JP5587220B2 - Thermally conductive adhesive sheet - Google Patents

Description

  The present invention relates to a heat conductive adhesive sheet, and more particularly to a heat conductive adhesive sheet used in power electronics technology.

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

  For example, a heat conductive sheet containing a plate-like boron nitride powder and an acrylate copolymer resin has been proposed (see, for example, Patent Document 1).

  In the heat conductive sheet of Patent Document 1, the boron nitride powder is oriented so that its long axis direction (direction orthogonal to the plate thickness of the boron nitride powder) is along the thickness direction of the sheet. The thermal conductivity in the thickness direction of the conductive sheet is improved.

JP 2008-280496 A

  However, the thermal conductive sheet may be required to have high thermal conductivity in the orthogonal direction (plane direction) orthogonal to the thickness direction depending on the application and purpose. In that case, in the heat conductive sheet of Patent Document 1, since the long axis direction of the boron nitride powder is orthogonal (crossed) to the surface direction, the heat conductivity in the surface direction is insufficient. There is a bug.

  In addition, the heat conductive sheet may require excellent adhesion or tackiness to the heat dissipation object depending on its use. However, the heat conduction sheet of Patent Document 1 has insufficient adhesion or tackiness to the heat dissipation object. There is a problem of being.

  The objective of this invention is providing the heat conductive adhesive sheet which is excellent also in adhesiveness or adhesiveness, while being excellent in the heat conductivity of a surface direction.

  In order to achieve the above object, the thermally conductive adhesive sheet of the present invention is a thermally conductive layer containing plate-like boron nitride particles, and has a thermal conductivity perpendicular to the thickness direction of the thermally conductive layer. Is provided with a heat conductive layer of 4 W / m · K or more and an adhesive layer or a pressure-sensitive adhesive layer laminated on at least one surface of the heat conductive layer.

  The heat conductive adhesive sheet of this invention is excellent also in adhesiveness or adhesiveness, while being excellent in the heat conductivity of the surface direction orthogonal to the thickness direction.

  Therefore, the heat conductive adhesive sheet of the present invention can dissipate the heat of the heat dissipation target along the surface direction while being able to adhere or adhere to the heat dissipation target with excellent adhesiveness or tackiness.

FIG. 1 shows a cross-sectional view of one embodiment of the thermally conductive adhesive sheet of the present invention. FIG. 2 is a process diagram for explaining a method for producing a heat conductive layer of the heat conductive adhesive sheet shown in FIG. 1, wherein (a) is a step of hot pressing a mixture or a laminated sheet; Is a step of dividing the press sheet into a plurality of pieces, and (c) is a step of laminating the divided sheets. FIG. 3 shows a perspective view of the thermally conductive layer shown in FIG. FIG. 4 is a process diagram for explaining a method of adhering the heat conductive adhesive sheet shown in FIG. 1 to an electronic component and a mounting substrate. FIG. 4A shows a heat conductive adhesive sheet and a mounting substrate, respectively. Step (b) shows a step of bonding the heat conductive adhesive sheet to the electronic component and the mounting substrate, and then bonding them by heating. FIG. 5 shows a cross-sectional view of another embodiment of the thermally conductive adhesive sheet of the present invention (a mode in which an opening is formed in the adhesive / adhesive layer). FIG. 6 is a process diagram for explaining a method of adhering the heat conductive adhesive sheet shown in FIG. 5 to an electronic component and a mounting substrate. FIG. 6A shows a heat conductive adhesive sheet and a mounting substrate, respectively. Step (b) shows a step of bonding a heat conductive adhesive sheet to an electronic component and a mounting substrate and then bonding or sticking them by heating.

  FIG. 1 is a cross-sectional view of an embodiment of a heat conductive adhesive sheet of the present invention, FIG. 2 is a process diagram for explaining a method for producing a heat conductive layer of the heat conductive adhesive sheet shown in FIG. 3 is a perspective view of the heat conductive layer shown in FIG. 2, and FIG. 4 is a process diagram for explaining a method of adhering or sticking the heat conductive adhesive sheet shown in FIG. 1 to an electronic component and a mounting board.

  In FIG. 1, the heat conductive adhesive sheet 1 includes a heat conductive layer 2, an adhesive layer 3 or an adhesive layer 3 (hereinafter referred to as “adhesive / adhesive layer 3”) laminated on the surface of the heat conductive layer 2. Are sometimes collectively referred to as “.”.

  The thermally conductive layer 2 is formed in a flat sheet shape and contains boron nitride particles.

  Specifically, the heat conductive layer 2 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 scale shape), and are dispersed in a form oriented in a predetermined direction (described later) in the heat conductive layer 2.

  The boron nitride particles have an average length in the longitudinal direction (maximum length in a direction perpendicular to the thickness direction of the plate), for example, 1 to 100 μm, preferably 3 to 90 μm. 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, and most preferably 40 μm or more. 100 μm or less, preferably 90 μm or less.

  Moreover, the average of the thickness (length in the thickness direction of the plate, that is, the length in the short direction of the particles) of the boron nitride particles is, for example, 0.01 to 20 μm, preferably 0.1 to 15 μm.

  The aspect ratio (length / thickness in the longitudinal direction) of the boron nitride particles is, for example, 2 to 10000, preferably 10 to 5000.

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

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

  If the average particle diameter measured by the light scattering method of the boron nitride particles is less than the above range, the heat conductive layer 2 becomes brittle and the handleability may be lowered.

Further, 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 .

  As the boron nitride particles, a commercially available product or a processed product obtained by processing it can be used. Examples of commercially available boron nitride particles include the “PT” series (for example, “PT-110”, etc.) manufactured by Momentive Performance Materials Japan, and the “Shobi N UHP” series (manufactured by Showa Denko) ( For example, “Shoubi N UHP-1” and the like are included.

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

  Examples of the thermosetting resin component include epoxy resins, thermosetting polyimides, phenol resins, urea resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, silicone resins, and thermosetting urethane resins.

  Examples of the thermoplastic resin component include 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, polycarbonate, polyacetal, polyethylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyallylsulfone, thermoplastic polyimide, thermoplastic urethane resin, polyaminobis Maleimide, polyamideimide, polyetherimide, bismaleimide triazine resin, polymethylpentene, fluororesin, liquid crystal polymer, Fin - vinyl alcohol copolymer, ionomer, polyarylate, acrylonitrile - ethylene - styrene copolymers, acrylonitrile - butadiene - styrene copolymer, acrylonitrile - styrene copolymer.

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

  Of the resin components, an epoxy resin is preferable.

  The epoxy resin is in a liquid, semi-solid, or solid form at normal temperature.

