KR20110089105A - Thermally conductive sheet - Google Patents

Abstract

PURPOSE: A thermally conductive sheet is provided to ensure excellent thermal conductivity of a plane direction vertical to the thickness direction of the thermally conductive sheet and a high heat dissipation property. CONSTITUTION: A thermally conductive sheet comprises a thermally conductive sheet(1) containing plate-like boron nitride particles. The thermal conductivity of the direction vertical to the thickness direction of the thermally conductive sheet is 4W/m·K. The glass transition point obtained as the peak value of tan δ obtained by measuring dynamic viscoelasticity in the frequency of 10 Hertz is 125°C or greater.

Description

Thermally conductive sheet {THERMALLY CONDUCTIVE SHEET}

The present invention relates to a thermally conductive sheet, in particular a thermally conductive sheet used in power electronics technology.

In recent years, in the hybrid device, the high-brightness LED device, the electromagnetic induction heating device, and the like, a power electronics technology that converts and controls power by a semiconductor element has been adopted. In power electronics technology, high heat dissipation (high thermal conductivity) is required for a material disposed in the vicinity of a semiconductor element in order to convert a large current into heat or the like.

For example, a heat conductive sheet containing a plate-like boron nitride powder and an acrylic acid ester copolymer resin has been proposed (see, for example, Japanese Unexamined Patent Application Publication No. 2008-280496).

In the heat conductive sheet of JP2008-280496A, the boron nitride powder is oriented so that its major axis direction (direction orthogonal to the plate thickness of the boron nitride powder) is along the thickness direction of the sheet, whereby The thermal conductivity in the thickness direction of the thermal conductive sheet is improved.

By the way, the thermally conductive sheet may require high thermal conductivity in the orthogonal direction (surface direction) orthogonal to a thickness direction by a use and an objective. In that case, in the heat conductive sheet of JP2008-280496A, since the long axis direction of the boron nitride powder is orthogonal (intersected) with respect to the plane direction, there is a problem that the thermal conductivity in this plane direction is insufficient. .

In addition, since such a thermally conductive sheet is used by being adhered to various devices, for example, in order to conduct (heat radiate) heat generated from various devices, it is deformed by the heat and excellent heat resistance so as not to peel off from the various devices. Deformability) is required.

An object of the present invention is to provide a thermally conductive sheet which is excellent in thermal conductivity in the plane direction and also excellent in heat resistance.

The thermally conductive sheet of the present invention is a thermally conductive sheet containing boron nitride particles having a plate shape, wherein the thermal conductivity in the direction orthogonal to the thickness direction of the thermally conductive sheet is 4 W / m · K or more, and is dynamic at a frequency of 10 Hz. It is characterized by the glass transition point calculated | required as the peak value of tan-delta obtained when viscoelasticity measurement is carried out 125 degreeC or more.

In the heat conductive sheet of this invention, it is excellent in the thermal conductivity of the surface direction orthogonal to a thickness direction, and also excellent in heat resistance.

Therefore, the thermally conductive sheet of the present invention can be used for various heat dissipation applications as a thermally conductive sheet which reduces deformation under high temperature, suppresses peeling, suppresses peeling, and has excellent handleability and excellent thermal conductivity in the plane direction. .

1 is a perspective view of one embodiment of a thermally conductive sheet of the present invention.
FIG. 2 is a process chart for explaining the manufacturing method of the thermally conductive sheet shown in FIG. 1, (a) is a step of hot pressing a mixture or a laminated sheet, and (b) is a step of dividing a press sheet into a plurality. (c) is a figure which shows the process of laminating | stacking a division sheet.
3 is a perspective view of a type I test apparatus (before the flex resistance test) of the flex resistance test.
4 is a perspective view of a type I test device (during the flex resistance test) of the flex resistance test.

The thermally conductive sheet of the present invention contains boron nitride particles.

Specifically, the thermally conductive sheet contains boron nitride (BN) particles as an essential component, and further contains, for example, a resin component.

The boron nitride particles are formed in a plate shape (or scaly pieces) and are dispersed in a form oriented in a predetermined direction (to be described later) in the thermally conductive sheet.

As for the boron nitride particle, the average of a longitudinal direction length (maximum length in the orthogonal direction with respect to the thickness direction of a board | plate) is 1-100 micrometers, Preferably it is 3-90 micrometers. The average length of the boron nitride particles in the longitudinal direction is 5 µm or more, preferably 10 µm or more, more preferably 20 µm or more, particularly preferably 30 µm or more, most preferably 40 µm or more, and the usual examples. For example, it is 100 micrometers or less, Preferably it is 90 micrometers or less.

In addition, the average of the thickness (thickness direction length of a board | plate, ie, the short-direction length of particle | grains) of a boron nitride particle | grain is 0.01-20 micrometers, Preferably it is 0.1-15 micrometers.

In addition, the aspect ratio (long direction length / thickness) of a boron nitride particle | grain is 2-10000, Preferably it is 10-5000.

The average particle diameter measured by the light scattering method of the boron nitride particles is, for example, 5 µm or more, preferably 10 µm or more, more preferably 20 µm or more, particularly preferably 30 µm or more, most preferably Is 40 µm or more and usually 100 µm or less.

In addition, the average particle diameter measured by the light scattering method is the volume average particle diameter measured by the dynamic light scattering type particle size distribution measuring apparatus.

When the average particle diameter measured by the light scattering method of boron nitride particle | grains does not reach the said range, a thermally conductive sheet may fall down and handleability may fall.

