JP2021155737A - Resin composition, thermally conductive resin sheet, laminated heat radiation sheet, heat dissipating circuit board and power semiconductor device - Google Patents

Abstract

To provide a thermally conductive resin sheet having excellent moisture absorption reflow resistance.SOLUTION: There is provided a resin composition comprising a thermoplastic resin and a thermally conductive filler, wherein the tensile storage modulus (E'(200)) at 200°C of the thermoplastic resin is 8.0×107 or more and 1.0×1010 Pa or less and the mass increasing rate at 85°C and 85% RH of the resin composition is 0.15% or less. Further, there is provided a resin composition comprising a thermoplastic resin and a thermally conductive filler, wherein the tensile storage modulus (E'(300)) at 300°C of the thermoplastic resin is 4.0×107 Pa or more and 1.0×109 Pa or less and the mass increasing rate at 85°C and 85% RH of the resin composition is 0.15% or less.

Description

The present invention relates to a resin composition, a heat-conductive resin sheet made of the resin composition, a laminated heat-dissipating sheet in which a metal plate-like material is laminated on the heat-conductive resin sheet, and a heat-dissipating circuit substrate in which a conductive circuit is laminated. Regarding.

In recent years, power semiconductor devices used in various fields such as railways, automobiles, industrial use, and general household appliances have been replaced with conventional Si power semiconductors in order to further reduce the size, cost, and efficiency. , SiC, AlN, GaN and the like are shifting to power semiconductors.
A power semiconductor device is generally used as a power semiconductor module in which a plurality of semiconductor devices are arranged on a common heat sink and packaged.

Various problems have been pointed out toward the practical use of such power semiconductor devices, and one of them is the problem of heat generation from the device. Power semiconductor devices can be operated at high temperatures to achieve high output and high density, but there is concern that heat generation and the like associated with device switching may reduce the reliability of power semiconductor devices.

In recent years, especially in the fields of electricity and electronics, heat generation due to high density of integrated circuits has become a big problem, and how to dissipate heat has become an urgent issue. As one method for solving this problem, a ceramic substrate having high thermal conductivity such as an alumina substrate or an aluminum nitride substrate is used as a heat dissipation substrate on which a power semiconductor device is mounted. However, ceramic substrates have drawbacks such as being easily broken by impact, being difficult to thin film, and being difficult to miniaturize.

Therefore, a heat radiating sheet using a thermosetting resin such as an epoxy resin and an inorganic filler has been proposed. For example, Patent Document 1 describes a heat-dissipating resin sheet containing an epoxy resin having a Tg of 60 ° C. or lower and boron nitride, and having a boron nitride content of 30% by volume or more and 60% by volume or less. Proposed.

Patent Document 2 proposes a film for a metal substrate, which comprises an inorganic filler having an average major axis of 1 to 50 μm with respect to a polyetherketone-based resin.

Patent Document 3 proposes a heat-resistant thermally conductive packing in which polyetheretherketone (PEEK) is filled with a thermally conductive filler.

Further, Patent Document 4 proposes a polymer composition in which one or more types of oxide having an electronegativity in a specific range and one or more nitrides having an electronegativity in a specific range are added to a semicrystalline polymer. ..

On the other hand, Patent Document 5 has a structure in which boron nitride particles as a highly thermally conductive filler are dispersed in a resin as a matrix, and the boron nitride particles delaminate secondary particles which are a laminate of primary particles. An inorganic-organic composite material has been proposed, which is dispersed in a resin in the state of "peeled flat particles" generated by undergoing a step of causing the particles to grow.

JP-A-2017-036415 Japanese Unexamined Patent Publication No. 03-020354 Japanese Unexamined Patent Publication No. 07-157569 Japanese Patent Application Laid-Open No. 2008-524362 Japanese Unexamined Patent Publication No. 2012-255055

One of the processes for assembling a power semiconductor module is a reflow process. In the reflow process, the temperature of the members is rapidly raised to melt the solder and join the metal members together. In recent years, since the operating temperature has risen with the increase in output and density of power semiconductor devices, heat resistance is also required for the solder used in the reflow process, and high-temperature solder that requires a reflow temperature of 290 ° C is used. It is becoming more common to use it. Therefore, in the reflow step, the step of heating the temperature to around 290 ° C. where the high temperature solder flows and then cooling it is repeated.
Further, when the power semiconductor device is mounted on the module, heating and cooling are repeated in the same manner.

When a circuit board in which a metal plate or the like is attached to a conventional heat-dissipating resin sheet is used, thermal expansion and contraction occur due to repeated temperature changes in the reflow process and the like, and the coefficient of thermal expansion of the resin and the metal plate is increased. Due to the difference, the interface between the heat radiating resin sheet and the metal plate may be peeled off, and the performance of the power semiconductor module may be deteriorated.
In addition, the performance of the power semiconductor module may be further deteriorated because the members absorb moisture during storage before the reflow process and the deterioration of the members in the reflow process is significantly promoted.

Therefore, an object of the present invention is to provide a heat conductive resin sheet having excellent resistance to moisture absorption and reflow.
In addition, in this specification, "moisture absorption reflow resistance" means after making a heat conductive resin sheet a laminate with a metal plate and storing it under high temperature and high humidity conditions (for example, in an environment of 85 ° C. and 85% RH for 3 days). Even after performing a moisture absorption reflow test in which a reflow test (for example, 290 ° C.) is performed, it has high withstand voltage resistance and does not cause deformation due to interfacial peeling with a metal plate and foaming of a heat conductive resin sheet. say.

The resin composition according to one aspect of the present invention is a resin composition containing a thermoplastic resin and a heat conductive filler, and the tensile storage elastic modulus (E'(200)) of the thermoplastic resin at 200 ° C. is 8 It is 0.0 × 10 ⁷ Pa or more and 1.0 × 10 ¹⁰ Pa or less, and the mass increase rate of the resin composition at 85 ° C. and 85% RH is 0.15% or less.
Further, the resin composition according to another aspect of the present invention is a resin composition containing a thermoplastic resin and a heat conductive filler, and has a tensile storage elastic modulus (E'(300)) of the thermoplastic resin at 300 ° C. )) Is 4.0 × 10 ⁷ Pa or more and 1.0 × 10 ⁹ Pa or less, and the mass increase rate of the resin composition at 85 ° C. and 85% RH is 0.15% or less.

The thermally conductive resin sheet obtained from the resin composition of the present invention is excellent in moisture absorption reflow resistance.

It is a cross-sectional SEM image which concerns on an example of embodiment of this invention. It is a schematic diagram which concerns on another example of embodiment of this invention. It is a cross-sectional SEM image which concerns on another example of embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

<Structure of the present invention>
Hereinafter, the configuration of the present invention will be described.

1. 1. Resin Composition The resin composition of the present invention contains a thermoplastic resin and a thermally conductive filler.

The heat conductive resin sheet of the present invention preferably has a mass increase rate of 0.15% or less at 85 ° C. and 85% RH. Among them, it is preferably 0% or more and 0.15% or less, more preferably 0% or more and 0.12% or less, and further preferably 0% or more and 0.10% or less. When the mass increase rate is equal to or less than the above upper limit, the moisture absorbed by the resin composition in a moist heat environment is vaporized and expanded by heating in the reflow process, and foaming inside the heat conductive resin sheet is suppressed. Be done. Therefore, after performing the moisture absorption reflow test, the withstand voltage is less likely to be lowered, the thermal conductivity in the sheet thickness direction is lowered, and the interface with the metal plate is less likely to be peeled off.
The mass increase rate can be measured by the method described in Examples.
The mass increase rate can be adjusted by the type and content of the thermoplastic resin, the type and content of the thermally conductive filler, and the like. However, it is not limited to these.

Hereinafter, each component constituting the resin composition of the present invention will be described in detail.

(1) Thermoplastic resin
Tensile storage modulus at 200 ° C. for the thermoplastic resin in the present invention (E '(200)) is, 8.0 × 1.0 × is preferably from ¹⁰ 10 Pa or more ^{10 7 Pa, 8.0 × 10 7} Pa or higher more preferably at most 5.0 × ¹⁰ 9 Pa, more preferably 8.0 × ¹⁰ 7 Pa or more 3.0 × ¹⁰ 9 Pa or less, and more is 8.0 × ¹⁰ 7 Pa or more 2.0 × ¹⁰ 9 Pa or less More preferred. Further, 1.0 × 10 ⁸ Pa or more and 1.0 × 10 ¹⁰ Pa or less is preferable, 1.0 × 10 ⁸ Pa or more and 5.0 × 10 ⁹ Pa or less is more preferable, and 1.0 × 10 ⁸ Pa or more and 3 It is more preferably 0.0 × 10 ⁹ Pa or less, and even more preferably 1.0 × 10 ⁸ Pa or more and 2.0 × 10 ⁹ Pa or less. Further, 2.0 × 10 ⁸ Pa or more and 1.0 × 10 ¹⁰ Pa or less is preferable, 2.0 × 10 ⁸ Pa or more and 5.0 × 10 ⁹ Pa or less is more preferable, and 2.0 × 10 ⁸ Pa or more and 3 more preferably .0 × ¹⁰ 9 Pa or less, even more preferably from 2.0 × ¹⁰ 8 Pa or more 2.0 × ¹⁰ 9 Pa or less. Further, 3.0 × 10 ⁸ Pa or more and 1.0 × 10 ¹⁰ Pa or less is preferable, 3.0 × 10 ⁸ Pa or more and 5.0 × 10 ⁹ Pa or less is more preferable, and 3.0 × 10 ⁸ Pa or more and 3 more preferably .0 × ¹⁰ 9 Pa or less, more preferably more ^{2.0 × 10 9 Pa 3.0 × 10} 8 Pa or more.
The tensile storage elastic modulus (E'(300)) of the thermoplastic resin in the present invention at 300 ° C. ^{is preferably 4.0 × 10 7} Pa or more and 1.0 × 10 ⁹ Pa or less, preferably 4.0 × 10 ⁷ Pa or more and 6.0 × 10 ⁸ Pa or less are more preferable, 4.0 × 10 ⁷ Pa or more and 4.0 × 10 ⁸ Pa or less are more preferable, 4.0 × 10 ⁷ Pa or more and 2.0 × 10 ⁸ Pa or less. Is even more preferable. Further, 6.0 × 10 ⁷ Pa or more and 1.0 × 10 ⁹ Pa or less are preferable, 6.0 × 10 ⁷ Pa or more and 6.0 × 10 ⁸ Pa or less are more preferable, and 6.0 × 10 ⁷ Pa or more and 4 more preferably .0 × ¹⁰ 8 Pa or less, even more preferably from 6.0 × ¹⁰ 7 Pa or more 2.0 × ¹⁰ 8 Pa or less. Further, 8.0 × 10 ⁷ Pa or more and 1.0 × 10 ⁹ Pa or less are preferable, 8.0 × 10 ⁷ Pa or more and 6.0 × 10 ⁸ Pa or less are more preferable, and 8.0 × 10 ⁷ Pa or more and 4 more preferably .0 × ¹⁰ 8 Pa or less, even more preferably from 8.0 × ¹⁰ 7 Pa or more 2.0 × ¹⁰ 8 Pa or less. Further, 1.0 × 10 ⁸ Pa or more and 1.0 × 10 ⁹ Pa or less are preferable, 1.0 × 10 ⁸ Pa or more and 6.0 × 10 ⁸ Pa or less are more preferable, and 1.0 × 10 ⁸ Pa or more and 4 more preferably .0 × ¹⁰ 8 Pa or less, even more preferably from 1.0 × ¹⁰ 8 Pa or more 2.0 × ¹⁰ 8 Pa or less.
When the tensile storage elastic modulus (E'(200)) is within the above range, the resin composition absorbs moisture in a moist heat environment, and even if the moisture is vaporized by heating in the reflow step, the inside of the thermally conductive resin sheet or It is possible to suppress the generation of bubbles generated at the interface between the sheet and the metal plate, and to suppress the large expansion of the generated bubbles. Therefore, it is possible to suppress a decrease in thermal conductivity and a decrease in withstand voltage due to the generation of bubbles, and it is also possible to suppress peeling of the heat conductive resin sheet from the metal plate.
Further, when the tensile storage elastic modulus (E'(300)) is within the above range, the reflow resistance becomes better, and the decrease in thermal conductivity and the decrease in withstand voltage due to the generation of bubbles can be further suppressed. Further, it is possible to further suppress the thermal conductive resin sheet from peeling off from the metal plate.
The tensile storage elastic modulus (E'(200) and E'(300)) can be measured by the method described in Examples.

