CN102169856A - heat dissipation structure - Google Patents

Abstract

The heat dissipation structure includes a substrate, an electronic component mounted on the substrate, a heat dissipation member for dissipating heat generated by the electronic component, and a thermally conductive adhesive sheet provided on the substrate so as to cover the electronic component. . The thermally conductive adhesive sheet includes a thermally conductive layer containing flaky boron nitride particles. The thermal conductivity of the thermal conductive layer in a direction perpendicular to the thickness direction of the thermal conductive layer is 4 W/m·K or more, and the thermal conductive adhesive sheet is in contact with the heat dissipation member.

Description

heat dissipation structure

technical field

The present invention relates to a heat dissipation structure.

Background technique

In recent years, electronic components such as memories have increased the amount of heat generated during operation as their capacity has increased, which may degrade electronic components. Therefore, structures including electronic components and substrates on which they are mounted require high heat dissipation (high thermal conductivity) sex).

For example, the following structure has been proposed: on a plurality of memory devices mounted on a substrate, a plate-shaped heat sink for memory made of aluminum is placed, and a structure in which the substrate, each memory, and heat sink for memory is clamped by a clamp (such as a memory For the heat sink, refer to the Internet (URL: http://www.ainex.jp/products/hm-02.htm)).

In the structure of the heat sink for the memory and the Internet, the heat generated by the memory is dissipated by the heat sink for the memory by making the heat sink for the memory contact the upper surface of the memory.

Contents of the invention

The problem to be solved by the invention

However, in the structure of the above-mentioned heat sink for memory and the Internet, the side surface of the memory is not in contact with the flat heat sink for memory, and when the thickness of each memory is different, the upper surface of the thin memory and the memory Create gaps between heat sinks. Therefore, there is a problem that the heat generated by the memory cannot be sufficiently dissipated.

An object of the present invention is to provide a heat dissipation structure excellent in heat dissipation.

solutions to problems

The heat dissipation structure of the present invention is characterized in that it includes a substrate, an electronic component mounted on the substrate, a heat dissipation member for dissipating heat generated by the electronic component, and a heat dissipation member provided on the electronic component so as to cover the electronic component. The thermally conductive adhesive sheet on the substrate, the thermally conductive adhesive sheet has a thermally conductive layer containing flaky boron nitride particles, and the thermally conductive layer has a direction perpendicular to the thickness direction of the thermally conductive layer. The heat conductivity is 4 W/m·K or more, and the heat conductive adhesive sheet is in contact with the heat dissipation member.

In addition, in the heat dissipation structure of the present invention, preferably, the thermally conductive adhesive sheet includes an adhesive layer or an adhesive layer laminated on at least one surface of the thermally conductive layer, and the adhesive layer or the aforementioned The adhesive layer adheres or adheres to the aforementioned substrate.

The effect of the invention

In the heat dissipation structure of the present invention, since the electronic component is covered with the thermally conductive adhesive sheet, heat generated by the electronic component can be thermally conducted from the upper surface and the side surface of the electronic component to the thermally conductive adhesive sheet. Then, the heat can be thermally conducted from the thermally conductive adhesive sheet to the heat dissipation member, and dissipated to the outside in the heat dissipation member.

Therefore, the heat generated by the electronic component can be efficiently dissipated through the thermally conductive adhesive sheet and the heat dissipating member.

Description of drawings

FIG. 1 shows a cross-sectional view of one embodiment of the heat dissipation structure of the present invention.

2 is a process diagram for explaining a method of manufacturing a thermally conductive layer,

(a) represents the process of hot-pressing the mixture or the laminated sheet,

(b) represents the process of dividing the pressed sheet into multiple parts,

(c) shows the step of laminating the divided sheets.

Fig. 3 shows a perspective view of a thermally conductive layer.

Fig. 4 shows a cross-sectional view of a heat conductive adhesive sheet.

5 is a process diagram for manufacturing the heat dissipation structure shown in FIG. 1 , showing a process of fixing a substrate on which electronic components are mounted on a case supporting a frame and preparing a thermally conductive adhesive sheet.

Fig. 6 shows a cross-sectional view of another embodiment (a form in which a heat conductive adhesive sheet is formed of a heat conductive layer) of the heat dissipation structure of the present invention.

7 is a process diagram for manufacturing the heat dissipation structure of FIG. 6 , showing a process of fixing a substrate on which electronic components are mounted on a case supporting a frame and preparing a thermally conductive adhesive sheet.

Fig. 8 is a cross-sectional view showing another embodiment (a form in which the other end of the thermally conductive adhesive sheet is in contact with the case) of the heat dissipation structure of the present invention.

Fig. 9 shows a cross-sectional view of another embodiment (a form in which an adhesive/adhesive layer is in contact with an upper surface of an electronic component) of the heat dissipation structure of the present invention.

Fig. 10 shows a perspective view of a type I test device (before the bending resistance test) of the bending resistance test.

FIG. 11 shows a perspective view of a type I test device (in the bending resistance test) of the bending resistance test.

Detailed ways

1 shows a cross-sectional view of one embodiment of the heat dissipation structure of the present invention, FIG. 2 is a process diagram for explaining a method of manufacturing a thermally conductive layer, FIG. 3 shows a perspective view of the thermally conductive layer, and FIG. As a cross-sectional view of the adhesive sheet, FIG. 5 is a process diagram for manufacturing the heat dissipation structure of FIG. 1 .

In FIG. 1, the heat dissipation structure 1 includes a substrate 2, an electronic component 3 mounted on the substrate 2, a frame 4 as a heat dissipation member for dissipating heat generated by the electronic component 3 (heat transmission, heat conduction), and Thermally conductive adhesive sheet 5 provided on substrate 2 .

The substrate 2 is formed in a substantially flat plate shape, and is made of, for example, ceramics such as aluminum nitride and alumina; for example, glass and epoxy resin; for example, polyimide, polyamideimide, acrylic resin, polyethernitrile, polyethersulfone, Made of synthetic resins such as polyethylene terephthalate, polyethylene naphthalate, and polyvinyl chloride.

The electronic component 3 includes, for example, an IC (Integrated Circuit) chip 20 , a capacitor 21 , a coil 22 and/or a resistor 23 . In addition, the electronic component 3 controls, for example, a voltage of less than 5V and/or a current of less than 1A. The electronic components 3 are mounted on the upper surface of the substrate 2 and are arranged at intervals in the planar direction (the planar direction of the substrate 2 , the left-right direction and the depth direction in FIG. 1 ). The thickness of the electronic component 3 is, for example, about 1 μm to 1 cm.

The frame 4 is supported by a case (not shown in FIG. 1 ) that accommodates the substrate 2 , is arranged at intervals outside the substrate 2 (side surface), and is formed in a substantially frame shape surrounding the substrate 2 in plan view. In addition, the frame 4 is formed in a substantially rectangular shape that is long in the vertical direction when viewed in cross section. The frame 4 is formed of, for example, metal such as aluminum, stainless steel, copper, iron, or the like.

The thermally conductive adhesive sheet 5 is provided on the substrate 2 so as to cover the electronic component 3 . In addition, the thermally conductive adhesive sheet 5 is arranged such that one end (the right end in FIG. 1 ) is in contact with the surface (upper surface and side surface) of the electronic component 3, and the other end (the upper left end in FIG. 1 part) is in contact with the inner surface (right side surface) of the frame 4.

Specifically, the thermally conductive adhesive sheet 5 has a substantially L-shaped cross-section in the heat dissipation structure 1, and the center (the center in the left-right direction) and one end are arranged on the upper surface of the substrate 2 so as to extend in the plane direction. The other end portion is bent upward from one end edge (left end edge) of the substrate 2 , and the other end portion of the thermally conductive adhesive sheet 5 is arranged to extend upward on the right side surface (inner surface) of the frame 4 .

This thermally conductive adhesive sheet 5 includes a thermally conductive layer 6 as shown in FIG. "Adhesive/adhesive layer 7".).

The thermally conductive layer 6 is formed in a sheet shape and contains boron nitride particles.

Specifically, the thermally conductive layer 6 contains boron nitride (BN) particles as an essential component, and further contains, for example, a resin component.

The boron nitride particles are formed into flakes (or scales) and dispersed in the thermally conductive layer 6 in a form oriented in a predetermined direction (described later).

