SBIR-STTR Award

Increased performance requirements of high-power or high-frequency electronics require novel thermal management materials. Boron nitride nanotubes (BNNTs) enhance performance of polymer-based electrically-insulating thermal interface materials (TIMs). This work will incorporate BNNTs into common micro-particle polymer composites to increase thermal transport between particles. Thermal impedance within TIMs is dominated by resistivity of the polymer which holds the thermally-conductive particles together in the matrix. Typically, inter-particulate space is 20% of interfaces volume. A multi-scale, bottoms-up approach to fabricating the filler material is expected to increase the thermal conductivity of many TIMs to above 10 W/mK. TIMs based on epoxy, cyanoacrylate, silicone, silicone oil, nylon multipolymer thermoplastic, and polytetrafluoroethylene matrices will be explored. Preliminary in-house work already dramatically increased thermal conductivity to nearly 6 W/mK in thermoplastics doped with BNNTs, implying an increase in inter-particle conductivity of ~20X. The TIMs produced in this study will be characterized for in- and through-plane thermal conductivity, and filler material development will be aided by scanning electron microscope imaging and surface area analysis of the densified powders to determine optimal ratios of components. The TIMs fabricated will be applicable within components, and as adhesives, pastes, top-side coatings, substrates, underfills, gap fillers, gap pads, and laminates.

Benefit:
By an anticipated 100X improvement in thermal conductivity of electrically-insulating polymers, performance-limiting heat can be extracted from electronics, even deep within integrated circuits and packages in spaces narrower than 50 m. Benefits will include improving performance, increasing efficiency, lengthening lifetime, and reducing lifecycle/O&M costs. The resultant enhancements will reduce stress on power systems (including system batteries), and even reduce risk of fires. These innovations will be broadly commercialized across the electronics industry, including naval and other defense systems, and will enable new systems previously prevented by heat management barriers.

Keywords:
Boron Nitride Nanotubes (BNNT), Boron Nitride Nanotubes (BNNT), thermal interface management (TIM), high-power electronics, top-side coatings, thermally-conductive electrically-insulating composites, Underfills, passive cooling., Adhesives

Heat dissipation requirements have become the critical limiter of performance, efficiency, lifetime, and lifecycle costs as performance demands on electronics increase. This is especially a challenge in naval systems, including phased-array radar, smart weapons, electronic countermeasures (ECM), directed energy weapons, and electronics counter-countermeasures (ECCM). High performance passive cooling requires the use of advanced materials capable of dissipating heat from deep within circuits, where only electrical insulators can be placed. The thermal performance of existing dielectric thermal materials is often inadequate, and they are frequently incompatible with physical and mechanical requirements and fabrication processes. The proposed work will incorporate boron nitride nanotubes (BNNTs) into common microparticle-polymer composites to increase heat transfer between particles and?is expected to increase the thermal conductivity of many thermal management materials to > 10 W/mK. In-house experiments have validated this concept achieving > 3 W/mK while maintaining dielectric character. In Phase II, prototype formulations of multiple thermal materials, gap fillers, thermal greases, adhesives, topside coatings, transport materials, and heat spreaders, will be optimized and evaluated based on thermal performance, secondary performance characteristics, and will be integrated into relevant simulated environments.

Benefit:
By an anticipated 100X improvement in thermal conductivity of electrically-insulating polymers, performance-and lifetime-limiting heat can be dissipated from electronics, even deep within integrated circuits and packages where bond lines are below 50 m. Benefits will include improving performance, increasing efficiency, lengthening lifetime, and reducing lifecycle/O&M costs. The resultant enhancements will reduce stress on power systems (including system batteries), and even reduce risk of fires. These innovations will be broadly commercialized across the electronics industry, including naval and other defense systems, and will enable new systems previously prevented by heat management barriers

Keywords:
electrical insulation, Thermal interface materials (TIMs), gap fillers, carrier material, Thermal Management, Boron Nitride Nanotubes (BNNT), thermal conductivity, high-power electronics