for 2 hours at the same press pressure.).
As a result, a laminate (resin molding) was obtained in which the layer of the cured product of the highly thermally conductive curable composition was sandwiched between the copper foils from above and below.

<Evaluation>
·Heat resistance: measurement of softening point The softening point (°C) of the resin molding obtained above (not including thermally conductive particles) was measured. Particles were measured in compositions that did not contain thermally conductive particles, as this precludes quantitative determination of softening points.
Specifically, using a TMA (Thermal Mechanical Analyzer) test device (TMA/SS6100 manufactured by Seiko Instruments Inc.), a temperature increase rate of 10 ° C./min, a load of 0.05 N, a compression mode, a measurement temperature range of 30 to 330 The temperature at the inflection point of the thermal expansion curve plotted with temperature on the horizontal axis and displacement on the vertical axis was measured by extrapolation. was obtained and used as the softening point.

Coefficient of thermal expansion: coefficient of linear expansion at 50 to 150° C. The coefficient of thermal expansion was obtained from the slope of the linear deformation portion below the softening point of the thermal expansion curve obtained by the above softening point measurement.
It should be noted that, as the knowledge of the present inventors, a resin molded article formed from a composition that does not contain thermally conductive particles and a resin molded article formed from a composition that does not contain thermally conductive particles have substantially the same linear expansion. indicates the coefficient.

・ Td5: 5% weight loss temperature Using a simultaneous differential thermogravimetric measurement device (manufactured by Seiko Instruments, TG / DTA6200 type), under the conditions of a temperature increase rate of 10 ° C./min under a dry nitrogen stream, the sample was By increasing the temperature from 30°C to 650°C, the temperature (Td5) at which the weight of the sample decreases by 5% was calculated.
As a sample, the above-prepared highly thermally conductive curable composition containing no thermally conductive particles (prepared by mixing the components in Table 1 or Table 2 in a mortar) was heated at 220°C for 2 hours. After heating for 1 hour at 160°C and then 2 hours at 220°C for Example 2, a cured product was obtained, which was dried at 100°C for 1 hour before measurement.

・Thermal conductivity (thickness direction)
A small piece with a diameter of 10 mm and a thickness of 0.2 mm is cut out from the resin molded body (not containing thermally conductive particles) or laminate (containing thermally conductive particles) obtained above, and the thermal conductivity in the thickness direction is It was used as a test piece for measurement.
Next, using a Xe flash analyzer TD-1RTV manufactured by ULVAC, the thermal diffusion coefficient (α) in the thickness direction of the plate-shaped test piece was measured by the laser flash method. The measurement was performed at 25° C. in an air atmosphere.
From the measured values of the thermal diffusion coefficient (α), specific heat (Cp), and specific gravity (SP) obtained, thermal conductivity was calculated based on the following formula.
Thermal conductivity [W/m·K]=α[mm ² /s]×Cp[J/kg·K]×Sp[g/cm ³ ]
In Tables 1 and 2, the thermal conductivity of the resin molding (not containing thermally conductive particles) is defined as "thermal conductivity (resin)", and the thermal conductivity of the laminate (containing thermally conductive particles) is defined as "thermal conductivity (resin)". conductivity (composite)”.

The details of the resin components in the table are as follows. In addition, each component below was prepared by synthesizing according to a standard method or by purchasing a commercially available product.

<Cyanate compound>
4HBAHY-OCN: a compound represented by the following chemical formula

PT30: Novolak-type cyanate resin (manufactured by Lonza Japan, having a structure corresponding to the above general formula (a2))

<Benzoxazine compound>
BP-a: a compound represented by the following chemical formula

Pd: a compound represented by the following chemical formula (manufactured by Shikoku Kasei Co., Ltd.)

<Epoxy compound>

Epoxy compound 1: bisphenol A diglycidyl ether represented by the following chemical formula (DGEBA, manufactured by Tokyo Chemical Industry Co., Ltd.)

Epoxy compound 2: terephthalylidene type epoxy resin (DGETAM) represented by the following chemical formula

Curing agent 1: diaminodiphenylmethane (DDM, manufactured by Tokyo Chemical Industry Co., Ltd.)
Curing agent 2: 4,4'-diaminodiphenylethane (DDEt, manufactured by Tokyo Chemical Industry Co., Ltd.)
Curing accelerator 1: 2-methylimidazole (2MZ, manufactured by Tokyo Chemical Industry Co., Ltd.)