The average length of the boron nitride particles in the longitudinal direction (the maximum length in the direction perpendicular to the thickness direction of the sheet) is, for example, 1 to 100 μm, preferably 3 to 90 μm. In addition, 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, especially preferably 30 μm or more, most preferably 40 μm or more, usually, for example, 100 μm or less, preferably 90 μm or less.

In addition, the average thickness of the boron nitride particles (the length in the thickness direction of the sheet, that is, the length in the lateral direction of the particles) is, for example, 0.01 to 20 μm, preferably 0.1 to 15 μm.

In addition, the aspect ratio (length in the longitudinal direction/thickness) of the boron nitride particles is, for example, 2 to 10,000, preferably 10 to 5,000.

Next, 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, especially preferably 30 μm or more, most preferably 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 of the boron nitride particles measured by the light scattering method does not satisfy the above-mentioned range, the thermally conductive layer 6 may become brittle and the handleability may decrease.

In addition, 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, the boron nitride particle can use a commercial item or the processed product obtained by processing it. Commercially available boron nitride particles include, for example, the "PT" series manufactured by MomentivePerformance Materials Japan LCC (such as "PT-110", etc.), the "SHOBN UHP" series manufactured by Showa Denko Corporation (such as "SHOBN UHP- 1", etc.) etc.

The resin component is a substance capable of dispersing boron nitride particles, that is, a dispersion solvent (matrix) for dispersing boron nitride particles, and examples thereof include resin components such as thermosetting resin components and thermoplastic resin components.

Examples of the thermosetting resin component include epoxy resin, thermosetting polyimide, phenolic resin, urea resin, melamine resin, unsaturated polyester resin, diallyl phthalate resin, silicone resin, thermosetting polyurethane resin, etc.

Examples of thermoplastic resin components include polyolefins (such as polyethylene, polypropylene, ethylene-propylene copolymers, etc.), acrylic resins (such as polymethyl methacrylate, etc.), polyvinyl acetate, ethylene-vinyl acetate, etc. Ester copolymer, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide, polycarbonate, polyacetal, polyethylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polysulfone, poly Ethersulfone, polyether ether ketone, polyallyl sulfone, thermoplastic polyimide, thermoplastic polyurethane resin, polyaminobismaleimide, polyamideimide, polyetherimide, Bismaleimide triazine resin, polymethylpentene, fluorinated resin, liquid crystal polymer, olefin-vinyl alcohol copolymer, ionomer, polyarylate, acrylonitrile-ethylene-styrene copolymer, propylene Nitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, etc.

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

Among the resin components, preferably an epoxy resin is used.

Epoxy resin is in any form of liquid, semi-solid and solid at room temperature.

Specifically, examples of epoxy resins include bisphenol epoxy resins (such as bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, hydrogenated bisphenol A epoxy resins), and bisphenol A epoxy resins. Epoxy resin, dimer acid modified bisphenol type epoxy resin, etc.), novolac type epoxy resin (such as phenol novolak type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resins, etc.), naphthalene-type epoxy resins, fluorene-type epoxy resins (such as bisarylfluorene-type epoxy resins, etc.), triphenylmethane-type epoxy resins (such as trihydroxybenzenemethane-type epoxy resins, etc.) Aromatic epoxy resins such as triepoxypropyl isocyanurate (triglycidyl isocyanurate), hydantoin epoxy resin and other nitrogen-containing ring epoxy resins; such as aliphatic type epoxy resin; such as alicyclic type epoxy resin (such as bicyclic ring type epoxy resin, etc.); such as glycidyl ether type epoxy resin; such as glycidylamine type epoxy resin, etc.

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

Preferably, a combination of a liquid epoxy resin and a solid epoxy resin is used, and more preferably, a combination of a liquid aromatic epoxy resin and a solid aromatic epoxy resin is used. As such a combination, specifically, 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 combination of resins.

In addition, as the epoxy resin, preferably, a semi-solid epoxy resin used alone is used, and more preferably, a semi-solid aromatic epoxy resin used alone is used. Specific examples of such epoxy resins include semi-solid fluorene epoxy resins.

If it is a combination of a liquid epoxy resin and a solid epoxy resin, or a semi-solid epoxy resin, the level difference followability of the thermally conductive layer 6 can be improved (described later).

In addition, the epoxy equivalent of the epoxy resin is, 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 It is 70°C or lower (specifically, 25 to 70°C).

In addition, the melt viscosity of the epoxy resin at 80° C. is, for example, 10 to 20000 mPa·s, preferably 50 to 15000 mPa·s. When two or more epoxy resins are used in combination, the melt viscosity of their mixture is set within the above-mentioned range.

In addition, when an epoxy resin that is solid at room temperature and an epoxy resin that is liquid at room temperature are used in combination, the first epoxy resin having a softening temperature of, for example, less than 45° C., preferably 35° C. or lower, and a softening temperature of, for example, The second epoxy resin is 45°C or higher, preferably 55°C or higher. Thereby, the kinematic viscosity (according to JIS K 7233, described later) of the resin component (mixture) can be set in a desired range, and the height difference followability of the thermally conductive layer 6 can be improved.

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

The curing agent is a latent curing agent (epoxy resin curing agent) capable of curing epoxy resin by heating, and examples thereof include imidazole compounds, amine compounds, acid anhydride compounds, amide compounds, hydrazide compounds, and imidazoline compounds. Moreover, in addition to the above, a phenolic compound, a urea compound, a polythioether compound, etc. are 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 amine compounds include aliphatic polyamines such as ethylenediamine, propylenediamine, diethylenetriamine, and triethylenetetramine; for example, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylmethane, and Aromatic polyamines such as phenyl sulfone, etc.

Examples of acid anhydride compounds include phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 4-methyl-hexahydrophthalic anhydride, methyl sodium Methyl nadic anhydride, pyromellitic anhydride, dodecenyl succinic anhydride, dichlorosuccinic anhydride, benzophenone tetracarboxylic anhydride, chlorendic anhydride, etc.

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

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

Examples of imidazoline compounds include methylimidazoline, 2-ethyl-4-methylimidazoline, ethylimidazoline, isopropylimidazoline, 2,4-dimethylimidazoline, phenylimidazole line, undecylimidazoline, heptadecylimidazoline, 2-phenyl-4-methylimidazoline, etc.

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

As a curing agent, preferably an imidazole compound is used.

As the curing accelerator, tertiary amine compounds such as triethylenediamine and triethylenediamine, three-2,4,6-dimethylaminomethylphenol; for example, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, O , Phosphorus compounds such as tetra-n-butylphosphonium diethyl dithiophosphate; such as quaternary ammonium salt compounds, organometallic salt compounds, their derivatives, etc. These curing accelerators may be used alone or in combination of two or more.

The proportion 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; the proportion of the curing accelerator is, for example, 0.1 to 10 parts by mass , Preferably it is 0.2-5 mass parts.

The above-mentioned curing agent and/or curing accelerator can be prepared and used as a solvent solution and/or a solvent dispersion liquid dissolved and/or dispersed in a solvent as needed.

Examples of the solvent include ketones such as acetone and methyl ethyl ketone (MEK), esters such as ethyl acetate, organic solvents such as amides such as N,N-dimethylformamide, and the like. In addition, examples of the solvent include aqueous solvents such as water and alcohols such as methanol, ethanol, propanol, and isopropanol. As the solvent, organic solvents are preferably used, and ketones and amides are more preferable.

In addition, the content of the resin component was measured by a kinematic viscosity test (temperature: 25°C ± 0.5°C, solvent: butyl carbitol, resin component (solid content) concentration: 40% by mass) according to JIS K 7233 (bubble viscometer method) The 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, more preferably 0.4×10 ^-4 to 1.8×10 ^-4 m ² /s. In addition, the above-mentioned kinematic viscosity can also be set, for example, at 0.22×10 ^-4 to 1.00×10 ^-4 m ² /s, preferably at 0.3×10 ^-4 to 0.9×10 ^-4 m ² /s, more preferably at 0.4×10 -4 m 2 /s, 10 ^-4 ~ 0.8×10 ^-4 m ² /s.

When the kinematic viscosity of the resin component exceeds the above-mentioned range, excellent flexibility and step followability (described later) may not be imparted to the thermally conductive layer 6 . On the other hand, when the kinematic viscosity of the resin component does not satisfy the above-mentioned range, boron nitride particles may not be oriented in a predetermined direction.