  Specifically, as the epoxy resin, for example, bisphenol type epoxy resin (for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, dimer acid modified bisphenol type) Epoxy resin), novolak epoxy resin (eg, phenol novolac epoxy resin, cresol novolac epoxy resin, biphenyl epoxy resin), naphthalene epoxy resin, fluorene epoxy resin (eg, bisarylfluorene epoxy resin, etc.) ), Aromatic epoxy resins such as triphenylmethane type epoxy resin (for example, trishydroxyphenylmethane type epoxy resin), for example, triepoxypropyl isocyanur Nitrogen-containing ring epoxy resins such as sulfonate (triglycidyl isocyanurate) and hydantoin epoxy resins, for example, aliphatic epoxy resins, such as alicyclic epoxy resins (such as dicyclocyclic epoxy resins), such as glycidyl An ether type epoxy resin, for example, a glycidylamine type epoxy resin can be used.

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

  A combination of a liquid epoxy resin and a solid epoxy resin is preferable, and a combination of a liquid aromatic epoxy resin and a solid aromatic epoxy resin is more preferable. Specific examples of such combinations include a combination of a liquid bisphenol type epoxy resin and a solid triphenylmethane type epoxy resin, a combination of a liquid bisphenol type epoxy resin and a solid bisphenol type epoxy resin. .

  Moreover, as an epoxy resin, Preferably, the single use of a semi-solid epoxy resin is mentioned, More preferably, the single use of a semi-solid aromatic epoxy resin is mentioned. Specific examples of such epoxy resins include semi-solid fluorene type epoxy resins.

  If it is a combination of a liquid epoxy resin and a solid epoxy resin, or a semi-solid epoxy resin, the step following property (described later) of the heat conductive layer can be improved.

  The epoxy resin has an epoxy equivalent of, for example, 100 to 1000 g / eqiv. , Preferably 160 to 700 g / eqiv. The softening temperature (ring and ball method) is, for example, 80 ° C. or lower (specifically 20 to 80 ° C.), preferably 70 ° C. or lower (specifically 25 to 70 ° C.).

  Moreover, the melt viscosity at 80 ° C. of the epoxy resin is, for example, 10 to 20,000 mPa · s, preferably 50 to 15,000 mPa · s. When using 2 or more types of epoxy resins together, the melt viscosity as a mixture thereof is set within the above-described range.

  Further, in the case where an epoxy resin that is solid at room temperature and an epoxy resin that is liquid at room temperature are used in combination, the softening temperature is, for example, less than 45 ° C, preferably 35 ° C or less, and the softening temperature. However, it has together with the 2nd epoxy resin of 45 degreeC or more, for example, Preferably 55 degreeC or more. Thereby, the kinematic viscosity (conforming to JIS K 7233, described later) of the resin component (mixture) can be set in a desired range, and the step followability of the heat conductive layer can be improved.

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

  The curing agent is a latent curing agent (epoxy resin curing agent) that can cure the 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, and the like. Is mentioned. In addition to the above, phenol compounds, urea compounds, polysulfide compounds and the like can also be mentioned.

  Examples of the imidazole compound include 2-phenylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and the like.

  Examples of the amine compound include aliphatic polyamines such as ethylenediamine, propylenediamine, diethylenetriamine, and triethylenetetramine, and aromatic polyamines such as metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone.

  Examples of the acid anhydride compound include phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 4-methyl-hexahydrophthalic anhydride, methyl nadic acid anhydride, and pyromellitic acid. Anhydride, dodecenyl succinic anhydride, dichlorosuccinic anhydride, benzophenone tetracarboxylic acid anhydride, chlorendic acid anhydride and the like can be mentioned.

  Examples of the amide compound include dicyandiamide and polyamide.

  Examples of the hydrazide compound include adipic acid dihydrazide.

  Examples of the imidazoline compound include 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. Examples include imidazoline.

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

  As the curing agent, an imidazole compound is preferable.

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

  The compounding ratio of the curing agent in the epoxy resin composition is, for example, 0.5 to 50 parts by mass, preferably 1 to 10 parts by mass with respect to 100 parts by mass of the epoxy resin. For example, 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass.

  The above-mentioned curing agent and / or curing accelerator can be prepared and used as a solvent solution and / or a solvent dispersion dissolved and / or dispersed with a solvent, if necessary.

  Examples of the solvent include organic solvents such as ketones such as acetone and methyl ethyl ketone (MEK), esters such as ethyl acetate, and amides such as N, N-dimethylformamide. Examples of the solvent include water-based solvents such as water, for example, alcohols such as methanol, ethanol, propanol, and isopropanol. The solvent is preferably an organic solvent, more preferably ketones and amides.

  Of the thermoplastic resin components, preferably, polyolefin is used.

  Preferred examples of the polyolefin include polyethylene and ethylene-propylene copolymer.

  Examples of polyethylene include low density polyethylene and high density polyethylene.

  Examples of the ethylene-propylene copolymer include a random copolymer, a block copolymer, or a graft copolymer of ethylene and propylene.

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

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

  Polyolefins can be used alone or in combination.

In addition, according to a kinematic viscosity test (temperature: 25 ° C. ± 0.5 ° C., solvent: butyl carbitol, resin component (solid content) concentration: 40% by mass) based on JIS K 7233 (foam viscometer method) of the resin component The measured kinematic viscosity 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. s, more preferably 0.4 × 10 ^{−4 to} 1.8 × 10 ⁻⁴ m ² / s. Further, the kinematic viscosity of the, for ^{example, 0.22 × 10 -4 ~1.00 × 10} -4 m 2 / s, ^{preferably, 0.3 × 10 -4 ~0.9 × 10} -4 m 2 / S, more preferably 0.4 × 10 ^{−4 to} 0.8 × 10 ⁻⁴ m ² / s.

  When the kinematic viscosity of the resin component exceeds the above range, it may be impossible to impart excellent flexibility and step following ability (described later) to the heat conductive layer 2. On the other hand, when the kinematic viscosity of the resin component is less than 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 (foam viscometer method), the rising speed of the foam in the resin component sample is compared with the rising speed of the foam in the standard sample (kinematic viscosity is known). The kinematic viscosity of the resin component is measured by determining that the matching kinematic viscosity of the standard sample is the kinematic viscosity of the resin component.

  In the thermally conductive layer 2, the volume-based content ratio of the boron nitride particles (solid content, that is, the volume percentage of the boron nitride particles with respect to the total volume of the resin component and the boron nitride particles) is, for example, 35% by volume or more, Preferably, it is 60% by volume or more, preferably 65% by volume or more, usually 95% by volume or less, preferably 90% by volume or less.

  If the volume-based content ratio of the boron nitride particles is less than the above range, the boron nitride particles may not be oriented in a predetermined direction in the thermally conductive layer 2. On the other hand, when the volume-based content ratio of the boron nitride particles exceeds the above-described range, the heat conductive layer 2 becomes brittle, and the handleability and the step following ability may be deteriorated.

