JP2005272648A - Method for producing thermally conductive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a thermally conductive material satisfying both of the high heat conductivity and the softness at a low cost by reducing the amount of a thermally conductive filler added. <P>SOLUTION: This method for producing the thermally conductive material comprises mixing and dispersing a thermally conductive filler having high polarity into a nonpolar and crosslinkable polymer material to prepare a composition, carrying out heat treatment of the composition once under conditions not causing crosslinkage and then crosslinking the heat-treated composition. By formulating the thermally conductive filler having high polarity into the non-polar polymer material lowering viscosity at high temperature, the viscosity of the polymer material is lowered and fluidity of the polymer material is raised when heat-treated, and thermally conductive fillers are made to aggregate to each other and link is readily formed by affinity among thermally conductive fillers. As a result, the thermally conductive material having high thermal conductivity can be obtained. In addition, the production method, does not require formulation of the thermally conductive filler in high content and impart flexibility as well as high thermal conductivity to the thermally conductive material, because thermal conductivity obtained when the conductive material is formulated in a small amount is equivalent to or higher than the thermal conductivity obtained when formulated in a large amount. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a heat conductive material having excellent heat dissipation, and more particularly to a method for manufacturing a heat conductive material in which the heat conductive filler is aggregated in a compound by heat treatment.

  In recent years, LSIs such as CPUs, driver ICs, and memories used in electronic devices such as personal computers, digital video disks, and mobile phones have increased power consumption and heat generation as the degree of integration has increased and the operation speed has increased. As a result, it has become a cause of malfunction of electronic devices and damage of electronic components, so that heat dissipation measures have become a major problem. In addition, in recent years, resinization of the parts that used ceramic substrates has been progressing, but in this case, the thermal conductivity of the substrate itself has decreased, and heat dissipation measures have been recognized as a very important issue. Yes.

  Conventionally, in an electronic device or the like, a heat sink using a metal plate having a high thermal conductivity such as brass is used in order to suppress the temperature rise of the electronic component during use. The heat sink conducts heat generated by the electronic component and releases the heat from the surface due to a temperature difference from the outside air. In order to efficiently transfer the heat generated from the electronic component to the heat sink, the heat sink needs to be in close contact with the electronic component. A heat conduction sheet or the like is used as an interface between the electronic component and the heat sink to efficiently heat the electronic component. Conducting. In addition, heat countermeasures are taken by attaching a heat-dissipating sheet having a higher thermal conductivity than the substrate to the resin substrate.

  However, recent electronic equipment-related parts have been processed at high speed and the amount of heat generation has increased, so that conventional thermal conductive sheets are often unable to take heat countermeasures due to insufficient thermal conductivity.

  Therefore, Patent Document 1 and Patent Document 2 describe the use of a heat conductive sheet or the like highly filled with a heat conductive filler such as diamond or boron nitride having high heat conductivity.

  In addition, if the affinity between the polymer material and the heat conductive filler (such as intermolecular force) is strong, the heat conductive filler can be efficiently dispersed in the polymer material. The property is deteriorated because the dispersion of the filler is improved. This is because there is a polymer material with low thermal conductivity between the filler and the heat conduction is hindered (phonon lattice vibration is attenuated). Therefore, in general, the heat conductive sheet is mixed with a large amount of a heat conductive filler in a polymer material, or close-packed with fillers having different particle sizes so that the matrix component is reduced as much as possible. The composition is made and high heat conductivity is aimed at. (Patent Document 3)

JP 2002-30217 A JP 2000-195337 A JP 2000-151160 A

  However, if a large amount of expensive thermally conductive filler is used as in the prior art, there is a problem that the cost is increased and the flexibility of the sheet is lost. It has been difficult to produce a heat conductive material with both high thermal conductivity and flexibility.

  The present invention addresses such problems, and provides a method for producing a low-cost thermally conductive material by reducing the amount of thermally conductive filler added to achieve both high thermal conductivity and flexibility. .