In addition, 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 (kinematic viscosity is known), and the rising speed is the same The kinematic viscosity of the standard sample is judged as the kinematic viscosity of the resin component, and the kinematic viscosity of the resin component is measured in this way.

Next, in the thermally conductive layer 6, the volume-based content ratio of the boron nitride particles (solid content, that is, the volume percentage of the boron nitride particles to the total volume of the resin component and the boron nitride particles) is, for example, 35 volume % or more, preferably 60 volume % or more, preferably 65 volume % or more; usually, for example, 95 volume % or less, preferably 90 volume % or less.

When the volume-based content ratio of the boron nitride particles does not satisfy the above range, the boron nitride particles may not be oriented in a predetermined direction in the thermally conductive layer 6 . On the other hand, when the volume-based content ratio of the boron nitride particles exceeds the above-mentioned range, the thermally conductive layer 6 may become brittle and the handleability may decrease.

In addition, with respect to 100 parts by mass of the total amount (total solid content) of each component (boron nitride particle and resin component) forming the thermally conductive layer 6, the compounding ratio of the boron nitride particle on a mass basis is, for example, 40 to 95 parts by mass, preferably 65 to 90 parts by mass; the compounding ratio of the resin component based on mass is, for example, 5 to 60 parts by mass with respect to 100 parts by mass of the total amount of the components forming the thermally conductive layer 6 , preferably 10 to 35 mass. Moreover, the compounding ratio by mass of boron nitride particle|grains with respect to 100 mass parts of resin components is 60-1900 mass parts, for example, Preferably it is 185-900 mass parts.

In addition, when two epoxy resins (the first epoxy resin and the second epoxy resin) are used in combination, the mass ratio of the first epoxy resin to the second epoxy resin (mass of the first epoxy resin/second epoxy resin) The quality of the epoxy resin) can be appropriately set according to the softening temperature of each epoxy resin (the first epoxy resin and the second epoxy resin), for example, it is 1/99～99/1, preferably 10/90～ 90/10.

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

Next, a method for forming the thermally conductive layer 6 will be described.

In this method, first, each of the above-mentioned components is blended in the above-mentioned blending ratio, and stirred and mixed to prepare a mixture.

In stirring and mixing, each component should be mixed efficiently. For example, a solvent and each of the above-mentioned components may be mixed together, or a resin component (preferably a thermoplastic resin component) may be melted by heating, for example.

Examples of the solvent include the same organic solvents as those described above. In addition, when the above-mentioned curing agent and/or curing accelerator is prepared as a solvent solution and/or a solvent dispersion, no solvent may be added during stirring and mixing, and the solvent of the solvent solution and/or solvent dispersion may be used as it is for stirring. Mixed solvent mixtures are available. Alternatively, a solvent may be further added as a mixed solvent during stirring and mixing.

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

For the removal of the solvent, for example, leave it at room temperature for 1 to 48 hours, or for example, heat at 40 to 100° C. for 0.5 to 3 hours, or for example, heat at 20 to 60° C. for 0.5 to 3 hours under a reduced pressure atmosphere of 0.001 to 50 kPa. Hour.

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

Next, the resulting mixture is hot-pressed in the process.

Specifically, as shown in FIG. 2( a ), for example, the mixture is hot-pressed through two mold release films (mold release film) 12 as needed, thereby obtaining a pressed sheet 6A. The hot pressing conditions are as follows: the temperature is, for example, 50-150°C, preferably 60-140°C; the pressure, for example, is 1-100MPa, preferably 5-50MPa; the time is, for example, 0.1-100 minutes, preferably 1-30 minutes.

It is further preferred to subject the mixture to vacuum heat pressing. The degree of vacuum of the vacuum heat press is, for example, 1 to 100 Pa, preferably 5 to 50 Pa; the temperature, pressure and time are the same as those of the heat press described above.

When the temperature, pressure, and/or time in hot pressing are outside the above-mentioned ranges, the porosity P (described later) of the heat conductive layer 6 may not be adjusted to a desired value.

The thickness of the pressed sheet 6A obtained by hot pressing is, for example, 50 to 1000 μm, preferably 100 to 800 μm.

Next, in this method, as shown in FIG. 2( b ), the pressed sheet 6A is divided into a plurality (for example, four) to obtain divided sheets 6B (dividing step). In the division of the pressed sheet 6A, the pressed sheet 6A is cut in its thickness direction so as to be split into a plurality when projected in the thickness direction. In addition, the pressed sheet 6A is cut so that each divided sheet 6B has the same shape when projected in the thickness direction.

Next, in this method, as shown in FIG. 2( c ), each divided sheet 6B is stacked in the thickness direction to obtain a stacked sheet 6C (stacking step).

Thereafter, in this method, as shown in FIG. 2( a ), the laminated sheet 6C is hot-pressed (preferably vacuum hot-pressed) (hot-pressing step). The conditions of hot pressing are the same as those of the above-mentioned mixture.

The thickness of the laminated sheet 6C after hot pressing is, for example, 1 mm or less, preferably 0.8 mm or less; usually, for example, 0.05 mm or more, preferably 0.1 mm or more.

Thereafter, as shown in FIG. 3 , in order to effectively orient the boron nitride particles 8 in the resin component 9 in a predetermined direction in the thermally conductive layer 6 , the above-mentioned dividing step ( FIG. 2 ( b )) and the stacking step are repeatedly implemented. ((c) of FIG. 2 ) and a series of processes of the hot pressing process ((a) of FIG. 2 ). The number of repetitions is not particularly limited, and can be appropriately set according to the filling state of the boron nitride particles, for example, 1 to 10 times, preferably 2 to 7 times.

In addition, in the above-mentioned hot pressing step ((a) of FIG. 2 ), for example, the mixture and the laminated sheet 6C may be rolled by a plurality of calender rolls or the like.

Thereby, the thermally conductive layer 6 shown in FIGS. 3 and 4 can be formed.

The thickness of the formed thermally conductive layer 6 is, for example, 1 mm or less, preferably 0.8 mm or less; usually, for example, 0.05 mm or more, preferably 0.1 mm or more.

In addition, the volume-based content ratio of the boron nitride particles 8 in the thermally conductive layer 6 (solid content, that is, the volume of the boron nitride particles 8 with respect to the total volume of the resin component 9 and the boron nitride particles 8 Percentage) is as above, for example, 35 vol% or more (preferably 60 vol% or more, more preferably 75 vol% or more); usually 95 vol% or less (preferably 90 vol% or less).

When the content ratio of the boron nitride particles 8 does not satisfy the above-mentioned range, the boron nitride particles 8 may not be oriented in a predetermined direction in the thermally conductive layer 6 .

In addition, when the resin component 9 is a thermosetting resin component, for example, the above-mentioned dividing step ((b) of FIG. 2 ), laminating step ((c) of FIG. 2 ) and hot pressing step (Fig. A series of steps in (a)) of 2 obtains the thermally conductive layer 6 in an uncured state as it is. In addition, when the thermally conductive adhesive sheet 5 is bonded to the electronic component 3 and the substrate 2 , the uncured thermally conductive layer 6 is thermally cured.

Next, in the thermally conductive layer 6 formed in this way, as shown in FIG. Orientation SD Orientation.

In addition, the arithmetic mean of the angle formed by the longitudinal direction LD of the boron nitride particles 8 and the surface direction SD of the thermally conductive layer 6 (orientation angle α of the boron nitride particles 8 with respect to the thermally conductive layer 6) is, for example, 25 degrees or less, Preferably it is 20 degrees or less; usually 0 degrees or more.

In addition, the orientation angle α of the boron nitride particles 8 with respect to the thermally conductive layer 6 is calculated by cutting the thermally conductive layer 6 in the thickness direction with a cross-section polisher (CP), and examining the resulting orientation angle α with a scanning electron microscope (SEM). The cross-section of the boron nitride particles 8 can be observed under the magnification of the magnification of the field of view of more than 200 boron nitride particles 8. According to the obtained SEM photos, the longitudinal direction LD of the boron nitride particles 8 is obtained relative to the plane direction SD of the thermally conductive layer 6 (and The inclination angle α in the direction perpendicular to the thickness direction TD) was calculated, and its average value was calculated.

Accordingly, the thermal conductivity of the thermally conductive layer 6 in the plane direction SD is 4 W/m·K or higher, preferably 5 W/m·K or higher, more preferably 10 W/m·K or higher, and still more preferably 15 W/m·K or higher. , especially preferably 25 W/m·K or more, usually 200 W/m·K or less.