  Moreover, the blending ratio of the boron nitride particles based on 100 parts by mass of the total amount (solid content) of each component (boron nitride particles and resin component) forming the heat conductive layer 2 is, for example, 40 to 95 parts by mass, Preferably, it is 65 to 90 parts by mass, and the blending ratio of the resin component based on the mass of the total amount of each component forming the heat conductive layer 2 is, for example, 5 to 60 parts by mass, preferably 10 to 10 parts by mass. 35 parts by mass. In addition, the mixture ratio of the mass reference | standard of boron nitride particle with respect to 100 mass parts of resin components is 60-1900 mass parts, for example, Preferably, it is also 185-900 mass parts.

  Further, when two types of epoxy resins (first epoxy resin and second epoxy resin) are used in combination, the mass ratio of the first epoxy resin to the second epoxy resin (the mass of the first epoxy resin / the mass of the second epoxy resin) ) Can 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.

  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-described components (polymerized products).

  Next, a method for forming the heat conductive layer 2 will be described.

  In this method, first, the above-described components are blended at the blending ratio described above, and the mixture is prepared by stirring and mixing.

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

  Examples of the solvent include the same organic solvents as described above. In addition, when the above-described curing agent and / or curing accelerator is prepared as a solvent solution and / or a solvent dispersion, the solvent of the solvent solution and / or the solvent dispersion without adding a solvent in the stirring and mixing. Can be used as a mixed solvent for stirring and mixing as it is. Alternatively, a solvent can be further added as a mixed solvent in the stirring and mixing.

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

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

  When the resin component is melted by heating, the heating temperature is, for example, a temperature near or exceeding the softening temperature of the resin component, specifically, 40 to 150 ° C., preferably 70 to 140 ° C. It is.

  In this method, the resulting mixture is then hot pressed.

  Specifically, as shown in FIG. 2A, the mixture is hot-pressed through, for example, two release films 6 as necessary to obtain a press sheet 2A. The conditions of the hot press are that the temperature is, for example, 50 to 150 ° C., preferably 60 to 140 ° C., the pressure is, for example, 1 to 100 MPa, preferably 5 to 50 MPa, and the time is, for example, 0 .1 to 100 minutes, preferably 1 to 30 minutes.

  More preferably, the mixture is vacuum hot pressed. The degree of vacuum in the vacuum hot press is, for example, 1 to 100 Pa, preferably 5 to 50 Pa, and the temperature, pressure, and time are the same as those in the above-described hot press.

  When the temperature, pressure and / or time in the hot press are out of the above range, the porosity P (described later) of the heat conductive layer 2 may not be adjusted to a desired value.

  The thickness of the press sheet 2A obtained by hot pressing is, for example, 50 to 1000 μm, or preferably 100 to 800 μm.

  Next, in this method, as shown in FIG. 2B, the press sheet 2A is divided into a plurality (for example, four) to obtain a divided sheet 2B (dividing step). In the division of the press sheet 2A, the press sheet 2A is cut along the thickness direction so as to be divided into a plurality when projected in the thickness direction. The press sheet 2A is cut so as to have the same shape when each divided sheet 2B is projected in the thickness direction.

  Next, in this method, as shown in FIG. 2C, the divided sheets 2B are laminated in the thickness direction to obtain a laminated sheet 2C (laminating step).

  Thereafter, in this method, as shown in FIG. 2A, the laminated sheet 2C is hot-pressed (preferably vacuum hot-pressed) (hot-pressing step). The conditions for the hot press are the same as the conditions for the hot press of the mixture described above.

  The thickness of the laminated sheet 2C after hot pressing is, for example, 1 mm or less, preferably 0.8 mm or less, and usually 0.05 mm or more, preferably 0.1 mm or more.

  Thereafter, as shown in FIG. 3, in order to efficiently orient the boron nitride particles 4 in the resin component 5 in a predetermined direction in the heat conductive layer 2, the above-described dividing step (FIG. 2 (b)), lamination A series of steps of the step (FIG. 2C) and the hot press step (FIG. 2A) are repeatedly performed. The number of repetitions is not particularly limited, and can be appropriately set according to the filling state of the boron nitride particles, and is, for example, 1 to 10 times, preferably 2 to 7 times.

  In the above-described hot pressing step (FIG. 2A), for example, the mixture and the laminated sheet 2C can be rolled with a plurality of calendar rolls.

  Thereby, the heat conductive layer 2 shown in FIG. 2 and FIG. 3 can be formed.

  The formed heat conductive layer 2 has a thickness of, for example, 1 mm or less, preferably 0.8 mm or less, usually 0.05 mm or more, preferably 0.1 mm or more.

  Further, the volume-based content ratio of the boron nitride particles 4 in the heat conductive layer 2 (solid content, that is, the volume percentage of the boron nitride particles 4 with respect to the total volume of the resin component 5 and the boron nitride particles 4) is as described 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 4 is less than the above range, the boron nitride particles 4 may not be oriented in a predetermined direction in the heat conductive layer 2.

  Further, when the resin component 5 is a thermosetting resin component, for example, the above-described dividing step (FIG. 2B), laminating step (FIG. 2C), and hot pressing step (FIG. 2A). ) Is repeatedly performed in an uncured state to obtain the uncured thermally conductive layer 2 as it is. The uncured thermally conductive layer 2 is thermally cured when the thermally conductive adhesive sheet 1 is bonded or adhered to the electronic component 8 and the mounting substrate 7.

  In the heat conductive layer 2 thus formed, the longitudinal direction LD of the boron nitride particles 4 intersects the thickness direction TD of the heat conductive layer 2 as shown in FIG. 3 and a partially enlarged schematic view thereof. They are oriented along the (orthogonal) plane direction SD.

  The arithmetic average of the angles formed by the longitudinal direction LD of the boron nitride particles 4 in the plane direction SD of the thermally conductive layer 2 (the orientation angle α of the boron nitride particles 4 with respect to the thermally conductive layer 2) is, for example, 25 degrees or less, Preferably, it is 20 degrees or less, and is usually 0 degrees or more.

  The orientation angle α of the boron nitride particles 4 with respect to the thermally conductive layer 2 is determined by cutting the thermally conductive layer 2 along the thickness direction with a cross section polisher (CP), and the resulting cross section is scanned with an electron microscope ( With SEM), a photograph was taken at a magnification of the field of view where 200 or more boron nitride particles 4 can be observed. From the obtained SEM photograph, the longitudinal direction LD of the boron nitride particles 4 and the surface direction SD ( The inclination angle α with respect to the direction orthogonal to the thickness direction TD is acquired and calculated as an average value thereof.