The bulk density (JIS K 5101, apparent density) of the boron nitride particles is, for example, 0.3 to 1.5 g / cm 3, preferably 0.5 to 1.0 g / cm 3.

In addition, a boron nitride particle can use a commercial item or the processed article which processed it. As a commercial item of a boron nitride particle, "PT" series (for example, "PT-110") made by Momentive Performance Materials Japan, "Showbien UHP" series made by Showa Denko Co., Ltd. (for example) , "Sobien UHP-1", etc. are mentioned.

The resin component is one capable of dispersing boron nitride particles, that is, a dispersion medium (matrix) in which the boron nitride particles are dispersed, and examples thereof include resin components such as thermosetting resin components and thermoplastic resin components.

As a thermosetting resin component, an epoxy resin, a thermosetting polyimide, a phenol resin, a urea resin, a melamine resin, an unsaturated polyester resin, a diallyl phthalate resin, a silicone resin, a thermosetting urethane resin, etc. are mentioned, for example.

As the thermoplastic resin component, for example, polyolefin (for example, polyethylene, polypropylene, ethylene-propylene copolymer, etc.), acrylic resin (for example, polymethyl methacrylate, etc.), polyvinyl acetate, ethylene-vinyl acetate Copolymer, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide (nylon (registered trademark)), polycarbonate, polyacetal, polyethylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polysulfone, poly Ether sulfone, polyether ether ketone, polyallyl sulfone, thermoplastic polyimide, thermoplastic urethane resin, polyaminobismaleimide, polyamideimide, polyetherimide, bismaleimide triazine resin, polymethylpentene, fluorinated resin, liquid crystal polymer , Olefin-vinyl alcohol copolymer, ionomer, polyarylate, acrylonitrile-ethylene-styrene Styrene copolymer-polymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile.

These resin components can be used alone or in combination of two or more.

Among the thermosetting resin components, epoxy resins are preferable.

An epoxy resin is a form of any one of a liquid state, a semisolid form, and a solid form at normal temperature.

Specifically, as an epoxy resin, it is bisphenol-type epoxy resin (for example, bisphenol-A epoxy resin, bisphenol F-type epoxy resin, bisphenol S-type epoxy resin, hydrogenated bisphenol A-type epoxy resin, dimer acid modified bisphenol, for example. Epoxy resins, etc.), novolac epoxy resins (e.g., phenol novolac epoxy resins, cresol novolac epoxy resins, biphenyl epoxy resins, etc.), naphthalene epoxy resins, fluorene epoxy resins (examples) For example, aromatic epoxy resins such as bisaryl fluorene type epoxy resins) and triphenylmethane type epoxy resins (eg, trishydroxyphenylmethane type epoxy resins, etc.), for example, triepoxypropyl isocyanurate Nitrogen containing ring epoxy resins, such as a lysate (triglycidyl isocyanurate) and hydantoin epoxy resin, for example, an aliphatic epoxy resin, for example For example, an alicyclic epoxy resin (for example, a dicyclo cyclic epoxy resin etc.), for example, a glycidyl ether type epoxy resin, for example, a glycidyl amine type epoxy resin, etc. are mentioned.

These epoxy resins can be used alone or in combination of two or more.

Further, the epoxy resin has an epoxy equivalent of, for example, 100 to 1000 g / eqiv., Preferably 180 to 700 g / eqiv., And a softening temperature (circulation method), for example, 80 ° C. or less (specifically, 20-80 degreeC), Preferably it is 70 degrees C or less (specifically, 35-70 degreeC).

The melt viscosity at 80 ° C of the epoxy resin is, for example, 10 to 20000 mPa · s, preferably 50 to 10000 mPa · s. When using 2 or more types of epoxy resins together, melt viscosity as those mixture is set in the said range.

Moreover, when using 2 or more types of epoxy resins together, for example, a combination of a liquid epoxy resin and a solid epoxy resin, More preferably, a combination of a liquid aromatic epoxy resin and a solid aromatic epoxy resin, etc. Can be mentioned. As such a combination, the combination of a liquid bisphenol type epoxy resin and a solid triphenylmethane type epoxy resin, or a combination of a liquid bisphenol type epoxy resin and a solid bisphenol type epoxy resin is mentioned specifically ,.

Moreover, as an epoxy resin, Preferably the use of the semi-solid epoxy resin is mentioned preferably, More preferably, the use of the semi-solid aromatic epoxy resin is mentioned more preferably. As such an epoxy resin, a semisolid fluorene type epoxy resin is mentioned more specifically.

If it is a combination of a liquid epoxy resin and a solid epoxy resin, or a semi-solid epoxy resin, the level | step difference followability (after-mentioned) of a heat conductive sheet can be improved.

Moreover, by combining several epoxy resin from which a property differs, glass transition temperature can be made into a desired range.

In addition, when using 2 or more types of epoxy resins together, 1st epoxy resin whose softening temperature is less than 45 degreeC, Preferably it is 35 degrees C or less, and softening temperature is 45 degreeC or more, Preferably, The 2nd epoxy resin which is 55 degreeC or more is used together. Thereby, the kinematic viscosity (based on JIS K 7233, mentioned later) of the resin component (mixture) can be set to a desired range, and the level | step difference followability of a thermally conductive sheet can be improved.

In addition, an epoxy resin can be manufactured as an epoxy resin composition, for example, by containing a hardening | curing agent and a hardening accelerator.