In addition, when the resin component 9 is a thermosetting resin component, the thermal conductivity in the plane direction SD of the thermally conductive layer 6 is substantially the same before and after thermosetting.

If the thermal conductivity in the plane direction SD of the thermally conductive layer 6 does not satisfy the above-mentioned range, the thermal conductivity in the plane direction SD is insufficient, so it may not be used for heat dissipation applications that require the thermal conductivity in the plane direction SD.

In addition, the thermal conductivity in the plane direction SD of the thermally conductive layer 6 was measured by a pulse heating method. In the pulse heating method, a xenon flash analyzer (type LFA-447) (manufactured by NETZSCH) can be used.

In addition, the thermal conductivity in the thickness direction TD of the thermally conductive layer 6 is, for example, 0.5 to 15 W/m·K, preferably 1 to 10 W/m·K.

In addition, the thermal conductivity in the thickness direction TD of the thermally conductive layer 6 can be measured by a pulse heating method, a laser flash method, or a TWA method (temperature wave analysis). In the pulse heating method, the same equipment as above can be used; in the laser flash method, "TC-9000" (manufactured by ULVAC-RIKO, Inc.) can be used; in the TWA method, "ai-Phase mobiLe" can be used (manufactured by ai-Phase Co., Ltd.).

Accordingly, the ratio of the thermal conductivity in the plane direction SD of the thermally conductive layer 6 to the thermal conductivity in the thickness direction TD of the thermally conductive layer 6 (thermal conductivity in the plane direction SD/thermal conductivity in the thickness direction TD) is, for example, 1.5 or more, preferably 3 or more, more preferably 4 or more; usually 20 or less.

In addition, although not shown in FIG. 3 , for example, voids (gaps) are formed in the thermally conductive layer 6 .

The ratio of the pores in the thermally conductive layer 6, that is, the porosity P, can be determined by the content ratio of the boron nitride particles 8 (based on volume), and then the hot pressing of the mixture of the boron nitride particles 8 and the resin component 9 (Fig. 2 ( a)) by adjusting the temperature, pressure and/or time, specifically, by setting the temperature, pressure and/or time of the hot press ((a) of FIG. 2 ) within the above range.

The porosity P in the thermally conductive layer 6 is, for example, 30% by volume or less, preferably 10% by volume or less.

The above-mentioned porosity P can be measured, for example, by the following method: First, the thermally conductive layer 6 is cut along the thickness direction by using a cross-section polisher (CP), and the resulting cross-section is viewed with a scanning electron microscope (SEM) at 200 times. Observe and obtain an image, binarize the void portion and the remaining portion from the obtained image, and then calculate the area ratio of the void portion to the overall cross-sectional area of the thermally conductive layer 6 .

In addition, in the heat conductive layer 6 , the porosity P2 after curing is, for example, less than 100%, and specifically, preferably 50% or less with respect to the porosity P1 before curing.

In the measurement of the porosity P (P1), when the resin component 9 is a thermosetting resin component, the thermally conductive layer 6 before thermosetting is used.

If the porosity P of the thermally conductive layer 6 is within the above-mentioned range, the level difference followability of the thermally conductive layer 6 can be improved (described later).

In addition, when the thermally conductive layer 6 is evaluated under the following test conditions in the bending resistance test based on the cylindrical mandrel method (mandrel method) of JIS K 5600-5-1, it is preferable that no fracture is observed.

Test conditions

Test device: Type I

Mandrel: 10mm in diameter

Bending angle: more than 90 degrees

Thickness of thermally conductive layer 6: 0.3 mm

In addition, FIG. 10 and FIG. 11 show perspective views of the type I test device, and the type I test device will be described below.

In Fig. 10 and Fig. 11, the test apparatus 90 of type I comprises: first plate 91; Second plate 92, it is arranged side by side with first plate 91; And mandrel (axis of rotation) 93, it is for the first The flat plate 91 and the second flat plate 92 are arranged to rotate relative to each other.

The first flat plate 91 is formed in a substantially rectangular flat plate shape. In addition, a stopper 94 is provided on one end portion (movable end portion) of the first plate 91 . The stopper 94 is formed on the surface of the first flat plate 91 so as to extend along one end portion of the first flat plate 91 .

The second flat plate 92 has a substantially rectangular flat plate shape, so that one side thereof is adjacent to one side of the first flat plate 91 (the side of the other end portion (base end portion) on the side opposite to the end portion on which the stopper 94 is provided) configured in a way.

The mandrel 93 is formed to extend along one side of the first flat plate 91 and the second flat plate 92 adjacent to each other.

As shown in FIG. 10 , before starting the bending resistance test, the surface of the first flat plate 91 and the surface of the second flat plate 92 of this type I test device 90 were made to be on the same plane.

In addition, when performing the bending resistance test, the thermally conductive layer 6 was placed on the surface of the first flat plate 91 and the surface of the second flat plate 92 . In addition, the heat conductive layer 6 is placed so that one side thereof abuts against the stopper 94 .

Next, as shown in FIG. 11 , the first flat plate 91 and the second flat plate 92 are relatively rotated. Specifically, the movable end portion of the first plate 91 and the movable end portion of the second plate 92 are rotated by a predetermined angle around the spindle 93 . Specifically, the first flat plate 91 and the second flat plate 92 are rotated so that the surfaces of the movable end portions of the first flat plate 91 and the second flat plate 92 approach (opposite) each other.

Thereby, the heat conductive layer 6 bends around the mandrel 93 while following the rotation of the first flat plate 91 and the second flat plate 92 .

More preferably, the thermally conductive layer 6 is not broken even when the bending angle is set to 180 degrees under the above-mentioned experimental conditions.

In addition, when the resin component 9 is a thermosetting resin component, the thermally conductive layer 6 provided in the bending test is a semi-cured (B-stage state) thermally conductive layer 6 .

In the bending resistance test at the bending angle described above, when the thermally conductive layer 6 is observed to be broken, the thermally conductive layer 6 may not be able to impart excellent flexibility.

In addition, when the thermally conductive layer 6 is evaluated under the following test conditions in a three-point bending test based on JIS K 7171 (2008), for example, no fracture is observed.

Test conditions

Test piece: size 20mm×15mm

Distance between fulcrums: 5mm

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

Bending angle: 120 degrees

Evaluation method: When testing under the above-mentioned test conditions, the center of the test piece was visually observed for fractures such as cracks.

In addition, in the three-point bending test, when the resin component 3 is a thermosetting resin component, the heat conductive layer 6 before thermosetting was used.

Next, since no breakage was observed in the above-mentioned three-point bending test, this thermally conductive layer 6 was found to be excellent in height difference followability. In addition, the height difference followability means that when the thermal conductive layer 6 is installed on an installation object with a height difference (such as the above-mentioned substrate 2, etc.), it can follow the height difference (such as the height difference formed by the above-mentioned electronic component 3) The characteristics of sealing.

In addition, marks such as letters and symbols may be attached to the heat conductive layer 6 , for example. That is, the thermally conductive layer 6 is excellent in marking adhesion. The mark adhesion refers to the property that the above mark can be reliably attached to the thermally conductive layer 6 .

Specifically, the mark can be attached to the thermally conductive layer 6 by printing, engraving, or the like (coating, fixing, or fixing).

As printing, inkjet printing, letterpress printing, gravure printing, laser printing etc. are mentioned, for example.

In addition, when the mark is printed by inkjet printing, letterpress printing or gravure printing, for example, an ink fixing layer for improving the fixability of the mark can be provided on the surface of the thermally conductive layer 6 (the surface on the printing side, the upper surface, the surface relative to the adhesive surface, etc.). The opposite side surface of the adhesive layer 7).

In addition, when printing a mark by laser printing, for example, a toner fixing layer for improving the fixability of the mark can be provided on the surface of the thermally conductive layer 6 (the surface on the printing side, the upper surface, and the surface of the bonding/adhesive agent). the opposite side surface of layer 7).

As marking, laser marking, punching, etc. are mentioned, for example.

In addition, the thermally conductive layer 6 has insulation and adhesiveness (slightly adhesive).

Specifically, the volume resistance (JIS K6271) of the thermally conductive layer 6 is, for example, 1×10 ¹⁰ Ω·cm or more, preferably 1×10 ¹² Ω·cm or more, and usually 1×10 ²⁰ Ω·cm or less.