It is preferable that the thermoplastic resin used for the heat conductive resin sheet of the present invention does not cause any abnormality even at 290 ° C. for 5 minutes, which is a reflow condition of the heat-dissipating circuit board. To satisfy this, it is recommended to use an amorphous thermoplastic resin having a glass transition temperature (Tg) of at least 300 ° C. or a crystalline thermoplastic resin having a melting point (Tm) of at least 300 ° C. preferable.

In the present invention, the "amorphous thermoplastic resin" refers to a thermoplastic resin having no melting point. On the other hand, the "crystalline thermoplastic resin" refers to a thermoplastic resin having a melting point.

Heat-resistant non-crystalline thermoplastic resins available as commercially available raw materials include polycarbonate resin (Tg: 152 ° C.), modified polyphenylene ether resin (Tg: 211 ° C.), polysulfone resin (Tg: 190 ° C.), and polyphenyl monkey. Examples thereof include phon resin (Tg: 220 ° C.), polyether sulfone resin (Tg: 225 ° C.), and polyetherimide resin (Tg: 217 ° C.).
However, none of these commercially available heat-resistant amorphous thermoplastic resins greatly reaches the glass transition temperature of 300 ° C. or higher.
Further, a thermoplastic polyimide resin having a glass transition temperature of 300 ° C. or higher is commercially available. However, since the thermoplastic polyimide resin has a very high moldable temperature and a very high melt viscosity at the moldable temperature, it is difficult to fill a large amount of the thermally conductive filler. Furthermore, since the molecular structure contains an imide group, it is not preferable to use it as the main component of the thermoplastic resin of the present invention because of its high hygroscopicity.

From the above, the main component of the thermoplastic resin used as the matrix resin in the present invention is preferably a crystalline thermoplastic resin having a melting point of 300 ° C. or higher.
In the present invention, the "main component of the thermoplastic resin" occupies 50% by mass or more of the thermoplastic resin used as the matrix resin in the present invention, particularly 60% by mass or more, and particularly 70% by mass or more. It means that the component occupies 80% by mass or more, and 90% by mass or more (including 100% by mass).

The melting point of the crystalline thermoplastic resin can be measured by the method specified in ISO 1183. Specifically, it can be obtained from the crystal melting peak temperature at the time of secondary temperature rise when the crystalline thermoplastic resin is measured by a differential scanning calorimeter (DSC). As the crystalline thermoplastic resin in the present invention, it is preferable to use a resin in which at least the endothermic peak due to crystal melting can be clearly confirmed and the peak top temperature thereof is 300 ° C. or higher.
Even when the resin composition to which the heat conductive filler is added is measured by a differential scanning calorimetry (DSC), the deterioration of the matrix resin during heat molding is promoted by the addition of the heat conductive filler, except when the deterioration is promoted. Therefore, there is no big difference in melting point.

The melting point of the crystalline thermoplastic resin in the present invention is more preferably 310 ° C. or higher, more preferably 320 ° C. or higher, still more preferably 330 ° C. or higher, from the viewpoint of moisture absorption / reflow resistance at 290 ° C. On the other hand, the upper limit of the melting point is not particularly limited. Above all, from the viewpoint of molding processability and productivity, it is more preferably 380 ° C. or lower, more preferably 370 ° C. or lower, and further preferably 360 ° C. or lower.
If the melting point is 300 ° C. or higher, the elastic modulus of the resin raw material decreases during the moisture absorption reflow at 290 ° C., causing fluid deformation of the resin and restoring the elastic strain of the resin layer, resulting in thermal conductivity. It is possible to reduce the possibility that the surface appearance of the resin sheet is deteriorated, the thickness of the heat conductive resin sheet is not uniform, and sufficient adhesion strength with the metal substrate cannot be obtained.
Further, it is possible to reduce the possibility that the heat conductive resin sheet is foamed due to the expansion of the moisture absorbed by the resin composition in a moist heat environment. Further, when foaming occurs inside the heat conductive resin sheet, there is a risk of a significant decrease in the dielectric breakdown voltage, which can be reduced. Further, when a heat-dissipating metal material is laminated on one surface of the heat-dissipating resin sheet, if foaming occurs near the interface between the heat-dissipating metal material and the heat-conductive resin sheet, the heat-dissipating metal material is released. There is a risk of peeling and a significant decrease in thermal conductivity, which can also be reduced. Furthermore, when a conductive circuit pattern is formed on the other surface of the heat conductive resin sheet, if foaming occurs near the interface between the conductive circuit pattern and the heat conductive resin sheet, the conductive circuit pattern is peeled off. Or, it may fall off, causing the above to occur in the electric circuit, or the thermal conductivity of the thermally conductive resin sheet may be significantly reduced, which can also be reduced.

Specific examples of the heat-resistant crystalline thermoplastic resin include polybutylene terephthalate resin (PBT, melting point: 224 ° C.), polyamide 6 (nylon 6, melting point: 225 ° C.), polyamide 66 (nylon 66, melting point: 265 ° C.). ), Liquid crystal polymer (LCP, melting point: 320 ° C to 344 ° C), polyether ketone resin (melting point: 303 ° C to 400 ° C), polytetrafluoroethylene resin (PTFE, melting point: 327 ° C), ethylene tetrafluoride. Examples thereof include perfluoroalkoxyethylene copolymer resin (PFA, melting point: 302 ° C. to 310 ° C.), ethylene tetrafluoride / propylene hexafluoride copolymer resin (FEP, melting point: 250 ° C. to 290 ° C.), and the like.
Among them, examples of the crystalline thermoplastic resin used in the present invention include liquid crystal polymers, polyetherketone resins, PTFE, and PFA because they have a melting point of 300 ° C. or higher.

Among the crystalline thermoplastic resins having a melting point of 300 ° C. or higher, a liquid crystal polymer and / or a polyetherketone resin is preferable from the viewpoint of moldability and the like.
Further, among the above, a polyetherketone-based resin is preferable from the viewpoint of adhesiveness to a metal material for heat dissipation such as a copper plate.

The polyetherketone-based resin that can be used in the present invention is a general term for thermoplastic resins having a repeating unit represented by the formula (1) (m and n in the formula are 1 or 2).

Examples of the polyetherketone resin include polyetherketone (PEK; m = 1, n = 1, melting point 373 ° C.), polyetheretherketone (PEEK; m = 2, n = 1, melting point 343 ° C.), and polyetherketone. Ketone (PEKK; m = 1, n = 2, melting point 303 ° C to 400 ° C), polyetheretherketoneketone (PEEKK; m = 2, n = 2, melting point 358 ° C), polyetherketone etherketoneketone (PEKEKK; An example of a copolymer containing both the structural unit of m = 1 and n = 1 and the structural unit of m = 1 and n = 2 (melting point 387 ° C.) and the like can be exemplified. Both are available as commercially available raw materials.

Among the polyetherketone resins, it has been demonstrated that the melting point is sufficiently high, the molding processing temperature is relatively low, the molding cycle can be shortened, and the continuous heat resistant temperature is 200 ° C or higher, so that it can be used without any trouble in heat resistant applications. It has the most chemically stable structure among polyetherketone resins, and has excellent heat resistance and chemical resistance. Polyetheretherketone (PEEK) can be particularly preferably used in consideration of the points, the fact that the price has been adjusted due to its widespread use, and the like.

As PEEK, various commercially available products can be used. For example, obtain various melt viscosities from Solvay's "Kita Spire (registered trademark)", Daicel Evonik's "Vestakeep (registered trademark)", Victrex's "Victorex PEEK", etc. Can be done.
As these PEEK raw materials, a single grade may be used, or a plurality of grades having different melt viscosities may be blended and used.

