JP6298243B2 - Thermally conductive laminate for electronic equipment - Google Patents

Description

  The present invention relates to a heat conductive laminate for electronic equipment for efficiently radiating heat inside the electronic equipment to the outside.

  In electronic devices that require miniaturization, such as smartphones, electronic components that are densely integrated generate a large amount of heat, and this heat causes failure. A heat sink material is provided. Since the heat sink material is generally provided between an electronic component that is a heating element and a metal casing, a heat radiation grease or a heat radiation gel with high unevenness followability, and urethane foam are impregnated with the heat radiation material. The thing etc. are used (for example, patent document 1).

JP 2003-31980 A

Although the heat dissipating grease has good heat dissipating property, once the grease is applied, it is difficult to reapply it, and there is a problem that the yield of the product is lowered. On the other hand, the heat-dissipating gel is generally difficult to process into a sheet having a thickness of 1 mm or less, and there is a problem that the shape is deformed when compressed. Furthermore, there is a problem that a thin sheet has high compressive strength and low flexibility.
The urethane foam is difficult to be processed into a sheet with a thickness of 1 mm or less due to its manufacturing method, and a thin sheet-like molded product is difficult to increase the expansion ratio. There is a problem of loss of sex.

  The present invention has been made in view of the above-described conventional problems, and has a thinness and flexibility that can be suitably used inside an electronic device, and has excellent thermal conductivity. An object of the present invention is to provide a conductive laminate.

  The present invention provides a thermal conductivity having a thermal conductivity of 200 W / m · K or more on at least one surface of a foam sheet having a 25% compressive strength of 200 kPa or less and a thickness of 0.05 to 1.0 mm. And a heat conductive laminate for electronic equipment having a thickness of 0.08 to 1.50 mm.

  ADVANTAGE OF THE INVENTION According to this invention, the heat conductive laminated body for electronic devices which has the thinness and the softness | flexibility which can be used conveniently inside an electronic device, and is excellent in thermal conductivity can be provided.

It is a figure which shows the apparatus for measuring the thermal radiation performance of the laminated body created in the Example and the comparative example.

  The heat conductive laminate for electronic equipment of the present invention has a thermal conductivity of 200 W on at least one surface of a foam sheet having a 25% compressive strength of 200 kPa or less and a thickness of 0.05 to 1.0 mm. It has a heat conductive sheet that is not less than / m · K and has a thickness of 0.08 to 1.50 mm.

<Foam sheet>
The 25% compressive strength of the foam sheet used in the present invention is 200 kPa or less. When the compressive strength exceeds 200 kPa, the flexibility of the foam sheet decreases, which is not preferable. From the viewpoint of the flexibility of the foam sheet, the 25% compressive strength of the foam sheet is preferably 5 kPa or more, more preferably 50 kPa or more, further preferably 55 kPa or more, and preferably 190 kPa or less, more preferably 180 kPa or less, 150 kPa or less is still more preferable, and 100 kPa or less is still more preferable.
The specific numerical value of the 25% compressive strength of the foam sheet is preferably 5 to 190 kPa, more preferably 50 to 190 kPa, still more preferably 50 to 150 kPa, and still more preferably 55 to 100 kPa.

The foam sheet used in the present invention is composed of an elastomer resin containing 10% by mass or more of a liquid elastomer, and the 50% compressive strength of the foam sheet is preferably 200 kPa or less. If the 50% compressive strength of the foam sheet is 200 kPa or less, it can be suitably used for thin electronic devices such as mobile terminals.
From the viewpoint of improving flexibility, the 50% compressive strength of the foam sheet is more preferably 150 kPa or less, and even more preferably 100 kPa or less.
The liquid elastomer content in the elastomer resin is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less.

  The thickness of the foam sheet is 0.05 to 1 mm. When the thickness of the foam sheet is less than 0.05 mm, the foam sheet is easily torn, and when it exceeds 1 mm, it is difficult to use the foam sheet in a small electronic device. From the viewpoint of the strength of the foam sheet, the thickness of the foam sheet is preferably 0.05 to 0.8 mm, more preferably 0.05 to 0.7 mm, and still more preferably 0.05 to 0.5 mm.

  The thermal conductivity of the foam sheet is preferably 0.01 to 10 W / m · K, and more preferably 0.05 to 2 W / m · K. When the thermal conductivity of the foam sheet is within the above range, it becomes possible to efficiently dissipate heat inside the electronic device to the outside.

The foaming ratio of the foam sheet is preferably 1.5 to 6 times, and more preferably 1.5 to 5.5 times. When the foaming ratio of the foam sheet is within the above range, both the thinness and flexibility of the sheet can be achieved.
The apparent density of the foam sheet is preferably about 0.1 to 1.5 g / cm ³ , and preferably about 0.15 to 1.2 g / cm ³ .