The volume resistance R of the thermally conductive layer 6 is measured in accordance with JIS K 6911 (General Test Methods for Thermosetting Plastics, 2006 edition).

When the volume resistance R of the thermally conductive layer 6 does not satisfy the above-mentioned range, it may not be possible to prevent a short circuit between electronic components which will be described later.

In addition, in the thermally conductive layer 6, when the resin component 9 is a thermosetting resin component, the volume resistance R is the value of the thermally conductive layer 6 after hardening.

In addition, the heat conductive layer 6 did not come off from the adherend, for example, in the following initial adhesion test (1). That is, the thermally conductive layer 6 and the adherend maintain a temporarily fixed state.

Initial adhesion test (1): The thermally conductive layer 6 was temporarily fixed on the adherend along the horizontal direction by heat and pressure, and left to stand for 10 minutes, and the adherend was turned upside down.

As a to-be-adhered body, the board|substrate 2 etc. which mounted the said electronic component are mentioned, for example. The pressure bonding is, for example, rolling a sponge roller made of resin such as silicone resin on the surface of the thermally conductive layer 6 while pressing the thermally conductive layer 6 .

Moreover, when the resin component 9 is a thermosetting resin component (for example, an epoxy resin), the temperature of thermocompression bonding is 80 degreeC, for example.

On the other hand, when the resin component 9 is a thermoplastic resin component (such as polyethylene), the temperature of thermocompression bonding is, for example, the softening point or melting point of the thermoplastic resin component plus a temperature of 10 to 30° C., preferably the softening point of the thermoplastic resin component. Or the melting point plus a temperature of 15 to 25°C, more preferably the softening point or melting point of the thermoplastic resin component plus a temperature of 20°C, specifically 120°C (that is, the softening point or melting point of the thermoplastic resin component is 100°C, The 100°C plus a temperature of 20°C).

When the thermally conductive layer 6 falls off from the adherend in the above-mentioned initial adhesion test (1), that is, when the temporarily fixed state of the thermally conductive layer 6 and the adherend cannot be maintained, the thermally conductive layer 6 may not be reliably temporarily fixed. Fixed on the adherend.

In addition, when the resin component 9 is a thermosetting resin component, the thermally conductive layer 6 for the initial adhesion test (1) and the initial adhesion test (2) (described later) is an uncured thermally conductive layer 6, By heat-compression bonding in the initial adhesive strength test (1) and the initial adhesive strength test (2), the heat conductive layer 6 becomes a B-stage state.

In addition, when the resin component 9 is a thermoplastic resin component, the thermally conductive layer 6 for the initial adhesion test (1) and the initial adhesion test (2) (described later) is a solid thermally conductive layer 6, and the The thermocompression bonding in the relay test (1) and the initial adhesion test (2) brought the heat conductive layer 6 into a softened state.

It is preferable that the heat conductive layer 6 does not come off from the adherend in both the above-mentioned initial adhesion test (1) and the following initial adhesion test (2). That is, the temporarily fixed state of the thermally conductive layer 6 and the adherend can be maintained.

Initial adhesion test (2): The thermally conductive layer 6 was bonded to the adherend in the horizontal direction by heat and pressure, temporarily fixed, left for 10 minutes, and then the adherend was arranged in the vertical direction (vertical direction).

The temperature in the thermocompression bonding in the initial adhesive strength test (2) was the same as the temperature in the thermocompression bonding in the initial adhesive strength test (1) described above.

The bonding/bonding layer 7 is formed on the back surface of the thermally conductive layer 6 as shown in FIG. 4 . Specifically, as shown in FIG. 1 , the bonding/bonding layer 7 is formed on the lower surface of the thermally conductive layer 6 facing the substrate 2 exposed from the electronic component 3 .

Adhesive/adhesive layer 7 has flexibility in a normal temperature atmosphere and a heated atmosphere, and has adhesiveness or cohesiveness (tackiness). Or an adhesive composition capable of exhibiting an adhesive effect (the effect of bonding, that is, the effect of pressure-sensitive bonding).

As an adhesive agent, a thermosetting adhesive agent, a hot-melt adhesive agent, etc. are mentioned, for example.

The thermosetting adhesive is solidified by thermal curing by heating, and adheres to the substrate 2 . Examples of thermosetting adhesives include epoxy-based thermosetting adhesives, polyurethane-based thermosetting adhesives, acrylic thermosetting adhesives, and the like. Preferably, epoxy-based thermosetting adhesives are 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 to be thermally fused to the substrate 2 , and then solidified by cooling to adhere to the substrate 2 . Examples of the hot-melt adhesive include rubber-based hot-melt adhesives, polyester-based hot-melt adhesives, and olefin-based hot-melt adhesives. Preferably, rubber-based hot-melt adhesives are used.

The softening temperature (ring and ball method) of the hot-melt adhesive is, for example, 100 to 200°C. In addition, the melt viscosity of the hot-melt adhesive is, for example, 100 to 30000 mPa·s at 180°C.

In addition, the above-mentioned adhesive may contain, for example, thermally conductive particles as necessary.

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

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

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

Examples of the shape of the heat conductive particles include a block shape, a needle shape, a flake shape, a layer shape, a tube shape, and the like. The average particle diameter (maximum length) of the heat conductive particles is, for example, 0.1 to 1000 μm.

In addition, the thermally conductive particles have, for example, anisotropic thermal conductivity or isotropic thermal conductivity. It preferably has isotropic thermal conductivity.

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

The mixing ratio of the heat conductive particles is, for example, 190 parts by mass or less, preferably 900 parts by mass or less, based on 100 parts by mass of the resin component of the adhesive. Moreover, the compounding ratio by volume of a heat conductive particle is 95 volume% or less, Preferably it is 90 volume% or less.

When mixing the thermally conductive particles into the adhesive, the thermally conductive particles are added to the adhesive in the above blending ratio, and stirred and mixed.

Thus, the adhesive was prepared as a thermally conductive adhesive.

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

As the adhesive, for example, it is suitably selected from the following known adhesives: acrylic adhesives, silicone adhesives, rubber adhesives, vinyl alkyl ether adhesives, polyester adhesives, Adhesives, polyamide adhesives, polyurethane adhesives, styrene-diene block copolymer adhesives, etc. Binders can be used alone or in combination of two or more. As the adhesive, preferably an acrylic adhesive, a silicone adhesive, and a rubber adhesive are used; more preferably, an acrylic adhesive and a silicone adhesive are used. In addition, the above-mentioned thermally conductive particles may be contained in the binder in the same ratio as above, and the binder may be prepared as a thermally conductive binder. The thermal conductivity of the thermally conductive adhesive is the same as above.

The thickness T of the bonding/bonding layer 7 is, for example, 50 μm or less, preferably 25 μm or less, more preferably 15 μm or less; usually 1 μm or more. When the thickness T of the adhesive/adhesive layer 7 exceeds the above-mentioned range, heat generated in the electronic component 3 may not be thermally conducted from the thermally conductive layer 6 to the frame 4 through the adhesive/adhesive layer 7 .

Then, in order to obtain the heat conductive adhesive sheet 5, as shown in FIG.

Specifically, a varnish is prepared by mixing the above-mentioned solvent with an adhesive (preferably a thermosetting adhesive) or an adhesive to dissolve it, and the varnish is coated on the surface of the separator, and then , The organic solvent of the varnish is distilled off by normal pressure drying or vacuum (reduced pressure) drying. Moreover, the solid content concentration of a varnish is 10-90 mass %, for example.

Thereafter, the adhesive/adhesive layer 7 is bonded to the heat conductive layer 6 . When bonding the adhesive/adhesive layer 7 and the thermally conductive layer 6, they are pressure-bonded or thermocompression-bonded as necessary.

Next, the manufacturing method of the heat radiation structure 1 is demonstrated using FIG. 5. FIG.

First, in this method, as shown in FIG. 5 , substrate 2 on which electronic components 3 are mounted is fixed to a case (not shown) supporting frame 4 , and thermally conductive adhesive sheet 5 is prepared.

In addition, the outer shape of the thermally conductive adhesive sheet 5 is processed so as to include the substrate 2 when projected in the thickness direction. Specifically, the thermally conductive adhesive sheet 5 is cut to a size such that its center and one end overlap the substrate 2 , and the other end does not overlap the substrate 2 .

