Heat-conductive noise suppression sheet

Abstract

A heat-conductive noise suppression sheet according to an embodiment includes first ferrite particles, second ferrite particles, a heat-conducting material, and a matrix material. The first ferrite particles are spherical particles having an average particle diameter in the range of 50 μm to 150 μm, the content of the first ferrite particles with respect to the total amount of solid components being in the range of 5 vol % to 25 vol %. The second ferrite particles are irregularly shaped particles having an average particle diameter in the range of 50 μm or less, the content of the second ferrite particles with respect the total amount of solid components being in the range of 5 vol % to 45 vol %.

Description

CLAIM OF PRIORITY[0001]This application is a Continuation of International Application No. PCT / JP2009 / 062377 filed on Jul. 7, 2009, which claims benefit of Japanese Patent Application No. 2008-179664 filed on Jul. 10, 2008. The entire contents of each application noted above are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a heat-conductive noise suppression sheet having a high noise suppression effect over a wide frequency range from the hundred megahertz range to the gigahertz range and high thermal conductivity.[0004]2. Description of the Related Art[0005]As described in Japanese Unexamined Patent Application Publication No. 2001-68312 and Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2006-504272, structures in which a heat-conductive noise suppression sheet is interposed between a semiconductor component, such as an IC, and a heat sink are known.[0006]A ...

AI Technical Summary

Benefits of technology

[0011]The present invention has been made to solve the above-described problem of the related art, and provides a heat-conductive noise suppression sheet having a high noise suppression effect over a wide frequency range from the hundred megahertz range to the gigahertz range and high thermal conductivity.

[0015]According to the present invention, attention is focused not only on the imaginary part μ″ of the complex relative permeability but also on the imaginary part ε″ of the complex relative permittivity to obtain a high noise suppression effect over a wide frequency range from the hundred megahertz range to the gigahertz range. More specifically, according to the present invention, the imaginary part μ″ of the complex relative permeability can be increased in the hundred megahertz range. Even though the imaginary part μ″ of the complex relative permeability is reduced in the gigahertz range, according to the present invention, the imaginary part ε″ of the complex relative permittivity can be reduced in the gigahertz range. Therefore, a high noise suppression effect can be obtained over a wide frequency range from the hundred megahertz range to the gigahertz range.

[0016]According to the present invention, the first ferrite particles, which are spherical particles having a larger average particle diameter than that of the second ferrite particles, are contained and the content of the first ferrite particles is appropriately regulated. Therefore, the compressibility can be increased while maintaining a high coefficient of thermal conductivity. As a result, the thermal conductivity can be effectively increased.

[0025]According to the present invention, the content of the second ferrite particles may be set to a relatively small value by setting the content of the first ferrite particles to a relatively large value. In such a case, even when the total filler content is not very large, a high noise suppression effect can be obtained. In addition, a high coefficient of thermal conductivity and high compressibility can be obtained, so that high thermal conductivity can be obtained.

[0029]According to the heat-conductive noise suppression sheet of the present invention, a high noise suppression effect can be obtained over a wide frequency range from the hundred megahertz range to the gigahertz range. In addition, high thermal conductivity can be obtained.

Problems solved by technology

However, it has been found that it is difficult to effectively increase the noise suppression effect in both the hundred megahertz range and the gigahertz range simply by adjusting the imaginary part μ″ of the complex relative permeability.

However, it has been found that even when the coefficient of thermal conductivity is increased by increasing the content of filler, the thermal conductivity cannot be effectively increased, owing to a reduction in compressibility.

If the compressibility of the sheet is low, the adhesion between the sheet and the heat sink and the adhesion between the sheet and the substrate decrease, which causes a reduction in thermal conductivity.

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