The melt viscosity of the crystalline thermoplastic resin in the present invention is not particularly limited. Above all, since a relatively large amount of the heat conductive filler is blended, 0.60 kPa · s or less is preferable, and 0.30 kPa · s or less is more preferable, in order to facilitate the heat molding process. When the melt viscosity is within the above range, it is not necessary to set the temperature of the molding machine excessively high, and deterioration of the raw material can be suppressed. On the other hand, the lower limit of the melt viscosity is not particularly limited. Above all, 0.01 kPa · s or more is preferable.
The melt viscosity is based on ASTM D3835, and is a value measured under the conditions of ^{a shear rate of 1000 s -1 and a temperature of 400 ° C.}

The mass average molecular weight (Mw) of the crystalline thermoplastic resin is preferably 48,000 or more, and more preferably 49000 or more, and more preferably 50,000 or more, from the viewpoint of long-term durability in a heating environment. On the other hand, from the viewpoint of moldability, it is preferably 120,000 or less, more preferably 110,000 or less, and even more preferably 100,000 or less.
The MFR of the crystalline thermoplastic resin is preferably 8 g / 10 minutes or more, particularly 9 g / 10 minutes or more, from the viewpoint of moldability and difficulty in forming voids between the crystalline thermoplastic resin and the added heat conductive filler. Above all, it is more preferably 10 g / 10 minutes or more. On the other hand, from the viewpoint of long-term durability in a heating environment, it is preferably 180 g / 10 minutes or less, more preferably 170 g / 10 minutes or less, and more preferably 160 g / 10 minutes or less.
The MFR is a value measured at 380 ° C. and 5 kgf in accordance with JIS K7210 (2014).

When polyetheretherketone (PEEK) is used as the crystalline thermoplastic resin of the present invention, it may be blended with other thermoplastic resins. The types of other thermoplastic resins are not particularly limited. Among them, as the other thermoplastic resin, a compatible resin having an effect of compensating for the insufficient performance when only the polyetheretherketone is used for the application of the present invention is preferable.
When other thermoplastic resins are blended, the melting point of the blended resin is preferably 300 ° C. or higher.

As the compatible resin, polyetherimide (PEI) is more preferable. By combining PEEK and PEI, not only the crystallinity (calorific value of crystal melting) of PEEK can be adjusted, but also the crystallization rate of PEEK can be adjusted, and the glass when the resin composition is in an amorphous state. The transition temperature can be increased (PEEK Tg is 143 ° C, PEI Tg is 217 ° C). Since PEI is an amorphous resin, the melting point of the resin itself does not change even if PEEK and PEI are combined.
In addition, in the present invention, by using PEI having an imide group and being amorphous, the adhesiveness to a metal material for heat dissipation such as a copper plate can be improved.

The amount of PEI added is preferably 50% by mass or less, with the total amount of the resin composition being 100% by mass. By setting the amount of PEI added to 50% by mass or less, it is possible to improve the adhesiveness to the metal material for heat dissipation while maintaining the heat resistance in the moisture absorption reflow test by the crystallinity of PEEK.

(2) Thermally Conductive Filler The resin composition of the present invention provides electrically insulating heat in order to improve the thermal conductivity of the obtained thermally conductive resin sheet, suppress the linear expansion coefficient, and secure the insulating performance. It preferably contains a conductive filler.
By suppressing the coefficient of linear expansion of the heat conductive resin sheet of the present invention, for example, the heat conductive resin sheet of the present invention is laminated and integrated with a different material such as a copper plate, and has a low temperature (for example, −40 ° C.) and a high temperature. Even if the temperature change is repeated between (for example, 200 ° C.), the interfacial peeling between the thermally conductive resin sheet and the dissimilar material can be suppressed.
In the present invention, the thermally conductive filler refers to particles having a thermal conductivity of 1.0 W / m · K or more, preferably 1.2 W / m · K or more.

Examples of the thermally conductive filler include fillers composed only of carbon and having electrical insulation properties, metal carbides or semi-metal carbides, metal oxides or semi-metal oxides, metal nitrides or semi-metal nitrides, and the like.

Examples of the filler composed of only carbon and having electrical insulation include diamond (thermal conductivity: about 2000 W / m · K) and the like.
Examples of the metal carbide or semi-metal carbide include silicon carbide (thermal conductivity: about 60 to 270 W / m ・ K), titanium carbide (thermal conductivity: about 21 W / m ・ K), and tungsten carbide (thermal conductivity: about 21 W / m ・ K). 120 W / m · K) and the like.

Examples of metal oxides or semi-metal oxides include magnesium oxide (thermal conductivity: about 40 W / m ・ K), aluminum oxide (thermal conductivity: about 20 to 35 W / m ・ K), and silicon oxide (thermal conductivity: about 20 to 35 W / m ・ K). Rate: Approximately 1.2 W / m ・ K), Zinc Oxide (Thermal Conductivity: Approximately 54 W / m ・ K), Ittrium Oxide (Thermal Conductivity: Approximately 27 W / m ・ K), Zirconium Oxide (Thermal Conductivity: Approx. 3W / mK), Itterbium oxide (thermal conductivity: about 38.5W / mK), Berylium oxide (thermal conductivity: about 250W / mK), "Sialon" (silicon, aluminum, oxygen, nitrogen) Ceramics made of, thermal conductivity: about 21 W / m · K) and the like can be mentioned.
Examples of metal nitrides or semi-metal nitrides include boron nitride (thermal conductivity of plate-like particles of hexagonal boron nitride (h-BN) in the plane direction: about 200 to 500 W / m · K), aluminum nitride ( Thermal conductivity: about 160 to 285 W / m · K), silicon nitride (thermal conductivity: about 30 to 80 W / m · K) and the like.

Only one kind of these thermally conductive fillers may be used, or two or more kinds thereof may be used in combination.

Further, when the thermally conductive resin sheet of the present invention is used for power semiconductor device applications, it is preferably an inorganic compound having excellent insulating properties because electrical insulation is required. From this point of view, the volume resistivity of the thermally conductive filler at 20 ° C. ^{is preferably 10 13} Ω · cm or more, and more preferably 10 ¹⁴ Ω · cm or more.
Among them, metal oxides, semimetal oxides, metal nitrides or semimetal nitrides are preferable from the viewpoint that the electrical insulation of the heat conductive resin sheet can be easily made sufficient. Specific examples of such a thermally conductive filler include aluminum oxide (Al ₂ O ₃ , volume resistivity:> 10 ¹⁴ Ω · cm) and aluminum nitride (AlN, volume resistivity:> 10 ¹⁴ Ω · cm). , Boron nitride (BN, volume resistivity:> 10 ¹⁴ Ω · cm), silicon nitride (Si ₃ N ₄ , volume resistivity:> 10 ¹⁴ Ω · cm), silica (SiO ₂ , volume resistivity:> 10 ¹⁴⁾ Ω ・ cm) and the like.
Of these, aluminum oxide, aluminum nitride, boron nitride, and silica are preferable, and aluminum oxide and boron nitride are particularly preferable because they can impart high insulating properties to the heat conductive resin sheet.

Among the above, this is because there are few problems of moisture absorption during heat molding, the toxicity is low, the thermal conductivity can be efficiently increased, and the thermally conductive resin sheet can be provided with high insulation. The thermally conductive filler of the present invention preferably contains boron nitride.
The boron nitride preferably contains boron nitride agglomerated particles as a main component, which are formed by agglomerating primary particles of boron nitride. "Containing boron nitride agglomerated particles as a main component" means that the boron nitride agglomerated particles occupy 50% by mass or more of boron nitride, 70% by mass or more, 80% by mass or more, and 90% by mass. It means that it occupies the above (including 100% by mass).

Further, boron nitride may be used in combination with another thermally conductive filler. However, the heat transfer behavior in the heat conductive resin sheet does not simply depend on the heat conductivity inside the heat conductive filler as described later. Therefore, among the particles exemplified above, the thermal conductivity in the thickness direction of the thermally conductive resin sheet is extremely increased even when diamond particles or the like, which have extremely high thermal conductivity but are extremely expensive, are used. There is no such thing. Therefore, when boron nitride and other thermally conductive fillers are used in combination, the main focus is on cost cutting of the composition. Therefore, from the viewpoint of relatively low cost and relatively high thermal conductivity, the heat conductive filler to be used in combination with boron nitride is appropriately selected from magnesium oxide, aluminum oxide, tungsten carbide, silicon carbide, aluminum nitride and the like. It is preferable to do so.

The shape of the thermally conductive filler may be amorphous particles, spheres, whiskers, fibers, plates, or aggregates or mixtures thereof.
Above all, the shape of the thermally conductive filler of the present invention is preferably spherical. “Spherical” usually has an aspect ratio (ratio of major axis to minor axis) of 1 or more and 2 or less, preferably 1 or more and 1.75 or less, more preferably 1 or more and 1.5 or less, and further preferably 1 or more and 1.4. It means that it is as follows.
The aspect ratio is obtained by arbitrarily selecting 200 or more particles from an image of the cross section of the heat conductive resin sheet taken by SEM, calculating the ratio of the major axis to the minor axis of each, and calculating the average value. be able to.

The thermally conductive filler of the present invention preferably contains boron nitride agglomerated particles (also referred to as "secondary particles") formed by aggregating flat plate-shaped boron nitride particles (also referred to as "primary particles").
Examples of the primary particles include cubic boron nitride and hexagonal boron nitride (h-BN). Of these, hexagonal boron nitride is preferable from the viewpoint of improving thermal conductivity.

Hexagonal boron nitride particles have a shape called a flat plate or a scale shape, and have a feature of extremely high thermal conductivity in the flat surface direction (about 200 to 500 W / m · K). However, due to this shape, when a resin sheet is prepared by a normal thermoplastic resin molding method (for example, a sheet extrusion using an extruder equipped with a twin-screw and a T-die), most of the added boron nitride is resin. It is oriented parallel to the sheet surface. Therefore, the thermal conductivity in the thickness direction of the resin sheet may be lower than that when a spherical filler having the same thermal conductivity is added. Therefore, by aggregating the flat plate-shaped boron nitride particles (primary particles) into boron nitride agglomerated particles (secondary particles), the orientation of the flat plate-shaped particles in a specific direction is suppressed, and the heat in the thickness direction is suppressed. The conductivity can also be improved.