<Thermal conductive sheet>
In the present invention, a thermal conductive sheet having a thermal conductivity of 200 W / m · K or more is provided on at least one surface of the foam sheet. In the present invention, by providing this thermally conductive sheet, the heat inside the electronic device can be radiated to the outside of the device even more efficiently. From the viewpoint of efficiently releasing heat to the outside, the thermal conductivity of the heat conductive sheet is preferably 300 to 3,000 W / m · K, and more preferably 300 to 2,000 W / m · K.
The thermal conductive sheet may be anything as long as it satisfies the range of the thermal conductivity, and specifically, copper, aluminum, gold, silver, iron, graphite, graphene, and the like are preferable.
The heat conductive sheet is preferably 3 to 500 μm, and more preferably 20 to 170 μm, from the viewpoint of use in a precision instrument.

<Laminate>
The thickness of the laminate of the present invention is 0.08 to 1.50 mm. When the thickness of the laminated body is less than 0.08 mm, it is easily broken, and when it exceeds 1.50 mm, it is difficult to use it for a gap inside a small electronic device. The thickness of the laminate is preferably from 0.1 to 1.25 mm, more preferably from 0.2 to 0.95 mm.

<Elastomer resin>
Examples of elastomer resins that can be used in the present invention include acrylonitrile butadiene rubber, liquid acrylonitrile butadiene rubber, linear low density polyethylene, ethylene-propylene-diene rubber, liquid ethylene-propylene-diene rubber, ethylene-propylene rubber, and liquid ethylene-propylene. Rubber, natural rubber, liquid natural rubber, polybutadiene rubber, liquid polybutadiene rubber, polyisoprene rubber, liquid polyisoprene rubber, styrene-butadiene block copolymer, liquid styrene-butadiene block copolymer, hydrogenated styrene-butadiene block copolymer Coal, liquid hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, liquid hydrogenated styrene-butadiene-styrene block Copolymer, hydrogenated styrene-isoprene block copolymer, liquid hydrogenated styrene-isoprene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, liquid hydrogenated styrene-isoprene-styrene block copolymer, etc. Among these, acrylonitrile butadiene rubber, liquid acrylonitrile butadiene rubber, ethylene-propylene-diene rubber, liquid ethylene-propylene-diene rubber, and linear low density polyethylene are preferable.

<Thermal conductive filler>
In the present invention, a heat conductive filler may be contained in the elastomer resin. Examples of the thermally conductive filler include aluminum oxide, magnesium oxide, boron nitride, talc, aluminum nitride, graphite, and graphene. Among these, aluminum oxide and magnesium oxide are preferable. These heat conductive fillers may be used individually by 1 type, and 2 or more types may be mixed and used for them.
The thermal conductivity of the thermally conductive filler is preferably 5 W / m · K or more, and more preferably 20 W / m · K or more. When the thermal conductivity is within the above range, the thermal conductivity of the foam sheet is sufficiently high.

  The content of the heat conductive filler is preferably 100 to 500 parts by mass, more preferably 120 to 480 parts by mass, and more preferably 150 to 450 parts by mass with respect to 100 parts by mass of the elastomer resin. If content of a heat conductive filler exists in the said range, sufficient heat conductivity can be provided, without reducing the softness | flexibility of a foam sheet.

<Optional component>
In the present invention, various additive components can be contained as necessary within the range in which the object of the present invention is not impaired.
The kind of the additive component is not particularly limited, and various additives usually used for foam molding can be used. Examples of such additives include lubricants, shrinkage inhibitors, cell nucleating agents, crystal nucleating agents, plasticizers, colorants (pigments, dyes, etc.), ultraviolet absorbers, antioxidants, anti-aging agents, and the above-described conductivity imparting. Examples include fillers excluding materials, reinforcing agents, flame retardants, flame retardant aids, antistatic agents, surfactants, vulcanizing agents, and surface treatment agents. The addition amount of the additive can be appropriately selected within a range that does not impair the formation of bubbles and the like, and the addition amount used for normal resin foaming and molding can be adopted. Such additives can be used alone or in combination of two or more.

  The lubricant has the effect of improving the fluidity of the resin and suppressing the thermal deterioration of the resin. The lubricant used in the present invention is not particularly limited as long as it has an effect on improving the fluidity of the resin. For example, hydrocarbon lubricants such as liquid paraffin, paraffin wax, microwax, polyethylene wax; fatty acid lubricants such as stearic acid, behenic acid, 12-hydroxystearic acid; butyl stearate, monoglyceride stearate, pentaerythritol tetrastearate And ester lubricants such as hydrogenated castor oil and stearyl stearate.