  Thereby, the thermal conductivity in the surface direction SD of the heat conductive layer 2 is 4 W / m · K or more, preferably 5 W / m · K or more, more preferably 10 W / m · K or more, and still more preferably, It is 15 W / m · K or more, particularly preferably 25 W / m · K or more, and usually 200 W / m · K or less.

  The thermal conductivity in the surface direction SD of the heat conductive layer 2 is substantially the same before and after thermosetting when the resin component 5 is a thermosetting resin component.

  If the thermal conductivity in the surface direction SD of the thermal conductive layer 2 is less than the above range, the thermal conductivity in the surface direction SD is not sufficient, and therefore for heat dissipation applications that require such thermal conductivity in the surface direction SD. It may not be used.

  The thermal conductivity in the surface direction SD of the heat conductive layer 2 is measured by a pulse heating method. In the pulse heating method, a xenon flash analyzer “LFA-447 type” (manufactured by NETZSCH) is used.

  Moreover, the heat conductivity of the thickness direction TD of the heat conductive layer 2 is 0.5-15 W / m * K, for example, Preferably, it is 1-10 W / m * K.

  The thermal conductivity in the thickness direction TD of the thermal conductive layer 2 is measured by a pulse heating method, a laser flash method, or a TWA method. In the pulse heating method, the same one as described above is used, in the laser flash method, “TC-9000” (manufactured by ULVAC-RIKO) is used, and in the TWA method, “ai-Phase mobile” (manufactured by Eye Phase). Is used.

  Thereby, the ratio of the thermal conductivity in the surface direction SD of the heat conductive layer 2 to the heat conductivity in the thickness direction TD of the heat conductive layer 2 (heat conductivity in the surface direction SD / heat conductivity in the thickness direction TD). 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. 3, for example, a gap (gap) is formed in the heat conductive layer 2.

  The void ratio in the heat conductive layer 2, that is, the void ratio P is the content ratio (volume basis) of the boron nitride particles 4, and further, hot pressing of a mixture of the boron nitride particles 4 and the resin component 5 (FIG. 2A )) Can be adjusted by the temperature, pressure and / or time. Specifically, the temperature, pressure and / or time of the above-described hot press (FIG. 2 (a)) is set within the above range. Can be adjusted.

  The porosity P in the heat conductive layer 2 is, for example, 30% by volume or less, and preferably 10% by volume or less.

  For example, the porosity P described above is obtained by first cutting the thermal conductive layer 2 along the thickness direction with a cross section polisher (CP), and using a scanning electron microscope (SEM) to show a cross section that appears as 200 The image is obtained by observing at a magnification, and the void portion and the other portion are binarized from the obtained image, and then the area ratio of the void portion to the cross-sectional area of the entire heat conductive layer 2 is determined. It is measured by calculating.

  In the heat conductive layer 2, 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 5 is a thermosetting resin component, the thermally conductive layer 2 before thermosetting is used.

  If the porosity P of the heat conductive layer 2 is in the above-described range, the step following property (described later) of the heat conductive layer 2 can be improved.

  Further, the thermal conductive layer 2 is preferably not observed to break when evaluated under the following test conditions in a bending resistance test based on the cylindrical mandrel method of JIS K 5600-5-1.

Test conditions Test equipment: Type I
Mandrel: 10mm in diameter
Bending angle: 90 degrees or more Thickness of the heat conductive layer 2: 0.3 mm
More preferably, the thermal conductive layer 2 is not observed to break even when the bending angle is set to 180 degrees under the test conditions described above.

  In addition, when the resin component 5 is a thermosetting resin component, the heat conductive layer 2 subjected to the bendability test is a semi-cured (B stage state) heat conductive layer 2).

  When breakage is observed in the heat conductive layer 2 in the above-described bending resistance test at the bending angle, it may be impossible to impart excellent flexibility to the heat conductive layer 2.

  Moreover, this heat conductive layer 2 does not observe a fracture | rupture, for example, when it evaluates on the following test conditions in the 3 point | piece bending test based on JISK7171 (2008).

Test conditions Test piece: Size 20mm x 15mm
Distance between fulcrums: 5mm
Test speed: 20 mm / min (pressing speed of indenter)
Bending angle: 120 degrees Evaluation method: When tested under the above test conditions, the presence or absence of breakage such as cracks at the center of the test piece is visually observed.

  In the three-point bending test, when the resin component 5 is a thermosetting resin component, the thermally conductive layer 2 before thermosetting is used.

  Therefore, this thermal conductive layer 2 is excellent in step followability because no breakage is observed in the above three-point bending test. Note that the step followability means that when the thermal conductive layer 2 is provided on an installation target having a step (for example, a mounting substrate 7 to be described later, see FIG. 4), the step (for example, by an electronic component 8 to be described later). This is a characteristic of following the step so as to be closely adhered along the step formed (see FIG. 4).

  Moreover, marks, such as a character and a symbol, can be made to adhere to the heat conductive layer 2, for example. That is, the heat conductive layer 2 is excellent in mark adhesion. The mark adhesion is a characteristic that allows the above-described mark to be reliably adhered to the heat conductive layer 2.

  Specifically, the mark is attached (applied, fixed or fixed) to the heat conductive layer 2 by printing or engraving.

  Examples of printing include ink jet printing, letterpress printing, intaglio printing, and laser printing.

  In addition, when a mark is printed by inkjet printing, letterpress printing, or intaglio printing, for example, an ink fixing layer for improving the fixability of the mark is attached to the surface (printing side surface, adhesive The side opposite to the adhesive layer 3).

  When the mark is printed by laser printing, for example, a toner fixing layer for improving the fixability of the mark is used as the surface of the heat conductive layer 2 (printing side, opposite side to the adhesive / adhesive layer 3). .).

  Examples of the marking include laser marking and stamping.

  The adhesive / adhesive layer 3 is formed on the entire lower surface of the heat conductive layer 2 as shown in FIG.

  The adhesive / adhesive layer 3 has flexibility and adhesiveness or tackiness (tackiness) in a normal temperature atmosphere and a heating atmosphere, and can exhibit an adhesive action by heating or cooling after heating. It consists of an adhesive or an adhesive that can exhibit an adhesive action. Examples of the adhesive include a thermosetting adhesive and a hot melt adhesive.

  The thermosetting adhesive adheres to the adherend by being cured by heating and solidified. Examples of the thermosetting adhesive include an epoxy thermosetting adhesive, a urethane thermosetting adhesive, and an acrylic thermosetting adhesive. Preferably, an epoxy thermosetting adhesive is used.

  The curing temperature of the thermosetting adhesive is, for example, 100 to 200 ° C.