A hardening | curing agent is a latent hardening | curing agent (epoxy resin hardening | curing agent) which can harden an epoxy resin by heating, For example, an imidazole compound, an amine compound, an acid anhydride compound, an amide compound, a hydrazide compound, an imidazoline compound, etc. Can be mentioned. Moreover, a phenol compound, a urea compound, a polysulfide compound etc. can also be mentioned in addition to the above.

As an imidazole compound, 2-phenylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, etc. are mentioned, for example. Can be mentioned.

As an amine compound, For example, aliphatic polyamines, such as ethylenediamine, propylenediamine, diethylenetriamine, and triethylenetetramine, For example, aromatic polyamine, such as metaphenylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone Etc. can be mentioned.

As the acid anhydride compound, for example, phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 4-methyl-hexahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, dodecenyl succinic anhydride, dichloro Succinic anhydride, benzophenone tetracarboxylic anhydride, chloric anhydride and the like.

As an amide compound, dicyandiamide, polyamide, etc. are mentioned, for example.

As a hydrazide compound, adipic acid dihydrazide etc. are mentioned, for example.

As an imidazoline compound, for example, methyl imidazoline, 2-ethyl-4-methyl imidazoline, ethyl imidazoline, isopropyl imidazoline, 2, 4- dimethyl imidazoline, phenyl imidazoline, Undecyl imidazoline, heptadecyl imidazoline, 2-phenyl-4-methyl imidazoline, etc. are mentioned.

These hardeners can be used alone or in combination of two or more.

As a hardening | curing agent, Preferably an imidazole compound is mentioned.

As the curing accelerator, for example, tertiary amine compounds such as triethylenediamine and tri-2,4,6-dimethylaminomethylphenol, for example triphenylphosphine, tetraphenylphosphonium tetraphenylborate and tetra-n- Phosphorus compounds such as butylphosphonium-o, o-diethylphosphorodithioate, for example, quaternary ammonium salt compounds, for example organometallic salt compounds, and derivatives thereof. These curing accelerators can be used alone or in combination of two or more.

The compounding ratio of the hardening | curing agent in an epoxy resin composition is 0.5-50 mass parts with respect to 100 mass parts of epoxy resins, Preferably it is 1-10 mass parts, The compounding ratio of a hardening accelerator is 0.1, for example. To 10 parts by mass, preferably 0.2 to 5 parts by mass.

Said hardening | curing agent and / or hardening accelerator can be manufactured and used as a solvent solution and / or a solvent dispersion liquid melt | dissolved and / or dispersed with a solvent as needed.

Examples of the solvent include ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and organic solvents such as amides such as N, N-dimethylformamide. Moreover, as a solvent, aqueous solvents, such as alcohol, such as water, for example, methanol, ethanol, a propanol, isopropanol, are mentioned, for example. The solvent is preferably an organic solvent, more preferably ketones or amides.

Among the thermoplastic resin components, polyolefins are preferable.

As a polyolefin, Preferably, polyethylene and an ethylene-propylene copolymer are mentioned.

As polyethylene, a low density polyethylene, a high density polyethylene, etc. are mentioned, for example.

As an ethylene-propylene copolymer, a random copolymer, a block copolymer, or a graft copolymer of ethylene and propylene, etc. are mentioned, for example.

These polyolefins can be used alone or in combination of two or more.

In addition, the weight average molecular weight and / or number average molecular weight of a polyolefin are 1000-10000, for example.

In addition, a polyolefin can be used individually or in combination.

Preferred among the resin components are thermosetting resin components, more preferably epoxy resins.

In addition, the kinematic viscosity measured by the kinematic viscosity test (temperature: 25 degreeC ± 0.5 degreeC, solvent: butyl carbitol, resin component (solid content) concentration: 40 mass%) based on JISK7233 (bubble viscometer method) of a resin component is For example, 0.22 × 10 ^-4 to 2.00 × 10 ^-4 m 2 / s, preferably 0.3 × 10 ^-4 to 1.9 × 10 ^-4 m 2 / s, more preferably 0.4 × 10 ^-4 to 1.8 × 10 ^-4 m 2 / s. Further, the kinematic viscosity described above is, for example, 0.22 × 10 ⁻⁴ to 1.00 × 10 ⁻⁴ m 2 / s, preferably 0.3 × 10 ⁻⁴ to 0.9 × 10 ⁻⁴ m 2 / s, more preferably 0.4 × 10 ^It may also be set to ^-4 to 0.8 × 10 ⁻⁴ m 2 / s.

When the kinematic viscosity of the resin component exceeds the above range, it may not be possible to impart excellent flexibility and step-followability (to be described later) to the thermally conductive sheet. On the other hand, when the kinematic viscosity of the resin component does not fall within the above range, the boron nitride particles may not be oriented in a predetermined direction.

In the kinematic viscosity test based on JIS K 7233 (Bubble Viscometer Method), the rising speed of the bubbles in the resin component sample is compared with the rising speed of the bubbles in the standard sample (the kinematic viscosity is known). The kinematic viscosity of the resin component is measured by determining that the kinematic viscosity of the corresponding standard sample is the kinematic viscosity of the resin component.

In addition, in the thermally conductive sheet, the content ratio (volume percentage of the boron nitride particles to the total volume of the solid component, that is, the resin component and the boron nitride particles) based on the volume of the boron nitride particles is, for example, 35 vol% or more, preferably Preferably it is at least 60% by volume, preferably at least 75% by volume, usually at most 95% by volume, preferably at most 90% by volume.