  The addition amount of the lubricant is preferably about 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, and still more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the resin. If the amount added exceeds 5 parts by mass, the fluidity may become too high and the expansion ratio may decrease, and if it is less than 0.01 parts by mass, the fluidity cannot be improved, and the stretchability at the time of foaming is low. There is a risk that the expansion ratio will decrease.

Examples of the flame retardant include bromine-based flame retardants such as decabromodiphenyl ether and phosphorus-based flame retardants such as ammonium polyphosphate in addition to metal hydroxides such as aluminum hydroxide and magnesium hydroxide.
Antimony compounds such as antimony trioxide, antimony tetroxide, antimony pentoxide, sodium pyroantimonate, antimony trichloride, antimony trisulfide, antimony oxychloride, antimony perchloropentane dichloride, potassium antimonate, etc. And boron compounds such as zinc metaborate, zinc tetraborate, zinc borate, basic zinc borate, zirconium oxide, tin oxide, molybdenum oxide, and the like.

<Method for producing foam sheet>
The heat conductive laminate for electronic equipment of the present invention can be produced by a known chemical foaming method or physical foaming method, and the production method is not particularly limited.
In addition, the foaming processing method can use a well-known method including the method described in the plastic foam handbook (Makihiro, Atsushi Kosaka edit Nikkan Kogyo Shimbun 1973).

Examples The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
The materials used in the following examples and comparative examples are as follows.
(1) Linear low density polyethylene Nippon Polyethylene Corporation, trade name “Kernel KF370”
Density: 1.00 g / cm ³
(2) Acrylonitrile butadiene rubber (NBR)
Product name “Nipol 1041” manufactured by Nippon Zeon Co., Ltd.
Density: 1.00 g / cm ³
Acrylonitrile component: 40.5% by mass
(3) Ethylene-propylene rubber-diene rubber (EPDM)
Product name “EP21” manufactured by JSR Corporation
Density: 0.86 g / cm ³
Propylene content: 34% by mass
(4) Liquid ethylene-propylene-diene rubber (liquid EPDM)
Product name “PX-068” manufactured by Mitsui Chemicals, Inc.
Density: 0.9 g / cm ³
Propylene content: 39% by mass
(5) Azodicarbonamide, trade name “SO-L” manufactured by Otsuka Chemical Co., Ltd.
(6) Aluminum oxide
Micron Corporation, spherical alumina, trade name “AX3-32”, average particle size 3 μm
(7) Magnesium oxide manufactured by Ube Materials Co., Ltd., trade name “RF-10C-SC”, round crushed product,
Average particle size 4μm
(8) Phenol antioxidant manufactured by Ciba Specialty Chemicals Co., Ltd., trade name “Irganox 1010”

<Examples 1-4, Comparative Examples 1-4>
Example 1
By melt-kneading 100 parts by mass of linear low density polyethylene obtained by using a metallocene compound as a polymerization catalyst, 3.0 parts by mass of azodicarbonamide, and 0.1 parts by mass of a phenolic antioxidant, and then pressing A foamable resin sheet having a thickness of 0.36 mm was obtained.
Next, the foamable resin sheet was foamed by heating the sheet to 250 ° C. after cross-linking the foamable resin sheet by irradiating the foamable resin sheet with 4 Mrad of an electron beam with an acceleration voltage of 500 kV on both surfaces. A foam sheet having an apparent density of 0.20 g / cm ³ and a thickness of 0.5 mm was obtained.
A copper foil tape with a thickness of 150 μm (3M tape No: 2194) was bonded to one surface of the obtained foam sheet to obtain a laminate of the foam and the copper foil.

Example 2
A foamable resin sheet having a thickness of 0.4 mm is obtained by melting and kneading 100 parts by mass of acrylonitrile butadiene rubber, 15 parts by mass of azodicarbonamide, 400 parts by mass of aluminum oxide, and 0.1 parts by mass of a phenolic antioxidant, and then pressing. Got.
Both surfaces of the obtained foamable resin sheet were irradiated with an electron beam of 1.2 Mrad at an acceleration voltage of 500 keV to crosslink the foamable resin sheet. Next, the foamable resin sheet was foamed by heating the sheet to 250 ° C. to obtain a foam sheet having an apparent density of 0.98 g / cm ³ and a thickness of 0.5 mm.
A copper foil tape with a thickness of 150 μm (3M tape No: 2194) was bonded to one surface of the obtained foam sheet to obtain a laminate of the foam and the copper foil.

Example 3
After melt-kneading 70 parts by mass of ethylene-propylene-diene rubber, 30 parts by mass of liquid ethylene-propylene-diene rubber, 17.5 parts by mass of azodicarbonamide, 400 parts by mass of aluminum oxide, and 0.1 parts by mass of phenolic antioxidant, A foamable resin sheet having a thickness of 0.4 mm was obtained by pressing.
The foamable resin sheet was crosslinked by irradiating 3.0 Mrad of an electron beam at an acceleration voltage of 500 keV on both surfaces of the obtained foamable resin sheet. Next, the foamable resin sheet was foamed by heating the sheet to 250 ° C. to obtain a foam sheet having an apparent density of 0.47 g / cm ³ and a thickness of 0.5 mm.
A copper foil tape with a thickness of 150 μm (3M tape No: 2194) was bonded to one surface of the obtained foam sheet to obtain a laminate of the foam and the copper foil.