  The hot-melt adhesive is melted or softened by heating, thermally fused to the adherend, and then solidified by cooling to adhere to the adherend. Examples of the hot melt adhesive include rubber hot melt adhesives, polyester hot melt adhesives, and olefin hot melt adhesives. Preferably, a rubber-based hot melt adhesive is used.

  The softening temperature (ring ball method) of the hot melt adhesive is, for example, 100 to 200 ° C. The melt viscosity of the hot melt adhesive is 180 ° C., for example, 100 to 30,000 mPa · s.

  Moreover, for example, heat conductive particles can be included in the above-described adhesive as necessary.

  As a heat conductive particle, a heat conductive inorganic particle and a heat conductive organic particle are mentioned, for example, Preferably, a heat conductive inorganic particle is mentioned.

  Examples of the thermally conductive inorganic particles include nitride particles such as boron nitride particles, aluminum nitride particles, silicon nitride particles, and gallium nitride particles, for example, hydroxide particles such as aluminum hydroxide particles and magnesium hydroxide particles, , Silicon oxide particles, aluminum oxide particles, titanium oxide particles, zinc oxide particles, tin oxide particles, copper oxide particles, oxide particles such as nickel oxide particles, for example, carbide particles such as silicon carbide particles, for example, calcium carbonate particles, etc. Carbonate particles such as metal salt particles such as titanate particles such as barium titanate particles and potassium titanate particles, such as copper particles, silver particles, gold particles, nickel particles, aluminum particles, platinum particles, etc. Examples thereof include metal particles.

  These heat conductive particles can be used alone or in combination of two or more.

  Examples of the shape of the heat conductive particles include a bulk shape, a needle shape, a plate shape, a layer shape, and a tube shape. The average particle diameter of the heat conductive particles is, for example, 0.1 to 1000 μm.

  The heat conductive particles have, for example, anisotropic heat conductivity or isotropic heat conductivity. Preferably, it has isotropic thermal conductivity.

  The thermal conductivity of the thermally conductive particles is, for example, 1 W / m · K or more, preferably 2 W / m · K or more, more preferably 3 W / m · K or more, and usually 1000 W / m · K or less. It is.

  The blending ratio of the heat conductive particles is, for example, 0.01 to 10 parts by mass with respect to 100 parts by mass of the adhesive.

  When blending the thermally conductive particles in the adhesive, the thermally conductive particles are added to the adhesive in the above-described blending ratio and mixed by stirring.

  Thereby, an adhesive agent is prepared as a heat conductive adhesive agent.

  The heat conductivity of the heat conductive adhesive is, for example, 0.01 W / m · K or more, and usually 100 W / m · K or less.

  Examples of the pressure-sensitive adhesive include a rubber-based pressure-sensitive adhesive and a silicone-based pressure-sensitive adhesive. Moreover, an adhesive can be prepared as a heat conductive adhesive by making the above-mentioned heat conductive particle contain in the ratio similar to the above. The thermal conductivity of the heat conductive adhesive is the same as described above.

  The thickness of the adhesion / adhesion layer 3 is, for example, 10 to 500 μm, preferably 20 to 200 μm.

  In order to obtain the heat conductive adhesive sheet 1, first, the above-described heat conductive layer 2 is prepared, and then the adhesive / adhesive layer 3 is laminated on the surface of the heat conductive layer 2.

  A varnish is prepared by blending and dissolving the above-mentioned solvent in an adhesive (specifically, a thermosetting adhesive) or a pressure-sensitive adhesive, and applying the varnish to the surface of the separator, and then drying at normal pressure or The organic solvent of the varnish is distilled off by vacuum (reduced pressure) drying. In addition, the solid content density | concentration of a varnish is 10-90 mass%, for example.

  Thereafter, the adhesive / adhesive layer 3 is bonded to the heat conductive layer 2. When the adhesive / adhesive layer 3 and the heat conductive layer 2 are bonded together, pressure bonding or thermocompression bonding is performed as necessary.

  Next, a method for bonding the heat conductive adhesive sheet 1 to the electronic component 8 and the mounting substrate 7 will be described with reference to FIG.

  First, in this method, as shown in FIG. 4A, a heat conductive adhesive sheet 1 and a mounting substrate 7 are prepared.

  The mounting substrate 7 has the electronic component 8 mounted on the surface (upper surface) thereof.

  The electronic component 8 includes, for example, an IC (integrated circuit) chip 9, a capacitor 10, a coil 11 and / or a resistor 12. Although not shown in FIG. 4, the electronic component 8 may include, for example, a light emitting diode in addition to the above. The electronic components 8 are arranged on the mounting substrate 7 at intervals in the surface direction (surface direction of the mounting substrate 7).

  Next, in this method, as shown in FIG. 4B, the heat conductive adhesive sheet 1 is thermocompression bonded to the electronic component 8 and the mounting substrate 7.

  Specifically, first, the heat conductive adhesive sheet 1 and the mounting substrate 7 are arranged so that the adhesive / adhesive layer 3 faces the electronic component 8, and then they are brought into contact with each other to conduct heat conduction. The heat conductive adhesive sheet 1 is pressure-bonded (pressed, thermocompression bonded) toward the mounting substrate 7 while heating the conductive adhesive sheet 1.

  For the pressure bonding, for example, a back surface of the heat conductive adhesive sheet 1 (an upper surface of the heat conductive layer 2) is rolled while pressing a sponge roll made of a resin such as a silicone resin against the heat conductive adhesive sheet 1. .

  The heating temperature is, for example, 40 to 120 ° C.

  In this thermocompression bonding, the flexibility of the adhesive / adhesive layer 3 is further improved. Therefore, the electronic component 8 protruding from the surface (upper surface) of the mounting substrate 7 to the front side (upper side) breaks through the adhesive / adhesive layer 3, and the electronic component 8 The surface (upper surface) of is in contact with the surface (lower surface) of the heat conductive layer 2. Further, a gap (for example, a gap between the resistor 12 and the mounting substrate 7) 14 formed around the electronic component 8 is filled with the adhesive / adhesive layer 3. Furthermore, the adhesive / adhesive layer 3 is entangled and covered with terminals and / or wires 15 (not shown) for connecting the electronic component 8 (specifically, the IC chip 9 and the resistor 12) and the mounting substrate 7. .

  Specifically, the upper surface (and the upper part of the side surface) of the electronic component 8 is covered with the heat conductive layer 2.

  On the other hand, the side surface (lower side surface) of the electronic component 8 is coated (adhered or adhered) to the adhesive / adhesive layer 3 pierced by the electronic component 8.

  More specifically, in thermocompression bonding, when the resin component 5 is a thermosetting resin component, the resin component 5 is in a B-stage state, so that the thermally conductive layer 2 is exposed from the electronic component 8. It adheres to the surface (upper surface) of the substrate 7. Further, when the thickness of the electronic component 8 is thicker than the thickness of the adhesive / adhesive layer 3, the upper part of the electronic component 8 enters the heat conductive layer 2 from the surface of the heat conductive layer 2 toward the inside. .