When the volume ratio content of boron nitride particles does not fall within the above range, the boron nitride particles may not be oriented in a predetermined direction in the thermally conductive sheet. On the other hand, when the volume ratio content of boron nitride particle | grains exceeds the said range, a thermally conductive sheet may fall, and handleability and a step track | tracking property may fall.

In addition, the mixing | blending ratio of the boron nitride particle | grains with respect to 100 mass parts of total amounts (solid content total amount) of each component (boron nitride particle and resin component) which forms a thermally conductive sheet is 40-95 mass parts, Preferably Is 65-90 mass parts, and the compounding ratio of the mass component of the resin component with respect to 100 mass parts of each component total amount which forms a thermally conductive sheet is 5-60 mass parts, Preferably it is 10-35 mass parts. . In addition, the mixing | blending ratio of a mass reference with respect to 100 mass parts of resin components of a boron nitride particle | grain is 60-1900 mass parts, Preferably it is also 185-900 mass parts.

In addition, when using 2 types of epoxy resins (1st epoxy resin and 2nd epoxy resin) together, the mass ratio (mass of 1st epoxy resin / 2nd epoxy resin of 1st epoxy resin) with respect to 2nd epoxy resin of 1st epoxy resin Mass) may be appropriately set according to the softening temperature of each epoxy resin (first epoxy resin and second epoxy resin), for example, 1/99 to 99/1, preferably 10/90 to 90/10. to be.

In addition, the resin component includes, for example, a polymer precursor (for example, a low molecular weight polymer including an oligomer) and / or a monomer, in addition to the above components (polymer).

BRIEF DESCRIPTION OF THE DRAWINGS The perspective view of one Embodiment of the heat conductive sheet of this invention, FIG. 2 shows the process diagram for demonstrating the manufacturing method of the heat conductive sheet shown in FIG.

Next, the method of manufacturing one Embodiment of the heat conductive sheet of this invention is demonstrated with reference to FIG.

In this method, a mixture is first prepared by blending each of the above components in the above-mentioned blending ratio and stirring and mixing.

In stirring mixing, in order to mix each component efficiently, a solvent can be mix | blended with each component mentioned above, for example, or a resin component (preferably thermoplastic resin component) can be melted by heating, for example.

As a solvent, the organic solvent similar to the above is mentioned. In addition, when the said hardening | curing agent and / or hardening accelerator are manufactured as a solvent solution and / or a solvent dispersion liquid, without adding a solvent in stirring mixing, the solvent of a solvent solution and / or a solvent dispersion liquid for stirring mixing as it is is carried out as it is. It can provide as a mixed solvent. Alternatively, the solvent may be further added as a mixed solvent in stirring mixing.

When stirring and mixing using a solvent, after stirring and mixing, a solvent is removed.

To remove the solvent, for example, it is left at room temperature for 1 to 48 hours, for example, heated at 40 to 100 ° C. for 0.5 to 3 hours, or at 20 to 60 ° C. under a reduced pressure atmosphere of, for example, 0.001 to 50 kPa. Heat 0.5 to 3 hours.

When melting a resin component (preferably a thermoplastic resin component) by heating, the heating temperature is, for example, a temperature near or above the softening temperature of the resin component, specifically 40 to 150 ° C, preferably 70-140 degreeC.

Subsequently, in this method, the obtained mixture is hot pressed.

Specifically, as illustrated in FIG. 2A, the press sheet 1A is obtained by hot pressing the mixture through, for example, two release films 4 as necessary. The conditions of a hot press are 50-150 degreeC, Preferably it is 60-140 degreeC, the pressure is 1-100 MPa, Preferably it is 5-50 MPa, and time is, for example, 0.1 to 100 minutes, preferably 1 to 30 minutes.

More preferably the mixture is vacuum heat pressed. The vacuum degree in a vacuum hot press is 1-100 Pa, for example, Preferably it is 5-50 Pa, and temperature, a pressure, and time are the same as those of said heat press.

When the temperature, pressure and / or time in the hot press are outside the above ranges, the porosity P (described later) of the thermal conductive sheet 1 may not be adjusted to a desired value.

The thickness of 1 A of press sheets obtained by hot press is 50-1000 micrometers, Preferably it is 100-800 micrometers.

Subsequently, in this method, as shown in FIG. 2B, the press sheet 1A is divided into a plurality of pieces (for example, four pieces) to obtain a divided sheet 1B (dividing step). . In division of 1 A of press sheets, 1 A of press sheets are cut | disconnected along the thickness direction so that it may divide into several pieces when it projects in the thickness direction. In addition, 1 A of press sheets are cut | disconnected so that it may become the same shape, when each division sheet 1B is projected in the thickness direction.

Subsequently, in this method, as shown in FIG.2 (c), each divided sheet 1B is laminated | stacked in the thickness direction, and the laminated sheet 1C is obtained (lamination process).

Then, in this method, as shown to Fig.2 (a), 1 C of laminated sheets are hot-pressed (preferably vacuum hot-pressing) (heat press process). The conditions of the hot press are the same as the conditions of the hot press of the mixture described above.

The thickness of the laminated sheet 1C after hot pressing is, for example, 1 mm or less, preferably 0.8 mm or less, for example, 0.05 mm or more, preferably 0.1 mm or more.

Subsequently, in order to orient the boron nitride particles 2 in the resin component 3 efficiently in a predetermined direction in the thermal conductive sheet 1, the above-described dividing step (FIG. 2B) and the laminating step (FIG. 2 (c)) and a series of processes of a hot press process (FIG. 2 (a)) are performed repeatedly. The number of repetitions is not particularly limited and may be appropriately set depending on the state of filling of the boron nitride particles, for example, 1 to 10 times, preferably 2 to 7 times.