  The invention described in claims 1 and 2 of the present invention is a mixture prepared by mixing and dispersing a nonpolar crosslinkable polymer material with a heat conductive filler having high polarity, and under a condition that the composition is not crosslinked. There is a method for producing a heat conductive material that is once heat-treated and crosslinked, and a non-polar thermoplastic polymer material is mixed and dispersed with a heat conductive filler having a high polarity to produce a composition. This is a method for producing a heat conductive material that is solidified after heat treatment under conditions where the product is not cross-linked, and thus has a high polarity in a polymer material that is nonpolar and undergoes low viscosity at high temperatures. When the heat conductive filler is added, the viscosity of the polymer material decreases and the fluidity increases during the heat treatment, and heat is generated by the affinity between the heat conductive fillers (dipole-dipole interaction). Conductive fillers aggregate and form links It is possible to obtain a thermally conductive material having high thermal conductivity is easier. In addition, it is not necessary to add a high amount of heat conductive filler, and even a small amount can provide a thermal conductivity equal to or higher than that of the high compound, so that flexibility can be imparted in addition to high heat conductivity.

  The inventions according to claims 3 to 5 of the present invention are characterized in that the nonpolar crosslinkable polymer material is at least one synthetic rubber selected from isoprene rubber, butadiene rubber, styrene butadiene rubber, butyl rubber, ethylene propylene rubber, and silicone rubber. In the case where the heat conductive filler having a high polarity is blended in the composition in a volume fraction of 5 to 40% by volume, or the heat conductive filler having a high polarity is aluminum oxide, aluminum hydroxide, The case of at least one powder selected from magnesium oxide, zinc oxide, aluminum nitride, silicon nitride, boron nitride, and silicon dioxide is included.

  As described above, according to the present invention, when a thermally conductive filler having a high polarity is blended in a non-polar and thermoplasticized crosslinkable or thermoplastic polymer material, the viscosity of the polymer material is increased during the heat treatment. The fluidity is lowered and the fluidity is increased, and the heat conductive fillers are easily aggregated to form a link, so that a heat conductive material having high heat conductivity can be obtained. There is no need for blending, and even a small amount of blending can provide thermal conductivity equal to or higher than that of high blending, and flexibility can be imparted in addition to high thermal conductivity.

  The composition before the heat treatment is added to a non-polar crosslinkable or thermoplastic polymer material by a closed kneader or a screw extruder and a granular heat conductive filler having high polarity is added and kneaded to form a sheet. Rolled into In this case, the thermally conductive filler is dispersed without agglomeration. And when the composition before heat processing is heated at 80-120 degreeC for 10 to 30 minutes and is thermoplasticized, the viscosity of a polymeric material will fall, fluidity | liquidity will increase, and the granular heat conductivity which has high polarity. The filler aggregates to easily form a link, and high thermal conductivity can be obtained. When a crosslinkable polymer material is used, it can be heated and crosslinked at a normal temperature for a time to obtain a heat conducting material. On the other hand, when a thermoplastic polymer material is used, it is cooled and solidified. To make a heat conductive material.

  The heat conductive filler is blended in the composition in a volume fraction of 5 to 40% by volume. However, when the volume is less than 5% by volume, the amount of the heat conductive filler is small, and even if heat treatment is performed, it is linked by aggregation. It becomes difficult to form and heat conductivity cannot be expected. On the other hand, if it exceeds 40% by volume, the amount of the thermally conductive filler is excessively increased, resulting in an increase in cost and flexibility.

  Nonpolar polymer materials used here include isoprene rubber, butadiene rubber, styrene butadiene rubber, butyl rubber, ethylene propylene rubber, silicone rubber and other crosslinkable synthetic rubbers, olefin thermoplastic elastomers, styrene thermoplastic elastomers And thermoplastic elastomers such as polyethylene, polypropylene, and polyamide.