Examples of the aggregated structure of the boron nitride agglutinated particles include a cabbage structure and a cardhouse structure. Above all, the card house structure is preferable from the viewpoint of improving the thermal conductivity.
The aggregated structure of the boron nitride agglutinated particles can be confirmed by a scanning electron microscope (SEM).

The cabbage structure refers to a structure in which flat-plate-shaped primary particles are collected and aggregated into a spherical shape like a cabbage structure. When the agglomerated particles having a cabbage structure are added to the resin sheet, the boron nitride primary particles constituting the boron nitride agglomerated particles are not oriented only in the plane direction of the heat conductive resin sheet, and thus are oriented in the thickness direction of the sheet. The thermal conductivity of the above can also be easily increased as compared with the case where the primary particles of boron nitride are simply added. However, when viewed in the radial direction from the substantially central portion of the aggregated particles of the cabbage structure, most of the primary particles have their flat plate surfaces oriented perpendicular to the radial direction. Therefore, some of the primary particles are certainly oriented in the thickness direction of the sheet or oriented toward the thickness direction, but only a limited number of particles can effectively conduct heat in the thickness direction. It will only be.
FIG. 1 shows a cross-sectional SEM image of a case where boron nitride agglomerated particles having a cabbage structure are added to a thermoplastic resin and heat-press molded. With reference to FIG. 1, it can be seen that many boron nitride primary particles are oriented at a shallow angle with respect to the surface direction of the resin sheet.

On the other hand, the card house structure is a structure in which plate-shaped particles are not oriented and are intricately laminated, and is described in "Ceramics 43. No. 2" (published by the Japan Ceramic Society in 2008). More specifically, it refers to a structure in which the planar portion of the primary particles forming the agglomerated particles and the end face portions of other primary particles existing in the agglomerated particles are in contact with each other. A schematic diagram of the card house structure is shown in FIG.
The agglomerated particles of the card house structure have extremely high breaking strength due to their structure, and are not crushed even in the pressurizing step performed at the time of forming the heat-dissipating resin sheet. Therefore, primary particles that are normally oriented in the longitudinal direction of the heat-dissipating resin sheet can be present in random directions. Therefore, high thermal conductivity can be achieved not only in the longitudinal direction of the heat-dissipating resin sheet but also in the thickness direction.
FIG. 3 shows a cross-sectional SEM image of a card house structure in which boron nitride agglomerated particles are added to a thermoplastic resin and heat-press molded. It can be seen that there are more particles oriented at a shallow angle with respect to the thickness direction of the heat conductive resin sheet, as compared with FIG. 1 in which the same mass of boron nitride agglomerated particles having a cabbage structure is added. As described above, the boron nitride agglomerated particles having a card house structure have more primary particles oriented in the thickness direction than the boron nitride agglomerated particles having a cabbage structure, so that heat conduction can be effectively performed in the thickness direction. It is possible to further increase the thermal conductivity in the thickness direction.
Boron nitride agglomerated particles having a cardhouse structure can be produced, for example, by the method described in International Publication No. 2015/11198.

When boron nitride agglomerated particles having a card house structure are used, the particles may be surface-treated with a surface treatment agent. As the surface treatment agent, a known surface treatment such as a silane coupling treatment can be used as an example. In general, there is often no direct affinity or adhesion between the thermally conductive filler and the thermoplastic resin, which is the boron nitride agglomerated particles having a cardhouse structure as the thermally conductive filler. The same applies when used. It is considered that the thermal conductivity attenuation at the interface can be further reduced by increasing the adhesion at the interface between the thermally conductive filler and the matrix resin by chemical treatment.

By using the boron nitride agglomerated particles as the heat conductive filler of the present invention, the particle size can be increased as compared with the heat conductive filler using the primary particles as they are. By increasing the particle size of the heat conductive filler, the heat transfer path between the heat transfer fillers via the thermoplastic resin having low heat conductivity can be reduced, and therefore the heat resistance in the heat transfer path in the thickness direction can be reduced. The increase can be reduced.

From the above viewpoint, the lower limit of the maximum particle size Dmax (hereinafter, also referred to as “maximum particle size”) based on the volume of the thermally conductive filler is preferably 20 μm or more, more preferably 30 μm or more, still more preferably 50 μm. That is all. On the other hand, the upper limit of the maximum particle size Dmax is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, and even more preferably 90 μm or less.

The lower limit of the volume-based average particle size D50 of the thermally conductive filler is preferably 2 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, still more preferably 20 μm or more. On the other hand, the upper limit of the average particle size D50 is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, and even more preferably 80 μm or less.

When the maximum particle size of the thermally conductive filler is equal to or less than the above upper limit, the interface between the matrix resin and the thermally conductive filler is reduced when the matrix resin contains the thermally conductive filler, and as a result, the thermal resistance is reduced. Therefore, high thermal conductivity can be achieved, and a high-quality film without surface roughness can be formed. When the maximum particle size is at least the above lower limit, a sufficient effect of improving thermal conductivity as a thermal conductive filler required for a power semiconductor device can be obtained.

Further, the influence of the thermal resistance at the interface between the matrix resin and the heat conductive filler on the thickness of the heat conductive resin sheet becomes remarkable because the size of the heat conductive filler with respect to the thickness of the heat conductive resin sheet is 1. It is considered that the case is / 10 or less. In particular, in the case of power semiconductor devices, a heat conductive resin sheet having a thickness of 100 μm to 300 μm is often applied. Therefore, from the viewpoint of heat conductivity, the maximum particle size Dmax based on the volume of the heat conductive filler is set. It is preferably larger than the above lower limit.
Further, when the maximum particle size Dmax of the heat conductive filler is equal to or more than the above lower limit, not only the heat conductive attenuation caused by the interface between the heat conductive filler and the matrix resin is suppressed, but also the required inter-particle spacing is suppressed. The number of heat conductive passes is reduced, and the probability of connecting from one surface to the other in the thickness direction of the heat conductive resin sheet is increased.
Further, since the maximum particle diameter Dmax of the heat conductive filler is equal to or more than the above lower limit, the interface area between the matrix resin and the heat conductive filler is smaller than that when particles having a Dmax smaller than the above lower limit are used in the same mass. Therefore, it is possible to reduce the generation of voids that are likely to occur at the interface between the matrix resin and the heat conductive filler in the heat conductive resin sheet, and it is easy to obtain excellent withstand voltage characteristics.
On the other hand, when the maximum particle diameter Dmax based on the volume of the heat conductive filler is not more than the above upper limit, the protrusion of the heat conductive filler on the surface of the heat conductive resin sheet is suppressed, and a good surface without surface roughness is suppressed. Since the shape can be obtained, when a sheet bonded to the copper substrate is produced, it has sufficient adhesion and excellent withstand voltage characteristics can be obtained.

The ratio (Dmax / thickness) of the size (Dmax) of the heat conductive filler to the thickness of the heat conductive resin sheet is preferably 0.3 or more and 1.0 or less, and more than 0.35 or 0. It is more preferably 95 or less, more preferably 0.4 or more or 0.9 or less.

The maximum particle size Dmax and the average particle size D50 of the heat conductive filler can be measured by, for example, the following methods.
Laser diffraction / scattering type for a sample in which a heat conductive filler is dispersed in a solvent, specifically, a sample in which a heat conductive filler is dispersed in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer. The particle size distribution can be measured with a particle size distribution measuring device LA-920 (manufactured by Horiba Seisakusho Co., Ltd.), and the maximum particle size Dmax and the average particle size D50 of the heat conductive filler can be obtained from the obtained particle size distribution.
It is also possible to obtain the maximum particle size and the average particle size with a dry particle size distribution measuring device such as Moforogi G3 (manufactured by Malvern).
Regarding the maximum particle size Dmax and the average particle size D50 of the heat conductive filler added to the thermoplastic resin, the heat conductive filler is also dissolved or removed or swollen in a solvent (including a heating solvent). It is possible to measure by the same method as described above by physically removing the resin component after reducing the adhesion strength with the resin, and further removing the resin component by heating it in the atmosphere to incinerate it.

(3) Content of Each Component The content of the thermoplastic resin in 100% by mass of the resin composition of the present invention is preferably 15% by mass or more and 40% by mass or less, and more preferably 15% by mass or more and 35% by mass or less. Further, it is preferably 20% by mass or more and 40% by mass or less, and more preferably 20% by mass or more and 35% by mass or less.
The content of the thermally conductive filler in 100% by mass of the resin composition of the present invention is preferably 60% by mass or more and 85% by mass or less, and more preferably 60% by mass or more and 80% by mass or less. Further, it is preferably 65% by mass or more and 85% by mass or less, and more preferably 65% by mass or more and 80% by mass or less.
When the content of the heat conductive filler is at least the above lower limit value, the effect of improving the heat conductivity by the heat conductive filler and the effect of controlling the coefficient of linear expansion are satisfactorily exhibited. On the other hand, when the content of the thermally conductive filler is not more than the above upper limit value, the moldability of the resin composition and the interfacial adhesiveness with different materials are improved.

In general, the blending ratio of the heat conductive resin composition is often specified by the volume fraction of each of the matrix resin and the heat conductive filler (hence, the area ratio in the cross section of the heat conductive resin sheet). .. Thermal conductivity The thermal conductivity in the thickness direction of the resin sheet is not determined only by the volume fraction, but is related to various factors such as the above-mentioned preferable particle size, particle orientation, and particle shape. Therefore, in the present invention, the mass fraction is used for the convenience of actual compounding.
In particular, when boron nitride agglomerated particles having a cardhouse structure are used as the heat conductive filler, the particles are not only characterized by the cardhouse structure as an internal structure, but are oriented in the radial direction on the particle surface. A large number of the flat plate-shaped primary boron nitride particles are formed in a so-called squid-like or gold-flat sugar-like protrusion state, and the protrusions of adjacent cardhouse structure particles come into physical contact with each other. A heat transfer path having a small heat resistance in the thickness direction is formed. Therefore, it may not be easy to determine the volume fractions of the matrix resin and the heat conductive filler by observation with a normal scanning electron microscope (SEM). Further, when the amount of boron nitride agglomerated particles added in the card house structure is increased, the particles are not in point contact where the particles come into contact with each other as spherical particles due to the pressure applied during heat press molding of the resin composition. It is observed that the portions in contact with each other are deformed and the contact portions are in linear contact, that is, in a planar shape. In such a contact state, the addition of boron nitride in the card house structure enables efficient heat conduction path formation. However, even in such a case, it is not easy to determine the volume fractions of the matrix resin and the heat conductive filler by SEM observation.