Thereby, the thermal conductive sheet 1 can be obtained.

The thickness of the thermally conductive sheet 1 obtained is, for example, 1 mm or less, preferably 0.8 mm or less, for example, 0.05 mm or more, preferably 0.1 mm or more.

In addition, the content ratio (volume percentage of the boron nitride particle with respect to the total volume of a solid content, ie, a resin component and a boron nitride particle | grains) of the volume reference of the boron nitride particle in the thermal conductive sheet 1 is an example as mentioned above. For example, it is 35 volume% or more (preferably 60 volume% or more, more preferably 75 volume% or more), and usually 95 volume% or less (preferably 90 volume% or less).

When the content ratio of the boron nitride particles does not fall within the above range, the boron nitride particles may not be oriented in a predetermined direction in the thermally conductive sheet.

In addition, when the resin component 3 is a thermosetting resin component, for example, the above-described dividing process (FIG. 2B), lamination process (FIG. 2C) and the hot press process (FIG. 2 ( A series of steps of a)) are repeatedly performed in an uncured state (or semi-cured state (B stage state)) and uncured after the heat press process (FIG. 2A) in the final process. The heat conductive sheet 1 after hardening is produced by thermosetting the heat conductive sheet 1 (or semi-hardening (B stage state)).

In order to thermoset the thermally conductive sheet 1, the above-mentioned hot press or dryer is used. Preferably a dryer is used. The conditions of such thermosetting are temperature, for example, 60-250 degreeC, Preferably it is 80-200 degreeC, and a pressure is 100 MPa or less, Preferably it is 50 MPa or less.

In the thermally conductive sheet 1 thus obtained, as shown in FIG. 1 and a partially enlarged schematic diagram, the longitudinal direction LD of the boron nitride particles 2 is the thickness of the thermally conductive sheet 1. Orientation is carried out along the plane direction SD crossing (orthogonal) to the direction TD.

Moreover, the arithmetic mean (the orientation of the boron nitride particles 2 with respect to the thermally conductive sheet 1 of the angle which the longitudinal direction LD of the boron nitride particle | grains 2 makes into the surface direction SD of the thermal conductive sheet 1). Angle (alpha) is 25 degrees or less, for example, Preferably it is 20 degrees or less, and is 0 degrees or more normally.

In addition, the orientation angle (alpha) with respect to the thermally conductive sheet 1 of the boron nitride particle 2 cut | disconnects the thermally conductive sheet 1 with the cross section polisher CP along the thickness direction, and thereby The cross section which appears is photographed by the scanning electron microscope (SEM) by the magnification of the visual field which can observe 200 or more boron nitride particles 2, and the longitudinal direction of the boron nitride particle 2 from the SEM photograph obtained The inclination angle (alpha) with respect to the surface direction SD (direction orthogonal to the thickness direction TD) of the thermal conductive sheet 1 of LD is acquired, and it calculates as an average value.

Thereby, the thermal conductivity of the surface direction SD of the thermal conductive sheet 1 is 4W / m * K or more, Preferably it is 5W / m * K or more, More preferably, it is 10W / m * K or more, More preferably, 15 W / m * K or more, Especially preferably, it is 25 W / m * K or more, and is 200 W / m * K or less normally.

In addition, when the resin component 3 is a thermosetting resin component, the thermal conductivity of the surface direction SD of the thermal conductive sheet 1 is substantially the same before and after thermosetting.

If the thermal conductivity of the surface direction SD of the thermal conductive sheet 1 does not fall within the above range, the thermal conductivity of the surface direction SD is not sufficient, so that the thermal conductivity in such a surface direction SD is required. It may not be available.

In addition, the thermal conductivity of the surface direction SD of the thermal conductive sheet 1 is measured by the pulse heating method. In the pulse heating method, xenon flash analyzer "LFA-447 type" (manufactured by NETZSCH) is used.

In addition, the thermal conductivity of the thickness direction TD of the thermal conductive sheet 1 is 0.5-15 W / m * K, for example, Preferably it is 1-10 W / m * K.

In addition, the thermal conductivity of the thickness direction TD of the thermal conductive sheet 1 is measured by the pulse heating method, the laser flash method, or the TWA method. In the pulse heating method, the same thing as the above is used, "TC-9000" (made by Albak Rikosha) is used by the laser flash method, and "ai-Phase mobile" by the TWA method (made by Eye Phase Co., Ltd.). ) Is used.

Thereby, the ratio of the thermal conductivity of the surface direction SD of the thermal conductive sheet 1 to the thermal conductivity of the thickness direction TD of the thermal conductive sheet 1 (thermal conductivity of the surface direction SD / thickness direction TD) Thermal conductivity) is, for example, 1.5 or more, preferably 3 or more, more preferably 4 or more, and usually 20 or less.

In addition, although not shown in FIG. 1, the space | interval (gap) is formed in the thermal conductive sheet 1, for example.

The proportion of the voids in the thermally conductive sheet 1, that is, the porosity P, is a content ratio (volume basis) of the boron nitride particles 2, and further, a mixture of the boron nitride particles 2 and the resin component 3. Can be adjusted by the temperature, pressure and / or time of the heat press (FIG. 2A), and specifically, the temperature, pressure and / or time of the above-mentioned hot press (FIG. 2A) It can adjust by setting in the said range.

The porosity P in the thermal conductive sheet 1 is 30 volume% or less, for example, Preferably it is 10 volume% or less.