Example 4
60 parts by mass of ethylene-propylene-diene rubber, 40 parts by mass of liquid ethylene-propylene-diene rubber, 17 parts by mass of azodicarbonamide, 360 parts by mass of magnesium oxide, and 0.1 parts by mass of phenolic antioxidant are melt-kneaded and then pressed. Thus, a foamable resin sheet having a thickness of 0.4 mm was obtained.
The foamable resin sheet was crosslinked by irradiating 3.0 Mrad of an electron beam at an acceleration voltage of 500 keV on both surfaces of the obtained foamable resin sheet. Next, the foamable resin sheet was foamed by heating the sheet to 250 ° C. to obtain a foam sheet having an apparent density of 0.60 g / cm ³ and a thickness of 0.5 mm.
A copper foil tape with a thickness of 150 μm (3M tape No: 2194) was bonded to one surface of the obtained foam sheet to obtain a laminate of the foam and the copper foil.

Comparative Example 1
A foam sheet was obtained in the same manner as in Example 1 except that the copper foil was not bonded.
Comparative Example 2
A foam sheet was obtained in the same manner as in Example 2 except that the copper foil was not bonded.
Comparative Example 3
A foam sheet was obtained in the same manner as in Example 3 except that the copper foil was not attached and the expansion ratio was changed as shown in Table 1.
Comparative Example 4
A foam sheet was obtained in the same manner as in Example 4 except that the copper foil was not bonded.

<Physical properties>
The physical properties of the obtained foam sheet were measured as follows. Each measurement result is shown in Table 1.
[25% compressive strength]
The 25% compressive stress in the thickness direction of the foam sheet was measured according to JIS K6767-7.2.3 (JIS2009).
[Foaming ratio]
The expansion ratio was calculated by dividing the specific gravity of the foam sheet by the specific gravity of the foamable sheet. [Thermal conductivity of foam sheet]
The thermal conductivity was measured at 25 ° C. using “TC-7000” manufactured by ULVAC-RIKO Co., Ltd. by a laser flash method.
[Apparent density]
It measured based on JISK7222.
[Heat conduction performance]
As shown in FIG. 1, a heater of 25 mm × 25 mm × 2 mm (Sakaguchi Electric Heat Co., Ltd. micro ceramic heater, model number “MS5”) is placed on a heat insulating material, and stainless steel of 60 mm × 100 mm × 0.6 mm is placed thereon. Stack the plates (SUS304). Further, a sample 60 mm × 100 mm and a glass plate 60 mm × 100 mm × 0.5 mm created in the examples and comparative examples are stacked thereon. In this state, 2.6 W of electric power (power that rises to 90 ° C with the heater alone) is applied to the heater, and when the heater temperature becomes constant after 15 minutes, the temperature [T] (° C) is measured. did. A smaller value indicates better heat conduction performance.

  From the results of Examples and Comparative Examples, it can be seen that the thermally conductive laminate for electronic equipment of the present invention has excellent thermal conductivity as well as being thin and flexible.

Claims (6)

At least one surface of a foam sheet having a 25% compressive strength of 50 to 190 kPa, a thickness of 0.05 to 1.0 mm, and an apparent density of 0.1 to 1.5 g / cm ³ , Thermally conductive laminate for electronic equipment having a thermal conductive sheet having a thermal conductivity of 200 W / m · K or more, wherein the foam sheet is made of an elastomer resin and has a thickness of 0.08 to 1.50 mm body.   The electronic device according to claim 1, wherein the elastomer resin constituting the foam sheet contains at least one heat conductive filler selected from the group consisting of aluminum oxide, magnesium oxide, boron nitride, talc, and aluminum nitride. Thermally conductive laminate.   The heat conductive laminated body for electronic devices of Claim 2 whose content of the said heat conductive filler with respect to 100 mass parts of said elastomer resins is 100-500 mass parts.   The thermally conductive laminate for an electronic device according to any one of claims 1 to 3, wherein the foam sheet has an expansion ratio of 1.5 to 6 times.   The thermally conductive laminate for an electronic device according to any one of claims 1 to 4, wherein the thermally conductive sheet is a sheet selected from copper, aluminum, and graphite. The thermally conductive laminate for an electronic device according to any one of claims 1 to 5, wherein the elastomer resin constituting the foam sheet is acrylonitrile butadiene rubber or linear low density polyethylene.