Next, in this method, as shown in FIG. 5 , the thermally conductive adhesive sheet 5 is bonded to the electronic component 3 , the substrate 2 , and the frame 4 by thermocompression.

Specifically, the central part and one end of the thermally conductive adhesive sheet 5 are bonded to the electronic component 3 and the substrate 2 by thermocompression, and the other end of the thermally conductive adhesive sheet 5 is bonded to the frame 4 by thermocompression. .

In detail, first, as shown by the dotted line in FIG. The other end of the adhesive sheet 5 is bent.

Next, as indicated by the arrows in FIG. 5 , the central portion and one end of the thermally conductive adhesive sheet 5 are brought into contact with the electronic component 3 and the substrate 2 , and the other end of the thermally conductive adhesive sheet 5 is brought into contact with the frame. 4 contact, then, heat the thermally conductive adhesive sheet 5, and at the same time press the central part and one end of the thermally conductive adhesive sheet 5 toward the substrate 2 (press, ie thermocompression bonding), and apply the thermally conductive adhesive The other end of the connecting sheet 5 is crimped (pressed, that is, thermally crimped) toward the frame 4 .

For pressure bonding, for example, a sponge roller made of a resin such as silicone resin is rolled on the surface of the thermally conductive adhesive sheet 5 (upper surface of the thermally conductive layer 6 ) while pressing the thermally conductive adhesive sheet 5 .

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

In this thermocompression bonding, since the flexibility of the adhesive/adhesive layer 7 is improved, as shown in FIG. · Adhesive layer 7 is such that the surface (upper surface) of electronic component 3 is in contact with the back surface (lower surface) of thermally conductive layer 6 . In addition, a gap 14 formed around the electronic component 3 (for example, a gap between the resistor 23 and the substrate 2 ) is filled with the bonding/adhesive layer 7 . Furthermore, the adhesive/adhesive layer 7 is wound around and covers terminals and/or leads 15 (not shown) for connecting the electronic component 3 (specifically, the IC chip 20 and the resistor 23 ) and the substrate 2 .

In detail, the upper surface and the upper part of the side surface of the electronic component 3 are covered with the thermally conductive layer 6 .

On the other hand, the lower portion of the side surface of the electronic part 3 is covered (adhesive or bonded) with the adhesive·adhesive layer 7 pierced by the electronic part 3 .

More specifically, in thermocompression bonding, when the resin component 9 is a thermosetting resin component, the resin component 9 becomes a B-stage, so the thermally conductive layer 6 adheres to the surface (upper surface) of the substrate 2 exposed from the electronic component 3. ). Furthermore, when the thickness of the electronic component 3 is thicker than that of the bonding/bonding layer 7 , the upper part of the electronic component 3 enters the inside of the thermally conductive layer 6 from the back surface of the thermally conductive layer 6 .

In addition, when the adhesive is a hot-melt adhesive, the adhesive/adhesive layer 7 is melted or softened by the thermocompression bonding, and the central part and one end of the adhesive/adhesive layer 7 are bonded to the surface of the substrate 2. It is thermally welded to the side surface of the electronic component 3 , and the other end portion of the bonding/adhesive layer 7 is thermally welded to the inner surface of the frame 4 .

When the adhesive is a thermosetting adhesive, the adhesive/adhesive layer 7 is in a B-stage state by the thermocompression bonding, and the central portion and one end portion of the adhesive/adhesive layer 7 are temporarily fixed to the bottom of the substrate 2. The upper surface, the side surface of the electronic component 3 , and the other end of the adhesive/adhesive layer 7 are temporarily fixed to the inner surface of the frame 4 .

Thereafter, when the resin component 9 is a thermosetting resin component, the thermally conductive layer 6 is thermally cured, and when the adhesive is a thermosetting adhesive, the bonding/bonding layer 7 is thermally cured.

In order to thermally cure the thermally conductive layer 6 and the bonding/adhesive layer 7, for example, the frame 4 to which the thermally conductive adhesive sheet 5 is temporarily fixed, the substrate 2, and the electronic component 3 are put into a dryer. Conditions for thermosetting are: the heating temperature is, for example, 100 to 250° C., preferably 120 to 200° C.; the heating time is, for example, 10 to 200 minutes, preferably 60 to 150 minutes.

Thus, the central portion and one end portion of the thermally conductive adhesive sheet 5 are bonded to the electronic component 3 and the substrate 2 , and the other end portion of the thermally conductive adhesive sheet 5 is bonded to the frame 4 .

Next, in the above-mentioned heat dissipation structure 1, since the electronic component 3 is covered by the thermally conductive adhesive sheet 5, heat generated by the electronic component 3 can be thermally conducted from the upper surface and the side surface of the electronic component 3 to the thermally conductive adhesive sheet. Material 5. Then, the heat can be thermally conducted from the thermally conductive adhesive sheet 5 to the frame 4 and dissipated in the frame 4 to the outside.

Therefore, the heat generated by the electronic component 3 can be efficiently dissipated through the thermally conductive adhesive sheet 5 and the frame 4 .

In addition, the heat generated by the electronic component 3 can be dissipated due to the simple and excellent workability of disposing the heat conductive adhesive sheet 5 on the substrate 2 so as to cover the electronic component 3 .

Fig. 6 shows the sectional view of the other embodiment (form that the thermally conductive adhesive sheet is made of thermally conductive layer) of the heat dissipation structure of the present invention; Fig. 7 is a process diagram for making the heat dissipation structure of Fig. 6; Fig. 8 shows a cross-sectional view of another embodiment of the heat dissipation structure of the present invention (the other end of the thermally conductive adhesive sheet is in contact with the housing); FIG. 9 shows another embodiment of the heat dissipation structure of the present invention ( Adhesive/adhesive layer contacting the upper surface of the electronic component) is a cross-sectional view.

In addition, in each of the following drawings, the same reference numerals are given to members corresponding to the above-mentioned respective parts, and detailed description thereof will be omitted.

In the above description, although the thermally conductive adhesive sheet 5 is provided with the adhesive/adhesive layer 7, for example, as shown in FIG. A thermally conductive adhesive sheet 5 is formed.

In FIG. 6 , the side surface of electronic component 3 is in contact with thermally conductive layer 6 . Specifically, the upper surface of the substrate 2 exposed from the electronic component 3 and all side surfaces of the electronic component 3 are in contact with the thermally conductive layer 6 .

In order to obtain this heat dissipation structure 1, as shown in FIG. 7, the board|substrate 2 mounted with the electronic component 3 is fixed to the case (not shown) of the support frame 4, and the thermally conductive adhesive sheet 5 is prepared. The thermally conductive adhesive sheet 5 is composed of a thermally conductive layer 6 .

Next, as shown by the dotted line in FIG. 7, the thermally conductive adhesive sheet 5 is bent, and then, as shown by the arrows in FIG. Components 3 and substrate 2 , and the other end of thermally conductive adhesive sheet 5 is bonded to frame 4 by thermocompression.

In thermocompression bonding of the thermally conductive adhesive sheet 5, when the resin component 9 is a thermosetting resin component, since the resin component 9 becomes a B-stage state, the gap 14 formed around the electronic component 3 is covered by the thermally conductive layer 6. filling.

Thereby, the heat conductive adhesive sheet 5 is temporarily fixed to the board|substrate 2 and the frame 4. As shown in FIG.

Thereafter, when the resin component 9 is a thermosetting resin component, the thermally conductive layer 6 is thermally cured.

Thus, the central part and one end of the thermally conductive layer 6 are bonded to the upper surface and the side surface of the electronic component 3, and the upper surface of the substrate 2 exposed from the electronic component 3, and the other end of the thermally conductive layer 6 is Bonded to the right surface of frame 4.

In this heat dissipation structure 1 , the thermally conductive layer 6 is in direct contact with the surface of the electronic component 3 and the right side surface of the frame 4 . Therefore, the heat dissipation structure 1 of FIG. 6 can dissipate heat generated from the electronic component 3 through the heat conductive layer 6 more effectively than the heat dissipation structure 1 of FIG. 1 .

On the other hand, in the heat dissipation structure 1 of FIG. 1 , the thermally conductive layer 6 is bonded to the substrate 2 and the frame 4 through the bonding/adhesive layer 7. Therefore, compared with the heat dissipation structure 1 of FIG. The bonding sheet 5 is more reliably bonded, and can exhibit more excellent heat dissipation for a long time.