Said porosity P cuts the thermal conductive sheet 1 first with the cross section polisher CP along the thickness direction, for example, and the cross section shown by it is carried out by a scanning electron microscope SEM, for example. It is measured by observing at 200 times to obtain an image, and binarizing and other portions from the obtained image are binarized, and then calculating the area ratio of the void portion to the cross-sectional area of the entire thermally conductive sheet 1.

In the thermal conductive sheet 1, the porosity P2 after curing is, for example, 100% or less, preferably 50% or less with respect to the porosity P1 before curing.

In the measurement of the porosity P (P1), when the resin component 3 is a thermosetting resin component, the thermal conductive sheet 1 before thermosetting is used.

If the porosity P of the thermally conductive sheet 1 is in the above-mentioned range, the step followingability (described later) of the thermally conductive sheet 1 can be improved.

The glass transition point of the thermally conductive sheet 1 is 125 ° C or higher, preferably 130 ° C or higher, more preferably 140 ° C or higher, further 150 ° C or higher, further 170 ° C or higher, further 190 ° C or higher, and 210 ° C or higher. The above is preferable and is 300 degrees C or less normally.

If the glass transition point is more than the said minimum, since the outstanding heat resistance of a thermally conductive sheet can be ensured, deformation under high temperature can be reduced and peeling can be suppressed.

That is, in the case where the thermal conductive sheet 1 is bonded to various devices, when the temperature of the device rises and exceeds the glass transition point of the thermal conductive sheet 1, the change in the coefficient of linear expansion, The thermal conductive sheet 1 may be peeled from various devices. However, in this thermal conductive sheet 1, since the glass transition point is more than the said upper limit, even if the temperature of a device rises, it can suppress that it exceeds the glass transition point of the thermal conductive sheet 1, As a result, Deformation of the thermal conductive sheet 1 can be reduced, and peeling can be suppressed.

In addition, a glass transition point is calculated | required as a peak value of tan-delta (loss tangent) obtained when dynamic viscoelasticity measurement is performed at the frequency of 10 hertz.

In the bending resistance test based on the cylindrical mandrel method of JIS K 5600-5-1, when the thermal conductive sheet 1 is evaluated under the following test conditions, fracture is not observed preferably.

Exam conditions

Test device: type I

Mandrel: Diameter 10mm

Bend Angle: More Than 90 Degree

Thickness of Thermally Conductive Sheet 1: 0.3mm

3 and 4 show a perspective view of a type I test apparatus, and a type I test apparatus will be described below.

3 and 4, the type I test apparatus 10 includes a first flat plate 11, a second flat plate 12 arranged in parallel with the first flat plate 11, and a first flat plate 11. And a mandrel (rotation shaft) 13 formed to relatively rotate the second flat plate 12.

The first flat plate 11 is formed in a substantially rectangular flat plate shape. In addition, a stopper 14 is formed at one end (free end) of the first flat plate 11. The stopper 14 is formed to extend along one end of the second flat plate 12 on the surface of the second flat plate 12.

The second flat plate 12 has a substantially rectangular flat plate shape and is disposed such that one side thereof is adjacent to one side of the first flat plate 11 (one side of the other end (base end) opposite to one end where the stopper 14 is formed). It is.

The mandrel 13 is formed to extend along one side of the first flat plate 11 and the second flat plate 12 adjacent to each other.

In this type I test apparatus 10, as shown in FIG. 3, the surface of the first flat plate 11 and the surface of the second flat plate 12 are flat before starting the flex resistance test.

And in order to perform a bending resistance test, the thermal conductive sheet 1 is mounted on the surface of the 1st flat plate 11, and the surface of the 2nd flat plate 12. As shown in FIG. Moreover, the thermal conductive sheet 1 is mounted so that one side thereof may contact the stopper 14.

Subsequently, as shown in FIG. 4, the first flat plate 11 and the second flat plate 12 are rotated relatively. Specifically, the free end of the first flat plate 11 and the free end of the second flat plate 12 are rotated by a predetermined angle around the mandrel 13. Specifically, the first flat plate 11 and the second flat plate 12 are rotated so that the surfaces of their free ends are close (facing).

Thereby, the thermal conductive sheet 1 bends around the mandrel 13 while following the rotation of the first flat plate 11 and the second flat plate 12.

More preferably, no fracture is observed in the thermally conductive sheet 1 even when the bending angle is set to 180 degrees under the above test conditions.

In addition, when the resin component 3 is a thermosetting resin component, the thermal conductive sheet 1 provided for the bending test is the thermal conductive sheet 1 of the semi-hardened (B stage state) (that is, the thermal conductivity before thermal curing). Sheet 1).

In the case where breakage is observed in the thermally conductive sheet 1 in the bending resistance test by the aforementioned bending angle, excellent flexibility may not be provided to the thermally conductive sheet 1.

In addition, when this thermal conductive sheet 1 evaluates on the following test conditions in the three-point bending test based on JISK7171 (2008), a fracture is not observed, for example.

Exam conditions

Test piece: size 20 mm x 15 mm

 Distance between points: 5 mm

Test speed: 20 mm / min (pressing speed of indenter)

Bending angle: 120 degree

Evaluation method: When testing on the said test conditions, the presence or absence of fracture | rupture, such as a crack in the center part of a test piece, is visually observed.

In addition, in the 3-point bending test, when the resin component 3 is a thermosetting resin component, the thermal conductive sheet 1 before thermosetting is used.