The thermally conductive filler of the present invention preferably contains 50% by mass or more of boron nitride agglomerated particles, more preferably 60% by mass or more, and 70% by mass or more in 100% by mass of the thermally conductive filler. It is even more preferable, and it is even more preferable that the content is 80% by mass or more. The total amount (100% by mass) of the thermally conductive filler may be boron nitride agglomerated particles.
When the content of the boron nitride agglomerated particles is at least the above lower limit value, the thermal conductivity in the thickness direction of the thermally conductive resin sheet becomes high.

The resin composition of the present invention may contain other components in addition to the crystalline thermoplastic resin and the thermally conductive filler. However, from the viewpoint of increasing thermal conductivity, it is preferable not to contain other components.
Other components include phosphorus-based, phenol-based and other various antioxidants, phenol-acrylate-based other process stabilizers, heat stabilizers, hindered amine-based radical supplements (HAAS), impact modifiers, processing aids, and metal-free products. Additives that improve the affinity between thermally conductive fillers such as activators, copper damage inhibitors, antistatic agents, flame retardants, and silane coupling agents and thermoplastic resins, as well as resins such as silane coupling agents. Additives, bulking agents, etc. that can be expected to have the effect of increasing the adhesion strength between the sheet and the metal plate-like material can be mentioned. When these additives are used, the amount to be added may generally be in the range of the amount used for these purposes.

2. Thermally conductive resin sheet The thermally conductive resin sheet of the present invention is made of the above resin composition, has excellent moisture absorption and reflow resistance, and is less likely to cause interfacial peeling due to thermal expansion and contraction when formed into a laminate with a metal plate.

The thermal conductivity of the heat conductive resin sheet in the thickness direction at 25 ° C. is preferably 5.0 W / m · K or more, more preferably 7.0 W / m · K or more, and 9.0 W / m · K or more. It is more preferably m · K or more. When the thermal conductivity in the thickness direction is at least the above lower limit value, it can be suitably used for a power semiconductor device or the like operated at a high temperature.
The thermal conductivity includes physical properties such as the type and melt viscosity of the thermoplastic resin, the type and content of the thermally conductive filler, the mixing method of the thermoplastic resin and the thermally conductive filler, the conditions in the heat kneading step described later, and the like. Can be adjusted by.

Further, the heat conductive resin sheet of the present invention preferably has a thermal conductivity in the thickness direction at 200 ° C. of 90% or more, preferably 92% or more of the thermal conductivity in the thickness direction at 25 ° C. More preferred. When the thermal conductivity in the thickness direction at 200 ° C. is at least the above lower limit value, it can be suitably used for a power semiconductor device or the like operated at a high temperature.

The lower limit of the thickness of the heat conductive resin sheet is preferably 50 μm or more, more preferably 60 μm or more, and further preferably 70 μm or more. On the other hand, the upper limit of the thickness is preferably 300 μm or less, more preferably 200 μm or less, and further preferably 160 μm or less. By setting the thickness of the heat conductive resin sheet to 50 μm or more, sufficient withstand voltage characteristics can be ensured. On the other hand, by setting the thickness to 300 μm or less, it is possible to achieve miniaturization and thinning, especially when the heat conductive resin sheet is used for a power semiconductor device or the like, and compared with an insulating heat conductive layer made of a ceramic material. , The effect of reducing the thermal resistance in the thickness direction by thinning the film can be obtained.

In the heat conductive resin sheet of the present invention, it is preferable to lower the orientation of the primary particles of the heat conductive filler in order to reduce the anisotropy of the heat conductivity and increase the heat conductivity in the thickness direction. ..
Regarding the orientation of the primary particles, when the heat conductive resin sheet is measured by the X-ray diffraction method, the diffraction peak intensity of the (002) plane is I (002), and the diffraction peak intensity of the (100) plane is I (100). ), It can be evaluated by obtaining the ratio "I (002) / I (100)".
The ratio "I (002) / I (100)" is preferably 20.0 or less, more preferably 17.0 or less, and even more preferably 15.0 or less. If the above ratio exceeds 20.0, the thermally conductive filler has collapsed in the melt-kneading step, or the thermally conductive filler has been excessively crushed in the press pressurizing step, and the surface direction of the thermally conductive resin sheet. There are many thermally conductive fillers that are parallel to or form a small angle with. In this case, even if the content of the thermally conductive filler is increased, it is difficult to increase the thermal conductivity in the thickness direction.
The lower limit of the ratio "I (002) / I (100)" is not particularly limited. For example, when boron nitride agglomerated particles having a cardhouse structure are used as the heat conductive filler, the ratio “I (002) / I (100)” of the particles alone is about 4.5 to 6.6. Therefore, it is considered that 4.5 is the lower limit value except when the intentional orientation operation is performed.

From the viewpoint of simplifying the manufacturing process, it is preferable to adjust the orientation of the primary particles of the thermally conductive filler without performing an intentional orientation operation. The orientation is determined by, for example, physical characteristics such as the type and melt viscosity of the thermoplastic resin, the type and content of the thermally conductive filler, the mixing method of the thermoplastic resin and the thermally conductive filler, and the conditions in the heat kneading step described later. Etc. can be adjusted as appropriate.

3. 3. Method for producing a heat conductive resin sheet Hereinafter, as an example of the method for producing a heat conductive resin sheet of the present invention, a heat kneading step of heating and kneading a thermoplastic resin and a heat conductive filler to obtain a resin composition, Examples thereof include a press molding step of pressing the resin composition with a heating body to form a sheet. However, the method for producing the heat conductive resin sheet of the present invention is not limited to the following production method.

(1) Heat-kneading step In the heat-kneading step, the thermoplastic resin and the thermally conductive filler are melt-kneaded by heating.
In the heat kneading step, the thermoplastic resin and the heat conductive filler can be put into a processing machine to perform melt kneading.
The processing machine used in the heat kneading step may be generally used for the purpose of kneading a thermally conductive filler and various additives into the resin. Examples thereof include a continuous kneader, a plast mill kneader, a twin-screw extruder type kneader in the same direction, a twin-screw extruder type kneader in a different direction, and a single-screw extruder type kneader.
The melt-kneading temperature is preferably 370 ° C. to 430 ° C., more preferably 380 ° C. to 420 ° C., as the set temperature of the molding machine (in the case of an extruder type melt-kneading device, the set temperature of the cylinder heater, etc.). By setting the melt-kneading temperature to 370 ° C. or higher, the resin viscosity can be sufficiently lowered and the load increase of the molding machine can be suppressed. Further, since the heat conductive filler can be prevented from being sheared and broken during kneading, the heat conductivity of the obtained heat conductive resin sheet is improved. On the other hand, by setting the melt-kneading temperature to 450 ° C. or lower, deterioration of the resin itself and deterioration of the physical properties of the molded heat conductive resin sheet can be suppressed.

(2) Press Molding Step The resin composition of the present invention, which has been heat-melted and kneaded, has a lumpy to powdery shape even after the heat-kneading step because the resin composition contains a large amount of a heat conductive filler. In many cases. Therefore, it is often difficult to perform a manufacturing method in which the sheet is molded in a process continuous with the melt-kneading step and wound up, as in the case of sheet molding of a normal thermoplastic resin composition. Therefore, in the present invention, it is preferable that the mass-powdered mixture obtained above is made into a sheet by press molding, which is a batch process. However, the method for producing a heat conductive resin sheet of the present invention is not limited to batch pressing, and if there is a sheet forming device by the steel belt method capable of continuous molding at a certain high temperature and high pressure, It is considered that it can be manufactured as a continuous sheet.

In press molding, which is a batch process, various known press devices for molding thermoplastic resins can be used. From the viewpoint of preventing resin deterioration during the heating press, it is particularly preferable to use a vacuum pressing device capable of reducing the amount of oxygen in the pressing machine during heating or a pressing device provided with a nitrogen substitution device.
In the pressing process, in addition to the purpose of forming the melt-kneaded product into a sheet body having a uniform thickness, the purpose is to join the added heat conductive fillers to form a heat path, to eliminate voids and voids in the sheet, and the like. , It is preferable to set the pressurizing pressure. From this point of view, the pressure in the press step is usually 8 MPa or more, preferably 9 MPa or more, and more preferably 10 MPa or more as the actual pressure applied to the sample. Further, it is preferably 50 MPa or less, more preferably 40 MPa or less, and further preferably 30 MPa or less. By setting the pressure at the time of pressurization to the above upper limit value or less, crushing of the heat conductive filler can be prevented, and a heat conductive resin sheet having high heat conductivity can be obtained. Further, by setting the press pressure to the above lower limit value or more, the contact between the heat conductive fillers becomes good, the heat conduction path can be easily formed, and a sheet having high heat conductivity can be obtained. In addition, a resin sheet can be obtained. Since the number of voids inside can be reduced, the heat conductive resin sheet having a high breakdown voltage can be obtained even after the moisture absorption reflow test.

In the press molding step, the set temperature of the resin press device is preferably 370 ° C to 440 ° C, and more preferably 380 ° C or higher or 420 ° C or lower.
By performing press molding at a temperature in this range, it is possible to impart good thickness uniformity and high thermal conductivity due to good contact between the added thermally conductive fillers to the obtained thermally conductive resin sheet. When the molding temperature is 370 ° C. or higher, the resin viscosity is lowered to a level sufficient for shaping processing, and sufficient thickness uniformity can be imparted to the heat conductive resin sheet to be molded. On the other hand, when the set temperature of the press machine is 440 ° C. or lower, deterioration of the resin itself and deterioration of the physical properties of the molded heat conductive resin sheet can be suppressed.

