Researchers from Fujitsu Laboratories has developed an adhesive sheet composed of carbon nanotubes with extremely high thermal conductivity of up to 100 W/mK (watt per meter per Kelvin), enabling practical use as a heat dissipation material in electronic vehicles (EVs).
Researchers Develop Adhesive Sheet Technology for Electronic Vehicles
Laminated Carbon Nanotubes Adhesive Sheet for Heat Dissipation
Carbon nanotubes have high thermal conductivity and represent a promising candidate for heat dissipation from heat sources including semiconductor devices. Nevertheless, the material remains difficult to handle due to its fragility, rendering it impractical for many purposes. To address this, Fujitsu has successfully developed a technology for laminating vertically aligned carbon nanotubes, while maintaining their original characteristics of high thermal conductivity and flexibility, as well as a technology for bonding them with sufficient adhesion. The technology facilitates the cutting and handling of carbon nanotube sheets, making it possible to use them as a heat dissipation material, for example, in automotive power modules for electric vehicles.
Features of the Newly Developed Technology
Adhesive Sheet Laminated Technology
Fujitsu has developed a technique for laminating vertically aligned carbon nanotubes while maintaining the alignment. The laminate layer consists of two layers, a protective sheet and an adhesive layer, and has a laminate structure in which the laminate layer protects the top and bottom of carbon nanotubes. Carbon nanotubes are difficult to use as heat dissipating materials because they easily lose their shape. However, this technology protects the carbon nanotubes themselves with a laminate layer, making them stable in shape and making cutting and handling easier, which was difficult with conventional technologies.
High-thermal-conductivity Adhesive Sheet Bonding Technology
The adhesive layer that makes up the laminate layer is made of a polymer that is several microns thick. Because even a small amount of resin can cause large thermal resistance, it has become an issue that must be solved to achieve both adhesiveness and thermal conductivity. Thus, by optimizing three or more correlation parameters, such as the density of carbon nanotubes, the type and thickness of the resin, and the bonding conditions, utilizing knowledge of thermal resistance at the interface between carbon nanotubes and resins cultivated over many years, it becomes possible to bond carbon nanotubes while maintaining sufficient adhesive properties without impairing thermal conductivity.
Applications of the Adhesive Sheet Technology
The sheet is laminated with adhesive and protective layers, it can be easily cut and handled, and can be used for applications requiring adhesion. The technology will make it possible to put carbon nanotubes into practical use as heat dissipating materials, including in automotive power modules for EVs.
Going forward, Fujitsu Laboratories will license the use of its carbon nanotube adhesive sheets to companies in the materials and electrical industries. and will continue to support their commercialization and practical use.
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