Therefore, this thermally conductive sheet 1 is excellent in step | following trackability, in that break is not observed in the said 3-point bending test. In addition, step | step difference followable | trackability is a characteristic which follows the step which adheres so that the thermal conductive sheet 1 may be adhere | attached along the step | step, when installing in the installation object with a step | step.

In addition, the heat conductive sheet 1 can be attached with marks such as letters and symbols. That is, the thermal conductive sheet 1 is excellent in mark adhesion. Mark adhesiveness is a characteristic which can reliably adhere the mark to the thermal conductive sheet 1.

Specifically, the mark is attached (coated, fixed or fixed) to the thermal conductive sheet 1 by printing or stamping.

As printing, inkjet printing, iron plate printing, intaglio printing, laser printing, etc. are mentioned, for example.

In addition, when a mark is printed by inkjet printing, iron plate printing, or intaglio printing, for example, an ink fixing layer for improving the fixability of the mark is formed on the surface (print side) of the thermal conductive sheet 1. can do.

When the mark is printed by laser printing, for example, a toner fixing layer for improving the fixability of the mark can be formed on the surface (print side) of the thermal conductive sheet 1.

As a marking, laser engraving, a steering angle, etc. are mentioned, for example.

And in this heat conductive sheet 1, it is excellent in the thermal conductivity of the surface direction orthogonal to a thickness direction, and also excellent in heat resistance.

Therefore, as a thermally conductive sheet which reduces deformation under high temperature, suppresses peeling, and has excellent handleability and excellent thermal conductivity in the plane direction, thermoelectrics employed in various heat dissipation applications, specifically, power electronics technology As a conductive sheet, it can be used in more detail as a heat conductive sheet applied to a LED heat radiation board | substrate and a heat dissipation material for batteries, for example.

In addition, in said hot press process (FIG. 2 (a)), the mixture and 1 C of laminated sheets can also be rolled with a some calender roll etc., for example.

In addition, when the resin component 3 is a thermosetting resin component, the heat conductive sheet of this invention can also be obtained as an unhardened heat conductive sheet 1, without making it thermoset as mentioned above.

That is, the thermally conductive sheet of the present invention is not particularly limited in the case where the resin component is a thermosetting resin component, and whether or not the thermal curing is performed, for example, as described above, after the lamination step (FIG. 2C). Or after a predetermined period has elapsed from the above-mentioned hot press step (FIG. 2A, a hot press of the mixture, which is not heat cured), or specifically from the application to the power electronics technology or from the application thereof. You may heat-cure after a predetermined period of time.

Example

Although an Example is shown to the following and this invention is demonstrated further more concretely, this invention is not limited to an Example at all.

Example 1

13.42 g of PT-110 (brand name, plate-shaped boron nitride particle, average particle diameter (light scattering method), Momentive Performance Materials Japan company) and JER828 (brand name, bisphenol A type epoxy resin, liquid, epoxy equivalent 184 To 194 g / eqiv., Softening temperature (recirculation method) below 25 ° C., melt viscosity (80 ° C.) 70 mPa · s, manufactured by Japan Epoxy Resin Co., Ltd. 1 g and EPPN-501HY (trade name, triphenylmethane type epoxy resin, solid state, epoxy Equivalent 163-175 g / eqiv., Softening temperature (recirculation method) 57-63 degreeC, 2 g of Nippon Kayaku Co., Ltd., and 3 g of 5 mass% methyl ethyl ketone solutions of a curing agent (Cure-sol 2PZ (brand name, the product made by Shikoku Chemical Co., Ltd.)) (Solid content 0.15 g) (5 mass% with respect to the total amount of JER828 and EPPN-501HY, which are epoxy resins), was mixed and stirred, and left overnight at room temperature (23 ° C.) to volatilize methyl ethyl ketone (dispersant of hardener), A semisolid mixture was prepared.

In addition, in the said mixing | blending, the volume percentage (vol%) of the boron nitride particle with respect to the total volume of solid content (namely, boron nitride particle | grains and solid content of an epoxy resin) except a hardening | curing agent was 70 volume%.

Subsequently, the obtained mixture was sandwiched between two release films subjected to siliconization, and they were hot pressed for 2 minutes at a load (20 MPa) of 5 tons at 80 ° C and 10 Pa atmosphere (vacuum atmosphere) by a vacuum heating press. This obtained the press sheet of thickness 0.3mm (refer FIG. 2 (a)).

Then, when the obtained press sheet is projected in the thickness direction of a press sheet, it cut | disconnects so that it may divide into several pieces, and obtains a division sheet (refer FIG.2 (b)), and then laminates | stacks a division sheet in a thickness direction, and is laminated | stacked sheet | seat Was obtained (see FIG. 2 (c)).

Subsequently, the obtained laminated sheet was hot-pressed on the conditions similar to the above by the vacuum heating press machine similar to the above (refer FIG.2 (a)).

Subsequently, the series of operations (see FIG. 2) of the above cutting, lamination and hot press were repeated four times to obtain a thermally conductive sheet (B stage) having a thickness of 0.3 mm.

Then, the obtained thermal conductive sheet was put into a drier and heat-hardened by heating at 150 degreeC for 120 minutes.

Examples 2-14

Based on the formulation prescription of Tables 1-3, and manufacturing conditions, it processed like Example 1 and obtained the thermal conductive sheet.

(evaluation)

1. Thermal conductivity

About the thermally conductive sheets obtained in Examples 1-14, thermal conductivity was measured.

That is, the thermal conductivity in the surface direction SD was measured by the pulse heating method using a xenon flash analyzer "LFA-447 type" (made by Nescher).