The pressurization time is usually 30 seconds or longer, preferably 1 minute or longer, more preferably 3 minutes or longer, still more preferably 5 minutes or longer. Further, it is preferably 1 hour or less, more preferably 30 minutes or less, and further preferably 15 minutes or less. When it is below the above upper limit, the manufacturing process time of the heat conductive resin sheet can be suppressed, the cycle time can be shortened as compared with the heat conductive resin sheet using the heat-resistant thermosetting resin, and the production cost can be suppressed. There is a tendency to be able to do it. Further, when it is at least the above lower limit value, the uniformity of the thickness of the heat conductive resin sheet can be sufficiently obtained, internal voids and voids can be sufficiently removed, and the heat conduction performance and withstand voltage characteristics are non-uniform. Can be prevented.

4. Laminated Heat Dissipating Sheet The laminated heat radiating sheet of the present invention is obtained by laminating a heat radiating material on one surface of the heat conductive resin sheet of the present invention.
The heat-dissipating material is not particularly limited as long as it is made of a material having good thermal conductivity. Above all, in order to increase the thermal conductivity in the laminated structure, it is preferable to use a metal material for heat dissipation, and above all, it is more preferable to use a flat metal material.
The material of the metal material is not particularly limited. Among them, a copper plate, an aluminum plate, an aluminum alloy plate, etc., which have good thermal conductivity and are relatively inexpensive, are preferable.

When a flat plate-shaped metal material is used as the heat-dissipating metal material in the laminated heat-dissipating sheet, the thickness of the metal material is preferably 0.03 to 6 mm from the viewpoint of ensuring sufficient heat-dissipating properties. It is more preferably 1 mm or more or 5 mm or less.

Regarding adhesion to metal materials for heat dissipation, various types of surface roughening treatments such as soft etching, discoloration plating treatment, oxidation-reduction treatment, etc., and various types for ensuring adhesion durability on the surface of the metal material on the side where it is laminated with the heat conductive resin sheet. Surface treatment such as plating treatment of metal / metal alloy, organic surface treatment including silane coupling treatment such as amino type and mercapto type, and surface treatment with organic / inorganic composite material may be performed. By performing these surface treatments, the initial adhesive strength, the durability of the adhesive strength, and the effect of suppressing interfacial peeling after the moisture absorption reflow test can be further improved.

On the other hand, the surface of the heat-dissipating metal material on the side opposite to the side to be laminated with the heat conductive resin sheet does not have to be a simple flat plate, and has a surface area to secure a contact area with a cooling medium which is a gas or liquid. May be processed to increase the amount of heat.
Examples of processing for increasing the surface area include roughening the surface by brazing to increase the surface area, and cutting or pressing metal for heat dissipation of V-shaped or rectangular grooves or irregularities of various shapes. A method of forming directly on the material, a metal layer for heat dissipation made of a flat metal material, is further subjected to processing for increasing the surface area by casting, diffusion bonding, bolt fastening, soldering, brazing, etc. For example, joining another metal material or embedding a metal pin. Further, it is also conceivable to directly press-laminate the heat conductive resin sheet on the heat-dissipating metal layer having a cavity for passing the cooling medium. However, since the pressing pressure between the heat conductive resin sheet and the heat radiating metal plate is relatively high, in these cases, a flat metal material and a heat conductive resin sheet are laminated and integrated in a later process. , It is preferable to integrate the grooved metal plate or the metal layer having a cavity through which the refrigerant flows by soldering, brazing, bolting or the like.

For the laminated integration of the heat-dissipating metal material and the heat-conductive resin sheet in the laminated heat-dissipating sheet, press molding, which is a batch process, can be preferably used. The press equipment, press conditions, and the like in this case are the same as the range of press molding conditions for obtaining the above-mentioned heat conductive resin sheet.

5. Heat-dissipating circuit board The heat-dissipating circuit board of the present invention has the above-mentioned laminated heat-dissipating sheet. The heat-dissipating circuit board has, for example, a structure in which a heat-dissipating metal material is laminated on one surface of the heat-conductive resin sheet of the present invention. Of these, for example, the conductive circuit may be laminated on the surface opposite to the surface on which the heat-dissipating metal material of the heat conductive resin sheet is laminated by an etching process or the like in a subsequent step.
As the configuration of the heat-dissipating circuit board, it is more preferable that the heat-dissipating circuit board is integrated with "heat-dissipating metal material / heat-conductive resin sheet / conductive circuit". As a state before circuit etching, for example, in an integrated configuration of "metal material for heat dissipation / heat conductive resin sheet / metal material for forming a conductive circuit", the metal material for forming a conductive circuit is flat and has a heat conductive resin. Examples thereof include those formed on the entire surface on one side of the sheet and those formed on a part of the area.

The material of the metal material for forming the conductive circuit is not particularly limited. Above all, in general, it is preferably formed of a thin copper plate having a thickness of 0.05 mm or more and 1.2 mm or less from the viewpoints of good electrical conductivity, good etching property, cost, and the like.

The dielectric breakdown voltage of the heat-dissipating circuit board is preferably 40 kV / mm or more, more preferably 50 kV / mm or more, further preferably 60 kV / mm or more, still more preferably 80 kV / mm or more. When the dielectric breakdown voltage is 40 kV / mm or more, for example, even with a heat conductive resin sheet having a thickness of 100 μm, a dielectric breakdown voltage of 4 kV or more can be obtained, and if the dielectric breakdown voltage is 80 kV / mm or more. Since a dielectric breakdown voltage of 4 kV or more can be obtained even with a thickness of 50 μm, it has sufficient withstand voltage performance while using a thin thermally conductive resin layer that is advantageous in terms of thermal resistance, and dielectric breakdown occurs when a high voltage is applied. Can be suppressed.

6. Power semiconductor device The thermally conductive resin sheet of the present invention can be suitably used as a heat dissipation sheet for a power semiconductor device, and a highly reliable power semiconductor module can be realized.
The power semiconductor device is a power semiconductor device using the heat conductive resin sheet or the laminated heat radiating sheet, and the heat conductive resin sheet or the laminated heat radiating sheet is mounted on the power semiconductor device device as a heat radiating circuit board. It is a thing.
The power semiconductor device device has a heat dissipation effect due to high thermal conductivity, and can achieve high output and high density with high reliability.
In a power semiconductor device device, conventionally known members can be appropriately adopted as members such as aluminum wiring, encapsulant, packaging material, heat sink, thermal paste, and solder other than the heat conductive resin sheet or the laminated heat radiation sheet.

<Explanation of words>
When expressed as "X to Y" (X, Y are arbitrary numbers) in the present invention, unless otherwise specified, it means "X or more and Y or less" and "preferably larger than X" or "preferably more than Y". It also includes the meaning of "small".
Further, when expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it means "preferably larger than X" or "preferably less than Y". Including intention.
In the present invention, the "sheet" conceptually includes a sheet, a film, and a tape.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

<Examples 1 to 6, Comparative Examples 1 to 4>
The materials used, the manufacturing method, and the measurement conditions / evaluation methods of the heat conductive resin sheets in Examples 1 to 6 and Comparative Examples 1 to 4 are as follows.

[Material used]
(Thermoplastic resin)
Thermoplastic resin 1: Polyetheretherketone "Vestakeep 1000G" (manufactured by Daicel Ebonic, melting point 343 ° C., melt viscosity: 0.14 kPa · s (400 ° C.), MFR: 158 g / 10 minutes (380 ° C.), mass Average molecular weight (Mw): 52000) (hereinafter referred to as "PEEK1")
Thermoplastic resin 2: Polyetheretherketone "Vestakeep 4000G" (manufactured by Daicel Ebonic, melting point: 343 ° C., melt viscosity: 0.26 kPa · s (400 ° C.), MFR: 13 g / 10 minutes (380 ° C.), Mass average molecular weight (Mw): 96000) (hereinafter referred to as "PEEK2")
Thermoplastic resin 3: Polyetherimide resin "Ultem 1000" (manufactured by Sabic: glass transition temperature 217 ° C, amorphous, melt viscosity: 0.33 kPa · s (400 ° C), MFR: 25 g / 10 minutes (380 ° C) ° C.), mass average molecular weight (Mw): 61000)
Thermoplastic resin 4: Polybutylene terephthalate resin "Novaduran 5010R" (manufactured by Mitsubishi Engineering Plastics, melting point 224 ° C, melt viscosity: 0.12 kPa · s (300 ° C), MFR: 16 g / 10 minutes (MVR (cm ³ /)) Converted value from 10 minutes), 250 ° C, 2.16 kg), mass average molecular weight: 88000)

The melt viscosity of each resin is a melt viscosity at a shear rate of 1000 s ^-1 and a temperature of 400 ° C. according to ASTM D3835. The melt viscosity of homopolybutylene terephthalate is the melt viscosity at a shear rate of 1000 s ^-1 and a temperature of 300 ° C. The MFR of the thermoplastic resins 1 to 3 is a value measured at 380 ° C. in accordance with JIS K7210 (2014).
As shown in Table 1, these thermoplastic resins were used in a single resin composition or as a blend composition.

(Thermosetting resin)
-Thermosetting resin 1: Bisphenol F type solid epoxy resin (manufactured by Mitsubishi Chemical Corporation, polystyrene-equivalent mass average molecular weight (Mw): 60000)
-Thermosetting resin 2: A polyfunctional epoxy resin having a structure containing 4 or more glycidyl groups per molecule (manufactured by Nagase ChemteX Corporation)
-Thermosetting resin 3: Hydrogenated bisphenol A type liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation)
-Thermosetting resin 4: p-aminophenol type liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation)

-Curing agent: Phenol resin-based curing agent "MEH-8000H" (manufactured by Meiwa Kasei Co., Ltd.)
-Curing catalyst 1: 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl-17')]-ethyl-s-triazine ("2E4MZ-A", manufactured by Shikoku Kasei Co., Ltd., nitrogen atom A compound having a triazine ring as a heterocyclic structure contained. Molecular weight: 247)

(Thermal conductive filler)
Thermally conductive filler 1: Flat plate-shaped boron nitride primary particles "AP-10S" (manufactured by MARUKA, average particle size (D50) 3.0 μm, specific surface area 10 m ² / g).
-Thermal conductive filler 2: Agglomerated particles (secondary particles) "PTX25" (manufactured by Momentive Co., Ltd., average particle diameter) having a so-called "cabbet" structure in which flat plate-shaped boron nitride particles (primary particles) are collected and aggregated into a spherical shape. (D50) 25 μm, specific surface area 7 m ² / g).
Thermally Conductive Filler 3: Bawnitride agglomerated particles having a card house structure manufactured based on International Publication No. 2015/11198 (average particle size (D50) 35 μm, maximum particle size (Dmax) 90 μm).