In addition, in the above description of FIG. 1 and FIG. 6, although the frame 4 was illustrated as the heat dissipation member in the present invention, the heat dissipation member is not limited thereto. For example, the case 10 ( FIG. 8 ), A heat sink (not shown), a reinforcing bundle (not shown), etc.

In FIG. 8 , the casing 10 has a bottomed box shape with an open upper side, and integrally includes a bottom wall 13 and a side wall 11 extending upward from the peripheral end thereof. The side wall 11 is arranged around the substrate 2 , and the bottom wall 13 is arranged under the substrate 2 . The casing 10 is formed of metal such as aluminum, stainless steel, copper, iron, or the like.

In addition, the other end portion from the central portion of the thermally conductive adhesive sheet 5 is bent downward from one end edge of the substrate 2; inner surface) extending downward. The other end of the thermally conductive adhesive sheet 5 is in contact with the lower portion of the right side surface of the frame 4 (specifically, the vicinity of the connecting portion between the side wall 11 and the bottom wall 13 ).

In addition, in the above description, although the adhesive/adhesive layer 7 is laminated on one side (back side) of the thermally conductive layer 6, for example, as shown by the dotted line in FIG. 1 and the dotted line in FIG. Both sides (front and back) of the adhesive sheet 5.

In addition, in the description of FIG. 1 above, the thermocompression bonding is carried out so that the adhesive/adhesive layer 7 is pierced by the electronic component 3, but for example, it may be implemented with reference to FIG. 9 so that the adhesive/adhesive layer 7 is not damaged. The electronic component 3 is pierced and covers the upper surface of the electronic component 3 .

Adhesive/adhesive layer 7 can be disposed so as to be in contact with the upper surface of electronic component 3 on the one hand, and not to be in contact with the upper surface of substrate 2 exposed from electronic component 3 on the other hand, and to be separated from the upper surface of substrate 2 by a certain interval ( Gap) configuration.

This heat dissipation structure 1 can also conduct heat from the electronic component 3 to the thermally conductive layer 6 through the bonding/adhesive layer 7 , and further, the heat conductive layer 6 can thermally transport the heat to the heat dissipation member 4 .

Example

The present invention will be described more specifically by showing preparation examples, examples, and production examples below, but the present invention is not limited to the examples at all.

Preparation of thermally conductive layer

Preparation Example 1

Mix 13.42g PT-110 (trade name, flaky boron nitride particles, average particle diameter (light scattering method) 45μm, manufactured by Momentive Performance Materials Japan.LLC), 1.0g JER828 (trade name, bisphenol A type epoxy Resin, No. 1 epoxy resin, liquid, epoxy equivalent 184-194g/eqiv., softening temperature (ring and ball method) less than 25°C, melt viscosity (80°C) 70mPa·s, manufactured by Japan Epoxy Resins Co., Ltd.) , and 2.0g EPPN-501HY (trade name, triphenylmethane type epoxy resin, the second epoxy resin, solid state, epoxy equivalent 163-175g/eqiv., softening temperature (ring and ball method) 57-63 ℃, Japan Kayaku Co., Ltd.) and 3 g (solid content 0.15 g) of a curing agent (Curezol 2P4MHZ-PW (trade name, manufactured by Shikoku Chemical Co., Ltd.) of 5% by mass methyl ethyl ketone dispersion) (with respect to epoxy resins, that is, JER828 and EPPN-501HY The total amount was 5% by mass) and stirred, and left overnight at room temperature (23° C.) to volatilize methyl ethyl ketone (a dispersant for a curing agent) to prepare a semi-solid mixture.

In addition, in the above compounding, the volume percentage (vol %) of the boron nitride particles was 70 vol% with respect to the total volume of the solid content excluding the curing agent (ie, the solid content of the boron nitride particles and the epoxy resin).

Next, sandwich the resulting mixture with two release films treated with silicone, and heat it for 2 minutes with a load of 5 tons (20 MPa) at 80° C. and an atmosphere of 10 Pa (vacuum atmosphere). Pressing, thereby obtaining a pressed sheet having a thickness of 0.3 mm (see (a) of FIG. 2 ).

Thereafter, the resulting pressed sheet is cut into multiple pieces when projected in the thickness direction of the pressed sheet to obtain a divided sheet (see FIG. 2( b )), and then the divided sheets are stacked in the thickness direction material to obtain a laminated sheet (see FIG. 2(c)).

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

Next, the above-mentioned series of operations of cutting, lamination, and heat pressing (see FIG. 2 ) were repeated four times to obtain a thermally conductive layer with a thickness of 0.3 mm (uncured state, see FIG. 3 ).

Preparation example 2-16

According to the compounding ratio and manufacturing conditions of Table 1-Table 3, the same process as Preparation Example 1 was performed, and the thermally conductive layer was obtained (Preparation Examples 2-16, refer FIG. 3).

Production of thermally conductive adhesive sheets

Production example 1

A varnish of an acrylic adhesive (solvent: MEK, solid content concentration: 50% by mass, filler-free type) was applied on the surface of the separator so that the thickness when dried was 10 μm. Next, MEK was distilled off by vacuum drying to form an adhesive layer.

Next, the adhesive layer of Preparation Example 1 was pressure-bonded to the thermally conductive layer, thereby producing a thermally conductive adhesive sheet (see FIG. 4 ).

Production examples 2 to 16

Except having used the heat conductive layers of Preparation Examples 2-16, respectively, it processed similarly to Preparation Example 1, and obtained the heat conductive adhesive sheet (Preparation Examples 2-16) (refer FIG. 4).

Fabrication of heat dissipation structure

Example 1

A flat board made of polyimide, electronic components mounted thereon (IC chip 2 mm thick, capacitor 1 mm, coil 4 mm, resistor 0.5 mm), and a frame (see FIG. 5 ) were prepared.

Next, the thermally conductive adhesive sheet of Production Example 1 was cut into a size such that the central portion and one end overlap the substrate, and the other end does not overlap the substrate.

Next, the thermally conductive adhesive sheet and the substrate are arranged such that the central portion and one end of the adhesive layer face the electronic component, and then the other end of the thermally conductive adhesive sheet is bent upward, and thereafter, Using a sponge roller made of silicone resin, the thermally conductive adhesive sheet was crimped (temporarily fixed) toward the electronic component and the frame (see FIG. 9 ).

As a result, the central portion and one end portion of the thermally conductive adhesive sheet are bonded to the upper surface of the electronic component, and the other end portion of the thermally conductive adhesive sheet is bonded to the frame.

In addition, gaps are formed between the central portion and one end portion of the thermally conductive adhesive sheet and the substrate exposed from the electronic component (see FIG. 9 ).

Examples 2-16

Except for using the thermally conductive adhesive sheets of Production Examples 2 to 16 described in Table 4 instead of the thermally conductive adhesive sheet of Production Example 1, heat dissipation structures were formed in the same manner as in Example 1 (Examples 2 to 16). 16).

Example 17

Except not having provided the adhesive layer in preparation of a heat conductive adhesive sheet, it carried out similarly to Example 1, and produced the heat radiation structure (refer FIG. 6).

Examples 18-32

Except not having provided the adhesive layer in preparation of a heat conductive adhesive sheet, it carried out similarly to Examples 2-16, and produced the heat radiation structure (Examples 18-32) (refer FIG. 6).

evaluate

1. Thermal conductivity

The thermal conductivity of the thermally conductive layers of 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 lamp analyzer "LFA-447" (manufactured by NETZS CH).

The results are shown in Tables 1 to 3.

2. Porosity (P)

The porosity (P1) of the heat conductive layer before thermosetting of Preparation Examples 1-16 was measured by the following method.

Measuring method of porosity: Firstly, cut the thermally conductive sheet along the thickness direction with a cross-section polisher (CP), and observe the resulting cross-section with a scanning electron microscope (SEM) at 200 times to obtain an image. Thereafter, from the obtained image, the void portion and other portions were binarized, and then the area ratio of the void portion to the cross-sectional area of the entire thermally conductive sheet was calculated.

The results are shown in Tables 1 to 3.

3. Height difference followability (three-point bending test)

The thermally conductive layers before thermosetting of Production Examples 1 to 16 were subjected to a three-point bending test in accordance with JIS K7171 (2008) under the following test conditions to evaluate height difference followability according to the following evaluation criteria. The results are shown in Tables 1 to 3.

