Heat buildup is a significant problem and limiting design factor for many electronic products. For example, LEDs are emerging as the next generation lighting materials due to their low power utilization and long life. Some lamps have multiple LEDs within an enclosure, which generates undesirable heat during operation. It is important to dissipate this heat efficiently to ensure proper operation of the device, enhance brightness, increase lifetime and prevent fogging.
Traditionally, heat-sink materials have been made of metal such as aluminum and formed into the proper design shape for the most efficient convective heat transfer. However, these metal components add significant weight and other design limitations for electronic products. Thermally conductive plastics represent the opportunity to design functional parts with heat management capabilities while eliminating many of the negative features of metallic heat sink materials.
Through Battelle’s Nanotechnology program we are developing thermally conductive thermoplastic materials for complex net shape geometries, as well as spray-on, conformal, thermally conductive coatings for efficient heat spreading over large areas. Battelle has been exploring emerging nanoparticles such as carbon nanotubes, graphene and boron nitride and their dispersion into polymers to create the next generation of thermally conductive materials. These thermally conductive polymers can be designed to meet very specific needs in the industry; for example, some of the polymers are electrically conducting while others are electrically insulating. They also have different mechanical properties such as flexibility, strength or durability that may make them more or less suitable for specific applications. They can be processed by plastics processing approaches such as extrusion and injection molding.
Generally, the challenge of achieving high thermal conductivity is related to high interfacial transfer from the particle to the matrix. Likewise, good wetting must be achieved between the heat sink and the heat source in order to maximize the efficiency of the heat transfer. The former can be tuned by appropriate functionalization of the nanoparticle additives. The latter can be facilitated by topographical, surface energy and mechanical property changes to either interface.
The new thermoplastic materials under development at Battelle offer significant advantages for the next generation of consumer and industrial electronics.
- For LEDs, thermally conductive thermoplastics can be injection molded into a net-shaped heat sink and mechanical enclosure that can be 3-dimensionally complex for added convective surface, without the need for subsequent machining. In addition, the materials can be up to 40% lighter than conventional metal components.
- We also have developed a spray-on thermally conductive coating to provide a uniform thermally conductive layer for efficient heat spreading over large areas. Unlike traditional laminates, the spray coating can be retrofit onto existing components and can be applied to irregularly shaped parts.