Granulation method of insulating exothermic sheet and boron nitride

Abstract

PROBLEM TO BE SOLVED: To provide an insulation heat dissipation sheet which is advantageous in productivity and cost, and excellent in heat conductivity and electric insulation properties, and a granulation method for boron nitride used therefor.SOLUTION: According to a granulation method of boron nitride, the boron nitride is made flow within a flowing layer and granulated while spraying a silane coupling agent containing the amino group. Therefore, a heat dissipation sheet can be provided which is advantageous in productivity and cost and excellent in heat conductivity and an electric insulation property.

Description

technical field [0001] The present invention relates to an insulating heat radiation sheet for transferring heat from a heat generating member to a heat radiation member of electric, electronic equipment, lighting equipment, etc. and a granulation method of boron nitride used for the sheet. Background technique [0002] In the past, heat conduction layers that conduct heat from heat-generating components such as electric, electronic equipment, and light-emitting equipment to heat-radiating components have been required to have high thermal conductivity and insulation properties. As heat conduction layers that meet such requirements, widely used Insulating and exothermic sheet in which filler is dispersed in resin or rubber. Among them, hexagonal boron nitride (h-BN) having high thermal conductivity and insulating properties was used as the filler. [0003] The crystal structure of hexagonal boron nitride is the same layered structure as graphite, and its particle shape is s...

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Problems solved by technology

[0014] However, the methods of Patent Documents 1 to 4 all require special equipment and complicated manufacturing steps, so they are disadvantageous in terms of productivity and cost.

[0015] On the other hand, in the method of Patent Document 5, when the average major diameter of the primary particles of the scaly boron nitride constituting the secondary aggregated particles is large, the primary particles aggregate in the same direction, and the manufacturing process of the heat releasing sheet The secondary aggregated particles are easy to collapse when mixing, stirring, pressing, etc.

Therefore, even if such secondary aggregated particles are oriented, the thermal conductivity in the thickness direction of the sheet cannot be sufficiently improved.

In addition, since the heat releasing sheet of Patent Document 5 contains only 1 to 20% by mass of secondary aggregated particles having a particle diameter of 50 μm or more, thermal conductivity is insufficient.

[0016] In addition, in the methods of Patent Documents 6 to 7, by firing at about 2,000°C, I 002 / I 100 6 to 20, but the method of Patent Document 6 requires a high temperature of about 2,000°C not only when producing scaly boron nitride primary particles but also when producing secondary aggregated particles, which is disadvantageous in terms of cost.

In Patent Document 7, compared with the general-purpose method of producing primary particles of flaky boron nitride, it takes time to produce boron nitride, which is disadvantageous in terms of cost.

[0017] In the method of Patent Document 8, boron nitride is surface-modified with a silane coupling agent containing amino and mercapto groups, but this method only modifies the surface of the primary particles of flaky boron nitride. Orientation in such a way that the long-diameter direction of the sheet is consistent with the direction of the sheet surface

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