Test conditions

Test piece: size 20mm×15mm

Distance between fulcrums: 5mm

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

Bending angle: 120 degrees

Evaluation benchmark

⊚: No breakage was observed at all.

◯: Cracks are hardly observed.

x: Cracks were clearly observed.

4. Recognition of printed marks (printed mark adhesion: by inkjet printing or Laser printing marking adhesion)

Marks were printed on the thermally conductive layers of Preparation Examples 1 to 16 by inkjet printing and laser printing, and the marks were observed.

As a result, in any of the thermally conductive layers of Preparation Examples 1 to 16, marks by both inkjet printing and laser printing could be recognized favorably, and it was confirmed that the print mark adhesion was good.

5. Volume resistance

The volume resistance (R) of the thermally conductive layers of Preparation Examples 1-16 was measured.

That is, the volume resistance (R) of the thermally conductive layer was measured in accordance with JIS K 6911 (General Test Methods for Thermosetting Plastics, 2006 Edition).

The results are shown in Tables 1 to 3.

6. Initial adhesion test

6-1. Initial adhesion test to notebook mounting substrates

For the uncured thermally conductive layers of Preparation Examples 1 to 16, the initial adhesion tests (1) and (2) were implemented with respect to a mounting board for notebooks on which a plurality of electronic components were mounted.

That is, using a sponge roller made of silicone resin, heat-compression bond the thermally conductive layer to a notebook in the horizontal direction at 80°C (Preparation Examples 1 to 9 and Preparation Examples 11 to 16) or 120°C (Preparation Example 10). The surface of the computer mounting board was temporarily fixed, and after leaving it for 10 minutes, the notebook mounting board was placed in the vertical direction (initial adhesion test (2)).

Next, the mounting substrate for a notebook computer was set so that the thermally conductive layer was directed downward (that is, it was turned upside down from the state just temporarily fixed) (initial adhesion test (1)).

Next, in the above-mentioned initial adhesion test (1) and initial adhesion test (2), the thermally conductive layer was evaluated according to the following criteria. The results are shown in Tables 1 to 3.

standard

◯: It was confirmed that the thermally conductive layer did not fall off from the mounting substrate for notebook personal computers.

x: It was confirmed that the thermally conductive layer was peeled off from the mounting substrate for notebook personal computers.

6-2. Initial adhesion test to stainless steel substrate

About the uncured heat conductive layer of the preparation examples 1-16, the initial stage adhesive force test (1) and (2) with respect to the stainless steel board|substrate (made by SUS304) were implemented similarly to the above.

Next, in the above-mentioned initial adhesion test (1) and initial adhesion test (2), the thermally conductive layer was evaluated according to the following criteria. The results are shown in Tables 1 to 3.

standard

◯: It was confirmed that the thermally conductive layer did not come off the stainless steel substrate.

×: It was confirmed that the thermally conductive layer was peeled off from the stainless steel substrate.

7. Volume resistance

The volume resistance (R) of the uncured heat conductive layer of Preparation Examples 1-16 was measured.

That is, the volume resistance (R) of the thermally conductive layer was measured in accordance with JIS K 6911 (General Test Methods for Thermosetting Plastics, 2006 Edition).

The results are shown in Tables 1 to 3.

8. Heat dissipation

The electronic components in the heat dissipation structures of Examples 1 to 32 were operated for one hour. The surface temperature of the thermally conductive adhesive sheet during operation was measured with an infrared camera, and it was 70° C., and it was confirmed that the temperature rise was suppressed.

On the other hand, when the same evaluation was performed on the substrate not using the thermally conductive adhesive sheet (the substrate in the heat dissipation structure of Comparative Example 1), the temperature vertically above the electronic component was 130°C.

From this, it was confirmed that the heat dissipation structures of Examples 1 to 32 were excellent in heat dissipation.

Table 1

g ^＊A : Fitting mass

[Volume%] ^*B : Percentage relative to the total volume of the thermally conductive sheet (excluding curing agent)

[Volume%] ^*C : Percentage relative to the total volume of the thermally conductive sheet

Number of times] ^＊D : Number of times of hot pressing of the laminated sheet

Table 2

g ^＊A : Fitting mass

[Volume%] ^*B : Percentage relative to the total volume of the thermally conductive sheet (excluding curing agent)

[Volume%] ^*C : Percentage relative to the total volume of the thermally conductive sheet

Number of times ^＊D : The number of times of hot pressing of laminated sheets

table 3

g ^＊A : Fitting mass

[Volume%] ^*B : Percentage relative to the total volume of the thermally conductive sheet (excluding curing agent)

[Volume%] ^*C : Percentage relative to the total volume of the thermally conductive sheet

Number of times ^＊D : The number of times of hot pressing of laminated sheets

Table 4

The numerical value in each component in Table 1 - Table 3 shows the number of grams unless otherwise indicated.

In addition, in the column of boron nitride particles in Tables 1 to 3, the upper value is the compounding mass (g) of boron nitride particles, and the middle value is the solid content of the thermally conductive sheet excluding the curing agent. (that is, the total volume of boron nitride particles, and the solid content of epoxy resin or polyethylene), the volume percentage (volume %) of boron nitride particles, and the following values are relative to the solid content of the thermally conductive sheet (that is, , the total volume of boron nitride particles, and the solid content of epoxy resin or curing agent), the volume percentage (volume %) of boron nitride particles.

In addition, for each component in Tables 1 to 3, the details of the components marked with * are described below.

PT-100 ^*1 : Trade name, flaky boron nitride particles, average particle size (light scattering method) 45 μm, manufactured by Momentive Performance Materials Japan LLC

UHP-1 ^*2 : Trade name: SHOBN UHP-1, flake-shaped boron nitride particles, average particle size (light scattering method) 9 μm, manufactured by Showa Denko

Epoxy Resin A ^※3 : OGSOL EG (trade name), bisaryl fluorene type epoxy resin, semi-solid, epoxy equivalent 294g/eqiv., softening temperature (ring and ball method) 47°C, melt viscosity (80°C) 1360mPa s, manufactured by Osaka Gas Chemicals Co., Ltd.

Epoxy Resin B ^※4 : JER828 (trade name), bisphenol A type epoxy resin, liquid, epoxy equivalent 184～194/eqiv., softening temperature (ring and ball method) less than 25°C, melt viscosity (80°C) 70mPa s, manufactured by Japan Epoxy Resins Co., Ltd.

Epoxy Resin C ^※5 : JER1002 (trade name), bisphenol A type epoxy resin, solid, epoxy equivalent 600~700g/eqiv., softening temperature (ring and ball method) 78°C, melt viscosity (80°C) 10000mPa · s or more (above the measurement limit), manufactured by Japan EpoxyResins Co., Ltd.

Epoxy resin D ^※6 : EPPN-501HY (trade name), triphenylmethane type epoxy resin, solid state, epoxy equivalent 163-175/eqiv., softening temperature (ring and ball method) 57-63 ℃, Nippon Kayaku Co., Ltd. manufacture

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

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

Polyethylene ^*9 : Low-density polyethylene, weight average molecular weight (Mw) 4000, number average molecular weight (Mn) 1700, manufactured by Aldrich

In addition, although the above-mentioned description is provided as an exemplary embodiment of the present invention, this is merely an illustration and should not be interpreted as a limitation. Modifications of the present invention that are obvious to those skilled in the art are also included in the scope of the patent claims.

Claims (2)

1. a heat-radiating structure is characterized in that,

It possesses substrate, be installed on the electronic component of described substrate, be used for the thermal diffusivity member that will be dispelled the heat by the heat that described electronic component produces and be arranged at thermal conductivity adhesive sheet on the described substrate in the mode that covers described electronic component,

Described thermal conductivity adhesive sheet possesses the thermal conductivity layer of the boron nitride particle that contains sheet,

Thermal conductivity with direction described thermal conductivity layer thickness direction quadrature described thermal conductivity layer is more than the 4W/mK,

Described thermal conductivity adhesive sheet contacts with described thermal diffusivity member.

2. heat-radiating structure according to claim 1 is characterized in that,

Described thermal conductivity adhesive sheet has the bond layer or the adhesive phase of one side at least that is layered in described thermal conductivity layer,

Described bond layer or described adhesive phase and described substrate bonding or bonding.

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