  The heat conductive filler having a high polarity is at least one powder selected from aluminum oxide, aluminum hydroxide, magnesium oxide, zinc oxide, aluminum nitride, silicon nitride, boron nitride, and silicon dioxide. The average primary particle size of the heat conductive filler is 1 to 100 μm.

  Other compounding agents are also used in ordinary rubber compositions. For example, zinc oxide as a crosslinking aid, fatty acid such as stearic acid as processing aid, various plasticizers, tackifiers, etc. It is possible to use. As the crosslinking system, various crosslinking systems such as sulfur crosslinking, organic peroxide crosslinking, metal oxide crosslinking, and resin crosslinking can be used.

  Examples of the organic peroxide include diacyl peroxide, peroxy ester, diallyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, 2.5-dimethyl-2.5- Di (t-butylperoxy) -hexane-3,1,3-bis (t-butylperoxy-isopropyl) benzene, 1,1-di-butylperoxy-3,3,5-trimethylcyclohexane, etc. A one-minute half-life of 150 to 250 ° C. by thermal decomposition is preferred.

Hereinafter, the present invention will be described in more detail with reference to examples.
Examples 1-3, Comparative Examples 1-2

  The rubber compound shown in Table 1 was kneaded in a closed kneader and then rolled to a sheet having a thickness of about 1 mm. The rolled sheet was thermoplasticized by placing it in an oven adjusted to 100 ° C. for 30 minutes and heat-treating it. When this was completed, the sheet was placed in a temperature-controlled oven at a temperature of 163 ° C. for 20 minutes for crosslinking to produce a heat conductive sheet.

  The thermal conductivity measurement of the obtained thermal conductive sheet was calculated from the value of thermal diffusivity measured using a laser flash method thermal constant measuring device TC-7000 (manufactured by Vacuum Riko Co., Ltd.). The Shore A hardness was measured according to JIS K6253. The results are also shown in Table 1.

  From Example 1 and Comparative Example 1, it was found that a rubber composition having higher thermal conductivity can be obtained by heat-treating a rubber composition containing aluminum oxide having a high polarity. In addition, in Example 2 and Example 3 in the same manner as in Example 1, it was found that a compound containing aluminum nitride and aluminum hydroxide as polar fillers also had high thermal conductivity. Furthermore, from Example 1 and Comparative Example 2, in the case of a rubber composition containing silicon carbide, which is a nonpolar heat conductive filler, the heat conductivity of the filler itself is 56 W / mK and aluminum oxide (36 W / mK). Despite being larger, the result showed lower thermal conductivity than the rubber composition containing the heat-treated aluminum oxide. This indicates that since the filler is non-polar, the filler hardly aggregated in the polymer material during the heat treatment.

The heat conductive material excellent in heat dissipation according to the present invention is used for a heat sink that conducts heat generated by an electronic component and releases the heat to the outside.

Claims (5)

  A composition is prepared by mixing and dispersing a non-polar crosslinkable polymer material with a highly conductive heat conductive filler, and the composition is subjected to heat treatment under conditions that do not crosslink and then crosslinked. A method for producing a heat conductive material.   A non-polar thermoplastic polymer material is mixed and dispersed with a heat conductive filler having a high polarity to produce a composition, which is heat-treated under the conditions that the composition does not crosslink, and then solidified. A method for producing a heat conducting material.   2. The heat conductive material according to claim 1, wherein the nonpolar crosslinkable polymer material comprises at least one synthetic rubber selected from isoprene rubber, butadiene rubber, styrene butadiene rubber, butyl rubber, ethylene propylene rubber, and silicone rubber. Method.   The manufacturing method of the heat conductive material in any one of Claims 1-3 with which the heat conductive filler which has high polarity is mix | blended with the volume fraction in the composition at 5-40 volume%. The thermally conductive filler having a high polarity is at least one powder selected from aluminum oxide, aluminum hydroxide, magnesium oxide, zinc oxide, aluminum nitride, silicon nitride, boron nitride, and silicon dioxide. The manufacturing method of the heat conductive material in any one of.