The results are shown in Tables 1-3.

2. Glass transition point

About the thermal conductive sheet obtained in Examples 1-14, the glass transition point was measured.

That is, the thermally conductive sheet was analyzed by a dynamic viscoelasticity measuring device (model number: DMS6100, manufactured by Seiko Denshi Kogyo Co., Ltd.) at a temperature increase rate of 1 ° C / min and a frequency of 10 hertz.

From the obtained data, the glass transition point was calculated | required as the peak value of tan-delta.

The results are shown in Tables 1-3.

3. Porosity (P)

The porosity P1 of the thermally conductive sheet before thermosetting of Examples 1-14 was measured by the following measuring method.

Method for Measuring Porosity: First, the thermally conductive sheet was cut by a cross section polisher (CP) along the thickness direction, and the cross section shown therein was observed at 200 times by a scanning electron microscope (SEM) to obtain an image. Then, the void part and the other part were binarized from the obtained phase, and the area ratio of the void part with respect to the cross-sectional area of the whole heat conductive sheet was computed.

The results are shown in Tables 1-3.

4. Step followability (3-point bending test)

The step conformability was evaluated according to the following evaluation criteria by performing the 3-point bending test in the following test conditions on the thermally conductive sheet | seat before the thermosetting of Examples 1-14 based on JISK7171 (2010). did. The results are shown in Tables 1-3.

Exam conditions

  Test piece: size 20 mm x 15 mm

 Distance between points: 5 mm

Test speed: 20 mm / min (pressing speed of indenter)

Bending angle: 120 degree

(Evaluation standard)

(Double-circle): No break was observed at all.

○: Almost no fracture was observed.

X: The fracture was clearly observed.

5. Print mark visibility (print mark adhesion: mark adhesion by inkjet printing or laser printing)

Marks were printed on the thermally conductive sheets of Examples 1 to 14 by inkjet printing and laser printing, and such marks were observed.

As a result, in any of the thermally conductive sheets of Examples 1 to 14, the marks by both the inkjet printing and the laser printing could be visually recognized well, and the print mark adhesion was confirmed to be good.

The numerical value in each component in Tables 1-3 shows the number of g, when there is no special description.

In addition, in the column of the boron nitride particle of Tables 1-3, the numerical value of an upper stage is a compounding mass (g) of boron nitride particle, and the numerical value of an intermediate | middle stage except solid content (namely, a hardening | curing agent in a thermally conductive sheet) The volume percentage (volume%) of the boron nitride particles with respect to the total volume of the boron nitride particles and the solid content of the epoxy resin, and the numerical value at the bottom is the solid content (that is, the boron nitride particles, the epoxy resin and the curing agent of the thermally conductive sheet). Volume percentage of the boron nitride particles to the total volume of solids).

In addition, about each component of Table 1-Table 3, the detail is described below about the component which attached *.

PT-110 ^{* 1} : Brand name, plate-shaped boron nitride particle, average particle diameter (light scattering method) 45 micrometers, the moment performance performance materials Japan company make

UHP-1 ^{* 2} : Product name: Shobien UHP-1, plate-like boron nitride particles, average particle diameter (light scattering method) 9 µm, manufactured by Showa Denko Corporation

Epoxy Resin A ^{* 3} : Ogsol EG (brand name), bisaryl fluorene type epoxy resin, semisolid, epoxy equivalent 294 g / eqiv., Softening temperature (circulation method) 47 ° C, melt viscosity (80 ° C) 1360 mPas, Osaka Gas Chemical Co., Ltd.

Epoxy resin B ^{* 4} : JER828 (brand name), bisphenol A type epoxy resin, liquid phase, epoxy equivalent 184-194 g / eqiv., Softening temperature (recirculation method) below 25 degreeC, melt viscosity (80 degreeC) 70 mPa * s, Japan epoxy Resin Priest

Epoxy Resin C ^{* 5} : JER1002 (brand name), bisphenol A type epoxy resin, solid form, epoxy equivalent 600 to 700 g / eqiv., Softening temperature (circulation method) 78 ° C, melt viscosity (80 ° C) 10000 mPa · s or more Above limit), product made in Japan epoxy resin company

Epoxy Resin D ^{* 6} : EPPN-501HY (trade name), triphenylmethane type epoxy resin, solid form, epoxy equivalent 163 to 175 g / eqiv., Softening temperature (cyclic method) 57 to 63 ° C, manufactured by Nippon Kayaku Co., Ltd.

Curing agent ^{* 7} : 5% by mass methyl ethyl ketone solution of Cursol 2PZ (trade name, manufactured by Shikoku Chemical Co., Ltd.)

Curing agent ^{* 8} : 5% by mass methyl ethyl ketone dispersion of cursol 2P4MHZ-PW (trade name, manufactured by Shikoku Chemical Co., Ltd.)

In addition, although the said description was provided as illustrated embodiment of this invention, this is only a mere illustration and should not interpret it limitedly. Modifications of the present invention which are apparent to those skilled in the art are included in the following claims.

Claims (1)

It is a thermally conductive sheet containing plate-like boron nitride particles,
The thermal conductivity of the orthogonal direction with respect to the thickness direction of the said heat conductive sheet is 4 W / m * K or more,
The glass conductive point calculated | required as the peak value of tan-delta obtained when dynamic viscoelasticity measurement is performed at the frequency of 10 hertz is 125 degreeC or more, The thermal conductive sheet characterized by the above-mentioned.

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