[Preparation of thermally conductive resin sheets of Examples 1 to 6 and Comparative Examples 1 and 2]
(Melting and kneading of thermoplastic resin and thermally conductive filler)
The heat conductive resin sheets of Examples 1 to 6 and Comparative Examples 1 and 2 were mixed according to the types and amounts of the thermoplastic resins and heat conductive fillers shown in Table 1 and prepared by the following methods. ..
The thermoplastic resin and the thermally conductive filler were kneaded with a laboplast mill (“4C150”, manufactured by Toyo Seiki Co., Ltd.) at 380 ° C. for 5 minutes to obtain a melt-kneaded product of the thermoplastic resin and the thermally conductive filler.

For the above 5 minutes, the total amount of the mixture of the thermoplastic resin and the heat conductive filler is about 60 to 80 g, and the thermoplastic resin divided into small amounts is first put into a lab plast mill. After adding and confirming that it has been plasticized, repeat the procedure of adding the heat conductive filler divided into small amounts in the same manner, and after the total amount of about 60 to 80 g of the compound has been added, another 5 minutes. It means that melt kneading was carried out.
The amount of the compound to be added was appropriately adjusted so that the bulk specific gravity of the compound and the internal volume (about 37.5 cm ^{3) of the laboplast mill were substantially the same.}

(Sheet by press molding of melt-kneaded product)
Using a high-temperature vacuum press device (manufactured by Kitagawa Seiki Co., Ltd.), the melt-kneaded product was pressed at a press temperature of 395 ° C. and a press surface pressure of 10 MPa for 10 minutes. A heat conductive resin sheet having a thickness of 500 μm was obtained.

Here, for the above 10 minutes, the inside of the vacuum press machine is preheated to 150 ° C., and the melt-kneaded product is put into the melt-kneaded product as a press-prepared component, and the vacuum pump is operated to form the melt-kneaded product. A light pressurization of several MPa was applied, the internal temperature of the press was set to 395 ° C., the temperature was raised for 40 minutes, the press surface pressure was set to 10 MPa, and then the press was performed for 10 minutes. Means.
After 10 minutes had passed, the internal temperature of the press was set to 150 ° C. again, the vacuum was released when the internal temperature gradually approached 150 ° C., and the heat conductive resin sheet was taken out.

The press-prepared component is a spacer in which a frame-shaped spacer having a thickness of 6 mm and an outer side of 20 cm in length and width and an opening of 15 cm in length and width of 15 cm is placed inside the lower plated plate. A mass to powdery mixture obtained by melt-kneading with the above-mentioned laboplast mill having a mass required to obtain a press sheet having a thickness of 150 μm or a thickness of 500 μm is sprayed therein, and a thickness of 15 cm × 15 cm is further filled in the opening. At 5.85 mm (when collecting a sample thickness of 150 μm) or 5.50 mm (when collecting a sample thickness of 500 μm), a drop lid of 14.6 cm × 14.6 cm in length and width was fitted, and an upper plating plate was placed. , A component required for a single press in a batch.

However, with respect to Comparative Example 1, since the homopolybutylene terephthalate resin "Novaduran 5010R" having a melting point of 224 ° C. is used as the thermoplastic resin, the melt-kneading temperature in the laboplast mill is set to 290 ° C. and press molding is performed. A heat conductive resin sheet having a thickness of 150 μm and a thickness of 500 μm is obtained at a temperature of 300 ° C.

[Preparation of Thermally Conductive Resin Sheets of Comparative Examples 3 and 4]
For Comparative Examples 3 and 4 in which an epoxy resin which is a thermosetting resin is used instead of the thermoplastic resin as the resin component, a heat conductive resin sheet was prepared as follows.

71.5% by mass of the thermally conductive filler 3 was added to each of the resin compositions shown in Table 2, and a mixture was prepared so that the total amount of the resin component and the thermally conductive filler was 100% by mass.
From there, a mixed solution of MEK and cyclohexanone (mixing ratio (volume ratio) 1: 1) was 37.2 so that the total solid content concentration of the resin component and the heat conductive filler was 62.8% by mass. Mass% was added and mixed. In mixing these, after manual stirring, stirring was performed for 2 minutes using a self-revolving stirrer "Awatori Rentaro" AR-250.

The coating slurry obtained above is coated on a polyethylene terephthalate film (hereinafter referred to as "PET film") having a thickness of 38 μm by a doctor blade method, heated and dried at 60 ° C. for 120 minutes, and then pressed at a press temperature of 42 ° C. Pressing was performed at a surface pressure of 15 MPa for 10 minutes to obtain an epoxy resin sheet-like molded product that was uncured or had a very slight curing reaction. A heat conductive resin sheet having a thickness of 150 μm and a thickness of 500 μm was obtained and used as a specimen.

<Measurement conditions and evaluation method>
The heat conductive resin sheets of Examples 1 to 6 and Comparative Examples 1 to 4 were measured and evaluated by the following methods.

[Tension storage elastic modulus of resin component at 200 ° C. (E'(200))]
A resin sheet having a thickness of 500 μm, which was produced by the same method as in each Example, Comparative Example and Reference Example except that the thermally conductive filler was not added, was cut into 4 mm × 80 mm to obtain a test piece.
Using a viscoelastic spectrometer (trade name "DVA-200"), manufactured by IT Measurement Co., Ltd., the conditions are that the vibration frequency is 10 Hz, the strain is 0.1%, the heating rate is 3 ° C./min, and the chuck distance is 1 cm. Below, the dynamic viscoelasticity was measured in the measurement temperature range of −100 ° C. to 250 ° C., and the storage elastic modulus (E'(200)) at a temperature of 200 ° C. was read.

[Tension storage elastic modulus of resin component at 300 ° C. (E'(300))]
A test piece was prepared by the same method as the measurement of E'(200) above, and a viscoelastic spectrometer (trade name "DVA-200"), manufactured by IT Measurement Co., Ltd. was used to generate a vibration frequency of 10 Hz and distortion of 0. Under the conditions of 1%, heating rate of 3 ° C./min, and chuck distance of 1 cm, dynamic viscoelasticity was measured in the measurement temperature range of -100 ° C to 350 ° C, and the storage elastic modulus at a temperature of 300 ° C (E'( 300)) was read.
Since the thermally conductive resin sheet of Comparative Example 1 was in a molten state and the tensile storage elastic modulus at 300 ° C. could not be measured, it was set as "not measurable".
Moreover, since the measurement was not performed on the heat conductive resin sheet of Comparative Examples 3 and 4, it was set as "-". Thermally conductive resin sheet of Comparative Example 3 and 4, since the tensile storage modulus at above 200 ℃ (E '(200) ) is below the already 4.0 × ¹⁰ 7 Pa, tensile in these 300 ° C. Storage modulus (E '(300)) are also considered below 4.0 × ¹⁰ 7 Pa.

[Mass increase rate at 85 ° C. and 85% RH]
The heat conductive resin sheet having a thickness of 500 μm prepared in each Example, Comparative Example and Reference Example was cut into a size of 8 cm × 8 cm and used as a test piece.
First, each test piece was dried at 150 ° C. for 1 hour, and the dry mass a (g) of the test piece was measured.
Next, each test piece is stored in an environment of 85 ° C. and 85% RH using a constant temperature and humidity chamber "SH-221" (manufactured by ESPEC), weighed every 24 hours, and the mass does not change. (Constant mass) b (g) was measured.
From the dry mass a (g) and the mass (constant amount) b (g) obtained above, the mass increase rate was calculated by the following formula.
Mass increase rate (%) = {(ba) / a} x 100

[Dielectric breakdown voltage (BDV) after moisture absorption reflow test]
(Manufacturing of circuit board for heat dissipation)
A heat conductive resin sheet having a thickness of 150 μm produced in each Example and Comparative Example is cut into a size of 40 mm × 80 mm to form a metal plate-like material for heat dissipation, a copper plate having a size of 40 mm × 80 mm, a thickness of 2000 μm, and conductivity. The surface of each copper plate having a size of 40 mm × 80 mm and a thickness of 500 μm, which serves as a copper plate for circuit formation, was roughened by polishing one side with # 100 sandpaper in advance. The heat conductive resin sheet is sandwiched so that the roughened surface of each copper plate of different thickness faces the heat conductive resin sheet, and a press is performed to obtain "metal plate-like material for heat dissipation (copper plate) / heat conduction". A laminated heat-dissipating sheet made of "sexual resin sheet / copper plate for forming a conductive circuit" was obtained.
The press conditions were as follows: for Examples 1 to 4, the press temperature was 390 ° C. and the press surface pressure was 13 MPa for 10 minutes, and for Examples 5, 6 and Comparative Example 2, the press temperature was 370 ° C. and the press surface pressure was 13 MPa. For 10 minutes, for Comparative Example 1, the press temperature was 300 ° C. and the press surface pressure was 13 MPa for 10 minutes.

Regarding Comparative Examples 3 and 4, which are heat conductive resin sheets made of a heat-curable resin, an epoxy resin sheet having a thickness of 150 μm, which is uncured or has a very slight curing reaction, is pressed at a pressing temperature of 175 ° C. Pressing is performed at a press surface pressure of 10 MPa for 30 minutes to complete the curing reaction of the heat-curable resin, and a laminated heat-dissipating sheet composed of "metal plate-like material for heat dissipation (copper plate) / heat conductive resin sheet / copper plate for forming conductive circuit". Got

Further, the copper plates for forming the conductive circuit of each of the laminated heat-dissipating sheets were etched by a predetermined method and patterned to obtain a heat-dissipating circuit board. The pattern was such that two copper plates for a conductive circuit having a circular pattern of φ25 mm remained on a heat conductive resin sheet of 40 mm × 80 mm.