As can be seen from Tables 1 and 2, the softening points of the resin moldings of Examples 1 to 4 using cyanate compounds and benzoxazine compounds as resin components are higher than those of Comparative Examples 1 and 2 using epoxy compounds. was also significantly higher. This indicates that the composition of the present embodiment has good heat resistance and can be preferably applied to power modules and the like.

In addition to the softening point, the following can be read or presumed from the examples.
・The coefficient of linear expansion at 50 to 150°C was 30 to 50 ppm/°C. This means that when a film of the composition of the present embodiment is provided on a copper layer, damage, peeling, etc. due to repeated thermal expansion and contraction can be suppressed.
- The thermal conductivity (resin) of the compositions of Examples 1 to 4 was comparable to or better than the comparative example. In other words, it can be said that the heat dissipation properties of the cured product of the cyanate compound and the benzoxazine compound are substantially equal to or higher than the heat dissipation properties of the cured product of the epoxy compound.
- The thermal conductivity (composite) of Examples 1, 2 and 4 was comparable to or better than the Comparative Example. It can be said that the cured product of the highly thermally conductive curable composition of the present embodiment has sufficient thermal conductivity and improved heat resistance. Note that the thermal conductivity (composite) value of Example 3 is small. It is presumed that this is because a uniform cured film including thermally conductive particles and silica particles could not be produced due to poor solubility of some components in the solvent (cyclohexanone). Since the value of the thermal conductivity (resin) of Example 3 is about the same as the others, if the thermally conductive particles and silica particles can be appropriately dispersed, the thermal conductivity (resin) of Examples 1, 2 and 4 can be improved. It is considered to be obtained.
・A composition containing a phenolic compound tended to have a higher thermal conductivity than a composition containing no phenolic compound.

2 Power Semiconductor Element 3 Adhesive Layer 4 Thermal Conductive Grease 5 Radiation Fin 6 Sealing Material 7 Bonding Wire 8 Chip Capacitor 9 Chip Resistor 10 Solder Resist 11 Power Module 100 Metal Base Laminate 101 Metal Substrate 102 Insulating Layer 103 Metal Layer 103a Metal Layer 103b metal layer

Claims (7)

a cyanate compound;
a benzoxazine compound represented by the following general formula (b1) or (b2) ;
at least one thermally conductive particle selected from the group consisting of alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide and magnesium oxide;
a phenolic compound;
A highly thermally conductive curable composition comprising:

In the general formula (b1),
R ₁ is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group or an alkynyl group;
_R2 is a hydrogen atom, an aliphatic hydrocarbon group or an aromatic hydrocarbon group,
R is a group containing a single bond or a conjugated double bond group,
two R ₁ may be the same or different, and when two or more R ₂ are present, each R ₂ may be the same or different;
a is an integer from 0 to 3;
In general formula (b2),
R ₃ is a hydrogen atom, an aliphatic hydrocarbon group or an aromatic hydrocarbon group,
R is a group containing a conjugated double bond group;
when more than one R3 is present _{, each} R3 may be the same or different;
b is an integer from 0 to 4; A highly thermally conductive curable composition according to claim 1,
A high thermal conductivity curable composition wherein the cyanate compound contains a conjugated double bond and/or R in the benzoxazine compound is a group containing a conjugated double bond group . The highly thermally conductive curable composition according to claim 1 or 2,
A highly thermally conductive curable composition further comprising silica particles. A highly thermally conductive cured film produced using the highly thermally conductive curable composition according to any one of claims 1 to 3,
A highly thermally conductive cured film having a linear expansion coefficient of 36 to 47 ppm/°C at 50 to 150°C. a metal layer;
A laminate comprising a cured product of the highly thermally conductive curable composition according to any one of claims 1 to 3 provided on at least one side of the metal layer. A laminate according to claim 5,
A laminate, wherein the metal layer is a copper layer. A laminate according to claim 5 or 6,
and an electronic component provided on the laminate.

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