  When the adhesive is a hot-melt adhesive, the adhesive / adhesive layer 3 is melted or softened by the above-described thermocompression bonding, and is thermally bonded to the surface of the mounting substrate 7 and the side surface of the electronic component 8. To do. Next, the thermally conductive adhesive sheet 1 is allowed to cool at room temperature, whereby the adhesive / adhesive layer 3 adheres to the surface of the mounting substrate 7 and the side surface of the electronic component 8.

  On the other hand, when the adhesive layer in the adhesive / adhesive layer 3 is a thermosetting adhesive, the adhesive is in a B-stage state by the above-described thermocompression bonding, and the thermally conductive adhesive sheet 1 is formed of the mounting substrate 7 and the electronic component. 8 is temporarily fixed, and then the heat conductive adhesive sheet 1 is further heated, whereby the adhesive / adhesive layer 3 is thermally cured and adhered to the surface of the mounting substrate 7 and the side surface of the electronic component 8.

  A heat press or a dryer is used to thermally cure the adhesive / adhesive layer 3. Preferably, a dryer is used. The heating conditions are such that the heating temperature is, for example, 100 to 250 ° C., preferably 120 to 200 ° C., and the heating time is, for example, 10 to 200 minutes, preferably 60 to 150 minutes.

  Further, when the resin component 5 in the heat conductive layer 2 is a thermosetting resin component, the uncured heat conductive layer 2 is formed simultaneously with the heat fusion and / or heat curing of the adhesive / adhesive layer 3. Heat cure.

  And the above-mentioned heat conductive adhesive sheet 1 is excellent also in adhesiveness or adhesiveness, while being excellent in the heat conductivity of the surface direction SD.

  Therefore, the heat conductive adhesive sheet 1 can dissipate the heat of the electronic component 8 along the surface direction SD while being able to adhere or adhere to the mounting substrate 7 and the electronic component 8 with excellent adhesiveness or tackiness. Can do.

  In particular, even when the mounting substrate 7 and the electronic component 8 are subjected to vibration, repeated stress and / or thermal cycle (repetitive process of heating and cooling) over a long period of time, the mounting substrate 7 required for the durability described above. And the heat conductive adhesive sheet 1 can be used for adhesion and heat dissipation of the electronic component 8.

  Further, in the above-described heat conductive adhesive sheet 1, the adhesive / adhesive layer 3 is formed on the entire surface of the heat conductive layer 2, and the electronic component 8 breaks through the adhesive / adhesive layer 3, so that the heat conductive adhesive sheet 1 is not required to be accurately positioned with respect to the electronic component 8, and the heat conductive adhesive sheet 1 may be thermocompression-bonded after the heat conductive adhesive sheet 1 is disposed opposite to the mounting substrate 7. Can be easily adhered or adhered.

  When the adhesive / adhesive layer 3 is formed on the entire surface of the heat conductive layer 2, the adhesive / adhesive layer 3 is preferably formed from a heat conductive adhesive or a heat conductive adhesive.

  FIG. 5 is a cross-sectional view of another embodiment of the heat conductive adhesive sheet of the present invention (a mode in which an opening is formed in the adhesive / adhesive layer), and FIG. Process drawing for demonstrating the method of making it adhere or adhere to components and a mounting board is shown.

  In addition, in each subsequent drawing, about the member corresponding to each above-mentioned part, the same referential mark is attached | subjected and the detailed description is abbreviate | omitted.

  In the description of FIG. 1 and FIG. 4A described above, the adhesive / adhesive layer 3 is formed on the entire surface of the heat conductive layer 2. For example, as shown in FIG. 5 and FIG. It can also be formed on a part of the surface of the heat conductive layer 2.

  In FIG. 5, an opening 13 penetrating the thickness direction is formed in the adhesive / adhesive layer 3.

  The openings 13 are opened in the same pattern as the electronic component 8 in the adhesive / adhesive layer 3. In other words, each opening 13 is formed in the same outer shape as each electronic component 8 when it is arranged opposite to the mounting substrate 7 and projected in the thickness direction. In other words, the opening 13 is formed in a pattern that fits with the electronic component 8 when the heat conductive adhesive sheet 1 described later is pressed against the mounting substrate 7.

  Further, the adhesive / pressure-sensitive adhesive layer 3 is preferably formed from an adhesive or pressure-sensitive adhesive that does not contain thermally conductive particles.

  In order to laminate the adhesive layer 3 on the surface of the heat conductive layer 2, the adhesive / pressure-sensitive adhesive is applied to the surface of the heat conductive layer 2 through a mask (not shown) having the same pattern as the opening 13. Application or thermocompression bonding, and then lift the mask. The mask is made of, for example, a metal material such as stainless steel, and the back surface (the surface facing the heat conductive layer 2) is subjected to mold release treatment with a silicone compound as necessary. The thickness of the mask is, for example, 10 to 1000 μm.

  In order to adhere or adhere the thermally conductive adhesive sheet 1 including the adhesive / adhesive layer 3 having the opening 13 to the mounting substrate 7 and the electronic component 8, first, as shown in FIG. The sheet 1 and the mounting substrate 7 are respectively prepared, and then the heat conductive adhesive sheet 1 is thermocompression bonded to the mounting substrate 7 as shown in FIG.

  In the thermocompression bonding of the heat conductive adhesive sheet 1, the electronic component 8 and the opening 13 of the adhesive layer 3 are located at the same position when the heat conductive adhesive sheet 1 is projected in the thickness direction. After positioning with respect to 8, while heating the heat conductive adhesive sheet 1, the electronic component 8 is filled in the opening 13 of the adhesive / adhesive layer 3 so that the electronic component 8 fits into the opening 13. Accommodate.

  Therefore, the heat conductive layer 2 can contact the upper surface (and upper side surface) of the electronic component 8 reliably, and can adhere or adhere directly.

  As a result, the heat of the electronic component 8 can be reliably radiated along the surface direction SD.

  In the above description, the opening 13 penetrating in the thickness direction is formed in the adhesive / adhesive layer 3. For example, instead of the opening 13, the opening 13 corresponds to the thickness of the electronic component 8. As described above, a concave portion that is recessed from the surface of the adhesive / pressure-sensitive adhesive layer 3 toward the inside can also be formed.

  In the above description, the adhesive / adhesive layer 3 is laminated on one side of the thermally conductive layer 2. For example, as shown by the imaginary line in FIG. 1 and the imaginary line in FIG. It can also be formed on both surfaces (upper surface and lower surface) of the sheet 1.

