The present invention relates to a thermal conductive polymer molded article and a method for producing the same. More particularly, the present invention concerns a thermal conductive polymer molded article that can satisfactorily utilize advantageous features of a thermotropic liquid crystalline polymer including electrical insulation properties and low density, and that can achieve excellent thermal conductivity, and a method for producing the same.
In recent years, the integration degree and speed in LSIs have increased, in accordance with a trend toward high performance, downsizing, and reduction in weight of electronic equipments, and the mounting density in semiconductor packages. Accordingly, the heat generated by various electronic parts has increased, and measures for dissipating heat out of the electronic parts become a very important task. For achieving this task, a thermally conductive molded article comprised of a heat-radiating material, such as a metal, ceramic, or a polymer composition, is used in printed circuit boards, semiconductor packages, housings, and heat-radiating members, such as heat pipes, radiating panels, and heat diffusion panels.
Among these radiating members, a thermally conductive molded article comprised of a polymer composition (hereinafter referred to as “thermally conductive polymer molded article”) is easily molded into a desired shape and lightweight, and hence is widely used.
A polymer composition constituting a thermally conductive polymer molded article is known in the art that comprises a thermally conductive filler having a high thermal conductivity and which is incorporated in a polymer matrix such as a resin or a rubber. Examples of thermally conductive fillers include metal oxides, such as aluminum oxide, magnesium oxide, zinc oxide, and quartz; metal nitrides, such as boron nitride and aluminum nitride; metal carbides, such as silicon carbide; metal hydroxides, such as aluminum hydroxide; metals, such as gold, silver, and copper; carbon fibers; and graphite.
In an application that requires high heat resistance without deformation of the radiating member under high temperature conditions during mounting of electronic parts or when being used, a polymer composition and a thermally conductive polymer molded article using as a matrix a thermotropic liquid crystalline polymer have been proposed. Such thermotropic liquid crystalline polymer has excellent moldability and excellent heat resistance. For example, Japanese Laid-open Patent Publication No. 62-100577 discloses a composition, having excellent thermal conductivity, comprising a specific thermally conductive filler and a thermotropic liquid crystalline polymer. Japanese Laid-open Patent Publication No. 5-271465 discloses an electrical insulating composition having excellent thermal conductivity, which comprises 50 to 90% by weight of zircon as a thermally conductive filler and 50 to 10% by weight of a thermotropic liquid crystalline polymer. Further, Japanese National Phase Laid-open Publication No. 2001-523892 discloses a composition comprising 20 to 80% by weight of thermally conductive filler, such as carbon fibers, and 80 to 20% by weight of a thermotropic liquid crystalline polymer.
However, the conventional thermal conductive polymer composition contains a large amount of thermal conductive filler, in addition to the thermotropic liquid crystalline polymer, and has a problem in that the thermal conductive filler inhibits the thermotropic liquid crystalline polymer from exhibiting excellent features, such as electrical insulation properties and low density.