(Measurement of dielectric breakdown voltage (BDV))
The heat-dissipating circuit boards of each example and comparative example were stored in an environment of 85 ° C. and 85% RH for 3 days using a constant temperature and humidity chamber SH-221 (manufactured by ESPEC), and then placed in a nitrogen atmosphere within 30 minutes. The temperature was raised from room temperature to 290 ° C. in 12 minutes, held at 290 ° C. for 10 minutes, and then cooled to room temperature (moisture absorption reflow test). After that, the heat-dissipating circuit board was immersed in Fluorinert FC-40 (manufactured by 3M), and the heat-dissipating circuit board was patterned by etching using an ultra-high voltage withstand voltage tester 7470 (manufactured by Measurement Technology Research Institute) with a diameter of 25 mm. An electrode having a diameter of 25 mm was placed on a copper plate, a voltage of 0.5 kV was applied, the voltage was boosted by 0.5 kV every 60 seconds, and measurements were carried out until dielectric breakdown occurred. The measurement was carried out at a frequency of 60 Hz and a boost speed of 1000 V / sec.

If the dielectric breakdown voltage is 60 kV / mm or more per unit thickness (converted value when the thickness is 1 mm), it is "○", if it is 40 kV / mm or more and less than 60 kV / mm, it is "△", less than 40 kV / mm. In the case of, it is written as "x". The results of these measurements are shown in Table 1 and Table 2.
The evaluation of the dielectric breakdown voltage (BDV) after the moisture absorption reflow test can be regarded as the evaluation of the moisture absorption reflow resistance.

[Interface observation after moisture absorption reflow test]
After performing a moisture absorption reflow test on the heat-dissipating circuit boards of each example and comparative example in the same manner as above, the copper electrode of φ25 mm and heat conduction patterned by the above etching by the ultrasonic imaging device FinSAT (FS300III) (manufactured by Hitachi Power Solutions). The interface of the sex resin sheet was observed. A probe having a frequency of 50 MHz was used for the measurement, the gain was 30 dB, the pitch was 0.2 mm, and the sample was placed in water.

Those with no peeling, floating, or voids on the surface are marked with "○", and those with peeling, floating, or voids on the interface are marked with "x". The evaluation results are also shown in Tables 1 and 2.
The evaluation of the interface observation after the moisture absorption reflow test is that when the heat conductive resin sheet is laminated with the metal plate and the reflow process is performed, the interface is peeled off due to thermal expansion and contraction and the deformation due to the foaming of the heat conductive resin sheet occurs. It can be used as an evaluation of whether or not it is likely to occur.

[Thermal conductivity at 25 ° C]
Using a measurement sample cut out to a size of 10 mm square from the heat conductive resin sheet with a thickness of 500 μm produced in each Example and Comparative Example, "Laser light absorption spray (" Black Guard Spray FC-" manufactured by Fine Chemical Japan Co., Ltd. 153 ") was thinly applied to both sides and dried, and then the thermal diffusivity in the thickness direction of the resin sheet at a measurement temperature of 25 ° C. was measured by a laser flash method using a xenon flash analyzer ("LFA447 / NanoFlash300" manufactured by NETZSCH). (Mm ² / sec) was measured. The measurement was carried out for 5 points cut out from the same sheet, and the arithmetic mean value was calculated.

^{Further, the density ρ (g / m 3} ) of the resin sheet was determined using a specific gravity measuring machine (manufactured by A & D Co., Ltd.), and the ratio at 25 ° C. using a DSC measuring device (ThermoPlusEvo DSC8230, manufactured by Rigaku Co., Ltd.). The heat capacity c (J / (g · K)) was measured.
From each of these measured values, the thermal conductivity (W / m · k) in the sheet thickness direction at 25 ° C. was determined as “H = a × ρ × c”.

Since there is no JIS standard for the thermal diffusivity and thermal conductivity of resin-based materials, the thermal diffusivity a (mm ^{2 / sec) is JIS R1611.12010 (heat diffusivity by the flash method of fine ceramics).}・ Measurement method of specific heat capacity and thermal conductivity) is referred to, and since the standard stipulates that "the thickness of the sample is 0.5 mm or more and 5 mm or less", only the sample to be used for thermal conductivity measurement. It is measured with a thickness of 0.5 mm. The density ρ is a value obtained by the Archimedes method in accordance with JIS K6268. Further, the specific heat capacity c is a value obtained by using a DSC measuring device in accordance with JIS K7123.

As the specimens for measuring the thermal conductivity of Comparative Examples 3 and 4 using the thermosetting resin, the ones collected with a thickness of 500 μm among the sheet-shaped molded bodies were further subjected to a hot air oven at 170 ° C. together with the PET film. After the sheet-shaped molded body was cured, the PET film was peeled off to prepare a test piece.

In the heat conductive resin sheets of Examples 1 to 6, the tensile storage elastic modulus (E'(200)) of the resin component at 200 ° C. is 8.0 × 10 ⁷ Pa or more and 1.0 × 10 ¹⁰ Pa or less. The mass increase rate of the resin composition at 85 ° C. and 85% RH was 0.15% or less, and the moisture absorption reflow resistance was good. These thermally conductive resin sheets had a tensile storage elastic modulus (E'(300)) of the resin component at 300 ° C. of 4.0 × 10 ⁷ Pa or more and 1.0 × 10 ⁹ Pa or less.
On the other hand, the heat conductive resin sheets of Comparative Examples 1 to 4 in which the tensile storage elastic modulus (E'(200), E'(300)) or the mass increase rate is not within the above range are the dielectric breakdown voltage after the moisture absorption reflow test. Was less than 40 kV / mm, and the withstand voltage was lowered. In particular, in Comparative Examples 3 and 4, not only the dielectric breakdown voltage after the moisture absorption reflow test was low, but also peeling and floating at the interface between the heat conductive resin sheet and the copper electrode, and the generation of relatively remarkable voids were observed. ..
From the above, the heat conductive resin sheet of the present invention has a tensile storage elasticity (E') of the resin component at 200 ° C. of 8.0 × 10 ⁷ Pa or more and 1.0 × 10 ¹⁰ Pa or less, and is a resin. 85 ° C. of the composition, the mass increase rate in the 85% RH is not more than 0.15%, or, the tensile storage elastic modulus at 300 ° C. of the resin component (E '(300)) is 4.0 × ¹⁰ 7 Pa A thermoplastic resin having good moldability and processability is used because it is 1.0 × 10 ⁹ Pa or less and the mass increase rate of the resin composition at 85 ° C. and 85% RH is 0.15% or less. However, it was found that the moisture absorption and reflow resistance is better than that of the conventional heat conductive resin sheet using a heat-curable resin such as epoxy.

Further, from Examples 1 to 3, when boron nitride is used as the thermally conductive filler, the thermal conductivity is higher when the boron nitride agglomerated particles are used than when the flat plate-shaped boron nitride primary particles are used. It was found that the thermal conductivity was higher when the boron nitride agglomerated particles having a card house structure were used than when the boron nitride agglomerated particles were used.

Examples 5 and 6 use a blend of PEEK, which is a crystalline thermoplastic resin having a melting point of 300 ° C. or higher, and PEI, which is an amorphous thermoplastic resin. From Examples 3, 5, and 6, it was found that the tensile storage elastic modulus (E'(200)) of the resin component at 200 ° C. can be increased by blending PEI having a high glass transition temperature. In Examples 5 and 6, since the glass transition temperature of the blended PEI is 217 ° C., the tensile storage elastic modulus (E'(300)) of the resin component at 300 ° C. is lower than that in Example 3. since E '(300) is 4.0 × ¹⁰ 7 Pa or more, it had no effect on moisture absorption reflow resistance. Further, in Examples 5 and 6, the mass increase rate is increased as compared with Example 3 by blending PEI, but if the mass increase rate is 0.15% or less, the moisture absorption reflow resistance is affected. It turned out that there was no.
From the above, it was found that the thermally conductive resin sheet of the present invention is preferably a crystalline thermoplastic resin in which the main component of the thermoplastic resin has a melting point of 300 ° C. or higher.

Claims (15)

A resin composition containing a thermoplastic resin and a thermally conductive filler.
The tensile storage elastic modulus (E'(200)) of the thermoplastic resin at 200 ° C. is 8.0 × 10 ⁷ Pa or more and 1.0 × 10 ¹⁰ Pa or less.
A resin composition having a mass increase rate of 0.15% or less at 85 ° C. and 85% RH of the resin composition. A resin composition containing a thermoplastic resin and a thermally conductive filler.
The tensile storage elastic modulus (E'(300)) of the thermoplastic resin at 300 ° C. is 4.0 × 10 ⁷ Pa or more and 1.0 × 10 ⁹ Pa or less.
A resin composition having a mass increase rate of 0.15% or less at 85 ° C. and 85% RH of the resin composition. The resin composition according to claim 1 or 2, wherein the main component of the thermoplastic resin is a crystalline thermoplastic resin having a melting point of 300 ° C. or higher. The resin composition according to claim 3, wherein the crystalline thermoplastic resin having a melting point of 300 ° C. or higher is a polyetherketone-based resin. The resin composition according to claim 4, wherein the polyetherketone-based resin is a polyetheretherketone. Any one of claims 1 to 5, wherein the resin composition contains 15% by mass or more and 40% by mass or less of the thermoplastic resin and 60% by mass or more and 85% by mass or less of the thermally conductive filler in 100% by mass of the resin composition. The resin composition according to the section. The resin composition according to any one of claims 1 to 6, wherein the thermally conductive filler is boron nitride agglomerated particles. The resin composition according to any one of claims 1 to 7, wherein the boron nitride agglomerated particles have a card house structure. A heat conductive resin sheet comprising the resin composition according to any one of claims 1 to 8. The heat conductive resin sheet according to claim 9, wherein the thickness is 50 μm or more and 300 μm or less. The heat conductive resin sheet according to claim 9 or 10, wherein the heat conductivity in the thickness direction at 25 ° C. is 5.0 W / m · K or more. A laminated heat-dissipating sheet in which a heat-dissipating metal material is laminated on one surface of the heat-conductive resin sheet according to any one of claims 9 to 11. A heat-dissipating circuit board having the laminated heat-dissipating sheet according to claim 12. The heat-dissipating circuit board according to claim 13, wherein the conductive circuit is laminated on the other surface of the heat-conductive resin sheet. A power semiconductor device having a heat-dissipating circuit board according to claim 13 or 14.

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