  In the above description, the adhesive / adhesive layer 3 is laminated on both surfaces of the heat conductive layer 2 (the phantom line in FIG. 1), or is laminated on a part of both surfaces of the heat conductive layer 2. (Virtual line in FIG. 5), for example, as shown by a solid line and a broken line in FIG. 5, the adhesive / adhesive layer 3 is formed on the entire upper surface (broken line, one entire surface) of the heat conductive layer 2, and heat It can also be formed on a part of the lower surface of the conductive layer 2 (solid line, part of the other surface).

Preparation Examples , Examples and Comparative Examples are shown below to further illustrate the present invention, but the present invention is not limited to them.

(Preparation of heat conductive layer)
Preparation Example 1
PT-110 (trade name, plate-like boron nitride particles, average particle diameter (light scattering method) 45 μm, manufactured by Momentive Performance Materials Japan) 13.42 g and JER828 (trade name, bisphenol A type epoxy resin) , First epoxy resin, liquid, epoxy equivalent 184 to 194 g / eqiv, softening temperature (ring and ball method) less than 25 ° C., melt viscosity (80 ° C.) 70 mPa · s, manufactured by Japan Epoxy Resin Co., Ltd. 1.0 g, and EPPN -501HY (trade name, triphenylmethane type epoxy resin, second epoxy resin, solid, epoxy equivalent of 163 to 175 g / eqiv., Softening temperature (ring and ball method) 57 to 63 ° C., manufactured by Nippon Kayaku Co., Ltd.) 2.0 g And a curing agent (Curazole 2P4MHZ-PW (trade name, 2-phenyl-4-methyl-5-hydroxymethyl ester) 5 wt% methyl ethyl ketone dispersion of dazole, manufactured by Shikoku Kasei Co., Ltd.) 3 g (solid content 0.15 g) (5 wt% based on the total amount of epoxy resins JER828 and EPPN-501HY) and stirred, The mixture was left overnight at room temperature (23 ° C.) to volatilize methyl ethyl ketone (a dispersion medium of a curing agent) to prepare a semi-solid mixture.

  In the above formulation, the volume percentage (volume%) of the boron nitride particles with respect to the total volume of the solid content excluding the curing agent (that is, the solid content of the boron nitride particles and the epoxy resin) was 70% by volume. .

  Next, the obtained mixture was sandwiched between two release films treated with silicone, and they were placed in a vacuum heating press machine at 80 ° C. in an atmosphere of 10 Pa (vacuum atmosphere) under a load of 5 tons (20 MPa) for 2 minutes. A press sheet having a thickness of 0.3 mm was obtained by hot pressing (see FIG. 2A).

  After that, when the obtained press sheet is projected in the thickness direction of the press sheet, a divided sheet is obtained by cutting so as to be divided into a plurality of pieces (see FIG. 2B), and then the divided sheet. Were laminated in the thickness direction to obtain a laminated sheet (see FIG. 2C).

  Subsequently, the obtained laminated sheet was hot-pressed under the same conditions as described above using a vacuum heating press similar to the above (see FIG. 2A).

  Subsequently, the above-described series of operations of cutting, laminating and hot pressing (see FIG. 2) was repeated four times to obtain a thermally conductive layer (uncured state) having a thickness of 0.3 mm (see FIG. 3).

Preparation Examples 2 to 16
Based on the formulation and production conditions in Tables 1 to 3, the same treatment as in Example 1 was performed to obtain a heat conductive layer (uncured state).

(Preparation of heat conductive adhesive sheet)
Example 1
An epoxy thermosetting adhesive varnish (solvent: MEK, solid content concentration: 50 mass%, fillerless type) was applied to the surface of the separator so that the thickness upon drying was 25 μm. Subsequently, MEK was distilled off by vacuum drying to form an adhesive layer.

  Next, the adhesive layer was pressure-bonded to the heat conductive layer of Preparation Example 1, thereby producing a heat conductive adhesive sheet (see FIG. 3).

Examples 2-8, Comparative Examples 9-11, and Examples 12-16
The heat conductive adhesive sheet was treated in the same manner as in Example 1 except that the heat conductive layers of Preparation Examples 2 to 16 shown in Table 4 were used instead of the heat conductive layer of Preparation Example 1, respectively. It produced (refer FIG. 3).

Example 17
On the thermally conductive layer of Example 1, a stainless steel metal mask (thickness 100 μm, silicone release treatment on the back surface) having the same pattern as the electronic components (IC chip, capacitor, coil and resistor) described in detail in the next evaluation. The rubber hot melt adhesive (trade name: HM409, softening temperature 110 ° C., melt viscosity (180 ° C.) 1200 mPa · s, manufactured by Cemedine) is laminated, and then the metal mask is pulled up. Thus, an adhesive layer having a thickness of 100 μm in which an opening was formed was formed. Thus, a thermally conductive adhesive sheet was produced (see FIG. 5).

Examples 18-24, Comparative Examples 25-27, and Examples 28-32
The heat conductive adhesive sheet was processed in the same manner as in Example 17 except that the heat conductive layers of Preparation Examples 2 to 16 described in Table 4 were used instead of the heat conductive layer of Preparation Example 1, respectively. It produced (refer FIG. 5).

(Adhesion of heat conductive adhesive sheet and mounting board)
A. Bonding of Thermally Conductive Adhesive Sheets and Mounting Boards of Examples 1 to 8, Comparative Examples 9 to 11 and Examples 12 to 16 A mounting board on which electronic components (IC chip, capacitor, coil and resistor) are mounted Prepared (see FIG. 4A).

Subsequently, the heat conductive adhesive sheets of Examples 1 to 8, Comparative Examples 9 to 11, and Examples 12 to 16 were heated at 80 ° C. using a sponge roll made of silicone resin on the electronic component and the mounting substrate, respectively. Crimped and temporarily fixed. In thermocompression bonding, the electronic component broke through the adhesive layer and contacted the thermally conductive layer.

  Thereafter, by heating at 150 ° C. for 120 minutes, both the heat conductive layer and the adhesive layer were thermally cured, and the heat conductive adhesive sheet was bonded to the electronic component and the mounting substrate (see FIG. 4B). ).

In thermosetting, the heat conductive layer adhered to the surface of the electronic component, and the adhesive layer adhered to the surface of the mounting substrate and the side surface of the electronic component.
B. Adhesion of heat conductive adhesive sheets and mounting substrates of Examples 17 to 24, Comparative Examples 25 to 27, and Examples 28 to 32 Mounting substrate on which electronic components (IC chip, capacitor, coil and resistor) are mounted Was prepared (see FIG. 6A).

Next, in the thickness direction of the heat conductive adhesive sheets of Examples 17 to 24, Comparative Examples 25 to 27, and Examples 28 to 32, the electronic component and the opening of the adhesive layer are located at the same position. Then, after positioning with respect to the electronic component, the electronic component was fitted into the opening, and the thermally conductive adhesive sheet was thermocompression bonded to the mounting substrate at 120 ° C., respectively.

