Water-Based Ink Technology Expands the Application of Carbon Nanotubes in Heat Dissipation

Following its water-based carbon nanotube heat-dissipating spray coating for thermal management in consumer electronic products, Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences (hereinafter referred to as Chengdu Organic Chemistry) has successfully developed another new product: carbon nanotube water-based heat-dissipating printing ink.

Carbon nanotubes (CNTs) are ideal functional fillers for heat dissipation applications. Known as the blackest material in the world, CNTs feature an emissivity close to 1 and rank among the best thermal conductive materials available today. Compared with granular heat-conductive fillers, fibrous CNTs can more easily form thermal conductive networks inside coatings, significantly reinforcing and toughening coating films. This enables ultra-thin coating construction, reduces thermal resistance, and delivers optimal performance.

Water-based CNT heat-dissipating coatings are applied onto the surface of electronic components via spraying, delivering excellent heat equalization, low thermal resistance and high thermal emissivity to enhance heat dissipation of metal substrates. Nevertheless, electronic components inside mobile phones are compact and lightweight; the spraying process suffers from low production efficiency and consequently high manufacturing costs.

Advancements in automated equipment, particularly the launch of high-precision fully automatic screen printing machines, enable fully automatic printing, custom pattern fabrication and precise control over coating thickness with a precision of less than 1 micrometer. This paves the way for large-scale application of CNTs in mobile phone thermal management.

Through in-depth collaboration with Shenzhen Heruitong Technology Co., Ltd., Chengdu Organic Chemistry has successfully adopted water-based ink technology to deposit CNT heat-dissipating coatings on metal strips via screen printing. The treated metal substrates including nickel silver, stainless steel and tinplate are endowed with outstanding thermal dissipation performance. Test results show the coating achieves an emissivity above 0.98, Class 0 adhesion in the cross-hatch test, pencil hardness of 3–4H, and stable performance with no degradation after 200 hours of aging treatment at 100°C. The newly developed CNT water-based heat-dissipating ink addresses pain points that cannot be resolved by conventional thermal conductive and heat-uniform materials, supporting disruptive product design. At present, leading mobile phone brands have adopted this product in mass production for shielding covers and LED backlight heat dissipation, while numerous other brands are conducting design verification.

Smartphones and tablets are equipped with multiple radio frequency components and antennas. Electromagnetic waves may cause crosstalk to high-speed semiconductor chips such as CPUs, DRAMs and flash memory devices. Shielding covers fabricated from metals (nickel silver, stainless steel, tinplate) printed with CNT heat-dissipating ink can radiate and transfer heat generated by internal electronic components, ensuring long-term stable operation of core devices. Since no ventilation holes are required for heat dissipation on these printed shielding covers, electromagnetic shielding performance can be maximized and mutual interference between frequency components is eliminated. Such shielding covers are compatible with fully automatic PCBA mounting (verified via wave soldering and reflow soldering temperature profile tests). Manufacturers can omit the manual graphite sheet laminating process, cutting production costs and greatly boosting production efficiency.

High heat is generated during the operation of mobile phone LED backlight units. Traditional thermal management solutions rely on graphite sheets for heat homogenization. An innovative design leverages the high emissivity of CNT coatings to radiate heat from the front side of displays into ambient air for convective cooling. Research data also verifies that the CNT coating features a specular reflectance of only 2.6% and diffuse reflectance as low as 0.1%, making it applicable for light shielding on LED back frames.

By adopting CNT heat-dissipating ink through screen printing on shielding covers as well as spraying or printing on middle frames and bottom housings, mobile phones can efficiently transfer and dissipate heat generated by internal components, greatly improving end-user experience.

The CNT coating integrates both heat dissipation and electrostatic discharge (ESD) functions, with a surface resistivity ranging from 10⁷ Ω to 10⁸ Ω. During mobile phone structural design, static electricity can be guided to the coating for dissipation, protecting personal safety and mitigating electrostatic damage to electronic components.

Copper foils printed with CNT heat-dissipating ink deliver integrated functions including thermal conduction, heat homogenization, radiative cooling, electrostatic discharge and electromagnetic shielding. In addition, these CNT thermal conductive copper foils are flexible, pattern-customizable, easy to die-cut, and boast a high lamination yield rate, capable of fully replacing manually applied graphite thermal conductive sheets.

Currently, Chengdu Organic Chemistry is working closely with Shenzhen Heruitong Technology Co., Ltd. to vigorously promote the new carbon nanotube water-based heat-dissipating ink, with Heruitong providing full-cycle technical support for thermal design.