  By this thermocompression bonding, the adhesive layer is melted and thermally fused to the surface of the mounting substrate and the side surface of the electronic component, and the thermally conductive layer is thermally cured and solidified to adhere to the surface of the electronic component. . Thereafter, the adhesive was solidified by being allowed to cool at room temperature, and adhered to the surface of the mounting substrate and the side surface of the electronic component.

  Thereby, the heat conductive adhesive sheet was adhere | attached on the mounting board | substrate (refer FIG.6 (b)).

(Evaluation)
1. Thermal conductivity The thermal conductivity of the thermal conductive layers obtained in Preparation Examples 1 to 16 was measured.

  That is, the thermal conductivity in the plane direction (SD) was measured by a pulse heating method using a xenon flash analyzer “LFA-447 type” (manufactured by NETZSCH).

The results are shown in Tables 1 to 3.
2. Adhesiveness 1 to 8, Comparative Examples 9 to 11, Examples 12 to 24, Comparative Examples 25 to 27, and Examples 28 to 32 were to be peeled from the mounting substrate. Tried. As a result, cohesive failure (that is, failure of the adhesive layer) occurred in any of the thermally conductive adhesive sheets.

Therefore, the adhesiveness or adhesiveness of the heat conductive adhesive sheets of Examples 1 to 8, Comparative Examples 9 to 11, Examples 12 to 24, Comparative Examples 25 to 27, and Examples 28 to 32 are excellent. Was confirmed.
3. Porosity (P)
The porosity (P1) of the heat conductive layer before thermosetting of Preparation Examples 1 to 16 was measured by the following measurement method.

Method for measuring porosity: First, a thermally conductive sheet is cut along a thickness direction by a cross section polisher (CP), and a cross section that appears is observed at 200 times with a scanning electron microscope (SEM). And got a statue. Thereafter, the void portion and other portions were binarized from the obtained image, and then the area ratio of the void portion to the cross-sectional area of the entire heat conductive sheet was calculated. The results are shown in Tables 1 to 3.
4). Step following ability (3-point bending test)
About the heat conductive layer before thermosetting of Preparation Examples 1-16, a three-point bending test in the following test conditions is carried out according to JIS K7171 (2008), and the step following property is evaluated according to the following evaluation criteria. Evaluated according to. The results are shown in Tables 1 to 3.

Test conditions Test piece: Size 20mm x 15mm
Distance between fulcrums: 5mm
Test speed: 20 mm / min (pressing speed of indenter)
Bending angle: 120 degrees (evaluation criteria)
A: No fracture was observed at all.

  ○: Fracture was hardly observed.

X: Breakage was clearly observed.
5. Print mark visibility (print mark adhesion: mark adhesion by inkjet printing or laser printing)
A mark was printed on the heat conductive layers of Preparation Examples 1 to 16 by inkjet printing and laser printing, and the mark was observed.

  As a result, it was confirmed that in any of the heat conductive layers of Preparation Examples 1 to 16, marks by both ink jet printing and laser printing could be seen well, and the print mark adhesion was good.

  The numerical value in each component in Tables 1 to 3 indicates the number of grams unless otherwise specified.

  In the column of boron nitride particles in Tables 1 to 3, the upper numerical value is the compounding weight (g) of boron nitride particles, and the intermediate numerical value is the solid content excluding the curing agent in the thermally conductive layer (that is, 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 or polyethylene), and the lower number is the solid content of the thermally conductive layer (that is, boron nitride particles) And the volume percentage (volume%) of the boron nitride particles with respect to the total volume of the solid content of the epoxy resin and the curing agent.

Details of the components marked with * among the components in Tables 1 to 3 are described below.
PT-110 ^{* 1} : Product name, plate-like boron nitride particles, average particle size (light scattering method) 45 μm, UHP-1 manufactured by Momentive Performance Materials Japan Ltd. ^{* 2} : Product name: Shovie N UHP- 1, plate-like boron nitride particles, average particle diameter (light scattering method) 9 μm, Showa Denko Epoxy Resin A ^{* 3} : Ogsol EG (trade name), bisarylfluorene type epoxy resin, semi-solid, epoxy equivalent 294 g / Eqiv. , Softening temperature (ring and ball method) 47 ° C., melt viscosity (80 ° C.) 1360 mPa · s, epoxy resin B manufactured by Osaka Gas Chemical Co., Ltd. ^{* 4} : JER828 (trade name), bisphenol A type epoxy resin, liquid, epoxy equivalent 184 to 194 g / Eqiv. , Softening temperature (ring ball method) less than 25 ° C., melt viscosity (80 ° C.) 70 mPa · s, epoxy resin C ^{* 5} manufactured by Japan Epoxy Resin Co., Ltd .: JER1002 (trade name), bisphenol A type epoxy resin, solid, epoxy equivalent 600 -700 g / eqiv. , Softening temperature (ring and ball method) 78 ° C., melt viscosity (80 ° C.) 10000 mPa · s or more (measurement limit or more), epoxy resin D ^{* 6} manufactured by Japan Epoxy Resin Co., Ltd .: EPPN-501HY (trade name), triphenylmethane type epoxy Resin, solid, epoxy equivalent 163-175 g / eqiv. , Softening temperature (ring and ball method) 57-63 ° C., Nippon Kayaku Co., Ltd. curing agent ^{* 7} : Curazole 2PZ (trade name, manufactured by Shikoku Kasei Co., Ltd.) 5 mass% methyl ethyl ketone solution curing agent ^{* 8} : Cureazole 2P4MHZ-PW (Product) Name, manufactured by Shikoku Kasei Co., Ltd.) 5% by weight methyl ethyl ketone dispersion polyethylene ^{* 9} : low density polyethylene, weight average molecular weight (Mw) 4000, number average molecular weight (Mn) 1700, manufactured by Aldrich

1 Thermal Conductive Adhesive Sheet 2 Thermal Conductive Layer 3 Adhesive / Adhesive Layer 4 Boron Nitride Particles TD Thickness Direction SD Surface Direction (Orthogonal Direction)

Claims (1)

A thermal conductive layer containing plate-like boron nitride particles and an epoxy resin , wherein the thermal conductivity in the direction perpendicular to the thickness direction of the thermal conductive layer is 4 W / m · K or more When,
An adhesive layer or an adhesive layer laminated on at least one surface of the thermally conductive layer ,
The epoxy resin is a combination of liquid epoxy resins and solid epoxy resins, semi-solid epoxy resin, and characterized by at least one Tsudea Rukoto selected from the group consisting of liquid epoxy resin, Thermally conductive adhesive sheet.

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